bluuebunny/crossref_metadata_2025_split huggingface dataset:
On/off switching on polymer conformation
Authors: Yoshikawa Kenichi 
Published: October 2003

AbstractThe manner of folding transition from elongated coil to compact globule of single polymer chain is discussed. Based on theoretical consideration, it is argued the semi‐flexible polymer chain exhibits large discrete transition on the level of individual single chains, whereas the transition looks continuous, or cooperative, on the ensemble of chains. As the experimental verification, in the present article thermodynamic and kinetic aspects of folding transition of single giant DNA molecules are described. It is shown that rich variety of nano‐ordered structures are obtained from single DNA molecules through suitable setup of the experimental conditions. The stability of such nano‐structures generated from single polymer chain is discussed in relation to the ordered compact structure with large number of chains in semi‐dilute and concentrated polymer solutions.
Polymer‐modification of an anti‐cancer drug: effects on hydrodynamic properties
Authors: Sohn Jung‐Sun , Choi Soo‐Kyung , Jo Byung‐Wook , Hess Michael , Zähres Manfred 
Published: October 2003

AbstractCoupling of a hydrophobic pharmaceutical agents with the hydrophilic poly(ethylene oxide) chain can make the drug water soluble which is necessary for some applications. The modification of the polymer chain results in a different solution behaviour of the macromolecules compared with the unmodified polymer. There are strong indications that shape and rigidity of the modified molecule differ significantly from the simple chain. Some results from measurements of the self‐diffusion coefficient and solution viscosity are discussed. The results are important for further engineering on active drug systems.
New biodegradable polymers for delivery of bioactive agents
Authors: Kwon Young Min , Kim Sung Wan 
Published: October 2003

AbstractBiodegradable, thermosensitive triblock copolymer, PLGA‐PEG‐PLGA, can be easily fabricated into drug‐loaded microspheres or injectable in situ hydrogel system for protein or water‐insoluble drugs without use of organic solvent. Aqueous‐based microsphere exhibited continuous release of intact insulin in vitro for 3 weeks while the microspheres prepared using dichloromethane showed initial burst and incomplete release. Confocal miscoscopy images of microspheres corroborated the release pattern. Next study with an injectable in situ hydrogel (ReGelTM) exhibited zero‐order insulin release in vitro and sustained plasma insulin level for 2 weeks in vivo upon single subcutaneous injection in SD rats.
The processing of starch as a thermoplastic
Authors: Stepto R.F.T. 
Published: October 2003

AbstractThe thermoplastics processing of native starch in the presence of water is a recent development with very wide possible applications. Eventually, oil‐based polymer materials have to be replaced in many applications by sustainable, inexpensive, natural materials from renewable resources. As with conventional thermoplastics, starch‐water melts may be processed by injection moulding and extrusion. The present contribution focuses on injection moulding. The bases of the processing and the thermal and molecular changes occurring are described. In addition, the rheological behaviour of the starch‐water melts during processing is analysed quantitatively to give apparent melt viscosities. The dimensional, thermal and mechanical properties of moulded thermoplastic starch polymer (TSP) materials and the products presently being produced from them are discussed.
Assessing the economic and ecological impact of plastic products
Authors: Feuerherd Karl‐Heinz 
Published: October 2003

AbstractThe framework of the International Standard Organization's (ISO) 14040 series provides the practitioner with rules to deal with different aspects of analysis and assessment of the life cycle of products. The standard emphasizes the importance of accurate data to perform a valid analysis. This premise lets LCA (life cycle assessment) studies become time‐consuming and expensive. But, sound decision‐making by management in enterprises can be done even in cases where data are incomplete or vary, when the eco‐efficiency analysis methodology is used that has been developed and applied by BASF in more than 150 projects during the last five years.
New methodology for synthesizing polyolefinic graft block copolymers and their morphological features
Authors: Kashiwa Norio , Kojoh Shin‐ichi , Kawahara Nobuo , Matsuo Shingo , Kaneko Hideyuki , Matsugi Tomoaki 
Published: October 2003

AbstractThis paper describes a new synthetic route for polyolefinic graft block copolymers by adopting coupling reaction between terminally hydroxylated polyolefins and maleic anhydride grafted polyolefins. Terminally hydroxylated polypropylene (PP‐OH) was coupled with maleic anhydride modified polyethylene (PE‐g‐MAH) and such ethylene‐propylene random copolymer (EPR‐g‐MAH) to give polyolefinic graft block copolymers (PE‐g‐PP and EPR‐g‐PP, respectively). The formation of PE‐g‐PP was confirmed by enhancement on molecular weight and it brought about distinctive decrease in size of dispersed domain in its phase separation morphology. Occurrence of coupling reaction to give EPR‐g‐PP was indicated by extreme decrease in its solubility to n‐decane and it led to unique morphology demonstrating lamella microstructure that had never been reported for a comparable polyolefin composite.
A fluorescence study on critical exponents during sol‐gel phase transition in complex monomeric systems
Authors: Kaya Demet , Pekcan Önder 
Published: October 2003

AbstractMethyl methacrylate (MMA), ethyl methacrylate (EMA) and various combinations of MMA with EMA were used during FCC experiments. Pyrene (Py) was introduced as a fluorescence probe and fluorescence lifetimes from its decay traces were measured during sol‐gel phase transitions. The fast transient fluorescence (FTRF) technique was used to study the critical exponents during sol‐gel phase transition in free‐radical crosslinking copolymerization (FCC). The results were interpreted in the view of percolation theory. The critical exponents of gel fraction, β and weight average degree of polymerization, γ were measured near the point of gel effect and found to be around 0.37 ± 0.015 and 1.69 ± 0.05 in all systems studied respectively.
Study of nucleation induced structure modification in isotactic polypropylene by DMTA and solid state NMR
Authors: Romankiewicz Anna , Jurga Jan , Sterzynski Tomasz 
Published: October 2003

AbstractIsotactic polypropylene (iPP) modified by heterogeneous nucleation and molten state drawing was investigated using the DMTA and NMR methods. The nucleation was realized by specific α and β nucleating agents, 1,3,2,4‐bis(3,4‐dimetylobenzylideno) sorbitol (Millad 3988, Miliken) leading to the creation of the α phase, and N,N′‐dicyklohexylo‐2,6‐naftaleno dikarboxy amid (NJ100) as the β phase promoter. The processing induced modification was performed by molten state drawing during an extrusion in the range between the die exit and the calibration unit. An increase of the glass transition temperature of iPP was found to be drawing independent for the β‐nucleated samples, and dependent in the case of the α‐iPP. Changes in the macromolecular mobility, depending on the α/β iPP structure and molten state drawing, was found by NMR lineshape and second moment measurements.
Kinetics of reactions of coal with polystyrene: TGA‐DSC approach
Authors: Straka P. , Náhunková J. , Brožová Z. 
Published: October 2003

AbstractKinetics of thermal reactions of coal with polystyrene by TGA and DSC methods was studied. In the range of about 350‐550°C a thermal degradation of coal proceeds, and gas, tar and coke are evolved. Simultaneously, decomposition of polystyrene occurs (360‐470°C). Unsaturated products of polystyrene decomposition are hydrogenated by coal, because coal is a strong H‐donor. Moreover, some aromatic products react with coal tar structures and new aromates are formed. The yield of tar from copyrolysis is then higher in comparison with pyrolysis of coal alone. Kinetic parameters of the process were evaluated and discussed.
Chaos and synchronization of Colpitts oscillators
Authors: Li Guo‐Hui 
Published: October 2003

AbstractIn this work we numerically investigate the nonlinear dynamics of the Colpitts oscillator. Bifurcation diagrams of consecutive plots of the values of electrical current minima are presented, according to the circuit parameters. By following observer‐based synchronization, two identical Colpitts oscillators with scalar transmitted signals are developed. Computer simulation results are given. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 446–449, 2003
Effect of device gain compression on V‐band pHEMT mixer performance
Authors: Brabetz T. , Buchanan N. B. , Fusco V. F. 
Published: October 2003

AbstractAn examination of conversion gain compression impact on mixer performance at 65 GHz demonstrates that the compression properties of upconverters are inherently worse than those of downconverters, and that narrow‐gate devices (when used in downconverters) and wide‐gate devices (when used in upconverters) yield the best conversion‐gain performance characteristics. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 468–469, 2003
New configurations of single‐ and multi‐level bandpass filters with excellent harmonic suppression
Authors: Gururajan Kala , Peddibhotla Harish , Settaluri Raghu K. 
Published: October 2003

AbstractNew configurations of high‐frequency quasi‐lumped capacitive configurations and composite structures with application to bandpass filters are presented. These structures show distinct advantages that facilitate compactness and higher harmonic suppression and have been analyzed according to suitable network models. Simple design equations have been used to synthesize new filter configurations, which exhibit excellent higher‐order harmonic suppression. The proposed new designs have been validated by measurement. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 39: 490–493, 2003
Characterization of cell‐ and region‐specific abnormalities in the epididymis of cathepsin a deficient mice
Authors: Korah Nadine , Smith Charles E. , d'Azzo Alessandra , Mui Jeannie , Hermo Louis 
Published: October 2003

AbstractCathepsin A (PPCA), a lysosomal carboxypeptidase that functions as a protective protein for α‐neuraminidase and β‐galactosidase in a multi‐enzyme complex, has been shown to be expressed in the epithelial cells of the epididymis. In the present study, the epididymis of PPCA−/− mice from 2 to 10 months of age was compared with those of their wild‐type counterparts. Major accumulations of pale vacuoles, corresponding to lysosomes, were noted in principal and narrow/apical cells in PPCA−/− mice, and clear cells also appearing highly vacuolated, were grossly enlarged in size. This was especially evident in the caput and corpus regions, where quantitative analyses confirmed that the epithelium of the tubules in these regions was expanding in profile area. In addition, the base of the epithelium in these regions was often greatly vacuolated, corresponding to cells that presented no identifiable features and appeared to be degenerating. Halo cells dispersed at various levels in the epithelium also appeared to be abnormal, accumulating pale lysosomes. Furthermore, numerous macrophages were observed in the intertubular space of the entire duct, presenting a large size and plethora of pale lysosomes. Taken together, the present data indicate major lysosomal abnormalities in the epididymis of PPCA−/− mice in a cell type and region specific manner. In addition, it is suggested that the compromised halo cells, due to PPCA deficiency within their lysosomes, cannot function properly and as a result there is a recruitment of macrophages in the intertubular space. Mol. Reprod. Dev. 66: 358–373, 2003. © 2003 Wiley‐Liss, Inc.
Cyclin A2 is phosphorylated during the G2/M transition in mouse two‐cell embryos
Authors: Ohashi Akihiro , Imai Hiroshi , Minami Naojiro 
Published: October 2003

AbstractIn the present study, we investigated the expression of cyclin A2 in mouse two‐cell embryos to elucidate the role of cyclin A2 at the G2/M transition. Two forms of cyclin A2 on SDS–PAGE (an upper and a lower band) were detected in two‐cell embryos synchronized at the M phase by nocodazole. To investigate the nature of this shift, embryos synchronized at the M phase were treated with alkaline phosphatase (AP). The upper band of cyclin A2 was fainter in AP‐treated embryos than in nontreated embryos. This result indicates that cyclin A2 in mouse two‐cell embryos is phosphorylated and the band on SDS–PAGE shifts up during the G2/M transition. In addition, we examined the sequential expression of cyclin A2 in two‐cell blocked embryos after OA treatment. The upper band of cyclin A2 was first detected at 2 hr after the treatment, corresponding to the timing of Cdc2 kinase activation. In two‐cell embryos after removal from nocodazole treatment, the phosphorylated form of cyclin A2 protein decreased abruptly just before cytokinesis. These results suggest that the mechanism of cyclin A2 degradation in mouse two‐cell embryos may be different from that in somatic cells. Mol. Reprod. Dev. 66: 343–348, 2003. © 2003 Wiley‐Liss, Inc.
Ground response curves for rock masses exhibiting strain‐softening behaviour
Authors: Alonso E. , Alejano L. R. , Varas F. , Fdez‐Manin G. , Carranza‐Torres C. 
Published: October 2003

AbstractA literature review has shown that there exist adequate techniques to obtain ground reaction curves for tunnels excavated in elastic‐brittle and perfectly plastic materials. However, for strain‐softening materials it seems that the problem has not been sufficiently analysed. In this paper, a one‐dimensional numerical solution to obtain the ground reaction curve (GRC) for circular tunnels excavated in strain‐softening materials is presented.The problem is formulated in a very general form and leads to a system of ordinary differential equations. By adequately defining a fictitious ‘time’ variable and re‐scaling some variables the problem is converted into an initial value one, which can be solved numerically by a Runge–Kutta–Fehlberg method, which is implemented in MATLAB environment.The method has been developed for various common particular behaviour models including Tresca, Mohr–Coulomb and Hoek–Brown failure criteria, in all cases with non‐associative flow rules and two‐segment piecewise linear functions related to a principal strain‐dependent plastic parameter to model the transition between peak and residual failure criteria.Some particular examples for the different failure criteria have been run, which agree well with closed‐form solutions—if existing—or with FDM‐based code results. Parametric studies and specific charts are created to highlight the influence of different parameters.The proposed methodology intends to be a wider and general numerical basis where standard and newly featured behaviour modes focusing on obtaining GRC for tunnels excavated in strain‐softening materials can be implemented. This way of solving such problems has proved to be more efficient and less time consuming than using FEM‐ or FDM‐based numerical 2D codes. Copyright © 2003 John Wiley & Sons, Ltd.
Fabric evolution of granular assembly under K0 loading/unloading
Authors: Liou Jyh‐Chau , Pan Yii‐Wen 
Published: October 2003

AbstractThis study attempted to investigate the fabric evolution in K0 loading/unloading. The work made use of a field simulator to control K0 loading/unloading in large specimens prepared by air‐pluviation. In each loading stage, wave velocities along various propagation directions were measured. On the basis of the theories of micro‐mechanics and wave propagation, the microscopic parameters of the granular assembly were back calculated to investigate the fabric evolution of granular soil during K0 loading/unloading.In this study, the Geometric fabric was modelled by fabric tensors of ranks 2 and 4. The comparison of calibrated results using ranks 2 and 4 revealed the advantage of the usage of rank‐4 fabric tensor in modelling fabric evolution in spite of its complexity.By comparing relative magnitudes of vertical and horizontal components of geometric fabric, it was demonstrated that relative constraint in lateral directions increased during K0‐unloading in order to maintain a K0 condition. It revealed that fabric evolution was responsible for a higher K0 in unloading than K0 in loading. Copyright © 2003 John Wiley & Sons, Ltd.
A model for step‐stress accelerated life testing
Authors: Dharmadhikari A.D. , Rahman Md. Monsur 
Published: October 2003

AbstractModern technology is producing high reliability products. Life testing for such products under normal use condition takes a lot of time to obtain a reasonable number of failures. In this situation a step‐stress procedure is preferred for accelerated life testing. In this paper we assume a Weibull and Lognormal model whose scale parameter depends upon the present level as well as the age at the entry in the present stress level. On the basis of that we propose a parametric model to the life distribution for step‐stress testing and suggest a suitable design to estimate the parameters involved in the model. A simulation study has been done by the proposed model based on maximum likelihood estimation. © 2003 Wiley Periodicals, Inc. Naval Research Logistics, 2003
The stochastic single resource service‐provision problem
Authors: Dye Shane , Stougie Leen , Tomasgard Asgeir 
Published: October 2003

AbstractThe service‐provision problem described in this paper comes from an application of distributed processing in telecommunications networks. The objective is to maximize a service provider's profit from offering computational‐based services to customers. The service provider has limited capacity and must choose which of a set of software applications he would like to offer. This can be done dynamically, taking into consideration that demand for the different services is uncertain. The problem is examined in the framework of stochastic integer programming. Approximations and complexity are examined for the case when demand is described by a discrete probability distribution. For the deterministic counterpart, a fully polynomial approximation scheme is known S. Dye, L. Stougie, and A. Tomasgard, Approximation algorithms and relaxations for a service provision problem on a telecommunication network, Working Paper #2‐98, Department of Industrial Economics and Technology Management, Norwegian University of Science and Technology, Trondheim, Norway, 1998, Discrete Appl Math, to appear. We show that introduction of stochasticity makes the problem strongly NP‐hard, implying that the existence of such a scheme for the stochastic problem is highly unlikely. For the general case a heuristic with a worst‐case performance ratio that increases in the number of scenarios is presented. Restricting the class of problem instances in a way that many reasonable practical problem instances satisfy allows for the derivation of a heuristic with a constant worst‐case performance ratio. Worst‐case performance analysis of approximation algorithms is classical in the field of combinatorial optimization, but in stochastic programming the authors are not aware of any previous results in this direction. © 2003 Wiley Periodicals, Inc. Naval Research Logistics, 2003
The value of information sharing in a two‐stage supply chain with production capacity constraints
Authors: Simchi‐Levi David , Zhao Yao 
Published: October 2003

AbstractWe consider a simple two‐stage supply chain with a single retailer facing i.i.d. demand and a single manufacturer with finite production capacity. We analyze the value of information sharing between the retailer and the manufacturer over a finite time horizon. In our model, the manufacturer receives demand information from the retailer even during time periods in which the retailer does not order. To analyze the impact of information sharing, we consider the following three strategies: (1) the retailer does not share demand information with the manufacturer; (2) the retailer does share demand information with the manufacturer and the manufacturer uses the optimal policy to schedule production; (3) the retailer shares demand information with the manufacturer and the manufacturer uses a greedy policy to schedule production. These strategies allow us to study the impact of information sharing on the manufacturer as a function of the production capacity, and the frequency and timing in which demand information is shared. © 2003 Wiley Periodicals, Inc. Naval Research Logistics, 2003
When to commit in a serial supply chain with forecast updating
Authors: Ferguson Mark E. 
Published: October 2003

AbstractNegotiations between an end product manufacturer and a parts supplier often revolve around two main issues: the supplier's price and the length of time the manufacturer is contractually held to its order quantity, commonly termed the “commitment time frame.” Because actual demand is unknown, the specification of the commitment time frame determines how the demand risk is shared among the members of the supply chain. Casual observation indicates that most manufacturers prefer to delay commitments as long as possible while suppliers prefer early commitments. In this paper, we investigate whether these goals are always in the firm's best interest. In particular, we find that the manufacturer may sometimes be better off with a contract that requires an early commitment to its order quantity, before the supplier commits resources and the supplier may sometimes be better off with a delayed commitment. We also find that the preferred commitment time frame depends upon which member of the supply chain has the power to set their exchange price. © 2003 Wiley Periodicals, Inc. Naval Research Logistics, 2003
A Bayesian analysis on the effect of multiple supply options in a quick response environment
Authors: Kim Hag‐Soo 
Published: October 2003

AbstractIn the apparel industry, vendors often suffer from high mismatches in supply and demand. To cope with this problem, they procure the same style product from different suppliers with different manufacturing costs. Especially in the quick response environment, which allows vendors to monitor trends in customer demand and search for available suppliers through the electronic market, they have additional opportunities to improve their decision‐making. In this paper, we propose an analytical profit maximization model and develop efficient decision tools to help both the middle and lower level managers pursuing this strategy. Furthermore, we have shown how significantly the vendors' potential competitive edge can be improved by exploiting multiple supply options, even at the expense of high premium procurement costs for late orders. The effect is critical, especially in a highly competitive market, and it has important implications for the top managers. © 2003 Wiley Periodicals, Inc. Naval Research Logistics, 2003
The modeling and numerical analysis of wrinkled membranes
Authors: Ding Hongli , Yang Bingen 
Published: October 2003

AbstractIn this paper three fundamental issues regarding modeling and analysis of wrinkled membranes are addressed. First, a new membrane model with viable Young's modulus and Poisson's ratio is proposed, which physically characterizes stress relaxation phenomena in membrane wrinkling, and expresses taut, wrinkled and slack states of a membrane in a systematic manner. Second, a parametric variational principle is developed for the new membrane model. Third, by the variational principle, the original membrane problem is converted to a non‐linear complementarity problem in mathematical programming. A parametric finite element discretization and a smoothing Newton method are then used for numerical solution. The proposed membrane model and numerical method are capable of delivering convergent results for membranes with a mixture of wrinkled and slack regions, without iteration of membrane stresses. Three numerical examples are provided. Copyright © 2003 John Wiley & Sons, Ltd.