bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Drosophila U1-70K Protein Is Required for Viability, but Its Arginine-Rich Domain Is Dispensable
Authors: Salz Helen K , Mancebo Ricardo S Y , Nagengast Alexis A , Speck Olga , Psotka Mitchell , Mount Stephen M 
Published: December 2004

Abstract
The conserved spliceosomal U1-70K protein is thought to play a key role in RNA splicing by linking the U1 snRNP particle to regulatory RNA-binding proteins. Although these protein interactions are mediated by repeating units rich in arginines and serines (RS domains) in vitro, tests of this domain's importance in intact multicellular organisms have not been carried out. Here we report a comprehensive genetic analysis of U1-70K function in Drosophila. Consistent with the idea that U1-70K is an essential splicing factor, we find that loss of U1-70K function results in lethality during embryogenesis. Surprisingly, and contrary to the current view of U1-70K function, animals carrying a mutant U1-70K protein lacking the arginine-rich domain, which includes two embedded sets of RS dipeptide repeats, have no discernible mutant phenotype. Through double-mutant studies, however, we show that the U1-70K RS domain deletion no longer supports viability when combined with a viable mutation in another U1 snRNP component. Together our studies demonstrate that while the protein interactions mediated by the U1-70K RS domain are not essential for viability, they nevertheless contribute to an essential U1 snRNP function.
Biodegradable Polymer (Biopol®)
Authors: Asrar Jawed , Gruys Kenneth J. 
Published: December 2004

AbstractIntroductionHistorical OutlineMicrobial Biosynthesis of PHAsPlant Production of Biopol®Properties of Biopol®Morphology of Biopol®and other PHAsComposition and Molecular Structure of PHAsCrystallization Behavior of Biopol®Thermal Properties of Biopol®Melt Rheology of Biopol®and its Impact on ProcessingEffect of Branching in Biopol®Processing Characteristics of PHAsEffect of Nucleating AgentsEffect of PlasticizersPhysical and Mechanical Properties of Biopol®Block Copolymers Using Hydroxy‐terminated PHAsMelt Processing of Biopol®MoldingExtrusionMelt Coating of Biopol®on Paper and PaperboardMelt Spinning of FibersMultifilamentNon‐wovensCoated Non‐wovensBiodegradation of Biopol®and Related PHAsBiocompatibility of PHAsApplications of Biopol®Fishing Lines and NetsOther Marine ApplicationsBiomedical ApplicationsCopolymers with Long Alkyl Chain and other FunctionalitiesPatents Describing Production and Properties of Biopol®and Related PHAs
Biodegradation of Polyethers (Polyethylene Glycol, Polypropylene Glycol, Polytetramethylene glycol, and Others)
Authors: Kawai Fusako 
Published: December 2004

AbstractIntroductionHistorical OutlineChemical StructuresBiodegradation of PEGAerobic Biodegradation of PEGAnaerobic Biodegradation and Metabolism of PEGExtracellular One‐electron Oxidation of PEGBiodegradation of PPGBiodegradation of PTMGBiodegradation of Miscellaneous PolyethersPhysiologyProductionOutlook and PerspectivesPatentsAcknowledgments
Applications of Biopolymers in Construction Engineering
Authors: Plank Johann 
Published: December 2004

AbstractIntroductionHistorical OutlineThe Construction IndustrySize of the IndustryBuilding MaterialsChemicals Used in ConstructionMajor Building MaterialsConcreteGrouts and MortarsWall PlastersPlasterboardsPaints and CoatingsOil and Gas Well ConstructionBiopolymers Used in ConstructionLignosulfonatesBiopolymers from SoilHydrocarbon‐based BiopolymersProtein‐based BiopolymersStarch and Cellulose DerivativesSeed GumsExudate Gums and Root ResinsMicrobial BiopolymersChitosanBiodegradable PolymersBiopolymers with Potential for Future UseTanninsCollagen and GelatinAlginates and CarrageenanPectinTamarind and CassiaGum Arabic, Gum Karaya and Gum TragacanthDextran and PullulanOutlook and Perspectives
Doping‐Induced Charge Trapping in Organic Light‐Emitting Devices
Authors: Nüesch F. , Berner D. , Tutiš E. , Schaer M. , Ma C. , Wang X. , Zhang B. , Zuppiroli L. 
Published: December 2004

AbstractBy using pyran‐containing donor–acceptor dyes as doping molecules in organic light‐emitting devices (OLEDs), we scrutinize the effects of charge trapping and polarization induced by the guest molecules in the electro‐active host material. Laser dyes 4‐(dicyanomethylene)‐2‐methyl‐6‐[2‐(julolidin‐9‐yl)phenyl]ethenyl]‐4H‐pyran (DCM2) and the novel 4‐(dicyanomethylene)‐2‐methyl‐6‐{2‐[(4‐diphenylamino)phenyl]ethenyl}‐4H‐pyran (DCM‐TPA) are used as model compounds. The emission color of these polar dyes depends strongly on doping concentration, which we have attributed to polarization effects induced by the doping molecules themselves. Their frontier orbital energy levels are situated within the bandgap of the tris(8‐hydroxyquinoline)aluminum (Alq3) host matrix and allow the investigation of either electron trapping or both electron and hole trapping. In the case of DCM‐TPA doping, we were able to show that electron trapping leads to a partial shift of the recombination zone out of the doped Alq3 region. To impede charge‐recombination processes taking place in the undoped host matrix, a charge‐blocking layer efficiently confines the recombination zone inside the doped zone and gives rise to increased luminous efficiency. For a doping concentration of 1 wt.‐% we obtain a maximum luminous efficiency of 10.4 cd A–1. At this doping concentration, the yellow emission spectrum shows excellent color saturation with CIE chromaticity coordinates x, y of 0.49 and 0.50, respectively. In the case of DCM2 the recombination zone is much less affected for the same doping concentrations, which is ascribed to the fact that both electrons and holes are being trapped. The experimental findings are corroborated with a numerical simulation of the doped multilayer devices.
Using Self‐Assembling Dipole Molecules to Improve Hole Injection in Conjugated Polymers
Authors: Khodabakhsh S. , Poplavskyy D. , Heutz S. , Nelson J. , Bradley D. D. C. , Murata H. , Jones T. S. 
Published: December 2004

AbstractSurface modification of indium‐tin‐oxide (ITO)‐coated substrates through the use of self‐assembled monolayers (SAMs) of molecules with permanent dipole moments has been used to control the ITO work function and device performance in polymer light‐emitting diodes based on a polyfluorene hole transporting copolymer. Measured current–voltage characteristics of the devices reveal greatly increased hole injection currents from the SAM‐altered electrodes with higher work function, in agreement with an expected reduction in the barrier for hole injection. In particular, it is shown that the SAM‐modified electrode with the highest work function provides an ohmic contact for hole injection into the studied polymer. Injection from the widely used poly(2,3‐ethylenedioxythiophene)/polystyrenesulphonic acid (PEDOT:PSS)‐coated ITO anode system, is less efficient compared with some of the studied SAM‐coated ITO anodes despite the significantly higher work function measured by a Kelvin probe. This apparently anomalous situation is attributed to the inhomogenities in the injection processes that occur over the area of the device when the PEDOT:PSS‐coated ITO electrode is used.
Growth of Bulk ZnO Single Crystals via a Novel Hydrothermal Oxidative Pressure‐Relief Route
Authors: Zheng W. , Guo F. , Qian Y. 
Published: December 2004

AbstractA novel hydrothermal oxidative pressure‐relief (HOPR) route has been successfully developed for the growth of high‐quality bulk ZnO single crystals, using metallic zinc and H2O2 as the raw materials, at 400 °C for 20 h in an alkali solvent. X‐ray powder diffraction reveals the ZnO crystals have a wurtzite structure. Two typical morphologies of perfect hexagonal pyramidal and hexagonal prismatic ZnO single crystals, and bidirectional adhesive crystals, are identified by scanning electron microscopy analysis. The average size of the single crystals is ∼ 1.0 mm in length and ∼ 0.2 mm in diameter. Short hexagonal prismatic, novel polygonal layer‐like, and nanowire ZnO crystals are also obtained by altering the reaction conditions, such as the reaction time and the speed of pressure release. The growth mechanism is a spontaneous nucleation and self‐growth process. This novel HOPR route gives an alternative choice for obtaining well‐crystallized ZnO bulk crystals from solution.
Limitations of the Förster Description of Singlet Exciton Migration: The Illustrative Example of Energy Transfer to Ketonic Defects in Ladder‐type Poly(para‐phenylenes)
Authors: Wiesenhofer H. , Beljonne D. , Scholes G. D. , Hennebicq E. , Brédas J.‐L. , Zojer E. 
Published: December 2004

AbstractEnergy‐transfer processes in phenylene‐based materials are studied via two different approaches: i) the original Förster model, which relies on a simple point‐dipole approximation; and ii) an improved Förster model accounting for an atomistic description of the interacting chromophores. Here, to illustrate the impact of excited‐state localization and the failure of the point‐dipole approximation, we consider a simple model system which consists of two interacting chains, the first a pristine ladder‐type poly(para‐phenylene) (LPPP) chain and the second an LPPP‐chain bearing a ketonic defect. The latter chain displays both localized electronic excitations close to the ketonic sites as well as excited states that are delocalized over the whole conjugated chain. Singlet hopping rates have been computed for energy transfer pathways involving these two types of excitations. A generalized Förster critical distance is introduced to account for the errors associated with averaging out the actual molecular structures in the original Förster model.
Photolithographic Route to the Fabrication of Micro/Nanowires of III–V Semiconductors
Authors: Sun Y. , Khang D.‐Y. , Hua F. , Hurley K. , Nuzzo R. G. , Rogers J. A. 
Published: December 2004

AbstractNano/microwires of semiconducting materials (e.g., GaAs and InP) with triangular cross‐sections can be fabricated by “top–down” approaches that combine lithography of high‐quality bulk wafers (using either traditional photolithography or phase‐shift optical lithography) with anisotropic chemical etching. This method gives good control over the lateral dimensions, lengths, and morphologies of free‐standing wires. The behaviors of many different resist layers and etching chemistries are presented. It is shown how wire arrays with highly ordered alignments can be transfer printed onto plastic substrates. This “top–down” approach provides a simple, effective, and versatile way of generating high‐quality single‐crystalline wires of various compound semiconductors. The resultant wires and wire arrays have potential applications in electronics, optics, optoelectronics, and sensing.
Role of the cation‐exchange capacity in the formation of polystyrene–clay nanocomposites by in situ intercalative polymerization
Authors: Aphiwantrakul S. , Srikhirin T. , Triampo D. , Putiworanat R. , Limpanart S. , Osotchan T. , Udomkichdecha W. 
Published: December 2004

AbstractAn effect of the cation‐exchange capacity (CEC) on the formation of polystyrene–clay nanocomposites is reported. Two types of 2:1 layered silicates with different CECs, Wyoming (97 mequiv/100 g of clay) and bentonite H (BNH; 131 mequiv/100 g of clay) were investigated. The organoclay was prepared through the mixing of purified clay and octadecyldimethylammonium chloride (ODA) in an aqueous solution. The packing of the intercalated ODA surfactant depended on the CEC and the degree of solvent extraction. Two possible phases of the interlayer packing, solidlike and liquidlike, were detected for the extracted BNH because of the charge heterogeneity of the clay. The liquidlike phase showed a good affinity toward the styrene monomer, which promoted the formation of exfoliated nanocomposites. On the other hand, the solidlike phase showed a restricted dispersion in the styrene monomer. The organoclay interlayer showed limited expansion by the styrene monomer. This led to the formation of intercalated nanocomposites. An increase in the organoclay loading hindered the formation of the exfoliated nanocomposites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 785–789, 2005
Transport and adhesion properties of an unlined and a liquid‐crystalline polymer–lined vinyl ester thermoset exposed to severe environments
Authors: Römhild S. , Bergman G. , Hedenqvist M. S. 
Published: December 2004

AbstractThe application of liquid‐crystalline polymers (LCP) as lining materials for fiber‐reinforced plastics was investigated. The lining consisted of one uniaxially and one biaxially oriented LCP and, for comparison, a fluorinated ethylene propylene copolymer. The lining was attached to a glass‐fiber–reinforced vinyl ester thermoset. The laminates were examined with respect to their chemical resistance, transport/barrier properties, and lining/matrix adhesion behavior. The transport properties were determined by gravimetric desorption measurements and cup tests. It was shown that the LCP was suitable as a lining in organic solvent and nonoxidizing acid environments. Diffusivities, equilibrium concentrations, and transmission rates of water, methanol, toluene, and trichloroethylene were obtained in the LCP, the fluorinated ethylene propylene copolymer, and also, in the case of the vinyl ester, of hydrochloric acid. In general, the diffusivity and transmission rate in the LCP were one to several orders of magnitude lower than those of the fluorinated ethylene propylene copolymer and the vinyl ester. The reinforcement in the glass‐fiber–reinforced plastic led to an increase in the water and methanol diffusivities and transmission rates, which was probably attributable to liquid capillary diffusion. The lap‐shear bonding strength between the LCP and the vinyl ester was poor, but it was improved almost sixfold by a combined abrasive and oxygen plasma treatment. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 797–806, 2005
Microwave promoted synthesis of chitosan‐graft‐poly(acrylonitrile)
Authors: Singh Vandana , Tripathi Devendra Narayan , Tiwari Ashutosh , Sanghi Rashmi 
Published: December 2004

AbstractUsing microwave (MW) irradiation, polyacrylonitrile was grafted onto chitosan with 170% grafting yield under homogeneous conditions in 1.5 min in the absence of any radical initiator or catalyst. Under similar conditions a maximum grafting of 105% could be achieved when the K2S2O8/ascorbic acid redox system was used as radical initiator in a thermostatic water bath at 35 ± 2°C. The representative graft copolymer was characterized by Fourier transform infrared spectra, thermogravimetric analysis, and X‐ray diffraction measurement, taking chitosan as a reference. The effects of such reaction variables as monomer/chitosan concentration, MW power, and exposure time on the graft co polymerization were studied. A probable mechanism for grafting without the redox system under microwaves was proposed. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 820–825, 2005
Use of natural rubber‐g‐polystyrene as a compatibilizer in casting natural rubber/polystyrene blend films
Authors: Chuayjuljit S. , Moolsin S. , Potiyaraj P. 
Published: December 2004

AbstractNatural rubber/polystyrene (NR/PS) blend films with weight ratios of 70/30, 60/40, and 50/50 were prepared using polystyrene grafted natural rubber copolymers (NR‐g‐PS) as the compatibilizer. Copolymers with molar ratios of 90/10, 80/20, and 70/30 were synthesized via emulsion copolymerization using tert‐butyl hydroperoxide/tetraethylene pentamine as an initiator. The copolymers were subsequently added into the blends at 0, 5, 10, 15, 20, 25, and 30 phr. The mixtures were cast into films by the solution‐casting method using toluene as the casting solvent. Mechanical and morphological properties of the prepared films were investigated. The film prepared from 80/20 NR‐g‐PS showed higher tensile and tear strength, as well as finer domain size of the dispersed phase, than those prepared from 90/10 and 70/30 NR‐g‐PS. However, the mechanical properties of the films were decreased at high loading of the copolymers. In addition, themogravimetric analysis revealed that weight loss was decreased upon introduction of the compatibilizer. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 826–831, 2005
Effects of molecular weight and arm number on properties of star‐shape styrene–butadiene–styrene triblock copolymer
Authors: Xiong Xiaopeng , Zhang Lina , Ma Zhaocheng , Li Yang 
Published: December 2004

AbstractA star‐shape styrene–butadiene–styrene triblock copolymer SBS (802) was synthesized and fractionated into four fractions coded as 802‐F1 (four arms), 802‐F2 (two arms), 802‐F3 (one arm), and 802‐F4 by repeating fractional precipitation. Their weight‐average molecular weight (Mw) was measured by size‐exclusion chromatography combined with laser light scattering to be 16.0 × 104, 8.2 × 104, 4.3 × 104, and 1.19 × 104, respectively. The samples were, respectively, compression‐molded and solution‐cast to obtain the sheets coded as 802C, 802‐F1C, 802‐F2C, and 802S, 802‐F1S, 802‐F2S. The structures and mechanical properties of the sheets were characterized by 1H‐NMR, scanning electron microscope, wide‐angle X‐ray diffractometer, tensile testing, and dynamic mechanical thermal analysis. The results indicated that the compression‐molded 802‐F1C exhibited the higher tensile strength (σb, 28.4 MPa) and elongation at break (εb, 1610%), and its optical transmittance is much higher than those of 802C and 802‐F2C. This work revealed that the star‐shape SBS with four arms could be helpful in the enhancement of the properties as a result of good miscibility of the compression‐molded SBS sheets. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 832–840, 2005
Role of capillarity in penetration into and flow through fibrous barrier materials
Authors: Unsal E. , Schwartz P. , Dane J. H. 
Published: December 2004

AbstractHydrophobic fibrous media, in the form of barriers, provide protection to its user against fluids. Important aspects to consider are the pressure at which liquids (nonwetting fluids) will penetrate into the fabric and the rate at which it will flow through. At the same time we need to consider the comfort level that the fabric provides, that is, the pores should be large enough to allow the exchange of air. The objective of this study was to develop an experimental technique to determine (1) the displacement pressure of medical barrier fabrics in combination with aqueous solutions and (2) the flow rates once the aqueous solutions had penetrated. A pressure/flow cell was used to make these determinations during sequences of increasing and decreasing pressures applied to the nonwetting fluids (aqueous solution). The resulting flow rate–pressure curves exhibited hysteresis, that is, lower flow rates existed during increasing pressures (increasing liquid contact) than during decreasing pressures (decreasing liquid contact) at corresponding pressure values. The reasons for this hysteresis were investigated. The flow rate–pressure curves also provided information about the pore size distributions of the fabrics. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 841–846, 2005
Degradation of low density polyethylene during extrusion. III. Volatile compounds in extruded films creating off‐flavor
Authors: Andersson Thorbjörn , Nielsen Tim , Wesslén Bengt 
Published: December 2004

AbstractThis study was aimed at finding a correlation between the experienced off‐flavor in packaged foods and the presence of specific degradation products in PE packaging films. The possibility to trap degradation products by chemical reactions with scavengers, that is, zeolites and maleic anhydride grafted LLDPE, were investigated. This trapping would prevent the degradation products from migrating to the polymer film surface and further into food in contact with the film. This work concludes that off‐flavor in water packed in LDPE‐films depends on extrusion temperature and the content of oxidation products in the polymer film. At lower extrusion temperatures, reactive additives to the LDPE material could control the release of off‐flavor giving components. Adsorbents, such as zeolites, which are able to adsorb degradation products, are effective also at higher extrusion temperatures. The amount of oxidized degradation products in the films correlated well to the perceived off‐flavor in the packed water. The presence of aldehydes and ketones have a clear impact on the off‐flavor. The best correlation between off‐flavor and oxidized components were found for C7C9 ketones, and aldehydes in the range of C5 to C8. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 847–858, 2005
Analysis and discussion of the modulus–strain curves of poly(ethylene terephthalate) and polyamide industrial yarns
Authors: Jing Lv , Shanyuan Wang 
Published: December 2004

AbstractThe stress–strain and modulus–strain curves from the treatment of tensile test data are more complete and suitable for examining the mechanical properties of fibers than just the stress–strain curve. This article analyzes typical modulus–strain curves of poly(ethylene terephthalate) and polyamide fibers through the physical structure changes in these fibers during stretching and discusses how to enhance the modulus for industrial use. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 859–862, 2005
DNA–polycation complexation and polyplex stability in the presence of competing polyanions
Authors: Danielsen Signe , Maurstad Gjertrud , Stokke Bjørn T. 
Published: December 2004

AbstractPolyelectrolyte complex (polyplex) formation was studied by employing tapping mode atomic force microscopy (AFM) and an ethidium bromide fluorescence assay. The polycations chitosan and poly‐L‐lysine were used to compact DNA and the stability of the polyplexes was evaluated upon exposure to competing polyanions (alginate and xanthan). Furthermore, the relative preference of these polycations for DNA and the competing polyanion was investigated. The results showed that neither poly‐L‐lysine nor chitosan displayed any selectivity in binding to DNA relative to the competing polyanions, demonstrating the importance of electrostatics in the binding of a polycation to a polyanion. However, the ability of the polyanions to destabilize the DNA–polycation complexes depended on both the polyanion and the polycation employed, indicating that polymer‐specific properties are also important for the complexation behavior and polyplex stability. Destabilization experiments further showed that annealing yielded complexes that were less prone to disruption upon subsequent exposure to alginate. Annealing experiments of plasmid DNA–chitosan complexes showed an increased fraction of rods following temperature treatment, indicating that the rods most likely are the more stable morphology for this system. © 2004 Wiley Periodicals, Inc. Biopolymers, 2005