bluuebunny/crossref_metadata_2025_split huggingface dataset:
Sparsely cross‐linked “nanogels” for microchannel DNA sequencing
Authors: Doherty Erin A. S. , Kan Cheuk Wai , Barron Annelise E. 
Published: December 2003

AbstractWe have developed sparsely cross‐linked “nanogels”, sub‐colloidal polymer structures composed of covalently linked, linear polyacrylamide chains, as novel DNA sequencing matrices for capillary electrophoresis. The presence of covalent cross‐links affords nanogel matrices with enhanced network stability relative to standard, linear polyacrylamide (LPA), improving the separation of large DNA fragments. Nanogels were synthesized via inverse emulsion (water‐in‐oil) copolymerization of acrylamide and N,N‐methylenebisacrylamide (Bis). In order to retain the fluidity necessary in a replaceable polymer matrix for capillary array electrophoresis (CAE), a low percentage of the Bis cross‐linker (< 10−4 mol%) was used. Nanogels were characterized by multiangle laser light scattering and rheometry, and were tested for DNA sequencing by CAE with four‐color laser‐induced fluorescence (LIF) detection. The properties and performance of nanogel matrices were compared to those of a commercially available LPA network, which was matched for both weight‐average molar mass (Mw) and extent of interchain entanglements (c/c*). Nanogels presented in this work have an average radius of gyration of 226 nm and a weight‐average molar mass of 8.8×106 g/mol. At concentrations above the overlap threshold, nanogels form a clear, viscous solution, similar to the LPA matrix (Mw ∼ 8.9×106 g/mol). The two matrices have similar flow and viscosity characteristics. However, because of the physical network stability provided by the internally cross‐linked structure of the nanogels, a substantially longer read length (∼ 63 bases, a 10.4% improvement) is obtained with the nanogel matrix at 98.5% accuracy of base‐calling. The nanogel network provides higher‐selectivity separation of ssDNA sequencing fragments longer than 375 bases. Moreover, nanogel matrices require 30% less polymer per unit volume than LPA. This is the first report of a sequencing matrix that provides better performance than LPA, in a side‐by‐side comparison of polymer matrices matched for Mw and extent of interchain entanglements.
Piperazine quaternary diammonium salts as additives to background electrolytes in capillary zone electrophoresis
Authors: Sebastiano Roberto , Lapadula Marta , Righetti Pier Giorgio , Gelfi Cecilia , Citterio Attilio 
Published: December 2003

AbstractThe differential behavior of five different quaternary mono‐ and diammonium salts, among the 18 investigated, in modulating the electroendoosmotic flow (EOF) and analyte separations in capillary zone electrophoresis is evaluated. It is found that quaternary diammonium salts with positive charges separated by more than four carbon atoms, while exhibiting a very strong affinity for chromatographic silica beads, to the point of exhibiting Rf values close to zero, display, on the contrary, a very poor affinity for the silica wall of capillaries. Compounds separated only by a C2 unit (i.e., 1,4‐dialkyl‐1,4‐diazoniabicyclo[2,2,2,]octane, salts 17 and 18) show high Rf values due to strong ion pair association. The unique behavior of quaternary monoammonium salts possessing an iodinated alkyl (butyl or octyl) tail (i.e., 1, 6, and 7) is attributed to their ability to be covalently affixed to the silica wall via alkylation of ionized silanols at alkaline pH values. They thus strongly modulate and typically invert the EOF, even when not present in the background electrolyte. On the contrary, all diammonium salts, devoid of such alkyl tails, are unable to modulate the EOF and to prevent analyte binding to the silica wall, since they are rapidly removed from the wall by the voltage gradient. However, if added in small amount to the background electrolyte, they offer excellent separations of mixtures of very similar organic acids and prevent any interaction with the capillary wall.
Factors related to depression in rural and urban noncustodial, low‐income fathers
Authors: Hoard Laura R. , Anderson Elaine A. 
Published: December 2003

AbstractAlthough the past 20 years have seen an increased focus on fatherhood, few studies have examined the relationship between a father's geographic location and his psychological well‐being. To address this gap, this study examined low‐income, noncustodial, predominantly African American fathers' depression in relation to locality, social support, and life stresses. Participants were 96 urban and 31 rural noncustodial fathers. Findings indicate depression is positively related to life stress and inversely related to social support. Locality, social support, and life stress accounted for a significant proportion of the variation in fathers' depression. Policy implications and direction for future research is discussed. © 2004 Wiley Periodicals, Inc. J Comm Psychol 32: 103–119, 2004.
Cultural and practical barriers to seeking mental health treatment for Chinese Americans
Authors: Kung Winnie W. 
Published: December 2003

AbstractBased on a sample of 1747 from the Chinese American Psychiatric Epidemiological Study, this report examined perceived barriers to mental health treatment. Two factors emerged, namely practical barriers, which included cost of treatment, time, knowledge of access, and language, and cultural barriers consisting of credibility of treatment, recognition of need, and fear of loss of face. Average ratings of all practical barrier items were higher than cultural barrier items, demonstrating the importance of pragmatic considerations for this population. In a novel attempt, this study examined the empirical link between these perceived barriers and actual mental health service use. The practical barrier factor showed significance in predicting service use for both the whole sample and a subsample of individuals with at least one lifetime mental disorder. Cultural barriers, however, did not attain significance. Practice and research implications of the findings are discussed. © 2004 Wiley Periodicals, Inc. J Comm Psychol 32: 27–43, 2004.
Bystander education: Bringing a broader community perspective to sexual violence prevention
Authors: Banyard Victoria L. , Plante Elizabethe G. , Moynihan Mary M. 
Published: December 2003

AbstractRecent research documents the problem of sexual violence across communities, often finding its causes to be embedded in community and cultural norms, thus demonstrating the need for community‐focused solutions. In this article we synthesize research from community psychology on community change and prevention with more individually focused studies of sexual violence prevention programs and bystander behavior in emergency and crime situations. The purpose of bringing together this research is to outline a new area of focus for sexual violence prevention: the mobilization of prosocial behavior on the part of potential bystanders. This approach has utility for increasing community receptivity to prevention messages, by decreasing resistance to them, and for increasing the likelihood of community members taking an active role in prevention and intervention. The specific case of sexual violence prevention on college campus communities illustrates this approach. © 2004 Wiley Periodicals, Inc. J Comm Psychol 32: 61–79, 2004.
Involvement of brain lactate in neuronal metabolism
Authors: Serres Sébastien , Bouyer Jean‐Jacques , Bezancon Eric , Canioni Paul , Merle Michel 
Published: December 2003

AbstractThe involvement of brain lactate in neuronal metabolism was analyzed by ex vivo NMR spectroscopy with rats under the effects of pentobarbital, αchloralose or morphine, which were infused with a solution of either [1‐13C]glucose+lactate or glucose+[3‐13C]lactate for 20 min. Electroencephalogram recordings indicated different brain electrical activity levels under the three drugs with a clear distinction between pentobarbital, on the one hand, and αchloralose and morphine on the other. Labeling of metabolites in brain perchloric acid extracts and of blood glucose and lactate was determined by 13C‐ and/or 1H‐observed/13C‐edited‐NMR spectroscopy. The following were found: (i) the ratio between glutamate C3 and C4 13C‐enrichments increased from pentobarbital to αchloralose and morphine whatever the labeled precursor, indicating a link between metabolic and electrical activity; (ii) under glucose+[3‐13C]lactate infusion, alanine C3 and acetyl–CoA C2 enrichments were higher than that of lactate C3, revealing the occurrence of an isotopic dilution of the brain exogenous lactate (arising from blood) by lactate from brain (endogenous lactate); the latter was synthesized from glycolysis in a compartment other than the neurons; (iii) the contributions of labeled glucose and lactate to acetyl–CoA C2 enrichment indicated that the involvement of blood glucose relative to that of blood lactate to brain metabolism was correlated with brain activity. It can therefore be concluded that the brain electrical activity‐dependent increase in the contribution of blood glucose relative to that of blood lactate to brain metabolism occurred partly via the increase in the metabolism of lactate generated from astrocytic glycolysis. This conclusion supports the hypothesis of an astrocyte–neuron lactate shuttle component in the coupling mechanism between cerebral activity and energy metabolism. Copyright © 2003 John Wiley & Sons, Ltd.
Localized in vivo13C NMR spectroscopy of the brain
Authors: Gruetter Rolf , Adriany Gregor , Choi In‐Young , Henry Pierre‐Gilles , Lei Hongxia , Öz Gülin 
Published: December 2003

AbstractLocalized 13C NMR spectroscopy provides a new investigative tool for studying cerebral metabolism. The application of 13C NMR spectroscopy to living intact humans and animals presents the investigator with a number of unique challenges. This review provides in the first part a tutorial insight into the ingredients required for achieving a successful implementation of localized 13C NMR spectroscopy. The difficulties in establishing 13C NMR are the need for decoupling of the one‐bond 13C–1H heteronuclear J coupling, the large chemical shift range, the low sensitivity and the need for localization of the signals. The methodological consequences of these technical problems are discussed, particularly with respect to (a) RF front‐end considerations, (b) localization methods, (c) the low sensitivity, and (d) quantification methods. Lastly, some achievements of in vivo localized 13C NMR spectroscopy of the brain are reviewed, such as: (a) the measurement of brain glutamine synthesis and the feasibility of quantifying glutamatergic action in the brain; (b) the demonstration of significant anaplerotic fluxes in the brain; (c) the demonstration of a highly regulated malate‐aspartate shuttle in brain energy metabolism and isotope flux; (d) quantification of neuronal and glial energy metabolism; and (e) brain glycogen metabolism in hypoglycemia in rats and humans. We conclude that the unique and novel insights provided by 13C NMR spectroscopy have opened many new research areas that are likely to improve the understanding of brain carbohydrate metabolism in health and disease. Copyright © 2003 John Wiley & Sons, Ltd.
Role of glial metabolism in diabetic encephalopathy as detected by high resolution 13C NMR
Authors: García‐Espinosa María A. , García‐Martín María L. , Cerdán Sebastián 
Published: December 2003

AbstractThe roles of glial energetics and of the glutamine cycle in diabetic encephalopathy have been investigated ex vivo by 13C NMR in extracts of adult rat brain. Streptozotocin‐induced diabetic or euglycemic animals received intravenous infusions of (1‐13C) glucose in the absence and presence of trifluoroacetic acid or methionine sulfoximine, two selective inhibitors of the glial tricarboxylic acid cycle or of glutamine synthase, respectively. (1‐13C) glucose infusions resulted in smaller 13C incorporation in all carbons of cerebral glutamate, glutamine and GABA in the diabetic animals. Co‐infusion of trifluoroacetic acid with (1‐13C) glucose further reduced the 13C enrichments in cerebral glutamate and glutamine, the decrease being larger in the diabetic animals than in the corresponding euglycemic controls. Methionine sulfoximine decreased to undetectable levels the fractional 13C enrichment in the carbons of cerebral glutamine in both groups and had no significant effect on 13C incorporation in glutamate and GABA, suggesting that glutamine is not the main precursor of glutamate and GABA. Additional animals were infused with (1,2‐13C2) acetate, a major substrate of glial metabolism. In this case, (1,2‐13C2) acetate infusions resulted in increased 13C incorporation in all carbons of glutamate, glutamine and GABA in the diabetic animals. Together, these results reveal that diabetic encephalopathy has an important effect in astroglial metabolism, decreasing glucose transport and metabolism and increasing the relative contribution of glial oxidative metabolism to the support of glutamatergic and GABAergic neurotransmissions. Copyright © 2003 John Wiley & Sons, Ltd.
Feeding versus infusion: a novel approach to study the NAA metabolism in rat brain
Authors: Karelson Gunnar , Ziegler André , Künnecke Basil , Seelig Joachim 
Published: December 2003

AbstractUsing in vivo 13C‐NMR spectroscopy, the energy metabolism in rat brain has commonly been studied via infusion of 13C‐labeled substrates on a minute to hour time scale. In the present study, as a novel approach, 13C‐enriched animal chow was administered over several days and compared with a 2 h infusion of [U‐13C6]‐glucose. Rats received chow containing either [U‐13C6]‐glucose or [U‐13C]‐biomass (a mixture of proteins, lipids, DNA, and carbohydrates) during 3 to 5 days. During feeding with 13C‐labeled glucose and biomass, in vivo 13C‐NMR spectroscopy was carried out daily and revealed slow but successive label incorporation into a large number of metabolites. Lipids and proteins were not significantly 13C‐enriched during a 2 h infusion of 13C‐labeled glucose, but became the most prominent resonances in the 13C feeding experiment. Likewise, feeding with 13C‐enriched biomass led to additional 13C‐label incorporation into creatine, urea carbons and glycogen. Finally, only the acetyl moiety of N‐acetyl‐aspartate (NAA) became significantly enriched during the 2 h infusion experiment, whereas the aspartyl moiety remained at natural abundance levels. In the feeding experiments, however, label incorporation into all carbons of NAA could be observed. Moreover, isotopomer analysis of brain extracts revealed that the acetyl moiety of NAA in feeding experiments was always more strongly 13C‐enriched than its aspartyl moiety, suggesting that the turnover of the acetyl moiety is faster than that of the aspartyl moiety. The different enrichment kinetics of acetyl and aspartyl moiety could be explained by the existence of two different metabolic pathways reflecting the compartmentalised synthesis of NAA. Copyright © 2003 John Wiley & Sons, Ltd.
In vivo1H‐[13C]‐NMR spectroscopy of cerebral metabolism
Authors: de Graaf Robin A. , Mason Graeme F. , Patel Anant B. , Behar Kevin L. , Rothman Douglas L. 
Published: December 2003

Abstract13C NMR spectroscopy in combination with the infusion of13C‐labeled precursors is currently the only technique that is capable of quantitatively studying energy metabolism, neurotransmission and other metabolic pathways non‐invasivelyin vivo.1H‐[13C]‐NMR spectroscopy is a high‐sensitivity alternative to direct13C NMR spectroscopy. The development of improved NMR methods for water suppression, spatial localization, broadband decoupling, shimming and signal quantification, together with the availability of high magnetic field strengths, has made1H‐[13C]‐NMR spectroscopy the method of choice for the detection of metabolism at a high spatial and/or temporal resolution.1H‐[13C]‐NMR spectroscopy can now be used to discriminate glutamatergic (excitatory) and GABAergic (inhibitory) neuronal activity. The improved sensitivity allows the detection of metabolism in different tissues (e.g. gray and white matter) and potentially even in smaller structures, like cortical layers. Finally,1H‐[13C]‐NMR spectroscopy allows the detection of energy metabolism and neurotransmission during functional activation, thereby further strengthening our understanding of the neurochemical basis of brain function. Copyright © 2003 John Wiley & Sons, Ltd.
Regulation of glial metabolism studied by 13C‐NMR
Authors: Zwingmann Claudia , Leibfritz Dieter 
Published: December 2003

AbstractGlial metabolism and their metabolic trafficking with neurons are essential parts of neuronal function, as they modulate, by this means, neuronal activity. Ex vivo and in vitro 13C‐NMR spectroscopy have been used to monitor neural cellular and tissue metabolism. Special emphasis has been given to the metabolic specialization of astrocytes and its enzymatic regulation. For this purpose primary cell cultures are useful tools to study neuronal–glial metabolic relationships as the extracellular fluid can be investigated and manipulated by various stimuli. In astrocytes, glucose is utilized predominantly anaerobically. Glycolysis is interrelated to the astrocytic TCA cycle via bi‐directional signals and metabolic exchange processes between astrocytes and neurons. Besides glucose oxidation, neuronally released glutamate is metabolized through the glial TCA cycle. The flexibility of glutamate metabolism, depending on ammonia and energy homeostasis, and the discovered pyruvate recycling pathway in astrocytes, modulates the glutamine–glutamate cycle. 13C‐NMR studies have extended the concept of the ‘non‐stoichiometric’ glutamate–glutamine cycle between neurons and astrocytes. An alanine–lactate shuttle between neurons and astrocytes contributes to nitrogen transfer from neurons to astrocytes, recycles energy substrates for neurons, and in return promotes intercellular glutamine–glutamate cycling. The conversion of alanine to lactate in astrocytes is regulated by intracytosolic pyruvate compartmentation. In essence, the metabolic flexibility and compartmentalized enzymatic specialization of astrocytes buffers the brain tissue against metabolic impairments and excitotoxicity in response to extracellular stimuli, some of them being released by neurons. These in vitro studies using 13C‐NMR spectroscopy provide important knowledge regarding physiological and pathophysiological regulation of neural metabolism to improve our understanding of general brain function. Copyright © 2003 John Wiley & Sons, Ltd.
Iterative solution of large linear systems with non‐smooth submatrices using partial wavelet transforms and split‐matrix matrix–vector multiplication
Authors: González Patricia , Cabaleiro José C. , Pena Tomás F. 
Published: December 2003

AbstractThe iterative solution of large linear systems with highly irregular matrices cannot be accelerated by wavelet transformation and subsequent sparsification if the transformed matrix is still highly irregular. In this paper we show that if the irregularity of the original matrix is limited to a relatively small known set of rows or columns (as is the case in significant applications), then acceleration can be achieved by a mixed approach in which only the ‘smooth’ submatrix is transformed and iterative solution is implemented using a novel ‘split‐matrix’ form of matrix–vector multiplication. Copyright © 2003 John Wiley & Sons, Ltd.
Stabilized finite element methods with reduced integration techniques for miscible displacements in porous media
Authors: Dias C. M. , Coutinho A. L. G. A. 
Published: December 2003

AbstractThe objective of this work is to study some techniques to increase computational performance of stabilized finite element simulations of miscible displacements. We propose the use of a reduced integration technique for bilinear quadrilateral elements in the determination of the pressure and concentration fields. We also study the evaluation of pressure gradient (Darcy's velocity) by differentiation at super‐convergent points. Numerical examples are shown to validate our approach, accessing its efficiency and accuracy. Copyright © 2003 John Wiley & Sons, Ltd.
An unconditionally stable three level finite difference scheme for solving parabolic two‐step micro heat transport equations in a three‐dimensional double‐layered thin film
Authors: Dai Weizhong , Li Quang , Nassar Raja , Shen Lixin 
Published: December 2003

AbstractHeat transport at the microscale is of vital importance in microtechnology applications. The heat transport equations are parabolic two‐step equations, which are different from the traditional heat diffusion equation. In this study, we develop a three‐level finite difference scheme for solving the micro heat transport equations in a three‐dimensional double‐layered thin film. It is shown by the discrete energy method that the scheme is unconditionally stable. Numerical results for thermal analysis of a gold layer on a chromium padding layer are obtained. Copyright © 2003 John Wiley & Sons, Ltd.
Numerical modelling of void inclusions in porous media
Authors: Rodríguez‐Ferran Antonio , Sarrate Josep , Huerta Antonio 
Published: December 2003

AbstractNumerical modelling of porous flow in a low‐permeability matrix with high‐permeability inclusions is a challenging task because the large ratio of permeabilities ill‐conditions the finite element system of equations. We propose a coupled model where Darcy flow is used for the porous matrix and potential flow is used for the inclusions. We discuss appropriate interface conditions in detail and show that the head drop in the inclusions can be prescribed in a very simple way. Algorithmic aspects are treated in full detail. Numerical examples show that this coupled approach precludes ill‐conditioning and is more efficient than heterogeneous Darcy flow. Copyright © 2003 John Wiley & Sons, Ltd.
Development of novel flame‐retardant thermosets based on benzoxazine–phenolic resins and a glycidyl phosphinate
Authors: Espinosa M. A. , Cádiz V. , Galiá M. 
Published: December 2003

AbstractModified novolac resins with benzoxazine rings were prepared and copolymerized with a glycidyl phosphinate. Their curing behavior and the thermal properties of the curing resins were studied. Copolymerization was studied with model compounds considering the functionality of the benzoxazine‐based phenolic resins and the easy isomerization of the glycidyl phosphinate. Phenolic novolac resin acts as an initiator but p‐toluensulfonic acid had to be used to decrease the curing temperature and to prevent glycidyl phosphinate from isomerizing. The materials obtained exhibited high glass‐transition temperatures and retardation on thermal degradation rates. V‐0 materials were obtained when the materials were tested for ignition resistance with the UL‐94 test. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 279–289, 2004
Chain‐growth limiting reactions in the cationic polymerization of 3‐ethyl‐3‐hydroxymethyloxetane
Authors: Bednarek Melania , Kubisa Przemysław 
Published: December 2003

Abstract3‐Ethyl‐3‐hydroxymethyloxetane (EOX) polymerizes readily to branched multihydroxyl polyethers. Molecular weights of the polymers are, however, limited, and macromolecules are predominantly cyclic. This indicates that intramolecular chain transfer to polymer (back‐biting) proceeds in the system. Repeating units in poly‐EOX contain two nucleophilic sites that may participate in back‐biting, namely ether groups and hydroxyl groups. Analysis of matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectra of poly‐EOX prepared in the presence of analogous polyether that does not contain HO groups (poly(3,3‐dimethyloxetane)‐poly‐DMOX) shows that the ether group in the repeating unit of poly‐DMOX does not participate in chain transfer to the polymer. However, when DMOX was polymerized in the presence of poly‐EOX, clear evidence of participation of HOgroups in intramolecular chain transfer was obtained. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 245–252, 2004