Plasma Electron Beam Welder for Space Vehicles Final Report

Feasibility of developing plasma electron beam welding system for earth orbiting vehicl

Blue light regenerates functional visual pigments in mammals through a retinyl-phospholipid intermediate.

The light absorbing chromophore in opsin visual pigments is the protonated Schiff base of 11-cis-retinaldehyde (11cRAL). Absorption of a photon isomerizes 11cRAL to all-trans-retinaldehyde (atRAL), briefly activating the pigment before it dissociates. Light sensitivity is restored when apo-opsin combines with another 11cRAL to form a new visual pigment. Conversion of atRAL to 11cRAL is carried out by enzyme pathways in neighboring cells. Here we show that blue (450-nm) light converts atRAL specifically to 11cRAL through a retinyl-phospholipid intermediate in photoreceptor membranes. The quantum efficiency of this photoconversion is similar to rhodopsin. Photoreceptor membranes synthesize 11cRAL chromophore faster under blue light than in darkness. Live mice regenerate rhodopsin more rapidly in blue light. Finally, whole retinas and isolated cone cells show increased photosensitivity following exposure to blue light. These results indicate that light contributes to visual-pigment renewal in mammalian rods and cones through a non-enzymatic process involving retinyl-phospholipids.It is currently thought that visual pigments in vertebrate photoreceptors are regenerated exclusively through enzymatic cycles. Here the authors show that mammalian photoreceptors also regenerate opsin pigments in light through photoisomerization of N-ret-PE (N-retinylidene-phosphatidylethanolamine

Lubricants Optimized for use with R-32 and Related Low GWP Refrigerant Blends

Lubricants are important components of almost all air conditioning and refrigeration systems. Their primary function is to lubricate the compressor, provide sealing of clearances between low and high pressure sides of the compressor and remove frictional heat. But the lubricant is in contact with refrigerant at all times and plays a thermo-fluidic role in the air conditioning system that can impact both system capacity and coefficient of performance (COP). Lubricants can influence capacity by altering the refrigerant-side heat transfer coefficients, and increasing pressure drop required to maintain set point temperatures. Lubricants can also affect the isentropic efficiency of the compressor. The transition to lower global warming potential (GWP) alternative refrigerants is critical to the realization of environmentally sustainable and more energy efficient refrigeration technologies. Leading candidates to replace R-22 and R-410A in air conditioning and heat pump applications include R-32 (difluoromethane) and a plethora of HFC/hydrofluoro-olefin blends with GWPs in the range of 400-650. Considerable data has been generated comparing R-410A with various low GWP alternative refrigerants in full system tests. Most notable is the work sponsored by AHRI under the Alternative Refrigerant Evaluation Program (AREP). But these studies have either been refrigerant “drop in” tests to commercial R-410A systems or “soft optimized” tests, where minor component modifications were made to better adapt a system to the properties of the new refrigerants. In all cases, the lubricants used for these studies were the commercial polyol ester (POE) lubricants used with R-410A. But commercial POE lubricants used today are much less compatible with R-32 and HFC/HFO blends. There is concern that issues may arise with long term reliability of compressors due to inadequate lubrication, poor oil return to the compressor and undesirable lubricant hold up in the system; problems that would not be observed in the short term capacity and energy efficiency tests. But regardless, there is also interest in understanding if properly optimized lubricants can improve the overall performance of low GWP-based systems. This paper presents the results of a study of the solution phase behavior and lubricating performance of several commercial and new developmental POE lubricants with low GWP R-410A replacement refrigerants. The results suggest that POE lubricants used today with R-410A may not be acceptable for use with R-32 or related HFC/HFO blends. An undesirable miscibility gap is observed in mixtures of traditional POEs with R-32 in the concentration range of 10-40 wt% lubricant in refrigerant. In addition, the viscosity dilution of refrigerant/lubricant mixtures at high lubricant concentrations (typical of those observed in the compressor sump) is as much as 50% more pronounced with R-32 than R-410A. Studies conducted with a new class of advanced polyol esters show that it is possible to design synthetic lubricants optimized for R-32, combining good refrigerant miscibility with limited viscosity dilution

Solution Properties Of Polyol Ester Lubricants Designed For Use With R-32 And Related Low GWP Refrigerant Blends

Since the Montreal and Kyoto protocols mandated the phase-out of refrigerants which deplete the ozone layer and have high global warming potential, respectively, there has been an extensive global initiative to identify suitable environmentally sustainable alternatives. Replacement of CFCs and HCFCs with HFCs has successfully addressed the objectives of the Montreal protocol. However, most HFCs used today are not acceptable for the long term because they have GWPs greater than 1,000. Low GWP refrigerants that are, or will be, considered as replacements for HFCs include R32, hydrocarbons such as R290, carbon dioxide (R744), and hydroflouro olefins such as HFO1234yf and HFO1234ze(E).It has already been determined that in many cases new lubricants will be required for these refrigerants to ensure long term compressor reliability and the best possible system performance. The primary issue that must be addressed is the unacceptable high mutual solubility of the refrigerant and lubricant at high lubricant concentrations. The first consequence of this high solubility is the excessive reduction of viscosity that affects proper lubrication of the compressor and components, sealing of clearances between low and high pressure sides of the compressor. The second is a significant change in the steady state amount of oil in the circulation stream in the system, which can impact the heat transfer performance in both the evaporator and condenser.Another potential minor issue is refrigerant flash evaporation at discharge creating excessive foaming and noise. This paper describes details of a method used to measure the thermophysical properties of refrigerant lubricant mixtures. The general methods for data acquisition and processing, along with creation of Daniel charts were in accord with those developed by Chris Seeton. The results of measurements involving mixtures of traditional POEs with R-32 or R-410A shows that lubricant viscosities in the compressor at various conditions within the normal operating envelope decrease by as much as 25-54%. This illustrates the excessive lubricant viscosity dilution of R-32 relative to R-410A with traditional POs used today with HFCs refrigerants. The solution property measurement technique was also used to develop a class of advanced ester POE lubricants optimized for R-32 to eliminates the viscosity dilution problem. Significant energy savings can be achieved through proper optimization of lubricant/refrigerant solution properties to provide the best balance of lubrication in the compressor while maintaining excellent heat transfer in the refrigeration cycle

Solution Properties Of Polyol Ester Lubricants Designed For Use With R-32 And Related Low GWP Refrigerant Blends

Since the Montreal and Kyoto protocols mandated the phase-out of refrigerants which deplete the ozone layer and have high global warming potential, respectively, there has been an extensive global initiative to identify suitable environmentally sustainable alternatives. Replacement of CFCs and HCFCs with HFCs has successfully addressed the objectives of the Montreal protocol. However, most HFCs used today are not acceptable for the long term because they have GWPs greater than 1,000. Low GWP refrigerants that are, or will be, considered as replacements for HFCs include R32, hydrocarbons such as R290, carbon dioxide (R744), and hydroflouro olefins such as HFO1234yf and HFO1234ze(E).It has already been determined that in many cases new lubricants will be required for these refrigerants to ensure long term compressor reliability and the best possible system performance. The primary issue that must be addressed is the unacceptable high mutual solubility of the refrigerant and lubricant at high lubricant concentrations. The first consequence of this high solubility is the excessive reduction of viscosity that affects proper lubrication of the compressor and components, sealing of clearances between low and high pressure sides of the compressor. The second is a significant change in the steady state amount of oil in the circulation stream in the system, which can impact the heat transfer performance in both the evaporator and condenser.Another potential minor issue is refrigerant flash evaporation at discharge creating excessive foaming and noise. This paper describes details of a method used to measure the thermophysical properties of refrigerant lubricant mixtures. The general methods for data acquisition and processing, along with creation of Daniel charts were in accord with those developed by Chris Seeton. The results of measurements involving mixtures of traditional POEs with R-32 or R-410A shows that lubricant viscosities in the compressor at various conditions within the normal operating envelope decrease by as much as 25-54%. This illustrates the excessive lubricant viscosity dilution of R-32 relative to R-410A with traditional POs used today with HFCs refrigerants. The solution property measurement technique was also used to develop a class of advanced ester POE lubricants optimized for R-32 to eliminates the viscosity dilution problem. Significant energy savings can be achieved through proper optimization of lubricant/refrigerant solution properties to provide the best balance of lubrication in the compressor while maintaining excellent heat transfer in the refrigeration cycle

A stochastic movement simulator improves estimates of landscape connectivity

Acknowledgments This publication issued from the project TenLamas funded by the French Ministère de l'Energie, de l'Ecologie, du Développement Durable et de la Mer through the EU FP6 BiodivERsA Eranet; by the Agence Nationale de la Recherche (ANR) through the open call INDHET and 6th extinction MOBIGEN to V. M. Stevens, M. Baguette, and A. Coulon, and young researcher GEMS (ANR-13-JSV7-0010-01) to V. M. Stevens and M. Baguette; and by a VLIR-VLADOC scholarship awarded to J. Aben. L. Lens, J. Aben, D. Strubbe, and E. Matthysen are grateful to the Research Foundation Flanders (FWO) for financial support of fieldwork and genetic analysis (grant G.0308.13). V. M. Stevens and M. Baguette are members of the “Laboratoire d'Excellence” (LABEX) entitled TULIP (ANR-10-LABX-41). J. M. J. Travis and S. C. F. Palmer also acknowledge the support of NERC. A. Coulon and J. Aben contributed equally to the work.Peer reviewedPublisher PD

A quantitative model of normal Caenorhabditis elegans embryogenesis and its disruption after stress

AbstractThe invariant lineage of Caenorhabditis elegans has powerful potential for quantifying developmental variability in normal and stressed embryos. Previous studies of division timing by automated lineage tracing suggested that variability in cell cycle timing is low in younger embryos, but manual lineage tracing of specific lineages suggested that variability may increase for later divisions. We developed improved automated lineage tracing methods that allowroutine lineage tracing through the last round of embryonic cell divisions and we applied these methods to trace the lineage of 18 wild-type embryos. Cell cycle lengths, division axes and cell positions are remarkably consistent among these embryos at all stages, with only slight increase in variability later in development. The resulting quantitative 4-dimensional model of embryogenesis provides a powerful reference dataset to identify defects in mutants or in embryos that have experienced environmental perturbations. We also traced the lineages of embryos imaged at higher temperatures to quantify the decay in developmental robustness under temperature stress. Developmental variability increases modestly at 25°C compared with 22°C and dramatically at 26°C, and we identify homeotic transformations in a subset of embryos grown at 26°C. The deep lineage tracing methods provide a powerful tool for analysis of normal development, gene expression and mutants and we provide a graphical user interface to allow other researchers to explore the average behavior of arbitrary cells in a reference embryo