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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 112 (2000), S. 1560-1564 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The helical twisting power βM determines the pitch of the chiral nematic phase produced when a nematic liquid crystal is doped with a low concentration of chiral solute molecules. Molecules with large βM values have potential applications in electro-optic displays and in optical data storage. This paper describes a new simulation technique which allows the prediction of both the sign and magnitude of βM. The method employs Monte Carlo simulations of a fully atomistic model of a chiral dopant in the presence of a twisted nematic solvent composed of Gay–Berne particles. Calculations are presented for five different chiral dopants, with results that are in good agreement with existing experimental data. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Genomics and Human Genetics 4 (2003), S. 119-141 
    ISSN: 1527-8204
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Debate on the validity and reliability of scientific methods often arises in the courtroom. When the government (i.e., the prosecution) is the proponent of evidence, the defense is obliged to challenge its admissibility. Regardless, those who seek to use DNA typing methodologies to analyze forensic biological evidence have a responsibility to understand the technology and its applications so a proper foundation(s) for its use can be laid. Mitochondrial DNA (mtDNA), an extranuclear genome, has certain features that make it desirable for forensics, namely, high copy number, lack of recombination, and matrilineal inheritance. mtDNA typing has become routine in forensic biology and is used to analyze old bones, teeth, hair shafts, and other biological samples where nuclear DNA content is low. To evaluate results obtained by sequencing the two hypervariable regions of the control region of the human mtDNA genome, one must consider the genetically related issues of nomenclature, reference population databases, heteroplasmy, paternal leakage, recombination, and, of course, interpretation of results. We describe the approaches, the impact some issues may have on interpretation of mtDNA analyses, and some issues raised in the courtroom.
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 8654-8663 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Molecular dynamics simulations are described for liquid crystal molecules composed of two Gay-Berne particles connected by an eight-site Lennard-Jones alkyl chain. Calculations have been carried out for 512 molecules in the NVE and NPT ensembles for simulation times of up to 6.4 ns. The system exhibits the sequence of phases: isotropic liquid, smectic-A, smectic-B, and the simulations demonstrate the spontaneous growth of a smectic-A liquid crystal over a period of approximately 6 ns on cooling from the isotropic liquid. Model molecules are seen to remain flexible and able to change conformation in the smectic-A phase. As temperature is reduced molecules become elongated as the number of gauche conformations drops, leading to a small increase in the spacing of smectic layers. The latter is seen through the temperature dependence of the Gay-Berne radial distribution function resolved parallel to the direction of orientational order. Results are presented which show an odd–even variation of orientational order parameters for bonds in the alkyl chain, and a change in effective torsional potentials as the system is cooled from isotropic liquid to a smectic-A phase. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 2850-2858 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this paper we present a molecular dynamics calculation of the Frank elastic constants of a nematic liquid crystal. We study two well-known variants of the Gay–Berne potential, and determine the elastic constants by measuring orientational fluctuations as a function of wave vector, using reasonably large system sizes in the range 1000–8000 molecules. For some of the simulations, a set of Lagrangian constraints was applied in order to keep the director fixed along one of the box axes, facilitating the measurement of fluctuations in components of the reciprocal-space order tensor Qˆ(k) in the director frame. © 1996 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Genomics and Human Genetics 4 (2003), S. 119-141 
    ISSN: 1527-8204
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Biology
    Notes: Debate on the validity and reliability of scientific methods often arises in the courtroom. When the government (i.e., the prosecution) is the proponent of evidence, the defense is obliged to challenge its admissibility. Regardless, those who seek to use DNA typing methodologies to analyze forensic biological evidence have a responsibility to understand the technology and its applications so a proper foundation(s) for its use can be laid. Mitochondrial DNA (mtDNA), an extranuclear genome, has certain features that make it desirable for forensics, namely, high copy number, lack of recombination, and matrilineal inheritance. mtDNA typing has become routine in forensic biology and is used to analyze old bones, teeth, hair shafts, and other biological samples where nuclear DNA content is low. To evaluate results obtained by sequencing the two hypervariable regions of the control region of the human mtDNA genome, one must consider the genetically related issues of nomenclature, reference population databases, heteroplasmy, paternal leakage, recombination, and, of course, interpretation of results. We describe the approaches, the impact some issues may have on interpretation of mtDNA analyses, and some issues raised in the courtroom.
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  • 6
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] The rate and pattern of sequence substitutions in the mitochondrial DNA (mtDNA) control region (CR) is of central importance to studies of human evolution and to forensic identity testing. Here, we report a direct measurement of the intergenerational substitution rate in the human CR. We compared ...
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of computer aided molecular design 3 (1989), S. 335-353 
    ISSN: 1573-4951
    Keywords: Molecular dynamics ; Nematic liquid crystal ; Smectic liquid crystal ; Columnar liquid crystal ; Molecular modelling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary We review recent progress in the computer simulation of liquid crystals, with special emphasis on hard particle models. Surprisingly, the simplest molecular models, taking account only of molecular size and shape, are sufficient to generate a wide variety of liquid crystalline phases, closely analogous to those observed in real life. Thermodynamic stability of different phases is very sensitive to shape, and presumably will also be sensitive to further details of intermolecular interactions as they are incorporated into the model. Realistic atom-atom potential models of liquid crystals are available, but the associated simulations are quite expensive. Thus, while idealized models may be used to study quite general, fundamental properties of mesophases, the modelling of specific liquid crystal systems in a realistic way remains a great challenge. Progress continues to be made on both these fronts.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 18 (1997), S. 478-488 
    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The implementation of parallel molecular dynamics techniques is discussed in the context of the simulation of single-site anisotropic potentials. We describe the use of both replicated data and domain decomposition approaches to molecular dynamics and present results for systems of up to 65536 Gay-Berne molecules on a range of parallel computers (Transtech i860/XP Paramid, Intel iPSC/860 Hypercube, Cray T3D). We find that excellent parallel speed-ups are possible for both techniques, with the domain decomposition method found to be the most efficient for the largest systems studied. © 1997 by John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 9
    ISSN: 0173-0835
    Keywords: Capillary electrophoresis ; DNA ; Mitochondrial DNA ; Forensic DNA typing ; Polymerase chain reaction analysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: The polymorphic control region of mitochondrial DNA (mtDNA) is becoming more commonly used in forensic applications to differentiate among individuals in a population. Two hypervariable regions (HV1 and HV2) are often sequenced following amplification of the mtDNA via the polymerase chain reaction (PCR). More rapid screening assays would reduce both the effort and the expenses of comparing two samples. A methodology has been developed that first uses restriction endonuclease digestion of the PCR-amplified mtDNA using RsaI and Mn/I and then capillary electrophoresis (CE) to separate and size the PCR-RFLP fragments. This rapid procedure offers an alternative method for screening of polymorphisms in amplified mtDNA samples. In addition, the presence of a T→C transition at position 16189, which gives rise to the so-called “C-stretch” in HV1, may be predicted from the presence of nonspecific PCR products in the CE results.
    Additional Material: 4 Ill.
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  • 10
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