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  • 1
    ISSN: 1573-1634
    Keywords: non-Brownian particle ; particle capture ; probability density ; hydrodynamics ; inertial impaction.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Technology
    Notes: Abstract We have studied the transport and capture of non-Brownian particles in porous media, when the particles are mainly submitted to hydrodynamic and weak inertial effects. Visualization experiments have been performed using several models of porous media which consist of transparent etched networks of interconnected channels. Typical particle deposits have been observed at the corners of the grains of the porous medium. Their shape and their orientation were dependent on flow rate and on the anisotropy of the flow field. A trajectory analysis model has been applied to a porous medium made of a doubly periodic array of rectangular grains very close to the experimental model. This numerical model has been used to localize particle deposits and to determine particle capture efficiency on the grains over a range of low Stokes numbers, grain aspect ratios and flow-field anisotropy ratios. The results have been interpreted in terms of shape of particle deposits and compared successfully to experimental observations.
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  • 2
    ISSN: 1572-879X
    Keywords: Lanthana-modified alumina ; alumina-supported ceria ; oxygen storage ; three-way catalyst ; X-ray photoelectron spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract X-ray photoelectron spectroscopy measurements indicate that the Ce3+ fraction in Al2O3-supported CeO2 can be decreased by the incorporation of La3+. If La3+ is incorporated into the Al2O3 before CeO2 is added, a higher CeO2 dispersion and a greater range of reversible reducibility of the CeO2 may also be obtained. These changes offer potential for improvement in the oxygen storage capacity provided by CeO2 in three-way catalysts.
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  • 3
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: 1For the calculation of the scattering curve of a chain molecule, represented by a flexible filament, a formula was derived according to an expression comprising exactly both limiting cases, the GAUSS coil and the rigid rod. This formula leads, in its distance statistics, to agreement with the theoretically required one up to r̄4. In order to achieve this, we determined for the r̄4 as calculated already somewhere else for the non-continuous model, the limit for the “worm like” chain. Instead of a summation, an integration over all contributions of intensity of possible distances yields here the total intensity in dependence on the angle μ. The formula had been split apart in such a way, that an integral as already calculated by other authors with, however, taking into consideration only r̄2, is obtained separately, and the amendmend with r̄4 can be regarded as a kind of correction to it. The calculation has been carried out by means of an electronic computer (IBM 650). We calculated, for chains up to a length of 300 persistence units, the scattering curves. Besides, the case of the infinitely long molecule was treated separately according to an integrated formula. The results show a considerably better fit of the shape of the curve to the division into three parts of the scattering curve of chain molecules as required by theory, than it had been the case with other calculations.The linear running out portion of the curve, which is setting in cleanly at an angle of about μ = 5, is also exhibited clearly. A discrepancy to former work is the position of the transition point, which is found for the infinitely long molecule at 1,5 in this work. A next approximation might bring about a clarification here. Finally, a clear dependence of the transition point on the chain length was found.2The experimental arrangement for measuring the scattering curves is described. A small angle camera free of collimation error is being used. The monochromatisation is done by means of the filter difference method, the measurement of the intensity by means of a GEIGER counter. For measuring the intensity of the primary beam, which is necessary for the calculation of the absolute intensity, a rotor with a very small hole is used for the diminuation.3The slit shaped primary beam makes a correction for the collimation error necessary, whereby the finite length has to be taken into consideration. A correction for the collimation error with regard to width is also applied.4The measurements were carried out with cellulose nitrate samples of various origin in the concentration range of 0.55 to 6.65%. The degree of polymerization lies between the limits of 1640 and 3500. The shape of the curves obtained corresponds fairly well to that expected from the theory. The persistence lengths are found to be in the range of about 40Å for samples from cotton with low nitrogen content (13,83%); with higher nitrogen content (14,14%) in dependence on the concentration between 50 and 70Å; dilution is enhancing the persistence length. Considerable deviations are found with samples from pulp (Halleiner Fichte): persistence lengths between 22 and 28 Å are obtained.5The absolute measurement lead to a degree of association of exactly 1.
    Notes: 1Für die Berechnung der Streukurven eines Fadenmoleküls, das durch einen biegsamen Faden dargestellt wird, wurde nach einem Ansatz, der die beiden Grenzfälle des unendlich großen GAUSS-Knäuels und des starren Stäbchens exakt enthält, eine Formel abgeleitet, die in ihrer Abstandsstatistik eine Übereinstimmung mit der theoretisch geforderten bis zum r̄4 erzielt. Dazu vollzogen wir an dem für das unstetige Modell schon anderswo berechneten r̄4 den Grenzübergang zur „wormlike chain“. Statt der Summation ergibt hier eine Integration über alle Intensitätsbeiträge der möglichen Abstände die gesamte Streuintensität in Abhängigkeit vom Winkel μ. Die Formel wurde so aufgespalten, daß ein von anderen Autoren schon berechnetes Integral, in welchem nur das r̄2 berücksichtigt wird, getrennt erhalten wird und die Verbesserung mit dem r̄4 als eine Art Korrektur dazu betrachtet werden kann. Die Berechnung wurde mittels einer elektronischen Rechenanlage (IBM 650) durchgeführt. Für Fäden bis zu einer Länge von 300 Persistenzeinheiten berechneten wir die Streukurven, wobei wir außerdem den Fall des unendlich langen Moleküls nach einer ausintegrierten Formel gesondert behandelten. Die Ergebnisse zeigen eine wesentlich bessere Anpassung der Kurvenform an die theoretisch geforderte Dreiteilung der Streukurve für Fadenmoleküle als es bei anderen Berechnungen der Fall war. Der lineare Kurvenauslauf, der ungefähr bei einem Winkel von μ = 5 rein einsetzt, tritt ebenfalls klar in Erscheinung. Eine Diskrepanz gegenüber früheren Arbeiten stellt die Lage des Übergangspunktes für das unendlich lange Molekül dar, für die sich in der vorliegenden Untersuchung μ = 1,5 ergibt. Eine nächste Näherung könnte hier eine Klärung bringen. Schließlich wurde gefunden, daß sich der Übergangspunkt bei Knäuein endlicher Größe mit abnehmender Fadenlänge gegen größere μ  -  Werte verschiebt.2Die experimentelle Anordnung zur Messung der Streukurven wird beschrieben. Es gelangt eine „blendenstreuungsfreie“ Kleinwinkelkamera zur Anwendung. Die Monochromatisierung erfolgt mit dem Filterdifferenzverfahren, die Messung der gestreuten Intensität mit einem GEIGER-MÜLLER-Zählrohr. Bei der Messung der Intensität des Primärstrahls, die zur Berechnung der Absolutintensität erforderlich ist, wird zur Schwächung ein Rotator mit sehr kleinem Loch benützt.3Der spaltförmige Primärstrahl macht eine Entschmierung notwendig, wobei die endliche Länge zu berücksichtigen ist. Es wird auch eine Breitenentschmierung durchgeführt.4Gemessen werden Cellulosenitrate verschiedener Herkunft im Konzentrationsbereich von 0,55 bis 6,65%. Der DP liegt in den Grenzen zwischen 1640 und 3500. Die erhaltene Kurvenform entspricht sehr weitgehend den Erwartungen der Theorie. Die Persistenzlängen liegen für die Präparate aus Baumwolle bei niedrigerem Stickstoffgehalt (13,83%) in der Gegend von 40Å, bei höherem Stickstoffgehalt (14,14%) in Abhängigkeit von der Konzentration zwischen 50 und 70Å, wobei Verdunnung die Persistenzlange vergrößert. Merklich aus der Reihe fallen Präparate aus Halleiner Fichte (Persistenzlängen zwischen 22 und 28Å).5Die Absolutmessung führt auf einen Assoziationsgrad von genau 1.
    Additional Material: 26 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
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  • 5
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 4 Ill.
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  • 6
    ISSN: 1432-1955
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract LEWIS rats, in contrast to NMRI mice, have been found to be resistant to an oral infection withNematospiroides dubius (Baylis, 1926). Comparative studies of the peritoneal response to infection showed a strong increase in the cell number predominantly of eosinophilic and neutrophilic granulocytes in rats, whereas in mice only a weak reaction occurred. As shown by the chemiluminescence response to either antibody — or complement-coated larvae, the granulocyte reaction caused an increased production of toxic oxygen species by the peritoneal cells. Purified granulocytes from rats or mice showed about a tenfold higher oxidant generation than macrophages. The higher metabolic activity of granulocytes of either species resulted in rapid and strong killing of antibody or complement-coated infective larvae by granulocytes of either species, whereas macrophages failed to express a significant larvicidal potency. From these results we concluded that the activated oxygen species derived from the metabolic burst of granulocytes are essential for an effective control of the primary infection withN. dubius. This suggests that the rapid and strong granulocyte response may form the basis of the resistance in rats. Thus, in mice, the ability ofN. dubius to prevent the granulocyte response may serve as an escape mechanism of the parasite.
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  • 7
    ISSN: 1617-7134
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
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  • 8
    ISSN: 0142-2421
    Keywords: thermoplastic olefin (TPO) ; valence band ; XPS ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: In this study we evaluate the utility of using x-ray-excited valence band measurements for the determination of the surface composition of simple model thermoplastic olefin systems composed of binary blends of semicrystalline polypropylene (PP) and an amorphous ethylene-propylene copolymer (E-co-P). Blend compositions included combinations of high- and low-molecular-weight (MW) PP and E-co-P composed of 60 wt.% PP/40 wt.% E-co-P and 80 wt.% PP/20 wt.% E-co-P blends. Results demonstrate that experimental valence band spectra for the polyolefin blends can be approximated by a linear combination of the pure-component valence band spectra. Bulk compositions determined from spectra recorded from cryomicrotomed cross-sections were found to be consistent with the bulk component wt.%. The surface compositions of the binary blends were all found to be enriched in PP. Measurements taken from the 60/40 wt.% blends were 10-20% higher in PP concentration than the bulk compositions, and were found to vary depending on the MW combination of the components. No MW dependence was observed for the 80/20 wt.% blends, apparently due to a near saturation of the surface with PP. The development of methods for assessing the surface composition of these types of materials may prove useful in monitoring changes in composition with material formulation and process conditions. Information of this nature could be helpful in permitting an evaluation of potential influences of composition on adhesion. © 1997 by John Wiley & Sons, Ltd
    Additional Material: 7 Ill.
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  • 9
    ISSN: 0730-2312
    Keywords: melanoma ; TNFα ; isolation perfusion ; melphalan ; interferon-γ ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Recombinant tumor necrosis factor-alpha (rTNFα) has potent antitumor activity in experimental studies on human tumor xenografts. However, in humans, the administration of rTNFα is hampered by severe systemic side-effects. The maximum tolerated dose range from 350 to 500 mg/m2, which is at least 10-fold less than the efficient dose in animals. Isolation perfusion of the limbs (ILP) allows the delivery of high dose rTNFα in a closed system with acceptable side-effects. A protocol with a triple-drug regimen was based on the reported synergism of rTNFα with chemotherapy, with interferon-y, and with hydperthermia. In melanoma-in-transit metastases (stage IIIA or AB) we obtained a 91% complete response, compared with 52% after ILP with melphalan alone. Release of nanograms levels of TNFα in the systemic circulation was evident but control of this leakage and appropriate intensive care resulted in acceptable toxicity. Angiographic, immunohistological, and immunological studies suggest that the efficacy of this prtocol is due to a dual targeting: rTNFα activates and electively lyses the tumor endothelial cells while melphalan is mainly cytoxic to the tumor cells. ILP with rTNFα appears to be a useful model for studying the biochemotherapy of cancer in man.
    Additional Material: 2 Ill.
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  • 10
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    Halle (Saale): Leibniz-Institut für Agrarentwicklung in Mittel- und Osteuropa (IAMO)
    Publication Date: 2013-05-22
    Description: This paper addresses the question whether the institutional environment of transition countries in Eastern Europe affects productivity growth in the agricultural sector. Situated in a neoclassical growth framework, a dynamic panel model for the period 1996-2005 provides evidence that poor institutional quality leads to a slowdown in agricultural productivity growth. Productivity growth is limited by a high degree of corruption, which is of particular importance given that corruption has been proven to be most prevalent in Eastern European countries. Moreover, agricultural productivity in countries where privatisation and transferability of land is restricted is found to grow at a slower rate than countries supporting market-oriented land reforms. Interestingly, the results suggest that a high degree of openness leads to a loss in agricultural productivity, suggesting that timing and sequencing of trade reforms matter. An improvement of the poor institutional quality is thus of central importance to accelerate productivity growth in Eastern European countries.
    Keywords: ddc:330 ; Eastern Europe ; Transition ; Productivity growth
    Repository Name: EconStor: OA server of the German National Library of Economics - Leibniz Information Centre for Economics
    Language: English
    Type: doc-type:conferenceObject
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