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  • Chemistry  (3)
  • lake restoration  (2)
  • 1990-1994  (5)
  • 1992  (3)
  • 1990  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Coupling of phytoplankton and detritus in a shallow, eutrophic lake (Lake Loosdrecht, The Netherlands) (1992)
    Springer
    Hydrobiologia 233 (1992), S. 51-59 
    Details
    ISSN: 1573-5117
    Keywords: phytoplankton ; Oscillatoria limnetica ; Prochlorothrix hollandica ; detritus ; shallow lakes ; lake restoration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract An oscillating steady state is described of phytoplankton, dominated by Prochlorothrix hollandica and Oscillatoria limnetica, and sestonic detritus in shallow, eutrophic Lake Loosdrecht (The Netherlands). A steady-state model for the coupling of the phytoplankton and detritus is discussed in relation to field and experimental data on phytoplankton growth and decomposition. According to model predictions, the phytoplankton to detritus ratio decreases hyperbolically at increasing phytoplankton growth rate and is independent of a lake's trophic state. The seston in L. Loosdrecht contains more detritus than phytoplankton as will apply to many other lakes. The model provides a basis for estimating the loss rate of the detritus, including decomposition, sedimentation and hydraulic loss. In a shallow lake like L. Loosdrecht detritus will continue to influence the water quality for years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00016095
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Dynamics of phytoplankton detritus in a shallow, eutrophic lake (Lake Loosdrecht, The Netherlands) (1992)
    Springer
    Hydrobiologia 233 (1992), S. 61-67 
    Details
    ISSN: 1573-5117
    Keywords: phytoplankton ; epipelon ; Oscillatoria limnetica ; detritus ; shallow lakes ; lake restoration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A study was made of the mortality and aerobic decomposition of light- and phosphorus-limited cultures of Oscillatoria limnetica, a dominant phytoplankton species in shallow, eutrophic Lake Loosdrecht (The Netherlands). When placed in the dark at 20 °C, most cells died and lysed within twelve days. The labile organic matter was completely decomposed within three weeks. Absorbance spectra indicated that blue green algae may contributed significantly to the refractory dissolved substances in the lake. Refractory particulate matter constituted from 7 to 24% of the biomass of O. limnetica, depending on the growth rate before incubation in the dark. The decomposition rate of this fraction was 0.005 d−1. On a basis of a steady-state model of the dynamics of phytoplankton detritus, the areal organic dry weight concentration of the detritus in the lake is ca. 60 g m−2. This means the quantities of detritus in the seston and epipelon are about equal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00016096
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    MD simulation of subtilisin BPN′ in a crystal environment (1992)
    New York, NY : Wiley-Blackwell
    Proteins: Structure, Function, and Genetics 14 (1992), S. 451-464 
    Details
    ISSN: 0887-3585
    Keywords: protein force field ; protein crystal ; protein hydration ; Ca2+ binding site ; molecular dynamics ; subtilisin ; computer simulation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine
    Notes: In this paper we present a molecular dynamics (MD) simulation of subtilisin BPN′ in a crystalline environment containing four protein molecules and solvent. Con-formational and dynamic properties of the molecules are compared with each other and with respect to the X-ray structure to test the validity of the force field. The agreement between simulated and experimental structure using the GROMOS force field is better than that obtained in the literature using other force fields for protein crystals. The overall shape of the molecule is well preserved, as is the conformation of α-helices and β-strands. Structural differences are mainly found in loop regions. Solvent networks found in the X-ray structure were reproduced by the simulation, which was unbiased with respect to the crystalline hydration structure. These networks seem to play an important role in the stability of the protein; evidence of this is found in the structure of the active site. The weak ion binding site in the X-ray structure of subtilisin BPN′ is occupied by a monovalent ion. When a calcium ion is placed in the initial structure, three peptide ligands are replaced by 5 water ligands, whereas a potassium ion retains (in part) its original ligands. Existing force fields yield a reliable method to probe local structure and short-time dynamics of proteins, providing an accuracy of about 0.1 nm. © 1992 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prot.340140406
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  • 4
    Electronic Resource
    Electronic Resource
    Moleküldynamik-Computersimulationen; Methodik, Anwendungen und Perspektiven in der Chemie (1990)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 102 (1990), S. 1020-1055 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Während der letzten Jahrzehnte ist es möglich geworden, die Dynamik molekularer Systeme mit dem Computer zu simulieren. Bei Moleküldynamik(MD)-Simulationen löst man Newtons Bewegungsgleichungen für ein molekulares System, wobei die Trajektorien aller im System vorhandenen Atome erhalten werden. Aus diesen atomaren Trajektorien kann eine Vielzahl von Eigenschaften berechnet werden. Computersimulationen molekularer Systeme haben das Ziel, makroskopisches Verhalten aus mikroskopischen Wechselwirkungen zu errechnen. Die wesentlichen Beiträge, die eine mikroskopische Betrachtungsweise liefern kann, sind 1) das Verständnis, 2) die Interpretation experimenteller Ergebnisse, 3) halbquantitative Abschätzungen experimenteller Resultate und 4) die Fähigkeit, experimentelle Daten in Bereiche zu interpolieren oder zu extrapolieren, die im Labor nur schwer zugänglich sind. Eines der beiden grundlegenden Probleme auf dem Gebiet der Modellierung und Simulation molekularer Systeme besteht darin, den riesigen Konfigurationsraum, der von allen möglichen Molekülkonformationen aufgespannt wird, auf effiziente Weise nach jenen Bereichen global niedriger (freier) Enthalpie zu durchsuchen, die von einem molekularen System im thermischen Gleichgewieht besetzt sind. Das andere Grundproblem ist die Ableitung einer hinreichend exakten Energiefunktion oder eines Kraftfelds für Wechselwirkungen im zu untersuchenden molekularen System. Die Kunst der Computersimulation besteht auch darin, die unvermeidbaren Annahmen, Näherungen und Vereinfachungen für das molekulare Modell und den Rechenvorgang so zu treffen, daß ihre jeweiligen Beiträge zur Gesamtungenauigkeit von ähnlicher Größe sind, ohne dabei die interessierende Systemeigenschaft signifikant zu beeinflussen. Die Methodik und einige praktische Anwendungen der Computersimulation auf dem Gebiet der (Bio)chemie sind der Gegenstand dieser Übersicht.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19901020907
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  • 5
    Electronic Resource
    Electronic Resource
    Computer Simulation of Molecular Dynamics: Methodology, Applications, and Perspectives in Chemistry (1990)
    Weinheim : Wiley-Blackwell
    Angewandte Chemie International Edition in English 29 (1990), S. 992-1023 
    Details
    ISSN: 0570-0833
    Keywords: Molecular dynamics ; Computer chemistry ; Force field calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: During recent decades it has become feasible to simulate the dynamics of molecular systems on a computer. The method of molecular dynamics (MD) solves Newton's equations of motion for a molecular system, which results in trajectories for all atoms in the system. From these atomic trajectories a variety of properties can be calculated. The aim of computer simulations of molecular systems is to compute macroscopic behavior from microscopic interactions. The main contributions a microscopic consideration can offer are (1) the understanding and (2) interpretation of experimental results, (3) semiquantitative estimates of experimental results, and (4) the capability to interpolate or extrapolate experimental data into regions that are only difficultly accessible in the laboratory. One of the two basic problems in the field of molecular modeling and simulation is how to efficiently search the vast configuration space which is spanned by all possible molecular conformations for the global low (free) energy regions which will be populated by a molecular system in thermal equilibrium. The other basic problem is the derivation of a sufficiently accurate interaction energy function or force field for the molecular system of interest. An important part of the art of computer simulation is to choose the unavoidable assumptions, approximations and simplifications of the molecular model and computational procedure such that their contributions to the overall inaccuracy are of comparable size, without affecting significantly the property of interest. Methodology and some practical applications of computer simulation in the field of (bio)chemistry will be reviewed.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/anie.199009921
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    Paper (German National Licenses)
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