bluuebunny/crossref_metadata_2025 huggingface dataset:
Polymerization of 4‐Methyl‐1,3‐pentadiene with Catalysts Based on Cyclopentadienyl Titanium Chlorides: Effect of anti/syn Isomerism of the Allylic Group on the Chemoselectivity and the Role of Backbiting Coordination in 1,3‐Diene Polymerization
Authors: Cugini Cecilia , Rombolà Ottavio A. , Giarrusso Antonino , Porri Lido , Ricci Giovanni
Published: August 2005

Summary: Homopolymerization of 4‐methyl‐1,3‐pentadiene (MP) and copolymerization of 4‐methyl‐1,3‐pentadiene with alkenes (ethylene, 1‐pentene, 4‐methyl‐1‐pentene) were performed to investigate the effect of the so‐called backbiting coordination on the chemoselectivity of 1,3‐diene polymerization. Three homogeneous catalyst systems were used: CpTiCl3‐MAO, Cp2TiCl2‐MAO and Cp2TiCl‐MAO. Backbiting coordination is possible with the first catalyst, but not with the other two. The three catalysts gave similar results, which indicates that backbiting has no effect on the polymerization chemoselectivity, contrary to what has been reported in recent literature. An interpretation is presented for the formation of 1,4 units in MP/alkene copolymers. This interpretation is based on the fact that allyl groups have predominantly a syn configuration in MP homopolymerization, whereas allyl groups of anti configuration are formed in MP/alkene copolymerization. The role of backbiting in diene polymerization is discussed.

The effect of anti/syn isomerism on the chemoselectivity in the different polymerizations.

image

The effect of anti/syn isomerism on the chemoselectivity in the different polymerizations.
Decomposition Kinetics, Life Estimation, and Dielectric Study of an Acrylate based Photopolymer for Microfabrication and Photonic Applications
Authors: Nguyen Le Huong , Gu Min
Published: August 2005

Summary: Kinetics of thermal decomposition of the acrylate‐based photopolymer LN1 for microfabrication was studied with dynamic thermogravimetric analysis experiments. The kinetic parameters including the activation energy, pre‐exponential factor, and rate constant, which were calculated by the Flynn and Wall method, are presented. The results indicate that thermal degradation of the material consists of three distinct reaction stages. A mechanism of thermal decomposition was proposed, which is in good agreement with the experimental results. The lifetime of the material was estimated by the method of Toop, giving the key information for microelectronics and photonic applications. In addition, the curing behavior of the system was studied by dielectric analysis providing valuable information for processing and fabrication control.

Conversion time versus temperature (a), percentage conversion versus time (b).

image

Conversion time versus temperature (a), percentage conversion versus time (b).
Grafting of Hindered Amine Stabilizer in Poly(propylene) Films under γ‐Irradiation
Authors: Kaci Mustapha , Touati Naima , Setnescu Radu , Zaharescu Traian , Setnescu Tanta , Jipa Silviu
Published: August 2005

Summary: In this paper, the grafting of a hindered amine stabilizer (HAS) is studied in isotactic poly(propylene) (PP) films under γ‐irradiation. The HAS used has a definite structure that combines a hindered amine functionality and a UV‐absorbing unit (benzylidene malonate ester group) detectable at 308 nm in the UV spectrum of PP film and 314 nm in chloroform. The stabilizer is added to the polymer at various concentration ratios: 0.1, 0.2, and 0.3 wt.‐%. The percentage of HAS grafting in the PP film at various additive concentrations is determined as a function of γ‐radiation dose in the range of 0–100 kGy by direct spectroscopic measurements through the absorption band of the stabilizer in the UV spectra of the PP film. The percentage of free HAS extracted with chloroform from the PP film versus the radiation dose is determined by UV spectroscopy for all the additive concentrations used. This study reveals that only 80% of the HAS is grafted on the 100 kGy irradiated PP matrix independent of the additive concentration used. However, the percentage of HAS grafted on PP films displays an exponential dependence on γ‐radiation dose. These results are consistent with the data obtained on the free HAS content. γ‐Irradiation grafting of HAS in the PP is accompanied by the oxidative degradation of the polymer substrate that is evaluated by increasing the carbonyl index and reducing significantly the oxidation induction time of the PP films.

The percentage of hindered amine stabilizer grafted to the PP film as a function of γ‐radiation dose.

magnified image

The percentage of hindered amine stabilizer grafted to the PP film as a function of γ‐radiation dose.
Characterization of pig vasa homolog gene and specific expression in germ cell lineage
Authors: Lee Gab Sang , Kim Hye Soo , Lee So Hyun , Kang Min Soo , Kim Dae Yong , Lee Chang Kyu , Kang Sung Keun , Lee Byeong Chun , Hwang Woo Suk
Published: August 2005

The vasa gene is known to be an important factor for germ cell development in both invertebrates and vertebrates. In the present study, we cloned the porcine vasa homolog (Pvh, 2,172 bps) and investigated its expression at mRNA and protein levels. The isolated cDNA had deduced 724 amino acid residues with significant homology to mouse (85%) and human (91%) vasa. In adult tissues, Pvh transcript was restricted to the ovary and testis, and was undetectable in somatic tissues. During preimplantation embryo development, Pvh was transcribed in oocytes and fertilized 2‐cell embryos, but not in other preimplantation embryos. In fetal stage, the transcript of Pvh gene was expressed in all fetal stage, except in day 17–18. Immunohistochemical analysis of fetal and adult gonad revealed that the Pvh protein was localized in oocytes and spermatocytes, consistent with mRNA expression. Interestingly, Pvh protein was also observed in proliferating primordial germ cells (PGCs) and freshly isolated PGCs, but not in embryonic germ cells. Our results suggest that Pvh gene can be a useful marker for germ cell development in pigs. Mol. Reprod. Dev. © 2005 Wiley‐Liss, Inc.
Quantity discount pricing policies for heterogeneous retailers with price sensitive demand
Authors: Wang Qinan , Wang Ruifang
Published: August 2005

Although quantity discount policies have been extensively analyzed, they are not well understood when there are many different buyers. This is especially the case when buyers face price‐sensitive demand. In this paper we study a supplier's optimal quantity discount policy for a group of independent and heterogeneous retailers, when each retailer faces a demand that is a decreasing function of its retail price. The problem is analyzed as a Stackelberg game whereby the supplier acts as the leader and buyers act as followers. We show that a common quantity discount policy that is designed according to buyers' individual cost and demand structures and their rational economic behavior is able to significantly stimulate demand, improve channel efficiency, and substantially increase profits for both the supplier and buyers. Furthermore, we show that the selection of all‐units or incremental quantity discount policies has no effect on the benefits that can be obtained from quantity discounts. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2005
Fourth‐order finite difference scheme for a system of quasilinear elliptic equations
Authors: Stys Tadeusz , Stys Krystyna
Published: August 2005

The system of two quasilinear elliptic equations is approximated by the method of lines, which has the truncation error O(h2) at points neighboring the boundary and O(h4) at the most interior points. It is proved that the global error of the method is O(h4) at all mesh points. The two‐point boundary value problem for the system of ordinary differential equations that arises from the method of lines is solved by the O(h4) convergent finite difference scheme, suitable to the equations of the form uxx = f(x, u) without the first derivative ux. The system of algebraic equations obtained by the full discretization is solved by Gauss elimination method for three diagonal matrices combined with the method of iterations. A numerical example is presented.
Finite element method in the solution of the Euler and Navier‐Stokes equations for internal flow
Authors: Habashi W. G. , Baruzzi G. , Peeters M. F. , Hafez M. M.
Published: August 2005

Finite element solutions of the Euler and Navier‐Stokes equations are presented, using a simple dissipation model. The discretization is based on the weak‐Galerkin weighted residual method and equal interpolation functions for all the unknowns are permitted. The nonlinearity is iterated upon using a Newton method and at each iteration the linear algebraic system is solved by a direct solver with all unknowns fully coupled. Results are presented for two‐dimensional transonic inviscid flows and two‐ and three‐dimensional incompressible viscous flows. Convergence of the algorithm is shown to be quadratic, reaching machine accuracy in very few iterations. The inviscid results demonstrate the existence of nonunique numerical solutions to the steady Euler equations.
Purication of betulinic acid from Eugenia florida (Myrtaceae) by high‐speed counter‐current chromatography
Authors: Frighetto Nelson , Welendorf Rodolfo Max , da Silva Ana Maria Pereira , Nakamura Marcos Jun , Siani Antonio Carlos
Published: August 2005

A high yield of betulinic acid (up to 17% from the ethanolic extract) was found in the leaves of Eugenia florida collected in south‐eastern Brazil, making this species a potential commercial source of the title compound. Extracts of E. florida were subjected to solvent partition, and rapid high‐speed counter‐current chromatography (HSCCC) was applied to the semi‐crude extracts to afford betulinic acid in high purity. The mobile and stationary phases were derived from the two‐phase solvent system composed of n‐hexane–ethyl acetate–methanol–water (10:5:2.5:1). The developing solvent system (stationary and mobile phases) for optimum HSCCC separation was chosen by dissolving the fraction to be chromatographed in the proposed solvent mixture and determining the amount of betulinic acid in each phase by densitometric TLC. Puried betulinic acid was characterized by 13C‐NMR, GC‐MS and co‐injection of its methyl ester with standards in GC‐FID. The HSCCC technique is commonly employed to isolate triterpene glycosides, but is applied in this study to an aglycone. Copyright © 2005 John Wiley & Sons, Ltd.
Hybrid metal–polymer composites from functional block copolymers
Authors: Grubbs Robert B.
Published: August 2005

The combination of metals and polymers in hybrid materials is a research area of great current interest. A number of methods for controlling the positioning of metallic species within polymer matrices on the nanometer scale have been developed. This highlight focuses on the use of functional block copolymers for the localization of metal species, especially nanoparticles, on the nanometer scale through block copolymer phase segregation. Research from the author's group on the use of alkyne‐functional block copolymers for the preparation of cobalt‐containing materials is discussed in this context. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4323–4336, 2005
Angiosarcoma associated with a vascular graft: Case report
Authors: Brito Dulce A. , Carneiro Filomena , Pedro Mónica , Salgueiro Lina , Palhano Maria J. , Nunes José S. , de Pádua Fernando , Madeira Hugo C.
Published: August 2005

We describe a case of retroperitoneal angiosarcoma in association with an aorta-bifemoral Dacron graft. Surgery was not performed and the patient died. At autopsy, a local extensive, high-grade angiosarcoma was confirmed and a left pulmonar metastase was found. A sarcoma should always be considered in the differential diagnosis of any mass associated with vascular grafts, and an extensive investigation of possible and unsuspected distant metastasis is mandatory in all cases.
Survey of chronic pain in Europe: Prevalence, impact on daily life, and treatment
Authors: Breivik Harald , Collett Beverly , Ventafridda Vittorio , Cohen Rob , Gallacher Derek
Published: August 2005

This large scale computer‐assisted telephone survey was undertaken to explore the prevalence, severity, treatment and impact of chronic pain in 15 European countries and Israel. Screening interviews identified respondents aged ≥18 years with chronic pain for in‐depth interviews. 19% of 46,394 respondents willing to participate (refusal rate 46%) had suffered pain for ≥6 months, had experienced pain in the last month and several times during the last week. Their pain intensity was ≥5 on a 10‐point Numeric Rating Scale (NRS) (1 = no pain, 10 = worst pain imaginable) during last episode of pain. In‐depth interviews with 4839 respondents with chronic pain (about 300 per country) showed: 66% had moderate pain (NRS = 5–7), 34% had severe pain (NRS = 8–10), 46% had constant pain, 54% had intermittent pain. 59% had suffered with pain for two to 15 years, 21% had been diagnosed with depression because of their pain, 61% were less able or unable to work outside the home, 19% had lost their job and 13% had changed jobs because of their pain. 60% visited their doctor about their pain 2–9 times in the last six months. Only 2% were currently treated by a pain management specialist. One‐third of the chronic pain sufferers were currently not being treated. Two‐thirds used non‐medication treatments, e.g,. massage (30%), physical therapy (21%), acupuncture (13%). Almost half were taking non‐prescription analgesics; ‘over the counter’ (OTC) NSAIDs (55%), paracetamol (43%), weak opioids (13%). Two‐thirds were taking prescription medicines: NSAIDs (44%), weak opioids (23%), paracetamol (18%), COX‐2 inhibitors (1‐36%), and strong opioids (5%). Forty percent had inadequate management of their pain. Interesting differences between countries were observed, possibly reflecting differences in cultural background and local traditions in managing chronic pain. Conclusions: Chronic pain of moderate to severe intensity occurs in 19% of adult Europeans, seriously affecting the quality of their social and working lives. Very few were managed by pain specialists and nearly half received inadequate pain management. Although differences were observed between the 16 countries, we have documented that chronic pain is a major health care problem in Europe that needs to be taken more seriously.
New developments in a strongly coupled cardiac electromechanical model
Authors: Nickerson David , Smith Nicolas , Hunter Peter
Published: August 2005

Aim

The aim of this study is to develop a coupled three-dimensional computational model of cardiac electromechanics to investigate fibre length transients and the role of electrical heterogeneity in determining left ventricular function.

Methods

A mathematical model of cellular electromechanics was embedded in a simple geometric model of the cardiac left ventricle. Electrical and mechanical boundary conditions were applied based on Purkinje fibre activation times and ventricular volumes through the heart cycle. The mono-domain reaction diffusion equations and finite deformation elasticity equations were solved simultaneously through the full pump cycle. Simulations were run to assess the importance of cellular electrical heterogeneity on myocardial mechanics.

Results

Following electrical activation, mechanical contraction moves out through the wall to the circumferentially oriented mid-wall fibres, producing a progressively longitudinal and twisting deformation. This is followed by a more spherical deformation as the inclined epicardial fibres are activated. Mid-way between base and apex peak tensions and fibre shortening of 40 kPa and 5%, respectively, are generated at the endocardial surface with values of 18 kPa and 12% at the epicardial surface. Embedding an electrically homogeneous cell model for the same simulations produced equivalent values of 36.5 kPa, 4% at the endocardium and 14 kPa, 13.5% at the epicardium.

Conclusion

The substantial redistribution of fibre lengths during the early pre-ejection phase of systole may play a significant role in preparing the mid-wall fibres to contract. The inclusion of transmural heterogeneity of action potential duration has a marked effect on reducing sarcomere length transmural dispersion during repolarization.
MicroRNA function in animal development
Authors: Wienholds Erno , Plasterk Ronald H.A.
Published: August 2005

MicroRNAs (miRNAs) are small non‐coding RNA molecules that post‐transcriptionally regulate gene expression by base‐pairing to mRNAs. Hundreds of miRNAs have been identified in various multicellular organisms and many miRNAs are evolutionarily conserved. Although the biological functions of most miRNAs are unknown, miRNAs are predicted to regulate up to 30% of the genes within the human genome. Gradually, we are beginning to understand the functions of individual miRNAs and the general function of miRNA action. Here, we review the recent advances in miRNA biology in animals. Particularly, we focus on the roles of miRNAs in vertebrate development and disease.
Beam-Weibel filamentation instability in near-term and fast-ignition experiments
Authors: Hill Jeremy Martin , Key Michael H. , Hatchett Stephen P. , Freeman Richard R.
Published: August 2005

High intensity laser-plasma interactions accelerate electrons to suprathermal velocities. Their current is neutralized by an induced cold electron return current. These inter-penetrating and anti-parallel currents are subject to electrostatic and electromagnetic instability. Two analytical models for electron transport are used to predict the growth rates of the linear electromagnetic beam-Weibel filamentation instability in both near-term laser-solid experiments as well as in future fast-ignition experiments. Specifications and calculations of the relevant physical parameters are made. Both models predict that instability growth is significant for the fast-ignition case. Instability development in near-term experiments is also significant, but with a greater difference between the models’ predictions at low densities.
Detailed characterization of the early x-ray emission of a plasma produced by point-like laser irradiation of solid Al targets
Authors: Labate L. , Cecchetti C. A. , Galimberti M. , Giulietti A. , Giulietti D. , Gizzi L. A.
Published: August 2005

A study of the dynamics of the x-ray emission from a point-like Al plasma produced by tight-focusing laser irradiation of a thick target is reported. Two-dimensional maps of the x-ray emission calculated at selected wavelengths show that, due to the rapid expansion cooling, x-ray emission mostly originates from a thin spatial layer. These properties enabled the results of the simulations to be compared with time-resolved x-ray spectra obtained under well-controlled experimental conditions. The outcome of this comparison is discussed in details, in view of the results reported in a recently published Letter [L. A. Gizzi, C. A. Cecchetti, M. Galimberti, A. Giulietti, D. Giulietti, L. Labate, S. Laville, and B. Tomassini, Phys. Plasmas 10, 4601 (2003)]. Moreover, the x-ray-reabsorption issues and the role of the Doppler decoupling mechanism in the presence of the strong velocity gradient typical of our experimental condition are discussed, also in view of a possible dedicated experiment.
Hyperpolarizabilities for the one-dimensional infinite single-electron periodic systems. II. Dipole-dipole versus current-current correlations
Authors: Xu Minzhong , Jiang Shidong
Published: August 2005

Based on Takayama–Lin–Liu–Maki model, analytical expressions for the third-harmonic generation, dc Kerr effect, dc-induced second-harmonic optical Kerr effect, optical Kerr effect or intensity-dependent index of refraction, and dc-electric-field-induced optical rectification are derived under the static current-current (J0J0) correlation for one-dimensional infinite chains. The results of hyperpolarizabilities under J0J0 correlation are then compared with those obtained using the dipole-dipole correlation. The comparison shows that the conventional J0J0 correlation, albeit quite successful for the linear case, is incorrect for studying the nonlinear optical properties of periodic systems.
Dynamical alignment in three species tokamak edge turbulence
Authors: Scott Bruce D.
Published: August 2005

Three-dimensional computations of self-consistent three species gyrofluid turbulence are carried out for tokamak edge conditions. Profiles as well as disturbances in dependent variables are followed, running the dynamical system to transport equilibrium. The third species density shows a significant correlation with that of the electrons, regardless of initial conditions and drive mechanisms. For decaying systems the densities evolve toward each other. Companion investigations with a simple two-dimensional drift wave model show this persists even if the third species is a passively advected test species field. Similarity in the transport character of electrons and the trace species does not imply that the electrons themselves have a test particle transport character.
Nanosecond freezing of water under multiple shock wave compression: Continuum modeling and wave profile measurements
Authors: Dolan D. H. , Johnson J. N. , Gupta Y. M.
Published: August 2005

Using real time optical transmission and imaging measurements in multiple shock wave compression experiments, water was shown to solidify on nanosecond time scales [D. H. Dolan and Y. M. Gupta, J. Chem. Phys. 121, 9050 (2004)]. Continuum modeling and wave profile measurements, presented here, provide a complementary approach to examine the freezing of shocked water. The water model consisted of thermodynamically consistent descriptions of liquid and solid (ice VII) water, relationships for phase coexistence, and a time-dependent transition description to simulate freezing dynamics. Continuum calculations using the water model demonstrate that, unlike single shock compression, multiple shock compression results in pressure-temperature conditions where the ice VIII phase is thermodynamically favored over the liquid phase. Wave profile measurements, using laser interferometry, were obtained with quartz and sapphire windows at a peak pressure of 5 GPa. For water confined between sapphire windows, numerical simulations corresponding to a purely liquid response are in excellent agreement with the measured wave profile. For water confined between quartz windows (to provide a nucleating surface), wave profile measurements demonstrate a pure liquid response for an incubation time of approximately 100 ns followed by a time-dependent transformation. Analysis of the wave profiles after the onset of transformation suggests that water changes from a metastable liquid to a denser phase, consistent with the formation of a high-pressure ice phase. Continuum analyses and simulations underscore the need for multiple time scales to model the freezing transition. Findings from the present continuum work are extremely consistent with optical results reported previously. These studies constitute the first comprehensive investigation reported for freezing of a liquid at very short time scales.
A general formulation for magnetic exchange coupling within long-distance radical ion pairs
Authors: Weiss Emily A. , Wasielewski Michael R. , Ratner Mark A.
Published: August 2005

A Hubbard model-based expression for the magnetic exchange interaction, 2J, between the spins of a radical ion pair is derived for a generic donor-bridge-acceptor (D-Bn-A) system in terms of the superexchange coupling, t, between molecular orbitals of the donor, bridge, and acceptor and the energies, ε, and same-site Coulomb repulsions, U, of these orbitals. The formulation is used to predict 2J for the photophysically well-characterized series phenothiazine-p-(phenylene)n-perylene diimide, n=2,3,4,5, where the superexchange coupling is calculated with multipathway, second- and third-order perturbation theory coupled with the extended Huckel formalism. U and ε are estimated through experimentally determined electrochemical potentials. Due to multiple interactions arising from the large distance between magnetic centers in these donor-bridge-acceptor systems, agreement with experiment was substantially improved when third-order corrections were included in the calculation of t and 2J.
Ultrafast bit addressing in a magnetic memory matrix
Authors: Schumacher H. W.
Published: August 2005

An ultrafast bit addressing scheme for magnetic random access memories (MRAMs) in a crossed wire geometry is proposed. In the addressing scheme a word of cells is programmed simultaneously by subnanosecond field pulses making use of the magnetization precession of the free layer. Single-spin simulations of the free-layer dynamics show that the pulse parameters for programming an arbitrary word of the array can be chosen, such that the magnetization of the cells to be written performs either a half or a full precessional turn during application of the programming pulse depending on the initial and final magnetization orientations of the addressed cells. Such bit addressing scheme leads to a suppression of the magnetization ringing in all cells of the memory array, thereby allowing ultrahigh MRAM write clock rates above 1 GHz.
Transport properties of composites consisting of periodic arrays of exponentially graded cylinders with cylindrically orthotropic materials
Authors: Chen Tungyang , Kuo Hsin-Yi
Published: August 2005

The work is concerned with the determination of effective conductivities and field potentials of matrix-based composites consisting of periodic arrays of cylinders which are cylindrically orthotropic and exponentially graded along the radial direction. We generalize Rayleigh’s method to account for the periodic arrangements of these cylinders. The potential field and effective conductivities of composite systems were calculated to a very high order to achieve a sufficient accuracy. We find that the cylindrical orthotropy of the inclusions has a dramatic effect on the potential field of the inclusions. In addition, we discuss the effect of the grading factor on the effective conductivity. Interestingly, we find that when the inclusions are purely cylindrically orthotropic, their effects can be fully described by homogeneous isotropic cylinders. This equivalent isotropic conductivity is simply the geometric mean of the radial and tangential conductivities of cylindrically orthotropic cylinders.
Effect of heat transfer on the performance of two-stage semiconductor thermoelectric refrigerators
Authors: Chen Lingen , Li Jun , Sun Fengrui , Wu Chih
Published: August 2005

A model of two-stage semiconductor thermoelectric refrigerators with external heat transfer is proposed. The performance of the refrigerator obeying Newton’s heat transfer law is analyzed using the combination of finite-time thermodynamics and nonequilibrium thermodynamics. Two analytical formulas for cooling load versus working electrical current, and the coefficient of performance (COP) versus working electrical current, are derived. For a fixed total heat transfer surface area of two heat exchangers, the ratio of the heat transfer surface area of the high-temperature-side heat exchanger to the total heat transfer surface area of the heat exchangers is optimized to maximize the cooling load and the COP of the thermoelectric refrigerator. For a fixed total number of thermoelectric elements, the ratio of the number of thermoelectric elements of the top stage to the total number of thermoelectric elements is also optimized to maximize both the cooling load and the COP of the thermoelectric refrigerator. The effects of design factors on the performance are analyzed.
Up-gradient transport in a probabilistic transport model
Authors: Gavnholt J. , Rasmussen J. Juul , Garcia O. E. , Naulin V. , Nielsen A. H.
Published: August 2005

The transport of particles or heat against the driving gradient is studied by employing a probabilistic transport model with a characteristic particle step length that depends on the local concentration or heat gradient. When this gradient is larger than a prescribed critical value, the standard deviation of the step size is large compared to its value when the gradient is below critical. For symmetric as well as asymmetric off-axis fueling, the model is capable of producing profiles peaking at the axis. Additionally, profile consistency is obtained over a broad range of source strengths. These results supplement recent works by van Milligen et al. [Phys. Plasmas 11, 3787 (2004)], which applied Lévy distributed step sizes in the case of supercritical gradients to obtain the up-gradient transport.
Micromechanical analysis of fracture and domain switching in barium titanate single crystal using cathodoluminescence piezospectroscopy
Authors: Yamashita Yasuhisa , Sakakibara Souichi , Yamamoto Hiroshi , Sakabe Yukio , Pezzotti Giuseppe
Published: August 2005

It is shown that the combination of scanning electron microscopy and spectral cathodoluminescence (CL) can be a very valuable tool for analyzing the presence of applied or residual stress fields in barium titanate (BaTiO3) single crystal. This may enable a direct experimental confirmation of some important aspects of existing theories of domain switching and its effect on the fracture behavior of piezoelectric ceramics. The visible CL spectrum of BaTiO3 single crystal was first systematically collected as a function of crystallographic orientation and the observed bands assigned to proper transitions in the energy gap, according to existing theories on band schemes. Moreover, in agreement with general piezospectroscopic rules, a definite correlation between the spectral wavelength of the visible CL spectrum, mainly arising from the optical activity of O and Ba vacancies, and the local trace of the stress tensor could be observed. The found correlation suggests the possibility of quantitatively characterizing the magnitude of residual stress fields in BaTiO3 with a submicrometric spatial resolution, thus clarifying the stress state piled up in BaTiO3 devices during the manufacturing process or those developed during operative life.
Nucleation of deformation twins in nanocrystalline face-centered-cubic metals processed by severe plastic deformation
Authors: Zhu Y. T. , Liao X. Z. , Srinivasan S. G. , Lavernia E. J.
Published: August 2005

Nanocrystalline (nc) materials are known to deform via mechanisms not accessible to their coarse-grained counterparts. For example, deformation twins and partial dislocations emitted from grain boundaries have been observed in nc Al and Cu synthesized by severe plastic deformation (SPD). This paper further develops an earlier dislocation-based model on the nucleation of deformation twins in nc face-centered-cubic (fcc) metals. It is found that there exists an optimum grain-size range in which deformation twins nucleate most readily. The critical twinning stress is found determined primarily by the stacking fault energy while the optimum grain size is largely determined by ratio of shear modulus to stacking fault energy. This model formulated herein is applicable to fcc nanomaterials synthesized by SPD techniques and provide a lower bound to the critical twining stress.
Superconducting properties of ultrathin Bi2Sr2CaCu2O8+x single crystals
Authors: You L. X. , Yurgens A. , Winkler D. , Lin C. T. , Liang B.
Published: August 2005

We use Ar-ion milling to thin Bi2Sr2CaCu2O8+x (Bi2212) single crystals down to a few nanometers or one to two (CuO2)2 layers. In decreasing the thickness, the superconducting transition temperature gradually decreases to zero and the in-plane resistivity increases to large values indicating the existence of a superconductor-insulator transition in ultrathin Bi2212 single crystals.
Commuting quantum traces for quadratic algebras
Authors: Nagy Zoltán , Avan Jean , Doikou Anastasia , Rollet Geneviève
Published: August 2005

Consistent tensor products on auxiliary spaces, hereafter denoted “fusion procedures,” and commuting transfer matrices are defined for general quadratic algebras, nondynamical and dynamical, inspired by results on reflection algebras. Applications of these procedures then yield integer-indexed families of commuting Hamiltonians.
The global strong solutions of Hasegawa-Mima-Charney-Obukhov equation
Authors: Gao Hongjun , Zhu Anyou
Published: August 2005

The quasigeostrophic model is a simplified geophysical fluid model at asymptotically high rotation rate or at small Rossby number. We consider the quasigeostrophic equation with no dissipation term which was obtained as an asymptotic model from the Euler equations with free surface under a quasigeostrophic velocity field assumption. It is called the Hasegawa-Mima-Charney-Obukhov equation, which also arises from plasmas theory. We use a priori estimates to get the global existence of strong solutions for an Hasegawa-Mima-Charney-Obukhov equation.
Enhanced light emission from InAs quantum dots in single-defect photonic crystal microcavities at room temperature
Authors: Chen W.-Y. , Chang W.-H. , Chang H.-S. , Hsu T. M. , Lee Chien-Chieh , Chen Chii-Chang , Luan P. G. , Chang J.-Y. , Hsieh T.-P. , Chyi J.-I.
Published: August 2005

The optical properties of InAs quantum dots with photonic crystal microcavity emitting near 1.3μm were investigated at room temperature. The photoluminescence (PL) intensity for quantum dots in cavity was enhanced by two orders of magnitude. The large PL enhancement was attributed to the effects combining the improved extraction efficiency and the enhanced spontaneous emission rate due to the Purcell effect. A threefold Purcell enhancement is observed at room temperature, which is predominantly achieved by the very small mode volume of the photonic crystal microcavity.
Observation of piezoelectric resonance in time domain transient current of ferroelectric ceramics and crystals
Authors: Jin Li , Yao Xi , Wei Xiaoyong , Xi Zengzhe
Published: August 2005

An abnormal resonance behavior was observed from the transient current in the time domain for both ferroelectric ceramics and single crystals excited with a stepwise electric field. The phenomenon can be accounted for as piezoelectric resonance. Corresponding resonant peaks in the frequency spectrum of impedance verified the piezoelectric origin of the abnormal resonance. Using a RLC series equivalent circuit of the piezoelectric resonance model, the resonance behavior of the transient current can be calculated and well fitted with experiments.
In vivo
transcriptional regulation of N-Myc target genes is controlled by E-box methylation
Authors: Perini Giovanni , Diolaiti Daniel , Porro Antonio , Della Valle Giuliano
Published: August 2005

N-Myc is a transcription factor that forms heterodimers with the protein Max and binds gene promoters by recognizing a DNA sequence, CACGTG, called E-box. The identification of N-myc target genes is an important step for understanding N-Myc biological functions in both physiological and pathological contexts. In this study, we describe the identification of N-Myc-responsive genes through chromatin immunoprecipitation and methylation-sensitive restriction analysis. Results show that N-Myc is a direct regulator of several identified genes, and that methylation of the CpG dinucleotide within the E-box prevents the access of N-Myc to gene promoters
in vivo
. Furthermore, methylation profile of the E-box within the promoters of
EGFR
and
CASP8
, two genes directly controlled by Myc, is cell type-specific, suggesting that differential E-box methylation may contribute to generating unique patterns of Myc-dependent transcription. This study illuminates a central role of DNA methylation in controlling N-Myc occupancy at gene promoters and modulating its transcriptional activity in cancer cells.
A role for
Arabidopsis
cryptochromes and COP1 in the regulation of stomatal opening
Authors: Mao Jian , Zhang Yan-Chun , Sang Yi , Li Qing-Hua , Yang Hong-Quan
Published: August 2005

Cryptochromes (CRY) are blue light photoreceptors that mediate various light-induced responses in plants and animals.
Arabidopsis
CRY (CRY1 and CRY2) functions through negatively regulating constitutive photomorphogenic (COP) 1, a repressor of photomorphogenesis. Water evaporation and photosynthesis are regulated by the stomatal pores in plants, which are closed in darkness but open in response to blue light. There is evidence only for the phototropin blue light receptors (PHOT1 and PHOT2) in mediating blue light regulation of stomatal opening. Here, we report a previously uncharacterized role for
Arabidopsis
CRY and COP1 in the regulation of stomatal opening. Stomata of the
cry1 cry2
double mutant showed reduced blue light response, whereas those of the CRY1-overexpressing plants showed hypersensitive response to blue light. In addition, stomata of the
phot1 phot2
double mutant responded to blue light, but those of the
cry1 cry2 phot1 phot2
quadruple mutant hardly responded. Strikingly, stomata of the
cop1
mutant were constitutively open in darkness and stomata of the
cry1 cry2 cop1
and
phot1 phot2 cop1
triple mutants were open as wide as those of the
cop1
single mutant under blue light. These results indicate that CRY functions additively with PHOT in mediating blue light-induced stomatal opening and that COP1 is a repressor of stomatal opening and likely acts downstream of CRY and PHOT signaling pathways.
Brain and muscle Arnt-like protein-1 (BMAL1), a component of the molecular clock, regulates adipogenesis
Authors: Shimba Shigeki , Ishii Norimasa , Ohta Yuki , Ohno Toshiharu , Watabe Yuichi , Hayashi Mitsuaki , Wada Taira , Aoyagi Toshinori , Tezuka Masakatsu
Published: August 2005

Brain and muscle Arnt-like protein-1 (BMAL1; also known as MOP3 or Arnt3) is a transcription factor known to regulate circadian rhythm. Here, we established its involvement in the control of adipogenesis and lipid metabolism activity in mature adipocytes. During adipose differentiation in 3T3-L1 cells, the level of BMAL1 mRNA began to increase 4 days after induction and was highly expressed in differentiated cells. In white adipose tissues isolated from C57BL/6J mice, BMAL1 was predominantly expressed in a fraction containing adipocytes, as compared with the stromal-vascular fraction. BMAL1 knockout mice embryonic fibroblast cells failed to be differentiated into adipocytes. Importantly, adding BMAL1 back by adenovirus gene transfer restored the ability of BMAL1 knockout mice embryonic fibroblast cells to differentiate. Knock-down of BMAL1 expression in 3T3-L1 cells by an RNA interference technique allowed the cells to accumulate only minimum amounts of lipid droplets in the cells. Adenovirus-mediated expression of BMAL1 in 3T3-L1 adipocytes resulted in induction of several factors involved in lipogenesis. The promoter activity of these genes was stimulated in a BMAL1-dependent manner. Interestingly, expression of these factors showed clear circadian rhythm in mice adipose tissue. Furthermore, overexpression of BMAL1 in adipocytes increased lipid synthesis activity. These results indicate that BMAL1, a master regulator of circadian rhythm, also plays important roles in the regulation of adipose differentiation and lipogenesis in mature adipocytes.
Absence of detectable transgenes in local landraces of maize in Oaxaca, Mexico (2003–2004)
Authors: Ortiz-García S. , Ezcurra E. , Schoel B. , Acevedo F. , Soberón J. , Snow A. A.
Published: August 2005

In 2000, transgenes were detected in local maize varieties (landraces) in the mountains of Oaxaca, Mexico [Quist, D. & Chapela, I. H. (2001)
Nature
414, 541–543]. This region is part of the Mesoamerican center of origin for maize (
Zea mays
L.), and the genetic diversity that is maintained in open-pollinated landraces is recognized as an important genetic resource of great cultural value. The presence of transgenes in landraces was significant because transgenic maize has never been approved for cultivation in Mexico. Here we provide a systematic survey of the frequency of transgenes in currently grown landraces. We sampled maize seeds from 870 plants in 125 fields and 18 localities in the state of Oaxaca during 2003 and 2004. We then screened 153,746 sampled seeds for the presence of two transgene elements from the 35S promoter of the cauliflower mosaic virus and the nopaline synthase gene (nopaline synthase terminator) from
Agrobacterium tumefaciens
. One or both of these transgene elements are present in all transgenic commercial varieties of maize. No transgenic sequences were detected with highly sensitive PCR-based markers, appropriate positive and negative controls, and duplicate samples for DNA extraction. We conclude that transgenic maize seeds were absent or extremely rare in the sampled fields. This study provides a much-needed preliminary baseline for understanding the biological, socioeconomic, and ethical implications of the inadvertent dispersal of transgenes from the United States and elsewhere to local landraces of maize in Mexico.
Vitamin A and immune function: Retinoic acid modulates population dynamics in antigen receptor and CD38-stimulated splenic B cells
Authors: Chen Qiuyan , Ross A. Catharine
Published: August 2005

Vitamin A and its active metabolite,all-transretinoic acid (RA), regulate the antibody responsein vivo, although the underlying mechanisms are not well understood. We have investigated the regulation by RA of B cell population dynamics and Ig gene expression in purified splenic mouse B cells stimulated through the B cell antigen receptor (BCR) and/or CD38, a BCR coreceptor. After ligation of the BCR and/or CD38, B cells became more heterogeneous in size. RA substantially restrained this change, concomitant with inhibition of cell proliferation. To examine B cell heterogeneity more closely, we categorized stimulated B cells by size (forward angle light scatter) and determined cell division dynamics, germ-line Ig heavy chain gene transcription and surface IgG1 (sIgG1) expression. Flow cytometric analysis of carboxyfluorescein diacetate succinimidyl ester-labeled B cells costained for sIgG1 showed that the more proliferative groups of B cells were smaller, whereas cells expressing more sIgG1 were larger. RA enriched the latter population, whereas cell division frequency in general and the number of smaller B cells that had undergone division cycles were reduced. Although RA significantly inhibited Ig germ-line transcript levels in the total B cell population, CD19-IgG1+B cells, which represent a more differentiated phenotype, were enriched. Furthermore,pax-5mRNA was decreased and activation-induced cytidine deaminase mRNA was increased in RA-treated stimulated B cells. Thus, RA regulated factors known to be required for Ig class switch recombination and modulated the population dynamics of ligation-stimulated B cells, while promoting the progression of a fraction of B cells into differentiated sIgG-expressing cells.
Large-scale identification of yeast integral membrane protein interactions
Authors: Miller John P. , Lo Russell S. , Ben-Hur Asa , Desmarais Cynthia , Stagljar Igor , Noble William Stafford , Fields Stanley
Published: August 2005

We carried out a large-scale screen to identify interactions between integral membrane proteins of
Saccharomyces cerevisiae
by using a modified split-ubiquitin technique. Among 705 proteins annotated as integral membrane, we identified 1,985 putative interactions involving 536 proteins. To ascribe confidence levels to the interactions, we used a support vector machine algorithm to classify interactions based on the assay results and protein data derived from the literature. Previously identified and computationally supported interactions were used to train the support vector machine, which identified 131 interactions of highest confidence, 209 of the next highest confidence, 468 of the next highest, and the remaining 1,085 of low confidence. This study provides numerous putative interactions among a class of proteins that have been difficult to analyze on a high-throughput basis by other approaches. The results identify potential previously undescribed components of established biological processes and roles for integral membrane proteins of ascribed functions.
Australian Aboriginal plant foods: a consideration of their nutritional composition and health implications
Authors: Brand-Miller Janette C. , Holt Susanne H. A.
Published: August 2005

For at least 40–50 000 years, plants played an important but supplementary role in the animal-dominated diet of Australian Aboriginal (AA) hunter-gatherers. New knowledge of the nutrient composition and the special physiological effects of their foods provides another perspective in the current debate on the composition of the ‘prudent’ diet and the diet on which humans evolved. In the present paper we have calculated the average nutrient composition of over 800 Aboriginal plant foods (in total and by food group) and highlighted the differences between these and modern cultivated foods. The data enable us to calculate the absolute contribution of plant foods to total food and nutrient intake of traditional living AA. If plants provided 20–40% of the energy in the diet (the most likely range), then plants would have contributed 22–44g protein, 18–36g fat, 101–202g carbohydrate, 40–80g fibre and 90–180mg vitamin C in a 12500kJ (3000 kcal) diet. Since all the carbohydrate came from plant foods, the traditional AA diet would have been relatively low in carbohydrate (especially starch) but high in dietary fibre in comparison with current recommendations. Over half the carbohydrate could have been in the form of sugars derived from fruit and honey. The low glycaemic index of their carbohydrate foods, however, would generate a relatively low demand for insulin secretion and this characteristic may have protected AA from a genetic predisposition to insulin resistance and its consequences (non-insulin-dependent diabetes mellitus, coronary heart disease, obesity). The dietary pattern and active lifestyle of recent hunter-gatherers such as AA may be a reference standard for modem human nutrition and a model for defence against diseases of affluence.
Food choice and intake: towards a unifying framework of learning and feeding motivation
Authors: Day Jon E. L. , Kyriazakis Ilias , Rogers Peter J.
Published: August 2005

The food choice and intake of animals (including humans) has typically been studied using frameworks of learning and feeding motivation. When used in isolation such frameworks could be criticized because learning paradigms give little consideration to how new food items are included or excluded from an individual's diet, and motivational paradigms do not explain how individuals decide which food to eat when given a choice. Consequently we are posed with the question of whether individuals actively interact with the food items present in their environment to learn about their nutritional properties? The thesis of this review is that individuals aremotivatedto actively sample food items in order to assess whether they are nutritionally beneficial or harmful. We offer a unifying framework, centred upon the concept of exploratory motivation, which is a synthesis of learning and paradigms of feeding motivation. In this framework information gathering occurs on two levels through exploratory behaviour: (i) the discrimination of food from nonfood items, and (ii) the continued monitoring and storage of information concerning the nutritional properties of these food items. We expect that this framework will advance our understanding of the behavioural control of nutrient intake by explaining how new food items are identified in the environment, and how individuals are able to monitor changes in the nutritional content of their food resource.