6,056 research outputs found

    HEALTH AND SAFETY REGULATION OF SMALL, HIGH-RISK SUBPOPULATIONS

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    The choice of decision framework used to set regulatory tolerance levels for hazardous substances can be divided into rigid and flexible tolerance levels. Rigid decision frameworks include zero or deminimis that fix risk levels for some subpopulation. and/or highly tolerances The accelerating identification of highly sensitive exposed individuals and the division of the population into ever smaller subpopulations at higher risk could prove to be tremendously burdensome on regulatory systems, particularly for rigid decision frameworks. Rigid tolerance levels, philosophically based on "rights" to zero or arbitrarily low excess risks for individuals, do not contain sufficient flexibility to account for small high-risk subpopulations. Furthermore, the equal protection for all such groups is an illusion, mainly because of the potentially large number of such subgroups and the relatively fixed regulatory resources. Thus, deminimis regulation is seen as a minimal but inadequate improvement over zero risk regulation. with improved measures of the heterogeneous demand for risk reduction by various high-risk subpopulations, augmented cost-benefit analyses leading to flexible tolEr2.nces could provide a richer analytic framework for more efficient regulatory decisions. Additionally, it may be useful to attempt to c2.tegorize hazards and subpopulations on the basis of the ability to self-protect.De minimis, sensitive, decision framework, cost benefit, Food Consumption/Nutrition/Food Safety, Health Economics and Policy,

    A New Approach to Black Hole Microstates

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    If one encodes the gravitational degrees of freedom in an orthonormal frame field there is a very natural first order action one can write down (which in four dimensions is known as the Goldberg action). In this essay we will show that this action contains a boundary action for certain microscopic degrees of freedom living at the horizon of a black hole, and argue that these degrees of freedom hold great promise for explaining the microstates responsible for black hole entropy, in any number of spacetime dimensions. This approach faces many interesting challenges, both technical and conceptual.Comment: 6 pages, 0 figures, LaTeX; submitted to Mod. Phys. Lett. A.; this essay received "honorable mention" from the Gravity Research Foundation, 199

    Reflections on the responsible conduct of cancer research

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    Most cancer researchers regularly practice the responsible conduct of research (RCR) without consciously considering it. As professional scientists, we simply do what we are trained to do. However, as we train a new generation of cancer researchers in our laboratories, we must be vigilant against undue complacency. In an age when misconduct in research is receiving more media attention than ever before, we should periodically take a moment of pause and reflect upon the meaning and practice of responsibly conducting research. Rather than meeting minimum standards in a compliance-driven manner, we should practice forethought and periodically consider how we can improve. We, as leaders in cancer research, must then push our peers to do the same. By embedding RCR into the culture of cancer research through a multilayer approach, including regular assessment at the levels of individual research groups, departmentally, and institutionally, we will become a model discipline in the responsible conduct of research

    Evolution of the stellar mass function and infrared luminosity function of galaxies since z = 1.2

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    © 2019. The American Astronomical Society. All rights reserved. We measured evolution of the K-band luminosity function and stellar mass function (SMF) for red and blue galaxies at z 0.4 luminosity and mass function measurements. Using an evolving relation for K-band mass-to-light ratios as a function of (B-V) color, we found a slowly decreasing rate of growth in red galaxy stellar mass density of ×2.3 from z ∼ 1.1 to z ∼ 0.3, indicating a slowly decreasing rate of migration from the blue cloud to the red sequence. Unlike some studies of the SMF, we find that massive red galaxies grow by a factor of ×1.7 from z ∼ 1.1 to z ∼ 0.3, with the rate of growth due to mergers decreasing with time. These results are comparable with measurements of merger rates and clustering, and they are also consistent with the red galaxy stellar mass growth implied by comparing K-band luminosity evolution with the fading of passive stellar population models

    Helicopter tail rotor thrust and main rotor wake coupling in crosswind flight

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    The tail rotor of a helicopter with a single main rotor configuration can experience a significant reduction in thrust when the aircraft operates in crosswind flight. Brown’s vorticity transport model has been used to simulate a main rotor and tail rotor system translating at a sideslip angle that causes the tail rotor to interact with the main rotor tip vortices as they propagate downstream at the lateral extremities of the wake. The tail rotor is shown to exhibit a distinct directionally dependent mode during which tail rotors that are configured so that the blades travel forward at the top of the disk develop less thrust than tail rotors with the reverse sense of rotation. The range of flight speeds over which this mode exists is shown to vary considerably with the vertical location of the tail rotor. At low flight speeds, the directionally dependent mode occurs because the tail rotor is immersed within not only the downwash from the main rotor but also the rotational flow associated with clusters of largely disorganized vorticity within the main rotor wake. At higher flight speeds, however, the tail rotor is immersed within a coherent supervortex that strongly influences the velocity field surrounding the tail rotor

    Dependence of the Fundamental Plane Scatter on Galaxy Age

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    The fundamental plane (FP) has an intrinsic scatter that can not be explained purely by observational errors. Using recently available age estimates for nearby early type galaxies, we show that a galaxy's position relative to the FP depends on its age. In particular, the mean FP corresponds to ellipticals with an age of ~10 Gyr. Younger galaxies are systematically brighter with higher surface brightness relative to the mean relation. Old ellipticals form an `upper envelope' to the FP. For our sample of mostly non-cluster galaxies, age can account for almost half of the scatter in the B band FP. Distance determinations based on the FP may have a systematic bias, if the mean age of the sample varies with redshift. We also show that fundamental plane residuals, B-V colors and Mg_2 line strength are consistent with an ageing central burst superposed on an old stellar population. This reinforces the view that these age estimates are tracing the last major episode of star formation induced by a gaseous merger event. We briefly discuss the empirical `evolutionary tracks' of merger-remnants and young ellipticals in terms of their key observational parameters.Comment: 14 pages, Latex, 2 figures, accepted by ApJ Letter

    Centrifugal Compressor Application Sizing, Selection, And Modelling.

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    Tutorialpg. 195-202The objective here is to build on the fan law paper presented at the Twentieth Turbomachinery Symposium [1]. The centrifugal sizing and modelling tutorial draws on the pseudo compressor stage curves presented in the fan law paper. The presenters will elaborate and demonstrate the effects of curve shape, gas properties, and other factors on stage matching. For comparison, fan law and actual section properties will be compared to help the ultimate practitioner with the decision of when various methods are reasonable and applicable. Estimating centrifugal compressor fit for a given application using manufacturer's catalog data will be covered, along with aerodynamic modelling of actual compressor hardware after purchase for monitoring of off-design, fouling, or potential rerating

    ATP-binding cassette systems in Burkholderia pseudomallei and Burkholderia mallei

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    BACKGROUND: ATP binding cassette (ABC) systems are responsible for the import and export of a wide variety of molecules across cell membranes and comprise one of largest protein superfamilies found in prokarya, eukarya and archea. ABC systems play important roles in bacterial lifestyle, virulence and survival. In this study, an inventory of the ABC systems of Burkholderia pseudomallei strain K96243 and Burkholderia mallei strain ATCC 23344 has been compiled using bioinformatic techniques. RESULTS: The ABC systems in the genomes of B. pseudomallei and B. mallei have been reannotated and subsequently compared. Differences in the number and types of encoded ABC systems in belonging to these organisms have been identified. For example, ABC systems involved in iron acquisition appear to be correlated with differences in genome size and lifestyles between these two closely related organisms. CONCLUSION: The availability of complete inventories of the ABC systems in B. pseudomallei and B. mallei has enabled a more detailed comparison of the encoded proteins in this family. This has resulted in the identification of ABC systems which may play key roles in the different lifestyles and pathogenic properties of these two bacteria. This information has the potential to be exploited for improved clinical identification of these organisms as well as in the development of new vaccines and therapeutics targeted against the diseases caused by these organisms
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