Method and apparatus for determining optical absorption and emission characteristics of a crystal or non-crystalline fiber

This invention relates generally to spectroscopy and, more particularly, to a method and apparatus for performing spectroscopic analysis of crystal and noncrystalline fibers. The invention provides a complete absorption curve for a material using a crystal fiber which can be more easily produced than the types of samples required for other methods of obtaining substantially the same absorption curve for identical materials

The ultimate efficiency of photosensitive systems

These systems have in common two important but not independent features: they can produce a storable fuel, and they are sensitive only to radiant energy with a characteristic absorption spectrum. General analyses of the conversion efficiencies were made using the operational characteristics of each particular system. An efficiency analysis of a generalized system consisting of a blackbody source, a radiant energy converter having a threshold energy and operating temperature, and a reservoir is reported. This analysis is based upon the first and second laws of thermodynamics, and leads to a determination of the limiting or ultimate efficiency for an energy conversion system having a characteristic threshold

Thermodynamic limits to the efficiency of solar energy conversion by quantum devices

The second law of thermodynamics imposes a strict limitation to the energy converted from direct solar radiation to useful work by a quantum device. This limitation requires that the amount of energy converted to useful work (energy in any form other than heat) can be no greater than the change in free energy of the radiation fields. Futhermore, in any real energy conversion device, not all of this available free energy in the radiation field can be converted to work because of basic limitations inherent in the device itself. A thermodynamic analysis of solar energy conversion by a completely general prototypical quantum device is presented. This device is completely described by two parameters, its operating temperature T sub R and the energy threshold of its absorption spectrum. An expression for the maximum thermodynamic efficiency of a quantum solar converter was derived in terms of these two parameters and the incident radiation spectrum. Efficiency curves for assumed solar spectral irradiance corresponding to air mass zero and air mass 1.5 are presented

Thermodynamic limits for solar energy conversion by a quantum-thermal hybrid system

The limits are presented fo air mass 1.5 conditions. A maximum conversion efficiency of 74 percent is thermodynamically achievable for the quantum device operating at 3500 K and the heat engine in contact with a reservoir at 0 K. The efficiency drops to 56 percent for a cold reservoir at approximately room temperature conditions. Hybrid system efficiencies exceed 50 percent over receiver temperatures ranging from 1400 K to 4000 K, suggesting little benefit is gained in operating the system above 1400 K. The results are applied to a system consisting of a photovoltaic solar cell in series with a heat engine

Development of superconducting YBa2Cu3O(x) wires with low resistance electrical contacts

Materials exhibiting superconductivity above liquid nitrogen temperatures (77 K) will enable new applications of this phenomena. One of the first commercial applications of this technology will be superconducting magnets for medical imaging. However, a large number of aerospace applications of the high temperature superconducting materials have also been identified. These include magnetic suspension and balance of models in wind tunnels and resistanceless leads to anemometers. The development of superconducting wires fabricated from the ceramic materials is critical for these applications. The progress in application of a patented fiber process developed by Clemson University for the fabrication of superconducting wires is reviewed. The effect of particle size and heat treatment on the quality of materials is discussed. Recent advances made at Christopher Newport College in the development of micro-ohm resistance electrical contacts which are capable of carrying the highest reported direct current to this material is presented

Glaciohydrogeology

International audienceHydrogeology is defined as the science of the occurrence, distribution, and movement of water below the Earth's surface. This chapter will focus on groundwater occurrence and movement below or at the periphery of ancient and modern ice sheets (e.g., glaciohydrogeology), but also on the interaction of meltwater with the sediments and rocks within glaciated terrain. The growth of ice sheets has a largescale and long-term impact on groundwater flow as evidenced by modern groundwater flow which locally did not recover from the Late Pleistocene glacial period (Lemieux et al., 2008b). Over the last 20 years, the interest in glacial hydrogeology from glaciologists, hydrologists, and glacial geologists has significantly increased because of the impact of groundwater flow on ice sheet dynamics, water budgets in glacial catchments, solute fluxes, and tunnel valley genesis

Glycoxidation and inflammatory markers in patients on treatment with PMMA-based protein-leaking dialyzers

Background. High-molecular-weight solutes such as glycation and oxidation protein products are putative proinflammatory mediators found in the uremic blood. The elimination of these and other large solutes by protein-leaking dialyzers (PLD) might help to correct the inflammatory status of maintenance hemodialysis (HD) patients. Methods. Two matched groups of 13 standard 3 times/week HD patients were treated for 6 months with PMMA-based PLD and non–protein-leaking dialyzers (NPLD), respectively. At baseline, 1, 3, and 6 months, we measured the blood levels of the inflammatory cytokines IL-1b, TNF-a, IL-6, the acute-phase protein C-reactive protein (CRP), the adhesion molecules ICAM-1, VCAM-1, and selectine-E, the chemotaxis factors MCP-1, and the glycation and oxidation protein end products pentosidine, protein carbonyls, and AOPP. Results. In all the patients at baseline, pre-HD levels of glycation and oxidation protein markers, and inflammatory parameters were significantly higher than in healthy control subjects (P < 0.01 or greater). After 6 months, in the group on treatment with PLD, but not in that on NPLD, there was a significant decrease (P < 0.05 or greater) of pre-HD values of total pentosidine (mainly represented by pentosidine in serum albumin; −43%), protein carbonyls (−42%), AOPP (−38%), and the inflammatory cytokines IL-1b (−49%), IL-6 (−39%), and TNF-a (−20%), while IL-10 and INF-c increased by 67% and 37%, respectively. Proinflammatory cytokines, and particularly IL-6, showed a positive correlation with the levels of circulating pentosidine. Protidemia was not significantly modified at the end of the study in both the groups. Conclusion. The results in this pilot study show that the removal of large solutes by PLD can improve some indices of chronic inflammation in HD patients. Further studies are required to determine the relevance of the individual solutes removed with PLD as proinflammatory mediators in the uremic environment

Effect of daily hemodialysis on monocytes apoptosis

Uremia is associated with a state of immune dysfunction with increased susceptibility to infection and malignancy possibly related to dysregulation of immune system cell apoptosis. Peritoneal dialysis can restore plasma apoptosis activity on monocytes compared to intermittent hemodialysis. Whether the continuous modality or diverse clearance mechanisms involved are responsible is unknown. Apoptosis rates correlate with phagocytic function highlighting the benefit of efficient toxin clearance. The plasma of 16 patients on daily hemodialysis (D-HD) was incubated with U937 monocytes and compared to 18 hemodialysis (HD) patients, 5 chronic renal failure (CRF) subjects and 5 healthy volunteers ( controls). Apoptosis was evaluated by immunofluorescence microscopy dyes ( Hoechst 33342, propidium iodide) and annexin V cytoflowmetry at 96 h. Plasma-induced U937 apoptosis ( mean values) was significantly enhanced in D-HD ( 18.8 +/- 4.1), HD ( 19.67 +/- 5.5) and CRF patients (20.8 +/- 4.7) compared to controls (9.6 +/- 3.6; p < 0.05 for CRF vs. controls, HD vs. controls and D-HD vs. controls). No significant differences were observed between D-HD, HD and CRF sera on apoptosis rate, caspase-3 activity and phagocytic capacity of U937 monocytes. This study demonstrates that the plasma of various HD schedules was unable to reduce monocyte apoptosis induced by uremia. Copyright (C) 2005 S. Karger AG, Basel