bluuebunny/crossref_metadata_2025 huggingface dataset:
In vivo neuroprotective adaptation of the glutamate/glutamine cycle to neuronal death
Authors: Ramonet D. , Rodríguez M.J. , Fredriksson K. , Bernal F. , Mahy N.
Published: June 2004

Synaptic increase of glutamate level, when not coupled to a heightened energy production, renders neurons susceptible to death. Astrocyte uptake and recycling of synaptic glutamate as glutamine is a major metabolic pathway dependent on energy metabolism, which interrelationships are not fully understood and remain controversial. We examine how the glutamate‐glutamine cycle and glucose metabolism are modified in two in vivo models of severe and mild brain injury. Graded reductions of glutaminase, the glutamate synthetic enzyme, were evidenced combined with increases in glutamine synthetase, the inactivating glutamate enzyme. Increased lactate dhydrogenase (LDH) activity was only present after a more severe injury. These results indicate an in vivo adaptation of the glutamate‐glutamine cycle in order to increase the net glutamine output, reduce glutamate excitotoxicity, and avoid neuronal death. We conclude that the graded modification of the glutamate‐glutamine correlation and neuronal lactate availability may be key factors in the apoptotic and necrotic neuronal demise, whose control may prove highly useful to potentiate neuronal survival. © 2004 Wiley‐Liss, Inc.
Characteristics of solidification and melting in the water‐saturated porous medium cooled from the top (response of solid–liquid interface due to time‐varying cooling temperature)
Authors: Kimura Shigeo , Okajima Atsushi , Kiwata Takahiro , Nakamura Taiki
Published: June 2004

This paper describes the response of a solid–liquid interface in a water‐saturated porous box to a time‐varying cooling temperature. Spherical soda glass beads with an average diameter of 5 mm constitute a porous matrix. The lower boundary of the matrix is kept at 8°C at all times during the experiments, while the upper plate is set at a temperature, lower than the liquids 0°C. After a steady state is reached, the cooling temperature is varied periodically with a fixed amplitude of 4°C. The solid–liquid interface positions are measured and the characteristic amplitudes and the phase delays are determined for different periods ranging from one hour to ten hours at four different cooling temperatures. It has been found that the amplitude of the interface is proportional to the cooling temperature period length, and that a thicker solid layer causes larger phase delays. The proposed one‐dimensional model has been found appropriate for predicting the response of the horizontally averaged position of the solid–liquid interface. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(5): 330–341, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20015
Experimental research of pool boiling heat transfer in horizontal narrow spaces
Authors: Long Enshen , Xin Mindao , Wang Yong
Published: June 2004

Much progress has been made in high‐performance electronic chips, the miniaturization of electronic circuits and other compact systems recently, which brings about a great demand for developing efficient heat removal techniques to accommodate these high heat fluxes. With this objective in mind, experiments were carried out on five kinds of test elements with distilled water and ethanol as working liquids. The test elements used in these experiments consisted of five parallel discs with diameters varying from 5 mm to 40 mm. The experiments were performed with the discs oriented horizontally and uniform heat fluxes applied at the bottom surfaces. The influence of narrow spacing, space size, working liquid property, and heat flux on boiling heat transfer performance in narrow spaces has been investigated. Experimental results showed that the boiling heat transfer coefficient of a narrow space was 3 to 6 times higher than that of pool boiling when the narrow space size and heat flux combine adequately, but the critical heat flux was lower than that of pool boiling. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(5): 307–315, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20017
Thermal radiation effects of a high‐temperature developing laminar flow in a tube
Authors: Xia Xin‐Lin , Ren De‐Peng , Tan He‐Ping
Published: June 2004

The thermal radiation effects of a high‐temperature developing laminar flow in a tube are investigated numerically. The two‐dimensional steady flow and heat transfer are considered for an absorbing‐emitting gray medium, whose density is dependent on the temperature. The governing equations of the coupled process are simultaneously solved by the discrete ordinate method combined with the control volume method. For a moderate optical thickness, the velocity distribution, the temperature distribution, and the radial heat flux distribution in the medium as well as the heat flux distribution on the tube wall are presented and discussed. The results show that the thermal radiation effects of a high‐temperature medium are significant under a moderate optical thickness. The flow and convective heat transfer are weakened, and the development of temperature distribution is accelerated noticeably. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(5): 299–306, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20018
Internal radiation effects in semitransparent high‐temperature coatings
Authors: Wang Ping‐Yang , Cheng Hui‐Er , Tan He‐Ping
Published: June 2004

Internal thermal radiation in semitransparent coatings should be considered in the calculation of temperature and heat flux distribution in metal wall with a thermal barrier coating. In this paper, a ray tracing/node analysis method is used in the numerical simulation of a coupled transient radiative and conductive heat transfer in an absorbing‐scattering non‐gray coating. The present results show that the operating temperature is higher than the design temperature when the radiation is not considered. © 2004 Wiley Periodicals, Inc. Heat Trans Asian Res, 33(5): 271–278, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20021
Ultrastructural study of mineralization of a strontium‐containing hydroxyapatite (Sr‐HA) cement in vivo
Authors: Wong C. T. , Chen Q. Z. , Lu W. W. , Leong J. C. Y. , Chan W. K. , Cheung K. M. C. , Luk K. D. K.
Published: June 2004

The purpose of this study was to investigate the mineralization leading to osseointegration of strontium‐containing hydroxyapatite (Sr‐HA) bioactive bone cement injected into cancellous bone in vivo. Sr‐HA cement was injected into the ilium of rabbits for 1, 3, and 6 months. The bone mineralization area was found to be largest at 3 months, then at 1 month, and smallest at 6 months (p < 0.01) measured with tetracycline labeling. Osseointegration of Sr‐HA cement was achieved at 3 months as observed by scanning electron microscopy. A high calcium and phosphorus area was observed at the interface of bone–Sr‐HA cement determined by energy‐dispersive X‐ray analysis. Transmission electron microscopy gave evidence of the mechanism of bone formation. Dissolution of Sr‐HA into debris by the bone remodeling process was thought to increase the concentration of calcium and phosphorus at the interface of bone–Sr‐HA cement and stimulate bone formation. Crystalline Sr‐HA formed an amorphous layer and dissolved into the surrounding solution, then apatite crystallites were precipitated and formed new bone at 3 months. This young bone then becomes mature bone, which bonds tightly to the Sr‐HA cement with collagen fibers inserted perpendicularly after 6 months. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 70A: 428–435, 2004
Lysophospholipids in development: Miles apart and edging in
Authors: Saba Julie D.
Published: June 2004

Sphingosine‐1‐phosphate (S1P) and lysophosphatidic acid (LPA) are endogenous bioactive lipids that participate in the regulation of mammalian cell proliferation, apoptosis, migration, and angiogenesis. These processes are each critical for successful embryogenesis, raising the possibility that lysophospholipid signaling may contribute to normal animal development. In fact, recent studies in developmental model systems have established that S1P and LPA are necessary for diverse developmental programs including those required for morphogenesis of vertebrate reproductive, cardiovascular and central and peripheral nervous systems (PNS), as well as the establishment of maternal‐fetal circulation and the immune system. Genetic, morphological, and biochemical characterization of developmental model systems offer powerful approaches to elucidating the molecular mechanisms of lysophospholipid signaling and its contributions to animal development and postnatal physiology. In this review, the routes of S1P and LPA metabolism and our current understanding of lysophospholipid‐mediated signal transduction in mammalian cells will be summarized. The evidence implicating lysophospholipid signaling in the development of specific vertebrate systems will then be reviewed, with an emphasis on signals mediated through G protein‐coupled receptors of the Edg family. Lastly, recent insights derived from the study of simple metazoan models and implications regarding lysophospholipid signaling in organisms in which Edg receptors are not conserved will be explored. © 2004 Wiley‐Liss, Inc.
Constructions of optimal optical orthogonal codes with weight five
Authors: Ma Shikui , Chang Yanxun
Published: June 2004

Several direct constructions via skew starters and Weil's theorem on character sum estimates are given in this paper for optimal (gv, 5, 1) optical orthogonal codes (OOCs) where 60 ≤ g ≤ 180 satisfying g ≡ 0 (mod 20) and v is a product of primes greater than 5. These improve the known existence results on optimal OOCs. Especially, we provide an optimal (v, 5, 1)‐OOC for any integer v ≡ 60, 420, 660, 780, 1020, 1140, 1380, 1740 (mod 1800). © 2004 Wiley Periodicals, Inc. J Combin Designs 13: 54–69, 2005.
Characterization of rat liver microsomal metabolites of AM‐630, a potent cannabinoid receptor antagonist, by high‐performance liquid chromatography/electrospray ionization tandem mass spectrometry
Authors: Zhang Qiang , Ma Peng , Wang Weiqun , Cole Richard B. , Wang Guangdi
Published: June 2004

The in vitro metabolism of AM‐630 was studied by high‐performance liquid chromatography coupled with tandem mass spectrometry. AM‐630 is an aminoalkylindole analogue that behaves primarily as a potent CB2‐selective antagonist. In this study, 17 metabolic products were identified that resulted from the incubation of AM‐630 in rat liver microsome preparations. Six metabolic pathways were proposed to account for all detected metabolites: (1) o‐demethylation of the methoxyphenyl group, (2) morpholinyl ring opening, (3) hydroxylation on the methoxy/hydroxyl phenyl ring, (4) hydroxylation on the indole ring, (5) hydroxylation on the morpholine ring and (6) loss of the morpholine ring leading to metabolites containing either a hydroxylated or a carboxylated alkyl terminal. Three metabolites were identified as morpholinyl ring‐opening products: M1, M6 and M13. Six metabolites (M2–M5, M7 and M8) were proposed to be the products of o‐demethylation, hydroxylation on the methoxyphenyl group or the morpholinyl ring, dehydration following morpholinyl ring monohydroxylation, or a combination of the above metabolic pathways. The remaining eight metabolites were attributed to a pathway involving the loss of the morpholine ring at various points during the metabolic processes. Copyright © 2004 John Wiley & Sons, Ltd.
Lipase Catalyzed Copolymerization of 3(S)‐Isopropylmorpholine‐2,5‐dione and D,L‐Lactide
Authors: Feng Yakai , Klee Doris , Höcker Hartwig
Published: June 2004

Summary: The polymerization and copolymerization of 3(S)‐isopropylmorpholine‐2,5‐dione (IPMD) and D,L‐lactide (DLLA) were carried out in the presence of Porcine pancreatic lipase type II (PPL) as a catalyst at 100 °C for 168 h. Homopolymers and random copolymers of various compositions were obtained with a carboxylic acid group at one end and a hydroxyl group at the other end. The glass transition temperature of the copolymers decreases with increasing mole fraction of DLLA residue in the copolymers.

The copolymerization of 3(S)‐isopropylmorpholine‐2,5‐dione (IPMD) and D,L‐lactide (DLLA).

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The copolymerization of 3(S)‐isopropylmorpholine‐2,5‐dione (IPMD) and D,L‐lactide (DLLA).
Elastic Properties of Poly(hydroxybutyrate) Molecules
Authors: Špitalský Zdenko , Bleha Tomáš
Published: June 2004

Summary: Elasticity of various poly(hydroxybutyrate) (PHB) molecules of regular and irregular conformational structure was examined by the molecular mechanics (MM) calculations. Force – distance functions and the Young's moduli E were computed by stretching of PHB molecules. Unwinding of the 21 helical conformation H is characterized at small deformations by the Young's modulus E = 1.8 GPa. The H form is transformed on stretching into the highly extended twisted form E, similar to the β‐structure observed earlier by X‐ray fiber diffraction. The computations revealed that in contrast to paraffins, the planar all‐trans structure of undeformed PHB is bent. Hence, a PHB molecule attains the maximum contour length in highly straightened, but slightly twisted conformations. A dependence of the single‐chain moduli of regular and disordered conformations on the chain extension ratio x was found. The computed data were used to analyze elastic response of tie (bridging) molecules in the interlamellar (IL) region of a semi‐crystalline PHB. A modification of the chain length distribution function of tie molecules τ(N) due to secondary crystallization of PHB was conjectured. The resulting narrow distribution τ(N) comprises the taut tie molecules of higher chain moduli prone to overstressing. The molecular model outlined is in line with the macroscopically observed increase in the modulus and brittleness of PHB with storage time.

The force – length plots of deformation of the helical H form (○) and of the non‐planar Tn form (▪) of the PHB hexamer.

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The force – length plots of deformation of the helical H form (○) and of the non‐planar Tn form (▪) of the PHB hexamer.
PHEMA Hydrogels Obtained by a Novel Low‐Heat Curing Procedure with a Potential for In Situ Preparation
Authors: Ferruti Paolo , Grigolini Michela , Ranucci Elisabetta
Published: June 2004

Summary: In this work, we report on poly(2‐hydroxyethyl methacrylate) (PHEMA) hydrogels obtained by a low heat curing reaction. These materials are suitable for in situ preparation and therefore endowed with a potential for several biomedical applications. The novel procedure adopted involves as the first step the synthesis of a soluble oligomeric PHEMA precursor containing polymerizable functions as side substituents. As the second step, the precursor is dissolved in equal amounts of 2‐hydroxyethyl methacrylate (HEMA) and water, to form a viscous but still injectable syrup. A low temperature water soluble initiator is then added. The curing reaction starts promptly and is completed within few minutes. During the entire process the internal temperature never rises above 40 °C. Preliminary mechanical characterizations performed on the hydrogels in their water‐swollen state and diffusion tests in absorption/desorption experiments clearly indicated that on all respects the novel hydrogels are comparable with conventional PHEMA hydrogels obtained according to literature from HEMA in the presence of divinyl crosslinkers. However, the much shorter curing time combined with the far lower curing temperature endow the new hydrogels with a higher potential in view of specific surgical requirements, and particularly for in situ preparation.

Thermal profile of the curing reaction of different PHEMA hydrogel samples.

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Thermal profile of the curing reaction of different PHEMA hydrogel samples.
Temperature‐Sensitive Polyamidoamine Dendrimer/Poly(N‐isopropylacrylamide) Hydrogels with Improved Responsive Properties
Authors: Zhang Jian‐Tao , Huang Shi‐Wen , Zhuo Ren‐Xi
Published: June 2004

Summary: Novel temperature‐sensitive poly(N‐isopropylacrylamide)/amine‐terminated polyamidoamine dendrimer G6‐NH2 hydrogels with fast responsive properties were synthesized by forming semi‐interpenetrating polymeric networks. In contrast to the conventional PNIPA hydrogel, these new gels showed rapid shrinking rate at the temperature above lower critical solution temperature (LCST), and exhibited higher equilibrium swelling ratio at room temperature. All these properties might be attributed to the incorporation of polyamidoamine dendrimer G6‐NH2, which forms water‐releasing channels and increases the hydrophilicity of PNIPA network. The novel hydrogels have potential applications in drug and gene delivery.

Shrinking kinetics of homogeneous PNIPA hydrogel (H0) and novel PAMAM dendrimer G6‐NH2‐containing hydrogels (H10, H20 and H30).

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Shrinking kinetics of homogeneous PNIPA hydrogel (H0) and novel PAMAM dendrimer G6‐NH2‐containing hydrogels (H10, H20 and H30).
A New Technique for the Experimental Measurement of Monomer Partition Coefficients
Authors: Fortuny Montserrat , Graillat Christian , McKenna Timothy F.
Published: June 2004

Summary: A new method for the measurement of monomer partitioning for emulsion polymerisation is presented. The method is based on measuring the partition coefficients for films cast from different latexes. Its validity was demonstrated for methyl methacrylate (MMA) and butyl acrylate (BA), as well as for mixtures of these two species, by comparing the data to model predictions using literature data. The model predictions and experimental results agreed quite well for MMA, but less so for BA due to its extremely low water solubility.

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Structure Property Correlation of Thermally Treated Hemp Fiber
Authors: Prasad Bhuwan M. , Sain Mohini M. , Roy Dibyendu N.
Published: June 2004

Summary: Hemp (Cannabis sativa L.) is an important ligno‐cellulosic raw material for the manufacture of cost‐effective environmentally friendly composite materials. Hemp plant samples of different initial condition (stem and bast fibers) were subjected to heating varying the temperature (from 160 to 260 °C) and the ambient heating environment (air and inert atmosphere). Weight measurements showed that all heat treatment resulted in a reduced weight of hemp. Those treated in air showed drastic decline in weight compared with those treated under nitrogen, especially at a temperature higher than 220 °C. Observation using optical and scanning microscope showed the possibilities of opening up of the fiber bundles in both heating environments. However, higher temperature and presence of air had a more severe effect on fibers and associated tissues compared to effects under nitrogen. Heat treatment at 220 °C under nitrogen seemed to provide enough fiber opening without affecting tissues of the fibers.

SEM micrograph of the cross‐section of hemp fiber heat treated in air environment.

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SEM micrograph of the cross‐section of hemp fiber heat treated in air environment.
Synthesis and Characterization of Biodegradable Poly(ε‐caprolactone)‐Polyglycolide‐Poly(ethylene glycol) Monomethyl Ether Random Copolymer
Authors: Zhou Shaobing , Xu Jinggang , Yang Hua , Deng Xianmo
Published: June 2004

Summary: Poly(ε‐caprolactone)‐polyglycolide‐poly(ethylene glycol) monomethyl ether random copolymers were synthesized from ε‐caprolactone (ε‐CL), glycolide (GA) and poly(ethylene glycol) monomethyl ether (MPEG) using stannous octoate as catalyst at 160 °C by bulk polymerization. The copolymers with different composition were synthesized by adjusting the weight ration of reaction mixture. The resultant copolymer with a weight ratio (10:15:75) of MPEG2000, GA, and CL was characterized by IR, 1H NMR, GPC and DSC. The new biodegradable copolymer has potential for medical applications since it is combined with properties of PCL, PGA and MPEG.

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Exertion of Inhibiting Effect by Aluminosilicate Layers on Swelling of Solution Blended EVA/Clay Nanocomposite
Authors: Pramanik Monoj , Acharya Himadri , Srivastava Suneel K.
Published: June 2004

Summary: Ethylene vinyl acetate (EVA) copolymer/dodecyl ammonium ion intercalated montmorillonite (12Me‐MMT) nanocomposites were swelled in xylene under atmospheric condition. Swelling index of these nanocomposites decreased with filler loading indicating that the solvent uptake of these nanocomposites was inversely related to the filler contents. The volume fractions of nanocomposites showed an increasing trend with filler concentration because of unswelling effect exerted by aluminosilicate layers. The cross‐link density was determined using the Flory‐Rehner equation and it was observed that the cross‐link density of these nanocomposites also showed an increasing trend with increasing filler loading. Free energy change (ΔGmix) and the change in entropy (ΔSmix) on swelling of EVA/12Me‐MMT nanocomposites in xylene were calculated and these values reaffirmed that the interaction between polymer chains and silicate layers was very strong which induced remarkable inhibiting ability on EVA matrix when swelled in xylene.

TEM photograph of EVA/12Me‐MMT nanocomposite containing 8 wt.‐% 12Me‐MMT.

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TEM photograph of EVA/12Me‐MMT nanocomposite containing 8 wt.‐% 12Me‐MMT.
Trust and relationship commitment in the United Kingdom voluntary sector: Determinants of donor behavior
Authors: Sargeant Adrian , Lee Stephen
Published: June 2004

This article explores the relationship between trust, relationship commitment, and giving behavior. It operationalizes trust and commitment, develops measurement scales for each construct, and uses the technique of structural equation modeling to determine whether trust impacts directly on giving behavior or whether its effects are mediated by commitment. It concludes that commitment plays a mediating role and discusses implications for professional fund‐raising practice. © 2004 Wiley Periodicals, Inc.
Unfolding consumer impulsivity: An existential–phenomenological study of consumers with attention deficit disorder
Authors: Kaufman‐Scarborough Carol , Cohen Judy
Published: June 2004

This article attempts to unfold consumer impulsivity by gathering in‐depth stories from persons whose impulsivity is a lifetime trait because of their attention deficit disorder (ADD/ADHD). The manuscript provides overviews of impulsivity, ADD, and impulsive consumer behavior. Insights into possible consumer‐behavior challenges are offered from an information‐processing perspective. Through thematic analysis of the respondents' lifetime stories, this study helps illuminate the black box of the consumer's mind with respect to impulsive consumption, by relating impulsive consumer behavior to specific problems in information processing. As such, it not only contributes to understanding of the consumer behavior of those with ADD, but also presents a kinder and gentler picture of consumers who are dealing with information overload and frustration, rather than what might be a more common stereotype of consumers who are simply out of control. © 2004 Wiley Periodicals, Inc.
Consumer knowledge of the world wide web: Conceptualization and measurement
Authors: Page Kelly , Uncles Mark
Published: June 2004

User‐directed technologies such as the Web are becoming more prevalent. To understand the usage of these technologies the characteristics of users need to be studied. The focus here is on one user characteristic: consumer knowledge content. Based on qualitative and quantitative analyses, four scales are developed to measure common declarative, common procedural, specialized declarative, and specialized procedural knowledge content of the Web. In addition, an illustration is provided to show how these scales might be used for segmenting consumers. The procedures used may be of value in a wide range of studies where the focus is on investigating users of user‐directed electronic technologies. © 2004 Wiley Periodicals, Inc.
Biology and chemistry of the inhibition of nitric oxide synthases by pteridine‐derivatives as therapeutic agents
Authors: Matter Hans , Kotsonis Peter
Published: June 2004

Inhibitors of the family of nitric oxide synthases (NOS‐I–III; EC 1.14.13.39) are of interest as pharmacological agents to modulate pathologically high nitric oxide (NO) levels in inflammation, sepsis, and stroke. In this article, we discuss the approach for targeting the unique (6R)‐5,6,7,8‐tetrahydro‐l‐biopterin (H4Bip) binding site of NOS by appropriate inhibitors. This binding site maximally increases enzyme activity and NO production from the substrate l‐arginine upon cofactor binding. The first generation of H4Bip‐based NOS inhibitors was based on 4‐amino H4Bip derivatives in analogy to anti‐folates such as methotrexate. In addition, we discuss the structure–activity relationship of a related series of 4‐oxo‐pteridine derivatives. Furthermore, molecular modeling studies provide an understanding of pterin antagonism on a structural level based on favorable and unfavorable interactions between protein binding site and ligands. These techniques include 3D‐QSAR (CoMFA, CoMSIA) to understand ligand affinity and GRID/consensus principal component analysis (CPCA) to learn about selectivity requirements. Collectively these approaches, in combination with the presented SAR and structural data, provide useful information for the design of novel NOS inhibitors with increased isoform selectivity. © 2004 Wiley Periodicals, Inc. Med Res Rev, 24, No. 5, 662–684, 2004
A quasi‐static boundary value problem in multi‐surface elastoplasticity: Part 1—Analysis
Authors: Brokate Martin , Carstensen Carsten , Valdman Jan
Published: June 2004

The quasi‐static evolution of an elastoplastic body with a multi‐surface constitutive law of linear kinematic hardening type allows the modelling of curved stress–strain relations. It generalizes classical small‐strain elastoplasticity from one to various plastic phases. This paper presents the mathematical models and proves existence and uniqueness of the solution of the corresponding initial‐boundary value problem. The analysis involves an explicit estimate for the effective ellipticity constant. Copyright © 2004 John Wiley & Sons, Ltd.
Mathematical analysis and stability of a chemotaxis model with logistic term
Authors: Tello J. Ignacio
Published: June 2004

In this paper we study a non‐linear system of differential equations arising in chemotaxis. The system consists of a PDE that describes the evolution of a population and an ODE which models the concentration of a chemical substance. We study the number of steady states under suitable assumptions, the existence of one global solution to the evolution problem in terms of weak solutions and the stability of the steady states. Copyright © 2004 John Wiley & Sons, Ltd.
On the growth of filamentary structures in planar media
Authors: Andreucci D. , Herrero M. A. , Velázquez J. J. L.
Published: June 2004

We analyse a mathematical model for the growth of thin filaments into a two dimensional medium. More exactly, we focus on a certain reaction/diffusion system, describing the interaction between three chemicals (an activator, an inhibitor and a growth factor), and including a fourth cell variable characterising irreversible incorporation to a filament. Such a model has been shown numerically to generate structures shaped like nets. We perform an asymptotical analysis of the behaviour of solutions, in the case when the system has parameters very large and very small, thereby allowing the onset of different time and space scales. In particular, we describe the motion of the tip of a filament, and the changes in the relevant chemical species nearby. Copyright © 2004 John Wiley & Sons, Ltd.
Bandwidth enhancement of circularly polarized microstrip patch antenna using multiple L‐shaped probe feeds
Authors: Lo Wai‐Kwok , Chan Chi‐Hou , Luk Kwai‐Man
Published: June 2004

Impedance‐bandwidth enhancement of microstrip antennas using an L‐shaped probe feed has previously been demonstrated. In this paper, axial‐ratio bandwidth enhancement is achieved for circularly polarized (CP) microstrip patch antenna using dual and four L‐shaped probe feeds. By controlling the excitation phase and angular orientation of the horizontal portion of each L‐probe, circular polarization can be generated with wide axial‐ratio bandwidth by exciting the circular patch. In the dual L‐shaped probe case, the impedance and axial‐ratio bandwidth are 42% and 27.23%, respectively. On the other hand, for the four L‐shaped probes case, both of these figures increase to 45%. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 263–265, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20272
Cancellation of local oscillator phase‐noise in 60‐GHz high‐data‐rate wireless systems
Authors: Loyez C. , Fryziel M. , Boe A. , Rolland N. , Rolland P. A.
Published: June 2004

A cancellation device of phase‐noise is implemented in a wireless system at 60 GHz. By using only MMIC VCOs to perform frequency conversions, such a system effectively transmits signals with a QPSK‐modulation scheme. For a 50 Mb/s data‐rate, performances are similar to that of an ideal conventional system. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 268–272, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20274
A three‐stage Ka band PHEMT wideband amplifier MMIC
Authors: Huang C. W. , Chang S. J. , Wu W. , Wu C. L. , Chang C. S.
Published: June 2004

In this paper, a Ka‐Band 24‐dBm AlGaAs/InGaAs/GaAs PHEMT MMIC power amplifier is demonstrated. This three‐stage amplifier is designed to fully match for 50Ω input and output impedances. With 4 V and 250‐mA DC bias, we achieve 15‐dB small‐signal gain, 24 dBm P−1dB, 24.3% PAE, and better than 10‐dB input return loss from 31 to 37 GHz. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 277–280, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20277
Broadband millimeter‐wave planar antenna array with a waveguide and microstrip‐feed network
Authors: Oh Soon‐Soo , Heo John , Kim Dong‐Hyeon , Lee Jae‐Wook , Song Myung‐Sun , Kim Young‐Sik
Published: June 2004

In this paper, we describe a fixed‐beam broadband planar antenna array at millimeter‐wave frequencies. The antenna is fed by waveguide‐feed and microstrip‐feed networks. In order to ensure fixed beams and a broad bandwidth, a subarray concept is introduced. For efficient coupling, a novel waveguide‐to‐slot transition consisting of a slot pair and a narrow conductive bar is proposed. Simulated and measured bandwidth is found to be more than 7.1% from 40.5–43.5 GHz. The main beam directions are broadside over all frequencies. The maximum measured antenna gain is 30.2 dBi at 42.0 GHz. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 283–287, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20279
An internal metal‐plate antenna for a folder‐type mobile phone
Authors: Chiu Ching‐Yuan , Wong Kin‐Lu
Published: June 2004

A compact shorted metal‐plate antenna suitable to be concealed within the casing of a folder‐type mobile phone as an internal antenna is presented. A design example of the proposed antenna for operating in the UMTS band (1920–2170 MHz) is demonstrated. Details of the experimental results of the constructed prototypes are presented and discussed. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 294–296, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20282
Pattern‐reconfigurable quasi‐yagi microstrip antenna using a photonic band gap structure
Authors: Yang Xue‐Song , Wang Bing‐Zhong , Zhang Yong
Published: June 2004

A pattern‐reconfigurable quasi‐Yagi microstrip antenna is presented. Its main beam in the E‐plane can scan from −66° to +63° in the upper‐half space by using a switch‐controlled photonic band gap (PBG) structure, while maintaining an operating frequency of approximately 9.65 GHz. The antenna is analyzed using Ansoft HFSS. The measured and simulated results of the three configurations of the antenna are provided. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 296–297, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20283
Fast analysis of interconnect response illuminated by an external electromagnetic field using G‐FDTD
Authors: Jin Hong‐Fang , Li Er‐Ping , Wang Sheng , Li Le‐Wei , Yuan Wei Liang
Published: June 2004

A modified finite‐difference time‐domain (FDTD) method, called generalized total‐field/scattered‐field (G‐TF/SF) FDTD, is applied to compute the interconnect response on an infinite dielectric substrate illuminated by an external electromagnetic field. This method is also extended form 2D to 3D. The current distributions on the strips obtained by using the 3D G‐FDTD method are presented and are in good agreement with the results computed via the method of moments (MoM). The simulation results indicate that this method is efficient and accurate for the modeling of an infinite scatterer problem with a compact FDTD grid. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 304–307, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20286
Dual‐frequency and dual‐polarization multilayer microstrip antenna element
Authors: Michail Georgios Ch. , Uzunoglu Nikolaos K.
Published: June 2004

A dual‐frequency and dual‐linear polarization multilayer microstrip antenna element for array‐antenna applications is presented. The performance of the element was computed using a commercial software based on the finite‐element‐method (FEM) algorithm. A prototype with dimensions based on the simulations was built and tested. Good agreement between the measured and numerical results is obtained. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 311–315, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20288
Effect of metal contact's reflection on the effective coupling coefficient of second‐order DFB laser diodes
Authors: Zhong Yuan , Zhu Xiaopeng , Song Guofeng , Huang Yidong , Chen Lianghui
Published: June 2004

For a second‐order DFB‐LD, the presence of a metal contact layer can reduce 1st‐order radiation. Part of the reflected power is redistributed into guided modes and results in a variation of the effective coupling coefficient κeff. In this paper, we study the effect of the Au top contact's reflection on the κeff of 2nd‐order DFB lasers. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 339–342, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20296
A 2‐watt balanced power amplifier MMIC for Ku‐band satellite communications
Authors: Kim Jeong‐Geun , Park Hyun‐Min , Kim Jae‐Young , Jeon Sun‐Ik , Hong Songcheol
Published: June 2004

A Ku‐band power amplifier MMIC has been developed using 0.25‐μm GaAs pHEMT technology. To achieve small chip size and simple drain‐bias connection, a bus‐bar power combiner is used. Also, balanced‐power amplifier topology is used to obtain good input/output return losses. The small‐signal gain is about 15 dB and the gain variation is less than 1 dB from 12 to 17 GHz. Good input/output return losses are achieved at less than −15 dB due to the balanced topology.P1dBof 32.6 dBm and PAE of 23.5% are achieved at 14 GHz. The effective chip area is 4.2 × 3.2 mm. Because the power amplifier is implemented using the balanced topology with the bus‐bar power combiner, compact size, high output power, and good input/output return losses can be achieved simultaneously. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 342–344, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20297
Remarks on “A 2D TLM model for electromagnetic wave propagation in Tellegen media”
Authors: Mackay Tom G.
Published: June 2004

Cabeceira et al. recently presented a time‐domain analysis of wave propagation in a Tellegen medium [1]. Their analysis is ill‐founded because (i) the existence of any Tellegen medium is not tenable within modern electromagnetic theory; and (ii) the constitutive relations employed are not consistent with the principle of causality.© 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 345–346, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20298
Melting point depression and cocrystallization behavior of poly(ethylene‐co‐butylene 2,6‐naphthalate) copolymers
Authors: Papageorgiou George Z , Achilias Dimitris S , Karayannidis George P
Published: June 2004

The melting point depression and cocrystallization behavior of a series of random poly(ethylene‐co‐butylene 2,6‐naphthalate) P(EN‐co‐BN) copolymers were investigated using differential scanning calorimetry (DSC) and wide‐angle X‐ray diffraction (WAXD). These copolymers crystallize over the entire range of composition and they exhibit eutectic behavior. WAXD patterns showed that copolymers form exclusively poly(ethylene 2,6‐naphthalate) (PEN) type crystals or poly(butylene 2,6‐naphthalate) (PBN) type crystals. A transition from the PEN‐ to PBN‐type crystal was observed in the middle of the copolymer composition. This confirms that the P(EN‐co‐BN) copolymers show isodimorphic cocrystallization. The cocrystallization was thermodynamically analyzed using the Wendling–Suter model. The defect free energy was found to be about 12.17 kJ mol−1 in the case of incorporation of BN units in the PEN‐type crystals, and about 5.66 kJ mol−1 in the case of incorporation of EN units in the PBN‐type crystal. This means that the incorporation of bulkier BN units in the PEN crystals is more difficult. For low comonomer concentrations it was found that comonomer exclusion is probable. Copyright © 2004 Society of Chemical Industry
Characterization of molecularly imprinted polymers employing crosslinkers with nonsymmetric polymerizable groups
Authors: Sibrian‐Vazquez Martha , Spivak David A.
Published: June 2004

Crosslinking monomers have been developed with a combination of methacrylamide and methacrylate or vinyl ketone polymerizable groups that provide molecularly imprinted polymers (MIPs) with improved binding and selectivity. The differential reactivity rates of the polymerizable groups prompted an investigation into the time‐dependent behavior of the crosslinkers, which suggests a new mechanism for MIP formation. The mechanism involves the formation of long sections of linear poly(vinyl ketone) with pendant methacrylamide groups that form a highly crosslinked network in a subsequent step. This has implications for the sequence morphology of polymers, affecting the structure and improving the binding properties of MIPs. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3668–3675, 2004
Birefringence study of drawn Nafion films
Authors: Van Der Heijden Peter , Bouzenad Faycal , Diat Olivier
Published: June 2004

Nafion films are birefringent. This optical property has been studied as a function of the draw ratio to obtain insight into the film morphology. At small draw ratios, the structure shows biaxial behavior. At higher draw ratios (>150%), Nafion can be considered to have a uniaxial symmetry. The influence on the birefringence of three different counterions (hydrogen, lithium, and tetramethylammonium) is negligible. Undrawn Nafion shows preorientation, which can be eliminated with drawing in the proper direction. X‐ray experiments suggest that the physical origin of the birefringence in Nafion is mainly due to the orientation of the polymer chains and not due to deformation or form birefringence. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2857–2870, 2004
Synthesis of Energetic Polymers by the Introduction of Energetic Groups onto Polymeric Primary and Secondary Amines
Authors: Bellamy Anthony J. , King David S. , Golding Peter
Published: June 2004

Energetic polymers have been synthesised by the introduction of picryl groups onto linear polyethylenimine and polyvinylamine. The degree of substitution was 70–97% for polyethylenimine, depending upon the molecular weight of the polymer, and around 70% for polyvinylamine. N‐Picrylation of low molecular weight, model compounds was also studied. The results illustrate the influence of molecular weight on the chemical accessibility of a reaction site and reflect the difficulty of modelling polymer modification reactions using small molecules.
Ab Initio Calculation of BN Generation from Boron and Nitrogen Oxides
Authors: Wang Zhong , Li Shu Fen , Zhang Li Min , Sheng Zhen Yu , Yu Shu Qin
Published: June 2004

Boron Nitride (BN) is one of the products produced in the burning of boron‐containing propellant. A possible reaction mechanism for the reactions of boron and nitrogen oxides (NO, NO2, N2O) has been studied using the G2MP2 method. The BN product can be formed in the reactions of B(4P) with NO, NO2 and N2O. Among these three reactions, B(4P)+NO2 and B(4P)+N2O are 181.42 kJ/mol and 160.92 kJ/mol more‐exothermic than the B(4P)+NO reaction. The barrier heights from intermediates to transition states are 64.85 kJ/mol and 111.75 kJ/mol for B(4P)+NO2 and B(4P)+N2O, respectively. However, in the reaction B(4P)+NO , the transition from intermediate to product (IM3→BN+O) is very endothermic by 420.70 kJ/mol. So B(4P)+ N2O→BN+NO and B(4P)+NO2→BN+O2 are more likely reactions to generate BN than B(4P)+NO→BN+O.
Synthesis, Crystal Structure and Theoretical Study of Tetranitrodiazidoacetylhexaazaisowurtzitane (TNDAIW)
Authors: Yukai Wu , Yuxiang Ou , Jinquan Liu , Lihua Liu , Boren Chen , Zhiguo Liu
Published: June 2004

A novel polycyclic caged compound, tetranitrodiazidoacetylhexaazaisowurtzitane (TNDAIW), has been synthesized by a six‐step reaction. The molecular structures of two key intermediates and TNDAIW were identified. The crystal structure of the titled compound was established by X‐ray crystallography. Semi‐empirical MO calculations were performed with AM1 and PM3 methods based on the crystal structure. The corresponding data of β‐CL‐20 are also given for comparison.
Simulation of Explosive Welding with ANFO Mixtures
Authors: Mousavi A. A. Akbari , Burley Stephen J. , Al‐Hassani S. T. S. , Byers Brown W.
Published: June 2004

The work described here arose from a study into explosive welding. As part of that study, the impact velocity of stainless steel and titanium plates to grazing detonation of ANFO/perlite, the velocity of detonation were measured. Computer simulation required a new model which copes with an equation of state of low explosives.
Divergent Detonation Wave Processes in PBX Based on RDX
Authors: Mendes Ricardo A. L. , de A. Campos José L. S. , Plaksin Igor Y. , Ribeiro Jose M. B. M.
Published: June 2004

In order to characterize the initial phase of the divergent detonation wave in PBX, a hemispheric explosive sample was initiated by a long cylindrical charge of the same explosive. The tested PBX is composed of 85 wt% of RDX and 15 wt% of binder based on HTPB. This PBX‐RDX presents an effective density of 1.57 g/cm3, and a detonation velocity of 7.90 mm/μs.
Large‐scale prediction of protein geometry and stability changes for arbitrary single point mutations
Authors: Bordner A. J. , Abagyan R. A.
Published: June 2004

We have developed a method to both predict the geometry and the relative stability of point mutants that may be used for arbitrary mutations. The geometry optimization procedure was first tested on a new benchmark of 2141 ordered pairs of X‐ray crystal structures of proteins that differ by a single point mutation, the largest data set to date. An empirical energy function, which includes terms representing the energy contributions of the folded and denatured proteins and uses the predicted mutant side chain conformation, was fit to a training set consisting of half of a diverse set of 1816 experimental stability values for single point mutations in 81 different proteins. The data included a substantial number of small to large residue mutations not considered by previous prediction studies. After removing 22 (≈2%) outliers, the stability calculation gave a standard deviation of 1.08 kcal/mol with a correlation coefficient of 0.82. The prediction method was then tested on the remaining half of the experimental data, giving a standard deviation of 1.10 kcal/mol and covariance of 0.66 for 97% of the test set. A regression fit of the energy function to a subset of 137 mutants, for which both native and mutant structures were available, gave a prediction error comparable to that for the complete training set with predicted side chain conformations. We found that about half of the variation is due to conformation‐independent residue contributions. Finally, a fit to the experimental stability data using these residue parameters exclusively suggests guidelines for improving protein stability in the absence of detailed structure information. Proteins 2004. © 2004 Wiley‐Liss, Inc.
Predicting interactions of winged‐helix transcription factors with DNA
Authors: Roberts Victoria A. , Case David A. , Tsui Vickie
Published: June 2004

Determining protein–DNA interactions is important for understanding gene regulation, DNA repair and chromatin structure. Unfortunately, the structures of DNA‐bound complexes are often difficult to obtain experimentally, so the development of computational methods that provide good models of these complexes would be valuable. Here, we present a rigid‐body docking approach using the computer program DOT. DOT performs a complete, six‐dimensional search of all orientations for two rigid molecules and calculates the interaction energy as the sum of electrostatic and van der Waals terms. DOT was applied to three winged‐helix transcription factors that share similar DNA‐binding structural motifs but bind DNA in different ways. Docking with linear B‐form DNA models accomplished several objectives; it (1) distinguished the different ways the transcription factors bind DNA, (2) identified each protein's DNA‐binding site and the DNA orientation at the site and (3) gave at least one solution among the three best‐ranked that shows the protein side chain–DNA base interactions responsible for recognition. Furthermore, the ensemble of top‐ranked, docked linear B‐DNA fragments indicated the DNA bending induced upon protein binding. Docking linear B‐DNA to structures of the transcription factor FadR suggests that the allosteric, conformational change induced upon effector binding results in loss of the ability to bend DNA as well as loss of sequence‐specific interactions with DNA. The electrostatic energy term calculated by DOT is comparable to the electrostatic binding energy calculated by Poisson–Boltzmann methods. Our results show rigid‐body docking that includes a rigorous treatment of the electrostatic interaction energy can be effective in predicting protein–DNA interactions. Proteins 2004. © 2004 Wiley‐Liss, Inc.
Molecular dynamics simulation of C60 encapsulated in boron nitride nanotubes
Authors: Moon Won Ha , Son Myung Sik , Lee Jun Ha , Hwang Ho Jung
Published: June 2004

This issue's Editor's Choice [1] reports molecular dynamics investigations of the encapsulation of fullerene molecules in boron nitride nanotubes, a hybrid system with large potential for various materials applications.

The cover picture shows possible positions for the diffusion of C60 into the BN nanotube. The light colored C60 (I–III) can be encapsulated in the tube. The yellow colored C60 (IV) with some atoms located above the tube wall, however, is quickly adsorbed and moves on the surface of the tube. The dark line hence indicates the border for diffusion.

The corresponding author Ho Jung Hwang is Professor of Electrical and Electronic Engineering and Dean of the College of Engineering at Chung‐Ang University, Seoul, Korea. His main interests are in semiconductor technology, process/equipment simulation, nanotechnology, and nanosimulation.