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  • 1
    Electronic Resource
    Electronic Resource
    POSIT – a method for structure determination of small partially known molecules from powder diffraction data.Structure of 6-methyl-1,2,3,4-tetrahydropyrimidine-2,4-dione (6-methyluracil) (1988)
    [S.l.] : International Union of Crystallography (IUCr)
    Acta crystallographica 44 (1988), S. 417-421 
    Details
    ISSN: 1600-5724
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Chemistry and Pharmacology , Geosciences , Physics
    Notes: POSIT is a computer program package for the determination of the approximate structure of small organic molecules using known molecular fragments. The orientation and the translation vector of this fragment are determined and refined by a special R-value analysis. In contrast to other molecular replacement methods, only a few low-order strong reflections are needed to start the structure analysis. Therefore, this method is suitable for the determination of crystal structures of small rigid or semi-rigid organic molecules without heavy atoms from powder diffraction data. C5H6N2O2, Mr = 126.11, monoclinic, P21/c, a = 4.5137 (7), b = 10.9888 (12), c = 11.7224 (9) Å, β = 97.554 (8)°, V = 576.39 (7) Å3, Z = 4, Dx = 1.453 Mg m-3, λ (Cu Kα) = 1.54178 Å, μ = 0.987 mm-1, F(000) = 264, T = 297 K, final R = 0.04 for 165 approximate structure factors obtained from a powder diffraction measurement. The molecules were found in the diketo form. They are linked by a two-dimensional network of hydrogen bonds forming layers parallel to the yz plane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0108767388000315
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  • 2
    Electronic Resource
    Electronic Resource
    In vivo ^3^1P NMR spectroscopy of energy rich phosphates in the brain of the hyperammonemic rat
    Amsterdam : Elsevier
    Biochemical and Biophysical Research Communications 159 (1989), S. 815-820 
    Details
    ISSN: 0006-291X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0006-291X(89)90067-3
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  • 3
    Electronic Resource
    Electronic Resource
    Experimental Amyloidosis and Tolerance (1966)
    [s.l.] : Nature Publishing Group
    Nature 210 (1966), S. 390-391 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] RECENT work on experimental amyloidosis (induced . by means of repeated antigenic stimulation) has produced general agreement that this lesion is produced during the course of a protracted immune response1. However, this statement should be made with caution, since the immune response which is ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/210390a0
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  • 4
    Electronic Resource
    Electronic Resource
    A-ring conformational stability and progesterone-receptor binding affinity of 4-en-3-one steroids
    Amsterdam : Elsevier
    Journal of Steroid Biochemistry 23 (1985), S. 895-900 
    Details
    ISSN: 0022-4731
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0022-4731(85)90044-5
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  • 5
    Electronic Resource
    Electronic Resource
    A computer program for the determination of the correct positions of misplaced molecules in crystal structures (1984)
    Copenhagen : International Union of Crystallography (IUCr)
    Applied crystallography online 17 (1984), S. 484-485 
    Details
    ISSN: 1600-5767
    Source: Crystallography Journals Online : IUCR Backfile Archive 1948-2001
    Topics: Geosciences , Physics
    Notes: A program is described to determine the position of a correctly oriented but misplaced molecule with known or at least partially known stereochemistry. The program is written in Fortran IV and based on the combination of three methods: 1. Residual analysis. 2. Analysis of the packing. 3. Calculation of a figure of merit derived from the fulfilment of strong phase relationships based on triplets. By this program a unique determination of the translational parameters of the molecule was possible in most cases even for complex problems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1107/S0021889884012000
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  • 6
    Electronic Resource
    Electronic Resource
    Ordering and phase transitions in ising systems with competing short range and dipolar interactions (1979)
    Springer
    The European physical journal 34 (1979), S. 375-392 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract As a simple model of order-disorder ferroelectrics or dipolar magnets we consider a simple cubic Ising-system with nearest neighbor exchangeJ and dipolar interaction of strengthµ 2/a 3. ForJa 3/µ 2〈−1.3384 the ground-state is antiferromagnetic, while for −1.3384〈Ja 3/µ 2〈0.1270 the ground state consists of ferromagnetic rows (in spin direction) arranged antiferromagnetically in the plane perpendicular to it. AtJa 3/µ 2=0.1279 the structure changes to a layered antiferromagnetic structure with a twocomponent order parameter, while forJa 3/µ 2〉0.16429 the ferromagnetic phase becomes stable (with domain arrangements depending on the shape of the sample). For all critical values ofJa 3/µ 2 where the bulk energies of two phases become equal also the interface energy between these phases is found to be zero. The ordering at nonzero temperature is studied by means of mean-field approximations (MFA) and Monte Carlo (MC) calculations. It turns out that forJa 3/µ 2 of order unity the MFA overestimates ordering temperatures by about a factor of two, and predicts multicritical points (between the disordered and two ordered phases) at nonzero temperature, including two biaxial Lifshitz points which the MC work suggests to occur atT=0. In contrast to MFA the layered antiferromagnetic structure is found to be stable only at extremely lowT, because a metastable spin-glass phase (with random arrangement of ferromagnetic rows in the spin direction) has only slightly higher energy. The MFA also yields two regimes of helical phases which are “locked in” to the antiferromagnetic phases at uniaxial Lifshitz points occurring at the Brillouin zone boundary. In the MC-work various methods of treating the long-range interaction are investigated. While all kinds of truncations as well as compensating field methods are rather unsatisfactory in our case, Ewald summation techniques yield satisfactory results. Nevertheless strong fluctuations as well as strong finite size effects prevent us from making accurate exponent estimates, but arguments are given that there is no regime of broad visibility of Landaulike critical behavior. Finally the extension of our results to other lattices as well as experimental applications are briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01325203
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  • 7
    Electronic Resource
    Electronic Resource
    Elektronenmikroskopische Untersuchungen des Quellungsvorgangs bei Makromolekülen (1964)
    Springer
    Colloid & polymer science 197 (1964), S. 45-51 
    Details
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Zusammenfassung In dünnen Schichten von Polymethylmethacrylat werden Feinstrukturen gefunden, die unabhängig von dem nach üblichen Methoden in verdünnten Lösungen gefundenen Molekulargewicht etwa sphärische Gebilde mit einem mittleren Durchmesser von 40 Å darstellen. Diese Feinstrukturen lagern leicht Lösungsmittel an und können sich bis ca. 130 Å - abhängig vom Trocknungsgrad der Schichten — vergrößern. Weichmacher lagern sich in das Polymer als kolloidale Zerteilung feiner Tröpfchen ein, ohne die Feinstruktur zu beeinflussen. Es ist noch nicht zu entscheiden, ob die Moleküle des PMMA in Lösungen Assoziate darstellen oder ob ein langes Molekül in gleichmäßigen Teilknäueln aufknäuelt.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01500185
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  • 8
    Electronic Resource
    Electronic Resource
    Elektronenmikroskopische Untersuchungen des Quellungsvorgangs hei Makromolekülen (1964)
    Springer
    Colloid & polymer science 197 (1964), S. 51-55 
    Details
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Zusammenfassung Aus elektronenmikroskopischen Aufnahmen nach verschiedenen Präparationsmethoden resultiert in dünnen Schichten des Copolymers Styrol-Butadien Buna BH 150/Pt 733 immer wieder eine sphärische Feinstruktur mit dem mittleren Durchmesser 70 Å. Die Elemente der Feinstruktur halten Lösungsmittel in der Oberfläche nicht fest und lagern Weichmacher kolloidal in Tropfenform, getrennt vom eigentlichen Copolymer, ein. Es ist mit den bisher verwendeten Methoden nicht zu unterscheiden, ob sich eine lange Kette des Polymers in regelmäßigen Teilabschnitten aufknäuelt oder ob das wirkliche Molekulargewicht des Polymers bei etwa 100000 liegt und das in verdünnten Lösungen mit normalen Methoden ermittelte Molekulargewicht sich auf Assoziate mit dem mittleren Assoziationsgrad 7 bezieht.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01500186
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  • 9
    Electronic Resource
    Electronic Resource
    Versuch einer Deutung der bei der elektronenmikroskopischen Untersuchung von festen Polymeren auftretenden mikromorphologischen Struktureinheiten (1966)
    Springer
    Colloid & polymer science 211 (1966), S. 53-62 
    Details
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Summary Ultrasonic degradation of amorphous high polymers results in products of defined molecular weights in the limits of 20000 to 50000. The authors try to coordinate the degradation of some polymers characterized by viscosity molecular weight and the fine structures visible at high magnification and resolution in photographs by electron microscope. The fine structures are found invariant against all kinds of mechanical degradation. The final molecular weight after degradation is the same as calculated for the weight of the structural units in the electron micrographs. These structural units are probably a real basic constant of the polymeric materials.
    Notes: Zusammenfassung Beim Ultraschallabbau von amorphen Hochpolymeren wurden Endmolekulargewichte gefunden, die bei allen untersuchten Polymeren zwischen 20000 und 50000 lagen. Mit Hilfe elektronenmikroskopischer Methoden wurde versucht, direkt die Abnahme der Molekülgröße zu verfolgen. Als Ergebnis wurde gefunden, daß bei allen untersuchten Polymeren Feinstrukturen abgebildet wurden, die invariant gegen den Ultraschallabbau waren, und daß die Endmolekulargewichte nach Abbau mit den Molekulargewichten für die Feinstrukturen — betrachtet man diese als Einzelindividuen — gut übereinstimmen. Es wird daraus geschlossen, daß der mechanische Abbau von Polymeren nur bis zum Auftrennen in diskrete primäre Struktureinheiten führt. Diese Struktureinheiten scheinen eine grundlegende Materialkonstante zu sein.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01500208
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  • 10
    Electronic Resource
    Electronic Resource
    Linear and nonlinear relaxation and cluster dynamics near critical points (1976)
    Springer
    Journal of statistical physics 15 (1976), S. 267-297 
    Details
    ISSN: 1572-9613
    Keywords: Critical points ; relaxation ; clusters ; cluster waves ; linear response ; nonlinear response ; Ising models ; Glauber models ; lattice dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The critical slowing down of anisotropic magnets, binary mixtures, and systems undergoing structural transitions is interpreted in terms of suitable defined “clusters,” their growth, and their motions (cluster reactions, cluster diffusion, and cluster waves). Our previous studies of the Glauber model are extended considerably by numerical calculations, including the use of the cluster model of Reatto and Rastelli. The behavior of the relaxation function is very insensitive to the details of the models used. A scaling theory of nonlinear response is given, which is far more general than the cluster dynamics treatment. Two different cases occur:(i) at fixed “relative nonlinearity” the critical exponents agree with the corresponding exponents of linear response; (ii) if the initial state is held fixed, different exponents are found, however, which agree with predictions of Racz, and are consistent with Monte Carlo simulations of the nonlinear slowing down of the energy in kinetic Ising models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01023054
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