bluuebunny/crossref_metadata_2025 huggingface dataset:
SUPERCONDUCTIVITY AND WEAK FERROMAGNETIC ORDER OF THE NEW RuCa2RCu2O8+δ (R=Pr, Nd, Sm, Eu, Gd) SYSTEM
Authors: LIN Y. C. , CHIU T. Y. , TAI M. F. , LIN B. N. , GUAN P. C. , KU H. C.
Published: April 2005

Superconducting onset temperatures T c up to 23-44 K are reported for the new RuCa 2 RCu 2 O 8+δ ( R = Pr , Nd , Sm , Eu , Gd ) system with a Ru -1212 RuCa 2 PrCu 2 O 8+δ-type structure. Preliminary study indicates that the crystal structure is an orthorhombic distortion of the tetragonal RuSr 2 GdCu 2 O 8+δ-type structure ,which has space group P4/mmm, T m~136 K , and T c( max )~65 K . With similar RuO 6 octahedral and CuO 5 pyramidal units, superconductivity from the Cu - O bi-layers apparently coexists with the weak ferromagnetic (WFM) order with magnetic ordering temperature T m~49 K . Low temperature anomalous in magnetic properties observed in both field-cooled (FC) and zero-field-cooled (ZFC) modes are closely related to the complex interplay and coexistence between weak ferromagnetic order and superconductivity as well as from structural distortion and sensitive sample oxygen concentration variation. No superconductivity or Ru -1212 structure can be detected for larger rare earth compounds R = La and Ce .
DOPING EFFECT OF NANO-YBCO ADDITIVE ON MgB2
Authors: RUI X. F. , SUN X. F. , XU X. L. , ZHANG L. , ZHANG H.
Published: April 2005

The effect of YBCO nanoparticles added into MgB 2 on Tc, Jc, and flux pinning was studied for MgB 2( YBCO )x with x =0, 5, 10, 15 wt%. Phase analysis shows that none of elements are doped into the MgB 2 lattice in the samples with YBCO addition. For the samples with YBCO addition, the Jc-H characteristics behave poorly in comparison with the pure sample. Our experimental results show that the nanoscale size of addition dosen't comprise the only condition for its effectiveness as pinning centers.
FABRICATION OF JOSEPHSON JUNCTIONS ON MgB2 THIN FILMS USING FOCUSED-ION-BEAM (FIB)
Authors: KIM SANG-JAE , KIM GUI-SIK , TAKANO YOSHIHIKO , ARISAWA SHUNICHI , YUN KYUNG-SUNG , ISHII AKIRA , HATANO TAKESHI , LEE HYUN-SOOK , CHOI EUN-MI , KIM KIJOON H. P. , LEE SUNG-IK
Published: April 2005

We fabricated nano-bridges on MgB 2 thin films so as to demonstrate Josephson effect. Those bridges smaller than 200 nm widths show the resistively-shunted-junction (RSJ)-like current (I)-voltage (V) curves with hysteresis. We also observed a few of microwave-induced steps that correspond to the Josephson voltage-frequency relations at 33 K.
A SUPERHIGH SPEED HTS MAGLEV VEHICLE
Authors: WANG JIASU , WANG SUYU , DENG CHANGYAN , ZENG YOUWEN , SONG HONGHAI , HUANG HAIYU
Published: April 2005

When the velocity of the normal ground traffic transportation is higher than 350 km/h of the speed limit, not only the running noise of the ground traffic vehicle is higher, but also the 90% driving power is dissipated in the aerodynamic resistance. The high speed may be realized when a high temperature superconducting (HTS) Maglev vehicle runs in low-pressure tube or evacuated tube transport (ETT). Its speed is over 3000 km/h. As a new ground transportation system the HTS Maglev vehicle is presented after the experiment results of HTS Maglev vehicle are discussed in this paper.
FEM ANALYSIS OF A NEW HYBRID SUPERCONDUCTING MAGNETIC LEVITATION SYSTEM
Authors: WANG XINGZHI , WANG SUYU , WANG JIASU
Published: April 2005

A superconducting magnetic levitation system, with permanent magnet guideway and bulk superconductors, can realize a more advantageous system for transportation. The calculations of electromagnetic force characteristics are presented using finite element method analysis. The hysteretic behavior of the forces has been reproduced assuming a critical state model for the superconductor, and the results of the analysis are compared with the experimental data. Prom these results we have confirmed that the three-dimensional structure of magnetic field and the electromagnetic performance of superconductors strongly influence the characteristic of the electromagnetic force. Furthermore, a new hybrid superconducting magnetic levitation system has been designed to optimize the electromagnetic force.
THE GROWTH TRACES OF SINGLE-DOMAIN YBCO BULK SUPERCONDUCTORS WITH C-AXIS PARALLEL TO THE TOP SURFACE
Authors: YANG W. M. , CHAO X. X. , BIN B. X. , ZHOU L. , YONG F. , ZHANG P. X. , XU Q. M.
Published: April 2005

The morphology of the top surface and the vertical section of single-domain YBCO bulk samples with c-axis parallel to the top surface have been clearly revealed. The sample with c-axis parallel to the top surface grows epitaxial from the seed (in the center) to the edge in all the four regions divided by grown cross traces on the top surface, but the growth style is different in the adjacent regions. If YBCO crystal grows along a (or b) axis in one region, it must be grow along c-axis in the adjacent regions. The grown traces on the top surface forms a 78° angle when the four regions meet each other. The clear traces are formed by the different growth rates, styles along c-axis and a (or b) axis and also the slightly height difference of YBCO crystal between adjacent regions.
SCANNING SQUID MICROSCOPE AND ITS APPLICATION IN DETECTING WEAK CURRENTS
Authors: ZHONG CHAORONG , LI FEI , ZHANG FENGHUI , DING HONGSHENG , LUO SHENG , LIN DEHUA , HE YUSHENG
Published: April 2005

A scanning SQUID microscope based on HTS dc SQUID has been developed. One of the applications of this microscope is to detect weak currents inside the sample. Considering that what being detected by the SQUID is the vertical component of the magnetic field on a plan where the SQUID lies, whereas the current which produces the magnetic field is actually located in a plan below the SQUID, a TWO PLAN model has been established. In this model Biot-Savart force laws and Fourier transformation were used to inverse the detected magnetic field into the underneath weak current. It has been shown that the distance between the current and the SQUID and the noise ratio of the experimental data have significant effects on the quality of the inverse process.
INVERSE MELTING OF VORTEX LATTICE IN LAYERED SUPERCONDUCTORS
Authors: WU W. J. , HE Y. W. , ZHAO Z. G. , LIU M. , YANG Y. H.
Published: April 2005

Using molecular dynamic simulations for the melting transition of a flux line lattice(FLL) with point disordered pinnings, thermal fluctuations and magnetic interactions between pancake vortices, we study the disorder-driven melting transition from a disentangled and ordered Bragg glass (BG) to an entangled amorphous vortex glass (VG) or a vortex liquid (VL) in the pinning strength-temperature phase diagram. A portion of the BG region is found to be sandwiched in between the VG phase at lower temperatures and VL phase at higher temperatures, exhibiting inverse melting behavior observed recently on BSCCO crystals.
STUDY OF KINETIC FRICTION OF SOLID USING DRIVEN LATTICE OF QUANTIZED VORTEX IN HIGH-TEMPERATURE SUPERCONDUCTORS–A NEW ROUTE TO STUDY SOLID-SOLID FRICTION
Authors: MAEDA ATSUTAKA , INOUE YUKICHI , KITANO HARUHISA , OKAYASU SATORU , TSUKADA ICHIRO
Published: April 2005

We show that quantized magnetic vortex lattice in high-temperature cuprate superconductors driven by dc or ac current is a very good model system for investigating physics of friction of solid. Based on the dc I-V characteristic measurement and viscosity measurement using microwave techniques in Bi 2 Sr 2 CaCu 2 O y and La 1.85 Sr 0.15 CuO 4, the corresponding kinetic friction was obtained as functions of temperature, magnetic field and driving current density. With increasing magnetic field and temperature, velocity dependence of kinetic friction behaves as that at interfaces with weak interaction of solid. This result means that we can control the kinetic friction, and that systematic experiments are available in a reproducible manner with using this system. Behavior of the kinetic friction at higher velocities (~1 km/s) agrees well with a two-class potential model at finite temperatures. Irradiation of the columnar defects was found to move the system closer to the so-called Amontons-Coulomb friction. This suggests that the random potential created by the strong pinning centers plays an important role of the validity of Amontons-Coulomb law.
CHARACTERISTICS OF SINGLE INTRINSIC JOSEPHSON JUNCTION
Authors: WANG Z. H. , NIE Y. , DING S. Y. , GAO J.
Published: April 2005

A single intrinsic Josephson junction has been observed in a Bi 2.3 Pb 0.1 Sr 2 CaCu 2 O 8 mesa structure. The isothermal voltage-current curves with hysteresis were measured from 5K to 65.09K. The critical current of the junction is almost a constant while the return current depends on the temperature. The temperature dependence of jumping voltage spacing deviates strongly from the BCS one. The temperature dependence of McCumber parameter βc is shown.
INTERFACIAL TRANSPORT IN YBa2Cu3O7-δ/La0.67Ca0.33MnO3 HETEROSTRUCTURES
Authors: WU H. , LUO P. S. , DONG X. L. , XU B. , CAO L. X. , QIU X. G. , ZHAO B. R.
Published: April 2005

YBa2Cu3O7-δ/La0.67Ca0.33MnO3 heterostructures were fabricated and patterned to study the interfacial transport between a ferromagnet (FM) and a dx2-y2-wave superconductor. Zero bias conductance peaks (ZBCPs) in the differential conductance spectra were observed in the interface where a YBCO layer shows a mixed c- and a-axis orientation. In contrast, a zero bias conductance dip (ZBCD) was observed in the interface with a purely c-axis oriented YBCO layer.
EXPERIMENTAL RESEARCH ON THE INFLUENCE OF JET PUMP ON THE COOLING STORAGE PROPERTY OF GAS HYDRATES
Authors: LI K. N. , TONG M. W. , LIN K.
Published: April 2005

In this experimental research, jet pump is added to the cooling storage circulation of gas hydrates for the first time. The research result shows that: jet pump strengthened the mixture of water and refrigerant and formed the hydrate nucleus in jet pump. Compared with the circling without jet, the sub-cooled nucleation temperature reduced 2~4°C, the mixture time of hydrates shortened 13%~25% in the experimental parameter. There is a best jet proportion, which is about 0.4.
COOLING FLOOR AC SYSTEMS
Authors: JUN LU , HAO DING , HONG ZHANG , CE GAO DIAN
Published: April 2005

The present HVAC equipments for the residential buildings in the Hot-summer-and-Cold-winter climate region are still at a high energy consuming level. So that the high efficiency HVAC system is an urgently need for achieving the preset government energy saving goal. With its advantage of highly sanitary, highly comfortable and uniform of temperature field, the hot-water resource floor radiation heating system has been widely accepted. This paper has put forward a new way in air-conditioning, which combines the fresh-air supply unit and such floor radiation system for the dehumidification and cooling in summer or heating in winter. By analyze its advantages and limitations, we found that this so called Cooling/ Heating Floor AC System can improve the IAQ of residential building while keep high efficiency quality. We also recommend a methodology for the HVAC system designing, which will ensure the reduction of energy cost of users.
APPLICATION OF CASCADE REFRIGERATION SYSTEM WITH MIXING REFRIGERANT IN COLD AIR CUTTING
Authors: YANG Y. , TONG M. W. , YANG G. , WANG X. P.
Published: April 2005

In the mechanical cutting process, the replacement of traditional cutting solution with cold air can avoid the pollution of environment. In order to high efficient the refrigerating device and flexible adjust the temperature of cold air, it is necessary to use cascade refrigeration system to supply cool quantity for the compressed air. The introduction of a two-component non-azeotropic mixing refrigerant into the cryogenic part of the cascade system, can effectively solve the problems of the system working at too high pressure and the volume expanding of refrigerant in case of the cascade refrigeration sets closed down. However, the filling ratio of mixing refrigerants impact on the relationships among the closing down pressure, refrigerating output and refrigerating efficiency. On the basis of computing and experiment, the optimal mixing ratio of refrigerant R22/R13 and a low temperature of -60° were obtained in this study. A cold air injecting device possessing high efficiency in energy saving has also been designed and manufactured. The cold air, generated from this cascade system and employed in a cutting process, takes good comprehensive effects on machining and cutting.
ELECTRONICALLY DRIVEN FERROELECTRICITY IN THE EXTENDED FALICOV-KIMBALL MODEL
Authors: BONČA J. , BATISTA C. D. , GUBERNATIS J. E. , LIN H. Q.
Published: April 2005

We calculate the quantum phase diagram of an extended Falicov-Kimball model in the intermediate coupling regime using a constrained path quantum Monte Carlo technique. The mixed-valence regime is dominated by a Bose-Einstein condensation of excitons with a built-in electric polarization.
UNIVERSAL RELATIONSHIP BETWEEN MAGNETIZATION AND CHANGES IN THE LOCAL STRUCTURE IN QUASICUBIC AND BILAYER MANGANITES
Authors: BRIDGES FRANK , DOWNWARD LISA , NEUMEIER J. J. , MITCHELL J. , ZHENG HONG
Published: April 2005

We extend our previous EXAFS investigations on the relationship between magnetization and local distortions to the bilayer materials La 2-2x Sr 1+2x Mn 2 O 7 and to higher magnetic fields, for quasicubic La 0.7 Ca 0.3 MnO 3. For each, there is a significant change in the broadening parameter σ of the Mn-O pair distribution function (PDF) associated with polaron formation as T is increased through T c. Applying a magnetic field reduces the local distortion of the Ca sample for temperatures near T c. For samples with sharp transitions, there is still a significant change of σ2 with T below T c when the sample is fully magnetized, i.e. distortions are still present and continuing to be removed as T is lowered well below T c. A simple model is presented for the magnetization process.
Pb VOLATILIZATION EFFECT ON DIELECTRIC AND PIEZOELECTRIC PROPERTIES IN A Ta-DOPED PMN-PT CERAMIC THICK DISK
Authors: ZHANG C. , WANG J. T. , SHEN S. X. , FENG Y. , AKUJOBI I. , CHEN T. P.
Published: April 2005

A thick ceramic disk of 0.7 Pb ( Mg 1/3( Nb 0.9 Ta 0.1)2/3) O 3-0.3 PbTiO 3 ( PMNT - PT ) was prepared by columbite precursor method with PbO powder buffer surrounding the disk during the sintering process. The dielectric and piezoelectric properties and the microstructure of PMNT - PT samples cut from the different depths of the disk are studied. The phase purity is homogenous in the whole disk within our x-ray diffraction resolution. The dielectric constants, and the piezoelectric effect, d 33, vary with different samples. The samples cut from the middle parts of the disk have the higher d 33. It is believed that the sample processes, especially the Pb volatilization is responsible for these results.
FABRICATION OF PERPENDICULAR BA-FERRITE FILMS BY MAGNETRON SPUTTERING WITH IN SITU PROCESS
Authors: YEH W. J. , ABUZIR A. R. , PETRUS R.
Published: April 2005

Barium ferrite films (BaFe12O19) with perpendicular orientation are attractive candidates for microwave device applications and ultrahigh density perpendicular recording. An in situ annealing process is developed for the deposition of Barium ferrite films by rf magnetron sputtering. The substrates are held at temperatures of 550 to 600°C during the sputtering. After the deposition, the substrate temperature is immediately raised to 900°C in the vacuum chamber in Ar and O2 atmosphere. c-axis orientated films are obtianed. The films exhibit coercivity value of 4270 Oe and squareness of 0.87 in perpendicular direction.
EXPERIMENTAL STUDIES OF ELECTRON DRAG EFFECT ON CARBON NANOTUBE SURFACE
Authors: CAO C. L. , WANG W. L. , LIAO K. J. , XIONG W. , LU J. W. , YANG F. F.
Published: April 2005

The electron drag effect of carbon nanotubes in electrolyte was studied. The carbon nanotubes in this study were synthesized by hot filament CVD. The experimental results showed there is a striking induced voltage on the surface of carbon nanotubes in flowing electrolytes. It was also found that the induced voltage was closely depended on the electrolyte concentration. The response time of induced voltage was relative to the kind and concentration of electrolytes. The origin of induced voltage was discussed.
FLOW BOILING HEAT TRANSFER AND TWO-PHASE PRESSURE DROP OF R134A IN A MICROFINNED HELICALLY COILED TUBE
Authors: CUI W. Z. , LI L. J. , CHEN Q. H. , XIN M. D.
Published: April 2005

The performance of evaporator is of importance in cryogenic and refrigeration systems. In this paper, evaporative heat transfer and pressure drop characteristics of refrigerant R134a boiling inside a new geometry microfinned helically coiled tube is experimentally studied. Compared with corresponding smooth helically coiled tube, the heat transfer enhancement factors of microfinned helically coiled tube are up to 2.2 with the varieties of mass flux and heat flux. The frictional pressure drop values are obtained by subtracting acceleration pressure drop and gravitational pressure drop from the measured total pressure drop. The frictional pressure drop data can be well correlated using Lockhart–Martinelli method.
MAGNETORHEOLOGICAL FLUIDS AND THEIR PROPERTIES
Authors: HE J. M. , HUANG J.
Published: April 2005

Magnetorheological (MR) fluids are materials that respond to an applied magnetic field with a change in their rheological properties. Upon application of a magnetic field, MR fluids have a variable yield strength. Altering the strength of the applied magnetic field will control the yield stress of these fluids. In this paper, the method for measuring the yield stress of MR fluids is proposed. The curves between the yield stress of the MR fluid and the applied magnetic field are obtained from the experiment. The result indicates that with the increase of the applied magnetic field the yield stress of the MR fluids goes up rapidly.
EFFECT OF MAGNETIC FIELD ON PROPERTIES OF MR FLUIDS
Authors: HUANG J. , ZHANG J. Q. , LIU J. N.
Published: April 2005

The yield stress is one of the most important parameters that characterize viscoplastic properties of magnetorheological (MR) fluids. Based on the microstructure of magnetic-chain a theoretical model is developed to analyze the effect of the applied magnetic field on the yield stress. It has been shown that the values of the yield stress calculated by the model agree well with the experimental data.
EFFECT OF NEW SEED LAYERNiFeNbON ELECTRIC PROPERTIES OF NANOMETER PERMALLOY FILMS
Authors: LIU JUN , ZHENG R. L.
Published: April 2005

Using the Ternary alloy NiFeNb as a new seed layer, ( Ni82Fe18)72.9Nb27.1(35Å)/ Ni28Fe18(tÅ)/ Ta (30Å) films with various NiFe thickness (t) are prepared with a DC magnetron sputtering system. The zero field resistivity ρ and other electric properties are measured. Variations of ρ with t are studied systematically. Dong's model based on Fishman Model has been adapted to analyze our measurements. Results show that: 1) the new seed layer NiFeNb is better than both NiFeCr and Ta in significant enhancing ρ of permalloy films, which decreases the current shunting effect in sensors; 2) Decreasing of grain sizes caused by NiFeNb seed layer and rough interface between the NiFeNb and NiFe layers contribute to improvement of ρ and other electric properties.
INFLUENCE OF SEED LAYERNiFeNbON MAGNETIC PROPERTIES OF NANOMETER PERMALLOY FILMS
Authors: LIU JUN , DUAN CHANG-KUI , ZHENG R. L.
Published: April 2005

Using the Ternary alloy NiFeNb as a new seed layer, ( Ni82Fe18)72.9Nb27.1(35Å)/ Ni28Fe18(tÅ)/ Ta (30Å) films with various NiFe thickness t are prepared with a DC magnetron sputtering system. Magnetoresistance (MR) and other magnetic properties of as-grown and annealed films are measured. Variations of MR with t are studied systematically. The approach of Li and co-workers is adapted to analyze our measurements. Result shows that: 1) the new seed layer NiFeNb is better than both NiFeCr and Ta in significant enhancing MR of permalloy films through medium temperature annealing; 2) Small grain sizes caused by NiFeNb seed layer and rough interface between the NiFeNb and NiFe layers contribute to improvement of MR and other magnetic properties.
HEAT TRANSFER OF HC290-OIL MIXTURES IN A HORIZONTAL CONDENSING MICRO-FIN TUBE
Authors: TONG M. W. , DONG M. L. , LI Y.
Published: April 2005

Heat transfer coefficients was experimentally determined for a horizontal micro-fin tube (2m in length, 11.44mm ID) with HC290-oil mixtures. The oil is Suniso 3GS, which is a widely used oil in refrigerant systems. The micro-fin tube is a internally enhanced tube, which has 60 fins with a height of 0.25mm and 20° spiral angle. The condensation temperatures varied from 40° to 45° and the refrigerant mass flux was varied from 40kg/(m2s) to 220kg/(m2s). The results showed that the mean condensation heat transfer coefficients on the test section (inlet vapor quality 1, outlet vapor quality 0.1~0.25) decreased as the oil concentrations were increased and the condensation temperature had negligible effect on the heat transfer coefficients.
SEEBECK EFFECT IN CARBON NANOTUBE FILMS
Authors: WAN B. Y. , WANG W. L. , LIAO K. J. , LV J. W.
Published: April 2005

In this paper, the Seebeck effect of mutilwalled carbon nanotube films has been studied. The carbon nanotubes were synthesized by hot filament chemical vapor deposition using Ni - Fe as a catalyst. It was found that the thermoelectromotive force (thermo emf) changed approximately linearly with the temperature at the hot end at room temperature, and the Seebeck coefficient of carbon nanotube films was about 10~50 μv/k. The experimental results were discussed in detail.
STUDY ON FORMATION OF CARBON NANOTIPS BY NEGATIVE BIAS-ENHANCED HOT FILAMENT CHEMICAL VAPOR DEPOSITION WITHOUT CATALYST
Authors: WANG B. B. , LEE SOONIL , WANG W. L. , LIAO K. J. , YAN H.
Published: April 2005

Carbon nanotips were grown on a silicon substrate by negative bias-enhanced hot filament chemical vapor deposition without catalyst, using a mixture of methane, ammonia and hydrogen as the reaction gases. It was evidenced that the plasma caused by the bias played a key role in the formation of the carbon nanotips. Due to occurrence of plasma during growing carbon nanotips, the gases were ionized into various ions. Based on different effects of the ions, a growth mechanism of the carbon nanotips was put forward.
MAGHETOTHERMO POWER OF ZnO FILMS
Authors: WANG W. L. , LI L. , LIAO K. J. , ZHANG J. , ZHANG R. J. , YANG F. F. , FU G. Z.
Published: April 2005

The Magnetothermoelectric and thermoelectric power of nano- ZnO films was investigated. The ZnO films in this study were prepared by DC reactive sputtering using a Zn target (99.99%) containing AL of 1.5%. The films obtained were characterized by SEM, x-ray diffraction, optical and electrical measurements. It was found that the sputtering ZnO films were highly orientation growth with the c-axis perpendicular to the substrate surface. The measurements showed that there was a striking seebeck effect in the ZnO films, and their thermoelectric power was linearly increased with increasing temperature. The experimental results were also demonstrated that the thermoelectric power was degraded under the magnetic field. This finding may ascribe to the magneto resistive effect.
A KIND OF ELECTROLYTIC METHOD TO DEPOSITE NANO CARBON FILM IN MOLTEN SALT
Authors: XIAO F. , FANG L. , ZHANG J. , YANG L. C. , LIU G. B.
Published: April 2005

A new kind of electrolytic deposition method to obtain activated carbon atoms to prepare nano carbon film in molten salt was developed. The experimental results on various substrates indicated that nano carbon film could be synthesized on substrates of nickel, copper, iron and titanium by an electrolytic deposition method in molten salt under suitable conditions. Decreasing reasonably carbonate ion concentration is an efficient methods to accelerate the growth of deposition film and improve its quality.
FABRICATION OF UNIFORM ARRAY OF NANO-DOTS AND ITS APPLICATIONS
Authors: YEH W. J. , CHENG BO , YANG KUN
Published: April 2005

We have developed a novel technique to fabricate extremely uniform arrays of nano-sized dots. Regular arrays of nanometer-sized metallic dots are obtianed by magnetron sputtering deposition through a nanochannel glass replica mask. The platinum replica masks are fabricated using thin film deposition on an etched nanochannel glass and contain hexagonally patterned uniform voids with diameters as small as 50 nanometers. The metallic dot density can be as high as 5×1011 per square centimeter. The magnetic properties of Ni and Co dot arrays have been studied by a Alternating Gradient Magnetometer. The magnetic dot array can be used as pinning centers for superconductors and also can be used as the discrete magnetic media for magnetic recording.
A STUDY ON THE CHARACTER OF TWO-PHASE EQUILIBRIUM STATE BY MOLECULAR DYNAMICS SIMULATION
Authors: ZENG D. L. , ZHANG X. M. , WANG D. M. , LIU J. F.
Published: April 2005

A molecular dynamics simulation (MDS) was performed to investigate the characteristics of the interfacial feature between coexisting phases in equilibrium. It is considered that the interface is a fractal surface. The fractal configuration and the dimension of it were presented in the paper.
GROWTH PROPERTY OF SILICON NANOWIRES UNDER OAG
Authors: ZHU YABO , ZHU YAQUN
Published: April 2005

Using a simplified model, the surface energy of the Si / SiO 2 interface in silicon nanowires ( SiNWs ) is derived. Our theoretical results show that the nanowires along <112> and <110> have very low surface energy, so their yields should be high. Experimental observation testifies that the SiNWs fabricated by the oxide-assisted growth (OAG) are mostly of these two orientations. This supports the consideration that during growth process, surface energy is the chief factor to determine the axis orientation of nanowires under OAG.
SELF-TRAPPING ENERGY AND EFFECTIVE MASS OF POLARON IN WURTZITE NITRIDE SEMICONDUCTORS
Authors: YAN ZU-WEI
Published: April 2005

A variational approach is used to study the intermediate-coupling polaron in bulk III-V nitride semiconductors with wurtzite crystal structure within the macroscopic dielectric continuum model and the uniaxial model. The polaronic self-trapping energy and effective mass are theoretically derived for the LO and TO polarizations mixing due to the anisotropy effect. The numerical computation has been performed for the polaronic self-trapping energy and effective mass for wurtzite nitrides GaN , AlN and InN . The results show that the self-trapping energies of the wurtzite nitrides are bigger than the zinc-blende structures above calculated materials. It is also found that the structure anisotropy increases the electron–phonon interaction in wurtizte nitride semiconductors. It indicates that the LO-like phonon influence on the polaronic effective mass and self-trapping energy are dominant and anisotropy effect is obvious.
ELASTICITY OF A HELICAL RIBBON WITH NONCIRCULAR CROSS SECTION
Authors: ZHOU ZICONG
Published: April 2005

We derive the general shape equations in terms of Euler angles for an elastic model of uniform ribbon with noncircular cross section and vanishing spontaneous curvatures. We show that it has in general not a planar solution for a closed ribbon free of external force and torque. We study the conditions to form a helix with the axis along the direction of the applied force for a ribbon under external force and twisting. We find that if the bending rigidity is greater than the twisting rigidity, then no such helical rod can exist. Our stability analysis shows that a helical ribbon is in general stable or at least metastable under arbitrary force and torque. We find that the extension of the ribbon may undergo a discontinuous transition from a twisted straight rod to a helical ribbon. The intrinsic asymmetric elasticity of a helical ribbon under external torque is also studied.
MODELING AUDITORY PATHWAY FOR INTELLIGENT INFORMATION ACQUISITION
Authors: PARK HYUNG-MIN , LEE JONG-HWAN , KIM TAESU , BAE UN-MIN , KIM BYUNG TAEK , PARK KI-YOUNG , KIM CHANG-MIN , LEE SOO-YOUNG
Published: April 2005

An auditory model has been developed for an intelligent speech information acquisition system in real-world noisy environment. The developed mathematical model of the human auditory pathway consists of three components, i.e. the nonlinear feature extraction from cochlea to auditory cortex, the binaural processing at superior olivery complex, and the top-down attention from higher brain to the cochlea. The feature extraction is based on information-theoretic sparse coding throughout the auditory pathway. Also, the time-frequency masking is incorporated as a model of the lateral inhibition in both time and frequency domain. The binaural processing is modeled as the blind signal separation and adaptive noise canceling based on the independent component analysis with hundreds of time-delays for noisy reverberated signals. The Top-Down (TD) attention comes from familiarity and/or importance of the sensory information, i.e. the sound, and a simple but efficient TD attention model had been developed based on the error backpropagation algorithm. Also, the binaural processing and top-down attention are combined for speech signals with heavy noises. This auditory model requires extensive computing, and special hardware had been developed for real-time applications. Experimental results demonstrate much better recognition performance in real-world noisy environments.
REMEMBERING WINTER: Toward a Molecular Understanding of Vernalization
Authors: Sung Sibum , Amasino Richard M.
Published: April 2005

Exposure to the prolonged cold of winter is an important environmental cue that favors flowering in the spring in many types of plants. The process by which exposure to cold promotes flowering is known as vernalization. In Arabidopsis and certain cereals, the block to flowering in plants that have not been vernalized is due to the expression of flowering repressors. The promotion of flowering is due to the cold-mediated suppression of these repressors. Recent work has demonstrated that covalent modifications of histones in the chromatin of target loci are part of the molecular mechanism by which certain repressors are silenced during vernalization.
Cytokine-dependent regulation of hepatic organic anion transporter gene transactivators in mouse liver
Authors: Geier Andreas , Dietrich Christoph G. , Voigt Sebastian , Ananthanarayanan Meenakshisundaram , Lammert Frank , Schmitz Anne , Trauner Michael , Wasmuth Hermann E. , Boraschi Diana , Balasubramaniyan Natarajan , Suchy Frederick J. , Matern Siegfried , Gartung Carsten
Published: April 2005

Proinflammatory cytokines such as TNF-α and IL-1β lead to downregulation of hepatic organic anion transporters in cholestasis. This adapted response is transcriptionally mediated by nuclear hormone receptors and liver-specific transcription factors. Because little is known in vivo about cytokine-dependent regulatory events, mice were treated with either TNF-α or IL-1β for up to 16 h. Transporter mRNA expression was determined by Northern blot analysis, nuclear activity, and protein-expression of transactivators by EMSA and Western blotting. TNF-α induces a sustained decrease in Ntcp, Oatp1/Oatp1a1, and Bsep mRNA expression but exerts only transient [multidrug resistance-associated protein 2 (Mrp2)] or no effects (Mrp3) on Mrps. In addition to Ntcp and Oatp1/Oatp1a1, IL-1β also downregulates Bsep, Mrp2, and Mrp3 mRNAs to some extent. To study transcriptional regulation, Ntcp and Bsep promoters were first cloned from mice revealing a new distal Ntcp hepatocyte nuclear factor 1 (HNF-1) element but otherwise show a conserved localization to known rat regulatory elements. Changes in transporter-expression are preceeded by a reduction in binding activities at IR-1, ER-8, DR-5, and HNF-1α sites after 4 h by either cytokine, which remained more sustained by TNF-α in the case of nuclear receptors. Nuclear protein levels of retinoid X receptor (RXR)-α are significantly decreased by TNF-α but only transiently affected by IL-1β. Minor reductions of retinoic acid receptor, farnesoid X receptor, pregnane X receptor, and constitutive androstane receptor nuclear proteins are restricted to 4 h after cytokine application and paralleled by a decrease in mRNA levels. Basolateral and canalicular transporter systems are downregulated by both cytokines, TNF-α and IL-1β. Activity of HNF-1α as regulator of mNtcp is suppressed by both cytokines. Decreased binding activities of nuclear receptor heterodimers may be explained by a reduction of the ubiquitous heterodimerization partner RXR-α.
Retinoic acid formation from retinol in the human gastric mucosa: role of class IV alcohol dehydrogenase and its relevance to morphological changes
Authors: Matsumoto Michinaga , Yokoyama Hirokazu , Suzuki Hidekazu , Shiraishi-Yokoyama Haruko , Hibi Toshifumi
Published: April 2005

Alcohol dehydrogenase (ADH) participates in the formation of retinoic acid from retinol in various organs including the gastric mucosa. However, its clinical significance still remains to be clarified. In this study, we identified the ADH isoforms responsible for the retinoic acid formation among various ADH isoforms and examined associations among the ADH activities, the retinoic acid formation level, and morphological changes in the human gastric mucosa. Human gastric samples were endoscopically obtained from 67 male subjects. Morphological changes were assessed by the Sydney system and activities of class I, III, and IV ADH isoforms were determined in each specimen. In 26 cases, levels of all- trans retinoic acid (ATRA) formation from all- trans retinol were examined. Among activities of the three ADH isoforms, class IV ADH activity was solely associated with the ATRA formation level. This association was found even when subjects' age and Helicobacter pylori infection status were adjusted. As the degrees of inflammation, atrophy, and intestinal metaplasia increased, the class IV ADH activity as well as the potential for the ATRA formation decreased. Class IV ADH is a major enzyme in the retinoic acid supply in the human gastric mucosa, and the reduction of its activity was associated with decreasing retinoic acid supply and progression of inflammation, atrophy, and intestinal metaplasia in the gastric mucosa. In that retinoic acid is a key molecule for maintaining normal morphology, the reduction of class IV ADH activity may be involved in the pathogenesis of these morphological changes in the human gastric mucosa.
Polyamine depletion inhibits irradiation-induced apoptosis in intestinal epithelia
Authors: Deng Wenlin , Viar Mary Jane , Johnson Leonard R.
Published: April 2005

Our group has previously shown that polyamine depletion delays apoptosis in rat intestinal epithelial (IEC-6) cells (Ray RM, Viar MJ, Yuan Q, and Johnson LR , Am J Physiol Cell Physiol 278: C480–C489, 2000). Here, we demonstrate that polyamine depletion inhibits γ-irradiation-induced apoptosis in vitro and in vivo. Pretreatment of IEC-6 cells with 5 mM α-difluoromethylornithine (DFMO) for 4 days significantly reduced radiation-induced caspase-3 activity and DNA fragmentation. This protective effect was prevented by the addition of 10 μM exogenous putrescine. Radiation exposure to mice resulted in a high frequency of apoptosis over cells positioned fourth to seventh in crypt-villus units. Pretreatment of mice with 2% DFMO in drinking water significantly reduced apoptotic cells from ∼2.75 to 1.61 per crypt-villus unit, accompanied by significant decreases in caspase-3 levels. Further examination showed that DFMO pretreatment inhibited the radiation-induced increase in the proapoptotic protein Bax. Moreover, DFMO pretreatment significantly enhanced the intestinal crypt survival rate by 2.1-fold subsequent to radiation and ameliorated mucosal structural damage. We conclude that polyamine depletion by DFMO inhibits γ-irradiation-induced apoptosis of intestinal epithelial cells both in vitro and in vivo through inhibition of Bax and caspase-3 activity, which leads to attenuation of radiation-inflicted intestinal injury. These data indicate that DFMO may be therapeutically useful to counteract the gastrointestinal toxicity caused by chemoradiotherapy. This is the first demonstration that polyamines are required for apoptosis in vivo.
Differential acquisition of specific components of a classically conditioned arterial blood pressure response in rat
Authors: El-Wazir Yasser M. , Li Sheng-Gang , Williams Daniel T. , Sprinkle Aletia G. , Brown David R. , Randall David C.
Published: April 2005

Presenting a 15-s pulsed tone, the conditional stimulus (CS+), followed by 0.5-s tail shock, to a well-trained rat causes a sudden, but transient, pressor response (C1). Blood pressure (BP) then drops before increasing again (C2). A steady tone of the same frequency never followed by a shock (a discriminative stimulus, or CS−) evokes a C1but not a C2response. Experiment 1 tested the hypothesis that this BP response pattern does not depend on the nature of the tone (i.e., pulsed vs. steady) used for CS+and CS−. The tones were reversed from the traditional paradigm, above, in nine rats. The C1BP increase for a steady-tone CS+(+4.8 ± 1.9 mmHg, mean change ± SE) and a pulsed CS−(+2.9 ± 1.3 mmHg) did not differ. Conversely, C2showed a clear discrimination (CS+: +5.1 ± 1.2 mmHg, CS−: +0 .7 ± 0.8 mmHg; P < 0.05). Experiment 2 tested the hypothesis that the C1and C2BP responses first appear at different times during training. On training day 1, five 15-s pulsed tones (CS+) were presented to each of 18 rats; the last tone was followed by a tail shock. Likewise, five steady CS−tones never followed by shock were given. Training continued for 2 more days, with each CS+followed by shock. At the end of day 2, CS+evoked a C1BP response (+3.9 ± 0.9 mmHg) but no C2(+0.6 ± 0.4 mmHg, not significant vs. pretone). By the end of day 3, CS+evoked a significant (vs. baseline) C1(+7.3 ± 1.4 mmHg) and C2(+3.3 ± 0.8 mmHg). Conversely, although CS−evoked a C1response (3.5 ± 1.3 mmHg), there was no C2(+0.7 ± 0.5 mmHg; not significant). We conclude that 1) C1and C2are acquired at different rates, 2) early in training C1is an orienting response evoked by both tones, and 3) C2is only acquired as an animal learns to associate the CS+tone with shock. This suggests that C1and C2are controlled by different processes in the brain.
White adipose tissue sensory nerve denervation mimics lipectomy-induced compensatory increases in adiposity
Authors: Shi Haifei , Bartness Timothy J.
Published: April 2005

The sensory innervation of white adipose tissue (WAT) is indicated by the labeling of sensory bipolar neurons in the dorsal root ganglion after retrograde dye placement into WAT. In addition, immunoreactivity (ir) for sensory-associated neuropeptides such as calcitonin gene-related peptide (CGRP) and substance P in WAT pads also supports the notion of WAT sensory innervation. The function of this sensory innervation is unknown but could involve conveying the degree of adiposity to the brain. In tests of total body fat regulation, partial surgical lipectomy triggers compensatory increases in the mass of nonexcised WAT, ultimately resulting in restoration of total body fat levels in Siberian hamsters and other animals. The signal that triggers this compensation is unknown but could involve disruption of WAT sensory innervation that accompanies lipectomy. Therefore, a local and selective sensory denervation was accomplished by microinjecting the sensory nerve neurotoxin capsaicin bilaterally into epididymal WAT (EWAT) of Siberian hamsters, whereas controls received vehicle injections. Additional hamsters had bilateral EWAT lipectomy (EWATx) or sham lipectomy. As seen previously, EWATx resulted in significantly increased retroperitoneal WAT (RWAT) and inguinal WAT (IWAT) masses. Capsaicin treatment significantly decreased CGRP- but not tyrosine hydroxylase-ir, attesting to the diminished and selective sensory innervation. Capsaicin-treated hamsters also had increased RWAT and, to a lesser degree, IWAT mass largely mimicking the WAT mass increases seen after lipectomy. Collectively, these data suggest the possibility that information related to peripheral lipid stores may be conveyed to the brain via the sensory innervation of WAT.
Thermoregulatory responses of rats to conventional preparations of lipopolysaccharide are caused by lipopolysaccharide per se— not by lipoprotein contaminants
Authors: Steiner Alexandre A. , Chakravarty Sumana , Robbins Jared R. , Dragic Alexander S. , Pan Jennifer , Herkenham Miles , Romanovsky Andrej A.
Published: April 2005

LPS preparations cause a variety of body temperature (Tb) responses: monophasic fever, different phases of polyphasic fever, and hypothermia. Conventional (c) LPS preparations contain highly active lipoprotein contaminants (endotoxin proteins). Whereas LPS signals predominantly via the Toll-like receptor (TLR) 4, endotoxin proteins signal via TLR2. Several TLR2-dependent responses of immunocytes to cLPS in vitro are triggered by endotoxin proteins and not by LPS itself. We tested whether any Tbresponse to cLPS from Escherichia coli 055:B5 is triggered by non-TLR4-signaling contaminants. A decontaminated (d) LPS preparation (free of endotoxin proteins) was produced by subjecting cLPS to phenol-water reextraction. The presence of non-TLR4-signaling contaminants in cLPS (and their absence in dLPS) was confirmed by showing that cLPS (but not dLPS) induced IL-1β expression in the spleen and increased serum levels of TNF-α and IL-1β of C3H/HeJ mice; these mice bear a nonfunctional TLR4. Yet, both cLPS and dLPS caused cytokine responses in C3H/HeOuJ mice; these mice bear a fully functional TLR4. We then studied the Tbresponses to cLPS and dLPS in Wistar rats preimplanted with jugular catheters. At a neutral ambient temperature (30°C), a low (0.1 μg/kg iv) dose of cLPS caused a monophasic fever, whereas a moderate (10 μg/kg iv) dose produced a polyphasic fever. In the cold (20°C), a high (500 μg/kg iv) dose of cLPS caused hypothermia. All Tbresponses to dLPS were identical to those of cLPS. We conclude that all known Tbresponses to LPS preparations are triggered by LPS per se and not by non-TLR4-signaling contaminants of such preparations.
Muscle Na-K-pump and fatigue responses to progressive exercise in normoxia and hypoxia
Authors: Sandiford S. D. , Green H. J. , Duhamel T. A. , Schertzer J. D. , Perco J. D. , Ouyang J.
Published: April 2005

To investigate the effects of hypoxia and incremental exercise on muscle contractility, membrane excitability, and maximal Na+-K+-ATPase activity, 10 untrained volunteers (age = 20 ± 0.37 yr and weight = 80.0 ± 3.54 kg; ± SE) performed progressive cycle exercise to fatigue on two occasions: while breathing normal room air (Norm; FiO2= 0.21) and while breathing a normobaric hypoxic gas mixture (Hypox; FiO2= 0.14). Muscle samples extracted from the vastus lateralis before exercise and at fatigue were analyzed for maximal Na+-K+-ATPase (K+-stimulated 3-O-methylfluorescein phosphatase) activity in homogenates. A 32% reduction ( P < 0.05) in Na+-K+-ATPase activity was observed (90.9 ± 7.6 vs. 62.1 ± 6.4 nmol·mg protein−1·h−1) in Norm. At fatigue, the reductions in Hypox were not different (81 ± 5.6 vs. 57.2 ± 7.5 nmol·mg protein−1·h−1) from Norm. Measurement of quadriceps neuromuscular function, assessed before and after exercise, indicated a generalized reduction ( P < 0.05) in maximal voluntary contractile force (MVC) and in force elicited at all frequencies of stimulation (10, 20, 30, 50, and 100 Hz). In general, no differences were observed between Norm and Hypox. The properties of the compound action potential, amplitude, duration, and area, which represent the electomyographic response to a single, supramaximal stimulus, were not altered by exercise or oxygen condition when assessed both during and after the progressive cycle task. Progressive exercise, conducted in Hypox, results in an inhibition of Na+-K+-ATPase activity and reductions in MVC and force at different frequencies of stimulation; these results are not different from those observed with Norm. These changes occur in the absence of reductions in neuromuscular excitability.
Corticotropin-releasing hormone effects on human pregnant vs. nonpregnant myometrium explants estimated from a mathematical model of uterine contraction
Authors: Mignot Thérèse-Marie , Paris Brigitte , Carbonne Bruno , Vauge Christian , Ferré Françoise , Vaiman Daniel
Published: April 2005

In this paper, we applied a new theoretical model of uterine contraction to a large panel of human pregnant and nonpregnant myometrial strips, treated or not by corticotrophin-releasing hormone (CRH). This model is based on a fine analysis of the contraction curves. This analysis yielded four mathematical parameters (beta, theta, tau 1, and tau 2) related to excitability, duration of plateau phase, and time constants for relaxation describing, respectively, the different portions of the contraction cycle. This leads to specific differences in spontaneous contractile activity between pregnant and nonpregnant states. The relaxing effect of CRH in the pregnant state is presumably correlated with the origin of the strips (the lower uterine segment). Besides our observation of a specific receptor-dependent relaxing effect of CRH in both pregnant and nonpregnant myometrium, we could identify highly significant effects at given CRH concentration for beta in nonpregnant myometrium and for theta, tau 1, and tau 2 in pregnant myometrium. In addition, highly significant differences were found between pregnant and nonpregnant myometrium. Also, we discovered a strong correlation between theta and tau 1, specifically in the pregnant state. Although the biochemical signification of these results remains to be elucidated, they contribute to emphasize the complex network of CRH action at the myometrial level. Furthermore, our approach could pave the way toward a better analysis of the efficacy of the uterine contractile behavior.
Blood pressure and blood flow variation during postural change from sitting to standing: model development and validation
Authors: Olufsen Mette S. , Ottesen Johnny T. , Tran Hien T. , Ellwein Laura M. , Lipsitz Lewis A. , Novak Vera
Published: April 2005

Short-term cardiovascular responses to postural change from sitting to standing involve complex interactions between the autonomic nervous system, which regulates blood pressure, and cerebral autoregulation, which maintains cerebral perfusion. We present a mathematical model that can predict dynamic changes in beat-to-beat arterial blood pressure and middle cerebral artery blood flow velocity during postural change from sitting to standing. Our cardiovascular model utilizes 11 compartments to describe blood pressure, blood flow, compliance, and resistance in the heart and systemic circulation. To include dynamics due to the pulsatile nature of blood pressure and blood flow, resistances in the large systemic arteries are modeled using nonlinear functions of pressure. A physiologically based submodel is used to describe effects of gravity on venous blood pooling during postural change. Two types of control mechanisms are included: 1) autonomic regulation mediated by sympathetic and parasympathetic responses, which affect heart rate, cardiac contractility, resistance, and compliance, and 2) autoregulation mediated by responses to local changes in myogenic tone, metabolic demand, and CO2 concentration, which affect cerebrovascular resistance. Finally, we formulate an inverse least-squares problem to estimate parameters and demonstrate that our mathematical model is in agreement with physiological data from a young subject during postural change from sitting to standing.