bluuebunny/crossref_metadata_2025_split huggingface dataset:
Patterns of Sequence Divergence in 5′ Intergenic Spacers and Linked Coding Regions in 10 Species of Pathogenic Bacteria Reveal Distinct Recombinational Histories
Authors: Hughes Austin L , Friedman Robert 
Published: December 2004

Abstract
We compared the pattern of nucleotide difference in 8034 genes and in their 5′ intergenic spacers between conspecific pairs of genomes from 10 species of pathogenic bacteria. Certain genes or spacers showed much greater sequence divergence between the genotypes compared to others; such divergent regions plausibly originated by recombinational events by which a gene and/or spacers was donated from a divergent genome. Different patterns of divergence in genes and spacers identified different recombinational patterns. For example, in Chlamydophila pneumoniae, there were examples of both unusually divergent spacers and unusually divergent genes, but there were no cases in which a gene and its spacer were both unusually divergent. This pattern suggests that, in C. pneumoniae, recombination events have broken up the linkage between genes and 5′ spacers. By contrast, in Streptococcus agalactiae, there were a number of cases in which both spacer and gene were unusually divergent, indicating that a number of large-scale recombination events that included both genes and 5′ spacers have occurred; there was evidence of at least two large-scale recombination events in the genomic region including the pur genes in S. agalactiae.
Does Chromosome Size Affect Map Distance and Genetic Interference in Budding Yeast?
Authors: Turney Dana , de los Santos Teresa , Hollingsworth Nancy M 
Published: December 2004

Abstract
The hypothesis that chromosome size affects the rate and distribution of meiotic crossovers in budding yeast was tested. Map distance and interference were measured in the same genetic intervals present on either small (340 and 508 kb) or large (917 and 1085 kb) chromosomes, respectively. No differences were observed.
Spontaneous Mutations in Diploid Saccharomyces cerevisiae
Authors: Joseph Sarah B , Hall David W 
Published: December 2004

Abstract
We performed a 1012-generation mutation-accumulation (MA) experiment in the yeast, Saccharomyces cerevisiae. The MA lines exhibited a significant reduction in mean fitness and a significant increase in variance in fitness. We found that 5.75% of the fitness-altering mutations accumulated were beneficial. This finding contradicts the widely held belief that nearly all fitness-altering mutations are deleterious. The mutation rate was estimated as 6.3 × 10−5 mutations per haploid genome per generation and the average heterozygous fitness effect of a mutation as 0.061. These estimates are compatible with previous estimates in yeast.
End-Joining Repair of Double-Strand Breaks in Drosophila melanogaster Is Largely DNA Ligase IV Independent
Authors: McVey Mitch , Radut Dora , Sekelsky Jeff J 
Published: December 2004

Abstract
Repair of DNA double-strand breaks can occur by either nonhomologous end joining or homologous recombination. Most nonhomologous end joining requires a specialized ligase, DNA ligase IV (Lig4). In Drosophila melanogaster, double-strand breaks created by excision of a P element are usually repaired by a homologous recombination pathway called synthesis-dependent strand annealing (SDSA). SDSA requires strand invasion mediated by DmRad51, the product of the spn-A gene. In spn-A mutants, repair proceeds through a nonconservative pathway involving the annealing of microhomologies found within the 17-nt overhangs produced by P excision. We report here that end joining of P-element breaks in the absence of DmRad51 does not require Drosophila LIG4. In wild-type flies, SDSA is sometimes incomplete, and repair is finished by an end-joining pathway that also appears to be independent of LIG4. Loss of LIG4 does not increase sensitivity to ionizing radiation in late-stage larvae, but lig4 spn-A double mutants do show heightened sensitivity relative to spn-A single mutants. Together, our results suggest that a LIG4-independent end-joining pathway is responsible for the majority of double-strand break repair in the absence of homologous recombination in flies.
Fine Mapping of a Grain-Weight Quantitative Trait Locus in the Pericentromeric Region of Rice Chromosome 3
Authors: Li Jiming , Thomson Michael , McCouch Susan R 
Published: December 2004

Abstract
As the basis for fine mapping of a grain-weight QTL, gw3.1, a set of near isogenic lines (NILs), was developed from an Oryza sativa, cv. Jefferson × O. rufipogon (IRGC105491) population based on five generations of backcrossing and seven generations of selfing. Despite the use of an interspecific cross for mapping and the pericentromeric location of the QTL, we observed no suppression of recombination and have been able to narrow down the location of the gene underlying this QTL to a 93.8-kb region. The locus was associated with transgressive variation for grain size and grain weight in this population and features prominently in many other inter- and intraspecific crosses of rice. The phenotype was difficult to evaluate due to the large amount of variance in size and weight among grains on a panicle and between grains on primary and secondary panicles, underscoring the value of using multiple approaches to phenotyping, including extreme sampling and NIL group-mean comparisons. The fact that a QTL for kernel size has also been identified in a homeologous region of maize chromosome 1 suggests that this locus, in which the dominant O. rufipogon allele confers small seed size, may be associated with domestication in cereals.
One‐ and Two‐Dimensionally Structured Polymer Networks in Liquid Crystals for Switchable Diffractive Optical Applications
Authors: Kossyrev P. , Sousa M. E. , Crawford G. 
Published: December 2004

AbstractWe have created one‐ and two‐dimensionally structured polymer networks dispersed in a liquid‐crystal solvent using a holographic exposure technique. These structures have potential for electrically switchable, reverse‐mode, polarization selective and non‐selective diffractive optical elements. Using a simple phenomenological model to describe our diffraction measurements in conjunction with microscopic studies, we are able to estimate the structured polymer wall thickness as a function of monomer concentration.
Cd1–xMnxS Diluted Magnetic Semiconductors as Nanostructured Guest Species in Mesoporous Thin‐Film Silica Host Media
Authors: Kouzema A. V. , Fröba M. , Chen L. , Klar P. J. , Heimbrodt W. 
Published: December 2004

AbstractRecently, we demonstrated the possibility of synthesizing ordered nanowires of diluted magnetic II/VI semiconductors inside the channels of mesoporous silica host structures. Here, we expand this procedure from mesoporous powders to mesoporous thin films. Diluted magnetic semiconductors Cd1–xMnxS were synthesized within the pores of mesoporous thin‐film silica host structures by a wet‐impregnation technique using an aqueous solution of the respective metal acetates, followed by drying steps and a conversion to sulfide by thermal H2S treatment. The presence of Cd1–xMnxS nanoparticles inside the pores was proved by powder X‐ray diffraction, infrared and Raman spectroscopy, and transmission electron microscopy. Photoluminescence excitation measurements clearly demonstrate the quantum size effect of the incorporated nanostructured guest species. The quality of the nanoparticles incorporated into the mesoporous films is comparable to that of those inside the mesoporous powders.
In Search of High‐Performance Platinum(II) Phosphorescent Materials for the Fabrication of Red Electroluminescent Devices
Authors: Kavitha J. , Chang S.‐Y. , Chi Y. , Yu J.‐K. , Hu Y.‐H. , Chou P.‐T. , Peng S.‐M. , Lee G.‐H. , Tao Y.‐T. , Chien C.‐H. , Carty A. J. 
Published: December 2004

AbstractThe rational design and syntheses of Pt(iqdz)2 (1) and Pt(pydz)2 (2) bearing isoquinolinyl indazole (iqdz)H or pyridyl indazole (pydz)H groups on the coordinating ligands are reported. Single‐crystal X‐ray diffraction studies of 1 reveal a square planar geometry, in which two iqdz ligands adopt a trans‐configuration. Short N…H contacts (∼2.21 Å) are detected between the ortho‐hydrogen atom of isoquinoline and the adjacent N atom of the indazole fragment, making the overall molecular geometry analogous to that of the platinum(II) porphyrinato complexes. The lowest absorption bands for both complexes reveal strong state mixings between singlet and triplet (metal‐to‐ligand charge transfer and intra‐ligand) manifolds. This, in combination with the introduction of a camphor‐like structure to avoid the stacking effect, leads to phosphorescence with unprecedented brightness both in solution and in the solid state. Organic light‐emitting diode (OLED) devices fabricated using 1 as a dopant emitter have been achieved in a multilayer configuration. The results constitute the first highly efficient PtII‐based red OLED.
Seed‐Assisted Synthesis of BaCrO4 Nanoparticles and Nanostructures in Water‐in‐Oil Microemulsions
Authors: Johnson C. J. , Li M. , Mann S. 
Published: December 2004

AbstractIsooctane dispersions of discrete isometric BaCrO4 nanoparticles or self‐assembled linear chains of prismatic BaCrO4 nanoparticles were added as surfactant‐coated seed crystals/nanostructures to Na2CrO4/NaAOT/Ba(AOT)2/isooctane microemulsion reaction solutions prepared at w = 10 with molar ratios favoring the de novo synthesis of either nanoparticle chains ([Ba2+]/ [CrO42–] = 1:1) or isolated nanoparticles ([Ba2+]/[CrO42–] = 1:5.5). Addition of BaCrO4 nanoparticles or chains under particle‐ or chain‐producing conditions, respectively, resulted in preferential growth of the seeds with retention of particle morphology and nanostructure architecture. In contrast, addition of linear chains to microemulsion reaction solutions under particle‐producing conditions resulted in disruption of the seed nanostructure and overgrowth of the released prismatic nanoparticles to produce discrete oval‐shaped or cuboidal nanocrystals depending on the seed concentration used. Discrete faceted nanoparticles were also produced by seed‐assisted synthesis when isometric nanoparticles were added at relatively high concentrations to chain‐producing microemulsion reaction solutions; however, decreasing the seed population resulted in intact self‐assembled linear chains and superlattices that consisted of interlinked prismatic nanoparticles with end‐capped pseudo‐hexagonal morphology. Growth of the seeds and their assembly/disassembly was consistent with a model of coupled synthesis and self‐organization based on the strength of electrostatic interactions at the surfactant‐crystal interface. The results suggest that microemulsion‐based processes could be of general importance for controlling the secondary growth of pre‐organized nanoparticle‐based superstructures, as well as the morphological refinement of their constituent building blocks.
Shape‐memory behaviors of sensitizing radiation‐crosslinked polycaprolactone with polyfunctional poly(ester acrylate)
Authors: Zhu G. M. , Xu Q. Y. , Liang G. Z. , Zhou H. F. 
Published: December 2004

AbstractThe sensitizing effects of polyfunctional poly(ester acrylate) on the radiation crosslinking of polycaprolactone (PCL) were studied. The influences of the use of the polyfunctional material, the number of functional groups, and the radiation dose on the radiation crosslinking, dynamic mechanical properties, and shape‐memory behaviors of PCL, respectively, were investigated. The radiation crosslinking of PCL, under the conditions in which the polyfunctional material was applied, did not follow the classic Charlesby–Pinner equation but instead followed the Chen–Liu–Tang relation. The efficiency of the radiation crosslinking of PCL was distinctly improved with the polyfunctional material. The greater the usage and functional group number were, the greater gel content and the more distinctive the radiation‐crosslinking effects were. This also indicated that the polyfunctional material directly participated in the crosslinking reaction. Dynamic mechanical analysis indicated that enhanced radiation crosslinking better raised the heat deformation temperature of PCL and presented a higher and wider rubbery‐state plateau; it also produced greater strength at temperatures higher than the melting temperature and provided greater force for recovering the deformation than pure PCL. The shape‐memory results revealed that sensitizing crosslinked PCL presented 100% recoverable deformation and a quicker recovery rate. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 634–639, 2005
Development of discrete nanopores. II. Comparison between layered films and blends of polyolefins
Authors: Lee Jonghwi , Macosko Christopher W. , Bates Frank S. 
Published: December 2004

AbstractDiscrete nanopores develop in the interfacial regions of polyolefin blends and layered films under tension. They originate from crazelike structures in the early development stage, which later undergo disruption processes with an increase in strain. The disruption processes appear to be triggered by the existence of adjacent ductile polyolefins and their micromechanical deformations. The degree of nanopore development significantly varies among blends and layered systems, depending on several material parameters, such as the interfacial strength. Discrete nanopores are observed more often in metallocene systems and blends than in Ziegler–Natta systems and layered films. Macroscopically, with the development of discrete nanopores, metallocene systems show higher strain to break and significant shear yielding under tension. The disruption mechanism can be used to prepare nanoporous materials or to improve the mechanical performances of polyolefins. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 708–718, 2005
Hydrolytic depolymerization of poly(ethylene terephthalate) under microwave irradiation
Authors: Liu Lixin , Zhang Dong , An Lijia , Zhang Huayang , Tian Yiguang 
Published: December 2004

AbstractThis article covers the depolymerization of poly(ethylene terephthalate) (PET) under microwave irradiation in neutral water. The reaction was carried out in a sealed reaction vessel in which the pressure (or temperature) was controlled. The hydrolytic product contained terephthalic acid, ethylene glycol, and diethylene glycol characterized by IR spectrometry and gas chromatography. The undepolymerized PET was identified by gel permeation chromatography. Both the yield of terephthalic acid and the degree of PET depolymerization were seriously influenced by pressure (or temperature), the weight ratio of water to PET, and the reaction time. The applied irradiation power had little influence on the degree of PET depolymerization. With a pressure of 20 bar (temperature = 220°C), a reaction time of 90–120 min, and a weight ratio of water to PET of 10:1, the PET resin was depolymerized completely. The molecular weight and the molecular weight distribution indicated that the hydrolytic depolymerization of PET obeyed the regular chain‐scission mechanism to some extent. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 719–723, 2005
Influence of swelling solutions on the behavior of cholesteric networks
Authors: Wang Xiaohua , Wang Linge , Huang Yong 
Published: December 2004

AbstractThe swelling behavior of an ethyl‐cyanoethyl cellulose/crosslinked poly(acrylic acid) cholesteric network in different swelling solutions was studied. The swelling behavior of the cholesteric network was reversible in acid or neutral solutions and was irreversible in basic solutions. The cholesteric network retained the cholesteric structure during the swelling process in NaCl aqueous solutions, and the swelling behavior was incompletely reversible. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 724–729, 2005
Electromagnetic radiation shielding by composites of conducting polymers and wood
Authors: Sapurina Irina , Kazantseva Natalia E. , Ryvkina Natalia G. , Prokeš Jan , Sáha Petr , Stejskal Jaroslav 
Published: December 2004

AbstractPolyaniline or polypyrrole composites with fir or oak wood have been prepared by in situ polymerization of the corresponding monomers in an aqueous suspension of wood sawdust. The percolation threshold of compressed coated particles is located below 5 wt % of the conducting component and, above this limit, the conductivity of most composites was higher than 10−3 S cm−1. The conductivity of composites containing ca 30 wt % of conducting polymer was of the order of 10−1 S cm−1, an order of magnitude lower than that of the corresponding homopolymers, polyaniline and polypyrrole. The conductivity stability has been tested at 175°C. The polypyrrole‐based composites generally lasted for a longer time than pyrrole homopolymers, also on account of the improved mechanical integrity of the samples provided by the presence of wood. The reverse order was found with polyaniline composites. The dielectric properties of the composites were determined in the range of 100 MHz–3 GHz, indicating that thick layers of composite material, ∼ 100 mm, are needed for the screening of the electromagnetic radiation below −10 dB level in this frequency range. Nevertheless, considering the potential production cost of composites and their low weight, such composite materials could be of practical interest in the shielding of electromagnetic interference. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 807–814, 2005
The kinetics of B‐a and P‐a type copolybenzoxazine via the ring opening process
Authors: Su Yi‐Che , Yei Ding‐Ru , Chang Feng‐Chih 
Published: December 2004

AbstractThe structure of benzoxazines is similar to that of phenolic resin through thermal self‐curing of the heterocyclic ring opening reaction that neither requires catalyst nor releases any condensation byproduct. These polybenzoxazine resins have several outstanding properties such as high thermal stability and high glass transition temperature. To better understand the curing kinetics of this copolybenzoxazine thermosetting resin, dynamic and isothermal differential scanning calorimetry measurements were performed. Three models, the Kissinger method, the Flynn–Wall–Osawa method, and the Kamal method, were used to describe the curing process. Dynamic kinetic activation energies based on Kissinger and Flynn–Wall–Osawa methods are 72.11 and 84.06 KJ/mol, respectively. The Kamal method based on an autocatalytic model results in a total order of reaction between 2.66 and 3.03, depending on curing temperature. Its activation energy and Arrhenius preexponential are 50.3 KJ/mol and 7959, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 730–737, 2005
Preparation and porous structure characterization of 4,4′‐diphenylmethane dimethacrylate/divinylbenzene polymeric particles
Authors: Maciejewska Małgorzata , Gawdzik Barbara 
Published: December 2004

AbstractCopolymers of isobutyl 4,4′‐diphenylmethane dimethacrylate and divinylbenzene in the form of microspheres were obtained. For their preparation, the following techniques of heterogeneous polymerization were used: suspension polymerization, suspension–emulsion polymerization, and precipitation polymerization. Among the obtained microspheres, those synthesized by suspenson–emulsion polymerization were of a size suitable for high‐performance liquid chromatography, whereas the product of suspension polymerization could be used as a packing material for gas chromatography. Their porous structure was studied in details. The influence of the polymerization technique on the particle size and morphology was examined. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 863–870, 2005
Relationship between the separation performances and free volume distributions of polyimide/Ag3O4 composite membranes
Authors: Shi Baoli , Feng Chunsheng , Wu Yonglie 
Published: December 2004

AbstractFirst, water, methanol, ethanol, acetone, and methyl t‐butyl ether were used as molecular probes to measure the free volume distribution of a type of polyimide membrane material (HQDEA–DMMDA). The methods were equilibrium swelling and separation membrane technologies. From the Kirchheim theory of free volume distribution, a Gaussian distribution function was determined. The Gaussian distribution function was confirmed with tensile testing and wide‐angle X‐ray diffraction of the polyimide films. Second, polyimide/Ag3O4 composite hollow‐fiber membranes were prepared by dry/wet phase inversion. The separation performances of the composite membranes were characterized with a methanol/methyl t‐butyl ether mixture. The change in the separation performances was explained by the free volume distribution function very well. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 871–879, 2005
Phosphazene cyclomatrix network polymers: Some aspects of the synthesis, characterization, and flame‐retardant mechanisms of polymer
Authors: Zhang Teng , Cai Qing , Wu De‐Zhen , Jin Ri‐Guang 
Published: December 2004

AbstractNovel phosphazene cyclomatrix network polymers were synthesized via nucleophilic displacement of activated nitro groups of tri(4‐nitrophenoxy)tri(phenoxy)cyclotriphosphazene and hexa(p‐nitrophenoxy)cyclotriphosphazene with the hydroxyls of bisphenol A. Both the monomers and polymers were characterized by Fourier transform infrared (FTIR) and 1H‐NMR spectroscopy, and their structures were identified. The thermal and flame‐retardant properties of the polymers were investigated with thermogravimetric analysis in air, pyrolysis, and combustion experiments. Both solid and gaseous degradation products were collected in a pyrolysis process and analyzed with FTIR spectroscopy, gas chromatography/mass spectrometry, and scanning electron microscopy. The results demonstrated that the cyclomatrix phosphazene polymer would have excellent thermal stability and flame‐retardant properties if it could form a crosslinked phosphorous oxynitride structure during pyrolysis or combustion. A flame‐retardant mechanism of “intumescent” was proposed to elucidate the pyrolysis and combustion process. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 880–889, 2005
Complexation of titanium alkoxides with pentenoic acid and allylacetoacetate and their hydrolysis and addition reactions with H‐silanes
Authors: Kayan Asgar , Hoebbel Dagobert , Schmidt Helmut 
Published: December 2004

AbstractComplexation reactions of titanium tetraethoxide [Ti(OEt)4] and titanium tetra‐n‐butoxide [Ti(OBun)4] with 3‐pentenoic acid (PA) and allylacetoacetate (AAA), in a 1 : 1M ratio, were studied in ethanol solution at room temperature. 13C‐NMR and FTIR spectra showed that all PA and AAA completely reacted with both titanium alkoxides. Hydridosilane compounds such as triethoxysilane and triethylsilane were added to titanium chelate complexes in a 1 : 1M ratio. The investigation of products by 13C‐ and 29Si‐NMR and FTIR showed additions of SiH to the CC double bond. The hydrolysis of titanium–PA and AAA complexes, by water in 1 : 4 ratios, resulted in released PA in an amount of 10% and AAA of 20%. The stability of hydrolyzed products was investigated by 13C‐NMR, 29Si‐NMR, and FTIR. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 790–796, 2005