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The transmission measurements point out a deep decrease of the waves speeds in conjunction with a dramatic decrease of the maximum frequency transmitted. The marble acts as a low pass filter whose characteristic frequency cut decreases with ageing. This pattern occurs also for the Rayleigh wave surface measurements. The speed change in conjunction with the bandwidth translation is shown to be correlated to the material de-structuration during ageing.
With a similar behavior but reversed in time, the same king of phenomena have been observed trough sol-gel materials during their structuration from liquid to solid state Martinez, L. Ultrasonics, 42 1 , A model is proposed to interpret the acoustical measurements. Characterization of magnetic colloids by means of magnetooptics.
A new, efficient method for the characterization of magnetic colloids based on the Faraday effect is proposed. According to the main principles of this technique, it is possible to detect the stray magnetic field of the colloidal particles induced inside the magnetooptical layer.
The magnetic properties of individual particles can be determined providing measurements in a wide range of magnetic fields. The magnetization curves of capped colloids and paramagnetic colloids were measured by means of the proposed approach. The registration of the magnetooptical signals from each colloidal particle in an ensemble permits the use of this technique for testing the magnetic monodispersity of colloidal suspensions.
Characterizing permanent magnet blocks with Helmholtz coils. Most of the insertion devices to be installed at the Advanced Photon Source will utilize permanent magnets in their magnetic structures. The quality of the spectral output is sensitive to the errors in the field of the device which are related to variations in the magnetic properties of the individual blocks. The Advanced Photon Source will have a measurement facility to map the field in the completed insertion devices and equipment to test and modify the magnetic strength of the individual magnet blocks.
One component of the facility, the Helmholtz coil permanent magnet block measurement system, has been assembled and tested. This system measures the total magnetic moment vector of a block with a precision better than 0. The design and performance of the system will be presented.
Characterization of nicosulfuron availability in aged soils. Sorption-desorption interactions of pesticides with soil determine their availability for transport, plant uptake, and microbial degradation. These interactions are affected by the physical-chemical properties of the pesticide and soil, and for some pesticides, their residence time in the soil. Aging significantly increased sorption.
For instance, after the day incubation, calculated K d,app increased by a factor of 2 to 3 in Mollisols from the Midwestern United States and by a factor of 5 to 9 in Oxisols from Brazil and Hawaii, as compared to freshly treated soils. In view of this outcome, potential transport of nicosulfuron would be overpredicted if freshly treated soil K d values were used to predict transport. The fact that the nicosulfuron solution concentration decreased faster than the soil concentration with time suggested that the increase in sorption was because the rate of degradation in solution and on labile sites was faster than the rate of desorption of the neutral species from the soil particles.
It may have also been due to nicosulfuron anion diffusion to less accessible sites with time, leaving the more strongly bound neutral molecules for the sorption characterization. Regardless of the mechanism, these results are further evidence that increases in sorption during pesticide aging should be taken into account during the characterization of the sorption process for mathematical models of pesticide degradation and transport.
Characterization of magnetic force microscopy probe tip remagnetization for measurements in external in-plane magnetic fields. A quantitative analysis of magnetic force microscopy MFM images taken in external in-plane magnetic fields is difficult because of the influence of the magnetic field on the magnetization state of the magnetic probe tip. We prepared calibration samples by ion bombardment induced magnetic patterning with a topographically flat magnetic pattern magnetically stable in a certain external magnetic field range for a quantitative characterization of the MFM probe tip magnetization in point-dipole approximation.
Crystallographic, hyperfine and magnetic characterization of a maraging alloy. Alves, T. Maraginglike alloys were made by arc-melting iron with the alloy elements i. The results revealed that the as-solubilized sample is martensitic and ferromagnetic. Its residual induction and coercive field increase monotonically with the maximum applied field of a magnetization minor loop and both curves presented very similar shapes.
The area of the minor loops varies parabolically with this maximum applied field. The aging induced an atomic rearrangement in the martensite phase, involving change in the composition and lattice parameters, reversion of austenite and the formation of the Fe 3 Mo 2 intermetallic compound.
Comparisons are presented between the results obtained by us for these alloys and those obtained for Maraging steel samples. Therapeutic magnetic microcarriers characterization by measuring magnetophoretic attributes.
We have proposed to embed magnetic nanoparticles in therapeutic or diagnostic agents in order to magnetically control them. A modified clinical Magnetic Resonance Imaging MRI scanner is used to provide the driving force that allows these magnetically embedded microcarriers to navigate the vascular human network.
By using specific Magnetic Resonance MR gradient sequences this method has been validated in previous research works. Magnetophoresis is the term used to describe the fact that a magnetic particle changes its trajectory under the influence of a magnetic force while being carried by a fluid flow. This movement depends on the particle's magnetic characteristics, the particle's geometric shape, the fluid flow's attributes and other factors.
In our proposed method, magnetic microcarriers can be produced in several different ways, and so their response will differ to the same magnetic force and fluid flow conditions. Such characterization is essential for determining the optimal sequences of magnetic gradients to deflect their trajectory through relatively complex vascular networks in order to reach a pre-defined target.
A microfluidic device was fabricated to validate the design. Magnetophoretic velocities are measured and a simple tracking method is proposed. The preliminary experimental results indicate that, despite some limitations, the proposed technique has the potential to be appropriate. Quadrupole magnetic field-flow fractionation: A novel technique for the characterization of magnetic particles.
In the last few decades, the development and use of nanotechnology has become of increasing importance. Magnetic nanoparticles, because of their unique properties, have been employed in many different areas of application. They are generally made of a core of magnetic material coated with some other material to stabilize them and to help disperse them in suspension. The unique feature of magnetic nanoparticles is their response to a magnetic field.
They are generally superparamagnetic, in which case they become magnetized only in a magnetic field and lose their magnetization when the field is removed. It is this feature that makes them so useful for drug targeting, hyperthermia and bioseparation. For many of these applications, the synthesis of uniformly sized magnetic nanoparticles is of key importance because their magnetic properties depend strongly on their dimensions. Because of the difficulty of synthesizing monodisperse particulate materials, a technique capable of characterizing the magnetic properties of polydisperse samples is of great importance.
Quadrupole magnetic field-flow fractionation MgFFF is a technique capable of fractionating magnetic particles based on their content of magnetite or other magnetic material. In MgFFF, the interplay of hydrodynamic and magnetic forces separates the particles as they are carried along a separation channel. Since the magnetic field and the gradient in magnetic field acting on the particles during their migration are known, it is possible to calculate the quantity of magnetic material in the particles according to their time of emergence at the channel outlet.
Knowing the magnetic properties of the core material, MgFFF can be used to determine both the size distribution and the mean size of the magnetic cores of polydisperse samples. When magnetic material is distributed throughout the volume of the particles, the derived data corresponds to a distribution in equivalent spherical diameters of magnetic material in. Eddy current characterization of magnetic treatment of nickel Eddy current methods have been applied to characterize the effect of magnetic treatments on component service-life extension.
Coil impedance measurements were acquired and analyzed on nickel specimens that have been subjected to many mechanical and magnetic engineering processes: annealing, applied strain, magnetic field, shot peening, and magnetic field after peening. Experimental results have demonstrated a functional relationship between coil impedance, resistance and reactance, and specimens subjected to various engineering processes.
It has shown that magnetic treatment does induce changes in electromagnetic properties of nickel that then exhibit evidence of stress relief. However, further fundamental studies are necessary for a thorough understanding of the exact mechanism of the magnetic field processing effect on machine-tool service life.
Influence of coating on nanocrystalline magnetic properties during high temperature thermal ageing. Since their birth or mergence the late s, the nanocrystalline ultrasoft magnetic materials are taking a great importance in power electronic systems conception. One of the main advantages that make them more attractive nowadays is their ability to be packaged since the reduction of the magnetostrictive constant to almost zero.
Consequently, the magnetic thermal ageing may occur but is, unfortunately, weakly studied. This paper focuses on the influence of the coating packaging type on the magnetic nanocrystalline performances during a thermal ageing. Based on a dedicated monitoring protocol, a large magnetic characterization has been done and analyzed. Elsewhere, X-Ray Diffraction and magnetostriction measurements were carried out to support the study of the anisotropy energies evolution with ageing. This latter is discussed in this paper to explain and give hypothesis about the ageing phenomena.
System characterization of a magnetically suspended flywheel. The purpose of flywheel energy storage is to provide a means to save energy during times when the satellite is in sunlight, and then return the energy during the time when the satellite is in darkness. Typically, an energy storage device operates cyclically, where for satellites in Low Earth Orbit LEO the typical period is 60 minutes of sunlight followed by 30 minutes of darkness. If a lifetime of 17 years is required the energy storage system must be capable of sustaining approximately , cycles.
The recent developments at the University of Maryland and how these progressions apply to a Watt-hour magnetically suspended flywheel stack energy storage system are covered. The work includes hardware testing results from a stack flywheel energy storage system, improvements in the area of non-contacting displacement transducers, and performance enhancements of magnetic bearings. The experimental results show that a stack flywheel energy storage system is a feasible technology.
Magnetic hyaluronate hydrogels: preparation and characterization. A novel soft way of hyaluronate HyA based magnetic hydrogel preparation was revealed. Magnetite nanoparticles MNPs were prepared by co-precipitation. The results suggest that the HyA-based magnetic hydrogels may be promising formulations for future biomedical applications, e. This dissertation research has involved microscopic characterization of magnetic nanostructures using off-axis electron holography and Lorentz microscopy.
The studies have confirmed the capability of holography to describe the behavior of magnetic structures at the nanoscale. The phase changes caused by the fringing fields of chains consisting of Co NPs were measured and calculated. The difference between chains with different numbers of Co NPs followed the trend indicated by calculations.
The most likely explanation is that magnetic fields are confined within the shells and form closed loops. The multiple- magnetic -domain structure of iron carbide cores in carbon spirals was imaged using phase maps of the fringing fields. The strength and range of this fringing field was insufficient for manipulating the carbon spirals with an external applied magnetic field. Degaussing and MFM scans ruled out the possibility that saturated magnetization and sample preparation had degraded the anisotropy, and the magnetism , respectively.
The results suggested that these nanopillars were not suitable as candidates for prototypical bit information storage devices. Observations of Ni-Zn-Co spinel ferrite thin films in plan-view geometry indicated a multigrain magnetic domain structure and the magnetic fields were oriented in-plane only with no preferred magnetization distribution. This domain structure helps explain this. Versatile magnetometer assembly for characterizing magnetic properties of nanoparticles.
We constructed a versatile magnetometer assembly for characterizing iron oxide nanoparticles. The magnetometer can be operated at room temperature or inside a cryocooler at temperatures as low as 6 K. The magnetometer's sensor can be easily exchanged and different detection electronics can be used. We tested the assembly with a non-cryogenic commercial Hall sensor and a benchtop multimeter in a four-wire resistance measurement scheme.
A magnetic moment sensitivity of 8. To illustrate the capability of the assembly, we synthesized iron oxide nanoparticles coated with different amounts of a triblock copolymer, Pluronic F, and characterized their magnetic properties. We determined that the polymer coating does not affect the magnetization of the particles at room temperature and demonstrates that it is possible to estimate the average size of coating layers from measurements of the magnetic field of the sample.
In aircraft applications, the energy efficiency must be associated with a maximum reduction of mass and volume, so a high components compactness. A consequence from this compactness is the increase of operating temperature. Thus, the magnetic materials used in these applications, have to work at high temperature.
It raises the question of the thermal ageing problem. The reliability of these components operating at this condition becomes a real problem which deserves serious interest. Our work takes part in this context by studying the magnetic material thermal ageing. The nanocrystalline materials are getting more and more used in power electronic applications.
Main advantages of nanocrystalline materials compared to ferrite are: high saturation flux density of almost 1. The nanocrystalline Fe An important experimental work of magnetic characterization is being done following a specific monitoring protocol. Indeed, every year tons of Unexploded-ordnance are discovered in France. Magnetic measurements are useful to localize magnetized objects.
Moreover, it is the cheapest geophysical method which does not impact environment and which is relatively fast to perform. Fluxgate magnetometers three components are used to measure magnetic properties bellow the ground. These magnetic sensors are not absolute, so they need to be calibrated before the onset of the measurements.
The advantage is that they allow magnetic compensation of the equipment attached to the sensor. So the choice of this kind sensor gives the opportunity to install the equipment aboard different magnetized supports: boat, quad bike, unmanned aerial vehicle, aircraft, Indeed, this methodology permits to perform magnetic mapping with different scale and different elevation above ground level. An old French aerial military plant was chosen to perform this multi-scale approach.
The advantage of the site is that it contains a lot of different targets with variable sizes and depth, e. The comparison between measured maps at different elevations and the prolonged map highlights the maximum distance for the target's detection figure.
Submicron magnetic core conducting polypyrrole polymer shell: Preparation and characterization. Magnetic particles are of great interest in various biomedical applications, such as, sample preparation, in vitro biomedical diagnosis, and both in vivo diagnosis and therapy.
For in vitro applications and especially in labs-on-a-chip, microfluidics, microsystems, or biosensors, the needed magnetic dispersion should answer various criteria, for instance, submicron size in order to avoid a rapid sedimentation rate, fast separations under an applied magnetic field, and appreciable colloidal stability stable dispersion under shearing process. Then, the aim of this work was to prepare highly magnetic particles with a magnetic core and conducting polymer shell particles in order to be used not only as a carrier, but also for the in vitro detection step.
The prepared magnetic seed dispersions were functionalized using pyrrole and pyrrolecarboxylic acid. The obtained core-shell particles were characterized in terms of particle size, size distribution, magnetization properties, FTIR analysis, surface morphology, chemical composition, and finally, the conducting property of those particles were evaluated by cyclic voltammetry.
The obtained functional submicron highly magnetic particles are found to be conducting material bearing function carboxylic group on the surface. These promising conducting magnetic particles can be used for both transport and lab-on-a-chip detection. Published by Elsevier B.
Modular magnetic tweezers for single-molecule characterizations of helicases. Magnetic tweezers provide a versatile toolkit supporting the mechanistic investigation of helicases. In the present article, we show that custom magnetic tweezers setups are straightforward to construct and can easily be extended to provide adaptable platforms, capable of addressing a multitude of enquiries regarding the functions of these fascinating molecular machines.
We first address the fundamental components of a basic magnetic tweezers scheme and review some previous results to demonstrate the versatility of this instrument. We then elaborate on several extensions to the basic magnetic tweezers scheme, and demonstrate their applications with data from ongoing research.
As our methodological overview illustrates, magnetic tweezers are an extremely useful tool for the characterization of helicases and a custom built instrument can be specifically tailored to suit the experimenter's needs. All rights reserved. Characterization of magnetic nanoparticles using programmed quadrupole magnetic field-flow fractionation. Quadrupole magnetic field-flow fractionation is a relatively new technique for the separation and characterization of magnetic nanoparticles.
Magnetic nanoparticles are often of composite nature having a magnetic component, which may be a very finely divided material, and a polymeric or other material coating that incorporates this magnetic material and stabilizes the particles in suspension. There may be other components such as antibodies on the surface for specific binding to biological cells, or chemotherapeutic drugs for magnetic drug delivery.
Magnetic field-flow fractionation MgFFF has the potential for determining the distribution of the magnetic material among the particles in a given sample. MgFFF differs from most other forms of field-flow fractionation in that the magnetic field that brings about particle separation induces magnetic dipole moments in the nanoparticles, and these potentially can interact with one another and perturb the separation.
This aspect is examined in the present work. Samples of magnetic nanoparticles were analysed under different experimental conditions to determine the sensitivity of the method to variation of conditions. The results are shown to be consistent and insensitive to conditions, although magnetite content appeared to be somewhat higher than expected.
Magnetic characterization of isolated candidate vertebrate magnetoreceptor cells. Eder, Stephan H. However, the underlying sensory physiology remains poorly understood due to the elusiveness of the magnetosensory structures. Here we present an effective method for isolating and characterizing potential magnetite-based magnetoreceptor cells.
In essence, a rotating magnetic field is employed to visually identify, within a dissociated tissue preparation, cells that contain magnetic material by their rotational behavior. As a tissue of choice, we selected trout olfactory epithelium that has been previously suggested to host candidate magnetoreceptor cells.
We were able to reproducibly detect magnetic cells and to determine their magnetic dipole moment. In confocal reflectance imaging, these produce bright reflective spots close to the cell membrane. The magnetic inclusions are found to be firmly coupled to the cell membrane, enabling a direct transduction of mechanical stress produced by magnetic torque acting on the cellular dipole in situ. Our results show that the magnetically identified cells clearly meet the physical requirements for a magnetoreceptor capable of rapidly detecting small changes in the external magnetic field.
This would also explain interference of ac powerline magnetic fields with magnetoreception, as reported in cattle. Molecular and histological characterization of age spots. Age spots, also called solar lentigines and lentigo senilis, are light brown to black pigmented lesions of various sizes that typically develop in chronically sun-exposed skin.
It is well known that age spots are strongly related to chronic sun exposure and are associated with photodamage and an increased risk for skin cancer, however, the mechanism s underlying their development remain poorly understood. We used immunohistochemical analysis and microarray analysis to investigate the processes involved in their formation, focusing on specific markers associated with the functions and proliferation of melanocytes and keratinocytes.
A total of genes were differentially expressed in age spots but melanocyte pigment genes were not among them. The increased expression of keratins 5 and 10, markers of basal and suprabasal keratinocytes, respectively, in age spots suggests that the increased proliferation of basal keratinocytes combined with the decreased turnover of suprabasal keratinocytes leads to the exaggerated formation of rete ridges in lesional epidermis which in turn disrupts the normal processing of melanin upwards from the basal layer.
Based on our results, we propose a model for the development of age spots that explains the accumulation of melanin and the development of extensive rete ridges in those hyperpigmented lesions. Scanning microwave microscopy technique for nanoscale characterization of magnetic materials. Joseph, C. In this work, microwave characterization of magnetic materials using the scanning microwave microscopy SMM technique is presented.
The capabilities of the SMM are employed for analyzing and imaging local magnetic properties of the materials under test at the nanoscale. The analyses are performed by acquiring both amplitude and phase of the reflected microwave signal.
The changes in the reflection coefficient S11 are related to the local properties of the material under investigation, and the changes in its magnetic properties have been studied as a function of an external DC magnetic bias. An equivalent electromagnetic transmission line model is discussed for the quantitative analysis of the local magnetic properties. We also observed the hysteretic behavior of the reflection coefficient S11 with an external bias field.
The imaging and spectroscopy analysis on the experimental results are evidently indicating the possibilities of measuring local changes in the intrinsic magnetic properties on the surface of the material. Preparation and Characterization of an Amphipathic Magnetic Nanosphere. The amphipathic magnetic nanospheres were synthesized using C8 and polyethylene glycol as ligands. Their morphology, structure, and composition were characterized by transmission electron microscope, Fourier transform infrared, and elementary analysis.
The magnetic characteristics of magnetic nanomaterials were measured by vibrating sample magnetometer. The adsorption capability was also studied by static tests, and the material was applied to enrich benzenesulfonamide from calf serum. The results exhibited that the C8-PEG phase owned better adsorption capability, biocompatible property, and dispersivity in aqueous samples. Preparation and characterization of biocompatible magnetic carbon nanotubes.
Also, their biocompatibility was compared with naked carbon nanotubes. The results showed that after coated with Fe3O4 nanoparticles, the obtained magnetic carbon nanotubes show superparamagnetic characteristic at room temperature, and their blocking temperature is about 80 K. The magnetic properties of the nanotubes are relevant to the content of magnetic particles, increasing content of magnetic nanoparticles leads to higher blocking temperature and saturation magnetization.
The results of antimicrobial activities to bacterial cells Escherichia coli showed that the MWNTs have antimicrobial activity, while the magnetic nanotubes are biocompatible even with a higher concentration than that of MWNTs. Sm and Y radiolabeled magnetic fluids: magnetic and magneto-optical characterization. Aquino, R. We report on magnetic fluids based on samarium and ytrium-doped nanoparticles. The nanostructures chemical composition is checked and X-ray diffraction provides both their mean size and a structural characterization.
Magnetization and magneto-optical birefringence results are presented and well agree with the pure maghemite behavior. Since these particles can become radioactive after neutron activation, they could therefore represent a new perspective for biomedical applications in the radiation therapy of cancer. Quantitative characterization of nanoscale polycrystalline magnets with electron magnetic circular dichroism.
Electron magnetic circular dichroism EMCD allows the quantitative, element-selective determination of spin and orbital magnetic moments, similar to its well-established X-ray counterpart, X-ray magnetic circular dichroism XMCD. As an advantage over XMCD, EMCD measurements are made using transmission electron microscopes, which are routinely operated at sub-nanometre resolution, thereby potentially allowing nanometre magnetic characterization.
However, because of the low intensity of the EMCD signal, it has not yet been possible to obtain quantitative information from EMCD signals at the nanoscale. Here we demonstrate a new approach to EMCD measurements that considerably enhances the outreach of the technique. The statistical analysis introduced here yields robust quantitative EMCD signals. Moreover, we demonstrate that quantitative magnetic information can be routinely obtained using electron beams of only a few nanometres in diameter without imposing any restriction regarding the crystalline order of the specimen.
Methods for characterizing magnetic footprints of perpendicular magnetic recording writer heads. In this work, the magnetic footprints, along with some of its dynamic features in recording process, of perpendicular magnetic recording writer heads have been characterized by using three different techniques. Those techniques are the spin-stand stationary footprint technique, the spin-stand dynamic footprint technique, and the coherent writing technique combined with magnetic force microscope imaging method.
The characteristics of those techniques have been compared to one another. It was found experimentally that the spin-stand stationary method could not precisely catch some peculiar recording dynamics of the write heads in certain conditions. The advantages and disadvantages among all those techniques are also examined and discussed in detail. Fabrication and nanoscale characterization of magnetic multilayer nanowires.
Magnetic multilayers nanowires are scientifically fascinating and have potential industrial applications in many areas of advanced nanotechnology. These applications arise due to the nanoscale dimensions of nanostructures that lead to unique physical properties. Magnetic multilayer nanowires have been successfully produced by electrodeposition into templates. Anodic Aluminium Oxide AAO membranes were used as templates in this process; the templates were fabricated by anodization method in acidic solutions at a fixed voltage.
The fabrication method of a range of magnetic multilayer nanowires is described in this study and their structure and dimensions were analyzed using scanning electron microscope SEM , Transmission electron microscope TEM and scanning transmission electron microscopy STEM. Individual nanowires have uniform structure and regular periodicity. The magnetic and nonmagnetic layers are polycrystalline, with randomly oriented fcc lattice structure crystallites.
The electrical and magnetoresistance properties of individual magnetic multilayer nanowires have been measured inside a SEM using two sharp tip electrodes attached to in situ nanomanipulators and a new electromagnet technique. The giant magnetoresistance GMR effect of individual magnetic multilayer nanowires was measured in the current - perpendicular to the plane CPP geometry using a new in situ method at variable magnetic field strength and different orientations..
On predicting the extent of magnetic aging in electrical steels. Magnetic aging of steels is essentially the result of an increase in coercive force, inhibition of ferrite domain wall movement by precipitated carbide particles being the main cause of this increase.
In the present work, the nature of the carbides precipitating in four grades of electrical steels has been looked into. The model of Drabecki and Wyslocki when applied to the case of metastable carbide predicts its contribution to the coercive force fairly accurately. None of the existing models, however, succeeds in suggesting the extent of the increases accruing from the presence of the stable carbide cementite particles.
Each of the models takes into account only one or two of the isolated aspects of magnetic interaction between matrix and precipitate. It appears that for cementite, whose several magnetic characteristics are quite different from those of the ferrite matrix, all possible interaction parameters have to be taken into account to determine the actual mechanism. Optical and magnetic characterization of theranostic magnetite particles Conference Presentation.
Magnetic nanoparticles MNPs have a major role as contrast agent in diagnostic imaging and therapeutic monitoring. In order to research on MNP exposition, degradation and elimination of those nano composites as well as the consequences of the MNP exposition in relation with social economic relevant diseases cancer, infectious diseases , the comprehensive characterization of magnetic and structural properties is of high importance.
Within this contribution, the magnetic characterization of theranostic relevant MNPs is introduced. Employing Raman spectroscopy, the typical fingerprint information of magnetite is detected. By increasing the laser power, the transition to maghemite and hematite due to the oxidation of the magnetic core is illustrated.
Moreover, IR spectroscopy is applied to characterize the coating material e. To determine the stability of MNPs as well as the MNP's elimination under physiological conditions, different buffer systems were tested i. The investigated MNPs are stable in SBF; thus, the stability in blood after injection of the contrast agent is guaranteed. Role of aging time on the magnetic properties of Sm2Co17 permanent magnets processed through cold isostatic pressing.
The effect of aging time on the magnetic properties of Sm2Co17 permanent magnets processed through a novel method of cold isostatic pressing was investigated. Sintered Sm2Co17 samples were subjected to different aging times in the range of h and their respective microstructures were correlated with the magnetic properties obtained.
The values of remanant magnetization Br were observed to be constant in samples aged from h beyond which a gradual decrease in Br values was observed. The values of coercivity Hc displayed a sharp increase in samples aged from 10 to 20 h beyond which the coercivity values showed marginal improvement. Hence a good combination of magnetic properties could be achieved in samples aged for 20 h. A maximum energy product of 27 MGOe was achieved in the 20 h aged sample processed through a novel route.
Effect of thermal aging on stability of transformer oil based temperature sensitive magnetic fluids. Synthesizing stable temperature sensitive magnetic fluids with tunable magnetic properties that can be used as coolant in transformers is of great interest, however not exploited commercially due to the lack of its stability at elevated temperatures in bulk quantities.
The task is quite challenging as the performance parameters of magnetic fluids are strongly influenced by thermal aging. In this article, we report the effect of thermal aging on colloidal stability and magnetic properties of Mn1-xZnxFe2O4 magnetic fluids prepared in industrial grade transformer oil.
As-synthesized magnetic fluids possess good dispersion stability and tunable magnetic properties. Effect of accelerated thermal aging on the dispersion stability and magnetic properties have been evaluated by photon correlation spectroscopy and vibration sample magnetometry, respectively. Dark field imaging system for size characterization of magnetic micromarkers.
In this paper we demonstrate a dark field video imaging system for the detection and size characterization of individual magnetic micromarkers suspended in liquid and the detection of pathogens utilizing magnetically labelled E. The developed detection method can be used to obtain clinical information about liquid contents when an additional biological protocol is provided, i. Some of the major advantages of our method are the increased sizing precision in the micro- and nano-range as well as the setup's simplicity making it a perfect candidate for miniaturized devices.
Measurements can thus be carried out in a quick, inexpensive, and compact manner. A minor limitation is that the concentration range of micromarkers in a liquid sample needs to be adjusted in such a manner that the number of individual particles in the microscope's field of view is sufficient. L-arginine modified magnetic nanoparticles: green synthesis and characterization.
In recent years, there has been considerable interest in Arg which is a unique, nontoxic, and biocompatible biomolecule since it can be utilized as an agent for the functionalization and subsequent stabilization of MNPs against oxidation and aggregation, during or after a synthesis procedure.
Our studies demonstrate that Arg has great impacts on MNPs with the decreasing size of the particle. Also, saturation magnetization and electrostatic interactions of RMNPs have a direct impact on biological molecules such as proteins and nucleic acids. By controlling the concentration of Arg, it is possible to accurately control the above-mentioned characteristics, which are useful tools for applications such as connecting to antibodies, catalysis, drug loading, and modification of MNP stability.
Colorimetric analysis showed the existence of Arg in the synthesized samples. Magnetic field shimming of a permanent magnet using a combination of pieces of permanent magnets and a single-channel shim coil for skeletal age assessment of children.
We adopted a combination of pieces of permanent magnets and a single-channel SC shim coil to shim the magnetic field in a magnetic resonance imaging system dedicated for skeletal age assessment of children. The target magnet was a 0. The homogeneity of the magnetic field was first improved by shimming using pieces of permanent magnets. The residual local inhomogeneity was then compensated for by shimming using the SC shim coil.
The effectiveness of the shimming was measured by imaging the left hands of human subjects and evaluating the image quality. The magnetic resonance images for the child subject clearly visualized anatomical structures of all bones necessary for skeletal age assessment, demonstrating the usefulness of combined shimming. In this project, we investigate the effects of magnetic activity on the Lithium Depletion Boundary LDB to recalibrate the measured ages for star clusters, using the open cluster Blanco 1 as a pilot study.
Although observations have shown that magnetic activity directly affects stellar radius and temperature, most PMS models do not include the effects of magnetic activity on stellar properties. Since the lithium abundance of a star depends on its radius and temperature, we expect that LDB ages are affected by magnetic activity. Gold and gold-iron oxide magnetic glyconanoparticles: synthesis, characterization and magnetic properties.
The preparation, characterization and the magnetic properties of gold and gold-iron oxide glyconanoparticles GNPs are described. Glyconanoparticles were prepared in a single step procedure in the presence of aqueous solution of thiol functionalized neoglycoconjugates and either gold salts or both gold and iron salts. Neoglycoconjugates of lactose and maltose disaccharides with different linkers were used. Iron-free gold or gold-iron oxide GNPs with controlled gold-iron ratios were obtained.
The average core-size diameters are in the range of 1. Inductive plasma-atomic emission spectrometry ICP and elemental analysis gave the average number of neoglycoconjugates per cluster. The most remarkable results was the observation of a permanent magnetism up to room temperature in the iron-free gold GNPs, that was not present in the corresponding gold-iron oxide GNPs.
The magnetic anomalies of the high arctic are dominated by a large domain x km; the High Arctic Magnetic High, HAMH consisting of numerous high-amplitude magnetic high ridges with a complex set of orientations and by other smaller, but still fundamentally highly magnetic , domains. The magnetic potential anomaly field also known as pseudogravity of the HAMH shows a single large intensity high and underscores the crustal-scale thickness of this geophysical feature which also forms a prominent anomaly on satellite magnetic maps.
The seafloor morphology of this region includes the complex linear trends of the Alpha and Mendeleev ridges, but the magnetic expression of this domain extends beyond the complex bathymetry to include areas where Canada Basin sediments have covered the complex basement topography.
The calculated magnetic effect of the bathymetric ridges matches some of the observed magnetic anomalies, but not others. We have analyzed and modeled the distinctive HAMH and other smaller magnetic high domains to generate estimates of their volume and to characterize the directionality of their component features.
Complimentary processing and modeling of high arctic gravity anomalies allows characterization of the density component of these geophysical features. Spatially, the HAMH encompasses the Alpha and Mendeleev "ridges," that are considered to represent a major mafic igneous province. On this map the province is described as "alkali basalt with ages between and 90 Ma". New seismic and bathymetric data, collected as part of on-going research efforts for definition of extended continental shelf, are revealing new details about the Alpha ridge.
One interesting development is the possible identification of a supervolcano that may represent a major locus of igneous activity. Characterizing cognitive aging in humans with links to animal models. Alexander, Gene E. With the population of older adults expected to grow rapidly over the next two decades, it has become increasingly important to advance research efforts to elucidate the mechanisms associated with cognitive aging , with the ultimate goal of developing effective interventions and prevention therapies.
Although there has been a vast research literature on the use of cognitive tests to evaluate the effects of aging and age -related neurodegenerative disease, the need for a set of standardized measures to characterize the cognitive profiles specific to healthy aging has been widely recognized. Here we present a review of selected methods and approaches that have been applied in human research studies to evaluate the effects of aging on cognition, including executive function, memory, processing speed, language, and visuospatial function.
Further, we consider those measures that have clear conceptual and methodological links to tasks currently in use for non-human animal studies of aging , as well as those that have the potential for translation to animal aging research. Having a complementary set of measures to assess the cognitive profiles of healthy aging across species provides a unique opportunity to enhance research efforts for cross-sectional, longitudinal, and intervention studies of cognitive aging.
Taking a cross-species, translational approach will help to advance cognitive aging research, leading to a greater understanding of associated neurobiological mechanisms with the potential for developing effective interventions and prevention therapies for age -related cognitive decline. Characterization of a turbomolecular-pumped magnetic sector mass spectrometer. A Perkin Elmer MGA, turbomolecular-pumped, magnetic sector, multiple gas analyzer mass spectrometer with modified inlet for fast response was characterized for the analysis of hydrogen, helium, oxygen and argon in nitrogen and helium background gases.
Linearity, precision, drift, detection limits and accuracy among other analytical parameters for each of the background gas were studied to evaluate the performance of the instrument. The result demonstrates that H2S2 mass spectrometer is a stable instrument and can be utilized for the quantitative analytical determination of hydrogen, helium, oxygen and argon in nitrogen and helium background gases.
Oleic acid coated magnetic nano-particles: Synthesis and characterizations. The particle size obtained from width of Bragg peak is about Characterization of hearing loss in aged type II diabetics. Presbycusis — age -related hearing loss — is the number one communicative disorder and a significant chronic medical condition of the aged.
Little is known about how type II diabetes, another prevalent age -related medical condition, and presbycusis interact. The present investigation aimed to comprehensively characterize the nature of hearing impairment in aged type II diabetics. Hearing tests measuring both peripheral cochlea and central brainstem and cortex auditory processing were utilized. The majority of differences between the hearing abilities of the aged diabetics and their age -matched controls were found in measures of inner ear function.
For example, large differences were found in pure-tone audiograms, wideband noise and speech reception thresholds, and otoacoustic emissions. The greatest deficits tended to be at low frequencies. In addition, there was a strong tendency for diabetes to affect the right ear more than the left. One possible interpretation is that as one develops presbycusis, the right ear advantage is lost, and this decline is accelerated by diabetes.
In contrast, auditory processing tests that measure both peripheral and central processing showed fewer declines between the elderly diabetics and the control group. Consequences of elevated blood sugar levels as possible underlying physiological mechanisms for the hearing loss are discussed.
Dynamics of aging magnetic clouds. The dynamics of radially expanding magnetic clouds is rigorously analyzed within the framework of ideal MHD. The cloud is modelled as a cylindrically symmetric magnetic flux rope. In the force balance we include the gas pressure gradient and the Lorentz force.
Interaction with the ambient solar wind due to expansion of the magnetic cloud is represented by a drag force proportional to the bulk velocity. We consider the self-similar expansion of a polytrope, and reduce the problem to an ordinary nonlinear differential equation for the evolution function. Analyzing the asymptotic behavior of the evolution function, we formulate theoretical expectations for the long-term behavior of cloud parameters.
We focus on the temporal evolution of 1 the magnetic field strength; 2 the twist of the field lines; 3 the asymmetry of the total field profile; and 4 the bulk flow speed. We present data from two magnetic clouds observed at 1 AU and 2 AU, respectively, and find good agreement with theoretical expectations.
For a peak magnetic field strength at 1 AU of 25 nT and a polytropic index of 0. Taking larger magnetic fields and bigger polytropic indices this distance can double. A hybrid superconductor magnet bearing uses magnetic forces between permanent magnets to provide lift and the flux pinning force between permanent magnets and superconductors to stabilize against instabilities intrinsic to the magnetic force between magnets.
We have constructed a prototype kinetic energy storage system, using a hybrid superconductor magnet bearing to support a 42 lb. With five sensors on the periphery of the flywheel, we have monitored the position and attitude of the flywheel during its spin down. The results indicate low values of stiffnesses for the bearing. The implications of this and other consequences will be discussed.
Magnetic , in situ, mineral characterization of Chelyabinsk meteorite thin section. Magnetic images of Chelyabinsk meteorite's fragment F1 removed from Chebarkul lake thin section have been unraveled by a magnetic scanning system from Youngwood Science and Engineering YSE capable of resolving magnetic anomalies down to mT range from about 0. Anomalies were produced repeatedly, each time after application of magnetic field pulse of varying amplitude and constant, normal or reversed, direction.
This process resulted in both magnetizing and demagnetizing of the meteorite thin section, while keeping the magnetization vector in the plane of the thin section. Analysis of the magnetic data allows determination of coercivity of remanence Bcr for the magnetic sources in situ. Value of Bcr is critical for calculating magnetic forces applicable during missions to asteroids where gravity is compromised.
Bcr was estimated by two methods. First method measured varying dipole magnetic field strength produced by each anomaly in the direction of magnetic pulses. Second method measured deflections of the dipole direction from the direction of magnetic pulses. Bcr of magnetic sources in Chelyabinsk meteorite ranges between 4 and 7 mT.
These magnetic sources enter their saturation states when applying 40 mT external magnetic field pulse. Eddy current-shielded x-space relaxometer for sensitive magnetic nanoparticle characterization. Bauer, L. The development of magnetic particle imaging MPI has created a need for optimized magnetic nanoparticles. Magnetic particle relaxometry is an excellent tool for characterizing potential tracers for MPI.
In this paper, we describe the design and construction of a high-throughput tabletop relaxometer that is able to make sensitive measurements of MPI tracers without the need for a dedicated shield room. Spindly cobalt ferrite nanocrystals: preparation, characterization and magnetic properties.
Furthermore, we found that other ferrite nanocrystals with a needle-like shape, such as zinc ferrite ZnFe 2 O 4 and nickel ferrite NiFe 2 O 4 , can be prepared by the same process. Needle-shaped CoFe 2 O 4 nanocrystals dispersed in an aqueous solution containing oleic acid exhibit excellent stability and the formed colloid does not produce any precipitations after two months, which is of prime importance if these materials are applied in magnetic fluids.
X-ray diffraction XRD measurements were used to characterize the phase and component of the co-precipitation products, and demonstrate that they are spinel ferrite with a cubic symmetry. Varying the concentration of oleic acid did not bring about any obvious influence on the size distribution and shapes of CoFe 2 O 4. Earth and Mercury are the only terrestrial planets in our solar system with present-day magnetic dipole fields generated by internal dynamo systems.
In contrast, Mars and the Moon show evidence of past dipole fields in the form of crustal magnetic anomalies; to hold measurable magnetizations , crustal materials must have been exposed to an applied field. While the physical principles of magnetic recording are consistent between terrestrial planets, the particular conditions at each planet control the mechanisms by which crustal materials may be magnetized and limit the types of minerals that can retain magnetic remanence.
As the suite of magnetic materials used for studies of remanence expands, the need for new methods follows. The integration of rock magnetic techniques with microscopy and chemical analyses enables the reconstruction of increasingly comprehensive narratives of remanence acquisition and alteration, even in materials that are challenging to study using traditional methods.
This thesis demonstrates the utility of a materials approach to rock magnetism by applying techniques designed for terrestrial use in a planetary context. We then calculate the linear susceptibility and second-order hyper-susceptibility of molecular-hydrogen chains whith different bond-length alternations, and assess the quality of nodal surfaces derived from density-functional theory or from Hartree-Fock.
Umari, A. Williamson, G. Galli, and N. As a spatially extended dissipated system, atmospheric-pressure dielectric barrier discharges DBDs could in principle possess complex nonlinear behaviors. In order to improve the stability and uniformity of atmospheric-pressure dielectric barrier discharges, studies on temporal behaviors and radial structure of discharges with strong nonlinear behaviors under different controlling parameters are much desirable.
In this paper, a two-dimensional fluid model is developed to simulate the radial discharge structure of period -doubling bifurcation, chaos, and inverse period -doubling bifurcation in an atmospheric-pressure DBD. In period -2n or chaos, not only the shape of current pulses doesn't remains exactly the same from one cycle to another, but also the radial structures , such as discharge spatial evolution process and the strongest breakdown region, are different in each neighboring discharge event.
Current-voltage characteristics of the discharge system are studied for further understanding of the radial structure. Structural , dielectric and electrical properties of Sm-modified Pb The a. On structural , optical and dielectric properties of zinc aluminate C placed on a heating man Coherent structures induced by dielectric barrier discharge plasma actuator. The structures of a flow field induced by a plasma actuator were investigated experimentally in quiescent air using high-speed Particle Image Velocimetry PIV technology.
The motivation behind was to figure out the flow control mechanism of the plasma technique. The high speed PIV measurement of the induced airflow suggested that the plasma actuator could excite the flow instabilities which lead to production of the roll-up vortex. Analysis of transient results indicated that the roll-up vortices had the process of formation, movement, merging and breakdown.
This could promote the entrainment effect of plasma actuator between the outside airflow and boundary layer flow, which is very important for flow control applications. Bright compact photon sources, which utilize electron beam interaction with periodic structures , may benefit a broad range of medical, industrial and scientific applications. Target-distributed accelerators TDA , in which an additional electric field compensates for lost beam energy in internal targets, have been shown to provide the necessary means to drive a high flux subcritical reactor HFSR for nuclear waste transmutation.
The TDA may also be suitable for positron and nuclear isomer production, X-ray lithography and monochromatic computer tomography. One of the early assumptions of the theory of dielectric wake-field acceleration was that, in electrodynamics, the vector potential was proportional to the scalar potential. The analysis takes into consideration a wide range of TDA design aspects including the wave model of observed phenomena, a layered compound separated by a Van der Waals gap and a compact energy source based on fission electric cells FEC with a multistage collector.
The FEC is a high-voltage power source that directly converts the kinetic energy of the fission fragments into electrical potential of about 2MV. Structure and Properties of Epitaxial Dielectrics on gallium nitride. GaN is recognized as a possible material for metal oxide semiconductor field effect transistors MOSFETs used in high temperature, high power and high speed electronic applications.
However, high gate leakage and low device breakdown voltages limit their use in these applications. La2O3 and Sc2O 3 are rare earth oxides with a large Eg 6. Epitaxial growth of oxides is a possible approach to reducing leakage current and Fermi level pinning related to a high density of interface states for dielectrics on compound semiconductors. GaN surface treatments were examined as a means for additional interface passivation and influencing subsequent oxide formation.
Potassium persulfate K2 SO4 2 and potassium hydroxide KOH were explored as a way to achieve improved passivation and desired surface termination for GaN films deposited on sapphire substrates by metal organic chemical vapor deposition MOCVD. X-ray photoelectron spectroscopy XPS showed that KOH left a nitrogen-rich interface, while K2 SO 4 2 left a gallium-rich interface, which provides a way to control surface oxide formation.
K2 SO4 2 exhibited a shift in the O1s peak indicating the formation of a gallium-rich GaOx at the surface with decreased carbon contaminants. GaO x acts as a passivating layer prior to dielectric deposition, which resulted in an order of magnitude reduction in leakage current, a reduced hysteresis window, and an overall improvement in device performance. Furthermore, K2 SO4 2 resulted in an additional 0. Structural , optical and dielectric properties of graphene oxide.
The Modified Hummers method has been used to synthesize Graphene oxide nanoparticles. Microstructural analyses were carried out by X-ray diffraction and Fourier transform infrared spectroscopy. Optical properties were studied by UV-visible spectroscopy in the range of nm.
The energy band gap was calculated with the help of Tauc relation. The frequency dependence of dielectric constant and dielectric loss were studied over a range of the frequency 75Hz to 5MHz at room temperature. The dispersion in dielectric constant can be explained with the help of Maxwell-Wagner model in studied nanoparticles. Confinement of light in periodic structures with negative phase velocity. We discuss unusual features of wave propagation in periodic arrays of slabs made of transparent left-handed metamaterials with simultaneously negative dielectric permittivity and magnetic permeability, and demonstrate the possibility of light confinement due to the appearance of complete photonic band-gaps in such one-dimensional structures.
With an appropriate choice of the parameters, we show that it is possible to realize an absolute or omnidirectional band gap for either transverse electric TE or transverse magnetic TM polarizations of the electromagnetic waves. A combination of two multilayer structures composed of right-handed material RHM and left-handed metamaterials LHM is proposed to realize, in a certain range of frequency, an omnidirectional reflector of light for both polarizations.
Wakefield accelerator with hybrid plasma- dielectric structure of rectangular cross-section. Increase of wakefield intensity at its excitation by a long train of relativistic electron bunches in the rectangular dielectric structure when it is filled with plasma of resonant density was experimentally observed.
The first portion of the bunches, produced by electron linac 'Almaz-2', ionizes gas at atmospheric pressure so that plasma frequency becomes equal to bunch repetition frequency and to the frequency of principal Eigen mode of the dielectric structure. Excitation enhancement at such resonant conditions is being studied taking into account the improvement of bunch train propagation in the transit channel caused by charge compensation with plasma and the electrodynamics change of the dielectric structure at filling with plasma.
The highlights of the research performed are: l The defects in adhesive joints decrease the real and imaginary dielectric permittivity in the frequency domain and induce additional peaks in the time domain spectra; Influence of refraction index strength on the light propagation in dielectrics material with periodic refraction index.
This study investigated the influence of refraction index strength on the light propagation in refraction index-varied dielectric material. This dielectric material served as photonic lattice. The behavior of light propagation influenced by variation of refraction index in photonic lattice was investigated. Modes of the guiding light were determined numerically using squared-operator iteration method. It was found that the greater the strength of refraction index, the smaller the guiding modes.
Transition from two-dimensional photonic crystals to dielectric metasurfaces in the optical diffraction with a fine structure. Rybin, Mikhail V. We study experimentally a fine structure of the optical Laue diffraction from two-dimensional periodic photonic lattices.
The periodic photonic lattices with the C4v square symmetry, orthogonal C2v symmetry, and hexagonal C6v symmetry are composed of submicron dielectric elements fabricated by the direct laser writing technique. We observe surprisingly strong optical diffraction from a finite number of elements that provides an excellent tool to determine not only the symmetry but also exact number of particles in the finite-length structure and the sample shape.
Using different samples with orthogonal C2v symmetry and varying the lattice spacing, we observe experimentally a transition between the regime of multi-order diffraction, being typical for photonic crystals to the regime where only the zero-order diffraction can be observed, being is a clear fingerprint of dielectric metasurfaces characterized by effective parameters. Full Text Available A subdomain precise integration method is developed for the dynamical responses of periodic structures comprising many identical structural cells.
The proposed method is based on the precise integration method, the subdomain scheme, and the repeatability of the periodic structures. In the proposed method, each structural cell is seen as a super element that is solved using the precise integration method, considering the repeatability of the structural cells.
The computational efforts and the memory size of the proposed method are reduced, while high computational accuracy is achieved. Therefore, the proposed method is particularly suitable to solve the dynamical responses of periodic structures.
Two numerical examples are presented to demonstrate the accuracy and efficiency of the proposed method through comparison with the Newmark and Runge-Kutta methods. Calculation of longitudinal and transverse wake-field effects in dielectric structures.
The electro-magnetic radiation of a charged particle passing through a dielectric structure has many applications to accelerator physics. Recently a new acceleration scheme, called the dielectric wake field accelerator, has been proposed. It also can be used as a pick up system for a storage ring because of its slow wave characteristics.
In order to study these effects in detail, in this paper we will calculate the wake field effects produced in a dielectric structure by a charged particle. Studies on the structural , optical and dielectric properties of samarium coordinated with salicylic acid single crystal. Samarium coordinated with salicylic acid was successfully grown as a single crystal by low temperature solution technique using mixed solvent of methanol and water in equal ratio.
Dielectric constant and dielectric loss have been measured over the frequency range Hz - 30MHz. The decrease in dielectric constant with increases in frequency is due to the transition from interfacial polarization to dipolar polarization. The small value of dielectric constant at higher frequency ensures that the crystal is good candidate for NLO devices.
Dielectric loss represents the resistive nature of the material. Polarization insensitive metamaterial absorber based on E-shaped all- dielectric structure. Full Text Available In this paper, we designed a metamaterial absorber performed in microwave frequency band.
This absorber is composed of E-shaped dielectrics which are arranged along different directions. The E-shaped all- dielectric structure is made of microwave ceramics with high permittivity and low loss. This absorber is polarization insensitive and is stable for incident angles.
It is figured out that the polarization insensitive absorption is caused by the nearly located varied resonant modes which are excited by the E-shaped all- dielectric resonators with the same size but in the different direction. The E-shaped dielectric absorber contains intensive resonant points. Our research work paves a way for designing all- dielectric absorber. Structure -property relationship in dielectric mixtures: application of the spectral density theory.
This paper presents numerical simulations performed on dielectric properties of two-dimensional binary composites. The influence of structural differences and intrinsic electrical properties of constituents on the composite's overall electrical properties is investigated.
The structural differences are resolved by fitting the dielectric data with an empirical formula and by the spectral density representation approach. At low concentrations of inclusions concentrations lower than the percolation threshold , the spectral density functions are delta-sequences, which corresponds to the predictions of the general Maxwell-Garnett MG mixture formula.
At high concentrations of inclusions close to the percolation threshold systems exhibit non-Debye-type dielectric dispersions, and the spectral density functions differ from each other and that predicted by the MG expression. The analysis of the dielectric dispersions with an empirical formula also brings out the structural differences between the considered geometries, however, the information is not qualitative.
The empirical formula can only be used to compare structures. The spectral representation method on the other hand is a concrete way of characterizing the structures of the dielectric mixtures. This can be achieved by generating dielectric data for known structures by using ab initio calculations, as presented and emphasized in this study. The numerical technique presented here is not based on any a priori assumption methods.
The thrust of Stanford's program is to conduct research on high-gradient dielectric accelerator structures driven with high repetition-rate, tabletop infrared lasers. The close collaboration between Stanford and SLAC Stanford Linear Accelerator Center is critical to the success of this project, because it provides a unique environment where prototype dielectric accelerator structures can be rapidly fabricated and tested with a relativistic electron beam.
High pressure dielectric studies on the structural and orientational glass. It was shown that in both compounds, the structural relaxation is weakly sensitive to compression. This experimental finding seems to be quite intriguing since the TTP rule was shown to work well in the van der Waals liquids, while in the strongly associating compounds, it is very often violated. We have also demonstrated that the sensitivity of the structural relaxation process to the temperature change measured by the steepness index mp drops with pressure.
Interestingly, this change is much more significant in the case of D-glucose with respect to levoglucosan, where the fragility changes only slightly with compression. Finally, kinetics of ODIC-crystal phase transition was studied at high compression. It is worth mentioning that in the recent paper, Tombari and Johari [J.
On the other hand, our isochronal measurements performed at varying thermodynamic conditions indicated unquestionably that the application of pressure favors solid ODIC -solid crystal transition in 1,6-anhydro-D-glucose. This result mimics the impact of pressure on the. Dielectric structures with bound modes for microcavity lasers.
Cavity modes of dielectric microsphcres and vertical cavity surface emitting lasers, in spite of their high Q, are never exactly bound, but have a finite width due to leakage at the borders. We propose types of microstructures that sustain three-dimensionally bound modes of the radiation field when.
Dielectric properties of supramolecular ionic structures obtained from multifunctional carboxylic acids and amines. The dielectric properties of several supramolecular ionic polymers and networks, linked by the ammonium salts of hexamethylene diamine HMDA , tris 2-aminoethyl amine TAEA , poly propylene imine PPI dendrimers and two short bis carboxymethyl ether-terminated poly ethylene glycol s Di All supramolecular ionic polymers and networks exhibit very high relative dielectric permittivities 3 0 10 2 — 10 6 at low frequencies, and signi fi cantly lower values from 1 up to 26 at high frequencies.
Additionally, the dielectric properties of supramolecular ionic Here the relative dielectric permittivities of the supramolecular ionic structures formed with the multifunctional carboxylic acids were lower than those from the supramolecular ionic structures formed with the two carboxymethyl ether-terminated poly ethylene glycol s Electromagnetic Radiation of Electrons in Periodic Structures.
Periodic magnetic structures undulators are widely used in accelerators to generate monochromatic undulator radiation UR in the range from far infrared to the hard X-ray region. Another periodic crystalline structure is used to produce quasimonochromatic polarized photon beams via the coherent bremsstrahlung mechanism CBS. Due to such characteristics as monochromaticity, polarization and adjustability, these types of radiation is of large interest for applied and basic research of accelerator-emitted radiation.
The book provides a detailed overview of the fundamental principles behind electromagnetic radiation emitted from accelerated charged particles e. UR, CBS, radiation of fast electrons in Laser flash fields as well as a unified description of relatively new radiation mechanisms which attracted great interest in recent years. This are the so-called polarization radiation excited by the Coulomb field of incident particles in periodic structures , parametric X-rays, resonant transition radiation a Multiscale periodic structure in the Io wake.
The decametric radio emissions from Jupiter are known to be influenced by the Galilean satellite Io. It is believed that the structure in these emissions is associated with the Alfven-wave wake downstream of Io. However, recent studies have shown that the structure of the wake cannot be as simple as originally thought. Here we present preliminary results from an eigenmode synthesis of the Alfven waves launched by Io, and find that several important periodicities emerge.
Observations of the decametric emissions reveal fine, medium-and large-scale structure. The simulation we present here can provide structure on each of these scales, unlike earlier models. Dielectric response of capacitor structures based on PZT annealed at different temperatures. Kamenshchikov, Mikhail V. Petersburg Russian Federation. It was found that dielectric properties of these structures depend on the synthesis temperature.
Stability of a polarized state is considered on the basis of the analysis of hysteresis loops and capacitance—voltage C—V characteristics. The contribution of the domain mechanism in the dielectric response of the capacitor structure comprising a ferroelectric is discussed. Extreme dependences of electrophysical characteristics of PZT films on their synthesis temperature were observed.
Correlation of dielectric properties with microstructure of these films is found out. Diffraction of polarized light on periodic structures. Periodic structures as photonic crystals are widely used in modern laser devices, communication technologies and for creating various beam splitters and filters. Diffraction gratings are applied for creating 3D television sets, DVD and Blu-ray drives and reflective structures Berkley mirror. It is important to simulate diffraction on such structures to design optical systems with predetermined properties based on photonic crystals and diffraction gratings.
Methods of simulating diffraction on periodic structures uses theory of Floquet-Bloch and rigorous coupled-wave analysis RCWA. Current work is dedicated to analysis of photonic band gaps and simulating diffraction on one-dimensional binary diffraction grating using RCWA. The Maxwell's equations for isotropic media and constitutive relations based on the cgs system were used as a model.
There are two main elements in the research program: 1 high-power tests of DLA structures using the magnicon output 20 MW The work during this period has focused on a study of the use of an axial magnetic field to suppress multipactor in DLA structures , with several new high power tests carried out at NRL, and on preparation of the accelerator for the electron acceleration experiments.
Structural and dielectric properties of yttrium-substituted hydroxyapatites. Kaygili, Omer, E-mail: okaygili firat. Hydroxyapatite HAp samples doped with 0, 2 and 4 at. The crystallite size, crystallinity degree and lattice parameters of the samples were changed with Y content. The volume of the unit cell was gradually decreased with the addition of Y. Undoped and Y-containing HAp samples were screened to determine their in vitro antimicrobial activities against the standard strains.
It was found that no samples have any antimicrobial effect. The relative dielectric permittivity and dielectric loss are affected by Y content. While the alternating current conductivity increases with increasing frequency, it decreases with increasing Y content.
Structural , optical, morphological and dielectric properties of cerium oxide nanoparticles. Cerium oxide CeO 2 nanoparticles were prepared by the precipitation method. The average crystallite size of cerium oxide nanoparticles was calculated from the X-ray diffraction XRD pattern and found to be 11 nm.
The FT-IR spectrum clearly indicated the strong presence of cerium oxide nanoparticles. Raman spectrum confirmed the cubic nature of the cerium oxide nanoparticles. The Scanning Electron Microscopy SEM analysis showed that the nanoparticles agglomerated forming spherical-shaped particles. The Transmission Electron Microscopic TEM analysis confirmed the prepared cerium oxide nanoparticles with the particle size being found to be 16 nm.
The optical absorption spectrum showed a blue shift by the cerium oxide nanoparticles due to the quantum confinement effect. The dielectric properties of cerium oxide nanoparticles were studied for different frequencies at different temperatures. The dielectric constant and the dielectric loss of the cerium oxide nanoparticles decreased with increase in frequency. The AC electrical conductivity study revealed that the conduction depended on both the frequency and the temperature.
Kaygili, Omer; Dorozhkin, Sergey V. Structural and optical characterization of Cr2O3 nanostructures: Evaluation of its dielectric properties. The structural , optical and dielectric properties of as-grown Cr 2 O 3 nanostructures are demonstrated in this paper. FE-SEM image illustrated the mixture of different shapes disk, particle and rod of as-grown nanostructures whereas; EDS spectrum confirmed the elemental purity of the material.
Energy band gap 3. The dielectric properties of the material were checked in the wide frequency region Hz MHz. In the low frequency region, the matrix of the dielectric behaves like source as well as sink of electrical energy within the relaxation time. Low value of dielectric loss exhibits that the materials posses good optical quality with lesser defects.
The ac conductivity of the material in the high frequency region was found according to frequency power law. The physical-mechanism and the theoretical-interpretation of dielectric -properties of Cr 2 O 3 nanostructures attest the potential candidature of the material as an efficient dielectric medium. Resonant cavity light-emitting diodes based on dielectric passive cavity structures. A novel design for high brightness planar technology light-emitting diodes LEDs and LED on-wafer arrays on absorbing substrates is proposed.
A multilayer dielectric structure containing a cavity layer and dielectric DBRs is further processed by etching into a micrometer-scale pattern. An oxide-confined aperture is further amended for current and light confinement. We study the impact of the placement of the active region into the maximum or minimum of the optical field intensity and study an impact of the active region positioning on light extraction efficiency.
We also study an etching profile composed of symmetric rings in the etched passive cavity over the light emitting area. The bottom semiconductor is an AlGaAs-AlAs multilayer DBR selectively oxidized with the conversion of the AlAs layers into AlOx to increase the stopband width preventing the light from entering the semiconductor substrate.
The approach allows to achieve very high light extraction efficiency in a narrow vertical angle keeping the reasonable thermal and current conductivity properties. Cylindrically-symmetric structures with multiple ring patterns are modeled. It is demonstrated that the extraction coefficient of light to the air can be increased from 1. Infinte Periodic Structure of Lightweight Elements.
Lightweight wooden structures have become more popular as a sustainable, environmental- friendly and cost-effective alternative to concrete, steel and masonry buildings. However, there are certain drawbacks regarding noise and vibration due to the smaller weight and stiffness of wooden buildings Furthermore, lightweight building elements are typically periodic structures that behave as filters for sound propagation within certain frequency ranges stop bands , thus only allowing transmission within the pass bands.
Hence, traditional methods based on statistical energy analysis cannot be used Instead, this paper discusses and compares the use of finite element analysis and a wave approach based on Floquet theory. The present analysis has focus on the effect of periodicity on vibration transmission within semi-infinite beam structures. Split-field FDTD method for oblique incidence study of periodic dispersive metallic structures.
The study of periodic structures illuminated by a normally incident plane wave is a simple task that can be numerically simulated by the finite-difference time-domain FDTD method. On the contrary, for off-normal incidence, a widely modified algorithm must be developed in order to bypass the frequency dependence appearing in the periodic boundary conditions.
After recently implementing this FDTD algorithm for pure dielectric materials, we here extend it to the study of metallic structures where dispersion can be described by analytical models. The accuracy of our code is demonstrated through comparisons with already-published results in the case of 1D and 3D structures. The plane Helmholtz problem of the periodical disc structures with the phase shifts conditions of the solutions along the basis lattice vectors and the Dirichlet conditions on the basic boundaries is considered.
The Green function satisfying the quasi periodical conditions on the lattice is constructed. The Helmholtz problem is reduced to the boundary integral equations for the simple layer potentials of this Green function. The methods of the discretization of the arising integral equations are proposed.
The procedures of calculation of the matrix elements are discussed. The reality of the spectral parameter of the nonlinear continuous and discretized problems is shown. Population structure of the Classic period Maya. This study examines the population structure of Classic period A. The hypothesis that isolation by distance characterized Classic period Maya population structure is tested using Relethford and Blangero's Hum Biol 62 approach to R matrix analysis for quantitative traits.
These results provide important biological data for understanding ancient Maya population history, particularly the effects of the competing Tikal and Calakmul hegemonies on patterns of lowland Maya site interaction. An overall F ST of 0. Principal coordinates plots derived from the R matrix analysis show little regional patterning in the data, though the geographic outliers of Kaminaljuyu and a pooled Pacific Coast sample did not cluster with the lowland Maya sites.
Mantel tests comparing the biological distance matrix to a geographic distance matrix found no association between genetic and geographic distance. In the Relethford-Blangero analysis, most sites possess negative or near-zero residuals, indicating minimal extraregional gene flow. The exceptions were Barton Ramie, Kaminaljuyu, and Seibal.
A scaled R matrix analysis clarifies that genetic drift is a consideration for understanding Classic Maya population structure. All results indicate that isolation by distance does not describe Classic period Maya population structure. The transition mechanism from a symmetric single period discharge to a period -doubling discharge in atmospheric helium dielectric -barrier discharge. Period -doubling and chaos phenomenon have been frequently observed in atmospheric-pressure dielectric -barrier discharges.
However, how a normal single period discharge bifurcates into period -doubling state is still unclear. In this paper, by changing the driving frequency, we study numerically the transition mechanisms from a normal single period discharge to a period -doubling state using a one-dimensional self-consistent fluid model.
The results show that before a discharge bifurcates into a period -doubling state, it first deviates from its normal operation and transforms into an asymmetric single period discharge mode. Then the weaker discharge in this asymmetric discharge will be enhanced gradually with increasing of the frequency until it makes the subsequent discharge weaken and results in the discharge entering a period -doubling state.
In the whole transition process, the spatial distribution of the charged particle density and the electric field plays a definitive role. The conclusions are further confirmed by changing the gap width and the amplitude of the applied voltage. Structural , dielectric and ferroelectric characterization of PZT thin films. Films of 0. Electrical and ferroelectric characterization were carried out in these films. The measured value of the dielectric constant for films was Remanent polarization for films presented value around 5.
Periodic orbits and TDHF phase space structure. The collective motion of atomic nuclei is closely coupled with the motion of nucleons, therefore, it is nonlinear, and the contents of the motion change largely with the increase of its amplitude. As the framework which describes the collective motion accompanied by the change of internal structure , time-dependent Hurtley Fock TDHF method is suitable.
At present, the authors try to make the method for studying the large region structure in quantum system by utilizing the features of the TDHF phase space. The studies made so far are briefed. In this report, the correspondence of the large region patterns appearing in the band structure chart of three-level model with the periodic orbit group in the TDHF phase space is described.
The Husimi function is made, and it possesses the information on the form of respective corresponding intrinsic state. The method of making the band structure chart is explained. There are three kinds of the tendency in the intrinsic state group. The E-T charts are made for the band structure charts to quantitatively express the large region tendency.
It became to be known that the large region properties of the quantum intrinsic state group of three-level model can be forecast by examining the properties of the periodic orbit group in the TDHF phase space. Polaritons in periodic and quasiperiodic structures. In recent years there have been exciting developments in techniques for producing multilayered structures of different materials, often with thicknesses as small as only a few atomic layers. These artificial structures , known as superlattices, can either be grown with the layers stacked in an alternating fashion the periodic case or according to some other well-defined mathematical rule the quasiperiodic case.
This book describes research on the excitations or wave-like behavior of these materials, with emphasis on how the material properties are coupled to photons the quanta of the l. Effect of crystal structure on strontium titanate thin films and their dielectric properties. We characterized such film structures as lattice parameters, out-of-plane grain size, in-plane grain size, thickness, roughness, strains, and defects using ellipsometry, atomic force microscopy, and a high-resolution X-ray diffractometry.
In plane grain size and percentage of defects were found to play a major role on the dielectric performance of the films. Electromagnetic radiation of electrons in periodic structures. This are the so-called polarization radiation excited by the Coulomb field of incident particles in periodic structures , parametric X-rays, resonant transition radiation and the Smith-Purcell effect.
Characteristics of such radiation sources and perspectives of their usage are discussed. The recent experimental results as well as their interpretation are presented. Plasmon mediated inverse Faraday effect in a graphene- dielectric -metal structure. The constants of propagation and attenuation of the surface plasmon-polariton modes are calculated.
The possibility to control the distribution of the magnetic field by chemical potential of graphene is shown. The concept of strain-driven control of the IFE in the structure has been proposed and investigated. Modelling of space-charge accumulation process in dielectrics of MDS structures under irradiation. Diffusion-drift model which takes account of trap heterogeneous distribution within dielectric volume and channeling of carriers captured at traps represents basis for calculations.
Main physical processes affecting RISC accumulation are picked out and character of capture filling in dielectric volume under stress in MOS structure shutter during irradiation on the basis of comparison of experimental results for different thickness oxides with calculation data are predicted. We revisit the standard Nicolson Ross Weir method of effective permittivity and permeability restoration of photonic structures for the case of subwavelength metal- dielectric multilayers.
We show that the direct application of the standard method yields a false zero-epsilon point and an associated Structural and dielectric properties of Gd doped bismuth ferrite-lead titanate. Structural characterization was performed by X-ray diffraction and studied that the materials show tetragonal structure at room temperature for all concentration of Gd. Structural , morphological and dielectric studies of zirconium substituted CoFe2O4 nanoparticles.
Full Text Available In this work, the influence of zirconium substitution in cubic spinel nanocrystalline CoFe2O4 on the structural , morphological and dielectric properties are reported. The structural and morphological investigations using powder X-ray diffraction and high resolution scanning electron microscope HRSEM analysis are reported.
Scherrer plot, Williamson—Hall analysis and Size-strain plot method were used to calculate the crystallite size and lattice strain of the samples. High purity chemical composition of the sample was confirmed by energy dispersive X-ray analysis. The temperature-dependent dielectric properties of zirconium substituted cobalt ferrite nanoparticles were also carried out.
The dielectric constant and dielectric loss values of the sample decreased with increasing in the frequency of the applied signal. Structural , magnetic and dielectric investigations in antimony doped nano-phased nickel-zinc ferrites. Lakshmi, Ch. Nanocrystalline Ni—Zn—Sb ferrites synthesized by hydrothermal method are reported. Phase identification, lattice parameter and crystallite size studies are carried out using by X-ray diffraction XRD.
Addition of dopant resulted for decrease in lattice parameter. Crystallite size gets reduced from 62 nm to 38 nm with doping of Antimony. Crystallite size and porosity exhibit similar trends with doping. Increase of porosity is attributed to the grain size. Doping with Antimony results for decrease in saturation magnetization and increase in coercivity. Reversed trend of coercivity with crystallite size are observed. Variation of dielectric constant infers hopping type of conductivity mechanism.
Higher saturation magnetization and enhanced dielectric response directs for a possible utility as microwave oscillators and switches. Spatially variant periodic structures in electromagnetics. Spatial transforms are a popular technique for designing periodic structures that are macroscopically inhomogeneous. The structures are often required to be anisotropic, provide a magnetic response, and to have extreme values for the constitutive parameters in Maxwell's equations.
Metamaterials and photonic crystals are capable of providing these, although sometimes only approximately. The problem still remains about how to generate the geometry of the final lattice when it is functionally graded, or spatially varied. This paper describes a simple numerical technique to spatially vary any periodic structure while minimizing deformations to the unit cells that would weaken or destroy the electromagnetic properties. New developments in this algorithm are disclosed that increase efficiency, improve the quality of the lattices and provide the ability to design aplanatic metasurfaces.
The ability to spatially vary a lattice in this manner enables new design paradigms that are not possible using spatial transforms, three of which are discussed here. First, spatially variant self-collimating photonic crystals are shown to flow unguided waves around very tight bends using ordinary materials with low refractive index. Second, multi-mode waveguides in spatially variant band gap materials are shown to guide waves around bends without mixing power between the modes. Third, spatially variant anisotropic materials are shown to sculpt the near-field around electric components.
This can be used to improve electromagnetic compatibility between components in close proximity. Nonlinearities in Periodic Structures and Metamaterials. Optical information processing of the future is associated with a new generation of compact nanoscale optical devices operating entirely with light. Moreover, adaptive features such as self-guiding, reconfiguration and switching become more and more important. Nonlinear devices offer an enormous potential for these applications.
Consequently, innovative concepts for all-optical communication and information technologies based on nonlinear effects in photonic-crystal physics and nanoscale devices as metamaterials are of high interest. This book focuses on nonlinear optical phenomena in periodic media, such as photonic crystals, optically-induced, adaptive lattices, atomic lattices or metamaterials.
The main purpose is to describe and overview new physical phenomena that result from the interplay between nonlinearities and structural periodicities and is a guide to actual and future developments for the expert reader in optical information processing, as well as in the physics of cold atoms in optical lattices.
Full Text Available In this research, the causal relationship between the dielectric properties and the structural characteristics of 0. Dielectric properties and microstructure of BaTio3 ceramics were significantly influenced by the addition of a small amount of Ta2O5. Dielectric properties were investigated by measuring the dielectric constant k as a function of temperature and frequency. It was observed that the grain size decreased markedly above a doping concentration of 0. Although fine grain size down to - nm was attained, grain sizes in the range of The fine-grain quality and high density of the Ta2O5 doped BaTiO3 ceramic resulted in tenfold increase of dielectric constant.
Experiments divulged that incorporation of a proper content of Ta2O5 in BaTiO3 could control the grain growth, shift the Curie temperature and hence significantly improve the dielectric property of the BaTiO3 ceramics. Although fine grain size down to nm was attained, grain sizes in the range of Influence of Zn doping on structural , optical and dielectric properties of LaFeO3. These samples are synthesized using conventional solid state reaction route.
X-ray diffraction patterns with Rietveld analysis confirm the single phase nature of samples. Further, the sample formation has been confirmed by FTIR spectroscopy. All the samples are formed in orthorhombic crystal symmetry with Pbnm space group. Rietveld refinement technique is used to determine lattice parameters, bond lengths and unit cell volume. Williamson-Hall analysis has been performed to calculate the crystallite size and lattice strain. Zn doping leads to the expansion of volume due to the tensile strain.
Zinc doping in LaFeO3 leads to decrease in optical bandgap. Dielectric constant as a function of frequency is measured in the frequency range of 75 kHz—5 MHz. Cole-Cole analysis has been done that confirms the dielectric material does not follow the ideal Debye theory but shows distribution of relaxation times. Investigations of structural , dielectric and optical properties on silicon ion irradiated glycine monophosphate single crystals.
Kanagasekaran, T. The 50 MeV silicon ion irradiation induced modifications on structural , optical and dielectric properties of solution grown glycine monophosphate GMP crystals were studied. The high-resolution X-ray diffraction study shows the unaltered value of integrated intensity on irradiation. The dielectric constant as a function of frequency and temperature was studied.
UV-visible studies reveal the decrease in bandgap values on irradiation and presence of F-centers. The fluorescence spectrum shows the existence of some energy levels, which remains unaffected after irradiation. The scanning electron micrographs reveal the defects formed on irradiation. Effect of energy emission from evanescent electromagnetic wave at scattering by a dielectric structure. Gulyaev, Yu. E-mail: yu. We present an optical theorem for evanescent near field electromagnetic wave scattering by a dielectric structure.
The derivation is based on the formalism of angular spectrum wave amplitudes. The optical theorem shows that an energy flux at scattering is emitted in the direction of incident evanescent wave decay. Photon-pair generation in nonlinear metal- dielectric one-dimensional photonic structures. A general centroid determination methodology, with application to multilayer dielectric structures and thermally stimulated current measurements.
A general methodology is developed to experimentally characterize the spatial distribution of occupied traps in dielectric films on a semiconductor. The effects of parasitics such as leakage, charge transport through more than one interface, and interface trap charge are quantitatively addressed. Charge transport with contributions from multiple charge species is rigorously treated. The methodology is independent of the charge transport mechanism s , and is directly applicable to multilayer dielectric structures.
The centroid capacitance, rather than the centroid itself, is introduced as the fundamental quantity that permits the generic analysis of multilayer structures. The experimental methodology is illustrated with an application using thermally stimulated current TSC measurements.
The centroid of changes via thermal emission in the amount of trapped charge was determined for two different samples of a triple-layer dielectric structure. A direct consequence of the TSC analyses is the rigorous proof that changes in interface trap charge can contribute, though typically not significantly, to thermally stimulated current.
Dielectric relaxation spectra of liquid crystals in relation to molecular structure. The dielectric spectra obtained for some members of two homologous series, i. It is additionally assumed that the molecular reorientations take place about the principal axes of the inertia tensor. The distribution of correlation times, which is strongly temperature dependent in the vicinity of the clearing point, is interpreted as being caused by fluctuations of the principal axes frame which are due to conformation changes inside the end chains.
The Bauer equation is used to describe both principal molecular reorientations, i. The energies and entropies of activation have been computed for both principal reorientations. The differences between the high frequency limit of the dielectric permittivity and the refractive index squared of liquid crystals are explained in terms of two librational motions of the molecules observed by other experimental techniques, viz. It has been shown qualitatively that intramolecular libratory motions greatly effect the high frequency dielectric spectrum.
Finally, molecular motions in liquid crystals are divided into two types: coherent and incoherent. Periodic cellular structures Venugopal, E-mail: paduruvenugopalreddy gmail. Post, Hyderabad, India. With a view to understand the influence of doping Bismuth ferrite with Yttrium on structural , magnetic and dielectric behavior, a series of samples were prepared by the solid state reaction technique. The dielectric constant is also found to exhibit two transitions and efforts were made to explain the observed behavior.
Influence of the local structure in phase-change materials on their dielectric permittivity. Ge-Sb-Te alloys, which belong to the phase-change materials, are promising materials for data storage and display and data visualization applications due to their unique properties.
This includes a remarkable difference of their electrical and optical properties in the amorphous and crystalline state. Pronounced change of optical properties for Ge-Sb-Te alloys is linked to the different bonding types and different atomic arrangements in amorphous and crystalline states. The dielectric function of phase-change materials has been investigated in the far infrared FIR range. Phonons have been detected by FTIR spectroscopy.
Difference of the dispersion of the dielectric permittivity of amorphous and crystalline samples is caused by different structures in different states which contribute to the dielectric permittivity. Molecular structures at the surface and buried interface of an amorphous ultralow-k pSiCOH dielectric film were quantitatively characterized before and after reactive ion etching RIE and subsequent dielectric repair using sum frequency generation SFG vibrational spectroscopy and Auger electron spectroscopy.
Beyond characterizing low-k materials, the developed methodology is general and can be used to distinguish and characterize different molecular structures and elemental compositions at the surface, in the bulk, and at the buried interface of many different polymer or organic thin films. Laser-powered dielectric-structures for the production of high-brightness electron and x-ray beams.
Laser powered accelerators have been under intensive study for the past decade due to their promise of high gradients and leveraging of rapid technological progress in photonics. Of the various acceleration schemes under examination, those based on dielectric structures may enable the production of relativistic electron beams in breadbox sized systems. When combined with undulators having optical-wavelength periods , these systems could produce high brilliance x-rays which find application in, for instance, medical and industrial imaging.
These beams also may open the way for table-top atto-second sciences. Development and testing of these dielectric structures faces a number of challenges including complex beam dynamics, new demands on lasers and optical coupling, beam injection schemes, and fabrication. A structure similar to the MAP has also been designed which produces periodic deflections and acts as an undulator for radiation production, and the prospects for this device will be considered. The lessons learned from the multi-year effort to realize these devices will be presented.
Challenges remain with acceleration of sub-relativistic beams, focusing, beam phase stability and extension of these devices to higher beam energies. Our progress in addressing these hurdles will be summarized. Finally, the demands on laser technology and optical coupling will be detailed. Computer simulation of the current-voltage characteristics of such structures has shown that the built-in field arises in a dielectric due to polarization of the trapped charge by localized centers.
This results in current hysteresis and negative differential resistance region at the current-voltage characteristics when the bias polarity is changed. At temperature below K, the portion of negative differential resistance vanishes.
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