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Of Systems (of + system)

Distribution by Scientific Domains
Life Sciences37%
Chemistry37%

Kinds of Of Systems

  • variety of system
    		•

    Selected Abstracts

    Quantitative Assessment of Seizure Severity for Clinical Trials: A Review of Approaches to Seizure Components

    EPILEPSIA, Issue 1 2001
    Joyce A. Cramer
    Summary: Quantitative assessment of seizure severity has been approached using a variety of systems. This review describes currently available methods and possible new approaches to seizure assessment for clinical trials. A review of the literature on methods of seizure assessments resulted in tabulation of the seizure rating scales known as VA, Chalfont-National Hospital, Liverpool, Hague, and the Occupational Hazard Scale. Seizures have been evaluated by simply counting all events, counting events by type, by clinician ratings, patient ratings, and combinations. Each of the scales has advantages and disadvantages. Most scales share core components: seizure frequency, seizure type, seizure duration, postictal events, postictal duration, automatisms, seizure clusters, known patterns, warnings, tongue biting, incontinence, injuries, and functional impairment. This review revealed a partial consensus about aspects of seizures that are important markers for severity. However, usefulness of the existing scales is limited by lack of data on responsiveness. New approaches are needed to assess changes in seizure severity as a result of an intervention in a clinical trial. [source]

    Molecular magnetism via resonating valence bonds for conjugated radicals and selected transition metal complexes

    INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 4-5 2001
    D. J. Klein
    Abstract Currently there is considerable interest in the nature of exchange interactions leading to unpaired electrons in molecular and cluster magnets. Here, the focus is largely at a qualitative level, via a novel "mean-field" resonance-theoretic view, to deal with exchange couplings, so as to allow unpaired electrons in either (or both of) the ,- and ,-parts of a (largely organic) bipartite (or alternate) molecular network. The (quantitative) number and (qualitative) location of unpaired spins are dealt with by this simple approach, which also offers some (qualitative) information on the occurrence of low-lying higher-spin states. To illustrate the approach it is applied to a variety of systems where the spin sources are conjugated ,-network molecules and polymers, carbenes, variously defected graphites, and a few species involving transition metals, especially Cu. The discussion deals not only with traditional conjugated organics compounds but also with selected inorganic species. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001 [source]

    High-pressure single-crystal X-ray diffraction facilities on station 9.8 at the SRS Daresbury Laboratory , hydrogen location in the high-pressure structure of ethanol

    JOURNAL OF SYNCHROTRON RADIATION, Issue 1 2001
    David R. Allan
    A new high-pressure single-crystal diffraction facility has been constructed on station 9.8 at the Synchrotron Radiation Source, Daresbury Laboratory, for a range of studies on a variety of systems of relevance to physics, chemistry and materials science that would otherwise prove intractable with conventional laboratory-based methods. The station has been equipped with a modified Enraf,Nonius CAD4 four-circle diffractometer for high-pressure studies which can be conveniently, and rapidly, interchanged with the Bruker SMART CCD area-detector system when more routine ambient-pressure diffraction work is to be undertaken. This rapid change-over has been achieved by permanently mounting the CAD4 on its own jacking table, formerly used for the station's white-beam diffraction mode, which allows the alignment of the SMART diffractometer to remain undisturbed when the CAD4 is in use. Early results on the test low-melting-point compound ethanol (CH3CH2OH) reveal that excellent refined structures can be obtained, including the location and refinement of the H atoms, demonstrating that one of the original, and major, objectives of the station has been accomplished. [source]

    INVITED REVIEW: Quantitative trait locus mapping in natural populations: progress, caveats and future directions

    MOLECULAR ECOLOGY, Issue 2 2005
    JON SLATE
    Abstract Over the last 15 years quantitative trait locus (QTL) mapping has become a popular method for understanding the genetic basis of continuous variation in a variety of systems. For example, the technique is now an integral tool in medical genetics, livestock production, plant breeding and population genetics of model organisms. Ten years ago, it was suggested that the method could be used to understand continuous variation in natural populations. In this review I: (i) clarify what is meant by natural population in the QTL context, (ii) discuss whether evolutionary biologists have successfully mapped QTL in natural populations, (iii) highlight some of the questions that have been addressed by QTL mapping in natural populations, (iv) describe how QTL mapping can be conducted in unmanipulated natural populations, (v) highlight some of the limitations of QTL mapping and (vi) try to predict some future directions for QTL mapping in natural populations. [source]

    Biodiversity effects on ecosystem functioning: emerging issues and their experimental test in aquatic environments

    OIKOS, Issue 3 2004
    Paul S. Giller
    Recent experiments, mainly in terrestrial environments, have provided evidence of the functional importance of biodiversity to ecosystem processes and properties. Compared to terrestrial systems, aquatic ecosystems are characterised by greater propagule and material exchange, often steeper physical and chemical gradients, more rapid biological processes and, in marine systems, higher metazoan phylogenetic diversity. These characteristics limit the potential to transfer conclusions derived from terrestrial experiments to aquatic ecosystems whilst at the same time provide opportunities for testing the general validity of hypotheses about effects of biodiversity on ecosystem functioning. Here, we focus on a number of unique features of aquatic experimental systems, propose an expansion to the scope of diversity facets to be considered when assessing the functional consequences of changes in biodiversity and outline a hierarchical classification scheme of ecosystem functions and their corresponding response variables. We then briefly highlight some recent controversial and newly emerging issues relating to biodiversity-ecosystem functioning relationships. Based on lessons learnt from previous experimental and theoretical work, we finally present four novel experimental designs to address largely unresolved questions about biodiversity-ecosystem functioning relationships. These include (1) investigating the effects of non-random species loss through the manipulation of the order and magnitude of such loss using dilution experiments; (2) combining factorial manipulation of diversity in interconnected habitat patches to test the additivity of ecosystem functioning between habitats; (3) disentangling the impact of local processes from the effect of ecosystem openness via factorial manipulation of the rate of recruitment and biodiversity within patches and within an available propagule pool; and (4) addressing how non-random species extinction following sequential exposure to different stressors may affect ecosystem functioning. Implementing these kinds of experimental designs in a variety of systems will, we believe, shift the focus of investigations from a species richness-centred approach to a broader consideration of the multifarious aspects of biodiversity that may well be critical to understanding effects of biodiversity changes on overall ecosystem functioning and to identifying some of the potential underlying mechanisms involved. [source]

    Purification, crystallization, X-ray diffraction analysis and phasing of a Fab fragment of monoclonal neuroantibody ,D11 against nerve growth factor

    ACTA CRYSTALLOGRAPHICA SECTION D, Issue 7 2004
    Sonia Covaceuszach
    The rat monoclonal neuroantibody ,D11 is a potent antagonist that prevents the binding of nerve growth factor (NGF) to its tyrosine kinase A receptor (TrkA) in a variety of systems, most notably in two in vivo systems linked to crucial pathological states, such as Alzheimer's disease and HIV infection. To provide further insights into the mechanism of action of this potentially therapeutic monoclonal antibody, structural studies of the antigen-binding fragment (Fab) of ,D11 were performed. ,D11 IgG2a immunoglobulin was obtained from hybridomas by in vitro tissue culture. The ,D11 Fab crystallizes in two crystal forms. Form I belongs to space group P1, with unit-cell parameters a = 42.7, b = 50.6, c = 102.7,Å, , = 82.0, , = 89.1, , = 86.0°. With two molecules in the asymmetric unit, VM is 2.3,Å3,Da,1 and the solvent content is 46%. A complete data set has been collected at 2.7,Å resolution on beamline XRD-1 (ELETTRA, Trieste, Italy). Form II belongs to space group C2, with unit-cell parameters a = 114.8, b = 69.4, c = 64.10,Å, , = 117.0°. With one molecule in the asymmetric unit, VM is 2.4,Å3,Da,1 and the solvent content is 48%. A complete data set has been collected at 1.7,Å resolution on beamline ID14-1 (ESRF, Grenoble, France). Phasing was successfully performed by Patterson search techniques and refinement of the structures is currently under way. Crystal forms I and II display a close-packing pattern. [source]

    The spliceosome: the most complex macromolecular machine in the cell?

    BIOESSAYS, Issue 12 2003
    Timothy W. Nilsen
    The primary transcripts, pre-mRNAs, of almost all protein-coding genes in higher eukaryotes contain multiple non-coding intervening sequences, introns, which must be precisely removed to yield translatable mRNAs. The process of intron excision, splicing, takes place in a massive ribonucleoprotein complex known as the spliceosome. Extensive studies, both genetic and biochemical, in a variety of systems have revealed that essential components of the spliceosome include five small RNAs,U1, U2, U4, U5 and U6, each of which functions as a RNA, protein complex called an snRNP (small nuclear ribonucleoprotein). In addition to snRNPs, splicing requires many non-snRNP protein factors, the exact nature and number of which has been unclear. Technical advances, including new affinity purification methods and improved mass spectrometry techniques, coupled with the completion of many genome sequences, have now permitted a number of proteomic analyses of purified spliceosomes. These studies, recently reviewed by Jurica and Moore,1 reveal that the spliceosome is composed of as many as 300 distinct proteins and five RNAs, making it among the most complex macromolecular machines known. BioEssays 25:1147,1149, 2003. © 2003 Wiley Periodicals, Inc. [source]

    TRUST AS A TRADABLE COMMODITY: A FOUNDATION FOR SAFE ELECTRONIC MARKETPLACES

    COMPUTATIONAL INTELLIGENCE, Issue 2 2010
    Reid Kerr
    In large electronic marketplaces populated by buying and selling agents, it is difficult to judge trustworthiness. A variety of systems have been proposed to help traders to find trustworthy partners by learning to discount or disregard disreputable parties. In this article, we present a novel model for providing safe electronic marketplaces: Commodity Trunits, a system that considers trust as a tradable commodity. In this system, sellers require units of trust (trunits) to participate in transactions, and risk losing trunits if they act dishonestly. Sellers can purchase trunits when needed, and sell excess quantities. We demonstrate that under Commodity Trunits, rational sellers will choose to be honest, since this is the profit maximizing strategy. We also show that Commodity Trunits provides protection from a number of vulnerabilities common in existing trust and reputation systems, e.g., the important,exit problem, where sellers can cheat without fear of repercussions if they intend to leave the market. We then present a simulation that validates the system by demonstrating that a market operator can manage the trunit marketplace to ensure sustainability. We conclude with a discussion of the value of Commodity Trunits as a method for promoting trust in electronic marketplaces. [source]