An alternate method for achieving temperature control in the -130 C to 75 C range

Thermal vacuum testing often requires temperature control of chamber shrouds and heat exchangers within the -130 C to 75 C range. There are two conventional methods which are normally employed to achieve control through this intermediate temperature range: (1) single-pass flow where control is achieved by alternately pulsing hot gaseous nitrogen (GN2) and cold LN2 into the feed line to yield the setpoint temperature; and (2) closed-loop circulation where control is achieved by either electrically heating or LN2 cooling the circulating GN2 to yield the setpoint temperature. A third method, using a mass flow ratio controller along with modulating control valves on GN2 and LN2 lines, provides excellent control but equipment for this method is expensive and cost-prohibitive for all but long-term continuous processes. The single-pass method provides marginal control and can result in unexpected overcooling of the test article from even a short pulse of LN2. The closed-loop circulation method provides excellent control but requires an expensive blower capable of operating at elevated pressures and cryogenic temperatures. Where precise control is needed (plus or minus 2 C), single-pass flow systems typically have not provided the precision required, primarily because of overcooling temperature excursions. Where several individual circuits are to be controlled at different temperatures, the use of expensive cryogenic blowers for each circuit is also cost-prohibitive, especially for short duration of one-of-a-kind tests. At JPL, a variant of the single-pass method was developed that was shown to provide precise temperature control in the -130 C to 75 C range while exhibiting minimal setpoint overshoot during temperature transitions. This alternate method uses a commercially available temperature controller along with a GN2/LN2 mixer to dampen the amplitude of cold temperature spikes caused by LN2 pulsing. The design of the GN2/LN2 mixer, the overall control system configuration, the operational procedure, and the prototype system test results are described

A new approach for performing contamination control bakeouts in JPL thermal vacuum test chambers

Contamination control requirements for the Wide Field/Planetary Camera II (WF/PC II) are necessarily stringent to protect against post-launch contamination of the sensitive optical surfaces, particularly the cold charge coupled device (CCD) imaging surfaces. Typically, thermal vacuum test chambers have employed a liquid nitrogen (LN2) cold trap to collect outgassed contaminants. This approach has the disadvantage of risking recontamination of the test article from shroud offgassing during post-test warmup of the chamber or from any shroud warming of even a few degrees during the bakeout process. By using an enclave, essentially a chamber within a chamber, configured concentrically and internally within an LN2 shroud, a method was developed, based on a design concept by Taylor, for preventing recontamination of test articles during bakeouts and subsequent post-test warmup of the vacuum chamber. Enclaves for testing WF/PC II components were designed and fabricated, then installed in three of JPL's Environmental Test Lab chambers. The design concepts, operating procedures, and test results of this development are discussed

Loss of Signal, Aeromedical Lessons Learned for the STS-I07 Columbia Space Shuttle Mishap

Loss of Signal, a NASA publication to be available in May 2014, presents the aeromedical lessons learned from the Columbia accident that will enhance crew safety and survival on human space flight missions. These lessons were presented to limited audiences at three separate Aerospace Medical Association (AsMA) conferences: in 2004 in Anchorage, Alaska, on the causes of the accident; in 2005 in Kansas City, Missouri, on the response, recovery, and identification aspects of the investigation; and in 2011, again in Anchorage, Alaska, on future implications for human space flight. As we embark on the development of new spacefaring vehicles through both government and commercial efforts, the NASA Johnson Space Center Human Health and Performance Directorate is continuing to make this information available to a wider audience engaged in the design and development of future space vehicles. Loss of Signal summarizes and consolidates the aeromedical impacts of the Columbia mishap process-the response, recovery, identification, investigative studies, medical and legal forensic analysis, and future preparation that are needed to respond to spacecraft mishaps. The goals of this book are to provide an account of the aeromedical aspects of the Columbia accident and the investigation that followed, and to encourage aerospace medical specialists to continue to capture information, learn from it, and improve procedures and spacecraft designs for the safety of future crews

Interferometric Observations of Explosive Variables: V838 Mon, Nova Aql 2005, and RS Oph

During the last two years we have used the Palomar Testbed Interferometer to observe several explosive variable stars, including V838 Monocerotis, V1663 Aquilae and recently RS Ophiuchi. We observed V838 Monocerotis approximately 34 months after its eruption, and were able to resolve the ejecta. Observations of V1663 Aql were obtained starting 9 days after peak brightness and continued for 10 days. We were able to resolve the milliarcsecond-scale emission and follow the expansion of the nova photosphere. When combined with radial-velocity information, these observations can be used to infer the distance to the nova. Finally we have resolved the recurrent nova RS Oph and can draw some preliminary conclusions regarding the emission morphology.Comment: 8 Pages, SPIE Astronomical Telescopes and Instrumentation 2006, Advances in Stellar Interferometery, 6268-16

A Statement on the Appropriate Role for Research and Development in Climate Policy

This statement is issued by a group of economists and scientists which met at Stanford University on October 18, 2008 to discuss the role of research and development (R&D) in developing effective policies for addressing the adverse potential consequences of climate change. We believe that climate change is a serious issue that governments need to address. We also believe that research and development needs to be a central part of governments’ strategies for responding to this challenge. Solutions to manage long-term risks will require the development and global deployment of a range of technologies for energy supply and end-use, land-use, agriculture and adaptation that are not currently commercial. A key potential benefit of focused scientific and technological research and development investment is that it could dramatically reduce the cost of restricting greenhouse gas emissions by encouraging the development of more affordable, better performing technologies.

Multi-taxa consequences of management for an avian umbrella species

Whether management for so-called umbrella species actually benefits co-occurring biota has rarely been tested. Here, we studied consequences for multiple invertebrate taxa of two ground-disturbance treatments designed to support an avian umbrella species (Eurasian stone-curlew, Burhinus oedicnemus), and whether analysing ecological requirements across the regional species pool predicted beneficiaries. Responses were assessed for the abundance of five bird species of conservation concern, and the abundance, species richness and composition of carabids, staphylinids, other beetles (non-carabid, non-staphylinid), true bugs and ants, sampling 31258 individuals of 402 species in an extensively-replicated experiment across the UK’s largest grass-heath. Both treatments provided suitable habitat for the umbrella species, in contrast to controls. Treatment influenced the abundance of only one bird species; but carabid, other beetle and ant richness increased with one or both treatments, while staphylinid richness and abundance increased and true bug richness and abundance decreased with both treatments. Richness of ‘priority’ (rare, scarce or threatened) invertebrates a priori considered to share ecological requirements with the umbrella species (predicted beneficiaries) increased with both treatments. Resampling and rarefaction showed landscapes diversified by treatment supported a greater cumulative species richness of other beetles, ants and true bugs, and importantly priority invertebrates, than a landscape comprising only untreated controls. Such experiments provide strong evidence to assess co-benefits of umbrella species management, but are costly and time consuming. The systematic examination of the autoecological requirements of co-occurring taxa (the ‘Biodiversity Audit Approach’) successfully predicted likely beneficiaries. Demonstrating wider biodiversity benefits strengthens the case for avian conservation management

Book Reviews

It was peculiarly fortunate for the cause of the American Revolution that the sympathies of the French people and the policies of the French foreign office which knew no diplomatic methods save those of secret diplomacy, were for once heartily in accord in support of the American revolutionists. Professor Corwin in this book deals entirely with the complicated and obscure political plots and counter-plots which eventually led France to espouse openly the cause of the revolting colonies. The whole question of the timely aid France gave to America has, of course, a very particular value at the present time when this country is preparing to repay the debt we have owed France for so long. That the.author does not deal with the social conditions and the sympathic temper of the French people, which in a real sense underlay the action of France, but confines himself wholly to hante politique does not in any sense take away from the value of his work. He reveals a new side to this very interesting phase in our contest for independence, at least one that will be new to those who are not deeply read in American history. The tendency heretofore has been to emphasize the popular and moral support of the French people and to overlook the political reasons which led to the action of the king and his ministers. The author has throughout relied upon the monumental researches of Doniol and has carefully fortified every point by copious references and quotations

Clinical relevance of findings in trials of CBT for depression

Cognitive behavioural therapy (CBT) is beneficial in depression. Symptom scores can be translated into Clinical Global Impression (CGI) scale scores to indicate clinical relevance. We aimed to assess the clinical relevance of findings of randomised controlled trials (RCTs) of CBT in depression. We identified RCTs of CBT that used the Hamilton Rating Scale for Depression (HAMD). HAMD scores were translated into Clinical Global Impression – Change scale (CGI-I) scores to measure clinical relevance. One hundred and seventy datasets from 82 studies were included. The mean percentage HAMD change for treatment arms was 53.66%, and 29.81% for control arms, a statistically significant difference. Combined active therapies showed the biggest improvement on CGI-I score, followed by CBT alone. All active treatments had better than expected HAMD percentage reduction and CGI-I scores. CBT has a clinically relevant effect in depression, with a notional CGI-I score of 2.2, indicating a significant clinical response. The non-specific or placebo effect of being in a psychotherapy trial was a 29% reduction of HAMD