bluuebunny/crossref_metadata_2025 huggingface dataset:
β‐Aminoisobutyric Acid Prevents Diet‐induced Obesity in Mice With Partial Leptin Deficiency
Authors: Begriche Karima , Massart Julie , Abbey‐Toby Adjé , Igoudjil Anissa , Lettéron Philippe , Fromenty Bernard
Published: August 2008

β‐Aminoisobutyric acid (BAIBA), a thymine catabolite, increases fatty acid oxidation (FAO) in liver and reduces the gain of body fat mass in Swiss (lean) mice fed a standard chow. We determined whether BAIBA could prevent obesity and related metabolic disorders in different murine models. To this end, BAIBA (100 or 500 mg/kg/day) was administered for 4 months in mice totally deficient in leptin (ob/ob). BAIBA (100 mg/kg/day) was also given for 4 months in wild‐type (+/+) mice and mice partially deficient in leptin (ob/+) fed a high‐calorie (HC) diet. BAIBA did not limit obesity and hepatic steatosis in ob/ob mice, but reduced liver cytolysis and inflammation. In ob/+ mice fed the HC diet, BAIBA fully prevented, or limited, the gain of body fat, steatosis and necroinflammation, glucose intolerance, and hypertriglyceridemia. Plasma β‐hydroxybutyrate was increased, whereas expression of carnitine palmitoyltransferase‐1 was augmented in liver and white adipose tissue. Acetyl‐CoA carboxylase was more phosphorylated, andde novolipogenesis was less induced in liver. These favorable effects of BAIBA in ob/+ mice were associated with a restoration of plasma leptin levels. The reduction of body adiposity afforded by BAIBA was less marked in +/+ mice. Finally, BAIBA significantly stimulated the secretion of leptin in isolated ob/+ adipose cells, but not in +/+ cells. Thus, BAIBA could limit triglyceride accretion in tissues through a leptin‐dependent stimulation of FAO. As partial leptin deficiency is not uncommon in the general population, supplementation with BAIBA may help to prevent diet‐induced obesity and related metabolic disorders in low leptin secretors.
Weight Loss Maintenance in a Population‐based Sample of German Adults
Authors: De Zwaan Martina , Hilbert Anja , Herpertz Stephan , Zipfel Stephan , Beutel Manfred , Gefeller Olaf , Muehlhans Barbara
Published: August 2008

The objective of this study was to investigate the prevalence of weight loss maintenance in a population‐based sample of the German adult population. German adults were recruited based on the random digital‐dialing methodology. Using computer‐assisted telephone interviewing, weight loss maintenance was assessed, defined as having intentionally lost at least 10% from maximum weight and having maintained it for at least 1 year at the time of the survey. A total of 2,095 noninstitutionalized adults were randomly selected from all parts of Germany and the data of 957 respondents were included into the analysis. Of those who were at least overweight (BMI ≥ 25 kg/m2) at their maximum weight, 17.7% reported having maintained a current weight loss of ≥10% of their maximum weight for at least 1 year. Among participants who reported a maximum weight in the obese range (BMI ≥ 30 kg/m2), 29.7% reported successful 1‐year weight loss maintenance. Among at least overweight participants, being younger and female, and having a higher maximum BMI were significant predictors of successful 1‐year weight loss maintenance. The results suggest that successful weight loss maintenance is not uncommon in the general population, particularly in formerly obese participants. More should be learned about the strategies that successful weight maintainers use to avoid regaining weight.
Gender Differences in the Relationship of ENPP1/PC‐1 Variants to Obesity in a Turkish Population
Authors: Tanyolaç Sinan , Mahley Robert W. , Hodoglugil Uğur , Goldfine Ira D.
Published: August 2008

The ectoenzyme ENPP1 (also termed membrane glycoprotein PC‐1 or ENPP1/PC‐1) is an inhibitor of insulin‐induced activation of the insulin receptor. There is evidence from previous studies that coding variants of ENPP1/PC‐1 (K121Q) are associated with type 2 diabetes (T2D) and obesity. Studies in the general Turkish population have demonstrated: unique plasma lipid characteristics, a high prevalence of cardiovascular risk factors, and an increased prevalence of obesity and T2D. We investigated, therefore, the association of ENPP1/PC‐1 variants with obesity and T2D in Turkish individuals. The TaqMan allelic discrimination assay was used for genotyping the relationship of ENPP1/PC‐1 variants to obesity and T2D in a genetic association study of 1,553 genotyped, randomly selected subjects from the Turkish Heart Study. The K121Q (rs1044498) variant and other previously reported variants (rs997509, rs1799774, rs1044548, rs11964389, rs7754561) were analyzed. In this cohort, the minor allele frequency (MAF) of the K121Q variant was associated with obesity in male, but not in female subjects (male, odds ratio 1.64, 95% confidence interval 1.004–2.698, P = 0.048; female, odds ratio 1.003, 95% confidence interval 0.684–1.471, P = ns). In addition, the previously reported ENPP1/PC‐1 “risk haplotype” (Q (rs1044498), delT (rs1799774), and G (rs7754561) alleles) was found to be associated with obesity in male, but not in female, subjects (P = 0.035). In contrast, there was no association of either the K121Q variant or the ENPP1/PC‐1 haplotype with T2D. We find evidence that variants of ENPP1/PC‐1 are associated with obesity in the male Turkish population; thus, these variants may contribute to the development of the obesity in these individuals.
The cytotoxic effect of unconjugated bilirubin in human neuroblastoma SH-SY5Y cells is modulated by the expression level of MRP1 but not MDR1
Authors: Corich Lucia , Aranda Alejandro , Carrassa Laura , Bellarosa Cristina , Ostrow J. Donald , Tiribelli Claudio
Published: August 2008

In vitro and in vivo studies have demonstrated that UCB (unconjugated bilirubin) is neurotoxic. Although previous studies suggested that both MRP1 (multidrug resistance-associated protein 1) and MDR1 (multidrug resistance protein 1) may protect cells against accumulation of UCB, direct comparison of their role in UCB transport was never performed. To this end, we used an inducible siRNA (small interfering RNA) expression system to silence the expression of MRP1 and MDR1 in human neuroblastoma SH-SY5Y cells. The effects of in vitro exposure to clinically-relevant levels of unbound UCB were compared between unsilenced (control) cells and cells with similar reductions in the expression of MRP1 or MDR1, documented by RT–PCR (reverse transcription–PCR) (mRNA), immunoblotting (protein), and for MDR1, the enhanced net uptake of a specific fluorescent substrate. Cytotoxicity was assessed by the MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide] test. MRP1-deficient cells accumulated significantly more UCB and suffered greater cytotoxicity than controls. By contrast, MDR1-deficient cells exhibited UCB uptake and cytotoxicity comparable with controls. At intermediate levels of silencing, the increased susceptibility to UCB toxicity closely correlated with the decrease in the expression of MRP1, but not of MDR1. These data support the concept that limitation of cellular UCB accumulation, due to UCB export mediated by MRP1, but not MDR1, plays an important role in preventing bilirubin encephalopathy in the newborn.
Proteomic identification of the silkworm (Bombyx mori L) prothoracic glands during the fifth instar stage
Authors: Wu Xiao-feng , Li Xing-hua , Yue Wan-fu , Roy Bhaskar , Li Guang-li , Liu Jian-mei , Zhong Bo-xiong , Gao Qi-kang , David Wan Chi Cheong , Miao Yun-gen
Published: August 2008

Although the ecdysteroid of the silkworm had been studied for decades, the proteome of the prothoracic gland, the primary source of ecdysteroid hormones, has not been studied previously. In the present paper, we utilized a proteomic approach to investigate the fifth instar prothoracic gland during the growth and development of the silkworm, Bombyx mori L. The two-dimensional electrophoresis results showed that the majority of proteins were acidic proteins, especially concentrated in the area of 25–65 kDa, with pI values of between 4 and 7, and the difference was not distinct. When compared with Qiufeng (Japanese strain), the interspecific distinction was larger than the intraspecific distinction, and 19 particular spots, excized from the third, fifth and ninth days of p50 (Chinese strain) and Qiufeng were subjected to MALDI-TOF–MS (matrix-assisted laser-desorption ionization–time-of-flight MS) analysis. We sorted them into seven catagories: energetics and/or metabolism, storage proteins, protection, lipid metabolism, signal transduction, cell function and unknown function proteins. Of these proteins, arginine methyltransferase is discussed as playing an important role in regulating the activation of ecdysteroidogenesis via transcription or translation.
Strain effect on electronic structures of graphene nanoribbons: A first-principles study
Authors: Sun Lian , Li Qunxiang , Ren Hao , Su Haibin , Shi Q. W. , Yang Jinlong
Published: August 2008

We report a first-principles study on the electronic structures of deformed graphene nanoribbons (GNRs). Our theoretical results show that the electronic properties of zigzag GNRs are not sensitive to uniaxial strain, while the energy gap modification of armchair GNRs (AGNRs) as a function of uniaxial strain displays a nonmonotonic relationship with a zigzag pattern. The subband spacings and spatial distributions of the AGNRs can be tuned by applying an external strain. Scanning tunneling microscopy dI/dV maps can be used to characterize the nature of the strain states, compressive or tensile, of AGNRs. In addition, we find that the nearest neighbor hopping integrals between π-orbitals of carbon atoms are responsible for energy gap modification under uniaxial strain based on our tight binding approximation simulations.
Multistate vibronic interactions in difluorobenzene radical cations. I. Electronic structure calculations
Authors: Faraji Shirin , Köppel Horst
Published: August 2008

The multimode multistate vibronic interactions between the five lowest electronic states of all three isomers of the difluorobenzene radical cation are investigated theoretically, based on ab initio electronic structure data, and employing a well-established vibronic coupling model. The approach rests on the linear vibronic coupling scheme, augmented by quadratic coupling terms for the totally symmetric modes. The underlying ionization potentials and coupling constants are obtained from ab initio coupled-cluster calculations. Low-energy conical intersections and strong vibronic couplings are found to prevail within the sets of X̃-Ã and B̃-C̃-D̃ cationic states, while the interactions between these two sets of states are found to be weaker and depend on the isomer. The inclusion of the aforementioned quadratic couplings is found to be essential to correctly reproduce the lowest-energy conical intersections between the two different sets of electronic states. Differences between the three isomers regarding these quantities are pointed out. The results will be used as basis for multidimensional wave-packet dynamical simulations for these coupled potential energy surfaces to be presented in the following paper (Paper II).
Properties of the electron beam in a room-temperature electron beam ion source investigated by position sensitive x-ray detection
Authors: Silze A. , Zschornack G. , Ovsyannikov V. P. , Ullmann F.
Published: August 2008

The evolution of the charge state distribution inside an electron beam ion source or trap (EBIS/T) is determined by interactions of the electron beam with the ions in the trap region. Hence, detailed information about the electron beam is required for evaluations of spectroscopic and ion extraction measurements performed at EBIS/T facilities. This article presents the results of investigations on the electron beam properties of an ion source of the Dresden EBIS type. For the first time theoretical predictions of the shape of the beam were tested for a noncryogenic EBIS working with low magnetic flux densities provided by permanent magnets. Position and width of the electron beam were measured at different electron energies showing an oscillation in the beam structure. At an energy of Ee=16 keV and an emission current of Ie=30 mA the beam is compressed to a radius of re=57 μm (80% current). This refers to an average current density of ⟨je⟩=232 A/cm2.
Nanofabrication and the realization of Feynman’s two-slit experiment
Authors: Frabboni Stefano , Gazzadi Gian Carlo , Pozzi Giulio
Published: August 2008

Two nanosized slits are opened by focused ion beam milling in a membrane to observe, with a transmission electron microscope, electron interference fringes. Then, on the same sample, one of the slits is closed by focused ion beam induced deposition and the corresponding transmitted intensity is recorded. The comparison between the two measurements provides an impressive experimental evidence of the probability amplitude of quantum mechanics following step by step the original idea proposed by Feynman [The Feynman Lectures on Physics (Addison-Wesley, Reading, MA, 1966), Vol. 3, Chap. 1].
Growth, crystal structure, and properties of epitaxial BiScO3 thin films
Authors: Trolier-McKinstry Susan , Biegalski Michael D. , Wang Junling , Belik Alexei A. , Takayama-Muromachi Eiji , Levin Igor
Published: August 2008

Epitaxial thin films of BiScO3—a compound thermodynamically unstable under ambient conditions—were grown on BiFeO3-buffered SrTiO3 substrates. X-ray diffraction confirmed the reasonable crystalline quality of the films with a full width at half maximum of 0.58° in ω (004 reflection), 0.80° in ϕ (222 reflection), and 0.28° in θ. The epitaxial thin films of BiScO3 on SrTiO3 retain the principal structural features of bulk BiScO3 (i.e., octahedral tilting and the pattern of Bi displacements) that give rise to a pseudo-orthorhombic unit cell 2√2ac×√2ac×4ac (ac≈4Å refers to the lattice parameter of an ideal cubic perovskite). Films grown on {100} substrates adopt the bulk monoclinic structure, whereas films on the (110) substrates appear to exhibit an orthorhombic symmetry. The dielectric permittivities were modest (≈30) with low loss tangents (<1% at low fields); no maxima were observed over a temperature range of −200to+350°C. There is no evidence of significant hysteresis (either ferroelectric or antiferroelectric) at room temperature up to the breakdown strength of the films.
Time-resolved characterization of InAsP∕InP quantum dots emitting in the C-band telecommunication window
Authors: Hostein R. , Michon A. , Beaudoin G. , Gogneau N. , Patriache G. , Marzin J.-Y. , Robert-Philip I. , Sagnes I. , Beveratos A.
Published: August 2008

The dynamic response of InAsP quantum dots, grown on InP(001) substrates by low-pressure metalorganic vapor phase epitaxy emitting around 1.55μm, is investigated by means of time-resolved microphotoluminescence as a function of temperature. Exciton lifetime steadily increases from 1ns at low temperature to reach 4ns at 300K while the integrated photoluminescence intensity decreases only by a factor of 23. These characteristics give evidence that such InAsP∕InP quantum dots provide a strong carrier confinement even at room temperature and that their dynamic response is not affected by thermally activated nonradiative recombination up to room temperature.
Giant magnetoelectric effect in sintered multilayered composite structures
Authors: Islam Rashed A. , Ni Yong , Khachaturyan Armen G. , Priya Shashank
Published: August 2008

Trilayer composites consisting of 0.9Pb(Zr0.52Ti0.48)O3–0.1Pb(Zn1/3Nb2/3)O3 (0.9 PZT-0.1 PZN) and Ni0.6Cu0.2Zn0.2Fe2O4 (NCZF) in the configuration NCZF-(0.9 PZT-0.1 PZN)-NCZF were synthesized using pressure assisted sintering. Composites with optimized magnetostrictive to piezoelectric thickness ratio showed a high magnetoelectric (ME) coefficient of 525 mV/cm Oe. Further enhancement in the magnitude of ME coefficient was obtained (595 mV/cm Oe) when the angle of applied dc magnetic field was changed to 45°. Changing the intermediate piezoelectric layer from single to trilayer stack geometry configuration leads to the realization of giant ME response of 782 mV/cm Oe in sintered composites.
Structural hysteresis and hierarchy in adsorbed glycoproteins
Authors: Horvath Robert , McColl James , Yakubov Gleb E. , Ramsden Jeremy J.
Published: August 2008

The adsorption and desorption of the giant heavily glycosylated protein mucin from solutions of different bulk concentrations have been followed at the nanometer scale using high resolution molecular microscopy based on optical waveguide lightmode spectroscopy. Modeling the layer as a uniaxial thin film allowed the in situ determination of adsorbed mass, mean layer thickness, and structural anisotropy. These parameters manifest highly significant adsorption-desorption hysteresis, indicating at least two dominant glycoprotein conformational types (i.e., molecular states, structurally and kinetically distinguishable). One of them is proposed to be a conformationally extended state that engenders uniaxial symmetry and dominates layers generated from low bulk concentrations. The revealed structure and the mechanism by which it is formed are postulated to be a general feature of the self-assembly of large glycoproteins. We expect that, inter alia, this knowledge will be relevant for understanding the extraordinary effectiveness of mucin thin films as boundary lubricants.
Magnetic levitation of an iron ball
Authors: Sakurai Yuryo
Published: August 2008

The mechanism of magnetic levitation of an iron ball in a plastic box [S. Sasaki, I. Yagi, and M. Murakami, J. Appl. Phys. 95, 2090 (2004)]. was investigated quantitatively using measurement of the magnetic moment of the iron ball and ring magnet used in the levitation experiment. This phenomenon is very interesting not only as a physical phenomenon but also from the viewpoint of application. In order to better understand this phenomenon, we examined the method for controlling the movement of the iron ball. Through trial and error, we developed the equipment to observe the delicate movement of the iron ball from floating to falling over a short time (–1 min). Moreover, though it was not possible to perfectly float the iron ball with no contact, there was a clear indication of this possibility.
Steplike versus continuous domain propagation in Co/Pd multilayer films
Authors: Günther C. M. , Radu F. , Menzel A. , Eisebitt S. , Schlotter W. F. , Rick R. , Lüning J. , Hellwig O.
Published: August 2008

We investigate the microscopic reversal behavior in perpendicular-anisotropy magnetic thin films using an integrated mask-sample design that allows probing a nanoscale sample region with soft x-rays. Local hysteresis loops and spectroholography images are obtained from the transmitted signal exploiting x-ray magnetic circular dichroism. Our data provide direct evidence of microscopic spin-flip avalanches, such as responsible for Barkhausen noise. In comparison with macroscopic magnetometry measurements we find evidence for the sputter pressure dependent introduction of local defects that prevent a continuous domain wall motion but are not strong enough to introduce the appearance of microscopic return point memory.
Metal organic vapor phase epitaxy of InAsP/InP(001) quantum dots for 1.55μm applications: Growth, structural, and optical properties
Authors: Michon A. , Hostein R. , Patriarche G. , Gogneau N. , Beaudoin G. , Beveratos A. , Robert-Philip I. , Laurent S. , Sauvage S. , Boucaud P. , Sagnes I.
Published: August 2008

This contribution reports the metal organic vapor phase epitaxy of InAsP/InP(001) quantum dots with a voluntary V-alloying obtained owing to an additional phosphine flux during InAs quantum dot growth. The quantum dots were studied by photoluminescence and transmission electron microscopy. We show that the additional phosphine flux allows to tune quantum dot emission around 1.55 μm while improving their optical properties. The comparison of the optical and structural properties of the InAsP quantum dots allows to deduce their phosphorus composition, ranging from 0% to 30% when the phosphine/arsine flow ratio is varying between 0 and 50. On the basis of the compositions deduced, we discuss on the effects of the phosphine flow and of the alloying on the quantum dot growth, structural, and optical properties.
The relationship between network morphology and conductivity in nanotube films
Authors: Lyons Philip E. , De Sukanta , Blighe Fiona , Nicolosi Valeria , Pereira Luiz Felipe C. , Ferreira Mauro S. , Coleman Jonathan N.
Published: August 2008

We have characterized both the direct current conductivity and morphology of a wide range of films made from bundled nanotubes, produced by a selection of commercial suppliers. The conductivity increases with increasing nanotube graphitization but decreases with increasing film porosity P and mean bundle diameter ⟨D⟩. Computational studies show that the network conductivity is expected to scale linearly with the number density of interbundle junctions. A simple expression is derived to relate the junction number density to the porosity and mean bundle diameter. Plotting the experimental network conductivities versus the junction number density calculated from porosity and bundle diameter shows an approximate linear relationship. Such a linear relationship implies that the conductivity scales quadratically with the nanotube volume fraction, reminiscent of percolation theory. More importantly it shows the conductivity to scale with ⟨D⟩−3. Well-defined scaling with diameter and porosity allows the calculation of a specific conductivity expected for films with porosity of 50% and mean bundle diameter of 2 nm. This predicted specific conductivity scales well with the level of nanotube graphitization, reaching values as high as 1.5×107 S/m for well graphitized HiPCO single walled nanotubes.
Assembly of ordered magnetic microsphere arrays
Authors: Xu Wanling , Ketterson John
Published: August 2008

We have developed a straightforward technique to assemble ordered arrays of magnetic microspheres on patterned thin Permalloy (Py) films deposited on the surface of a silicon wafer. Droplets containing micrometer-sized carboxyl paramagnetic microspheres are placed on a horizontally oriented wafer. The field produced by a permanent magnet placed under the wafer is rendered inhomogeneous by the patterned Py features and the resulting field gradients attract and hold the paramagnetic microspheres to these features. While the magnetic microspheres are being attracted to and secured on the pattered Permalloy features, a horizontal flow is created by a pipette, which also removes loose (unsecured) microspheres. By applying this technique to a cocktail of individually functionalized microspheres, a sensor could be realized, which will screen, in parallel, for a large number of targets per unit area. The ability to resolve individual microspheres is close to 100%. A desirable feature is that the substrate is reusable; removing the magnet allows an existing batch of microspheres, which may have lost sensitivity due to environmental exposure, to be flushed from the substrate and replaced with a new batch. The technique complements existing approaches in the field of microarrays widely used in immunoassay, DNA fragment detection, pathogen detection, and other applications in functional genomics and diagnostics.
Angular dependence of longitudinal and perpendicular exchange biases in FeMn/(FeNi/FeMn)n multilayers
Authors: Sun Li , Xing Hao
Published: August 2008

Perpendicular exchange bias can be established in ferromagnetic/antiferromagnetic multilayers with intrinsic in-plane shape anisotropy through out-of-plane field cooling. The induced anisotropy along the hard axis possesses the same interfacial nature as that after the conventional in-plane field cooling. While the in-plane angular dependence of longitudinal exchange bias can be well described by the uniaxial coherent rotation model, out-of-plane measurements show totally different angular dependent hysteretic behaviors for both longitudinal and perpendicular exchange biases. After taking into account the competitive field cooling induced anisotropy, the thin film shape anisotropy, the three-dimensional coherent rotation model alone can quantitatively explain the observed out-of-plane angular dependent magnetization reversal for both field cooling geometries. Magnetization reversal is found to be accomplished by coherent rotation out of the plane determined by anisotropic axis and applied field. The model is also applicable in predicting the more general thin-film magnetization reversal with out-of-plane applied fields.
Fully nonlocal kinetic energy density functionals: A proposal and a general assessment for atomic systems
Authors: García-Aldea David , Alvarellos J. E.
Published: August 2008

Following some recent ideas on the construction of kinetic energy density functionals that reproduce the linear response function of the homogeneous electron gas, a family of them with a nonlocal term based on the von Weizsäcker functional and with a dependence on the logarithm of the density is presented. As localized systems are the most difficult to study with explicit kinetic functionals, in this paper we apply to atomic systems a number of families of fully nonlocal kinetic functionals. We have put our attention in both the total kinetic energy and the local behavior of the kinetic energy density, and the results clearly show the quality of these fully nonlocal functionals. They make a good description of the local behavior of the kinetic energy density and maintain good results for the total kinetic energies. We must remark that almost all the functionals discussed in the paper, when using an adequate reference density, can be evaluated as a single integral in momentum space, with a quasilinear scaling for the computational cost.
Intense white upconversion emission in Pr/Er/Yb codoped tellurite glass
Authors: Dwivedi Y. , Rai Anita , Rai S. B.
Published: August 2008

Near infrared sensitized white light emitting glass has been developed and demonstrated. The white light comes from a combination of radiations emitted from triple rare earth ions (Er, Pr, and Yb) doped in tellurite glass. White light emission is possible by suitably mixing the red-green-blue (RGB) intensities emitted from these rare earth ions. The 980 nm radiation sensitized Yb3+ ions transfer their excitation energy to the Er3+ and Pr3+ ions to promote them to the upper states. The green and red emissions come mainly from Er3+ ion whereas blue emission from Yb3+ and Pr3+ ions. The RGB intensities could be adjusted by tuning the rare earth ion concentration. The optical quality of white light was adjudged using the Commission Internationale de l’ Eclairage coordinates by the rare earth ion concentration and incident power density.
Enhancement of critical current density and flux pinning properties of Gd-doped (Bi, Pb)-2212 superconductor
Authors: Vinu S. , Sarun P. M. , Shabna R. , Biju A. , Syamaprasad U.
Published: August 2008

The enhanced critical current density (JC) and flux pinning properties of Bi1.7Pb0.4Sr2-xGdxCa1.1Cu2.1O8+δ (where x=0.0, 0.1, 0.2, and 0.3) system prepared by solid-state synthesis in bulk polycrystalline form were studied. Phase analysis, microstructural investigation, and superconducting characterization were performed to evaluate the relative performance of the samples. The x-ray diffraction and energy dispersive spectroscopy analyses show that Gd atoms are successfully doped in place of Sr in the system. It is found that Gd in (Bi, Pb)-2212 enhances the critical temperature (TC), JC, and flux pinning strength of the system. The flux pinning force (FP) calculated from the field dependant JC values shows that the irreversibility line of the Gd-doped (Bi, Pb)-2212 shift toward higher fields to different extents depending on the value of x. The samples with x=0.2 show maximum FP of 645 kN m−3 and the peak position of FP shifts to higher fields (0.68 T) as against 26 kN m−3 and 0.12 T for the pure sample. Also, the values of self-field JC and pinning potential (U0) are maximum for this sample (x=0.2). The enhancements of TC, self-field JC, JC(B) characteristics, U0, and FP are explained on the basis of the hole optimization and formation of point defects due to the doping of Gd in (Bi, Pb)-2212 system.
Magnetic quartz crystal microbalance: A multilayer gold/nickel stack
Authors: Yu George Y. , Janata Jiří
Published: August 2008

A stack of alternating layers of nickel and gold was electroplated on a quartz crystal microbalance (QCM). When external magnetic fields of up to 10 kG were applied, changes in the QCM admittance magnitude and phase were observed. A mass-equivalent stack of continuous consecutive layers of nickel and gold was also exposed to magnetic field, but no admittance magnitude and phase changes were observed. The Butterworth–van Dyke model was used to mimic the observed effects by varying only the equivalent resistor component. Since the resistor component changes are attributed to internal shear friction effects, it indicates that the friction at the nickel/gold interface is modulated by the magnetic field.
A ferroelectric solid solution of (1−x)Ba(Yb1/2Nb1/2)O3−xPbTiO3 with morphotropic phase boundary
Authors: Wang Zujian , Li Xiuzhi , Wei Qian , Long Xifa , Ye Zuo-Guang
Published: August 2008

A new ferroelectric solid solution of (1−x)Ba(Yb1/2Nb1/2)O3−xPbTiO3(0≤x≤1) (PT) has been synthesized in the form of ceramics by solid-state reactions and characterized by means of x-ray diffraction, ferroelectric measurements, and dielectric spectroscopy. All ceramics with different compositions crystallize in the pure perovskite phase. With increasing PT content, the properties of ceramics gradually transfer from dielectrics (x≤0.5) to relaxors (0.50≤x≤0.70), and then to normal ferroelectrics (x>0.70). Based on the x-ray and dielectric measurements, a partial phase diagram of the system is established, which exhibits a morphotropic phase boundary with compositions 0.65<x<0.70.
Electronic structure and optical properties of 1T-TiS2 and lithium intercalated 1T-TiS2 for lithium batteries
Authors: Reshak A. H. , Kityk I. V. , Auluck S.
Published: August 2008

We report results of first-principles calculations of electronic and optical properties of pristine 1T-TiS2 and 1T-TiS2 intercalated with lithium. Calculations have been performed using the full-potential linearized augmented plane wave method based on density functional theory together with the local density approximation for the exchange correlation energy functional. We have calculated the band structure, density of states, and the linear optical properties. We compare our results of the intercalated 1T-LiTiS2 with the host 1T-TiS2 to ascertain the effect of Li intercalation on the electronic and optical properties. The Li-s and Li-p bands are very broad and do not contribute much to the density of states. Our calculations show that the electronic and optical properties are influenced significantly when TiS2 is intercalated with lithium.
Application of classical models of chirality to optical rectification
Authors: Wang Xiao-Ou , Gong Li-Jing , Li Chun-Fei
Published: August 2008

Classical models of chirality are used to investigate the optical rectification effect in chiral molecular media. Calculation of the zero frequency first hyperpolarizabilities of chiral molecules with different structures is performed and applied to the derivation of a dc electric-dipole polarization. The expression of second-order nonlinear static-electric-dipole susceptibilities is obtained by theoretical derivation in the isotropic chiral thin films. The microscopic mechanism producing optical rectification is analyzed in view of this calculation. We find that optical rectification is derived from interaction between the electric field gradient (spatial dispersion) and chiral molecules in optically active liquids and solution by our calculation, which is consistent with the result given by Woźniak and Wagnière [Opt. Commun. 114, 131 (1995)]: The optical rectification depends on the fourth-order electric-dipole susceptibilities.
Charge localization and Jahn–Teller distortions in the benzene dimer cation
Authors: Pieniazek Piotr A. , Bradforth Stephen E. , Krylov Anna I.
Published: August 2008

Jahn–Teller (JT) distortions and charge localization in the benzene dimer cation are analyzed using the equation-of-motion coupled cluster with single and double substitutions for ionization potential (EOM-IP-CCSD) method. Ionization of the dimer changes the bonding from noncovalent to covalent and induces significant geometrical distortions, e.g., shorter interfragment distance and JT displacements. Relaxation along interfragment coordinates lowers the energy of the t-shaped and displaced sandwich isomers by 0.07 and 0.23 eV, respectively, whereas JT displacements result in additional 0.18 and 0.23 eV. Energetically, the effect of JT distortion on the dimer is similar to the monomer where JT relaxation lowers the energy by 0.18 eV. While the change in the interfragment distance has dramatic spectroscopic consequences, the JT distortion causes only a small perturbation in the electronic spectra. The two geometrical relaxations in the t-shaped isomer lead to opposing effects on hole localization. Intermolecular relaxation leads to an increased delocalization, whereas JT ring distortion localizes the charge. In the sandwich isomers, breaking the symmetry by ring rotation does not induce considerable charge localization. The optimization and property calculations were performed using a new implementation of EOM-IP-CCSD energies and gradients in the Q-CHEM electronic structure package.
Energy of hydrodynamic and magnetohydrodynamic waves with point and continuous spectra
Authors: Hirota M. , Fukumoto Y.
Published: August 2008

Energy of waves (or eigenmodes) in an ideal fluid and plasma is formulated in the noncanonical Hamiltonian context. By imposing the kinematical constraint on perturbations, the linearized Hamiltonian equation provides a formal definition of wave energy not only for eigenmodes corresponding to point spectra but also for singular ones corresponding to a continuous spectrum. The latter becomes dominant when mean fields have inhomogeneity originating from shear or gradient of the fields. The energy of each wave is represented by the eigenfrequency multiplied by the wave action, which is nothing but the action variable and, moreover, is associated with a derivative of a suitably defined dispersion relation. The sign of the action variable is crucial to the occurrence of Hopf bifurcation in Hamiltonian systems of finite degrees of freedom [M. G. Krein, Dokl. Akad. Nauk SSSR, Ser. A 73, 445 (1950)]. Krein’s idea is extended to the case of coalescence between point and continuous spectra.
Kinetic theory on the current-filamentation instability in collisional plasmas
Authors: Hao Biao , Sheng Z.-M. , Zhang J.
Published: August 2008

The current filamentation instability (CFI) or Weibel-type instability is studied for a nonrelativistic electron beam penetrating an infinite uniform plasma, taking into account both the collisional effects and the space-charge effect (SCE). We consider three configurations for the beam and plasma: the kinetic domain, the hydrodynamic domain, and the hybrid domain with one in kinetic and the other in hydrodynamic domain. It is shown that the CFI is determined by the current-driven drift-anisotropy rather than the classical anisotropy of the beam and the background plasma. Therefore, collisional effects can either attenuate or enhance the CFI depending on the drift-anisotropy of the beam and the background plasma. It is found that the collisional effects usually attenuate the CFI for nearly symmetric counterstreaming in the whole unstable range but enhance it for asymmetric counterstreaming in the long wavelength region both in the kinetic and the hydrodynamic domains, although the mechanisms are different. As for the case of the hybrid domain the collisional effects enhance the CFI growth rate in the long wavelength region but reduce it in the short wavelength region. The SCE can be ignored for the hydrodynamic domain while for the kinetic and the hybrid domains it is still significant though damped by the collisional effects. The combination of the SCE and the collisional effects usually reduce the CFI growth rate and suppress the unstable range further, especially in the short wavelength region.
Anisotropic hole-mass tensor of CuIn1−xGax(S,Se)2: Presence of free carriers narrows the energy gap
Authors: Persson Clas
Published: August 2008

Analysis of the band edges of CuIn1−xGax(S,Se)2 with x=0.0, 0.5, and 1.0 reveals that (i) CuIn1−xGaxS2 has larger effective electron mc and hole mv masses than CuIn1−xGaxSe2; (ii) whereas Ga content affects band curvatures only slightly, the sign of the crystal-field split Δcf as well as the spin-orbit coupling affect mv strongly; (iii) the optical response ε2(ℏω) is comparable for all six compounds; and (iv) band filling of electrons (n=1019 cm−3) and holes (p=n) narrows the band gap by Eg≈Eg0−0.1 eV and generates an optical band gap of Egopt≈Eg+0.2 eV.
Modeling of compressible magnetohydrodynamic turbulence in electrically and heat conducting fluid using large eddy simulation
Authors: Chernyshov A. A. , Karelsky K. V. , Petrosyan A. S.
Published: August 2008

Many electrically and heat conducting fluid flows cannot be described within the framework of incompressible medium or by compressible magnetohydrodynamic equations on the assumption of polytropic (or adiabatic) process. Therefore, we consider a heat conducting compressible fluid with the use of an energy equation. Application of large eddy simulation approach to heat conducting compressible magnetohydrodynamics is considered. The system of the filtered magnetohydrodynamic equations with the total energy equation using the mass-weighted filtering procedure has been obtained. It is shown that novel subgrid-scale terms arise in the Favre-filtered equations due to the presence of a magnetic field in the total energy equation. Parametrizations of these extra terms are developed. In order to derive these subgrid-scale terms, we use an approach based on generalized central moments. Computations at various Mach numbers are made for decaying compressible magnetohydrodynamic turbulence. The obtained numerical large eddy simulation results are analyzed on the basis of comparison with results of numerical experiments performed by direct numerical simulation. Validity of large eddy simulation method is thus demonstrated. It is shown that consideration of the subgrid-scale terms in the total energy equation scarcely affects the kinetic and the magnetic energy for low and even high Mach number, while for the temperature the presence of subgrid-scale models in the energy equation is an important condition for improvement in calculation accuracy of thermodynamic quantities. The technique with the mass-weighted filtering and with the use of various types of subgrid-scale models provides good calculation accuracy for different problems for compressible fluid in the absence of discontinuities, associated with the appearance of shocks, in other words, when the value of the Mach number is low or moderate (that is, the flow is subsonic). For supersonic magnetohydrodynamic flows, it is necessary to use special numerical methods.
Monte Carlo study of apparent magnetoresistance mobility in nanometer scale metal oxide semiconductor field effect transistors
Authors: Huet Karim , Querlioz Damien , Chaisantikulwat Wipa , Saint-Martin Jérôme , Bournel Arnaud , Mouis Mireille , Dollfus Philippe
Published: August 2008

This paper investigates the mobility extraction from channel magnetoresistance, which is widespreading as a powerful experimental method to study transport in short gate devices. A fully self-consistent Monte Carlo device simulator is used to simulate the influence of a transverse magnetic field on electron transport in nanometer scale devices. After validation on a simple silicon magnetic sensor, the method is applied to the simulation of the channel magnetoresistance of nanoscale double gate metal oxide semiconductor field effect transistors. Apparent magnetoresistance mobilities μMR are extracted from channel resistance variation with the applied magnetic field, using a measurement-inspired extraction method. The simulated temperature trends obtained by simulation are consistent with experimental data. As experimentally observed elsewhere, the extracted apparent mobility decreases with the shrinking of the channel length. No additional scattering mechanism specific to short channel devices was needed to observe this effect. This apparent mobility reduction observed in the simulated results is shown to originate from nonstationary transport, which is discussed and interpreted using simple numerical calculations. We propose a Mathiessen-like formalism in order to quantify this effect. Finally, ballistic transport is shown to have a significant impact on the apparent mobility extraction and must be taken into account if the apparent magnetoresistance mobility is to be used as a figure of merit to assess short device performance.
Annealing effect on the chemical structure of diamondlike carbon
Authors: Takabayashi Susumu , Okamoto Keishi , Sakaue Hiroyuki , Takahagi Takayuki , Shimada Kenya , Nakatani Tatsuyuki
Published: August 2008

The effect of annealing in an ultrahigh vacuum on the chemical structure of diamondlike carbon (DLC) was investigated using photoelectron spectroscopy, thermal desorption spectroscopy, electrical resistivity, and micro-Raman spectroscopy measurements. The line shapes of the C 1s photoelectron spectra depended on annealing temperature. The relative intensities of four chemical components in the spectra were quantitatively evaluated: sp3 carbon with carbon-carbon bonds (C–C sp3 carbon), sp2 carbon with carbon-carbon bonds (C–C sp2 carbon), sp2 carbon with hydrogen-carbon bonds (H–C sp2 carbon), and sp3 carbon with hydrogen-carbon bonds (H–C sp3 carbon). The variation of the ratio of the components demonstrated that hydrogen in DLC is emitted to the outside in between 450 and 600 °C, and the remaining DLC is graphized above 600 °C. The increase in the asymmetry of the C 1s spectra and the decrease in the electrical resistivity of the DLC film with annealing temperature agree with the picture that the H–C bonds in DLC produces large free spaces in the structure, which inhibit conductive routes and lead to high electrical resistivity.
Orbital-free effective embedding potential at nuclear cusps
Authors: Lastra Juan Maria Garcia , Kaminski Jakub W. , Wesolowski Tomasz A.
Published: August 2008

A strategy to construct approximants to the kinetic-energy-functional dependent component (vt[ρA,ρB](r⃗)) of the effective potential in one-electron equations for orbitals embedded in a frozen-density environment [Eqs. (20) and (21) in Wesolowski and Warshel, J. Phys. Chem. 97, (1993) 8050] is proposed. In order to improve the local behavior of the orbital-free effective embedding potential near nuclei in the environment, the exact behavior of vt[ρA,ρB](r⃗) at ρA→0 and ∫ρBdr⃗=2 is taken into account. As a result, the properties depending on the quality of this potential are invariably improved compared to the ones obtained using conventional approximants which violated the considered exact condition. The approximants obtained following the proposed strategy and especially the simplest one constructed in this work are nondecomposable, i.e., cannot be used to obtain the analytic expression for the functional of the total kinetic energy.
A study of terahertz quantum cascade lasers: Experiment versus simulation
Authors: Li H. , Cao J. C. , Han Y. J. , Guo X. G. , Tan Z. Y. , Lü J. T. , Luo H. , Laframboise S. R. , Liu H. C.
Published: August 2008

The authors present the testing method and electrical and optical characteristics of a 4.1 THz quantum cascade laser with a four-well resonant-phonon design. The mode evolution in pulsed and continuous wave modes as a function of drive current has been investigated. An ensemble Monte Carlo model is used to analyze the carrier transport and output characteristics of the device. The calculated current density, lasing domain, and lasing frequency as a function of electric field are consistent with the measured results.
Hydrodynamic loads during early stage of flat plate impact onto water surface
Authors: Iafrati Alessandro , Korobkin Alexander A.
Published: August 2008

The hydrodynamic loads during the water entry of a flat plate are investigated. Initially the water is at rest and the plate is floating on the water surface. Then the plate starts suddenly its vertical motion. The analysis is focused on the early stage during which the highest hydrodynamic loads are generated. The liquid is assumed ideal and incompressible; gravity and surface tension effects are not taken into account. The flow generated by the impact is two dimensional and potential. The penetration depth is either a given function of time or calculated by using the equation of the body motion. A theoretical estimate of the loads during the early stage of the water impact is derived with the help of the method of matched asymptotic expansions. The ratio of the plate displacement to the plate half-width plays the role of a small parameter. The second-order uniformly valid solution of the problem is derived. In order to evaluate the hydrodynamic loads, the second-order pressure distribution is asymptotically integrated along the plate. It is shown that the initial asymptotics of the loads involve a logarithmic term and a negative noninteger power of the nondimensional plate displacement, the latter contribution is related to the inner solution. In addition to the theoretical estimate, a numerical model of the unsteady free-surface flow generated by plate impact is developed. The hydrodynamic loads are numerically evaluated and compared to their asymptotic estimates. A fairly good agreement between the theoretical and numerical predictions of the hydrodynamic loads just after the impact has been found. In the case of constant velocity of the body, it is shown that the relative difference between the theoretical and numerical predictions of the hydrodynamic force is less than 5% when the nondimensional plate displacement is one-fifth and rises to 20% when the nondimensional plate displacement is equal to unity. Similar results are found in the free fall case when the comparison is established in terms of hydrodynamic loads. The theoretical and numerical predictions are remarkably close to each other, even for moderate displacements of the plate, if the comparison is established in terms of the entry velocity.
Solvation thermodynamics of alkali and halide ions in ionic liquids through integral equations
Authors: Bruzzone Samantha , Malvaldi Marco , Chiappe Cinzia
Published: August 2008

In this work, we study the solvation thermodynamics and other solvation properties of small ions in two room-temperature ionic liquids, dimethyl imidazolium hexafluorophosphate [mmim] [pf6] and dimethyl imidazolium chloride [mmim][cl] with the reference interaction site model (RISM). The nature of the charge affects several aspects of solvation, from electrostriction to the mutual disposition of cations around the solute; nevertheless, the long-range screening behavior of the liquid appears to be insensitive to both charge and dimensions of the solute. The ion solvation is energy driven, as expected for the nature of the solvent, and displays a marked asymmetry between cation and anion solvation chemical potential. Such asymmetry is dependent, even qualitatively, on the ionic liquid chosen as solvent. Partial molar volumes of ions in solution are found to follow the nature of ion-solvent interaction.