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Sample records for performance post-post-modern sublime

  1. Experimental Investigation of Transient Sublimator Performance

    NASA Technical Reports Server (NTRS)

    Sheth, Rubik B.; Stephan, Ryan A.; Leimkuehler, Thomas O.

    2012-01-01

    Sublimators have been used as heat rejection devices for a variety of space applications including the Apollo Lunar Module and the Extravehicular Mobility Unit (EMU). Sublimators typically operate with steady-state feedwater utilization at or near 100%. However, sublimators are currently being considered for operations in a cyclical topping mode, which represents a new mode of operation for sublimators. Sublimators can be used as a supplemental heat rejection device during mission phases where the environmental temperature or heat rejection requirement changes rapidly. This scenario may occur during low lunar orbit, low earth orbit, or other planetary orbits. In these mission phases, the need for supplemental heat rejection will vary between zero and some fraction of the overall heat load. In particular, supplemental heat rejection is required for the portion of the orbit where the radiative sink temperature exceeds the system setpoint temperature. This paper will describe the effects of these transient starts and stops on the feedwater utilization during various feedwater timing scenarios. Experimental data from various scenarios is analyzed to investigate feedwater consumption efficiency under the cyclical conditions. Start up utilization tests were conducted to better understand the transient performance. This paper also provides recommendations for future sublimator design and transient operation.

  2. Experimental Investigation of Sublimator Performance at Transient Heat Loads

    NASA Technical Reports Server (NTRS)

    Sheth, Rubik B.; Stephen, Ryan A.; Leimkuehler, Thomas O.

    2011-01-01

    Sublimators have been used as heat rejection devices for a variety of space applications including the Apollo Lunar Module and the Extravehicular Mobility Unit (EMU). Sublimators typically operate with steady-state feedwater utilization at or near 100%. However, sublimators are currently being considered to operate in a cyclical topping mode, which represents a new mode of operation for sublimators. Sublimators can be used as a topper during mission phases such as low lunar or low earth orbit. In these mission phases, the sublimator will be repeatedly started and stopped during each orbit to provide supplemental heat rejection for the portion of the orbit where the radiative sink temperature exceeds the system setpoint temperature. This paper will summarize the effort put into understanding sublimator response under a transient heat load. The performance will be assessed by detailing the changes in feedwater utilization due to transient starts and stops during various feedwater timing scenarios. Sublimator start up utilization will be assessed as a possible relationship to transient performance of a sublimator. This paper will also provide recommendations for future sublimator designs and/or feedwater control.

  3. Meteorological conditions associated to high sublimation amounts in semiarid high-elevation Andes decrease the performance of empirical melt models

    NASA Astrophysics Data System (ADS)

    Ayala, Alvaro; Pellicciotti, Francesca; MacDonell, Shelley; McPhee, James; Burlando, Paolo

    2015-04-01

    Empirical melt (EM) models are often preferred to surface energy balance (SEB) models to calculate melt amounts of snow and ice in hydrological modelling of high-elevation catchments. The most common reasons to support this decision are that, in comparison to SEB models, EM models require lower levels of meteorological data, complexity and computational costs. However, EM models assume that melt can be characterized by means of a few index variables only, and their results strongly depend on the transferability in space and time of the calibrated empirical parameters. In addition, they are intrinsically limited in accounting for specific process components, the complexity of which cannot be easily reconciled with the empirical nature of the model. As an example of an EM model, in this study we use the Enhanced Temperature Index (ETI) model, which calculates melt amounts using air temperature and the shortwave radiation balance as index variables. We evaluate the performance of the ETI model on dry high-elevation sites where sublimation amounts - that are not explicitly accounted for the EM model - represent a relevant percentage of total ablation (1.1 to 8.7%). We analyse a data set of four Automatic Weather Stations (AWS), which were collected during the ablation season 2013-14, at elevations between 3466 and 4775 m asl, on the glaciers El Tapado, San Francisco, Bello and El Yeso, which are located in the semiarid Andes of central Chile. We complement our analysis using data from past studies in Juncal Norte Glacier (Chile) and Haut Glacier d'Arolla (Switzerland), during the ablation seasons 2008-09 and 2006, respectively. We use the results of a SEB model, applied to each study site, along the entire season, to calibrate the ETI model. The ETI model was not designed to calculate sublimation amounts, however, results show that their ability is low also to simulate melt amounts at sites where sublimation represents larger percentages of total ablation. In fact, we

  4. The Sublime and Education

    ERIC Educational Resources Information Center

    Carson, Jamin

    2006-01-01

    The sublime is a theory of aesthetics that reached its highest popularity in British literature during the Romantic period (c. 1785-1832). This article (1) explicates philosophers' different meanings of the sublime; (2) show how the sublime is relevant to education; and (3) show how the sublime "works" in literature by analyzing William Blake's…

  5. Enhanced performance of CdS/CdTe thin-film devices through temperature profiling techniques applied to close-spaced sublimation deposition

    SciTech Connect

    Xiaonan Li; Sheldon, P.; Moutinho, H.; Matson, R.

    1996-05-01

    The authors describe a methodology developed and applied to the close-spaced sublimation technique for thin-film CdTe deposition. The developed temperature profiles consisted of three discrete temperature segments, which the authors called the nucleation, plugging, and annealing temperatures. They have demonstrated that these temperature profiles can be used to grow large-grain material, plug pinholes, and improve CdS/CdTe photovoltaic device performance by about 15%. The improved material and device properties have been obtained while maintaining deposition temperatures compatible with commercially available substrates. This temperature profiling technique can be easily applied to a manufacturing environment by adjusting the temperature as a function of substrate position instead of time.

  6. The effect of substrate temperature on material properties and the device performance of close-spaced sublimation deposited CdTe/CdS devices

    NASA Astrophysics Data System (ADS)

    Li, X.; Albin, D.; Asher, S.; Moutinho, H.; Keyes, B.; Matson, R.; Hasoon, F.; Sheldon, P.

    1996-01-01

    High-efficiency polycrystalline CdS/CdTe solar cells have been fabricated using CdTe absorber layers deposited by close-spaced sublimation (CSS). CSS employs high substrate temperatures (Tsub) during film growth, which can promote the formation of larger grains and higher Voc's yielding better device performance. However, as Tsub increases beyond 610 °C, voids or pinholes begin to form in the CdTe layer. When the back contact is applied, these voids serve as shunt paths that effectively lower Voc. In this fashion, benefits associated with higher substrate temperatures are seriously compromised. Concurrent with voiding is the observation that higher temperatures promote interdiffusion at the CdS/CdTe interface such that the effective thickness of the CdS layer is reduced. Variations in processing that correct for these detrimental effects have led to a total-area device efficiency of 12%.

  7. A sublimation heat engine

    NASA Astrophysics Data System (ADS)

    Wells, Gary G.; Ledesma-Aguilar, Rodrigo; McHale, Glen; Sefiane, Khellil

    2015-03-01

    Heat engines are based on the physical realization of a thermodynamic cycle, most famously the liquid-vapour Rankine cycle used for steam engines. Here we present a sublimation heat engine, which can convert temperature differences into mechanical work via the Leidenfrost effect. Through controlled experiments, quantified by a hydrodynamic model, we show that levitating dry-ice blocks rotate on hot turbine-like surfaces at a rate controlled by the turbine geometry, temperature difference and solid material properties. The rotational motion of the dry-ice loads is converted into electric power by coupling to a magnetic coil system. We extend our concept to liquid loads, generalizing the realization of the new engine to both sublimation and the instantaneous vapourization of liquids. Our results support the feasibility of low-friction in situ energy harvesting from both liquids and ices. Our concept is potentially relevant in challenging situations such as deep drilling, outer space exploration or micro-mechanical manipulation.

  8. A sublimation heat engine.

    PubMed

    Wells, Gary G; Ledesma-Aguilar, Rodrigo; McHale, Glen; Sefiane, Khellil

    2015-03-03

    Heat engines are based on the physical realization of a thermodynamic cycle, most famously the liquid-vapour Rankine cycle used for steam engines. Here we present a sublimation heat engine, which can convert temperature differences into mechanical work via the Leidenfrost effect. Through controlled experiments, quantified by a hydrodynamic model, we show that levitating dry-ice blocks rotate on hot turbine-like surfaces at a rate controlled by the turbine geometry, temperature difference and solid material properties. The rotational motion of the dry-ice loads is converted into electric power by coupling to a magnetic coil system. We extend our concept to liquid loads, generalizing the realization of the new engine to both sublimation and the instantaneous vapourization of liquids. Our results support the feasibility of low-friction in situ energy harvesting from both liquids and ices. Our concept is potentially relevant in challenging situations such as deep drilling, outer space exploration or micro-mechanical manipulation.

  9. A sublimation heat engine

    PubMed Central

    Wells, Gary G.; Ledesma-Aguilar, Rodrigo; McHale, Glen; Sefiane, Khellil

    2015-01-01

    Heat engines are based on the physical realization of a thermodynamic cycle, most famously the liquid–vapour Rankine cycle used for steam engines. Here we present a sublimation heat engine, which can convert temperature differences into mechanical work via the Leidenfrost effect. Through controlled experiments, quantified by a hydrodynamic model, we show that levitating dry-ice blocks rotate on hot turbine-like surfaces at a rate controlled by the turbine geometry, temperature difference and solid material properties. The rotational motion of the dry-ice loads is converted into electric power by coupling to a magnetic coil system. We extend our concept to liquid loads, generalizing the realization of the new engine to both sublimation and the instantaneous vapourization of liquids. Our results support the feasibility of low-friction in situ energy harvesting from both liquids and ices. Our concept is potentially relevant in challenging situations such as deep drilling, outer space exploration or micro-mechanical manipulation. PMID:25731669

  10. Modelling Sublimation of Carbon Dioxide

    ERIC Educational Resources Information Center

    Winkel, Brian

    2012-01-01

    In this article, the author reports results in their efforts to model sublimation of carbon dioxide and the associated kinetics order and parameter estimation issues in their model. They have offered the reader two sets of data and several approaches to determine the rate of sublimation of a piece of solid dry ice. They presented several models…

  11. The Sublime and the Vulgar.

    ERIC Educational Resources Information Center

    Swann, Karen

    1990-01-01

    Explores how Edmund Burke's discourse on the sublime helps illuminate attacks on the vulgarization of culture (as typified by Allan Bloom), both for the presumedly "vulgar" reader and for the champions of high culture. (MG)

  12. Sublimation systems and associated methods

    DOEpatents

    Turner, Terry D.; McKellar, Michael G.; Wilding, Bruce M.

    2016-02-09

    A system for vaporizing and sublimating a slurry comprising a fluid including solid particles therein. The system includes a first heat exchanger configured to receive the fluid including solid particles and vaporize the fluid and a second heat exchanger configured to receive the vaporized fluid and solid particles and sublimate the solid particles. A method for vaporizing and sublimating a fluid including solid particles therein is also disclosed. The method includes feeding the fluid including solid particles to a first heat exchanger, vaporizing the fluid, feeding the vaporized fluid and solid particles to a second heat exchanger and sublimating the solid particles. In some embodiments the fluid including solid particles is liquid natural gas or methane including solid carbon dioxide particles.

  13. Enantioenrichment in sublimed amino acid mixtures.

    PubMed

    Viedma, Cristóbal; Ortiz, José E; de Torres, Trinidad; Cintas, Pedro

    2012-04-14

    A real amplification of an initial enantiomeric excess can be detected when two amino acids are sublimed at high temperature, even if one of the components is a racemic compound that does not convert into a conglomerate by sublimation.

  14. Eisenhower and the American Sublime

    ERIC Educational Resources Information Center

    O'Gorman, Ned

    2008-01-01

    This essay presents Dwight D. Eisenhower's presidential rhetoric as an iteration of an American synecdochal sublime. Eisenhower's rhetoric sought to re-aim civic sight beyond corporeal objects to the nation's transcendental essence. This rhetoric is intimately connected to prevailing political anxieties and exigencies, especially the problem of…

  15. Displacement, Substitution, Sublimation: A Bibliography.

    ERIC Educational Resources Information Center

    Pedrini, D. T.; Pedrini, Bonnie C.

    Sigmund Freund worked with the mechanisms of displacement, substitution, and sublimation. These mechanisms have many similarities and have been studied diagnostically and therapeutically. Displacement and substitution seem to fit in well with phobias, hysterias, somatiyations, prejudices, and scapegoating. Phobias, prejudices, and scapegoating…

  16. Membrane evaporator/sublimator investigation

    NASA Technical Reports Server (NTRS)

    Elam, J.; Ruder, J.; Strumpf, H.

    1974-01-01

    Data are presented on a new evaporator/sublimator concept using a hollow fiber membrane unit with a high permeability to liquid water. The aim of the program was to obtain a more reliable, lightweight and simpler Extra Vehicular Life Support System (EVLSS) cooling concept than is currently being used.

  17. APPARATUS FOR CONDENSATION AND SUBLIMATION

    DOEpatents

    Schmidt, R.J.; Fuis, F. Jr.

    1958-10-01

    An apparatus is presented for the sublimation and condensation of uranium compounds in order to obtain an improved crystalline structure of this material. The apparatus comprises a vaporizing chamber and condensing structure connected thereto. There condenser is fitted with a removable liner having a demountable baffle attached to the liner by means of brackets and a removable pin. The baffle is of spiral cross-section and is provided with cooling coils disposed between the surfaces of the baffle for circulation of a temperature controlling liquid within the baffle. The cooling coll provides for controlllng the temperature of the baffle to insure formatlon of a satisfactory condensate, and the removable liner facilitates the removal of condensate formed during tbe sublimation process.

  18. Calculational criticality analyses of 10- and 20-MW UF[sub 6] freezer/sublimer vessels

    SciTech Connect

    Jordan, W.C.

    1993-02-01

    Calculational criticality analyses have been performed for 10- and 20-MW UF[sub 6] freezer/sublimer vessels. The freezer/sublimers have been analyzed over a range of conditions that encompass normal operation and abnormal conditions. The effects of HF moderation of the UF[sub 6] in each vessel have been considered for uranium enriched between 2 and 5 wt % [sup 235]U. The results indicate that the nuclearly safe enrichments originally established for the operation of a 10-MW freezer/sublimer, based on a hydrogen-to-uranium moderation ratio of 0.33, are acceptable. If strict moderation control can be demonstrated for hydrogen-to-uranium moderation ratios that are less than 0.33, then the enrichment limits for the 10-MW freezer/sublimer may be increased slightly. The calculations performed also allow safe enrichment limits to be established for a 20-NM freezer/sublimer under moderation control.

  19. Schopenhauer, Nietzsche, and the Aesthetically Sublime

    ERIC Educational Resources Information Center

    Vandenabeele, Bart

    2003-01-01

    Much has been written on the relationship between Arthur Schopenhauer and Friedrich Nietzsche. Much remains to be said, however, concerning their respective theories of the sublime. In this article, the author first argues against the traditional, dialectical view of Schopenhauer's theory of the sublime that stresses the crucial role the sublime…

  20. Isotopic Fractionation of Water-Ice from Sublimation

    NASA Astrophysics Data System (ADS)

    Christensen, E.; Boyer, C.; Park, M.; Gormally, J.; Benitez, E.; Dominguez, G.

    2015-12-01

    Elizabeth Christensen, Charisa Boyer, Manesseh Park, Ezra Benitez, Gerardo Dominguez Understanding the multi-isotopic fractionation of water-ice that results from its sublimation may be important for understanding the isotopic composition of cometary ices. Here we describe an experimental setup whose purpose is to understand the effects of various astrophysical processes on the δD and δ18O and δ17O composition of water-ices. Our setup consists of an ultrahigh vacuum (UHV) chamber with oil free pumping, a closed cycle He cryostat to achieve low temperatures (capable of reaching 6K), and a vacuum line connected to the chamber via a UHV feed-through. Water isotopologues H216O, H218O, H217O, and HD16O samples can be measured after sublimation of water-ice with a cavity ring-down spectrometer (Picarro L2120-i) that is connected to the vacuum line. To perform these experiments, ambient water vapor was introduced into, frozen, and purified inside the UHV chamber (T< 150 K). Water-ice samples were sublimated for varying amounts of time to collect various fractions of the original reservoir. We will present the first results on the oxygen and deuterium isotopic fractionation of water-ice sublimation and discuss their implications for interpreting the isotopic compositions of cometary ices.

  1. Canopy Effects on Macroscale Snow Sublimation

    NASA Astrophysics Data System (ADS)

    Svoma, B. M.

    2015-12-01

    Sublimation of snow cover directly affects snow accumulation, impacting ecosystem processes, soil moisture, soil porosity, biogeochemical processes, wildfire, and water resources. Available energy, the exposed surface area of a snow cover, and exposure time with the atmosphere vary greatly in complex terrain (e.g., aspect, elevation, forest cover), with latitude, and with continentality. It is therefore difficult to scale up results from site specific short term studies. Using the 32-km NARR, the 4-km PRISM, with 30-m terrain and forest cover data, meteorological variables are downscaled to simulate sublimation from canopy intercepted snow and from the snowpack over the Salt River Basin in Arizona for a wet and dry year. Simulations indicate that: (1) total sublimation is highly variable in response to variability in both sublimation rate and snow cover duration; (2) total canopy sublimation is similar for both years while ground sublimation is considerably greater during the wet year; (3) sublimation is a relatively greater contribution to the snow water budget during the dry year (28% vs. 20% of total snowfall); (4) at high elevations, ground sublimation is less in open areas than forested areas during the dry year, while the reverse is evident during the wet year as snowpack lasted longer into spring. While a reduction in leaf area index leads to a reduction of total sublimation due to less interception in both years, ground sublimation increases during the dry year, possibly due to less sheltering from solar radiation and wind. This reduction in sheltering results in a large decrease in snowpack duration (i.e., ten days in spring) at mid-elevations for the wet year, leading to a decrease in ground sublimation. This results in a 500 meter difference in the elevation of maximum sublimation reduction upon reduced leaf area index between the two years. Forest cover properties can vary considerably on short and long time scales through natural (wildfire, bark beetle

  2. Contamination Effects of Getter Ion and Titanium Sublimation Pumped Systems on Optical Surfaces

    NASA Technical Reports Server (NTRS)

    Visentine, James T.; Richmond, Robert G.

    1973-01-01

    Previous studies have indicated that ultraclean vacuum can be produced when titanium sublimation pumps are used in conjunction with getter-ion pumps. Experiments are described in which the degrees of cleanliness of a typical getter-ion, titanium sublimation-pumped system were monitored by measuring the effects of surface contamination on the reflectance of evaporated vacuum ultraviolet mirrors. Results are presented which indicate that severe reflectance losses occurred when startup of a getter-ion pump was initiated at too high a chamber pressure. Significant reflectance losses also occurred as a result of titanium sublimation-pump operation. These data are reviewed and recommendations for improved system performance are presented.

  3. Coating Thermoelectric Devices To Suppress Sublimation

    NASA Technical Reports Server (NTRS)

    Sakamoto, Jeffrey; Caillat, Thierry; Fleurial, Jean-Pierre; Snyder, G. Jeffrey

    2007-01-01

    A technique for suppressing sublimation of key elements from skutterudite compounds in advanced thermoelectric devices has been demonstrated. The essence of the technique is to cover what would otherwise be the exposed skutterudite surface of such a device with a thin, continuous film of a chemically and physically compatible metal. Although similar to other sublimation-suppression techniques, this technique has been specifically tailored for application to skutterudite antimonides. The primary cause of deterioration of most thermoelectric materials is thermal decomposition or sublimation - one or more elements sublime from the hot side of a thermoelectric couple, changing the stoichiometry of the device. Examples of elements that sublime from their respective thermoelectric materials are Ge from SiGe, Te from Pb/Te, and now Sb from skutterudite antimonides. The skutterudite antimonides of primary interest are CoSb3 [electron-donor (n) type] and CeFe(3-x)Co(x)Sb12 [electron-acceptor (p) type]. When these compounds are subjected to typical operating conditions [temperature of 700 C and pressure <10(exp -5) torr (0.0013 Pa)], Sb sublimes from their surfaces, with the result that Sb depletion layers form and advance toward their interiors. As the depletion layer advances in a given device, the change in stoichiometry diminishes the thermal-to-electric conversion efficiency of the device. The problem, then, is to prevent sublimation, or at least reduce it to an acceptably low level. In preparation for an experiment on suppression of sublimation, a specimen of CoSb3 was tightly wrapped in a foil of niobium, which was selected for its chemical stability. In the experiment, the wrapped specimen was heated to a temperature of 700 C in a vacuum of residual pressure <10(exp -5) torr (0.0013 Pa), then cooled and sectioned. Examination of the sectioned specimen revealed that no depletion layer had formed, indicating the niobium foil prevented sublimation of antimony at 700 C

  4. System and method for suppressing sublimation using opacified aerogel

    NASA Technical Reports Server (NTRS)

    Sakamoto, Jeff S. (Inventor); Snyder, G. Jeffrey (Inventor); Calliat, Thierry (Inventor); Fleurial, Jean-Pierre (Inventor); Jones, Steven M. (Inventor); Palk, Jong-Ah (Inventor)

    2008-01-01

    The present invention relates to a castable, aerogel-based, ultra-low thermal conductivity opacified insulation to suppress sublimation. More specifically, the present invention relates to an aerogel opacified with various opacifying or reflecting constituents to suppress sublimation and provide thermal insulation in thermoelectric modules. The opacifying constituent can be graded within the aerogel for increased sublimation suppression, and the density of the aerogel can similarly be graded to achieve optimal thermal insulation and sublimation suppression.

  5. No reduction using sublimation of cyanuric acid

    DOEpatents

    Perry, Robert A.

    1990-01-01

    An arrangement for reducing the NO content of a gas stream comprises contacting the gas stream with NHCO into a temperature effective for heat induced decomposition of HNCO and for resultant lowering of the NO content of the gas stream. Preferably, the HNCO is generated by sublimation of cyanuric acid.

  6. NO reduction using sublimation of cyanuric acid

    DOEpatents

    Perry, Robert A.

    1988-01-01

    An arrangement for reducing the NO content of a gas stream comprises contacting the gas stream with HNCO at a temperature effective for heat induced decomposition of HNCO and for resultant lowering of the NO content of the gas stream. Preferably, the HNCO is generated by sublimation of cyanuric acid.

  7. Heat of Sublimation of I-2.

    ERIC Educational Resources Information Center

    Henderson, Giles; Robarts, Ronald A., Jr.

    1978-01-01

    Describes an inexpensive double-beam laser photometry experiment to determine the molar heat of sublimation of I-2. The experiment employs common laboratory materials and components and gives results with a two percent to three percent accuracy. (Author/GA)

  8. Matrix Sublimation/Recrystallization for Imaging Proteins by Mass Spectrometry at High Spatial Resolution

    PubMed Central

    Yang, Junhai; Caprioli, Richard M.

    2011-01-01

    We have employed matrix deposition by sublimation for protein image analysis on tissue sections using a hydration/recrystallization process that produces high quality MALDI mass spectra and high spatial resolution ion images. We systematically investigated different washing protocols, the effect of tissue section thickness, the amount of sublimated matrix per unit area and different recrystallization conditions. The results show that an organic solvent rinse followed by ethanol/water rinses substantially increased sensitivity for the detection of proteins. Both the thickness of tissue section and amount of sinapinic acid sublimated per unit area have optimal ranges for maximal protein signal intensity. Ion images of mouse and rat brain sections at 50, 20 and 10 µm spatial resolution are presented and are correlated with H&E stained optical images. For targeted analysis, histology directed imaging can be performed using this protocol where MS analysis and H&E staining are performed on the same section. PMID:21639088

  9. A New Method for Estimating Bacterial Abundances in Natural Samples using Sublimation

    NASA Technical Reports Server (NTRS)

    Glavin, Daniel P.; Cleaves, H. James; Schubert, Michael; Aubrey, Andrew; Bada, Jeffrey L.

    2004-01-01

    We have developed a new method based on the sublimation of adenine from Escherichia coli to estimate bacterial cell counts in natural samples. To demonstrate this technique, several types of natural samples including beach sand, seawater, deep-sea sediment, and two soil samples from the Atacama Desert were heated to a temperature of 500 C for several seconds under reduced pressure. The sublimate was collected on a cold finger and the amount of adenine released from the samples then determined by high performance liquid chromatography (HPLC) with UV absorbance detection. Based on the total amount of adenine recovered from DNA and RNA in these samples, we estimated bacterial cell counts ranging from approx. l0(exp 5) to l0(exp 9) E. coli cell equivalents per gram. For most of these samples, the sublimation based cell counts were in agreement with total bacterial counts obtained by traditional DAPI staining. The simplicity and robustness of the sublimation technique compared to the DAPI staining method makes this approach particularly attractive for use by spacecraft instrumentation. NASA is currently planning to send a lander to Mars in 2009 in order to assess whether or not organic compounds, especially those that might be associated with life, are present in Martian surface samples. Based on our analyses of the Atacama Desert soil samples, several million bacterial cells per gam of Martian soil should be detectable using this sublimation technique.

  10. Psychotherapy. Sublimation and the psychodynamics of birding.

    PubMed

    Clemens, Norman A

    2012-07-01

    An adventure in extreme birding prompted the psychoanalyst author to reflect on "why do people do this?" Like myriad human interests, vocations, and avocations, the activity of bird watching is a socially acceptable activity that is the final pathway for multiple motivations that are likely to have a long history in the individual's development. It may have origins in basic survival skills. Various psychological defense mechanisms may be involved, the most mature and successful one being sublimation. Success of a defense-like sublimation may be viewed in terms of freedom from anxiety or from obsessive extremes that interfere with the individual's wellbeing, important relationships, or physical or financial health. The author considers whether the characters in the film The Big Year exemplify such success or the lack of it.

  11. No reduction using sublimation of cyanuric acid

    DOEpatents

    Perry, Robert

    1989-01-01

    An arrangement for reducing the NO content of a gas stream comprises contacting the gas stream with HNCO at a temperature effective for heat induced decomposition of HNCO and for resultant lowering of the NO content of the gas stream. Preferably, the HNCO is generated by sublimation of cyanuric acid and CO or other H-atom generating species is also present or added to the gas stream.

  12. D/H fractionation during the sublimation of water ice

    NASA Astrophysics Data System (ADS)

    Lécuyer, Christophe; Royer, Aurélien; Fourel, François; Seris, Magali; Simon, Laurent; Robert, François

    2017-03-01

    Experiments of sublimation of pure water ice have been performed in the temperature range -105 °C to -30 °C and atmospheric partial pressures ranging from 10-6 to 10-1 mb. Sampling of both vapour and residual ice fractions has been performed with the use of a vacuum line designed for the extraction and purification of gases before the measurement of their D/H ratios. Sublimation was responsible for sizable isotopic fractionation factors in the range 0.969-1.123 for temperatures lying between -105 °C and -30 °C. The fractionation factor exhibits a cross-over at temperatures around -50 °C with the water vapour fraction being D-depleted relative to the residual ice fraction at T < -50 °C (αice-vapour = 0.969-0.995). This cross-over has implications for the understanding of the atmospheric water cycle of some terrestrial planets such as the Earth or Mars. The magnitude of deuterium enrichment or depletion between ice and water vapour cannot explain the differences in the D/H ratios amongst Jupiter comets and long-period comets families nor those that have been documented between Earth's and cometary water.

  13. New method for estimating bacterial cell abundances in natural samples by use of sublimation.

    PubMed

    Glavin, Daniel P; Cleaves, H James; Schubert, Michael; Aubrey, Andrew; Bada, Jeffrey L

    2004-10-01

    We have developed a new method based on the sublimation of adenine from Escherichia coli to estimate bacterial cell counts in natural samples. To demonstrate this technique, several types of natural samples, including beach sand, seawater, deep-sea sediment, and two soil samples from the Atacama Desert, were heated to a temperature of 500 degrees C for several seconds under reduced pressure. The sublimate was collected on a cold finger, and the amount of adenine released from the samples was then determined by high-performance liquid chromatography with UV absorbance detection. Based on the total amount of adenine recovered from DNA and RNA in these samples, we estimated bacterial cell counts ranging from approximately 10(5) to 10(9) E. coli cell equivalents per gram. For most of these samples, the sublimation-based cell counts were in agreement with total bacterial counts obtained by traditional DAPI (4,6-diamidino-2-phenylindole) staining.

  14. New method for estimating bacterial cell abundances in natural samples by use of sublimation

    NASA Technical Reports Server (NTRS)

    Glavin, Daniel P.; Cleaves, H. James; Schubert, Michael; Aubrey, Andrew; Bada, Jeffrey L.

    2004-01-01

    We have developed a new method based on the sublimation of adenine from Escherichia coli to estimate bacterial cell counts in natural samples. To demonstrate this technique, several types of natural samples, including beach sand, seawater, deep-sea sediment, and two soil samples from the Atacama Desert, were heated to a temperature of 500 degrees C for several seconds under reduced pressure. The sublimate was collected on a cold finger, and the amount of adenine released from the samples was then determined by high-performance liquid chromatography with UV absorbance detection. Based on the total amount of adenine recovered from DNA and RNA in these samples, we estimated bacterial cell counts ranging from approximately 10(5) to 10(9) E. coli cell equivalents per gram. For most of these samples, the sublimation-based cell counts were in agreement with total bacterial counts obtained by traditional DAPI (4,6-diamidino-2-phenylindole) staining.

  15. Static sublimation purification process and characterization of LiZnP semiconductor material

    NASA Astrophysics Data System (ADS)

    Montag, Benjamin W.; Reichenberger, Michael A.; Edwards, Nathan; Ugorowski, Philip B.; Sunder, Madhana; Weeks, Joseph; McGregor, Douglas S.

    2015-06-01

    Refinement of the class AIBIICV materials continue as a candidate for solid-state neutron detectors. Such a device would have greater efficiency, in a compact form, than present day gas-filled 3He and 10BF3 detectors. The 6Li(n,t)4He reaction yields a total Q value of 4.78 MeV, larger than 10B, and easily identified above background radiations. Hence, devices composed of either natural Li (nominally 7.5% 6Li) or enriched 6Li (usually 95% 6Li) may provide a semiconductor material for compact high efficiency neutron detectors. A sub-branch of the III-V semiconductors, the filled tetrahedral compounds, AIBIICV, known as Nowotny-Juza compounds, are known for their desirable cubic crystal structure. Starting material was synthesized by combining equimolar portions of Li, Zn, and P sealed under vacuum (10-6 Torr) in quartz ampoules, having boron nitride liners, and subsequently reacted in a compounding furnace (Montag et al., 2015, J. of Cryst. Growth). A static vacuum sublimation in quartz was performed to help purify the synthesized material. The chemical composition of the sublimed material and remaining material was confirmed by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Lithium was not detected in the sublimed material, however, approximately stoichiometric concentrations of each constituent element were found in the remaining LiZnP material. X-ray diffraction phase identification scans of the remains material and sublimed material were compared, and further indicated the impurity materials were sublimed away from the synthesized materials. The resulting material from the sublimation process showed characteristics of a higher purity ternary compound.

  16. Sublimating grains model of cometary coma.

    NASA Astrophysics Data System (ADS)

    Faggi, S.; Tozzi, G. P.; Brucato, J. R.

    Billion years of space weathering produces a crust of organic matter (see e.g. Kanuchova et al. 2012) that will be released when a comet enter for the first time in the inner Solar System. New comets, coming form the Oort Colud at their first passage close to the Sun, are particularly important because they are not differentiated by the Solar radiation and they are supposed to have a large quantity of ice organic matter close to the surface. When a comet approach to the Sun, its activity is driven by the sublimation of these nucleus ices: if the heliocentric distances, R_H , is greater than 3 AU the sublimation of CO and CO_2 ices is the main source of comet activity, otherwise at shorter distances, the sublimation of water become the most important mechanism of activity. These gases, escaping from the nucleus, drag in the coma grains that can be refractory dust (silicates, carbon), water ice and/or organic ices. Oort comets at their first passage in the inner Solar System, should produce an halo of organic or water icy particles. Our group has been monitoring new, inbound, bright Oort comets (C/2011 F1, C/2012 S1, C/2012 K1, C/2013 V5, C/2012 F3, C/2013 US10, C/2013 X1) to search for these icy grains. The method consists in detecting the cloud of sublimating grains in the inner coma by using the Sigma Af function (Tozzi et al. 2007) directly from images. However this over-population of grains, beside the sublimation, can be also due to short time activity (outburst) or too big grains expanding at very slow velocity, as it has been found in comet 67P/C-G (Tozzi eta al, 2011, A&A, 531, 54). To disentangle between the phenomena it is necessary to monitor the comet both at short timescale, for the outbursts (by repeating the observations after few nights), and at long term (weeks-months). If the cloud does not expand with the decreasing of the heliocentric distance there is high probability that we are in presence of organic and/or water ice grains. We can disentangle

  17. Science Sublime: The Philosophy of the Sublime, Dewey's Aesthetics, and Science Education

    ERIC Educational Resources Information Center

    Cavanaugh, Shane

    2014-01-01

    Feelings of awe, wonder, and appreciation have been largely ignored in the working lives of scientists and, in turn, science education has not accurately portrayed science to students. In an effort to bring the affective qualities of science into the classroom, this work draws on the writings of the sublime by Burke, Kant, Emerson, and Wordsworth…

  18. Sublimation as a Continuous and Transient Source of Water in Europa's Exosphere

    NASA Astrophysics Data System (ADS)

    Hayne, Paul O.

    2016-10-01

    Europa's crust is composed primarily of water ice, which may be vaporized by sputtering and sublimation when exposed to the jovian radiation environment. Models of H2O in Europa's exosphere have focused primarily on the contribution of sputtering by energetic particles, with globally averaged production rates estimated to be ~1015 H2O m-2 s-1. Although sublimation rates at Europa's average dayside temperature of ~106 K are much lower at ~1010 H2O m-2 s-1, surfaces at low- to mid-latitude experiences temperatures in excess of 130 K, with expected sublimation rates of >1015 H2O m-2 s-1 possible. These production rates would be reduced where the surface ice is mixed with impurities, or through development of a non-ice lag deposit. In addition to the continuous flux due to sublimation, transient outgassing may be caused by exposure of fresh ice to direct sunlight, for example by mass wasting on steep slopes. Here, we revisit the process of sublimation on Europa's surface to quantify possible H2O vapor production on a range of spatial and temporal scales.The model includes solar heating, conduction, and vapor diffusion. Temperatures and sublimation rates are calculated by the instantaneous energy budget within each model layer, and outgassing to the exosphere depends on the surface vapor pressure and molecular thermal velocities. Vapor densities and line-of-sight column abundances can be directly compared to observations. Our results show that for surfaces composed of pure ice, sublimation contributes significant quantities to the dayside exosphere. The production rate declines as a sublimation lag develops, with a characteristic timescale of ~1 - 10 kyr at the equator. Freshly exposed ice may produce localized sources. For example, a fresh exposure of ice at 60° latitude with dimension ~2 km would be expected to produce a line-of-sight column abundance of ~1020 H2O m-2 near the limb. However, expansion of the plume would lead to lower column abundance at higher

  19. Reassessing Aesthetic Appreciation of Nature in the Kantian Sublime

    ERIC Educational Resources Information Center

    Brady, Emily

    2012-01-01

    The sublime has been a relatively neglected topic in recent work in philosophical aesthetics, with existing discussions confined mainly to problems in Kant's theory. Given the revival of interest in his aesthetic theory and the influence of the Kantian sublime compared to other eighteenth-century accounts, this focus is not surprising. Kant's…

  20. The SCITEAS experiment: Optical characterizations of sublimating icy planetary analogues

    NASA Astrophysics Data System (ADS)

    Pommerol, A.; Jost, B.; Poch, O.; El-Maarry, M. R.; Vuitel, B.; Thomas, N.

    2015-05-01

    We have designed and built a laboratory facility to investigate the spectro-photometric and morphologic properties of different types of ice-bearing planetary surface analogs and follow their evolution upon exposure to a low pressure and low temperature environment. The results obtained with this experiment are used to verify and improve our interpretations of current optical remote-sensing datasets. They also provide valuable information for the development and operation of future optical instruments. The Simulation Chamber for Imaging the Temporal Evolution of Analogue Samples (SCITEAS) is a small thermal vacuum chamber equipped with a variety of ports and feedthroughs that permit both in-situ and remote characterizations as well as interacting with the sample. A large quartz window located directly above the sample is used to observe its surface from outside with a set of visible and near-infrared cameras. The sample holder can be easily and quickly inserted and removed from the chamber and is compatible with the other measurement facilities of the Laboratory for Outflow Studies of Sublimating Materials (LOSSy) at the University of Bern. We report here on the results of two of the first experiments performed in the SCITEAS chamber. In the first experiment, fine-grained water ice mixed with dark organic and mineral matter was left to sublime in vacuum and at low temperature, simulating the evolution of the surface of a comet nucleus approaching the Sun. We observed and characterized the formation and evolution of a crust of refractory organic and mineral matter at the surface of the sample and linked the evolution of its structure and texture to its spectro-photometric properties. In the second experiment, a frozen soil was prepared by freezing a mixture of smectite mineral and water. The sample was then left to sublime for 6 h to simulate the loss of volatiles from icy soil at high latitudes on Mars. Colour images were produced using the definitions of the

  1. In situ transmission electron microscopy of cadmium selenide nanorod sublimation

    SciTech Connect

    Hellebusch, Daniel J.; Manthiram, Karthish; Beberwyck, Brandon J.; Alivisatos, A. Paul

    2015-01-23

    In situ electron microscopy is used to observe the morphological evolution of cadmium selenide nanorods as they sublime under vacuum at a series of elevated temperatures. Mass loss occurs anisotropically along the nanorod’s long axis. At temperatures close to the sublimation threshold, the phase change occurs from both tips of the nanorods and proceeds unevenly with periods of rapid mass loss punctuated by periods of relative stability. At higher temperatures, the nanorods sublime at a faster, more uniform rate, but mass loss occurs from only a single end of the rod. Furthermore, we propose a mechanism that accounts for the observed sublimation behavior based on the terrace–ledge–kink (TLK) model and how the nanorod surface chemical environment influences the kinetic barrier of sublimation.

  2. In Situ Transmission Electron Microscopy of Cadmium Selenide Nanorod Sublimation.

    PubMed

    Hellebusch, Daniel J; Manthiram, Karthish; Beberwyck, Brandon J; Alivisatos, A Paul

    2015-02-19

    In situ electron microscopy is used to observe the morphological evolution of cadmium selenide nanorods as they sublime under vacuum at a series of elevated temperatures. Mass loss occurs anisotropically along the nanorod's long axis. At temperatures close to the sublimation threshold, the phase change occurs from both tips of the nanorods and proceeds unevenly with periods of rapid mass loss punctuated by periods of relative stability. At higher temperatures, the nanorods sublime at a faster, more uniform rate, but mass loss occurs from only a single end of the rod. We propose a mechanism that accounts for the observed sublimation behavior based on the terrace-ledge-kink (TLK) model and how the nanorod surface chemical environment influences the kinetic barrier of sublimation.

  3. In situ transmission electron microscopy of cadmium selenide nanorod sublimation

    DOE PAGES

    Hellebusch, Daniel J.; Manthiram, Karthish; Beberwyck, Brandon J.; ...

    2015-01-23

    In situ electron microscopy is used to observe the morphological evolution of cadmium selenide nanorods as they sublime under vacuum at a series of elevated temperatures. Mass loss occurs anisotropically along the nanorod’s long axis. At temperatures close to the sublimation threshold, the phase change occurs from both tips of the nanorods and proceeds unevenly with periods of rapid mass loss punctuated by periods of relative stability. At higher temperatures, the nanorods sublime at a faster, more uniform rate, but mass loss occurs from only a single end of the rod. Furthermore, we propose a mechanism that accounts for themore » observed sublimation behavior based on the terrace–ledge–kink (TLK) model and how the nanorod surface chemical environment influences the kinetic barrier of sublimation.« less

  4. Sublime science: Teaching for scientific sublime experiences in middle school classrooms

    NASA Astrophysics Data System (ADS)

    Cavanaugh, Shane

    Due to a historical separation of cognition and emotion, the affective aspects of learning are often seen as trivial in comparison to the more 'essential' cognitive qualities - particularly in the domain of science. As a result of this disconnect, feelings of awe, wonder, and astonishment as well as appreciation have been largely ignored in the working lives of scientists. In turn, I believe that science education has not accurately portrayed the world of science to our students. In an effort to bring the affective qualities of science into the science classroom, I have drawn on past research in the field of aesthetic science teaching and learning as well as works by, Burke, Kant, and Dewey to explore a new construct I have called the "scientific sublime". Scientific sublime experiences represent a sophisticated treatment of the cognitive as well as affective qualities of science learning. The scientific sublime represents feelings of awe, wonder, and appreciation that come from a deep understanding. It is only through this understanding of a phenomenon that we can appreciate its true complexity and intricacies, and these understandings when mixed with the emotions of awe and reverence, are sublime. Scientific sublime experiences are an attempt at the re-integration of cognition and feeling. The goal of this research was twofold: to create and teach a curriculum that fosters scientific sublime experiences in middle school science classes, and to better understand how these experiences are manifested in students. In order to create an approach to teaching for scientific sublime experiences, it was first necessary for me to identify key characteristics of such an experience and a then to create a pedagogical approach, both of which are described in detail in the dissertation. This research was conducted as two studies in two different middle schools. My pedagogical approach was used to create and teach two five-week 7 th grade science units---one on weather

  5. Static sublimation purification process and characterization of LiZnAs semiconductor material

    NASA Astrophysics Data System (ADS)

    Montag, Benjamin W.; Reichenberger, Michael A.; Edwards, Nathaniel S.; Ugorowski, Philip B.; Sunder, Madhana; Weeks, Joseph; McGregor, Douglas S.

    2016-03-01

    Refinement of the class AIBIICV materials continue as a candidate for solid-state neutron detectors. Such a device would have greater efficiency, in a compact form, than present day gas-filled 3He and 10BF3 detectors. The 6Li(n,t)4He reaction yields a total Q value of 4.78 MeV, larger than 10B, and easily identified above background radiations. Hence, devices composed of either natural Li (nominally 7.5% 6Li) or enriched 6Li (usually 95% 6Li) may provide a semiconductor material for compact high efficiency neutron detectors. A sub-branch of the III-V semiconductors, the filled tetrahedral compounds, AIBIICV, known as Nowotny-Juza compounds, are known for their desirable cubic crystal structure. Starting material was synthesized by equimolar portions of Li, Zn, and As sealed under vacuum (10-6 Torr) in quartz ampoules with a boron nitride lining, and reacted in a compounding furnace [1]. The synthesized material showed signs of high impurity levels from material and electrical property characterization. In the present work, a static vacuum sublimation of synthesized LiZnAs loaded in a quartz vessel was performed to help purify the synthesized material. The chemical composition of the sublimed material and remains material was confirmed by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Lithium was not detected in the sublimed material, however, near stoichiometric amounts of each constituent element were found in the remains material for LiZnAs. X-ray diffraction phase identification scans of the remains material and sublimed material were compared, and further indicated the impurity materials were removed from the synthesized materials. The remaining powder post the sublimation process showed characteristics of a higher purity ternary compound.

  6. Development and Testing of the Contaminant Insensitive Sublimator

    NASA Technical Reports Server (NTRS)

    Leimkuehler, Thomas O.; Stephan, Ryan A.; Westheimer, David T.

    2006-01-01

    Sublimators have been used for heat rejection for a variety of space applications including the Apollo Lunar Module and the Extravehicular Mobility Unit (EMU). Some of the attractive features of sublimators are that they are compact, lightweight, and self-regulating. One of the drawbacks of previous designs has been sensitivity to non-volatile contamination in the feedwater, which can clog relatively small pores (approx.3-6 microns) in the porous plates where ice forms and sublimates. A new design that is less sensitive to contaminants is being developed at the Johnson Space Center. This paper describes the design, fabrication, and testing of the Contaminant Insensitive Sublimator (CIS) Engineering Development Unit (EDU).

  7. Development and Testing of the Contaminant Insensitive Sublimator

    NASA Technical Reports Server (NTRS)

    Leimkuehler, Thomas O.; Stephan, Ryan A.

    2007-01-01

    Sublimators have been used for heat rejection for a variety of space applications including the Apollo Lunar Module and the Extravehicular Mobility Unit (EMU). Some of the attractive features of sublimators are that they are compact, lightweight, and self-regulating. One of the drawbacks of previous designs has been sensitivity to non-volatile contamination in the feedwater, which can clog relatively small pores (approx. 3-6 micrometers) in the porous plates where ice forms and sublimates. A new design that is less sensitive to contaminants is being developed at the Johnson Space Center (JSC). This paper describes the design, fabrication, and testing of the Contaminant Insensitive Sublimator (CIS) Engineering Development Unit (EDU).

  8. Scanning electron microscope observations of sublimates from Merapi Volcano, Indonesia

    USGS Publications Warehouse

    Symonds, R.

    1993-01-01

    Sublimates were sampled from high-temperature (up to 800??C) fumaroles at Merapi volcano in January 1984. Sampling is accomplished by inserting silica tubes into high-temperature vents. Volcanic glass flows through the tubes and sublimates precipitate on the inner walls in response to the temperature gradient. With decreasing temperature (800-500??C) in the tubes, there are five sublimate zones. Texturally, the sublimate phases grade from large, well-formed crystals at their highest-temperature occurrence to more numerous, smaller crystals that are less perfect at lower temperatures. These changes imply that the crystal nucleation and growth rates increase and decrease, respectively, as temperature decreases. Overall, the textural data suggest that the gas is saturated or slightly super-saturated with the phases at their hottest occurrence, but that the gas becomes increasingly super-saturated with the phases at lower temperatures. -from Author

  9. Sublimation as a Landform-Shaping Process on Pluto

    NASA Technical Reports Server (NTRS)

    Moore, J. M.; Howard, A. D.; White, O. L.; Umurhan, O. M.; Schenk, P. M.; Beyer, R. A.; McKinnon, W. B.; Singer, K. N.; Spencer, J. R.; Stern, S. A.; Young, L. A.; Weaver, H.; Olkin, C. B.; Ennico, K.

    2016-01-01

    Several icy-world surfaces in the solar system exhibit sublimation-driven landform modification erosion, condensation, and mass wasting [1]. In addition to the obvious role of gravity, mass wasting can work in conjunction with internal disaggregation of a landform's relief-supporting material through the loss (or deteriorating alteration) of its cohesive matrix. To give a conspicuous example, Callisto's landscape exhibits widespread erosion from sublimation erosion of slopes, which results in smooth, undulating, low albedo plains composed of lag deposits, with isolated high albedo pinnacles perched on remnants of crater rims due to the re-precipitation of ice on local cold traps [2, 3, 4]. Sublimation-driven mass wasting was anticipated on Pluto prior to the encounter (see refs in [5]). Here we report on several landscapes on Pluto we interpret to be formed, or at least heavily modified, by sublimation erosion.

  10. Dynamics and Mechanisms of Exfoliated Black Phosphorus Sublimation.

    PubMed

    Fortin-Deschênes, Matthieu; Levesque, Pierre L; Martel, Richard; Moutanabbir, Oussama

    2016-05-05

    We report on real time observations of the sublimation of exfoliated black phosphorus layers throughout annealing using in situ low energy electron microscopy. We found that sublimation manifests itself above 375 ± 20 °C through the nucleation and expansion of asymmetric, faceted holes with the long axis aligned along the [100] direction and sharp tips defined by edges consisting of alternating (10) and (11) steps. This thermally activated process repeats itself via successive sublimation of individual layers. Calculations and simulations using density functional theory and kinetic Monte Carlo allowed to determine the involved atomic pathways. Sublimation is found to occur via detachments of phosphorus dimers rather than single atoms. This behavior and the role of defects is described using an analytical model that captures all essential features. This work establishes an atomistic-level understanding of the thermal stability of exfoliated black phosphorus and defines the temperature window available for material and device processing.

  11. Nietzsche's View of Sublimation in the Educational Process

    ERIC Educational Resources Information Center

    Sharp, Ann Margaret

    1975-01-01

    Article outlined Nietzsche's beliefs on the primary aim of education, the conscious production of the free man through the process of sublimation, the active redirecting of one's life energy in the service of creativity. (Editor/RK)

  12. Sublimation in bright spots on (1) Ceres

    NASA Astrophysics Data System (ADS)

    Nathues, A.; Hoffmann, M.; Schaefer, M.; Le Corre, L.; Reddy, V.; Platz, T.; Cloutis, E. A.; Christensen, U.; Kneissl, T.; Li, J.-Y.; Mengel, K.; Schmedemann, N.; Schaefer, T.; Russell, C. T.; Applin, D. M.; Buczkowski, D. L.; Izawa, M. R. M.; Keller, H. U.; O'Brien, D. P.; Pieters, C. M.; Raymond, C. A.; Ripken, J.; Schenk, P. M.; Schmidt, B. E.; Sierks, H.; Sykes, M. V.; Thangjam, G. S.; Vincent, J.-B.

    2015-12-01

    The dwarf planet (1) Ceres, the largest object in the main asteroid belt with a mean diameter of about 950 kilometres, is located at a mean distance from the Sun of about 2.8 astronomical units (one astronomical unit is the Earth-Sun distance). Thermal evolution models suggest that it is a differentiated body with potential geological activity. Unlike on the icy satellites of Jupiter and Saturn, where tidal forces are responsible for spewing briny water into space, no tidal forces are acting on Ceres. In the absence of such forces, most objects in the main asteroid belt are expected to be geologically inert. The recent discovery of water vapour absorption near Ceres and previous detection of bound water and OH near and on Ceres (refs 5, 6, 7) have raised interest in the possible presence of surface ice. Here we report the presence of localized bright areas on Ceres from an orbiting imager. These unusual areas are consistent with hydrated magnesium sulfates mixed with dark background material, although other compositions are possible. Of particular interest is a bright pit on the floor of crater Occator that exhibits probable sublimation of water ice, producing haze clouds inside the crater that appear and disappear with a diurnal rhythm. Slow-moving condensed-ice or dust particles may explain this haze. We conclude that Ceres must have accreted material from beyond the ‘snow line’, which is the distance from the Sun at which water molecules condense.

  13. Sulfur "Concrete" for Lunar Applications - Sublimation Concerns

    NASA Technical Reports Server (NTRS)

    Grugel, Richard N.; Toutanji, Houssam

    2006-01-01

    Melting sulfur and mixing it with an aggregate to form "concrete" is commercially well established and constitutes a material that is particularly well-suited for use in corrosive environments. Discovery of the mineral troilite (FeS) on the moon poses the question of extracting the sulfur for use as a lunar construction material. This would be an attractive alternative to conventional concrete as it does not require water. However, the viability of sulfur concrete in a lunar environment, which is characterized by lack of an atmosphere and extreme temperatures, is not well understood. Here it is assumed that the lunar ore can be mined, refined, and the raw sulfur melded with appropriate lunar regolith to form, for example, bricks. This study evaluates pure sulfur and two sets of small sulfur concrete samples that have been prepared using JSC-1 lunar stimulant and SiO2 powder as aggregate additions. Each set was subjected to extended periods in a vacuum environment to evaluate sublimation issues. Results from these experiments are presented and discussed within the context of the lunar environment.

  14. Sublimation in bright spots on (1) Ceres.

    PubMed

    Nathues, A; Hoffmann, M; Schaefer, M; Le Corre, L; Reddy, V; Platz, T; Cloutis, E A; Christensen, U; Kneissl, T; Li, J-Y; Mengel, K; Schmedemann, N; Schaefer, T; Russell, C T; Applin, D M; Buczkowski, D L; Izawa, M R M; Keller, H U; O'Brien, D P; Pieters, C M; Raymond, C A; Ripken, J; Schenk, P M; Schmidt, B E; Sierks, H; Sykes, M V; Thangjam, G S; Vincent, J-B

    2015-12-10

    The dwarf planet (1) Ceres, the largest object in the main asteroid belt with a mean diameter of about 950 kilometres, is located at a mean distance from the Sun of about 2.8 astronomical units (one astronomical unit is the Earth-Sun distance). Thermal evolution models suggest that it is a differentiated body with potential geological activity. Unlike on the icy satellites of Jupiter and Saturn, where tidal forces are responsible for spewing briny water into space, no tidal forces are acting on Ceres. In the absence of such forces, most objects in the main asteroid belt are expected to be geologically inert. The recent discovery of water vapour absorption near Ceres and previous detection of bound water and OH near and on Ceres (refs 5-7) have raised interest in the possible presence of surface ice. Here we report the presence of localized bright areas on Ceres from an orbiting imager. These unusual areas are consistent with hydrated magnesium sulfates mixed with dark background material, although other compositions are possible. Of particular interest is a bright pit on the floor of crater Occator that exhibits probable sublimation of water ice, producing haze clouds inside the crater that appear and disappear with a diurnal rhythm. Slow-moving condensed-ice or dust particles may explain this haze. We conclude that Ceres must have accreted material from beyond the 'snow line', which is the distance from the Sun at which water molecules condense.

  15. Sublimation TiN Coating of RF Power Components

    NASA Astrophysics Data System (ADS)

    Lorkiewicz, J.; Kula, J.; Pszona, S.; Sobczak, J.; Bilinski, A.

    2008-03-01

    Titanium evaporation in a reactive atmosphere of ammonia has been chosen to deposit thin (up to 10 nm) protective surface layers containing titanium nitride and titanium oxinitrides which suppress secondary electron emission. The coating procedure, applied by the author in DESY (Hamburg) for TESLA couplers anti-multipactor protection, has been recently implemented in The Andrzej Soltan Institute for Nuclear Studies (IPJ) where a new coating device is used, equipped with a special titanium sublimation setup in a 100 1 vacuum chamber. Several arrays of cylindrical and coaxial RF coupler windows have been coated so far after optimizing the processing parameters. A check of the obtained surface layers ability to attenuate secondary electron emission has been performed; measurements of the secondary electron yield from TiN layers deposited on alumina samples were done in IPJ on as-delivered coated samples, then after vacuum bake-out and finally after additional electron bombardment of their surfaces. Also chemical composition of the surface layers has been studied using XPS in the Institute of Physical Chemistry (IChF).

  16. Characterization of Sulfur and Nanostructured Sulfur Battery Cathodes in Electron Microscopy Without Sublimation Artifacts.

    PubMed

    Levin, Barnaby D A; Zachman, Michael J; Werner, Jörg G; Sahore, Ritu; Nguyen, Kayla X; Han, Yimo; Xie, Baoquan; Ma, Lin; Archer, Lynden A; Giannelis, Emmanuel P; Wiesner, Ulrich; Kourkoutis, Lena F; Muller, David A

    2017-02-01

    Lithium sulfur (Li-S) batteries have the potential to provide higher energy storage density at lower cost than conventional lithium ion batteries. A key challenge for Li-S batteries is the loss of sulfur to the electrolyte during cycling. This loss can be mitigated by sequestering the sulfur in nanostructured carbon-sulfur composites. The nanoscale characterization of the sulfur distribution within these complex nanostructured electrodes is normally performed by electron microscopy, but sulfur sublimates and redistributes in the high-vacuum conditions of conventional electron microscopes. The resulting sublimation artifacts render characterization of sulfur in conventional electron microscopes problematic and unreliable. Here, we demonstrate two techniques, cryogenic transmission electron microscopy (cryo-TEM) and scanning electron microscopy in air (airSEM), that enable the reliable characterization of sulfur across multiple length scales by suppressing sulfur sublimation. We use cryo-TEM and airSEM to examine carbon-sulfur composites synthesized for use as Li-S battery cathodes, noting several cases where the commonly employed sulfur melt infusion method is highly inefficient at infiltrating sulfur into porous carbon hosts.

  17. Surface and snowdrift sublimation at Princess Elisabeth station, East Antarctica

    NASA Astrophysics Data System (ADS)

    Thiery, W.; Gorodetskaya, I. V.; Bintanja, R.; Van Lipzig, N. P. M.; Van den Broeke, M. R.; Reijmer, C. H.; Kuipers Munneke, P.

    2012-08-01

    In the near-coastal regions of Antarctica, a significant fraction of the snow precipitating onto the surface is removed again through sublimation - either directly from the surface or from drifting snow particles. Meteorological observations from an Automatic Weather Station (AWS) near the Belgian research station Princess Elisabeth in Dronning Maud Land, East-Antarctica, are used to study surface and snowdrift sublimation and to assess their impacts on both the surface mass balance and the surface energy balance during 2009 and 2010. Comparison to three other AWSs in Dronning Maud Land with 11 to 13 yr of observations shows that sublimation has a significant influence on the surface mass balance at katabatic locations by removing 10-23% of their total precipitation, but at the same time reveals anomalously low surface and snowdrift sublimation rates at Princess Elisabeth (17 mm w.e. yr-1 compared to 42 mm w.e. yr-1 at Svea Cross and 52 mm w.e. yr-1 at Wasa/Aboa). This anomaly is attributed to local topography, which shields the station from strong katabatic influence, and, therefore, on the one hand allows for a strong surface inversion to persist throughout most of the year and on the other hand causes a lower probability of occurrence of intermediately strong winds. This wind speed class turns out to contribute most to the total snowdrift sublimation mass flux, given its ability to lift a high number of particles while still allowing for considerable undersaturation.

  18. Sublimation rates of explosive materials : method development and initial results.

    SciTech Connect

    Phelan, James M.; Patton, Robert Thomas

    2004-08-01

    Vapor detection of explosives continues to be a technological basis for security applications. This study began experimental work to measure the chemical emanation rates of pure explosive materials as a basis for determining emanation rates of security threats containing explosives. Sublimation rates for TNT were determined with thermo gravimetric analysis using two different techniques. Data were compared with other literature values to provide sublimation rates from 25 to 70 C. The enthalpy of sublimation for the combined data was found to be 115 kJ/mol, which corresponds well with previously reported data from vapor pressure determinations. A simple Gaussian atmospheric dispersion model was used to estimate downrange concentrations based on continuous, steady-state conditions at 20, 45 and 62 C for a nominal exposed block of TNT under low wind conditions. Recommendations are made for extension of the experimental vapor emanation rate determinations and development of turbulent flow computational fluid dynamics based atmospheric dispersion estimates of standoff vapor concentrations.

  19. On the interaction of sublimating gas with cometary bodies

    NASA Astrophysics Data System (ADS)

    Steckloff, Jordan K.

    Sublimation of volatiles is a defining process of comet nuclei, and profoundly affects their dynamics, structure, and appearance. Central to understanding the processes by which comets formed and subsequently evolved is a careful computation of this sublimation pressure as a function of heliocentric distance. Unlike previous efforts, I develop a thermodynamic method to numerically compute the sublimation pressure of any species from limited knowledge of its physical properties. I then describe a novel cometary disruption mechanism in which this sublimation pressure induces differential stresses within the body of the nucleus that exceed its material strength, resulting in structural failure and breakup of the nucleus. I show that this mechanism is consistent with the behavior of Comet ISON (C/2012 S1), and use it to estimate the cohesive strength of ISON's nucleus, a first for a Long-Period Comet. Sublimating volatiles can also generate sublimative torques that alter the rotation state of the nucleus. However, computing these torques requires high-resolution information on the shape and activity of the nucleus, which is available only for the few nuclei visited by spacecraft. To remedy this, I develop a novel framework based on the YORP Effect (the torques asteroids experience by emitting thermal photons from their asymmetric shapes) to study the effects of sublimative torques on populations of cometary bodies. I take advantage of the similar manner in which surfaces emit both thermal photons and sublimating molecules to derive numerical relationships that describe sublimative torques by appropriately scaling the YORP torque equations. I then use this framework to explain the formation of dust striae (long linear features in the tails of Long-Period Comets that align with the Sun), which has remained an enigma for more than a century. I show that the observed ˜10-100 m chunks ejected from comet nuclei experience sublimative torques that spin them up to the point

  20. Formation of filamentary sublimate residues (FSR) from mineral grains

    SciTech Connect

    Storrs, A.D.; Fanale, F.P.; Saunders, R.S.; Stephens, J.B.

    1988-12-01

    The significant interparticle forces observed between solar system dust grains upon desorption or sublimation of excess volatiles in simulated Martian or cometary environments are presently investigated, in order to more precisely define these mechanisms and to simulate the types of deposits thereby formed. Some classes of phyllosilicate mineral grains are noted to bond together to form a highly porous filamentary sublimate residue (FSR) exhibiting an exceptionally high tensile strength for its density; this may be important in its control of erosion and sublimation in Martian and cometary environments. It is concluded that FSR formation from clean mineral grains in water ice may be important in the formation of the Martian polar layered terrain. 41 references.

  1. MALDI Imaging of Lipids after Matrix Sublimation/Deposition

    PubMed Central

    Murphy, Robert C.; Hankin, Joseph A.; Barkley, Robert M.; Zemski Berry, Karin A.

    2011-01-01

    Mass spectrometric techniques have been developed to record mass spectra of biomolecules including lipids as they naturally exist within tissues and thereby permit the generation of images displaying the distribution of specific lipids in tissues, organs, and intact animals. These techniques are based on matrix-assisted laser desorption/ionization (MALDI) that requires matrix application onto the tissue surface prior to analysis. One technique of application that has recently shown significant advantages for lipid analysis is sublimation of matrix followed by vapor deposition directly onto the tissue. Explanations for enhanced sensitivity realized by sublimation/deposition related to sample temperature after a laser pulse and matrix crystal size are presented. Specific examples of sublimation/deposition in lipid imaging of various organs including brain, ocular tissue, and kidney are presented. PMID:21571091

  2. Micro-computed tomography observation of sublimation interface and image analysis on sublimation process during freeze-drying.

    PubMed

    Xiao, Xin; Tao, Le-Ren; Hua, Tse-Chao

    2007-01-01

    The freeze-drying process is complicated with complex heat and mass transfer during sublimation. The sublimation interface of freeze-drying has become more attractive and meaningful recently. In this study, apple slices undergoing sublimation were scanned by a Micro-CT scanner. The cross-sectional images were reconstructed with those scanning images respectively. The technique of grey value analysis was used to recognize the procedure. The results showed that, from direct scanning images and 2-D reconstructed images, a 3-D moving mode of sublimation interface which contracted to the centre of the sample could be seen, sublimation process proceeded from edge to center gradually. The grey value of ice crystals was determined to be 154 through gauss calculation. By comparing frozen sample with freeze-dried one, the ice crystals regions in the beginning became the porous regions after drying, grey values increased correspondingly. Samples shrunk slightly after drying for 3 to 7 hours, which could be distinguished by the change in grey values.

  3. Snowmelt and sublimation: field experiments and modelling in the High Atlas Mountains of Morocco

    NASA Astrophysics Data System (ADS)

    Schulz, O.; de Jong, C.

    Snow in the High Atlas Mountains is a major source for freshwater renewal and for water availability in the semi-arid lowlands of south-eastern Morocco. Snowfall- and snow-ablation monitoring and modelling is important for estimating potential water delivery from the mountain water towers to the forelands. This study is part of GLOWA-IMPETUS, an integrated management project dealing with scarce water resources in West Africa. The Ameskar study area is located to the south of the High Atlas Mountains, in their rain shadow. As a part of the M’Goun river basin within the upper Dr'valley, the study area is characterised by high radiation inputs, low atmospheric humidity and long periods with sub-zero temperatures. Its altitude ranges between 2000 m and 4000 m, with dominant north- and south-facing slopes. Snowfall occurs mainly from November to April but even summit regions can become repeatedly devoid of snow cover. Snow cover maps for the M’Goun basin (1240 km2) are derived from calculations of NDSI (Normalized Difference Snow Index) from MODIS satellite images and snow depth is monitored at four automatic weather stations between 2000-4000 m. Snowfall events are infrequent at lower altitudes. The presence of snow penitentes at altitudes above 3000 m indicates that snow sublimation is an important component of snow ablation. Snow ablation was modelled with the UEB Utah Energy Balance Model (Tarboton and Luce, 1996). This single layer, physically-based, point energy and mass balance model is driven by meteorological variables recorded at the automatic weather stations at Tounza (2960 m) and Tichki (3260 m). Data from snow pillows at Tounza and Tichki are used to validate the model’s physical performance in terms of energy and water balances for a sequence of two snowfall events in the winter of 2003/4. First UEB modelling results show good overall performance and timing of snowmelt and sublimation compared to field investigations. Up to 44% of snow ablation is

  4. Canopy effects on snow sublimation from a central Arizona Basin

    NASA Astrophysics Data System (ADS)

    Svoma, Bohumil M.

    2017-01-01

    Guided by 30 m terrain and forest cover data, snow sublimation from the Salt River basin in the Southwest U.S. is simulated for years 2008 (wet year) and 2007 (dry year). Downscaled meteorological input correlates well (r 0.80) with independent observations at AmeriFlux sites. Additionally, model correlation and bias with eddy-covariance vapor flux observations is comparable to previous localized modeling efforts. Upon a 30% reduction in effective leaf area index, canopy sublimation decreases by 1.29 mm (27.0%) and 1.05 mm (23.0%) at the basin scale for the 2008 and 2007 simulations, respectively. Ground sublimation decreases 0.72 mm (4.75%) in 2008 and only 0.17 mm (1.5%) in 2007. Canopy snow-holding capacity and frequent unloading events at lower elevations limit the variability in canopy sublimation from wet year to dry year at the basin scale. The greater decrease in snowpack sublimation in the wet year is partly due to decreased longwave radiation from the canopy reduction over a more extensive snowpack than the dry year. This decrease overcomes the increased solar radiation and wind speed during winter. A second factor is that a greater extent of the snowpack persisted into spring in 2008 than 2007, and the large increase in shortwave flux upon canopy reduction increases melt rates, reducing duration. Only in heavily forested high elevations (>2900 m above sea level) in 2008 does the snowpack persist long enough into spring to result in increased ground sublimation upon canopy reduction. As forest cover change can occur rapidly, these results are critical from water resource and ecosystem function perspectives.

  5. Contactless prompt tumbling rebound of drops from a sublimating slope

    NASA Astrophysics Data System (ADS)

    Antonini, Carlo; Jung, Stefan; Wetzel, Andreas; Heer, Emmanuel; Schoch, Philippe; Moqaddam, Ali Mazloomi; Chikatamarla, Shyam S.; Karlin, Ilya; Marengo, Marco; Poulikakos, Dimos

    2016-05-01

    We have uncovered a drop rebound regime, characteristic of highly viscous liquids impacting tilted sublimating surfaces. Here the drops, rather than showing a slide, spread, recoil, and rebound behavior, exhibit a prompt tumbling rebound. As a result, glycerol surprisingly rebounds faster than three orders of magnitude less viscous water. When a viscous drop impacts a sublimating surface, part of its initial linear momentum is converted into angular momentum: Lattice Boltzmann simulations confirmed that tumbling owes its appearance to the rapid transition of the internal angular velocity prior to rebound to a constant value, as in a tumbling solid body.

  6. Enthalpy of sublimation as measured using a silicon oscillator

    NASA Astrophysics Data System (ADS)

    Shakeel, Hamza; Pomeroy, J. M.

    In this study, we report the enthalpy of sublimation of common gases (nitrogen, oxygen, argon, carbon dioxide, neon, krypton, xenon, and water vapor) using a large area silicon oscillator with a sub-ng (~0.027 ng/cm2) mass sensitivity. The double paddle oscillator design enables high frequency stability (17 ppb) at cryogenic temperatures and provides a consistent technique for enthalpy measurements. The enthalpies of sublimation are derived from the rate of mass loss during programmed thermal desorption and are detected as a change in the resonance frequency of the self-tracking oscillator. These measured enthalpy values show excellent agreement with the accepted literature values.

  7. Alumina Paste Sublimation Suppression Barrier for Thermoelectric Device

    NASA Technical Reports Server (NTRS)

    Paik, Jong-Ah (Inventor); Caillat, Thierry (Inventor)

    2014-01-01

    Alumina as a sublimation suppression barrier for a Zintl thermoelectric material in a thermoelectric power generation device operating at high temperature, e.g. at or above 1000K, is disclosed. The Zintl thermoelectric material may comprise Yb.sub.14MnSb.sub.11. The alumina may be applied as an adhesive paste dried and cured on a substantially oxide free surface of the Zintl thermoelectric material and polished to a final thickness. The sublimation suppression barrier may be finalized by baking out the alumina layer on the Zintl thermoelectric material until it becomes substantially clogged with ytterbia.

  8. Laboratory experiments to explore the sediment transport capacity of carbon dioxide sublimation under martian conditions

    NASA Astrophysics Data System (ADS)

    Sylvest, Matthew; Conway, Susan; Patel, Manish; Dixon, John; Barnes, Adam

    2015-04-01

    Every spring, the solid carbon dioxide deposited over the martian high latitudes sublimates. Several, unusual surface features, including dark spots and flows on sand dunes, as well as recent activity in martian gullies, have been associated with this CO2 sublimation. Water and/or brines have also been proposed as potential agents for these events, but the timing of these phenomena suggest CO2 sublimation is more likely. However, the exact mechanism by which CO2 sublimation moves sediment is not fully understood, and this understanding is required to validate the CO2 hypothesis. Here we present the results of the first ever laboratory simulations of this process under martian conditions, and show that significant quantities of loose sediment can be transported. The centrepiece of the apparatus is a 1m diameter, 2m long Mars simulation chamber, housed at The Open University, UK. JSC Mars-1A regolith simulant was formed into a slope, inside a box, ~30 cm long, 23 cm wide by 12 cm deep. The box is constructed of coiled, copper tubing to allow cooling of the regolith by liquid nitrogen. The experimental procedure consists of four stages: 1) establishment of a dry atmosphere in the chamber, 2) cooling the regolith sufficiently to support condensation of CO2 frost at reduced pressure, 3) introduction of cooled CO2 gas above the regolith to deposit as frost, and 4) video recording the surface evolution under radiant heating (~100 mins). Two High Definition digital video cameras were mounted above the box and image pairs taken from the videos were then used to create digital elevation models (DEMs) in Agisoft Photoscan at regular intervals. In our initial experiments we performed four experimental runs where the slope was set at or near the angle of repose (~30°). In each case we observed mass wasting events triggered by the sublimation of the deposited CO2 over the whole duration of the insolation. The highest levels of activity occurred in the first third of the run

  9. Alumina Paste Layer as a Sublimation Suppression Barrier for Yb14MnSb11

    NASA Technical Reports Server (NTRS)

    Paik, Jong-Ah; Caillat, Thierry

    2010-01-01

    Sublimation is a major cause of degradation of thermoelectric power generation systems. Most thermoelectric materials tend to have peak values at the temperature where sublimation occurs. A sublimation barrier is needed that is stable at operating temperatures, inert against thermoelectric materials, and able to withstand thermal cycling stress. A porous alumina paste layer is suitable as a sublimation barrier for Yb14MnSb11. It can accommodate stress generated by the thermal expansion discrepancy between the suppression layer and thermoelectric materials. Sublimation suppression is achieved by filling pores naturally with YbO2, a natural byproduct of sublimation. YbO2 generated during the sublimation of Yb14MnSb11 fills the porous structure of the alumina paste, causing sublimation to decrease with time as the pores become filled.

  10. System for NO reduction using sublimation of cyanuric acid

    DOEpatents

    Perry, Robert A.

    1989-01-01

    An arrangement for reducing the NO content of a gas stream comprises contacting the gas stream with HNCO at a temperature effective for heat induced decomposition of HNCO and for resultant lowering of the NO content of the gas stream. Preferably, the HNCO is generated by sublimation of cyanuric acid.

  11. Modeling the development of martian sublimation thermokarst landforms

    USGS Publications Warehouse

    Dundas, Colin M.; Byrne, Shane; McEwen, Alfred S.

    2015-01-01

    Sublimation-thermokarst landforms result from collapse of the surface when ice is lost from the subsurface. On Mars, scalloped landforms with scales of decameters to kilometers are observed in the mid-latitudes and considered likely thermokarst features. We describe a landscape evolution model that couples diffusive mass movement and subsurface ice loss due to sublimation. Over periods of tens of thousands of Mars years under conditions similar to the present, the model produces scallop-like features similar to those on the Martian surface, starting from much smaller initial disturbances. The model also indicates crater expansion when impacts occur in surfaces underlain by excess ice to some depth, with morphologies similar to observed landforms on the Martian northern plains. In order to produce these landforms by sublimation, substantial quantities of excess ice are required, at least comparable to the vertical extent of the landform, and such ice must remain in adjacent terrain to support the non-deflated surface. We suggest that Martian thermokarst features are consistent with formation by sublimation, without melting, and that significant thicknesses of very clean excess ice (up to many tens of meters, the depth of some scalloped depressions) are locally present in the Martian mid-latitudes. Climate conditions leading to melting at significant depth are not required.

  12. Literary Study, Measurement, and the Sublime: Disciplinary Assessment

    ERIC Educational Resources Information Center

    Heiland, Donna, Ed.; Rosenthal, Laura J., Ed.

    2011-01-01

    This collection of essays, "Literary Study, Measurement, and the Sublime: Disciplinary Assessment," edited by Donna Heiland and Laura J. Rosenthal, represents an important new venture in the Foundation's communication program. The book is the product of many authors, including the editors, both of whom have written essays for it. But it…

  13. Modeling the development of martian sublimation thermokarst landforms

    NASA Astrophysics Data System (ADS)

    Dundas, Colin M.; Byrne, Shane; McEwen, Alfred S.

    2015-12-01

    Sublimation-thermokarst landforms result from collapse of the surface when ice is lost from the subsurface. On Mars, scalloped landforms with scales of decameters to kilometers are observed in the mid-latitudes and considered likely thermokarst features. We describe a landscape evolution model that couples diffusive mass movement and subsurface ice loss due to sublimation. Over periods of tens of thousands of Mars years under conditions similar to the present, the model produces scallop-like features similar to those on the martian surface, starting from much smaller initial disturbances. The model also indicates crater expansion when impacts occur in surfaces underlain by excess ice to some depth, with morphologies similar to observed landforms on the martian northern plains. In order to produce these landforms by sublimation, substantial quantities of excess ice are required, at least comparable to the vertical extent of the landform, and such ice must remain in adjacent terrain to support the non-deflated surface. We suggest that martian thermokarst features are consistent with formation by sublimation, without melting, and that significant thicknesses of very clean excess ice (up to many tens of meters, the depth of some scalloped depressions) are locally present in the martian mid-latitudes. Climate conditions leading to melting at significant depth are not required.

  14. The Digital Sublime: Lessons from Kelli Connell's "Double Life"

    ERIC Educational Resources Information Center

    Huang, Yi-hui

    2012-01-01

    The digital sublime refers to digital-composite photography that presents "the existence of something unpresentable" and that renders a matchless look a sophisticated fabrication, a perfect and clean composition, a maximum color saturation, a multiple-point perspective, and stunning or newfangled content. Abandoning the traditional one-shot mode…

  15. Optimization of Fast Dissolving Etoricoxib Tablets Prepared by Sublimation Technique

    PubMed Central

    Patel, D. M.; Patel, M. M.

    2008-01-01

    The purpose of this investigation was to develop fast dissolving tablets of etoricoxib. Granules containing etoricoxib, menthol, crospovidone, aspartame and mannitol were prepared by wet granulation technique. Menthol was sublimed from the granules by exposing the granules to vacuum. The porous granules were then compressed in to tablets. Alternatively, tablets were first prepared and later exposed to vacuum. The tablets were evaluated for percentage friability and disintegration time. A 32 full factorial design was applied to investigate the combined effect of 2 formulation variables: amount of menthol and crospovidone. The results of multiple regression analysis indicated that for obtaining fast dissolving tablets; optimum amount of menthol and higher percentage of crospovidone should be used. A surface response plots are also presented to graphically represent the effect of the independent variables on the percentage friability and disintegration time. The validity of a generated mathematical model was tested by preparing a checkpoint batch. Sublimation of menthol from tablets resulted in rapid disintegration as compared with the tablets prepared from granules that were exposed to vacuum. The optimized tablet formulation was compared with conventional marketed tablets for percentage drug dissolved in 30 min (Q30) and dissolution efficiency after 30 min (DE30). From the results, it was concluded that fast dissolving tablets with improved etoricoxib dissolution could be prepared by sublimation of tablets containing suitable subliming agent. PMID:20390084

  16. System for NO reduction using sublimation of cyanuric acid

    DOEpatents

    Perry, R.A.

    1989-01-24

    An arrangement for reducing the NO content of a gas stream comprises contacting the gas stream with HNCO at a temperature effective for heat induced decomposition of HNCO and for resultant lowering of the NO content of the gas stream. Preferably, the HNCO is generated by sublimation of cyanuric acid. 1 fig.

  17. Differential Sublimation of Terrestrial Permafrost and the Ramifications for Terrain Features on Mars

    NASA Astrophysics Data System (ADS)

    Douglas, T. A.; Mellon, M. T.

    2016-09-01

    Sublimation loss of ice wedge ice in CRREL Permafrost Tunnel in Alaska (2.8 mm) is linear over 386 days, while ice cemented silt sublimation follows a decreasing relationship with time over 51 years with little sublimation over the past 20 years.

  18. Relationship between molecular descriptors and the enthalpies of sublimation of natural amino acids

    NASA Astrophysics Data System (ADS)

    Badelin, V. G.; Tyunina, V. V.; Girichev, G. V.; Tyunina, E. Yu.

    2016-07-01

    A multiparameter correlation between the enthalpies of sublimation and molecular descriptors of natural amino acids is proposed, based on generalized experimental and literature data on the heat effects of sublimation. The contributions from Van der Waals interactions, hydrogen bond formation, and electrostatic effects into enthalpy of sublimation has been evaluated using regression coefficients.

  19. Advances in sublimation studies for particles of explosives

    NASA Astrophysics Data System (ADS)

    Furstenberg, Robert; Nguyen, Viet; Fischer, Thomas; Abrishami, Tara; Papantonakis, Michael; Kendziora, Chris; Mott, David R.; McGill, R. Andrew

    2015-05-01

    When handling explosives, or related surfaces, the hands routinely become contaminated with particles of explosives and related materials. Subsequent contact with a solid surface results in particle crushing and deposition. These particles provide an evidentiary trail which is useful for security applications. As such, the opto-physico-chemical characteristics of these particles are critical to trace explosives detection applications in DOD or DHS arenas. As the persistence of these particles is vital to their forensic exploitation, it is important to understand which factors influence their persistence. The longevity or stability of explosives particles on a substrate is a function of several environmental parameters or particle properties including: Vapor pressure, particle geometry, airflow, particle field size, substrate topography, humidity, reactivity, adlayers, admixtures, particle areal density, and temperature. In this work we deposited particles of 2,4-dinitrotoluene on standard microscopy glass slides by particle sieving and studied their sublimation as a function of airflow velocity, areal particle density and particle field size. Analysis of 2D microscopic images was used to compute and track particle size and geometrical characteristics. The humidity, temperature and substrate type were kept constant for each experiment. A custom airflow cell, using standard microscopy glass slide, allowed in-situ photomicroscopy. Areal particle densities and airflow velocities were selected to provide relevant loadings and flow velocities for a range of potential applications. For a chemical of interest, we define the radial sublimation velocity (RSV) for the equivalent sphere of a particle as the parameter to characterize the sublimation rate. The RSV is a useful parameter because it is independent of particle size. The sublimation rate for an ensemble of particles was found to significantly depend on airflow velocity, the areal density of the particles, and the

  20. Aerosol volatility and enthalpy of sublimation of carboxylic acids.

    PubMed

    Salo, Kent; Jonsson, Asa M; Andersson, Patrik U; Hallquist, Mattias

    2010-04-08

    The enthalpy of sublimation has been determined for nine carboxylic acids, two cyclic (pinonic and pinic acid) and seven straight-chain dicarboxylic acids (C(4) to C(10)). The enthalpy of sublimation was determined from volatility measurements of nano aerosol particles using a volatility tandem differential mobility analyzer (VTDMA) set-up. Compared to the previous use of a VTDMA, this novel method gives enthalpy of sublimation determined over an extended temperature range (DeltaT approximately 40 K). The determined enthalpy of sublimation for the straight-chain dicarboxylic acids ranged from 96 to 161 kJ mol(-1), and the calculated vapor pressures at 298 K are in the range of 10(-6)-10(-3) Pa. These values indicate that dicarboxylic acids can take part in gas-to-particle partitioning at ambient conditions and may contribute to atmospheric nucleation, even though homogeneous nucleation is unlikely. To obtain consistent results, some experimental complications in producing nanosized crystalline aerosol particles were addressed. It was demonstrated that pinonic acid "used as received" needed a further purification step before being suspended as a nanoparticle aerosol. Furthermore, it was noted from distinct differences in thermal properties that aerosols generated from pimelic acid solutions gave two types of particles. These two types were attributed to crystalline and amorphous configurations, and based on measured thermal properties, the enthalpy of vaporization was 127 kJ mol(-1) and that of sublimation was 161 kJ mol(-1). This paper describes a new method that is complementary to other similar methods and provides an extension of existing experimental data on physical properties of atmospherically relevant compounds.

  1. Measuring Enthalpy of Sublimation of Volatiles by Means of Piezoelectric Crystal Microbalances

    NASA Astrophysics Data System (ADS)

    Dirri, Fabrizio; Palomba, Ernesto; Longobardo, Andrea; Zampetti, Emiliano

    2016-09-01

    Piezoelectric Crystal Microbalances (PCM's) are widely used to study the chemical processes involving volatile compounds in any environment, such as condensation process. Since PCM's are miniaturized sensor, they are very suitable for planetary in situ missions, where can be used to detect and to measure the mass amount of astrobiologically significant compounds, such as water and organics. This work focuses on the realization and testing of a new experimental setup, able to characterize volatiles which can be found in a planetary environment. In particular the enthalpy of sublimation of some dicarboxylic acids has been measured. The importance of dicarboxylic acids in planetology and astrobiology is due to the fact that they have been detected in carbonaceous chondritic material (e.g. Murchinson), among the most pristine material present in our Solar System. In this work, a sample of acid was heated in an effusion cell up to its sublimation. For a set of temperatures (from 30 °C to 75 °C), the deposition rate on the PCM surface has been measured. From these measurements, it has been possible to infer the enthalpy of sublimation of Adipic acid, i.e. ΔH = 141.6 ± 0.8 kJ/mol and Succinic acid, i.e. ΔH = 113.3 ± 1.3 kJ/mol. This technique has so demonstrated to be a good choice to recognise a single compound or a mixture (with an analysis upstream) even if some improvements concerning the thermal stabilization of the system will be implemented in order to enhance the results' accuracy. The experiment has been performed in support of the VISTA (Volatile In Situ Thermogravimetry Analyzer) project, which is included in the scientific payload of the ESA MarcoPolo-R mission study.

  2. Measuring Enthalpy of Sublimation of Volatiles by Means of Piezoelectric Crystal Microbalances.

    PubMed

    Dirri, Fabrizio; Palomba, Ernesto; Longobardo, Andrea; Zampetti, Emiliano

    2016-09-15

    Piezoelectric Crystal Microbalances (PCM's) are widely used to study the chemical processes involving volatile compounds in any environment, such as condensation process. Since PCM's are miniaturized sensor, they are very suitable for planetary in situ missions, where can be used to detect and to measure the mass amount of astrobiologically significant compounds, such as water and organics. This work focuses on the realization and testing of a new experimental setup, able to characterize volatiles which can be found in a planetary environment. In particular the enthalpy of sublimation of some dicarboxylic acids has been measured. The importance of dicarboxylic acids in planetology and astrobiology is due to the fact that they have been detected in carbonaceous chondritic material (e.g. Murchinson), among the most pristine material present in our Solar System. In this work, a sample of acid was heated in an effusion cell up to its sublimation. For a set of temperatures (from 30 °C to 75 °C), the deposition rate on the PCM surface has been measured. From these measurements, it has been possible to infer the enthalpy of sublimation of Adipic acid, i.e. ΔH = 141.6 ± 0.8 kJ/mol and Succinic acid, i.e. ΔH = 113.3 ± 1.3 kJ/mol. This technique has so demonstrated to be a good choice to recognise a single compound or a mixture (with an analysis upstream) even if some improvements concerning the thermal stabilization of the system will be implemented in order to enhance the results' accuracy. The experiment has been performed in support of the VISTA (Volatile In Situ Thermogravimetry Analyzer) project, which is included in the scientific payload of the ESA MarcoPolo-R mission study.

  3. Piezoelectric crystal microbalance measurements of enthalpy of sublimation of C2-C9 dicarboxylic acids

    NASA Astrophysics Data System (ADS)

    Dirri, F.; Palomba, E.; Longobardo, A.; Zampetti, E.

    2015-07-01

    We present here a novel experimental setup able to measure the enthalpy of sublimation of a given compound by means of Piezoelectric Crystal Microbalances (PCM). This experiment was performed in the TG-Lab facility in IAPS-INAF, dedicated to the development of TGA sensors for space measurements, such as detection of organic and non-organic volatile species and refractory materials in planetary environments. In order to study physical-chemical processes concerning the Volatile Organic Compounds (VOC) present in atmospheric environments, the setup has been tested on Dicarboxylic acids. Acids with low molecular weight are among the components of organic fraction of particulate matter in the atmosphere, coming from different sources (biogenic and anthropogenic). Considering their relative abundance, it is useful to consider Dicarboxylic acid as "markers" to define the biogenic or anthropogenic origin of the aerosol, thus obtaining some information of the emission sources. In this work, a temperature controlled effusion cell was used to sublimate VOC, creating a molecular flux that was collimated onto a cold PCM. The VOC re-condensed onto the PCM quartz crystal allowing the determination of the deposition rate. From the measurements of deposition rates, it was possible to infer the enthalpy of sublimation of Adipic acid, i.e. Δ Hsub: 141.6 ± 0.8 kJ mol-1, Succinic acid, i.e. 113.3 ± 1.3 kJ mol-1, Oxalic acid, i.e. 62.5 ± 3.1 kJ mol-1 and Azelaic acid, i.e. 124.2 ± 1.2 kJ mol-1 (weight average values). The results obtained are in very good agreement with literature within 10 % for the Adipic, Succinic and Oxalic acid.

  4. Surface engineering of SiC via sublimation etching

    NASA Astrophysics Data System (ADS)

    Jokubavicius, Valdas; Yazdi, Gholam R.; Ivanov, Ivan G.; Niu, Yuran; Zakharov, Alexei; Iakimov, Tihomir; Syväjärvi, Mikael; Yakimova, Rositsa

    2016-12-01

    We present a technique for etching of SiC which is based on sublimation and can be used to modify the morphology and reconstruction of silicon carbide surface for subsequent epitaxial growth of various materials, for example graphene. The sublimation etching of 6H-, 4H- and 3C-SiC was explored in vacuum (10-5 mbar) and Ar (700 mbar) ambient using two different etching arrangements which can be considered as Si-C and Si-C-Ta chemical systems exhibiting different vapor phase stoichiometry at a given temperature. The surfaces of different polytypes etched under similar conditions are compared and the etching mechanism is discussed with an emphasis on the role of tantalum as a carbon getter. To demonstrate applicability of such etching process graphene nanoribbons were grown on a 4H-SiC surface that was pre-patterned using the thermal etching technique presented in this study.

  5. Effects of varying obliquity on Martian sublimation thermokarst landforms

    USGS Publications Warehouse

    Dundas, Colin M.

    2017-01-01

    Scalloped depressions in the Martian mid-latitudes are likely formed by sublimation of ice-rich ground. The stability of subsurface ice changes with the planetary obliquity, generally becoming less stable at lower axial tilt. As a result, the relative rates of sublimation and creep change over time. A landscape evolution model shows that these variations produce internal structure in scalloped depressions, commonly in the form of arcuate ridges, which emerge as depressions resume growth after pausing or slowing. In other scenarios, the formation of internal structure is minimal. Significant uncertainties in past climate and model parameters permit a range of scenarios. Ridges observed in some Martian scalloped depressions could date from obliquity lows or periods of low ice stability occurring <5 Ma, suggesting that the pits are young features and may be actively evolving.

  6. Measuring enthalpy of sublimation of volatiles by means of micro-thermogravimetry: the case of Dicarboxylic acids

    NASA Astrophysics Data System (ADS)

    Dirri, F.; Longobardo, A.; Palomba, E.; Zampetti, E.; Biondi, D.; Boccaccini, A.; Saggin, B.; Bearzotti, A.; Macagnano, A.

    2013-09-01

    VISTA (Volatile In Situ Thermogravimetry Analyser) is a thermogravimeter currently under study for the proposed mission MarcoPolo-R [1,2]. In the framework of this project, we developed a set-up to measure the enthalpy of sublimation ΔH of three dicarboxylic acids, i.e. adipic, succinic and oxalic. The obtained results are in good agreement with literature, and this demonstrates the capability of our device to perform this kind of measurements.

  7. Sublimator Driven Coldplate Engineering Development Unit Test Results and Development of Second Generation SDC

    NASA Technical Reports Server (NTRS)

    Stephan, Ryan A.; Sheth, Rubik B.

    2009-01-01

    The Sublimator Driven Coldplate (SDC) is a unique piece of thermal control hardware that has several advantages over a traditional thermal control scheme. The principal advantage is the possible elimination of a pumped fluid loop, potentially increasing reliability and reducing complexity while saving both mass and power. Furthermore, the Integrated Sublimator Driven Coldplate (ISDC) concept couples a coolant loop with the previously described SDC hardware. This combination allows the SDC to be used as a traditional coldplate during long mission phases. The previously developed SDC technology cannot be used for long mission phases due to the fact that it requires a consumable feedwater for heat rejection. Adding a coolant loop also provides for dissimilar redundancy on the Altair Lander ascent module thermal control system, which is the target application for this technology. Tests were performed on an Engineering Development Unit at NASA s Johnson Space Center to quantify and assess the performance of the SDC. Correlated thermal math models were developed to help explain the test data. The paper also outlines the preliminary results of an ISDC concept being developed.

  8. Coupled fluid-thermal analysis of low-pressure sublimation and condensation with application to freeze-drying

    NASA Astrophysics Data System (ADS)

    Ganguly, Arnab

    Freeze-drying is a low-pressure, low-temperature condensation pumping process widely used in the manufacture of bio-pharmaceuticals for removal of solvents by sublimation. The goal of the process is to provide a stable dosage form by removing the solvent in such a way that the sensitive molecular structure of the active substance is least disturbed. The vacuum environment presents unique challenges for understanding and controlling heat and mass transfer in the process. As a result, the design of equipment and associated processes has been largely empirical, slow and inefficient. A comprehensive simulation framework to predict both, process and equipment performance is critical to improve current practice. A part of the dissertation is aimed at performing coupled fluid-thermal analysis of low-pressure sublimation-condensation processes typical of freeze-drying technologies. Both, experimental and computational models are used to first understand the key heat transfer modes during the process. A modeling and computational framework, validated with experiments for analysis of sublimation, water-vapor flow and condensation in application to pharmaceutical freeze-drying is developed. Augmented with computational fluid dynamics modeling, the simulation framework presented here allows to predict for the first time, dynamic product/process conditions taking into consideration specifics of equipment design. Moreover, by applying the modeling framework to process design based on a design-space approach, it has demonstrated that there is a viable alternative to empiricism.

  9. Formulation and evaluation of fast dissolving tablets of cinnarizine using superdisintegrant blends and subliming material

    PubMed Central

    Basu, Biswajit; Bagadiya, Abhishek; Makwana, Sagar; Vipul, Vora; Batt, Devraj; Dharamsi, Abhay

    2011-01-01

    The aim of this investigation was to develop fast dissolving tablet of cinnarizine. A combination of super disintegrants, i.e., sodium starch glycolate (SSG) and crosscarmellose sodium (CCS) were used along with camphor as a subliming material. An optimized concentration of camphor was added to aid the porosity of the tablet. A 32 full factorial design was applied to investigate the combined effect of two formulation variables: Amount of SSG and CCS. Infrared (IR) spectroscopy was performed to identify the physicochemical interaction between drug and polymer. IR spectroscopy showed that there is no interaction of drug with polymer. In the present study, direct compression was used to prepare the tablets. The powder mixtures were compressed into tablet using flat face multi punch tablet machine. Camphor was sublimed from the tablet by exposing the tablet to vacuum drier at 60°C for 12 hours. All the formulations were evaluated for their characteristics such as average weight, hardness, wetting time, friability, content uniformity, dispersion time (DT), and dissolution rate. An optimized tablet formulation (F 9) was found to have good hardness of 3.30 ± 0.10 kg/cm2, wetting time of 42.33 ± 4.04 seconds, DT of 34.67 ± 1.53 seconds, and cumulative drug release of not less than 99% in 16 minutes. PMID:22247895

  10. The enthalpy of sublimation and thermodynamic functions of fermium

    SciTech Connect

    Haire, R.G.; Gibson, J.K. , Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6375 )

    1989-12-01

    The enthalpy of sublimation of fermium (Fm), element 100, has now been determined directly by measuring the partial pressure of Fm over alloys, for the temperature range of 642 to 905 K. The partial pressures were determined using Knudsen effusion and target collection techniques. Dilute (10{sup {minus}5}--10{sup {minus}7} atom %) solid alloys of Fm and mixtures of Fm and Es in both Sm and Yb solvents were studied. The presence of Es in two of the alloys allowed a direct comparison of the behavior of Fm and Es, where the latter could be used as a reference. It was possible to calculate enthalpies of sublimation and a hypothetical vapor pressure/temperature relationship for pure Fm metal by selecting Yb as the solvent most likely to form a nearly ideal alloy with Fm. From the experimental vapor pressure data, we derived average Second Law values of 33.8{plus minus}3 kcal/mol and 23.5{plus minus}3 cal/mol deg for the enthalpy and entropy of sublimation of Fm at 298 K. Third Law enthalpy values were also calculated using the experimental partial pressure data and entropies estimated from derived free energy functions and heat capacities for the solid and gaseous forms of Fm. The average Third Law values (34.8 kcal/mol and 25.1 cal/mol deg, respectively, at 298 K) are in agreement with those obtained via the Second Law. These results establish that Fm, like Es (element 99), is a divalent metal. The finding that Fm metal is the second divalent actinide element experimentally establishes the trend towards metallic divalency expected in the second half of the actinide series.

  11. Measuring enthalpy of sublimation of volatiles by means of micro-thermogravimetry for the study of water and organic in planetary environments

    NASA Astrophysics Data System (ADS)

    Dirri, F.; Palomba, E.; Longobardo, A.; Zampetti, E.; Biondi, D.; Boccaccini, A.; Pantalei, S.; Zinzi, A.

    In this work, we present a new experimental set up to infer the enthalpy of sublimation for a known specie of dicarboxylic acid, i.e. adipic acid. This type of acids, with various concentrations are present in different environments (e.g. marine, rural, urban). The experiment is performed in the framework of the VISTA (Volatile In Situ Thermogravimetry Analyser) project, an instrument currently under study for the ESA Cosmic Vision proposed mission MarcoPolo-R. The enthalpy of sublimation of adipic acid was measured by means of micro-thermogravimetric analysis (mu -TGA), a widely used technique to investigate condensation/sublimation and absorption/desorption processes of volatile compounds. The measurements were performed with a 10 MHz temperature controlled piezoelectric crystal microbalance (PCM), placed in a vacuum chamber (10-6 mbar). The obtained enthalpy of sublimation is (123±16) kJ× mol-1, a value in good agreement with literature within 10%. This result (connected to the deposition rate curve, from 30 o to 75 oC), demonstrates the capability of our device to perform this kind of measurements.

  12. Dynamic sublimation pressure and the catastrophic breakup of Comet ISON

    NASA Astrophysics Data System (ADS)

    Steckloff, Jordan K.; Johnson, Brandon C.; Bowling, Timothy; Jay Melosh, H.; Minton, David; Lisse, Carey M.; Battams, Karl

    2015-09-01

    Previously proposed mechanisms have difficulty explaining the disruption of Comet C/2012 S1 (ISON) as it approached the Sun. We describe a novel cometary disruption mechanism whereby comet nuclei fragment and disperse through dynamic sublimation pressure, which induces differential stresses within the interior of the nucleus. When these differential stresses exceed its material strength, the nucleus breaks into fragments. We model the sublimation process thermodynamically and propose that it is responsible for the disruption of Comet ISON. We estimate the bulk unconfined crushing strength of Comet ISON's nucleus and the resulting fragments to be 0.5 Pa and 1-9 Pa, respectively, assuming typical Jupiter Family Comet (JFC) albedos. However, if Comet ISON has an albedo similar to Pluto, this strength estimate drops to 0.2 Pa for the intact nucleus and 0.6-4 Pa for its fragments. Regardless of assumed albedo, these are similar to previous strength estimates of JFCs. This suggests that, if Comet ISON is representative of dynamically new comets, then low bulk strength is a primordial property of some comet nuclei, and not due to thermal processing during migration into the Jupiter Family.

  13. Testing and Model Correlation of Sublimator Driven Coldplate Coupons and EDU

    NASA Technical Reports Server (NTRS)

    Leimkuehler, Thomas O.

    2009-01-01

    The Sublimator Driven Coldplate (SDC) is a unique piece of thermal control hardware that has several advantages over a more traditional thermal control system. The principal advantage is the possible elimination of a pumped fluid loop, potentially saving mass, power, and complexity. Because this concept relies on evaporative heat rejection techniques, it is primarily useful for short mission durations. Additionally, the concept requires a conductive path between the heat-generating component and the heat rejection device. Therefore, it is mostly a relevant solution for a vehicle with a relatively low heat rejection requirement and/or short transport distances. Tests were performed on coupons and an Engineering Development Unit (EDU) at NASA s Johnson Space Center to better understand the basic operational principles and to validate the analytical methods being used for the SDC development. This paper outlines the results of the SDC tests, the subsequent thermal model correlation, and a description of the SDC Engineering Development Unit test results.

  14. Pan-Observation Results on Snow Sublimation and its Parameterization in Both forested and Open Environment in Taiga of Eastern Siberia

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Suzuki, K.; Kubota, J.; Kadota, T.; Ohata, T.

    2002-12-01

    normally changed by 24 hr interval due to a few temperature difference. The daily values of snow sublimation using pan method were averaged to be 0.36, 0.41 and 0.32 mm/d from March 8 to April 12 of 2002 at Site LF, OP and ES respectively. As a result of observation on snow sublimation in the period of 1977-83 (Vasilenko, 1997), average value of sublimation to maximum water equivalent of snow was 11% (seven years), but was 29% during 1978-79. Having performed the modeling work on snow ablation processes, Suzuki et al. (In submitting) reveal that sublimation was increase from middle of March, and takes about 50% to annual snowfall. Kojima (1979) demonstrated that snow sublimation is determined by wind speed and atmospheric saturation deficit using the following equation: E' = CeU (esa- ea) (mm/d) (1) where E' is the sublimation (mm/d), U is daily mean wind speed (m/s), esa and ea are daily mean saturated vapor pressure and the vapor pressure (hPa) at a given height above the ground surface, respectively, and Ce is a coefficient that parameterized based on profile method. Using the meteorological data, the terms as shown in Table 1, Ce was calculated to 0.24 with range of 0.03 at three observation sites.

  15. Thermodynamic investigations of nitroxoline sublimation by simultaneous DSC-FTIR method and isothermal TG analysis.

    PubMed

    Gao, Gau-Yi; Lin, Shan-Yang

    2010-01-01

    To investigate the physicochemical characteristics, thermodynamics, possible sublimation process and kinetics of nitroxoline, differential scanning calorimetry (DSC), isothermal thermogravimetry (TG), and Fourier transform infrared (FTIR) microspectroscopy equipped with a micro hot-stage of DSC microscopy assembly (simultaneous DSC-FTIR method) were used. The DSC result indicates that nitroxoline exhibited a sharp endothermic peak at 182 degrees C with enthalpy of 103.1 J/g due to the melting point of nitroxoline. A sublimation behavior of nitroxoline was found from 129 degrees C by gradual weight loss in TG curve. However, the nonisothermal DSC-FTIR method reveals that the temperature at 95 degrees C was the onset temperature of nitroxoline sublimation. A significant difference between DSC-FTIR method and TG analysis suggests that the simultaneous DSC-FTIR method was more sensitive than that of the TG analysis to detect the beginning temperature of nitroxoline sublimation. The sublimation kinetics of nitroxoline determined by isothermal TG analysis evidenced that the zero-order kinetics was followed over the sublimation time. The sublimation enthalpy correction was also carried out by a group additivity approach for the estimation of heat capacity. The enthalpy of nitroxoline sublimation estimated was 86.14 KJ/mol at 298.15 K.

  16. Matrix isolation sublimation: An apparatus for producing cryogenic beams of atoms and molecules.

    PubMed

    Sacramento, R L; Oliveira, A N; Alves, B X; Silva, B A; Li, M S; Wolff, W; Cesar, C L

    2015-07-01

    We describe the apparatus to generate cryogenic beams of atoms and molecules based on matrix isolation sublimation. Isolation matrices of Ne and H2 are hosts for atomic and molecular species which are sublimated into vacuum at cryogenic temperatures. The resulting cryogenic beams are used for high-resolution laser spectroscopy. The technique also aims at loading atomic and molecular traps.

  17. Matrix isolation sublimation: An apparatus for producing cryogenic beams of atoms and molecules

    SciTech Connect

    Sacramento, R. L.; Alves, B. X.; Silva, B. A.; Wolff, W.; Cesar, C. L.; Oliveira, A. N.; Li, M. S.

    2015-07-15

    We describe the apparatus to generate cryogenic beams of atoms and molecules based on matrix isolation sublimation. Isolation matrices of Ne and H{sub 2} are hosts for atomic and molecular species which are sublimated into vacuum at cryogenic temperatures. The resulting cryogenic beams are used for high-resolution laser spectroscopy. The technique also aims at loading atomic and molecular traps.

  18. Mass wasting triggered by seasonal CO2 sublimation under Martian atmospheric conditions: Laboratory experiments

    NASA Astrophysics Data System (ADS)

    Sylvest, Matthew E.; Conway, Susan J.; Patel, Manish R.; Dixon, John C.; Barnes, Adam

    2016-12-01

    Sublimation is a recognized process by which planetary landscapes can be modified. However, interpretation of whether sublimation is involved in downslope movements on Mars and other bodies is restricted by a lack of empirical data to constrain this mechanism of sediment transport and its influence on landform morphology. Here we present the first set of laboratory experiments under Martian atmospheric conditions which demonstrate that the sublimation of CO2 ice from within the sediment body can trigger failure of unconsolidated, regolith slopes and can measurably alter the landscape. Previous theoretical studies required CO2 slab ice for movements, but we find that only frost is required. Hence, sediment transport by CO2 sublimation could be more widely applicable (in space and time) on Mars than previously thought. This supports recent work suggesting CO2 sublimation could be responsible for recent modification in Martian gullies.

  19. Direct Isolation of Purines and Pyrimidines from Nucleic Acids Using Sublimation

    NASA Technical Reports Server (NTRS)

    Glavin, Daniel P.; Schubert, Michael; Bada, Jeffrey L.

    2003-01-01

    A sublimation technique was developed to isolate purines and pyrimidines directly from lambda-deoxyribonucleic acid (lambda-DNA) and Escherichia coli cells. The sublimation of adenine, cytosine, guanine, and thymine from lambda-DNA was tested under reduced pressure (approx. 0.5 Torr) at temperatures of >150 C. With the exception of guanine, approximately 60 -75% of each base was sublimed directly from the lambda-DNA and recovered on a coldfinger of the sublimation apparatus after heating to 450 C. Several nucleobases including adenine, cytosine, thymine, and uracil were also recovered from E. coli bacteria after heating the cells to the same temperature, although some thermal decomposition of the bases also occurred. These results demonstrate the feasibility of using sublimation to isolate purines and pyrimidines from native E. coli DNA and RNA without any chemical treatment of the cells.

  20. Methods of conveying fluids and methods of sublimating solid particles

    DOEpatents

    Turner, Terry D; Wilding, Bruce M

    2013-10-01

    A heat exchanger and associated methods for sublimating solid particles therein, for conveying fluids therethrough, or both. The heat exchanger includes a chamber and a porous member having a porous wall having pores in communication with the chamber and with an interior of the porous member. A first fluid is conveyed into the porous member while a second fluid is conveyed into the porous member through the porous wall. The second fluid may form a positive flow boundary layer along the porous wall to reduce or eliminate substantial contact between the first fluid and the interior of the porous wall. The combined first and second fluids are conveyed out of the porous member. Additionally, the first fluid and the second fluid may each be conveyed into the porous member at different temperatures and may exit the porous member at substantially the same temperature.

  1. Uranium hexaflouride freezer/sublimer process simulator/trainer

    SciTech Connect

    Carnal, C.L. ); Belcher, J.D.; Tapp, P.A.; Ruppel, F.R.; Wells, J.C. )

    1991-01-01

    This paper describes a software and hardware simulation of a freezer/sublimer unit used in gaseous diffusion processing of uranium hexafluoride (UF{sub 6}). The objective of the project was to build a plant simulator that reads control signals and produces plant signals to mimic the behavior of an actual plant. The model is based on physical principles and process data. Advanced Continuous Simulation Language (ACSL) was used to develop the model. Once the simulation was validated with actual plant process data, the ACSL model was translated into Advanced Communication and Control Oriented Language (ACCOL). A Bristol Babcock Distributed Process Controller (DPC) Model 3330 was the hardware platform used to host the ACCOL model and process the real world signals. The DPC will be used as a surrogate plant to debug control system hardware/software and to train operators to use the new distributed control system without disturbing the process. 2 refs., 4 figs.

  2. Estimating surface sublimation losses from snowpacks in a mountain catchment using eddy covariance and turbulent transfer calculations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sublimation is a critical component of the snow cover mass balance. While sublimation can be directly measured using eddy covariance (EC), such measurements are relatively uncommon in complex mountainous environments. EC measurements of surface snowpack sublimation from three consecutive winter sea...

  3. Sublimation Model for Formation of Martian Residual Cap Depressions

    NASA Astrophysics Data System (ADS)

    Byrne, S.; Ingersoll, A. P.

    2000-10-01

    In an effort for explain the formation of the 'Swiss-cheese' terrain visible on the southern residual cap of Mars, we have developed a radiative model to follow the growth/decay of an initial depression due to sublimation/condensation of carbon dioxide. The pits making up this terrain have many distinctive features, they are shallow ( 10m deep), with steep walls and flat floors and contain an interior moat which runs along the bottom of the walls. They have lateral sizes ranging from a few 10's of meters to a kilometer and are quasi-circular. The model accounts for incident sunlight, emitted thermal radiation, and scattered short and long wave radiation. We have investigated many cases involving pure dry-ice with constant albedo, albedo as a function of insolation, and differing albedo for fresh and residual frost (the latter has lower albedo). The last case mentioned shows the most promising results to date. With these conditions it is possible for the depressions to grow and develop flat central portions although they still lack the observed steep walls of the pits. In the other cases mentioned the initial depressions heal themselves and disappear into the surrounding terrain. Other processes or materials could be responsible for the remainder of the observed features. Water ice stored a few meters under a carbon dioxide covering would have dramatic effects on the growth of any depression which encounters it, both due to its low sublimation rate and its ability to store heat. We will extend the current model to include a water ice layer and account for the subsequent heat storage which could possibly follow. For water ice models, a challenge is to reproduce the low brightness temperatures that persist throughout the summer at the residual south polar cap.

  4. Sublimation rates of carbon monoxide and carbon dioxide from comets at large heliocentric distances

    NASA Technical Reports Server (NTRS)

    Sekanina, Zdenek

    1992-01-01

    Using a simple model for outgassing from a small flat surface area, the sublimation rates of carbon monoxide and carbon dioxide, two species more volatile than water ice that are known to be present in comets, are calculated for a suddenly activated discrete source on the rotating nucleus. The instantaneous sublimation rate depends upon the comet's heliocentric distance and the Sun's zenith angle at the location of the source. The values are derived for the constants of CO and CO2 in an expression that yields the local rotation-averaged sublimation rate as a function of the comet's spin parameters and the source's cometocentric latitude.

  5. Ice sublimation and rheology - Implications for the Martian polar layered deposits

    NASA Technical Reports Server (NTRS)

    Hofstadter, Mark D.; Murray, Bruce C.

    1990-01-01

    If the sublimation and creep of water ice are important processes in the Martian polar layered deposits, ice-rich scenario formation and evolution schemes must invoke a mechanism for the inhibition of sublimation, such as a dust layer derived from the residue of the sublimating deposits. This layer could be of the order of 1 m in thickness. If the deposits are ice-rich, flows of more than 1 km should have occurred. It is noted that the dust particles in question may be cemented by such ice that may be present, but that impurities may also have served to cement dust particles together even in the absence of ice.

  6. Schiller Goes to the Movies: Locating the Sublime in "Thelma and Louise."

    ERIC Educational Resources Information Center

    Hoyng, Peter

    1997-01-01

    Endeavors to make students aware of similarities between today's movie culture and the theater of the 18th century; parallels between a traditional drama and a movie script; and Schiller's understanding of the sublime. (36 references) (Author/CK)

  7. Bion and the sublime: the origins of an aesthetic paradigm.

    PubMed

    Civitarese, Giuseppe

    2014-12-01

    In constructing his theory Bion drew on a number of symbolic matrices: psychoanalysis, philosophy, mathematics, literature, aesthetics. The least investigated of these is the last. True, we know that Bion cites many authors of the Romantic period, such as Coleridge, Keats, Blake and Wordsworth, as well as others who were held in high esteem in the Romantic period, such as Milton. However, less is known about the influence exerted on him by the aesthetics of the sublime, which while chronologically preceding Romanticism is in fact one of its components. My working hypothesis is that tracing a number of Bion's concepts back to this secret model can serve several purposes: firstly, it contributes to the study of the sources, and, secondly, it makes these concepts appear much less occasional and idiosyncratic than we might believe, being as they are mostly those less immediately understandable but not less important (O, negative capability, nameless dread, the infinite, the language of achievement, unison etc.). Finally, connecting these notions to a matrix, that is, disclosing the meaning of elements that are not simply juxtaposed but dynamically interrelated, in my view significantly increases not only their theoretical intelligibility but also their usefulness in clinical practice. In conclusion, one could legitimately argue that Bion gradually subsumed all the other paradigms he drew on within the aesthetic paradigm.

  8. Rare earths behaviour during the deposition of volcanic sublimates

    NASA Astrophysics Data System (ADS)

    Censi, P.; Sortino, F.; Zuddas, P.; Saiano, F.; Brusca, L.; Chiavetta, S.; Falcone, E. E.

    2017-02-01

    In this study, the REE distribution between volcanic fluids and related solids in fumaroles with temperatures ranging from approximately 100 to 421 °C was investigated in different geological scenarios. The treatment of geochemical REE data was carried out by calculating the REE enrichment factors (EFREE) relative to the volcanic host rocks in studied sites under the assumption that the REE transport takes place as silicate aerosol in volcanic fluids. Shale-normalised REE concentrations in these fluids have been assessed to investigate whether the REE transport as aqueous complexes in water-saturated volcanic gas is reasonable. The REE behaviour in alkaline condensates according to the above mentioned treatments of geochemical data is very similar, being characterised by positive Ce and Gd anomalies and significant W-type tetrad effects. These evidences suggest that the geochemical behaviour of REE in fumarolic fluids is firstly influenced by the sublimate deposition along the fumarolic conduit or around the vents rather than by the transport mechanism of these elements in volcanic fluids.

  9. Possibility of graphene growth by close space sublimation.

    PubMed

    Sopinskyy, Mykola V; Khomchenko, Viktoriya S; Strelchuk, Viktor V; Nikolenko, Andrii S; Olchovyk, Genadiy P; Vishnyak, Volodymyr V; Stonis, Viktor V

    2014-04-14

    Carbon films on the Si/SiO2 substrate are fabricated using modified method of close space sublimation at atmospheric pressure. The film properties have been characterized by micro-Raman and X-ray photoelectron spectroscopy and monochromatic ellipsometry methods. Ellipsometrical measurements demonstrated an increase of the silicon oxide film thickness in the course of manufacturing process. The XPS survey spectra of the as-prepared samples indicate that the main elements in the near-surface region are carbon, silicon, and oxygen. The narrow-scan spectra of C1s, Si2p, O1s regions indicate that silicon and oxygen are mainly in the SiOx (x ≈ 2) oxide form, whereas the main component of C1s spectrum at 284.4 eV comes from the sp2-hybridized carbon phase. Micro-Raman spectra confirmed the formation of graphene films with the number of layers that depended on the distance between the graphite source and substrate.

  10. Transformation of Polar Ice Sublimate Residue into Martian Circumpolar Sand

    NASA Technical Reports Server (NTRS)

    Saunders, R. S.; Parker, T. J.; Stephens, J. B.; Laue, E. G.; Fanale, F. P.

    1985-01-01

    The experimental demonstration that a credible Martian sand may be formed from dust-bearing ice provides a new set of possible explanations for some of the observed Martian aeolian landforms. It is hypothesized that a light-weight fluffy rind is formed on the polar caps. This could provide material easily entrainable by Martian winds, which generally blow equatorward from the poles. These winds would peel the fluffy rind from the surface of the sublimating summer polar caps and from the equatorward slopes of the polar troughs. These pieces of material would then be rolled into lumps (of high sailarea/mass ratio) by the wind. They would become pigmented as they saltate across the surface, perhaps gathering carbonaceous meteoritic dust or other impurities on their surfaces, or through chemical reactions with the ice-free environment away from their point of origin. Once they became trapped in topographic wind shadows, they would form dune structures because they are hydraulically equivalent to sand particles.

  11. Generalized Orbital Projections of a Sublimating Ice Particle

    NASA Technical Reports Server (NTRS)

    Menkin, Evgeny; Bacon, Jack

    2006-01-01

    The issue of orbital debris resulting from human activities in space is a growing concern for the space users' community. Waste generated in Low Earth Orbit (LEO) can stay in orbit for a long time, creating significant hazards for other spacecraft flying at lower intercepting orbits. Many spacecraft, especially crewed vehicles, are required to vent fluids into space. These fluids include propellant, wastewater, excess condensate, and others. It is important to analyze the behavior of particles that result from these activities, since each individual particle is capable of damaging or destroying a spacecraft in a lower, crossing orbit, and such particles are invisible to tracking radar systems on the ground. The deorbit trajectory of an ice particle is complex. It depends on factors including attitude of the vehicle during vent, initial velocities of particles, altitude at which the vent occurred, and numerous evaporation and sublimation factors. These include contamination within the vented water, evolution of bubbles within the clear water, and sun flux factors such as time of the year and current beta angle. The purpose of this study is to examine the influences of these factors on the trajectories of ice particles resulting from condensate water dumps, and to bound the safe trajectories of spacecraft that lie below the venting spacecraft.

  12. Climatological observations and predicted sublimation rates at Lake Hoare, Antarctica.

    USGS Publications Warehouse

    Clow, G.D.; McKay, C.P.; Simmons, G.M.; Wharton, R.A.

    1988-01-01

    In December 1985, an automated meteorological station was established at Lake Hoare in the dry valley region of Antarctica. Here, we report on the first year-round observations available for any site in Taylor Valley. This dataset augments the year-round data obtained at Lake Vanda (Wright Valley) by winter-over crews during the late 1960s and early 1970s. The mean annual solar flux at Lake Hoare was 92 W m-2 during 1986, the mean air temperature -17.3 degrees C, and the mean 3-m wind speed 3.3 m s-1. The local climate is controlled by the wind regime during the 4-month sunless winter and by seasonal and diurnal variations in the incident solar flux during the remainder of the year. Temperature increases of 20 degrees-30 degrees C are frequently observed during the winter due to strong fo??hn winds descending from the Polar Plateau. A model incorporating nonsteady molecular diffusion into Kolmogorov-scale eddies in the interfacial layer and similarity-theory flux-profiles in the surface sublayer, is used to determine the rate of ice sublimation from the acquired meteorological data. Despite the frequent occurrence of strong winter fo??hns, the bulk of the annual ablation occurs during the summer due to elevated temperatures and persistent moderate winds. The annual ablation from Lake Hoare is estimated to have been 35.0 +/- 6.3 cm for 1986.

  13. Comparison of methods for quantifying surface sublimation over seasonally snow-covered terrain

    USGS Publications Warehouse

    Sexstone, Graham A.; Clow, David W.; Stannard, David I.; Fassnacht, Steven R.

    2016-01-01

    Snow sublimation can be an important component of the snow-cover mass balance, and there is considerable interest in quantifying the role of this process within the water and energy balance of snow-covered regions. In recent years, robust eddy covariance (EC) instrumentation has been used to quantify snow sublimation over snow-covered surfaces in complex mountainous terrain. However, EC can be challenging for monitoring turbulent fluxes in snow-covered environments because of intensive data, power, and fetch requirements, and alternative methods of estimating snow sublimation are often relied upon. To evaluate the relative merits of methods for quantifying surface sublimation, fluxes calculated by the EC, Bowen ratio–energy balance (BR), bulk aerodynamic flux (BF), and aerodynamic profile (AP) methods and their associated uncertainty were compared at two forested openings in the Colorado Rocky Mountains. Biases between methods are evaluated over a range of environmental conditions, and limitations of each method are discussed. Mean surface sublimation rates from both sites ranged from 0.33 to 0.36 mm day−1, 0.14 to 0.37 mm day−1, 0.10 to 0.17 mm day−1, and 0.03 to 0.10 mm day−1 for the EC, BR, BF and AP methods, respectively. The EC and/or BF methods are concluded to be superior for estimating surface sublimation in snow-covered forested openings. The surface sublimation rates quantified in this study are generally smaller in magnitude compared with previously published studies in this region and help to refine sublimation estimates for forested openings in the Colorado Rocky Mountains.

  14. Vacuum chamber with distributed titanium sublimation pumping for the G-line wiggler at Cornell High Energy Synchrotron Source

    NASA Astrophysics Data System (ADS)

    Li, Y.; He, Y.; Mistry, N. B.

    2003-07-01

    This article describes a 3-m-long vacuum chamber for the new wiggler magnet at the Cornell Electron Storage Ring (CESR) for the synchrotron light beam line of the Cornell High Energy Synchrotron Source (CHESS). Copper was chosen as the main chamber material for its good electric and thermal conductivities. Proper mechanical design and welding procedure were implemented to meet very tight tolerances to ensure adequate vertical aperture for the stored beams in CESR while allowing the required small wiggler gap. Distributed titanium sublimation pumping is incorporated along the 3 m length of the chamber to provide sufficient pumping speed and capacity for CESR and CHESS operations. The chamber pumping performance was evaluated prior to installation. Linear distributed pumping speeds at the beam line of ~720 l/s/m for N2 and CO and ~4000 l/s/m for H2 were measured. The measured pumping capacities for N2, CO and H2 are ~1.0, ~2.0 and ~77 Torr l, respectively, for each titanium sublimation cycle. Measurements also showed that CO molecules adsorb on the N2 and H2 saturated titanium films with virtually the same initial sticking coefficient as on a fresh titanium film. Analyses indicated very different CO adsorption mechanisms between the N2 and H2 saturated titanium films. While the replacement of surface H2 by CO was observed, little desorption of nitrogen was measured. Operational experience showed excellent vacuum pumping performance over two years after the chamber installation.

  15. Collection-efficient, axisymmetric vacuum sublimation module for the purification of solid materials

    NASA Astrophysics Data System (ADS)

    May, Michael; Paul, Elizabeth; Katovic, Vladimir

    2015-11-01

    A vacuum sublimation module of axisymmetric geometry was developed and employed to purify solid-phase materials. The module provides certain practical advantages and it comprises: a metering valve, glass collector, glass lower body, main seal, threaded bushing, and glass internal cartridge (the latter to contain starting material). A complementary process was developed to de-solvate, sublime, weigh, and collect solid chemical materials exemplified by oxalic acid, ferrocene, pentachlorobenzene, chrysene, and urea. The oxalic acid sublimate was analyzed by titration, melting range, Fourier Transform Infrared (FT-IR) Spectroscopy, cyclic voltammetry, and its (aqueous phase) electrolytically generated gas. The analytical data were consistent with a high-purity, anhydrous oxalic acid sublimate. Cyclic voltammograms of 0.11 mol. % oxalic acid in water displayed a 2.1 V window on glassy carbon electrode beyond which electrolytic decomposition occurs. During module testing, fifteen relatively pure materials were sublimed with (energy efficient) passive cooling and the solid-phase recovery averaged 95 mass %. Key module design features include: compact vertical geometry, low-angle conical collector, uniformly compressed main seal, modest power consumption, transparency, glovebox compatibility, cooling options, and preferential conductive heat transfer. To help evaluate the structural (module) heat transfer, vertical temperature profiles along the dynamically evacuated lower body were measured versus electric heater power: for example, an input of 18.6 W generated a temperature 443-K at the bottom. Experimental results and engineering calculations indicate that during sublimation, solid conduction is the primary mode of heat transfer to the starting material.

  16. Collection-efficient, axisymmetric vacuum sublimation module for the purification of solid materials.

    PubMed

    May, Michael; Paul, Elizabeth; Katovic, Vladimir

    2015-11-01

    A vacuum sublimation module of axisymmetric geometry was developed and employed to purify solid-phase materials. The module provides certain practical advantages and it comprises: a metering valve, glass collector, glass lower body, main seal, threaded bushing, and glass internal cartridge (the latter to contain starting material). A complementary process was developed to de-solvate, sublime, weigh, and collect solid chemical materials exemplified by oxalic acid, ferrocene, pentachlorobenzene, chrysene, and urea. The oxalic acid sublimate was analyzed by titration, melting range, Fourier Transform Infrared (FT-IR) Spectroscopy, cyclic voltammetry, and its (aqueous phase) electrolytically generated gas. The analytical data were consistent with a high-purity, anhydrous oxalic acid sublimate. Cyclic voltammograms of 0.11 mol. % oxalic acid in water displayed a 2.1 V window on glassy carbon electrode beyond which electrolytic decomposition occurs. During module testing, fifteen relatively pure materials were sublimed with (energy efficient) passive cooling and the solid-phase recovery averaged 95 mass %. Key module design features include: compact vertical geometry, low-angle conical collector, uniformly compressed main seal, modest power consumption, transparency, glovebox compatibility, cooling options, and preferential conductive heat transfer. To help evaluate the structural (module) heat transfer, vertical temperature profiles along the dynamically evacuated lower body were measured versus electric heater power: for example, an input of 18.6 W generated a temperature 443-K at the bottom. Experimental results and engineering calculations indicate that during sublimation, solid conduction is the primary mode of heat transfer to the starting material.

  17. Estimates of the Volume of Snowpack Sublimation in Arizona's Salt River Watershed

    NASA Astrophysics Data System (ADS)

    Svoma, B. M.

    2012-12-01

    The liquid equivalent volumes of snowpack sublimation, melt, and snowfall over the Salt River watershed, a major source of water for the Phoenix metropolitan area, will be estimated using the National Operational Hydrologic Remote Sensing Center's Snow Data Assimilation System (SNODAS) for the nine water years on record (i.e., 2004-2012). SNODAS integrates data from satellites, aircraft, and ground stations with downscaled output from numerical weather prediction models and an energy/mass balance snowpack model. The SNODAS dataset contains daily values of sublimation, snow water equivalent, snowfall, and melt, among other variables, at high (< 1 km2) resolution providing the opportunity to accurately estimate the volumes of snowpack balance variables for regions with complex topography. Snowpack ablation consists of sublimation and melting. Snow particles at sub-freezing temperatures will sublimate rather than melt if surrounded by air that is below the equilibrium water vapor pressure with respect to ice. When sublimation occurs, there is a direct loss of water from the given drainage basin when the vapor is carried away by the prevailing atmospheric flow. Preliminary analyses of water years 2005 (wet El Niño), 2007 (dry El Niño), 2008 (wet La Niña), and 2012 (dry La Niña) suggest that there is a substantial amount of sublimation over the Salt River watershed. From October 1 to April 30, approximately 16 percent of snowfall sublimated during the four years, ranging from approximately 98 million cubic meters (79,884 acre-feet) in water year 2005 to approximately 208 million cubic meters (168,726 acre-feet) in water year 2012. Sublimation is the most prevalent at the highest elevations of the watershed with more than 30 percent of snowfall sublimating at elevations above 2,744 meters above sea level. Of the four years analyzed, the sublimation to snowfall ratio was the highest for the two water years with anomalously high precipitation (i.e, 2005 and 2008). This

  18. Desorption and sublimation kinetics for fluorinated aluminum nitride surfaces

    SciTech Connect

    King, Sean W. Davis, Robert F.; Nemanich, Robert J.

    2014-09-01

    an additional high temperature peak at 910 °C with E{sub d} = 370 ± 10 kJ/mol that is consistent with both the dehydrogenation of surface AlOH species and H{sub 2} assisted sublimation of AlN. Similarly, N{sub 2} exhibited a similar higher temperature desorption peak with E{sub d} = 535 ± 40 kJ/mol that is consistent with the activation energy for direct sublimation of AlN.

  19. A centre-triggered magnesium fuelled cathodic arc thruster uses sublimation to deliver a record high specific impulse

    NASA Astrophysics Data System (ADS)

    Neumann, Patrick R. C.; Bilek, Marcela; McKenzie, David R.

    2016-08-01

    The cathodic arc is a high current, low voltage discharge that operates in vacuum and provides a stream of highly ionised plasma from a solid conducting cathode. The high ion velocities, together with the high ionisation fraction and the quasineutrality of the exhaust stream, make the cathodic arc an attractive plasma source for spacecraft propulsion applications. The specific impulse of the cathodic arc thruster is substantially increased when the emission of neutral species is reduced. Here, we demonstrate a reduction of neutral emission by exploiting sublimation in cathode spots and enhanced ionisation of the plasma in short, high-current pulses. This, combined with the enhanced directionality due to the efficient erosion profiles created by centre-triggering, substantially increases the specific impulse. We present experimentally measured specific impulses and jet power efficiencies for titanium and magnesium fuels. Our Mg fuelled source provides the highest reported specific impulse for a gridless ion thruster and is competitive with all flight rated ion thrusters. We present a model based on cathode sublimation and melting at the cathodic arc spot explaining the outstanding performance of the Mg fuelled source. A further significant advantage of an Mg-fuelled thruster is the abundance of Mg in asteroidal material and in space junk, providing an opportunity for utilising these resources in space.

  20. Experimental Study of influence on The Moving of Sublimation Interface by Precooling Rate and Drying Temperature During Freeze-drying

    NASA Astrophysics Data System (ADS)

    Xiao, Xin; Tao, Le-Ren

    2007-06-01

    For complex heat and mass transfer during freeze-drying, the shape and the moving rate of sublimation interface have not been clearly recognized yet. In this paper, Micro-CT scanner was used to follow the moving interface during sublimation. Apple slices cut into 16mm in diameter and 8mm in thickness were used as experimental samples, they were scanned every two hours during sublimation. The scanning images were analyzed and measured, then variation curves of grey value and curves of sublimation rate in two directions were obtained. The moving rates of sublimation interface under various precooling rates and primary drying temperatures were compared. The results show that, heat and mass transfer happens both at the upper and the under surface of the sample. Also it happens at the side surface to some extent. The interface shows as a three-dimensional moving mode, contracts to the geometric centre of the sample and presents an approximately spheral shape. Apple samples frozen at low rate sublimated more quickly than those by high rate. While drying temperature was higher, the sublimation interface moved more quickly. Under slow precooling condition, the sublimation rate rose quickly near the end of sublimation not only in vertical direction, but in horizontal direction.

  1. Mechanism and kinetics for ammonium dinitramide (ADN) sublimation: a first-principles study.

    PubMed

    Zhu, R S; Chen, Hui-Lung; Lin, M C

    2012-11-08

    The mechanism for sublimation of NH(4)N(NO(2))(2) (ADN) has been investigated quantum-mechanically with generalized gradient approximation plane-wave density functional theory calculations; the solid surface is represented by a slab model and the periodic boundary conditions are applied. The calculated lattice constants for the bulk ADN, which were found to consist of NH(4)(+)[ON(O)NNO(2)](-) units, instead of NH(4)(+)[N(NO(2))(2)](-), agree quite well with experimental values. Results show that three steps are involved in the sublimation/decomposition of ADN. The first step is the relaxation of the surface layer with 1.6 kcal/mol energy per NH(4)ON(O)NNO(2) unit; the second step is the sublimation of the surface layer to form a molecular [NH(3)]-[HON(O)NNO(2)] complex with a 29.4 kcal/mol sublimation energy, consistent with the experimental observation of Korobeinichev et al. (10) The last step is the dissociation of the [H(3)N]-[HON(O)NNO(2)] complex to give NH(3) and HON(O)NNO(2) with the dissociation energy of 13.9 kcal/mol. Direct formation of NO(2) (g) from solid ADN costs a much higher energy, 58.3 kcal/mol. Our calculated total sublimation enthalpy for ADN(s) → NH(3)(g) + HON(O)NNO(2)) (g), 44.9 kcal/mol via three steps, is in good agreement with the value, 42.1 kcal/mol predicted for the one-step sublimation process in this work and the value 44.0 kcal/mol computed by Politzer et al. (11) using experimental thermochemical data. The sublimation rate constant for the rate-controlling step 2 can be represented as k(sub) = 2.18 × 10(12) exp (-30.5 kcal/mol/RT) s(-1), which agrees well with available experimental data within the temperature range studied. The high pressure limit decomposition rate constant for the molecular complex H(3)N···HON(O)NNO(2) can be expressed by k(dec) = 3.18 × 10(13) exp (-15.09 kcal/mol/RT) s(-1). In addition, water molecules were found to increase the sublimation enthalpy of ADN, contrary to that found in the ammonium

  2. A neurobiological enquiry into the origins of our experience of the sublime and beautiful

    PubMed Central

    Ishizu, Tomohiro; Zeki, Semir

    2014-01-01

    Philosophies of aesthetics have posited that experience of the sublime—commonly but not exclusively derived from scenes of natural grandeur—is distinct from that of beauty and is a counterpoint to it. We wanted to chart the pattern of brain activity which correlates with the declared intensity of experience of the sublime, and to learn whether it differs from the pattern that correlates with the experience of beauty, reported in our previous studies (e.g., Ishizu and Zeki, 2011). 21 subjects participated in a functional magnetic resonance imaging experiment. Prior to the experiment, they viewed pictures of landscapes, which they rated on a scale of 1–5, with 5 being the most sublime and 1 being the least. This allowed us to select, for each subject, five sets of stimuli—from ones experienced as very sublime to those experienced as not at all sublime—which subjects viewed and re-rated in the scanner while their brain activity was imaged. The results revealed a distinctly different pattern of brain activity from that obtained with the experience of beauty, with none of the areas active with the latter experience also active during experience of the sublime. Sublime and beautiful experiences thus appear to engage separate and distinct brain systems. PMID:25426046

  3. Observations of the northern seasonal polar cap on Mars: I. Spring sublimation activity and processes

    USGS Publications Warehouse

    Hansen, C.J.; Byrne, S.; Portyankina, G.; Bourke, M.; Dundas, C.; McEwen, A.; Mellon, M.; Pommerol, A.; Thomas, N.

    2013-01-01

    Spring sublimation of the seasonal CO2 northern polar cap is a dynamic process in the current Mars climate. Phenomena include dark fans of dune material propelled out onto the seasonal ice layer, polygonal cracks in the seasonal ice, sand flow down slipfaces, and outbreaks of gas and sand around the dune margins. These phenomena are concentrated on the north polar erg that encircles the northern residual polar cap. The Mars Reconnaissance Orbiter has been in orbit for three Mars years, allowing us to observe three northern spring seasons. Activity is consistent with and well described by the Kieffer model of basal sublimation of the seasonal layer of ice applied originally in the southern hemisphere. Three typical weak spots have been identified on the dunes for escape of gas sublimed from the bottom of the seasonal ice layer: the crest of the dune, the interface of the dune with the interdune substrate, and through polygonal cracks in the ice. Pressurized gas flows through these vents and carries out material entrained from the dune. Furrows in the dunes channel gas to outbreak points and may be the northern equivalent of southern radially-organized channels (“araneiform” terrain), albeit not permanent. Properties of the seasonal CO2 ice layer are derived from timing of seasonal events such as when final sublimation occurs. Modification of dune morphology shows that landscape evolution is occurring on Mars today, driven by seasonal activity associated with sublimation of the seasonal CO2 polar cap.

  4. Distributed modelling of climate change impacts on snow sublimation in Northern Mongolia

    NASA Astrophysics Data System (ADS)

    Wimmer, F.; Schlaffer, S.; Aus der Beek, T.; Menzel, L.

    2009-08-01

    Sublimation of snow is an important factor of the hydrological cycle in Mongolia and is likely to increase according to future climate projections. In this study the hydrological model TRAIN was used to assess spatially distributed current and future sublimation rates based on interpolated daily data of precipitation, air temperature, air humidity, wind speed and solar radiation. An automated procedure for the interpolation of the input data is provided. Depending on the meteorological parameter and the data availability for the individual days, the most appropriate interpolation method is chosen automatically from inverse distance weighting, Ordinary Least Squares interpolation, Ordinary or Universal Kriging. Depending on elevation simulated annual sublimation in the period 1986-2006 was 23 to 35 mm, i.e. approximately 80% of total snowfall. Moreover, future climate projections for 2071-2100 of ECHAM5 and HadCM3, based on the A1B emission scenario of the Intergovernmental Panel on Climate Change, were analysed with TRAIN. In the case of ECHAM5 simulated sublimation increases by up to 17% (26...41 mm) while it remains at the same level for HadCM3 (24...34 mm). The differences are mainly due to a distinct increase in winter precipitation for ECHAM5. Simulated changes of the all-season hydrological conditions, e.g. the sublimation-to-precipitation ratio, were ambiguous due to diverse precipitation patterns derived by the global circulation models.

  5. Sublimation and Irradiation of Glycolaldehyde/Water Ices

    NASA Astrophysics Data System (ADS)

    Burke, Daren; Brown, W. A.; Viti, S.; Woods, P. M.; Slater, B.

    2012-05-01

    There is currently great interest among astronomers and astrobiologists in the inventory of organic molecules in space, in particular in star and planet-forming regions. Observations towards the Galactic Centre have revealed a rich and complex chemistry, from simple organic molecules such as methane (CH4) and methanol (CH3OH) to the recent detection of ethyl formate (C2H5OCHO) and n-propyl cyanide (C3H7CN). Amongst the most important organic species detected in space is glycolaldehyde (CH2OHCHO), an isomer of methyl formate (HCOOCH3) and acetic acid (CH3COOH). Glycolaldehyde is the simplest of the monosaccharide sugars and it reacts with propenal to form ribose, a central constituent of RNA. As a consequence, it is thought that glycolaldehyde may have a role in the origins of life in our universe. We present a detailed investigation of the adsorption and desorption of glycolaldehyde and methyl formate using temperature programmed desorption (TPD) and reflection absorption infrared spectroscopy (RAIRS) under ultra-high vacuum. The sublimation of glycolaldehyde/water and methyl formate/water containing ices from a model carbonaceous grain surface (graphite) will be presented, along with kinetic parameters for desorption (such as the binding energy, order of desorption and desorption pre-exponential factor) derived from analysis of TPD. These experimental parameters will be incorporated into astronomical models of star-forming regions. Additional experiments investigating the stability of glycolaldehyde/water containing ices to electron/UV irradiation will also be discussed. Electron irradiation (simulating the effect of cosmic ray ionisation, which produces electrons) and UV irradiation (over a range of wavelengths) is used to examine competing routes for non-thermal desorption, decomposition and formation. RAIRS and TPD will be used to identify any reaction products and to monitor the desorption/decomposition of glycolaldehyde as a function of irradiation time. This

  6. On the Size Dependences of the Metallic Nanoparticle Evaporation and Sublimation Heats: Thermodynamics and Atomistic Modeling

    NASA Astrophysics Data System (ADS)

    Bembel, A. G.

    2017-02-01

    Size dependences of the nanocrystal sublimation and the evaporation heats of the corresponding nanodrops are investigated using the isothermal molecular dynamics and the tight-binding potential (on examples of Ni and Au nanoparticles). Results of computer simulation demonstrating linear dependences of the evaporation and sublimation heats on the particle reciprocal radius are compared with results of thermodynamic calculations as well as with experimental data for bulk phases of the same metals. It has been found that the size dependences of the evaporation and sublimation heats are directly related with the behavior of the size dependence of the melting heat that in its turn correlates with structural transformations in nanoparticles induced by the change of their size. The conclusion is drawn that there is some characteristic nanoparticle size (of the order of 1 nm) at which its crystal and liquid states become indistinguishable.

  7. Sublimation and reformation of icy grains in the primitive solar nebula

    NASA Technical Reports Server (NTRS)

    Lunine, Jonathan I.; Engel, Steffi; Rizk, Bashar; Horanyi, Mihaly

    1991-01-01

    The quantity of water ice that sublimates during the free fall of grains into the solar nebula from a surrounding interstellar cloud varies from over 90 percent of the grain mass as 30 AU from the nebular center to less than 10 percent at more than 100 AU. Virtually all the water that is sublimated ultimately recondenses, since the cold nebular gas lying beyond 10 AU is unable to hold more than a small portion as vapor. The return of most of the gas to solid phase near the nebular ambient temperature, of about 50 K, may result in at least two grain populations consisting, in one case, of unaltered interstellar grains which did not undergo sublimation, and in the other of water ice which cocondensed with more volatile gases at nebular ambient temperatures to yield volatile-rich amorphous phases.

  8. Conduction type control from n to p type for organic pigment films purified by reactive sublimation

    NASA Astrophysics Data System (ADS)

    Hiramoto, Masahiro; Ihara, Kiyoaki; Fukusumi, Hiroyuki; Yokoyama, Masaaki

    1995-12-01

    The effects of purification by reactive sublimation technique and bromine doping on the Fermi level and the photovoltaic properties of n-type perylene pigment films were investigated. Photovoltage arisen from the Schottky junction between n-type perylene pigment film and Au increased significantly by repeating the train sublimation under methylamine gas atmosphere. This phenomenon was revealed to be due to the negative shift of the Fermi level resulting from the effective removal of unknown but specific impurity acting as an acceptor by reactive sublimation. On the other hand, by bromine doping, Fermi level of the pigment film shifted largely to a positive direction and reached the nearby valence band, while the direction of photocurrent flow arising from the Schottky junction with Au was reversed. This result is a clear demonstration of alternating the type of conduction from n type to p type. This means that the pn control of organic semiconductors is possible.

  9. The Effect of CO2 Ice Cap Sublimation on Mars Atmosphere

    NASA Technical Reports Server (NTRS)

    Batterson, Courtney

    2016-01-01

    Sublimation of the polar CO2 ice caps on Mars is an ongoing phenomenon that may be contributing to secular climate change on Mars. The transfer of CO2 between the surface and atmosphere via sublimation and deposition may alter atmospheric mass such that net atmospheric mass is increasing despite seasonal variations in CO2 transfer. My study builds on previous studies by Kahre and Haberle that analyze and compare data from the Phoenix and Viking Landers 1 and 2 to determine whether secular climate change is happening on Mars. In this project, I use two years worth of temperature, pressure, and elevation data from the MSL Curiosity rover to create a program that allows for successful comparison of Curiosity pressure data to Viking Lander pressure data so a conclusion can be drawn regarding whether CO2 ice cap sublimation is causing a net increase in atmospheric mass and is thus contributing to secular climate change on Mars.

  10. On the sublimation of blowing snow and of snow in canopies

    NASA Astrophysics Data System (ADS)

    Taylor, P. A.; Simon, K.; Gordon, M.; Weng, W.

    2003-04-01

    Tests have been made within the Canadian Land Surface Scheme (CLASS) of various parameterizations of sublimation of blowing snow, and tested in the context of data from weather stations (Goose Bay and Resolute) in northern Canada. We will focus on parameterization schemes based on results obtained with the PIEKTUK model of blowing snow. In addition we will present preliminary results concerning the parameterization of sublimation of snow caught in tree canopies, using schemes similar to those for evaporation from wet canopies. This is considered to be a major factor in the water budgets of forested areas in northern Canada.

  11. Matrix sublimation method for the formation of high-density amorphous ice

    NASA Astrophysics Data System (ADS)

    Kouchi, A.; Hama, T.; Kimura, Y.; Hidaka, H.; Escribano, R.; Watanabe, N.

    2016-08-01

    A novel method for the formation of amorphous ice involving matrix sublimation has been developed. A CO-rich CO:H2O mixed ice was deposited at 8-10 K under ultra-high vacuum condition, which was then allowed to warm. After the sublimation of matrix CO at 35 K, amorphous ice remained. The amorphous ice formed exhibits a highly porous microscale texture; however, it also rather exhibits a density similar to that of high-density amorphous ice formed under high pressure. Furthermore, unlike conventional vapor-deposited amorphous ice, the amorphous ice is stable up to 140 K, where it transforms directly to cubic ice Ic.

  12. Sublimation of hydrofullerenes C 60H 36 and C 60H 18

    NASA Astrophysics Data System (ADS)

    Dorozhko, P. A.; Lobach, A. S.; Popov, A. A.; Senyavin, V. M.; Korobov, M. V.

    2001-03-01

    Thermal behavior of two hydrofullerenes, C 60H 36 and C 60H 18, was studied by means of Knudsen cell mass-spectrometry and infrared spectroscopy. Vapor pressures and enthalpies of sublimation at T=550-685 K were measured. Sublimation of the hydrofullerenes was accompanied by partial loss of hydrogen. Decomposition of C 60H 36 was confirmed to be a stepwise process with formation of C 60H 18 as an intermediate product. The material of the Knudsen cell strongly affected the partial pressures and mass-spectra of the hydrofullerene vapor species.

  13. Recommendations for a Kalman filter to estimate and control freeze and sublime rates of gaseous diffusion plant freezer/sublimer systems

    SciTech Connect

    Ruppel, F.R.

    1992-09-01

    A signal is required to control the flow of UF{sub 6} in gaseous diffusion plant freezer/sublimer systems. The original strategy envisioned for deriving a flow signal was to take the derivative of the freezer/sublimer weigh cell signal. However, the derivative of the digitized weight signal is noisy, preventing good control. In addition, a disturbance is introduced into the weight derivative signal because a refrigerant is circulated through a shell-and-tube heat exchanger inside the freezer/sublimer. The weight of the refrigerant is included in the weight measured by the weigh cell. If the circulation rate of the refrigerant is not steady state, a disturbance exists. Measurements of upstream pressure, vessel pressure, and output to the system control valve are available to the control system. Thus, if the flow through the control valve is characterized properly by these measurements, a Kalman filter can be used in conjunction with these auxiliary inputs and the weigh cell input to overcome the noise and disturbance problem and provide an improved estimate of flow rate. A discussion of the development of a Kalman filter that could be used for this application is given, and recommendations are given for its implementation.

  14. Sorbent, Sublimation, and Icing Modeling Methods: Experimental Validation and Application to an Integrated MTSA Subassembly Thermal Model

    NASA Technical Reports Server (NTRS)

    Bower, Chad; Padilla, Sebastian; Iacomini, Christie; Paul, Heather L.

    2010-01-01

    This paper details the validation of modeling methods for the three core components of a Metabolic heat regenerated Temperature Swing Adsorption (MTSA) subassembly, developed for use in a Portable Life Support System (PLSS). The first core component in the subassembly is a sorbent bed, used to capture and reject metabolically produced carbon dioxide (CO2). The sorbent bed performance can be augmented with a temperature swing driven by a liquid CO2 (LCO2) sublimation heat exchanger (SHX) for cooling the sorbent bed, and a condensing, icing heat exchanger (CIHX) for warming the sorbent bed. As part of the overall MTSA effort, scaled design validation test articles for each of these three components have been independently tested in laboratory conditions. Previously described modeling methodologies developed for implementation in Thermal Desktop and SINDA/FLUINT are reviewed and updated, their application in test article models outlined, and the results of those model correlations relayed. Assessment of the applicability of each modeling methodology to the challenge of simulating the response of the test articles and their extensibility to a full scale integrated subassembly model is given. The independent verified and validated modeling methods are applied to the development of a MTSA subassembly prototype model and predictions of the subassembly performance are given. These models and modeling methodologies capture simulation of several challenging and novel physical phenomena in the Thermal Desktop and SINDA/FLUINT software suite. Novel methodologies include CO2 adsorption front tracking and associated thermal response in the sorbent bed, heat transfer associated with sublimation of entrained solid CO2 in the SHX, and water mass transfer in the form of ice as low as 210 K in the CIHX.

  15. Arrays of widely spaced atomic steps on Si(1 1 1) mesas due to sublimation

    NASA Astrophysics Data System (ADS)

    Chang, Kee-Chul; Blakely, Jack M.

    2005-10-01

    Steps with spacings of microns form on top of mesas fabricated on Si(1 1 1) that is annealed at temperatures where sublimation becomes important. Upon annealing, mesas first develop ridges along their edges, effectively creating craters which then become step-free by a step flow process described in the literature [S. Tanaka, C.C. Umbach, J.M. Blakely, R.M. Tromp, M. Mankos, Appl. Phys. Lett. 69 (9) (1996) 1235; Y. Homma, N. Aizawa, T. Ogino, Jpn. J. Appl. Phys. 35 (2B) (1996) L241]. Due to the miscut of the average surface from (1 1 1), ridge breakdown occurs on one edge of each mesa as sublimation proceeds. The breakdown point then acts as a source of steps which spread out over the mesa surface. The distribution of steps in the resulting step train depends on the sublimation rate, direct step-step interaction and the diffusive exchange of atoms among the steps. Insight into the role of these processes on the self-organization of the wide terrace distributions is provided by computer simulations using BCF (Burton, Cabrera and Frank) theory. This shows that step spacing can be controlled by varying the annealing temperature and the deposition flux. Comparison of the experimental and predicted step distributions suggest that the dynamics of the widely spaced steps are sublimation limited.

  16. Undergraduate Laboratory Experiment Facilitating Active Learning of Concepts in Transport Phenomena: Experiment with a Subliming Solid

    ERIC Educational Resources Information Center

    Utgikar, Vivek P.

    2015-01-01

    An experiment based on the sublimation of a solid was introduced in the undergraduate Transport Phenomena course. The experiment required the students to devise their own apparatus and measurement techniques. The theoretical basis, assignment of the experiment, experimental results, and student/instructor observations are described in this paper.…

  17. How to Kill a Journalism School: The Digital Sublime in the Discourse of Discontinuance

    ERIC Educational Resources Information Center

    McDevitt, Michael; Sindorf, Shannon

    2012-01-01

    The authors argue that journalism's uncertain identity in academia has made it vulnerable to unreflective instrumentalism in the digital era. They show how instrumentalism intertwined with the digital sublime constitutes a rhetorically resonate rationale for closing a journalism school. Evidence comes from documents and testimony associated with…

  18. Sublimation process and physical properties of vapor grown γ-In2Se3 platelet crystals

    NASA Astrophysics Data System (ADS)

    Ajayakumar, C. J.; Kunjomana, A. G.

    2016-11-01

    Indium selenide (γ-In2Se3) crystals have been grown by the closed tube sublimation process in the absence of seed crystals and chemical transporting agents. The composition, structure and morphology of the samples grown under different vacuum conditions were examined by energy dispersive analysis, X-ray diffraction, and scanning electron microscope. Structural features of the crystals obtained in a vacuum of 10-3 mbar exhibited a few reflections not belonging to γ phase, whereas X-ray diffraction spectra of the crystals deposited under a vacuum of 10-6 mbar revealed evidence of sharp peaks with high intensities of γ-In2Se3 crystalline phase. When growth runs were performed for 72 h, voids were observed on the surface whereas for a duration of 120 h, platelet crystals were obtained. Optical properties of these samples were investigated using the FT-IR and photoluminescence spectroscopy. The average transmittance of the platelets in the visible and near infrared region of solar spectrum was found to be ∼81% and an optical band gap of ∼2.05 eV was computed from the transmission spectrum. Photoluminescence spectra of the grown In2Se3 crystals recorded at room temperature using an excitation laser of wavelength 355 nm showed a peak in the near band edge emission (NBE) corresponding to an energy of 2.01 eV. Under an illumination power of 12 mW/cm2, the photocurrent increased linearly with applied voltage and the dark current was found to be 2.5×10-9 A for 10 V. These results suggest that the as-grown γ-In2Se3 platelets crystallized from vapor deposition, possess superior optoelectronic properties than the other phases for solar cell applications.

  19. Sublimation of ice-tholins mixtures: A morphological and spectro-photometric study

    NASA Astrophysics Data System (ADS)

    Poch, Olivier; Pommerol, Antoine; Jost, Bernhard; Carrasco, Nathalie; Szopa, Cyril; Thomas, Nicolas

    2016-03-01

    Sublimation, the direct transition from solid to gas phase, is a process responsible for shaping and changing the reflectance properties of many Solar System surfaces. In this study, we have characterized the evolution of the structure/texture and of the visible and near-infrared (VIS-NIR) spectral reflectance of surfaces made of water ice mixed with analogues of complex extraterrestrial organic matter, named tholins, under low temperature (<-70 °C) and pressure (10-5 mbar) conditions. The experiments were carried out in the SCITEAS simulation setup recently built as part of the Laboratory for Outflow Studies of Sublimating Materials (LOSSy) at the University of Bern (Pommerol, A. et al. [2015a]. Planet. Space Sci. 109-110, 106-122). As the water ice sublimated, we observed in situ the formation of a sublimation lag deposit made of a water-free porous (>90% porosity) network of organic filaments on top of the ice. The temporal evolution of the tholins and water ice spectral features (reflectance at the absorption bands wavelengths, red slope, from 0.40 to 1.90 μm) are analyzed throughout the sublimation of the samples. We studied how different mixtures of tholins with water (0.1 wt.% tholins as coating or inclusions within the water particles), and different ice particle sizes (4.5 ± 2.5 or 67 ± 31 μm) influence the morphological and spectral evolutions of the samples. The sublimation of the ice below the mantle produces a gas flow responsible for the ejection of mm to cm-sized fragments of the deposit in outbursts-like events. The results show remarkable differences between these samples in term of mantle structure, speed of mantle building, rates and surface area of mantle ejections. These data provide useful references for interpreting remote-sensing observations of icy Solar System surfaces, in particular the activity of comet nuclei where sublimation of organic-rich ices and deposition of organic-dust particles likely play a major role. Consequently, the

  20. Sublimation of natural amino acids and induction of asymmetry by meteoritic amino acids

    NASA Astrophysics Data System (ADS)

    Tarasevych, Arkadii V.; Guillemin, Jean-Claude

    It is believed that the homochirality of building blocks of life like amino acids (AAs) and sugars is a prerequisite requirement for the origin and evolution of life. Among different mechanisms that might have triggered the initial disparity in the enantiomeric ratio on the primitive Earth, the key roles were assigned to: (i) local chiral symmetry breaking and (ii) the inflow of extraterrestrial matter (eg the carbonaceous meteorites containing non-racemic AAs). Recently it has been revealed that sublimation, a subject almost completely neglected for a long time, gives a pathway to enantioenrichment of natural AAs (1,2 and references herein). Sublimation is however one of the key physical processes that occur on comets. Starting from a mixture with a low content of an enantiopure AA, a partial sublimation gives an important enrichment of the sublimate (1,2). The resulted disparity in the ratio between enantiomers of a partial sublimate is determined by the crystalline nature of the starting mixture: we observed a drastic difference in the behavior of (i) mixtures based on true racemic compounds and (ii) mechanical mixtures of two enantiopure solid phases. On the other hand, combination of crystallization and sublimation can lead to segregation of enantioenriched fractions starting from racemic composition of sublimable aliphatic AAs (Ala, Leu, Pro, Val) in mixtures with non-volatile enantiopure ones (Asn, Asp, Glu, Ser, Thr) (3). The resulted sense of chirality correlates with the handedness of the non-volatile AAs: the observed changes in enantiomeric ratios clearly demonstrate the preferential homochiral interactions and a tendency of natural amino acids to homochiral self-organization. It is noteworthy that just these 5 (Asn, Asp, Glu, Ser, Thr) out of 22 proteinogenic amino acids are able to local symmetry breaking. On the other hand, recent data on the enantiomeric composition of the Tagish Lake, a C2-type carbonaceous meteorite, revealed a large L

  1. Spring Sublimation of the Seasonal Condensates on Mars from Omega/Mars Express

    NASA Astrophysics Data System (ADS)

    Schmitt, B.; Douté, S.; Langevin, Y.; Forget, F.; Bibring, J.; Bellucci, G.; Altieri, F.; Poulet, F.; Gondet, B.

    2005-12-01

    The formation and sublimation of the seasonal deposits on Mars surface are major elements controlling its atmospheric circulation and its climate. A complex competition occurs between sublimation of CO2 frost, inter-hemispheric transports and snow deposition/condensation in the opposite polar regions. Water is released by different sources (caps, condensates, soil) but their locations and contributions are not yet well known. Before the Mars Express mission the evolution of the seasonal condensations have been essentially monitored by following the albedo and temperature changes of the surface (TES, MOC/MGS). Since January 2004 the OMEGA imaging spectrometer allows us to directly monitor the abundance, physical state and distribution of the CO2, water and dust components of the martian frosts and ices through their visible and near-infrared spectral signatures. In particular, the monitoring of the evolution of the frost composing the seasonal caps provides strong constraints on the microphysics of the sublimation/condensation/deposition processes of volatiles as well as on their seasonal cycle. The abundance of the dust co-deposited with ices should also constrain the dust loading and transport processes. We present the latitudinal evolution of the composition and physical state of the ices composing the seasonal deposits from the north pole to the crocus line, as seen by OMEGA. Then we describe the temporal evolution of the spatial distribution of CO2 frost and H2O ice during spring sublimation of the northern seasonal condensates. In particular a wide annulus of a thin layer of dusty water ice forms at the fringe of the recessing CO2 seasonal cap and moves towards higher latitudes as sublimation progress. All this information allows us to draw a coupled microphysical and latitudinal evolution sketch of the seasonal frosts. Implications and constraints on Mars GCMs will be analyzed.

  2. Preparation of highly porous gastroretentive metformin tablets using a sublimation method.

    PubMed

    Oh, Tack-Oon; Kim, Ju-Young; Ha, Jung-Myung; Chi, Sang-Cheol; Rhee, Yun-Seok; Park, Chun-Woong; Park, Eun-Seok

    2013-04-01

    The present investigation is aimed to formulate floating gastroretentive tablets containing metformin using a sublimation material. In this study, the release of the drug from a matrix tablet was highly dependent on the polymer concentrations. In all formulations, initial rapid drug release was observed, possibly due to the properties of the drug and polymer. The effect of the amount of PEO on swelling and eroding of the tablets was determined. The water-uptake and erosion behavior of the gastroretentive (GR) tablets were highly dependent on the amount of PEO. The water-uptake increased with increasing PEO concentration in the tablet matrix. The weight loss from tablets decreased with increasing amounts of PEO. Camphor was used as the sublimation material to prepare GR tablets that are low-density and easily floatable. Camphor was changed to pores in the tablet during the sublimation process. SEM revealed that the GR tablets have a highly porous morphology. Floating properties of tablets and tablet density were affected by the sublimation of camphor. Prepared floating gastroretentive tablets floated for over 24 h and had no floating lag time. However, as the amount of camphor in the tablet matrix increased, the crushing strength of the tablet decreased after sublimation. Release profiles of the drug from the GR tablets were not affected by tablet density or porosity. In pharmacokinetic studies, the mean plasma concentration of the GR tablets after oral administration was greater than the concentration of glucophase XR. Also, the mean AUC(0-∞) values for the GR tablets were significantly greater than the plasma concentrations of glucophase XR.

  3. "Back-fire to lust": G. Stanley Hall, sex-segregated schooling, and the engine of sublimation.

    PubMed

    Graebner, William

    2006-08-01

    G. Stanley Hall was an advocate of sex-segregated schooling long after most Americans had accepted coeducation. His position was based in part on personal experience: observations of his father and mother, a repressed and guilt-ridden boyhood sexuality, and his conviction that his own career success was a product of sublimated sexual desire, of erotic energy converted into mental energy. Hall theorized that coeducation put sublimation at risk, and that sex-segregated schools, by contributing to proper gendered development and by prolonging and sublimating the sexual tensions of adolescence, would produce social progress.

  4. Three-dimensional textures and defects of soft material layering revealed by thermal sublimation

    PubMed Central

    Yoon, Dong Ki; Kim, Yun Ho; Kim, Dae Seok; Oh, Seong Dae; Smalyukh, Ivan I.; Clark, Noel A.; Jung, Hee-Tae

    2013-01-01

    Layering is found and exploited in a variety of soft material systems, ranging from complex macromolecular self-assemblies to block copolymer and small-molecule liquid crystals. Because the control of layer structure is required for applications and characterization, and because defects reveal key features of the symmetries of layered phases, a variety of techniques have been developed for the study of soft-layer structure and defects, including X-ray diffraction and visualization using optical transmission and fluorescence confocal polarizing microscopy, atomic force microscopy, and SEM and transmission electron microscopy, including freeze-fracture transmission electron microscopy. Here, it is shown that thermal sublimation can be usefully combined with such techniques to enable visualization of the 3D structure of soft materials. Sequential sublimation removes material in a stepwise fashion, leaving a remnant layer structure largely unchanged and viewable using SEM, as demonstrated here using a lamellar smectic liquid crystal. PMID:24218602

  5. Water drops dancing on ice: how sublimation leads to drop rebound.

    PubMed

    Antonini, C; Bernagozzi, I; Jung, S; Poulikakos, D; Marengo, M

    2013-07-05

    Drop rebound is a spectacular event that appears after impact on hydrophobic or superhydrophobic surfaces but can also be induced through the so-called Leidenfrost effect. Here we demonstrate that drop rebound can also originate from another physical phenomenon, the solid substrate sublimation. Through drop impact experiments on a superhydrophobic surface, a hot plate, and solid carbon dioxide (commonly known as dry ice), we compare drop rebound based on three different physical mechanisms, which apparently share nothing in common (superhydrophobicity, evaporation, and sublimation), but lead to the same rebound phenomenon in an extremely wide temperature range, from 300 °C down to even below -79 °C. The formation and unprecedented visualization of an air vortex ring around an impacting drop are also reported.

  6. Controlling Gaussian and mean curvatures at microscale by sublimation and condensation of smectic liquid crystals

    NASA Astrophysics Data System (ADS)

    Kim, Dae Seok; Cha, Yun Jeong; Kim, Mun Ho; Lavrentovich, Oleg D.; Yoon, Dong Ki

    2016-01-01

    Soft materials with layered structure such as membranes, block copolymers and smectics exhibit intriguing morphologies with nontrivial curvatures. Here, we report restructuring the Gaussian and mean curvatures of smectic A films with free surface in the process of sintering, that is, reshaping at elevated temperatures. The pattern of alternating patches of negative, zero and positive mean curvature of the air-smectic interface has a profound effect on the rate of sublimation. As a result of sublimation, condensation and restructuring, initially equilibrium smectic films with negative and zero Gaussian curvature are transformed into structures with pronounced positive Gaussian curvature of layers packing, which are rare in the samples obtained by cooling from the isotropic melt. The observed relationship between the curvatures, bulk elastic behaviour and interfacial geometries in sintering of smectic liquid crystals might pave the way for new approaches to control soft morphologies at micron and submicron scales.

  7. Adamantane derivatives of sulfonamides: sublimation, solubility, solvation and transfer processes in biologically relevant solvents.

    PubMed

    Perlovich, G L; Volkova, T V; Sharapova, A V; Kazachenko, V P; Strakhova, N N; Proshin, A N

    2016-04-07

    Eight adamantane derivatives of sulfonamides were synthesized and characterized. Temperature dependencies of saturation vapor pressure were obtained using the transpiration method and thermodynamic functions of the sublimation processes were calculated. Solubility values of the selected compounds in buffer (pH 7.4), 1-octanol and 1-hexane were determined at different temperatures using the isothermal saturation method. Thermophysical characteristics of fusion processes (melting points and fusion enthalpies) of the substances were studied using the DSC method. Transfer processes from buffer to 1-octanol, from buffer to 1-hexane and 1-hexane to 1-octanol were analyzed. The impact of the molecules' structural modification on sublimation, solubility and solvation/hydration processes in the solvents was studied. Correlation equations connecting the thermodynamic functions with physicochemical descriptors were obtained.

  8. Darwin's sublime: the contest between reason and imagination in On the Origin of Species.

    PubMed

    Bradley, Benjamin Sylvester

    2011-01-01

    Recent Darwin scholarship has provided grounds for recognising the Origin as a literary as well as a scientific achievement. While Darwin was an acute observer, a gifted experimentalist and indefatigable theorist, this essay argues that it was also crucial to his impact that the Origin transcended the putative divide between the scientific and the literary. Analysis of Darwin's development as a writer between his journal-keeping on HMS Beagle and his construction of the Origin argues the latter draws on the pattern of the Romantic or Kantian sublime. The Origin repeatedly uses strategies which challenge the natural-theological appeal to the imagination in conceiving nature. Darwin's sublime coaches the Origin's readers into a position from which to envision nature that reduces and contains its otherwise overwhelming complexity. As such, it was Darwin's literary achievement that enabled him to fashion a new 'habit of looking at things in a given way' that is the centrepiece of the scientific revolution bearing his name.

  9. Dehydration polycondensation of dicarboxylic acids and diols using sublimating strong brønsted acids.

    PubMed

    Moyori, Takaya; Tang, Tang; Takasu, Akinori

    2012-05-14

    We investigated catalytic activities of strong brønsted acids for dehydration polycondensations of dicarboxylic acids and diols, which were carried out at low temperature (<100 °C) under reduced pressure (0.3-3 mmHg). Strong Brønsted acids, bis(perfluoroalkanesulfonyl)imide and perfluoroalkanesulfonic acid, showed higher activity than p-toluenesulfonic acid or rare-earth catalysts at 60 °C. In particular, bis(nonafluorobutanesulfonyl)imide (Nf(2)NH) showed the highest activity to synthesize not only aliphatic polyester (M(n) > 19000) but also aromatic polyester (M(n) > 7000). The used Nf(2)NH was sublimated from the reaction flask during polycondensation, and the sublimate, Nf(2)NH, was extra pure so that we can reuse the catalyst without loss of the activity in the dehydration polycondensations.

  10. Spectroscopy of lithium atoms sublimated from isolation matrix of solid Ne.

    PubMed

    Sacramento, R L; Scudeller, L A; Lambo, R; Crivelli, P; Cesar, C L

    2011-10-07

    We have studied, via laser absorption spectroscopy, the velocity distribution of (7)Li atoms released from a solid neon matrix at cryogenic temperatures. The Li atoms are implanted into the Ne matrix by laser ablation of a solid Li precursor. A heat pulse is then applied to the sapphire substrate sublimating the matrix together with the isolated atoms at around 12 K. We find interesting differences in the velocity distribution of the released Li atoms from the model developed for our previous experiment with Cr [R. Lambo, C. C. Rodegheri, D. M. Silveira, and C. L. Cesar, Phys. Rev. A 76, 061401(R) (2007)]. This may be due to the sublimation regime, which is at much lower flux for the Li experiment than for the Cr experiment, as well as to the different collisional cross sections between those species to the Ne gas. We find a drift velocity compatible with Li being thermally sublimated at 11-13 K, while the velocity dispersion around this drift velocity is low, around 5-7 K. With a slow sublimation of the matrix we can determine the penetration depth of the laser ablated Li atoms into the Ne matrix, an important information that is not usually available in most matrix isolation spectroscopy setups. The present results with Li, together with the previous results with Cr suggest this to be a general technique for obtaining cryogenic atoms, for spectroscopic studies, as well as for trap loading. The release of the isolated atoms is also a useful tool to study and confirm details of the matrix isolated atoms which are masked or poorly understood in the solid.

  11. APPARATUS FOR CHARGING A RECEPTACLE WITH A DENSE SUBLIMATE FORM OF URANIUM CHLORIDE

    DOEpatents

    Davidson, P.H.

    1959-08-18

    An apparatus for filling a tubular storage receptacle with a dense massive form of uranium chloride is described. The apparatus includes an evacuated housing divided into a vaporizing chamber and a portion adapted to receive the receptacle. A nozzle conducts vaporized uranium chloride from the chamber to the interior of the receptacle. The nozzle is withdrawable to progressively deposit the uranium chloride under controlled conditions to produce a dense sublimate which fills the receptacle.

  12. Sublimating icy planetesimals as the source of nucleation seeds for grain condensation in classical novae

    NASA Technical Reports Server (NTRS)

    Matese, John J.; Whitmire, D. P.; Reynolds, R. T.

    1989-01-01

    The problem of grain nucleation during novae outbursts is a major obstacle to our understanding of dust formation in these systems. How nucleation seeds can form in the hostile post-outburst environment remains an unresolved matter. It is suggested that the material for seeding the condensation of ejecta outflow is stored in a primordial disk of icy planetesimals surrounding the system. Evidence is presented that the requisite number of nucleation seeds can be released by sublimation of the planetesimals during outbursts.

  13. Glaciers of the McMurdo dry valleys: Terrestrial analog for Martian polar sublimation

    NASA Astrophysics Data System (ADS)

    MacClune, Karen Lewis; Fountain, Andrew G.; Kargel, Jeffery S.; MacAyeal, Douglas R.

    2003-04-01

    The surfaces of the Martian north and south polar residual caps are marked by unusual ice features: Dark spiralesque troughs up to 1 km deep, 10 km wide, and 300 km long appear on both ice caps, and circular pits that make up the ``Swiss cheese'' terrain appear on the south polar cap. Both types of features are of interest to researchers as a potential means of understanding ice composition and flow rates. Some glaciers of the McMurdo dry valleys have surface features unknown elsewhere on terrestrial glaciers, including canyons over 6 km long, 100 m wide, and tens of meters deep and basins up to 100 m across. High sublimation, dust accumulation, and very little melting is key to their origin. These processes and ice landforms are suggested as terrestrial analogs for the sublimation behavior of Martian ice caps, where dust accumulation and sublimation are significant but surface melting is absent. We have developed a solar radiation model of canyon formation and have applied it to the Martian polar caps. The modeled processes do well to describe direct and reflected radiation within V grooves, a process that may be significant in the development of the spiral troughs and Swiss cheese terrain. The model fails to reproduce the low observed slopes of the Martian troughs. The grooves are too shallow, with opening angles of ~165° compared with model predictions of ~90°. The reason for the failure may be that we have not included creep closure, which should flatten their slopes.

  14. Formulation Design and Optimization of Orodispersible Tablets of Quetiapine Fumarate by Sublimation Method

    PubMed Central

    Kalyankar, P.; Panzade, P.; Lahoti, S.

    2015-01-01

    The objective of present study was to formulate directly compressible orodispersible tablets of quetiapine fumarate by sublimation method with a view to enhance patient compliance. A full 32 factorial design was used to investigate the effect of two variables viz., concentration of Indion 414 and camphor. Indion 414 (3-5 % w/w) was used as superdisintegrant and camphor (5-15 % w/w) as subliming agent. The tablets were evaluated for thickness, weight variation, hardness, friability, content uniformity, wetting time, porosity, in vitro disintegration time and in vitro drug release. The formulation containing 5% w/w of Indion 414 and 5% w/w camphor was emerged as promising based on evaluation parameters. The disintegration time for optimized formulation was 18.66 s. The tablet surface was evaluated for presence of pores by scanning electron microscopy before and after sublimation. Differential scanning colorimetric study did not indicate any drug excipient incompatibility, either during mixing or after compression. The effect of independent variables on disintegration time, % drug release and friability is presented graphically by surface response plots. Short-term stability studies on the optimized formulation indicated no significant changes in drug content and in vitro disintegration time. The directly compressible orodispersible tablets of quetiapine fumarate with lower friability, greater drug release and shorter disintegration times were obtained using Indion 414 and camphor at optimum concentrations. PMID:26180271

  15. Enhancement of Sublimation of Single Graphene Layer by Interacting with Gas Molecules in Rarefied Environment

    NASA Astrophysics Data System (ADS)

    Murugesan, Ramki; Park, Jae Hyun

    2014-11-01

    Graphene has excellent mechanical properties. One of them is the resistance to high temperature environment. Since the sublimation temperature of graphene is over 4500 K, it has been used for diverse high temperature applications in order to protect the system. In this study, using extensive molecular dynamics simulations, we show that the sublimation of graphene could be enhanced (occurs at the lower temperature) by interacting with the gas molecules. With increase in temperature, the bonds in graphene becomes so sensitive to interact with the incoming gas molecules. When the temperature is low, the graphene is stable to the impingement of gas molecules: The light H2 gases are stick to the graphene surface and remains being attached while the heavy CO2 and H2O are bounced back from the surface. However, at high temperature H2 gases are absorbed on the graphene and destroy the C -C bonds by forming C -H bonds. The local breakage of bond at the impingement spot spreads the entire graphene soon, causing a complete sublimation. Even though the heavy CO2 and H2O molecules also break the C -C bonds at high temperature,but their impingement effect is localized and the breakage does not propagate over the entire surface. This research was supported by Agency for Defence Development (ADD).

  16. Formation of the dumbbell-like nucleus of a comet by sublimation

    NASA Astrophysics Data System (ADS)

    Vavilov, Dmitrii; Medvedev, Yurii; Zatitskiy, Pavel

    2016-10-01

    The nucleus of the comet 67P/Churyumov-Gerasimenko is an elongated body with a deep groove around the middle. There are also other comets that look like dumbbells (e.g. 103P/Hartley 2, 19P/Borrelly, 1P/Halley). Two most probable interpretations are discussed in the scientific society. The first hypothesis explains the creation of such an object as sticking of two cometesimals during the process of formation. The second one suggests that the sublimation process can change the nucleus shape and make a groove in the middle.In this work we consider the second hypothesis. It was assumed that the spin axis of the nucleus is perpendicular to the plane of the cometary orbit and that initially the nucleus shape is a sphere. Thus, the problem is represented as a differential equation, which describes the change of the cometary nucleus. We solved this equation analytically. It was shown that initially a convex cometary nucleus (e.g. a sphere), consisting of homogeneous material, can not be transformed into a dumbbell-like body by the influence of sublimation. However, assuming that the density in the centre of the nucleus is less than on the surface, a groove can arise on the equator of the cometary nucleus as a result of sublimation.

  17. Formulation Design and Optimization of Orodispersible Tablets of Quetiapine Fumarate by Sublimation Method.

    PubMed

    Kalyankar, P; Panzade, P; Lahoti, S

    2015-01-01

    The objective of present study was to formulate directly compressible orodispersible tablets of quetiapine fumarate by sublimation method with a view to enhance patient compliance. A full 3(2) factorial design was used to investigate the effect of two variables viz., concentration of Indion 414 and camphor. Indion 414 (3-5 % w/w) was used as superdisintegrant and camphor (5-15 % w/w) as subliming agent. The tablets were evaluated for thickness, weight variation, hardness, friability, content uniformity, wetting time, porosity, in vitro disintegration time and in vitro drug release. The formulation containing 5% w/w of Indion 414 and 5% w/w camphor was emerged as promising based on evaluation parameters. The disintegration time for optimized formulation was 18.66 s. The tablet surface was evaluated for presence of pores by scanning electron microscopy before and after sublimation. Differential scanning colorimetric study did not indicate any drug excipient incompatibility, either during mixing or after compression. The effect of independent variables on disintegration time, % drug release and friability is presented graphically by surface response plots. Short-term stability studies on the optimized formulation indicated no significant changes in drug content and in vitro disintegration time. The directly compressible orodispersible tablets of quetiapine fumarate with lower friability, greater drug release and shorter disintegration times were obtained using Indion 414 and camphor at optimum concentrations.

  18. Formulation Development and Characterization of Meclizine Hydrochloride Sublimated Fast Dissolving Tablets.

    PubMed

    Vemula, Sateesh Kumar; Vangala, Mohan

    2014-01-01

    The intention of present research is to formulate and develop the meclizine hydrochloride fast dissolving tablets using sublimation method to enhance the dissolution rate. In this study an attempt was made to fasten the drug release from the oral tablets by incorporating the superdisintegrants and camphor as sublimating agent. The prepared fast dissolving tablets were subjected to precompression properties and characterized for hardness, weight variation, friability, wetting time, water absorption ratio, and disintegration time. From in vitro release studies, the formulation F9 exhibited fast release profile of about 98.61% in 30 min, and disintegration time 47 sec when compared with other formulations. The percent drug release in 30 min (Q 30) and initial dissolution rate for formulation F9 was 98.61 ± 0.25%, 3.29%/min. These were very much higher compared to marketed tablets (65.43 ± 0.57%, 2.18%/min). The dissolution efficiency was found to be 63.37 and it is increased by 1.4-fold with F9 FDT tablets compared to marketed tablets. Differential scanning calorimetry and Fourier transform infrared spectroscopy studies revealed that there was no possibility of interactions. Thus the development of meclizine hydrochloride fast dissolving tablets by sublimation method is a suitable approach to improve the dissolution rate.

  19. Formulation Development and Characterization of Meclizine Hydrochloride Sublimated Fast Dissolving Tablets

    PubMed Central

    Vangala, Mohan

    2014-01-01

    The intention of present research is to formulate and develop the meclizine hydrochloride fast dissolving tablets using sublimation method to enhance the dissolution rate. In this study an attempt was made to fasten the drug release from the oral tablets by incorporating the superdisintegrants and camphor as sublimating agent. The prepared fast dissolving tablets were subjected to precompression properties and characterized for hardness, weight variation, friability, wetting time, water absorption ratio, and disintegration time. From in vitro release studies, the formulation F9 exhibited fast release profile of about 98.61% in 30 min, and disintegration time 47 sec when compared with other formulations. The percent drug release in 30 min (Q30) and initial dissolution rate for formulation F9 was 98.61 ± 0.25%, 3.29%/min. These were very much higher compared to marketed tablets (65.43 ± 0.57%, 2.18%/min). The dissolution efficiency was found to be 63.37 and it is increased by 1.4-fold with F9 FDT tablets compared to marketed tablets. Differential scanning calorimetry and Fourier transform infrared spectroscopy studies revealed that there was no possibility of interactions. Thus the development of meclizine hydrochloride fast dissolving tablets by sublimation method is a suitable approach to improve the dissolution rate. PMID:27355021

  20. Application of a Kalman filter to UF sub 6 gaseous diffusion plant freezer/sublimer systems

    SciTech Connect

    Ruppel, F.R.

    1992-03-01

    A signal is required to control the flow of UF{sub 6} in gaseous diffusion plant freezer/sublimer systems. The original strategy envisioned for deriving a flow signal was to take the derivative of the freezer/sublimer weigh cell signal. However, the derivative of the digitized weight signal is noisy, preventing good control. In addition, a bias is introduced into the weight derivative signal because a refrigerant is circulated through a shell-and-tube heat exchanger inside the freezer/sublimer. The weight of the refrigerant is included in the weight measured by the weigh cell. If the circulation rate of the refrigerent is not steady state, a bias exists. Measurements of upstream pressure, vessel pressure, and output to the system control valve are available to the control system. Thus, if the flow through the control valve is characterized properly by the measurements, a Kalman filter can be used in conjunction with these auxiliary inputs and the weigh cell input to overcome the noise and bias problem and provide an improve estimate of flow rate. A discussion of the development and the current status of a Kalman filter used for this application is given. 5 refs.

  1. Deviations from Ideal Sublimation Vapor Pressure Behavior in Mixtures of Polycyclic Aromatic Compounds with Interacting Heteroatoms.

    PubMed

    Goldfarb, Jillian L; Suuberg, Eric M

    2010-08-01

    Despite the relatively small atomic fraction of a given heteroatom in a binary mixture of polycyclic aromatic compounds (PAC), the inclusion of heteroatomic substituted compounds can significantly impact mixture vapor pressure behavior over a wide range of temperatures. The vapor pressures of several binary PAC mixtures containing various heteroatoms show varying behavior, from practically ideal behavior following Raoult's law to significant deviations from ideality depending on the heteroatom(s) present in the mixture. Mixtures were synthesized using the quench-cool technique with equimolar amounts of two PAC, both containing heteroatoms such as aldehyde, carboxyl, nitrogen, and sulfur substituent groups. For some mixtures, deviation from ideality is inversely related to temperature, though in other cases we see deviations from ideality increasing with temperature, whereas some appear independent of temperature. Most commonly we see lower vapor pressures than predicted by Raoult's law, which indicates that the interacting heteroatoms prefer the solid mixture phase as opposed to the vapor phase. Although negative deviations predominate from Raoult's Law, the varying mixtures investigated show both higher and lower enthalpies and entropies of sublimation than predicted. In each mixture, a higher enthalpy of sublimation leads to higher entropy of sublimation than predicted, and vice versa.

  2. Properties of Filamentary Sublimation Residues from Dispersions of Clay in Ice

    NASA Technical Reports Server (NTRS)

    Stephens, J. B.; Parker, T. J.; Saunders, R. S.; Laue, E. G.; Fanale, F. P.

    1985-01-01

    The properties of sublimate residues are of considerable interest in studies of the thermal modeling of Martian and cometary ice surfaces. The study of the formation of sand grains from this mantle on Martian polar ice is also supported by these experiments. To understand these properties, a series of low temperature vacuum experiments were run during which dirty ices that might be expected to be found in Martian polar caps and in comet nuclei were made and then freeze dried. In addition to using particulate material of appropriate grain size and minerology, particle nucleated ices were simulated by dispersing the particulates in the ice so that they did not contact one another. This noncontact dispersion was the most difficult requirement to achieve but the most rewarding in that it produced a new filamentary sublimate residue that was not a relic of the frozen dispersion. If the siliceous particles are allowed to touch one another in the ice the structure of the contacting particles in the ice will remain as a relic after the ice is sublimed away.

  3. Sublimation kinetics and diffusion coefficients of TNT, PETN, and RDX in air by thermogravimetry.

    PubMed

    Hikal, Walid M; Weeks, Brandon L

    2014-07-01

    The diffusion coefficients of explosives are crucial in their trace detection and lifetime estimation. We report on the experimental values of diffusion coefficients of three of the most important explosives in both military and industry: TNT, PETN, and RDX. Thermogravimetric analysis (TGA) was used to determine the sublimation rates of TNT, PETN, and RDX powders in the form of cylindrical billets. The TGA was calibrated using ferrocene as a standard material of well-characterized sublimation rates and vapor pressures to determine the vapor pressures of TNT, PETN, and RDX. The determined sublimation rates and vapor pressures were used to indirectly determine the diffusion coefficients of TNT, PETN, and RDX for the first time. A linear log-log dependence of the diffusion coefficients on temperature is observed for the three materials. The diffusion coefficients of TNT, PETN, and RDX at 273 K were determined to be 5.76×10(-6)m(2)/sec, 4.94×10(-6)m(2)/s, and 5.89×10(-6)m(2)/s, respectively. Values are in excellent agreement with the theoretical values in literature.

  4. First-order feasibility analysis of a space suit radiator concept based on estimation of water mass sublimation using Apollo mission data

    NASA Astrophysics Data System (ADS)

    Metts, Jonathan G.; Klaus, David M.

    2012-01-01

    EVAs, and solar elevation angles were added to predict the performance of an electrochromic space suit radiator under Apollo conditions. Then, using these actual data sets, the hypothetical water mass savings that would be expected had this technology been employed were calculated. The results indicate that electrochromic suit radiators would have reduced sublimator water consumption by 69.0% across the entire Apollo program, for a total mass savings of 68.5 kg to the lunar surface. Further analysis is needed to determine the net impact as a function of the complete system, taking into account both suit components and consumable mass, but the water mass reduction found in this study suggests a favorable system trade is likely.

  5. Impact of sublimation losses in the mass balance of glaciers in semi-arid mountain regions

    NASA Astrophysics Data System (ADS)

    Ayala, Alvaro; Pellicciotti, Francesca; Burlando, Paolo; MacDonell, Shelley; McPhee, James

    2016-04-01

    Glaciers in semiarid mountain regions may lose an important part of their winter snow accumulation through sublimation processes that are enhanced by the high-elevation, intense radiation and dry atmosphere of these environments. As glaciers in these regions secure freshwater resources to lower valleys during summer and drought periods, it is important to advance in a detailed quantification of their sublimation losses. However, logistical concerns and complex meteorological features make the measuring and modelling of glacier mass balances a difficult task. In this study, we estimated the spring-summer mass balances of Tapado and Juncal Norte glaciers in the semiarid Andes of north-central Chile by running a distributed energy balance model that accounts for melt, refreezing and sublimation from the surface and blowing snow. Meteorological input data were available from on-glacier Automatic Weather Stations (AWS) that were installed during the ablation season of years 2005-06, 2008-09, 2013-14 and 2014-15. Snow pits, ablation stakes and a time-lapse camera that provided surface albedo were also available. Distributed air temperature and wind speed were dynamically downscaled from NASA MERRA reanalysis using the software WINDSIM and validated against the data from the AWSs. The rest of the meteorological variables were distributed using statistical relations with air temperature derived from the AWSs data. Initial snow conditions were estimated using satellite images and distributed manual snow depth measurements. Preliminary results show that total ablation diminishes with elevation and that, during the early ablation season (October-November), melt is the main ablation component below 4500 m with sublimation dominating the ablation above this elevation. Above 4500 m an important fraction of meltwater refreezes during night. As the ablation season advances (December-February), melt extends to higher elevations, refreezing plays a smaller role and sublimation is

  6. Sublimating grains in the coma of new comets originating from the Oort Cloud

    NASA Astrophysics Data System (ADS)

    Faggi, S.; Tozzi, G.; Brucato, J.; Bruni, I.; Licandro, J.; Mazzotta Epifani, E.; Meech, K.; Mottola, S.

    2014-07-01

    It is expected that a billion of years of space weathering (see, e.g., Kanuchova et al., 2012, Icarus, 221, 12) produces a crust of organic matter that will be released when a comet enters, for the first time, in the inner Solar System. When approaching to the Sun, a comet is at heliocentric distances r_h greater than 3 au, the sublimation of CO and CO_2 is the main source of cometary activity. At shorter distances, the sublimation of water becomes the most important mechanism of activity. The gases escaping from the nucleus cause drag for the coma grains that can be refractory dust (silicates, carbon), water ice, and/or organic ices. Oort comets at their first passage in the inner Solar System, should produce an halo of organic or water ice particles. Recently, our group started to monitor new, inbound, bright Oort comets (C/2011 F1, C/2012 S1, C/2012 K1, C/2013 V5, C/2012 F3) to search for these grains. The method consists of detecting the cloud of sublimating grains in the inner coma by using the ΣAf(ρ) function (Tozzi et al., 2007, A&A, 476, 979). However, this over-population of grains, beside the sublimation, can be also due to short-time activity (outburst) or too large grains expanding at very slow velocity, as it has been found in comet 67P/C-G (Tozzi et al., 2011, A&A, 531, 54). To discriminate between the phenomena, it is necessary to monitor the comet both at short timescales for the outbursts (by repeating the observations after a few nights), and in a longer term (weeks to months). If the cloud does not expand with decreasing heliocentric distance, there is a high probability that organic and/or water-ice grains are present. We can discriminate between organic and water-ice grains by measuring their color and spectra. In this work, we will present the results obtained from the observations of C/2011 F1 (LINEAR) and C/2012 S1 (ISON). The comparison between data and theoretical simulations, obtained with a simple model assuming sublimating grains

  7. HMT production and sublimation during thermal process of cometary organic analogs. Implications for its detection with the ROSETTA instruments

    NASA Astrophysics Data System (ADS)

    Briani, Giacomo; Fray, Nicolas; Cottin, Hervé; Benilan, Yves; Gazeau, Marie-Claire; Perrier, Sebastien

    2013-09-01

    One important component of refractory organic residues synthesized from interstellar/cometary ice analogues is hexamethylenetetramine (HMT, C6H12N4). However, HMT has never been observed in any astrophysical or planetary environment so far. We investigated thermal evolution of HMT above ambient temperature. The synthesis of the organic residue (ice deposition, photolysis and warming) as well as its heating to temperatures higher than 300 K are performed by means of the same experimental apparatus. The later also allows in situ continuous monitoring of both the solid organic residue (by FTIR spectrometry) and of the gas species (by mass spectrometry). Two different ice mixtures, composed of H2O:CH3OH:NH3 = 10:1:1 and H2O:CH3OH:NH3:CO2 = 10:1:1:2, were deposited and simultaneously photolyzed at 29 K. Warming these photolyzed ices up to 300 K allows the production of refractory organic residues. At 300 K the organic residues clearly show the presence of HMT, but also some difference, in particular in their oxygenated components. Different evolutions of the organic residues are observed for temperatures >300 K. We characterized the organic residue thermal evolution for temperatures up to 500 K. We observed that HMT is still produced at temperatures higher than 300 K. Production of solid HMT and sublimation are simultaneous. HMT observed in the solid phase could be only a minor fraction of the total HMT production, the major fraction being sublimated. The kinetics of the HMT thermal evolution strongly depends on the organic residue composition at 300 K and seems to depend on the exact nature of the oxygenated fraction of the organic residue. The maximum temperature at which solid HMT is observed is 450 K. As HMT forms only for temperatures greater than 280 K in laboratory conditions, it implies that the detection of solid HMT in extraterrestrial samples will provide a strong indication of their thermal history. Consequently, the search for HMT in both solid cometary

  8. Characterization of CdMnTe films deposited from polycrystalline powder source using closed-space sublimation method

    SciTech Connect

    Lai, Jianming; Wang, Junnan; Wang, Lin; Ji, Huanhuan; Xu, Run; Zhang, Jijun; Huang, Jian; Shen, Yue; Min, Jiahua; Wang, Linjun Xia, Yiben

    2015-09-15

    CdMnTe films were prepared on quartz substrates by closed-space sublimation of polycrystalline Cd{sub 0.74}Mn{sub 0.26}Te powders. This was performed at different substrate temperatures (T{sub s} = 200, 300, 350, and 400 °C). The interfacial adhesion strength between the films and substrates, when fabricated from polycrystalline powders, was greater than that of films grown using a bulk source. X-ray diffraction studies revealed that the as-deposited films had a zinc blende structure with a preferential (111) orientation. Precipitation of Te occurred in the films deposited at T{sub s} = 200 °C, as confirmed using scanning electron microscopy, x-ray diffraction, and Raman spectroscopy. The growth mode and re-evaporation dependence on the value of T{sub s} of the films were investigated. Our results suggested that materials suitable for radiation detection can be grown from a powder source at lower substrate temperatures then when grown from a bulk source.

  9. 12% efficient CdTe/CdS thin film solar cells deposited by low-temperature close space sublimation

    NASA Astrophysics Data System (ADS)

    Schaffner, Judith; Motzko, Markus; Tueschen, Alexander; Swirschuk, Andreas; Schimper, Hermann-Josef; Klein, Andreas; Modes, Thomas; Zywitzki, Olaf; Jaegermann, Wolfram

    2011-09-01

    We report 12% efficient CdS/CdTe thin film solar cells prepared by low temperature close space sublimation (CSS). Both semiconductor films, CdS and CdTe, were deposited by high vacuum CSS in superstrate configuration on glass substrates with fluorine doped tin oxide (FTO) front contact. The CdTe deposition was carried out at a substrate temperature (Tsub) of ≤340 ∘C, which is much lower than that used in conventional processes (>500 ∘C). The CdTe films were treated with the usual CdCl2 activation process. Different optimal annealing times and temperatures were found for low-temperature cells (Tsub≤ 340 ∘C) compared to high-temperature cells (Tsub = 520 ∘C). The influence of the activation step on the morphology of high-temperature and low-temperature CdTe is determined by XRD, AFM, SEM top views, and SEM cross-sections. Grain growth, strong recrystallization, and a reduction of planar defects during the activation step are observed, especially for low-temperature CdTe. Further, the influence of CdS deposition parameters on the solar cell performance is investigated by using three different sets of parameters with different deposition rates and substrate temperatures for the CdS preparation. Efficiencies about 10.9% with a copper-free back contact and 12.0% with a copper-containing back contact were achieved using the low temperature CdTe process.

  10. Time Variability of the Dust Sublimation Zones in Pre-Main Sequence Disk Systems

    NASA Technical Reports Server (NTRS)

    Sitko, Michael L.; Carpenter, W. J.; Grady, C. A.; Russel, R. W.; Lynch, D. K.; Rudy, R. J.; Mazuk, S. M.; Venturini, C. C.; Kimes, R. L.; Beerman, L. C.; Ablordeppey, K. E.; Puetter, R. C.; Wisnewski, P.; Brafford, S. M.; Polomski, E. R.; Hammel, H. B.; Perry, R. B.; Wilde, J. L.

    2007-01-01

    The dust sublimation zone (DSZ) is the region of pre-main sequence (PMS) disks where dust grains most easily anneal, sublime, and condense out of the gas. Because of this, it is a location where crystalline material may be enhanced and redistributed throughout the rest of the disk. A decade-long program to monitor the thermal emission of the grains located in this region demonstrates that large changes in emitted flux occur in many systems. Changes in the thermal emission between 3 and 13.5 microns were observed in HD 31648 (MWC 480), HD 163296 (MWC 275), and DG Tau. This emission is consistent with it being produced at the DSZ, where the transition from a disk of gas to one of gas+dust occurs. In the case of DG Tau, the outbursts were accompanied by increased emission on the 10 micron silicate band on one occasion, while on another occasion it went into absorption. This requires lofting of the material above the disk into the line of sight. Such changes will affect the determination of the inner disk structure obtained through interferometry measurements, and this has been confirmed in the case of HD 163296. Cyclic variations in the heating of the DSZ will lead to the annealing of large grains, the sublimation of smaller grains, possibly followed by re-condensation as the zone enters a cooling phase. Lofting of dust above the disk plane, and outward acceleration by stellar winds and radiation pressure, can re-distribute the processed material to cooler regions of the disk, where cometesimals form. This processing is consistent with the detection of the preferential concentration of large crystalline grains in the inner few AU of PMS disks using interferometric spectroscopy with the VLTI.

  11. Dynamical screening of van der Waals interactions in nanostructured solids: Sublimation of fullerenes

    NASA Astrophysics Data System (ADS)

    Tao, Jianmin; Yang, Jing; Rappe, Andrew M.

    2015-04-01

    Sublimation energy is one of the most important properties of molecular crystals, but it is difficult to study, because the attractive long-range van der Waals (vdW) interaction plays an important role. Here, we apply efficient semilocal density functional theory (DFT), corrected with the dynamically screened vdW interaction (DFT + vdW), the Rutgers-Chalmers nonlocal vdW-DF, and the pairwise-based dispersion-corrected DFT-D2 developed by Grimme and co-workers, to study the sublimation of fullerenes. We find that the short-range part, which accounts for the interaction due to the orbital overlap between fullerenes, is negligibly small. Our calculation shows that there exists a strong screening effect on the vdW interaction arising from the valence electrons of fullerenes. On the other hand, higher-order contributions can be as important as the leading-order term. The reasons are that (i) the surface of fullerene molecules is metallic and thus highly polarizable, (ii) the band gap of fullerene solids is small (less than 2 eV), and (iii) fullerene molecules in the solid phase are so densely packed, yielding the high valence electron density and small equilibrium intermolecular distances (the first nearest neighbor distance is only about 10 Å for C60). However, these two effects make opposite contributions, leading to significant error cancellation between these two contributions. We demonstrate that, by considering higher-order contributions and the dynamical screening, the DFT + vdW method can yield sublimation energies of fullerenes in good agreement with reference values, followed by vdW-DF and DFT-D2. The insights from this study are important for a better understanding of the long-range nature of vdW interactions in nanostructured solids.

  12. Piezoelectric crystal microbalance measurements of enthalpy of sublimation of C2-C9 dicarboxylic acids

    NASA Astrophysics Data System (ADS)

    Dirri, F.; Palomba, E.; Longobardo, A.; Zampetti, E.

    2016-02-01

    We present here a novel experimental set-up that is able to measure the enthalpy of sublimation of a given compound by means of piezoelectric crystal microbalances (PCMs). The PCM sensors have already been used for space measurements, such as for the detection of organic and non-organic volatile species and refractory materials in planetary environments. In Earth atmospherics applications, PCMs can be also used to obtain some physical-chemical processes concerning the volatile organic compounds (VOCs) present in atmospheric environments. The experimental set-up has been developed and tested on dicarboxylic acids. In this work, a temperature-controlled effusion cell was used to sublimate VOC, creating a molecular flux that was collimated onto a cold PCM. The VOC recondensed onto the PCM quartz crystal, allowing the determination of the deposition rate. From the measurements of deposition rates, it has been possible to infer the enthalpy of sublimation of adipic acid, i.e. ΔHsub : 141.6 ± 0.8 kJ mol-1, succinic acid, i.e. 113.3 ± 1.3 kJ mol-1, oxalic acid, i.e. 62.5 ± 3.1 kJ mol-1, and azelaic acid, i.e. 124.2 ± 1.2 kJ mol-1. The results obtained show an accuracy of 1 % for succinic, adipic, and azelaic acid and within 5 % for oxalic acid and are in very good agreement with previous works (within 6 % for adipic, succinic, and oxalic acid and within 11 % or larger for azelaic acid).

  13. Sublimation-driven erosion on Hyperion: Topographic analysis and landform simulation model tests

    NASA Astrophysics Data System (ADS)

    Howard, Alan D.; Moore, Jeffrey M.; Schenk, Paul M.; White, Oliver L.; Spencer, John

    2012-07-01

    The unique appearance of Hyperion can be explained in part by the loss to space of ballistic ejecta during impact events, as was proposed by Thomas et al. (Thomas, P.C. et al. [2007a]. Icarus 190, 573-584). We conclude that such loss is a partial explanation, accounting for the lack of appreciable intercrater plains on a saturation-cratered surface. In order to create the smooth surfaces and the reticulate, honeycomb pattern of narrow divides between old craters, appreciable subsequent modification of crater morphology must occur through mass-wasting processes accompanied by sublimation, probably facilitated by the loss of CO2 as a component of the relief-supporting matrix of the bedrock. During early stages of crater degradation, steep, crenulate bedrock slopes occupy the upper crater walls with abrupt transitions downslope onto smooth slopes near the angle of repose mantled by mass wasting debris, as can be seen within young craters. Long-continued mass wasting eventually results in slopes totally mantled with particulate debris. This mass wasting effectively destroys small craters, at least in part accounting for the paucity of sub-kilometer craters on Hyperion. Surface temperatures measured by Cassini CIRS range from 58 K to 127 K and imply a surface thermal inertia of 11 ± 2 J m-2 K-1 s-1/2 and bolometric albedo ranging from 0.05 to 0.33. Resulting H2O sublimation rates are only tens of cm per billion years for most of the surface, so the evolution of the observed landforms is likely to require sublimation of more volatile species such as CO2.

  14. Large area and structured epitaxial graphene produced by confinement controlled sublimation of silicon carbide.

    PubMed

    de Heer, Walt A; Berger, Claire; Ruan, Ming; Sprinkle, Mike; Li, Xuebin; Hu, Yike; Zhang, Baiqian; Hankinson, John; Conrad, Edward

    2011-10-11

    After the pioneering investigations into graphene-based electronics at Georgia Tech, great strides have been made developing epitaxial graphene on silicon carbide (EG) as a new electronic material. EG has not only demonstrated its potential for large scale applications, it also has become an important material for fundamental two-dimensional electron gas physics. It was long known that graphene mono and multilayers grow on SiC crystals at high temperatures in ultrahigh vacuum. At these temperatures, silicon sublimes from the surface and the carbon rich surface layer transforms to graphene. However the quality of the graphene produced in ultrahigh vacuum is poor due to the high sublimation rates at relatively low temperatures. The Georgia Tech team developed growth methods involving encapsulating the SiC crystals in graphite enclosures, thereby sequestering the evaporated silicon and bringing growth process closer to equilibrium. In this confinement controlled sublimation (CCS) process, very high-quality graphene is grown on both polar faces of the SiC crystals. Since 2003, over 50 publications used CCS grown graphene, where it is known as the "furnace grown" graphene. Graphene multilayers grown on the carbon-terminated face of SiC, using the CCS method, were shown to consist of decoupled high mobility graphene layers. The CCS method is now applied on structured silicon carbide surfaces to produce high mobility nano-patterned graphene structures thereby demonstrating that EG is a viable contender for next-generation electronics. Here we present for the first time the CCS method that outperforms other epitaxial graphene production methods.

  15. Dynamical screening of van der Waals interactions in nanostructured solids: Sublimation of fullerenes

    SciTech Connect

    Tao, Jianmin; Yang, Jing; Rappe, Andrew M.

    2015-04-28

    Sublimation energy is one of the most important properties of molecular crystals, but it is difficult to study, because the attractive long-range van der Waals (vdW) interaction plays an important role. Here, we apply efficient semilocal density functional theory (DFT), corrected with the dynamically screened vdW interaction (DFT + vdW), the Rutgers-Chalmers nonlocal vdW-DF, and the pairwise-based dispersion-corrected DFT-D2 developed by Grimme and co-workers, to study the sublimation of fullerenes. We find that the short-range part, which accounts for the interaction due to the orbital overlap between fullerenes, is negligibly small. Our calculation shows that there exists a strong screening effect on the vdW interaction arising from the valence electrons of fullerenes. On the other hand, higher-order contributions can be as important as the leading-order term. The reasons are that (i) the surface of fullerene molecules is metallic and thus highly polarizable, (ii) the band gap of fullerene solids is small (less than 2 eV), and (iii) fullerene molecules in the solid phase are so densely packed, yielding the high valence electron density and small equilibrium intermolecular distances (the first nearest neighbor distance is only about 10 Å for C{sub 60}). However, these two effects make opposite contributions, leading to significant error cancellation between these two contributions. We demonstrate that, by considering higher-order contributions and the dynamical screening, the DFT + vdW method can yield sublimation energies of fullerenes in good agreement with reference values, followed by vdW-DF and DFT-D2. The insights from this study are important for a better understanding of the long-range nature of vdW interactions in nanostructured solids.

  16. Large area and structured epitaxial graphene produced by confinement controlled sublimation of silicon carbide

    PubMed Central

    de Heer, Walt A.; Berger, Claire; Ruan, Ming; Sprinkle, Mike; Li, Xuebin; Hu, Yike; Zhang, Baiqian; Hankinson, John; Conrad, Edward

    2011-01-01

    After the pioneering investigations into graphene-based electronics at Georgia Tech, great strides have been made developing epitaxial graphene on silicon carbide (EG) as a new electronic material. EG has not only demonstrated its potential for large scale applications, it also has become an important material for fundamental two-dimensional electron gas physics. It was long known that graphene mono and multilayers grow on SiC crystals at high temperatures in ultrahigh vacuum. At these temperatures, silicon sublimes from the surface and the carbon rich surface layer transforms to graphene. However the quality of the graphene produced in ultrahigh vacuum is poor due to the high sublimation rates at relatively low temperatures. The Georgia Tech team developed growth methods involving encapsulating the SiC crystals in graphite enclosures, thereby sequestering the evaporated silicon and bringing growth process closer to equilibrium. In this confinement controlled sublimation (CCS) process, very high-quality graphene is grown on both polar faces of the SiC crystals. Since 2003, over 50 publications used CCS grown graphene, where it is known as the “furnace grown” graphene. Graphene multilayers grown on the carbon-terminated face of SiC, using the CCS method, were shown to consist of decoupled high mobility graphene layers. The CCS method is now applied on structured silicon carbide surfaces to produce high mobility nano-patterned graphene structures thereby demonstrating that EG is a viable contender for next-generation electronics. Here we present for the first time the CCS method that outperforms other epitaxial graphene production methods. PMID:21960446

  17. A Novel, Sublimation-Driven YORP-like Effect, and The Formation of Dust Striae in Cometary Tails

    NASA Astrophysics Data System (ADS)

    Steckloff, Jordan; Jacobson, Seth A.

    2014-11-01

    The dust tails of some great comets exhibit linear dust features that align with the Sun (striae). Striae are thought to form from icy chunks of dust ejected from the nucleus that are delayed in time before fragmenting [1]. Models show that striae formation is best fit through a mechanism of continuous fragmentation [2], but the physical mechanism responsible for this delayed fragmentation is unknown. We propose that striae form through a novel rotational fragmentation mechanism driven by the sublimation of volatile ices present in the ejected chunk.We note that sublimating gas molecules scatter off of the surface of a non-specular material similarly to photons (i.e. Lambertian scattering), however gas molecules carry significantly more momentum. By comparing the momentum flux from a sublimating gas with solar radiation pressure, we are able to scale the YORP timescale [3] to derive its sublimation-driven equivalent. We find that this Sublimative YORP-like timescale is significantly shorter than the YORP timescales by 4-5 orders of magnitude for H2O sublimation.We apply this mechanism to Comet West, which exhibited prominent striae in its dust tail. For ejected dust clumps to drift behind the nucleus to form the observed dust striae near 0.4 AU, [1] estimated the β-parameter of the chunks (ratio of solar radiation to solar gravitational forces) to be between 0.6 and 2.4. We equate this to a new parameter βsub (the ratio of dynamic sublimation to solar gravitational forces), which corresponds to icy chunks with radii of 5-20 cm, consistent with chunks ejected from Comet Wild 2 [4]. The sublimation-driven YORP timescales for chunks of this size is 1-3 hours, which allows for a cascade of rotational spin-up and fragmentation of daughter chunks to occur within the ~50-85 hour delay [1] between chunk ejection and striae formation. Thus, Comet West’s dust tail striae are consistent with this novel rotational fragmentation mechanism, which is driven by the sublimation

  18. Modeling of Sublimation-Driven Erosion and Ice Pinnacle Formation on Callisto

    NASA Astrophysics Data System (ADS)

    White, Oliver; Umurhan, Orkan M.; Howard, Alan D.; Moore, Jeffrey M.

    2014-11-01

    Most of the areas observed at high resolution on the Galilean satellite Callisto have a morphology that implies sublimation-driven landform modification and mass wasting is at work [Moore et al., 1999]. These areas comprise rolling dark plains with interspersed bright pinnacles. Howard and Moore [2008], using the MARSSIM landform evolution model, simulated evolution of this landscape as a combination of bedrock volatile sublimation, mass wasting of the dark, non-coherent residue, and redeposition of ice at high-elevation cold traps sheltered from thermal re-radiation to form the pinnacles.The goal of our study is to further investigate the details of pinnacle formation by refining this model, and by constraining values for the variable environmental parameters within the model such that they are consistent with the current understanding of Callisto’s surface environment. We present the results of the updated model and our experimentation with varying key parameters.Our refinement of the model has caused us to revise the result of Howard and Moore [2008] that the pinnacles represent an ice cover of several tens to hundreds of meters. Instead, our results indicate an ice coverage reaching several meters at most, a figure that is consistent with the prediction of Moore et al. [2004]. We have also modified the model such that ice contained within the pinnacles is now subject to sublimation itself.Using Fick’s Law to solve for the diffusive transport rate between a volatile table and an atmosphere [Moore et al., 1996], we have determined that the loss rate of H2O ice from the volatile-refractory bedrock through sublimation is too slow 10-20 kg m-2 s-1) to account for the formation of the ice pinnacles, and that a volatile mixture that contains H2O ice is necessary to facilitate its loss. We find that CO2 hydrate fulfills this role well: loss rates of CO2●6H2O 10-10 kg m-2 s-1) are sufficient to produce deposited ice thicknesses reaching several meters, with the

  19. Search of the Na in the Region of the Sublimation of the Near-Sun Dust

    NASA Astrophysics Data System (ADS)

    Delone, A. B.; Divlekeev, M. I.; Suchanov, E. A.; Gulyaev, R. A.; Yakunina, G. V.; Porfir'eva, G. A.

    An evaluation of the Na number in the sublimation zone of the near-Sun interplanetary dust, based on a comparison with the intensity of the radiation of the Na in the Earth atmosphere, has been obtained. The abundance of the Na in the column along the line of sight is less than 2 x 108atom cm-2. This result is compared with the values, determined on the base of the brightness of the zodiacal light, F-corona and by direct measurements of the dust density with space experiments.

  20. The number of sodium atoms in the region of circumsolar sublimation of interplanetary dust

    NASA Astrophysics Data System (ADS)

    Delone, A. B.; Divlekeev, M. I.; Sukhanov, E. A.; Gulyaev, R. A.; Yakunina, G. V.; Porfir'eva, G. A.

    2008-02-01

    Sodium emission fromthe zone of circumsolar sublimation of interplanetary dust was searched for during the total solar eclipse of March 29, 2006, using a Fabry-Perot interferometer and interference filter transmitting at 590 nm. The upper limit for the column density sodium atoms is 2 × 108 atoms/cm2, is based on the comparison with the atmospheric sodium emission. This result is compared with the brightness of the zodiacal light and F-corona, as well as the dust density directly measured onboard spacecraft.

  1. The Anomalous Drift of Comet ISON (C/2012 S1) due to Sublimating Volatiles near Perihelion

    NASA Astrophysics Data System (ADS)

    Steckloff, J. K.; Keane, J. V.; Milam, S.; Coulson, I.; Knight, M. M.

    2014-12-01

    Prior to perihelion passage on 28 November 2013, the observed right ascension (RA) and declination (Dec) coordinates of comet C/2012 S1 (ISON) significantly lagged the predicted JPL (# 53) ephemeris. We show that this "braking effect" is due to a dynamic pressure exerted by sublimating gases on the sunward side of the nucleus [1]. Comet ISON was observed November 23 through November 28 using the SCUBA-2 sub-millimeter camera on the James Clerk Maxwell Telescope (JCMT). Imaging is achieved simultaneously at wavelengths of 850 μm and 450 μm, with RA and Dec determined from the central peak in the coma brightness [2]. When comet ISON was first detected at 850 μm, the 1-mm-sized dust particles were tightly bound to the comet nucleus until at least November 23. Three days later, the dust was less tightly bound, elongated and diffuse, spread out over as much as 120 arc seconds (80,000 km) in the anti-solar direction, suggesting a fragmentation event. We compute the average braking velocity of the nucleus of comet ISON by first measuring the distance between the central RA position and the predicted JPL ephemeris. We then calculate the change in this distance between subsequent observations, and divide this value by the elapsed time between the two observations to yield an average drift velocity of the nucleus over this time interval. We assume that comet ISON, like a number of Jupiter Family Comets visited by spacecraft [3], has low thermal inertia. Thus, the sublimating gases are emitted predominantly on the sunward side of the nucleus. Additionally, we assume that water ice dominates the sublimating gases [4]. We then calculate the pressure on the surface of the nucleus due to the emitted gases using the procedure described in [1]. We match the average drift velocity of the nucleus due to this sublimation pressure with the observed average drift velocity from the JCMT observations, which is sensitive to the size of the body, allowing us to estimate the size of the

  2. A process simulator/trainer for the process inventory control system 20-MW freezer/sublimer

    SciTech Connect

    Tapp, P.A.; Carnal, C.L.; Wells, J.C.; Belcher, J.D.; Gibson, F.R.; Ruppel, F.R.

    1991-05-01

    This report describes the development of a process simulator/trainer for the Process Inventory Control System project. The main objective of this work was to build a plant simulator that accepts control signals from the Texas Instruments D/3 distributed control system and produces plant signals to mimic the behavior of a 20-MW freezer/sublimer unit. The simulator/trainer will be used as a surrogate plant to debug control system hardware/software and to train operators to use the new D/3 distributed control system without disturbing the processing of the Paducah Gaseous Diffusion Plant. 4 refs., 28 figs., 8 tabs.

  3. Sublime Science

    ERIC Educational Resources Information Center

    Girod, Mark

    2007-01-01

    One of the shortcomings in most efforts to integrate art and science is that many people have a shallow understanding of art, which inevitably leads to shallow connections between art and science. Coloring drawings of planets, building sculptures of volcanoes, and decorating scientific diagrams are fine activities, but they do not link science and…

  4. Salicylamide cocrystals: screening, crystal structure, sublimation thermodynamics, dissolution, and solid-state DFT calculations.

    PubMed

    Manin, Alex N; Voronin, Alexander P; Manin, Nikolay G; Vener, Mikhail V; Shishkina, Anastasia V; Lermontov, Anatoly S; Perlovich, German L

    2014-06-19

    A new cocrystal of 2-hydroxybenzamide (A) with 4-acetamidobenzoic acid (B) has been obtained by the DSC screening method. Thermophysical analysis of the aggregate [A:B] has been conducted and a fusion diagram has been plotted. Cocrystal formation from melts was studied by using thermomicroscopy. A cocrystal single-crystal was grown and its crystal structure was determined. The pattern of noncovalent interactions has been quantified using the solid-state DFT computations coupled with the Bader analysis of the periodic electron density. The sublimation processes of A-B cocrystal have been studied and its thermodynamic functions have been calculated. The classical method of substance transfer by inert gas-carrier was chosen to investigate sublimation processes experimentally. The lattice energy is found to be 143 ± 4 kJ/mol. It is lower than the sum of the corresponding values of the cocrystal pure components. The theoretical value of the lattice energy, 156 kJ/mol, is in reasonable agreement with the experimental one. A ternary phase diagram of solubility (A-B-ethanol) has been plotted and the areas with solutions for growing thermodynamically stable cocrystals have been determined.

  5. Formation of gullies on Mars by debris flows triggered by CO2 sublimation

    NASA Astrophysics Data System (ADS)

    Pilorget, C.; Forget, F.

    2016-01-01

    Martian gully landforms resemble terrestrial debris flows formed by the action of liquid water and have thus been interpreted as evidence for potential habitable environments on Mars within the past few millennia. However, ongoing gully formation has been detected under surface conditions much too cold for liquid water, but at times in the martian year when a thin layer of seasonal CO2 frost is present and defrosting above the regolith. These observations suggest that the CO2 condensation-sublimation cycle could play a role in gully formation. Here we use a thermo-physical numerical model of the martian regolith underlying a CO2 ice layer and atmosphere to show that the pores beneath the ice layer can be filled with CO2 ice and subjected to extreme pressure variations during the defrosting season. The subsequent gas fluxes can destabilize the regolith material and induce gas-lubricated debris flows with geomorphic characteristics similar to martian gullies. Moreover, we find that subsurface CO2 ice condensation, sublimation and pressurization occurs at conditions found at latitudes and slope orientations where gullies are observed. We conclude that martian gullies can result from geologic dry ice processes that have no terrestrial analogues and do not require liquid water. Such dry ice processes may have helped shape the evolution of landforms elsewhere on the martian surface.

  6. [Research on the polycrystalline CdS thin films prepared by close-spaced sublimation].

    PubMed

    Yang, Ding-Yu; Xia, Geng-Pei; Zheng, Jia-Gui; Feng, Liang-Huan; Cai, Ya-Ping

    2009-01-01

    In the present paper, the factors of influence on the deposition rate of CdS films prepared by close-spaced sublimation (CSS) were first studied systematically, and it was found from the experiments that the deposition rate increased with the raised temperature of sublimation source, while decreased with the raised substrate temperature and the deposition pressure. The structure, morphology and light transmittance of the prepared samples were tested subsequently, and the results show: (1) The CdS films deposited under different oxygen partial pressure all present predominating growth lattice orientation (103), and further more the films will be strengthened after annealed under CdCl2 atmosphere. (2) The AFM images of CdS show that the films are compact and uniform in grain diameter, and the grain size becomes larger with the increased substrate temperature. Along with it, the film roughness was also augmented. (3) The transmittance in the shortwave region of visible light through the CdS films would be enhanced when its thickness is reduced, and that will help improve the shortwave spectral response of CdTe solar cells. Finally, the prepared CdS films were employed to fabricate CdTe solar cells, which have achieved a conversion efficiency of 10.29%, and thus the feasibility of CSS process in the manufacture of CdTe solar cells was validated primarily.

  7. EVOLUTION OF SIZE DISTRIBUTION OF ICY GRAINS BY SUBLIMATION AND CONDENSATION

    SciTech Connect

    Kuroiwa, Takuto; Sirono, Sin-iti

    2011-09-20

    In the outer part of a protoplanetary disk, dust grains consist of silicate core covered by an ice mantle. A temporal heating event in the disk results in sublimation of the ice mantle. After the end of the heating event, as the temperature decreases, H{sub 2}O molecules recondense on the surface of the dust grain. Ultimately, the dust grain is covered by an ice mantle. Because the equilibrium vapor pressure on the grain surface decreases with the grain size, a large grain grows faster than a small grain. As a result, the size of an icy dust grain changes as a result of the heating event. The change in size also affects the mechanical properties of the dust aggregates formed by the icy grains. In this paper, we investigated the evolution of the size distribution of icy dust grains during sublimation and condensation. We found that the size evolution of icy grains can be divided into two stages. In the first stage, the icy grains grow through condensation of H{sub 2}O molecules. In the second stage, the size of grains changes further as H{sub 2}O molecules are transferred between icy grains while the surrounding gas condenses. The size distribution of the icy dust grains becomes bimodal, with a small number of relatively large grains and many small grains without an icy mantle. Possible effects of the size change on the evolution of icy dust aggregates are discussed.

  8. Cadmium sulfide thin films deposited by close spaced sublimation and cadmium sulfide/cadmium telluride solar cells

    NASA Astrophysics Data System (ADS)

    Marinskiy, Dmitriy Nikolaevich

    1998-12-01

    One of the applications of CdS films is as a window layer in CdTe and Cu(In,Ga)Sesb2 solar cells. The study of the optical and structural properties of CdS films deposited by close spaced sublimation as well as their influence on CdS/CdTe solar cell performance is part of the CdTe solar cell program at the University of South Florida. CdS films have been deposited by the close-spaced sublimation technique. The influence of the main process parameters, the substrate and source temperatures, and the ambient in the deposition chamber has been investigated. As-deposited films have been subjected to heat treatments in Hsb2 ambient, in CdClsb2 atmosphere, and in atmosphere with small amounts of oxygen. A special annealing chamber was built to carry out the annealing experiments in the presence of CdClsb2 vapor and oxygen. Several CSS chambers were assembled to study the influence of various process parameters simultaneously and validate the results. Results of scanning electron microscopy and photoluminescence measurements have been used as the primary characterization techniques. X-ray diffraction, electron microprobe analysis, and transmission measurements have also been carried out. It was found that as deposited CdS films have a hexagonal structure independent of the process parameters used. The presence of a CdO phase was detected in the samples grown with the highest oxygen concentration in the ambient. The resistivity of CdS films is controlled by intergrain barriers. Photoluminescence measurements showed the presence of oxygen-acceptor transition and a wide variation in the intensity of deep emission bands. The variation in the intensities was correlated with the variation in the deposition and annealing conditions. However, no correlation was found between the PL intensities of defect bands and cell performance. CdS/CdTe junctions have been fabricated using standard deposition and postgrowth techniques developed in the USF solar cells laboratory. All cells have

  9. THE EFFECTS ON BIOLOGICAL MATERIALS OF FREEZING AND DRYING BY VACUUM SUBLIMATION

    PubMed Central

    Greiff, Donald; Blumenthal, Herman; Chiga, Masahiro; Pinkerton, Henry

    1954-01-01

    The infectivity titre of influenza virus-infected allantoic fluid was determined after a variety of procedures involving cyclic slow freezing and thawing, freezing at various rates with subsequent storage at different temperatures freezing at various rates with subsequent dehydration at various temperatures, and different degrees of dehydration. All these factors were found to influence the survival rate of the virus particles. Five freeze-thaw cycles resulted in a fall in titre from 10–8.6 to 10–0.8 cycles 2, 3, and 4 causing much greater losses than cycles 1 and 5. Rapid cooling to –40°C. or slow cooling to –80 or 190°C. did not cause significant titre loss, but rapid cooling to temperatures above –40° or slow cooling to temperatures above –80°C. caused definite titre loss. Loss of titre on storage occurred only at temperatures above –40deg;C. The effect of lyophilization depends both on the preliminary treatment and on the dehydration temperature. Better conservation of titre was obtained after preliminary cooling to –190 or –80°C. than after preliminary cooling to higher temperatures. The most effective sublimation temperatures were 0 and –80°.; the least effective was +20°C. Titre losses in suspensions sublimated at –10, –30, and –60°C. were in general intermediate. No loss in titre occurred after preliminary cooling to –80 or –190°C. and subsequent dehydration at –80 or 0°C. The degree of dehydration definitely affects the survival of virus on storage at 0°C., but sublimation for 4 hours at 0°C. gave complete protection against titre loss on storage at this temperature. Possible explanations of the observations made are suggested, based on known physiochemical phenomena such as supercooling, vitrification, variations in size and shape of ice crystals with different freezing speeds, differential enzyme inactivation, changes in salt concentration, and changes in energy levels. PMID:13163341

  10. The Sublime Corpse in Gertrudis Gomez de Avellaneda's Women's Journal "Album Cubano de lo Bueno y lo Bello" (1860)

    ERIC Educational Resources Information Center

    LaGreca, Nancy

    2009-01-01

    This article examines Gertrudis Gomez de Avellaneda's choice to include articles depicting the advanced decay of cadavers, which are simultaneously horrible and awesome, in her women's periodical "Album Cubano de lo Bueno y lo Bello". Background on Avellaneda's biography, women's print culture, and theories of the sublime provide a frame for the…

  11. Formation of the molecular crystal structure during the vacuum sublimation of paracetamol

    NASA Astrophysics Data System (ADS)

    Belyaev, A. P.; Rubets, V. P.; Antipov, V. V.; Bordei, N. S.

    2015-04-01

    The results from structural and thermal studies on the formation of molecular crystals during the vacuum sublimation of paracetamol from its vapor phase are given. It is established that the vapor-crystal phase transition proceeds in a complicated way as the superposition of two phase transitions: a first-order phase transition with a change in density, and a second-order phase transition with a change in ordering. It is shown that the latter is a smeared phase transition that proceeds with the formation of a pretransitional phase that is irreversibly dissipated during phase transformation, leading to the formation of crystals of the rhombic syngony. Data from differential scanning calorimetry and X-ray diffraction analysis are presented along with microphotographs.

  12. Switchover software reliability estimate for Paducah Freezer/Sublimer computer systems

    SciTech Connect

    Flanagan, D.M.; Davis, J.N.

    1993-04-01

    K-25 Engineering Division purchased a series of redundant computer systems and developed software for the purpose of providing continuous process monitoring and control for the Freezer/Sublimer equipment in the gaseous diffusion process at the Paducah Gaseous Diffusion Plant. The application software is loaded on two central processing units (CPU) so that in the event of a failure of the primary unit, the processing can switch to the backup unit and continue processing without error. It is the purpose of this document to demonstrate the reliability of this system with respect to its ability to switch properly between redundant CPU. The total reliability estimation problem -- which considers the computer hardware, the operating system software, and the application software -- has been reduced to one that considers only the application software directly involved in the switchover process. Estimates are provided for software reliability and the testing coverage. Software and hardware reliability models and reliability growth models are considered in addition to Bayesian approaches.

  13. Latent fingermark visualisation using reduced-pressure sublimation of copper phthalocyanine.

    PubMed

    Williams, Geraint; ap Llwyd Dafydd, Hefin; Watts, Alun; McMurray, Neil

    2011-01-30

    The sublimation of copper phthalocyanine (CuPc) at a temperature of 400°C under conditions of reduced pressure is shown to be an effective method of developing latent fingermarks on certain types of surface. Preliminary experiments on a limited selection of surfaces including paper, plastic and ceramic tiles were carried out using a simple apparatus consisting of a vacuum desiccator and a resistive heater. CuPc from the gas phase condenses preferentially on fingermark deposits, revealing deep blue patterns with excellent ridge detail clarity on light coloured surfaces. The technique is shown to be most effective on porous surfaces such as paper, but relatively ineffective on non-porous ceramic and plastic surfaces.

  14. Near-equilibrium growth of thick, high quality beta-SiC by sublimation

    NASA Technical Reports Server (NTRS)

    Shields, Virgil B.; Fekade, Konjit; Spencer, Michael G.

    1993-01-01

    A close spaced near-equilibrium growth technique was used to produce thick, high quality epitaxial layers of beta-silicon carbide. The process utilized a sublimation method to grow morphologically smooth layers. The beta silicon carbide growth layers varied from about 200 to 750 microns in thickness. Chemical vapor deposition grown, 2-10 microns, beta silicon carbide films were used as seeds at 1860 and 1910 C growth temperatures. The respective average growth rates were 20 and 30 microns per hour. The layers are p-type with a 3.1 x 10 exp 17/cu cm carrier concentration. Electrical measurements indicate considerable improvement in the breakdown voltage of Schottky barriers on growth samples. Breakdown values ranged from 25 to 60 V. These measurements represent the highest values reported for 3C-SiC.

  15. Enthalpie de sublimation du soufre α : mesure calorimétrique

    NASA Astrophysics Data System (ADS)

    Chastel, R.; Ezzine, M.

    1993-04-01

    An effusion cell-calorimetric method has been used to determine the sublimation enthalpy of α sulfur at 298.15 K. The value 13.05 ± 0. 1 kJ/gram atom, is compared to literature data. L'existence d'une phase vapeur de composition complexe au-dessus de certains éléments rend délicate la définition d'une enthalpie d'évaporation par atome-gramme de l'élément : dans le cas du soufre α, nous avons utilisé une méthode calorimétrique directe qui conduit à : Δ H_{vap(298,15 K)}= 13,05± 0,1 kJ/atome-gramme.

  16. Modeling the Seasonal South Polar Cap Sublimation Rates at Dust Storm Conditions

    NASA Technical Reports Server (NTRS)

    Bonev, B. P.; James, P. B.; Wolff, M. J.; Bjorkman, J. E.; Hansen, G. B.; Benson, J. L.

    2003-01-01

    Carbon dioxide is the principal component of the Martian atmosphere and its interaction with the polar caps forms the CO2 seasonal cycle on the planet. A significant fraction of the atmospheric constituent condenses on the surface during the polar winter and sublimes back during spring. The basic aspects of the CO2 cycle have been outlined by Leighton and Murray and a number of follow-up theoretical models ranging from energy balance to general circulation models have been used to study the physical processes involved in the cycle. This paper presents a modeling study on the seasonal south polar cap subliminiation rate under dust storm conditions. Mars Global Surveyor observations are also presented.

  17. Impact of nonintentional Al impurity to carrier lifetime and diffusion in sublimation grown 3C heterostructures

    NASA Astrophysics Data System (ADS)

    Ščajev, P.; Jarašiunas, K.; Kadys, A.; Storasta, J.; Abramov, P. L.; Lebedev, S. P.; Lebedev, A. A.

    2010-11-01

    Using optical techniques, we analyzed an impact of non-intentional Al mpurity and twin boundaries to photoelectrical properties of sublimation-grown 3C heterostructures. Differential transmission techniques revealed Al related contribution to probe beam absorption with cross-section σAl = (1.8±0.5)×10-17 cm2 at 1064 nm, being four times stronger that the free-carrier absorption cross-section at given wavelength. Temperature dependent carrier recombination rates provided trap activation energy of 170 and 210 meV in two samples with different Al concentration. Saturation of probe beam absorption with excitation allowed determination of electrically active Al concentration, not gettered at grain boundaries. Increase of room-temperature mobility with injection in the highly defective layer and the corresponding lifetime decrease pointed out contribution of point and structural defects to carrier scattering.

  18. Sublimation of Ices Containing Organics and/or Minerals and Implications for Icy Bodies Surface Structure and Spectral Properties

    NASA Astrophysics Data System (ADS)

    Poch, O.; Pommerol, A.; Jost, B.; Yoldi, Z.; Carrasco, N.; Szopa, C.; Thomas, N.

    2015-12-01

    The surfaces of many objects in the Solar System comprise substantial quantities of water ice either in pure form or mixed with minerals and/or organic molecules. Sublimation is a process responsible for shaping and changing the reflectance properties of these objects. We present laboratory data on the evolution of the structure and the visible and near-infrared spectral reflectance of icy surfaces made of mixtures of water ice and non-volatile components (complex organic matter and silicates), as they undergo sublimation of the water ice under low temperature and pressure conditions (Poch et al., under review). We prepared icy surfaces which are potential analogues of ices found on comets, icy satellites or trans-neptunian objects (TNOs). The experiments were carried out in the SCITEAS simulation setup recently built as part of the Laboratory for Outflow Studies of Sublimating Materials (LOSSy) at the University of Bern (Pommerol et al., 2015a). As the water ice sublimated, we observed in situ the formation of a sublimation lag deposit, or sublimation mantle, made of the non-volatiles at the top of the samples. The texture (porosity, internal cohesiveness etc.), the activity (outbursts and ejection of mantle fragments) and the spectro-photometric properties of this mantle are found to differ strongly depending on the chemical nature of the non-volatiles, the size of their particles, the way they are mixed with the volatile component and the dust/ice mass ratio. The results also indicate how the band depths of the sub-surface water ice evolve during the build-up of the sublimation mantle. These data provide useful references for interpreting remote-sensing observations of Rosetta (see Pommerol et al., 2015b), and also New Horizons. Poch, O., et al., under review in IcarusPommerol, A., et al., 2015a, Planet. Space Sci. 109-110, 106-122. http://dx.doi.org/10.1016/j.pss.2015.02.004Pommerol, A., et al., 2015b, Astronomy and Astrophysics, in press. http://dx.doi.org/10.1051/0004-6361/201525977

  19. Formulation Design and Optimization of Fast Dissolving Clonazepam Tablets by Sublimation Method

    PubMed Central

    Shirsand, S. B.; Suresh, Sarasija; Kusumdevi, V.; Swamy, P. V.

    2011-01-01

    Fast dissolving tablets of clonazepam were prepared by sublimation method with a view to enhance patient compliance. A 32 full factorial design was applied to investigate the combined effect of two formulation variables: amount of croscarmellose sodium and camphor. Croscarmellose sodium (2-8% w/w) was used as superdisintegrant and camphor (20-40% w/w) was used as subliming agent, to increase the porosity of the tablets, since it helps water to penetrate into the tablets, along with directly compressible mannitol to enhance mouth feel. The tablets were evaluated for hardness, friability, thickness, drug content uniformity, in vitro dispersion time, wetting time and water absorption ratio. Based on in vitro dispersion time (approximately 11 s); the formulation containing 5% w/w croscarmellose sodium and 40% w/w camphor was found to be promising and tested for in vitro drug release pattern (in pH 6.8 phosphate buffer). Short-term stability (at 40°/75% relative humidity for 3 mo) and drug-excipient interaction. Surface response plots are presented to graphically represent the effect of independent variables on the in vitro dispersion time. The validity of the generated mathematical model was tested by preparing two extra-design checkpoints. The optimized tablet formulation was compared with conventional commercial tablet formulation for drug release profiles. This formulation showed nearly nine-fold faster drug release (t50% 1.8 min) compared to the conventional commercial tablet formulation (t50% 16.4 min). Short-term stability studies on the formulation indicated that there are no significant changes in drug content and in vitro dispersion time (P<0.05). PMID:22923860

  20. Estimating snow sublimation using natural chemical and isotopic tracers across a gradient of solar radiation

    NASA Astrophysics Data System (ADS)

    Gustafson, Joseph R.; Brooks, P. D.; Molotch, N. P.; Veatch, W. C.

    2010-12-01

    Changes in both climate and vegetation may dramatically impact the amount of water stored in seasonal snow cover and the timing of spring snowmelt. This study quantifies how spatial variability in solar radiation affects the spatial and temporal patterns in snow water equivalent (SWE), snow chemistry, and snow water isotopes in the Jemez Mountains, New Mexico. Depth, density, stratigraphy, temperature, and snow samples were collected approximately monthly from five locations between January and April 2007 to quantify the effects of solar forcing on snowpack water and chemical balance. Locations varied in solar forcing due to topography and vegetation, while minimizing variability in precipitation, elevation, aspect, interception, and wind redistribution. Snowfall (340 ± 5 mm) was similar across all sites, but peak SWE at maximum accumulation ranged from 187 to 340 mm. Solute concentrations were highest directly under canopies, intermediate in nonshaded forest openings, and lowest in shaded forest openings. Conservative solute concentrations (SO42-, R2 = 0.80), Cl- (R2 = 0.60), and isotope values (δ18O R2 = 0.96) were inversely related to SWE at maximum accumulation. Mass balance estimates of snowpack water balance using solute concentrations and isotopes indicated that sublimation ranged from <2% to ˜20% of winter precipitation, consistent with previous studies at the site. The strong relationships between solar forcing, SWE, and chemistry suggest that snow chemistry at maximum accumulation can be used to estimate overwinter sublimation. Furthermore, variability in solar forcing also can be used to refine spatial estimates of catchment solute and isotope input at melt.

  1. Fe embedded in ice: The impacts of sublimation and energetic particle bombardment

    NASA Astrophysics Data System (ADS)

    Frankland, Victoria L.; Plane, John M. C.

    2015-05-01

    Icy particles containing a variety of Fe compounds are present in the upper atmospheres of planets such as the Earth and Saturn. In order to explore the role of ice sublimation and energetic ion bombardment in releasing Fe species into the gas phase, Fe-dosed ice films were prepared under UHV conditions in the laboratory. Temperature-programmed desorption studies of Fe/H2O films revealed that no Fe atoms or Fe-containing species co-desorbed along with the H2O molecules. This implies that when noctilucent ice cloud particles sublimate in the terrestrial mesosphere, the metallic species embedded in them will coalesce to form residual particles. Sputtering of the Fe-ice films by energetic Ar+ ions was shown to be an efficient mechanism for releasing Fe into the gas phase, with a yield of 0.08 (Ar+ energy=600 eV). Extrapolating with a semi-empirical sputtering model to the conditions of a proton aurora indicates that sputtering by energetic protons (>100 keV) should also be efficient. However, the proton flux in even an intense aurora will be too low for the resulting injection of Fe species into the gas phase to compete with that from meteoric ablation. In contrast, sputtering of the icy particles in the main rings of Saturn by energetic O+ ions may be the source of recently observed Fe+ in the Saturnian magnetosphere. Electron sputtering (9.5 keV) produced no detectable Fe atoms or Fe-containing species. Finally, it was observed that Fe(OH)2 was produced when Fe was dosed onto an ice film at 140 K (but not at 95 K). Electronic structure theory shows that the reaction which forms this hydroxide from adsorbed Fe has a large barrier of about 0.7 eV, from which we conclude that the reaction requires both translationally hot Fe atoms and mobile H2O molecules on the ice surface.

  2. Formulation design and optimization of fast dissolving clonazepam tablets by sublimation method.

    PubMed

    Shirsand, S B; Suresh, Sarasija; Kusumdevi, V; Swamy, P V

    2011-09-01

    Fast dissolving tablets of clonazepam were prepared by sublimation method with a view to enhance patient compliance. A 3(2) full factorial design was applied to investigate the combined effect of two formulation variables: amount of croscarmellose sodium and camphor. Croscarmellose sodium (2-8% w/w) was used as superdisintegrant and camphor (20-40% w/w) was used as subliming agent, to increase the porosity of the tablets, since it helps water to penetrate into the tablets, along with directly compressible mannitol to enhance mouth feel. The tablets were evaluated for hardness, friability, thickness, drug content uniformity, in vitro dispersion time, wetting time and water absorption ratio. Based on in vitro dispersion time (approximately 11 s); the formulation containing 5% w/w croscarmellose sodium and 40% w/w camphor was found to be promising and tested for in vitro drug release pattern (in pH 6.8 phosphate buffer). Short-term stability (at 40°/75% relative humidity for 3 mo) and drug-excipient interaction. Surface response plots are presented to graphically represent the effect of independent variables on the in vitro dispersion time. The validity of the generated mathematical model was tested by preparing two extra-design checkpoints. The optimized tablet formulation was compared with conventional commercial tablet formulation for drug release profiles. This formulation showed nearly nine-fold faster drug release (t(50%) 1.8 min) compared to the conventional commercial tablet formulation (t(50%) 16.4 min). Short-term stability studies on the formulation indicated that there are no significant changes in drug content and in vitro dispersion time (P<0.05).

  3. CURVED WALLS: GRAIN GROWTH, SETTLING, AND COMPOSITION PATTERNS IN T TAURI DISK DUST SUBLIMATION FRONTS

    SciTech Connect

    McClure, M. K.; Calvet, N.; Hartmann, L.; Ingleby, L.; D'Alessio, P.; Espaillat, C.; Sargent, B.; Watson, D. M.; Hernández, J. E-mail: ncalvet@umich.edu E-mail: lingleby@umich.edu E-mail: cespaillat@cfa.harvard.edu E-mail: dmw@pas.rochester.edu

    2013-10-01

    The dust sublimation walls of disks around T Tauri stars represent a directly observable cross-section through the disk atmosphere and midplane. Their emission properties can probe the grain size distribution and composition of the innermost regions of the disk, where terrestrial planets form. Here we calculate the inner dust sublimation wall properties for four classical T Tauri stars with a narrow range of spectral types and inclination angles and a wide range of mass accretion rates to determine the extent to which the walls are radially curved. Best fits to the near- and mid-IR excesses are found for curved, two-layer walls in which the lower layer contains larger, hotter, amorphous pyroxene grains with Mg/(Mg+Fe) = 0.6 and the upper layer contains submicron, cooler, mixed amorphous olivine and forsterite grains. As the mass accretion rates decrease from 10{sup –8} to 10{sup –10} M{sub ☉} yr{sup –1}, the maximum grain size in the lower layer decreases from ∼3 to 0.5 μm. We attribute this to a decrease in fragmentation and turbulent support for micron-sized grains with decreasing viscous heating. The atmosphere of these disks is depleted of dust with dust-gas mass ratios 1 × 10{sup –4} of the interstellar medium (ISM) value, while the midplane is enhanced to eight times the ISM value. For all accretion rates, the wall contributes at least half of the flux in the optically thin 10 μm silicate feature. Finally, we find evidence for an iron gradient in the disk, suggestive of that found in our solar system.

  4. Origin of Sublimation Polygons in the Antarctic Western Dry Valleys: Implications for Patterned Ground Development on Mars

    NASA Astrophysics Data System (ADS)

    Marchant, D. R.; Head, J. W.

    2003-12-01

    Two hypotheses have been developed in order to address the age, origin, and evolution of surface polygons in the western Dry Valleys region of southern Victoria Land. Resolution of this debate has direct relevance and implications for patterned ground in ice-rich terrain on Mars. One hypothesis, the dynamic hypothesis, states that growth of sand-wedges pervasively deforms sediment across polygonal terrain, recycling sediment from troughs to polygon centers and back again over time scales of thousands of years. A second hypothesis, the stability hypothesis, states that deformation associated with sand-wedge polygons, particularly those that form over buried ice, is restricted to polygon troughs; the implication is that polygon centers may contain undisturbed soils >1 million years old. Evidence comes from field data that show that the age, origin, and morphology of polygons that form over buried ice in the western Dry Valleys region is tied collectively to the location and rate of sublimation of underlying ice. In Beacon Valley, sublimation of debris-rich ice produces a dry surface lag that insulates and slows loss of remaining ice. Sub-zero temperature cycling of near-surface ice and soil creates tensile stresses that result in a network of hexagonal cracks, extending upward from buried ice toward the ground surface. Where fines sift downward into open thermal-contraction cracks, a coarse-grained lag deposit forms on top of the ice. Owing to spatial variations in till texture, rates of sublimation vary across the ice surface. High rates occur below coarse-grained lags that cap contraction cracks; low rates are found at polygon centers beneath fine-grained low porosity/permeability debris. Measured concentrations of in-situ produced cosmogenic 3He in two depth profiles through sublimation till show a steady decrease with depth, indicating negligible recycling of surface materials on million-year time scales. These data suggest that once polygon troughs deepen

  5. Thermal alteration in carbonaceous chondrites and implications for sublimation in rock comets

    NASA Astrophysics Data System (ADS)

    Springmann, Alessondra; Lauretta, Dante S.; Steckloff, Jordan K.

    2015-11-01

    Rock comets are small solar system bodies in Sun-skirting orbits (perihelion q < ~0.15 AU) that form comae rich in mineral sublimation products, but lack typical cometary ice sublimation products (H2O, CO2, etc.). B-class asteroid (3200) Phaethon, considered to be the parent body of the Geminid meteor shower, is the only rock comet currently known to periodically eject dust and form a coma. Thermal fracturing or thermal decomposition of surface materials may be driving Phaethon’s cometary activity (Li & Jewitt, 2013). Phaethon-like asteroids have dynamically unstable orbits, and their perihelia can change rapidly over their ~10 Myr lifetimes (de León et al., 2010), raising the possibility that other asteroids may have been rock comets in the past. Here, we propose using spectroscopic observations of mercury (Hg) as a tracer of an asteroid’s thermal metamorphic history, and therefore as a constraint on its minimum achieved perihelion distance.B-class asteroids such as Phaethon have an initial composition similar to aqueously altered primitive meteorites such as CI- or CM-type meteorites (Clark et al., 2010). Laboratory heating experiments of ~mm sized samples of carbonaceous chondrite meteorites from 300K to 1200K at a rate of 15K/minute show mobilization and volatilization of various labile elements at temperatures that could be reached by Mercury-crossing asteroids. Samples became rapidly depleted in labile elements and, in particular, lost ~75% of their Hg content when heated from ~500-700 K, which corresponds to heliocentric distances of ~0.15-0.3 au, consistent with our thermal models. Mercury has strong emission lines in the UV (~ 185 nm) and thus its presence (or absence) relative to carbonaceous chondrite abundances would indicate if these bodies had perihelia in their dynamical histories inside of 0.15 AU, and therefore may have previously been Phaethon-like rock comets. Future space telescopes or balloon-borne observing platforms equipped with a UV

  6. A comprehensive numerical simulation of Io’s sublimation-driven atmosphere

    NASA Astrophysics Data System (ADS)

    Walker, Andrew C.; Gratiy, Sergey L.; Goldstein, David B.; Moore, Chris H.; Varghese, Philip L.; Trafton, Laurence M.; Levin, Deborah A.; Stewart, Bénédicte

    2010-05-01

    Io's sublimation-driven atmosphere is modeled using the direct simulation Monte Carlo (DSMC) method. These rarefied gas dynamics simulations improve upon earlier models by using a three-dimensional domain encompassing the entire planet computed in parallel. The effects of plasma heating, planetary rotation, inhomogeneous surface frost, molecular residence time of SO 2 on the exposed (non-volatile) rocky surface, and surface temperature distribution are investigated. Circumplanetary flow is predicted to develop from the warm dayside toward the cooler nightside. Io's rotation leads to a highly asymmetric frost surface temperature distribution (due to the frost's high thermal inertia) which results in circumplanetary flow that is not axi-symmetric about the subsolar point. The non-equilibrium thermal structure of the atmosphere, specifically vibrational and rotational temperatures, is also examined. Plasma heating is found to significantly inflate the atmosphere on both the dayside and nightside. The plasma energy flux causes high temperatures at high altitudes but plasma energy depletion through the dense gas column above the warmest frost permits gas temperatures cooler than the surface at low altitudes. A frost map (Douté, S., Schmitt, B., Lopes-Gautier, R., Carlson, R., Soderblom, L., Shirley, J., and the Galileo NIMS Team [2001]. Icarus 149, 107-132) is used to control the sublimated flux of SO 2 which can result in inhomogeneous column densities that vary by nearly a factor of four for the same surface temperature. A short residence time for SO 2 molecules on the "rock" component is found to smooth lateral atmospheric inhomogeneities caused by variations in the surface frost distribution, creating an atmosphere that looks nearly identical to one with uniform frost coverage. A longer residence time is found to agree better with mid-infrared observations (Spencer, J.R., Lellouch, E., Richter, M.J., López-Valverde, M.A., Jessup, K.L, Greathouse, T.K., Flaud, J

  7. Time-Dependent SSI Multispectral Properties for Rock, Soil, Ice, and Sublimation Lags at the Phoenix Landing Site on Mars

    NASA Astrophysics Data System (ADS)

    Morris, R. V.; Lemmon, M. T.; Arvidson, R. E.; Blaney, D. L.; Ellehoj, M. D.; Mellon, M. T.; Phoenix, S. T.

    2008-12-01

    The Surface Stereo Imager (SSI) on the Phoenix Lander is a 15 band multispectral imager covering the spectral range from 0.45 to 1.00 micrometers. More than 250 15-filter spectral image cubes have been obtained for surface targets at the Phoenix landing site in the north polar region of Mars. The spectra of surface soils and rocks are dominated by a ferric absorption edge from nanophase ferric oxide, and they are broadly similar to most multispectral data obtained during the Pathfinder and MER missions. Negative spectral slopes between about 0.70 and 1.00 micrometers, indicative of high concentrations of olivine in the El Dorado sand sheet at Gusev crater, were not detected. The albedo (cos(i) corrected) of Phoenix surface spectra is highly dependent on the time of sol (albedo at 0.80 micrometers varies by a factor of 2), consistent with opposition and phase function effects. Subsurface layers bearing water ice were exposed at a depth of about 4 cm by digging with the robotic arm scoop. The SSI spectra of icy materials are highly variable, ranging from typical ice (spectrally neutral and high albedo near 0.7) at the Dodo-Goldilocks trench to low albedo spectra (about 0.3 at 0.80 micrometers) with a ferric absorption edge at the Snow White trench. The differences are attributed, respectively, to low and high concentrations of fine-grained and ferric-rich material dispersed throughout the ice. The spectra of the icy surfaces are dependent on time as the ice sublimes. At Snow White, an optically thick (about 300 micrometers) sublimate lag develops within two sols. At Dodo- Goldilocks, the time scale for development of an optically thick sublimate lag is 5 to greater than 60 sols, depending on location within the trench. The spectra of sublimate lag are equivalent to those for fine-grained soil.

  8. Isolation of Purines and Pyrimidines from the Murchison Meteorite Using Sublimation

    NASA Technical Reports Server (NTRS)

    Glavin, D. P.; Bada, J. L.

    2004-01-01

    The origin of life on Earth, and possibly on other planets such as Mars, would have required the presence of liquid water and a continuous supply of prebiotic organic compounds. The exogenous delivery of organic matter by asteroids, comets, and carbonaceous meteorites could have contributed to the early Earth s prebiotic inventory by seeding the planet with biologically important organic compounds. A wide variety of prebiotic organic compounds have previously been detected in the Murchison CM type carbonaceous chondrite including amino acids, purines and pyrimidines. These compounds dominate terrestrial biochemistry and are integral components of proteins, DNA and RNA. Several purines including adenine, guanine, hypoxanthine, and xanthine, as well as the pyrimidine uracil, have previously been detected in water or formic acid extracts of Murchison using ion-exclusion chromatography and ultraviolet spectroscopy. However, even after purification of these extracts, the accurate identification and quantification of nucleobases is difficult due to interfering UV absorbing compounds. In order to reduce these effects, we have developed an extraction technique using sublimation to isolate purines and pyrimidines from other non-volatile organic compounds in Murchison acid extracts.

  9. Modeling Io's Sublimation-Driven Atmosphere: Gas Dynamics and Radiation Emission

    SciTech Connect

    Walker, Andrew C.; Goldstein, David B.; Varghese, Philip L.; Trafton, Laurence M.; Moore, Chris H.; Stewart, Benedicte; Gratiy, Sergey L.; Levin, Deborah A.

    2008-12-31

    Io's sublimation-driven atmosphere is modeled using the direct simulation Monte Carlo method. These rarefied gas dynamics simulations improve upon earlier models by using a three-dimensional domain encompassing the entire planet computed in parallel. The effects of plasma impact heating, planetary rotation, and inhomogeneous surface frost are investigated. Circumplanetary flow is predicted to develop from the warm subsolar region toward the colder night-side. The non-equilibrium thermal structure of the atmosphere, including vibrational and rotational temperatures, is also presented. Io's rotation leads to an asymmetric surface temperature distribution which is found to strengthen circumplanetary flow near the dusk terminator. Plasma heating is found to significantly inflate the atmosphere on both day- and night-sides. The plasma energy flux also causes high temperatures at high altitudes but permits relatively cooler temperatures at low altitudes near the dense subsolar point due to plasma energy depletion. To validate the atmospheric model, a radiative transfer model was developed utilizing the backward Monte Carlo method. The model allows the calculation of the atmospheric radiation from emitting/absorbing and scattering gas using an arbitrary scattering law and an arbitrary surface reflectivity. The model calculates the spectra in the {nu}{sub 2} vibrational band of SO{sub 2} which are then compared to the observational data.

  10. Sublimation and combustion of coal particles in the erosion laser torch

    SciTech Connect

    Bulat, A.; Shumrikov, V.; Osenny, V.

    2005-07-01

    Rate of coal particles' combustion in low-temperature plasma is of interest both from application and scientific points of view. Necessity of knowing parameters of the process of coal particles' combustion in plasma torch with the temperature of 2500-3000 K is governed by arising a number of state-of-the-art technological tasks related to the problems of finding new methods of power production, generation of high-calorific synthetic gases and using carbon as a high temperature structural material in nuclear power engineering. The present work deals with a rate of combustion of the sorbed coal particles in the erosion laser torch formed by means of interaction of pulse laser radiation (wave length {lambda} = 1,06 {mu}m, power density j = 10{sup 5} - 10{sup 7} Wcm{sup 2} with coals of various grades (in the wide range of carbon concentrations (80-95 %)). Physical and mathematical modeling of the process of coal particles' sublimation and combustion in non-equilibrium plasma flows with weight-average temperature of 2500-3000 K showed a good convergence of results for the particles of 10-100 {mu}m diameter and satisfactory one for the particles of {gt} 250{mu}m diameter.

  11. The impacts of moisture transport on drifting snow sublimation in the saltation layer

    NASA Astrophysics Data System (ADS)

    Huang, Ning; Dai, Xiaoqing; Zhang, Jie

    2016-06-01

    Drifting snow sublimation (DSS) is an important physical process related to moisture and heat transfer that happens in the atmospheric boundary layer, which is of glaciological and hydrological importance. It is also essential in order to understand the mass balance of the Antarctic ice sheets and the global climate system. Previous studies mainly focused on the DSS of suspended snow and ignored that in the saltation layer. Here, a drifting snow model combined with balance equations for heat and moisture is established to simulate the physical DSS process in the saltation layer. The simulated results show that DSS can strongly increase humidity and cooling effects, which in turn can significantly reduce DSS in the saltation layer. However, effective moisture transport can dramatically weaken the feedback effects. Due to moisture advection, DSS rate in the saltation layer can be several orders of magnitude greater than that of the suspended particles. Thus, DSS in the saltation layer has an important influence on the distribution and mass-energy balance of snow cover.

  12. Sublimation studies of NpO sub 2 F sub 2

    SciTech Connect

    Kleinschmidt, P.D. ); Lau, K.H.; Hildenbrand, D.L. )

    1992-08-15

    Using Knudsen effusion mass spectrometry, we have identified the following reaction as the sublimation decomposition mechanism of NpO{sub 2}F{sub 2}({ital s}): 2NpO{sub 2}F{sub 2}({ital s})=NpO{sub 2}({ital s})+O{sub 2}({ital g})+NpF{sub 4}({ital g}). From second-law analysis of the measured pressures of NpF{sub 4}({ital g}) over the temperature range 820--985 K the derived enthalpy change at 298 K is 556.8{plus minus}12.2 kJ/mol and the entropy change is 342.4 {plus minus}13.8 J/K mol. From these values and enthalpies of formation and entropies reported in the literature for the other species we calculate the enthalpy of formation of NpO{sub 2}F{sub 2}({ital s}) to be {minus}1608{plus minus}10 kJ/mol and the entropy to be 147{plus minus}9 J/K mol.

  13. The growth of sublimation crystals and surface hoar on the Antarctic plateau

    NASA Astrophysics Data System (ADS)

    Gallet, J.-C.; Domine, F.; Savarino, J.; Dumont, M.; Brun, E.

    2014-07-01

    On the Antarctic plateau, precipitation quantities are so low that the surface mass budget is for an important part determined by exchanges of water vapor between the snow surface and the atmosphere surface. At Dome C (75° S, 123° E), we have frequently observed the growth of crystals on the snow surface under calm sunny weather. Here we present the time variations of specific surface area (SSA) and density of these crystals. Using the detailed snow model Crocus, we conclude that the formation of these crystals was very likely due to the nighttime formation of surface hoar crystals and to the daytime formation of sublimation crystals. These latter crystals form by processes similar to those involved in the formation of frost flowers on young sea ice. The formation of these crystals impacts the albedo, mass and energy budget of the Antarctic plateau. In particular, the SSA variations of the surface layer can induce an instantaneous forcing at the snow surface up to -10 W m-2 at noon, resulting in a surface temperature drop of 0.45 K. This result confirms that snow SSA is a crucial variable to consider in the energy budget and climate of snow-covered surfaces.

  14. Fluctuations and instabilities of steps in the growth and sublimation of crystals

    NASA Astrophysics Data System (ADS)

    Uwaha, Makio; Saito, Yukio; Sato, Masahide

    1995-01-01

    Asymmetry in step kinetics (Schwoebel effect) has drastic effects on the motion of steps, and we study them theoretically and by simulation. With asymmetric step kinetics a step becomes smooth when it melts, whereas it becomes increasingly rough when it grows. When the Mullins-Sekerka type of instability takes place, the step does not form any stable pattern but shows a chaotic behavior although the crystal anisotropy influences the morphology. For a vicinal face consisting of equidistant steps, a similar enhancement of the step fluctuation in growth occurs while the fluctuation of step separation (terrace width) is suppressed because of the interference of the diffusion field. In sublimation, on the other hand, the step width is reduced but the fluctuation of the terrace width is enhanced. This leads to a bunching instability of steps. With one-sided step kinetics, steps always form pairwise bound states which have a hierarchical structure. In general various types of bound states appear, some of which lead to a morphological instability of the vicinal face.

  15. Selective crystallization of indigo B by a modified sublimation method and its redetermined structure

    PubMed Central

    Kettner, Florian; Hüter, Lucie; Schäfer, Johanna; Röder, Konstantin; Purgahn, Uta; Krautscheid, Harald

    2011-01-01

    Good-quality single crystals of the title compound, indigo B [systematic name: 2-(3-oxoindolin-2-yl­idene)indolin-3-one], C16H10N2O2, have been prepared with high selectivity by a sublimation process. The previous structure of indigo B [Süsse & Wolf (1980 ▶). Naturwissenschaften, 67, 453], which showed that the complete mol­ecule is generated by crystallographic inversion symmetry has been confirmed, but the present study reports more realistic geometrical parameters and modern standards of precision (e.g. σ for C—C bonds = 0.002–0.003 Å). Each mol­ecule features two intra­molecular N—H⋯O hydrogen bonds. In the crystal, mol­ecules are linked by strong face-to-face π–π stacking inter­actions involving both the six- and five-membered rings [centroid–centroid separations = 3.6290 (14) and 3.6506 (14) Å] and inter­molecular N—H⋯O hydrogen bonds. PMID:22219907

  16. Selective crystallization of indigo B by a modified sublimation method and its redetermined structure.

    PubMed

    Kettner, Florian; Hüter, Lucie; Schäfer, Johanna; Röder, Konstantin; Purgahn, Uta; Krautscheid, Harald

    2011-11-01

    Good-quality single crystals of the title compound, indigo B [systematic name: 2-(3-oxoindolin-2-yl-idene)indolin-3-one], C(16)H(10)N(2)O(2), have been prepared with high selectivity by a sublimation process. The previous structure of indigo B [Süsse & Wolf (1980 ▶). Naturwissenschaften, 67, 453], which showed that the complete mol-ecule is generated by crystallographic inversion symmetry has been confirmed, but the present study reports more realistic geometrical parameters and modern standards of precision (e.g. σ for C-C bonds = 0.002-0.003 Å). Each mol-ecule features two intra-molecular N-H⋯O hydrogen bonds. In the crystal, mol-ecules are linked by strong face-to-face π-π stacking inter-actions involving both the six- and five-membered rings [centroid-centroid separations = 3.6290 (14) and 3.6506 (14) Å] and inter-molecular N-H⋯O hydrogen bonds.

  17. STRUCTURAL CHANGES OF THE SUBLIMATION WALL IN PROTOPLANETARY DISKS DUE TO VARYING ACCRETION ILLUMINATION: A MECHANISM FOR RAPID INFRARED VARIABILITY

    SciTech Connect

    Nagel, E.; Flaherty, K. M.; Muzerolle, J.

    2015-08-01

    We study the changes in the sublimation wall structure due to variable illumination of a stellar hot spot on the dusty surroundings of a young star. The model includes the settling of large grains toward the disk midplane and the effect of the vertical density profile on the shaping of the sublimation wall. From a survey of objects in the young cluster IC 348, we extract three objects (LRLL 32, 40, and 63) that present typical variability in the [3.6] and [4.5] IRAC bands. We use the Spitzer photometry and ground-based 2–5 μm spectra for comparison with the models. Even though there is a correlation between accretion luminosity and dust emission based on the observations, we conclude from the modeling that the systems with lower mass accretion rates (LRLL 32 and 63) cannot be explained simply by a variable hot spot illuminating a sublimation wall. The observed variability amplitude for LRLL 40 (the system with the largest value of the mass accretion rate) can be obtained using the mechanism presented here. When considering a wide range of hot spot sizes and temperatures, the models can reproduce the infrared fluctuations seen in recent surveys, but only with accretion rate fluctuations that are orders of magnitude larger than is typically observed. These results highlight the relevance of accretion as a variability mechanism as well as its limitations in producing the full extent of the observed infrared variability.

  18. Application of a Kalman filter to UF{sub 6} gaseous diffusion plant freezer/sublimer systems

    SciTech Connect

    Ruppel, F.R.

    1992-03-01

    A signal is required to control the flow of UF{sub 6} in gaseous diffusion plant freezer/sublimer systems. The original strategy envisioned for deriving a flow signal was to take the derivative of the freezer/sublimer weigh cell signal. However, the derivative of the digitized weight signal is noisy, preventing good control. In addition, a bias is introduced into the weight derivative signal because a refrigerant is circulated through a shell-and-tube heat exchanger inside the freezer/sublimer. The weight of the refrigerant is included in the weight measured by the weigh cell. If the circulation rate of the refrigerent is not steady state, a bias exists. Measurements of upstream pressure, vessel pressure, and output to the system control valve are available to the control system. Thus, if the flow through the control valve is characterized properly by the measurements, a Kalman filter can be used in conjunction with these auxiliary inputs and the weigh cell input to overcome the noise and bias problem and provide an improve estimate of flow rate. A discussion of the development and the current status of a Kalman filter used for this application is given. 5 refs.

  19. Properties of filamentary sublimation residues from dispersions of clay in ice. [on Martian poles, comet nuclei, and icy satellites

    NASA Technical Reports Server (NTRS)

    Saunders, R. S.; Parker, T. J.; Stephens, J. B.; Fanale, F. P.; Sutton, S.

    1986-01-01

    Results are reported from experimental studies of the formation of ice mixed with mineral particles in an effort to simulate similar processes on natural surfaces such as at the Martian poles, on comet nuclei and on icy satellites. The study consisted of low-pressure, low-temperature sublimations of water ice from dilutions of water-clay (montmorillonite and Cabosil) dispersions of various component ratios. Liquid dispersions were sprayed into liquid nitrogen to form droplets at about -50 C. Both clay-water dispersions left a filamentary residue on the bottom of the Dewar after the water ice had sublimated off. The residue was studied with optical and SEM microscopy, the latter method revealing a high electrical conductivity in the residue. The results suggest that the sublimation of the water ice can leave a surface crust, which may be analogous to processes at the Martian poles and on comet nuclei. The process could proceed by the attachment of water molecules to salt crystals during the hottest part of the Martian year. The residue remaining was found to remain stable up to 370 C, be porous, and remain resilient, which could allow it to insulate ice bodies such as comets in space.

  20. Characterization of the Sublimation and Vapor Pressure of 2-(2-Nitrovinyl) Furan (G-0) Using Thermogravimetric Analysis: Effects of Complexation with Cyclodextrins.

    PubMed

    Ruz, Vivian; González, Mirtha Mayra; Winant, Danny; Rodríguez, Zenaida; Van den Mooter, Guy

    2015-08-19

    In the present work, the sublimation of crystalline solid 2-(2-nitrovinyl) furan (G-0) in the temperature range of 35 to 60 °C (below the melting point of the drug) was studied using thermogravimetric analysis (TGA). The sublimated product was characterized using Fourier-transformed-infrared spectroscopy (FT-IR) and thin layer chromatography (TLC). The sublimation rate at each temperature was obtained using the slope of the linear regression model and followed apparent zero-order kinetics. The sublimation enthalpy from 35 to 60 °C was obtained from the Eyring equation. The Gückel method was used to estimate the sublimation rate and vapor pressure at 25 °C. Physical mixtures, kneaded and freeze-dried complexes were prepared with 2-hydroxypropyl-β-cyclodextrin (HP-β-CD) and sulfobutyl ether-β-cyclodextrin (SBE-β-CD) and analyzed using isothermal TGA at 50 °C. The complexation contributed to reducing the sublimation process. The best results were achieved using freeze-dried complexes with both cyclodextrins.

  1. In-Situ Growth of Yb2O3 Layer for Sublimation Suppression for Yb14MnSb11 Thermoelectric Material for Space Power Applications

    NASA Technical Reports Server (NTRS)

    Nesbitt, James A.; Opila, Elizabeth J.; Nathal, Michael V.

    2012-01-01

    The compound Yb14MnSb11 is a p-type thermoelectric material of interest to the National Aeronautics and Space Administration (NASA) as a candidate replacement for the state-of-the-art Si-Ge used in current radioisotope thermoelectric generators (RTGs). Ideally, the hot end of this leg would operate at 1000 C in the vacuum of space. Although Yb14MnSb11 shows the potential to double the value of the thermoelectric figure of merit (zT) over that of Si-Ge at 1000 C, it suffers from a high sublimation rate at elevated temperatures and would require a coating in order to survive the required RTG lifetime of 14 years. The purpose of the present work is to measure the sublimation rate of Yb14MnSb11 and to investigate sublimation suppression for this material. This paper reports on the sublimation rate of Yb14MnSb11 at 1000 C (approximately 3 x 10(exp -3) grams per square centimeter hour) and efforts to reduce the sublimation rate with an in situ grown Yb2O3 layer. Despite the success in forming thin, dense, continuous, and adherent oxide scales on Yb14MnSb11, the scales did not prove to be sublimation barriers.

  2. Formation of dust-rich planetesimals from sublimated pebbles inside of the snow line

    NASA Astrophysics Data System (ADS)

    Ida, S.; Guillot, T.

    2016-11-01

    Context. For up to a few millions of years, pebbles must provide a quasi-steady inflow of solids from the outer parts of protoplanetary disks to their inner regions. Aims: We wish to understand how a significant fraction of the pebbles grows into planetesimals instead of being lost to the host star. Methods: We examined analytically how the inward flow of pebbles is affected by the snow line and under which conditions dust-rich (rocky) planetesimals form. When calculating the inward drift of solids that is due to gas drag, we included the back-reaction of the gas to the motion of the solids. Results: We show that in low-viscosity protoplanetary disks (with a monotonous surface density similar to that of the minimum-mass solar nebula), the flow of pebbles does not usually reach the required surface density to form planetesimals by streaming instability. We show, however, that if the pebble-to-gas-mass flux exceeds a critical value, no steady solution can be found for the solid-to-gas ratio. This is particularly important for low-viscosity disks (α< 10-3) where we show that inside of the snow line, silicate-dust grains ejected from sublimating pebbles can accumulate, eventually leading to the formation of dust-rich planetesimals directly by gravitational instability. Conclusions: This formation of dust-rich planetesimals may occur for extended periods of time, while the snow line sweeps from several au to inside of 1 au. The rock-to-ice ratio may thus be globally significantly higher in planetesimals and planets than in the central star.

  3. AdS/QCD, Light-Front Holography, and Sublimated Gluons

    SciTech Connect

    Brodsky, Stanley J.; de Teramond, Guy F.; /Costa Rica U.

    2012-02-16

    The gauge/gravity duality leads to a simple analytical and phenomenologically compelling nonperturbative approximation to the full light-front QCD Hamiltonian - 'Light-Front Holography', which provides a Lorentz-invariant first-approximation to QCD, and successfully describes the spectroscopy of light-quark meson and baryons, their elastic and transition form factors, and other hadronic properties. The bound-state Schroedinger and Dirac equations of the soft-wall AdS/QCD model predict linear Regge trajectories which have the same slope in orbital angular momentum L and radial quantum number n for both mesons and baryons. Light-front holography connects the fifth-dimensional coordinate of AdS space z to an invariant impact separation variable {zeta} in 3+1 space at fixed light-front time. A key feature is the determination of the frame-independent light-front wavefunctions of hadrons - the relativistic analogs of the Schroedinger wavefunctions of atomic physics which allow one to compute form factors, transversity distributions, spin properties of the valence quarks, jet hadronization, and other hadronic observables. One thus obtains a one-parameter color-confining model for hadron physics at the amplitude level. AdS/QCD also predicts the form of the non-perturbative effective coupling {alpha}{sub s}{sup AdS} (Q) and its {beta}-function with an infrared fixed point which agrees with the effective coupling a{sub g1} (Q{sup 2}) extracted from measurements of the Bjorken sum rule below Q{sup 2} < 1 GeV{sup 2}. This is consistent with a flux-tube interpretation of QCD where soft gluons with virtualities Q{sup 2} < 1 GeV{sup 2} are sublimated into a color-confining potential for quarks. We discuss a number of phenomenological hadronic properties which support this picture.

  4. SUBLIMATION-DRIVEN ACTIVITY IN MAIN-BELT COMET 313P/GIBBS

    SciTech Connect

    Hsieh, Henry H.; Hainaut, Olivier; Novaković, Bojan; Bolin, Bryce; Denneau, Larry; Haghighipour, Nader; Kleyna, Jan; Meech, Karen J.; Schunova, Eva; Wainscoat, Richard J.; Fitzsimmons, Alan; Kokotanekova, Rosita; Snodgrass, Colin; Lacerda, Pedro; Micheli, Marco; Moskovitz, Nick; Wasserman, Lawrence; Waszczak, Adam

    2015-02-10

    We present an observational and dynamical study of newly discovered main-belt comet 313P/Gibbs. We find that the object is clearly active both in observations obtained in 2014 and in precovery observations obtained in 2003 by the Sloan Digital Sky Survey, strongly suggesting that its activity is sublimation-driven. This conclusion is supported by a photometric analysis showing an increase in the total brightness of the comet over the 2014 observing period, and dust modeling results showing that the dust emission persists over at least three months during both active periods, where we find start dates for emission no later than 2003 July 24 ± 10 for the 2003 active period and 2014 July 28 ± 10 for the 2014 active period. From serendipitous observations by the Subaru Telescope in 2004 when the object was apparently inactive, we estimate that the nucleus has an absolute R-band magnitude of H{sub R} = 17.1 ± 0.3, corresponding to an effective nucleus radius of r{sub e} ∼ 1.00 ± 0.15 km. The object’s faintness at that time means we cannot rule out the presence of activity, and so this computed radius should be considered an upper limit. We find that 313P’s orbit is intrinsically chaotic, having a Lyapunov time of T{sub l} = 12,000 yr and being located near two three-body mean-motion resonances with Jupiter and Saturn, 11J-1S-5A and 10J+12S-7A, yet appears stable over >50 Myr in an apparent example of stable chaos. We furthermore find that 313P is the second main-belt comet, after P/2012 T1 (PANSTARRS), to belong to the ∼155 Myr old Lixiaohua asteroid family.

  5. Aluminum Nitride-Silicon Carbide Alloy Crystals Grown on SiC Substrates by Sublimation

    SciTech Connect

    Gu, Z; Du, Li; Edgar, J H; Payzant, E Andrew; Walker, Larry R; Liu, R; Engelhard, M H

    2005-01-01

    AlN-SiC alloy crystals, with a thickness greater than 500μm, were grown on 4H- and 6H-SiC substrates from a mixture of AlN and SiC powders by the sublimation-recondensation method at 1860-1990 C. On-axis SiC substrates produced a rough surface covered with hexagonal grains, while 6H- and 4H- off-axis SiC substrates with different miscut angles (8 or 3.68 ) formed a relatively smooth surface with terraces and steps. The substrate misorientation ensured that the AlNSiC alloy crystals grew two dimensionally as identified by scanning electron microscopy (SEM). Xray diffraction (XRD) and transmission electron microscopy (TEM) confirmed that the AlN-SiC alloys had the wurtzite structure. Electron probe microanalysis (EPMA) and x-ray photoelectron spectroscopy (XPS) demonstrated that the resultant alloy crystals had non-stoichiometric ratios of Al:N and Si:C and a uniform composition throughout the alloy crystal from the interface to the surface. The composition ratio of Al:Si of the alloy crystals changed with the growth temperature, and differed from the original source composition, which was consistent with the results predicted by thermodynamic calculation of the solid-vapor distribution of each element. XPS detected the bonding between Si-C, Si-N, Si-O for the Si 2p spectra. The dislocation density decreased with the growth, which was lower than 10^6cm-2 at the alloy surface, more than two orders of magnitude lower compared to regions close to the crystal/substrate interface, as determined by TEM.

  6. Mass removal by oxidation and sublimation of porous graphite during fiber laser irradiation

    NASA Astrophysics Data System (ADS)

    Phillips, Grady T.; Bauer, William A.; Fox, Charles D.; Gonzales, Ashley E.; Herr, Nicholas C.; Gosse, Ryan C.; Perram, Glen P.

    2017-01-01

    The various effects of laser heating of carbon materials are key to assessing laser weapon effectiveness. Porous graphite plates, cylinders, and cones with densities of 1.55 to 1.82 g/cm3 were irradiated by a 10-kW fiber laser at 0.075 to 3.525 kW/cm2 for 120 s to study mass removal and crater formation. Surface temperatures reached steady state values as high as 3767 K. The total decrease in sample mass ranged from 0.06 to 6.29 g, with crater volumes of 0.52 to 838 mm3, and penetration times for 12.7-mm-thick plates as short as 38 s. Minor contaminants in the graphite samples produced calcium and iron oxide to be redeposited on the graphite surface. Dramatic graphite crystalline structures are also produced at higher laser irradiances. Significantly increased porosity of the sample is observed even outside the laser-irradiated region. Total mass removed increases with deposited laser energy at a rate of 4.83 g/MJ for medium extruded graphite with an apparent threshold of 0.15 MJ. At ˜3.5 kW/cm2, the fractions of the mass removed from the cylindrical samples in the crater, surrounding trench, and outer region of decreased porosity are 38%, 47%, and 15%, respectively. Graphite is particularly resistant to damage by high power lasers. The new understanding of graphite combustion and sublimation during laser irradiation is vital to the more complex behavior of carbon composites.

  7. CdZnS thin films sublimated by closed space using mechanical mixing: A new approach

    NASA Astrophysics Data System (ADS)

    Mahmood, Waqar; Shah, Nazar Abbas

    2014-06-01

    Cadmium sulfide (CdS) is a prominent material for its tunable band gap used as a window layer in II-VI semiconductor solar cells. The light trapping capability of window layer is one of the powerful tools to enhance the efficiency of the cell. CdS and zinc (Zn) powders were mixed mechanically with different weight percents to make CdZnS (CZS) powder. CZS was deposited onto an ultrasonically cleaned glass substrate using close spaced sublimation (CSS) technique. CZS as-deposited thin films were characterized for structural, surface morphology with energy dispersive X-rays (EDX) and optical properties for the use of window layer in CdS/CdTe based solar cells. The different Zn concentrations in CZS played a vital role on crystallite size in structural analysis and optical properties e.g. transmission, absorption coefficient and energy band gap, etc. The crystallite size of as-deposited CZS thin films were increased as Zn concentration was increased up to certain value. The energy band gap varies from 2.42 eV to 2.57 eV for as-deposited CZS thin films with increasing Zn concentrations and surface morphology changes also. These changes were occurred due to zinc diffusion in CdS thin films. An angle resolved transmission data was taken to check the behavior of CdS and CZS thin film at different angles. A comparative study was carried out between CdS thin films and CZS thin films for the use of good window layer material.

  8. Age and stability of sublimation till over buried glacier ice, inferred from 21Ne measurements, Ong Valley, Antarctica

    NASA Astrophysics Data System (ADS)

    Bibby, T.; Putkonen, J.; Morgan, D. J.; Balco, G.

    2014-12-01

    Ong Valley, in the Central Transantarctic Mountains, contains three distinct glacial drifts deposited by past advances of the Argosy glacier into the valley. Massive ice occurs below two of the till deposits. Potentially, such buried ice under shallow regolith cover could provide access to past climate and biological records more easily than deep ice coring. We measured cosmic-ray produced 21Ne in these tills as a means of constraining the age and stability of the three drifts, as well as the ice below them. We collected samples in vertical profiles from two hand-dug sections through each drift. The pits from two drifts overlying buried ice extended to the buried ice surface. The hypothesis that these are sublimation tills implies that 21Ne concentrations are a function of i) any inheritance from prior exposure; ii) the age since emplacement of the ice and till; iii) the sublimation rate of the ice; and iv) the surface erosion rate of the till. 21Ne concentrations in the youngest drift are ca. 10 M atoms/g and invariant with depth, indicating that they are predominantly due to inheritance, and provide only a weak maximum age constraint of ca. 0.1 Mya. The two older drifts have surface 21Ne concentrations of 200-250 M atoms/ g and depth concentration profiles consistent with a sublimation till origin. Given that 21Ne concentrations in the deepest samples in each of the two older drifts provide an upper limit on the inherited 21Ne concentration, these imply minimum ages of 1 Mya for the middle drift and 1.6 Mya for the oldest. This implies a 1 Mya minimum age for the ice underlying the middle drift.

  9. Sublimation rates of carbon monoxide and carbon dioxide from comet nuclei at large distances from the Sun

    NASA Technical Reports Server (NTRS)

    Sekanina, Zdenek

    1991-01-01

    One of the more attractive among the plausible scenarios for the major emission event recently observed on Comet Halley at a heliocentric distance of 14.3 AU is activation of a source of ejecta driven by an icy substance much more volatile than water. As prerequisite for the forthcoming detailed analysis of the imaging observations of this event, a simple model is proposed that yields the sublimation rate versus time at any location on the surface of a rotating cometary nucleus for two candidate ices: carbon monoxide and carbon dioxide. The model's variable parameters are the comet's heliocentric distance r and the Sun's instantaneous zenith angle z.

  10. Hg1-xCdxTe vapor deposition on CdZnTe substrates by Closed Space Sublimation technique

    NASA Astrophysics Data System (ADS)

    Rubio, Sandra; Sochinskii, Nikolai V.; Repiso, Eva; Tsybrii, Zinoviia; Sizov, Fiodor; Plaza, Jose Luis; Diéguez, Ernesto

    2017-01-01

    Closed Space Sublimation (CSS) technique has been studied to deposit Hg1-xCdxTe polycrystalline films on CdZnTe substrates at the improved pressure-temperature conditions. The experimental results on film characterization suggest that the CSS optimal conditions are the argon atmospheric pressure (1013 mbar) and the deposition temperature in the range of 500-550 °C. These conditions provide macro-defect free Hg1-xCdxTe films with the uniform size and surface distribution of polycrystals.

  11. Effect of acoustic streaming on the mass transfer from a sublimating sphere

    NASA Astrophysics Data System (ADS)

    Kawahara, N.; Yarin, A. L.; Brenn, G.; Kastner, O.; Durst, F.

    2000-04-01

    particles much smaller than the sound wavelength. Good agreement between experiment and the theory of Yarin et al. is demonstrated. The time-averaged heat and mass transfer rates over a sphere surface are greatest at the sphere's equator and least at its poles in the experiment as predicted by the theory (the ultrasonic standing wave spans the vertical axis passing through the poles). The measured distribution of the mass transfer rate over the sphere surface also agrees with the theoretical predictions, which shows that in strong acoustic fields sublimation (or evaporation) results from the acoustic streaming.

  12. Redetermination of the crystal structure of boron subphthalocyanine chloride (Cl-BsubPc) enabled by slow train sublimation.

    PubMed

    Virdo, Jessica D; Lough, Alan J; Bender, Timothy P

    2016-04-01

    The crystal structure of boron subphthalocyanine chloride [systematic name: chlorido(subphthalocyaninato)boron], C24H12BClN6, a material of widespread interest in organic electronic device applications, has been redetermined with a higher precision using large single crystals obtained via slow train sublimation. Details are given for the construction and operation of the train sublimation system, which has been designed to reproducibly yield single crystals suitable for diffraction experiments in a manner which approximates the vacuum deposition conditions commonly used to fabricate organic electronic devices. Diffraction experiments were conducted using two crystal samples and four temperatures (90, 123, 147 and 295 K), enabling a discussion of changes in the unit cell and intermolecular interactions with respect to temperature and in comparison to two previously published structures of Cl-BsubPc. The redetermined structure confirms the original structure published 41 years ago [Meller & Ossko (1972). Monatsh. Chem. 103, 150-155], with significantly improved precision for the geometric parameters. Analysis of the crystal structure revealed three intersecting ribbon motifs formed through a combination of π-π and halogen-π (specifically B-Cl...π) interactions. H atoms were refined independently in order to facilitate a thorough discussion of these intermolecular interactions using Hirshfeld surface analysis.

  13. An enhanced model of the contemporary and long-term (200 ka) sublimation of the massive subsurface ice in Beacon Valley, Antarctica

    NASA Astrophysics Data System (ADS)

    Liu, Lu; Sletten, Ronald S.; Hagedorn, Birgit; Hallet, Bernard; McKay, Christopher P.; Stone, John O.

    2015-08-01

    A massive ice body buried under several decimeters of dry regolith in Beacon Valley, Antarctica, is believed to be more than 1 Ma old and perhaps over 8.1 Ma; however, vapor diffusion models suggest that subsurface ice in this region is not stable under current climate conditions. To better understand the controls on sublimation rates and stability of this massive ice, we have modeled vapor diffusion using 12 years of climate and soil temperature data from 1999 to 2011, including field measurements of episodic snow cover and snowmelt events that have not been represented in previous models of ground ice sublimation. The model is then extended to reconstruct the sublimation history over the last 200 ka using paleotemperatures estimated from ice core data from nearby Taylor Dome and a relationship between atmospheric temperature and humidity derived from our meteorological records. The model quantifies the impact of episodic snow events; they account for a nearly 30% reduction in the massive ice loss. The sublimation rate of ground ice averages 0.11 mm a-1 between 1999 and 2011 in Beacon Valley. Parameterized with past environmental conditions and assuming the same regolith thickness, the modeled sublimation rate of ground ice in Beacon Valley averages 0.09 mm a-1 for the last 200 ka, comparable to the long-term average rate estimated independently from various studies based on cosmogenic isotopes. This study provides a realistic estimate of the long-term sublimation history and supports the inference that the buried ice in Beacon Valley is older than 1 Ma.

  14. The not-so-sublime early Earth recorded in Hadean zircons

    NASA Astrophysics Data System (ADS)

    Cavosie, A. J.

    2011-12-01

    oxygen isotope ratios (up to 7.5 %) are evidence that the early formed crust was evolved (granitic), rather than primitive (gabbroic). (4) Variable oxygen and Li isotope ratios in zircon record processes of surface alteration and subsequent magmatic recycling of altered crust, constraining the appearance of low surface temperatures and liquid water oceans by 4.3 to 4.2 Ga. (5) Evidence for the Late Heavy Bombardment has not been identified in Hadean zircons; planar microstructures known to form in shock metamorphosed zircon have not been found in Hadean grains. (6) Other claims, including reports of modern-style plate interactions based on zircon mineral inclusion barometry, and the presence of diamond inclusions in Hadean zircons, remain controversial, and open to interpretation. Many aspects of the Hadean are therefore similar to the Archean; distinguishing the two eons thus remains a challenge. However, the cooling and condensation of liquid surface water and its subsequent effect on magma chemistry, as recorded in Hadean zircons from 4.3 to 4.2 Ga, suggests a global-scale process that created habitats for life, and clearly marked the end of 'hell-like' Hadean surface conditions. As the timescale and processes active on the early Earth become better quantified through careful documentation and measurement of these ancient zircons, the Hadean becomes somewhat less sublime.

  15. Investigations in Martian geology. Part 1: Nature of the mantling deposit in the heavily cratered terrain of northeastern Arabia, Mars. Part 2: Experimental studies of clean and dust-or-sand-covered ice sublimation under Mars-like conditions

    SciTech Connect

    Moore, J.M.

    1990-01-01

    This dissertation consists of two parts. Part 1 describes the geomorphology of a portion of northeastern Arabia, Mars. This surface is covered by an extensive, layered deposit which has been, in places, substantially eroded. Speculative origins for the deposit include formation as a differentially welded pyroclastic tuff, or a differentially compacted, zonally indurated aeolian dust deposit. Part 2 is an experimental study of the sublimation rate of H{sub 2}O ice, both from clean surfaces and from under thin layers of dust or sand, in a Mars-like environment. The major conclusions drawn from the results of this experiment are: (1) even very thin layers of dust greatly lower the sublimation rate of an underlying ice substrate being heated from above, whereas thin layers of sand suppress the sublimation rate of underlying ice being heated from above to a significantly lesser extent; (2) thin layers of dust or sand only mildly suppress the sublimation rate of an underlying ice substrate when sample is wholly isothermal; (3) even a low-flux, desiccated gas flow over the sample surface significantly increases the sublimation rate of any given sample; (4) dry sublimation of ice underlying thin layers of dust or sand may modify the surface texture as a function of particle cohesion and as the ratio of particle layer thickness to the amount by which the surface was lowered; and (5) the actual sublimation rate of clean ice is several factors lower than the sublimation rate predicted by a commonly used formula.

  16. Origin, Evolution, and Preservation of Cold Based Debris Covered Glaciers: Quantifying Sublimation Rates of Ancient Buried Ice in Antarctica

    NASA Astrophysics Data System (ADS)

    Kowalewski, D. E.; Marchant, D. R.

    2007-12-01

    Growing interest in our planet's climate history has placed a premium on acquiring detailed records of past climate change. Of considerable interest are archives of ancient atmosphere trapped within the debris-covered alpine glaciers of the western Dry Valleys region of Antarctica. The Mullins Valley debris-covered glacier (~8 km in length) is sourced from local snowfall at the steep headwall of the valley. The first 1.2 km of this glacier is generally free of overlying debris except for isolated cobbles and boulders. Thereafter, the ice surface is covered with a thin, continuous sheet of dolerite-rich rubble. Factors that influence the origin and modification of this ice include atmospheric temperature and relative humidity, precipitation, incoming solar radiance, surface albedo, till texture, winds, surface roughness, salts, and secondary ice lenses. We applied a diffusion model to track vapor flux within a sublimation till overlying the Mullins Valley debris-covered glacier, purportedly the world's oldest debris-covered alpine glacier. As input, we used meteorological data from HOBO data loggers that captured climate change and till temperatures. Results show that vapor flows into and out of the sublimation till at rates dependent on the non-linear variation of soil temperature with depth. Sublimation rates along the Mullins Glacier varied as a function of till thickness, local climate (using a calculated regional lapse rate of 0.88°C per 100 m), and till texture. Ice loss during the study interval (November 27, 2006 to December 24, 2006) ranged from as high as 2.12 mm for exposed glacier ice in the upper ablation zone, to as low as 0.01 mm for buried ice beneath till >50 cm in thickness. Averaged over the entire ablation zone (6.7 km2), this yields a net ice-surface lowering of 0.32 mm during the study interval. Numerical modeling suggests that a modest ice accumulation rate at the headwall of ~1 cm a-1 appears sufficient to maintain current ice volumes

  17. Material composition assessment and discovering sublimation activity on asteroids 145 Adeona, 704 Interamnia, 779 Nina, and 1474 Beira

    NASA Astrophysics Data System (ADS)

    Busarev, V. V.; Barabanov, S. I.; Puzin, V. B.

    2016-07-01

    Spectrophotometric observations of 145 Adeona, 704 Interamnia, 779 Nina, and 1474 Beira—asteroids of close primitive types—allowed us to detect similar mineralogical absorption bands in their reflectance spectra centered in the range 0.35 to 0.92 μm; the bands are at 0.38, 0.44, and 0.67-0.71 μm. On the same asteroids, the spectral signs of simultaneous sublimation activity were found for the first time. Namely, there are maxima at ˜0.35-0.60 μm in the reflectance spectra of Adeona, Interamnia, and Nina and at ˜0.55-075 μm in the spectra of Beira. We connect this activity with small heliocentric distances of the asteroids and, consequently, with a high insolation at their surfaces. Examination of the samples of probable analogues allowed us to identify Fe3+ and Fe2+ in the material of these asteroids through the mentioned absorption bands. For analogues, we took powdered samples of carbonaceous chondrites Orgueil (CI), Mighei (CM2), Murchison (CM2), and Boriskino (CM2), as well as hydrosilicates of the serpentine group. Laboratory spectral reflectance study of the samples of low-iron Mg serpentines (<2 wt % FeO) showed that the equivalent width of the absorption band centered at 0.44-0.46 μm strongly correlates with the content of Fe3+ in octahedral and tetrahedral coordinations. Our conclusion is that this absorption band can be used as a qualitative indicator of Fe3+ in the surface matter of asteroids and other solid celestial bodies. The comparison of the listed analog samples and the asteroids by parameters of the spectral features suggests that the silicate component of the asteroids' surface material is a mixture of hydrated and oxidized compounds, including oxides and hydroxides of bivalent and trivalent iron and carbonaceous-chondritic material. At the same time, the sublimation activity of Adeona, Interamnia, Nina, and Beira at high surface temperatures points to a substantial content of water ice in their material. This contradicts the

  18. On the sublimation of ice particles on the surface of Mars; with applications to the 2007/8 Phoenix Scout mission

    NASA Astrophysics Data System (ADS)

    Taylor, Peter A.; Baibakov, Konstantin; Brown, Stephen; Hecht, Michael H.; Hudson, Troy L.; Li, P.-Y.; Lange, Carlos F.; Prieto, Luis; Savelyev, Sergiy

    2006-04-01

    Experimental studies related to the sublimation of ice, in bulk or as small particles, alone or mixed with dust similar to that expected on the surface of Mars, are reported. The experiments, a cloud physics particle sublimation model, and a convection model presented by Ingersoll, all indicate a strong dependence of sublimation rate on temperature, and this appears to be the dominant factor, assuming that the relative humidity of the air is fairly low. In addition the rate of loss of water vapour appears to depend primarily on exposed surface area and less on particle size and the total mass of the sample, or the mass of ice in the sample. The 2007/8 Phoenix Scout mission plans to obtain and analyse samples of sub-surface ice from about 70° N on Mars. A concern is that these samples, in the form of ice chips of size about 1 mm diameter, could be prone to sublimation when exposed for prolonged periods (many hours) to a relatively warm and dry atmosphere. Our laboratory simulations confirm that this could be a problem if particles are simply left lying on the surface, but also indicate that samples kept suitably cold and collected together in confined piles will survive long enough for the collection and delivery (to the analysis instruments) procedure to be completed.

  19. The Role of Sublimation and Condensation in the Dynamics of Aeolian Ice Sedimentation Waves on the North Polar Cap of Mars

    NASA Astrophysics Data System (ADS)

    Herny, C.; Carpy, S.; Bourgeois, O.; Spiga, A.; Rodriguez, S.; Massé, M.; Le Mouélic, S.

    2016-09-01

    We explore the role of sublimation and condensation of water vapor in the development of ice sedimentation waves on the North Polar Cap of Mars. Our observations and simulations are in accordance with the hypothesis that sedimentation waves can migrate upwind or downwind.

  20. Method of fabricating conducting oxide-silicon solar cells utilizing electron beam sublimation and deposition of the oxide

    DOEpatents

    Feng, Tom; Ghosh, Amal K.

    1979-01-01

    In preparing tin oxide and indium tin oxide-silicon heterojunction solar cells by electron beam sublimation of the oxide and subsequent deposition thereof on the silicon, the engineering efficiency of the resultant cell is enhanced by depositing the oxide at a predetermined favorable angle of incidence. Typically the angle of incidence is between 40.degree. and 70.degree. and preferably between 55.degree. and 65.degree. when the oxide is tin oxide and between 40.degree. and 70.degree. when the oxide deposited is indium tin oxide. gi The Government of the United States of America has rights in this invention pursuant to Department of Energy Contract No. EY-76-C-03-1283.

  1. The role of oxygen in CdS/CdTe solar cells deposited by close-spaced sublimation

    SciTech Connect

    Rose, D.H.; Levi, D.H.; Matson, R.J.

    1996-05-01

    The presence of oxygen during close-spaced sublimation (CSS) of CdTe has been previously reported to be essential for high-efficiency CdS/CdTe solar cells because it increases the acceptor density in the absorber. The authors find that the presence of oxygen during CSS increases the nucleation site density of CdTe, thus decreasing pinhole density and grain size. Photoluminescence showed that oxygen decreases material quality in the bulk of the CdTe film, but positively impacts the critical CdS/CdTe interface. Through device characterization the authors were unable to verify an increase in acceptor density with increased oxygen. These results, along with the achievement of high-efficiency cells (13% AM1.5) without the use of oxygen, led the authors to conclude that the use of oxygen during CSS deposition of CdTe can be useful but is not essential.

  2. Volatilization, transport and sublimation of metallic and non-metallic elements in high temperature gases at Merapi Volcano, Indonesia

    USGS Publications Warehouse

    Symonds, R.B.; Rose, William I.; Reed, M.H.; Lichte, F.E.; Finnegan, David L.

    1987-01-01

    Condensates, silica tube sublimates and incrustations were sampled from 500-800??C fumaroles and lava samples were collected at Merapi Volcano, Indonesia in Jan.-Feb., 1984. With respect to the magma, Merapi gases are enriched by factors greater than 105 in Se, Re, Bi and Cd; 104-105 in Au, Br, In, Pb and W; 103-104 in Mo, Cl, Cs, S, Sn and Ag; 102-103 in As, Zn, F and Rb; and 1-102 in Cu, K, Na, Sb, Ni, Ga, V, Fe, Mn and Li. The fumaroles are transporting more than 106 grams/day ( g d) of S, Cl and F; 104-106 g/d of Al, Br, Zn, Fe, K and Mg; 103-104 g d of Pb, As, Mo, Mn, V, W and Sr; and less than 103 g d of Ni, Cu, Cr, Ga, Sb, Bi, Cd, Li, Co and U. With decreasing temperature (800-500??C) there were five sublimate zones found in silica tubes: 1) cristobalite and magnetite (first deposition of Si, Fe and Al); 2) K-Ca sulfate, acmite, halite, sylvite and pyrite (maximum deposition of Cl, Na, K, Si, S, Fe, Mo, Br, Al, Rb, Cs, Mn, W, P, Ca, Re, Ag, Au and Co); 3) aphthitalite (K-Na sulfate), sphalerite, galena and Cs-K. sulfate (maximum deposition of Zn, Bi, Cd, Se and In; higher deposition of Pb and Sn); 4) Pb-K chloride and Na-K-Fe sulfate (maximum deposition of Pb, Sn and Cu); and 5) Zn, Cu and K-Pb sulfates (maximum deposition of Pb, Sn, Ti, As and Sb). The incrustations surrounding the fumaroles are also chemically zoned. Bi, Cd, Pb, W, Mo, Zn, Cu, K, Na, V, Fe and Mn are concentrated most in or very close to the vent as expected with cooling, atmospheric contamination and dispersion. The highly volatile elements Br, Cl, As and Sb are transported primarily away from high temperature vents. Ba, Si, P, Al, Ca and Cr are derived from wall rock reactions. Incomplete degassing of shallow magma at 915??C is the origin of most of the elements in the Merapi volcanic gas, although it is partly contaminated by particles or wall rock reactions. The metals are transported predominantly as chloride species. As the gas cools in the fumarolic environment, it becomes saturated

  3. Numerical simulation of temperature fields during the sublimation growth of SiC single crystals, using WIAS-HiTNIHS

    NASA Astrophysics Data System (ADS)

    Geiser, Jürgen; Klein, Olaf; Philip, Peter

    2007-05-01

    We present numerical computations of the temperature fields in axisymmetric growth apparatus for sublimation growth of silicon carbide (SiC) bulk single crystals by physical vapor transport (PVT) (modified Lely method). The results are computed using our software WIAS-HiTNIHS, the WIAS High Temperature Numerical Induction Heating Simulator; pronunciation: ˜hit-nice, by solving the energy balance in the entire growth apparatus, taking into account the heat conduction in the solid parts as well as in gas cavities, and also accounting for the radiative heat transfer between the surfaces of the gas cavities. The insulation in a PVT growth apparatus usually consists of graphite felt, where the fibers are aligned in one particular direction, resulting in an anisotropic thermal conductivity. We show that neglecting this anisotropy can overestimate the SiC crystal's temperature by 70 K or underestimate the required heating power by 800 W.

  4. Volatilization, transport and sublimation of metallic and non-metallic elements in high temperature gases at Merapi Volcano, Indonesia

    NASA Astrophysics Data System (ADS)

    Symonds, Robert B.; Rose, William I.; Reed, Mark H.; Lichte, Frederick E.; Finnegan, David L.

    1987-08-01

    Condensates, silica tube sublimates and incrustations were sampled from 500-800°C fumaroles and lava samples were collected at Merapi Volcano, Indonesia in Jan.-Feb., 1984. With respect to the magma, Merapi gases are enriched by factors greater than 10 5 in Se, Re, Bi and Cd; 10 4-10 5 in Au, Br, In, Pb and W; 10 3-10 4 in Mo, Cl, Cs, S, Sn and Ag; 10 2-10 3 in As, Zn, F and Rb; and 1-10 2 in Cu, K, Na, Sb, Ni, Ga, V, Fe, Mn and Li. The fumaroles are transporting more than 10 6 grams/day ( g/d) of S, Cl and F; 10 4-10 6 g/d of Al, Br, Zn, Fe, K and Mg; 10 3-10 4g/d of Pb, As, Mo, Mn, V, W and Sr; and less than 10 3g/d of Ni, Cu, Cr, Ga, Sb, Bi, Cd, Li, Co and U. With decreasing temperature (800-500°C) there were five sublimate zones found in silica tubes: 1) cristobalite and magnetite (first deposition of Si, Fe and Al); 2) K-Ca sulfate, acmite, halite, sylvite and pyrite (maximum deposition of Cl, Na, K, Si, S, Fe, Mo, Br, Al, Rb, Cs, Mn, W, P, Ca, Re, Ag, Au and Co); 3) aphthitalite (K-Na sulfate), sphalerite, galena and Cs-K. sulfate (maximum deposition of Zn, Bi, Cd, Se and In; higher deposition of Pb and Sn); 4) Pb-K chloride and Na-K-Fe sulfate (maximum deposition of Pb, Sn and Cu); and 5) Zn, Cu and K-Pb sulfates (maximum deposition of Pb, Sn, Ti, As and Sb). The incrustations surrounding the fumaroles are also chemically zoned. Bi, Cd, Pb, W, Mo, Zn, Cu, K, Na, V, Fe and Mn are concentrated most in or very close to the vent as expected with cooling, atmospheric contamination and dispersion. The highly volatile elements Br, Cl, As and Sb are transported primarily away from high temperature vents. Ba, Si, P, Al, Ca and Cr are derived from wall rock reactions. Incomplete degassing of shallow magma at 915°C is the origin of most of the elements in the Merapi volcanic gas, although it is partly contaminated by particles or wall rock reactions. The metals are transported predominantly as chloride species. As the gas cools in the fumarolic environment, it

  5. A macroscale mixture theory analysis of deposition and sublimation rates during heat and mass transfer in dry snow

    NASA Astrophysics Data System (ADS)

    Hansen, A. C.; Foslien, W. E.

    2015-09-01

    The microstructure of a dry alpine snowpack is a dynamic environment where microstructural evolution is driven by seasonal density profiles and weather conditions. Notably, temperature gradients on the order of 10-20 K m-1, or larger, are known to produce a faceted snow microstructure exhibiting little strength. However, while strong temperature gradients are widely accepted as the primary driver for kinetic growth, they do not fully account for the range of experimental observations. An additional factor influencing snow metamorphism is believed to be the rate of mass transfer at the macroscale. We develop a mixture theory capable of predicting macroscale deposition and/or sublimation in a snow cover under temperature gradient conditions. Temperature gradients and mass exchange are tracked over periods ranging from 1 to 10 days. Interesting heat and mass transfer behavior is observed near the ground, near the surface, as well as immediately above and below dense ice crusts. Information about deposition (condensation) and sublimation rates may help explain snow metamorphism phenomena that cannot be accounted for by temperature gradients alone. The macroscale heat and mass transfer analysis requires accurate representations of the effective thermal conductivity and the effective mass diffusion coefficient for snow. We develop analytical models for these parameters based on first principles at the microscale. The expressions derived contain no empirical adjustments, and further, provide self consistent values for effective thermal conductivity and the effective diffusion coefficient for the limiting cases of air and solid ice. The predicted values for these macroscale material parameters are also in excellent agreement with numerical results based on microscale finite element analyses of representative volume elements generated from X-ray tomography.

  6. Pedestal Craters in Utopia Planitia and Malea Planum: Evidence for a Past Ice-Rich Substrate from Marginal Sublimation Pits.

    NASA Astrophysics Data System (ADS)

    Kadish, S. J.; Head, J. W.; Barlow, N. G.; Marchant, D. R.

    2008-09-01

    Introduction: Pedestal craters (Pd) are a subclass of impact craters unique to Mars [1] characterized by a crater perched near the center of a pedestal (mesa or plateau) that is surrounded by a quasi-circular, outward-facing scarp. The marginal scarp is usually several crater diameters from the crater rim (Figs. 2,4,5), and tens to over 100 meters above the surrounding plains (Fig. 2). Pd have been interpreted to form by armoring of the proximal substrate during the impact event. Hypotheses for the armoring mechanism include an ejecta covering [e.g., 3], increased ejecta mobilization caused by volatile substrates [4], distal glassy/melt-rich veneers [5], and/or an atmospheric blast/thermal effect [6]. Subsequently, a marginal scarp forms by preferential erosion of the substrate surrounding the armored region, most commonly thought to involve eolian removal of fine-grained, non-armored material [e.g., 3]. An understanding of the distribution of Pd, which form predominantly poleward of ~40°N and S latitude [7-9] (Fig. 1), and the role of redistribution of ice and dust during periods of climate change [e.g., 10-11], suggests that the substrate might have been volatile-rich [8-9, 12-14]. As such, some researchers [e.g., 8-9] have proposed a model for Pd formation that involves impact during periods of higher obliquity, when mid- to high-latitude substrates were characterized by thick deposits of snow and ice [e.g., 15]. Subsequent sublimation of the volatile units, except below the armored regions, yielded the perched Pd. Thus, this model predicts that thick deposits of snow/ice should underlie Pd. This is in contrast to the eolian model [3], which calls primarily for deflation of sand and dust. Here, we show the results of our study [8,16] that has documented and characterized 2461 Pd on Mars equatorward of ~65° N and S latitude (Fig. 1) in order to test these hypotheses for the origin of pedestal craters. In particular, we report on the detection of 50 Pd in Utopia

  7. Experimental and theoretical simulation of sublimating dusty water ice with implications for D/H ratios of water ice on Comets and Mars

    NASA Astrophysics Data System (ADS)

    Moores, John E.; Brown, Robert H.; Lauretta, Dante S.; Smith, Peter H.

    2012-12-01

    Sublimation experiments have been carried out to determine the effect of the mineral dust content of porous ices on the isotopic composition of the sublimate gas over medium (days to weeks) timescales. Whenever mineral dust of any kind was present, the D/H ratio of the sublimated gas was seen to decrease with time from the bulk ratio. Fractionations of up to 2.5 were observed for dust mixing ratios of 9 wt% and higher of JSC MARS-1 regolith simulant 1-10 μm crushed and sieved fraction. These favored the presence of the light isotope, H2O, in the gas phase. The more dust was added to the mixture, the more pronounced was this effect. Theoretical modeling of gas migration within the porous samples and adsorption on the excavated dust grains was undertaken to explain the results. Adsorption onto the dust grains is able to explain the low D/H ratios in the sublimate gas if adsorption favors retention of HDO over H2O. This leads to significant isotopic enrichment of HDO on the dust over time and depletion in the amount of HDO escaping the system as sublimate gas. This effect is significant for planetary bodies on which water moves mainly through the gas phase and a significant surface reservoir of dust may be found, such as on Comets and Mars. For each of these, inferences about the bulk water D/H ratio as inferred from gas phase measurements needs to be reassessed in light of the volatile cycling history of each body.

  8. Experimental and theoretical simulation of sublimating dusty water ice with implications for D/H ratios of water ice on Comets and Mars

    NASA Astrophysics Data System (ADS)

    Moores, John E.; Brown, Robert H.; Lauretta, Dante S.; Smith, Peter H.

    2012-04-01

    Sublimation experiments have been carried out to determine the effect of the mineral dust content of porous ices on the isotopic composition of the sublimate gas over medium (days to weeks) timescales. Whenever mineral dust of any kind was present, the D/H ratio of the sublimated gas was seen to decrease with time from the bulk ratio. Fractionations of up to 2.5 were observed for dust mixing ratios of 9 wt% and higher of JSC MARS-1 regolith simulant 1-10 μm crushed and sieved fraction. These favored the presence of the light isotope, H2O, in the gas phase. The more dust was added to the mixture, the more pronounced was this effect. Theoretical modeling of gas migration within the porous samples and adsorption on the excavated dust grains was undertaken to explain the results. Adsorption onto the dust grains is able to explain the low D/H ratios in the sublimate gas if adsorption favors retention of HDO over H2O. This leads to significant isotopic enrichment of HDO on the dust over time and depletion in the amount of HDO escaping the system as sublimate gas. This effect is significant for planetary bodies on which water moves mainly through the gas phase and a significant surface reservoir of dust may be found, such as on Comets and Mars. For each of these, inferences about the bulk water D/H ratio as inferred from gas phase measurements needs to be reassessed in light of the volatile cycling history of each body.

  9. Re-analysis of martian gully orientation and slope for comparison with climate model predictions of freeze-thaw and dry-ice sublimation.

    NASA Astrophysics Data System (ADS)

    Conway, Susan; Harrison, Tanya; Lewis, Stephen; Balme, Matthew; Soare, Richard; Britton, Andrew

    2016-04-01

    during which the surface temperature was below the CO2 condensation point of 149K. We use these data as a proxy for where CO2sublimation processes can be active. (ii) The number of sols for which the daily minimum is below 273K and the daily maximum is above 273K. We use these data as a proxy for where ice could be stable and then melt during freeze-thaw cycles. Our results reveal that neither of these simple modelling cases exactly fits the observational data, therefore we conclude that it is likely that a mixture of CO2 and water related processes are responsible for forming martian gullies. We aim to perform a number of tests to assess both the applicability of these simple proxies and to test a wider range of substrate properties (buried ice) and orbital parameters (perihelion and increased atmospheric pressure at high obliquity) to see if they give better fits to our observations.

  10. A field study of the geomorphic effects of sublimating CO2 blocks on dune slopes at Coral Pink Dunes, Utah.

    NASA Astrophysics Data System (ADS)

    Bourke, Mary; Nield, Jo; Diniega, Serina; Hansen, Candy; McElwaine, Jim

    2016-04-01

    The seasonal sublimation of CO2 ice is an active driver of present-day surface change on Mars. Diniega et al (2013) proposed that a discrete type of Martian gully, found on southern hemisphere dunes, were formed by the movement of CO2 seasonal ice blocks. These 'Linear Gullies' consist primarily of long (100 m - 2.5 km) grooves with near-uniform width (few-10 m wide), and typical depth of <2 m. They are near-linear throughout most of their length but sometimes contains zones of low-to-high sinuosity. They are commonly bounded by levées. The groove is generally prefaced by a small alcove that originates at the dune brink. We present the results of a set of field experiments that were undertaken at the Coral Pink sand dunes, Utah. These are sister experiments to those undertaken in Arizona (Bourke et al, 2016). The experiments were undertaken on an active barchan dune with a 16 m long lee slope (30.3°). Ambient air temperature was 30°C and relative humidity was 25%; sand surface temperatures were 26.5°C. A CO2 ice block (60x205x210 mm) was placed at the dune brink and with a gentle nudge it moved downslope. The dynamics of the block movement were recorded using a pair of high resolution video cameras. Geomorphological observations were noted and topographic change was quantified using a Leica P20 terrestrial laser scanner with a resolution of 0.8 mm at 10 m, and change detection limits less than 3 mm. The block run was repeated a total of 10 times and launched from the same location at the dune brink. The experiment ran for 45 minutes. The block size was reduced to (45 x 190 x 195 mm) by the end of the run series. The resultant geomorphology shows that the separate block runs occupied different tracks leading to a triangular plan form shape with a maximum width of 3.5 m. This is different from the findings in Arizona where a narrower track span was recorded (1.7m) (Bourke et al, 2016). Similar block dynamics were observed at both sites (as blocks moved straight

  11. Adsorptive fractionation of HDO on JSC MARS-1 during sublimation with implications for the regolith of Mars

    NASA Astrophysics Data System (ADS)

    Moores, John E.; Smith, Peter H.; Boynton, William V.

    2011-02-01

    A chamber was constructed to simulate the boundary between the ice table, regolith and atmosphere of Mars and to examine fractionation between H 2O and HDO during sublimation under realistic martian conditions of temperature and pressure. Thirteen experimental runs were conducted with regolith overlying the ice. The thickness and characteristic grain size of the regolith layer as well as the temperature of the underlying ice was varied. From these runs, values for the effective diffusivity, taking into account the effects of adsorption, of the regolith were derived. These effective diffusivities ranged from 1.8 × 10 -4 m 2 s -1 to 2.2 × 10 -3 m 2 s -1 for bare ice and from 2.4 × 10 -11 m 2 s -1 to 2.0 × 10 -9 m 2 s -1 with an adsorptive layer present. From these, latent heats of adsorption of 8.6 ± 2.6 kJ mol -1 and 9.3 ± 2.8 kJ mol -1 were derived at ice-surface temperatures above 223 ± 8 K and 96 ± 28 kJ mol -1 and 104 ± 31 kJ mol -1 respectively for H 2O and HDO were derived at colder temperatures. For temperatures below 223 K, the effective diffusivity of HDO was found to be lower than the diffusivity of H 2O by 40% on average, suggesting that the regolith was adsorptively fractionating the sublimating gas with a fractionation factor of 1.96 ± 0.74. Applying these values to Mars predicts that adsorbed water on the regolith is enriched in HDO compared to the atmosphere, particularly where the regolith is colder. Based on current observations, the D/H ratio of the regolith may be as high as 21 ± 8 times VSMOW at 12°S and L S = 357° if the regolith is hydrated primarily by the atmosphere, neglecting any hydration from subsurface ice.

  12. In-Space Propulsion Engine Architecture Based on Sublimation of Planetary Resources: From Exploration Robots to NED Mitigation

    NASA Technical Reports Server (NTRS)

    Sibille, Laurent; Mantovani, James G.

    2011-01-01

    Volatile solids occur naturally on most planetary bodies including the Moon, Mars, asteroids and comets. Examples of recent discoveries include water ice, frozen carbon dioxide and hydrocarbons. The ability to utilize readily available resources for in-space propulsion and for powering surface systems during a planetary mission will help minimize the overall cost and extend the op.erational life of a mission. The utilization of volatile solids to achieve these goals is attractive for its simplicity. We have investigated the potential of subliming in situ volatiles and silicate minerals to power propulsion engines for a wide range of in-space applications where environmental conditions are favorable. This paper addresses the' practicality of using planetary solid volatiles as a power source for propulsion and surface systems by presenting results of modeling involving thermodynamic and physical mechanics calculations, and laboratory testing to measure the thrust obtained from ,a volatile solid engine (VSE). Applications of a VSE for planetary exploration are discussed as a means for propulsion and for mechanical actuators and surface mobility platforms.

  13. Solid sulfur in vacuum: Sublimation effects on surface microtexture, color and spectral reflectance, and applications to planetary surfaces

    NASA Technical Reports Server (NTRS)

    Nash, D. B.

    1987-01-01

    A form of sulfur that is white at room temperature and very fluffy in texture has been found in laboratory experiments on the effects of vacuum sublimation (evaporation) on solid sulfur. This work is an outgrowth of proton sputtering experiments on sulfur directed toward understanding Jovian magnetospheric effects on the surface of Io. Fluffy white sulfur is formed on the surface of solid yellow, tan, or brown sulfur melt freezes in vacuum by differential (fractional) evaporation of two or more sulfur molecular species present in the original sulfur; S(8) ring sulfur is thought to be the dominant sublimination phase lost to the vacuum sink, and polymeric chain sulfur S(u) the dominant residual phase that remains in place, forming the residual fluffy surface layer. The reflectance spectrum of the original sulfur surface is greaty modified by formation of the fluffy layer: the blue absorption band-edge and shoulder move 0.05 to 0.06 microns toward shorter wavelengths resulting in a permanent increase in reflectivity near 0.42 to 0.46 microns; the UV reflectivity below 0.40 microns is reduced. This form of sulfur should exist in large quantity on the surface of Io, especially in hotspot regions if there is solid free sulfur there that has solidified from a melt. Its color and spectra will indicate relative crystallization age on a scale of days to months and/or surface temperature distribution history.

  14. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap

    USGS Publications Warehouse

    Kieffer, H.H.; Christensen, P.R.; Titus, T.N.

    2006-01-01

    The martian polar caps are among the most dynamic regions on Mars, growing substantially in winter as a significant fraction of the atmosphere freezes out in the form of CO2 ice. Unusual dark spots, fans and blotches form as the south-polar seasonal CO2 ice cap retreats during spring and summer. Small radial channel networks are often associated with the location of spots once the ice disappears. The spots have been proposed to be simply bare, defrosted ground; the formation of the channels has remained uncertain. Here we report infrared and visible observations that show that the spots and fans remain at CO2 ice temperatures well into summer, and must be granular materials that have been brought up to the surface of the ice, requiring a complex suite of processes to get them there. We propose that the seasonal ice cap forms an impermeable, translucent slab of CO2 ice that sublimates from the base, building up high-pressure gas beneath the slab. This gas levitates the ice, which eventually ruptures, producing high-velocity CO 2 vents that erupt sand-sized grains in jets to form the spots and erode the channels. These processes are unlike any observed on Earth. ?? 2006 Nature Publishing Group.

  15. CO2 jets formed by sublimation beneath translucent slab ice in Mars' seasonal south polar ice cap.

    PubMed

    Kieffer, Hugh H; Christensen, Philip R; Titus, Timothy N

    2006-08-17

    The martian polar caps are among the most dynamic regions on Mars, growing substantially in winter as a significant fraction of the atmosphere freezes out in the form of CO2 ice. Unusual dark spots, fans and blotches form as the south-polar seasonal CO2 ice cap retreats during spring and summer. Small radial channel networks are often associated with the location of spots once the ice disappears. The spots have been proposed to be simply bare, defrosted ground; the formation of the channels has remained uncertain. Here we report infrared and visible observations that show that the spots and fans remain at CO2 ice temperatures well into summer, and must be granular materials that have been brought up to the surface of the ice, requiring a complex suite of processes to get them there. We propose that the seasonal ice cap forms an impermeable, translucent slab of CO2 ice that sublimates from the base, building up high-pressure gas beneath the slab. This gas levitates the ice, which eventually ruptures, producing high-velocity CO2 vents that erupt sand-sized grains in jets to form the spots and erode the channels. These processes are unlike any observed on Earth.

  16. HiRISE observations of gas sublimation-driven activity in Mars’ southern polar regions: III. Models of processes involving translucent ice

    NASA Astrophysics Data System (ADS)

    Portyankina, Ganna; Markiewicz, Wojciech J.; Thomas, Nicolas; Hansen, Candice J.; Milazzo, Moses

    2010-01-01

    Enigmatic surface features, known as 'spiders', found at high southern martian latitudes, are probably caused by sublimation-driven erosion under the seasonal carbon dioxide ice cap. The Mars Reconnaissance Orbiter (MRO) High Resolution Imaging Science Experiment (HiRISE) has imaged this terrain in unprecedented details throughout southern spring. It has been postulated [Kieffer, H.H., Titus, T.N., Mullins, K.F., Christensen, P.R., 2000. J. Geophys. Res. 105, 9653-9700] that translucent CO slab ice traps gas sublimating at the ice surface boundary. Wherever the pressure is released the escaping gas jet entrains loose surface material and carries it to the top of the ice where it is carried downslope and/or downwind and deposited in a fan shape. Here we model two stages of this scenario: first, the cleaning of CO slab ice from dust, and then, the breaking of the slab ice plate under the pressure built below it by subliming ice. Our modeling results and analysis of HiRISE images support the gas jet hypothesis and show that outbursts happen very early in spring.

  17. HiRISE observations of gas sublimation-driven activity in Mars' southern polar regions: III. Models of processes involving translucent ice

    USGS Publications Warehouse

    Portyankina, G.; Markiewicz, W.J.; Thomas, N.; Hansen, C.J.; Milazzo, M.

    2010-01-01

    Enigmatic surface features, known as 'spiders', found at high southern martian latitudes, are probably caused by sublimation-driven erosion under the seasonal carbon dioxide ice cap. The Mars Reconnaissance Orbiter (MRO) High Resolution Imaging Science Experiment (HiRISE) has imaged this terrain in unprecedented details throughout southern spring. It has been postulated [Kieffer, H.H., Titus, T.N., Mullins, K.F., Christensen, P.R., 2000. J. Geophys. Res. 105, 9653-9700] that translucent CO2 slab ice traps gas sublimating at the ice surface boundary. Wherever the pressure is released the escaping gas jet entrains loose surface material and carries it to the top of the ice where it is carried downslope and/or downwind and deposited in a fan shape. Here we model two stages of this scenario: first, the cleaning of CO2 slab ice from dust, and then, the breaking of the slab ice plate under the pressure built below it by subliming ice. Our modeling results and analysis of HiRISE images support the gas jet hypothesis and show that outbursts happen very early in spring. ?? 2009 Elsevier Inc. All rights reserved.

  18. A redetermination of the ice/vapor ratio of Enceladus’ plumes: Implications for sublimation and the lack of a liquid water reservoir

    NASA Astrophysics Data System (ADS)

    Kieffer, Susan W.; Lu, Xinli; McFarquhar, Greg; Wohletz, Kenneth H.

    2009-09-01

    The discovery of plumes of H 2O vapor and ice particles erupting from the south pole of Enceladus, the tiny frigid satellite of Saturn, sparked controversy over whether these plumes are produced by boiling, or by sublimation with subsequent recondensation of the sublimated vapor [Porco, C.C., Helfenstein, P., Thomas, P.C., Ingersoll, A.P., Wisdom, J., West, R., Neukum, G., Denk, T., Wagner, R., Roatsch, T., Kieffer, S., Turtle, E., McEwen, A., Johnson, T.V., Rathbun, J., Veverka, J., Wilson, D., Perry, J., Spitale, J., Brahic, A., Burns, J.A., DelGenio, A.D., Dones, L., Murray, C.D., Squyres, S., 2006. Science 311, 1393-1401]. Porco et al.'s analysis that the masses of ice (I) and vapor (V) in the plume were comparable was taken to argue against the occurrence of sublimation and recondensation, leading to the hypothesis that the reservoir was boiling water, possibly as close as 7 m to the surface. Thus, it has been advocated that Enceladus should be a target for astrobiology exploration. Here we show, with recalculations using the original data and methodologies, as well as with new sensitivity studies, that the mass of ice in the column is significantly less than the mass of water vapor, and that by considering three additional effects, I/V is likely to be <0.2-0.1. This means that the plume is dominated by vapor that the thermodynamics permits to be easily produced by sublimation with recondensation. The low I/V ratio provides no compelling criterion for consideration of a liquid water reservoir. The uncertainties on the I/V ratio have not previously been discussed in the literature. Although the I/V ratio is sensitive to particle sizes and size distributions, the masses of ice (I) and vapor (V) are not comparable in any scenario constrained by available observations. We thus discuss the implications of sublimation from a thermodynamic point of view in a context that has not been presented previously. Constraints on I/V ratio from future spacecraft measurements

  19. Recent ice-rich deposits formed at high latitudes on Mars by sublimation of unstable equatorial ice during low obliquity.

    PubMed

    Levrard, Benjamin; Forget, François; Montmessin, Franck; Laskar, Jacques

    2004-10-28

    Observations from the gamma-ray spectrometer instrument suite on the Mars Odyssey spacecraft have been interpreted as indicating the presence of vast reservoirs of near-surface ice in high latitudes of both martian hemispheres. Ice concentrations are estimated to range from 70 per cent at 60 degrees latitude to 100 per cent near the poles, possibly overlain by a few centimetres of ice-free material in most places. This result is supported by morphological evidence of metres-thick layered deposits that are rich in water-ice and periglacial-like features found only at high latitudes. Diffusive exchange of water between the pore space of the regolith and the atmosphere has been proposed to explain this distribution, but such a degree of concentration is difficult to accommodate with such processes. Alternatively, there are suggestions that ice-rich deposits form by transport of ice from polar reservoirs and direct redeposition in high latitudes during periods of higher obliquity, but these results have been difficult to reproduce with other models. Here we propose instead that, during periods of low obliquity (less than 25 degrees), high-latitude ice deposits form in both hemispheres by direct deposition of ice, as a result of sublimation from an equatorial ice reservoir that formed earlier, during a prolonged high-obliquity excursion. Using the ice accumulation rates estimated from global climate model simulations we show that, over the past ten million years, large variations of Mars' obliquity have allowed the formation of such metres-thick, sedimentary layered deposits in high latitude and polar regions.

  20. Fate of outflow channel effluents in the northern lowlands of Mars: The Vastitas Borealis Formation as a sublimation residue from frozen ponded bodies of water

    NASA Astrophysics Data System (ADS)

    Kreslavsky, Mikhail A.; Head, James W.

    2002-12-01

    We analyze the fate of the Hesperian-aged outflow channel effluents emplaced into the northern lowlands of Mars. We have modeled the evolution of these effluents under the assumption that they were emplaced under a range of atmospheric conditions comparable to those of today and thought to have prevailed in the Hesperian. Under these conditions we find that the evolution of the sediment-loaded water after it left the channels includes three phases. Phase 1: Emplacement and intensive cooling: Violent emplacement of water followed by a short period of intensive evaporation from the surface and near-surface layer, and intensive convection. During this phase the water maintained and redistributed its large suspended sediment load. Water vapor strongly influenced the climate, at least for a geologically short time. When the temperature of the water reached the temperature of the maximum density or the freezing point, boiling and intensive convection ceased and the water deposited the sediments. Phase 2: Freezing solid: Geologically rapid freezing of the water body accompanied by weak convective water movement occurred over a period of the order of ~104 years. Phase 3: Sublimation and loss: This period involved sublimation of the ice and lasted longer than the freezing phase. The rate and latitudinal dependence of the sublimation, as well as the location of water vapor condensation, crucially depend on the planetary obliquity, climate, and sedimentary veneering of the ice. Phase 3 would have been very short geologically (~105-106 years) if an insulating sedimentary layer did not build up rapidly. If such an insulating layer did form rapidly, sublimation could cease and residual ice hundreds of meters thick could remain below the surface today. The northern lowlands of Mars are largely covered by the Late Hesperian-aged Vastitas Borealis Formation (VBF), which has sharp boundaries clearly seen in the map of kilometer-scale roughness, and a distinctive kilometer

  1. THE DUST SUBLIMATION RADIUS AS AN OUTER ENVELOPE TO THE BULK OF THE NARROW Fe Kα LINE EMISSION IN TYPE 1 AGNs

    SciTech Connect

    Gandhi, Poshak; Hönig, Sebastian F.; Kishimoto, Makoto

    2015-10-20

    The Fe Kα emission line is the most ubiquitous feature in the X-ray spectra of active galactic nuclei (AGNs), but the origin of its narrow core remains uncertain. Here, we investigate the connection between the sizes of the Fe Kα core emission regions and the measured sizes of the dusty tori in 13 local Type 1 AGNs. The observed Fe Kα emission radii (R{sub Fe}) are determined from spectrally resolved line widths in X-ray grating spectra, and the dust sublimation radii (R{sub dust}) are measured either from optical/near-infrared (NIR) reverberation time lags or from resolved NIR interferometric data. This direct comparison shows, on an object-by-object basis, that the dust sublimation radius forms an outer envelope to the bulk of the Fe Kα emission. R{sub Fe} matches R{sub dust} well in the AGNs, with the best constrained line widths currently. In a significant fraction of objects without a clear narrow line core, R{sub Fe} is similar to, or smaller than, the radius of the optical broad line region. These facts place important constraints on the torus geometries for our sample. Extended tori in which the solid angle of fluorescing gas peaks at well beyond the dust sublimation radius can be ruled out. We also test for luminosity scalings of R{sub Fe}, finding that the Eddington ratio is not a prime driver in determining the line location in our sample. We also discuss in detail potential caveats of data analysis and instrumental limitations, simplistic line modeling, uncertain black hole masses, and sample selection, showing that none of these is likely to bias our core result. The calorimeter on board Astro-H will soon vastly increase the parameter space over which line measurements can be made, overcoming many of these limitations.

  2. Sublimation of icy aggregates in the coma of comet 67P/Churyumov-Gerasimenko detected with the OSIRIS cameras on board Rosetta

    NASA Astrophysics Data System (ADS)

    Gicquel, A.; Vincent, J.-B.; Agarwal, J.; A'Hearn, M. F.; Bertini, I.; Bodewits, D.; Sierks, H.; Lin, Z.-Y.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; Barucci, M. A.; Bertaux, J.-L.; Besse, S.; Cremonese, G.; Da Deppo, V.; Davidsson, B.; Debei, S.; Deller, J.; De Cecco, M.; Frattin, E.; El-Maarry, M. R.; Fornasier, S.; Fulle, M.; Groussin, O.; Gutiérrez, P. J.; Gutiérrez-Marquez, P.; Güttler, C.; Höfner, S.; Hofmann, M.; Hu, X.; Hviid, S. F.; Ip, W.-H.; Jorda, L.; Knollenberg, J.; Kovacs, G.; Kramm, J.-R.; Kührt, E.; Küppers, M.; Lara, L. M.; Lazzarin, M.; Moreno, J. J. Lopez; Lowry, S.; Marzari, F.; Masoumzadeh, N.; Massironi, M.; Moreno, F.; Mottola, S.; Naletto, G.; Oklay, N.; Pajola, M.; Pommerol, A.; Preusker, F.; Scholten, F.; Shi, X.; Thomas, N.; Toth, I.; Tubiana, C.

    2016-11-01

    Beginning in 2014 March, the OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) cameras began capturing images of the nucleus and coma (gas and dust) of comet 67P/Churyumov-Gerasimenko using both the wide angle camera (WAC) and the narrow angle camera (NAC). The many observations taken since July of 2014 have been used to study the morphology, location, and temporal variation of the comet's dust jets. We analysed the dust monitoring observations shortly after the southern vernal equinox on 2015 May 30 and 31 with the WAC at the heliocentric distance Rh = 1.53 AU, where it is possible to observe that the jet rotates with the nucleus. We found that the decline of brightness as a function of the distance of the jet is much steeper than the background coma, which is a first indication of sublimation. We adapted a model of sublimation of icy aggregates and studied the effect as a function of the physical properties of the aggregates (composition and size). The major finding of this paper was that through the sublimation of the aggregates of dirty grains (radius a between 5 and 50 μm) we were able to completely reproduce the radial brightness profile of a jet beyond 4 km from the nucleus. To reproduce the data, we needed to inject a number of aggregates between 8.5 × 1013 and 8.5 × 1010 for a = 5 and 50 μm, respectively, or an initial mass of H2O ice around 22 kg.

  3. Gas-phase enthalpies of formation and enthalpies of sublimation of amino acids based on isodesmic reaction calculations.

    PubMed

    Dorofeeva, Olga V; Ryzhova, Oxana N

    2014-05-15

    Accurate gas-phase enthalpies of formation (ΔfH298°) of 20 common α-amino acids, seven uncommon amino acids, and three small peptides were calculated by combining G4 theory calculations with an isodesmic reaction approach. The internal consistency over a set of ΔfH298°(g) values was achieved by sequential adjustment of their values through the isodesmic reactions. Four amino acids, alanine, β-alanine, sarcosine, and glycine, with reliable internally self-consistent experimental data, were chosen as the key reference compounds. These amino acids together with about 100 compounds with reliable experimental data (their accuracy was supported by G4 calculations) were used to estimate the enthalpies of formation of remaining amino acids. All of the amino acids with the previously established enthalpies of formation were later used as the reference species in the isodesmic reactions for the other amino acids. A systematic comparison was made of 14 experimentally determined enthalpies of formation with the results of calculations. The experimental enthalpies of formation for 10 amino acids were reproduced with good accuracy, but the experimental and calculated values for 4 compounds differed by 11–21 kJ/mol. For these species, the theoretical ΔfH298°(g) values were suggested as more reliable than the experimental values. On the basis of theoretical results, the recommended values for the gas-phase enthalpies of formation were also provided for amino acids for which the experimental ΔfH298°(g) were not available. The enthalpies of sublimation were evaluated for all compounds by taking into account the literature data on the solid-phase enthalpies of formation and the ΔfH298°(g) values recommended in our work. A special attention was paid to the accurate prediction of enthalpies of formation of amino acids from the atomization reactions. The problems associated with conformational flexibility of these compounds and harmonic treatment of low frequency torsional

  4. A close-space sublimation driven pathway for the manipulation of substrate-supported micro- and nanostructures

    NASA Astrophysics Data System (ADS)

    Sundar, Aarthi

    gold beneath the grid selectively attaches to it due to the surface energy gradient which drives gold from the low surface energy oxide surface to the higher surface energy nickel mesh. With this process being confined to areas adjacent to and in contact with the grid surface the film ruptures at well-defined locations to form isolated islands of gold and subsequently, a periodic array of microstructures. The process can be carried out on substrates of different crystallographic orientations leading to nanostructures which are formed epitaxially and have orientations based on underlying substrate orientations. The process can be extended by placing a metallic foil of Pt or Ni over preformed templates, in which case a reduction in the size of the initial structures is observed. Placing a foil on structures with random placement and a wide size distribution results, not only in a size reduction, but also a narrowed size distribution. Additive processes are carried out by using materials which possess high vapor pressures much below the sublimation temperature of the template materials. In this case a germanium substrate was used as a source of germanium adatoms while gold or silver nanostructures were used as heterogeneous nucleation sites. At elevated temperatures the adatoms collect in sufficient quantities to transform each site into a liquid alloy which, upon cooling, phase separates into elemental components sharing a common interface and, hence, resulting in the formation of heterodimers and hollowed metal nanocrescents upon etching away the Ge. A process which combined aspects of the additive and subtractive process was carried out by using a metallic foil with a high vapor pressure and higher surface energy than the substrate surface (in this case Pd foil). This process resulted in the initial preformed gold templates being annihilated and replaced by nanostructures of palladium, thereby altering their chemical composition. The assembly process relies on the

  5. The Thermodynamic Characteristics of Sublimation of Aluminum and Indium Complexes with Tetraphenylporphin according to the High-Temperature Mass Spectrometry Data

    NASA Astrophysics Data System (ADS)

    Stuzhina, O. V.; Lomova, T. N.; Pelipets, O. V.; Girichev, G. V.

    2008-02-01

    The thermodynamic characteristics of vaporization of meso-tetraphenylporphin complexes (X)MTPP (M = Al, In; X = Cl, OH; TPP is the meso-tetraphenylporphin H2TPP dianion) were studied by the Knudsen effusion method with mass spectrometric control of vapor composition. Chloride complexes sublimed as monomers over the temperature range 480-590 K. The hydroxo complex of aluminotetraphenylporphin was transferred into the gas phase in the form of the μ-oxo dimer. The temperature dependences of saturated vapor pressure were used to determine the enthalpies of sublimation of metalloporphyrins, which were found to be 203 ± 3.5 and 207 ± 6 kJ/mol for the chloride complexes of In and Al, respectively, and 206 ± 8 and 406 ± 40 kJ/mol for the monomer and μ-oxo dimer of (hydroxy)aluminum(III)porphyrin, respectively. The thermodynamic parameters of vaporization and the melting point of (OH)AlTPP were also determined (ΔvapH° = 116 ± 6 kJ/mol, ΔapS° = 72 ± 11 J/(mol K), and Tm = 579 K). Composition-thermodynamic property correlations were analyzed for metalloporphyrins.

  6. Phase Transition Enthalpy Measurements of Organic and Organometallic Compounds and Ionic Liquids. Sublimation, Vaporization, and Fusion Enthalpies from 1880 to 2015. Part 2. C11-C192

    NASA Astrophysics Data System (ADS)

    Acree, William; Chickos, James S.

    2017-03-01

    The second part of this compendium concludes with a collection of phase change enthalpies of organic molecules inclusive of C11-C192 reported over the period 1880-2015. Also included are phase change enthalpies including fusion, vaporization, and sublimation enthalpies for organometallic, ionic liquids, and a few inorganic compounds. Paper I of this compendium, published separately, includes organic compounds from C1 to C10 and describes a group additivity method for evaluating solid, liquid, and gas phase heat capacities as well as temperature adjustments of phase changes. Paper II of this compendium also includes an updated version of a group additivity method for evaluating total phase change entropies which together with the fusion temperature can be useful in estimating total phase change enthalpies. Other uses include application in identifying potential substances that either form liquid or plastic crystals or exhibit additional phase changes such as undetected solid-solid transitions or behave anisotropically in the liquid state.

  7. Towards an understanding of the molecular mechanism of solvation of drug molecules: a thermodynamic approach by crystal lattice energy, sublimation, and solubility exemplified by paracetamol, acetanilide, and phenacetin.

    PubMed

    Perlovich, German L; Volkova, Tatyana V; Bauer-Brandl, Annette

    2006-10-01

    Temperature dependencies of saturated vapor pressure for the monoclinic modification of paracetamol (acetaminophen), acetanilide, and phenacetin (acetophenetidin) were measured and thermodynamic functions of sublimation calculated (paracetamol: DeltaGsub298=60.0 kJ/mol; DeltaHsub298=117.9+/-0.7 kJ/mol; DeltaSsub298=190+/-2 J/mol.K; acetanilide: DeltaGsub298=40.5 kJ/mol; DeltaHsub298=99.8+/-0.8 kJ/mol; DeltaSsub298=197+/-2 J/mol.K; phenacetin: DeltaGsub298=52.3 kJ/mol; DeltaHsub298=121.8+/-0.7 kJ/mol; DeltaSsub298=226+/-2 J/mol.K). Analysis of packing energies based on geometry optimization of molecules in the crystal lattices using diffraction data and the program Dmol3 was carried out. Parameters analyzed were: (a) energetic contribution of van der Waals forces and hydrogen bonding to the total packing energy; (b) contributions of fragments of the molecules to the packing energy. The fraction of hydrogen bond energy in the packing energy increases as: phenacetin (17.5%)sublimation and fusion. Activity coefficients of the drugs in n-octanol were calculated from cryoscopic data and by estimation of dilution enthalpy obtained from solubility and calorimetric experiments (for infinite dissolution). Solubility temperature dependencies in n-octanol and n-hexane were measured. The thermodynamic functions of solubility and solvation processes were deduced. Specific and nonspecific solvation terms were distinguished using the transfer from the "inert" n-hexane to the other solvents. The transfer of the molecules from water to n-octanol is enthalpy driven for paracetamol; for acetanilide and phenacetin, entropy driven.

  8. Comparison study of close-spaced sublimated and chemical bath deposited CdS films: Effects on CdTe solar cells

    SciTech Connect

    Albin, D.; Rose, D.; Dhere, R.; Levi, D.; Woods, L.; Swartzlander, A.; Sheldon, P.

    1997-12-31

    Close-spaced-sublimated (CSS) CdS films exhibit strong fundamental edge luminescence, high optical absorption, and a bandgap of {approximately}2.41 eV. Structurally, these films show good crystallinity with thickness-dependent grain sizes that vary between 100--400 nm. In contrast, chemical-bath, deposited (CBD) CdS exhibits subband luminescence, lower absorption, and a thickness-dependent bandgap. These films have CdS grains typically less than 50 nm in size and poorer crystallinity. However, CdTe devices fabricated with these lower quality CBD CdS films yield higher V{sub oc}`s and fill factors. Carrier lifetimes in finished CSS CdS devices measured between 100 and 200 ps while lifetimes in CBD CdS devices were much higher (>500 ps). Compositional differences in the Cd/(S+Te) ratio at the interface suggest the possibility of lower CdS doping and higher CdTe compensation as one reason for lower V{sub oc}`s in CSS CdS devices.

  9. Structure and sublimation of water ice films grown in vacuo at 120-190 K studied by positron and positronium annihilation.

    PubMed

    Townrow, S; Coleman, P G

    2014-03-26

    The crystalline structure of ∼ 5-20 μm water ice films grown at 165 and 172 K has been probed by measuring the fraction of positrons forming ortho-positronium (ortho-Ps) and decaying into three gamma photons. It has been established that films grown at slower rates (water vapour pressure ≥ 1 mPa) have lower concentrations of lattice defects and closed pores, which act as Ps traps, than those grown at higher rates (vapour pressure ∼ 100 mPa), evidenced by ortho-Ps diffusion lengths being approximately four times greater in the former. By varying the growth temperature between 162 and 182 K it was found that films become less disordered at temperatures above ∼ 172 K, with the ortho-Ps diffusion length rising by ∼ 60%, in this range. The sublimation energy for water ice films grown on copper has been measured to be 0.462(5) eV using the time dependence of positron annihilation parameters from 165 to 195 K, in agreement with earlier studies and with no measurable dependence on growth rate and thermal history.

  10. Thin-Layer Matrix Sublimation with Vapor-Sorption Induced Co-Crystallization for Sensitive and Reproducible SAMDI-TOF MS Analysis of Protein Biosensors

    NASA Astrophysics Data System (ADS)

    Roth, Michael J.; Kim, Jaekuk; Maresh, Erica M.; Plymire, Daniel A.; Corbett, John R.; Zhang, Junmei; Patrie, Steven M.

    2012-10-01

    Coupling immunoassays on self-assembled monolayers (SAMs) to matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) provides improved assay selectivity compared with traditional photometric detection techniques. We show that thin-layer-transfer (TLT) of α-cyano-4-hydroxycinnaminic acid (CHCA) MALDI matrix via vacuum sublimation followed by organic solvent-based vapor-sorption induced co-crystallization (VIC) results in unique matrix/analyte co-crystallization tendencies that optimizes assay reproducibility and sensitivity. Unique matrix crystal morphologies resulted from VIC solvent vapors, indicating nucleation and crystal growth characteristics depend upon VIC parameters. We observed that CHCA microcrystals generated by methanol VIC resulted in >10× better sensitivity, increased analyte charging, and improved precision compared with dried droplet measurements. The uniformity of matrix/analyte co-crystallization across planar immunoassays directed at intact proteins yielded low spectral variation for single shot replicates (18.5 % relative standard deviation, RSD) and signal averaged spectra (<10 % RSD). We envision that TLT and VIC for MALDI-TOF will enable high-throughput, reproducible array-based immunoassays for protein molecular diagnostic assays in diverse biochemical and clinical applications.

  11. Hysteresis and change of transition temperature in thin films of Fe{[Me2Pyrz]3BH}2, a new sublimable spin-crossover molecule.

    PubMed

    Davesne, V; Gruber, M; Studniarek, M; Doh, W H; Zafeiratos, S; Joly, L; Sirotti, F; Silly, M G; Gaspar, A B; Real, J A; Schmerber, G; Bowen, M; Weber, W; Boukari, S; Da Costa, V; Arabski, J; Wulfhekel, W; Beaurepaire, E

    2015-05-21

    Thin films of the spin-crossover (SCO) molecule Fe{[Me2Pyrz]3BH}2 (Fe-pyrz) were sublimed on Si/SiO2 and quartz substrates, and their properties investigated by X-ray absorption and photoemission spectroscopies, optical absorption, atomic force microscopy, and superconducting quantum interference device. Contrary to the previously studied Fe(phen)2(NCS)2, the films are not smooth but granular. The thin films qualitatively retain the typical SCO properties of the powder sample (SCO, thermal hysteresis, soft X-ray induced excited spin-state trapping, and light induced excited spin-state trapping) but present intriguing variations even in micrometer-thick films: the transition temperature decreases when the thickness is decreased, and the hysteresis is affected. We explain this behavior in the light of recent studies focusing on the role of surface energy in the thermodynamics of the spin transition in nano-structures. In the high-spin state at room temperature, the films have a large optical gap (∼5 eV), decreasing at thickness below 50 nm, possibly due to film morphology.

  12. Hysteresis and change of transition temperature in thin films of Fe{[Me2Pyrz]3BH}2, a new sublimable spin-crossover molecule

    NASA Astrophysics Data System (ADS)

    Davesne, V.; Gruber, M.; Studniarek, M.; Doh, W. H.; Zafeiratos, S.; Joly, L.; Sirotti, F.; Silly, M. G.; Gaspar, A. B.; Real, J. A.; Schmerber, G.; Bowen, M.; Weber, W.; Boukari, S.; Da Costa, V.; Arabski, J.; Wulfhekel, W.; Beaurepaire, E.

    2015-05-01

    Thin films of the spin-crossover (SCO) molecule Fe{[Me2Pyrz]3BH}2 (Fe-pyrz) were sublimed on Si/SiO2 and quartz substrates, and their properties investigated by X-ray absorption and photoemission spectroscopies, optical absorption, atomic force microscopy, and superconducting quantum interference device. Contrary to the previously studied Fe(phen)2(NCS)2, the films are not smooth but granular. The thin films qualitatively retain the typical SCO properties of the powder sample (SCO, thermal hysteresis, soft X-ray induced excited spin-state trapping, and light induced excited spin-state trapping) but present intriguing variations even in micrometer-thick films: the transition temperature decreases when the thickness is decreased, and the hysteresis is affected. We explain this behavior in the light of recent studies focusing on the role of surface energy in the thermodynamics of the spin transition in nano-structures. In the high-spin state at room temperature, the films have a large optical gap (˜5 eV), decreasing at thickness below 50 nm, possibly due to film morphology.

  13. Structural and optical properties of AgAlTe{sub 2} layers grown on sapphire substrates by closed space sublimation method

    SciTech Connect

    Uruno, A. Usui, A.; Kobayashi, M.

    2014-11-14

    AgAlTe{sub 2} layers were grown on a- and c-plane sapphire substrates using a closed space sublimation method. Grown layers were confirmed to be single phase layers of AgAlTe{sub 2} by X-ray diffraction. AgAlTe{sub 2} layers were grown to have a strong preference for the (112) orientation on both kinds of substrates. The variation in the orientation of grown layers was analyzed in detail using the X-ray diffraction pole figure measurement, which revealed that the AgAlTe{sub 2} had a preferential epitaxial relationship with the c-plane sapphire substrate. The atomic arrangement between the (112) AgAlTe{sub 2} layer and sapphire substrates was compared. It was considered that the high order of the lattice arrangement symmetry probably effectively accommodated the lattice mismatch. The optical properties of the grown layer were also evaluated by transmittance measurements. The bandgap energy was found to be around 2.3 eV, which was in agreement with the theoretical bandgap energy of AgAlTe{sub 2}.

  14. Structural properties and dielectric function of graphene grown by high-temperature sublimation on 4H-SiC(000-1)

    SciTech Connect

    Bouhafs, C. Darakchieva, V.; Persson, I. L.; Persson, P. O. Å.; Yakimova, R.; Tiberj, A.; Paillet, M.; Zahab, A.-A.; Landois, P.; Juillaguet, S.; Schöche, S.; Schubert, M.

    2015-02-28

    Understanding and controlling growth of graphene on the carbon face (C-face) of SiC presents a significant challenge. In this work, we study the structural, vibrational, and dielectric function properties of graphene grown on the C-face of 4H-SiC by high-temperature sublimation in an argon atmosphere. The effect of growth temperature on the graphene number of layers and crystallite size is investigated and discussed in relation to graphene coverage and thickness homogeneity. An amorphous carbon layer at the interface between SiC and the graphene is identified, and its evolution with growth temperature is established. Atomic force microscopy, micro-Raman scattering spectroscopy, spectroscopic ellipsometry, and high-resolution cross-sectional transmission electron microscopy are combined to determine and correlate thickness, stacking order, dielectric function, and interface properties of graphene. The role of surface defects and growth temperature on the graphene growth mechanism and stacking is discussed, and a conclusion about the critical factors to achieve decoupled graphene layers is drawn.

  15. [Spectral analyzing effects of atmosphere states on the structure and characteristics of CdTe polycrystalline thin films made by close-spaced sublimation].

    PubMed

    Zheng, Hua-jing; Zheng, Jia-gui; Feng, Liang-huan; Zhang, Jing-quan; Xie, Er-qing

    2005-07-01

    The structure and characteristics of CdTe thin films are dependent on the working atmosphere states in close-spaced sublimation. In the present paper, CdTe polycrystalline thin films were deposited by CSS in mixture atmosphere of argon and oxygen. The physical mechanism of CSS was analyzed, and the temperature distribution in CSS system was measured. The dependence of preliminary nucleus creation on the atmosphere states (involving component and pressure) was studied. Transparencies were measured and optic energy gaps were calculated. The results show that: (1) The CdTe films deposited in different atmospheres are cubic structure. With increasing oxygen concentration, a increases and reaches the maximum at 6% oxygen concentration, then reduces, and increases again after passing the point at 12% oxygen concentration. Among them, the sample depositing at 9% oxygen concentration is the best. The optic energy gaps are 1.50-1.51 eV for all CdTe films. (2) The samples depositing at different pressures at 9% oxygen concentration are all cubical structure of CdTe, and the diffraction peaks of CdS and SnO2:F still appear. With the gas pressure increasing, the crystal size of CdTe minishes, the transparency of the thin film goes down, and the absorption side shifts to the short-wave direction. (3) The polycrystalline thin films with high quality deposit in 4 minutes under the depositing condition that the substrate temperature is 550 degrees C, and source temperature is 620 degrees C at 9% oxygen concentration.

  16. The influence of snow sublimation and meltwater evaporation on δD of water vapor in the atmospheric boundary layer of central Europe

    NASA Astrophysics Data System (ADS)

    Christner, Emanuel; Kohler, Martin; Schneider, Matthias

    2017-01-01

    Post-depositional fractionation of stable water isotopes due to fractionating surface evaporation introduces uncertainty to various isotope applications such as the reconstruction of paleotemperatures, paleoaltimetry, and the investigation of groundwater formation. In this study, we investigate isotope fractionation at snow-covered moisture sources by combining 17 months of observations of isotope concentration ratios [HD16O] / [H216O] in low-level water vapor in central Europe with a new Lagrangian isotope model. The isotope model is capable of reproducing variations of the observed isotope ratios with a correlation coefficient R of 0.82. Observations from 38 days were associated with cold snaps and moisture uptake in snow-covered regions. Deviations between modeled and measured isotope ratios during the cold snaps were related to differences in skin temperatures (Tskin). Analysis of Tskin provided by the Global Data Assimilation System (GDAS) of the NCEP implies the existence of two regimes of Tskin with different types of isotope fractionation during evaporation: a cold regime with Tskin < Tsubl,max = -7.7 °C, which is dominated by non-fractionating sublimation of snow, and a warmer regime with Tsubl,max < Tskin < 0 °C, which is dominated by fractionating evaporation of meltwater. Based on a sensitivity study, we assess an uncertainty range of the determined Tsubl,max of -11.9 to -2.9 °C. The existence of the two fractionation regimes has important implications for the interpretation of isotope records from snow-covered regions as well as for a more realistic modeling of isotope fractionation at snow-covered moisture sources. For these reasons, more detailed experimental studies at snow-covered sites are needed to better constrain the Tsubl,max and to further investigate isotope fractionation in the two regimes.

  17. Space Suit Radiator Performance in Lunar and Mars Environments

    NASA Technical Reports Server (NTRS)

    Paul, Heather; Trevino, Luis; Nabity, James; Mason, Georgia; Copeland, Robert; Libberton, Kerry; Stephan, Ryan

    2007-01-01

    During an ExtraVehicular Activity (EVA), both the heat generated by the astronaut's metabolism and that produced by the Portable Life Support System (PLSS) must be rejected to space. The heat sources include the heat of adsorption of metabolic CO2, the heat of condensation of water, the heat removed from the body by the liquid cooling garment and the load from the electrical components. Although the sublimator hardware to reject this load weighs only 3.48 lbs, an additional eight pounds of water are loaded into the unit of which about six to eight are sublimated and lost; this is the single largest expendable during an eight-hour EVA. Using a radiator to reject heat from the Astronaut during an EVA, we can significantly reduce the amount of expendable water consumed by the sublimator. Last year we reported on the design and initial operational assessment tests of our novel radiator designated the Radiator And Freeze Tolerant heat eXchanger (RAFT-X). Herein, we report on tests conducted in the NASA Johnson Space Center Chamber E Thermal Vacuum Test Facility. Up to 800 Btu/h of heat were rejected in lunar and Mars environments with temperatures as cold as 150 F. Tilting the radiator did not cause an observable loss in performance. The RAFT-X endured freeze/thaw cycles and in fact, the heat exchanger was completely frozen three times without any apparent damage to the unit. We were also able to operate the heat exchanger in a partially frozen configuration to throttle the heat rejection rate from 530 Btu/h at low water flow rate down to 300 Btu/h. Finally, the deliberate loss of a single loop heat pipe only degraded the heat rejection performance by about 2 to 5%.

  18. Space Suit Radiator Performance in Lunar and Mars Environments

    NASA Technical Reports Server (NTRS)

    Nabity, James; Mason, Georgia; Copeland, Robert; Libberton, Kerry; Trevino, Luis; Stephan, Ryan; Paul, Heather

    2007-01-01

    During an ExtraVehicular Activity (EVA), both the heat generated by the astronaut's metabolism and that produced by the Portable Life Support System (PLSS) must be rejected to space. The heat sources include the heat of adsorption of metabolic CO2, the heat of condensation of water, the heat removed from the body by the liquid cooling garment and the load from the electrical components. Although the sublimator hardware to reject this load weighs only 3.48 lbs, an additional eight pounds of water are loaded into the unit of which about six to eight are sublimated and lost; this is the single largest expendable during an eight-hour EVA. Using a radiator to reject heat from the Astronaut during an EVA, we can significantly reduce the amount of expendable water consumed by the sublimator. Last year we reported on the design and initial operational assessment tests of our novel radiator designated the Radiator And Freeze Tolerant heat eXchanger (RAFT-X). Herein, we report on tests conducted in the NASA Johnson Space Center Chamber E Thermal Vacuum Test Facility. Up to 800 Btu/h of heat were rejected in lunar and Mars environments with temperatures as cold as -150 F. Tilting the radiator did not cause an observable loss in performance. The RAFT-X endured freeze / thaw cycles and in fact, the heat exchanger was completely frozen three times without any apparent damage to the unit. We were also able to operate the heat exchanger in a partially frozen configuration to throttle the heat rejection rate from 530 Btu/h at low water flow rate down to 300 Btu/h. Finally, the deliberate loss of a single loop heat pipe only degraded the heat rejection performance by about 2 to 5%.

  19. Transport phenomena in the close-spaced sublimation deposition process for manufacture of large-area cadmium telluride photovoltaic panels: Modeling and optimization

    NASA Astrophysics Data System (ADS)

    Malhotra, C. P.

    With increasing national and global demand for energy and concerns about the effect of fossil fuels on global climate change, there is an increasing emphasis on the development and use of renewable sources of energy. Solar cells or photovoltaics constitute an important renewable energy technology but the major impediment to their widespread adoption has been their high initial cost. Although thin-film photovoltaic semiconductors such as cadmium sulfide-cadmium telluride (CdS/CdTe) can potentially be inexpensively manufactured using large area deposition techniques such as close-spaced sublimation (CSS), their low stability has prevented them from becoming an alternative to traditional polycrystalline silicon solar cells. A key factor affecting the stability of CdS/CdTe cells is the uniformity of deposition of the thin films. Currently no models exist that can relate the processing parameters in a CSS setup with the film deposition uniformity. Central to the development of these models is a fundamental understanding of the complex transport phenomena which constitute the deposition process which include coupled conduction and radiation as well as transition regime rarefied gas flow. This thesis is aimed at filling these knowledge gaps and thereby leading to the development of the relevant models. The specific process under consideration is the CSS setup developed by the Materials Engineering Group at the Colorado State University (CSU). Initially, a 3-D radiation-conduction model of a single processing station was developed using the commercial finite-element software ABAQUS and validated against data from steady-state experiments carried out at CSU. A simplified model was then optimized for maximizing the steady-state thermal uniformity within the substrate. It was inferred that contrary to traditional top and bottom infrared lamp heating, a lamp configuration that directs heat from the periphery of the sources towards the center results in the minimum temperature

  20. Modeling of the effects of different substrate materials on the residual thermal stresses in the aluminum nitride crystal grown by sublimation

    NASA Astrophysics Data System (ADS)

    Lee, R. G.; Idesman, A.; Nyakiti, L.; Chaudhuri, J.

    2009-02-01

    A three-dimensional numerical finite element modeling method is applied to compare interfacial residual thermal stress distribution in AlN single crystals grown by using different substrates such as silicon carbide, boron nitride, tungsten, tantalum carbide, and niobium carbide. A dimensionless coordinate system is used which reduces the numbers of computations and hence simplifies the stress analysis. All components of the stress distribution, both in the film and in the substrate, including the normal stress along the growth direction as well as in-plane normal stresses and shear stresses are fully investigated. This information about the stress distribution provides insight into understanding and controlling the AlN single crystal growth by the sublimation technique. The normal stress in the film at the interface along the growth direction and the shear stresses are zero except at the edges, whereas in-plane stresses are nonzero. The in-plane stresses are compressive when TaC and NbC substrates are used. A small compressive stress might be beneficial in prohibiting crack growth in the film. The compressive stress in the AlN is lower for the TaC substrate than that for the NbC. Tensile in-plane stresses are formed in the AlN for 6H-SiC, BN, and W substrates. This tensile stress in the film is detrimental as it will assist in the crack growth. The stress concentration at the edges of the AlN film at the interface is compressive in nature when TaC and NbC are used as a substrate. This causes the film to bend downward (i.e., convex shape) and assist it to adhere to the substrate. The AlN film curves upward or in a concave shape when SiC, BN, and W substrates are used since the stress concentration at the edges of the AlN film is tensile at the interface and this may cause detachment of the film from the substrate.

  1. The Repression of the Sublime

    ERIC Educational Resources Information Center

    Haronian, Frank

    1977-01-01

    Psychosynthesis is one approach that strives to reach from the lower unconscious to the self, helping man to recognize his higher as well as his lower impulses, to accept the responsibility of deciding which to express and which to renounce, and to deal with the anxiety that is an inescapable aspect of the process of self-actualization. (Author)

  2. Computer modeling of thermoelectric generator performance

    NASA Technical Reports Server (NTRS)

    Chmielewski, A. B.; Shields, V.

    1982-01-01

    Features of the DEGRA 2 computer code for simulating the operations of a spacecraft thermoelectric generator are described. The code models the physical processes occurring during operation. Input variables include the thermoelectric couple geometry and composition, the thermoelectric materials' properties, interfaces and insulation in the thermopile, the heat source characteristics, mission trajectory, and generator electrical requirements. Time steps can be specified and sublimation of the leg and hot shoe is accounted for, as are shorts between legs. Calculations are performed for conduction, Peltier, Thomson, and Joule heating, the cold junction can be adjusted for solar radition, and the legs of the thermoelectric couple are segmented to enhance the approximation accuracy. A trial run covering 18 couple modules yielded data with 0.3% accuracy with regard to test data. The model has been successful with selenide materials, SiGe, and SiN4, with output of all critical operational variables.

  3. Towards a general scenario for spring sublimation of volatiles in the South Polar Regions of Mars: insights from MRO high-resolution observations by HiRISE and CRISM.

    NASA Astrophysics Data System (ADS)

    Pommerol, Antoine; Portyankina, Ganna; Thomas, Nicolas; Aye, Klaus-Michael; Vincendon, Mathieu; Langevin, Yves

    The sublimation of the seasonal deposits of volatiles during Martian spring results in strong temporal variations of the appearance of the southern Polar Regions terrains. The intense dust and CO2 jet-like activity [1] is the most spectacular manifestation of these processes. The high spatial resolution capabilities of the MRO instruments now offer the possibility of new analyses at an unprecedented level of detail. Results from the analyses of HiRISE images as well as complementary work on the physical modeling of the involved processes have recently been published [2,3,4]. We are now completing this work by extending the number of regions of interest and by including CRISM spectral information in our analyses. We have derived the temporal evolution of albedo during spring in ten different areas from the HiRISE and CRISM datasets. In addition, the evolution of the strengths of the CO2-and H2O-ice spectral features are extracted from the CRISM observations. The color imaging capabilities of HiRISE were extensively used to discriminate the different terrains. Composite color images built from spectra measured by CRISM in the visible spectral range provide the ideal context for the HiRISE images. Together, our observations allow us to propose a plausible scenario for the progressive subli-mation of the volatiles deposits that involves a succession of three steps characterized by the predominance of different processes. This updates and enhances the previous work of [5]. First, an intense and early episode of jet activity results in the deposition of large dust fans accom-panied by the condensation of fined grained CO2 frost. In an apparent contradiction with the "Kieffer model" [5], we do not observe the spectral signature of the hypothetical clean slab of CO2-ice at that time. The clean ice is hidden by a quasi-homogeneous layer that is highly contaminated by mineral dust, as already revealed by the OMEGA instrument [6]. We propose a hypothesis to bypass this

  4. Nacelle aerodynamic performance

    NASA Technical Reports Server (NTRS)

    Obara, Clifford J.; Dodbele, S. S.

    1987-01-01

    The boundary layer transition location was measured on a nacelle shape using the sublimating chemical flow visualization technique. This technique involves coating the surface with a thin film of volatile chemical solid, which, during exposure to a free stream airflow, rapidly sublimates in the turbulent boundary layer as a result of high shear stress and high mass transfer near the surface. Transition is indicated because the chemical coating remains relatively unaffected in the laminar region due to lower shear and low mass transfer. The slow response time of the chemical in a laminar boundary allowed for two test conditions during the same flight. The aircraft was first flown at the desired airspeed and altitude with the noise source off. Once a pattern had developed, the noise source was turned on to the desired setting and a new chemical pattern was sought. In this fashion a direct comparison of the effect of the noise could be determined.

  5. Performativity, Performance and Education

    ERIC Educational Resources Information Center

    Locke, Kirsten

    2015-01-01

    This article explores Lyotard's notion of performativity through an engagement with McKenzie's analysis of performance as a "formation of knowledge and power" that has displaced the notion of discipline as the tool for social evaluation. Through conditions of "performance" capitalism, education is to conform to a…

  6. Hysteresis and change of transition temperature in thin films of Fe([Me{sub 2}Pyrz]{sub 3}BH){sub 2}, a new sublimable spin-crossover molecule

    SciTech Connect

    Davesne, V.; Gruber, M.; Studniarek, M.; Doh, W. H.; Zafeiratos, S.; Joly, L.; Schmerber, G.; Bowen, M.; Weber, W.; Boukari, S.; Da Costa, V.; Arabski, J.; Beaurepaire, E.; Sirotti, F.; Silly, M. G.; Gaspar, A. B.; Real, J. A. [Institut de Ciència Molecular , Universitat de València, C and others

    2015-05-21

    Thin films of the spin-crossover (SCO) molecule Fe([Me{sub 2}Pyrz]{sub 3}BH){sub 2} (Fe-pyrz) were sublimed on Si/SiO{sub 2} and quartz substrates, and their properties investigated by X-ray absorption and photoemission spectroscopies, optical absorption, atomic force microscopy, and superconducting quantum interference device. Contrary to the previously studied Fe(phen){sub 2}(NCS){sub 2}, the films are not smooth but granular. The thin films qualitatively retain the typical SCO properties of the powder sample (SCO, thermal hysteresis, soft X-ray induced excited spin-state trapping, and light induced excited spin-state trapping) but present intriguing variations even in micrometer-thick films: the transition temperature decreases when the thickness is decreased, and the hysteresis is affected. We explain this behavior in the light of recent studies focusing on the role of surface energy in the thermodynamics of the spin transition in nano-structures. In the high-spin state at room temperature, the films have a large optical gap (∼5 eV), decreasing at thickness below 50 nm, possibly due to film morphology.

  7. Qualification of a sublimation tool applied to the case of metalorganic chemical vapor deposition of In{sub 2}O{sub 3} from In(tmhd){sub 3} as a solid precursor

    SciTech Connect

    Szkutnik, P. D. Jiménez, C.; Angélidès, L.; Todorova, V.

    2016-02-15

    A solid delivery system consisting of a source canister, a gas management, and temperature controlled enclosure designed and manufactured by Air Liquide Electronics Systems was tested in the context of gas-phase delivery of the In(tmhd){sub 3} solid precursor. The precursor stream was delivered to a thermal metalorganic chemical vapor deposition reactor to quantify deposition yield under various conditions of carrier gas flow and sublimation temperature. The data collected allowed the determination of characteristic parameters such as the maximum precursor flow rate (18.2 mg min{sup −1} in specified conditions) and the critical mass (defined as the minimum amount of precursor able to attain the maximum flow rate) found to be about 2.4 g, as well as an understanding of the influence of powder distribution inside the canister. Furthermore, this qualification enabled the determination of optimal delivery conditions which allowed for stable and reproducible precursor flow rates over long deposition times (equivalent to more than 47 h of experiment). The resulting In{sub 2}O{sub 3} layers was compared with those elaborated via pulsed liquid injection obtained in the same chemical vapor deposition chamber and under the same deposition conditions.

  8. Performance, Performance System, and High Performance System

    ERIC Educational Resources Information Center

    Jang, Hwan Young

    2009-01-01

    This article proposes needed transitions in the field of human performance technology. The following three transitions are discussed: transitioning from training to performance, transitioning from performance to performance system, and transitioning from learning organization to high performance system. A proposed framework that comprises…

  9. Core-shell-like Y2O3:[(Tb3+-Yb3+), Li+]/CdZnS heterostructure synthesized by super-close-space sublimation for broadband down-conversion

    NASA Astrophysics Data System (ADS)

    Wu, Xiaojie; Zhang, Zhenzhong; Meng, Fanzhi; Yu, Yingning; Han, Lin; Liu, Xiaojuan; Meng, Jian

    2014-04-01

    Combination with semiconductors is a promising approach to the realization of broadband excitation of light conversion materials based on rare earth compounds, to boost the energy efficiency of silicon solar cells. Cd1-xZnxS is a wide bandgap semiconductor with large exciton binding energy. By changing its composition, the bandgap of Cd1-xZnxS can be tuned to match the absorption of trivalent lanthanide (Ln) ions, which makes it a competent energy donor for the Ln3+-Yb3+ couple. In this work, we designed a clean route to a broadband down-converter based on a core-shell-like Y2O3:[(Tb3+-Yb3+), Li+]/Cd0.81Zn0.19S (CdZnS) heterostructure. By hot-pressing and subsequent annealing of a Y2O3:[(Tb3+-Yb3+), Li+]/CdZnS mixture, highly pure CdZnS was sublimated and deposited on the Y2O3:[(Tb3+-Yb3+), Li+] grains while maintaining the original composition of the precursor. The CdZnS shell acted as a light absorber and energy donor for the Tb3+-Yb3+ quantum cutting couple. Because the use of solvents was avoided during the formation of the heterostructures, few impurities were incorporated into the samples, and the non-radiative transition was therefore markedly suppressed. The Y2O3:[(Tb3+-Yb3+), Li+]/CdZnS heterostructures possess strong near-infrared (NIR) luminescence from Yb3+. Broadband down-conversion to the Yb3+ NIR emission was obtained in a wide range of 250-650 nm.

  10. Core-shell-like Y2O3:[(Tb3+-Yb3+), Li+]/CdZnS heterostructure synthesized by super-close-space sublimation for broadband down-conversion.

    PubMed

    Wu, Xiaojie; Zhang, Zhenzhong; Meng, Fanzhi; Yu, Yingning; Han, Lin; Liu, Xiaojuan; Meng, Jian

    2014-05-07

    Combination with semiconductors is a promising approach to the realization of broadband excitation of light conversion materials based on rare earth compounds, to boost the energy efficiency of silicon solar cells. Cd(1-x)Zn(x)S is a wide bandgap semiconductor with large exciton binding energy. By changing its composition, the bandgap of Cd(1-x)Zn(x)S can be tuned to match the absorption of trivalent lanthanide (Ln) ions, which makes it a competent energy donor for the Ln(3+)-Yb(3+) couple. In this work, we designed a clean route to a broadband down-converter based on a core-shell-like Y2O3:[(Tb(3+)-Yb(3+)), Li(+)]/Cd0.81Zn0.19S (CdZnS) heterostructure. By hot-pressing and subsequent annealing of a Y2O3:[(Tb(3+)-Yb(3+)), Li(+)]/CdZnS mixture, highly pure CdZnS was sublimated and deposited on the Y2O3:[(Tb(3+)-Yb(3+)), Li(+)] grains while maintaining the original composition of the precursor. The CdZnS shell acted as a light absorber and energy donor for the Tb(3+)-Yb(3+) quantum cutting couple. Because the use of solvents was avoided during the formation of the heterostructures, few impurities were incorporated into the samples, and the non-radiative transition was therefore markedly suppressed. The Y2O3:[(Tb(3+)-Yb(3+)), Li(+)]/CdZnS heterostructures possess strong near-infrared (NIR) luminescence from Yb(3+). Broadband down-conversion to the Yb(3+) NIR emission was obtained in a wide range of 250-650 nm.

  11. No reduction using sublimation of cyanuric acid

    DOEpatents

    Perry, Robert A.

    1993-01-01

    A method of reducing the NO content of a gas stream comprises contacting the gas stream with an amount of HNCO at a temperature effective for heat-induced decomposition of HNCO, said amount and temperature being effective for resultant lowering of the NO content of the gas stream, said solid agent being particulate and having a particle size of less than 90 .mu.m.

  12. NO reduction using sublimation of cyanuric acid

    DOEpatents

    Perry, R.A.

    1993-01-19

    A method of reducing the NO content of a gas stream comprises contacting the gas stream with an amount of HNCO at a temperature effective for heat-induced decomposition of HNCO, said amount and temperature being effective for resultant lowering of the NO content of the gas stream, said solid agent being particulate and having a particle size of less than 90 [mu]m.

  13. Sublimation of Iodine at Various Pressures

    ERIC Educational Resources Information Center

    Leenson, Ilya A.

    2005-01-01

    Various phenomena that are observed in the process of heating solid iodine in closed vessels at different pressures and temperatures are described. When solid iodine is heated in an evacuated ampoule where the pressure is less than 10(super -3), no noticeable color appears and immediate condensation of tiny iodine crystals is visible higher up on…

  14. Disorders, sublime menu: the DSM-5.

    PubMed

    Sullivan, Danny

    2013-09-01

    The release of the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) is the culmination of a long and remarkably public discussion which was accompanied by a great deal of controversy. Diagnostic criteria for many disorders have changed, the structure of the DSM is different, and there remain significant concerns about the forensic application of the DSM. This column briefly covers the primary changes and summarises the debate about various diagnoses, with a particular focus on diagnoses of relevance to medico-legal psychiatry and the legal system. Underlying concerns about the validity of diagnostic criteria and their applicability to forensic issues are discussed. Concerns about the DSM-5 are not only due to the specific diagnoses and their criteria, but the methodology of checklist criteria. This is amplified in medico-legal settings, but is also in part necessary. Clinicians, lawyers, and judges will all need to think carefully about how they use the DSM and its ilk in forensic settings.

  15. Sublimation-Condensation of Multiscale Tellurium Structures

    SciTech Connect

    Riley, Brian J.; Johnson, Bradley R.; Schaef, Herbert T.; Sundaram, S. K.

    2013-03-11

    This paper presents a simple technique for making tellurium (Te) nano and microtubes of widely varying dimensions with Multi-Scale Processing (MSP). In this process, the Te metal is placed in a reaction vessel (e.g., borosilicate or fused quartz), the vessel is evacuated, and then sealed under vacuum with a torch. The vessel is heat-treated in a temperature gradient where a portion of the tube that can also contain an additional substrate, is under a decreasing temperature gradient. Scanning and transmission electron microscopies have shown that multifaceted crystalline tubes have been formed extending from nano- up to micron-scale with diameters ranging from 51.2 ± 5.9 to 1042 ± 134 nm between temperatures of 157 and 224 °C, respectively. One-dimensional tubular features are seen at lower temperatures, while three-dimensional features, at the higher temperatures. These features have been characterized with X-ray diffraction and found to be trigonal Te with space group P3121. Our results show that the MSP can adequately be described using a simple Arrhenius equation.

  16. NO reduction using sublimation of cyanuric acid

    DOEpatents

    Perry, R.A.

    1996-05-21

    A method of reducing the NO content of a gas stream comprises contacting the gas stream with an amount of HNCO at a temperature effective for heat-induced decomposition of cyanuric acid, said amount and temperature being effective for the resultant lowering of the NO content of the gas stream, said cyanuric acid being particulate and having a particle size of less than 90 {micro}m. 1 fig.

  17. Cute, Creepy and Sublime Unnamed Childhood Monstrosities

    ERIC Educational Resources Information Center

    Tesar, Marek; Koro-Ljungberg, Mirka

    2016-01-01

    Strangers, Gods, and monsters are all names for the experience of alterity and otherness within and amongst us. We need monsters in our lives. In this paper we use philosophy as a method to explore language, developmental and cultural instabilities, and terrifying (and discursive) monstrosity located within children's literature and childhood…

  18. Enhanced thermoelectric performance of (Ba,In) double-filled skutterudites via randomly arranged micropores

    SciTech Connect

    Yu, Jian; Zhao, Wen-Yu E-mail: zhangqj@whut.edu.cn; Wei, Ping; Zhu, Wan-Ting; Zhou, Hong-Yu; Liu, Zhi-Yuan; Tang, Ding-Guo; Lei, Bing; Zhang, Qing-Jie E-mail: zhangqj@whut.edu.cn

    2014-04-07

    Porous (Ba,In) double-filled skutterudite materials with pore diameter about 1–4 μm were prepared by the decomposition of metastable ZnSb inclusions induced by the Zn sublimation. Transport measurements revealed that the Seebeck coefficient was increased due to the electron filtering effect induced by nanostructures in the surfaces of pores, the electrical conductivity was almost unchanged because of the percolation effect of conducted network composed of filled skutterudites, and the lattice thermal conductivity was dramatically suppressed due to the enhanced pore-edge boundary scattering of long-wavelength phonons. As a result, a maximum ZT of 1.36 was obtained, increased by 22.5% as compared to that of the bulk material with same chemical composition. This work demonstrates that by introducing porous structures is thought to be an efficient approach to improve the thermoelectric performance of bulk materials.

  19. Performance Improvement.

    ERIC Educational Resources Information Center

    1996

    This document contains four papers presented at a symposium on performance improvement moderated by Edward Schorer at the 1996 conference of the Academy of Human Resource Development (AHRD) "The Organizational Ecology of Ethical Problems: International Case Studies in the Light of HPT [Human Performance Technology]" (Peter J. Dean,…

  20. Pilot performance

    NASA Technical Reports Server (NTRS)

    Nicholls, Jennifer

    1988-01-01

    For many years, the emphasis has been placed on the performance of the aircraft, rather than on those who fly the aircraft. This is largely due to the relative safety of flying. Just in the last few years there have been several major accidents that have shown that flying is not quite as safe as it was thought to be. Sixty-five percent of these accidents are a result of pilot performance decrements, and so it is obvious that there is a need to reduce that figure. A study has been mandated to evaluate the performance of pilots. This includes workload, circadium rhythms, jet lag, and any other factors which might affect a pilot's performance in the cockpit. The purpose of this study is to find out when and why the decrement in a pilot's performance occur and how to remedy the situation.

  1. Device Performance

    SciTech Connect

    Not Available

    2006-06-01

    In the Device Performance group, within the National Center for Photovoltaic's Measurements and Characterization Division, we measure the performance of PV cells and modules with respect to standard reporting conditions--defined as a reference temperature (25 C), total irradiance (1000 Wm-2), and spectral irradiance distribution (IEC standard 60904-3). Typically, these are ''global'' reference conditions, but we can measure with respect to any reference set. To determine device performance, we conduct two general categories of measurements: spectral responsivity (SR) and current versus voltage (I-V). We usually perform these measurements using standard procedures, but we develop new procedures when required by new technologies. We also serve as an independent facility for verifying device performance for the entire PV community. We help the PV community solve its special measurement problems, giving advice on solar simulation, instrumentation for I-V measurements, reference cells, measurement procedures, and anomalous results. And we collaborate with researchers to analyze devices and materials.

  2. Performance tests.

    PubMed Central

    Wetherell, A

    1996-01-01

    This paper discusses the use of psychological performance tests to assess the effects of environmental stressors. The large number and the variety of performance tests are illustrated, and the differences between performance tests and other psychological tests are described in terms of their design, construction, use, and purpose. The stressor emphasis is on the effects of drugs since that is where most performance tests have found their main application, although other stressors, e.g., fatigue, toxic chemicals, are mentioned where appropriate. Diazepam is used as an example. There is no particular performance emphasis since the tests are intended to have wide applicability. However, vehicle-driving performance is discussed because it has been the subject of a great deal of research and is probably one of the most important areas of application. Performance tests are discussed in terms of the four main underlying models--factor analysis, general information processing, multiple resource and strategy models, and processing-stage models--and in terms of their psychometric properties--sensitivity, reliability, and content, criterion, construct, and face validity. Some test taxonomies are presented. Standardization is also discussed with reference to the reaction time, mathematical processing, memory search, spatial processing, unstable tracking, verbal processing, and dual task tests used in the AGARD STRES battery. Some comments on measurement strengths and appropriate study designs and methods are included. PMID:9182033

  3. The Performance of Performance Standards.

    ERIC Educational Resources Information Center

    Heckman, James J.; Heinrich, Carolyn; Smith, Jeffery

    2002-01-01

    A model demonstrating how performance incentives may encourage cream skimming (selecting participants with a high likelihood of success) was applied to data from 16 Job Training Partnership Act training centers. Short-term performance measures were weakly and perversely related to long-term impacts, but efficiency gains/losses from skimming were…

  4. Performance Support for Performance Analysis

    ERIC Educational Resources Information Center

    Schaffer, Scott; Douglas, Ian

    2004-01-01

    Over the past several years, there has been a shift in emphasis in many business, industry, government and military training organizations toward human performance technology or HPT (Rossett, 2002; Dean, 1995). This trend has required organizations to increase the human performance knowledge, skills, and abilities of the training workforce.…

  5. Engineering Performance

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Under Goddard Space Flight Center and Jet Propulsion Laboratory SBIR (Small Business Innovative Research) contracts, AST Engineering Services, Inc. developed a system engineering computer software tool to model how certain applications will affect a proposed system's performance. Quantitative System Engineering (QASE) evaluates system timing, capacity and availability. The system is used to predict performance of proposed real-time, aerospace systems, embedded systems, and/or scientific systems, as well as in support of NASA's EDOS (Earth Observing System (EOS) Data and Operations System) initiative.

  6. Good Performers

    ERIC Educational Resources Information Center

    Bennett, Bob

    2009-01-01

    Soaring energy prices and tightening school budgets don't mix well. In fact, millions of children across the United States are being educated in energy-leaking, unhealthful facilities in dire need of physical upgrade and systems modernization. Increasing numbers of K-12 districts and institutions of higher learning are turning to performance-based…

  7. Performing Resistance

    ERIC Educational Resources Information Center

    Garoian, Charles R.; Gaudelius, Yvonne M.

    2004-01-01

    Many contemporary artists, critical theorists, and educators challenge the cultural assumptions that are embedded in our understandings of technology and its relationship to art, the body, and human life. In this article, we discuss the performance artworks of osseus labyrint, Goat Island, and Guillermo Gomez-Pena, Roberto Sifuentes, and Juan…

  8. Performance Testing

    NASA Technical Reports Server (NTRS)

    1991-01-01

    Systems Technology, Inc., Hawthorne, CA, developed an electronic Critical Tracking Task (CTT) system that analyzes and rates a subject's visual/motor responses for Ames Research Center. Originally applied to measuring the effects of long term confinement in the mid 1960's, the CTT system is now marketed as FACTOR 1000 by Performance Factors, Inc. Alameda, CA, under a licensing agreement with Systems Technology. The system is a non-invasive, self-administered test that takes less than a minute and detects impairment from a broad range of causes, including stress, fatigue, illness, drugs, or alcohol. It is used daily by Old Town Trolley Tours, San Diego, CA, to assess each driver's physical coordination skills prior to the start of each shift. FACTOR 1000 reduces liabilities and costs related to accidents, and costs less than one dollar per day per employee. Performance Factors is now BioFactors, Inc.

  9. Performance Assessment: Lessons from Performers

    ERIC Educational Resources Information Center

    Parkes, Kelly A.

    2010-01-01

    The performing arts studio is a highly complex learning setting, and assessing student outcomes relative to reliable and valid standards has presented challenges to this teaching and learning method. Building from the general international higher education literature, this article illustrates details, processes, and solutions, drawing on…

  10. Pay for Performance: Whose Performance?

    ERIC Educational Resources Information Center

    Tienken, Christopher H.

    2011-01-01

    Education reform proposals are not in short supply. Recent issues of the "Kappa Delta Pi Record" examined two of these: Common Core State Standards (Winter 2011) and Charter Schools (Spring 2011). Teacher pay for performance is another policy gaining traction in state legislatures and at the federal level. The Race to the Top (RTTT)…

  11. Performance of Water Recirculation Loop Maintenance Components for the Advanced Spacesuit Water Membrane Evaporator

    NASA Technical Reports Server (NTRS)

    Rector, Tony; Peyton, Barbara M.; Steele, John W.; Makinen, Janice; Bue, Grant C.; Campbell, Colin

    2014-01-01

    Water loop maintenance components to maintain the water quality of the Advanced Spacesuit Water Membrane Evaporation (SWME) water recirculation loop have undergone a comparative performance evaluation with a recirculating control loop which had no water quality maintenance. Results show that periodic water maintenance can improve performance of the SWME. The SWME is a heat rejection device under development at the NASA Johnson Space Center to perform thermal control for advanced spacesuits. One advantage of this technology is the potential for a significantly greater degree of tolerance to contamination when compared to the existing sublimator technology. The driver for the evaluation of water recirculation maintenance components was to enhance the robustness of the SWME through the leveraging of fluid loop management lessons learned from the International Space Station (ISS). A patented bed design that was developed for a United Technologies Aerospace System military application provided a low pressure drop means for water maintenance in the SWME recirculation loop. The bed design is coupled with high capacity ion exchange resins, organic adsorbents, and a cyclic methodology developed for the Extravehicular Mobility Unit (EMU) Transport Water loop. The maintenance cycle included the use of a biocide delivery component developed for the ISS to introduce a biocide in a microgravity compatible manner for the Internal Active Thermal Control System (IATCS). The leveraging of these water maintenance technologies to the SWME recirculation loop is a unique demonstration of applying the valuable lessons learned on the ISS to the next generation of manned spaceflight Environmental Control and Life Support System (ECLSS) hardware.

  12. Performance of the cometary experiment MUPUS on the body Earth

    NASA Astrophysics Data System (ADS)

    Marczewski, W.; Usowicz, B.; Schröer, K.; Seiferlin, K.; Spohn, T.

    2003-04-01

    Thermal experiment MUPUS for the Rosetta mission was extensively experience in field and laboratory conditions to predict its performance under physical processes available on the Earth. The goal was not guessing a cometary material in the ground but available behavior of thermal sensor responses monitoring mass and energy transfer. The processes expected on a comet are different in composition and environmental from those met on the Earth but basically similar in physics. Nature of energy powering the processes is also essentially the same - solar radiation. Several simple laboratory experiments with freezing and thawing with water ice, with mixture of water and oil and water layers strongly diverged by salinity revealed capability of recognition layered structure of the medium under test. More over effects of slow convection and latent heat related to the layers are also observed well. Cometary environment without atmosphere makes process of sublimation dominant. Open air conditions on the Earth may also offer a change of state in matter but between different phases. Learning temperature gradient in snow layers under thawing show that effects stimulated by a cause of daily cycling may be detected thermally. Results from investigations in snow made on Spitzbergen are good proofs on capability of the method. Relevance of thermal effects to heat powered processes of mass transport in the matter of ground is meaningful for the cometary experiment of MUPUS and for Earth sciences much concerned on water, gas and solid matter transport in the terrestrial ground. Results leading to energy balance studied on the Earth surface may be interesting also for the experiment on the comet and are to be discussed.

  13. Performance of a hypersonic hot fuselage structure with a carbon dioxide frost projected, nonintegral cryogenic tank

    NASA Technical Reports Server (NTRS)

    Sharpe, E. L.; Jackson, L. R.

    1975-01-01

    A model which consisted of a hot structure and a nonintegral tank protected by a carbon dioxide frost thermal protection system was tested under the following conditions: (1) room temperature loading and (2) heating and loading corresponding to the Mach 8 flight of an air-breathing launch vehicle. In the simulated flight tests, liquid nitrogen inside the tank was withdrawn at the rate fuel would be consumed. Prior to each simulated flight test, carbon dioxide was cryodeposited in the insulation surrounding the tank; during the tests, subliming CO2 frost absorbed heat and provided a purge gas for the space between the tank and the structure. A method of flame spraying the joints between panels with a nickel-aluminum material was developed to prevent excessive leakage of the purge gas through the outer structure. The tests indicated that the hot structure (with a joint repaired by riveting), the nonintegral tank and suspension system, and the carbon dioxide frost thermal protection system provide a workable concept with predictable performance.

  14. Effect of Freezing on Lyophilization Process Performance and Drug Product Cake Appearance.

    PubMed

    Esfandiary, Reza; Gattu, Shravan K; Stewart, John M; Patel, Sajal M

    2016-04-01

    This study highlights the significance of the freezing step and the critical role it can play in modulating process performance and product quality during freeze-drying. For the model protein formulation evaluated, the mechanism of freezing had a significant impact on cake appearance, a potential critical product quality attribute for a lyophilized drug product. Contrary to common knowledge, a freezing step with annealing resulted in 20% increase in primary drying time compared to without annealing. In addition, annealing resulted in poor cake appearance with shrinkage, cracks, and formation of a distinct skin at the top surface of the cake. Finally, higher product resistance (7.5 cm(2).Torr.hr/g) was observed in the case of annealing compared to when annealing was not included (5 cm(2).Torr.hr/g), which explains the longer primary drying time due to reduced sublimation rates. An alternative freezing option using controlled ice nucleation resulted in reduced primary drying time (i.e., 30% reduction compared to annealing) and a more homogenous batch with elegant uniform (i.e., significantly improved) cake appearance. Here, a mechanistic understanding of the distinct differences in cake appearance as a function of freezing mechanism is proposed within the context of ice nucleation temperature, ice crystal growth, and presumed solute distribution within the frozen matrix.

  15. Study protocol for a double blind, randomised, placebo-controlled trial of continuous subpectoral local anaesthetic infusion for pain and shoulder function following mastectomy: SUB-pectoral Local anaesthetic Infusion following MastEctomy (SUBLIME) study

    PubMed Central

    Langford, R; Brown, I; Vickery, J; Mitchell, K; Pritchard, C; Creanor, S

    2014-01-01

    Introduction Over 16 000 mastectomies are performed in England and Wales annually. Acute postoperative pain and nausea are common. The most frequently occurring long-term complications are chronic pain (up to 50%) and reduced shoulder function (reported at 35%). Regional techniques that improve acute postoperative pain relief may reduce the incidence of these complications. This study assesses the effectiveness of a 24-hour continuous local anaesthetic in the subpectoral plane in improving postoperative pain and quality of life in patients undergoing mastectomy. Methods and analysis This is a randomised, double blind, placebo-controlled, two-centre, parallel group trial in women undergoing mastectomy with or without axillary involvement. One hundred and sixty participants will be randomised in a 1:1 ratio to receive either 0.25% levobupivacaine or 0.9% saline by subpectoral infusion postoperatively for 24 h. All participants will be provided with an intravenous morphine patient-controlled analgesia (PCA) system. Participants will be followed-up for 24 h in hospital and at approximately 14 days and 6 months postoperatively. Joint primary outcome measures are total morphine consumption and total pain score (captured via patient-recorded visual analogue scale (VAS) 4 hourly) during the first 24 h postoperatively. Primary statistical analysis of total pain is based on the area under the curve of pain versus time graph. Secondary outcomes include PCA attempts in first 24 h; VAS pain scores and shoulder function by goniometry at 24 h, 14 days (approximately) and 6 months; Verbal Rating Scale pain scores in first 24 h; Brief Pain Inventory and Oxford Shoulder Score at 6 months; duration of hospital stay; incidence of postoperative nausea and vomiting; cost-effectiveness. Ethics and dissemination The study is approved by the South West England Research Ethics Committee (12/SW/0149). Results will be published in a peer-reviewed journal and presented

  16. Performance Monitoring Based on UML Performance Profile

    NASA Astrophysics Data System (ADS)

    Kim, Dong Kwan; Kim, Chul Jin; Cho, Eun Sook

    In this paper we propose a way of measuring software performance metrics such as response time, throughput, and resource utilization. It is obvious that performance-related Quality of Service (QoS) is one of the important factors which are satisfied for users' needs. The proposed approach uses UML performance profile for the performance specification and aspect-oriented paradigm for the performance measurement. Code instrumentation in AOP is a mechanism to insert source code for performance measurement into business logic code. We used AspectJ, an aspect-oriented extension to the Java. AspectJ code for performance measurement is separated from Java code for functional requirements. Both AspectJ and Java code can be woven together for the performance measurement. The key component of the proposed approach is an AspectJ code generator. It creates AspectJ code for the performance measurement from the UML [1] models containing performance profile.

  17. Asserting Performance Expectations (Formerly Performance Assertions: A Performance Diagnosis Tool)

    SciTech Connect

    Vetter, J S; Worley, P

    2002-07-24

    Traditional techniques for performance analysis provide a means for extracting and analyzing raw performance information from applications. Users then reason about and compare this raw performance data to their performance expectations for important application constructs. This comparison can be tedious, difficult, and error-prone for the scale and complexity of today's architectures and software systems. To address this situation, we present a methodology and prototype that allows users to assert performance expectations explicitly in their source code using performance assertions. As the application executes, each performance assertion in the application collects data implicitly to verify the assertion. By allowing the user to specify a performance expectation with individual code segments, the runtime system can jettison raw data for measurements that pass their expectation, while reacting to failures with a variety of responses. We present several compelling uses of performance assertions with our operational prototype including raising a performance exception, validating a performance model, and adapting an algorithm to an architecture empirically at runtime.

  18. The Performer as Writer.

    ERIC Educational Resources Information Center

    Gentile, John S.

    Most performer-writers accept the writing process simply as a means to an end: the shared performance event with a live audience. While writer-performers regard a script as more important than the performance, a solo performance is, however, a showcase of the artist's talent, and creating one's own text offers the performer artistic control. Some…

  19. High Performance Work Practices and Firm Performance.

    ERIC Educational Resources Information Center

    Department of Labor, Washington, DC. Office of the American Workplace.

    A literature survey established that a substantial amount of research has been conducted on the relationship between productivity and the following specific high performance work practices: employee involvement in decision making, compensation linked to firm or worker performance, and training. According to these studies, high performance work…

  20. Performance of Pain, Performance of Beauty

    ERIC Educational Resources Information Center

    Thompson, James

    2006-01-01

    "Performance of pain, performance of beauty" explores performance projects in war zones using Elaine Scarry's definitions of "pain" and "beauty" as a starting point. The way in which pain constricts the body and the experience that beauty can take a person beyond the body become a contested framework for considering…

  1. Performance of a Water Recirculation Loop Maintenance Device and Process for the Advanced Spacesuit Water Membrane Evaporator

    NASA Technical Reports Server (NTRS)

    Rector, Tony; Steele, John W.; Bue, Grant C.; Campbell, Colin; Makinen, Janice

    2012-01-01

    A water loop maintenance device and process to maintain the water quality of the Advanced Spacesuit Water Membrane Evaporation (SWME) water recirculation loop has been undergoing a performance evaluation. The SWME is a heat rejection device under development at the NASA Johnson Space Center to perform thermal control for advanced spacesuits. One advantage to this technology is the potential for a significantly greater degree of tolerance to contamination when compared to the existing Sublimator technology. The driver for the water recirculation maintenance device and process is to further enhance this advantage through the leveraging of fluid loop management lessons-learned from the International Space Station (ISS). A bed design that was developed for a Hamilton Sundstrand military application, and considered for a potential ISS application with the Urine Processor Assembly, provides a low pressure drop means for water maintenance in a recirculation loop. The bed design is coupled with high capacity ion exchange resins, organic adsorbents, and a cyclic methodology developed for the Extravehicular Mobility Unit (EMU) Transport Water loop. The maintenance process further leverages a sorbent developed for ISS that introduces a biocide in a microgravity-compatible manner for the Internal Active Thermal Control System (IATCS). The leveraging of these water maintenance technologies to the SWME recirculation loop is a unique demonstration of applying the valuable lessons learned on the ISS to the next generation of manned spaceflight Environmental Control and Life Support System (ECLSS) hardware. This

  2. Performing Surgery: Commonalities with Performers Outside Medicine

    PubMed Central

    Kneebone, Roger L.

    2016-01-01

    This paper argues for the inclusion of surgery within the canon of performance science. The world of medicine presents rich, complex but relatively under-researched sites of performance. Performative aspects of clinical practice are overshadowed by a focus on the processes and outcomes of medical care, such as diagnostic accuracy and the results of treatment. The primacy of this “clinical” viewpoint—framed by clinical professionals as the application of medical knowledge—hides resonances with performance in other domains. Yet the language of performance is embedded in the culture of surgery—surgeons “perform” operations, work in an operating “theater” and use “instruments.” This paper asks what might come into view if we take this performative language at face value and interrogate surgery from the perspective of performance science. PMID:27630587

  3. Emerson's "Nature" as an Early Manifestation of the Biological Sublime

    ERIC Educational Resources Information Center

    Tindol, Robert

    2013-01-01

    Ralph Waldo Emerson's first essay, "Nature," has been viewed as a reconciliation of the world of nature with the world of mind. A close analysis shows that Emerson was in fact attempting to come to terms with human fragility in a unique way by delineating the point at which the worldly and the transcendental are demarcated. Because…

  4. The Rebirth of Cool: Toward a Science Sublime

    ERIC Educational Resources Information Center

    Wong, E. David

    2007-01-01

    Teachers love and hate "the cool." As educators, few things are more coveted than being recognized as teaching the "coolest" class in the school. However, teachers may also feel an uneasy ambivalence, admonishing themselves that serious science is substantial, enduring, and intellectual, and wonder whether their "cool" class was merely…

  5. Vocal Warm-Ups: From the Sublime to the Ridiculous.

    ERIC Educational Resources Information Center

    Briggs, Robert

    2000-01-01

    Recommends using "activation exercises," or warm-ups, to awaken students' voices, minds, and breathing mechanisms when singing choral music. Describes three activation exercises: (1) plainchant melodies; (2) the five-note scale; and (3) tongue twisters sung to melodies or scale patterns. Explains why the first and third exercises work.…

  6. SEPARATION OF NEPTUNIUM FROM PLUTONIUM BY CHLORINATION AND SUBLIMATION

    DOEpatents

    Fried, S.M.

    1958-11-18

    A process is described for separating neptunium from plutonium. The method consists in chlorinating a mixture of the oxides of Np and Pu by contacting the mixture with carbon tetrachloride at about 500 icient laborato C. ln this manner the Np is converted to the tetrachlorlde and the Pu converted to the trichloride. Since NpCl/sub 4/ is more latile than PuCl/sub 3/, the separation ls effected by vaporing sad subsequently condenslng the NpCl/sub 4/.

  7. A sublimation model for martian south polar ice features.

    PubMed

    Byrne, Shane; Ingersoll, Andrew P

    2003-02-14

    In their pioneering work, Leighton and Murray argued that the Mars atmosphere, which at present is 95% carbon dioxide, is controlled by vapor equilibrium with a much larger polar reservoir of solid carbon dioxide. Here we argue that the polar reservoir is small and cannot function as a long-term buffer to the more massive atmosphere. Our work is based on modeling of the circular depressions commonly found on the south polar cap. We argue that a carbon dioxide ice layer about 8 meters thick is being etched away to reveal water ice underneath. This is consistent with thermal infrared data from the Mars Odyssey mission.

  8. From the Meticulous to the Sublime: Transformations in Ink.

    ERIC Educational Resources Information Center

    King, Steve

    1998-01-01

    Provides a lesson that gives students the opportunity to master the medium of pen and ink through a project called "Transformations." Explains that students choose two pictures, copying each one, and then combine them to create a transformation where one object transforms into the other, such as a bolt with butterfly wings. (CMK)

  9. Method of Suppressing Sublimation in Advanced Thermoelectric Devices

    NASA Technical Reports Server (NTRS)

    Sakamoto, Jeffrey S. (Inventor); Caillat, Thierry (Inventor); Fleurial, Jean-Pierre (Inventor); Snyder, G. Jeffrey (Inventor)

    2009-01-01

    A method of applying a physical barrier to suppress thermal decomposition near a surface of a thermoelectric material including applying a continuous metal foil to a predetermined portion of the surface of the thermoelectric material, physically binding the continuous metal foil to the surface of the thermoelectric material using a binding member, and heating in a predetermined atmosphere the applied and physically bound continuous metal foil and the thermoelectric material to a sufficient temperature in order to promote bonding between the continuous metal foil and the surface of the thermoelectric material. The continuous metal foil forms a physical barrier to enclose a predetermined portion of the surface. Thermal decomposition is suppressed at the surface of the thermoelectric material enclosed by the physical barrier when the thermoelectric element is in operation.

  10. The Sublime Objects of Education Policy: Quality, Equity and Ideology

    ERIC Educational Resources Information Center

    Clarke, Matthew

    2014-01-01

    Quality and equity are touchstones of education policy in the twenty-first century in a range of global contexts. On the surface, this seems fitting: after all, who could object to more quality and greater equity in education? Yet what do we mean by quality and equity, and how are they related? This paper draws on Lacanian psychoanalytic theory to…

  11. Speculations on Orbital Forcing of Sublimation from the Polar Caps

    NASA Technical Reports Server (NTRS)

    Hecht, M. H.

    2003-01-01

    Calculation of the periodic variations in the martian orbital parameters by Ward and subsequent refinements to the theory have inspired numerous models of variation of the martian water cycle. The limitations of models such as this can not be overstated. Albedo, for example, has a much greater influence on temperature than orbital forcing, and seems to be linked to insolation, possibly via its influence on dust transport. To make further progress, either new constraints must be identified, or additional clues must be obtained from remote sensing and in situ exploration.

  12. Method and apparatus for cutting and abrading with sublimable particles

    DOEpatents

    Bingham, Dennis N.

    1995-01-01

    A gas delivery system provides a first gas as a liquid under extreme pressure and as a gas under intermediate pressure. Another gas delivery system provides a second gas under moderate pressure. The second gas is selected to solidify at a temperature at or above the temperature of the liquified gas. A nozzle assembly connected to the gas delivery systems produces a stream containing a liquid component, a solid component, and a gas component. The liquid component of the stream consists of a high velocity jet of the liquified first gas. The high velocity jet is surrounded by a particle sheath that consists of solid particles of the second gas which solidifies in the nozzle upon contact with the liquified gas of the high velocity jet. The gas component of the stream is a high velocity flow of the first gas that encircles the particle sheath, forming an outer jacket.

  13. Method and apparatus for cutting and abrading with sublimable particles

    DOEpatents

    Bingham, D.N.

    1995-10-10

    A gas delivery system provides a first gas as a liquid under extreme pressure and as a gas under intermediate pressure. Another gas delivery system provides a second gas under moderate pressure. The second gas is selected to solidify at a temperature at or above the temperature of the liquefied gas. A nozzle assembly connected to the gas delivery systems produces a stream containing a liquid component, a solid component, and a gas component. The liquid component of the stream consists of a high velocity jet of the liquefied first gas. The high velocity jet is surrounded by a particle sheath that consists of solid particles of the second gas which solidifies in the nozzle upon contact with the liquefied gas of the high velocity jet. The gas component of the stream is a high velocity flow of the first gas that encircles the particle sheath, forming an outer jacket. 6 figs.

  14. The Sublime and Depictions of Violence in Some Contemporary Artworks

    ERIC Educational Resources Information Center

    Johnson, Gearold; McKee, Patrick; Ragouzis, Perry

    2009-01-01

    Images of extreme and ever more graphic violence are a part of contemporary culture. Since students cannot avoid them, such images should be addressed by aesthetic educators. But this will require a theory for the analysis and evaluation of the aesthetic properties of violent imagery. The main thesis of this essay is that depiction of violence in…

  15. Distributed performance counters

    DOEpatents

    Davis, Kristan D; Evans, Kahn C; Gara, Alan; Satterfield, David L

    2013-11-26

    A plurality of first performance counter modules is coupled to a plurality of processing cores. The plurality of first performance counter modules is operable to collect performance data associated with the plurality of processing cores respectively. A plurality of second performance counter modules are coupled to a plurality of L2 cache units, and the plurality of second performance counter modules are operable to collect performance data associated with the plurality of L2 cache units respectively. A central performance counter module may be operable to coordinate counter data from the plurality of first performance counter modules and the plurality of second performance modules, the a central performance counter module, the plurality of first performance counter modules, and the plurality of second performance counter modules connected by a daisy chain connection.

  16. Space Suit Radiator Performance in Lunar and Mars Environments

    NASA Technical Reports Server (NTRS)

    Nabity, James; Mason, Georgia; Copeland, Robert; Libberton, Kerry; Stephan, Ryan; Trevino, Luis; Paul, Heather

    2005-01-01

    During an ExtraVehicular Activity (EVA), both the heat generated by the astronaut's metabolism and that produced by the Portable Life Support System (PLSS) must be rejected to space. The heat sources include the heat of adsorption of metabolic CO2, the heat of condensation of water, the heat removed from the body by the liquid cooling garment and the load from the electrical components. Although the sublimator hardware to reject this load weighs only 1.58 kg (3.48 lbm), an additional 3.6 kg (8 lbm) of water are loaded into the unit, most of which is sublimated and lost to thus become the single largest expendable during an eight hour EVA. We can significantly reduce the amount of expendable water consumed in the sublimator by using a radiator to reject heat from the Astronaut during an EVA. Last year we reported on the design and initial operational assessment tests of our novel radiator designated the Radiator And Freeze Tolerant heat eXchanger (RAFT-X). Herein, we report on tests conducted in the NASA Johnson Space Center Chamber E Thermal Vacuum Test Facility. Up to 260 W (900 Btu/h) of heat were rejected in Lunar and Mars environments with temperatures as cold as -170 C (- 275 F). Further, the RAFT-X endured several freeze / thaw cycles and in fact, the heat exchanger was completely frozen three times without any apparent damage to the unit.

  17. High Performance Work Systems and Firm Performance.

    ERIC Educational Resources Information Center

    Kling, Jeffrey

    1995-01-01

    A review of 17 studies of high-performance work systems concludes that benefits of employee involvement, skill training, and other high-performance work practices tend to be greater when new methods are adopted as part of a consistent whole. (Author)

  18. Initial Cognitive Performance Predicts Longitudinal Aviator Performance

    PubMed Central

    Jo, Booil; Adamson, Maheen M.; Kennedy, Quinn; Noda, Art; Hernandez, Beatriz; Zeitzer, Jamie M.; Friedman, Leah F.; Fairchild, Kaci; Scanlon, Blake K.; Murphy, Greer M.; Taylor, Joy L.

    2011-01-01

    Objectives. The goal of the study was to improve prediction of longitudinal flight simulator performance by studying cognitive factors that may moderate the influence of chronological age. Method. We examined age-related change in aviation performance in aircraft pilots in relation to baseline cognitive ability measures and aviation expertise. Participants were aircraft pilots (N = 276) aged 40–77.9. Flight simulator performance and cognition were tested yearly; there were an average of 4.3 (± 2.7; range 1–13) data points per participant. Each participant was classified into one of the three levels of aviation expertise based on Federal Aviation Administration pilot proficiency ratings: least, moderate, or high expertise. Results. Addition of measures of cognitive processing speed and executive function to a model of age-related change in aviation performance significantly improved the model. Processing speed and executive function performance interacted such that the slowest rate of decline in flight simulator performance was found in aviators with the highest scores on tests of these abilities. Expertise was beneficial to pilots across the age range studied; however, expertise did not show evidence of reducing the effect of age. Discussion. These data suggest that longitudinal performance on an important real-world activity can be predicted by initial assessment of relevant cognitive abilities. PMID:21586627

  19. Performance of Water Recirculation Loop Maintentance Components for the Advanced Spacesuit Water Membrane Evaporator

    NASA Technical Reports Server (NTRS)

    Rector, Tony; Peyton, Barbara; Steele, John W.; Bue, Grant C.; Campbell, Colin; Makinen, Janice

    2014-01-01

    Water loop maintenance components to maintain the water quality of the Advanced Spacesuit Water Membrane Evaporation (SWME) water recirculation loop have undergone a comparative performance evaluation with a second SWME water recirculation loop with no water quality maintenance. Results show the benefits of periodic water maintenance. The SWME is a heat rejection device under development at the NASA Johnson Space Center to perform thermal control for advanced spacesuits. One advantage to this technology is the potential for a significantly greater degree of tolerance to contamination when compared to the existing Sublimator technology. The driver for the evaluation of water recirculation maintenance components was to further enhance this advantage through the leveraging of fluid loop management lessonslearned from the International Space Station (ISS). A bed design that was developed for a UTAS military application, and considered for a potential ISS application with the Urine Processor Assembly, provided a low pressure drop means for water maintenance in a recirculation loop. The bed design is coupled with high capacity ion exchange resins, organic adsorbents, and a cyclic methodology developed for the Extravehicular Mobility Unit (EMU) Transport Water loop. The maintenance cycle included the use of a biocide delivery component developed for ISS to introduce a biocide in a microgravity-compatible manner for the Internal Active Thermal Control System (IATCS). The leveraging of these water maintenance technologies to the SWME recirculation loop is a unique demonstration of applying the valuable lessons learned on the ISS to the next generation of manned spaceflight Environmental Control and Life Support System (ECLSS) hardware.

  20. Thermal Performance of Orion Active Thermal Control System With Seven-Panel Reduced-Curvature Radiator

    NASA Technical Reports Server (NTRS)

    Wang, Xiao-Yen J.; Yuko, James R.

    2010-01-01

    The active thermal control system (ATCS) of the crew exploration vehicle (Orion) uses radiator panels with fluid loops as the primary system to reject heat from spacecraft. The Lockheed Martin (LM) baseline Orion ATCS uses eight-panel radiator coated with silver Teflon coating (STC) for International Space Station (ISS) missions, and uses seven-panel radiator coated with AZ 93 white paint for lunar missions. As an option to increase the radiator area with minimal impact on other component locations and interfaces, the reduced-curvature (RC) radiator concept was introduced and investigated here for the thermal perspective. Each RC radiator panel has 15 percent more area than each Lockheed Martin (LM) baseline radiator panel. The objective was to determine if the RC seven-panel radiator concept could be used in the ATCS for both ISS and lunar missions. Three radiator configurations the LM baseline, an RC seven-panel radiator with STC, and an RC seven-panel radiator with AZ 93 coating were considered in the ATCS for ISS missions. Two radiator configurations the LM baseline and an RC seven-panel radiator with AZ 93 coating were considered in the ATCS for lunar missions. A Simulink/MATLAB model of the ATCS was used to compute the ATCS performance. Some major hot phases on the thermal timeline were selected because of concern about the large amount of water sublimated for thermal topping. It was concluded that an ATCS with an RC seven-panel radiator could be used for both ISS and lunar missions, but with two different coatings STC for ISS missions and AZ 93 for lunar missions to provide performance similar to or better than that of the LM baseline ATCS.

  1. Performance of Water Recirculation Loop Maintenance Components for the Advanced Spacesuit Water Membrane Evaporator

    NASA Technical Reports Server (NTRS)

    Rector, Tony; Peyton, Barbara M.; Steele, John W.; Makinen, Janice; Bue, Grant C.; Campbell, Colin

    2014-01-01

    Water loop maintenance components to maintain the water quality of the Advanced Spacesuit Water Membrane Evaporation (SWME) water recirculation loop have undergone a comparative performance evaluation with a second SWME water recirculation loop with no water quality maintenance. Results show the benefits of periodic water maintenance. The SWME is a heat rejection device under development at the NASA Johnson Space Center to perform thermal control for advanced spacesuits. One advantage to this technology is the potential for a significantly greater degree of tolerance to contamination when compared to the existing Sublimator technology. The driver for the evaluation of water recirculation maintenance components was to further enhance this advantage through the leveraging of fluid loop management lessons learned from the International Space Station (ISS). A bed design that was developed for a UTAS military application, and considered for a potential ISS application with the Urine Processor Assembly, provided a low pressure drop means for water maintenance in a recirculation loop. The bed design is coupled with high capacity ion exchange resins, organic adsorbents, and a cyclic methodology developed for the Extravehicular Mobility Unit (EMU) Transport Water loop. The maintenance cycle included the use of a biocide delivery component developed for ISS to introduce a biocide in a microgravity compatible manner for the Internal Active Thermal Control System (IATCS). The leveraging of these water maintenance technologies to the SWME recirculation loop is a unique demonstration of applying the valuable lessons learned on the ISS to the next generation of manned spaceflight Environmental Control and Life Support System (ECLSS) hardware.

  2. Conceptualising Research Performance

    ERIC Educational Resources Information Center

    Bazeley, Pat

    2010-01-01

    In a context of increasing emphasis on academic performance and accountability, data from a structured survey in which academics elaborated on eight different attributes of high-performing researchers were used to build a conceptual model of research performance. Research performance was seen to comprise two basic components, with six secondary…

  3. Performance of a Water Recirculation Loop Maintenance Device and Process for the Advanced Spacesuit Water Membrane Evaporator

    NASA Technical Reports Server (NTRS)

    Steele, John W.; Rector, Tony; Bue, Grant C.; Campbell, Colin; Makinen, Janice

    2013-01-01

    A dual-bed device to maintain the water quality of the Advanced Spacesuit Water Membrane Evaporation (SWME) water recirculation loop has been designed and is undergoing testing. The SWME is a heat rejection device under development at the NASA Johnson Space Center to perform thermal control for advanced spacesuits. One advantage to this technology is the potential for a significantly greater degree of tolerance to contamination when compared to the existing Sublimator technology. The driver for the development of a water recirculation maintenance device is to further enhance this advantage through the leveraging of fluid loop management lessons-learned from the International Space Station (ISS). A bed design that was developed for a Hamilton Sundstrand military application, and considered for a potential ISS application with the Urine Processor Assembly, provides a low pressure drop means for water maintenance in a recirculation loop. The bed design is coupled with high capacity ion exchange resins, organic adsorbents, and a cyclic methodology developed for the Extravehicular Mobility Unit (EMU) Transport Water loop. The bed design further leverages a sorbent developed for ISS that introduces a biocide in a microgravity-compatible manner for the Internal Active Thermal Control System (IATCS). The leveraging of these water maintenance technologies to the SWME recirculation loop is a unique demonstration of applying the valuable lessons learned on the ISS to the next generation of manned spaceflight Environmental Control and Life Support System (ECLSS) hardware.

  4. How Performance Improves

    SciTech Connect

    Jerry L. Harbour; Julie L. Marble

    2005-09-01

    Countless articles and books have been written about and numerous programs have been developed to improve performance. Despite this plethora of activity on how to improve performance, we have largely failed to address the more fundamental question of how performance actually improves. To begin exploring this more basic question, we have plotted some 1,200 performance records to date and found that irrespective of venue, industry, or business, there seems to be a fundamental and repeatable set of concepts regarding how performance improves over time. Such gained insights represent both opportunities and challenges to the performance technologist. Differences in performance outcomes may, for example, be as much a function of the life cycle stage of a performance system as the efficacy of the selected improvement method itself. Accordingly, it may be more difficult to compare differing performance improvement methods than previously thought.

  5. Kinesics and Performance

    ERIC Educational Resources Information Center

    Schechner, Richard; Mintz, Cynthia

    1973-01-01

    Current teaching and thinking about theatre performances tend to ignore kinesics. Kinesics study answers the need for consideration of analogical thinking and nonverbal communication distinctive to theatrical performance. (CH)

  6. Performing Narrative Medicine

    ERIC Educational Resources Information Center

    Langellier, Kristin M.

    2009-01-01

    In this article, the author weaves narrative medicine and performance together to consider what might it mean to call narrative medicine a performance. To name narrative medicine as performance is to recognize the texts and bodies, the stories and selves, that participate in its practice--patients' and physicians' embodied stories as well as the…

  7. Integrating Learning and Performance.

    ERIC Educational Resources Information Center

    1998

    This document contains four papers from a symposium on integrating learning and performance in human resource development (HRD). "Action Imperatives that Impact Knowledge Performance and Financial Performance in the Learning Organization: An Exploratory Model" (Gary L. Selden, Karen E. Watkins, Thomas Valentine, Victoria J. Marsick)…

  8. IR DIAL performance modeling

    SciTech Connect

    Sharlemann, E.T.

    1994-07-01

    We are developing a DIAL performance model for CALIOPE at LLNL. The intent of the model is to provide quick and interactive parameter sensitivity calculations with immediate graphical output. A brief overview of the features of the performance model is given, along with an example of performance calculations for a non-CALIOPE application.

  9. Teaching Tips: Performance Literacy

    ERIC Educational Resources Information Center

    Dillingham, Brett

    2005-01-01

    As educators struggle to find ways to engage students in literacy development and content area exploration, performance literacy is emerging as an important pedagogical tool. This article defines performance literacy as the process of teaching students to write and perform stories. The author lists the five major components in the development of…

  10. Seven Performance Drivers.

    ERIC Educational Resources Information Center

    Ross, Linda

    2003-01-01

    Recent work with automotive e-commerce clients led to the development of a performance analysis methodology called the Seven Performance Drivers, including: standards, incentives, capacity, knowledge and skill, measurement, feedback, and analysis. This methodology has been highly effective in introducing and implementing performance improvement.…

  11. Performance Support in Perspective.

    ERIC Educational Resources Information Center

    Banerji, Ashok

    1999-01-01

    Discusses the integrated concept of electronic performance support systems (EPSS) as a solution to meet performance needs of knowledge-rich workplaces where information overload is often a problem. Considers the adoption of information technology, task performance time, and support functions, and gives an example of an EPSS for marine shipping…

  12. Nutrition and Mental Performance

    ERIC Educational Resources Information Center

    Stein, Zena; And Others

    1972-01-01

    Prenatal exposure to the Dutch famine of 1944-45 had no detectable effects on the adult mental performance of surviving male offspring; birth weight was not related to mental performance; and the association of social class with mental performance was strong. (AL)

  13. Rhythms of Mental Performance

    ERIC Educational Resources Information Center

    Valdez, Pablo; Reilly, Thomas; Waterhouse, Jim

    2008-01-01

    Cognitive performance is affected by an individual's characteristics and the environment, as well as by the nature of the task and the amount of practice at it. Mental performance tests range in complexity and include subjective estimates of mood, simple objective tests (reaction time), and measures of complex performance that require decisions to…

  14. Performance Measurement Redux.

    ERIC Educational Resources Information Center

    Feller, Irwin

    2002-01-01

    Continues the exploration of the effective use and misuse of performance indicators that has been conducted by various authors in this journal. Identifies some further limitations on the use of performance measurement and notes that many performance measurement undertakings make no provision for evaluating the impact of the undertakings…

  15. Performance Improvement Assuming Complexity

    ERIC Educational Resources Information Center

    Rowland, Gordon

    2007-01-01

    Individual performers, work teams, and organizations may be considered complex adaptive systems, while most current human performance technologies appear to assume simple determinism. This article explores the apparent mismatch and speculates on future efforts to enhance performance if complexity rather than simplicity is assumed. Included are…

  16. Fiscal Year 2009 Performance Budget: Performance Plan

    ERIC Educational Resources Information Center

    US Department of Education, 2008

    2008-01-01

    The U.S. Department of Education set the following goals as measures of their annual performance: (1) Improve student achievement, with a focus on bringing all students to grade level in reading and mathematics by 2014; (2) Increase the academic achievement of all high school students; and (3) Ensure the accessibility, affordability and…

  17. Algorithm performance evaluation

    NASA Astrophysics Data System (ADS)

    Smith, Richard N.; Greci, Anthony M.; Bradley, Philip A.

    1995-03-01

    Traditionally, the performance of adaptive antenna systems is measured using automated antenna array pattern measuring equipment. This measurement equipment produces a plot of the receive gain of the antenna array as a function of angle. However, communications system users more readily accept and understand bit error rate (BER) as a performance measure. The work reported on here was conducted to characterize adaptive antenna receiver performance in terms of overall communications system performance using BER as a performance measure. The adaptive antenna system selected for this work featured a linear array, least mean square (LMS) adaptive algorithm and a high speed phase shift keyed (PSK) communications modem.

  18. Predictive performance models and multiple task performance

    NASA Technical Reports Server (NTRS)

    Wickens, Christopher D.; Larish, Inge; Contorer, Aaron

    1989-01-01

    Five models that predict how performance of multiple tasks will interact in complex task scenarios are discussed. The models are shown in terms of the assumptions they make about human operator divided attention. The different assumptions about attention are then empirically validated in a multitask helicopter flight simulation. It is concluded from this simulation that the most important assumption relates to the coding of demand level of different component tasks.

  19. Developing Human Performance Measures

    SciTech Connect

    Jeffrey Joe; Bruce Hallbert; Larry Blackwood; Donald Dudehoeffer; Kent Hansen

    2006-05-01

    Through the reactor oversight process (ROP), the U.S. Nuclear Regulatory Commission (NRC) monitors the performance of utilities licensed to operate nuclear power plants. The process is designed to assure public health and safety by providing reasonable assurance that licensees are meeting the cornerstones of safety and designated crosscutting elements. The reactor inspection program, together with performance indicators (PIs), and enforcement activities form the basis for the NRC’s risk-informed, performance based regulatory framework. While human performance is a key component in the safe operation of nuclear power plants and is a designated cross-cutting element of the ROP, there is currently no direct inspection or performance indicator for assessing human performance. Rather, when human performance is identified as a substantive cross cutting element in any 1 of 3 categories (resources, organizational or personnel), it is then evaluated for common themes to determine if follow-up actions are warranted. However, variability in human performance occurs from day to day, across activities that vary in complexity, and workgroups, contributing to the uncertainty in the outcomes of performance. While some variability in human performance may be random, much of the variability may be attributed to factors that are not currently assessed. There is a need to identify and assess aspects of human performance that relate to plant safety and to develop measures that can be used to successfully assure licensee performance and indicate when additional investigation may be required. This paper presents research that establishes a technical basis for developing human performance measures. In particular, we discuss: 1) how historical data already gives some indication of connection between human performance and overall plant performance, 2) how industry led efforts to measure and model human performance and organizational factors could serve as a data source and basis for a

  20. High performance polymer development

    NASA Technical Reports Server (NTRS)

    Hergenrother, Paul M.

    1991-01-01

    The term high performance as applied to polymers is generally associated with polymers that operate at high temperatures. High performance is used to describe polymers that perform at temperatures of 177 C or higher. In addition to temperature, other factors obviously influence the performance of polymers such as thermal cycling, stress level, and environmental effects. Some recent developments at NASA Langley in polyimides, poly(arylene ethers), and acetylenic terminated materials are discussed. The high performance/high temperature polymers discussed are representative of the type of work underway at NASA Langley Research Center. Further improvement in these materials as well as the development of new polymers will provide technology to help meet NASA future needs in high performance/high temperature applications. In addition, because of the combination of properties offered by many of these polymers, they should find use in many other applications.

  1. Cognitive aspects of performance.

    PubMed Central

    Kane, J. E.

    1978-01-01

    The study of cognitive structures and processes in the control of skilled performance is considered and reviewed with special reference to a proposed hierarchical system incorporating levels of motor integration. Cognitive styles and dispositions of general behaviour are suggested as factors which may determine performance levels. The relative importance of these personal factors and stronger personality traits in accounting for variance in performance is considered in the light of a critique of the current interactional controversy. PMID:444808

  2. Behavioral Health & Performance

    NASA Video Gallery

    Summary of the Behavioral Health and Performance Operations Group’s work including an overview of astronaut selection, behavioral health services provided to astronauts, the psychological aspects o...

  3. Photovoltaic array performance model.

    SciTech Connect

    Kratochvil, Jay A.; Boyson, William Earl; King, David L.

    2004-08-01

    This document summarizes the equations and applications associated with the photovoltaic array performance model developed at Sandia National Laboratories over the last twelve years. Electrical, thermal, and optical characteristics for photovoltaic modules are included in the model, and the model is designed to use hourly solar resource and meteorological data. The versatility and accuracy of the model has been validated for flat-plate modules (all technologies) and for concentrator modules, as well as for large arrays of modules. Applications include system design and sizing, 'translation' of field performance measurements to standard reporting conditions, system performance optimization, and real-time comparison of measured versus expected system performance.

  4. OLEM Performance Assessment Information

    EPA Pesticide Factsheets

    This asset includes a variety of data sets that measure the performance of Office of Land and Emergency Management (OLEM) programs in support of the Office of the Chief Financial Officer's Annual Commitment System (ACS) and Performance Evaluation Reporting System (PERS). Information is drawn from OLEM's ACRES, RCRAInfo, CERCLIS/SEMS, ICIS, and LUST4 systems, as well as input manually by authorized individuals in OLEM's program offices. Information is reviewed by OLEM program staff prior to being pushed to ACS and entered into PERS. This data asset also pulls in certain performance information input directly by Regional Office staff into ACS. Information is managed by the Performance Assessment Tool (PAT) and displayed in the PAT Dashboard.Information in this asset include:--Government Performance and Results Act (GPRA) of 1993: Measures reported for Innovations, Partnerships and Communications Office (IPCO), the Office of Brownfields and Land Revitalization (OBLR), the Office of Emergency Management (OEM), the Office of Resource Conservation and Recovery (ORCR), the Office of Superfund Remediation and Technology Innovation (OSRTI), and the Office of Underground Storage Tanks (OUST).-- Performance and Environmental Results System (PERS): Includes OLEM's information on performance results and baselines for the EPA Annual Plan and Budget.--Key Performance Indicators: OLEM has identified five KPIs that are tracked annually.--Integrated Cleanup Initiative: A pilot pe

  5. Managing employee performance.

    PubMed

    McConnell, Charles R

    2004-01-01

    Performance management consists of significantly more than periodic evaluation of performance. It is the art and science of dealing with employees in a manner intended to positively influence their thinking and behavior to achieve a desired level of performance. It is essential for the manager to always model positive behavior concerning performance; what one does or says as a manager always has an influence on others. The kinds of employee behavior most likely encountered relative to performance management efforts stem from resistance to change and lack of complete understanding of what is expected. Employee participation must be elicited whenever possible for performance improvement; as far as the inner working details of a specific job are concerned, there is no one who knows the job better than the person who does it everyday. For each task to be done, an employee needs to know what output is expected, how this output will be measured, and what standards are applied in assessing the output. Managing employee performance requires ongoing contact with each employee, regular feedback, and whatever coaching, counseling, and training are necessary to bring an employee back on track when a problem appears. Sustaining efficient and effective employee performance requires the manager's ongoing attention and involvement.

  6. Performance Improvement [in HRD].

    ERIC Educational Resources Information Center

    1995

    These four papers are from a symposium that was facilitated by Richard J. Torraco at the 1995 conference of the Academy of Human Resource Development (HRD). "Performance Technology--Isn't It Time We Found Some New Models?" (William J. Rothwell) reviews briefly two classic models, describes criteria for the high performance workplace…

  7. Technology Performance Exchange

    SciTech Connect

    2015-09-01

    To address the need for accessible, high-quality data, the Department of Energy has developed the Technology Performance Exchange (TPEx). TPEx enables technology suppliers, third-party testing laboratories, and other entities to share product performance data. These data are automatically transformed into a format that technology evaluators can easily use in their energy modeling assessments to inform procurement decisions.

  8. Developing Effective Performance Measures

    DTIC Science & Technology

    2014-10-14

    center (after receiving the training). 5. Post -course survey results of veterans that took the training. 38 Developing Effective Performance...PV)) Estimate at Completion (EAC) Budget at Completion ( BAC ) Budgeted Cost of Work Performed (BCWP) Schedule Variance (SV) at time t1 Cost

  9. Performance Measurement at OIT

    DTIC Science & Technology

    2014-08-01

    after receiving the training). 5. Post -course survey results of veterans that took the training. 27 Performance Measurement at OIT Mark Kasunic...EAC) Budget at Completion ( BAC ) Budgeted Cost of Work Performed (BCWP) Schedule Variance (SV) at time t1 Cost Variance (CV) at time t1 (a.k.a. EV

  10. Performance Simulation: The Method.

    ERIC Educational Resources Information Center

    Rucker, Lance M.

    A logical, performer-based approach to teaching psychomotor skills is described. Four phases of surgical psychomotor skills training are identified, using an example from a dental preclinical training curriculum: (1) dental students are acquainted with the postural and positional parameters of balanced psychomotor performances; (2) students learn…

  11. Apprentice Performance Evaluation.

    ERIC Educational Resources Information Center

    Gast, Clyde W.

    The Granite City (Illinois) Steel apprentices are under a performance evaluation from entry to graduation. Federally approved, the program is guided by joint apprenticeship committees whose monthly meetings include performance evaluation from three information sources: journeymen, supervisors, and instructors. Journeymen's evaluations are made…

  12. Test and Performance Anxiety

    ERIC Educational Resources Information Center

    Huberty, Thomas J.

    2010-01-01

    Test and performance anxiety is not recognized easily in schools, in large part because adolescents rarely refer themselves for emotional concerns. Not wanting to risk teasing or public attention, anxious adolescents suffer in silence and under perform on school-related tasks. In school, anxiety is experienced often by students when being…

  13. Untangling Performance from Success

    NASA Astrophysics Data System (ADS)

    Yucesoy, Burcu; Barabasi, Albert-Laszlo

    Fame, popularity and celebrity status, frequently used tokens of success, are often loosely related to, or even divorced from professional performance. This dichotomy is partly rooted in the difficulty to distinguish performance, an individual measure that captures the actions of a performer, from success, a collective measure that captures a community's reactions to these actions. Yet, finding the relationship between the two measures is essential for all areas that aim to objectively reward excellence, from science to business. Here we quantify the relationship between performance and success by focusing on tennis, an individual sport where the two quantities can be independently measured. We show that a predictive model, relying only on a tennis player's performance in tournaments, can accurately predict an athlete's popularity, both during a player's active years and after retirement. Hence the model establishes a direct link between performance and momentary popularity. The agreement between the performance-driven and observed popularity suggests that in most areas of human achievement exceptional visibility may be rooted in detectable performance measures. This research was supported by Air Force Office of Scientific Research (AFOSR) under agreement FA9550-15-1-0077.

  14. Holley Stick Performance Analysis

    DTIC Science & Technology

    2013-04-01

    TECHNICAL REPORT 2015 April 2013 Holley Stick Performance Analysis Steven T. Holste , Ph.D Jeffrey J. Person...Performance Analysis Steven T. Holste , PhD. Jeffrey J. Person Approved for public release...IEDs on U.S. and coalition forces. Figure 2 depicts OEF casualties from 2008 through 2012, indicating Total and IED-caused Killed in Action (KIA

  15. Performance Teaching in ELT.

    ERIC Educational Resources Information Center

    Crouch, Christopher

    1989-01-01

    Reports the effects on student classroom behavior of a performance teaching strategy in which teacher trainees of English as a second language "perform" to better engage students. Students paid attention more immediately and sustained attention longer, engaged more willingly in subsequent tasks, and appeared to enjoy the lesson more.…

  16. Emotions and Golf Performance

    ERIC Educational Resources Information Center

    Cohen, Alexander B.; Tenenbaum, Gershon; English, R. William

    2006-01-01

    A multiple case study investigation is reported in which emotions and performance were assessed within the probabilistic individual zone of optimal functioning (IZOF) model (Kamata, Tenenbaum, & Hanin, 2002) to develop idiosyncratic emotion-performance profiles. These profiles were incorporated into a psychological skills training (PST)…

  17. Infiniband Performance Testing

    SciTech Connect

    Minich, M

    2005-10-13

    A look at the performance of the infiniband interconnect using the Voltaire host stack. This will attempt to compare not only infiniband to other high-performance interconnects, but will also take a look at comparing some of the different hardware choices available at the time of writing (e.g. Opteron, EM64T, pci-express and pci-x).

  18. Measuring Clerical Job Performance

    ERIC Educational Resources Information Center

    Ronan, William W.; And Others

    1976-01-01

    Describes research which attempts to provide a solution to the performance criterion problem, concluding that is seems possible to measure many aspects of clerical work using psychometric measures that are highly job related; recommends that such devices be used to supplement ratings in the performance evaluation process.

  19. Performance Improvement Processes.

    ERIC Educational Resources Information Center

    1997

    This document contains four papers from a symposium on performance improvement processes. In "Never the Twain Shall Meet?: A Glimpse into High Performance Work Practices and Downsizing" (Laurie J. Bassi, Mark E. Van Buren) evidence from a national cross-industry of more than 200 establishments is used to demonstrate that high-performance…

  20. Music and academic performance.

    PubMed

    Arnaud Cabanac; Perlovsky, Leonid; Bonniot-Cabanac, Marie-Claude; Cabanac, Michel

    2013-11-01

    In a previous study we demonstrated that listening to a pleasant music while performing an academic test helped students to overcome stress, to devote more time to more stressful and more complicated task and the grades were higher. Yet, there remained ambiguities as for the causes of the higher test performance of these students: do they perform better because they hear music during their examinations, or would they perform better anyway because they are more gifted/motivated? This motivated the current study as a preliminary step toward that general question: Do students who like/perform music have better grades than the others? Our results confirmed this hypothesis: students studying music have better grades in all subjects.

  1. Performance Test Results of a Skutterudite-Based Unicouple with a Metallic Coating

    NASA Astrophysics Data System (ADS)

    Saber, Hamed H.; El-Genk, Mohamed S.; Caillat, Thierry

    2005-02-01

    A performance test of a Skutterudite-based unicouple (MAY-04) with a metallic coating to suppress the sublimation of antimony from the legs near the hot junction is performed in vacuum (˜ 9 ×10-7 torr) for ˜ 2,000 hours at hot and cold junction temperatures of 892.1 ± 11.9 K and 316.1 ± 5.5 K, respectively. The p-leg is made of CeFe3.5Co0.5Sb12 and the n-leg is made of CoSb3. Presented are the measured voltage-current characteristics, electrical power, open-circuit voltage, and the Seebeck coefficients of the legs as functions of cumulative test time. Also presented is the estimate of the conversion efficiency, ˜ 96 hrs after the start of test. To demonstrate the effectiveness of the metallic coating, the measurements for MAY-04 are compared with those of two uncoated unicouples of the same leg materials (MAR-03 and JUN-03), which had been tested earlier. The cross-sectional areas of the legs in MAY-04 are larger than those in MAR-03 and JUN-03, tested in argon cover gas at ˜ 0.051-0.068 MPa for 450 and 1200 hours, respectively. The open circuit voltage, Voc (204 mV) of MAY-04 at Beginning-Of-Test (BOT) is almost the same as that of MAR-03, but higher than that of JUN-03 (˜180 mV). Although the argon gas effectively decreased antimony loss from legs of MAR-03 and JUN-03, marked degradations in performance occurred with time in these tests. Conversely, the metallic coating in MAY-04 effectively reduced the performance degradation with cumulative test time. The estimated peak efficiency of MAY-04, shortly after BOT (10.65%) is only ˜ 0.37 percentage point lower than the theoretical value, assuming zero side heat losses and zero contact resistance per leg. The peak power of MAY-04 decreased by only ˜12%, from its BOT value of ˜1.6 We to ˜1.4 We after ˜2,000 of cumulative testing.

  2. PPC750 Performance Monitor

    NASA Technical Reports Server (NTRS)

    Meyer, Donald; Uchenik, Igor

    2007-01-01

    The PPC750 Performance Monitor (Perfmon) is a computer program that helps the user to assess the performance characteristics of application programs running under the Wind River VxWorks real-time operating system on a PPC750 computer. Perfmon generates a user-friendly interface and collects performance data by use of performance registers provided by the PPC750 architecture. It processes and presents run-time statistics on a per-task basis over a repeating time interval (typically, several seconds or minutes) specified by the user. When the Perfmon software module is loaded with the user s software modules, it is available for use through Perfmon commands, without any modification of the user s code and at negligible performance penalty. Per-task run-time performance data made available by Perfmon include percentage time, number of instructions executed per unit time, dispatch ratio, stack high water mark, and level-1 instruction and data cache miss rates. The performance data are written to a file specified by the user or to the serial port of the computer

  3. Precision performance lamp technology

    NASA Astrophysics Data System (ADS)

    Bell, Dean A.; Kiesa, James E.; Dean, Raymond A.

    1997-09-01

    A principal function of a lamp is to produce light output with designated spectra, intensity, and/or geometric radiation patterns. The function of a precision performance lamp is to go beyond these parameters and into the precision repeatability of performance. All lamps are not equal. There are a variety of incandescent lamps, from the vacuum incandescent indictor lamp to the precision lamp of a blood analyzer. In the past the definition of a precision lamp was described in terms of wattage, light center length (LCL), filament position, and/or spot alignment. This paper presents a new view of precision lamps through the discussion of a new segment of lamp design, which we term precision performance lamps. The definition of precision performance lamps will include (must include) the factors of a precision lamp. But what makes a precision lamp a precision performance lamp is the manner in which the design factors of amperage, mscp (mean spherical candlepower), efficacy (lumens/watt), life, not considered individually but rather considered collectively. There is a statistical bias in a precision performance lamp for each of these factors; taken individually and as a whole. When properly considered the results can be dramatic to the system design engineer, system production manage and the system end-user. It can be shown that for the lamp user, the use of precision performance lamps can translate to: (1) ease of system design, (2) simplification of electronics, (3) superior signal to noise ratios, (4) higher manufacturing yields, (5) lower system costs, (6) better product performance. The factors mentioned above are described along with their interdependent relationships. It is statistically shown how the benefits listed above are achievable. Examples are provided to illustrate how proper attention to precision performance lamp characteristics actually aid in system product design and manufacturing to build and market more, market acceptable product products in the

  4. Deodorants, value, and performance.

    PubMed

    Newcomer, L N

    1997-11-01

    For the health-care market, like the deodorant market, the message is clear: Add value or your product will not be competitive. For physicians of all specialties, the best way to add value is to measure and improve performance. Performance measurement is critical to improvement in health care. Without measurement, there can be no improvement in quality. Without improvement in quality, there is no added value. Oncologists can take at least two actions to add value for their health plans: (1) measure practice performance and demonstrate a quality improvement; and (2) become the personal-care physician for cancer patients.

  5. Performance Management Plan

    SciTech Connect

    IT Corporation, Las Vegas, NV

    2002-08-21

    This Performance Management Plan describes the approach for accelerating cleanup activities of U.S. Department of Energy (DOE), National Nuclear Security Administration Nevada Operations Office (NNSA/NV) Environmental Management (EM) Program. This approach accelerates the reduction of risk at NNSA/NV sites while performing the work responsibly, effectively, and more efficiently. In May 2002, NNSA/NV EM and the Nevada Division of Environmental Protection signed a Letter of Intent formalizing an agreement to pursue accelerated risk reduction and cleanup for activities within the State of Nevada. This Performance Management Plan provides the strategic direction for implementing the Letter of Intent.

  6. Evaluating Performance of Components

    NASA Technical Reports Server (NTRS)

    Katz, Daniel; Tisdale, Edwin; Norton, Charles

    2004-01-01

    Parallel Component Performance Benchmarks is a computer program developed to aid the evaluation of the Common Component Architecture (CCA) - a software architecture, based on a component model, that was conceived to foster high-performance computing, including parallel computing. More specifically, this program compares the performances (principally by measuring computing times) of componentized versus conventional versions of the Parallel Pyramid 2D Adaptive Mesh Refinement library - a software library that is used to generate computational meshes for solving physical problems and that is typical of software libraries in use at NASA s Jet Propulsion Laboratory.

  7. Neoliberalism, Performativity and Research

    NASA Astrophysics Data System (ADS)

    Roberts, Peter

    2007-07-01

    This paper provides a critical analysis of New Zealand's Performance Based Research Fund (PBRF). The first section sketches the development and implementation of the PBRF. The second section evaluates the scheme, concentrating on three themes: the relationship between privatization, competition and research performance; the standardization of research; and motivations for research. The paper acknowledges the thorough work completed by the Tertiary Education Advisory Commission and other policy groups in laying the foundation for the adoption of performance-based research funding in New Zealand. It is argued, however, that when viewed in its larger context, the PBRF constitutes a continuation of neoliberal trends already well established in New Zealand's tertiary education system.

  8. Performance and Accountability Report

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The NASA Fiscal Year 2002 Performance and Accountability Report is presented. Over the past year, significant changes have been implemented to greatly improve NASA's management while continuing to break new ground in science and technology. Excellent progress has been made in implementing the President's Management Agenda. NASA is leading the government in its implementation of the five government-wide initiatives. NASA received an unqualified audit opinion on FY 2002 financial statements. The vast majority of performance goals have been achieved, furthering each area of NASA's mission. The contents include: 1) NASA Vision and Mission; 2) Management's Discussion and Analysis; 3) Performance; and 4) Financial.

  9. Breakfast and performance.

    PubMed

    Cueto, S

    2001-12-01

    Evidence suggests that the effect of fasting on performance is not uniform, but it is dependent on the basal nutritional status of the subject. Breakfast consumption has a short-term effect in improving selected learning skills, especially work memory. School breakfast programmes have a positive effect on the nutritional status of children, on school attendance and probably on dropout rates. The effect of breakfast consumption on school performance depends on the interaction between the programme, student characteristics (malnutrition) and school organisation. Unless the school setting guarantees a minimum quality standard, the benefits of breakfast consumption will not be evident in performance in complex areas like language or maths.

  10. Measures of rowing performance.

    PubMed

    Smith, T Brett; Hopkins, Will G

    2012-04-01

    Accurate measures of performance are important for assessing competitive athletes in practi~al and research settings. We present here a review of rowing performance measures, focusing on the errors in these measures and the implications for testing rowers. The yardstick for assessing error in a performance measure is the random variation (typical or standard error of measurement) in an elite athlete's competitive performance from race to race: ∼1.0% for time in 2000 m rowing events. There has been little research interest in on-water time trials for assessing rowing performance, owing to logistic difficulties and environmental perturbations in performance time with such tests. Mobile ergometry via instrumented oars or rowlocks should reduce these problems, but the associated errors have not yet been reported. Measurement of boat speed to monitor on-water training performance is common; one device based on global positioning system (GPS) technology contributes negligible extra random error (0.2%) in speed measured over 2000 m, but extra error is substantial (1-10%) with other GPS devices or with an impeller, especially over shorter distances. The problems with on-water testing have led to widespread use of the Concept II rowing ergometer. The standard error of the estimate of on-water 2000 m time predicted by 2000 m ergometer performance was 2.6% and 7.2% in two studies, reflecting different effects of skill, body mass and environment in on-water versus ergometer performance. However, well trained rowers have a typical error in performance time of only ∼0.5% between repeated 2000 m time trials on this ergometer, so such trials are suitable for tracking changes in physiological performance and factors affecting it. Many researchers have used the 2000 m ergometer performance time as a criterion to identify other predictors of rowing performance. Standard errors of the estimate vary widely between studies even for the same predictor, but the lowest

  11. Identity verifier performance

    SciTech Connect

    Maxwell, R.

    1987-01-01

    This report is a transcript of a paper given at the Smart Card Applications and Technologies Conference, October 14, 1987. Identity verification techniques are identified and discussed, and statistical performance data is given. 20 figs. (JF)

  12. Desalination processes and performance

    SciTech Connect

    Summers, L. J.

    1995-06-01

    Different desalination processes are evaluated for feed, capacity, performance, energy requirements, and cost. These include distillation, reverse osmosis, or electrodialysis. Detailed information is given on distillation processes and membrane processes.

  13. DAS performance analysis

    SciTech Connect

    Bates, G.; Bodine, S.; Carroll, T.; Keller, M.

    1984-02-01

    This report begins with an overview of the Data Acquisition System (DAS), which supports several of PPPL's experimental devices. Performance measurements which were taken on DAS and the tools used to make them are then described.

  14. On Time Performance Pressure

    NASA Technical Reports Server (NTRS)

    Connell, Linda; Wichner, David; Jakey, Abegael

    2013-01-01

    Within many operations, the pressures for on-time performance are high. Each month, on-time statistics are reported to the Department of Transportation and made public. There is a natural tendency for employees under pressure to do their best to meet these objectives. As a result, pressure to get the job done within the allotted time may cause personnel to deviate from procedures and policies. Additionally, inadequate or unavailable resources may drive employees to work around standard processes that are seen as barriers. However, bypassing practices to enable on-time performance may affect more than the statistics. ASRS reports often highlight on-time performance pressures which may result in impact across all workgroups in an attempt to achieve on-time performance. Reporters often provide in-depth insights into their experiences which can be used by industry to identify and focus on the implementation of systemic fixes.

  15. GPS Timing Performance

    DTIC Science & Technology

    2014-01-01

    U.S. Naval Observatory (USNO) [1]. Interoperability with Galileo, and perhaps someday with other Global Navigation Satellite Systems ( GNSS ), is to...be established through transmission of the differences between the GNSS system times. This paper describes the performance of the GPS system, which...interoperable GNSS systems will benefit from the additional satellites, and in certain situations markedly so. 2. Current Performance Under Optimal

  16. Roller drive materials performance

    NASA Technical Reports Server (NTRS)

    Rohn, Douglas A.

    1988-01-01

    Roller traction performance basics, a test program to measure performance, and the need for and typical use of the information are outlined. A test rig was designed and fabricated to develop this information. Parametric conditions and specimen materials were chosen so that the resulting data will be valuable to the design and development of advanced, roller-driven space mechanisms, from precision positioning devices to telerobot joints.

  17. Embarking on performance improvement.

    PubMed

    Brown, Bobbi; Falk, Leslie Hough

    2014-06-01

    Healthcare organizations should approach performance improvement as a program, not a project. The program should be led by a guidance team that identifies goals, prioritizes work, and removes barriers to enable clinical improvement teams and work groups to realize performance improvements. A healthcare enterprise data warehouse can provide the initial foundation for the program analytics. Evidence-based best practices can help achieve improved outcomes and reduced costs.

  18. Intellectual Performance Under Stress

    DTIC Science & Technology

    1976-09-01

    Jeffery Miller - Asst. Prof. Univ. Cal. San Diego Donald Polzella Asst. Prof. Univ. of Dayton Andrew Rose American Institute of Research Douglas Stokes...Research, 1974, 71, 39!-400. (0l0588—26-J) Polzella , D.J. The effect of sleep-deprivation on short-term recognition memory. Human Performance Center...Technical Report No. 47, April, 1974. (010588-19-1’) Polzella , D.J. Remembering the functional sentence. Human Performance Center Technical Report No

  19. Examples Performance Testing Templates.

    SciTech Connect

    Siple, Bud H.

    2014-07-01

    The purpose of this Performance Testing Program Plan is to identify the process and phased approach that will be implemented at Site XYZ . The purpose of the testing program at Site XYZ is specifically designed to evaluate the effectiveness of systems that are employed at this site. This plan defines tasks to be accomplished to ensure that performance testing is conducted as effectively and efficiently as possible.

  20. High Performance Polymers

    NASA Technical Reports Server (NTRS)

    Venumbaka, Sreenivasulu R.; Cassidy, Patrick E.

    2003-01-01

    This report summarizes results from research on high performance polymers. The research areas proposed in this report include: 1) Effort to improve the synthesis and to understand and replicate the dielectric behavior of 6HC17-PEK; 2) Continue preparation and evaluation of flexible, low dielectric silicon- and fluorine- containing polymers with improved toughness; and 3) Synthesis and characterization of high performance polymers containing the spirodilactam moiety.

  1. Performance assurance program plan

    SciTech Connect

    Rogers, B.H.

    1997-11-06

    B and W Protec, Inc. (BWP) is responsible for implementing the Performance Assurance Program for the Project Hanford Management Contract (PHMC) in accordance with DOE Order 470.1, Safeguards and Security Program (DOE 1995a). The Performance Assurance Program applies to safeguards and security (SAS) systems and their essential components (equipment, hardware, administrative procedures, Protective Force personnel, and other personnel) in direct support of Category I and H special nuclear material (SNM) protection. Performance assurance includes several Hanford Site activities that conduct performance, acceptance, operability, effectiveness, and validation tests. These activities encompass areas of training, exercises, quality assurance, conduct of operations, total quality management, self assessment, classified matter protection and control, emergency preparedness, and corrective actions tracking and trending. The objective of the Performance Assurance Program is to capture the critical data of the tests, training, etc., in a cost-effective, manageable program that reflects the overall effectiveness of the program while minimizing operational impacts. To aid in achieving this objective, BWP will coordinate the Performance Assurance Program for Fluor Daniel Hanford, Inc. (FDH) and serve as the central point for data collection.

  2. Repository performance confirmation.

    SciTech Connect

    Hansen, Francis D.

    2011-09-01

    Repository performance confirmation links the technical bases of repository science and societal acceptance. This paper explores the myriad aspects of what has been labeled performance confirmation in U.S. programs, which involves monitoring as a collection of distinct activities combining technical and social significance in radioactive waste management. This paper is divided into four parts: (1) A distinction is drawn between performance confirmation monitoring and other testing and monitoring objectives; (2) A case study illustrates confirmation activities integrated within a long-term testing and monitoring strategy for Yucca Mountain; (3) A case study reviews compliance monitoring developed and implemented for the Waste Isolation Pilot Plant; and (4) An approach for developing, evaluating and implementing the next generation of performance confirmation monitoring is presented. International interest in repository monitoring is exhibited by the European Commission Seventh Framework Programme 'Monitoring Developments for Safe Repository Operation and Staged Closure' (MoDeRn) Project. The MoDeRn partners are considering the role of monitoring in a phased approach to the geological disposal of radioactive waste. As repository plans advance in different countries, the need to consider monitoring strategies within a controlled framework has become more apparent. The MoDeRn project pulls together technical and societal experts to assimilate a common understanding of a process that could be followed to develop a monitoring program. A fundamental consideration is the differentiation of confirmation monitoring from the many other testing and monitoring activities. Recently, the license application for Yucca Mountain provided a case study including a technical process for meeting regulatory requirements to confirm repository performance as well as considerations related to the preservation of retrievability. The performance confirmation plan developed as part of the

  3. EVA Performance Prediction

    NASA Technical Reports Server (NTRS)

    Peacock, Brian; Maida, James; Rajulu, Sudhakar

    2004-01-01

    Astronaut physical performance capabilities in micro gravity EV A or on planetary surfaces when encumbered by a life support suit and debilitated by a long exposure to micro gravity will be less than unencumbered pre flight capabilities. The big question addressed by human factors engineers is: what can the astronaut be expected to do on EVA or when we arrive at a planetary surface? A second question is: what aids to performance will be needed to enhance the human physical capability? These questions are important for a number of reasons. First it is necessary to carry out accurate planning of human physical demands to ensure that time and energy critical tasks can be carried out with confidence. Second it is important that the crew members (and their ground or planetary base monitors) have a realistic picture of their own capabilities, as excessive fatigue can lead to catastrophic failure. Third it is important to design appropriate equipment to enhance human sensory capabilities, locomotion, materials handling and manipulation. The evidence from physiological research points to musculoskeletal, cardiovascular and neurovestibular degradation during long duration exposure to micro gravity . The evidence from the biomechanics laboratory (and the Neutral Buoyancy Laboratory) points to a reduction in range of motion, strength and stamina when encumbered by a pressurized suit. The evidence from a long history of EVAs is that crewmembers are indeed restricted in their physical capabilities. There is a wealth of evidence in the literature on the causes and effects of degraded human performance in the laboratory, in sports and athletics, in industry and in other physically demanding jobs. One approach to this challenge is through biomechanical and performance modeling. Such models must be based on thorough task analysis, reliable human performance data from controlled studies, and functional extrapolations validated in analog contexts. The task analyses currently carried

  4. Instrument performance evaluation

    SciTech Connect

    Swinth, K.L.

    1993-03-01

    Deficiencies exist in both the performance and the quality of health physics instruments. Recognizing the implications of such deficiencies for the protection of workers and the public, in the early 1980s the DOE and the NRC encouraged the development of a performance standard and established a program to test a series of instruments against criteria in the standard. The purpose of the testing was to establish the practicality of the criteria in the standard, to determine the performance of a cross section of available instruments, and to establish a testing capability. Over 100 instruments were tested, resulting in a practical standard and an understanding of the deficiencies in available instruments. In parallel with the instrument testing, a value-impact study clearly established the benefits of implementing a formal testing program. An ad hoc committee also met several times to establish recommendations for the voluntary implementation of a testing program based on the studies and the performance standard. For several reasons, a formal program did not materialize. Ongoing tests and studies have supported the development of specific instruments and have helped specific clients understand the performance of their instruments. The purpose of this presentation is to trace the history of instrument testing to date and suggest the benefits of a centralized formal program.

  5. The performance measurement manifesto.

    PubMed

    Eccles, R G

    1991-01-01

    The leading indicators of business performance cannot be found in financial data alone. Quality, customer satisfaction, innovation, market share--metrics like these often reflect a company's economic condition and growth prospects better than its reported earnings do. Depending on an accounting department to reveal a company's future will leave it hopelessly mired in the past. More and more managers are changing their company's performance measurement systems to track nonfinancial measures and reinforce new competitive strategies. Five activities are essential: developing an information architecture; putting the technology in place to support this architecture; aligning bonuses and other incentives with the new system; drawing on outside resources; and designing an internal process to ensure the other four activities occur. New technologies and more sophisticated databases have made the change to nonfinancial performance measurement systems possible and economically feasible. Industry and trade associations, consulting firms, and public accounting firms that already have well-developed methods for assessing market share and other performance metrics can add to the revolution's momentum--as well as profit from the business opportunities it presents. Every company will have its own key measures and distinctive process for implementing the change. But making it happen will always require careful preparation, perseverance, and the conviction of the CEO that it must be carried through. When one leading company can demonstrate the long-term advantage of its superior performance on quality or innovation or any other nonfinancial measure, it will change the rules for all its rivals forever.

  6. Cognitive performance and dehydration.

    PubMed

    Adan, Ana

    2012-04-01

    No matter how mild, dehydration is not a desirable condition because there is an imbalance in the homeostatic function of the internal environment. This can adversely affect cognitive performance, not only in groups more vulnerable to dehydration, such as children and the elderly, but also in young adults. However, few studies have examined the impact of mild or moderate dehydration on cognitive performance. This paper reviews the principal findings from studies published to date examining cognitive skills. Being dehydrated by just 2% impairs performance in tasks that require attention, psychomotor, and immediate memory skills, as well as assessment of the subjective state. In contrast, the performance of long-term and working memory tasks and executive functions is more preserved, especially if the cause of dehydration is moderate physical exercise. The lack of consistency in the evidence published to date is largely due to the different methodology applied, and an attempt should be made to standardize methods for future studies. These differences relate to the assessment of cognitive performance, the method used to cause dehydration, and the characteristics of the participants.

  7. Establishing maintenance performance indicators

    SciTech Connect

    Baca, B.

    1994-10-01

    Maintenance Performance Indicators (PI) specify where the maintenance department is and which direction it is going allowing for a quick and accurate assessment of the performance of the Maintenance Management Program (MMP). Establishing PI`s for the maintenance department will allow a measure of productivity and a means of feedback for methods improvement. Effective performance of the maintenance department directly effects plant profitability. Improvements in the quality and productivity of the maintenance work force will significantly reduce maintenance costs. The level of performance attained by the maintenance work force is usually guessed at. Guessing will not identify areas needing improvement or help to initiate a corrective action. Maintenance PI`s are required for maintenance departments whose goal is to control maintenance costs while increasing productivity. The application of basic statistical methods will allow a maintenance department to know where they are and which direction they are going. The data presented in this paper is a representation of indicators used in industry as well as developed indicators to establish a complete maintenance performance indicator program. The methodology used in developing this program can be used as a way to manage a cost effective maintenance management program.

  8. Internet Performance to Africa

    SciTech Connect

    Cottrell, L

    2003-10-01

    We report the first results ever for real-time Internet performance to Africa using the PingER methodology. Multiple monitoring hosts were used to enable comparisons with performance from different parts of the world. From these preliminary measurements, we have found that Internet packet losses to some African sites in recent months range from very poor to bad (> 12%), some getting better, others are holding steady or getting worse. This, together with the average monthly Round Trip Times, imply end-to-end maximum TCP throughputs that are order of magnitudes different between countries in the region. Africa is shown to be far from the Internet performance in industrialized nations due to the poor infrastructure in place today. These monitoring efforts can provide valuable information to analyze the relative rates of future improvement and today they help us to quantify the digital divide and can provide quantitative information to policy makers.

  9. Cyclone performance and optimization

    SciTech Connect

    Leith, D.

    1989-06-15

    The objectives of this project are: to characterize the gas flow pattern within cyclones, to revise the theory for cyclone performance on the basis of these findings, and to design and test cyclones whose dimensions have been optimized using revised performance theory. This work is important because its successful completion will aid in the technology for combustion of coal in pressurized, fluidized beds. We have now received all the equipment necessary for the flow visualization studies described over the last two progress reports. We have begun more detailed studies of the gas flow pattern within cyclones as detailed below. Third, we have begun studies of the effect of particle concentration on cyclone performance. This work is critical to application of our results to commercial operations. 1 fig.

  10. High performance steam development

    SciTech Connect

    Duffy, T.; Schneider, P.

    1995-12-31

    DOE has launched a program to make a step change in power plant to 1500 F steam, since the highest possible performance gains can be achieved in a 1500 F steam system when using a topping turbine in a back pressure steam turbine for cogeneration. A 500-hour proof-of-concept steam generator test module was designed, fabricated, and successfully tested. It has four once-through steam generator circuits. The complete HPSS (high performance steam system) was tested above 1500 F and 1500 psig for over 102 hours at full power.

  11. Human performance during spaceflight.

    PubMed

    Manzey, D; Lorenz, B

    1999-04-01

    The paper focuses on three different questions: (1) What attributes cause space to be an extreme environment for humans? (2) What do we know about mental performance during spaceflight? (3) What kinds of psychological countermeasures are currently applied and/or conceivable for prolonged spaceflight which might help maintain mental efficiency and stabilize the emotional state of astronauts? Topics discussed include stressors that originate in the space environment, stressors related to the space habitat and its life-support system, stressors related to the mission specific workload of astronauts, stressors that arise from the psychosocial situation in a space habitat, manual performance during spaceflight, and psychological countermeasures for prolonged spaceflight.

  12. Photovoltaic lighting system performance

    SciTech Connect

    Harrington, S.R.; Hund, T.D.

    1996-06-01

    The performance of 21 PV-powered low pressure sodium lighting systems on a multi-use has been documented in this paper. Specific areas for evaluation include the vandal resistant PV modules, constant voltage and on/off PV charge controllers, flooded deep-cycle lead-antimony and valve regulated lead-acid (VLRA) gel batteries, and low pressure sodium ballasts and lights. The PV lighting system maintenance intervals and lessons learned have been documented over the past 2.5 years. The above performance data has shown that with careful hardware selection, installation, and maintenance intervals the PV lighting systems will operate reliably.

  13. Dependability and performability analysis

    NASA Technical Reports Server (NTRS)

    Trivedi, Kishor S.; Ciardo, Gianfranco; Malhotra, Manish; Sahner, Robin A.

    1993-01-01

    Several practical issues regarding specifications and solution of dependability and performability models are discussed. Model types with and without rewards are compared. Continuous-time Markov chains (CTMC's) are compared with (continuous-time) Markov reward models (MRM's) and generalized stochastic Petri nets (GSPN's) are compared with stochastic reward nets (SRN's). It is shown that reward-based models could lead to more concise model specifications and solution of a variety of new measures. With respect to the solution of dependability and performability models, three practical issues were identified: largeness, stiffness, and non-exponentiality, and a variety of approaches are discussed to deal with them, including some of the latest research efforts.

  14. Human target acquisition performance

    NASA Astrophysics Data System (ADS)

    Teaney, Brian P.; Du Bosq, Todd W.; Reynolds, Joseph P.; Thompson, Roger; Aghera, Sameer; Moyer, Steven K.; Flug, Eric; Espinola, Richard; Hixson, Jonathan

    2012-06-01

    The battlefield has shifted from armored vehicles to armed insurgents. Target acquisition (identification, recognition, and detection) range performance involving humans as targets is vital for modern warfare. The acquisition and neutralization of armed insurgents while at the same time minimizing fratricide and civilian casualties is a mounting concern. U.S. Army RDECOM CERDEC NVESD has conducted many experiments involving human targets for infrared and reflective band sensors. The target sets include human activities, hand-held objects, uniforms & armament, and other tactically relevant targets. This paper will define a set of standard task difficulty values for identification and recognition associated with human target acquisition performance.

  15. Performance of gigabit FDDI

    NASA Technical Reports Server (NTRS)

    Game, David; Maly, Kurt J.

    1990-01-01

    Great interest exists in developing high speed protocols which will be able to support data rates at gigabit speeds. Hardware currently exists which can experimentally transmit at data rates exceeding a gigabit per second, but it is not clear as to what types of protocols will provide the best performance. One possibility is to examine current protocols and their extensibility to these speeds. Scaling of Fiber Distributed Data Interface (FDDI) to gigabit speeds is studied. More specifically, delay statistics are included to provide insight as to which parameters (network length, packet length or number of nodes) have the greatest effect on performance.

  16. Human Performance Assessment Methods

    DTIC Science & Technology

    1989-05-01

    deja aborde let problmes souleves par e’tude des performances humaines en situation op ~ rationnelle mais tr~s souvent il t’est av&r impossiblc de faire...La mission dii Groupe fit dl󈨁abortr inc batterie standardiq~e de tests et de rechercher et crs~er unc structure pour I𔄀change de donnees. La...fit de compiler ct dc publier in Annusire international des 6quipes de recherche en performances humaines. Cette publication. quoique loin d

  17. MIND performance and prototyping

    SciTech Connect

    Cervera-Villanueva, A.

    2008-02-21

    The performance of MIND (Magnetised Iron Neutrino Detector) at a neutrino factory has been revisited in a new analysis. In particular, the low neutrino energy region is studied, obtaining an efficiency plateau around 5 GeV for a background level below 10{sup -3}. A first look has been given into the detector optimisation and prototyping.

  18. Cyclone performance by velocity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cyclones are used almost exclusively in the US cotton ginning industry for emission abatement on pneumatic conveying system exhausts because of their high efficiency, and low capital and operating cost.. Cyclone performance is improved by increasing collection effectiveness or decreasing energy cons...

  19. Ion thruster performance model

    NASA Technical Reports Server (NTRS)

    Brophy, J. R.

    1984-01-01

    A model of ion thruster performance is developed for high flux density, cusped magnetic field thruster designs. This model is formulated in terms of the average energy required to produce an ion in the discharge chamber plasma and the fraction of these ions that are extracted to form the beam. The direct loss of high energy (primary) electrons from the plasma to the anode is shown to have a major effect on thruster performance. The model provides simple algebraic equations enabling one to calculate the beam ion energy cost, the average discharge chamber plasma ion energy cost, the primary electron density, the primary-to-Maxwellian electron density ratio and the Maxwellian electron temperature. Experiments indicate that the model correctly predicts the variation in plasma ion energy cost for changes in propellant gas (Ar, Kr and Xe), grid transparency to neutral atoms, beam extraction area, discharge voltage, and discharge chamber wall temperature. The model and experiments indicate that thruster performance may be described in terms of only four thruster configuration dependent parameters and two operating parameters. The model also suggests that improved performance should be exhibited by thruster designs which extract a large fraction of the ions produced in the discharge chamber, which have good primary electron and neutral atom containment and which operate at high propellant flow rates.

  20. Enhancing Workgroup Performance.

    ERIC Educational Resources Information Center

    1998

    This document contains four papers from a symposium on enhancing workgroup performance in human resource development (HRD). "Formation of Cross-Cultural Global Teams: Making Informed Choices on Team Composition" (Robert L. Dilworth) describes how a mixed class of U.S. and international students identified their cultural and learning…

  1. Improving Surface Irrigation Performance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Surface irrigation systems often have a reputation for poor performance. One key feature of efficient surface irrigation systems is precision (e.g. laser-guided) land grading. Poor land grading can make other improvements ineffective. An important issue, related to land shaping, is developing the pr...

  2. Confronting Poor Performance.

    ERIC Educational Resources Information Center

    Dennis, Bruce L.

    Responsible and effective administrative leadership requires confronting those members of the teaching staff who are a negative influence on the institution. Importantly, the absence of expressed appreciation for good work can have a devastating impact on a principal's image if he or she suddenly begins to confront poor performances. Actually, the…

  3. Performance Measurement Revisited

    ERIC Educational Resources Information Center

    Axford, H. William

    1973-01-01

    Performance measurement, through unit-cost study programs, can be a step toward evaluating the value of systems. This article reports the application of unit-cost studies in technical service functions at a large state university, and presents three tables for labor costs in terms of minutes and dollars per volume. (4 references) (Author/SJ)

  4. Women and Performance Issue.

    ERIC Educational Resources Information Center

    Kirby, Michael, Ed.

    1980-01-01

    The diversity of important work being done by women in many aspects of theatrical performance in the United States is illustrated in this journal issue. The nine articles provide discussions of the following: (1) women's careers, images, and movements in the American theatre; (2) the evolution of La Mama, an off-off-Broadway theatre group begun in…

  5. Performing Arts Annual 1987.

    ERIC Educational Resources Information Center

    Newsom, Iris, Ed.

    Liberally illustrated with photographs and drawings, this book is comprised of articles on the history of the performing arts at the Library of Congress. The articles, listed with their authors, are (1) "Stranger in Paradise: The Writer in Hollywood" (Virginia M. Clark); (2) "Live Television Is Alive and Well at the Library of…

  6. High performance systems

    SciTech Connect

    Vigil, M.B.

    1995-03-01

    This document provides a written compilation of the presentations and viewgraphs from the 1994 Conference on High Speed Computing given at the High Speed Computing Conference, {open_quotes}High Performance Systems,{close_quotes} held at Gleneden Beach, Oregon, on April 18 through 21, 1994.

  7. Performance Pay for Teachers

    ERIC Educational Resources Information Center

    Protheroe, Nancy

    2011-01-01

    During the past few years, interest in shifting at least a portion of what teachers are paid away from a reliance on a traditional salary schedule to one that incorporates a pay for performance component has reached a new high. Proponents of the approach view it as a way to improve teacher quality by both motivating teachers and--through higher…

  8. Performance, Accountability, and Results.

    ERIC Educational Resources Information Center

    Drucker, Peter F.

    1992-01-01

    Although technology might greatly increase school performance, the economics will be hard to manage and explain to a tax-paying public. As in hospitals, technology is an expensive investment that will not replace people. Schooling's true challenge is not handling machinery but creating a multicultural society. To succeed, schools must emphasize…

  9. Cooperative Performance Incentive Plans.

    ERIC Educational Resources Information Center

    Raham, Helen

    2000-01-01

    Discusses what is known about cooperative performance incentive (CPI) plans, which are award programs that offer teachers and other school staff pay bonuses for achievement of specific schoolwide educational objectives. The paper describes and compares existing CPI models worldwide, analyzes their impact on student learning and school practices,…

  10. Functional performance of pyrovalves

    NASA Technical Reports Server (NTRS)

    Bement, Laurence J.

    1996-01-01

    Following several flight and ground test failures of spacecraft systems using single-shot, 'normally closed' pyrotechnically actuated valves (pyrovalves), a Government/Industry cooperative program was initiated to assess the functional performance of five qualified designs. The goal of the program was to provide information on functional performance of pyrovalves to allow users the opportunity to improve procurement requirements. Specific objectives included the demonstration of performance test methods, the seating; these gases/particles entered the fluid path of measurement of 'blowby' (the passage of gases from the pyrotechnic energy source around the activating piston into the valve's fluid path), and the quantification of functional margins for each design. Experiments were conducted at NASA's Langley Research Center on several units for each of the five valve designs. The test methods used for this program measured the forces and energies required to actuate the valves, as well as the energies and the pressures (where possible) delivered by the pyrotechnic sources. Functional performance ranged widely among the designs. Blowby cannot be prevented by o-ring seals; metal-to-metal seals were effective. Functional margin was determined by dividing the energy delivered by the pyrotechnic sources in excess to that required to accomplish the function by the energy required for that function. Two of the five designs had inadequate functional margins with the pyrotechnic cartridges evaluated.

  11. Functional Performance of Pyrovalves

    NASA Technical Reports Server (NTRS)

    Bement, Laurence J.

    1996-01-01

    Following several flight and ground test failures of spacecraft systems using single-shot, 'normally closed' pyrotechnically actuated valves (pyrovalves), a government/industry cooperative program was initiated to assess the functional performance of five qualified designs. The goal of the program was to improve performance-based requirements for the procurement of pyrovalves. Specific objectives included the demonstration of performance test methods, the measurement of 'blowby' (the passage of gases from the pyrotechnic energy source around the activating piston into the valve's fluid path), and the quantification of functional margins for each design. Experiments were conducted in-house at NASA on several units each of the five valve designs. The test methods used for this program measured the forces and energies required to actuate the valves, as well as the energies and the pressures (where possible) delivered by the pyrotechnic sources. Functional performance ranged widely among the designs. Blowby cannot be prevented by o-ring seals; metal-to-metal seals were effective. Functional margin was determined by dividing the energy delivered by the pyrotechnic sources in excess to that required to accomplish the function by the energy required for that function. All but two designs had adequate functional margins with the pyrotechnic cartridges evaluated.

  12. Antenna performance and resolution

    NASA Technical Reports Server (NTRS)

    Carney, J. J.

    1974-01-01

    The performance of the antenna throughout SL-2, SL-3, and SL-4 was investigated along with the antenna resolution of brightness temperature during flight. The target area selected for the test flights was the Gulf of California, as it offered land/water interface. The coordinate transformations and antenna orientation, flight path simulation, and integration over the radiometric target are discussed.

  13. Performing arts medicine.

    PubMed Central

    Ostwald, P F; Baron, B C; Byl, N M; Wilson, F R

    1994-01-01

    Arts medicine has come of age, resulting from 3 important developments over the past decade: improved methods of diagnosis and treatment, an awareness that artists suffer from special problems related to their occupation and lifestyle, and the establishment of health programs emphasizing an interdisciplinary approach to these patients. We focus on the patterns of illness afflicting performing artists, specifically dancers, singers, actors, and instrumental musicians, and explain some of the things a health care team can do in treating these patients. The conditions governing these patients' lives--early exposure to high expectations of excellence, incessant demands for perfection, long periods of intense practicing, fierce competition, high levels of anxiety associated with performance, and uncertain careers--need to be understood. Levels of disease and disability are remarkably high, but artists often ignore symptoms. We discuss the musculoskeletal, neurologic, vocal, psychological, and other syndromes found among performers and some of the difficulties in treating them. The prevention of injury, conservative management, collaboration with teachers, and a psychotherapeutic approach are desirable. Arts medicine programs for professional consultation exist in several major cities of the United States and abroad. Although research is needed regarding the effectiveness of health care services for performing artists, the scientific literature devoted to this field is growing. PMID:8128702

  14. High performance parallel architectures

    SciTech Connect

    Anderson, R.E. )

    1989-09-01

    In this paper the author describes current high performance parallel computer architectures. A taxonomy is presented to show computer architecture from the user programmer's point-of-view. The effects of the taxonomy upon the programming model are described. Some current architectures are described with respect to the taxonomy. Finally, some predictions about future systems are presented. 5 refs., 1 fig.

  15. High-Performance Happy

    ERIC Educational Resources Information Center

    O'Hanlon, Charlene

    2007-01-01

    Traditionally, the high-performance computing (HPC) systems used to conduct research at universities have amounted to silos of technology scattered across the campus and falling under the purview of the researchers themselves. This article reports that a growing number of universities are now taking over the management of those systems and…

  16. Assessing Scientific Performance.

    ERIC Educational Resources Information Center

    Weiner, John M.; And Others

    1984-01-01

    A method for assessing scientific performance based on relationships displayed numerically in published documents is proposed and illustrated using published documents in pediatric oncology for the period 1979-1982. Contributions of a major clinical investigations group, the Childrens Cancer Study Group, are analyzed. Twenty-nine references are…

  17. Defining performance of organizations.

    PubMed

    1993-07-01

    Quality is and always has been in the beholder's eye. It is therefore necessary, as argued in this excerpt from The Measurement Mandate, the latest text on the Joint Commission's Agenda for Change indicator development and testing methodology, to concentrate on the best ways to measure, assess, and improve the discernible, quantifiable dimensions of an organization's performance.

  18. The Power To Perform.

    ERIC Educational Resources Information Center

    Education Next, 2003

    2003-01-01

    Argues that attracting nontraditional leaders to school administration requires the adoption of results-based practices tying compensation to performance. Includes profiles of two nontraditional leaders: Jennifer Henry, executive director of the Academy for Urban School Leadership in Chicago and Paula Dawning, superintendent of the Benton Harbor…

  19. New Source Performance Standards

    ERIC Educational Resources Information Center

    Jenkins, Richard E.; McCutchen, Gary D.

    1972-01-01

    This feature article outlines the concept and procedures followed in establishing performance standards for new emission sources and summarizes the standards that have been established to date. Five source catagories are enumerated: fossil fuel-fired steam generators, municipal incinerators, Portland cement plants, nitric acid plants, and sulfuric…

  20. PREVAPORATION PERFORMANCE PREDICTION SOFTWARE

    EPA Science Inventory

    The Pervaporation, Performance, Prediction Software and Database (PPPS&D) computer software program is currently being developed within the USEPA, NRMRL. The purpose of the PPPS&D program is to educate and assist potential users in identifying opportunities for using pervaporati...

  1. High Performance Window Retrofit

    SciTech Connect

    Shrestha, Som S; Hun, Diana E; Desjarlais, Andre Omer

    2013-12-01

    The US Department of Energy (DOE) Office of Energy Efficiency and Renewable Energy (EERE) and Traco partnered to develop high-performance windows for commercial building that are cost-effective. The main performance requirement for these windows was that they needed to have an R-value of at least 5 ft2 F h/Btu. This project seeks to quantify the potential energy savings from installing these windows in commercial buildings that are at least 20 years old. To this end, we are conducting evaluations at a two-story test facility that is representative of a commercial building from the 1980s, and are gathering measurements on the performance of its windows before and after double-pane, clear-glazed units are upgraded with R5 windows. Additionally, we will use these data to calibrate EnergyPlus models that we will allow us to extrapolate results to other climates. Findings from this project will provide empirical data on the benefits from high-performance windows, which will help promote their adoption in new and existing commercial buildings. This report describes the experimental setup, and includes some of the field and simulation results.

  2. Low power arcjet performance

    NASA Technical Reports Server (NTRS)

    Curran, Francis M.; Sarmiento, Charles J.

    1990-01-01

    An experimental investigation was performed to evaluate arc jet operation at low power. A standard, 1 kW, constricted arc jet was run using nozzles with three different constrictor diameters. Each nozzle was run over a range of current and mass flow rates to explore stability and performance in the low power engine. A standard pulse-width modulated power processor was modified to accommodate the high operating voltages required under certain conditions. Stable, reliable operation at power levels below 0.5 kW was obtained at efficiencies between 30 and 40 percent. The operating range was found to be somewhat dependent on constrictor geometry at low mass flow rates. Quasi-periodic voltage fluctuations were observed at the low power end of the operating envelope, The nozzle insert geometry was found to have little effect on the performance of the device. The observed performance levels show that specific impulse levels above 350 seconds can be obtained at the 0.5 kW power level.

  3. MCNP Progress & Performance Improvements

    SciTech Connect

    Brown, Forrest B.; Bull, Jeffrey S.; Rising, Michael Evan

    2015-04-14

    Twenty-eight slides give information about the work of the US DOE/NNSA Nuclear Criticality Safety Program on MCNP6 under the following headings: MCNP6.1.1 Release, with ENDF/B-VII.1; Verification/Validation; User Support & Training; Performance Improvements; and Work in Progress. Whisper methodology will be incorporated into the code, and run speed should be increased.

  4. Performance Management and Reward

    NASA Astrophysics Data System (ADS)

    Yiannis, Triantafyllopoulos; Ioannis, Seimenis; Nikolaos, Konstantopoulos

    2009-08-01

    The article aims to examine, current Performance Management practices on Reward, financial or non-financial using lessons from the literature and the results of a qualitative analysis as these revealed from the interview of some executive members of Greek companies.

  5. Nuclear Enterprise Performance Measurement

    DTIC Science & Technology

    2011-03-01

    sustainability metrics ( Sikdar , 2009). It is used by the Environmental Protection Agency to help determine which biofuels are most sustainable. The method... Sikdar , 2009). ∏ / / (3) This method is...performance metrics. Aggregation metric D is a method developed to aggregate environmental sustainability metrics ( Sikdar , 2009). It is used by the

  6. Performance Evaluation Process.

    ERIC Educational Resources Information Center

    1998

    This document contains four papers from a symposium on the performance evaluation process and human resource development (HRD). "Assessing the Effectiveness of OJT (On the Job Training): A Case Study Approach" (Julie Furst-Bowe, Debra Gates) is a case study of the effectiveness of OJT in one of a high-tech manufacturing company's product…

  7. Performance Theory: Southeast Asia.

    ERIC Educational Resources Information Center

    Kirby, Michael, Ed.

    1979-01-01

    Focusing on the contemporary theatre in Southeast Asia, this journal issue sheds light on the intercultural relationships that exist between that part of the world and the Western world. In addition to a transcript of a Balinese "topeng" (storytelling) performance, the journal contains eight articles that provide information on the…

  8. Amphetamines and Sports Performance.

    ERIC Educational Resources Information Center

    Cooter, G. Rankin

    1980-01-01

    A large number of athletes have resorted to drugs to improve performance in competition. Research literature on the use of amphetamines, both pro and con, is currently confounded with poor research designs and lack of controls, and further research is needed. (CJ)

  9. TRAC performance estimates

    NASA Technical Reports Server (NTRS)

    Everett, L.

    1992-01-01

    This report documents the performance characteristics of a Targeting Reflective Alignment Concept (TRAC) sensor. The performance will be documented for both short and long ranges. For long ranges, the sensor is used without the flat mirror attached to the target. To better understand the capabilities of the TRAC based sensors, an engineering model is required. The model can be used to better design the system for a particular application. This is necessary because there are many interrelated design variables in application. These include lense parameters, camera, and target configuration. The report presents first an analytical development of the performance, and second an experimental verification of the equations. In the analytical presentation it is assumed that the best vision resolution is a single pixel element. The experimental results suggest however that the resolution is better than 1 pixel. Hence the analytical results should be considered worst case conditions. The report also discusses advantages and limitations of the TRAC sensor in light of the performance estimates. Finally the report discusses potential improvements.

  10. Assessing Team Performance.

    ERIC Educational Resources Information Center

    Trimble, Susan; Rottier, Jerry

    Interdisciplinary middle school level teams capitalize on the idea that the whole is greater than the sum of its parts. Administrators and team members can maximize the advantages of teamwork using team assessments to increase the benefits for students, teachers, and the school environment. Assessing team performance can lead to high performing…

  11. Performance Funding in Pennsylvania

    ERIC Educational Resources Information Center

    Cavanaugh, John C.; Garland, Peter

    2012-01-01

    Greater accountability in public higher education systems is a fact of life in the current political climate. Increasingly, one form this accountability takes is performance funding, which arises from elected officials' need for assurance that taxpayer funds are not only being invested and used properly but are resulting in desired outcomes at…

  12. Speaking "over" Performativity

    ERIC Educational Resources Information Center

    White, Julie

    2010-01-01

    In a time where standards and accountability override trust in teachers and principals, mandated versions of pedagogy have recently appeared in the Australian landscape. This article critiques one pedagogical reform initiative and suggests that in performative times, it may be preferable for principals and teachers to speak "over" reform…

  13. Structuralist Performance Issue.

    ERIC Educational Resources Information Center

    Kirby, Michael, Ed.

    1979-01-01

    Defining structuralism as an unannounced aesthetic movement that involves not only the theatre but all arts, this journal issue focuses on structuralist performance. The nine articles provide information on the following topics: the French theatre group, Atelier Theatre et Musique; "Tell Me," a play by Guy de Cointet; patterning in "Five…

  14. Asymptotic Parachute Performance Sensitivity

    NASA Technical Reports Server (NTRS)

    Way, David W.; Powell, Richard W.; Chen, Allen; Steltzner, Adam D.

    2006-01-01

    In 2010, the Mars Science Laboratory mission will pioneer the next generation of robotic Entry, Descent, and Landing systems by delivering the largest and most capable rover to date to the surface of Mars. In addition to landing more mass than any other mission to Mars, Mars Science Laboratory will also provide scientists with unprecedented access to regions of Mars that have been previously unreachable. By providing an Entry, Descent, and Landing system capable of landing at altitudes as high as 2 km above the reference gravitational equipotential surface, or areoid, as defined by the Mars Orbiting Laser Altimeter program, Mars Science Laboratory will demonstrate sufficient performance to land on 83% of the planet s surface. By contrast, the highest altitude landing to date on Mars has been the Mars Exploration Rover at 1.3 km below the areoid. The coupling of this improved altitude performance with latitude limits as large as 60 degrees off of the equator and a precise delivery to within 10 km of a surface target, will allow the science community to select the Mars Science Laboratory landing site from thousands of scientifically interesting possibilities. In meeting these requirements, Mars Science Laboratory is extending the limits of the Entry, Descent, and Landing technologies qualified by the Mars Viking, Mars Pathfinder, and Mars Exploration Rover missions. Specifically, the drag deceleration provided by a Viking-heritage 16.15 m supersonic Disk-Gap-Band parachute in the thin atmosphere of Mars is insufficient, at the altitudes and ballistic coefficients under consideration by the Mars Science Laboratory project, to maintain necessary altitude performance and timeline margin. This paper defines and discusses the asymptotic parachute performance observed in Monte Carlo simulation and performance analysis and its effect on the Mars Science Laboratory Entry, Descent, and Landing architecture.

  15. EMU Suit Performance Simulation

    NASA Technical Reports Server (NTRS)

    Cowley, Matthew S.; Benson, Elizabeth; Harvill, Lauren; Rajulu, Sudhakar

    2014-01-01

    Introduction: Designing a planetary suit is very complex and often requires difficult trade-offs between performance, cost, mass, and system complexity. To verify that new suit designs meet requirements, full prototypes must be built and tested with human subjects. However, numerous design iterations will occur before the hardware meets those requirements. Traditional draw-prototype-test paradigms for research and development are prohibitively expensive with today's shrinking Government budgets. Personnel at NASA are developing modern simulation techniques that focus on a human-centric design paradigm. These new techniques make use of virtual prototype simulations and fully adjustable physical prototypes of suit hardware. This is extremely advantageous and enables comprehensive design down-selections to be made early in the design process. Objectives: The primary objective was to test modern simulation techniques for evaluating the human performance component of two EMU suit concepts, pivoted and planar style hard upper torso (HUT). Methods: This project simulated variations in EVA suit shoulder joint design and subject anthropometry and then measured the differences in shoulder mobility caused by the modifications. These estimations were compared to human-in-the-loop test data gathered during past suited testing using four subjects (two large males, two small females). Results: Results demonstrated that EVA suit modeling and simulation are feasible design tools for evaluating and optimizing suit design based on simulated performance. The suit simulation model was found to be advantageous in its ability to visually represent complex motions and volumetric reach zones in three dimensions, giving designers a faster and deeper comprehension of suit component performance vs. human performance. Suit models were able to discern differing movement capabilities between EMU HUT configurations, generic suit fit concerns, and specific suit fit concerns for crewmembers based

  16. System Performance Characterization

    SciTech Connect

    van Dam, M A

    2004-05-26

    Characterizing an adaptive optics (AO) system refers to understanding its performance and limitations. The goal of an AO system is to correct wavefront aberrations. The uncorrected aberrations, called the residual errors and referred to in what follows simply as the errors, degrade the image quality in the science camera. Understanding the source of these errors is a great aid in designing an AO system and optimizing its performance. This chapter explains how to estimate the wavefront error terms and the relationship between the wavefront error and the degradation of the image. The analysis deals with the particular case of a HartmannShack wavefront sensor (WFS) and a continuous deformable mirror (DM), although the principles involved can be applied to any AO system.

  17. Cyclone performance and optimization

    SciTech Connect

    Leith, D.

    1990-06-15

    The objectives of this project are: to characterize the gas flow pattern within cyclones, to revise the theory for cyclone performance on the basis of these findings, and to design and test cyclones whose dimensions have been optimized using revised performance theory. This work is important because its successful completion will aid in the technology for combustion of coal in pressurized, fluidized beds. During the past quarter, we have nearly completed modeling work that employs the flow field measurements made during the past six months. In addition, we have begun final work using the results of this project to develop improved design methods for cyclones. This work involves optimization using the Iozia-Leith efficiency model and the Dirgo pressure drop model. This work will be completed this summer. 9 figs.

  18. NCCDS performance model

    NASA Technical Reports Server (NTRS)

    Richmond, Eric; Vallone, Antonio

    1994-01-01

    The NASA/GSFC Network Control Center (NCC) provides communication services between ground facilities and spacecraft missions in near-earth orbit that use the Space Network. The NCC Data System (NCCDS) provides computational support and is expected to be highly utilized by the service requests needed in the future years. A performance model of the NCCDS has been developed to assess the future workload and possible enhancements. The model computes message volumes from mission request profiles and SN resource levels and generates the loads for NCCDS configurations as a function of operational scenarios and processing activities. The model has been calibrated using the results of benchmarks performed on the operational NCCDS facility and used to assess some future SN service request scenarios.

  19. Human Performance in Space

    NASA Technical Reports Server (NTRS)

    Jones, Patricia M.; Fiedler, Edna

    2010-01-01

    Human factors is a critical discipline for human spaceflight. Nearly every human factors research area is relevant to space exploration -- from the ergonomics of hand tools used by astronauts, to the displays and controls of a spacecraft cockpit or mission control workstation, to levels of automation designed into rovers on Mars, to organizational issues of communication between crew and ground. This chapter focuses more on the ways in which the space environment (especially altered gravity and the isolated and confined nature of long-duration spaceflight) affects crew performance, and thus has specific novel implications for human factors research and practice. We focus on four aspects of human performance: neurovestibular integration, motor control and musculo-skeletal effects, cognitive effects, and behavioral health. We also provide a sampler of recent human factors studies from NASA.

  20. High Performance, Dependable Multiprocessor

    NASA Technical Reports Server (NTRS)

    Ramos, Jeremy; Samson, John R.; Troxel, Ian; Subramaniyan, Rajagopal; Jacobs, Adam; Greco, James; Cieslewski, Grzegorz; Curreri, John; Fischer, Michael; Grobelny, Eric; George, Alan; Aggarwal, Vikas; Patel, Minesh; Some, Raphael

    2006-01-01

    With the ever increasing demand for higher bandwidth and processing capacity of today's space exploration, space science, and defense missions, the ability to efficiently apply commercial-off-the-shelf (COTS) processors for on-board computing is now a critical need. In response to this need, NASA's New Millennium Program office has commissioned the development of Dependable Multiprocessor (DM) technology for use in payload and robotic missions. The Dependable Multiprocessor technology is a COTS-based, power efficient, high performance, highly dependable, fault tolerant cluster computer. To date, Honeywell has successfully demonstrated a TRL4 prototype of the Dependable Multiprocessor [I], and is now working on the development of a TRLS prototype. For the present effort Honeywell has teamed up with the University of Florida's High-performance Computing and Simulation (HCS) Lab, and together the team has demonstrated major elements of the Dependable Multiprocessor TRLS system.

  1. MIR Performance Analysis

    SciTech Connect

    Hazen, Damian; Hick, Jason

    2012-06-12

    We provide analysis of Oracle StorageTek T10000 Generation B (T10KB) Media Information Record (MIR) Performance Data gathered over the course of a year from our production High Performance Storage System (HPSS). The analysis shows information in the MIR may be used to improve tape subsystem operations. Most notably, we found the MIR information to be helpful in determining whether the drive or tape was most suspect given a read or write error, and for helping identify which tapes should not be reused given their history of read or write errors. We also explored using the MIR Assisted Search to order file retrieval requests. We found that MIR Assisted Search may be used to reduce the time needed to retrieve collections of files from a tape volume.

  2. High performance collectors

    NASA Astrophysics Data System (ADS)

    Ogawa, H.; Hozumi, S.; Mitsumata, T.; Yoshino, K.; Aso, S.; Ebisu, K.

    1983-04-01

    Materials and structures used for flat plate solar collectors and evacuated tubular collectors were examined relative to their overall performance to project effectiveness for building heating and cooling and the feasibility of use for generating industrial process heat. Thermal efficiencies were calculated for black paint single glazed, selective surface single glazed, and selective surface double glazed flat plate collectors. The efficiencies of a single tube and central tube accompanied by two side tube collectors were also studied. Techniques for extending the lifetimes of the collectors were defined. The selective surface collectors proved to have a performance superior to other collectors in terms of the average annual energy delivered. Addition of a black chrome-coated fin system to the evacuated collectors produced significant collection efficiency increases.

  3. Environmental Performance Report 2015

    SciTech Connect

    2016-07-01

    The National Renewable Energy Laboratory's (NREL's) Environmental Performance Report provides a description of the laboratory's environmental management activities for 2015, including information on environmental and sustainability performance, environmental compliance activities and status, and environmental protection programs, highlights, and successes. The purpose of this report is to ensure that U.S. Department of Energy (DOE) and the public receive timely, accurate information about events that have affected or could adversely affect the health, safety, and security of the public or workers; the environment; or the operations of DOE facilities. This report meets the requirements of the Annual Site Environmental Report and is prepared in accordance with the DOE Order 231.1B, Environment, Safety and Health Reporting.

  4. Enhancing Decision Performance

    DTIC Science & Technology

    2002-07-09

    The first is temporary storage of information, as proposed by Atkinson and Shiffrin (1968) in their model of short term memory . The second demand...Reference: Atkinson , R.C., & Shiffrin , R.M. (1968). Human memory : A proposed system and its control processes. In K.W. Spence (Ed.), The psychology of...Flexiablity in Performance Study 2: Use and Memory of Configural and Holistic Information Study 3: Time Pressure REPORT DOCUMENTATION PAGE Form Approved

  5. Distributed Explosive Performance Model

    DTIC Science & Technology

    1998-01-01

    18 Analytic Code ( DEPAC ). DEPAC is a restructured and an upgraded one-stop code of the previous version of the Linear Explosive Array Performance...findings1. 3. Developed the initial version of DEPAC (LEAP and LAM) 3. 4. Released three Technical Results (TRs). 5. Established the methodology for quick...the input files for each run for CTH, process the data generated by CTH, and create the input database files for DEPAC . The line charge is composed of

  6. DART AVGS Performance

    NASA Technical Reports Server (NTRS)

    Howard, Richard T.; Bryan, Thomas C.

    2007-01-01

    The Advanced Video Guidance Sensor (AVGS) was designed to be the proximity operations sensor for the Demonstration of Autonomous Rendezvous Technologies (DART). The DART mission flew in April of2005 and was a partial success. The AVGS did not get the opportunity to operate in every mode in orbit, but those modes in which it did operate were completely successful. This paper will detail the development, testing, and on-orbit performance of the AVGS.

  7. High performance polymeric foams

    SciTech Connect

    Gargiulo, M.; Sorrentino, L.; Iannace, S.

    2008-08-28

    The aim of this work was to investigate the foamability of high-performance polymers (polyethersulfone, polyphenylsulfone, polyetherimide and polyethylenenaphtalate). Two different methods have been used to prepare the foam samples: high temperature expansion and two-stage batch process. The effects of processing parameters (saturation time and pressure, foaming temperature) on the densities and microcellular structures of these foams were analyzed by using scanning electron microscopy.

  8. CF6 performance improvement

    NASA Technical Reports Server (NTRS)

    Lennard, D. J.

    1978-01-01

    Potential CF6 engine performance improvements directed at reduced fuel consumption were identified and screened relative to airline acceptability and are reviewed. The screening process developed to provide evaluations of fuel savings and economic factors including return on investment and direct operating cost is described. In addition, assessments of development risk and production potential are made. Several promising concepts selected for full-scale development based on a ranking involving these factors are discussed.

  9. Evaluating steam trap performance

    SciTech Connect

    Fuller, N.Y.

    1985-08-08

    This paper presents a method for evaluating the performance level of steam traps by preparing an economic analysis of several types to determine the equivalent uniform annual cost. A series of tests on steam traps supplied by six manufacturers provided data for determining the relative efficiencies of each unit. The comparison was made using a program developed for the Texas Instruments T1-59 programmable calculator to evaluate overall steam trap economics.

  10. Cyclone performance and optimization

    SciTech Connect

    Leith, D.

    1990-09-15

    The objectives of this project are: to characterize the gas flow pattern within cyclones, to revise the theory for cyclone performance on the basis of these findings, and to design and test cyclones whose dimensions have been optimized using revised performance theory. This work is important because its successful completion will aid in the technology for combustion of coal in pressurized, fluidized beds. This quarter, an empirical model for predicting pressure drop across a cyclone was developed through a statistical analysis of pressure drop data for 98 cyclone designs. The model is shown to perform better than the pressure drop models of First (1950), Alexander (1949), Barth (1956), Stairmand (1949), and Shepherd-Lapple (1940). This model is used with the efficiency model of Iozia and Leith (1990) to develop an optimization curve which predicts the minimum pressure drop and the dimension rations of the optimized cyclone for a given aerodynamic cut diameter, d{sub 50}. The effect of variation in cyclone height, cyclone diameter, and flow on the optimization curve is determined. The optimization results are used to develop a design procedure for optimized cyclones. 37 refs., 10 figs., 4 tabs.

  11. High Performance Buildings Database

    DOE Data Explorer

    The High Performance Buildings Database is a shared resource for the building industry, a unique central repository of in-depth information and data on high-performance, green building projects across the United States and abroad. The database includes information on the energy use, environmental performance, design process, finances, and other aspects of each project. Members of the design and construction teams are listed, as are sources for additional information. In total, up to twelve screens of detailed information are provided for each project profile. Projects range in size from small single-family homes or tenant fit-outs within buildings to large commercial and institutional buildings and even entire campuses. The database is a data repository as well. A series of Web-based data-entry templates allows anyone to enter information about a building project into the database. Once a project has been submitted, each of the partner organizations can review the entry and choose whether or not to publish that particular project on its own Web site.

  12. Diet and physical performance.

    PubMed

    Montain, Scott J; Young, Andrew J

    2003-06-01

    This paper provides a historical summary of military nutrition research into the role of diet for sustaining soldier physical performance. Studies of underfeeding document that physical performance is preserved during several days of underfeeding provided sufficient carbohydrate and minerals are consumed to minimize the diuresis associated with semi-starvation diets and serial intake of carbohydrate is available to support metabolism during prolonged work. The Military Recommended Dietary Allowances, AR 40-25, currently recommends that when restricted rations are required, that the ration contain at least 1,100-1,500 kcal, 50-70 g of protein, and a minimum of 100 g of carbohydrate on a daily basis. This low energy diet, however, is not recommended for subsistence for longer than 10 consecutive days. Dietary carbohydrate intakes of approximately 300-400 g will more closely match the quantity of carbohydrate oxidized to meet daily energy requirements during field operations. Research into the potential advantages of dietary supplements has generally not proved advantageous when compared to eating a well balanced diet. Future investigations of the role of diet for sustaining soldier health and performance should be directed toward a better understanding of the influence of energy intake and macro-nutrient composition for preserving lean body mass, reducing susceptibility to illness and injury and enhancing recovery during and after sustained operations.

  13. ATR performance modeling concepts

    NASA Astrophysics Data System (ADS)

    Ross, Timothy D.; Baker, Hyatt B.; Nolan, Adam R.; McGinnis, Ryan E.; Paulson, Christopher R.

    2016-05-01

    Performance models are needed for automatic target recognition (ATR) development and use. ATRs consume sensor data and produce decisions about the scene observed. ATR performance models (APMs) on the other hand consume operating conditions (OCs) and produce probabilities about what the ATR will produce. APMs are needed for many modeling roles of many kinds of ATRs (each with different sensing modality and exploitation functionality combinations); moreover, there are different approaches to constructing the APMs. Therefore, although many APMs have been developed, there is rarely one that fits a particular need. Clarified APM concepts may allow us to recognize new uses of existing APMs and identify new APM technologies and components that better support coverage of the needed APMs. The concepts begin with thinking of ATRs as mapping OCs of the real scene (including the sensor data) to reports. An APM is then a mapping from explicit quantized OCs (represented with less resolution than the real OCs) and latent OC distributions to report distributions. The roles of APMs can be distinguished by the explicit OCs they consume. APMs used in simulations consume the true state that the ATR is attempting to report. APMs used online with the exploitation consume the sensor signal and derivatives, such as match scores. APMs used in sensor management consume neither of those, but estimate performance from other OCs. This paper will summarize the major building blocks for APMs, including knowledge sources, OC models, look-up tables, analytical and learned mappings, and tools for signal synthesis and exploitation.

  14. NASA Performance Plan

    NASA Technical Reports Server (NTRS)

    1999-01-01

    The Government Performance and Results Act (GPRA) passed by Congress and signed by the President in 1993 provides a new tool to improve the efficiency of all Federal agencies. The goals of GPRA are to: Improve citizen confidence in Government performance; Improve Federal program management, effectiveness, and public accountability; and Improve congressional decisionmaking on where to commit the Nation's financial and human resources. The Act directs Executive Branch agencies to develop a customer-focused strategic plan that aligns activities with concrete missions and goals. The first plans were submitted in September 1998 as part of the Fiscal Year 1999 (FY99) budget process. These budget submissions were expected to support the goals expressed in the agency strategic plans. The Act also directs agencies to manage and measure results to justify congressional appropriations and authorizations. Six months after the completion of the fiscal year, agencies will report on the degree of success in achieving the goals and evaluation measures defined in the strategic and performance plans. The plans required by GPRA have been submitted to the Office of Management and Budget (OMB) and to Congress. Copies of NASA plans are available from the Office of Policy and Plans at NASA Headquarters and can be accessed on the i nterinet web sites identified in the Appendix.

  15. Behavior and Performance Project

    NASA Technical Reports Server (NTRS)

    Washburn, David A.; Rumbaugh, Duane M.; Shlyk, Galina; Vassilieva, Oxana; Richardson, W. Kirk

    1998-01-01

    Behavior is an overt manifestation of underlying biology. As such, alterations in biological systems that result from spaceflight would be expected to evidence themselves in subtle or even pronounced changes in the behavior of that organism. These alterations in visible behavior may then indicate or even be diagnostic of alterations in the physical well-being of humans and other animals as they adapt to space environments or readapt to Earth--alterations that might not otherwise be detected without relatively invasive and frequently expensive procedures. Moreover, behavior and performance constitute the central standard for evaluating the mission success of spaceflight ventures. The success or failure of any excursion into space is primarily indexed by the ability of astronauts and cosmonauts to perform the tasks and experiments of any particular mission, to land a re-entry vehicle after extended exposure to microgravity (as with the space shuttle), or to make time-critical and life-saving repairs or other decisions while in orbit (as with the recent Mir events). Thus, understanding the effects spaceflight on behavior and performance is inherently important, in addition to those insights that behavior can provide about the physiological consequences of space adaptation.

  16. Mentoring Human Performance - 12480

    SciTech Connect

    Geis, John A.; Haugen, Christian N.

    2012-07-01

    Although the positive effects of implementing a human performance approach to operations can be hard to quantify, many organizations and industry areas are finding tangible benefits to such a program. Recently, a unique mentoring program was established and implemented focusing on improving the performance of managers, supervisors, and work crews, using the principles of Human Performance Improvement (HPI). The goal of this mentoring was to affect behaviors and habits that reliably implement the principles of HPI to ensure continuous improvement in implementation of an Integrated Safety Management System (ISMS) within a Conduct of Operations framework. Mentors engaged with personnel in a one-on-one, or one-on-many dialogue, which focused on what behaviors were observed, what factors underlie the behaviors, and what changes in behavior could prevent errors or events, and improve performance. A senior management sponsor was essential to gain broad management support. A clear charter and management plan describing the goals, objectives, methodology, and expected outcomes was established. Mentors were carefully selected with senior management endorsement. Mentors were assigned to projects and work teams based on the following three criteria: 1) knowledge of the work scope; 2) experience in similar project areas; and 3) perceived level of trust they would have with project management, supervision, and work teams. This program was restructured significantly when the American Reinvestment and Recovery Act (ARRA) and the associated funding came to an end. The program was restructured based on an understanding of the observations, attributed successes and identified shortfalls, and the consolidation of those lessons. Mentoring the application of proven methods for improving human performance was shown effective at increasing success in day-to-day activities and increasing confidence and level of skill of supervisors. While mentoring program effectiveness is difficult to

  17. Functional Performance Evaluation

    NASA Technical Reports Server (NTRS)

    Greenisen, Michael C.; Hayes, Judith C.; Siconolfi, Steven F.; Moore, Alan D.

    1999-01-01

    The Extended Duration Orbiter Medical Project (EDOMP) was established to address specific issues associated with optimizing the ability of crews to complete mission tasks deemed essential to entry, landing, and egress for spaceflights lasting up to 16 days. The main objectives of this functional performance evaluation were to investigate the physiological effects of long-duration spaceflight on skeletal muscle strength and endurance, as well as aerobic capacity and orthostatic function. Long-duration exposure to a microgravity environment may produce physiological alterations that affect crew ability to complete critical tasks such as extravehicular activity (EVA), intravehicular activity (IVA), and nominal or emergency egress. Ultimately, this information will be used to develop and verify countermeasures. The answers to three specific functional performance questions were sought: (1) What are the performance decrements resulting from missions of varying durations? (2) What are the physical requirements for successful entry, landing, and emergency egress from the Shuttle? and (3) What combination of preflight fitness training and in-flight countermeasures will minimize in-flight muscle performance decrements? To answer these questions, the Exercise Countermeasures Project looked at physiological changes associated with muscle degradation as well as orthostatic intolerance. A means of ensuring motor coordination was necessary to maintain proficiency in piloting skills, EVA, and IVA tasks. In addition, it was necessary to maintain musculoskeletal strength and function to meet the rigors associated with moderate altitude bailout and with nominal or emergency egress from the landed Orbiter. Eight investigations, referred to as Detailed Supplementary Objectives (DSOs) 475, 476, 477, 606, 608, 617, 618, and 624, were conducted to study muscle degradation and the effects of exercise on exercise capacity and orthostatic function (Table 3-1). This chapter is divided into

  18. Caffeine and sports performance.

    PubMed

    Burke, Louise M

    2008-12-01

    Athletes are among the groups of people who are interested in the effects of caffeine on endurance and exercise capacity. Although many studies have investigated the effect of caffeine ingestion on exercise, not all are suited to draw conclusions regarding caffeine and sports performance. Characteristics of studies that can better explore the issues of athletes include the use of well-trained subjects, conditions that reflect actual practices in sport, and exercise protocols that simulate real-life events. There is a scarcity of field-based studies and investigations involving elite performers. Researchers are encouraged to use statistical analyses that consider the magnitude of changes, and to establish whether these are meaningful to the outcome of sport. The available literature that follows such guidelines suggests that performance benefits can be seen with moderate amounts (~3 mg.kg-1 body mass) of caffeine. Furthermore, these benefits are likely to occur across a range of sports, including endurance events, stop-and-go events (e.g., team and racquet sports), and sports involving sustained high-intensity activity lasting from 1-60 min (e.g., swimming, rowing, and middle and distance running races). The direct effects on single events involving strength and power, such as lifts, throws, and sprints, are unclear. Further studies are needed to better elucidate the range of protocols (timing and amount of doses) that produce benefits and the range of sports to which these may apply. Individual responses, the politics of sport, and the effects of caffeine on other goals, such as sleep, hydration, and refuelling, also need to be considered.

  19. Spaceport Performance Measures

    NASA Technical Reports Server (NTRS)

    Finger, G. Wayne

    2010-01-01

    Spaceports have traditionally been characterized by performance measures associated with their site characteristics. Measures such as "Latitude" (proximity to the equator), "Azimuth" (range of available launch azimuths) and "Weather" (days of favorable weather) are commonly used to characterize a particular spaceport. However, other spaceport performance measures may now be of greater value. These measures can provide insight into areas of operational differences between competing spaceports and identify areas for improving the performance of spaceports. This paper suggests Figures of Merit (FOMs) for spaceport "Capacity" (number of potential launch opportunities per year and / or potential mass' to low earth orbit (LEO) per year); "Throughput" (actual mass to orbit per year compared to capacity); "Productivity" (labor effort hours per unit mass to orbit); "Energy Efficiency" (joules expended at spaceport per unit mass to orbit); "Carbon Footprint" tons CO2 per unit mass to orbit). Additional FOMS are investigated with regards to those areas of special interest to commercial launch operators, such as "Assignment Schedule" (days required for a binding assignment of a launch site from the spaceport); "Approval Schedule" (days to complete a range safety assessment leading to an approval or disapproval of a launch vehicle); "Affordability" (cost for a spaceport to assess a new launch vehicle); "Launch Affordability" (fixed range costs per launch); "Reconfigure Time" (hours to reconfigure the range from one vehicle's launch ready configuration to another vehicle's configuration); "Turn,Around Time" (minimum range hours required between launches of an identical type launch vehicle). Available or notional data is analyzed for the KSC/CCAFS area and other spaceports. Observations regarding progress over the past few decades are made. Areas where improvement are needed or indicated are suggested.

  20. Performance analysis in saber.

    PubMed

    Aquili, Andrea; Tancredi, Virginia; Triossi, Tamara; De Sanctis, Desiree; Padua, Elvira; DʼArcangelo, Giovanna; Melchiorri, Giovanni

    2013-03-01

    Fencing is a sport practiced by both men and women, which uses 3 weapons: foil, épée, and saber. In general, there are few scientific studies available in international literature; they are limited to the performance analysis of fencing bouts, yet there is nothing about saber. There are 2 kinds of competitions in the World Cup for both men and women: the "FIE GP" and "A." The aim of this study was to carry out a saber performance analysis to gain useful indicators for the definition of a performance model. In addition, it is expected to verify if it could be influenced by the type of competition and if there are differences between men and women. Sixty bouts: 33 FIE GP and 27 "A" competitions (35 men's and 25 women's saber bouts) were analyzed. The results indicated that most actions are offensive (55% for men and 49% for women); the central area of the piste is mostly used (72% for men and 67% for women); the effective fighting time is 13.6% for men and 17.1% for women, and the ratio between the action and break times is 1:6.5 for men and 1:5.1 for women. A lunge is carried out every 23.9 seconds by men and every 20 seconds by women, and a direction change is carried out every 65.3 seconds by men and every 59.7 seconds by women. The data confirm the differences between the saber and the other 2 weapons. There is no significant difference between the data of the 2 different kinds of competitions.

  1. Should Aid Reward Performance?

    PubMed Central

    Olken, Benjamin A.; Onishi, Junko; Wong, Susan

    2014-01-01

    We report an experiment in 3,000 villages that tested whether incentives improve aid efficacy. Villages received block grants for maternal and child health and education that incorporated relative performance incentives. Subdistricts were randomized into incentives, an otherwise identical program without incentives, or control. Incentives initially improved preventative health indicators, particularly in underdeveloped areas, and spending efficiency increased. While school enrollments improved overall, incentives had no differential impact on education, and incentive health effects diminished over time. Reductions in neonatal mortality in non-incentivized areas did not persist with incentives. We find no systematic scoring manipulation nor funding reallocation toward richer areas. PMID:25485039

  2. High Performance Liquid Chromatography

    NASA Astrophysics Data System (ADS)

    Talcott, Stephen

    High performance liquid chromatography (HPLC) has many applications in food chemistry. Food components that have been analyzed with HPLC include organic acids, vitamins, amino acids, sugars, nitrosamines, certain pesticides, metabolites, fatty acids, aflatoxins, pigments, and certain food additives. Unlike gas chromatography, it is not necessary for the compound being analyzed to be volatile. It is necessary, however, for the compounds to have some solubility in the mobile phase. It is important that the solubilized samples for injection be free from all particulate matter, so centrifugation and filtration are common procedures. Also, solid-phase extraction is used commonly in sample preparation to remove interfering compounds from the sample matrix prior to HPLC analysis.

  3. WFIRST Observatory Performance

    NASA Technical Reports Server (NTRS)

    Kruk, Jeffrey W.

    2012-01-01

    The WFIRST observatory will be a powerful and flexible wide-field near-infrared facility. The planned surveys will provide data applicable to an enormous variety of astrophysical science. This presentation will provide a description of the observatory and its performance characteristics. This will include a discussion of the point spread function, signal-to-noise budgets for representative observing scenarios and the corresponding limiting sensitivity. Emphasis will be given to providing prospective Guest Observers with information needed to begin thinking about new observing programs.

  4. Predicting photothermal field performance

    NASA Technical Reports Server (NTRS)

    Gonzalez, C. C.; Ross, R. G., Jr.

    1984-01-01

    Photothermal field performance in flat plate solar collectors was predicted. An analytical model which incorporates the measured dependency between transmittance loss and UV and temperature exposure levels was developed. The model uses SOLMET weather data extrapolated to 30 years for various sites and module mounting configurations. It is concluded that the temperature is the key to photothermally induced transmittance loss. The sensitivity of transmittance loss to UV level is nonlinear with minimum in curve near one sun. The ethylene vinyl acetate (EVA) results are consistent with 30 year life allocation.

  5. Performance of Dental Ceramics

    PubMed Central

    Rekow, E.D.; Silva, N.R.F.A.; Coelho, P.G.; Zhang, Y.; Guess, P.; Thompson, V.P.

    2011-01-01

    The clinical success of modern dental ceramics depends on an array of factors, ranging from initial physical properties of the material itself, to the fabrication and clinical procedures that inevitably damage these brittle materials, and the oral environment. Understanding the influence of these factors on clinical performance has engaged the dental, ceramics, and engineering communities alike. The objective of this review is to first summarize clinical, experimental, and analytic results reported in the recent literature. Additionally, it seeks to address how this new information adds insight into predictive test procedures and reveals challenges for future improvements. PMID:21224408

  6. High performance cyclone development

    SciTech Connect

    Giles, W.B.

    1981-01-01

    The results of cold flow experiments at atmospheric conditions of an air-shielded 18 in-dia electrocyclone with a central cusped electrode are reported using fine test dusts of both flyash and nickel powder. These results are found to confirm expectations of enhanced performance, similar to earlier work on a 12 in-dia model. An analysis of the combined inertial-electrostatic force field is also presented which identifies general design goals and scaling laws. From this, it is found that electrostatic enhancement will be particularly beneficial for fine dusts in large cyclones. Recommendations for further improvement in cyclone collection efficiency are proposed.

  7. LISA Instrument Performance

    NASA Technical Reports Server (NTRS)

    Livas, Jeffrey C.; Thorpe, James Ira

    2008-01-01

    Laser Interferometer Space Antenna (LISA) is designed to observe gravitational waves in the frequency band from 10(exp -1) to 10(exp -4) Hz where a rich spectrum of sources is expected. The measurements must be made from space to avoid the large motions of the earth that prevent the current generations (eg. LIGO) from operating at these freq8uencies. The technology and expected performance behind this measurement capability will be reviewed with an emphasis on the interferometric measurement system., including recent laboratory results showing a novel tunable frequency stabilized laser.

  8. High Performance FORTRAN

    NASA Technical Reports Server (NTRS)

    Mehrotra, Piyush

    1994-01-01

    High performance FORTRAN is a set of extensions for FORTRAN 90 designed to allow specification of data parallel algorithms. The programmer annotates the program with distribution directives to specify the desired layout of data. The underlying programming model provides a global name space and a single thread of control. Explicitly parallel constructs allow the expression of fairly controlled forms of parallelism in particular data parallelism. Thus the code is specified in a high level portable manner with no explicit tasking or communication statements. The goal is to allow architecture specific compilers to generate efficient code for a wide variety of architectures including SIMD, MIMD shared and distributed memory machines.

  9. Loudspeaker Performance Aid

    NASA Technical Reports Server (NTRS)

    1980-01-01

    Many manufacturers of loudspeakers are now using a magnetic liquid cooling agent known as ferrofluid. Commercialized by Ferrofluids Corporation, ferrofluid is a liquid material in which sub-microscopic particles of iron oxide are permanently suspended. Injected into the voice coil segment of speaker system, magnetic liquid serves as superior heat transfer medium for cooling the voice coil, thus substantially increasing the system's ability to handle higher power levels and decreasing chance of speaker failure. Ferrofluid offers several additional advantages which add up to improved speaker performance, lower manufacturing costs and fewer rejects.

  10. Altair performance and upgrades

    NASA Astrophysics Data System (ADS)

    Lai, Olivier; Véran, Jean-Pierre; Herriot, Glen; White, John; Ball, Jesse; Trujillo, Chad

    2014-07-01

    Altair is the facility single conjugate AO system for Gemini North. Although it has been in operation for more than 10 years (and upgraded to LGS in 2007), Altair's performance is degraded by three main issues: vibrations of the telescope and instrument support structure, spatial aliasing on centroid offsets from the M2 support structure print-through on the optical surface and static non-common path aberrations. Monte-Carlo simulations can reproduce the behavior of Altair when including these three effects and they are roughly of the same order of magnitude. Solutions or mitigations are being investigated to overcome these nefarious effects and restore Altair's performance to its nominal level. A simplex algorithm as well as a phase diversity approach are being investigated to measure and correct for static aberrations. A high accuracy phase map of the M2 print-through has been obtained and is being used to calibrate and/or filter centroids affected by aliasing. A new real time computer is under consideration, to be able to handle more advanced controllers, especially notch filters to combat vibrations. In this paper we will report on the various simulations and on-sky results of this rejuvenation of one of Gemini's workhorse instruments.

  11. Cyclone performance and optimization

    SciTech Connect

    Leith, D.

    1989-03-15

    The objectives of this project are: to characterize the gas flow pattern within cyclones, to revise the theory for cyclone performance on the basis of these findings, and to design and test cyclones whose dimensions have been optimized using revised performance theory. This work is important because its successful completion will aid in the technology for combustion of coal in pressurized, fluidized beds. This quarter, we have been hampered somewhat by flow delivery of the bubble generation system and arc lighting system placed on order last fall. This equipment is necessary to map the flow field within cyclones using the techniques described in last quarter's report. Using the bubble generator, we completed this quarter a study of the natural length'' of cyclones of 18 different configurations, each configuration operated at five different gas flows. Results suggest that the equation by Alexander for natural length is incorrect; natural length as measured with the bubble generation system is always below the bottom of the cyclones regardless of the cyclone configuration or gas flow, within the limits of the experimental cyclones tested. This finding is important because natural length is a term in equations used to predict cyclone efficiency. 1 tab.

  12. Anaerobic performance at altitude.

    PubMed

    Coudert, J

    1992-10-01

    Anaerobic metabolism is usually evaluated by the determination of the anaerobic capacity and the maximal anaerobic mechanical external power (Wmax). Conflicting results are reported on anaerobic capacity evaluated by maximal oxygen deficit and debt, and maximal blood lactate concentration during acute or chronic hypoxia (acclimatized subjects). Data on muscle biopsies (lactate concentration, changes in ATP, phosphocreatine and glycogen stores, glycolytic enzyme activities) and the few studies on lactate flux give in most cases evidence of a non-alteration of the anaerobic capacity for altitudes up to 5,500 m. No differences are observed in Wmax measured at high altitudes up to 5,200 m during intense short-term exercises: (1) jumps on a force platform which is a good indicator of alactic Wmax, and (2) 7-10 s sprints (i.e. force-velocity test) which solicit alactic metabolism but also lactic pathway. For exercises of duration equal or more than 30 s (i.e. Wingate test), there are conflicting results because a lower participation of aerobic metabolism during this test at high altitude can interfere with anaerobic performance. In conclusion, we can admit that anaerobic performances are not altered by high altitudes up to 5,200 m if the length of exposure does not exceed 5 weeks. After this period, muscle mass begins to decrease.

  13. Assessment of sensor performance

    NASA Astrophysics Data System (ADS)

    Waldmann, C.; Tamburri, M.; Prien, R. D.; Fietzek, P.

    2010-02-01

    There is an international commitment to develop a comprehensive, coordinated and sustained ocean observation system. However, a foundation for any observing, monitoring or research effort is effective and reliable in situ sensor technologies that accurately measure key environmental parameters. Ultimately, the data used for modelling efforts, management decisions and rapid responses to ocean hazards are only as good as the instruments that collect them. There is also a compelling need to develop and incorporate new or novel technologies to improve all aspects of existing observing systems and meet various emerging challenges. Assessment of Sensor Performance was a cross-cutting issues session at the international OceanSensors08 workshop in Warnemünde, Germany, which also has penetrated some of the papers published as a result of the workshop (Denuault, 2009; Kröger et al., 2009; Zielinski et al., 2009). The discussions were focused on how best to classify and validate the instruments required for effective and reliable ocean observations and research. The following is a summary of the discussions and conclusions drawn from this workshop, which specifically addresses the characterisation of sensor systems, technology readiness levels, verification of sensor performance and quality management of sensor systems.

  14. Thermal Performance Benchmarking

    SciTech Connect

    Feng, Xuhui; Moreno, Gilbert; Bennion, Kevin

    2016-06-07

    The goal for this project is to thoroughly characterize the thermal performance of state-of-the-art (SOA) in-production automotive power electronics and electric motor thermal management systems. Information obtained from these studies will be used to: evaluate advantages and disadvantages of different thermal management strategies; establish baseline metrics for the thermal management systems; identify methods of improvement to advance the SOA; increase the publicly available information related to automotive traction-drive thermal management systems; help guide future electric drive technologies (EDT) research and development (R&D) efforts. The thermal performance results combined with component efficiency and heat generation information obtained by Oak Ridge National Laboratory (ORNL) may then be used to determine the operating temperatures for the EDT components under drive-cycle conditions. In FY16, the 2012 Nissan LEAF power electronics and 2014 Honda Accord Hybrid power electronics thermal management system were characterized. Comparison of the two power electronics thermal management systems was also conducted to provide insight into the various cooling strategies to understand the current SOA in thermal management for automotive power electronics and electric motors.

  15. High Performance Parallel Architectures

    NASA Technical Reports Server (NTRS)

    El-Ghazawi, Tarek; Kaewpijit, Sinthop

    1998-01-01

    Traditional remote sensing instruments are multispectral, where observations are collected at a few different spectral bands. Recently, many hyperspectral instruments, that can collect observations at hundreds of bands, have been operational. Furthermore, there have been ongoing research efforts on ultraspectral instruments that can produce observations at thousands of spectral bands. While these remote sensing technology developments hold great promise for new findings in the area of Earth and space science, they present many challenges. These include the need for faster processing of such increased data volumes, and methods for data reduction. Dimension Reduction is a spectral transformation, aimed at concentrating the vital information and discarding redundant data. One such transformation, which is widely used in remote sensing, is the Principal Components Analysis (PCA). This report summarizes our progress on the development of a parallel PCA and its implementation on two Beowulf cluster configuration; one with fast Ethernet switch and the other with a Myrinet interconnection. Details of the implementation and performance results, for typical sets of multispectral and hyperspectral NASA remote sensing data, are presented and analyzed based on the algorithm requirements and the underlying machine configuration. It will be shown that the PCA application is quite challenging and hard to scale on Ethernet-based clusters. However, the measurements also show that a high- performance interconnection network, such as Myrinet, better matches the high communication demand of PCA and can lead to a more efficient PCA execution.

  16. High performing micromachined retroreflector

    NASA Astrophysics Data System (ADS)

    Lundvall, Axel; Nikolajeff, Fredrik; Lindstrom, Tomas

    2003-10-01

    This paper reports on the realization of a type of micromachined retroreflecting sheeting material. The geometry presented has high reflection efficiency even at large incident angles, and it can be manufactured through polymer replication techniques. The paper consists of two parts: A theoretical section outlining the design parameters and their impact on the optical performance, and secondly, an experimental part comprising both manufacturing and optical evaluation for a candidate retroreflecting sheet material in traffic control devices. Experimental data show that the retroreflecting properties are promising. The retroreflector consists of a front layer of densely packed spherical microlenses, a back surface of densely packed spherical micromirrors, and a transparent spacer layer. The thickness of the spacer layer determines in part the optical characteristics of the retroreflector.

  17. RLV Turbine Performance Optimization

    NASA Technical Reports Server (NTRS)

    Griffin, Lisa W.; Dorney, Daniel J.

    2001-01-01

    A task was developed at NASA/Marshall Space Flight Center (MSFC) to improve turbine aerodynamic performance through the application of advanced design and analysis tools. There are four major objectives of this task: 1) to develop, enhance, and integrate advanced turbine aerodynamic design and analysis tools; 2) to develop the methodology for application of the analytical techniques; 3) to demonstrate the benefits of the advanced turbine design procedure through its application to a relevant turbine design point; and 4) to verify the optimized design and analysis with testing. Final results of the preliminary design and the results of the two-dimensional (2D) detailed design of the first-stage vane of a supersonic turbine suitable for a reusable launch vehicle (R-LV) are presented. Analytical techniques for obtaining the results are also discussed.

  18. System performance conclusions

    NASA Technical Reports Server (NTRS)

    Arndt, G. D.

    1980-01-01

    The advantages and disadvantages of reducing power levels and using antennas with diameters smaller than 1 Km were evaluated if rectenna costs and land usage requirements become major factors, operating at 5800 megahertz should be considered. Three sequences (random, incoherent phasing, and concentric rings - center to edge) provided satisfactory performance in that the resultant sidelobe levels during startup/ shutdown were lower than the steady-state levels present during normal operations. Grating lobe peaks and scattered power levels were used to determine the array/subarray mechanical alignment requirements. The antenna alignment requirement is 1 min or 3 min depending on phase control configuration. System error parameters were defined to minimize scattered microwave power.

  19. Trust in performance indicators?

    PubMed Central

    Davies, H. T.; Lampel, J.

    1998-01-01

    The 1980s and 90s have seen the proliferation of all forms of performance indicators as part of attempts to command and control health services. The latest area to receive attention is health outcomes. Published league tables of mortality and other health outcomes have been available in the United States for some time and in Scotland since the early 1990s; they have now been developed for England and Wales. Publication of these data has proceeded despite warnings as to their limited meaningfulness and usefulness. The time has come to ask whether the remedy is worse than the malady: are published health outcomes contributing to quality efforts or subverting more constructive approaches? This paper argues that attempts to force improvements through publishing health outcomes can be counterproductive, and outlines an alternative approach which involves fostering greater trust in professionalism as a basis for quality enhancements. PMID:10185142

  20. RTA gun performance

    SciTech Connect

    Andersen, D E; Eylon, S; Henestroza, E; Houck, T L; Lidia, S M; Vanecek, D L; Westenskow, G A; Yu, S S

    1998-08-10

    The technical challenge for making two-beam accelerators into realizable power sources for high-energy colliders lie in the creation of the drive beam and in its propagation over long distances through multiple extraction sections. This year we have constructed a 1.2-kA, 1-MeV, electron induction injector for the RTA accelerator. The electron source will be a 8.9 cm diameter, thermionic, flat-surface cathode with a maximum shroud field stress of approximately 165 kV/cm. The injector's pulse length should be over 120-ns flat top (1% energy variation) with a normalized edge emittance of less than 200 π-mm-mr. Details of the design and performance of the injector, beam line, and diagnostics will be presented.