bluuebunny/crossref_metadata_2025 huggingface dataset:
Developments in genetic algorithm techniques for structure solution from powder diffraction data
Authors: Harris Kenneth D. M. , Habershon Scott , Cheung Eugene Y. , Johnston Roy L.
Published: December 2004

This paper presents an overview of developments that have taken place in recent years in the genetic algorithm technique for structure solution from powder diffraction data. After a brief resumé, of the essential features of the genetic algorithm technique for structure solution, the paper highlights recent developments in fundamental aspects of the technique, including the development of parallel computing concepts, the analysis of the evolutionary history in genetic algorithm structure solution calculations and the combination of energy information together with the powder diffraction data in structure solution. Several examples are also given to illustrate the application of the genetic algorithm technique to solve crystal structures of different types of organic molecular materials, including oligopeptides and multi-component co-crystals.
Powder diffraction based structural studies of pharmaceuticals
Authors: Shankland Kenneth , Markvardsen Anders J. , David William I. F.
Published: December 2004

Recent methodological and algorithmic developments in the field of structure determination of materials of pharmaceutical interest from powder diffraction data are discussed.
Association Test Algorithm Between a Qualitative Phenotype and a Haplotype or Haplotype Set Using Simultaneous Estimation of Haplotype Frequencies, Diplotype Configurations and Diplotype-Based Penetrances
Authors: Ito Toshikazu , Inoue Eisuke , Kamatani Naoyuki
Published: December 2004

Analysis of the association between haplotypes and phenotypes is becoming increasingly important. We have devised an expectation-maximization (EM)-based algorithm to test the association between a phenotype and a haplotype or a haplotype set and to estimate diplotype-based penetrance using individual genotype and phenotype data from cohort studies and clinical trials. The algorithm estimates, in addition to haplotype frequencies, penetrances for subjects with a given haplotype and those without it (dominant mode). Relative risk can thus also be estimated. In the dominant mode, the maximum likelihood under the assumption of no association between the phenotype and presence of the haplotype (L0max) and the maximum likelihood under the assumption of association (Lmax) were calculated. The statistic −2 log(L0max/Lmax) was used to test the association. The present algorithm along with the analyses in recessive and genotype modes was implemented in the computer program PENHAPLO. Results of analysis of simulated data indicated that the test had considerable power under certain conditions. Analyses of two real data sets from cohort studies, one concerning the MTHFR gene and the other the NAT2 gene, revealed significant associations between the presence of haplotypes and occurrence of side effects. Our algorithm may be especially useful for analyzing data concerning the association between genetic information and individual responses to drugs.
Decreased Diversity but Increased Substitution Rate in Host mtDNA as a Consequence of Wolbachia Endosymbiont Infection
Authors: Shoemaker D DeWayne , Dyer Kelly A , Ahrens Mike , McAbee Kevin , Jaenike John
Published: December 2004

A substantial fraction of insects and other terrestrial arthropods are infected with parasitic, maternally transmitted endosymbiotic bacteria that manipulate host reproduction. In addition to imposing direct selection on the host to resist these effects, endosymbionts may also have indirect effects on the evolution of the mtDNA with which they are cotransmitted. Patterns of mtDNA diversity and evolution were examined in Drosophila recens, which is infected with the endosymbiont Wolbachia, and its uninfected sister species D. subquinaria. The level of mitochondrial, but not nuclear, DNA diversity is much lower in D. recens than in D. subquinaria, consistent with the hypothesized diversity-purging effects of an evolutionarily recent Wolbachia sweep. The dN/dS ratio in mtDNA is significantly greater in D. recens, suggesting that Muller's ratchet has brought about an increased rate of substitution of slightly deleterious mutations. The data also reveal elevated rates of synonymous substitutions in D. recens, suggesting that these sites may experience weak selection. These findings show that maternally transmitted endosymbionts can severely depress levels of mtDNA diversity within an infected host species, while accelerating the rate of divergence among mtDNA lineages in different species.
Differential Activation of eIF2 Kinases in Response to Cellular Stresses in Schizosaccharomyces pombe
Authors: Zhan Ke , Narasimhan Jana , Wek Ronald C
Published: December 2004

Phosphorylation of eukaryotic initiation factor-2 (eIF2) is an important mechanism mitigating cellular injury in response to diverse environmental stresses. While all eukaryotic organisms characterized to date contain an eIF2 kinase stress response pathway, the composition of eIF2 kinases differs, with mammals containing four distinct family members and the well-studied lower eukaryote Saccharomyces cerevisiae expressing only a single eIF2 kinase. We are interested in the mechanisms by which multiple eIF2 kinases interface with complex stress signals and elicit response pathways. In this report we find that in addition to two previously described eIF2 kinases related to mammalian HRI, designated Hri1p and Hri2p, the yeast Schizosaccharomyces pombe expresses a third eIF2 kinase, a Gcn2p ortholog. To delineate the roles of each eIF2 kinase, we constructed S. pombe strains expressing only a single eIF2 kinase gene or deleted for the entire eIF2 kinase family. We find that Hri2p is the primary activated eIF2 kinase in response to exposure to heat shock, arsenite, or cadmium. Gcn2p serves as the primary eIF2 kinase induced during a nutrient downshift, treatment with the amino acid biosynthetic inhibitor 3-aminotriazole, or upon exposure to high concentrations of sodium chloride. In one stress example, exposure to H2O2, there is early tandem activation of both Hri2p and Gcn2p. Interestingly, with extended stress conditions there is activation of alternative secondary eIF2 kinases, suggesting that eukaryotes have mechanisms of coordinate activation of eIF2 kinase in their stress remediation responses. Deletion of these eIF2 kinases renders S. pombe more sensitive to many of these stress conditions.
Genetic Architecture of Flowering Time in Maize As Inferred From Quantitative Trait Loci Meta-analysis and Synteny Conservation With the Rice Genome
Authors: Chardon Fabien , Virlon Bérangère , Moreau Laurence , Falque Matthieu , Joets Johann , Decousset Laurent , Murigneux Alain , Charcosset Alain
Published: December 2004

Genetic architecture of flowering time in maize was addressed by synthesizing a total of 313 quantitative trait loci (QTL) available for this trait. These were analyzed first with an overview statistic that highlighted regions of key importance and then with a meta-analysis method that yielded a synthetic genetic model with 62 consensus QTL. Six of these displayed a major effect. Meta-analysis led in this case to a twofold increase in the precision in QTL position estimation, when compared to the most precise initial QTL position within the corresponding region. The 62 consensus QTL were compared first to the positions of the few flowering-time candidate genes that have been mapped in maize. We then projected rice candidate genes onto the maize genome using a synteny conservation approach based on comparative mapping between the maize genetic map and japonica rice physical map. This yielded 19 associations between maize QTL and genes involved in flowering time in rice and in Arabidopsis. Results suggest that the combination of meta-analysis within a species of interest and synteny-based projections from a related model plant can be an efficient strategy for identifying new candidate genes for trait variation.
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

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

Introduction

Historical Outline

Microbial Biosynthesis of PHAs

Plant Production of Biopol®

Properties of Biopol®

Morphology of Biopol®and other PHAs

Composition and Molecular Structure of PHAs

Crystallization Behavior of Biopol®

Thermal Properties of Biopol®

Melt Rheology of Biopol®and its Impact on Processing

Effect of Branching in Biopol®

Processing Characteristics of PHAs

Effect of Nucleating Agents

Effect of Plasticizers

Physical and Mechanical Properties of Biopol®

Block Copolymers Using Hydroxy‐terminated PHAs

Melt Processing of Biopol®

Molding

Extrusion

Melt Coating of Biopol®on Paper and Paperboard

Melt Spinning of Fibers

Multifilament

Non‐wovens

Coated Non‐wovens

Biodegradation of Biopol®and Related PHAs

Biocompatibility of PHAs

Applications of Biopol®

Fishing Lines and Nets

Other Marine Applications

Biomedical Applications

Copolymers with Long Alkyl Chain and other Functionalities

Patents 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

Introduction

Historical Outline

Chemical Structures

Biodegradation of PEG

Aerobic Biodegradation of PEG

Anaerobic Biodegradation and Metabolism of PEG

Extracellular One‐electron Oxidation of PEG

Biodegradation of PPG

Biodegradation of PTMG

Biodegradation of Miscellaneous Polyethers

Physiology

Production

Outlook and Perspectives

Patents

Acknowledgments
Applications of Biopolymers in Construction Engineering
Authors: Plank Johann
Published: December 2004

Introduction

Historical Outline

The Construction Industry

Size of the Industry

Building Materials

Chemicals Used in Construction

Major Building Materials

Concrete

Grouts and Mortars

Wall Plasters

Plasterboards

Paints and Coatings

Oil and Gas Well Construction

Biopolymers Used in Construction

Lignosulfonates

Biopolymers from Soil

Hydrocarbon‐based Biopolymers

Protein‐based Biopolymers

Starch and Cellulose Derivatives

Seed Gums

Exudate Gums and Root Resins

Microbial Biopolymers

Chitosan

Biodegradable Polymers

Biopolymers with Potential for Future Use

Tannins

Collagen and Gelatin

Alginates and Carrageenan

Pectin

Tamarind and Cassia

Gum Arabic, Gum Karaya and Gum Tragacanth

Dextran and Pullulan

Outlook 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

By 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

Surface 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

A 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

Energy‐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

Nano/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

An 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

The 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

Using 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

Natural 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

A 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

Hydrophobic 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

This 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

The 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

Polyelectrolyte 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
Synthesis of single‐ and multiple‐stranded cystine‐rich peptides
Authors: Moroder Luis , Musiol Hans‐Jürgen , Götz Marion , Renner Christian
Published: December 2004

The large abundance of bioactive single‐ and multiple‐stranded cystine‐rich peptides in nature has fostered the development of orthogonal thiol‐protection schemes and of efficient chemistries for regioselective disulfide formation in synthetic replica for decades. In parallel to these entirely synthetic strategies, an increased knowledge of oxidative refolding mechanisms of proteins has been accumulated, and the collective experience with air oxidation of cysteine‐rich peptides into their native disulfide frameworks have largely confirmed Anfinsen′s principle of the self‐assembly of polypeptide chains. In fact, a continuously growing number of cysteine‐rich bioactive peptides from the most diverse sources and with differing cysteine patterns were found to retain the critical sequence‐encoded structural information for correct oxidative folding into the native structures as dominant isomers, although in the biosynthetic pathways the mature peptide forms are mostly generated by posttranslational processing of folded precursors. Such self‐assembly processes can be optimized by opportune manipulation of the experimental conditions or by induction of productive intermediates. But there are also numerous cases where folding and disulfide formation are thermodynamically not coupled and where the application of a defined succession of regioselective cysteine pairings still represents the method of choice to install the desired native or non‐native cystine frameworks. Among our contributions to the state of the art in the synthesis of cystine‐rich peptides, we have mainly addressed the induction of correct oxidative refolding of single‐stranded cysteine‐rich peptides into their native structures by the use of selenocysteine and suitable strategies for disulfide‐mediated assembly of monomers into defined oligomers as mimics of homo‐ and heterotrimeric collagens as a synthetic approach for the development of new biomaterials. © 2004 Wiley Periodicals, Inc. Biopolymers (Pept Sci), 2005
Turn stabilization in short peptides by Cα‐methylated α‐amino acids
Authors: Crisma Marco , Moretto Alessandro , De Zotti Marta , Formaggio Fernando , Kaptein Bernard , Broxterman Quirinus B. , Toniolo Claudio
Published: December 2004

The crystal‐state conformations of three protected tripeptides, four tetrapeptides, and one pentapeptide, heavily based on the chiral Cα‐methylated α‐amino acids Iva, (αMe)Nva, and (Me)Val, were assessed by X‐ray diffraction analyses. The eight peptide sequences are as follows: Z(DIva)2DValOMe, ZDIvaLIvaGlyOtBu, ZLProDIvaLIvaGlyOtBu, ZLProLIvaDIvaGlyOtBu, ZAib[L(αMe)Nva]2OtBu, Ac[L(αMe)Val]3D(αMe)ValOtBu, Z[L(αMe)Val]4OH, and ZLAla[L(αMe)Nva]4OtBu. Two independent molecules were observed in the asymmetric units of ZDIvaLIvaGlyOtBu and ZAib[L(αMe)Nva]2OtBu, while three independent molecules were seen in ZLAla[L(αMe)Nva]4OtBu. All peptides are folded in a single or multiple β‐turn conformations. Interestingly: (i) a water bridge within the N‐terminal β‐turn is seen in ZLProLIvaDIvaGlyOtBu (dihydrate), and (ii) the hydroxyl group of the C‐terminal carboxyl functionality of Z[L(αMe)Val]4OH generates an oxy‐analogue of a β‐turn. The N‐terminal β‐turn is missing in molecules A and B, but it does occur, although poorly stabilized, in molecule C, of ZLAla[L(αMe)Nva]4OtBu. © 2004 Wiley Periodicals, Inc. Biopolymers (Pept Sci), 2005
Asymmetric Diethyl‐ and Diphenylzinc Additions to Aldehydes by Using a Fluorine‐Containing Chiral Amino Alcohol: A Striking Temperature Effect on the Enantioselectivity, a Minimal Amino Alcohol Loading, and an Efficient Recycling of the Amino Alcohol
Authors: Park Jin Kyoon , Lee Hong Geun , Bolm Carsten , Kim B. Moon
Published: December 2004

A chiral pyrrolidinylmethanol derivative containing perfluoro‐ponytails (5) was prepared from (S)‐proline. The use of this perfluoro‐substituted amino alcohol in catalytic asymmetric additions of organozinc reagents to aldehydes affords products with high enantioselectivities in both pure hexane and a mixture of hexane and FC‐72 (perfluorohexane). Enantiomeric excesses up to 94 and 88 % ee have been achieved in Et2Zn and Ph2Zn additions, respectively. For the reactions in the biphasic solvent system a striking temperature effect was observed. Thus, when the temperature was raised from 0 to 40 °C the ee value of the product increased from 81 to 92 %. Furthermore, the catalyst loading could be remarkably low, and with only 0.1 mol % of amino alcohol 5 a product with 90 % ee was obtained in the Et2Zn addition to benzaldehyde in hexane. The perfluoro‐ligand was easily recovered by simple phase separation, and until the ninth repetition its reuse proceeded without significant loss of enantioselectivity and reactivity.
Titanium‐Based Molecular Squares and Rectangles: Syntheses by Self‐Assembly Reactions of Titanocene Fragments and Aromatic N‐Heterocycles
Authors: Kraft Susanne , Hanuschek Edith , Beckhaus Rüdiger , Haase Detlev , Saak Wolfgang
Published: December 2004

This paper reports on the potential of titanium compounds as building blocks for supramolecular polygons. Self‐assembly reactions of low‐valent titanocene units and N‐heterocyclic bridging ligands lead to novel titanium‐based supramolecular squares. Pyrazine (3), 4,4′‐bipyridine (4), and tetrazine (5) were used as bridging ligands, and the acetylene complexes [Cp2Ti{η2‐C2(SiMe3)2}] (1) and [(tBuCp)2Ti{η2‐C2(SiMe3)2}] (2) as sources of titanocene fragments. Molecular rectangles can be synthesized by stepwise reduction of the titanocene dichlorides [Cp2TiCl2] and [(tBuCp)2TiCl2] and consecutive coordination of two different bridging ligands. The resulting complexes are the first examples of molecular rectangles containing bent metallocene corner units. Single‐crystal X‐ray analyses of the tetranuclear compounds revealed the geometric properties of the molecular polygons in the solid state. Comparison of bond lengths and angles in coordinated and free ligands reveals the reduced state of the bridging ligand in the low‐valent titanium compounds. The syntheses and properties of these novel, highly air‐ and moisture‐sensitive compounds are discussed.
Phase II study of irinotecan (CPT‐11) as salvage therapy for advanced nasopharyngeal carcinoma
Authors: Poon Donald , Chowbay Balram , Cheung Yin‐Bun , Leong Swan‐Swan , Tan Eng‐Huat
Published: December 2004

BACKGROUND

This Phase II study was designed to evaluate the efficacy and safety of irinotecan in patients with advanced nasopharyngeal carcinoma (NPC).

METHODS

Patients with disseminated, undifferentiated NPC that progressed during or within 3 months of platinum‐based and/or taxane‐based regimen were eligible. Irinotecan at a dose of 100 mg/m2 was administered on Days 1, 8, and 15 every 28 days, up to a maximum of 6 cycles, until disease progression or the appearance of intolerable toxicity.

RESULTS

Twenty‐eight patients were evaluable for toxicity and response. Patient characteristics were as follows: The median age was 46.5 years (range, 40.3–71.6 years), the median number of prior lines of chemotherapy was 2 (range, 1–9), the majority of patients (89%) had good Eastern Cooperative Oncology Group performance status (0–1), and the majority of patients (82.1%) had ≥ 2 sites of distant metastases. A total of 79 cycles of irinotecan with a median of 3 cycles per patient were administered. Toxicity > Grade 3 included neutropenia in 5 patients (17%), anemia in 5 patients (17%), and diarrhea in 4 patients (14%). The best response outcomes were 4 patients (14%) who achieved partial responses and 1 patient (4%) who achieved stable disease. Global quality‐of‐life scores were stable during treatment. Using the Kaplan–Meier method, the median progression‐free survival was 3.9 months, and the median overall survival was 11.4 months. The partial responders had a durable response (range, 5.7–12.2 months).

CONCLUSIONS

Results from this trial suggest that irinotecan is an active salvage agent with modest toxicity in patients with advanced NPC who are refractory to platinum/taxane‐based chemotherapy. Studies combining irinotecan with other active agents in the first‐line setting are warranted. Cancer 2005. © 2004 American Cancer Society.
Predicting psychological morbidity in Chinese women after surgery for breast carcinoma
Authors: Lam Wendy W. T. , Fielding Richard , Ho Ella Y. Y.
Published: December 2004

BACKGROUND

Between 30% and 70% of western women experience psychological morbidity after undergoing surgery for breast carcinoma; however, the rates and risk factors among Chinese women are unknown. Identifying at‐risk women enables preventive intervention.

METHODS

Among 430 Chinese women who were approached within 1 week after undergoing surgery for early‐stage breast carcinoma (baseline), 405 women (94%) completed measures of self‐efficacy and psychological morbidity (the Chinese Health Questionnaire 12‐item instrument [CHQ12]) and completed retrospective measures of treatment decision‐making (TDM) difficulties, satisfaction with TDM involvement, and satisfaction with consultation and treatment outcome expectations. One‐month postsurgery follow‐up (follow‐up), CHQ12 scores for 367 of 405 women (91%) were adjusted for concurrent physical symptom distress and trait optimism (the revised Chinese Life Orientation Test) and baseline predictors using stepwise multivariate regression.

RESULTS

At baseline 28% of women evidenced mild psychological morbidity, and 42% of women evidenced moderate‐to‐severe psychological morbidity: At follow‐up, the respective rates were 32% and 36%. Preferred TDM involvement was associated with lower psychological morbidity (F = 6.702;P< 0.001). Baseline CHQ12 scores were predicted by outcome expectancies and TDM difficulties (adjusted regression coefficient [R2] = 0.192). Baseline CHQ12 scores and follow‐up chemotherapy, in turn, predicted physical symptom distress at follow‐up. After adjustment, high physical symptom distress, baseline psychological morbidity, low optimism, and no chemotherapy independently predicted follow‐up CHQ12 scores (adjusted R2= 0.585).

CONCLUSIONS

Psychological morbidity was linked to women's TDM difficulties, their inability to anticipate treatment effects accurately, and physical symptom distress, possibly exacerbated by symptom misattribution. Optimizing TDM support and helping women accurately determine outcomes in terms of symptom experience and meaning and physical appearance may help to reduce psychological morbidity. Women who have TDM difficulties should be considered to be at high risk for psychological distress. Cancer 2005. © 2004 American Cancer Society.
Overexpression of macrophage migration inhibitory factor induces angiogenesis and deteriorates prognosis after radical resection for hepatocellular carcinoma
Authors: Hira Eiji , Ono Takashi , Dhar Dipok Kumar , El‐Assal Osama N. , Hishikawa Yoshitaka , Yamanoi Akira , Nagasue Naofumi
Published: December 2004

BACKGROUND

Macrophage migration inhibitory factor (MIF) is a pivotal cytokine that regulates inflammatory and immune responses. Recently, many investigators reported that MIF is expressed highly in several tumors, including hepatocellular carcinoma (HCC). However, the role of MIF in tumor angiogenesis and patient prognosis has not been examined in patients with HCC.

METHODS

The authors evaluated MIF expression in 56 samples of HCC by Western blot analysis, and the results were correlated with clinicopathologic factors and patient prognosis. MIF localization was determined by immunohistochemical methods, and the results were compared with tumor microvessel density (MVD), as assessed by anti‐CD34 antibody. Furthermore, to validate the role of MIF in angiogenesis, both MIF expression during culture of HCC cells (using the Hep3B, HepG2, and Huh7 cell lines) under hypoxic condition and the angiogenic potential of recombinant MIF in an in vitro angiogenic model were examined.

RESULTS

Tumors with high MIF expression had high α‐fetoprotein levels (P = 0.049) and frequent intrahepatic recurrence (P = 0.043). Immunohistochemical MIF scores had a significant correlation with MVD (P = 0.007). Patients who had tumors with high MIF expression levels had a significantly worse (P = 0.025) disease‐free survival, and this finding remained significant as an independent prognostic factor in the multivariate analysis. Hep3B cells had high expression of MIF at 6 hours and 12 hours after hypoxic stress and exogenous MIF stimulated endothelial tube formation in in vitro angiogenesis.

CONCLUSIONS

The current findings suggest that MIF expression may play a pivotal role in the dismal prognosis of patients with HCC that may be attributable to the modulation of angiogenesis. Cancer 2005. © 2004 American Cancer Society.
Glycinergic neurons expressing enhanced green fluorescent protein in bacterial artificial chromosome transgenic mice
Authors: Zeilhofer Hanns Ulrich , Studler Barbara , Arabadzisz Dimitrula , Schweizer Claude , Ahmadi Seifollah , Layh Beate , Bösl Michael R. , Fritschy Jean‐Marc
Published: December 2004

Although glycine is a major inhibitory transmitter in the mammalian CNS, the role of glycinergic neurons in defined neuronal circuits remains ill defined. This is due in part to difficulties in identifying these cells in living slice preparations for electrophysiological recordings and visualizing their axonal projections. To facilitate the morphological and functional analysis of glycinergic neurons, we generated bacterial artificial chromosome (BAC) transgenic mice, which specifically express enhanced green fluorescent protein (EGFP) under the control of the promotor of the glycine transporter (GlyT) 2 gene, which is a reliable marker for glycinergic neurons. Neurons expressing GlyT2‐EGFP were intensely fluorescent, and their dendrites and axons could be visualized in great detail. Numerous positive neurons were detected in the spinal cord, brainstem, and cerebellum. The hypothalamus, intralaminar nuclei of the thalamus, and basal forebrain also received a dense GlyT2‐EGFP innervation, whereas in the olfactory bulb, striatum, neocortex, hippocampus, and amygdala positive fibers were much less abundant. No GlyT2‐EGFP‐positive cell bodies were seen in the forebrain. On the subcellular level, GlyT2‐EGFP fluorescence was colocalized extensively with glycine immunoreactivity in somata and dendrites and with both glycine and GlyT2 immunoreactivity in axon terminals, as shown by triple staining at all levels of the neuraxis, confirming the selective expression of the transgene in glycinergic neurons. In slice preparations of the spinal cord, no difference between the functional properties of EGFP‐positive and negative neurons could be detected, confirming the utility of visually identifying glycinergic neurons to investigate their functional role in electrophysiological studies. J. Comp. Neurol. 482:123–141, 2005. © 2004 Wiley‐Liss, Inc.
Gap‐junction communication between subtypes of direction‐selective ganglion cells in the developing retina
Authors: DeBoer Darrell J. , Vaney David I.
Published: December 2004

The On‐Off direction‐selective ganglion cells (DSGCs) in the rabbit retina comprise four distinct subtypes that respond preferentially to image motion in four orthogonal directions; each subtype forms a regular territorial array, which is overlapped by the other three arrays. In this study, ganglion cells in the developing retina were injected with Neurobiotin, a gap‐junction‐permeable tracer, and the DSGCs were identified by their characteristic type 1 bistratified (BiS1) morphology. The complex patterns of tracer coupling shown by the BiS1 ganglion cells changed systematically during the course of postnatal development. BiS1 cells appear to be coupled together around the time of birth, but, over the next 10 days, BiS1 cells decouple from each other, leading to the mature pattern in which only one subtype is coupled. At about postnatal day 5, before the ganglion cells become visually responsive, each of the BiS1 cells commonly showed tracer coupling both to a regular array of neighboring BiS1 cells, presumably destined to be DSGCs of the same subtype, and to a regular array of overlapping BiS1 cells, presumably destined to be DSGCs of a different subtype. The gap‐junction intercellular communication between subtypes of DSGCs with different preferred directions may play an important role in the differentiation of their synaptic connectivity, with respect to either the inputs that DSGCs receive from retinal interneurons or the outputs that DSGCs make to geniculate neurons. J. Comp. Neurol. 482:85–93, 2005. © 2004 Wiley‐Liss, Inc.