bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison between observed and modelled radiative properties of stratocumulus clouds
Authors: Sun Zhian , Pethick David
Published: January 2003

Measurements of radiative and microphysical characteristics of stratocumulus clouds in a coastal region of South Australia are reported. The measurements were taken on 14 April 1999 using two aircraft from Airborne Research Australia based at the Flinders University of South Australia during the Kangaroo Island Radiation and Cloud Experiments (KIRCE). The measurements include radiation, cloud liquid‐water content, ambient temperature and humidity. A new method to process the measurements is described. Cloud albedo and absorption were determined using the observed solar irradiances at the cloud top and base and the results were compared with theoretical calculations. Five water‐cloud optical parametrization schemes were tested against the observations. In addition, some observational data from the Joint Air–Sea Interaction (JASIN) experiment were used in the comparisons. It has been found that measured cloud properties from the KIRCE experiment are very similar to those of the JASIN experiment. The modelled results from most schemes are compatible and generally in good agreement with the measurements. Copyright © 2002 Royal Meteorological Society.
Wind Energy Technologies for use in the Built Environment
Authors: Blanch M.J.
Published: January 2003

Technologies are being developed to harness power from the wind using buildings. These are described with their current stage of development and with the plans and possibilities of further developments. These technologies may be able to make valuable contributions to the renewable component of an urban area's power supply. This new market is potentially enormous. Feeding power directly into the building's own electrical circuits avoids costs otherwise associated with a separate connection to the local utility electrical distribution network. The economic value of the energy is equal to that otherwise charged by the client's electrical supplier, which is considerably higher than would normally be paid for wind energy supplied directly to the grid.
Surface oxidation of styrene butadiene copolymers: Study by laser ablation and secondary ion mass spectrometry
Authors: Ruch D. , Boes C. , Zimmer R. , Migeon H.‐N. , Muller J. F.
Published: January 2003

The capabilities of ion bombardment and laser ablation coupled to mass spectrometry as independent techniques to investigate the surface thermooxidative stability of polystyrene, polybutadiene polymers, and styrene butadiene rubber (SBR) copolymers were investigated. Surface chemical modifications were detected according to the polymeric structure. The degradation products detected by static secondary ion mass spectrometry appeared at m/z 29, 43, and 55. Their compositions were related to the general formulae CnHmO+ with n = 1–3 and m = 1–3 for polybutadiene and styrene butadiene copolymers, whereas polystyrene was not affected by the aging treatment. The CnHmO+ ions result from butadiene unit degradation. The laser ablation ionization Fourier transform ion cyclotron resonance mass‐spectrometry results confirmed the detection of CnHmO+ ions. Finally, it may be considered that the surface thermooxidative process of SBR copolymers begins with butadiene unit degradation. The development of butadiene unit oxidation showed a dynamic oxidation phase, which coincided with a loss of unsaturation. The influence of the polymer conformation (blocked, branched, and random) on the surface oxidation for 30% styrene SBR compounds was also studied. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1910–1917, 2003
Molecular weight development in emulsion copolymerization of n‐butyl acrylate and styrene
Authors: Zoco Nuria , de Arbina Lourdes López , Leiza José R. , Asua José M. , Arzamendi Gurutze
Published: January 2003

The seeded emulsion copolymerization of n‐butyl acrylate and styrene in a weight ratio of 50/50 was investigated. The effect of the type of process (batch vs. semicontinuous) and the amounts of initiator and emulsifier charged into the reactor on the time evolution of the fractional conversion, number of polymer particles, and weight‐average molecular weight (Mw) was analyzed. It was found that the Mw depends to a slight extent on the type of process and the emulsifier concentration and to a larger extent on the initiator concentration. The molecular weight distributions (MWDs) and the gel content of the final latexes were also analyzed. In the absence of chain transfer agents (CTAs), the fraction of gel was higher in the semicontinuous processes. It was also found that the gel content increased with increasing initiator concentration in the recipe. The addition of 1 wt % CTA avoided gel formation and led to an important reduction of the Mw. Nevertheless, the MWDs presented a shoulder or even a second peak at high molecular weights that was due to reactions of chain transfer to the polymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1918–1926, 2003
Effect of diluents on the curing behavior of vinyl ester resin
Authors: Agrawal S. , Mishra A. , Rai J.S.P.
Published: January 2003

An acidic vinyl ester resin (∼6 mg KOH per gram of solid) was prepared by reacting a bisphenol‐A‐based epoxy resin with acrylic acid in the presence of tributyl amine. The acrylated epoxy resin thus obtained was characterized by Fourier transform infrared spectroscopy. Five samples of vinyl ester resin containing styrene and methyl methacrylate (MMA) in the weight ratios 40:0, 30:10, 20:20, 10:30, and 0:40 were prepared at 30°C, and their curing behavior was studied by differential scanning calorimetry in the presence of benzoyl peroxide (2 phr). Curing behavior was dependent on the ratio of the two monomers used as reactive diluents. The kinetic parameters were determined by Ozawa's method. The energy of activation and frequency factor varied from 17 to 23 kcal mol−1 and 8.47 × 109 to 5.21 × 1012 min−1, respectively and were lowest for the samples containing 30:10 and 10:30 styrene/MMA weight ratios. The curing reactions followed first‐order kinetics and obeyed the Arrhenius rate expression. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1948–1951, 2003
Preparation and characterization of poly(dimethyldiallyl ammonium)chloride and antiglobulin tests for antibody detection
Authors: Yang Xujie , Wang Xin , Wang Hengzhi , Zhu Junwu , Lu Lude , Zhou Tongbin , Lian Jianfeng
Published: January 2003

Poly(dimethyldiallyl ammonium)chloride [poly(DMDAAC)] was prepared in our laboratory and monomer‐to‐polymer structures were characterized by infrared (IR), proton, and carbon‐13 nuclear magnetic resonance (NMR) as well as DEPT techniques. The polyelectrolytes were used to detect the antibodies of red blood cells (RBCs) in human sera and the results were compared with hexadimethrine bromide (polybrene), bromeline, and other methods. This article presents data supporting the use of the manual poly(DMDAAC) test; the 1‐min procedure at room temperature provided a rapid and sensitive test. The states of agglutination of RBCs were investigated by transmission electron microscopy (TEM). The results of the morphology were in agreement with the manual poly(DMDAAC) test. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1957–1961, 2003
Electrical properties and EMI shielding characteristics of polypyrrole–nylon 6 composite fabrics
Authors: Kim Seong Hun , Jang Soon Ho , Byun Sung Weon , Lee Jun Young , Joo Jin Soo , Jeong Sung Hoon , Park Myung‐Ja
Published: January 2003

Polypyrrole (PPy) was polymerized both chemically and electrochemically in sequence on nylon 6 woven fabrics, giving rise to polypyrrole–nylon 6 composite fabrics (PPy–N) with a high electric conductivity. The stability of the composite prepared by electrochemical polymerization (ECP) on chemical oxidative polymerization (COP) fabric was better than that of the composite prepared solely by the COP process, since the AQSA dopant was able to strongly interact with the PPy main chain and had a large molecular structure. The temperature dependence of the conductivity of the composites was verified over four heating and cooling cycles. The change in conductivity over these four repeated heating and cooling cycles was affected by the interaction between the thermal stability of the dopant and the rearrangement of the PPy main chain. The electromagnetic interference shielding efficiency (EMI SE) values were in the range 5–40 dB and depended on the conductivity and the layer array sequence of the conductive fabric. The composites with a high conductivity represented reflection‐dominant EMI shielding characteristics, which are typical of the EMI shielding characteristics of metals. However, composites with low conductivity showed absorption‐dominant EMI shielding characteristics. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1969–1974, 2003
Effect of the crystallization conditions on the phase behavior of syndiotactic polystyrene/poly(phenylene oxide) blends
Authors: Dutt G. , Kit K. M.
Published: January 2003

Syndiotactic polystyrene (sPS) and poly(phenylene oxide) (PPO) blends, miscible in the melt state, were crystallized from the melt and the quenched state at different temperatures. The effect of the crystallization temperature on the phase behavior of the blends and the polymorphic changes in sPS was investigated by dynamic mechanical analysis (DMA), wide‐angle X‐ray diffraction (WAXD), and density measurements. In most blends, the crystallization of sPS induced segregation into two homogeneous amorphous phases of different compositions. The temperatures of the DMA relaxations of the neat homopolymers and crystallized blends were fit by the Gordon–Taylor relation to calculate the compositions of these phases. In melt‐crystallized blends, with slower crystallization, the major amorphous phase became sPS‐rich, whereas the minor phase became PPO‐rich. These major and minor amorphous phases could be tentatively assigned to interfibrillar and interlamellar regions, respectively. In cold‐crystallized blends, slower crystallization decreased the sPS concentration in both phases, and the scale of segregation was much smaller. WAXD studies and density measurements indicated a complex polymorphic behavior of sPS after it was blended with PPO. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1975–1983, 2003
Effect of time/temperature treatment parameters on depolymerization of chitosan
Authors: No Hong Kyoon , Nah Jae Woon , Meyers Samuel P.
Published: January 2003

Depolymerization of the biopolymer chitosan by an autoclaving process at 121°C and 15 psi was investigated using various treatments. Acetic acid was found to be the most effective solvent in decreasing chitosan viscosity among the six organic acids tested. The rate of viscosity decrease increased with increasing chitosan concentration. The viscosity of 1% chitosan in 1% acetic acid decreased rapidly to 91% of the initial viscosity following the initial 15 min of autoclaving. This decreased gradually to 93% and 94% in 30 and 60 min, respectively, without being adversely affected by the chitosan solution volume. The degree of deacetylation was comparable before and after autoclaving for 60 min. Chitosan at three molecular weights (Mr = 1597, 1110, and 789 kDa) decreased in molecular weight by 46%–51% in the 15‐min treatment, 55%–60% in the 30‐min treatment, and 60%–62% in the 60‐min treatment. The addition of 0.1%–1.0% (v/v) concentrations of hydrogen peroxide to the chitosan solution autoclaved for 15 min decreased viscosity by 94%–98% and molecular weight by 69%–83%. This process is a simple, timesaving, homogeneous depolymerization procedure, and it is possible to prepare partially hydrolyzed chitosan with specified molecular weights by regulating the time of treatment. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1890–1894, 2003
Study of glycolysis of poly(ethylene terephthalate) recycled from postconsumer soft‐drink bottles. III. Further investigation
Authors: Chen Cheng‐Ho
Published: January 2003

A modified glycolysis reaction of recycled poly(ethylene terephthalate) (PET) bottles by ethylene glycol (EG) was investigated. Influences of the glycolysis temperature, the glycolysis time, and the amount of catalysts (per kg of recycled PET) were illustrated in this study. The manganese acetate was used as a glycolysis catalyst in this study. Bis‐2‐hydroxyethyl terephthalate (BHET) and its dimer were predominately glycolysis products. It was found the optimum glycolysis temperature is 190°C. And the best glycolysis condition is 190°C of glycolysis temperature, 1.5 h of glycolysis time, and 0.025 moles of manganese acetate based on per kg of recycled PET. If the best glycolysis condition is conducted, the glycolysis conversion may be as high as 100%. For a given reaction time (1.0 h), the ln(% glycolysis conversion) is linear to 1/T (K−1) and the activation energy (E) of glycolysis reaction is around 92.175 kJ/(g mole). The glycolysis conversion rate increases significantly with increasing the glycolysis temperature, the glycolysis time, or the amount of manganese acetate (glycolysis catalyst). Thermal analyses of glycolysis products were examined by a differential scanning calorimetry (DSC) and a thermogravimetric analysis (TGA). According to the definition of a 23 factorial experimental design, the sequence of the main effects on the glycolysis conversion of the recycled PET, in ascending order, is the glycolysis time (0.18) < the amount of catalyst per kg of the recycled PET (0.34) < the glycolysis temperature (0.40). Meanwhile, the prediction equation of glycolysis conversion from the result of a 23 factorial experimental design is Ŷ = 0.259+0.20X1+0.09X2+0.17X3+0.06X1
X2+0.145X1X3+0.05X2X3+0.035X1X2X3. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2004–2010, 2003
Influence of maleated polypropylene on mechanical properties of composite made of viscose fiber and polypropylene
Authors: Paunikallio Teemu , Kasanen Jossi , Suvanto Mika , Pakkanen Tuula T.
Published: January 2003

The purpose of this work was to study how viscose fiber behaves in polypropylene (PP) matrix when maleated polypropylene (MAPP) is used as a coupling agent. The influences of processing conditions on composite properties was of interest. Composites were characterized by FTIR and mechanical testing. The most notable result was the effect of the MAPP concentration on the tensile strength of the composites; the tensile strength increased from 40 to 69 MPa when MAPP was added in amounts up to 6 wt % of the fiber weight. The interaction between MAPP and fiber was confirmed with FTIR. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1895–1900, 2003
Crosslinking cotton with poly(itaconic acid) and in situ polymerization of itaconic acid: Fabric mechanical strength retention
Authors: Yang Charles Q. , Hu Cheng , Lickfield Gary C.
Published: January 2003

Polycarboxylic acids have been used as nonformaldehyde durable press finishing agents for cotton fabrics. Previously, we found that itaconic acid (IA) polymerized in situ on cotton fabric and also in an aqueous solution in the presence of a K2S2O8/NaH2PO2 initiation system. Both poly(itaconic acid) (PIA) and the polymer formed by in situ polymerization of IA are able to crosslink cotton cellulose, thus imparting wrinkle resistance to cotton. In this research, we compared the performance of the cotton fabric crosslinked by PIA and that crosslinked by in situ polymerization of IA. The fabric treated with PIA and that treated with IA had similar wrinkle recovery angles. The cotton fabric treated with IA, however, lost more tensile strength than that treated with PIA due to cellulose degradation. We determined the magnitude of the fabric tensile strength loss attributed to crosslinking by separating the tensile strength loss due to cellulose degradation from the total tensile strength loss, and found that the tensile strength loss caused by crosslinking for the fabric treated with PIA was significantly higher than that for the fabric treated with IA. This can probably be attributed to more concentrated crosslinkages formed on the near surface of the PIA‐treated cotton fabric. PIA had poorer penetration into the amorphous cellulose region in fiber interior due to its much larger molecular size, thus increasing its concentration on the fabric's near surface. The data also suggest that more concentrated crosslinkages on the fabric surface reduced fabric abrasion resistance. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2023–2030, 2003
Ligand‐accelerated cadmium‐catalyzed asymmetric allylation reactions in aqueous media
Authors: Kobayashi Shū , Aoyama Naohiro , Manabe Kei
Published: January 2003

Catalytic asymmetric allylation of aldehydes with allyltributyltin in aqueous media has been realized using combinations of cadmium bromide and chiral diamine ligands. These ligands were found to accelerate the reactions significantly. Chirality 15:124–126, 2003. © 2003 Wiley‐Liss, Inc.
New bulky chiral Lewis acid catalyst: 3,3′‐di(2‐mesitylethynyl)binaphthol–titanium(iv) complex
Authors: Ishihara Kazuaki , Kobayashi Jun , Nakano Kazuhiko , Ishibashi Hideaki , Yamamoto Hisashi
Published: January 2003

A new chiral Lewis acid catalyst 9 was prepared in situ from a 1:2 molar mixture of (R)‐3,3′‐di(2‐mesitylethynyl)binaphthol (6) and titanium(IV) isopropoxide at ambient temperature. The 3‐ and 3′‐substituents on 6 were effective for preventing undesired aggregation between Ti(IV) complexes and increasing the enantioselectivity (up to 82% ee) in the Diels–Alder reaction of methacrolein with cyclopentadiene. Chirality 15:135–138, 2003. © 2003 Wiley‐Liss, Inc.
Synthesis of 9‐N‐cinchona alkaloid peptide hybrid derivatives: preparation and conformational study of 9‐N‐acylamino(9‐deoxy)cinchona alkaloids
Authors: Sundermeier Uta , Döbler Christian , Mehltretter Gerald M. , Baumann Wolfgang , Beller Matthias
Published: January 2003

The synthesis and conformational analyses of several 9‐N‐acylamino(9‐deoxy)cinchona alkaloids is presented. Peptides were connected to cinchona alkaloids via a 9‐amino group. The synthesis of the new cinchona alkaloid derivatives was performed straightforwardly from 9‐amino(9‐deoxy)dihydroquinidine via coupling with carboxylic acid chlorides and several dipeptides. Both alkaloid derivatives with the configuration of the corresponding natural product as well as its unnatural epimer were studied. The conformations of the prepared derivatives in solution were determined by NMR spectroscopy. It is shown that the conformation is strongly influenced by the configuration at the 9‐position. Chirality 15:127–134, 2003. © 2003 Wiley‐Liss, Inc.
Derivatization, complexation, and absolute configurational assignment of chiral primary amines: Application of exciton‐coupled circular dichroism
Authors: Zhang Jing , Holmes Andrea E. , Sharma Akanksha , Brooks Neil R. , Rarig Randy S. , Zubieta Jon , Canary James W.
Published: January 2003

We report here a sensitive method for the determination of the absolute configurations of primary amines using exciton‐coupled circular dichroism (ECCD). The method works on a microgram scale by derivatization of chiral amines with quinoline chromophores. Complexation of the chiral ligands with metal ion fixes the geometry of the chromophores, resulting in a twist that is governed by the asymmetric carbon configuration and steric environment of the amine. The absolute configurations of the primary amines can be interpreted from the couplets of the ECCD spectra of the derivatized complexes. Crystal structures, 2D NMR studies, and semiempirical calculations provide structural evidence for our model. Chirality 15:180–189, 2003. © 2003 Wiley‐Liss, Inc.
Determination of the absolute configuration and solution conformation of gossypol by vibrational circular dichroism
Authors: Freedman Teresa B. , Cao Xiaolin , Oliveira Regina V. , Cass Quezia B. , Nafie Laurence A.
Published: January 2003

Vibrational circular dichroism (VCD) measurements and density functional theory (DFT) calculations were used to obtain the first definitive assignment of the absolute configuration for the polyphenolic binaphpthyl dialdehyde gossypol and a determination of the solution conformation in CDCl3. VCD spectra recorded for the two resolved enantiomers are near mirror images and excellent agreement between the observed IR and VCD spectra and intensity calculations carried out at the DFT (B3LYP/6‐31G*) level establish the absolute configurations of (+)‐gossypol as P and (−)‐gossypol as M, with two conformations in CDCl3 solution that differ in isopropyl group orientation. Chirality 15:196–200, 2003. © 2003 Wiley‐Liss, Inc.
Enantiomerically pure nucleophiles in diastereoselective palladium catalysed allylic substitution reactions
Authors: Humphries Mark E. , Clark Barry P. , Regini Samantha , Acemoglu Lara , Williams Jonathan M.J.
Published: January 2003

Enantiomerically pure α‐amino esters were applied in palladium catalysed allylic substitution reactions with moderate diastereoselectivity (up to 70% d.e.) using achiral ligands on symmetrical allylic acetates. Nucleophilic substitution of amino esters with enantiomerically pure ligands enabled diastereoselective ratios of 95:5 to be obtained. Chirality 15:190–195, 2003. © 2003 Wiley‐Liss, Inc.
Stereostructure–activity studies on agonists at the AMPA and kainate subtypes of ionotropic glutamate receptors
Authors: Johansen Tommy N. , Greenwood Jeremy R. , Frydenvang Karla , Madsen Ulf , Krogsgaard‐Larsen Povl
Published: January 2003

(S)‐Glutamic acid (Glu), the major excitatory neurotransmitter in the central nervous system, operates through ionotropic as well as metabotropic receptors and is considered to be involved in certain neurological disorders and degenerative brain diseases that are currently without any satisfactory therapeutic treatment. Until recently, development of selective Glu receptor agonists had mainly been based on lead compounds, which were frequently naturally occurring excitants structurally related to Glu. These Glu receptor agonists generally contain heterocyclic acidic moieties, which has stimulated the use of bioisosteric replacement approaches for the design of subtype‐selective agonists. Furthermore, most of these leads are conformationally restricted and stereochemically well‐defined Glu analogs. Crystallization of the agonist binding domain of the GluR2 subunit of the (RS)‐2‐amino‐3‐(3‐hydroxy‐5‐methyl‐4‐isoxazolyl)propionic acid (AMPA) receptor subtype of ionotropic Glu receptors in the presence or absence of an agonist has provided important information about ligand–receptor interaction mechanisms. The availability of these binding domain crystal structures has formed the basis for rational design of ligands, especially for the AMPA and kainate subtypes of ionotropic Glu receptors. This mini‐review will focus on structure–activity relationships on AMPA and kainate receptor agonists with special emphasis on stereochemical and three‐dimensional aspects. Chirality 15:167–179, 2003. © 2003 Wiley‐Liss, Inc.
First asymmetric synthesis of chiral β‐iodo Baylis‐Hillman esters via tandem 1,4‐conjugate addition/carbonyl coupling reactions
Authors: Xu Xin , Chen Dianjun , Wei Han‐Xun , Li Guigen , Xiao Tom Ling , Armstrong Daniel W.
Published: January 2003

A new asymmetric approach to chiral β‐iodo Baylis‐Hillman hydroxy esters was developed via a tandem asymmetric I‐C/C‐C formation reaction. The reaction was conveniently carried out by slow addition of diethylaluminum iodide into a mixture of aldehyde and α,β‐acetylenic menthyl ester in dichloromethane at −23°C. Excellent geometric selectivity, promising diastereoselectivity and modest to high yields (up to 91%) were obtained. Chirality 15:139–142, 2003. © 2003 Wiley‐Liss, Inc.
Studies on the racemization of a stereolabile 5‐aryl‐thiazolidinedione
Authors: Welch Christopher J. , Kress Michael H. , Beconi Maria , Mathre David J.
Published: January 2003

The enantiomers of the stereolabile peroxisome proliferator‐activated receptor (PPAR) agonist, 1, were isolated by preparative chiral chromatography and their absolute configuration established using a combination of chromatographic and NMR methods. Enantiomer interconversion was investigated under a variety of conditions, with rapid racemization being observed in most solvents, including all aqueous systems studied, irrespective of pH. Rapid racemization in both dog and human plasma was confirmed by chiral HPLC with MS detection. Chirality 15:143–147, 2003. © 2003 Wiley‐Liss, Inc.
Concise stereocontrolled routes to fumagillol, fumagillin, and TNP‐470
Authors: Vosburg David A. , Weiler Sven , Sorensen Erik J.
Published: January 2003

A concise, diastereoselective synthesis of (±)‐fumagillol (3) and formal, enantioselective syntheses of the potent angiogenesis inhibitors fumagillin (1) and TNP‐470 (2) are reported. The origin of asymmetry is a highly diastereoselective Diels‐Alder reaction using a diene with a chiral oxazolidinone auxiliary. The stereochemical course of a key conjugate addition reaction is controlled by the cup‐shaped architecture of a cis‐fused bicyclic enal. Other key steps include a facile hetero‐Claisen rearrangement and a site‐selective Sharpless epoxidation. Chirality 15:156–166, 2003. © 2003 Wiley‐Liss, Inc.
Analyticity and nonexistence of classical steady Hele‐Shaw fingers
Authors: Tanveer Saleh , Xie Xuming
Published: January 2003

This paper concerns analyticity of a classical steadily translating finger in a Hele‐Shaw cell and nonexistence of solutions when relative finger width λ is smaller than ½. It is proved that any classical solution to the finger problem, if it exists for sufficiently small but nonzero surface tension and is close to some Saffman‐Taylor zero‐surface‐tension solution and satisfies some algebraic decay conditions at ∞, must belong to the analytic function space A0, as defined in Section 1, and chosen in a previous study [34] of existence of finger solutions. Further, it is proved that for any fixed λ ∈ (0, ½), there can be no classical steady finger solution when surface tension is sufficiently small, in disagreement with a previous conclusion based on numerical simulation. © 2002 Wiley Periodicals, Inc.
Critical exponents for semilinear equations of mixed elliptic‐hyperbolic and degenerate types
Authors: Lupo Daniela , Payne Kevin R.
Published: January 2003

For semilinear Gellerstedt equations with Tricomi, Goursat or Dirichlet boundary conditions we prove Pohozaev type identities and derive non existence results that exploit an invariance of the linear part with respect to certain nonhomogeneous dilations. A critical exponent phenomenon of power type in the nonlinearity is exhibited in these mixed elliptic hyperbolic or degenerate settings where the power is one less than the critical exponent in a relevant Sobolev imbedding. © 2002 Wiley Periodicals, Inc.
The Grid Portal Development Kit
Authors: Novotny Jason
Published: January 2003

Computational science portals are emerging as useful and necessary interfaces for performing operations on the Grid. The Grid Portal Development Kit (GPDK) facilitates the development of Grid portals and provides several key reusable components for accessing various Grid services. A Grid portal provides a customizable interface allowing scientists to perform a variety of Grid operations including remote program submission, file staging, and querying of information services from a single, secure gateway.

The GPDK leverages off existing Globus/Grid middleware infrastructure as well as commodity Web technology including Java Server Pages and servlets. The design and architecture of the GPDK is presented as well as a discussion on the portal building capabilities of the GPDK, allowing application developers to build customized portals more effectively by reusing common core services provided by the GPDK. Copyright © 2002 John Wiley & Sons, Ltd.
The ASCI Computational Grid: initial deployment
Authors: Rheinheimer Randal , Beiriger Judy I. , Bivens Hugh P. , Humphreys Steven L.
Published: January 2003

Grid Services, a Department of Energy Accelerated Strategic Computing Initiative program, has designed, implemented, and deployed a grid‐based solution for customer access to large computing resources at DOE weapons labs and plants. Customers can access and monitor diverse, geographically distributed resources using the common Grid Services interfaces. This paper discusses the architecture, security, and user interfaces of the Grid Services infrastructure. Published in 2002 by John Wiley & Sons, Ltd.
Ecce—a problem‐solving environment's evolution toward Grid services and a Web architecture
Authors: Schuchardt Karen , Didier Brett , Black Gary
Published: January 2003

The Extensible Computational Chemistry Environment (Ecce), an innovative problem‐solving environment, was designed a decade ago, before the emergence of the Web and Grid computing services. In this paper, we briefly examine the original Ecce architecture and discuss how it is evolving to incorporate both Grid services and components of the Web to increase its range of services, reduce deployment and maintenance costs, and reach a wider audience. We show that Ecce operates in both Grid and non‐Grid environments, an important consideration given Ecce's broad range of uses and user community, and discuss the strategies for loosely coupled components that make this possible. Both in‐progress work and conceptual plans for how Ecce will evolve are presented. Copyright © 2002 John Wiley & Sons, Ltd.
Mississippi Computational Web Portal
Authors: Haupt Tomasz , Bangalore Purushotham , Henley Gregory
Published: January 2003

This paper describes design and implementation of an open, extensible object‐oriented framework that allows the integration of new and legacy components into a single user‐friendly Grid computing environment. Thus we extend the researcher's desktop by providing seamless access to remote resources (that is, hardware, software, and data), and thereby simplifying currently difficult to comprehend and changing interfaces and emerging protocols. The user, through the familiar Web browser interface, is able to compose complex computational tasks represented as a collection of middle‐tier objects serving as proxies for services rendered by the back‐end. The proxies through a Grid resource broker use the Grid services, as defined by the Global Grid Forum, to access remote computational resources. The middle‐tier objects are persistent, and therefore once configured, simulation can be reused, shared between users, or undergo transition into operational or educational use. Copyright © 2002 John Wiley & Sons, Ltd.
The integrated simulation environment TENT
Authors: Schreiber Andreas
Published: January 2003

This paper describes recent development efforts on the integrated simulation environment TENT. TENT is a component‐based software integration and workflow management system using the capabilities of CORBA and Java. It is used to integrate the applications required to form complex workflows, which are typical of multidisciplinary simulations in engineering, in which different simulation codes have to be coupled.

We present our work in integrating TENT with the Globus Toolkit to create a Grid computing environment. The Java Commodity Grid Toolkit has been especially useful for this work. Copyright © 2002 John Wiley & Sons, Ltd.
Web‐based access to the Grid using the Grid Resource Broker portal
Authors: Aloisio Giovanni , Cafaro Massimo
Published: January 2003

This paper describes the Grid Resource Broker (GRB) portal, a Web gateway to computational Grids in use at the University of Lecce. The portal allows trusted users seamless access to computational resources and Grid services, providing a friendly computing environment that takes advantage of the underlying Globus Toolkit middleware, enhancing its basic services and capabilities. Copyright © 2002 John Wiley & Sons, Ltd.
A software development environment for Grid computing
Authors: Müller M. S. , Gabriel E. , Resch M. M.
Published: January 2003

Grid computing has become a popular concept in the last few years. While in the beginning the driving force was metacomputing, the focus has now shifted towards resource management issues and concepts like ubiquitous computing. For the High‐Performance Computing Center Stuttgart (HLRS) the key challenges of Grid computing have come from the demands of its users and customers. With high‐speed networks in place, programmers expect to be able to exploit the overall performance of several instruments and high‐speed systems for their applications. In order to meet these demands, HLRS has set out a research effort to provide these users with the necessary tools to develop and run their codes on clusters of supercomputers. This has resulted in the development of a basic Grid‐computing environment for technical and scientific computing. In this paper we describe the building blocks of this software development environment and focus specifically on communication and debugging. We present the Grid‐enabled MPI implementation PACX‐MPI and the MPI debugger MARMOT. Copyright © 2002 John Wiley & Sons, Ltd.
The Gateway computational Web portal
Authors: Pierce Marlon E. , Youn Choonhan , Fox Geoffrey C.
Published: January 2003

In this paper we describe the basic services and architecture of Gateway, a commodity‐based Web portal that provides secure remote access to unclassified Department of Defense computational resources. The portal consists of a dynamically generated, browser‐based user interface supplemented by client applications and a distributed middle tier, WebFlow. WebFlow provides a coarse‐grained approach to accessing both stand‐alone and Grid‐enabled back‐end computing resources. We describe in detail the implementation of basic portal features such as job submission, file transfer, and job monitoring and discuss how the portal addresses security requirements of the deployment centers. Finally, we outline future plans, including integration of Gateway with Department of Defense testbed Grids. Copyright © 2002 John Wiley & Sons, Ltd.
pyGlobus: a Python interface to the Globus Toolkit™
Authors: Jackson Keith R.
Published: January 2003

Developing high‐performance, problem‐solving environments/applications that allow scientists to easily harness the power of the emerging national‐scale ‘Grid’ infrastructure is currently a difficult task. Although many of the necessary low‐level services, e.g. security, resource discovery, remote access to computation/data resource, etc., are available, it can be a challenge to rapidly integrate them into a new application.

To address this difficulty we have begun the development of a Python‐based high‐level interface to the Grid services provided by the Globus Toolkit. In this paper we will explain why rapid application development using Grid services is important, look briefly at a motivating example, and finally look at the design and implementation of the pyGlobus package. Copyright © 2002 John Wiley & Sons, Ltd.
Engineering an interoperable computational collaboratory on the Grid
Authors: Mann Vijay , Parashar Manish
Published: January 2003

The growth of the Internet and the advent of the computational Grid have made it possible to develop and deploy advanced computational collaboratories. These systems build on high‐end computational resources, communication technologies and enabling services underlying the Grid, and provide seamless and collaborative access to resources, applications and data. Combining these focused collaboratories and allowing them to interoperate has many advantages and can lead to truly collaborative, multidisciplinary and multi‐institutional problem solving. However, integrating these collaboratories presents significant challenges, as each of these collaboratories has a unique architecture and implementation, and builds on different enabling technologies. This paper investigates the issues involved in integrating collaboratories operating on the Grid. It then presents the design and implementation of a prototype middleware substrate to enable a peer‐to‐peer integration of and global access to multiple, geographically distributed instances of the DISCOVER computational collaboratory. An experimental evaluation of the middleware substrate is presented. Copyright © 2002 John Wiley & Sons, Ltd.
Community software development with the Astrophysics Simulation Collaboratory
Authors: von Laszewski Gregor , Russell Michael , Foster Ian , Shalf John , Allen Gabrielle , Daues Greg , Novotny Jason , Seidel Edward
Published: January 2003

We describe a Grid‐based collaboratory that supports the collaborative development and use of advanced simulation codes. Our implementation of this collaboratory uses a mix of Web technologies (for thin‐client access) and Grid services (for secure remote access to, and management of, distributed resources). Our collaboratory enables researchers in geographically disperse locations to share and access compute, storage, and code resources, without regard to institutional boundaries. Specialized services support community code development, via specialized Grid services, such as online code repositories. We use this framework to construct the Astrophysics Simulation Collaboratory, a domain‐specific collaboratory for the astrophysics simulation community. This Grid‐based collaboratory enables researchers in the field of numerical relativity to study astrophysical phenomena by using the Cactus computational toolkit. Copyright © 2002 John Wiley & Sons, Ltd.
UNICORE—a Grid computing environment
Authors: Erwin Dietmar W.
Published: January 2003

This paper gives an overview of the goals, functions, architecture and future development of UNICORE. Its primary goal is to give researchers a seamless access to distributed resources that are available at remote sites. A graphical interface aids users to formulate jobs which are to be performed in a system and site independent fashion. This procedure allows switching between systems without having to change the job. Complex jobs with individual applications running on different systems at different sites may be formulated. UNICORE will perform synchronization and data transfers as required without any user intervention. UNICORE uses X.509 certificates to authenticate users, software and systems and provide secure communication over the internet. Copyright © 2002 John Wiley & Sons, Ltd.
The Perl Commodity Grid Toolkit
Authors: Mock Stephen , Thomas Mary , Dahan Maytal , Mueller Kurt , Mills Catherine , von Lazewski Gregor
Published: January 2003

The Perl Commodity Grid Toolkit (Perl CoG Kit) is a software project aimed at bringing the complexities and power of the computational Grid to developers of Perl applications. In this paper we describe the history and motivation of the project, the benefits of bringing the Grid to Perl developers, the architecture and status of the Perl CoG Kit and the future plans for the project. Copyright © 2002 John Wiley & Sons, Ltd.
The Virtual Laboratory: a toolset to enable distributed molecular modelling for drug design on the World‐Wide Grid
Authors: Buyya Rajkumar , Branson Kim , Giddy Jon , Abramson David
Published: January 2003

Computational Grids are emerging as a new paradigm for sharing and aggregation of geographically distributed resources for solving large‐scale compute and data intensive problems in science, engineering and commerce. However, application development, resource management and scheduling in these environments is a complex undertaking. In this paper, we illustrate the development of a Virtual Laboratory environment by leveraging existing Grid technologies to enable molecular modelling for drug design on geographically distributed resources. It involves screening millions of compounds in the chemical database (CDB) against a protein target to identify those with potential use for drug design. We have used the Nimrod‐G parameter specification language to transform the existing molecular docking application into a parameter sweep application for executing on distributed systems. We have developed new tools for enabling access to ligand records/molecules in the CDB from remote resources. The Nimrod‐G resource broker along with molecule CDB data broker is used for scheduling and on‐demand processing of docking jobs on the World‐Wide Grid (WWG) resources. The results demonstrate the ease of use and power of the Nimrod‐G and virtual laboratory tools for grid computing. Copyright © 2003 John Wiley & Sons, Ltd.
A stochastic load balancing algorithm for i‐Computing
Authors: Wong Yuk‐Yin , Leung Kwong‐Sak , Lee Kin‐Hong
Published: January 2003

This paper presents a stochastic dynamic load balancing algorithm for Internet computing, which is a new type of distributed computing involving heterogeneous workstations from different organizations on the Internet. To realize the practical environment, we assume the system to be comprised of heterogeneous, untrusted and non‐dedicated workstations connected by a non‐dedicated network. Our algorithm uses the product of the average processing time and the queue length of system jobs as the load index. Dynamic communication delay is included in the execution cost calculation. The transfer policy and the location policy are combined in a stochastic algorithm. State information exchange is done via information feedback and mutual updating. Simulations demonstrate that our algorithm outperforms conventional approaches over a wide range of system parameters. These results are reconfirmed by empirical experiments after we have implemented the algorithms on the Distributed Java Machine global virtual machine. Copyright © 2003 John Wiley & Sons, Ltd.
Clustering revealed in high‐resolution simulations and visualization of multi‐resolution features in fluid–particle models
Authors: Boryczko Krzysztof , Dzwinel Witold , Yuen David A.
Published: January 2003

Simulating natural phenomena at greater accuracy results in an explosive growth of data. Large‐scale simulations with particles currently involve ensembles consisting of between 106 and 109 particles, which cover 105–106 time steps. Thus, the data files produced in a single run can reach from tens of gigabytes to hundreds of terabytes. This data bank allows one to reconstruct the spatio‐temporal evolution of both the particle system as a whole and each particle separately. Realistically, for one to look at a large data set at full resolution at all times is not possible and, in fact, not necessary. We have developed an agglomerative clustering technique, based on the concept of a mutual nearest neighbor (MNN). This procedure can be easily adapted for efficient visualization of extremely large data sets from simulations with particles at various resolution levels. We present the parallel algorithm for MNN clustering and its timings on the IBM SP and SGI/Origin 3800 multiprocessor systems for up to 16 million fluid particles. The high efficiency obtained is mainly due to the similarity in the algorithmic structure of MNN clustering and particle methods. We show various examples drawn from MNN applications in visualization and analysis of the order of a few hundred gigabytes of data from discrete particle simulations, using dissipative particle dynamics and fluid particle models. Because data clustering is the first step in this concept extraction procedure, we may employ this clustering procedure to many other fields such as data mining, earthquake events and stellar populations in nebula clusters. Copyright © 2003 John Wiley & Sons, Ltd.
Modular specification of frame properties in JML
Authors: Müller Peter , Poetzsch‐Heffter Arnd , Leavens Gary T.
Published: January 2003

We present a modular specification technique for frame properties. The technique uses modifies clauses and abstract fields with declared dependencies. Modularity is guaranteed by a programming model that enforces data abstraction by preventing representation and argument exposure, a semantics of modifies clauses that uses a notion of ‘relevant location’, and by modularity rules for dependencies. For concreteness, we adapt this technique to the Java Modeling Language, JML. Copyright © 2003 John Wiley & Sons, Ltd.
Estimation of token bucket parameters for aggregated VoIP sources
Authors: Garroppo Rosario G. , Giordano Stefano , Pagano Michele
Published: January 2003

The paper presents an analytical study aimed to establish a dimensioning procedure for the token bucket algorithm, used as a meter in a Differentiated Services network architecture, when a stochastic model for the multiplexed traffic is available. In the work, we propose an equivalent queueing system method to ‘on line’ estimate the linear bounded arrival processes (LBAP) parameters when a non‐zero probability of non‐conforming packets is accepted. Then, we validate our approach considering an aggregation of fluidic On‐Off processes with exponentially distributed sojourn time in each state, used to model telephone sources with voice activity detection (VAD). To test the goodness of our analytical results, we employ discrete event simulations, which have highlighted the accuracy of the proposed dimensioning procedure in a voice over IP (VoIP) scenario. Moreover, we investigate the multiplexing gain and the effect of different parameters on the LBAP characterization of the VoIP traffic, taking into account a non‐zero probability of non‐conforming packets. Copyright © 2002 John Wiley & Sons, Ltd.
Erlang capacity analysis of hybrid FDMA/CDMA systems supporting multi‐class services according to channel assignment methods
Authors: Koo Insoo , Yang Jeongrok , Ahmad Aftab , Kim Kiseon
Published: January 2003

In this paper, we focus on the evaluation of the Erlang capacity for hybrid FDMA/CDMA systems supporting multi‐class services with two channel allocation schemes: independent carrier channel assignment (ICCA) and combined carrier channel assignment (CCCA). For the performance analysis, a multi‐dimensional Markov chain model is developed. The effect of the number of carriers of hybrid FDMA/CDMA system on the Erlang capacity is observed, and the optimum values of the system parameters such as the number of channel elements (CEs) and the number of carriers are selected with respect to the Erlang capacity. As a numerical example, we consider an FDMA/CDMA system supporting voice/data services. We find out that, even though the benefit of CCCA scheme over ICCA scheme is negligible for small number of CEs, the scenario changes significantly when the number of CEs increases beyond a certain point. An improvement of as much as 74% can be achieved in the Erlang capacity when 5 carriers are employed. We also find the capacity knees for different number of carriers. The results of this paper could be helpful in the traffic engineering of FDMA/CDMA systems providing multi‐class services. Copyright © 2002 John Wiley & Sons, Ltd.
An Internet friendly transport protocol for continuous media over best effort networks
Authors: ElAarag Hala , Bassiouni Mostafa
Published: January 2003

In this paper, we design and evaluate an Internet friendly transport‐level protocol (IFTP) for solving the TCP‐friendly problem. IFTP has two modes of operation. In the standard mode, the IFTP connection faithfully emulates the behaviour of TCP in order to roughly obtain a bandwidth equal to that of a TCP connection. In the extended mode, a simple modification is used to grant QoS‐differentiated services to selected connections. Connections running in the extended mode can get enhanced bandwidth while still emulating the general behaviour of TCP. We develop an analytical model for the congestion control mechanism of IFTP. We also derive analytically the amount of bandwidth that IFTP may be able to claim from TCP in ideal and non‐ideal environments. We evaluate IFTP through simulation and prove its TCP friendliness as well as provide performance results on some of the important metrics such as packet delay, delay jitter, packet loss and link utilization. Copyright © 2002 John Wiley & Sons, Ltd.