420 research outputs found

    Globalizing racism and de-provincializing Muslim Africa

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    Between surveillance and recognition: rethinking digital identity in aid

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    Identification technologies like biometrics have long been associated with securitisation, coercion and surveillance but have also, in recent years, become constitutive of a politics of empowerment, particularly in contexts of international aid. Aid organisations tend to see digital identification technologies as tools of recognition and inclusion rather than oppressive forms of monitoring, tracking and top-down control. In addition, practices that many critical scholars describe as aiding surveillance are often experienced differently by humanitarian subjects. This commentary examines the fraught questions this raises for scholars of international aid, surveillance studies and critical data studies. We put forward a research agenda that tackles head-on how critical theories of data and society can better account for the ambivalent dynamics of ‘power over’ and ‘power to’ that digital aid interventions instantiate

    Measurements of neutron capture in U²³⁸ in lattices of uranium rods in heavy water

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    "NYO-9659."Also issued as a Ph. D. thesis in the Dept. of Nuclear Engineering, 1962Includes bibliographical references (pages 119-145)Contract AT(30-1)-234

    Physiological role for nitrate-reducing oral bacteria in blood pressure control

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    AbstractCirculating nitrate (NO3−), derived from dietary sources or endogenous nitric oxide production, is extracted from blood by the salivary glands, accumulates in saliva, and is then reduced to nitrite (NO2−) by the oral microflora. This process has historically been viewed as harmful, because nitrite can promote formation of potentially carcinogenic N-nitrosamines. More recent research, however, suggests that nitrite can also serve as a precursor for systemic generation of vasodilatory nitric oxide, and exogenous administration of nitrate reduces blood pressure in humans. However, whether oral nitrate-reducing bacteria participate in “setting” blood pressure is unknown. We investigated whether suppression of the oral microflora affects systemic nitrite levels and hence blood pressure in healthy individuals. We measured blood pressure (clinic, home, and 24-h ambulatory) in 19 healthy volunteers during an initial 7-day control period followed by a 7-day treatment period with a chlorhexidine-based antiseptic mouthwash. Oral nitrate-reducing capacity and nitrite levels were measured after each study period. Antiseptic mouthwash treatment reduced oral nitrite production by 90% (p < 0.001) and plasma nitrite levels by 25% (p = 0.001) compared to the control period. Systolic and diastolic blood pressure increased by 2–3 .5mmHg, increases correlated to a decrease in circulating nitrite concentrations (r2 = 0.56, p = 0.002). The blood pressure effect appeared within 1 day of disruption of the oral microflora and was sustained during the 7-day mouthwash intervention. These results suggest that the recycling of endogenous nitrate by oral bacteria plays an important role in determination of plasma nitrite levels and thereby in the physiological control of blood pressure

    Circulating Precursor Levels of Endothelin-1 and Adrenomedullin, Two Endothelium-Derived, Counteracting Substances, in Sepsis

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    Plasma levels of endothelin-1 (ET-1) and adrenomedullin (ADM), two opposingly acting peptides, correlate with mortality in endotoxemia, but their measurement is cumbersome. New sandwich assays have been introduced that measure more stable precursor fragments. The objective of this study was to investigate the counterplay of their precursor peptides in septic patients and to compare them with disease severity and other biomarkers. Blood samples of an observational study in 95 consecutive critically ill patients admitted to the intensive care unit (ICU) were analyzed. CT-proET-1 and MR-proADM concentrations on admission were measured using new sandwich immunoassays. Depending on the clinical severity of the infection, both CT-proET-1 and MR-proADM levels exhibited a gradual increase from Systemic Inflammatory Response Syndrome (SIRS) to sepsis and septic shock (p < .001). Compared to the group of survivors, the group of non-survivors had higher median values of MR-proADM (5.7 nmol/L [range 0.4 to 21.0] versus 1.9 nmol/L [range 0.3 to 17.1], p < .02) and similar CT-proET-1 levels (56.0pmol/L [range 0.5 to 271.0] versus 54.1pmol/L [range 1.0 to 506.0], p = .86). Receiver operating characteristics (ROC) curve analysis showed a higher prognostic accuracy of the calculated ratio of both counteracting substances as compared to CT-proET-1 (p = 0.001) and C-reactive protein (CRP) (p = .001) and in the range of MR-proADM (p = .51), procalcitonin (p = 0.22), and the APACHE II score (p = .61). Endothelin-1 and adrenomedullin precursor peptides gradually increase with increasing severities of infection in critically ill patients. The ratio of the two counteracting peptides correlates with mortality and shows aprognostic accuracy to predict adverse outcome comparable to the APACHE II score

    Affordable Development and Demonstration of a Small NTR Engine and Stage: How Small is Big Enough?

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    The Nuclear Thermal Rocket (NTR) derives its energy from fission of uranium-235 atoms contained within fuel elements that comprise the engine's reactor core. It generates high thrust and has a specific impulse potential of approximately 900 seconds - a 100% increase over today's best chemical rockets. The Nuclear Thermal Propulsion (NTP) project, funded by NASA's AES program, includes five key task activities: (1) Recapture, demonstration, and validation of heritage graphite composite (GC) fuel (selected as the "Lead Fuel" option); (2) Engine Conceptual Design; (3) Operating Requirements Definition; (4) Identification of Affordable Options for Ground Testing; and (5) Formulation of an Affordable Development Strategy. During FY'14, a preliminary DDT&E plan and schedule for NTP development was outlined by GRC, DOE and industry that involved significant system-level demonstration projects that included GTD tests at the NNSS, followed by a FTD mission. To reduce cost for the GTD tests and FTD mission, small NTR engines, in either the 7.5 or 16.5 klbf thrust class, were considered. Both engine options used GC fuel and a "common" fuel element (FE) design. The small approximately 7.5 klbf "criticality-limited" engine produces approximately 157 megawatts of thermal power (MWt) and its core is configured with parallel rows of hexagonal-shaped FEs and tie tubes (TTs) with a FE to TT ratio of approximately 1:1. The larger approximately 16.5 klbf Small Nuclear Rocket Engine (SNRE), developed by LANL at the end of the Rover program, produces approximately 367 MWt and has a FE to TT ratio of approximately 2:1. Although both engines use a common 35 inch (approximately 89 cm) long FE, the SNRE's larger diameter core contains approximately 300 more FEs needed to produce an additional 210 MWt of power. To reduce the cost of the FTD mission, a simple "1-burn" lunar flyby mission was considered to reduce the LH2 propellant loading, the stage size and complexity. Use of existing and flight proven liquid rocket and stage hardware (e.g., from the RL10B-2 engine and Delta Cryogenic Second Stage) was also maximized to further aid affordability. This paper examines the pros and cons of using these two small engine options, including their potential to support future human exploration missions to the Moon, near Earth asteroids, and Mars, and recommends a preferred size. It also provides a preliminary assessment of the key activities, development options, and schedule required to affordably build, ground test and fly a small NTR engine and stage within a 10-year timeframe
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