bluuebunny/crossref_metadata_2025_split huggingface dataset:
Free Radical Bulk Polymerization of Styrene: Simulation of Molecular Weight Distributions to High Conversion Using Experimentally Obtained Rate Coefficients
Authors: Zetterlund Per B. , Yamazoe Hirotomo , Yamada Bunichiro 
Published: July 2003

AbstractPreviously obtained experimental conversion‐dependences of the propagation rate coefficient (kp), the termination rate coefficient (kt) and the initiator efficiency (f) for the free‐radical bulk polymerization of styrene at 70 °C have been used to simulate the full molecular weight distributions (MWD) to high conversion using the software package PREDICI, providing a robust test of the kinetic model adopted. Satisfactory agreement with the experimental MWD's (GPC) was obtained up to approximately 70% conversion. Beyond 70% conversion, the high MW shoulder that appears was correctly predicted, although the amount of such polymer was somewhat underestimated. This discrepancy is believed to probably have its origin in experimental error in the conversion‐dependences of kp, kt and f, in particular kt, that were employed in the simulations, rather than indicate a more fundamental short‐coming of the model employed.image
Simulation of Molecular Weight Distributions Obtained by Pulsed Laser Polymerization (PLP): New Analytical Expressions Including Intramolecular Chain Transfer to the Polymer
Authors: Nikitin Anatoly N. , Castignolles Patrice , Charleux Bernadette , Vairon Jean‐Pierre 
Published: July 2003

AbstractA new approach for the simulation of PLP (pulsed laser polymerization) is presented. This approach allows one to obtain new analytical solutions for different polymerization schemes, including either chain transfer to the monomer or intramolecular chain transfer to the polymer. The first results of the simulation of PLP experiments on n‐butyl acrylate at 20 °C and ambient pressure are presented.MWDs simulated for PLP of n‐butyl acrylate, in bulk at 20 °C and ambient pressure using three models: the model with intramolecular chain transfer to the polymer (solid line), the model with chain transfer to monomer (dashed line), and the classical model (dotted line).imageMWDs simulated for PLP of n‐butyl acrylate, in bulk at 20 °C and ambient pressure using three models: the model with intramolecular chain transfer to the polymer (solid line), the model with chain transfer to monomer (dashed line), and the classical model (dotted line).
Ets protein Elf‐1 bidirectionally suppresses transcriptional activities of the tumor suppressor Tsc2 gene and the repair‐related Nth1 gene
Authors: Honda Satoshi , Kobayashi Toshiyuki , Kajino Kazunori , Urakami Shinji , Igawa Mikio , Hino Okio 
Published: July 2003

AbstractAlterations in the rat tuberous sclerosis gene (Tsc2) cause renal cell carcinomas (RCCs) with complete penetrance. In this study, it was shown that the minimal core promoters of the rat Tsc2 and endonuclease III 1 (Nth1) genes, lying in a 5′‐to‐5′ arrangement, were localized in a 0.11‐kb region containing two Ets binding sites (EBSs). This region worked as a bidirectional promoter in a single reporter plasmid. Mutational inactivation of each of the two EBSs significantly reduced promoter activity. Moreover, gel shift assays revealed the presence of specific EBSs‐protein complexes. These results demonstrate that some members of the Ets family positively regulate the promoter activities of the Tsc2/Nth1 genes by binding to the EBSs. We identified Elf‐1 as a binding factor for EBSs through super‐shift assays, and detected ∼35 kDa bands with an EBSs‐containing DNA probe by Southwestern blot analysis. Forced expression of Elf‐1 in cells, however, bidirectionally suppressed the activities of the Tsc2/Nth1 promoters. Elf‐1 may be a negative regulator of Tsc2/Nth1 gene expression and may compete against positive regulators for binding to the EBSs. Our observations suggest that mechanisms that inactivate Tsc2 gene expression, such as promoter suppression, may exist. © 2003 Wiley‐Liss, Inc.
Prostate‐specific antitumor activity by probasin promoter‐directed p202 expression
Authors: Wen Yong , Giri Dipak , Yan Duen‐Hwa , Spohn Bill , Zinner Ralph G. , Xia Weiya , Thompson Timothy C. , Matusik Robert J. , Hung Mien‐Chie 
Published: July 2003

Abstractp202, an interferon (IFN) inducible protein, arrests cell cycle at G1 phase leading to cell growth retardation. We previously showed that ectopic expression of p202 in human prostate cancer cells renders growth inhibition and suppression of transformation phenotype in vitro. In this report, we showed that prostate cancer cells with stable expression of p202 were less tumorigenic than the parental cells. The antitumor activity of p202 was further demonstrated by an ex vivo treatment of prostate cancer cells with p202 expression vector that showed significant tumor suppression in mouse xenograft model. Importantly, to achieve a prostate‐specific antitumor effect by p202, we employed a prostate‐specific probasin (ARR2PB) gene promoter to direct p202 expression (ARR2PB‐p202) in an androgen receptor (AR)–positive manner. The ARR2PB‐p202/liposome complex was systemically administered into mice bearing orthotopic AR‐positive prostate tumors. We showed that parenteral administration of an ARR2PB‐p202/liposome preparation led to prostate‐specific p202 expression and tumor suppression in orthotopic prostate cancer xenograft model. Furthermore, with DNA array technique, we showed that the expression of p202 was accompanied by downregulation of G2/M phase cell‐cycle regulators, cyclin B, and p55cdc. Together, our results suggest that p202 suppresses prostate tumor growth, and that a prostate‐specific antitumor effect can be achieved by systemic administration of liposome‐mediated delivery of ARR2PB‐p202. © 2003 Wiley‐Liss, Inc.
The facility location problem with general cost functions
Authors: Hajiaghayi M. T. , Mahdian M. , Mirrokni V. S. 
Published: July 2003

AbstractIn this paper, we introduce a generalized version of the facility location problem in which the facility cost is a function of the number of clients assigned to the facility. We focus on the case of concave facility cost functions. We observe that this problem can be reduced to the uncapacitated facility location problem. We analyze a natural greedy algorithm for this problem and show that its approximation factor is at most 1.861. We also consider several generalizations and variants of this problem. © 2003 Wiley Periodicals, Inc.
Solving the p‐Center problem with Tabu Search and Variable Neighborhood Search
Authors: Mladenović Nenad , Labbé Martine , Hansen Pierre 
Published: July 2003

AbstractThe p‐Center problem consists of locating p facilities and assigning clients to them in order to minimize the maximum distance between a client and the facility to which he or she is allocated. In this paper, we present a basic Variable Neighborhood Search and two Tabu Search heuristics for the p‐Center problem without the triangle inequality. Both proposed methods use the 1‐interchange (or vertex substitution) neighborhood structure. We show how this neighborhood can be used even more efficiently than for solving the p‐Median problem. Multistart 1‐interchange, Variable Neighborhood Search, Tabu Search, and a few early heuristics are compared on small‐ and large‐scale test problems from the literature. © 2003 Wiley Periodicals, Inc.
Brain aromatase, 5α‐reductase, and 5β‐reductase change seasonally in wild male song sparrows: Relationship to aggressive and sexual behavior
Authors: Soma Kiran K. , Schlinger Barney A. , Wingfield John C. , Saldanha Colin J. 
Published: July 2003

AbstractIn many species, territoriality is expressed only during the breeding season, when plasma testosterone (T) is elevated. In contrast, in song sparrows (Melospiza melodia morphna), males are highly territorial during the breeding (spring) and nonbreeding (autumn) seasons, but not during molt (late summer). In autumn, plasma sex steroids are basal, and castration has no effect on aggression. However, inhibition of aromatase reduces nonbreeding aggression, suggesting that neural steroid metabolism may regulate aggressive behavior. In wild male song sparrows, we examined the neural distribution of aromatase mRNA and seasonal changes in the activities of aromatase, 5α‐, and 5β‐reductase, enzymes that convert T to 17β‐estradiol, 5α‐dihydrotestosterone (5α‐DHT, a potent androgen), or 5β‐DHT (an inactive metabolite), respectively. Enzyme activities were measured in the diencephalon, ventromedial telencephalon (vmTEL, which includes avian amygdala), caudomedial neostriatum (NCM), and the hippocampus of birds captured during spring, molt, or autumn. Aromatase and 5β‐reductase changed seasonally in a region‐specific manner. Aromatase in the diencephalon was higher in spring than in molt and autumn, similar to seasonal changes in male sexual behavior. Aromatase activity in the vmTEL was high in both spring and autumn but significantly reduced at molt, similar to seasonal changes in aggression. 5β‐Reductase was not elevated during molt, suggesting that low aggression during molt is not a result of increased inactivation of androgens. These data highlight the relevance of neural steroid metabolism to the expression of natural behaviors by free‐living animals. © 2003 Wiley Periodicals, Inc. J Neurobiol 56: 209–221, 2003
PTPμ‐dependent growth cone rearrangement is regulated by Cdc42
Authors: Rosdahl Jullia A. , Ensslen Sonya E. , Niedenthal Jared A. , Brady‐Kalnay Susann M. 
Published: July 2003

AbstractPTPμ is expressed in the developing nervous system and promotes growth and guidance of chick retinal ganglion cells. Using a newly developed growth cone rearrangement assay, we examined whether the small G‐proteins were involved in PTPμ‐dependent signaling. The stimulation of retinal cultures with purified PTPμ resulted in a striking morphological change in the growth cone, which becomes dominated by filopodia within 5 min of addition. This rearrangement in response to PTPμ stimulation was mediated by homophilic binding. We perturbed GTPase signaling using Toxin B, which inhibits Cdc42, Rac, and Rho, as well as the toxin Exoenzyme C3 that inhibits Rho. The PTPμ‐induced growth cone rearrangement was blocked by Toxin B, but not by Exoenzyme C3. This result suggests that either Cdc42 or Rac are required but not Rho. To determine which GTPase was involved in PTPμ signaling, we utilized dominant‐negative mutants of Cdc42 and Rac. Dominant‐negative Cdc42 blocked PTPμ‐induced rearrangement, while wild‐type Cdc42 and dominant‐negative Rac did not. Together, these results suggest a molecular signaling cascade beginning with PTPμ homophilic binding at the plasma membrane and the activation of Cdc42, which acts on the actin cytoskeleton to result in rearrangement of the growth cone. © 2003 Wiley Periodicals, Inc. J Neurobiol 56:199–208, 2003
Androgen receptor expression in the developing male and female rat visual and prefrontal cortex
Authors: Nuñez J.L. , Huppenbauer C.B. , McAbee M.D. , Juraska J.M. , DonCarlos L.L. 
Published: July 2003

AbstractGonadal steroid hormones are known to influence the development of the cerebral cortex of mammals. Steroid hormone action involves hormone binding to cytoplasmic or nuclear receptors, followed by DNA binding and gene transcription. The goals of the present study were twofold: to determine whether androgen receptors are present during development in two known androgen sensitive regions of the rat cerebral cortex, the primary visual cortex (Oc1) and the anterior cingulate/frontal cortex (Cg1/Fr2); and to determine whether androgen receptor (AR) expression in these regions differs between developing males and females. We used immunocytochemistry to detect AR protein on postnatal days 0, 4, and 10, and in situ hybridization to detect AR mRNA on postnatal day 10 in male and female rats. The level of AR expression was specific to the cortical region, with higher AR immunoreactive cell density and more AR mRNA in Oc1 than in Cg1/Fr2. AR immunoreactive cell density increased with age in both regions. Finally, on postnatal day 10, males had a higher AR immunoreactive cell density and more AR mRNA in Oc1 than did females. Thus, the presence of ARs may allow androgens to directly influence the development the cerebral cortex. © 2003 Wiley Periodicals, Inc. J Neurobiol 56: 293–302, 2003
Control of flexor motoneuron activity during single leg walking of the stick insect on an electronically controlled treadwheel
Authors: Peter Gabriel Jens , Scharstein Hans , Schmidt Joachim , Büschges Ansgar 
Published: July 2003

AbstractIn the present study, motoneurons innervating the flexor tibiae muscle of the stick insect (Cuniculina impigra) middle leg were recorded intracellularly while the single leg performed walking‐like movements on a treadwheel. Different levels of belt friction (equivalent to a change in load) were used to study the control of activity of flexor motoneurons. During slow leg movements no fast motoneurons were active, but a recruitment of these neurons could be observed during faster leg movements. The firing rate of slow and fast motoneurons increased with incremented belt friction. Also, the force applied to the treadwheel at different frictional levels was adapted closely to the friction of the treadwheel to be overcome. The motoneurons innervating the flexor tibiae were recruited progressively during the stance phase, with the slow motoneurons being active earlier than the fast (half‐maximal spike frequency after 10–15% and 50–60% of the stance phase, respectively). The resting membrane potential was more hyperpolarized in fast motoneurons (64.6 ± 6.5 mV) than in slow motoneurons (−52.9 ± 5.4 mV). However, the threshold for the initiation of action potentials was not statistically significantly different in both types of flexor motoneurons. Therefore, action potentials were generated in fast motoneurons after a longer period of depolarization and thus later during the stance phase than in slow motoneurons. We show that motoneurons of the flexor tibiae receive substantial common excitatory inputs during the stance phase and that the difference in resting membrane potential between slow and fast motoneurons is likely to play a crucial role in their consecutive recruitment. © 2003 Wiley Periodicals, Inc. J Neurobiol 56: 237–251, 2003
Direct injection of venom by a predatory wasp into cockroach brain
Authors: Haspel Gal , Rosenberg Lior Ann , Libersat Frederic 
Published: July 2003

AbstractIn this article, we provide direct evidence for injection of venom by a wasp into the central nervous system of its cockroach prey. Venomous predators use neurotoxins that generally act at the neuromuscular junction, resulting in different types of prey paralysis. The sting of the parasitoid wasp Ampulex compressa is unusual, as it induces grooming behavior, followed by a long‐term lethargic state of its insect prey, thus ultimately providing a living meal for the newborn wasp larvae. These behavioral modifications are induced only when a sting is inflicted into the head. These unique effects of the wasp venom on prey behavior suggest that the venom targets the insect's central nervous system. The mechanism by which behavior modifying compounds in the venom transverse the blood‐brain barrier to induce these central and long‐lasting effects has been the subject of debate. In this article, we demonstrate that the wasp stings directly into the target ganglia in the head of its prey. To prove this assertion, we produced “hot” wasps by injecting them with 14C radiolabeled amino acids and used a combination of liquid scintillation and light microscopy autoradiography to trace radiolabeled venom in the prey. To our knowledge, this is the first direct evidence documenting targeted delivery of venom by a predator into the brain of its prey. © 2003 Wiley Periodicals, Inc. J Neurobiol 56: 287‐292, 2003
Protein synthesis at synapse versus cell body: Enhanced but transient expression of long‐term facilitation at isolated synapses
Authors: Liu Ke , Hu Jiang‐Yuan , Wang Denong , Schacher Samuel 
Published: July 2003

AbstractProtein synthesis at synaptic terminals contributes to LTP in hippocampus and to the formation of new synaptic connections by sensory neurons (SNs) of Aplysia. Here we report that after removal of the SN cell body, isolated SN synapses of Aplysia in culture express protein‐synthesis dependent long‐term facilitation (LTF) produced by 5‐HT that decays rapidly. Changes in expression of a SN‐specific neuropeptide sensorin in isolated SN varicosities parallel the changes in synaptic efficacy. At 24 h after 5‐HT the magnitude of LTF produced at isolated SN synapses was significantly greater than that produced when SN cell bodies were present. LTF was maintained at 48 h at connections with SN cell bodies, but not at isolated SN synapses. The increase in synaptic efficacy at isolated SN synapses at 24 h was blocked by the protein synthesis inhibitor anisomycin. LTF was accompanied by changes in expression of sensorin. The increase in sensorin level at isolated SN varicosities with 5‐HT was blocked by anisomycin or was reversed 48 h after 5‐HT treatment alone. The results suggest that, as is the case for initial synapse formation between SNs and L7, changes in protein synthesis at synaptic terminals may contribute directly to LTF of stable synapses. Changes in expression within the cell body provide additional contributions for long‐term maintenance of the new level of synaptic efficacy that was initiated directly by local changes in protein synthesis at or near synaptic terminals. © 2003 Wiley Periodicals, Inc. J Neurobiol 56: 275–286, 2003
Research methods: Managing primary study quality in meta‐analyses
Authors: Conn Vicki S. , Rantz Marilyn J. 
Published: July 2003

AbstractMeta‐analyses synthesize multiple primary studies and identify patterns of relationships. Differences in primary study methodological quality must be addressed for meta‐analysis to produce meaningful results. No single standard exists for addressing these quality variations. Quality measurement scales are fraught with development and application problems. Several strategies have been proposed to address quality. Researchers can set minimum levels for inclusion or require that certain quality attributes be present. An inclusive method is to weight effect sizes by quality scores. This allows the inclusion of diverse studies but relies on questionable quality measures. By considering quality an empirical question, meta‐analysts can examine associations between quality and effect sizes and thus preserve the purpose of meta‐analysis to systematically examine data. Researchers increasingly are combining strategies to overcome the limitations of using a single approach. Future work to develop valid measures of primary study quality dimensions will improve the ability of meta‐analysis to inform research and nursing practice. © 2003 Wiley Periodicals, Inc. Res Nurs Health 26:322–333, 2003
Synthesis and characterization of polyurethane/polybenzoxazine‐based interpenetrating polymer networks (IPNs)
Authors: Cui Yanjun , Chen Ye , Wang Xinling , Tian Guohua , Tang Xiaozhen 
Published: July 2003

AbstractSequential interpenetrating polymer networks (IPNs), based on polyurethane and polybenzoxazine, were synthesized. Fourier Transform infrared spectrometry was employed to monitor the formation kinetics, which indicated that only physical bonding existed in the resulting IPNs. Morphological investigations revealed a lightly phase separation behaviour in all of the IPNs studied.© 2003 Society of Chemical Industry
Study of impact properties and morphology of 4,4′‐diaminodiphenyl methane cured epoxy resin toughened with acrylate‐based liquid rubbers
Authors: Kar S , Gupta D , Banthia AK , Ratna D 
Published: July 2003

AbstractRandomized carboxyl poly(2‐ethylhexyl acrylate) (A‐1) and randomized epoxy poly(2‐ethylhexyl acrylate) (B‐1) rubbers were synthesized in the form of liquid rubber by a solution polymerization technique. The liquid rubbers A‐1 and B‐1 were characterized by 1H NMR and IR spectroscopic analysis, non‐aqueous titration, viscosity measurements and gel permeation chromatography. The liquid rubbers A‐1 (M̄n = 3900 g mol−1), B‐1 (M̄n = 4100 g mol−1) and a (1:1) mixture of A‐1 and B‐1 were pre‐reacted with epoxy resin separately and the modified epoxy networks were made by curing with high temperature curing agent. The modified epoxy networks were evaluated by unnotched Izod impact testing. The morphology and toughening behaviour were analysed by scanning electron microscopy. Optimum properties were obtained with the mixture of A‐1 and B‐1. Copyright © 2003 Society of Chemical Industry
Spin probe study of semi‐interpenetrating polymer networks based on polyurethane and polymethacrylate functional prepolymers
Authors: Čulin Jelena , Veksli Zorica , Anžlovar Alojz , Žigon Majda 
Published: July 2003

AbstractThe motional transition and heterogeneity of semi‐interpenetrating networks (SIPNs) based on polyurethane (PU) with carboxylic groups and methacrylic copolymer (PM) with tertiary amine groups were studied by the electron spin resonance (ESR) spin probe method. The concentration of functional groups in both prepolymers varied from 0 to 0.45 mmol g−1. Spin‐probed SIPNs show that the temperature‐dependent spectra are sensitive to polymer interactions imposed by functional groups. These interactions determine the free volume distribution in the matrix and temperature at which motional transition takes place. The fraction of free volume increases with functional group concentration and reaches its maximum at 0.25 mmol g−1. Further increases in the functional group concentration reduce the free volume. The results of the networks with strong interactions are discussed in terms of the interference of the plasticizing effect of the PU component and the formation of possible cluster cross‐links, which restricts segmental motions. Copyright © 2003 Society of Chemical Industry
Intumescence in poly(butylene terephthalate): the effect of 2‐methyl‐1,2‐oxaphospholan‐5‐one 2‐oxide and ammonium polyphosphate
Authors: Balabanovich Alexander I , Balabanovich Ala M , Engelmann Jochen 
Published: July 2003

AbstractThe flame‐retardant effect of 2‐methyl‐1,2‐oxaphospholan‐5‐one 2‐oxide (OP) and ammonium polyphosphate (APP) in poly(butylene terephthalate) (PBT) was studied by the limiting oxygen index and the UL94 test. A self‐extinguishing formulation (V‐0 rating) was achieved by the addition of 15 wt% APP and 10 wt% OP. The fire‐retardant effect was attributed to the condensed‐phase mechanism of intumescence. Mechanistic studies were performed using thermogravimetry, IR characterization of solid residues and GC–MS characterization of the gaseous and high‐boiling products. OP–APP was shown to cause ammonolysis of PBT, formation of aromatic nitriles in the high‐boiling products and phosphorus ester groups and polyphosphoric acid–phosphorus pentaoxide in the solid residue. Copyright © 2003 Society of Chemical Industry
Synthesis and characterization of a fully aromatic polyazomethine with rotaxane architecture
Authors: Farcas Aurica , Grigoras Mircea 
Published: July 2003

AbstractThis paper reports the preparation and characterization of a new aromatic polyazomethine with rotaxane architecture. The complex of β‐cyclodextrin and 1,4‐phenylenediamine was treated with N‐n‐butyl‐3,6‐diformylcarbazole, which is large enough to prevent dethreading. The polycondensation reaction was performed in N,N‐dimethylformamide leading to polyazomethine soluble in polar solvents. Measurements made by gel permeation chromatography of the dimethylformamide‐soluble (DMF) soluble polyazomethine show the presence of high molecular weight material. The structure and thermal properties of the resulting polymer were characterized by IR, 1H NMR, TGA and DSC techniques. Copyright © 2003 Society of Chemical Industry