bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Visceral Obesity and Liver Fat on Vascular Structure and Function in Obese Subjects
Authors: Sturm Wolfgang , Sandhofer Anton , Engl Julia , Laimer Markus , Molnar Clemens , Kaser Susanne , Weiss Helmut , Tilg Herbert , Ebenbichler Christoph F. , Patsch Josef R.
Published: March 2009

Endothelial dysfunction and increased intima–media thickness (IMT) have been found in obese patients. Both regional fat distribution and liver steatosis may influence these markers of subclinical atherosclerosis. We sought to determine the interrelationships of endothelial function, carotid IMT, visceral and subcutaneous adipose tissue accumulation, and liver steatosis in severely obese subjects. In 64 severely obese patients (BMI 42.3 ± 4.3 kg/m²), we determined (i) endothelial function as flow‐mediated dilation (FMD) of the brachial artery, (ii) carotid IMT, (iii) visceral fat diameter, and (iv) degree of liver steatosis using ultrasound. FMD was associated inversely with visceral fat diameter and degree of steatosis (r = −0.577, P < 0.0001 and r = −0.523, P < 0.0001, respectively). Carotid IMT correlated with visceral fat mass (r = 0.343, P = 0.007) but not with liver steatosis. After adjustment for conventional cardiovascular risk factors, FMD was predicted independently by the visceral fat diameter, age, and sex (r2 = 0.48, P < 0.0001), but not by the degree of liver steatosis or plasma adiponectin levels. In contrast, age and sex were the only predictors of IMT (r2 = 0.33, P < 0.001). In obese patients, visceral fat diameter is a major determinant of endothelial dysfunction, independent of traditional risk factors or the degree of liver steatosis and plasma adiponectin. Measurement of visceral fat diameter by ultrasound is a novel and simple method to identify subjects with an increased risk for atherosclerosis within an obese population.
Food Intake‐independent Effects of CB1 Antagonism on Glucose and Lipid Metabolism
Authors: Cota Daniela , Sandoval Darleen A. , Olivieri Massimiliano , Prodi Elena , D'Alessio David A. , Woods Stephen C. , Seeley Randy J. , Obici Silvana
Published: March 2009

Overactivity of the endocannabinoid system (ECS) has been linked to abdominal obesity and other risk factors for cardiovascular disease and type 2 diabetes. Conversely, administration of cannabinoid receptor type 1 (CB1) antagonists reduces adiposity in obese animals and humans. This effect is only in part secondary to the anorectic action of CB1 agonists. In order to assess the actions of CB1 antagonism on glucose homeostasis, diet‐induced obese (DIO) rats received the CB1 antagonist rimonabant (10 mg/kg, intraperitoneally (IP)) or its vehicle for 4 weeks, or were pair‐fed to the rimonabant‐treated group for the same length of time. Rimonabant treatment transiently reduced food intake, while inducing body weight loss throughout the study. Rats receiving rimonabant had significantly less body fat and circulating leptin compared to both vehicle and pair‐fed groups. Rimonabant, but not pair‐feeding, also significantly decreased circulating nonesterified fatty acid (NEFA) and triacylglycerol (TG) levels, and reduced TG content in oxidative skeletal muscle. Although no effects were observed during a glucose tolerance test (GTT), rimonabant restored insulin sensitivity to that of chow‐fed, lean controls during an insulin tolerance test (ITT). Conversely, a single dose of rimonabant to DIO rats had no acute effect on insulin sensitivity. These findings suggest that in diet‐induced obesity, chronic CB1 antagonism causes weight loss and improves insulin sensitivity by diverting lipids from storage toward utilization. These effects are independent of the anorectic action of the drug.
Effect of B content on the magnetic properties, phase evolution, and aftereffect of nanocrystalline FeCoPtB ribbons
Authors: Chang C. W. , Chang H. W. , Hsieh C. C. , Guo Z. H. , Chang W. C.
Published: March 2009

Effect of B content on the magnetic properties, phase evolution, magnetic after effect, and the activation energy (Ea) for the melt-spun [(Fe0.7Co0.3)0.725Pt0.275]100−xBx (x=14–18) ribbons has been investigated. Sufficient amount of boron addition effectively decreases the activation energy of ordering transformation, and also refines the grain size of the studied ribbons after thermal annealing, resulting in the improvement of Hic from 3.4 kOe for x=14 to 6.2 kOe for x=18. The highest permanent magnetic properties of Br=10.1 kG, Hic=5.4 kOe, and (BH)max=15.7 MGOe can be achieved in [(Fe0.7Co0.3)0.725Pt0.275]85B15 ribbons. Meanwhile, the magnetic after effect study evidences that the activation volume is reduced with the increase in B content from V=41.33×10−19 cm3 for x=14 to V=21.71×10−19 cm3 for x=18, arisen from the lower volume fraction of magnetically soft phases and the stronger exchange-coupling effect between magnetic grains.
Compression of boundary element matrix in micromagnetic simulations
Authors: Knittel A. , Franchin M. , Bordignon G. , Fischbacher T. , Bending S. , Fangohr H.
Published: March 2009

A hybrid finite element method/boundary element method (FEM/BEM) is a standard approach for calculating the magnetostatic potential within micromagnetics [D. Fredkin and T. Koehler, IEEE Trans. Magn. 26, 415 (1990)]. This involves dealing with a dense N×N matrix Bij, with N being the number of mesh surface nodes. In order to apply the method to ferromagnetic structures with a large surface, one needs to apply matrix compression techniques on Bij. An efficient approach is to approximate Bij by hierarchical matrices (or H matrices). We have used HLIB [http://www.hlib.org], a library containing implementations of the hierarchical matrix methodology, together with the micromagnetic finite element solver NMAG in order to optimize the hybrid FEM/BEM. In this article we present a study of the efficiency of algorithms implemented in HLIB concerning the storage requirements and the matrix assembly time in micromagnetic simulations.
Structural and magnetic properties of chemically synthesized Fe doped ZnO
Authors: Kumar Shalendra , Kim Y. J. , Koo B. H. , Sharma S. K. , Vargas J. M. , Knobel M. , Gautam S. , Chae K. H. , Kim D. K. , Kim Y. K. , Lee C. G.
Published: March 2009

We report on the synthesis of Fe-doped ZnO with nominal composition of Zn0.99Fe0.01O by using a coprecipitation method. X-ray diffraction and selective area electron diffraction studies reveal a single phase wurtzite crystal structure without any secondary phase. Field emission transmission electron microscopy measurements infer that Zn0.99Fe0.01O have nanorod-type microstructures. Magnetic hysteresis measurement performed at different temperatures show that Zn0.99Fe0.01O exhibits a weak ferromagnetic behavior at room temperature. A detailed investigation of the electronic and local structure using O K-, Fe L3,2 near edge x-ray absorption fine structure suggests that Fe is substituting Zn in ZnO matrix and is in Fe3+ state.
Small, highly oriented Ru grains in intermediate layer realized through suppressing relaxation of low-angle grain boundaries for perpendicular recording media
Authors: Itagaki Norikazu , Saito Shin , Takahashi Migaku
Published: March 2009

Through analyzing the growth mechanism of the Ru layer in a nonmagnetic intermediate layer (NMIL) for perpendicular magnetic recording media, a concept for the NMIL is proposed in order to realize a recording layer of small, highly c-plane oriented grains with no intergranular exchange coupling. It was found that (1) fast Fourier transform analysis of plan-view transmission electron microscopy lattice images of Ru layers revealed that hexagonal close packed Ru grains in a c-plane oriented film readily coalesce with each other due to the disappearance of low-angle tilt boundaries. (2) A promising candidate for a NMIL consists of three individual epitaxially grown functional layers: a large-grain seed layer with a highly oriented sheet texture, a first interlayer of small grains, and a second interlayer of nonmagnetic grains isolated by a segregated oxide. (3) The Ru–SiO2/Ru/Mg NMIL based on the proposed concept exhibited small (diameter: 4.8 nm) Ru grains while retaining a narrow orientation distribution of 4.1°.
Study of dielectric breakdown distributions in magnetic tunneling junction with MgO barrier
Authors: Chen Q. , Min T. , Torng T. , Horng C. , Tang D. , Wang P.
Published: March 2009

The breakdown distribution of a magnetic tunnel junction (MTJ) with an ultrathin (∼1.2 nm) MgO barrier was studied, and two distinct distributions were identified. The breakdown distribution with high value demonstrates a wide peak-to-peak separation (∼13.4σ) to the critical spin torque induced switching voltage. However, the peak-to-peak separation is only ∼8.4σ for the devices showing low breakdown value. Both abrupt and gradual breakdown events were observed in two distributions. The dependence of the percentage of low breakdown devices as a function of bias polarity, test and stress conditions, MTJ film properties, and process conditions was investigated. The low breakdown percentage can be significantly reduced by increasing the RA value and MTJ process optimization.
Reorientation of exchange anisotropy in epitaxial (002) IrMn/CoFe system
Authors: Huang Hsin-Hung , Yang Chih-Yen , Lai Chih-Huang
Published: March 2009

We investigated the reorientation of exchange anisotropy in the epitaxial (002) IrMn/CoFe bilayers. Transitions of exchange-bias field from a negative field to a positive field with increasing time scale were observed at room temperature. The negatively magnetized state combining with the strong magnetocrystalline anisotropy of CoFe may raise the probability that the interfacial spins of thin IrMn layers were thermally relaxed to the direction of CoFe magnetization; therefore, after a period of time, the exchange-bias direction was reversed. This process can be further enhanced when samples were placed under the setting field. The double-shifted magnetization curve observed in this system was used as a good indicator for the relaxation of interfacial spins of IrMn.
Capillary turbulence on the surface of normal and superfluid He4
Authors: Abdurakhimov L. V. , Brazhnikov M. Yu. , Levchenko A. A.
Published: March 2009

The capillary turbulence on the surface of liquid helium with excitation of surface waves by a harmonic force at low frequency ωp is investigated. It is shown for the first time that at the transition of helium out of the superfluid into the normal state the high-frequency edge ωb of the inertial interval shifts in the direction of low frequencies. The magnitude of the shift is described well on the basis of the theory of weak wave turbulence. In the superfluid state the relative width ωb∕ωp of the inertial interval, where a developed turbulent cascade is established, can reach two decades.
Spectrum of Landau levels of a double quantum well in an inclined magnetic field
Authors: Arapov Yu. G. , Neverov V. N. , Harus G. I. , Shelushinina N. G. , Yakunin M. Ya.
Published: March 2009

A semi-classical calculation of the spectrum of Landau levels in an inclined magnetic field is performed for a double quantum well taking account of the energy dependences of the cyclotron effective masses. A comparison is made with a quantum-mechanical calculation in weak perpendicular magnetic fields (N. Kumada et al., Phys. Rev. B 77, 155324 (2008)). It is found that both computational methods are in good agreement with one another.
FePt-C nanogranular films for perpendicular magnetic recording
Authors: Perumal A. , Takahashi Y. K. , Hono K.
Published: March 2009

We report the study of L10 ordered FePt-C nanogranular perpendicular anisotropy films and a media consisting of an 8 nm thick FePt-C hard magnetic layer covered with a 2 nm thick soft magnetic layer (CoFe and FePt-C). All the films were fabricated on oxidized Si substrates with a (100) textured polycrystalline MgO intermediate layer of 10 nm in thickness. Cosputtering of Fe, Pt, and C on the MgO layer results the formation of L10 ordered FePt nanogranular films with a strong c-axis texture and the average FePt particle size of about 5 nm with a narrow particle size distribution of 1.4 nm in standard deviation. Perpendicular coercivity is controllable between 7 and 12 kOe. The coercivity and the saturation field of the FePt-C granular films can be reduced by 55% and 38%, respectively, with the capping of thin soft magnetic layer. This study demonstrates that the FePt-C system accomplishes suitable nanogranular structures and magnetic properties for ultrahigh-density perpendicular recording media.
Effect of rotor eccentricity on electric parameters in a PM brushless motor with parallel winding connections
Authors: Chen H. S. , Tsai M. C.
Published: March 2009

In this paper, the parallel winding of a 20-pole, 18-slot permanent magnet (PM) brushless motor with common and uncommon neutral points is used to investigate static rotor eccentricity effects. Static rotor eccentricity will cause an imbalance of the back-EMF in each parallel winding and may result in high torque ripple. However, as the common neutral point is applied, it can be observed that the back-EMF becomes balanced and may reduce torque ripple. Moreover, the winding current and inductance in the eccentric motor with a common neutral point are also discussed. This paper provides motor designers with analyses of the relationship between static rotor eccentricity and electric motor parameters, such as back-EMF, winding current, and incremental inductances.
Validation of the microelectromechanical system flux concentrator concept for minimizing the effect of 1/f noise
Authors: Edelstein A. S. , Burnette J. E. , Fischer G. A. , Olver K. , Egelhoff Wm. , Nowak E. , Cheng Shu-Fan
Published: March 2009

With the microelectromechanical system (MEMS) flux concentrator, we have been able to increase the operating frequency of small magnetic sensors above the region where 1/f noise dominates. The device accomplished this by modulating the field via the oscillatory motion of flux concentrators on MEMS flaps. Electrostatic comb drives were used to drive the MEMS flaps. We have demonstrated an increase in the signal to noise ratio at 1 Hz, that the power signal correctly depends on V4 where V is the amplitude of the voltage energizing the comb drives, and that the signal increases dramatically with vacuum packaging.
Strong increase in critical field and current in magnet-superconductor hybrids
Authors: Ozmetin A. E. , Rathnayaka K. D. D. , Naugle D. G. , Lyuksyutov I. F.
Published: March 2009

Superconducting properties of 60 nm thick lead bismuth (Pb82Bi18) films in a spatially varying magnetic field created by a hybrid structure of soft magnetic (25 μm wide iron) and nonmagnetic (250 μm wide brass) layers perpendicular to the superconducting film surface are reported. The applied homogeneous external magnetic field is redistributed in the superconducting film due to the high magnetic permeability of iron. This results in alternating parallel stripes of regions of low and high magnetic field. Thus the values of second critical field HC2 and critical current density are also much higher for current parallel to the magnetic stripes than in a control superconducting film without any magnetic field modulation. For the current perpendicular to the magnetic stripes, the superconductor behaves like an inhomogeneous resistor with regions of low and higher TC in series. Thus, the critical current IC for the perpendicular case is much less than either the control film or the case for current parallel to the magnetic sheets. These results demonstrate that it is possible to strongly increase IC and HC2 by simple redirection of magnetic flux with a soft magnetic microstructure.
Modeling of temperature profile during magnetic thermotherapy for cancer treatment
Authors: Sawyer Carolyn A. , Habib Ashfaque H. , Miller Kelsey , Collier Kelly N. , Ondeck Courtney L. , McHenry Michael E.
Published: March 2009

Magnetic nanoparticles (MNPs) used as heat sources for cancer thermotherapy have received much recent attention. While the mechanism for power dissipation in MNPs in a rf field is well understood, a challenge in moving to clinical trials is an inadequate understanding of the power dissipation in MNP-impregnated systems and the discrepancy between the predicted and observed heating rates in the same. Here we use the Rosensweig [J. Magn. Magn. Mater. 252, 370 (2002)] model for heat generation in a single MNP, considering immediate heating of the MNPs, and the double spherical-shell heat transfer equations developed by Andrä et al. [J. Magn. Magn. Mater. 194, 197 (1999)] to model the heat distribution in and around a ferrofluid sample or a tumor impregnated with MNPs. We model the heat generated at the edge of a 2.15 cm spherical sample of FeCo/(Fe,Co)3O4 agglomerates containing 95 vol % MNPs with mean radius of 9 nm, dispersed at 1.5–1.6 vol % in bisphenol F. We match the model against experimental data for a similar system produced in our laboratory and find good agreement. Finite element models, extensible to more complex systems, have also been developed and checked against the analytical model and the data.
Bifurcation of no-return transition states in many-body chemical reactions
Authors: Li Chun-Biu , Toda Mikito , Komatsuzaki Tamiki
Published: March 2009

A new method is presented to study bifurcation of no-return transition states (TSs) at potential saddles for systems of many degrees of freedom (dof). The method enables us to investigate analytically when and how the no-return TS bifurcates. Our method reveals a new aspect of bifurcation for systems of many dof, i.e., the action variables of the bath dof play a role of control parameters as long as they remain approximately conserved. As an illustrative example, we demonstrate our new method by using a three atomic exchange reaction. The bifurcation of no-return TSs gives rise to a short-lived intermediate state at the saddle, which results in the overestimation of the reaction rate. Hence, the understanding of the bifurcation of the no-return TS is crucial to capture the complexity in kinetics and dynamics of the reactions. The definability of no-return TSs in many-body chemical reactions is also addressed under the occurrence of bifurcation above the reaction threshold.
Highly stabilized and photoluminescence enhancement of ZnS:Mn2+ nanoparticles in biotin matrix
Authors: Keshari Ashish K. , Pandey Avinash C.
Published: March 2009

We synthesized the ZnS:Mn2+ nanoparticles passivated by biocompatible layer, namely, biotin by chemical precipitation route and studied their temporal evolution for size, structure, optical, and photoluminescence stability. To monitor the structural and optoelectronic properties of the nanoparticles with time, we have characterized the grown product by x-ray diffraction, small angle x-ray scattering, UV visible, and photoluminescence spectroscopic techniques at a regular interval for a period of three months. Results showed that the properties of nanophosphors capped with biotin are remaining the same even after 3 months. Energy dispersive x-ray analysis of 3 month aged sample shows long time compatibility between ZnS:Mn2+ nanoparticles and the biotin. This is also confirmed by electron microscopy that the growth of the nanoparticles is strongly arrested by the biotin. X-ray photoelectron spectra were also recorded to show the chemical state of the elements. Enhanced ratio of Zn 2p to Mn 2p peaks in the x-ray photoelectron spectra of ZnS:Mn2+ nanoparticles shows that the Mn2+ ions are incorporated within ZnS host matrix. We found that biotin capping will enhance the luminescence from ZnS:Mn2+ nanoparticles as compared to without capped particles. Absence of biotin will gradually degrade the luminescence upon aging while drastic degradation in luminescence intensity was observed after annealing. Properties show that biotin also protected the nanoparticles from any environmental attack.
Current-induced reversal in magnetic nanopillars passivated by silicon
Authors: Urazhdin Sergei , Tabor Phillip
Published: March 2009

We demonstrate that magnetic multilayer nanopillars can be efficiently protected from oxidation by coating with silicon. Both the protected and the oxidized nanopillars exhibit an increase of reversal current at cryogenic temperatures. However, the magnetic excitation onset current increases only in the oxidized samples. We show that oxidized nanopillars exhibit anomalous switching statistics at low temperature, providing a simple test for the quality of magnetic nanodevices.
Hydrogen effect on near-atmospheric nitrogen plasma assisted chemical vapor deposition of GaN film growth
Authors: Nagata T. , Haemori M. , Sakuma Y. , Chikyow T. , Anzai J. , Uehara T.
Published: March 2009

The effect of hydrogen on near-atmospheric nitrogen plasma and low temperature growth of GaN thin film was investigated. To investigate nitrogen plasma diluted with hydrogen, optical emission spectroscopy (OES) was employed. OES indicates that hydrogen enhances the generation of the nitrogen first positive system and first negative systems by providing an additional kinetic pathway. The plasma also decomposed triethylgallium and generated Ga ions even at room temperature. Using this plasma, GaN film grew on sapphire substrate epitaxially at growth temperatures of above 170 °C and crystallized at 55 °C.
Automorphisms of the Heisenberg–Weyl algebra and d-orthogonal polynomials
Authors: Vinet Luc , Zhedanov Alexei
Published: March 2009

We show that the d-orthogonal Charlier and Hermite polynomials appear naturally as matrix elements of nonunitary transformations corresponding to automorphisms of the Heisenberg–Weyl (oscillator) algebra. Basic properties (duality, recurrence, and difference equations) of the d-orthogonal Charlier polynomials can be derived directly from representations of the Heisenberg–Weyl algebra.
Effect of a tilted electric field on the magnetoexciton ground state in a semiconductor quantum dot
Authors: Wang Dali , Jin Guojun , Zhang Yongyou , Ma Yu-qiang
Published: March 2009

The variational approach within the effective mass approximation is used to investigate the effect of a tilted electric field on the energy and wave function of a magnetoexciton in a cylindrical quantum dot with a finite thickness. Calculations are performed for parameters of a typical GaAs quantum dot. We reveal the dependence of the ground-state binding energy of the magnetoexciton on the magnitude and orientation of the applied electric field. It is found that in weak magnetic fields, the electric field direction can strongly influence the magnetoexciton binding energy and thus give rise to a measurable Stark shift. However, in very strong magnetic fields, the binding energy is almost independent of electric field orientation. In addition, we discuss the competition between the tilted electric field and the magnetic field and find that the configuration of the applied electric and magnetic fields can cause either the redshift or blueshift of the exciton energy.
Preparation and structure characterization of SmCo5(0001) epitaxial thin films grown on Cu(111) underlayers
Authors: Ohtake Mitsuru , Nukaga Yuri , Kirino Fumiyoshi , Futamoto Masaaki
Published: March 2009

SmCo 5 ( 0001 ) epitaxial films were prepared on Cu(111) single-crystal underlayers formed on Al2O3(0001) substrates at 500 °C. The nucleation and growth mechanism of (0001)-oriented SmCo5 crystal on Cu(111) underlayer is investigated and a method to control the nucleation is proposed. The SmCo5 epitaxial thin film formed directly on Cu underlayer consists of two types of domains whose orientations are rotated around the film normal by 30° each other. By introducing a thin Co seed layer on the Cu underlayer, a SmCo5(0001) single-crystal thin film is successfully obtained. Nucleation of SmCo5 crystal on Cu underlayer seems controllable by varying the interaction between the Cu underlayer and the SmCo5 layer.
Enhanced magnetic properties of FeCo ribbons nanocrystallized in magnetic field
Authors: Marín P. , Hernando A.
Published: March 2009

Tailoring the structure of nanocrystalline microstructures is an important step toward controlled design of novel nanostructured materials and devices. We demonstrate how the nanocrystalline microstructure of Co-rich ribbons can be tuned by annealing under magnetic field. The intensity of the field allows controlling different degrees of order at annealing temperatures corresponding to the first stages of the nanocrystallization process. The energy barrier for nucleation is directionally affected by the applied field. The influence of grains assembling on exchange coupling between grains has been analyzed by means of magnetic domains observation and magnetic characterization by means of a hysteresis loop.
Spectroscopic measurements of high frequency plasma in supercritical carbon dioxide
Authors: Maehara T. , Kawashima A. , Iwamae A. , Mukasa S. , Takemori T. , Watanabe T. , Kurokawa K. , Toyota H. , Nomura S.
Published: March 2009

Spectroscopic measurements of high frequency (hf) plasma were performed under high pressure conditions (5 and 7 MPa) and supercritical (sc) CO2 conditions (8–20 MPa). Temperature evaluated from C2 Swan bands (d 3Πg→a 3Πu) increased from 3600 to 4600 K with an increase in pressure. The first observation of broadening and shifting of the O I line profile (3p5 P3,2,1→3s5 S20) of hf plasma under sc CO2 conditions was carried out. However, the origin of broadening and the shifting cannot be understood because the present theory explaining them is not valid for such high pressure conditions.
Rotational excitation of hydrogen molecules in low temperature plasmas
Authors: Shikama T. , Kado S. , Kurihara K. , Kuwahara Y.
Published: March 2009

The excitation mechanism of the H2 rotational temperature has been studied in a hollow-cathode glow discharge apparatus based on the measurements of relation between the rotational and cathode surface temperature. The rotational temperature evaluated by an excitation-emission model for the Fulcher-α transition indicates clear correlation with the surface temperature. Depending on the plasma parameters and neutral gas pressures, slight difference between both the temperatures is also observed. The temporal evolution of the rotational population densities predicted by rate equations suggests that the difference is attributable to an inequilibrium between the translational and surface temperature. Further possibility of an inequilibrium among the rotational, translational, and surface temperature is expected in low pressure or high electron density conditions.
Two components of the magnetostriction of the crystalline metallic V3Si superconductor
Authors: Nabialek A. , Chabanenko V. , Vasiliev S. , Shushmakova G. , Szymczak H. , Kodess B.
Published: March 2009

Transverse and longitudinal magnetostrictions of a disk-shape crystalline conventional V3Si superconductor were studied by the strain gauge technique in an external magnetic field up to 12 T. It has been found that the observed magnetostriction consists of two components. The first component reveals a strong irreversibility correlated with the pinning phenomenon. The second component saturates when the external magnetic field reaches the value of the second critical field Hc2 corresponding to the changes in the free enthalpy of the superconductor in the external magnetic field. One has also observed the phenomena of the thermomagnetic avalanches, which manifest themselves as the jumps of the surface self-field of the investigated sample as well as the jumps of the magnetostriction.
Suitability of using far-infrared imaging system for noncontact evaluation on working state of implantable medical devices
Authors: Yang Yang , Wei Xiao-Juan , Liu Jing
Published: March 2009

The far-infrared thermal imaging is a promising noncontact way to assess the working state of an implantable medical device (IMD). The unique merit of this method lies in its direct detection of the unusual skin surface temperature distribution caused by the implanted IMD. This paper is dedicated to present a comprehensive investigation on the suitability of using far-infrared system to evaluate the thermal state at the skin surface above the implantation location of the IMD under various working, physiological, or environmental thermal conditions. It was found that an evident variation in temperature as disclosed on the skin surface is beneficial for the far-infrared thermal imaging detection. In addition, numerical simulations were also performed on three dimensional bioheat transfer problems in human bodies embedded with IMD by different implantation depth and physical characteristics. Both theoretical analysis and numerical simulation indicated that for a specific image system with fixed temperature resolution, when the IMD is embedded as close as possible to the superficial skin, the abnormal region of temperature on skin surface can be much more visible. Conceptual experiments either in vitro or in vivo are implemented to preliminarily demonstrate the theoretical predictions. To further improve the detection of an implanted IMD, intentional cooling by the alcohol was proposed and evaluated. Given the fact that several information of an implanted IMD can be revealed through the infrared thermograph, such noncontact imaging method could serve well as an assessment approach without causing any wound and radiation to human body.
Magnetic susceptibilities, crystal field Stark energies, and hyperfine behavior of Sm3+ in hexagonal single crystals of Sm(CF3SO3)3⋅9H2O
Authors: Mondal J. , Acharya S. , Bisui D. , Chattopadhyay K. N. , Ghosh M. , Chakrabarti P. K.
Published: March 2009

Single crystals of samarium trifluoromethanesulfonate (SmTFMS) were prepared from the slow evaporation of the aqueous solution of SmTFMS. The crystals are elongated along the symmetry axis c of the hexagonal crystal. At room temperature, the c axis of the crystal sets parallel with the applied magnetic field which indicates that the susceptibility parallel to the c axis (χ∥) is greater than the susceptibility perpendicular to the c axis (χ⊥). χ∥ and χ⊥ were measured from 300 down to 14 K. Magnetic anisotropy (Δχ=χ∥−χ⊥) obtained from the values of χ∥ and χ⊥ was also checked by direct measurements of Δχ and both these results agreed very well. A crossover between χ∥ and χ⊥ has been observed at ∼56 K i.e., below this temperature χ∥<χ⊥. A good theoretical simulation of the observed magnetic data of SmTFMS has been achieved using the one-electron crystal field (CF) theory. Ordering effects in the observed magnetic data were not noticed down to the lowest temperature (∼14 K) attained, indicating the interionic interaction to be of predominantly dipolar type. To substantiate the CF analysis, the Raman and Fourier transform infrared (FTIR) spectra of the single crystal of SmTFMS were recorded in the wave number ranges of 100–1800 and 400–7000 cm−1, respectively. The calculated values of the CF Stark energies of all the excited multiplets are in agreement with those extracted from the Raman and FTIR spectra. Thermal variation of the calculated electronic specific heat shows Schottky anomaly at ∼8 K. The temperature dependences of quadruple splitting and hyperfine heat capacity were also studied.
Effect on the divertor and scrape-off layer plasma properties of the distribution of power and particle influxes from the core
Authors: Stacey W. M.
Published: March 2009

Calculations of the profiles along the field lines within the divertor and scrape-off layer (SOL) of differences in the plasma ion density, temperature, parallel current, parallel flow velocity, and electrostatic potential, which result from using different poloidal distributions of the particle and heat influxes crossing the separatrix from the core plasma into the SOL, are presented and discussed vis-à-vis experimental observations. The calculations show that the stronger outboard than inboard particle and heat fluxes into the SOL caused by the geometric compression/expansion of flux surfaces predicted by magnetohydrodynamic equilibrium calculations lead to a prediction of higher plasma temperature at the outboard divertor than at the inboard divertor, a result that is consistent with experimental observation and that confirms a previous prediction (made without accounting for drifts) of a possible cause of the observed in-out divertor power asymmetry. The calculations also illustrate the effect of the poloidal distribution of particle and power influx into the SOL on the flow velocity, parallel current, and electrostatic potential distributions in the SOL and divertor.
Effect of charge fluctuation on two dimensional dust clusters in elliptical confinement
Authors: Rouaiguia L. , Djebli M. , Drir M.
Published: March 2009

The structural and melting properties of two dimensional clusters consisting of finite positively charged dust particles are studied. The particles interact through a screened Coulomb potential in an elliptical confinement where Monte Carlo numerical simulation is performed for two different situations. The first one is dealing with constant dust charge and the second one with the charge fluctuation. It is showed that a ground state configuration and a transition from zigzag configuration to linear chain depend on the anisotropic parameter and the number of particles. The effect of charge fluctuation is found to be significant for lower positively charged dust particles. A comparison is made with numerical and experimental results.
Response to “Comment on ‘Turbulent equipartition theory of toroidal momentum pinch’ ” [Phys. Plasmas 16, 034703 (2009)]
Authors: Hahm T. S. , Diamond P. H. , Gurcan O. D. , Rewoldt G.
Published: March 2009

This response demonstrates that the comment by Peeters et al. contains an incorrect and misleading interpretation of our paper [T. S. Hahm et al., Phys. Plasmas 15, 055902 (2008)] regarding the density gradient dependence of momentum pinch and the turbulent equipartition theory.
Gyrocenter-gauge kinetic algorithm for high frequency waves in magnetized plasmas
Authors: Yu Zhi , Qin Hong
Published: March 2009

A kinetic simulation algorithm for high-frequency electromagnetic waves has been developed based on the gyrocenter-gauge kinetic theory. The magnetized plasma system is simulated in the gyrocenter coordinate system. The gyrocenter distribution function F is sampled on the gyrocenter, parallel velocity, and magnetic moment coordinates. The gyrocenter-gauge function S is sampled on the Kruskal rings and shares the first five coordinates with F. The moment integral of pullback transformation is directly calculated using the Monte Carlo method and an explicit difference scheme for Maxwell’s equations in terms of potentials is adopted. The new algorithm has been successfully applied to the simulation studies of high frequency extraordinary wave, electron Bernstein wave, and the mode conversion process between the extraordinary wave and the electron Bernstein wave in inhomogeneous plasmas.
Steady state and transient photoluminescence in poly-p-phenylene vinylene films and nanofibers
Authors: Massuyeau F. , Faulques E. , Athalin H. , Lefrant S. , Duvail J. L. , Wéry J. , Mulazzi E. , Perego R.
Published: March 2009

We report in this paper experimental data on steady state and transient photoluminescence of poly-p-phenylene vinylene in the form of nanofibers prepared with a template method and converted at 110 °C. Results are compared to those obtained from films of different thicknesses converted at the same temperature. Data are analyzed by a model of bimodal distribution of conjugation lengths and the photoluminescence band shapes, evaluated in the framework of this model, are also presented.
High pressure investigation of α-form and CH4-loaded β-form of hydroquinone compounds
Authors: Lee Yongjae , Lee Jong-Won , Lee Hyun-Hwi , Lee Dong Ryeol , Kao Chi-Chang , Kawamura Taro , Yamamoto Yoshitaka , Yoon Ji-Ho
Published: March 2009

The high pressure compression behaviors of two hydroquinone compounds have been investigated using a combination of in situ synchrotron x-ray powder diffraction and Raman spectroscopy up to ca. 7 GPa. The structural integrity of the α-form hydroquinone clathrate is maintained throughout the pressure range, whereas the CH4-loaded β-form hydroquinone clathrate decomposes and transforms to a new high pressure phase near 5 GPa. The bulk modulus (K) and its pressure derivative (K′) of the α-form and the CH4-loaded β-form hydroquinones are measured to be 8.2(3) GPa and 8.4(4), and 10(1) GPa and 9(2), respectively, representing one of the most compressible classes of crystalline solids reported in the literature. The corresponding axial compression behaviors, however, show greater contrast between the two hydroquinone compounds; the elastic anisotropy of the α-form is only marginal, being K(a):K(c)=1.08:1, whereas that of the CH4-loaded β-form is rather drastic, being K(a):K(c)=11.8:1. This is attributed to the different dimensionality of the hydrogen bonding networks between the two structures and might in turn explain the observed structural instability of the β-form, compared to the α-form.
Quantitative analysis of the lattice reconstruction of ion-implanted SiC after visible light laser irradiation
Authors: Brink D. J. , Peyre H. , Camassel J.
Published: March 2009

We report on a quantitative analysis of the effect of visible light laser irradiation (VLLI) on hexagonal (α) silicon carbide implanted with nitrogen and aluminum. In both cases of 4H and 6H polytypes we show that a short, but intense, irradiation with the 532 nm wavelength of a frequency-doubled neodymium: ytterbium aluminum garnet (Nd:YAG) laser results in a substantial reduction in the damage level produced by room temperature ion implantation. Up to now the recovery could not be made complete but, in the best conditions, it could reach ∼80% of the initial damage value. This is not enough to qualify VLLI as a full activation step but, rather, suggests to use it as a new processing tool in order to lower the constraints of high temperature ion implantation or, after implantation performed at room temperature, to reduce the total budget for high temperature annealing and activation steps.
Design of a triple quantum coherence excitation scheme for protons in solid state NMR
Authors: Leskes Michal , Vega Shimon
Published: March 2009

We present a rf scheme designed to excite triple quantum (TQ) coherences for proton solid state NMR. This recoupling scheme is based on the phase modulated Lee Goldburg sequence combined with echo pulses and applied nonsynchronous with the magic angle spinning period. Based on the effective bimodal Floquet Hamiltonian we optimize the conditions for TQ coherence excitation. Numerical simulations are used to further adjust the recoupling conditions as well as define the sequence limitations. Experimental TQ filtered one-dimensional spectra and two-dimensional correlations of TQ to single quantum coherences are presented for standard amino acids. These results are compared with the crystal structures showing that this scheme can aid in resonance assignments and in resolving local spin topologies.
Fast imaging system on Tore Supra
Authors: Géraud A. , Salasca S. , Verger J. M. , Alarcon T. , Agarici G. , Bremond S. , Chenevois J. P. , Geynet M. , Migozzi J. B. , Reux C.
Published: March 2009

A new endoscope aiming at transferring the image of a poloidal section of the Tore Supra plasma to a fast camera able to record frames at a speed up to 4800 frames per second at full resolution, or much faster for a limited number of pixel, has been installed on Tore Supra. First movies showing the light emission associated to fast phenomena such as plasma start up, disruptions or gas and pellet injections have been produced.
A new electronic structure method for doublet states: Configuration interaction in the space of ionized 1h and 2h1p determinants
Authors: Golubeva Anna A. , Pieniazek Piotr A. , Krylov Anna I.
Published: March 2009

An implementation of gradient and energy calculations for configuration interaction variant of equation-of-motion coupled cluster with single and double substitutions for ionization potentials (EOM-IP-CCSD) is reported. The method (termed IP-CISD) treats the ground and excited doublet electronic states of an N-electron system as ionizing excitations from a closed-shell N+1-electron reference state. The method is naturally spin adapted, variational, and size intensive. The computational scaling is N5, in contrast with the N6 scaling of EOM-IP-CCSD. The performance and capabilities of the new approach are demonstrated by application to the uracil cation and water and benzene dimer cations by benchmarking IP-CISD against more accurate IP-CCSD. The equilibrium geometries, especially relative differences between different ionized states, are well reproduced. The average absolute errors and the standard deviations averaged for all bond lengths in all electronic states (58 values in total) are 0.014 and 0.007 Å, respectively. IP-CISD systematically underestimates intramolecular distances and overestimates intermolecular ones, because of the underlying uncorrelated Hartree–Fock reference wave function. The IP-CISD excitation energies of the cations are of a semiquantitative value only, showing maximum errors of 0.35 eV relative to EOM-IP-CCSD. Trends in properties such as dipole moments, transition dipoles, and charge distributions are well reproduced by IP-CISD.
Coupled cluster and density functional studies on geometries and energies of excited C2v states of ozone
Authors: Grein Friedrich
Published: March 2009

The performance of single-determinant methods for finding geometries and energies of excited states is tested on the ozone molecule. Geometries for low-lying singlet and triplet states of ozone were optimized by CCSD(T) and density functional theory (DFT) (with BPW91 functional) methods. DFT geometries were found to lie close to CCSD(T) values. Most CCSD(T) and DFT geometries and energies are in good agreement with available experimental and recent high-level theoretical values, with deviations lying within 0.02 Å, 2°, and 0.3 eV. An exception is the 1 B12 state, having a larger deviation of bond distance and energy. A multiconfigurational treatment is required for this state. DFT geometry optimizations and calculations of vibrational frequencies were extended to higher states, covering over 30 excited states of ozone, with adiabatic excitation energies up to about 6 eV. Calculated harmonic frequencies showed several states, including 1 B12, to be saddle points. Multireference configuration interaction (MRCI) bending potentials for first and second singlet and triplet states were used in verifying the CCSD(T) and DFT geometries and for locating additional minima. For first states, DFT bending potentials are compared with MRCI potentials. As a criterion for the quality of single-determinant geometries and energies of excited states, comparison of their vertical excitation energies with MRCI or time-dependent DFT values is recommended.
Unconventional exchange bias in CoCr2O4/Cr2O3 nanocomposites
Authors: Guo S. , Liu X. H. , Cui W. B. , Liu W. , Zhao X. G. , Li D. , Zhang Z. D.
Published: March 2009

Unconventional exchange bias (EB) has been studied in CoCr2O4/Cr2O3 nanocomposites, in which the Curie temperature of the ferrimagnetic CoCr2O4 is much lower than the Néel temperature of the antiferromagnetic Cr2O3. A negative EB field of about 2.5 kOe at 5 K is achieved upon cooling in a field of 30 kOe. Meanwhile, the coercivity of the CoCr2O4 nanoparticles has been enhanced significantly by coupling with Cr2O3. The effect of the cooling field on the EB field and coercivity at 10 K has also been investigated. The domain-state model is used to interpret the unconventional EB. Cooling field may play a decisive role in the creation of the interfacial spin configuration for the unconventional EB, not only by exchange interaction between the induced magnetization of a polarized paramagnet and interfacial spins of an antiferromagnet but also by Zeeman interaction between the domain-state surplus magnetization and the external field.
Mechanically induced fcc phase formation in nanocrystalline hafnium
Authors: Seelam U. M. R. , Suryanarayana C.
Published: March 2009

A face-centered-cubic (fcc) phase was obtained in high-purity hafnium (Hf) metal powders subjected to mechanical milling in a high-energy SPEX shaker mill. X-ray diffraction and electron microscopy techniques were employed to evaluate the structural changes in the milled powder as a function of milling time. The effects of mechanical milling included a reduction in grain size, an increase in lattice strain, and formation of an fcc phase instead of an equilibrium hexagonal-close-packed (hcp) phase. During milling, the grain size of Hf decreased to below about 7 nm. Additionally, there was approximately 6% increase in atomic volume during the formation of the fcc phase. Chemical analysis of the milled powder indicated the presence of significant amounts of interstitial impurities. Even though any or all of the above factors could contribute to the formation of the fcc phase in the milled powder, it appears that the high level of interstitial impurities is at least partially responsible for the formation of the fcc phase.
Specific heat relaxation of an alcohol and implications for dielectric comparison
Authors: Tombari E. , Ferrari C. , Salvetti G. , Johari G. P.
Published: March 2009

The dynamic and the apparent specific heats of 5-methyl-2-hexanol were measured in its vitrification temperature range during its cooling and then heating at the same and exceptionally slow rates of 12 K/h and 60 K/h. The relaxation time determined from dynamic measurements is 48 s at 149.8 K. The relaxation time estimated from the onset of the apparent Cp-endotherm measured on heating is found to be inconsistent with that determined from dynamic Cp measurements. The fitting of a nonexponential nonlinear relaxation model to the Cp,app data shows that β varies slightly with the heating rate, and this is attributed to contributions to temperature-dependent energy from change in the hydrogen-bond population. The unrelaxed Cp of the ultraviscous liquid is closer to that of its glassy state, thus showing that the vibrational part of Cp does not increase in a sigmoid-shape manner when the glass structure kinetically unfreezes on heating. The results have implications for use of calorimetry in inferring the dielectric relaxation mechanism.
Cu-doping induced ferromagnetism in ZnO nanowires
Authors: Xu Congkang , Yang Kaikun , Huang Liwei , Wang Howard
Published: March 2009

Cu-doped and undoped ZnO nanowires have been successfully fabricated at 600 °C using a vapor transport approach. Comprehensive structural analyses on as-fabricated nanowires reveal highly crystalline ZnO nanowires with 0.5 at. % of substitutional Cu doping. Ferromagnetism has been observed in Cu-doped ZnO nanowires but not in undoped ones, which is probably associated with defects involving both Cu dopants and Zn interstitials.
Rovibrational structure of the Xe–CO complex based on a new three-dimensional ab initio potential
Authors: Feng Eryin , Zhang Yu , Wang Zhongquan , Niu Mei , Cui Zhifeng
Published: March 2009

The first three-dimensional interaction potential energy surface of the Xe–CO complex is developed using the single and double excitation coupled cluster theory with noniterative treatment of triple excitations. Mixed basis sets, aug-cc-pVQZ for the C and O atoms and aug-cc-pVQZ-PP for the Xe atom, including an additional (3s3p2d2f1g) set of midbond functions are used. The calculated single point energies at five fixed rco values are fitted to an analytic two-dimensional potential model, and further the five model potentials are used to construct the three-dimensional potential energy surface by interpolating along (r−re). Dynamical calculations with the vibrationally averaged potentials are performed to determine the energy levels and the frequencies of various rovibrational transitions. Our results agree well with the experiment. For example, the IR transitions of 508 lines are precisely reproduced with only a total rms error of 0.105 cm−1.