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Sample records for close-spaced sublimation deposition

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

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

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

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

    SciTech Connect

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

    1996-05-01

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

  3. 12% efficient CdTe/CdS thin film solar cells deposited by low-temperature close space sublimation

    NASA Astrophysics Data System (ADS)

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

    2011-09-01

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

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

    SciTech Connect

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

    2015-09-15

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

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

    NASA Astrophysics Data System (ADS)

    Marinskiy, Dmitriy Nikolaevich

    1998-12-01

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

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

    SciTech Connect

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

    1996-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1996-01-01

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

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

    SciTech Connect

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

    1997-12-31

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

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

    NASA Astrophysics Data System (ADS)

    Malhotra, C. P.

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

  10. Possibility of graphene growth by close space sublimation.

    PubMed

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

    2014-04-14

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

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

    PubMed

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

    2009-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Mahmood, Waqar; Shah, Nazar Abbas

    2014-06-01

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

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

    PubMed

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

    2005-07-01

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

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

    NASA Astrophysics Data System (ADS)

    Sundar, Aarthi

    The ability to fabricate structures and engineer materials on the nanoscale leads to the development of new devices and the study of exciting phenomena. Nanostructures attached to the surface of a substrate, in a manner that renders them immobile, have numerous potential applications in a diverse number of areas. Substrate-supported nanostructures can be fabricated using numerous modalities; however the easiest and most inexpensive technique to create a large area of randomly distributed particles is by the technique of thermal dewetting. In this process a metastable thin film is deposited at room temperature and heated, causing the film to lower its surface energy by agglomerating into droplet-like nanostructures. The main drawbacks of nanostructure fabrication via this technique are the substantial size distributions realized and the lack of control over nanostructure placement. In this doctoral dissertation, a new pathway for imposing order onto the thermal dewetting process and for manipulating the size, placement, shape and composition of preformed templates is described. It sees the confinement of substrate-supported thin films or nanostructure templates by the free surface of a metal film or a second substrate surface. Confining the templates in this manner and heating them to elevated temperatures leads to changes in the characteristics of the nanostructures formed. Three different modalities are demonstrated which alters the preformed structures by: (i) subtracting atoms from the templates, (ii) adding atoms to the template or (iii) simultaneously adding and subtracting atoms. The ability to carry out such processes depends on the choice of the confining surface and the nanostructured templates used. A subtractive process occurs when an electroformed nickel mesh is placed in conformal contact with a continuous gold film while it dewets, resulting in the formation of a periodic array of gold microstructures on an oxide substrate surface. When heated the

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

    SciTech Connect

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

    2014-11-14

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

  16. MALDI Imaging of Lipids after Matrix Sublimation/Deposition

    PubMed Central

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

    2011-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Hofstadter, Mark D.; Murray, Bruce C.

    1990-01-01

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

  18. Rare earths behaviour during the deposition of volcanic sublimates

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

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

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

    PubMed

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

    2014-05-07

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

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

    DOEpatents

    Feng, Tom; Ghosh, Amal K.

    1979-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

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

    PubMed

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

    2004-10-28

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

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

    SciTech Connect

    Moore, J.M.

    1990-01-01

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

  5. A search for closely spaced gravitational lenses

    SciTech Connect

    Crampton, D.; Mcclure, R.D.; Fletcher, J.M.; Hutchings, J.B. National Research Council of Canada, Herzberg Institute of Astrophysics, Ottawa )

    1989-10-01

    A new image-stabilizing camera was used to search for closely spaced images of a sample of 25 intrinsically luminous quasars with z greater than 1.6 and m smaller than 19. Observations of seven similarly selected quasars with the regular CCD camera in good seeing conditions are also reported. Of the 32 quasars, seven are gravitational lens candidates. Two of these have subarcsecond separations. Additional information on all these candidates is required. 22 refs.

  6. The Sublime and Education

    ERIC Educational Resources Information Center

    Carson, Jamin

    2006-01-01

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

  7. Controlled Microbial Cenoses in Closed Spaces

    NASA Astrophysics Data System (ADS)

    Somova, Lydia; Mikheeva, Galina

    Controlled microbial cenoses have good prospects in closed spaces: for air treatment in LSS and cellars industrial premises; for sewage treatment in LSS; for increase of productivity and protect of plants from infections in LSS. Possible methods of formation of microbiocenoses are: selection, autoselection, artificial formation taking into account their biochemical properties and metabolic interactions. Experimental microbiocenoses, has been produced on the basis of natural association of microorganisms by long cultivation on specially developed medium. Dominating groups are bacteria of genera: Lactobacillus, Streptococcus, Leuconostoc, Bidobac-terium, Rhodopseudomonas and yeast of genera: Kluyveromyces, Saccharomyces and Torulop-sis. Microbiocenoses do not contain pathogenic and conditionally pathogenic microorganisms, they possess opposing and probiotic properties. Different examples of microbial cenoses actions are to be presented in the paper.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  9. 46 CFR 72.15-15 - Ventilation for closed spaces.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 3 2014-10-01 2014-10-01 false Ventilation for closed spaces. 72.15-15 Section 72.15-15... ARRANGEMENT Ventilation § 72.15-15 Ventilation for closed spaces. (a) All enclosed spaces within the vessel... spaces and for closing all doorways, ventilators and annular spaces around funnels and other openings...

  10. 46 CFR 92.15-10 - Ventilation for closed spaces.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 4 2014-10-01 2014-10-01 false Ventilation for closed spaces. 92.15-10 Section 92.15-10... CONSTRUCTION AND ARRANGEMENT Ventilation § 92.15-10 Ventilation for closed spaces. (a) Except as noted in paragraph (c) of this section, all enclosed spaces within the vessel shall be properly vented or...

  11. 46 CFR 72.15-15 - Ventilation for closed spaces.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 3 2012-10-01 2012-10-01 false Ventilation for closed spaces. 72.15-15 Section 72.15-15... ARRANGEMENT Ventilation § 72.15-15 Ventilation for closed spaces. (a) All enclosed spaces within the vessel... spaces and for closing all doorways, ventilators and annular spaces around funnels and other openings...

  12. 46 CFR 190.15-10 - Ventilation for closed spaces.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 46 Shipping 7 2014-10-01 2014-10-01 false Ventilation for closed spaces. 190.15-10 Section 190.15... CONSTRUCTION AND ARRANGEMENT Ventilation § 190.15-10 Ventilation for closed spaces. (a) All enclosed spaces... chemical laboratories, scientific laboratories, chemical storerooms, and machinery spaces and for...

  13. 46 CFR 72.15-15 - Ventilation for closed spaces.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 3 2013-10-01 2013-10-01 false Ventilation for closed spaces. 72.15-15 Section 72.15-15... ARRANGEMENT Ventilation § 72.15-15 Ventilation for closed spaces. (a) All enclosed spaces within the vessel... spaces and for closing all doorways, ventilators and annular spaces around funnels and other openings...

  14. 46 CFR 92.15-10 - Ventilation for closed spaces.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 4 2013-10-01 2013-10-01 false Ventilation for closed spaces. 92.15-10 Section 92.15-10... CONSTRUCTION AND ARRANGEMENT Ventilation § 92.15-10 Ventilation for closed spaces. (a) Except as noted in paragraph (c) of this section, all enclosed spaces within the vessel shall be properly vented or...

  15. 46 CFR 190.15-10 - Ventilation for closed spaces.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 7 2012-10-01 2012-10-01 false Ventilation for closed spaces. 190.15-10 Section 190.15... CONSTRUCTION AND ARRANGEMENT Ventilation § 190.15-10 Ventilation for closed spaces. (a) All enclosed spaces... chemical laboratories, scientific laboratories, chemical storerooms, and machinery spaces and for...

  16. 46 CFR 190.15-10 - Ventilation for closed spaces.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 46 Shipping 7 2013-10-01 2013-10-01 false Ventilation for closed spaces. 190.15-10 Section 190.15... CONSTRUCTION AND ARRANGEMENT Ventilation § 190.15-10 Ventilation for closed spaces. (a) All enclosed spaces... chemical laboratories, scientific laboratories, chemical storerooms, and machinery spaces and for...

  17. 46 CFR 92.15-10 - Ventilation for closed spaces.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 46 Shipping 4 2012-10-01 2012-10-01 false Ventilation for closed spaces. 92.15-10 Section 92.15-10... CONSTRUCTION AND ARRANGEMENT Ventilation § 92.15-10 Ventilation for closed spaces. (a) Except as noted in paragraph (c) of this section, all enclosed spaces within the vessel shall be properly vented or...

  18. 46 CFR 190.15-10 - Ventilation for closed spaces.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 7 2011-10-01 2011-10-01 false Ventilation for closed spaces. 190.15-10 Section 190.15... CONSTRUCTION AND ARRANGEMENT Ventilation § 190.15-10 Ventilation for closed spaces. (a) All enclosed spaces... chemical laboratories, scientific laboratories, chemical storerooms, and machinery spaces and for...

  19. 46 CFR 92.15-10 - Ventilation for closed spaces.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 4 2010-10-01 2010-10-01 false Ventilation for closed spaces. 92.15-10 Section 92.15-10... CONSTRUCTION AND ARRANGEMENT Ventilation § 92.15-10 Ventilation for closed spaces. (a) Except as noted in paragraph (c) of this section, all enclosed spaces within the vessel shall be properly vented or...

  20. 46 CFR 72.15-15 - Ventilation for closed spaces.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 3 2010-10-01 2010-10-01 false Ventilation for closed spaces. 72.15-15 Section 72.15-15... ARRANGEMENT Ventilation § 72.15-15 Ventilation for closed spaces. (a) All enclosed spaces within the vessel... spaces and for closing all doorways, ventilators and annular spaces around funnels and other openings...

  1. 46 CFR 72.15-15 - Ventilation for closed spaces.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 3 2011-10-01 2011-10-01 false Ventilation for closed spaces. 72.15-15 Section 72.15-15... ARRANGEMENT Ventilation § 72.15-15 Ventilation for closed spaces. (a) All enclosed spaces within the vessel... spaces and for closing all doorways, ventilators and annular spaces around funnels and other openings...

  2. 46 CFR 190.15-10 - Ventilation for closed spaces.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 46 Shipping 7 2010-10-01 2010-10-01 false Ventilation for closed spaces. 190.15-10 Section 190.15... CONSTRUCTION AND ARRANGEMENT Ventilation § 190.15-10 Ventilation for closed spaces. (a) All enclosed spaces... chemical laboratories, scientific laboratories, chemical storerooms, and machinery spaces and for...

  3. 46 CFR 92.15-10 - Ventilation for closed spaces.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 46 Shipping 4 2011-10-01 2011-10-01 false Ventilation for closed spaces. 92.15-10 Section 92.15-10... CONSTRUCTION AND ARRANGEMENT Ventilation § 92.15-10 Ventilation for closed spaces. (a) Except as noted in paragraph (c) of this section, all enclosed spaces within the vessel shall be properly vented or...

  4. Judging Criterion of Controlled Structures with Closely Spaced Natural Frequencies

    SciTech Connect

    Xie Faxiang; Sun Limin

    2010-05-21

    The structures with closely spaced natural frequencies widely exist in civil engineering; however, the judging criterion of the density of closely spaced frequencies is in dispute. This paper suggests a judging criterion for structures with closely spaced natural frequencies based on the analysis on a controlled 2-DOF structure. The analysis results indicate that the optimal control gain of the structure with velocity feedback is dependent on the frequency density parameter of structure and the maximum attainable additional modal damping ratio is 1.72 times of the frequency density parameter when state feedback is applied. Based on a brief review on the previous researches, a judging criterion related the minimum frequency density parameter and the required mode damping ratio was proposed.

  5. Modal vector estimation for closely spaced frequency modes

    NASA Technical Reports Server (NTRS)

    Craig, R. R., Jr.; Chung, Y. T.; Blair, M.

    1982-01-01

    Techniques for obtaining improved modal vector estimates for systems with closely spaced frequency modes are discussed. In describing the dynamical behavior of a complex structure modal parameters are often analyzed: undamped natural frequency, mode shape, modal mass, modal stiffness and modal damping. From both an analytical standpoint and an experimental standpoint, identification of modal parameters is more difficult if the system has repeated frequencies or even closely spaced frequencies. The more complex the structure, the more likely it is to have closely spaced frequencies. This makes it difficult to determine valid mode shapes using single shaker test methods. By employing band selectable analysis (zoom) techniques and by employing Kennedy-Pancu circle fitting or some multiple degree of freedom (MDOF) curve fit procedure, the usefulness of the single shaker approach can be extended.

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

    SciTech Connect

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

    2016-02-15

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

  7. A hybrid genetic algorithm for resolving closely spaced objects

    NASA Technical Reports Server (NTRS)

    Abbott, R. J.; Lillo, W. E.; Schulenburg, N.

    1995-01-01

    A hybrid genetic algorithm is described for performing the difficult optimization task of resolving closely spaced objects appearing in space based and ground based surveillance data. This application of genetic algorithms is unusual in that it uses a powerful domain-specific operation as a genetic operator. Results of applying the algorithm to real data from telescopic observations of a star field are presented.

  8. A sublimation heat engine

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  9. A sublimation heat engine.

    PubMed

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

    2015-03-03

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

  10. Underwater acoustic source localization using closely spaced hydrophone pairs

    NASA Astrophysics Data System (ADS)

    Sim, Min Seop; Choi, Bok-Kyoung; Kim, Byoung-Nam; Lee, Kyun Kyung

    2016-07-01

    Underwater sound source position is determined using a line array. However, performance degradation occurs owing to a multipath environment, which generates incoherent signals. In this paper, a hydrophone array is proposed for underwater source position estimation robust to a multipath environment. The array is composed of three pairs of sensors placed on the same line. The source position is estimated by performing generalized cross-correlation (GCC). The proposed system is not affected by a multipath time delay because of the close distance between closely spaced sensors. The validity of the array is confirmed by simulation using acoustic signals synthesized by eigenrays.

  11. CFD simulation of boundary effects on closely spaced jets

    NASA Astrophysics Data System (ADS)

    Shrivastava, Ishita; Adams, Eric

    2015-11-01

    In coastal areas characterized by shallow water depth, industrial effluents are often diluted using multiple closely spaced jets. Examples of such effluents include brine from desalination plants, treated wastewater from sewage treatment plants and heated water from thermal power plants. These jets are arranged in various orientations, such as unidirectional diffusers and rosette groups, to maximize mixing with ambient water. Due to effects of dynamic pressure, the jets interact with each other leading to mixing characteristics which are quite different from those of individual jets. The effect of mutual interaction is exaggerated under confinement, when a large number of closely spaced jets discharge into shallow depth. Dilution through an outfall, consisting of multiple jets, depends on various outfall and ambient parameters. Here we observe the effects of shoreline proximity, in relation to diffuser length and water depth, on the performance of unidirectional diffusers discharging to quiescent water. For diffusers located closer to shore, less dilution is observed due to the limited availability of ambient water for dilution. We report on the results of Computational Fluid Dynamics (CFD) simulations and compare the results with experimental observations.

  12. A sublimation heat engine

    PubMed Central

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

    2015-01-01

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

  13. Sublimation as a Landform-Shaping Process on Pluto

    NASA Technical Reports Server (NTRS)

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

    2016-01-01

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

  14. Modelling Sublimation of Carbon Dioxide

    ERIC Educational Resources Information Center

    Winkel, Brian

    2012-01-01

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

  15. Temporal extent of surface potentials between closely spaced metals.

    PubMed

    Pollack, S E; Schlamminger, S; Gundlach, J H

    2008-08-15

    Variations in the electrostatic surface potential between the proof mass and electrode housing in the space-based gravitational wave mission Laser Interferometer Space Antenna (LISA) is one of the largest contributors of noise at frequencies below a few mHz. Torsion balances provide an ideal test bed for investigating these effects in conditions emulative of LISA. Our apparatus consists of a Au coated Cu plate brought near a Au coated Si plate pendulum suspended from a thin W wire. We have measured a white noise level of 30 microV/sqrt Hz above approximately 0.1 mHz, rising at lower frequencies, for the surface potential variations between these two closely spaced metals.

  16. Approximating the Generalized Voronoi Diagram of Closely Spaced Objects

    SciTech Connect

    Edwards, John; Daniel, Eric; Pascucci, Valerio; Bajaj, Chandrajit

    2015-06-22

    We present an algorithm to compute an approximation of the generalized Voronoi diagram (GVD) on arbitrary collections of 2D or 3D geometric objects. In particular, we focus on datasets with closely spaced objects; GVD approximation is expensive and sometimes intractable on these datasets using previous algorithms. With our approach, the GVD can be computed using commodity hardware even on datasets with many, extremely tightly packed objects. Our approach is to subdivide the space with an octree that is represented with an adjacency structure. We then use a novel adaptive distance transform to compute the distance function on octree vertices. The computed distance field is sampled more densely in areas of close object spacing, enabling robust and parallelizable GVD surface generation. We demonstrate our method on a variety of data and show example applications of the GVD in 2D and 3D.

  17. NASA Research For Instrument Approaches To Closely Spaced Parallel Runways

    NASA Technical Reports Server (NTRS)

    Elliott, Dawn M.; Perry, R. Brad

    2000-01-01

    Within the NASA Aviation Systems Capacity Program, the Terminal Area Productivity (TAP) Project is addressing airport capacity enhancements during instrument meteorological condition (IMC). The Airborne Information for Lateral Spacing (AILS) research within TAP has focused on an airborne centered approach for independent instrument approaches to closely spaced parallel runways using Differential Global Positioning System (DGPS) and Automatic Dependent Surveillance-Broadcast (ADS-B) technologies. NASA Langley Research Center (LaRC), working in partnership with Honeywell, Inc., completed in AILS simulation study, flight test, and demonstration in 1999 examining normal approaches and potential collision scenarios to runways with separation distances of 3,400 and 2,500 feet. The results of the flight test and demonstration validate the simulation study.

  18. Close-spaced vapor transport and photoelectrochemistry of gallium arsenide for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Ritenour, Andrew J.

    The high balance-of-system costs of photovoltaic installations indicate that reductions in absorber cost alone are likely insufficient for photovoltaic electricity to reach grid parity unless energy conversion efficiency is also increased. Technologies which both yield high-efficiency cells (>25%) and maintain low costs are needed. GaAs and related III--V semiconductors are used in the highest-efficiency single- and multi-junction photovoltaics, but the technology is too expensive for non-concentrated terrestrial applications. This is due in part to the limited scalability of traditional syntheses, which rely on expensive reactors and employ toxic and pyrophoric gas-phase precursors such as arsine and trimethyl gallium. This work describes GaAs films made by close-spaced vapor transport, a potentially scalable technique which is carried out at atmospheric pressure and requires only bulk GaAs, water vapor, and a temperature gradient to deposit crystalline films with similar electronic properties to GaAs prepared using traditional syntheses. Although close-spaced vapor transport of GaAs was first developed in 1963, there were few examples of GaAs photovoltaic devices made using this method in the literature at the onset of this project. Furthermore, it was unclear whether close-spaced vapor transport could produce GaAs films appropriate for use in photovoltaics. The goal of this project was to create and study GaAs devices made using close-spaced vapor transport and determine whether the technique could be used for production of grid-connected GaAs photovoltaics. In Chapter I the design of the vapor transport reactor, the chemistry of crystal growth, and optoelectronic characterization techniques are discussed. Chapter II focuses on compositional measurements, doping, and improved electronic quality in CSVT GaAs. Chapter III describes several aspects of the interplay between structure and electronic properties of photoelectrochemical devices. Chapter IV addresses

  19. CFD simulations of closely spaced jets in shallow flowing ambient

    NASA Astrophysics Data System (ADS)

    Shrivastava, Ishita; Adams, E. Eric

    2016-11-01

    In shallow water bodies, multiple closely spaced jets are often used to discharge industrial effluents such as brine from desalination plants, heated water from thermal power plants and wastewater from wastewater treatment plants. The jets interact with each other due to effects of dynamic pressure and result in jet trajectories and mixing that are significantly different from non-interfering jets. Here, we look at the case of a unidirectional diffuser, which consists of a linear array of jets discharging horizontally in the direction perpendicular to the diffuser. Dilution through such an arrangement of jets depends on various discharge and ambient parameters, such as effluent buoyancy, water depth and ambient current. We present results of computational fluid dynamics (CFD) simulations and compare them with experimental observations to examine the effects of shallowness, shoreline separation and ambient currents on the mixing of a unidirectional diffuser. We observe that shallow depth, shoreline proximity and crossflow, all result in increased interaction among the jets and reduced mixing.

  20. The Sublime and the Vulgar.

    ERIC Educational Resources Information Center

    Swann, Karen

    1990-01-01

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

  1. Sublimation systems and associated methods

    DOEpatents

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

    2016-02-09

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

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

    SciTech Connect

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

    1988-12-01

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

  3. Enantioenrichment in sublimed amino acid mixtures.

    PubMed

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

    2012-04-14

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

  4. Eisenhower and the American Sublime

    ERIC Educational Resources Information Center

    O'Gorman, Ned

    2008-01-01

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

  5. Displacement, Substitution, Sublimation: A Bibliography.

    ERIC Educational Resources Information Center

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

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

  6. Membrane evaporator/sublimator investigation

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

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

  7. Low-Cost Growth of III-V Layers on Si Using Close-Spaced Vapor Transport

    SciTech Connect

    Boucher, Jason W.; Greenaway, Ann L.; Ritenour, Andrew J.; Davis, Allison L.; Bachman, Benjamin F.; Aloni, Shaul; Boettcher, Shannon W.

    2015-06-14

    Close-spaced vapor transport (CSVT) uses solid precursors to deposit material at high rates and with high precursor utilization. The use of solid precursors could significantly reduce the costs associated with III-V photovoltaics, particularly if growth on Si substrates can be demonstrated. We present preliminary results of the growth of GaAs1-xPx with x ≈ 0.3 and 0.6, showing that CSVT can be used to produce III-V-V’ alloys with band gaps suitable for tandem devices. Additionally, we have grown GaAs on Si by first thermally depositing films of Ge and subsequently depositing GaAs by CSVT. Patterning the Ge into islands prevents cracking due to thermal mismatch and is useful for potential tandem structures.

  8. Advances in sublimation studies for particles of explosives

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

  9. APPARATUS FOR CONDENSATION AND SUBLIMATION

    DOEpatents

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

    1958-10-01

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

  10. Potential Sedimentary Evidence of Two Closely Spaced Tsunamis on the West Coast of Aceh, Indonesia

    NASA Astrophysics Data System (ADS)

    Monecke, Katrin; Meilianda, Ella; Rushdy, Ibnu; Moena, Abudzar; Yolanda, Irvan P.

    2016-04-01

    Recent research in the coastal regions of Aceh, Indonesia, an area that was largely affected by the 2004 Sumatra Andaman earthquake and ensuing Indian Ocean tsunami, suggests the possibility that two closely spaced tsunamis occurred at the turn of the 14th to 15th century (Meltzner et al., 2010; Sieh et al., 2015). Here, we present evidence of two buried sand layers in the coastal marshes of West Aceh, possibly representing these penultimate predecessors of the 2004 tsunami. We discovered the sand layers in an until recently inaccessible area of a previously studied beach ridge plain about 15 km North of Meulaboh, West Aceh. Here, the 2004 tsunami left a continuous, typically a few cm thick sand sheet in the coastal hinterland in low-lying swales that accumulate organic-rich deposits and separate the sandy beach ridges. In keeping with the long-term progradation of the coastline, older deposits have to be sought after further inland. Using a hand auger, the buried sand layers were discovered in 3 cores in a flooded and highly vegetated swale in about 1 km distance to the shoreline. The pair of sand layers occurs in 70-100 cm depth and overlies 40-60 cm of dark-brown peat that rests on the basal sand of the beach ridge plain. The lower sand layer is only 1-6 cm thick, whereas the upper layer is consistently thicker, measuring 11-17 cm, with 8-14 cm of peat in between sand sheets. Both layers consist of massive, grey, medium sand and include plant fragments. They show very sharp upper and lower boundaries clearly distinguishing them from the surrounding peat and indicating an abrupt depositional event. A previously developed age model for sediments of this beach ridge plain suggest that this pair of layers could indeed correlate to a nearby buried sand sheet interpreted as tsunamigenic and deposited soon after 1290-1400AD (Monecke et al., 2008). The superb preservation at this new site allows the clear distinction of two depositional events, which, based on a first

  11. Closely-spaced double-row microstrip RF arrays for parallel MR imaging at ultrahigh fields

    PubMed Central

    Yan, Xinqiang; Xue, Rong; Zhang, Xiaoliang

    2015-01-01

    Radiofrequency (RF) coil arrays with high count of elements, e.g., closely-spaced multi-row arrays, exhibit superior parallel imaging performance in MRI. However, it is technically challenging and time-consuming to build multi-row arrays due to complex coupling issues. This paper presents a novel and simple method for closely-spaced multi-row RF array designs. Induced current elimination (ICE) decoupling method has shown the capability of reducing coupling between microstrip elements from different rows. In this study, its capability for decoupling array elements from the same row was investigated and validated by bench tests, with an isolation improvement from −8.9 dB to −20.7 dB. Based on this feature, a closely-spaced double-row microstrip array with 16 elements was built at 7T. S21 between any two elements of the 16-channel closely-spaced was better than −14 dB. In addition, its feasibility and performance was validated by MRI experiments. No significant image reconstruction- related noise amplifications were observed for parallel imaging even when reduced factor (R) achieves 4. The experimental results demonstrated that the proposed design might be a simple and efficient approach in fabricating closely-spaced multi-row RF arrays. PMID:26508810

  12. Closely-spaced double-row microstrip RF arrays for parallel MR imaging at ultrahigh fields.

    PubMed

    Yan, Xinqiang; Xue, Rong; Zhang, Xiaoliang

    2015-11-01

    Radiofrequency (RF) coil arrays with high count of elements, e.g., closely-spaced multi-row arrays, exhibit superior parallel imaging performance in MRI. However, it is technically challenging and time-consuming to build multi-row arrays due to complex coupling issues. This paper presents a novel and simple method for closely-spaced multi-row RF array designs. Induced current elimination (ICE) decoupling method has shown the capability of reducing coupling between microstrip elements from different rows. In this study, its capability for decoupling array elements from the same row was investigated and validated by bench tests, with an isolation improvement from -8.9 dB to -20.7 dB. Based on this feature, a closely-spaced double-row microstrip array with 16 elements was built at 7T. S21 between any two elements of the 16-channel closely-spaced was better than -14 dB. In addition, its feasibility and performance was validated by MRI experiments. No significant image reconstruction- related noise amplifications were observed for parallel imaging even when reduced factor (R) achieves 4. The experimental results demonstrated that the proposed design might be a simple and efficient approach in fabricating closely-spaced multi-row RF arrays.

  13. Schopenhauer, Nietzsche, and the Aesthetically Sublime

    ERIC Educational Resources Information Center

    Vandenabeele, Bart

    2003-01-01

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

  14. Physicochemical bases of autonomous maintenance of humidity and temperature in closed spaces

    NASA Astrophysics Data System (ADS)

    Aristov, Yu. I.; Vasiliev, L. L.; Glaznev, I. S.; Gordeeva, L. G.; Zhuravlev, A. S.; Kovaleva, M. N.

    2012-09-01

    An inexpensive adsorption humidistat working in the static and dynamic regimes is proposed. This humidistat is designed for maintenance of the relative humidity and temperature in a closed space at levels (15-18%, 20-25°C) necessary for reliable storage of rare books, manuscripts, pictures, and museum valuables and for their safe transportation in the process of visiting exhibitions. Principles of maintenance of the relative humidity in a closed space with the use of chemical substances and autonomous thermostatting of this space are considered. Results of testing of some new moisture buffers under laboratory and real conditions are presented.

  15. Canopy Effects on Macroscale Snow Sublimation

    NASA Astrophysics Data System (ADS)

    Svoma, B. M.

    2015-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  17. Pilot Non-Conformance to Alerting System Commands During Closely Spaced Parallel Approaches

    NASA Technical Reports Server (NTRS)

    Pritchett, Amy R.; Hansman, R. John

    1997-01-01

    Pilot non-conformance to alerting system commands has been noted in general and to a TCAS-like collision avoidance system in a previous experiment. This paper details two experiments studying collision avoidance during closely-spaced parallel approaches in instrument meteorological conditions (IMC), and specifically examining possible causal factors of, and design solutions to, pilot non-conformance.

  18. Probabilistic Analysis of Impact of Wake Vortices on Closely-Spaced Parallel Approaches

    NASA Technical Reports Server (NTRS)

    Hardy, Gordon H.; Rossow, Vernon J.; Meyn, Larry A.

    2005-01-01

    One of the primary constraints on the capacity of the nation's air transportation system is the landing capacity of its largest airports. Many airports with closely spaced parallel runways suffer a severe runway acceptance rate when the weather conditions do not allow full utilization of these parallel runways. The present requirement for simultaneous independent landings in Instrument Meteorological Conditions, IMC, is at least 4300 feet of lateral runway spacing (as close as 3000 feet for runways with a Precision Runway Monitor). Operations in Visual Meteorological Conditions, VMC, to Closely Spaced Parallel Approaches only require a lateral runway spacing greater than 750 feet. A study by Hardy and Lewis integrated and extended earlier studies and concepts in lateral traffic separation, longitudinal station keeping, wake prediction, wake display, and the concepts of R N P into a preliminary system concept for Closely Spaced Parallel Approaches in IMC. This system allows IMC airport acceptance rates to approach those for VMC. The system concept that was developed, presented traffic and wake information on the NAVigation Display, NAV, and developed operational procedures for a mix of conventional and Runway Independent Aircraft with different approach speeds to Closely Spaced Parallel Runways. This paper first describes some improvements made on the technology needed to better predict and formulate a probabilistic representation for the time-dependent motion and spreading of the hazardous region associated with the lift-generated vortex wakes of preceding aircraft. In this way, the time at which the vortex wakes of leading aircraft intrude into the airspace of adjacent flight-corridor/runway combinations can be more reliably predicted. Such a prediction is needed because it determines restraints to be placed on in-trail separation distances; or, the allowable time intervals between aircraft executing nearly simultaneous landings or takeoffs on very closely-spaced

  19. Experimental Investigation of Transient Sublimator Performance

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  20. Arsenic antisite and oxygen incorporation trends in GaAs grown by water-mediated close-spaced vapor transport

    NASA Astrophysics Data System (ADS)

    Boucher, Jason; Boettcher, Shannon

    2017-03-01

    Close-spaced vapor transport (CSVT) provides a plausible path to lower the costs of GaAs deposition as it uses only solid precursors and provides precursor utilization in principle approaching 100%. However, the use of H2O as a transport agent causes O to be incorporated in CSVT films, and O has been associated with a number of electrically active defect centers in GaAs, which decrease minority carrier lifetimes. Using deep-level transient spectroscopy, we study the effect of H2O concentration and substrate temperature on electron trap concentrations in n-type GaAs. We find that the most-prominent O-related center (ELO) typically has a much higher concentration than the center usually associated with As antisites (EL2), but that overall defect concentrations can be as low as those in films deposited by common vapor phase techniques. The trends with increasing H2O concentration suggest that ELO is most likely a defect complex with two As antisites. We also consider the optimal conditions for achieving high growth rates and low defect concentrations using CSVT. The results of this study have implications for the future CSVT growth using halide transport agents, where the ELO defect would be eliminated but EL2 might have a higher concentration.

  1. Coating Thermoelectric Devices To Suppress Sublimation

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2005-12-01

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

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

    PubMed Central

    Yang, Junhai; Caprioli, Richard M.

    2011-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Batterson, Courtney

    2016-01-01

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

  5. Experimental Studies Of Pilot Performance At Collision Avoidance During Closely Spaced Parallel Approaches

    NASA Technical Reports Server (NTRS)

    Pritchett, Amy R.; Hansman, R. John

    1997-01-01

    Efforts to increase airport capacity include studies of aircraft systems that would enable simultaneous approaches to closely spaced parallel runway in Instrument Meteorological Conditions (IMC). The time-critical nature of a parallel approach results in key design issues for current and future collision avoidance systems. Two part-task flight simulator studies have examined the procedural and display issues inherent in such a time-critical task, the interaction of the pilot with a collision avoidance system, and the alerting criteria and avoidance maneuvers preferred by subjects.

  6. Evaluating Nextgen Closely Spaced Parallel Operations Concepts with Validated Human Performance Models: Flight Deck Guidelines

    NASA Technical Reports Server (NTRS)

    Hooey, Becky Lee; Gore, Brian Francis; Mahlstedt, Eric; Foyle, David C.

    2013-01-01

    The objectives of the current research were to develop valid human performance models (HPMs) of approach and land operations; use these models to evaluate the impact of NextGen Closely Spaced Parallel Operations (CSPO) on pilot performance; and draw conclusions regarding flight deck display design and pilot-ATC roles and responsibilities for NextGen CSPO concepts. This document presents guidelines and implications for flight deck display designs and candidate roles and responsibilities. A companion document (Gore, Hooey, Mahlstedt, & Foyle, 2013) provides complete scenario descriptions and results including predictions of pilot workload, visual attention and time to detect off-nominal events.

  7. Wake Encounter Analysis for a Closely Spaced Parallel Runway Paired Approach Simulation

    NASA Technical Reports Server (NTRS)

    Mckissick,Burnell T.; Rico-Cusi, Fernando J.; Murdoch, Jennifer; Oseguera-Lohr, Rosa M.; Stough, Harry P, III; O'Connor, Cornelius J.; Syed, Hazari I.

    2009-01-01

    A Monte Carlo simulation of simultaneous approaches performed by two transport category aircraft from the final approach fix to a pair of closely spaced parallel runways was conducted to explore the aft boundary of the safe zone in which separation assurance and wake avoidance are provided. The simulation included variations in runway centerline separation, initial longitudinal spacing of the aircraft, crosswind speed, and aircraft speed during the approach. The data from the simulation showed that the majority of the wake encounters occurred near or over the runway and the aft boundaries of the safe zones were identified for all simulation conditions.

  8. Field flatness tuning of TM110 mode cavities with closely spaced modes

    SciTech Connect

    Leo Bellantoni et al.

    2003-10-31

    Superconducting cavities for the CKM RF separated kaon beamline at Fermilab have modes that are closely spaced compared to the resonance bandwidths when warm, and this complicates the field flatness (warm) tuning process. Additionally, it is necessary to maintain the azimuthal orientation of the mode during the tuning deformations. the authors present two analytic techniques to warm-tune cavities with overlapping modes, a finite-element analysis of the tuning process, the design of a warm tuner which maintains mode polarization, and the results of tuning a cavity in which initial manufacturing variations caused the desired {pi} and nearby {pi}-1 modes to be indistinguishable before field flatness tuning.

  9. GelBandFitter--a computer program for analysis of closely spaced electrophoretic and immunoblotted bands.

    PubMed

    Mitov, Mihail I; Greaser, Marion L; Campbell, Kenneth S

    2009-03-01

    GelBandFitter is a computer program that uses non-linear regression techniques to fit mathematical functions to densitometry profiles of protein gels. This allows for improved quantification of gels with partially overlapping and potentially asymmetric protein bands. The program can also be used to analyze immunoblots with closely spaced bands. GelBandFitter was developed in Matlab and the source code and/or a Windows executable file can be downloaded at no cost to academic users from http://www.gelbandfitter.org.

  10. Multiport well design for sampling of ground water at closely spaced vertical intervals

    SciTech Connect

    Delin, G.N.; Landon, M.K.

    1996-11-01

    Detailed vertical sampling is useful in aquifers where vertical mixing is limited and steep vertical gradients in chemical concentrations are expected. Samples can be collected at closely spaced vertical intervals from nested wells with short screened intervals. However, this approach may not be appropriate in all situations. An easy-to-construct and easy-to-install multiport sampling well to collect ground-water samples from closely spaced vertical intervals was developed and tested. The multiport sampling well was designed to sample ground water from surficial sand-and-gravel aquifers. The device consists of multiple stainless-steel tubes within a polyvinyl chloride (PVC) protective casing. The tubes protrude through the wall of the PVC casing at the desired sampling depths. A peristaltic pump is used to collect ground-water samples form the sampling ports. The difference in hydraulic head between any two sampling ports can be measured with a vacuum pump and a modified manometer. The usefulness and versatility of this multiport well design was demonstrated at an agricultural research site near Princeton, Minnesota where sampling ports were installed to a maximum depth of about 12 m below land surface. Trace experiments were conducted using potassium bromide to document the degree to which short-circuiting occurred between sampling ports. Samples were successfully collected for analysis of major cations and anions, nutrients, selected herbicides, isotopes, dissolved gases, and chlorofluorocarbon concentrations.

  11. Multiport well design for sampling of ground water at closely spaced vertical intervals

    USGS Publications Warehouse

    Delin, G.N.; Landon, M.K.

    1996-01-01

    Detailed vertical sampling is useful in aquifers where vertical mixing is limited and steep vertical gradients in chemical concentrations are expected. Samples can be collected at closely spaced vertical intervals from nested wells with short screened intervals. However, this approach may not be appropriate in all situations. An easy-to-construct and easy-to-install multiport sampling well to collect ground-water samples from closely spaced vertical intervals was developed and tested. The multiport sampling well was designed to sample ground water from surficial sand-and-gravel aquifers. The device consists of multiple stainless-steel tubes within a polyvinyl chloride (PVC) protective casing. The tubes protrude through the wall of the PVC casing at the desired sampling depths. A peristaltic pump is used to collect ground-water samples from the sampling ports. The difference in hydraulic head between any two sampling ports can be measured with a vacuum pump and a modified manometer. The usefulness and versatility of this multiport well design was demonstrated at an agricultural research site near Princeton, Minnesota where sampling ports were installed to a maximum depth of about 12 m below land surface. Tracer experiments were conducted using potassium bromide to document the degree to which short-circuiting occurred between sampling ports. Samples were successfully collected for analysis of major cations and anions, nutrients, selected herbicides, isotopes, dissolved gases, and chlorofluorcarbon concentrations.

  12. System and method for suppressing sublimation using opacified aerogel

    NASA Technical Reports Server (NTRS)

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

    2008-01-01

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

  13. No reduction using sublimation of cyanuric acid

    DOEpatents

    Perry, Robert A.

    1990-01-01

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

  14. NO reduction using sublimation of cyanuric acid

    DOEpatents

    Perry, Robert A.

    1988-01-01

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

  15. Heat of Sublimation of I-2.

    ERIC Educational Resources Information Center

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

    1978-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  17. Homojunction GaAs solar cells grown by close space vapor transport

    SciTech Connect

    Boucher, Jason W.; Ritenour, Andrew J.; Greenaway, Ann L.; Aloni, Shaul; Boettcher, Shannon W.

    2014-06-08

    We report on the first pn junction solar cells grown by homoepitaxy of GaAs using close space vapor transport (CSVT). Cells were grown both on commercial wafer substrates and on a CSVT absorber film, and had efficiencies reaching 8.1%, open circuit voltages reaching 909 mV, and internal quantum efficiency of 90%. The performance of these cells is partly limited by the electron diffusion lengths in the wafer substrates, as evidenced by the improved peak internal quantum efficiency in devices fabricated on a CSVT absorber film. Unoptimized highly-doped n-type emitters also limit the photocurrent, indicating that thinner emitters with reduced doping, and ultimately wider band gap window or surface passivation layers, are required to increase the efficiency.

  18. Principles for RNA metabolism and alternative transcription initiation within closely spaced promoters

    PubMed Central

    Chen, Yun; Pai, Athma A.; Herudek, Jan; Lubas, Michal; Meola, Nicola; Järvelin, Aino I.; Andersson, Robin; Pelechano, Vicent; Steinmetz, Lars M.; Heick Jensen, Torben; Sandelin, Albin

    2016-01-01

    Mammalian transcriptomes are complex and formed by extensive promoter activity. In addition, gene promoters are largely divergent and initiate transcription of reverse-oriented promoter upstream transcripts (PROMPTs). Although PROMPTs are commonly terminated early, influenced by polyadenylation sites, promoters often cluster so that the divergent activity of one might impact another. Here, we find that the distance between promoters strongly correlates with the expression, stability and length of their associated PROMPTs. Adjacent promoters driving divergent mRNA transcription support PROMPT formation, but due to polyadenylation site constraints, these transcripts tend to spread into the neighboring mRNA on the same strand. This mechanism to derive new alternative mRNA transcription start sites (TSSs) is also evident at closely spaced promoters supporting convergent mRNA transcription. We suggest that basic building blocks of divergently transcribed core promoter pairs, in combination with the wealth of TSSs in mammalian genomes, provides a framework with which evolution shapes transcriptomes. PMID:27455346

  19. Comparison of Procedures for Dual and Triple Closely Spaced Parallel Runways

    NASA Technical Reports Server (NTRS)

    Verma, Savita; Ballinger, Deborah; Subramanian Shobana; Kozon, Thomas

    2012-01-01

    A human-in-the-loop high fidelity flight simulation experiment was conducted, which investigated and compared breakout procedures for Very Closely Spaced Parallel Approaches (VCSPA) with two and three runways. To understand the feasibility, usability and human factors of two and three runway VCSPA, data were collected and analyzed on the dependent variables of breakout cross track error and pilot workload. Independent variables included number of runways, cause of breakout and location of breakout. Results indicated larger cross track error and higher workload using three runways as compared to 2-runway operations. Significant interaction effects involving breakout cause and breakout location were also observed. Across all conditions, cross track error values showed high levels of breakout trajectory accuracy and pilot workload remained manageable. Results suggest possible avenues of future adaptation for adopting these procedures (e.g., pilot training), while also showing potential promise of the concept.

  20. Doping and electronic properties of GaAs grown by close-spaced vapor transport from powder sources for scalable III–V photovoltaics

    SciTech Connect

    Ritenour, Andrew J.; Boucher, Jason W.; DeLancey, Robert; Greenaway, Ann L.; Aloni, Shaul; Boettcher, Shannon W.

    2014-09-01

    We report the use of a simple close-spaced vapor transport technique for the growth of high-quality epitaxial GaAs films using potentially inexpensive GaAs powders as precursors. The free carrier type and density (1016 to 1019 cm–3) of the films were adjusted by addition of Te or Zn powder to the GaAs source powder. We show using photoelectrochemical and electron beam-induced current analyses that the minority carrier diffusion lengths of the n- and p-GaAs films reached ~3 μm and ~8 μm, respectively. Hall mobilities approach those achieved for GaAs grown by metal–organic chemical vapor deposition, 1000–4200 cm2 V–1 s–1 for n-GaAs and 50–240 cm V–1 s–1 for p-GaAs depending on doping level. We conclude that the electronic quality of GaAs grown by close-spaced vapor transport is similar to that of GaAs made using conventional techniques and is thus sufficient for high-performance photovoltaic applications.

  1. Doping and electronic properties of GaAs grown by close-spaced vapor transport from powder sources for scalable III–V photovoltaics

    DOE PAGES

    Ritenour, Andrew J.; Boucher, Jason W.; DeLancey, Robert; ...

    2014-09-01

    We report the use of a simple close-spaced vapor transport technique for the growth of high-quality epitaxial GaAs films using potentially inexpensive GaAs powders as precursors. The free carrier type and density (1016 to 1019 cm–3) of the films were adjusted by addition of Te or Zn powder to the GaAs source powder. We show using photoelectrochemical and electron beam-induced current analyses that the minority carrier diffusion lengths of the n- and p-GaAs films reached ~3 μm and ~8 μm, respectively. Hall mobilities approach those achieved for GaAs grown by metal–organic chemical vapor deposition, 1000–4200 cm2 V–1 s–1 for n-GaAsmore » and 50–240 cm V–1 s–1 for p-GaAs depending on doping level. We conclude that the electronic quality of GaAs grown by close-spaced vapor transport is similar to that of GaAs made using conventional techniques and is thus sufficient for high-performance photovoltaic applications.« less

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

    NASA Astrophysics Data System (ADS)

    Hayne, Paul O.

    2016-10-01

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

  3. Psychotherapy. Sublimation and the psychodynamics of birding.

    PubMed

    Clemens, Norman A

    2012-07-01

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

  4. No reduction using sublimation of cyanuric acid

    DOEpatents

    Perry, Robert

    1989-01-01

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

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

    DOEpatents

    Davidson, P.H.

    1959-08-18

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

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

    NASA Astrophysics Data System (ADS)

    Chang, Kee-Chul; Blakely, Jack M.

    2005-10-01

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

  7. Experimental Investigation of Sublimator Performance at Transient Heat Loads

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

  8. Importance of closely spaced vertical sampling in delineating chemical and microbiological gradients in groundwater studies

    USGS Publications Warehouse

    Smith, R.L.; Harvey, R.W.; LeBlanc, D.R.

    1991-01-01

    Vertical gradients of selected chemical constituents, bacterial populations, bacterial activity and electron acceptors were investigated for an unconfined aquifer contaminated with nitrate and organic compounds on Cape Cod, Massachusetts, U.S.A. Fifteen-port multilevel sampling devices (MLS's) were installed within the contaminant plume at the source of the contamination, and at 250 and 2100 m downgradient from the source. Depth profiles of specific conductance and dissolved oxygen at the downgradient sites exhibited vertical gradients that were both steep and inversely related. Narrow zones (2-4 m thick) of high N2O and NH4+ concentrations were also detected within the contaminant plume. A 27-fold change in bacterial abundance; a 35-fold change in frequency of dividing cells (FDC), an indicator of bacterial growth; a 23-fold change in 3H-glucose uptake, a measure of heterotrophic activity; and substantial changes in overall cell morphology were evident within a 9-m vertical interval at 250 m downgradient. The existence of these gradients argues for the need for closely spaced vertical sampling in groundwater studies because small differences in the vertical placement of a well screen can lead to incorrect conclusions about the chemical and microbiological processes within an aquifer.Vertical gradients of selected chemical constituents, bacterial populations, bacterial activity and electron acceptors were investigated for an unconfined aquifer contaminated with nitrate and organic compounds on Cape Cod, Massachusetts, USA. Fifteen-port multilevel sampling devices (MLS's) were installed within the contaminant plume at the source of the contamination, and at 250 and 2100 m downgradient from the source. Depth profiles of specific conductance and dissolved oxygen at the downgradient sites exhibited vertical gradients that were both steep and inversely related. Narrow zones (2-4 m thick) of high N2O and NH4+ concentrations were also detected within the contaminant plume

  9. Transcription termination between polo and snap, two closely spaced tandem genes of D. melanogaster.

    PubMed

    Henriques, Telmo; Ji, Zhe; Tan-Wong, Sue Mei; Carmo, Alexandre M; Tian, Bin; Proudfoot, Nicholas J; Moreira, Alexandra

    2012-01-01

    Transcription termination of RNA polymerase II between closely spaced genes is an important, though poorly understood, mechanism. This is true, in particular, in the Drosophila genome, where approximately 52% of tandem genes are separated by less than 1 kb. We show that a set of Drosophila tandem genes has a negative correlation of gene expression and display several molecular marks indicative of promoter pausing. We find that an intergenic spacing of 168 bp is sufficient for efficient transcription termination between the polo-snap tandem gene pair, by a mechanism that is independent of Pcf11 and Xrn2. In contrast, analysis of a tandem gene pair containing a longer intergenic region reveals that termination occurs farther downstream of the poly(A) signal and is, in this case, dependent on Pcf11 and Xrn2. For polo-snap, displacement of poised polymerase from the snap promoter by depletion of the initiation factor TFIIB results in an increase of polo transcriptional read-through. This suggests that poised polymerase is necessary for transcription termination. Interestingly, we observe that polo forms a TFIIB dependent gene loop between its promoter and terminator regions. Furthermore, in a plasmid containing the polo-snap locus, deletion of the polo promoter causes an increase in snap expression, as does deletion of polo poly(A) signals. Taken together, our results indicate that polo forms a gene loop and polo transcription termination occurs by an Xrn2 and Pcf11 independent mechanism that requires TFIIB.

  10. Tunneling spectroscopy of close-spaced dangling-bond pairs in Si(001):H

    PubMed Central

    Engelund, Mads; Zuzak, Rafał; Godlewski, Szymon; Kolmer, Marek; Frederiksen, Thomas; García-Lekue, Aran; Sánchez-Portal, Daniel; Szymonski, Marek

    2015-01-01

    We present a combined experimental and theoretical study of the electronic properties of close-spaced dangling-bond (DB) pairs in a hydrogen-passivated Si(001):H p-doped surface. Two types of DB pairs are considered, called “cross” and “line” structures. Our scanning tunneling spectroscopy (STS) data show that, although the spectra taken over different DBs in each pair exhibit a remarkable resemblance, they appear shifted by a constant energy that depends on the DB-pair type. This spontaneous asymmetry persists after repeated STS measurements. By comparison with density functional theory (DFT) calculations, we demonstrate that the magnitude of this shift and the relative position of the STS peaks can be explained by distinct charge states for each DB in the pair. We also explain how the charge state is modified by the presence of the scanning tunneling microscopy (STM) tip and the applied bias. Our results indicate that, using the STM tip, it is possible to control the charge state of individual DBs in complex structures, even if they are in close proximity. This observation might have important consequences for the design of electronic circuits and logic gates based on DBs in passivated silicon surfaces. PMID:26404520

  11. Effects of ATC automation on precision approaches to closely space parallel runways

    NASA Technical Reports Server (NTRS)

    Slattery, R.; Lee, K.; Sanford, B.

    1995-01-01

    Improved navigational technology (such as the Microwave Landing System and the Global Positioning System) installed in modern aircraft will enable air traffic controllers to better utilize available airspace. Consequently, arrival traffic can fly approaches to parallel runways separated by smaller distances than are currently allowed. Previous simulation studies of advanced navigation approaches have found that controller workload is increased when there is a combination of aircraft that are capable of following advanced navigation routes and aircraft that are not. Research into Air Traffic Control automation at Ames Research Center has led to the development of the Center-TRACON Automation System (CTAS). The Final Approach Spacing Tool (FAST) is the component of the CTAS used in the TRACON area. The work in this paper examines, via simulation, the effects of FAST used for aircraft landing on closely spaced parallel runways. The simulation contained various combinations of aircraft, equipped and unequipped with advanced navigation systems. A set of simulations was run both manually and with an augmented set of FAST advisories to sequence aircraft, assign runways, and avoid conflicts. The results of the simulations are analyzed, measuring the airport throughput, aircraft delay, loss of separation, and controller workload.

  12. Simulated Wake Characteristics Data for Closely Spaced Parallel Runway Operations Analysis

    NASA Technical Reports Server (NTRS)

    Guerreiro, Nelson M.; Neitzke, Kurt W.

    2012-01-01

    A simulation experiment was performed to generate and compile wake characteristics data relevant to the evaluation and feasibility analysis of closely spaced parallel runway (CSPR) operational concepts. While the experiment in this work is not tailored to any particular operational concept, the generated data applies to the broader class of CSPR concepts, where a trailing aircraft on a CSPR approach is required to stay ahead of the wake vortices generated by a lead aircraft on an adjacent CSPR. Data for wake age, circulation strength, and wake altitude change, at various lateral offset distances from the wake-generating lead aircraft approach path were compiled for a set of nine aircraft spanning the full range of FAA and ICAO wake classifications. A total of 54 scenarios were simulated to generate data related to key parameters that determine wake behavior. Of particular interest are wake age characteristics that can be used to evaluate both time- and distance- based in-trail separation concepts for all aircraft wake-class combinations. A simple first-order difference model was developed to enable the computation of wake parameter estimates for aircraft models having weight, wingspan and speed characteristics similar to those of the nine aircraft modeled in this work.

  13. Parallel Operation of Multiple Closely Spaced Small Aspect Ratio Rod Pinches

    DOE PAGES

    Harper-Slaboszewicz, Victor J.; Leckbee, Joshua; Bennett, Nichelle; ...

    2014-12-10

    A series of simulations and experiments to resolve questions about the operation of arrays of closely spaced small aspect ratio rod pinches has been performed. Design and post-shot analysis of the experimental results are supported by 3D particle-in-cell simulations. Both simulations and experiments support these conclusions. Penetration of current to the interior of the array appears to be efficient, as the current on the center rods is essentially equal to the current on the outer rods. Current loss in the feed due to the formation of magnetic nulls was avoided in these experiments by design of the feed surface ofmore » the cathode and control of the gap to keep the electric fields on the cathode below the emission threshold. Some asymmetry in the electron flow to the rod was observed, but the flow appeared to symmetrize as it reached the end of the rod. Interaction between the rod pinches can be controlled to allow the stable and consistent operation of arrays of rod pinches.« less

  14. Parallel Operation of Multiple Closely Spaced Small Aspect Ratio Rod Pinches

    SciTech Connect

    Harper-Slaboszewicz, Victor J.; Leckbee, Joshua; Bennett, Nichelle; Madrid, Elizabeth A.; Rose, David V.; Thoma, Carsten; Welch, Dale R.; Lake, Patrick W.; McCourt, Andrew L.

    2014-12-10

    A series of simulations and experiments to resolve questions about the operation of arrays of closely spaced small aspect ratio rod pinches has been performed. Design and post-shot analysis of the experimental results are supported by 3D particle-in-cell simulations. Both simulations and experiments support these conclusions. Penetration of current to the interior of the array appears to be efficient, as the current on the center rods is essentially equal to the current on the outer rods. Current loss in the feed due to the formation of magnetic nulls was avoided in these experiments by design of the feed surface of the cathode and control of the gap to keep the electric fields on the cathode below the emission threshold. Some asymmetry in the electron flow to the rod was observed, but the flow appeared to symmetrize as it reached the end of the rod. Interaction between the rod pinches can be controlled to allow the stable and consistent operation of arrays of rod pinches.

  15. Closely spaced multiple mutations as potential signatures of transient hypermutability in human genes.

    PubMed

    Chen, Jian-Min; Férec, Claude; Cooper, David N

    2009-10-01

    Data from diverse organisms suggests that transient hypermutability is a general mutational mechanism with the potential to generate multiple synchronous mutations, a phenomenon probably best exemplified by closely spaced multiple mutations (CSMMs). Here we have attempted to extend the concept of transient hypermutability from somatic cells to the germline, using human inherited disease-causing multiple mutations as a model system. Employing stringent criteria for data inclusion, we have retrospectively identified numerous potential examples of pathogenic CSMMs that exhibit marked similarities to the CSMMs reported in other systems. These examples include (1) eight multiple mutations, each comprising three or more components within a sequence tract of <100 bp; (2) three possible instances of "mutation showers"; and (3) numerous highly informative "homocoordinate" mutations. Using the proportion of CpG substitution as a crude indicator of the relative likelihood of transient hypermutability, we present evidence to suggest that CSMMs comprising at least one pair of mutations separated by < or =100 bp may constitute signatures of transient hypermutability in human genes. Although this analysis extends the generality of the concept of transient hypermutability and provides new insights into what may be considered a novel mechanism of mutagenesis underlying human inherited disease, it has raised serious concerns regarding current practices in mutation screening.

  16. Sublimating grains model of cometary coma.

    NASA Astrophysics Data System (ADS)

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

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

  17. TacSat-2: Path finder for a Close Space Support Asset

    NASA Astrophysics Data System (ADS)

    Bhopale, A.; Finley, C.

    2008-08-01

    that mak e it eff ectiv e and su itable for a Tactical Operator emp loying it as a Close Space Support asset. The TacSat-2 story was tru ly a story of survival in the low-budget, high-expectation spacecraft world . The mission su ccesses w ere signif icant and ground- breaking, but they w ere, almost w ithou t exception, compromised successes. Most importan tly, you w ill see an asset th at was unquestionably bo th effective and suitable for military operators, but only worth the investmen t if curren t responsiveness deficiencies dr ive leadership towards a so lution where Close Space Support platforms are a pursued alternativ e. This p aper w ill present the objective positive and negative r esults of the TacSat-2 system' s space/ground components and CONO PS and w ill use these resu lts to project th e co mplexion of an OpSat-X that could best fulfill the role of a Close Sp ace Support p latform directly employed by a front-lin e tactical oper ator to responsively return a product that meets an immediate need.

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

    ERIC Educational Resources Information Center

    Cavanaugh, Shane

    2014-01-01

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

  19. Pilot Non-Conformance to Alerting System Commands During Closely Spaced Parallel Approaches

    NASA Technical Reports Server (NTRS)

    Pritchett, Amy Ruth; Hansman, R. John; Corker, Kevin (Technical Monitor)

    1997-01-01

    Cockpit alerting systems monitor potentially hazardous situations, both inside and outside the aircraft. When a hazard is projected to occur, the alerting system displays alerts and/or command decisions to the pilot. However, pilots have been observed to not conform to alerting system commands by delaying their response or by not following the automatic commands exactly. This non-conformance to the automatic alerting system can reduce its benefit. Therefore, a need exists to understand the causes and effects of pilot non-conformance in order to develop automatic alerting systems whose commands the pilots are more likely to follow. These considerations were examined through flight simulator evaluations of the collision avoidance task during closely spaced parallel approaches. This task provided a useful case-study because the effects of non-conformance can be significant, given the time-critical nature of the task. A preliminary evaluation of alerting systems identified non-conformance in over 40% of the cases and a corresponding drop in collision avoidance performance. A follow-on experiment found subjects' alerting and maneuver selection criteria were consistent with different strategies than those used by automatic systems, indicating the pilot may potentially disagree with the alerting system if the pilot attempts to verify automatic alerts and commanded avoidance maneuvers. A final experiment found supporting automatic alerts with the explicit display of its underlying criteria resulted in more consistent subject reactions. In light of these experimental results, a general discussion of pilot non-conformance is provided. Contributing factors in pilot non-conformance include a lack of confidence in the automatic system and mismatches between the alerting system's commands and the pilots' own decisions based on the information available to them. The effects of non-conformance on system performance are discussed. Possible methods of reconciling mismatches are

  20. Experimental Study of Collision Detection Schema Used by Pilots During Closely Spaced Parallel Approaches

    NASA Technical Reports Server (NTRS)

    Pritchett, Amy R.; Hansman, R. John

    1996-01-01

    An experimental flight simulator study was conducted to examine the mental alerting logic and thresholds used by subjects to issue an alert and execute an avoidance maneuver. Subjects flew a series of autopilot landing approaches with traffic on a closely-spaced parallel approach; during some runs, the traffic would deviate towards the subject and the subject was to indicate the point when they recognized the potential traffic conflict, and then indicate a direction of flight for an avoidance maneuver. A variety of subjects, including graduate students, general aviation pilots and airline pilots, were tested. Five traffic displays were evaluated, with a moving map TCAS-type traffic display as a baseline. A side-task created both high and low workload situations. Subjects appeared to use the lateral deviation of the intruder aircraft from its approach path as the criteria for an alert regardless of the display available. However, with displays showing heading and/or trend information, their alerting thresholds were significantly lowered. This type of range-only schema still resulted in many near misses, as a high convergence rate was often established by the time of the subject's alert. Therefore, the properties of the intruder's trajectory had the greatest effect on the resultant near miss rate; no display system reliably caused alerts timely enough for certain collision avoidance. Subjects' performance dropped significantly on a side-task while they analyzed the need for an alert, showing alert generation can be a high workload situation at critical times. No variation was found between subjects with and with out piloting experience. These results suggest the design of automatic alerting systems should take into account the range-type alerting schema used by the human, such that the rationale for the automatic alert should be obvious to, and trusted by, the operator. Although careful display design may help generate pilot/automation trust, issues such as user non

  1. Dynamical Instability and Accretion in the Closely-Spaced Inner Uranian Moon System

    NASA Astrophysics Data System (ADS)

    Meyer, J. A.; Lissauer, J. J.

    2005-08-01

    We have numerically integrated the 13 largest Uranian regular satellites, including mutual gravitation, for a period of three million years. We used the hybrid symplectic integrator in the Mercury package (Chambers 1999, MNRAS 304, 793). Each collision was modeled as completely inelastic. The simulations include the five classical moons as well as the eight brightest inner moons. The Voyager-discovered satellite masses are ill-constrained, due to the lack of observed gravitational perturbations. The masses are estimated using the observed radii combined with an assumed density. We simultaneously simulate these uncertainties in mass and explore the dynamical interactions of closely-spaced satellite systems by allowing the common density of the non-classical moons to run from 0.1 to 30 g/cc. For integrations neglecting Uranus's oblateness, the 3 Myr interval was sufficient time for one to six collisions, with smaller assumed densities resulting in later and fewer collisions. Calculations including the effects of Uranus's oblateness show fewer collisions, with almost all runs showing at least one collision within 3 Myr. While Uranus's classical moons appear stable for the duration of the integrations, the inner moons are much less stable and collide on a timescale well within the Solar System's lifetime. These short collision times imply that the non-classical moons are significantly younger than the rest of the Solar System and highly chaotic. First collision times agree qualitatively with the results of Duncan and Lissauer (1997, Icarus 125, 1). Our novel results include the study of subsequent collisions, the study of the low-density regime, and eccentricity analysis. I will also present the results of integrations that include tidal damping of eccentricities. These calculations constrain the importance of tidal effects in the system and allow us to draw conclusions about the formation history of the Uranian satellites.

  2. Dynamical Instability and Accretion in Systems of Closely-Spaced Inner Moons

    NASA Astrophysics Data System (ADS)

    Meyer, J. A.; Lissauer, J. J.

    2005-05-01

    We have numerically integrated the 13 largest Uranian regular satellites, including mutual gravitation, for a period of three million years. We used the hybrid symplectic integrator in the Mercury package (Chambers 1999, MNRAS 304, 793). The simulations include the five classical moons as well as the eight largest inner moons. The Voyager-discovered satellites' masses are ill-constrained, due to the lack of observed gravitational perturbations. The masses are estimated using the observed radii combined with an assumed density; for moons of unknown radii, the albedo was assumed to be similar to that of nearby moons. We simultaneously simulate these uncertainties in mass and explore the dynamical interactions of closely-spaced satellite systems by allowing the common density of the non-classical moons to run from 0.1 to 30 g/cc. For our initial integrations, which neglected Uranus's oblateness, the 3 Myr interval was sufficient time for one to six collisions, depending on the density assumed for the inner moons. Each collision was modeled as completely inelastic. While Uranus's outer classical moons appear stable for the duration of the integrations, the inner moons are much less stable and collide on a timescale well within the solar system's lifetime. Results of calculations including the effects of Uranus's oblateness will also be presented. Preliminary results indicate that including the J2 and J4 moments leads to later collision times in the low density range. First collision times agree qualitatively with the results of Duncan and Lissauer (Icarus 125, 1, 1997). Our novel results include the study of subsequent collisions and implications for the formation history of the Uranian satellites.

  3. Kinematic Modeling of Separation Compression for Paired Approaches to Closely-Spaced Parallel Runways

    NASA Technical Reports Server (NTRS)

    Madden, Michael M.

    2014-01-01

    In a simultaneous paired approach to closely-spaced parallel runways, a pair of aircraft flies in close proximity on parallel approach paths. The longitudinal separation between the aircraft must be maintained within a range that avoids wake encounters and, if one of the aircraft blunders, avoids collision. To increase operational availability, the approach procedure must accommodate a mixture of aircraft sizes and, consequently, approach speeds. In these procedures, the slower aircraft is placed in the lead position. The faster aircraft maintains separation from the slow aircraft in a dependent operation until final approach and flies independently afterward. Due to the higher approach speed of the fast aircraft, longitudinal separation will decrease during final approach. Therefore, the fast aircraft must position itself before the final approach so that it will remain within the safe range of separation as separation decreases. Given the approach geometry and speed schedule for each aircraft, one can use kinematics to estimate the separation loss between a pair of aircraft. A kinematic model can complement fast-time Monte-Carlo simulations of the approach by enabling a tailored reduction in the variation of starting position for the fast aircraft. One could also implement the kinematic model in ground-based or on-board decision support tools to compute the optimal initial separation for a given pair of aircraft. To better match the auto-coupled flight of real aircraft, the paper derives a kinematic model where the speed schedule is flown using equivalent airspeed. The predicted time of flight using the equivalent airspeed kinematic model compares well against a high-fidelity aircraft simulation performing the same approach. This model also demonstrates a modest increase in the predicted loss of separation when contrasted against a kinematic model that assumes the scheduled speed is true airspeed.

  4. Sublimation TiN Coating of RF Power Components

    NASA Astrophysics Data System (ADS)

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

    2008-03-01

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

  5. Drift velocity of the ionospheric irregularities measured by closely-spaced GNSS receivers in Tromsoe, Norway

    NASA Astrophysics Data System (ADS)

    Ito, Y.; Otsuka, Y.; Shiokawa, K.; Hosokawa, K.; Ogawa, Y.

    2013-12-01

    estimated from the closely-spaced GNSS receivers. In this presentation, we discuss relationship of the irregularity drift velocity with aurora structure and movement based on these observations.

  6. Reassessing Aesthetic Appreciation of Nature in the Kantian Sublime

    ERIC Educational Resources Information Center

    Brady, Emily

    2012-01-01

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

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

    SciTech Connect

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

    2015-01-23

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

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

    PubMed

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

    2015-02-19

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

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

    DOE PAGES

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

    2015-01-23

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Cavanaugh, Shane

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

  12. Effects of oxygen partial pressure, deposition temperature, and annealing on the optical response of CdS:O thin films as studied by spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Junda, Maxwell M.; Grice, Corey R.; Subedi, Indra; Yan, Yanfa; Podraza, Nikolas J.

    2016-07-01

    Ex-situ spectroscopic ellipsometry measurements are made on radio frequency magnetron sputtered oxygenated cadmium sulfide (CdS:O) thin films. Films are deposited onto glass substrates at room temperature and at 270 °C with varying oxygen to total gas flow ratios in the sputtering ambient. Ellipsometric spectra from 0.74 to 5.89 eV are collected before and after annealing at 607 °C to simulate the thermal processes during close-space sublimation of overlying cadmium telluride in that solar cell configuration. Complex dielectric function (ɛ = ɛ1 + iɛ2) spectra are extracted for films as a function of oxygen gas flow ratio, deposition temperature, and post-deposition annealing using a parametric model accounting for critical point transitions and an Urbach tail for sub-band gap absorption. The results suggest an inverse relationship between degree of crystallinity and oxygen gas flow ratio, whereas annealing is shown to increase crystallinity in all samples. Direct band gap energies are determined from the parametric modeling of ɛ and linear extrapolations of the square of the absorption coefficient. As-deposited samples feature a range of band gap energies whereas annealing is shown to result in gap energies ranging only from 2.40 to 2.45 eV, which is close to typical band gaps for pure cadmium sulfide.

  13. Development and Testing of the Contaminant Insensitive Sublimator

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

  14. Development and Testing of the Contaminant Insensitive Sublimator

    NASA Technical Reports Server (NTRS)

    Leimkuehler, Thomas O.; Stephan, Ryan A.

    2007-01-01

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

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

    USGS Publications Warehouse

    Symonds, R.

    1993-01-01

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

  16. Dynamics and Mechanisms of Exfoliated Black Phosphorus Sublimation.

    PubMed

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

    2016-05-05

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

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

    ERIC Educational Resources Information Center

    Sharp, Ann Margaret

    1975-01-01

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

  18. Sublimation in bright spots on (1) Ceres

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    NASA Technical Reports Server (NTRS)

    Grugel, Richard N.; Toutanji, Houssam

    2006-01-01

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

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

    PubMed

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

    2015-12-10

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

  1. VTOL in ground effect flows for closely spaced jets. [to predict pressure and upwash forces on aircraft structures

    NASA Technical Reports Server (NTRS)

    Migdal, D.; Hill, W. G., Jr.; Jenkins, R. C.

    1979-01-01

    Results of a series of in ground effect twin jet tests are presented along with flow models for closely spaced jets to help predict pressure and upwash forces on simulated aircraft surfaces. The isolated twin jet tests revealed unstable fountains over a range of spacings and jet heights, regions of below ambient pressure on the ground, and negative pressure differential in the upwash flow field. A separate computer code was developed for vertically oriented, incompressible jets. This model more accurately reflects fountain behavior without fully formed wall jets, and adequately predicts ground isobars, upwash dynamic pressure decay, and fountain lift force variation with height above ground.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  4. Tunable Lattice Coupling of Multipole Plasmon Modes and Near-Field Enhancement in Closely Spaced Gold Nanorod Arrays

    PubMed Central

    Huang, Yu; Zhang, Xian; Ringe, Emilie; Hou, Mengjing; Ma, Lingwei; Zhang, Zhengjun

    2016-01-01

    Considering the nanogap and lattice effects, there is an attractive structure in plasmonics: closely spaced metallic nanoarrays. In this work, we demonstrate experimentally and theoretically the lattice coupling of multipole plasmon modes for closely spaced gold nanorod arrays, offering a new insight into the higher order cavity modes coupled with each other in the lattice. The resonances can be greatly tuned by changes in inter-rod gaps and nanorod heights while the influence of the nanorod diameter is relatively insignificant. Experimentally, pronounced suppressions of the reflectance are observed. Meanwhile, the near-field enhancement can be further enhanced, as demonstrated through surface enhanced Raman scattering (SERS). We then confirm the correlation between the near-field and far-field plasmonic responses, which is significantly important for maximizing the near-field enhancement at a specific excitation wavelength. This lattice coupling of multipole plasmon modes is of broad interest not only for SERS but also for other plasmonic applications, such as subwavelength imaging or metamaterials. PMID:26983501

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

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-08-01

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

  7. Heat transfer from combustion gases to a single row of closely spaced tubes in a swirl crossflow Stirling engine heater

    NASA Technical Reports Server (NTRS)

    Bankston, C. P.; Back, L. H.

    1982-01-01

    This paper describes an experimental program to determine the heat-transfer characteristics of a combustor and heat-exchanger system in a hybrid solar receiver which utilizes a Stirling engine. The system consists of a swirl combustor with a crossflow heat exchanger composed of a single row of 48 closely spaced curved tubes. In the present study, heat-transfer characteristics of the combustor/heat-exchanger system without a Stirling engine have been studied over a range of operating conditions and output levels using water as the working fluid. Nondimensional heat-transfer coefficients based on total heat transfer have been obtained and are compared with available literature data. The results show significantly enhanced heat transfer for the present geometry and test conditions. Also, heat transfer along the length of the tubes is found to vary, the effect depending upon test condition.

  8. Differential tolerance to biological and subjective effects of four closely spaced doses of N,N-dimethyltryptamine in humans.

    PubMed

    Strassman, R J; Qualls, C R; Berg, L M

    1996-05-01

    Tolerance of the behavioral effects of the short-acting, endogenous hallucinogen, N,N-dimethyltryptamine (DMT) is seen inconsistently in animals, and has not been produced in humans. The nature and time course of responses to repetitive, closely spaced administrations of an hallucinogenic dose of DMT were characterized. Thirteen experienced hallucinogen users received intravenous 0.3 mg/kg DMT fumarate, or saline placebo, four times, at 30 min intervals, on 2 separate days, in a randomized, double-blind, design. Tolerance to "psychedelic" subjective effects did not occur according to either clinical interview or Hallucinogen Rating Scale scores. Adrenocorticotropic hormone (ACTH), prolactin, cortisol, and heart rate responses decreased with repeated DMT administration, although blood pressure did not. These data demonstrate the unique properties of DMT relative to other hallucinogens and underscore the differential regulation of the multiple processes mediating the effects of DMT.

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

    SciTech Connect

    Phelan, James M.; Patton, Robert Thomas

    2004-08-01

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

  10. On the interaction of sublimating gas with cometary bodies

    NASA Astrophysics Data System (ADS)

    Steckloff, Jordan K.

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

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

    NASA Astrophysics Data System (ADS)

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

    2003-12-01

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

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

    PubMed

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

    2007-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Svoma, Bohumil M.

    2017-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

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

    PubMed

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

    2016-09-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  17. Enthalpy of sublimation as measured using a silicon oscillator

    NASA Astrophysics Data System (ADS)

    Shakeel, Hamza; Pomeroy, J. M.

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

  18. Alumina Paste Sublimation Suppression Barrier for Thermoelectric Device

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Paik, Jong-Ah; Caillat, Thierry

    2010-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  1. Isotopic Fractionation of Water-Ice from Sublimation

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  2. System for NO reduction using sublimation of cyanuric acid

    DOEpatents

    Perry, Robert A.

    1989-01-01

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

  3. Modeling the development of martian sublimation thermokarst landforms

    USGS Publications Warehouse

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

    2015-01-01

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

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

    ERIC Educational Resources Information Center

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

    2011-01-01

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

  5. Modeling the development of martian sublimation thermokarst landforms

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

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

    ERIC Educational Resources Information Center

    Huang, Yi-hui

    2012-01-01

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

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

    PubMed Central

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

    2008-01-01

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

  8. System for NO reduction using sublimation of cyanuric acid

    DOEpatents

    Perry, R.A.

    1989-01-24

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

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

    PubMed

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

    2010-04-08

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

  12. Efficient n-GaAs photoelectrodes grown by close-spaced vapor transport from a solid source.

    PubMed

    Ritenour, Andrew J; Cramer, Richard C; Levinrad, Solomon; Boettcher, Shannon W

    2012-01-01

    n-GaAs films were grown epitaxially on n(+)-GaAs substrates by a close-spaced vapor transport method and their photoelectrochemical energy conversion properties studied. Under 100 mW cm(-2) of ELH solar simulation, conversion efficiencies up to 9.3% for CSVT n-GaAs photoanodes were measured in an unoptimized ferrocene/ferrocenium test cell. This value was significantly higher than the 5.7% measured for similarly doped commercial n-GaAs wafers. Spectral response experiments showed that the higher performance of CSVT n-GaAs films relative to the commercial wafers was due to longer minority carrier diffusion lengths (L(D)), up to 1,020 nm in the CSVT films compared to 260 nm in the commercial n-GaAs wafers. Routes to improve the performance of CSVT GaAs and the implications of these results for the development of scalable GaAs-based solar energy conversion devices are discussed.

  13. Level sequence and splitting identification of closely spaced energy levels by angle-resolved analysis of fluorescence light

    NASA Astrophysics Data System (ADS)

    Wu, Z. W.; Volotka, A. V.; Surzhykov, A.; Dong, C. Z.; Fritzsche, S.

    2016-06-01

    The angular distribution and linear polarization of the fluorescence light following the resonant photoexcitation is investigated within the framework of density matrix and second-order perturbation theory. Emphasis has been placed on "signatures" for determining the level sequence and splitting of intermediate (partially) overlapping resonances, if analyzed as a function of photon energy of incident light. Detailed computations within the multiconfiguration Dirac-Fock method have been performed, especially for the 1 s22 s22 p63 s ,Ji=1 /2 +γ1→(1s22 s 2 p63 s ) 13 p3 /2,J =1 /2 ,3 /2 →1 s22 s22 p63 s ,Jf=1 /2 +γ2 photoexcitation and subsequent fluorescence emission of atomic sodium. A remarkably strong dependence of the angular distribution and linear polarization of the γ2 fluorescence emission is found upon the level sequence and splitting of the intermediate (1s22 s 2 p63 s ) 13 p3 /2,J =1 /2 ,3 /2 overlapping resonances owing to their finite lifetime (linewidth). We therefore suggest that accurate measurements of the angular distribution and linear polarization might help identify the sequence and small splittings of closely spaced energy levels, even if they cannot be spectroscopically resolved.

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

    PubMed

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

    2011-01-30

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

  15. Giant enhancement of noncontact friction between closely spaced bodies by dielectric films and two-dimensional systems

    SciTech Connect

    Volokitin, A. I. Persson, B. N. J.; Ueba, H.

    2007-02-15

    The effect of an external bias voltage and spatial variations of the surface potential on the damping of cantilever vibrations in an atomic force microscope (AFM) is considered. The damping is due to an electrostatic friction that arises due to dissipation of the energy of an electromagnetic field generated in the sample by oscillating static charges induced on the surface of the AFM probe tip by the bias voltage or spatial variations of the surface potential. A similar effect appears when the tip is oscillating in an electrostatic field created by charged defects present in the dielectric sample. The electrostatic friction is compared to the van der Waals (vdW) friction between closely spaced bodies, which is caused by a fluctuating electromagnetic field related to the quantum and thermal fluctuations of current density inside the bodies. It is shown that the electrostatic friction and the vdW friction can be strongly enhanced in the presence of dielectric films or two-dimensional (2D) structures-such as a 2D electron system or an incommensurate layer of adsorbed ions exhibiting acoustic oscillations-on the probe tip and sample surfaces. It is also shown that the damping of cantilever oscillations caused by the electrostatic friction in the presence of such 2D structures can have the same order of magnitude and the same dependence on the distance as observed in experiment by Stipe et al. [Phys. Rev. Lett. 87, 096801 (2001)]. At small distances, the vdW friction can be large enough to be measured in experiment. In interpreting the experimental data that obey a quadratic dependence on the bias voltage, one can reject a phonon mechanism according to which the friction depends on the fourth power of the voltage.

  16. Surface engineering of SiC via sublimation etching

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  17. Effects of varying obliquity on Martian sublimation thermokarst landforms

    USGS Publications Warehouse

    Dundas, Colin M.

    2017-01-01

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

  18. All-Vacuum-Deposited Stoichiometrically Balanced Inorganic Cesium Lead Halide Perovskite Solar Cells with Stabilized Efficiency Exceeding 11.

    PubMed

    Chen, Chien-Yu; Lin, Hung-Yu; Chiang, Kai-Ming; Tsai, Wei-Lun; Huang, Yu-Ching; Tsao, Cheng-Si; Lin, Hao-Wu

    2017-03-01

    Vacuum-sublimed inorganic cesium lead halide perovskite thin films are prepared and integrated in all-vacuum-deposited solar cells. Special care is taken to determine the stoichiometric balance of the sublimation precursors, which has great influence on the device performance. The mixed halide devices exhibit exceptional stabilized power conversion efficiency (11.8%) and promising thermal and long-term stabilities.

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

    NASA Astrophysics Data System (ADS)

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

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

  20. A Validated Set of MIDAS V5 Task Network Model Scenarios to Evaluate Nextgen Closely Spaced Parallel Operations Concepts

    NASA Technical Reports Server (NTRS)

    Gore, Brian Francis; Hooey, Becky Lee; Haan, Nancy; Socash, Connie; Mahlstedt, Eric; Foyle, David C.

    2013-01-01

    The Closely Spaced Parallel Operations (CSPO) scenario is a complex, human performance model scenario that tested alternate operator roles and responsibilities to a series of off-nominal operations on approach and landing (see Gore, Hooey, Mahlstedt, Foyle, 2013). The model links together the procedures, equipment, crewstation, and external environment to produce predictions of operator performance in response to Next Generation system designs, like those expected in the National Airspaces NextGen concepts. The task analysis that is contained in the present report comes from the task analysis window in the MIDAS software. These tasks link definitions and states for equipment components, environmental features as well as operational contexts. The current task analysis culminated in 3300 tasks that included over 1000 Subject Matter Expert (SME)-vetted, re-usable procedural sets for three critical phases of flight; the Descent, Approach, and Land procedural sets (see Gore et al., 2011 for a description of the development of the tasks included in the model; Gore, Hooey, Mahlstedt, Foyle, 2013 for a description of the model, and its results; Hooey, Gore, Mahlstedt, Foyle, 2013 for a description of the guidelines that were generated from the models results; Gore, Hooey, Foyle, 2012 for a description of the models implementation and its settings). The rollout, after landing checks, taxi to gate and arrive at gate illustrated in Figure 1 were not used in the approach and divert scenarios exercised. The other networks in Figure 1 set up appropriate context settings for the flight deck.The current report presents the models task decomposition from the tophighest level and decomposes it to finer-grained levels. The first task that is completed by the model is to set all of the initial settings for the scenario runs included in the model (network 75 in Figure 1). This initialization process also resets the CAD graphic files contained with MIDAS, as well as the embedded

  1. Diverse lavas from closely spaced volcanoes drawing from a common parent: Emmons Lake Volcanic Center, Eastern Aleutian Arc

    USGS Publications Warehouse

    Mangan, M.; Miller, T.; Waythomas, C.; Trusdell, F.; Calvert, A.; Layer, P.

    2009-01-01

    Emmons Lake Volcanic Center (ELVC) on the lower Alaskan Peninsula is one of the largest and most diverse volcanic centers in the Aleutian Arc. Since the Middle Pleistocene, eruption of ~ 350 km3 of basalt through rhyolite has produced a 30 km, arc front chain of nested calderas and overlapping stratovolcanoes. ELVC has experienced as many as five major caldera-forming eruptions, the most recent, at ~ 27 ka, produced ~ 50 km3 of rhyolitic ignimbrite and ash fall. These violent silicic events were interspersed with less energetic, but prodigious, outpourings of basalt through dacite. Holocene eruptions are mostly basaltic andesite to andesite and historically recorded activity includes over 40 eruptions within the last 200 yr, all from Pavlof volcano, the most active site in the Aleutian Arc. Geochemical and geophysical observations suggest that although all ELVC eruptions derive from a common clinopyroxene + spinel + plagioclase fractionating high-aluminum basalt parent in the lower crust, magma follows one of two closely spaced, but distinct paths to the surface. Under the eastern end of the chain, magma moves rapidly and cleanly through a relatively young (~ 28 ka), hydraulically connected dike plexus. Steady supply, short magma residence times, and limited interaction with crustal rocks preserve the geochemistry of deep crustal processes. Below the western part of the chain, magma moves haltingly through a long-lived (~ 500 ka) and complex intrusive column in which many generations of basaltic to andesitic melts have mingled and fractionated. Buoyant, silicic melts periodically separate from the lower parts of the column to feed voluminous eruptions of dacite and rhyolite. Mafic lavas record a complicated passage through cumulate zones and hydrous silicic residues as manifested by disequilibrium phenocryst textures, incompatible element enrichments, and decoupling of REEs and HFSEs ratios. Such features are absent in mafic lavas from the younger part of the chain

  2. Unsteady Reynolds averaged Navier-Stokes simulation of the post-critical flow around a closely spaced group of silos

    NASA Astrophysics Data System (ADS)

    Hillewaere, J.; Dooms, D.; Van Quekelberghe, B.; Degroote, J.; Vierendeels, J.; De Roeck, G.; Lombaert, G.; Degrande, G.

    2012-04-01

    During a storm in October 2002, wind induced ovalling vibrations were observed on several empty silos of a closely spaced group (pitch-to-diameter ratio of 1.05) consisting of 8 by 5 silos in the port of Antwerp (Belgium). Numerical simulations of the turbulent wind flow are performed to clarify the occurrence of the observed ovalling vibrations near the lee side corner of the group by studying the dynamic wind pressures on the silo surfaces and linking to the dynamic properties of the silo structures. As the orientation of the group largely affects the pressure distribution around the cylinders of the group, the influence of the angle of incidence of the wind flow on these ovalling vibrations is examined while other parameters, such as spacing ratio and Reynolds number are unchanged. To achieve results within a reasonable computation time, 2D unsteady Reynolds averaged Navier-Stokes (URANS) equations using Menter's shear stress transport turbulence model were performed. In order to elucidate the influence of the applied turbulence model and to qualitatively validate the spatial and temporal discretization of the 2D highly turbulent post-critical (Re=1.24×107) flow simulations for the silo group, single cylinder simulations were used. The geometric resemblance of the group arrangement with rectangular cylinders on the one hand and of the interstitial spaces with tube arrays (e.g. heat exchangers) on the other hand is used to qualitatively compare the observed flow phenomena. The simulations show that the silo group can be treated neither as a tube array nor as a solid bluff body. Subsequent linking of dynamic wind pressures to dynamic properties of the silo structures reveals strong narrow band frequency peaks in the turbulent pressure coefficient spectra of the silos near the lee side corners of the group that match the structural natural frequencies of the third and fourth ovalling mode shape of the silos. This match indicates a forced, resonant response which

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    USGS Publications Warehouse

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

    1987-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1987-08-01

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

  6. The enthalpy of sublimation and thermodynamic functions of fermium

    SciTech Connect

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

    1989-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

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

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

    PubMed

    Gao, Gau-Yi; Lin, Shan-Yang

    2010-01-01

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

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

    PubMed

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

    2015-07-01

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

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

    SciTech Connect

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

    2015-07-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

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

    SciTech Connect

    Jordan, W.C.

    1993-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

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

    PubMed

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

    2016-04-01

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

  17. Annealing effects on the chemical deposited CdS films and the electrical properties of CdS/CdTe solar cells

    SciTech Connect

    Han, Junfeng; Liao, Cheng; Jiang, Tao; Fu, Ganhua; Krishnakumar, V.; Spanheimer, C.; Haindl, G.; Zhao, Kui; Klein, A.; Jaegermann, W.

    2011-02-15

    Graphical abstract: From XPS core level spectras, compared with as-depositing CdS (sample A), the Fermi level is shifting closer to the conduction band after annealing treatment in the oxygen (sample B) while it is shifting closer to the valence band after annealing treatment in the argon-hydrogen (sample C). That might be the main reason of the different performance of the final devices. The open circuit voltage of the CdS/CdTe solar cell increases when the CBD CdS is annealed with oxygen, while the performance of the solar cell decreases when the CBD CdS is annealed with argon-hydrogen. Research highlights: {yields} Two different methods (oxidation and reduction) were used to anneal CdS films for CdTe solar cells. {yields} Electrical properties were analyzed by XPS (Fermi levels of CdS films). {yields} Annealing treatment in oxidation atmosphere could shift Fermi level of CdS film to higher position and consequently improve the CdS/CdTe junction and performance of solar cells. -- Abstract: CdS layers grown by chemical bath deposition (CBD) are annealed in the oxygen and argon-hydrogen atmosphere respectively. It has been found that the open circuit voltage of the CdS/CdTe solar cell increases when the CBD CdS is annealed with oxygen before the deposition of CdTe by close spaced sublimation (CSS), while the performance of the solar cell decreases when the CBD CdS is annealed with argon-hydrogen. Electronic properties of the CdS films are investigated using X-ray photo-electron spectroscopy (XPS), which indicates that the Fermi level is shifting closer to the conduction band after annealing in the oxygen and consequently a higher open circuit voltage of the solar cell can be obtained.

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

    DOEpatents

    Turner, Terry D; Wilding, Bruce M

    2013-10-01

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

  19. Uranium hexaflouride freezer/sublimer process simulator/trainer

    SciTech Connect

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

    1991-01-01

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

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  1. Sublimation Model for Formation of Martian Residual Cap Depressions

    NASA Astrophysics Data System (ADS)

    Byrne, S.; Ingersoll, A. P.

    2000-10-01

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

  2. Advanced Research Deposition System (ARDS) for processing CdTe solar cells

    NASA Astrophysics Data System (ADS)

    Barricklow, Keegan Corey

    CdTe solar cells have been commercialized at the Gigawatt/year level. The development of volume manufacturing processes for next generation CdTe photovoltaics (PV) with higher efficiencies requires research systems with flexibility, scalability, repeatability and automation. The Advanced Research Deposition Systems (ARDS) developed by the Materials Engineering Laboratory (MEL) provides such a platform for the investigation of materials and manufacturing processes necessary to produce the next generation of CdTe PV. Limited by previous research systems, the ARDS was developed to provide process and hardware flexibility, accommodating advanced processing techniques, and capable of producing device quality films. The ARDS is a unique, in-line process tool with nine processing stations. The system was designed, built and assembled at the Materials Engineering Laboratory. Final assembly, startup, characterization and process development are the focus of this research. Many technical challenges encountered during the startup of the ARDS were addressed in this research. In this study, several hardware modifications needed for the reliable operation of the ARDS were designed, constructed and successfully incorporated into the ARDS. The effect of process condition on film properties for each process step was quantified. Process development to achieve 12% efficient baseline solar cell required investigation of discrete processing steps, troubleshooting process variation, and developing performance correlations. Subsequent to this research, many advances have been demonstrated with the ARDS. The ARDS consistently produces devices of 12% +/-.5% by the process of record (POR). The champion cell produced to date utilizing the ARDS has an efficiency of 16.2% on low cost commercial sodalime glass and utilizes advanced films. The ARDS has enabled investigation of advanced concepts for processing CdTe devices including, Plasma Cleaning, Plasma Enhanced Closed Space Sublimation

  3. Plasma-Enhanced Chemical Vapor Deposition as a Method for the Deposition of Peptide Nanotubes

    DTIC Science & Technology

    2013-09-17

    45432, United States Distribution A: Approved for public release; distribution is unlimited. 2    Introduction: The unique ability of dipeptides ...Using physical vapor deposition (PVD) well-ordered assemblies of peptide nanotubes (PNTs) composed of dipeptide subunits are obtained on various...the PECVD deposition chamber with sublimation capability in the laboratory of Dr. Rajesh Naik (AFRL/RXAS) and conditions were modified for dipeptide

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

    NASA Astrophysics Data System (ADS)

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

    2010-01-01

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

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

    USGS Publications Warehouse

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

    2010-01-01

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

  6. Structural-acoustic optimum design of shell structures in open/closed space based on a free-form optimization method

    NASA Astrophysics Data System (ADS)

    Shimoda, Masatoshi; Shimoide, Kensuke; Shi, Jin-Xing

    2016-03-01

    Noise reduction by structural geometry optimization has attracted much attention among designers. In the present work, we propose a free-form optimization method for the structural-acoustic design optimization of shell structures to reduce the noise of a targeted frequency or frequency range in an open or closed space. The objective of the design optimization is to minimize the average structural vibration-induced sound pressure at the evaluation points in the acoustic field under a volume constraint. For the shape design optimization, we carry out structural-acoustic coupling analysis and adjoint analysis to calculate the shape gradient functions. Then, we use the shape gradient functions in velocity analysis to update the shape of shell structures. We repeat this process until convergence is confirmed to obtain the optimum shape of the shell structures in a structural-acoustic coupling system. The numerical results for the considered examples showed that the proposed design optimization process can significantly reduce the noise in both open and closed spaces.

  7. Rapid, Single-Molecule Assays in Nano/Micro-Fluidic Chips with Arrays of Closely Spaced Parallel Channels Fabricated by Femtosecond Laser Machining

    PubMed Central

    Canfield, Brian K.; King, Jason K.; Robinson, William N.; Hofmeister, William H.; Davis, Lloyd M.

    2014-01-01

    Cost-effective pharmaceutical drug discovery depends on increasing assay throughput while reducing reagent needs. To this end, we are developing an ultrasensitive, fluorescence-based platform that incorporates a nano/micro-fluidic chip with an array of closely spaced channels for parallelized optical readout of single-molecule assays. Here we describe the use of direct femtosecond laser machining to fabricate several hundred closely spaced channels on the surfaces of fused silica substrates. The channels are sealed by bonding to a microscope cover slip spin-coated with a thin film of poly(dimethylsiloxane). Single-molecule detection experiments are conducted using a custom-built, wide-field microscope. The array of channels is epi-illuminated by a line-generating red diode laser, resulting in a line focus just a few microns thick across a 500 micron field of view. A dilute aqueous solution of fluorescently labeled biomolecules is loaded into the device and fluorescence is detected with an electron-multiplying CCD camera, allowing acquisition rates up to 7 kHz for each microchannel. Matched digital filtering based on experimental parameters is used to perform an initial, rapid assessment of detected fluorescence. More detailed analysis is obtained through fluorescence correlation spectroscopy. Simulated fluorescence data is shown to agree well with experimental values. PMID:25140634

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

    NASA Technical Reports Server (NTRS)

    Visentine, James T.; Richmond, Robert G.

    1973-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Sekanina, Zdenek

    1992-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2008-09-01

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

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

    ERIC Educational Resources Information Center

    Hoyng, Peter

    1997-01-01

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

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

    PubMed

    Civitarese, Giuseppe

    2014-12-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

  15. Generalized Orbital Projections of a Sublimating Ice Particle

    NASA Technical Reports Server (NTRS)

    Menkin, Evgeny; Bacon, Jack

    2006-01-01

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

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

    USGS Publications Warehouse

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

    1988-01-01

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

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

    USGS Publications Warehouse

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

    2016-01-01

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

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

    NASA Astrophysics Data System (ADS)

    May, Michael; Paul, Elizabeth; Katovic, Vladimir

    2015-11-01

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

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

    PubMed

    May, Michael; Paul, Elizabeth; Katovic, Vladimir

    2015-11-01

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

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

    NASA Astrophysics Data System (ADS)

    Svoma, B. M.

    2012-12-01

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

  1. Desorption and sublimation kinetics for fluorinated aluminum nitride surfaces

    SciTech Connect

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

    2014-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Kreslavsky, Mikhail A.; Head, James W.

    2002-12-01

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

  4. Efficacy and safety of two closely spaced doses of praziquantel against Schistosoma haematobium and S. mansoni and re-infection patterns in school-aged children in Niger.

    PubMed

    Garba, Amadou; Lamine, Mariama S; Barkiré, Nouhou; Djibo, Ali; Sofo, Boubacar; Gouvras, Anouk N; Labbo, Rabiou; Sebangou, Hannatou; Webster, Joanne P; Fenwick, Alan; Utzinger, Jürg

    2013-11-01

    The aim of this study was to assess the efficacy and safety of two closely spaced doses of praziquantel (PZQ) against Schistosoma haematobium and S. mansoni infection in school-aged children, and to characterise re-infection patterns over a 12-month period. The study was carried out in five villages in western Niger: Falmado, Seberi and Libore (single S. haematobium infection foci), and Diambala and Namarigoungou (mixed S. haematobium-S. mansoni infection foci). Parasitological examinations consisted of triplicate urine filtrations and triplicate Kato-Katz thick smears at each visit. Two 40mg/kg oral doses of PZQ were administered 3 weeks apart. Adverse events were monitored within 4h after dosing by the survey team and 24h after treatment using a questionnaire. Our final study cohort comprised 877 children who were infected with either S. haematobium, or S. mansoni, or both species concurrently and received both doses of PZQ. Follow-up visits were conducted 6 weeks, 6 months and 12 months after the first dose of PZQ. At baseline, the geometric mean (GM) infection intensity of S. haematobium ranged from 3.6 (Diambala) to 30.3eggs/10ml of urine (Falmado). The GM infection intensity of S. mansoni ranged from 86.7 (Diambala) to 151.4eggs/g of stool (Namarigoungou). Adverse events were reported by 33.0% and 1.5% of the children after the first and second doses of PZQ, respectively. We found cure rates (CRs) in S. haematobium-infected children 3 weeks after the second dose of PZQ ranging between 49.2% (Falmado) and 98.4% (Namarigoungou) and moderate-to-high egg reduction rates (ERRs) (71.4-100%). Regarding S. mansoni, only moderate CRs and ERRs were found (51.7-58.8% in Diambala, 55.2-60.2% in Namarigoungou). Twelve months post-treatment, prevalence rates approached pre-treatment levels, but infection intensities remained low. In conclusion, PZQ, given in two closely spaced doses, is efficacious against S. haematobium, but the low ERR observed against S. mansoni raises

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

    NASA Astrophysics Data System (ADS)

    Xiao, Xin; Tao, Le-Ren

    2007-06-01

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

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

    PubMed

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

    2012-11-08

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

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

    PubMed Central

    Ishizu, Tomohiro; Zeki, Semir

    2014-01-01

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

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

    USGS Publications Warehouse

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

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-08-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  11. Sublimation and Irradiation of Glycolaldehyde/Water Ices

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

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

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

    NASA Astrophysics Data System (ADS)

    Bembel, A. G.

    2017-02-01

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

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

    PubMed

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

    2004-10-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1995-12-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2003-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2001-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

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

    SciTech Connect

    Ruppel, F.R.

    1992-09-01

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

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

    ERIC Educational Resources Information Center

    Utgikar, Vivek P.

    2015-01-01

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

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

    ERIC Educational Resources Information Center

    McDevitt, Michael; Sindorf, Shannon

    2012-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Tarasevych, Arkadii V.; Guillemin, Jean-Claude

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

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

    PubMed

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

    2013-04-01

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

  7. Low latitude ionospheric scintillation and zonal irregularity drifts observed with GPS-SCINDA system and closely spaced VHF receivers in Kenya

    NASA Astrophysics Data System (ADS)

    Olwendo, O. J.; Baluku, T.; Baki, P.; Cilliers, P. J.; Mito, C.; Doherty, P.

    2013-05-01

    In this study we have used VHF and GPS-SCINDA receivers located at Nairobi (36.8°E, 1.3°S, dip -24.1°) in Kenya, to investigate the ionospheric scintillation and zonal drift irregularities of a few hundred meter-scale irregularities associated with equatorial plasma density bubbles for the period 2011. From simultaneous observations of amplitude scintillation at VHF and L-band frequencies, it is evident that the scintillation activity is higher during the post sunset hours of the equinoctial months than at the solstice. While it is noted that there is practically no signatures of the L-band scintillation in solstice months (June, July, December, January) and after midnight, VHF scintillation does occur in the solstice months and show post midnight activity through all the seasons. VHF scintillation is characterized by long duration of activity and slow fading that lasts till early morning hours (05:00 LT). Equinoctial asymmetry in scintillation occurs with higher occurrence in March-April than in September-October. The occurrence of post midnight VHF scintillation in this region is unusual and suggests some mechanisms for the formation of scintillation structure that might not be clearly understood. Zonal drift velocities of irregularities were measured using cross-correlation analysis with time series of the VHF scintillation structure from two closely spaced antennas. Statistical analyses of the distribution of zonal drift velocities after sunset hours indicate that the range of the velocities is 30-160 m/s. This is the first analysis of the zonal plasma drift velocity over this region. Based on these results we suggest that the east-west component of the plasma drift velocity may be related to the evolution of plasma bubble irregularities caused by the prereversal enhancement of the eastward electric fields. The equinoctial asymmetry of the drift velocities and scintillation could be attributed to the asymmetry of neutral winds in the thermosphere that drives

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

    PubMed

    Graebner, William

    2006-08-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    , swiveled and bounced downslope). Distinctive pits with arcuate rims on their downslope edge were formed where blocks bounced on the surface. These pits are at an almost equidistant spacing. Despite a longer slope (16 m as opposed to 8m at Grand Falls), no depositional apron was formed. Levee development was less consistent compared to the Arizona site, but a pronounced unpaired-levee formed towards the base of the lee slope. These data show that sublimating blocks of CO2 ice leave signatures of transport paths and are capable of eroding and transporting sediment. Diniega,S. et al (2013) A new dry hypothesis for the formation of Martian linear gullies. Icarus. Vol. 225, 1, p. 526-537. Bourke, M.C. et al (2016) The geomorphic effect of sublimating CO2 blocks on dune lee slopes at Grand Falls, Arizona. LPSC

  10. Freeze drying for gas chromatography stationary phase deposition

    DOEpatents

    Sylwester, Alan P.

    2007-01-02

    The present disclosure relates to methods for deposition of gas chromatography (GC) stationary phases into chromatography columns, for example gas chromatography columns. A chromatographic medium is dissolved or suspended in a solvent to form a composition. The composition may be inserted into a chromatographic column. Alternatively, portions of the chromatographic column may be exposed or filled with the composition. The composition is permitted to solidify, and at least a portion of the solvent is removed by vacuum sublimation.

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

    PubMed Central

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

    2013-01-01

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

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

    PubMed

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

    2013-07-05

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

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

    PubMed

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

    2016-04-07

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

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

    PubMed

    Bradley, Benjamin Sylvester

    2011-01-01

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

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

    PubMed

    Moyori, Takaya; Tang, Tang; Takasu, Akinori

    2012-05-14

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

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

    PubMed

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

    2011-10-07

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

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

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2003-04-01

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

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

    PubMed

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

    2017-02-01

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

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

    PubMed Central

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Murugesan, Ramki; Park, Jae Hyun

    2014-11-01

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

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

    NASA Astrophysics Data System (ADS)

    Vavilov, Dmitrii; Medvedev, Yurii; Zatitskiy, Pavel

    2016-10-01

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

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

    PubMed

    Kalyankar, P; Panzade, P; Lahoti, S

    2015-01-01

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

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

    PubMed

    Vemula, Sateesh Kumar; Vangala, Mohan

    2014-01-01

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

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

    PubMed Central

    Vangala, Mohan

    2014-01-01

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

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

    SciTech Connect

    Ruppel, F.R.

    1992-03-01

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

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

    PubMed

    Goldfarb, Jillian L; Suuberg, Eric M

    2010-08-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1985-01-01

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

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

    PubMed

    Hikal, Walid M; Weeks, Brandon L

    2014-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Schulz, O.; de Jong, C.

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  14. The Astroni volcano: the only example of closely spaced eruptions in the same vent area during the recent history of the Campi Flegrei caldera (Italy)

    NASA Astrophysics Data System (ADS)

    Isaia, Roberto; D'Antonio, Massimo; Dell'Erba, Francesco; Di Vito, Mauro; Orsi, Giovanni

    2004-05-01

    The Astroni volcano formed during the third and most recent epoch of activity (4.8-3.8 ka) of the Campi Flegrei caldera (CFc). The activity of the volcano was dominated by explosive, mostly phreatomagmatic eruptions, with only subordinate lava effusions. We have grouped the sequence of deposits into seven distinct units, separated by erosional unconformities or very thin paleosols. The units include mostly surge beds, with subordinate strombolian deposits and lavas, and one plinian fallout layer. The total volume of erupted magma is 0.45 km 3 (DRE), while the total mass is 1.12×10 12 kg. The magma feeding the first five eruptions was alkali-trachytic and slightly zoned, while the last two eruptions tapped a magma batch resulting from mixing of the previously extruded alkali-trachytic and a less evolved trachytic magma. The volcano grew at the northwestern edge of the polygonal volcano-tectonic collapse, northwest-southeast elongated, which accompanied the Agnano-Monte Spina eruption (4.1 ka), the largest of the third epoch. Available radiometric dates and stratigraphical data constrain the age of the volcano in the final part of the 4.1-3.8 ka time span. This implies that the seven eruptions followed each other at very short time intervals. This conclusion is also supported by constancy in archaeological facies of findings within the paleosols between variable Astroni units, in the plain north of the caldera. The sequence of close eruptions in the same area, although with a slight migration of the vent from northwest to southeast, makes the Astroni volcano peculiar in the recent history of the CFc. Therefore, the definition of its history is very important in order to understand one of the past phenomenologies of the caldera, relevant elements to forecast its behavior.

  15. Fundamental studies of the mechanisms of slag deposit formation: Final report

    SciTech Connect

    Austin, L.G.; Benson, S.; Rabinovich, A.; Tangsathitkulchai, M.; Schobert H.H.

    1987-07-01

    The kinetics of ash deposition on utility boilers have been studied. A heated tube furnace system was used in the study. Areas of consideration in the deposition mechanics were: close space knowledge of chemical composition and distribution of inorganic constituents in coal, transformations and reactions of the inorganic constituents in the flame, ash transport mechanisms, initial adhesion of ash particles to heat transfer surfaces and subsequently to each other to form a deposit, and further interactions of the deposited ash to grow a strong deposit. Interactions of deposited ash that cause changes in physical and chemical properties in an aged deposit are due to processes such as sintering, chemical reactions, and melting. The degree of these changes increases as the deposit grows from the heat transfer surfaces where it forms. All of these changes during the deposit formation process are coal-specific and are strongly dependent on the boiler configuration and operating conditions. 18 refs., 55 figs., 42 tabs.

  16. Generality of forming stable organic glasses by vapor deposition

    NASA Astrophysics Data System (ADS)

    Zhu, Lei; Yu, Lian

    2010-10-01

    Organic glasses of exceptional thermodynamic and kinetic stability have been prepared for the first time for four substances by vapor deposition in simple sublimation apparatus. This study, together with previous studies, demonstrates the generality of the phenomenon; the simple apparatus makes these interesting materials more accessible for research. Substances forming stable glasses by vapor deposition tend to undergo surface-enhanced crystal growth, suggesting both phenomena could be linked to surface mobility. Stable organic glasses are potentially useful for drug delivery, organic electronics, and thin-film technologies.

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

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-07-01

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

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

    PubMed

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

    2011-10-11

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

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

    SciTech Connect

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

    2015-04-28

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

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

    PubMed Central

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

    2011-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Steckloff, Jordan; Jacobson, Seth A.

    2014-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Astrophysics Data System (ADS)

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

    2008-02-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    SciTech Connect

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

    1991-05-01

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

  8. Sublime Science

    ERIC Educational Resources Information Center

    Girod, Mark

    2007-01-01

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

  9. Evaluating the Age of Buried Ice in Antarctica Using Ashfall Deposits: New Insights from Deposit Morphology, Grain Shape, and LA-ICP-MS Trace-Element Geochemistry

    NASA Astrophysics Data System (ADS)

    Lewis, A. R.; Marchant, D. R.

    2003-12-01

    Dating of buried ice in the western Dry Valleys region relies on 40Ar/39Ar analysis of ashfall deposits within sublimation tills that rest directly on stagnant glacier ice. The oldest ice so dated is >8.1 Ma. The fundamental assumption is that dated ashes are in-situ and have not been transported from surface deposits elsewhere in the Dry Valleys region. Given that the surface of sublimation tills shows well-developed patterned ground, the presumption of ground stability and long-term preservation of in-situ ashfall is questioned. As a test of ground stability, we examined ash-deposit morphology, grain shape, and glass-shard trace-element geochemistry from several ashfall deposits used to provide limiting ages on buried ice and tills in the western Dry Valleys. Detailed field analyses show that ashfall that collects in sublimation tills over buried ice occurs in one of three morphologic settings: surface troughs that delineate sand-wedge polygons, void spaces in gravel-and-cobble lags that overlie active sand wedges, and 1 to 2-cm-wide thermal contraction cracks. Post-depositional sublimation of underlying ice may distort initial deposit morphology through uneven surface lowering. Microscopic analyses of concentrated ashfall deposits that lack detrital sand grains show highly angular glass shards that preserve delicate hair-like spires and thin bubble-wall vesicles. Grain edges are sharp with no chipped, fractured, or pitted surfaces. In contrast, ash deposits containing detrital sand grains show subangular to subrounded shard morphologies with concave fractures and pits on grain edges, all of which are suggestive of abrasion during transport. In such deposits, grains preserving delicate bubble walls and hair-like spires are conspicuously absent. Laser ablation-inductively coupled plasma-mass spectrometry shows that glass shards within each ashfall deposit have uniform trace-element geochemical signatures. If ashfall were eroded and transported after initial

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

    PubMed

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

    2014-06-19

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

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

    NASA Astrophysics Data System (ADS)

    Pilorget, C.; Forget, F.

    2016-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Stephan, Ryan A.; Sheth, Rubik B.

    2009-01-01

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

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

    PubMed Central

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

    2011-01-01

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

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

    SciTech Connect

    Kuroiwa, Takuto; Sirono, Sin-iti

    2011-09-20

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

  15. Polyimide films from vapor deposition: toward high strength, NIF capsules

    SciTech Connect

    Cook, R C; Hsieh, E J; Letts, S A; Roberts, C C; Saculla, M

    1998-10-16

    The focus of recent efforts at LLNL has been to demonstrate that vapor deposition processing is a suitable technique to form polyimide fnms with sufficient strength for current national ignition facility target specifications. Production of polyimide films with controlled stoichiometry was acccomplished by: 1) depositing a novel co-functional monomer and 2) matching the vapor pressure of each monomer in PMDA/ODA co-depositions. The sublimation and deposition rate for the monomers was determined over a range of temperatures. Polyimide films with thicknesses up to 30 p.m were fabricated. Composition, structure and strength were assessed using FTIR, SEM and biaxial burst testing. The best films had a tensile strength of approximately 100 MPa. A qualitative relationship between the stoichiometry and tensile strength of the film was demonstrated. Thin films ({approximately}3.5 {micro}m) were typically smooth with an rms of 1.5 nm.

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

    PubMed Central

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

    1954-01-01

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

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

    ERIC Educational Resources Information Center

    LaGreca, Nancy

    2009-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Leimkuehler, Thomas O.

    2009-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

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

    SciTech Connect

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

    1993-04-01

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

  1. Enthalpie de sublimation du soufre α : mesure calorimétrique

    NASA Astrophysics Data System (ADS)

    Chastel, R.; Ezzine, M.

    1993-04-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-11-01

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

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

    PubMed Central

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

    2011-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

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

    PubMed

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

    2011-09-01

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

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

    SciTech Connect

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

    2013-10-01

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

  9. A transformer of closely spaced pulsed waveforms

    NASA Technical Reports Server (NTRS)

    Niedra, J.

    1970-01-01

    Passive circuit, using diodes, transistors, and magnetic cores, transforms the voltage of repetitive positive or negative pulses. It combines a pulse transformer with switching devices to effect a resonant flux reset and can transform various pulsed waveforms that have a nonzero average value and are relatively cosely spaced in time.

  10. Weathering and erosion of the polar layered deposits on Mars

    NASA Technical Reports Server (NTRS)

    Herkenhoff, K. E.

    1990-01-01

    The Martial polar layered deposits are widely believed to be composed of water ice and silicates, but the relative amount of each component is unknown. The conventional wisdom among Mars researchers is that the deposits were formed by periodic variations in the deposition of dust and ice caused by climate changes over the last 10 to 100 million years. It is assumed here that water ice is an important constituent of the layered deposits, that the deposits were formed by eolian processes, and that the origin and evolution of the north and south polar deposits were similar. Weathering of the layered deposits by sublimation of water ice can account for the geologic relationships in the polar regions. The nonvolatile components of the layered deposits appears to consist mainly of bright red dust, with small amounts of dark dust or sand. Dark dust, perhaps similar to the magnetic material found at the Viking Lander sites, may perferentially form filamentary residue particles upon weathering of the deposits. Once eroded, these particles may saltate to form the dark dunes found in both polar regions.

  11. Weathering and erosion of the polar layered deposits on Mars

    NASA Astrophysics Data System (ADS)

    Herkenhoff, K. E.

    The Martial polar layered deposits are widely believed to be composed of water ice and silicates, but the relative amount of each component is unknown. The conventional wisdom among Mars researchers is that the deposits were formed by periodic variations in the deposition of dust and ice caused by climate changes over the last 10 to 100 million years. It is assumed here that water ice is an important constituent of the layered deposits, that the deposits were formed by eolian processes, and that the origin and evolution of the north and south polar deposits were similar. Weathering of the layered deposits by sublimation of water ice can account for the geologic relationships in the polar regions. The nonvolatile components of the layered deposits appears to consist mainly of bright red dust, with small amounts of dark dust or sand. Dark dust, perhaps similar to the magnetic material found at the Viking Lander sites, may perferentially form filamentary residue particles upon weathering of the deposits. Once eroded, these particles may saltate to form the dark dunes found in both polar regions.

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

    NASA Astrophysics Data System (ADS)

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

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

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

    SciTech Connect

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

    2008-12-31

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

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

    SciTech Connect

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

    2005-07-01

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

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

    NASA Astrophysics Data System (ADS)

    Huang, Ning; Dai, Xiaoqing; Zhang, Jie

    2016-06-01

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

  1. Sublimation studies of NpO sub 2 F sub 2

    SciTech Connect

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

    1992-08-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

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

    NASA Astrophysics Data System (ADS)

    Uwaha, Makio; Saito, Yukio; Sato, Masahide

    1995-01-01

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

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

    PubMed Central

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

    2011-01-01

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

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

    PubMed

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

    2011-11-01

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

  6. Preservation of ancient ice at Pavonis and Arsia Mons: Tropical mountain glacier deposits on Mars

    NASA Astrophysics Data System (ADS)

    Head, James W.; Weiss, David K.

    2014-11-01

    Large tropical mountain glacier (TMG) deposits on the northwest flanks of the Tharsis Montes and Olympus Mons volcanoes are interpreted to be the record of ancient climates characteristic of Mars several hundred million years ago when planetary spin-axis obliquity was ~45°. During this era, polar volatiles (predominantly H2O) were mobilized and transferred equatorward, undergoing adiabatic cooling on the Tharsis volcano flanks, and precipitating snow and ice to form cold-based tropical mountain glaciers up to several kilometers in thickness. Subsequent climate change resulted in retreat, sublimation and collapse of the tropical mountain glaciers, leaving the three typical facies observed today: (1) concentric ridges, the ridged facies, interpreted as drop moraines; (2) knobby facies, interpreted as debris-dominated sublimation residue; and (3) the smooth facies, interpreted as remnant alpine glacial deposits. Ring-mold craters (RMCs) are distinctive features formed by impacts into debris-covered ice. We describe a set of relatively fresh ring-mold craters superposed on the Arsia and Pavonis Mons TMG deposits; we interpret these to indicate that the impact events penetrated a veneer of sublimation lag and excavated buried remnant glacial ice, despite the lack of detection of buried ice by orbital radar instruments. The diameter distribution of the RMCs suggest that the remnant ice lies at a depth of at least 16 m. The TMG deposit ages suggest that these ice deposits date from a period in the range of 125-220 million years before the present; the remnant ice may thus preserve records of the ancient atmospheric gas content and microbiota, as is common in terrestrial glacial ice. Preservation of this ice and the lack of any associated fluvial features suggest that the post-glacial climate has been cold, and related surface temperatures have not been sufficient to bring the buried deposits to the melting point of water.

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

    NASA Astrophysics Data System (ADS)

    Ganguly, Arnab

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

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

    SciTech Connect

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

    2015-08-01

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

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

    SciTech Connect

    Ruppel, F.R.

    1992-03-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

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

    PubMed

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

    2015-08-19

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

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  13. Architectural facies analysis of nonmarine depositional systems in upper Triassic Chinle Formation, southeastern Utah

    SciTech Connect

    Dubiel, R.F.

    1989-03-01

    The Upper Triassic Chinle Formation in southeastern Utah consists of nonmarine strata deposited in a back-arc cratonic basin. Architectural analysis of exposures in subparallel canyons reveals an intricately interbedded fluvial-deltaic-lacustrine system characterized by (1) mobile fluvial-channel belts consisting of stacked channel complexes; (2) overbank deposits of levees, paleosols, marshes, and small flood-plain lakes interfingered with crevasse splays and lacustrine deltas; and (3) extensive lacustrine strata deposited over the entire study area. Stratigraphic panels using closely spaced measured sections drawn either perpendicular or parallel to depositional dip show lateral facies relations within the extra-channel strata and the relations to channel complexes. Successions of panels through several canyons depict the three-dimensional architecture of the Chinle depositional system.

  14. Near-failure detonation behavior of vapor-deposited hexanitrostilbene (HNS) films

    NASA Astrophysics Data System (ADS)

    Knepper, Robert; Wixom, Ryan R.; Marquez, Michael P.; Tappan, Alexander S.

    2017-01-01

    Hexanitrostilbene (HNS) films were deposited onto polycarbonate substrates using vacuum thermal sublimation. The deposition conditions were varied in order to alter porosity in the films, and the resulting microstructures were quantified by analyzing ion-polished cross-sections using scanning electron microscopy. The effects of these changes in microstructure on detonation velocity and the critical thickness needed to sustain detonation were determined. The polycarbonate substrates also acted as recording plates for detonation experiments, and films near the critical thickness displayed distinct patterns in the dent tracks that indicate instabilities in the detonation front when approaching failure conditions.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  16. Advanced deposition model for thermal activated chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Cai, Dang

    reactions on the substrate surface, conductive, convective, inductive and radiative heat transfer, species transport and thereto-elastic stress distributions. Gas phase and surface reactions are studied thermodynamically and kinetically. Based on experimental results, detailed reaction mechanisms are proposed and the deposition rates are predicted. The deposition model proposed could be used for other experiments with similar operating conditions. Four different growth systems are presented in this thesis to discuss comprehensive transport phenomena in crystal growth from vapor. The first is the polysilicon bulk growth by modified Siemens technique in which a silicon tube is used as the starting material. The research effort has been focused on system design, geometric and operating parameters optimization, and heterogeneous and homogeneous silane pyrolysis analysis. The second is the GaN thin film growth by iodine vapor phase epitaxy technique. Heat and mass transport is studied analytically and numerically. Gas phase and surface reactions are analyzed thermodynamically and kinetically. Quasi-equilibrium and kinetic deposition models are developed to predict the growth rate. The third one is the AlN thin film growth by halide vapor phase epitaxy technique. The effects of gas phase and surface reactions on the crystal growth rate and deposition uniformity are studied. The last one is the AlN sublimation growth system. The research effort has been focused on the effect of thermal environment evolution on the crystal growth process. The thermoelastic stress formed in the as-grown AlN crystal is also calculated.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    Gullies on Mars are kilometre-scale landforms, comprising an erosional alcove and channel and a terminal debris apron/fan. These landforms are similar to features on Earth carved by the flow of liquid water, or by the action of water rich debris flows. The majority gullies on Mars are believed to be (at most) ˜5 Ma old and both erosion and deposition within these features have been observed within the last 10 years of orbital observations. At present liquid water is not thermodynamically stable at the martian surface and many of the recent changes in surface morphology occur during winter and early spring, when temperatures are too low for even metastable liquid water to be produced. Therefore, researchers have proposed an alternative mechanism for gully-formation - the sublimation of solid CO2, which is deposited on the maritan surface every winter. Previous studies have revealed that gully-density and orientation varies systematically with latitude - a fact that led to the development of many climate-based hypotheses for their formation. Here, we use the global database of martian gullies and extract the orientation and slope-angle of gully-hosting-slopes. We find that gully-orientation is more even strongly controlled by latitude than previous studies, where more sparse data were used. From ˜30-40° latitude in both hemispheres, gullies are almost never found on equator-facing slopes, and polewards of 40° gullies have a tendency to be located on equator-facing slopes. We use a 1D version of the LMD Mars climate model physics to simulate surface temperature on slopes up to 35° , oriented to face north or south, for all latitudes (5° spacing), and for orbital obliquities of 5-55° . We otherwise use current orbital conditions (ellipticity, date of perihelion) and we use a constant thermal inertia of the substrate of 1000 Jm-2K-1s-1/2and a bare soil albedo of 0.2. We extracted two pieces of information from a complete annual cycle: (i) The number of hours

  18. Depositional history of the Apollo 16 deep drill core

    NASA Technical Reports Server (NTRS)

    Gose, W. A.; Morris, R. V.

    1977-01-01

    Ferromagnetic resonance and magnetic hysteresis loop measurements were performed on 212 samples from the Apollo 16 deep drill core. The total iron content is generally uniform with a mean value of 5.7 plus or minus 0.9 wt%. The soils range in maturity from immature to mature. Two major contacts were observed. The contact at 13 cm depth represents a fossil surface whereas the contact at 190 cm depth has no time-stratigraphic significance. The data suggest that the core section below 13 cm depth was deposited in a single impact event and subjected to meteoritic gardening for about 450 m.y. However, our data do not preclude deposition by a series of closely spaced events. About 50 m.y. ago, the top 13 cm were added. Comparison with the Apollo 16 double drive tube 60009/60010 does not yield any evidence for a stratigraphic correlation with the deep drill core.

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

    NASA Astrophysics Data System (ADS)

    Ida, S.; Guillot, T.

    2016-11-01

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

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

    SciTech Connect

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

    2012-02-16

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

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

    SciTech Connect

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

    2015-02-10

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

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

    SciTech Connect

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

    2005-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Christner, Emanuel; Kohler, Martin; Schneider, Matthias

    2017-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Sekanina, Zdenek

    1991-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2000-04-01

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

  6. The Origin of the Terra Meridiani Sediments: Volatile Transport and the Formation of Sulfate Bearing Layered Deposits on Mars

    NASA Technical Reports Server (NTRS)

    Niles, P.B.

    2008-01-01

    The chemistry, sedimentology, and geology of the Meridiani sedimentary deposits are best explained by eolian reworking of the sublimation residue of a large scale ice/dust deposit. This large ice deposit was located in close proximity to Terra Meridiani and incorporated large amounts of dust, sand, and SO2 aerosols generated by impacts and volcanism during early martian history. Sulfate formation and chemical weathering of the initial igneous material is hypothesized to have occurred inside of the ice when the darker mineral grains were heated by solar radiant energy. This created conditions in which small films of liquid water were created in and around the mineral grains. This water dissolved the SO2 and reacted with the mineral grains forming an acidic environment under low water/rock conditions. Subsequent sublimation of this ice deposit left behind large amounts of weathered sublimation residue which became the source material for the eolian process that deposited the Terra Meridiani deposit. The following features of the Meridiani sediments are best explained by this model: The large scale of the deposit, its mineralogic similarity across large distances, the cation-conservative nature of the weathering processes, the presence of acidic groundwaters on a basaltic planet, the accumulation of a thick sedimentary sequence outside of a topographic basin, and the low water/rock ratio needed to explain the presence of very soluble minerals and elements in the deposit. Remote sensing studies have linked the Meridiani deposits to a number of other martian surface features through mineralogic similarities, geomorphic similarities, and regional associations. These include layered deposits in Arabia Terra, interior layered deposits in the Valles Marineris system, southern Elysium/Aeolis, Amazonis Planitia, and the Hellas basin, Aram Chaos, Aureum Chaos, and Ioni Chaos. The common properties shared by these deposits suggest that all of these deposits share a common

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

    NASA Astrophysics Data System (ADS)

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

    2003-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  9. Access to uncombined titanium through an inhibiting film in sublimation pumping of deuterium

    NASA Technical Reports Server (NTRS)

    Steinberg, R.; Alger, D. L.

    1972-01-01

    It was demonstrated, through a series of experiments, that it is possible (by the addition of a thin layer of titanium to an apparently occluded surface) to gain access to previously deposited sublayers of uncombined titanium in spite of the presence of an inhibiting film (such as an oxide) on the surface.

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

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

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

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

    NASA Astrophysics Data System (ADS)

    Cavosie, A. J.

    2011-12-01

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

  12. Growth of α-V2O5 nanostructured thin films as a function of deposition process

    NASA Astrophysics Data System (ADS)

    Singh, Megha; Sharma, Rabindar K.; Reddy, G. B.

    2016-05-01

    In this communication, we synthesizedvanadium pentoxide (α-V2O5) nanostructured thin films (NSTs) using four different methods for obtaining vanadate species namely thermal evaporation (source of vanadate species are V2O5 powder and vanadium metal foil) and plasma assisted sublimation process (source of vanadate species are V2O5 powder and vanadium metal foil). The effect of plasmaon morphological and structural propertieshave been systematicallystudied. XRD revealed thermal evaporation process yielded amorphous films whereassublimation process yielded highly crystalline α-V2O5 films. HRTEM of nanobelts show, the growth is preferred in (001) crystallographic direction with interplanar distance of 0.43 nm. XPS revealed O/V ratio of ~2.4, which nearly agrees with standard V2O5 stoichiometry. SEM revealed deposition process affect morphology of films; thermal evaporation results in smoother film while plasma assisted sublimation process reveals nanoflakes and nanobelts (NBs). All the results are inconcordance with each other.

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

    NASA Astrophysics Data System (ADS)

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

    2002-12-01

    In the sub-arctic region of Siberia, like the Lena and Bikal basins, the snow cover is a dominant hydrological component to affect the river discharge and regional water resource. Sublimation from snow surface, which can sustained about seven months (later October to earlier May), has been identified as important hydrological process in high altitude and latitude region, which, as result of particularly complex mass and energy exchanges, remain incompletely, understood, though there has been recent progress in process studies. A survey of snow sublimation values from North American and Russian mass balance studies (Mcnay et al., 1988; Barry, 1991;) suggests that in boreal, montane and subalpine forests 25-45 % of the annual snowfall can sublimate from snow (Pomeroy and Gray, 1995). This range has been confirmed for other snowy environments such as maritime Japan (Nakai et al., 1993). From March to May of 2002, intensive observations on snow sublimation using pan method and meteorological condition of near ground surface atmosphere were made in Mogot experimental watershed, which is located in the southern mountain region of eastern Siberia (55.5°N, 124.7°E) approximately 60 km north of Tynda, in the Amur region, Russia. The land surface is predominantly covered by larch forest, but birch forest partly covers the ridge area and higher elevations are covered by pine forest. The observations, including the snow and meteorological elements, were conducted at three sites with different vegetation cover and surface condition: A sparse larch forest covers Site LF; Site OP is grassland and Site ES contains a sparse larch forest of east slope. The transparent plastic pan used for sublimation measurement was in diameter of 22 cm and depth of 20 cm. A natural snow bulk of the same size and shape as the pan was set at the 1 cm higher level than surrounding snow surface. The snow bulk in the pan was renewed according its temperature difference with surrounding snow. But it

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

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  16. Chemical Vapor Deposition of Phosphorous- and Boron-Doped Graphene Using Phenyl-Containing Molecules.

    PubMed

    Mekan Ovezmyradov; Magedov, Igor V; Frolova, Liliya V; Chandler, Gary; Garcia, Jill; Bethke, Donald; Shaner, Eric A; Kalugin, Nikolai G

    2015-07-01

    Simultaneous chemical vapor deposition (CVD) of graphene and "in-situ" phosphorous or boron doping of graphene was accomplished using Triphenylphosphine (TPP) and 4-Methoxyphenylboronic acid (4-MPBA). The TPP and 4-MPBA molecules were sublimated and supplied along with CH4 molecules during graphene growth at atmospheric pressure. The grown graphene samples were characterized using Raman spectroscopy. Phosphorous and boron presence in phosphorous and boron doped graphene was confirmed with Auger electron spectroscopy. The possibility of obtaining phosphorous and boron doped graphene using solid-source molecule precursors via CVD can lead to an easy and rapid production of modified large area graphene.

  17. Metal delocalization and surface decoration in direct-write nanolithography by electron beam induced deposition

    NASA Astrophysics Data System (ADS)

    Gopal, Vidyut; Stach, Eric A.; Radmilovic, Velimir R.; Mowat, Ian A.

    2004-07-01

    The ability to interconnect different nanostructures is crucial to nanocircuit fabrication efforts. A simple and versatile direct-write nanolithography technique for the fabrication of interconnects is presented. Decomposition of a metalorganic precursor gas by a focused electron beam resulted in the deposition of conductive platinum nanowires. The combination of in situ secondary electron imaging with deposition allows for the simultaneous identification and interconnection of nanoscale components. However, the deposition was not entirely localized to the electron beam raster area, as shown by secondary ion mass spectrometry measurements. The electrical impact of the metallic spread was quantified by measuring the leakage current between closely spaced wires. The origins of the spread and strategies for minimizing it are discussed. These results indicate that, while this direct-write methodology is a convenient one for rapid prototyping of nanocircuits, caution must be used to avoid unwanted decoration of nanostructures by metallic species.

  18. Metal delocalization and surface decoration in direct-write nanolithography by electron beam induced deposition

    SciTech Connect

    Gopal, Vidyut; Stach, Eric A.; Radmilovic, Velimir R.; Mowat, Ian A.

    2004-07-05

    The ability to interconnect different nanostructures is crucial to nanocircuit fabrication efforts. A simple and versatile direct-write nanolithography technique for the fabrication of interconnects is presented. Decomposition of a metalorganic precursor gas by a focused electron beam resulted in the deposition of conductive platinum nanowires. The combination of in situ secondary electron imaging with deposition allows for the simultaneous identification and interconnection of nanoscale components. However, the deposition was not entirely localized to the electron beam raster area, as shown by secondary ion mass spectrometry measurements. The electrical impact of the metallic spread was quantified by measuring the leakage current between closely spaced wires. The origins of the spread and strategies for minimizing it are discussed. These results indicate that, while this direct-write methodology is a convenient one for rapid prototyping of nanocircuits, caution must be used to avoid unwanted decoration of nanostructures by metallic species.

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

    NASA Astrophysics Data System (ADS)

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

    2006-04-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

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

    NASA Astrophysics Data System (ADS)

    Geiser, Jürgen; Klein, Olaf; Philip, Peter

    2007-05-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

  3. Effective role of deposition duration on the growth of V2O5 nanostructured thin films

    NASA Astrophysics Data System (ADS)

    Sharma, Rabindar Kumar; Saini, Sujit Kumar; Singh, Megha; Reddy, G. B.

    2016-05-01

    In this report, vanadium pentoxide nanostructured thin films (NSTs) with nanoplates (NPs) have synthesized on Ni coated glass substrate employing plasma assisted sublimation process (PASP), as a function of deposition/growth durations. The effect of deposition durations on the morphological, structural, vibrational, and compositional properties have been investigated one by one. The structural and vibrational studies endorsed that the grown NPs have only orthorhombic phase, no other sub oxide phases are recorded in the limit of resolution. The morphological results of all samples using SEM, revealed that the features, coverage density, and alignments of NPs are greatly controlled by deposition duration and the best sample is obtained for 25 min (S2). Further, the more insight information is accomplished by HRTEM/SAED on the best featured sample, which confirmed the single crystalline nature of NPs. The XPS result again confirmed the compositional purity and the nearly stoichiometric nature of NPs.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

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

  6. Mass Wasting and Ground Collapse in Terrains of Volatile-Rich Deposits as a Solar System-Wide Geological Process: The Pre-Galileo View

    NASA Technical Reports Server (NTRS)

    Moore, Jeffrey M.; Mellon, Michael T.; Zent, Aaron P.

    1996-01-01

    The polar terrains of Mars are covered in many places with irregular pits and retreating scarps, as are some of the surfaces of the outer-planet satellites. These features are interpreted by us as diagnostic of exogenic degradation due to the loss of a volatile rock-forming matrix or cement. In this study we propose that sublimation degradation is a plausible Solar Systemwide geological process. Candidate examples have been identified on Mars, Io, and Triton, and possibly Europa and Ganymede. We envision this process as having two end-member expressions (pits and scarps), for which we hypothesize two end-member mechanisms (massive localized lenses and areally extensive basal layers). In this study we focus on the role this process may play on the surfaces of the galilean satellites. Our principle modeling results are that for these satellites, H2S, CO2, and NH3 are the only viable candidate volatiles for sublimation degradation of landforms, in light of galilean satellite cosmochemistry. For Io's polar regions only H2S, and then only from slopes that face the Sun and have thin lags, is volatile enough to cause the observed sublimation-induced erosion at those latitudes. SO2 is not a viable candidate as an agent of erosion, especially for these polar landforms. In the case of Europa, only CO2 and H2S are viable candidates (given surface age constraints). Both species could be efficient eroders in nonpolar regions. H2S could generate erosion within the polar regions if the deposition and erosion conditions were essentially identical as those we invoked for Io's polar regions. For Ganymede (and Callisto) NH3 might be an agent of erosion in equatorial terrains of great age. The sublimation of CO2 and H2S is much more robust than NH3. The much slower rate of sublimation degradation from NH3 might be detectable by Galileo and used as a compositional indicator.

  7. Impact of In doping on GeTe phase-change materials thin films obtained by means of an innovative plasma enhanced metalorganic chemical vapor deposition process

    NASA Astrophysics Data System (ADS)

    Szkutnik, P. D.; Aoukar, M.; Todorova, V.; Angélidès, L.; Pelissier, B.; Jourde, D.; Michallon, P.; Vallée, C.; Noé, P.

    2017-03-01

    We investigated the deposition and the phase-change properties of In-doped GeTe thin films obtained by plasma enhanced metalorganic chemical vapor deposition and doped with indium using a solid delivery system. The sublimated indium precursor flow rate was calculated as a function of sublimation and deposition parameters. Indium related optical emission recorded by means of optical emission spectroscopy during deposition plasma allowed proposing the dissociation mechanisms of the [In(CH3)2N(CH3)2]2 solid precursor. In particular, using an Ar + H2 + NH3 deposition plasma, sublimated indium molecules are completely dissociated and do not induce by-product contamination by addition of nitrogen or carbon in the films. X-ray photoelectron spectroscopy evidences the formation of In-Te bonds in amorphous as-deposited In-doped GeTe films. The formation of an InTe phase after 400 °C annealing is also evidenced by means of X-ray diffraction analysis. The crystallization temperature Tx, deduced from monitoring of optical reflectivity of In-doped GeTe films with doping up to 11 at. % slightly varies as a function of the In dopant level with a decrease of Tx down to a minimum value for an In doping level of about 6-8 at. %. In this In doping range, the structure of crystallized In-GeTe films changes and is dominated by the presence of a crystalline In2Te3 phase. Finally, the Kissinger activation energy for crystallization Ea is showing to monotonically decrease as the indium content in the GeTe film is increased indicating a promising effect of In doping on crystallization speed in memory devices while keeping a good thermal stability for data retention.

  8. Homoepitaxial seeding and growth of bulk AlN by sublimation

    NASA Astrophysics Data System (ADS)

    Hartmann, Carsten; Wollweber, Jürgen; Seitz, Christoph; Albrecht, Martin; Fornari, Roberto

    2008-03-01

    AlN boules, 35 mm in diameter and up to 25-mm long, were grown on TaC crucible lid in an inductively heated reactor. The growth rates range between 100 and 300 μm/h. The boules grown on TaC show a columnar structure mostly composed of <0 0 0 1> grains. The largest grains (4-5 mm in diameter) were sliced and used for subsequent growth runs. Successful epitaxial seeding and growth on the starting AlN wafer was demonstrated and confirmed by electron back-scatter diffraction (EBSD) measurements. Crystals were grown on both Al and N surfaces of the seeds up to a maximum diameter of about 9 mm so far. Formation of oxy-nitride layers, very detrimental to the further AlN deposition, could be avoided when starting from pre-sintered source powder. Secondary ion mass spectroscopy (SIMS) measurements on axial cuts revealed a relatively low oxygen content, with variable distribution along the growth direction (290 ppm near seed, 100 ppm near external surface).

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

    NASA Astrophysics Data System (ADS)

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

    2011-02-01

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

  10. Deposition head for laser

    DOEpatents

    Lewis, Gary K.; Less, Richard M.

    1999-01-01

    A deposition head for use as a part of apparatus for forming articles from materials in particulate form in which the materials are melted by a laser beam and deposited at points along a tool path to form an article of the desired shape and dimensions. The deposition head delivers the laser beam and powder to a deposition zone, which is formed at the tip of the deposition head. A controller comprised of a digital computer directs movement of the deposition zone along the tool path and provides control signals to adjust apparatus functions, such as the speed at which the deposition head moves along the tool path.

  11. Evaluation of the Corrosivity of Dust Deposited on Waste Packages at Yucca Mountain, Nevada

    SciTech Connect

    C. Bryan; R. Jarek; T. Wolery; D. Shields; M. Sutton; E. Hardin; D. Barr

    2005-03-18

    Small amounts of dust will be deposited on the surfaces of waste packages in drifts at Yucca Mountain during the operational and the preclosure ventilation periods. Salts present in the dust will deliquesce as the waste packages cool and relative humidity in the drifts increases. In this paper, we evaluate the potential for brines formed by dust deliquescence to initiate and sustain localized corrosion that results in failure of the waste package outer barrier and early failure of the waste package. These arguments have been used to show that dust deliquescence-induced localized or crevice corrosion of the waste package outer barrier (Alloy 22) is of low consequence with respect to repository performance. Measured atmospheric and underground dust compositions are the basis of thermodynamic modeling and experimental studies to evaluate the likelihood of brine formation and persistence, the volume of brines that may form, and the relative corrosivity of the initial deliquescent brines and of brines modified by processes on the waste package surface. In addition, we evaluate several mechanisms that could inhibit or stifle localized corrosion should it initiate. The dust compositions considered include both tunnel dust samples from Yucca Mountain, National Airfall Deposition Program rainout data, and collected windblown dust samples. Also considered is sublimation of ammonium salts, a process that could affect dust composition prior to deliquescence. Ammonium chlorides, nitrates, and even sulfates sublimate readily into ammonia and acid gases, and will be lost from the surface of the waste package prior to deliquescence.

  12. Electric-field-ratio profiling at the Silsilah tin-bearing greisen deposit, Kingdom of Saudi Arabia

    USGS Publications Warehouse

    Kamilli, R.J.; Zablocki, C.J.

    1993-01-01

    Buried, possibly mineralized granite cupolas at the Silsilah tin deposit in Saudi Arabia have been successfully located using a closely spaced electric-field-ratio profiling technique. In this study electrical fields at 27 and 270 Hz across grounded electrodes spaced 50m apart were measured along six traverses. The technique allowed the authors to identify and distinguish among unroofed granite cupolas, cupolas with their aplite-pegmatite apical contact zones intact, strong and weak greisens, dikes, faults, and pervasively argillized rocks. -from Authors

  13. Novel interconnect deposition technology

    NASA Astrophysics Data System (ADS)

    Speckman, D. M.; Wendt, J. P.

    1991-12-01

    A new series of experiments was initiated to improve current interconnect deposition technology for integrated circuits. Preliminary aluminum deposition experiments were carried out using trimethylamine(alane) as the precursor, and some mildly reflective, uniform aluminum films were successfully deposited on glass slides, suggesting that chemical vapor deposition (CVD) will be a practicable deposition technique for advanced integrated circuit interconnect films. CVD studies of aluminum and zirconium- and hafnium-diboride thin films are continuing.

  14. Deposit model for volcanogenic uranium deposits

    USGS Publications Warehouse

    Breit, George N.; Hall, Susan M.

    2011-01-01

    The International Atomic Energy Agency's tabulation of volcanogenic uranium deposits lists 100 deposits in 20 countries, with major deposits in Russia, Mongolia, and China. Collectively these deposits are estimated to contain uranium resources of approximately 500,000 tons of uranium, which amounts to 6 percent of the known global resources. Prior to the 1990s, these deposits were considered to be small (less than 10,000 tons of uranium) with relatively low to moderate grades (0.05 to 0.2 weight percent of uranium). Recent availability of information on volcanogenic uranium deposits in Asia highlighted the large resource potential of this deposit type. For example, the Streltsovskoye district in eastern Russia produced more than 100,000 tons of uranium as of 2005; with equivalent resources remaining. Known volcanogenic uranium deposits within the United States are located in Idaho, Nevada, Oregon, and Utah. These deposits produced an estimated total of 800 tons of uranium during mining from the 1950s through the 1970s and have known resources of 30,000 tons of uranium. The most recent estimate of speculative resources proposed an endowment of 200,000 tons of uranium.

  15. Fundamental investigations of CdTe deposited by MBE for applications in thin-film solar photovoltaics

    NASA Astrophysics Data System (ADS)

    Colegrove, Eric

    Model CdTe systems --both single-crystalline (sx) and poly-crystalline (px) --are investigated experimentally as a means to understand the role of competing material properties and processing steps in improving the performance of standard thin-film solar cells. Previous device optimization work is reviewed explaining the close space sublimation growth technique and ongoing analysis using scanning transmission electron microscopy. This is followed by motivation for molecular beam epitaxy (MBE) growth studies of CdTe and the results of fundamental material investigations. The results show that (a) the minority carrier lifetimes in hetero-epitaxial layers is limited by surface recombination, (b) source selection and anneals can be tuned to achieve p-type carrier density of 6x1015 cm-3, and (c) counter-intuitively, the increase in p-density is associated with increased mobility in lower crystal quality samples, suggesting the role of anneal. Finally, controlled and re-growth of px-CdTe by MBE studies are discussed with results indicating that shorter lifetimes are directly correlated with the increased surface/interface density.

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

    NASA Technical Reports Server (NTRS)

    Sibille, Laurent; Mantovani, James G.

    2011-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Nash, D. B.

    1987-01-01

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

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

    USGS Publications Warehouse

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

    2006-01-01

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

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

    PubMed

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

    2006-08-17

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

  20. Stratigraphy and evolution of the buried CO2 deposit in the Martian south polar cap

    NASA Astrophysics Data System (ADS)

    Bierson, C. J.; Phillips, R. J.; Smith, I. B.; Wood, S. E.; Putzig, N. E.; Nunes, D.; Byrne, S.

    2016-05-01

    Observations by the Shallow Radar instrument on Mars Reconnaissance Orbiter reveal several deposits of buried CO2 ice within the south polar layered deposits. Here we present mapping that demonstrates this unit is 18% larger than previously estimated, containing enough mass to double the atmospheric pressure on Mars if sublimated. We find three distinct subunits of CO2 ice, each capped by a thin (10-60 m) bounding layer (BL). Multiple lines of evidence suggest that each BL is dominated by water ice. We model the history of CO2 accumulation at the poles based on obliquity and insolation variability during the last 1 Myr assuming a total mass budget consisting of the current atmosphere and the sequestered ice. Our model predicts that CO2 ice has accumulated over large areas several times during that period, in agreement with the radar findings of multiple periods of accumulation.

  1. Remnant buried ice in the equatorial regions of Mars: Morphological indicators associated with the Arsia Mons tropical mountain glacier deposits

    NASA Astrophysics Data System (ADS)

    Scanlon, Kathleen E.; Head, James W.; Marchant, David R.

    2015-06-01

    The fan-shaped deposit (FSD) on the western and northwestern flanks of Arsia Mons is the remnant of tropical mountain glaciers, deposited several tens to hundreds of millions of years ago during periods of high spin-axis obliquity. Previous workers have argued that the Smooth Facies in the FSD contains a core of ancient glacial ice. Here, we find evidence that additional glacial ice remains preserved within several other landforms in the Smooth Facies and Ridged Facies. These include landforms that we interpret as kame and kettle topography on the basis of their distribution, size, and morphologies ranging progressively from knobs to degraded knobs to pits. We argue that some moraines in the Ridged Facies are ice-cored on the basis of their interactions with lava flows and the axial troughs at the crests of some moraines. We also argue that dunes with axial troughs, found in and surrounding the FSD, are the remnants of sediment-covered snow dunes formed by reworking of snow or glacial ice, and that the axial troughs form as tension cracks in the sediment and deepen by sublimation of the underlying ice. Long-term preservation of water ice in equatorial environments is assisted by a meters- to decameters-thick debris cover (lag) formed from sublimation of dirty ice, as well as burial beneath volcanic tephra and aeolian deposits. This ancient ice could contain preserved biosignatures, provide information on Martian climate and atmospheric history, and serve as a resource for human exploration.

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

    NASA Astrophysics Data System (ADS)

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

    2009-09-01

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

  3. Dark material in the polar layered deposits and dunes on Mars

    USGS Publications Warehouse

    Herkenhoff, K. E.; Vasavada, A.R.

    1999-01-01

    Viking infrared thermal mapping and bistatic radar data suggest that the bulk density of the north polar erg material is much lower than that of the average Martian surface or of dark dunes at lower latitudes. We have derived a thermal inertia of 245-280 J m-2 s-1/2 K-1 (5.9-6.7 ?? 10-3 cal cm-2 s-1/2 K-1) for the Proctor dune field and 25-150 J m-2 s-1/2 K-1 (0.6-3.6 ?? 10-3 cal cm-2 s-1/2 K-1) for the north polar erg. The uniqueness of the thermophysical properties of the north polar erg material may be due to a unique polar process that has created them. The visible and near-infrared spectral reflectance of the erg suggests that the dark material may be composed of basalt or ferrous clays. These data are consistent with the dark material being composed of basaltic ash or filamentary sublimate residue (FSR) particles derived from erosion of the layered deposits. Dark dust may be preferentially concentrated at the surface of the layered deposits by the formation of FSR particles upon sublimation of water ice. Further weathering and erosion of these areas of exposed layered deposits may form the dark, saltating material that is found in both polar regions. Dark FSR particles may saltate for great distances before eventually breaking down into dust grains, re-mixing with the global dust reservoir, and being recycled into the polar layered deposits via atmospheric suspension. Copyright 1999 by the American Geophysical Union.

  4. Search for Climatic Signal in Pavonis Mons Fan Deposits, Mars

    NASA Astrophysics Data System (ADS)

    Foing, B. H.; Orsi, A.; Cord, A.; Rossi, A.

    2007-08-01

    Introduction: Mars has experienced large variations in its orbital parameters throughout its history. They are calculable for the last 10 million years, with periodicity of 120 000 years for its obliquity, 95 to 100 000 years for its excentricity, and 51 000 years for its precession, however they become undetermined beyond 20 Myr [1]. Laskar et al [2] define a standard model of Mars' insolation parameters over 4 Gyr with the most probable values 0.068 for the eccentricity and 41.80 degree for the obliquity. Climatic consequences: At high obliquity, significant amount of ice can be deposited as ice at low latitudes. General circulation models predict an annual net accumulation rate of ice on the west of Tharsis volcanoes. Pavonis fan shaped deposits: We analysed Mars Express images obtained over orbit 946, of the west fan deposit at Pavonis Mons. The analysis of the HRSC images shows around 15 ridges, with interval 0.5 - 4.5 km. The interaction with the underlying surface can be seen, indicating the overlap of different episodes. The ridges are interpreted as drop debris on the front edge of a cold glaciar during its slow retreat. On the other hand isotropic knobbies , circular sub-km-scale hills are interpreted as results of fast glaciar sublimation. By texture analysis we could distinguish ridges, knobbies from various episodes and relate them with geological studies [3]. Glaciar model: For this basic study, we choose the simplest model of glacier. The bed is believed to be horizontal, and does not interfere with the glacier. If the ridges are due to obliquity oscillation, the rate of snow fall and sublimation must depend slightly on obliquity. Indeed, with accumulation rates and ablation rates at the same order, we are able to find oscillation of the glacier extent. We can see oscillations of the glacier extent from the beginning. It is interesting to notice that this shape is consistent with the observation of older outer sets of ridges, and young inner ones

  5. Metallogeny of epithermal gold deposits in the western US Cordillera

    SciTech Connect

    Duke, N.A.

    1985-01-01

    The mid-Tertiary sediment-, volcanic-, and detachment fault-hosted epithermal gold deposits (EGDs) of the western US Cordillera favor the outboard side of the tectonically thickened miogeoanticlines. Post Mesozoic accretion, this cratonic shelf-oceanic basin transition zone underwent a period of extensional uplift that thinned the brittle upper crust through listric-normal and detachment faulting, and the decoupled metamorphic infrastructure by ductile necking. The EDGs formed in the upper crust peripheral to tectonically exposed metamorphic core complexes synchronously with active extension. They demonstrate close space/time relationships to the centers of ash flow tuff eruptions that characterized this period. In general the metal concentrated in EDGs had a common source and transport mechanism. The fact that major EGDs occur along obducted oceanic thrust plates indicates that the gold was originally scavaged from oceanic successions during dewatering along the thrust structures. The metal was again mobilized in meteoric dominated hot spring systems operating within volcani-tectonic sinks occurring at ignimbrite eruptive centers. As a result, the siting of both sediment- and volcanic-hosted EGDs is controlled largely by proximity to the mid-Tertiary paleosurface. Specific controls for the precipitation of gold varies with deposit type but critical behavior of the ore-bearing fluid and/or redox reactions between migrating fluids and reduced lithology crosscut by permeable structures are primary.

  6. Biomimetic thin film deposition

    NASA Astrophysics Data System (ADS)

    Rieke, P. C.; Campbell, A. A.; Tarasevich, B. J.; Fryxell, G. E.; Bentjen, S. B.

    1991-04-01

    Surfaces derivatized with organic functional groups were used to promote the deposition of thin films of inorganic minerals. These derivatized surfaces were designed to mimic the nucleation proteins that control mineral deposition during formation of bone, shell, and other hard tissues in living organisms. By the use of derivatized substrates control was obtained over the phase of mineral deposited, the orientation of the crystal lattice and the location of deposition. These features are of considerable importance in many technically important thin films, coatings, and composite materials. Methods of derivatizing surfaces are considered and examples of controlled mineral deposition are presented.

  7. Dry deposition velocities

    SciTech Connect

    Sehmel, G.A.

    1984-03-01

    Dry deposition velocities are very difficult to predict accurately. In this article, reported values of dry deposition velocities are summarized. This summary includes values from the literature on field measurements of gas and particle dry deposition velocities, and the uncertainties inherent in extrapolating field results to predict dry deposition velocities are discussed. A new method is described for predicting dry deposition velocity using a least-squares correlation of surface mass transfer resistances evaluated in wind tunnel experiments. 14 references, 4 figures, 1 table.

  8. Modeling the Stability of the Large CO2 Deposits on Mars South Polar Cap

    NASA Astrophysics Data System (ADS)

    Thomason, C.; Phillips, R. J.; Mellon, M. T.

    2013-12-01

    The Mars Reconnaissance Orbiter's Shallow Radar instrument (SHARAD) revealed that the geologic unit AA3 (Tanaka et al. 2007) in Mars' South Polar Layered Deposits is composed of CO2 ice (Phillips et al. 2011). This deposit is estimated to contain ~10,000 km3 of CO2 ice, making its stability an important consideration in understanding recent climate change, as the deposit mass approaches that of the present atmosphere. Such a large mass would likely be deposited during a period of low obliquity, however different values for the emissivity and albedo of the CO2 frost can dramatically change age estimates (Armstrong et al. 2004). Previous models have focused on the stability of the South Pole Residual Cap (SPRC) where the CO2 ice is exposed to the atmosphere. AA3 however, is largely covered by the SPRC and other thinner deposits. In this research we evaluate the age and long-term stability of the AA3 deposit using standard thermal and sublimation modeling techniques. Our model incorporates diurnal and annual thermal variations that are allowed to propagate into the subsurface. In order to address the effect of the overlying layers on AA3 we take account for both surface and subsurface sublimation. Any gas produced in the subsurface is then allowed to diffuse through the overlying material. Results are compared to a variety of spacecraft observations including visible imagery and thermal measurements. Additionally, these results should help guide interpretation of SHARAD data in the AA3 region and point to locales for new observations. References: Tanaka et al. 2007, 'Recent advances in the stratigraphy of the polar regions of Mars.' Paper presented at the Seventh International Conference on Mars, Pasadena, CA, 9 to 13 July 2007, 3276. Phillips et al. 2011, Massive CO2 Ice Deposits Sequestered in the South Polar Layered Deposits of Mars, Science 332: 838-841. Armstrong et al. 2004, A 1 Gyr climate model for Mars: new orbital statistics and the importance of seasonally

  9. Small-scale slump deposits, Middle Atlantic Continental Slope, off eastern United States

    USGS Publications Warehouse

    Knebes, H.J.; Carson, Bobb

    1979-01-01

    Analyses of 24 high-resolution seismic-reflection profiles that were collected during local and regional surveys show that small-scale slump deposite are ubiquitous whthin the intercanyon areas of the Continental Slope of the Middle Atlantic Bight. The deposits involve the upper 10-90 m of sediments, extend downslops for 1.8-7.2 km, and are present at water depths ranging from 545 to 1500 m. The characteristics of the deposits vary from thin, homogeneous or fairly regularly bedded lenses of sediment, to masses of intermediate thickness with contorted bedding, to relatively large slump blocks. A detailed survey of one slump mass just south of Hudson Canyon (by means of close-spaced Minisparker profiles and sediment cores) showed that it had a thickness of about 30 m and a volume of at least 0.4 km3 and consisted of homogeneous clay which accumulated rapidly during the late Pleistocene or Holocene. Although some of the slump deposits undoubtedly are relict, stemming from sediment instability porduced by rapid deposition during Pleistocene sea-level regressions, others were formed relatively recently. Possible causes of modern slumps include gas generation in the sediments, bottom-water turbulence on the upper slope, and shallow faulting. This study indicates that small-scale slumping in the intercanyon areas may be an important process in transporting sediments to the deep sea and suggests that recent mass movements may constitute a geologic hazard to future economic development of this part of the Continental Slope. ?? 1979.

  10. 78 FR 56583 - Deposit Insurance Regulations; Definition of Insured Deposit

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-13

    ... Part 330 RIN 3064-AE00 Deposit Insurance Regulations; Definition of Insured Deposit AGENCY: Federal...)(1), 12 U.S.C. 1821(f)(1). A. Definition of ``Deposit'' The term ``deposit'' is defined in section 3... between domestic and foreign deposits. The current statutory definition of ``deposit'' under section...

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

    SciTech Connect

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

    2015-10-20

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

  13. Airfoil deposition model

    NASA Technical Reports Server (NTRS)

    Kohl, F. J.

    1982-01-01

    The methodology to predict deposit evolution (deposition rate and subsequent flow of liquid deposits) as a function of fuel and air impurity content and relevant aerodynamic parameters for turbine airfoils is developed in this research. The spectrum of deposition conditions encountered in gas turbine operations includes the mechanisms of vapor deposition, small particle deposition with thermophoresis, and larger particle deposition with inertial effects. The focus is on using a simplified version of the comprehensive multicomponent vapor diffusion formalism to make deposition predictions for: (1) simple geometry collectors; and (2) gas turbine blade shapes, including both developing laminar and turbulent boundary layers. For the gas turbine blade the insights developed in previous programs are being combined with heat and mass transfer coefficient calculations using the STAN 5 boundary layer code to predict vapor deposition rates and corresponding liquid layer thicknesses on turbine blades. A computer program is being written which utilizes the local values of the calculated deposition rate and skin friction to calculate the increment in liquid condensate layer growth along a collector surface.

  14. The polar layered deposits on Mars: Inference from thermal inertia modeling and geologic studies

    NASA Technical Reports Server (NTRS)

    Herkenhoff, K. E.

    1992-01-01

    It is widely believed that the Martian polar layered deposits record climate variations over at least the last 10 to 100 m.y., but the details of the processes involved and their relative roles in layer formation and evolution remain obscure. Weathering of the Martian layered deposits by sublimation of water ice can account for the thermal inertias, water vapor abundances, and geologic relationships observed in the Martian polar regions. The nonvolatile components of the layered deposits appears to consist mainly of bright red dust, with small amounts of dark dust. Dark dust, perhaps similar to the magnetic material found at the Viking Lander sites, may preferentially form filamentary residue particles upon weathering of the deposits. Once eroded, these particles may saltate to form the dark dunes found in both polar regions. This scenario for the origin and evolution of the dark material within the polar layered deposits is consistent with the available imaging and thermal data. Further experimental measurements of the thermophysical properties of magnetite and maghemite under Martian conditions are needed to better test this hypothesis.

  15. Seasonal Changes in the Thickness of Martian Polar Crater Deposits From the Mars Orbiter Laser Altimeter

    NASA Astrophysics Data System (ADS)

    Schmerr, N. C.; Garvin, J. B.; Neumann, G. A.; Sakimoto, S. E.

    2001-12-01

    This study uses near-repeat topographic profiles and gridded data from the Mars Orbiter Laser Altimeter to investigate temporal changes in several ice-filled craters in the North Polar Region of Mars. The craters we investigated are Korolev (73° N, 163° E), "Sasquatch" (77° N, 89° E) and "Frosty" (77° N, 215° E) [Garvin et. al., 2000, Icarus, 144, 329-352]. Profiles are corrected using crossovers that are not affected by seasonal changes. We find that spatially matched but temporally separated MOLA profiles of the central ice deposits within these craters show vertical variation on the order of 1-5 meters. This change in topography temporally correlates to the seasonal deposition and sublimation of frost in the North Polar Region of Mars [Zuber et al., this session] but is locally greater in magnitude. The change is also localized to the south-facing slopes of the ice deposits within the craters. This suggests that up to 5 m of carbon dioxide frost deposition and ablation may be taking place on the south-facing slopes of these craters each Martian year. This rapid change in ice deposit thickness provides a mechanism for geologically swift modification of the polar-layered terrains.

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

    NASA Astrophysics Data System (ADS)

    Metts, Jonathan G.; Klaus, David M.

    2012-01-01

    Thermal control of a space suit during extravehicular activity (EVA) is typically accomplished by sublimating water to provide system cooling. Spacecraft, on the other hand, primarily rely on radiators to dissipate heat. Integrating a radiator into a space suit has been proposed as an alternative design that does not require mass consumption for heat transfer. While providing cooling without water loss offers potential benefits for EVA application, it is not currently practical to rely on a directional, fixed-emissivity radiator to maintain thermal equilibrium of a spacesuit where the radiator orientation, environmental temperature, and crew member metabolic heat load fluctuate unpredictably. One approach that might make this feasible, however, is the use of electrochromic devices that are capable of infrared emissivity modulation and can be actively controlled across the entire suit surface to regulate net heat flux for the system. Integrating these devices onto the irregular, compliant space suit material requires that they be fabricated on a flexible substrate, such as Kapton film. An initial assessment of whether or not this candidate technology presents a feasible design option was conducted by first characterizing the mass of water loss from sublimation that could theoretically be saved if an electrochromic suit radiator was employed for thermal control. This is particularly important for lunar surface exploration, where the expense of transporting water from Earth is excessive, but the technology is potentially beneficial for other space missions as well. In order to define a baseline for this analysis by comparison to actual data, historical documents from the Apollo missions were mined for comprehensive, detailed metabolic data from each lunar surface outing, and related data from NASA's more recent "Advanced Lunar Walkback" tests were also analyzed. This metabolic database was then used to validate estimates for sublimator water consumption during surface

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

    PubMed

    Dorofeeva, Olga V; Ryzhova, Oxana N

    2014-05-15

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

  18. VTOL in-ground effect flows for closely spaced jets

    NASA Technical Reports Server (NTRS)

    Siclari, M. J.; Hill, W. G., Jr.; Jenkins, R. C.; Migdal, D.

    1980-01-01

    The interaction of two vertically impinging incompressible jets is studied through the invention of physical flow models that approximate the behavior of colliding wall jets as the incident jets are brought closer together. The mechanism for upwash formation is studied and momentum models for the upwash sheet are postulated. An approximate method for computing the ground isobar pattern of jet and upwash deflection zones is presented and compared with test data. A method for computing the upwash impingement force in the absence of secondary induced flow effects is also presented and reasonably good agreement is achieved with experimental data for cylindrical fuselage shapes of circular and rectangular cross section.

  19. Noncontact Friction and Force Fluctuations between Closely Spaced Bodies

    SciTech Connect

    Stipe, B. C.; Mamin, H. J.; Stowe, T. D.; Kenny, T. W.; Rugar, D.

    2001-08-27

    Noncontact friction between a Au(111) surface and an ultrasensitive gold-coated cantilever was measured as a function of tip-sample spacing, temperature, and bias voltage using observations of cantilever damping and Brownian motion. The importance of the inhomogeneous contact potential is discussed and comparison is made to measurements over dielectric surfaces. Using the fluctuation-dissipation theorem, the force fluctuations are interpreted in terms of near-surface fluctuating electric fields interacting with static surface charge.

  20. TACSAT-2: Pathfinder for a Close Space Support Asset

    DTIC Science & Technology

    2008-08-01

    two in-house Exercises, Lost Kitten / Cat Nab, a Joint US/UK/Canadian Exercise. The benefit of these events is that they were specifically designed...was proven. o Creating a direct access to spacecraft via UHF or secure World Wide Web. 3.3. Lost Kitten / Cat Nab Lost Kitten and Cat Nab...had recently participated in combat operations and assessed to be “realistic”. In a fictional scenario for part one (Lost Kitten ), a CIA Agent

  1. Legislative Environmental Impact Statement. M-X Closely Spaced Basing

    DTIC Science & Technology

    1982-10-18

    near Roswell, New Mexico, Amarilio/ Dalhart , Texas , and in central Nevada. If M-X were to be deployed in these areas, a new main operating base would...University, Tempe Years of Experience: 25 25043 5-40 Stephen C. Helfert, Wildlife Biologist B.A., 1976, Fish and Wildlife Biology, Texas A&M University...M.S., 1978, Biology, University of Texas at El Paso Years of Experience: 6 Ching-San Huang, E.E., P.E. B.S., 1966, Civil Engineering, Cheng-Kung

  2. Ionized cluster beam deposition

    NASA Technical Reports Server (NTRS)

    Kirkpatrick, A. R.

    1983-01-01

    Ionized Cluster Beam (ICB) deposition, a new technique originated by Takagi of Kyoto University in Japan, offers a number of unique capabilities for thin film metallization as well as for deposition of active semiconductor materials. ICB allows average energy per deposited atom to be controlled and involves impact kinetics which result in high diffusion energies of atoms on the growth surface. To a greater degree than in other techniques, ICB involves quantitative process parameters which can be utilized to strongly control the characteristics of films being deposited. In the ICB deposition process, material to be deposited is vaporized into a vacuum chamber from a confinement crucible at high temperature. Crucible nozzle configuration and operating temperature are such that emerging vapor undergoes supercondensation following adiabatic expansion through the nozzle.

  3. ElectroSpark Deposition

    DTIC Science & Technology

    2007-01-25

    ElectroSpark Deposition Hard Chrome Alternatives Team Joint Cadmium Alternatives Team Canadian Hard Chrome Alternatives Team Joint Group on Pollution...00-2007 to 00-00-2007 4. TITLE AND SUBTITLE ElectroSpark Deposition 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S...Processes, Inc. ElectroSpark Deposition (ESD) Results of Materials Testing and Technology Insertion January 25, 2007 Advanced Surfaces And Processes, Inc. 3

  4. Reading the climate record of the martian polar layered deposits

    USGS Publications Warehouse

    Hvidberg, C.S.; Fishbaugh, K.E.; Winstrup, M.; Svensson, A.; Byrne, S.; Herkenhoff, K. E.

    2012-01-01

    The martian polar regions have layered deposits of ice and dust. The stratigraphy of these deposits is exposed within scarps and trough walls and is thought to have formed due to climate variations in the past. Insolation has varied significantly over time and caused dramatic changes in climate, but it has remained unclear whether insolation variations could be linked to the stratigraphic record. We present a model of layer formation based on physical processes that expresses polar deposition rates of ice and dust in terms of insolation. In this model, layer formation is controlled by the insolation record, and dust-rich layers form by two mechanisms: (1) increased summer sublimation during high obliquity, and (2) variations in the polar deposition of dust modulated by obliquity variations. The model is simple, yet physically plausible, and allows for investigations of the climate control of the polar layered deposits (PLD). We compare the model to a stratigraphic column obtained from the north polar layered deposits (NPLD) (Fishbaugh, K.E., Hvidberg, C.S., Byrne, S., Russel, P.S., Herkenhoff, K.E., Winstrup, M., Kirk, R. [2010a]. Geophys. Res. Lett., 37, L07201) and show that the model can be tuned to reproduce complex layer sequences. The comparison with observations cannot uniquely constrain the PLD chronology, and it is limited by our interpretation of the observed stratigraphic column as a proxy for NPLD composition. We identified, however, a set of parameters that provides a chronology of the NPLD tied to the insolation record and consistently explains layer formation in accordance with observations of NPLD stratigraphy. This model dates the top 500 m of the NPLD back to ∼1 million years with an average net deposition rate of ice and dust of 0.55 mm a−1. The model stratigraphy contains a quasi-periodic ∼30 m cycle, similar to a previously suggested cycle in brightness profiles from the NPLD (Laskar, J., Levrard, B., Mustard, F. [2002]. Nature, 419, 375

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

    NASA Astrophysics Data System (ADS)

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

    2008-02-01

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

  6. Radionuclide deposition control

    DOEpatents

    Brehm, William F.; McGuire, Joseph C.

    1980-01-01

    The deposition of radionuclides manganese-54, cobalt-58 and cobalt-60 from liquid sodium coolant is controlled by providing surfaces of nickel or high nickel alloys to extract the radionuclides from the liquid sodium, and by providing surfaces of tungsten, molybdenum or tantalum to prevent or retard radionuclide deposition.

  7. Domestic phosphate deposits

    USGS Publications Warehouse

    McKelvey, V.E.; Cathcart, J.B.; Altschuler, Z.S.; Swanson, R.W.; Lutz, Katherine

    1953-01-01

    Most of the worlds phosphate deposits can be grouped into six types: 1) igneous apatite deposits; 2) marine phosphorites; 3) residual phosphorites; 4) river pebble deposits; 5) phosphatized rock; and 6) guano. The igneous apatites and marine phosphorites form deposits measurable in millions or billions of tons; the residual deposits are measurable in thousands or millions; and the other types generally only in thousands of tons. Igneous apatite deposits have been mined on a small scale in New York, New Jersey, and Virginia. Marine phosphorites have been mined in Montana, Idaho, Utah, Wyoming, Arkansas, Tennessee, North Carolina, South Carolina, Georgia, and Florida. Residual phosphorites have been mined in Tennessee, Pennsylvania, and Florida. River pebble has been produced in South Carolina and Florida; phosphatized rock in Tennessee and Florida; and guano in New Mexico and Texas. Present production is limited almost entirely to Florida, Tennessee, Montana, Idaho, and Wyoming. Incomplete but recently partly revised estimates indicate the presence of about 5 billion tons of phosphate deposits in the United States that is minable under present economic conditions. Deposits too lean in quality or thickness to compete with those in the western and southeastern fields probably contain tens of billions of tons.

  8. Deposition of the late Wisconsin Johnstown moraine, south-central Wisconsin

    USGS Publications Warehouse

    Lundqvist, J.; Clayton, L.; Mickelson, D.M.

    1993-01-01

    The Johnstown moraine is made up of three different materials. The lower part of the sequence consists of closely spaced bodies of boulder gravel, which are cylindrical and plunge upglacier several degrees. They are interpreted to be esker bodies. They grade distally into proglacial outwash fans. The esker bodies are overlain by sandy till, some of which is uniform and some of which has colour layers. The colour layers are a few millimetres to a metre thick, drape over the eskers and dip upglacier several degrees. Both the uniform and layered till have pebbles plunging upglacier several degrees steeper than the dip of the layers. Both the uniform and layered till are interpreted to have been deposited subglacially, probably both by melting out and by lodgement. The till is overlain by a thin layer of boulder gravel interpreted to be washed supraglacial sediment. ?? 1993.

  9. Carbon-14 wiggle-match dating of peat deposits: advantages and limitations

    NASA Astrophysics Data System (ADS)

    Blaauw, Maarten; van Geel, Bas; Mauquoy, Dmitri; van der Plicht, Johannes

    2004-02-01

    Carbon-14 wiggle-match dating (WMD) of peat deposits uses the non-linear relationship between 14C age and calendar age to match the shape of a series of closely spaced peat 14C dates with the 14C calibration curve. The method of WMD is discussed, and its advantages and limitations are compared with calibration of individual dates. A numerical approach to WMD is introduced that makes it possible to assess the precision of WMD chronologies. During several intervals of the Holocene, the 14C calibration curve shows less pronounced fluctuations. We assess whether wiggle-matching is also a feasible strategy for these parts of the 14C calibration curve. High-precision chronologies, such as obtainable with WMD, are needed for studies of rapid climate changes and their possible causes during the Holocene. Copyright

  10. Plasma deposition of tungsten

    SciTech Connect

    Greenberg, K.E.

    1986-12-01

    Tungsten films were plasma-deposited using an abnormal glow discharge through a mixture of tungsten hexafluoride, hydrogen, and argon. The films adhered well to silicon, silicon dioxide, gallium arsenide, and aluminum substrates placed directly on the discharge cathode. Typical deposition rates were on the order of 160 Angstroms/minute with as-deposited film resistivities of 40 to 70 microohm-cm. The tungsten was analyzed using a number of techniques including x-ray diffraction, scanning electron microscopy, and Auger spectroscopy. Low-resistivity (<10 microohm-cm) films that adhered well to silicon dioxide were obtained with a two-step process utilizing plasma deposition and conventional chemical vapor deposition.

  11. Stratiform chromite deposit model

    USGS Publications Warehouse

    Schulte, Ruth F.; Taylor, Ryan D.; Piatak, Nadine M.; Seal, Robert R., II

    2010-01-01

    Stratiform chromite deposits are of great economic importance, yet their origin and evolution remain highly debated. Layered igneous intrusions such as the Bushveld, Great Dyke, Kemi, and Stillwater Complexes, provide opportunities for studying magmatic differentiation processes and assimilation within the crust, as well as related ore-deposit formation. Chromite-rich seams within layered intrusions host the majority of the world's chromium reserves and may contain significant platinum-group-element (PGE) mineralization. This model of stratiform chromite deposits is part of an effort by the U.S. Geological Survey's Mineral Resources Program to update existing models and develop new descriptive mineral deposit models to supplement previously published models for use in mineral-resource and mineral-environmental assessments. The model focuses on features that may be common to all stratiform chromite deposits as a way to gain insight into the processes that gave rise to their emplacement and to the significant economic resources contained in them.

  12. Solution deposition assembly

    SciTech Connect

    Roussillon, Yann; Scholz, Jeremy H; Shelton, Addison; Green, Geoff T; Utthachoo, Piyaphant

    2014-01-21

    Methods and devices are provided for improved deposition systems. In one embodiment of the present invention, a deposition system is provided for use with a solution and a substrate. The system comprises of a solution deposition apparatus; at least one heating chamber, at least one assembly for holding a solution over the substrate; and a substrate curling apparatus for curling at least one edge of the substrate to define a zone capable of containing a volume of the solution over the substrate. In another embodiment of the present invention, a deposition system for use with a substrate, the system comprising a solution deposition apparatus; at heating chamber; and at least assembly for holding solution over the substrate to allow for a depth of at least about 0.5 microns to 10 mm.

  13. Atomic layer deposition of lead sulfide quantum dots on nanowire surfaces.

    PubMed

    Dasgupta, Neil P; Jung, Hee Joon; Trejo, Orlando; McDowell, Matthew T; Hryciw, Aaron; Brongersma, Mark; Sinclair, Robert; Prinz, Fritz B

    2011-03-09

    Quantum dots provide unique advantages in the design of novel optoelectronic devices owing to the ability to tune their properties as a function of size. Here we demonstrate a new technique for fabrication of quantum dots during the nucleation stage of atomic layer deposition (ALD) of PbS. Islands with sub-10 nm diameters were observed during the initial ALD cycles by transmission electron microscopy, and in situ observations of the coalescence and sublimation behavior of these islands show the possibility of further modifying the size and density of dots by annealing. The ALD process can be used to cover high-aspect-ratio nanostructures, as demonstrated by the uniform coating of a Si nanowire array with a single layer of PbS quantum dots. Photoluminescence measurements on the quantum dot/nanowire composites show a blue shift when the number of ALD cycles is decreased, suggesting a route to fabricate unique three-dimensional nanostructured devices such as solar cells.

  14. EDITORIAL: Atomic layer deposition Atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Godlewski, Marek

    2012-07-01

    The growth method of atomic layer deposition (ALD) was introduced in Finland by Suntola under the name of atomic layer epitaxy (ALE). The method was originally used for deposition of thin films of sulphides (ZnS, CaS, SrS) activated with manganese or rare-earth ions. Such films were grown for applications in thin-film electroluminescence (TFEL) displays. The ALE mode of growth was also tested in the case of molecular beam epitaxy. Films grown by ALD are commonly polycrystalline or even amorphous. Thus, the name ALE has been replaced by ALD. In the 80s ALD was developed mostly in Finland and neighboring Baltic countries. Deposition of a range of different materials was demonstrated at that time, including II-VI semiconductors (e.g. CdTe, CdS) and III-V (e.g. GaAs, GaN), with possible applications in e.g. photovoltaics. The number of publications on ALD was slowly increasing, approaching about 100 each year. A real boom in interest came with the development of deposition methods of thin films of high-k dielectrics. This research was motivated by a high leakage current in field-effect transistors with SiO2-based gate dielectrics. In 2007 Intel introduced a new generation of integrated circuits (ICs) with thin films of HfO2 used as gate isolating layers. In these and subsequent ICs, films of HfO2 are deposited by the ALD method. This is due to their unique properties. The introduction of ALD to the electronics industry led to a booming interest in the ALD growth method, with the number of publications increasing rapidly to well above 1000 each year. A number of new applications were proposed, as reflected in this special issue of Semiconductor Science and Technology. The included articles cover a wide range of possible applications—in microelectronics, transparent electronics, optoelectronics, photovoltaics and spintronics. Research papers and reviews on the basics of ALD growth are also included, reflecting a growing interest in precursor chemistry and growth

  15. Erosion, Transportation, and Deposition on Outer Solar System Satellites: Landform Evolution Modeling Studies

    NASA Technical Reports Server (NTRS)

    Moore, Jeffrey Morgan; Howard, Alan D.; Schenk, Paul M.

    2013-01-01

    Mass movement and landform degradation reduces topographic relief by moving surface materials to a lower gravitational potential. In addition to the obvious role of gravity, abrasive mechanical erosion plays a role, often in combination with the lowering of cohesion, which allows disaggregation of the relief-forming material. The identification of specific landform types associated with mass movement and landform degradation provides information about local sediment particle size and abundance and transportation processes. Generally, mass movements can be classified in terms of the particle sizes of the transported material and the speed the material moved during transport. Most degradation on outer planet satellites appears consistent with sliding or slumping, impact erosion, and regolith evolution. Some satellites, such as Callisto and perhaps Hyperion and Iapetus, have an appearance that implies that some additional process is at work, most likely sublimation-driven landform modification and mass wasting. A variant on this process is thermally driven frost segregation as seen on all three icy Galilean satellites and perhaps elsewhere. Titan is unique among outer planet satellites in that Aeolian and fluvial processes also operate to erode, transport, and deposit material. We will evaluate the sequence and extent of various landform-modifying erosional and volatile redistribution processes that have shaped these icy satellites using a 3-D model that simulates the following surface and subsurface processes: 1) sublimation and re-condensation of volatiles; 2) development of refractory lag deposits; 3) disaggregation and downward sloughing of surficial material; 4) radiative heating/cooling of the surface (including reflection, emission, and shadowing by other surface elements); 5) thermal diffusion; and 6) vapor diffusion. The model will provide explicit simulations of landform development and thusly predicts the topographic and volatile evolution of the surface

  16. Chemical vapor deposition growth

    NASA Technical Reports Server (NTRS)

    Ruth, R. P.; Manasevit, H. M.; Kenty, J. L.; Moudy, L. A.; Simpson, W. I.; Yang, J. J.

    1976-01-01

    A chemical vapor deposition (CVD) reactor system with a vertical deposition chamber was used for the growth of Si films on glass, glass-ceramic, and polycrystalline ceramic substrates. Silicon vapor was produced by pyrolysis of SiH4 in a H2 or He carrier gas. Preliminary deposition experiments with two of the available glasses were not encouraging. Moderately encouraging results, however, were obtained with fired polycrystalline alumina substrates, which were used for Si deposition at temperatures above 1,000 C. The surfaces of both the substrates and the films were characterized by X-ray diffraction, reflection electron diffraction, scanning electron microscopy optical microscopy, and surface profilometric techniques. Several experiments were conducted to establish baseline performance data for the reactor system, including temperature distributions on the sample pedestal, effects of carrier gas flow rate on temperature and film thickness, and Si film growth rate as a function of temperature.

  17. World oil shale deposits

    SciTech Connect

    Hook, C.O.; Russell, P.L.

    1982-01-01

    The article estimates resources in-place and their oil equivalent. The major deposits are described in the U.S., Australia, USSR, Peoples Republic of China, Morocco, Israel, Jordan, Syria, Europe and South America. 2 refs.

  18. Electrospark deposition coatings

    NASA Astrophysics Data System (ADS)

    Sheely, W. F.

    1986-11-01

    Hard surfacing for wear resistant and low-friction coatings has been improved by means of advances in the computer controls in electronic circuitry of the electrospark deposition (ESD) process. coatings of nearly any electrically conductive metal alloy or cermet can be deposited on conductive materials. Thickness is usually two mils or less, but can be as high as 10 mils. ESD coatings can quadrupole cutting tool life.

  19. Electrospark deposition coatings

    SciTech Connect

    Sheely, W.F.

    1986-11-19

    Hard surfacing for wear resistant and low-friction coatings has been improved by means of advances in the computer controls in electronic circuitry of the electrospark deposition (ESD) process. coatings of nearly any electrically conductive metal alloy or cermet can be deposited on conductive materials. Thickness is usually two mils or less, but can be as high as 10 mils. ESD coatings can quadrupole cutting tool life. (DLC)

  20. Gemstone deposits of Serbia

    NASA Astrophysics Data System (ADS)

    Miladinović, Zoran; Simić, Vladimir; Jelenković, Rade; Ilić, Miloje

    2016-06-01

    Gemstone minerals in Serbia have never been regarded as an interesting and significant resource. Nevertheless, more than 150 deposits and occurrences have been recorded and some of them preliminarily explored in the last 50 years. The majority of deposits and occurrences are located within the Serbo-Macedonian metallogenic province and the most significant metallogenic units at the existing level of knowledge are the Fruska Gora ore district, Cer ore district, Sumadija metallogenic zone, Kopaonik metallogenic zone and Lece-Halkidiki metallogenic zone. The most important genetic type of deposits is hydrothermal, particularly in case of serpentinite/peridotite as host/parent rock. Placer deposits are also economically important. The dominant gemstones are silica minerals: chalcedony (Chrysoprase, carnelian, bluish chalcedony etc.), jasper (picture, landscape, red etc.), common opal (dendritic, green, milky white etc.), silica masses (undivided), and quartz (rock crystal, amethyst etc.). Beside silica minerals significant gemstones in Serbia include also beryl (aquamarine), garnet (almandine and pyrope), tourmaline, fluorite, rhodochrosite, carbonate-silica breccia, carbonate-silica onyx, silicified wood, howlite, serpentinite, marble onyx, and kyanite. This paper aims to present an overview of Serbian gemstone deposits and occurrences and their position based on a simplified gemstone metallogenic map of Serbia, as well as genetic-industrial classification of gemstone deposits and gemstone varieties.

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

    NASA Astrophysics Data System (ADS)

    Acree, William; Chickos, James S.

    2017-03-01

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

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

    PubMed

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

    2006-10-01

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

  3. Becquerel Crater Deposit

    NASA Technical Reports Server (NTRS)

    2002-01-01

    (Released 28 May 2002) The finely layered deposit in Becquerel crater, seen in the center of this THEMIS image, is slowly being eroded away by the action of windblown sand. Dark sand from a source north of the bright deposit is collecting along its northern edge, forming impressive barchan style dunes. These vaguely boomerang-shaped dunes form with their two points extending in the downwind direction, demonstrating that the winds capable of moving sand grains come from the north. Grains that leave the dunes climb the eroding stair-stepped layers, collecting along the cliff faces before reaching the crest of the deposit. Once there, the sand grains are unimpeded and continue down the south side of the deposit without any significant accumulation until they fall off the steep cliffs of the southern margin. The boat-hull shaped mounds and ridges of bright material called yardangs form in response to the scouring action of the migrating sand. To the west, the deposit has thinned enough that the barchan dunes extend well into the deeply eroded north-south trending canyons. Sand that reaches the south side collects and reforms barchan dunes with the same orientation as those on the north side of the deposit. Note the abrupt transition between the bright material and the dark crater floor on the southern margin. Steep cliffs are present with no indication of rubble from the obvious erosion that produced them. The lack of debris at the base of the cliffs is evidence that the bright material is readily broken up into particles that can be transported away by the wind. The geological processes that are destroying the Becquerel crater deposit appear active today. But it is also possible that they are dormant, awaiting a particular set of climatic conditions that produces the right winds and perhaps even temperatures to allow the erosion to continue.

  4. 78 FR 11604 - Deposit Insurance Regulations; Definition of Insured Deposit

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-19

    ...; Definition of Insured Deposit AGENCY: Federal Deposit Insurance Corporation (FDIC). SUMMARY: The FDIC is... FDI Act definition of the term ``deposit'' expressly excludes any obligation of a bank that is payable... purposes of national depositor preference. III. Statutory Framework A. Definition of ``Deposit'' The...

  5. Chemically deposited CdS by an ammonia-free process for solar cells window layers

    SciTech Connect

    Ochoa-Landin, R.; Sastre-Hernandez, J.; Vigil-Galan, O.; Ramirez-Bon, R.

    2010-02-15

    Chemically deposited CdS window layers were studied on two different transparent conductive substrates, namely indium tin oxide (ITO) and fluorine doped tin oxide (FTO), to determine the influence of their properties on CdS/CdTe solar cells performance. Three types of CdS films obtained from different chemical bath deposition (CBD) processes were studied. The three CBD processes employed sodium citrate as the complexing agent in partial or full substitution of ammonia. The CdS films were studied by X-ray diffraction, optical transmission spectroscopy and atomic force microscopy. CdS/CdTe devices were completed by depositing 3 {mu}m thick CdTe absorbent layers by means of the close-spaced vapor transport technique (CSVT). Evaporated Cu-Au was used as the back contact in all the solar cells. Dark and under illumination J-V characteristic and quantum efficiency measurements were done on the CdS/CdTe devices to determine their conversion efficiency and spectral response. The efficiency of the cells depended on the window layer and on the transparent contact with values between 5.7% and 8.7%. (author)

  6. Oxide Deposition By PECVD

    NASA Astrophysics Data System (ADS)

    Ibbotson, Dale E.; Hsieh, Julian J.; Flamm, Daniel L.; Mucha, J. A.

    1989-03-01

    We have studied the chemical and physical properties of silicon oxide films plasma deposited from TEOS (tetraethoxysilane), to gain an understanding of the origins of (1) step coverage and (2) film stability. TEOS was diluted in helium/oxygen mixtures and deposited as a function of discharge frequency (150 kHz and 14 MHz) and 02 flow in a parallel plate reactor. The typical deposition conditions were 1 torr total pressure, 320°C substrate temperature, 1 -9% TEOS, 1 -80% 02, and -0.1 W/cm2 discharge power. Films deposited at high frequency with excess oxygen were generally oxygen-rich, chemically unstable and hygroscopic, while films deposited at low frequency were stable to moisture and slightly deficient in oxygen. However, coverage profiles of high frequency films showed an unusual degree of directionality, which could be used to advantage for the coating of high aspect ratio features. We suggest that a judicious combination of high and low frequency discharges may improve film properties while maintaining directional step coverage. Isotopic labeling experiments were performed using 1802 to gain insight into the origins of the oxygen that is contained in these PECVD films. Complete isotopic scrambling was not observed. Film composition data suggest that there is one tenacious Si-0 bond which remains with the silicon from the original TEOS molecule during the reaction to form Si02.

  7. Interannual and seasonal changes in the north polar ice deposits of Mars: Observations from MY 29-31 using MARCI

    NASA Astrophysics Data System (ADS)

    Calvin, W. M.; James, P. B.; Cantor, B. A.; Dixon, E. M.

    2015-05-01

    The MARCI camera on the Mars Reconnaissance Orbiter provides daily synoptic coverage that allows monitoring of seasonal cap retreat and interannual changes that occur between Mars year (MY) and over the northern summer. The northern seasonal cap evolution was observed in MY 29, 30 and 31 (12/2007-04/2012). Observation over multiple Mars years allows us to compare changes between years as well as longer-term evolution of the high albedo deposits at the poles. Significant variability in the early season is noted in all years and the retreating seasonal cap edge is extremely dynamic. Detailed coverage of the entire seasonal and residual ice caps allows a broader view of variations in the high albedo coverage and identifies numerous regions where high albedo areas are changing with time. Large areas of disappearance and reappearance of high albedo features (Gemini Scopuli) are seasonally cyclical, while smaller areas are variable on multi-year time scales (Abalso Mensae and Olympia Planitia). These seasonal and interannual changes directly bear on the surface-atmosphere exchange of dust and volatiles and understanding the current net processes of deposition and erosion of the residual ice deposits. Local and regional variation in high albedo areas reflects an interplay between frost deposition, evolution, and sublimation along with deposition and removal of dust.

  8. Venus - Landslide Deposits

    NASA Technical Reports Server (NTRS)

    1992-01-01

    The Magellan spacecraft has observed remnant landslide deposits apparently resulting from the collapse of volcanic structures. This image, centered at 45.2 degrees south latitude, 201.4 degrees east longitude, shows a collapse deposit 70 kilometers (43 miles) across. The bright, highly textured deposit near the center of the image probably consists of huge blocks of fractured volcanic rock, many as large as several hundred meters across. A remnant of the volcano itself, about 20 kilometers (12.4 miles) across, is seen at the center of the image. The distorted radar appearance of the volcano is a result of extremely steep slopes on the 'scars' from which the landslide material originated. A field of numerous small volcanic domes can be seen in the northern half of the image. The bright irregular lineaments trending to the north-northwest are ridges caused by regional tectonic deformation of the upper layers of the Venusian crust.

  9. Turbine Airfoil Deposition Models

    NASA Technical Reports Server (NTRS)

    Rosner, D. E.

    1984-01-01

    Gas turbine failures associated with sea-salt ingestion and sulfur-containing fuel impurities have directed attention to alkali sulfate deposition and the associated hot corrosion of gas turbine (GT) blades under some GT operating conditions. These salt deposits form thin, molten films which undermine the protective metal oxide coating normally found on GT blades. The prediction of molten salt deposition, flow and oxide dissolution, and their effects on the lifetime of turbine blades are examined. Goals include rationalizing and helping to predict corrosion patterns on operational GT rotor blades and stators, and ultimately providing some of the tools required to design laboratory simulators and future corrosion-resistant high-performance engines. Necessary background developments are reviewed first, and then recent results and tentative conclusions are presented along with a brief account of the present research plans.

  10. Near-Failure Detonation Behavior of Vapor-Deposited Hexanitrostilbene (HNS) Films

    NASA Astrophysics Data System (ADS)

    Knepper, Robert; Wixom, Ryan; Tappan, Alexander

    2015-06-01

    Physical vapor deposition is an attractive method to produce sub-millimeter explosive samples for studying detonation behavior at near-failure conditions. In this work, we examine hexanitrostilbene (HNS) films deposited onto polycarbonate substrates using vacuum thermal sublimation. Deposition conditions are varied in order to alter porosity in the films, and the resulting microstructures are quantified by analyzing ion-polished cross-sections using scanning electron microscopy. The effects of these changes in microstructure on detonation velocity and the critical thickness needed to sustain detonation are determined. The polycarbonate substrates can act as recording plates for detonation experiments, and films near the critical thickness display distinct patterns in the dent tracks that indicate instabilities in the detonation front when approaching failure conditions. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  11. Facile plasma-enhanced deposition of ultrathin crosslinked amino acid films for conformal biometallization.

    PubMed

    Anderson, Kyle D; Slocik, Joseph M; McConney, Michael E; Enlow, Jesse O; Jakubiak, Rachel; Bunning, Timothy J; Naik, Rajesh R; Tsukruk, Vladimir V

    2009-03-01

    A novel method for the facile fabrication of conformal, ultrathin, and uniform synthetic amino acid coatings on a variety of practical surfaces by plasma-enhanced chemical vapor deposition is introduced. Tyrosine, which is utilized as an agent to reduce gold nanoparticles from solution, is sublimed into the plasma field and directly deposited on a variety of substrates to form a homogeneous, conformal, and robust polyamino acid coating in a one-step, solvent-free process. This approach is applicable to many practical surfaces and allows surface-induced biometallization while avoiding multiple wet-chemistry treatments that can damage many soft materials. Moreover, by placing a mask over the substrate during deposition, the tyrosine coating can be micropatterned. Upon its exposure to a solution of gold chloride, a network of gold nanoparticles forms on the surface, replicating the initial micropattern. This method of templated biometallization is adaptable to a variety of practical inorganic and organic substrates, such as silicon, glass, nitrocellulose, polystyrene, polydimethylsiloxane, polytetrafluoroethylene, polyethylene, and woven silk fibers. No special pretreatment is necessary, and the technique results in a rapid, conformal amino acid coating that can be utilized for further biometallization.

  12. Deposition Rates of High Power Impulse Magnetron Sputtering: Physics and Economics

    SciTech Connect

    Anders, Andre

    2009-11-22

    Deposition by high power impulse magnetron sputtering (HIPIMS) is considered by some as the new paradigm of advanced sputtering technology, yet this is met with skepticism by others for the reported lower deposition rates, if compared to rates of more conventional sputtering of equal average power. In this contribution, the underlying physical reasons for the rate changes are discussed, including (i) ion return to the target and self-sputtering, (ii) the less-than-linear increase of the sputtering yield with increasing ion energy, (iii) yield changes due to the shift of species responsible for sputtering, (iv) changes to due to greater film density, limited sticking, and self-sputtering on the substrate, (v) noticeable power losses in the switch module, (vi) changes of the magnetic balance and particle confinement of the magnetron due to self-fields at high current, and (vii) superposition of sputtering and sublimation/evaporation for selected materials. The situation is even more complicated for reactive systems where the target surface chemistry is a function of the reactive gas partial pressure and discharge conditions. While most of these factors imply a reduction of the normalized deposition rate, increased rates have been reported for certain conditions using hot targets and less poisoned targets. Finally, some points of economics and HIPIMS benefits considered.

  13. Evidence for Possible Exposed Water Ice Deposits in Martian Low Latitude Chasms and Chaos

    NASA Technical Reports Server (NTRS)

    Leovy, C.; Wood, S. E.; Catling, D.; Montgomery, D. R.; Moore, J.; Barnhart, C.; Ginder, E.; Louie, M.

    2004-01-01

    A light-toned interior layer deposit (ILD) on the floor of the deep martian depression Juventae Chasma is found to have a relatively high thermal inertia approx. 500 J m(exp -2) s(exp -1/2) K(exp -1). This could imply rock, but is also similar to the average value of thermal inertia found for north polar layered deposits. Furthermore, ILD-B is found to exhibit a bluff and terrace structure . A terrace structure arises naturally in model simulations of the sublimation of large ice deposits. Such a staircase terrain, of course, is a further characteristic of north polar layered terrain. Morphological similarity, thermal inertia in the range of thermal inertias of the north polar cap layered terrain, and relatively high albedo lead us to propose that the ILD-B may consist of residual water ice partially covered by, and perhaps mixed with, varying amounts of dust or sand. Other ILDs (A-C) are also found in Juventae Chasma. While these ILDs lack the close morphological resemblance to the north polar cap, they share many other common features and appear to be part of the same formation. Similar ILDs are found in chaotic terrain elsewhere in the martian tropics. This leads us to propose that water ice may exist in the martian tropics today and may be implicit in the formation of chaotic terrain.

  14. Laser assisted deposition

    NASA Technical Reports Server (NTRS)

    Dutta, S.

    1983-01-01

    Applications of laser-based processing techniques to solar cell metallization are discussed. Laser-assisted thermal or photolytic maskless deposition from organometallic vapors or solutions may provide a viable alternative to photovoltaic metallization systems currently in use. High power, defocused excimer lasers may be used in conjunction with masks as an alternative to direct laser writing to provide higher throughput. Repeated pulsing with excimer lasers may eliminate the need for secondary plating techniques for metal film buildup. A comparison between the thermal and photochemical deposition processes is made.

  15. "Total Deposition (TDEP) Maps"

    EPA Science Inventory

    The presentation provides an update on the use of a hybrid methodology that relies on measured values from national monitoring networks and modeled values from CMAQ to produce of maps of total deposition for use in critical loads and other ecological assessments. Additionally, c...

  16. Shaping by Deposition

    DTIC Science & Technology

    1991-01-01

    pasticprototypegreater design flexibility , rapid fabrication, and reduce cost.odels are built directly fronm liquid photopolymers by Shaping deposition processes build...ate on design models to help the designer create manufactura - ble designs on the basis of requirements and limitations of the This paper describes the

  17. Volcanogenic Massive Sulfide Deposit Density

    USGS Publications Warehouse

    Mosier, Dan L.; Singer, Donald A.; Berger, Vladimir I.

    2007-01-01

    A mineral-deposit density model for volcanogenic massive sulfide deposits was constructed from 38 well-explored control areas from around the world. Control areas contain at least one exposed volcanogenic massive sulfide deposit. The control areas used in this study contain 150 kuroko, 14 Urals, and 25 Cyprus massive sulfide subtypes of volcanogenic massive sulfide deposits. For each control area, extent of permissive rock, number of exposed volcanogenic massive sulfide deposits, map scale, deposit age, and deposit density were determined. The frequency distribution of deposit densities in these 38 control areas provides probabilistic estimates of the number of deposits for tracts that are permissive for volcanogenic massive sulfide deposits-90 percent of the control areas have densities of 100 or more deposits per 100,000 square kilometers, 50 percent of the control areas have densities of 700 or more deposits per 100,000 square kilometers, and 10 percent of the control areas have densities of 3,700 or more deposits per 100,000 square kilometers. Both map scale and the size of the control area are shown to be predictors of deposit density. Probabilistic estimates of the number of volcanogenic massive sulfide deposits can be made by conditioning the estimates on sizes of permissive area. The model constructed for this study provides a powerful tool for estimating the number of undiscovered volcanogenic massive sulfide deposits when conducting resource assessments. The value of these deposit densities is due to the consistency of these models with the grade and tonnage and the descriptive models. Mineral-deposit density models combined with grade and tonnage models allow reasonable estimates of the number, size, and grades of volcanogenic massive sulfide deposits to be made.

  18. Trouvelot Crater Deposit

    NASA Technical Reports Server (NTRS)

    2002-01-01

    [figure removed for brevity, see original site]

    Like many of the craters in the Oxia Palus region of Mars, Trouvelot Crater hosts an eroded, light-toned, sedimentary deposit on its floor. Compared with the much larger example in Becquerel Crater to the NE, the Trouvelot deposit has been so eroded by the scouring action of dark, wind-blown sand that very little of it remains. Tiny outliers of bright material separated from the main mass attest to the once, more really extensive coverage by the deposit. A similar observation can be made for White Rock, the best known example of a bright, crater interior deposit. The origin of the sediments in these deposits remains enigmatic but they are likely the result of fallout from ash or dust carried by the thin martian atmosphere.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  19. X-ray absorption and photoemission spectroscopy of zinc protoporphyrin adsorbed on rutile TiO{sub 2}(110) prepared by in situ electrospray deposition

    SciTech Connect

    Rienzo, Anna; Mayor, Louise C.; Magnano, Graziano; Satterley, Christopher J.; O'Shea, James N.; Ataman, Evren; Schnadt, Joachim; Schulte, Karina

    2010-02-28

    Zinc-protoporphyrin, adsorbed on the rutile TiO{sub 2}(110) surface, has been studied using photoemission spectroscopy and near-edge absorption fine structure spectroscopy to deduce the nature of the molecule-surface bonding and the chemical environment of the central metal atom. To overcome the difficulties associated with sublimation of the porphyrin molecules, samples were prepared in situ using ultrahigh vacuum electrospray deposition, a technique which facilitates the deposition of nonvolatile and fragile molecules. Monolayers of Zn protoporphyrin are found to bond to the surface via the oxygen atoms of the deprotonated carboxyl groups. The molecules initially lie largely parallel to the surface, reorienting to an upright geometry as the coverage is increased up to a monolayer. For those molecules directly chemisorbed to the surface, the interaction is sufficiently strong to pull the central metal atom out of the molecule.

  20. Controlled injection of a liquid into ultra-high vacuum: Submonolayers of adenosine triphosphate deposited on Cu(110)

    NASA Astrophysics Data System (ADS)

    Sobrado, J. M.; Martín-Gago, J. A.

    2016-10-01

    We have combined a fast-valve device with vacuum technology for implementing a new method that allows introducing liquid solutions in an ultra-high vacuum chamber in the form of very small droplets. This technical development allows the easy deposition of (bio) organic molecules or small nanoparticles on a surface in a fully in-situ process, avoiding possible contamination due to the handle of the material. Moreover, our experimental set-up is suitable for any liquid and does not require any voltage application as in electrospray. We can easily change the operating regime from liquid droplet injection to the formation of a highly dispersive jet of micro-droplets by exclusively adjusting external parameters. Due to the nature of the injection process, the operational protocol makes possible the deposition of delicate molecular species that cannot be thermally sublimated. In particular, we have used this system to study the deposition of adenosine triphosphate on Cu(110). The structure of the layer was analyzed by X-ray photoemission spectroscopy and the evolution of the signal from the deposited molecule with the number of injections indicates that the molecular coverage can be controlled with submonolayer precision.

  1. Hydroxyapatite Deposition Disease

    DTIC Science & Technology

    2006-11-01

    calcific tendinitis or calcific periarthritis, is characterized by the deposition of calcium phosphate crystals (predominantly hydroxyapatite) in...site of HADD is the hip, where calcifications are usually found in the gluteus medius tendon or along the femur at various sites of tendinous ...posterolateral femoral diaphysis, as well as in various other tendinous attachments to the femur. Computed tomography is also helpful in the demonstration

  2. Uranium deposits of Brazil

    SciTech Connect

    1991-09-01

    Brazil is a country of vast natural resources, including numerous uranium deposits. In support of the country`s nuclear power program, Brazil has developed the most active uranium industry in South America. Brazil has one operating reactor (Angra 1, a 626-MWe PWR), and two under construction. The country`s economic challenges have slowed the progress of its nuclear program. At present, the Pocos de Caldas district is the only active uranium production. In 1990, the Cercado open-pit mine produced approximately 45 metric tons (MT) U{sub 3}O{sub 8} (100 thousand pounds). Brazil`s state-owned uranium production and processing company, Uranio do Brasil, announced it has decided to begin shifting its production from the high-cost and nearly depleted deposits at Pocos de Caldas, to lower-cost reserves at Lagoa Real. Production at Lagoa Real is schedules to begin by 1993. In addition to these two districts, Brazil has many other known uranium deposits, and as a whole, it is estimated that Brazil has over 275,000 MT U{sub 3}O{sub 8} (600 million pounds U{sub 3}O{sub 8}) in reserves.

  3. Electrophoretic deposition of biomaterials

    PubMed Central

    Boccaccini, A. R.; Keim, S.; Ma, R.; Li, Y.; Zhitomirsky, I.

    2010-01-01

    Electrophoretic deposition (EPD) is attracting increasing attention as an effective technique for the processing of biomaterials, specifically bioactive coatings and biomedical nanostructures. The well-known advantages of EPD for the production of a wide range of microstructures and nanostructures as well as unique and complex material combinations are being exploited, starting from well-dispersed suspensions of biomaterials in particulate form (microsized and nanoscale particles, nanotubes, nanoplatelets). EPD of biological entities such as enzymes, bacteria and cells is also being investigated. The review presents a comprehensive summary and discussion of relevant recent work on EPD describing the specific application of the technique in the processing of several biomaterials, focusing on (i) conventional bioactive (inorganic) coatings, e.g. hydroxyapatite or bioactive glass coatings on orthopaedic implants, and (ii) biomedical nanostructures, including biopolymer–ceramic nanocomposites, carbon nanotube coatings, tissue engineering scaffolds, deposition of proteins and other biological entities for sensors and advanced functional coatings. It is the intention to inform the reader on how EPD has become an important tool in advanced biomaterials processing, as a convenient alternative to conventional methods, and to present the potential of the technique to manipulate and control the deposition of a range of nanomaterials of interest in the biomedical and biotechnology fields. PMID:20504802

  4. Inkjet deposited circuit components

    NASA Astrophysics Data System (ADS)

    Bidoki, S. M.; Nouri, J.; Heidari, A. A.

    2010-05-01

    All-printed electronics as a means of achieving ultra-low-cost electronic circuits has attracted great interest in recent years. Inkjet printing is one of the most promising techniques by which the circuit components can be ultimately drawn (i.e. printed) onto the substrate in one step. Here, the inkjet printing technique was used to chemically deposit silver nanoparticles (10-200 nm) simply by ejection of silver nitrate and reducing solutions onto different substrates such as paper, PET plastic film and textile fabrics. The silver patterns were tested for their functionality to work as circuit components like conductor, resistor, capacitor and inductor. Different levels of conductivity were achieved simply by changing the printing sequence, inks ratio and concentration. The highest level of conductivity achieved by an office thermal inkjet printer (300 dpi) was 5.54 × 105 S m-1 on paper. Inkjet deposited capacitors could exhibit a capacitance of more than 1.5 nF (parallel plate 45 × 45 mm2) and induction coils displayed an inductance of around 400 µH (planar coil 10 cm in diameter). Comparison of electronic performance of inkjet deposited components to the performance of conventionally etched items makes the technique highly promising for fabricating different printed electronic devices.

  5. Intricately Rippled Sand Deposits

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Click on the image for Intricately Rippled Sand Deposits (QTVR)

    NASA's Mars Exploration Rover Spirit welcomed the beginning of 2006 on Earth by taking this striking panorama of intricately rippled sand deposits in Gusev Crater on Mars. This is an approximate true-color rendering of the 'El Dorado' ripple field provided by Spirit over the New Year's holiday weekend. The view spans about 160 degrees in azimuth from left to right and consists of images acquired by Spirit's panoramic camera on Spirit's 708th and 710th Martian days, or sols, (Dec. 30, 2005 and Jan. 1, 2006). Spirit used the Pancam's 750-nanometer, 530-nanometer and 430-nanometer filters to capture the colors on Mars. Scientists have eliminated seams between individual frames in the sky portion of the mosaic to better simulate the vista a person standing on Mars would see. Spirit spent several days acquiring images, spectral data, and compositional and mineralogical information about these large sand deposits before continuing downhill toward 'Home Plate.'

  6. Particle Deposition onto Enclosure Surfaces

    DTIC Science & Technology

    2009-08-20

    Rate, P 16 4.3 Comparison of vd and fi 16 5. Methods for Measurement of Particle Deposition 19 5.1 Measuring Particle Deposition Rate, p 19...deposition. 18 5. Methods for Measurement of Particle Deposition Owing to its importance for numerous engineering systems, the processes of particle...particle counter, time-of-flight aerosol spectrometer, electrical aerosol mobility analyzer, as well as aerosol generation methods , can be found in

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

    PubMed

    Townrow, S; Coleman, P G

    2014-03-26

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

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

    PubMed

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

    2015-05-21

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-05-01

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

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

    SciTech Connect

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

    2015-02-28

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

  12. Deposition of SOCs in forests

    SciTech Connect

    Horstmann, M.; McLachlan, M.S.

    1995-12-31

    The bulk deposition, wet-only deposition, dry-only deposition and ambient air concentrations of PCDD/Fs, PCBs and PAHs were measured in an 80 year old spruce forest, an 80 year old mixed deciduous (beech and oak) forest, and in an adjacent clearing over a period of 1--2 years. The deposition of the less volatile compounds that are primarily particle bound in the atmosphere was similar at both sites. These compounds were deposited primarily through wet deposition, as shown by the measurements in the clearing. In contrast, the deposition of the more volatile compounds was much higher at the forest sites than in the clearing. For instance, the annual deposition of Cl{sub 4}DF was 5 times higher in the spruce forest and 8 times higher in the deciduous forest. The excess deposition in the deciduous forest was almost completely due to the leaf fall in October--December, while about half of the excess deposition in the spruce forest was the result of needle fall. A further, as yet unexplained deposition mechanism accounted for the remainder of the flux in the spruce forest. Other studies have shown that more volatile SOCs are deposited to vegetation primarily through dry gaseous deposition. Hence, while forests have little influence on the deposition of less volatile compounds like the higher chlorinated PCDD/Fs and the 5--6 ring PAHs, dry deposition to leaves/needles and their subsequent falling to the forest floor make forest soils an extremely important sink for more volatile SOC.

  13. Fluidized Crater Ejecta Deposit

    NASA Technical Reports Server (NTRS)

    1998-01-01

    The Mars Orbiter Camera (MOC) onboard the Mars Global Surveyor (MGS) spacecraft continued to obtain high resolution images of the red planet into August 1998. At this time, each ground track (the portion of Mars available for MOC imaging on a given orbit) covers areas from about 40oN on the late afternoon side of the planet, up over the sunlit north polar cap, and down the early morning side of Mars to about 20oN latitude. Early morning and late afternoon views provide good shadowing to reveal subtle details on the martian surface. Views of Mars with such excellent lighting conditions will not be seen by MOC once MGS's Science Phasing Orbits end in mid-September 1998.

    The image shown here, MOC image 47903, was targeted on Friday afternoon (PDT), August 7, 1998. This picture of ejecta from a nameless 9.1 kilometer (5.7 mile)-diameter crater was designed to take full advantage of the present lighting conditions. When the image was taken (around 5:38 p.m. (PDT) on Saturday, August 8, 1998), the Sun had just risen and was only about 6o above the eastern horizon. With the Sun so low in the local sky, the contrast between sunlit and shadowed surfaces allowed new, subtle details to be revealed on the surface of the crater ejecta deposit.

    The crater shown here has ejecta of a type that was first identified in Mariner 9 and Viking Orbiter images as 'fluidized' ejecta. Ejecta is the material that is thrown out from the crater during the explosion that results when a meteor--piece of a comet or asteroid--collides with the planet. Fluidized ejecta is characterized by its lobate appearance, and sometimes by the presence of a ridge along the margin of the ejecta deposit. In the case of the crater shown here, there are two ridges that encircle the crater ejecta--this type of ejecta deposit is sometimes called a double-lobe rampart deposit. The MOC image shows that this particular crater also has 'normal' ejecta that occurs out on the plains, beyond the outermost ridge of

  14. Coffee ring deposition in bands

    NASA Astrophysics Data System (ADS)

    Mandre, Shreyas; Wu, Ning; Aizenberg, Joanna; Mahadevan, Lakshminarayanan

    2010-11-01

    Microscopic particles suspended in a liquid are transported and deposited at a contact line, as the contact line recedes due to evaporation. A particle layer of uniform thickness is deposited if the particle concentration is above a threshold; below this threshold the deposit forms periodic bands oriented parallel to the contact line. We present a model for the formation of these bands based on evaporation leading to the breakup of the thin liquid film near the contact line. The threshold results from a competition between evaporation speed and deposition speed. Using this model, we predict the thickness and length of the bands, making the control of patterned deposition possible.

  15. Database of recent tsunami deposits

    USGS Publications Warehouse

    Peters, Robert; Jaffe, Bruce E.

    2010-01-01

    This report describes a database of sedimentary characteristics of tsunami deposits derived from published accounts of tsunami deposit investigations conducted shortly after the occurrence of a tsunami. The database contains 228 entries, each entry containing data from up to 71 categories. It includes data from 51 publications covering 15 tsunamis distributed between 16 countries. The database encompasses a wide range of depositional settings including tropical islands, beaches, coastal plains, river banks, agricultural fields, and urban environments. It includes data from both local tsunamis and teletsunamis. The data are valuable for interpreting prehistorical, historical, and modern tsunami deposits, and for the development of criteria to identify tsunami deposits in the geologic record.

  16. Multi-chamber deposition system

    DOEpatents

    Jacobson, Richard L.; Jeffrey, Frank R.; Westerberg, Roger K.

    1989-10-17

    A system for the simultaneous deposition of different coatings onto a thin web within a large volume vacuum chamber is disclosed which chamber is provided with a plurality of deposition chambers in which the different layers are deposited onto the film as its moves from a supply roll to a finished take-up roll of coated web. The deposition chambers provided within the large vacuum chamber are provided with separate seals which minimize back diffusion of any dopant gas from adjacent deposition chambers.

  17. Multi-chamber deposition system

    DOEpatents

    Jacobson, Richard L.; Jeffrey, Frank R.; Westerberg, Roger K.

    1989-06-27

    A system for the simultaneous deposition of different coatings onto a thin web within a large volume vacuum chamber is disclosed which chamber is provided with a plurality of deposition chambers in which the different layers are deposited onto the film as its moves from a supply roll to a finished take-up roll of coated web. The deposition chambers provided within the large vacuum chamber are provided with separate seals which minimize back diffusion of any dopant gas from adjacent deposition chambers.

  18. Electrophoretic Deposition for Fabricating Microbatteries

    NASA Technical Reports Server (NTRS)

    West, William; Whitacre, Jay; Bugga, Ratnakumar

    2003-01-01

    An improved method of fabrication of cathodes of microbatteries is based on electrophoretic deposition. Heretofore, sputtering (for deposition) and the use of photoresist and liftoff (for patterning) have been the primary methods of fabricating components of microbatteries. The volume of active electrode material that can be deposited by sputtering is limited, and the discharge capacities of prior microbatteries have been limited accordingly. In addition, sputter deposition is slow. In contrast, electrophoretic deposition is much faster and has shown promise for increasing discharge capacities by a factor of 10, relative to those of microbatteries fabricated by prior methods.

  19. The Chilean nitrate deposits.

    USGS Publications Warehouse

    Ericksen, G.E.

    1983-01-01

    The nitrate deposits in the arid Atacama desert of northern Chile consist of saline-cemented surficial material, apparently formed in and near a playa lake that formerly covered the area. Many features of their distribution and chemical composition are unique. The author believes the principal sources of the saline constituents were the volcanic rocks of late Tertiary and Quaternary age in the Andes and that the nitrate is of organic origin. Possible sources of the nitrate, iodate, perchlorate and chromate are discussed. -J.J.Robertson

  20. Canyon Floor Deposits

    NASA Technical Reports Server (NTRS)

    2005-01-01

    [figure removed for brevity, see original site] Context image for PIA03598 Canyon Floor Deposits

    The layered and wind eroded deposits seen in this VIS image occur on the floor of Chandor Chasma.

    Image information: VIS instrument. Latitude 5.2S, Longitude 283.4E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  1. Radioactive deposits in California

    USGS Publications Warehouse

    Walker, George W.; Lovering, Tom G.

    1954-01-01

    Reconnaissance examination by Government geologists of many areas, mine properties, and prospects in California during the period between 1948 and 1953 has confirmed the presence of radioactive materials in place at more than 40 localities. Abnormal radioactivity at these localities is due to concentrations of primary and secondary uranium minerals, to radon gas, radium (?), and to thorium minerals. Of the known occurrences only three were thought to contain uranium oxide (uranitite or pitchblende), 4 contained uranium-bearing columbate, tantalate, or titanate minerals, 12 contained secondary uranium minerals, such as autunite, carnotite, and torbernite, one contained radon gas, 7 contained thorium minerals, and, at the remaining 16 localities, the source of the anomalous radiation was not positively determined. The occurrences in which uranium oxide has been tentatively identified include the Rathgeb mine (Calaveras County), the Yerih group of claims (San Bernardino County), and the Rainbow claim (Madera County). Occurrences of secondary uranium minerals are largely confined to the arid desert regions of south-eastern California including deposits in San Bernardino, Kern, Inyo, and Imperial Counties. Uranium-bearing columbate, tantalate, or titanate minerals have been reported from pegmatite and granitic rock in southeastern and eastern California. Thorium minerals have been found in vein deposits in eastern San Bernardino County and from pegmatites and granitic rocks in various parts of southeastern California; placer concentrations of thorium minerals are known from nearly all areas in the State that are underlain, in part, by plutonic crystalline rocks. The primary uranium minerals occur principally as minute accessory crystals in pegmatite or granitic rock, or with base-metal sulfide minerals in veins. Thorium minerals also occur as accessory crystals in pegmatite or granitic rock, in placer deposits derived from such rock, and, at Mountain Pass, in veins

  2. 20 CFR 703.306 - Kinds of negotiable securities that may be deposited; conditions of deposit; acceptance of deposits.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...' COMPENSATION ACT AND RELATED STATUTES INSURANCE REGULATIONS Authorization of Self-Insurers § 703.306 Kinds of negotiable securities that may be deposited; conditions of deposit; acceptance of deposits. A self-insurer or... deposited; conditions of deposit; acceptance of deposits. 703.306 Section 703.306 Employees' Benefits...

  3. 20 CFR 703.306 - Kinds of negotiable securities that may be deposited; conditions of deposit; acceptance of deposits.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...' COMPENSATION ACT AND RELATED STATUTES INSURANCE REGULATIONS Authorization of Self-Insurers § 703.306 Kinds of negotiable securities that may be deposited; conditions of deposit; acceptance of deposits. A self-insurer or... deposited; conditions of deposit; acceptance of deposits. 703.306 Section 703.306 Employees' Benefits...

  4. 20 CFR 703.306 - Kinds of negotiable securities that may be deposited; conditions of deposit; acceptance of deposits.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...' COMPENSATION ACT AND RELATED STATUTES INSURANCE REGULATIONS Authorization of Self-Insurers § 703.306 Kinds of negotiable securities that may be deposited; conditions of deposit; acceptance of deposits. A self-insurer or... deposited; conditions of deposit; acceptance of deposits. 703.306 Section 703.306 Employees' Benefits...

  5. 20 CFR 703.306 - Kinds of negotiable securities that may be deposited; conditions of deposit; acceptance of deposits.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...' COMPENSATION ACT AND RELATED STATUTES INSURANCE REGULATIONS Authorization of Self-Insurers § 703.306 Kinds of negotiable securities that may be deposited; conditions of deposit; acceptance of deposits. A self-insurer or... deposited; conditions of deposit; acceptance of deposits. 703.306 Section 703.306 Employees' Benefits...

  6. 20 CFR 703.306 - Kinds of negotiable securities that may be deposited; conditions of deposit; acceptance of deposits.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... AND RELATED STATUTES INSURANCE REGULATIONS Authorization of Self-Insurers § 703.306 Kinds of negotiable securities that may be deposited; conditions of deposit; acceptance of deposits. A self-insurer or... deposited; conditions of deposit; acceptance of deposits. 703.306 Section 703.306 Employees'...

  7. Acid deposition in Asia: Emissions, deposition, and ecosystem effects

    NASA Astrophysics Data System (ADS)

    Duan, Lei; Yu, Qian; Zhang, Qiang; Wang, Zifa; Pan, Yuepeng; Larssen, Thorjørn; Tang, Jie; Mulder, Jan

    2016-12-01

    We review and synthesize the current state of knowledge regarding acid deposition and its environmental effects across Asia. The extent and magnitude of acid deposition in Asia became apparent only about one decade after this issue was well described in Europe and North America. In addition to the temperate zone, much of eastern and southern Asia is situated in the tropics and subtropics, climate zones hitherto little studied with respect to the effects of high loads of acid deposition. Surface waters across Asia are generally not sensitive to the effects of acid deposition, whereas soils in some regions are sensitive to acidification due to low mineral weathering. However, soil acidification was largely neutralized by such processes as base cation deposition, nitrate (NO3-) denitrification, and sulfate (SO42-) adsorption. Accompanying the decrease in S deposition in recent years, N deposition is of increasing concern in Asia. The acidifying effect of N deposition may be more important than S deposition in well drained tropical/subtropical soils due to high SO42- adsorption. The risk of regional soil acidification is a major threat in Eastern Asia, indicated by critical load exceedance in large areas.

  8. Deposition and degradation of a volatile-rich layer in Utopia Planitia and implications for climate history on Mars

    NASA Astrophysics Data System (ADS)

    Morgenstern, Anne; Hauber, Ernst; Reiss, Dennis; van Gasselt, Stephan; Grosse, Guido; Schirrmeister, Lutz

    2007-06-01

    We investigate the surface morphology of a study area in western Utopia Planitia, Mars, which is characterized by a variety of landforms that resemble those of terrestrial periglacial landscapes. Polygonally fractured ground and thermokarst-like depressions are found to be located in a young mantling deposit with a thickness of several tens of meters. We observe a latitudinal dependence of the degradation of this mantling deposit. Larger depressions, whose floors reveal the underlying basement rocks, cover a higher fraction of the total terrain in the southern part of the study area than in the northern part, indicating a more intense degradation of the mantle in the south. All depressions have an asymmetric cross section in north-south direction, interpreted to be the result of the different solar radiation on differently oriented slopes. On the basis of our morphological observations, we develop a conceptual model for landscape evolution in western Utopia Planitia. It involves subaerial deposition of a layered, ice-rich mantle and its subsequent degradation by polygon formation and sublimation. A terrestrial analog to the polygonally fractured mantling deposit and its thermokarst-like depressions is the Siberian Ice Complex or ``Yedoma,'' which consists of subaerial ice-rich deposits and is connected to nonglaciated landscapes with highly continental cold-climatic environmental conditions. Our comparison suggests that no unusual or exotic processes need to be invoked to explain the current morphology of western Utopia. However, the young age of the deposition and degradation implies climatic excursions in the very recent past on Mars.

  9. Experimental reproduction of tsunami deposit

    NASA Astrophysics Data System (ADS)

    Yoshii, T.; Matsuyama, M.; Tanaka, S.

    2015-12-01

    Understanding the process of sediment transport and deposition under a tsunami inundation is essential to provide the credible information about potential tsunamis from tsunami deposits. Detections of tsunami deposit has contributed to reveal centuries-old record of tsunami incursions. However, our knowledge is still not enough for evaluating the scale of past tsunamis using deposits. In this study, a laboratory experiment was conducted to investigate the relationship between the hydraulic condition and sedimentological features of tsunami deposit. The large wave flume in CRIEPI, one of the largest wave flume in the world, which has 205 m length, 3.4 m width and 6 m depth was used. The sandy beach with uniform slope (1/50) were made in the flume. Sand dune of 0.2 high was placed near the shoreline. The tsunami was made by the wave generator which has 2.2 m stroke. The wave at the shore line has 0.6 m depth and the horizontal velocity reached up to 3.5 m/s. The incursion of the wave and its return flow completely washed out the dune and resulted in the deposition especially near the dune. The thickness of deposit shows landward thinning and fining, which has been widely confirmed by field observations. In addition, sedimentary structures of the deposit was investigated using the method similar to that used in geological survey such as core sampling and relief peel sampling. The obtained samples were investigated using a X-ray computed tomography. The obtained CT-images shows that most part of deposition consists two or more subsections divided by horizontal lamination although the deposition near the dune has drastic and complex change thickness and grain size. The subsections shows upward-fining and upward-coarsening which are been reported as common sedimentary structures of tsunami deposit from field surveys. Considering the similarity of sedimentary structures in the deposit reconstructed in this experiment and actual tsunami deposits, this experiment succeeded

  10. Chemical vapor deposition growth

    NASA Technical Reports Server (NTRS)

    Ruth, R. P.; Manasevit, H. M.; Kenty, J. L.; Moudy, L. A.; Simpson, W. I.; Yang, J. J.

    1976-01-01

    The chemical vapor deposition (CVD) method for the growth of Si sheet on inexpensive substrate materials is investigated. The objective is to develop CVD techniques for producing large areas of Si sheet on inexpensive substrate materials, with sheet properties suitable for fabricating solar cells meeting the technical goals of the Low Cost Silicon Solar Array Project. Specific areas covered include: (1) modification and test of existing CVD reactor system; (2) identification and/or development of suitable inexpensive substrate materials; (3) experimental investigation of CVD process parameters using various candidate substrate materials; (4) preparation of Si sheet samples for various special studies, including solar cell fabrication; (5) evaluation of the properties of the Si sheet material produced by the CVD process; and (6) fabrication and evaluation of experimental solar cell structures, using standard and near-standard processing techniques.

  11. Volcanology and mineral deposits

    USGS Publications Warehouse

    Lipman, P.W.

    1990-01-01

    In contrast, old volcanic regions, which host many of the world's major hydrothermal-vein, porphyry, and massive-sulfide ore deposits, have been studied mainly by economic geologists, regional stratigraphers, and structural geologists who have limited familiarity with the complexities of volcanic processes. Such "dead" volcanoes, ranging in age from a few million million years (tertiary) to a few billion years (Precambrian), are commonly incompletely and discontinuously preserved due to rapid erosion of originally high-standing volcanic edifices. They can be difficult to date reliably, especially in terms of the time scales of individual volcanic events, and are variably hydrothermally altered-impeding high-resolution petrologic and geochemical studies. Many volcanologists, geochemists, and geophysicists who work on active volcanoes accordingly have been reluctant to become involved in studies of such less tractable rocks. 

  12. High-Efficiency, Commercial Ready CdTe Solar Cells

    SciTech Connect

    Sites, James R.

    2015-11-19

    Colorado State’s F-PACE project explored several ways to increase the efficiency of CdTe solar cells and to better understand the device physics of those cells under study. Increases in voltage, current, and fill factor resulted in efficiencies above 17%. The three project tasks and additional studies are described in detail in the final report. Most cells studied were fabricated at Colorado State using an industry-compatible single-vacuum closed-space-sublimation (CSS) chamber for deposition of the key semiconductor layers. Additionally, some cells were supplied by First Solar for comparison purposes, and a small number of modules were supplied by Abound Solar.

  13. Idiosyncrasies of Physical Vapor Deposition Processes from Various Knudsen Cells for Quinacridone Thin Film Growth on Silicon Dioxide.

    PubMed

    Scherwitzl, Boris; Röthel, Christian; Jones, Andrew O F; Kunert, Birgit; Salzmann, Ingo; Resel, Roland; Leising, Günther; Winkler, Adolf

    2015-09-10

    Thin films of quinacridone deposited by physical vapor deposition on silicon dioxide were investigated by thermal desorption spectroscopy (TDS), mass spectrometry (MS), atomic force microscopy (AFM), specular and grazing incidence X-ray diffraction (XRD, GIXD), and Raman spectroscopy. Using a stainless steel Knudsen cell did not allow the preparation of a pure quinacridone film. TDS and MS unambiguously showed that in addition to quinacridone, desorbing at about 500 K (γ-peak), significant amounts of indigo desorbed at about 420 K (β-peak). The existence of these two species on the surface was verified by XRD, GIXD, and Raman spectroscopy. The latter spectroscopies revealed that additional species are contained in the films, not detected by TDS. In the film mainly composed of indigo a species was identified which we tentatively attribute to carbazole. The film consisting of mainly quinacridone contained in addition p-sexiphenyl. The reason for the various decomposition species effusing from the metal Knudsen cell is the comparably high sublimation temperature of the hydrogen bonded quinacridone. With special experimental methods and by using glass Knudsen-type cells we were able to prepare films which exclusively consist of molecules either corresponding to the β-peak or the γ-peak. These findings are of relevance for choosing the proper deposition techniques in the preparation of quinacridone films in the context of organic electronic devices.

  14. Idiosyncrasies of Physical Vapor Deposition Processes from Various Knudsen Cells for Quinacridone Thin Film Growth on Silicon Dioxide

    PubMed Central

    2015-01-01

    Thin films of quinacridone deposited by physical vapor deposition on silicon dioxide were investigated by thermal desorption spectroscopy (TDS), mass spectrometry (MS), atomic force microscopy (AFM), specular and grazing incidence X-ray diffraction (XRD, GIXD), and Raman spectroscopy. Using a stainless steel Knudsen cell did not allow the preparation of a pure quinacridone film. TDS and MS unambiguously showed that in addition to quinacridone, desorbing at about 500 K (γ-peak), significant amounts of indigo desorbed at about 420 K (β-peak). The existence of these two species on the surface was verified by XRD, GIXD, and Raman spectroscopy. The latter spectroscopies revealed that additional species are contained in the films, not detected by TDS. In the film mainly composed of indigo a species was identified which we tentatively attribute to carbazole. The film consisting of mainly quinacridone contained in addition p-sexiphenyl. The reason for the various decomposition species effusing from the metal Knudsen cell is the comparably high sublimation temperature of the hydrogen bonded quinacridone. With special experimental methods and by using glass Knudsen-type cells we were able to prepare films which exclusively consist of molecules either corresponding to the β-peak or the γ-peak. These findings are of relevance for choosing the proper deposition techniques in the preparation of quinacridone films in the context of organic electronic devices. PMID:26401189

  15. The deposit size frequency method for estimating undiscovered uranium deposits

    USGS Publications Warehouse

    McCammon, R.B.; Finch, W.I.

    1993-01-01

    The deposit size frequency (DSF) method has been developed as a generalization of the method that was used in the National Uranium Resource Evaluation (NURE) program to estimate the uranium endowment of the United States. The DSF method overcomes difficulties encountered during the NURE program when geologists were asked to provide subjective estimates of (1) the endowed fraction of an area judged favorable (factor F) for the occurrence of undiscovered uranium deposits and (2) the tons of endowed rock per unit area (factor T) within the endowed fraction of the favorable area. Because the magnitudes of factors F and T were unfamiliar to nearly all of the geologists, most geologists responded by estimating the number of undiscovered deposits likely to occur within the favorable area and the average size of these deposits. The DSF method combines factors F and T into a single factor (F??T) that represents the tons of endowed rock per unit area of the undiscovered deposits within the favorable area. Factor F??T, provided by the geologist, is the estimated number of undiscovered deposits per unit area in each of a number of specified deposit-size classes. The number of deposit-size classes and the size interval of each class are based on the data collected from the deposits in known (control) areas. The DSF method affords greater latitude in making subjective estimates than the NURE method and emphasizes more of the everyday experience of exploration geologists. Using the DSF method, new assessments have been made for the "young, organic-rich" surficial uranium deposits in Washington and idaho and for the solution-collapse breccia pipe uranium deposits in the Grand Canyon region in Arizona and adjacent Utah. ?? 1993 Oxford University Press.

  16. Momentum Deposition in Curvilinear Coordinates

    SciTech Connect

    Cleveland, Mathew Allen; Lowrie, Robert Byron; Rockefeller, Gabriel M.; Thompson, Kelly Glen; Wollaber, Allan Benton

    2015-08-03

    The momentum imparted into a material by thermal radiation deposition is an important physical process in astrophysics and inertial confinement fusion (ICF) simulations. In recent work we presented a new method of evaluating momentum deposition that relies on the combination of a time-averaged approximation and a numerical integration scheme. This approach robustly and efficiently evaluates the momentum deposition in spherical geometry. Future work will look to extend this approach to 2D cylindrical geometries.

  17. (Acidic deposition and the environment)

    SciTech Connect

    Garten, C.T.; Lindberg, S.E.; Van Miegroet, H.

    1990-10-24

    The travelers presented several papers at the Fourth International Conference on Acidic Deposition. These covered the following topics: atmospheric chemistry and deposition of airborne nitrogen compounds, soil solution chemistry in high-elevation spruce forests, and forest throughfall measurements for estimating total sulfur deposition to ecosystems. In addition, S. E. Lindberg was invited to organize and chair a conference session on Throughfall and Stemflow Experiments, and to present an invited lecture on Atmospheric Deposition and Canopy Interactions of Metals and Nitrogen in Forest Ecosystems: The Influence of Global Change'' at the 110th Anniversary Celebration of the Free University of Amsterdam.

  18. Characterization and depositional and evolutionary history of the Apollo 17 deep drill core

    NASA Technical Reports Server (NTRS)

    Morris, R. V.; Lauer, H. V., Jr.; Gose, W. A.

    1979-01-01

    With a depth resolution of about 0.5 cm, the stratigraphy of the approximately 3 m Apollo 17 deep drill core by measurement of the total FeO concentration is characterized along with the FMR surface exposure (maturity) index Is/FeO, the metallic iron concentration Fe-vsm, and the FMR linewidth delta-H. For stratigraphic characterization, the first two parameters are the most important. Most of the core is characterized by a FeO concentration of approximately 15.5 wt. %; there is a more mafic zone in the upper approximately 75 cm where the maximum FeO concentration is approximately 18.5 wt. %, and a more felsic zone between approximately 225 and 260 cm where the minimum FeO concentration is approximately 14.0%. As indicated by Is/FeO, most of the soil in the core is submature to mature; the only immature zone is located between approximately 20 and 60 cm and is one of the most distinctive features in the core. A two stage model for the depositional and evolutionary history of the Apollo 17 deep drill core is proposed: (1) deposition by one event approximately 110 m.y. ago or deposition by a sequence of closely spaced events initating a maximum of approximately 200 m.y. ago and terminating approximately 110 m.y. ago, (2) in situ reworking (gardening) to a depth of approximately 26 cm in the period between approximately 110 m.y. ago and the present day.

  19. Geochemistry of sedimentary ore deposits

    SciTech Connect

    Maynard, J. B.

    1983-01-01

    A text providing a sedimentological treatment of a study on ore deposits, and especially as related to geochemistry. Excellently documented (about 5000 citations). Well indexed with the index of deposits and localities separated. Contents, Iron. Copper and silver. Aluminum and nickel. Manganese. Uranium. Lead and zinc. Volcanic-sedimentary ores. Appendix. Indexes.

  20. MODELING DEPOSITION OF INHALED PARTICLES

    EPA Science Inventory

    Modeling Deposition of Inhaled Particles: ABSTRACT

    The mathematical modeling of the deposition and distribution of inhaled aerosols within human lungs is an invaluable tool in predicting both the health risks associated with inhaled environmental aerosols and the therapeut...

  1. Particle Deposition in Granular Media

    SciTech Connect

    Tien, C.

    1992-01-01

    Objective is to understand aerosol deposition from gas streams flowing through granular media; this is important to the design of granular filtration systems. The following investigations were carried out: transient behavior of granular filtration of aerosols, and stochastic simulation of aerosol deposition in granular media.

  2. Variable temperature semiconductor film deposition

    DOEpatents

    Li, Xiaonan; Sheldon, Peter

    1998-01-01

    A method of depositing a semiconductor material on a substrate. The method sequentially comprises (a) providing the semiconductor material in a depositable state such as a vapor for deposition on the substrate; (b) depositing the semiconductor material on the substrate while heating the substrate to a first temperature sufficient to cause the semiconductor material to form a first film layer having a first grain size; (c) continually depositing the semiconductor material on the substrate while cooling the substrate to a second temperature sufficient to cause the semiconductor material to form a second film layer deposited on the first film layer and having a second grain size smaller than the first grain size; and (d) raising the substrate temperature, while either continuing or not continuing to deposit semiconductor material to form a third film layer, to thereby anneal the film layers into a single layer having favorable efficiency characteristics in photovoltaic applications. A preferred semiconductor material is cadmium telluride deposited on a glass/tin oxide substrate already having thereon a film layer of cadmium sulfide.

  3. Variable temperature semiconductor film deposition

    DOEpatents

    Li, X.; Sheldon, P.

    1998-01-27

    A method of depositing a semiconductor material on a substrate is disclosed. The method sequentially comprises (a) providing the semiconductor material in a depositable state such as a vapor for deposition on the substrate; (b) depositing the semiconductor material on the substrate while heating the substrate to a first temperature sufficient to cause the semiconductor material to form a first film layer having a first grain size; (c) continually depositing the semiconductor material on the substrate while cooling the substrate to a second temperature sufficient to cause the semiconductor material to form a second film layer deposited on the first film layer and having a second grain size smaller than the first grain size; and (d) raising the substrate temperature, while either continuing or not continuing to deposit semiconductor material to form a third film layer, to thereby anneal the film layers into a single layer having favorable efficiency characteristics in photovoltaic applications. A preferred semiconductor material is cadmium telluride deposited on a glass/tin oxide substrate already having thereon a film layer of cadmium sulfide.

  4. Deposited films with improved microstructures

    DOEpatents

    Patten, James W.; Moss, Ronald W.; McClanahan, Edwin D.

    1984-01-01

    Methods for improving microstructures of line-of-sight deposited films are described. Columnar growth defects ordinarily produced by geometrical shadowing during deposition of such films are eliminated without resorting to post-deposition thermal or mechanical treatments. The native, as-deposited coating qualities, including homogeneity, fine grain size, and high coating-to-substrate adherence, can thus be retained. The preferred method includes the steps of emitting material from a source toward a substrate to deposit a coating non-uniformly on the substrate surface, removing a portion of the coating uniformly over the surface, again depositing material onto the surface, but from a different direction, and repeating the foregoing steps. The quality of line-of-sight deposited films such as those produced by sputtering, progressively deteriorates as the angle of incidence between the flux and the surface becomes increasingly acute. Depositing non-uniformly, so that the coating becomes progressively thinner as quality deteriorates, followed by uniformly removing some of the coating, such as by resputtering, eliminates the poor quality portions, leaving only high quality portions of the coating. Subsequently sputtering from a different direction applies a high quality coating to other regions of the surface. Such steps can be performed either simultaneously or sequentially to apply coatings of a uniformly high quality, closed microstructure to three-dimensional or large planar surfaces.

  5. Chemical vapor deposition growth

    NASA Technical Reports Server (NTRS)

    Ruth, R. P.; Manasevit, H. M.; Campbell, A. G.; Johnson, R. E.; Kenty, J. L.; Moudy, L. A.; Shaw, G. L.; Simpson, W. I.; Yang, J. J.

    1978-01-01

    The objective was to investigate and develop chemical vapor deposition (CVD) techniques for the growth of large areas of Si sheet on inexpensive substrate materials, with resulting sheet properties suitable for fabricating solar cells that would meet the technical goals of the Low Cost Silicon Solar Array Project. The program involved six main technical tasks: (1) modification and test of an existing vertical-chamber CVD reactor system; (2) identification and/or development of suitable inexpensive substrate materials; (3) experimental investigation of CVD process parameters using various candidate substrate materials; (4) preparation of Si sheet samples for various special studies, including solar cell fabrication; (5) evaluation of the properties of the Si sheet material produced by the CVD process; and (6) fabrication and evaluation of experimental solar cell structures, using impurity diffusion and other standard and near-standard processing techniques supplemented late in the program by the in situ CVD growth of n(+)/p/p(+) sheet structures subsequently processed into experimental cells.

  6. Chemical vapor deposition growth

    NASA Technical Reports Server (NTRS)

    Ruth, R. P.; Manasevit, H. M.; Johnson, R. E.; Kenty, J. L.; Moudy, L. A.; Simpson, W. I.; Yang, J. J.

    1976-01-01

    A laboratory type CVD reactor system with a vertical deposition chamber and sample pedestal heated by an external RF coil has been extensively modified by installation of mass flow controllers, automatic process sequence timers, and special bellows-sealed air-operated valves for overall improved performance. Various film characterization procedures, including classical metallography, SEM analyses, X ray diffraction analyses, surface profilometry, and electrical measurements (resistivity, carrier concentration, mobility, spreading resistance profiles, and minority-carrier lifetime by the C-V-t method) area used to correlate Si sheet properties with CVD parameters and substrate properties. Evaluation procedures and measurements are given. Experimental solar cell structures were made both in epitaxial Si sheet (on sapphire substrates) and in polycrystalline material on alumina substrates, the former to provide an indication of what might be an upper limit on performance of the latter. Preliminary results are given, as obtained in cell structures not specially designed to allow for the unique properties of the sheet material, and fabricated in material known to be far from optimum for photovoltaic performance. Low power conversion efficiencies have been obtained in the epitaxial as well as the polycrystalline Si sheet.

  7. Radioactive deposits of Nevada

    USGS Publications Warehouse

    Lovering, T.G.

    1954-01-01

    Thirty-five occurrences of radioactive rocks had been reported from Nevada prior to 1952. Twenty-five of these had been investigated by personnel of the U. S. Geological Surveyor of the U. S. Atomic Energy Commission. Of those investigated, uranium minerals were identified at 13 sites; two sites contained a thorium mineral (monazite); the source of radioactivity on nine properties was not ascertained, and one showed no abnormal radioactivity. Of the other reported occurrences, one is said to contain uraniferous hydrocarbons and nine are placers containing thorian monazite. Pitchblende occurs at two localities, the East Walker River area, and the Stalin's Present prospect, where it is sparsely disseminated in tabular bodies cutting granitic rocks. Other uranium minerals found in the state include: carnotite, tyuyamunite, autunite, torbernite, gummite, uranophane, kasolite, and an unidentified mineral which may be dumontite. Monazite is the only thorium mineral of possible economic importance that has been reported. From an economic standpoint, only four of the properties examined showed reserves of uranium ore in 1952; these are: the Green Monster mine, which shipped 5 tons of ore to Marysvale, Utah, during 1951; the Majuba Hill mine; the Stalin's Present prospect; and the West Willys claim in the Washington district. No estimate has been made of thorium reserves and no commercial deposits of thorium are known.

  8. Radioactive deposits of Nevada

    USGS Publications Warehouse

    Lovering, T.G.

    1953-01-01

    Thirty-five occurrences of radioactive rocks had been reported from Nevada prior to 1952. Twenty-five of these had been investigated by the U. S. Geological Survey and the U. S. Atomic Energy Commission. Of those investigated, uranium minerals were identified in 13; two contained a thorium mineral (monazite); the source of radioactivity on 7 properties was not ascertained; and one showed no abnormal radioactivity. Of the other reported occurrences, one is said to contain uraniferous hydrocarbons and 9 are placers containing thorian monazite. Pitchblende occurs at two localities; the East Walker River area, and the Stalin's Present prospect, where it is sparsely disseminated in tabular bodies cutting granitic rocks. Other uranium minerals found in the state include: carnotite, tyuyamunite, autunite, torbernite, gummite, uranophane, kasolite, and an unidentified mineral which may be dumontit. Monazite is the only thorium mineral of possible economic importance that has been reported. From an economic standpoint 9 only 4 of the properties examined showed reserves of uranium ore in 1952; these are: the Green Monster mine, which shipped 5 tons of ore to Marysvale, Utah, during 1951, the Majuba Hill mine, the Stalin's Present prospect, and the West Willys claim in the Washington district. Reserves of ore grade are small on all of these properties and probably cannot be developed commercially unless an ore-buying station is set up nearby. No estimate has been made of thorium reserves and no commercial deposits of thorium are known.

  9. Ni-Co laterite deposits

    USGS Publications Warehouse

    Marsh, Erin E.; Anderson, Eric D.

    2011-01-01

    Nickel-cobalt (Ni-Co) laterite deposits are an important source of nickel (Ni). Currently, there is a decline in magmatic Ni-bearing sulfide lode deposit resources. New efforts to develop an alternative source of Ni, particularly with improved metallurgy processes, make the Ni-Co laterites an important exploration target in anticipation of the future demand for Ni. This deposit model provides a general description of the geology and mineralogy of Ni-Co laterite deposits, and contains discussion of the influences of climate, geomorphology (relief), drainage, tectonism, structure, and protolith on the development of favorable weathering profiles. This model of Ni-Co laterite deposits represents part of the U.S. Geological Survey Mineral Resources Program's effort to update the existing models to be used for an upcoming national mineral resource assessment.

  10. Vapor deposition and characterization of supramolecular assemblies for integrated nonlinear optics

    NASA Astrophysics Data System (ADS)

    Esembeson, Bweh

    Very recently, some organic molecules have been developed that are very compact and have exceptionally high molecular polarizabilities which approach the fundamental quantum limit. Supramolecular assemblies created from such highly nonlinear molecules could find applications in integrated nonlinear optics such as all-optical signal processing, electro-optic modulators and frequency conversion. In this work, we have constructed a versatile vacuum deposition system for the creation of organic thin films from these molecules that can be sublimated without decomposition. We have used deposition temperatures of the order of 100--200°C in a high vacuum of 10-6--10 -7 Torrs. While some molecules showed a tendency to form polycrystalline films, others led to very high optical quality films, with a roughness of less than 10 nm over tens of micrometers and no grains detected down to a size of 2 nm, as seen in Atomic Force and Scanning Electron Microscopy studies. The best material we developed has a linear refractive index of 1.8 +/- 0.1 at 1.5 mum and an off-resonant third order susceptibility, chi (3), measured through Degenerate Four Wave Mixing, of 2 +/- 1 x 10-19 m2V-2 at 1.5 mum, a value three orders of magnitude larger than fused silica. This vapor deposited thin film may represent one of the best materials demonstrated to date whereby a large third order susceptibility, high optical quality, and simplicity of fabrication and integration are in perfect harmony for integrated nonlinear optical applications. We have used this novel organic material to create a hybrid organic/silicon-on-insulator waveguide that showed a record high nonlinearity coefficient of 10 5 W-1m-1 and has been used as an all-optical switch for demultiplexing a 120 Gbit/s data stream to 10 Gbit/s on a 6 mm long device.

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

    NASA Astrophysics Data System (ADS)

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

    2009-02-01

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

  12. TULSA UNIVERSITY PARAFFIN DEPOSITION PROJECTS

    SciTech Connect

    Michael Volk; Cem Sarica

    2003-10-01

    As oil and gas production moves to deeper and colder water, subsea multiphase production systems become critical for economic feasibility. It will also become increasingly imperative to adequately identify the conditions for paraffin precipitation and predict paraffin deposition rates to optimize the design and operation of these multiphase production systems. Although several oil companies have paraffin deposition predictive capabilities for single-phase oil flow, these predictive capabilities are not suitable for the multiphase flow conditions encountered in most flowlines and wellbores. For deepwater applications in the Gulf of Mexico, it is likely that multiphase production streams consisting of crude oil, produced water and gas will be transported in a single multiphase pipeline to minimize capital cost and complexity at the mudline. Existing single-phase (crude oil) paraffin deposition predictive tools are clearly inadequate to accurately design these pipelines because they do not account for the second and third phases, namely, produced water and gas. The objective of this program is to utilize the current test facilities at The University of Tulsa, as well as member company expertise, to accomplish the following: enhance our understanding of paraffin deposition in single and two-phase (gas-oil) flows; conduct focused experiments to better understand various aspects of deposition physics; and, utilize knowledge gained from experimental modeling studies to enhance the computer programs developed in the previous JIP for predicting paraffin deposition in single and two-phase flow environments. These refined computer models will then be tested against field data from member company pipelines. The following deliverables are scheduled during the first three projects of the program: (1) Single-Phase Studies, with three different black oils, which will yield an enhanced computer code for predicting paraffin deposition in deepwater and surface pipelines. (2) Two

  13. South Polar Layered Deposits

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Released 17 July 2003

    Similar to ice cores taken from Greenland and Antarctica, Mars also has fine-scale layered deposits in both the north and south polar regions. In this image from the south pole, alternating light and dark bands represent varying amounts of dust or sand mixed in with carbon dioxide ice. These layers are related in part to climate cycles caused by variations in the tilt of Mars' rotational axis, as well as other orbital variations that occur on geologic time scales (tens of thousands of years).

    Image information: VIS instrument. Latitude -80.1, Longitude 260.4 East (99.6 West). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  14. Deposition + Erosion = Textures

    NASA Technical Reports Server (NTRS)

    2003-01-01

    [figure removed for brevity, see original site]

    Released 7 May 2003

    Toward the westernmost extent of the Medusae Fossae Formation, a 5000+ km long belt of eroding sediments, the interleaving of erosional surfaces produces dramatic textural variations. In the lower third of this image, the cross-hatched MFF layer is being stripped back from a surface that was already heavily eroded before the MFF layer was deposited. Also, note the sinuous and, in places, dendritic ridges that are either linear dunes or inverted channels.

    Image information: VIS instrument. Latitude -3.9, Longitude 154.1East (205.9). 19 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  15. Glacial atmospheric phosphorus deposition

    NASA Astrophysics Data System (ADS)

    Kjær, Helle Astrid; Dallmayr, Remi; Gabrieli, Jacopo; Goto-Azuma, Kumiko; Hirabayashi, Motohiro; Svensson, Anders; Vallelonga, Paul

    2016-04-01

    Phosphorus in the atmosphere is poorly studied and thus not much is known about atmospheric phosphorus and phosphate transport and deposition changes over time, though it is well known that phosphorus can be a source of long-range nutrient transport, e.g. Saharan dust transported to the tropical forests of Brazil. In glacial times it has been speculated that transport of phosphorus from exposed shelves would increase the ocean productivity by wash out. However whether the exposed shelf would also increase the atmospheric load to more remote places has not been investigated. Polar ice cores offer a unique opportunity to study the atmospheric transport of aerosols on various timescales, from glacial-interglacial periods to recent anthropogenic influences. We have for the first time determined the atmospheric transport of phosphorus to the Arctic by means of ice core analysis. Both total and dissolved reactive phosphorus were measured to investigate current and past atmospheric transport of phosphorus to the Arctic. Results show that glacial cold stadials had increased atmospheric total phosphorus mass loads of 70 times higher than in the past century, while DRP was only increased by a factor of 14. In the recent period we find evidence of a phosphorus increase over the past 50 yrs in ice cores close to human occupation likely correlated to forest fires. References: Kjær, Helle Astrid, et al. "Continuous flow analysis method for determination of dissolved reactive phosphorus in ice cores." Environmental science & technology 47.21 (2013): 12325-12332. Kjær, Helle Astrid, et al. "Greenland ice cores constrain glacial atmospheric fluxes of phosphorus." Journal of Geophysical Research: Atmospheres120.20 (2015).

  16. The Repression of the Sublime

    ERIC Educational Resources Information Center

    Haronian, Frank

    1977-01-01

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

  17. Subsurface Structure in the Martian Polar Layered Deposits: The Deep Space 2 Impact Accelerometry Experiment

    NASA Technical Reports Server (NTRS)

    Moersch, J. E.; Lorenz, R. D.

    1998-01-01

    While primarily a technology demonstration mission, the New Millenium Mars Microprobes (also known as Deep Space 2, or simply DS2)will also provide the first in situ science measurements of the martian subsurface. The DS2 impact accelerometry experiment will provide both engineering data about the depth of probe emplacement and science data about the physical nature of the subsurface at the probes' landing sites. Little is known about the detailed physical properties or small-scale vertical structure of the subsurface at the DS2 landing site in the southern martian polar layered deposits. Imaging data from the Viking Orbiters and Mars Global Surveyor reveal alternating bands of light and dark material in this region with thicknesses at least as small as the limit of resolution, about 10 m. The overall composition of these layers is poorly constrained, but generally thought to be a mixture of dust and ice with the layers being caused by variations in the dust/ice ratio, or perhaps by dust deposits of different densities. Low thermal inertias in the region suggest that the top few centimeters of the surface are composed of a mantling of fine-grained dust. However, 3.5-cm radar returns indicate that the maximum depth of this dust is not greater than a few tens of centimeters. Thermal models generally agree that, while the layered deposits do provide a potential near-surface reservoir for ice, the uppermost few centimeters to meters in these regions are likely to be ice-free because of sublimation losses. Finally, while it is generally agreed that the layered deposits are the product of variations in the martian climate, no direct correlation has been made between band sequences and specific climate changes. Our intention is to shed light on some of these questions about the martian polar layered deposits by using the DS2 accelerometry experiment to determine the physical nature of the layered deposits, and to detect the presence of any subsurface layering of dust, ice

  18. Sputter Deposition of Metallic Sponges

    SciTech Connect

    Jankowski, A F; Hayes, J P

    2002-01-18

    Metallic films are grown with a sponge-like morphology in the as-deposited condition using planar magnetron sputtering. The morphology of the deposit is characterized by metallic continuity in three dimensions with continuous porosity on the sub-micron scale. The stabilization of the metallic sponge is directly correlated with a limited range for the sputter deposition parameters of working gas pressure and substrate temperature. This sponge-like morphology augments the features as generally understood in the classic zone models of growth for physical vapor deposits. Nickel coatings are deposited with working gas pressures up to 4 Pa and for substrate temperatures up to 1100 K. The morphology of the deposits is examined in plan and in cross-section with scanning electron microscopy. The parametric range of gas pressure and substrate temperature (relative to absolute melt point) for the deposition processing under which the metallic sponges are produced appear universal for many metals, as for example, including gold, silver, and aluminum.

  19. Jet aircraft fuel system deposits

    SciTech Connect

    Hazlett, R.N.; Hall, J.M.

    1981-03-01

    Deposits samples were from the valve cavity of a fuel nozzle of a CF6-50A engine, from the fuel manifold adjacent to the combustor nozzles of a TR-30 engine, fuel test devices, and heat exchange tubes, operated in the laboratories of the Naval Air Propulsion Center and the Air Force Aero Propulsion Laboratory. Carbon, hydrogen, nitrogen and oxygen in the deposits were determined with a Perkin Elmer Elemental Analyzer. Sulfur was determined on a separate sample by modifying ASTM method D3120-75. The high amount of oxygen, nitrogen and sulfur found in the deposits is noteworthy. The data reported generally corroborates the information from the literature. All of the deposits from the engines and the test devices point to the importance of compounds containing hereto atoms. The importance of oxidation in triggering solids formation has been reviewed. It would appear that the trace primary oxidation reactions occurring in a fuel system would be insufficient to give the high concentration of oxygen in the deposit. However, if the compounds undergoing oxidation were oxygen-containing compounds rather than hydrocarbons the high oxygen concentrations in the deposit would be more reasonable. The high enhancement factors observed, causes one to conclude that some nitrogen and sulfur compounds found in fuels are very susceptible to oxidation and subsequent deposit formation. The high concentrations of hereto atoms implies that the deposits have highly polar characteristics. Since such material would have little attraction for the non-polar fuel, the insolubility of deposits may be due primarily to polarity differences rather than high molecular weight.

  20. Holocene valley-floor deposition and incision in a small drainage basin in western Colorado, USA

    NASA Astrophysics Data System (ADS)

    Jones, Lawrence S.; Rosenburg, Margaret; Figueroa, Maria del Mar; McKee, Kathleen; Haravitch, Ben; Hunter, Jenna

    2010-09-01

    The valley floor of a 33.9 km 2 watershed in western Colorado experienced gradual sedimentation from before ˜ 6765 to ˜ 500 cal yr BP followed by deep incision, renewed aggradation, and secondary incision. In contrast, at least four terraces and widespread cut-and-fill architecture in the valley floor downstream indicate multiple episodes of incision and deposition occurred during the same time interval. The upper valley fill history is atypical compared to other drainages in the Colorado Plateau. One possible reason for these differences is that a bedrock canyon between the upper and lower valley prevented headward erosion from reaching the upper valley fill. Another possibility is that widespread, sand-rich, clay-poor lithologies in the upper drainage limited surface runoff and generally favored alluviation, whereas more clay-rich lithologies in the lower drainage resulted in increased surface runoff and more frequent incision. Twenty-two dates from valley fill charcoal indicate an approximate forest fire recurrence interval of several hundred years, similar to that from other studies in juniper-piñon woodlands. Results show that closely spaced vertical sampling of alluvium in headwater valleys where linkages between hillslope processes and fluvial activity are relatively direct can provide insight about the role of fires in alluvial chronologies of semi-arid watersheds.