bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrological stability and otter trophic diversity: a scale-insensitive pattern?
Authors: Clavero M. , Prenda J. , Blanco-Garrido F. , Delibes M.
Published: October 2008

Two recent works related Eurasian otter ( Lutra lutra (L., 1758)) trophic patterns over large areas with the stability of aquatic ecosystems. Higher levels of instability lead to reduced availability and (or) predictability of fish, and consequently, to a decrease in fish consumption by otters. The aim of the present study is to test these macrogeographical patterns in otter diet at regional and local scales. We analysed otter diet in Mediterranean streams in southwestern Iberian Peninsula where clear hydrological stability gradients (related to drainage area or distance to the sea) could be defined. Hydrological stability was directly related to fish consumption and inversely to otter diet diversity in terms of occurrence and biomass, both at regional and local scales. The level of stability of aquatic ecosystems appears to be a critical indirect factor that modulates otter diet through its effects on fish populations. The resulting trophic patterns are maintained from local to macrogeographical scales.
Responses of Great Horned Owls (Bubo virginianus), Barred Owls (Strix varia), and Northern Saw-whet Owls (Aegolius acadicus) to forest cover and configuration in an agricultural landscape in Alberta, Canada
Authors: Grossman S. R. , Hannon S. J. , Sánchez-Azofeifa A.
Published: October 2008

Studies on the effects of forest fragmentation on birds have focussed primarily on passerines, with few studies on owls. We assessed the influence of forest amount and configuration on the abundance and distribution of three species of forest owls, Great Horned Owl ( Bubo virginianus (Gmelin, 1788)), Barred Owl ( Strix varia Barton, 1799), and Northern Saw-whet Owl ( Aegolius acadicus (Gmelin, 1788)), in agricultural landscapes with varying amounts of forest cover in central Alberta, Canada. All three species were positively associated with forest cover: Barred Owls were most prevalent in landscapes with >66% forest cover, Great Horned Owls in landscapes with between 36% and 65% forest cover, and Northern Saw-whet Owls in landscapes with between 16% and 100% forest cover. Regression models containing configuration variables were chosen as best models using AIC for all three species. Great Horned Owls were most abundant in landscapes with high heterogeneity: more forest–nonforest edges and higher forest patch area variation. Barred Owls were more likely to occur in landscapes with larger forest patch areas and Northern Saw-whet Owls were more abundant in landscapes that were more connected. These relationships are consistent with predictions based on body size of owls and local habitat relationships described in the literature.
Degeneration of the midgut epithelium in Epilachna cf. nylanderi (Insecta, Coccinellidae): apoptosis, autophagy, and necrosis
Authors: Rost-Roszkowska Magdalena M. , Poprawa Izabela , Klag Jerzy , Migula Paweł , Mesjasz-Przybyłowicz Jolanta , Przybyłowicz Wojciech
Published: October 2008

This study investigates mechanisms of adaptation to metal toxicity peculiar to the midgut epithelium of Epilachna cf. nylanderi (Mulsant, 1850) (Coccinellidae). This species of beetle has currently been identified in only one locality in South Africa and is known to feed on the nickel hyperaccumulator Berkheya coddii Roessl. (Asteraceae), an endemic plant species of the South African ultramafic ecosystem. Our focus involves an analysis of the morphological features of cells forming the midgut epithelium, which is the first organ exposed to toxic levels of metals ingested by the insect. Through the three key processes of apoptosis, necrosis, and autophagy, excess metals are eliminated from the organism and homeostatic conditions are maintained. Apoptosis and necrosis are both known to be involved in the degradation of midgut epithelial cells, while the role of autophagy is mainly implicated in the disintegration of the organelles of cells. This study reports on the participation of these three key degenerative processes in the removal of excess metals based on targeted observations of the insect midgut epithelium by light and electron microscopies. Additionally, the TUNEL reaction was specifically used to detect apoptosis.
Surviving on cached foods — the energetics of egg-caching by arctic foxes
Authors: Careau V. , Giroux J.-F. , Gauthier G. , Berteaux D.
Published: October 2008

Food-caching by arctic foxes ( Vulpes lagopus (L., 1758)) is a behavioural adaptation thought to increase winter survival, especially in bird colonies where a large number of eggs can be cached during a short nesting season. In this paper, we measured the energy content of greater snow goose ( Chen caerulescens atlantica Kennard, 1927) eggs and evaluated their perishability when cached in tundra soil for a whole summer. We estimated that eggs lost only ~8% of their dry mass over 60 days of storage in the ground. We used published estimates on digestibility of nutrients by arctic foxes to estimate that fresh and stored goose eggs contained 816 and 730 kJ of metabolizable energy, respectively, a difference of 11%. Using information on arctic fox energetics, we evaluated that 145 stored eggs were required to sustain the growth of one pup from the age of 1 to 3 months (nutritional independence). Moreover, 23 stored eggs were energetically equivalent to the average fat deposit of an arctic fox during winter. Finally, we calculated that an adult arctic fox would need to recover 160–220 stored eggs to survive 6 months in resting conditions during cold winter temperatures. This value increased to 480 when considering activity cost. Based on egg acquisition and caching rates observed in many goose colonies, we conclude that cached eggs represent an important source of energy relative to the needs of an arctic fox during winter, and have thus a high fitness value.
Nest-site characteristics and breeding success of three species of boreal songbirds in western Newfoundland, Canada
Authors: Dalley Kate L. , Taylor Philip D. , Shutler Dave
Published: October 2008

Delineating habitat requirements and preferences of species is essential for conservation planning. We studied nest habitat use and effects of microsite vegetation characteristics on breeding success of yellow-rumped warblers ( Dendroica coronata (L., 1766)), blackpoll warblers ( Dendroica striata (J.R. Forster, 1772)), and white-throated sparrows ( Zonotrichia albicollis (Gmelin, 1789)) in an area with a low extent (<6% of available land) of forest harvest in northwestern Newfoundland. During 2004 and 2005, 99 nests were located and monitored, and the characteristics of nest sites measured. Vegetation at yellow-rumped and blackpoll warbler nest sites differed from random sites; however, within used sites, no vegetation characteristics were significantly associated with success. White-throated sparrow nest sites contained more downed wood and less ground vegetation than did random sites; however, successful nests were associated with different variables than those that distinguished them from random sites, including less canopy cover and less woody debris. Thus, whereas yellow-rumped and blackpoll warblers used specific nest-site characteristics and white-throated sparrows had higher nest success associated with certain characteristics, the nest characteristics these birds appeared to choose did not have demonstrable fitness benefits.
Chiasmate meiosis in male black fly (Diptera: Simuliidae) larvae associated with mermithid infections (Nematoda: Mermithidae)
Authors: Sharp A. L. , Hunter F. F.
Published: October 2008

Mermithid nematodes (Nematoda: Mermithidae) parasitize larval, pupal, and adult black flies (Diptera: Simuliidae) and may result in the development of intersex adults, generally considered to be feminized males. Simuliid gonad morphology and meiotic chromosome condition were examined in both early-instar larvae and late-instar larvae (≈ pharate pupae) to determine the developmental stage at which mermithid-associated feminization was initiated. We found that feminization occurred in early-instar larvae prior to gill histoblast formation. Infected larvae were morphologically male (rounded testes present) or female (elongated ovaries present), with morphological males exhibiting either male (achiasmate) or female (chiasmate) meiotic chromosomes; morphological females only had chiasmate chromosomes. Mermithid infection can also inhibit simuliid gonad development completely.
SPIN-2 ISING MODEL ON THE BILAYER BETHE LATTICE
Authors: ALBAYRAK ERHAN , AKKAYA SEYMA , YILMAZ SABAN
Published: October 2008

A spin-2 system consisting of two layers of Bethe lattices each with a branching ratio of q Ising spins was analyzed by the use of the exact recursion relations in a pairwise approach. The upper layer interacting with nearest-neighbor (NN) bilinear interaction J1 is laid over the top of the lower layer interacting with bilinear NN interaction J2, and the two layers are tied together via the bilinear interaction between the vertically aligned adjacent NN spins denoted as J3. The study of the ground state phase diagrams on the (J2/|J3|, J1/|J3|) plane with J3>0 and J3<0 and on the (J2/J1, J3/q J1) plane with J1>0 has yielded five distinct ground state configurations. The temperature dependent phase diagrams are obtained for the case with intralayer coupling constants of the two layers with ferromagnetic type J1 and J2>0, and the interlayer coupling constant of the layers with either ferromagnetic J3>0 or antiferromagnetic type J3<0 on the (kT/J1, J3/J1) planes for given values of the J2/J1 for various values of the coordination numbers. As a result, we have found that the model presents both second- and first-order phase transitions, therefore, tricritical points.
THERMODYNAMIC PROPERTIES OF A TRAPPED BOSE GAS: A DIFFUSION MONTE CARLO STUDY
Authors: DATTA S.
Published: October 2008

We investigate the thermodynamic properties of a trapped Bose gas of Rb atoms interacting through a repulsive potential at low but finite temperature (kBT < μ < Tc) by Quantum Monte Carlo method based upon the generalization of Feynman-Kac method1-3 applicable to many-body systems at T=0 to finite temperatures. In this paper, we report temperature variation of condensation fraction, chemical potential, density profile, total energy of the system, release energy, frequency shifts and moment of inertia within the realistic potential model (Morse type) for the first time by diffusion Monte Carlo technique. The most remarkable success was in achieving the same trend in the temperature variation of frequency shifts as was observed in JILA4 for both m=2 and m=0 modes. For other things, we agree with the work of Giorgini et al.,5 Pitaevskii et al.6 and Krauth.7
EFFECT ON HEAT CAPACITY OF DEGENERATED ELECTRON GAS IN DIMENSIONALLY QUANTIZED THIN FILMS
Authors: KORKUT ABDULKADİR , EMİNBEYLİ RAMAZAN
Published: October 2008

In this work, the heat capacity in dimensionally quantized semiconductor thin films with Kane's dispersion law is investigated. Under certain conditions, quantum size effect occurs, depending on the thickness of the thin film, the concentration of conductive electrons, and the non-parabolicity parameters. In thin films having non-parabolic energy spectrum in degenerate electron gas, the film thickness depends on the subband number and the concentration. Therefore, heat capacity takes the form of the saw toothwise and changes as non-monotonous.
SPECTROSCOPY OF TRAPS IN COLORLESS MICROCLINE AS DETERMINED BY CGCD AND VHR
Authors: NABACHANDRA SINGH A. , ARUNKUMAR SHARMA B. , NABADWIP SINGH S.
Published: October 2008

Glow curves of natural thermoluminescence (NTL) of colorless microcline (triclinic form of KAlSi 3 O 8 feldspar) have been subjected to the rigorous Computerized Glow Curve Deconvolution (CGCD) in the framework of kinetic formalism and Various Heating Rates (VHR) methods to compare the spectroscopy of traps. It is observed that trapping parameters obtained by the two methods are coincident, which is well-supported by the standard error analyses, i.e., Figure of Merit (FOM) and Chi-square test. Further analysis shows that the value of Urbach's constant (Um) is no more constant in the present case for the whole temperature range, but has certain values for a certain temperature zone.
TIME-DEPENDENT EVOLUTION OF A WAVE PACKET IN QUANTUM SYSTEMS
Authors: TANG CHI-SHUNG , LUAN PI-GANG
Published: October 2008

We consider wave packet propagation in mesoscopic quantum systems. A number of approaches are compared to look at the general solution of a time-dependent Schrödinger equation and the validity of the Ehrenfest theorem. Detailed calculations are presented to illustrate the results of a charged particle motion in the time-dependent systems, and show that the Ehrenfest theorem is not directly applicable in topologically nontrivial systems.
SUPPRESSING SPIRAL WAVES IN EXCITABLE MEDIA VIA UNIDIRECTIONAL COUPLING
Authors: QIAN YU , XUE YU , CHEN GUANG-ZHI
Published: October 2008

A unidirectional coupling method to successfully suppress spiral waves in excitable media is proposed. It is shown that this control method has high control efficiency and is robust. It adapts to control of spiral waves for catalytic CO oxidation on platinum as well as for the FHN model. The power law n ~ c-kof control time steps n versus the coupling strength c for different models has been obtained.
LAG PROJECTIVE STOCHASTIC PERTURBED SYNCHRONIZATION FOR CHAOTIC SYSTEMS AND ITS APPLICATION IN SECURE COMMUNICATION
Authors: TANG YANG , FANG JIAN-AN , CHEN LIANG
Published: October 2008

In this paper, a simple and systematic adaptive feedback method for achieving lag projective stochastic perturbed synchronization of a new four-wing chaotic system with unknown parameters is presented. Moreover, a secure communication scheme based on the adaptive feedback lag projective synchronization of the new chaotic systems with stochastic perturbation and unknown parameters is presented. The simulation results show the feasibility of the proposed method.
FORMATION OF NANOCRYSTALS AND AMORPHOUS Al2O3 FILM GROWN BY REACTIVE MAGNETRON SPUTTERING
Authors: UDOMKANA NITINAI , LIMSUWAN PICHET
Published: October 2008

Al 2 O 3 films were deposited by reactive magnetron sputtering. As measured with Raman spectroscopy, the atomic force microscopy (AFM), nanohardness and spectrophotometer, respectively. Raman microscopy was then employed to follow their characteristics of optical and acoustic phonon modes. At the optimal sputtering time of 30 minutes, defect-induced first and second order Raman spectra were observed in the 100–900 cm-1 band, which was related to coating composition. However, at the thickness at 250, 300, 450 and 500 nm crystals of the order of nano size of α- Al 2 O 3 phase were achieved, which could be clearly identified by the presence of Raman peaks at 388, 417 cm-1 and 521 cm-1 assigned to Si substrate. The average nano grain size is measured by atomic force microscopy (AFM). It was found that the hardness was strongly dependent on the roughness of the films, the maximum of which was achieved at 20.01 GPa. The optical band gap of Al 2 O 3 films was found to be in the range of 5.55 eV. All these results were analyzed and presented as a function of the deposition parameters and composition, and crystalline phases excited in the films.
CONTROLLING THE QUANTUM COMPUTATIONAL SPEED
Authors: METWALLY NASSER , ABDEL-ATY M. , SEBAWE ABDALLA M.
Published: October 2008

The speed of quantum computation is investigated through the time evolution of the speed of the orthogonality. The external field components for classical treatment besides the detuning and the coupling parameters for quantum treatment play important roles on the computational speed. It has been shown that the number of photons has no significant effect on the speed of computation. However, it is very sensitive to the variation in both detuning and the interaction coupling parameters.
BIFURCATION ANALYSIS OF AN IMPACT MODEL FOR FOREST FIRE PREDICTION
Authors: BIZZARRI FEDERICO , STORACE MARCO , COLOMBO ALESSANDRO
Published: October 2008

This paper concerns the bifurcation analysis of a recently proposed second-order impact model for forest fire prediction. The analysis is carried out with respect to four pairs of system parameters and is based on a one-dimensional piecewise-smooth map naturally induced by the two-dimensional flow. The results of the analysis confirm those reported in the literature and extend them, pointing out the different roles played by several system parameters in influencing the qualitative behavior of fire regimes.
CONTROL OF CHAOS THROUGH AN INSTANTANEOUS LYAPUNOV EXPONENT TARGETING CONTROL ALGORITHM
Authors: OTEAFY AHMED , ZRIBI MOHAMED , SMAOUI NEJIB
Published: October 2008

This paper presents an approach to control the chaotic dynamics of discrete-time (or discretizable) systems. The objective of the paper is to focus on the suppression of the chaotic dynamics and the restoration of order with a state feedback controller. The proposed control method works by targeting instantaneous measures of the Lyapunov exponents of a system and setting them to desired values. At first, the paper presents an instantaneous measure of the Lyapunov exponents; this measure is used to control the system's dynamics. Then, the formulation of the control algorithm to suppress chaos is presented. Two cases for the control structure are considered. The first case corresponds to the case when the number of control inputs is equal to the number of states; the second case corresponds to the case when the number of control inputs is less than the number of states. The Lorenz system, the smooth Chua Oscillator system, the Rössler-hyperchaos system and a fourth order chaotic oscillator system are used as examples to illustrate the proposed control scheme. The simulation results show the efficacy of the proposed control approach.
DYNAMICS AND CHAOS CONTROL OF NONLINEAR SYSTEMS WITH ATTRACTION/REPULSION FUNCTION
Authors: LIU XIAN , WANG JINZHI , DUAN ZHISHENG , HUANG LIN
Published: October 2008

In this paper, a more general third-order chaotic system with attraction/repulsion function is introduced on the basis of [Duan et al., 2005]. A gallery of chaotic attractors, bifurcation diagrams and Lyapunov exponent spectra are presented to show the interesting phenomena of the given system. Based on the absolute stability theory and linear matrix inequality (LMI), a simple method of chaos control for the system is proposed and a stabilizing controller is derived such that chaos oscillations of the system disappear and all chaotic trajectories of it are led to certain equilibrium. Numerical simulations are provided to illustrate the efficiency of the proposed method.
ADAPTIVE OBSERVER BASED SYNCHRONIZATION OF A CLASS OF UNCERTAIN CHAOTIC SYSTEMS
Authors: BOWONG SAMUEL , YAMAPI RENÉ
Published: October 2008

This study addresses the adaptive synchronization of a class of uncertain chaotic systems in the drive-response framework. For a class of uncertain chaotic systems with parameter mismatch and external disturbances, a robust adaptive observer based on the response system is constructed to practically synchronize the uncertain drive chaotic system. Lyapunov stability theory ensures the practical synchronization between the drive and response systems even if Lipschitz constants on function matrices and bounds on uncertainties are unknown. Numerical simulation of two illustrative examples are given to verify the effectiveness of the proposed method.
ANALYSIS AND CONTROL OF BIFURCATION AND CHAOS IN AVERAGE QUEUE LENGTH IN TCP/RED MODEL
Authors: NGA J. H. C. , IU H. H. C. , LING B. W. K. , LAM H. K.
Published: October 2008

This paper studies the bifurcation and chaos phenomena in average queue length in a developed Transmission Control Protocol (TCP) model with Random Early Detection (RED) mechanism. Bifurcation and chaos phenomena are nonlinear behavior in network systems that lead to degradation of the network performance. The TCP/RED model used is a model validated previously. In our study, only the average queue size [Formula: see text] is considered, and the results are based on analytical model rather than actual measurements. The instabilities in the model are studied numerically using the conventional nonlinear bifurcation analysis. Extending from this bifurcation analysis, a modified RED algorithm is derived to prevent the observed bifurcation and chaos regardless of the selected parameters. Our modification is for the simple scenario of a single RED router carrying only TCP traffic. The algorithm neither compromises the throughput nor the average queuing delay of the system.
GEOMETRICALLY INDUCED NONLINEAR DYNAMICS IN ONE-DIMENSIONAL LATTICES
Authors: HAMILTON M. , DE ALCANTARA BONFIM O. F.
Published: October 2008

We present a simple lattice model consisting of a chain of coupled oscillators, where their masses are interconnected by linear springs and allowed to move along a common axis, as in a monorail. In the transverse direction each mass is also attached to two other springs, one on each side of the mass. The ends of these springs are kept at fixed positions. The nonlinearity in the model arises from the geometric constraints imposed on the motion of the masses, as well as from the configuration of the springs, where in the transverse directions the springs are either in the extended or compressed state depending on the position of the mass. Under these conditions we show that solitary waves (domain walls) are present in the system. In the long wavelength limit an analytical solution for these nonlinear waves is found. Numerical integrations of the equations of motion in the full discrete system are also performed to analyze the stability of the domain wall solution. Nonlinear supratransmission is also shown to exist in the model and a discussion of mechanism is presented.
PREPROCESSING AND GRAPHICS ASSOCIATED WITH CYCLIC SYMMETRY
Authors: MARAMBEDU KARTHIKEYAN R. , SANJEEVI SUJEEVRAJA , SRINIVASAN VIJAY , NAGENDRAN LATHA , RAMAMURTI V.
Published: October 2008

This paper presents a user-friendly procedure for preprocessing nodal and element data to be used in problems associated with cyclic symmetry. The concept of master, slave, adjacent and interior nodes is employed. Three types of industrial applications using plate elements are discussed.
A NEW PARTIAL DISCRETIZATION METHODOLOGY FOR NARROW COMPOSITE BEAMS UNDER PLANE STRESS CONDITIONS
Authors: KANT TARUN , PENDHARI SANDEEP S. , DESAI YOGESH M.
Published: October 2008

A partial discretization formulation with two-noded finite elements (FEs) under plane stress conditions has been developed for flexural analysis of composite and sandwich beams subjected to transverse loading. The methodology consists in defining a two-point boundary value problem (BVP) governed by a set of coupled first-order ordinary differential equations (ODEs) with four degrees of freedom (u, w, τxz and σz) per node. Continuity of interlaminar transverse stresses and displacements at laminae interfaces is implicitly enforced in the formulation. All the fundamental elasticity relationships between the components of stress, strain and displacement fields are explicitly maintained throughout the elastic continuum. Results have been obtained for cross-ply composite and sandwich beams. Excellent agreement with available analytical, mixed semianalytical and FE solutions is observed. Some new results with clamped support conditions have also been obtained and are presented to serve as benchmark solutions for future reference and to show the generality of the formulation.
NUMERICAL EXPERIMENTS ON THE HYPERCHAOTIC CHEN SYSTEM BY THE ADOMIAN DECOMPOSITION METHOD
Authors: AL-SAWALHA M. MOSSA , NOORANI M. S. M. , HASHIM I.
Published: October 2008

The aim of this paper is to investigate the accuracy of the Adomian decomposition method (ADM) for solving the hyperchaotic Chen system, which is a four-dimensional system of ODEs with quadratic nonlinearities. Comparisons between the decomposition solutions and the fourth order Runge–Kutta (RK4) solutions are made. We look particularly at the accuracy of the ADM as the hyperchaotic Chen system has higher Lyapunov exponents than the hyperchaotic Rössler system. A comparison with the hyperchaotic Rössler system is given.
NECKLACE SWAP PROBLEM FOR RHYTHMIC SIMILARITY MEASURES
Authors: ARDILA YOAN JOSÉ PINZÓN , CLIFFORD RAPHAËL , ILIOPOULOS COSTAS S. , LANDAU GAD M. , MOHAMED MANAL
Published: October 2008

Given two n-bit (cyclic) binary strings, A and B, represented on a circle (necklace instances), let each sequence have the same number (k) of 1's. We are interested in computing the cyclic swap distance between A and B, i.e. the minimum number of swaps needed to convert A to B, minimized over all possible rotations of B. We show that, given the compressed representation of A and B, this distance may be computed in O(k2).
FUNCTIONAL CATHODE MATERIALS FOR Li-ION BATTERIES — PART I: FUNDAMENTALS
Authors: MOLENDA JANINA , MARZEC JACEK
Published: October 2008

The paper presents basics of the lithium intercalation process into cathode materials used in lithium batteries. The ability and efficiency of lithium intercalation into transition metal compounds have been shown to depend strongly on their electronic structure. A correlation between chemical bonding, electronic structure and electrochemical properties of the cathode materials Li x M a X b (M = transition metal; X = O , S , Se ) has been pointed out.
CATALYTIC REQUIREMENTS FOR MIXED REACTANT FUEL CELLS
Authors: RIESS ILAN
Published: October 2008

Significant advantage could be achieved if mixed reactant fuel cells, MR-FC, were functioning. These cells are intended to operate on a mixture of air and fuel introduced into both the cathode and anode compartment. Symmetry is broken by using different electrode materials exhibiting special and different catalytic properties. No high temperature fuel cell was reported to date to function as a true MR-FC and only one, low temperature type, did function properly. We discuss the required catalytic properties which are unique in that they promote electrochemical reactions and suppress chemical ones as well as possible ways to search for them. The chemical reaction which has to be suppressed is the direct reaction of fuel and oxygen as the two components are premixed and the mixture is then introduced into the fuel cell at both electrode compartments. The electrochemical reactions that should be promoted are the reduction of oxygen at the cathode and the oxidation of fuel at the anode only by oxygen ions that emerge from the solid electrolyte. Conditions to promote this selectivity are discussed. These are derived from the theory of chemisorption as applied to heterogeneous catalysis.
SINGLE CRYSTAL GROWTH AND TEXTURING OF LEAD-BASED PIEZOELECTRIC CERAMICS VIA TEMPLATED GRAIN GROWTH PROCESS
Authors: RICHTER THOMAS , SCHUH CARSTEN , MOOS RALF , SUVACI ENDER
Published: October 2008

In the field of high-performance piezoelectric materials, PMN-PT single crystals and textured ceramics have been attracting increased research interest for several years. On the other hand, the growth of single crystals from melt for PZT-based compositions is impossible due to its incongruent melting behavior. In order to obtain the characteristics of pure single crystal PZT as closely as possible, the PZT must be textured by secondary recrystallization of introduced seeds in a fine-grained matrix. Zirconium was therefore added to a PMN-PT-ceramic with 32 mol% PT ( Pb ( Mg 1/3 Nb 2/3)0.68 Ti 0.32 O 3) in order to obtain a PMN-PZT-ceramic with 37 mol% PT and 21 mol% PZ ( Pb ( Mg 1/3 Nb 2/3)0.42( Ti 0.638 Zr 0.362)0.58 O 3). Initially, the growth mechanism of (001)-oriented BaTiO 3 (BT) single crystals in those matrices was investigated. The piezoelectric single crystals were produced via a process that starts with the hot pressing of a BT single crystal in cold isostatically pressed ceramics, followed by an additional sintering step in order to achieve a secondary recrystallization. The measured growth lengths in PMN-PT and PMN-PZT matrices were up to 140 μm and 65 μm, respectively. Having developed this understanding, both ceramics were textured via the templated grain growth (TGG) process by using (001)-oriented BT templates. Sintering of templated grain bodies resulted in template growth into the matrix to produce textured ceramics with Lotgering factors up to 0.99 for both compositions. In textured samples unipolar strain s33 was enhanced by a factor of up to 1.8 compared to randomly oriented ceramics. By contrast, BT single crystal growth in an alternative PZT matrix with NdMn doping was not successful. Hence, in the present work, growth experiments in this NdMn -doped PZT were first performed using PZT fibers of similar composition as seeds. Growth of the fiber diameter of up to 100 μm was observed in that matrix.
DISORDER ENHANCED MAGNETIC MOMENT IN Fe2CrAl RIBBONS
Authors: LUO H. Z. , ZHANG H. W. , CHEN J. L. , WU G. H. , DAI X. F. , ZHU X. X. , JIANG C. B. , XU H. B.
Published: October 2008

The electronic structure and magnetic properties of Fe 2 CrAl have been investigated theoretically and experimentally. The theoretical calculations show that there is an energy gap in the minority-spin band in the electronic structure of ordered Fe 2 CrAl with the L21 structure and that the spin-polarization ratio is as high as 93%. The calculated total spin moment is 0.97 μB/f.u. However, in melt-spun Fe 2 CrAl ribbons, the B2 type structure, an atomic-site disordered L21 structure, is found and this atomic site disorder gives rise to a magnetic moment of 2.02 μB in the ribbons which is much higher than the theoretical value. The calculations prove that the enhanced magnetic moment is mainly due to the Fe – Cr and Fe – Al types of disorder. In contrast, the Cr – Al type disorder has little influence on the total spin moment and the spin-polarization ratio.
MODELING AND APPLICATION STUDIES OF AN ELECTROCHEMICAL HYBRID SYSTEM
Authors: SIKHA GODFREY , POPOV BRANKO N.
Published: October 2008

A first principle based mathematical model is presented to simulate the performance of a lithium-ion battery/electrochemical capacitor hybrid system. The advantages of the hybrid system over the battery system are discussed for pulse type of loads. The hybrid system predicted better utilization of the battery operated under high frequencies and low duty ratio pulse loads. Simulated specific energy and power relationships (Ragone plots) are also presented to identify regimes where the hybrid systems performed better than the battery system on a unit mass basis. The model was validated by comparing the simulations to the experimental data obtained from a Sony US 18650 lithium-ion battery/Maxwell PC100F electrochemical capacitor network hybrid system. Finally a case study comparing the response of the battery and a hybrid system to two different high power pulse profiles encountered in real time applications is presented. Simulation results indicate that hybrid systems exhibited superior performance over the battery system for pulse power profiles with sufficient relaxation times.
SCALING BEHAVIOR OF DYNAMIC HYSTERESIS IN PZT-BASED FERROELECTRIC BULK CERAMICS
Authors: YIMNIRUN RATTIKORN
Published: October 2008

The scaling relations for the hysteresis loops of soft and hard PZT bulk ceramics were obtained in the forms of  ∝ f -0.25E0 and [Formula: see text], respectively, while those for the minor loops took the forms of [Formula: see text] and [Formula: see text]. The similarity of the scaling relations suggested that the scaling behaviors of the two types of bulk ceramics were in the same universality class and that the complex defects contributed only slightly to the dynamic behaviors. Finally, this study implied that the domain structures played significant role in controlling dynamic hysteresis behavior of ferroelectric materials.
POROUS NANOCOMPOSITE POLYMER ELECTROLYTE PREPARED BY A NON-SOLVENT INDUCED PHASE SEPARATION PROCESS
Authors: LI Z. H. , XIAO Q. Z. , ZHANG P. , ZHANG H. P. , WU Y. P. , VAN REE T.
Published: October 2008

A non-solvent induced phase separation (NIPS) process was used to prepare a new kind of porous nanocomposite polymer electrolyte using glycerol as non-solvent for poly(vinylidene difluoride-co-hexafluoropropylene) copolymer. TiO 2 nanoparticles were incorporated by in situ hydrolysis of Ti ( OC 4 H 9)4 and dispersed uniformly in the polymer matrix. They affected the porous structure of the obtained nanocomposite polymer membranes (NCPMs). When the amount of TiO 2 arrived at 7.6 wt.%, the NCPM reached the maximum porosity of 70.5%. The resulting nanocomposite polymer electrolyte (NCPE) presents an ionic conductivity of up to 1.98 × 10-3 S · cm-1 at room temperature and an apparent activation energy for ion transport of 13.32 kJ · mol-1, suggesting its promising application in lithium ion batteries.
CRYSTALLIZATION BEHAVIOR OF AMORPHOUS TI-NI-CU ALLOY RIBBONS
Authors: NAM JUNG MIN , LEE YONG HEE , NAM TAE HYUN , KIM YEON WOOK , LEE JUNG MOO
Published: October 2008

Amorphous Ti 50 Ni (50-x) Cu x (at.%) (x = 15, 20 and 25) alloy ribbons were prepared by melt spinning, and then their crystallization behavior was investigated by optical microscopy, transmission electron microscopy, X-ray diffraction and differential scanning calorimetry. Wavenumber (Qp) decreased from 29.40 nm-1 to 29.29 nm-1 and ΔT(T g - T x ) increased from 31 K to 36 K with increasing Cu content from 15 at.% to 25 at.%, suggesting that glass forming ability of Ti – Ni – Cu alloy ribbons increased with increasing Cu content. Activation energy for crystallization decreased from 211.5 kJ/mol to 136.4 kJ/mol with increasing Cu content from 15 at.% to 25 at.%, suggesting that a stability of Ti – Ni – Cu amorphous decreased with increasing Cu content.
TNBS-induced inflammation modulates the function of one class of low-threshold rectal mechanoreceptors in the guinea pig
Authors: Lynn P. A. , Chen B. N. , Zagorodnyuk V. P. , Costa M. , Brookes S. J. H.
Published: October 2008

The effects of trinitrobenzene sulfonic acid (TNBS)-induced inflammation on specialized, low-threshold, slowly adapting rectal mechanoreceptors were investigated in the guinea pig. Under isoflurane anesthesia, 300 μl saline or TNBS (15 mg/ml) in 30% ethanol was instilled 7 cm from the anal sphincter. Six or 30 days later, single unit extracellular recordings were made from rectal nerve trunks in flat-sheet in vitro preparations attached to a mechanical tissue stretcher. TNBS treatment caused macroscopic ulceration of the rectal mucosa at 6 days, which fully resolved by 30 days. Muscle contractility was unaffected by TNBS treatment. At 6 days posttreatment, responses of low-threshold rectal mechanoreceptors to circumferential stretch were increased, and the proportion of afferents responding with von Frey hair thresholds ≤0.1 mN and mechanoreceptor excitability in response to electrical stimulation were increased in TNBS-treated tissue, suggesting increased sensitivity of the mechanotransducer. Mechanoreceptor function at 30 days posttreatment was in most cases unchanged. The inflammatory mediator prostaglandin E2 (1 μM) activated mechanoreceptors (6 days) in conjunction with contractile activity, but capsaicin (1 μM) failed to activate mechanoreceptors. Bradykinin (1 μM) activated mechanoreceptors independently of contractile activity and responses to stretch were increased in the presence of bradykinin. Both capsaicin and bradykinin activated unidentified stretch-insensitive afferents independently of contractile activity. Mechanoreceptor function is modulated at 6 days posttreatment but not at 30 days, suggesting a moderate increase in mechanoreceptor sensitivity in inflamed tissue but not after recovery. Other unclassified stretch-insensitive afferents are responsive to inflammatory mediators and capsaicin and may be involved in aspects of visceral sensation.
Somatostatin stimulates menin gene expression by inhibiting protein kinase A
Authors: Mensah-Osman Edith , Zavros Yana , Merchant Juanita L.
Published: October 2008

Somatostatin is a potent inhibitor of gastrin secretion and gene expression. Menin is a 67-kDa protein product of the multiple endocrine neoplasia type 1 (MEN1) gene that when mutated leads to duodenal gastrinomas, a tumor that overproduces the hormone gastrin. These observations suggest that menin might normally inhibit gastrin gene expression in its role as a tumor suppressor. Since somatostatin and ostensibly menin are both inhibitors of gastrin, we hypothesized that somatostatin signaling directly induces menin. Menin protein expression was significantly lower in somatostatin-null mice, which are hypergastrinemic. We found by immunohistochemistry that somatostatin receptor-positive cells (SSTR2A) express menin. Mice were treated with the somatostatin analog octreotide to determine whether activation of somatostatin signaling induced menin. We found that octreotide increased the number of menin-expressing cells, menin mRNA, and menin protein expression. Moreover, the induction by octreotide was greater in the duodenum than in the antrum. The increase in menin observed in vivo was recapitulated by treating AGS and STC cell lines with octreotide, demonstrating that the regulation was direct. The induction required suppression of protein kinase A (PKA) since forskolin treatment suppressed menin protein levels and octreotide inhibited PKA enzyme activity. Small-interfering RNA-mediated suppression of PKA levels raised basal levels of menin protein and prevented further induction by octreotide. Using AGS cells, we also showed for the first time that menin directly inhibits endogenous gastrin gene expression. In conclusion, somatostatin receptor activation induces menin expression by suppressing PKA activation.
Mechanisms and regulation of vitamin C uptake: studies of the hSVCT systems in human liver epithelial cells
Authors: Reidling Jack C. , Subramanian Veedamali S. , Dahhan Tamara , Sadat Mohammed , Said Hamid M.
Published: October 2008

Humans use two sodium-ascorbate cotransporters (hSVCT1 and hSVCT2) for transporting the dietary essential micronutrient ascorbic acid, the reduced and active form of vitamin C. Although the human liver plays a pivotal role in regulating and maintaining vitamin C homeostasis, vitamin C transport physiology and regulation of the hSVCT systems in this organ have not been well defined. Thus, this research used a human hepatic cell line (HepG2), confirming certain results with primary human hepatocytes and determined the initial rate of ascorbic acid uptake to be Na+ gradient, pH dependent, and saturable as a function of concentration over low and high micromolar ranges. Additionally, hSVCT2 protein and mRNA are expressed at higher levels in HepG2 cells and native human liver, and the cloned hSVCT2 promoter has more activity in HepG2 cells. Results using short interfering RNA suggest that in HepG2 cells, decreasing hSVCT2 message levels reduces the overall ascorbic acid uptake process more than decreasing hSVCT1 message levels. Activation of PKC intracellular regulatory pathways caused a downregulation in ascorbic acid uptake not mediated by a single predicted PKC-specific amino acid phosphorylation site in hSVCT1 or hSVCT2. However, PKC activation causes internalization of hSVCT1 but not hSVCT2. Examination of other intracellular regulatory pathways on ascorbic acid uptake determined that regulation also potentially occurs by PKA, PTK, and Ca2+/calmodulin, but not by nitric oxide-dependent pathways. These studies are the first to determine the overall ascorbic acid uptake process and relative expression, regulation, and contribution of the hSVCT systems in human liver epithelial cells.
Protein kinase D1 mediates NF-κB activation induced by cholecystokinin and cholinergic signaling in pancreatic acinar cells
Authors: Yuan Jingzhen , Lugea Aurelia , Zheng Ling , Gukovsky Ilya , Edderkaoui Mouad , Rozengurt Enrique , Pandol Stephen J.
Published: October 2008

The transcription factor NF-κB plays a critical role in inflammatory and cell death responses during acute pancreatitis. Previous studies in our laboratory demonstrated that protein kinase C (PKC) isoforms PKCδ and ε are key regulators of NF-κB activation induced by cholecystokinin-8 (CCK-8), tumor necrosis factor-α, and ethanol. However, the downstream participants in regulating NF-κB activation in exocrine pancreas remain poorly understood. Here, we demonstrate that protein kinase D1 (PKD1) is a key downstream target of PKCδ and PKCε in pancreatic acinar cells stimulated by two major secretagogues, CCK-8 and the cholinergic agonist carbachol (CCh), and that PKD1 is necessary for NF-κB activation induced by CCK-8 and CCh. Both CCK-8 and CCh dose dependently induced a rapid and striking activation of PKD1 in rat pancreatic acinar cells, as measured by in vitro kinase assay and by phosphorylation at PKD1 activation loop (Ser744/748) or autophosphorylation site (Ser916). The phosphorylation and activation of PKD1 correlated with NF-κB activity stimulated by CCK-8 or CCh, as measured by NF-κB DNA binding. Either inhibition of PKCδ or ε by isoform-specific inhibitory peptides, genetic deletion of PKCδ and ε in pancreatic acinar cells, or knockdown of PKD1 by using small interfering RNAs in AR42J cells resulted in a marked decrease in PKD1 and NF-κB activation stimulated by CCK-8 or CCh. Conversely, overexpression of PKD1 resulted in augmentation of CCK-8- and CCh-stimulated NF-κB activation. Finally, the kinetics of PKD1 and NF-κB activation during cerulein-induced rat pancreatitis showed that both PKD1 and NF-κB activation were early events during acute pancreatitis and that their time courses of response were similar. Our results identify PKD1 as a novel early convergent point for PKCδ and ε in the signaling pathways mediating NF-κB activation in pancreatitis.
Negative reciprocity between angiotensin II type 1 and dopamine D1 receptors in rat renal proximal tubule cells
Authors: Khan Farah , Špicarová Zuzana , Zelenin Sergey , Holtbäck Ulla , Scott Lena , Aperia Anita
Published: October 2008

Sodium excretion is bidirectionally regulated by dopamine, acting on D1-like receptors (D1R) and angiotensin II, acting on AT1 receptors (AT1R). Since sodium excretion has to be regulated with great precision within a short frame of time, we tested the short-term effects of agonist binding on the function of the reciprocal receptor within the D1R-AT1R complex in renal proximal tubule cells. Exposure of rat renal proximal tubule cells to a D1 agonist was found to result in a rapid partial internalization of AT1R and complete abolishment of AT1R signaling. Similarly, exposure of rat proximal tubule cells and renal tissue to angiotensin II resulted in a rapid partial internalization of D1R and abolishment of D1R signaling. D1R and AT1R were, by use of coimmunoprecipitation studies and glutathione- S-transferase pull-down assays, shown to be partners in a multiprotein complex. Na+-K+-ATPase, the target for both receptors, was included in this complex, and a region in the COOH-terminal tail of D1R (residues 397-416) was found to interact with both AT1R and Na+-K+-ATPase. Results indicate that AT1R and D1R function as a unit of opposites, which should provide a highly versatile and sensitive system for short-term regulation of sodium excretion.
Enhanced renal sensitivity of the spontaneously hypertensive rat to urotensin II
Authors: Abdel-Razik Alaa E. S. , Balment Richard J. , Ashton Nick
Published: October 2008

Urotensin II (UII) has been implicated widely in cardiovascular disease. The mechanism(s) through which it contributes to elevated blood pressure is unknown, but its emerging role as a regulator of mammalian renal function suggests that the kidney might be involved. The aim of this study was to determine the effect of UII on renal function in the spontaneously hypertensive rat (SHR). UII infusion (6 pmol·min−1·100 g body wt−1) in anesthetized SHR and control Wistar-Kyoto (WKY) rats produced marked reductions in glomerular filtration rate (ΔGFR WKY, n = 7, −0.3 ± 0.1 vs. SHR, n = 7, −0.6 ± 0.1 ml·min−1·100 g body wt−1, P = 0.03), urine flow, and sodium excretion rates, which were greater in SHR by comparison with WKY rats. WKY rats also showed an increase in fractional excretion of sodium (ΔFENa; +0.6 ± 0.1%, P = 0.02) in contrast to SHR in which no such change was observed (ΔFENa −0.6 ± 0.2%). Blockade of the UII receptor (UT), and thus endogenous UII activity, with urantide evoked an increase in GFR which was greater in SHR (+0.3 ± 0.1) compared with WKY rats (+0.1 ± 0.1 ml·min−1·100 g body wt−1, P = 0.04) and was accompanied by a diuresis and natriuresis. UII and UT mRNA expression were greater in the renal medulla than the cortex of both strains; however, expression levels were up to threefold higher in SHR tissue. SHR are more sensitive than WKY to UII, which acts primarily to lower GFR thus favoring salt retention in this model of hypertension.
Ablation of developing podocytes disrupts cellular interactions and nephrogenesis both inside and outside the glomerulus
Authors: Jia Qunshan , McDill Bradley W. , Sankarapandian Bala , Wu Sen , Liapis Helen , Holzman Lawrence B. , Capecchi Mario R. , Miner Jeffrey H. , Chen Feng
Published: October 2008

Podocyte loss in adults leads to glomerulosclerosis. However, the impact of podocyte loss on glomerulogenesis and the development of the kidney as a whole has not been directly studied. Here, we used a podocyte-specific Cre transgene to direct the production of diphtheria toxin (DTA) inside podocytes during nephrogenesis. Affected podocytes underwent translational arrest and apoptosis, leading to oliguria, proteinuria, hematuria, interstitial hemorrhage, and perinatal death. Glomerular cell-cell interactions were disrupted, even before overt podocyte apoptosis. VEGF production by podocytes was greatly decreased, and this was associated with reduced endothelial fenestration and altered glomerular vascular architecture. In addition to these glomerular anomalies, embryonic podocyte ablation also led to structural changes and increased apoptosis in proximal tubules. The collecting ducts, however, only showed molecular changes that are likely an indirect effect of the greatly reduced urine flow. Although podocyte loss significantly impacted the development and maintenance of the vasculature both inside and outside the glomerulus, our results suggest that there is a lack of long-range signaling from deep-seated, mature glomeruli to the differentiating cells in the outer nephrogenic zone. This study illustrates the tight integration of various cell types in the developing kidney and shows that the impact of podocyte loss during development is much greater than that in adults. This study also shows the specificity and effectiveness of a genetically controlled podocyte ablation system in mice where the additional readily available tools can further expand its applications.