Cycling Joule Thomson refrigerator

A symmetrical adsorption pump/compressor system having a pair of mirror image legs and a Joule Thomson expander, or valve, interposed between the legs thereof for providing a, efficient refrigeration cycle is described. The system further includes a plurality of gas operational heat switches adapted selectively to transfer heat from a thermal load and to transfer or discharge heat through a heat projector, such as a radiator or the like. The heat switches comprise heat pressurizable chambers adapted for alternate pressurization in response to adsorption and desorption of a pressurizing gas confined therein

Miniature Long-life Space Cryocoolers

TRW has designed, built, and tested a miniature integral Stirling cooler and a miniature pulse tube cooler intended for long-life space application. Both efficient, low-vibration coolers were developed for cooling IR sensors to temperatures as low as 50 K on lightsats. The vibrationally balanced nonwearing design Stirling cooler incorporates clearance seals maintained by flexure springs for both the compressor and the drive displacer. The design achieved its performance goal of 0.25 W at 65 K for an input power to the compressor of 12 W. The cooler recently passed launch vibration tests prior to its entry into an extended life test and its first scheduled flight in 1995. The vibrationally balanced, miniature pulse tube cooler intended for a 10-year long-life space application incorporates a flexure bearing compressor vibrationally balanced by a motor-controlled balancer and a completely passive pulse tube cold head

Proceedings of the Cold Electronics Workshop

The benefits and problems of the use of cold semiconductor electronics and the research and development effort required to bring cold electronics into more widespread use were examined

A closed cycle cascade Joule Thomson refrigerator for cooling Josephson junction magnetometers

A closed cycle cascade Joule Thomson refrigerator designed to cool Josephson Junction magnetometers to liquid helium temperature is being developed. The refrigerator incorporates 4 stages of cooling using the working fluids CF4 and He. The high pressure gases are provided by a small compressor designed for this purpose. The upper stages have been operated and performance will be described

Cascade Joule-Thomson refrigerators

The design criteria for cascade Joule-Thomson refrigerators for cooling in the temperature range from 300 K to 4.2 K were studied. The systems considered use three or four refrigeration stages with various working gases to achieve the low temperatures. Each stage results in cooling to a progressively lower temperature and provides cooling at intermediate temperatures to remove the substantial amount of parasitic heat load encountered in a typical dewar. With careful dewar design considerable cooling can be achieved with moderate gas flows. For many applications, e.g., in the cooling of sensitive sensors, the fact that the refrigerator contains no moving parts and may be remotely located from the gas source is of considerable advantage. A small compressor suitable for providing the gas flows required was constructed

Library Program: Assisting Elderly Patrons with Technology

When considering which population requires the most support in relation to technology use and adaptation, the elderly community immediately comes to mind. As noted by Meeks (1994), “With an aging world society, policy makers, researchers, and producers need to give more attention to the role of technology in helping the elderly maintain independence and self-sufficiency” (p. 15). Since technology has been advancing so drastically and quickly, it is important to ensure that the elderly community does not fall behind on essential trends. There are many classes offered at libraries and through other entities to help individuals with technology use, but usually, they cater to people from all different demographics. When creating a lesson for the elderly community, there are many additional aspects to consider, and it would be safe to argue that the rate at which elderly people pick up on technological use and the speed at which they are able to perform these tasks independently are vastly different in relation to a younger adult or teenager. As well, the way of instruction must take into consideration features which are important for the elderly regarding their retention of memory and the speed at which the lesson progresses

Expression of alternative oxidase in the copepod T. californicus when exposed to environmental stressors

In addition to the typical electron transport system in animal mitochondria responsible for oxidative phosphorylation, some species possess an alternative oxidase (AOX) pathway, which causes electrons to bypass proton pumping complexes. Although AOX appears to be energetically wasteful, studies have revealed its wide taxonomic distribution, and indicate it plays a role in environmental stress tolerance. AOX discovery in animals is recent, and further research into its expression, regulation, and physiological role has been impeded by the lack of an experimental model organism. DNA database searches using bioinformatics revealed an AOX sequence present in the arthropod Tigriopus californicus. Multiple sequence alignments compared known AOX proteins to that of T. californicus and examined the conservation of amino acid residues involved in AOX catalytic function and post-translational regulation. The physiological function of a native AOX has never been identified in an animal that produces it, but I hypothesize that AOX protein levels will change in response to environmental stress in T. californicus. In order to test this hypothesis, copepods were exposed to five different temperatures (6, 10, 15, 22 and 28°C), and extended periods of light/dark. Samples were taken after 24 hours (acute) and 1 week (chronic) of incubation at each stress treatment. In conclusion, T. californicus possesses the necessary residues required for AOX function. Furthermore, Western blots demonstrate that there are fluctuations in AOX expression when exposing T. californicus to temperature stress. In contrast, during light stress AOX is constitutively expressed when animals were subjected to changes in their circadian rhythms. AOX has been most thoroughly characterized in a number of plants; however, the physiological function of a native AOX has never been identified in an animal that produces it. This is the second study to confirm AOX protein expression in an animal and is the first study to look at a native AOX protein in an animal and its response to biotic stress. By understanding why T. californicus possesses AOX, we can better understand why some other organisms, including humans, do not express or have lost the AOX gene. More thorough investigation of AOX in copepods may aid in the development of a drug that can be added to fish aquaculture to exterminate parasitic copepods and prevent the loss of economically valuable fish

Expression of alternative oxidase in the copepod T. californicus when exposed to environmental stressors

In addition to the typical electron transport system in animal mitochondria responsible for oxidative phosphorylation, some species possess an alternative oxidase (AOX) pathway, which causes electrons to bypass proton pumping complexes. Although AOX appears to be energetically wasteful, studies have revealed its wide taxonomic distribution, and indicate it plays a role in environmental stress tolerance. AOX discovery in animals is recent, and further research into its expression, regulation, and physiological role has been impeded by the lack of an experimental model organism. DNA database searches using bioinformatics revealed an AOX sequence present in the arthropod Tigriopus californicus. Multiple sequence alignments compared known AOX proteins to that of T. californicus and examined the conservation of amino acid residues involved in AOX catalytic function and post-translational regulation. The physiological function of a native AOX has never been identified in an animal that produces it, but I hypothesize that AOX protein levels will change in response to environmental stress in T. californicus. In order to test this hypothesis, copepods were exposed to five different temperatures (6, 10, 15, 22 and 28°C), and extended periods of light/dark. Samples were taken after 24 hours (acute) and 1 week (chronic) of incubation at each stress treatment. In conclusion, T. californicus possesses the necessary residues required for AOX function. Furthermore, Western blots demonstrate that there are fluctuations in AOX expression when exposing T. californicus to temperature stress. In contrast, during light stress AOX is constitutively expressed when animals were subjected to changes in their circadian rhythms. AOX has been most thoroughly characterized in a number of plants; however, the physiological function of a native AOX has never been identified in an animal that produces it. This is the second study to confirm AOX protein expression in an animal and is the first study to look at a native AOX protein in an animal and its response to biotic stress. By understanding why T. californicus possesses AOX, we can better understand why some other organisms, including humans, do not express or have lost the AOX gene. More thorough investigation of AOX in copepods may aid in the development of a drug that can be added to fish aquaculture to exterminate parasitic copepods and prevent the loss of economically valuable fish

Identification of the alternative oxidase gene and its expression in the copepod Tigriopus californicus

In addition to the typical electron transport system (ETS) in animal mitochondria responsible for oxidative phosphorylation, in some species there exists an alternative oxidase (AOX) pathway capable of catalyzing the oxidation of ubiquinol and the reduction of oxygen to water. The discovery of AOX in animals is recent and further investigations into its expression, regulation, and physiological role have been hampered by the lack of a tractable experimental model organism. Our recent DNA database searches using bioinformatics revealed an AOX sequence in several marine copepods including Tigriopus californicus. This species lives in tidepools along the west coast of North America and is subject to a wide variety of daily environmental stresses. Here we verify the presence of the AOX gene in T. californicus and the expression of AOX mRNA and AOX protein in various life stages of the animal. We demonstrate that levels of the AOX protein increase in T. californicus in response to cold and heat stress compared to normal rearing temperature. We predict that a functional AOX pathway is present in T. californicus, propose that this species will be a useful model organism for the study of AOX in animals, and discuss future directions for animal AOX research

Superconductor-sapphire cavity for an all-cryogenic SCSO

To develop a superconducting cavity stabilized oscillator (SCSO) as a frequency standard, we are studying the properties of cavities consisting of a single crystal of sapphire surrounded by a superconducting film. Measurements of quality factors of spherical and cylindrical samples of sapphire are reported. Loss values less than 2 × 10^-9 have been measured at a temperature of 1.45K. A design for an all-cryogenic SCSO is described, with particular emphasis on the cavity requirements. We conclude that such a design would allow greatly enhanced stability of operation due substantially to the thermal and physical properties of the sapphire substrate. Cavity Q requirements are relatively modest, with better than 10^-16 frequency stability predicted for a Q of 10^8