16,929 research outputs found

    Viral pathogen discovery.

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    Viral pathogen discovery is of critical importance to clinical microbiology, infectious diseases, and public health. Genomic approaches for pathogen discovery, including consensus polymerase chain reaction (PCR), microarrays, and unbiased next-generation sequencing (NGS), have the capacity to comprehensively identify novel microbes present in clinical samples. Although numerous challenges remain to be addressed, including the bioinformatics analysis and interpretation of large datasets, these technologies have been successful in rapidly identifying emerging outbreak threats, screening vaccines and other biological products for microbial contamination, and discovering novel viruses associated with both acute and chronic illnesses. Downstream studies such as genome assembly, epidemiologic screening, and a culture system or animal model of infection are necessary to establish an association of a candidate pathogen with disease

    Voltage-Mode Highpass, Bandpass, Lowpass and Notch Biquadratic Filters Using Single DDCC

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    A new voltage-mode multifunction biquadratic filter using one differential difference current conveyor (DDCC), two grounded capacitors and three resistors is presented. The proposed circuit offers the following attractive advantages: realizing highpass, bandpass, lowpass and notch filter functions, simultaneously, from the same circuit configuration; employing grounded capacitors, which is ideal for integration and simpler circuit configuration

    When Does Competition Lead to Efficient Investments?

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    The paper studies agents’ investment decisions between general and speci…c in-vestments under di¤erent ownership structures in a thin, decentralized market where each agent’s decision a¤ects the decisions and welfare of other (otherwise unrelated) agents mainly through indirect market linkages. The paper demonstrates that “excess competition among investors,” in every equilibrium, will lead to e¢cient investments, regardless of asset ownership. In the absence of such excess competition, in every equilibrium, ine¢cient investments will result, unless some special ownership arrange-ment is made. The problem in which the choice variable is investment level, instead of investment type, is also studied.

    An enhanced integrated aerodynamic load/dynamic optimization procedure for helicopter rotor blades

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    An enhanced integrated aerodynamic load/dynamic optimization procedure is developed to minimize vibratory root shears and moments. The optimization is formulated with 4/rev vertical and 3/rev inplane shears at the blade root as objective functions and constraints, and 4/rev lagging moment. Constraints are also imposed on blade natural frequencies, weight, autorotational inertia, centrifugal stress, and rotor thrust. The 'Global Criteria Approach' is used for formulating the multi-objective optimization. Design variables include spanwise distributions of bending stiffnesses, torsional stiffness, nonstructural mass, chord, radius of gyration, and blade taper ratio. The program CAMRAD is coupled with an optimizer, which consists of the program CONMIN and an approximate analysis, to obtain optimum designs. The optimization procedure is applied to an advanced rotor as a reference design. Optimum blade designs, obtained with and without a constraint on the rotor thrust, are presented and are compared to the reference blade. Substantial reductions are obtained in the vibratory root forces and moments. As a byproduct, improvements are also found in some performance parameters, such as total power required, which were not considered during optimization

    From Value Protection to Value Creation: Rethinking Corporate Governance Standards for Firm Innovation

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    A company’s pro-innovation needs are often met by the exploitation of its resources, widely defined. The resource-based theory of the firm provides immense empirical insights into how a firm’s corporate governance factors can contribute to promoting innovation. However, these implications may conflict with the prevailing standards of corporate governance imposed on many securities markets for listed companies, which have developed based on theoretical models supporting a shareholder-centered and agency-based theory of the firm. Although prevailing corporate governance standards can to an extent support firm innovation, tensions are created in some circumstances where companies pit their corporate governance compliance against resource-based needs that promote innovation. In the present context of steady internationalization and convergence in corporate governance standards in global securities markets towards a shareholder-centered agency-based model, we argue that there is a need to provide some room for accommodating the resource-based needs for companies in relation to promoting innovation. We explore a number of options and suggest that the most practicable option would be the development of recognized exceptions that deviate from prevailing corporate governance standards. We further suggest as to how an exceptions-based regime can be implemented in the U.K. and U.S., comparing the rules-based regime in the U.S. with the principles-based regime in the U.K

    The aurora as a source of planetary-scale waves in the middle atmosphere

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    Photographs of global-scale auroral forms taken by scanning radiometers onboard U.S. Air Force weather satellites in 1972 show that auroral bands exhibit well-organized wave motion with typical zonal wave number of 5 or so. The scale size of these waves is in agreement with that of well-organized neutral wind fields measured by the 1967-50B satellite in the 150- to 220-km region during the geomagnetic storm of May 27, 1967. The horizontal scale size revealed by these observations is in agreement with that of high-altitude traveling ionospheric disturbances. It is conjectured that the geomagnetic storm is a source of planetary and synoptic scale neutral atmospheric waves in the middle atmosphere. The possible existence of a source of waves of the proper scale size to trigger instabilities in middle atmospheric circulation systems may be significant in the study of lower atmospheric response to geomagnetic activity
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