bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dispersion copolymerization of methyl methacrylate and acrylic acid in polar media: effects of reaction parameters on the particle size and size distribution of the copolymer microspheres
Authors: Huang Jin‐Xia , Yuan Xiao‐Ya , Yu Xiang‐Lin , Zhang Hong‐Tao 
Published: April 2003

AbstractMicron‐size functional crosslinked poly(methyl methacrylate) (PMMA) particles with narrow size distribution in the range of 1∼5 µm were prepared by dispersion copolymerization in polar media with poly(N‐vinylpyrrolidone)(PVP) as steric stabilizer, 2,2′‐azobisisobutyronitrile(AIBN) as initiator and ethylene glycol dimethylacrylate (EGDMA) as crosslinking agent. The effects of functional comonomer acrylic acid (AA) concentration, contents in AIBN, EGDMA and PVP, media polarity as well as reaction temperature on the particle size and size distribution were investigated. Particle size initially increased, and then decreased with increasing AA concentration in the range of 0.7∼3.5 mol l−1, having a maximum of 5.01 µm at the concentration of 2.1 mol l−1, while size distribution became broader. This was regarded as the result of different roles of PAA in the process. Particle size increased with decreasing media polarity and stabilizer concentration, and with increasing initiator concentration and reaction temperature. The resulting particle shapes were observed by transmission electron microscopy and the presence of carboxyl groups on the surface of the particles was confirmed by Fourier‐transform infrared spectroscopy. Copyright © 2003 Society of Chemical Industry
Comparative study of the radiation‐induced grafting of styrene onto poly(tetrafluoroethylene‐co‐perfluoropropylvinyl ether) and polypropylene substrates. I: Kinetics and structural investigation
Authors: Cardona F , George GA , Hill DJT , Perera S 
Published: April 2003

AbstractA comparative study has been made of the radiation grafting of styrene onto poly(tetrafluoroethylene‐co‐perfluoropropyl vinyl ether) (PFA) and polypropylene (PP) substrates, using the simultaneous irradiation method. Effects of grafting conditions such as monomer concentrations, type of solvent, dose rate and irradiation dose on the grafting yield were investigated. Under the same grafting conditions it was found that a higher degree of grafting of styrene was obtained using a mixture of dichloromethane/methanol solvents for PFA and methanol for PP and the degree of grafting was higher in PP than in PFA at all doses. However, the micro‐Raman spectroscopy analysis of the graft revealed that, for the same degree of grafting, the penetration depth of the grafted polystyrene into the substrate was higher in PFA than in PP substrates. In both polymers the crystallinity was hardly affected by the grafting process and the degree of crystallinity decreased slightly with grafting dose. The dependence of the initial rate of grafting on the dose rate and the monomer concentration was found to be 0.6 and 1.4 order for PFA and 0.15 and 2.2 for PP, respectively. The degree of grafting increased with increasing radiation dose in both polymers. However, the grafting yield decreased with an increase in the dose rate. The increase in the overall grafting yield for PFA and PP was accompanied by a proportional increase in the penetration depth of the graft into the substrates. Copyright © 2003 Society of Chemical Industry
Log‐normal distribution for a description of the molecular weight distribution of N‐acetylated chitosans depolymerized with hydrolytic enzyme
Authors: Shin‐ya Yoshitsune , Yoshizawa Toru , Hong Kyung‐Jin , Lee Moo‐Yeal , Kajiuchi Toshio 
Published: April 2003

AbstractN‐acetylated chitosans (NACs) with different degrees of N‐acetylation (DAs) were enzymatically depolymerized at pH 5.1 and 40 °C, and the molecular weight distributions (MWDs) of the depolymerized NACs were then measured by size exclusion chromatography and were fitted by the log‐normal distribution function with two distribution parameters, β and M0. We discuss also the time‐evolution of the distribution parameters derived from the experimentally obtained MWD as well as the effects of experimental conditions, such as DA and initial NAC concentration (S0), on the distribution parameters. Copyright © 2003 Society of Chemical Industry
Syntheses and properties of polyurethanes containing side‐chain azobenzene groups
Authors: Kim Mi‐Ra , Kim Phan‐Seok , Kang Eun‐Hee , Ha Chang‐Sik , Lee Jin‐Kook 
Published: April 2003

AbstractPolymers containing azobenzene groups have the characteristic reaction of photo‐induced cis–trans isomerism. The study of new materials for optical information storage has prompted making use of these photo‐isomerizations. In this study, we report the syntheses and properties of four different polyurethanes (DR‐PUns) containing azobenzene groups in the side‐chains. The structurally similar polyurethanes (DR‐PUns) were synthesized by the polycondensation reaction of Disperse Red 19 (DR 19) and four different diisocyanates in dimethylformamide. By introducing of DR 19 into the polymer, we obtained polymers containing a photochromic group in the side‐chain. The weight‐average molecular weights of the DR‐PUns were in the range 5500–12 900. The Tgs of the DR‐PUns range from 119.5 °C to 157.0 °C, depending on the structure of the diisocyanate. Optical properties and solubilities of the polyurethanes were compared. The diffraction efficiencies of films were measured as a function of the reaction time. Typically, the diffraction efficiencies of the DR‐PU1 film prepared from toluene 2,4‐diisocyanate were observed up to a level of 0.25%. For the DR‐PU1 film, the effect of the intensity of the induced laser beam on the diffraction efficiency is also discussed.© 2003 Society of Chemical Industry
Swelling of acrylamide gels made at various onset temperatures: an optical transmission study
Authors: Pekcan Önder , Kara Selim 
Published: April 2003

AbstractOptical transmission experiments were performed using a UV–visible spectrometer during the swelling of polyacrylamide (PAAm) gels. These gels were prepared from acrylamide with N,N′‐methylenebisacrylamide at various onset temperatures (Ton) by free radical crosslinking copolymerization in water and dried before use for swelling experiments. Transmitted light intensity (Itr) from the gels increased during early stages when PAAm gels were immersed in water at room temperature and then decreased continuously as swelling time was increased. Decrease in Itr was attributed to the increase in the scattered light intensity which may originate from the contrast between ‘frozen blob clusters’ and holes in the swelling gel. Decrease in Itr was modelled using the Li–Tanaka equation from which time constants (τ1) and collective diffusion coefficients (D0) were determined for the PAAm gels prepared at different onset temperatures. τ1 and D0 were found to be dependent on Ton. The correlation between Ton and τ1 and D0 was explained in terms of the size of microgels formed during gelation.© 2003 Society of Chemical Industry
Erratum: Solution of periodic Poisson's equation and the Hartree‐Fock approach for solids with extended electron states: Application to linear augmented plane wave method, International Journal of Quantum Chemistry Volume 89, Number 2, 2002, pages 57–85
Authors: Nikolaev A.V. , Dyachkov P.N. 
Published: April 2003

AbstractThe original article to which this Erratum refers was published in Int J Quantum Chem 2002, 89, 57–85International Journal of Quantum Chemistry (2002) 89(2) 57–85
Dynamic Lie algebraic formulation of second‐order optical nonlinearity for substituted benzenes
Authors: Zhao Xian , Guan Daren , Yi Xizhang , Xu Guibao , Jiang Minhua 
Published: April 2003

AbstractA dynamic Lie algebraic (DLA) formulation is applied to the study of nonlinear optical properties of the substituted benzenes. We have described the generation of the dynamic Lie algebra for the model Hamiltonian used in the present study. In terms of these elements of the dynamic algebra we express the evolution operator as a function of the group parameters, which can be determined by means of solving a system of coupled nonlinear differential equations. Thus, in terms of the density matrix operator formalism in statistical mechanics we obtain the statistical averages of the electric polarization and then derive readily an expression for the hyperpolarizability of the paradisubstituted benzenes. Comparisons with experimental observations and other quantum calculations of the hyperpolarizabilities for the paradisubstituted benzenes are made qualitatively and quantitatively. These results imply that the DLA method appears useful in describing the nonlinear optical phenomena in the substituted benzene molecules. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem 93: 335–343, 2003
Long term depression of human nociceptive skin senses induced by thin fibre stimulation
Authors: Nilsson Hans‐Jörgen , Psouni Elia , Schouenborg Jens 
Published: April 2003

AbstractWe have recently shown that stimulation, through a multi‐electrode array, of thin nerve fibres close to the dermo‐epidermal junction in the skin, produces powerful inhibition of itch and, to a lesser degree, cutaneous pain in humans. Here, we have studied the induction time and frequency dependency (range 1–10 Hz) of the inhibitory effects of such stimulation on itch, mechanical, and thermal pain, in 20 healthy subjects. Sixteen electrodes applied on the skin were consecutively stimulated using a method termed cutaneous field stimulation (CFS). The results show that different treatment periods with CFS were required for the induction of significant inhibitory effects on different nociceptive qualities: 1st heat pain (1 min), itch (3 min), 2nd heat pain (6 min), pinch evoked pain (8 min). Six to ten minutes stimulation sufficed to induce peak inhibitory effects on all these sensory qualities while longer stimulation (up to 40 min) did not cause significantly stronger inhibition. The effects on itch, 1st and 2nd heat pain lasted over 55 min after termination of CFS. There was no effect on prickle. No significant difference in inhibitory effects of different stimulation frequencies (1, 4 and 10 Hz/electrode) was found. The induction time and effective stimulation frequencies may suggest that the underlying mechanisms are similar to those of long term depression (LTD) previously described in the spinal cord in animal experiments.
SamCluster: an integrated scheme for automatic discovery of
sample classes using gene expression profile
Authors: Li Wuju , Fan Ming , Xiong Momiao 
Published: April 2003

Abstract
Motivation: Feature (gene) selection can dramatically improve the accuracy of gene expression profile based sample class prediction. Many statistical methods for feature (gene) selection such as stepwise optimization and Monte Carlo simulation have been developed for tissue sample classification. In contrast to class prediction, few statistical and computational methods for feature selection have been applied to clustering algorithms for pattern discovery.
Results: An integrated scheme and corresponding program SamCluster for automatic discovery of sample classes based on gene expression profile is presented in this report. The scheme incorporates the feature selection algorithms based on the calculation of CV (coefficient of variation) and t-test into hierarchical clustering and proceeds as follows. At first, the genes with their CV greater than the pre-specified threshold are selected for cluster analysis, which results in two putative sample classes. Then, significantly differentially expressed genes in the two putative sample classes with p-values ≤ 0.01, 0.05, or 0.1 from t-test are selected for further cluster analysis. The above processes were iterated until the two stable sample classes were found. Finally, the consensus sample classes are constructed from the putative classes that are derived from the different CV thresholds, and the best putative sample classes that have the minimum distance between the consensus classes and the putative classes are identified. To evaluate the performance of the feature selection for cluster analysis, the proposed scheme was applied to four expression datasets COLON, LEUKEMIA72, LEUKEMIA38, and OVARIAN. The results show that there are only 5, 1, 0, and 0 samples that have been misclassified, respectively. We conclude that the proposed scheme, SamCluster, is an efficient method for discovery of sample classes using gene expression profile.
Availability: The related program SamCluster is available upon request or from the web page http://www.sph.uth.tmc.edu:8052/hgc/Downloads.asp
Contact: wujuli@yahoo.com
* To whom correspondence should be addressed.
Role of Murine Cytomegalovirus US22 Gene Family Members in Replication in Macrophages
Authors: Ménard Carine , Wagner Markus , Ruzsics Zsolt , Holak Karina , Brune Wolfram , Campbell Ann E. , Koszinowski Ulrich H. 
Published: April 2003

ABSTRACT
The large cytomegalovirus (CMV) US22 gene family, found in all betaherpesviruses, comprises 12 members in both human cytomegalovirus (HCMV) and murine cytomegalovirus (MCMV). Conserved sequence motifs suggested a common ancestry and related functions for these gene products. Two members of this family, m140 and m141, were recently shown to affect MCMV replication on macrophages. To test the role of all US22 members in cell tropism, we analyzed the growth properties in different cell types of MCMV mutants carrying transposon insertions in all 12 US22 gene family members. When necessary, additional targeted mutants with gene deletions, ATG deletions, and ectopic gene revertants were constructed. Mutants with disruption of genes M23, M24, m25.1, m25.2, and m128 (ie2) showed no obvious growth phenotype, whereas growth of M43 mutants was reduced in a number of cell lines. Genes m142 and m143 were shown to be essential for virus replication. Growth of mutants with insertions into genes M36, m139, m140, and m141 in macrophages was severely affected. The common phenotype of the m139, m140, and m141 mutants was explained by an interaction at the protein level. The M36-dependent macrophage growth phenotype could be explained by the antiapoptotic function of the gene that was required for growth on macrophages but not for growth on other cell types. Together, the comprehensive set of mutants of the US22 gene family suggests that individual family members have diverged through evolution to serve a variety of functions for the virus.
Intranasal Vaccination Using Interleukin-12 and Cholera Toxin Subunit B as Adjuvants To Enhance Mucosal and Systemic Immunity to Human Immunodeficiency Virus Type 1 Glycoproteins
Authors: Albu Diana I. , Jones-Trower Agnes , Woron Amy M. , Stellrecht Kathleen , Broder Christopher C. , Metzger Dennis W. 
Published: April 2003

ABSTRACTWe have investigated the induction of protective mucosal immunity to human immunodeficiency virus type 1 (HIV-1) isolate 89.6 by intranasal (i.n.) immunization of mice with gp120 and gp140 together with interleukin-12 (IL-12) and cholera toxin subunit B (CTB) as adjuvants. It was found that both IL-12 and CTB were required to elicit mucosal antibody responses and that i.n. immunization resulted in increased total, immunoglobulin G1 (IgG1), and IgG2a anti-HIV-1 antibody levels in serum; increased total, IgG1, IgG2a, and IgA antibody expression in bronchoalveolar lavage fluids; and increased IgA antibody levels in vaginal washes. Levels of anti-HIV-1 antibodies in both sera and secretions were higher in groups immunized with gp140 than in those immunized with gp120. However, only gp120-specific mucosal antibodies demonstrated neutralizing activity against HIV-1 89.6. Taken together, the results show that IL-12 and CTB act synergistically to enhance both systemic and local mucosal antibody responses to HIV-1 glycoproteins and that even though gp140 induces higher antibody titers than gp120, only gp120-specific mucosal antibodies interfere with virus infectivity.
L-Particle Production during Primary Replication of Pseudorabies Virus in the Nasal Mucosa of Swine
Authors: Alemañ Nuria , Quiroga María Isabel , López-Peña Mónica , Vázquez Sonia , Guerrero Florentina H. , Nieto José M. 
Published: April 2003

ABSTRACT
Different tissue culture cell lines infected with a number of alphaherpesviruses produce, in addition to virions, light particles (L particles). L particles are composed of the envelope and tegument components of the virion but totally lack the proteins of the capsid and the virus genome; therefore, they are noninfectious. In this electron microscopy report, we show that L particles are produced during primary replication of the alphaherpesvirus pseudorabies virus (PRV) in the nasal mucosa of experimentally infected swine, its natural host. Although PRV infected different types of cells of the respiratory and olfactory mucosae, PRV L particles were found to be produced exclusively by epithelial cells and fibroblasts. We observed that formation of noninfectious particles occurred by budding of condensed tegument at the inner nuclear membrane and at membranes of cytoplasmic vesicles, resulting in intracisternal and intravesicular L particles, respectively. Both forms of capsidless particles were clearly distinguishable by the presence of prominent surface projections on the envelope and the higher electron density of the tegument, morphological features which were only observed in intravesicular L particles. Moreover, intravesicular but not intracisternal L particles were found to be released by exocytosis and were also identified extracellularly. Comparative analysis between PRV virion and L-particle morphogenesis indicates that both types of virus particles share a common intracellular pathway of assembly and egress but that they show different production patterns during the replication cycle of PRV.
A Novel Genetic Pathway of Human Immunodeficiency Virus Type 1 Resistance to Stavudine Mediated by the K65R Mutation
Authors: García-Lerma J. Gerardo , MacInnes Hamish , Bennett Diane , Reid Patrick , Nidtha Soumya , Weinstock Hillard , Kaplan Jonathan E. , Heneine Walid 
Published: April 2003

ABSTRACTStavudine (d4T) and zidovudine (AZT) are thymidine analogs widely used in the treatment of human immunodeficiency virus type 1 (HIV-1)-infected persons. Resistance to d4T is not fully understood, although the selection of AZT resistance mutations in patients treated with d4T suggests that both drugs have similar pathways of resistance. Through the analysis of genotypic changes in nine recombinant viruses cultured with d4T, we identified a new pathway for d4T resistance mediated by K65R, a mutation not selected by AZT. Passaged viruses were derived from treatment-naïve persons or HIV-1HXB2and had wild-type reverse transcriptase (RT) or T215C/D mutations. K65R was selected in seven viruses and was associated with a high level of enzymatic resistance to d4T-triphosphate (median, 16-fold; range, 5- to 48-fold). The role of K65R in d4T resistance was confirmed in site-directed mutants generated in three different RT backgrounds. Phenotypic assays based on recombinant single-cycle replication or a whole-virus multiple replication cycle were unable to detect d4T resistance in d4T-selected mutants with K65R but detected cross-resistance to other nucleoside RT inhibitors. Four of the six viruses that had 215C/D mutations at baseline acquired the 215Y mutation alone or in association with K65R. Mutants having K65R and T215Y replicated less efficiently than viruses that had T215Y only, suggesting that selection of T215Y in patients treated with d4T may be favored. Our results demonstrate that K65R plays a role in d4T resistance and indicate that resistance pathways for d4T and AZT may not be identical. Biochemical analysis and improved replication assays are both required for a full phenotypic characterization of resistance to d4T. These findings highlight the complexity of the genetic pathways of d4T resistance and its phenotypic expression.
In Vitro and In Ovo Expression of Chicken Gamma Interferon by a Defective RNA of Avian Coronavirus Infectious Bronchitis Virus
Authors: Hackney Karen , Cavanagh Dave , Kaiser Pete , Britton Paul 
Published: April 2003

ABSTRACT
Coronavirus defective RNAs (D-RNAs) have been used for site-directed mutagenesis of coronavirus genomes and for expression of heterologous genes. D-RNA CD-61 derived from the avian coronavirus infectious bronchitis virus (IBV) was used as an RNA vector for the expression of chicken gamma interferon (chIFN-γ). D-RNAs expressing chIFN-γ were shown to be capable of rescue, replication, and packaging into virions in a helper virus-dependent system following electroporation of in vitro-derived T7 RNA transcripts into IBV-infected cells. Secreted chIFN-γ, under the control of an IBV transcription-associated sequence derived from gene 5 of the Beaudette strain, was expressed from two different positions within CD-61 and shown to be biologically active. In addition, following infection of 10-day-old chicken embryos with IBV containing D-RNAs expressing chIFN-γ, the allantoic fluid was shown to contain biologically active chIFN-γ, demonstrating that IBV D-RNAs can express heterologous genes in vivo.
Disruption of Gammaherpesvirus 68 Gene 50 Demonstrates that Rta Is Essential for Virus Replication
Authors: Pavlova Iglika V. , Virgin Herbert W. , Speck Samuel H. 
Published: April 2003

ABSTRACT

Gammaherpesvirus pathogenesis is dependent on the ability of these viruses to establish a lifelong latent infection and the ability to reactivate from latency. Immediate-early genes of theses viruses are thought to be critical regulators of lytic replication and reactivation from latency. The gene 50-encoded Rta is the only immediate-early gene product that appears to be conserved among all characterized gammaherpesviruses. Previous studies have demonstrated that, in Epstein-Barr virus (EBV), Kaposi's sarcoma-associated virus, and gammaherpesvirus 68 (γHV68, also referred to as murine gammaherpesvirus 68), ectopic expression of Rta in latently infected cell lines can lead to induction of the viral cycle. Recently, studies employing null mutants of EBV have provided a formal demonstration that both Rta and the BZLF1 gene product, Zta, the two EBV immediate-early gene products, are essential for EBV replication. Here we generate and characterize a gene 50-null mutant γHV68 and demonstrate that the gene 50 product Rta is essential for virus replication. Providing γHV68 Rta in
trans
was sufficient to restore replication of the gene 50-null virus. Notably, Rta expressed from the spliced form of the gene 50 transcript was sufficient to complement growth of the gene 50-null virus. In addition, we provide evidence that loss of Rta expression leads to a complete defect in viral DNA replication and a significant defect in late antigen expression. This work lays the foundation for characterizing the role of Rta in γHV68 chronic infection of mice.