WorldWideScience

Sample records for space exposed surfaces

  1. Contaminations of inner surface of magnesium fluoride windows in the `Expose-R' experiment on the International Space Station

    Science.gov (United States)

    Skurat, V. E.

    2017-10-01

    A series of experiments was carried out previously on board of the International Space Station in `EXPOSE-R', a multi-user expose facility, provided by European Space Agency attached to the external surface of the Russian Segment. In one experiment, spores of microorganisms and species of higher plant seeds, in heat-sealed polymer bags were irradiated by solar radiation passed through MgF2 windows in a high space vacuum. After sample exposure, it was found that in many cases the inner surfaces of windows were contaminated. Analysis of the contamination revealed the presence of chemical groups CH2, CH3, NH, OH, C═O, Si-CH3 (Demets et al. in 2015). Their presence in deposits was explained by photofixation of gaseous precursors - some of the vapours of glues and additives in polymeric materials in the core facility of `Expose-R'. Carbon-, oxygen- and silicon-containing groups may be deposited from outer intrinsic atmosphere. This atmosphere is connected with sample compartments and core facility. However, the presence of NH groups on inner surfaces of windows was not expected. This paper shows that the process responsible for carbon-, nitrogen- and oxygen-containing group formation can be a photopolymerization of caprolactam, which is released from the outer Nylon 6 layer of polymer bags under Solar vacuum ultraviolet radiation.

  2. EXPOSE-R2: The Astrobiological ESA Mission on Board of the International Space Station

    Directory of Open Access Journals (Sweden)

    Elke Rabbow

    2017-08-01

    Full Text Available On July 23, 2014, the Progress cargo spacecraft 56P was launched from Baikonur to the International Space Station (ISS, carrying EXPOSE-R2, the third ESA (European Space Agency EXPOSE facility, the second EXPOSE on the outside platform of the Russian Zvezda module, with four international astrobiological experiments into space. More than 600 biological samples of archaea, bacteria (as biofilms and in planktonic form, lichens, fungi, plant seeds, triops eggs, mosses and 150 samples of organic compounds were exposed to the harsh space environment and to parameters similar to those on the Mars surface. Radiation dosimeters distributed over the whole facility complemented the scientific payload. Three extravehicular activities later the chemical samples were returned to Earth on March 2, 2016, with Soyuz 44S, having spent 588 days in space. The biological samples arrived back later, on June 18, 2016, with 45S, after a total duration in space of 531 days. The exposure of the samples to Low Earth Orbit vacuum lasted for 531 days and was divided in two parts: protected against solar irradiation during the first 62 days, followed by exposure to solar radiation during the subsequent 469 days. In parallel to the space mission, a Mission Ground Reference (MGR experiment with a flight identical Hardware and a complete flight identical set of samples was performed at the premises of DLR (German Aerospace Center in Cologne by MUSC (Microgravity User Support Center, according to the mission data either downloaded from the ISS (temperature data, facility status, inner pressure status or provided by RedShift Design and Engineering BVBA, Belgium (calculated ultra violet radiation fluence data. In this paper, the EXPOSE-R2 facility, the experimental samples, mission parameters, environmental parameters, and the overall mission and MGR sequences are described, building the background for the research papers of the individual experiments, their analysis and results.

  3. EXPOSE-E: an ESA astrobiology mission 1.5 years in space.

    Science.gov (United States)

    Rabbow, Elke; Rettberg, Petra; Barczyk, Simon; Bohmeier, Maria; Parpart, André; Panitz, Corinna; Horneck, Gerda; von Heise-Rotenburg, Ralf; Hoppenbrouwers, Tom; Willnecker, Rainer; Baglioni, Pietro; Demets, René; Dettmann, Jan; Reitz, Guenther

    2012-05-01

    The multi-user facility EXPOSE-E was designed by the European Space Agency to enable astrobiology research in space (low-Earth orbit). On 7 February 2008, EXPOSE-E was carried to the International Space Station (ISS) on the European Technology Exposure Facility (EuTEF) platform in the cargo bay of Space Shuttle STS-122 Atlantis. The facility was installed at the starboard cone of the Columbus module by extravehicular activity, where it remained in space for 1.5 years. EXPOSE-E was returned to Earth with STS-128 Discovery on 12 September 2009 for subsequent sample analysis. EXPOSE-E provided accommodation in three exposure trays for a variety of astrobiological test samples that were exposed to selected space conditions: either to space vacuum, solar electromagnetic radiation at >110 nm and cosmic radiation (trays 1 and 3) or to simulated martian surface conditions (tray 2). Data on UV radiation, cosmic radiation, and temperature were measured every 10 s and downlinked by telemetry. A parallel mission ground reference (MGR) experiment was performed on ground with a parallel set of hardware and samples under simulated space conditions. EXPOSE-E performed a successful 1.5-year mission in space.

  4. Electron microscope observations of impact crater debris amongst contaminating particulates on materials surfaces exposed in space in low-Earth orbit

    Science.gov (United States)

    Murr, L. E.; Rivas, J. M.; Quinones, S.; Niou, C.-S.; Advani, A. H.; Marquez, B.

    1993-01-01

    Debris particles extracted from a small sampling region on the leading edge of the Long Duration Exposure Facility (LDEF) spacecraft have been examined by analytical transmission electron microscopy and the elemental frequency observed by energy-dispersive X-ray spectrometry and compared with upper atmosphere (Earth) particle elemental frequency and the average elemental compositions of interplanetary dust particles. A much broader elemental distribution was observed for the exposed spacecraft surface debris milieu. Numerous metal microfragment analyses, particularly aluminum and stainless steel, were compared with scanning electron microscope observations-of impact crater features, and the corresponding elemental spectra on selected LDEF aluminium tray clamps and stainless steel bolts. The compositions and melt features for these impact craters and ejecta have been shown to be consistent with microcrystalline debris fragments in the case of aluminum, and these observations suggest an ever changing debris milieu on exposed surfaces for space craft and space system materials.

  5. Survival of Spores of Trichoderma longibrachiatum in Space: data from the Space Experiment SPORES on EXPOSE-R

    Science.gov (United States)

    Neuberger, Katja; Lux-Endrich, Astrid; Panitz, Corinna

    2015-01-01

    In the space experiment `Spores in artificial meteorites' (SPORES), spores of the fungus Trichoderma longibrachiatum were exposed to low-Earth orbit for nearly 2 years on board the EXPOSE-R facility outside of the International Space Station. The environmental conditions tested in space were: space vacuum at 10-7-10-4 Pa or argon atmosphere at 105 Pa as inert gas atmosphere, solar extraterrestrial ultraviolet (UV) radiation at λ > 110 nm or λ > 200 nm with fluences up to 5.8 × 108 J m-2, cosmic radiation of a total dose range from 225 to 320 mGy, and temperature fluctuations from -25 to +50°C, applied isolated or in combination. Comparable control experiments were performed on ground. After retrieval, viability of spores was analysed by two methods: (i) ethidium bromide staining and (ii) test of germination capability. About 30% of the spores in vacuum survived the space travel, if shielded against insolation. However, in most cases no significant decrease was observed for spores exposed in addition to the full spectrum of solar UV irradiation. As the spores were exposed in clusters, the outer layers of spores may have shielded the inner part. The results give some information about the likelihood of lithopanspermia, the natural transfer of micro-organisms between planets. In addition to the parameters of outer space, sojourn time in space seems to be one of the limiting parameters.

  6. Alteration of Lunar Rock Surfaces through Interaction with the Space Environment

    Science.gov (United States)

    Frushour, A. M.; Noble, S. K; Christoffersen, R.; Keller, L P.

    2014-01-01

    Space weathering occurs on all ex-posed surfaces of lunar rocks, as well as on the surfaces of smaller grains in the lunar regolith. Space weather-ing alters these exposed surfaces primarily through the action of solar wind ions and micrometeorite impact processes. On lunar rocks specifically, the alteration products produced by space weathering form surface coatings known as patina. Patinas can have spectral reflectance properties different than the underlying rock. An understanding of patina composition and thickness is therefore important for interpreting re-motely sensed data from airless solar system bodies. The purpose of this study is to try to understand the physical and chemical properties of patina by expanding the number of patinas known and characterized in the lunar rock sample collection.

  7. The Affect of the Space Environment on the Survival of Halorubrum Chaoviator and Synechococcus (Nageli): Data from the Space Experiment OSMO on EXPOSE-R

    Science.gov (United States)

    Mancinelli, R. L.

    2014-01-01

    We have shown using ESA's Biopan facility flown in Earth orbit that when exposed to the space environment for 2 weeks the survival rate of Synechococcus (Nageli), a halophilic cyanobacterium isolated from the evaporitic gypsum-halite crusts that form along the marine intertidal, and Halorubrum chaoviator a member of the Halobacteriaceae isolated from an evaporitic NaCl crystal obtained from a salt evaporation pond, were higher than all other test organisms except Bacillus spores. These results led to the EXPOSE-R mission to extend and refine these experiments as part of the experimental package for the external platform space exposure facility on the ISS. The experiment was flown in February 2009 and the organisms were exposed to low-Earth orbit for nearly 2 years. Samples were either exposed to solar ultraviolet (UV)-radiation (lambda is greater than 110 nm or lambda is greater than 200 nm, cosmic radiation (dosage range 225-320 mGy), or kept in darkness shielded from solar UV-radiation. Half of each of the UV-radiation exposed samples and dark samples were exposed to space vacuum and half kept at 105 pascals in argon. Duplicate samples were kept in the laboratory to serve as unexposed controls. Ground simulation control experiments were also performed. After retrieval, organism viability was tested using Molecular Probes Live-Dead Bac-Lite stain and by their reproduction capability. Samples kept in the dark, but exposed to space vacuum had a 90 +/- 5% survival rate compared to the ground controls. Samples exposed to full UV-radiation for over a year were bleached and although results from Molecular Probes Live-Dead stain suggested approximately 10% survival, the data indicate that no survival was detected using cell growth and division using the most probable number method. Those samples exposed to attenuated UV-radiation exhibited limited survival. Results from of this study are relevant to understanding adaptation and evolution of life, the future of life

  8. Characterizing the effects of regolith surface roughness on photoemission from surfaces in space

    Science.gov (United States)

    Dove, A.; Horanyi, M.; Wang, X.

    2017-12-01

    Surfaces of airless bodies and spacecraft in space are exposed to a variety of charging environments. A balance of currents due to plasma bombardment, photoemission, electron and ion emission and collection, and secondary electron emission determines the surface's charge. Photoelectron emission is the dominant charging process on sunlit surfaces in the inner solar system due to the intense solar UV radiation. This can result in a net positive surface potential, with a cloud of photoelectrons immediately above the surface, called the photoelectron sheath. Conversely, the unlit side of the body will charge negatively due the collection of the fast-moving solar wind electrons. The interaction of charged dust grains with these positively and negatively charged surfaces, and within the photoelectron and plasma sheaths may explain the occurrence of dust lofting, levitation and transport above the lunar surface. The surface potential of exposed objects is also dependent on the material properties of their surfaces. Composition and particle size primarily affect the quantum efficiency of photoelectron generation; however, surface roughness can also control the charging process. In order to characterize these effects, we have conducted laboratory experiments to examine the role of surface roughness in generating photoelectrons in dedicated laboratory experiments using solid and dusty surfaces of the same composition (CeO2), and initial comparisons with JSC-1 lunar simulant. Using Langmuir probe measurements, we explore the measured potentials above insulating surfaces exposed to UV and an electric field, and we show that the photoemission current from a dusty surface is largely reduced due to its higher surface roughness, which causes a significant fraction of the emitted photoelectrons to be re-absorbed within the surface. We will discuss these results in context of similar situations on planetary surfaces.

  9. The affect of the space environment on the survival of Halorubrum chaoviator and Synechococcus (Nägeli): data from the Space Experiment OSMO on EXPOSE-R

    Science.gov (United States)

    Mancinelli, R. L.

    2015-01-01

    We have shown using ESA's Biopan facility flown in Earth orbit that when exposed to the space environment for 2 weeks the survival rate of Synechococcus (Nägeli), a halophilic cyanobacterium isolated from the evaporitic gypsum-halite crusts that form along the marine intertidal, and Halorubrum chaoviator a member of the Halobacteriaceae isolated from an evaporitic NaCl crystal obtained from a salt evaporation pond, were higher than all other test organisms except Bacillus spores. These results led to the EXPOSE-R mission to extend and refine these experiments as part of the experimental package for the external platform space exposure facility on the ISS. The experiment was flown in February 2009 and the organisms were exposed to low-Earth orbit for nearly 2 years. Samples were either exposed to solar ultraviolet (UV)-radiation (λ > 110 nm or λ > 200 nm, cosmic radiation (dosage range 225-320 mGy), or kept in darkness shielded from solar UV-radiation. Half of each of the UV-radiation exposed samples and dark samples were exposed to space vacuum and half kept at 105 pascals in argon. Duplicate samples were kept in the laboratory to serve as unexposed controls. Ground simulation control experiments were also performed. After retrieval, organism viability was tested using Molecular Probes Live-Dead Bac-Lite stain and by their reproduction capability. Samples kept in the dark, but exposed to space vacuum had a 90 +/- 5% survival rate compared to the ground controls. Samples exposed to full UV-radiation for over a year were bleached and although results from Molecular Probes Live-Dead stain suggested ~10% survival, the data indicate that no survival was detected using cell growth and division using the most probable number method. Those samples exposed to attenuated UV-radiation exhibited limited survival. Results from of this study are relevant to understanding adaptation and evolution of life, the future of life beyond earth, the potential for interplanetary

  10. Chromosome aberrations in space-exposed seeds of Allium cepa L

    International Nuclear Information System (INIS)

    Wang, S.

    1994-01-01

    Onion (Allium cepa L.) seeds c.v. Patti King were packed in sealed canisters and launched into space orbit about 296 km above earth by the space shuttle Challenger in April 1984. After more than five years exposure to space, the seeds were retrieved by the space shuttle Columbia and returned to earth in January, 1990. Somatic chromosomes at anaphase and telophase stages were analyzed and cells with normal or abnormal chromosome separations were recorded. Space-exposed and control seeds showed an average of 10.9% and 2.8% chromosome aberrations, respectively. Seeds contained in the two exterior layers of the canister had 16.5 to 18.5% chromosome aberration. The results indicated that irradiation in space would be a direct cause for chromosome aberrations in onion seeds. Analysis of seed germination rate and vigor were also determined. The average germination rate for space-exposed and control seeds were 53.3% and 19.8%, respectively. Possible reasons for the results obtained are discussed [it

  11. Expose-R experiment on effects of open space condition on survivorship in dormant stages of aquatic invertebrates

    Science.gov (United States)

    Alekseev, Victor; Novikova, Nataliya; Levinskikh, Margarita; Sychev, Vladimir; Yusoff, Fatimah; Azuraidi, Osman

    2012-07-01

    Dormancy protects animals and plants in harsh environmental conditions from months up to hundred years. This phenomenon is perspective for space researches especially for interplanetary missions. Direct experiments in open space BYORYSK supported in principle the fact of survivorship of bacteria, fungi spores, seed of plants and crustacean dormant cysts. Even though the rate of survivorship in long-term treatments was low but good enough to conclude that biological invasion even to Mars is a real danger. As soon as the BYORYSK lunch was made of metal the possibility for resting stages to survive under UV treatment in vacuum without some protection was not clear. To test it an ESA and RSA equipment titled EXPOSE-R was applied. The EXPOSE-R facility was an external facility attached to the outside of the Zvezda Service Module in ISS in the end of November 2008. It had glace windows transparent for UV-radiation and possibility to measure temperature, space- and UV-radiation. Among a number of experiments requiring exposure to the open space environment it had a biological launch containing resting stages of terrestrial and aquatic organisms. These stages included dried ephippia of cladoceran Daphnia magna differentiated on size, dormant eggs of ostracode Eucypris ornate, cysts of fair-shrimp Streptocephalus torvicornis ( all from hemi desert Caspian area) and Artemis salina from salt lake Crimean populations. All dormant stages were kept in transparent to UV plastic bags placed in three layers. After about two years of exposing in open space dormant stages of 3 species A. salina, D. magna, S. torvicornis successfully survived at different scales but in second and third layers only . The highest level of survivorship was found in A. salina cysts. In preliminary land experiments that imitated land EXPOSE imitation of outside space station UV and vacuum conditions survivorship in resting eggs of D .magna, S. torvicornis and E. ornate was tested also. The total UV dose of

  12. Space-like surfaces with free boundary in the Lorentz-Minkowski space

    International Nuclear Information System (INIS)

    López, R; Pyo, J

    2012-01-01

    We investigate a variational problem in the Lorentz-Minkowski space L 3 whose critical points are space-like surfaces with a constant mean curvature and making a constant contact angle with a given support surface along its common boundary. We show that if the support surface is a pseudosphere, then the surface is a planar disc or a hyperbolic cap. We also study the problem of space-like hypersurfaces with free boundary in the higher dimensional Lorentz-Minkowski space L n+1 . (paper)

  13. Identification of Surface Exposed Elementary Body Antigens of ...

    African Journals Online (AJOL)

    This study sought to identify the surface exposed antigenic components of Cowdria ruminantium elementary body (EB) by biotin labeling, determine effect of reducing and non-reducing conditions and heat on the mobility of these antigens and their reactivity to antibodies from immunized animals by Western blotting.

  14. Survival of spores of the UV-resistant Bacillus subtilis strain MW01 after exposure to low-earth orbit and simulated martian conditions: data from the space experiment ADAPT on EXPOSE-E.

    Science.gov (United States)

    Wassmann, Marko; Moeller, Ralf; Rabbow, Elke; Panitz, Corinna; Horneck, Gerda; Reitz, Günther; Douki, Thierry; Cadet, Jean; Stan-Lotter, Helga; Cockell, Charles S; Rettberg, Petra

    2012-05-01

    In the space experiment "Molecular adaptation strategies of microorganisms to different space and planetary UV climate conditions" (ADAPT), bacterial endospores of the highly UV-resistant Bacillus subtilis strain MW01 were exposed to low-Earth orbit (LEO) and simulated martian surface conditions for 559 days on board the European Space Agency's exposure facility EXPOSE-E, mounted outside the International Space Station. The survival of B. subtilis MW01 spores from both assays (LEO and simulated martian conditions) was determined by a colony-formation assay after retrieval. It was clearly shown that solar extraterrestrial UV radiation (λ≥110 nm) as well as the martian UV spectrum (λ≥200 nm) was the most deleterious factor applied; in some samples only a few spore survivors were recovered from B. subtilis MW01 spores exposed in monolayers. However, if shielded from solar irradiation, about 8% of MW01 spores survived in LEO conditions, and 100% survived in simulated martian conditions, compared to the laboratory controls. The results demonstrate the effect of shielding against the high inactivation potential of extraterrestrial solar UV radiation, which limits the chances of survival of even the highly UV-resistant strain of B. subtilis MW01 in the harsh environments of outer space and the martian surface.

  15. Ultrastructural changes of photodegradation of wood surfaces exposed to UV

    International Nuclear Information System (INIS)

    Kuo, M.L.; Hu, N.

    1991-01-01

    Red pine sapwood transverse and radial surfaces were exposed to ultraviolet (UV) light for 3 to 40 days. Effect of UV irradiation on ultrastructural changes of cell walls were studied by scanning (SEM) and transmission (TEM) electron microscopy. SEM study of transverse sections showed that during initial stages of UV irradiation, lignin in cell corners and in the compound middle lamellae was preferentially degraded and that the radial middle lamellae substained a greater rate of UV degradation than did the tangential middle lamellae. Massive cell wall degradation, as indicated by cell wall thinning, did not occur until surfaces were exposed to UV light for more than 10 days. TEM study of radial cell wall surfaces indicated that lignin lining the warty layer was removed by UV irradiation in 3 days and that warts were destroyed by a UV irradiation in 7 days. UV irradiation of cell wall surfaces produced a substantial amount of water-soluble degradation products. After 30 days of UV irradiation, the S3 layer was totally removed and revealed the very fragile S2 layer. (author)

  16. LIFE experiment: isolation of cryptoendolithic organisms from Antarctic colonized sandstone exposed to space and simulated Mars conditions on the international space station.

    Science.gov (United States)

    Scalzi, Giuliano; Selbmann, Laura; Zucconi, Laura; Rabbow, Elke; Horneck, Gerda; Albertano, Patrizia; Onofri, Silvano

    2012-06-01

    Desiccated Antarctic rocks colonized by cryptoendolithic communities were exposed on the International Space Station (ISS) to space and simulated Mars conditions (LiFE-Lichens and Fungi Experiment). After 1.5 years in space samples were retrieved, rehydrated and spread on different culture media. Colonies of a green alga and a pink-coloured fungus developed on Malt-Agar medium; they were isolated from a sample exposed to simulated Mars conditions beneath a 0.1 % T Suprasil neutral density filter and from a sample exposed to space vacuum without solar radiation exposure, respectively. None of the other flight samples showed any growth after incubation. The two organisms able to grow were identified at genus level by Small SubUnit (SSU) and Internal Transcribed Spacer (ITS) rDNA sequencing as Stichococcus sp. (green alga) and Acarospora sp. (lichenized fungal genus) respectively. The data in the present study provide experimental information on the possibility of eukaryotic life transfer from one planet to another by means of rocks and of survival in Mars environment.

  17. Surface-Exposed Lipoproteins: An Emerging Secretion Phenomenon in Gram-Negative Bacteria.

    Science.gov (United States)

    Wilson, Marlena M; Bernstein, Harris D

    2016-03-01

    Bacterial lipoproteins are hydrophilic proteins that are anchored to a cell membrane by N-terminally linked fatty acids. It is widely believed that nearly all lipoproteins produced by Gram-negative bacteria are either retained in the inner membrane (IM) or transferred to the inner leaflet of the outer membrane (OM). Lipoproteins that are exposed on the cell surface have also been reported but are generally considered to be rare. Results from a variety of recent studies, however, now suggest that the prevalence of surface-exposed lipoproteins has been underestimated. In this review we describe the evidence that the surface exposure of lipoproteins in Gram-negative bacteria is a widespread phenomenon and discuss possible mechanisms by which these proteins might be transported across the OM. Published by Elsevier Ltd.

  18. OLTARIS: An Efficient Web-Based Tool for Analyzing Materials Exposed to Space Radiation

    Science.gov (United States)

    Slaba, Tony; McMullen, Amelia M.; Thibeault, Sheila A.; Sandridge, Chris A.; Clowdsley, Martha S.; Blatting, Steve R.

    2011-01-01

    The near-Earth space radiation environment includes energetic galactic cosmic rays (GCR), high intensity proton and electron belts, and the potential for solar particle events (SPE). These sources may penetrate shielding materials and deposit significant energy in sensitive electronic devices on board spacecraft and satellites. Material and design optimization methods may be used to reduce the exposure and extend the operational lifetime of individual components and systems. Since laboratory experiments are expensive and may not cover the range of particles and energies relevant for space applications, such optimization may be done computationally with efficient algorithms that include the various constraints placed on the component, system, or mission. In the present work, the web-based tool OLTARIS (On-Line Tool for the Assessment of Radiation in Space) is presented, and the applicability of the tool for rapidly analyzing exposure levels within either complicated shielding geometries or user-defined material slabs exposed to space radiation is demonstrated. An example approach for material optimization is also presented. Slabs of various advanced multifunctional materials are defined and exposed to several space radiation environments. The materials and thicknesses defining each layer in the slab are then systematically adjusted to arrive at an optimal slab configuration.

  19. Determining eyeball surface area directly exposed to the effects of external factors.

    Science.gov (United States)

    Juliszewski, Tadeusz; Kadłuczka, Filip; Kiełbasa, Paweł

    2016-01-01

    This article discusses determining the surface area of eyeballs of men and women exposed to the direct effects of external factors in the working environment. For one eye, the mean surface is 172-182 mm(2). The determined surface area can be used in formulas for calculating the exposure of eyeballs to harmful chemical substances in workplace air.

  20. Surface-knots in 4-space an introduction

    CERN Document Server

    Kamada, Seiichi

    2017-01-01

    This introductory volume provides the basics of surface-knots and related topics, not only for researchers in these areas but also for graduate students and researchers who are not familiar with the field. Knot theory is one of the most active research fields in modern mathematics. Knots and links are closed curves (one-dimensional manifolds) in Euclidean 3-space, and they are related to braids and 3-manifolds. These notions are generalized into higher dimensions. Surface-knots or surface-links are closed surfaces (two-dimensional manifolds) in Euclidean 4-space, which are related to two-dimensional braids and 4-manifolds. Surface-knot theory treats not only closed surfaces but also surfaces with boundaries in 4-manifolds. For example, knot concordance and knot cobordism, which are also important objects in knot theory, are surfaces in the product space of the 3-sphere and the interval. Included in this book are basics of surface-knots and the related topics of classical knots, the motion picture method, surf...

  1. Erosion of graphite surface exposed to hot supersonic hydrogen gas

    Science.gov (United States)

    Sharma, O. P.

    1972-01-01

    A theoretical model based on laminar boundary layer flow equations was developed to predict the erosion rate of a graphite (AGCarb-101) surface exposed to a hot supersonic stream of hydrogen gas. The supersonic flow in the nozzle outside the boundary layer formed over the surface of the specimen was determined by assuming one-dimensional isentropic conditions. An overall surface reaction rate expression based on experimental studies was used to describe the interaction of hydrogen with graphite. A satisfactory agreement was found between the results of the computation, and the available experimental data. Some shortcomings of the model and further possible improvements are discussed.

  2. Reactivity of lithium exposed graphite surface

    International Nuclear Information System (INIS)

    Harilal, S.S.; Allain, J.P.; Hassanein, A.; Hendricks, M.R.; Nieto-Perez, M.

    2009-01-01

    Lithium as a plasma-facing component has many attractive features in fusion devices. We investigated chemical properties of the lithiated graphite surfaces during deposition using X-ray photoelectron spectroscopy and low-energy ion scattering spectroscopy. In this study we try to address some of the known issues during lithium deposition, viz., the chemical state of lithium on graphite substrate, oxide layer formation mechanisms, Li passivation effects over time, and chemical change during exposure of the sample to ambient air. X-ray photoelectron studies indicate changes in the chemical composition with various thickness of lithium on graphite during deposition. An oxide layer formation is noticed during lithium deposition even though all the experiments were performed in ultrahigh vacuum. The metal oxide is immediately transformed into carbonate when the deposited sample is exposed to air.

  3. Embrittlement of MISSE 5 Polymers After 13 Months of Space Exposure

    Science.gov (United States)

    Guo, Aobo; Yi, Grace T.; Ashmead, Claire C.; Mitchell, Gianna G.; deGroh, Kim K.

    2012-01-01

    Understanding space environment induced degradation of spacecraft materials is essential when designing durable and stable spacecraft components. As a result of space radiation, debris impacts, atomic oxygen interaction, and thermal cycling, the outer surfaces of space materials degrade when exposed to low Earth orbit (LEO). The objective of this study was to measure the embrittlement of 37 thin film polymers after LEO space exposure. The polymers were flown aboard the International Space Station and exposed to the LEO space environment as part of the Materials International Space Station Experiment 5 (MISSE 5). The samples were flown in a nadir-facing position for 13 months and were exposed to thermal cycling along with low doses of atomic oxygen, direct solar radiation and omnidirectional charged particle radiation. The samples were analyzed for space-induced embrittlement using a bend-test procedure in which the strain necessary to induce surface cracking was determined. Bend-testing was conducted using successively smaller mandrels to apply a surface strain to samples placed on a semi-suspended pliable platform. A pristine sample was also tested for each flight sample. Eighteen of the 37 flight samples experienced some degree of surface cracking during bend-testing, while none of the pristine samples experienced any degree of cracking. The results indicate that 49 percent of the MISSE 5 thin film polymers became embrittled in the space environment even though they were exposed to low doses (approx.2.75 krad (Si) dose through 127 mm Kapton) of ionizing radiation.

  4. EDITORIAL: From reciprocal space to real space in surface science From reciprocal space to real space in surface science

    Science.gov (United States)

    Bartels, Ludwig; Ernst, Karl-Heinz

    2012-09-01

    This issue is dedicated to Karl-Heinz Rieder on the occasion of his 70th birthday. It contains contributions written by his former students and colleagues from all over the world. Experimental techniques based on free electrons, such as photoelectron spectroscopy, electron microscopy and low energy electron diffraction (LEED), were foundational to surface science. While the first revealed the band structures of materials, the second provided nanometer scale imagery and the latter elucidated the atomic scale periodicity of surfaces. All required an (ultra-)high vacuum, and LEED illustrated impressively that adsorbates, such as carbon monoxide, hydrogen or oxygen, can markedly and periodically restructure surfaces from their bulk termination, even at pressures ten orders of magnitude or more below atmospheric. Yet these techniques were not generally able to reveal atomic scale surface defects, nor could they faithfully show adsorption of light atoms such as hydrogen. Although a complete atom, helium can also be regarded as a wave with a de Broglie wavelength that allows the study of surface atomic periodicities at a delicateness and sensitivity exceeding that of electrons-based techniques. In combination, these and other techniques generated insight into the periodicity of surfaces and their vibrational properties, yet were limited to simple and periodic surface setups. All that changed with the advent of scanning tunneling microscopy (STM) roughly 30 years ago, allowing real space access to surface defects and individual adsorbates. Applied at low temperatures, not only can STM establish a height profile of surfaces, but can also perform spectroscopy and serve as an actuator capable of rearranging individual species at atomic scale resolution. The direct and intuitive manner in which STM provided access as a spectator and as an actor to the atomic scale was foundational to today's surface science and to the development of the concepts of nanoscience in general. The

  5. Organic surfaces exposed by self-assembled organothiol monolayers: Preparation, characterization, and application

    Science.gov (United States)

    Kind, Martin; Wöll, Christof

    2009-07-01

    Organic surfaces play a major role in materials science. Most surfaces that we touch in our daily lives are made from organic materials, e.g., vegetables, fruit, skin, wood, and textiles made from natural fibers. In the context of biology, organic surfaces play a prominent role too, proteins docking onto cell surfaces are a good example. To better understand the characteristics of organic surfaces, including physico-chemical properties like wettability or chemical reactivities and physical properties like friction and lubrication, a structurally well-defined model system that can be investigated with numerous analytical techniques is desirable. In the last two decades, one particular system, self-assembled monolayers or SAMs, have demonstrated their suitability for this purpose. In particular, organothiols consisting of an organic molecule with an attached SH-group are well suited to fabricating structurally well-defined adlayers of monolayer thickness on gold substrates using a simple preparation procedure. These ultrathin monolayers expose an organic surface with properties that can be tailored by varying the type of organothiol employed. After a short introduction into the preparation of SAMs, this article provides an overview of the possibilities and limitations of organic surfaces exposed by Au-thiolate SAMs. Applications are as diverse as the metallization of organic surfaces, a fundamental problem in materials science, and the fabrication of surfaces that resist the adsorption of proteins. In addition to a number of different case studies, we will also discuss the most powerful analytical techniques needed to characterize these important model systems.

  6. Seismic Technology Adapted to Analyzing and Developing Geothermal Systems Below Surface-Exposed High-Velocity Rocks Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Hardage, Bob A. [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; DeAngelo, Michael V. [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Ermolaeva, Elena [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Hardage, Bob A. [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Remington, Randy [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Sava, Diana [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Wagner, Donald [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology; Wei, Shuijion [Univ. of Texas, Austin, TX (United States). Bureau of Economic Geology

    2013-02-01

    The objective of our research was to develop and demonstrate seismic data-acquisition and data-processing technologies that allow geothermal prospects below high-velocity rock outcrops to be evaluated. To do this, we acquired a 3-component seismic test line across an area of exposed high-velocity rocks in Brewster County, Texas, where there is high heat flow and surface conditions mimic those found at numerous geothermal prospects. Seismic contractors have not succeeded in creating good-quality seismic data in this area for companies who have acquired data for oil and gas exploitation purposes. Our test profile traversed an area where high-velocity rocks and low-velocity sediment were exposed on the surface in alternating patterns that repeated along the test line. We verified that these surface conditions cause non-ending reverberations of Love waves, Rayleigh waves, and shallow critical refractions to travel across the earth surface between the boundaries of the fast-velocity and slow-velocity material exposed on the surface. These reverberating surface waves form the high level of noise in this area that does not allow reflections from deep interfaces to be seen and utilized. Our data-acquisition method of deploying a box array of closely spaced geophones allowed us to recognize and evaluate these surface-wave noise modes regardless of the azimuth direction to the surface anomaly that backscattered the waves and caused them to return to the test-line profile. With this knowledge of the surface-wave noise, we were able to process these test-line data to create P-P and SH-SH images that were superior to those produced by a skilled seismic data-processing contractor. Compared to the P-P data acquired along the test line, the SH-SH data provided a better detection of faults and could be used to trace these faults upward to the boundaries of exposed surface rocks. We expanded our comparison of the relative value of S-wave and P-wave seismic data for geothermal

  7. Temperature thresholds for surface blistering of platinum and stainless steel exposed to curium-242 alpha radiations

    International Nuclear Information System (INIS)

    McDonell, W.R.; Dillich, S.

    1981-01-01

    Implantation of helium in materials exposed to alpha-emitting radionuclides such as 242 Cm causes surface blistering at elevated temperatures. The temperature thresholds for such blistering are of practical importance to the selection of suitable container materials for radionuclides, and are of fundamental interest with regard to the mechanisms of helium blistering of materials in radiation environments. The purpose of this investigation was to establish temperature thresholds for surface blistering of platinum and stainless-steel container materials by post-irradiation heating of specimens exposed at room temperature to alpha particles from an external 242 Cm source. These thresholds were compared with (1) the analogous temperature thresholds for surface blistering of materials exposed to external beams of accelerator helium ions, and (2) thresholds for swelling and grain-boundary cracking of materials in which helium is generated internally by (n,α) reactions during reactor exposures

  8. Spinorial characterizations of surfaces into 3-dimensional psuedo-Riemannian space forms

    OpenAIRE

    Lawn , Marie-Amélie; Roth , Julien

    2011-01-01

    9 pages; We give a spinorial characterization of isometrically immersed surfaces of arbitrary signature into 3-dimensional pseudo-Riemannian space forms. For Lorentzian surfaces, this generalizes a recent work of the first author in $\\mathbb{R}^{2,1}$ to other Lorentzian space forms. We also characterize immersions of Riemannian surfaces in these spaces. From this we can deduce analogous results for timelike immersions of Lorentzian surfaces in space forms of corresponding signature, as well ...

  9. Spinorial Characterizations of Surfaces into 3-dimensional Pseudo-Riemannian Space Forms

    International Nuclear Information System (INIS)

    Lawn, Marie-Amélie; Roth, Julien

    2011-01-01

    We give a spinorial characterization of isometrically immersed surfaces of arbitrary signature into 3-dimensional pseudo-Riemannian space forms. This generalizes a recent work of the first author for spacelike immersed Lorentzian surfaces in ℝ 2,1 to other Lorentzian space forms. We also characterize immersions of Riemannian surfaces in these spaces. From this we can deduce analogous results for timelike immersions of Lorentzian surfaces in space forms of corresponding signature, as well as for spacelike and timelike immersions of surfaces of signature (0, 2), hence achieving a complete spinorial description for this class of pseudo-Riemannian immersions.

  10. Pose Space Surface Manipulation

    Directory of Open Access Journals (Sweden)

    Yusuke Yoshiyasu

    2012-01-01

    Full Text Available Example-based mesh deformation techniques produce natural and realistic shapes by learning the space of deformations from examples. However, skeleton-based methods cannot manipulate a global mesh structure naturally, whereas the mesh-based approaches based on a translational control do not allow the user to edit a local mesh structure intuitively. This paper presents an example-driven mesh editing framework that achieves both global and local pose manipulations. The proposed system is built with a surface deformation method based on a two-step linear optimization technique and achieves direct manipulations of a model surface using translational and rotational controls. With the translational control, the user can create a model in natural poses easily. The rotational control can adjust the local pose intuitively by bending and twisting. We encode example deformations with a rotation-invariant mesh representation which handles large rotations in examples. To incorporate example deformations, we infer a pose from the handle translations/rotations and perform pose space interpolation, thereby avoiding involved nonlinear optimization. With the two-step linear approach combined with the proposed multiresolution deformation method, we can edit models at interactive rates without losing important deformation effects such as muscle bulging.

  11. Moduli spaces of convex projective structures on surfaces

    DEFF Research Database (Denmark)

    Fock, V. V.; Goncharov, A. B.

    2007-01-01

    We introduce explicit parametrisations of the moduli space of convex projective structures on surfaces, and show that the latter moduli space is identified with the higher Teichmüller space for defined in [V.V. Fock, A.B. Goncharov, Moduli spaces of local systems and higher Teichmüller theory, math.......AG/0311149]. We investigate the cluster structure of this moduli space, and define its quantum version....

  12. Potentials of surfaces in space

    International Nuclear Information System (INIS)

    Whipple, E.C.

    1981-01-01

    The potential of a body in space is determined by a balance between various charging currents such as the transfer of charge from plasma particles, photoemission, and secondary electron emission. These processes are evaluated for bodies in the solar system and in interstellar space under the headings; an overview of charging, survey of early work on charging, charging processes, effects of non-isotropic plasmas and magnetic and electric fields, calculation of surface potentials, differential charging, potential barriers and discharge processes, measurements of potential, potential modification and control on spacecraft, and astrophysical applications. (U.K.)

  13. Effect of surface topography and morphology on space charge packets in polyethylene

    International Nuclear Information System (INIS)

    Zhou Yuanxiang; Wang Yunshan; Sun Qinghua; Wang Ninghua

    2009-01-01

    Polyethylene (PE) is a major kind of internal insulating material. With great progresses of space charge measurement technologies in the last three decades, lots of researches are focused on space charge in PE. The heat pressing and annealing condition of polyethylene affect its morphology obviously. During the heat pressing, the surface of PE forms different surface topographies because of different substrate materials. Surface topography has great relation to the epitaxial crystallization layer and influences the space charge characteristic of PE dramatically. This paper studied the formation process of different surface topographies and their micrographic characters in low density polyethylene (LDPE). pulsed electro-acoustic (PEA) method was used to measure the space charge distribution of samples with different surface topographies and morphologies in LDPE. The effect of surface topography and morphology to space charge packet were studied. The surface topography has great influence on space charge packet polarity and morphology has influence on both movement speed rate and polarity of space charge packet.

  14. Surface and microstructural characterization of commercial breeder reactor candidate alloys exposed to 7000C sodium

    International Nuclear Information System (INIS)

    Anantatmula, R.P.; Brehm, W.F.

    1979-03-01

    Sodium compatibility screening tests were performed on several commercial austenitic alloys at 700 0 C for 2000 hours for applications as breeder reactor fuel cladding. The sodium-exposed surfaces were characterized by Optical Metallography, Scanning Electron Microscopy (SEM) and Electron Probe Micro Analysis (EPMA). Sodium exposure generally resulted in the depletion of Ni, Cr, Ti, Si, Mn and Nb, and enrichment of Fe and Mo at the surface. The average thickness of the depleted zone was 5 μm. The alloys can be divided into three groups based on corrosion rate, and each group has its own characteristic surface structure. Grain-orientation dependent striations were seen in alloys with low corrosion rates, while alloys with intermediate corrosion rates displayed micron-size nodes enriched with Fe and Mo. The high corrosion rate alloys exhibited scale-like formations on the surface with irregularly shaped holes. In addition, the data importantly point out that a ferrite layer will form at the sodium-exposed surface of these austenitic alloys after prolonged exposure

  15. Cytogenetic damage in human blood lymphocytes exposed in vitro and in vivo to space-relevant HZE-particles

    Science.gov (United States)

    Lee, Ryonfa; Nasonova, Elena; Sommer, Sylvester; Hartel, Carola; Ritter, Sylvia

    During space missions astronauts are exposed to cosmic radiations which are different from natural background radiation on Earth in both quantity and quality. Dose rate in space environment is at least 100 times higher than that on Earth. In addition, the natural radiation on Earth consists mainly of X-, γ-rays and α-emitters, while in space charged particles from protons to iron ions are predominant. The composition of radiation environment of outer space is well understood, however, due to a lack of data on the biological effects of dose, dose-rate and especially HZE (high charge Z and energy E) particles, large uncertainties exist in estimating the health risks for long-term space mission. To contribute to this issue, we investigated cytogenetic damage induced by heavy charged particles in human lymphocytes, since chromosome aberration yield is a biomarker showing an association with cancer risk. Lymphocytes collected from a healthy donor were irradiated with carbon ions (C-ions) in vitro with various energies (11.4 to 400 MeV/u; LET values 11 to 175 keV/µm) at either UNILAC or SIS facility (GSI, Germany) or exposed to X-rays. Additionally, peripheral blood was obtained from prostate cancer patients, treated with intensity modulated radiation therapy (IMRT) or IMRT combined with C-ion boost. Samples were taken before, during and after the radiotherapy. Chromosome samples were stained with FPG-technique to enable aberration analysis in 1st cycle metaphases. After in vitro exposure to C-ions, RBE values for the induction of chromosome aberrations increased with sampling time. The effect was most pronounced in samples exposed to 175 keV/µm C-ions and can be attributed to a pronounced cell cycle delay of heavily damaged cells. Thus, for a reliable risk assessment, the effect of selective cell cycle delay following particle exposure should be taken into account. M-FISH analysis of selected samples to assess aberration quality revealed higher frequencies of

  16. Energy Accommodation from Surface Catalyzed Reactions in Air Plasmas

    Data.gov (United States)

    National Aeronautics and Space Administration — Understanding energy transport at the gas-surface interface between catalytic/reacting surfaces exposed to highly dissociated plasmas remains a significant research...

  17. Water infiltration into exposed fractured rock surfaces

    International Nuclear Information System (INIS)

    Rasmussen, T.C.; Evans, D.D.

    1993-01-01

    Fractured rock media are present at many existing and potential waste disposal sites, yet characterization data and physical relationships are not well developed for such media. This study focused on water infiltration characteristics of an exposed fractured rock as an approach for defining the upper boundary condition for unsaturated-zone water percolation and contaminant transport modeling. Two adjacent watersheds of 0.24 and 1.73 ha with slopes up to 45% were instrumented for measuring rainfall and runoff. Fracture density was measured from readily observable fracture traces on the surface. Three methods were employed to evaluate the rainfall-runoff relationship. The first method used the annual totals and indicated that only 22.5% of rainfall occurred as runoff for the 1990-1991 water year, which demonstrates a high water intake rate by the exposed fracture system. The second method employed total rainfall and runoff for individual storms in conjunction with the commonly used USDA Soil Conservation Service curve number method developed for wide ranges of soils and vegetation. Curve numbers between 75 and 85 were observed for summer and winter storms with dry antecedent runoff conditions, while values exceeded 90 for wet conditions. The third method used a mass-balance approach for four major storms, which indicated that water intake rates ranged from 2.0 to 7.3 mm h -1 , yielding fracture intake velocities ranging from 122 to 293 m h -1 . The three analyses show the complexity of the infiltration process for fractured rock. However, they contribute to a better understanding of the upper boundary condition for predicting contaminant transport through an unsaturated fractured rock medium. 17 refs., 4 figs., 1 tab

  18. Zero mean curvature surfaces of mixed type in Minkowski space

    International Nuclear Information System (INIS)

    Klyachin, V A

    2003-01-01

    We investigate zero mean curvature surfaces in the Minkowski space R 3 1 such that their first fundamental quadratic form changes signature. Part of such a surface is space-like and part is time-like. We obtain complete information about the structure of the set of points where the surface changes type and prove the related existence and uniqueness theorems

  19. Molecular-dynamics analysis of mobile helium cluster reactions near surfaces of plasma-exposed tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Hu, Lin; Maroudas, Dimitrios, E-mail: maroudas@ecs.umass.edu [Department of Chemical Engineering, University of Massachusetts, Amherst, Massachusetts 01003-9303 (United States); Hammond, Karl D. [Department of Chemical Engineering, University of Missouri, Columbia, Missouri 65211 (United States); Wirth, Brian D. [Department of Nuclear Engineering, University of Tennessee, Knoxville, Tennessee 37996 (United States)

    2015-10-28

    We report the results of a systematic atomic-scale analysis of the reactions of small mobile helium clusters (He{sub n}, 4 ≤ n ≤ 7) near low-Miller-index tungsten (W) surfaces, aiming at a fundamental understanding of the near-surface dynamics of helium-carrying species in plasma-exposed tungsten. These small mobile helium clusters are attracted to the surface and migrate to the surface by Fickian diffusion and drift due to the thermodynamic driving force for surface segregation. As the clusters migrate toward the surface, trap mutation (TM) and cluster dissociation reactions are activated at rates higher than in the bulk. TM produces W adatoms and immobile complexes of helium clusters surrounding W vacancies located within the lattice planes at a short distance from the surface. These reactions are identified and characterized in detail based on the analysis of a large number of molecular-dynamics trajectories for each such mobile cluster near W(100), W(110), and W(111) surfaces. TM is found to be the dominant cluster reaction for all cluster and surface combinations, except for the He{sub 4} and He{sub 5} clusters near W(100) where cluster partial dissociation following TM dominates. We find that there exists a critical cluster size, n = 4 near W(100) and W(111) and n = 5 near W(110), beyond which the formation of multiple W adatoms and vacancies in the TM reactions is observed. The identified cluster reactions are responsible for important structural, morphological, and compositional features in the plasma-exposed tungsten, including surface adatom populations, near-surface immobile helium-vacancy complexes, and retained helium content, which are expected to influence the amount of hydrogen re-cycling and tritium retention in fusion tokamaks.

  20. Surface chloride salt formation on Space Shuttle exhaust alumina

    Science.gov (United States)

    Cofer, W. R., III; Pellett, G. L.; Sebacher, D. I.; Wakelyn, N. T.

    1984-01-01

    Aluminum oxide samples from the exhaust of Space Shuttle launches STS-1, STS-4, STS-5, and STS-6 were collected from surfaces on or around the launch pad complex and chemically analyzed. The results indicate that the particulate solid-propellant rocket motor (SRM) alumina was heavily chlorided. Concentrations of water-soluble aluminum (III) ion were large, suggesting that the surface of the SRM alumina particles was rendered soluble by prior reactions with HCl and H2O in the SRM exhaust cloud. These results suggest that Space Shuttle exhaust alumina particles are good sites for nucleation and condensation of atmospheric water. Laboratory experiments conducted at 220 C suggest that partial surface chloriding of alumina may occur in hot Space Shuttle exhaust plumes.

  1. On the invariant theory of Weingarten surfaces in Euclidean space

    International Nuclear Information System (INIS)

    Ganchev, Georgi; Mihova, Vesselka

    2010-01-01

    On any Weingarten surface in Euclidean space (strongly regular or rotational), we introduce locally geometric principal parameters and prove that such a surface is determined uniquely up to a motion by a special invariant function, which satisfies a natural nonlinear partial differential equation. This result can be interpreted as a solution to the Lund-Regge reduction problem for Weingarten surfaces in Euclidean space. We apply this theory to fractional-linear Weingarten surfaces and obtain the nonlinear partial differential equations describing them.

  2. An Exposed-Core Grapefruit Fibers Based Surface Plasmon Resonance Sensor

    Directory of Open Access Journals (Sweden)

    Xianchao Yang

    2015-07-01

    Full Text Available To solve the problem of air hole coating and analyte filling in microstructured optical fiber-based surface plasmon resonance (SPR sensors, we designed an exposed-core grapefruit fiber (EC-GFs-based SPR sensor. The exposed section of the EC-GF is coated with a SPR, supporting thin silver film, which can sense the analyte in the external environment. The asymmetrically coated fiber can support two separate resonance peaks (x- and y-polarized peaks with orthogonal polarizations and x-polarized peak, providing a much higher peak loss than y-polarized, also the x-polarized peak has higher wavelength and amplitude sensitivities. A large analyte refractive index (RI range from 1.33 to 1.42 is calculated to investigate the sensing performance of the sensor, and an extremely high wavelength sensitivity of 13,500 nm/refractive index unit (RIU is obtained. The silver layer thickness, which may affect the sensing performance, is also discussed. This work can provide a reference for developing a high sensitivity, real-time, fast-response, and distributed SPR RI sensor.

  3. General Rotational Surfaces in Pseudo-Euclidean 4-Space with Neutral Metric

    OpenAIRE

    Aleksieva, Yana; Milousheva, Velichka; Turgay, Nurettin Cenk

    2016-01-01

    We define general rotational surfaces of elliptic and hyperbolic type in the pseudo-Euclidean 4-space with neutral metric which are analogous to the general rotational surfaces of C. Moore in the Euclidean 4-space. We study Lorentz general rotational surfaces with plane meridian curves and give the complete classification of minimal general rotational surfaces of elliptic and hyperbolic type, general rotational surfaces with parallel normalized mean curvature vector field, flat general rotati...

  4. On the Stability of Deinoxanthin Exposed to Mars Conditions during a Long-Term Space Mission and Implications for Biomarker Detection on Other Planets

    Directory of Open Access Journals (Sweden)

    Stefan Leuko

    2017-09-01

    Full Text Available Outer space, the final frontier, is a hostile and unforgiving place for any form of life as we know it. The unique environment of space allows for a close simulation of Mars surface conditions that cannot be simulated as accurately on the Earth. For this experiment, we tested the resistance of Deinococcus radiodurans to survive exposure to simulated Mars-like conditions in low-Earth orbit for a prolonged period of time as part of the Biology and Mars experiment (BIOMEX project. Special focus was placed on the integrity of the carotenoid deinoxanthin, which may serve as a potential biomarker to search for remnants of life on other planets. Survival was investigated by evaluating colony forming units, damage inflicted to the 16S rRNA gene by quantitative PCR, and the integrity and detectability of deinoxanthin by Raman spectroscopy. Exposure to space conditions had a strong detrimental effect on the survival of the strains and the 16S rRNA integrity, yet results show that deinoxanthin survives exposure to conditions as they prevail on Mars. Solar radiation is not only strongly detrimental to the survival and 16S rRNA integrity but also to the Raman signal of deinoxanthin. Samples not exposed to solar radiation showed only minuscule signs of deterioration. To test whether deinoxanthin is able to withstand the tested parameters without the protection of the cell, it was extracted from cell homogenate and exposed to high/low temperatures, vacuum, germicidal UV-C radiation, and simulated solar radiation. Results obtained by Raman investigations showed a strong resistance of deinoxanthin against outer space and Mars conditions, with the only exception of the exposure to simulated solar radiation. Therefore, deinoxanthin proved to be a suitable easily detectable biomarker for the search of Earth-like organic pigment-containing life on other planets.

  5. Surface analyses of TiC coated molybdenum limiter material exposed to high heat flux electron beam

    International Nuclear Information System (INIS)

    Onozuka, M.; Uchikawa, T.; Yamao, H.; Kawai, H.; Kousaku, A.; Nakamura, H.; Niikura, S.

    1987-01-01

    Observation and surface analyses of TiC coated molybdenum exposed to high heat flux have been performed to study thermal damage resistance of TiC coated molybdenum limiter material. High heat loads were provided by a 120 kW electron beam facility. SEM, AES and EPMA have been applied to the surface analyses

  6. Metabolism of tritium uptake due to handling of metal surfaces exposed to tritiated hydrogen gas

    International Nuclear Information System (INIS)

    Johnson, J.R.; Peterman, B.F.

    1987-08-01

    Hairless rats were exposed to tritium by rubbing HT contaminated stainless steel planchets on them. The pattern of tritium excretion in the urine (n=4), shows the OBT (organically bound tritium) retention curve to be approximated by the sum of 2 exponential curves, one with a half-life of 0.4 days and another with a half-life of 1.4 days. The retention of HTO fit a single exponential curve with a half-life of 3.1 days. Exposed skin, unexposed skin, liver, muscle and blood (n=6) were assayed for HBO, and free HTO. Highest activity was found in the exposed skin, other organs with high activity are the unexposed skin and liver. Examination of the exposed skin showed HTO to be concentrated in the uppermost layers. The distribution of OBT was similar but was incorporated at a faster rate. The basal layer is exposed to a tritium concentration between 70-90% of that of the surface. The two macromolecule fractions with the highest amount of radioactivity were lipid and insoluble protein (mainly collagen)

  7. Methods to introduce sub-micrometer, symmetry-breaking surface corrugation to silicon substrates to increase light trapping

    Energy Technology Data Exchange (ETDEWEB)

    Han, Sang Eon; Hoard, Brittany R.; Han, Sang M.; Ghosh, Swapnadip

    2018-04-10

    Provided is a method for fabricating a nanopatterned surface. The method includes forming a mask on a substrate, patterning the substrate to include a plurality of symmetry-breaking surface corrugations, and removing the mask. The mask includes a pattern defined by mask material portions that cover first surface portions of the substrate and a plurality of mask space portions that expose second surface portions of the substrate, wherein the plurality of mask space portions are arranged in a lattice arrangement having a row and column, and the row is not oriented parallel to a [110] direction of the substrate. The patterning the substrate includes anisotropically removing portions of the substrate exposed by the plurality of spaces.

  8. Deuterium retention and surface modification of tungsten macrobrush samples exposed in FTU Tokamak

    Science.gov (United States)

    Maddaluno, G.; Giacomi, G.; Rufoloni, A.; Verdini, L.

    2007-06-01

    The effect of discrete structures such as macrobrush or castellated surfaces on power handling and deuterium retention of plasma facing components is to be assessed since such geometrical configurations are needed for increasing the lifetime of the armour to heat-sink joint. Four small macrobrush W and W + 1%La2O3 samples have been exposed in the Frascati Tokamak Upgrade (FTU) scrape-off layer up to the last closed flux surface by means of the Sample Introduction System. FTU is an all metal machine with no carbon source inside vacuum vessel; it exhibits ITER relevant energy and particle fluxes on the plasma facing components. Here, results on morphological surface changes (SEM), chemical composition (EDX) and deuterium retention (TDS) are reported.

  9. Radiation durability and functional reliability of polymeric materials in space systems

    International Nuclear Information System (INIS)

    Haruvy, Y.

    1990-01-01

    Polymeric materials are preferred for the light-weight construction of space-systems. Materials in space systems are required to fulfill a complete set of specifications, at utmost reliability, throughout the whole period of service in space, while being exposed to the hazardous influence of the space environment. The major threats of the space environment in orbits at the geostationary altitude (GSO) arise from ionizing radiations, the main constituents of which are highly energetic protons (affecting mainly the surface) and fast electrons (which produce the main threat to the electronic components). The maximum dose of ionizing radiation (within the limits of uncertainty of the calculations) at the surface of a material mounted on a space system, namely the ''Skin-Dose'', is ca. 2500 Mrads/yr. Space systems such as telecommunication satellites are planned to serve for prolonged periods of 30 years and longer. The cumulative predicted dose of ionizing-radiation over such periods presents a severe threat of chemical degradation to most of the polymeric construction materials commonly utilized in space systems. The reliability of each of the polymeric materials must be evaluated in detail, considering each of the relevant typical threats, such as ionizing-radiation, UV radiation, meteoroides flux, thermal cycling and ultra-high vacuum. For each of the exposed materials, conservation of the set of functional characteristics such as mechanical integrity, electrical and thermo-optical properties, electrical conductivity, surface charging and outgassing properties, which may cause contamination of neighboring systems, is evaluated. The reliability of functioning of the materials exposed to the space environment can thus be predicted, utilizing data from the literature, experimental results reported from space flights and laboratory simulations, and by chemical similarity of untested polymers to others. (author)

  10. Combined Contamination and Space Environmental Effects on Solar Cells and Thermal Control Surfaces

    Science.gov (United States)

    Dever, Joyce A.; Bruckner, Eric J.; Scheiman, David A.; Stidham, Curtis R.

    1994-01-01

    For spacecraft in low Earth orbit (LEO), contamination can occur from thruster fuel, sputter contamination products and from products of silicone degradation. This paper describes laboratory testing in which solar cell materials and thermal control surfaces were exposed to simulated spacecraft environmental effects including contamination, atomic oxygen, ultraviolet radiation and thermal cycling. The objective of these experiments was to determine how the interaction of the natural LEO environmental effects with contaminated spacecraft surfaces impacts the performance of these materials. Optical properties of samples were measured and solar cell performance data was obtained. In general, exposure to contamination by thruster fuel resulted in degradation of solar absorptance for fused silica and various thermal control surfaces and degradation of solar cell performance. Fused silica samples which were subsequently exposed to an atomic oxygen/vacuum ultraviolet radiation environment showed reversal of this degradation. These results imply that solar cells and thermal control surfaces which are susceptible to thruster fuel contamination and which also receive atomic oxygen exposure may not undergo significant performance degradation. Materials which were exposed to only vacuum ultraviolet radiation subsequent to contamination showed slight additional degradation in solar absorptance.

  11. Experimental Investigation of Space Radiation Processing in Lunar Soil Ilmenite: Combining Perspectives from Surface Science and Transmission Electron Microscopy

    Science.gov (United States)

    Christoffersen, R.; Keller, L. P.; Rahman, Z.; Baragiola, R.

    2010-01-01

    Energetic ions mostly from the solar wind play a major role in lunar space weathering because they contribute structural and chemical changes to the space-exposed surfaces of lunar regolith grains. In mature mare soils, ilmenite (FeTiO3) grains in the finest size fraction have been shown in transmission electron microscope (TEM) studies to exhibit key differences in their response to space radiation processing relative to silicates [1,2,3]. In ilmenite, solar ion radiation alters host grain outer margins to produce 10-100 nm thick layers that are microstructurally complex, but dominantly crystalline compared to the amorphous radiation-processed rims on silicates [1,2,3]. Spatially well-resolved analytical TEM measurements also show nm-scale compositional and chemical state changes in these layers [1,3]. These include shifts in Fe/Ti ratio from strong surface Fe-enrichment (Fe/Ti >> 1), to Fe depletion (Fe/Ti < 1) at 40-50 nm below the grain surface [1,3]. These compositional changes are not observed in the radiation-processed rims on silicates [4]. Several mechanism(s) to explain the overall relations in the ilmenite grain rims by radiation processing and/or additional space weathering processes were proposed by [1], and remain under current consideration [3]. A key issue has concerned the ability of ion radiation processing alone to produce some of the deeper- penetrating compositional changes. In order to provide some experimental constraints on these questions, we have performed a combined X-ray photoelectron spectroscopy (XPS) and field-emission scanning transmission electron (FE-STEM) study of experimentally ion-irradiated ilmenite. A key feature of this work is the combination of analytical techniques sensitive to changes in the irradiated samples at depth scales going from the immediate surface (approx.5 nm; XPS), to deeper in the grain interior (5-100 nm; FE-STEM).

  12. Microcanonical rates, gap times, and phase space dividing surfaces

    NARCIS (Netherlands)

    Ezra, Gregory S.; Waalkens, Holger; Wiggins, Stephen

    2009-01-01

    The general approach to classical unimolecular reaction rates due to Thiele is revisited in light of recent advances in the phase space formulation of transition state theory for multidimensional systems. Key concepts, such as the phase space dividing surface separating reactants from products, the

  13. "PROCESS and UVolution: photochemistry experiments in Low Earth Orbit": investigation of the photostability of organic and mineral material exposed to Mars surface UV radiation conditions

    Science.gov (United States)

    Stalport, Fabien; Guan, Yuan Yong; Noblet, Audrey; Coll, Patrice; Szopa, Cyril; Macari, Frederique; Person, Alain; Chaput, Didier; Raulin, Francois; Cottin, Hervé

    The harsh martian environment could explain the lack of organics and minerals such as car-bonates by destroying them: i) no organic molecule has been found at the two different landing sites of the Viking landers within the detection limits of the instruments onboard, ii) to date, no large deposits of carbonates have been detected and their detection is specific of local ar-eas and in very low amounts. In this context several experimental and numerical modelling studies were led to evaluate the possibility for the destruction or evolution of the organics and carbonates under the martian surface environmental conditions. The presence of UV radiation has been proposed to explain the photodecomposition of such material. This is the reason why, to investigate the nature, abundance, and stability of organic and mineral material that could survive under such environmental conditions, we exposed in low Earth orbit organic molecules and carbonates (also biominerals) with martian relevance to solar UV radiation ¿ 200 nm, in the frame of the experiment UVolution, onboard the BIOPAN ESA module which was set outside a Russian Foton automated capsule and exposed to space condition during 12 days in September 2007, and the experiment PROCESS (hervé peux tu rajouter quelques infos sur le temps exact d'exposition stp) which was set outside the International Space Station (ISS). Here, we present results with regard to the impact of solar UV radiation on the targeted molecules. Preliminary results indicate that that no organic sample seems to resist to the solar UV radiation if directly exposed to it. Conversely our results show that the exposed carbonates seem to be stable to the solar UV radiation if directly exposed to it. Moreover, the stability of the biominerals strengthens the interest to explore deeper their potential as life records at Mars. Hence they should be considered as primary targets for in situ analyses during future missions.

  14. A Class of Weingarten Surfaces in Euclidean 3-Space

    Directory of Open Access Journals (Sweden)

    Yu Fu

    2013-01-01

    Full Text Available The class of biconservative surfaces in Euclidean 3-space 3 are defined in (Caddeo et al., 2012 by the equation A(grad H=-H grad H for the mean curvature function H and the Weingarten operator A. In this paper, we consider the more general case that surfaces in 3 satisfying A(grad H=kH grad H for some constant k are called generalized bi-conservative surfaces. We show that this class of surfaces are linear Weingarten surfaces. We also give a complete classification of generalized bi-conservative surfaces in 3.

  15. Advanced Space Surface Systems Operations

    Science.gov (United States)

    Huffaker, Zachary Lynn; Mueller, Robert P.

    2014-01-01

    The importance of advanced surface systems is becoming increasingly relevant in the modern age of space technology. Specifically, projects pursued by the Granular Mechanics and Regolith Operations (GMRO) Lab are unparalleled in the field of planetary resourcefulness. This internship opportunity involved projects that support properly utilizing natural resources from other celestial bodies. Beginning with the tele-robotic workstation, mechanical upgrades were necessary to consider for specific portions of the workstation consoles and successfully designed in concept. This would provide more means for innovation and creativity concerning advanced robotic operations. Project RASSOR is a regolith excavator robot whose primary objective is to mine, store, and dump regolith efficiently on other planetary surfaces. Mechanical adjustments were made to improve this robot's functionality, although there were some minor system changes left to perform before the opportunity ended. On the topic of excavator robots, the notes taken by the GMRO staff during the 2013 and 2014 Robotic Mining Competitions were effectively organized and analyzed for logistical purposes. Lessons learned from these annual competitions at Kennedy Space Center are greatly influential to the GMRO engineers and roboticists. Another project that GMRO staff support is Project Morpheus. Support for this project included successfully producing mathematical models of the eroded landing pad surface for the vertical testbed vehicle to predict a timeline for pad reparation. And finally, the last project this opportunity made contribution to was Project Neo, a project exterior to GMRO Lab projects, which focuses on rocket propulsion systems. Additions were successfully installed to the support structure of an original vertical testbed rocket engine, thus making progress towards futuristic test firings in which data will be analyzed by students affiliated with Rocket University. Each project will be explained in

  16. Droplet impaction on solid surfaces exposed to impinging jet fires

    Energy Technology Data Exchange (ETDEWEB)

    Kazemi, Zia

    2005-12-15

    The thermal response of hot surfaces exposed to impinging jet fire and subsequent impacting water droplets is investigated. The research was done mainly experimentally by utilizing three different concepts. This included experiments on a laboratory scale steel plate and large outdoor fire tests with a quadratic steel channel and steel plates. Besides the horizontal jet flame itself was characterized in a comprehensive study. As a comparative study, the last three types of the experiment were additionally modeled by the CFD-code Kameleon FireEx for validation of results. The purpose of the experiments done on bench scale steel plate (L x W x T : 300 x 200 x 8 mm) was mainly to map data on wetting temperature, water droplet size, droplet impingement angle, and droplet velocity prior to large scale jet fire tests. The droplet release angle normal to hot surface gives best cooling effect, when the surface is oriented in upright position. The partial wetting begins at about 165 degrees C. When the surface is positioned in horizontal plane, the droplet of about 5 mm in diameter wets the hot surface partially at around 240-250 degrees C within an impaction distance of 20 cm. At about 150 degrees C, the droplet is entirely attached to the surface with almost zero contact angle, and cools down the solid at a critical heat flux equivalent to 1750 kW/m{sup 2}. The cooling effectiveness is about 8 % with a Weber number of 68. Although in the event of horizontal channel (L x W x T : 1000 x 200 x 8 mm) water droplets were not applied, however, the knowledge gained with jet fire tests gave valuable information about temperature progress in solids (steels and insulation) and their response to impinging jet fire during long duration experiments. The temperature of the insulated area of the channel keeps 200 degrees C below that of the exposed surface, as long as the insulation material remained intact. Upon long test fire durations, the insulation either burns or degrades despite

  17. Imaging the Surfaces of Stars from Space

    Science.gov (United States)

    Carpenter, Kenneth; Rau, Gioia

    2018-04-01

    Imaging of Stellar Surfacess has been dominated to-date by ground-based observations, but space-based facilities offer tremendous potential for extending the wavelength coverage and ultimately the resolution of such efforts. We review the imaging accomplished so far from space and then talk about exciting future prospects. The earliest attempts from space indirectly produced surface maps via the Doppler Imaging Technique, using UV spectra obtained with the International Ultraviolet Explorer (IUE). Later, the first direct UV images were obtained with the Hubble Space Telescope (HST), of Mira and Betelgeuse, using the Faint Object Camera (FOC). We will show this work and then investigate prospects for IR imaging with the James Webb Space Telescope (JWST). The real potential of space-based Imaging of Stellar Surfacess, however, lies in the future, when large-baseline Fizeau interferometers, such as the UV-optical Stellar Imager (SI) Vision Mission, with a 30-element array and 500m max baseline, are flown. We describe SI and its science goals, which include 0.1 milli-arcsec spectral Imaging of Stellar Surfacess and the probing of internal structure and flows via asteroseismology.

  18. Microparticle impacts in space: Results from Solar Max and shuttle witness plate inspections

    Science.gov (United States)

    Mckay, David S.

    1989-01-01

    The Solar Maximum Satellite developed electronic problems after operating successfully in space for several years. Astronauts on Space Shuttle mission STS-41C retrieved the satellite into the orbiter cargo bay, replaced defective components, and re-deployed the repaired satellite into orbit. The defective components were returned to Earth for study. The space-exposed surfaces were examined. The approach and objectives were to: document morphology of impact; find and analyze projectile residue; classify impact by origin; determine flux distribution; and determine implications for space exposure. The purpose of the shuttle witness plate experiment was to detect impacts from PAM D2 solid rocket motor; determine flux and size distribution of particles; and determine abrasion effects on various conditions. Results are given for aluminum surfaces, copper surfaces, stainless steel surfaces, Inconel surfaces, and quartz glass surfaces.

  19. Surface analyses of TiC coated molybdenum limiter material exposed to high heat flux electron beam

    International Nuclear Information System (INIS)

    Onozuka, M.; Uchikawa, T.; Yamao, H.; Kawai, H.; Kousaku, A.; Nakamura, H.; Niikura, S.

    1986-01-01

    Observation and surface analyses of TiC coated molybdenum exposed to high heat flux have been performed to study thermal damage resistance of TiC coated molybdenum limiter material. High heat loads were provided by a 120 kW electron beam facility. (author)

  20. Exposure of phototrophs to 548 days in low Earth orbit: microbial selection pressures in outer space and on early earth.

    Science.gov (United States)

    Cockell, Charles S; Rettberg, Petra; Rabbow, Elke; Olsson-Francis, Karen

    2011-10-01

    An epilithic microbial community was launched into low Earth orbit, and exposed to conditions in outer space for 548 days on the European Space Agency EXPOSE-E facility outside the International Space Station. The natural phototroph biofilm was augmented with akinetes of Anabaena cylindrica and vegetative cells of Nostoc commune and Chroococcidiopsis. In space-exposed dark controls, two algae (Chlorella and Rosenvingiella spp.), a cyanobacterium (Gloeocapsa sp.) and two bacteria associated with the natural community survived. Of the augmented organisms, cells of A. cylindrica and Chroococcidiopsis survived, but no cells of N. commune. Only cells of Chroococcidiopsis were cultured from samples exposed to the unattenuated extraterrestrial ultraviolet (UV) spectrum (>110 nm or 200 nm). Raman spectroscopy and bright-field microscopy showed that under these conditions the surface cells were bleached and their carotenoids were destroyed, although cell morphology was preserved. These experiments demonstrate that outer space can act as a selection pressure on the composition of microbial communities. The results obtained from samples exposed to >200 nm UV (simulating the putative worst-case UV exposure on the early Earth) demonstrate the potential for epilithic colonization of land masses during that time, but that UV radiation on anoxic planets can act as a strong selection pressure on surface-dwelling organisms. Finally, these experiments have yielded new phototrophic organisms of potential use in biomass and oxygen production in space exploration.

  1. Aerogels Materials as Space Debris Collectors

    Directory of Open Access Journals (Sweden)

    Thierry Woignier

    2013-01-01

    Full Text Available Material degradation due to the specific space environment becomes a key parameter for space missions. The use of large surface of brittle materials on satellites can produce, if impacted by hypervelocity particles, ejected volumes of mater 100 times higher than the impacting one. The presented work is devoted to the use of silica aerogels as passive detectors. Aerogels have been exposed to the low earth orbit of the ISS for 18 months. The study describes the aerogels process and the choice of synthesis parameters in such a way to get expected features in terms of porosity, mechanical properties, internal stresses, and transparency. Low-density aerogels (0.09 g·cm−3 have been prepared. The control of transparency necessary to see and identify particles and fragments collected is obtained using a base catalysis during gel synthesis. After return to earth, the aerogels samples have been observed using optical microscopy to detect and quantify craters on the exposed surface. First results obtained on a small part of the aerogels indicate a large number of debris collected in the materials.

  2. Interrogating the Plasmodium Sporozoite Surface: Identification of Surface-Exposed Proteins and Demonstration of Glycosylation on CSP and TRAP by Mass Spectrometry-Based Proteomics.

    Directory of Open Access Journals (Sweden)

    Kristian E Swearingen

    2016-04-01

    Full Text Available Malaria parasite infection is initiated by the mosquito-transmitted sporozoite stage, a highly motile invasive cell that targets hepatocytes in the liver for infection. A promising approach to developing a malaria vaccine is the use of proteins located on the sporozoite surface as antigens to elicit humoral immune responses that prevent the establishment of infection. Very little of the P. falciparum genome has been considered as potential vaccine targets, and candidate vaccines have been almost exclusively based on single antigens, generating the need for novel target identification. The most advanced malaria vaccine to date, RTS,S, a subunit vaccine consisting of a portion of the major surface protein circumsporozoite protein (CSP, conferred limited protection in Phase III trials, falling short of community-established vaccine efficacy goals. In striking contrast to the limited protection seen in current vaccine trials, sterilizing immunity can be achieved by immunization with radiation-attenuated sporozoites, suggesting that more potent protection may be achievable with a multivalent protein vaccine. Here, we provide the most comprehensive analysis to date of proteins located on the surface of or secreted by Plasmodium falciparum salivary gland sporozoites. We used chemical labeling to isolate surface-exposed proteins on sporozoites and identified these proteins by mass spectrometry. We validated several of these targets and also provide evidence that components of the inner membrane complex are in fact surface-exposed and accessible to antibodies in live sporozoites. Finally, our mass spectrometry data provide the first direct evidence that the Plasmodium surface proteins CSP and TRAP are glycosylated in sporozoites, a finding that could impact the selection of vaccine antigens.

  3. Surface Plasmon Scattering in Exposed Core Optical Fiber for Enhanced Resolution Refractive Index Sensing.

    Science.gov (United States)

    Klantsataya, Elizaveta; François, Alexandre; Ebendorff-Heidepriem, Heike; Hoffmann, Peter; Monro, Tanya M

    2015-09-29

    Refractometric sensors based on optical excitation of surface plasmons on the side of an optical fiber is an established sensing architecture that has enabled laboratory demonstrations of cost effective portable devices for biological and chemical applications. Here we report a Surface Plasmon Resonance (SPR) configuration realized in an Exposed Core Microstructured Optical Fiber (ECF) capable of optimizing both sensitivity and resolution. To the best of our knowledge, this is the first demonstration of fabrication of a rough metal coating suitable for spectral interrogation of scattered plasmonic wave using chemical electroless plating technique on a 10 μm diameter exposed core of the ECF. Performance of the sensor in terms of its refractive index sensitivity and full width at half maximum (FWHM) of SPR response is compared to that achieved with an unstructured bare core fiber with 140 μm core diameter. The experimental improvement in FWHM, and therefore the detection limit, is found to be a factor of two (75 nm for ECF in comparison to 150 nm for the large core fiber). Refractive index sensitivity of 1800 nm/RIU was achieved for both fibers in the sensing range of aqueous environment (1.33-1.37) suitable for biosensing applications.

  4. Plasma surface treatment to improve surface charge accumulation and dissipation of epoxy resin exposed to DC and nanosecond-pulse voltages

    Science.gov (United States)

    Zhang, Cheng; Lin, Haofan; Zhang, Shuai; Xie, Qin; Ren, Chengyan; Shao, Tao

    2017-10-01

    In this paper, deposition by non-thermal plasma is used as a surface modification technique to change the surface characteristics of epoxy resin exposed to DC and nanosecond-pulse voltages. The corresponding surface characteristics in both cases of DC and nanosecond-pulse voltages before and after the modification are compared and investigated. The measurement of the surface potential provides the surface charge distribution, which is used to show the accumulation and dissipation process of the surface charges. Morphology observations, chemical composition and electrical parameters measurements are used to evaluate the treatment effects. The experimental results show that, before the plasma treatment, the accumulated surface charges in the case of the DC voltage are more than that in the case of the nanosecond-pulse voltage. Moreover, the decay rate of the surface charges for the DC voltage is higher than that for the nanosecond-pulse voltage. However, the decay rate is no more than 41% after 1800 s for both types of voltages. After the plasma treatment, the maximum surface potentials decrease to 57.33% and 32.57% of their values before treatment for the DC and nanosecond-pulse voltages, respectively, indicating a decrease in the accumulated surface charges. The decay rate exceeds 90% for both types of voltages. These changes are mainly attributed to a change in the surface nanostructure, an increase in conductivity, and a decrease in the depth of energy level.

  5. Plasma surface treatment to improve surface charge accumulation and dissipation of epoxy resin exposed to DC and nanosecond-pulse voltages

    International Nuclear Information System (INIS)

    Zhang, Cheng; Lin, Haofan; Zhang, Shuai; Ren, Chengyan; Shao, Tao; Xie, Qin

    2017-01-01

    In this paper, deposition by non-thermal plasma is used as a surface modification technique to change the surface characteristics of epoxy resin exposed to DC and nanosecond-pulse voltages. The corresponding surface characteristics in both cases of DC and nanosecond-pulse voltages before and after the modification are compared and investigated. The measurement of the surface potential provides the surface charge distribution, which is used to show the accumulation and dissipation process of the surface charges. Morphology observations, chemical composition and electrical parameters measurements are used to evaluate the treatment effects. The experimental results show that, before the plasma treatment, the accumulated surface charges in the case of the DC voltage are more than that in the case of the nanosecond-pulse voltage. Moreover, the decay rate of the surface charges for the DC voltage is higher than that for the nanosecond-pulse voltage. However, the decay rate is no more than 41% after 1800 s for both types of voltages. After the plasma treatment, the maximum surface potentials decrease to 57.33% and 32.57% of their values before treatment for the DC and nanosecond-pulse voltages, respectively, indicating a decrease in the accumulated surface charges. The decay rate exceeds 90% for both types of voltages. These changes are mainly attributed to a change in the surface nanostructure, an increase in conductivity, and a decrease in the depth of energy level. (paper)

  6. Symplectic geometry on moduli spaces of holomorphic bundles over complex surfaces

    OpenAIRE

    Khesin, Boris; Rosly, Alexei

    2000-01-01

    We give a comparative description of the Poisson structures on the moduli spaces of flat connections on real surfaces and holomorphic Poisson structures on the moduli spaces of holomorphic bundles on complex surfaces. The symplectic leaves of the latter are classified by restrictions of the bundles to certain divisors. This can be regarded as fixing a "complex analogue of the holonomy" of a connection along a "complex analogue of the boundary" in analogy with the real case.

  7. Hydrogen isotope transport across tungsten surfaces exposed to a fusion relevant He ion fluence

    Science.gov (United States)

    Baldwin, M. J.; Doerner, R. P.

    2017-07-01

    Tungsten targets are exposed to controlled sequences of D2 and He, and He and D2 plasma in the Pisces-A linear plasma device, with a view to studying the outward and inward transport of D across a He implanted surface, using thermal desorption mass spectrometry. Differences in transport are interpreted from changes in peak desorption temperature and amplitude for D2 release, compared against that of control targets exposed to just D2 plasma. Desorption data are modeled with Tmap-7 to infer the nature by which He leads to the ‘reduced inventory’ effect for H isotope uptake. A dual segment (surface-30 nm, bulk) W Tmap-7 model is developed, that simulates both plasma exposure and thermal desorption. Good agreement between desorption data and model is found for D2 release from control targets provided that the implanted flux is reduced, similar to that reported by others. For He affected release, the H isotope transport properties of the surface segment are adjusted away from control target bulk values during the computation. Modeling that examines outward D transport through the He implanted layer suggests that a permeation barrier is active, but bubble induced porosity is insufficient to fully explain the barrier strength. Moderately increased diffusional migration energy in the model over the He affected region, however, gives a barrier strength consistent with experiment. The same model, applied to inward transport, predicts the reduced inventory effect, but a further reduction in the implanted D flux is necessary for precise agreement.

  8. Methylation and in vivo expression of the surface-exposed Leptospira interrogans outer-membrane protein OmpL32.

    Science.gov (United States)

    Eshghi, Azad; Pinne, Marija; Haake, David A; Zuerner, Richard L; Frank, Ami; Cameron, Caroline E

    2012-03-01

    Recent studies have revealed that bacterial protein methylation is a widespread post-translational modification that is required for virulence in selected pathogenic bacteria. In particular, altered methylation of outer-membrane proteins has been shown to modulate the effectiveness of the host immune response. In this study, 2D gel electrophoresis combined with MALDI-TOF MS identified a Leptospira interrogans serovar Copenhageni strain Fiocruz L1-130 protein, corresponding to ORF LIC11848, which undergoes extensive and differential methylation of glutamic acid residues. Immunofluorescence microscopy implicated LIC11848 as a surface-exposed outer-membrane protein, prompting the designation OmpL32. Indirect immunofluorescence microscopy of golden Syrian hamster liver and kidney sections revealed expression of OmpL32 during colonization of these organs. Identification of methylated surface-exposed outer-membrane proteins, such as OmpL32, provides a foundation for delineating the role of this post-translational modification in leptospiral virulence.

  9. A method for visualizing surface-exposed and internal PfEMP1 adhesion antigens in Plasmodium falciparum infected erythrocytes

    Directory of Open Access Journals (Sweden)

    Arnot David E

    2008-06-01

    Full Text Available Abstract Background The insertion of parasite antigens into the host erythrocyte membrane and the structure and distribution of Plasmodium falciparum adhesion receptors on that membrane are poorly understood. Laser scanning confocal microscopy (LSCM and a novel labelling and fixation method have been used to obtain high resolution immuno-fluorescent images of erythrocyte surface PfEMP1 and internal antigens which allow analysis of the accumulation of PfEMP1 on the erythrocyte membrane during asexual development. Methods A novel staining technique has been developed which permits distinction between erythrocyte surface PfEMP1 and intracellular PfEMP1, in parasites whose nuclear material is exceptionally well resolved. Primary antibody detection by fluorescence is carried out on the live parasitized erythrocyte. The surface labelled cells are then fixed using paraformaldehyde and permeabilized with a non-ionic detergent to permit access of antibodies to internal parasite antigens. Differentiation between surface and internal antigens is achieved using antibodies labelled with different fluorochromes and confocal microscopy Results Surface exposed PfEMP1 is first detectable by antibodies at the trophozoite stage of intracellular parasite development although the improved detection method indicates that there are differences between different laboratory isolates in the kinetics of accumulation of surface-exposed PfEMP1. Conclusion A sensitive method for labelling surface and internal PfEMP1 with up to three different fluorochromes has been developed for laser scanning confocal optical microscopy and the analysis of the developmental expression of malaria adhesion antigens.

  10. Standard practice for exposing and evaluating metals and alloys in surface seawater

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2000-01-01

    1.1 This practice covers conditions for the exposure of metals, alloys, and other materials in natural surface seawater such as those typically found in bays, harbors, channels, and so forth, as contrasted with deep ocean testing. This practice covers full immersion, tidal zone and related splash, and spray zone exposures. 1.2 This practice sets forth general procedures that should be followed in conducting seawater exposure tests so that meaningful comparisons may be made from one location to another. 1.3 This practice identifies recommended procedures for evaluating the effects of natural surface seawater on the materials exposed. 1.4 The values stated in SI units are to be regarded as the standard. The values given in parentheses are for information only. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regula...

  11. Surface Layer Fluorination-Modulated Space Charge Behaviors in HVDC Cable Accessory

    Directory of Open Access Journals (Sweden)

    Jin Li

    2018-05-01

    Full Text Available Space charges tend to accumulate on the surface and at the interface of ethylene–propylene–diene terpolymer (EPDM, serving as high voltage direct current (HVDC cable accessory insulation, which likely induces electrical field distortion and dielectric breakdown. Direct fluorination is an effective method to modify the surface characteristics of the EPDM without altering the bulk properties too much. In this paper, the surface morphology, hydrophobic properties, relative permittivity, and DC conductivity of the EPDM before and after fluorination treatment were tested. Furthermore, the surface and interface charge behaviors in the HVDC cable accessory were investigated by the pulsed electroacoustic (PEA method, and explained from the point of view of trap distribution. The results show that fluorination helps the EPDM polymer obtain lower surface energy and relative permittivity, which is beneficial to the interface match in composite insulation systems. The lowest degree of space charge accumulation occurs in EPDM with 30 min of fluorination. After analyzing the results of the 3D potentials and the density of states (DOS behaviors in EPDM before and after fluorination, it can be found that fluorination treatment introduces shallower electron traps, and the special electrostatic potential after fluorination can significantly suppress the space charge accumulation at the interface in the HVDC cable accessory.

  12. Surface potential distribution and airflow performance of different air-exposed electrode plasma actuators at different alternating current/direct current voltages

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Liang; Yan, Hui-Jie; Qi, Xiao-Hua; Hua, Yue; Ren, Chun-Sheng, E-mail: rchsh@dlut.edu.cn [School of Physics and Optoelectronic Technology, Key laboratory of Materials Modification by Laser, Ion and Electron Beams, Ministry of Education, Dalian University of Technology, Dalian 116023 (China)

    2015-04-15

    Asymmetric surface dielectric barrier discharge (SDBD) plasma actuators have been intensely studied for a number of years due to their potential applications for aerodynamic control. In this paper, four types of actuators with different configurations of exposed electrode are proposed. The SDBD actuators investigated are driven by dual-power supply, referred to as a fixed AC high voltage and an adjustable DC bias. The effects of the electrode structures on the dielectric surface potential distribution, the electric wind velocity, and the mean thrust production are studied, and the dominative factors of airflow acceleration behavior are revealed. The results have shown that the actions of the SDBD actuator are mainly dependent on the geometry of the exposed electrode. Besides, the surface potential distribution can effectively affect the airflow acceleration behavior. With the application of an appropriate additional DC bias, the surface potential will be modified. As a result, the performance of the electric wind produced by a single SDBD can be significantly improved. In addition, the work also illustrates that the actuators with more negative surface potential present better mechanical performance.

  13. Surface potential distribution and airflow performance of different air-exposed electrode plasma actuators at different alternating current/direct current voltages

    International Nuclear Information System (INIS)

    Yang, Liang; Yan, Hui-Jie; Qi, Xiao-Hua; Hua, Yue; Ren, Chun-Sheng

    2015-01-01

    Asymmetric surface dielectric barrier discharge (SDBD) plasma actuators have been intensely studied for a number of years due to their potential applications for aerodynamic control. In this paper, four types of actuators with different configurations of exposed electrode are proposed. The SDBD actuators investigated are driven by dual-power supply, referred to as a fixed AC high voltage and an adjustable DC bias. The effects of the electrode structures on the dielectric surface potential distribution, the electric wind velocity, and the mean thrust production are studied, and the dominative factors of airflow acceleration behavior are revealed. The results have shown that the actions of the SDBD actuator are mainly dependent on the geometry of the exposed electrode. Besides, the surface potential distribution can effectively affect the airflow acceleration behavior. With the application of an appropriate additional DC bias, the surface potential will be modified. As a result, the performance of the electric wind produced by a single SDBD can be significantly improved. In addition, the work also illustrates that the actuators with more negative surface potential present better mechanical performance

  14. Field desorption and field ion surface studies of samples exposed to the plasmas of PLT and ISX

    International Nuclear Information System (INIS)

    Kellogg, G.L.; Panitz, J.A.

    1978-01-01

    Modifications to the surface of field-ion specimens exposed to plasma discharges in PLT and ISX determined by Imaging Probe, Field Ion Microscope, and Transmission Electron Microscope analysis have in the past shown several consistent features. Surface films consisting primarily of limiter material with trapped plasma and impurity species have been found to reside on samples with direct line of sight exposure to the plasma during the discharges. Control specimens placed in the tokamak, but shielded from the plasma, on the other hand, remained free of deposits. When exposed to only high power plasma discharges, samples placed at the wall position in PLT and ISX have survived the exposures with no evidence of damage or implantation. In this paper we describe the results of a recent exposure in PLT in which for the first time samples of stainless steel were included for High-Field Surface Analysis. Tokamak operating conditions, including stainless-steel limiters, titanium gettering between discharges, and the occurrence of a disruption, also distinguished this exposure from those carried out previously. Surprisingly, even with stainless-steel limiters, carbon films were found to be deposited on the samples at a rate

  15. Plasma diagnostics surface analysis and interactions

    CERN Document Server

    Auciello, Orlando

    2013-01-01

    Plasmas and their interaction with materials have become subjects of major interest because of their importance in modern forefront technologies such as microelectronics, fusion energy, and space. Plasmas are used in microelectronics to process semiconductors (etching of patterns for microcircuits, plasma-induced deposition of thin films, etc.); plasmas produce deleterious erosion effects on surfaces of materials used for fusion devices and spaceships exposed to the low earth environment.Diagnostics of plasmas and materials exposed to them are fundamental to the understanding of the physical a

  16. The Picard group of the moduli space of r-Spin Riemann surfaces

    DEFF Research Database (Denmark)

    Randal-Williams, Oscar

    2012-01-01

    An r-Spin Riemann surface is a Riemann surface equipped with a choice of rth root of the (co)tangent bundle. We give a careful construction of the moduli space (orbifold) of r-Spin Riemann surfaces, and explain how to establish a Madsen–Weiss theorem for it. This allows us to prove the “Mumford...... conjecture” for these moduli spaces, but more interestingly allows us to compute their algebraic Picard groups (for g≥10, or g≥9 in the 2-Spin case). We give a complete description of these Picard groups, in terms of explicitly constructed line bundles....

  17. Spectrophotometric analysis of tomato plants produced from seeds exposed under space flight conditions for a long time

    Science.gov (United States)

    Nechitailo, Galina S.; Yurov, S.; Cojocaru, A.; Revin, A.

    The analysis of the lycopene and other carotenoids in tomatoes produced from seeds exposed under space flight conditions at the orbital station MIR for six years is presented in this work. Our previous experiments with tomato plants showed the germination of seeds to be 32%Genetic investigations revealed 18%in the experiment and 8%experiments were conducted to study the capacity of various stimulating factors to increase germination of seeds exposed for a long time to the action of space flight factors. An increase of 20%achieved but at the same time mutants having no analogues in the control variants were detected. For the present investigations of the third generation of plants produced from seeds stored for a long time under space flight conditions 80 tomatoes from forty plants were selected. The concentration of lycopene in the experimental specimens was 2.5-3 times higher than in the control variants. The spectrophotometric analysis of ripe tomatoes revealed typical three-peaked carotenoid spectra with a high maximum of lycopene (a medium maximum at 474 nm), a moderate maximum of its predecessor, phytoin, (a medium maximum at 267 nm) and a low maximum of carotenes. In green tomatoes, on the contrary, a high maximum of phytoin, a moderate maximum of lycopene and a low maximum of carotenes were observed. The results of the spectral analysis point to the retardation of biosynthesis of carotenes while the production of lycopene is increased and to the synthesis of lycopene from phytoin. Electric conduction of tomato juice in the experimental samples is increased thus suggesting higher amounts of carotenoids, including lycopene and electrolytes. The higher is the value of electric conduction of a specimen, the higher are the spectral maxima of lycopene. The hydrogen ion exponent of the juice of ripe tomatoes increases due to which the efficiency of ATP biosynthesis in cell mitochondria is likely to increase, too. The results demonstrating an increase in the content

  18. Observing at-surface irradiance and albedo from space : The Tibet experiment

    NARCIS (Netherlands)

    Roupioz, L.

    2015-01-01

    Monitoring the solar radiation budget on a daily basis is a prerequisite to study land surface processes, especially in climatology and hydrology, and in derived applications like drought early warning. Current space-born radiometers can provide daily observations to derive surface radiative fluxes

  19. Space environment effects on polymers in low earth orbit

    International Nuclear Information System (INIS)

    Grossman, E.; Gouzman, I.

    2003-01-01

    Polymers are widely used in space vehicles and systems as structural materials, thermal blankets, thermal control coatings, conformal coatings, adhesives, lubricants, etc. The low earth orbit (LEO) space environment includes hazards such as atomic oxygen, UV radiation, ionizing radiation (electrons, protons), high vacuum, plasma, micrometeoroids and debris, as well as severe temperature cycles. Exposure of polymers and composites to the space environment may result in different detrimental effects via modification of their chemical, electrical, thermal, optical and mechanical properties as well as surface erosion. The high vacuum induces material outgassing (e.g. low-molecular weight residues, plasticizers and additives) and consequent contamination of nearby surfaces. The present work reviews the LEO space environment constituents and their interactions with polymers. Examples of degradation of materials exposed in ground simulation facilities are presented. The issues discussed include the erosion mechanisms of polymers, formation of contaminants and their interaction with the space environment, and protection of materials from the harsh space environment

  20. Simulation of Martian surface-atmosphere interaction in a space-simulator: Technical considerations and feasibility

    Science.gov (United States)

    Moehlmann, D.; Kochan, H.

    1992-01-01

    The Space Simulator of the German Aerospace Research Establishment at Cologne, formerly used for testing satellites, is now, since 1987, the central unit within the research sub-program 'Comet-Simulation' (KOSI). The KOSI team has investigated physical processes relevant to comets and their surfaces. As a byproduct we gained experience in sample-handling under simulated space conditions. In broadening the scope of the research activities of the DLR Institute of Space Simulation an extension to 'Laboratory-Planetology' is planned. Following the KOSI-experiments a Mars Surface-Simulation with realistic minerals and surface soil in a suited environment (temperature, pressure, and CO2-atmosphere) is foreseen as the next step. Here, our main interest is centered on thermophysical properties of the Martian surface and energy transport (and related gas transport) through the surface. These laboratory simulation activities can be related to space missions as typical pre-mission and during-the-mission support of the experiments design and operations (simulation in parallel). Post mission experiments for confirmation and interpretation of results are of great value. The physical dimensions of the Space Simulator (cylinder of about 2.5 m diameter and 5 m length) allows for testing and qualification of experimental hardware under realistic Martian conditions.

  1. Mars Surface Environmental Issues

    Science.gov (United States)

    Charles, John

    2002-01-01

    Planetary exploration by astronauts will require extended periods of habitation on a planet's surface, under the influence of environmental factors that are different from those of Earth and the spacecraft that delivered the crew to the planet. Human exploration of Mars, a possible near-term planetary objective, can be considered a challenging scenario. Mission scenarios currently under consideration call for surface habitation periods of from 1 to 18 months on even the earliest expeditions. Methods: Environmental issues associated with Mars exploration have been investigated by NASA and the National Space Biomedical Research Institute (NSBRI) as part of the Bioastronautics Critical Path Roadmap Project (see http ://criticalpath.jsc.nasa.gov). Results: Arrival on Mars will immediately expose the crew to gravity only 38% of that at Earth's surface in possibly the first prolonged exposure to gravity other than the 1G of Earth's surface and the zero G of weightless space flight, with yet unknown effects on crew physiology. The radiation at Mars' surface is not well documented, although the planet's bulk and even its thin atmosphere may moderate the influx of galactic cosmic radiation and energetic protons from solar flares. Secondary radiation from activated components of the soil must also be considered. Ultrafine and larger respirable and nonrespirable particles in Martian dust introduced into the habitat after surface excursions may induce pulmonary inflammation exacerbated by the additive reactive and oxidizing nature of the dust. Stringent decontamination cannot eliminate mechanical and corrosive effects of the dust on pressure suits and exposed machinery. The biohazard potential of putative indigenous Martian microorganisms may be assessed by comparison with analog environments on Earth. Even in their absence, human microorganisms, if not properly controlled, can be a threat to the crew's health. Conclusions: Mars' surface offers a substantial challenge to the

  2. Surface treatment influences electrochemical stability of cpTi exposed to mouthwashes

    International Nuclear Information System (INIS)

    Beline, Thamara; Garcia, Camila S.; Ogawa, Erika S.; Marques, Isabella S.V.; Matos, Adaias O.; Sukotjo, Cortino; Mathew, Mathew T.

    2016-01-01

    The role of surface treatment on the electrochemical behavior of commercially pure titanium (cpTi) exposed to mouthwashes was tested. Seventy-five disks were divided into 15 groups according to surface treatment (machined, sandblasted with Al 2 O 3 , and acid etched) and electrolyte solution (artificial saliva — control, 0.12% chlorhexidine digluconate, 0.05% cetylpyridinium chloride, 0.2% sodium fluoride, and 1.5% hydrogen peroxide) (n = 5). Open-circuit-potential and electrochemical impedance spectroscopy were conducted at baseline and after 7 and 14 days of immersion in each solution. Potentiodynamic test and total weight loss of disks were performed after 14 days of immersion. Scanning electron microscopy, energy dispersive spectroscopy, white light interferometry and profilometry were conducted for surface characterization before and after the electrochemical tests. Sandblasting promoted the lowest polarization resistance (R p ) (P < .0001) and the highest capacitance (CPE) (P < .006), corrosion current density (I corr ) and corrosion rate (P < .0001). In contrast, acid etching increased R p and reduced CPE, independent to the mouthwash; while hydrogen peroxide reduced R p (P < .008) and increased I corr and corrosion rate (P < .0001). The highest CPE values were found for hydrogen peroxide and 0.2% sodium fluoride. Immersion for longer period improved the electrochemical stability of cpTi (P < .05). In conclusion, acid etching enhanced the electrochemical stability of cpTi. Hydrogen peroxide and sodium fluoride reduced the resistance to corrosion of cpTi, independent to the surface treatment. Chlorhexidine gluconate and cetylpyridinium chloride did not alter the corrosive behavior of cpTi. - Highlights: • Acid etching enhanced the electrochemical stability of cpTi. • Hydrogen peroxide and sodium fluoride reduced the corrosion resistance of cpTi. • Chlorhexidine gluconate and cetylpyridinium chloride can be safely used.

  3. Surface treatment influences electrochemical stability of cpTi exposed to mouthwashes

    Energy Technology Data Exchange (ETDEWEB)

    Beline, Thamara [Department of Prosthodontics and Periodontology, Piracicaba Dental School, University of Campinas (UNICAMP), Av Limeira, 901, Piracicaba, São Paulo 13414-903 (Brazil); IBTN/Br — Institute of Biomaterials, Tribocorrosion and Nanomedicine, Brazilian Branch (Brazil); Garcia, Camila S. [Department of Prosthodontics and Periodontology, Piracicaba Dental School, University of Campinas (UNICAMP), Av Limeira, 901, Piracicaba, São Paulo 13414-903 (Brazil); Ogawa, Erika S. [Department of Prosthodontics and Periodontology, Piracicaba Dental School, University of Campinas (UNICAMP), Av Limeira, 901, Piracicaba, São Paulo 13414-903 (Brazil); IBTN/Br — Institute of Biomaterials, Tribocorrosion and Nanomedicine, Brazilian Branch (Brazil); Marques, Isabella S.V. [Department of Prosthodontics and Periodontology, Piracicaba Dental School, University of Campinas (UNICAMP), Av Limeira, 901, Piracicaba, São Paulo 13414-903 (Brazil); Matos, Adaias O. [Department of Prosthodontics and Periodontology, Piracicaba Dental School, University of Campinas (UNICAMP), Av Limeira, 901, Piracicaba, São Paulo 13414-903 (Brazil); IBTN/Br — Institute of Biomaterials, Tribocorrosion and Nanomedicine, Brazilian Branch (Brazil); Sukotjo, Cortino [Department of Restorative Dentistry, University of Illinois at Chicago, College of Dentistry, 801 S Paulina, Chicago, IL 60612 (United States); IBTN — Institute of Biomaterials, Tribocorrosion and Nanomedicine (United States); Mathew, Mathew T. [IBTN — Institute of Biomaterials, Tribocorrosion and Nanomedicine (United States); Department of Orthopedic Surgery, Rush University Medical Center, 1611 W Harrison, Chicago, IL 60612 (United States); and others

    2016-02-01

    The role of surface treatment on the electrochemical behavior of commercially pure titanium (cpTi) exposed to mouthwashes was tested. Seventy-five disks were divided into 15 groups according to surface treatment (machined, sandblasted with Al{sub 2}O{sub 3}, and acid etched) and electrolyte solution (artificial saliva — control, 0.12% chlorhexidine digluconate, 0.05% cetylpyridinium chloride, 0.2% sodium fluoride, and 1.5% hydrogen peroxide) (n = 5). Open-circuit-potential and electrochemical impedance spectroscopy were conducted at baseline and after 7 and 14 days of immersion in each solution. Potentiodynamic test and total weight loss of disks were performed after 14 days of immersion. Scanning electron microscopy, energy dispersive spectroscopy, white light interferometry and profilometry were conducted for surface characterization before and after the electrochemical tests. Sandblasting promoted the lowest polarization resistance (R{sub p}) (P < .0001) and the highest capacitance (CPE) (P < .006), corrosion current density (I{sub corr}) and corrosion rate (P < .0001). In contrast, acid etching increased R{sub p} and reduced CPE, independent to the mouthwash; while hydrogen peroxide reduced R{sub p} (P < .008) and increased I{sub corr} and corrosion rate (P < .0001). The highest CPE values were found for hydrogen peroxide and 0.2% sodium fluoride. Immersion for longer period improved the electrochemical stability of cpTi (P < .05). In conclusion, acid etching enhanced the electrochemical stability of cpTi. Hydrogen peroxide and sodium fluoride reduced the resistance to corrosion of cpTi, independent to the surface treatment. Chlorhexidine gluconate and cetylpyridinium chloride did not alter the corrosive behavior of cpTi. - Highlights: • Acid etching enhanced the electrochemical stability of cpTi. • Hydrogen peroxide and sodium fluoride reduced the corrosion resistance of cpTi. • Chlorhexidine gluconate and cetylpyridinium chloride can be safely used.

  4. Description of surfaces associated with Grassmannian sigma models on Minkowski space

    International Nuclear Information System (INIS)

    Grundland, A.M.; Snobl, L.

    2005-01-01

    We construct and investigate smooth orientable surfaces in su(N) algebras. The structural equations of surfaces associated with Grassmannian sigma models on Minkowski space are studied using moving frames adapted to the surfaces. The first and second fundamental forms of these surfaces as well as the relations between them as expressed in the Gauss-Weingarten and Gauss-Codazzi-Ricci equations are found. The scalar curvature and the mean curvature vector expressed in terms of a solution of Grassmanian sigma model are obtained

  5. Effect of Lamina Thickness of Prepreg on the Surface Accuracy of Carbon Fiber Composite Space Mirrors

    Science.gov (United States)

    Yang, Zhiyong; Tang, Zhanwen; Xie, Yongjie; Shi, Hanqiao; Zhang, Boming; Guo, Hongjun

    2018-02-01

    Composite space mirror can completely replicate the high-precision surface of mould by replication process, but the actual surface accuracy of the replication composite mirror always decreases. Lamina thickness of prepreg affects the layers and layup sequence of composite space mirror, and which would affect surface accuracy of space mirror. In our research, two groups of contrasting cases through finite element analyses (FEA) and comparative experiments were studied; the effect of different lamina thicknesses of prepreg and corresponding lay-up sequences was focused as well. We describe a special analysis model, validated process and result analysis. The simulated and measured surface figures both get the same conclusion. Reducing lamina thickness of prepreg used in replicating composite space mirror is propitious to optimal design of layup sequence for fabricating composite mirror, and could improve its surface accuracy.

  6. Planetary and Space Simulation Facilities (PSI) at DLR

    Science.gov (United States)

    Panitz, Corinna; Rabbow, E.; Rettberg, P.; Kloss, M.; Reitz, G.; Horneck, G.

    2010-05-01

    organisms in space and will contribute to the understanding of the organic chemistry processes in space, the biological adaptation strategies to extreme conditions, e.g. on early Earth and Mars, and the distribution of life beyond its planet of origin The results gained during the simulation experiments demonstrated mission preparation as a basic requirement for successful and significant results of every space flight experiment. Hence, the Mission preparation program that was performed in the context of the space missions EXPOSE-E and EXPOSE-R proofed the outstanding importance and accentuated need for ground based experiments before and during a space mission. The facilities are also necessary for the performance of the ground control experiment during the mission, the so-called Mission Simulation Test (MST) under simulated space conditions, by parallel exposure of samples to simulated space parameters according to flight data received by telemetry. Finally the facilities also provide the possibility to simulate the surface and climate conditions of the planet Mars. In this way they offer the possibility to investigate under simulated Mars conditions the chances for development of life on Mars and to gain previous knowledge for the search for life on today's Mars and in this context especially the parameters for a manned mission to Mars. References [1] Rabbow E, Rettberg P, Panitz C, Drescher J, Horneck G, Reitz G (2005) SSIOUX - Space Simulation for Investigating Organics, Evolution and Exobiology, Adv. Space Res. 36 (2) 297-302, doi:10.1016/j.asr.2005.08.040Aman, A. and Bman, B. (1997) JGR, 90,1151-1154. [2] Fekete A, Modos K, Hegedüs M, Kovacs G, Ronto Gy, Peter A, Lammer H, Panitz C (2005) DNA Damage under simulated extraterrestrial conditions in bacteriophage T7 Adv. Space Res. 305-310Aman, A. et al. (1997) Meteoritics & Planet. Sci., 32,A74. [3] Cockell Ch, Schuerger AC, Billi D., Friedmann EI, Panitz C (2005) Effects of a Simulated Martian UV Flux on the

  7. Surface behaviour of the phase-space distribution for heavy nuclei

    International Nuclear Information System (INIS)

    Durand, M.

    1987-06-01

    A part of the oscillations of the phase space distribution function is shown to be a surface effect. A series expansion for this function is given, which takes partially into account this oscillatory structure

  8. The homology groups of moduli spaces on non-classical Klein surfaces

    International Nuclear Information System (INIS)

    Zaw, Myint

    2001-08-01

    We describe the moduli space M-vector±(g,c) of non-classical directed Klein surfaces of genus g=h-c-1 with c≥0 distinguished points as a configuration space B ± (h,c) of classes h-slit pairs in C. Based on this model, we prove that M-vector ± (g,c) is non-orientable for any g and c and we compute the homology groups of the moduli spaces M-vector ± (g,c) for g≤2. (author)

  9. Phase-dependent space weathering effects and spectroscopic identification of retained helium in a lunar soil grain

    Science.gov (United States)

    Burgess, K. D.; Stroud, R. M.

    2018-03-01

    The solar wind is an important driver of space weathering on airless bodies. Over time, solar wind exposure alters the physical, chemical, and optical properties of exposed materials and can also impart a significant amount of helium into the surfaces of these bodies. However, common materials on the surface of the Moon, such as glass, crystalline silicates, and oxides, have highly variable responses to solar wind irradiation. We used scanning transmission electron microscopy (STEM) with electron energy loss spectroscopy (EELS) to examine the morphology and chemistry of a single grain of lunar soil that includes silicate glass, chromite and ilmenite, all present and exposed along the same surface. The exposure of the silicate glass and oxides to the same space weathering conditions allows for direct comparisons of the responses of natural materials to the complex lunar surface environment. The silicate glass shows minimal effects of solar wind irradiation, whereas both the chromite and ilmenite exhibit defect-rich rims that currently contain trapped helium. Only the weathered rim in ilmenite is rich in nanophase metallic iron (npFe0) and larger vesicles that retain helium at a range of internal pressures. The multiple exposed surfaces of the single grain of ilmenite demonstrate strong crystallographic controls of planar defects and non-spherical npFe0. The direct spectroscopic identification of helium in the vesicles and planar defects in the oxides provides additional evidence of the central role of solar wind irradiation in the formation of some common space weathering features.

  10. The Space Physics of Life: Searching for Biosignatures on Habitable Icy Worlds Affected by Space Weathering

    Science.gov (United States)

    Cooper, John F.

    2006-01-01

    Accessible surfaces of the most likely astrobiological habitats (Mars, Europa, Titan) in the solar system beyond Earth are exposed to various chemical and hydrologic weathering processes directly or indirectly induced by interaction with the overlying space environment. These processes can be both beneficial, through provision of chemical compounds and energy, and destructive, through chemical dissociation or burial, to detectable presence of biosignatures. Orbital, suborbital, and surface platforms carrying astrobiological instrumentation must survive, and preferably exploit, space environment interactions to reach these habitats and search for evidence of life or its precursors. Experience from Mars suggests that any detection of biosignatures must be accompanied by characterization of the local chemical environment and energy sources including irradiation by solar ultraviolet photons and energetic particles from the space environment. Orbital and suborbital surveys of surface chemistry and astrobiological potential in the context of the space environment should precede targeted in-situ measurements to maximize probability of biosignature detection through site selection. The Space Physics of Life (SPOL) investigation has recently been proposed to the NASA Astrobiology Institute and is briefly described in this presentation. SPOL is the astrobiologically relevant study of the interactions and relationships of potentially? or previously inhabited, bodies of the solar system with the surrounding environments. This requires an interdisciplinary effort in space physics, planetary science, and radiation biology. The proposed investigation addresses the search for habitable environments, chemical resources to support life, and techniques for detection of organic and inorganic signs of life in the context of the space environment.

  11. Ion accelerators for space

    International Nuclear Information System (INIS)

    Slobodrian, R.J.; Potvin, L.

    1991-01-01

    The main purpose of the accelerators is to allow ion implantation in space stations and their neighborhoods. There are several applications of interest immediately useful in such environment: as ion engines and thrusters, as implanters for material science and for hardening of surfaces (relevant to improve resistance to micrometeorite bombardment of exposed external components), production of man made alloys, etc. The microgravity environment of space stations allows the production of substances (crystalline and amorphous) under conditions unknown on earth, leading to special materials. Ion implantation in situ of those materials would thus lead uninterruptedly to new substances. Accelerators for space require special design. On the one hand it is possible to forego vacuum systems simplifying the design and operation but, on the other hand, it is necessary to pay special attention to heat dissipation. Hence it is necessary to construct a simulator in vacuum to properly test prototypes under conditions prevailing in space

  12. Residual stresses relaxation in surface-hardened half-space under creep conditions

    Directory of Open Access Journals (Sweden)

    Vladimir P. Radchenko

    2015-09-01

    Full Text Available We developed the method for solving the problem of residual stresses relaxation in surface-hardened layer of half-space under creep conditions. At the first stage we made the reconstruction of stress-strain state in half-space after plastic surface hardening procedure based on partial information about distribution for one residual stress tensor component experimentally detected. At the second stage using a numerical method we solve the problem of relaxation of self-balanced residual stresses under creep conditions. To solve this problem we introduce the following Cartesian system: x0y plane is aligned with hardened surface of half-space and 0z axis is directed to the depth of hardened layer. We also introduce the hypotheses of plane sections parallel to x0z and y0z planes. Detailed analysis of the problem has been done. Comparison of the calculated data with the corresponding test data was made for plane specimens (rectangular parallelepipeds made of EP742 alloy during T=650°C after the ultrasonic hardening with four hardening modes. We use half-space to model these specimens because penetration's depth of residual stresses is less than specimen general size in two digit exponent. There is enough correspondence of experimental and calculated data. It is shown that there is a decay (in modulus of pressing residual stresses under creep in 1.4–1.6 times.

  13. The Surface Extraction from TIN based Search-space Minimization (SETSM) algorithm

    Science.gov (United States)

    Noh, Myoung-Jong; Howat, Ian M.

    2017-07-01

    Digital Elevation Models (DEMs) provide critical information for a wide range of scientific, navigational and engineering activities. Submeter resolution, stereoscopic satellite imagery with high geometric and radiometric quality, and wide spatial coverage are becoming increasingly accessible for generating stereo-photogrammetric DEMs. However, low contrast and repeatedly-textured surfaces, such as snow and glacial ice at high latitudes, and mountainous terrains challenge existing stereo-photogrammetric DEM generation techniques, particularly without a-priori information such as existing seed DEMs or the manual setting of terrain-specific parameters. To utilize these data for fully-automatic DEM extraction at a large scale, we developed the Surface Extraction from TIN-based Search-space Minimization (SETSM) algorithm. SETSM is fully automatic (i.e. no search parameter settings are needed) and uses only the sensor model Rational Polynomial Coefficients (RPCs). SETSM adopts a hierarchical, combined image- and object-space matching strategy utilizing weighted normalized cross-correlation with both original distorted and geometrically corrected images for overcoming ambiguities caused by foreshortening and occlusions. In addition, SETSM optimally minimizes search-spaces to extract optimal matches over problematic terrains by iteratively updating object surfaces within a Triangulated Irregular Network, and utilizes a geometric-constrained blunder and outlier detection in object space. We prove the ability of SETSM to mitigate typical stereo-photogrammetric matching problems over a range of challenging terrains. SETSM is the primary DEM generation software for the US National Science Foundation's ArcticDEM project.

  14. Mercury's Weather-Beaten Surface: Understanding Mercury in the Context of Lunar and Asteroid Space Weathering Studies

    Science.gov (United States)

    Dominque, Deborah L.; Chapman, Clark R.; Killen, Rosemary M.; Zurbuchen, Thomas H.; Gilbert, Jason A.; Sarantos, Menelaos; Benna, Mehdi; Slavin, James A.; Orlando, Thomas M.; Schriver, David; hide

    2011-01-01

    Understanding the composition of Mercury's crust is key to comprehending the formation of the planet. The regolith, derived from the crustal bedrock, has been altered via a set of space weathering processes. These processes are the same set of mechanisms that work to form Mercury's exosphere, and are moderated by the local space environment and the presence of an intrinsic planetary magnetic field. The alterations need to be understood in order to determine the initial crustal compositions. The complex interrelationships between Mercury's exospheric processes, the space environment, and surface composition are examined and reviewed. The processes are examined in the context of our understanding of these same processes on the lunar and asteroid regoliths. Keywords: Mercury (planet) Space weathering Surface processes Exosphere Surface composition Space environment 3

  15. Influence of Layup Sequence on the Surface Accuracy of Carbon Fiber Composite Space Mirrors

    Science.gov (United States)

    Yang, Zhiyong; Liu, Qingnian; Zhang, Boming; Xu, Liang; Tang, Zhanwen; Xie, Yongjie

    2018-04-01

    Layup sequence is directly related to stiffness and deformation resistance of the composite space mirror, and error caused by layup sequence can affect the surface precision of composite mirrors evidently. Variation of layup sequence with the same total thickness of composite space mirror changes surface form of the composite mirror, which is the focus of our study. In our research, the influence of varied quasi-isotropic stacking sequences and random angular deviation on the surface accuracy of composite space mirrors was investigated through finite element analyses (FEA). We established a simulation model for the studied concave mirror with 500 mm diameter, essential factors of layup sequences and random angular deviations on different plies were discussed. Five guiding findings were described in this study. Increasing total plies, optimizing stacking sequence and keeping consistency of ply alignment in ply placement are effective to improve surface accuracy of composite mirror.

  16. Surface analysis, by SNMS, of 316L steel exposed to simulated BWR conditions

    International Nuclear Information System (INIS)

    Buckley, D.; Schenker, E.

    1994-01-01

    Samples of 316L steel have been exposed to Boiling Light Water Reactor chemistry for between forty and seven thousand hours. These samples, with three different surface finishes, 'as-delivered', mechanically polished and electro-polished, have been analysed by Sputtered Neutral Mass Spectrometry and profiles of the constituent alloying elements have been obtained. Differences in the oxide that has built-up are compared and discussed in terms of current ideas of corrosion mechanisms. The structure of the oxide changes with exposure time for the experimental conditions. The effect of surface finish and water velocity have a clear marked effect on the oxide structure and growth rate, respectively: samples in a low water velocity stream form the protective oxide, chromia, and some mixed spinels; electro-polished samples have no chromium layer but show possible secondary passivation through the build-up of nickel; and samples in high velocity water form a simple structured oxide that does not reach a saturation thickness after 291 days but steadily increases. (author) 9 figs., 3 tabs., 7 refs

  17. Analysis of Pseudomonas aeruginosa Cell Envelope Proteome by Capture of Surface-Exposed Proteins on Activated Magnetic Nanoparticles

    OpenAIRE

    Vecchietti, Davide; Di Silvestre, Dario; Miriani, Matteo; Bonomi, Francesco; Marengo, Mauro; Bragonzi, Alessandra; Cova, Lara; Franceschi, Eleonora; Mauri, Pierluigi; Bertoni, Giovanni

    2012-01-01

    We report on specific magneto-capturing followed by Multidimensional Protein Identification Technology (MudPIT) for the analysis of surface-exposed proteins of intact cells of the bacterial opportunistic pathogen Pseudomonas aeruginosa. The magneto-separation of cell envelope fragments from the soluble cytoplasmic fraction allowed the MudPIT identification of the captured and neighboring proteins. Remarkably, we identified 63 proteins captured directly by nanoparticles and 67 proteins embedde...

  18. Organoselenium Surface Modification of Stainless Steel Surfaces To Prevent Biofouling in Treatment of Space Wastestreams, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective of this work is to quantify the reduction of biofilm formation in a water distribution system resulting from an organoselenium surface coating on...

  19. Changes in silver nanoparticles exposed to human synthetic stomach fluid: Effects of particle size and surface chemistry

    International Nuclear Information System (INIS)

    Mwilu, Samuel K.; El Badawy, Amro M.; Bradham, Karen; Nelson, Clay; Thomas, David; Scheckel, Kirk G.; Tolaymat, Thabet; Ma, Longzhou; Rogers, Kim R.

    2013-01-01

    The significant rise in consumer products and applications utilizing the antibacterial properties of silver nanoparticles (AgNPs) has increased the possibility of human exposure. The mobility and bioavailability of AgNPs through the ingestion pathway will depend, in part, on properties such as particle size and the surface chemistries that will influence their physical and chemical reactivities during transit through the gastrointestinal tract. This study investigates the interactions between synthetic stomach fluid and AgNPs of different sizes and with different capping agents. Changes in morphology, size and chemical composition were determined during a 30 min exposure to synthetic human stomach fluid (SSF) using Absorbance Spectroscopy, High Resolution Transmission Electron and Scanning Electron Microscopy (TEM/SEM), Dynamic Light Scattering (DLS), and Nanoparticle Tracking Analysis (NTA). AgNPs exposed to SSF were found to aggregate significantly and also released ionic silver which physically associated with the particle aggregates as silver chloride. Generally, the smaller sized AgNPs (< 10 nm) showed higher rates of aggregation and physical transformation than larger particles (75 nm). Polyvinylpyrrolidone (pvp)-stabilized AgNPs prepared in house behaved differently in SSF than particles obtained from a commercial source despite having similar surface coating and size distribution characteristics. - Highlights: ► Interactions between synthetic stomach fluid (SSF) and silver nanoparticles (AgNPs) are described. ► AgNPs exposed to SSF aggregate and silver chloride are associated with the particle aggregates. ► Smaller AgNPs (< 10 nm) showed higher rates of aggregation and transformation than larger particles (75 nm). ► Polyvinylpyrrolidone-stabilized AgNPs obtained from different sources aggregated at different rates when exposed to SSF

  20. Nuclear data needs for the space exploration initiative

    International Nuclear Information System (INIS)

    Howe, S.D.; Auchampaugh, G.

    1991-01-01

    On July 20, 1989, the President of the United States announced a new direction for the US Space Program. The new Space Exploration Initiative (SEI) is intended to emplace a permanent base on the Lunar surface and a manned outpost on the Mars surface by 2019. In order to achieve this ambitious challenge, new, innovative and robust technologies will have to be developed to support crew operations. Nuclear power and propulsion have been recognized as technologies that are at least mission enhancing and, in some scenarios, mission enabling. Because of the extreme operating conditions present in a nuclear rocket core, accurate modeling of the rocket will require cross section data sets which do not currently exist. In order to successfully achieve the goals of the SEI, major obstacles inherent in long duration space travel will have to be overcome. One of these obstacles is the radiation environment to which the astronauts will be exposed. In general, an unshielded crew will be exposed to roughly one REM per week in free space. For missions to Mars, the total dose could exceed more than one-half the total allowed lifetime level. Shielding of the crew may be possible, but accurate assessments of shield composition and thickness are critical if shield masses are to be kept at acceptable levels. In addition, the entire ship design may be altered by the differential neutron production by heavy ions (Galactic Cosmic Rays) incident on ship structures. The components of the radiation environment, current modeling capability and envisioned experiments will be discussed

  1. Physical interpretation and geometrical representation of constant curvature surfaces in Euclidean and pseudo-Euclidean spaces

    International Nuclear Information System (INIS)

    Catoni, Francesco; Cannata, Roberto; Zampetti, Paolo

    2005-08-01

    The Riemann and Lorentz constant curvature surfaces are investigated from an Euclidean point of view. The four surfaces (constant positive and constant negative curvatures with definite and non-definite fine elements) are represented as surfaces in a Riemannian or in a particular semi-Riemannian flat space and it is shown that the complex and the hyperbolic numbers allow to obtain the same equations for the corresponding Riemann and Lorentz surfaces, respectively. Moreover it is shown that the geodesics on the Lorentz surfaces states, from a physical point of view, a link between curvature and fields. This result is obtained just as a consequence of the space-time geometrical symmetry, without invoking the famous Einstein general relativity postulate [it

  2. Whole-Genome Expression Analysis of Human Mesenchymal Stromal Cells Exposed to Ultrasmooth Tantalum vs. Titanium Oxide Surfaces

    DEFF Research Database (Denmark)

    Stiehler, C.; Bunger, C.; Overall, R. W.

    2013-01-01

    to titanium (Ti) surface. The aim of this study was to extend the previous investigation of biocompatibility by monitoring temporal gene expression of MSCs on topographically comparable smooth Ta and Ti surfaces using whole-genome gene expression analysis. Total RNA samples from telomerase-immortalized human...... MSCs cultivated on plain sputter-coated surfaces of Ta or Ti for 1, 2, 4, and 8 days were hybridized to n = 16 U133 Plus 2.0 arrays (Affymetrix(A (R))). Functional annotation, cluster and pathway analyses were performed. The vast majority of genes were differentially regulated after 4 days...... of cultivation and genes upregulated by MSCs exposed to Ta and Ti were predominantly related to the processes of differentiation and transcription, respectively. Functional annotation analysis of the 1,000 temporally most significantly regulated genes suggests earlier cellular differentiation on Ta compared...

  3. Singularities of spacelike constant mean curvature surfaces in Lorentz-Minkowski space

    DEFF Research Database (Denmark)

    Brander, David

    2011-01-01

    We study singularities of spacelike, constant (non-zero) mean curvature (CMC) surfaces in the Lorentz-Minkowski 3-space L-3. We show how to solve the singular Bjorling problem for such surfaces, which is stated as follows: given a real analytic null-curve f(0)(x), and a real analytic null vector...... field v(x) parallel to the tangent field of f(0), find a conformally parameterized (generalized) CMC H surface in L-3 which contains this curve as a singular set and such that the partial derivatives f(x) and f(y) are given by df(0)/dx and v along the curve. Within the class of generalized surfaces...

  4. Space-Based Diagnosis of Surface Ozone Sensitivity to Anthropogenic Emissions

    Science.gov (United States)

    Martin, Randall V.; Fiore, Arlene M.; VanDonkelaar, Aaron

    2004-01-01

    We present a novel capability in satellite remote sensing with implications for air pollution control strategy. We show that the ratio of formaldehyde columns to tropospheric nitrogen dioxide columns is an indicator of the relative sensitivity of surface ozone to emissions of nitrogen oxides (NO(x) = NO + NO2) and volatile organic compounds (VOCs). The diagnosis from these space-based observations is highly consistent with current understanding of surface ozone chemistry based on in situ observations. The satellite-derived ratios indicate that surface ozone is more sensitive to emissions of NO(x) than of VOCs throughout most continental regions of the Northern Hemisphere during summer. Exceptions include Los Angeles and industrial areas of Germany. A seasonal transition occurs in the fall when surface ozone becomes less sensitive to NOx and more sensitive to VOCs.

  5. Evolution of space dependent growth in the teleost Astyanax mexicanus.

    Directory of Open Access Journals (Sweden)

    Natalya D Gallo

    Full Text Available The relationship between growth rate and environmental space is an unresolved issue in teleosts. While it is known from aquaculture studies that stocking density has a negative relationship to growth, the underlying mechanisms have not been elucidated, primarily because the growth rate of populations rather than individual fish were the subject of all previous studies. Here we investigate this problem in the teleost Astyanax mexicanus, which consists of a sighted surface-dwelling form (surface fish and several blind cave-dwelling (cavefish forms. Surface fish and cavefish are distinguished by living in spatially contrasting environments and therefore are excellent models to study the effects of environmental size on growth. Multiple controlled growth experiments with individual fish raised in confined or unconfined spaces showed that environmental size has a major impact on growth rate in surface fish, a trait we have termed space dependent growth (SDG. In contrast, SDG has regressed to different degrees in the Pachón and Tinaja populations of cavefish. Mating experiments between surface and Pachón cavefish show that SDG is inherited as a dominant trait and is controlled by multiple genetic factors. Despite its regression in blind cavefish, SDG is not affected when sighted surface fish are raised in darkness, indicating that vision is not required to perceive and react to environmental space. Analysis of plasma cortisol levels showed that an elevation above basal levels occurred soon after surface fish were exposed to confined space. This initial cortisol peak was absent in Pachón cavefish, suggesting that the effects of confined space on growth may be mediated partly through a stress response. We conclude that Astyanax reacts to confined spaces by exhibiting SDG, which has a genetic component and shows evolutionary regression during adaptation of cavefish to confined environments.

  6. Invariant description of solutions of hydrodynamic-type systems in hodograph space: hydrodynamic surfaces

    International Nuclear Information System (INIS)

    Ferapontov, E.V.

    2002-01-01

    Hydrodynamic surfaces are solutions of hydrodynamic-type systems viewed as non-parametrized submanifolds of the hodograph space. We propose an invariant differential-geometric characterization of hydrodynamic surfaces by expressing the curvature form of the characteristic web in terms of the reciprocal invariants. (author)

  7. Monthly version of HadISST sea surface temperature state-space components

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — State-Space Decomposition of Monthly version of HadISST sea surface temperature component (1-degree). See Rayner, N. A., Parker, D. E., Horton, E. B., Folland, C....

  8. Surface water assessment on the influence of space distribution on ...

    African Journals Online (AJOL)

    In this work, the influence of space distribution on physico-chemical parameters of refinery effluent discharge has been studied, using treated effluent water discharged from the Port Harcourt Refinery Company (PHRC) into the Ekerekana Creek in Okrika as reference. Samples were collected at surface level from the ...

  9. Dispersion surfaces and ion wave instabilities in space plasmas

    International Nuclear Information System (INIS)

    Andre, M

    1985-08-01

    In this thesis, the dispersion relation of linear waves in a non-relativistic, collisionless and homogeneous plasma in a uniform magnetic field, is solved numerically. Both electrostatic and elecromagnetic waves with frequencies from below the ion gyrofrequency to above the electron gyrofrequency are studied for all angles of propagation. Modes occurring in a cold plasma as well as waves dependent on thermal effects are included. Dispersion surfaces, that is plots of frequency versus wavevector components, are presented for some models of space plasmas. Waves with frequencies of the order of the ion gyrofrequency (ion waves), are well known to exist in space plasmas. In this thesis, the generation of ion waves by ion distributions with loss-cones or temperature anisotropies, or by beams of charged particles, is investigated by numerical methods. Effects of heavy ions are considered. Dispersion surfaces and analytical arguments are used to clarify the results. It is shown that particle beams and ion loss-cone distributions can generate electrostatic ion waves, even when a significant amount of the electrons are cool. These calculations are in agreement with simultaneous observatons of waves and particles obtained by a satellite on auroral field lines. (author)

  10. Aquarius and Remote Sensing of Sea Surface Salinity from Space

    Science.gov (United States)

    LeVine, David M.; Lagerloef, G. S. E.; Torrusio, S.

    2012-01-01

    Aquarius is an L-band radiometer and scatterometer instrument combination designed to map the salinity field at the surface of the ocean from space. The instrument is designed to provide global salinity maps on a monthly basis with a spatial resolution of 150 km and an accuracy of 0.2 psu. The science objective is to monitor the seasonal and interannual variation of the large scale features of the surface salinity field in the open ocean. This data will promote understanding of ocean circulation and its role in the global water cycle and climate.

  11. Identification of Surface-Exposed Protein Radicals and A Substrate Oxidation Site in A-Class Dye-Decolorizing Peroxidase from Thermomonospora curvata

    Energy Technology Data Exchange (ETDEWEB)

    Shrestha, Ruben; Chen, Xuejie; Ramyar, Kasra X.; Hayati, Zahra; Carlson, Eric A.; Bossmann, Stefan H.; Song, Likai; Geisbrecht, Brian V.; Li, Ping (FSU); (KSU)

    2016-12-12

    Dye-decolorizing peroxidases (DyPs) are a family of heme peroxidases in which a catalytic distal aspartate is involved in H2O2 activation to catalyze oxidations under acidic conditions. They have received much attention due to their potential applications in lignin compound degradation and biofuel production from biomass. However, the mode of oxidation in bacterial DyPs remains unknown. We have recently reported that the bacterial TcDyP from Thermomonospora curvata is among the most active DyPs and shows activity toward phenolic lignin model compounds. On the basis of the X-ray crystal structure solved at 1.75 Å, sigmoidal steady-state kinetics with Reactive Blue 19 (RB19), and formation of compound II like product in the absence of reducing substrates observed with stopped-flow spectroscopy and electron paramagnetic resonance (EPR), we hypothesized that the TcDyP catalyzes oxidation of large-size substrates via multiple surface-exposed protein radicals. Among 7 tryptophans and 3 tyrosines in TcDyP consisting of 376 residues for the matured protein, W263, W376, and Y332 were identified as surface-exposed protein radicals. Only the W263 was also characterized as one of the surface-exposed oxidation sites. SDS-PAGE and size-exclusion chromatography demonstrated that W376 represents an off-pathway destination for electron transfer, resulting in the cross-linking of proteins in the absence of substrates. Mutation of W376 improved compound I stability and overall catalytic efficiency toward RB19. While Y332 is highly conserved across all four classes of DyPs, its catalytic function in A-class TcDyP is minimal, possibly due to its extremely small solvent-accessible areas. Identification of surface-exposed protein radicals and substrate oxidation sites is important for understanding the DyP mechanism and modulating its catalytic functions for improved activity on phenolic lignin.

  12. Bacillus subtilis spores PROTECT experiment Space-exposed and Mars-exposed vs. Earth-control

    Data.gov (United States)

    National Aeronautics and Space Administration — Because of their ubiquity and resistance to spacecraft decontamination bacterial spores are considered likely potential forward contaminants on robotic missions to...

  13. The properties degradation of exposed GFRP roof

    Science.gov (United States)

    Zainudin, Mohammad; Diharjo, Kuncoro; Kaavessina, Mujtahid; Setyanto, Djoko

    2018-02-01

    There is much consideration of roof selection as a protector of a building against the outside weather, such as lightweight, strong stiff, corrosion resistant and guarantee for the availability of products. Based on these considerations, glass fiber reinforced polymer (GFRP) roof is a roof which can fulfill the requirement. The objective of this research is to investigate the degradation of physical and mechanical properties of GFRP roof exposed in outside weather. This GFRP roof composite was produced using a sheet molding compound (SMC) supplied by PT Intec Persada, Tangerang, Indonesia. There are two kinds GFRP roofs evaluated in this research that are GFRP roof exposed within 7 years and new GFRP roof that has not been exposed. The GFRP roofs were cut manually for preparing the specimens for hardness test, tensile test, SEM and FTIR test. The results show that the GFRP roof exposed within 7 years had the degradation of properties compared to the new GFRP roof. The exposed GFRP roof had lower strength and hardness compared to the new GFRP roof. The SEM observation indicates that exposed GFRP roof had the debonding of fiber on the surface, and in contrast, there are no debonding of fiber in the new GFRP roof surface. It can be recommended that the exposed GFRP roof may be repaired to enhance its performance and can re-increase its properties using the coating.

  14. Torsional surface waves in an inhomogeneous layer over a gravitating anisotropic porous half-space

    International Nuclear Information System (INIS)

    Gupta, Shishir; Pramanik, Abhijit

    2015-01-01

    The present work aims to deal with the propagation of torsional surface wave in an inhomogeneous layer over a gravitating anisotropic porous half space. The inhomogeneous layer exhibits the inhomogeneity of quadratic type. In order to show the effect of gravity the equation for the velocity of torsional wave has been obtained. It is also observed that for a layer over a homogeneous half space without gravity, the torsional surface wave does not propagate. An attempt is also made to assess the possible propagation of torsional surface waves in that medium in the absence of the upper layer. The effects of inhomogeneity factors and porosity on the phase velocity are depicted by means of graphs. (paper)

  15. Prime focus architectures for large space telescopes: reduce surfaces to save cost

    Science.gov (United States)

    Breckinridge, J. B.; Lillie, C. F.

    2016-07-01

    Conceptual architectures are now being developed to identify future directions for post JWST large space telescope systems to operate in the UV Optical and near IR regions of the spectrum. Here we show that the cost of optical surfaces within large aperture telescope/instrument systems can exceed $100M/reflection when expressed in terms of the aperture increase needed to over come internal absorption loss. We recommend a program in innovative optical design to minimize the number of surfaces by considering multiple functions for mirrors. An example is given using the Rowland circle imaging spectrometer systems for UV space science. With few exceptions, current space telescope architectures are based on systems optimized for ground-based astronomy. Both HST and JWST are classical "Cassegrain" telescopes derived from the ground-based tradition to co-locate the massive primary mirror and the instruments at the same end of the metrology structure. This requirement derives from the dual need to minimize observatory dome size and cost in the presence of the Earth's 1-g gravitational field. Space telescopes, however function in the zero gravity of space and the 1- g constraint is relieved to the advantage of astronomers. Here we suggest that a prime focus large aperture telescope system in space may have potentially have higher transmittance, better pointing, improved thermal and structural control, less internal polarization and broader wavelength coverage than Cassegrain telescopes. An example is given showing how UV astronomy telescopes use single optical elements for multiple functions and therefore have a minimum number of reflections.

  16. Effect of four dental varnishes on the colonization of cariogenic bacteria on exposed sound root surfaces.

    Science.gov (United States)

    Ekenbäck, S B; Linder, L E; Lönnies, H

    2000-01-01

    The aim of this study was to evaluate the effect of four different dental varnishes on the colonization of mutans streptococci, total streptococci and lactobacilli on exposed sound root surfaces. Sixty-five individuals were randomly allotted to one of four groups for treatment with Cervitec((R) ) varnish containing 1% chlorhexidine and 1% thymol, a thymol varnish or one of two different fluoride varnishes, Fluor Protector and Duraphat. The varnish was applied to three buccal root surfaces in each patient at baseline and after 1 week. Dental plaque from the root surfaces was collected and analysed on four different occasions: at baseline, after 1 week, 1 month and 6 months. The Cervitec varnish caused a statistically significant reduction in the number of mutans streptococci over time. The reduction was significant at 1 week and 1 month relative to baseline. The numbers of total streptococci and lactobacilli were not significantly affected by treatment with Cervitec. No statistically significant difference over time was found for mutans streptococci, lactobacilli or total streptococci after treatment with the fluoride varnishes or the thymol varnish.

  17. Analysis of Pseudomonas aeruginosa cell envelope proteome by capture of surface-exposed proteins on activated magnetic nanoparticles.

    Directory of Open Access Journals (Sweden)

    Davide Vecchietti

    Full Text Available We report on specific magneto-capturing followed by Multidimensional Protein Identification Technology (MudPIT for the analysis of surface-exposed proteins of intact cells of the bacterial opportunistic pathogen Pseudomonas aeruginosa. The magneto-separation of cell envelope fragments from the soluble cytoplasmic fraction allowed the MudPIT identification of the captured and neighboring proteins. Remarkably, we identified 63 proteins captured directly by nanoparticles and 67 proteins embedded in the cell envelope fragments. For a high number of proteins, our analysis strongly indicates either surface exposure or localization in an envelope district. The localization of most identified proteins was only predicted or totally unknown. This novel approach greatly improves the sensitivity and specificity of the previous methods, such as surface shaving with proteases that was also tested on P. aeruginosa. The magneto-capture procedure is simple, safe, and rapid, and appears to be well-suited for envelope studies in highly pathogenic bacteria.

  18. Analysis of Pseudomonas aeruginosa Cell Envelope Proteome by Capture of Surface-Exposed Proteins on Activated Magnetic Nanoparticles

    Science.gov (United States)

    Vecchietti, Davide; Di Silvestre, Dario; Miriani, Matteo; Bonomi, Francesco; Marengo, Mauro; Bragonzi, Alessandra; Cova, Lara; Franceschi, Eleonora; Mauri, Pierluigi; Bertoni, Giovanni

    2012-01-01

    We report on specific magneto-capturing followed by Multidimensional Protein Identification Technology (MudPIT) for the analysis of surface-exposed proteins of intact cells of the bacterial opportunistic pathogen Pseudomonas aeruginosa. The magneto-separation of cell envelope fragments from the soluble cytoplasmic fraction allowed the MudPIT identification of the captured and neighboring proteins. Remarkably, we identified 63 proteins captured directly by nanoparticles and 67 proteins embedded in the cell envelope fragments. For a high number of proteins, our analysis strongly indicates either surface exposure or localization in an envelope district. The localization of most identified proteins was only predicted or totally unknown. This novel approach greatly improves the sensitivity and specificity of the previous methods, such as surface shaving with proteases that was also tested on P. aeruginosa. The magneto-capture procedure is simple, safe, and rapid, and appears to be well-suited for envelope studies in highly pathogenic bacteria. PMID:23226459

  19. A Screen Space GPGPU Surface LIC Algorithm for Distributed Memory Data Parallel Sort Last Rendering Infrastructures

    Energy Technology Data Exchange (ETDEWEB)

    Loring, Burlen; Karimabadi, Homa; Rortershteyn, Vadim

    2014-07-01

    The surface line integral convolution(LIC) visualization technique produces dense visualization of vector fields on arbitrary surfaces. We present a screen space surface LIC algorithm for use in distributed memory data parallel sort last rendering infrastructures. The motivations for our work are to support analysis of datasets that are too large to fit in the main memory of a single computer and compatibility with prevalent parallel scientific visualization tools such as ParaView and VisIt. By working in screen space using OpenGL we can leverage the computational power of GPUs when they are available and run without them when they are not. We address efficiency and performance issues that arise from the transformation of data from physical to screen space by selecting an alternate screen space domain decomposition. We analyze the algorithm's scaling behavior with and without GPUs on two high performance computing systems using data from turbulent plasma simulations.

  20. Space environment durability of beta cloth in LDEF thermal blankets

    Science.gov (United States)

    Linton, Roger C.; Whitaker, Ann F.; Finckenor, Miria M.

    1993-01-01

    Beta cloth performance for use on long-term space vehicles such as Space Station Freedom (S.S. Freedom) requires resistance to the degrading effects of the space environment. The major issues are retention of thermal insulating properties through maintaining optical properties, preserving mechanical integrity, and generating minimal particulates for contamination-sensitive spacecraft surfaces and payloads. The longest in-flight test of beta cloth's durability was on the Long Duration Exposure Facility (LDEF), where it was exposed to the space environment for 68 months. The LDEF contained 57 experiments which further defined the space environment and its effects on spacecraft materials. It was deployed into low-Earth orbit (LEO) in Apr. 1984 and retrieved Jan. 1990 by the space shuttle. Among the 10,000 plus material constituents and samples onboard were thermal control blankets of multilayer insulation with a beta cloth outer cover and Velcro attachments. These blankets were exposed to hard vacuum, thermal cycling, charged particles, meteoroid/debris impacts, ultraviolet (UV) radiation, and atomic oxygen (AO). Of these space environmental exposure elements, AO appears to have had the greatest effect on the beta cloth. The beta cloth analyzed in this report came from the MSFC Experiment S1005 (Transverse Flat-Plate Heat Pipe) tray oriented approximately 22 deg from the leading edge vector of the LDEF satellite. The location of the tray on LDEF and the placement of the beta cloth thermal blankets are shown. The specific space environment exposure conditions for this material are listed.

  1. Proteome analysis and serological characterization of surface-exposed proteins of Rickettsia heilongjiangensis.

    Directory of Open Access Journals (Sweden)

    Yong Qi

    Full Text Available BACKGROUND: Rickettsia heilongjiangensis, the agent of Far-Eastern spotted fever (FESF, is an obligate intracellular bacterium. The surface-exposed proteins (SEPs of rickettsiae are involved in rickettsial adherence to and invasion of host cells, intracellular bacterial growth, and/or interaction with immune cells. They are also potential molecular candidates for the development of diagnostic reagents and vaccines against rickettsiosis. METHODS: R. heilongjiangensis SEPs were identified by biotin-streptavidin affinity purification and 2D electrophoreses coupled with ESI-MS/MS. Recombinant SEPs were probed with various sera to analyze their serological characteristics using a protein microarray and an enzyme-linked immune sorbent assay (ELISA. RESULTS: Twenty-five SEPs were identified, most of which were predicted to reside on the surface of R. heilongjiangensis cells. Bioinformatics analysis suggests that these proteins could be involved in bacterial pathogenesis. Eleven of the 25 SEPs were recognized as major seroreactive antigens by sera from R. heilongjiangensis-infected mice and FESF patients. Among the major seroreactive SEPs, microarray assays and/or ELISAs revealed that GroEL, OmpA-2, OmpB-3, PrsA, RplY, RpsB, SurA and YbgF had modest sensitivity and specificity for recognizing R. heilongjiangensis infection and/or spotted fever. CONCLUSIONS: Many of the SEPs identified herein have potentially important roles in R. heilongjiangensis pathogenicity. Some of them have potential as serodiagnostic antigens or as subunit vaccine antigens against the disease.

  2. Sub-nanoscale surface ruggedness provides a water-tight seal for exposed regions in soluble protein structure.

    Directory of Open Access Journals (Sweden)

    Erica Schulz

    2010-09-01

    Full Text Available Soluble proteins must maintain backbone hydrogen bonds (BHBs water-tight to ensure structural integrity. This protection is often achieved by burying the BHBs or wrapping them through intermolecular associations. On the other hand, water has low coordination resilience, with loss of hydrogen-bonding partnerships carrying significant thermodynamic cost. Thus, a core problem in structural biology is whether natural design actually exploits the water coordination stiffness to seal the backbone in regions that are exposed to the solvent. This work explores the molecular design features that make this type of seal operative, focusing on the side-chain arrangements that shield the protein backbone. We show that an efficient sealing is achieved by adapting the sub-nanoscale surface topography to the stringency of water coordination: an exposed BHB may be kept dry if the local concave curvature is small enough to impede formation of the coordination shell of a penetrating water molecule. Examination of an exhaustive database of uncomplexed proteins reveals that exposed BHBs invariably occur within such sub-nanoscale cavities in native folds, while this level of local ruggedness is absent in other regions. By contrast, BHB exposure in misfolded proteins occurs with larger local curvature promoting backbone hydration and consequently, structure disruption. These findings unravel physical constraints fitting a spatially dependent least-action for water coordination, introduce a molecular design concept, and herald the advent of water-tight peptide-based materials with sufficient backbone exposure to remain flexible.

  3. Application of the moving frame method to deformed Willmore surfaces in space forms

    Science.gov (United States)

    Paragoda, Thanuja

    2018-06-01

    The main goal of this paper is to use the theory of exterior differential forms in deriving variations of the deformed Willmore energy in space forms and study the minimizers of the deformed Willmore energy in space forms. We derive both first and second order variations of deformed Willmore energy in space forms explicitly using moving frame method. We prove that the second order variation of deformed Willmore energy depends on the intrinsic Laplace Beltrami operator, the sectional curvature and some special operators along with mean and Gauss curvatures of the surface embedded in space forms, while the first order variation depends on the extrinsic Laplace Beltrami operator.

  4. Lunar and planetary surface conditions advances in space science and technology

    CERN Document Server

    Weil, Nicholas A

    1965-01-01

    Lunar and Planetary Surface Conditions considers the inferential knowledge concerning the surfaces of the Moon and the planetary companions in the Solar System. The information presented in this four-chapter book is based on remote observations and measurements from the vantage point of Earth and on the results obtained from accelerated space program of the United States and U.S.S.R. Chapter 1 presents the prevalent hypotheses on the origin and age of the Solar System, followed by a brief description of the methods and feasibility of information acquisition concerning lunar and planetary data,

  5. Interaction of Al with O2 exposed Mo2BC

    International Nuclear Information System (INIS)

    Bolvardi, Hamid; Music, Denis; Schneider, Jochen M.

    2015-01-01

    Highlights: • Al adheres to many surfaces. • Solid–solid interactions challenging for real (oxidized) surfaces. • Dissociative O 2 adsorption on Mo 2 BC(0 4 0). • Al nonamer is disrupted on oxidized Mo 2 BC(0 4 0). • Adhesion of a residual Al on the native oxide. - Abstract: A Mo 2 BC(0 4 0) surface was exposed to O 2 . The gas interaction was investigated using ab initio molecular dynamics and X-ray photoelectron spectroscopy (XPS) of air exposed surfaces. The calculations suggest that the most dominating physical mechanism is dissociative O 2 adsorption whereby Mo−O, O−Mo−O and Mo 2 −C−O bond formation is observed. To validate these results, Mo 2 BC thin films were synthesized utilizing high power pulsed magnetron sputtering and air exposed surfaces were probed by XPS. MoO 2 and MoO 3 bond formation is observed and is consistent with here obtained ab initio data. Additionally, the interfacial interactions of O 2 exposed Mo 2 BC(0 4 0) surface with an Al nonamer is studied with ab initio molecular dynamics to describe on the atomic scale the interaction between this surface and Al to mimic the interface present during cold forming processes of Al based alloys. The Al nonamer was disrupted and Al forms chemical bonds with oxygen contained in the O 2 exposed Mo 2 BC(0 4 0) surface. Based on the comparison of here calculated adsorption energy with literature data, Al−Al bonds are shown to be significantly weaker than the Al−O bonds formed across the interface. Hence, Al−Al bond rupture is expected for a mechanically loaded interface. Therefore the adhesion of a residual Al on the native oxide layer is predicted. This is consistent with experimental observations. The data presented here may also be relevant for other oxygen containing surfaces in a contact with Al or Al based alloys for example during forming operations

  6. Null polygonal Wilson loops and minimal surfaces in Anti-de-Sitter space

    International Nuclear Information System (INIS)

    Alday, Luis F.; Maldacena, Juan

    2009-01-01

    We consider minimal surfaces in three dimensional anti-de-Sitter space that end at the AdS boundary on a polygon given by a sequence of null segments. The problem can be reduced to a certain generalized Sinh-Gordon equation and to SU(2) Hitchin equations. We describe in detail the mathematical problem that needs to be solved. This problem is mathematically the same as the one studied by Gaiotto, Moore and Neitzke in the context of the moduli space of certain supersymmetric theories. Using their results we can find the explicit answer for the area of a surface that ends on an eight-sided polygon. Via the gauge/gravity duality this can also be interpreted as a certain eight-gluon scattering amplitude at strong coupling. In addition, we give fairly explicit solutions for regular polygons.

  7. Novel CNC Grinding Process Control for Nanometric Surface Roughness for Aspheric Space Optical Surfaces

    Directory of Open Access Journals (Sweden)

    Jeong-Yeol Han

    2004-06-01

    Full Text Available Optics fabrication process for precision space optical parts includes bound abrasive grinding, loose abrasive lapping and polishing. The traditional bound abrasive grinding with bronze bond cupped diamond wheel leaves the machine marks of about 20 μm rms in height and the subsurface damage of about 1 μm rms in height to be removed by subsequent loose abrasive lapping. We explored an efficient quantitative control of precision CNC grinding. The machining parameters such as grain size, work-piece rotation speed and feed rate were altered while grinding the work-piece surfaces of 20-100 mm in diameter. The input grinding variables and the resulting surface quality data were used to build grinding prediction models using empirical and multi-variable regression analysis. The effectiveness of such grinding prediction models was then examined by running a series of precision CNC grinding operation with a set of controlled input variables and predicted output surface quality indicators. The experiment achieved the predictability down to ±20 nm in height and the surface roughness down to 36 nm in height. This study contributed to improvement of the process efficiency reaching directly the polishing and figuring process without the need for the loose abrasive lapping stage.

  8. Holomorphic representation of constant mean curvature surfaces in Minkowski space: Consequences of non-compactness in loop group methods

    DEFF Research Database (Denmark)

    Brander, David; Rossman, Wayne; Schmitt, Nicholas

    2010-01-01

    We give an infinite dimensional generalized Weierstrass representation for spacelike constant mean curvature (CMC) surfaces in Minkowski 3-space $\\R^{2,1}$. The formulation is analogous to that given by Dorfmeister, Pedit and Wu for CMC surfaces in Euclidean space, replacing the group $SU_2$ with...

  9. 57Fe Moessbauer spectroscopic study on surface products of thin iron plates exposed to ambient atmosphere as a means of environmental monitoring

    International Nuclear Information System (INIS)

    Matsuo, Motoyuki; Kobayashi, Takaaki

    1993-01-01

    Conversion electron and transmission Moessbauer spectroscopy were applied to the analysis of thin iron plates exposed to the ambient atmosphere. The degree of corrosion of the iron plates was classified into three categories according to the kind and thickness of rust evaluated by Moessbauer spectra. The severe corrosion took place in seaside and roadside areas. The medium corrosion was observed in urban areas, and the weak corrosion occurred in suburban and mountainous areas. This fact implies that the surface products of iron plates can successfully reflect the ambient atmosphere to which the plates were exposed. (orig.)

  10. Riemannian metric optimization on surfaces (RMOS) for intrinsic brain mapping in the Laplace-Beltrami embedding space.

    Science.gov (United States)

    Gahm, Jin Kyu; Shi, Yonggang

    2018-05-01

    Surface mapping methods play an important role in various brain imaging studies from tracking the maturation of adolescent brains to mapping gray matter atrophy patterns in Alzheimer's disease. Popular surface mapping approaches based on spherical registration, however, have inherent numerical limitations when severe metric distortions are present during the spherical parameterization step. In this paper, we propose a novel computational framework for intrinsic surface mapping in the Laplace-Beltrami (LB) embedding space based on Riemannian metric optimization on surfaces (RMOS). Given a diffeomorphism between two surfaces, an isometry can be defined using the pullback metric, which in turn results in identical LB embeddings from the two surfaces. The proposed RMOS approach builds upon this mathematical foundation and achieves general feature-driven surface mapping in the LB embedding space by iteratively optimizing the Riemannian metric defined on the edges of triangular meshes. At the core of our framework is an optimization engine that converts an energy function for surface mapping into a distance measure in the LB embedding space, which can be effectively optimized using gradients of the LB eigen-system with respect to the Riemannian metrics. In the experimental results, we compare the RMOS algorithm with spherical registration using large-scale brain imaging data, and show that RMOS achieves superior performance in the prediction of hippocampal subfields and cortical gyral labels, and the holistic mapping of striatal surfaces for the construction of a striatal connectivity atlas from substantia nigra. Copyright © 2018 Elsevier B.V. All rights reserved.

  11. Hybrid Heat Pipes for Lunar and Martian Surface and High Heat Flux Space Applications

    Science.gov (United States)

    Ababneh, Mohammed T.; Tarau, Calin; Anderson, William G.; Farmer, Jeffery T.; Alvarez-Hernandez, Angel R.

    2016-01-01

    Novel hybrid wick heat pipes are developed to operate against gravity on planetary surfaces, operate in space carrying power over long distances and act as thermosyphons on the planetary surface for Lunar and Martian landers and rovers. These hybrid heat pipes will be capable of operating at the higher heat flux requirements expected in NASA's future spacecraft and on the next generation of polar rovers and equatorial landers. In addition, the sintered evaporator wicks mitigate the start-up problems in vertical gravity aided heat pipes because of large number of nucleation sites in wicks which will allow easy boiling initiation. ACT, NASA Marshall Space Flight Center, and NASA Johnson Space Center, are working together on the Advanced Passive Thermal experiment (APTx) to test and validate the operation of a hybrid wick VCHP with warm reservoir and HiK"TM" plates in microgravity environment on the ISS.

  12. Emergent Momentum-Space Skyrmion Texture on the Surface of Topological Insulators

    Science.gov (United States)

    Mohanta, Narayan; Kampf, Arno P.; Kopp, Thilo

    The quantum anomalous Hall effect has been theoretically predicted and experimentally verified in magnetic topological insulators. In addition, the surface states of these materials exhibit a hedgehog-like ``spin'' texture in momentum space. Here, we apply the previously formulated low-energy model for Bi2Se3, a parent compound for magnetic topological insulators, to a slab geometry in which an exchange field acts only within one of the surface layers. In this sample set up, the hedgehog transforms into a skyrmion texture beyond a critical exchange field. This critical field marks a transition between two topologically distinct phases. The topological phase transition takes place without energy gap closing at the Fermi level and leaves the transverse Hall conductance unchanged and quantized to e2 / 2 h . The momentum-space skyrmion texture persists in a finite field range. It may find its realization in hybrid heterostructures with an interface between a three-dimensional topological insulator and a ferromagnetic insulator. The work was supported by the Deutsche Forschungsgemeinschaft through TRR 80.

  13. Functional models for commutative systems of linear operators and de Branges spaces on a Riemann surface

    International Nuclear Information System (INIS)

    Zolotarev, Vladimir A

    2009-01-01

    Functional models are constructed for commutative systems {A 1 ,A 2 } of bounded linear non-self-adjoint operators which do not contain dissipative operators (which means that ξ 1 A 1 +ξ 2 A 2 is not a dissipative operator for any ξ 1 , ξ 2 element of R). A significant role is played here by the de Branges transform and the function classes occurring in this context. Classes of commutative systems of operators {A 1 ,A 2 } for which such a construction is possible are distinguished. Realizations of functional models in special spaces of meromorphic functions on Riemann surfaces are found, which lead to reasonable analogues of de Branges spaces on these Riemann surfaces. It turns out that the functions E(p) and E-tilde(p) determining the order of growth in de Branges spaces on Riemann surfaces coincide with the well-known Baker-Akhiezer functions. Bibliography: 11 titles.

  14. Biofilm Composition and Threshold Concentration for Growth of Legionella pneumophila on Surfaces Exposed to Flowing Warm Tap Water without Disinfectant.

    Science.gov (United States)

    van der Kooij, Dick; Bakker, Geo L; Italiaander, Ronald; Veenendaal, Harm R; Wullings, Bart A

    2017-03-01

    Legionella pneumophila in potable water installations poses a potential health risk, but quantitative information about its replication in biofilms in relation to water quality is scarce. Therefore, biofilm formation on the surfaces of glass and chlorinated polyvinyl chloride (CPVC) in contact with tap water at 34 to 39°C was investigated under controlled hydraulic conditions in a model system inoculated with biofilm-grown L. pneumophila The biofilm on glass (average steady-state concentration, 23 ± 9 pg ATP cm -2 ) exposed to treated aerobic groundwater (0.3 mg C liter -1 ; 1 μg assimilable organic carbon [AOC] liter -1 ) did not support growth of the organism, which also disappeared from the biofilm on CPVC (49 ± 9 pg ATP cm -2 ) after initial growth. L. pneumophila attained a level of 4.3 log CFU cm -2 in the biofilms on glass (1,055 ± 225 pg ATP cm -2 ) and CPVC (2,755 ± 460 pg ATP cm -2 ) exposed to treated anaerobic groundwater (7.9 mg C liter -1 ; 10 μg AOC liter -1 ). An elevated biofilm concentration and growth of L. pneumophila were also observed with tap water from the laboratory. The Betaproteobacteria Piscinibacter and Methyloversatilis and amoeba-resisting Alphaproteobacteria predominated in the clones and isolates retrieved from the biofilms. In the biofilms, the Legionella colony count correlated significantly with the total cell count (TCC), heterotrophic plate count, ATP concentration, and presence of Vermamoeba vermiformis This amoeba was rarely detected at biofilm concentrations of water-associated disease outbreaks reported in the United States. The organism proliferates in biofilms on surfaces exposed to warm water in engineered freshwater installations. An investigation with a test system supplied with different types of warm drinking water without disinfectant under controlled hydraulic conditions showed that treated aerobic groundwater (0.3 mg liter -1 of organic carbon) induced a low biofilm concentration that supported no or very

  15. Comparative analysis of the surface exposed proteome of two canine osteosarcoma cell lines and normal canine osteoblasts.

    Science.gov (United States)

    Milovancev, Milan; Hilgart-Martiszus, Ian; McNamara, Michael J; Goodall, Cheri P; Seguin, Bernard; Bracha, Shay; Wickramasekara, Samanthi I

    2013-06-13

    Osteosarcoma (OSA) is the most common primary bone tumor of dogs and carries a poor prognosis despite aggressive treatment. An improved understanding of the biology of OSA is critically needed to allow for development of novel diagnostic, prognostic, and therapeutic tools. The surface-exposed proteome (SEP) of a cancerous cell includes a multifarious array of proteins critical to cellular processes such as proliferation, migration, adhesion, and inter-cellular communication. The specific aim of this study was to define a SEP profile of two validated canine OSA cell lines and a normal canine osteoblast cell line utilizing a biotinylation/streptavidin system to selectively label, purify, and identify surface-exposed proteins by mass spectrometry (MS) analysis. Additionally, we sought to validate a subset of our MS-based observations via quantitative real-time PCR, Western blot and semi-quantitative immunocytochemistry. Our hypothesis was that MS would detect differences in the SEP composition between the OSA and the normal osteoblast cells. Shotgun MS identified 133 putative surface proteins when output from all samples were combined, with good consistency between biological replicates. Eleven of the MS-detected proteins underwent analysis of gene expression by PCR, all of which were actively transcribed, but varied in expression level. Western blot of whole cell lysates from all three cell lines was effective for Thrombospondin-1, CYR61 and CD44, and indicated that all three proteins were present in each cell line. Semi-quantitative immunofluorescence indicated that CD44 was expressed at much higher levels on the surface of the OSA than the normal osteoblast cell lines. The results of the present study identified numerous differences, and similarities, in the SEP of canine OSA cell lines and normal canine osteoblasts. The PCR, Western blot, and immunocytochemistry results, for the subset of proteins evaluated, were generally supportive of the mass spectrometry data

  16. Photoluminescence of anti-modulation doped near-surface GaAs/AlGaAs single quantum well structures exposed to hydrogen plasma

    CERN Document Server

    Bumaj, Y A; Goldkhan, R; Shtajn, N; Golombek, A; Nakov, V; Cheng, T S

    2002-01-01

    The anti-modulation Si-doped GaAs/AlGaAs structures with near-surface single quantum wells grown by molecular-beam epitaxy were exposed to hydrogen plasma at 260 deg C and investigated by low-temperature photoluminescence, photoluminescence excitation and photoreflectance spectroscopy. After hydrogenation, the quenching of the exciton luminescence for the below AlGaAs band gap excitation due to the increase of electric field in the structure has been observed. The effect is consistent with unpinning of Fermi level from mid gap of nominally undoped (p-type) GaAs cap layer due to passivation of surface states by hydrogen without neutralization of shallow impurities in the epilayers

  17. A space-charge treatment of the increased concentration of reactive species at the surface of a ceria solid solution

    Energy Technology Data Exchange (ETDEWEB)

    Zurhelle, Alexander F.; Souza, Roger A. de [Institute of Physical Chemistry, RWTH Aachen University (Germany); Tong, Xiaorui; Mebane, David S. [Department of Mechanical and Aerospace Engineering, West Virginia University, Morgantown, WV (United States); Klein, Andreas [Institute of Materials Science, TU Darmstadt (Germany)

    2017-11-13

    A space-charge theory applicable to concentrated solid solutions (Poisson-Cahn theory) was applied to describe quantitatively as a function of temperature and oxygen partial pressure published data obtained by in situ X-ray photoelectron spectroscopy (XPS) for the concentration of Ce{sup 3+} (the reactive species) at the surface of the oxide catalyst Ce{sub 0.8}Sm{sub 0.2}O{sub 1.9}. In contrast to previous theoretical treatments, these calculations clearly indicate that the surface is positively charged and compensated by an attendant negative space-charge zone. The high space-charge potential that develops at the surface (>0.8 V) is demonstrated to be hardly detectable by XPS measurements because of the short extent of the space-charge layer. This approach emphasizes the need to take into account defect interactions and to allow deviations from local charge neutrality when considering the surfaces of oxide catalysts. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. Mercury's Weather-Beaten Surface: Understanding Mercury in the Context of Lunar and Asteroidal Space Weathering Studies

    Science.gov (United States)

    Domingue, Deborah L.; Chapman, Clark. R.; Killen, Rosemary M.; Zurbuchen, Thomas H.; Gilbert, Jason A.; Sarantos, Menelaos; Benna, Mehdi; Slavin, James A.; Schriver, David; Travnicek, Pavel M.; hide

    2014-01-01

    Mercury's regolith, derived from the crustal bedrock, has been altered by a set of space weathering processes. Before we can interpret crustal composition, it is necessary to understand the nature of these surface alterations. The processes that space weather the surface are the same as those that form Mercury's exosphere (micrometeoroid flux and solar wind interactions) and are moderated by the local space environment and the presence of a global magnetic field. To comprehend how space weathering acts on Mercury's regolith, an understanding is needed of how contributing processes act as an interactive system. As no direct information (e.g., from returned samples) is available about how the system of space weathering affects Mercury's regolith, we use as a basis for comparison the current understanding of these same processes on lunar and asteroidal regoliths as well as laboratory simulations. These comparisons suggest that Mercury's regolith is overturned more frequently (though the characteristic surface time for a grain is unknown even relative to the lunar case), more than an order of magnitude more melt and vapor per unit time and unit area is produced by impact processes than on the Moon (creating a higher glass content via grain coatings and agglutinates), the degree of surface irradiation is comparable to or greater than that on the Moon, and photon irradiation is up to an order of magnitude greater (creating amorphous grain rims, chemically reducing the upper layers of grains to produce nanometer scale particles of metallic iron, and depleting surface grains in volatile elements and alkali metals). The processes that chemically reduce the surface and produce nanometer-scale particles on Mercury are suggested to be more effective than similar processes on the Moon. Estimated abundances of nanometer-scale particles can account for Mercury's dark surface relative to that of the Moon without requiring macroscopic grains of opaque minerals. The presence of

  19. Deep Space Gateway Support of Lunar Surface Ops and Tele-Operational Transfer of Surface Assets to the Next Landing Site

    Science.gov (United States)

    Kring, D. A.

    2018-02-01

    The Deep Space Gateway can support astronauts on the lunar surface, providing them a departure and returning rendezvous point, a communication relay from the lunar farside to Earth, and a transfer point to Orion for return to Earth.

  20. Effect of Space Radiation Processing on Lunar Soil Surface Chemistry: X-Ray Photoelectron Spectroscopy Studies

    Science.gov (United States)

    Dukes, C.; Loeffler, M.J.; Baragiola, R.; Christoffersen, R.; Keller, J.

    2009-01-01

    Current understanding of the chemistry and microstructure of the surfaces of lunar soil grains is dominated by a reference frame derived mainly from electron microscopy observations [e.g. 1,2]. These studies have shown that the outermost 10-100 nm of grain surfaces in mature lunar soil finest fractions have been modified by the combined effects of solar wind exposure, surface deposition of vapors and accretion of impact melt products [1,2]. These processes produce surface-correlated nanophase Feo, host grain amorphization, formation of surface patinas and other complex changes [1,2]. What is less well understood is how these changes are reflected directly at the surface, defined as the outermost 1-5 atomic monolayers, a region not easily chemically characterized by TEM. We are currently employing X-ray Photoelectron Spectroscopy (XPS) to study the surface chemistry of lunar soil samples that have been previously studied by TEM. This work includes modification of the grain surfaces by in situ irradiation with ions at solar wind energies to better understand how irradiated surfaces in lunar grains change their chemistry once exposed to ambient conditions on earth.

  1. Potential fields on the ventricular surface of the exposed dog heart during normal excitation.

    Science.gov (United States)

    Arisi, G; Macchi, E; Baruffi, S; Spaggiari, S; Taccardi, B

    1983-06-01

    We studied the normal spread of excitation on the anterior and posterior ventricular surface of open-chest dogs by recording unipolar electrograms from an array of 1124 electrodes spaced 2 mm apart. The array had the shape of the ventricular surface of the heart. The electrograms were processed by a computer and displayed as epicardial equipotential maps at 1-msec intervals. Isochrone maps also were drawn. Several new features of epicardial potential fields were identified: (1) a high number of breakthrough points; (2) the topography, apparent widths, velocities of the wavefronts and the related potential drop; (3) the topography of positive potential peaks in relation to the wavefronts. Fifteen to 24 breakthrough points were located on the anterior, and 10 to 13 on the posterior ventricular surface. Some were in previously described locations and many others in new locations. Specifically, 3 to 5 breakthrough points appeared close to the atrioventricular groove on the anterior right ventricle and 2 to 4 on the posterior heart aspect; these basal breakthrough points appeared when a large portion of ventricular surface was still unexcited. Due to the presence of numerous breakthrough points on the anterior and posterior aspect of the heart which had not previously been described, the spread of excitation on the ventricular surface was "mosaic-like," with activation wavefronts spreading in all directions, rather than radially from the two breakthrough points, as traditionally described. The positive potential peaks which lay ahead of the expanding wavefronts moved along preferential directions which were probably related to the myocardial fiber direction.

  2. Surface photo-discoloration and degradation of dyed wood veneer exposed to different wavelengths of artificial light

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yi [MOE Key Laboratory of Wooden Material Science and Application, Beijing Forestry University, Beijing 100083 (China); Beijing Key Laboratory of Wood Science and Engineering, Beijing Forestry University, Beijing 100083 (China); MOE Engineering Research Center of Forestry Biomass Materials and Bioenergy, Beijing Forestry University, Beijing 100083 (China); Forest Products Development Center, School of Forestry and Wildlife Sciences, Auburn University, Auburn, AL 36830 (United States); Shao, Lingmin [MOE Key Laboratory of Wooden Material Science and Application, Beijing Forestry University, Beijing 100083 (China); Gao, Jianmin, E-mail: jmgao@bjfu.edu.cn [MOE Key Laboratory of Wooden Material Science and Application, Beijing Forestry University, Beijing 100083 (China); Beijing Key Laboratory of Wood Science and Engineering, Beijing Forestry University, Beijing 100083 (China); MOE Engineering Research Center of Forestry Biomass Materials and Bioenergy, Beijing Forestry University, Beijing 100083 (China); Guo, Hongwu, E-mail: hwg5052@163.com [MOE Key Laboratory of Wooden Material Science and Application, Beijing Forestry University, Beijing 100083 (China); Beijing Key Laboratory of Wood Science and Engineering, Beijing Forestry University, Beijing 100083 (China); MOE Engineering Research Center of Forestry Biomass Materials and Bioenergy, Beijing Forestry University, Beijing 100083 (China); Chen, Yao [MOE Key Laboratory of Wooden Material Science and Application, Beijing Forestry University, Beijing 100083 (China); Beijing Key Laboratory of Wood Science and Engineering, Beijing Forestry University, Beijing 100083 (China); MOE Engineering Research Center of Forestry Biomass Materials and Bioenergy, Beijing Forestry University, Beijing 100083 (China); Cheng, Qingzheng; Via, Brian K. [Forest Products Development Center, School of Forestry and Wildlife Sciences, Auburn University, Auburn, AL 36830 (United States)

    2015-03-15

    Highlights: • Investigate the selective absorption of different wavelengths of UV–vis light by dyed wood chromophores. • Identify connection between light wavelengths and surface color changes and chemical structure degradation. • Study hypochromic effect based on surface reflectance and K/S absorption changes during UV–vis irradiation. - Abstract: The surface of dyed wood is prone to discoloration when exposed to light irradiation which significantly decreases its decorative effect and shortens its service life. The influence of light wavelength exposure to the surface of dyed wood was investigated to study the effect on discoloration and degradation. Acid Blue V and Acid Red GR dyed wood veneers were subjected to light exposure with different wavelengths from the UV to visible region (254–420 nm). Results showed that the surface discoloration of dyed wood was linearly related to lignin concentration and dyes degradation and the consequent transformation of chromophoric groups such as aromatic (C=C) and carbonyl (C=O) through methoxy reaction. The dyes, lignin and some active constituents were degraded severely, even at short exposures. Acid Blue V dyed wood exhibited greater discoloration than the Acid Red GR treatment. The reflectance and K/S absorption curve showed a hypochromic effect on the dyed wood surface. The dyes and wood chemical structure played a complex and combined role on the selective absorption of different wavelengths of light. The color change rate was apparent with 254 nm exposure in the initial stages, but a greater discoloration rate occurred on the samples irradiated at 313 and 340 nm than at 254 and 420 nm with the time prolonged. The degradation rate and degree of discoloration correlated well with the light energy and wavelength.

  3. Expose : procedure and results of the joint experiment verification tests

    Science.gov (United States)

    Panitz, C.; Rettberg, P.; Horneck, G.; Rabbow, E.; Baglioni, P.

    The International Space Station will carry the EXPOSE facility accommodated at the universal workplace URM-D located outside the Russian Service Module. The launch will be affected in 2005 and it is planned to stay in space for 1.5 years. The tray like structure will accomodate 2 chemical and 6 biological PI-experiments or experiment systems of the ROSE (Response of Organisms to Space Environment) consortium. EXPOSE will support long-term in situ studies of microbes in artificial meteorites, as well as of microbial communities from special ecological niches, such as endolithic and evaporitic ecosystems. The either vented or sealed experiment pockets will be covered by an optical filter system to control intensity and spectral range of solar UV irradiation. Control of sun exposure will be achieved by the use of individual shutters. To test the compatibility of the different biological systems and their adaptation to the opportunities and constraints of space conditions a profound ground support program has been developed. The procedure and first results of this joint Experiment Verification Tests (EVT) will be presented. The results will be essential for the success of the EXPOSE mission and have been done in parallel with the development and construction of the final hardware design of the facility. The results of the mission will contribute to the understanding of the organic chemistry processes in space, the biological adaptation strategies to extreme conditions, e.g. on early Earth and Mars, and the distribution of life beyond its planet of origin.

  4. Control of the interparticle spacing in superparamagnetic iron oxide nanoparticle clusters by surface ligand engineering

    Science.gov (United States)

    Dan, Wang; Bingbing, Lin; Taipeng, Shen; Jun, Wu; Fuhua, Hao; Chunchao, Xia; Qiyong, Gong; Huiru, Tang; Bin, Song; Hua, Ai

    2016-07-01

    Polymer-mediated self-assembly of superparamagnetic iron oxide (SPIO) nanoparticles allows modulation of the structure of SPIO nanocrystal cluster and their magnetic properties. In this study, dopamine-functionalized polyesters (DA-polyester) were used to directly control the magnetic nanoparticle spacing and its effect on magnetic resonance relaxation properties of these clusters was investigated. Monodisperse SPIO nanocrystals with different surface coating materials (poly(ɛ-caprolactone), poly(lactic acid)) of different molecular weights containing dopamine (DA) structure (DA-PCL2k, DA-PCL1k, DA-PLA1k)) were prepared via ligand exchange reaction, and these nanocrystals were encapsulated inside amphiphilic polymer micelles to modulate the SPIO nanocrystal interparticle spacing. Small-angle x-ray scattering (SAXS) was applied to quantify the interparticle spacing of SPIO clusters. The results demonstrated that the tailored magnetic nanoparticle clusters featured controllable interparticle spacing providing directly by the different surface coating of SPIO nanocrystals. Systematic modulation of SPIO nanocrystal interparticle spacing can regulate the saturation magnetization (M s) and T 2 relaxation of the aggregation, and lead to increased magnetic resonance (MR) relaxation properties with decreased interparticle spacing. Project supported by the National Key Basic Research Program of China (Grant No. 2013CB933903), the National Key Technology R&D Program of China (Grant No. 2012BAI23B08), and the National Natural Science Foundation of China (Grant Nos. 20974065, 51173117, and 50830107).

  5. Composite Materials With Uncured Epoxy Matrix Exposed in Stratosphere During NASA Stratospheric Balloon Flight

    Science.gov (United States)

    Kondyurin, Alexey; Kondyurina, Irina; Bilek, Marcela; de Groh, Kim K.

    2013-01-01

    A cassette of uncured composite materials with epoxy resin matrixes was exposed in the stratosphere (40 km altitude) over three days. Temperature variations of -76 to 32.5C and pressure up to 2.1 torr were recorded during flight. An analysis of the chemical structure of the composites showed, that the polymer matrix exposed in the stratosphere becomes crosslinked, while the ground control materials react by way of polymerization reaction of epoxy groups. The space irradiations are considered to be responsible for crosslinking of the uncured polymers exposed in the stratosphere. The composites were cured on Earth after landing. Analysis of the cured composites showed that the polymer matrix remains active under stratospheric conditions. The results can be used for predicting curing processes of polymer composites in a free space environment during an orbital space flight.

  6. Interaction of Al with O{sub 2} exposed Mo{sub 2}BC

    Energy Technology Data Exchange (ETDEWEB)

    Bolvardi, Hamid; Music, Denis, E-mail: music@mch.rwth-aachen.de; Schneider, Jochen M.

    2015-03-30

    Highlights: • Al adheres to many surfaces. • Solid–solid interactions challenging for real (oxidized) surfaces. • Dissociative O{sub 2} adsorption on Mo{sub 2}BC(0 4 0). • Al nonamer is disrupted on oxidized Mo{sub 2}BC(0 4 0). • Adhesion of a residual Al on the native oxide. - Abstract: A Mo{sub 2}BC(0 4 0) surface was exposed to O{sub 2}. The gas interaction was investigated using ab initio molecular dynamics and X-ray photoelectron spectroscopy (XPS) of air exposed surfaces. The calculations suggest that the most dominating physical mechanism is dissociative O{sub 2} adsorption whereby Mo−O, O−Mo−O and Mo{sub 2}−C−O bond formation is observed. To validate these results, Mo{sub 2}BC thin films were synthesized utilizing high power pulsed magnetron sputtering and air exposed surfaces were probed by XPS. MoO{sub 2} and MoO{sub 3} bond formation is observed and is consistent with here obtained ab initio data. Additionally, the interfacial interactions of O{sub 2} exposed Mo{sub 2}BC(0 4 0) surface with an Al nonamer is studied with ab initio molecular dynamics to describe on the atomic scale the interaction between this surface and Al to mimic the interface present during cold forming processes of Al based alloys. The Al nonamer was disrupted and Al forms chemical bonds with oxygen contained in the O{sub 2} exposed Mo{sub 2}BC(0 4 0) surface. Based on the comparison of here calculated adsorption energy with literature data, Al−Al bonds are shown to be significantly weaker than the Al−O bonds formed across the interface. Hence, Al−Al bond rupture is expected for a mechanically loaded interface. Therefore the adhesion of a residual Al on the native oxide layer is predicted. This is consistent with experimental observations. The data presented here may also be relevant for other oxygen containing surfaces in a contact with Al or Al based alloys for example during forming operations.

  7. Characterization of Outer Space Radiation Induced Changes in Extremophiles Utilizing Deep Space Gateway Opportunities

    Science.gov (United States)

    Venkateswaran, K.; Wang, C.; Smith, D.; Mason, C.; Landry, K.; Rettberg, P.

    2018-02-01

    Extremophilic microbial survival, adaptation, biological functions, and molecular mechanisms associated with outer space radiation can be tested by exposing them onto Deep Space Gateway hardware (inside/outside) using microbiology and molecular biology techniques.

  8. Filamentation of a surface plasma wave over a semiconductor-free space interface

    Science.gov (United States)

    Kumar, Gagan; Tripathi, V. K.

    2007-12-01

    A large amplitude surface plasma wave (SPW), propagating over a semiconductor-free space interface, is susceptible to filamentation instability. A small perturbation in the amplitude of the SPW across the direction of propagation exerts a ponderomotive force on free electrons and holes, causing spatial modulation in free carrier density and hence the effective permittivity ɛeff of the semiconductor. The regions with higher ɛeff attract more power from the nieghborhood, leading to the growth of the perturbation. The growth rate increases with the intensity of the surface wave. It decreases with the frequency of the SPW.

  9. Estimating space-time mean concentrations of nutrients in surface waters of variable depth

    NARCIS (Netherlands)

    Knotters, M.; Brus, D.J.

    2010-01-01

    A monitoring scheme has been designed to test whether the space-time mean concentration total Nitrogen (N-total) in the surface water in the Northern Frisian Woodlands (NFW, The Netherlands) complies with standards of the European Water Framework directive. Since in statistical testing for

  10. Surface displacements and energy release rates for constant stress drop slip zones in joined elastic quarter spaces

    Science.gov (United States)

    Rodgers, Michael J.; Wen, Shengmin; Keer, Leon M.

    2000-08-01

    A three-dimensional quasi-static model of faulting in an elastic half-space with a horizontal change of material properties (i.e., joined elastic quarter spaces) is considered. A boundary element method is used with a stress drop slip zone approach so that the fault surface relative displacements as well as the free surface displacements are approximated in elements over their respective domains. Stress intensity factors and free surface displacements are calculated for a variety of cases to show the phenomenological behavior of faulting in such a medium. These calculations showed that the behavior could be distinguished from a uniform half-space. Slip in a stiffer material increases, while slip in a softer material decreases the energy release rate and the free surface displacements. Also, the 1989 Kalapana earthquake was located on the basis of a series of forward searches using this method and leveling data. The located depth is 8 km, which is the closer to the seismically inferred depth than that determined from other models. Finally, the energy release rate, which can be used as a fracture criterion for fracture at this depth, is calculated to be 11.1×106 J m-2.

  11. Characterization of Candidate Solar Sail Material Exposed to Space Environmental Effects

    Science.gov (United States)

    Edwards, David; Hovater, Mary; Hubbs, Whitney; Wertz, George; Hollerman, William; Gray, Perry

    2003-01-01

    Solar sailing is a unique form of propulsion where a spacecraft gains momentum from incident photons. Solar sails are not limited by reaction mass and provide continual acceleration, reduced only by the lifetime of the lightweight film in the space environment and the distance to the Sun. Once thought to be difficult or impossible, solar sailing has come out of science fiction and into the realm of possibility. Any spacecraft using this method would need to deploy a thin sail that could be as large as many kilometers in extent. The availability of strong, ultra lightweight, and radiation resistant materials will determine the future of solar sailing. The National Aeronautics and Space Administration's Marshall Space Flight Center (MSFC) is concentrating research into the utilization of ultra lightweight materials for spacecraft propulsion. The Space Environmental Effects Team at MSFC is actively characterizing candidate solar sail material to evaluate the thermo-optical and mechanical properties after exposure to space environmental effects. This paper will describe the exposure of candidate solar sail materials to emulated space environmental effects including energetic electrons, combined electrons and Ultraviolet radiation, and hypervelocity impact of irradiated solar sail material. This paper will describe the testing procedure and the material characterization results of this investigation.

  12. Simulation of reflecting surface deviations of centimeter-band parabolic space radiotelescope (SRT) with the large-size mirror

    Science.gov (United States)

    Kotik, A.; Usyukin, V.; Vinogradov, I.; Arkhipov, M.

    2017-11-01

    he realization of astrophysical researches requires the development of high-sensitive centimeterband parabolic space radiotelescopes (SRT) with the large-size mirrors. Constructively such SRT with the mirror size more than 10 m can be realized as deployable rigid structures. Mesh-structures of such size do not provide the reflector reflecting surface accuracy which is necessary for the centimeter band observations. Now such telescope with the 10 m diameter mirror is developed in Russia in the frame of "SPECTR - R" program. External dimensions of the telescope is more than the size of existing thermo-vacuum chambers used to prove SRT reflecting surface accuracy parameters under the action of space environment factors. That's why the numerical simulation turns out to be the basis required to accept the taken designs. Such modeling should be based on experimental working of the basic constructive materials and elements of the future reflector. In the article computational modeling of reflecting surface deviations of a centimeter-band of a large-sized deployable space reflector at a stage of his orbital functioning is considered. The analysis of the factors that determines the deviations - both determined (temperatures fields) and not-determined (telescope manufacturing and installation faults; the deformations caused by features of composite materials behavior in space) is carried out. The finite-element model and complex of methods are developed. They allow to carry out computational modeling of reflecting surface deviations caused by influence of all factors and to take into account the deviations correction by space vehicle orientation system. The results of modeling for two modes of functioning (orientation at the Sun) SRT are presented.

  13. Bacterial DNA of Ocean and Land on the Surface of the International Space Station.

    Science.gov (United States)

    Grebennikova, Tatiana

    A.V. Syroeshkin2, T.V. Grebennikova1, E.V. Shubralova3, V.A. Shuvalov3, O.S. Tsygankov4, V.B. Lapshin2 1D. I. Ivanovsky Virology Institute, Moscow, Russia 2 Academician E. K. Fedorov Institute of Applied Geophysics, Moscow, Russia 3S.P. Korolev Rocket and Space Corporation «Energia» Korolev, Russia 4Central Research Institute of Machine Building, Korolev, Russia Existence of biological molecules as markers of microorganisms in the space environment has always attracted attention of researchers. There is great attention to the search for extraterrestrial life forms [Nicholson W.L. 2009, Kawaguchi Y. et al 2013], and as well as the coping mechanisms of living organisms in the interplanetary space [Hotchin J. et al 1965, Baranov V.M. 2009, Horneck G. et al 2010]. Experiments on American and Japanese segments of the International Space Station (ISS) over the different nature of resistance during prolonged stay in space were conducted [Scalzi G et al 2012, Wassmann M. et al 2012]. As a result of these experiments confirmed the possibility of preserving the viability of organisms in an open space for a long time. Consequence, became interested in the transfer of living matter from the stratosphere to near-Earth space [Smith D.J. 2013]. We hypothesized that viable forms, or at least, intact DNA can be transferred to the orbit of the ISS with the ascending branch of the global electric circuit. Samples of cosmic dust collected from the surface of the window of the ISS during the exit of an astronaut in space. Samples (washes with material of tampons and tampons) which were in vacuo, were analyzed for the presence of bacterial DNA by nested PCR using primers specific DNA genus Mycobacterium, the DNA of the strain of the genus Bacillus anthracis and DNA encoding the bacterial 16S ribosomal RNA after transportation of the samples to Earth. The results of amplification, followed by sequencing and phylogenetic analysis showed the presence in samples of cosmic dust DNA

  14. Identification of Novel Surface-Exposed Proteins of Rickettsia rickettsii by Affinity Purification and Proteomics

    Science.gov (United States)

    Gong, Wenping; Xiong, Xiaolu; Qi, Yong; Jiao, Jun; Duan, Changsong; Wen, Bohai

    2014-01-01

    Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever, is the most pathogenic member among Rickettsia spp. Surface-exposed proteins (SEPs) of R. rickettsii may play important roles in its pathogenesis or immunity. In this study, R. rickettsii organisms were surface-labeled with sulfo-NHS-SS-biotin and the labeled proteins were affinity-purified with streptavidin. The isolated proteins were separated by two-dimensional electrophoresis, and 10 proteins were identified among 23 protein spots by electrospray ionization tandem mass spectrometry. Five (OmpA, OmpB, GroEL, GroES, and a DNA-binding protein) of the 10 proteins were previously characterized as surface proteins of R. rickettsii. Another 5 proteins (Adr1, Adr2, OmpW, Porin_4, and TolC) were first recognized as SEPs of R. rickettsii herein. The genes encoding the 5 novel SEPs were expressed in Escherichia coli cells, resulting in 5 recombinant SEPs (rSEPs), which were used to immunize mice. After challenge with viable R. rickettsii cells, the rickettsial load in the spleen, liver, or lung of mice immunized with rAdr2 and in the lungs of mice immunized with other rSEPs excluding rTolC was significantly lower than in mice that were mock-immunized with PBS. The in vitro neutralization test revealed that sera from mice immunized with rAdr1, rAdr2, or rOmpW reduced R. rickettsii adherence to and invasion of vascular endothelial cells. The immuno-electron microscopic assay clearly showed that the novel SEPs were located in the outer and/or inner membrane of R. rickettsii. Altogether, the 5 novel SEPs identified herein might be involved in the interaction of R. rickettsii with vascular endothelial cells, and all of them except TolC were protective antigens. PMID:24950252

  15. Identification of novel surface-exposed proteins of Rickettsia rickettsii by affinity purification and proteomics.

    Directory of Open Access Journals (Sweden)

    Wenping Gong

    Full Text Available Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever, is the most pathogenic member among Rickettsia spp. Surface-exposed proteins (SEPs of R. rickettsii may play important roles in its pathogenesis or immunity. In this study, R. rickettsii organisms were surface-labeled with sulfo-NHS-SS-biotin and the labeled proteins were affinity-purified with streptavidin. The isolated proteins were separated by two-dimensional electrophoresis, and 10 proteins were identified among 23 protein spots by electrospray ionization tandem mass spectrometry. Five (OmpA, OmpB, GroEL, GroES, and a DNA-binding protein of the 10 proteins were previously characterized as surface proteins of R. rickettsii. Another 5 proteins (Adr1, Adr2, OmpW, Porin_4, and TolC were first recognized as SEPs of R. rickettsii herein. The genes encoding the 5 novel SEPs were expressed in Escherichia coli cells, resulting in 5 recombinant SEPs (rSEPs, which were used to immunize mice. After challenge with viable R. rickettsii cells, the rickettsial load in the spleen, liver, or lung of mice immunized with rAdr2 and in the lungs of mice immunized with other rSEPs excluding rTolC was significantly lower than in mice that were mock-immunized with PBS. The in vitro neutralization test revealed that sera from mice immunized with rAdr1, rAdr2, or rOmpW reduced R. rickettsii adherence to and invasion of vascular endothelial cells. The immuno-electron microscopic assay clearly showed that the novel SEPs were located in the outer and/or inner membrane of R. rickettsii. Altogether, the 5 novel SEPs identified herein might be involved in the interaction of R. rickettsii with vascular endothelial cells, and all of them except TolC were protective antigens.

  16. Underground spaces/cybernetic spaces

    Directory of Open Access Journals (Sweden)

    Tomaž Novljan

    2000-01-01

    Full Text Available A modern city space is a space where in the vertical and horizontal direction dynamic, non-linear processes exist, similar as in nature. Alongside the “common” city surface, cities have underground spaces as well that are increasingly affecting the functioning of the former. It is the space of material and cybernetic communication/transport. The psychophysical specifics of using underground places have an important role in their conceptualisation. The most evident facts being their limited volume and often limited connections to the surface and increased level of potential dangers of all kinds. An efficient mode for alleviating the effects of these specific features are artistic interventions, such as: shape, colour, lighting, all applications of the basic principles of fractal theory.

  17. Integrating Satellite, Radar and Surface Observation with Time and Space Matching

    Science.gov (United States)

    Ho, Y.; Weber, J.

    2015-12-01

    The Integrated Data Viewer (IDV) from Unidata is a Java™-based software framework for analyzing and visualizing geoscience data. It brings together the ability to display and work with satellite imagery, gridded data, surface observations, balloon soundings, NWS WSR-88D Level II and Level III RADAR data, and NOAA National Profiler Network data, all within a unified interface. Applying time and space matching on the satellite, radar and surface observation datasets will automatically synchronize the display from different data sources and spatially subset to match the display area in the view window. These features allow the IDV users to effectively integrate these observations and provide 3 dimensional views of the weather system to better understand the underlying dynamics and physics of weather phenomena.

  18. On the Gauss Map of Surfaces of Revolution with Lightlike Axis in Minkowski 3-Space

    Directory of Open Access Journals (Sweden)

    Minghao Jin

    2013-01-01

    Full Text Available By studying the Gauss map G and Laplace operator Δh of the second fundamental form h, we will classify surfaces of revolution with a lightlike axis in 3-dimensional Minkowski space and also obtain the surface of Enneper of the 2nd kind, the surface of Enneper of the 3rd kind, the de Sitter pseudosphere, and the hyperbolic pseudosphere that satisfy condition ΔhG=ΛG, Λ being a 3×3 real matrix.

  19. Equilibrium Crystal Shape of BaZrO{sub 3} and Space Charge Formation in the (011) Surface by Using Ab-Initio Thermodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Ji-Su; Kim, Yeong-Cheol [Korea University of Technology and Education, Cheonan (Korea, Republic of)

    2017-01-15

    We investigated the equilibrium crystal shape of BaZrO{sub 3} and the space charge formation in an O-terminated (011) surface by using ab-initio thermodynamics. Twenty-two low-indexed (001), (011), and (111) surfaces were calculated to analyze their surface Gibbs-free energy under the stable condition of BaZrO{sub 3}. Based on the Gibbs-Wulff theorem, the equilibrium crystal shape of BaZrO{sub 3} changed from cubic to decaoctahedral with decreasing Ba chemical potential. The dominant facets of BaZrO{sub 3} were {001} and {011}, which were well consistent with experimental observations. The space charge formation in the (011) surface was evaluated using the space-charge model. We found that the (011) surface was even more resistive than the (001) surface.

  20. New Method to Characterize Degradation of First Surface Aluminum Reflectors: Preprint

    Energy Technology Data Exchange (ETDEWEB)

    Sutter, F.; Heller, P.; Meyen, S.; Pitz-Paal, R.; Kennedy, C.; Fernandez-Garcia, A.; Schmucker, M.

    2010-10-01

    This paper reports the development of a new optical instrument capable of characterizing the aging process of enhanced first surface aluminum reflectors for concentrating solar power (CSP) application. Samples were exposed outdoors at different sites and in accelerated exposure tests. All samples exposed outdoors showed localized corrosion spots. Degradation originated from points of damage in the protective coating, but propagated underneath the protective coating. The degraded samples were analyzed with a microscope and with a newly designed space-resolved specular reflectometer (SR)2 that is capable of optically detecting and characterizing the corrosion spots. The device measures the specular reflectance at three acceptance angles and the wavelengths with spatial resolution using a digital camera's CMOS sensor. It can be used to measure the corrosion growth rate during outdoor and accelerated exposure tests. These results will allow a correlation between the degraded mirror surface and its specular reflectance.

  1. Convection heat transfer of closely-spaced spheres with surface blowing

    Energy Technology Data Exchange (ETDEWEB)

    Kleinstreuer, C. (North Carolina State Univ., Raleigh, NC (United States). Dept. of Mechanical and Aerospace Engineering); Chiang, H. (Thermofluid Technology Div., Industrial Technology Research Inst., Chutung (Taiwan, Province of China))

    1993-05-01

    A validated computer simulation model has been developed for the analysis of colinear spheres in a heated gas stream. Using the Galerkin finite element method, the steady-state Navier-Stokes and heat transfer equations have been solved describing laminar axisymmetric thermal flow past closely-spaced monodisperse spheres with fluid injection. Of interest are the coupled nonlinear interaction effects on the temperature fields and ultimately on the Nusselt number of each sphere for different free stream Reynolds numbers (20 [<=] Re [<=] 200) and intersphere distances (1.5 [<=] d[sub ij] [<=] 6.0) in the presence of surface blowing (0 [<=] v[sub b] [<=] 0.1). Fluid injection (i.e. blowing) and associated wake effects generate lower average heat transfer coefficients for each interacting sphere when the Reynolds number increases (Re > 100). Heat transfer is also reduced at small spacings especially for the second and third sphere. A Nusselt number correlation for each interacting (porous) sphere has been developed based on computer experiments. (orig.)

  2. Evaluation of space environmental effects on metals and optical thin films on EOIM-3

    Energy Technology Data Exchange (ETDEWEB)

    Vaughn, J.A.; Linton, R.C.; Finckenor, M.M.; Kamenetzky, R.R.

    1995-02-01

    Metals and optical thin films exposed to the space environment on the Third Flight of the Evaluation of Oxygen Interactions with Materials (EOIM-3) payload, onboard Space Shuttle mission STS-46 were evaluated. The materials effects described in this paper include the effects of space exposure on various pure metals, optical thin films, and optical thin film metals. The changes induced by exposure to the space environment in the material properties were evaluated using bidirectional reflectance distribution function (BRDF), specular reflectance (250 nm to 2500 nm), ESCA, VUV reflectance (120 nm to 200 nm), ellipsometry, FTIR and optical properties. Using these analysis techniques gold optically thin film metal mirrors with nickel undercoats were observed to darken due to nickel diffusion through the gold to the surface. Also, thin film nickel mirrors formed nickel oxide due to exposure to both the atmosphere and space.

  3. Evaluation of space environmental effects on metals and optical thin films on EOIM-3

    Science.gov (United States)

    Vaughn, Jason A.; Linton, Roger C.; Finckenor, Miria M.; Kamenetzky, Rachel R.

    1995-01-01

    Metals and optical thin films exposed to the space environment on the Third Flight of the Evaluation of Oxygen Interactions with Materials (EOIM-3) payload, onboard Space Shuttle mission STS-46 were evaluated. The materials effects described in this paper include the effects of space exposure on various pure metals, optical thin films, and optical thin film metals. The changes induced by exposure to the space environment in the material properties were evaluated using bidirectional reflectance distribution function (BRDF), specular reflectance (250 nm to 2500 nm), ESCA, VUV reflectance (120 nm to 200 nm), ellipsometry, FTIR and optical properties. Using these analysis techniques gold optically thin film metal mirrors with nickel undercoats were observed to darken due to nickel diffusion through the gold to the surface. Also, thin film nickel mirrors formed nickel oxide due to exposure to both the atmosphere and space.

  4. Space vehicle chassis

    Science.gov (United States)

    Judd, Stephen; Dallmann, Nicholas; Seitz, Daniel; Martinez, John; Storms, Steven; Kestell, Gayle

    2017-07-18

    A modular space vehicle chassis may facilitate convenient access to internal components of the space vehicle. Each module may be removable from the others such that each module may be worked on individually. Multiple panels of at least one of the modules may swing open or otherwise be removable, exposing large portions of the internal components of the space vehicle. Such chassis architectures may reduce the time required for and difficulty of performing maintenance or modifications, may allow multiple space vehicles to take advantage of a common chassis design, and may further allow for highly customizable space vehicles.

  5. Structural evolution of derived species on FeAl surface exposed to a N2 + SO2 atmosphere: Experimental and theoretical study

    International Nuclear Information System (INIS)

    Espinosa-Medina, M.A.; Liu, H.B.; Canizal, G.; Ascencio, J.A.

    2007-01-01

    Characterizations were performed by scanning electron microscopy analysis with energy dispersive spectrometry and scanning probe microscope for structural evolution of derived species on FeAl surface exposed to a N 2 + SO 2 atmosphere at high temperature. First principle calculations were also employed in order to clarify the formation of new product on the surface and its mechanism. The results demonstrate that the tendency of the structure with oxygen atoms involve a stronger interaction and lower energy to be formed with the surface and consequently the possible production of oxide-species is more probable and multiple aggregates with different shapes can be generated for the temperatures of 625 and 700 deg. C, with no preferential crystal habit. Sample treated at 775 deg. C denotes the production of hexagonal crystals, which is externally characterized by polyhedrons growing in axial direction as fibbers with flat faces that match with the alumina

  6. Cold Atmospheric Plasma Technology for Decontamination of Space Equipment

    Science.gov (United States)

    Thomas, Hubertus; Rettberg, Petra; Shimizu, Tetsuji; Thoma, Markus; Morfill, Gregor; Zimmermann, Julia; Müller, Meike; Semenov, Igor

    2016-07-01

    Cold atmospheric plasma (CAP) technology is very fast and effective in inactivation of all kinds of pathogens. It is used in hygiene and especially in medicine, since the plasma treatment can be applied to sensitive surfaces, like skin, too. In a first study to use CAP for the decontamination of space equipment we could show its potential as a quite promising alternative to the standard "dry heat" and H2O2 methods [Shimizu et al. Planetary and Space Science, 90, 60-71. (2014)]. In a follow-on study we continue the investigations to reach high application level of the technology. First, we redesign the actual setup to a plasma-gas circulation system, increasing the effectivity of inactivation and the sustainability. Additionally, we want to learn more about the plasma chemistry processes involved in the inactivation. Therefore, we perform detailed plasma and gas measurements and compare them to numerical simulations. The latter will finally be used to scale the decontamination system to sizes useful also for larger space equipment. Typical materials relevant for space equipment will be tested and investigated on surface material changes due to the plasma treatment. Additionally, it is planned to use electronic boards and compare their functionality before and after the CAP expose. We will give an overview on the status of the plasma decontamination project funded by the Bavarian Ministry of Economics.

  7. Attention bias in earthquake-exposed survivors: an event-related potential study.

    Science.gov (United States)

    Zhang, Yan; Kong, Fanchang; Han, Li; Najam Ul Hasan, Abbasi; Chen, Hong

    2014-12-01

    The Chinese Wenchuan earthquake, which happened on the 28th of May in 2008, may leave deep invisible scars in individuals. China has a large number of children and adolescents, who tend to be most vulnerable because they are in an early stage of human development and possible post-traumatic psychological distress may have a life-long consequence. Trauma survivors without post-traumatic stress disorder (PTSD) have received little attention in previous studies, especially in event-related potential (ERP) studies. We compared the attention bias to threat stimuli between the earthquake-exposed group and the control group in a masked version of the dot probe task. The target probe presented at the same space location consistent with earthquake-related words was the congruent trial, while in the space location of neutral words was the incongruent trial. Thirteen earthquake-exposed middle school students without PTSD and 13 matched controls were included in this investigation. The earthquake-exposed group showed significantly faster RTs to congruent trials than to incongruent trials. The earthquake-exposed group produced significantly shorter C1 and P1 latencies and larger C1, P1 and P2 amplitudes than the control group. In particular, enhanced P1 amplitude to threat stimuli was observed in the earthquake-exposed group. These findings are in agreement with the prediction that earthquake-exposed survivors have an attention bias to threat stimuli. The traumatic event had a much greater effect on earthquake-exposed survivors even if they showed no PTSD symptoms than individuals in the controls. These results will provide neurobiological evidences for effective intervention and prevention to post-traumatic mental problems. Copyright © 2014 Elsevier B.V. All rights reserved.

  8. Morphological study of polymer surfaces exposed to non-thermal plasma based on contact angle and the use of scaling laws

    Science.gov (United States)

    Felix, T.; Cassini, F. A.; Benetoli, L. O. B.; Dotto, M. E. R.; Debacher, N. A.

    2017-05-01

    The experiments presented in this communication have the purpose to elaborate an explanation for the morphological evolution of the growth of polymeric surfaces provided by the treatment of non-thermal plasma. According to the roughness analysis and the model proposed by scaling laws it is possible relate to a predictable or merely random effect. Polyethylene terephthalate (PET) and poly(etherether)ketone (PEEK) samples were exposed to a non-thermal plasma discharge and the resulting surfaces roughness were analyzed based on the measurements from contact angle, scanning electron microscopy and atomic force microscopy coupled with scaling laws analysis which can help to describe and understand the dynamic of formation of a wide variety of rough surfaces. The roughness, RRMS (RMS- Root Mean Square) values for polymer surface range between 19.8 nm and 110.9 nm. The contact angle and the AFM (Atomic Force Microscopy) measurements as a function of the plasma exposure time were in agreement with both polar and dispersive components according to the surface roughness and also with the morphology evaluated described by Wolf-Villain model, with proximate values of α between 0.91(PET) and 0.88(PEEK), β = 0.25(PET) and z = 3,64(PET).

  9. Silver deposition on stainless steel container surfaces in contact with disinfectant silver aqueous solutions

    International Nuclear Information System (INIS)

    Petala, M.; Tsiridis, V.; Mintsouli, I.; Pliatsikas, N.; Spanos, Th.; Rebeyre, P.; Darakas, E.; Patsalas, P.; Vourlias, G.; Kostoglou, M.; Sotiropoulos, S.; Karapantsios, Th.

    2017-01-01

    Highlights: • Silver is one of the biocides of water consumed in the International Space Station. • Ionic silver is depleted from potable water when in contact with stainless steel (SS). • SEM and XPS analysis reveal a uniform silver deposition over the SS surface. • Silver deposits in its metallic form, in line with a galvanic deposition mechanism. • Evidence is provided that Cr and/ or Ni oxide builds-up on SS surfaces. - Abstract: Silver is the preservative used on the Russian segment of the International Space Station (ISS) to prevent microbial proliferation within potable water supplies. Yet, in the frame of the European Automated Transfer Vehicle (ATV) missions to ISS, silver depletion from water has been detected during ground transportation of this water to launch site, thereby indicating a degradation of water quality. This study investigates the silver loss from water when in contact with stainless steel surfaces. Experiments are conducted with several types of stainless steel surfaces being exposed to water containing 10 or 0.5 mg/L silver ions. Results show that silver deposits on stainless steel surfaces even when a passivation layer protects the metallic surface. The highest protection to silver deposition is offered by acid passivated and electropolished SS 316L. SEM and XPS experiments were carried out at several locations of the sample area that was in contact with the Ag solution and found similar morphological (SEM) and compositional (sputter-etch XPS) results. The results reveal that silver deposits uniformly across the wetted surface to a thickness larger than 3 nm. Moreover, evidence is provided that silver deposits in its metallic form on all stainless steel surfaces, in line with a galvanic deposition mechanism. Combination of ICP-MS and XPS results suggests a mechanism for Ag deposition/reduction with simultaneous substrate oxidation resulting in oxide growth at the exposed stainless steel surface.

  10. Silver deposition on stainless steel container surfaces in contact with disinfectant silver aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Petala, M., E-mail: petala@civil.auth.gr [Department of Civil Engineering, Aristotle University of Thessaloniki, Thessaloniki, 54124 (Greece); Tsiridis, V. [Department of Civil Engineering, Aristotle University of Thessaloniki, Thessaloniki, 54124 (Greece); Mintsouli, I. [Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki, 54124 (Greece); Pliatsikas, N. [Department of Physics, Aristotle University of Thessaloniki, Thessaloniki, 54124 (Greece); Spanos, Th. [Department of Petroleum and Mechanical Engineering Sciences, Eastern Macedonia and Thrace Institute of Technology, Kavala, 65404 (Greece); Rebeyre, P. [ESA/ESTEC, P.O.Box 299, 2200 AG, Noordwijk (Netherlands); Darakas, E. [Department of Civil Engineering, Aristotle University of Thessaloniki, Thessaloniki, 54124 (Greece); Patsalas, P.; Vourlias, G. [Department of Physics, Aristotle University of Thessaloniki, Thessaloniki, 54124 (Greece); Kostoglou, M.; Sotiropoulos, S.; Karapantsios, Th. [Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki, 54124 (Greece)

    2017-02-28

    Highlights: • Silver is one of the biocides of water consumed in the International Space Station. • Ionic silver is depleted from potable water when in contact with stainless steel (SS). • SEM and XPS analysis reveal a uniform silver deposition over the SS surface. • Silver deposits in its metallic form, in line with a galvanic deposition mechanism. • Evidence is provided that Cr and/ or Ni oxide builds-up on SS surfaces. - Abstract: Silver is the preservative used on the Russian segment of the International Space Station (ISS) to prevent microbial proliferation within potable water supplies. Yet, in the frame of the European Automated Transfer Vehicle (ATV) missions to ISS, silver depletion from water has been detected during ground transportation of this water to launch site, thereby indicating a degradation of water quality. This study investigates the silver loss from water when in contact with stainless steel surfaces. Experiments are conducted with several types of stainless steel surfaces being exposed to water containing 10 or 0.5 mg/L silver ions. Results show that silver deposits on stainless steel surfaces even when a passivation layer protects the metallic surface. The highest protection to silver deposition is offered by acid passivated and electropolished SS 316L. SEM and XPS experiments were carried out at several locations of the sample area that was in contact with the Ag solution and found similar morphological (SEM) and compositional (sputter-etch XPS) results. The results reveal that silver deposits uniformly across the wetted surface to a thickness larger than 3 nm. Moreover, evidence is provided that silver deposits in its metallic form on all stainless steel surfaces, in line with a galvanic deposition mechanism. Combination of ICP-MS and XPS results suggests a mechanism for Ag deposition/reduction with simultaneous substrate oxidation resulting in oxide growth at the exposed stainless steel surface.

  11. Fracture behaviour of the 14Cr ODS steel exposed to helium and liquid lead

    Science.gov (United States)

    Hojna, Anna; Di Gabriele, Fosca; Hadraba, Hynek; Husak, Roman; Kubena, Ivo; Rozumova, Lucia; Bublikova, Petra; Kalivodova, Jana; Matejicek, Jiri

    2017-07-01

    This work describes the fracture behaviour of the 14Cr ODS steel produced by mechanical alloying process, after high temperature exposures. Small specimens were exposed to helium gas in a furnace at 720 °C for 500 h. Another set of specimens was exposed to flowing liquid lead in the COLONRI II loop at 650 °C for 1000 h. All specimens were tested for the impact and tensile behaviour. The impact test results are compared to other sets of specimens in the as received state and after isothermal annealing at 650 °C for 1000 h. The impact curves of the exposed materials showed positive shifts on the transition temperature. While the upper shelf value did not change in the Pb exposed ODS steel, it significantly increased in the He exposed one. The differences are discussed in terms of surface and subsurface microscopy observation. The embrittlement can be explained as the effect of a slight change in the grain boundary and size distribution combined with the depletion of sub-surface region from alloying elements forming oxide scale on the surface.

  12. Psyche's UV Reflectance Spectra: Exploring the origins of the largest exposed-core metallic asteroid

    Science.gov (United States)

    Becker, Tracy

    2016-10-01

    (16) Psyche is the largest of the M-class asteroids, and is presumed to be the exposed core of a differentiated asteroid stripped of its mantle through hit-and-run collisions. However, other origins for Psyche have been proposed, including that it formed from a highly-reduced, metal rich material in the inner solar system or that its surface is olivine that has been space weathered. If (16) Psyche is an exposed core, then studying its properties enhances our understanding of the cores of all terrestrial planets, including the Earth's. If it accreted in the inner part of the solar system and was later injected into the asteroid belt, then Psyche sheds light on the conditions and subsequent evolution of the early solar system. Lastly, if Psyche is weathered olivine, then olivine may be more abundant in the solar system than currently measured, rectifying the so-called Great Dunite Shortage. Our program to obtain high-resolution UV spectra of Psyche with the COS G140L mode and the STIS NUV MAMA G230L mode to measure spectral signatures between 90 - 315 nm is designed to distinguish between the 3 hypothesized cases. These observations will enable identification of absorption bands, especially Fe-O charge transfer bands and will be sensitive to spectral blueing that occurs at UV wavelengths for space-weathered objects. When combined, the presence of these UV features, or not, provides a novel test of Psyche formation theories.

  13. Fracture behaviour of the 14Cr ODS steel exposed to helium and liquid lead

    Energy Technology Data Exchange (ETDEWEB)

    Hojna, Anna, E-mail: Anna.Hojna@cvrez.cz [Centrum Vyzkumu Rez s.r.o., UJV Group, Rez 130, 250 68 Husinec (Czech Republic); Di Gabriele, Fosca [Centrum Vyzkumu Rez s.r.o., UJV Group, Rez 130, 250 68 Husinec (Czech Republic); Hadraba, Hynek; Husak, Roman; Kubena, Ivo [CEITEC IPM, Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Zizkova 22, 616 62 Brno (Czech Republic); Rozumova, Lucia; Bublikova, Petra; Kalivodova, Jana [Centrum Vyzkumu Rez s.r.o., UJV Group, Rez 130, 250 68 Husinec (Czech Republic); Matejicek, Jiri [Institute of Plasma Physics, Academy of Sciences of the Czech Republic, Za Slovankou 1782/3, 182 00 Praha (Czech Republic)

    2017-07-15

    This work describes the fracture behaviour of the 14Cr ODS steel produced by mechanical alloying process, after high temperature exposures. Small specimens were exposed to helium gas in a furnace at 720 °C for 500 h. Another set of specimens was exposed to flowing liquid lead in the COLONRI II loop at 650 °C for 1000 h. All specimens were tested for the impact and tensile behaviour. The impact test results are compared to other sets of specimens in the as received state and after isothermal annealing at 650 °C for 1000 h. The impact curves of the exposed materials showed positive shifts on the transition temperature. While the upper shelf value did not change in the Pb exposed ODS steel, it significantly increased in the He exposed one. The differences are discussed in terms of surface and subsurface microscopy observation. The embrittlement can be explained as the effect of a slight change in the grain boundary and size distribution combined with the depletion of sub-surface region from alloying elements forming oxide scale on the surface. - Highlights: •We compared the impact energy curves of as received, isothermally aged and He/Pb exposed ODS steel samples. •The highest transition temperature showed the ODS steel exposed to liquid Pb at 650 °C for 1000 h. •We observed the higher tendency of the He exposed samples to crack arrester delamination than the Pb exposed ones. •The crack arrested delamination induced apparent increase of impact energies.

  14. Contamination of optical surfaces in Earth orbit

    Science.gov (United States)

    Kinser, Donald L.; Weller, Robert A.; Mendenhall, M. H.; Wiedlocher, D. E.; Nichols, R.; Tucker, D.; Whitaker, A.

    1992-01-01

    Glass and glass ceramic samples exposed to the low earth orbit environment for approximately 5.5 years on the Long Duration Exposure Facility (LDEF) were found to display limited degradation in optical transmission. Commercial optical quality fused silica samples display decreases in transmission in the 200 to 400 nm wavelength region, and this degradation appears to be a consequence of surface contamination. The contamination, found only on internal surfaces of samples, was measured by medium energy backscattering spectrometry and found to be primarily carbon. Additional thin film contamination by a species with atomic mass near 64, which was present at the level of about 8 x 10 exp 14/sq. cm has not been identified. These observations are consistent with the interpretation that organic binders used in the black absorbing paint (Chem Glaze Z-306) inside the sample holding tray were concentrated in the vicinity of the samples and photolytically cracked by solar UV radiation. The resulting decomposition products were deposited on the interior sample surface and gave rise to the optical transmission loss. No detectable contamination was observed on the external or space exposed surface of the samples. No measurable damage was detected which could be attributed to the direct action of gamma or UV radiation on the glass samples. These results emphasize the need for special precautions in the preparation of spacecraft carrying precision optical components on long duration missions.

  15. Fabrication of Al2O3 Nano-Structure Functional Film on a Cellulose Insulation Polymer Surface and Its Space Charge Suppression Effect

    Directory of Open Access Journals (Sweden)

    Jian Hao

    2017-10-01

    Full Text Available Cellulose insulation polymer (paper/pressboard has been widely used in high voltage direct current (HVDC transformers. One of the most challenging issues in the insulation material used for HVDC equipment is the space charge accumulation. Effective ways to suppress the space charge injection/accumulation in insulation material is currently a popular research topic. In this study, an aluminium oxide functional film was deposited on a cellulose insulation pressboard surface using reactive radio frequency (RF magnetron sputtering. The sputtered thin film was characterized by the scanning electron microscopy/energy dispersive spectrometer (SEM/EDS, X-ray photoelectron spectroscopy (XPS, and X-ray diffraction (XRD. The influence of the deposited functional film on the dielectric properties and the space charge injection/accumulation behaviour was investigated. A preliminary exploration of the space charge suppression effect is discussed. SEM/EDS, XPS, and XRD results show that the nano-structured Al2O3 film with amorphous phase was successfully fabricated onto the fibre surface. The cellulose insulation pressboard surface sputtered by Al2O3 film has lower permittivity, conductivity, and dissipation factor values in the lower frequency (<103 Hz region. The oil-impregnated sputtered pressboard presents an apparent space-charge suppression effect. Compared with the pressboard sputtered with Al2O3 film for 90 min, the pressboard sputtered with Al2O3 film for 60 min had a better space charge suppression effect. Ultra-small Al2O3 particles (<10 nm grew on the surface of the larger nanoparticles. The nano-structured Al2O3 film sputtered on the fibre surface could act as a functional barrier layer for suppression of the charge injection and accumulation. This study offers a new perspective in favour of the application of insulation pressboard with a nano-structured function surface against space charge injection/accumulation in HVDC equipment.

  16. Morphological study of polymer surfaces exposed to non-thermal plasma based on contact angle and the use of scaling laws

    Energy Technology Data Exchange (ETDEWEB)

    Felix, T., E-mail: tsfelix81@gmail.com [Chemistry Department, Federal University of Santa Catarina, Campus Trindade, 88040-900 Florianópolis, SC (Brazil); Cassini, F.A.; Benetoli, L.O.B. [Chemistry Department, Federal University of Santa Catarina, Campus Trindade, 88040-900 Florianópolis, SC (Brazil); Dotto, M.E.R. [Physics Department, Federal University of Santa Catarina, Campus Trindade, 88040-900 Florianópolis, SC (Brazil); Debacher, N.A. [Chemistry Department, Federal University of Santa Catarina, Campus Trindade, 88040-900 Florianópolis, SC (Brazil)

    2017-05-01

    Highlights: • Polymeric surfaces were etched using non-thermal plasma at different intensities. • Polymers of low mechanical hardness reached the saturation level faster. • A mathematical model based on scaling laws was proposed. - Abstract: The experiments presented in this communication have the purpose to elaborate an explanation for the morphological evolution of the growth of polymeric surfaces provided by the treatment of non-thermal plasma. According to the roughness analysis and the model proposed by scaling laws it is possible relate to a predictable or merely random effect. Polyethylene terephthalate (PET) and poly(etherether)ketone (PEEK) samples were exposed to a non-thermal plasma discharge and the resulting surfaces roughness were analyzed based on the measurements from contact angle, scanning electron microscopy and atomic force microscopy coupled with scaling laws analysis which can help to describe and understand the dynamic of formation of a wide variety of rough surfaces. The roughness, R{sub RMS} (RMS- Root Mean Square) values for polymer surface range between 19.8 nm and 110.9 nm. The contact angle and the AFM (Atomic Force Microscopy) measurements as a function of the plasma exposure time were in agreement with both polar and dispersive components according to the surface roughness and also with the morphology evaluated described by Wolf-Villain model, with proximate values of α between 0.91{sub (PET)} and 0.88{sub (PEEK)}, β = 0.25{sub (PET)} and z = 3,64{sub (PET)}.

  17. Morphological study of polymer surfaces exposed to non-thermal plasma based on contact angle and the use of scaling laws

    International Nuclear Information System (INIS)

    Felix, T.; Cassini, F.A.; Benetoli, L.O.B.; Dotto, M.E.R.; Debacher, N.A.

    2017-01-01

    Highlights: • Polymeric surfaces were etched using non-thermal plasma at different intensities. • Polymers of low mechanical hardness reached the saturation level faster. • A mathematical model based on scaling laws was proposed. - Abstract: The experiments presented in this communication have the purpose to elaborate an explanation for the morphological evolution of the growth of polymeric surfaces provided by the treatment of non-thermal plasma. According to the roughness analysis and the model proposed by scaling laws it is possible relate to a predictable or merely random effect. Polyethylene terephthalate (PET) and poly(etherether)ketone (PEEK) samples were exposed to a non-thermal plasma discharge and the resulting surfaces roughness were analyzed based on the measurements from contact angle, scanning electron microscopy and atomic force microscopy coupled with scaling laws analysis which can help to describe and understand the dynamic of formation of a wide variety of rough surfaces. The roughness, R_R_M_S (RMS- Root Mean Square) values for polymer surface range between 19.8 nm and 110.9 nm. The contact angle and the AFM (Atomic Force Microscopy) measurements as a function of the plasma exposure time were in agreement with both polar and dispersive components according to the surface roughness and also with the morphology evaluated described by Wolf-Villain model, with proximate values of α between 0.91_(_P_E_T_) and 0.88_(_P_E_E_K_), β = 0.25_(_P_E_T_) and z = 3,64_(_P_E_T_).

  18. Fabrication and photovoltaic performance of niobium doped TiO{sub 2} hierarchical microspheres with exposed {001} facets and high specific surface area

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yongqiang; Ran, Huili [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001 (China); State Centre for International Cooperation on Designer Low-Carbon and Environmental Materials, Zhengzhou University, Zhengzhou 450001 (China); Fan, Jiajie, E-mail: fanjiajie@zzu.edu.cn [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001 (China); State Centre for International Cooperation on Designer Low-Carbon and Environmental Materials, Zhengzhou University, Zhengzhou 450001 (China); Zhang, Xiaoli; Mao, Jing [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001 (China); State Centre for International Cooperation on Designer Low-Carbon and Environmental Materials, Zhengzhou University, Zhengzhou 450001 (China); Shao, Guosheng [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001 (China); State Centre for International Cooperation on Designer Low-Carbon and Environmental Materials, Zhengzhou University, Zhengzhou 450001 (China); Institute for Renewable Energy and Environmental Technologies, University of Bolton, Bolton BL3 5AB (United Kingdom)

    2017-07-15

    Highlights: • Nb-doped hierarchical TiO{sub 2} microsphere DSSCs show enhanced performance. • Nb{sup 5+} dopant replaces Ti{sup 4+} cation in TiO{sub 2} lattice. • Electrons transport was enhanced due to the down-shifted conduction band minimum. • Exposed (001) facets and high specific surface area allows high dye-loading. - Abstract: The niobium doped hierarchical anatase TiO{sub 2} microspheres, which are consist of a serried nano-thorns and plicate nano-ribbons with exposed {001} facets, were synthesized using hydrothermal method followed by heat treatment. The effects of niobium on the microstructures and photovoltaic performances of the dye-sensitized solar cells (DSSCs) were studied. The results revealed that Nb{sup 5+} doping replaces Ti{sup 4+} cations in TiO{sub 2} lattice, and the bandgap of the films varies with increasing Nb doping concentration because of the downshift of the conduction band minimum (CBM). The niobium-doped TiO{sub 2} DSSCs with moderate loadings show enhanced performance comparing with their pure TiO{sub 2} counterparts. Optimally, the conversion efficiency of the Nb-3.5 (Nb 3.5 mol%) DSSC is 4.99%. This is higher than that (4.39%) of pure TiO{sub 2} cells by 13.7%. This is due to the fact that the Nb-doped solar cells have increased the number of the photo-induced electrons because of their exposed (001) facets and higher specific surface area; and enhanced electrons collection and transport because of the downshifted CBM of the Nb-doped TiO{sub 2}. However, heavy Nb doping results in the decrease of the performance of the niobium-doped cells due to the excessive defects within the Nb-TiO{sub 2} samples resulting in enhanced charge recombination at defects.

  19. Chemical stabilization of graphite surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Bistrika, Alexander A.; Lerner, Michael M.

    2018-04-03

    Embodiments of a device, or a component of a device, including a stabilized graphite surface, methods of stabilizing graphite surfaces, and uses for the devices or components are disclosed. The device or component includes a surface comprising graphite, and a plurality of haloaryl ions and/or haloalkyl ions bound to at least a portion of the graphite. The ions may be perhaloaryl ions and/or perhaloalkyl ions. In certain embodiments, the ions are perfluorobenzenesulfonate anions. Embodiments of the device or component including stabilized graphite surfaces may maintain a steady-state oxidation or reduction surface current density after being exposed to continuous oxidation conditions for a period of at least 1-100 hours. The device or component is prepared by exposing a graphite-containing surface to an acidic aqueous solution of the ions under oxidizing conditions. The device or component can be exposed in situ to the solution.

  20. Reduction mechanisms of ethylene carbonate on si anodes of lithium-ion batteries: effects of degree of lithiation and nature of exposed surface.

    Science.gov (United States)

    Martinez de la Hoz, Julibeth M; Leung, Kevin; Balbuena, Perla B

    2013-12-26

    Ab initio molecular dynamics simulations are used to identify mechanisms of reduction of ethylene carbonate on Si surfaces at various degrees of lithiation, where the low-coordinated surface Si atoms are saturated with O, OH, or H functional groups. The lowest Si content surfaces are represented by quasi-amorphous LiSi4 and LiSi2; intermediate lithiation is given by LiSi crystalline facets, and the highest Li content is studied through Li13Si4 surfaces. It is found that ethylene carbonate (EC) reduction mechanisms depend significantly on the degree of lithiation of the surface. On LiSi surfaces EC is reduced according to two different two-electron mechanisms (one simultaneous and one sequential), which are independent of specific surface functionalization or nature of exposed facets. On the less lithiated surfaces, the simultaneous two-electron reduction is found more frequently. In that mechanism, the EC reduction is initiated by the formation of a C-Si bond that allows adsorption of the intact molecule to the surface and is followed by electron transfer and ring-opening. Strongly lithiated Li13Si4 surfaces are found to be highly reactive. Reduction of adsorbed EC molecules occurs via a four-electron mechanism yielding as reduction products CO(2-) and O(C2H4)O(2-). Direct transfer of two electrons to EC molecules in liquid phase is also possible, resulting in the presence of O(C2H4)OCO(2-) anions in the liquid phase.

  1. Simulated Space Environmental Effects on Thin Film Solar Array Components

    Science.gov (United States)

    Finckenor, Miria; Carr, John; SanSoucie, Michael; Boyd, Darren; Phillips, Brandon

    2017-01-01

    The Lightweight Integrated Solar Array and Transceiver (LISA-T) experiment consists of thin-film, low mass, low volume solar panels. Given the variety of thin solar cells and cover materials and the lack of environmental protection typically afforded by thick coverglasses, a series of tests were conducted in Marshall Space Flight Center's Space Environmental Effects Facility to evaluate the performance of these materials. Candidate thin polymeric films and nitinol wires used for deployment were also exposed. Simulated space environment exposures were selected based on SSP 30425 rev. B, "Space Station Program Natural Environment Definition for Design" or AIAA Standard S-111A-2014, "Qualification and Quality Requirements for Space Solar Cells." One set of candidate materials were exposed to 5 eV atomic oxygen and concurrent vacuum ultraviolet (VUV) radiation for low Earth orbit simulation. A second set of materials were exposed to 1 MeV electrons. A third set of samples were exposed to 50, 100, 500, and 700 keV energy protons, and a fourth set were exposed to >2,000 hours of near ultraviolet (NUV) radiation. A final set was rapidly thermal cycled between -55 and +125degC. This test series provides data on enhanced power generation, particularly for small satellites with reduced mass and volume resources. Performance versus mass and cost per Watt is discussed.

  2. Transient space-time surface waves characterization using Gabor analysis

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, L; Wilkie-Chancellier, N; Caplain, E [Universite de Cergy Pontoise, ENS Cachan, UMR CNRS 8029, Laboratoire Systemes et Applications des Techniques de l' Information et de l' Energie (SATIE), 5 mail Gay-Lussac, F 9500 Cergy-Pontoise (France); Glorieux, C; Sarens, B, E-mail: nicolas.wilkie-chancellier@u-cergy.f [Katholieke Universiteit Leuven, Laboratorium voor Akoestiek en Thermische Fysica (LATF), Celestijnenlaan 200D, B-3001 Leuven (Belgium)

    2009-11-01

    Laser ultrasonics allow the observation of transient surface waves along their propagation media and their interaction with encountered objects like cracks, holes, borders. In order to characterize and localize these transient aspects in the Space-Time-Wave number-Frequency domains, the 1D, 2D and 3D Gabor transforms are presented. The Gabor transform enables the identification of several properties of the local wavefronts such as their shape, wavelength, frequency, attenuation, group velocity and the full conversion sequence along propagation. The ability of local properties identification by Gabor transform is illustrated by two experimental studies: Lamb waves generated by an annular source on a circular quartz and Lamb wave interaction with a fluid droplet. In both cases, results obtained with Gabor transform enable ones to identify the observed local waves.

  3. Transversal Surfaces of Timelike Ruled Surfaces in Minkowski 3-Space

    OpenAIRE

    Önder, Mehmet

    2012-01-01

    In this study we give definitions and characterizations of transversal surfaces of timelike ruled surfaces. We study some special cases such as the striction curve is a geodesic, an asymptotic line or a line of curvature. Moreover, we obtain developable conditions for transversal surfaces of a timelike ruled surface.

  4. Atomic friction at exposed and buried graphite step edges: Experiments and simulations

    Energy Technology Data Exchange (ETDEWEB)

    Ye, Zhijiang; Martini, Ashlie, E-mail: amartini@ucmerced.edu [School of Engineering, University of California Merced, 5200 N. Lake Road, Merced, California 95343 (United States)

    2015-06-08

    The surfaces of layered materials such as graphite exhibit step edges that affect friction. Step edges can be exposed, where the step occurs at the outmost layer, or buried, where the step is underneath another layer of material. Here, we study friction at exposed and buried step edges on graphite using an atomic force microscope (AFM) and complementary molecular dynamics simulations of the AFM tip apex. Exposed and buried steps exhibit distinct friction behavior, and the friction on either step is affected by the direction of sliding, i.e., moving up or down the step, and the bluntness of the tip. These trends are analyzing in terms of the trajectory of the AFM tip as it moves over the step, which is a convolution of the topography of the surface and the tip shape.

  5. Atomic friction at exposed and buried graphite step edges: Experiments and simulations

    International Nuclear Information System (INIS)

    Ye, Zhijiang; Martini, Ashlie

    2015-01-01

    The surfaces of layered materials such as graphite exhibit step edges that affect friction. Step edges can be exposed, where the step occurs at the outmost layer, or buried, where the step is underneath another layer of material. Here, we study friction at exposed and buried step edges on graphite using an atomic force microscope (AFM) and complementary molecular dynamics simulations of the AFM tip apex. Exposed and buried steps exhibit distinct friction behavior, and the friction on either step is affected by the direction of sliding, i.e., moving up or down the step, and the bluntness of the tip. These trends are analyzing in terms of the trajectory of the AFM tip as it moves over the step, which is a convolution of the topography of the surface and the tip shape

  6. Interaction of Space Suits with Windblown Soil: Preliminary Mars Wind Tunnel Results

    Science.gov (United States)

    Marshall, J.; Bratton, C.; Kosmo, J.; Trevino, R.

    1999-09-01

    Experiments in the Mars Wind Tunnel at NASA Ames Research Center show that under Mars conditions, spacesuit materials are highly susceptible to dust contamination when exposed to windblown soil. This effect was suspected from knowledge of the interaction of electrostatically adhesive dust with solid surfaces in general. However, it is important to evaluate the respective roles of materials, meteorological and radiation effects, and the character of the soil. The tunnel permits evaluation of dust contamination and sand abrasion of space suits by simulating both pressure and wind conditions on Mars. The long-term function of space suits on Mars will be primarily threatened by dust contamination. Lunar EVA activities caused heavy contamination of space suits, but the problem was never seriously manifest because of the brief utilization of the suits, and the suits were never reused. Electrostatically adhering dust grains have various detrimental effects: (1) penetration and subsequent wear of suit fabrics, (2) viewing obscuration through visors and scratching/pitting of visor surfaces, (3) penetration, wear, and subsequent seizing-up of mechanical suit joints, (4) changes in albedo and therefore of radiation properties of external heat-exchanger systems, (5) changes in electrical conductivity of suit surfaces which may affect tribocharging of suits and create spurious discharge effects detrimental to suit electronics/radio systems. Additional information is contained in the original.

  7. Structural features and activity of Brazzein and its mutants upon substitution of a surfaced exposed alanine.

    Science.gov (United States)

    Ghanavatian, Parisa; Khalifeh, Khosrow; Jafarian, Vahab

    2016-12-01

    Brazzein (Brz) is a member of sweet-tasting protein containing four disulfide bonds. It was reported as a compact and heat-resistant protein. Here, we have used site-directed mutagenesis and replaced a surface-exposed alanine with aspartic acid (A19D mutant), lysine (A19K mutant) and glycine (A19G mutant). Activity comparisons of wild-type (WT) and mutants using taste panel test procedure showed that A19G variant has the same activity as WT protein. However, introduction of a positive charge in A19K mutant led to significant increase in Brz's sweetness, while A19D has reduced sweetness compared to WT protein. Docking studies showed that mutation at position 19 results in slight chain mobility of protein at the binding surface and changing the patterns of interactions toward more effective binding of E9K variant in the concave surface of sweet taste receptor. Far-UV CD data spectra have a characteristic shape of beta structure for all variants, however different magnitudes of spectra suggest that beta-sheet structure in WT and A19G is more stable than that of A19D and A19K. Equilibrium unfolding studies with fluorescence spectroscopy and using urea and dithiothritol (DTT) as chemical denaturants indicates that A19G mutant gains more stability against urea denaturation; while conformational stability of A19D and A19K decreases when compared with WT and A19G variants. We concluded that the positive charge at the surface of protein is important factor responsible for the interaction of protein with the human sweet receptor and Ala 19 can be considered as a key region for investigating the mechanism of the interaction of Brz with corresponding receptor. Copyright © 2016 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.

  8. Near Space Hypersonic Unmanned Aerial Vehicle Dynamic Surface Backstepping Control Design

    Directory of Open Access Journals (Sweden)

    Jinyong YU

    2014-07-01

    Full Text Available Compared with traditional aircraft, the near space hypersonic unmanned aerial vehicle control system design must deal with the extra prominent dynamics characters, which are differ from the traditional aircrafts control system design. A new robust adaptive control design method is proposed for one hypersonic unmanned aerial vehicle (HSUAV uncertain MIMO nonaffine block control system by using multilayer neural networks, feedback linearization technology, and dynamic surface backstepping. Multilayer neural networks are used to compensate the influence from the uncertain, which designs the robust terms to solve the problem from approach error. Adaptive backstepping is adopted designed to ensure control law, the dynamic surface control strategy to eliminate “the explosion of terms” by introducing a series of first order filters to obtain the differentiation of the virtual control inputs. Finally, nonlinear six-degree-of-freedom (6-DOF numerical simulation results for a HSUAV model are presented to demonstrate the effectiveness of the proposed method.

  9. Space weathering and the color indexes of minor bodies in the outer Solar System

    Science.gov (United States)

    Kaňuchová, Zuzana; Brunetto, Rosario; Melita, Mario; Strazzulla, Giovanni

    2012-09-01

    The surfaces of small bodies in the outer Solar System are rich in organic compounds and carbonaceous refractories mixed with ices and silicates. As made clear by dedicated laboratory experiments space weathering (e.g. energetic ion bombardment) can produce red colored materials starting from bright and spectrally flat ices. In a classical scenario, the space weathering processes “nurture” alter the small bodies surface spectra but are in competition with resurfacing agents that restore the original colors, and the result of these competing processes continuously modifying the surfaces is supposed to be responsible for the observed spectral variety of those small bodies. However an alternative point of view is that the different colors are due to “nature” i.e. to the different primordial composition of different objects. In this paper we present a model, based on laboratory results, that gives an original contribution to the “nature” vs. “nurture” debate by addressing the case of surfaces showing different fractions of rejuvenated vs. space weathered surface, and calculating the corresponding color variations. We will show how a combination of increasing dose coupled to different resurfacing can reproduce the whole range of observations of small outer Solar System bodies. Here we demonstrate, for the first time that objects having a fully weathered material turn back in the color-color diagrams. At the same time, object with the different ratio of pristine and weathered surface areas lay on specific lines in color-color diagrams, if exposed to the same amount of irradiation.

  10. Ionization steps and phase-space metamorphoses in the pulsed microwave ionization of highly excited hydrogen atoms

    International Nuclear Information System (INIS)

    Bayfield, J.E.; Luie, S.Y.; Perotti, L.C.; Skrzypkowski, M.P.

    1996-01-01

    As the peak electric field of the microwave pulse is increased, steps in the classical microwave ionization probability of the highly excited hydrogen atom are produced by phase-space metamorphosis. They arise from new layers of Kolmogorov-Arnold-Moser (KAM) islands being exposed as KAM surfaces are destroyed. Both quantum numerical calculations and laboratory experiments exhibit the ionization steps, showing that such metamorphoses influence pulsed semiclassical systems. copyright 1996 The American Physical Society

  11. Radiation effects in space

    International Nuclear Information System (INIS)

    Fry, R.J.M.

    1986-01-01

    The paper discusses the radiation environment in space that astronauts are likely to be exposed to. Emphasis is on proton and HZE particle effects. Recommendations for radiation protection guidelines are presented

  12. Phase space barriers and dividing surfaces in the absence of critical points of the potential energy: Application to roaming in ozone

    Energy Technology Data Exchange (ETDEWEB)

    Mauguière, Frédéric A. L., E-mail: frederic.mauguiere@bristol.ac.uk; Collins, Peter, E-mail: peter.collins@bristol.ac.uk; Wiggins, Stephen, E-mail: stephen.wiggins@mac.com [School of Mathematics, University of Bristol, Bristol BS8 1TW (United Kingdom); Kramer, Zeb C., E-mail: zebcolterkramer@gmail.com; Ezra, Gregory S., E-mail: gse1@cornell.edu [Department of Chemistry and Chemical Biology, Baker Laboratory, Cornell University, Ithaca, New York 14853 (United States); Carpenter, Barry K., E-mail: carpenterb1@cardiff.ac.uk [School of Chemistry, Cardiff University, Cardiff CF10 3AT (United Kingdom); Farantos, Stavros C., E-mail: farantos@iesl.forth.gr [Institute of Electronic Structure and Laser, Foundation for Research and Technology - Hellas, and Department of Chemistry, University of Crete, Iraklion 711 10, Crete (Greece)

    2016-02-07

    We examine the phase space structures that govern reaction dynamics in the absence of critical points on the potential energy surface. We show that in the vicinity of hyperbolic invariant tori, it is possible to define phase space dividing surfaces that are analogous to the dividing surfaces governing transition from reactants to products near a critical point of the potential energy surface. We investigate the problem of capture of an atom by a diatomic molecule and show that a normally hyperbolic invariant manifold exists at large atom-diatom distances, away from any critical points on the potential. This normally hyperbolic invariant manifold is the anchor for the construction of a dividing surface in phase space, which defines the outer or loose transition state governing capture dynamics. We present an algorithm for sampling an approximate capture dividing surface, and apply our methods to the recombination of the ozone molecule. We treat both 2 and 3 degrees of freedom models with zero total angular momentum. We have located the normally hyperbolic invariant manifold from which the orbiting (outer) transition state is constructed. This forms the basis for our analysis of trajectories for ozone in general, but with particular emphasis on the roaming trajectories.

  13. Problems at the Leading Edge of Space Weathering as Revealed by TEM Combined with Surface Science Techniques

    Science.gov (United States)

    Christoffersen, R.; Dukes, C. A.; Keller, L. P.; Rahman, Z.; Baragiola, R. A.

    2015-01-01

    Both transmission electron micros-copy (TEM) and surface analysis techniques such as X-ray photoelectron spectroscopy (XPS) were instrumen-tal in making the first characterizations of material generated by space weathering in lunar samples [1,2]. Without them, the nature of nanophase metallic Fe (npFe0) correlated with the surface of lunar regolith grains would have taken much longer to become rec-ognized and understood. Our groups at JSC and UVa have been using both techniques in a cross-correlated way to investigate how the solar wind contributes to space weathering [e.g., 3]. These efforts have identified a number of ongoing problems and knowledge gaps. Key insights made by UVa group leader Raul Barag-iola during this work are gratefully remembered.

  14. Studying the Association between Green Space Characteristics and Land Surface Temperature for Sustainable Urban Environments: An Analysis of Beijing and Islamabad

    Directory of Open Access Journals (Sweden)

    Shahid Naeem

    2018-01-01

    Full Text Available Increasing trends of urbanization lead to vegetation degradation in big cities and affect the urban thermal environment. This study investigated (1 the cooling effect of urban green space spatial patterns on Land Surface Temperature (LST; (2 how the surrounding environment influences the green space cool islands (GCI, and vice versa. The study was conducted in two Asian capitals: Beijing, China and Islamabad, Pakistan by utilizing Gaofen-1 (GF-1 and Landsat-8 satellite imagery. Pearson’s correlation and normalized mutual information (NMI were applied to investigate the relationship between green space characteristics and LST. Landscape metrics of green spaces including Percentage of Landscape (PLAND, Patch Density (PD, Edge Density (ED, and Landscape Shape Index (LSI were selected to calculate the spatial patterns of green spaces, whereas GCI indicators were defined by Green Space Range (GR, Temperature Difference (TD, and Temperature Gradient (TG. The results indicate that both vegetation composition and configuration influence LST distributions; however, vegetation composition appeared to have a slightly greater effect. The cooling effect can be produced more effectively by increasing green space percentage, planting trees in large patches with equal distribution, and avoiding complex-shaped green spaces. The GCI principle indicates that LST can be decreased by increasing the green space area, increasing the water body fraction, or by decreasing the fraction of impervious surfaces. GCI can also be strengthened by decreasing the fraction of impervious surfaces and increasing the fraction of water body or vegetation in the surrounding environment. The cooling effect of vegetation and water could be explained based on their thermal properties. Beijing has already enacted the green-wedge initiative to increase the vegetation canopy. While designing the future urban layout of Islamabad, the construction of artificial lakes within the urban green

  15. An augmented space recursive method for the first principles study of concentration profiles at CuNi alloy surfaces

    International Nuclear Information System (INIS)

    Dasgupta, I.; Mookerjee, A.

    1995-07-01

    We present here a first principle method for the calculation of effective cluster interactions for semi-infinite solid alloys required for the study of surface segregation and surface ordering on disordered surfaces. Our method is based on the augmented space recursion coupled with the orbital peeling method of Burke in the framework of the TB-LMTO. Our study of surface segregation in CuNi alloys demonstrates strong copper segregation and a monotonic concentration profile throughout the concentration range. (author). 35 refs, 4 figs, 2 tabs

  16. System survivability in nuclear and space environments

    International Nuclear Information System (INIS)

    Rudie, N.J.

    1987-01-01

    Space systems must operate in the hostile natural environment of space. In the event of a war, these systems may also be exposed to the radiation environments created by the explosions of nuclear warheads. The effects of these environments on a space system and hardening techniques are discussed in the paper

  17. Solar Effects on Tensile and Optical Properties of Hubble Space Telescope Silver-Teflon(Registered Trademark) Insulation

    Science.gov (United States)

    deGroh, Kim, K.; Dever, Joyce A.; Snyder, Aaron; Kaminski, Sharon; McCarthy, Catherine E.; Rapoport, Alison L.; Rucker, Rochelle N.

    2006-01-01

    A section of the retrieved Hubble Space Telescope (HST) solar array drive arm (SADA) multilayer insulation (MLI), which experienced 8.25 years of space exposure, was analyzed for environmental durability of the top layer of silver-Teflon (DuPont) fluorinated ethylene propylene (Ag-FEP). Because the SADA MLI had solar and anti-solar facing surfaces and was exposed to the space environment for a long duration, it provided a unique opportunity to study solar effects on the environmental degradation of Ag-FEP, a commonly used spacecraft thermal control material. Data obtained included tensile properties, solar absorptance, surface morphology and chemistry. The solar facing surface was found to be extremely embrittled and contained numerous through-thickness cracks. Tensile testing indicated that the solar facing surface lost 60% of its mechanical strength and 90% of its elasticity while the anti-solar facing surface had ductility similar to pristine FEP. The solar absorptance of both the solar facing surface (0.155 plus or minus 0.032) and the anti-solar facing surface (0.208 plus or minus 0.012) were found to be greater than pristine Ag-FEP (0.074). Solar facing and anti-solar facing surfaces were microscopically textured, and locations of isolated contamination were present on the anti-solar surface resulting in increased localized texturing. Yet, the overall texture was significantly more pronounced on the solar facing surface indicating a synergistic effect of combined solar exposure and increased heating with atomic oxygen erosion. The results indicate a very strong dependence of degradation, particularly embrittlement, upon solar exposure with orbital thermal cycling having a significant effect.

  18. SEM and TEM Observation of the Surfaces of the Fine-Grained Particles Retrieved from the Muses-C Regio on the Asteroid 25413 Itokawa

    Science.gov (United States)

    Noguchi, T.; Nakamura, T.; Zolensky, Michael E.; Tanaka, M.; Hashimoto, T.; Konno, M.; Nakato, A.; Ogami, T.; Fujimura, A.; Abe, M.; hide

    2011-01-01

    Surface materials on airless solar system bodies exposed to interplanetary space are gradually changed their visible to near-infrared reflectance spectra by the process called "space weathering", which makes the spectra darker and redder. Hapke et al. proposed a model of space weathering: vapor deposition of nanophase reduced iron (npFe(sup 0)) on the surfaces of the grains within the very surface of lunar regolith. This model has been proved by detailed observation of the surfaces of the lunar soil grains by transmission electron microscope (TEM). They demonstrated that npFe(sup 0) was formed by a combination of vapor deposition and irradiation effects. In other words, both micrometeorite impacts and irradiation by solar wind and galactic cosmic ray play roles on the space weathering on the Moon. Because there is a continuum of reflectance spectra from those of Q-type asteroids (almost the same as those of ordinary chondrites) to those of S-type asteroids, it is strongly suggested that reflectance spectra of asteroids composed of ordinary chondrite-like materials were modified over time to those of S-type asteroids due to space weathering. It is predicted that a small amount of npFe(sup 0) on the surface of grains in the asteroidal regolith composed of ordinary chondrite-like materials is the main agent of asteroidal space weathering.

  19. Space Environmental Effects on Colored Coatings and Anodizes

    Science.gov (United States)

    Kamenetzky, Rachel R.; Finckenor, Miria M.; Vaughn, Jason A.

    1999-01-01

    Colored coatings and anodizes are used on spacecraft as markers and astronaut visual aids. These materials must be stable in the space environment and withstand atomic oxygen, ultraviolet radiation, particulate radiation, thermal cycling, and high vacuum without significant change in optical and mechanical properties. A variety of colored coatings and anodizes have been exposed to simulated space environments at Marshall Space Flight Center and also actual space environment as part of the Passive Optical Sample Assembly (POSA) - I flight experiment. Colored coatings were developed by AZ Technology, Huntsville, AL, under a NASA contract for International Space Station (ISS). These include yellow, red, blue, and black paints suitable for Extra-Vehicular Activity (EVA) visual aids and ISS emblems. AaChron, Inc., Minneapolis, MN, developed stable colored anodizes, also in yellow, red, blue, and black, for astronaut visual aids. These coatings were exposed in the laboratory to approximately 550 equivalent sun-hours of solar ultraviolet radiation and approximately 1 x 10(exp 21) atoms/sq cm of atomic oxygen in vacuum. The AZ Technology yellow colored coating, designated TMS800IY, and all four AaChron colored anodizes were flown on POSA-I. POSA-I was a Risk Mitigation Experiment for ISS. It was attached to the exterior of the Mir space station docking module by EVA and was exposed for 18 months. The laboratory-simulated space environment, the natural space environment and the unique environment of an orbiting, active space station and their effects on these developmental materials are discussed.

  20. Avoiding unstable regions in the design space of EUV mirror systems comprising high-order aspheric surfaces

    NARCIS (Netherlands)

    Marinescu, O.; Bociort, F.; Braat, J.

    2004-01-01

    When Extreme Ultraviolet mirror systems having several high-order aspheric surfaces are optimized, the configurations often enter into highly unstable regions of the parameter space. Small changes of system parameters lead then to large changes in ray paths, and therefore optimization algorithms

  1. Anti-Microbial and Self-Cleaning Properties of Photocatalytic Surface Treatments and their Potential Use for Space-Based Applications

    Data.gov (United States)

    National Aeronautics and Space Administration — The purpose of this project was to implement a method to assess self-cleaning properties of commercially available photocatalytic surface treatments for their...

  2. Space Colonization Using Space-Elevators from Phobos

    Science.gov (United States)

    Weinstein, Leonard M.

    2003-01-01

    A novel approach is examined for creating an industrial civilization beyond Earth. The approach would take advantage of the unique configuration of Mars and its moon Phobos to make a transportation system capable of raising mass from the surface of Mars to space at a low cost. Mars would be used as the primary location for support personnel and infrastructure. Phobos would be used as a source of raw materials for space-based activity, and as an anchor for tethered carbon-nanotube-based space-elevators. One space-elevator would terminate at the upper edge of Mars' atmosphere. Small craft would be launched from Mars' surface to rendezvous with the moving elevator tip and their payloads detached and raised with solar powered loop elevators to Phobos. Another space-elevator would be extended outward from Phobos to launch craft toward the Earth/Moon system or the asteroid belt. The outward tip would also be used to catch arriving craft. This approach would allow Mars to be colonized, and allow transportation of people and supplies from Mars to support the space industry. In addition, large quantities of material obtained from Phobos could be used to construct space habitats and also supply propellant and material for space industry in the Earth/Moon system as well as around Mars.

  3. Survival of the lichen model system Circinaria gyrosa before flight to the ISS (EXPOSE R2 mission)

    Science.gov (United States)

    De la Torre Noetzel, Rosa

    Abstract Space Verification Tests (SVT) are necessary for selection of the most promising biological organisms for flight experiments in Low Earth Orbit or other space destinations: Simulation of sample assembly, exposure to expected space parameters and sample disassembly are significantly advanced by such tests, will be performed with this tests, allowing post-analysis of the exposed biological material and thus a deeper understanding of the individual and synergistic effects of space. In this work we present the results obtained with the lichen species Circinaria gyrosa after the SVT 2 run-2 tests concerning the EXPOSE-R2 Mission Preflight Test Program, performed at the planetary and space simulation facilities at DLR (Deutsches Zentrum für Luft- und Raumfahrt, Cologne, Germany) [1], from October 2013 to January 2014. This vagrant lichen species was collected at the steppic highlands of Central Spain and defined as “astrobiological model system” due to previous test at space missions (BIOPAN-6, Foton M-3) [2, 3], Therefore, C. gyrosa is part of the BIOMEX experiment (Biology and Mars Experiment, ESA) [4] which will be exposed from July 2014 to January 2016 on board of EXPOSE R2 on the International Space Station. C. gyrosa was exposed at DLR to simulated space- and Mars parameters: a) space vacuum 10-5 Pa, space UV-radiation (200-400 nm, fluence of 12 months mission = 5 x 105 kJm-2) and temperature fluctuations (-25 ºC to 10 ºC); b); Mars Simulated CO2 atmosphere, Mars pressure of 103 Pa, Mars UV-radiation (200-400 nm), and temperature fluctuations (-25 ºC to 10 ºC). In line with the lichen's well studied adaptations to harsh environmental conditions [5, 6] we observed a high recovery- and resistance capacity of C. gyrosa which was demonstrated after a 72 hours re-activation process of in the UV-Radiation and Bioclimatology Laboratories of INTA (Atmospheric Research and Instrumentation, Dept. Earth Observation). These results confirm the high survival

  4. Examining the temperature behavior of stainless steel surfaces exposed to hydrogen plasmas in the Lithium Tokamak eXperiment (LTX)

    Science.gov (United States)

    Bedoya, Felipe; Allain, Jean Paul; Kaita, Robert; Lucia, Matthew; St-Onge, Denis; Ellis, Robert; Majeski, Richard

    2014-10-01

    The Materials Analysis Particle Probe (MAPP) is an in-situ diagnostic designed to characterize plasma-facing components (PFCs) in tokamak devices. MAPP is installed in LTX at Princeton Plasma Physics Laboratory. MAPP's capabilities include remotely operated XPS acquisition and temperature control of four samples. The recent addition of a focused ion beam allows XPS depth profiling analysis. Recent published results show an apparent correlation between hydrogen retention and temperature of Li coated stainless steel (SS) PFCs exposed to plasmas like those of LTX. According to XPS data, the retention of hydrogen by the coated surfaces decreases at above 180 °C. In the present study MAPP will be used to study the oxidation of Li coatings as a function of time and temperature of the walls when Li coatings are applied. Experiments in the ion-surface interaction experiment (IIAX) varying the hydrogen fluence on the SS samples will be also performed. Conclusions resulting from this study will be key to explain the PFC temperature-dependent variation of plasma performance observed in LTX. This work was supported by U.S. DOE Contracts DE-AC02-09CH11466, DE-AC52-07NA27344 and DE-SC0010717.

  5. Space and Atmospheric Environments: From Low Earth Orbits to Deep Space

    Science.gov (United States)

    Barth, Janet L.

    2003-01-01

    Natural space and atmospheric environments pose a difficult challenge for designers of technological systems in space. The deleterious effects of environment interactions with the systems include degradation of materials, thermal changes, contamination, excitation, spacecraft glow, charging, radiation damage, and induced background interference. Design accommodations must be realistic with minimum impact on performance while maintaining a balance between cost and risk. The goal of applied research in space environments and effects is to limit environmental impacts at low cost relative to spacecraft cost and to infuse enabling and commercial off-the-shelf technologies into space programs. The need to perform applied research to understand the space environment in a practical sense and to develop methods to mitigate these environment effects is frequently underestimated by space agencies and industry. Applied science research in this area is critical because the complexity of spacecraft systems is increasing, and they are exposed simultaneously to a multitude of space environments.

  6. Antibodies from malaria-exposed pregnant women recognize trypsin resistant epitopes on the surface of Plasmodium falciparum-infected erythrocytes selected for adhesion to chondroitin sulphate A

    DEFF Research Database (Denmark)

    Sharling, Lisa; Enevold, Anders; Sowa, Kordai M P

    2004-01-01

    of CSA binding and surface recognition of CSA selected parasites by serum IgG from malaria exposed pregnant women. Thus, the complete molecular definition of an antigenic P. falciparum erythrocyte surface protein that can be used as a malaria in pregnancy vaccine has not yet been achieved.......-specific antibodies induced as a result of pregnancy associated malaria (PAM). METHODS: Fluorescence activated cell sorting (FACS) was used to measure the levels of adult Scottish and Ghanaian male, and Ghanaian pregnant female plasma immunoglobulin G (IgG) that bind to the surface of infected erythrocytes. P....... falciparum infected erythrocytes selected for adhesion to CSA were found to express trypsin-resistant VSA that are the target of naturally acquired antibodies from pregnant women living in a malaria endemic region of Ghana. However in vitro adhesion to CSA and HA was relatively trypsin sensitive. An improved...

  7. Methane formation in tritium gas exposed to stainless steel

    International Nuclear Information System (INIS)

    Morris, G.A.

    1977-01-01

    Tests were performed to determine the effect cleanliness of a surface exposed to tritium gas had on methane formation. These tests performed on 304 stainless steel vessels, cleaned in various ways, showed that the methane formation was reduced by the use of various cleaning procedures

  8. Potential contribution of exposed resin to ecosystem emissions of monoterpenes

    Science.gov (United States)

    Eller, Allyson S. D.; Harley, Peter; Monson, Russell K.

    2013-10-01

    Conifers, especially pines, produce and store under pressure monoterpene-laden resin in canals located throughout the plant. When the plants are damaged and resin canals punctured, the resin is exuded and the monoterpenes are released into the atmosphere, a process that has been shown to influence ecosystem-level monoterpene emissions. Less attention has been paid to the small amounts of resin that are exuded from branches, expanding needles, developing pollen cones, and terminal buds in the absence of any damage. The goal of this study was to provide the first estimate of the potential of this naturally-exposed resin to influence emissions of monoterpenes from ponderosa pine (Pinus ponderosa) ecosystems. When resin is first exuded as small spherical beads from undamaged tissues it emits monoterpenes to the atmosphere at a rate that is four orders of magnitude greater than needle tissue with an equivalent exposed surface area and the emissions from exuded beads decline exponentially as the resin dries. We made measurements of resin beads on the branches of ponderosa pine trees in the middle of the growing season and found, on average, 0.15 cm2 of exposed resin bead surface area and 1250 cm2 of total needle surface area per branch tip. If the resin emerged over the course of 10 days, resin emissions would make up 10% of the ecosystem emissions each day. Since we only accounted for exposed resin at a single point in time, this is probably an underestimate of how much total resin is exuded from undamaged pine tissues over the course of a growing season. Our observations, however, reveal the importance of this previously unrecognized source of monoterpenes emitted from pine forests and its potential to influence regional atmospheric chemistry dynamics.

  9. Extracting Hydrologic Understanding from the Unique Space-time Sampling of the Surface Water and Ocean Topography (SWOT) Mission

    Science.gov (United States)

    Nickles, C.; Zhao, Y.; Beighley, E.; Durand, M. T.; David, C. H.; Lee, H.

    2017-12-01

    The Surface Water and Ocean Topography (SWOT) satellite mission is jointly developed by NASA, the French space agency (CNES), with participation from the Canadian and UK space agencies to serve both the hydrology and oceanography communities. The SWOT mission will sample global surface water extents and elevations (lakes/reservoirs, rivers, estuaries, oceans, sea and land ice) at a finer spatial resolution than is currently possible enabling hydrologic discovery, model advancements and new applications that are not currently possible or likely even conceivable. Although the mission will provide global cover, analysis and interpolation of the data generated from the irregular space/time sampling represents a significant challenge. In this study, we explore the applicability of the unique space/time sampling for understanding river discharge dynamics throughout the Ohio River Basin. River network topology, SWOT sampling (i.e., orbit and identified SWOT river reaches) and spatial interpolation concepts are used to quantify the fraction of effective sampling of river reaches each day of the three-year mission. Streamflow statistics for SWOT generated river discharge time series are compared to continuous daily river discharge series. Relationships are presented to transform SWOT generated streamflow statistics to equivalent continuous daily discharge time series statistics intended to support hydrologic applications using low-flow and annual flow duration statistics.

  10. Evaluation of the Airborne CASI/TASI Ts-VI Space Method for Estimating Near-Surface Soil Moisture

    Directory of Open Access Journals (Sweden)

    Lei Fan

    2015-03-01

    Full Text Available High spatial resolution airborne data with little sub-pixel heterogeneity were used to evaluate the suitability of the temperature/vegetation (Ts/VI space method developed from satellite observations, and were explored to improve the performance of the Ts/VI space method for estimating soil moisture (SM. An evaluation of the airborne ΔTs/Fr space (incorporated with air temperature revealed that normalized difference vegetation index (NDVI saturation and disturbed pixels were hindering the appropriate construction of the space. The non-disturbed ΔTs/Fr space, which was modified by adjusting the NDVI saturation and eliminating the disturbed pixels, was clearly correlated with the measured SM. The SM estimations of the non-disturbed ΔTs/Fr  space using the evaporative fraction (EF and temperature vegetation dryness index (TVDI were validated by using the SM measured at a depth of 4 cm, which was determined according to the land surface types. The validation results show that the EF approach provides superior estimates with a lower RMSE (0.023 m3·m−3 value and a higher correlation coefficient (0.68 than the TVDI. The application of the airborne ΔTs/Fr  space shows that the two modifications proposed in this study strengthen the link between the ΔTs/Fr space and SM, which is important for improving the precision of the remote sensing Ts/VI space method for monitoring SM.

  11. Interseismic and coseismic surface deformation deduced from space geodetic observations : with inferences on seismic hazard, tectonic processes, earthquake complexity, and slip distribution

    NARCIS (Netherlands)

    Bos, A.G. (Annemarie Gerredina)

    2003-01-01

    In this thesis I am concerned with modeling the kinematics of surface deformation using space geodetic observations in order to advance insight in both interseismic and coseismic surface response. To model the surface deformation field I adopt the method of Spakman and Nyst (2002) which resolves the

  12. On the theory of inelastic scattering of slow electrons by surface excitations: 1. Half-space formalism

    International Nuclear Information System (INIS)

    Nkoma, J.S.

    1982-08-01

    A quantum-mechanical theory for the inelastic scattering of slow electrons (ISSE) by surface excitations is developed within the half-space model. The process of transmission of incident electrons into the crystal is described by the homogeneous Schroedinger equation, while the scattering process inside the crystal is described by an inhomogeneous Schroedinger equation. The scattering cross-section for ISSE by surface excitations is derived and is found to be small since it is dependent on an inverse sum of wavevectors which is large. It is also dependent on the fluctuations in the scattering potential. (author)

  13. A FMM-FFT accelerated hybrid volume surface integral equation solver for electromagnetic analysis of re-entry space vehicles

    KAUST Repository

    Yü cel, Abdulkadir C.; Gomez, Luis J.; Liu, Yang; Bagci, Hakan; Michielssen, Eric

    2014-01-01

    Space vehicles that re-enter the atmosphere often experience communication blackout. The blackout occurs when the vehicle becomes engulfed in plasma produced by interactions between the vehicle surface and the atmosphere. The plasma often

  14. An Examination of the Space Weathering Patina of Lunar Rock 76015

    Science.gov (United States)

    Noble, S.; Chrisoffersen, R.; Rahman, Z.

    2011-01-01

    Space weathering discussions have generally centered around soils but exposed rocks will also incur the effects of weathering. Rocks have much longer surface lifetimes than an individual soil grain and thus record a longer history of exposure. By studying the weathering products which have built up on a rock surface, we can gain a deeper perspective on the weathering process and better assess the relative importance of various weathering components. The weathered coating, or patina, of the lunar rock 76015 has been previously studied under SEM and also by TEM using ultramicrotome sample preparation methods. However, to really understand the products involved in creating these coatings, it is helpful to examine the patina in cross section, something which is now possible though the use of Focused Ion Beam (FIB) sample prep techniques, which allows us to preserve intact the delicate stratigraphy of the patina coating and provides a unique cross-sectional view of the space weathering process. Several samples have been prepared from the rock and the coatings are found to be quite variable in thickness and composition from one sample to the next.

  15. Adaptive strategies of remote systems operators exposed to perturbed camera-viewing conditions

    Science.gov (United States)

    Stuart, Mark A.; Manahan, Meera K.; Bierschwale, John M.; Sampaio, Carlos E.; Legendre, A. J.

    1991-01-01

    This report describes a preliminary investigation of the use of perturbed visual feedback during the performance of simulated space-based remote manipulation tasks. The primary objective of this NASA evaluation was to determine to what extent operators exhibit adaptive strategies which allow them to perform these specific types of remote manipulation tasks more efficiently while exposed to perturbed visual feedback. A secondary objective of this evaluation was to establish a set of preliminary guidelines for enhancing remote manipulation performance and reducing the adverse effects. These objectives were accomplished by studying the remote manipulator performance of test subjects exposed to various perturbed camera-viewing conditions while performing a simulated space-based remote manipulation task. Statistical analysis of performance and subjective data revealed that remote manipulation performance was adversely affected by the use of perturbed visual feedback and performance tended to improve with successive trials in most perturbed viewing conditions.

  16. O-6 Optical Property Degradation of the Hubble Space Telescope's Wide Field Camera-2 Pick Off Mirror

    Science.gov (United States)

    McNamara, Karen M.; Hughes, D. W.; Lauer, H. V.; Burkett, P. J.; Reed, B. B.

    2011-01-01

    Degradation in the performance of optical components can be greatly affected by exposure to the space environment. Many factors can contribute to such degradation including surface contaminants; outgassing; vacuum, UV, and atomic oxygen exposure; temperature cycling; or combinations of parameters. In-situ observations give important clues to degradation processes, but there are relatively few opportunities to correlate those observations with post-flight ground analyses. The return of instruments from the Hubble Space Telescope (HST) after its final servicing mission in May 2009 provided such an opportunity. Among the instruments returned from HST was the Wide-Field Planetary Camera-2 (WFPC-2), which had been exposed to the space environment for 16 years. This work focuses on the identifying the sources of degradation in the performance of the Pick-off mirror (POM) from WFPC-2. Techniques including surface reflectivity measurements, spectroscopic ellipsometry, FTIR (and ATR-FTIR) analyses, SEM/EDS, X-ray photoelectron spectroscopy (XPS) with and without ion milling, and wet and dry physical surface sampling were performed. Destructive and contact analyses took place only after completion of the non-destructive measurements. Spectroscopic ellipsometry was then repeated to determine the extent of contaminant removal by the destructive techniques, providing insight into the nature and extent of polymerization of the contaminant layer.

  17. Dynamics of Soil Deflation Features in Kangerlussuaq, Greenland Revealed by Variations in Lichen Diameters on Exposed Surfaces

    Science.gov (United States)

    Heindel, R. C.; Kelly, M. A.; Virginia, R. A.

    2013-12-01

    Little is known about the pervasive soil deflation features in the Kangerlussuaq region, West Greenland, an area deglaciated between ~6,800 and 150 years ago. While the majority of the landscape is vegetated with low-lying shrubs and graminoids, wind erosion has removed loess and vegetation from distinct patches ranging in size from a few to tens of meters across, leaving the underlying glacial till or bedrock exposed. Although previous work has considered aeolian landforms and regional loess deposition along the Watson River Valley, these deflation features have not been investigated in detail. We aim to determine both the timing and mechanisms of formation of the deflation features and will examine whether these mechanisms were related to regional climatic conditions, such as increased aridity, to fluctuations in the Greenland Ice Sheet, or to other factors. Our ongoing research investigating these features includes geomorphic mapping using field observations and satellite imagery, lichenometry of the exposed surfaces, and cosmogenic nuclide dating of boulders and bedrock within and near the deflation features. Here we present initial results from our lichenometry studies. During the summer of 2013, we measured maximum lichen (Rhizocarpon sp.) diameters on boulder and bedrock surfaces in 15 soil deflation features located between Kangerlussuaq and the ice sheet margin. Lichen diameters vary from only a few millimeters at the outer margins of deflation features to multiple centimeters (maximum ~50 mm) in the centers of the unvegetated patches. This distinct pattern suggests that the outer margins of the soil deflation features are currently active. Based on a previously established lichen growth curve for Rhizocarpon sp. in West Greenland, our results indicate that the features are expanding at a rate of ~1.5 m per 100 yrs. In addition, the large lichen diameters (~40-50 mm) that occur in the centers of deflation features suggest that the formation mechanism has

  18. Mapping Carrier Dynamics on Material Surfaces in Space and Time using Scanning Ultrafast Electron Microscopy

    KAUST Repository

    Sun, Jingya; Adhikari, Aniruddha; Shaheen, Basamat; Yang, Haoze; Mohammed, Omar F.

    2016-01-01

    Selectively capturing the ultrafast dynamics of charge carriers on materials surfaces and at interfaces is crucial to the design of solar cells and optoelectronic devices. Despite extensive research efforts over the past few decades, information and understanding about surface-dynamical processes, including carrier trapping and recombination remains extremely limited. A key challenge is to selectively map such dynamic processes, a capability that is hitherto impractical by time-resolved laser techniques, which are limited by the laser’s relatively large penetration depth and consequently they record mainly bulk information. Such surface dynamics can only be mapped in real space and time by applying four-dimensional (4D) scanning ultrafast electron microscopy (S-UEM), which records snapshots of materials surfaces with nanometer spatial and sub-picosecond temporal resolutions. In this method, the secondary electron (SE) signal emitted from the sample’s surface is extremely sensitive to the surface dynamics and is detected in real time. In several unique applications, we spatially and temporally visualize the SE energy gain and loss, the charge carrier dynamics on the surface of InGaN nanowires and CdSe single crystals and its powder film. We also provide the mechanisms for the observed dynamics, which will be the foundation for future potential applications of S-UEM to a wide range of studies on material surfaces and device interfaces.

  19. Mapping Carrier Dynamics on Material Surfaces in Space and Time using Scanning Ultrafast Electron Microscopy

    KAUST Repository

    Sun, Jingya

    2016-02-25

    Selectively capturing the ultrafast dynamics of charge carriers on materials surfaces and at interfaces is crucial to the design of solar cells and optoelectronic devices. Despite extensive research efforts over the past few decades, information and understanding about surface-dynamical processes, including carrier trapping and recombination remains extremely limited. A key challenge is to selectively map such dynamic processes, a capability that is hitherto impractical by time-resolved laser techniques, which are limited by the laser’s relatively large penetration depth and consequently they record mainly bulk information. Such surface dynamics can only be mapped in real space and time by applying four-dimensional (4D) scanning ultrafast electron microscopy (S-UEM), which records snapshots of materials surfaces with nanometer spatial and sub-picosecond temporal resolutions. In this method, the secondary electron (SE) signal emitted from the sample’s surface is extremely sensitive to the surface dynamics and is detected in real time. In several unique applications, we spatially and temporally visualize the SE energy gain and loss, the charge carrier dynamics on the surface of InGaN nanowires and CdSe single crystals and its powder film. We also provide the mechanisms for the observed dynamics, which will be the foundation for future potential applications of S-UEM to a wide range of studies on material surfaces and device interfaces.

  20. Sorption Energy Maps of Clay Mineral Surfaces

    International Nuclear Information System (INIS)

    Cygan, Randall T.; Kirkpatrick, R. James

    1999-01-01

    A molecular-level understanding of mineral-water interactions is critical for the evaluation and prediction of the sorption properties of clay minerals that may be used in various chemical and radioactive waste disposal methods. Molecular models of metal sorption incorporate empirical energy force fields, based on molecular orbital calculations and spectroscopic data, that account for Coulombic, van der Waals attractive, and short-range repulsive energies. The summation of the non-bonded energy terms at equally-spaced grid points surrounding a mineral substrate provides a three dimensional potential energy grid. The energy map can be used to determine the optimal sorption sites of metal ions on the exposed surfaces of the mineral. By using this approach, we have evaluated the crystallographic and compositional control of metal sorption on the surfaces of kaolinite and illite. Estimates of the relative sorption energy and most stable sorption sites are derived based on a rigid ion approximation

  1. Some results of the effect of space flight factors on Drosophila melanogaster

    International Nuclear Information System (INIS)

    Filatova, L.P.; Vaulina, E.N.

    1983-01-01

    Chromosomal effects of space flight factors were investigated in Drosophila melanogaster flown aboard the Salyut 6 orbital station. Drosophila males heterozygous for four linked traits were exposed to space flight conditions for periods of eight days, and the progeny when the males were mated with homozygous recessive females were compared with those from control flies exposed to the same vibration and acceleration environment, and the progeny of laboratory controls. Increases in recombination and nondisjunction frequencies were observed in the flies exposed to the space environment, with recombinant flies also found in the F1 generation of the vibration and acceleration controls. Results suggest that it is the action of heavy particles that accounts for the major portion of the genetic effects observed. 17 references

  2. Biology relevant to space radiation

    International Nuclear Information System (INIS)

    Fry, R.J.M.

    1996-01-01

    The biological effects of the radiations to which mankind on earth are exposed are becoming known with an increasing degree of detail. This knowledge is the basis of the estimates of risk that, in turn, fosters a comprehensive and evolving radiation protection system. The substantial body of information has been, and is being, applied to questions about the biological effects of radiation is space and the associated risk estimates. The purpose of this paper is not to recount all the biological effect of radiation but to concentrate on those that may occur as a result from exposure to the radiations encountered in space. In general, the biological effects of radiation in space are the same as those on earth. However, the evidence that the effects on certain tissues by the heaviest-charged particles can be interpreted on the basis of our knowledge about other high-LET radiation is equivocal. This specific question will be discussed in greater detail later. It is important to point out the that there are only limited data about the effects on humans of two components of the radiations in space, namely protons and heavy ions. Thus predictions of effects on space crews are based on experimental systems exposed on earth at rates and fluences that are higher than those in space and one the effects of gamma or x rays with estimates of the equivalent doses using quality factors

  3. Non-uniqueness of quantum transition state theory and general dividing surfaces in the path integral space.

    Science.gov (United States)

    Jang, Seogjoo; Voth, Gregory A

    2017-05-07

    Despite the fact that quantum mechanical principles do not allow the establishment of an exact quantum analogue of the classical transition state theory (TST), the development of a quantum TST (QTST) with a proper dynamical justification, while recovering the TST in the classical limit, has been a long standing theoretical challenge in chemical physics. One of the most recent efforts of this kind was put forth by Hele and Althorpe (HA) [J. Chem. Phys. 138, 084108 (2013)], which can be specified for any cyclically invariant dividing surface defined in the space of the imaginary time path integral. The present work revisits the issue of the non-uniqueness of QTST and provides a detailed theoretical analysis of HA-QTST for a general class of such path integral dividing surfaces. While we confirm that HA-QTST reproduces the result based on the ring polymer molecular dynamics (RPMD) rate theory for dividing surfaces containing only a quadratic form of low frequency Fourier modes, we find that it produces different results for those containing higher frequency imaginary time paths which accommodate greater quantum fluctuations. This result confirms the assessment made in our previous work [Jang and Voth, J. Chem. Phys. 144, 084110 (2016)] that HA-QTST does not provide a derivation of RPMD-TST in general and points to a new ambiguity of HA-QTST with respect to its justification for general cyclically invariant dividing surfaces defined in the space of imaginary time path integrals. Our analysis also offers new insights into similar path integral based QTST approaches.

  4. 2-surface twistors, embeddings and symmetries

    International Nuclear Information System (INIS)

    Jeffryes, B.P.

    1987-01-01

    2-Surface twistor space was introduced in connection with a proposal for a quasi-local definition of mass and angular momentum within general relativity. Properties of the 2-surface twistor space are related to the possibilities for embedding the 2-surface in real and complex conformally flat spaces. The additional properties of the twistor space resulting from symmetries of the 2-surface are discussed, with particular detail on axisymmetric 2-surfaces. (author)

  5. Orbifold Riemann surfaces: Teichmueller spaces and algebras of geodesic functions

    Energy Technology Data Exchange (ETDEWEB)

    Mazzocco, Marta [Loughborough University, Loughborough (United Kingdom); Chekhov, Leonid O [Institute for Theoretical and Experimental Physics (Russian Federation State Scientific Center), Moscow (Russian Federation)

    2009-12-31

    A fat graph description is given for Teichmueller spaces of Riemann surfaces with holes and with Z{sub 2}- and Z{sub 3}-orbifold points (conical singularities) in the Poincare uniformization. The corresponding mapping class group transformations are presented, geodesic functions are constructed, and the Poisson structure is introduced. The resulting Poisson algebras are then quantized. In the particular cases of surfaces with n Z{sub 2}-orbifold points and with one and two holes, the respective algebras A{sub n} and D{sub n} of geodesic functions (classical and quantum) are obtained. The infinite-dimensional Poisson algebra D{sub n}, which is the semiclassical limit of the twisted q-Yangian algebra Y'{sub q}(o{sub n}) for the orthogonal Lie algebra o{sub n}, is associated with the algebra of geodesic functions on an annulus with n Z{sub 2}-orbifold points, and the braid group action on this algebra is found. From this result the braid group actions are constructed on the finite-dimensional reductions of this algebra: the p-level reduction and the algebra D{sub n}. The central elements for these reductions are found. Also, the algebra D{sub n} is interpreted as the Poisson algebra of monodromy data of a Frobenius manifold in the vicinity of a non-semisimple point. Bibliography: 36 titles.

  6. Analytical chemistry in space

    CERN Document Server

    Wainerdi, Richard E

    1970-01-01

    Analytical Chemistry in Space presents an analysis of the chemical constitution of space, particularly the particles in the solar wind, of the planetary atmospheres, and the surfaces of the moon and planets. Topics range from space engineering considerations to solar system atmospheres and recovered extraterrestrial materials. Mass spectroscopy in space exploration is also discussed, along with lunar and planetary surface analysis using neutron inelastic scattering. This book is comprised of seven chapters and opens with a discussion on the possibilities for exploration of the solar system by

  7. Surface Displacement Field of a Coated Elastic Half-Space Under the Influence of a Moving Distributional Load

    Directory of Open Access Journals (Sweden)

    Onur Şahin

    2017-04-01

    Full Text Available An analysis of the distributed moving load along the surface of a coated half space is presented. The formulation of the problem depends on the hyperbolic-elliptic asymptotic model developed earlier by the authors. The integral solution of the longitudinal and transverse displacements along the surface for the sub and super-Rayleigh cases are obtained by using the uniform stationary phase method. Numerical comparisons of the exact and asymptotic solutions of the longitudinal displacement are illustrated for the certain cross-sections of the profile.

  8. Real-space Mapping of Surface Trap States in CIGSe Nanocrystals using 4D Electron Microscopy

    KAUST Repository

    Bose, Riya

    2016-05-26

    Surface trap states in semiconductor copper indium gallium selenide nanocrystals (NCs) which serve as undesirable channels for non-radiative carrier recombination, remain a great challenge impeding the development of solar and optoelectronics devices based on these NCs. In order to design efficient passivation techniques to minimize these trap states, a precise knowledge about the charge carrier dynamics on the NCs surface is essential. However, selective mapping of surface traps requires capabilities beyond the reach of conventional laser spectroscopy and static electron microscopy; it can only be accessed by using a one-of-a-kind, second-generation four-dimensional scanning ultrafast electron microscope (4D S-UEM) with sub-picosecond temporal and nanometer spatial resolutions. Here, we precisely map the surface charge carrier dynamics of copper indium gallium selenide NCs before and after surface passivation in real space and time using S-UEM. The time-resolved snapshots clearly demonstrate that the density of the trap states is significantly reduced after zinc sulfide (ZnS) shelling. Furthermore, removal of trap states and elongation of carrier lifetime are confirmed by the increased photocurrent of the self-biased photodetector fabricated using the shelled NCs.

  9. Real-space Mapping of Surface Trap States in CIGSe Nanocrystals using 4D Electron Microscopy

    KAUST Repository

    Bose, Riya; Bera, Ashok; Parida, Manas R.; Adhikari, Aniruddha; Shaheen, Basamat; Alarousu, Erkki; Sun, Jingya; Wu, Tao; Bakr, Osman; Mohammed, Omar F.

    2016-01-01

    Surface trap states in semiconductor copper indium gallium selenide nanocrystals (NCs) which serve as undesirable channels for non-radiative carrier recombination, remain a great challenge impeding the development of solar and optoelectronics devices based on these NCs. In order to design efficient passivation techniques to minimize these trap states, a precise knowledge about the charge carrier dynamics on the NCs surface is essential. However, selective mapping of surface traps requires capabilities beyond the reach of conventional laser spectroscopy and static electron microscopy; it can only be accessed by using a one-of-a-kind, second-generation four-dimensional scanning ultrafast electron microscope (4D S-UEM) with sub-picosecond temporal and nanometer spatial resolutions. Here, we precisely map the surface charge carrier dynamics of copper indium gallium selenide NCs before and after surface passivation in real space and time using S-UEM. The time-resolved snapshots clearly demonstrate that the density of the trap states is significantly reduced after zinc sulfide (ZnS) shelling. Furthermore, removal of trap states and elongation of carrier lifetime are confirmed by the increased photocurrent of the self-biased photodetector fabricated using the shelled NCs.

  10. Standard practice for measurement of time-of-wetness on surfaces exposed to wetting conditions as in atmospheric corrosion testing

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    1989-01-01

    1.1 This practice covers a technique for monitoring time-of-wetness (TOW) on surfaces exposed to cyclic atmospheric conditions which produce depositions of moisture. 1.2 The practice is also applicable for detecting and monitoring condensation within a wall or roof assembly and in test apparatus. 1.3 Exposure site calibration or characterization can be significantly enhanced if TOW is measured for comparison with other sites, particularly if this data is used in conjunction with other site-specific instrumentation techniques. 1.4 The values stated in SI units are to be regarded as the standard. This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  11. Surface nucleation and independent growth of Ce(OH)4 within confinement space on modified carbon black surface to prepare nano-CeO2 without agglomeration

    Science.gov (United States)

    Zhang, Xinyue; Xia, Chunhui; Li, Kaitao; Lin, Yanjun

    2018-04-01

    Highly dispersed negative carboxyl groups can be formed on carbon black (CB) surface modified with strong nitric acid. Therefore positive cations can be uniformly absorbed by carboxyl groups and precipitated within a confinement space on modified CB surface to prepare highly dispersed nanomaterials. In this paper, the formation and dispersion status of surface negative carboxyl groups, adsorption status of Ce3+, surface confinement nucleation, crystallization and calcination process were studied by EDS, SEM, and laser particle size analysis. The results show that the carboxyl groups formed on modified CB surface are highly dispersed, and Ce3+ cations can be uniformly anchored by carboxyl groups. Therefore, highly dispersed Ce3+ can react with OH- within a confinement surface region to form positive nano-Ce(OH)4 nuclei which also can be adsorbed by electrostatic attraction. After independent growth of Ce(OH)4 without agglomeration, highly dispersed CeO2 nanoparticles without agglomeration can be prepared together with the help of effectively isolates by CO2 released in the combustion of CB.

  12. Survey of surface proteins from the pathogenic Mycoplasma hyopneumoniae strain 7448 using a biotin cell surface labeling approach.

    Science.gov (United States)

    Reolon, Luciano Antonio; Martello, Carolina Lumertz; Schrank, Irene Silveira; Ferreira, Henrique Bunselmeyer

    2014-01-01

    The characterization of the repertoire of proteins exposed on the cell surface by Mycoplasma hyopneumoniae (M. hyopneumoniae), the etiological agent of enzootic pneumonia in pigs, is critical to understand physiological processes associated with bacterial infection capacity, survival and pathogenesis. Previous in silico studies predicted that about a third of the genes in the M. hyopneumoniae genome code for surface proteins, but so far, just a few of them have experimental confirmation of their expression and surface localization. In this work, M. hyopneumoniae surface proteins were labeled in intact cells with biotin, and affinity-captured biotin-labeled proteins were identified by a gel-based liquid chromatography-tandem mass spectrometry approach. A total of 20 gel slices were separately analyzed by mass spectrometry, resulting in 165 protein identifications corresponding to 59 different protein species. The identified surface exposed proteins better defined the set of M. hyopneumoniae proteins exposed to the host and added confidence to in silico predictions. Several proteins potentially related to pathogenesis, were identified, including known adhesins and also hypothetical proteins with adhesin-like topologies, consisting of a transmembrane helix and a large tail exposed at the cell surface. The results provided a better picture of the M. hyopneumoniae cell surface that will help in the understanding of processes important for bacterial pathogenesis. Considering the experimental demonstration of surface exposure, adhesion-like topology predictions and absence of orthologs in the closely related, non-pathogenic species Mycoplasma flocculare, several proteins could be proposed as potential targets for the development of drugs, vaccines and/or immunodiagnostic tests for enzootic pneumonia.

  13. Survey of surface proteins from the pathogenic Mycoplasma hyopneumoniae strain 7448 using a biotin cell surface labeling approach.

    Directory of Open Access Journals (Sweden)

    Luciano Antonio Reolon

    Full Text Available The characterization of the repertoire of proteins exposed on the cell surface by Mycoplasma hyopneumoniae (M. hyopneumoniae, the etiological agent of enzootic pneumonia in pigs, is critical to understand physiological processes associated with bacterial infection capacity, survival and pathogenesis. Previous in silico studies predicted that about a third of the genes in the M. hyopneumoniae genome code for surface proteins, but so far, just a few of them have experimental confirmation of their expression and surface localization. In this work, M. hyopneumoniae surface proteins were labeled in intact cells with biotin, and affinity-captured biotin-labeled proteins were identified by a gel-based liquid chromatography-tandem mass spectrometry approach. A total of 20 gel slices were separately analyzed by mass spectrometry, resulting in 165 protein identifications corresponding to 59 different protein species. The identified surface exposed proteins better defined the set of M. hyopneumoniae proteins exposed to the host and added confidence to in silico predictions. Several proteins potentially related to pathogenesis, were identified, including known adhesins and also hypothetical proteins with adhesin-like topologies, consisting of a transmembrane helix and a large tail exposed at the cell surface. The results provided a better picture of the M. hyopneumoniae cell surface that will help in the understanding of processes important for bacterial pathogenesis. Considering the experimental demonstration of surface exposure, adhesion-like topology predictions and absence of orthologs in the closely related, non-pathogenic species Mycoplasma flocculare, several proteins could be proposed as potential targets for the development of drugs, vaccines and/or immunodiagnostic tests for enzootic pneumonia.

  14. Genetic Analysis of Mice Skin Exposed by Hyper-Gravity

    Science.gov (United States)

    Takahashi, Rika; Terada, Masahiro; Seki, Masaya; Higashibata, Akira; Majima, Hideyuki J.; Ohira, Yoshinobu; Mukai, Chiaki; Ishioka, Noriaki

    2013-02-01

    In the space environment, physiological alterations, such as low bone density, muscle weakness and decreased immunity, are caused by microgravity and cosmic radiation. On the other hand, it is known that the leg muscles are hypertrophy by 2G-gravity. An understanding of the effects on human body from microgravity to hyper-gravity is very important. Recently, the Japan Aerospace Exploration Agency (JAXA) has started a project to detect the changes on gene expression and mineral metabolism caused by microgravity by analyzing the hair of astronauts who stay in the international Space Station (ISS) for a long time. From these results of human hair’s research, the genetic effects of human hair roots by microgravity will become clear. However, it is unclear how the gene expression of hair roots was effected by hypergravity. Therefore, in this experiment, we analyzed the effect on mice skin contained hair roots by comparing microgravity or hypergravity exposed mice. The purpose of this experiment is to evaluate the genetic effects on mice skin by microgravity or 2G-gravity. The samples were taken from mice exposed to space flight (FL) or hypergravity environment (2G) for 3-months, respectively. The extracted and amplified RNA from these mice skin was used to DNA microarray analysis. in this experiment, we analyzed the effect of gravity by using mice skin contained hair roots, which exposed space (FL) and hyper-gravity (2G) for 3 months and each control. By DNA microarray analysis, we found the common 98 genes changed in both FL and 2G. Among these 98 genes, the functions and pathways were identified by Gene Ontology (GO) analysis and Ingenuity Pathways Analysis (IPA) software. Next, we focused the one of the identified pathways and compared the effects on each molecules in this pathways by the different environments, such as FL and 2G. As the results, we could detect some interesting molecules, which might be depended on the gravity levels. In addition, to investigate

  15. Development of Space Life Supporting System Using Radiation Technology (Top Brand Project)

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Ju Woon; Kim, Jae Hun; Song, Beom Seok; Choi, Jong Il; Yoon, Yo Han; Park, Jin Kyu; Park, Jae Nam; Han, In Jun; Lee, Yoon Jong [KAERI, Daejeon (Korea, Republic of)

    2010-08-15

    To simulate the space environment of microgravity and expose to space radiation, Hindlimb Suspension Model was established in Gamma Phytotron. Hindlimb suspended group exposed to irradiation, non-suspended group not exposed to irradiation, and non-suspended group exposed to irradiation were experimented for 2 weeks at the dose rate of 3.2 mSV/day. The results showed that muscle weight was decreased by suspension. To develop the countermeasure to physiological changes in space environment, the peptides from soy beam was selected to evaluate the effect with the space environment simulation model. Suing the microscopic and fluorescent images, the growth of microorganisms were detected. The species were identified based on primer-targeted gene sequence analysis. Also, the radiation resistance of species was defined. To research on sustainable nutritional supply and improvement of human physiology in space environment, four kinds of new Korean space foods (Bulgogi, Bibimbap, Seaweed soup, and Mulberry beverage) were developed using the irradiation technology and certified as space foods by the Russian Institute of Biomedical Problems. The contract on joint research of MARS-500 between KAERI and IBMP was made. In the experiment, crews for expedition to Mars will eat Korean space foods (Bulgogi, Bibimbap, Seaweed soup, Mulberry beverage, Kimchi, Sujeonggwa) for 120 days, then their immunity will be examined and compared with it on the ground. The developed technology and know-how could be spun out to the various fields, such as aircraft, automobile, military, information and communication, bio technologies. Moreover, the results obtained from this research can be used for the further development for military use or special food area such as foods for patient

  16. Development of Space Life Supporting System Using Radiation Technology (Top Brand Project)

    International Nuclear Information System (INIS)

    Lee, Ju Woon; Kim, Jae Hun; Song, Beom Seok; Choi, Jong Il; Yoon, Yo Han; Park, Jin Kyu; Park, Jae Nam; Han, In Jun; Lee, Yoon Jong

    2010-08-01

    To simulate the space environment of microgravity and expose to space radiation, Hindlimb Suspension Model was established in Gamma Phytotron. Hindlimb suspended group exposed to irradiation, non-suspended group not exposed to irradiation, and non-suspended group exposed to irradiation were experimented for 2 weeks at the dose rate of 3.2 mSV/day. The results showed that muscle weight was decreased by suspension. To develop the countermeasure to physiological changes in space environment, the peptides from soy beam was selected to evaluate the effect with the space environment simulation model. Suing the microscopic and fluorescent images, the growth of microorganisms were detected. The species were identified based on primer-targeted gene sequence analysis. Also, the radiation resistance of species was defined. To research on sustainable nutritional supply and improvement of human physiology in space environment, four kinds of new Korean space foods (Bulgogi, Bibimbap, Seaweed soup, and Mulberry beverage) were developed using the irradiation technology and certified as space foods by the Russian Institute of Biomedical Problems. The contract on joint research of MARS-500 between KAERI and IBMP was made. In the experiment, crews for expedition to Mars will eat Korean space foods (Bulgogi, Bibimbap, Seaweed soup, Mulberry beverage, Kimchi, Sujeonggwa) for 120 days, then their immunity will be examined and compared with it on the ground. The developed technology and know-how could be spun out to the various fields, such as aircraft, automobile, military, information and communication, bio technologies. Moreover, the results obtained from this research can be used for the further development for military use or special food area such as foods for patient

  17. The Effect of Dose Rate on Composite Durability When Exposed to a Simulated Long-Term Lunar Radiation Environment

    Science.gov (United States)

    Rojdev, Kristina; O'Rourke, Mary Jane; Hill, Charles; Nutt, Steven; Atwell, William

    2011-01-01

    Human exploration of space beyond low Earth orbit (LEO) requires a safe living and working environment for crew. Composite materials are one type of material being investigated by NASA as a multi-functional structural approach to habitats for long-term use in space or on planetary surfaces with limited magnetic fields and atmosphere. These materials provide high strength with the potential for decreased weight and increased radiation protection of crew and electronics when compared with conventional aluminum structures. However, these materials have not been evaluated in a harsh radiation environment, as would be experienced outside of LEO or on a planetary surface. Thus, NASA has been investigating the durability of select composite materials in a long-term radiation environment. Previously, NASA exposed composite samples to a simulated, accelerated 30-year radiation treatment and tensile stresses similar to those of a habitat pressure vessel. The results showed evidence of potential surface oxidation and enhanced cross-linking of the matrix. As a follow-on study, we performed the same accelerated exposure alongside an exposure with a decreased dose rate. The slower dose ]rate is comparable to a realistic scenario, although still accelerated. Strain measurements were collected during exposure and showed that with a fastdose rate, the strain decreased with time, but with a slow ]dose rate, the strain increased with time. After the radiation exposures, samples were characterized via tensile tests, flexure tests, Fourier Transform Infrared Spectroscopy (FTIR), and Differential Scanning Calorimetry (DSC). The results of these tests will be discussed.

  18. Simulated non-contact atomic force microscopy for GaAs surfaces based on real-space pseudopotentials

    International Nuclear Information System (INIS)

    Kim, Minjung; Chelikowsky, James R.

    2014-01-01

    We simulate non-contact atomic force microscopy (AFM) with a GaAs(1 1 0) surface using a real-space ab initio pseudopotential method. While most ab initio simulations include an explicit model for the AFM tip, our method does not introduce the tip modeling step. This approach results in a considerable reduction of computational work, and also provides complete AFM images, which can be directly compared to experiment. By analyzing tip-surface interaction forces in both our results and previous ab initio simulations, we find that our method provides very similar force profile to the pure Si tip results. We conclude that our method works well for systems in which the tip is not chemically active.

  19. Effect of steel surface conditions on reinforcing steel corrosion in concrete exposed to marine environments

    Directory of Open Access Journals (Sweden)

    Anzola, E.

    2005-09-01

    Full Text Available Laboratory methods and experimental tests were deployed in the present study to evaluate corrosion in reinforced concrete exposed to marine environments. Reinforcing steel exhibiting two different surface conditions prior to embedment in concrete were studied, one the one hand to assess the electrochemical behaviour of the bars during exposure of the concrete specimens to a simulated marine environment, and on the other to determine the strength of the steel/concrete bond. The reinforced concrete specimens prepared were adapted as required for electrochemical potential and corrosion rate testing. A total of 56 7x15-cm cylindrical specimens containing 3/8" steel rods anchored at a depth of 11.5 cm were made to evaluate the steel / concrete bond and exposed to a natural marine environment for 28 or 190 days prior to testing. All the specimens were made with ready-mixed concrete. It may be concluded from the results of the corrosion tests on reinforcing steel with different surface conditions that the oxide initially covering the bars was dissolved and the steel passivated by the alkalinity in the concrete. The chief finding of the bonding study was that the layer of oxide formed in pre-embedment steel deterioration contributed to establishing a better bond.

    En el contexto de esta investigación, se tomaron en consideración métodos y ensayos experimentales de laboratorio, que permiten hacer una evaluación de la corrosión del hormigón armado expuesto en ambientes marinos. Por una parte se evaluó el comportamiento electroquímico de dos condiciones de estados superficiales del acero embebido en el hormigón, exponiéndolo en un ambiente marino simulado y, por otra parte, se estudió la adherencia entre el acero y el hormigón, con los mismos estados superficiales usados para la evaluación electroquímica. Las probetas se fabricaron de hormigón con acero de refuerzo en su interior, adecuándolas para realizar los ensayos de potenciales

  20. Energy spectrum of iron nuclei measured inside the MIR space craft using CR-39 track detectors

    International Nuclear Information System (INIS)

    Guenther, W.; Leugner, D.; Becker, E.; Flesch, F.; Heinrich, W.; Huentrup, G.; Reitz, G.; Roecher, H.; Streibel, T.

    1999-01-01

    We have exposed stacks of CR-39 plastic nuclear track detectors inside the MIR space craft during the EUROMIR95 space mission for almost 6 months. Over this long period a large number of tracks of high LET events was accumulated in the detector foils. The etching and measuring conditions for this experiment were optimized to detect tracks of stopping iron nuclei. We found 185 stopping iron nuclei inside the stack and identified their trajectories through the material of the experiment. Based on the energy-range relation the energy at the surface of the stack was determined. These particles allow the determination of the low energy part of the spectrum of iron nuclei behind shielding material inside the MIR station

  1. Influence of the radial spacing between cathodes on the surface composition of iron samples sintered by hollow cathode electric discharge

    Directory of Open Access Journals (Sweden)

    Brunatto S.F.

    2001-01-01

    Full Text Available The present work reports an investigation of the influence of the radial spacing between cathodes on the iron sintering process by hollow cathode electrical discharge, with surface enrichment of the alloying elements Cr and Ni. Pressed cylindrical samples of 9.5 mm diameter and density of 7.0 ± 0.1 g/cm³ were prepared by compaction of Ancorsteel 1000C iron powder. These samples, constituting the central cathode, were positioned concentrically in the interior of an external cathode machined from a tube of stainless steel AISI 310 (containing: 25% Cr, 16% Ni, 1.5% Mn, 1.5% Si, 0.03% C and the remainder Fe. Sintering was done at 1150 °C, for 120 min, utilizing radial spacings between the central and hollow cathodes of 3, 6 and 9 mm and a gas mixture of 80% Ar and 20% H2, with a flow rate of 5 cm³/s at a pressure of 3 Torr. The electric discharge was generated using a pulsed voltage power source, with a period of 200 mus. The radial spacing had only a slight influence on the quantity of atoms of alloying elements deposited and diffused on the surface of the sample. Analysis with a microprobe showed the presence of chrome (up to 4.0% and nickel (up to 3.0%, in at. % at the surface of the samples. This surface enrichment can be attributed to the mechanism of sputtering of the metallic atoms present in the external cathode, with the deposition of these elements on the sample surface and consequent diffusion within the sample.

  2. Thermal dimensioning of the deep repository. Influence of canister spacing, canister power, rock thermal properties and nearfield design on the maximum canister surface temperature

    International Nuclear Information System (INIS)

    Hoekmark, Harald; Faelth, Billy

    2003-12-01

    The report addresses the problem of the minimum spacing required between neighbouring canisters in the deep repository. That spacing is calculated for a number of assumptions regarding the conditions that govern the temperature in the nearfield and at the surfaces of the canisters. The spacing criterion is that the temperature at the canister surfaces must not exceed 100 deg C .The results are given in the form of nomographic charts, such that it is in principle possible to determine the spacing as soon as site data, i.e. the initial undisturbed rock temperature and the host rock heat transport properties, are available. Results of canister spacing calculations are given for the KBS-3V concept as well as for the KBS-3H concept. A combination of numerical and analytical methods is used for the KBS-3H calculations, while the KBS-3V calculations are purely analytical. Both methods are described in detail. Open gaps are assigned equivalent heat conductivities, calculated such that the conduction across the gaps will include also the heat transferred by radiation. The equivalent heat conductivities are based on the emissivities of the different gap surfaces. For the canister copper surface, the emissivity is determined by back-calculation of temperatures measured in the Prototype experiment at Aespoe HRL. The size of the different gaps and the emissivity values are of great importance for the results and will be investigated further in the future

  3. Overview of the ISS Radiation Environment Observed during the ESA EXPOSE-R2 Mission in 2014-2016

    Science.gov (United States)

    Dachev, T. P.; Bankov, N. G.; Tomov, B. T.; Matviichuk, Yu. N.; Dimitrov, Pl. G.; Häder, D.-P.; Horneck, G.

    2017-11-01

    The radiation risk radiometer-dosimeter (R3D)-R2 solid-state detector performed radiation measurements at the European Space Agency EXPOSE-R2 platform outside of the Russian "Zvezda" module at the International Space Station (ISS) from 24 October 2014 to 11 January 2016. The ISS orbital parameters were average altitude of 415 km and 51.6° inclination. We developed special software and used experimentally obtained formulas to determine the radiation flux-to-dose ratio from the R3DR2 Liulin-type deposited-energy spectrometer. We provide for the first time simultaneous, long-term estimates of radiation dose external to the ISS for four source categories: (i) galactic cosmic ray particles and their secondary products; (ii) protons in the South Atlantic Anomaly region of the inner radiation belt (IRB); (iii) relativistic electrons and/or bremsstrahlung in the outer radiation belt (ORB); and (iv) solar energetic particle (SEP) events. The latter category is new in this study. Additionally, in this study, secondary particles (SP) resulting from energetic particle interaction with the detector and nearby materials are identified. These are observed continuously at high latitudes. The detected SPs are identified using the same sorting requirements as SEP protons. The IRB protons provide the highest consistent hourly dose, while the ORB electrons and SEPs provide the most extreme hourly doses. SEPs were observed 11 times during the study interval. The R3DR2 data support calculation of average equivalent doses. The 30 day and 1 year average equivalent doses are much smaller than the skin and eyes doses recommendations by the National Council on Radiation Protection (Report 132), which provides radiation protection guidance for Low Earth Orbit.

  4. Soil, Groundwater, Surface Water, and Sediments of Kennedy Space Center, Florida: Background Chemical and Physical Characteristics

    Science.gov (United States)

    Shmalzer, Paul A.; Hensley, Melissa A.; Mota, Mario; Hall, Carlton R.; Dunlevy, Colleen A.

    2000-01-01

    This study documented background chemical composition of soils, groundwater, surface; water, and sediments of Kennedy Space Center. Two hundred soil samples were collected, 20 each in 10 soil classes. Fifty-one groundwater wells were installed in 4 subaquifers of the Surficial Aquifer and sampled; there were 24 shallow, 16 intermediate, and 11 deep wells. Forty surface water and sediment samples were collected in major watershed basins. All samples were away from sites of known contamination. Samples were analyzed for organochlorine pesticides, aroclors, chlorinated herbicides, polycyclic aromatic hydrocarbons (PAH), total metals, and other parameters. All aroclors (6) were below detection in all media. Some organochlorine pesticides were detected at very low frequencies in soil, sediment, and surface water. Chlorinated herbicides were detected at very low frequencies in soil and sediments. PAH occurred in low frequencies in soiL, shallow groundwater, surface water, and sediments. Concentrations of some metals differed among soil classes, with subaquifers and depths, and among watershed basins for surface water but not sediments. Most of the variation in metal concentrations was natural, but agriculture had increased Cr, Cu, Mn, and Zn.

  5. The recognition and interpretation of micro-particle impacts on space craft surfaces

    Science.gov (United States)

    Kearsley, Anton

    Modern analysis instruments now allow the rapid examination of returned spacecraft surfaces, enabling the location and identification of impact features, and the attribution of their impactor origins. This paper describes application of novel electron, ion and micro-X-ray Fluorescence techniques to impacts on diverse compositions of substrate, including solar cell glass, poly-sulfone and fluoro-polymer-impregnated glass fibre composites, multilayer insulation foils, aluminium and titanium alloys. Examples will include two generations of solar cells and stiffener materials from the Hubble Space Telescope (HST), Beta-cloth from the NASA Mir-Trek cover blanket, aluminised Kapton foils from the Japanese Space Flyer Unit (SFU) and the European Retrievable Carrier (EuReCa), Al-alloy plates from the Long Duration Exposure Facility (LDEF), Al foils from the NASA Stardust mission, Al-alloy and Zinc orthotitanate (ZOT) painted alloy plate from HST, and titanium alloys from a re-entered titanium pressure tank. Each type of spacecraft surface poses unique problems of analysis, especially in the recognition of extraneous signatures from the impacting particle, especially if a complex chemical composition is already present in the target. For example, solar cells provide an excellent capture and analysis medium for monitoring fluxes of micrometre-scale orbital debris from solid rocket motor firings in low Earth orbit. However, they provide a hard and dense capture medium upon which substantial modification of the impactor may occur, making the precise identification of micrometeoroid components difficult. Unfortunately, extensive spallation by larger (> 100 micrometre) particle impacts on the thin and brittle structure of solar cells also usually results in complete loss of impactor signature. Although thick alloy surfaces may prevent complete impact penetration, the analysis of particle residues within their deep concavity has proven difficult, until the recent introduction of

  6. Transcription profiling of Drosophila exposed to a levitation magnet for different lengths of time

    Data.gov (United States)

    National Aeronautics and Space Administration — Drosophila samples were exposed to the levitation magnet inside a 25mm diameter tubes with 3 ml of yeast-based Drosophila food in the bottom and a chamber of only 5...

  7. Space radiation dosimetry

    International Nuclear Information System (INIS)

    Reitz, G.; Beaujean, R.; Heilmann, C.; Kopp, J.; Strauch, K.; Heinrich, W.

    1996-01-01

    Detector packages consisting of plastic nuclear track detectors, nuclear emusions, and thermoluminescence detectors were exposed at different locations inside the space laboratory Spacelab and at the astronauts' body and in different sections of the MIR space station. Total dose measurements, particle fluence rate and linear energy transfer (LET) spectra of heavy ions, number of nuclear disintegrations and fast neutron fluence rate from this exposure are given in this report. The dose equivalent received by the PSs were calculated from the measurements and range from 190 μSv d -1 to 770 μSv d -3 . (orig.) [de

  8. Vital role of nuclear data in space missions

    International Nuclear Information System (INIS)

    Tripathi, R.K.

    2008-01-01

    Nasa has a new vision for space exploration in the 21. Century encompassing a broad range of human and robotic missions including missions to Moon, Mars and beyond. Exposure from the hazards of severe space radiation in deep space long duration missions is a critical design driver. Thus, protection from the hazards of severe space radiation is of paramount importance for the new vision. Accurate risk assessments critically depend on the accuracy of the input information about the interaction of ions with materials, electronics and tissues. We have discussed some of the state-of-the-art cross sections database at Nasa and have demonstrated the role nuclear interaction plays in space missions. The impact of the cross sections on space missions has been shown by the assessment of dose exposure on Moon surface behind a number of materials with increasing hydrogen contents known to be a better radiation shielding material. In addition we have examined an approach to introduce reliability based design methods into shield evaluation and optimization procedure as a means to assess and control the uncertainties in shield design. Applications to Lunar missions for short and long-term duration display a large impact on the design outcome and the choice of the materials. For short duration missions all the examined materials have similar performance. However, for career astronauts who are exposed to longer duration space radiation over the period of time the choice of material plays a very critical role. Computational procedures based on deterministic solution of the Boltzmann equation are well suited for such procedures allowing optimization processes to be implemented, evaluation of biologically important rare events,and rapid analysis of possible shield optimization outcomes resulting from the biological model uncertainty parameter space

  9. A Gauss-Newton method for the integration of spatial normal fields in shape Space

    KAUST Repository

    Balzer, Jonathan

    2011-08-09

    We address the task of adjusting a surface to a vector field of desired surface normals in space. The described method is entirely geometric in the sense, that it does not depend on a particular parametrization of the surface in question. It amounts to solving a nonlinear least-squares problem in shape space. Previously, the corresponding minimization has been performed by gradient descent, which suffers from slow convergence and susceptibility to local minima. Newton-type methods, although significantly more robust and efficient, have not been attempted as they require second-order Hadamard differentials. These are difficult to compute for the problem of interest and in general fail to be positive-definite symmetric. We propose a novel approximation of the shape Hessian, which is not only rigorously justified but also leads to excellent numerical performance of the actual optimization. Moreover, a remarkable connection to Sobolev flows is exposed. Three other established algorithms from image and geometry processing turn out to be special cases of ours. Our numerical implementation founds on a fast finite-elements formulation on the minimizing sequence of triangulated shapes. A series of examples from a wide range of different applications is discussed to underline flexibility and efficiency of the approach. © 2011 Springer Science+Business Media, LLC.

  10. Capability of space-spectral analysis used for studying underground nuclear explosions effect on ground surface condition

    International Nuclear Information System (INIS)

    Melent'ev, M.I.; Velikanov, A.E.

    2003-01-01

    The article describes the results of the work of study of the influence underground nucleus blasts (UNB) on condition of the day surface of the site Balapan on the territory of Semipalatinsk Test Site using materials of remote space sensing. The estimation of the cosmic spectral analysis information density is given for revealing the post-explosive geo- dynamic processes. (author)

  11. Imaging space charge regions in Sm-doped ceria using electrochemical strain microscopy

    International Nuclear Information System (INIS)

    Chen, Qian Nataly; Li, Jiangyu; Adler, Stuart B.

    2014-01-01

    Nanocrystalline ceria exhibits a total conductivity several orders of magnitude higher than microcrystalline ceria in air at high temperature. The most widely accepted theory for this enhancement (based on fitting of conductivity data to various transport and kinetic models) is that relatively immobile positively charged defects and/or impurities accumulate at the grain boundary core, leading to a counterbalancing increase in the number of mobile electrons (small polarons) within a diffuse space charge region adjacent to each grain boundary. In an effort to validate this model, we have applied electrochemical strain microscopy to image the location and relative population of mobile electrons near grain boundaries in polycrystalline Sm-doped ceria in air at 20–200 °C. Our results show the first direct (spatially resolved) evidence that such a diffuse space charge region does exist in ceria, and is localized to both grain boundaries and the gas-exposed surface

  12. Imaging space charge regions in Sm-doped ceria using electrochemical strain microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Qian Nataly; Li, Jiangyu, E-mail: jjli@uw.edu [Department of Mechanical Engineering, University of Washington, Seattle, Washington 98195 (United States); Adler, Stuart B., E-mail: stuadler@uw.edu [Department of Chemical Engineering, University of Washington, Seattle, Washington 98195 (United States)

    2014-11-17

    Nanocrystalline ceria exhibits a total conductivity several orders of magnitude higher than microcrystalline ceria in air at high temperature. The most widely accepted theory for this enhancement (based on fitting of conductivity data to various transport and kinetic models) is that relatively immobile positively charged defects and/or impurities accumulate at the grain boundary core, leading to a counterbalancing increase in the number of mobile electrons (small polarons) within a diffuse space charge region adjacent to each grain boundary. In an effort to validate this model, we have applied electrochemical strain microscopy to image the location and relative population of mobile electrons near grain boundaries in polycrystalline Sm-doped ceria in air at 20–200 °C. Our results show the first direct (spatially resolved) evidence that such a diffuse space charge region does exist in ceria, and is localized to both grain boundaries and the gas-exposed surface.

  13. 9 CFR 430.4 - Control of Listeria monocytogenes in post-lethality exposed ready-to-eat products.

    Science.gov (United States)

    2010-01-01

    ... post-lethality exposed ready-to-eat products. 430.4 Section 430.4 Animals and Animal Products FOOD... Control of Listeria monocytogenes in post-lethality exposed ready-to-eat products. (a) Listeria... comes into direct contact with a food contact surface which is contaminated with L. monocytogenes. (b...

  14. Space-Charge Effect

    International Nuclear Information System (INIS)

    Chauvin, N

    2013-01-01

    First, this chapter introduces the expressions for the electric and magnetic space-charge internal fields and forces induced by high-intensity beams. Then, the root-mean-square equation with space charge is derived and discussed. In the third section, the one-dimensional Child-Langmuir law, which gives the maximum current density that can be extracted from an ion source, is exposed. Space-charge compensation can occur in the low-energy beam transport lines (located after the ion source). This phenomenon, which counteracts the spacecharge defocusing effect, is explained and its main parameters are presented. The fifth section presents an overview of the principal methods to perform beam dynamics numerical simulations. An example of a particles-in-cells code, SolMaxP, which takes into account space-charge compensation, is given. Finally, beam dynamics simulation results obtained with this code in the case of the IFMIF injector are presented. (author)

  15. Space-Charge Effect

    CERN Document Server

    Chauvin, N.

    2013-12-16

    First, this chapter introduces the expressions for the electric and magnetic space-charge internal fields and forces induced by high-intensity beams. Then, the root-mean-square equation with space charge is derived and discussed. In the third section, the one-dimensional Child-Langmuir law, which gives the maximum current density that can be extracted from an ion source, is exposed. Space-charge compensation can occur in the low-energy beam transport lines (located after the ion source). This phenomenon, which counteracts the spacecharge defocusing effect, is explained and its main parameters are presented. The fifth section presents an overview of the principal methods to perform beam dynamics numerical simulations. An example of a particles-in-cells code, SolMaxP, which takes into account space-charge compensation, is given. Finally, beam dynamics simulation results obtained with this code in the case of the IFMIF injector are presented.

  16. A preliminary evaluation of short-term thunderstorm forecasting using surface winds at Kennedy Space Center

    Science.gov (United States)

    Watson, Andrew I.; Holle, Ronald L.; Lopez, Raul E.; Nicholson, James R.

    1990-01-01

    In 1987 NASA expanded its surface wind network onto the mainland west of Kennedy Space Center, increasing the network area from nearly 800 sq km to over 1600 sq km. Here, the results of this expansion are reported using three years of wind and lightning information collected during June, July, August, and September of 1987, 1988, and 1989. The divergence-lightning relationships and the importance of wind direction are addressed, and the verification is summarized.

  17. Surface composition of Cd{sub 1–x}Fe(Mn){sub x}Te{sub 1–y}Se{sub y} systems exposed to air

    Energy Technology Data Exchange (ETDEWEB)

    Bundaleski, Nenad [University of Belgrade–Vinča Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade (Serbia); Universidade Nova de Lisboa–Faculdade de Ciências e Tecnologia, Quinta da Torre, 2829–516 Caparica (Portugal); Radisavljević, Ivana, E-mail: iva@vin.bg.ac.rs [University of Belgrade–Vinča Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade (Serbia); Trigueiro, João [Universidade Nova de Lisboa–Faculdade de Ciências e Tecnologia, Quinta da Torre, 2829–516 Caparica (Portugal); Tolstogouzov, Alexander [Universidade Nova de Lisboa–Faculdade de Ciências e Tecnologia, Quinta da Torre, 2829–516 Caparica (Portugal); Ryazan State Radio Engineering University, Gagarin 59/1, 390005 Ryazan (Russian Federation); Rakočević, Zlatko; Medić, Mirjana [University of Belgrade–Vinča Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade (Serbia); Teodoro, Orlando M.N.D. [Universidade Nova de Lisboa–Faculdade de Ciências e Tecnologia, Quinta da Torre, 2829–516 Caparica (Portugal); Romčević, Nebojša [University of Belgrade–Institute of Physics, Pregrevica 118, 11000 Belgrade (Serbia); Ivanović, Nenad [University of Belgrade–Vinča Institute of Nuclear Sciences, P.O. Box 522, 11001 Belgrade (Serbia)

    2017-03-01

    Using X–ray induced Photoelectron Spectroscopy, Time–of–Flight Secondary Ion Mass Spectrometry and Atomic Force Microscopy we have investigated elemental composition, structure and oxidation process taking place at the surfaces of polycrystalline Cd{sub 0.99}Fe{sub 0.01}Te{sub 0.97}Se{sub 0.03} and Cd{sub 0.95}Mn{sub 0.05}Te{sub 0.97}Se{sub 0.03} systems stored in ambient conditions. The surface oxidation destroys the native CdTe matrix and provokes substantial atomic rearrangement in the first few atomic layers. The near–surface region of both systems is enriched in Cd and to some extent Te–deficient, but the surface structure, morphology and the native oxide composition are all found to be considerably different. In Cd{sub 0.99}Fe{sub 0.01}Te{sub 0.97}Se{sub 0.03} system both Fe and Se dopants diffuse into the bulk and oxidation of its surface results in formation of a thin CdTeO{sub 3} layer which covers the CdTe matrix. In Cd{sub 0.95}Mn{sub 0.05}Te{sub 0.97}Se{sub 0.03} system oxygen–rich atmosphere triggers Mn and Se out–diffusion and the nonuniform oxide layer predominantly consists of MnO and a small amount of Te–oxide which both lay underneath a thin layer of metallic Cd segregated at the top of the surface. - Highlights: • Nature of the CdFe(Mn)TeSe surfaces exposed to air is substantially different. • Near–surface region is enriched in Cd and to some extent Te–deficient. • Presence of Mn drastically changes the surface oxidation conditions. • The surface oxidation in ambient conditions undergoes different mechanisms. • Oxygen triggers Mn out–diffusion, while Fe diffuses into the bulk.

  18. Space environments and their effects on space automation and robotics

    Science.gov (United States)

    Garrett, Henry B.

    1990-01-01

    Automated and robotic systems will be exposed to a variety of environmental anomalies as a result of adverse interactions with the space environment. As an example, the coupling of electrical transients into control systems, due to EMI from plasma interactions and solar array arcing, may cause spurious commands that could be difficult to detect and correct in time to prevent damage during critical operations. Spacecraft glow and space debris could introduce false imaging information into optical sensor systems. The presentation provides a brief overview of the primary environments (plasma, neutral atmosphere, magnetic and electric fields, and solid particulates) that cause such adverse interactions. The descriptions, while brief, are intended to provide a basis for the other papers presented at this conference which detail the key interactions with automated and robotic systems. Given the growing complexity and sensitivity of automated and robotic space systems, an understanding of adverse space environments will be crucial to mitigating their effects.

  19. Solid-Core, Gas-Cooled Reactor for Space and Surface Power

    International Nuclear Information System (INIS)

    King, Jeffrey C.; El-Genk, Mohamed S.

    2006-01-01

    The solid-core, gas-cooled, Submersion-Subcritical Safe Space (S and 4) reactor is developed for future space power applications and avoidance of single point failures. The Mo-14%Re reactor core is loaded with uranium nitride fuel in enclosed cavities, cooled by He-30%Xe, and sized to provide 550 kWth for seven years of equivalent full power operation. The beryllium oxide reflector disassembles upon impact on water or soil. In addition to decreasing the reactor and shadow shield mass, Spectral Shift Absorber (SSA) materials added to the reactor core ensure that it remains subcritical in the worst-case submersion accident. With a 0.1 mm thick boron carbide coating on the outside surface of the core block and 0.25 mm thick iridium sleeves around the fuel stacks, the reflector outer diameter is 43.5 cm and the combined reactor and shadow shield mass is 935.1 kg. With 12.5 atom% gadolinium-155 added to the fuel, 2.0 mm diameter gadolinium-155 sesquioxide intersititial pins, and a 0.1 mm thick gadolinium-155 sesquioxide coating, the S and 4 reactor has a slightly smaller reflector outer diameter of 43.0 cm, and a total reactor and shield mass of 901.7 kg. With 8.0 atom% europium-151 added to the fuel, 2.0 mm diameter europium-151 sesquioxide interstitial pins, and a 0.1 mm thick europium-151 sesquioxide coating, the reflector's outer diameter and the total reactor and shield mass are further reduced to 41.5 cm and 869.2 kg, respectively

  20. Radiant heat transfer during the natural evaporation from free surfaces exposed to solar radiation; Transferencia de calor radiante durante a evaporacao natural em superficies livres expostas a radiacao solar

    Energy Technology Data Exchange (ETDEWEB)

    Teixeira, C O.M. [Universidade Federal, Rio de Janeiro, RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia; Hackenberg, C M [Universidade Federal do Rio de Janeiro, RJ (Brazil). Escola de Quimica

    1985-12-31

    In this work a conductive-convective-radiant model which includes phase change behavior, is developed in order to determine the rate of evaporation from free surface exposed to solar radiation and consequently the most important parameters, and their effects, on the design of salt solutions concentrating natural evaporation reservoirs may be analysed. The numerical solutions of the resulting of system of equations are shown to represent very well the experimental results measured on evaporation chambers specially built for daily operations. The thermal effect of spectrally selective surfaces as coating agents for the reservoir is also analysed. (author). 11 refs., 8 figs

  1. Fibrosis biomarkers in workers exposed to MWCNTs

    International Nuclear Information System (INIS)

    Fatkhutdinova, Liliya M.; Khaliullin, Timur O.; Vasil'yeva, Olga L.; Zalyalov, Ramil R.; Mustafin, Ilshat G.; Kisin, Elena R.; Birch, M. Eileen; Yanamala, Naveena; Shvedova, Anna A.

    2016-01-01

    Multi-walled carbon nanotubes (MWCNT) with their unique physico-chemical properties offer numerous technological advantages and are projected to drive the next generation of manufacturing growth. As MWCNT have already found utility in different industries including construction, engineering, energy production, space exploration and biomedicine, large quantities of MWCNT may reach the environment and inadvertently lead to human exposure. This necessitates the urgent assessment of their potential health effects in humans. The current study was carried out at NanotechCenter Ltd. Enterprise (Tambov, Russia) where large-scale manufacturing of MWCNT along with relatively high occupational exposure levels was reported. The goal of this small cross-sectional study was to evaluate potential biomarkers during occupational exposure to MWCNT. All air samples were collected at the workplaces from both specific areas and personal breathing zones using filter-based devices to quantitate elemental carbon and perform particle analysis by TEM. Biological fluids of nasal lavage, induced sputum and blood serum were obtained from MWCNT-exposed and non-exposed workers for assessment of inflammatory and fibrotic markers. It was found that exposure to MWCNTs caused significant increase in IL-1β, IL6, TNF-α, inflammatory cytokines and KL-6, a serological biomarker for interstitial lung disease in collected sputum samples. Moreover, the level of TGF-β1 was increased in serum obtained from young exposed workers. Overall, the results from this study revealed accumulation of inflammatory and fibrotic biomarkers in biofluids of workers manufacturing MWCNTs. Therefore, the biomarkers analyzed should be considered for the assessment of health effects of occupational exposure to MWCNT in cross-sectional epidemiological studies. - Highlights: • The effects of MWCNT exposure in humans remain unclear. • We found increased KL-6/TGF-β levels in the biofluids of MWCNT-exposed workers.

  2. Fibrosis biomarkers in workers exposed to MWCNTs

    Energy Technology Data Exchange (ETDEWEB)

    Fatkhutdinova, Liliya M., E-mail: liliya.fatkhutdinova@gmail.com [Kazan State Medical University, ul. Butlerova 49, Kazan 420012 (Russian Federation); Khaliullin, Timur O., E-mail: Khaliullin.40k@gmail.com [Kazan State Medical University, ul. Butlerova 49, Kazan 420012 (Russian Federation); Department of Physiology & Pharmacology, WVU, Morgantown, WV (United States); Vasil' yeva, Olga L., E-mail: volgaleon@gmail.com [Kazan State Medical University, ul. Butlerova 49, Kazan 420012 (Russian Federation); Zalyalov, Ramil R., E-mail: zalyalov.ramil@gmail.com [Kazan State Medical University, ul. Butlerova 49, Kazan 420012 (Russian Federation); Mustafin, Ilshat G., E-mail: ilshat64@mail.ru [Kazan State Medical University, ul. Butlerova 49, Kazan 420012 (Russian Federation); Kisin, Elena R., E-mail: edk8@cdc.gov [National Institute for Occupational Safety and Health, Morgantown, WV (United States); Birch, M. Eileen, E-mail: mib2@cdc.gov [National Institute for Occupational Safety and Health, Cincinnati, OH (United States); Yanamala, Naveena, E-mail: wqu1@cdc.gov [National Institute for Occupational Safety and Health, Morgantown, WV (United States); Shvedova, Anna A., E-mail: ats1@cdc.gov [National Institute for Occupational Safety and Health, Morgantown, WV (United States); Department of Physiology & Pharmacology, WVU, Morgantown, WV (United States)

    2016-05-15

    Multi-walled carbon nanotubes (MWCNT) with their unique physico-chemical properties offer numerous technological advantages and are projected to drive the next generation of manufacturing growth. As MWCNT have already found utility in different industries including construction, engineering, energy production, space exploration and biomedicine, large quantities of MWCNT may reach the environment and inadvertently lead to human exposure. This necessitates the urgent assessment of their potential health effects in humans. The current study was carried out at NanotechCenter Ltd. Enterprise (Tambov, Russia) where large-scale manufacturing of MWCNT along with relatively high occupational exposure levels was reported. The goal of this small cross-sectional study was to evaluate potential biomarkers during occupational exposure to MWCNT. All air samples were collected at the workplaces from both specific areas and personal breathing zones using filter-based devices to quantitate elemental carbon and perform particle analysis by TEM. Biological fluids of nasal lavage, induced sputum and blood serum were obtained from MWCNT-exposed and non-exposed workers for assessment of inflammatory and fibrotic markers. It was found that exposure to MWCNTs caused significant increase in IL-1β, IL6, TNF-α, inflammatory cytokines and KL-6, a serological biomarker for interstitial lung disease in collected sputum samples. Moreover, the level of TGF-β1 was increased in serum obtained from young exposed workers. Overall, the results from this study revealed accumulation of inflammatory and fibrotic biomarkers in biofluids of workers manufacturing MWCNTs. Therefore, the biomarkers analyzed should be considered for the assessment of health effects of occupational exposure to MWCNT in cross-sectional epidemiological studies. - Highlights: • The effects of MWCNT exposure in humans remain unclear. • We found increased KL-6/TGF-β levels in the biofluids of MWCNT-exposed workers.

  3. Image restorations constrained by a multiply exposed picture

    International Nuclear Information System (INIS)

    Breedlove, J.R. Jr.; Kruger, R.P.; Trussell, H.J.; Hunt, B.R.

    1977-01-01

    There are a number of possible industrial and scientific applications of nanosecond cineradiographs. While the technology exists to produce closely spaced pulses of x rays for this application, the quality of the time-resolved radiographs is severely limited. The limitations arise from the necessity of using a fluorescent screen to convert the transmitted x rays to light and then using electro-optical imaging systems to gate and to record the images with conventional high-speed cameras. It has been proposed that in addition to the time-resolved images, a conventional multiply-exposed radiograph be obtained. Simulations are used to demonstrate that the additional information supplied by the multiply-exposed radiograph can be used to improve the quality of digital image restorations of the time-resolved pictures over what could be achieved with the degraded images alone. Because of the need for image registration and rubber sheet transformations, this problem is one which can best be solved on a digital, as opposed to an optical, computer

  4. Blackfolds, plane waves and minimal surfaces

    Science.gov (United States)

    Armas, Jay; Blau, Matthias

    2015-07-01

    Minimal surfaces in Euclidean space provide examples of possible non-compact horizon geometries and topologies in asymptotically flat space-time. On the other hand, the existence of limiting surfaces in the space-time provides a simple mechanism for making these configurations compact. Limiting surfaces appear naturally in a given space-time by making minimal surfaces rotate but they are also inherent to plane wave or de Sitter space-times in which case minimal surfaces can be static and compact. We use the blackfold approach in order to scan for possible black hole horizon geometries and topologies in asymptotically flat, plane wave and de Sitter space-times. In the process we uncover several new configurations, such as black helicoids and catenoids, some of which have an asymptotically flat counterpart. In particular, we find that the ultraspinning regime of singly-spinning Myers-Perry black holes, described in terms of the simplest minimal surface (the plane), can be obtained as a limit of a black helicoid, suggesting that these two families of black holes are connected. We also show that minimal surfaces embedded in spheres rather than Euclidean space can be used to construct static compact horizons in asymptotically de Sitter space-times.

  5. Blackfolds, plane waves and minimal surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Armas, Jay [Physique Théorique et Mathématique, Université Libre de Bruxelles and International Solvay Institutes, ULB-Campus Plaine CP231, B-1050 Brussels (Belgium); Albert Einstein Center for Fundamental Physics, University of Bern,Sidlerstrasse 5, 3012 Bern (Switzerland); Blau, Matthias [Albert Einstein Center for Fundamental Physics, University of Bern,Sidlerstrasse 5, 3012 Bern (Switzerland)

    2015-07-29

    Minimal surfaces in Euclidean space provide examples of possible non-compact horizon geometries and topologies in asymptotically flat space-time. On the other hand, the existence of limiting surfaces in the space-time provides a simple mechanism for making these configurations compact. Limiting surfaces appear naturally in a given space-time by making minimal surfaces rotate but they are also inherent to plane wave or de Sitter space-times in which case minimal surfaces can be static and compact. We use the blackfold approach in order to scan for possible black hole horizon geometries and topologies in asymptotically flat, plane wave and de Sitter space-times. In the process we uncover several new configurations, such as black helicoids and catenoids, some of which have an asymptotically flat counterpart. In particular, we find that the ultraspinning regime of singly-spinning Myers-Perry black holes, described in terms of the simplest minimal surface (the plane), can be obtained as a limit of a black helicoid, suggesting that these two families of black holes are connected. We also show that minimal surfaces embedded in spheres rather than Euclidean space can be used to construct static compact horizons in asymptotically de Sitter space-times.

  6. Ultrafast changes in the optical properties of a titanium surface and femtosecond laser writing of one-dimensional quasi-periodic nanogratings of its relief

    International Nuclear Information System (INIS)

    Golosov, E. V.; Ionin, A. A.; Kolobov, Yu. R.; Kudryashov, S. I.; Ligachev, A. E.; Novoselov, Yu. N.; Seleznev, L. V.; Sinitsyn, D. V.

    2011-01-01

    One-dimensional quasi-periodic nanogratings with spacings in the range from 160 to 600 nm are written on a dry or wet titanium surface exposed to linearly polarized femtosecond IR and UV laser pulses with different surface energy densities. The topological properties of the obtained surface nanostructures are studied by scanning electron microscopy. Despite the observation of many harmonics of the one-dimensional surface relief in its Fourier spectra, a weak decreasing dependence of the first-harmonic wavenumber (nanograting spacing) on the laser fluence is found. Studies of the instantaneous optical characteristics of the material during laser irradiation by measuring the reflection of laser pump pulses and their simulation based on the Drude model taking into account the dominant interband absorption allowed us to estimate the length of the excited surface electromagnetic (plasmon-polariton) wave for different excitation conditions. This wavelength is quantitatively consistent with the corresponding nanograting spacings of the first harmonic of the relief of the dry and wet titanium surfaces. It is shown that the dependence of the first-harmonic nanograting spacing on the laser fluence is determined by a change in the instantaneous optical characteristics of the material and the saturation of the interband absorption along with the increasing role of intraband transitions. Three new methods are proposed for writing separate subwave surface nanogratings or their sets by femtosecond laser pulses using the near-threshold nanostructuring, the forced adjustment of the optical characteristics of the material or selecting the spectral range of laser radiation, and also by selecting an adjacent dielectric.

  7. Analyses of Hubble Space Telescope Aluminized-Teflon Multilayer Insulation Blankets Retrieved After 19 Years of Space Exposure

    Science.gov (United States)

    de Groh, Kim K.; Perry, Bruce A.; Mohammed, Jelila S.; Banks, Bruce

    2015-01-01

    Since its launch in April 1990, the Hubble Space Telescope (HST) has made many important observations from its vantage point in low Earth orbit (LEO). However, as seen during five servicing missions, the outer layer of multilayer insulation (MLI) has become increasingly embrittled and has cracked in many areas. In May 2009, during the 5th servicing mission (called SM4), two MLI blankets were replaced with new insulation and the space-exposed MLI blankets were retrieved for degradation analyses by teams at NASA Glenn Research Center (GRC) and NASA Goddard Space Flight Center (GSFC). The retrieved MLI blankets were from Equipment Bay 8, which received direct sunlight, and Equipment Bay 5, which received grazing sunlight. Each blanket was divided into several regions based on environmental exposure and/or physical appearance. The aluminized-Teflon (DuPont, Wilmington, DE) fluorinated ethylene propylene (Al-FEP) outer layers of the retrieved MLI blankets have been analyzed for changes in optical, physical, and mechanical properties, along with chemical and morphological changes. Pristine and as-retrieved samples (materials) were heat treated to help understand degradation mechanisms. When compared to pristine material, the analyses have shown how the Al-FEP was severely affected by the space environment. Most notably, the Al-FEP was highly embrittled, fracturing like glass at strains of 1 to 8 percent. Across all measured properties, more significant degradation was observed for Bay 8 material as compared to Bay 5 material. This paper reviews the tensile and bend-test properties, density, thickness, solar absorptance, thermal emittance, x-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy (EDS) elemental composition measurements, surface and crack morphologies, and atomic oxygen erosion yields of the Al-FEP outer layer of the retrieved HST blankets after 19 years of space exposure.

  8. Spatial distribution of absorbed dose onboard of International Space Station

    International Nuclear Information System (INIS)

    Jadrnickova, I.; Spumy, F.; Tateyama, R.; Yasuda, N.; Kawashima, H.; Kurano, M.; Uchihori, Y.; Kitamura, H.; Akatov, Yu.; Shurshakov, V.; Kobayashi, I.; Ohguchi, H.; Koguchi, Y.

    2009-01-01

    The passive detectors (LD and PNTD) were exposed onboard of Russian Service Module Qn the International Space Station (ISS) from August 2004 to October 2005 (425 days). The detectors were located at 6 different positions inside the Service Module and also in 32 pockets on the surface of the spherical tissue-equivalent phantom located in crew cabin. Distribution of absorbed doses and dose equivalents measured with passive detectors, as well as LET spectra of fluences of registered particles, are presented as the function of detectors' location. The variation of dose characteristics for different locations can be up to factor of 2. In some cases, data measured with passive detectors are also compared with the data obtained by means of active instruments. (authors)

  9. Controlling the interparticle spacing of Au-salt loaded micelles and Au nanoparticles on flat surfaces.

    Science.gov (United States)

    Bansmann, J; Kielbassa, S; Hoster, H; Weigl, F; Boyen, H G; Wiedwald, U; Ziemann, P; Behm, R J

    2007-09-25

    The self-organization of diblock copolymers into micellar structures in an appropriate solvent allows the deposition of well ordered arrays of pure metal and alloy nanoparticles on flat surfaces with narrow distributions in particle size and interparticle spacing. Here we investigated the influence of the materials (substrate and polymer) and deposition parameters (temperature and emersion velocity) on the deposition of metal salt loaded micelles by dip-coating from solution and on the order and inter-particle spacing of the micellar deposits and thus of the metal nanoparticle arrays resulting after plasma removal of the polymer shell. For identical substrate and polymer, variation of the process parameters temperature and emersion velocity enables the controlled modification of the interparticle distance within a certain length regime. Moreover, also the degree of hexagonal order of the final array depends sensitively on these parameters.

  10. Responsive acoustic surfaces

    DEFF Research Database (Denmark)

    Peters, Brady; Tamke, Martin; Nielsen, Stig Anton

    2011-01-01

    Acoustic performance is defined by the parameter of reverberation time; however, this does not capture the acoustic experience in some types of open plan spaces. As many working and learning activities now take place in open plan spaces, it is important to be able to understand and design...... for the acoustic conditions of these spaces. This paper describes an experimental research project that studied the design processes necessary to design for sound. A responsive acoustic surface was designed, fabricated and tested. This acoustic surface was designed to create specific sonic effects. The design...... was simulated using custom integrated acoustic software and also using Odeon acoustic analysis software. The research demonstrates a method for designing space- and sound-defining surfaces, defines the concept of acoustic subspace, and suggests some new parameters for defining acoustic subspaces....

  11. AISI/DOE Technology Roadmap Program: Improved Surface Quality of Exposed Automotive Sheet Steels

    Energy Technology Data Exchange (ETDEWEB)

    John G. Speer; David K. Matlock; Noel Meyers; Young-Min Choi

    2002-10-10

    Surface quality of sheet steels is an important economic and technical issue for applications such as critical automotive surfaces. This project was therefore initiated to develop a more quantitative methodology for measuring surface imperfections, and to assess their response to forming and painting, particularly with respect to their visibility or invisibility after painting. The objectives were met, and included evaluation of a variety of imperfections present on commercial sheet surfaces or simulated using methods developed in the laboratory. The results are expected to have significant implications with respect to the methodology for assessing surface imperfections, development of quantitative criteria for surface inspection, and understanding and improving key painting process characteristics that influence the perceived quality of sheet steel surfaces.

  12. Space-weathering processes and products on volatile-rich asteroids

    Science.gov (United States)

    Britt, D.; Schelling, P.; Consolmagno, G.; Bradley, T.

    2014-07-01

    Space weathering is a generic term for the effects on atmosphereless solid bodies in the solar system from a range of processes associated with direct exposure to the space environment. These include impact processes (shock, vaporization, fragmentation, heating, melting, and ejecta formation), radiation damage (from galactic and solar cosmic rays), solar-wind effects (irradiation, ion implantation, and sputtering), and the chemical reactions driven by these processes. The classic example of space weathering is the formation of the lunar spectral red slope associated with the production of nanophase Fe (npFe0) in the dusty lunar regolith (C.R. Chapman, 2004, Annual Review of Earth & Planet. Sci. 32, C.M. Pieters, 2000, MAPS 35). Similar npFe0 has been recovered from asteroid (25143) Itokawa and some asteroid classes do exhibit modest spectral red slopes (T. Noguchi, 2011, Science 333). Space weathering can be thought of as driven by a combination of the chemical environment of space (hard vacuum, low oxygen fugacity, solar-wind implantation of hydrogen) along with thermal energy supplied by micrometeorite impacts. The forward modeling of space weathering as thermodynamically-driven decomposition of common rock-forming minerals suggests the production of a range of daughter products: (1) The silicate products typically lose oxygen, other volatile elements (i.e., sulfur and sodium), and metallic cations, producing minerals that are typically more disordered and less optically active than the original parent materials. (2) The decomposed metallic cations form in nano-sized blebs including npFe0, on the surfaces or in condensing rims of mineral grains. This creates a powerful optical component as seen in the lunar red slope. Surfaces with exposed npFe0 are an ideal environment for catalyzing further reactions. (3) The liberated volatile elements and gases (O, S, Na) may form an observable exosphere (e.g., Moon and Mercury) and can either escape from the body or

  13. Astronaut exposure to space radiation - Space Shuttle experience

    International Nuclear Information System (INIS)

    Atwell, W.

    1990-01-01

    Space Shuttle astronauts are exposed to both the trapped radiation and the galactic cosmic radiation environments. In addition, the sun periodically emits high-energy particles which could pose a serious threat to flight crews. NASA adheres to federal regulations and recommended exposure limits for radiation protection and has established a radiological health and risk assessment program. Using models of the space radiation environment, a Shuttle shielding model, and an anatomical human model, crew exposure estimates are made for each Shuttle flight. The various models are reviewed. Dosimeters are worn by each astronaut and are flown at several fixed locations to obtain inflight measurements. The dosimetry complement is discussed in detail. A comparison between the premission calculations and measurements is presented. Extrapolation of Shuttle experience to long-duration exposure is explored. 14 refs

  14. Space Elevators: Building a Permanent Bridge for Space Exploration and Economic Development

    Science.gov (United States)

    Smitherman, David V., Jr.; Howell, Joe T. (Technical Monitor)

    2000-01-01

    A space elevator is a physical connection from the surface of the Earth to a geo-stationary orbit above the Earth approximately 35,786 km in altitude. Its center of mass is at the geo-stationary point such that it has a 24-hour orbit, and stays over the same point above the equator as the Earth rotates on its axis. The structure is utilized as a transportation and utility system for moving payloads, power, and gases between the surface of the Earth and space. It makes the physical connection from Earth to space in the same way a bridge connects two cities across a body of' water. The space elevator may be an important concept for the future development of space in the latter part of the 21th century. It has the potential to provide mass-transportation to space in the same way highways, railroads, power lines, and pipelines provide mass-transportation across the Earth's surface. The low energy requirements for moving payloads up and down the elevator make it one of only a few concepts that has the potential of lowering the cost to orbit to less than $10 per kilogram. This paper will summarize the findings from a 1999 NASA workshop on Space Elevators held at the NASA Marshall Space Flight Center (MSFC). The workshop was sponsored by the Advanced Projects Office in the Flight Projects Directorate at MSFC, and was organized in cooperation with the Advanced Space Transportation Program at MSFC and the Advanced Concepts Office in the Office of Space Flight at NASA Headquarters. New concepts will be examined for space elevator construction and a number of issues will be discussed that has helped to bring the space elevator concept out of the realm of science fiction and into the realm of possibility. In conclusion, it appears that the space elevator concept may well he possible in the latter part of the 21st century if proper planning and technology development is emphasized to resolve key issues in the development of this advanced space infrastructure concept.

  15. A variational model of disjoining pressure: Liquid film on a nonplanar surface

    Energy Technology Data Exchange (ETDEWEB)

    Silin, D.; Virnovsky, G.

    2009-06-01

    Variational methods have been successfully used in modelling thin liquid films in numerous theoretical studies of wettability. In this paper, the variational model of the disjoining pressure is extended to the general case of a two-dimensional solid surface. The Helmgoltz free energy functional depends both on the disjoining pressure isotherm and the shape of the solid surface. The augmented Young-Laplace equation (AYLE) is a nonlinear second-order partial differential equation. A number of solutions describing wetting films on spherical grains have been obtained. In the case of cylindrical films, the phase portrait technique describes the entire variety of mathematically feasible solutions. It turns out that a periodic solution, which would describe wave-like wetting films, does not satisfy the Jacobi's condition of the classical calculus of variations. Therefore, such a solution is nonphysical. The roughness of the solid surface significantly affects liquid film stability. AYLE solutions suggest that film rupture is more likely at a location where the pore-wall surface is most exposed into the pore space and the curvature is positive.

  16. Exploded view diagrams of mathematical surfaces

    KAUST Repository

    Karpenko, Olga A.; Li, Wilmot; Mitra, Niloy J.; Agrawala, Maneesh

    2010-01-01

    We present a technique for visualizing complicated mathematical surfaces that is inspired by hand-designed topological illustrations. Our approach generates exploded views that expose the internal structure of such a surface by partitioning

  17. Assessment of radiation shielding materials for protection of space crews using CR-39 plastic nuclear track detector

    International Nuclear Information System (INIS)

    DeWitt, J.M.; Benton, E.R.; Uchihori, Y.; Yasuda, N.; Benton, E.V.; Frank, A.L.

    2009-01-01

    A significant obstacle to long duration human space exploration such as the establishment of a permanent base on the surface of the Moon or a human mission to Mars is the risk posed by prolonged exposure to space radiation. In order to keep mission costs at acceptable levels while simultaneously minimizing the risk from radiation to space crew health and safety, a judicious use of optimized shielding materials will be required. We have undertaken a comprehensive study using CR-39 plastic nuclear track detector (PNTD) to characterize the radiation shielding properties of a range of materials-both common baseline materials such as Al and polyethylene, and novel multifunctional materials such as carbon composites-at heavy ion accelerators. The study consists of analyzing CR-39 PNTD exposed in front of and behind shielding targets of varying composition and at a number of depths (target thicknesses) relevant to the development and testing of materials for space radiation shielding. Most targets consist of 10 cm x 10 cm slabs of solid materials ranging in thickness from 1 to >30 g/cm 2 . Exposures have been made to beams of C, O, Ne, Si, Ar, and Fe at energies ranging from 290 MeV/amu to 1 GeV/amu at the National Institute of Radiological Sciences HIMAC and the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory. Analysis of the exposed detectors yields LET spectrum, dose, and dose equivalent as functions of target depth and composition, and incident heavy ion charge, energy, and fluence. Efforts are currently underway to properly weigh and combine these results into a single quantitative estimate of a material's ability to shield space crews from the interplanetary galactic cosmic ray flux.

  18. Long-Lived Glass Mirrors For Outer Space

    Science.gov (United States)

    Bouquet, Frank L.; Maag, Carl R.; Heggen, Philip M.

    1988-01-01

    Paper summarizes available knowledge about glass mirrors for use in outer space. Strengths and weaknesses of various types of first and second reflective surfaces identified. Second-surface glass mirrors used in outer space designed to different criteria more stringent for terrestrial mirrors. Protons, electrons, cosmic rays, meteorites, and orbiting space debris affect longevities of components. Contamination also factor in space.

  19. Evaluating a Space-Based Indicator of Surface Ozone-NO x -VOC Sensitivity Over Midlatitude Source Regions and Application to Decadal Trends.

    Science.gov (United States)

    Jin, Xiaomeng; Fiore, Arlene M; Murray, Lee T; Valin, Lukas C; Lamsal, Lok N; Duncan, Bryan; Boersma, K Folkert; De Smedt, Isabelle; Abad, Gonzalo Gonzalez; Chance, Kelly; Tonnesen, Gail S

    2017-10-16

    Determining effective strategies for mitigating surface ozone (O 3 ) pollution requires knowledge of the relative ambient concentrations of its precursors, NO x , and VOCs. The space-based tropospheric column ratio of formaldehyde to NO 2 (FNR) has been used as an indicator to identify NO x -limited versus NO x -saturated O 3 formation regimes. Quantitative use of this indicator ratio is subject to three major uncertainties: (1) the split between NO x -limited and NO x -saturated conditions may shift in space and time, (2) the ratio of the vertically integrated column may not represent the near-surface environment, and (3) satellite products contain errors. We use the GEOS-Chem global chemical transport model to evaluate the quantitative utility of FNR observed from the Ozone Monitoring Instrument over three northern midlatitude source regions. We find that FNR in the model surface layer is a robust predictor of the simulated near-surface O 3 production regime. Extending this surface-based predictor to a column-based FNR requires accounting for differences in the HCHO and NO 2 vertical profiles. We compare four combinations of two OMI HCHO and NO 2 retrievals with modeled FNR. The spatial and temporal correlations between the modeled and satellite-derived FNR vary with the choice of NO 2 product, while the mean offset depends on the choice of HCHO product. Space-based FNR indicates that the spring transition to NO x -limited regimes has shifted at least a month earlier over major cities (e.g., New York, London, and Seoul) between 2005 and 2015. This increase in NO x sensitivity implies that NO x emission controls will improve O 3 air quality more now than it would have a decade ago.

  20. Metrics on the Phase Space and Non-Selfadjoint Pseudo-Differential Operators

    CERN Document Server

    Lerner, Nicolas

    2010-01-01

    This book is devoted to the study of pseudo-differential operators, with special emphasis on non-selfadjoint operators, a priori estimates and localization in the phase space. We expose the most recent developments of the theory with its applications to local solvability and semi-classical estimates for nonselfadjoint operators. The first chapter is introductory and gives a presentation of classical classes of pseudo-differential operators. The second chapter is dealing with the general notion of metrics on the phase space. We expose some elements of the so-called Wick calculus and introduce g

  1. Electron Stimulated Desorption of Condensed Gases on Cryogenic Surfaces

    CERN Document Server

    Tratnik, H; Hilleret, Noël

    2005-01-01

    In ultra-high vacuum systems outgassing from vacuum chamber walls and desorption from surface adsorbates are usually the factors which in°uence pressure and residual gas composition. In particular in beam vacuum systems of accelerators like the LHC, where surfaces are exposed to intense synchro- tron radiation and bombardment by energetic ions and electrons, properties like the molecular desorption yield or secondary electron yield can strongly in°uence the performance of the accelerator. In high-energy particle accelerators operating at liquid helium temperature, cold surfaces are exposed to the bombardment of energetic photons, electrons and ions. The gases released by the subsequent desorption are re-condensed on the cold surfaces and can be re-desorbed by the impinging electrons and ions. The equilibrium coverage reached on the surfaces exposed to the impact of energetic particles depends on the desorption yield of the condensed gases and can a®ect the operation of the accelerator by modifying th...

  2. The summer thermal behaviour of 'skin' materials for vertical surfaces in Athens, Greece, as a decisive parameter for their selection

    Energy Technology Data Exchange (ETDEWEB)

    Bougiatioti, F.; Evangelinos, E.; Poulakos, G.; Zacharopoulos, E. [National Technical University of Athens, School of Architecture, Department of Architectural Technology, 42, Patission Street, 10682 Athens (Greece)

    2009-04-15

    This paper analyses the thermal behaviour of the materials, which are widely used on the vertical surfaces of Greek cities. This analysis is based on surface temperatures measurements, which were carried out both in situ in various buildings of Athens, Greece and experimentally on samples of building materials exposed to solar radiation on a building's flat roof. The study includes surfacing materials, which are usually applied on building facades around Greece. The study leads to a number of conclusions concerning the effect of colour and orientation on the summer surface temperatures of materials, used on vertical city surfaces. These conclusions indicate how surfacing materials should be chosen in order to help mitigate the urban heat island and improve thermal comfort conditions in the outdoor spaces of Greek cities during the overheated summer period. (author)

  3. Geometric influences of a particle confined to a curved surface embedded in three-dimensional Euclidean space

    Science.gov (United States)

    Wang, Yong-Long; Jiang, Hua; Zong, Hong-Shi

    2017-08-01

    In the spirit of the thin-layer quantization approach, we give the formula of the geometric influences of a particle confined to a curved surface embedded in three-dimensional Euclidean space. The geometric contributions can result from the reduced commutation relation between the acted function depending on normal variable and the normal derivative. According to the formula, we obtain the geometric potential, geometric momentum, geometric orbital angular momentum, geometric linear Rashba, and cubic Dresselhaus spin-orbit couplings. As an example, a truncated cone surface is considered. We find that the geometric orbital angular momentum can provide an azimuthal polarization for spin, and the sign of the geometric Dresselhaus spin-orbit coupling can be flipped through the inclination angle of generatrix.

  4. Short-term forecasting of lightning based on the surface wind field at Kennedy Space Center

    Science.gov (United States)

    Watson, Andrew I.; Lopez, Raul E.; Ortiz, Robert; Holle, Ronald L.

    1987-01-01

    Cloud-to-ground lightning is related in time and space to surface convergence for 244 days during the summer over a 790 sqkm network. The method uses surface convergence, particularly the average over the area, to identify the potential for new, local thunderstorm growth, and can be used to specify the likely time and location of lightning during the life cycle of the convection. A threshold of 0.0000075/sec change in divergence is used to define a convergence event, and a separation of 30 min between flashes defines a lightning event. Time intervals are found to be on the order of 1 hr from beginning convergence to first flash, and (CH110) 2 hr from beginning convergence to the end of lightning. Major differences between the convergence-lightning relationships based on low-level mean onshore and offshore flow are noted.

  5. Exposing Microorganisms in the Stratosphere for Planetary Protection

    Data.gov (United States)

    National Aeronautics and Space Administration — Earth’s stratosphere is similar to the surface of Mars: rarified air which is dry, cold, and irradiated. E-MIST is a balloon payload that has 4 independently...

  6. Surface properties of ceramic/metal composite materials for thermionic converter applications

    International Nuclear Information System (INIS)

    Davis, P.R.; Bozack, M.J.; Swanson, L.W.

    1983-01-01

    Ceramic/metal composite electrode materials are of interest for thermionic energy conversion (TEC) applications for several reasons. These materials consist of submicron metal fibers or islands in an oxide matrix and therefore provide a basis for fabricating finely structured electrodes, with projecting or recessed metallic regions for more efficient electron emission or collection. Furthermore, evaporation and surface diffusion of matrix oxides may provide oxygen enhancement of cesium adsorption and work function lowering at both the collecting and emitting electrode surfaces of the TEC. Finally, the high work function oxide matrix or oxide-metal interfaces may provide efficient surface ionization of cesium for space-charge reduction in the device. The authors are investigating two types of ceramic/metal composite materials. One type is a directionally solidified eutectic consisting of a bulk oxide matrix such as UO 2 or stabilized ZrO 2 with parallel metal fibers (W) running through the oxide being exposed at the surface by cutting perpendicular to the fiber direction. The second type of material, called a surface eutectic, consists of a refractory substrate (Mo) with a thin layer of deposited and segregated material (Mo-Cr 2 O 3 -A1 2 O 3 ) on the surface. The final configuration of this layer is an oxide matrix with metallic islands scattered throughout

  7. Z-2 Space Suit: A Case Study in Human Spaceflight Public Outreach

    Science.gov (United States)

    McFarland, Shane M.

    2016-01-01

    NASA Johnson Space Center's Z-series of planetary space suit prototypes is an iterative development platform with a Mars-forward design philosophy, targeting a Mars surface mission in the mid-2030s. The first space suit assembly, called the Z-1, was delivered in 2012. While meeting the project's stated requirements and objectives, the general public's reception primarily focused on the color scheme, which vaguely invoked similarity to a certain animated cartoon character. The public at large has and continues to be exposed to varying space suit design aesthetics from popular culture and low TRL technology maturation efforts such as mechanical counterpressure. The lesson learned was that while the design aesthetic is not important from an engineering perspective, the perception of the public is important for NASA and human spaceflight in general. For the Z-2 space suit, an integrated public outreach strategy was employed to engage, excite and educate the public on the current technology of space suits and NASA's plans moving forward. The keystone of this strategy was a public vote on three different suit cover layer aesthetics, the winner of which would be used as inspiration in fabrication. Other components included social media, university collaboration, and select media appearances, the cumulative result of which, while intangible in its benefit, was ultimately a positive effect in terms of the image of NASA as well as the dissemination of information vital to dispelling public misconceptions.

  8. Method of evaluating the surface color of concrete; Concrete hyomenshoku hyoka shuho

    Energy Technology Data Exchange (ETDEWEB)

    Kondo, Y; Kotani, K; Imadate, F; Ito, N; Watanabe, K [Kajima Corp., Tokyo (Japan)

    1995-12-20

    As a part of the evaluation of landscape of civil engineering structures, a method was studied for quantitative evaluation of surface color and color hue of the exposed concrete. The surface colors of concrete structures constructed at more than one sites were measured using a colorimeter and were statistically processed. The colorimeter can measure colors by irradiating the standard light onto the surface of the object and dividing the reflection light into ingredients, lightness L and color phase a and b in the CIELAB equal color space. The L/a/b measuring data were plotted which were obtained from 2010 measuring surfaces of 49 structures at 7 construction sites. As for the surface color of concrete, it was found that ingredient L measured by the colorimeter reacts on variations of color very sensitively and agrees well with the trend of evaluation by eyes. Namely, human being senses the difference of concrete color mainly from the difference in lightness and senses the difference as the color hue. Further, using the neural network, an evaluation method was established which was the same as the human sense. 1 ref., 8 figs., 3 tabs.

  9. XPS Study of Chemical Changes on the La/Ce Treated Surface of A361 Aluminium Alloy Exposed to Air at Temperatures up to 500∘C

    Directory of Open Access Journals (Sweden)

    A. Pardo

    2009-01-01

    Full Text Available The chemical changes that take place on the rare earth treated surface of the A361 aluminium alloy exposed to air at temperatures between 100 and 500∘C have been examined using X-ray photoelectron spectroscopy (XPS. The most notable features discussed in this work are the disappearance of Mg and Si signals at the tested temperatures and disappearance of the Ce signal at temperatures of 400–500∘C. The biphasic microstructure of the A361 alloy, constituted by close to 12 wt% Si and the Al matrix, plays an important role in many of the results obtained. The notable growth of aluminium oxide across the conversion coating in the case of the Ce-treated surface is related to the structural transformation experienced by the cerium oxide coating at 400–500∘C.

  10. Massive Modularity of Space and Surface Systems

    Data.gov (United States)

    National Aeronautics and Space Administration — This project will conduct a systems level investigation of a modular design and operations approach for future NASA exploration systems. Particular emphasis will be...

  11. Image-based Exploration of Iso-surfaces for Large Multi- Variable Datasets using Parameter Space.

    KAUST Repository

    Binyahib, Roba S.

    2013-05-13

    With an increase in processing power, more complex simulations have resulted in larger data size, with higher resolution and more variables. Many techniques have been developed to help the user to visualize and analyze data from such simulations. However, dealing with a large amount of multivariate data is challenging, time- consuming and often requires high-end clusters. Consequently, novel visualization techniques are needed to explore such data. Many users would like to visually explore their data and change certain visual aspects without the need to use special clusters or having to load a large amount of data. This is the idea behind explorable images (EI). Explorable images are a novel approach that provides limited interactive visualization without the need to re-render from the original data [40]. In this work, the concept of EI has been used to create a workflow that deals with explorable iso-surfaces for scalar fields in a multivariate, time-varying dataset. As a pre-processing step, a set of iso-values for each scalar field is inferred and extracted from a user-assisted sampling technique in time-parameter space. These iso-values are then used to generate iso- surfaces that are then pre-rendered (from a fixed viewpoint) along with additional buffers (i.e. normals, depth, values of other fields, etc.) to provide a compressed representation of iso-surfaces in the dataset. We present a tool that at run-time allows the user to interactively browse and calculate a combination of iso-surfaces superimposed on each other. The result is the same as calculating multiple iso- surfaces from the original data but without the memory and processing overhead. Our tool also allows the user to change the (scalar) values superimposed on each of the surfaces, modify their color map, and interactively re-light the surfaces. We demonstrate the effectiveness of our approach over a multi-terabyte combustion dataset. We also illustrate the efficiency and accuracy of our

  12. Coherent states and rational surfaces

    International Nuclear Information System (INIS)

    Brody, Dorje C; Graefe, Eva-Maria

    2010-01-01

    The state spaces of generalized coherent states associated with special unitary groups are shown to form rational curves and surfaces in the space of pure states. These curves and surfaces are generated by the various Veronese embeddings of the underlying state space into higher dimensional state spaces. This construction is applied to the parameterization of generalized coherent states, which is useful for practical calculations, and provides an elementary combinatorial approach to the geometry of the coherent state space. The results are extended to Hilbert spaces with indefinite inner products, leading to the introduction of a new kind of generalized coherent states.

  13. On maximal surfaces in asymptotically flat space-times

    International Nuclear Information System (INIS)

    Bartnik, R.; Chrusciel, P.T.; O Murchadha, N.

    1990-01-01

    Existence of maximal and 'almost maximal' hypersurfaces in asymptotically flat space-times is established under boundary conditions weaker than those considered previously. We show in particular that every vacuum evolution of asymptotically flat data for Einstein equations can be foliated by slices maximal outside a spatially compact set and that every (strictly) stationary asymptotically flat space-time can be foliated by maximal hypersurfaces. Amongst other uniqueness results, we show that maximal hypersurface can be used to 'partially fix' an asymptotic Poincare group. (orig.)

  14. Shape space exploration of constrained meshes

    KAUST Repository

    Yang, Yongliang; Yang, Yijun; Pottmann, Helmut; Mitra, Niloy J.

    2011-01-01

    We present a general computational framework to locally characterize any shape space of meshes implicitly prescribed by a collection of non-linear constraints. We computationally access such manifolds, typically of high dimension and co-dimension, through first and second order approximants, namely tangent spaces and quadratically parameterized osculant surfaces. Exploration and navigation of desirable subspaces of the shape space with regard to application specific quality measures are enabled using approximants that are intrinsic to the underlying manifold and directly computable in the parameter space of the osculant surface. We demonstrate our framework on shape spaces of planar quad (PQ) meshes, where each mesh face is constrained to be (nearly) planar, and circular meshes, where each face has a circumcircle. We evaluate our framework for navigation and design exploration on a variety of inputs, while keeping context specific properties such as fairness, proximity to a reference surface, etc. © 2011 ACM.

  15. Shape space exploration of constrained meshes

    KAUST Repository

    Yang, Yongliang

    2011-12-12

    We present a general computational framework to locally characterize any shape space of meshes implicitly prescribed by a collection of non-linear constraints. We computationally access such manifolds, typically of high dimension and co-dimension, through first and second order approximants, namely tangent spaces and quadratically parameterized osculant surfaces. Exploration and navigation of desirable subspaces of the shape space with regard to application specific quality measures are enabled using approximants that are intrinsic to the underlying manifold and directly computable in the parameter space of the osculant surface. We demonstrate our framework on shape spaces of planar quad (PQ) meshes, where each mesh face is constrained to be (nearly) planar, and circular meshes, where each face has a circumcircle. We evaluate our framework for navigation and design exploration on a variety of inputs, while keeping context specific properties such as fairness, proximity to a reference surface, etc. © 2011 ACM.

  16. Rainfall-induced runoff from exposed streambed sediments: an important source of water pollution.

    Science.gov (United States)

    Frey, S K; Gottschall, N; Wilkes, G; Grégoire, D S; Topp, E; Pintar, K D M; Sunohara, M; Marti, R; Lapen, D R

    2015-01-01

    When surface water levels decline, exposed streambed sediments can be mobilized and washed into the water course when subjected to erosive rainfall. In this study, rainfall simulations were conducted over exposed sediments along stream banks at four distinct locations in an agriculturally dominated river basin with the objective of quantifying the potential for contaminant loading from these often overlooked runoff source areas. At each location, simulations were performed at three different sites. Nitrogen, phosphorus, sediment, fecal indicator bacteria, pathogenic bacteria, and microbial source tracking (MST) markers were examined in both prerainfall sediments and rainfall-induced runoff water. Runoff generation and sediment mobilization occurred quickly (10-150 s) after rainfall initiation. Temporal trends in runoff concentrations were highly variable within and between locations. Total runoff event loads were considered large for many pollutants considered. For instance, the maximum observed total phosphorus runoff load was on the order of 1.5 kg ha. Results also demonstrate that runoff from exposed sediments can be a source of pathogenic bacteria. spp. and spp. were present in runoff from one and three locations, respectively. Ruminant MST markers were also present in runoff from two locations, one of which hosted pasturing cattle with stream access. Overall, this study demonstrated that rainfall-induced runoff from exposed streambed sediments can be an important source of surface water pollution. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  17. Space Vehicle Valve System

    Science.gov (United States)

    Kelley, Anthony R. (Inventor); Lindner, Jeffrey L. (Inventor)

    2014-01-01

    The present invention is a space vehicle valve system which controls the internal pressure of a space vehicle and the flow rate of purged gases at a given internal pressure and aperture site. A plurality of quasi-unique variable dimension peaked valve structures cover the purge apertures on a space vehicle. Interchangeable sheet guards configured to cover valve apertures on the peaked valve structure contain a pressure-activated surface on the inner surface. Sheet guards move outwardly from the peaked valve structure when in structural contact with a purge gas stream flowing through the apertures on the space vehicle. Changing the properties of the sheet guards changes the response of the sheet guards at a given internal pressure, providing control of the flow rate at a given aperture site.

  18. Space-confined preparation of high surface area tungsten oxide and tungsten nitride inside the pores of mesoporous silica SBA-15

    DEFF Research Database (Denmark)

    Meyer, Simon; Beyer, Hans; Köhler, Klaus

    2015-01-01

    For the direct preparation of high surface area nitride materials, a lack of suitable precursors exists. Indirect preparation by gas phase nitridation (e.g. by ammonia) requires high temperatures and often results in sintering. The present work demonstrates that the space-confined preparation of ...

  19. Space Nutrition

    Science.gov (United States)

    Smith, Scott M.

    2009-01-01

    Optimal nutrition will be critical for crew members who embark on space exploration missions. Nutritional assessment provides an opportunity to ensure that crewmembers begin their missions in optimal nutritional status, to document changes during a mission and, if necessary, to provide intervention to maintain that status throughout the mission, and to assesses changes after landing in order to facilitate the return to their normal status as soon as possible after landing. We report here the findings from our nutritional assessment of astronauts who participated in the International Space Station (ISS) missions, along with flight and ground-based research findings. We also present ongoing and planned nutrition research activities. These studies provide evidence that bone loss, compromised vitamin status, and oxidative damage are the critical nutritional concerns for space travelers. Other nutrient issues exist, including concerns about the stability of nutrients in the food system, which are exposed to longterm storage and radiation during flight. Defining nutrient requirements, and being able to provide and maintain those nutrients on exploration missions, will be critical for maintaining crew member health.

  20. Femtosecond laser-induced surface wettability modification of polystyrene surface

    Science.gov (United States)

    Wang, Bing; Wang, XinCai; Zheng, HongYu; Lam, YeeCheong

    2016-12-01

    In this paper, we demonstrated a simple method to create either a hydrophilic or hydrophobic surface. With femtosecond laser irradiation at different laser parameters, the water contact angle (WCA) on polystyrene's surface can be modified to either 12.7° or 156.2° from its original WCA of 88.2°. With properly spaced micro-pits created, the surface became hydrophilic probably due to the spread of the water droplets into the micro-pits. While with properly spaced micro-grooves created, the surface became rough and more hydrophobic. We investigated the effect of laser parameters on WCAs and analyzed the laser-treated surface roughness, profiles and chemical bonds by surface profilometer, scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). For the laser-treated surface with low roughness, the polar (such as C—O, C=O, and O—C=O bonds) and non-polar (such as C—C or C—H bonds) groups were found to be responsible for the wettability changes. While for a rough surface, the surface roughness or the surface topography structure played a more significant role in the changes of the surface WCA. The mechanisms involved in the laser surface wettability modification process were discussed.

  1. Fermi surface contours obtained from scanning tunneling microscope images around surface point defects

    International Nuclear Information System (INIS)

    Khotkevych-Sanina, N V; Kolesnichenko, Yu A; Van Ruitenbeek, J M

    2013-01-01

    We present a theoretical analysis of the standing wave patterns in scanning tunneling microscope (STM) images, which occur around surface point defects. We consider arbitrary dispersion relations for the surface states and calculate the conductance for a system containing a small-size tunnel contact and a surface impurity. We find rigorous theoretical relations between the interference patterns in the real-space STM images, their Fourier transforms and the Fermi contours of two-dimensional electrons. We propose a new method for reconstructing Fermi contours of surface electron states, directly from the real-space STM images around isolated surface defects. (paper)

  2. Lysosomal responses in the digestive gland of the freshwater mussel, Dreissena polymorpha, experimentally exposed to cadmium

    International Nuclear Information System (INIS)

    Giamberini, Laure; Cajaraville, Miren P.

    2005-01-01

    In order to examine the possible use of lysosomal response as a biomarker of freshwater quality, structural changes of lysosomes were measured by image analysis in the digestive gland of the zebra mussel, Dreissena polymorpha, exposed in laboratory conditions to cadmium. Mussels were exposed to the metal (10 and 200 μg/L) for 3 weeks and randomly collected after 7 and 21 days. At each treatment day, digestive tissues were excised and β-glucuronidase activity was revealed in cryotome sections. Four stereological parameters were calculated: lysosomal volume density, lysosomal surface density, lysosomal surface to volume ratio, and lysosomal numerical density. The changes observed in this study reflected a general activation of the lysosomal system, including an increase in both the number and the size of lysosomes in the digestive gland cells of mussels exposed to cadmium. The digestive lysosomal response in zebra mussels was related to exposure time and to metal concentration, demonstrating the potential of this biomarker in freshwater biomonitoring

  3. A study of aluminium-exposed fish using a scanning proton microprobe

    Energy Technology Data Exchange (ETDEWEB)

    Cholewa, M; Legge, G L.F. [Melbourne Univ., Parkville, VIC (Australia). School of Physics; Eeckhaoudt, S; Van Grieken, R [Universitaire Instelling Antwerpen, Antwerp (Belgium)

    1994-12-31

    A major problem has arisen in Europe with the depopulation of fresh water fish in lakes and streams collecting acid rain. The sensitivity to acidification is species specific and appears to be associated with metal levels. The Scanning Proton Microprobe (SPMP) at the Micro Analytical Research Centre of the University of Melbourne was used to study the subcellular distribution of aluminium and other elements in the gills of fish exposed to acidified water with elevated Al-levels. Experiments were performed on thin sections taken from fish exposed to media with different pH and aluminium concentration. Aluminium was found on the surface of the gill lamellae, but also inside the tissue. Bulk analysis of the gills showed much higher concentrations in the aluminium-exposed fish, compared to the control ones, but no information regarding the actual accumulation sites can be inferred. Extensive study of damage done to the sample by intense proton beams during elemental analysis was performed with scanning transmission ion microscopy. 3 refs., 3 figs.

  4. A study of aluminium-exposed fish using a scanning proton microprobe

    Energy Technology Data Exchange (ETDEWEB)

    Cholewa, M.; Legge, G.L.F. [Melbourne Univ., Parkville, VIC (Australia). School of Physics; Eeckhaoudt, S.; Van Grieken, R. [Universitaire Instelling Antwerpen, Antwerp (Belgium)

    1993-12-31

    A major problem has arisen in Europe with the depopulation of fresh water fish in lakes and streams collecting acid rain. The sensitivity to acidification is species specific and appears to be associated with metal levels. The Scanning Proton Microprobe (SPMP) at the Micro Analytical Research Centre of the University of Melbourne was used to study the subcellular distribution of aluminium and other elements in the gills of fish exposed to acidified water with elevated Al-levels. Experiments were performed on thin sections taken from fish exposed to media with different pH and aluminium concentration. Aluminium was found on the surface of the gill lamellae, but also inside the tissue. Bulk analysis of the gills showed much higher concentrations in the aluminium-exposed fish, compared to the control ones, but no information regarding the actual accumulation sites can be inferred. Extensive study of damage done to the sample by intense proton beams during elemental analysis was performed with scanning transmission ion microscopy. 3 refs., 3 figs.

  5. A study of aluminium-exposed fish using a scanning proton microprobe

    International Nuclear Information System (INIS)

    Cholewa, M.; Legge, G.L.F.

    1993-01-01

    A major problem has arisen in Europe with the depopulation of fresh water fish in lakes and streams collecting acid rain. The sensitivity to acidification is species specific and appears to be associated with metal levels. The Scanning Proton Microprobe (SPMP) at the Micro Analytical Research Centre of the University of Melbourne was used to study the subcellular distribution of aluminium and other elements in the gills of fish exposed to acidified water with elevated Al-levels. Experiments were performed on thin sections taken from fish exposed to media with different pH and aluminium concentration. Aluminium was found on the surface of the gill lamellae, but also inside the tissue. Bulk analysis of the gills showed much higher concentrations in the aluminium-exposed fish, compared to the control ones, but no information regarding the actual accumulation sites can be inferred. Extensive study of damage done to the sample by intense proton beams during elemental analysis was performed with scanning transmission ion microscopy. 3 refs., 3 figs

  6. Real-Space Imaging of Carrier Dynamics of Materials Surfaces by Second-Generation Four-Dimensional Scanning Ultrafast Electron Microscopy

    KAUST Repository

    Sun, Jingya

    2015-09-14

    In the fields of photocatalysis and photovoltaics, ultrafast dynamical processes, including carrier trapping and recombination on material surfaces, are among the key factors that determine the overall energy conversion efficiency. A precise knowledge of these dynamical events on the nanometer (nm) and femtosecond (fs) scales was not accessible until recently. The only way to access such fundamental processes fully is to map the surface dynamics selectively in real space and time. In this study, we establish a second generation of four-dimensional scanning ultrafast electron microscopy (4D S-UEM) and demonstrate the ability to record time-resolved images (snapshots) of material surfaces with 650 fs and ∼5 nm temporal and spatial resolutions, respectively. In this method, the surface of a specimen is excited by a clocking optical pulse and imaged using a pulsed primary electron beam as a probe pulse, generating secondary electrons (SEs), which are emitted from the surface of the specimen in a manner that is sensitive to the local electron/hole density. This method provides direct and controllable information regarding surface dynamics. We clearly demonstrate how the surface morphology, grains, defects, and nanostructured features can significantly impact the overall dynamical processes on the surface of photoactive-materials. In addition, the ability to access two regimes of dynamical probing in a single experiment and the energy loss of SEs in semiconductor-nanoscale materials will also be discussed.

  7. Effects of temperature on surface modification of W exposed to He particles

    International Nuclear Information System (INIS)

    Li, C.; Greuner, H.; Yuan, Y.; Luo, G.N.; Böswirth, B.; Fu, B.Q.; Xu, H.Y.; Jia, Y.Z.; Liu, W.

    2014-01-01

    Highlights: • Blisters were observed on W surface under He beam heating at ∼950 °C. • He-induced blistering shows a clear grain orientation dependence. • An evolution to a coral-like structure was observed under loading at ∼2700 °C. • A texture with 〈0 0 1〉 parallel to the surface normal direction will be beneficial. - Abstract: The effect of combined heating and helium particle flux on annealed tungsten samples has been studied in the neutral beam facility GLADIS. He beams with power densities of 2.4 MW/m 2 and 9.5 MW/m 2 were used to adiabatically load the samples to peak surface temperatures from ∼950 °C (1223 K) to ∼2700 °C (2973 K). Changes in the surface morphology resulting from combined heat and the flux exposure were studied for He fluences up to 3 × 10 22 /m 2 . Typical structures for the sample loaded at ∼950 °C (1223 K) were blisters with a clear grain orientation dependence and the largest blisters formed on grains with 〈0 0 1〉 surface normal. However at higher temperatures, blistering was more easily suppressed for grains near this orientation because the growth of larger blister takes place more slowly. An evolution from a “porous structure” to a “coral-like structure” with increasing fluence was observed on the samples loaded at the highest temperature. Based on these results mechanisms for surface modification at different temperatures are discussed and a texture with 〈0 0 1〉 parallel to the normal direction of the grains is suggested to optimize the plasma facing material due to their stronger resistance to early stage blistering

  8. Apparatus and method for carbon fiber surface treatment

    Science.gov (United States)

    Paulauskas, Felix L; Sherman, Daniel M

    2014-06-03

    An apparatus and method for enhancing the surface energy and/or surface chemistry of carbon fibers involves exposing the fibers to direct or indirect contact with atmospheric pressure plasma generated using a background gas containing at least some oxygen or other reactive species. The fiber may be exposed directly to the plasma, provided that the plasma is nonfilamentary, or the fiber may be exposed indirectly through contact with gases exhausting from a plasma discharge maintained in a separate volume. In either case, the process is carried out at or near atmospheric pressure, thereby eliminating the need for vacuum equipment. The process may be further modified by moistening the fibers with selected oxygen-containing liquids before exposure to the plasma.

  9. Conceptualising Curricular Space in Busyness Education

    DEFF Research Database (Denmark)

    Blasco, Maribel

    2016-01-01

    This article outlines a conceptual framework for conceptualising students’ experiences of curricular space from an aesthetic perspective. The curriculum is conceived as a three-dimensional, aesthetic artefact that elicits sensory responses and judgements about meaning that can impact learning. Sp...... and creative thinking. The Japanese concept of ma is proposed as a fruitful way of thinking about space in curricula not as wasteful, inefficient or a mere void to be filled but as the element that enables learning to result from exposing students to structures and content...

  10. Redefining neighborhoods using common destinations: social characteristics of activity spaces and home census tracts compared.

    Science.gov (United States)

    Jones, Malia; Pebley, Anne R

    2014-06-01

    Research on neighborhood effects has focused largely on residential neighborhoods, but people are exposed to many other places in the course of their daily lives-at school, at work, when shopping, and so on. Thus, studies of residential neighborhoods consider only a subset of the social-spatial environment affecting individuals. In this article, we examine the characteristics of adults' "activity spaces"-spaces defined by locations that individuals visit regularly-in Los Angeles County, California. Using geographic information system (GIS) methods, we define activity spaces in two ways and estimate their socioeconomic characteristics. Our research has two goals. First, we determine whether residential neighborhoods represent the social conditions to which adults are exposed in the course of their regular activities. Second, we evaluate whether particular groups are exposed to a broader or narrower range of social contexts in the course of their daily activities. We find that activity spaces are substantially more heterogeneous in terms of key social characteristics, compared to residential neighborhoods. However, the characteristics of both home neighborhoods and activity spaces are closely associated with individual characteristics. Our results suggest that most people experience substantial segregation across the range of spaces in their daily lives, not just at home.

  11. Elements of linear space

    CERN Document Server

    Amir-Moez, A R; Sneddon, I N

    1962-01-01

    Elements of Linear Space is a detailed treatment of the elements of linear spaces, including real spaces with no more than three dimensions and complex n-dimensional spaces. The geometry of conic sections and quadric surfaces is considered, along with algebraic structures, especially vector spaces and transformations. Problems drawn from various branches of geometry are given.Comprised of 12 chapters, this volume begins with an introduction to real Euclidean space, followed by a discussion on linear transformations and matrices. The addition and multiplication of transformations and matrices a

  12. Eryptosis in lead-exposed workers

    International Nuclear Information System (INIS)

    Aguilar-Dorado, Itzel-Citlalli; Hernández, Gerardo; Quintanar-Escorza, Martha-Angelica; Maldonado-Vega, María; Rosas-Flores, Margarita; Calderón-Salinas, José-Víctor

    2014-01-01

    Eryptosis is a physiological phenomenon in which old and damaged erythrocytes are removed from circulation. Erythrocytes incubated with lead have exhibited major eryptosis. In the present work we found evidence of high levels of eryptosis in lead exposed workers possibly via oxidation. Blood samples were taken from 40 male workers exposed to lead (mean blood lead concentration 64.8 μg/dl) and non-exposed workers (4.2 μg/dl). The exposure to lead produced an intoxication characterized by 88.3% less δ-aminolevulinic acid dehydratase (δALAD) activity in lead exposed workers with respect to non-lead exposed workers. An increment of oxidation in lead exposed workers was characterized by 2.4 times higher thiobarbituric acid-reactive substance (TBARS) concentration and 32.8% lower reduced/oxidized glutathione (GSH/GSSG) ratio. Oxidative stress in erythrocytes of lead exposed workers is expressed in 192% higher free calcium concentration [Ca 2+ ] i and 1.6 times higher μ-calpain activity with respect to non-lead exposed workers. The adenosine triphosphate (ATP) concentration was not significantly different between the two worker groups. No externalization of phosphatidylserine (PS) was found in non-lead exposed workers (< 0.1%), but lead exposed workers showed 2.82% externalization. Lead intoxication induces eryptosis possibly through a molecular pathway that includes oxidation, depletion of reduced glutathione (GSH), increment of [Ca 2+ ], μ-calpain activation and externalization of PS in erythrocytes. Identifying molecular signals that induce eryptosis in lead intoxication is necessary to understand its physiopathology and chronic complications. - Graphical abstract: Fig. 1. (A) Blood lead concentration (PbB) and (B) phosphatidylserine externalization on erythrocyte membranes of non-lead exposed (□) and lead exposed workers (■). Values are mean ± SD. *Significantly different (P < 0.001). - Highlights: • Erythrocytes of lead exposed workers showed higher PS

  13. Eryptosis in lead-exposed workers

    Energy Technology Data Exchange (ETDEWEB)

    Aguilar-Dorado, Itzel-Citlalli [Biochemistry Department, Centro de Investigación y Estudios Avanzados IPN, México, DF (Mexico); Hernández, Gerardo [Section of Methodology of Science, Centro de Investigación y Estudios Avanzados IPN, México, DF (Mexico); Quintanar-Escorza, Martha-Angelica [Faculty of Medicine, UJED, Durango, DGO (Mexico); Maldonado-Vega, María [CIATEC, León, GTO (Mexico); Rosas-Flores, Margarita [Biochemistry Department, Centro de Investigación y Estudios Avanzados IPN, México, DF (Mexico); Calderón-Salinas, José-Víctor, E-mail: jcalder@cinvestav.mx [Biochemistry Department, Centro de Investigación y Estudios Avanzados IPN, México, DF (Mexico)

    2014-12-01

    Eryptosis is a physiological phenomenon in which old and damaged erythrocytes are removed from circulation. Erythrocytes incubated with lead have exhibited major eryptosis. In the present work we found evidence of high levels of eryptosis in lead exposed workers possibly via oxidation. Blood samples were taken from 40 male workers exposed to lead (mean blood lead concentration 64.8 μg/dl) and non-exposed workers (4.2 μg/dl). The exposure to lead produced an intoxication characterized by 88.3% less δ-aminolevulinic acid dehydratase (δALAD) activity in lead exposed workers with respect to non-lead exposed workers. An increment of oxidation in lead exposed workers was characterized by 2.4 times higher thiobarbituric acid-reactive substance (TBARS) concentration and 32.8% lower reduced/oxidized glutathione (GSH/GSSG) ratio. Oxidative stress in erythrocytes of lead exposed workers is expressed in 192% higher free calcium concentration [Ca{sup 2+}]{sub i} and 1.6 times higher μ-calpain activity with respect to non-lead exposed workers. The adenosine triphosphate (ATP) concentration was not significantly different between the two worker groups. No externalization of phosphatidylserine (PS) was found in non-lead exposed workers (< 0.1%), but lead exposed workers showed 2.82% externalization. Lead intoxication induces eryptosis possibly through a molecular pathway that includes oxidation, depletion of reduced glutathione (GSH), increment of [Ca{sup 2+}], μ-calpain activation and externalization of PS in erythrocytes. Identifying molecular signals that induce eryptosis in lead intoxication is necessary to understand its physiopathology and chronic complications. - Graphical abstract: Fig. 1. (A) Blood lead concentration (PbB) and (B) phosphatidylserine externalization on erythrocyte membranes of non-lead exposed (□) and lead exposed workers (■). Values are mean ± SD. *Significantly different (P < 0.001). - Highlights: • Erythrocytes of lead exposed workers

  14. Chemical and Microstructural Changes in Metallic and Ceramic Materials Exposed to Venusian Surface Conditions

    Science.gov (United States)

    Costa, Gustavo C. C.; Jacobson, Nathan S.; Lukco, Dorothy; Hunter, Gary W.; Nakley, Leah; Radoman-Shaw, Brandon G.; Harvey, Ralph P.

    2017-01-01

    The chemical and microstructural behavior of steels (304, 310, 316, and 1018), nickel-based alloys (beta-NiAl, G30, and 625), gold, coatings (4YSZ, SilcoNert(TradeMark) 1040 (SilcoTek Co.), Dursan(TradeMark)? (SilcoTek Co.), and porcelain), and bulk ceramics (alpha-Al2O3, fused quartz, beta-SiC, and alpha-Si3N4) were probed after exposure to supercritical fluid with temperature, pressure, and composition mimicking the Venus lower atmosphere. Exposures were carried out in the Glenn Extreme Environments Rig (GEER) chamber with the Venusian gas mixture (96.5% CO2, 3.5% N2, 30 ppm H2O, 150 ppm SO2, 28 ppm CO, 15 ppm OCS, 3 ppm H2S, 0.5 ppm HCl, and 5 ppb HF) at 92 bar (1330 psi) and 467 C (873 F) for durations of 10 and 42 days. An additional 21-day exposure was done to stainless steel uncoated and coated with SilcoNert(TradeMark) and Dursan(TradeMark). Samples were characterized before and after the experiment by gravimetric analysis, X-ray diffraction, X-ray photoelectron and Auger electron spectroscopies, and cross section electron microscopy analysis. All steels exposed for 10 and 42 days formed double-layered scales consisting mainly of metal (Cr, Fe, Ni) oxides and sulfides showing different chemistry, microstructure, and crystalline phases. The alloys G30 and 625 formed double-layered scales consisting mainly of nickel sulfides. After 10 days, the beta-NiAl exhibited no detectable scale, suggesting only a very thin film was formed. The 304 and 316 stainless steels coated with 4YSZ that were exposed for 10 and 42 days exhibited no significant oxidation. Steel 1018 coated with 4YSZ exhibited a corrosion scale of iron and/or chromium oxide formed at the base of the alloy. The 304 steel coated with porcelain did not exhibit corrosion, although the coating exhibited recession. SilcoNert(TradeMark) exposed for 10 and 42 days exhibited recession, although no oxidation was found to occur at the base of the alloy. Stainless steel 316 coated with Dursan

  15. Diminished metal accumulation in riverine fishes exposed to acid mine drainage over five decades.

    Directory of Open Access Journals (Sweden)

    Ross A Jeffree

    Full Text Available Bony bream (Nematalosa erebi and black catfish (Neosilurus ater were sampled from the fresh surface waters of the Finniss River in tropical northern Australia, along a metal pollution gradient draining the Rum Jungle copper/uranium mine, a contaminant source for over five decades. Paradoxically, populations of both fish species exposed to the highest concentrations of mine-related metals (cobalt, copper, lead, manganese, nickel, uranium and zinc in surface water and sediment had the lowest tissue (bone, liver and muscle concentrations of these metals. The degree of reduction in tissue concentrations of exposed populations was also specific to each metal and inversely related to its degree of environmental increase above background. Several explanations for diminished metal bioaccumulation in fishes from the contaminated region were evaluated. Geochemical speciation modeling of metal bioavailability in surface water showed no differences between the contaminated region and the control sites. Also, the macro-nutrient (calcium, magnesium and sodium water concentrations, that may competitively inhibit metal uptake, were not elevated with trace metal contamination. Reduced exposure to contaminants due to avoidance behavior was unlikely due to the absence of refugial water bodies with the requisite metal concentrations lower than the control sites and very reduced connectivity at time of sampling. The most plausible interpretation of these results is that populations of both fish species have modified kinetics within their metal bioaccumulation physiology, via adaptation or tolerance responses, to reduce their body burdens of metals. This hypothesis is consistent with (i reduced tissue concentrations of calcium, magnesium and sodium (macro-nutrients, in exposed populations of both species, (ii experimental findings for other fish species from the Finniss River and other contaminated regions, and (iii the number of generations exposed to likely

  16. Cryogenic Selective Surfaces

    Data.gov (United States)

    National Aeronautics and Space Administration — Selective surfaces have wavelength dependent emissivity/absorption. These surfaces can be designed to reflect solar radiation, while maximizing infrared emittance,...

  17. Dose limits for cosmic radiation during space flights

    International Nuclear Information System (INIS)

    Draaisma, F.S.

    1991-01-01

    Astronauts are exposed to raised levels of ionizing radiation, which may cause biologic effects during space flights. Insights in these effects should lead to doselimits for astronauts during their full career. (author). 4 refs.; 4 tabs

  18. Geodesic deviation and Minikowski space

    International Nuclear Information System (INIS)

    Barraco, D.; Kozameh, C.; Newman, E.T.; Tod, P.

    1990-01-01

    The authors study the properties of the solution space of local surface-forming null sub-congruences in the neighborhood of a given null geodesic in a pseudo-Riemannian space-time. This solution space is a three-dimensional manifold, naturally endowed with a conformal Minkowski metric

  19. Overview of fiber optics in the natural space environment

    International Nuclear Information System (INIS)

    Barnes, C.; Dorsky, L.; Johnston, A.; Bergman, L.; Stassinopoulos, E.

    1991-01-01

    The potential applications of fiber-optic (FO) systems in spacecraft which will be exposed to the space radiation environment are discussed in view of tests conducted aboard the Long-Duration Exposure Facility and the Comet Rendezvous and Asteroid Flyby spacecraft. Attention is given to anticipated trends in the use of FO in spacecraft communications systems. The natural space radiation environment is noted to be far more benign than the military space environment, which encompasses displacement-damage effects due to significant neutron influences

  20. Iron cycling at corroding carbon steel surfaces

    Science.gov (United States)

    Lee, Jason S.; McBeth, Joyce M.; Ray, Richard I.; Little, Brenda J.; Emerson, David

    2013-01-01

    Surfaces of carbon steel (CS) exposed to mixed cultures of iron-oxidizing bacteria (FeOB) and dissimilatory iron-reducing bacteria (FeRB) in seawater media under aerobic conditions were rougher than surfaces of CS exposed to pure cultures of either type of microorganism. The roughened surface, demonstrated by profilometry, is an indication of loss of metal from the surface. In the presence of CS, aerobically grown FeOB produced tight, twisted helical stalks encrusted with iron oxides. When CS was exposed anaerobically in the presence of FeRB, some surface oxides were removed. However, when the same FeOB and FeRB were grown together in an aerobic medium, FeOB stalks were less encrusted with iron oxides and appeared less tightly coiled. These observations suggest that iron oxides on the stalks were reduced and solubilized by the FeRB. Roughened surfaces of CS and denuded stalks were replicated with three culture combinations of different species of FeOB and FeRB under three experimental conditions. Measurements of electrochemical polarization resistance established different rates of corrosion of CS in aerobic and anaerobic media, but could not differentiate rate differences between sterile controls and inoculated exposures for a given bulk concentration of dissolved oxygen. Similarly, total iron in the electrolyte could not be used to differentiate treatments. The experiments demonstrate the potential for iron cycling (oxidation and reduction) on corroding CS in aerobic seawater media. PMID:24093730

  1. Method and means of reducing erosion of components of plasma devices exposed to helium and hydrogen isotope radiation

    International Nuclear Information System (INIS)

    Kaminsky, M.S.; Das, S.K.; Rossing, T.D.

    1977-01-01

    Surfaces of components of plasma devices exposed to radiation by atoms or ions of helium or isotopes of hydrogen can be protected from damage due to blistering by shielding the surfaces with a structure formed by sintering a powder of aluminum or beryllium and its oxide or by coating the surfaces with such a sintered metal powder. 7 claims

  2. Eryptosis in lead-exposed workers.

    Science.gov (United States)

    Aguilar-Dorado, Itzel-Citlalli; Hernández, Gerardo; Quintanar-Escorza, Martha-Angelica; Maldonado-Vega, María; Rosas-Flores, Margarita; Calderón-Salinas, José-Víctor

    2014-12-01

    Eryptosis is a physiological phenomenon in which old and damaged erythrocytes are removed from circulation. Erythrocytes incubated with lead have exhibited major eryptosis. In the present work we found evidence of high levels of eryptosis in lead exposed workers possibly via oxidation. Blood samples were taken from 40 male workers exposed to lead (mean blood lead concentration 64.8μg/dl) and non-exposed workers (4.2μg/dl). The exposure to lead produced an intoxication characterized by 88.3% less δ-aminolevulinic acid dehydratase (δALAD) activity in lead exposed workers with respect to non-lead exposed workers. An increment of oxidation in lead exposed workers was characterized by 2.4 times higher thiobarbituric acid-reactive substance (TBARS) concentration and 32.8% lower reduced/oxidized glutathione (GSH/GSSG) ratio. Oxidative stress in erythrocytes of lead exposed workers is expressed in 192% higher free calcium concentration [Ca(2+)]i and 1.6 times higher μ-calpain activity with respect to non-lead exposed workers. The adenosine triphosphate (ATP) concentration was not significantly different between the two worker groups. No externalization of phosphatidylserine (PS) was found in non-lead exposed workers (lead exposed workers showed 2.82% externalization. Lead intoxication induces eryptosis possibly through a molecular pathway that includes oxidation, depletion of reduced glutathione (GSH), increment of [Ca(2+)], μ-calpain activation and externalization of PS in erythrocytes. Identifying molecular signals that induce eryptosis in lead intoxication is necessary to understand its physiopathology and chronic complications. Copyright © 2014 Elsevier Inc. All rights reserved.

  3. The method of determining surface water erosion influence on agricultural valorization of soils with usage of geoprocessing techniques and spatial information systems

    Directory of Open Access Journals (Sweden)

    Prus Barbara

    2016-12-01

    Full Text Available The aim of the paper is to propose methodical solutions concerning synthetic agricultural analysis of production space which consists in combined (synthetic – in spatial and statistical contexts – analysis and evaluation of quality and farming utility of soils in connection with soils erosive risk level. The paper is aimed at presentation of methodology useful in such type of analyses as well as demonstration to what extent the areas of farming production space being subject to restrictive protection are exposed to destructive effect of surface water erosion. Own factor (HDSP.E was suggested, which is a high degree synthesis of soil protection in connection with degrees of surface water erosion risk. The proposed methodology was used for detailed spatial analyses performed for Tomice – the Małopolska rural commune (case study. The area model elaborated for the proposed methodology’s purpose faced with soils mechanical composition allowed to make a model of surface water erosion in five-grade scale. Synthetic evaluation (product of spatial objects on numerous thematic layers of quality and farming utility of soils and also zones of surface water erosion risk allowed to assign spatial distribution of HDSP.E factor (abbreviation of high degree of soil protection combined with erosion. The analyses enabled to determine proportional contribution of the most valuable resources of farming production space that are subject to soil erosion negative phenomenon. Geoprocessing techniques used for the analyses of environmental elements of farming production space were applied in the paper. The analysis of spatial distribution of researched phenomena was elaborated in Quantum GIS programme.

  4. Radiation risk in space exploration

    International Nuclear Information System (INIS)

    Schimmerling, W.; Wilson, J.W.; Cucinotta, F.; Kim, M.H.Y.

    1997-01-01

    Humans living and working in space are exposed to energetic charged particle radiation due to galactic cosmic rays and solar particle emissions. In order to keep the risk due to radiation exposure of astronauts below acceptable levels, the physical interaction of these particles with space structures and the biological consequences for crew members need to be understood. Such knowledge is, to a large extent, very sparse when it is available at all. Radiation limits established for space radiation protection purposes are based on extrapolation of risk from Japanese survivor data, and have been found to have large uncertainties. In space, attempting to account for large uncertainties by worst-case design results in excessive costs and accurate risk prediction is essential. It is best developed at ground-based laboratories, using particle accelerator beams to simulate individual components of space radiation. Development of mechanistic models of the action of space radiation is expected to lead to the required improvements in the accuracy of predictions, to optimization of space structures for radiation protection and, eventually, to the development of biological methods of prevention and intervention against radiation injury. (author)

  5. AQUARIUS: A Passive/Active Microwave Sensor to Monitor Sea Surface Salinity Globally from Space

    Science.gov (United States)

    LeVine, David; Lagerloef, Gary S. E.; Colomb, F. Raul; Chao, Yi

    2004-01-01

    Salinity is important for understanding ocean dynamics, energy exchange with the atmosphere and the global water cycle. Existing data is limited and much of the ocean has never even been sampled. Sea surface salinity can be measured remotely by satellite and a three year mission for this purpose called AquariudSAC-D has recently been selected by NASA's Earth System Science Pathfinder (ESSP) program. The objective is to map the salinity field globally with a spatial resolution of 100 km and a monthly average accuracy of 0.2 psu. The mission, scheduled for launch in 2008, is a partnership of the United States National Aeronautics and Space Agency (NASA) and the Argentine Comision National de Actividades Epaciales (CONAE).

  6. Surviving space flight: case study on MELiSSA's CIII nitrifying compartment

    Science.gov (United States)

    Ilgrande, Chiara; Lasseur, Christophe; Mastroleo, Felice; Paille, Christel; Leys, Natalie; Morozova, Julia; Ilyin, Vyacheslav; Clauwaert, Peter; Christiaens, Marlies E. R.; Lindeboom, Ralph E. F.; Vlaeminck, Siegfried; Prat, Delphine; Arroyo, Jose M. C.; Conincx, Ilse; Van Hoey, Olivier; Roume, Hugo; Udert, Kai; Sas, Benedikt

    2016-07-01

    Space synthetic biology offers key opportunities for long-term space missions. Planets mining, terraformation, space medicine and Life Support technologies would all benefit from an integrative biological approach. However, space is a harsh environment for life: microgravity, temperature, UV and cosmic radiation can affect the health and functionality of microorganisms and plants, possibly preventing the optimal performance of the systems. The European Space Agency's Life Support System (MELiSSA) has been developed as a model for future long term Space missions and Space habitation. MELiSSA is a 5 compartment artificial ecosystem with microorganisms and higher, that aims at completely recycling gas, liquid and solid waste. In this study, the survival and functional activity after Lower Earth Orbit conditions of microbial nitrogen conversions, relevant for MELiSSA's CIII compartment, was tested. Synthetic communities containing Nitrosomonas europeae, Nitrosomonas ureae, Nitrobacter winogradskyi, Nitrospira moscoviensis and Cupriavidus pinatubonensis were exposed to the Lower Earth Orbit conditions of the International Space Station (ISS) for 7 days. Nitrosomonas europeae, Nitrobacter winogradskyi, Cupriavidus pinatubonensis, and three mixed communities (a urine nitrification sludge, a sludge containing aerobic ammonia oxidizing bacteria and anammox bacteria (OLAND), and an aquaculture sludge containing ammonia oxidizing archaea) were exposed to Lower Earth Orbit conditions for 44 days. Survival after both space flights was demonstrated because nitritation, nitratation, denitrification and anammox activity could be restored at a rate comparable to ground storage conditions. Our results validate the potential survival feasibility and suggest future space applications for N-related microorganisms.

  7. Lessons learned from the development and manufacture of ceramic reusable surface insulation materials for the space shuttle orbiters

    Science.gov (United States)

    Banas, R. P.; Elgin, D. R.; Cordia, E. R.; Nickel, K. N.; Gzowski, E. R.; Aguiler, L.

    1983-01-01

    Three ceramic, reusable surface insulation materials and two borosilicate glass coatings were used in the fabrication of tiles for the Space Shuttle orbiters. Approximately 77,000 tiles were made from these materials for the first three orbiters, Columbia, Challenger, and Discovery. Lessons learned in the development, scale up to production and manufacturing phases of these materials will benefit future production of ceramic reusable surface insulation materials. Processing of raw materials into tile blanks and coating slurries; programming and machining of tiles using numerical controlled milling machines; preparing and spraying tiles with the two coatings; and controlling material shrinkage during the high temperature (2100-2275 F) coating glazing cycles are among the topics discussed.

  8. Formation of periodic mesoscale structures arranged in a circular symmetry at the silicon surface exposed to radiation of a single femtosecond laser pulse

    Energy Technology Data Exchange (ETDEWEB)

    Romashevskiy, S.A., E-mail: sa.romashevskiy@gmail.com [Joint Institute for High Temperatures of the Russian Academy of Sciences, Izhorskaya st. 13, Bd. 2, Moscow 125412 (Russian Federation); Ashitkov, S.I.; Ovchinnikov, A.V. [Joint Institute for High Temperatures of the Russian Academy of Sciences, Izhorskaya st. 13, Bd. 2, Moscow 125412 (Russian Federation); Kondratenko, P.S. [Nuclear Safety Institute of the Russian Academy of Sciences, Bol' shaya Tul' skaya st. 53, Moscow 115191 (Russian Federation); Moscow Institute of Physics and Technology, 9 Institutskiy per., Dolgoprudny, Moscow Region 141700 (Russian Federation); Agranat, M.B. [Joint Institute for High Temperatures of the Russian Academy of Sciences, Izhorskaya st. 13, Bd. 2, Moscow 125412 (Russian Federation)

    2016-06-30

    Graphical abstract: - Highlights: • Single pulse irradiation of silicon gave rise to the periodic mesoscale structures. • The number of the periodic structures depends on the incident laser fluence. • The theory of periodically modulated absorption of laser energy is proposed. - Abstract: The periodic mesoscale structures arranged in a circular symmetry were found at the silicon surface exposed to radiation of the single femtosecond laser pulse with a Gaussian intensity profile in the ambient air conditions. These peculiar structures have the appearance of the protrusions of ∼10 nm height and of ∼600 nm width (at a FWHM) separately located inside the ablated region with a period of the incident laser wavelength. It was found that their position at the surface corresponds to the specified laser intensity slightly above the ablation threshold. The number of the formed periodic structures varies with the fluence of the incident laser pulse and in our experiments it was found to have changed from one to eleven. We suppose that formation of these mesoscale structures is caused by heating of a microscale volume to the strongly defined temperature. The theoretical model was proposed to explain the obtained data. It assumes that the interference of incident laser radiation with laser-induced surface electromagnetic waves results in generation of periodic distribution of electron temperature. Thus formation of the periodic structures at the specified laser intensity is attributed to periodically modulated absorption of laser energy at a focal laser spot.

  9. Space Biology in Russia Today

    Science.gov (United States)

    Grigoriev, Anatoly; Sychev, Vladimir; Ilyin, Eugene

    At present space biology research in Russia is making significant progress in several areas of high priority. Gravitational biology. In April-May 2013, a successful 30-day flight of the biological satellite (biosatellite) Bion-M1 was conducted, which carried rodents (mice and gerbils), geckos, fish, mollusks, crustaceans, microorganisms, insects, lower and higher plants, seeds, etc. The investigations were performed by Russian scientists as well as by researchers from NASA, CNES, DLR and South Korea. Foton-M4 carrying various biological specimens is scheduled to launch in 2014. Work has begun to develop science research programs to be implemented onboard Bion-M2 and Bion-M3 as well as on high apogee recoverable spacecraft. Study of the effects of microgravity on the growth and development of higher plants cultivated over several generations on the International Space Station (ISS) has been recently completed. Space radiobiology. Regular experiments aimed at investigating the effects of high-energy galactic cosmic rays on the animal central nervous system and behavior are being carried out using the Particle Accelerator in the town of Dubna. Biological (environmental) life support systems. In recent years, experiments have been performed on the ISS to upgrade technologies of plant cultivation in microgravity. Advanced greenhouse mockups have been built and are currentlyundergoing bioengineering tests. Technologies of waste utilization in space are being developed. Astrobiology experiments in orbital missions. In 2010, the Biorisk experiment on bacterial and fungal spores, seeds and dormant forms of organisms was completed. The payload containing the specimens was installed on the exterior wall of the ISS and was exposed to outer space for 31 months. In addition, Bion-M1 also carried seeds, bacterial spores and microbes that were exposed to outer space effects. The survival rate of bacterial spores incorporated into man-made meteorites, that were attached to the

  10. Test Method for Spalling of Fire Exposed Concrete

    DEFF Research Database (Denmark)

    Hertz, Kristian Dahl; Sørensen, Lars Schiøtt

    2005-01-01

    A new material test method is presented for determining whether or not an actual concrete may suffer from explosive spalling at a specified moisture level. The method takes into account the effect of stresses from hindered thermal expansion at the fire-exposed surface. Cylinders are used, which...... in many countries serve as standard specimens for testing the compressive strength. Consequently, the method is quick, cheap and easy to use in comparison to the alternative of testing full-scale or semi full-scale structures with correct humidity, load and boundary conditions. A number of concretes have...

  11. GaN growth on silane exposed AlN seed layers

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz-Zepeda, F. [Posgrado en Fisica de Materiales, Centro de Investigacion Cientifica y de Educacion Superior de Ensenada, Km. 107 Carret, Tijuana-Ensenada, C.P. 22860, Ensenada, B.C. (Mexico); Contreras, O. [Centro de Ciencias de la Materia Condesada, Universidad Nacional Autonoma de Mexico, Apdo. Postal 356, C.P. 22800, Ensenada, B.C. (Mexico); Dadgar, A.; Krost, A. [Otto-von-Guericke-Universitaet Magdeburg, FNW-IEP, Universitaetsplatz 2, 39106 Magdeburg (Germany)

    2008-07-01

    The microstructure and surface morphology of GaN films grown on AlN seed layers exposed to silane flow has been studied by TEM and AFM. The epilayers were grown on silicon(111) substrates by MOCVD. The AlN seed layer surface was treated at different SiH{sub 4} exposure times prior to the growth of the GaN film. A reduction in the density of threading dislocations is observed in the GaN films and their surface roughness is minimized for an optimal SiH{sub 4} exposure time between 75-90 sec. At this optimal condition a step-flow growth mode of GaN film is predominant. The improvement of the surface and structure quality of the epilayers is observed to be related to an annihilation process of threading dislocations done by SiN{sub x} masking. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  12. An acceleration of the characteristics by a space-angle two-level method using surface discontinuity factors

    Energy Technology Data Exchange (ETDEWEB)

    Grassi, G. [Commissariat a l' Energie Atomique, CEA de Saclay, DM2S/SERMA/LENR, 91191, Gif-sur-Yvette (France)

    2006-07-01

    We present a non-linear space-angle two-level acceleration scheme for the method of the characteristics (MOC). To the fine level on which the MOC transport calculation is performed, we associate a more coarsely discretized phase space in which a low-order problem is solved as an acceleration step. Cross sections on the coarse level are obtained by a flux-volume homogenisation technique, which entails the non-linearity of the acceleration. Discontinuity factors per surface are introduced as additional degrees of freedom on the coarse level in order to ensure the equivalence of the heterogeneous and the homogenised problem. After each fine transport iteration, a low-order transport problem is iteratively solved on the homogenised grid. The solution of this problem is then used to correct the angular moments of the flux resulting from the previous free transport sweep. Numerical tests for a given benchmark have been performed. Results are discussed. (authors)

  13. An acceleration of the characteristics by a space-angle two-level method using surface discontinuity factors

    International Nuclear Information System (INIS)

    Grassi, G.

    2006-01-01

    We present a non-linear space-angle two-level acceleration scheme for the method of the characteristics (MOC). To the fine level on which the MOC transport calculation is performed, we associate a more coarsely discretized phase space in which a low-order problem is solved as an acceleration step. Cross sections on the coarse level are obtained by a flux-volume homogenisation technique, which entails the non-linearity of the acceleration. Discontinuity factors per surface are introduced as additional degrees of freedom on the coarse level in order to ensure the equivalence of the heterogeneous and the homogenised problem. After each fine transport iteration, a low-order transport problem is iteratively solved on the homogenised grid. The solution of this problem is then used to correct the angular moments of the flux resulting from the previous free transport sweep. Numerical tests for a given benchmark have been performed. Results are discussed. (authors)

  14. Chaos control and synchronization of two neurons exposed to ELF external electric field

    International Nuclear Information System (INIS)

    Wang Jiang; Zhang Ting; Che Yanqiu

    2007-01-01

    Chaos control and synchronization of two unidirectional coupled neurons exposed to ELF electrical field via nonlinear control technique is investigated. Based on results of space-time characteristics of trans-membrane voltage, the variation of cell trans-membrane voltage exposed to extremely low frequency (ELF) electric field is analyzed. The dynamical behaviors of the modified Hodgkin-Huxley (HH) model are identified under the periodic ELF electric field using both analytical and numerical analysis. Then, using the results of the analysis, a nonlinear feedback linearization control scheme and a modified adaptive control strategy are designed to synchronize the two unidirectional coupled neurons and stabilize the chaotic trajectory of the slave system to desired periodic orbit of the master system. The simulation results demonstrated the efficiency of the proposed algorithms

  15. Response of concrete exposed to a high heat flux on one surface

    International Nuclear Information System (INIS)

    Muir, J.F.

    1977-11-01

    Experiments were performed to investigate the response of concrete to severe thermal environments such as might be encountered during the interaction of molten reactor core materials with the containment substructure following a hypothetical fuel melt accident. The dominant mechanism for erosion of both limestone and basaltic concrete appears to be melting of the cementitious material in the matrix. The erosion proceeded in a quiescent manner with negligible spallation. The erosion rate increased with heat flux, becoming as large as approximately 70 cm/hr for a net surface heat flux of roughly 190 W/cm 2 . Analyses reveal the surface temperature to be the single most significant parameter affecting the net surface heat flux, through its importance to emitted radiation; and that the greatest fraction of the net energy transmitted to the concrete goes into sensible heat

  16. Cast Stone Oxidation Front Evaluation: Preliminary Results For Samples Exposed To Moist Air

    International Nuclear Information System (INIS)

    Langton, C. A.; Almond, P. M.

    2013-01-01

    The rate of oxidation is important to the long-term performance of reducing salt waste forms because the solubility of some contaminants, e.g., technetium, is a function of oxidation state. TcO 4 - in the salt solution is reduced to Tc(IV) and has been shown to react with ingredients in the waste form to precipitate low solubility sulfide and/or oxide phases. Upon exposure to oxygen, the compounds containing Tc(IV) oxidize to the pertechnetate ion, Tc(VII)O 4 - , which is very soluble. Consequently the rate of technetium oxidation front advancement into a monolith and the technetium leaching profile as a function of depth from an exposed surface are important to waste form performance and ground water concentration predictions. An approach for measuring contaminant oxidation rate (effective contaminant specific oxidation rate) based on leaching of select contaminants of concern is described in this report. In addition, the relationship between reduction capacity and contaminant oxidation is addressed. Chromate (Cr(VI) was used as a non-radioactive surrogate for pertechnetate, Tc(VII), in Cast Stone samples prepared with 5 M Simulant. Cast Stone spiked with pertechnetate was also prepared and tested. Depth discrete subsamples spiked with Cr were cut from Cast Stone exposed to Savannah River Site (SRS) outdoor ambient temperature fluctuations and moist air. Depth discrete subsamples spiked with Tc-99 were cut from Cast Stone exposed to laboratory ambient temperature fluctuations and moist air. Similar conditions are expected to be encountered in the Cast Stone curing container. The leachability of Cr and Tc-99 and the reduction capacities, measured by the Angus-Glasser method, were determined for each subsample as a function of depth from the exposed surface. The results obtained to date were focused on continued method development and are preliminary and apply to the sample composition and curing / exposure conditions described in this report. The Cr oxidation front

  17. Space Radiation Peculiarities in the Extra Vehicular Environment of the International Space Station (ISS)

    Science.gov (United States)

    Dachev, Tsvetan; Bankov, Nikolay; Tomov, Borislav; Matviichuk, Yury; Dimitrov, Plamen

    2013-12-01

    The space weather and the connected with it ionizing radiation were recognized as a one of the main health concern to the International Space Station (ISS) crew. Estimation the effects of radiation on humans in ISS requires at first order accurate knowledge of the accumulated by them absorbed dose rates, which depend of the global space radiation distribution and the local variations generated by the 3D surrounding shielding distribution. The R3DE (Radiation Risks Radiometer-Dosimeter (R3D) for the EXPOSE-E platform on the European Technological Exposure Facility (EuTEF) worked successfully outside of the European Columbus module between February 2008 and September 2009. Very similar instrument named R3DR for the EXPOSE-R platform worked outside Russian Zvezda module of ISS between March 2009 and August 2010. Both are Liulin type, Bulgarian build miniature spectrometers-dosimeters. They accumulated about 5 million measurements of the flux and absorbed dose rate with 10 seconds resolution behind less than 0.41 g cm-2 shielding, which is very similar to the Russian and American space suits [1-3] average shielding. That is why all obtained data can be interpreted as possible doses during Extra Vehicular Activities (EVA) of the cosmonauts and astronauts. The paper first analyses the obtained long-term results in the different radiation environments of: Galactic Cosmic Rays (GCR), inner radiation belt trapped protons in the region of the South Atlantic Anomaly (SAA) and outer radiation belt (ORB) relativistic electrons. The large data base was used for development of an empirical model for calculation of the absorbed dose rates in the extra vehicular environment of ISS at 359 km altitude. The model approximate the averaged in a grid empirical dose rate values to predict the values at required from the user geographical point, station orbit or area in geographic coordinate system. Further in the paper it is presented an intercomparison between predicted by the model dose

  18. Minimal surfaces

    CERN Document Server

    Dierkes, Ulrich; Sauvigny, Friedrich; Jakob, Ruben; Kuster, Albrecht

    2010-01-01

    Minimal Surfaces is the first volume of a three volume treatise on minimal surfaces (Grundlehren Nr. 339-341). Each volume can be read and studied independently of the others. The central theme is boundary value problems for minimal surfaces. The treatise is a substantially revised and extended version of the monograph Minimal Surfaces I, II (Grundlehren Nr. 295 & 296). The first volume begins with an exposition of basic ideas of the theory of surfaces in three-dimensional Euclidean space, followed by an introduction of minimal surfaces as stationary points of area, or equivalently

  19. Dental health of young children prenatally exposed to buprenorphine. A concern of child neglect?

    Science.gov (United States)

    Kivistö, K; Alapulli, H; Tupola, S; Alaluusua, S; Kivitie-Kallio, S

    2014-06-01

    To study the oral health and dental neglect of prenatally buprenorphine-exposed 3-year-old children. The study consisted of 51 children who as newborns tested positive for buprenorphine in a urine screen. The control group comprised 68 children previously unexposed to narcotics. The dentist examined the children and interviewed their guardians. Buprenorphine-exposed children exhibited significantly more early childhood caries than did the control group. Caries indices, the number of decayed, missing and filled teeth or tooth surfaces and decayed teeth were greater in the buprenorphine-exposed children than the control children (p = 0.004, p = 0.004, p = 0.001, respectively). In the buprenorphine group, more children showed visible plaque (p = 0.003) and fewer children were caries-free (p = 0.009) than in the control group. The control children's teeth were also brushed more often than the buprenorphine-exposed children's teeth (p = 0.001) and the parents were more involved in their children's tooth brushing than were those in the buprenorphine-exposed group (p = 0.035). More caries and dental neglect were found in buprenorphine-exposed children than in controls. These findings highlight the importance of routine dental appointments, caries screening and preventive care for children in substance-abusing families.

  20. Dry cooling systems with plastic surfaces

    International Nuclear Information System (INIS)

    Roma, Carlo; Leonelli, Vincenzo

    1975-01-01

    Research and experiments made on dry cooling systems with plastic surfaces are described. The demonstration program planned in Italy for a 100Gcal/h dry cooling system is exposed, and an installation intended for a large 1300Mwe nuclear power station is described with reference to the assembly (exploitation and maintenance included). The performance and economic data relating to this installation are also exposed [fr

  1. Porphyrin metabolism in lymphocytes of miners exposed to diesel exhaust at oil shale mine

    Energy Technology Data Exchange (ETDEWEB)

    Muzyka, V.; Bogovski, S.; Lang, I.; Schmidt, N.; Ryazanov, V.; Veidebaum, T. [Laboratory of Environmental Carcinogens, Institute of Experimental and Clinical Medicine, Hiiu 42, Tallinn 11619 (Estonia); Scheepers, P.T.J. [Department of Epidemiology and Biostatistics, University Medical Centre St Radboud, P.O. Box 9101, Nijmegen NL 6500 HB (Netherlands)

    2004-04-25

    The present study was carried out on the evaluation and application of new biomarkers for populations exposed to occupational diesel exhaust at oil shale mines. Since not only genotoxic effects may play an important role in the generation of tumors, the level of porphyrin metabolism was proposed as a biomarker of diesel exhaust exposure effects. The data on determination of 5-aminolevulinic acid (ALA) synthesis and heme formation in lymphocytes from groups of 50 miners exposed to diesel exhaust and 50 unexposed surface workers of oil shale mine are presented. All workers were examined and interviewed using structured questionnaires. The levels of benzene, carbon monoxide and nitric oxides in air as well as concentrations of 1-nitropyrene and elemental carbon in particulate matter were used for evaluation of exposure to diesel exhaust in mine. The levels of ALA and protoporphyrin (PP), activities of ALA synthetase (ALA-S) and ferrochelatase (FC), as well as levels of PP associated with DNA (PP/DNA) were investigated in lymphocytes spectrophotometrically. Significant differences in activity of ALA synthesis and heme formation between exposed miners and surface workers were found (207{+-}23 vs. 166{+-}14 pmol/10{sup 6} lymp./30' for ALA-S and 46.1{+-}3.8 vs. 54.8{+-}4.1 pmol/10{sup 6} lymp./60' for FC activities, respectively, P<0.001). ALA-S activity was higher and ALA accumulated in lymphocytes of exposed miners. Inhibition of FC activity caused PP cellular accumulation and an increase in the PP/DNA level (P<0.05). Tobacco smoking led to the increase of ALA biosynthesis in lymphocytes of both surface and underground smokers. The comparison of data obtained for non-smokers and smokers of both groups of workers has shown a significant difference (P<0.05). The work duration of underground or surface workers did not significantly influence the investigated biochemical parameters. The determination of ALA synthesis in lymphocytes could be a useful biomonitoring

  2. Atoms for space

    Energy Technology Data Exchange (ETDEWEB)

    Buden, D.

    1990-10-01

    Nuclear technology offers many advantages in an expanded solar system space exploration program. These cover a range of possible applications such as power for spacecraft, lunar and planetary surfaces, and electric propulsion; rocket propulsion for lunar and Mars vehicles; space radiation protection; water and sewage treatment; space mining; process heat; medical isotopes; and self-luminous systems. In addition, space offers opportunities to perform scientific research and develop systems that can solve problems here on Earth. These might include fusion and antimatter research, using the Moon as a source of helium-3 fusion fuel, and manufacturing perfect fusion targets. In addition, nuclear technologies can be used to reduce risk and costs of the Space Exploration Initiative. 1 fig.

  3. Atoms for space

    International Nuclear Information System (INIS)

    Buden, D.

    1990-10-01

    Nuclear technology offers many advantages in an expanded solar system space exploration program. These cover a range of possible applications such as power for spacecraft, lunar and planetary surfaces, and electric propulsion; rocket propulsion for lunar and Mars vehicles; space radiation protection; water and sewage treatment; space mining; process heat; medical isotopes; and self-luminous systems. In addition, space offers opportunities to perform scientific research and develop systems that can solve problems here on Earth. These might include fusion and antimatter research, using the Moon as a source of helium-3 fusion fuel, and manufacturing perfect fusion targets. In addition, nuclear technologies can be used to reduce risk and costs of the Space Exploration Initiative. 1 fig

  4. Degradation of Silicon Carbide Reflective Surfaces in the LEO Environment

    Science.gov (United States)

    Mileti, Sandro; Coluzzi, Plinio; Marchetti, Mario

    2009-01-01

    Space mirrors in Low Earth Orbit (LEO) encounter a degradation problem caused by the impact of atomic oxygen (ATOX) in the space environment. This paper presents an experiment of the atomic oxygen impact degradation and UV synergic effects on ground simulation. The experiment was carried out in a dedicated ATOX simulation vacuum chamber. As target materials, a polished CVD Beta-silicon carbide (SiC) coating was investigated. The selection of silicon carbide is due to its high potential candidate as a mirror layer substrate material for its good reflectance at UV wavelengths and excellent thermal diffusivity. It has highly desirable mechanical and thermal properties and can achieve an excellent surface finish. The deposition of the coatings were on carbon-based material substrate; i.e., silicon impregnated carbon fiber composite (C/SiC). Mechanical and thermal properties of the coatings such as hardness and Coefficient of Thermal Expansion (CTE) were achieved. Several atomic oxygen impact angles were studied tilting the target samples respect to the flux direction. The various impact angles permitted to analyze the different erosion rates and typologies which the mirrors would encounter in LEO environment. The degradation was analyzed in various aspects. Macroscopic mass loss per unit area, surface roughness and morphology change were basically analyzed. The exposed surfaces of the materials were observed through a Scanning Electron Microscope (SEM). Secondly, optical diagnostic of the surfaces were performed in order to investigate their variation in optical properties as the evaluation of reflectance degradation. The presence of micro-cracks caused by shrinkage, grinding, polishing or thermal cycling and the porosity in the coatings, could have led to the undercutting phenomenon. Observation of uprising of undercutting was also conducted. Remarks are given regarding capabilities in short-term mission exposures to the LEO environment of this coating.

  5. Radiation Effects in the Space Telecommunications Environment

    Energy Technology Data Exchange (ETDEWEB)

    Fleetwood, Daniel M.; Winokur, Peter S.

    1999-05-17

    Trapped protons and electrons in the Earth's radiation belts and cosmic rays present significant challenges for electronics that must operate reliably in the natural space environment. Single event effects (SEE) can lead to sudden device or system failure, and total dose effects can reduce the lifetime of a telecommmiications system with significant space assets. One of the greatest sources of uncertainty in developing radiation requirements for a space system is accounting for the small but finite probability that the system will be exposed to a massive solar particle event. Once specifications are decided, standard laboratory tests are available to predict the total dose response of MOS and bipolar components in space, but SEE testing of components can be more challenging. Prospects are discussed for device modeling and for the use of standard commercial electronics in space.

  6. Radiation Effects in the Space Telecommunications Environment

    International Nuclear Information System (INIS)

    Fleetwood, Daniel M.; Winokur, Peter S.

    1999-01-01

    Trapped protons and electrons in the Earth's radiation belts and cosmic rays present significant challenges for electronics that must operate reliably in the natural space environment. Single event effects (SEE) can lead to sudden device or system failure, and total dose effects can reduce the lifetime of a telecommmiications system with significant space assets. One of the greatest sources of uncertainty in developing radiation requirements for a space system is accounting for the small but finite probability that the system will be exposed to a massive solar particle event. Once specifications are decided, standard laboratory tests are available to predict the total dose response of MOS and bipolar components in space, but SEE testing of components can be more challenging. Prospects are discussed for device modeling and for the use of standard commercial electronics in space

  7. Assessment of broiler surface temperature variation when exposed to different air temperatures

    Directory of Open Access Journals (Sweden)

    GR Nascimento

    2011-12-01

    Full Text Available This study was conducted to determine the effect of the air temperature variation on the mean surface temperature (MST of 7- to 35-day-old broiler chickens using infrared thermometry to estimate MST, and to study surface temperature variation of the wings, head, legs, back and comb as affected by air temperature and broiler age. One hundred Cobb® broilers were used in the experiment. Starting on day 7, 10 birds were weekly selected at random, housed in an environmental chamber and reared under three distinct temperatures (18, 25 and 32 ºC to record their thermal profile using an infrared thermal camera. The recorded images were processed to estimate MST by selecting the whole area of the bird within the picture and comparing it with the values obtained using selected equations in literature, and to record the surface temperatures of the body parts. The MST estimated by infrared images were not statistically different (p > 0.05 from the values obtained by the equations. MST values significantly increased (p < 0.05 when the air temperature increased, but were not affected by bird age. However, age influenced the difference between MST and air temperature, which was highest on day 14. The technique of infrared thermal image analysis was useful to estimate the mean surface temperature of broiler chickens.

  8. Surface Plasmon Singularities

    Directory of Open Access Journals (Sweden)

    Gabriel Martínez-Niconoff

    2012-01-01

    Full Text Available With the purpose to compare the physical features of the electromagnetic field, we describe the synthesis of optical singularities propagating in the free space and on a metal surface. In both cases the electromagnetic field has a slit-shaped curve as a boundary condition, and the singularities correspond to a shock wave that is a consequence of the curvature of the slit curve. As prototypes, we generate singularities that correspond to fold and cusped regions. We show that singularities in free space may generate bifurcation effects while plasmon fields do not generate these kinds of effects. Experimental results for free-space propagation are presented and for surface plasmon fields, computer simulations are shown.

  9. The Drosophila surface glia transcriptome: evolutionary conserved blood-brain barrier processes.

    Directory of Open Access Journals (Sweden)

    Michael K DeSalvo

    2014-11-01

    Full Text Available AbstractCentral nervous system (CNS function is dependent on the stringent regulation of metabolites, drugs, cells, and pathogens exposed to the CNS space. Cellular blood-brain barrier (BBB structures are highly specific checkpoints governing entry and exit of all small molecules to and from the brain interstitial space, but the precise mechanisms that regulate the BBB are not well understood. In addition, the BBB has long been a challenging obstacle to the pharmacologic treatment of CNS diseases; thus model systems that can parse the functions of the BBB are highly desirable. In this study, we sought to define the transcriptome of the adult Drosophila melanogaster BBB by isolating the BBB surface glia with FACS and profiling their gene expression with microarrays. By comparing the transcriptome of these surface glia to that of all brain glia, brain neurons, and whole brains, we present a catalog of transcripts that are selectively enriched at the Drosophila BBB. We found that the fly surface glia show high expression of many ABC and SLC transporters, cell adhesion molecules, metabolic enzymes, signaling molecules, and components of xenobiotic metabolism pathways. Using gene sequence-based alignments, we compare the Drosophila and Murine BBB transcriptomes and discover many shared chemoprotective and small molecule control pathways, thus affirming the relevance of invertebrate models for studying evolutionary conserved BBB properties. The Drosophila BBB transcriptome is valuable to vertebrate and insect biologists alike as a resource for studying proteins underlying diffusion barrier development and maintenance, glial biology, and regulation of drug transport at tissue barriers.

  10. The Drosophila surface glia transcriptome: evolutionary conserved blood-brain barrier processes.

    Science.gov (United States)

    DeSalvo, Michael K; Hindle, Samantha J; Rusan, Zeid M; Orng, Souvinh; Eddison, Mark; Halliwill, Kyle; Bainton, Roland J

    2014-01-01

    Central nervous system (CNS) function is dependent on the stringent regulation of metabolites, drugs, cells, and pathogens exposed to the CNS space. Cellular blood-brain barrier (BBB) structures are highly specific checkpoints governing entry and exit of all small molecules to and from the brain interstitial space, but the precise mechanisms that regulate the BBB are not well understood. In addition, the BBB has long been a challenging obstacle to the pharmacologic treatment of CNS diseases; thus model systems that can parse the functions of the BBB are highly desirable. In this study, we sought to define the transcriptome of the adult Drosophila melanogaster BBB by isolating the BBB surface glia with fluorescence activated cell sorting (FACS) and profiling their gene expression with microarrays. By comparing the transcriptome of these surface glia to that of all brain glia, brain neurons, and whole brains, we present a catalog of transcripts that are selectively enriched at the Drosophila BBB. We found that the fly surface glia show high expression of many ATP-binding cassette (ABC) and solute carrier (SLC) transporters, cell adhesion molecules, metabolic enzymes, signaling molecules, and components of xenobiotic metabolism pathways. Using gene sequence-based alignments, we compare the Drosophila and Murine BBB transcriptomes and discover many shared chemoprotective and small molecule control pathways, thus affirming the relevance of invertebrate models for studying evolutionary conserved BBB properties. The Drosophila BBB transcriptome is valuable to vertebrate and insect biologists alike as a resource for studying proteins underlying diffusion barrier development and maintenance, glial biology, and regulation of drug transport at tissue barriers.

  11. Time-resolved PHERMEX image restorations constrained with an additional multiply-exposed image

    International Nuclear Information System (INIS)

    Kruger, R.P.; Breedlove, J.R. Jr.; Trussell, H.J.

    1978-06-01

    There are a number of possible industrial and scientific applications of nanosecond cineradiographs. Although the technology exists to produce closely spaced pulses of x rays for this application, the quality of the time-resolved radiographs is severely limited. The limitations arise from the necessity of using a fluorescent screen to convert the transmitted x rays to light and then using electro-optical imaging systems to gate and to record the images with conventional high-speed cameras. It has been proposed that, in addition to the time-resolved images, a conventional multiply exposed radiograph be obtained. This report uses both PHERMEX and conventional photographic simulations to demonstrate that the additional information supplied by the multiply exposed radiograph can be used to improve the quality of digital image restorations of the time-resolved pictures over what could be achieved with the degraded images alone

  12. Surface damage of W exposed to combined stationary D plasma and ELMs-like pulsed plasma

    Energy Technology Data Exchange (ETDEWEB)

    Jia, Y.Z., E-mail: jaja880816@aliyun.com [Science and Technology on Reactor Fuel and Materials Laboratory, Nuclear Power Institute of China, Chengdu, Sichuan 610213 (China); Laboratory of Advanced Materials, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Liu, W., E-mail: liuw@mail.tsinghua.edu.cn [Laboratory of Advanced Materials, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Xu, B.; Qu, S.L. [Laboratory of Advanced Materials, School of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Morgan, T.W. [FOM Institute DIFFER-Dutch Institute for Fundamental Energy Research, 5612AJ Eindhoven (Netherlands)

    2017-04-15

    The surface damage of W under D plasma and ELMs-like transient heat loads was studied by combined stationary and pulsed D plasma. Low-flux transient heat loads will promote blister formation due to the gas expansion inside the blisters. On the contrary, high-flux transient heat loads will mitigate blistering due to the high surface temperature. Therefore, blistering on W surface first increased and then decreased with the increasing transient heat loads. The promotion effect of pulsed plasma on blistering is more obvious on [001] and [110] surfaces than on [111] surface, and the orientation dependence of blisters was mitigated by the transient heat loads. Surface modification induced by transient heat loads only formed on [001] and [110] surfaces, but did not form on [111] surface. The orientation dependence of surface modification was mainly due to the slipping system of dislocations.

  13. The Initial Nine Space Settlements

    Science.gov (United States)

    Gale, Anita E.; Edwards, Richard P.

    2003-01-01

    The co-authors describe a chronology of space infrastructure development illustrating how each element of infrastructure enables development of subsequent more ambitious infrastructure. This is likened to the ``Southern California freeway phenomenon'', wherein a new freeway built in a remote area promotes establishment of gas stations, restaurants, hotels, housing, and eventually entire new communities. The chronology includes new launch vehicles, inter-orbit vehicles, multiple LEO space stations, lunar mining, on-orbit manufacturing, tourist destinations, and supporting technologies required to make it all happen. The space settlements encompassed by the chronology are in Earth orbit (L5 and L4), on the lunar surface, in Mars orbit, on the Martian surface, and in the asteroid belt. Each space settlement is justified with a business rationale for construction. This paper is based on materials developed for Space Settlement Design Competitions that enable high school students to experience the technical and management challenges of working on an industry proposal team.

  14. Potential Use of In Situ Material Composites such as Regolith/Polyethylene for Shielding Space Radiation

    Science.gov (United States)

    Theriot, Corey A.; Gersey, Buddy; Bacon, Eugene; Johnson, Quincy; Zhang, Ye; Norman, Jullian; Foley, Ijette; Wilkins, Rick; Zhou, Jianren; Wu, Honglu

    2010-01-01

    NASA has an extensive program for studying materials and methods for the shielding of astronauts to reduce the effects of space radiation when on the surfaces of the Moon and Mars, especially in the use of in situ materials native to the destination reducing the expense of materials transport. The most studied material from the Moon is Lunar regolith and has been shown to be as efficient as aluminum for shielding purposes (1). The addition of hydrogenous materials such as polyethylene should increase shielding effectiveness and provide mechanical properties necessary of structural materials (2). The neutron radiation shielding effectiveness of polyethylene/regolith stimulant (JSC-1A) composites were studied using confluent human fibroblast cell cultures exposed to a beam of high-energy spallation neutrons at the 30deg-left beam line (ICE house) at the Los Alamos Neutron Science Center. At this angle, the radiation spectrum mimics the energy spectrum of secondary neutrons generated in the upper atmosphere and encountered when aboard spacecraft and high-altitude aircraft. Cell samples were exposed in series either directly to the neutron beam, within a habitat created using regolith composite blocks, or behind 25 g/sq cm of loose regolith bulk material. In another experiment, cells were also exposed in series directly to the neutron beam in T-25 flasks completely filled with either media or water up to a depth of 20 cm to test shielding effectiveness versus depth and investigate the possible influence of secondary particle generation. All samples were sent directly back to JSC for sub-culturing and micronucleus analysis. This presentation is of work performed in collaboration with the NASA sponsored Center for Radiation Engineering and Science for Space Exploration (CRESSE) at Prairie View A&M.

  15. 30 CFR 77.508 - Lightning arresters, ungrounded and exposed power conductors and telephone wires.

    Science.gov (United States)

    2010-07-01

    ... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Lightning arresters, ungrounded and exposed... AND SURFACE WORK AREAS OF UNDERGROUND COAL MINES Electrical Equipment-General § 77.508 Lightning... conductors and telephone wires shall be equipped with suitable lightning arresters which are adequately...

  16. Buildings exposed to fire

    International Nuclear Information System (INIS)

    1987-01-01

    The 24 lectures presented to the colloquium cover the following subject fields: (1) Behaviour of structural components exposed to fire; (2) Behaviour of building materials exposed to fire; (3) Thermal processes; (4) Safety related, theoretical studies. (PW) [de

  17. Characterization of polymer surface structure and surface mechanical behaviour by sum frequency generation surface vibrational spectroscopy and atomic force microscopy

    International Nuclear Information System (INIS)

    Opdahl, Aric; Koffas, Telly S; Amitay-Sadovsky, Ella; Kim, Joonyeong; Somorjai, Gabor A

    2004-01-01

    Sum frequency generation (SFG) vibrational spectroscopy and atomic force microscopy (AFM) have been used to study polymer surface structure and surface mechanical behaviour, specifically to study the relationships between the surface properties of polymers and their bulk compositions and the environment to which the polymer is exposed. The combination of SFG surface vibrational spectroscopy and AFM has been used to study surface segregation behaviour of polyolefin blends at the polymer/air and polymer/solid interfaces. SFG surface vibrational spectroscopy and AFM experiments have also been performed to characterize the properties of polymer/liquid and polymer/polymer interfaces, focusing on hydrogel materials. A method was developed to study the surface properties of hydrogel contact lens materials at various hydration conditions. Finally, the effect of mechanical stretching on the surface composition and surface mechanical behaviour of phase-separated polyurethanes, used in biomedical implant devices, has been studied by both SFG surface vibrational spectroscopy and AFM. (topical review)

  18. Hygrothermal Simulation of Wood Exposed To the Effect of External Climate

    Science.gov (United States)

    Dohnal, Jakub; Hradil, Petr; Pencik, Jan

    2017-10-01

    The article is focused on simulation of moisture transfer in wood of norway spruce (Picea abies L.). Experimental specimen was exposed to the northern climatic conditions in Lund University, Sweden. The moisture content of wood was measured 10 mm from the surface for nearly three years. The ABAQUS program was used for numerical modelling of moisture transfer simulation in 3D. The surface sorption of wood was simulated using user defined subroutine DFLUX developed by VTT Research Centre of Finland Ltd. for the needs of European Project Durable Timber Bridges. Climate data for the analysis was used from insitu measurement nearby realized by weather station. The temperature, relative humidity of the air and precipitation data was record each hour. Numerical analysis took into account influence of rain effect on different parts of specimen surface.

  19. A Potential Method for Body and Surface Wave Propagation in Transversely Isotropic Half- and Full-Spaces

    Directory of Open Access Journals (Sweden)

    Mehdi Raoofian Naeeni

    2016-12-01

    Full Text Available The problem of propagation of plane wave including body and surface waves propagating in a transversely isotropic half-space with a depth-wise axis of material symmetry is investigated in details. Using the advantage of representation of displacement fields in terms of two complete scalar potential functions, the coupled equations of motion are uncoupled and reduced to two independent equations for potential functions. In this paper, the secular equations for determination of body and surface wave velocities are derived in terms of both elasticity coefficients and the direction of propagation. In particular, the longitudinal, transverse and Rayleigh wave velocities are determined in explicit forms. It is also shown that in transversely isotropic materials, a Rayleigh wave may propagate in different manner from that of isotropic materials. Some numerical results for synthetic transversely isotropic materials are also illustrated to show the behavior of wave motion due to anisotropic nature of the problem.

  20. Projective and superconformal structures on surfaces

    International Nuclear Information System (INIS)

    Harvey, W.J.

    1990-01-01

    Much attention has recently been given to the study of super Riemann surfaces. Detailed accounts of these objects and their infinitesimal deformation theory are referenced where they are fitted into the framework of complex supermanifolds, superconformal structures and graded sheaves. One difficulty, which seems even more of a barrier than in the case of classical deformations of Riemann surface structure, is the lack of a good global description of super-moduli spaces. In this note, we outline an approach which places the theory in the classical setting of projective structures on variable Riemann surfaces. We explain how to construct a distribution (family of vector subspaces) inside the holomorphic cotangent space to the moduli space M g of Riemann surfaces with genus g and furnished with a level-4 homology structure, such that the corresponding rank-(2g-2) complex vector bundle models the soul deformations of a family of super-Riemann surfaces. The keystone in this construction is the existence of holomorphic sections for the space of non-singular odd theta characteristics on C g the universal curve over M g . (author)

  1. Analysis of the Thermo-Elastic Response of Space Reflectors to Simulated Space Environment

    Science.gov (United States)

    Allegri, G.; Ivagnes, M. M.; Marchetti, M.; Poscente, F.

    2002-01-01

    The evaluation of space environment effects on materials and structures is a key matter to develop a proper design of long duration missions: since a large part of satellites operating in the earth orbital environment are employed for telecommunications, the development of space antennas and reflectors featured by high dimensional stability versus space environment interactions represents a major challenge for designers. The structural layout of state of the art space antennas and reflectors is very complex, since several different sensible elements and materials are employed: particular care must be placed in evaluating the actual geometrical configuration of the reflectors operating in the space environment, since very limited distortions of the designed layout can produce severe effects on the quality of the signal both received and transmitted, especially for antennas operating at high frequencies. The effects of thermal loads due to direct sunlight exposition and to earth and moon albedo can be easily taken into account employing the standard methods of structural analysis: on the other hand the thermal cycling and the exposition to the vacuum environment produce a long term damage accumulation which affects the whole structure. The typical effects of the just mentioned exposition are the outgassing of polymeric materials and the contamination of the exposed surface, which can affect sensibly the thermo-mechanical properties of the materials themselves and, therefore, the structural global response. The main aim of the present paper is to evaluate the synergistic effects of thermal cycling and of the exposition to high vacuum environment on an innovative antenna developed by Alenia Spazio S.p.a.: to this purpose, both an experimental and numerical research activity has been developed. A complete prototype of the antenna has been exposed to the space environment simulated by the SAS facility: this latter is constituted by an high vacuum chamber, equipped by

  2. Solar Atmosphere to Earth's Surface: Long Lead Time dB/dt Predictions with the Space Weather Modeling Framework

    Science.gov (United States)

    Welling, D. T.; Manchester, W.; Savani, N.; Sokolov, I.; van der Holst, B.; Jin, M.; Toth, G.; Liemohn, M. W.; Gombosi, T. I.

    2017-12-01

    The future of space weather prediction depends on the community's ability to predict L1 values from observations of the solar atmosphere, which can yield hours of lead time. While both empirical and physics-based L1 forecast methods exist, it is not yet known if this nascent capability can translate to skilled dB/dt forecasts at the Earth's surface. This paper shows results for the first forecast-quality, solar-atmosphere-to-Earth's-surface dB/dt predictions. Two methods are used to predict solar wind and IMF conditions at L1 for several real-world coronal mass ejection events. The first method is an empirical and observationally based system to estimate the plasma characteristics. The magnetic field predictions are based on the Bz4Cast system which assumes that the CME has a cylindrical flux rope geometry locally around Earth's trajectory. The remaining plasma parameters of density, temperature and velocity are estimated from white-light coronagraphs via a variety of triangulation methods and forward based modelling. The second is a first-principles-based approach that combines the Eruptive Event Generator using Gibson-Low configuration (EEGGL) model with the Alfven Wave Solar Model (AWSoM). EEGGL specifies parameters for the Gibson-Low flux rope such that it erupts, driving a CME in the coronal model that reproduces coronagraph observations and propagates to 1AU. The resulting solar wind predictions are used to drive the operational Space Weather Modeling Framework (SWMF) for geospace. Following the configuration used by NOAA's Space Weather Prediction Center, this setup couples the BATS-R-US global magnetohydromagnetic model to the Rice Convection Model (RCM) ring current model and a height-integrated ionosphere electrodynamics model. The long lead time predictions of dB/dt are compared to model results that are driven by L1 solar wind observations. Both are compared to real-world observations from surface magnetometers at a variety of geomagnetic latitudes

  3. Erosion of pyrolytic carbon under high surface energy deposition from a pulsed hydrogen plasma

    International Nuclear Information System (INIS)

    Bolt, H.

    1992-01-01

    Carbon materials are widely applied as plasma facing materials in nuclear fusion devices and are also the prime candidate materials for the next generation of experimental fusion reactors. During operation these materials are frequently subjected to high energy deposition from plasma disruptions. The erosion of carbon materials is regarded as the main issue governing the operational lifetime of plasma facing components. Laboratory experiments have been performed to study the thermal erosion behaviour of carbon in a plasma environment. In the experiments the surface of pyrolytic carbon specimens was exposed to pulsed energy deposition of up to 3.8 MJ m -2 from a hydrogen plasma. The behaviour of the eroded carbon species in the plasma was measured by time-resolved and space-resolved spectroscopy. Intense line radiation of ionic carbon has been measured in the plasma in front of the carbon surface. The results show that the eroded carbon is immediately ionised in the vicinity of the material surface, with a fraction of it being ionised to the double-charged state. (Author)

  4. Simulation and preparation of surface EVA in reduced gravity at the Marseilles Bay subsea analogue sites

    Science.gov (United States)

    Weiss, P.; Gardette, B.; Chirié, B.; Collina-Girard, J.; Delauze, H. G.

    2012-12-01

    Extravehicular activity (EVA) of astronauts during space missions is simulated nowadays underwater in neutral buoyancy facilities. Certain aspects of weightlessness can be reproduced underwater by adding buoyancy to a diver-astronaut, therefore exposing the subject to the difficulties of working without gravity. Such tests were done at the COMEX' test pool in Marseilles in the 1980s to train for a French-Russian mission to the MIR station, for the development of the European HERMES shuttle and the COLUMBUS laboratory. However, space agencies are currently studying missions to other destinations than the International Space Station in orbit, such as the return to the Moon, NEO (near-Earth objects) or Mars. All these objects expose different gravities: Moon has one sixth of Earth's gravity, Mars has a third of Earth's gravity and asteroids have virtually no surface gravity; the astronaut "floats" above the ground. The preparation of such missions calls for a new concept in neutral buoyancy training, not on man-made structures, but on natural terrain, underwater, to simulate EVA operations such as sampling, locomotion or even anchoring in low gravity. Underwater sites can be used not only to simulate the reduced gravity that astronauts will experience during their field trips, also human factors like stress are more realistically reproduced in such environment. The Bay of Marseille hosts several underwater sites that can be used to simulate various geologic morphologies, such as sink-holes which can be used to simulate astronaut descends into craters, caves where explorations of lava tubes can be trained or monolithic rock structures that can be used to test anchoring devices (e.g., near Earth objects). Marseilles with its aerospace and maritime/offshore heritage hosts the necessary logistics and expertise that is needed to perform such simulations underwater in a safe manner (training of astronaut-divers in local test pools, research vessels, subsea robots and

  5. Influence of space radiation on satellite magnetics

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, M K [Vikram Sarabhai Space Centre, Trivandrum (India)

    1978-12-01

    The magnetic circuits and devices used in space-borne systems such as satellites are naturally exposed to space environments having among others, hazardous radiations. Such radiations, in turn, may be of solar, cosmic or nuclear origin depending upon the altitude as well as the propulsion/power systems involving mini atomic reactors when utilised. The influence of such radiations on the magnetic components of the satellite have been analysed revealing the critical hazards in the latter circuits system. Remedial measures by appropriate shielding, etc. necessary for maintaining optimum performance of the satellite have been discussed.

  6. Electrodynamic Dust Shield for Space Applications

    Science.gov (United States)

    Mackey, Paul J.; Johansen, Michael R.; Olsen, Robert C.; Raines, Matthew G.; Phillips, James R., III; Cox, Rachel E.; Hogue, Michael D.; Pollard, Jacob R. S.; Calle, Carlos I.

    2016-01-01

    Dust mitigation technology has been highlighted by NASA and the International Space Exploration Coordination Group (ISECG) as a Global Exploration Roadmap (GER) critical technology need in order to reduce life cycle cost and risk, and increase the probability of mission success. The Electrostatics and Surface Physics Lab in Swamp Works at the Kennedy Space Center has developed an Electrodynamic Dust Shield (EDS) to remove dust from multiple surfaces, including glass shields and thermal radiators. Further development is underway to improve the operation and reliability of the EDS as well as to perform material and component testing outside of the International Space Station (ISS) on the Materials on International Space Station Experiment (MISSE). This experiment is designed to verify that the EDS can withstand the harsh environment of space and will look to closely replicate the solar environment experienced on the Moon.

  7. On the radiation dosimetry in space

    International Nuclear Information System (INIS)

    Doke, Tadayoshi

    2005-01-01

    The radiation dosimetry in space is considerably different from that on the earth surface, because, on the earth surface, the quality factor for radiation is roughly given for its energy but, in space, it is defined as a continuous function of LET. Thus, the contribution to the dose equivalent from heavy charged particles included in galactic cosmic rays is more than 50%, because of their high LET values. To evaluate such dose equivalent within an uncertainty of 30%, we must determine the true LET distribution. This paper describes the essence of such a new radiation dosimetry in space. (author)

  8. A contribution of geography to the landscape evaluation and space ordering

    Directory of Open Access Journals (Sweden)

    Klaus Wolf

    1997-12-01

    Full Text Available The paper discusses the significance of contemporaij social geography for the landscape evalution and space ordering. Exposed is the geographical approach in triangle: description-explanation-application.

  9. Minimal Surfaces for Hitchin Representations

    DEFF Research Database (Denmark)

    Li, Qiongling; Dai, Song

    2018-01-01

    . In this paper, we investigate the properties of immersed minimal surfaces inside symmetric space associated to a subloci of Hitchin component: $q_n$ and $q_{n-1}$ case. First, we show that the pullback metric of the minimal surface dominates a constant multiple of the hyperbolic metric in the same conformal...... class and has a strong rigidity property. Secondly, we show that the immersed minimal surface is never tangential to any flat inside the symmetric space. As a direct corollary, the pullback metric of the minimal surface is always strictly negatively curved. In the end, we find a fully decoupled system...

  10. The exposed proteomes of Brachyspira hyodysenteriae and B. pilosicoli.

    Directory of Open Access Journals (Sweden)

    Vanessa Casas

    2016-07-01

    Full Text Available B. hyodysenteriae and B. pilosicoli are well-known intestinal pathogens in pigs. B. hyodysenteriae is the causative agent of swine dysentery, a disease with an important impact on pig production while B. pilosicoli is responsible of a milder diarrheal disease in these animals, porcine intestinal spirochetosis. Recent sequencing projects have provided information for the genome of these species facilitating the search of vaccine candidates using reverse vaccinology approaches. However, practically no experimental evidence exists of the actual gene products being expressed and of those proteins exposed on the cell surface or released to the cell media. Using a cell-shaving strategy and a shotgun proteomic approach we carried out a large-scale characterization of the exposed proteins on the bacterial surface in these species as well as of peptides and proteins in the extracellular medium. The study included 3 strains of B. hyodysenteriae and 2 strains of B. pilosicoli and involved 148 LC-MS/MS runs on a high resolution Orbitrap instrument. Overall, we provided evidence for more than 29000 different peptides pointing to 1625 and 1338 different proteins in B. hyodysenteriae and B. pilosicoli, respectively. Many of the most abundant proteins detected corresponded to described virulence factors and vaccine candidates. The level of expression of these proteins, however, was different among species and strains, stressing the value of determining actual gene product levels as a complement of genomic-based approaches for vaccine design.

  11. Dynamical speckles in watery surfaces

    International Nuclear Information System (INIS)

    Llovera-Gonzalez, J.J.; Moreno-Yeras, A.; Garcia-Diaz, M.; Alvarez-Salgado, Y.

    2009-01-01

    Recovery of watery surfaces with monolayer of surfactant substances is of interest in diverse technological applications. The format ion and study of molecular monolayer deposited in these surfaces require the application of measurements techniques that allow evaluating the recovery grade locally without modifying practically the studied surface. In this paper the preliminary results obtained by the authors it plows exposed applying the technique of dynamic speckle interferometry in watery surfaces and their consideration like to possible resource to measure the grade of local recovery of these surfaces on the it bases that the speckles pattern dog reveal the dynamics of evaporation that takes place in the same ones. (Author)

  12. Effect of land cover and green space on land surface temperature of a fast growing economic region in Malaysia

    Science.gov (United States)

    Sheikhi, A.; Kanniah, K. D.; Ho, C. H.

    2015-10-01

    Green space must be increased in the development of new cities as green space can moderate temperature in the cities. In this study we estimated the land surface temperature (LST) and established relationships between LST and land cover and various vegetation and urban surface indices in the Iskandar Malaysia (IM) region. IM is one of the emerging economic gateways of Malaysia, and is envisaged to transform into a metropolis by 2025. This change may cause increased temperature in IM and therefore we conducted a study by using Landsat 5 image covering the study region (2,217 km2) to estimate LST, classify different land covers and calculate spectral indices. Results show that urban surface had highest LST (24.49 °C) and the lowest temperature was recorded in, forest, rubber and water bodies ( 20.69 to 21.02°C). Oil palm plantations showed intermediate mean LST values with 21.65 °C. We further investigated the relationship between vegetation and build up densities with temperature. We extracted 1000 collocated pure pixels of Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), Normalized Difference Built-up Index (NDBI), Urban Index (UI) and LST in the study area. Results show a strong and significant negative correlation with (R2= -0.74 and -0.79) respectively between NDVI, NDWI and LST . Meanwhile a strong positive correlation (R2=0.8 and 0.86) exists between NDBI, UI and LST. These results show the importance of increasing green cover in urban environment to combat any adverse effects of climate change.

  13. A method for the dynamic and thermal stress analysis of space shuttle surface insulation

    Science.gov (United States)

    Ojalvo, I. U.; Levy, A.; Austin, F.

    1975-01-01

    The thermal protection system of the space shuttle consists of thousands of separate insulation tiles bonded to the orbiter's surface through a soft strain-isolation layer. The individual tiles are relatively thick and possess nonuniform properties. Therefore, each is idealized by finite-element assemblages containing up to 2500 degrees of freedom. Since the tiles affixed to a given structural panel will, in general, interact with one another, application of the standard direct-stiffness method would require equation systems involving excessive numbers of unknowns. This paper presents a method which overcomes this problem through an efficient iterative procedure which requires treatment of only a single tile at any given time. Results of associated static, dynamic, and thermal stress analyses and sufficient conditions for convergence of the iterative solution method are given.

  14. Optically stimulated luminescence (OSL) as a chronometer for surface exposure dating

    DEFF Research Database (Denmark)

    Sohbati, Reza; Murray, Andrew S.; Chapot, Melissa S.

    2012-01-01

    We pioneer a technique of surface-exposure dating based upon the characteristic form of an optically stimulated luminescence (OSL) bleaching profile beneath a rock surface; this evolves as a function of depth and time. As a field illustration of this new method, the maximum age of a premier example...... exposure histories; one of these samples was exposed at the time of sampling and one was buried and no longer light exposed. A third sample is known to have been first exposed 80 years ago and was still exposed at the time of sampling. First, the OSL-depth profile of the known-age sample is modeled...... to estimate material-dependent and environmental parameters. These parameters are then used to fit the model to the corresponding data for the samples of unknown exposure history. From these fits we calculate that the buried sample was light exposed for similar to 700 years before burial and that the unburied...

  15. Surface Chemical Characterisation of Pyrite Exposed to Acidithiobacillus ferrooxidans and Associated Extracellular Polymeric Substances

    Directory of Open Access Journals (Sweden)

    Sian M. La Vars

    2018-03-01

    Full Text Available A. ferrooxidans and their metabolic products have previously been explored as a viable alternative depressant of pyrite for froth flotation; however, the mechanism by which separation is achieved is not completely understood. Scanning electron microscopy (SEM, photoemission electron microscopy (PEEM, time-of-flight secondary ion mass spectrometry (ToF-SIMS and captive bubble contact angle measurements have been used to examine the surface physicochemical properties of pyrite upon exposure to A. ferrooxidans grown in HH medium at pH 1.8. C K-edge near edge X-ray absorption fine structure (NEXAFS spectra collected from PEEM images indicate hydrophilic lipids, fatty acids and biopolymers are formed at the mineral surface during early exposure. After 168 h, the spectra indicate a shift towards protein and DNA, corresponding to an increase in cell population and biofilm formation on the surface, as observed by SEM. The Fe L-edge NEXAFS show gradual oxidation of the mineral surface from Fe(II sulfide to Fe(III oxyhydroxides. The oxidation of the iron species at the pyrite surface is accelerated in the presence of A. ferrooxidans and extracellular polymeric substances (EPS as compared to HH medium controls. The surface chemical changes induced by the interaction with A. ferrooxidans show a significant decrease in surface hydrophobicity within the first 2 h of exposure. The implications of these findings are the potential use of EPS produced during early attachment of A. ferrooxidans, as a depressant for bioflotation.

  16. Biopan-survival I: exposure of the osmophiles synechococcus sp. (Nageli) and haloarcula sp. to the space environment

    Science.gov (United States)

    Mancinelli, R. L.; White, M. R.; Rothschild, L. J.

    The objective of this study was to determine the survivability of osmophilic microorganisms in space, as well as examine the DNA breakage in osmophilic cells exposed to solar UV-radiation plus vacuum and to vacuum only. The organisms used were an unidentified species of Synechococcus (Nägeli) that inhabits the evaporitic gypsum-halite crusts that form along the marine intertidal, and an unidentified species of the extremely halophilic genus Haloarcula (designated as isolate G) isolated from a evaporitic NaCl crystal. Because these organisms are desiccation resistant and gypsum-halite as well as NaCl attenuate UV-radiation, we hypothesized that these organisms would survive in the space environment, better than most others. The organisms were exposed to the space environment for 2 weeks while in earth orbit aboard the Biopan facility. Ground controls were tested in a space simulation facility. All samples were compared to unexposed samples. Survivability was determined by plate counts and the most probable number technique. DNA breakage was determined by labeling breaks in the DNA with ^32P followed by translation. Results indicate that the osmophilic microbes survived the 2 week exposure. The major cause of cell death was DNA damage. The number of strand breaks in the DNA from vacuum UV exposed cells was greater than the vacuum only exposed cells.

  17. Schools of Excellence and Equity? Using Equity Audits as a Tool to Expose a Flawed System of Recognition

    Science.gov (United States)

    Brown, Kathleen M.

    2010-01-01

    The purpose of this article is to demonstrate how equity audits can be used as a tool to expose disparate achievement in schools that, on the surface and to the public, appear quite similar. To that end, the researcher probed beyond surface-level performance composite scores into deeper, more hidden data associated with state-recognized…

  18. Space Flight Ionizing Radiation Environments

    Science.gov (United States)

    Koontz, Steve

    2017-01-01

    The space-flight ionizing radiation (IR) environment is dominated by very high-kinetic energy-charged particles with relatively smaller contributions from X-rays and gamma rays. The Earth's surface IR environment is not dominated by the natural radioisotope decay processes. Dr. Steven Koontz's lecture will provide a solid foundation in the basic engineering physics of space radiation environments, beginning with the space radiation environment on the International Space Station and moving outward through the Van Allen belts to cislunar space. The benefits and limitations of radiation shielding materials will also be summarized.

  19. Radiative cooling test facility and performance evaluation of 4-MIL aluminized polyvinyl fluoride and white-paint surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kruskopf, M.S.; Berdahl, P.; Martin, M.; Sakkal, F.; Sobolewski, M.

    1980-11-01

    A test facility designed to measure the amount of radiative cooling a specific material or assembly of materials will produce when exposed to the sky is described. Emphasis is placed upon assemblies which are specifically designed to produce radiative cooling and which therefore offer promise for the reduction of temperatures and/or humidities in occupied spaces. The hardware and software used to operate the facility are documented and the results of the first comprehensive experiments are presented. A microcomputer-based control/data acquisition system was employed to study the performance of two prototype radiator surfaces: 4-mil aluminized polyvinyl fluoride (PVF) and white painted surfaces set below polyethylene windscreens. The cooling rates for materials tested were determined and can be approximated by an equation (given). A computer model developed to simulate the cooling process is presented. (MCW)

  20. Statistical analysis of the surface figure of the James Webb Space Telescope

    Science.gov (United States)

    Lightsey, Paul A.; Chaney, David; Gallagher, Benjamin B.; Brown, Bob J.; Smith, Koby; Schwenker, John

    2012-09-01

    The performance of an optical system is best characterized by either the point spread function (PSF) or the optical transfer function (OTF). However, for system budgeting purposes, it is convenient to use a single scalar metric, or a combination of a few scalar metrics to track performance. For the James Webb Space Telescope, the Observatory level requirements were expressed in metrics of Strehl Ratio, and Encircled Energy. These in turn were converted to the metrics of total rms WFE and rms WFE within spatial frequency domains. The 18 individual mirror segments for the primary mirror segment assemblies (PMSA), the secondary mirror (SM), tertiary mirror (TM), and Fine Steering Mirror have all been fabricated. They are polished beryllium mirrors with a protected gold reflective coating. The statistical analysis of the resulting Surface Figure Error of these mirrors has been analyzed. The average spatial frequency distribution and the mirror-to-mirror consistency of the spatial frequency distribution are reported. The results provide insight to system budgeting processes for similar optical systems.

  1. Damage of natural stone tablets exposed to exhaust gas under laboratory conditions

    Science.gov (United States)

    Farkas, Orsolya; Szabados, György; Török, Ákos

    2016-04-01

    Natural stone tablets were exposed to exhaust gas under laboratory conditions to assess urban stone damage. Cylindrical test specimens (3 cm in diameter) were made from travertine, non-porous limestone, porous limestone, rhyolite tuff, sandstone, andesite, granite and marble. The samples were exposed to exhaust gas that was generated from diesel engine combustion (engine type: RÁBA D10 UTSLL 160, EURO II). The operating condition of the internal combustion engine was: 1300 r/m (app 50%). The exhaust gas was diverted into a pipe system where the samples were placed perpendicular to main flow for 1, 2, 4, 8 and 10 hours, respectively. The exhaust emission was measured by using AVL particulate measurement technology; filter paper method (AVL 415). The stone samples were documented and selective parameters were measured prior to and after exhaust gas exposure. Density, volume, ultrasonic pulse velocity, mineral composition and penetration depth of emission related particulate matter were recorded. The first results indicate that after 10 hours of exposure significant amount of particulate matter deposited on the stone surface independently from the surface properties and porosity. The black soot particles uniformly covered all types of stones, making hard to differentiate the specimens.

  2. Effect of precipitate on yield strength of ferritic/martensitic steel exposed to 650 .deg. C liquid sodium

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Tae Yong; Lee, Jeonghyeon; Kim, Ji Hyun [UNIST, Ulsan (Korea, Republic of); Shin, Sang Hun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2016-10-15

    Ferritic/martensitic steels(FMS) which are used as one of cladding and structure materials in UCFR, have high creep strength at 600~650°C, low expansion coefficient, and dimensional stability with irradiation-induced void swelling in circumstance of fast neutrons compared to austenitic stainless steel. However, as exposed to high temperature liquid sodium during the design life time (30 to 60 years), the surface of FMS experienced Cr-depletion and decarburization by dissolution of components into sodium and formed oxidations by reacting with sodium. This changes chemical compositions of inter-surface and effects on behavior of precipitations. This change can cause a degradation of mechanical strength of structure material of UCFR. The research about FMS on effects of long term exposure in liquid sodium at 650 °C involve analysis of yield strength by change of microstructure, solid solution hardening and precipitation hardening. It shows how this three parts occupy total yield strength respectively and change over time. In a specific procedure, the microstructure and the surface phenomenon of FMS (Gr. 92) that are exposed to liquid sodium at 650°C, 20 ppm oxygen and are aged in high pure Argon gas environment to express bulk have been investigated by using scanning electron microscope (SEM) and transmission electron microscope (TEM). When specimens were exposed to 650 °C liquid sodium for 1583, 3095 hours and Ar-gas 1601, 2973 hours, mechanical properties of materials were analyzed quantitatively. After experiment, NaCrO{sub 2} oxidation was formed on the surface of Gr.92 at sodium environment. Also, change of microstructure, dissolution of elements, and nucleation and growth of precipitation was raised. During exposed to high temperature at sodium or Ar-gas, annealed lath structure as well as coarsening of tempered martensite structure affects reduction of mechanical properties. And dissolution of elements results in reduction of solid solution hardening. This

  3. The mortality experience of a group of Newfoundland fluorspar miners exposed to Rn progeny

    International Nuclear Information System (INIS)

    Morrison, H.; Semenciw, R.; Mao, Y.; Wigle, D.

    1988-02-01

    A cohort study of the mortality experience (1950-1984) of 1,772 Newfoundland fluorspar miners occupationally exposed to high levels of radon daughters has been conducted using two control groups (surface workers and Newfoundland males). Observed numbers of cancers of the lung, salivary gland and buccal cavity/pharynx were significantly elevated among underground miners. A highly significant relationship was noted between radon daughter exposure and risk of dying of lung cancer; the small numbers of salivary gland (n = 2) and buccal cavity/pharynx cancers (n = 6) precluded meaningful analysis of dose-response. Also significantly elevated among underground miners were deaths from silicosis and pneumoconioses. No statistically significant excess was found for any cause of death among surface workers. Using external controls, attributable and relative risk coefficients for lung cancer were estimated as 6.3 per working level month per million person-years and 0.89 percent per working level month respectively. Attributable risk coefficients were similar to some, but not all related mining studies. Relative risk coefficients were highest for those first exposed attributable risks to non-smokers. Relative risks fell sharply with age at observation whereas attributable risks were lowest in the youngest and oldest age groups. Using the risk coefficients from the present study, a miner exposed for 30 years at 4 WLM per year from age 20 has a risk of 7,366 per 100,000 of dying of lung cancer by age 70 using the relative risk model and a risk of 6,371 per 100,000 using the attributable risk model. This compares to 3,740 per 100,000 for a non-exposed male. 85 refs

  4. The Effect of Topography on the Exposure of Airless Bodies to Space Radiation: Phobos Case Study

    Science.gov (United States)

    Stubbs, T. J.; Wang, Y.; Guo, J.; Schwadron, N.; Cooper, J. F.; Wimmer-Schweingruber, R. F.; Spence, H. E.; Jordan, A.; Sturner, S. J.; Glenar, D. A.; Wilson, J. K.

    2017-12-01

    The surfaces of airless bodies, such as the Moon and Phobos (innermost Martian moon), are directly exposed to the surrounding space environment, including energetic particle radiation from both the ever-present flux of galactic cosmic rays (GCRs) and episodic bursts of solar energetic particles (SEPs). Characterizing this radiation exposure is critical to our understanding of the evolution of these bodies from space weathering processes, such as radiation damage of regolith, radiolysis of organics and volatiles, and dielectric breakdown. Similarly, this also has important implications for the long-term radiation exposure of future astronauts and equipment on the surface. In this study, the focus is the influence of Phobian topography on the direct exposure of Phobos to space radiation. For a given point on its surface, this exposure depends on: (i) the solid angle subtended by the sky, (ii) the solid angle of the sky blocked by Mars, and (iii) the energy and angular distributions of ambient energetic particle populations. The sky solid angle, determined using the elevation of the local horizon calculated from a digital elevation model (DEM), can be significantly reduced around topographic lows, such as crater floors, or increased near highs like crater rims. The DEM used in this study was produced using images from the Mars Express High Resolution Stereo Camera (HRSC), and has the highest available spatial resolution ( 100m). The proximity of Phobos to Mars means the Martian disk appears large in the Phobian sky, but this only effects the moon's near side due its tidally locked orbit. Only isotropic distributions of energetic particles are initially considered, which is typically a reasonable assumption for GCRs and sometimes for SEPs. Observations of the radiation environments on Mars by Curiosity's Radiation Assessment Detector (RAD), and the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) onboard the Lunar Reconnaissance Orbiter (LRO) at the Moon

  5. Sterilization of space hardware.

    Science.gov (United States)

    Pflug, I. J.

    1971-01-01

    Discussion of various techniques of sterilization of space flight hardware using either destructive heating or the action of chemicals. Factors considered in the dry-heat destruction of microorganisms include the effects of microbial water content, temperature, the physicochemical properties of the microorganism and adjacent support, and nature of the surrounding gas atmosphere. Dry-heat destruction rates of microorganisms on the surface, between mated surface areas, or buried in the solid material of space vehicle hardware are reviewed, along with alternative dry-heat sterilization cycles, thermodynamic considerations, and considerations of final sterilization-process design. Discussed sterilization chemicals include ethylene oxide, formaldehyde, methyl bromide, dimethyl sulfoxide, peracetic acid, and beta-propiolactone.

  6. Surface temperature and distortion of optical elements exposed to high power synchrotron radiation beams

    International Nuclear Information System (INIS)

    Mourikis, S.; Jark, W.; Koch, E.E.; Saile, V.

    1989-01-01

    Mirrors made of various materials have been investigated under surface power densities of approximately 1--2 W/mm 2 emitted by a powerful hybrid wiggler installed in the 5.3-GeV DORIS storage ring. Thermal inhomogeneities and deformations at surfaces with a height resolution of 50 nm have been determined quantitatively. The only material withstanding these power levels without a significant deformation is SiC. Conventional cooling geometries are found to be useless for a reduction of the surface distortion

  7. Space weather in the EU’s FP7 Space Theme

    Directory of Open Access Journals (Sweden)

    Chiarini Paola

    2013-11-01

    Full Text Available Technological infrastructures in space and on ground provide services on which modern society and economies rely. Space weather related research is funded under the 7th Framework Programme for Research and Innovation (FP7 of the European Union in response to the need of protecting such critical infrastructures from the damage which could be caused by extreme space weather events. The calls for proposals published under the topic “Security of space assets from space weather events” of the FP7 Space Theme aimed to improve forecasts and predictions of disruptive space weather events as well as identify best practices to limit the impacts on space- and ground-based infrastructures and their data provision. Space weather related work was also funded under the topic “Exploitation of space science and exploration data”, which aims to add value to space missions and Earth-based observations by contributing to the effective scientific exploitation of collected data. Since 2007 a total of 20 collaborative projects have been funded, covering a variety of physical phenomena associated with space weather, from ionospheric disturbances and scintillation, to geomagnetically induced currents at Earth’s surface, to coronal mass ejections and solar energetic particles. This article provides an overview of the funded projects, touching upon some results and referring to specific websites for a more exhaustive description of the projects’ outcomes.

  8. Automation of Space Inventory Management

    Science.gov (United States)

    Fink, Patrick W.; Ngo, Phong; Wagner, Raymond; Barton, Richard; Gifford, Kevin

    2009-01-01

    This viewgraph presentation describes the utilization of automated space-based inventory management through handheld RFID readers and BioNet Middleware. The contents include: 1) Space-Based INventory Management; 2) Real-Time RFID Location and Tracking; 3) Surface Acoustic Wave (SAW) RFID; and 4) BioNet Middleware.

  9. Mesoscopic nonequilibrium thermodynamics of solid surfaces and interfaces with triple junction singularities under the capillary and electromigration forces in anisotropic three-dimensional space.

    Science.gov (United States)

    Ogurtani, Tarik Omer

    2006-04-14

    A theory of irreversible thermodynamics of curved surfaces and interfaces with triple junction singularities is elaborated to give a full consideration of the effects of the specific surface Gibbs free energy anisotropy in addition to the diffusional anisotropy, on the morphological evolution of surfaces and interfaces in crystalline solids. To entangle this intricate problem, the internal entropy production associated with arbitrary virtual displacements of triple junction and ordinary points on the interfacial layers, embedded in a multicomponent, multiphase, anisotropic composite continuum system, is formulated by adapting a mesoscopic description of the orientation dependence of the chemical potentials in terms of the rotational degree of freedom of individual microelements. The rate of local internal entropy production resulted generalized forces and conjugated fluxes not only for the grain boundary triple junction transversal and longitudinal movements, but also for the ordinary points. The natural combination of the mesoscopic approach coupled with the rigorous theory of irreversible thermodynamics developed previously by the global entropy production hypothesis yields a well-posed, nonlinear, moving free-boundary value problem in two-dimensional (2D) space, as a unified theory. The results obtained for 2D space are generalized into the three-dimensional continuum by utilizing the invariant properties of the vector operators in connection with the descriptions of curved surfaces in differential geometry. This mathematical model after normalization and scaling procedures may be easily adapted for computer simulation studies without introducing any additional phenomenological system parameters (the generalized mobilities), other than the enlarged concept of the surface stiffness.

  10. Boron nitride protective coating of beryllium window surfaces

    International Nuclear Information System (INIS)

    Gmuer, N.F.

    1991-12-01

    The use of beryllium windows on white synchrotron radiation beamlines is constrained by the fact that the downstream surfaces of these windows should not be exposed to ambient atmosphere. They should, rather, be protected by a tail-piece under vacuum or containing helium atmosphere. This tailpiece is typically capped by Kapton (3M Corporation, St. Paul, MN) or aluminum foil. The reason for such an arrangement is due to the health risk associated with contaminants (BeO) which from on the exposed beryllium window surfaces and due to possible loss of integrity of the windows. Such a tail-piece may, however, add unwanted complications to the beamline in the form of vacuum pumps or helium supplies and their related monitoring systems. The Kapton windows may burn through in the case of high intensity beams and lower energy radiation may be absorbed in the case of aluminum foil windows. A more ideal situation would be to provide a coating for the exposed beryllium window surface, sealing it off from the atmosphere, thus preventing contamination and/or degradation of the window, and eliminating the need for helium or vacuum equipment

  11. China Accomplished Its First Space Rendezvous and Docking

    Institute of Scientific and Technical Information of China (English)

    Chen Xiaoli

    2011-01-01

    At 1:36 am on November 3,China's Shenzhou 8 unmanned spaceship and Tiangong 1 space lab spacecraft accomplished the country's first space docking procedure and coupling in space at more than 343km above Earth's surface,marking a great leap in China's space program.

  12. The corrosion behavior of steel exposed to a DC electric field in the simulated wet-dry cyclic environment

    Energy Technology Data Exchange (ETDEWEB)

    Dai, Nianwei [Shanghai Key Laboratory of Materials Protection and Advanced Materials in Electric Power, Shanghai University of Electric Power, Shanghai 200090 (China); Department of Materials Science, Fudan University, Shanghai 200433 (China); Chen, Qimeng [Shanghai Key Laboratory of Materials Protection and Advanced Materials in Electric Power, Shanghai University of Electric Power, Shanghai 200090 (China); Zhang, Junxi, E-mail: zhangjunxi@shiep.edu.cn [Shanghai Key Laboratory of Materials Protection and Advanced Materials in Electric Power, Shanghai University of Electric Power, Shanghai 200090 (China); Zhang, Xin; Ni, Qingzhao [Shanghai Key Laboratory of Materials Protection and Advanced Materials in Electric Power, Shanghai University of Electric Power, Shanghai 200090 (China); Jiang, Yiming; Li, Jin [Department of Materials Science, Fudan University, Shanghai 200433 (China)

    2017-05-01

    The corrosion of steel exposed under a direct current (DC) electric field during simulated wet-dry cycles was investigated using weight gain, electrochemical tests, X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The results show that the steel exposed to a DC electric field exhibits a higher corrosion rate than those exposed under no DC electric field. The higher the DC electric field intensity, the higher the corrosion rate of steel. The XRD and SEM analyses indicate that more γ-FeOOH and cracks appear in the rust formed on steel exposed to the DC electric field. The porous γ-FeOOH, formation and expansion of cracks enhance the transfer of oxygen and corrosion products, thereby accelerating corrosion of steel exposed to DC electric field. - Highlights: • Effect of DC electric field on the corrosion of steel in wet/dry cycles was studied. • DC electric field accelerates the steel corrosion in wet/dry cyclic processes. • More γ-FeOOH is generated on the surface of steel exposed under a DC electric field. • More cracks appear in the rust formed on the steel exposed under a DC electric filed.

  13. The corrosion behavior of steel exposed to a DC electric field in the simulated wet-dry cyclic environment

    International Nuclear Information System (INIS)

    Dai, Nianwei; Chen, Qimeng; Zhang, Junxi; Zhang, Xin; Ni, Qingzhao; Jiang, Yiming; Li, Jin

    2017-01-01

    The corrosion of steel exposed under a direct current (DC) electric field during simulated wet-dry cycles was investigated using weight gain, electrochemical tests, X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The results show that the steel exposed to a DC electric field exhibits a higher corrosion rate than those exposed under no DC electric field. The higher the DC electric field intensity, the higher the corrosion rate of steel. The XRD and SEM analyses indicate that more γ-FeOOH and cracks appear in the rust formed on steel exposed to the DC electric field. The porous γ-FeOOH, formation and expansion of cracks enhance the transfer of oxygen and corrosion products, thereby accelerating corrosion of steel exposed to DC electric field. - Highlights: • Effect of DC electric field on the corrosion of steel in wet/dry cycles was studied. • DC electric field accelerates the steel corrosion in wet/dry cyclic processes. • More γ-FeOOH is generated on the surface of steel exposed under a DC electric field. • More cracks appear in the rust formed on the steel exposed under a DC electric filed.

  14. Survivability of bare, individual Bacillus subtilis spores to high-velocity surface impact: Implications for microbial transfer through space

    Science.gov (United States)

    Barney, Brandon L.; Pratt, Sara N.; Austin, Daniel E.

    2016-06-01

    Laboratory experiments show that endospores of Bacillus subtilis survive impact against a solid surface at velocities as high as 299 ±28 m/s. During impact, spores experience and survive accelerations of at least 1010 m/s2. The spores were introduced into a vacuum chamber using an electrospray source and accelerated to a narrow velocity distribution by entrainment in a differentially pumped gas flow. Different velocity ranges were studied by modifying the gas flow parameters. The spores were electrically charged, allowing direct measurement of the velocity of each spore as it passed through an image charge detector prior to surface impact. Spores impacted a glass surface and were collected for subsequent analysis by culturing. Most spores survived impact at all measured velocities. These experiments differ fundamentally from other studies that show either shock or impact survivability of bacteria embedded within or on the surface of a projectile. Bacteria in the present experiments undergo a single interaction with a solid surface at the full impact velocity, in the absence of any other effects such as cushioning due to microbe agglomerations, deceleration due to air or vapor, or transfer of impact shock through solid or liquid media. During these full-velocity impact events, the spores experience extremely high decelerations. This study is the first reported instance of accelerations of this magnitude experienced during a bacteria impact event. These results are discussed in the context of potential transfer of viable microbes in space and other scenarios involving surface impacts at high velocities.

  15. Interaction of solutions containing phenothiazines exposed to laser radiation with materials surfaces, in view of biomedical applications

    NARCIS (Netherlands)

    Simon, A.; Alexandru, T.; Boni, M.; Damian, V.; Stoicu, A.; Dutschk, Victoria; Pascu, M.L.

    2014-01-01

    Phenothiazine drugs - chlorpromazine (CPZ), promazine (PZ) and promethazine (PMZ) - were exposed to 266 nm (fourth harmonic of the Nd:YAG pulsed laser radiation) in order to be modified at molecular level and to produce an enhancement of their antibacterial activity. The irradiated samples were

  16. Lunar rock surfaces as detectors of solar processes

    International Nuclear Information System (INIS)

    Hartung, J.B.; Hunter College, New York, NY)

    1980-01-01

    Lunar rock surfaces exposed at or just below the lunar surface are considered as detectors of the solar wind, solar flares and solar-derived magnetic fields through their interactions with galactic cosmic rays. The degradation of the solar detector capabilities of lunar surface rocks by meteoroid impact erosion, accreta deposition, loose dust, and sputtering, amorphous layer formation and accelerated diffusion due to solar particles and illumination is discussed, and it is noted that the complex interactions of factors affecting the outer micron of exposed surface material has so far prevented the development of a satisfactory model for a particle detector on the submicron scale. Methods for the determination of surface exposure ages based on the accumulation of light solar wind noble gases, Fe and Mg, impact craters, solar flare tracks, and cosmogenic Kr isotopes are examined, and the systematic variations in the ages determined by the various clocks are discussed. It is concluded that a means of obtaining satisfactory quantitative rate or flux data has not yet been established

  17. Space-Charge-Limited Emission Models for Particle Simulation

    Science.gov (United States)

    Verboncoeur, J. P.; Cartwright, K. L.; Murphy, T.

    2004-11-01

    Space-charge-limited (SCL) emission of electrons from various materials is a common method of generating the high current beams required to drive high power microwave (HPM) sources. In the SCL emission process, sufficient space charge is extracted from a surface, often of complicated geometry, to drive the electric field normal to the surface close to zero. The emitted current is highly dominated by space charge effects as well as ambient fields near the surface. In this work, we consider computational models for the macroscopic SCL emission process including application of Gauss's law and the Child-Langmuir law for space-charge-limited emission. Models are described for ideal conductors, lossy conductors, and dielectrics. Also considered is the discretization of these models, and the implications for the emission physics. Previous work on primary and dual-cell emission models [Watrous et al., Phys. Plasmas 8, 289-296 (2001)] is reexamined, and aspects of the performance, including fidelity and noise properties, are improved. Models for one-dimensional diodes are considered, as well as multidimensional emitting surfaces, which include corners and transverse fields.

  18. UV laser-ablated surface textures as potential regulator of cellular response.

    Science.gov (United States)

    Chandra, Prafulla; Lai, Karen; Sung, Hak-Joon; Murthy, N Sanjeeva; Kohn, Joachim

    2010-06-01

    Textured surfaces obtained by UV laser ablation of poly(ethylene terephthalate) films were used to study the effect of shape and spacing of surface features on cellular response. Two distinct patterns, cones and ripples with spacing from 2 to 25 μm, were produced. Surface features with different shapes and spacings were produced by varying pulse repetition rate, laser fluence, and exposure time. The effects of the surface texture parameters, i.e., shape and spacing, on cell attachment, proliferation, and morphology of neonatal human dermal fibroblasts and mouse fibroblasts were studied. Cell attachment was the highest in the regions with cones at ∼4 μm spacing. As feature spacing increased, cell spreading decreased, and the fibroblasts became more circular, indicating a stress-mediated cell shrinkage. This study shows that UV laser ablation is a useful alternative to lithographic techniques to produce surface patterns for controlling cell attachment and growth on biomaterial surfaces.

  19. Arc-textured metal surfaces for high thermal emittance space radiators

    International Nuclear Information System (INIS)

    Banks, B.A.; Rutledge, S.K.; Mirtich, M.J.; Behrend, T.; Hotes, D.; Kussmaul, M.; Barry, J.; Stidham, C.; Stueber, T.; DiFilippo, F.

    1994-01-01

    Carbon arc electrical discharges struck across the surfaces of metals such as Nb-1% Zr, alter the morphology to produce a high thermal emittance surface. Metal from the surface and carbon from the arc electrode vaporize during arcing, and then condense on the metal surface to produce a microscopically rough surface having a high thermal emittance. Quantitative spectral reflectance measurements from 0.33 to 15 μm were made on metal surfaces which were carbon arc treated in an inert gas environment. The resulting spectral reflectance data were then used to calculate thermal emittance as a function of temperature for various methods of arc treatment. The results of arc treatment on various metals are presented for both ac and dc arcs. Surface characterization data, including thermal emittance as a function of temperature, scanning electron microscopy, and atomic oxygen durability, are also presented. Ac arc texturing was found to increase the thermal emittance at 800 K from 0.05. to 0.70

  20. Space remote sensing systems an introduction

    CERN Document Server

    Chen, H S

    1985-01-01

    Space Remote Sensing Systems: An Introduction discusses the space remote sensing system, which is a modern high-technology field developed from earth sciences, engineering, and space systems technology for environmental protection, resource monitoring, climate prediction, weather forecasting, ocean measurement, and many other applications. This book consists of 10 chapters. Chapter 1 describes the science of the atmosphere and the earth's surface. Chapter 2 discusses spaceborne radiation collector systems, while Chapter 3 focuses on space detector and CCD systems. The passive space optical rad

  1. Effect of polar and non-polar surfaces of ZnO nanostructures on photocatalytic properties

    International Nuclear Information System (INIS)

    Yang Jinghai; Wang Jian; Li Xiuyan; Lang Jihui; Liu Fuzhu; Yang Lili; Zhai Hongju; Gao Ming; Zhao Xiaoting

    2012-01-01

    Highlights: ► Large-scale arrayed ZnO nanocrystals including ZnO hexagonal platforms and hamburger-like samples have been successfully fabricated by a simple hydrothermal method. ► ZnO with hexagonal platform-like morphology exhibited higher photocatalytic activity compared with that of the hamburger-like ZnO nanostructures. ► The theories of expose surfaces and oxygen vacancies were utilized to explain the photocatalytic mechanism. - Abstract: Large-scale arrayed ZnO nanocrystals with two different expose surfaces, including ZnO hexagonal nanoplatforms with the major expose plane of (0 0 0 1) and hamburger-like samples with the nonpolar planes of {101 ¯ 0} mainly exposed, were successfully fabricated by a simple hydrothermal method. Mechanisms for compare the photocatalytic activity of two typical ZnO nanostructures were systematic explained as the key point in the paper. Compared with the hamburger-like ZnO nanostructures, the ZnO with hexagonal platform-like morphology exhibited improved ability on the photocatalytic degradation of Rhodamine B (RhB) in aqueous solution under UV radiation. The relative higher photocatalytic activity of the ZnO hexagonal nanoplatforms was attributed to the exposed polar surfaces and the content of oxygen vacancy on the nanostructures surface. The Zn-terminated (0 0 0 1) polar face and the surface defects are facile to adsorb O 2− and OH − ions, resulting in a greater production rate of O 2 · − and OH· − , hence promoting the photocatalysis reaction.

  2. Few helium atoms in quasi two-dimensional space

    International Nuclear Information System (INIS)

    Kilic, Srecko; Vranjes, Leandra

    2003-01-01

    Two, three and four 3 He and 4 He atoms in quasi two-dimensional space above graphite and cesium surfaces and in 'harmonic' potential perpendicular to the surface have been studied. Using some previously examined variational wave functions and the Diffusion Monte Carlo procedure, it has been shown that all molecules: dimers, trimers and tetramers, are bound more strongly than in pure two- and three-dimensional space. The enhancement of binding with respect to unrestricted space is more pronounced on cesium than on graphite. Furthermore, for 3 He 3 ( 3 He 4 ) on all studied surfaces, there is an indication that the configuration of a dimer and a 'free' particle (two dimers) may be equivalently established

  3. Vulnerability assessment of a space based weapon platform electronic system exposed to a thermonuclear weapon detonation

    Science.gov (United States)

    Perez, C. L.; Johnson, J. O.

    Rapidly changing world events, the increased number of nations with inter-continental ballistic missile capability, and the proliferation of nuclear weapon technology will increase the number of nuclear threats facing the world today. Monitoring these nation's activities and providing an early warning and/or intercept system via reconnaissance and surveillance satellites and space based weapon platforms is a viable deterrent against a surprise nuclear attack. However, the deployment of satellite and weapon platform assets in space will subject the sensitive electronic equipment to a variety of natural and man-made radiation environments. These include Van Allen Belt protons and electrons; galactic and solar flare protons; and neutrons, gamma rays, and x-rays from intentionally detonated fission and fusion weapons. In this paper, the MASH vl.0 code system is used to estimate the dose to the critical electronics components of an idealized space based weapon platform from neutron and gamma-ray radiation emitted from a thermonuclear weapon detonation in space. Fluence and dose assessments were performed for the platform fully loaded, and in several stages representing limited engagement scenarios. The results indicate vulnerabilities to the Command, Control, and Communication bay instruments from radiation damage for a nuclear weapon detonation for certain source/platform orientations. The distance at which damage occurs will depend on the weapon yield (n,(gamma)/kiloton) and size (kilotons).

  4. Relationship of CD86 surface marker expression and cytotoxicity on dendritic cells exposed to chemical allergen

    International Nuclear Information System (INIS)

    Hulette, Ben C.; Ryan, Cindy A.; Gildea, Lucy A.; Gerberick, G. Frank

    2005-01-01

    Human peripheral blood-derived dendritic cells (DC) respond to a variety of chemical allergens by up-regulating expression of the co-stimulatory molecule CD86. It has been postulated that this measure might provide the basis for an in vitro alternative approach for the identification of skin sensitizing chemicals. We recently reported that DC, exposed in culture to the highest non-cytotoxic concentrations of various chemical allergens, displayed marginal up-regulation of membrane CD86 expression; the interpretation being that such changes were insufficiently sensitive for the purposes of hazard identification. For the work presented here, immature DC were derived from human monocytes and treated with the chemical allergens 2,4-dinitrobenzenesulfonic acid (DNBS), nickel sulfate (NiSO 4 ), p-phenylenediamine (PPD), Bandrowski's base (BB), hydroquinone (HQ) and propyl gallate (PG) for 48 h at concentrations which induced both no to slight to moderate cytotoxicity. For comparison, DC were treated with the irritants sodium dodecyl sulfate (SDS), benzoic acid (BA), and benzalkonium chloride (BZC) at concentrations resulting in comparable levels of cytotoxicity. CD86 expression, as measured by flow cytometry, was consistently up-regulated (ranging from 162 to 386% control) on DC treated with concentrations of chemical allergens that induced approximately 10-15% cytotoxicity. The irritants BA and BZC did not induce up-regulation of CD86 expression when tested at concentrations that induced similar levels of cytotoxicity. SDS, however, up-regulated CD86 expression to 125-138% of control in 2/4 preparations when tested at concentrations which induced similar toxicity. Our results confirm that chemical allergens up-regulate CD86 expression on blood-derived DC and illustrate further that up-regulation of CD86 surface marker expression is more robust when DC are treated with concentrations of chemical allergen that induce slight to moderate cytotoxicity

  5. Temperature and entropy of Schwarzschild-de Sitter space-time

    International Nuclear Information System (INIS)

    Shankaranarayanan, S.

    2003-01-01

    In the light of recent interest in quantum gravity in de Sitter space, we investigate semiclassical aspects of four-dimensional Schwarzschild-de Sitter space-time using the method of complex paths. The standard semiclassical techniques (such as Bogoliubov coefficients and Euclidean field theory) have been useful to study quantum effects in space-times with single horizons; however, none of these approaches seem to work for Schwarzschild-de Sitter space-time or, in general, for space-times with multiple horizons. We extend the method of complex paths to space-times with multiple horizons and obtain the spectrum of particles produced in these space-times. We show that the temperature of radiation in these space-times is proportional to the effective surface gravity--the inverse harmonic sum of surface gravity of each horizon. For the Schwarzschild-de Sitter space-time, we apply the method of complex paths to three different coordinate systems--spherically symmetric, Painleve, and Lemaitre. We show that the equilibrium temperature in Schwarzschild-de Sitter space-time is the harmonic mean of cosmological and event horizon temperatures. We obtain Bogoliubov coefficients for space-times with multiple horizons by analyzing the mode functions of the quantum fields near the horizons. We propose a new definition of entropy for space-times with multiple horizons, analogous to the entropic definition for space-times with a single horizon. We define entropy for these space-times to be inversely proportional to the square of the effective surface gravity. We show that this definition of entropy for Schwarzschild-de Sitter space-time satisfies the D-bound conjecture

  6. SP-100 nuclear space power systems with application to space commercialization

    International Nuclear Information System (INIS)

    Smith, J.M.

    1988-01-01

    The purpose of this paper is to familiarize the Space Commercialization Community with the status and characteristics of the SP-100 space nuclear power system. The program is a joint undertaking by the Department of Defense, the Department of Energy and NASA. The goal of the program is to develop, validate, and demonstrate the technology for space nuclear power systems in the range of 10 to 1000 kWe electric for use in the future civilian and military space missions. Also discussed are mission applications which are enhanced and/or enabled by SP-100 technology and how this technology compares to that of more familiar solar power systems. The mission applications include earth orbiting platforms and lunar/Mars surface power

  7. Observations of suppressed retention and blistering for tungsten exposed to deuterium-helium mixture plasmas

    International Nuclear Information System (INIS)

    Miyamoto, M.; Morito, S.; Ono, K.; Nishijima, D.; Doerner, R.P.; Baldwin, M.J.; Hanna, J.; Ueda, Y.; Kurishita, H.

    2009-01-01

    Blister formation and D retention in W have been investigated for low energy (∼55 ± 15 eV), high flux (∼10 22 m -2 s -1 ), high fluence (≤4.5 x 10 26 m -2 ) ion bombardment at moderate temperature (∼573 K) in mixed species D+He plasmas in the linear divertor plasma simulator PISCES-A. The amount of D retained in W is found to decrease significantly when compared with that in W exposed to pure D plasmas, as measured with high resolution thermal desorption spectroscopy. Scanning electron microscopy observations reveal the suppression of the blisters, a surface feature known to drive up retention, in the D + He mixture plasma exposed W samples. Reduced D retention is accompanied by the formation of nano-sized high density He bubbles in the near surface, observed with a transmission electron microscope (TEM). It is believed that the nano-bubbles act as a diffusion barrier to implanted D atoms and consequently reduce the amount of uptake in the W material. This newly observed effect implies that current predictions of D retention in W, in actual fusion devices, may be overestimated, since there will be He ash in fusion plasma. Toughness enhanced, fine-grained (grain size of ∼1 μm) W-TiC samples, exposed to pure D plasma conditions, also show little or no evidence of blistering. The measured D retention in the W-TiC samples was approximately 1 x 10 19 D m -2 corresponding to about 2 x 10 -7 of the implanted D fluence, and is very low compared with the retention in pure stress relieved W, which exhibited surface blisters and had a D retention of about 1 x 10 21 D m -2 .

  8. 46 CFR 108.409 - Location and spacing of tubing in pneumatic fire detection system.

    Science.gov (United States)

    2010-10-01

    ... detection system. 108.409 Section 108.409 Shipping COAST GUARD, DEPARTMENT OF HOMELAND SECURITY (CONTINUED... and spacing of tubing in pneumatic fire detection system. (a) All tubing in a pneumatic fire detection... exposed in the space. (c) A pneumatic fire detection system must be set to activate after approximately a...

  9. Switching between pitch surfaces

    DEFF Research Database (Denmark)

    Rago, Vincenzo; Silva, João R; Brito, João

    2018-01-01

    Soccer training and completion is conventionally practiced on natural grass (NG) or artificial turf (AT). Recently, AT pitches for training / competition, and of unstable surfaces for injury prevention training has increased. Therefore, soccer players are frequently exposed to variations in pitch...... surface during either training or competition. These ground changes may impact physical and physiological responses, adaptations as well as the injury. The aim of this review was to summarize the acute physical and physiological responses, chronic adaptations, and injury risk associated with exercising...... on different pitch surfaces in soccer. Eligible studies were published in English, had pitch surface as an independent variable, and had physical, physiological or epidemiological information as outcome variables. Specific data extracted from the articles included the training response, training adaptations...

  10. Mutation of exposed hydrophobic amino acids to arginine to increase protein stability

    OpenAIRE

    Strub, Caroline; Alies, Carole; Lougarre, Andrée; Ladurantie, Caroline; Czaplicki, Jerzy; Fournier, Didier

    2004-01-01

    Abstract Background One strategy to increase the stability of proteins is to reduce the area of water-accessible hydrophobic surface. Results In order to test it, we replaced 14 solvent-exposed hydrophobic residues of acetylcholinesterase by arginine. The stabilities of the resulting proteins were tested using denaturation by high temperature, organic solvents, urea and by proteolytic digestion. Conclusion Altough the mutational effects were rather small, this strategy proved to be successful...

  11. Space Flight Experiments to Measure Polymer Erosion and Contamination on Spacecraft

    Science.gov (United States)

    Lillis, Maura C.; Youngstrom, Erica E.; Marx, Laura M.; Hammerstrom, Anne M.; Finefrock, Katherine D.; Youngstrom, Christiane A.; Kaminski, Carolyn; Fine, Elizabeth S.; Hunt, Patricia K.; deGroh, Kim K.

    2002-01-01

    Atomic oxygen erosion and silicone contamination are serious issues that could damage or destroy spacecraft components after orbiting for an extended period of time, such as on a space station or satellite. An experiment, the Polymer Erosion And Contamination Experiment (PEACE) will be conducted to study the effects of atomic oxygen (AO) erosion and silicone contamination, and it will provide information and contribute to a solution for these problems. PEACE will fly 43 different polymer materials that will be analyzed for AO erosion effects through two techniques: mass loss measurement and recession depth measurement. Pinhole cameras will provide information about the arrival direction of AO, and silicone contamination pinhole cameras will identify the source of silicone contamination on a spacecraft. All experimental hardware will be passively exposed to AO for up to two weeks in the actual space environment when it flies in the bay of a space shuttle. A second set of the PEACE Polymers is being exposed to the space environment for erosion yield determination as part of a second experiment, Materials International Space Station Experiment (MISSE). MISSE is a collaboration between several federal agencies and aerospace companies. During a space walk on August 16, 2001, MISSE was attached to the outside of the International Space Station (ISS) during an extravehicular activity (EVA), where it began its exposure to AO for approximately 1.5 years. The PEACE polymers, therefore, will be analyzed after both short-term and long-term AO exposures for a more complete study of AO effects.

  12. Preliminary analysis of accelerated space flight ionizing radiation testing

    Science.gov (United States)

    Wilson, J. W.; Stock, L. V.; Carter, D. J.; Chang, C. K.

    1982-01-01

    A preliminary analysis shows that radiation dose equivalent to 30 years in the geosynchronous environment can be accumulated in a typical composite material exposed to space for 2 years or less onboard a spacecraft orbiting from perigee of 300 km out to the peak of the inner electron belt (approximately 2750 km). Future work to determine spacecraft orbits better tailored to materials accelerated testing is indicated. It is predicted that a range of 10 to the 9th power to 10 to the 10th power rads would be accumulated in 3-6 mil thick epoxy/graphite exposed by a test spacecraft orbiting in the inner electron belt. This dose is equivalent to the accumulated dose that this material would be expected to have after 30 years in a geosynchronous orbit. It is anticipated that material specimens would be brought back to Earth after 2 years in the radiation environment so that space radiation effects on materials could be analyzed by laboratory methods.

  13. Drawing Millions of Spaces

    DEFF Research Database (Denmark)

    Brabrand, Helle

    2017-01-01

    a flat surface in actual space for projection of line-, photo-, and video effects, and then, out of this surface-context, provoke a participator to move and extract different atmospheric perspectives. Presently, the work is presented as a video. In The Art-Architecture Complex Hal Foster criticizes what...... of process - movement - time. Asking very basic architectural questions, his focus is on elevation, on what happens to your body when the elevation is shifting: how do you cut into space, gather the land in a volume, and hold that volume? Serra’s concern is moving body-space experiences: ‘when you face...... a concave shape, the whole breadth of the curvilinear volume opens up in front of you; but once you walk around the edge, it changes to an opaque convexity that reveals itself only through walking – you can’t see the openness of the field or how the volume sucks into it. Just turning the corner opens up...

  14. MESSENGER, MErcury: Surface, Space ENvironment, GEochemistry, and Ranging; A Mission to Orbit and Explore the Planet Mercury

    Science.gov (United States)

    1999-01-01

    MESSENGER is a scientific mission to Mercury. Understanding this extraordinary planet and the forces that have shaped it is fundamental to understanding the processes that have governed the formation, evolution, and dynamics of the terrestrial planets. MESSENGER is a MErcury Surface, Space ENvironment, GEochemistry and Ranging mission to orbit Mercury for one Earth year after completing two flybys of that planet following two flybys of Venus. The necessary flybys return significant new data early in the mission, while the orbital phase, guided by the flyby data, enables a focused scientific investigation of this least-studied terrestrial planet. Answers to key questions about Mercury's high density, crustal composition and structure, volcanic history, core structure, magnetic field generation, polar deposits, exosphere, overall volatile inventory, and magnetosphere are provided by an optimized set of miniaturized space instruments. Our goal is to gain new insight into the formation and evolution of the solar system, including Earth. By traveling to the inner edge of the solar system and exploring a poorly known world, MESSENGER fulfills this quest.

  15. Modeling of 3d Space-time Surface of Potential Fields and Hydrogeologic Modeling of Nuclear Waste Disposal Sites

    Science.gov (United States)

    Shestopalov, V.; Bondarenko, Y.; Zayonts, I.; Rudenko, Y.

    Introduction After the Chernobyl Nuclear Power Plant (CNPP) disaster (04.26.1986) a huge amount (over 2000 sq. km) of nuclear wastes appeared within so-called "Cher- nobyl Exclusion Zone" (CEZ). At present there are not enough storage facilities in the Ukraine for safe disposal of nuclear wastes and hazardous chemical wastes. The urgent problem now is safe isolation of these dangerous wastes. According to the developed state program of radioactive waste management, the construction of a na- tional storage facility of nuclear wastes is planned. It is also possible to create regional storage facilities for hazardous chemical wastes. The region of our exploration cov- ers the eastern part of the Korosten Plutone and its slope, reaching the CNPP. 3D Space-Time Surface Imaging of Geophysical Fields. There are only three direct meth- ods of stress field reconstruction in present practice, namely the field investigations based on the large-scale fracturing tests, petrotectonic and optical polarization meth- ods. Unfortunately, all these methods are extremely laborious and need the regular field tests, which is difficult to conduct in the areas of anisotropic rock outcrops. A compilation of magnetic and gravity data covering the CNPP area was carried out as a prelude to an interpretation study. More than thirty map products were generated from magnetic, gravity and geodesy data to prepare the 3D Space-Time Surface Images (3D STSI). Multi-layer topography and geophysic surfaces included: total magnetic intensity, isostatically-corrected Bouguer gravity, aspect and slope, first and second derivatives, vertical and horizontal curvature, histogram characteristics and space cor- relation coefficients between the gradient fields. Many maps shows the first and sec- ond derivatives of the potential fields, with the results of lineament (edge) structure detection superimposed. The lineament or edges of the potential fields are located from maximal gradient in many directions

  16. Reduction of surface erosion in fusion reactors

    International Nuclear Information System (INIS)

    Rossing, T.D.; Das, S.K.; Kaminsky, M.

    1976-01-01

    Some of the major processes leading to surface erosion in fusion reactors are reviewed briefly, including blistering by implanted gas, sputtering by ions, atoms, and neutrons, and vaporization by local heating. Surface erosion affects the structural integrity and limits the lifetime of reactor components exposed to plasma radiation. In addition, some of the processes leading to surface erosion also cause the release of plasma contaminants. Methods proposed to reduce surface erosion have included control of surface temperature, selection of materials with a favorable microstructure, chemical and mechanical treatment of surfaces, and employment of protective surface coatings, wall liners, and divertors. The advantages and disadvantages of some of these methods are discussed

  17. Laughter and collective awareness: The cinema auditorium as public space

    Directory of Open Access Journals (Sweden)

    Julian Hanich

    2014-12-01

    Full Text Available This article looks at how the collective experience of laughter in the movie theater is related to the idea of the cinema as a public space. Through the nonverbal expression of laughter the audience ‘constructs’ a public space the viewers may not have been aware of to the same degree prior to the collective public expression. Moreover, the public space created through laughter allows for an expedient type of monitoring: inappropriate laughter may be exposed in front of others. With viewers who laugh approvingly about racist violence or misogynist jokes, we can easily lay bare the ethical implications.

  18. Space optical materials and space qualification of optics; Proceedings of the Meeting, Orlando, FL, Mar. 30, 31, 1989

    Science.gov (United States)

    Hale, Robert R.

    1989-10-01

    The present conference on space optical materials discusses current metals and nonmetals-related processing R&D efforts, investigations of space optical effects, and the spaceborne qualification of optical components and systems. Attention is given to CVD SiC for optical applications, optical materials for space-based lasers, the high-efficiency acoustooptic and optoelectronic crystalline material Tl3AsSe3, HIPed Be for low-scatter cryogenic optics, durable solar-reflective surfacing for Be optics, thermal effects on Be mirrors, contamination effects on optical surfaces in the monolayer regime, and IR background signature survey experiment results. Also discussed are the contamination-control program for the EUE instrument, an optical multipass radiation system for the heating of levitated samples, optical sample-position sensing for electrostatic levitation, and the qualification of space lighting systems.

  19. In search of the structure of human olfactory space

    Directory of Open Access Journals (Sweden)

    Alexei eKoulakov

    2011-09-01

    Full Text Available We analyze the responses of human observers to an ensemble of monomolecular odorants. Each odorant is characterized by a set of 146 perceptual descriptors obtained from a database of odor character profiles. Each odorant is therefore represented by a point in a highly multidimensional sensory space. In this work we study the arrangement of odorants in this perceptual space. We argue that odorants densely sample a two-dimensional curved surface embedded in the multidimensional sensory space. This surface can account for more than half of the variance of the perceptual data. We also show that only 12% of experimental variance cannot be explained by curved surfaces of substantially small dimensionality (<10. We suggest that these curved manifolds represent the relevant spaces sampled by the human olfactory system, thereby providing surrogates for olfactory sensory space. For the case of 2D approximation, we relate the two parameters on the curved surface to the physico-chemical parameters of odorant molecules. We show that one of the dimensions is related to eigenvalues of molecules’ connectivity matrix, while the other is correlated with measures of molecules’ polarity. We discuss the behavioral significance of these findings.

  20. Mutation of exposed hydrophobic amino acids to arginine to increase protein stability

    Directory of Open Access Journals (Sweden)

    Czaplicki Jerzy

    2004-07-01

    Full Text Available Abstract Background One strategy to increase the stability of proteins is to reduce the area of water-accessible hydrophobic surface. Results In order to test it, we replaced 14 solvent-exposed hydrophobic residues of acetylcholinesterase by arginine. The stabilities of the resulting proteins were tested using denaturation by high temperature, organic solvents, urea and by proteolytic digestion. Conclusion Altough the mutational effects were rather small, this strategy proved to be successful since half of the mutants showed an increased stability. This stability may originate from the suppression of unfavorable interactions of nonpolar residues with water or from addition of new hydrogen bonds with the solvent. Other mechanisms may also contribute to the increased stability observed with some mutants. For example, introduction of a charge at the surface of the protein may provide a new coulombic interaction on the protein surface.

  1. Nutritional Status among the Children of Age Group 5-14 Years in Selected Arsenic Exposed and Non-Exposed Areas of Bangladesh.

    Science.gov (United States)

    Rezaul Karim, Mohammad; Ahmad, Sk Akhtar

    2014-12-01

    To assess and compare the nutritional status of children aged 5-14 years in arsenic exposed and non- exposed areas. It was a cross sectional study conducted on 600 children of age 5-14 years from arsenic exposed and non-exposed areas in Bangladesh. Designed questionnaire and check list were used for collection of data. To estimate BMI necessary anthropometric measurements of the studied children were done. Dietary intakes of the study children were assessed using 24-hours recall method. The difference of socio-economic conditions between the children of exposed area and non-exposed area was not significant. On an average the body mass index was found to be significantly (p < 0.01) lower among the children of arsenic exposed area (49%) in comparison to that of children in non-exposed area (38%). Stunting (p < 0.01), wasting (p < 0.05) and underweight (p < 0.05) were significantly higher in exposed group in comparison to non-exposed group. No significant difference of nutrition intake was found between exposed and non-exposed children as well as thin and normal children. In this study children exposed to arsenic contaminated water were found to be suffered from lower nutritional status.

  2. Attitudes and Practices Regarding Child Spacing in Chikwawa District

    African Journals Online (AJOL)

    assurance action plan for facilitating informed choice, medical monitoring and ... timely planning and decision making. In 1991 we .... In the previous child spacing policy the approval of .... and emotional component 5 and is very influential in a person's subsequent ... constantly exposed to messages by radio and at various.

  3. F2 excimer laser (157 nm) radiation modification and surface ablation of PHEMA hydrogels and the effects on bioactivity: Surface attachment and proliferation of human corneal epithelial cells

    International Nuclear Information System (INIS)

    Zainuddin; Chirila, Traian V.; Barnard, Zeke; Watson, Gregory S.; Toh, Chiong; Blakey, Idriss; Whittaker, Andrew K.; Hill, David J.T.

    2011-01-01

    Physical and chemical changes at the surface of poly(2-hydroxyethyl methacrylate) (PHEMA) hydrogels modified by ablation with an F 2 excimer laser were investigated experimentally. An important observation was that only the outer exposed surface layers of the hydrogel were affected by the exposure to 157 nm radiation. The effect of the surface changes on the tendency of cells to adhere to the PHEMA was also investigated. A 0.5 cm 2 area of the hydrogel surfaces was exposed to laser irradiation at 157 nm to fluences of 0.8 and 4 J cm -2 . The changes in surface topography were analysed by light microscopy and atomic force microscopy, while the surface chemistry was characterized by attenuated total reflection infrared and X-ray photoelectron spectroscopies. Cell-interfacial interactions were examined based on the proliferation of human corneal limbal epithelial (HLE) cells cultured on the laser-modified hydrogels, and on the unexposed hydrogels and tissue culture plastic for comparison. It was observed that the surface topography of laser-exposed hydrogels showed rippled patterns with a surface roughness increasing at the higher exposure dose. The changes in surface chemistry were affected not only by an indirect effect of hydrogen and hydroxyl radicals, formed by water photolysis, on the PHEMA, but also by the direct action of laser radiation on PHEMA if the surface layers of the gel become depleted of water. The laser treatment led to a change in the surface characteristics, with a lower concentration of ester side-chains and the formation of new oxygenated species at the surface. The surface also became more hydrophobic. Most importantly, the surface chemistry and the newly created surface topographical features were able to improve the attachment, spreading and growth of HLE cells.

  4. Risk assessment for adult butterflies exposed to the mosquito control pesticide naled

    Science.gov (United States)

    Bargar, Timothy A.

    2012-01-01

    A prospective risk assessment was conducted for adult butterflies potentially exposed to the mosquito control insecticide naled. Published acute mortality data, exposure data collected during field studies, and morphometric data (total surface area and fresh body weight) for adult butterflies were combined in a probabilistic estimate of the likelihood that adult butterfly exposure to naled following aerial applications would exceed levels associated with acute mortality. Adult butterfly exposure was estimated based on the product of (1) naled residues on samplers and (2) an exposure metric that normalized total surface area for adult butterflies to their fresh weight. The likelihood that the 10th percentile refined effect estimate for adult butterflies exposed to naled would be exceeded following aerial naled applications was 67 to 80%. The greatest risk would be for butterflies in the family Lycaenidae, and the lowest risk would be for those in the family Hesperidae, assuming equivalent sensitivity to naled. A range of potential guideline naled deposition levels is presented that, if not exceeded, would reduce the risk of adult butterfly mortality. The results for this risk assessment were compared with other risk estimates for butterflies, and the implications for adult butterflies in areas targeted by aerial naled applications are discussed.

  5. Risk assessment for adult butterflies exposed to the mosquito control pesticide naled.

    Science.gov (United States)

    Bargar, Timothy A

    2012-04-01

    A prospective risk assessment was conducted for adult butterflies potentially exposed to the mosquito control insecticide naled. Published acute mortality data, exposure data collected during field studies, and morphometric data (total surface area and fresh body weight) for adult butterflies were combined in a probabilistic estimate of the likelihood that adult butterfly exposure to naled following aerial applications would exceed levels associated with acute mortality. Adult butterfly exposure was estimated based on the product of (1) naled residues on samplers and (2) an exposure metric that normalized total surface area for adult butterflies to their fresh weight. The likelihood that the 10th percentile refined effect estimate for adult butterflies exposed to naled would be exceeded following aerial naled applications was 67 to 80%. The greatest risk would be for butterflies in the family Lycaenidae, and the lowest risk would be for those in the family Hesperidae, assuming equivalent sensitivity to naled. A range of potential guideline naled deposition levels is presented that, if not exceeded, would reduce the risk of adult butterfly mortality. The results for this risk assessment were compared with other risk estimates for butterflies, and the implications for adult butterflies in areas targeted by aerial naled applications are discussed. Copyright © 2012 SETAC.

  6. Kin-aesthetic Space-making

    DEFF Research Database (Denmark)

    Brabrand, Helle

    2016-01-01

    Body Space Object Symposium 26.02.2016 Strand: The (Moving) Body as Archive Title: Kin-aesthetic Space-making The paper presents a cross-medial practice exchanging body movement and tectonic space. Working with a performative model of gesture, the practice takes up a dialogue with Jean......’s How the Body Shapes the Mind forms part of the theoretical approach to motile kin-aesthetical forces of art-making, underlying this paper. In my practice I work with body- and space gestures, interchanging through a ‘third’ material, featured on screens. The hybrid production includes animated 2 and 3......D drawings, video sequences, and technological treatment constituted by movement of camera, light and diverse editing. Creating a mutable changing sensory surface, the modelling gestures draw attention to their actual occurring in space-time, articulating and transforming space-time configurations...

  7. Einstein-Weyl spaces and third-order differential equations

    Science.gov (United States)

    Tod, K. P.

    2000-08-01

    The three-dimensional null-surface formalism of Tanimoto [M. Tanimoto, "On the null surface formalism," Report No. gr-qc/9703003 (1997)] and Forni et al. [Forni et al., "Null surfaces formation in 3D," J. Math Phys. (submitted)] are extended to describe Einstein-Weyl spaces, following Cartan [E. Cartan, "Les espaces généralisées et l'integration de certaines classes d'equations différentielles," C. R. Acad. Sci. 206, 1425-1429 (1938); "La geometria de las ecuaciones diferenciales de tercer order," Rev. Mat. Hispano-Am. 4, 1-31 (1941)]. In the resulting formalism, Einstein-Weyl spaces are obtained from a particular class of third-order differential equations. Some examples of the construction which include some new Einstein-Weyl spaces are given.

  8. Nuclear Energy in Space Exploration

    Energy Technology Data Exchange (ETDEWEB)

    Seaborg, Glenn T.

    1968-01-01

    Nuclear space programs under development by the Atomic Energy Commission are reviewed including the Rover Program, systems for nuclear rocket propulsion and, the SNAP Program, systems for generating electric power in space. The letters S-N-A-P stands for Systems for Nuclear Auxiliary Power. Some of the projected uses of nuclear systems in space are briefly discussed including lunar orbit, lunar transportation from lunar orbit to lunar surface and base stations; planetary exploration, and longer space missions. The limitations of other sources of energy such as solar, fuel cells, and electric batteries are discussed. The excitement and visionary possibilities of the Age of Space are discussed.

  9. Differential topology of complex surfaces elliptic surfaces with p g=1 smooth classification

    CERN Document Server

    Morgan, John W

    1993-01-01

    This book is about the smooth classification of a certain class of algebraicsurfaces, namely regular elliptic surfaces of geometric genus one, i.e. elliptic surfaces with b1 = 0 and b2+ = 3. The authors give a complete classification of these surfaces up to diffeomorphism. They achieve this result by partially computing one of Donalson's polynomial invariants. The computation is carried out using techniques from algebraic geometry. In these computations both thebasic facts about the Donaldson invariants and the relationship of the moduli space of ASD connections with the moduli space of stable bundles are assumed known. Some familiarity with the basic facts of the theory of moduliof sheaves and bundles on a surface is also assumed. This work gives a good and fairly comprehensive indication of how the methods of algebraic geometry can be used to compute Donaldson invariants.

  10. Bayesian Maximum Entropy space/time estimation of surface water chloride in Maryland using river distances.

    Science.gov (United States)

    Jat, Prahlad; Serre, Marc L

    2016-12-01

    Widespread contamination of surface water chloride is an emerging environmental concern. Consequently accurate and cost-effective methods are needed to estimate chloride along all river miles of potentially contaminated watersheds. Here we introduce a Bayesian Maximum Entropy (BME) space/time geostatistical estimation framework that uses river distances, and we compare it with Euclidean BME to estimate surface water chloride from 2005 to 2014 in the Gunpowder-Patapsco, Severn, and Patuxent subbasins in Maryland. River BME improves the cross-validation R 2 by 23.67% over Euclidean BME, and river BME maps are significantly different than Euclidean BME maps, indicating that it is important to use river BME maps to assess water quality impairment. The river BME maps of chloride concentration show wide contamination throughout Baltimore and Columbia-Ellicott cities, the disappearance of a clean buffer separating these two large urban areas, and the emergence of multiple localized pockets of contamination in surrounding areas. The number of impaired river miles increased by 0.55% per year in 2005-2009 and by 1.23% per year in 2011-2014, corresponding to a marked acceleration of the rate of impairment. Our results support the need for control measures and increased monitoring of unassessed river miles. Copyright © 2016. Published by Elsevier Ltd.

  11. Earth's youngest exposed granite and its tectonic implications: the 10-0.8 Ma Kurobegawa Granite.

    Science.gov (United States)

    Ito, Hisatoshi; Yamada, Ryuji; Tamura, Akihiro; Arai, Shoji; Horie, Kenji; Hokada, Tomokazu

    2013-01-01

    Although the quest for Earth's oldest rock is of great importance, identifying the youngest exposed pluton on Earth is also of interest. A pluton is a body of intrusive igneous rock that crystallized from slowly cooling magma at depths of several kilometers beneath the surface of the Earth. Therefore, the youngest exposed pluton represents the most recent tectonic uplift and highest exhumation. The youngest exposed pluton reported to date is the Takidani Granodiorite (~ 1.4 Ma) in the Hida Mountain Range of central Japan. Using LA-ICP-MS and SHRIMP U-Pb zircon dating methods, this study demonstrates that the Kurobegawa Granite, also situated in the Hida Mountain Range, is as young as ~ 0.8 Ma. In addition, data indicate multiple intrusion episodes in this pluton since 10 Ma with a ~ 2-million-year period of quiescence; hence, a future intrusion event is likely within 1 million years.

  12. Nutritional Status among the Children of Age Group 5-14 Years in Selected Arsenic Exposed and Non-Exposed Areas of Bangladesh.

    Directory of Open Access Journals (Sweden)

    Mohammad Rezaul Karim

    2014-12-01

    Full Text Available To assess and compare the nutritional status of children aged 5-14 years in arsenic exposed and non- exposed areas.It was a cross sectional study conducted on 600 children of age 5-14 years from arsenic exposed and non-exposed areas in Bangladesh. Designed questionnaire and check list were used for collection of data. To estimate BMI necessary anthropometric measurements of the studied children were done. Dietary intakes of the study children were assessed using 24-hours recall method.The difference of socio-economic conditions between the children of exposed area and non-exposed area was not significant. On an average the body mass index was found to be significantly (p < 0.01 lower among the children of arsenic exposed area (49% in comparison to that of children in non-exposed area (38%. Stunting (p < 0.01, wasting (p < 0.05 and underweight (p < 0.05 were significantly higher in exposed group in comparison to non-exposed group. No significant difference of nutrition intake was found between exposed and non-exposed children as well as thin and normal children.In this study children exposed to arsenic contaminated water were found to be suffered from lower nutritional status.

  13. Europa's surface radiation environment and considerations for in-situ sampling and biosignature detection

    Science.gov (United States)

    Nordheim, T.; Paranicas, C.; Hand, K. P.

    2017-12-01

    Jupiter's moon Europa is embedded deep within the Jovian magnetosphere and is thus exposed to bombardment by charged particles, from thermal plasma to more energetic particles at radiation belt energies. In particular, energetic charged particles are capable of affecting the uppermost layer of surface material on Europa, in some cases down to depths of several meters (Johnson et al., 2004; Paranicas et al., 2009, 2002). Examples of radiation-induced surface alteration include sputtering, radiolysis and grain sintering; processes that are capable of significantly altering the physical properties of surface material. Radiolysis of surface ices containing sulfur-bearing contaminants from Io has been invoked as a possible explanation for hydrated sulfuric acid detected on Europa's surface (Carlson et al., 2002, 1999) and radiolytic production of oxidants represents a potential source of energy for life that could reside within Europa's sub-surface ocean (Chyba, 2000; Hand et al., 2007; Johnson et al., 2003; Vance et al., 2016). Accurate knowledge of Europa's surface radiation environment is essential to the interpretation of space and Earth-based observations of Europa's surface and exosphere. Furthermore, future landed missions may seek to sample endogenic material emplaced on Europa's surface to investigate its chemical composition and to search for biosignatures contained within. Such material would likely be sampled from the shallow sub-surface, and thus, it becomes crucial to know to which degree this material is expected to have been radiation processed.Here we will present modeling results of energetic electron and proton bombardment of Europa's surface, including interactions between these particles and surface material. In addition, we will present predictions for biosignature destruction at different geographical locations and burial depths and discuss the implications of these results for surface sampling by future missions to Europa's surface.

  14. THE REGULARITIES OF THE SPACE-TEMPORAL DISTRIBUTION OF THE RADIATION BALANCE OF THE UNDERLYING SURFACE IN ARAKS BASIN ON MOUNTAINOUS TERRITORY OF THE REPUBLIC OF ARMENIA

    Directory of Open Access Journals (Sweden)

    V. G. Margaryan

    2017-12-01

    Full Text Available The regularities of the space-temporal distribution of the radiation balance of the underlying surface for the conditions of the mountainous territory of the Republic of Armenia were discussed and analyzed.

  15. Hydrophobic patches on protein surfaces

    NARCIS (Netherlands)

    Lijnzaad, P.

    2007-01-01

    Hydrophobicity is a prime determinant of the structure and function of proteins. It is the driving force behind the folding of soluble proteins, and when exposed on the surface, it is frequently involved in recognition and binding of ligands and other proteins. The energetic cost of

  16. Influence of corrosive solutions on microhardness and chemistry of magnesium oxide /001/ surfaces

    Science.gov (United States)

    Ishigaki, H.; Miyoshi, K.; Buckley, D. H.

    1982-01-01

    X-ray photoelectron spectroscopy analyses and hardness experiments were conducted on cleaved magnesium oxide /001/ surfaces. The magnesium oxide bulk crystals were cleaved to specimen size along the /001/ surface, and indentations were made on the cleaved surface in corrosive solutions containing HCl, NaOH, or HNO3 and in water without exposing the specimen to any other environment. The results indicated that chloride (such as MgCl2) and sodium films are formed on the magnesium oxide surface as a result of interactions between an HCl-containing solution and a cleaved magnesium oxide surface. The chloride films soften the magnesium oxide surface. In this case microhardness is strongly influenced by the pH value of the solution. The lower the pH, the lower the microhardness. Sodium films, which are formed on the magnesium oxide surface exposed to an NaOH containing solution, do not soften the magnesium oxide surface.

  17. Surface assisted electric transport in Ag2S thin films

    International Nuclear Information System (INIS)

    Karashanova, D.; Starbov, N.

    2006-01-01

    Electric transport measurements of thickness-dependent electronic and ionic conductivity of epitaxial Ag 2 S films are used to split both kinds of conductivity into bulk and surface components. The established considerable electronic and ionic surface conductances demonstrate unambiguously the co-existance of electronic and ionic space charge regions in the vicinity of silver sulfide free surface oriented along the zone axes [1-bar 01-bar ]. The parameters of both space charge layers - surface potential, thickness of the space charge region and concentration of the surface compensating charges, are calculated. It is estimated that for intrinsic silver sulfide, the effective surface potential of (1-bar 01-bar ) Ag 2 S surface is negative, its value being about -610mV at 400K

  18. High Temperature Surface Parameters for Solar Power

    National Research Council Canada - National Science Library

    Butler, C. F; Jenkins, R. J; Rudkin, R. L; Laughridge, F. I

    1960-01-01

    ... at a given distance from the sun. Thermal conversion efficiencies with a concentration ratio of 50 have been computed for each surface when exposed to solar radiation at the Earth's mean orbital radius...

  19. Changes of hormones regulating electrolyte metabolism after space flight and hypokinesia

    Science.gov (United States)

    Macho, L.; Fickova, M.; Lichardus, B.; Kvetnansky, R.; Carrey, R. M.; Grigoriev, A.; Popova, I. A.; Tigranian, R. A.; Noskov, V. B.

    The changes of hormones in plasma involved in the body fluid regulation were studied in human subjects during and after space flights in relation to redistribution of body fluids in the state of weightlessness. Since hypokinesia was used as a model for simulation of some effects of the stay in microgravity the plasma hormone levels in rats exposed to hypokinesia were also investigated. Plasma aldosterone values showed great individual variations during the first inflight days, the increased levels were observed with prolongation of space flights. The important elevation was found in the recovery period, however it was interesting to note, that in some cosmonauts with repeated exposure to space flight, the postflight plasma aldosterone levels were not elevated. The urine excretion of aldosterone was increased inflight, however in postflight period the decrease or increase were found in the first 1-5 days. The increase of plasma renin activity was observed in flight and postflight period. The rats were exposed to hypokinesia (forced restriction of motor activity) for 1, 7 and 60 days and urine was collected during last 24 hours. The animals were sacrificed and the concentration of electrolytes and of levels of corticosterone aldosteron (A), ANF and plasma-renin activity (PRA) were determined in plasma. In urine excretion of sodium and potassium were estimated. An important increase of plasma renin activity and aldosterone concentration was found after short-term hypokinesia (1 day). These hormonal values appear to decrease with time (7 days) and are not significantly different from controls after long-term hypokinesia (60 days). A decrease of values ANF in plasma was observed after 1 and 7 days hypokinesia. After prolonged hypokinesia a decrease of sodium plasma concentration was observed. The excretion of sodium in urine was higher in long-term hypokinetic animals. There were no significant changes of plasma potassium levels in rats exposed to hypokinesia, however

  20. An explicit asymptotic model for the surface wave in a viscoelastic half-space based on applying Rabotnov's fractional exponential integral operators

    Science.gov (United States)

    Wilde, M. V.; Sergeeva, N. V.

    2018-05-01

    An explicit asymptotic model extracting the contribution of a surface wave to the dynamic response of a viscoelastic half-space is derived. Fractional exponential Rabotnov's integral operators are used for describing of material properties. The model is derived by extracting the principal part of the poles corresponding to the surface waves after applying Laplace and Fourier transforms. The simplified equations for the originals are written by using power series expansions. Padè approximation is constructed to unite short-time and long-time models. The form of this approximation allows to formulate the explicit model using a fractional exponential Rabotnov's integral operator with parameters depending on the properties of surface wave. The applicability of derived models is studied by comparing with the exact solutions of a model problem. It is revealed that the model based on Padè approximation is highly effective for all the possible time domains.

  1. Strata-1: An International Space Station Experiment into Fundamental Regolith Processes in Microgravity

    Science.gov (United States)

    Fries, M.; Abell, P.; Brisset, J.; Britt, D.; Colwell, J.; Durda, D.; Dove, A.; Graham, L.; Hartzell, C.; John, K.; hide

    2016-01-01

    The Strata-1 experiment will study the evolution of asteroidal regolith through long-duration exposure of simulant materials to the microgravity environment on the International Space Station (ISS). Many asteroids feature low bulk densities, which implies high values of porosity and a mechanical structure composed of loosely bound particles, (i.e. the "rubble pile" model), a prime example of a granular medium. Even the higher-density, mechanically coherent asteroids feature a significant surface layer of loose regolith. These bodies are subjected to a variety of forces and will evolve in response to very small perturbations such as micrometeoroid impacts, planetary flybys, and the YORP effect. Our understanding of this dynamical evolution and the inter-particle forces involved would benefit from long-term observations of granular materials exposed to small vibrations in microgravity. A detailed understanding of asteroid mechanical evolution is needed in order to predict the surface characteristics of as-of-yet unvisited bodies, to understand the larger context of samples collected by missions such as OSIRIS-REx and Hayabusa 1 and 2, and to mitigate risks for both manned and unmanned missions to asteroidal bodies. Understanding regolith dynamics will inform designs of how to land and set anchors, safely sample/move material on asteroidal surfaces, process large volumes of material for in situ resource utilization (ISRU) purposes, and, in general, predict behavior of large and small particles on disturbed asteroid surfaces.

  2. Supermanifolds and super Riemann surfaces

    International Nuclear Information System (INIS)

    Rabin, J.M.

    1986-09-01

    The theory of super Riemann surfaces is rigorously developed using Rogers' theory of supermanifolds. The global structures of super Teichmueller space and super moduli space are determined. The super modular group is shown to be precisely the ordinary modular group. Super moduli space is shown to be the gauge-fixing slice for the fermionic string path integral

  3. Genetic risks associated with radiation exposures during space flight

    International Nuclear Information System (INIS)

    Grahn, D.

    1983-01-01

    Although the genetic risks of space radiation do not pose a significant hazard to the general population, the risks may be very important to the individual astronaut. The present paper summarizes some experimental results on the induction of dominant lethal mutations and chromosomal damage in the first generation which may be used in the prediction of the genetic risks of radiation exposures of space crews. Young adult male mice were exposed to single, weekly and continuous doses of gamma rays, neutrons in single doses and weekly exposures and continuous doses of Pu-239 alpha particles. Evaluation of fetal survival rates in females mated to the exposed males shows the mutation rate in individuals exposed to gamma rays to decline as the exposure period is prolonged and the dose rate is reduced, while the response to neutrons is in the opposite direction. Cytological determinations show the rate of balanced chromosomal translocations to drop as gamma ray exposures change from one-time to continuous, however little or no dose rate effect is seen with neutron radiation and alpha particle exposure shows no regular dose-response. Based on the above results, it is predicted that the rate of dominant mutations and transmissible chromosome aberrations in astronauts on a 100-day mission will increase by 4.5 to 41.25 percent over the spontaneous rate. 35 references

  4. Assessment of zero gravity effects on space worker health and safety

    Science.gov (United States)

    1980-01-01

    One objective of the study is to assess the effects of all currently known deviations from normal of medical, physiological, and biochemical parameters which appear to be due to zero gravity (zero-g) environment and to acceleration and deceleration to be experienced, as outlined in the references Solar Power Satellites (SPS) design, by space worker. Study results include identification of possible health or safety effects on space workers either immediate or delayed due to the zero gravity environment and acceleration and deceleration; estimation of the probability that an individual will be adversely affected; description of the possible consequence to work efficiency in persons adversely affected; and description of the possible/probable consequences to immediate and future health of individuals exposed to this environment. A research plan, which addresses the uncertainties in current knowledge regarding the health and safety hazards to exposed SPS space workers, is presented. Although most adverse affects experienced during space flight soon disappeared upon return to the Earth's environment, there remains a definite concern for the long-term effects to SPS space workers who might spend as much as half their time in space during a possible five year career period. The proposed 90 day up/90 day down cycle, coupled with the fact that most of the effects of weightlessness may persist throughout the flight along with the realization that recovery may occupy much of the terrestrial stay, may keep the SPS workers in a deviant physical condition or state of flux for 60 to 100% of their five year career.

  5. Assessment of zero gravity effects on space worker health and safety

    Energy Technology Data Exchange (ETDEWEB)

    1980-11-01

    One objective of the study is to assess the effects of all currently known deviations from normal of medical, physiological, and biochemical parameters which appear to be due to zero gravity (zero-g) environment and to acceleration and deceleration to be experienced, as outlined in the reference Solar Power Satellite (SPS) design, by space worker. Study results include identification of possible health or safety effects on space workers - either immediate or delayed - due to the zero gravity environment and acceleration and deceleration; estimation of the probability that an individual will be adversely affected; description of the possible consequence to work efficiently in persons adversely affected; and description of the possible/probable consequences to immediate and future health of individuals exposed to this environment. A research plan, which addresses the uncertainties in current knowledge regarding the health and safety hazards to exposed SPS space workers, is presented. Although most adverse affects experienced during space flight soon disappeared upon return to the Earth's environment, there remains a definite concern for the long-term effects to SPS space workers who might spend as much as half their time in space during a possible five-year career period. The proposed 90-day up/90 day down cycle, coupled with the fact that most of the effects of weightlessness may persist throughout the flight along with the realization that recovery may occupy much of the terrestrial stay, may keep the SPS workers in a deviant physical condition or state of flux for 60 to 100% of their five-year career. (JGB)

  6. Tales from the tomb: the microbial ecology of exposed rock surfaces.

    Science.gov (United States)

    Brewer, Tess E; Fierer, Noah

    2018-03-01

    Although a broad diversity of eukaryotic and bacterial taxa reside on rock surfaces where they can influence the weathering of rocks and minerals, these communities and their contributions to mineral weathering remain poorly resolved. To build a more comprehensive understanding of the diversity, ecology and potential functional attributes of microbial communities living on rock, we sampled 149 tombstones across three continents and analysed their bacterial and eukaryotic communities via marker gene and shotgun metagenomic sequencing. We found that geographic location and climate were important factors structuring the composition of these communities. Moreover, the tombstone-associated microbial communities varied as a function of rock type, with granite and limestone tombstones from the same cemeteries harbouring taxonomically distinct microbial communities. The granite and limestone-associated communities also had distinct functional attributes, with granite-associated bacteria having more genes linked to acid tolerance and chemotaxis, while bacteria on limestone were more likely to be lichen associated and have genes involved in photosynthesis and radiation resistance. Together these results indicate that rock-dwelling microbes exhibit adaptations to survive the stresses of the rock surface, differ based on location, climate and rock type, and seem pre-disposed to different ecological strategies (symbiotic versus free-living lifestyles) depending on the rock type. © 2017 Society for Applied Microbiology and John Wiley & Sons Ltd.

  7. Pseudospherical surfaces with singularities

    DEFF Research Database (Denmark)

    Brander, David

    2017-01-01

    We study a generalization of constant Gauss curvature −1 surfaces in Euclidean 3-space, based on Lorentzian harmonic maps, that we call pseudospherical frontals. We analyse the singularities of these surfaces, dividing them into those of characteristic and non-characteristic type. We give methods...

  8. Study of the space environmental effects on spacecraft engineering materials

    Science.gov (United States)

    Obrien, Susan K.; Workman, Gary L.; Smith, Guy A.

    1995-01-01

    The space environment in which the Space Station Freedom and other space platforms will orbit is truly a hostile environment. For example, the current estimates of the integral fluence for electrons above 1 Mev at 2000 nautical miles is above 2 x 10(exp 10) electrons/sq cm/day. and the proton integral fluence is above 1 x 109 protons/sq cm/day. At the 200 - 400 nautical miles, which is more representative of the altitude which will provide the environment for the Space Station, each of these fluences will be proportionately less; however, the data indicates that the radiation environment will obviously have an effect on structural materials exposed to the environment for long durations. The effects of this combined environment is the issue which needs to be understood for the long term exposure of structures in space. In order to better understand the effect of these hostile phenomena on spacecraft, several types of studies are worth performing in order to simulate at some level the effect of the environment. For example the effect of protons and electrons impacting structural materials are easily simulated through experiments using the Van de Graff and Pelletron accelerators currently housed in the Environmental Effects Facility at MSFC. Proton fluxes with energies of 700 Kev-2.5 Mev can be generated and used to impinge on sample targets to determine the effects of the particles. Also the Environmental Effects Facility has the capability to generate electron beams with energies from 700 Kev to 2.5 Mev. These facilities will be used in this research to simulate space environmental effects from energetic particles. Ultraviolet radiation, particularly in the ultraviolet (less than 400 nm wavelength) is less well characterized at this time. The Environmental Effects Facility has a vacuum system dedicated to studying the effects of ultraviolet radiation on specific surface materials. This particular system was assembled in a previous study (NAS8-38609) in order to

  9. Integration Assessment of Visiting Vehicle Induced Electrical Charging of the International Space Station Structure

    Science.gov (United States)

    Kramer, Leonard; Kerslake, Thomas W.; Galofaro, Joel T.

    2010-01-01

    The International Space Station (ISS) undergoes electrical charging in low Earth orbit (LEO) due to positively biased, exposed conductors on solar arrays that collect electrical charges from the space plasma. Exposed solar array conductors predominately collect negatively charged electrons and thus drive the metal ISS structure electrical ground to a negative floating potential (FP) relative to plasma. This FP is variable in location and time as a result of local ionospheric conditions. ISS motion through Earth s magnetic field creates an addition inductive voltage up to 20 positive and negative volts across ISS structure depending on its attitude and location in orbit. ISS Visiting Vehicles (VVs), such as the planned Orion crew exploration vehicle, contribute to the ISS plasma charging processes. Upon physical contact with ISS, the current collection properties of VVs combine with ISS. This is an ISS integration concern as FP must be controlled to minimize arcing of ISS surfaces and ensure proper management of extra vehicular activity crewman shock hazards. This report is an assessment of ISS induced charging from docked Orion vehicles employing negatively grounded, 130 volt class, UltraFlex (ATK Space Systems) solar arrays. To assess plasma electron current collection characteristics, Orion solar cell test coupons were constructed and subjected to plasma chamber current collection measurements. During these tests, coupon solar cells were biased between 0 and 120 V while immersed in a simulated LEO plasma. Tests were performed using several different simulated LEO plasma densities and temperatures. These data and associated theoretical scaling of plasma properties, were combined in a numerical model which was integrated into the Boeing Plasma Interaction Model. It was found that the solar array design for Orion will not affect the ISS FP by more than about 2 V during worst case charging conditions. This assessment also motivated a trade study to determine

  10. A retrospective mortality study of workers exposed to radon in a Brazilian coal mine

    International Nuclear Information System (INIS)

    Veiga, Lene Holanda Sadler

    2004-08-01

    High levels of radon concentration were found in the underground workplace of an underground coal mine in Parana state, which has been in activity since 1942. Many of these workers were exposed for a long period of time to a work atmosphere with high radon, and radon decay products concentration. Taking this into account, it was decided to carry on a historical cohort, study with the workers' of this mining universe (underground and surface) in. order to evaluate the possible health effects related to this exposure, by means of a retrospective study of mortality. Through multiple strategies, it was possible to trace the vital status of 90% of the cohort. The causes of the deaths were identified by active search, of Death Declarations in the Health Office of Parana state and also in and other states. The success rate of cause of death identification was 100%. The final, cohort included 1946 underground workers and 910 surface workers. Standard mortality ratio (SMR) analysis showed lower mortality from all causes for both underground (SMR-88, 95%CI=78-98) and surface workers (SMR=96, 95%CI=81- 113). A highly significant SMR was observed for pneumonia cause of death among surface ((SMR=284, 95%CI=118-684) and underground miners (SMR-254, 95%CI=140-459), while a highly significant lung cancer mortality risk was observed only for underground miners (SMR=177, 95%CI=105-299) with a significant trend in relation to years of underground work (duration of exposure). Taking into account that mortality from smoking-related cancers other than lung cancer is not elevated in underground workers and diesel equipment were not used at this mine, the results suggest that the exposure to radon daughters may have been responsible for the lung cancer excess among underground workers. This work consists of the first historical Brazilian cohort involving miners exposed to radon and one of the few historical cohorts built in Brazil. It should be considered the fact that many workers of

  11. Moessbauer spectroscopy in space

    Energy Technology Data Exchange (ETDEWEB)

    Klingelhoefer, G [Technische Hochschule Darmstadt (Germany). Inst. fuer Kernphysik; Held, P [Technische Hochschule Darmstadt (Germany). Inst. fuer Kernphysik; Teucher, R [Technische Hochschule Darmstadt (Germany). Inst. fuer Kernphysik; Schlichting, F [Technische Hochschule Darmstadt (Germany). Inst. fuer Kernphysik; Foh, J [Technische Hochschule Darmstadt (Germany). Inst. fuer Kernphysik; Kankeleit, E [Technische Hochschule Darmstadt (Germany). Inst. fuer Kernphysik

    1995-03-01

    Nearly 40 years after the discovery of the Moessbauer effect for the first time a Moessbauer spectrometer will leave our planet to explore in situ the surface of another solar system body: the red planet Mars [1]. We are currently developing a miniaturized Moessbauer spectrometer (MIMOS) which is part of the scientific payload of the Russian Mars96 mission, to be launched within the next 2-4 years [2,3]. To fulfill the requirements for a space mission to the planet Mars, all parts of the spectrometer had to be extremely miniaturized and ruggedized to withstand the space flight and Mars environmental conditions. The relevant parts (e.g. drive, detector system, electronics etc.) will be described in more detail and its characteristics compared to standard systems. Because of this new development there now is a growing interest to include a Moessbauer (MB) instrument in future space missions to other solar system bodies as for instance Venus, the terrestrial Moon, and a comet nucleus. Because of extremely different environmental conditions (e.g. nearly zero gravity on the surface of a comet nucleus, high pressure and temperature on the surface of Venus, etc.) different instrument designs and concepts are required for different missions. We will present some ideas for various types of missions, as well as the motivation for using Moessbauer spectroscopy in these cases. (orig.)

  12. Elastic interaction between surface and spherical pore

    International Nuclear Information System (INIS)

    Ganeev, G.Z.; Kadyrzhanov, K.K.; Kislitsyn, S.B.; Turkebaev, T.Eh.

    2000-01-01

    The energy of elastic interaction of a gas-filled spherical cavity with a boundary of an elastic isotropic half-space is determined. The elastic field of a system of a spherical cavity - boundary is represented as an expansion in series of potential functions. The factors of expansions are determined by boundary conditions on a free surface of an elastic half-space and on a spherical surface of a cavity with pressure of gas P. Function of a Tresca-Miesesa on a surface of elastic surface is defined additionally with purpose creep condition determination caused by gas pressure in the cavity. (author)

  13. Investigation of surface effect on giant magnetoimpedance in microwires

    International Nuclear Information System (INIS)

    Tousignant, M.; Zabeida, O.; Rudkowska, G.; Yelon, A.

    2014-01-01

    Previous work from our group suggested that the giant magnetoimpedance (GMI) response of soft ferromagnetic microwires could be improved by removing a hypothetical hard magnetic shell on the surface of the cylindrical conductors. Therefore, we have been trying to increase the sensitivity of our samples by exposing them to a mild plasma etching treatment. Although we measured a reduction in diameter of the microwires and ensured that their bulk magnetic properties remained unchanged, it was found that the surface treatment did not improve the GMI behavior of the samples. We thus conclude that the sensitivity of ferromagnetic microwires must be limited by bulk inhomogeneities, yet to be investigated. - Highlights: • We have been trying to increase the sensitivity of our samples by exposing them to a mild plasma etching treatment. • Surface treatment did not improve the GMI behavior of the samples

  14. Disposal of tritium-exposed metal hydrides

    International Nuclear Information System (INIS)

    Nobile, A.; Motyka, T.

    1991-01-01

    A plan has been established for disposal of tritium-exposed metal hydrides used in Savannah River Site (SRS) tritium production or Materials Test Facility (MTF) R ampersand D operations. The recommended plan assumes that the first tritium-exposed metal hydrides will be disposed of after startup of the Solid Waste Disposal Facility (SWDF) Expansion Project in 1992, and thus the plan is consistent with the new disposal requiremkents that will be in effect for the SWDF Expansion Project. Process beds containing tritium-exposed metal hydride powder will be disposed of without removal of the powder from the bed; however, disposal of tritium-exposed metal hydride powder that has been removed from its process vessel is also addressed

  15. Surface-Activated Coupling Reactions Confined on a Surface.

    Science.gov (United States)

    Dong, Lei; Liu, Pei Nian; Lin, Nian

    2015-10-20

    Chemical reactions may take place in a pure phase of gas or liquid or at the interface of two phases (gas-solid or liquid-solid). Recently, the emerging field of "surface-confined coupling reactions" has attracted intensive attention. In this process, reactants, intermediates, and products of a coupling reaction are adsorbed on a solid-vacuum or a solid-liquid interface. The solid surface restricts all reaction steps on the interface, in other words, the reaction takes place within a lower-dimensional, for example, two-dimensional, space. Surface atoms that are fixed in the surface and adatoms that move on the surface often activate the surface-confined coupling reactions. The synergy of surface morphology and activity allow some reactions that are inefficient or prohibited in the gas or liquid phase to proceed efficiently when the reactions are confined on a surface. Over the past decade, dozens of well-known "textbook" coupling reactions have been shown to proceed as surface-confined coupling reactions. In most cases, the surface-confined coupling reactions were discovered by trial and error, and the reaction pathways are largely unknown. It is thus highly desirable to unravel the mechanisms, mechanisms of surface activation in particular, of the surface-confined coupling reactions. Because the reactions take place on surfaces, advanced surface science techniques can be applied to study the surface-confined coupling reactions. Among them, scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS) are the two most extensively used experimental tools. The former resolves submolecular structures of individual reactants, intermediates, and products in real space, while the latter monitors the chemical states during the reactions in real time. Combination of the two methods provides unprecedented spatial and temporal information on the reaction pathways. The experimental findings are complemented by theoretical modeling. In particular, density

  16. Deep Space Gateway Science Opportunities

    Science.gov (United States)

    Quincy, C. D.; Charles, J. B.; Hamill, Doris; Sidney, S. C.

    2018-01-01

    The NASA Life Sciences Research Capabilities Team (LSRCT) has been discussing deep space research needs for the last two years. NASA's programs conducting life sciences studies - the Human Research Program, Space Biology, Astrobiology, and Planetary Protection - see the Deep Space Gateway (DSG) as affording enormous opportunities to investigate biological organisms in a unique environment that cannot be replicated in Earth-based laboratories or on Low Earth Orbit science platforms. These investigations may provide in many cases the definitive answers to risks associated with exploration and living outside Earth's protective magnetic field. Unlike Low Earth Orbit or terrestrial locations, the Gateway location will be subjected to the true deep space spectrum and influence of both galactic cosmic and solar particle radiation and thus presents an opportunity to investigate their long-term exposure effects. The question of how a community of biological organisms change over time within the harsh environment of space flight outside of the magnetic field protection can be investigated. The biological response to the absence of Earth's geomagnetic field can be studied for the first time. Will organisms change in new and unique ways under these new conditions? This may be specifically true on investigations of microbial communities. The Gateway provides a platform for microbiology experiments both inside, to improve understanding of interactions between microbes and human habitats, and outside, to improve understanding of microbe-hardware interactions exposed to the space environment.

  17. Growth and liver histology of Channa punctatus exposed to a common biofertilizer.

    Science.gov (United States)

    Nath, S; Matozzo, V; Bhandari, D; Faggio, C

    2018-01-28

    Mustard oil cake (MOC) is widely used as biofertilizer in the field of agriculture and aquaculture. Channa punctatus was exposed to 0.42 g.L -1 sublethal concentration for 4, 7, 14, 21 and 28 days. Due to such exposure, body growth and histological changes in liver were observed. It was revealed that weight, length and breadth of fish were gradually increased with the days of exposure in compare to control fish, whereas, liver showed an increase in sinusoidal space and lipidosis during early days, followed by a recovery from the stress of MOC on the 28th day.

  18. Innovative Microbial Surface Sampler, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The QS Team will develop an Innovative Microbial Surface Sampling (IMSS) device design and provide prototype kits for use in the International Space Station (ISS)....

  19. Volumetrically-Derived Global Navigation Satellite System Performance Assessment from the Earths Surface through the Terrestrial Service Volume and the Space Service Volume

    Science.gov (United States)

    Welch, Bryan W.

    2016-01-01

    NASA is participating in the International Committee on Global Navigation Satellite Systems (GNSS) (ICG)'s efforts towards demonstrating the benefits to the space user from the Earth's surface through the Terrestrial Service Volume (TSV) to the edge of the Space Service Volume (SSV), when a multi-GNSS solution space approach is utilized. The ICG Working Group: Enhancement of GNSS Performance, New Services and Capabilities has started a three phase analysis initiative as an outcome of recommendations at the ICG-10 meeting, in preparation for the ICG-11 meeting. The first phase of that increasing complexity and fidelity analysis initiative was recently expanded to compare nadir-facing and zenith-facing user hemispherical antenna coverage with omnidirectional antenna coverage at different distances of 8,000 km altitude and 36,000 km altitude. This report summarizes the performance using these antenna coverage techniques at distances ranging from 100 km altitude to 36,000 km to be all encompassing, as well as the volumetrically-derived system availability metrics.

  20. Ethanol emission from loose corn silage and exposed silage particles

    Science.gov (United States)

    Hafner, Sasha D.; Montes, Felipe; Rotz, C. Alan; Mitloehner, Frank

    2010-11-01

    Silage on dairy farms has been identified as a major source of volatile organic compound (VOC) emissions. However, rates of VOC emission from silage are not accurately known. In this work, we measured ethanol (a dominant silage VOC) emission from loose corn silage and exposed corn silage particles using wind tunnel systems. Flux of ethanol was highest immediately after exposing loose silage samples to moving air (as high as 220 g m -2 h -1) and declined by as much as 76-fold over 12 h as ethanol was depleted from samples. Emission rate and cumulative 12 h emission increased with temperature, silage permeability, exposed surface area, and air velocity over silage samples. These responses suggest that VOC emission from silage on farms is sensitive to climate and management practices. Ethanol emission rates from loose silage were generally higher than previous estimates of total VOC emission rates from silage and mixed feed. For 15 cm deep loose samples, mean cumulative emission was as high as 170 g m -2 (80% of initial ethanol mass) after 12 h of exposure to an air velocity of 5 m s -1. Emission rates measured with an emission isolation flux chamber were lower than rates measured in a wind tunnel and in an open setting. Results show that the US EPA emission isolation flux chamber method is not appropriate for estimating VOC emission rates from silage in the field.

  1. Radiation processing of organics and biological materials exposed to ocean world surface conditions.

    Science.gov (United States)

    Hand, K. P.; Carlson, R. W.

    2017-12-01

    Assessing the habitability of ocean worlds, such as Europa and Enceladus, motivates a search for endogenous carbon compounds that could be indicative of a habitable, or even inhabited, subsurface liquid water environment. We have examined the role of destruction and synthesis of organic compounds via 10 keV electron bombardment of ices generated under temperature and pressure conditions comparable to Europa and Enceladus. Short-chain organics and ammonia, in combination with water, were exposed to Mrad to Grad doses and observed to evolve to a `lost' carbon fraction (CO and CO2) and a `retained' carbon fraction (consisting of a highly refractory `ocean world tholin' populated by highly radiation resistant carbonyl, aldehyde, and nitrile components). The retained fraction is of key importance as this likely represents the observable fraction for future spacecraft investigations. We also irradiated microbial spores (B. pumilis) to approximately 2 Grad and have found persistence of biomolecule fractions derived from proteins and nucleic acids.

  2. An experimental study of the surface chemistry and evaporation kinetics of liquid sodium

    International Nuclear Information System (INIS)

    Becker, C.H.

    1983-01-01

    The evaporation rate and internal energy distribution of Na 2 evaporating from clean liquid Na and liquid Na exposed separately to O 2 and benzene were investigated by laser spectroscopy. The evaporating Na 2 was always found to be in thermal equilibrium with the surface. Oxygen increased the evaporation rate while benzene diminished it. A 3 keV Ar + beam was used to examine the surface by monitoring secondary ion emission. Ion emission from clean and oxygen exposed Na was extremely low; only limits could be established. Ion emission from sodium exposed to benzene could be observed only at lowered temperatures. The secondary ion emission, as well as visual observations of Na( 2 P-> 2 S) emission, are found to correspond to the evaporation rate behavior indicating that the Na surface remains very metal rich even while reacting with impinging oxygen at high (10 monolayers/s) rates. (orig.)

  3. Reconstruction of Kinematic Surfaces from Scattered Data

    DEFF Research Database (Denmark)

    Randrup, Thomas; Pottmann, Helmut; Lee, I.-K.

    1998-01-01

    Given a surface in 3-space or scattered points from a surface, we present algorithms for fitting the data by a surface which can be generated by a one--parameter subgroup of the group of similarities. These surfaces are general cones and cylinders, surfaces of revolution, helical surfaces and spi...

  4. Ocean Surface Current Vectors from MODIS Terra/Aqua Sea Surface Temperature Image Pairs, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Satellites that record imagery of the same sea surface area, at times separated by a few hours, can be used to estimate ocean surface velocity fields based on the...

  5. Surface structure determinations of crystalline ionic thin films grown on transition metal single crystal surfaces by low energy electron diffraction

    Energy Technology Data Exchange (ETDEWEB)

    Roberts, Joel Glenn [Univ. of California, Berkeley, CA (United States)

    2000-05-01

    The surface structures of NaCl(100), LiF(100) and alpha-MgCl2(0001) adsorbed on various metal single crystals have been determined by low energy electron diffraction (LEED). Thin films of these salts were grown on metal substrates by exposing the heated metal surface to a molecular flux of salt emitted from a Knudsen cell. This method of investigating thin films of insulators (ionic salts) on a conducting substrate (metal) circumvents surface charging problems that plagued bulk studies, thereby allowing the use of electron-based techniques to characterize the surface.

  6. Powering the Space Exploration Initiative

    International Nuclear Information System (INIS)

    Bennett, G.L.

    1991-01-01

    The Space Exploration Initiative (SEI) establishes the long-term goal of returning to the Moon and then exploring Mars. One of the prerequisites of SEI is the Exploration Technology Program which includes program elements on space nuclear power and surface solar power. These program elements in turn build upon the ongoing NASA research and technology base program in space energy conversion. There is a wide range of missions in NASA's strategic planning and most would benefit from power sources with improved efficiency, lighter weight and reduced cost

  7. Autogenic feedback training experiment: A preventative method for space motion sickness

    Science.gov (United States)

    Cowings, Patricia S.

    1993-01-01

    Space motion sickness is a disorder which produces symptoms similar to those of motion sickness on Earth. This syndrome has affected approximately 50 percent of all astronauts and cosmonauts exposed to microgravity in space, but it differs from what is commonly known as motion sickness in a number of critical ways. There is currently no ground-based method for predicting susceptibility to motion sickness in space. Antimotion sickness drugs have had limited success in preventing or counteracting symptoms in space, and frequently caused debilitating side effects. The objectives were: (1) to evaluate the effectiveness of Autogenic-Feedback Training as a countermeasure for space motion sickness; (2) to compare physiological data and in-flight symptom reports to ground-based motion sickness data; and (3) to predict susceptibility to space motion sickness based on pre-flight data of each treatment group crew member.

  8. Research on Space Environmental Effect of Organic Composite Materials for Thermal Management of Satellites Using MC-50 Cyclotron

    Directory of Open Access Journals (Sweden)

    Dae-Weon Kim

    2005-12-01

    Full Text Available The organic material is one of the most popular material for the satellites and the spacecrafts in order to perform the thermal management, and to protect direct exposure from the space environment. The present paper observes material property changes of organic material under the space environment by using ground facilities. One of the representative organic thermal management material of satellites, 2 mil ITO(Indium Tin Oxide coated aluminized KAPTON was selected for experiments. In order to investigate the single parametric effect of protons in space environment, MC-50 cyclotron system in KIRAMS(Korea Institute of Radiological and Medical Science was utilized for the ion beam irradiation of protons and ion beam dose was set to the Very Large August 1972 EVENT model, the highest protons occurrence near the earth orbit in history. The energy of ion beam is fixed to 30MeV(mega electron volt, observed average energy, and the equivalent irradiance time conditions were set to 1-year, 3-year, 5-year and 10-year exposure in space. The procedure of analyses includes the measurement of the ultimate tensile strength for the assessment of quantitative degradation in material properties, and the imaging analyses of crystalline transformation and damages on the exposed surface by FE-SEM(Field Emission Scanning Electron Spectroscopy etc.

  9. Activities of the Center for Space Construction

    Science.gov (United States)

    1993-01-01

    The Center for Space Construction (CSC) at the University of Colorado at Boulder is one of eight University Space Engineering Research Centers established by NASA in 1988. The mission of the center is to conduct research into space technology and to directly contribute to space engineering education. The center reports to the Department of Aerospace Engineering Sciences and resides in the College of Engineering and Applied Science. The college has a long and successful track record of cultivating multi-disciplinary research and education programs. The Center for Space Construction is prominent evidence of this record. At the inception of CSC, the center was primarily founded on the need for research on in-space construction of large space systems like space stations and interplanetary space vehicles. The scope of CSC's research has now evolved to include the design and construction of all spacecraft, large and small. Within this broadened scope, our research projects seek to impact the underlying technological basis for such spacecraft as remote sensing satellites, communication satellites, and other special purpose spacecraft, as well as the technological basis for large space platforms. The center's research focuses on three areas: spacecraft structures, spacecraft operations and control, and regolith and surface systems. In the area of spacecraft structures, our current emphasis is on concepts and modeling of deployable structures, analysis of inflatable structures, structural damage detection algorithms, and composite materials for lightweight structures. In the area of spacecraft operations and control, we are continuing our previous efforts in process control of in-orbit structural assembly. In addition, we have begun two new efforts in formal approach to spacecraft flight software systems design and adaptive attitude control systems. In the area of regolith and surface systems, we are continuing the work of characterizing the physical properties of lunar

  10. Earth's youngest exposed granite and its tectonic implications: the 10–0.8 Ma Kurobegawa Granite

    Science.gov (United States)

    Ito, Hisatoshi; Yamada, Ryuji; Tamura, Akihiro; Arai, Shoji; Horie, Kenji; Hokada, Tomokazu

    2013-01-01

    Although the quest for Earth's oldest rock is of great importance, identifying the youngest exposed pluton on Earth is also of interest. A pluton is a body of intrusive igneous rock that crystallized from slowly cooling magma at depths of several kilometers beneath the surface of the Earth. Therefore, the youngest exposed pluton represents the most recent tectonic uplift and highest exhumation. The youngest exposed pluton reported to date is the Takidani Granodiorite (~ 1.4 Ma) in the Hida Mountain Range of central Japan. Using LA-ICP-MS and SHRIMP U-Pb zircon dating methods, this study demonstrates that the Kurobegawa Granite, also situated in the Hida Mountain Range, is as young as ~ 0.8 Ma. In addition, data indicate multiple intrusion episodes in this pluton since 10 Ma with a ~ 2-million-year period of quiescence; hence, a future intrusion event is likely within 1 million years. PMID:23419636

  11. Pure and Oxidized Copper Materials as Potential Antimicrobial Surfaces for Spaceflight Activities

    Science.gov (United States)

    Hahn, C.; Hans, M.; Hein, C.; Mancinelli, R. L.; Mücklich, F.; Wirth, R.; Rettberg, P.; Hellweg, C. E.; Moeller, R.

    2017-12-01

    Microbial biofilms can lead to persistent infections and degrade a variety of materials, and they are notorious for their persistence and resistance to eradication. During long-duration space missions, microbial biofilms present a danger to crew health and spacecraft integrity. The use of antimicrobial surfaces provides an alternative strategy for inhibiting microbial growth and biofilm formation to conventional cleaning procedures and the use of disinfectants. Antimicrobial surfaces contain organic or inorganic compounds, such as antimicrobial peptides or copper and silver, that inhibit microbial growth. The efficacy of wetted oxidized copper layers and pure copper surfaces as antimicrobial agents was tested by applying cultures of Escherichia coli and Staphylococcus cohnii to these metallic surfaces. Stainless steel surfaces were used as non-inhibitory control surfaces. The production of reactive oxygen species and membrane damage increased rapidly within 1 h of exposure on pure copper surfaces, but the effect on cell survival was negligible even after 2 h of exposure. However, longer exposure times of up to 4 h led to a rapid decrease in cell survival, whereby the survival of cells was additionally dependent on the exposed cell density. Finally, the release of metal ions was determined to identify a possible correlation between copper ions in suspension and cell survival. These measurements indicated a steady increase of free copper ions, which were released indirectly by cells presumably through excreted complexing agents. These data indicate that the application of antimicrobial surfaces in spaceflight facilities could improve crew health and mitigate material damage caused by microbial contamination and biofilm formation. Furthermore, the results of this study indicate that cuprous oxide layers were superior to pure copper surfaces related to the antimicrobial effect and that cell density is a significant factor that influences the time dependence of

  12. Central configurations of the collinear three-body problem and singular surfaces in the mass space

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Zhifu, E-mail: zxie@vsu.edu [Department of Mathematics and Computer Science, Virginia State University, Petersburg, VA 23806 (United States)

    2011-09-12

    This Letter is to provide a new approach to study the phenomena of degeneracy of the number of the collinear central configurations under geometric equivalence. A direct and simple explicit parametric expression of the singular surface H{sub 3} is constructed in the mass space (m{sub 1},m{sub 2},m{sub 3}) element of (R{sup +}){sup 3}. The construction of H{sub 3} is from an inverse respective, that is, by specifying positions for the bodies and then determining the masses that are possible to yield a central configuration. It reveals the relationship between the phenomena of degeneracy and the inverse problem of central configurations. We prove that the number of central configurations is decreased to 3!/2-1=2, m{sub 1}, m{sub 2}, and m{sub 3} are mutually distinct if m element of H{sub 3}. Moreover, we know not only the number of central configurations but also what the nonequivalent central configurations are. -- Highlights: → Provide a new method to study the degeneracy of number of CC. → Results advanced the understanding of number of central configurations. → Singular mass surface H{sub 3} is given by a direct and simple parametric expression. → The proof only requires some basic knowledge of linear algebra. → The method can be applied to some other collinear n-body problem.

  13. Alterations in physical state of silver nanoparticles exposed to synthetic human stomach fluid

    International Nuclear Information System (INIS)

    Rogers, Kim R.; Bradham, Karen; Tolaymat, Thabet; Thomas, David J.; Hartmann, Thomas; Ma, Longzhou; Williams, Alan

    2012-01-01

    The bioavailability of ingested silver nanoparticles (AgNPs) depends in large part on initial particle size, shape and surface coating, properties which will influence aggregation, solubility and chemical composition during transit of the gastrointestinal tract. Citrate-stabilized AgNPs were exposed to synthetic human stomach fluid (SSF) (pH 1.5) and changes in size, shape, zeta potential, hydrodynamic diameter and chemical composition were determined during a 1 h exposure period using Surface Plasmon Resonance (SPR), High Resolution Transmission Electron Microscopy/Energy Dispersive X-ray Spectroscopy (TEM/EDS), Dynamic Light Scattering (DLS) and X-ray Powder Diffraction (XRD) combined with Rietveld analysis. Exposure of AgNPs to SSF produced a rapid decrease in the SPR peak at 414 nm and the appearance of a broad absorbance peak in the near infrared (NIR) spectral region. During exposure to SSF, changes in zeta potential, aggregation and morphology of the particles were also observed as well as production of silver chloride which appeared physically associated with particle aggregates. - Highlights: ► Citrate-stabilized AgNPs were exposed to synthetic human stomach fluid (pH 1.5). ► Particle changes in chemical composition, zeta potential, aggregation and morphology were observed. ► Silver chloride appeared to be physically associated with the particle aggregates.

  14. Changes in viability of two Antarctic marine bacteria exposed to solar radiation in the water column: influence of vertical mixing

    International Nuclear Information System (INIS)

    Hernandez, E.A.

    2007-01-01

    The effect of UV radiation on two Antarctic marine bacterial strains (UVps and UVvi) was studied in the water column of Potter Cove (South Shetland, Antarctica). Quartz flasks were filled with the bacterial suspensions and exposed to solar radiation at 0 m, 1 m and 3 m depth. Assays using flasks exposed to direct solar radiation and others using flasks covered with/by interferential filters which discriminate between UVA and UVB, were performed. In other assays, a vertical mixing of 4 m/h was simulated. Both strains showed a significant decrease in viability (expressed as colony - forming units) when exposed to a surface UVB dose of 8.4 kJ m -2 . Studies with interferential filters showed a significant decrease at 0 and 1 m depth under both UV treatments. The UVps strain appeared to be more sensitive to UVB than to UVA. Damage produced by UVB was attenuated by the vertical mixing when the surface UVB dose was 4.8 kJ m -2 . This effect was not observed when surface UVB dose was 7.7 kJ m -2 . These results show that the negative effect caused by UVB radiation on the bacterio plankton would be significant only in the first meter of water column of the Antarctic coastal waters with high levels of suspended particulate material. (author) [es

  15. Evaluation of transport properties of nanofiltration membranes exposed to radioactive liquid waste

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Elizabeth E.M.; Barbosa, Celina C.R.; Bastos, Edna T.R., E-mail: eemo@ien.gov.br [Instituto de Engenharia Nuclear (IEN/CNEN-RJ), Rio de Janeira, RJ (Brazil); Afonso, Julio C., E-mail: Julio@iq.ufrj.br [Universidade Federal do Rio de Janeiro (UFRJ), RJ (Brazil). Inst. de Quimica. Dept. de Quimica Analitica

    2011-07-01

    The application of membrane separation processes (PSM) for treatment of radioactive waste requires the selection of a suitable membrane for the treatment of waste, as the membrane will be directly exposed to the radioactive liquid waste, and also exposed to ionizing radiation. The nanofiltration membrane is most suitable for treatment of radioactive waste, since it has high rejection of multivalent ions. Usually the membranes are made of polymers and depending on the composition of the waste, type and dose of radiation absorbed may be changes in the structure of the membrane, resulting in loss of its transport properties. We tested two commercial nanofiltration membranes: NF and SW Dow/Filmtec. The waste liquid used was obtained in the process of conversion of uranium hexafluoride gas to solid uranium dioxide, known as 'carbonated water'. The membranes were characterized as their transport properties (hydraulic permeability, permeate flux and salt rejection) before and after their immersion in the waste for 24 hours. The surface of the membranes was also evaluated by SEM and FTIR. It was observed that in both the porosity of the membrane selective layer was altered, but not the membrane surface charge, which is responsible for the selectivity of the membrane. The NF membranes and SW showed uranium ion rejection of 64% and 55% respectively. (author)

  16. Results of dosimetric measurements in space missions

    Science.gov (United States)

    Reitz, G.; Beaujean, R.; Heilmann, C.; Kopp, J.; Leicher, M.; Strauch, K.

    Detector packages consisting of plastic nuclear track detectors, nuclear emulsions, and thermoluminescence detectors were exposed at different locations inside the space laboratory Spacelab and at the astronauts' body and in different sections of the MIR space station. Total dose, particle fluence rate and linear energy transfer (LET) spectra of heavy ions, number of nuclear disintegrations and fast neutron fluence rates were determined of each exposure. The dose equivalent received by the Payload specialists (PSs) were calculated from the measurements, they range from 190 muSv d^-1 to 770 muSv d^-1. Finally, a preliminary investigation of results from a particle telescope of two silicon detectors, first used in the last BIORACK mission on STS 76, is reported.

  17. Land surface temperature distribution and development for green open space in Medan city using imagery-based satellite Landsat 8

    Science.gov (United States)

    Sulistiyono, N.; Basyuni, M.; Slamet, B.

    2018-03-01

    Green open space (GOS) is one of the requirements where a city is comfortable to stay. GOS might reduce land surface temperature (LST) and air pollution. Medan is one of the biggest towns in Indonesia that experienced rapid development. However, the early development tends to neglect the GOS existence for the city. The objective of the study is to determine the distribution of land surface temperature and the relationship between the normalized difference vegetation index (NDVI) and the priority of GOS development in Medan City using imagery-based satellite Landsat 8. The method approached to correlate the distribution of land surface temperature derived from the value of digital number band 10 with the NDVI which was from the ratio of groups five and four on satellite images of Landsat 8. The results showed that the distribution of land surface temperature in the Medan City in 2016 ranged 20.57 - 33.83 °C. The relationship between the distribution of LST distribution with NDVI was reversed with a negative correlation of -0.543 (sig 0,000). The direction of GOS in Medan City is therefore developed on the allocation of LST and divided into three priority classes namely first priority class had 5,119.71 ha, the second priority consisted of 16,935.76 ha, and third priority of 6,118.50 ha.

  18. Interactive Design and Visualization of Branched Covering Spaces.

    Science.gov (United States)

    Roy, Lawrence; Kumar, Prashant; Golbabaei, Sanaz; Zhang, Yue; Zhang, Eugene

    2018-01-01

    Branched covering spaces are a mathematical concept which originates from complex analysis and topology and has applications in tensor field topology and geometry remeshing. Given a manifold surface and an -way rotational symmetry field, a branched covering space is a manifold surface that has an -to-1 map to the original surface except at the ramification points, which correspond to the singularities in the rotational symmetry field. Understanding the notion and mathematical properties of branched covering spaces is important to researchers in tensor field visualization and geometry processing, and their application areas. In this paper, we provide a framework to interactively design and visualize the branched covering space (BCS) of an input mesh surface and a rotational symmetry field defined on it. In our framework, the user can visualize not only the BCSs but also their construction process. In addition, our system allows the user to design the geometric realization of the BCS using mesh deformation techniques as well as connecting tubes. This enables the user to verify important facts about BCSs such as that they are manifold surfaces around singularities, as well as the Riemann-Hurwitz formula which relates the Euler characteristic of the BCS to that of the original mesh. Our system is evaluated by student researchers in scientific visualization and geometry processing as well as faculty members in mathematics at our university who teach topology. We include their evaluations and feedback in the paper.

  19. Carbon Nanotube Based Chemical Sensors for Space and Terrestrial Applications

    Science.gov (United States)

    Li, Jing; Lu, Yijiang

    2009-01-01

    A nanosensor technology has been developed using nanostructures, such as single walled carbon nanotubes (SWNTs), on a pair of interdigitated electrodes (IDE) processed with a silicon-based microfabrication and micromachining technique. The IDE fingers were fabricated using photolithography and thin film metallization techniques. Both in-situ growth of nanostructure materials and casting of the nanostructure dispersions were used to make chemical sensing devices. These sensors have been exposed to nitrogen dioxide, acetone, benzene, nitrotoluene, chlorine, and ammonia in the concentration range of ppm to ppb at room temperature. The electronic molecular sensing of carbon nanotubes in our sensor platform can be understood by intra- and inter-tube electron modulation in terms of charge transfer mechanisms. As a result of the charge transfer, the conductance of p-type or hole-richer SWNTs in air will change. Due to the large surface area, low surface energy barrier and high thermal and mechanical stability, nanostructured chemical sensors potentially can offer higher sensitivity, lower power consumption and better robustness than the state-of-the-art systems, which make them more attractive for defense and space applications. Combined with MEMS technology, light weight and compact size sensors can be made in wafer scale with low cost. Additionally, a wireless capability of such a sensor chip can be used for networked mobile and fixed-site detection and warning systems for military bases, facilities and battlefield areas.

  20. Temperature impact on the micro structure of tungsten exposed to He irradiation in LHD

    International Nuclear Information System (INIS)

    Bernard, Elodie; Sakamoto, Ryuichi; Tokitani, Masayuki; Masuzaki, Suguru; Hayashi, Hiromi; Yamada, Hiroshi; Yoshida, Naoaki

    2017-01-01

    A new temperature controlled material probe was designed for the exposure of tungsten samples to helium plasma in the LHD. Samples were exposed to estimated fluences of ∼10 23  m −2 and temperatures ranging from 65 to 600 °C. Transmission Electron Microscopy analysis allowed the study of the impact of He irradiation under high temperatures on tungsten micro structure for the first time in real-plasma exposure conditions. Both dislocation loops and bubbles appeared from low to medium temperatures and saw an impressive increase of size (factor 4 to 6) most probably by coalescence as the temperature reaches 600 °C, with 500 °C appearing as a threshold for bubble growth. Annealing of the samples up to 800 C highlighted the stability of the dislocation damages formed by helium irradiation at high surface temperature, as bubbles and dislocation loops seem to conserve their characteristics. Additional studies on cross-sections showed that bubbles were formed much deeper (70–100 nm) than the heavily damaged surface layer (10–20 nm), raising concern about the impact on the material mechanical properties conservation and potential additional trapping of hydrogen isotopes. - Highlights: • Design and test of a temperature-controlled sample holder to expose samples in LHD. • Dislocation loops and bubbles created in W even at low fluences and temperatures. • Heavily damaged layer (10–20 nm thick) very rich in damages formed at the surface. • He bubbles observed much deeper than implantation range (until 100 nm). • He effects not only at the surface, raising concerns for properties conservation.

  1. Infrared and Raman spectroscopy on synthetic glasses as analogues of planetary surfaces.

    Science.gov (United States)

    Weber, Iris; Morlok, Andreas; Klemme, Stephan; Dittmer, Isabelle; Stojic, Aleksandra N.; Hiesinger, Harald; Sohn, Martin; Helbert, Jörn

    2015-04-01

    One of the fundamental aims of space mission is to understand the physical, chemical, and geologic processes and conditions of planetary formation and evolution. For this purpose, it is important to investigate analog material to correctly interpret the returned spacecraft data, including the spectral information from remote planetary surfaces. For example, mid-infrared spectroscopy provides detailed information on the mineralogical compositions of planetary surfaces via remote sensing. Data is affected by numerous factors such as grain size, illumination geometry, space weathering, and temperature. These features need to be systematically investigated on analog material in terrestrial laboratories in order to understand the mineralogy/composition of a planetary surface. In addition, Raman spectroscopy allows non-destructive analyses of planetary surfaces in the case of a landing mission. Our work at the IRIS (Infrared spectroscopy for Interplanetary Studies) laboratory at the Institut für Planetologie produces spectra for a database of the ESA/JAXA BepiColombo mission to Mercury. Onboard is a mid-infrared spectrometer (MERTIS-Mercury Radiometer and Thermal Infrared Spectrometer). This unique instrument allows us to map spectral features in the 7-14 µm range, with a spatial resolution of ~500 m [1-5]. Comparably, using our Raman spectrometer, we are continuously contributing to the Raman database for upcoming mission, e.g., the Raman Laser Spectrometer (RLS) onboard of ExoMars [6]. Material on the surface of Mercury and the other terrestrial bodies was exposed to heavy impact cratering [4]. Depending on the P/T conditions during the impact, minerals on planetary surfaces can react with the formation of glassy material. Thus, understanding the effects of impact shock and heat on the mineral structure and the resulting corresponding change in the spectral properties is of high interest for the MERTIS project. Here, we present spectral information on the first glass

  2. Direct observation of atoms on surfaces by scanning tunnelling microscopy

    International Nuclear Information System (INIS)

    Baldeschwieler, J.D.

    1989-01-01

    The scanning tunnelling microscope is a non-destructive means of achieving atomic level resolution of crystal surfaces in real space to elucidate surface structures, electronic properties and chemical composition. Scanning tunnelling microscope is a powerful, real space surface structure probe complementary to other techniques such as x-ray diffraction. 21 refs., 8 figs

  3. Gene Expression Profiling in Lung Tissues from Rat Exposed to Lunar Dust Particles

    Science.gov (United States)

    Zhang, Ye; Lam, Chiu-Wing; Zalesak, Selina M.; Kidane, Yared H.; Feiveson, Alan H.; Ploutz-Snyder, Robert; Scully, Robert R.; Williams, Kyle; Wu, Honglu; James, John T.

    2014-01-01

    The Moon's surface is covered by a layer of fine, reactive dust. Lunar dust contain about 1-2% of very fine dust (gene expression changes in lung tissues from rats exposed to lunar dust particles. F344 rats were exposed for 4 weeks (6h/d; 5d/wk) in nose-only inhalation chambers to concentrations of 0 (control air), 2.1, 6.8, 21, and 61 mg/m(exp 3) of lunar dust. Five rats per group were euthanized 1 day, and 3 months after the last inhalation exposure. The total RNAs were isolated from lung tissues after being lavaged. The Agilent Rat GE v3 microarray was used to profile global gene expression (44K). The genes with significant expression changes are identified and the gene expression data were further analyzed using various statistical tools.

  4. Computer representation of molecular surfaces

    International Nuclear Information System (INIS)

    Max, N.L.

    1981-01-01

    This review article surveys recent work on computer representation of molecular surfaces. Several different algorithms are discussed for producing vector or raster drawings of space-filling models formed as the union of spheres. Other smoother surfaces are also considered

  5. Optical detections from worn and unworn titanium compound surfaces

    DEFF Research Database (Denmark)

    Rasmussen, Inge Lise; Guibert, M.; Martin, J.-M.

    2010-01-01

    of a titanium nitride (TiN) layer we obtain an increase in the reflected light as a result of wear. The relative change of reflectance of light from the tribological TiAlN coated surface to the underlying layer of TiN is similar for non-worn surfaces and for surfaces exposed to an abrasive wear process...... of a residual thickness of realistic tribological coatings prior to complete wear....

  6. 9 CFR 78.8 - Brucellosis exposed cattle.

    Science.gov (United States)

    2010-01-01

    ... 9 Animals and Animal Products 1 2010-01-01 2010-01-01 false Brucellosis exposed cattle. 78.8... Restrictions on Interstate Movement of Cattle Because of Brucellosis § 78.8 Brucellosis exposed cattle. Brucellosis exposed cattle may be moved interstate only as follows: (a) Movement to recognized slaughtering...

  7. Effect of Blood Contamination on Marginal Adaptation and Surface Microstructure of Mineral Trioxide Aggregate: A SEM Study.

    Science.gov (United States)

    Salem Milani, Amin; Rahimi, Saeed; Froughreyhani, Mohammad; Vahid Pakdel, Mahdi

    2013-01-01

    In various clinical situations, mineral trioxide aggregate (MTA) may come into direct contact or even be mixed with blood. The aim of the present study was to evaluate the effect of exposure to blood on marginal adaptation and surface microstructure of MTA. Thirty extracted human single-rooted teeth were used. Standard root canal treatment was carried out. Root-ends were resected, and retrocavities were prepared. The teeth were randomly divided into two groups (n = 15): in group 1, the internal surface of the cavities was coated with fresh blood. Then, the cavities were filled with MTA. The roots were immersed in molds containing fresh blood. In group 2, the aforementioned procedures were performed except that synthetic tissue fluid (STF) was used instead of blood. To assess the marginal adaptation, "gap perimeter" and "maximum gap width" were measured under scanning electron microscope. The surface microstructure was also examined. Independent samples t-test and Mann-Whitney U test were used to analyze the data. Maximum gap width and gap perimeter in the blood-exposed group were significantly larger than those in the STF-exposed group (p < 0.01). In the blood-exposed group, the crystals tended to be more rounded and less angular compared with the STF-exposed group, and there was a general lack of needle-like crystals. Exposure to blood during setting has a negative effect on marginal adaptation of MTA, and blood-exposed MTA has a different surface microstructure compared to STF-exposed MTA.

  8. Leukemias in the progeny of exposed parents

    International Nuclear Information System (INIS)

    Kosenko, M.M.; Gudkova, N.V.

    1996-01-01

    The purpose of this study was to assess the incidence of leukemias among the progeny of exposed parents. The parents were exposed as a result of discharge of radioactive waste from the Mayak atomic plant into the Techa river in the Southern Urals. The doses per parents gonads, ranging from 0.035 to 1.27 Sv, were due to external exposure in 1950-1956 and to incorporation of Cs-137. Nine cases with leukemia and four with lympohoma were recorded in 13.500 antenatally exposed subjects and descendants of exposed parents over the period of 1950 to 1988. The leukemia morbidity index for the progeny of exposed parents was 2.51, which virtually not statistically differ from that in control group. Refs. 7, figs. 3, tabs. 3

  9. Single crystalline Co3O4 nanocrystals exposed with different crystal planes for Li-O2 batteries.

    Science.gov (United States)

    Su, Dawei; Dou, Shixue; Wang, Guoxiu

    2014-08-29

    Single crystalline Co3O4 nanocrystals exposed with different crystal planes were synthesised, including cubic Co3O4 nanocrystals enclosed by {100} crystal planes, pseudo octahedral Co3O4 enclosed by {100} and {110} crystal planes, Co3O4 nanosheets exposed by {110} crystal planes, hexagonal Co3O4 nanoplatelets exposed with {111} crystal planes, and Co3O4 nanolaminar exposed with {112} crystal planes. Well single crystalline features of these Co3O4 nanocrystals were confirmed by FESEM and HRTEM analyses. The electrochemical performance for Li-O2 batteries shows that Co3O4 nanocrystals can significantly reduce the discharge-charge over-potential via the effect on the oxygen evolution reaction (OER). From the comparison on their catalytic performances, we found that the essential factor to promote the oxygen evolution reactions is the surface crystal planes of Co3O4 nanocrystals, namely, crystal planes-dependent process. The correlation between different Co3O4 crystal planes and their effect on reducing charge-discharge over-potential was established: {100} < {110} < {112} < {111}.

  10. The CEOS-Land Surface Imaging Constellation Portal for GEOSS: A resource for land surface imaging system information and data access

    Science.gov (United States)

    Holm, Thomas; Gallo, Kevin P.; Bailey, Bryan

    2010-01-01

    The Committee on Earth Observation Satellites is an international group that coordinates civil space-borne observations of the Earth, and provides the space component of the Global Earth Observing System of Systems (GEOSS). The CEOS Virtual Constellations concept was implemented in an effort to engage and coordinate disparate Earth observing programs of CEOS member agencies and ultimately facilitate their contribution in supplying the space-based observations required to satisfy the requirements of the GEOSS. The CEOS initially established Study Teams for four prototype constellations that included precipitation, land surface imaging, ocean surface topography, and atmospheric composition. The basic mission of the Land Surface Imaging (LSI) Constellation [1] is to promote the efficient, effective, and comprehensive collection, distribution, and application of space-acquired image data of the global land surface, especially to meet societal needs of the global population, such as those addressed by the nine Group on Earth Observations (GEO) Societal Benefit Areas (SBAs) of agriculture, biodiversity, climate, disasters, ecosystems, energy, health, water, and weather. The LSI Constellation Portal is the result of an effort to address important goals within the LSI Constellation mission and provide resources to assist in planning for future space missions that might further contribute to meeting those goals.

  11. Space Radiation and Risks to Human Health

    Science.gov (United States)

    Huff, Janice L.; Patel, Zarana S.; Simonsen, Lisa C.

    2014-01-01

    The radiation environment in space poses significant challenges to human health and is a major concern for long duration manned space missions. Outside the Earth's protective magnetosphere, astronauts are exposed to higher levels of galactic cosmic rays, whose physical characteristics are distinct from terrestrial sources of radiation such as x-rays and gamma-rays. Galactic cosmic rays consist of high energy and high mass nuclei as well as high energy protons; they impart unique biological damage as they traverse through tissue with impacts on human health that are largely unknown. The major health issues of concern are the risks of radiation carcinogenesis, acute and late decrements to the central nervous system, degenerative tissue effects such as cardiovascular disease, as well as possible acute radiation syndromes due to an unshielded exposure to a large solar particle event. The NASA Human Research Program's Space Radiation Program Element is focused on characterization and mitigation of these space radiation health risks along with understanding these risks in context of the other biological stressors found in the space environment. In this overview, we will provide a description of these health risks and the Element's research strategies to understand and mitigate these risks.

  12. Structure of Hilbert space operators

    CERN Document Server

    Jiang, Chunlan

    2006-01-01

    This book exposes the internal structure of non-self-adjoint operators acting on complex separable infinite dimensional Hilbert space, by analyzing and studying the commutant of operators. A unique presentation of the theorem of Cowen-Douglas operators is given. The authors take the strongly irreducible operator as a basic model, and find complete similarity invariants of Cowen-Douglas operators by using K -theory, complex geometry and operator algebra tools. Sample Chapter(s). Chapter 1: Background (153 KB). Contents: Jordan Standard Theorem and K 0 -Group; Approximate Jordan Theorem of Opera

  13. Evaluating greater sage-grouse seasonal space use relative to leks: Implications for surface use designations in sagebrush ecosystems

    Science.gov (United States)

    Casazza, Michael L.; Coates, Peter S.

    2013-01-01

    The development of anthropogenic structures, especially those related to energy resources, in sagebrush ecosystems is an important concern among developers, conservationists, and land managers in relation to greater sage-grouse (Centrocercus urophasianus; hereafter, sage-grouse) populations. Sage-grouse are dependent on sagebrush ecosystems to meet their seasonal life-phase requirements, and research indicates that anthropogenic structures can adversely affect sage-grouse populations. Land management agencies have attempted to reduce the negative effects of anthropogenic development by assigning surface use (SU) designations, such as no surface occupancy, to areas around leks (breeding grounds). However, rationale for the size of these areas is often challenged. To help inform this issue, we used a spatial analysis of sage-grouse utilization distributions (UDs) to quantify seasonal (spring, summer and fall, winter) sage-grouse space use in relation to leks. We sampled UDs from 193 sage-grouse (11,878 telemetry locations) across 4 subpopulations within the Bi-State Distinct Population Segment (DPS, bordering California and Nevada) during 2003–2009. We quantified the volume of each UD (vUD) within a range of areas that varied in size and were centered on leks, up to a distance of 30 km from leks. We also quantified the percentage of nests within those areas. We then estimated the diminishing gains of vUD as area increased and produced continuous response curves that allow for flexibility in land management decisions. We found nearly 90% of the total vUD (all seasons combined) was contained within 5 km of leks, and we identified variation in vUD for a given distance related to season and migratory status. Five kilometers also represented the 95th percentile of the distribution of nesting distances. Because diminishing gains of vUD was not substantial until distances exceeded 8 km, managers should consider the theoretical optimal distances for SU designation

  14. Liquid Hydrogen Propellant Tank Sub-Surface Pressurization with Gaseous Helium

    Science.gov (United States)

    Stephens, J. R.; Cartagena, W.

    2015-01-01

    A series of tests were conducted to evaluate the performance of a propellant tank pressurization system with the pressurant diffuser intentionally submerged beneath the surface of the liquid. Propellant tanks and pressurization systems are typically designed with the diffuser positioned to apply pressurant gas directly into the tank ullage space when the liquid propellant is settled. Space vehicles, and potentially propellant depots, may need to conduct tank pressurization operations in micro-gravity environments where the exact location of the liquid relative to the diffuser is not well understood. If the diffuser is positioned to supply pressurant gas directly to the tank ullage space when the propellant is settled, then it may become partially or completely submerged when the liquid becomes unsettled in a microgravity environment. In such case, the pressurization system performance will be adversely affected requiring additional pressurant mass and longer pressurization times. This series of tests compares and evaluates pressurization system performance using the conventional method of supplying pressurant gas directly to the propellant tank ullage, and then supplying pressurant gas beneath the liquid surface. The pressurization tests were conducted on the Engineering Development Unit (EDU) located at Test Stand 300 at NASA Marshall Space Flight Center (MSFC). EDU is a ground based Cryogenic Fluid Management (CFM) test article supported by Glenn Research Center (GRC) and MSFC. A 150 ft3 propellant tank was filled with liquid hydrogen (LH2). The pressurization system used regulated ambient helium (GHe) as a pressurant, a variable position valve to maintain flow rate, and two identical independent pressurant diffusers. The ullage diffuser was located in the forward end of the tank and was completely exposed to the tank ullage. The submerged diffuser was located in the aft end of the tank and was completely submerged when the tank liquid level was 10% or greater

  15. Rate-Dependent Slip of Newtonian Liquid at Smooth Surfaces

    International Nuclear Information System (INIS)

    Zhu, Yingxi; Granick, Steve

    2001-01-01

    Newtonian fluids were placed between molecularly smooth surfaces whose spacing was vibrated at spacings where the fluid responded as a continuum. Hydrodynamic forces agreed with predictions from the no-slip boundary condition only provided that flow rate (peak velocity normalized by spacing) was low, but implied partial slip when it exceeded a critical level, different in different systems, correlated with contact angle (surface wettability). With increasing flow rate and partially wetted surfaces, hydrodynamic forces became up to 2--4 orders of magnitude less than expected by assuming the no-slip boundary condition that is commonly stated in textbooks

  16. Comparison of the light flash phenomena observed in space and in laboratory experiments

    International Nuclear Information System (INIS)

    McNulty, P.J.; Pease, V.P.; Bond, V.P.

    1976-01-01

    Astronauts on Apollo and Skylab missions have reported observing a variety of visual phenomena when their eyes were closed and adapted to darkness. These observations were studied under controlled conditions during a number of sessions on board Apollo and Skylab spacecraft and the data available to date on these so-called light flashes is in the form of descriptions of the phenomena and frequency of occurrence. Similar visual phenomena have been demonstrated in a number of laboratories by exposing the eyes of human subjects to beams of neutrons, alphas, pions, and protons. More than one physical mechanism is involved in the laboratory and space phenomena. No direct comparison of the laboratory and space observations has been made by observers who have experienced both. However, the range of visual phenomena observed in the laboratory is consistent with the Apollo and Skylab observations. Measured detection efficiencies can be used to estimate the frequencies with which various phenomena would be observed if the subject was exposed to cosmic rays in space

  17. A Review of Tribomaterial Technology for Space Nuclear Power Systems

    Science.gov (United States)

    Stanford, Malcolm K.

    2007-01-01

    The National Aeronautics and Space Administration (NASA) has recently proposed a nuclear closed-cycle electric power conversion system for generation of 100-kW of electrical power for space exploration missions. A critical issue is the tribological performance of sliding components within the power conversion unit that will be exposed to neutron radiation. This paper presents a review of the main considerations that have been made in the selection of solid lubricants for similar applications in the past as well as a recommendations for continuing development of the technology.

  18. Phase Identification and Internal Stress Analysis of Steamside Oxides on Plant Exposed Superheater Tubes

    DEFF Research Database (Denmark)

    Pantleon, Karen; Montgomery, Melanie

    2012-01-01

    During long-term, high-temperature exposure of superheater tubes in thermal power plants, various oxides are formed on the inner side (steamside) of the tubes, and oxide spallation is a serious problem for the power plant industry. Most often, oxidation in a steam atmosphere is investigated...... in laboratory experiments just mimicking the actual conditions in the power plant for simplified samples. On real plant-exposed superheater tubes, the steamside oxides are solely investigated microscopically. The feasibility of X-ray diffraction for the characterization of steamside oxidation on real plant......-exposed superheater tubes was proven in the current work; the challenges for depth-resolved phase analysis and phase-specific residual stress analysis at the inner side of the tubes with concave surface curvature are discussed. Essential differences between the steamside oxides formed on two different steels...

  19. Photocatalytic selective oxidation of phenol in suspensions of titanium dioxide with exposed {0 0 1} facets

    International Nuclear Information System (INIS)

    Ye, Hengpeng; Lu, Shaoming

    2013-01-01

    Anatase TiO 2 nanocrystals with exposed {0 0 1} facets were tailored by hydrothermal treatment of Ti(OC 4 H 9 ) 4 –HF–H 2 O mixed solution. The photocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), nitrogen adsorption–desorption isotherms and X-ray photoelectron spectroscopy (XPS). The effect of structure of the photocatalyst on the photocatalytic selective oxidation of phenol under UV irradiation was studied. The experiment results showed that (1) the percentage of the exposed {0 0 1} facets of the nanocrystal increases with increasing the nominal atomic ratio of fluorine to titanium (R F ), (2) catechol and hydroquinone are main intermediates detected during photocatalytic oxidation of phenol, and (3) both photocatalytic oxidation of phenol and selectivity (yield) of catechol are positively correlated with the percentage of exposed {0 0 1} facets of the high-energy TiO 2 nanocrystals. The enhanced conversion of phenol and selectivity (yield) of catechol were ascribed to the synergistic effects of the exposed high-energy {0 0 1} facets and surface fluorination. This study may provide new insight into the selective oxidation of organics.

  20. Inhibition of immune responses and related proteins in Rhamdia quelen exposed to diclofenac.

    Science.gov (United States)

    Ribas, João L C; Sherry, James P; Zampronio, Aleksander R; Silva de Assis, Helena C; Simmons, Denina B D

    2017-08-01

    Nonsteroidal anti-inflammatory drugs are among the most widely detected pharmaceuticals in surface water worldwide. The nonsteroidal anti-inflammatory drug diclofenac is used to treat many types of pain and inflammation. Diclofenac's potential to cause adverse effects in exposed wildlife is a growing concern. To evaluate the effects of waterborne diclofenac on the immune response in Rhamdia quelen (South American catfish), fish were exposed to 3 concentrations of diclofenac (0.2, 2.0, and 20.0 μg/L) for 14 d. Some of the exposed fish were also given an intraperitoneal injection on day 14 of 1 mg/kg of carrageenan to evaluate cell migration to the peritoneum. Total blood leukocyte count and carrageenan-induced leukocyte migration to the peritoneal cavity, particularly of polymorphonuclear cells, were significantly affected for all diclofenac exposure groups. Nitric oxide production was significantly reduced in the diclofenac-treated fish. Plasma and kidney proteins were analyzed by means of liquid chromatography-tandem mass spectrometry in a shotgun proteomic approach. In both plasma and kidney of diclofenac-exposed R. quelen, the expression of 20 proteins related to the inflammatory process, nitric oxide production, leukocyte migration, and the complement cascade was significantly altered. In addition, class I major histocompatibility complex was significantly decreased in plasma of diclofenac-treated fish. Thus, waterborne exposure to diclofenac could lead to suppression of the innate immune system in R. quelen. Environ Toxicol Chem 2017;36:2092-2107. © 2017 SETAC. © 2017 SETAC.