bluuebunny/crossref_metadata_2025_split huggingface dataset:
Erfahrungen mit Membranpumpen und Membranverdichtern
Authors: Schopenhauer H. 
Published: December 2004

AbstractDie Verwendung von Membranpumpen und ‐kompressoren ist nicht neu, doch konnten größere Betrebserfahrungen mit diesen Maschinen erst in den letzten Jahren gesammelt werden. Bestimmte Schäden lassen sich durch konstruktive Maßnahmen vermeiden, so z. B. das Hängenbleiben oder die Beschädigung der Membran und das Auftreten von Kompressionsschlägen, wenn ein Membranverdichter als Gasumwälzverdichter betrieben wird.
Ein Verfahren zur Oxidation von Alkylaromaten
Authors: Katzschmann E. 
Published: December 2004

AbstractEin Verfahren der Chemischen Werke Witten zur Herstellung von Terephthalsäure‐dimethylester durch Luftoxidation von p‐Xylol in flüssiger Phase hat in der Industrie eine beachtliche Bedeutung erlangt. Es wird die Entwicklung des Verfahrens beschrieben. Aus dem Reaktionsablauf wurden neue Erkenntnisse über den Oxidationsmechanismus gewonnen. Charakteristische Zwischenprodukte sind der p‐Toluylsäure‐methylester und der Terephthalsäure‐monomethylester.
Elektrochemische Eigenschaften gespülter Gas‐Diffusionselektroden
Authors: Wendtland R. , Winsel A. 
Published: December 2004

AbstractIn den Poren von Gas‐Diffusionselektroden werden durch Elektro‐Dialyse Konzentrationsverschiebungen verursacht, die in alkalischer Lösung zu Grenzstromdichten in Wasserstoff‐Anoden führen. Auch in Sauerstoff‐Kathoden wirkt sich die Konzentrationserhöhung in den Poren ungünstig auf die Polarisation aus. Man kann derartige Polarisationseffekte durch Spülung der Elektrodenporen mit frischer Elektrolytlösung vollständig beseitigen. Es wird über Meßergebnisse an gespülten Sauerstoff‐ und Wasserstoff‐Elektroden berichtet.
Elektrochemische Untersuchung des Stoffübergangs von einer Flüssigkeit an eine gasende Düse
Authors: Weder Erich 
Published: December 2004

AbstractMit einer elektrochemischen Meßmethode wurde der Stoffübergang von einer Flüssigkeit an eine horizontale Platte, in deren Zentrum sich eine einzelne gasende Düse befand, untersucht. Die Platte bestand aus 11 konzentrisch um die Düse angeordneten, elektrisch gegeneinander isolierten Nickel‐Ringen, an deren Stirnflächen sich die elektrochemische Meßreaktion abspielte. Mit dieser Sonde konnte der Stoffübergang als Funktion des Gasdurchsatzes sowie des Abstandes vom Düsenmittelpunkt gemessen werden. Mit einem Schnellschreiber wurde die Änderung des Stoffübergangs‐Koeffizienten mit der Blasenbildung aufgezeichnet. Durch gleichzeitiges Photographieren der Blasen erhielt man die Zuordnung Stoffübergang–Blasenwachstum.
Potentiometrische Bestimmung des Wasserdampf‐Dissoziationsgleichgewichtes zwischen 1000 und 1300°K mit einer Festelektrolytzelle
Authors: Hartung R. , Möbius Habil. H.‐H. 
Published: December 2004

AbstractNachdem die Fehlerquellen (verschiedene Eigenschaften des Festelektrolyten und der Elektroden, Einflüsse der Gasströmung und Mängel im Temperaturausgleich) bei potentiometrischen Bestimmungen an H2/H2O/Inertgas‐Gemischen durch Vorversuche erkannt waren, wurde die Konstante des Wasserdampf‐Dissoziationsgleichgewichts zwischen 1000 und 1300°K direkt elektrochemisch bestimmt, wobei die Genauigkeit der bekannten, unter Benutzung der Bildungswärme sowie spektroskopischer Daten indirekt erhaltenen Werte nahezu erreicht werden konnte. Die Wasserstoff‐ und Wasserdampf‐Bestimmungen zeigten, daß die gaspotentiometrische Methode unter optimalen Bedingungen gestattet, das Verhältnis P/P über den Bereich von etwa 10−5 bis 105 mit einer absoluten Genauigkeit von ⩽ 3% kontinuierlich zu messen.
Transportprozesse und thermische Instabilitäten bei porösen Katalysatoren
Authors: Hugo P. , Wicke E. 
Published: December 2004

AbstractZwei bis heute noch nicht vollständig gelöste Probleme werden behandelt: die Diffusion von Gasen in porösen Medien im Übergangsbereich zwischen Gas‐ und Knudsen‐Diffusion und die thermischen Instabilitäten einzelner Katalysatorkörner bei stark exothermen Umsetzungen. Die Porendiffusion wird mit einer neuen Methode untersucht, die auf der Selbstdiffusion von Wasserstoff in Mischungen von ortho‐ und para‐Wasserstoff beruht. Die Zusammenhänge zwischen der Druck‐ und Temperaturabhängigkeit der effektiven Diffusionskoeffizienten und der Porenstruktur der untersuchten Materialien werden diskutiert. Beim zweiten Problem werden zunächst die experimentellen Erfahrungen zusammengestellt. Sie führen zu dem Schluß, daß Instabilitäten allein im Korninnern, wie sie theoretisch vorausgesagt wurden, praktisch nicht auftreten können. Mit einer erweiterten Theorie, welche außer der bei exothermen Reaktionen auftretenden inneren Kornüberhitzung den äßeren Wärme‐ und Stoffübergang berücksichtigt, läßt sich zeigen, daß für die thermischen Instabilitäten die Bedingungen des äußeren Wärmeübergangs ausschlaggebend sind. Die zusätzliche innere Kornüberhitzung steigert dabei die parametrische Empfindlichkeit des Systems.
Normung aus der Sicht des chemischen Apparatebaues
Authors: Winter J. 
Published: December 2004

AbstractUnter dem Blickwinkel des Apparatebauers wird gezeigt, welche wirtschaftlichen Vorteile die bestehenden Apparatebau‐Normen bringen und welche Schwierigkeiten Normen insbesondere bei Angeboten für das Ausland verursachen können. Es gibt viele gute Werknormen, aber sie ermöglichen immer noch zu viele Variationen bei den Konstruktionen des Apparatebaues, wodurch die Fertigung von Serien und Wiederholteilen erschwert wird. Eine Normung, die der technischen Entwicklung entspricht, führt zu echter Kostensenkung.
Thermodynamische Bewertung chemischer Prozesse
Authors: Rant Z. 
Published: December 2004

AbstractDurch Ergänzen der bisher üblichen quantitativen Betrachtungen durch qualitative Überlegungen läßt sich ein tieferer Einblick in das Wesen der bei chemischen Prozessen auftretenden Energieumformungen erhalten. Zu diesem Zweck werden die Energieströme in zwei Teile zerlegt, von denen der eine die beliebig umformbaren Energien, die Exergie, und der andere den Rest, die Anergie, darstellt. Aufgrund solcher Überlegungen werden die bei den Energietransformationen auftretenden Nichtumkehrbarkeiten nach Größe und Ort ermittelt und ein exergetischer Wirkungsgrad definiert. Dieser ist ein eindeutiges Maß für die energetische Güte des Prozesses. Das Verfahren wird an einigen Beispielen erläutert.
Schlammentwässerung mit Preßfiltern
Authors: Alt Christian 
Published: December 2004

AbstractPreßfilter sind für die Verminderung der Restfeuchte bei bestimmten Filterkuchen geeignet. Mehrere diskontinuierliche und kontinuierliche Apparate und Maschinen haben sich zum Teil bewährt, andere befinden sich noch in der Erprobung. Nach einer kurzen theoretischen Behandlung, die einige Schlüsse für die verfahrenstechnischen Forderungen zuläßt, werden die Funktionen der wichtigsten Entwicklungen beschrieben und zusammenfassend deren typische Verhaltensweisen herausgestellt.
Is high‐dose intensity intraarterial cisplatin chemoradiotherapy for head and neck carcinoma feasible?
Authors: Robbins K. Thomas 
Published: January 2005

The author outlines his personal experience treating hundreds of patients with head and neck carcinoma using combined high‐dose intraarterial cisplatin chemotherapy and concomitant, radiation therapy, and he also highlights the published experience of other investigators, all of whom concluded that the high‐dose intensity approach is feasible and highly efficacious. This differs from the results reported in this issue by a group of investigators from the Mayo Clinic.See referenced original article on pages 559–68, this issue.
Reactions of K2[Fe(CO)3(PPh3)]: Reductive Sb−Sb Coupling with Ph2SbCl To Form trans‐[Fe(CO)3(PPh3)(Sb2Ph4)] and Salt Metathesis with Me3SbCl2 To Yield trans‐[Fe(CO)3(PPh3)(SbMe3)]
Authors: Lorenz Ingo‐Peter , Rudolph Stefan , Piotrowski Holger , Polborn Kurt 
Published: December 2004

AbstractIn contrast to the ferrate K2[Fe(CO)4], the phosphane‐substituted ferrate K2[Fe(CO)3(PPh3)] (1) reacts with the stibane derivative Ph2SbCl by metal‐assisted reductive Sb−Sb coupling to give the distibane complex trans‐[Fe(CO)3(PPh3)(Sb2Ph4)] (3). The distibane ligand in 3 is terminally η1‐coordinated trans to the phosphane ligand. However, the stiborane derivative Me3SbCl2 reacts with 1 in a metathetical substitution reaction to form the monostibane complex trans‐[Fe(CO)3(PPh3)(SbMe3)] (5). Both compounds have been characterized by spectroscopic (IR, NMR, MS), analytical (C, H) and X‐ray diffraction analyses. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Oxidation of a One‐Dimensional Coordination Polymer and Synthesis of the Macrocyclic Silver Complex [Ag12(PhS2P−PS2Ph)6(dppeS)6]
Authors: Fenske Dieter , Rothenberger Alexander , Fallah Maryam Shafaei 
Published: December 2004

AbstractThe cluster chemistry with functionalised trimethylsilyl reagents was investigated. The oxidation of the one‐dimensional coordination polymer 1/∞[{Ag2(PhS2P−PS2Ph)dppe}·dppe]∞ leads to the formation of [Ag12(PhS2P−PS2Ph)6(dppeS)6] (dppeS = Ph2P(CH2)2P(S)Ph2]. The dianionic ligand [PhPS2−PS2Ph]2− could possibly give rise to a new class of macrocyclic transition‐metal chalcogenides. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Approximate iterative methods for variational data assimilation
Authors: Lawless A. S. , Gratton S. , Nichols N. K. 
Published: December 2004

AbstractThe problem of four‐dimensional variational data assimilation can be considered as a non‐linear least squares problem. A common method for solving it is equivalent to a Gauss–Newton method. However, approximations must be made in order to solve the problem efficiently. In this paper we examine two approximations to the Gauss–Newton method and their effect on the data assimilation problem. Copyright © 2004 John Wiley & Sons, Ltd.
Intracellular pH regulation in rat Schwann cells
Authors: Nakhoul Nazih L. , Abdulnour‐Nakhoul Solange , Khuri Raja N. , Lieberman Edward M. , Hargittai Pal T. 
Published: December 2004

AbstractWe examined H+ and HCO3− transport mechanisms that are involved in the regulation of intracellular pH of Schwann cells. Primary cultures of Schwann cells were prepared from the sciatic nerves of 1–3‐day‐old rats. pHi of single cells attached to cover slips was continuously monitored by measuring the absorbance spectra of the pH‐sensitive dye dimethylcarboxyfluorescein incorporated intracellularly. The average pHi of neonatal Schwann cells bathed in HEPES mammalian solution was 7.17 ± 0.02 (n = 32). In the nominal absence of HCO3−, pHi spontaneously recovered from an acute acid load induced by exposing the Schwann cells to 20 mM NH4+ (NH4+ prepulse). This pHi recovery from the acute acid load was totally inhibited in the absence of external Na+ or in the presence of 1 mM amiloride. In both cases, the pHi recovery was readily restored upon readdition of external Na+ or removal of amiloride. In the steady‐state, addition of amiloride caused a small and slow decrease in pHi which was readily reversed upon removal of amiloride. In the presence of HCO3−, removal of external Cl‐ caused pHi to rapidly and reversibly increase by 0.23 = 0.03 (n = 15) and the initial rate of alkalinization was 20.6 ± 2.7 × 10‐4 pH/sec. In the absence of external Na+, removal of bath Cl− still caused pHi to increase by 0.15 ± 0.02 and the initial rate of pHi increase was not significantly altered. In the nominal absence of HCO3−, removal of bath Cl‐ caused pHi to increase very slightly (0.05 ± 0.01) with an initial dpHi/dt of only 4.4 ± 0.2 × 10−4 pH/sec (n = 4). Addition of 100 μM DIDS did not inhibit the pHi increase caused by removal of bath Cl−. These data indicate that (1) Rat Schwann cells regulate their pHi via an Na‐H exchange mechanism which is moderately active at steady‐state pHi. (2) In the presence of HCO3−, there is a Na‐independent Cl‐HCO3 (base) exchanger which also contributes to regulation of intracellular pH in Schwann cells. © 1994 Wiley‐Liss, Inc.
Loss of immunoreactivity for glial fibrillary acidic protein (GFAP) in astrocytes as a marker for profound tissue damage in substantia nigra and basal cortical areas after status epilepticus induced by pilocarpine in rat
Authors: Schmidt‐Kastner Rainald , Ingvar Martin 
Published: December 2004

AbstractStatus epilepticus induced by pilocarpine in rats induces massive tissue damage comprising neurons and astrocytes (incomplete infarction) in substantia nigra pars reticulata (SNR) and in basal cortical areas (BCTX). Immunohistochemistry with a polyclonal antiserum and a monoclonal antibody to GFAP were used here to study the astroglial damage in these regions. Control sections showed a strong labeling for glial fibrillary acidic protein (GFAP) for both antibodies in SNR and BCTX. At 1 day after induction of seizures, labeling with the polyclonal antibodies showed diffuse increase within the lesioned areas and enhanced staining of astrocytes at the border zones. However, staining with the monoclonal antibody was abolished. At 3 days, labeling with both the polyclonal antiserum and the monoclonal antibody was severely reduced within the damaged regions. Reactive astrocytes in the surround of the infarct showed enhanced labeling with both antibodies. This combination of enhanced labeling with polyclonal antibodies and decreased labeling with the specific monoclonal antibody for GFAP can be taken as indicator for acute glial cell damage in seizures and related experimental conditions.
Developmental changes in the number, size, and orientation of GFAP‐positive cells in the CA1 region of rat hippocampus
Authors: Nixdorf‐Bergweiler Barbara E. , Albrecht Dorothea , Heinemann Uwe 
Published: December 2004

AbstractChanges in extracellular potassium concentration as measured with ion‐selective microelectrodes revealed abnormally large accumulations in the hippocampus during postnatal development. While rises in [K+]o during stimulation of the Schaffer collaterals were limited to about 12 mM in adult animals, identical stimulations elicited rises to levels as large as 18 mM in juveniles. Since astrocytes are believed to play an important role in K+ homeostasis, we studied the postnatal development of astrocytes in the CA1 region of rat hippocampus in four age groups using a polyclonal antibody against glial fibrillary acidic protein (GFAP). The main proliferation of GFAP‐positive cells (GFAPpc) occurred in all laminae between postnatal days 8 and 16. The number of GFAP‐positive astrocytes per unit area was reached in stratum lacunosum‐moleculare and stratum oriens at about 2 weeks and in stratum radiatum at about 3 weeks of age. During further development—at the age of 24 days—the orientation of individual astrocytes in stratum radiatum became polar with an orientation almost perpendicular to stratum pyramidale. This was revealed by an analysis based on determination of the quotients between the angular orientation of the processes of single individual GFAP‐positive cells. When the crossing points of all glial processes over vertical and horizontal grid lines were determined and respective quotients evaluated, the same development towards a perpendicular orientation of astrocytes was noted in stratum radiatum. The same approach revealed a transient orientation parallel to the fissure in stratum lacunosum‐moleculare around day 24. Camera lucida drawings of GFAPpc in stratum radiatum revealed that astrocytes became larger during the first three postnatal weeks, followed by a reduction of various parameters (e.g., cell extension, branching pattern) until adulthood. The observed developmental changes of astroglial cells may contribute to the known delayed maturation of potassium regulation in rat hippocampus.
Blood monocytes and spleen macrophages differentiate into microglia‐like cells on monolayers of astrocytes: Membrane currents
Authors: Schmidtmayer Johann , Jacobsen Christian , Miksch Gundula , Sievers Jobst 
Published: December 2004

AbstractMicroglia, the resident macrophages of the central nervous system (CNS), can be distinguished from most other cells of the myelomonocytic lineage by a distinct pattern of memberane currents. In the accompanying paper we have shown that the characteristic morphological feature of microglia, ramification, develops both in microglia and other myelomonocytic cells when they are cocultured with astrocytes. We therefore propose that the electrophysiological properties of microglia also develop under the influence of astrocytes, and moreover, that these properties can also be induced in other cells of the myelomonocytic lineage. Microglia cultured on poly‐d‐lysine or on a monolayer of fibroblasts possess an inwardly rectifying K+ ‐current only, which is of composite nature. In single‐channel recordings two types of K+ ‐channels are found: (i) a non‐inactivating channel with a conductance of 43pS, and (ii) an inactivating channel with 32pS. Microglia cultured on a monolayer of astrocytes additionally develop an outward K+ ‐current and a Na+ ‐current. The electric parameters of activation and inactivation of the microglial Na+ ‐current are identical to those of the neuronal Na+ ‐current. Monocytes from peripheral blood and macrophages from spleen exhibit no inward currents. However, when these cells are cocultured with astrocytes they develop microglia‐like membrane currents, including the inward and outward K+ ‐rectifyer and the Na+ ‐current. By contrast, on fibroblasts they retain their macrophage current profile. The expression of the microglia‐like membrane currents in the monounclear phagocytes is induced by a diffusible factor released from the astrocytes into the culture medium, since monocytes and microglia develop the mature microglial current profile, when cultured in astrocyte conditioned medium. These findings show that the current profile of microglia develops only, when they are in association with astrocytes, and that it is induced in myelomonocytic cells from blood and spleen when these also are associated with astrocytes. These findings add to the growing body of evidence that microglia are derived from the myelmonocytic lineage and indicate that the astrocytes are involved in regulating their morphological and functional properties.
Differences in the disposition and toxicity of 1‐methyl‐4‐phenylpyridinium in cultured rat and mouse astrocytes
Authors: Tsai May J. , Lee Eminy H. Y. 
Published: December 2004

AbstractSpecies difference in the susceptibility to 1‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP) was investigated in cultured rat and mouse astrocytes, where 1‐methyl‐4‐phenylpyridinium (MPP+), the toxic mediator of MPTP, is formed. Type A monoamine oxidase (MAO) predominated in both rat and mouse astrocytes, while its activity was slightly higher in mouse cells compared to rat cells; MAO‐B activity, on the other hand, was significantly lower in mouse astrocytes than in rat astrocytes. Because both types of MAO have been reported to make similar contributions to MPP+ production in astrocytes, their total activity was examined and results indicated that there was no significant difference between these two species. In additon, MPP± caused a dose dependent loss of cell viability as judged by the amount of lactate dehydrogenase released into the incubation medium. The toxicity of MPP± on astrocytes started to be seen after a 2 day incubation period. Mouse astrocytes were more vulnerable to MPP± than rat astrocytes. The threshhold values for MPP± toxicity in mouse and rat cultures were 10 ±M and 70 ±M, respectively. After addition of [3H] MPP± to the medium, intracellular [3H] MPP± was found to increase in both cultures. Mouse astrocytes accumulated more MPP± than rat astrocytes (150 pmol/mg protein vs. 65 pmol/mg protein). When astrocytes were allowed to accumulate [3H] MPP± and then incubated in fresh medium medium not containing [3H] MPP±, intracellular levels of [3H] MPP± in both cells rapidly declined (110 pmol/protein in mouse vs. 40 pmol/mg protein in rat of MPP± been released). These results indicated that (1) MPP± could cross the plasma membrane of astrocytes despite of its charged chemical structure, (2) mouse astrocytes had a higher capacity for MPP± accumulation (approximately 2‐fold), as well as release (approximately 2.7‐fold), than rat astrocytes, and (3) mouse astrocytes were more vulnerable to MPP± than rat astrocytes.
On the existence of a cartilage‐like proteoglycan and link proteins in the central nervous system
Authors: Asher Richard A. , Scheibe Renate J. , Keiser Harold D. , Bignami Amico 
Published: December 2004

AbstractMonoclonal antibodies (mAbs) against the major constituents of cartilage extracellular matrix, aggrecan and link protein, were screened by indirect immunofluorescence on frozen sections of bovine spinal cord. Antibodies against aggrecan and link protein gave rise to very similar perineuronal labeling in spinal cord gray matter. Aggrecan and link protein reactivities were seen in other regions of the central nervous system (CNS), although their distributions were not always coincident. Pretreatment of the tissue section with Streptomyces hyaluronidase, which is hyaluronate‐specific, led to the loss of both reactivities. On Western blots, anti‐aggrecan mAbs reacted with a large chondroitin sulfate proteoglycan. The chondroitinase‐treated CNS proteoglycan co‐migrated with the chondroitinase‐ and keratanase‐treated cartilage proteoglycan. In CNS tissue homogenates, the addition of Streptomyces hyaluronidase brought about the release of the proteoglycan from the tissue. Anti‐link protein mAbs were reactive with two species in the bovine CNS, the mobilities of which were very similar to those of the cartilage link proteins. The release of these species from the tissue required hyaluronidase. A rabbit antiserum against aggrecan was used to identify a similar proteoglycan in the rat CNS. In spinal cord‐derived cell cultures, the labeled material was associated with astrocytes. An aggrecan cDNA hybridized to a 9.5 kb mRNA in the rat CNS. We conclude that the perineuronal matrix consists, in part, of a hyaluronate‐bound aggrecan‐like proteoglycan and link proteins, and that the former is produced by astrocytes. © 1995 Wiley‐Liss, Inc.