bluuebunny/crossref_metadata_2025 huggingface dataset:
BJ-HCC-20, a potential novel cancer-testis antigen
Authors: Dong Xue-Yuan , Li Yun-Yan , Yang Xiao-Ang , Chen Wei-Feng
Published: October 2004

In an effort to identify novel Cancer-Testis genes, we analyzed the sequence in the q26-28 region of human X chromosome by several on-line tools. The candidate sequences were then confirmed by experiments. We have obtained a novel Cancer-Testis gene, BJ-HCC-20. In vivo, it was found to have two isoforms. In samples of liver, colon, gastric and lung cancer tested, the expression frequency of BJ-HCC-20 is 25%, 17%, 21% and 15%, respectively. Full-length cDNAs of both BJ-HCC-20 isoforms were isolated and their gene structures and promoter regions were characterized. BJ-HCC-20 might have implications in theoretical and practical tumor biology.Key words: X chromosome analysis, CT gene, tumor immunotherapy.
Induction of G1 cell cycle arrest in human umbilical vein endothelial cells by flavone's inhibition of the extracellular signal regulated kinase cascade
Authors: Arakaki Naokatu , Toyofuku Ayako , Emoto Yuka , Nagao Tomoko , Kuramoto Yoshinori , Shibata Hirofumi , Higuti Tomihiko
Published: October 2004

Dietary flavonoids have demonstrated anti-carcinogenic activity in several animal models, but their mechanisms of action have not yet been clearly established. Here, we show that flavone, a parent compound of flavonoids, inhibits the proliferation, migration, and capillary tube formation of human umbilical vein endothelial cells (HUVECs). Flow cytometric analysis showed that flavone arrests the cell cycle progression at G1 phase in HUVECs. We observed the down-regulation of the hyperphosphorylated form of retinoblastoma gene product and cyclin-dependent kinases 2 and 4 in flavone-treated cells, but it had no affect on the expression of p53 and cyclin-dependent kinase inhibitors p21CIP/Waf1 and p27Kip. Flavone almost completely inhibited the activation of extracellular signal regulated kinase 1. The present results suggest that the flavone moiety of flavonoids is required for anti-proliferative activity of flavonoids and that anti-carcinogenic action of flavonoids in vivo was mediated, at least in part, by inhibiting angiogenesis.Key words: flavone, angiogenesis, human umbilical vein endothelial cells (HUVECs), cell cycle, retinoblastoma gene product (Rb), ERK.
Seismic cone penetration test and seismic tomography in permafrost
Authors: LeBlanc Anne-Marie , Fortier Richard , Allard Michel , Cosma Calin , Buteau Sylvie
Published: October 2004

Two high-resolution multi-offset vertical seismic profile (VSP) surveys were carried out in a permafrost mound near Umiujaq in northern Quebec, Canada, while performing seismic cone penetration tests (SCPT) to study the cryostratigraphy and assess the body waves velocities and the dynamic properties of warm permafrost. Penetrometer-mounted triaxial accelerometers were used as the VSP receivers, and a swept impact seismic technique (SIST) source generating both compressional and shear waves was moved near the surface following a cross configuration of 40 seismic shot-point locations surrounding each of the two SCPTs. The inversion of travel times based on a simultaneous iterative reconstruction technique (SIRT) provided tomographic images of the distribution of seismic velocities in permafrost. The Young's and shear moduli at low strains were then calculated from the seismic velocities and the permafrost density measured on core samples. The combination of multi-offset VSP survey, SCPT, SIST, and SIRT for tomographic imaging led to new insights in the dynamic properties of permafrost at temperatures close to 0 °C. The P- and S-wave velocities in permafrost vary from 2400 to 3200 m/s and from 900 to 1750 m/s, respectively, for a temperature range between 0.2 and 2.0 °C. The Young's modulus varies from 2.15 to 13.65 GPa, and the shear modulus varies from 1.00 to 4.75 GPa over the same range of temperature.Key words: permafrost, seismic cone penetration test, vertical seismic profiling, seismic tomography, dynamic properties.
METHOD OF QUANTITATIVE ANALYSIS OF FLUORINE IN ENVIRONMENTAL SAMPLES USING A PURE-Ge DETECTOR
Authors: SERA K. , TERASAKI K. , SAITOH Y. , ITOH J. , FUTATSUGAWA S. , MURAO S. , SAKURAI S.
Published: October 2004

We recently developed and reported a three-detector measuring system making use of a pure-Ge detector combined with two Si ( Li ) detectors. The efficiency curve of the pure-Ge detector was determined as relative efficiencies to those of the existing Si ( Li ) detectors and accuracy of it was confirmed by analyzing a few samples whose elemental concentrations were known. It was found that detection of fluorine becomes possible by analyzing prompt γ-rays and the detection limit was found to be less than 0.1 ppm for water samples. In this work, a method of quantitative analysis of fluorine has been established in order to investigate environmental contamination by fluorine. This method is based on the fact that both characteristic x-rays from many elements and 110 keV prompt γ-rays from fluorine can be detected in the same spectrum. The present method is applied to analyses of a few environmental samples such as tealeaves, feed for domestic animals and human bone. The results are consistent with those obtained by other methods and it is found that the present method is quite useful and convenient for investigation studies on regional pollution by fluorine.
MAPPING OF HEAVY METALS ACCUMULATED IN PLANTS USING A SUBMILLI-PIXE CAMERA
Authors: WATANABE R. , HARA J. , INOUE C. , CHIDA T. , AMARTAIVAN TS. , MATSUYAMA S. , YAMAZAKI H. , ISHII K.
Published: October 2004

Phytoremediation is a technology for remediation of contaminated soils. In this study, we used a submilli-PIXE camera to analyze plants and soils from a shooting range. Some heavy metals were rapidly and easily detected in these samples. Element dot-maps of the plant show Cu and Pb accumulated in the epidermis of subterranean stems and the venation of leaves. From these findings, it is possible to map the distribution of heavy metals and to detail their location in the plant, using the submilli-PIXE camera. PIXE analysis is an effective tool for undertaking phytoremediation research.
A COMBINATION OF REPLICA EXCHANGE MONTE CARLO AND ENERGY LANDSCAPE PAVING ALGORITHMS TO INCREASE THE EFFECTIVENESS OF CONFORMATIONAL SAMPLING
Authors: ARKIN HANDAN
Published: October 2004

A combination of replica exchange Monte Carlo sampling techniques and energy landscape paving approach is presented. This hybrid algorithm combines the features of the energy landscape paving (ELP) and replica exchange methods (REM). I have tested its performance in studying the low-energy conformations of the benchmark peptide Met-enkephalin.
THE KRAUSE–HEGSELMANN CONSENSUS MODEL WITH DISCRETE OPINIONS
Authors: FORTUNATO SANTO
Published: October 2004

The consensus model of Krause and Hegselmann can be naturally extended to the case in which opinions are integer instead of real numbers. Our algorithm is much faster than the original version and thus more suitable for applications. For the case of a society in which everybody can talk to everybody else, we find that the chance to reach consensus is much higher as compared to other models; if the number of possible opinions Q≤7, in fact, consensus is always reached, which might explain the stability of political coalitions with more than three or four parties. For Q>7 the number S of surviving opinions is approximately the same, independent of the size N of the population, as long as Q<N. We considered as well the more realistic case of a society structured like a Barabási–Albert network; here the consensus threshold depends on the out-degree of the nodes and we find a simple scaling law for S, as observed for the discretized Deffuant model.
EFFECTS OF AGING AND LINKS REMOVAL ON EPIDEMIC DYNAMICS IN SCALE-FREE NETWORKS
Authors: CHAN K. P. , ZHENG DAFANG , HUI P. M.
Published: October 2004

We study the combined effects of aging and links removal on epidemic dynamics in the Barabási–Albert scale-free networks. The epidemic is described by a susceptible-infected-refractory (SIR) model. The aging effect of a node introduced at time ti is described by an aging factor of the form (t-ti)-β in the probability of being connected to newly added nodes in a growing network under the preferential attachment scheme based on popularity of the existing nodes. SIR dynamics is studied in networks with a fraction 1-p of the links removed. Extensive numerical simulations reveal that there exists a threshold pc such that for p≥pc, epidemic breaks out in the network. For p<pc, only a local spread results. The dependence of pc on β is studied in detail. The function pc(β) separates the space formed by β and p into regions corresponding to local and global spreads, respectively.
ELECTRON CORRELATION EFFECTS FOR DOUBLY-EXCITED STATES OF Be-LIKE Ar14+ ION
Authors: GOU BINGCONG , LIU YIDONG , WANG FENG
Published: October 2004

The energies, radiative and Auger rates of the doubly excited states of Be-like Ar 14+ ion are studied by using the multi-configuration-interaction method and model potential method. The doubly excited states of Be-like Ar 14+ are labeled by the quantum numbers K, T and A to show the systematic regularity. The results show that the spectroscopy of Be-like ions is different from that of He-like ions because of the polarization and core penetration effects from the 1s2 core electrons.
COMPLEX NETWORK PROPERTIES OF CHINESE POWER GRID
Authors: XU TIAN , CHEN JIE , HE YUE , HE DA-REN
Published: October 2004

This article reports a statistical investigation on Chinese power grid. A new statistical parameter, averaged ratio of cycles, is suggested for describing the stratum structure of the grid. A dynamical model, which may reproduce the developing process of Chinese power grid, is also presented.
AN ALGORITHM OF CONSTRUCTING THE CONSERVATION LAWS OF NONLINEAR EVOLUTION EQUATIONS
Authors: YAO RUO-XIA , LI ZHI-BIN
Published: October 2004

An algorithm of constructing the polynomial type conservation laws of nonlinear evolution equations (either parameterized or non-parameterized) is described and a Maple package [Formula: see text] to automate the computation is presented. For parameterized equation(s), [Formula: see text] can determine the parameters constraints automatically such that a sequence of conservation laws exist.
TESTING FOR NONLINEARITY IN SHANGHAI STOCK MARKET
Authors: WANG HAIYAN , TANG LONGKUN
Published: October 2004

In this paper, we apply IAAFT to generate surrogate time series of measured multivariate time series. A quantitative method to detect nonlinearity in multivariate time series is proposed using the generalized redundancy and linear redundancy as the significance test statistic. The null hypothesis of a multivariate linear Gaussian random process is tested using the multivariate surrogate data. The validity of this method is demonstrated using two types models (linear and nonlinear) and applied to Shanghai stock market.
CHAOTIC ANALYSES FOR SPACE SERIES OF GOLD GRADE
Authors: XIE YAN-SHI , CHEN GUANG-HAO , TAN KAI-XUAN
Published: October 2004

A new powerful tool, chaotic theory, has been used to study mineralization through chaotic analysis for space series of gold grade in this paper. Both of the most important chaotic measures, Largest Lyapunov exponent (LLE) and fractal dimensional, for space series of gold grade in one gold deposit are computed. The positive LLE suggests that the space series of gold grade are chaotic series. When the phase space dimension approach 8~10, a chaotic attractor appears and their fractal dimension values vary from 1.94 to 3.99. It indicates that the evolution of ore-forming fluid and the enrichment and deposition of gold element are chaotic dynamic process.
INDUCED DEFECTS IN a-Si:H/a-SiNx:H MULTILAYERS BY USE OF A POSITRON ANNIHILATION TECHNIQUE
Authors: CAO GUO-RONG , GUO SHENG-KANG , WANG ZHI-CHAO , TENG MIN-KANG , CHEN CAI , LIU YIN-CHUN
Published: October 2004

In a - Si : H / a - SiN x: H multilayers, in addition to induced distortions, there are a large number of induced defects in the interface regions between a-Si:H and a - SiN x: H due to structural mismatch. In this experiment, we measured a series of a - Si : H / a - SiN x: H (x= 0.5) multilayers by the positron annihilation technique (PAT) and, on the basis of the measured results, present a structural model of the sublayers in the multilayer. Using this model, we have obtained theoretically the relative positron annihilation intensity I2 values of multilayers. The calculated values are in good agreement with the measured values. By this experiment, it is confirmed that the interface region structures on both sides of the sublayers are asymmetric and related to the growing direction of the film. Moreover, the following information in the a-Si:H sublayer is gained: There are a larger number of induced defects in the interface region away from the substrate, but few or no in the interface region near the substrate; The induced defects in the interface region are situated in the subregion not close to the interface but at a little distance, about 8 Å, from the interface, the thickness of the subregion is about 50 Å. The induced defect density in the subregion is estimated to be about 1011/ cm 3.
q-DEFORMED PHONONS
Authors: SWAMY P. NARAYANA
Published: October 2004

We make use of a recently identified distribution function for the q-deformed oscillators and apply it to the q-analog of phonons. The thermodynamic properties of such q-phonons and q-photons are derived and compared with the case of ordinary phonons.
OBSERVATION OF A LINEAR REGIME IN IMAGINARY χac OF Bi-2223 SUPERCONDUCTOR
Authors: RANI T. SOBHA , RAJARAM G.
Published: October 2004

Measurements of complex AC susceptibility were performed on Bi-2223/Bi-2212 high Tc superconductor at low excitation field amplitudes. Unusual features attributable to the Bi-2223 phase are observed in the imaginary part of the AC susceptibility, χ″(T), at different excitation field amplitudes, H m . The peak temperature, T p as a function of H m defines a region in (H, T) plane, where χ″ is independent of H m . Various possible interpretations are discussed, including that of a transition to a viscous flux flow regime.
ELECTRON DENSITY DETERMINATION OF LASER INDUCED PLASMA FROM POLYMETHYL METHACRYLATE USING PHASESHIFT DETECTION TECHNIQUE
Authors: VARIER GEETHA K. , HARILAL S.S. , BINDHU C.V. , ISSAC RIJU C. , NAMPOORI V.P.N. , VALLABHAN C.P.G.
Published: October 2004

Irradiation of a Polymethyl methacrylate target using a pulsed Nd-YAG laser causes plasma formation in the vicinity of the target. The refractive index gradient due to the presence of the plasma is probed using phase-shift detection technique. The phase-shift technique is a simple but sensitive technique for the determination of laser ablation threshold of solids. The number density of laser generated plasma above the ablation threshold from Polymethyl methacrylate is calculated as a function of laser fluence. The number density varies from 2×1016 cm −3 to 2×1017 cm −3 in the fluence interval 2.8−13 J · cm –2.
A SIMPLE AND ANALYTICAL STRUCTURE FACTOR FOR THE HARD-DISC FLUID
Authors: STUDART NELSON , DA SILVEIRA HAMILTON V. , DE FREITAS UMBELINO
Published: October 2004

We present an analytical expression for the static structure factor of hard-disc fluids by using the density–density response function in the mean-field-type approximation in which the effective potential between the particles is written in terms of the pair correlation function as proposed by Singwi, Tosi, Land and Sjölander. The structure factor exhibits the main features of the hard-disc system as compared with other theories and computer simulations at low and intermediate values of the packing fraction.
UPPER AND LOWER BOUNDS ON THE PARTITION FUNCTION OF THE HOFSTADTER MODEL
Authors: MOROZ ALEXANDER
Published: October 2004

Using unitary equivalence of magnetic translation operators, explicit upper and lower convex bounds on the partition function of the Hofstadter model are given for any rational “flux” and any value of Bloch momenta. These bounds (i) generalise straightforwardly to the case of a general asymmetric hopping and to the case of hopping of the form [Formula: see text] with n arbitrary integer larger than or equal 2, and (ii) allow to derive bounds on the derivatives of the partition function.
DENSITY OF STATES AND ORDER PARAMETER IN DIRTY SUPERCONDUCTORS WITH A WEAKLY BROKEN d-WAVE SYMMETRY
Authors: POKROVSKY SERGEI V.
Published: October 2004

It is shown by direct calculations that in a superconductor with a slightly violated d-wave symmetry of the order parameter (OP) the impurity driven phase transition from the gapless superconductivity to a state with a finite gap takes place at zero temperature. The corresponding scattering rate is close to the value at which the superconductivity vanishes in the d-superconductor. The behavior of the transition temperature, the OP and the density of states (DOS) is analyzed. The model is plausibly relevant to the BSCCO 2:2:1:2.
SYNTHESIS, CHARACTERISATION AND HIGH PRESSURE STUDIES OF Yb0.8Sr0.2Ba2Cu3O7−y SUPERCONDUCTOR
Authors: SEKAR A. , SARAVANAN V. , JAYA N. VICTOR , JEYABALAN K. , KALIYAPERUMAL L.K.
Published: October 2004

The superconducting compound Yb 0.8 Sr 0.2 Ba 2 Cu 3O7−y is synthesised, characterised and Tc measurements are made. It crystallises in a tetragonal cell with the lattice parameters a=3.813(6) Å, b=3.813(6) Å and c=11.705(4) Å. The compound exhibits superconductivity with a transition temperature of 68 K. High pressure electrical resistivity studies are performed upto 80 kbar using Bridgman opposed anvil high pressure device. The compound exhibits metallic behaviour and no phase transition is observed upto 80 kbar.
ON THE INTERATOMIC CORRELATIONS AND MEAN SQUARE RELATIVE ATOMIC DISPLACEMENTS IN AN ANHARMONIC SIMPLE CUBIC LATTICE
Authors: PASCUAL M.F. , ROSA A.L. , ZUBOV V.I.
Published: October 2004

In order to study the interatomic correlation moments (QCM) and the mean square relative atomic displacements (MSRD), there has been employed the correlative method of unsymmetrized self-consistent field (CUSF). In the second order of CUSF we have calculated the longitudinal and transversal components of QCM and MSRD between the nearest, second and fourth neighbors, in the simple cubic lattice. The results are discussed in relation to those obtained previously for low-dimensional models.
NORMAL STATE MAGNETISM OF Zn-DOPED AND OXYGEN DEFICIENT CaLaBaCu3O7 SUPERCONDUCTOR
Authors: AWANA V.P.S. , LANDINEZ D.A. , FERREIRA J.M. , AGUIAR J. ALBINO , SINGH RAJVIR , NARLIKAR A.V.
Published: October 2004

Both on-site Zn substitution and oxygen deficiencies in the CaLaBaCu 3 O 7 system decrease the superconducting transition temperature T c of the pristine sample. We observed that the normal state magnetism, measured in a field of 5 KOe, shows a Curie-Weiss behavior, in terms of a localized magnetic moment, presumably on Cu sites, in both cases. The pristine system, i.e. without Zn substitution or oxygen deficiencies, shows a weakly temperature dependent small magnetic susceptibility, in the normal state, i.e. above T c . It has been argued that the normal state magnetism of HTSC systems plays a vital role in determining the T c of these materials.
STUDY OF SCALING IN THE FRACTIONAL QUANTUM HALL EFFECT
Authors: XIE X.C. , LIU D.Z. , JAIN J.K.
Published: October 2004

In the composite fermion model of the fractional quantum Hall effect, composite fermions experience, in addition to the usual potential disorder, also a magnetic flux disorder. Motivated by this, we investigate the localization properties of a single fermion in two dimensions, moving in the presence of both static potential and static magnetic flux disorders, but with a non-zero average magnetic field. It is found that the exponent characterizing the divergence of the localization length is not changed upon the addition of the flux disorder, provided it is not too large.
PRESSURE COEFFICIENT OF THE SUPERCONDUCTING TRANSITION TEMPERATURE IN THE STRONG COUPLING LIMIT
Authors: BASU S. , SARKAR SUJIT , SIL S.
Published: October 2004

Pressure coefficient (β) of the superconducting transition temperature (T c ) for a two dimensional system is studied in presence of Coulomb interaction, using Eliashberg equation with the Einstein approximation for the phonon system, within the van Hove scenario. β is found to be high in the low-T c region and low in the high-T c region. β is positive in the underdoped region and becomes negative in the overdoped region. For a given value of Fermi energy, β increases in the underdoped region and decreases in the overdoped region with the increase of Coulomb repulsion.
A VARIATIONAL STUDY OF FERMI AND LUTTINGER LIQUID WAVEFUNCTIONS IN THE TWO-DIMENSIONAL t-J MODEL
Authors: FRANJIĆ FRANJO , SORELLA SANDRO
Published: October 2004

Using a recently developed technique, we determine the Jastrow potential of the variational wavefunction for the two-dimensional t-J model. This wavefunction describes a Fermi liquid ground state and is compared with the Luttinger liquid wavefunction used by Gros and Valentí. Estimates of the energy of these states are calculated using the variational Monte Carlo technique, showing that the Fermi liquid state has a little power energy.
NONEQUILIBRIUM THERMODYNAMICS OF JOSEPHSON DEVICES
Authors: VAN DEN BRINK ALEC MAASSEN , DEKKER H.
Published: October 2004

The rapid increase of the Josephson free energy as the temperature of a tunneling junction drops below the superconducting transition temperature T c is shown to make this transition of first order in a system in which the phase difference ϕ across the junction is constrained to have a nonzero value. Taking this effect into account, we introduce an availability potential governing the nonisothermal dynamics of the junction which, in contrast with previous results, has no artifacts like latent heat being released upon entering the — high temperature — normal state or a value in this state which depends on the — superconducting — phase difference. The thermodynamic analysis is preceded by a detailed calculation of the Josephson coupling in a model of two ideal BCS superconductors coupled by a tunneling Hamiltonian.
HEAT-TREATMENT INFLUENCE ON THE MAGNETIC AND ELECTRIC PROPERTIES OF HIGH-TcYBa2Cu3O7−δ SUPERCONDUCTOR
Authors: HOMORODEAN LAUREAN , POP IULIU , BURDOI ION
Published: October 2004

The changes in the temperature dependences of the magnetic susceptibility and the electrical resistivity of a very-high-T c superconducting YBa 2 Cu 3 O 7−δ sample during the thermal cycling between the liquid-nitrogen temperature and the room temperature are studied. Some singularities corresponding to the superconducting transition, the possible existence of a super-high-temperature superconducting phase and the migration of the oxygen atoms in the Cu-O chains are emphasized on these dependencies.
STRUCTURE AND DYNAMICS OF THE Al(110) SURFACE: A MOLECULAR DYNAMICS STUDY
Authors: SCHOMMERS W.
Published: October 2004

In this article we report on molecular dynamics calculations of Al (110) surfaces using a temperature-dependent pair potential. The pair correlation function as well as the mean-square displacements as a function of time have been investigated within a wide temperature range. The main qualitative trends and results agree well with experimental data. Comparison is made with the corresponding bulk data.
FOCK SPACE FOR GENERALIZED STATISTICS AND BOSON-FERMION SUPERSELECTION RULE
Authors: FALCO L. DE , MIGNANI R. , SCIPIONI R.
Published: October 2004

We introduce a generalized Fock space for a recently proposed operatorial deformation of the Heisenberg-Weyl (HW) algebra, aimed at describing statistics different from the Bose or Fermi ones. The new Fock space is obtained by the tensor product of the usual Fock space and the space spanned by the eigenstates of the deformation operator ĝ. We prove a “statistical Ehrenfest-like theorem”, stating that the expectation values of the ladder operators of the generalized HW algebra — taken in the ĝ-subspace — are creation and annihilation operators defined in the usual Fock space and obeying the ordinary statistics, according to the ĝ-eigenvalues. Moreover, such a “statistics” operator ĝ can be regarded as the generator of a boson-fermion superselection rule. As a consequence, the generalized Fock space decomposes into incoherent sectors, and therefore one gets a density matrix diagonal in the ĝ eigenstates. This leads, under suitable conditions, to the possibility of continuously interpolating between different statistics. In particular, it is necessary to assume a nonstandard Liouville-Von Neumann equation for the density matrix, of the type already considered e.g. in the framework of quantum gravity. It is also preliminarily shown that our formalism leads in a natural way — due to the very properties of the operator ĝ — to a grading of the HW algebra, and therefore to a supersymmetrical scheme.
NUMERICAL APPLICATION OF THE RECURSION METHOD TO THE ELECTRONIC STRUCTURE OF C60
Authors: LU JING , ZHANG LIYUAN
Published: October 2004

The recursion method is applied to study the electronic structure of a neutral C 60 molecule by numerically computing the density of states (DOS). A tight-binding Hamiltonian which considers the s and p valence electrons of carbon is used, and the coupling between orbitals is described by Harrison’s hopping formula. We obtain the overall molecular energy spectrum. The sequence orders and the degeneracies of π state levels, obtained when considering a mixture of the orbitals, agree well with those from the analytical method. We find that the inclusion of a nonzero next-nearest-neighbor hopping and even the inclusion of a nonzero next-next-nearest-neighbor hopping do not destroy icosahedral symmetry.
TIME-INDEPENDENT APPROACH FOR DISSIPATIVE SYSTEMS
Authors: LÓPEZ G. , MURGUÍA M. , SOSA M.
Published: October 2004

A new dissipative model is proposed for the small component of a mixture of a small and large component of gases, where the large component is treated as an ideal gas. The thermodynamic characteristics of the gas are derived through a statistical mechanical approach. The model requires for the small component to have a big dimension and its number of particles to be smaller than the large one. Using the associated partition function, the internal energy and the equation of state are calculated. The internal energy does not suffer any deviation from that of the two component ideal gas, but the equation of state deviates from that of the ideal gas for large values of the parameter which characterizes the dissipative model.
EXACT n-SPINON DYNAMIC STRUCTURE FACTOR OF THE HEISENBERG MODEL
Authors: BOUGOURZI A.H.
Published: October 2004

Using the spinon picture we derive an integral representation for the exact n-spinon dynamic structure factor of the spin-1/2 Heisenberg model.
INFLUENCE OF ELECTRON TEMPERATURE ON POPULATION INVERSION AMONG ELECTRONIC SUBBANDS IN OPTICALLY PUMPED SEMICONDUCTOR QUANTUM WELLS
Authors: XU W. , ZHANG C.
Published: October 2004

A detailed theoretical study on population inversion among different electronic subbands, induced by hot-electron interactions with LO-phonons and with photons, is presented for an optically pumped AlGaAs-GaAs double quantum well system which may behave as a 3-level far-infrared laser generator. The influence of electron temperature and pumping intensity on the population inversion in this laser system proposed very recently, has been studied through calculating the inter-subband electronic scattering rate caused by electron-LO-phonon interactions and by optical absorption scattering. Theoretical results obtained from this study indicate that at a fixed pumping intensity, the population inversion among different electronic subbands can be tuned by varying electron temperature through, e.g. applying an in-plane electric field.
A METHOD OF DESCRIPTION OF MAGNETIC OSCILLATIONS IN MESOSCOPIC SYSTEMS
Authors: WALCERZ STANISLAW
Published: October 2004

A model for calculation of magnetic properties of small planar systems is proposed. The model combines the Onsager theory of de Haas-van Alphen oscillations with the magnetic translation group approach. The proposed model suggests a method for both theoretical and experimental investigation of magnetic properties of mesoscale systems.
COUPLING CONSTANT AND MAGNON VELOCITY FOR A TWO-DIMENSIONAL QUANTUM HEISENBERG ANTIFERROMAGNET: THE CONTINUUM LIMIT
Authors: VILLAIN-GUILLOT SIMON , DANDOLOFF ROSSEN
Published: October 2004

We study Heisenberg spins on an infinite plane. Following an approach developed by Affleck, we find that the Heisenberg Hamiltonian is equivalent in the continuum limit to the nonlinear σ model. And we show that the auxiliary fields, which appear because of the conservation of the number of degrees of freedom, are related to the covariant derivatives of the order parameter. These auxiliary fields have to be taken into account in order to recover the expected values for the coupling constant and magnon velocity in two-dimensions.
BIFURCATION STRUCTURE AND PERIODIC ORBITS OF THE LORENZ EQUATIONS IN THE PRANDTL NUMBER SPACE
Authors: LAI C. H. , ZHOU C. T. , YU M. Y.
Published: October 2004

The bifurcation structure and periodic orbits of the Lorenz system with the Prandt1 number as the control parameter are investigated. It is shown that new bifurcation phenomena, both positive (forward) and inverse (backward) bifurcations, which do not appear together in the Rayleigh number space, can appear. The orbit characteristics in typical periodic windows are also studied.
MAGNETORESISTANCE AND ELECTRICAL NOISE IN THE SILVER CHALCOGENIDE Ag2Te
Authors: JIANG L. , NOWAK E. R.
Published: October 2004

The relatively large and linear magnetoresistance found in nonstoichiometric silver chalcogenides makes them attractive candidates for studying the mechanisms of linear magnetoresistance and for field sensing applications. After a brief review of the magnetoresistive properties of these materials, we report on the intrinsic electrical noise in bulk, polycrystalline Ag 2+δ Te . Low-frequency noise is due to resistance fluctuations having a 1/f-like power spectrum. The temperature dependence of the noise magnitude and its spectral slope indicate thermally activated kinetics which we attribute to some form of charge trapping-detrapping process occurring in or near the intergranular regions. The effective magnetic field noise in Ag 2+δ Te is also compared to other materials systems used in field sensing applications.
ENTANGLEMENT DEGRADATION IN A STRING OF ATOMS COUPLED BY THE ELECTROMAGNETIC FIELD
Authors: FÖLDI PÉTER , BENEDICT MIHÁLY G. , SERÉNYI TAMÁS , CZIRJÁK ATTILA
Published: October 2004

We investigate the dynamics of short linear chains consisting of two-level systems (atoms) coupled by the electromagnetic field. The environment of photon modes acts as a source of noise and leads to the disappearance of the initially present multipartite entanglement. The rate of this process (entanglement degradation) depends on the separation of the atoms, and also on the initial state. With the aid of the appropriate entanglement witnesses we show that this rate is exceptionally low for the so-called subradiant states. Below one resonant wavelength of atomic separation the effect of the environmental noise is weaker than the dipole-dipole interaction and multipartite entanglement can be formed in the initial stage of the time evolution.
Creatine feeding increases GLUT4 expression in rat skeletal muscle
Authors: Ju Jeong-Sun , Smith Jill L. , Oppelt Peter J. , Fisher Jonathan S.
Published: October 2004

The purpose of this study was to investigate the potential role of creatine in GLUT4 gene expression in rat skeletal muscle. Female Wistar rats were fed normal rat chow (controls) or chow containing 2% creatine monohydrate ad libitum for 3 wk. GLUT4 protein levels of creatine-fed rats were significantly increased in extensor digitorum longus (EDL), triceps, and epitrochlearis muscles compared with muscles from controls ( P < 0.05), and triceps GLUT4 mRNA levels were ∼100% greater in triceps muscles from creatine-fed rats than in muscles from controls ( P < 0.05). In epitrochlearis muscles from creatine-fed animals, glycogen content was ∼40% greater ( P < 0.05), and insulin-stimulated glucose transport rates were higher ( P < 0.05) than in epitrochlearis muscles from controls. Despite no changes in [ATP], [creatine], [phosphocreatine], or [AMP], creatine feeding increased AMP-activated protein kinase (AMPK) phosphorylation by 50% in rat EDL muscle ( P < 0.05). Creatinine content of EDL muscle was almost twofold higher for creatine-fed animals than for controls ( P < 0.05). Creatine feeding increased protein levels of myocyte enhancer factor 2 (MEF2) isoforms MEF2A (∼70%, P < 0.05), MEF2C (∼60%, P < 0.05), and MEF2D (∼90%, P < 0.05), which are transcription factors that regulate GLUT4 expression, in creatine-fed rat EDL muscle nuclear extracts. Electrophoretic mobility shift assay showed that DNA binding activity of MEF2 was increased by ∼40% ( P < 0.05) in creatine-fed rat EDL compared with controls. Our data suggest that creatine feeding enhances the nuclear content and DNA binding activity of MEF2 isoforms, which is concomitant with an increase in GLUT4 gene expression.
Expression and activity of steroid aldoketoreductases 1C in omental adipose tissue are positive correlates of adiposity in women
Authors: Blouin Karine , Blanchette Sophie , Richard Christian , Dupont Pierre , Luu-The Van , Tchernof André
Published: October 2004

We examined expression and activity of steroid aldoketoreductase (AKR) 1C enzymes in adipose tissue in women. AKR1C1 (20α-hydroxysteroid dehydrogenase; 20α-HSD), AKR1C2 (3α-HSD-3), and AKR1C3 (17β-HSD-5) are involved mainly in conversion of progesterone to 20α-hydroxyprogesterone and inactivation of dihydrotestosterone to 5α-androstane-3α,17β-diol. Abdominal subcutaneous and omental adipose tissue biopsies were obtained during abdominal hysterectomies in seven women with low visceral adipose tissue (VAT) area and seven age- and total body fat mass-matched women with visceral obesity. Women with elevated VAT areas were characterized by significantly higher omental adipose tissue 20α-HSD and 3α-HSD-3 mRNA abundance compared with women with low VAT accumulations (1.4- and 1.6-fold differences, respectively; P < 0.05). Omental and subcutaneous adipose tissue 3α-HSD activities were significantly higher in women with high vs. low VAT areas ( P < 0.05 for both comparisons). Total and visceral adiposities were positively associated with omental 20α-HSD mRNA level ( r = 0.75, P < 0.003 for fat mass; r = 0.57, P < 0.04 for VAT area) and omental 3α-HSD-3 mRNA level ( r = 0.68, P < 0.01 for fat mass; r = 0.74, P < 0.003 for VAT area). Enzyme activities in both depots were also positively correlated with adiposity measures. Omental adipose tissue enzyme expression and activity were positively associated with omental adipocyte size and LPL activity. In conclusion, mRNA abundance and activity of AKR1C enzymes in abdominal adipose tissue compartments are positive correlates of adiposity in women. Increased progesterone and/or dihydrotestosterone reduction in abdominal adipose tissue may impact locally on fat cell metabolism.
Micropuncture determination of nephron function in mice without tissue angiotensin-converting enzyme
Authors: Hashimoto Seiji , Adams Jon W. , Bernstein Kenneth E. , Schnermann Jurgen
Published: October 2004

To determine the role of the local renin-angiotensin system in renal function, micropuncture was performed on two lines of mice in which genetic changes to the angiotensin-converting enzyme (ACE) gene markedly reduced or eliminated the expression of renal tissue ACE. Whereas blood pressure is low in one line (ACE 2/2), it is normal in the other (ACE 1/3) due to ectopic hepatic ACE expression. When normalized for renal size, levels of glomerular filtration rate [GFR; μl·min−1·g kidney wt−1(KW)] and single-nephron GFR (SNGFR; nl·min−1·g KW−1) were similar between wild-type (WT) and ACE 1/3 mice, while both measures were significantly reduced in ACE 2/2 mice (WT: 500 ± 63 and 41.7 ± 3.5; ACE 1/3: 515.8 ± 71 and 44.3 ± 3.3; ACE 2/2: 131.4 ± 23 and 30.3 ± 3.5). Proximal fractional reabsorption was not significantly different between WT and ACE 1/3 mice (51 ± 3.5 and 49 ± 2.3%), and it was increased significantly in ACE 2/2 mice (74 ± 3.5%). Infusion of ANG II (50 ng·kg−1·min−1) increased mean arterial pressure by ∼7 mmHg in all groups of mice and reduced SNGFR in WT and ACE 1/3 mice (to 30.9 ± 2.8 and 31.9 ± 2.5 nl·min−1·g KW−1) while increasing it in ACE 2/2 mice (to 55.3 ± 5.3 nl·min−1·g KW−1) despite an increase in total renal vascular resistance. The tubuloglomerular feedback (TGF) response was markedly reduced in ACE 1/3 mice (stop-flow pressure change −2.5 ± 0.9 mmHg) compared with WT despite similar blood pressures (−8.3 ± 0.6 mmHg). In ACE 2/2 mice, TGF was absent (−0.7 ± 0.2 mmHg). We conclude that the chronic lack of ACE, and presumably ANG II generation, in the proximal tubule was not associated with sustained proximal fluid transport defects. However, renal tissue ACE is an important contributor to TGF.
Poly(ADP-ribose) polymerase-1 gene ablation protects mice from ischemic renal injury
Authors: Zheng Jianfeng , Devalaraja-Narashimha Kishor , Singaravelu Kurinji , Padanilam Babu J.
Published: October 2004

Increased generation of reactive oxygen species (ROS) and the subsequent DNA damage and excessive activation of poly(ADP-ribose) polymerase-1 (PARP-1) have been implicated in the pathogenesis of ischemic injury. We previously demonstrated that pharmacological inhibition of PARP protects against ischemic renal injury (IRI) in rats (Martin DR, Lewington AJ, Hammerman MR, and Padanilam BJ. Am J Physiol Regul Integr Comp Physiol 279: R1834–R1840, 2000). To further define the role of PARP-1 in IRI, we tested whether genetic ablation of PARP-1 attenuates tissue injury after renal ischemia. Twenty-four hours after reperfusion following 37 min of bilateral renal pedicle occlusion, the effects of the injury on renal functions in PARP−/− and PARP+/+ mice were assessed by determining glomerular filtration rate (GFR) and the plasma levels of creatinine. The levels of plasma creatinine were decreased and GFR was augmented in PARP−/− mice. Morphological evaluation of the kidney tissues showed that the extent of damage due to the injury in PARP−/− mice was less compared with their wild-type counterparts. The levels of ROS and DNA damage were comparable in the injured kidneys of PARP+/+ and PARP−/− mice. PARP activity was induced in ischemic kidneys of PARP+/+ mice at 6–24 h postinjury. At 6, 12, and 24 h after injury, ATP levels in the PARP+/+ mice kidney declined to 28, 26, and 43%, respectively, whereas it was preserved close to normal levels in PARP−/− mice. The inflammatory cascade was attenuated in PARP−/− mice as evidenced by decreased neutrophil infiltration and attenuated expression of inflammatory molecules such as TNF-α, IL-1β, and intercellular adhesion molecule-1. At 12 h postinjury, no apoptotic cell death was observed in PARP−/− mice kidneys. However, by 24 h postinjury, a comparable number of cells underwent apoptosis in both PARP−/− and PARP+/+ mice kidneys. Thus activation of PARP post-IRI contributes to cell death most likely by ATP depletion and augmentation of the inflammatory cascade in the mouse model. PARP ablation preserved ATP levels, renal functions, and attenuated inflammatory response in the setting of IRI in the mouse model. PARP inhibition may have clinical efficacy in preventing the progression of acute renal failure complications.
Time-Frequency Representation of Inspiratory Motor Output in Anesthetized C57BL/6 Mice In Vivo
Authors: O'Neal Marvin H. , Spiegel Evan T. , Chon Ki H. , Solomon Irene C.
Published: October 2004

Inspiratory motor discharges, in addition to long-time-scale rhythmic oscillatory bursting, exhibit short-time-scale rhythmic oscillations that have been identified, and subsequently characterized, using power spectral analyses [predominantly fast-Fourier transforms (FFT)]. These analyses assume that the signal being analyzed is stationary; however, this is not the case for most biological signals, which exhibit varying degrees of nonstationarity. To overcome this limitation, time-frequency methods, which provide not only the frequency content but also information regarding the timing of these fast rhythmic oscillations (i.e., dynamics of spectral activity), should be used. Thus this study was performed to investigate the dynamic or time-varying features of spectral activity in inspiratory motor output. Both conventional time-invariant and time-frequency (time-varying) spectral analysis methods were performed on recordings of diaphragm EMG, phrenic nerve, and hypoglossal nerve discharges obtained from spontaneously breathing urethan-anesthetized adult C57BL/6 mice. Conventional time-invariant spectral analysis using a FFT algorithm revealed three dominant peaks in the power spectrum, which were located at 1) 20–46, 2) 83–149, and 3) 177–227 Hz. Time-frequency spectral analysis using a generalized time-frequency representation (TFR) with the smoothed pseudo-Wigner-Ville distribution (SPWD) kernel confirmed the general location of these spectral peaks, identified additional spectral peaks within the frequency ranges described above, and revealed a time-dependent expression of spectral activity within the inspiratory burst for each of the frequency ranges. Furthermore, this method revealed that 1) little or no spectral activity occurs during the initial portion of the inspiratory burst in any of the frequency ranges identified, 2) transient oscillations in the magnitude of spectral power exist where spectral activity occurs, and 3) total spectral power exhibits an augmenting pattern over the course of the inspiratory burst. These data, which provide the first description of spectral content in inspiratory motor discharges in adult mice, show that both time-invariant and time-varying spectral analysis methods are capable of identifying short-time-scale rhythmic oscillations in inspiratory motor discharge (as expected); however, the dynamic (i.e., timing) features of this oscillatory activity can only be obtained using the time-frequency method. We suggest that time-frequency methods, such as the SPWD, should be used in future studies examining short-time-scale (fast) rhythmic oscillations in inspiratory motor discharges, because additional insight into the neural control mechanisms that participate in inspiratory-phase neuronal and motoneuronal synchronization may be obtained.
Uteroplacental insufficiency induces site-specific changes in histone H3 covalent modifications and affects DNA-histone H3 positioning in day 0 IUGR rat liver
Authors: Fu Qi , McKnight Robert A. , Yu Xing , Wang Laiyi , Callaway Christopher W. , Lane Robert H.
Published: October 2004

Uteroplacental insufficiency and subsequent intrauterine growth retardation (IUGR) increase the risk of adult onset insulin resistance and dyslipidemia in humans and rats. IUGR rats are further characterized by postnatal alterations in hepatic PPAR-γ coactivator (PGC-1) and carnitine-palmitoyl-transferase I (CPTI) expression, as well as overall hyperacetylation of histone H3. However, it is unknown whether the histone H3 hyperacetylation is site specific or relates to the changes in gene expression previously described in IUGR rats. We therefore hypothesized that uteroplacental insufficiency causes site-specific modifications in hepatic H3 acetylation and affects the association of acetylated histone H3 with PGC-1 and CPTI promoter sequences. Uteroplacental insufficiency was used to produce asymmetrical IUGR rats. IUGR significantly increased acetylation of H3 lysine-9 (H3/K9), lysine-14 (H3/K14), and lysine-18 (H3/K18) at day 0 of life, and these changes occurred in association with decreased nuclear protein levels of histone deacetylase 1 (HDAC1) and HDAC activity. Chromatin immunoprecipitation using acetyl-H3/K9 antibody and day 0 chromatin revealed that uteroplacental insufficiency affected the association between acetylated H3/K9 and the promoters of PGC-1 and CPTI, respectively, in IUGR liver. At day 21 of life, the neonatal pattern of H3 hyperacetylation persisted only in the IUGR males. We conclude that uteroplacental insufficiency increases H3 acetylation in a site-specific manner in IUGR liver and that these changes persist in male IUGR animals. The altered association of the PGC-1 and CPTI promoters with acetylated H3/K9 correlates with previous reports of IUGR altering the expression of these genes. We speculate that in utero alterations of chromatin structure contribute to fetal programming.
On the topology of D‐metric spaces and generation of D‐metric spaces from metric spaces
Authors: Naidu S. V. R. , Rao K. P. R. , Rao N. Srinivasa
Published: October 2004

An example of a D‐metric space is given, in which D‐metric
convergence does not define a topology and in which a convergent
sequence can have infinitely many limits. Certain methods for
constructing D‐metric spaces from a given metric space are
developed and are used in constructing (1) an example of a
D‐metric space in which D‐metric convergence defines a
topology which is T1 but not Hausdorff, and (2) an example of
a D‐metric space in which D‐metric convergence defines a
metrizable topology but the D‐metric is not continuous even in
a single variable.
The many faces of helping: possible costs and benefits of infant carrying and food transfer in wild moustached tamarins (Saguinus mystax)
Authors: Löttker Petra , Huck Maren , Heymann Eckhard
Published: October 2004

Various hypotheses about adaptive and non-adaptive mechanisms of non-parental infant care have been put forward for different taxa (Emlen et al., 1991). The Neotropical callitrichid primates are renowned for their cooperative care of the twin litters. None of the studies conducted in the wild included information on genetic relationships within groups. This, however, is indispensable to evaluate the relevance of competing hypotheses concerning direct or indirect fitness gains. We studied two groups of wild moustached tamarins with known genetic relationships over a one-year period to examine individual time-budgets and contributions to infant carrying and food-transfer. With these data we tested whether helping behaviour might be a non-adaptive trait and, if not, whether indirect benefits via kin-selection could be excluded as an evolutionary force maintaining it. Other hypotheses on direct fitness benefits were discussed as far as (anecdotal) data permitted. Changes in time-budgets suggest costs, thus clearly refuting hypotheses assuming non-adaptivity. High within-group relatedness suggests kin-selection to be one driving force of maintaining the trait. However, non-parental individuals may help despite low relatedness. Data were not sufficient to decide which possible direct benefits most likely play a role in inducing non-relatives to help. Yet, two (non-exclusive) explanations seem to be the most probable ones: The chance to inherit the main-breeding position, and a certain chance of own direct reproductive success (the latter only for male helpers) due to polyandrous mating by the female. Other adaptive mechanisms may enhance benefits but are unlikely to be major selective forces since fitness gains are presumably rather small or uncertain.