ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Ihre E-Mail wurde erfolgreich gesendet. Bitte prüfen Sie Ihren Maileingang.

Leider ist ein Fehler beim E-Mail-Versand aufgetreten. Bitte versuchen Sie es erneut.

Vorgang fortführen?

Exportieren
Filter
  • Aircraft Stability and Control  (6)
  • Biochemistry and Biotechnology  (4)
  • *Meteoroids  (3)
  • Electronics and Electrical Engineering  (3)
  • 1
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 56 (1997), S. 232-237 
    ISSN: 0006-3592
    Schlagwort(e): lipozyme ; esterification ; continuous reactor ; water activity ; organic solvent ; supercritical carbon dioxide ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: In the field of biocatalysis in nonaqueous media, water has been identified as a crucial parameter which has to be carefully controlled. This article studies the continuous operation of a water-producing enzymatic reaction, here the esterification of oleic acid by ethanol in n-hexane catalyzed by LipozymeTM. The conversion decreased significantly over time, eventually coming to a lower steady-state level. This would be due to the accumulation of the produced water into the enzyme fixed-bed reactor, n-hexane being unable to evacuate this water out of the reaction vessel, because of the low polarity of this solvent. Therefore the conversion decreased until the produced water could be eliminated by the solvent achieving a steady state with a lower conversion. In supercritical carbon dioxide, a more hydrophilic solvent, steady state is at once obtained. This approach has been extended to reaction producing a hydrophilic compound, here glycerol during the transesterification between triolein and ethanol, and similar conclusions can be made. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 56: 232-237, 1997.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 2
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 273-280 
    ISSN: 0006-3592
    Schlagwort(e): enzyme ; supercritical CO2 ; stability ; effect of water ; comparison with organic solvent ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: This study compares two solvents for enzymatic reactions: supercritical carbon dioxide (SCCO2) and organic solvent (n-hexane). The model reaction that was chosen was the esterification of oleic acid by ethanol catalyzed by an immobilized lipase from Mucor miehei (Lypozyme). The stability of the enzyme appeared to be quite good and similar in both media but was affected by the water content. Partition of water between solvents and immobilized enzyme has been calculated from experimental adsorption isotherms. The water content of the solid phase has a dramatic influence on the activity of the enzyme and its optimum value for activity was about 10% (w/w) in both media. A kinetic study enabled a Ping-Pong Bi-Bi reaction mechanism with inhibition by ethanol to be suggested. Despite some differences in kinetic constants, activity was in the same range in both media. Hypotheses for explaining the kinetic constant variations have been proposed and particular attention has been paid to the pH effects.
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 3
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 497-504 
    ISSN: 0006-3592
    Schlagwort(e): immobilized enzyme ; lipase ; esterification ; fatty acids ; supercritical carbon dioxide ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: The study of enzymatic esterification by an immobilized lipase in supercritical carbon dioxide (SCCO2) and in n-hexane, described in our previous works, was extended to continuous operation in a tubular fixed bed. The modeling of the reaction vessel operation was achieved through the use of the simple plug flow model coupled with the appropriate kinetic equation. Comparison with experiments proved to be satisfactory. The study of the postreactional separation, an important feature when using SCCO2, was undertaken experimentally and good selectivities and product recovery were obtained. © 1994 John Wiley & Sons, Inc.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 4
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 60 (1998), S. 362-368 
    ISSN: 0006-3592
    Schlagwort(e): esterification ; continuous reaction ; water activity ; lipase ; organic solvent ; packed-bed reactor ; Chemistry ; Biochemistry and Biotechnology
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: During continuous lipase-catalyzed oleic acid esterification by ethanol in n-hexane, the oleic acid conversion, initially at 95%, decreases to 20% after 2 h. This decrease is caused by the accumulation of the water produced in the course of the reaction in the packed-bed reactor (PBR). In order to improve the PBR efficiency, it is necessary to evacuate the water produced. In this study, different approaches have been tested to control the water content in the PBR during continuous esterification. The first approach consisted in improving the water solubility by increasing the reaction medium polarity. The addition of polar additives to n-hexane, the use of more polar solvents, and the use of solvent-free reaction medium were tested as a means to favor the water evacuation from the PBR. First of all, the use ofn-hexane supplemented with acetone (3 M) or 2-methyl-2-propanol (1 M) enabled the conversion to be maintained at higher values than those obtained in pure n-hexane. The replacement of n-hexane by a more polar solvent, like the 5-methyl-2-hexanone, resulted in the same effect. In all cases, conversions at steady-state were always less than 95%, as obtained in pure n-hexane. This is explained by a decrease in the enzyme activity due to the increase in the medium polarity. Nevertheless, an increase in enzyme quantity allowed 90% conversion to be maintained during 1 week using 3 M acetone amended n-hexane. Good results (a steady-state conversion of about 80%) were obtained when esterification was carried out in a solvent-free reaction medium containing 2 M 2-methyl-2-propanol as a polar additive. The second approach consisted in the evaporation of the accumulated water by use of an intermittent airflow. Although this process did not enable constant esterification rate to be maintained, it did enable the initial conversion (95%) to be restored intermittently. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 60: 362-368, 1998.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 5
    facet.materialart.
    Unbekannt
    American Association for the Advancement of Science (AAAS)
    Publikationsdatum: 2006-05-06
    Beschreibung: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Marty, Bernard -- New York, N.Y. -- Science. 2006 May 5;312(5774):706-7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Centre de Recherches Petrographiques et Geochimiques, Vandoeuvre-les-Nancy Cedex, 54501 France. bmarty@crpg.cnrs-nancy.fr〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16675689" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): *Cosmic Dust ; Deuterium/*analysis ; Evolution, Planetary ; *Meteoroids ; Nitrogen Isotopes/*analysis ; Organic Chemicals/*analysis ; Oxygen Isotopes ; *Solar System ; Ultraviolet Rays
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 6
    Publikationsdatum: 2012-10-16
    Beschreibung: Tissint (Morocco) is the fifth martian meteorite collected after it was witnessed falling to Earth. Our integrated mineralogical, petrological, and geochemical study shows that it is a depleted picritic shergottite similar to EETA79001A. Highly magnesian olivine and abundant glass containing martian atmosphere are present in Tissint. Refractory trace element, sulfur, and fluorine data for the matrix and glass veins in the meteorite indicate the presence of a martian surface component. Thus, the influence of in situ martian weathering can be unambiguously distinguished from terrestrial contamination in this meteorite. Martian weathering features in Tissint are compatible with the results of spacecraft observations of Mars. Tissint has a cosmic-ray exposure age of 0.7 +/- 0.3 million years, consistent with those of many other shergottites, notably EETA79001, suggesting that they were ejected from Mars during the same event.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Aoudjehane, H Chennaoui -- Avice, G -- Barrat, J-A -- Boudouma, O -- Chen, G -- Duke, M J M -- Franchi, I A -- Gattacceca, J -- Grady, M M -- Greenwood, R C -- Herd, C D K -- Hewins, R -- Jambon, A -- Marty, B -- Rochette, P -- Smith, C L -- Sautter, V -- Verchovsky, A -- Weber, P -- Zanda, B -- New York, N.Y. -- Science. 2012 Nov 9;338(6108):785-8. doi: 10.1126/science.1224514. Epub 2012 Oct 11.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Hassan II University Casablanca, Faculty of Sciences, Geosciences Appliquees a l'Ingenierie et l'Amenagement (GAIA) Laboratory, BP 5366 Maarif, Casablanca, Morocco. chennaoui_h@yahoo.fr〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23065902" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Carbon Isotopes/analysis ; Iron Compounds/analysis ; Magnesium Compounds/analysis ; *Mars ; *Meteoroids ; Nitrogen Isotopes/analysis ; Oxygen Isotopes/analysis ; Silicates/analysis
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 7
    Publikationsdatum: 2006-12-16
    Beschreibung: Hydrogen, carbon, nitrogen, and oxygen isotopic compositions are heterogeneous among comet 81P/Wild 2 particle fragments; however, extreme isotopic anomalies are rare, indicating that the comet is not a pristine aggregate of presolar materials. Nonterrestrial nitrogen and neon isotope ratios suggest that indigenous organic matter and highly volatile materials were successfully collected. Except for a single (17)O-enriched circumstellar stardust grain, silicate and oxide minerals have oxygen isotopic compositions consistent with solar system origin. One refractory grain is (16)O-enriched, like refractory inclusions in meteorites, suggesting that Wild 2 contains material formed at high temperature in the inner solar system and transported to the Kuiper belt before comet accretion.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉McKeegan, Kevin D -- Aleon, Jerome -- Bradley, John -- Brownlee, Donald -- Busemann, Henner -- Butterworth, Anna -- Chaussidon, Marc -- Fallon, Stewart -- Floss, Christine -- Gilmour, Jamie -- Gounelle, Matthieu -- Graham, Giles -- Guan, Yunbin -- Heck, Philipp R -- Hoppe, Peter -- Hutcheon, Ian D -- Huth, Joachim -- Ishii, Hope -- Ito, Motoo -- Jacobsen, Stein B -- Kearsley, Anton -- Leshin, Laurie A -- Liu, Ming-Chang -- Lyon, Ian -- Marhas, Kuljeet -- Marty, Bernard -- Matrajt, Graciela -- Meibom, Anders -- Messenger, Scott -- Mostefaoui, Smail -- Mukhopadhyay, Sujoy -- Nakamura-Messenger, Keiko -- Nittler, Larry -- Palma, Russ -- Pepin, Robert O -- Papanastassiou, Dimitri A -- Robert, Francois -- Schlutter, Dennis -- Snead, Christopher J -- Stadermann, Frank J -- Stroud, Rhonda -- Tsou, Peter -- Westphal, Andrew -- Young, Edward D -- Ziegler, Karen -- Zimmermann, Laurent -- Zinner, Ernst -- New York, N.Y. -- Science. 2006 Dec 15;314(5806):1724-8.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Earth and Space Sciences, University of California Los Angeles, Los Angeles, CA 90095-1567, USA. mckeegan@ess.ucla.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17170292" target="_blank"〉PubMed〈/a〉
    Schlagwort(e): Carbon Isotopes/*analysis ; Deuterium/*analysis ; Hydrogen/analysis ; Isotopes/*analysis ; *Meteoroids ; Neon/analysis ; Nitrogen Isotopes/*analysis ; Noble Gases/analysis ; Oxygen Isotopes/*analysis ; Spacecraft
    Print ISSN: 0036-8075
    Digitale ISSN: 1095-9203
    Thema: Biologie , Chemie und Pharmazie , Informatik , Medizin , Allgemeine Naturwissenschaft , Physik
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 8
    Publikationsdatum: 2016-06-07
    Beschreibung: Wavelets present a method for signal processing that may be useful for analyzing responses of dynamical systems. This paper describes several wavelet-based tools that have been developed to improve the efficiency of flight flutter testing. One of the tools uses correlation filtering to identify properties of several modes throughout a flight test for envelope expansion. Another tool uses features in time-frequency representations of responses to characterize nonlinearities in the system dynamics. A third tool uses modulus and phase information from a wavelet transform to estimate modal parameters that can be used to update a linear model and reduce conservatism in robust stability margins.
    Schlagwort(e): Aircraft Stability and Control
    Materialart: CEAS/AIAA/ICASE/NASA Langley International Forum on Aeroelasticity and Structural Dynamics 1999; Pt. 1; 393-402; NASA/CP-1999-209136/PT1
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 9
    Publikationsdatum: 2019-07-13
    Beschreibung: An approach for computing worst-case flutter margins has been formulated in a robust stability framework. Uncertainty operators are included with a linear model to describe modeling errors and flight variations. The structured singular value, micron, computes a stability margin which directly accounts for these uncertainties. This approach introduces a new method of computing flutter margins and an associated new parameter for describing these margins. The micron margins are robust margins which indicate worst-case stability estimates with respect to the defined uncertainty. Worst-case flutter margins are computed for the F/A-18 SRA using uncertainty sets generated by flight data analysis. The robust margins demonstrate flight conditions for flutter may lie closer to the flight envelope than previously estimated by p-k analysis.
    Schlagwort(e): Aircraft Stability and Control
    Materialart: NASA/TM-97-207564 , NAS 1.15:207564 , AIAA Paper 97-1266 , Structures, Structural Dynamics and Materials Conference; Apr 01, 1997; Orlando, FL; United States
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
  • 10
    Publikationsdatum: 2019-07-13
    Beschreibung: Wavelet analysis for filtering and system identification was used to improve the estimation of aeroservoelastic stability margins. The conservatism of the robust stability margins was reduced with parametric and nonparametric time-frequency analysis of flight data in the model validation process. Nonparametric wavelet processing of data was used to reduce the effects of external desirableness and unmodeled dynamics. Parametric estimates of modal stability were also extracted using the wavelet transform. Computation of robust stability margins for stability boundary prediction depends on uncertainty descriptions derived from the data for model validation. F-18 high Alpha Research Vehicle aeroservoelastic flight test data demonstrated improved robust stability prediction by extension of the stability boundary beyond the flight regime.
    Schlagwort(e): Aircraft Stability and Control
    Materialart: NASA/TM-1998-206545 , NAS 1.15:206545 , H-2222 , AIAA Paper 98-1896 , Structures, Structural Dynamics and Materials Conference; Apr 20, 1998 - Apr 23, 1998; Long Beach, CA; United States
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
Schließen ⊗
Diese Webseite nutzt Cookies und das Analyse-Tool Matomo. Weitere Informationen finden Sie hier...