bluuebunny/crossref_metadata_2025_split huggingface dataset:
Targeting human 8‐oxoguanine glycosylase to mitochondria of oligodendrocytes protects against menadione‐induced oxidative stress
Authors: Druzhyna Nadiya M. , Hollensworth Scott B. , Kelley Mark R. , Wilson Glenn L. , Ledoux Susan P. 
Published: April 2003

AbstractWithin the central nervous system (CNS), there is a differential susceptibility among cell types to certain pathological conditions believed to involve oxidative stress. Oligodendrocytes are extremely sensitive to oxidative stress, which correlates with a decreased ability to repair damage in mitochondrial DNA (mtDNA), as we have shown previously. To determine whether there is a causal relationship, studies were carried out to correct the deficit in repair of the oxidative damage in mtDNA in cultured oligodendrocytes. A vector containing a mitochondrial transport sequence (MTS) upstream of the sequence for human 8‐oxoguanine‐DNA glycosylase (OGG) was transfected into the cells. The efficiency of transfection and the localization of recombinant protein were determined by fluorescence microscopy and by Western blot analysis. Subsequent mtDNA repair studies, employing 100 μM menadione to produce reactive oxygen species, showed a significant enhancement in repair of oxidative lesions in mtDNA of MTS‐OGG transfected oligodendrocytes compared with cells transfected with vector only. Experiments were also conducted to determine the effect of changing mtDNA repair capacity on menadione‐induced apoptosis in oligodendrocytes. These experiments show that targeting the OGG repair enzyme to mitochondria reduces the release of cytochrome c from the intermitochondrial space and the activation of caspase 9 in oligodendrocytes after exposure to menadione. Therefore, targeting of DNA repair enzymes to mitochondria appears to be a viable approach for the protection of cells against some of the deleterious effects of oxidative stress. GLIA 42:370–378, 2003. © 2003 Wiley‐Liss, Inc.
Interactions of Atomic Iron Cation with Pyridine and Benzene: A Theoretical Study on an Unresolved Controversy of Bond Energies and Electronic Ground‐State Structures
Authors: Diefenbach Martin , Trage Claudia , Schwarz Helmut 
Published: April 2003

AbstractThe binding energies, geometries, and electronic structures of cationic ironbenzene and ironpyridine complexes have been studied by the two hybrid DFT‐HF approaches mPW1PW91 and B3LYP, as well as the AQCC and MR‐AQCC extension. The AQCC results confirm the experimental binding energies derived from threshold‐CID experiments reported by Meyer et al., and Rodgers et al. as well as the previously reported C2v‐symmetric quartet ground state of ironbenzene. The ironpyridine complex is coordinated via the N‐atom lone‐pair and has a sextet ground state. Bond energies determined by the kinetic method apparently yield a dissociation energy corresponding to the first excited quartet ironpyridine complex. Both DFT methods fail to predict the correct ground state for cationic iron pyridine.
The Structure of N1‐Hydroxylophine N3‐Oxide (=1‐Hydroxy‐2,4,5‐ triphenyl‐1H‐imidazole 3‐Oxide) in the Solid State
Authors: Sánchez‐Migallón Ana , de la Hoz Antonio , López Concepción , Claramunt Rosa M. , Infantes Lourdes , Motherwell Sam , Shankland Kenneth , Nowell Harriott , Alkorta Ibon , Elguero José 
Published: April 2003

AbstractThe crystal structure of 1‐hydroxy‐2,4,5‐triphenyl‐1H‐imidazole 3‐oxide (1) has been determined from laboratory X‐ray powder‐diffraction data. The two independent molecules in the asymmetric unit form chains via OH⋅⋅⋅O hydrogen bonds related by a twofold screw axis. One of the O⋅⋅⋅O distances is extremely short (2.32(1) and 2.43(1) Å). Solid‐state NMR spectroscopy (CPMAS) combined with calculation of absolute shieldings (GIAO/B3LYP/6‐31G*) allowed us to determine that the compound behaves as if the OH⋅⋅⋅O hydrogen bond has the proton in the middle (single‐well potential), resulting in the near identity of both 15N‐NMR signals.
Towards a Complete Description of a Polymorphic Crystal: The Example of Perylene
Authors: Botoshansky Mark , Herbstein Frank H. , Kapon Moshe 
Published: April 2003

AbstractCrystal structures of the two polymorphs of perylene have been determined at low temperatures (150 and 200 K), and the molecular geometry was compared with earlier crystallographic and NMR measurements. Cell dimensions have been measured for both polymorphs over the ranges 150–320 K for (EI‐β) and 150–420 K for (EII‐α). Combination of thermodynamic and crystallographic measurements has permitted inference of pressuretemperature phase diagrams for perylene and pyrene that are compatible with available measurements up to ca. 50 kbar. Perylene and pyrene are both enantiotropic systems, while phenazine appears to be monotropic.
Perception of correlated attributes involving African–American and white females' faces by 10‐month‐old infants
Authors: Levy Gary D. 
Published: April 2003

AbstractThirty‐two 10‐month‐olds were habituated to stimuli containing an African–American female face or a white female face paired with a specific object. Test stimuli maintained or violated habituation stimuli pairings (i.e. categories). Results add to an emerging literature showing that 10‐month‐olds perceive categories of social information based on detection of correlated attributes. Copyright © 2003 John Wiley & Sons, Ltd.
On asymmetric coverings and covering numbers
Authors: Applegate David , Rains E. M. , Sloane N. J. A. 
Published: April 2003

AbstractAn asymmetric covering ${\cal D}(n,R)$ is a collection of special subsets S of an n‐set such that every subset T of the n‐set is contained in at least one special S with $|S| - |T| \le R$. In this paper we compute the smallest size of any ${\cal D}(n,1)$ for $n \le 8.$ We also investigate “continuous” and “banded” versions of the problem. The latter involves the classical covering numbers $C(n,k,k-1)$, and we determine the following new values: $C(10,5,4) = 51$, $C(11,7,6) =84 $, $C(12,8,7) = 126 $, $C(13,9,8)= 185$, and $C(14,10,9) = 259$. We also find the number of non‐isomorphic minimal covering designs in several cases. © 2003 Wiley Periodicals, Inc. J Combin Designs 11: 218–228, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jcd.10022
New families of strongly regular graphs
Authors: Ionin Yury J. , Kharaghani Hadi 
Published: April 2003

AbstractWe apply symmetric balanced generalized weighing matrices with zero diagonal to construct four parametrically new infinite families of strongly regular graphs. © 2003 Wiley Periodicals, Inc. J Combin Designs 11: 208–217, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jcd.10038
Surface Immobilization of Bioactive Molecules on Polyurethane for Promotion of Cytocompatibility to Human Endothelial Cells
Authors: Gao Changyou , Guan Jianjun , Zhu Yabin , Shen Jiacong 
Published: April 2003

AbstractCytocompatible polymers are of increasing importance for tissue engineering scaffolds and implanted devices. Polyurethane (PU) membranes were modified by grafting polymerization of methacrylic acid (MAA) initiated by UV light and further covalent immobilization of gelatin or arginine‐glycine‐aspartic (RGD) peptide using 1‐ethyl‐3‐(3‐dimethylaminopropyl) carbodiimide hydrochloride as a condensing agent. The immobilization of gelatin or RGD peptide was confirmed by FTIR attenuated total reflection (ATR) spectroscopy and X‐ray photoelectron spectroscopy (XPS). The results for endothelial cells cultured in vitro proved that the PU membrane modified with gelatin or RGD peptide had better cytocompatibility than the control PU or the PMAA grafted PU membrane.
ATR‐FTIR spectra of PU‐graft‐PMAA (a), PU‐graft‐PMAA‐graft‐RGD (b), and their subtraction result (c). The PMAA grafting degree is 21.56 × 10−2 mg/cm2.magnified imageATR‐FTIR spectra of PU‐graft‐PMAA (a), PU‐graft‐PMAA‐graft‐RGD (b), and their subtraction result (c). The PMAA grafting degree is 21.56 × 10−2 mg/cm2.
Syntheses of polymeric cobalt dinitrogen complexes and reduction of the coordinated nitrogen
Authors: Koide Mikio , Kato Masayuki , Tsuchida Eishun , Kurimura Yoshimi 
Published: April 2003

AbstractPolymeric cobalt dinitrogen complexes were synthesized by two different methods: by the ligand substitution reaction of polymers 5a – c and 6a – c, containing 4‐diphenylphosphinophenylethylene units (3) or 4‐diphenylphosphinomethylphenylethylene units (4), respectively, with hydridodinitrogentris(triphenylphosphine)cobalt(I) (CoH(N2)(PPh3)3), or by the direct reaction of tris(acetylacetonato)cobalt(III) with triphenylphosphine, the polymers 5a – c or 6a – c, and triisobutylaluminium under nitrogen. The intensity of the v band in the IR spectrum of the polymeric dinitrogen complex was found to be about four times as that of CoH(N2)(PPh3)3. Ammonia was formed after hydrolysis of the complex, which was prepared by mixing a tetrahydrofuran solution of naphthaline, lithium, and titanium tetrachloride with the polymeric dinitrogen complex. The yields of ammonia in the case of the polymeric complexes were high in comparison with that obtained with CoH(N2)(PPh3)3. The highest yields of ammonia were obtained when a mole ratio [P̄]/[Co] < 1 ([P̄] is the concentration of phosphino groups in the polymer and [Co] is that of Co in CoH(N2)(PPh3)3), a temperature of −20°C, and a reaction time of 1 h were applied.
Structure of Cu/poly(L‐glutamic acid) complex
Authors: Koide Mikio , Tsuchida Eishun , Kurimura Yoshimi 
Published: April 2003

AbstractThe structure of the Cu/poly(L‐glutamic acid), (Cu/1), complex was studied by magnetic susceptibility, circular dichroism, electron spin resonance, and light scattering measurements. Cu/1 (pH 5,5) formed a binuclear complex by stabilizing the helix structure using [1]/[Cu] = 10. When the amount of Cu ions became small, the structure of the Cu/1 complex changed from a binuclear complex to a mononuclear one. Furthermore, it was obvious that an intermolecular bridged complex of Cu/1 was formed at pH = 5,5, because the molecular weight of the Cu/1 complex was about 13 fold that of 1, when the mixing mole ratio [1]/[Cu] was 10.
Polymerisation via macrozwitterions, 3. Ethyl and butyl cyanoacrylates polymerised by benzyldimethyl, triethyl and tribenzylamines
Authors: Johnston David Samuel , Pepper David Charles 
Published: April 2003

AbstractAnionic polymerisations of ethyl and butyl cyanoacrylates (ECA and BCA) in THF, initiated by benzyldimethylamine (BDMA), triethylamine (TEA) and tribenzylamine (TBA) were studied between 50 and −78°C. Initiator utilisation was very low, and polymer molecular weights correspondingly high, though believed to be depressed by acid impurities in the monomer samples. Conversion curves reached internal 1st order kinetics, almost instantaneously when the initiator was BDMA, more slowly with TEA, and only after a long acceleration period with TBA, which gave overall rates some two orders of magnitude lower than those induced by the other amines. With BCA initiated by BDMA or TEA, the rate constants increased as reaction temperature was lowered. A general kinetic scheme is suggested, postulating no intrinsic termination reactions, and complex initiation processes, which according to the nature of amine and monomer may involve either one or two pre‐initiation equilibria.
Mechanischer Scherabbau von Polymeren in Lösung mittels turbulenter Strömung, 1. Kinetik, Molekulargewichtsabhängigkeit und Frage des Bruchmechanismus
Authors: Müller Hans Georg , Klein Joachim 
Published: April 2003

AbstractThe mechanical shear degradation of poly(decyl methacrylate) with weight average molecular weights 1,0·106 ≤ M̄w ≤ 1,7·106, and molecular polydispersity ratio M̄w/M̄n = 5 in dilute solutions is studied in turbulent flow as a function of molecular weight using a special apparatus consisting of two vessels connected by a capillary. Shear stress and shear rate remained constant during degradation. The rate of degradation was followed up by molecular weight distribution curves using gel permeation chromatography and described by −dci/dt = ki·cn, i being a high molecular weight species of the distribution. The reaction was found to be of the first order (n = 1) independent of solvent and of capillary length. Rate constants ki in the molecular weight range from 3,2·106 to 13,5·106 proved to be proportional to the hydrodynamic volume of the polymer molecules expressed in terms of the product of intrinsic viscosity and molecular weight [η]i·Mi. This corresponds to a linear relationship between ki and Mi1,75. Additional experiments show that this type of dependence on molecular weight holds only for turbulent flow; in laminar flow the result of the literature could be confirmed that there is a linear relation between ki and Mi1. Both results are independent of capillary length. As to the mechanism of breakage in turbulent flow it seems that in one step each macromolecule is broken simultaneously into several smaller parts.
Application of electrostatic persistence length to polyelectrolyte solutions
Authors: Miyamoto Shigeaki 
Published: April 2003

AbstractThe effects of added simple salt and polyion charge on the chain flexibility of an alternating copolymer of isobutyl vinyl ether and maleic acid are analyzed. The persistence length of this polymer in aqueous NaCl solution is calculated from sedimentation and viscosity data on the basis of a worm‐like chain model. It is found that this polymer is in the state of a highly expanded conformation at low ionic strength, exhibiting a semi‐rigid macromolecular behaviour and that it behaves like a rather coiled polymer with small persistence length at high salt concentration. The electrostatic persistence length calculated from the theory of Fixman et al. shows a \documentclass{article}\pagestyle{empty}\begin{document}$ 1/\sqrt {C_{\rm s} } $\end{document}‐dependence on added salt concentration Cs.
Surface Functionalization of Silica with 2‐Vinylfuran by Cationic Polymerization
Authors: Höhne Susanne , Spange Stefan 
Published: April 2003

AbstractCationic surface polymerization of 2‐vinylfuran with chlorotriphenylmethane as initiator has been used for the functionalization of silica particles. The influence of monomer/initiator ratio and temperature on grafting efficiency, yield, and degree of grafting has been investigated. Grafting efficiency is a significant function of temperature and monomer/initiator ratio, because crosslinking reactions between cationically active chains increases the amount of the immobilized polyvinylfuran fraction. Thus, larger initiator concentrations on the silica cause higher polymer content on the surface. Polymer structure elucidation and surface properties are analyzed by means of solid‐state NMR spectroscopy, UV‐vis spectroscopy, BET – measurements, and scanning electron microscopy.
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The Influence of the Nature of the Catalytic System on Zirconocene‐Catalyzed Polymerization of Alkyl Methacrylates
Authors: Karanikolopoulos Giorgos , Batis Christos , Pitsikalis Marinos , Hadjichristidis Nikos 
Published: April 2003

AbstractThree non‐bridged dimethylzirconocene complexes; i.e., bis(η5‐cyclopentadienyl)dimethylzirconium (1), bis(η5‐tert‐butyl‐cyclopentadienyl)dimethylzirconium (2), bis(η5‐indenyl)dimethylzirconium (3), and the chiral zirconocene rac‐ethylenebis(η5‐indenyl)dimethylzirconium (4) were synthesized and used as catalysts for the polymerization of methyl methacrylate, MMA, combined with tris(pentafluorophenyl)borate (A) or tetrakis(pentafluorophenyl)borate dimethylanilinum salt (B) in the presence of ZnEt2. The evolution of the polymerization characteristics; i.e., molecular weight, molecular‐weight distribution, and yield were examined for the above systems. The influence of the nature of the solvent was also investigated. The aggregation behavior, the steric hindrance, and the lipophilicity of the active catalytic systems are the most important parameters determining the polymerization characteristics. The tacticity of the products is reported and the influence of the catalyst structure is discussed. Finally, the polymerization of other methacrylates (alkyl = butyl, hexyl, decyl, stearyl, and sec‐butyl), was conducted and the effect of the nature of the alkyl ester group on the molecular and structural characteristics was established.Plots of yield vs Mw for the polymerization of MMA with the catalytic systems: Cp2ZrMe2/B(C6F5)3, 1/A (▵); (ButCp)2ZrMe2/B(C6F5)3, 2/A (▿); Ind2ZrMe2/B(C6F5)3, 3/A (□); and rac‐Et(Ind)2ZrMe2/B(C6F5)3, 4/A (⋄).magnified imagePlots of yield vs Mw for the polymerization of MMA with the catalytic systems: Cp2ZrMe2/B(C6F5)3, 1/A (▵); (ButCp)2ZrMe2/B(C6F5)3, 2/A (▿); Ind2ZrMe2/B(C6F5)3, 3/A (□); and rac‐Et(Ind)2ZrMe2/B(C6F5)3, 4/A (⋄).
Synthesis, Characterization and Ionic Conductive Properties of Phosphorylated Chitosan Membranes
Authors: Wan Ying , Creber Katherine A. M. , Peppley Brant , Bui V. Tam 
Published: April 2003

AbstractPhosphorylated chitosan membranes were prepared from the reaction of orthophosphoric acid and urea on the surface of chitosan membranes in N,N‐dimethylformamide. Their ionic conductivity in the wet state was investigated. Chemical modifications contributed to improved ionic conductivities of the chitosan membranes. Compared to the unmodified chitosan membranes, it was found that hydrated phosphorylated chitosan membranes with an appropriate phosphorus content showed an increasing ionic conductivity of about one order of magnitude. The phosphorylation reaction mechanism was explained based on 13C and 31P NMR measurements. It was also observed that the crystallinity of the phosphorylated chitosan membranes and the corresponding swelling indices were changed pronouncedly, but these membranes did not lose either their tensile strength or thermal stability to a significant degree in comparison with the unmodified chitosan membranes.Possible reaction mechanism for preparation of phosphorylated chitosan membranes.magnified imagePossible reaction mechanism for preparation of phosphorylated chitosan membranes.
Nanostructures Developed from Semi‐Interpenetrating Polymer Network Structures
Authors: Jain Sachin H. , Murata Kazutaka , Anazawa Takanori 
Published: April 2003

AbstractMorphology development from a semi‐interpenetrating polymer network structure (semi‐IPN structure), induced by first‐stage photocuring and aided by annealing, is investigated in a binary blend of a photocurable polymer (2,2‐bis(4‐(acryloxydiethoxy)phenyl)propane; BPE4), and a linear polymer (polysulfone; PSU). A blend with a miscible semi‐IPN structure is produced by photocuring below the glass transition temperature (Tg) of the homogenous mixture of BPE4 and PSU, and is then annealed and post‐cured at a higher temperature. The investigation reveals that the phase structures, which can be controlled by appropriately tuning the annealing temperature, range from BPE4‐rich domain structures, through interconnected structures, to PSU‐rich domain structures. The BPE4‐rich domains are connected linearly to form an interconnected structure. The BPE4‐rich and PSU‐rich domains are restricted to the nanometre scale, with sizes of less than 100 nm over almost the entire operating range of annealing temperatures and compositions. By adjusting the degree of the crosslinking in the semi‐IPN structures, the characteristic length scale of the phase‐separated structures can be varied. The mechanical properties (tensile strength and modulus) are at a maximum in the blend with the interconnected structure, due to the high conversion of BPE4 and the strong interfacial adhesion between the two phases, supported by the stability of the morphology resulting from the annealing.Effect of annealing temperature on conversion of BPE4 in the blend with 50 wt.‐% PSU.magnified imageEffect of annealing temperature on conversion of BPE4 in the blend with 50 wt.‐% PSU.
A source of screw dislocation on polyethylene single crystals
Authors: Hirai Nishio 
Published: April 2003

AbstractSpiral structures on lamellar single crystals of polyethylene have been ascribed to screw dislocation. Several photographs are shown which seems to verify the possibility of origination of the screw dislocations due to the collision of two growing single crystals. This mechanism accounts for the following facts often found in these spiral structures. (1) Spiral structures often grow from the intersection of two single crystals. (2) The distances from the center of spirals to the nearest edges of the two crystals are approximately equal to each other. (3) Centers of the spirals are often located on the diagonal of the bottom single crystal on which they grew. (4) Daughter crystals formed on a contour line farther from the center of the mother crystal are smaller.
Environmental and socioeconomic multivariate analysis of the primary economic sector of Mexico
Authors: Beltrán Morales L. F. , García‐Rodríguez F. , Borges Contreras J. , Sánchez‐Mota G. , Ortega Rubio A. 
Published: April 2003

AbstractCanonical correspondence analyses were made for the primary economic sector of all 32 Mexican states. Environmental, social and economic indicators were considered in the analyses. Four homogeneous units, fisheries, forestry, agriculture and anthropogenic aptitude, were identified. Coastal states showed a higher contribution to the gross national product (GNP) than noncoastal states. Jalisco had the highest contribution to the GNP. Our analysis represents a useful tool to describe and arrange homogeneous state groups inside the country. This ordering will be useful to develop national strategies, both socioeconomic and environmental. We hope this kind of analysis will be useful for the decision makers not only in Mexico, but also in other countries that use this innovative approach. Copyright © 2003 John Wiley & Sons, Ltd. and ERP Environment
Basolateral Ca2+‐dependent K+‐channels play a key role in Cl—secretion induced by taurodeoxycholate from colon mucosa
Authors: Moschetta Antonio , Portincasa Piero , Debellis Lucantonio , Petruzzelli Michele , Montelli Roberta , Calamita Giuseppe , Gustavsson Pontus , Palasciano Giuseppe 
Published: April 2003

Abstract The diarrhea associated with malabsorption of bile salts such as the secondary hydrophobic taurodeoxycholate (TDC) may be partly explained by the TDC‐induced increase in colon Cl− secretion. We, therefore, investigated the effects of TDC (0.5–8 mM) on electrical parameters and electrolyte transport of rat proximal colon mucosa mounted in Ussing chambers. Colonic secretion, measured as short circuit current (I SC), progressively increased on mucosal incubation with TDC ranging 0.5–2 mM; up to TDC 2 mM, a spontaneous recovery toward control values with no changes in epithelial resistance (Rt), and lactate dehydrogenase (LDH) release was observed. In contrast, for TDC > 2 mM, I SC increased further and the effect was progressive and associated with a significant decrease in the Rt and increased LDH release, implying a cytolytic effect. Mucosal preincubation with the Cl− channel inhibitor 5‐nitro‐2‐(3‐phenylpropylamino) benzoic acid (NPPB), fully prevented the precytolytic effect of TDC on I SC. Serosal preincubation with furosemide, a Na+/K+/2Cl− cotransporter inhibitor, significantly reduced TDC‐induced increase in I SC. Inhibition of the basolateral Ca2+‐dependent K+ channel—rSK4—with serosal clotrimazole or incubation with mucosal Ca2+‐free (EGTA) buffer completely prevented precytolytic TDC‐induced increase in I SC. In conclusion, Cl− secretion is activated in colon mucosa by TDC low concentrations; while at higher concentrations, a detergent cytotoxic effect intervenes. Activation of the Ca2+‐dependent basolateral K+ pathway, through TDC‐induced apical Ca2+ influx, provides the Na+/K+/2Cl− basolateral activation, thereby the driving force for the apical exit of Cl− ions. These findings further enhance the knowledge of the pathogenic mechanisms of diarrhea associated with bile salt malabsorption.