bluuebunny/crossref_metadata_2025_split huggingface dataset:
Glutamatergic synaptic transmission participates in generating the hippocampal EEG
Authors: Leung L. Stan , Shen Bixia 
Published: May 2004

AbstractThe participation of ionotropic glutamatergic synapses in the generation of hippocampal electroencephalography (EEG) of behaving rats has not been systematically studied. In this study, field potentials in hippocampal CA1 were recorded following injection of N‐methyl‐D‐aspartate (NMDA) and α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) receptor antagonists, or vehicle control, either into the lateral ventricles or directly into the hippocampus or the medial septum. Intraventricular (i.c.v.) AMPA receptor antagonist 6,7‐dinitroquinoxaline‐2,3,dione (DNQX, 5–10 μg) decreased the commissural evoked potential and the amplitude of the hippocampal EEG, including the theta rhythm. Theta frequency was decreased by 10 μg, but not 5 μg DNQX i.c.v. Unilateral intrahippocampal injection of DNQX (5 μg) only decreased the amplitude, but not the frequency, of the theta rhythm near the site of injection, without affecting theta amplitude or frequency at the opposite hippocampus. Other than theta, the large irregular activity (with a delta frequency peak at 1–2 Hz) and gamma EEG (30–100 Hz) were also decreased by i.c.v. and intrahippocampal injections of DNQX. Intrahippocampal injection of NMDA receptor antagonist D‐2‐amino‐5‐phosphonovaleric acid (D‐APV, 2.5 μg) decreased the amplitude of the theta rhythm and, less consistently, the gamma EEG. The frequency of the theta rhythm and the peak of the commissural evoked potential were not significantly affected by intrahippocampal D‐APV injection. Medial septal injections of D‐APV or D,L‐APV (2.24 μg in 0.4 μl), but not DNQX (10 μg in 0.4 μl), decreased the amplitude of the hippocampal theta significantly, but theta frequency was not significantly affected. It is concluded that both NMDA and AMPA receptors in the hippocampus are involved in generating the amplitude of the hippocampal EEG of theta and gamma frequencies, while NMDA receptors in the medial septum are involved in controlling the amplitude of theta and gamma EEG in the hippocampus. Excitatory glutamatergic synaptic currents, activated by afferents from the entorhinal cortex and CA3, are suggested to participate in hippocampal EEG activities. © 2004 Wiley‐Liss, Inc.
Development of biodegradable poly(propylene fumarate)/poly(lactic‐co‐glycolic acid) blend microspheres. II. Controlled drug release and microsphere degradation
Authors: Kempen Diederik H. R. , Lu Lichun , Zhu Xun , Kim Choll , Jabbari Esmaiel , Dhert Wouter J. A. , Currier Bradford L. , Yaszemski Michael J. 
Published: June 2004

AbstractThis article describes the effects of six processing parameters on the release kinetics of a model drug Texas red dextran (TRD) from poly(propylene fumarate)/poly(lactic‐co‐glycolic acid) (PPF/PLGA) blend microspheres as well as the degradation of these microspheres. The microspheres were fabricated using a double emulsion‐solvent extraction technique in which the following six parameters were varied: PPF/PLGA ratio, polymer viscosity, vortex speed during emulsification, amount of internal aqueous phase, use of poly(vinyl alcohol) in the internal aqueous phase, and poly(vinyl alcohol) concentration in the external aqueous phase. We have previously characterized these microspheres in terms of microsphere morphology, size distribution, and TRD entrapment efficiency. In this work, the TRD release profiles in phosphate‐buffered saline were determined and all formulations showed an initial burst release in the first 2 days followed by a decreased sustained release over a 38‐day period. The initial burst release varied from 5.1 (±1.1) to 67.7 (±3.4)% of the entrapped TRD, and was affected most by the viscosity of the polymer solution used for microsphere fabrication. The sustained release between day 2 and day 38 ranged from 7.9 (±0.8) to 27.2 (±3.1)% of the entrapped TRD. During 11 weeks of in vitro degradation, the mass of the microspheres remained relatively constant for the first 3 weeks after which it decreased dramatically, whereas the molecular weight of the polymers decreased immediately upon placement in phosphate‐buffered saline. Increasing the PPF content in the PPF/PLGA blend resulted in slower microsphere degradation. Overall, this study provides further understanding of the effects of various processing parameters on the release kinetics from PPF/PLGA blend microspheres thus allowing modulation of drug release to achieve a wide spectrum of release profiles. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 70A: 293–302, 2004
Fatigue and damage tolerance of Y‐TZP ceramics in layered biomechanical systems
Authors: Zhang Yu , Pajares Antonia , Lawn Brian R. 
Published: June 2004

AbstractThe fatigue properties of fine‐grain Y‐TZP in cyclic flexural testing are studied. Comparative tests on a coarser‐grain alumina provide a baseline control. A bilayer configuration with ceramic plates bonded to a compliant polymeric substrate and loaded with concentrated forces at the top surfaces, simulating basic layer structures in dental crowns and hip replacement prostheses, is used as a basic test specimen. Critical times to initiate radial crack failure at the ceramic undersurfaces at prescribed maximum surface loads are measured for Y‐TZP with as‐polished surfaces, mechanically predamaged undersurfaces, and after a thermal aging treatment. No differences in critical failure conditions are observed between monotonic and cyclic loading on as‐polished surfaces, or between as‐polished and mechanically damaged surfaces in monotonic loading, consistent with fatigue controlled by slow crack growth. However, the data for mechanically damaged and aged specimens show substantial declines in sustainable stresses and times to failure in cyclic loading, indicating an augmenting role of mechanical and thermal processes in certain instances. In all cases, however, the sustainable stresses in the Y‐TZP remain higher than that of the alumina, suggesting that with proper measures to avoid inherent structural instabilities, Y‐TZP could provide superior performance in biomechanical applications. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 71B: 166–171, 2004
Prediction of resorption rates for composite polylactide/hydroxylapatite internal fixation devices based on initial degradation profiles
Authors: Hile David D. , Doherty Stephen A. , Trantolo Debra J. 
Published: June 2004

AbstractMechanical and physicochemical outcomes were used to predict the resorption rate of polylactide‐based internal fixation devices with and without incorporation of an osteoconductive buffer. Devices were degraded in vitro for 1 year. Addition of an osteoconductive buffer to a resorbable polymer internal fixation device controlled the rate of acid generation resulting from polymer hydrolysis. The pH of the physiological buffer remained neutral when it was exposed to the buffered screw, whereas the pH decreased to approximately 3.0 for the polylactide device. Neutralizaton of the acids generated during polymer hydrolysis increased the projected resorption time of the buffered device to 104 weeks in comparison to 71 weeks for a similar screw made from polylactide. In addition, the buffered device retained a higher percentage of its initial flexural strength throughout the course of degradation than the polylactide screw. The flexural strength of the polylactide screw decreased 20% during the first 4 weeks of polymer degradation, whereas the buffered device maintained its initial mechanical properties through 16 weeks of degradation. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 71B: 201–205, 2004
Hemolymph‐dependent and ‐independent responses in Drosophila immune tissue
Authors: Bettencourt Raul , Asha H. , Dearolf Charles , Ip Y. Tony 
Published: June 2004

AbstractInsects possess an antimicrobial defense response that is similar to the mammalian innate immune response. The innate immune system is designed to recognize conserved components of microorganisms called pathogen‐associated molecular patterns (PAMPs). How host receptors detect PAMPs and transmit the signals to mount the immune response is being elucidated. Using GFP‐Dorsal, ‐Dif, and ‐Relish reporter proteins in ex vivo assays, we demonstrate that Drosophila fat bodies, a major immune tissue, have both hemolymph‐dependent and ‐independent responses. Microbial preparations such as lipoteichoic acid (LTA) and peptidoglycan (PGN) can stimulate some responses from dissected and rinsed larval fat bodies. Therefore, at least some aspects of recognition can occur on fat body cell surfaces, bypassing the requirement of hemolymph. Our results also show that supernatants from bacterial cultures can stimulate the nuclear translocation of Dorsal in dissected fat bodies, but this stimulation is strictly hemolymph‐dependent. Various biochemical assays suggest that the factors from bacterial supernatants that stimulate the hemolymph‐dependent nuclear translocation are likely made up of proteins. We further show that Dorsal mutant larvae have much lower phenoloxidase activity, consistent with a more important role of Dorsal in innate immunity than previously shown. © 2004 Wiley‐Liss, Inc.
A self‐applied, Internet‐based intervention for fear of public speaking
Authors: Botella Cristina , Hofmann Stefan G. , Moscovitch David A. 
Published: June 2004

AbstractThe aim of this article is to introduce, illustrate, and present effectiveness data on a new telepsychology program for the treatment of fear of public speaking. The Talk to Me program is an Internet‐based self‐applied intervention that has several components, including a diagnostic assessment, a structured treatment, and an outcome protocol that evaluates treatment efficacy in a continuous manner. We describe the characteristics of the program and present a case study. Results demonstrated a significant decrease in levels of fear and avoidance related to speaking in public. © 2004 Wiley Periodicals, Inc. J Clin Psychol/In Session.
Etiology and treatment of social anxiety: A commentary
Authors: Bitran Stella , Barlow David H. 
Published: June 2004

AbstractSubstantial advances in our understanding of the etiology and treatment of performance anxiety have occurred during the past decade. It has become clear that the development of efficient and effective treatments cannot be divorced from knowledge of the specific form of psychopathology being treated and that treatments must be tailored to this psychopathology. After describing a current model of the etiology of performance anxiety and social phobia, this commentary notes the common factors present across the rich and diverse set of articles in this issue describing treatments from different approaches and different theoretical orientations. To the extent that these common factors are important mechanisms of action, it is possible that the future will introduce more unified and more effective, efficient, and theoretically informed treatment for performance anxiety as well as the potential for preventive techniques. © 2004 Wiley Periodicals, Inc. J Clin Psychol/In Session.
An investigation into the use of Raman microscopy for the detection of labelled compounds in living human cells
Authors: Kuhnert Nikolai , Thumser Alfred 
Published: June 2004

AbstractWe report on the first detection of vibrationally labelled compounds by Raman micro‐spectroscopy in living cells and demonstrate the feasibility of this technique for bioanalysis. Copyright © 2004 John Wiley & Sons, Ltd.
Ermittlung des Spannungszustandes von Böden aus Werten des Eindringwiderstandes von Sonden
Authors: Hartge Karl Heinrich , Bachmann Jörg 
Published: June 2004

AbstractMit handbetriebenen Drucksonden gemessene Eindringwiderstände (EW) sind die einzigen Festigkeitsparameter, die mit geringem apparativem Aufwand vor Ort sofort verfügbar sind. Diesem Vorteil steht die unzulängliche Auswertung als Nachteil gegenüber. Daher wird eine Möglichkeit beschrieben, die Messwerte im Rahmen der Spannungsverteilung im Boden zu interpretieren und dadurch Aussagen über den momentanen Vorverdichtungszustand dieses Bodens zu machen. Hierfür wird dem EW die horizontale Spannungskomponente (σx) zugeordnet und die dazugehörige vertikale (σz) mittels einer Hilfskonstruktion bestimmt. Hierfür wird für die unterste mit der Sonde erreichte Tiefe der hydrostatische Spannungszustand (σhydr) angenommen. In dem Koordinatensystem mit EW als Abszisse und der Tiefe im Boden als Ordinate wird die hydrostatische Spannungssituation an der Bodenoberfläche als Nullpunkt gesetzt. Für den Verlauf der hydrostatischen Spannungssituation zwischen diesen Endpunkten wird eine Gerade als Näherung genommen. Die Relation zwischen dem Messwert (EW) und dem wie beschrieben bestimmten Wert für die hydrostatische Komponente lässt sich als eine dem Ruhedruckkoeffizienten analoge Zahl (KOE) darstellen. An Beispielen wird gezeigt, dass KOE ≅ 1 für normalverdichtete Situationen, wie Waldböden und durch Tiefumbruch meliorierte Flächen, beträgt und sich von überverdichteten Standorten wie Äckern unterscheiden lässt (KOE > 2). Das Ausmaß der so erhaltenen Überverdichtung erlaubt eine Näherungsberechnung der Zusatzbelastung, die der Boden im Moment der EW‐Messung ohne plastische Verformung tragen kann.
Consequences of sodium exclusion for the osmotic potential in the rhizosphere – Comparison of two maize cultivars differing in Na+ uptake
Authors: Vetterlein Doris , Kuhn Katharina , Schubert Sven , Jahn Reinhold 
Published: June 2004

AbstractAccording to the biphasic model of growth response to salinity, growth is first reduced by a decrease in the soil osmotic potential (Ψo), i.e., growth reduction is an effect of salt outside rather than inside the plant, and genotypes differing in salt resistance respond identically in this first phase. However, if genotypes differ in Na+ uptake as it has been described for the two maize cultivars Pioneer 3906 and Across 8023, this should result in differences in Na+ concentrations in the rhizosphere soil solution and thus in the concentration of salt outside the plant. It was the aim of the present investigation to test this hypothesis and to investigate the effect of such potential differences in soil Ψo caused by Na+ exclusion on plant water relations. Sodium exclusion at the root surface of intact plants growing in soil was investigated by sampling soil solution from the rhizosphere of two maize cultivars (Across 8023, Pioneer 3906). Plants were grown in a model system, consisting of a root compartment separated from the bulk soil compartment by a nylon net (30 μm mesh size), which enabled independent measurements of the change of soil solution composition and soil water content with increasing distance from the root surface (nylon net). Across 8023 accumulated higher amounts of sodium in the shoot compared to the excluder (Pioneer 3906). The lower Na+ uptake in the excluder was partly compensated by higher K+ uptake. Pioneer 3906 not only excluded sodium from the shoot but also restricted sodium uptake more efficiently from roots relative to Across 8023. This was reflected by higher Na+ concentrations in the rhizosphere soil solution of the excluder 34 days after planting (DAP). The difference in Na+ concentration in rhizosphere soil solution between cultivars was neither due to differences in transpiration and thus in mass flow, nor due to differences in actual soil water content. As the lower Na+ uptake of the excluder (Pioneer 3906) was only partly compensated by increased uptake of K+, soil Ψo in the rhizosphere of the excluder was more negative compared to Across 8023. However, no significant negative effect of decreased soil Ψo on plant water relations (transpiration rate, leaf Ψo, leaf water potential, leaf area) could be detected. This may be explained by the fact that significant differences in soil Ψo between the two cultivars occurred only towards the end of the experiment (27 DAP, 34 DAP).
Nitrate leaching in forest soils: an analysis of long‐term monitoring sites in Germany
Authors: Borken Werner , Matzner Egbert 
Published: June 2004

AbstractElevated atmospheric inputs of NH4+ and NO3– have caused N saturation of many forest ecosystems in Central Europe, but the fate of deposited N that is not bounded by trees remains largely unknown. It is expected that an increase of NO3– leaching from forest soils may harm the quality of groundwater in many regions. The objective of this study was to analyze the input and output of NH4+ and NO3– at 57 sites with mature forest stands in Germany. These long‐term study sites are part of the European Level II program and comprise 17 beech, 14 spruce, 17 pine, and 9 oak stands. The chloride balance method was used to calculate seepage fluxes and inorganic N leaching below the rooting zone for the period from 1996 to 2001. Nitrogen input by throughfall was significantly different among most forest types, and was in the order: spruce > beech/oak > pine. These differences can be largely explained by the amount of precipitation and, thus, it mirrors the regional and climatic distribution of these forest types in Germany. Mean long‐term N output with seepage was log‐normal distributed, and ranged between 0 and 26.5 kg N ha–1 yr–1, whereby 29 % of the sites released more than 5 kg N ha–1 yr –1. Leaching of inorganic N was only significantly lower in the pine stands (P < 0.05) compared with leaching rates of the spruce stands. Median N output : input ratio ranged between 0.04 and 0.11 for the beech, oak, and pine stands, while the input : output ratio of the spruce stands was 0.24, suggesting a higher risk of NO3– leaching in spruce forests. Following log‐transformation of the data, N input explained 38 % of the variance in N output. The stratification of the data by the C : N ratio of the O horizon or the top mineral soil revealed that forests soils with a C : N ratio < 25 released significantly more NO3– (median of 4.6 kg N ha–1 yr–1) than forests with a C : N ratio > 25 (median of 0.8 kg N ha–1 yr–1). The stratification improved the correlation between N input and N output for sites with C : N ratios < 25 (r2 = 0.47) while the correlation for sites with C : N ratios > 25 was weaker (r = 0.21) compared with the complete data set. Our results suggest that NO3– leaching may increase in soils with wide C : N ratios when N deposition remains on a high level and that the potential to store inorganic N decreases with C : N ratios in the O horizons becoming more narrow.
Stress corrosion cracking of explosion welded steel‐aluminum joints
Authors: Czechowski M. 
Published: June 2004

AbstractThe article presents the test results of stress corrosion resistance of explosion welded steel‐aluminum elements. The tests were carried out by means of the slow strain rate test (10−6 s−1) in air and artificial sea water. The following parameters were measured: tensile strength, time‐to‐failure and destructive energy. The tested explosion welded joints show susceptibility to degradation of properties in the corrosive environment. Galvanic corrosion is the main reason of degradation of the measured values. Another mechanism of explosion welded joints' destruction was found in air and artificial sea water. The tests of the explosion welded elements in the fast flow of sea water showed substantial galvanic corrosion.
Influence of Surface Carbon Deposition on the Bulk Crystallization of Isotactic Polypropylene
Authors: Liu Jichun , Li Huihui , Duan Yongxin , Jiang Shidong , Miao Zhenjiang , Wang Jijun , Yan Shouke 
Published: June 2004

AbstractSummary: The effect of a surface‐vacuum‐evaporated ultrathin carbon layer on the bulk crystallization behavior of isotactic polypropylene (iPP) films was investigated by means of polarized optical microscopy, differential scanning calorimetry (DSC), and wide‐angle X‐ray diffraction. Results obtained from both isothermal crystallization and constant cooling experiments indicate that surface carbon deposition on an iPP film can remarkably increase the crystallization ability of it during the melt recrystallization process. Optical microscopy observations show that the melt recrystallization of iPP with a carbon coating starts about 10 °C earlier than the pure iPP during a re‐cooling process of 1 °C · min−1. Under isothermal crystallization conditions, a much shorter induction period for nucleation is required for the carbon‐coated iPP than the non‐carbon‐coated one. The wide‐angle X‐ray diffraction and DSC analyses further demonstrate a crystallinity increment of the carbon‐coated iPP with respect to its non‐carbon‐coated counterpart. This clearly indicates that the strong influence of the interfacial interaction between the vacuum‐evaporated carbon and the iPP film on its bulk crystallization can be extended deep into the bulk material.An OM micrograph of a hot‐pressed partially carbon‐coated (top half) iPP film.magnified imageAn OM micrograph of a hot‐pressed partially carbon‐coated (top half) iPP film.
Novel Carbazole‐Based Ladder‐Type Polymers for Electronic Applications
Authors: Dierschke Frank , Grimsdale Andrew C. , Müllen Klaus 
Published: May 2004

AbstractSummary: New carbazole‐based ladder‐polymers have been prepared utilising a 3,6‐diacyl‐2,7‐dibromocarbazole building block 4. Suzuki polycondensation of 4 with carbazole‐2,7‐diboronic acid followed by addition of methyl lithium and ring closure with boron trifluoride gave ladder‐polymers 9 with all methine bridges, analogous to ladder‐type poly(para‐phenylene). In very dilute solution, these polymers show blue‐green fluorescence similar to that from the corresponding LPPP. At higher concentrations, a broader red‐shifted emission is seen which suggests that the chains are aggregating in solution. Homopolymerisation of 4 followed by condensation of the carbonyls with boron sulfide produced a novel ladder‐type structure 13 with alternating five‐ and six‐membered rings. This ladder‐polymer displays bright yellow‐green fluorescence. Cyclic voltammetry indicated that these materials have HOMO energy levels comparable to the work function of ITO, making them good candidates for use as hole accepting emissive materials for LEDs.The ladder polymers synthesised.magnified imageThe ladder polymers synthesised.
Syndiospecific Homopolymerisation of Higher 1‐Alkenes with Two Different Bridged [(RPh)2C(Cp)(2,7‐tert‐BuFlu)]ZrCl2 Catalysts
Authors: Hoff Matthias , Kaminsky Walter 
Published: May 2004

AbstractSummary: Syndiotactic polymers of 1‐pentene, 1‐hexene and 1‐octene were obtained with the CS‐symmetric metallocene catalysts [Ph2C(Cp)(2,7‐tert‐Bu2Flu]ZrCl2 and [(4‐MePh)2C(Cp)(2,7‐tert‐Bu2Flu)]ZrCl2, which have already been proven to give high molar masses and excellent tacticities in propene polymerisation. The monomers were polymerised in bulk and in solution processes at temperatures between 0 and 60 °C using methylaluminoxane as a cocatalyst. The effects on catalyst activity as well as on polymer microstructure and molar mass were determined. Polymers with high syndiotacticities and molar masses (up to 550 000 g · mol−1 in the 1‐octene polymerisation) compared to other metallocenes were obtained.
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