bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of minority structures and mechanism of peroxide crosslinking of polyethylene
Authors: Lazár Milan , Kleinová Angela , Fiedlerová Agnesa , Janigová Ivica , Borsig Eberhard
Published: December 2003

Minority structures are considered to be defect structures that are formed during polyethylene (PE) preparation and during the crosslinking process in PE. The minority structures that play the predominant role in PE crosslinking are vinyl double bonds. Moreover, the decomposition of dicumyl peroxide in PE does not proceed according to first‐order kinetics, but induced peroxide decomposition also takes part. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 675–688, 2004
Biopolymers for biocatalysis: Structure and catalytic mechanism of hydroxynitrile lyases
Authors: Gruber Karl , Kratky Christoph
Published: December 2003

Hydroxynitrile lyases catalyze the reversible cleavage of α‐cyanohydrins to yield hydrocyanic acid and the corresponding aldehyde or ketone. Besides its biological interest, this class of enzymes is also of relevance in industrial biocatalysis for the enantioselective condensation of HCN with a variety of aldehydes and ketones. Several distinctly different types of hydroxynitrile lyases (HNLs) are known, which must have originated through convergent evolution from different ancestral proteins. Three‐dimensional structural data are known for three classes of hydroxynitrile lyases. Insights into the reaction mechanisms emerged from a combination of structural, enzyme kinetic, spectroscopic, and molecular modeling data. For all three types of HNLs, mechanisms involving acid–base catalysis were proposed. In members belonging to the α,β‐hydrolase type, the amino acid residues of the catalytic triad presumably act as general acid/base, whereas for flavine adenine dinucleotide (FAD)‐dependent HNLs a single histidine residue fulfills this function. In the third type of HNL—which is related to carboxypeptidase—acid–base catalysis involves the carboxylate of the C‐terminal residue. The catalytic relevance of a positive electrostatic potential in the active site was suggested in some of the mechanistic proposals. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 479–486, 2004
Thermal oxidation of nonstabilized and stabilized polymers and chemiluminescence
Authors: Matisová‐Rychlá L. , Rychlý J.
Published: December 2003

The chemiluminescence under isothermal and nonisothermal conditions accompanying the oxidation of some polymers (polyolefins, polyamides, and polysaccharides) has been examined from the viewpoint of its relationship with the rate of oxidation. The chemical structure of a given type of polymer plays a decisive role in the resulting shape of the chemiluminescence curves. In the presence of an antioxidant, the inhibition periods of oxidation are shifted to longer times and/or higher temperatures. This shift is directly proportional to the type and concentration of stabilizer. Attention has also been paid to the impact of the average molar mass on the oxidizability of the macromolecular material. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 648–660, 2004
Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry analysis of atom transfer radical polymerization macroinitiators derived from poly(3‐ethyl‐3‐hydroxymethyloxetane)
Authors: Bednarek Melania , Kubisa Przemysław
Published: December 2003

The matrix‐assisted laser desorption/ionization time‐of‐flight analysis of macroinitiators for atom transfer radical polymerization prepared by the functionalization of a multihydroxyl, highly branched polyether, poly(3‐ethyl‐3‐hydroxymethyloxetane), allows the exact determination of the macroinitiator functionality, providing information on the number of bromine atoms in individual macromolecules, in contrast to NMR analysis, which gives average values. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 608–614, 2004
Thermosensitive sol–gel transition behaviors of poly(ethylene oxide)/aliphatic polyester/poly(ethylene oxide) aqueous solutions
Authors: Song M. J. , Lee D. S. , Ahn J. H. , Kim D. J. , Kim S. C.
Published: December 2003

The thermoreversible gelation of Pluronic [poly(ethylene oxide) (PEO)–polypropylene oxide (PPO)–PEO] aqueous solutions originates from micelle formation and micelle volume changes due to PEO–water and PPO–water lower critical solution temperature behavior. The micelle volume fraction is known to dominate the sol–gel transition behavior of Pluronic aqueous solutions. Triblock copolymers of PEO and aliphatic polyesters, instead of PPO, were prepared by hexamethylene diisocyanate coupling and dicyclohexyl carbodiimide coupling. Through changes in the molecular weight and hydrophobicity of the polyester middle block, the hydrophobic–hydrophilic balance of each block was systematically controlled. The following aliphatic polyesters were used: poly(hexamethylene adipate) (PHA), poly(ethylene adipate) (PEA), and poly(ethylene succinate) (PESc). With the hydrophobicity and molecular weight of the middle block increasing, the critical micelle concentration at the same critical micelle temperature decreased, and the absolute value of the micellization free energy increased. The micelle size was rather insensitive to temperature but slightly decreased with increasing temperature. PEO–PHA–PEO and PEO–PEA–PEO triblock copolymers needed high polymer concentrations to form gels. This was ascribed to the tight aggregation of PHA and PEA chains in the micelle core due to strong hydrophobic interactions, which induced the contraction of the micelle core. However, because of the relatively hydrophilic core, a PEO–PESc–PEO aqueous solution showed gelation at a low polymer concentration. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 772–784, 2004
Hydrogen‐bonded supramolecular poly(ether ketone)s
Authors: Kunz Michael J. , Hayn Getraud , Saf Robert , Binder Wolfgang H.
Published: December 2003

The preparation of 2,4‐diamino‐1,3,5‐triazine telechelic poly(ether ketone)s (triazine PEKs) and the formation of supramolecular polymers with dodecyl‐(α‐ω)‐bis(5‐methyl‐1,3‐pyrimidine‐2,4‐dione) were investigated. Both structures interacted by complementing hydrogen‐bonding units present at their respective chain ends, this being reminiscent of triple hydrogen bonding in DNA. The preparation of the triazine PEKs started from hydroxyl‐terminated poly(ether ketone)s by a nucleophilic displacement reaction with 2,4‐diamino‐6‐(4‐fluorophenyl)‐1,3,5‐triazine. With this method and molecular weight control via the Carothers equation, a series of triazine PEKs with a complete degree of end‐group functionalization were prepared. The structure of the polymers was proven by 13C NMR spectroscopy and matrix‐assisted laser desorption/ionization spectroscopy. When mixed as a 1:1 complex in solution with dodecyl‐(α‐ω)‐bis(5‐methyl‐1,3‐pyrimidine‐2,4‐dione), short triazine PEKs (molecular weight = 5700 or 10,000) showed a temperature‐dependent association behavior visible via dynamic NMR spectroscopy. Additional proof of the formation of a supramolecular, hydrogen‐bonded network was derived from solid‐state NMR spectroscopy, differential scanning calorimetry, and rheological investigations. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 661–674, 2004
Structure and properties of poly(methyl methacrylate) particles prepared by a modified microemulsion polymerization
Authors: Jiang Wan , Yang Wuli , Zeng Xianbiao , Fu Shoukuan
Published: December 2003

Nanoscale poly(methyl methacrylate) (PMMA) particles were prepared by modified microemulsion polymerization. Different from particles made by traditional microemulsion polymerization, the particles prepared by modified microemulsion polymerization were multichain systems. PMMA samples, whether prepared by the traditional procedure or the modified procedure, had glass‐transition temperatures (Tg's) greater than 120 °C and were rich in syndiotactic content (55–61% rr). After the samples were dissolved in CHCl3, there were decreases in the Tg values for the polymers prepared by the traditional procedure and those prepared by the modified process. However, a more evident Tg decrease was observed in the former than in the latter; still, for both, Tg was greater than 120 °C. Polarizing optical microscopy and wide‐angle X‐ray diffraction indicated that some ordered regions formed in the particles prepared by modified microemulsion polymerization. The addition of a chain‐transfer agent resulted in a decrease in both the syndiotacticity and Tg through decreasing polymer molecular weight. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 733–741, 2004
Theoretical and experimental X‐ray photoelectron spectroscopy investigation of ion‐implanted nafion
Authors: Hoffmann Eufrozina A. , Fekete Zoltan A. , Korugic‐Karasz Ljiljana S. , Karasz Frank E. , Wilusz Eugene
Published: December 2003

The membrane properties of a Nafion surface can be modified by ion implantation with N+ or F+. The results are presented of an X‐ray photoelectron spectroscopy (XPS) study of implanted surfaces. For the interpretation of the XPS spectra, calculations using a semiempirical quantum chemical formalism (AM1) have been applied, in conjunction with a charge‐potential model, to predict the C1s core electron binding energies. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 551–556, 2004
Aminotelechelics: A convenient synthesis and characterization of primary amino‐terminated telechelic poly(propylene glycol) and polyisobutylene
Authors: Kéki Sándor , Nagy Miklós , Deák György , Herczegh Pál , Zsuga Miklós
Published: December 2003

The synthesis of amino‐terminated telechelic poly(propylene glycol) and polyisobutylene from their corresponding dihydroxy‐terminated derivatives was studied. The synthesis of these aminotelechelics was achieved by the coupling of imidazolylformates with ethylenediamine. The structure of the resulting amino‐functionalized polymers was determined by 1H NMR, 13C NMR, and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. On the basis of the spectroscopic and spectrometric results, a complete conversion of dihydroxy termini into diamino end groups was observed; that is, the number‐average functionality was found to be 2. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 587–596, 2004
My life with polymer science
Authors: Vogl Otto
Published: December 2003

This article describes the scientific investigations and accomplishments in the life of the author. After a dissertation on steroids, several years were spent on alkaloids and research on heterocyclic compounds. Much of the author's career was devoted to research on aldehyde polymerization, the discovery of the polymerization of higher aldehydes and their isotactic polymers, and haloaldehyde polymerization. The latter led to our work on the ceiling temperature of polymerization, on new polymerization techniques [involving the ceiling temperature and the concept of macromolecular asymmetry (polymer helicity)], and the genesis of chloral polymerization. Another important period was devoted to functional polymers, polymeric stabilizers, and polymeric drugs. Other research activities included studies of unusual polymers, head‐to‐head polymers, spacer groups in polymers, and oriental lacquers. Attention was also paid to the use of novel and unusual polymer intermediates, polymerization under extreme conditions and the preparation and behavior of uncommon polymer structures. Finally, it was recognized that macromolecules can be categorized with increasing frequency as polymers with broad and narrow molecular weight distributions and uniform polymers. The ultimate unity is isotopically pure uniform polymers, single macromolecular species. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 795–818, 2004
Toward self‐assembling dendritic macromolecules from conventional monomers by a combination of living radical polymerization and irreversible terminator multifunctional initiator
Authors: Percec Virgil , Grigoras Cristian , Kim Hyoung‐J.
Published: December 2003

TERMINI stands for irreversible terminator multifunctional initiator and represents a new concept elaborated in our laboratory for the design of novel macromolecules with complex architecture from a diversity of commercial monomers. TERMINI is a masked multifunctional initiator that quantitatively interrupts a living polymerization. After demasking, the TERMINI‐derived repeat unit provides access to a quantitative reinitiation of the same living polymerization in more than one direction, thus becoming a branching point. In this article, with a combination of self‐regulated metal‐catalyzed living radical polymerization and TERMINI, we demonstrate a new method for the divergent synthesis of dendritic poly(methyl methacrylate) containing a bifunctional core at its focal point. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 505–513, 2004
Molecular electronic structure problem solved by numerical one‐electron Green's functions
Authors: Merzel Franci
Published: December 2003

A method for the calculation of the electronic structure of molecules is presented that is based on the Kohn–Sham formulation of density functional theory. The method avoids calculating global molecular orbitals; therefore, the electron density is defined by means of numerically calculated one‐electron Green's functions. The method adopts a strategy of dividing a molecule into atomic subsystems whereby the favorable linear scaling of computational costs is obtained. Formulating the electronic structure problem by means of Green's functions allows the introduction of an additional coupling between subsystems that is not present in familiar methods. Although the method is general and can be applied to molecules with an arbitrary structure, it is at present tested only on some linear molecules. © 2003 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Nerve terminal glutamate immunoreactivity in the rat nucleus accumbens and ventral tegmental area after a short withdrawal from cocaine
Authors: Kozell L.B. , Meshul C.K.
Published: December 2003

Cocaine administration has been shown to alter glutamate transmission in numerous studies. Using quantitative electron microscopic immunogold labeling, our laboratory has previously reported that nerve terminal glutamate immunoreactivity is transiently altered following cocaine administration. The present study was undertaken to examine presynaptic nerve terminal glutamate immunoreactivity at shorter time points after withdrawal from cocaine. Animals received saline or cocaine for 7 days followed 3 days later by a cocaine or saline challenge. Most (>75%) cocaine‐challenged animals had a heightened locomotor response to cocaine compared to the first day of cocaine and were considered behaviorally sensitized. One day after the challenge, glutamate immunogold‐labeling was quantified in nerve terminals making asymmetrical synaptic contacts within the core and shell of the nucleus accumbens and ventral tegmental area. A single dose of cocaine did not alter the density of presynaptic nerve terminal glutamate immunoreactivity in the nucleus accumbens (NAc) or ventral tegmental area (VTA). The density of nerve terminal glutamate immunoreactivity in the shell, but not the core, was significantly increased in the animals receiving repeated cocaine. In the VTA the density of nerve terminal glutamate immunoreactivity did not change in the cocaine‐sensitized group, but was significantly increased in the nonsensitized group. The finding that repeated cocaine treatment increased glutamate nerve terminal immunolabeling within the nucleus accumbens shell, but not the core, supports the hypothesis that glutamate synapses in the core and shell are differentially sensitive to repeated cocaine administration. Overall, our study does not support a role for changes in presynaptic glutamate in the development of behavioral sensitization. Synapse 51:224–232, 2004. Published 2003 Wiley‐Liss, Inc.
Detailed distribution of neuropeptide FF receptors (NPFF1 and NPFF2) in the rat, mouse, octodon, rabbit, guinea pig, and marmoset monkey brains: A comparative autoradiographic study
Authors: Gouardères Christine , Puget Alain , Zajac Jean‐Marie
Published: December 2003

The distribution of neuropeptide FF receptors (NPFF1 and NPFF2) was analyzed throughout the central nervous system of rodents (rat, mouse, Octodon degus, and guinea pig), rabbit, and marmoset monkey brains, representing three orders of mammals. Quantitative in vitro receptor autoradiography with [125I]EYF ([125I]EYWSLAAPQRF‐NH2) and [125I]YVP ([125I]YVPNLPQRF‐NH2) as specific radioligands for NPFF2 and NPFF1 receptors, respectively, was used. The NPFF2 receptor is predominantly expressed in all species, except in the central nervous system of Octodon degus, in which it is undetectable. The density of the NPFF1 subtype is low in rat and mice, moderate in octodon, rabbit, and monkey, and relatively high in the guinea pig. The present study reveals prominent species differences in the NPFF receptors expression in the brain. The distribution pattern of NPFF2 receptors in the diencephalon and the superficial layers of the spinal cord is consistent with a hypothesized potential role for NPFF in the modulation of sensory input and opioid analgesia. In contrast, the constant presence of NPFF1 receptors in the septum, the nucleus of the tractus solitarius, and the hypothalamus suggest its participation in neuroendocrine functions. Synapse 51:249–269, 2004. © 2003 Wiley‐Liss, Inc.
Conditions for rapid sex determination in 47 avian species by PCR of genomic DNA from blood, shell‐membrane blood vessels, and feathers
Authors: Jensen Thomas , Pernasetti Flavia M. , Durrant Barbara
Published: December 2003

The ability to rapidly and reliably determine the sex of birds is very important for successful captive‐bird breeding programs, as well as for field research. Visual inspection of adult birds is sufficient for sexually dimorphic species, but nestlings and monomorphic species are difficult, if not impossible, to sex by sight only. A method for rapid extraction of gDNA from blood, shell‐membrane blood vessels, and fully grown feathers, using Chelex, and the PCR conditions for determination of sex‐specific bands in 47 species (39 genera, 21 families, and 10 orders) are described. The PCR primers used amplify a length of DNA spanning an intron in the CHD‐1 gene, which is present on both the W and Z chromosomes. The intron differs in size between the two sex chromosomes, resulting in PCR products that separate into two bands for females and a single band for males in most avian species (except ratites). Because this simple technique uses Chelex, a rapid gDNA isolation protocol, and sets of PCR primers independent of restriction enzyme digestion, birds can be accurately sexed within 5 hr of sample collection. Zoo Biol 22:561–571, 2003. © 2003 Wiley‐Liss, Inc.
Failure of a chemical spray to significantly reduce stereotypic licking in a captive giraffe
Authors: Tarou Loraine Rybiski , Bashaw Meredith J. , Maple Terry L.
Published: December 2003

The repetitive licking of nonfood substrates is a common stereotypic behavior in captive giraffes. In this study we attempted to reduce stereotypic licking in a Masai giraffe (Giraffa camelopardalis tippelskirchi) by applying a bitter chemical (marketed as a taste deterrent to prevent the unwanted licking and chewing of substrates) to the areas of the fence licked most frequently by the giraffe. We hypothesized that this treatment would reduce stereotypic licking. However, there were no significant overall changes in stereotypic licking following treatment with the chemical spray. Although licking of the treated area was observed to decrease, the behavior increased in nontreated areas. These results suggest that the underlying motivation driving the behavior was not affected by the aversive stimulus. Because stereotypic licking in giraffes may be based on a motivation to use their tongues in foraging, more effective techniques for reducing stereotypic fence‐licking in giraffes may include increasing feeding duration by increasing the quantity, processing time, or distribution range of food. Zoo Biol 22:601–607, 2003. © 2003 Wiley‐Liss, Inc.
An update on the effects of playing violent video games
Authors: Anderson Craig A
Published: December 2003

This article presents a brief overview of existing research on the effects of exposure to violent video games. An updated meta‐analysis reveals that exposure to violent video games is significantly linked to increases in aggressive behaviour, aggressive cognition, aggressive affect, and cardiovascular arousal, and to decreases in helping behaviour. Experimental studies reveal this linkage to be causal. Correlational studies reveal a linkage to serious, real‐world types of aggression. Methodologically weaker studies yielded smaller effect sizes than methodologically stronger studies, suggesting that previous meta‐analytic studies of violent video games underestimate the true magnitude of observed deleterious effects on behaviour, cognition, and affect.
Correlates of coping with perceived discriminatory experiences among African American adolescents
Authors: Scott Lionel D.
Published: December 2003

This study examined the relation of background and race‐related factors to the use of approach and avoidance strategies to cope with perceived discriminatory experiences among a sample of African American adolescents of relative affluence (n=71). Results showed that gender, family structure, socioeconomic status (SES), perceived control over discriminatory experiences, discrimination distress, and racism‐related socialization were significant correlates of coping with perceived discriminatory experiences. Results concerning gender, perceived control, and stress arousal were consistent with findings from the general adolescent stress and coping literature. Results concerning family structure, SES, and socialization suggest that certain factors may be very important for the positive adjustment of African American adolescents in the face of race‐related adversity.
Gender and identity status differences in late adolescents’ possible selves
Authors: Anthis Kristine S , Dunkel Curt S , Anderson Brian
Published: December 2003

The current study examined gender and identity status differences in late adolescents’ possible selves. The intent of the study was to clarify conflicts between theory and research on gender differences in identity by investigating the content of participants’ possible selves. Participants completed measures of identity and possible selves. The results indicated that there was a relationship between gender and the mean number of both feared and balanced interpersonally themed possible selves. The pattern of results is discussed in terms of prior findings regarding gender differences in both identity and possible selves. Suggestions for future research are also provided.
European reference values for Doppler indices of left ventricular diastolic filling
Authors: Sim M.F.Victor , Ho Shu F. , O'Mahony M.Sinead , Steward John A. , Buchalter Maurice , Burr Michael
Published: December 2003

The European Study Group on diastolic heart failure requires objective evidence of abnormal left ventricular diastolic function to establish the diagnosis of diastolic heart failure, which is common in older people. Reference values for Doppler indices of transmitral flow, used to assess left ventricular diastolic function, have not been reported for people 70 years and over in Europe. The aim of this study was to establish reference values for these Doppler indices of transmitral flow in older people. A random sample of 355 subjects aged 70 and over, living in the community underwent clinical assessment and echocardiography. Asymptomatic subjects with no cardiovascular disease and cardiovascular risk factors were identified. Measurements of five commonly used Doppler indices of transmitral flow from these subjects were obtained and reference range expressed as mean±2 standard deviations and as percentiles. We have therefore generated reference Doppler values of transmitral flow for people aged over 70 in a British population.
Physical distribution service quality in Internet retailing: service pricing, transaction attributes, and firm attributes
Authors: Rabinovich Elliot , Bailey Joseph P
Published: December 2003

This paper develops a theoretical framework and empirically investigates physical distribution service (PDS) quality by Internet retailers in their transactions with consumers. An analysis of data that measure hundreds of electronic commerce transactions along with data at the firm level shows that higher shipping and handling charges are good indicators of better PDS quality. Other transaction‐level conditions and firm‐level attributes also affect PDS quality, as measured by availability, timeliness, and reliability. Most notably, when the net price of products transacted increases, PDS reliability and availability decline. Furthermore, Internet‐retailer size is found to favor PDS availability whereas, surprisingly, newer Internet retailers exhibit a higher level of PDS availability than many of their incumbent competitors.
Menegazzia subsimilis, a widespread sorediate lichen
Authors: Bjerke Jarle W.
Published: December 2003

Studies of type specimens and other specimens of Menegazzia subsimilis and M. dissecta have shown that they are referable to the same taxon. Thus, M. dissecta is reduced to synonymy with M. subsimilis, which is characterized by lacerate soralia protruding from lobe apices or vertical lobules (protuberances), small perforations and the presence of the stictic acid complex in the medulla. It has 2-spored asci. The synonymy implies that M. subsimilis has a much wider distribution range than previously known. It is reported here from Oceania (Hawaii, Solomon Islands), Asia (Japan, Papua New Guinea, Russia), Europe (Austria, Germany, Portugal), South America (Ecuador, Peru), the Caribbean (Dominican Republic, Jamaica) and North America (Canada, USA).
The lichen genus Neofuscelia (Ascomycota, Parmeliaceae) in Italy
Authors: Giordani Paolo , Benesperi Renato , Rellini Ivano , Frati Luisa , Brunialti Giorgio , Paoli Luca , Isocrono Deborah , Elix John A.
Published: December 2003

Seven Neofuscelia species have been identified from Italy. A key to the species is provided and the distinguishing morphological and chemical characters, distribution, ecology, substratum preference and interrelationships of each are discussed. Neofuscelia perrugata is new to Italy. N. pyrenaica is new to Greece and Cyprus. New data on the distribution and ecology of N. perrugata, N. delisei and N. luteonotata are presented and these are consistent with their taxonomic rank.
Effective accumulation of polyion complex micelle to experimental choroidal neovascularization in rats
Authors: Ideta Ryuichi , Yanagi Yasuo , Tamaki Yasuhiro , Tasaka Fumitaka , Harada Atsushi , Kataoka Kazunori
Published: December 2003

Exudative age‐related macular degeneration, characterized by choroidal neovascularization (CNV), is a major cause of visual loss. In this study, we examined the distribution of the polyion complex (PIC) micelle encapsulating FITC‐P(Lys) in blood and in experimental CNV in rats to investigate whether PIC micelle can be used for treatment of CNV. We demonstrate that PIC micelle has long‐circulating characteristics, accumulating to the CNV lesions and is retained in the lesion for as long as 168 h after intravenous administration. These results raise the possibility that PIC micelles can be used for achieving effective drug targeting to CNV.
Absence of mechanical allodynia and Aβ‐fiber sprouting after sciatic nerve injury in mice lacking membrane‐type 5 matrix metalloproteinase
Authors: Komori Kiyoshi , Nonaka Takahiro , Okada Akiko , Kinoh Hiroaki , Hayashita-Kinoh Hiromi , Yoshida Nobuaki , Yana Ikuo , Seiki Motoharu
Published: December 2003

Matrix metalloproteinases (MMPs) are a family of endopeptidases that degrade extracellular matrix components. Membrane‐type 5 MMP (MT5‐MMP/MMP‐24) was identified as neuron‐specific, and is believed to contribute to neuronal circuit formation and plasticity. To elucidate its function in vivo, we have generated mice lacking MT5‐MMP by gene targeting. MT5‐MMP‐deficient mice were born without obvious morphological abnormalities. No apparent histological defects were observed in the nervous system either. However, MT5‐MMP‐deficient mice did not develop neuropathic pain with mechanical allodynia after sciatic nerve injury, though responses to acute noxious stimuli were normal. Neuropathic pain induced by peripheral nerve lesions is known to accompany structural reorganization of the nervous system. Intraneural injection of cholera toxin B subunit, a transganglionic tracer, into the injured sciatic nerve of wild‐type mice revealed that the myelinated Aβ‐fiber primary afferents sprouted from laminae III–VI of the dorsal horn of the spinal cord and invaded lamina II. However, no such sprouting and invasion of Aβ‐fibers were observed in MT5‐MMP‐deficient mice. These findings suggest that MT5‐MMP is essential for the development of mechanical allodynia and plays an important role in neuronal plasticity in this mouse model.
Effective reduction of antigenicity of hen egg lysozyme by site‐specific glycosylation
Authors: Usui Masakatsu , Shimizu Toshiaki , Goto Yasuko , Saito Akira , Kato Akio
Published: December 2003

Various mutant lysozymes were constructed by genetic modification and secreted in yeast expression system to evaluate the changes in the antigenicity of hen egg lysozyme (HEL). Although Arg68, the most critical residue to antigenicity of HEL, was substituted with Gln, the binding of monoclonal antibodies (mAbs) with the mutant lysozyme did not critically reduce, remaining 60% of the binding with mAb. In contrast, glycosylated mutant lysozyme G49N whose glycine was substituted with asparagine dramatically reduced the binding with mAb. The oligomannosyl type of G49N lysozyme reduced binding with mAb to one‐fifth, while the polymannosyl type of G49N lysozyme completely diminished the binding with mAb. This suggests that the site‐specific glycosylation of lysozyme in the interfacial region of lysozyme–antibody complex is more effective to reduce the antigenicity than the mutation of single amino acid substitution in the interfacial region.
Biophysical characterization of hepatitis C virus core protein: implications for interactions within the virus and host
Authors: Kunkel Meghan , Watowich Stanley J
Published: December 2003

A primary function of the hepatitis C virus (HCV) core protein is to package the viral genome within a nucleocapsid. In addition, core protein has been shown to interact with more than a dozen cellular proteins, and these interactions have been suggested to play critical roles in HCV pathogenesis. A more complete knowledge of the biophysical properties of the core protein may help to clarify its role in HCV pathogenesis and nucleocapsid assembly and provide a basis for the development of novel anti‐HCV therapies. Here we report that recombinant mature core protein exists as a large multimer in solution under physiological conditions. Far‐UV circular dichroism (CD) experiments showed that the mature core protein contains stable secondary structure. Studies with truncated core protein demonstrated that the C‐terminal region of the core protein is critical for its folding and oligomerization. Intrinsic fluorescence spectroscopy and near‐UV CD analysis indicated that the tryptophan‐rich region (residues 76–113) is largely solvent‐exposed and not likely responsible for multimerization of the mature core protein in vitro.
Two Arabidopsis thaliana genes encode functional pectin methylesterase inhibitors1
Authors: Raiola A , Camardella L , Giovane A , Mattei B , De Lorenzo G , Cervone F , Bellincampi D
Published: December 2003

We have identified, expressed and characterized two genes from Arabidopsis thaliana (AtPMEI‐1 and AtPMEI‐2) encoding functional inhibitors of pectin methylesterases. AtPMEI‐1 and AtPMEI‐2 are cell wall proteins sharing many features with the only pectin methylesterase inhibitor (PMEI) characterized so far from kiwi fruit. Both Arabidopsis proteins interact with and inhibit plant‐derived pectin methylesterases (PMEs) but not microbial enzymes. The occurrence of functional PMEIs in Arabidopsis indicates that a mechanism of controlling pectin esterification by inhibition of endogenous PMEs is present in different plant species.
Tyrosine phosphorylation of BIT on photic stimulation in the rat retina
Authors: Hamada Juri , Okumura Nobuaki , Inagaki Miho , Taniguchi Hiroyuki , Nakahata Yasukazu , Sano Shin-ichiro , Nagai Katsuya
Published: December 2003

BIT is a transmembrane glycoprotein with three immunoglobulin‐like domains in its extracellular region and tyrosine phosphorylation sites in its cytosolic region. We have previously shown that BIT was tyrosine phosphorylated in the hypothalamic suprachiasmatic nucleus in response to light exposure during the dark period, and suggested that it was involved in the light entrainment of the circadian clock. To further investigate the function of BIT in the nervous system, we examined the effect of photic stimulation on its tyrosine phosphorylation in the rat retina. It was found that the tyrosine phosphorylation level of BIT in the retina was higher in the light period than in the dark period. In addition, a light stimulation during the dark period resulted in a rapid phosphorylation of BIT and a subsequent association of BIT with SHP‐2. The phosphorylation state was quickly reverted when the light was turned off. The light‐dependent phosphorylation of BIT was also observed in isolated cultured retinas, and this was blocked by a specific Src‐family inhibitor, PP‐2. Immunohistochemical study showed that BIT was highly enriched in the inner and outer plexiform layers in the retina, where the immunoreactivity to anti‐SHP‐2 antibody was also detected. These results suggest that tyrosine phosphorylation of BIT is involved in neuronal transmission in the retina.
Long‐term changes in dissolved oxygen concentrations in the ocean caused by protracted global warming
Authors: Matear R. J. , Hirst A. C.
Published: December 2003

In the Earth's geological record massive marine ecological change has been attributed to the occurrence of widespread anoxia in the ocean [Jahren, 2002; White, 2002; Wignall and Twitchett, 1996]. Climate change projection till the end of this century predict a 4 to 7% decline in the dissolve oxygen in the ocean [Bopp et al., 2002; Matear et al., 2000; Plattner et al., 2001; Sarmiento et al., 1998] suggesting the potential for global warming to eventually drive the deep ocean anoxic. To examine the multicentury impact of protracted global warming on oceanic concentrations of dissolved oxygen, we use a climate system model and a low‐order oceanic biogeochemical model. The models are integrated for an atmospheric equivalent CO2 concentration, which is specified to triple according to a standard scenario from the late nineteenth to the late twenty‐first century, and then is subsequently held constant at that elevated level for an additional 6 centuries. For the present day, the model successfully reproduced the large‐scale features of the dissolved oxygen field in the ocean. In the global warming simulation, the physical model displays marked changes in high‐latitude oceanic stratification and overturning, including near‐cessation of deep water renewal for depths greater than about 1.5 km during the period of elevated stable CO2 concentration. Our model predicts a decline in oxygen concentration through most of the subsurface ocean. Concentration changes in the thermocline waters result mainly from solubility changes in the upstream source waters, while changes in the deep waters result mainly from lack of ventilation and ongoing consumption of oxygen by remineralization of sinking particulate organic matter. Changes in the upper 2 km of the ocean generally show signs of equilibration by the end of the integration, but at greater depths, there occurs a slow but steady decline through to the end of the integration. By the end of the integration, we simulate a doubling of the volume of hypoxic water (less than 10 μmol/kg) in the thermocline of the eastern equatorial Pacific Ocean. During the integration deep ocean oxygen concentrations generally decline by between 20 and 40%, but, significantly, no extensive deep ocean anoxia develops during the period of integration, nor does it appear that it would likely do so for at least a further 4000 years of integration. Subsurface oxygen decline is moderated by an overall reduction in export production of particulate organic matter, which reduces oxygen consumption in the ocean interior due to the remineralization of this material.
Regularized estimation of vertical total electron content from Global Positioning System data
Authors: Arikan F. , Erol C. B. , Arikan O.
Published: December 2003

A novel regularization technique which can combine signals from all Global Positioning System (GPS) satellites for a given instant and a given receiver is developed to estimate the vertical total electron content (VTEC) values for the 24‐hour period without missing any important features in the temporal domain. The algorithm is based on the minimization of a cost function which also includes a high pass penalty filter. Optional weighting function and sliding window median filter are added to enrich the processing and smoothing of the data. The developed regularized estimation algorithm is applied to GPS data for various locations for the solar maximum week of 23–28 April 2001. The parameter set that is required by the estimation algorithm is chosen optimally using appropriate error functions. This robust and optimum parameter set can be used for all latitudes and for both quiet and disturbed days. It is observed that the estimated TEC values are in general accordance with the TEC estimates from other global ionospheric maps, especially for quiet days and midlatitudes. Owing to its 30 s time resolution, the regularized VTEC estimates from the developed algorithm are very successful in representation and tracking of sudden temporal variations of the ionosphere, especially for high latitudes and during ionospheric disturbances.
Anthropogenic increase of oceanic pCO2 in the Barents Sea surface water
Authors: Omar Abdirahman , Johannessen Truls , Kaltin Staffan , Olsen Are
Published: December 2003

We evaluate the change of surface water CO2 partial pressure (pCO2sw) in the Barents Sea (BS) between 1967 and 2000–2001. We use temperature (T) data collected during a survey in the BS in 1967 and a relationship between surface water CO2 mole fraction and T identified by Kelley [1970] to estimate the 1967 pCO2sw. On the basis of data of total inorganic carbon, alkalinity, T, and salinity (S) collected during two recent surveys in the BS, we compute pCO2sw of 2000–2001. In order to be able to account for natural variations of pCO2sw we develop an empirical predictive equation for pCO2sw through multivariable linear regression with the 2000–2001 data of T, S, and apparent oxygen utilization (AOU). This relationship is applied to the 1967 T, S, and AOU data, and the output is compared to the 1967 estimates of pCO2sw. The difference is ascribed to net uptake of excess CO2. The computations show a pCO2sw increase of 42 ± 31 μatm between 1967 and 2000–2001, which is due to uptake of excess CO2. The pCO2 increase was uniformly distributed in the BS, suggesting that the uptake of the excess carbon from the atmosphere took place outside the BS rather than across the sea‐air interface within the BS. Moreover, the computed increase was comparable to the increase in atmospheric pCO2 (∼47 μatm), and thus the pCO2 gradient across the sea‐air interface has remained nearly unchanged relative to 1967.
Radar investigations of breaking water waves at low grazing angles with simultaneous high‐speed optical imagery
Authors: Sletten Mark A. , West Jim C. , Liu Xinan , Duncan Jim H.
Published: December 2003

This paper describes the results of radar scattering experiments carried out at the wavetank facility at the University of Maryland, College Park. Spilling and plunging breakers with a water wavelength of approximately 80 cm were generated through dispersive focusing of a chirped wave packet, and were then imaged with a high‐speed camera in conjunction with a laser sheet. Simultaneously, the radar backscatter generated by the breakers when viewed with an “up‐wave” look direction was measured by an ultrawideband, dual‐polarized, X‐band radar with a range resolution of approximately 4 cm. The nominal grazing angle of the radar was 12°. In addition to providing both quantitative profiles of the evolving water surface and the corresponding ultrahigh resolution radar backscatter, this experimental setup also included a moving instrument carriage that allowed the sensors to follow the breakers throughout their entire evolution. Numerical scattering simulations that use the measured surface profiles as inputs were also conducted in order to further dissect the scattering mechanism. An analysis of the results shows that for the spilling breaker, over 90% of the horizontally (HH) polarized radar backscatter is generated during the initial stage of breaking by the small bulge near the wave crest. For vertical (VV) polarization, the crest bulge produces about 60% of the total backscattered energy. For both polarizations, the Doppler velocity associated with this energy is very close to that of the phase speed of the dominant wave in the water wave packet. For VV, the remainder of the backscattered energy is generated by the turbulent, postbreaking surface, and in fact a close correlation is observed between increases in the VV backscatter amplitude and the shedding of vortex ripples after the wave breaks. For the plunging breaker, the initial feature on the crest (an overturning jet) generates a lower percentage of the total backscattered energy. For the spilling breaker, agreement between the experimental and numerical results is good, particularly in the Doppler domain. The simulations also indicate uncertainty in the polarization ratio measurements that is related to multipath scattering. To the extent that they can be applied to the open ocean, these results can serve as a guide for the development of future breaker models.
A tomographic image of the shallow crustal structure in the Eastern Marmara
Authors: Karabulut Hayrullah , Özalaybey Serdar , Taymaz Tuncay , Aktar Mustafa , Selvi Oğuz , Kocaoğlu Argun
Published: December 2003

We present a 2‐D tomographic seismic velocity image in eastern Marmara region along a N‐S trending 120‐km long seismic refraction profile, which traverses the northern branches of North Anatolian Fault (NAF) and tectonically active Çınarcık Basin, in the Sea of Marmara. The 2‐D velocity model, which is constrained down to upper crustal depth of 7 km, shows significant heterogeneities in the upper crust displayed by well‐constrained velocity anomalies. The seismicity observed following the 17 August, 1999 İzmit earthquake concentrates in three distinct zones and takes place near the inferred low velocity zones and below high velocity anomalies obtained from tomographic inversion. This correlation is interpreted as a result of intensely sheared zones of deformation imposed by strike‐slip motion of the northern branches of the North Anatolian Fault.
Atmospheric deposition of nutrients to the Atlantic Ocean
Authors: Baker A. R. , Kelly S. D. , Biswas K. F. , Witt M. , Jickells T. D.
Published: December 2003

The role of atmospheric deposition of iron, nitrogen and phosphorus in supplying nutrients to marine systems has been described, individually, in previous works. Here we examine atmospheric dry deposition of all these nutrients simultaneously, using samples collected during two meridional transects of the Atlantic Ocean. We find that, in line with previous work, desert dust supplies excess iron to the water column. However, primary production promoted by aerosol nitrogen can be sufficient to consume all of the soluble aerosol iron input in some situations. Aerosol N:P is universally very high, so that aerosol is always deficient in P relative to phytoplankton requirements. Nitrogen fixation stimulated by any excess atmospheric iron supply and phytoplankton utilisation of atmospheric nutrient inputs will therefore tend to drive the ecosystem towards P limitation. This emphasises the need to study the biogeochemical impact of atmospheric nutrient deposition in an integrated manner.
Implications of Jovian X‐ray emission for magnetosphere‐ionosphere coupling
Authors: Cravens T. E. , Waite J. H. , Gombosi T. I. , Lugaz N. , Gladstone G. R. , Mauk B. H. , MacDowall R. J.
Published: December 2003

The first observations of Jupiter made by the Chandra X‐Ray Observatory revealed a powerful X‐ray aurora located in the polar caps. The X‐ray emission exhibited a 40‐min periodicity. Such 40‐min periodicities have previously been seen in energetic particle fluxes and in Jovian radio emission. This paper develops scenarios in which the X‐ray emission is produced by energetic heavy ion precipitation, either on open field lines connecting to the solar wind or on closed field lines reaching to the outer magnetosphere. In order to produce enough X‐ray power, both scenarios require the existence of field‐aligned electric fields located somewhere between the ionosphere and the magnetosphere, most likely at a radial distance of a few Jovian radii. The potential needed for solar wind ions to produce the observed X‐rays is about 200 kV and the potential needed for the magnetospheric ions is at least 8 MV. Protons and helium ions are also accelerated by the potential and should produce an intense ultraviolet aurora. Downward electrical current is carried by the precipitating ions and also by upwardly accelerated secondary electrons produced by the primary ion precipitation. The estimated downward Birkeland current is about 1000 MA for the solar wind case and is about 10 MA for the magnetospheric case. For the magnetosphere scenario, this observed current represents part of the “return” current portion of the magnetospheric circuit associated with the departure of the mass‐loaded magnetospheric plasma from corotation. The auroral X‐ray emission maps at least part of this return current in the polar cap, whereas the main oval, produced by electron precipitation, is thought to map the region of upward Birkeland currents. The accelerated secondary electrons could be responsible for the periodic radio emission (i.e., QP‐40 bursts).