7,997 research outputs found

    Terlipressin or norepinephrine in septic shock: do we have the answer?

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    Comment on Terlipressin versus norepinephrine as infusion in patients with septic shock: a multicentre, randomised, double-blinded trial. [Intensive Care Med. 2018

    Observational constraints on interstellar dust models

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    No single model has been able to account for all of the observed spectroscopic properties of interstellar or circumstellar dust. The reason for this is that, despite the agreement that the grains are composed of silicaceous/metal oxide and carbonaceous material, there is strong disagreement as to their exact structure and composition. This led Draine and Lee (1984) to use interstellar extinction data to define an interstellar graphitic material; new observational findings have made even that identification uncertain. But the great advantage of their approach is that they used observations at all of the wavelengths available to define the material. Here, the authors attempt a variation of that approach. They examine recent UV and IR data and attempt to put constraints on the possible types of interstellar grain composition, and to connect these constraints with grain models. A summary of some of the important constraints imposed by the observations is given

    Polarization Aberrations

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    The analysis of the polarization characteristics displayed by optical systems can be divided into two categories: geometrical and physical. Geometrical analysis calculates the change in polarization of a wavefront between pupils in an optical instrument. Physical analysis propagates the polarized fields wherever the geometrical analysis is not valid, i.e., near the edges of stops, near images, in anisotropic media, etc. Polarization aberration theory provides a starting point for geometrical design and facilitates subsequent optimization. The polarization aberrations described arise from differences in the transmitted (or reflected) amplitudes and phases at interfaces. The polarization aberration matrix (PAM) is calculated for isotropic rotationally symmetric systems through fourth order and includes the interface phase, amplitude, linear diattenuation, and linear retardance aberrations. The exponential form of Jones matrices used are discussed. The PAM in Jones matrix is introduced. The exact calculation of polarization aberrations through polarization ray tracing is described. The report is divided into three sections: I. Rotationally Symmetric Optical Systems; II. Tilted and Decentered Optical Systems; and Polarization Analysis of LIDARs

    Peering into the Abyss: Non-State Actors and the 2016 Proliferation Environment; Nonproliferation Review v. 13, no. 2 (November 2006)

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    This article appeared in Strategic Insights (November 2006), v.13 no.

    Irregular Warfare and Future War: Strategy and Defense Planning; Strategic Insights, v. 10, Special issue (October 2011), 92-98. Topic: Global Trends and Future Warfare ; Part II: Technological and Doctrinal Innovation

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    This article appeared in Strategic Insights, v.10, Special issue (October 2011), 92-98. Topic: Global Trends and Future Warfare ; Part II: Technological and Doctrinal InnovationThe purpose of this paper is threefold: to speculate on the role and prominence of irregular warfare in the strategic environment over the next quarter century, to comment on the impact that phenomenon may have on shaping the postulated scenarios addressed in the US National Intelligence Councilï¾’s Global Trends 2025: A Transformed World (2025 Report), and to evaluate the relationship of this strategic environment to US defense-planning assumptions that will shape the capacities of the Defense Department to address threats to US interests over the next quarter century.Approved for public release; distribution is unlimited

    Twenty-First-Century Innovation Pathways for the U.S. Navy in the Age of Competition

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    Recent programs such as the littoral combat ship, the Zumwalt-class guided-missile destroyer, and the Ford-class aircraft carrier all have highlighted the Navy’s failure to produce innovative, afford-able ships in the quantity and of the quality needed to configure a larger, redesigned fleet. Unless the Navy can address mistakes made in these programs it will have difficulty innovating success-fully—with potentially disastrous consequences

    Gene expression in human sepsis: what have we learned?

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    In the previous issue of Critical Care, Tang and colleagues offer a very novel systematic review of 12 studies of gene expression in blood of human sepsis. The review concludes that there is no discernable transition from a pro- to an anti-inflammatory expression phenotype in blood in human sepsis. The authors found that upregulation of pathogen recognition receptors and signal transduction pathways was a consistent theme in expression studies. The review by Tang and colleagues has strengths, including defined screening criteria, broad literature review, strict inclusion criteria, and transparent methods for assessing strengths and weaknesses of studies. There are other issues to consider. First, one source of variation in gene expression studies in sepsis is variability in time from onset of sepsis to time of blood draw. Another source of variation is differences between tissues in gene expression at the same time in sepsis. Whole blood is a mélange of tissues (a variety of leukocytes); therefore, one assesses a weighted sum of all leukocyte classes. About half of the studies assessed peripheral mononuclear cells. A third great source of variable gene expression in sepsis is heterogeneity of causes and microbiology of sepsis. Only one study compared Gram-positive with Gram-negative sepsis. Only three studies confirmed microarray data with an independent measurement of expression. One interpretation is that two of three studies of early sepsis found increased expression of pro-inflammatory genes. In late sepsis, three of six studies found increased expression of pro-inflammatory genes whereas three of six studies found decreased expression of pro-inflammatory genes. The balance of pro- to anti-inflammatory gene expression is difficult to quantify. Sample size is highly variable in studies (n = 12 to 176). These limitations require a leap of faith to suggest that the paradigm of sepsis as a pro-inflammatory phenotype that shifts to an anti-inflammatory phenotype is flawed: the absence of evidence in expression studies is not the same as having well-conducted studies with clear negative evidence

    Asymmetrical Warfare: Today’s Challenge to U.S. Military Power,

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    During the late 1970s and early 1980s, a cacophony of voices arose (mostly from the conservative wing of the Republican Party) asserting that the United States was in danger of being eclipsed by the Soviet Union. In short, the argument was “the sky is falling.” President Reagan used the issue to great advantage during the 1980 presidential campaign, setting the stage for a massive increase in de- fense expenditures and the launching of the ambitious “Star Wars” pro- gram, the forerunner of the Clinton and Bush administrations’ attempt to build a national missile defense system
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