15,737 research outputs found
Solar cell radiation response near the interface of different atomic number materials
The response of cobalt 60 irradiated N/P silicon solar cells was measured as a function of the atomic number of the medium adjacent to the cell and the direction of the gamma ray beam. The interpositioning of various thicknesses of aluminum between the adjacent material and the cell had the effect of moving the cell to various locations in an approximate monatomic numbered medium. Using this technique the solar cell response was determined at various distances from the interface for gold and beryllium. The results were compared with predictions based upon ionization chamber measurements of dose perturbations in aluminum and found to agree within five percent. Ionization chamber data was then used to estimate the influence of various base contact materials
High efficiency thermal to electric energy conversion using selective emitters and spectrally tuned solar cells
Thermophotovoltaic (TPV) systems are attractive possibilities for direct thermal-to-electric energy conversion, but have typically required the use of black body radiators operating at high temperatures. Recent advances in both the understanding and performance of solid rare-earth oxide selective emitters make possible the use of TPV at temperatures as low as 1500 K. Depending on the nature of parasitic losses, overall thermal-to-electric conversion efficiencies greater than 20 percent are feasible
Circulating inflammatory and hemostatic biomarkers are associated with risk of myocardial infarction and coronary death, but not angina pectoris, in older men
Aims: The extent to which hemostatic and inflammatory biomarkers are related to angina pectoris as compared with myocardial infarction (MI) remains uncertain. We examined the relationship between a wide range of inflammatory and hemostatic biomarkers, including markers of activated coagulation, fibrinolysis and endothelial dysfunction and viscosity, with incident myocardial infarction (MI) or coronary heart disease (CHD) death and incident angina pectoris uncomplicated by MI or CHD death in older men. Methods: A prospective study of 3217 men aged 60-79 years with no baseline CHD (angina or MI) and who were not on warfarin, followed up for 7 years during which there were 198 MI/CHD death cases and 220 incident uncomplicated angina cases. Results: Inflammatory biomarkers [C-reactive protein (CRP), interleukin-6, fibrinogen], plasma viscosity and hemostatic biomarkers [von Willebrand factor (VWF) and fibrin D-dimer] were associated with a significant increased risk of MI/CHD death but not with uncomplicated angina even after adjustment for age and conventional risk factors. Adjustment for CRP attenuated the relationships between VWF, fibrin D-dimer and plasma viscosity with MI/CHD death. Comparisons of differing associations with risk of MI/CHD deaths and uncomplicated angina were significant for the inflammatory markers (P < 0.05) and marginally significant for fibrin D-dimer (P = 0.05). In contrast, established risk factors including blood pressure and high-density lipoprotein (HDL)-cholesterol were associated with both MI/CHD death and uncomplicated angina. Conclusion: Circulating biomarkers of inflammation and hemostasis are associated with incident MI/CHD death but not incident angina uncomplicated by MI or CHD death in older men
The effects of different alcoholic drinks on lipids, insulin and haemostatic and inflammatory markers in older men
Light to moderate drinking is associated with lower risk of coronary heart (CHD) than non-drinkers. We have examined the relationships between total alcohol intake and type of alcoholic beverage and several potential biological mechanisms. We carried out the study in 3158 men aged 60-79 years drawn from general practices in 24 British towns with no history of myocardial infarction, stroke or diabetes and who were not on warfarin. Total alcohol consumption showed a significant positive dose-response relationship with high density lipoprotein cholesterol (HDL-C), coagulation factor IX, haematocrit, blood viscosity, and tissue plasminogen (t-PA) antigen, and an inverse dose-response relationship with insulin, fibrinogen, von Wille- brand factor (vWF) and triglycerides after adjustment for possible confounders. Total alcohol consumption showed weak associations with plasma viscosity and fibrin D-dimer, and no association with factors VII,VIII, or C-reactive protein (CRP). Wine was specifically associated with lower CRP, plasma viscosity, factor VIII and triglycerides. The findings are consistent with the suggestion that HDL-C in particular but also insulin and haemostatic factors may contribute to the beneficial effect of light to moderate drinking on risk of CHD. Wine has effects that may confer greater protection than other alcoholic beverages
Eighty years of food-web response to interannual variation in discharge recorded in river diatom frustules from an ocean sediment core.
Little is known about the importance of food-web processes as controls of river primary production due to the paucity of both long-term studies and of depositional environments which would allow retrospective fossil analysis. To investigate how freshwater algal production in the Eel River, northern California, varied over eight decades, we quantified siliceous shells (frustules) of freshwater diatoms from a well-dated undisturbed sediment core in a nearshore marine environment. Abundances of freshwater diatom frustules exported to Eel Canyon sediment from 1988 to 2001 were positively correlated with annual biomass of Cladophora surveyed over these years in upper portions of the Eel basin. Over 28 years of contemporary field research, peak algal biomass was generally higher in summers following bankfull, bed-scouring winter floods. Field surveys and experiments suggested that bed-mobilizing floods scour away overwintering grazers, releasing algae from spring and early summer grazing. During wet years, growth conditions for algae could also be enhanced by increased nutrient loading from the watershed, or by sustained summer base flows. Total annual rainfall and frustule densities in laminae over a longer 83-year record were weakly and negatively correlated, however, suggesting that positive effects of floods on annual algal production were primarily mediated by "top-down" (consumer release) rather than "bottom-up" (growth promoting) controls
Mopra CO Observations of the Bubble HII Region RCW120
We use the Mopra radio telescope to test for expansion of the molecular gas
associated with the bubble HII region RCW120. A ring, or bubble, morphology is
common for Galactic HII regions, but the three-dimensional geometry of such
objects is still unclear. Detected near- and far-side expansion of the
associated molecular material would be consistent with a three-dimensional
spherical object. We map the transitions of CO,
CO, CO, and CO, and detect emission from all
isotopologues. We do not detect the masing lines of
CHOH at 108.8939 GHz. The strongest CO emission is from the
photodissociation region (PDR), and there is a deficit of emission toward the
bubble interior. We find no evidence for expansion of the molecular material
associated with RCW120 and therefore can make no claims about its geometry. The
lack of detected expansion is roughly in agreement with models for the
time-evolution of an HII region like RCW120, and is consistent with an
expansion speed of . Single-position CO spectra show
signatures of expansion, which underscores the importance of mapped spectra for
such work. Dust temperature enhancements outside the PDR of RCW120 coincide
with a deficit of emission in CO, confirming that these temperature
enhancements are due to holes in the RCW120 PDR. H emission shows that
RCW120 is leaking of the ionizing photons into the interstellar
medium (ISM) through PDR holes at the locations of the temperature
enhancements. H-alpha emission also shows a diffuse "halo" from leaked photons
not associated with discrete holes in the PDR. Overall of all
ionizing photons are leaking into the nearby ISM.Comment: 35 pages, 14 figures. Accepted to Ap
Checking and Enforcing Security through Opacity in Healthcare Applications
The Internet of Things (IoT) is a paradigm that can tremendously
revolutionize health care thus benefiting both hospitals, doctors and patients.
In this context, protecting the IoT in health care against interference,
including service attacks and malwares, is challenging. Opacity is a
confidentiality property capturing a system's ability to keep a subset of its
behavior hidden from passive observers. In this work, we seek to introduce an
IoT-based heart attack detection system, that could be life-saving for patients
without risking their need for privacy through the verification and enforcement
of opacity. Our main contributions are the use of a tool to verify opacity in
three of its forms, so as to detect privacy leaks in our system. Furthermore,
we develop an efficient, Symbolic Observation Graph (SOG)-based algorithm for
enforcing opacity
AdS/CFT and the Information Paradox
The information paradox in the quantum evolution of black holes is studied
within the framework of the AdS/CFT correspondence. The unitarity of the CFT
strongly suggests that all information about an initial state that forms a
black hole is returned in the Hawking radiation. The CFT dynamics implies an
information retention time of order the black hole lifetime. This fact
determines many qualitative properties of the non-local effects that must show
up in a semi-classical effective theory in the bulk. We argue that no
violations of causality are apparent to local observers, but the semi-classical
theory in the bulk duplicates degrees of freedom inside and outside the event
horizon. Non-local quantum effects are required to eliminate this redundancy.
This leads to a breakdown of the usual classical-quantum correspondence
principle in Lorentzian black hole spacetimes.Comment: 16 pages, harvmac, reference added, minor correction
Magnetic Fields and Passive Scalars in Polyakov's Conformal Turbulence
Polyakov has suggested that two dimensional turbulence might be described by
a minimal model of conformal field theory. However, there are many minimal
models satisfying the same physical inputs as Polyakov's solution (p,q)=(2,21).
Dynamical magnetic fields and passive scalars pose different physical
requirements. For large magnetic Reynolds number other minimal models arise.
The simplest one, (p,q)=(2,13) makes reasonable predictions that may be tested
in the astrophysical context. In particular, the equipartition theorem between
magnetic and kinetic energies does not hold: the magnetic one dominates at
larger distances.Comment: 12 pages, UR-1296, ER-745-4068
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