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Sample records for potassium titanate whiskers

  1. Synthesis of potassium hexatitanate whiskers starting from metatitanic acid and potassium carbonate and sulfate by calcination method

    SciTech Connect

    Liu Chunyan; Yin Hengbo Liu Yumin; Ren Min; Wang Aili; Ge Chen; Yao Hengping; Feng Hui; Chen Jun; Jiang Tingshun

    2009-05-06

    Potassium hexatitanate whiskers were synthesized starting from metatitanic acid (H{sub 2}TiO{sub 3}), potassium carbonate and sulfate by calcination method. The effects of mole ratios of K{sub 2}CO{sub 3} to metatitanic acid (H{sub 2}TiO{sub 3}), content of potassium sulfate, and calcination temperature on the crystallinity and morphology of the resultant potassium titanate whiskers were investigated by X-ray diffraction and scanning electron microscopy. Well crystallized potassium hexatitanate whiskers with an average length of 7.3 {mu}m and an average diameter of 0.62 {mu}m were synthesized when the molar ratio of K{sub 2}CO{sub 3} to metatitanic acid was kept at 1:3.5 and the calcination temperature was up to 1150 deg. C. The presence of K{sub 2}SO{sub 4} favored the formation of thin potassium hexatitanate whiskers as compared to the absence of K{sub 2}SO{sub 4}. The whiteness and brightness of the synthesized potassium hexatitanate whiskers were comparable to that of rutile TiO{sub 2} pigment.

  2. An improved automotive brake lining using fibrous potassium titanate

    NASA Technical Reports Server (NTRS)

    Mansfield, J. A.; Halberstadt, M. L.; Riccitiello, S. R.; Rhee, S. K.

    1976-01-01

    Simultaneous fade reduction and wear improvement of a commercial automotive brake lining were achieved by adding fibrous potassium titanate. The dependence of friction and wear characteristics on quantitative variations in potassium titanate, asbestos, phenolic binder, and organic and inorganic modifiers was evaluated.

  3. A green synthesis of a layered titanate, potassium lithium titanate; lower temperature solid-state reaction and improved materials performance

    SciTech Connect

    Ogawa, Makoto; Morita, Masashi; Igarashi, Shota; Sato, Soh

    2013-10-15

    A layered titanate, potassium lithium titanate, with the size range from 0.1 to 30 µm was prepared to show the effects of the particle size on the materials performance. The potassium lithium titanate was prepared by solid-state reaction as reported previously, where the reaction temperature was varied. The reported temperature for the titanate preparation was higher than 800 °C, though 600 °C is good enough to obtain single-phase potassium lithium titanate. The lower temperature synthesis is cost effective and the product exhibit better performance as photocatalysts due to surface reactivity. - Graphical abstract: Finite particle of a layered titanate, potassium lithium titanate, was prepared by solid-state reaction at lower temperature to show modified materials performance. Display Omitted - Highlights: • Potassium lithium titanate was prepared by solid-state reaction. • Lower temperature reaction resulted in smaller sized particles of titanate. • 600 °C was good enough to obtain single phased potassium lithium titanate. • The product exhibited better performance as photocatalyst.

  4. Polyethylene/Potassium Titanate Separators For Ni/H2 Cells

    NASA Technical Reports Server (NTRS)

    Scott, William E.

    1995-01-01

    Experimental separators fabricated on paper-making machine. Two-layer, paperlike composite of polyethylene fibers and potassium titanate pigment shows promise for replacing asbestos as separator material in nickel/hydrogen electrochemical cells.

  5. Evaluation of potassium titanate as a component of alkaline fuel cell matrices

    NASA Technical Reports Server (NTRS)

    Post, R. E.

    1976-01-01

    Various forms of potassium titanate were found to have almost complete resistance to chemical attack in 45 wt % KOH at 150 C (423 K) for up to 9600 hours. Electron microscopy and X-ray diffraction disclosed important differences with respect to fibricity and stability. The octatitanate appeared to possess the best combination of properties. It was concluded that potassium titanate could be produced in a more asbestos-like form. Fiber dispersion is important in matrix manufacture.

  6. Effects of potassium titanate fiber on the wear of automotive brake linings

    NASA Technical Reports Server (NTRS)

    Halberstadt, M. L.; Mansfield, J. A.; Rhee, S. K.

    1977-01-01

    Asbestos reinforcing fiber in an automotive friction material was replaced by an experimental ingredient having better thermal stability, and the effects on wear and friction were studied. A friction materials test machine (SAE J661a) was used to determine friction and wear, under constant energy output conditions, as a function of temperature between 121 and 343 C (250 and 650 F). When potassium titanate fiber replaced one half of the asbestos in a standard commercial lining, with a 40 percent upward adjustment of phenolic resin content, wear above 204 C (400 F) was improved by 40% and friction by 30%. Tests on a full-scale inertial dynamometer supported the findings of the sample dynamometer tests. It was demonstrated that the potassium titanate fiber contributes directly to the improvement in wear and friction.

  7. Process for making transition metal nitride whiskers

    DOEpatents

    Bamberger, C.E.

    1988-04-12

    A process for making metal nitrides, particularly titanium nitride whiskers, using a cyanide salt as a reducing agent for a metal compound in the presence of an alkali metal oxide. Sodium cyanide, various titanates and titanium oxide mixed with sodium oxide react to provide titanium nitride whiskers that can be used as reinforcement to ceramic composites. 1 fig., 1 tab.

  8. Process for making transition metal nitride whiskers

    DOEpatents

    Bamberger, Carlos E.

    1989-01-01

    A process for making metal nitrides, particularly titanium nitride whiskers, using a cyanide salt as a reducing agent for a metal compound in the presence of an alkali metal oxide. Sodium cyanide, various titanates and titanium oxide mixed with sodium oxide react to provide titanium nitride whiskers that can be used as reinforcement to ceramic composites.

  9. Titan!

    NASA Astrophysics Data System (ADS)

    Matson, Dennis L.

    2010-05-01

    Cassini-Huygens achieved Saturnian orbit on July 1, 2004. The first order of business was the safe delivery of the Huygens atmospheric probe to Titan that took place on January 14, 2005. Huygens descended under parachute obtaining observations all the way down to a safe landing. It revealed Titan for the first time. Stunning are the similarities between Titan and the Earth. Viewing the lakes and seas, the fluvial terrain, the sand dunes and other features through the hazy, nitrogen atmosphere, brings to mind the geological processes that created analogous features on the Earth. On Titan frozen water plays the geological role of rock; liquid methane takes the role of terrestrial water. The atmospheres of both Earth and Titan are predominately nitrogen gas. Titan's atmosphere contains 1.5% methane and no oxygen. The surface pressure on Titan is 1.5 times the Earth's. There are aerosol layers and clouds that come and go. Now, as Saturn proceeds along its solar orbit, the seasons are changing. The effects upon the transport of methane are starting to be seen. A large lake in the South Polar Region seems to be filling more as winter onsets. Will the size and number of the lakes in the South grow during winter? Will the northern lakes and seas diminish or dry up as northern summer progresses? How will the atmospheric circulation change? Much work remains not only for Cassini but also for future missions. Titan has many different environments to explore. These require more capable instruments and in situ probes. This work was conducted at the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration.

  10. Method for manufacturing whisker preforms and composites

    DOEpatents

    Lessing, P.A.

    1995-11-07

    A process is disclosed for manufacturing Si{sub 3}N{sub 4}/SiAlON whiskers by mixing silicon carbide powder with aluminum nitride powder, adding impurities such as calcium oxide or potassium chloride to control whisker characteristics, forming the mixture in a boron nitrogen mold of desired shaped and hot isostatically pressing the formed mixture in a nitrogen environment to produce whiskers comprised substantially of SiAlON at the nucleating end of the whisker and Si{sub 3}N{sub 4} at the other end of the whisker. In one embodiment, reinforced composites are formed by impregnating the Si{sub 3}N{sub 4}/SiAlON whisker preform with a matrix material such as resin binders, liquid metals, intermetallics or ceramic materials.

  11. Method for manufacturing whisker preforms and composites

    DOEpatents

    Lessing, Paul A.

    1995-01-01

    A process for manufacturing Si.sub.3 N.sub.4 /SiAlON whiskers by mixing silicon carbide powder with aluminum nitride powder, adding impurities such as calcium oxide or potassium chloride to control whisker characteristics, forming the mixture in a boron nitrogen mold of desired shaped and hot isostatically pressing the formed mixture in a nitrogen environment to produce whiskers comprised substantially of SiAlON at the nucleating end of the whisker and Si.sub.3 N.sub.4 at the other end of the whisker. In one embodiment, reinforced composites are formed by impregnating the Si.sub.3 N.sub.4 /SiAlON whisker preform with a matrix material such as resin binders, liquid metals, intermetallics or ceramic materials.

  12. High performance Aurivillius phase sodium-potassium bismuth titanate lead-free piezoelectric ceramics with lithium and cerium modification

    NASA Astrophysics Data System (ADS)

    Wang, Chun-Ming; Wang, Jin-Feng

    2006-11-01

    The piezoelectric properties of the lithium and cerium modified A-site vacancies sodium-potassium bismuth titanate (NKBT) lead-free piezoceramics are investigated. The piezoelectric activity of NKBT ceramics is significantly improved by the modification of lithium and cerium. The Curie temperature TC, piezoelectric coefficient d33, and mechanical quality factor Qm for the NKBT ceramics modified with 0.10mol% (LiCe) are found to be 660°C, 25pC/N, and 3135, respectively. The Curie temperature gradually decreases from 675to650°C with the increase of (LiCe) modification. The dielectric spectroscopy shows that all the samples possess stable piezoelectric properties, demonstrating that the (LiCe) modified NKBT-based ceramics are the promising candidates for high temperature applications.

  13. Potassium

    MedlinePlus

    Potassium is essential for the proper functioning of the heart, kidneys, muscles, nerves, and digestive system. Usually the food you eat supplies all of the potassium you need. However, certain diseases (e.g., kidney ...

  14. Potassium

    MedlinePlus

    ... blackberries Root vegetables, such as carrots and potatoes Citrus fruits, such as oranges and grapefruit Your kidneys help to keep the right amount of potassium in your body. If you have chronic kidney disease, your kidneys may not remove extra potassium from ...

  15. Mullite Whiskers and Mullite-whisker Felt

    NASA Technical Reports Server (NTRS)

    Talmy, Inna G.; Haught, Deborah A.

    1993-01-01

    The Naval Surface Warfare Center has developed processes for the preparation of mullite (3(Al2O3)(dot)2(SiO2)) whiskers and mullite-whisker felt. Three patents on the technology were issued in 1990. The processes are based on chemical reactions between AlF3, Al2O3, and SiO2. The felt is formed in-situ during the processing of shaped powdered precursors. It consists of randomly oriented whiskers which are mutually intergrown forming a rigid structure. The microstructure and properties of the felt and size of the whiskers can be modified by varying the amount of Al2O3 in the starting mixture. Loose mullite whiskers can be used as a reinforcement for polymer-, metal-, and ceramic-matrix composites. The felt can be used as preforms for fabricating composite materials as well as for thermal insulation and high temperature, chemically stable filters for liquids (melts) and gases.

  16. Modified silicon carbide whiskers

    DOEpatents

    Tiegs, Terry N.; Lindemer, Terrence B.

    1991-01-01

    Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparaging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

  17. Modified silicon carbide whiskers

    DOEpatents

    Tiegs, T.N.; Lindemer, T.B.

    1991-05-21

    Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

  18. Modeling tin whisker growth.

    SciTech Connect

    Weinberger, Christopher Robert

    2013-08-01

    Tin, lead, and lead-tin solders are the most commonly used solders due to their low melting temperatures. However, due to the toxicity problems, lead must now be removed from solder materials. This has lead to the re-emergence of the issue of tin whisker growth. Tin whiskers are a microelectronic packaging issue because they can lead to shorts if they grow to sufficient length. However, the cause of tin whisker growth is still not well understood and there is lack of robust methods to determine when and if whiskering will be a problem. This report summarizes some of the leading theories on whisker growth and attempts to provide some ideas towards establishing the role microstructure plays in whisker growth.

  19. Nickel sulfide hollow whisker formation

    SciTech Connect

    Holcomb, G.R.; Cramer, S.D.

    1997-02-01

    Hollow, high-aspect-ratio nickel sulfide whiskers were formed during aqueous corrosion experiments at 250 C by the US Department of Energy. The whiskers grew radially from Teflon thread at the waterline in acidic sodium sulfate solutions containing chloride additions. The hollow morphology is consistent with that reported for the mineral millerite found in nature in hematite cavities. The data suggest that iron and chloride impurities are necessary for the observed whisker structure. Hollow nickel sulfide whiskers were observed only in high-temperature corrosion experiments conducted on stainless steels; they were not observed in similar experiments on nickel-base alloys.

  20. Titan's Methane Cycle is Closed

    NASA Astrophysics Data System (ADS)

    Hofgartner, J. D.; Lunine, J. I.

    2013-12-01

    Doppler tracking of the Cassini spacecraft determined a polar moment of inertia for Titan of 0.34 (Iess et al., 2010, Science, 327, 1367). Assuming hydrostatic equilibrium, one interpretation is that Titan's silicate core is partially hydrated (Castillo-Rogez and Lunine, 2010, Geophys. Res. Lett., 37, L20205). These authors point out that for the core to have avoided complete thermal dehydration to the present day, at least 30% of the potassium content of Titan must have leached into an overlying water ocean by the end of the core overturn. We calculate that for probable ammonia compositions of Titan's ocean (compositions with greater than 1% ammonia by weight), that this amount of potassium leaching is achievable via the substitution of ammonium for potassium during the hydration epoch. Formation of a hydrous core early in Titan's history by serpentinization results in the loss of one hydrogen molecule for every hydrating water molecule. We calculate that complete serpentinization of Titan's core corresponds to the release of more than enough hydrogen to reconstitute all of the methane atoms photolyzed throughout Titan's history. Insertion of molecular hydrogen by double occupancy into crustal clathrates provides a storage medium and an opportunity for ethane to be converted back to methane slowly over time--potentially completing a cycle that extends the lifetime of methane in Titan's surface atmosphere system by factors of several to an order of magnitude over the photochemically-calculated lifetime.

  1. Box-and-Whisker Plots.

    ERIC Educational Resources Information Center

    Larsen, Russell D.

    1985-01-01

    Box-and-whisker plots (which give rapid visualization of batches of data) can be effectively used to present diverse collections of data used in traditional first-year chemistry courses. Construction of box-and-whisker plots and their use with bond energy data and data on heats of formation and solution are discussed. (JN)

  2. Sensing device with whisker elements

    NASA Technical Reports Server (NTRS)

    Hartmann, Mitra J. (Inventor); Solomon, Joseph H. (Inventor)

    2010-01-01

    A sensing device includes an elongated whisker element having a flexible cantilever region and a base region where a change in moment or curvature is generated by bending of the cantilever region when it contacts an object. One or more sensor elements cooperatively associated with the whisker element provide one or more output signals that is/are representative of two orthogonal components of change in moment or curvature at the whisker base region to permit determination of object distance, fluid velocity profile, or object contour (shape) with accounting for lateral slip of the whisker element and frictional characteristics of the object. Multiple sensing devices can be arranged in arrays in a manner to sense object contour without or with adjustment for lateral slip.

  3. Sensing Device with Whisker Elements

    NASA Technical Reports Server (NTRS)

    Hartmann, Mitra J. (Inventor); Solomon, Joseph H. (Inventor)

    2013-01-01

    A sensing device includes an elongated whisker element having a flexible cantilever region and a base region where a change in moment or curvature is generated by bending of the cantilever region when it contacts an object. One or more sensor elements cooperatively associated with the whisker element provide one or more output signals that is/are representative of two orthogonal components of change in moment or curvature at the whisker base region to permit determination of object distance, fluid velocity profile, or object contour (shape) with accounting for lateral slip of the whisker element and frictional characteristics of the object. Multiple sensing devices can be arranged in arrays in a manner to sense object contour without or with adjustment for lateral slip.

  4. Whisker reinforced glass ceramic

    SciTech Connect

    Hirschfeld, D.A.; Brown, J.J. Jr.

    1996-06-03

    The process for making an in-situ whisker reinforced glass-ceramic that is up to 1.5 times as strong as conventional glass-ceramics was developed at Virginia Tech and patented in 1993. This technology has been identified as having commercial potential for use in high temperature heat exchanger applications for the electric power generation field by the National Center for Appropriate Technology (NCAT). This technology was licensed by MATVA, Inc., a small Virginia business, for further development. In particular, the goal of this project was to develop a property database and conduct initial testing of heat exchanger prototypes to demonstrate its potential application. This final report describes how the glass precursor was formed, physical properties of the glass-ceramic, techniques for making heat exchanger prototypes.

  5. Electron Microscopy Study of Tin Whisker Growth

    SciTech Connect

    Norton, Murray G.; Lebret, Joel

    2003-03-30

    The growth of tin whiskers formed on sputtered tin layers deposited on brass was studied using electron microscopy. The occurrence of whiskers appeared to be largely independent of the macroscopic stress state in the film; rather it was microscopic compressive stresses arising from the formation of an intermetallic phase that appeared to be the necessary precursor. Whisker morphology was a result of whether nucleation had occurred on single grains or on multiple grains. In the latter case, the whiskers had a fluted or striated surface. The formation of whiskers on electron transparent samples was demonstrated. These samples showed the whiskers were monocrystalline and defect free, and that the growth direction could be determined.

  6. Electron beam induced growth of tin whiskers

    SciTech Connect

    Vasko, A. C.; Karpov, V. G.; Warrell, G. R.; Parsai, E. I.; Shvydka, Diana

    2015-09-28

    We have investigated the influence of electron irradiation on tin whisker growth. Sputtered tin samples exposed to electron beam of 6 MeV energy exhibited fast whisker growth, while control samples did not grow any whiskers. The statistics of e-beam induced whiskers was found to follow the log-normal distribution. The observed accelerated whisker growth is attributed to electrostatic effects due to charges trapped in an insulating substrate. These results offer promise for establishing whisker-related accelerated life testing protocols.

  7. Flow sensing by pinniped whiskers

    PubMed Central

    Miersch, L.; Hanke, W.; Wieskotten, S.; Hanke, F. D.; Oeffner, J.; Leder, A.; Brede, M.; Witte, M.; Dehnhardt, G.

    2011-01-01

    Beside their haptic function, vibrissae of harbour seals (Phocidae) and California sea lions (Otariidae) both represent highly sensitive hydrodynamic receptor systems, although their vibrissal hair shafts differ considerably in structure. To quantify the sensory performance of both hair types, isolated single whiskers were used to measure vortex shedding frequencies produced in the wake of a cylinder immersed in a rotational flow tank. These measurements revealed that both whisker types were able to detect the vortex shedding frequency but differed considerably with respect to the signal-to-noise ratio (SNR). While the signal detected by sea lion whiskers was substantially corrupted by noise, harbour seal whiskers showed a higher SNR with largely reduced noise. However, further analysis revealed that in sea lion whiskers, each noise signal contained a dominant frequency suggested to function as a characteristic carrier signal. While in harbour seal whiskers the unique surface structure explains its high sensitivity, this more or less steady fundamental frequency might represent the mechanism underlying hydrodynamic reception in the fast swimming sea lion by being modulated in response to hydrodynamic stimuli impinging on the hair. PMID:21969689

  8. Material factors influencing metallic whisker growth

    NASA Astrophysics Data System (ADS)

    Rodekohr, Chad L.

    Whiskering refers to the formation of slender, long, metallic filaments, much thinner than a human hair, that grow on a metallic thin film surface. They are readily observed for pure and alloyed zinc (Zn), silver (Ag), cadmium (Cd), indium (In), and tin (Sn) surfaces. The longest reported whisker length is 4.5 mm long but most high-aspect ratio whiskers range from 1-500 mum. The focus of this research is upon Sn whiskers. Sn whiskers pose serious reliability problems for the electronics industry and are known to be the source of failure in a wide range of electronic devices, such as nuclear power facilities, heart pacemakers, commercial satellites, aviation radar, telecommunication equipment, and desktop computers. The problem with whiskering has been recently exacerbated by the worldwide shift to lead (Pb) free electronics and the continuing reduction in electrical contact pitches. A thorough understanding of the growth mechanism of Sn whiskers is urgently needed. Currently, there is no universally accepted model that explains the broad range of observations on whiskering. The goals of this research are: (1) to develop a more detailed understanding of the physical mechanisms leading to the initiation and growth of Sn whiskers and (2) to outline reasonable mitigation strategies that could be followed to reduce or eliminate the problem of Sn whiskers. The major contributions of this work are: (1) A reliable method for growing Sn whiskers with predictable incubation times has been developed and tested. (2) A surface oxide is not necessary for whisker growth. (3) Intermetallic compounds (IMC) are not necessary for whisker growth. (4) Smoother, not rougher, substrate surfaces promote whisker growth. (5) Whiskers grow under both compressive and tensile thin film stress states. (6) Whisker growth increases with externally applied compression and tension forces. (7) Sn whiskers are composed of pure Sn except for the expected thin, native Sn oxide on their surface. (8) For

  9. Process for making whiskers, fibers and flakes of transition metal compounds

    DOEpatents

    Bamberger, Carlos E.

    1992-01-01

    A process for making titanium and chromium nitrides of known morphology by reacting potassium titanate and chromium oxide in the gas phase with NH.sub.3. The products exhibit the same morphology as the starting material.

  10. Process for making whiskers, fibers and flakes of transition metal compounds

    DOEpatents

    Bamberger, C.E.

    1992-06-02

    A process for making titanium and chromium nitrides of known morphology by reacting potassium titanate and chromium oxide in the gas phase with NH[sub 3]. The products exhibit the same morphology as the starting material.

  11. Graphene Oxide Modified TiO2 Micro Whiskers and Their Photo Electrochemical Performance.

    PubMed

    Rambabu, Y; Jaiswal, Manu; Roy, Somnath C

    2016-05-01

    Harnessing the solar energy and producing clean fuel hydrogen through efficient photo-electrochemical water splitting has remained one of the most challenging endeavors in materials science. The core problem is to develop a suitable photo-catalyst material that absorbs a significant part of the solar spectrum and produces electron-hole pairs that can be easily separated without recombination. In the recent times, the composite of Titanium dioxide with graphene have been investigated to explore the advantages of both class of materials. Here we report on the photo-electrochemical properties of reduced graphene oxide functionalised TiO2 whiskers. The TiO2 whiskers are obtained from potassium titanium oxide (KTi8O16) synthesized through hydrothermal technique followed by ion exchange method and heat treatment. Graphene oxide was deposited on the as prepared TiO2 whiskers using hydrothermal method. As formed samples were characterized by Raman spectroscopy to confirm the presence of reduced graphene oxide (RGO) attached to TiO2 whiskers. Comparative photo electrochemical studies were carried out for TiO2 and reduced graphene oxide modified TiO2 whiskers. Among these, RGO modified TiO2 whiskers show significantly higher photo current density possibly due to enhancement in charge separation ability and longer electron life times. PMID:27483830

  12. Graphene Oxide Modified TiO2 Micro Whiskers and Their Photo Electrochemical Performance.

    PubMed

    Rambabu, Y; Jaiswal, Manu; Roy, Somnath C

    2016-05-01

    Harnessing the solar energy and producing clean fuel hydrogen through efficient photo-electrochemical water splitting has remained one of the most challenging endeavors in materials science. The core problem is to develop a suitable photo-catalyst material that absorbs a significant part of the solar spectrum and produces electron-hole pairs that can be easily separated without recombination. In the recent times, the composite of Titanium dioxide with graphene have been investigated to explore the advantages of both class of materials. Here we report on the photo-electrochemical properties of reduced graphene oxide functionalised TiO2 whiskers. The TiO2 whiskers are obtained from potassium titanium oxide (KTi8O16) synthesized through hydrothermal technique followed by ion exchange method and heat treatment. Graphene oxide was deposited on the as prepared TiO2 whiskers using hydrothermal method. As formed samples were characterized by Raman spectroscopy to confirm the presence of reduced graphene oxide (RGO) attached to TiO2 whiskers. Comparative photo electrochemical studies were carried out for TiO2 and reduced graphene oxide modified TiO2 whiskers. Among these, RGO modified TiO2 whiskers show significantly higher photo current density possibly due to enhancement in charge separation ability and longer electron life times.

  13. NASA Goddard Space Flight Center Tin Whisker (and Other Metal Whisker) Homepage

    NASA Technical Reports Server (NTRS)

    Brusse, Jay; Sampson, Mike; Leidecker, Henning; Kadesch, Jong

    2004-01-01

    This website provides information about tin whiskers and related research. The independent research performed during the past 50+ years is so vast that it is impractical to cover all aspects of tin whiskers in this one resource. Therefore, the absence of information in this website about a particular aspect of tin whiskers should NOT be construed as evidence of absence.

  14. Metal Whiskers: Failure Modes and Mitigation Strategies

    NASA Technical Reports Server (NTRS)

    Brusse, Jay A.; Leidecker, Henning

    2007-01-01

    Metal coatings especially tin, zinc and cadmium are unpredictably susceptible to the formation of electrically conductive, crystalline filaments referred to as metal whiskers. The use of such coatings in and around electrical systems presents a risk of electrical shorting. Examples of metal whisker formation are shown with emphasis on optical inspection techniques to improve probability of detection. The failure modes (i.e., electrical shorting behavior) associated with metal whiskers are described. Based on an almost 9- year long study, the benefits of polyurethane conformal coat (namely, Arathane 5750) to protect electrical conductors from whisker-induced short circuit anomalies is discussed.

  15. Ceramic composites reinforced with modified silicon carbide whiskers and method for modifying the whiskers

    DOEpatents

    Tiegs, Terry N.; Lindemer, Terrence B.

    1991-01-01

    Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparaging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

  16. Ceramic composites reinforced with modified silicon carbide whiskers and method for modifying the whiskers

    DOEpatents

    Tiegs, T.N.; Lindemer, T.B.

    1991-02-19

    Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

  17. Platelet composite coatings for tin whisker mitigation

    DOE PAGES

    Rohwer, Lauren E. S.; Martin, James E.

    2015-09-14

    In this study, reliable methods for tin whisker mitigation are needed for applications that utilize tin-plated commercial components. Tin can grow whiskers that can lead to electrical shorting, possibly causing critical systems to fail catastrophically. The mechanisms of tin whisker growth are unclear and this makes prediction of the lifetimes of critical components uncertain. The development of robust methods for tin whisker mitigation is currently the best approach to eliminating the risk of shorting. Current mitigation methods are based on unfilled polymer coatings that are not impenetrable to tin whiskers. In this paper we report tin whisker mitigation results formore » several filled polymer coatings. The whisker-penetration resistance of the coatings was evaluated at elevated temperature and high humidity and under temperature cycling conditions. The composite coatings comprised Ni and MgF2-coated Al/Ni/Al platelets in epoxy resin or silicone rubber. In addition to improved whisker mitigation, these platelet composites have enhanced thermal conductivity and dielectric constant compared with unfilled polymers.« less

  18. Platelet composite coatings for tin whisker mitigation

    SciTech Connect

    Rohwer, Lauren E. S.; Martin, James E.

    2015-09-14

    In this study, reliable methods for tin whisker mitigation are needed for applications that utilize tin-plated commercial components. Tin can grow whiskers that can lead to electrical shorting, possibly causing critical systems to fail catastrophically. The mechanisms of tin whisker growth are unclear and this makes prediction of the lifetimes of critical components uncertain. The development of robust methods for tin whisker mitigation is currently the best approach to eliminating the risk of shorting. Current mitigation methods are based on unfilled polymer coatings that are not impenetrable to tin whiskers. In this paper we report tin whisker mitigation results for several filled polymer coatings. The whisker-penetration resistance of the coatings was evaluated at elevated temperature and high humidity and under temperature cycling conditions. The composite coatings comprised Ni and MgF2-coated Al/Ni/Al platelets in epoxy resin or silicone rubber. In addition to improved whisker mitigation, these platelet composites have enhanced thermal conductivity and dielectric constant compared with unfilled polymers.

  19. Prealloyed catalyst for growing silicon carbide whiskers

    DOEpatents

    Shalek, Peter D.; Katz, Joel D.; Hurley, George F.

    1988-01-01

    A prealloyed metal catalyst is used to grow silicon carbide whiskers, especially in the .beta. form. Pretreating the metal particles to increase the weight percentages of carbon or silicon or both carbon and silicon allows whisker growth to begin immediately upon reaching growth temperature.

  20. Silicon Whisker and Carbon Nanofiber Composite Anode

    NASA Technical Reports Server (NTRS)

    Ma, Junqing (Inventor); Newman, Aron (Inventor); Lennhoff, John (Inventor)

    2015-01-01

    A carbon nanofiber can have a surface and include at least one crystalline whisker extending from the surface of the carbon nanofiber. A battery anode composition can be formed from a plurality of carbon nanofibers each including a plurality of crystalline whiskers.

  1. Boron carbide whiskers produced by vapor deposition

    NASA Technical Reports Server (NTRS)

    1965-01-01

    Boron carbide whiskers have an excellent combination of properties for use as a reinforcement material. They are produced by vaporizing boron carbide powder and condensing the vapors on a substrate. Certain catalysts promote the growth rate and size of the whiskers.

  2. Electric field stimulated growth of Zn whiskers

    NASA Astrophysics Data System (ADS)

    Niraula, D.; McCulloch, J.; Warrell, G. R.; Irving, R.; Karpov, V. G.; Shvydka, Diana

    2016-07-01

    We have investigated the impact of strong (˜104 V/cm) electric fields on the development of Zn whiskers. The original samples, with considerable whisker infestation were cut from Zn-coated steel floors and then exposed to electric fields stresses for 10-20 hours at room temperature. We used various electric field sources, from charges accumulated in samples irradiated by: (1) the electron beam of a scanning electron microscope (SEM), (2) the electron beam of a medical linear accelerator, and (3) the ion beam of a linear accelerator; we also used (4) the electric field produced by a Van der Graaf generator. In all cases, the exposed samples exhibited a considerable (tens of percent) increase in whiskers concentration compared to the control sample. The acceleration factor defined as the ratio of the measured whisker growth rate over that in zero field, was estimated to approach several hundred. The statistics of lengths of e-beam induced whiskers was found to follow the log-normal distribution known previously for metal whiskers. The observed accelerated whisker growth is attributed to electrostatic effects. These results offer promise for establishing whisker-related accelerated life testing protocols.

  3. Platelet Composite Coatings for Tin Whisker Mitigation

    NASA Astrophysics Data System (ADS)

    Rohwer, Lauren E. S.; Martin, James E.

    2015-11-01

    Reliable methods for tin whisker mitigation are needed for applications that utilize tin-plated commercial components. Tin can grow whiskers that can lead to electrical shorting, possibly causing critical systems to fail catastrophically. The mechanisms of tin whisker growth are unclear and this makes prediction of the lifetimes of critical components uncertain. The development of robust methods for tin whisker mitigation is currently the best approach to eliminating the risk of shorting. Current mitigation methods are based on unfilled polymer coatings that are not impenetrable to tin whiskers. In this paper we report tin whisker mitigation results for several filled polymer coatings. The whisker-penetration resistance of the coatings was evaluated at elevated temperature and high humidity and under temperature cycling conditions. The composite coatings comprised Ni and MgF2-coated Al/Ni/Al platelets in epoxy resin or silicone rubber. In addition to improved whisker mitigation, these platelet composites have enhanced thermal conductivity and dielectric constant compared with unfilled polymers.

  4. Tapered whiskers are required for active tactile sensation

    PubMed Central

    Hires, Samuel Andrew; Pammer, Lorenz; Svoboda, Karel; Golomb, David

    2013-01-01

    Many mammals forage and burrow in dark constrained spaces. Touch through facial whiskers is important during these activities, but the close quarters makes whisker deployment challenging. The diverse shapes of facial whiskers reflect distinct ecological niches. Rodent whiskers are conical, often with a remarkably linear taper. Here we use theoretical and experimental methods to analyze interactions of mouse whiskers with objects. When pushed into objects, conical whiskers suddenly slip at a critical angle. In contrast, cylindrical whiskers do not slip for biologically plausible movements. Conical whiskers sweep across objects and textures in characteristic sequences of brief sticks and slips, which provide information about the tactile world. In contrast, cylindrical whiskers stick and remain stuck, even when sweeping across fine textures. Thus the conical whisker structure is adaptive for sensor mobility in constrained environments and in feature extraction during active haptic exploration of objects and surfaces. DOI: http://dx.doi.org/10.7554/eLife.01350.001 PMID:24252879

  5. Tin Whiskers: A History of Documented Electrical System Failures

    NASA Technical Reports Server (NTRS)

    Leidecker, Henning; Brusse, Jay

    2006-01-01

    This viewgraph presentation reviews the history of tin and other metal whiskers, and the damage they have caused equipment. There are pictures of whiskers on various pieces of electronic equipment, and microscopic views of whiskers. There is also a chart with information on the documented failures associated with metal whiskers. There are also examples of on-orbit failures believed to be caused by whiskers.

  6. The probabilistic distribution of metal whisker lengths

    SciTech Connect

    Niraula, D. Karpov, V. G.

    2015-11-28

    Significant reliability concerns in multiple industries are related to metal whiskers, which are random high aspect ratio filaments growing on metal surfaces and causing shorts in electronic packages. We derive a closed form expression for the probabilistic distribution of metal whisker lengths. Our consideration is based on the electrostatic theory of metal whiskers, according to which whisker growth is interrupted when its tip enters a random local “dead region” of a weak electric field. Here, we use the approximation neglecting the possibility of thermally activated escapes from the “dead regions,” which is later justified. We predict a one-parameter distribution with a peak at a length that depends on the metal surface charge density and surface tension. In the intermediate range, it fits well the log-normal distribution used in the experimental studies, although it decays more rapidly in the range of very long whiskers. In addition, our theory quantitatively explains how the typical whisker concentration is much lower than that of surface grains. Finally, it predicts the stop-and-go phenomenon for some of the whiskers growth.

  7. Whiskers aid anemotaxis in rats.

    PubMed

    Yu, Yan S W; Graff, Matthew M; Bresee, Chris S; Man, Yan B; Hartmann, Mitra J Z

    2016-08-01

    Observation of terrestrial mammals suggests that they can follow the wind (anemotaxis), but the sensory cues underlying this ability have not been studied. We identify a significant contribution to anemotaxis mediated by whiskers (vibrissae), a modality previously studied only in the context of direct tactile contact. Five rats trained on a five-alternative forced-choice airflow localization task exhibited significant performance decrements after vibrissal removal. In contrast, vibrissal removal did not disrupt the performance of control animals trained to localize a light source. The performance decrement of individual rats was related to their airspeed threshold for successful localization: animals that found the task more challenging relied more on the vibrissae for localization cues. Following vibrissal removal, the rats deviated more from the straight-line path to the air source, choosing sources farther from the correct location. Our results indicate that rats can perform anemotaxis and that whiskers greatly facilitate this ability. Because air currents carry information about both odor content and location, these findings are discussed in terms of the adaptive significance of the interaction between sniffing and whisking in rodents. PMID:27574705

  8. Whiskers aid anemotaxis in rats

    PubMed Central

    Yu, Yan S. W.; Graff, Matthew M.; Bresee, Chris S.; Man, Yan B.; Hartmann, Mitra J. Z.

    2016-01-01

    Observation of terrestrial mammals suggests that they can follow the wind (anemotaxis), but the sensory cues underlying this ability have not been studied. We identify a significant contribution to anemotaxis mediated by whiskers (vibrissae), a modality previously studied only in the context of direct tactile contact. Five rats trained on a five-alternative forced-choice airflow localization task exhibited significant performance decrements after vibrissal removal. In contrast, vibrissal removal did not disrupt the performance of control animals trained to localize a light source. The performance decrement of individual rats was related to their airspeed threshold for successful localization: animals that found the task more challenging relied more on the vibrissae for localization cues. Following vibrissal removal, the rats deviated more from the straight-line path to the air source, choosing sources farther from the correct location. Our results indicate that rats can perform anemotaxis and that whiskers greatly facilitate this ability. Because air currents carry information about both odor content and location, these findings are discussed in terms of the adaptive significance of the interaction between sniffing and whisking in rodents. PMID:27574705

  9. Whiskers aid anemotaxis in rats.

    PubMed

    Yu, Yan S W; Graff, Matthew M; Bresee, Chris S; Man, Yan B; Hartmann, Mitra J Z

    2016-08-01

    Observation of terrestrial mammals suggests that they can follow the wind (anemotaxis), but the sensory cues underlying this ability have not been studied. We identify a significant contribution to anemotaxis mediated by whiskers (vibrissae), a modality previously studied only in the context of direct tactile contact. Five rats trained on a five-alternative forced-choice airflow localization task exhibited significant performance decrements after vibrissal removal. In contrast, vibrissal removal did not disrupt the performance of control animals trained to localize a light source. The performance decrement of individual rats was related to their airspeed threshold for successful localization: animals that found the task more challenging relied more on the vibrissae for localization cues. Following vibrissal removal, the rats deviated more from the straight-line path to the air source, choosing sources farther from the correct location. Our results indicate that rats can perform anemotaxis and that whiskers greatly facilitate this ability. Because air currents carry information about both odor content and location, these findings are discussed in terms of the adaptive significance of the interaction between sniffing and whisking in rodents.

  10. Contact Whiskers for Millimeter Wave Diodes

    NASA Technical Reports Server (NTRS)

    Kerr, A. R.; Grange, J. A.; Lichtenberger, J. A.

    1978-01-01

    Several techniques are investigated for making short conical tips on wires (whiskers) used for contacting millimeter-wave Schottky diodes. One procedure, using a phosphoric and chromic acid etching solution (PCE), is found to give good results on 12 microns phosphor-bronze wires. Full cone angles of 60 degrees-80 degrees are consistently obtained, compared with the 15 degrees-20 degrees angles obtained with the widely used sodium hydroxide etch. Methods are also described for cleaning, increasing the tip diameter (i.e. blunting), gold plating, and testing the contact resistance of the whiskers. The effects of the whisker tip shape on the electrical resistance, inductance, and capacitance of the whiskers are studied, and examples given for typical sets of parameters.

  11. Space Shuttle Program Tin Whisker Mitigation

    NASA Technical Reports Server (NTRS)

    Nishimi, Keith

    2007-01-01

    The discovery of tin whiskers (TW) on space shuttle hardware led to a program to investigate and removal and mitigation of the source of the tin whiskers. A Flight Control System (FCS) avionics box failed during vehicle testing, and was routed to the NASA Shuttle Logistics Depot for testing and disassembly. The internal inspection of the box revealed TW growth visible without magnification. The results of the Tiger Team that was assembled to investigate and develop recommendations are reviewed in this viewgraph presentation.

  12. Growth process of Cu{sub 2}Al{sub 6}B{sub 4}O{sub 17} whiskers

    SciTech Connect

    Zhu Chengcai; Nai Xueying; Zhu Donghai; Guo Fengqin; Zhang Yongxing; Li Wu

    2013-01-15

    The reactions occurred and growth process in the preparation of copper aluminum borate (Cu{sub 2}Al{sub 6}B{sub 4}O{sub 17}) whiskers based on flux method (Al{sub 2}(SO{sub 4}){sub 3}/CuSO{sub 4}/H{sub 3}BO{sub 3} as raw materials, K{sub 2}SO{sub 4} as flux) were investigated. The thermogravimetric and differential scanning calorimetry analysis (TG-DSC), inductively coupled plasma atomic emission spectrum analysis (ICP-AES) and X-ray diffraction analysis (XRD) results of reactants mixture quenched at various temperatures and phase diagrams of K{sub 2}SO{sub 4}-Al{sub 2}(SO{sub 4}){sub 3} system and B{sub 2}O{sub 3}-Al{sub 2}O{sub 3} system showed that the reaction process proceeds through three steps: the formation and decomposition of two different kinds of potassium aluminum sulfate (K{sub 3}Al(SO{sub 4}){sub 3} and KAl(SO{sub 4}){sub 2}); the formation of aluminum borate (Al{sub 4}B{sub 2}O{sub 9}) and decomposition of copper sulfate (CuSO{sub 4}) and boric acid (H{sub 3}BO{sub 3}); growth and formation of copper aluminum borate (Cu{sub 2}Al{sub 6}B{sub 4}O{sub 17}) whiskers. The scanning electron microscopy (SEM) analysis results indicated that morphology in growth of Cu{sub 2}Al{sub 6}B{sub 4}O{sub 17} whiskers develops through three stages: nanoparticles, fan-shaped whiskers and agminate-needlelike whiskers. - Graphical abstract: The morphology in growth of Cu{sub 2}Al{sub 6}B{sub 4}O{sub 17} whiskers develops through three stages: nanoparticles, fan-shaped whiskers and agminate-needlelike whiskers. Highlights: Black-Right-Pointing-Pointer Reaction process in the preparation of Cu{sub 2}Al{sub 6}B{sub 4}O{sub 17} whiskers was researched systematically. Black-Right-Pointing-Pointer Crystal growth mechanism of Cu{sub 2}Al{sub 6}B{sub 4}O{sub 17} whiskers was proposed by theory and experiments. Black-Right-Pointing-Pointer Properties of Cu{sub 2}Al{sub 6}B{sub 4}O{sub 17} were analyzed by instruments, such as TG-DSC, ICP-AES, XRD and SEM.

  13. Potassium Counts.

    ERIC Educational Resources Information Center

    Gipps, John

    1995-01-01

    Presents an activity to determine whether the radioactivity of a pure potassium salt is directly proportional to the amount of potassium in it and whether this could be used as a method of analysis for potassium in a solid. (MKR)

  14. Methods for fast, reliable growth of Sn whiskers

    NASA Astrophysics Data System (ADS)

    Bozack, M. J.; Snipes, S. K.; Flowers, G. N.

    2016-10-01

    We report several methods to reliably grow dense fields of high-aspect ratio tin whiskers for research purposes in a period of days to weeks. The techniques offer marked improvements over previous means to grow whiskers, which have struggled against the highly variable incubation period of tin whiskers and slow growth rate. Control of the film stress is the key to fast-growing whiskers, owing to the fact that whisker incubation and growth are fundamentally a stress-relief phenomenon. The ability to grow high-density fields of whiskers (103-106/cm2) in a reasonable period of time (days, weeks) has accelerated progress in whisker growth and aided in development of whisker mitigation strategies.

  15. Radial furnace shows promise for growing straight boron carbide whiskers

    NASA Technical Reports Server (NTRS)

    Feingold, E.

    1967-01-01

    Radial furnace, with a long graphite vaporization tube, maintains a uniform thermal gradient, favoring the growth of straight boron carbide whiskers. This concept seems to offer potential for both the quality and yield of whiskers.

  16. Tensile Behavior of Single-Crystal Tin Whiskers

    NASA Astrophysics Data System (ADS)

    Singh, S. S.; Sarkar, R.; Xie, H.-X.; Mayer, C.; Rajagopalan, J.; Chawla, N.

    2014-04-01

    The growth of metallic (predominantly Sn) whiskers from pure metallic platings has been studied for over 50 years. While the phenomenon of Sn whiskering has been studied for decades, very little is known about the mechanical properties of these materials. This can be attributed to the difficulty in handling, gripping, and testing such fine-diameter and high-aspect-ratio whiskers. We report on the stress-strain behavior of Sn whiskers inside a dual-beam focused ion beam (FIB) with a scanning electron microscope (SEM). Lift-out of the whiskers was conducted in situ in the FIB, and the whiskers were tested using a microelectromechanical system tensile testing stage. Using this technique, the whiskers had minimum exposure to ambient air and were not handled by hand. SEM images after fracture enabled reliable calculation of the whisker cross-sectional area. Tests on two different whiskers revealed relatively high tensile strengths of 720 MPa and 880 MPa, respectively, and a limited strain to failure of ˜2% to 3%. For both whiskers, the Young's modulus was between 42 GPa and 45 GPa. It is interesting to note that the whiskers were quite strong and had limited ductility. These findings are intriguing and provide a basis for further work to understand the effect of Sn whisker mechanical properties on short circuits in electronics.

  17. Whisker Formation on SAC305 Soldered Assemblies

    NASA Astrophysics Data System (ADS)

    Meschter, S.; Snugovsky, P.; Bagheri, Z.; Kosiba, E.; Romansky, M.; Kennedy, J.; Snugovsky, L.; Perovic, D.

    2014-11-01

    This article describes the results of a whisker formation study on SAC305 assemblies, evaluating the effects of lead-frame materials and cleanliness in different environments: low-stress simulated power cycling (50-85°C thermal cycling), thermal shock (-55°C to 85°C), and high temperature/high humidity (85°C/85% RH). Cleaned and contaminated small outline transistors, large leaded quad flat packs (QFP), plastic leaded chip carrier packages, and solder balls with and without rare earth elements (REE) were soldered to custom designed test boards with Sn3Ag0.5Cu (SAC305) solder. After assembly, all the boards were cleaned, and half of them were recontaminated (1.56 µg/cm2 Cl-). Whisker length, diameter, and density were measured. Detailed metallurgical analysis on components before assembly and on solder joints before and after testing was performed. It was found that whiskers grow from solder joint fillets, where the thickness is less than 25 µm, unless REE was present. The influence of lead-frame and solder ball material, microstructure, cleanliness, and environment on whisker characteristics is discussed. This article provides detailed metallurgical observations and select whisker length data obtained during this multiyear testing program.

  18. Understanding the movements of metal whiskers

    NASA Astrophysics Data System (ADS)

    Karpov, V. G.

    2015-06-01

    Metal whiskers often grow across leads of electric equipment causing short circuits and raising significant reliability issues. Their nature remains a mystery after several decades of research. It was observed that metal whiskers exhibit large amplitude movements under gentle air flow or, according to some testimonies, without obvious stimuli. Understanding the physics behind that movements would give additional insights into the nature of metal whiskers. Here, we quantitatively analyze possible mechanisms of the observed movements: (1) minute air currents; (2) Brownian motion due to random bombardments with the air molecules; (3) mechanically caused movements, such as (a) transmitted external vibrations, and (b) torque exerted due to material propagation along curved whiskers (the garden hose instability); (4) time dependent electric fields due to diffusion of ions; and (5) non-equilibrium electric fields making it possible for some whiskers to move. For all these mechanisms, we provide numerical estimates. Our conclusion is that the observed movements are likely due to the air currents or electric recharging caused by external light or similar factors.

  19. Ceramic composites reinforced with modified silicon carbide whiskers

    DOEpatents

    Tiegs, Terry N.; Lindemer, Terrence B.

    1990-01-01

    Silicon carbide whisker-reinforced ceramic composites are fabricated in a highly reproducible manner by beneficating the surfaces of the silicon carbide whiskers prior to their usage in the ceramic composites. The silicon carbide whiskers which contain considerable concentrations of surface oxides and other impurities which interact with the ceramic composite material to form a chemical bond are significantly reduced so that only a relatively weak chemical bond is formed between the whisker and the ceramic material. Thus, when the whiskers interact with a crack propagating into the composite the crack is diverted or deflected along the whisker-matrix interface due to the weak chemical bonding so as to deter the crack propagation through the composite. The depletion of the oxygen-containing compounds and other impurities on the whisker surfaces and near surface region is effected by heat treating the whiskers in a suitable oxygen sparaging atmosphere at elevated temperatures. Additionally, a sedimentation technique may be utilized to remove whiskers which suffer structural and physical anomalies which render them undesirable for use in the composite. Also, a layer of carbon may be provided on the surface of the whiskers to further inhibit chemical bonding of the whiskers to the ceramic composite material.

  20. NASA GSFC Tin Whisker Homepage http://nepp.nasa.gov/whisker

    NASA Technical Reports Server (NTRS)

    Shaw, Harry

    2000-01-01

    The NASA GSFC Tin Whisker Homepage provides general information and GSFC Code 562 experimentation results regarding the well known phenomenon of tin whisker formation from pure tin plated substrates. The objective of this www site is to provide a central repository for information pertaining to this phenomenon and to provide status of the GSFC experiments to understand the behavior of tin whiskers in space environments. The Tin Whisker www site is produced by Code 562. This www site does not provide information pertaining to patented or proprietary information. All of the information contained in this www site is at the level of that produced by industry and university researchers and is published at international conferences.

  1. Whisker encoding of mechanical events during active tactile exploration

    PubMed Central

    Boubenec, Yves; Shulz, Daniel E.; Debrégeas, Georges

    2012-01-01

    Rats use their whiskers to extract a wealth of information about their immediate environment, such as the shape, position or texture of an object. The information is conveyed to mechanoreceptors located within the whisker follicle in the form of a sequence of whisker deflections induced by the whisker/object contact interaction. How the whiskers filter and shape the mechanical information and effectively participate in the coding of tactile features remains an open question to date. In the present article, a biomechanical model was developed that provides predictions of the whisker dynamics during active tactile exploration, amenable to quantitative experimental comparison. This model is based on a decomposition of the whisker profile into a slow, quasi-static sequence and rapid resonant small-scale vibrations. It was applied to the typical situation of a rat actively whisking across a solid object. Having derived the quasi-static sequence of whisker deformation, the resonant properties of the whisker were analyzed, taking into account the boundary conditions imposed by the whisker/surface contact. We then focused on two elementary mechanical events that are expected to trigger significant neural responses, namely (1) the whisker/object first contact and (2) the whisker detachment from the object. Both events were found to trigger a deflection wave propagating upward to the mystacial pad at constant velocity of ≈3–5 m/s. This yielded a characteristic mechanical signature at the whisker base, in the form of a large peak of negative curvature occurring ≈4 ms after the event has been triggered. The dependence in amplitude and lag of this mechanical signal with the main contextual parameters (such as radial or angular distance) was investigated. The model was validated experimentally by comparing its predictions to high-speed video recordings of shock-induced whisker deflections performed on anesthetized rats. The consequences of these results on possible tactile

  2. Growth of hollow nickel fluoride whiskers

    SciTech Connect

    Petrov, S. V.; Orekhov, Yu. F.; Fedorov, P. P.

    2009-07-15

    Hollow nickel fluoride whiskers have been obtained by condensation from the vapor phase onto a platinum substrate in a flow of hydrogen fluoride. Crystals up to 5 mm in length have a square cross section with a 300 {+-} 30-{mu}m side. The wall thickness is 85 {+-} 20 {mu}m.

  3. Titan Meteorology

    NASA Astrophysics Data System (ADS)

    Mitchell, Jonathan

    2012-04-01

    Titan’s methane clouds have received much attention since they were first discovered spectroscopically (Griffith et al. 1998). Titan's seasons evolve slowly, and there is growing evidence of a seasonal response in the regions of methane cloud formation (e.g. Rodriguez et al. 2009). A complete, three-dimensional view of Titan’s clouds is possible through the determination of cloud-top heights from Cassini images (e.g., Ádámkovics et al. 2010). Even though Titan’s surface is warmed by very little sunlight, we now know Titan’s methane clouds are convective, evolving through tens of kilometers of altitude on timescales of hours to days with dynamics similar to clouds that appear on Earth (Porco et al. 2005). Cassini ISS has also shown evidence of rain storms on Titan that produce surface accumulation of methane (Turtle et al. 2009). Most recently, Cassini has revealed a 1000-km-scale, arrow-shaped cloud at the equator followed by changes that appear to be evidence of surface precipitation (Turtle et al. 2011b). Individual convective towers simulated with high fidelity indicate that surface convergence of methane humidity and dynamic lifting are required to trigger deep, precipitating convection (e.g. Barth & Rafkin 2010). The global expanses of these cloud outbursts, the evidence for surface precipitation, and the requirement of dynamic convergence and lifting at the surface to trigger deep convection motivate an analysis of storm formation in the context of Titan’s global circulation. I will review our current understanding of Titan’s methane meteorology using Cassini and ground-based observations and, in particular, global circulation model simulations of Titan’s methane cycle. When compared with cloud observations, our simulations indicate an essential role for planetary-scale atmospheric waves in organizing convective storms on large scales (Mitchell et al. 2011). I will end with predictions of Titan’s weather during the upcoming northern

  4. Tin Whisker Formation - A Stress Relieve Phenomenon

    SciTech Connect

    Dittes, M.; Oberndorff, P.; Crema, P.; Su, P.

    2006-02-07

    With the move towards lead-free electronics also the solderable finish of electronic components' terminations are converted. While the typical finish was containing 5 % to 20 % lead (Pb) and thus was almost whisker free, lead (Pb)-free finishes such as pure tin or high tin alloys are rather prone to grow whisker. These whiskers are spontaneous protrusions that grow to a significant length of up to millimeters with a typical diameter in the range of few microns and are suspect to cause shorts in electronic assemblies. The latest details of the mechanisms are not yet understood. However it appears to be well established that the driving force for tin whisker growth is a compressive stress in the tin layer and that this stress is released by whisker formation. Besides the mechanism for whisker growth therefore the mechanism of the stress induction is of interest. The origin of that stress may have multiple sources. Among others the most important one is the volume increase within the tin layer due the formation of intermetallics at the interface to the base material. This applies to all copper based material. For base materials with a coefficient of thermal expansion (cte) significantly different from the tin finish another mechanism plays the dominant role. This is the induction of stress during thermal cycling due to the different expansion of the materials with every temperature change. Another mechanism for stress induction may be the oxidation of the finish, which also leads to a local volume increase. Based on the knowledge of stress induction various mitigation strategies can be deducted. Most common is the introduction of a diffusion barrier (e.g. Ni) in order to prevent the growth of the Cu-Sn intermetallics, the controlled growth of Cu-Sn intermetallics in order to prevent their irregularity or the introduction of a mechanical buffer material targeting at the minimisation of the cte mismatch between base and finish material. With respect to the stress

  5. Titanic: A Statistical Exploration.

    ERIC Educational Resources Information Center

    Takis, Sandra L.

    1999-01-01

    Uses the available data about the Titanic's passengers to interest students in exploring categorical data and the chi-square distribution. Describes activities incorporated into a statistics class and gives additional resources for collecting information about the Titanic. (ASK)

  6. Titan Haze

    NASA Technical Reports Server (NTRS)

    Anderson, Carrie M.; West, Robert; Lavvas, Panayotis

    2011-01-01

    The Titan haze exerts a dominating influence on surface visibility and atmospheric radiative heating at optical and near-infrared wavelengths and our desire to understand surface composition and atmospheric dynamics provides a strong motivation to study the properties of the haze. Prior to the Cassini/Huygens missions the haze was known to be global in extent, with a hemispheric contrast asymmetry, with a complicated structure in the polar vortex region poleward of about 55 deg latitude, and with a distinct layer near 370 km altitude outside of the polar vortex at the time of the Voyager 2 flyby. The haze particles measured by the Pioneer and Voyager spacecraft were both highly polarizing and strongly forward scattering, a combination that seems to require an aggregation of small (several tens of nm radius) primary particles. These same properties were seen in the Cassini orbiter and Huygens Probe data. The most extensive set of optical measurements were made inside the atmosphere by the Descent Imager/Spectral Radiometer (DISR) instrument on the Huygens Probe. At the probe location as determined by the DISR measurements the average haze particle contained about 3000 primary particles whose radius is about 40 nm. Three distinct vertical regions were seen in the DISR data with differing particle properties. Refractive indices of the particles in the main haze layer resemble those reported by Khare et al. between O.3S and about 0.7 micron but are more absorbing than the Khare et al. results between 0.7 micron and the long-wavelength limit of the DISR spectra at 1.6 micron. These and other results are described by Tomasko et al., and a broader summary of results was given by Tomasko and West,. New data continue to stream in from the Cassini spacecraft. New data analyses and new laboratory and model results continue to move the field forward. Titan's 'detached' haze layer suffered a dramatic drop in altitude near equinox in 2009 with implications for the circulation

  7. The Climate of Titan

    NASA Astrophysics Data System (ADS)

    Mitchell, Jonathan L.; Lora, Juan M.

    2016-06-01

    Over the past decade, the Cassini-Huygens mission to the Saturn system has revolutionized our understanding of Titan and its climate. Veiled in a thick organic haze, Titan's visible appearance belies an active, seasonal weather cycle operating in the lower atmosphere. Here we review the climate of Titan, as gleaned from observations and models. Titan's cold surface temperatures (˜90 K) allow methane to form clouds and precipitation analogously to Earth's hydrologic cycle. Because of Titan's slow rotation and small size, its atmospheric circulation falls into a regime resembling Earth's tropics, with weak horizontal temperature gradients. A general overview of how Titan's atmosphere responds to seasonal forcing is provided by estimating a number of climate-related timescales. Titan lacks a global ocean, but methane is cold-trapped at the poles in large seas, and models indicate that weak baroclinic storms form at the boundary of Titan's wet and dry regions. Titan's saturated troposphere is a substantial reservoir of methane, supplied by deep convection from the summer poles. A significant seasonal cycle, first revealed by observations of clouds, causes Titan's convergence zone to migrate deep into the summer hemispheres, but its connection to polar convection remains undetermined. Models suggest that downwelling of air at the winter pole communicates upper-level radiative cooling, reducing the stability of the middle troposphere and priming the atmosphere for spring and summer storms when sunlight returns to Titan's lakes. Despite great gains in our understanding of Titan, many challenges remain. The greatest mystery is how Titan is able to retain an abundance of atmospheric methane with only limited surface liquids, while methane is being irreversibly destroyed by photochemistry. A related mystery is how Titan is able to hide all the ethane that is produced in this process. Future studies will need to consider the interactions between Titan's atmosphere, surface

  8. A MRI-COMPATIBLE SYSTEM FOR WHISKER STIMULATION

    PubMed Central

    Li, Limin; Weiss, Craig; Talk, Andrew C.; Disterhoft, John F.; Wyrwicz, Alice M.

    2013-01-01

    We describe here a system for whisker stimulation designed for functional studies in high-field magnetic resonance imaging (MRI) environments. This system, which incorporates real-time optical monitoring of the vibration stimulus, can generate well-controlled and reproducible whisker deflections with amplitudes up to 2 mm and frequencies up to 75 Hz, suitable for functional magnetic resonance imaging (fMRI) studies of animals. Whiskers on either or both sides of the head can be stimulated selectively during fMRI experiments without removing the subject from the magnet. With a user-friendly graphical interface of a computer, a user can conveniently control both the whisker vibration and gating of the MR imager, and synchronize the stimulation with the fMRI acquisition to ensure precise timing of the stimulus presentation. This whisker stimulation system should facilitate a wide variety of fMRI investigations of the neural systems mediating sensory information from the whiskers. PMID:22322316

  9. Further development and application of polycrystalline metal whiskers

    NASA Technical Reports Server (NTRS)

    Schladitz, H. J.

    1979-01-01

    High strength metal whiskers have a larger versatile field of application than monocrystalline whiskers. Although polycrystalline metal whiskers can be used for composites, preferably by extrusion in thermoplastics or by infiltration of resins or metals into whisker networks, the chief application at present may be the production and various use of whisker networks. Such networks can be produced up to high degrees of porosity and besides high mechanical strength, they have high inside surfaces and high electric conductivity. There are for instance, applications concerning construction of electrodes for batteries and fuel cells, catalysts and also new heat-exchanger material, capable of preparing fuel oil and gasoline in order to assist a high-efficiency combustion. The technical application of polycrystalline metal whiskers require their modification as well as the construction of a pilot production unit.

  10. Does Titan have oceans?

    NASA Astrophysics Data System (ADS)

    Lunine, J. I.

    1994-04-01

    Titan is one of the few worlds in the solar system whose essential nature remains hidden. Satellite data from Voyager are examined. Remote sensing investigations from Earth are explored. Possible models of Titan's surface are reviewed. A closer look at Titan would provide useful information. The data to be gathered by the planetary mission Cassini is discussed.

  11. Pressureless sintering of whisker-toughened ceramic composites

    DOEpatents

    Tiegs, T.N.

    1993-05-04

    A pressureless sintering method is disclosed for use in the production of whisker-toughened ceramic composites wherein the sintered density of composites containing up to about 20 vol. % SiC whiskers is improved by reducing the average aspect ratio of the whiskers to from about 10 to about 20. Sintering aids further improve the density, permitting the production of composites containing 20 vol. % SiC with sintered densities of 94% or better of theoretical density by a pressureless sintering method.

  12. Pressureless sintering of whisker-toughened ceramic composites

    DOEpatents

    Tiegs, Terry N.

    1993-01-01

    A pressureless sintering method is disclosed for use in the production of whisker-toughened ceramic composites wherein the sintered density of composites containing up to about 20 vol. % SiC whiskers is improved by reducing the average aspect ratio of the whiskers to from about 10 to about 20. Sintering aids further improve the density, permitting the production of composites containing 20 vol. % SiC with sintered densities of 94% or better of theoretical density by a pressureless sintering method.

  13. Pressureless sintering of whiskered-toughened ceramic composites

    DOEpatents

    Tiegs, Terry N.

    1994-01-01

    A pressureless sintering method is disclosed for use in the production of whisker-toughened ceramic composites wherein the sintered density of composites containing up to about 20 vol. % SiC whiskers is improved by reducing the average aspect ratio of the whiskers to from about 10 to about 20. Sintering aids further improve the density, permitting the production of composites containing 20 vol. % SiC with sintered densities of 94% or better of theoretical density by a pressureless sintering method.

  14. EVALUATION OF LOCAL STRAIN EVOLUTION FROM METALLIC WHISKER FORMATION

    SciTech Connect

    Hoffman, E.; Lam, P.

    2011-05-11

    Evolution of local strain on electrodeposited tin films upon aging has been monitored by digital image correlation (DIC) for the first time. Maps of principal strains adjacent to whisker locations were constructed via comparing pre- and post-growth scanning electron microscopy (SEM) images. Results showed that the magnitude of the strain gradient plays an important role in whisker growth. DIC visualized the dynamic growth process in which the alteration of strain field has been identified to cause growth of subsequent whiskers.

  15. Plastic deformation of alumina reinforced with SiC whiskers

    SciTech Connect

    DeArellano-Lopez, A.R.; Dominguez-Rodriguez, A.; Goretta, K.C.; Routbort, J.L.

    1993-06-01

    Addition of small amounts of stiff reinforcement (SiC whiskers) to a polycrystalline AL{sub 2}O{sub 3} matrix partially inhibits grain boundary sliding because of an increase in threshold stress. When the concentration of whiskers is high enough, a pure diffusional mechanism takes over the control of plastic deformation of the composites. For higher whisker loadings, the materials creep properties depend on a microstructural feature different from the nominal grain size. A tentative correlation of this effective microstructural parameter with the spacing between the whiskers was established through a model.

  16. Effects of cellulose whiskers on properties of soy protein thermoplastics.

    PubMed

    Wang, Yixiang; Cao, Xiaodong; Zhang, Lina

    2006-07-14

    Environmentally-friendly SPI/cellulose whisker composites were successfully prepared using a colloidal suspension of cellulose whiskers, to reinforce soy protein isolate (SPI) plastics. The cellulose whiskers, having an average length of 1.2 microm and diameter of 90 nm, respectively, were prepared from cotton linter pulp by hydrolyzing with sulfuric acid aqueous solution. The effects of the whisker content on the morphology and properties of the glycerol-plasticized SPI composites were investigated by scanning electron microscopy, dynamic mechanical thermal analysis, differential scanning calorimetry, ultraviolet-visible spectroscopy, water-resistivity testing and tensile testing. The results indicated that, with the addition of 0 to 30 wt.-% of cellulose whiskers, strong interactions occurred both between the whiskers and between the filler and the SPI matrix, reinforcing the composites and preserving their biodegradability. Both the tensile strength and Young's modulus of the SPI/cellulose whisker composites increased from 5.8 to 8.1 MPa and from 44.7 to 133.2 MPa, respectively, at a relative humidity of 43%, following an increase of the whisker content from 0 to 30 wt.-%. Furthermore, the incorporation of the cellulose whiskers into the SPI matrix led to an improvement in the water resistance for the SPI-based composites.

  17. Silicon carbide whisker-zirconia reinforced mullite and alumina ceramics

    DOEpatents

    Becher, Paul F.; Tiegs, Terry N.

    1987-01-01

    The flexural strength and/or fracture toughness of SiC whisker-reinforced composites utilizing mullite or alumina as the matrix material for the composite are increased by the addition of zirconia in a monoclinic or tetragonal phase to the matrix. The zirconia addition also provides for a lower hot-pressing temperature and increases the flexural strength and/or fracture toughness of the SiC whisker-reinforced composites over SiC whisker-reinforced composites of the similar matrix materials reinforced with similar concentrations of SiC whiskers.

  18. Network array of zinc oxide whiskers

    NASA Astrophysics Data System (ADS)

    Xu, C. X.; Sun, X. W.; Chen, B. J.; Dong, Z. L.; Yu, M. B.; Zhang, X. H.; Chua, S. J.

    2005-01-01

    A zinc oxide (ZnO) whisker network array with sixfold symmetry was fabricated on ZnO-buffered (0001) sapphire substrate by the vapour-phase transport method using a mixture of zinc oxide and graphite powders as source materials and patterned gold as catalyst. From the ZnO buffer layer, hexagonal ZnO nanorods with identical in-plane structure grew epitaxially along the [0001] orientation to form vertical stems. The branches grew horizontally from six side-surfaces of the vertical stem along [01\\bar {1}0] and other equivalent directions. Most whiskers were confined along the six preferential orientations and interconnected with each other to form a regular network structure. The growth mechanism is discussed.

  19. Intensive Titan exploration begins

    NASA Technical Reports Server (NTRS)

    Mahaffy, Paul R.

    2005-01-01

    The Cassini Orbiter spacecraft first skimmed through the tenuous upper atmosphere of Titan on 26 October 2004. This moon of Saturn is unique in our solar system, with a dense nitrogen atmosphere that is cold enough in places to rain methane, the feedstock for the atmospheric chemistry that produces hydrocarbons, nitrile compounds, and Titan's orange haze. The data returned from this flyby supply new information on the magnetic field and plasma environment around Titan, expose new facets of the dynamics and chemistry of Titan's atmosphere, and provide the first glimpses of what appears to be a complex, fluid-processed, geologically young Titan surface.

  20. Intensive Titan exploration begins.

    PubMed

    Mahaffy, Paul R

    2005-05-13

    The Cassini Orbiter spacecraft first skimmed through the tenuous upper atmosphere of Titan on 26 October 2004. This moon of Saturn is unique in our solar system, with a dense nitrogen atmosphere that is cold enough in places to rain methane, the feedstock for the atmospheric chemistry that produces hydrocarbons, nitrile compounds, and Titan's orange haze. The data returned from this flyby supply new information on the magnetic field and plasma environment around Titan, expose new facets of the dynamics and chemistry of Titan's atmosphere, and provide the first glimpses of what appears to be a complex, fluid-processed, geologically young Titan surface.

  1. Whisker Formation in Porosity in Al Alloys

    NASA Astrophysics Data System (ADS)

    Griffiths, William David; Elsayed, Ahmed; El-Sayed, Mahmoud Ahmed

    2016-09-01

    An examination of the fracture surfaces of tensile test bars from Al alloy castings held in the liquid state for up to 20 minutes revealed porosity which in some cases contained whisker-like features. Energy-dispersive X-ray analysis in a SEM suggested that these might be oxide whiskers forming in an oxide-related pore or double oxide film defect. Such entrainment defects (also known as bifilms) may entrap a small amount of the local atmosphere when they form and become incorporated into the liquid metal. This atmosphere may be predominantly air, which then subsequently reacts with the surrounding melt, firstly by reaction with oxygen and secondly by reaction with nitrogen. A CFD model of the heat distribution associated with the reactions between the interior atmosphere of a double oxide film defect and the surrounding liquid alloy suggested that highly localized increases in temperature, up to about 2000 K to 5000 K (1727 °C to 4727 °C), could occur, over a scale of a few hundred micrometers. Such localized increases in temperature might lead to the evaporation or disassociation of oxide within the pore, followed by condensation, to form the whisker structures observed. Hydrogen might also be expected to diffuse into the bifilm and may play a role in the chemical reactions associated with the development of the bifilm.

  2. Transformation toughened and whisker reinforced ceramics

    SciTech Connect

    Becher, P.F.; Wei, G.C.

    1983-01-01

    Studies of transformation toughened alumina ceramics containing dispersions of zirconia particles have led to the development of high tensile strength (up to 1000 MPa, approx. 150,000 psi as measured in a four-point flexure test) Al/sub 2/O/sub 3/-ZrO/sub 2/ composite materials with K/sub IC/ values (8 to 13 MPa.m/sup 1/2/) which are two- to threefold greater than those of the toughest conventional ceramics. In addition, these composites exhibit much better resistance to static fatigue than do alumina ceramics. Development of SiC whisker reinforced oxide ceramic composites has also resulted in composites with fracture toughness values of up to 9 MPa.m/sup 1/2/ (Al/sub 2/O/sub 3/-20 vol % SiC whiskers). These studies indicate that the toughening process involves a whisker pullout mechanism. This toughening process is also activated during slow crack growth (fatigue) and, hence, substantially increases the slow crack growth resistance of the composite.

  3. Ferroelastic domains in lead-free barium zirconate titanate - barium calcium titanate piezoceramics

    NASA Astrophysics Data System (ADS)

    Ehmke, Matthias Claudius

    Piezoelectricity was first discovered by Pierre and Jaque Curie in the year 1880. Nowadays, piezoelectric materials are used in many application such as high voltage generation in gas igniters, actuation in micro-positioning devices, generation and detection of acoustic waves, emitters and receivers for sonar technology, ultrasonic cleaning, ultrasound medical therapy, and micropumps for ink-jet printers. The most commonly used piezoelectric material since the 1950's is the solid solution system lead zirconate titanate (PZT) that offers high piezoelectric performance under a large range of operating conditions. However, the toxicity of lead requires the replacement of PZT. The studied lead-free alternatives are commonly based on potassium sodium niobate (KNN) and bismuth sodium titanate (BNT), and more recently zirconium and calcium substituted barium titanate (BZT-BCT). The BZT-BCT system exhibits large piezoelectric coefficients that can exceed even those of most PZT compositions under certain conditions. Piezoelectricity was first discovered by Pierre and Jaque Curie in the year 1880. Nowadays, piezoelectric materials are used in many application such as high voltage generation in gas igniters, actuation in micro-positioning devices, generation and detection of acoustic waves, emitters and receivers for sonar technology, ultrasonic cleaning, ultrasound medical therapy, and micropumps for ink-jet printers. The most commonly used piezoelectric material since the 1950's is the solid solution system lead zirconate titanate (PZT) that offers high piezoelectric performance under a large range of operating conditions. However, the toxicity of lead requires the replacement of PZT. The studied lead-free alternatives are commonly based on potassium sodium niobate (KNN) and bismuth sodium titanate (BNT), and more recently zirconium and calcium substituted barium titanate (BZT-BCT). The BZT-BCT system exhibits large piezoelectric coefficients that can exceed even those of

  4. Optical Microscopy Techniques to Inspect for Metallic Whiskers

    NASA Technical Reports Server (NTRS)

    Brusse, Jay A.

    2006-01-01

    Metal surface finishes of tin, zinc and cadmium are often applied to electronic components, mechanical hardware and other structures. These finishes sometimes unpredictably may form metal whiskers over periods that can take from hours to months or even many years. The metal whiskers are crystalline structures commonly having uniform cross sectional area along their entire length. Typical whisker dimensions are nominally on the order of only a few microns (um) across while their lengths can extend from a few microns to several millimeters. Metal whiskers pose a reliability hazard to electronic systems primarily as an electrical shorting hazard. The extremely narrow dimensions of metal whiskers can make observation with optical techniques very challenging. The videos herein were compiled to demonstrate the complexities associated with optical microscope inspection of electronic and mechanical components and assemblies for the presence or absence of metal whiskers. The importance of magnification, light source and angle of illumination play critical roles in being able to detect metal whiskers when present. Furthermore, it is demonstrated how improper techniques can easily obscure detection. It is hoped that these videos will improve the probability of detecting metal whiskers with optical inspection techniques.

  5. Tensile creep of silicon carbide whisker-reinforced alumina composites

    NASA Astrophysics Data System (ADS)

    Quan, Guang-Chun

    Alumina composites with 10, 20 and 30 volume % SiC whiskers were fabricated using colloidal processing methods followed by uniaxial hot pressing. The tensile creep properties of these materials have been studied between 1200°C and 1400°C. The composite slurries showed the best stability at pH = 2, which led to uniform distribution of whiskers in the final products. However, at pH ≥ 6 flocculation occurred between whiskers, resulting in whisker agglomerates in the matrix. Distribution of whiskers was characterised using neutron diffraction methods, which indicated that the whisker orientation could not be altered significantly by adjusting pH. All the composites showed much superior tensile creep resistance compared to pure alumina and the effect of increasing whisker volume fraction was significant up to 30%. Relatively high stress exponents were found, which is most probably associated with much enhanced cavitational creep in tension. The activation energy varied with whisker volume fraction, temperature and applied stress in a complex manner. This combined with the temperature-dependent stress exponents makes the identification of creep mechanisms difficult. Nevertheless, it appears that at moderate stress level grain boundary diffusion and grain boundary sliding (GBS) become more significant as whisker volume fraction increases. The composites containing 20 and 30% whiskers showed significant anelastic strain recovery (˜0.001) following tensile creep, which is consistent with earlier reports that involved bending creep tests. The whisker bending effect was studied by measuring the peak width of (111) SiC planes (perpendicular to the whisker axis) at various conditions. The difference in the peak width at room temperature was found to be insignificant before and after creep. Moreover, during in-situ neutron diffraction measurement at 1400°C, no measurable variation in the peak width was recorded from the crept samples that were cooled under load. It may be

  6. Strengthening of phosphate ceramic foam by silicon carbide whiskers

    NASA Technical Reports Server (NTRS)

    Schetanov, B. V.; Prilepskiy, V. N.; Lapidovskaya, L. A.; Chernyak, A. I.; Romanovich, I. V.

    1987-01-01

    The influence of additions of SiC whiskers on the elastic modulus and flexural strength of phosphate ceramic foam is assessed. It is shown that the incorporation into the material composition of even small amounts (2.4 vol%) of SiC whiskers enhances the impact toughness and heat resistance of the ceramic foam. A 12.3 vol% of SiC whiskers leads to a more than threefold increase of the flexural strength. Strengthening of the phosphate ceramic foam is due to the fact that the whiskers hinder the propagation of matrix crack by increasing the work of matrix fracture. The whiskers reinforce only that volume of material which is occupied by solid matter, whereas they do not reinforce the pores.

  7. Titan Saturn System Mission

    NASA Technical Reports Server (NTRS)

    Reh, Kim R.

    2009-01-01

    Titan is a high priority for exploration, as recommended by NASA's 2006 Solar System Exploration (SSE) Roadmap. NASA's 2003 National Research Council (NRC) Decadal Survey and ESA's Cosmic Vision Program Themes. Recent revolutionary Cassini-Huygens discoveries have dramatically escalated interest in Titan as the next scientific target in the outer solar system. This study demonstrates that an exciting Titan Saturn System Mission (TSSM) that explores two worlds of intense astrobiological interest can be initiated now as a single NASA/ESA collaboration.

  8. Nonlinear elastic effects in bismuth whiskers

    NASA Astrophysics Data System (ADS)

    Powell, B. E.; Skove, M. J.

    1983-03-01

    Finite deformations have a stress (σ)-strain (ɛ) relation of the form ɛ=s'11σ +δ(s11σ)2, where s'11 is an elastic compliance and δ is a combination of second-order and third-order elastic constants. Tensile tests performed on bismuth whisker crystals oriented in the <111¯> and <11¯0> directions give δ111¯ =7.6±0.5 and δ11¯0 =0±0.3, respectively. Orientations are given in the rhombohedral system in which the angle between axes is approximately 57°.

  9. Potassium Iodide

    MedlinePlus

    Potassium iodide is used to protect the thyroid gland from taking in radioactive iodine that may be released during a nuclear radiation emergency. Radioactive iodine can damage the thyroid gland. You should only ...

  10. Potassium test

    MedlinePlus

    ... also be done if your provider suspects metabolic acidosis (for example, caused by uncontrolled diabetes) or alkalosis ( ... Hypoaldosteronism (very rare) Kidney failure Metabolic or respiratory acidosis Red blood cell destruction Too much potassium in ...

  11. Harbor seal whiskers synchronize with frequency of upstream wake

    NASA Astrophysics Data System (ADS)

    Beem, Heather; Triantafyllou, Michael

    2013-11-01

    Harbor seals are able to use their whiskers to track minute water movements, such as those left in the wake of a fish. The current study is a simple representation of what the whiskers experience as the seal chases a fish. A scaled whisker model (average cross-flow diameter: dw) is first tested in a towing tank by itself and then towed behind a larger cylinder (dc = 2 . 5dw), which serves as a wake generator. A flexing plate attached to the model base allows the whisker to freely vibrate in response to the flow. Measurements from strain gages on the plate are calibrated to tip deflections. While in the cylinder wake, the whisker vibrates with an amplitude up to ten times higher than it does on its own (A /dw = 0 . 15). Also, the whisker synchronizes with the vortex shedding frequency (fs =0/. 2 U dc) of the upstream cylinder over the range of reduced velocities tested, whereas on its own, the whisker oscillates around its own natural frequency in water. Seals may use the difference in vibration amplitude and frequency between these two cases to help detect the presence of a vortex wake.

  12. Automated tracking of whiskers in videos of head fixed rodents.

    PubMed

    Clack, Nathan G; O'Connor, Daniel H; Huber, Daniel; Petreanu, Leopoldo; Hires, Andrew; Peron, Simon; Svoboda, Karel; Myers, Eugene W

    2012-01-01

    We have developed software for fully automated tracking of vibrissae (whiskers) in high-speed videos (>500 Hz) of head-fixed, behaving rodents trimmed to a single row of whiskers. Performance was assessed against a manually curated dataset consisting of 1.32 million video frames comprising 4.5 million whisker traces. The current implementation detects whiskers with a recall of 99.998% and identifies individual whiskers with 99.997% accuracy. The average processing rate for these images was 8 Mpx/s/cpu (2.6 GHz Intel Core2, 2 GB RAM). This translates to 35 processed frames per second for a 640 px×352 px video of 4 whiskers. The speed and accuracy achieved enables quantitative behavioral studies where the analysis of millions of video frames is required. We used the software to analyze the evolving whisking strategies as mice learned a whisker-based detection task over the course of 6 days (8148 trials, 25 million frames) and measure the forces at the sensory follicle that most underlie haptic perception.

  13. Graphite whiskers in CV3 meteorites.

    PubMed

    Fries, Marc; Steele, Andrew

    2008-04-01

    Graphite whiskers (GWs), an allotrope of carbon that has been proposed to occur in space, have been discovered in three CV-type carbonaceous chondrites via Raman imaging and electron microscopy. The GWs are associated with high-temperature calcium-aluminum inclusion (CAI) rims and interiors, with the rim of a dark inclusion, and within an inclusion inside an unusual chondrule that bears mineralogy and texture indicative of high-temperature processing. Current understanding of CAI formation places their condensation, and that of associated GWs, relatively close to the Sun and early in the condensation sequence of protoplanetary disk materials. If this is the case, then it is a possibility that GWs are expelled from any young solar system early in its history, thus populating interstellar space with diffuse GWs. Graphite whiskers have been postulated to play a role in the near-infrared (near-IR) dimming of type Ia supernovae, as well as in the thermalization of both the cosmic IR and microwave background and in galactic center dimming between 3 and 9 micrometers. Our observations, along with the further possibility that GWs could be manufactured during supernovae, suggest that GWs may have substantial effects in observational astronomy.

  14. Atomizing apparatus for making polymer and metal powders and whiskers

    DOEpatents

    Otaigbe, Joshua U.; McAvoy, Jon M.; Anderson, Iver E.; Ting, Jason; Mi, Jia; Terpstra, Robert

    2003-03-18

    Method for making polymer particulates, such as spherical powder and whiskers, by melting a polymer material under conditions to avoid thermal degradation of the polymer material, atomizing the melt using gas jet means in a manner to form atomized droplets, and cooling the droplets to form polymer particulates, which are collected for further processing. Atomization parameters can be controlled to produce polymer particulates with controlled particle shape, particle size, and particle size distribution. For example, atomization parameters can be controlled to produce spherical polymer powders, polymer whiskers, and combinations of spherical powders and whiskers. Atomizing apparatus also is provided for atoomizing polymer and metallic materials.

  15. Pressureless sintering of whiskered-toughened ceramic composites

    DOEpatents

    Tiegs, T.N.

    1994-12-27

    A pressureless sintering method is disclosed for use in the production of whisker-toughened ceramic composites wherein the sintered density of composites containing up to about 20 vol. % SiC whiskers is improved by reducing the average aspect ratio of the whiskers to from about 10 to about 20. Sintering aids further improve the density, permitting the production of composites containing 20 vol. % SiC with sintered densities of 94% or better of theoretical density by a pressureless sintering method. 6 figures.

  16. Titan's Exotic Weather

    NASA Astrophysics Data System (ADS)

    Griffith, Caitlin A.

    2006-09-01

    Images of Titan, taken during the joint NASA and European Space Agency Cassini-Huygens mission, invoke a feeling of familiarity: washes wind downhill to damp lakebeds; massive cumuli form and quickly dissipate, suggestive of rain; and dark oval regions resemble lakes. These features arise from Titan's unique similarity with Earth: both cycle liquid between their surfaces and atmospheres, but in Titan's cool atmosphere it is methane that exists as a gas, liquid, and ice. While Titan enticingly resembles Earth, its atmosphere is 10 times thicker, so that its radiative time constant near the surface exceeds a Titan year, and prohibits large thermal gradients and seasonal surface temperature variations exceeding 3K. Titan also lacks oceans - central to Earth's climate - and instead stores much of its condensible in its atmosphere. As a result, Titan's weather differs remarkably from Earth's. Evidence for this difference appears in the location of Titan's large clouds, which frequent a narrow band at 40S latitude and a region within 30 latitude of the S. Pole. Ground-based and Cassini observations, combined with thermodynamic considerations, indicate that we are seeing large convective cloud systems. Detailed cloud models and general circulation models further suggest that these are severe rain storms, which will migrate with the change in season. Outside these migrating "gypsy" cloud bands, the atmosphere appears to be calm, humid and thus frequented by thin stratiform clouds. An intriguingly alien environment is predicted. Yet, the combined effects of Titan's patchy wet surface, atmospheric tides, possible ice volcanoes, and detailed seasonal variations remain unclear as we have witnessed only one season so far. This talk will review observations of Titan's lower atmosphere and modeling efforts to explain the observations, and explore the questions that still elude us.

  17. Aluminum nitride-silicon carbide whisker composites: Processing, properties, and microstructural stability

    SciTech Connect

    Cross, M.T.

    1990-01-01

    Aluminum nitride -- silicon carbide whisker composites with up to 20 vol % whiskers were fabricated by pressureless sintering (1750{degree}--1800{degree}C) and by hot-pressing (1700{degree}--1800{degree}C). Silicon carbide whiskers were found to degrade depending on the type of protective powder bed used during sintering. Whiskers were found to degraded in high oxygen containing samples by reaction with sintering additives. Whisker degradation was also due to the formation of silicon carbide -- aluminum nitride solid solution. No whisker degradation was observed in hot-pressed samples. For these samples Young's modulus and fracture toughness were measured. A 33% increase in the fracture toughness was measured by the indentation technique for a 20 vol % whisker composite. Operative toughening mechanisms were investigated using scanning electron microscopy. Crack deflection and whisker bridging were the dominant mechanisms. It was also shown that load transfer from matrix to whiskers can be a contributing factor to toughening. 88 refs., 34 figs., 11 tabs.

  18. The evolution of the Titan rocket - Titan I to Titan II

    NASA Astrophysics Data System (ADS)

    Adams, Laurence J.

    1990-10-01

    The Titan I and Titan II rockets are described. The designs of the stages, test stands, and basing systems are considered, and the developmental history of each rocket is briefly recapitulated. The ways in which Titan II represents an evolution from Titan I are pointed out.

  19. Process for growing silicon carbide whiskers by undercooling

    DOEpatents

    Shalek, P.D.

    1987-10-27

    A method of growing silicon carbide whiskers, especially in the [beta] form, is disclosed using a heating schedule wherein the temperature of the atmosphere in the growth zone of a furnace is first heated to or beyond the growth temperature and then is cooled to or below the growth temperature to induce nucleation of whiskers at catalyst sites at a desired point in time which results in the selection. 3 figs.

  20. Process for growing silicon carbide whiskers by undercooling

    DOEpatents

    Shalek, Peter D.

    1987-01-01

    A method of growing silicon carbide whiskers, especially in the .beta. form, using a heating schedule wherein the temperature of the atmosphere in the growth zone of a furnace is first heated to or beyond the growth temperature and then is cooled to or below the growth temperature to induce nucleation of whiskers at catalyst sites at a desired point in time which results in the selection.

  1. Titan's organic chemistry

    NASA Technical Reports Server (NTRS)

    Sagan, C.; Thompson, W. R.; Khare, B. N.

    1985-01-01

    Voyager discovered nine simple organic molecules in the atmosphere of Titan. Complex organic solids, called tholins, produced by irradiation of the simulated Titanian atmosphere, are consistent with measured properties of Titan from ultraviolet to microwave frequencies and are the likely main constituents of the observed red aerosols. The tholins contain many of the organic building blocks central to life on earth. At least 100-m, and possibly kms thicknesses of complex organics have been produced on Titan during the age of the solar system, and may exist today as submarine deposits beneath an extensive ocean of simple hydrocarbons.

  2. Evaluation of Effectiveness of Conformal Coatings as Tin Whisker Mitigation

    NASA Astrophysics Data System (ADS)

    Han, Sungwon; Osterman, Michael; Meschter, Stephan; Pecht, Michael

    2012-09-01

    The application of a conformal coat has been considered as a mitigation strategy to prevent unintended shorting events induced by tin whisker formation in electronic products. While various conformal coatings have been shown to be effective at containing tin whiskers on treated coupons, the effectiveness of conformal coating on actual assembled hardware has not been adequately examined. In this study, the ability of six types of conformal coatings to contain tin whiskers was examined through their application to assembled gull-wing lead quad flat package test specimens. Nonuniform coverage of conformal coating on the gull-wing leads was found to be a primary concern. Quantitative image analysis using scanning electron microscopy in backscattered electron mode was developed to aid in quantifying coating coverage. The ability of applied coatings to contain tin whiskers was examined after specimens were subjected to sequential temperature cycling and elevated temperature/humidity conditions as well as exposure to corrosive gases. For all but one coating, tin whiskers were observed to escape areas of relatively thin coating. Parylene C coating was found to be the most effective coating in providing uniform coverage and thickness, and containing whiskers.

  3. Potassium cyanide

    Integrated Risk Information System (IRIS)

    Jump to main content . Integrated Risk Information System Recent Additions | Contact Us Search : All EPA IRIS • You are here : EPA Home • Research • Environmental Assessment • IRIS • IRIS Summaries Redirect Page As of September 28 , 2010 , the assessment summary for potassium cyanide is included in

  4. Structure, function, and cortical representation of the rat submandibular whisker trident.

    PubMed

    Thé, Lydia; Wallace, Michael L; Chen, Christopher H; Chorev, Edith; Brecht, Michael

    2013-03-13

    Although the neurobiology of rodent facial whiskers has been studied intensively, little is known about sensing in other vibrissae. Here we describe the under-investigated submandibular "whisker trident" on the rat's chin. In this three-whisker array, a unique unpaired midline whisker is laterally flanked by two slightly shorter whiskers. All three whiskers point to the ground and are curved backwards. Unlike other whiskers, the trident is not located on an exposed body part. Trident vibrissae are not whisked and do not touch anything over long stretches of time. However, trident whiskers engage in sustained ground contact during head-down running while the animal is exploring or foraging. In biomechanical experiments, trident whiskers follow caudal ground movement more smoothly than facial whiskers. Remarkably, deflection angles decrease with increasing ground velocity. We identified one putative trident barrel in the left somatosensory cortex and two barrels in the right somatosensory cortex. The elongated putative trident-midline barrel is the longest and largest whisker barrel, suggesting that the midline trident whisker is of great functional significance. Cortical postsynaptic air-puff responses in the trident representation show much less temporal precision than facial whisker responses. Trident whiskers do not provide as much high-resolution information about object contacts as facial whiskers. Instead, our observations suggest an idiothetic function: their biomechanics allow trident whiskers to derive continuous measurements about ego motion from ground contacts. The midline position offers unique advantages in sensing heading direction in a laterally symmetric manner. The changes in trident deflection angle with velocity suggest that trident whiskers might function as a tactile speedometer.

  5. Parallel pathways from motor and somatosensory cortex for controlling whisker movements in mice

    PubMed Central

    Sreenivasan, Varun; Karmakar, Kajari; Rijli, Filippo M; Petersen, Carl C H

    2015-01-01

    Mice can gather tactile sensory information by actively moving their whiskers to palpate objects in their immediate surroundings. Whisker sensory perception therefore requires integration of sensory and motor information, which occurs prominently in the neocortex. The signalling pathways from the neocortex for controlling whisker movements are currently poorly understood in mice. Here, we delineate two pathways, one originating from primary whisker somatosensory cortex (wS1) and the other from whisker motor cortex (wM1), that control qualitatively distinct movements of contralateral whiskers. Optogenetic stimulation of wS1 drove retraction of contralateral whiskers while stimulation of wM1 drove rhythmic whisker protraction. To map brainstem pathways connecting these cortical areas to whisker motor neurons, we used a combination of anterograde tracing using adenoassociated virus injected into neocortex and retrograde tracing using monosynaptic rabies virus injected into whisker muscles. Our data are consistent with wS1 driving whisker retraction by exciting glutamatergic premotor neurons in the rostral spinal trigeminal interpolaris nucleus, which in turn activate the motor neurons innervating the extrinsic retractor muscle nasolabialis. The rhythmic whisker protraction evoked by wM1 stimulation might be driven by excitation of excitatory and inhibitory premotor neurons in the brainstem reticular formation innervating both intrinsic and extrinsic muscles. Our data therefore begin to unravel the neuronal circuits linking the neocortex to whisker motor neurons. PMID:25476605

  6. Raising the Titanic.

    ERIC Educational Resources Information Center

    Baker, Romona

    1990-01-01

    Described is an activity in which groups of students investigate engineering principles by writing a feasibility study to raise the luxury liner, Titanic. The problem statement and directions, and suggestions for problem solutions are included. (CW)

  7. The greenhouse of Titan.

    NASA Technical Reports Server (NTRS)

    Sagan, C.

    1973-01-01

    Analysis of non-gray radiative equilibrium and gray convective equilibrium on Titan suggests that a massive molecular-hydrogen greenhouse effect may be responsible for the disagreement between the observed IR temperatures and the equilibrium temperature of an atmosphereless Titan. Calculations of convection indicate a probable minimum optical depth of 14 which corresponds to a molecular hydrogen shell of substantial thickness with total pressures of about 0.1 bar. It is suggested that there is an equilibrium between outgassing and blow-off on the one hand and accretion from the protons trapped in a hypothetical Saturnian magnetic field on the other, in the present atmosphere of Titan. It is believed that an outgassing equivalent to the volatilization of a few kilometers of subsurface ice is required to maintain the present blow-off rate without compensation for all geological time. The presence of an extensive hydrogen corona around Titan is postulated, with surface temperatures up to 200 K.

  8. Titan Casts Revealing Shadow

    NASA Astrophysics Data System (ADS)

    2004-05-01

    A rare celestial event was captured by NASA's Chandra X-ray Observatory as Titan -- Saturn's largest moon and the only moon in the Solar System with a thick atmosphere -- crossed in front of the X-ray bright Crab Nebula. The X-ray shadow cast by Titan allowed astronomers to make the first X-ray measurement of the extent of its atmosphere. On January 5, 2003, Titan transited the Crab Nebula, the remnant of a supernova explosion that was observed to occur in the year 1054. Although Saturn and Titan pass within a few degrees of the Crab Nebula every 30 years, they rarely pass directly in front of it. "This may have been the first transit of the Crab Nebula by Titan since the birth of the Crab Nebula," said Koji Mori of Pennsylvania State University in University Park, and lead author on an Astrophysical Journal paper describing these results. "The next similar conjunction will take place in the year 2267, so this was truly a once in a lifetime event." Animation of Titan's Shadow on Crab Nebula Animation of Titan's Shadow on Crab Nebula Chandra's observation revealed that the diameter of the X-ray shadow cast by Titan was larger than the diameter of its solid surface. The difference in diameters gives a measurement of about 550 miles (880 kilometers) for the height of the X-ray absorbing region of Titan's atmosphere. The extent of the upper atmosphere is consistent with, or slightly (10-15%) larger, than that implied by Voyager I observations made at radio, infrared, and ultraviolet wavelengths in 1980. "Saturn was about 5% closer to the Sun in 2003, so increased solar heating of Titan may account for some of this atmospheric expansion," said Hiroshi Tsunemi of Osaka University in Japan, one of the coauthors on the paper. The X-ray brightness and extent of the Crab Nebula made it possible to study the tiny X-ray shadow cast by Titan during its transit. By using Chandra to precisely track Titan's position, astronomers were able to measure a shadow one arcsecond in

  9. Titan - Some new results

    SciTech Connect

    Owen, T.; Gautier, D.

    1989-01-01

    New analyses of Voyager spectra of Titan have led to improvements in the determination of abundances of minor constituents as a function of latitude and altitude. Ground-based microwave observations have extended the Voyager results for HCN, and have demonstrated that CO is mysteriously deficient in the stratosphere. The origin of the CH4, CO, and N2 in Titan's atmosphere is still unresolved. Both primordial and evolutionary sources are compatible with the available evidence. 21 refs.

  10. Clash of the Titans

    ERIC Educational Resources Information Center

    Subramaniam, Karthigeyan

    2010-01-01

    WebQuests and the 5E learning cycle are titans of the science classroom. These popular inquiry-based strategies are most often used as separate entities, but the author has discovered that using a combined WebQuest and 5E learning cycle format taps into the inherent power and potential of both strategies. In the lesson, "Clash of the Titans,"…

  11. Titan's Ammonia Feature

    NASA Technical Reports Server (NTRS)

    Smythe, W.; Nelson, R.; Boryta, M.; Choukroun, M.

    2011-01-01

    NH3 has long been considered an important component in the formation and evolution of the outer planet satellites. NH3 is particularly important for Titan, since it may serve as the reservoir for atmospheric nitrogen. A brightening seen on Titan starting in 2004 may arise from a transient low-lying fog or surface coating of ammonia. The spectral shape suggests the ammonia is anhydrous, a molecule that hydrates quickly in the presence of water.

  12. Is Titan Partially Differentiated?

    NASA Astrophysics Data System (ADS)

    Mitri, G.; Pappalardo, R. T.; Stevenson, D. J.

    2009-12-01

    The recent measurement of the gravity coefficients from the Radio Doppler data of the Cassini spacecraft has improved our knowledge of the interior structure of Titan (Rappaport et al. 2008 AGU, P21A-1343). The measured gravity field of Titan is dominated by near hydrostatic quadrupole components. We have used the measured gravitational coefficients, thermal models and the hydrostatic equilibrium theory to derive Titan's interior structure. The axial moment of inertia gives us an indication of the degree of the interior differentiation. The inferred axial moment of inertia, calculated using the quadrupole gravitational coefficients and the Radau-Darwin approximation, indicates that Titan is partially differentiated. If Titan is partially differentiated then the interior must avoid melting of the ice during its evolution. This suggests a relatively late formation of Titan to avoid the presence of short-lived radioisotopes (Al-26). This also suggests the onset of convection after accretion to efficiently remove the heat from the interior. The outer layer is likely composed mainly of water in solid phase. Thermal modeling indicates that water could be present also in liquid phase forming a subsurface ocean between an outer ice I shell and a high pressure ice layer. Acknowledgments: This work was conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

  13. Enhanced airglow at Titan

    NASA Astrophysics Data System (ADS)

    Royer, Emilie; Esposito, Larry; Wahlund, Jan-Erik

    2016-06-01

    The Cassini Ultraviolet Imaging Spectrograph (UVIS) instrument made thousand of observations of Titan since its arrival in the Saturnian system in 2004, but only few of them have been analyzed yet. Using the imaging capability of UVIS combined to a big data analytics approach, we have been able to uncover an unexpected pattern in this observations: on several occasions the Titan airglow exhibits an enhanced brightness by approximately a factor of 2, generally combined with a lower altitude of the airglow emission peak. These events typically last from 10 to 30 minutes and are followed and preceded by an airglow of regular and expected level of brightness and altitude. Observations made by the Cassini Plasma Spectrometer (CAPS) instrument onboard Cassini allowed us to correlate the enhanced airglow observed on T-32 with an electron burst. The timing of the burst and the level of energetic electrons (1 keV) observed by CAPS correspond to a brighter and lower than typical airglow displayed on the UVIS data. Furthermore, during T-32 Titan was inside the Saturn's magnetosheath and thus more subject to bombardment by energetic particles. However, our analysis demonstrates that the presence of Titan inside the magnetosheath is not a necessary condition for the production of an enhanced airglow, as we detected other similar events while Titan was within Saturn's magnetosphere. The study presented here aims to a better understanding of the interactions of Titan's upper atmosphere with its direct environment.

  14. Titan's surface and atmosphere

    NASA Astrophysics Data System (ADS)

    Hayes, Alexander G.; Soderblom, Jason M.; Ádámkovics, Máté

    2016-05-01

    Since its arrival in late 2004, the NASA/ESA Cassini-Huygens mission to Saturn has revealed Titan to be a world that is both strange and familiar. Titan is the only extraterrestrial body known to support standing bodies of stable liquid on its surface and, along with Earth and early Mars, is one of three places in the Solar System known to have had an active hydrologic cycle. With atmospheric pressures of 1.5 bar and temperatures of 90-95 K at the surface, methane and ethane condense out of Titan's nitrogen-dominated atmosphere and flow as liquids on the surface. Despite vast differences in environmental conditions and materials from Earth, Titan's methane-based hydrologic cycle drives climatic and geologic processes which generate landforms that are strikingly similar to their terrestrial counterparts, including vast equatorial dunes, well-organized channel networks that route material through erosional and depositional landscapes, and lakes and seas of liquid hydrocarbons. These similarities make Titan a natural laboratory for studying the processes that shape terrestrial landscapes and drive climates, probing extreme conditions impossible to recreate in earthbound laboratories. Titan's exotic environment ensures that even rudimentary measurements of atmospheric/surface interactions, such as wind-wave generation or aeolian dune development, provide valuable data to anchor physical models.

  15. The TITAN reversed-field-pinch fusion reactor study

    SciTech Connect

    Not Available

    1990-01-01

    This report discusses the following topics: overview of titan-2 design; titan-2 fusion-power-core engineering; titan-2 divertor engineering; titan-2 tritium systems; titan-2 safety design and radioactive-waste disposal; and titan-2 maintenance procedures.

  16. Witnessing Springtime on Titan

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-02-01

    Have you ever wondered what springtime is like on Saturns largest moon, Titan? A team of researchers has analyzed a decade of data from the Cassini spacecraft to determine how Titans gradual progression through seasons has affected its temperatures.Observing the Saturn SystemThough Titan orbits Saturn once every ~16 days, it is Saturns ~30-year march around the Sun that sets Titans seasons: each traditional season on Titan spans roughly 7.5 years. Thus, when the Cassini spacecraft first arrived at Saturn in 2004 to study the giant planet and its ring system and moons, Titans northern hemisphere was in early winter. A decade later, the season in the northern hemisphere had advanced to late spring.A team scientists led by Donald Jennings (Goddard Space Flight Center) has now used data from the Composite Infrared Spectrometer (CIRS) on board Cassini to analyze the evolution of Titans surface temperature between 2004 and 2014.Changing of SeasonsSurface brightness temperatures (with errors) on Titan are shown in blue for five time periods between 2004 and 2014. The location of maximum temperature migrates from 19S to 16N over the decade. Two climate models are also shown in green (high thermal inertia) and red (low thermal inertia). [Jennings et al. 2016]CIRS uses the decreased opacity of Titans atmosphere at 19 m to detect infrared emission from Titans surface at this wavelength. From this data, Jennings and collaborators determine Titans surface temperature for five time intervals between 2004 and 2014. They bin the data into 10 latitude bins that span from the south pole (90S) to the north pole (90N).The authors find that the maximum temperature on the moon stays stable over the ten-year period at 94 K, or a chilly -240F). But as time passes, the latitude with the warmest temperature shifts from 19S to 16N, marking the transition from early winter to late spring. Over the decade of monitoring, the surface temperature near the south pole decreased by ~2 K, and that

  17. Silicate interactions with ammonia-water fluids on early Titan

    NASA Astrophysics Data System (ADS)

    Engel, S.; Lunine, J. I.

    1994-02-01

    Plausible models of the early history of Titan suggest that ammonia and water were present in liquid form at the surface. We show here by thermodynamic modeling that such an ocean could have reacted with silicates to put substantial quantities of sodium and potassium into solution. Following the formation of an ice crust by cooling, mantle ammonia-water fluids enriched in potassium would have been brought to the surface through the cryogenic equivalent of volcanism. Later impacts would have released the Ar-40 produced by decay of the K-40 into the atmosphere. The abundance of atmospheric Ar-40, measurable by the Huygens probe gas chromatograph mass spectrometer, may be dominated by this source and hence gives a proxy indication of the volume of ammonia-water resurfacing on Titan over geologic time.

  18. Silicate interactions with ammonia-water fluids on early Titan

    NASA Technical Reports Server (NTRS)

    Engel, Steffi; Lunine, Jonathan I.

    1994-01-01

    Plausible models of the early history of Titan suggest that ammonia and water were present in liquid form at the surface. We show here by thermodynamic modeling that such an ocean could have reacted with silicates to put substantial quantities of sodium and potassium into solution. Following the formation of an ice crust by cooling, mantle ammonia-water fluids enriched in potassium would have been brought to the surface through the cryogenic equivalent of volcanism. Later impacts would have released the Ar-40 produced by decay of the K-40 into the atmosphere. The abundance of atmospheric Ar-40, measurable by the Huygens probe gas chromatograph mass spectrometer, may be dominated by this source and hence gives a proxy indication of the volume of ammonia-water resurfacing on Titan over geologic time.

  19. The environment of Titan, 1975

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Information regarding the physical characteristics of Titan and atmospheric models necessary to support design and mission planning of spacecraft that are to orbit Titan, enter its atmosphere or land on its surface is given.

  20. Effects of Conformal Coat on Tin Whisker Growth

    NASA Technical Reports Server (NTRS)

    Kadesch, Jong S.; Leidecker, Henning; Day, John H. (Technical Monitor)

    2000-01-01

    A whisker from a tin plated part was blamed for the loss of a commercial spacecraft in 1998. Although pure tin finishes are prohibited by NASA, tin plated parts, such as hybrids, relays and commercial off the shelf (COTS) parts, are something discovered to have been installed in NASA spacecraft. Invariably, the assumption is that a conformal coat will prevent the growth of, or short circuits caused by, tin whiskers. This study measures the effect a Uralane coating has on the initiation and growth of tin whiskers, on the ability of this coating to prevent a tin whisker from emerging from the coating, and on the ability to prevent shorting. A sample of fourteen brass substrates (1 inch by 4 inches by 1/16 inch) were plated by two separate processes: half of the specimens were 'bright' tin plated directly over the brass substrate and half received a copper flash over the brass substrate prior to 'bright' tin plating. Each specimen was coated on one half of the substrate with three bi-directional sprays of Uralane 5750 to a nominal thickness of 25 to 75 micrometers (1 to 3 mils). Several specimens of both types, Cu and non-Cu flashed, were placed in an oven maintained at 50 C as others' work suggests that this is the optimal temperature for whisker formation. The remaining specimens were maintained at room ambient conditions. The surfaces of each specimen have been regularly inspected using both optical (15 to 400x power) and Scanning Electronic Microscopy (SEM). Many types of growths, including needle-like whiskers, first appeared approximately three months after plating on the non-conformally coated sides of all specimens. At four months, 4 to 5 times more growth sites were observed on the coated side; however, the density of growth sites on the non-conformally coated side has since increased rapidly, and now, at one year, is about the same for both sides. The density of growth sites is estimated at 90/sq mm with 30 percent of the sites growing whiskers (needle

  1. Titan Polar Landscape Evolution

    NASA Technical Reports Server (NTRS)

    Moore, Jeffrey M.

    2016-01-01

    With the ongoing Cassini-era observations and studies of Titan it is clear that the intensity and distribution of surface processes (particularly fluvial erosion by methane and Aeolian transport) has changed through time. Currently however, alternate hypotheses substantially differ among specific scenarios with respect to the effects of atmospheric evolution, seasonal changes, and endogenic processes. We have studied the evolution of Titan's polar region through a combination of analysis of imaging, elevation data, and geomorphic mapping, spatially explicit simulations of landform evolution, and quantitative comparison of the simulated landscapes with corresponding Titan morphology. We have quantitatively evaluated alternate scenarios for the landform evolution of Titan's polar terrain. The investigations have been guided by recent geomorphic mapping and topographic characterization of the polar regions that are used to frame hypotheses of process interactions, which have been evaluated using simulation modeling. Topographic information about Titan's polar region is be based on SAR-Topography and altimetry archived on PDS, SAR-based stereo radar-grammetry, radar-sounding lake depth measurements, and superposition relationships between geomorphologic map units, which we will use to create a generalized topographic map.

  2. Methane drizzle on Titan.

    PubMed

    Tokano, Tetsuya; McKay, Christopher P; Neubauer, Fritz M; Atreya, Sushil K; Ferri, Francesca; Fulchignoni, Marcello; Niemann, Hasso B

    2006-07-27

    Saturn's moon Titan shows landscapes with fluvial features suggestive of hydrology based on liquid methane. Recent efforts in understanding Titan's methane hydrological cycle have focused on occasional cloud outbursts near the south pole or cloud streaks at southern mid-latitudes and the mechanisms of their formation. It is not known, however, if the clouds produce rain or if there are also non-convective clouds, as predicted by several models. Here we show that the in situ data on the methane concentration and temperature profile in Titan's troposphere point to the presence of layered optically thin stratiform clouds. The data indicate an upper methane ice cloud and a lower, barely visible, liquid methane-nitrogen cloud, with a gap in between. The lower, liquid, cloud produces drizzle that reaches the surface. These non-convective methane clouds are quasi-permanent features supported by the global atmospheric circulation, indicating that methane precipitation occurs wherever there is slow upward motion. This drizzle is a persistent component of Titan's methane hydrological cycle and, by wetting the surface on a global scale, plays an active role in the surface geology of Titan.

  3. Titan Orbiter Aerorover Mission

    NASA Technical Reports Server (NTRS)

    Sittler Jr., E. C.; Acuna, M.; Burchell, M. J.; Coates, A.; Farrell, W.; Flasar, M.; Goldstein, B. E.; Gorevan, S.; Hartle, R. E.; Johnson, W. T. K.

    2001-01-01

    We propose a combined Titan orbiter and Titan Aerorover mission with an emphasis on both in situ and remote sensing measurements of Titan's surface, atmosphere, ionosphere, and magnetospheric interaction. The biological aspect of the Titan environment will be emphasized by the mission (i.e., search for organic materials which may include simple organics to 'amono' analogues of amino acids and possibly more complex, lightening detection and infrared, ultraviolet, and charged particle interactions with Titan's surface and atmosphere). An international mission is assumed to control costs. NASA will provide the orbiter, launch vehicle, DSN coverage and operations, while international partners will provide the Aerorover and up to 30% of the cost for the scientific instruments through collaborative efforts. To further reduce costs we propose a single PI for orbiter science instruments and a single PI for Aerorover science instruments. This approach will provide single command/data and power interface between spacecraft and orbiter instruments that will have redundant central DPU and power converter for their instruments. A similar approach could be used for the Aerorover. The mission profile will be constructed to minimize conflicts between Aerorover science, orbiter radar science, orbiter radio science, orbiter imaging science, and orbiter fields and particles (FP) science. Additional information is contained in the original extended abstract.

  4. Methane ocean on Titan?

    NASA Astrophysics Data System (ADS)

    Bell, Peter M.

    There was an impressive list of names on a recent scientific communication that argues for the existence on Titan of an ocean of liquid methane (CH4) perhaps several hundred meters deep. C. Sagan and S. Dermott with helpful comments by S. Oter, S. Ostro, S. Peale, C. Yoder, W. Thompson, S. Squyres, G. Pettengill, P. Gierasch, and B. Khare speculate that such a methanic ocean, with its Saturnian tides and its tholinian floor, should exist all over Titan's surface; it should unless, they conclude, there is the ‘distracting coincidence [that] … the position of the surface of Titan [is] … near the liquidus in the CH4phase diagram [and, consequently, there is] …almost no methane ocean at all’ (Nature, 300, 731, 1982).We know very little about Titan and its surface; the way of checking into Sagan and Dermott's ideas appears to rest on the interpretation of radar reflectivity data. Preliminary attempts to obtain radar data were made in 1979 with the 305-m Arecibo telescope, but only broad limits resulted. The next opportunity for a measurement at Arecibo comes in the 1990's. Of course, the ideal circumstance would be to send spacecraft equipped with a radar reflectometer for a Titan flyby.

  5. Hypsometry of Titan

    USGS Publications Warehouse

    Lorenz, Ralph D.; Turtle, Elizabeth P.; Stiles, Bryan; Le Gall, Alice; Hayes, Alexander; Aharonson, Oded; Wood, Charles A.; Stofan, Ellen; Kirk, Randy

    2011-01-01

    Cassini RADAR topography data are used to evaluate Titan's hypsometric profile, and to make comparisons with other planetary bodies. Titan's hypsogram is unimodal and strikingly narrow compared with the terrestrial planets. To investigate topographic extremes, a novel variant on the classic hypsogram is introduced, with a logarithmic abscissa to highlight mountainous terrain. In such a plot, the top of the terrestrial hypsogram is quite distinct from those of Mars and Venus due to the 'glacial buzz-saw' that clips terrestrial topography above the snowline. In contrast to the positive skew seen in other hypsograms, with a long tail of positive relief due to mountains, there is an indication (weak, given the limited data for Titan so far) that the Titan hypsogram appears slightly negatively skewed, suggesting a significant population of unfilled depressions. Limited data permit only a simplistic comparison of Titan topography with other icy satellites but we find that the standard deviation of terrain height (albeit at different scales) is similar to those of Ganymede and Europa.

  6. Tin Whisker Electrical Short Circuit Characteristics Part 2

    NASA Technical Reports Server (NTRS)

    Courey, Karim J.; Asfour, Shihab S.; Bayliss, Jon A.; Ludwib, Lawrence L.; Zapata, Maria C.

    2007-01-01

    Existing risk simulations make the assumption that when a free tin whisker has bridged two adjacent exposed electrical conductors, the result is an electrical short circuit. This conservative assumption is made because shorting is a random event that has a currently unknown probability associated with it. Due to contact resistance electrical shorts may not occur at lower voltage levels. In this experiment, we study the effect of varying voltage on the breakdown of the contact resistance which leads to a short circuit. From this data we can estimate the probability of an electrical short, as a function of voltage, given that a free tin whisker has bridged two adjacent exposed electrical conductors. In addition, three tin whiskers grown from the same Space Shuttle Orbiter card guide used in the aforementioned experiment were cross-sectioned and studied using a focused ion beam (FIB).

  7. Bacteriophage T4 whiskers: a rudimentary environment-sensing device.

    PubMed Central

    Conley, M P; Wood, W B

    1975-01-01

    The 400 A filaments or "whiskers," which extend outward from the collar region of the phage, control retraction and extension of the tail fibers in response to certain environmental conditions. The tail fibers of normal phage retract in the absence of a required adsorption cofactor, at low pH, at low ionic strength, at low temperature, and at high concentrations of polyethylene glycol. The tail fibers of mutant whiskerless (wac) phage still retract under the first two conditions, but not the last three. Antibodies to whiskers neutralize T4, probably by fixing tail fibers in the retracted configuration. Phage with retracted tail fibers adsorb poorly to host bacterial cells, and their adsorption rate increases as the fibers become extended. These results suggest that one function of the whiskers is to retract the tail fibers and thereby prevent adsorption to host cells under certain conditions that might be unfavorable for production of phage progeny following infection. PMID:242007

  8. Plasma deposition of polymer composite films incorporating nanocellulose whiskers

    NASA Astrophysics Data System (ADS)

    Samyn, P.; Airoudj, A.; Laborie, M.-P.; Mathew, A. P.; Roucoules, V.

    2011-11-01

    In a trend for sustainable engineering and functionalization of surfaces, we explore the possibilities of gas phase processes to deposit nanocomposite films. From an analysis of pulsed plasma polymerization of maleic anhydride in the presence of nanocellulose whiskers, it seems that thin nanocomposite films can be deposited with various patterns. By specifically modifying plasma parameters such as total power, duty cycle, and monomer gas pressure, the nanocellulose whiskers are either incorporated into a buckled polymer film or single nanocellulose whiskers are deposited on top of a polymeric film. The density of the latter can be controlled by modifying the exact positioning of the substrate in the reactor. The resulting morphologies are evaluated by optical microscopy, AFM, contact angle measurements and ellipsometry.

  9. Cryovolcanic Features on Titan

    NASA Astrophysics Data System (ADS)

    Lopes, R. M. C.; Stofan, E. R.; Kirk, R. L.; Mitchell, K. L.; LeGall, A.; Barnes, J. W.; Hayes, A.; Kargel, J.; Radebaugh, J.; Janssen, M. A.; Neish, C. D.; Wood, C.; Wall, S. D.; Lunine, J. I.; Malaska, M. J.

    2013-09-01

    We present evidence to support the cryovolcanic origin of some features, which includes the deepest pit known on Titan (Sotra Patera) and some of the highest mountains (Doom and Erebor Montes). We interpret this region to be a cryovolcanic complex of multiple cones, craters, and flows. Elsewhere, a circular feature, approximately 100 km across, is morphologically similar to a laccolith, showing a cross pattern interpreted to be extensional fractures. However, we find that some other previously supposed cryovolcanic features were likely formed by other processes. We discuss implications for eruption style and composition of cryovolcanism on Titan. Our analysis shows the great value of combining data sets when interpreting Titan's geology and in particular stresses the value of topographic data.

  10. The tides of Titan.

    PubMed

    Iess, Luciano; Jacobson, Robert A; Ducci, Marco; Stevenson, David J; Lunine, Jonathan I; Armstrong, John W; Asmar, Sami W; Racioppa, Paolo; Rappaport, Nicole J; Tortora, Paolo

    2012-07-27

    We have detected in Cassini spacecraft data the signature of the periodic tidal stresses within Titan, driven by the eccentricity (e = 0.028) of its 16-day orbit around Saturn. Precise measurements of the acceleration of Cassini during six close flybys between 2006 and 2011 have revealed that Titan responds to the variable tidal field exerted by Saturn with periodic changes of its quadrupole gravity, at about 4% of the static value. Two independent determinations of the corresponding degree-2 Love number yield k(2) = 0.589 ± 0.150 and k(2) = 0.637 ± 0.224 (2σ). Such a large response to the tidal field requires that Titan's interior be deformable over time scales of the orbital period, in a way that is consistent with a global ocean at depth.

  11. The meteorology of Titan

    NASA Technical Reports Server (NTRS)

    Flasar, F. M.; Conrath, Barney J.

    1992-01-01

    Current knowledge of Titan's meteorology is reviewed, including diagnostic inferences of the large scale wind field and prognostic studies of thermal and momentum balances. Titan's winds were largely inferred from temperature maps whose spatial coverage is incomplete. The inferred winds are cyclostrophic, approximately 75 m/s in the upper stratosphere. The direction of the winds is ambiguous from the temperature data, but arguments based on the spin up of a planetary atmosphere from an initial state of rest strongly suggest that Titan's winds blow predominantly in the direction of the planetary rotation. Stratospheric temperatures exhibit a north-south asymmetry, suggesting that seasonal variations are controlled by a dynamical inertia associated with the need to transport angular momentum as well as heat. A consideration of the global angular momentum balance indicates that the zonally averaged winds near the surface are approximately 0.3 m/s.

  12. Models of Titan's Ionosphere

    NASA Astrophysics Data System (ADS)

    Robertson, I. P.; Cravens, T. E.; Waite, J. H.; Wahlund, J.; Yelle, R. V.; Vuitton, V.; Coates, A.; Magee, B.; Gell, D. A.

    2007-12-01

    During the TA and T18 encounters with Titan, in situ measurements were made of Titan's atmosphere and ionosphere by several instruments on board the Cassini Orbiter, including the Ion and Neutral Mass Spectrometer (INMS), the Langmuir probe on the Cassini Radio and Plasma Wave Experiment (RPWS), and the Cassini Plasma Spectrometer Subsystem (CAPS). Both of these encounters were on the day as well as the night side of Titan. The model uses neutral densities measured by the INMS instrument and the electron temperature was measured by the RPWS instrument. The model also includes energetic electron fluxes measured by the CAPS instrument, which act as an important source of ionization on the night side. The modeled ion densities are compared with densities measured by INMS in its Open Source mode.

  13. The tides of Titan.

    PubMed

    Iess, Luciano; Jacobson, Robert A; Ducci, Marco; Stevenson, David J; Lunine, Jonathan I; Armstrong, John W; Asmar, Sami W; Racioppa, Paolo; Rappaport, Nicole J; Tortora, Paolo

    2012-07-27

    We have detected in Cassini spacecraft data the signature of the periodic tidal stresses within Titan, driven by the eccentricity (e = 0.028) of its 16-day orbit around Saturn. Precise measurements of the acceleration of Cassini during six close flybys between 2006 and 2011 have revealed that Titan responds to the variable tidal field exerted by Saturn with periodic changes of its quadrupole gravity, at about 4% of the static value. Two independent determinations of the corresponding degree-2 Love number yield k(2) = 0.589 ± 0.150 and k(2) = 0.637 ± 0.224 (2σ). Such a large response to the tidal field requires that Titan's interior be deformable over time scales of the orbital period, in a way that is consistent with a global ocean at depth. PMID:22745254

  14. Titanic Weather Forecasting

    NASA Astrophysics Data System (ADS)

    2004-04-01

    New Detailed VLT Images of Saturn's Largest Moon Optimizing space missions Titan, the largest moon of Saturn was discovered by Dutch astronomer Christian Huygens in 1655 and certainly deserves its name. With a diameter of no less than 5,150 km, it is larger than Mercury and twice as large as Pluto. It is unique in having a hazy atmosphere of nitrogen, methane and oily hydrocarbons. Although it was explored in some detail by the NASA Voyager missions, many aspects of the atmosphere and surface still remain unknown. Thus, the existence of seasonal or diurnal phenomena, the presence of clouds, the surface composition and topography are still under debate. There have even been speculations that some kind of primitive life (now possibly extinct) may be found on Titan. Titan is the main target of the NASA/ESA Cassini/Huygens mission, launched in 1997 and scheduled to arrive at Saturn on July 1, 2004. The ESA Huygens probe is designed to enter the atmosphere of Titan, and to descend by parachute to the surface. Ground-based observations are essential to optimize the return of this space mission, because they will complement the information gained from space and add confidence to the interpretation of the data. Hence, the advent of the adaptive optics system NAOS-CONICA (NACO) [1] in combination with ESO's Very Large Telescope (VLT) at the Paranal Observatory in Chile now offers a unique opportunity to study the resolved disc of Titan with high sensitivity and increased spatial resolution. Adaptive Optics (AO) systems work by means of a computer-controlled deformable mirror that counteracts the image distortion induced by atmospheric turbulence. It is based on real-time optical corrections computed from image data obtained by a special camera at very high speed, many hundreds of times each second (see e.g. ESO Press Release 25/01 , ESO PR Photos 04a-c/02, ESO PR Photos 19a-c/02, ESO PR Photos 21a-c/02, ESO Press Release 17/02, and ESO Press Release 26/03 for earlier NACO

  15. Diurnal variations of Titan

    NASA Astrophysics Data System (ADS)

    Cui, J.; Galand, M.; Yelle, R. V.; Vuitton, V.; Wahlund, J.-E.; Lavvas, P. P.; Mueller-Wodarg, I. C. F.; Kasprzak, W. T.; Waite, J. H.

    2009-04-01

    We present our analysis of the diurnal variations of Titan's ionosphere (between 1,000 and 1,400 km) based on a sample of Ion Neutral Mass Spectrometer (INMS) measurements in the Open Source Ion (OSI) mode obtained from 8 close encounters of the Cassini spacecraft with Titan. Though there is an overall ion depletion well beyond the terminator, the ion content on Titan's nightside is still appreciable, with a density plateau of ~700 cm-3 below ~1,300 km. Such a plateau is associated with the combination of distinct diurnal variations of light and heavy ions. Light ions (e.g. CH5+, HCNH+, C2H5+) show strong diurnal variation, with clear bite-outs in their nightside distributions. In contrast, heavy ions (e.g. c-C3H3+, C2H3CNH+, C6H7+) present modest diurnal variation, with significant densities observed on the nightside. We propose that the distinctions between light and heavy ions are associated with their different chemical loss pathways, with the former primarily through "fast" ion-neutral chemistry and the latter through "slow" electron dissociative recombination. The INMS data suggest day-to-night transport as an important source of ions on Titan's nightside, to be distinguished from the conventional scenario of auroral ionization by magnetospheric particles as the only ionizing source on the nightside. This is supported by the strong correlation between the observed night-to-day ion density ratios and the associated ion lifetimes. We construct a time-dependent ion chemistry model to investigate the effects of day-to-night transport on the ionospheric structures of Titan. The predicted diurnal variation has similar general characteristics to those observed, with some apparent discrepancies which could be reconciled by imposing fast horizontal thermal winds in Titan's upper atmosphere.

  16. Impact craters on Titan

    USGS Publications Warehouse

    Wood, C.A.; Lorenz, R.; Kirk, R.; Lopes, R.; Mitchell, Ken; Stofan, E.

    2010-01-01

    Five certain impact craters and 44 additional nearly certain and probable ones have been identified on the 22% of Titan's surface imaged by Cassini's high-resolution radar through December 2007. The certain craters have morphologies similar to impact craters on rocky planets, as well as two with radar bright, jagged rims. The less certain craters often appear to be eroded versions of the certain ones. Titan's craters are modified by a variety of processes including fluvial erosion, mass wasting, burial by dunes and submergence in seas, but there is no compelling evidence of isostatic adjustments as on other icy moons, nor draping by thick atmospheric deposits. The paucity of craters implies that Titan's surface is quite young, but the modeled age depends on which published crater production rate is assumed. Using the model of Artemieva and Lunine (2005) suggests that craters with diameters smaller than about 35 km are younger than 200 million years old, and larger craters are older. Craters are not distributed uniformly; Xanadu has a crater density 2-9 times greater than the rest of Titan, and the density on equatorial dune areas is much lower than average. There is a small excess of craters on the leading hemisphere, and craters are deficient in the north polar region compared to the rest of the world. The youthful age of Titan overall, and the various erosional states of its likely impact craters, demonstrate that dynamic processes have destroyed most of the early history of the moon, and that multiple processes continue to strongly modify its surface. The existence of 24 possible impact craters with diameters less than 20 km appears consistent with the Ivanov, Basilevsky and Neukum (1997) model of the effectiveness of Titan's atmosphere in destroying most but not all small projectiles. ?? 2009 Elsevier Inc.

  17. Impact craters on Titan

    USGS Publications Warehouse

    Wood, Charles A.; Lorenz, Ralph; Kirk, Randy; Lopes, Rosaly; Mitchell, Karl; Stofan, Ellen; ,

    2010-01-01

    Five certain impact craters and 44 additional nearly certain and probable ones have been identified on the 22% of Titan's surface imaged by Cassini's high-resolution radar through December 2007. The certain craters have morphologies similar to impact craters on rocky planets, as well as two with radar bright, jagged rims. The less certain craters often appear to be eroded versions of the certain ones. Titan's craters are modified by a variety of processes including fluvial erosion, mass wasting, burial by dunes and submergence in seas, but there is no compelling evidence of isostatic adjustments as on other icy moons, nor draping by thick atmospheric deposits. The paucity of craters implies that Titan's surface is quite young, but the modeled age depends on which published crater production rate is assumed. Using the model of Artemieva and Lunine (2005) suggests that craters with diameters smaller than about 35 km are younger than 200 million years old, and larger craters are older. Craters are not distributed uniformly; Xanadu has a crater density 2-9 times greater than the rest of Titan, and the density on equatorial dune areas is much lower than average. There is a small excess of craters on the leading hemisphere, and craters are deficient in the north polar region compared to the rest of the world. The youthful age of Titan overall, and the various erosional states of its likely impact craters, demonstrate that dynamic processes have destroyed most of the early history of the moon, and that multiple processes continue to strongly modify its surface. The existence of 24 possible impact craters with diameters less than 20 km appears consistent with the Ivanov, Basilevsky and Neukum (1997) model of the effectiveness of Titan's atmosphere in destroying most but not all small projectiles.

  18. Coordinated Stem and NanoSIMS Analysis of Enstatite Whiskers in Interplanetary Dust Particles

    NASA Technical Reports Server (NTRS)

    Nakamura-Messenger, K.; Messenger, Scott; Keller, L. P.

    2009-01-01

    Enstatite whiskers (less than 10 micrometer length, less than 200 nanometer width) occur in chondritic-porous interplanetary dust particles (CP IDPs), an Antarctic micrometeorite and a comet 81P/Wild-2 sample. The whiskers are typically elongated along the [100] axis and contain axial screw dislocations, while those in terrestrial rocks and meteorites are elongated along [001]. The unique crystal morphologies and microstructures are consistent with the enstatite whiskers condensing above approximately 1300 K in a low-pressure nebular or circumstellar gas. To constrain the site of enstatite whisker formation, we carried out coordinated mineralogical, chemical and oxygen isotope measurements on enstatite whiskers in a CP IDP.

  19. Titan's Winter Polar Vortex

    NASA Technical Reports Server (NTRS)

    Flasar, F.M.; Achterberg, R.K.; Schinder, P.J.

    2008-01-01

    Titan's atmosphere has provided an interesting study in contrasts and similarities with Earth's. While both have N$_2$ as the dominant constituent and comparable surface pressures $\\sim1$ bar, Titan's next most abundant molecule is CH$_4$, not O$_2$, and the dissociative breakup of CH$_4$ and N$_2$ by sunlight and electron impact leads to a suite of hydrocarbons and nitriles, and ultimately the photochemical smog that enshrouds the moon. In addition, with a 15.95-day period, Titan is a slow rotator compared to Earth. While the mean zonal terrestrial winds are geostrophic, Titan's are mostly cyclostrophic, whipping around the moon in as little as 1 day. Despite the different dynamical regime, Titan's winter stratosphere exhibits several characteristics that should be familiar to terrestrial meteorologists. The cold winter pole near the 1 -mbar level is circumscribed by strong winds (up to 190 m/s) that act as a barrier to mixing with airmasses at lower latitudes. There is evidence of enhancement of several organic species over the winter pole, indicating subsidence. The adiabatic heating associated with this subsidence gives rise to a warm anomaly at the 0.01-mbar level, raising the stratopause two scale heights above its location at equatorial latitudes. Condensate ices have been detected in Titan's lower stratosphere within the winter polar vortex from infrared spectra. Although not always unambiguously identified, their spatial distribution exhibits a sharp gradient, decreasing precipitously across the vortex away from the winter pole. The interesting question of whether there is important heterogeneous chemistry occurring within the polar vortex, analogous to that occurring in the terrestrial polar stratospheric clouds in the ozone holes, has not been addressed. The breakup of Titan's winter polar vortex has not yet been observed. On Earth, the polar vortex is nonlinearly disrupted by interaction with large-amplitude planetary waves. Large-scale waves have not

  20. Flying by Titan

    NASA Technical Reports Server (NTRS)

    Pelletier, Frederic J.; Antreasian, Peter G.; Ardalan, Shadan M.; Criddle, Kevin E.; Ionasescu, Rodica; Jacobson, Robert A.; Jones, Jeremy B.; Parcher, Daniel W.; Roth, Duane C.; Thompson, Paul F.; Vaughan, Andrew T.

    2008-01-01

    The Cassini spacecraft encounters the massive Titan about once every month. These encounters are essential to the mission as Titan is the only satellite of Saturn that can provide enough gravity assist to shape the orbit tour and allow outstanding science for many years. From a navigation point of view, these encounters provide many challenges, in particular those that fly close enough to the surface for the atmospheric drag to perturb the orbit. This paper discusses the dynamics models developed to successfully navigate Cassini and determine its trajectory. This includes the moon's gravity pull with its second degree zonal harmonics J2, the attitude thrust control perturbations and the acceleration of drag.

  1. Titan's "Hot Cross Bun": A Titan Laccolith?

    NASA Astrophysics Data System (ADS)

    Lopes, Rosaly M. C.; Stofan, E. R.; Wall, S. D.; Wood, C.; Kirk, R. L.; Lucas, A.; Mitchell, K. L.; Lunine, J. I.; Turtle, E. P.; Radebaugh, J.; Malaska, M.; Cassini RADAR Team

    2012-10-01

    Cassini’s RADAR instrument acquired Synthetic Aperture Radar data during the T83 flyby on May 22, 2012. The data showed a feature centered at 38.5N, 203W that resembles a “hot cross bun”. This type of feature has not been seen on Titan before, even though 52% of Titan’s surface has been imaged using SAR. The feature, approximately 100 km across, is mostly radar bright but the cross pattern, interpreted to be extensional fractures, located roughly at the center of the brighter area, appears darker at radar wavelengths (2.3 cm). Radar illumination of the image indicates that the fractures are lower in elevation than the surrounding bright region. The morphology of the region is markedly similar to that of a 30-km dome-shaped feature on Venus that lies at the summit of the Kunapipi volcano. The Venus feature is interpreted to be the result of intrusion of magma at the summit of the volcano [1]. A similar feature, interpreted as a laccolith, is seen on the Moon near the crater Ramsden [2]. The lunar feature, imaged by the Lunar Reconnaissance Orbiter, shows the cross-shaped depression over a 300 m high rise. No topographic data for the feature on Titan are available at this time, but the morphology seen by the SAR data suggests that the feature may have been formed by material pushing up from below. Laccoliths form when an igneous intrusion splits apart two strata, resulting in a domeline structure. This previously unknown type of structure on Titan may be yet another indication of cryovolcanism. [1] Stofan, E.R., et al, Icarus, 152, 75-95, 2001. [2] Wichman, R.W. and Schultz, P. H. (1996). Icarus, 122, Issue 1, July 1996, pages 193-199. doi:10.1006/icar.1996.0118

  2. The effect of whisker movement on radial distance estimation: a case study in comparative robotics

    PubMed Central

    Evans, Mathew H.; Fox, Charles W.; Lepora, Nathan F.; Pearson, Martin J.; Sullivan, J. Charles; Prescott, Tony J.

    2013-01-01

    Whisker movement has been shown to be under active control in certain specialist animals such as rats and mice. Though this whisker movement is well characterized, the role and effect of this movement on subsequent sensing is poorly understood. One method for investigating this phenomena is to generate artificial whisker deflections with robotic hardware under different movement conditions. A limitation of this approach is that assumptions must be made in the design of any artificial whisker actuators, which will impose certain restrictions on the whisker-object interaction. In this paper we present three robotic whisker platforms, each with different mechanical whisker properties and actuation mechanisms. A feature-based classifier is used to simultaneously discriminate radial distance to contact and contact speed for the first time. We show that whisker-object contact speed predictably affects deflection magnitudes, invariant of whisker material or whisker movement trajectory. We propose that rodent whisker control allows the animal to improve sensing accuracy by regulating contact speed induced touch-to-touch variability. PMID:23293601

  3. Effect of aspect ratio and liquid-phase content on densification of alumina-silicon carbide whisker composites

    SciTech Connect

    Tiegs, T.N.; Dillard, D.M. . Metals and Ceramics Div.)

    1990-05-01

    This paper reports that densification of alumina-SiC whisker composites by pressureless sintering is inhibited as a result of whisker interference with particle rearrangement and composite shrinkage. Reduction of the aspect ratio improves densification by improving particle/whisker packing for increased green densities and enhances the ability of the whiskers to rearrange themselves during sintering. Increasing the amount of liquid phases present during sintering also improves densification by aiding whisker rearrangement.

  4. Fundamental studies of tin whiskering in microelectronics finishes

    NASA Astrophysics Data System (ADS)

    Pinol, Lesly Agnes

    Common electronics materials, such as tin, copper, steel, and brass, are ambient reactive under common use conditions, and as such are prone to corrosion. During the early 1940s, reports of failures due to electrical shorting of components caused by 'whisker' (i.e., filamentary surface protrusion) growth on many surface types---including the aforementioned metals---began to emerge. Lead alloying of tin (3--10% by weight, typically in the eutectic proportion) eliminated whiskering risk for decades, until the July 2006 adoption of the Restriction of Hazardous Substances (RoHS) directive was issued by the European Union. This directive, which has since been adopted by California and parts of China, severely restricted the use of lead (<1000 ppm) in all electrical and electronics equipment being placed on the EU market, imposing the need for developing reliable new "lead-free" alternatives to SnPb. In spite of the abundance of modern-day anecdotes chronicling whisker-related failures in satellites, nuclear power stations, missiles, pacemakers, and spacecraft navigation equipment, pure tin finishes are still increasingly being employed today, and the root cause(s) of tin whiskering remains elusive. This work describes a series of structured experiments exploring the fundamental relationships between the incidence of tin whiskering (as dependent variable) and numerous independent variables. These variables included deposition method (electroplating, electroless plating, template-based electrochemical synthesis, and various physical vapor deposition techniques, including resistive evaporation, electron beam evaporation, and sputtering), the inclusion of microparticles and organic contamination, the effects of sample geometry, and nanostructuring. Key findings pertain to correlations between sample geometry and whisker propensity, and also to the stress evolution across a series of 4"-diameter silicon wafers of varying thicknesses with respect to the degree of post

  5. Role of whiskers in sensorimotor development of C57BL/6 mice

    PubMed Central

    Arakawa, Hiroyuki; Erzurumlu, Reha S.

    2015-01-01

    The mystacial vibrissae (whiskers) of nocturnal rodents play a major role in their sensorimotor behaviors. Relatively little information exists on the role of whiskers during early development. We characterized the contribution of whiskers to sensorimotor development in postnatal C57BL/6 mice. A comparison between intact and whisker-clipped mice in a battery of behavioral tests from postnatal day (P) 4 to 17 revealed that both male and female pups develop reflexive motor behavior even when the whiskers are clipped. Daily whisker trimming from P3 onwards results in diminished weight gain by P17, and impairment in whisker sensorimotor coordination behaviors, such as cliff avoidance and littermate huddling from P4 through P17, while facilitation of righting reflex at P4 and grasp response at P12. Since active whisker palpation does not start until 2 weeks of age, passive whisker touch during early neonatal stage must play a role in regulating these behaviors. Around the onset of exploratory behaviors (P12) neonatal whisker-clipped pups also display persistent searching movements when they encounter cage walls as a compensatory mechanism of sensorimotor development. Spontaneous whisker motion (whisking) is distinct from respiratory fluttering of whiskers. It is a symmetrical vibration of whiskers at a rate of approximately ∼8 Hz, and begins around P10. Oriented, bundled movements of whiskers at higher frequencies of ∼12 Hz during scanning object surfaces, i.e., palpation whisking, emerges at P14. The establishment of locomotive body coordination before eyes open accompanies palpation whisking, indicating an important role in the guidance of exploratory motor behaviors. PMID:25823761

  6. Understanding and predicting metallic whisker growth and its effects on reliability : LDRD final report.

    SciTech Connect

    Michael, Joseph Richard; Grant, Richard P.; Rodriguez, Mark Andrew; Pillars, Jamin; Susan, Donald Francis; McKenzie, Bonnie Beth; Yelton, William Graham

    2012-01-01

    Tin (Sn) whiskers are conductive Sn filaments that grow from Sn-plated surfaces, such as surface finishes on electronic packages. The phenomenon of Sn whiskering has become a concern in recent years due to requirements for lead (Pb)-free soldering and surface finishes in commercial electronics. Pure Sn finishes are more prone to whisker growth than their Sn-Pb counterparts and high profile failures due to whisker formation (causing short circuits) in space applications have been documented. At Sandia, Sn whiskers are of interest due to increased use of Pb-free commercial off-the-shelf (COTS) parts and possible future requirements for Pb-free solders and surface finishes in high-reliability microelectronics. Lead-free solders and surface finishes are currently being used or considered for several Sandia applications. Despite the long history of Sn whisker research and the recently renewed interest in this topic, a comprehensive understanding of whisker growth remains elusive. This report describes recent research on characterization of Sn whiskers with the aim of understanding the underlying whisker growth mechanism(s). The report is divided into four sections and an Appendix. In Section 1, the Sn plating process is summarized. Specifically, the Sn plating parameters that were successful in producing samples with whiskers will be reviewed. In Section 2, the scanning electron microscopy (SEM) of Sn whiskers and time-lapse SEM studies of whisker growth will be discussed. This discussion includes the characterization of straight as well as kinked whiskers. In Section 3, a detailed discussion is given of SEM/EBSD (electron backscatter diffraction) techniques developed to determine the crystallography of Sn whiskers. In Section 4, these SEM/EBSD methods are employed to determine the crystallography of Sn whiskers, with a statistically significant number of whiskers analyzed. This is the largest study of Sn whisker crystallography ever reported. This section includes a

  7. The lakes of Titan

    USGS Publications Warehouse

    Stofan, E.R.; Elachi, C.; Lunine, J.I.; Lorenz, R.D.; Stiles, B.; Mitchell, K.L.; Ostro, S.; Soderblom, L.; Wood, C.; Zebker, H.; Wall, S.; Janssen, M.; Kirk, R.; Lopes, R.; Paganelli, F.; Radebaugh, J.; Wye, L.; Anderson, Y.; Allison, M.; Boehmer, R.; Callahan, P.; Encrenaz, P.; Flamini, E.; Francescetti, G.; Gim, Y.; Hamilton, G.; Hensley, S.; Johnson, W.T.K.; Kelleher, K.; Muhleman, D.; Paillou, P.; Picardi, G.; Posa, F.; Roth, L.; Seu, R.; Shaffer, S.; Vetrella, S.; West, R.

    2007-01-01

    The surface of Saturn's haze-shrouded moon Titan has long been proposed to have oceans or lakes, on the basis of the stability of liquid methane at the surface. Initial visible and radar imaging failed to find any evidence of an ocean, although abundant evidence was found that flowing liquids have existed on the surface. Here we provide definitive evidence for the presence of lakes on the surface of Titan, obtained during the Cassini Radar flyby of Titan on 22 July 2006 (T16). The radar imaging polewards of 70?? north shows more than 75 circular to irregular radar-dark patches, in a region where liquid methane and ethane are expected to be abundant and stable on the surface. The radar-dark patches are interpreted as lakes on the basis of their very low radar reflectivity and morphological similarities to lakes, including associated channels and location in topographic depressions. Some of the lakes do not completely fill the depressions in which they lie, and apparently dry depressions are present. We interpret this to indicate that lakes are present in a number of states, including partly dry and liquid-filled. These northern-hemisphere lakes constitute the strongest evidence yet that a condensable-liquid hydrological cycle is active in Titan's surface and atmosphere, in which the lakes are filled through rainfall and/or intersection with the subsurface 'liquid methane' table. ??2007 Nature Publishing Group.

  8. Sinking with the Titanic

    NASA Astrophysics Data System (ADS)

    Bagnoli, Franco

    2015-03-01

    In the Titanic movie, when the rear part of the ship is about to sink, Jack Dawson (Leonardo DiCaprio) says to Rose DeWitt Bukater (Kate Winslet) to get ready to swim, because the sinking body will suck them into the abysses. Is this sucking phenomenon really happening? And, if so, why?

  9. Radar reflectivity of titan.

    PubMed

    Muhleman, D O; Grossman, A W; Butler, B J; Slade, M A

    1990-05-25

    The present understanding of the atmosphere and surface conditions on Saturn's largest moon, Titan, including the stability of methane, and an application of thermodynamics leads to a strong prediction of liquid hydrocarbons in an ethane-methane mixture on the surface. Such a surface would have nearly unique microwave reflection properties due to the low dielectric constant. Attempts were made to obtain reflections at a wavelength of 3.5 centimeters by means of a 70-meter antenna in California as the transmitter and the Very Large Array in New Mexico as the receiving instrument. Statistically significant echoes were obtained that show Titan is not covered with a deep, global ocean of ethane, as previously thought. The experiment yielded radar cross sections normalized by the Titan disk of 0.38 +/- 0.15, 0.78 +/- 0.15, and 0.25 +/- 0.15 on three consecutive nights during which the sub-Earth longitude on Titan moved 50 degrees. The result for the combined data for the entire experiment is 0.35 +/- 0.08. The cross sections are very high, most consistent with those of the Galilean satellites; no evidence of the putative liquid ethane was seen in the reflection data. A global ocean as shallow as about 200 meters would have exhibited reflectivities smaller by an order of magnitude, and below the detection limit of the experiment. The measured emissivity at similar wavelengths of about 0.9 is somewhat inconsistent with the high reflectivity.

  10. One whisker whisking: unit recording during conditioned whisking in rats.

    PubMed

    Bermejo, R; Szwed, M; Friedman, W; Ahissar, E; Zeigler, H P

    2004-01-01

    Understanding of the functional neurobiology of the rodent whisker system would be advanced by neurobehavioral studies in awake, behaving animals that combine unit recording from structures at various levels of the system with quantitative characterization of the kinematics and temporal organization of whisking. Such studies require the solution of a number of methodological problems. These include: chronic recording procedures ensuring unit isolation, stability and maximum yield, monitoring and display of unit activity and whisker movements within the same (ms) timeframe and behavioral paradigms which bring whisking movement parameters under the control of the experimenter rather than the rat. Here we describe a head-fixed rodent preparation which makes possible chronic recording of unit activity in the awake, whisking rat, combined with real-time, high resolution monitoring of whisker and pad movements in two dimensions and under behavioral control. While the head-fixed "whisking" preparation has some inherent limitations, it may be used to address a number of important neurobehavioral problems. We suggest that it should contribute significantly to understanding the functional neurobiology of the whisker system.

  11. Method of making in-situ whisker reinforced glass ceramic

    DOEpatents

    Brown, Jesse J.; Hirschfeld, Deidre A.; Lee, K. H.

    1993-02-16

    A heat processing procedure is used to create reinforcing whiskers of TiO.sub.2 in glass-ceramic materials in the LAS and MAS family. The heat processing procedure has particular application in creating TiO.sub.2 in-situ in a modified .beta.-eucryptite system.

  12. Titanates and Titanate-Metal Compounds in Biological Contexts

    PubMed Central

    Chen, Yen-Wei; Drury, Jeanie L.; Chung, Whasun Oh; Hobbs, David T.; Wataha, John C.

    2015-01-01

    Metal ions are notorious environmental contaminants, some causing toxicity at exquisitely low (ppm-level) concentrations. Yet, the redox properties of metal ions make them attractive candidates for bio-therapeutics. Titanates are insoluble particulate compounds of titanium and oxygen with crystalline surfaces that bind metal ions; these compounds offer a means to scavenge metal ions in environmental contexts or deliver them in therapeutic contexts while limiting systemic exposure and toxicity. In either application, the toxicological properties of titanates are crucial. To date, the accurate measurement of the in vitro toxicity of titanates has been complicated by their particulate nature, which interferes with many assays that are optical density (OD)-dependent, and at present, little to no in vivo titanate toxicity data exist. Compatibility data garnered thus far for native titanates in vitro are inconsistent and lacking in mechanistic understanding. These data suggest that native titanates have little toxicity toward several oral and skin bacteria species, but do suppress mammalian cell metabolism in a cells-pecific manner. Titanate compounds bind several types of metal ions, including some common environmental toxins, and enhance delivery to bacteria or cells. Substantial work remains to address the practical applicability of titanates. Nevertheless, titanates have promise to serve as novel vehicles for metal-based therapeutics or as a new class of metal scavengers for environmental applications. PMID:26430701

  13. Alkali Silicate Glass Coatings for Mitigating the Risks of Tin Whiskers

    NASA Astrophysics Data System (ADS)

    Hillman, Dave; Wilcoxon, Ross; Lower, Nate; Grossman, Dan

    2015-12-01

    Alkali silicate glass (ASG) coatings were investigated as a possible method for inhibiting tin whisker initiation and growth. The aqueous-based ASG formulations used in this study were deposited with equipment and conditions that are typical of those used to apply conventional conformal coatings. Processes for controlling ASG coating properties were developed, and a number of ASG-based coating combinations were applied to test components with pure tin surfaces. Coatings were applied both in a laboratory environment at Rockwell Collins and in a manufacturing environment at Plasma Ruggedized Solutions. Testing in elevated humidity/temperature environments and subsequent inspection of the test articles identified coating combinations that inhibited tin whisker growth as well as other material combinations that actually accelerated tin whisker growth. None of the coatings evaluated in this study, including conventional acrylic and Parylene conformal coatings, completely prevented the formation of tin whiskers. Two of the coatings were particularly effective at reducing the risks of whisker growth, albeit through different mechanisms. Parylene conformal coating almost, but not completely, eliminated whisker formation, and only a few tin whiskers were found on these surfaces during the study. A composite of ASG and alumina nanoparticles inhibited whisker formation to a lesser degree than Parylene, but did disrupt whisker growth mechanisms so as to inhibit the formation of long, and more dangerous, tin whiskers. Additional testing also demonstrated that the conformal coatings had relatively little effect on the dielectric loss of a stripline test structure operating at frequencies over 30 GHz.

  14. A mechanistic study on the synthesis of β-Sialon whiskers from coal fly ash

    SciTech Connect

    Zhao, H.; Wang, P.Y.; Yu, J.L.; Zhang, J.

    2015-05-15

    Graphical abstract: The appearance of bead-like whiskers indicated that the growth mechanism of the β-Sialon whiskers was different from the conventional one, in which a chain of droplets were formed and then consumed to participate in the formation of the whiskers. - Highlights: • β-Sialon whiskers were synthesized using waste fly ash by carbothemal reduction reaction under nitrogen atmosphere. • Rod-like β-Sialon whiskers with a diameter of 100–500 nm were formed. • Bead-like whiskers as intermediate morphology of the growing β-Sialon whiskers were found with increasing sintering time. • The growth mechanism of β-Sialon whiskers was different from the conventional VLS mechanism. • A chain of droplets were formed and participated in the formation of the whiskers. - Abstract: β-Sialon whiskers were produced at 1420 °C through carbothemal reduction reaction under nitrogen atmosphere using fly ash from coal-fired power plants. The effects of sintering time on the phase formation and morphology of the products were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) techniques. Rod-like β-Sialon whiskers with the diameter of 100–500 nm were successfully formed. With increasing sintering time, bead-like morphology during the growth process of the whiskers was found, and growth mechanism of β-Sialon whiskers was also discussed in detail. The growth mechanism proposed in this study was different from the conventional vapor–liquid–solid (VLS) mechanism.

  15. Titan's global geologic processes

    NASA Astrophysics Data System (ADS)

    Malaska, Michael; Lopes, Rosaly M. C.; Schoenfeld, Ashley; Birch, Samuel; Hayes, Alexander; Williams, David A.; Solomonidou, Anezina; Janssen, Michael A.; Le Gall, Alice; Soderblom, Jason M.; Neish, Catherine; Turtle, Elizabeth P.; Cassini RADAR Team

    2016-10-01

    We have mapped the Cassini SAR imaged areas of Saturn's moon Titan in order to determine the geological properties that modify the surface [1]. We used the SAR dataset for mapping, but incorporated data from radiometry, VIMS, ISS, and SARTopo for terrain unit determination. This work extends our analyses of the mid-latitude/equatorial Afekan Crater region [2] and in the southern and northern polar regions [3]. We placed Titan terrains into six broad terrain classes: craters, mountain/hummocky, labyrinth, plains, dunes, and lakes. We also extended the fluvial mapping done by Burr et al. [4], and defined areas as potential cryovolcanic features [5]. We found that hummocky/mountainous and labyrinth areas are the oldest units on Titan, and that lakes and dunes are among the youngest. Plains units are the largest unit in terms of surface area, followed by the dunes unit. Radiometry data suggest that most of Titan's surface is covered in high-emissivity materials, consistent with organic materials, with only minor exposures of low-emissivity materials that are consistent with water ice, primarily in the mountain and hummocky areas and crater rims and ejecta [6, 7]. From examination of terrain orientation, we find that landscape evolution in the mid-latitude and equatorial regions is driven by aeolian processes, while polar landscapes are shaped by fluvial, lacrustine, and possibly dissolution or volatilization processes involving cycling organic materials [3, 8]. Although important in deciphering Titan's terrain evolution, impact processes play a very minor role in the modification of Titan's landscape [9]. We find no evidence for large-scale aqueous cryovolcanic deposits.References: [1] Lopes, R.M.C. et al. (2010) Icarus, 205, 540–558. [2] Malaska, M.J. et al. (2016) Icarus, 270, 130–161. [3] Birch et al., in revision. [4] Burr et al. (2013) GSA Bulletin 125, 299–321. [5] Lopes et al. JGR: Planets, 118, 1–20. [6] Janssen et al., (2009) Icarus, 200, 222–239. [7

  16. Characterisation of whisker control in the California sea lion (Zalophus californianus) during a complex, dynamic sensorimotor task.

    PubMed

    Milne, Alyx O; Grant, Robyn A

    2014-10-01

    Studies in pinniped whisker use have shown that their whiskers are extremely sensitive to tactile and hydrodynamic signals. While pinnipeds position their whiskers on to objects and have some control over their whisker protractions, it has always been thought that head movements are more responsible for whisker positioning than the movement of the whiskers themselves. This study uses ball balancing, a dynamic sensorimotor skill that is often used in human and robotic coordination studies, to promote sea lion whisker movements during the task. For the first time, using tracked video footage, we show that sea lion whisker movements respond quickly (26.70 ms) and mirror the movement of the ball, much more so than the head. We show that whisker asymmetry and spread are both altered to help sense and control the ball during balancing. We believe that by designing more dynamic sensorimotor tasks we can start to characterise the active nature of this specialised sensory system in pinnipeds.

  17. Lead zirconate titanate ceramics

    SciTech Connect

    Walker, B.E. Jr.

    1986-12-02

    This patent describes a lead zirconate titanate (PZT) piezoelectric ceramic composition which, based on total composition weight, consists essentially of a solid solution of lead zirconate and lead titanate in a PbZrO/sub 3/:PbTiO/sub 3/ ratio from about 0.505:0.495 to about 0.54:0.46; a halide salt selected from the group consisting of fluorides and chlorides of alkali metal and alkaline earth elements and mixtures thereof except for francium and radium in an amount from about 0.5 to 2 weight percent; and an oxide selected from the group consisting of magnesium, barium, scandium, aluminum, lanthanum, praesodynium, neodymium, samarium, and mixtures thereof in an amount from about 0.5 to about 6 weight percent, the relative amount of oxide being from about 1 to about 4 times that of the halide.

  18. Organic chemistry on Titan

    NASA Technical Reports Server (NTRS)

    Chang, S.; Scattergood, T.; Aronowitz, S.; Flores, J.

    1979-01-01

    Features taken from various models of Titan's atmosphere are combined in a working composite model that provides environmental constraints within which different pathways for organic chemical synthesis are determined. Experimental results and theoretical modeling suggest that the organic chemistry of the satellite is dominated by two processes: photochemistry and energetic particle bombardment. Photochemical reactions of CH4 in the upper atmosphere can account for the presence of C2 hydrocarbons. Reactions initiated at various levels of the atmosphere by cosmic rays, Saturn 'wind', and solar wind particle bombardment of a CH4-N2 atmospheric mixture can account for the UV-visible absorbing stratospheric haze, the reddish appearance of the satellite, and some of the C2 hydrocarbons. In the lower atmosphere photochemical processes will be important if surface temperatures are sufficiently high for gaseous NH3 to exist. It is concluded that the surface of Titan may contain ancient or recent organic matter (or both) produced in the atmosphere.

  19. Titanic exploration with GIS

    USGS Publications Warehouse

    Kerski, J.J.

    2004-01-01

    To help teachers and students investigate one of the world's most famous historical events using the geographic perspective and GIS tools and methods, the U.S. Geological Survey (USGS) created a set of educational lessons based on the RMS Titanic's April 1912 sailing. With these lessons, student researchers can learn about latitude and longitude, map projections, ocean currents, databases, maps, and images through the analysis of the route, warnings, sinking, rescue, and eventual discovery of the submerged ocean liner in 1985. They can also consider the human and physical aspects of the maiden voyage in the North Atlantic Ocean at a variety of scales, from global to regional to local. Likewise, their investigations can reveal how the sinking of the Titanic affected future shipping routes.

  20. RADAR Reveals Titan Topography

    NASA Technical Reports Server (NTRS)

    Kirk, R. L.; Callahan, P.; Seu, R.; Lorenz, R. D.; Paganelli, F.; Lopes, R.; Elachi, C.

    2005-01-01

    The Cassini Titan RADAR Mapper is a K(sub u)-band (13.78 GHz, lambda = 2.17 cm) linear polarized RADAR instrument capable of operating in synthetic aperture (SAR), scatterometer, altimeter and radiometer modes. During the first targeted flyby of Titan on 26 October, 2004 (referred to as Ta) observations were made in all modes. Evidence for topographic relief based on the Ta altimetry and SAR data are presented here. Additional SAR and altimetry observations are planned for the T3 encounter on 15 February, 2005, but have not been carried out at this writing. Results from the T3 encounter relevant to topography will be included in our presentation. Data obtained in the Ta encounter include a SAR image swath

  1. The Tides of Titan

    NASA Astrophysics Data System (ADS)

    Iess, Luciano; Jacobson, Robert A.; Ducci, Marco; Stevenson, David J.; Lunine, Jonathan I.; Armstrong, John W.; Asmar, Sami W.; Racioppa, Paolo; Rappaport, Nicole J.; Tortora, Paolo

    2012-07-01

    We have detected in Cassini spacecraft data the signature of the periodic tidal stresses within Titan, driven by the eccentricity (e = 0.028) of its 16-day orbit around Saturn. Precise measurements of the acceleration of Cassini during six close flybys between 2006 and 2011 have revealed that Titan responds to the variable tidal field exerted by Saturn with periodic changes of its quadrupole gravity, at about 4% of the static value. Two independent determinations of the corresponding degree-2 Love number yield k2 = 0.589 ± 0.150 and k2 = 0.637 ± 0.224 (2σ). Such a large response to the tidal field requires that Titan’s interior be deformable over time scales of the orbital period, in a way that is consistent with a global ocean at depth.

  2. Crystalline titanate catalyst supports

    DOEpatents

    Anthony, Rayford G.; Dosch, Robert G.

    1993-01-01

    A series of new crystalline titanates (CT) are shown to have considerable potential as catalyst supports. For Pd supported catalyst, the catalytic activity for pyrene hydrogenation was substantially different depending on the type of CT, and one was substantially more active than Pd on hydrous titanium oxide (HTO). For 1-hexene hydrogenation the activities of the new CTs were approximately the same as for the hydrous metal oxide supports.

  3. Crystalline titanate catalyst supports

    DOEpatents

    Anthony, R.G.; Dosch, R.G.

    1993-01-05

    A series of new crystalline titanates (CT) are shown to have considerable potential as catalyst supports. For Pd supported catalyst, the catalytic activity for pyrene hydrogenation was substantially different depending on the type of CT, and one was substantially more active than Pd on hydrous titanium oxide (HTO). For 1-hexene hydrogenation the activities of the new CTs were approximately the same as for the hydrous metal oxide supports.

  4. Changes on Titan's surface

    NASA Astrophysics Data System (ADS)

    Solomonidou, A.; Lopes, R. M. C.; Coustenis, A.; Malaska, M. J.; Sotin, C.; Rodriguez, S.; Janssen, M. A.; Drossart, P.; Lawrence, K. J.; Matsoukas, C. K.; Hirtzig, M.; Le Mouelic, S.; Jaumann, R.; Brown, R. H.; Bratsolis, E.

    2015-12-01

    Cassini's Visual and Infrared Mapping Spectrometer (VIMS) and the Titan Radar Mapper have investigated Titan's surface since 2004, unveiling a complex, dynamic and Earth-like surface. Understanding the distribution and interplay of geologic processes is important for constraining models of its interior, surface-atmospheric interactions, and climate evolution. We focus on understanding the origin of the major geomorphological units identified by Lopes et al. (2010, 2015) [1,2], Malaska et al. (2015) [3] and regions we studied in Solomonidou et al. (2014; 2015) [4,5]. Here, we investigate the nature of: Undifferentiated Plains, Hummocky/Mountainous terrains, candidate cryovolcanic sites, Labyrinth, and Dunes in terms of surface albedo behavior and spectral evolution with time to identify possible changes. Using a radiative transfer code, we find that temporal variations of surface albedo occur for some areas. Tui Regio and Sotra Patera, both candidate cryovolcanic regions, change with time, becoming darker and brighter respectively in surface albedo. In contrast, we find that the Undifferentiated Plains and the suggested evaporitic areas [6] in the equatorial regions do not present any significant changes. We are able to report the differences and similarities among the various regions and provide constraints on their chemical composition and specific processes of origin. Our results support the hypothesis that both endogenic and exogenic processes have played important roles in shaping Titan's geologic evolution. Such a variety of geologic processes and their relationship to the methane cycle make Titan important for astrobiology and habitability studies and particularly significant in solar system studies. [1] Lopes, R.M.C., et al.: Icarus, 205, 540-588, 2010; [2] Lopes, R.M.C., et al.: JGR, 118, 416-435, 2013; [3] Malaska, M., et al : Icarus, submitted, 2015;[4] Solomonidou et al.: JGR, 119, 1729-1747, 2014; [5] Solomonidou, A., et al.: In press, 2015; [6] Barnes

  5. Organic chemistry on Titan

    NASA Technical Reports Server (NTRS)

    Chang, S.; Scattergood, T.; Aronowitz, S.; Flores, J.

    1978-01-01

    Observations of nonequilibrium phenomena on the Saturn satellite Titan indicate the occurrence of organic chemical evolution. Greenhouse and thermal inversion models of Titan's atmosphere provide environmental constraints within which various pathways for organic chemical synthesis are assessed. Experimental results and theoretical modeling studies suggest that the organic chemistry of the satellite may be dominated by two atmospheric processes: energetic-particle bombardment and photochemistry. Reactions initiated in various levels of the atmosphere by cosmic ray, Saturn wind, and solar wind particle bombardment of a CH4 - N2 atmospheric mixture can account for the C2-hydrocarbons, the UV-visible-absorbing stratospheric haze, and the reddish color of the satellite. Photochemical reactions of CH4 can also account for the presence of C2-hydrocarbons. In the lower Titan atmosphere, photochemical processes will be important if surface temperatures are sufficiently high for gaseous NH3 to exist. Hot H-atom reactions initiated by photo-dissociation of NH3 can couple the chemical reactions of NH3 and CH4 and produce organic matter.

  6. Landscape Evolution of Titan

    NASA Technical Reports Server (NTRS)

    Moore, Jeffrey

    2012-01-01

    Titan may have acquired its massive atmosphere relatively recently in solar system history. The warming sun may have been key to generating Titan's atmosphere over time, starting from a thin atmosphere with condensed surface volatiles like Triton, with increased luminosity releasing methane, and then large amounts of nitrogen (perhaps suddenly), into the atmosphere. This thick atmosphere, initially with much more methane than at present, resulted in global fluvial erosion that has over time retreated towards the poles with the removal of methane from the atmosphere. Basement rock, as manifested by bright, rough, ridges, scarps, crenulated blocks, or aligned massifs, mostly appears within 30 degrees of the equator. This landscape was intensely eroded by fluvial processes as evidenced by numerous valley systems, fan-like depositional features and regularly-spaced ridges (crenulated terrain). Much of this bedrock landscape, however, is mantled by dunes, suggesting that fluvial erosion no longer dominates in equatorial regions. High midlatitude regions on Titan exhibit dissected sedimentary plains at a number of localities, suggesting deposition (perhaps by sediment eroded from equatorial regions) followed by erosion. The polar regions are mainly dominated by deposits of fluvial and lacustrine sediment. Fluvial processes are active in polar areas as evidenced by alkane lakes and occasional cloud cover.

  7. The mathematical whisker: A review of numerical models of the rat׳s vibrissa biomechanics.

    PubMed

    Lucianna, Facundo Adrián; Albarracín, Ana Lía; Vrech, Sonia Mariel; Farfán, Fernando Daniel; Felice, Carmelo José

    2016-07-01

    The vibrissal system of the rat refers to specialized hairs the animal uses for tactile sensory perception. Rats actively move their whiskers in a characteristic way called "whisking". Interaction with the environment produces elastic deformation of the whiskers, generating mechanical signals in the whisker-follicle complex. Advances in our understanding of the vibrissal complex biomechanics is of interest not only for the biological research field, but also for biomimetic approaches. The recent development of whisker numerical models has contributed to comprehending its sophisticated movements and its interactions with the follicle. The great diversity of behavioral patterns and complexities of the whisker-follicle ensemble encouraged the creation of many different biomechanical models. This review analyzes most of the whisker biomechanical models that have been developed so far. This review was written so as to render it accessible to readers coming from different research areas.

  8. Fabrication of α-chitin whisker-reinforced poly(vinyl alcohol) nanocomposite nanofibres by electrospinning

    NASA Astrophysics Data System (ADS)

    Junkasem, Jirawut; Rujiravanit, Ratana; Supaphol, Pitt

    2006-09-01

    The present contribution reports, for the first time, the successful fabrication of α-chitin whisker-reinforced poly(vinyl alcohol) (PVA) nanocomposite nanofibres by electrospinning. The α-chitin whiskers were prepared from α-chitin flakes from shrimp shells by acid hydrolysis. The as-prepared chitin whiskers exhibited lengths in the range 231-969 nm and widths in the range 12-65 nm, with the average length and width being about 549 and 31 nm, respectively. Successful incorporation of the chitin whiskers within the as-spun PVA/chitin whisker nanocomposite nanofibres was verified by infrared spectroscopic and thermogravimetric methods. The incorporation of chitin whiskers within the as-spun nanocomposite fibre mats increased the Young's modulus by about 4-8 times over that of the neat as-spun PVA fibre mat.

  9. Chitosan whiskers from shrimp shells incorporated into dimethacrylate-based dental resin sealant.

    PubMed

    Mahapoka, Ekamon; Arirachakaran, Pratanporn; Watthanaphanit, Anyarat; Rujiravanit, Ratana; Poolthong, Suchit

    2012-01-01

    A resin-based sealant containing chitosan whiskers was developed for use as a pit and fissure sealer. Chitosan whiskers were synthesized and then characterized using Fourier transform infrared spectrometry and transmission electron microscopy. The whiskers were next incorporated into dimethacrylate monomer at various ratios by weight and subsequently analyzed for their antimicrobial and physical properties. The dimethacrylate-based sealant containing chitosan whiskers had a greater antimicrobial activity than control sealant and they were comparable with antimicrobial commercial resin sealants. The inclusion of the whiskers did not reduce the curing depth or degree of double bond conversion and the reduction in hardness was minimal. In conclusion, a resin-based sealant containing chitosan whiskers can be considered an effective antimicrobial pit and fissure sealant.

  10. An Investigation of the Electrical Short Circuit Characteristics of Tin Whiskers

    NASA Technical Reports Server (NTRS)

    Courey, Karim J.

    2008-01-01

    In this experiment, an empirical model to quantify the probability of occurrence of an electrical short circuit from tin whiskers as a function of voltage was developed. This model can be used to improve existing risk simulation models FIB and TEM images of a tin whisker confirm the rare polycrystalline structure on one of the three whiskers studied. FIB cross-section of the card guides verified that the tin finish was bright tin.

  11. Processing and properties of hydroxyapaptite whisker reinforced polyaryletherketones for orthopaedic applications

    NASA Astrophysics Data System (ADS)

    Converse, Gabriel Leverne

    The overall objective of this study was to produce hydroxyapatite (HA) whisker reinforced polyaryletherketone (PAEK) biocomposites and scaffolds with tailored mechanical properties similar to those of bone tissue. The effects of the reaction temperature and carboxylic acid on the morphology and composition of HA whiskers synthesized by chelate decomposition were first studied using a controlled heating rate under static conditions. Reaction temperature affected both whisker composition and morphology, while the carboxylic acid used as the chelating agent affected whisker morphology. Polyetheretherketone (PEEK) was reinforced with up to 50 vol% HA whisker reinforcement using a novel powder processing and compression molding technique. Composites with 40-50 vol% HA whisker reinforcement exhibited elastic moduli similar to that of human cortical bone in the longitudinal direction. Composites with 10 and 20 vol% HA whisker reinforcement exhibited tensile strengths similar to that of human cortical bone in the longitudinal direction. HA whisker reinforced polyetherketoneketone (PEKK) scaffolds were successfully processed with 75-90% porosity and 20-40 vol% HA whisker reinforcement. The compression molding/particle leaching technique used in this study facilitated the incorporation of high levels of bioactive HA whisker reinforcements into the polymer matrix. Micro-CT indicated interconnected porosity in the size range required for bone ingrowth. The mechanical properties of HA whisker reinforced PEKK scaffolds were investigated in uniaxial compression. Scaffolds processed at 375°C with 75% porosity and 20 vol% HA whisker reinforcement exhibited an apparent modulus of 141 MPa and an apparent yield strength of 2.3 MPa. These values fall within the ranges reported for the modulus and strength of trabecular bone.

  12. Strong and bioactive composites containing nano-silica-fused whiskers for bone repair.

    PubMed

    Xu, Hockin H K; Smith, Douglas T; Simon, Carl G

    2004-08-01

    Self-hardening calcium phosphate cement (CPC) sets to form hydroxyapatite with high osteoconductivity, but its brittleness and low strength limit its use to only non-stress bearing locations. Previous studies developed bioactive composites containing hydroxyapatite fillers in Bis-GMA-based composites for bone repair applications, and they possessed higher strength values. However, these strengths were still lower than the strength of cortical bone. The aim of this study was to develop strong and bioactive composites by combining CPC fillers with nano-silica-fused whiskers in a resin matrix, and to characterize the mechanical properties and cell response. Silica particles were fused to silicon carbide whiskers to roughen the whisker surfaces for enhanced retention in the matrix. Mass ratios of whisker:CPC of 1:2, 1:1 and 2:1 were incorporated into a Bis-GMA-based resin and hardened by two-part chemical curing. Composite with only CPC fillers without whiskers served as a control. The specimens were tested using three-point flexure and nano-indentation. Composites with whisker:CPC ratios of 2:1 and 1:1 had flexural strengths (mean+/-SD; n=9) of (164+/-14) MPa and (139+/-22) MPa, respectively, nearly 3 times higher than (54+/-5) MPa of the control containing only CPC fillers (p<0.05). The strength of the new whisker-CPC composites was 3 times higher than the strength achieved in previous studies for conventional bioactive composites containing hydroxyapatite particles in Bis-GMA-based resins. The mechanical properties of the CPC-whisker composites nearly matched those of cortical bone and trabecular bone. Osteoblast-like cell adhesion, proliferation and viability were equivalent on the non-whisker control containing only CPC fillers, on the whisker composite at whisker:CPC of 1:1, and on the tissue culture polystyrene control, suggesting that the new CPC-whisker composite was non-cytotoxic.

  13. Study of metal whiskers growth and mitigation technique using additive manufacturing

    NASA Astrophysics Data System (ADS)

    Gullapalli, Vikranth

    For years, the alloy of choice for electroplating electronic components has been tin-lead (Sn-Pb) alloy. However, the legislation established in Europe on July 1, 2006, required significant lead (Pb) content reductions from electronic hardware due to its toxic nature. A popular alternative for coating electronic components is pure tin (Sn). However, pure tin has the tendency to spontaneously grow electrically conductive Sn whisker during storage. Sn whisker is usually a pure single crystal tin with filament or hair-like structures grown directly from the electroplated surfaces. Sn whisker is highly conductive, and can cause short circuits in electronic components, which is a very significant reliability problem. The damages caused by Sn whisker growth are reported in very critical applications such as aircraft, spacecraft, satellites, and military weapons systems. They are also naturally very strong and are believed to grow from compressive stresses developed in the Sn coating during deposition or over time. The new directive, even though environmentally friendly, has placed all lead-free electronic devices at risk because of whisker growth in pure tin. Additionally, interest has occurred about studying the nature of other metal whiskers such as zinc (Zn) whiskers and comparing their behavior to that of Sn whiskers. Zn whiskers can be found in flooring of data centers which can get inside electronic systems during equipment reorganization and movement and can also cause systems failure. Even though the topic of metal whiskers as reliability failure has been around for several decades to date, there is no successful method that can eliminate their growth. This thesis will give further insights towards the nature and behavior of Sn and Zn whiskers growth, and recommend a novel manufacturing technique that has potential to mitigate metal whiskers growth and extend life of many electronic devices.

  14. An Empirical Model for Estimating the Probability of Electrical Short Circuits from Tin Whiskers. Part 2

    NASA Technical Reports Server (NTRS)

    Courey, Karim; Wright, Clara; Asfour, Shihab; Onar, Arzu; Bayliss, Jon; Ludwig, Larry

    2009-01-01

    In this experiment, an empirical model to quantify the probability of occurrence of an electrical short circuit from tin whiskers as a function of voltage was developed. This empirical model can be used to improve existing risk simulation models. FIB and TEM images of a tin whisker confirm the rare polycrystalline structure on one of the three whiskers studied. FIB cross-section of the card guides verified that the tin finish was bright tin.

  15. Titan after Cassini Huygens

    NASA Astrophysics Data System (ADS)

    Beauchamp, P. M.; Lunine, J.; Lebreton, J.; Coustenis, A.; Matson, D.; Reh, K.; Erd, C.

    2008-12-01

    In 2005, the Huygens Probe gave us a snapshot of a world tantalizingly like our own, yet frozen in its evolution on the threshold of life. The descent under parachute, like that of Huygens in 2005, is happening again, but this time in the Saturn-cast twilight of winter in Titan's northern reaches. With a pop, the parachute is released, and then a muffled splash signals the beginning of the first floating exploration of an extraterrestrial sea-this one not of water but of liquid hydrocarbons. Meanwhile, thousands of miles away, a hot air balloon, a "montgolfiere," cruises 6 miles above sunnier terrain, imaging vistas of dunes, river channels, mountains and valleys carved in water ice, and probing the subsurface for vast quantities of "missing" methane and ethane that might be hidden within a porous icy crust. Balloon and floater return their data to a Titan Orbiter equipped to strip away Titan's mysteries with imaging, radar profiling, and atmospheric sampling, much more powerful and more complete than Cassini was capable of. This spacecraft, preparing to enter a circular orbit around Saturn's cloud-shrouded giant moon, has just completed a series of flybys of Enceladus, a tiny but active world with plumes that blow water and organics from the interior into space. Specialized instruments on the orbiter were able to analyze these plumes directly during the flybys. Titan and Enceladus could hardly seem more different, and yet they are linked by their origin in the Saturn system, by a magnetosphere that sweeps up mass and delivers energy, and by the possibility that one or both worlds harbor life. It is the goal of the NASA/ESA Titan Saturn System Mission (TSSM) to explore and investigate these exotic and inviting worlds, to understand their natures and assess the possibilities of habitability in this system so distant from our home world. Orbiting, landing, and ballooning at Titan represent a new and exciting approach to planetary exploration. The TSSM mission

  16. Peripheral optogenetic stimulation induces whisker movement and sensory perception in head-fixed mice.

    PubMed

    Park, Sunmee; Bandi, Akhil; Lee, Christian R; Margolis, David J

    2016-01-01

    We discovered that optical stimulation of the mystacial pad in Emx1-Cre;Ai27D transgenic mice induces whisker movements due to activation of ChR2 expressed in muscles controlling retraction and protraction. Using high-speed videography in anesthetized mice, we characterize the amplitude of whisker protractions evoked by varying the intensity, duration, and frequency of optogenetic stimulation. Recordings from primary somatosensory cortex (S1) in anesthetized mice indicated that optogenetic whisker pad stimulation evokes robust yet longer latency responses than mechanical whisker stimulation. In head-fixed mice trained to report optogenetic whisker pad stimulation, psychometric curves showed similar dependence on stimulus duration as evoked whisker movements and S1 activity. Furthermore, optogenetic stimulation of S1 in expert mice was sufficient to substitute for peripheral stimulation. We conclude that whisker protractions evoked by optogenetic activation of whisker pad muscles results in cortical activity and sensory perception, consistent with the coding of evoked whisker movements by reafferent sensory input. PMID:27269285

  17. Peripheral optogenetic stimulation induces whisker movement and sensory perception in head-fixed mice

    PubMed Central

    Park, Sunmee; Bandi, Akhil; Lee, Christian R; Margolis, David J

    2016-01-01

    We discovered that optical stimulation of the mystacial pad in Emx1-Cre;Ai27D transgenic mice induces whisker movements due to activation of ChR2 expressed in muscles controlling retraction and protraction. Using high-speed videography in anesthetized mice, we characterize the amplitude of whisker protractions evoked by varying the intensity, duration, and frequency of optogenetic stimulation. Recordings from primary somatosensory cortex (S1) in anesthetized mice indicated that optogenetic whisker pad stimulation evokes robust yet longer latency responses than mechanical whisker stimulation. In head-fixed mice trained to report optogenetic whisker pad stimulation, psychometric curves showed similar dependence on stimulus duration as evoked whisker movements and S1 activity. Furthermore, optogenetic stimulation of S1 in expert mice was sufficient to substitute for peripheral stimulation. We conclude that whisker protractions evoked by optogenetic activation of whisker pad muscles results in cortical activity and sensory perception, consistent with the coding of evoked whisker movements by reafferent sensory input. DOI: http://dx.doi.org/10.7554/eLife.14140.001 PMID:27269285

  18. Synthesis of nanosized sodium titanates

    SciTech Connect

    Hobbs, David T.; Taylor-Pashow, Kathryn M. L.; Elvington, Mark C.

    2015-09-29

    Methods directed to the synthesis and peroxide-modification of nanosized monosodium titanate are described. Methods include combination of reactants at a low concentration to a solution including a nonionic surfactant. The nanosized monosodium titanate can exhibit high selectivity for sorbing various metallic ions.

  19. Atomic force microscopy using ZnO whisker tip

    NASA Astrophysics Data System (ADS)

    Kado, H.; Yokoyama, K.; Tohda, T.

    1992-06-01

    We have developed an atomic force microscope (AFM) using a zinc oxide (ZnO) whisker crystal as a probing tip. The ZnO whisker crystal is tetrapodal in shape, with each leg having a length of 5-30 μm, a radius of curvature less than 10 nm, and a cone half angle of 1°-2°. Polyimide thin films rubbed with cloths as liquid-crystal aligning films were employed for AFM imaging. Due to the needle shape of the probing tip, the AFM was able to resolve the tiny grooves (3-5 nm deep, 60-80 nm apart) on these films more clearly than that using a conventional pyramidal tip. The new AFM will be available for precise evaluation of surfaces on which fine structures are microfabricated in nanometer scale.

  20. 'Where' and 'what' in the whisker sensorimotor system.

    PubMed

    Diamond, Mathew E; von Heimendahl, Moritz; Knutsen, Per Magne; Kleinfeld, David; Ahissar, Ehud

    2008-08-01

    In the visual system of primates, different neuronal pathways are specialized for processing information about the spatial coordinates of objects and their identity - that is, 'where' and 'what'. By contrast, rats and other nocturnal animals build up a neuronal representation of 'where' and 'what' by seeking out and palpating objects with their whiskers. We present recent evidence about how the brain constructs a representation of the surrounding world through whisker-mediated sense of touch. While considerable knowledge exists about the representation of the physical properties of stimuli - like texture, shape and position - we know little about how the brain represents their meaning. Future research may elucidate this and show how the transformation of one representation to another is achieved. PMID:18641667

  1. Silicon carbide whisker reinforced composites and method for making same

    DOEpatents

    Wei, G.C.

    1984-02-09

    The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties, especially increased fracture toughness. In the formation of these ceramic composites, the single-crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al/sub 2/O/sub 3/, mullite, or B/sub 4/C. The mixtures which contain a homogeneous dispersion of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600 to 1950/sup 0/C with pressing times varying from about 0.75 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MPa.m/sup 1/2/ which represents as much as a two-fold increase over that of the matrix material.

  2. Pulmonary response, in vivo, to silicon carbide whiskers.

    PubMed

    Vaughan, G L; Trently, S A; Wilson, R B

    1993-11-01

    Fischer rats were exposed to silicon carbide whiskers (SiCW), boron carbide whiskers (BCW), silicon carbide platelets (SiCP), or crocidolite asbestos separately administered by intratracheal instillation. SiCW proved to be the most toxic material within the test group. Dramatic increases in alveolar macrophage populations within 1 week of exposure to SiCW persisted for at least 28 days, evidence of the chronic inflammation observed in necropsies during the first months of the study. The most common finding in histological preparations of tissues taken from animals 18 months after exposure to SiCW was a high incidence (frequency > 0.85) of multiple pulmonary granulomas which occasionally occluded airways. Lesions associated with crocidolite were similar to those found with SiCW. Equivalent treatment with BCW and SiCP produced no significant histological changes within 18 months of exposure.

  3. Biomimetic whisker-shaped apatite coating of titanium powder.

    PubMed

    Sim, Young Uk; Kim, Jong Hee; Yang, Tae Young; Yoon, Seog Young; Park, Hong Chae

    2010-05-01

    Biomimetic apatite coatings on chemically modified titanium powder have been processed and the resulting coating layers evaluated in terms of morphology, composition and structure, using TF-XRD, XPS, SEM, TEM and FTIR analysis. After 7 days immersion in a simulated body fluid (SBF), nanometer-sized fine precipitates with an amorphous whisker-like phase and a Ca/P atomic ratio of 1.94 were obtained on the external surface of the titanium particles. When the immersion time in SBF was extended to 16 days, the coating layer consisted of the whisker-like nanostructured crystals of carbonated hydroxyapatite with a atomic ratio of 3; in such a case, a double coating layer was developed. The double layer could be divided into two regions and could be clearly distinguished: an inner dense region (approximately 200 nm in thickness) which may include hard agglomerated crystals and an outer less dense region (> 500 nm in thickness) in which crystals are loosely distributed.

  4. Protective coating for alumina-silicon carbide whisker composites

    DOEpatents

    Tiegs, Terry N.

    1989-01-01

    Ceramic composites formed of an alumina matrix reinforced with silicon carbide whiskers homogenously dispersed therein are provided with a protective coating for preventing fracture strength degradation of the composite by oxidation during exposure to high temperatures in oxygen-containing atmospheres. The coating prevents oxidation of the silicon carbide whiskers within the matrix by sealing off the exterior of the matrix so as to prevent oxygen transport into the interior of the matrix. The coating is formed of mullite or mullite plus silicon oxide and alumina and is formed in place by heating the composite in air to a temperature greater than 1200.degree. C. This coating is less than about 100 microns thick and adequately protects the underlying composite from fracture strength degradation due to oxidation.

  5. Crystalline instability of Bi-2212 superconducting whiskers near room temperature

    NASA Astrophysics Data System (ADS)

    Cagliero, Stefano; Agostino, Angelo; Khan, Mohammad Mizanur Rahman; Truccato, Marco; Orsini, Francesco; Marinone, Massimo; Poletti, Giulio; Lascialfari, Alessandro

    2009-05-01

    We report new evidences for the thermodynamic instability of whisker crystals in the Bi-Sr-Ca-Cu-O (BSCCO) system. Annealing treatments at 90°C have been performed on two sets of samples, which were monitored by means of X-Rays Diffraction (XRD) and Atomic Force Microscopy (AFM) measurements, respectively. Two main crystalline domains of Bi2Sr2CuCa2O8+ x (Bi-2212) were identified in the samples by the XRD data, which underwent an evident crystalline segregation after about 60 hours. Very fast dynamics of the surface modifications was also described by the AFM monitoring. Two typologies of surface structures formed after about 3 annealing hours: continuous arrays of dome shaped bodies were observed along the edges of the whiskers, while in the central regions a dense texture of flat bodies was found. These modifications are described in terms of the formation of simple oxide clusters involving a degradation of the internal layers.

  6. Bioinspired active whisker sensor for robotic vibrissal tactile sensing

    NASA Astrophysics Data System (ADS)

    Ju, Feng; Ling, Shih-Fu

    2014-12-01

    A whisker transducer (WT) inspired by rat’s vibrissal tactile perception is proposed based on a transduction matrix model characterizing the electro-mechanical transduction process in both forward and backward directions. It is capable of acting as an actuator to sweep the whisker and simultaneously as a sensor to sense the force, motion, and mechanical impedance at whisker tip. Its validity is confirmed by numerical simulation using a finite element model. A prototype is then fabricated and its transduction matrix is determined by parameter identification. The calibrated WT can accurately sense mechanical impedance which is directly related to stiffness, mass and damping. Subsequent vibrissal tactile sensing of sandpaper texture reveals that the real part of mechanical impedance sensed by WT is correlated with sandpaper roughness. Texture discrimination is successfully achieved by inputting the real part to a k-means clustering algorithm. The mechanical impedance sensing ability as well as other features of the WT such as simultaneous-actuation-and-sensing makes it a good solution to robotic tactile sensing.

  7. Neural coding in barrel cortex during whisker-guided locomotion

    PubMed Central

    Sofroniew, Nicholas James; Vlasov, Yurii A; Andrew Hires, Samuel; Freeman, Jeremy; Svoboda, Karel

    2015-01-01

    Animals seek out relevant information by moving through a dynamic world, but sensory systems are usually studied under highly constrained and passive conditions that may not probe important dimensions of the neural code. Here, we explored neural coding in the barrel cortex of head-fixed mice that tracked walls with their whiskers in tactile virtual reality. Optogenetic manipulations revealed that barrel cortex plays a role in wall-tracking. Closed-loop optogenetic control of layer 4 neurons can substitute for whisker-object contact to guide behavior resembling wall tracking. We measured neural activity using two-photon calcium imaging and extracellular recordings. Neurons were tuned to the distance between the animal snout and the contralateral wall, with monotonic, unimodal, and multimodal tuning curves. This rich representation of object location in the barrel cortex could not be predicted based on simple stimulus-response relationships involving individual whiskers and likely emerges within cortical circuits. DOI: http://dx.doi.org/10.7554/eLife.12559.001 PMID:26701910

  8. The Formation of Graphite Whiskers in the Primitive Solar Nebula

    NASA Technical Reports Server (NTRS)

    Nuth, Joseph A., III; Kimura, Yuki; Lucas, Christopher; Ferguson, Frank; Johnson, Natasha M.

    2010-01-01

    It has been suggested that carbonaceous grains are efficiently destroyed in the interstellar medium and must either reform in situ at very low pressures and temperatures or in an alternative environment more conducive to grain growth. Graphite whiskers have been discovered associated with high-temperature phases in meteorites such as calcium aluminum inclusions and chondrules, and it has been suggested that the expulsion of such material from proto stellar nebulae could significantly affect the optical properties of the average interstellar grain population. We have experimentally studied the potential for Fischer-Tropsch and Haber-Bosch type reactions to produce organic materials in protostellar systems from the abundant H2, CO, and N2 reacting on the surfaces of available silicate grains. When graphite grains are repeatedly exposed to H2, CO, and N2 at 875 K abundant graphite whiskers are observed to form on or from the surfaces of the graphite grains. In a dense, turbulent nebula, such extended whiskers are very likely to be broken off, and fragments could be ejected either in polar jets or by photon pressure after transport to the outer reaches of the nebula.

  9. Acetylene on Titan

    NASA Astrophysics Data System (ADS)

    Singh, Sandeep; McCord, Thomas B.; Combe, Jean-Philippe; Rodriguez, Sebastien; Cornet, Thomas; Le Mouélic, Stéphane; Clark, Roger Nelson; Maltagliati, Luca; Chevrier, Vincent

    2016-10-01

    Saturn's moon Titan possesses a thick atmosphere that is mainly composed of N2 (98%), CH4 (2 % overall, but 4.9% close to the surface) and less than 1% of minor species, mostly hydrocarbons [1]. A dissociation of N2 and CH4 forms complex hydrocarbons in the atmsophere and acetylene (C2H2) and ethane (C2H6) are produced most abundently. Since years, C2H2 has been speculated to exist on the surface of Titan based on its high production rate in the stratosphere predicted by photochemical models [2,3] and from its detection as trace gas sublimated/evaporated from the surface after the landing of the Huygens probe by the Gas Chromatograph Mass Spectrometer (GCMS) [1]. Here we show evidence of acetylene (C2H2) on the surface of Titan by detecting absorption bands at 1.55 µm and 4.93 µm using Cassini Visual and Infrared Mapping Spectrometer (VIMS) [4] at equatorial areas of eastern Shangri-La, and Fensal-Aztlan/Quivira.An anti-correlation of absorption band strength with albedo indicates greater concentrations of C2H2 in the dark terrains, such as sand dunes and near the Huygens landing site. The specific location of the C2H2 detections suggests that C2H2 is mobilized by surface processes, such as surface weathering by liquids through dissolution/evaporation processes.References:[1]Niemann et al., Nature 438, 779–784 (2005).[2]Lavvas et al., Planetary and Space Science 56, 67 – 99 (2008).[3]Lavvas et al., Planetary and Space Science 56, 27 – 66 (2008).[4] Brown et al., The Cassini-Huygens Mission 111–168 (Springer, 2004).

  10. Titan impacts and escape

    NASA Astrophysics Data System (ADS)

    Korycansky, D. G.; Zahnle, Kevin J.

    2011-01-01

    We report on hydrodynamic calculations of impacts of large (multi-kilometer) objects on Saturn's moon Titan. We assess escape from Titan, and evaluate the hypothesis that escaping ejecta blackened the leading hemisphere of Iapetus and peppered the surface of Hyperion. We carried out two- and three-dimensional simulations of impactors ranging in size from 4 to 100 km diameter, impact velocities between 7 and 15 km s -1, and impact angles from 0° to 75° from the vertical. We used the ZEUSMP2 hydrocode for the calculations. Simulations were made using three different geometries: three-dimensional Cartesian, two-dimensional axisymmetric spherical polar, and two-dimensional plane polar. Three-dimensional Cartesian geometry calculations were carried out over a limited domain (e.g. 240 km on a side for an impactor of size di = 10 km), and the results compared to ones with the same parameters done by Artemieva and Lunine (2005); in general the comparison was good. Being computationally less demanding, two-dimensional calculations were possible for much larger domains, covering global regions of the satellite (from 800 km below Titan's surface to the exobase altitude 1700 km above the surface). Axisymmetric spherical polar calculations were carried out for vertical impacts. Two-dimensional plane-polar geometry calculations were made for both vertical and oblique impacts. In general, calculations among all three geometries gave consistent results. Our basic result is that the amount of escaping material is less than or approximately equal to the impactor mass even for the most favorable cases. Amounts of escaping material scaled most strongly as a function of velocity, with high-velocity impacts generating the largest amount, as expected. Dependence of the relative amount of escaping mass fesc = mesc/ Mi on impactor diameter di was weak. Oblique impacts (impact angle θi > 45°) were more effective than vertical or near-vertical impacts; ratios of mesc/ Mi ˜ 1-2 were

  11. Zinc titanate sorbents

    DOEpatents

    Gupta, Raghubir P.; Gangwal, Santosh K.; Jain, Suresh C.

    1998-01-01

    The present invention provides a zinc titanate sorbent material useful in desulfurization applications. The zinc titanate material is in the form of generally spherical particles of substantially uniform chemical distribution. The sorbent material is capable of absorbing sulfur compounds from a gaseous feed in an amount of at least about 15 weight percent based on the weight of the sorbent. The sorbent material is prepared by a process including: (a) forming a zinc oxide/titanium dioxide dry blend, (b) preparing a substantially uniform aqueous slurry comprising the zinc oxide/titanium dioxide dry blend, organic binder, and at least about 1 weight percent inorganic binder based on the solids weight of the slurry, (c) spray drying the slurry to produce substantially spherical particles, and (d) calcining the particles at a temperature of between about 750.degree. C. to about 950.degree. C. The dry blend is formed by mixing between about 0.5 to about 2 parts zinc oxide having a median particle size of less than about 0.5 .mu., and about 1 part titanium dioxide having a median particle size of less than about 1 .mu.. The slurry contains substantially no free silica and may be prepared by the process including (1) preparing an aqueous solution of organic binder, (2) adding the dry blend to the aqueous solution of organic binder, and (3) adding the inorganic binder to the solution of organic binder, and blend. Additional reagents, such as a surfactant, may also be incorporated into the sorbent material. The present invention also provides a process for desulfurizing a gaseous stream. The process includes passing a gaseous stream through a reactor containing an attrition resistant zinc titanate sorbent material of the present invention.

  12. Zinc titanate sorbents

    DOEpatents

    Gupta, R.P.; Gangwal, S.K.; Jain, S.C.

    1998-02-03

    The present invention provides a zinc titanate sorbent material useful in desulfurization applications. The zinc titanate material is in the form of generally spherical particles of substantially uniform chemical distribution. The sorbent material is capable of absorbing sulfur compounds from a gaseous feed in an amount of at least about 15 weight percent based on the weight of the sorbent. The sorbent material is prepared by a process including: (a) forming a zinc oxide/titanium dioxide dry blend, (b) preparing a substantially uniform aqueous slurry comprising the zinc oxide/titanium dioxide dry blend, organic binder, and at least about 1 weight percent inorganic binder based on the solids weight of the slurry, (c) spray drying the slurry to produce substantially spherical particles, and (d) calcining the particles at a temperature of between about 750 to about 950 C. The dry blend is formed by mixing between about 0.5 to about 2 parts zinc oxide having a median particle size of less than about 0.5 microns, and about 1 part titanium dioxide having a median particle size of less than about 1 micron. The slurry contains substantially no free silica and may be prepared by the process including (1) preparing an aqueous solution of organic binder, (2) adding the dry blend to the aqueous solution of organic binder, and (3) adding the inorganic binder to the solution of organic binder, and blend. Additional reagents, such as a surfactant, may also be incorporated into the sorbent material. The present invention also provides a process for desulfurizing a gaseous stream. The process includes passing a gaseous stream through a reactor containing an attrition resistant zinc titanate sorbent material of the present invention.

  13. The Tides of Titan

    NASA Astrophysics Data System (ADS)

    Iess, L.; Jacobson, R.; Ducci, M.; Stevenson, D. J.; Lunine, J. I.; Armstrong, J. W.; Asmar, S.; Racioppa, P.; Rappaport, N. J.; Tortora, P.

    2012-12-01

    Titan has long been thought to host a subsurface water ocean. A liquid water or water-ammonia layer underneath the outer icy shell was invoked to explain the Voyager and Cassini observations of abundant methane (an easily dissociated species) in the atmosphere of the satellite. Given the paucity of surface hydrocarbon reservoirs, the atmospheric methane must be supplied by the interior, and an ocean can both provide a large storage volume and facilitate the outgassing from the deeper layers of the satellite to the surface. Huygens probe observations of a Schumann-like resonance point to the presence of an electrically conductive layer at a depth of 50-100 km, which has been interpreted to be the top of an ammonia-doped ocean [1]. Cassini gravity observations provide stronger evidence of the existence of such subsurface ocean. By combining precise measurements of the spacecraft range rate during six flybys, suitably distributed along Titan's orbit (three near pericenter, two near apocenter one near quadrature), we have been able to determine the k2 Love number to be k2 = 0.589±0.150 and k2 = 0.637±0.224 in two independent so-lutions (quoted uncertainties are 2-sigma) [2]. Such a large value indicates that Titan is highly deformable over time scales of days, as one would expect if a global ocean were hidden beneath the outer icy shell. The inclusion of time-variable gravity in the solution provided also a more reliable estimate of the static field, including an updated long-wavelength geoid. We discuss the methods adopted in our solutions and some implications of our results for the interior structure of Titan, and outline the expected improvements from the additional gravity flybys before the end of mission in 2017. [1] C. Beghin, C. Sotin, M. Hamelin, Comptes Rendue Geoscience, 342, 425 (2010). [2] L. Iess, R.A. Jacobson, M. Ducci, D.J. Stevenson, J.I. Lunine, J.W. Armstrong, S.W. Asmar, P. Racioppa, N.J. Rappaport, P. Tortora, Science, 337, 457 (2012).

  14. Titan Science Return Quantification

    NASA Technical Reports Server (NTRS)

    Weisbin, Charles R.; Lincoln, William

    2014-01-01

    Each proposal for a NASA mission concept includes a Science Traceability Matrix (STM), intended to show that what is being proposed would contribute to satisfying one or more of the agency's top-level science goals. But the information traditionally provided cannot be used directly to quantitatively compare anticipated science return. We added numerical elements to NASA's STM and developed a software tool to process the data. We then applied this methodology to evaluate a group of competing concepts for a proposed mission to Saturn's moon, Titan.

  15. Potassium carbonate poisoning

    MedlinePlus

    Potassium carbonate is a white powder used to make soap, glass, and other items. This article discusses poisoning from swallowing or breathing in potassium carbonate. This article is for information only. Do ...

  16. Titan's astrobiology: some new data

    NASA Astrophysics Data System (ADS)

    Raulin, Francois; Coll, Patrice; Buch, Arnaud; Cloix, Megane; Guan, Yuan Yong; Jerome, Murielle; Poch, Olivier; Ramirez, Sandra I.; Szopa, Cyril; Cottin, Hervé

    The Cassini-Huygens observations of Titan have strongly strengthened its astrobiological impor-tance, clearly showing that Titan is one of the key planetary bodies for astrobiological studies. Indeed the Cassini-Huygens data show that there are many similarities which can be found when comparing Titan and the early Earth, in spite of much lower temperatures for Titan. One of these similarities is the presence of an active and complex organic chemistry in Titan's environment, which occurs from the high atmosphere to the surface and very likely in the sub-surface. This organic chemistry involves several of the key compounds of terrestrial prebiotic chemistry, and it represents, by itself, a major astrobiological aspect of Titan. Moreover, the potential presence of an internal water-ocean makes Titan a potential habitable environment, of obvious astrobiological importance. In fact, after five years of close observation by remote sensing and in situ instrumentations from the Cassini-Huygens mission, Titan does not look any more like a frozen primitive Earth, but it looks like an evolving planet, geologically active, with cryo-volcanism, eolian erosion, clouds and precipitations, and a methane cycle analogous to the water cycle on Earth. But the new data also show that a complex organic chemistry is taking place in the very high atmospheric layers of the satellite, with the formation in the ionosphere of high molecular weight (up about 10 000 Daltons) ions. Are these ions abundant enough in the lower atmosphere zones to act as organic monomers which then grow by aggregation, sedimentation and condensation down to the surface? This is one of the key questions that chemical models have now to answer. Cassini-Huygens observations have shown that there is no large surface ocean on Titan, but large regional lakes which behave like evolving liquid media. Those lakes are probably accumulating complex organics of astrobiological interest, including organic aerosols, and could

  17. Touchdown on Titan

    NASA Technical Reports Server (NTRS)

    Morring, Frank, Jr.

    2004-01-01

    Europe's Huygens probe is on target for a Dec. 25 separation from the Cassini Saturn orbiter that has carried it like a baby for more than seven years. The probe will spend three weeks coasting to a plunge into Titan's thick atmosphere on the morning of Jan. 14. If all goes as planned, the 349-kg. Huygens will spend more than 2 hr. descending by parachute to the mysterious surface of the planet-sized moon, and hopefully devote yet more time to broadcasting data after it lands. Before the day is over, Huygens is programmed to beam about 30 megabytes of data - including some 1,100 images-back to Earth through Cassini, a trip that will take some 75 min. to complete over the 1- billion-km. distance that separates the two planets. Within that data should be answers to questions that date back to 1655, when Dutch astronomer Christiaan Huygens found the moon with a homemade telescope and named it for the family of giants the ancient Greeks believed once ruled the earth. In the Solar System, there is no other world like Titan, with a nitrogen and methane atmospheric and a cold, hidden surface darker than Earth under the full Moon.

  18. Titan's Emergence from Winter

    NASA Technical Reports Server (NTRS)

    Flasar, F. Michael; Achterberg, Richard; Jennings, Donald; Schinder, Paul

    2011-01-01

    We summarize the changes in Titans thermal structure derived from Cassini CIRS and radio-occultation data during the transition from winter to early spring. Titan's surface, and middle atmosphere show noticeable seasonal change, whereas that in most of the troposphere is mated. This can be understood in terms of the relatively small radiative relaxation time in the middle atmosphere and much larger time scale in the troposphere. The surface exhibits seasonal change because the heat capacity in an annual skin depth is much smaller than that in the lowest scale height of the troposphere. Surface temperatures rise 1 K at raid and high latitudes in the winter northern hemisphere and cool in the southern hemisphere. Changes in in the middle atmosphere are more complicated. Temperatures in the middle stratosphere (approximately 1 mbar) increase by a few kelvin at mid northern latitudes, but those at high latitudes first increase as that region moves out of winter shadow, and then decrease. This probably results from the combined effect of increased solar heating as the suit moves higher in the sky and the decreased adiabatic warming as the sinking motions associated with the cross-equatorial meridional cell weaken. Consistent with this interpretation, the warm temperatures observed higher up at the winter polar stratopause cool significantly.

  19. Monosodium Titanate Sludge Filtration

    SciTech Connect

    Dworjanyn, L.O.

    2000-11-07

    Good filterability of tetraphenylborate (TPB) slurry is attributed to the hydrophobic nature of crystalline organic TPB that forms a firm but porous filter cake, allowing salt solution to pass through without unduly compressing the cake. Addition of inorganic sludge or monosodium titanate (MST) has an adverse effect on filtration, but the overall filtration rate with TPB is satisfactory. Poor cross-flow filtration performance for the Salt Disposition Alternatives requiring MST filtration is attributed primarily to the difficulty in filtering the residual inorganic sludge rich in iron and aluminum precipitates. Ferric hydrolysis products and colloids form a bulky and sticky filter cake significantly reducing filtration rate. Similarly poor filtration rates were observed in the BNFL ferric/ferrous precipitation process, necessitating a change to permanganate precipitation. This report, based on a few sludge settling observations, does not resolve the MST/Sludge filterability issue. However, it does identify the need for a change in emphasis from cross-flow optimization to understanding and controlling the chemistry and physics of alkaline inorganic particle suspensions and filterability. Promising potential exists to identify or develop surfactants or flocculants to enhance filterability of SRS sludge and monosodium titanate. Additional work is needed to provide a basic understanding of the nature of caustic sludge filter cake formation.

  20. Investigation of crystal growth in zero gravity environment and investigation of metallic whiskers

    NASA Technical Reports Server (NTRS)

    Davis, J. H.; Lal, R. B.; Walter, H. U.; Castle, J. G., Jr.

    1972-01-01

    Theoretical and experimental work reported relates to the effects of near-zero gravity on growths of crystals and metallic whiskers during Skylab and Apollo flight experiments. Studies on growth and characterization of candidate materials for flight experiments cover indium-bismuth compounds, bismuth single crystals, gallium arsenide films and single crystals, and cadmium whiskers.

  1. Natural Whisker-Guided Behavior by Head-Fixed Mice in Tactile Virtual Reality

    PubMed Central

    Sofroniew, Nicholas J.; Cohen, Jeremy D.; Lee, Albert K.

    2014-01-01

    During many natural behaviors the relevant sensory stimuli and motor outputs are difficult to quantify. Furthermore, the high dimensionality of the space of possible stimuli and movements compounds the problem of experimental control. Head fixation facilitates stimulus control and movement tracking, and can be combined with techniques for recording and manipulating neural activity. However, head-fixed mouse behaviors are typically trained through extensive instrumental conditioning. Here we present a whisker-based, tactile virtual reality system for head-fixed mice running on a spherical treadmill. Head-fixed mice displayed natural movements, including running and rhythmic whisking at 16 Hz. Whisking was centered on a set point that changed in concert with running so that more protracted whisking was correlated with faster running. During turning, whiskers moved in an asymmetric manner, with more retracted whisker positions in the turn direction and protracted whisker movements on the other side. Under some conditions, whisker movements were phase-coupled to strides. We simulated a virtual reality tactile corridor, consisting of two moveable walls controlled in a closed-loop by running speed and direction. Mice used their whiskers to track the walls of the winding corridor without training. Whisker curvature changes, which cause forces in the sensory follicles at the base of the whiskers, were tightly coupled to distance from the walls. Our behavioral system allows for precise control of sensorimotor variables during natural tactile navigation. PMID:25031397

  2. Parallel coding schemes of whisker velocity in the rat's somatosensory system.

    PubMed

    Lottem, Eran; Gugig, Erez; Azouz, Rony

    2015-03-15

    The function of rodents' whisker somatosensory system is to transform tactile cues, in the form of vibrissa vibrations, into neuronal responses. It is well established that rodents can detect numerous tactile stimuli and tell them apart. However, the transformation of tactile stimuli obtained through whisker movements to neuronal responses is not well-understood. Here we examine the role of whisker velocity in tactile information transmission and its coding mechanisms. We show that in anaesthetized rats, whisker velocity is related to the radial distance of the object contacted and its own velocity. Whisker velocity is accurately and reliably coded in first-order neurons in parallel, by both the relative time interval between velocity-independent first spike latency of rapidly adapting neurons and velocity-dependent first spike latency of slowly adapting neurons. At the same time, whisker velocity is also coded, although less robustly, by the firing rates of slowly adapting neurons. Comparing first- and second-order neurons, we find similar decoding efficiencies for whisker velocity using either temporal or rate-based methods. Both coding schemes are sufficiently robust and hardly affected by neuronal noise. Our results suggest that whisker kinematic variables are coded by two parallel coding schemes and are disseminated in a similar way through various brain stem nuclei to multiple brain areas.

  3. Mapping products of Titan's surface

    USGS Publications Warehouse

    Stephan, Katrin; Jaumann, Ralf; Karkoschka, Erich; Barnes, Jason W.; Tomasko, Martin G.; Turtle, Elizabeth P.; Le Corre, Lucille; Langhans, Mirjam; Le Mouelic, Stephane; Lorenz, Ralf D.; Perry, Jason; Brown, Robert H.; Lebreton, Jean-Pierre

    2009-01-01

    Remote sensing instruments aboard the Cassini spacecraft have been observed the surface of Titan globally in the infrared and radar wavelength ranges as well as locally by the Huygens instruments revealing a wealth of new morphological features indicating a geologically active surface. We present a summary of mapping products of Titan's surface derived from data of the remote sensing instruments onboard the Cassini spacecraft (ISS, VIMS, RADAR) as well as the Huygens probe (DISR) that were achieved during the nominal Cassini mission including an overview of Titan's recent nomenclature.

  4. Mapping Methane in Titan's Atmosphere near Titan's Surface

    NASA Astrophysics Data System (ADS)

    Young, Eliot; Soderblom, Jason; Barnes, Jason

    2016-06-01

    Titan's atmospheric methane may be coupled to sources and sinks on its surface. In order to map methane concentrations in layers just above Titan's surface, we use data sets in which locations on Titan are imaged from a variety of viewing angles (and within a short time span). We also use a radiative transfer code based on the Markov Chain method of Esposito and House (1978, AJ 219, 1058) to accommodate spherical atmospheric geometries. We report on (a) selected Cassini/VIMS flybys that image terrain on Titan from different angles, (b) the expected vertical resolution of methane maps near the surface from these flybys and (c) preliminary results: 3D methane and haze distributions and surface albedos.

  5. Contributions of stress and oxidation on the formation of whiskers in Pb-free solders

    SciTech Connect

    Duncan, A. J.; Hoffman, E. N.

    2016-01-01

    Understanding the environmental factors influencing formation of tin whiskers on electrodeposited lead free, tin coatings over copper (or copper containing) substrates is the topic of this study . An interim report* summarized initial observations as to the role of stress and oxide formation on whisker growth. From the initial results, two main areas were chosen to be the focus of additional research: the demonstration of effects of elastic stress state in the nucleation of whiskers and the confirmation of the effect of oxygen content in the formation of whiskers. Different levels of elastic stress were induced with the incorporation of a custom designed fixture that loaded the sample in a four-point bending configuration and were maintained in an environmental chamber under conditions deemed favorable for whisker growth. The effects of oxygen content were studied by aging substrates in gas vials of varying absolute pressure and different oxygen partial pressure.

  6. Regulation of Potassium Homeostasis.

    PubMed

    Palmer, Biff F

    2015-06-01

    Potassium is the most abundant cation in the intracellular fluid, and maintaining the proper distribution of potassium across the cell membrane is critical for normal cell function. Long-term maintenance of potassium homeostasis is achieved by alterations in renal excretion of potassium in response to variations in intake. Understanding the mechanism and regulatory influences governing the internal distribution and renal clearance of potassium under normal circumstances can provide a framework for approaching disorders of potassium commonly encountered in clinical practice. This paper reviews key aspects of the normal regulation of potassium metabolism and is designed to serve as a readily accessible review for the well informed clinician as well as a resource for teaching trainees and medical students.

  7. Rat whisker motor cortex is subdivided into sensory-input and motor-output areas

    PubMed Central

    Smith, Jared B.; Alloway, Kevin D.

    2013-01-01

    Rodent whisking is an exploratory behavior that can be modified by sensory feedback. Consistent with this, many whisker-sensitive cortical regions project to agranular motor [motor cortex (MI)] cortex, but the relative topography of these afferent projections has not been established. Intracortical microstimulation (ICMS) evokes whisker movements that are used to map the functional organization of MI, but no study has compared the whisker-related inputs to MI with the ICMS sites that evoke whisker movements. To elucidate this relationship, anterograde tracers were placed in posterior parietal cortex (PPC) and in the primary somatosensory (SI) and secondary somatosensory (SII) cortical areas so that their labeled projections to MI could be analyzed with respect to ICMS sites that evoke whisker movements. Projections from SI and SII terminate in a narrow zone that marks the transition between the medial agranular (AGm) and lateral agranular (AGl) cortical areas, but PPC projects more medially and terminates in AGm proper. Paired recordings of MI neurons indicate that the region between AGm and AGl is highly responsive to whisker deflections, but neurons in AGm display negligible responses to whisker stimulation. By contrast, AGm microstimulation is more effective in evoking whisker movements than microstimulation of the transitional region between AGm and AGl. The AGm region was also found to contain a larger concentration of corticotectal neurons, which could convey whisker-related information to the facial nucleus. These results indicate that rat whisker MI is comprised of at least two functionally distinct subregions: a sensory processing zone in the transitional region between AGm and AGl, and a motor-output region located more medially in AGm proper. PMID:23372545

  8. The Mechanical Variables Underlying Object Localization along the Axis of the Whisker

    PubMed Central

    Pammer, Lorenz; O’Connor, Daniel H.; Hires, S. Andrew; Clack, Nathan G.; Huber, Daniel; Myers, Eugene W.; Svoboda, Karel

    2013-01-01

    Rodents move their whiskers to locate objects in space. Here we used psychophysical methods to show that head-fixed mice can localize objects along the axis of a single whisker, the radial dimension, with one-millimeter precision. High-speed videography allowed us to estimate the forces and bending moments at the base of the whisker, which underlie radial distance measurement. Mice judged radial object location based on multiple touches. Both the number of touches (1–17) and the forces exerted by the pole on the whisker (up to 573 µN; typical peak amplitude, 100 µN) varied greatly across trials. We manipulated the bending moment and lateral force pressing the whisker against the sides of the follicle and the axial force pushing the whisker into the follicle by varying the compliance of the object during behavior. The behavioral responses suggest that mice use multiple variables (bending moment, axial force, lateral force) to extract radial object localization. Characterization of whisker mechanics revealed that whisker bending stiffness decreases gradually with distance from the face over five orders of magnitude. As a result, the relative amplitudes of different stress variables change dramatically with radial object distance. Our data suggest that mice use distance-dependent whisker mechanics to estimate radial object location using an algorithm that does not rely on precise control of whisking, is robust to variability in whisker forces, and is independent of object compliance and object movement. More generally, our data imply that mice can measure the amplitudes of forces in the sensory follicles for tactile sensation. PMID:23595731

  9. Ices in Titan's Lower Stratosphere

    NASA Technical Reports Server (NTRS)

    Anderson, Carrie

    2010-01-01

    Analyses of Cassini CIRS far-infrared limb spectra of Titan at 15N, 15S, and 58S reveal a broad emission feature between 70 and 270/cm, restricted to altitudes between 60 and 100 km. This emission feature is chemically different from Titan's photochemical aerosol, which has an emission feature peak around 145 cm-1. The shape of the observed broad emission feature resembles a mixture of the solid component of the two most abundant nitrites in Titan's stratosphere, that of HCN and HC3N. Following the saturation vapor pressure vertical profiles of HCN and HC3N, the 60 to 100 km altitude range corresponds closely to the vertical location where these nitriles are expected to condense out and form small, suspended ice particles. This is the first time ices in Titan's stratosphere have been identified at latitudes south of 50N. Results and physical implications will be discussed.

  10. Titan's greenhouse and antigreenhouse effects

    NASA Technical Reports Server (NTRS)

    Mckay, Christopher P.; Pollack, James B.; Courtin, Regis

    1992-01-01

    Thermal mechanisms active in Titan's atmosphere are discussed in a brief review of data obtained during the Voyager I flyby in 1980. Particular attention is given to the greenhouse effect (GHE) produced by atmospheric H2, N2, and CH4; this GHE is stronger than that on earth, with CH4 and H2 playing roles similar to those of H2O and CO2 on earth. Also active on Titan is an antigreenhouse effect, in which dark-brown and orange organic aerosols block incoming solar light while allowing IR radiation from the Titan surface to escape. The combination of GHE and anti-GHE leads to a surface temperature about 12 C higher than it would be if Titan had no atmosphere.

  11. Seasonal Changes in Titan's Meteorology

    NASA Technical Reports Server (NTRS)

    Turtle, E. P.; DelGenio, A. D.; Barbara, J. M.; Perry, J. E.; Schaller, E. L.; McEwen, A. S.; West, R. A.; Ray, T. L.

    2011-01-01

    The Cassini Imaging Science Subsystem has observed Titan for 1/4 Titan year, and we report here the first evidence of seasonal shifts in preferred locations of tropospheric methane clouds. South \\polar convective cloud activity, common in late southern summer, has become rare. North \\polar and northern mid \\latitude clouds appeared during the approach to the northern spring equinox in August 2009. Recent observations have shown extensive cloud systems at low latitudes. In contrast, southern mid \\latitude and subtropical clouds have appeared sporadically throughout the mission, exhibiting little seasonality to date. These differences in behavior suggest that Titan s clouds, and thus its general circulation, are influenced by both the rapid temperature response of a low \\thermal \\inertia surface and the much longer radiative timescale of Titan s cold thick troposphere. North \\polar clouds are often seen near lakes and seas, suggesting that local increases in methane concentration and/or lifting generated by surface roughness gradients may promote cloud formation. Citation

  12. Effect of whisker surface treatments and processing conditions on the SiC/Al sub 2 O sub 3 interface

    SciTech Connect

    Alexander, K.B.; Angelini, P.; Becher, P.F.

    1990-01-01

    Various electron microscopy techniques have been used to evaluate the microstructural and interfacial characteristics of silicon carbide whisker-reinforced alumina composites. The effects of subjecting whiskers to oxidizing and reducing treatments prior to composite fabrication were examined. Whisker/matrix interfaces in which carbon coatings were applied to whiskers prior to specimen fabrication were also examined. Physical and thermodynamic arguments can be used to explain why it is difficult to greatly modify the physical nature of the whisker/matrix interface. 7 refs., 7 figs.

  13. Life on Titan

    NASA Astrophysics Data System (ADS)

    Potashko, Oleksandr

    Volcanoes engender life on heavenly bodies; they are pacemakers of life. All planets during their period of formation pass through volcanism hence - all planets and their satellites pass through the life. Tracks of life If we want to find tracks of life - most promising places are places with volcanic activity, current or past. In the case of just-in-time volcanic activity we have 100% probability to find a life. Therefore the most perspective “search for life” are Enceladus, Io and comets, further would be Venus, Jupiter’s satellites, Saturn’s satellites and first of all - Titan. Titan has atmosphere. It might be result of high volcanic activity - from one side, from other side atmosphere is a necessary condition development life from procaryota to eucaryota. Existence of a planet means that all its elements after hydrogen formed just there inside a planet. The forming of the elements leads to the formation of mineral and organic substances and further to the organic life. Development of the life depends upon many factors, e.g. the distance from star/s. The intensity of the processes of the element formation is inversely to the distance from the star. Therefore we may suppose that the intensity of the life in Mercury was very high. Hence we may detect tracks of life in Mercury, particularly near volcanoes. The distance from the star is only one parameter and now Titan looks very active - mainly due to interior reason. Its atmosphere compounds are analogous to comet tail compounds. Their collation may lead to interesting result as progress occurs at one of them. Volcanic activity is as a source of life origin as well a reason for a death of life. It depends upon the thickness of planet crust. In the case of small thickness of a crust the probability is high that volcanoes may destroy a life on a planet - like Noachian deluge. Destroying of the life under volcano influences doesn’t lead to full dead. As result we would have periodic Noachian deluge or

  14. The TITAN magnet configuration

    NASA Astrophysics Data System (ADS)

    Bathke, C. G.

    The TITAN study uses copper-alloy ohmic-heating coils (OHC) to start up inductively a reversed-field-pinch (RFP) fusion reactor. The plasma equilibrium is maintained with a pair of superconducting equilibrium-field coils (EFCs). A second pair of copper EFCs provides the necessary trimming of the equilibrium field during plasma transients. A compact toroidal-field-coil (TFC) set is provided by an integrated blanket/coil (IBC). The IBC concept also is applied to the toroidal-field divertor coils. Steady-state operation is achieved with oscillating-field current drive, which oscillates at low amplitude and frequency the OHCs, EFCs, the TFCs, and divertor coils about their steady-state currents. An integrated magnet design, which uses low-field, low technology coils, and the related design basis is given.

  15. Titan's rotation - Surface feature observed

    NASA Astrophysics Data System (ADS)

    Lemmon, M. T.; Karkoschka, E.; Tomasko, M.

    1993-06-01

    A surface feature or a near-surface fracture is suggested to account for the time variations in the 0.94, 1.08, and 1.28 micron atmospheric windows of Titan's geometric albedo, relative to its albedo in adjacent methane bands. These observations are noted to be consistent with synchronous rotation. They can also be explained by a 0.1-higher surface albedo on Titan's leading hemisphere.

  16. Simulations of Titan's paleoclimate

    NASA Astrophysics Data System (ADS)

    Lora, Juan M.; Lunine, Jonathan I.; Russell, Joellen L.; Hayes, Alexander G.

    2014-11-01

    We investigate the effects of varying Saturn's orbit on the atmospheric circulation and surface methane distribution of Titan. Using a new general circulation model of Titan's atmosphere, we simulate its climate under four characteristic configurations of orbital parameters that correspond to snapshots over the past 42 kyr, capturing the amplitude range of long-period cyclic variations in eccentricity and longitude of perihelion. The model, which covers pressures from the surface to 0.5 mbar, reproduces the present-day temperature profile and tropospheric superrotation. In all four simulations, the atmosphere efficiently transports methane poleward, drying out the low- and mid-latitudes, indicating that these regions have been desert-like for at least tens of thousands of years. Though circulation patterns are not significantly different, the amount of surface methane that builds up over either pole strongly depends on the insolation distribution; in the present-day, methane builds up preferentially in the north, in agreement with observations, where summer is milder but longer. The same is true, to a lesser extent, for the configuration 14 kyr ago, while the south pole gains more methane in the case for 28 kyr ago, and the system is almost symmetric 42 kyr ago. This confirms the hypothesis that orbital forcing influences the distribution of surface liquids, and that the current observed asymmetry could have been partially or fully reversed in the past. The evolution of the orbital forcing implies that the surface reservoir is transported on timescales of ∼30 kyr, in which case the asymmetry reverses with a period of ∼125 kyr. Otherwise, the orbital forcing does not produce a net asymmetry over longer timescales, and is not a likely mechanism for generating the observed dichotomy.

  17. From Titan's chemistry and exobiology to Titan's astrobiology

    NASA Astrophysics Data System (ADS)

    Raulin, François

    2015-04-01

    When the IDS proposal « Titan's chemistry and exobiology » was submitted to ESA 25 years ago, in the frame of what will become the Cassini-Huygens mission, Titan was already seen as a quite interesting planetary object in the solar system for Exobiology. Several organic compounds of prebiotic interest were identified in its atmosphere, which was thus was expected to be chemically very active, especially in term of organic processes. Atmospheric aerosols seemed to play a key role in this chemistry. Moreover, the presence of an internal aqueous ocean, compatible with life was suspected. A few years later, when astrobiology was (re)invented, Titan became one of the most interesting planetary target for this new (but very similar to exobiology) field. With the Cassini-Huygens mission, the exo/astrobiological interest of Titan has become more and more important. However, the mission has been providing a vision of Titan quite different from what it was supposed. Its atmospheric organic chemistry is very complex and starts in much higher zones than it was believed before, involving high molecular weight species in the ionosphere. Titan's surface appears to be far from homogeneous: instead of been covered by a global methane-ethane ocean, it is very diversified, with dunes, lakes, bright and dark areas, impact and volcanic craters with potential cryovolcanic activity. These various geological areas are continuously feeded by atmospheric aerosols, which represent an important step in the complexity of Titan's organic chemistry, but probably not the final one. Indeed, after being deposited on the surface, in the potential cryovolvanic zones, these particles may react with water ice and form compounds of exo/astrobiological interest, such as amino acids, purine and pyrimidine bases. Moreover, The Cassini-Huygens data strongly support the potential presence of an internal water ocean, which becomes less and less hypothetical and of great interest for exobiology. These

  18. Cloud formation in Titan's Stratosphere

    NASA Astrophysics Data System (ADS)

    Barth, Erika

    2016-06-01

    In addition to the organic haze particles produced photochemically in Titan's upper atmosphere, a number of trace gases are also created. These hydrocarbon and nitrile species include C2H6, C2H2, C4H10, HCN, HC3N, C2H5CN and many more. While both Voyager and Cassini observations have found evidence for ices (e.g. C4N2, HCN) in the atmosphere above Titan's poles, these species are also likely to condense at other latitudes forming optically thin ice layers in the stratosphere. A series of simulations have been conducted using Titan CARMA, a 1-D microphysics and radiative transfer model, to explore cloud particle formation with ˜20 of Titan's trace hydrocarbon and nitrile gases. These species reach their condensation temperatures between 60 and 110 km. Most condense solely as ices, however, C3H8 will condense first near 70 km as a liquid and then freeze as the droplets descend toward the surface. C3H8 and C2H6 join CH4 as a liquid at Titan's surface. Many ices have long condensation timescales resulting in particle radii ˜1 micron or less. Several (including HCN, C3H8, C2H2) will grow 10-50 times larger. Expected condensation altitudes and particle sizes will be presented, as well as the implications for the optical properties of Titan's stratospheric aerosol particles.

  19. The TITAN reversed-field-pinch fusion reactor study

    SciTech Connect

    Not Available

    1990-01-01

    This report discusses research on the titan-1 fusion power core. The major topics covered are: titan-1 fusion-power-core engineering; titan-1 divertor engineering; titan-1 tritium systems; titan-1 safety design and radioactive-waste disposal; and titan-1 maintenance procedures.

  20. MBE Growth of GaAs Whiskers on Si Nanowires

    SciTech Connect

    Maxwell Andrews, Aaron

    2010-01-04

    We present the growth of GaAs nanowhiskers by molecular beam epitaxy on Si (111) nanowires grown by low-pressure chemical vapor deposition. The whiskers grow in the wurtzite phase, along the [0001] direction, on the {l_brace}112{r_brace} facets of the Si nanowire, forming a star-like six-fold radial symmetry. The photoluminescence shows a 30 meV blue shift with respect to bulk GaAs, additionally a GaAs/AlAs core-shell heterostructure shows increased luminescence.

  1. Whiskers, cones and pyramids created in sputtering by ion bombardment

    NASA Technical Reports Server (NTRS)

    Wehner, G. K.

    1979-01-01

    A thorough study of the role which foreign atoms play in cone formation during sputtering of metals revealed many experimental facts. Two types of cone formation were distinquished, deposit cones and seed cones. Twenty-six combinations of metals for seed cone formation were tested. The sputtering yield variations with composition for combinations which form seed cones were measured. It was demonstrated that whisker growth becomes a common occurrence when low melting point material is sputter deposited on a hot nonsputtered high melting point electrode.

  2. An analysis of the wear behavior of SiC whisker reinforced alumina from 25 to 1200 C

    NASA Technical Reports Server (NTRS)

    Dellacorte, Christopher

    1991-01-01

    A model is described for predicting the wear behavior of whisker reinforced ceramics. The model was successfully applied to a silicon carbide whisker reinforced alumina ceramic composite subjected to sliding contact. The model compares the friction forces on the whiskers due to sliding, which act to pull or push them out of the matrix, to the clamping or compressive forces on the whiskers due to the matrix, which act to hold the whiskers in the composite. At low temperatures, the whiskers are held strongly in the matrix and are fractured into pieces during the wear process along with the matrix. At elevated temperatures differential thermal expansion between the whiskers and matrix can cause loosening of the whiskers and lead to pullout during the wear process and to higher wear. The model, which represents the combination of elastic stress analysis and a friction heating analysis, predicts a transition temperature at which the strength of the whiskers equals the clamping force holding them in the matrix. Above the transition the whiskers are pulled out of the matrix during sliding, and below the transition the whiskers are simply fractured. The existence of the transition gives rise to a dual wear mode or mechanism behavior for this material which was observed in laboratory experiments. The results from this model correlate well with experimentally observed behavior indicating that the model may be useful in obtaining a better understanding of material behavior and in making material improvements.

  3. The Surface Composition of Titan

    NASA Astrophysics Data System (ADS)

    Clark, R. N.; Pearson, N.; Brown, R. H.; Cruikshank, D. P.; Barnes, J. W.; Jaumann, R.; Soderblom, L. A.; Griffith, C. A.; Rodriguez, S.; Le Mouelic, S.; Lunine, J.; Sotin, C.; Baines, K. H.; Buratti, B. J.; Nicholson, P. D.; Nelson, R.; Stephan, K.

    2011-12-01

    Determining the surface composition of Titan has been inhibited by the lack of spectral properties of potential compounds. We have measured the 0.35 to 5-micron spectral reflectance of a wide range of compounds that might be relevant to Titan and trends are now coming to light with possible spectral matches for classes of materials. While some compounds have been identified and mapped on Titan's surface, such as liquid ethane + methane lakes and benzene, the compounds responsible for the main spectral properties have remained elusive (Clark et al, JGR 2010). Titan's surface is seen in the near infrared in only a few spectral windows, near 0.94, 1.1, 1.3, 1.6, 2.0, 2.68-2.78, and 4.9-5.1 microns in the Cassini Visual and Infrared Mapping Spectrometer (VIMS) spectral range. At shorter wavelengths, UV absorption in the spectra of Titan's haze constrains the surface composition because haze particles settle onto Titan's surface. The average apparent reflectance in the IR windows generally decreases with increasing wavelength except for the 2.7 and 5-micron windows which are at similar levels. The decrease has led researchers to infer a number of compounds responsible for the observed decreasing spectral shape; the most common being water ice. But ice is incompatible with the 2.78/2.68 micron I/F ratio. Many organic compounds have absorptions that are not seen in spectra of Titan, eliminating them as possible major components at the surface, including many polycyclic aromatic hydrocarbons (PAH) previously thought to be compatible with parts of Titan's spectrum. We find that ring compounds similar to benzene rings, but with some C-H bonds replaced by NH have a closer match to Titan's overall spectrum and can explain the relative intensities observed in the spectral windows, including the 2.68 and 2.78-micron double window, the low 3-5 micron reflectance, and increased absorption near 2.1-microns. Key among these compounds that show general properties that match Titan are

  4. Representation of egomotion in rat's trident and E-row whisker cortices.

    PubMed

    Chorev, Edith; Preston-Ferrer, Patricia; Brecht, Michael

    2016-10-01

    The whisker trident, a three-whisker array on the rat's chin, has been implicated in egomotion sensing and might function as a tactile speedometer. Here we study the cortical representation of trident whiskers and E-row whiskers in barrel cortex. Neurons identified in trident cortex of anesthetized animals showed sustained velocity-sensitive responses to ground motion. In freely moving animals, about two-thirds of the units in the trident and E-row whisker cortices were tuned to locomotion speed, a larger fraction of speed-tuned cells than in the somatosensory dysgranular zone. Similarly, more units were tuned to acceleration and showed sensitivity to turning in trident and E-row whisker cortices than in the dysgranular zone. Microstimulation in locomoting animals evoked small but significant speed changes, and such changes were larger in the trident and E-row whisker representations than in the dysgranular zone. Thus, activity in trident and E-row cortices represents egomotion information and influences locomotion behavior. PMID:27526205

  5. Long-term water-aging of whisker-reinforced polymer-matrix composites.

    PubMed

    Xu, H H K

    2003-01-01

    Long-term water exposure may degrade polymer-matrix composites. This study investigated the water-aging of whisker composites. It was hypothesized that whiskers would provide stable and substantial reinforcement, and that whisker type would affect water-aging resistance. Silica-fused Si(3)N(4) and SiC whiskers were incorporated into a resin. The specimens were tested by three-point flexure and nano-indentation vs. water-aging for 1 to 730 days. After 730 days, SiC composite had a strength (mean +/- SD; n = 6) of 185 +/- 33 MPa, similar to 146 +/- 44 MPa for Si(3)N(4) composite (p = 0.064); both were significantly higher than 67 +/- 23 MPa for an inlay/onlay control (p < 0.001). Compared with 1 day, the strength of the SiC composite showed no decrease, while that of the Si(3)N(4) composite decreased. The decrease was due to whisker weakening rather than to resin degradation or interface breakdown. Whisker composites also had higher moduli than the controls. In conclusion, silica-fused whiskers bonded to polymer matrix and resisted long-term water attack, resulting in much stronger composites than the controls after water-aging.

  6. Mapping of Titan: Results from the first Titan radar passes

    USGS Publications Warehouse

    Stofan, E.R.; Lunine, J.I.; Lopes, R.; Paganelli, F.; Lorenz, R.D.; Wood, C.A.; Kirk, R.; Wall, S.; Elachi, C.; Soderblom, L.A.; Ostro, S.; Janssen, M.; Radebaugh, J.; Wye, L.; Zebker, H.; Anderson, Y.; Allison, M.; Boehmer, R.; Callahan, P.; Encrenaz, P.; Flamini, E.; Francescetti, G.; Gim, Y.; Hamilton, G.; Hensley, S.; Johnson, W.T.K.; Kelleher, K.; Muhleman, D.; Picardi, G.; Posa, F.; Roth, L.; Seu, R.; Shaffer, S.; Stiles, B.; Vetrella, S.; West, R.

    2006-01-01

    The first two swaths collected by Cassini's Titan Radar Mapper were obtained in October of 2004 (Ta) and February of 2005 (T3). The Ta swath provides evidence for cryovolcanic processes, the possible occurrence of fluvial channels and lakes, and some tectonic activity. The T3 swath has extensive areas of dunes and two large impact craters. We interpret the brightness variations in much of the swaths to result from roughness variations caused by fracturing and erosion of Titan's icy surface, with additional contributions from a combination of volume scattering and compositional variations. Despite the small amount of Titan mapped to date, the significant differences between the terrains of the two swaths suggest that Titan is geologically complex. The overall scarcity of impact craters provides evidence that the surface imaged to date is relatively young, with resurfacing by cryovolcanism, fluvial erosion, aeolian erosion, and likely atmospheric deposition of materials. Future radar swaths will help to further define the nature of and extent to which internal and external processes have shaped Titan's surface. ?? 2006 Elsevier Inc. All rights reserved.

  7. Mechanism and Prevention of Spontaneous Tin Whisker Growth

    SciTech Connect

    Tu, King-Ning; Suh, Jong-ook; Wu, Albert Tzu-Chia; Tamura,Nobumichi; Tung, Chih-Hang

    2005-05-05

    Spontaneous Sn whisker growth on Cu leadframe finished withPb-free solder is a serious reliability problem in electrical andelectronic devices. Recently, Fortune magazine had an article to describethe urgency of the problem. The spontaneous growth is an irreversibleprocess, in which there are two atomic fluxes driven by two kinds ofdriving force. There are a flux of Cu atoms and a flux of Sn atoms. TheCu atoms diffuse from the leadframe into the solder finish driven bychemical potential gradient to form intermetallic compound of Cu6Sn5 inthe grain boundaries of the solder, and the growth of the compound atroom temperature generates a compressive stress in the solder. To relievethe stress, a flux of Snatoms driven by the stress gradient diffuses awayto grow a spontaneous Sn whisker which is stress-free. The typicalindustry solution is to inserta diffusion barrier of Ni between the Cuand solder to prevent the diffusion of Cu into the solder. It isinsufficient, because we have to uncouplethe irreversible processes andstop both the fluxes of Cu and Sn. A solution is presentedhere.

  8. Tin Whisker Electrical Short Circuit Characteristics. Part 2

    NASA Technical Reports Server (NTRS)

    Courey, Karim J.; Asfour, Shihab S.; Onar, Arzu; Bayliss, Jon A.; Ludwig, Lawrence L.; Wright, Maria C.

    2009-01-01

    Existing risk simulations make the assumption that when a free tin whisker has bridged two adjacent exposed electrical conductors, the result is an electrical short circuit. This conservative assumption is made because shorting is a random event that has an unknown probability associated with it. Note however that due to contact resistance electrical shorts may not occur at lower voltage levels. In our first article we developed an empirical probability model for tin whisker shorting. In this paper, we develop a more comprehensive empirical model using a refined experiment with a larger sample size, in which we studied the effect of varying voltage on the breakdown of the contact resistance which leads to a short circuit. From the resulting data we estimated the probability distribution of an electrical short, as a function of voltage. In addition, the unexpected polycrystalline structure seen in the focused ion beam (FIB) cross section in the first experiment was confirmed in this experiment using transmission electron microscopy (TEM). The FIB was also used to cross section two card guides to facilitate the measurement of the grain size of each card guide's tin plating to determine its finish.

  9. Whisker-related circuitry in the trigeminal nucleus principalis: Topographic precision.

    PubMed

    Jacquin, Mark F; Arends, Joop J A; Renehan, William E; Waite, Phil M E; Shortland, Peter J

    2015-01-01

    Single whiskers are topographically represented in the trigeminal (V) nucleus principalis (PrV) by a set of cylindrical aggregates of primary afferent terminals and somata (barrelettes). This isomorphic pattern is transmitted to the thalamus and barrel cortex. However, it is not known if terminals in PrV from neighboring whiskers interdigitate so as to violate rules of spatial parcellation predicted by barrelette borders; nor is it known the extent to which higher order inputs are topographic. The existence of inter-whisker arbor overlap or diffuse higher order inputs would demand additional theoretical principles to account for single whisker dominance in PrV cell responses. In adult rats, first, primary afferent pairs responding to the same or neighboring whiskers and injected with Neurobiotin or horseradish peroxidase were rendered brown or black to color-code their terminal boutons. When collaterals from both fibers appeared in the same topographic plane through PrV, the percentage of the summed area of the two arbor envelopes that overlapped was computed. For same-whisker pairs, overlap was 5 ± 6% (mean ± SD). For within-row neighbors, overlap was 2 ± 5%. For between-row neighbors, overlap was 1 ± 4%. Second, the areas of whisker primary afferent arbors and their corresponding barrelettes in the PrV were compared. In the transverse plane, arbor envelopes significantly exceeded the areas of cytochrome oxidase-stained barrelettes; arbors often extended into neighboring barrelettes. Third, bulk tracing of the projections from the spinal V subnucleus interpolaris (SpVi) to the PrV revealed strict topography such that they connect same-whisker barrelettes in the SpVi and PrV. Thus, whisker primary afferents do not exclusively project to their corresponding PrV barrelette, whereas higher order SpVi inputs to the PrV are precisely topographic. PMID:25019347

  10. Calcium silicate ceramic scaffolds toughened with hydroxyapatite whiskers for bone tissue engineering

    SciTech Connect

    Feng, Pei; Wei, Pingpin; Li, Pengjian; Gao, Chengde; Shuai, Cijun; Peng, Shuping

    2014-11-15

    Calcium silicate possessed excellent biocompatibility, bioactivity and degradability, while the high brittleness limited its application in load-bearing sites. Hydroxyapatite whiskers ranging from 0 to 30 wt.% were incorporated into the calcium silicate matrix to improve the strength and fracture resistance. Porous scaffolds were fabricated by selective laser sintering. The effects of hydroxyapatite whiskers on the mechanical properties and toughening mechanisms were investigated. The results showed that the scaffolds had a uniform and continuous inner network with the pore size ranging between 0.5 mm and 0.8 mm. The mechanical properties were enhanced with increasing hydroxyapatite whiskers, reached a maximum at 20 wt.% (compressive strength: 27.28 MPa, compressive Young's modulus: 156.2 MPa, flexural strength: 15.64 MPa and fracture toughness: 1.43 MPa·m{sup 1/2}) and then decreased by addition of more hydroxyapatite whiskers. The improvement of mechanical properties was due to whisker pull-out, crack deflection and crack bridging. Moreover, the degradation rate decreased with the increase of hydroxyapatite whisker content. A layer of bone-like apatite was formed on the scaffold surfaces after being soaked in simulated body fluid. Human osteoblast-like MG-63 cells spread well on the scaffolds and proliferated with increasing culture time. These findings suggested that the calcium silicate scaffolds reinforced with hydroxyapatite whiskers showed great potential for bone regeneration and tissue engineering applications. - Highlights: • HA whiskers were incorporated into CS to improve the properties. • The scaffolds were successfully fabricated by SLS. • Toughening mechanisms was whisker pull-out, crack deflection and bridging. • The scaffolds showed excellent apatite forming ability.

  11. Data on electrical properties of nickel modified potassium polytitanates compacted powders.

    PubMed

    Goffman, V G; Gorokhovsky, A V; Gorshkov, N V; Fedorov, F S; Tretychenko, E V; Sevrugin, A V

    2015-09-01

    Potassium polytitanates are new promising type of ferroelectric ceramic materials with high ionic conductivity, highly polarizable structure and extremely high permittivity. Its structure is formed by [TiO6] octahedral units to layers with mobile potassium and hydroxonium ions in-between. The treatment in solutions containing nickel ions allows forming heterostructured materials which consist of potassium polytitanate particles intercalated by Ni(2+) ions and/or decorated by nickel oxides NiO x . This modification route is fully dependant on solution pH, i.e. in acidic solutions the intercalation process prevails, in alkaline solutions potassium polytitanate is mostly decorated by the oxides. Therefore, electronic structure and electrical properties can be regulated depending on modification conditions, pH and ions concentration. Here we report the data on electric properties of potassium titanate modified in nickel sulfate solutions at different pH. PMID:26217788

  12. Data on electrical properties of nickel modified potassium polytitanates compacted powders

    PubMed Central

    Goffman, V.G.; Gorokhovsky, A.V.; Gorshkov, N.V.; Fedorov, F.S.; Tretychenko, E.V.; Sevrugin, A.V.

    2015-01-01

    Potassium polytitanates are new promising type of ferroelectric ceramic materials with high ionic conductivity, highly polarizable structure and extremely high permittivity. Its structure is formed by [TiO6] octahedral units to layers with mobile potassium and hydroxonium ions in-between. The treatment in solutions containing nickel ions allows forming heterostructured materials which consist of potassium polytitanate particles intercalated by Ni2+ ions and/or decorated by nickel oxides NiOx. This modification route is fully dependant on solution pH, i.e. in acidic solutions the intercalation process prevails, in alkaline solutions potassium polytitanate is mostly decorated by the oxides. Therefore, electronic structure and electrical properties can be regulated depending on modification conditions, pH and ions concentration. Here we report the data on electric properties of potassium titanate modified in nickel sulfate solutions at different pH. PMID:26217788

  13. Suppressing tin whisker growth in lead-free solders and platings

    DOEpatents

    Hoffman, Elizabeth N; Lam, Poh-Sang

    2014-04-29

    A process of irradiation Sn containing Pb-free solder to mitigate whisker formation and growth thereon is provided. The use of gamma radiation such as cobalt-60 has been applied to a substrate of Sn on copper has been found to change the morphology of the crystalline whisker growth to a more truncated hillock pattern. The change in morphology greatly reduces the tendency of whiskers to contribute to electrical short-circuits being used as a Pb-free solder system on a copper substrate.

  14. MgB2 superconducting whiskers synthesized by using the hybrid physical-chemical vapor deposition.

    PubMed

    Wang, Yazhou; Zhuang, Chenggang; Gao, Jingyun; Shan, Xudong; Zhang, Jingmin; Liao, Zhimin; Xu, Hongjun; Yu, Dapeng; Feng, Qingrong

    2009-02-25

    In this work, MgB(2) whiskers were fabricated on a copper substrate by using the hybrid physical-chemical vapor deposition, which was one of the most effective ways to make high quality pure MgB(2) films, with the possible growth mechanism discussed. The whiskers are hexagonal and conelike and grow along the [0001] direction with a single-crystal structure. The onset transition temperature is approximately 39 K, which is among the best in the published nanostructure MgB(2) papers. Fabrication of nanoscale MgB(2) whiskers provides the fundamental understanding of the effect of dimensionality and size on superconductivity.

  15. Deformation of an alumina-zirconia-silicon carbide-whisker reinforced composite

    SciTech Connect

    Calderon-Moreno, J.M.; DeArellano-Lopez, A.R.; Dominguez-Rodriguez, A.; Routbort, J.L.; Leasky, T.

    1993-04-01

    Alumina-zirconia composites (MERC) with the addition of 0 and 28 vol % of silicon carbide whiskers have been deformed under compression at constant rate at 1450C, in air. Mechanical results are compared with the behavior of a commercial alumina (ARCO) with analogous proportions of silicon carbide-whiskers (0 and 30 vol %), under the same testing conditions. Flow stresses are typically higher for ARCO materials than for MERC materials. The addition of SiC whiskers increases flow stresses in ARCO composites, and decreases them for MERC samples. Microstructural observations confirm that the change in flow stress is the result of the presence of a glass phase in the MERC samples.

  16. Organic chemistry on Titan: Surface interactions

    NASA Technical Reports Server (NTRS)

    Thompson, W. Reid; Sagan, Carl

    1992-01-01

    The interaction of Titan's organic sediments with the surface (solubility in nonpolar fluids) is discussed. How Titan's sediments can be exposed to an aqueous medium for short, but perhaps significant, periods of time is also discussed. Interactions with hydrocarbons and with volcanic magmas are considered. The alteration of Titan's organic sediments over geologic time by the impacts of meteorites and comets is discussed.

  17. Effects of local film properties on the nucleation and growth of tin whiskers and hillocks

    NASA Astrophysics Data System (ADS)

    Sarobol, Pylin

    Whiskers and hillocks grow spontaneously on Pb-free Sn electrodeposited films as a response to thin film stresses. Stress relaxation occurs by atom deposition to specific grain boundaries in the plane of the film, with hillocks being formed when grain boundary migration accompanies growth out of the plane of the film. The implication for whisker formation in electronics is serious: whiskers can grow to be millimeters long, sometimes causing short circuiting between adjacent components and, thereby, posing serious electrical reliability risks. In order to develop more effective whisker mitigation strategies, a predictive physics-based model has been needed. A growth model is developed, based on grain boundary faceting, localized Coble creep, as well as grain boundary sliding for whiskers, and grain boundary sliding with shear induced grain boundary migration for hillocks. In this model of whisker formation, two mechanisms are important: accretion of atoms by Coble creep on grain boundary planes normal to the growth direction inducing a grain boundary shear and grain boundary sliding in the direction of whisker growth. The model accurately captures the importance of the geometry of "surface grains"---shallow grains on film surfaces whose depths are significantly less than their in-plane grain sizes. A critical factor in the analysis is the ratio of the grain boundary sliding coefficient to the in-plane film compressive stress. If the accretion-induced shear stresses are not coupled to grain boundary motion and sliding occurs, a whisker forms. If the shear stress is coupled to grain boundary migration, a hillock forms. Based on this model, long whiskers grow from shallow surface grains with easy grain boundary sliding in the direction of growth. Other observed growth morphologies will be discussed in light of our model. Additional insights into the preferred sites for whisker and hillock growth were developed based on elastic anisotropy, local film microstructure

  18. Large Particle Titanate Sorbents

    SciTech Connect

    Taylor-Pashow, K.

    2015-10-08

    This research project was aimed at developing a synthesis technique for producing large particle size monosodium titanate (MST) to benefit high level waste (HLW) processing at the Savannah River Site (SRS). Two applications were targeted, first increasing the size of the powdered MST used in batch contact processing to improve the filtration performance of the material, and second preparing a form of MST suitable for deployment in a column configuration. Increasing the particle size should lead to improvements in filtration flux, and decreased frequency of filter cleaning leading to improved throughput. Deployment of MST in a column configuration would allow for movement from a batch process to a more continuous process. Modifications to the typical MST synthesis led to an increase in the average particle size. Filtration testing on dead-end filters showed improved filtration rates with the larger particle material; however, no improvement in filtration rate was realized on a crossflow filter. In order to produce materials suitable for column deployment several approaches were examined. First, attempts were made to coat zirconium oxide microspheres (196 µm) with a layer of MST. This proved largely unsuccessful. An alternate approach was then taken synthesizing a porous monolith of MST which could be used as a column. Several parameters were tested, and conditions were found that were able to produce a continuous structure versus an agglomeration of particles. This monolith material showed Sr uptake comparable to that of previously evaluated samples of engineered MST in batch contact testing.

  19. Structure of Titan's evaporites

    NASA Astrophysics Data System (ADS)

    Cordier, D.; Cornet, T.; Barnes, J. W.; MacKenzie, S. M.; Le Bahers, T.; Nna-Mvondo, D.; Rannou, P.; Ferreira, A. G.

    2016-05-01

    Numerous geological features that could be evaporitic in origin have been identified on the surface of Titan. Although they seem to be water-ice poor, their main properties - chemical composition, thickness, stratification - are essentially unknown. In this paper, which follows on a previous one focusing on the surface composition (Cordier, D., Barnes, J.W., Ferreira, A.G. [2013b]. Icarus 226(2),1431-1437), we provide some answers to these questions derived from a new model. This model, based on the up-to-date thermodynamic theory known as "PC-SAFT", has been validated with available laboratory measurements and specifically developed for our purpose. 1-D models confirm the possibility of an acetylene and/or butane enriched central layer of evaporitic deposit. The estimated thickness of this acetylene-butane layer could explain the strong RADAR brightness of the evaporites. The 2-D computations indicate an accumulation of poorly soluble species at the deposit's margin. Among these species, HCN or aerosols similar to tholins could play a dominant role. Our model predicts the existence of chemically trimodal "bathtub rings" which is consistent with what it is observed at the south polar lake Ontario Lacus. This work also provides plausible explanations to the lack of evaporites in the south polar region and to the high radar reflectivity of dry lakebeds.

  20. Potassium kinetics during hemodialysis.

    PubMed

    Agar, Baris U; Culleton, Bruce F; Fluck, Richard; Leypoldt, John K

    2015-01-01

    Hyperkalemia in hemodialysis patients is associated with high mortality, but prescription of low dialysate potassium concentrations to decrease serum potassium levels is associated with a high incidence of sudden cardiac arrest or sudden death. Improved clinical outcomes for these patients may be possible if rapid and substantial intradialysis decreases in serum potassium concentration can be avoided while maintaining adequate potassium removal. Data from kinetic modeling sessions during the HEMO Study of the dependence of serum potassium concentration on time during hemodialysis treatments and 30 minutes postdialysis were evaluated using a pseudo one-compartment model. Kinetic estimates of potassium mobilization clearance (K(M)) and predialysis central distribution volume (V(pre)) were determined in 551 hemodialysis patients. The studied patients were 58.8 ± 14.4 years of age with predialysis body weight of 72.1 ± 15.1 kg; 306 (55.4%) of the patients were female and 337 (61.2%) were black. K(M) and V(pre) for all patients were non-normally distributed with values of 158 (111, 235) (median [interquartile range]) mL/min and 15.6 (11.4, 22.8) L, respectively. K(M) was independent of dialysate potassium concentration (P > 0.2), but V(pre) was lower at higher dialysate potassium concentration (R = -0.188, P < 0.001). For patients with dialysate potassium concentration between 1.6 and 2.5 mEq/L (N = 437), multiple linear regression of K(M) and V(pre) demonstrated positive association with predialysis body weight and negative association with predialysis serum potassium concentration. Potassium kinetics during hemodialysis can be described using a pseudo one-compartment model.

  1. Mechanical characteristics of rat vibrissae: resonant frequencies and damping in isolated whiskers and in the awake behaving animal

    NASA Technical Reports Server (NTRS)

    Hartmann, Mitra J.; Johnson, Nicholas J.; Towal, R. Blythe; Assad, Christopher

    2003-01-01

    We investigated the natural resonance properties and damping characteristics of rat macrovibrissae (whiskers). Isolated whiskers rigidly fixed at the base showed first-mode resonance peaks between 27 and 260 Hz, principally depending on whisker length. These experimentally measured resonant frequencies were matched using a theoretical model of the whisker as a conical cantilever beam, with Young's modulus as the only free parameter. The best estimate for Young's modulus was approximately 3-4 GPa. Results of both vibration and impulse experiments showed that the whiskers are strongly damped, with damping ratios between 0.11 and 0.17. In the behaving animal, whiskers that deflected past an object were observed to resonate but were damped significantly more than isolated whiskers. The time course of damping varied depending on the individual whisker and the phase of the whisking cycle, which suggests that the rat may modulate biomechanical parameters that affect damping. No resonances were observed for whiskers that did not contact the object or during free whisking in air. Finally, whiskers on the same side of the face were sometimes observed to move in opposite directions over the full duration of a whisk. We discuss the potential roles of resonance during natural exploratory behavior and specifically suggest that resonant oscillations may be important in the rat's tactile detection of object boundaries.

  2. Penicillin V Potassium Oral

    MedlinePlus

    Penicillin V potassium is an antibiotic used to treat certain infections caused by bacteria such as pneumonia, scarlet fever, and ear, ... Penicillin V potassium comes as a tablet and liquid to take by mouth. It is usually taken every 6 hours (four ...

  3. Potassium food supplement

    NASA Technical Reports Server (NTRS)

    Bourland, C. T.; Huber, C. S.; Rambaut, C.; Heidelbaugh, N. D.

    1973-01-01

    Potassium gluconate is considered best supplementary source for potassium. Gluconate consistently received highest taste rating and was indistinguishable from nonsupplemented samples. No unfavorable side effects were found during use, and none are reported in literature. Gluconate is normal intermediary metabolite that is readily adsorbed and produces no evidence of gastrointestinal ulcerations.

  4. Widespread morning drizzle on Titan.

    PubMed

    Adámkovics, Máté; Wong, Michael H; Laver, Conor; de Pater, Imke

    2007-11-01

    Precipitation is expected in Titan's atmosphere, yet it has not been directly observed, and the geographical regions where rain occurs are unknown. Here we present near-infrared spectra from the Very Large Telescope and W. M. Keck Observatories that reveal an enhancement of opacity in Titan's troposphere on the morning side of the leading hemisphere. Retrieved extinction profiles are consistent with condensed methane in clouds at an altitude near 30 kilometers and concomitant methane drizzle below. The moisture encompasses the equatorial region over Titan's brightest continent, Xanadu. Diurnal temperature gradients that cause variations in methane relative humidity, winds, and topography may each be a contributing factor to the condensation mechanism. The clouds and precipitation are optically thin at 2.0 micrometers, and models of "subvisible" clouds suggest that the droplets are 0.1 millimeter or larger.

  5. Is titan wet or dry?

    PubMed

    Eshleman, V R; Lindal, G F; Tyler, G L

    1983-07-01

    Titan's dense and cold nitrogen atmosphere contains a small amount of methane under conditions at least approaching those at which one or both constituents would condense. The possibility of methane and nitrogen rain clouds and global methane oceans has been discussed widely. From specific features of radio occultation and other Voyager results, however, it is concluded that nitrogen does not condense on Titan and that Titan has neither global methane oceans nor a global cloud of liquid methane droplets. Certain results indirectly support the conjecture that methane does not condense at any location. However, other considerations favor a methane ice haze high in the troposphere, and liquid and solid methane might exist on the surface and as low clouds at polar latitudes.

  6. Charged particles in Titan's ionosphere

    NASA Astrophysics Data System (ADS)

    Tripathi, Sachchida

    2010-05-01

    Charged particles in Titan's ionosphere Marykutty Michael1, Sachchida Nand Tripathi1,2,3, Pratima Arya1 1Indian Institute of Technology Kanpur 2Oak Ridge Associated Universities 3NASA Goddard Space Flight Center Observations by two instruments onboard the Cassini spacecraft, Ion Neutral Mass Spectrometer (INMS) and CAssini Plasma Spectrometer (CAPS), revealed the existence of heavy hydrocarbon and nitrile species with masses of several thousand atomic mass units at altitudes of 950 - 1400 km in the atmosphere of Titan (Waite et al., 2007; Crary et al., 2009). Though these particles were believed to be molecules, they are most likely aerosols formed by the clumping of smaller molecules (Waite et al., 2009). These particles were estimated to have a density of 10-3 kg m-3 and a size of up to 256 nm. The existence of very heavy ions has also been observed by the CAPS components with a mass by charge ratio of up to 10000 (Coates et al., 2007, 2009; Sittler et al., 2009). The goal of this paper is to find out whether the so called heavy ions (or charged particles) are generated by the charge transfer of ions and electrons to the particles. The charging of these particles has been studied by using the charge balance equations that include positive ions, negative ions, electrons, neutral and charged particles. Information on the most abundant ion clusters are obtained from Vuitton et al., (2009) and Wilson and Atreya, (2004). Mass by charge ratio thus calculated will be compared with those observed by Coates et al. (2007). References: Coates AJ, et al., Discovery of heavy negative ions in Titan's ionosphere, Geophys. Res. Lett., 34:L22103, 2007. Coates AJ, et al., Heavy negative ions in titan's ionosphere: altitude and latitude dependence. Planet. Space Sci., doi:10.1016/j.pss.2009.05.009, 2009. Crary F.J., et al., Heavy ions, temperatures and winds in titan's ionosphere: Combined cassini caps and inms observations. Planet. Space Sci., doi:10.1016/j.pss.2009.09.006, 2009

  7. The induced magnetosphere of Titan

    NASA Astrophysics Data System (ADS)

    Ness, N. F.; Acuna, M. H.; Behannon, K. W.

    1982-03-01

    No evidence was found for an intrinsic magnetic field, nor for the development of a bow shock wave, as the corotating Saturnian magnetoplasma convected past Titan during the Voyager 1 close encounter of November 12, 1980. The observation of a well-developed, induced bipolar magnetic tail is evidence, however, of a strong electrodynamic interaction. Three thin, current-carrying regions were crossed which correspond to the inbound and outbound tail magnetopause and an imbedded tail neutral sheet. The interaction is unique among those observed to date in the solar system, in that it is intermediate with respect to sonic and Alfvenic Mach numbers by comparison with Titan in the solar wind and Io in the Jovian magnetosphere. The draping of the Saturnian magnetic field around the ionosphere of Titan is suggested by results of the analysis of magnetic field data.

  8. Diurnal variations of Titan's ionosphere

    NASA Astrophysics Data System (ADS)

    Cui, J.; Galand, M.; Yelle, R. V.; Vuitton, V.; Wahlund, J.-E.; Lavvas, P. P.; Müller-Wodarg, I. C. F.; Cravens, T. E.; Kasprzak, W. T.; Waite, J. H.

    2009-06-01

    We present our analysis of the diurnal variations of Titan's ionosphere (between 1000 and 1300 km) based on a sample of Ion Neutral Mass Spectrometer (INMS) measurements in the Open Source Ion (OSI) mode obtained from eight close encounters of the Cassini spacecraft with Titan. Although there is an overall ion depletion well beyond the terminator, the ion content on Titan's nightside is still appreciable, with a density plateau of ˜700 cm-3 below ˜1300 km. Such a plateau is a combined result of significant depletion of light ions and modest depletion of heavy ones on Titan's nightside. We propose that the distinctions between the diurnal variations of light and heavy ions are associated with their different chemical loss pathways, with the former primarily through “fast” ion-neutral chemistry and the latter through “slow” electron dissociative recombination. The strong correlation between the observed night-to-day ion density ratios and the associated ion lifetimes suggests a scenario in which the ions created on Titan's dayside may survive well to the nightside. The observed asymmetry between the dawn and dusk ion density profiles also supports such an interpretation. We construct a time-dependent ion chemistry model to investigate the effect of ion survival associated with solid body rotation alone as well as superrotating horizontal winds. For long-lived ions, the predicted diurnal variations have similar general characteristics to those observed. However, for short-lived ions, the model densities on the nightside are significantly lower than the observed values. This implies that electron precipitation from Saturn's magnetosphere may be an additional and important contributor to the densities of the short-lived ions observed on Titan's nightside.

  9. Ion cyclotron waves at Titan

    NASA Astrophysics Data System (ADS)

    Russell, C. T.; Wei, H. Y.; Cowee, M. M.; Neubauer, F. M.; Dougherty, M. K.

    2016-03-01

    During the interaction of Titan's thick atmosphere with the ambient plasma, it was expected that ion cyclotron waves would be generated by the free energy of the highly anisotropic velocity distribution of the freshly ionized atmospheric particles created in the interaction. However, ion cyclotron waves are rarely observed near Titan, due to the long growth times of waves associated with the major ion species from Titan's ionosphere, such as CH4+ and N2+. In the over 100 Titan flybys obtained by Cassini to date, there are only two wave events, for just a few minutes during T63 flyby and for tens of minutes during T98 flyby. These waves occur near the gyrofrequencies of proton and singly ionized molecular hydrogen. They are left-handed, elliptically polarized, and propagate nearly parallel to the field lines. Hybrid simulations are performed to understand the wave growth under various conditions in the Titan environment. The simulations using the plasma and field conditions during T63 show that pickup protons with densities ranging from 0.01 cm-3 to 0.02 cm-3 and singly ionized molecular hydrogens with densities ranging from 0.015 cm-3 to 0.25 cm-3 can drive ion cyclotron waves with amplitudes of ~0.02 nT and of ~0.04 nT within appropriate growth times at Titan, respectively. Since the T98 waves were seen farther upstream than the T63 waves, it is possible that the instability was stronger and grew faster on T98 than T63.

  10. Potassium and health.

    PubMed

    Weaver, Connie M

    2013-05-01

    Potassium was identified as a shortfall nutrient by the Dietary Guidelines for Americans 2010 Advisory Committee. The committee concluded that there was a moderate body of evidence of the association between potassium intake and blood pressure reduction in adults, which in turn influences the risk of stroke and coronary heart disease. Evidence is also accumulating of the protective effect of adequate dietary potassium on age-related bone loss and reduction of kidney stones. These benefits depend on organic anions associated with potassium as occurs in foods such as fruits and vegetables, in contrast to similar blood pressure-lowering benefits of potassium chloride. Benefits to blood pressure and bone health may occur at levels below current recommendations for potassium intake, especially from diet, but dose-response trials are needed to confirm this. Nevertheless, intakes considerably above current levels are needed for optimal health, and studies evaluating small increases in fruit and vegetable intake on bone and heart outcomes for short periods have had disappointing results. In modern societies, Western diets have led to a decrease in potassium intake with reduced consumption of fruits and vegetables with a concomitant increase in sodium consumption through increased consumption of processed foods. Consumption of white vegetables is associated with decreased risk of stroke, possibly related to their high potassium content. Potatoes are the highest source of dietary potassium, but the addition of salt should be limited. Low potassium-to-sodium intake ratios are more strongly related to cardiovascular disease risk than either nutrient alone. This relationship deserves further attention for multiple target tissue endpoints.

  11. Beta 2-adrenergic receptors are colocalized and coregulated with "whisker barrels" in rat somatosensory cortex.

    PubMed Central

    Vos, P; Kaufmann, D; Hand, P J; Wolfe, B B

    1990-01-01

    Autoradiography has been used to visualize independently the subtypes of beta-adrenergic receptors in rat somatosensory cortex. Beta 2-Adrenergic receptors, but not beta 1-adrenergic receptors colocalize with "whisker barrels" in this tissue. Thus, each whisker sends a specific multisynaptic pathway to the somatosensory cortex that can be histochemically visualized and only one subtype of beta-adrenergic receptor is specifically associated with this cortical representation. Additionally, neonatal lesion of any or all of the whisker follicles results in loss of the corresponding barrel(s) as shown by histochemical markers. This loss is paralleled by a similar loss in the organization of beta 2-adrenergic receptors in the somatosensory cortex. Other results indicate that these beta 2-adrenergic receptors are not involved in moment-to-moment signal transmission in this pathway and, additionally, are not involved in a gross way in the development of whisker-barrel array. Images PMID:2164222

  12. Preparation of integrated multifunction Pb3B10O16[OH]4 whisker by solvothermal method

    NASA Astrophysics Data System (ADS)

    Sun, Qing; Zhang, Quan-Ping; Zheng, Jian; Zhou, Dong; Li, Yin-Tao; Zhou, Yuan-Lin

    2016-03-01

    Elaborate design of multifunction materials is of great scientific and technological significance; but it is a great challenge. Here, a lead borate is successfully prepared via a facile solvothermal method. The results of XRD, SEM and TEM show the product is a kind of whiskers with uniform structure and high length-diameter ratio, which is represented as Pb3B10O16[OH]4. The whisker is capable of attenuating both γ-rays and neutrons and shows a little difference with that of the equal molar mass of Pb and B in mixture. In addition, the whisker displays good photoluminescence properties, especially for luminescent intensity. These significant results indicate an integrated multifunction whisker that will stimulate new application research.

  13. Titan and Enceladus mission (TANDEM)

    NASA Astrophysics Data System (ADS)

    Coustenis, A.

    2007-08-01

    Our understanding of Titan's atmosphere and surface has recently been enhanced by the data returned by the Cassini-Huygens mission. The Cassini orbiter will continue to be operational for about 3 more years during its extended mission. After this mission, any unanswered questions will forever remain unknown, unless we go back with an optimized orbital tour and advanced instrumentation. Considering the complementary nature of the geological, chemical and evolutionary history of Titan and Enceladus, we propose to carry out studies for a mission to perform an in situ exploration of these two objects in tandem. In our proposal we determine key science measurements, the types of samples that would be needed and the instrument suites for achieving the science goals. In particular, we develop conceptual designs for delivering the science payload, including orbiters, aerial platforms and probes, and define a launch/delivery/communication management architecture. This mission will require new technologies and capabilities so that the science goals can be achieved within the cost cap and acceptable risks. International participation will play a key role in achieving all the science goals of this mission. We will build this mission concept around a central core of single orbiter, a single Titan aerial probe and a core group of category 1 instruments. Aerobraking with Titan's atmosphere will be given serious consideration to minimize resource requirements and risk. This approach will allow a single orbiter to be used for both Enceladus science and Titan science with final orbit around Titan and later release of aerial probe(s) into Titan's atmosphere. The Titan aerial probe may be a Montgolfière balloon concept that will use the waster heat ~ 1000 watts from a single RTG power system. There will be a release of penetrator(s) on Enceladus also. This proposal addresses directly several of the scientific questions highlighted in the ESA Cosmic Vision 2015-2025 call, particularly

  14. Will Titan lose its veil?

    NASA Astrophysics Data System (ADS)

    Dimitrov, V.

    2007-08-01

    Methane CH4 is the only highly reactive and short-lived background component in Titan's atmosphere, so its overall reserve predetermines both features and duration of atmospheric chemical activity. Titan's global chemical activity is considered in terms of methane cycle. One cycle is defined as a period T0=7.0.1014s of complete photochemical destruction of methane's observable atmospheric content CH04 = 2.33.1017 kg. Cycle duration T0, number of the past NP =200±20, future NF =500±50 and total Nmax=NP+NF =700±70 cycles are the main quantitative indices of the global chemical activity [2]. The fact that the period T0 is much less than Titan's lifetime TT =1.42*1017s implies that the current content CH04 is continuously replenishing by methane global circulation. There are two sources of this replenishment, i.e. the outgassing of primordial methane reserve trapped in Titan's interior as the clathrate, and the (sub)ground liquidphase reduction of non-saturated final products of the atmospheric photochemical process. Internal reserve provides the dominant portion (>95%) of general recycling, while reducing reconversion is the minor constituent of the global balance. Yet, there is the problem of the availability of the off-the-shelf trapped methane. Overall admissible stock of the trapped methane depends on its internal allocation and falls in the range (CH4)max1,2=(15.3÷33.3).1020 kg, while continuous atmospheric activity during the whole Titan's life TSun 5.0.1017s needs only (CH4)crit=(CH04 ).Nmax = .(CH4)max 1.65.1020 kg. In turn, this bulk (CH4)crit depends on the clathrate cage-filling efficiency (molecular packing index) {kg CH4/kg clathrate} and can be provided if equals respectively to [1] crit1= (TSun/T0).[(CH4)0/[(CH4)max1] = 5.45.10-3 crit2= (TSun/T0).[(CH4)0/[(CH4)max2] = 2.51.10-3 Thus, the interrelation of overall trapped stock (CH4)max and crucial -values assigns the critical value (CH4)crit that in turn predetermines the very fate of Titan's veil

  15. Cholinergic signals in mouse barrel cortex during active whisker sensing.

    PubMed

    Eggermann, Emmanuel; Kremer, Yves; Crochet, Sylvain; Petersen, Carl C H

    2014-12-11

    Internal brain states affect sensory perception, cognition, and learning. Many neocortical areas exhibit changes in the pattern and synchrony of neuronal activity during quiet versus active behaviors. Active behaviors are typically associated with desynchronized cortical dynamics. Increased thalamic firing contributes importantly to desynchronize mouse barrel cortex during active whisker sensing. However, a whisking-related cortical state change persists after thalamic inactivation, which is mediated at least in part by acetylcholine, as we show here by using whole-cell recordings, local pharmacology, axonal calcium imaging, and optogenetic stimulation. During whisking, we find prominent cholinergic signals in the barrel cortex, which suppress spontaneous cortical activity. The desynchronized state of barrel cortex during whisking is therefore driven by at least two distinct signals with opposing functions: increased thalamic activity driving glutamatergic excitation of the cortex and increased cholinergic input suppressing spontaneous cortical activity.

  16. Fused Traditional and Geometric Morphometrics Demonstrate Pinniped Whisker Diversity

    PubMed Central

    Ginter, Carly C.; DeWitt, Thomas J.; Fish, Frank E.; Marshall, Christopher D.

    2012-01-01

    Vibrissae (whiskers) are important components of the mammalian tactile sensory system, and primarily function as detectors of vibrotactile information from the environment. Pinnipeds possess the largest vibrissae among mammals and their vibrissal hair shafts demonstrate a diversity of shapes. The vibrissae of most phocid seals exhibit a beaded morphology with repeating sequences of crests and troughs along their length. However, there are few detailed analyses of pinniped vibrissal morphology, and these are limited to a few species. Therefore, we comparatively characterized differences in vibrissal hair shaft morphologies among phocid species with a beaded profile, phocid species with a smooth profile, and otariids with a smooth profile using traditional and geometric morphometric methods. Traditional morphometric measurements (peak-to-peak distance, crest width, trough width and total length) were collected using digital photographs. Elliptic Fourier analysis (geometric morphometrics) was used to quantify the outlines of whole vibrissae. The traditional and geometric morphometric datasets were subsequently combined by mathematically scaling each to true rank, followed by a single eigendecomposition. Quadratic discriminant function analysis demonstrated that 79.3, 97.8 and 100% of individuals could be correctly classified to their species based on vibrissal shape variables in the traditional, geometric and combined morphometric analyses, respectively. Phocids with beaded vibrissae, phocids with smooth vibrissae, and otariids each occupied distinct morphospace in the geometric morphometric and combined data analyses. Otariids split into two groups in the geometric morphometric analysis and gray seals appeared intermediate between beaded- and smooth-whiskered species in the traditional and combined analyses. Vibrissal hair shafts modulate the transduction of environmental stimuli to the mechanoreceptors in the follicle-sinus complex (F-SC), which results in

  17. Highly sensitive electronic whiskers based on patterned carbon nanotube and silver nanoparticle composite films.

    PubMed

    Takei, Kuniharu; Yu, Zhibin; Zheng, Maxwell; Ota, Hiroki; Takahashi, Toshitake; Javey, Ali

    2014-02-01

    Mammalian whiskers present an important class of tactile sensors that complement the functionalities of skin for detecting wind with high sensitivity and navigation around local obstacles. Here, we report electronic whiskers based on highly tunable composite films of carbon nanotubes and silver nanoparticles that are patterned on high-aspect-ratio elastic fibers. The nanotubes form a conductive network matrix with excellent bendability, and nanoparticle loading enhances the conductivity and endows the composite with high strain sensitivity. The resistivity of the composites is highly sensitive to strain with a pressure sensitivity of up to ∼8%/Pa for the whiskers, which is >10× higher than all previously reported capacitive or resistive pressure sensors. It is notable that the resistivity and sensitivity of the composite films can be readily modulated by a few orders of magnitude by changing the composition ratio of the components, thereby allowing for exploration of whisker sensors with excellent performance. Systems consisting of whisker arrays are fabricated, and as a proof of concept, real-time two- and three-dimensional gas-flow mapping is demonstrated. The ultrahigh sensitivity and ease of fabrication of the demonstrated whiskers may enable a wide range of applications in advanced robotics and human-machine interfacing. PMID:24449857

  18. Alterations in functional thalamocortical connectivity following neonatal whisker trimming with adult regrowth

    PubMed Central

    Carvell, G. E.; Kyriazi, H. T.

    2015-01-01

    Neonatal whisker trimming followed by adult whisker regrowth leads to higher responsiveness and altered receptive field properties of cortical neurons in corresponding layer 4 barrels. Studies of functional thalamocortical (TC) connectivity in normally reared adult rats have provided insights into how experience-dependent TC synaptic plasticity could impact the establishment of feedforward excitatory and inhibitory receptive fields. The present study employed cross-correlation analyses to investigate lasting effects of neonatal whisker trimming on functional connections between simultaneously recorded thalamic neurons and regular-spike (RS), presumed excitatory, and fast-spike (FS), presumed inhibitory, barrel neurons. We find that, as reported previously, RS and FS cells in whisker-trimmed animals fire more during the earliest phase of their whisker-evoked responses, corresponding to the arrival of TC inputs, despite a lack of change or even a slight decrease in the firing of thalamic cells that contact them. Functional connections from thalamus to cortex are stronger. The probability of finding TC-RS connections was twofold greater in trimmed animals and similar to the frequency of TC-FS connections in control and trimmed animals, the latter being unaffected by whisker trimming. Unlike control cases, trimmed RS units are more likely to receive inputs from TC units (TCUs) and have mismatched angular tuning and even weakly responsive TCUs make strong functional connections on them. Results indicate that developmentally appropriate tactile experience early in life promotes the differential thalamic engagement of excitatory and inhibitory cortical neurons that underlies normal barrel function. PMID:26245317

  19. Mechanical characterization of SiC whisker-reinforced MoSi/sub 2/

    SciTech Connect

    Carter, D.H.; Gibbs, W.S.; Petrovic, J.J.

    1988-01-01

    The mechanical characteristics of an intermetallic matrix with two different reinforcements were studied. The matrix material was MoSi/sub 2/, with either Los Alamos VLS SiC whiskers or Huber VS SiC whiskers. The purpose of the reinforcement was to provide toughening at ambient temperature and strengthening at elevated temperatures. The VLS whiskers greatly improved the yield strength of the matrix at 1200/degree/C, and also increased the room temperature fracture toughness of the matrix. The VS whiskers were added because they are much smaller in length and diameter, and therefore decreased the mean free path between whiskers, at the same volume fraction. The VS whiskers improved the toughness of the matrix at ambient temperature, and increased the yield strength of MoSi/sub 2/ at 1400/degree/C by 470%. The high strength of this new composite places this material in the realm of attractive engineering materials for high-temperature applications. 11 refs., 6 refs., 1 tab.

  20. Microstructure and growth model for rice-hull-derived SiC whiskers

    NASA Technical Reports Server (NTRS)

    Nutt, Steven R.

    1988-01-01

    The microstructure of silicon carbide whiskers grown from rice hulls has been studied using methods of high-resolution analytical electron microscopy. Small, partially crystalline inclusions (about 10 nm) containing calcium, manganese, and oxygen are concentrated in whisker core regions, while peripheral regions are generally inclusion free. The distinct microphase distribution is evidence of a two-stage growth process in which the core region grows first, followed by normal growth toward whisker sides. Partial dislocations extend radially from the core region to the surface and tend to be paired in V-shaped configurations. Whisker surfaces exhibit microroughness due to a tendency to develop small facets on close-packed planes. The microstructural data obtained from TEM observations are used as a basis for discussion of the mechanisms involved in whisker growth, and a model of the growth process is proposed. The model includes a two-dimensional growth mechanism involving vapor, liquid, and solid phases, although it is significantly different from the classical vapor-liquid-solid (VLS) process of whisker growth.

  1. Effects of Chitin Whiskers on Physical Properties and Osteoblast Culture of Alginate Based Nanocomposite Hydrogels.

    PubMed

    Huang, Yao; Yao, Mengyu; Zheng, Xing; Liang, Xichao; Su, Xiaojuan; Zhang, Yu; Lu, Ang; Zhang, Lina

    2015-11-01

    Novel nanocomposite hydrogels composed of polyelectrolytes alginate and chitin whiskers with biocompatibility were successfully fabricated based on the pH-induced charge shifting behavior of chitin whiskers. The chitin whiskers with mean length and width of 300 and 20 nm were uniformly dispersed in negatively charged sodium alginate aqueous solution, leading to the formation of the homogeneous nanocomposite hydrogels. The experimental results indicated that their mechanical properties were significantly improved compared to alginate hydrogel and the swelling trends were inhibited as a result of the strong electrostatic interactions between the chitin whiskers and alginate. The nanocomposite hydrogels exhibited certain crystallinity and hierarchical structure with nanoscale chitin whiskers, similar to the structure of the native extracellular matrix. Moreover, the nanocomposite hydrogels were successfully applied as bone scaffolds for MC3T3-E1 osteoblast cells, showing their excellent biocompatibility and low cytotoxicity. The results of fluorescent micrographs and scanning electronic microscope (SEM) images revealed that the addition of chitin whiskers into the nanocomposite hydrogels markedly promoted the cell adhesion and proliferation of the osteoblast cells. The biocompatible nanocomposite hydrogels have potential application in bone tissue engineering. PMID:26393272

  2. Nano DCPA-whisker composites with high strength and Ca and PO(4) release.

    PubMed

    Xu, H H K; Sun, L; Weir, M D; Antonucci, J M; Takagi, S; Chow, L C; Peltz, M

    2006-08-01

    The main challenges facing composite restorations are secondary caries and bulk fracture. The objective of this study was to develop nano DCPA (dicalcium phosphate anhydrous)-whisker composites with high strength and Ca and PO(4) ion release to combat caries. Flexural strength for the nano DCPA-whisker composites at a nano DCPA:whisker mass ratio of 1:2 ranged from (148 +/- 9) MPa to (167 +/- 23) MPa, significantly higher than the (103 +/- 32) MPa of an inlay/onlay commercial control composite without Ca-PO(4) release. The nano DCPA-whisker composite released PO(4) to a concentration of (1.95 +/- 0.13) mmol/L and Ca of (0.68 +/- 0.05) mmol/L. Compared with previous conventional Ca- and PO(4)-releasing composites, the nano DCPA-whisker composites had strengths two-fold higher, and released comparable or higher levels of Ca and PO(4). In conclusion, combining nano-DCPA with whiskers yielded novel composites that released high levels of Ca and PO(4) requisite for remineralization. These high-strength composites may provide a unique combination of stress-bearing and caries-inhibiting capabilities.

  3. Effects of Chitin Whiskers on Physical Properties and Osteoblast Culture of Alginate Based Nanocomposite Hydrogels.

    PubMed

    Huang, Yao; Yao, Mengyu; Zheng, Xing; Liang, Xichao; Su, Xiaojuan; Zhang, Yu; Lu, Ang; Zhang, Lina

    2015-11-01

    Novel nanocomposite hydrogels composed of polyelectrolytes alginate and chitin whiskers with biocompatibility were successfully fabricated based on the pH-induced charge shifting behavior of chitin whiskers. The chitin whiskers with mean length and width of 300 and 20 nm were uniformly dispersed in negatively charged sodium alginate aqueous solution, leading to the formation of the homogeneous nanocomposite hydrogels. The experimental results indicated that their mechanical properties were significantly improved compared to alginate hydrogel and the swelling trends were inhibited as a result of the strong electrostatic interactions between the chitin whiskers and alginate. The nanocomposite hydrogels exhibited certain crystallinity and hierarchical structure with nanoscale chitin whiskers, similar to the structure of the native extracellular matrix. Moreover, the nanocomposite hydrogels were successfully applied as bone scaffolds for MC3T3-E1 osteoblast cells, showing their excellent biocompatibility and low cytotoxicity. The results of fluorescent micrographs and scanning electronic microscope (SEM) images revealed that the addition of chitin whiskers into the nanocomposite hydrogels markedly promoted the cell adhesion and proliferation of the osteoblast cells. The biocompatible nanocomposite hydrogels have potential application in bone tissue engineering.

  4. Hydrophobic modification of chitin whisker and its potential application in structuring oil.

    PubMed

    Huang, Yao; He, Meng; Lu, Ang; Zhou, Weizheng; Stoyanov, Simeon D; Pelan, Eddie G; Zhang, Lina

    2015-02-10

    A facile approach was developed to modify chitin whiskers by reacting them with bromohexadecane, and the potential application of modified whiskers in structuring oil was evaluated. The results of Fourier transform infrared spectra (FT-IR), wide-angle X-ray diffraction (XRD), elemental analysis, solid (13)C NMR, and differential scanning calorimeter (DSC) confirmed that the long alkyl chains were successfully introduced to the chitin whiskers and endowed them with improved hydrophobicity and thermal transition. By hot pressing the modified whiskers, the highly hydrophobic whisker sheets were constructed, showing high contact angles close to 150°. The hydrophobic interaction between the long alkyl chains and chitin backbone induced the crystal alignment with micro-nano structure, leading to the surface roughness and high hydrophobicity of the sheets. Furthermore, the modified whiskers could form a stable dispersion in sunflower oil, displaying a remarkable thickening effect. The viscosity of the oily suspension exhibited temperature dependence and shear-thinning behavior, suggesting great potentials to fabricate oleogel without adding any saturated fat. Furthermore, the intrinsic biocompatibility of α-chitin structure benefits its application in foodstuff, cosmetics, and medical fields.

  5. Nano DCPA-Whisker Composites with High Strength and Ca and PO4 Release

    PubMed Central

    Xu, H.H.K.; Sun, L.; Weir, M.D.; Antonucci, J.M.; Takagi, S.; Chow, L.C.; Peltz, M.

    2008-01-01

    The main challenges facing composite restorations are secondary caries and bulk fracture. The objective of this study was to develop nano DCPA (dicalcium phosphate anhydrous)-whisker composites with high strength and Ca and PO4 ion release to combat caries. Flexural strength for the nano DCPA-whisker composites at a nano DCPA:whisker mass ratio of 1:2 ranged from (148 ± 9) MPa to (167 ± 23) MPa, significantly higher than the (103 ± 32) MPa of an inlay/onlay commercial control composite without Ca-PO4 release. The nano DCPA-whisker composite released PO4 to a concentration of (1.95 ± 0.13) mmol/L and Ca of (0.68 ± 0.05) mmol/L. Compared with previous conventional Ca- and PO4-releasing composites, the nano DCPA-whisker composites had strengths two-fold higher, and released comparable or higher levels of Ca and PO4. In conclusion, combining nano-DCPA with whiskers yielded novel composites that released high levels of Ca and PO4 requisite for remineralization. These high-strength composites may provide a unique combination of stress-bearing and caries-inhibiting capabilities. PMID:16861289

  6. Contributions Of Stress And Oxidation On The Formation Of Whiskers In Pb-Free Solders

    SciTech Connect

    Duncan, A. J.; Hoffman, E. N.

    2014-03-25

    This report summarizes the research activities of WP-1754. The study focusses on the environmental factors influencing formation of lead free whiskers on electrodeposited tin coatings over copper (or copper containing) substrates. Much of the initial results are summarized in an interim report. From the initial results, two main areas were chosen to be the focus of additional research: the demonstration of effects of elastic stress state in the nucleation of whiskers and the confirmation of the effect of oxygen/nitrogen ratio in the formation of whiskers. Different levels of elastic stress were induced with the incorporation of a custom designed fixture that loaded the substrates in a four-point bending configuration and were maintained in an environmental chamber under conditions deemed favorable for whisker growth. The results show that induced elastic stress slightly increased the concentration of nucleation sites of whiskers. The effects of oxygen content were studied by aging substrates in gas vials of varying absolute pressure and different oxygen/nitrogen ratios. The concentration of whiskers were measured and appear to be sensitive to absolute pressure but are not sensitive to oxygen content (as previously observed).

  7. Hubble Observes Surface of Titan

    NASA Technical Reports Server (NTRS)

    1994-01-01

    Scientists for the first time have made images of the surface of Saturn's giant, haze-shrouded moon, Titan. They mapped light and dark features over the surface of the satellite during nearly a complete 16-day rotation. One prominent bright area they discovered is a surface feature 2,500 miles across, about the size of the continent of Australia.

    Titan, larger than Mercury and slightly smaller than Mars, is the only body in the solar system, other than Earth, that may have oceans and rainfall on its surface, albeit oceans and rain of ethane-methane rather than water. Scientists suspect that Titan's present environment -- although colder than minus 289 degrees Fahrenheit, so cold that water ice would be as hard as granite -- might be similar to that on Earth billions of years ago, before life began pumping oxygen into the atmosphere.

    Peter H. Smith of the University of Arizona Lunar and Planetary Laboratory and his team took the images with the Hubble Space Telescope during 14 observing runs between Oct. 4 - 18. Smith announced the team's first results last week at the 26th annual meeting of the American Astronomical Society Division for Planetary Sciences in Bethesda, Md. Co-investigators on the team are Mark Lemmon, a doctoral candidate with the UA Lunar and Planetary Laboratory; John Caldwell of York University, Canada; Larry Sromovsky of the University of Wisconsin; and Michael Allison of the Goddard Institute for Space Studies, New York City.

    Titan's atmosphere, about four times as dense as Earth's atmosphere, is primarily nitrogen laced with such poisonous substances as methane and ethane. This thick, orange, hydrocarbon haze was impenetrable to cameras aboard the Pioneer and Voyager spacecraft that flew by the Saturn system in the late 1970s and early 1980s. The haze is formed as methane in the atmosphere is destroyed by sunlight. The hydrocarbons produced by this methane destruction form a smog similar to that found over large cities, but is much

  8. Organic chemistry in Titan's atmosphere

    NASA Technical Reports Server (NTRS)

    Scattergood, T.

    1982-01-01

    Laboratory photochemical simulations and other types of chemical simulations are discussed. The chemistry of methane, which is the major known constituent of Titan's atmosphere was examined with stress on what can be learned from photochemistry and particle irradiation. The composition of dust that comprises the haze layer was determined. Isotope fractionation in planetary atmospheres is also discussed.

  9. The organic aerosols of Titan

    NASA Technical Reports Server (NTRS)

    Khare, B. N.; Sagan, C.; Thompson, W. R.; Arakawa, E. T.; Suits, F.; Calcott, T. A.; Williams, M. W.; Shrader, S.; Ogino, H.; Willingham, T. O.

    1986-01-01

    A dark reddish organic solid, called tholin, is synthesized from simulated Titanian atmospheres by irradiation with high energy electrons in a plasma discharge. The visible reflection spectrum of this tholin is found to be similar to that of high altitude aerosols responsible for the albedo and reddish color of Titan. The real (n) and imaginary (k) parts of the complex refractive index of thin films of Titan prepared by continuous dc discharge through a 0.9 N2/0.1 CH4 gas mixture at 0.2 mb is determined from X-ray to microwave frequencies. Values of n (approx. 1.65) and k (approx. 0.004 to 0.08) in the visible are consistent with deductions made by groundbased and spaceborne observations of Titan. Many infrared absorption features are present in k(lambda), including the 4.6 micrometer nitrile band. Molecular analysis of the volatile components of this tholin was performed by sequential and nonsequential pyrolytic gas chromatography/mass spectrometry. More than one hundred organic compounds are released; tentative identifications include saturated and unsaturated aliphatic hydrocarbons, substituted polycylic aromatics, nitriles, amines, pyrroles, pyrazines, pyridines, pyrimidines, and the purine, adenine. In addition,acid hydrolysis produces a racemic mixture of biological and nonbiological amino acids. Many of these molecules are implicated in the origin of life on Earth, suggesting Titan as a contemporary laboratory environment for prebiological organic chemistry on a planetary scale.

  10. The dynamics of Titan's troposphere.

    PubMed

    Tokano, Tetsuya

    2009-02-28

    While the Voyager mission could essentially not reveal the dynamics of Titan's troposphere, useful information was obtained by the Cassini spacecraft and, particularly, by the Huygens probe that landed on Titan's surface; this information can be interpreted by means of numerical models of atmospheric circulation. The meridional circulation is likely to consist of a large Hadley circulation asymmetric about the equator, but is susceptible to disruption by turbulence in clouds. The zonal wind in the troposphere is comparable to or even weaker than that in the terrestrial troposphere and contains zones of easterlies, much in contrast to the super-rotating stratosphere. Unique to Titan is the transition from a geostrophic to cyclostrophic wind balance in the upper troposphere. While Earth-like storm systems associated with baroclinic instability are absent, Saturn's gravitational tide introduces a planetary wave of wavenumber 2 and a periodical variation in the wind direction in the troposphere. Unlike on Earth, the wind over the equatorial surface is westerly. The seasonal reversal in the Hadley circulation sense and zonal wind direction is predicted to have a substantial influence on the formation of dunes as well as variation of Titan's rotation rate and length of day.

  11. The organic aerosols of Titan.

    PubMed

    Khare, B N; Sagan, C; Thompson, W R; Arakawa, E T; Suits, F; Callcott, T A; Williams, M W; Shrader, S; Ogino, H; Willingham, T O; Nagy, B

    1984-01-01

    A dark reddish organic solid, called tholin, is synthesized from simulated Titanian atmospheres by irradiation with high energy electrons in a plasma discharge. The visible reflection spectrum of this tholin is found to be similar to that of high altitude aerosols responsible for the albedo and reddish color of Titan. The real (n) and imaginary (k) parts of the complex refractive index of thin films of Titan tholin prepared by continuous D.C. discharge through a 0.9 N2/0.1 CH4 gas mixture at 0.2 mb is determined from x-ray to microwave frequencies. Values of n (approximately equal to 1.65) and k (approximately equal to 0.004 to 0.08) in the visible are consistent with deductions made by ground-based and spaceborne observations of Titan. Many infrared absorption features are present in k (lambda), including the 4.6 micrometers nitrile band. Molecular analysis of the volatile component of this tholin was performed by sequential and non-sequential pyrolytic gas chromatography/mass spectrometry. More than one hundred organic compounds are released; tentative identifications include saturated and unsaturated aliphatic hydrocarbons, substituted polycyclic aromatics, nitriles, amines, pyrroles, pyrazines, pyridines, pyrimidines, and the purine, adenine. In addition, acid hydrolysis produces a racemic mixture of biological and non-biological amino acids. Many of these molecules are implicated in the origin of life on Earth, suggesting Titan as a contemporary laboratory environment for prebiological organic chemistry on a planetary scale.

  12. Titan Aeromony and Climate Workshop

    NASA Astrophysics Data System (ADS)

    Bézard, Bruno; Lavvas, Panayotis; Rannou, Pascal; Sotin, Christophe; Strobel, Darrell; West, Robert A.; Yelle, Roger

    2016-06-01

    The observations of the Cassini spacecraft since 2004 revealed that Titan, the largest moon of Saturn, has an active climate cycle with a cloud cover related to the large scale atmospheric circulation, lakes of methane and hyrdrocarbons with variable depth, a dried fluvial system witnessing a past wetter climate, dunes, and deep changes in the weather and atmospheric structure as Titan went through the North Spring equinox. Moreover, the upper atmosphere is now considered the cradle of complex chemistry leading to aerosol formation, as well as the manifestation place of atmospheric waves. However, as the Cassini mission comes to its end, many fundamental questions remain unresolved... The objective of the workshop is to bring together international experts from different fields of Titan's research in order to have an overview of the current understanding, and to determine the remaining salient scientific issues and the actions that could be implemented to address them. PhD students and post-doc researchers are welcomed to present their studies. This conference aims to be a brainstorming event leaving abundant time for discussion during oral and poster presentations. Main Topics: - Atmospheric seasonal cycles and coupling with dynamics. - Composition and photochemistry of the atmosphere. - Formation and evolution of aerosols and their role in the atmosphere. - Spectroscopy, optical properties, and radiative transfer modeling of the atmosphere. - Surface composition, liquid reservoirs and interaction with atmosphere. - Evolution of the atmosphere. - Titan after Cassini, open questions and the path forward.

  13. Titan's gas and plasma torus

    NASA Technical Reports Server (NTRS)

    Eviatar, A.; Podolak, M.

    1983-01-01

    The implications of the Voyager observations for a steady state model of a torus of hydrogen and nitrogen neutral gas and plasma are assessed. Constraints are placed on the nitrogen neutral density, the neutral hydrogen and nitrogen escape fluxes (from Titan), and the diffusion rate in terms of observed or inferred quantities. The results obtained are consistent with the Voyager observations.

  14. Titan's Polar Atmosphere

    NASA Astrophysics Data System (ADS)

    Flasar, F. M.; Achterberg, R. K.; Schinder, P. J.

    2015-12-01

    Cassini CIRS and Radio-Occultation measurements obtained in 2004-2015 have tracked the evolution of temperatures and winds in Titan's polar atmosphere, as the winter season shifted from the northern hemisphere to the southern. The dissolution of the strong circumpolar vortex initially seen in the northern hemisphere has been gradual. There is no evidence of the rapid distortion and disruption forced by planetary waves that can occur on Earth. Indeed, neither Cassini experiment has identified any thermal signature attributable to planetary-scale waves. The south-polar region has turned wintry fairly abruptly: temperature and zonal wind maps from CIRS data show that the 1-mbar temperatures at high southern latitudes in late autumn are already much colder than those at the corresponding latitudes in the north in midwinter, when the first extensive polar measurements were obtained. The south-polar region now has a strong circumpolar vortex, with maximum stratospheric winds occurring near 60° S, in contrast to the northern hemisphere in winter, where the polar vortex was much broader, extending to 20°-30° N. Potential vorticity maps now indicate steep meridional gradients at high southern latitudes, implying a barrier to efficient mixing between the polar region and lower latitudes. Radio-occultations have higher vertical resolution than CIRS, and they have recently probed latitudes as high as 65° in both hemispheres (latitudes closer to the pole are precluded because of the geometry of Earth occultations and the season). Above 80 km at these latitudes, where the radiative damping times are small enough that temperatures have large seasonal variations, the stratosphere in the north has warmed, and it has become much colder in the south. The abrupt transition region with negative vertical temperature gradient between 80 and 100 km, which was seen at high northern latitudes in winter, has weakened, but it is still visible. In the south, one can see the early stage of

  15. Whisker formation in Sn and Pb-Sn coatings: Role of intermetallic growth, stress evolution, and plastic deformation processes

    SciTech Connect

    Chason, E.; Jadhav, N.; Kumar, K. S.; Chan, W. L.; Reinbold, L.

    2008-04-28

    We have simultaneously measured the evolution of intermetallic volume, stress, and whisker density in Sn and Pb-Sn alloy layers on Cu to study the fundamental mechanisms controlling whisker formation. For pure Sn, the stress becomes increasingly compressive and then saturates, corresponding to a plastically deformed region spreading away from the growing intermetallic particles. Whisker nucleation begins after the stress saturates. Pb-Sn layers have similar intermetallic growth kinetics but the resulting stress and whisker density are much less. Measurements after sputtering demonstrate the important role of the surface oxide in inhibiting stress relaxation.

  16. Temperate Lakes Discovered on Titan

    NASA Astrophysics Data System (ADS)

    Vixie, Graham; Barnes, Jason W.; Jackson, Brian; Wilson, Paul

    2012-04-01

    We have discovered two temperate lakes on Titan using Cassini's Visual and Infrared Mapping Spectrometer (VIMS). Three key features help to identify these surface features as lakes: morphology, albedo, and specular reflection. The presence of lakes at the mid-latitudes mean liquid can accumulate and remain stable outside of the poles. We first identify a lake surface by looking for possible shorelines with a lacustrine morphology. Then, we apply a simple atmospheric correction that produces an approximate surface albedo. Next, we prepare cylindrical projection maps of the brightness of the sky as seen from any points on the surface to identify specular reflections. Our techniques can then be applied to other areas, such as Arrakis Planitia, to test for liquid. Currently, all the known lakes on Titan are concentrated at the poles. Lakes have been suggested in the tropic zone by Griffith et al. Our discovery of non-transient, temperate lakes has important implications for Titan's hydrologic cycle. Clouds have been recorded accumulating in the mid-latitudes and areas have been darkened by rainfall but later brightened after evaporation (Turtle et al. 2011). Stable temperate lakes would affect total rainfall, liquid accumulation, evaporation rates, and infiltration. Polaznik Macula (Figure 1) is a great candidate for lake filling, evaporation rates, and stability. References: Griffith, C., et al.: "Evidence for Lakes on Titan's Tropical Surface". AAS/Division for Planetary Sciences Meeting Abstracts #42, Vol. 42, pp. 1077, 2010. Turtle, E. P., et al.: "Rapid and Extensive Surface Changes Near Titan's Equator: Evidence of April Showers". Science, Vol. 331, pp. 1414-, 2011. Figure 1: Polaznik Macula is the large, dark area central to the figure. The encircled dark blue areas represent positively identified lake regions in the T66 flyby. The light blue areas represent lake candidates still under analysis. The green circle marks a non-lake surface feature enclosed by a

  17. Nitrogen compounds in Titan's stratosphere

    NASA Astrophysics Data System (ADS)

    Coustenis, A.; Cirs Investigation Team

    Titan's atmosphere is essentially composed of molecular nitrogen (N2). The chemistry between the two mother molecules (N2 and CH4) leads to the formation of a certain number of nitriles observed in Titan's stratosphere as early as at the time of the Voyager 1 encounter in 1980. In the spectra taken by the Infrared Radiometer Interferometer Spectrometer (IRIS) the signatures of HCN, HC3N, C2N2 and C4N2 (in solid form) were found and reported. Subsequent observations from the ground better described the vertical profiles of these constituents and allowed for the detection of CH3CN (acetonitrile) in the mm range [3,4]. Recent data recorded by the Composite Infrared Spectrometer (CIRS) aboard the Cassini spacecraft during the Titan flybys (October 2004 - June 2006) give a handle on the temporal and latitudinal variations of these constituents. The nadir spectra characterize various regions on Titan from 85°S to 75°N with a variety of emission angles. We study the emission observed in the mid-infrared CIRS detector arrays (covering roughly the 600-1500 cm-1 spectral range with apodized resolutions of 2.54 or 0.53 cm-1 ). The composite spectrum shows several molecular signatures of nitriles. Information is retrieved on the meridional variations of the trace constituents and tied to predictions by dynamical-photochemical models [1,2,5]. The nitriles show a significant enhancement at high northern latitudes albeit not as marked as at the time of the Voyager encounter. We will give a review of our current understanding of the minor nitrile chemistry on Titan. References : [1] Coustenis et al., 2006. Icarus, in press. [2] Flasar et al., 2005. Science 308, 975. [3] Marten, A., et al., 2002, Icarus, 158, 532-544. [4] Marten, A. & Moreno, R., 2003. 35th Annual DPS Meeting, Monterey, Ca, BAAS, 35, 952. [5] Teanby et al., 2006. Icarus, 181, 243-255.

  18. Titan's Spectacular Volte-Face

    NASA Astrophysics Data System (ADS)

    Griffith, Caitlin A.

    2013-10-01

    Like Earth, Titan sports lakes, storms and rainfall. These features derive from a methane cycle, reminiscent of Earth's hydrological cycle; methane exists as an ice, liquid and gas and transfers between the surface and atmosphere, according to the seasonal weather. Titan's seasons contrast Earth’s. Imagine a summer trip to 70 latitude, where hurricane-sized storms burst forth out of a clear sky every few months for about 15 years. Then they vanish for another 15 years. Envision a trip to the winter polar region. Here the sky is perhaps clear except that the high haze, which filters sunlight like a translucent globe, is somewhat thicker than it is in the summer. Imperceptibly, you are blocking the diffuse organic matter, which is slowly settling out of the hazy orb, and accumulating on the polar surface. These effects are a few of the many that derive from Titan’s circulation and its seasonal changes during the satellite's 29.5 Earth year orbit about the Sun. In particular, and as indicated in recent observations, Titan's circulation flip-flopped. Before equinox in 2009, on average, air rose in the southern polar region and downwelled in the northern polar region. Now the reverse appears to be happening. Here we discuss the observations ranging from the surface to ~500 km altitude that reveal the symphony of responses of Titan's surface and atmosphere to this dramatic shift. In addition we discuss the syntheses of these effects, from theoretical efforts involving microphysical models, local cloud models and general circulation models, with the question of why Titan's seasonal changes are so much more spectacular compared to those of Earth.

  19. High potassium level

    MedlinePlus

    ... symptoms. Tests that may be ordered include: Electrocardiogram (ECG) Potassium level Your provider will likely check your ... have danger signs, such as changes in an ECG . Emergency treatment may include: Calcium given into your ...

  20. Potassium hydroxide poisoning

    MedlinePlus

    This article discusses poisoning from swallowing or touching potassium hydroxide or products that contain this chemical. This article is for information only. Do NOT use it to treat or manage an actual poison exposure. If ...

  1. What is Potassium?

    MedlinePlus

    ... carrots and beans. It's also found in dairy foods, meat, poultry, fish and nuts. Reach your recommended daily intake of potassium by frequently adding these foods to your daily menu: 1 cup cooked spinach: ...

  2. Potassium in diet

    MedlinePlus

    ... pressure. You may have hypokalemia if you: Take diuretics (water pills) to treat high blood pressure or ... and angiotensin 2 receptor blockers (ARBs) Potassium-sparing diuretics (water pills) such as spironolactone or amiloride Severe ...

  3. Potassium urine test

    MedlinePlus

    ... anti-inflammatory drugs (NSAIDs) Potassium supplements Water pills (diuretics) DO NOT stop taking any medicine before talking ... medicines, including beta blockers, lithium, trimethoprim, ... or nonsteroidal anti-inflammatory drugs (NSAIDs) Adrenal glands ...

  4. Low potassium level

    MedlinePlus

    ... laxative, which can cause diarrhea Chronic kidney disease Diuretic medicines (water pills), used to treat heart failure ... potassium through a vein (IV). If you need diuretics, your provider may: Switch you to a form ...

  5. Hubble Observes Surface of Titan

    NASA Technical Reports Server (NTRS)

    1994-01-01

    Scientists for the first time have made images of the surface of Saturn's giant, haze-shrouded moon, Titan. They mapped light and dark features over the surface of the satellite during nearly a complete 16-day rotation. One prominent bright area they discovered is a surface feature 2,500 miles across, about the size of the continent of Australia.

    Titan, larger than Mercury and slightly smaller than Mars, is the only body in the solar system, other than Earth, that may have oceans and rainfall on its surface, albeit oceans and rain of ethane-methane rather than water. Scientists suspect that Titan's present environment -- although colder than minus 289 degrees Fahrenheit, so cold that water ice would be as hard as granite -- might be similar to that on Earth billions of years ago, before life began pumping oxygen into the atmosphere.

    Peter H. Smith of the University of Arizona Lunar and Planetary Laboratory and his team took the images with the Hubble Space Telescope during 14 observing runs between Oct. 4 - 18. Smith announced the team's first results last week at the 26th annual meeting of the American Astronomical Society Division for Planetary Sciences in Bethesda, Md. Co-investigators on the team are Mark Lemmon, a doctoral candidate with the UA Lunar and Planetary Laboratory; John Caldwell of York University, Canada; Larry Sromovsky of the University of Wisconsin; and Michael Allison of the Goddard Institute for Space Studies, New York City.

    Titan's atmosphere, about four times as dense as Earth's atmosphere, is primarily nitrogen laced with such poisonous substances as methane and ethane. This thick, orange, hydrocarbon haze was impenetrable to cameras aboard the Pioneer and Voyager spacecraft that flew by the Saturn system in the late 1970s and early 1980s. The haze is formed as methane in the atmosphere is destroyed by sunlight. The hydrocarbons produced by this methane destruction form a smog similar to that found over large cities, but is much

  6. Electric Field Effects on the Intermolecular Interactions in Water Whiskers: Insight from Structures, Energetics, and Properties

    SciTech Connect

    Bai, Yang; He, Hui-Min; Li, Ying; Zhou, Zhong-Jun; Wang, Jia-Jun; Wu, Di; Chen, Wei; Gu, Feng-Long; Sumpter, Bobby G.; Huang, Jingsong

    2015-02-19

    Modulation of intermolecular interactions in response to external electric fields could be fundamental to the formation of unusual forms of water, such as water whiskers. However, a detailed understanding of the nature of intermolecular interactions in such systems is lacking. In this study, we present novel theoretical results based on electron correlation calculations regarding the nature of H-bonds in water whiskers, which is revealed by studying their evolution under external electric fields with various field strengths. We find that the water whiskers consisting of 2-7 water molecules all have a chain-length dependent critical electric field. Under the critical electric field, the most compact chain structures are obtained, featuring very strong H-bonds, herein referred to as covalent H-bonds. In the case of a water dimer whisker, the bond length of the novel covalent H-bond shortens by 25%, the covalent bond order increases by 9 times, and accordingly the H-bond energy is strengthened by 5 times compared to the normal H-bond in a (H2O)2 cluster. Below the critical electric field, it is observed that with increasing field strength, H-bonding orbitals display gradual evolutions in the orbital energy, orbital ordering, and orbital nature (i.e., from typical -style orbital to unusual -style double H-bonding orbital). We also show that beyond the critical electric field, a single water whisker may disintegrate to form a loosely bound zwitterionic chain due to a relay-style proton transfer, whereas two water whiskers may undergo intermolecular cross-linking to form a quasi-two-dimensional water network. In conclusion, these results help shed new insight on the effects of electric fields on water whisker formation.

  7. Electric Field Effects on the Intermolecular Interactions in Water Whiskers: Insight from Structures, Energetics, and Properties

    DOE PAGES

    Bai, Yang; He, Hui-Min; Li, Ying; Zhou, Zhong-Jun; Wang, Jia-Jun; Wu, Di; Chen, Wei; Gu, Feng-Long; Sumpter, Bobby G.; Huang, Jingsong

    2015-02-19

    Modulation of intermolecular interactions in response to external electric fields could be fundamental to the formation of unusual forms of water, such as water whiskers. However, a detailed understanding of the nature of intermolecular interactions in such systems is lacking. In this study, we present novel theoretical results based on electron correlation calculations regarding the nature of H-bonds in water whiskers, which is revealed by studying their evolution under external electric fields with various field strengths. We find that the water whiskers consisting of 2-7 water molecules all have a chain-length dependent critical electric field. Under the critical electric field,more » the most compact chain structures are obtained, featuring very strong H-bonds, herein referred to as covalent H-bonds. In the case of a water dimer whisker, the bond length of the novel covalent H-bond shortens by 25%, the covalent bond order increases by 9 times, and accordingly the H-bond energy is strengthened by 5 times compared to the normal H-bond in a (H2O)2 cluster. Below the critical electric field, it is observed that with increasing field strength, H-bonding orbitals display gradual evolutions in the orbital energy, orbital ordering, and orbital nature (i.e., from typical -style orbital to unusual -style double H-bonding orbital). We also show that beyond the critical electric field, a single water whisker may disintegrate to form a loosely bound zwitterionic chain due to a relay-style proton transfer, whereas two water whiskers may undergo intermolecular cross-linking to form a quasi-two-dimensional water network. In conclusion, these results help shed new insight on the effects of electric fields on water whisker formation.« less

  8. Dissolution on Titan and on Earth: Towards the age of Titan's karstic landscapes

    NASA Astrophysics Data System (ADS)

    Cornet, T.; Cordier, D.; Le Bahers, T.; Bourgeois, O.; Fleurant, C.; Le Mouélic, S.; Altobelli, N.

    2015-10-01

    The morphology of Titan's lacustrine depressions led to comparisons with terrestrial depressions developed by karstic dissolution. We tested this hypothesis by computing dissolution rates of Titan's solids in liquid methane. We inferred from these rates the timescales needed to create dissolution landforms of a given depth. Dissolution would be a very efficient geological process to shape Titan's surface, on timescales generally shorter than 100 Myrs, consistent with the youth of Titan's surface (<1 Gyr).

  9. Nitrogen Chemistry in Titan's Upper Atmosphere

    NASA Technical Reports Server (NTRS)

    McKay, Christopher P.; Cuzzi, Jeffrey (Technical Monitor)

    1996-01-01

    In Titan's upper atmosphere N2 is dissociated to N by solar UV and high energy electrons. This flux of N provides for interesting organic chemistry in the lower atmosphere of Titan. Previously the main pathway for the loss of this N was thought to be the formation of HCN, followed by diffusion of this HCN to lower altitudes leading ultimately to condensation. However, recent laboratory simulations of organic chemistry in Titan's atmosphere suggest that formation of the organic haze may be an important sink for atmospheric N. Because estimates of the eddy diffusion profile on Titan have been based on the HCN profile, inclusion of this additional sink for N will affect estimates for all transport processes in Titan's atmosphere. This and other implications of this sink for the N balance on Titan are considered.

  10. Photochemically driven collapse of Titan's atmosphere.

    PubMed

    Lorenz, R D; McKay, C P; Lunine, J I

    1997-01-31

    Saturn's giant moon Titan has a thick (1.5 bar) nitrogen atmosphere, which has a temperature structure that is controlled by the absorption of solar and thermal radiation by methane, hydrogen, and organic aerosols into which methane is irreversibly converted by photolysis. Previous studies of Titan's climate evolution have been done with the assumption that the methane abundance was maintained against photolytic depletion throughout Titan's history, either by continuous supply from the interior or by buffering by a surface or near surface reservoir. Radiative-convective and radiative-saturated equilibrium models of Titan's atmosphere show that methane depletion may have allowed Titan's atmosphere to cool so that nitrogen, its main constituent, condenses onto the surface, collapsing Titan into a Triton-like frozen state with a thin atmosphere. PMID:9005844

  11. Whisker-reinforced heat-cured dental resin composites: effects of filler level and heat-cure temperature and time.

    PubMed

    Xu, H H

    2000-06-01

    Currently available dental resin composites are inadequate for use in large stress-bearing crown and multiple-unit restorations. The aim of this study was to reinforce heat-cured composites with ceramic whiskers. It was hypothesized that whiskers substantially strengthen heat-cured composites. It was further hypothesized that whisker filler level and heat-cure temperature and time significantly influence composite properties. Silica particles were fused onto the whiskers to facilitate silanization and to roughen the whiskers for improved retention in the matrix. The whisker filler mass fraction was varied from 0% to 79%, the heat-cure temperature from 80 degrees C to 180 degrees C, and cure time from 10 min to 24 hrs. Flexural strength, work-of-fracture, and fracture toughness of the composites were measured, and specimen fracture surfaces were examined with scanning electron microscopy. Filler level had a significant effect on composite properties. The whisker composite with 70% filler level had a flexural strength in MPa (mean +/- SD; n = 6) of 248 +/- 23, significantly higher than 120 +/- 16 of an inlay/onlay composite control and 123 +/- 21 of a prosthetic composite control (Tukey's multiple comparison test; family confidence coefficient = 0.95). Heat-cure time also played a significant role. At 120 degrees C, the strength of composite cured for 10 min was 178 +/- 17, lower than 236 +/- 14 of composite cured for 3 hrs. The strength of whisker composite did not degrade after water-aging for 100 d. In conclusion, heat-cured composites were substantially reinforced with whiskers. The reinforcement mechanisms appeared to be whiskers bridging and resisting cracks. The strength and fracture toughness of whisker composite were nearly twice those of currently available inlay/onlay and prosthetic composites.

  12. The magnetic memory of Titan's ionized atmosphere.

    PubMed

    Bertucci, C; Achilleos, N; Dougherty, M K; Modolo, R; Coates, A J; Szego, K; Masters, A; Ma, Y; Neubauer, F M; Garnier, P; Wahlund, J-E; Young, D T

    2008-09-12

    After 3 years and 31 close flybys of Titan by the Cassini Orbiter, Titan was finally observed in the shocked solar wind, outside of Saturn's magnetosphere. These observations revealed that Titan's flow-induced magnetosphere was populated by "fossil" fields originating from Saturn, to which the satellite was exposed before its excursion through the magnetopause. In addition, strong magnetic shear observed at the edge of Titan's induced magnetosphere suggests that reconnection may have been involved in the replacement of the fossil fields by the interplanetary magnetic field. PMID:18787164

  13. The Global Energy Balance of Titan

    NASA Technical Reports Server (NTRS)

    Li, Liming; Nixon, Conor A.; Achterberg, Richard K.; Smith, Mark A.; Gorius, Nicolas J. P.; Jiang, Xun; Conrath, Barney J.; Gierasch, Peter J.; Simon-Miller, Amy A.; Flasar, F. Michael; Baines, Kevin H.; Ingersoll, Andrew P.; West, Robert A.; Vasavada, Ashwin R.; Ewald, Shawn P.

    2011-01-01

    We report the first measurement of the global emitted power of Titan. Longterm (2004-2010) observations conducted by the Composite Infrared Spectrometer (CIRS) onboard Cassini reveal that the total emitted power by Titan is (2.84 plus or minus 0.01) x 10(exp 8) watts. Together with previous measurements of the global absorbed solar power of Titan, the CIRS measurements indicate that the global energy budget of Titan is in equilibrium within measurement error. The uncertainty in the absorbed solar energy places an upper limit on the energy imbalance of 5.3%.

  14. Titan In Situ Exploration Concepts at JPL

    NASA Technical Reports Server (NTRS)

    Elliott, John O.; Hall, Jeffery L.; Jones, Jack; Reh, Kim

    2008-01-01

    This slide presentation reviews concepts for exploring Titan via balloon vehicles. The presentation includes information about the baseline options, the deployment scenario, and the balloon technology development.

  15. Can Titan generate tori in Saturn's magnetosphere?

    NASA Astrophysics Data System (ADS)

    Smith, H. T.; Johnson, R. E.; Rymer, A. M.; Mitchell, D. G.

    2011-12-01

    Prior to Cassini's arrival at Saturn, nitrogen ions were thought to dominate heavy plasma in Saturn's magnetosphere and that Titan's atmosphere was the source of this nitrogen. Therefore, the presence of a Titan nitrogen torus was anticipated. However, it is now known water-group ions dominate Saturn's heavy ion plasma. While nitrogen ions have been detected beyond the orbit of Rhea, they appear to be originating from the Enceladus plumes with little nitrogen plasma detected in the magnetosphere near Titan's orbit. These results appear inconsistent with the expectation that Titan's dense relatively unprotected atmosphere should provide a significant source of heavy particles to Saturn's magnetosphere. This inconsistency suggests that the plasma environment at Titan's orbit is much more complex than originally anticipated. In this talk, we expand on our previous research that categorizes the plasma environments near Titan to include all locations along Titan's orbit. Using these categories, we develop characteristic plasma spectra of each type of environment and use these results in a 3D Monte Carlo model to more accurately examine fate of nitrogen and methane escaping Titan's atmosphere. These results are compared to Cassini observations to determine if Titan is capable of generating tori.

  16. The magnetic memory of Titan's ionized atmosphere.

    PubMed

    Bertucci, C; Achilleos, N; Dougherty, M K; Modolo, R; Coates, A J; Szego, K; Masters, A; Ma, Y; Neubauer, F M; Garnier, P; Wahlund, J-E; Young, D T

    2008-09-12

    After 3 years and 31 close flybys of Titan by the Cassini Orbiter, Titan was finally observed in the shocked solar wind, outside of Saturn's magnetosphere. These observations revealed that Titan's flow-induced magnetosphere was populated by "fossil" fields originating from Saturn, to which the satellite was exposed before its excursion through the magnetopause. In addition, strong magnetic shear observed at the edge of Titan's induced magnetosphere suggests that reconnection may have been involved in the replacement of the fossil fields by the interplanetary magnetic field.

  17. Nitrogen fractionation in Titan's aerosols

    NASA Astrophysics Data System (ADS)

    Carrasco, Nathalie; Kuga, Maia; Marty, Bernard; Fleury, Benjamin; Marrocchi, Yves

    2016-06-01

    A strong nitrogen fractionation is found by Cassini in Titan's atmosphere with the detection of 15N-rich HCN relative to N2. Photodissociation of N2 associated or not to self-shielding might involve 15N-rich radicals prone to incorporation into forming organics. However the isotopic composition is only available for very simple gaseous N-bearing compounds, and the propagation and conservation of such a large N-isotopic fractionation upon polymerization is actually out of reach with the instruments onboard Cassini. We will therefore present a first laboratory investigation of the possible enrichment in the solid organic aerosols. We will also discuss the space instrumention required in the future to answer this pending issue on Titan.

  18. Ion Cyclotron Waves at Titan

    NASA Astrophysics Data System (ADS)

    Russell, C. T.; Wei, H.; Cowee, M.; Neubauer, F. M.; Dougherty, M. K.

    2014-12-01

    The observation of ion cyclotron waves was generally expected well before Cassini arrived at Titan in 2004, because strong ion cyclotron waves were seen at Io where its atmosphere interacted with the corotating magnetospheric plasma. However, the region of the interaction of the Saturnian magnetospheric plasma with the Titan atmosphere has been quite devoid of ion cyclotron waves. Finally, on pass T63, ion cyclotron waves were seen briefly. More recently, on pass T98, a longer sequence of ion cyclotron waves also occurred. On pass T63, the pick-up ion signature is that of both H+ and H2+, while on pass T98, only H+ ion cyclotron waves are observed. We examine the strength of these waves and their region of occurrence in the light of our previous work on the expected occurrence of these waves.

  19. Titan's geoid and hydrology: implications for Titan's geological evolution

    NASA Astrophysics Data System (ADS)

    Sotin, Christophe; Seignovert, Benoit; Lawrence, Kenneth; MacKenzie, Shannon; Barnes, Jason; Brown, Robert

    2014-05-01

    A 1x1 degree altitude map of Titan is constructed from the degree 4 gravity potential [1] and Titan's shape [2] determined by the Radio Science measurements and RADAR observations of the Cassini mission. The amplitude of the latitudinal altitude variations is equal to 300 m compared to 600 m for the amplitude of the latitudinal shape variations. The two polar caps form marked depressions with an abrupt change in topography at exactly 60 degrees at both caps. Three models are envisaged to explain the low altitude of the polar caps: (i) thinner ice crust due to higher heat flux at the poles, (ii) fossil shape acquired if Titan had higher spin rate in the past, and (iii) subsidence of the crust following the formation of a denser layer of clathrates as ethane rain reacts with the H2O ice crust [3]. The later model is favored because of the strong correlation between the location of the cloud system during the winter season and the latitude of the abrupt change in altitude. Low altitude polar caps would be the place where liquids would run to and eventually form large seas. Indeed, the large seas of Titan are found at the deepest locations at the North Pole. However, the lakes and terrains considered to be evaporite candidates due to their spectral characteristics in the infrared [4,5] seem to be perched. Lakes may have been filled during Titan's winter and then slowly evaporated leaving material on the surface. Interestingly, the largest evaporite deposits are located at the equator in a deep depression 150 m below the altitude of the northern seas. This observation seems to rule out the presence of a global subsurface hydrocarbon reservoir unless the evaporation rate at the equator is faster than the transport of fluids from the North Pole to the equator. This work has been performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. [1] Iess L. et al. (2012) Science, doi 10.1126/science.1219631. [2] Lorenz R.D. (2013

  20. Cassini Imaging Results at Titan

    NASA Technical Reports Server (NTRS)

    McEwen, A.; Turtle, E.; Perry J.; Fussner, S.; Porco, C.; West, R.; Johnson, T.; Collins, G.; DelGenio, T.; Barbara, J.

    2005-01-01

    The Cassini Imaging Science Subsystem (ISS) images show striking albedo markings on the surface of Titan. In equatorial regions the albedo patterns have high contrast and exhibit prominent lineaments and linear/angular boundaries suggestive of tectonic influences or fracturing of brittle surficial materials. There are intriguing dark curving lines near the south pole. Here we present several working hypotheses to explain these patterns. We also briefly summarize atmospheric science results.

  1. Tactile soft-sparse mean fluid-flow imaging with a robotic whisker array.

    PubMed

    Tuna, Cagdas; Jones, Douglas L; Kamalabadi, Farzad

    2015-08-01

    An array of whiskers is critical to many mammals to survive in their environment. However, current engineered systems generally employ vision, radar or sonar to explore the surroundings, not having sufficiently benefited from tactile perception. Inspired by the whisking animals, we present here a novel tomography-based tactile fluid-flow imaging technique for the reconstruction of surroundings with an artificial whisker array. The moment sensed at the whisker base is the weighted integral of the drag force per length, which is proportional to the relative velocity squared on a whisker segment. We demonstrate that the 2D cross-sectional mean fluid-flow velocity-field can be successfully mapped out by collecting moment measurements at different angular positions with the whisker array. We use a regularized version of the FOCal underdetermined system solver algorithm with a smoothness constraint to obtain soft-sparse static estimates of the 2D cross-sectional velocity-squared distribution. This new proposed approach has the strong potential to be an alternative environmental sensing technology, particularly in dark or murky environments. PMID:26241787

  2. Short Time-Scale Sensory Coding in S1 during Discrimination of Whisker Vibrotactile Sequences

    PubMed Central

    Miyashita, Toshio; Lee, Daniel J.; Smith, Katherine A.; Feldman, Daniel E.

    2016-01-01

    Rodent whisker input consists of dense microvibration sequences that are often temporally integrated for perceptual discrimination. Whether primary somatosensory cortex (S1) participates in temporal integration is unknown. We trained rats to discriminate whisker impulse sequences that varied in single-impulse kinematics (5–20-ms time scale) and mean speed (150-ms time scale). Rats appeared to use the integrated feature, mean speed, to guide discrimination in this task, consistent with similar prior studies. Despite this, 52% of S1 units, including 73% of units in L4 and L2/3, encoded sequences at fast time scales (≤20 ms, mostly 5–10 ms), accurately reflecting single impulse kinematics. 17% of units, mostly in L5, showed weaker impulse responses and a slow firing rate increase during sequences. However, these units did not effectively integrate whisker impulses, but instead combined weak impulse responses with a distinct, slow signal correlated to behavioral choice. A neural decoder could identify sequences from fast unit spike trains and behavioral choice from slow units. Thus, S1 encoded fast time scale whisker input without substantial temporal integration across whisker impulses. PMID:27574970

  3. The effects of smoking on whisker movements: A quantitative measure of exploratory behaviour in rodents.

    PubMed

    Grant, Robyn A; Cielen, Nele; Maes, Karen; Heulens, Nele; Galli, Gina L J; Janssens, Wim; Gayan-Ramirez, Ghislaine; Degens, Hans

    2016-07-01

    Nicotine, an important component of cigarette smoke, is a neurotransmitter that contributes to stress, depression and anxiety in smokers. In rodents, it increases anxiety and reduces exploratory behaviours. However, so far, the measurements of exploratory behaviour in rodents have only been semi-quantitative and lacking in sufficient detail to characterise the temporal effect of smoking cessation. As rodents, such as mice and rats, primarily use whiskers to explore their environment, we studied the effect of 3 months smoking with 1 and 2 weeks smoking cessation on whisker movements in mice, using high-speed video camera footage and image analysis. Both protraction and retraction whisker velocities were increased in smoking mice (p<0.001) and returned to normal following just one week of smoking cessation. In addition, locomotion speeds were decreased in smoking mice, and returned to normal following smoking cessation. Lung function was also impacted by smoking and remained impaired even following smoking cessation. We suggest that the increased whisker velocities in the smoking mice reflect reduced exploration and impeded tactile performance. The increase in whisker velocity with smoking, and its reduction following smoking cessation, also lends support to acetylcholine being involved in awareness, attention and alertness pathways. It also shows that smoking-induced behavioural changes can be reversed with smoking cessation, which may have implications for human smokers. PMID:27045697

  4. Morphology and properties of soy protein isolate thermoplastics reinforced with chitin whiskers.

    PubMed

    Lu, Yongshang; Weng, Lihui; Zhang, Lina

    2004-01-01

    Environmentally friendly thermoplastic nanocomposites were successfully developed using a colloidal suspension of chitin whiskers as a filler to reinforce soy protein isolate (SPI) plastics. The chitin whiskers, having lengths of 500 +/- 50 nm and diameters of 50 +/- 10 nm on average, were prepared from commercial chitin by acid hydrolysis. The dependence of morphology and properties on the chitin whiskers content in the range from 0 to 30 wt % for the glycerol plasticized SPI nanocomposites was investigated by dynamic mechanical thermal analysis, scanning electron microscopy, swelling experiment, and tensile testing. The results indicate that the strong interactions between fillers and between the filler and SPI matrix play an important role in reinforcing the composites without interfering with their biodegradability. The SPI/chitin whisker nanocomposites at 43% relative humidity increased in both tensile strength and Young's modulus from 3.3 MPa for the SPI sheet to 8.4 MPa and from 26 MPa for the SPI sheet to 158 MPa, respectively. Further, incorporating chitin whisker into the SPI matrix leads to an improvement in water resistance for the SPI based nanocomposites.

  5. Short Time-Scale Sensory Coding in S1 during Discrimination of Whisker Vibrotactile Sequences.

    PubMed

    McGuire, Leah M; Telian, Gregory; Laboy-Juárez, Keven J; Miyashita, Toshio; Lee, Daniel J; Smith, Katherine A; Feldman, Daniel E

    2016-08-01

    Rodent whisker input consists of dense microvibration sequences that are often temporally integrated for perceptual discrimination. Whether primary somatosensory cortex (S1) participates in temporal integration is unknown. We trained rats to discriminate whisker impulse sequences that varied in single-impulse kinematics (5-20-ms time scale) and mean speed (150-ms time scale). Rats appeared to use the integrated feature, mean speed, to guide discrimination in this task, consistent with similar prior studies. Despite this, 52% of S1 units, including 73% of units in L4 and L2/3, encoded sequences at fast time scales (≤20 ms, mostly 5-10 ms), accurately reflecting single impulse kinematics. 17% of units, mostly in L5, showed weaker impulse responses and a slow firing rate increase during sequences. However, these units did not effectively integrate whisker impulses, but instead combined weak impulse responses with a distinct, slow signal correlated to behavioral choice. A neural decoder could identify sequences from fast unit spike trains and behavioral choice from slow units. Thus, S1 encoded fast time scale whisker input without substantial temporal integration across whisker impulses. PMID:27574970

  6. Tactile soft-sparse mean fluid-flow imaging with a robotic whisker array.

    PubMed

    Tuna, Cagdas; Jones, Douglas L; Kamalabadi, Farzad

    2015-08-04

    An array of whiskers is critical to many mammals to survive in their environment. However, current engineered systems generally employ vision, radar or sonar to explore the surroundings, not having sufficiently benefited from tactile perception. Inspired by the whisking animals, we present here a novel tomography-based tactile fluid-flow imaging technique for the reconstruction of surroundings with an artificial whisker array. The moment sensed at the whisker base is the weighted integral of the drag force per length, which is proportional to the relative velocity squared on a whisker segment. We demonstrate that the 2D cross-sectional mean fluid-flow velocity-field can be successfully mapped out by collecting moment measurements at different angular positions with the whisker array. We use a regularized version of the FOCal underdetermined system solver algorithm with a smoothness constraint to obtain soft-sparse static estimates of the 2D cross-sectional velocity-squared distribution. This new proposed approach has the strong potential to be an alternative environmental sensing technology, particularly in dark or murky environments.

  7. Oxygen Chemistry in Titan's Atmosphere

    NASA Astrophysics Data System (ADS)

    Wilson, E. H.; Atreya, S. K.

    2002-09-01

    Oxygen chemistry in the atmosphere of Titan is controlled by the presence of CO and a likely influx of extraplanetary oxygen. The presence of water vapor, corroborated by the Infrared Space Observatory (ISO) stratospheric detection [1], combined with CO induces the formation of CO2, which has also been observed [2]. However, the high CO/H2O ratio in Titan's atmosphere causes the propagation of oxygen chemistry to follow a different path than what is predicted for the Jovian planets. Specifically, the efficient CO recycling mechanisms serve to inhibit significant formation of larger oxygen compounds such as CH3OH (methanol) and CH2CO (ketene). The results of a 1-D photochemical model are presented in the context of identifying possible oxygen compounds that might be detected by the Cassini/Huygens mission which will arrive at Titan in 2004. This work was supported by the NASA Planetary Atmospheres Program and by the GCMS Project of the Cassini/Huygens mission. [1] A. Coustenis et al., Astron. Astrophys., 336, L85-L89, 1998. [2] A. Coustenis et al., Icarus, 80, 54-76, 1989.

  8. Safe prescribing: a titanic challenge.

    PubMed

    Routledge, Philip A

    2012-10-01

    The challenge to achieve safe prescribing merits the adjective 'titanic'. The organisational and human errors leading to poor prescribing (e.g. underprescribing, overprescribing, misprescribing or medication errors) have parallels in the organisational and human errors that led to the loss of the Titanic 100 years ago this year. Prescribing can be adversely affected by communication failures, critical conditions, complacency, corner cutting, callowness and a lack of courage of conviction, all of which were also factors leading to the Titanic tragedy. These issues need to be addressed by a commitment to excellence, the final component of the 'Seven C's'. Optimal prescribing is dependent upon close communication and collaborative working between highly trained health professionals, whose role is to ensure maximum clinical effectiveness, whilst also protecting their patients from avoidable harm. Since humans are prone to error, and the environments in which they work are imperfect, it is not surprising that medication errors are common, occurring more often during the prescribing stage than during dispensing or administration. A commitment to excellence in prescribing includes a continued focus on lifelong learning (including interprofessional learning) in pharmacology and therapeutics. This should be accompanied by improvements in the clinical working environment of prescribers, and the encouragement of a strong safety culture (including reporting of adverse incidents as well as suspected adverse drug reactions whenever appropriate). Finally, members of the clinical team must be prepared to challenge each other, when necessary, to ensure that prescribing combines the highest likelihood of benefit with the lowest potential for harm.

  9. Large-scale synthesis of TiC whiskers by carbothermal reduction with microcrystalline cellulose as the carbon source

    NASA Astrophysics Data System (ADS)

    Xiong, Huiwen; Guo, Yu; Wen, Yu; Lv, Yaping; Li, Zhiyou; Zhou, Kechao

    2015-12-01

    TiC whiskers were synthesized by a typical chloride-assisted carbothermal reduction method with microcrystalline cellulose as a novel carbon source. When with nickel, the Vapor-Liquid-Solid (VLS) and Vapor-Solid (VS) mechanisms were confirmed to govern the whisker growth with different tip morphologies. Systematic investigation of the sintering schedule revealed that two steps sintering favored the formation of whiskers (over 90 vol% yield) with a low oxygen content (4.322 Å of the lattice parameter). Unlike previous research, faceted TiC whiskers on the titanium oxide particles (Ti3O5) were epitaxially grown via the VS mechanism without catalyst (nickel). An effect of carbon sources (cellulose, chars and pyrolytic carbon black) on the morphology of TiC whiskers has been studied. A two-dimensional (2-D) nucleation on the Ti3O5 substrate and persistent absorption of growth adatoms on the {111} faces (at the tip) was proposed to explain the formation of TiC whisker. This study provided not only a new simple method for synthesizing TiC whiskers but also a new insight into the growth mode for TiC whiskers.

  10. Fabrication of whisker-toughened alumina tubes. Final report

    SciTech Connect

    Loutfy, R.O.

    1993-09-01

    A process has been developed to fabricate whisker toughened alumina composites by slip casting dense colloidal suspensions of Al{sub 2}O{sub 3}-15% SiC{sub w}. Optimum processing parameters for slip casting we developed with slip viscosity of 60--70 centipoise and solids content 78--79 wt %. Slip-cast parts with green densities 65 to 68% theoretical were achieved. Composite parts were pressureless sintered to 96--97% theoretical density with <1% open porosity. The composites exhibited strengths of 500 MPa, toughness of 6.5 MPa m{sup 1/2}, and hardness of 17.26 GPa (1765 kg/mm{sup 2}). High temperature strength retention was maintained up to 1200C. Good thermal shock resistance with {Delta}T{sub cr} = 500C was also achieved. The process technology was transferred into pilot scale for producing prototype heat exchanger tubing up to 4 inches in diameter at the facilities of Vesuvius/McDanel.

  11. A new SiC-whisker-reinforced lithium aluminosilicate composite

    SciTech Connect

    Xue, L.A.; Chen, Iwei . Dept. of Materials Science and Engineering)

    1993-11-01

    The glass-ceramic matrix of the well-known lithium aluminosilicate (LAS)/SiC composite is usually formulated near the spodumene composition. The authors report a new composition which is rich in alumina and lean in silica and lithia. This formulation offers a new option of converting the glass-ceramic matrix to a mullite/alumina matrix upon annealing above 1,400 C, and hence better creep resistance and other high-temperature mechanical properties. Using a transient-phase processing method that they developed previously for the superplastic forming of mullite, the authors are able to hot-press a composite containing 30 vol% SiC whiskers at [approximately]1,350 C to achieve full density. Flexural strength measurements up to 1,400 C have confirmed the improved high-temperature strength and creep resistance over conventional LAS. The fracture toughness is also higher than that of LAS. The results suggest that the new composition may be chosen as a better candidate matrix for SiC-fiber-reinforced composites.

  12. Recipe for potassium

    SciTech Connect

    Izutani, Natsuko

    2012-11-12

    I investigate favorable conditions for producing potassium (K). Observations show [K/Fe] > 0 at low metallicities, while zero-metal supernova models show low [K/Fe] (< 0). Theoretically, it is natural that the odd-Z element, potassium decreases with lower metallicity, and thus, the observation should imply new and unknown sites for potassium. In this proceedings, I calculate proton-rich nucleosynthesis with three parameters, the initial Y{sub e} (from 0.51 to 0.60), the initial density {rho}{sub max} (10{sup 7}, 10{sup 8}, and 10{sup 9} [g/cm{sup 3}]), and the e-fold time {tau} for the density (0.01, 0.1, and 1.0 [sec]). Among 90 models I have calculated, only 26 models show [K/Fe] > 0, and they all have {rho}{sub max} = 10{sup 9}[g/cm{sup 3}]. I discuss parameter dependence of [K/Fe].

  13. High Temperature Stability of Potassium Beta Alumina

    NASA Technical Reports Server (NTRS)

    Williams, R. M.; Kisor, A.; Ryan, M. A.

    1996-01-01

    None. From Objectives section: Evaluate the stability of potassium beta alumina under potassium AMTEC operating conditions. Evaluate the stability regime in which potassium beta alumina can be fabricated.

  14. Whisker-reinforced bioactive composites containing calcium phosphate cement fillers: effects of filler ratio and surface treatments on mechanical properties.

    PubMed

    Xu, H H; Quinn, J B

    2001-11-01

    Calcium phosphate cement (CPC) sets to form microporous solid hydroxyapatite with excellent osteoconductivity, but its brittleness and low strength prohibit use in stress-bearing locations. The aim of this study was to incorporate prehardened CPC particles and ceramic whiskers in a resin matrix to improve the strength and fracture resistance, and to investigate the effects of key microstructural variables on composite mechanical properties. Two types of whiskers were used: silicon nitride, and silicon carbide. The whiskers were surface-treated by fusing with silica and by silanization. The CPC particle fillers were either silanized or not silanized. Seven mass ratios of whisker-silica/CPC were mixed: 0:1 (no whisker-silica), 1:5, 1:2, 1:1, 2:1, 5:1, and 1:0 (no CPC). Each powder was blended with a bisphenol-a-glycidyl methacrylate-based resin to harden in 2 x 2 x 25 mm molds by two-part chemical curing. The specimens were tested in three-point flexure to measure strength, work-of-fracture (toughness), and elastic modulus. Two-way analysis of variance was used to analyze the data, and scanning electron microscopy was used to examine specimen fracture surfaces. The whisker-silica/CPC ratio had significant effects on composite properties (p < 0.001). When this ratio was increased from 0:1 to 1:0, the strength was increased by about three times, work-of-fracture by five times, and modulus by two times. Whisker surface treatments and CPC filler silanization also had significant effects (p < 0.001) on composite properties. Scanning electron microscopy revealed rough fracture surfaces for the whisker composites with steps and whisker pullout. Resin remnants were observed on the surfaces of the pulled-out whiskers, indicating strong whisker-matrix bonding. In conclusion, incorporating highly osteoconductive CPC fillers and ceramic whiskers yielded composites with substantially improved mechanical properties compared with composites filled with CPC particles without

  15. Tapered ZnO Whiskers: {hkil}-Specific Mosaic Twinning VLS Growth from a Partially Molten Bottom Source

    PubMed Central

    2009-01-01

    Zn particulates overlaid with wurtzite (W)-type ZnO condensates having nearly orthogonal and facets were found to self-catalyze unusual tapered W-ZnO whiskers upon isothermal atmospheric annealing, i.e., thermal oxidation, at 600 °C. Analytical electron microscopic observations indicated that such whiskers formed tapered slabs having mosaic and twinned domains. The tapered whiskers can be rationalized by an alternative vapor–liquid–solid growth, i.e., {hkil}-specific coalescence twinning growth from the ZnO condensates taking advantage of a partially molten bottom source of Zn and the adsorption of atoms at the whisker tips and ledges under the influence of capillarity effect. The tapered whiskers having strong photoluminescence at 391 nm and with a considerable flexibility could have potential applications. PMID:20596385

  16. Potassium Beta-Alumina/Molybdenum/Potassium Electrochemical Cells

    NASA Technical Reports Server (NTRS)

    Williams, R.; Kisor, A.; Ryan, M.; Nakamura, B.; Kikert, S.; O'Connor, D.

    1994-01-01

    potassium alkali metal thermal-to-electric converter (K-AMTEC) cells utilizing potassium beta alumina solid electrolyte (K-BASE) are predicted to have improved properties for thermal to electric conversion at somewhat lower temperatures than sodium AMTEC's.

  17. Errors in potassium balance

    SciTech Connect

    Forbes, G.B.; Lantigua, R.; Amatruda, J.M.; Lockwood, D.H.

    1981-01-01

    Six overweight adult subjects given a low calorie diet containing adequate amounts of nitrogen but subnormal amounts of potassium (K) were observed on the Clinical Research Center for periods of 29 to 40 days. Metabolic balance of potassium was measured together with frequent assays of total body K by /sup 40/K counting. Metabolic K balance underestimated body K losses by 11 to 87% (average 43%): the intersubject variability is such as to preclude the use of a single correction value for unmeasured losses in K balance studies.

  18. Could Zinc Whiskers Be Impacting Your Electronic Systems? Raise Your Awareness. Revision D

    NASA Technical Reports Server (NTRS)

    Sampson, Michael; Brusse, Jay

    2003-01-01

    During the past several decades electrical short circuits induced by "Zinc Whiskers" have been cited as the root cause of failure for various electronic systems (e.g., apnea monitors, telecom switches). These tiny filaments of zinc that may grow from some zinc-coated items (especially those coated by electroplating processes) have the potential to induce electrical shorts in exposed circuitry. Through this article, the authors describe a particular failure scenario attributed to zinc whiskers that has affected many facilities (including some NASA facilities) that utilized zinc-coated raised "access" floor tiles and support structures. Zinc whiskers that may be growing beneath your raised floor have the potential to wreak havoc on electronic systems operating above the floor.

  19. Variation in plumage, molt, and morphology of the Whiskered Auklet (Aethia pygmaea) in Alaska

    USGS Publications Warehouse

    Pitocchelli, J.; Piatt, J.F.; Carter, H.R.

    2003-01-01

    We studied molt and size variation in Whiskered Auklets collected at sea in August from the Aleutian Islands in 1992 and 1993. We evaluated size differences from external and skeletal measurements. Adults were molting extensively in August, indicating that molt began in July. Primaries 1-5 had been completely replaced, while primaries 6-8 were in various stages of replacement, and primaries 9 and 10 were old in most birds. We also found that juveniles were not molting. This pattern is similar to other species of small auklets where breeding and molt in adults overlap, but juveniles do not molt until the following summer. This suggests that Whiskered Auklets are subjected to similar ecological constraints as other auklets. We provide the first skeletal measurements of Whiskered Auklets and some new external measurements. Results of statistical analyses indicate that there is no sexual dimorphism in adults. A small sample of juveniles suggests that they are similar in size to adults.

  20. Tribological characteristics of silicon carbide whisker-reinforced alumina at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Dellacorte, Christopher

    1991-01-01

    The enhanced fracture toughness of whisker reinforced ceramics makes them attractive candidates for sliding components of advanced hear engines. Examples include piston rings and valve stems for Stirling engines and other low heat rejection devices. However, the tribological behavior of whisker reinforced ceramics is largely unknown. This is especially true for the applications described where use temperatures can vary from below ambient to well over 1000 C. An experimental research program to identify the dominant wear mechanism(s) for a silicon carbide whisker reinforced alumina composite, SiCw-Al2O3 is described. In addition, a wear mechanism model is developed to explain and corroborate the experimental results and to provide insight for material improvement.

  1. Whisker/Cone growth on the thermal control surfaces experiment no. S0069

    NASA Technical Reports Server (NTRS)

    Zwiener, James M.; Coston, James E., Jr.; Miller, Edgar R.; Mell, Richard J.; Wilkes, Donald R.

    1995-01-01

    An unusual surface 'growth' was found during scanning electron microscope (SEM) investigations of the Thermal Control Surface Experiment (TCSE) S0069 front thermal cover. This 'growth' is similar to the cone type whisker growth phenomena as studied by G. K. Wehner beginning in the 1960's. Extensive analysis has identified the most probable composition of the whiskers to be a silicate type glass. Sources of the growth material are outgassing products from the experiment and orbital atomic oxygen, which occurs naturally at the orbital altitudes of the LDEF mission in the form of neutral atomic oxygen. The highly ordered symmetry and directionality of the whiskers are attributed to the long term (5.8 year) stable flight orientation of the LDEF.

  2. Sensory prediction on a whiskered robot: a tactile analogy to "optical flow".

    PubMed

    Schroeder, Christopher L; Hartmann, Mitra J Z

    2012-01-01

    When an animal moves an array of sensors (e.g., the hand, the eye) through the environment, spatial and temporal gradients of sensory data are related by the velocity of the moving sensory array. In vision, the relationship between spatial and temporal brightness gradients is quantified in the "optical flow" equation. In the present work, we suggest an analog to optical flow for the rodent vibrissal (whisker) array, in which the perceptual intensity that "flows" over the array is bending moment. Changes in bending moment are directly related to radial object distance, defined as the distance between the base of a whisker and the point of contact with the object. Using both simulations and a 1×5 array (row) of artificial whiskers, we demonstrate that local object curvature can be estimated based on differences in radial distance across the array. We then develop two algorithms, both based on tactile flow, to predict the future contact points that will be obtained as the whisker array translates along the object. The translation of the robotic whisker array represents the rat's head velocity. The first algorithm uses a calculation of the local object slope, while the second uses a calculation of the local object curvature. Both algorithms successfully predict future contact points for simple surfaces. The algorithm based on curvature was found to more accurately predict future contact points as surfaces became more irregular. We quantify the inter-related effects of whisker spacing and the object's spatial frequencies, and examine the issues that arise in the presence of real-world noise, friction, and slip.

  3. Ultrasharp carbon whisker optical fiber probes for scanning near-field optical microscopy

    NASA Astrophysics Data System (ADS)

    Mensi, Mounir; Mikhailov, Gennadii; Pyatkin, Sergey; Adamcik, Jozef; Sekatskii, Sergey; Dietler, Giovanni

    2010-05-01

    We report the growth of ultrasharp carbon whiskers onto apertured near-field optical glass fiber probes. The ultrasharp carbon whiskers are produced by the electron-assisted dissociation of residual oil vapors present in the vacuum chamber during the electron beam exposition of the tip. This cost effective manufacturing procedure is reproducible, fast and allows controlling the shape of the carbon whisker. The radius of curvature of the whisker apex is approximately 10 nm while its small total length is around 100 nm thus fulfilling the requirements of aperture Scanning Near-Field Optical Microscope (SNOM) probes, i.e. to keep the distance between the sample and the optical aperture during the scanning at subwavelength scale. Furthermore, due to the intrinsic properties of the amorphous carbon whisker, the probes are durable. The carbon whisker optical fiber probes are mounted on tuning-forks using the earlier discussed double-resonant principle. This process ensures a high quality factor of the sensor in the range 2000-5500, which enables to cope with the large stiffness of the tuning-fork actuator and obtain a characteristic noise-limited sensitivity smaller than 10pN necessary to image soft biological samples without destroying them. To illustrate the sensor's performances, transmission near-field optical images of SNOM calibration grating as well as high-resolution state-of-the-art topographic images of single DNA molecules are presented. Prospects of further improvements of the fabrication method enabling to achieve the lighting rod enhancement of the optical near-field (nano-antenna effect) are briefly discussed.

  4. Titania bound sodium titanate ion exchanger

    DOEpatents

    DeFilippi, Irene C. G.; Yates, Stephen Frederic; Shen, Jian-Kun; Gaita, Romulus; Sedath, Robert Henry; Seminara, Gary Joseph; Straszewski, Michael Peter; Anderson, David Joseph

    1999-03-23

    This invention is method for preparing a titania bound ion exchange composition comprising admixing crystalline sodium titanate and a hydrolyzable titanium compound and, thereafter drying the titania bound crystalline sodium titanate and subjecting the dried titania bound ion exchange composition to optional compaction and calcination steps to improve the physical strength of the titania bound composition.

  5. Nitrogen Ocean/Lakes on Early Titan

    NASA Astrophysics Data System (ADS)

    Toon, Owen B.; Tian, F.; McKay, C.; Moore, J. M.; Zahnle, K.; Howard, A. D.

    2010-10-01

    Today Titan's surface temperature is 95 K and its atmosphere contains 1.5 bars of N2. The standard model for Titan is that the current thick atmosphere has been present over the age of the Solar System. However, observations of Titan present some paradoxes for the standard model: the short life time of methane, the lack of good evidence for active cryovolcanism, and the inadequate surface deposit to account for the photochemical products that would have accumulated over 4.5 billion years. Thus alternative models are motivated. Today both surface albedo and greenhouse warming contribute to Titan's surface temperature and its atmosphere condition. The albedo could have been different if the surface of ancient Titan was covered by liquid nitrogen/methane or solid methane ice. The greenhouse effect depends on the existence of atmospheric methane and nitrogen. The variations of either factor could have made ancient Titan similar to present Triton with high surface albedo and little atmosphere. Alternatively early Titan could have had much larger fraction of its nitrogen and methane in liquid phase (ocean/lakes), which would have interesting geological implications. In this work we will explore the effect of changing surface albedo, surface reservoirs of nitrogen and methane, and greenhouse warming on ancient Titan's climate.

  6. Activity and stability studies of titanates and titanate-carbon nanotubes supported Ag anode catalysts for direct methanol fuel cell

    NASA Astrophysics Data System (ADS)

    Mohamed, Mohamed Mokhtar; Khairy, M.; Eid, Salah

    2016-02-01

    Titanate-SWCNT; synthesized via exploiting the interaction between TiO2 anatase with oxygen functionalized SWCNT, supported Ag nanoparticles and Ag/titanate are characterized using XRD, TEM-EDX-SAED, N2 adsorption, Photoluminescence, Raman and FTIR spectroscopy. These samples are tested for methanol electrooxidation via using cyclic voltammetry (CV) and impedance measurements. It is shown that Ag/titanate nanotubes exhibited superior electrocatalytic performance for methanol oxidation (4.2 mA cm-2) than titanate-SWCNT, Ag/titanate-SWCNT and titanate. This study reveals the existence of a strong metal-support interaction in Ag/titanate as explored via formation of Ti-O-Ag bond at 896 cm-1 and increasing surface area and pore volume (103 m2 g-1, 0.21 cm3 g-1) compared to Ag/titanate-SWCNT (71 m2 g-1, 0.175 cm3 g-1) that suffers perturbation and defects following incorporation of SWCNT and Ag. Embedding Ag preferably in SWCNT rather than titanate in Ag/titanate-SWCNT disturbs the electron transfer compared to Ag/titanate. Charge transfer resistance depicted from Nyquist impedance plots is found in the order of titanate > Ag/titanate-SWCNT > titanate-SWCNT > Ag/titanate. Accordingly, Ag/titanate indicates a slower current degradation over time compared to rest of catalysts. Conductivity measurements indicate that it follows the order Ag/titanate > Ag/titanate-SWCNT > titanate > titanate-SWCNT declaring that SWCNT affects seriously the conductivity of Ag(titanate) due to perturbations caused in titanate and sinking of electrons committed by Ago through SWCNT.

  7. Potassium and High Blood Pressure

    MedlinePlus

    ... in blood pressure to certain patterns of food consumption. For example, the D.A.S.H. (Dietary Approaches ... are good natural sources of potassium. Potassium-rich foods include: Sweet ... Levels Mean * ...

  8. Interpretation of Titan's atmospheric composition measured by Cassini-Huygens

    NASA Astrophysics Data System (ADS)

    Tobie, G.; Gautier, D.; Hersant, F.; Lunine, J. I.

    2008-09-01

    released, but as its primordial abundance is small, it remains below the detection limit of the GCMS. The detection of the 40K decay daughter 40Ar is a strong indicator of past and recent internal activities, thus confirming the scenario proposed here. While most of the detected 40Ar comes from the silicate phase, which contains a significant fraction of potassium, we show that only a small fraction of the detected 36Ar can originate from the silicate phase. This strongly suggests that most of the primordial 36Ar has been brought by the ice phase, and that a fraction of argon, even if it is small, has been incorporated at low temperature in the planetesimals that built Titan in the form of clathrate hydrate. This favors the scenario where today's methane mainly originate from the solar nebula, was stored in the interior and later released; and thus was not chemically produced H2O and CO2 in the satellite interior. In situ measurements to be done by a future mission on Titan [4] will permit to test the different ideas present here. In particular, a precise determination of D/H and O16/O18 ratios in H2O, CO2 and CO will provide pertinent tests on the origin of different volatile species. IR spectroscopy and direct sampling of the surface materials will allow to determine the amount of carbon dioxide present in the crust. Detection of 38Ar, Kr and possibly Xe, and estimation of isotopic ratios will also give key informations on the origin and evolution of Titan's atmosphere and interior, in particular on the trapping mechanismes of volatile in Saturn's environnement and on the differentiation processes of Titan's interior. References [1] Niemann, H. B., and 17 colleagues 2005. Nature 438, 779-784. [2] Hersant, F., Gautier, D., Tobie, G., Lunine, J. I. 2008. Planet Space Sci., in press. [3] Tobie, G., Lunine, J. I., Sotin, C. 2006. Nature, 440, 61-64. [4] Coustenis A. and the TANDEM consortium, 2008. Experimental Astron., in press.

  9. Potassium silver cyanide

    Integrated Risk Information System (IRIS)

    Jump to main content . Integrated Risk Information System Recent Additions | Contact Us Search : All EPA IRIS • You are here : EPA Home • Research • Environmental Assessment • IRIS • IRIS Summaries Redirect Page As of September 28 , 2010 , the assessment summary for potassium silver cyanide is inclu

  10. Extensive Hair Shaft Growth after Mouse Whisker Follicle Isolation, Cryopreservation and Transplantation in Nude Mice.

    PubMed

    Cao, Wenluo; Li, Lingna; Tran, Benjamin; Kajiura, Satoshi; Amoh, Yasuyuki; Liu, Fang; Hoffman, Robert M

    2015-01-01

    We previously demonstrated that whole hair follicles could be cryopreserved to maintain their stem-cells differentation potential. In the present study, we demonstrated that cryopreserved mouse whisker hair follicles maintain their hair growth potential. DMSO better cryopreserved mouse whisker follicles compared to glycerol. Cryopreserved hair follicles also maintained the hair follicle-associated-pluripotent (HAP) stem cells, evidenced by P75NTR expression. Subcutaneous transplantation of DMSO-cryopreserved hair follicles in nude mice resulted in extensive hair fiber growth over 8 weeks, indicating the functional recovery of hair shaft growth of cryopreserved hair follicles.

  11. Deduction of aerosol size distribution from particle sampling by whisker collectors

    NASA Astrophysics Data System (ADS)

    Schäfer, H. J.; Pfeifer, H. J.

    1983-12-01

    A method of deducing airborne particle size distributions from the deposition on a collector is described. The method basically consists in collecting submicron-sized particles on whisker filters for subsequent electron-microscopic examination. The empirical size distributions on the collectors can be approximated by log-normal functions. Moreover, it has been found that the variation in particle distribution across a four-stage whisker filter can be interpreted on the basis of a simple model of the collection process. The effective absorption coefficient derived from this modeling is used to correct the empirical data for the effect of a selective collection characteristic.

  12. Geologic, aeromagnetic and mineral resource potential maps of the Whisker Lake Wilderness, Florence County, Wisconsin

    USGS Publications Warehouse

    Schulz, Klaus J.

    1983-01-01

    The mineral resource potential of the Whisker Lake Wilderness in the Nicolet National Forest, Florence County, northeastern Wisconsin, was evaluated in 1982. The bedrock consists of recrystallized and deformed volcanic and sedimentary rocks of Early Proterozoic age. Sand and gravel are the only identified resources in the Whisker Lake Wilderness. However, the area is somewhat isolated from current markets and both commodities are abundant regionally. The wilderness also has low potential for peat in swampy lowlands. The southwestern part of the wilderness has a low to moderate mineral resource potential for stratabound massive-sulfide (copper-zinc-lead) deposits.

  13. Extensive Hair Shaft Growth after Mouse Whisker Follicle Isolation, Cryopreservation and Transplantation in Nude Mice.

    PubMed

    Cao, Wenluo; Li, Lingna; Tran, Benjamin; Kajiura, Satoshi; Amoh, Yasuyuki; Liu, Fang; Hoffman, Robert M

    2015-01-01

    We previously demonstrated that whole hair follicles could be cryopreserved to maintain their stem-cells differentation potential. In the present study, we demonstrated that cryopreserved mouse whisker hair follicles maintain their hair growth potential. DMSO better cryopreserved mouse whisker follicles compared to glycerol. Cryopreserved hair follicles also maintained the hair follicle-associated-pluripotent (HAP) stem cells, evidenced by P75NTR expression. Subcutaneous transplantation of DMSO-cryopreserved hair follicles in nude mice resulted in extensive hair fiber growth over 8 weeks, indicating the functional recovery of hair shaft growth of cryopreserved hair follicles. PMID:26716690

  14. Size and shape of Saturn's moon Titan.

    PubMed

    Zebker, Howard A; Stiles, Bryan; Hensley, Scott; Lorenz, Ralph; Kirk, Randolph L; Lunine, Jonathan

    2009-05-15

    Cassini observations show that Saturn's moon Titan is slightly oblate. A fourth-order spherical harmonic expansion yields north polar, south polar, and mean equatorial radii of 2574.32 +/- 0.05 kilometers (km), 2574.36 +/- 0.03 km, and 2574.91 +/- 0.11 km, respectively; its mean radius is 2574.73 +/- 0.09 km. Titan's shape approximates a hydrostatic, synchronously rotating triaxial ellipsoid but is best fit by such a body orbiting closer to Saturn than Titan presently does. Titan's lack of high relief implies that most--but not all--of the surface features observed with the Cassini imaging subsystem and synthetic aperture radar are uncorrelated with topography and elevation. Titan's depressed polar radii suggest that a constant geopotential hydrocarbon table could explain the confinement of the hydrocarbon lakes to high latitudes.

  15. Interaction of Titan's ionosphere with Saturn's magnetosphere.

    PubMed

    Coates, Andrew J

    2009-02-28

    Titan is the only Moon in the Solar System with a significant permanent atmosphere. Within this nitrogen-methane atmosphere, an ionosphere forms. Titan has no significant magnetic dipole moment, and is usually located inside Saturn's magnetosphere. Atmospheric particles are ionized both by sunlight and by particles from Saturn's magnetosphere, mainly electrons, which reach the top of the atmosphere. So far, the Cassini spacecraft has made over 45 close flybys of Titan, allowing measurements in the ionosphere and the surrounding magnetosphere under different conditions. Here we review how Titan's ionosphere and Saturn's magnetosphere interact, using measurements from Cassini low-energy particle detectors. In particular, we discuss ionization processes and ionospheric photoelectrons, including their effect on ion escape from the ionosphere. We also discuss one of the unexpected discoveries in Titan's ionosphere, the existence of extremely heavy negative ions up to 10000amu at 950km altitude. PMID:19073464

  16. The Lakes and Seas of Titan

    NASA Astrophysics Data System (ADS)

    Hayes, Alexander G.

    2016-06-01

    Analogous to Earth's water cycle, Titan's methane-based hydrologic cycle supports standing bodies of liquid and drives processes that result in common morphologic features including dunes, channels, lakes, and seas. Like lakes on Earth and early Mars, Titan's lakes and seas preserve a record of its climate and surface evolution. Unlike on Earth, the volume of liquid exposed on Titan's surface is only a small fraction of the atmospheric reservoir. The volume and bulk composition of the seas can constrain the age and nature of atmospheric methane, as well as its interaction with surface reservoirs. Similarly, the morphology of lacustrine basins chronicles the history of the polar landscape over multiple temporal and spatial scales. The distribution of trace species, such as noble gases and higher-order hydrocarbons and nitriles, can address Titan's origin and the potential for both prebiotic and biotic processes. Accordingly, Titan's lakes and seas represent a compelling target for exploration.

  17. Size and shape of Saturn's moon Titan

    USGS Publications Warehouse

    Zebker, Howard A.; Stiles, Bryan; Hensley, Scott; Lorenz, Ralph; Kirk, Randolph L.; Lunine, Jonathan

    2009-01-01

    Cassini observations show that Saturn's moon Titan is slightly oblate. A fourth-order spherical harmonic expansion yields north polar, south polar, and mean equatorial radii of 2574.32 ± 0.05 kilometers (km), 2574.36 ± 0.03 km, and 2574.91 ± 0.11 km, respectively; its mean radius is 2574.73 ± 0.09 km. Titan's shape approximates a hydrostatic, synchronously rotating triaxial ellipsoid but is best fit by such a body orbiting closer to Saturn than Titan presently does. Titan's lack of high relief implies that most—but not all—of the surface features observed with the Cassini imaging subsystem and synthetic aperture radar are uncorrelated with topography and elevation. Titan's depressed polar radii suggest that a constant geopotential hydrocarbon table could explain the confinement of the hydrocarbon lakes to high latitudes.

  18. Interaction of Titan's ionosphere with Saturn's magnetosphere.

    PubMed

    Coates, Andrew J

    2009-02-28

    Titan is the only Moon in the Solar System with a significant permanent atmosphere. Within this nitrogen-methane atmosphere, an ionosphere forms. Titan has no significant magnetic dipole moment, and is usually located inside Saturn's magnetosphere. Atmospheric particles are ionized both by sunlight and by particles from Saturn's magnetosphere, mainly electrons, which reach the top of the atmosphere. So far, the Cassini spacecraft has made over 45 close flybys of Titan, allowing measurements in the ionosphere and the surrounding magnetosphere under different conditions. Here we review how Titan's ionosphere and Saturn's magnetosphere interact, using measurements from Cassini low-energy particle detectors. In particular, we discuss ionization processes and ionospheric photoelectrons, including their effect on ion escape from the ionosphere. We also discuss one of the unexpected discoveries in Titan's ionosphere, the existence of extremely heavy negative ions up to 10000amu at 950km altitude.

  19. Titan as the Abode of Life.

    PubMed

    McKay, Christopher P

    2016-01-01

    Titan is the only world we know, other than Earth, that has a liquid on its surface. It also has a thick atmosphere composed of nitrogen and methane with a thick organic haze. There are lakes, rain, and clouds of methane and ethane. Here, we address the question of carbon-based life living in Titan liquids. Photochemically produced organics, particularly acetylene, in Titan's atmosphere could be a source of biological energy when reacted with atmospheric hydrogen. Light levels on the surface of Titan are more than adequate for photosynthesis, but the biochemical limitations due to the few elements available in the environment may lead only to simple ecosystems that only consume atmospheric nutrients. Life on Titan may make use of the trace metals and other inorganic elements produced by meteorites as they ablate in its atmosphere. It is conceivable that H₂O molecules on Titan could be used in a biochemistry that is rooted in hydrogen bonds in a way that metals are used in enzymes by life on Earth. Previous theoretical work has shown possible membrane structures, azotosomes, in Titan liquids, azotosomes, composed of small organic nitrogen compounds, such as acrylonitrile. The search for a plausible information molecule for life in Titan liquids remains an open research topic-polyethers have been considered and shown to be insoluble at Titan temperatures. Possible search strategies for life on Titan include looking for unusual concentrations of certain molecules reflecting biological selection. Homochirality is a special and powerful example of such biology selection. Environmentally, a depletion of hydrogen in the lower atmosphere may be a sign of metabolism. A discovery of life in liquid methane and ethane would be our first compelling indication that the universe is full of diverse and wondrous life forms. PMID:26848689

  20. Titan as the Abode of Life.

    PubMed

    McKay, Christopher P

    2016-01-01

    Titan is the only world we know, other than Earth, that has a liquid on its surface. It also has a thick atmosphere composed of nitrogen and methane with a thick organic haze. There are lakes, rain, and clouds of methane and ethane. Here, we address the question of carbon-based life living in Titan liquids. Photochemically produced organics, particularly acetylene, in Titan's atmosphere could be a source of biological energy when reacted with atmospheric hydrogen. Light levels on the surface of Titan are more than adequate for photosynthesis, but the biochemical limitations due to the few elements available in the environment may lead only to simple ecosystems that only consume atmospheric nutrients. Life on Titan may make use of the trace metals and other inorganic elements produced by meteorites as they ablate in its atmosphere. It is conceivable that H₂O molecules on Titan could be used in a biochemistry that is rooted in hydrogen bonds in a way that metals are used in enzymes by life on Earth. Previous theoretical work has shown possible membrane structures, azotosomes, in Titan liquids, azotosomes, composed of small organic nitrogen compounds, such as acrylonitrile. The search for a plausible information molecule for life in Titan liquids remains an open research topic-polyethers have been considered and shown to be insoluble at Titan temperatures. Possible search strategies for life on Titan include looking for unusual concentrations of certain molecules reflecting biological selection. Homochirality is a special and powerful example of such biology selection. Environmentally, a depletion of hydrogen in the lower atmosphere may be a sign of metabolism. A discovery of life in liquid methane and ethane would be our first compelling indication that the universe is full of diverse and wondrous life forms.

  1. Titan Orbiter with Aerorover Mission (TOAM)

    NASA Technical Reports Server (NTRS)

    Sittler, E. C., Jr.; Cooper, J. F.; Mahaffy, P.; Esper, J.; Fairbrother, D.; Farley, R.; Pitman, J.; Kojiro, D. R.; Acuna, M.; Allen, M.; Bjoraker, G.; Brasunas, J.; Farrell, W.; Burchell, M. J.; Burger, M.; Chin, G.; Coates, A. J.; Farrell, W.; Flasar, M.; Gerlach, B.; Gorevan, S.; Hartle, R. E.; Im, Eastwood; Jennings, D.; Johnson, R. E.

    2007-01-01

    We propose to develop a new mission to Titan called Titan Orbiter with Aerorover Mission (TOAM). This mission is motivated by the recent discoveries of Titan, its atmosphere and its surface by the Huygens Probe, and a combination of in situ, remote sensing and radar mapping measurements of Titan by the Cassini orbiter. Titan is a body for which Astrobiology (i.e., prebiotic chemistry) will be the primary science goal of any future missions to it. TOAM is planned to use an orbiter and balloon technology (i.e., aerorover). Aerobraking will be used to put payload into orbit around Titan. One could also use aerobraking to put spacecraft into orbit around Saturn first for an Enceladus phase of the mission and then later use aerocapture to put spacecraft into orbit around Titan. The Aerorover will probably use a hot air balloon concept using the waste heat from the MMRTG approx. 1000 watts. Orbiter support for the Aerorover is unique to our approach for Titan. Our strategy to use an orbiter is contrary to some studies using just a single probe with balloon. Autonomous operation and navigation of the Aerorover around Titan will be required, which will include descent near to the surface to collect surface samples for analysis (i.e., touch and go technique). The orbiter can provide both relay station and GPS roles for the Aerorover. The Aerorover will have all the instruments needed to sample Titan's atmosphere, surface, possible methane lakes-rivers, use multi-spectral imagers for surface reconnaissance; to take close up surface images; take core samples and deploy seismometers during landing phase. Both active and passive broadband remote sensing techniques will be used for surface topography, winds and composition measurements.

  2. Titan as the Abode of Life

    NASA Technical Reports Server (NTRS)

    Mckay, Christopher P.

    2016-01-01

    Titan is the only world we know other than Earth that has a liquid on its surface. It has a thick atmosphere composed of nitrogen and methane with a thick organic haze. There are lakes, rain, and clouds of methane and ethane. Here, we address the question of carbon-based life living in Titan liquids. Photochemically produced organics, particularly acetylene, in Titan's atmosphere could be a source of biological energy when reacted with atmospheric hydrogen. Light levels on the surface of Titan are more than adequate for photosynthesis but the biochemical limitations due to the few elements available in the environment may lead only to simple ecosystems that only consume atmospheric nutrients. Life on Titan may make use of the trace metals and other inorganic elements produced by meteorites as they ablate in the atmosphere. It is conceivable that H2O molecules on Titan could be used in a biochemistry that is rooted in hydrogen bonds in a way that metals are used in enzymes by life on Earth. Previous theoretical work has shown possible membrane structures in Titan liquids, azotosomes, composed of small organic nitrogen compounds, such as acrylonitrile. The search for a plausible information molecule for life in Titan liquids remains an open research topic - polyethers have been considered and shown to be insoluble at Titan temperatures. Possible search strategies for life on Titan include looking for unusual concentrations of certain molecules reflecting biological selection. Homochirality is a special and powerful example of such biology selection. Environmentally, a depletion of hydrogen in the lower atmosphere may be a sign of metabolism. A discovery of life in liquid methane and ethane would be our first compelling indication that the Universe is full of diverse and wondrous life forms.

  3. Processing science of barium titanate

    NASA Astrophysics Data System (ADS)

    Aygun, Seymen Murat

    Barium titanate and barium strontium titanate thin films were deposited on base metal foils via chemical solution deposition and radio frequency magnetron sputtering. The films were processed at elevated temperatures for densification and crystallization. Two unifying research goals underpin all experiments: (1) To improve our fundamental understanding of complex oxide processing science, and (2) to translate those improvements into materials with superior structural and electrical properties. The relationships linking dielectric response, grain size, and thermal budget for sputtered barium strontium titanate were illustrated. (Ba 0.6Sr0.4)TiO3 films were sputtered on nickel foils at temperatures ranging between 100-400°C. After the top electrode deposition, the films were co-fired at 900°C for densification and crystallization. The dielectric properties were observed to improve with increasing sputter temperature reaching a permittivity of 1800, a tunability of 10:1, and a loss tangent of less than 0.015 for the sample sputtered at 400°C. The data can be understood using a brick wall model incorporating a high permittivity grain interior with low permittivity grain boundary. However, this high permittivity value was achieved at a grain size of 80 nm, which is typically associated with strong suppression of the dielectric response. These results clearly show that conventional models that parameterize permittivity with crystal diameter or film thickness alone are insufficiently sophisticated. Better models are needed that incorporate the influence of microstructure and crystal structure. This thesis next explores the ability to tune microstructure and properties of chemically solution deposited BaTiO3 thin films by modulation of heat treatment thermal profiles and firing atmosphere composition. Barium titanate films were deposited on copper foils using hybrid-chelate chemistries. An in-situ gas analysis process was developed to probe the organic removal and the

  4. Spectral Characteristics of Titan's Surface

    NASA Astrophysics Data System (ADS)

    Griffith, Caitlin A.; Turner, Jake D.; Penteado, Paulo; Khamsi, Tymon B.; Soderblom, Jason M.

    2014-11-01

    Cassini/Huygens and ground-based measurements of Titan reveal an eroded surface, with lakes, dunes, and sinuous washes. These features, coupled with measurements of clouds and rain, indicate the transfer of methane between Titan’s surface and atmosphere. The presence of methane-damp lowlands suggests further that the atmospheric methane (which is continually depleted through photolysis) may be supplied by sub-surface reservoirs. The byproducts of methane photolysis condense onto the surface, leaving layers of organic sediments that record Titan’s past atmospheres.Thus knowledge of the source and history of Titan's atmosphere requires measurements of the large scale compositional makeup of Titan's surface, which is shrouded by a thick and hazy atmosphere. Towards this goal, we analyzed roughly 100,000 spectra recorded by Cassini’s Visual and Infrared Mapping Spectrometer (VIMS). Our study is confined to the latitude region (20S—20N) surrounding the landing site of the Huygens probe (at 10S, 192W), which supplied only measurement of the vertical profiles of the methane abundance and haze scattering characteristics. VIMS near-IR spectral images indicate subtle latitudinal and temporal variations in the haze characteristics in the tropics. We constrain these small changes with full radiative transfer analyses of each of the thousands of VIMS spectra, which were recorded of different terrains and at different lighting conditions. The resulting models of Titan’s atmosphere as a function of latitude and year indicate the seasonal migration of Titan’s tropical haze and enable the derivation of Titan’s surface albedo at 8 near-IR wavelength regions where Titan’s atmosphere is transparent enough to allow visibility to the surface. The resultant maps of Titan’s surface indicate a number of terrain types with distinct spectral characteristics that are suggestive of atmospheric and surficial processes, including the deposition of organic material, erosion of

  5. The energetics of Titan's ionosphere

    NASA Astrophysics Data System (ADS)

    Roboz, A.; Nagy, A. F.

    1994-02-01

    We have developed a comprehensive model to study the dynamics and energetics of the ionosphere of Titan. We solved the one-dimensional, time-dependent, coupled continuity and momentum equations for several ion species, together with single ion and electron energy equations, in order to calculate density, velocity, and temperature profiles. Calculations were carried out for several cases corresponding to different local times and configurations of the Titan-Saturn system. In our model the effects of horizontal magnetic fields were assumed to be negligible, except for their effect on reducing the electron and ion thermal conductivities and inhibiting vertical transport in the subram region. The ionospheric density peak was found to be at an altitude of about 1100 km, in accordance with earlier model calculations. The ionosphere is chemically controlled below an altitude of about 1500 km. Above this level, ion densities differ significantly from their chemical equilibrium values due to strong upward ion velocities. Heat is deposited in a narrow region around the ionospheric peak, resulting in temperature profiles increasing sharply and reaching nearly constant values of 800-1000 deg K for electrons and 300 deg K for ions in the topside, assuming conditions appropriate for the wake region. In the subram region magnetic correction factors make the electron heat conductivities negligible, resulting in electron temperatures increasing strongly with altitude and reaching values in the order of 5000 deg K at our upper boundary located at 2200 km. Ion chemical heating is found to play an important role in shaping the ion energy balance in Titan's ionosphere.

  6. Hydrogen diffusion in lead zirconate titanate and barium titanate

    NASA Astrophysics Data System (ADS)

    Alvine, K. J.; Vijayakumar, M.; Bowden, M. E.; Schemer-Kohrn, A. L.; Pitman, S. G.

    2012-08-01

    Hydrogen is a potential clean-burning, next-generation fuel for vehicle and stationary power. Unfortunately, hydrogen is also well known to have serious materials compatibility issues in metals, polymers, and ceramics. Piezoelectric actuator materials proposed for low-cost, high efficiency high-pressure hydrogen internal combustion engines (HICE) are known to degrade rapidly in hydrogen. This limits their potential use and poses challenges for HICE. Hydrogen-induced degradation of piezoelectrics is also an issue for low-pressure hydrogen passivation in ferroelectric random access memory. Currently, there is a lack of data in the literature on hydrogen species diffusion in piezoelectrics in the temperature range appropriate for the HICE as charged via a gaseous route. We present 1HNMR quantification of the local hydrogen species diffusion within lead zirconate titanate and barium titanate on samples charged by exposure to high-pressure gaseous hydrogen ˜32 MPa. Results are discussed in context of theoretically predicted interstitial hydrogen lattice sites and aqueous charging experiments from existing literature.

  7. Hydrogen diffusion in lead zirconate titanate and barium titanate

    SciTech Connect

    Alvine, K. J.; Vijayakumar, M.; Bowden, M. E.; Schemer-Kohrn, A. L.; Pitman, S. G.

    2012-08-28

    Hydrogen is a potential clean-burning, next-generation fuel for vehicle and stationary power. Unfortunately, hydrogen is also well known to have serious materials compatibility issues in metals, polymers, and ceramics. Piezoelectric actuator materials proposed for low-cost, high efficiency high-pressure hydrogen internal combustion engines (HICE) are known to degrade rapidly in hydrogen. This limits their potential use and poses challenges for HICE. Hydrogen-induced degradation of piezoelectrics is also an issue for low-pressure hydrogen passivation in ferroelectric random access memory. Currently, there is a lack of data in the literature on hydrogen species diffusion in piezoelectrics in the temperature range appropriate for the HICE as charged via a gaseous route. We present 1HNMR quantification of the local hydrogen species diffusion within lead zirconate titanate and barium titanate on samples charged by exposure to high-pressure gaseous hydrogen ~32 MPa. We discuss results in the context of theoretically predicted interstitial hydrogen lattice sites and aqueous charging experiments from existing literature.

  8. Aerosol growth in Titan's ionosphere.

    PubMed

    Lavvas, Panayotis; Yelle, Roger V; Koskinen, Tommi; Bazin, Axel; Vuitton, Véronique; Vigren, Erik; Galand, Marina; Wellbrock, Anne; Coates, Andrew J; Wahlund, Jan-Erik; Crary, Frank J; Snowden, Darci

    2013-02-19

    Photochemically produced aerosols are common among the atmospheres of our solar system and beyond. Observations and models have shown that photochemical aerosols have direct consequences on atmospheric properties as well as important astrobiological ramifications, but the mechanisms involved in their formation remain unclear. Here we show that the formation of aerosols in Titan's upper atmosphere is directly related to ion processes, and we provide a complete interpretation of observed mass spectra by the Cassini instruments from small to large masses. Because all planetary atmospheres possess ionospheres, we anticipate that the mechanisms identified here will be efficient in other environments as well, modulated by the chemical complexity of each atmosphere. PMID:23382231

  9. Fractal aggregates in Titan's atmosphere

    NASA Astrophysics Data System (ADS)

    Cabane, M.; Rannou, P.; Chassefiere, E.; Israel, G.

    1993-04-01

    The cluster structure of Titan's atmosphere was modeled by using an Eulerian microphysical model with the specific formulation of microphysical laws applying to fractal particles. The growth of aggregates in the settling phase was treated by introducing the fractal dimension as a parameter of the model. The model was used to obtain a vertical distribution of size and number density of the aggregates for different production altitudes. Results confirm previous estimates of the formation altitude of photochemical aerosols. The vertical profile of the effective radius of aggregates was calculated as a function of the visible optical depth.

  10. Condensation in Titan's lower atmosphere

    NASA Astrophysics Data System (ADS)

    Lavvas, P.; Griffith, C. A.; Yelle, R. V.

    2011-10-01

    We present a self-consistent description of Titan's aerosols-clouds-gases system and compare our results with the optical properties retrieved from measurements made by the Descent Imager / Spectral Radiometer (DISR) experiment on the Huygens probe [4]. Our calculations include the condensation of methane, ethane and hydrogen cyanide on photochemical aerosols produced in the thermosphere. Our results suggest that the two distinct extinction layers observed by DISR below 80 km are produced by HCN and methane condensation, respectively, while for the Huygens' equatorial conditions simulated here, the contribution of ethane clouds to the total opacity is negligible

  11. This is Commercial Titan, Inc

    NASA Astrophysics Data System (ADS)

    van Rensselaer, F. L.; Slovikoski, R. D.; Abels, T. C.

    1989-10-01

    Out of a quarter-century heritage of eminently successful expendable launch vehicle history with the U.S government, a commercial launch services enterprise which challenges the corporation as well as the competition has been launched within the Martin Marietta Corporation. This paper is an inside look at the philosophy, structure, and success of the new subsidiary, Commercial Titan, Inc., which is taking on its U.S. and foreign rocket-making competitors to win a share of the international communication satellite market as well as the U.S. government commercial launch services market.

  12. Adsorption and Photocatalytic Degradation of Methylene Blue Using Potassium Polytitanate and Solar Simulator.

    PubMed

    Shahid, Mohammad; El Saliby, Ibrahim; McDonagh, Andrew; Chekli, Laura; Tijing, Leonard D; Kim, Jong-Ho; Shon, Ho Kyong

    2016-05-01

    Solar photocatalytic degradation of organic water pollutants can be used to degrade toxic organic pollutants in water. In this study, potassium titanate nanofibres were synthesized by an aqueous peroxide route at high pH and examined as photocatalysts for photodegradation of methylene blue (MB) using a solar simulator. Initially, MB was adsorbed on the surface of potassium polytitanates to achieve adsorption equilibrium before the photocatalysts were illuminated using solar simulator. The results showed that potassium polytitanate nanofibres were effective adsorbents of MB and also facilitated its photocatalytic degradation. Sulphate ion evolution during photocatalysis confirmed that some mineralisation occurred and hence photo-oxidative degradation of MB took place. The optimum operational conditions for the photocatalytic degradation of MB were found at 0.05 g/L of photocatalyst load, 10 mg/L MB and pH 7. The stability and regeneration of the photocatalyst specimen was also studied for 3 degradation cycles using adsorption/photocatalysis model. Morphological structure analysis of potassium titanate showed nanocrystallines structure of longitudinally-oriented isolated fibre with a length up to several micrometres with diameters ranging from 10 to 20 nanometres.

  13. Adsorption and Photocatalytic Degradation of Methylene Blue Using Potassium Polytitanate and Solar Simulator.

    PubMed

    Shahid, Mohammad; El Saliby, Ibrahim; McDonagh, Andrew; Chekli, Laura; Tijing, Leonard D; Kim, Jong-Ho; Shon, Ho Kyong

    2016-05-01

    Solar photocatalytic degradation of organic water pollutants can be used to degrade toxic organic pollutants in water. In this study, potassium titanate nanofibres were synthesized by an aqueous peroxide route at high pH and examined as photocatalysts for photodegradation of methylene blue (MB) using a solar simulator. Initially, MB was adsorbed on the surface of potassium polytitanates to achieve adsorption equilibrium before the photocatalysts were illuminated using solar simulator. The results showed that potassium polytitanate nanofibres were effective adsorbents of MB and also facilitated its photocatalytic degradation. Sulphate ion evolution during photocatalysis confirmed that some mineralisation occurred and hence photo-oxidative degradation of MB took place. The optimum operational conditions for the photocatalytic degradation of MB were found at 0.05 g/L of photocatalyst load, 10 mg/L MB and pH 7. The stability and regeneration of the photocatalyst specimen was also studied for 3 degradation cycles using adsorption/photocatalysis model. Morphological structure analysis of potassium titanate showed nanocrystallines structure of longitudinally-oriented isolated fibre with a length up to several micrometres with diameters ranging from 10 to 20 nanometres. PMID:27483755

  14. Titan - a New Laboratory for Oceanography

    NASA Astrophysics Data System (ADS)

    Lorenz, R. D.

    2001-12-01

    Saturn's giant moon Titan has a thick (1.5 bar) nitrogen atmosphere, and quite probably large expanses of liquid hydrocarbons on its surface. The physical processes in these lakes and seas will open new vistas on oceanography and limnology. Although the Voyager-era paradigm of a deep, global ocean is ruled out by radar and infrared data showing that at least part of Titan's surface is icy, the photochemical arguments that originally led to the proposal of hydrocarbon oceans still apply. Even if the methane in the atmosphere is being resupplied by delivery from the interior, the ethane produced by photolysis would still accumulate to form large deposits on the surface. The near-infrared maps of Titan's surface from the Hubble Space Telescope and groundbased adaptive optics consistently show a number of dark (in fact, pitch-black!) regions that are strong candidates for hydrocarbon seas. These could be up to some 500km in extent. Titan promises to be a new laboratory for oceanography. Like in meteorology, many ocean processes are better parameterized than they are understood, and thus the different physical circumstances on Titan may shed new light on them. Titan has a lower gravity and its ocean fluids are of lower density, perhaps of lower viscosity (depending on solutes and suspended material) and probably rather more likely to cavitate. The ratio of atmospheric density to ocean density is much larger on Titan than on Earth, suggesting that liquid motions will be well-coupled to surface winds (although the distance from the sun is such that the energy in such winds is likely to be low.) Titan is also subject to strong tidal forces (the equilibrium tide due to Saturn's gravity is some 400x larger than that of the moon on Earth.) Although the 100m tidal bulge stays almost fixed because Titan rotates synchronously, the eccentricity of Titan's orbit leads to significant libration and variation in the tidal strength. The 500km seas allowed by the IR data may yet have a

  15. The mechanical behavior dependence on the TiB whisker realignment during hot-working in titanium matrix composites

    PubMed Central

    Ma, Fengcang; Liu, Ping; Li, Wei; Liu, Xinkuan; Chen, Xiaohong; Zhang, Ke; Pan, Deng; Lu, Weijie

    2016-01-01

    Low-cost TiB whiskers reinforced titanium matrix composite (TMCs) was fabricated with enhanced mechanical performances using in situ technologies and hot working. Morphologies observation indicates that needle-like TiB whiskers with a hexagonal transverse section grow along the [010] direction due to B27 crystal structure and its growth mechanism. Mechanical properties tests show that the mechanical behavior of the TiB whiskers reinforced TMCs is dependent on the deformation amplitudes applied in hot-working. The improvement in yield strength by hot-working is attributed to the TiB whiskers realignment and the refinement of microstructure. Models are constructed to evaluate the realignment of TiB whisker during deformation and the increase in yield strength of the composite at elevated temperatures. These models clarify the alignment effect of TiB whiskers under various deformation amplitudes applied in hot-workings and reveals the yield strength dependence on TiB whiskers orientation. PMID:27782201

  16. Transient clouds in Titan's lower atmosphere.

    PubMed

    Griffith, C A; Owen, T; Miller, G A; Geballe, T

    1998-10-01

    The 1980 encounter by the Voyager 1 spacecraft with Titan, Saturn's largest moon, revealed the presence of a thick atmosphere containing nitrogen and methane (1.4 and approximately 0.05 bar, respectively). Methane was found to be nearly saturated at Titan's tropopause, which, with other considerations, led to the hypothesis that Titan might experience a methane analogue of Earth's vigorous hydrological cycle, with clouds, rain and seas. Yet recent analyses of Voyager data indicate large areas of super-saturated methane, more indicative of dry and stagnant conditions. A resolution to this apparent contradiction requires observations of Titan's lower atmosphere, which was hidden from the Voyager cameras by the photochemical haze (or smog) in Titan's stratosphere. Here we report near-infrared spectroscopic observations of Titan within four narrow spectral windows where the moon's atmosphere is ostensibly transparent. We detect pronounced flux enhancements that indicate the presence of reflective methane condensation clouds in the troposphere. These clouds occur at a relatively low altitude (15+/-10 km), at low latitudes, and appear to cover approximately 9 per cent of Titan's disk.

  17. Future Missions to Titan and Enceladus.

    NASA Astrophysics Data System (ADS)

    Beauchamp, Patricia; Reh, Kim; Lunine, Jonathan; Coustenis, Athena; John, Elliott; Matson, Dennis L.; Lebreton, Jean-Pierre; Waite, Hunter; Turtle, Elizabeth

    A mission to Titan is a high priority for exploration, as recommended by the 2003 NRC report on New Frontiers in the Solar System (Decadal Survey). As anticipated by the NRC subcommittee, recent Cassini-Huygens discoveries have revolution-ized our understanding of Titan and its potential for harboring "ingredients" necessary for life. These discoveries reveal that Titan has a thick atmosphere that is rich in organics, possibly contains a vast liquid water subsurface ocean and has energy sources to drive chemical evolu-tion. Furthermore, insight into Titan's climate is important in understanding the climates of Earth, Venus and Mars. With these recent discoveries, interest in Titan as the next scientific target in the outer Solar System is strongly reinforced. Cassini's discovery of active geysers on Enceladus adds a second target in the Saturn system for such a mission, one that is synergistic with Titan in understanding planetary evolution and in adding a potential abode in the Saturn system for life. This presentation will provide an overview of the Titan Saturn System Mission (TSSM) concept, a discussion of other potential concepts, and current plans to advance technical readiness. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA.

  18. Cloud Formation In The Troposphere Of Titan

    NASA Astrophysics Data System (ADS)

    Tsai, I.-Chun; Chen, J.; Liang, M.

    2010-10-01

    Methane-nitrogen containing clouds are known to be present in the troposphere of Titan. However, their formation mechanism and chemical properties remain poorly known. One major difficulty is due to the lack of laboratory constraints, resulting in great uncertainties in modeling cloud formation using microphysical models. Recently CH4-N2 clouds are synthesized in lab under conditions similar to that of Titan, providing a crucial constraint for microphysics model. In this study, a detail microphysical model is developed and used to analyze nucleation and condensation processes occurred in the troposphere of Titan. Sensitivity for the most probable unary and binary nucleation pathways and the subsequent condensation growth of particles is performed based on observed chemical and thermodynamic conditions of Titan's atmosphere. The model is first validated using a laboratory simulation. Comparing to laboratory results, our model simulation shows that binary nucleation from CH4 and N2 produces reasonable particle number concentration as in Titan's atmosphere when appropriate accommodation coefficient for vapor condensation is applied. Applying this detailed model to a model Titan atmosphere, clouds can be formed between 10-30 km, depending on the updraft velocity, with particle sizes of 1-10 μm. These results provide not only information of the size and composition of particles in Titan's atmosphere but also help to design laboratory experiments for measuring critical thermodynamic parameters relevant to the particle production mechanisms, as well as for interpreting observations.

  19. Chemical investigation of Titan and Triton tholins

    NASA Technical Reports Server (NTRS)

    Mcdonald, Gene D.; Thompson, W. R.; Heinrich, Michael; Khare, Bishun N.; Sagan, Carl

    1994-01-01

    We report chromatographic and spectroscopic analyses of both Titan and Triton tholins, organic solids made from the plasma irradiation of 0.9:0.1 and 0.999:0.001 N2/CH4 gas mixtures, respectively. The lower CH4 mixing ratio leads to a nitrogen-richer tholin (N/C greater than 1), probably including nitrogen heterocyclic compounds. Unlike Titan tholin, bulk Triton tholin is poor in nitriles. From high-pressure liquid chromatography, ultraviolet and infrared spectroscopy, and molecular weight estimation by gel filtration chromatography, we conclude that (1) several H2O-soluble fractions, each with distinct UV and IR spectral signatures, are present, (2) these fractions are not identical in the two tholins, (3) the H2O-soluble fractions of Titan tholins do not contain significant amounts of nitriles, despite the major role of nitriles in bulk Titan tholin, and (4) the H2O-soluble fractions of both tholins are mainly molcules containing about 10 to 50 (C + N) atoms. We report yields of amino acids upon hydrolysis of Titan and Triton tholins. Titan tholin is largely insoluble in the putative hydrocarbon lakes or oceans on Titan, but can yield the H2O-soluble species investigated here upon contact with transient (e.g., impact-generated) liquid water.

  20. Neutral Chemistry in Titan's Ionospheric Simulated Conditions

    NASA Astrophysics Data System (ADS)

    Dubois, David; Carrasco, Nathalie; Petrucciani, Marie; Tigrine, Sarah; Vettier, Ludovic

    2016-10-01

    Titan's atmospheric gas phase chemistry leading to the formation of organic aerosols can be simulated in laboratory experiments. Typically, plasma reactors can be used to achieve Titan-like conditions. Such a discharge induces dissociation and ionization processes to the N2-CH4 mixture by electron impact. This faithfully reproduces the electron energy range of magnetospheric electrons entering Titan's atmosphere and can also approximate the solar UV input at Titan's ionosphere. In this context, it is deemed necessary to apply and exploit such a technique in order to better understand the chemical reactivity occurring in Titan-like conditions.In the present work, we use the PAMPRE cold dusty plasma experiment with an N2-CH4 gaseous mixture under controlled pressure and gas influx, hence, emphasizing on the gas phase which we know is key to the formation of aerosols on Titan. Besides, an internal cryogenic trap has been developed to accumulate the gas products during their formation and facilitate their detection. These products are identified and quantified by in situ mass spectroscopy and Fourier-Transform Infrared Spectroscopy. We present here results from this experiment in two experimental conditions: 90-10% and 99-1% N2-CH4 mixing ratios respectively. We use a quantitative approach on nitriles and polycyclic aromatic hydrocarbons.Key organic compounds reacting with each other are thus detected and quantified in order to better follow the chemistry occuring in the gas phase of Titan-like conditions. Indeed, these species acting as precursors to the solid phase are assumed to be relevant in the formation of Titan's organic aerosols. These organic aerosols are what make up Titan's hazy atmosphere.

  1. Titan as the Abode of Life

    PubMed Central

    McKay, Christopher P.

    2016-01-01

    Titan is the only world we know, other than Earth, that has a liquid on its surface. It also has a thick atmosphere composed of nitrogen and methane with a thick organic haze. There are lakes, rain, and clouds of methane and ethane. Here, we address the question of carbon-based life living in Titan liquids. Photochemically produced organics, particularly acetylene, in Titan’s atmosphere could be a source of biological energy when reacted with atmospheric hydrogen. Light levels on the surface of Titan are more than adequate for photosynthesis, but the biochemical limitations due to the few elements available in the environment may lead only to simple ecosystems that only consume atmospheric nutrients. Life on Titan may make use of the trace metals and other inorganic elements produced by meteorites as they ablate in its atmosphere. It is conceivable that H2O molecules on Titan could be used in a biochemistry that is rooted in hydrogen bonds in a way that metals are used in enzymes by life on Earth. Previous theoretical work has shown possible membrane structures, azotosomes, in Titan liquids, azotosomes, composed of small organic nitrogen compounds, such as acrylonitrile. The search for a plausible information molecule for life in Titan liquids remains an open research topic—polyethers have been considered and shown to be insoluble at Titan temperatures. Possible search strategies for life on Titan include looking for unusual concentrations of certain molecules reflecting biological selection. Homochirality is a special and powerful example of such biology selection. Environmentally, a depletion of hydrogen in the lower atmosphere may be a sign of metabolism. A discovery of life in liquid methane and ethane would be our first compelling indication that the universe is full of diverse and wondrous life forms. PMID:26848689

  2. Acceleration of electrons in Titan's ionosphere

    NASA Astrophysics Data System (ADS)

    Zaitsev, V. V.; Shaposhnikov, V. E.; Khodachenko, M. L.; Rucker, H. O.; Panchenko, M.

    2010-03-01

    A consideration of the acceleration mechanism which supplies the fast electrons to the source of Saturnian kilometric radiation (SKR) and an interpretation of the recently reported observational indications of the influence of Titan on the SKR are presented. The proposed mechanism operates by the effect of the different magnetization of the electrons and ions in Titan's ionosphere which in the course of Titan's motion through the Saturnian magnetic field causes the creation of a charge-separation electric field. This field has a component parallel to the magnetic field and accelerates part of the ionospheric electrons (called “runaway electrons”). The performed estimates show that the mechanism accelerates the runaway electrons up to an energy of ˜5 keV. The power of the acceleration mechanism is sufficient for SKR generation and also for the ultraviolet luminescence of Titan's atmosphere. The weakening of the SKR when Titan passes on the dayside of Saturn is due to a decrease of the magnetic field strength near the dayside magnetopause, when the Moon escapes the Saturnian magnetosphere, as well as due to the break in the magnetic connection between the electron acceleration region on Titan and the SKR sources. The latter prevents the penetration of the accelerated electrons into the radiation generation region. When Titan is on the nightside of Saturn, it enters into shell L˜14, which is stretched owing to the ring current. In this case, the electrons that accelerated in the ionosphere of Titan can reach the nightside SKR sources and activate them and therefore being the reason for the Titan influence on the SKR.

  3. Identification of Acetylene on Titan's Surface

    NASA Astrophysics Data System (ADS)

    Singh, S.; McCord, T. B.; Rodriguez, S.; Combe, J. P.; Cornet, T.; Le Mouelic, S.; Maltagliati, L.; Chevrier, V.; Clark, R. N.

    2015-12-01

    Titan's atmosphere is opaque in the near infrared due to gaseous absorptions, mainly by methane, and scattering by aerosols, except in a few "transparency windows" (e.g., Sotin et al., 2005). Thus, the composition of Titan surface remains difficult to access from space and is still poorly constrained, limited to ethane in the polar lakes (Brown et al., 2008) and a few possible organic molecules on the surface (Clark et al., 2010). Photochemical models suggest that most of the organic compounds formed in the atmosphere are heavy enough to condense and build up at the surface in liquid and solid states over geological timescale (Cordier et al., 2009, 2011). Acetylene (C2H2) is one of the most abundant organic molecules in the atmosphere and thus thought to present on the surface as well. Here we report direct evidence of solid C2H2 on Titan's surface using Cassini Visual and Infrared Mapping Spectrometer (VIMS) data. By comparing VIMS observations and laboratory measurements of solid and liquid C2H2, we identify a specific absorption at 1.55 µm that is widespread over Titan but is particularly strong in the brightest terrains. This surface variability suggests that C2H2 is mobilized by surface processes, such as surface weathering, topography, and dissolution/evaporation. The detection of C2H2 on the surface of Titan opens new paths to understand and constrain Titan's surface activity. Since C2H2 is highly soluble in Titan liquids (Singh et al. 2015), it can easily dissolve in methane/ethane and may play an important role in carving of fluvial channels and existence of karstic lakes at higher latitudes on Titan. These processes imply the existence of a dynamic surface with a continued history of erosion and deposition of C2H2 on Titan.

  4. Two whisker motor areas in the rat cortex: evidence from thalamocortical connections.

    PubMed

    Mohammed, Hisham; Jain, Neeraj

    2014-02-15

    In primates, the motor cortex consists of at least seven different areas, which are involved in movement planning, coordination, initiation, and execution. However, for rats, only the primary motor cortex has been well described. A rostrally located second motor area has been proposed, but its extent, organization, and even definitive existence remain uncertain. Only a rostral forelimb area (RFA) has been definitively described, besides few reports of a rostral hindlimb area. We have previously proposed existence of a second whisker area, which we termed the rostral whisker area (RWA), based on its differential response to intracortical microstimulation compared with the caudal whisker area (CWA) in animals under deep anesthesia (Tandon et al. [2008] Eur J Neurosci 27:228). To establish that RWA is distinct from the caudally contiguous CWA, we determined sources of thalamic inputs to the two proposed whisker areas. Sources of inputs to RFA, caudal forelimb area (CFA), and caudal hindlimb region were determined for comparison. The results show that RWA and CWA can be distinguished based on differences in their thalamic inputs. RWA receives major projections from mediodorsal and ventromedial nuclei, whereas the major projections to CWA are from the ventral anterior, ventrolateral, and posterior nuclei. Moreover, the thalamic nuclei that provide major inputs to RWA are the same as for RFA, and the nuclei projecting to CWA are same as for CFA. The results suggest that rats have a second rostrally located motor area with RWA and RFA as its constituents. PMID:23853077

  5. Microwave absorption behavior of ZnO whisker modified by nanosized Fe3O4 particles.

    PubMed

    Hu, Shuchun; Wu, Guofeng; Huang, Zhenhao; Chen, Xiaolang

    2010-11-01

    Tetra-needle-like ZnO whisker was magnetic modified through in situ synthesis of nanosized Fe3O4 particles on the surface of the whisker, and the microwave absorption behavior of the as-prepared product was investigated in detail. The result of the comparative microwave absorbing experiment showed that the magnetic modified ZnO whisker appeared more superior property of microwave absorption than that of the original ZnO whisker in 2-18 GHz. Further investigation indicated that the microwave absorption behavior of the product was influenced by ferrite content and Fe3O4 particles' distribution in the product. When the ferrite content of the product changed from 2 wt% to 9 wt%, the microwave absorbing ability of the product was increased; then, the microwave absorbing ability of the product decreased with the further increasing of ferrite content from 9 wt% to 16 wt%. The product with uniform distribution of Fe3O4 particles showed better microwave absorption property than that with irregular distribution of Fe3O4 particles, and this result inferred that the biphase interface between ZnO and Fe3O4 contributed to microwave absorption through interface polarization. PMID:21137989

  6. Influence of fabrication on mechanical properties of SiC-whisker-reinforced alumina

    SciTech Connect

    DeArellano-Lopez, A.R.; Dominguez-Rodriguez, A. . Dept. Materia Condensada); Goretta, K.C.; Routbort, J.L. )

    1991-10-01

    Samples of SiC-whisker-reinforced Al{sub 2}O{sub 3} composites obtained from three different sources have been crept in compression at 1400{degrees}C using both constant load (CL) and constant strain rate (CSR). Macroscopic results indicate some difference in behavior due to fabrication. TEM is used to support this hypothesis. 10 refs., 3 figs.

  7. The Transformation of Adaptation Specificity to Whisker Identity from Brainstem to Thalamus.

    PubMed

    Jubran, Muna; Mohar, Boaz; Lampl, Ilan

    2016-01-01

    Stimulus specific adaptation has been studied extensively in different modalities. High specificity implies that deviant stimulus induces a stronger response compared to a common stimulus. The thalamus gates sensory information to the cortex, therefore, the specificity of adaptation in the thalamus must have a great impact on cortical processing of sensory inputs. We studied the specificity of adaptation to whisker identity in the ventral posteromedial nucleus of the thalamus (VPM) in rats using extracellular and intracellular recordings. We found that subsequent to repetitive stimulation that induced strong adaptation, the response to stimulation of the same, or any other responsive whisker was equally adapted, indicating that thalamic adaptation is non-specific. In contrast, adaptation of single units in the upstream brainstem principal trigeminal nucleus (PrV) was significantly more specific. Depolarization of intracellularly recorded VPM cells demonstrated that adaptation is not due to buildup of inhibition. In addition, adaptation increased the probability of observing complete synaptic failures to tactile stimulation. In accordance with short-term synaptic depression models, the evoked synaptic potentials in response to whisker stimulation, subsequent to a response failure, were facilitated. In summary, we show that local short-term synaptic plasticity is involved in the transformation of adaptation in the trigemino-thalamic synapse and that the low specificity of adaptation in the VPM emerges locally rather than cascades from earlier stages. Taken together we suggest that during sustained stimulation, local thalamic mechanisms equally suppress inputs arriving from different whiskers before being gated to the cortex. PMID:27445716

  8. Vortex-Induced Vibration (VIV) Reduction Properties of Seal Whisker-Like Geometries

    NASA Astrophysics Data System (ADS)

    Hans, Hendrik; Miao, Jianmin; Triantafyllou, Michael

    2013-11-01

    Biological studies have shown that harbor seal whiskers are capable of reducing Vortex-Induced Vibrations (VIV). As the whiskers have convoluted geometry, it is necessary to evaluate the parameters that define their VIV reduction properties. Whisker-Like Geometries (WLGs) consisting of all but one feature on the true whisker geometry are designed. Comparison of VIV on these WLGs with VIV on circular and elliptical cylinders at Re = 500 is performed. Three-dimensional simulations of flow past these geometries, which are allowed to freely vibrate in crossflow, are performed with the Implicit Large Eddy Simulation as the turbulence model. The results indicate that the existence of axial undulations is the most dominant feature that affects the VIV reduction. The smallest VIV is observed on WLGs with dual-axial undulations and the largest VIV is observed on the circular cylinder. Variations in the features of the WLGs result in noticeable changes in their VIV. The circular cylinder is observed to response as a steady system while the WLGs with dual-axial undulations are observed to respond as a chaotic system. The response of WLGs with single-axial undulations is found to depend on their detailed features. I would like to acknowledge the support and funding from National Research Foundation (NRF) through CENSAM of Singapore-MIT Alliance for Research and Technology and Nanyang Technological University.

  9. The Transformation of Adaptation Specificity to Whisker Identity from Brainstem to Thalamus

    PubMed Central

    Jubran, Muna; Mohar, Boaz; Lampl, Ilan

    2016-01-01

    Stimulus specific adaptation has been studied extensively in different modalities. High specificity implies that deviant stimulus induces a stronger response compared to a common stimulus. The thalamus gates sensory information to the cortex, therefore, the specificity of adaptation in the thalamus must have a great impact on cortical processing of sensory inputs. We studied the specificity of adaptation to whisker identity in the ventral posteromedial nucleus of the thalamus (VPM) in rats using extracellular and intracellular recordings. We found that subsequent to repetitive stimulation that induced strong adaptation, the response to stimulation of the same, or any other responsive whisker was equally adapted, indicating that thalamic adaptation is non-specific. In contrast, adaptation of single units in the upstream brainstem principal trigeminal nucleus (PrV) was significantly more specific. Depolarization of intracellularly recorded VPM cells demonstrated that adaptation is not due to buildup of inhibition. In addition, adaptation increased the probability of observing complete synaptic failures to tactile stimulation. In accordance with short-term synaptic depression models, the evoked synaptic potentials in response to whisker stimulation, subsequent to a response failure, were facilitated. In summary, we show that local short-term synaptic plasticity is involved in the transformation of adaptation in the trigemino-thalamic synapse and that the low specificity of adaptation in the VPM emerges locally rather than cascades from earlier stages. Taken together we suggest that during sustained stimulation, local thalamic mechanisms equally suppress inputs arriving from different whiskers before being gated to the cortex. PMID:27445716

  10. Rheological behavior of injection-moldable silicon powder-silicon carbide whisker formulations

    SciTech Connect

    Tsao, I.; Danforth, S.C. . Dept. of Ceramic Engineering)

    1993-12-01

    The rheological behavior of injection-moldable formulations for reaction-bonded Si[sub 3]N[sub 4] toughened with silicon carbide whiskers was studied using capillary rheometry. The effects on rheology of the following parameters were examined: solids loading, powder/whisker volume ratio, particle size and type, and binder composition. Two important aspects of the flow behavior were delineated. First, corrections for end effects and slippage along the wall were made in order to interpret the experimental data properly. At high shearing rates slip may account for more than 50% of the total flow. Such slippage promotes flow into the smallest channels for corners of the mold and may appreciably facilitate molding. Consequently the careful study of slippage is an inherent requirement of the rheological characterization of these concentrated suspensions. Second, the suspension viscosities were delineated. An empirical equation for predicting relative viscosity was developed for formulations containing up to [approximately]30 vol% of silicon carbide whiskers. Suspension viscosities generally increased with decreasing particle size and increasing whisker contents. Particle surface roughness appears to affect the shearing behavior. Binders of low molecular weight resulted in higher relative viscosities than higher molecular weight binders, indicating possibly better dispersion of solids when more viscous binders are employed.

  11. Estimating the Probability of Electrical Short Circuits from Tin Whiskers. Part 2

    NASA Technical Reports Server (NTRS)

    Courey, Karim J.; Asfour, Shihab S.; Onar, Arzu; Bayliss, Jon A.; Ludwig, Larry L.; Wright, Maria C.

    2010-01-01

    To comply with lead-free legislation, many manufacturers have converted from tin-lead to pure tin finishes of electronic components. However, pure tin finishes have a greater propensity to grow tin whiskers than tin-lead finishes. Since tin whiskers present an electrical short circuit hazard in electronic components, simulations have been developed to quantify the risk of said short circuits occurring. Existing risk simulations make the assumption that when a free tin whisker has bridged two adjacent exposed electrical conductors, the result is an electrical short circuit. This conservative assumption is made because shorting is a random event that had an unknown probability associated with it. Note however that due to contact resistance electrical shorts may not occur at lower voltage levels. In our first article we developed an empirical probability model for tin whisker shorting. In this paper, we develop a more comprehensive empirical model using a refined experiment with a larger sample size, in which we studied the effect of varying voltage on the breakdown of the contact resistance which leads to a short circuit. From the resulting data we estimated the probability distribution of an electrical short, as a function of voltage. In addition, the unexpected polycrystalline structure seen in the focused ion beam (FIB) cross section in the first experiment was confirmed in this experiment using transmission electron microscopy (TEM). The FIB was also used to cross section two card guides to facilitate the measurement of the grain size of each card guide's tin plating to determine its finish .

  12. Estimating the Probability of Electrical Short Circuits from Tin Whiskers. Part 2

    NASA Technical Reports Server (NTRS)

    Courey, Karim J.; Asfour, Shihab S.; Onar, Arzu; Bayliss, Jon A.; Ludwig, Larry L.; Wright, Maria C.

    2009-01-01

    To comply with lead-free legislation, many manufacturers have converted from tin-lead to pure tin finishes of electronic components. However, pure tin finishes have a greater propensity to grow tin whiskers than tin-lead finishes. Since tin whiskers present an electrical short circuit hazard in electronic components, simulations have been developed to quantify the risk of said short circuits occurring. Existing risk simulations make the assumption that when a free tin whisker has bridged two adjacent exposed electrical conductors, the result is an electrical short circuit. This conservative assumption is made because shorting is a random event that had an unknown probability associated with it. Note however that due to contact resistance electrical shorts may not occur at lower voltage levels. In our first article we developed an empirical probability model for tin whisker shorting. In this paper, we develop a more comprehensive empirical model using a refined experiment with a larger sample size, in which we studied the effect of varying voltage on the breakdown of the contact resistance which leads to a short circuit. From the resulting data we estimated the probability distribution of an electrical short, as a function of voltage.

  13. Properties of thermoplastic starch and TPS/polycaprolactone blend reinforced with sisal whiskers using extrusion processing

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sisal whiskers (SW) were prepared by acid hydrolysis for subsequent evaluation as reinforcing material for biodegradable matrices of thermoplastic starch (TPS) and TPS/polycaprolactone (TPS/PCL) blends. The acid hydrolyzed SW had dimensions of 5±2 nm in diameter and 210±60 nm in length and 78% cryst...

  14. Cortical Dependence of Whisker Responses in Posterior Medial Thalamus In Vivo

    PubMed Central

    Mease, Rebecca A.; Sumser, Anton; Sakmann, Bert; Groh, Alexander

    2016-01-01

    Cortical layer 5B (L5B) thick-tufted pyramidal neurons have reliable responses to whisker stimulation in anesthetized rodents. These cells drive a corticothalamic pathway that evokes spikes in thalamic posterior medial nucleus (POm). While a subset of POm has been shown to integrate both cortical L5B and paralemniscal signals, the majority of POm neurons are suggested to receive driving input from L5B only. Here, we test this possibility by investigating the origin of whisker-evoked responses in POm and specifically the contribution of the L5B-POm pathway. We compare L5B spiking with POm spiking and subthreshold responses to whisker deflections in urethane anesthetized mice. We find that a subset of recorded POm neurons shows early (<50 ms) spike responses and early large EPSPs. In these neurons, the early large EPSPs matched L5B input criteria, were blocked by cortical inhibition, and also interacted with spontaneous Up state coupled large EPSPs. This result supports the view of POm subdivisions, one of which receives whisker signals predominantly via L5B neurons. PMID:27230219

  15. Extremely high-frequency piezoelectroacoustic transducer based on BN-tube/SiC-whiskers rope

    NASA Astrophysics Data System (ADS)

    Pokropivny, V.; Pokropivny, A.; Lohmus, A.; Lohmus, R.; Kovrygin, S.; Sylenko, P.; Partch, R.; Prilutskii, E.

    2007-03-01

    Innovative idea of piezoelectric electroacoustic transducer in extremely high-frequency terahertz range on the basis of BN-tube/SiC-whiskers rope is suggested and substantiated. Unlike an acoustic spectrum of solid rectangular pins and films used so far in ultrasonic pulsers and receivers, in the acoustic spectrum of circular hollow nanotubes, the peculiar squash E2g and the subsequent Eng modes of starlike chain belonging to a gallery of whispering acoustic modes was shown by ab initio RHF/6-31G calculations to exist in the Raman spectra. Inherent important feature of these standing vibrations is their weak attenuation and high frequency, which, as depended on the nanotube diameter, fall in the range of about ∼1 GHz-1 THz. Hypersound was suggested to be excited by resonant microwaves using the piezoelectric properties of BN heteropolar nanotubes and then to transmit it into a sample by high modulus encapsulated SiC-whiskers. Such BN-tube/SiC-whiskers of 100-800 nm in diameter and with ∼20 aspect ratio were synthesized by carbothermal and CVD techniques. Cactus-like arrays of SiC nanowhiskers were synthesized by CVD technique. A sketch of the hypersound generator/detector, with the piezoelectroacoustical transducer on the basis of the BN-tube/SiC-whisker assembly serving as hypersonic antenna, was advanced.

  16. Protocols for Ectopic Hair Growth from Transplanted Whisker Follicles on the Spinal Cord of Mice.

    PubMed

    Cao, Wenluo; Liu, Fang; Amoh, Yasuyuki; Hoffman, Robert M

    2016-01-01

    Isolated whisker follicles from nestin-driven green fluorescent protein (ND-GFP) mice, containing hair-associated pluripotent (HAP) stem cells, were histocultured in three dimensions on Gelfoam(®) for 3 weeks for subsequent transplantation to the spinal cord in order to heal an induced injury with the HAP stem cells. The hair shafts were removed from Gelfoam(®)-histocultured whisker follicles, and the remaining parts of the whisker follicles, containing GFP-nestin-expressing (HAP) stem cells, were transplanted into the injured spinal cord of nude mice, along with the Gelfoam(®). After 90 days, the mice were sacrificed and the spinal cord injuries were observed to have healed. ND-GFP expression was intense at the healed area of the spinal cord, as observed by fluorescence microscopy, demonstrating that the HAP stem cells were involved in healing the spinal cord. The transplanted whisker follicles produced remarkably long hair shafts in the spinal cord over 90 days and curved and enclosed the spinal cord. This result changes our concept of hair growth, demonstrating it is not limited to the skin and that hair growth appears related to HAP stem cells as both increased in tandem on the spinal cord.

  17. Optogenetic Patterning of Whisker-Barrel Cortical System in Transgenic Rat Expressing Channelrhodopsin-2

    PubMed Central

    Yokoyama, Yukinobu; Sumiyoshi, Akira; Shibuya, Yuma; Matsuzaka, Yoshiya; Kawashima, Ryuta; Mushiake, Hajime; Ishizuka, Toru; Yawo, Hiromu

    2014-01-01

    The rodent whisker-barrel system has been an ideal model for studying somatosensory representations in the cortex. However, it remains a challenge to experimentally stimulate whiskers with a given pattern under spatiotemporal precision. Recently the optogenetic manipulation of neuronal activity has made possible the analysis of the neuronal network with precise spatiotemporal resolution. Here we identified the selective expression of channelrhodopsin-2 (ChR2), an algal light-driven cation channel, in the large mechanoreceptive neurons in the trigeminal ganglion (TG) as well as their peripheral nerve endings innervating the whisker follicles of a transgenic rat. The spatiotemporal pattern of whisker irradiation thus produced a barrel-cortical response with a specific spatiotemporal pattern as evidenced by electrophysiological and functional MRI (fMRI) studies. Our methods of generating an optogenetic tactile pattern (OTP) can be expected to facilitate studies on how the spatiotemporal pattern of touch is represented in the somatosensory cortex, as Hubel and Wiesel did in the visual cortex. PMID:24695456

  18. Detecting potassium on Mercury

    NASA Technical Reports Server (NTRS)

    Killen, R. M.; Potter, A. E.; Morgan, T. H.

    1991-01-01

    A critical comment on the work of A.L. Sprague et al. (1990) is presented. It is argued that, in attributing an enhanced emission in the potassium D lines on Oct. 14, 1987 in the equatorial region of Mercury to a diffusion source centered on Caloris Basin, Sprague et al. misinterpreted the data. Sprague et al. present a reply, taking issue with the commenters.

  19. Method of making polymer powders and whiskers as well as particulate products of the method and atomizing apparatus

    DOEpatents

    Otaigbe, Joshua U.; McAvoy, Jon M.; Anderson, Iver E.; Ting, Jason; Mi, Jia; Terpstra, Robert

    2001-01-09

    Method for making polymer particulates, such as spherical powder and whiskers, by melting a polymer material under conditions to avoid thermal degradation of the polymer material, atomizing the melt using gas jet means in a manner to form atomized droplets, and cooling the droplets to form polymer particulates, which are collected for further processing. Atomization parameters can be controlled to produce polymer particulates with controlled particle shape, particle size, and particle size distribution. For example, atomization parameters can be controlled to produce spherical polymer powders, polymer whiskers, and combinations of spherical powders and whiskers. Atomizing apparatus also is provided for atoomizing polymer and metallic materials.

  20. An investigation of the growth of bismuth whiskers and nanowires during physical vapour deposition

    NASA Astrophysics Data System (ADS)

    Stanley, S. A.; Stuttle, C.; Caruana, A. J.; Cropper, M. D.; Walton, A. S. O.

    2012-10-01

    Bismuth thin films of thickness in the region of 500 nm have been prepared by planar magnetron sputtering onto glass, silicon and GaAs substrates. Electron microscopy of these films reveals that bismuth whiskers grow spontaneously when the substrate is heated to temperatures between 110 and 140 °C during deposition and the optimum temperature for such growth is largely independent of substrate. Depositing films under similar conditions using thermal evaporation does not, however, produce the whisker growth. X-ray diffraction has been employed to investigate film texture with temperature and it has been shown that the film crystallites are predominantly [1 1 0] and [1 1 1] oriented. The [1 1 0] orientation of the crystallites dominates at deposition temperatures above 110 °C for sputter deposition and the [1 1 1] at lower temperatures. The optimum temperature for whisker growth coincides with the temperature for the change between predominant orientations. While sputter deposition appears to favour films with crystallite orientation of [1 1 0], thermal evaporation favours [1 1 1] and has a higher change-over temperature. The whiskers that grow from the film emerge at off-normal angles between 43.3° and 69.2° with a mean of 54 ± 3°. The projected length of whiskers on a 500 nm film on a GaAs substrate shows a wide distribution to a maximum of more than 100 µm. The mean projected length for this sample was 16 ± 1 µm and the diameter is around 0.5 µm. Measurements of the electrical properties of the whiskers at room temperature reveals ohmic behaviour with an estimated resistivity of 2.2 ± 0.2 µΩ m. Detailed examination of scanning electron micrographs, eliminates all growth mechanisms except tip growth by a non-catalysed vapour-solid/vapour-liquid-solid method. By depositing thinner films it is shown that this spontaneous growth of whiskers offers a route to fabricate high quality bismuth nanowires of lengths exceeding 10 µm.

  1. Titan's organic chemistry: Results of simulation experiments

    NASA Technical Reports Server (NTRS)

    Sagan, Carl; Thompson, W. Reid; Khare, Bishun N.

    1992-01-01

    Recent low pressure continuous low plasma discharge simulations of the auroral electron driven organic chemistry in Titan's mesosphere are reviewed. These simulations yielded results in good accord with Voyager observations of gas phase organic species. Optical constants of the brownish solid tholins produced in similar experiments are in good accord with Voyager observations of the Titan haze. Titan tholins are rich in prebiotic organic constituents; the Huygens entry probe may shed light on some of the processes that led to the origin of life on Earth.

  2. The greenhouse and antigreenhouse effects on Titan

    NASA Technical Reports Server (NTRS)

    Mckay, Christopher P.; Pollack, James B.; Courtin, Regis

    1991-01-01

    The parallels between the atmospheric thermal structure of the Saturnian satellite Titan and the hypothesized terrestrial greenhouse effect can serve as bases for the evaluation of competing greenhouse theories. Attention is presently drawn to the similarity between the roles of H2 and CH4 on Titan and CO2 and H2O on earth. Titan also has an antigreenhouse effect due to a high-altitude haze layer which absorbs at solar wavelengths, while remaining transparent in the thermal IR; if this haze layer were removed, the antigreenhouse effect would be greatly reduced, exacerbating the greenhouse effect and raising surface temperature by over 20 K.

  3. Mapping products of Titan's surface: Chapter 19

    USGS Publications Warehouse

    Stephan, Katrin; Jaumann, Ralf; Karkoschka, Erich; Kirk, Randolph L.; Barnes, Jason W.; Tomasko, Martin G.; Turtle, Elizabeth P.; Le Corre, Lucille; Langhans, Mirjam; Le Mouélic, Stéphane; Lorenz, Ralph D.; Perry, Jason; Brown, Robert; Lebreton, Jean-Pierre; Waite, J. Hunter

    2010-01-01

    Remote sensing instruments aboard the Cassini spacecraft have been observed the surface of Titan globally in the infrared and radar wavelength ranges as well as locally by the Huygens instruments revealing a wealth of new morphological features indicating a geologically active surface. We present a summary of mapping products of Titan's surface derived from data of the remote sensing instruments onboard the Cassini spacecraft (ISS, VIMS, RADAR) as well as the Huygens probe (DISR) that were achieved during the nominal Cassini mission including an overview of Titan's recent nomenclature.

  4. Planetary science. The weather on Titan.

    PubMed

    Lorenz, R D

    2000-10-20

    When the Voyager 1 spacecraft returned images in 1980, the dense atmosphere of Saturn's moon Titan was assumed to be bland and featureless. As Lorenz discusses in his Perspective, recent ground-based spectroscopy, and images from the Hubble Space Telescope, are changing this perception. Observations such as the short-lived clouds in Titan's atmosphere reported by Griffith et al. suggest that although average precipitation is likely to be low, individual precipitation events may be heavy enough to cause deep valleys on Titan's surface.

  5. Detection of daily clouds on Titan.

    PubMed

    Griffith, C A; Hall, J L; Geballe, T R

    2000-10-20

    We have discovered frequent variations in the near-infrared spectrum of Titan, Saturn's largest moon, which are indicative of the daily presence of sparse clouds covering less than 1% of the area of the satellite. The thermodynamics of Titan's atmosphere and the clouds' altitudes suggest that convection governs their evolutions. Their short lives point to the presence of rain. We propose that Titan's atmosphere resembles Earth's, with clouds, rain, and an active weather cycle, driven by latent heat release from the primary condensible species.

  6. Planetary science. The weather on Titan.

    PubMed

    Lorenz, R D

    2000-10-20

    When the Voyager 1 spacecraft returned images in 1980, the dense atmosphere of Saturn's moon Titan was assumed to be bland and featureless. As Lorenz discusses in his Perspective, recent ground-based spectroscopy, and images from the Hubble Space Telescope, are changing this perception. Observations such as the short-lived clouds in Titan's atmosphere reported by Griffith et al. suggest that although average precipitation is likely to be low, individual precipitation events may be heavy enough to cause deep valleys on Titan's surface. PMID:11183770

  7. Validation of the dynamic recrystallization (DRX) mechanism for whisker and hillock growth on thin films

    SciTech Connect

    Vianco, Paul T.; Neilsen, Michael K.; Rejent, Jerome A.; Grant, Richard P.

    2015-05-01

    Our study was performed to validate a first-principles model for whisker and hillock formation based on the cyclic dynamic recrystallization (DRX) mechanism in conjunction with long-range diffusion. The test specimens were evaporated Sn films on Si having thicknesses of 0.25 μm, 0.50 μm, 1.0 μm, 2.0 μm, and 4.9 μm. Air annealing was performed at 35°C, 60°C, 100°C, 120°C, or 150°C over a time duration of 9 days. The stresses, anelastic strains, and strain rates in the Sn films were predicted by a computational model based upon the constitutive properties of 95.5Sn-3.9Ag-0.6Cu (wt.%) as a surrogate for pure Sn. The cyclic DRX mechanism and, in particular, whether long whiskers or hillocks were formed, was validated by comparing the empirical data against the three hierarchal requirements: (1) DRX to occur at all: εc = A D o m Z n , (2) DRX to be cyclic: D o < 2D r, and (3) Grain boundary pinning (thin films): h versus d. Continuous DRX took place in the 2.0-μm and 4.9-μm films that resulted in short stubby whiskers. Depleted zones, which resulted solely from a tensile stress-driven diffusion mechanism, confirmed the pervasiveness of long-range diffusion so that it did not control whisker or hillock formation other than a small loss of activity by reduced thermal activation at lower temperatures. Furthermore, a first-principles DRX model paves the way to develop like mitigation strategies against long whisker growth.

  8. Whisker motor cortex reorganization after superior colliculus output suppression in adult rats.

    PubMed

    Veronesi, Carlo; Maggiolini, Emma; Franchi, Gianfranco

    2013-10-01

    The effect of unilateral superior colliculus (SC) output suppression on the ipsilateral whisker motor cortex (WMC) was studied at different time points after tetrodotoxin and quinolinic acid injections, in adult rats. The WMC output was assessed by mapping the movement evoked by intracortical microstimulation (ICMS) and by recording the ICMS-evoked electromyographic (EMG) responses from contralateral whisker muscles. At 1 h after SC injections, the WMC showed: (i) a strong decrease in contralateral whisker sites, (ii) a strong increase in ipsilateral whisker sites and in ineffective sites, and (iii) a strong increase in threshold current values. At 6 h after injections, the WMC size had shrunk to 60% of the control value and forelimb representation had expanded into the lateral part of the normal WMC. Thereafter, the size of the WMC recovered, returning to nearly normal 12 h later (94% of control) and persisted unchanged over time (1-3 weeks). The ICMS-evoked EMG response area decreased at 1 h after SC lesion and had recovered its baseline value 12 h later. Conversely, the latency of ICMS-evoked EMG responses had increased by 1 h and continued to increase for as long as 3 weeks following the lesion. These findings provide physiological evidence that SC output suppression persistently withdrew the direct excitatory drive from whisker motoneurons and induced changes in the WMC. We suggest that the changes in the WMC are a form of reversible short-term reorganization that is induced by SC lesion. The persistent latency increase in the ICMS-evoked EMG response suggested that the recovery of basic WMC excitability did not take place with the recovery of normal explorative behaviour. PMID:23895333

  9. Validation of the dynamic recrystallization (DRX) mechanism for whisker and hillock growth on thin films

    DOE PAGES

    Vianco, Paul T.; Neilsen, Michael K.; Rejent, Jerome A.; Grant, Richard P.

    2015-05-01

    Our study was performed to validate a first-principles model for whisker and hillock formation based on the cyclic dynamic recrystallization (DRX) mechanism in conjunction with long-range diffusion. The test specimens were evaporated Sn films on Si having thicknesses of 0.25 μm, 0.50 μm, 1.0 μm, 2.0 μm, and 4.9 μm. Air annealing was performed at 35°C, 60°C, 100°C, 120°C, or 150°C over a time duration of 9 days. The stresses, anelastic strains, and strain rates in the Sn films were predicted by a computational model based upon the constitutive properties of 95.5Sn-3.9Ag-0.6Cu (wt.%) as a surrogate for pure Sn. Themore » cyclic DRX mechanism and, in particular, whether long whiskers or hillocks were formed, was validated by comparing the empirical data against the three hierarchal requirements: (1) DRX to occur at all: εc = A D o m Z n , (2) DRX to be cyclic: D o < 2D r, and (3) Grain boundary pinning (thin films): h versus d. Continuous DRX took place in the 2.0-μm and 4.9-μm films that resulted in short stubby whiskers. Depleted zones, which resulted solely from a tensile stress-driven diffusion mechanism, confirmed the pervasiveness of long-range diffusion so that it did not control whisker or hillock formation other than a small loss of activity by reduced thermal activation at lower temperatures. Furthermore, a first-principles DRX model paves the way to develop like mitigation strategies against long whisker growth.« less

  10. Reversal of an Unconditioned Behavioral Preference for Specific Food Pellets by Intervention of Whisker Sensory Inputs.

    PubMed

    Kim, Hannah; Lee, Yunjin; Kim, Ji-Eun; Han, Pyung-Lim

    2016-04-01

    Adenylyl cyclase type-5 (AC5) is preferentially expressed in the dorsal striatum. Recently, we reported that AC5 knockout (KO) mice preferred food pellets carrying an olfactory cue produced by AC5 KO mice during food consumption (AC5 KO pellets) over food pellets that had been taken by wildtype (WT) mice. In the present study, we demonstrated that whisker trimming on the right side of the face but not the left in AC5 KO mice blocked the behavioral preference for AC5 KO pellets. Conversely, whisker trimming on the right but not the left in WT mice induced a behavioral preference for AC5 KO pellets. Mice lacking D2 dopamine receptor (D2 KO mice) also showed a behavioral preference for AC5 KO pellets. In D2 mice, whisker trimming on the right side of the face but not the left blocked a behavioral preference for AC5 KO food pellets. AC5 KO mice had increased level of phospho-CaMKIIα in the dorsal striatum, and WT mice with whiskers cut on either side also showed increased p-CaMKIIα level in the dorsal striatum. The siRNA-mediated inhibition of CaMKIIα in the dorsal striatum in either the right or the left hemisphere in AC5 KO mice and D2 KO mice blocked the behavioral preference for AC5 KO pellets. However, behavioral changes induced by this inhibition on each side showed asymmetrical time courses. These results suggest that an unconditioned behavioral preference for specific food pellets can be switched on or off based on the balance of states of neural activity in the dorsal striatum regulated by a signaling pathway centered on AC5 and D2 and the sensory inputs of whiskers from the right side of the face.

  11. Behavioral verification of associative learning in whiskers-related fear conditioning in mice.

    PubMed

    Cybulska-Kłosowicz, Anita

    2016-01-01

    Fear-conditioning is one of the most widely used paradigms in attempts to unravel the processes and mechanisms underlying learning and plasticity. In most of the Pavlovian conditioning paradigms auditory stimulus is used as a conditioned stimulus (CS), but conditioning can be accomplished also to tactile CS. The whisker-to-barrel tactile system in mice offers convenient way to investigate the brain pathways and mechanisms of learning, and plasticity of the brain cortex. To support a claim that an animal learns during conditioning session and that the plastic changes are associative in nature, objective measures of behavior are necessary. Multiple types of conditioned responses can develop, depending on the training situation, CS and unconditioned stimulus (UCS) characteristics. These include physiological responses, such as salivation, heart rate, galvanic skin reaction, and also behavioral responses, such as startle reflex potentiation or suppression of the ongoing behavior. When studying learning with the whisker system in behaving mice, stimulation of individual whiskers in a well-controlled manner may require animal restrain with a disadvantage of only limited behavioral responses observed. Stimulation of whiskers in the neck-restraining apparatus evokes head movements. When whiskers stimulation (CS) is paired with an aversive UCS during conditioning, the head movements decrease in the course of the training. This reaction, called minifreezing, resembles freezing response, frequently used behavioral measure, however applicable only in freely moving animals. This article will review experimental evidences confirming that minifreezing is a relevant index of association formation between the neutral CS and the and the aversive UCS. PMID:27373946

  12. Potassium Channelopathies and Gastrointestinal Ulceration

    PubMed Central

    Han, Jaeyong; Lee, Seung Hun; Giebisch, Gerhard; Wang, Tong

    2016-01-01

    Potassium channels and transporters maintain potassium homeostasis and play significant roles in several different biological actions via potassium ion regulation. In previous decades, the key revelations that potassium channels and transporters are involved in the production of gastric acid and the regulation of secretion in the stomach have been recognized. Drugs used to treat peptic ulceration are often potassium transporter inhibitors. It has also been reported that potassium channels are involved in ulcerative colitis. Direct toxicity to the intestines from nonsteroidal anti-inflammatory drugs has been associated with altered potassium channel activities. Several reports have indicated that the long-term use of the antianginal drug Nicorandil, an adenosine triphosphate-sensitive potassium channel opener, increases the chances of ulceration and perforation from the oral to anal regions throughout the gastrointestinal (GI) tract. Several of these drug features provide further insights into the role of potassium channels in the occurrence of ulceration in the GI tract. The purpose of this review is to investigate whether potassium channelopathies are involved in the mechanisms responsible for ulceration that occurs throughout the GI tract. PMID:27784845

  13. Titan's Atmospheric Dynamics and Meteorology

    NASA Technical Reports Server (NTRS)

    Flasar, F. M.; Baines, K. H.; Bird, M. K.; Tokano, T.; West, R. A.

    2008-01-01

    Titan, after Venus, is the second example of an atmosphere with a global cyclostrophic circulation in the solar system, but a circulation that has a strong seasonal modulation in the middle atmosphere. Direct measurement of Titan's winds, particularly observations tracking the Huygens probe at 10degS, indicate that the zonal winds are generally in the sense of the satellites rotation. They become cyclostrophic approx. 35 km above the surface and generally increase with altitude, with the exception of a sharp minimum centered near 75 km, where the wind velocity decreases to nearly zero. Zonal winds derived from the temperature field retrieved from Cassini measurements, using the thermal wind equation, indicate a strong winter circumpolar vortex, with maximum winds at mid northern latitudes of 190 ms-' near 300 km. Above this level, the vortex decays. Curiously, the zonal winds and temperatures are symmetric about a pole that is offset from the surface pole by approx.4 degrees. The cause of this is not well understood, but it may reflect the response of a cyclostrophic circulation to the offset between the equator, where the distance to the rotation axis is greatest, and the solar equator. The mean meridional circulation can be inferred from the temperature field and the meridional distribution of organic molecules and condensates and hazes. Both the warm temperatures in the north polar region near 400 km and the enhanced concentration of several organic molecules suggests subsidence there during winter and early spring. Stratospheric condensates are localized at high northern latitudes, with a sharp cut-off near 50degN. Titan's winter polar vortex appears to share many of the same characteristics of winter vortices on Earth-the ozone holes. Global mapping of temperatures, winds, and composition in he troposphere, by contrast, is incomplete. The few suitable discrete clouds that have bee found for tracking indicate smaller velocities than aloft, consistent with the

  14. Potassium toxicity at low serum potassium levels with refeeding syndrome.

    PubMed

    Vemula, Praveen; Abela, Oliver G; Narisetty, Keerthy; Rhine, David; Abela, George S

    2015-01-01

    Refeeding syndrome is a life-threatening condition occurring in severely malnourished patients after initiating feeding. Severe hypophosphatemia with reduced adenosine triphosphate production has been implicated, but little data are available regarding electrolyte abnormalities. In this case, we report electrocardiographic changes consistent with hyperkalemia during potassium replacement after a serum level increase from 1.9 to 2.9 mEq/L. This was reversed by lowering serum potassium back to 2.0 mEq/L. In conclusion, the patient with prolonged malnutrition became adapted to low potassium levels and developed potassium toxicity with replacement.

  15. Titan's South Polar Vortex in Motion

    NASA Video Gallery

    This movie captured by NASA'S Cassini spacecraft shows a south polar vortex, or a swirling mass of gas around the pole in the atmosphere, at Saturn’s moon Titan. The swirling mass appears to exec...

  16. Taking on Titan: Meet Carrie Anderson

    NASA Video Gallery

    When she was a little girl, Carrie Anderson dreamed of becoming an astronomer. Now, as a space scientist at NASA Goddard Space Flight Center, Carrie studies the atmosphere on Titan: one of Saturn's...

  17. Cyanide Soap? Dissolved material in Titan's Seas

    NASA Astrophysics Data System (ADS)

    Lorenz, R. D.; Lunine, J. I.; Neish, C. D.

    2011-10-01

    Although it is evident that Titan's lakes and seas are dominated by ethane, methane, nitrogen, and (in some models) propane, there is divergence on the predicted relative abundance of minor constituents such as nitriles and C-4 alkanes. Nitriles such as hydrogen cyanide and acetonitrile, which have a significant dipole moment, may have a disproportionate influence on the dielectric properties of Titan seas and may act to solvate polar molecules such as water ice. The hypothesis is offered that such salvation may act to enhance the otherwise negligible solubility of water ice bedrock in liquid hydrocarbons. Such enhanced solubility may permit solution erosion as a formation mechanism for the widespread pits and apparently karstic lakes on Titan. Prospects for testing this hypothesis in the laboratory, and with measurements on Titan, will be discussed.

  18. Accelerated Application Development: The ORNL Titan Experience

    SciTech Connect

    Joubert, Wayne; Archibald, Richard K.; Berrill, Mark A.; Brown, W. Michael; Eisenbach, Markus; Grout, Ray; Larkin, Jeff; Levesque, John; Messer, Bronson; Norman, Matthew R.; Philip, Bobby; Sankaran, Ramanan; Tharrington, Arnold N.; Turner, John A.

    2015-05-09

    The use of computational accelerators such as NVIDIA GPUs and Intel Xeon Phi processors is now widespread in the high performance computing community, with many applications delivering impressive performance gains. However, programming these systems for high performance, performance portability and software maintainability has been a challenge. In this paper we discuss experiences porting applications to the Titan system. Titan, which began planning in 2009 and was deployed for general use in 2013, was the first multi-petaflop system based on accelerator hardware. To ready applications for accelerated computing, a preparedness effort was undertaken prior to delivery of Titan. In this paper we report experiences and lessons learned from this process and describe how users are currently making use of computational accelerators on Titan.

  19. Accelerated Application Development: The ORNL Titan Experience

    DOE PAGES

    Joubert, Wayne; Archibald, Richard K.; Berrill, Mark A.; Brown, W. Michael; Eisenbach, Markus; Grout, Ray; Larkin, Jeff; Levesque, John; Messer, Bronson; Norman, Matthew R.; et al

    2015-05-09

    The use of computational accelerators such as NVIDIA GPUs and Intel Xeon Phi processors is now widespread in the high performance computing community, with many applications delivering impressive performance gains. However, programming these systems for high performance, performance portability and software maintainability has been a challenge. In this paper we discuss experiences porting applications to the Titan system. Titan, which began planning in 2009 and was deployed for general use in 2013, was the first multi-petaflop system based on accelerator hardware. To ready applications for accelerated computing, a preparedness effort was undertaken prior to delivery of Titan. In this papermore » we report experiences and lessons learned from this process and describe how users are currently making use of computational accelerators on Titan.« less

  20. Geomorphologic Map of Titan's Polar Terrains

    NASA Astrophysics Data System (ADS)

    Birch, S. P. D.; Hayes, A. G.; Malaska, M. J.; Lopes, R. M. C.; Schoenfeld, A.; Williams, D. A.

    2016-06-01

    Titan's lakes and seas contain vast amounts of information regarding the history and evolution of Saturn's largest moon. To understand this landscape, we created a geomorphologic map, and then used our map to develop an evolutionary model.

  1. The tide in the seas of Titan

    NASA Technical Reports Server (NTRS)

    Sagan, C.; Dermott, S. F.

    1982-01-01

    The parameters of the tides in the near-global ocean that may exist on Titan are assessed. A formula for the difference between the maximum heights of the oceanic and body tides is used to determine that the amplitude of the apparent, near-stationary, oceanic tide on Titan is greater than about 100 m. The effects of tidal dissipation are evaluated, showing that the amplitude of the tide will vary by nine percent over its 15.95-day period. The observed eccentricity of Titan's orbit is used to establish limits on the satellite's surface topography and oceanic depths. It is concluded that either Titan is covered by a near-global methane ocean over 400 m deep, or that there is no methane ocean at all. Reflectivity measurements can decide between these alternatives.

  2. Ion Neutral Mass Spectrometer Measurements from Titan

    NASA Astrophysics Data System (ADS)

    Waite, J. H., Jr.; Niemann, H.; Yelle, R. V.; Kasprzak, W.; Cravens, T.; Luhmann, J.; McNutt, R.; Ip, W.-H.; Gell, D.; Muller-Wordag, I. C. F.; Ledvina, S.; Magee, B.; Borggren, N.; Fletcher, G.; Walter, E.; Miller, R.; Xu, J.; Block, B.; Arnett, K.

    2005-03-01

    In its first flyby of Titan, Cassini/INMS has found that the upper atmospheric structure remains virtually unchanged since the Voyager flyby 20 years ago. The data also provides isotopic clues about the evolution of the atmosphere.

  3. Prebiotic-like chemistry on Titan.

    PubMed

    Raulin, François; Brassé, Coralie; Poch, Olivier; Coll, Patrice

    2012-08-21

    Titan, the largest satellite of Saturn, is the only one in the solar system with a dense atmosphere. Mainly composed of dinitrogen with several % of methane, this atmosphere experiences complex organic processes, both in the gas and aerosol phases, which are of prebiotic interest and within an environment of astrobiological interest. This tutorial review presents the different approaches which can be followed to study such an exotic place and its chemistry: observation, theoretical modeling and experimental simulation. It describes the Cassini-Huygens mission, as an example of observational tools, and gives the new astrobiologically oriented vision of Titan which is now available by coupling the three approaches. This includes the many analogies between Titan and the Earth, in spite of the much lower temperature in the Saturn system, the complex organic chemistry in the atmosphere, from the gas to the aerosol phases, but also the potential organic chemistry on Titan's surface, and in its possible internal water ocean.

  4. Prebiotic-like chemistry on Titan.

    PubMed

    Raulin, François; Brassé, Coralie; Poch, Olivier; Coll, Patrice

    2012-08-21

    Titan, the largest satellite of Saturn, is the only one in the solar system with a dense atmosphere. Mainly composed of dinitrogen with several % of methane, this atmosphere experiences complex organic processes, both in the gas and aerosol phases, which are of prebiotic interest and within an environment of astrobiological interest. This tutorial review presents the different approaches which can be followed to study such an exotic place and its chemistry: observation, theoretical modeling and experimental simulation. It describes the Cassini-Huygens mission, as an example of observational tools, and gives the new astrobiologically oriented vision of Titan which is now available by coupling the three approaches. This includes the many analogies between Titan and the Earth, in spite of the much lower temperature in the Saturn system, the complex organic chemistry in the atmosphere, from the gas to the aerosol phases, but also the potential organic chemistry on Titan's surface, and in its possible internal water ocean. PMID:22481630

  5. Future Exploration of Titan and Enceladus

    NASA Astrophysics Data System (ADS)

    Matson, D. L.; Coustenis, A.; Lunine, J.; Lebreton, J.; Reh, K.; Beauchamp, P.

    2009-05-01

    The future exploration of Titan and Enceladus has become very important for the planetary community. The study conducted last year of the Titan Saturn System Mission (TSSM) led to an announcement in which ESA and NASA prioritized future OPF missions, stating that TSSM is planned after EJSM (for details see http://www.lpi.usra.edu/opag/). TSSM consists of a TSSM Orbiter that would carry two in situ elements: the Titan Montgolfiere hot air balloon and the Titan Lake Lander. The mission could launch in the 2023-2025 timeframe on a trajectory to arrive ~9 years later for a 4-year mission in the Saturn system. Soon after arrival at Saturn, the montgolfiere would be delivered to Titan to begin its mission of airborne, scientific observations of Titan from an altitude of about 10 km. The montgolfiere would have a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) power system and would be designed to last at least 6-12 months in Titan's atmosphere. With the predicted winds and weather, that would be sufficient to circumnavigate the globe! On a subsequent fly-by, the TSSM orbiter would release the Lake Lander on a trajectory toward Titan for a targeted entry. It would descend through the atmosphere making scientific measurements, much like Huygens did, and then land and float on one of Titan's seas. This would be its oceanographic phase, making a physical and chemical assessment of the sea. The Lake Lander would operate 8-10 hours until its batteries become depleted. Following the delivery of the in situ elements, the TSSM orbiter would explore the Saturn system via a 2-year tour that includes in situ sampling of Enceladus' plumes as well as Titan flybys. After the Saturn system tour, the TSSM orbiter would enter orbit around Titan for a global survey phase. Synergistic and coordinated observations would be carried out between the TSSM orbiter and the in situ elements. The scientific requirements were developed by the international TSSM Joint Science Definition

  6. Energy Deposition Processes in Titan's Upper Atmosphere

    NASA Technical Reports Server (NTRS)

    Sittler, Edward C., Jr.; Bertucci, Cesar; Coates, Andrew; Cravens, Tom; Dandouras, Iannis; Shemansky, Don

    2008-01-01

    Most of Titan's atmospheric organic and nitrogen chemistry, aerosol formation, and atmospheric loss are driven from external energy sources such as Solar UV, Saturn's magnetosphere, solar wind and galactic cosmic rays. The Solar UV tends to dominate the energy input at lower altitudes of approximately 1100 km but which can extend down to approximately 400 km, while the plasma interaction from Saturn's magnetosphere, Saturn's magnetosheath or solar wind are more important at higher altitudes of approximately 1400 km, but the heavy ion plasma [O(+)] of approximately 2 keV and energetic ions [H(+)] of approximately 30 keV or higher from Saturn's magnetosphere can penetrate below 950km. Cosmic rays with energies of greater than 1 GeV can penetrate much deeper into Titan's atmosphere with most of its energy deposited at approximately 100 km altitude. The haze layer tends to dominate between 100 km and 300 km. The induced magnetic field from Titan's interaction with the external plasma can be very complex and will tend to channel the flow of energy into Titan's upper atmosphere. Cassini observations combined with advanced hybrid simulations of the plasma interaction with Titan's upper atmosphere show significant changes in the character of the interaction with Saturn local time at Titan's orbit where the magnetosphere displays large and systematic changes with local time. The external solar wind can also drive sub-storms within the magnetosphere which can then modify the magnetospheric interaction with Titan. Another important parameter is solar zenith angle (SZA) with respect to the co-rotation direction of the magnetospheric flow. Titan's interaction can contribute to atmospheric loss via pickup ion loss, scavenging of Titan's ionospheric plasma, loss of ionospheric plasma down its induced magnetotail via an ionospheric wind, and non-thermal loss of the atmosphere via heating and sputtering induced by the bombardment of magnetospheric keV ions and electrons. This

  7. Huygens will soon set off for Titan

    NASA Astrophysics Data System (ADS)

    1997-09-01

    When it parachutes slowly down to the surface of Titan, in November 2004, Huygens will unmask the most enigmatic object in the Solar System. Baffled and tantalized, space scientists don't know how this moon of Saturn acquired a dense atmosphere, which is rich in nitrogen like the Earth's air but also possesses many carbon compounds. The scientists can't say whether the surface of Titan is solid or liquid, or a bit of each. But many are convinced that Titan offers them their best chance of discovering what the Earth and its chemistry were like, before life began. A heat shield will protect Huygens as it slams into Titan's atmosphere at 20,000 kilometres per second. A succession of parachutes will adjust Titan's speed of descent through the atmosphere. Radio signals from the probe will convey the results to the Cassini orbiter, for relaying tothe Earth, and will also reveal how Huygens and its parachute are blown about by the winds of Titan, during the descent. Huygens carries six sets of instruments devised by multinational teams of scientists in Europe and the USA. They will analyse the chemical composition of the haze that hides Titan's surface. They will gauge the weather of Titan during Huygens' descent, and image the clouds and the surface. A surface science package will report the true nature of Titan's surface. A televised launch Cassini-Huygens will be launched by a NASA Titan IVB rocket from the Cape Canaveral Air Station in Florida. The earliest launch date is 6 October, but this is now likely to slip, to allow for the repair of minor damage to insulation within the Huygens probe (see ESA Press Release Nr 27-97). Provided the launch occurs before 4 November, there will be no delay in the arrival at Saturn and Titan. ESA will provide a live TV transmission, free of charge, for European news organizations and other organizations wishing to receive it. Live pictures of the launch will be accompanied by interviews with scientists and engineers of ESA's Huygens

  8. Librations of Enceladus and Titan

    NASA Astrophysics Data System (ADS)

    Yseboodt, M.; Van Hoolst, T.; Baland, R. M.

    2015-12-01

    A moon in synchronous rotation has longitudinal librations (small deviations from the average rotation) because of its nonspherical mass distribution and its elliptical orbit around the planet. We study the long-period librations of Enceladus and Titan and include deformation effects and the existence of a subsurface ocean. We take into account the fact that the orbit is not Keplerian and has other periodicities than the main period of orbital motion around Saturn due to perturbations by the Sun, other planets and moons. An orbital theory is used to compute the orbital perturbations due to these other bodies.We numerically evaluate the amplitude of the long-period librations for many interior structure models of the moon constrained by the mass, radius and gravity field. Measurements of the librations may give constraints on the interior structure of the icy satellites.

  9. Parallel contingency statistics with Titan.

    SciTech Connect

    Thompson, David C.; Pebay, Philippe Pierre

    2009-09-01

    This report summarizes existing statistical engines in VTK/Titan and presents the recently parallelized contingency statistics engine. It is a sequel to [PT08] and [BPRT09] which studied the parallel descriptive, correlative, multi-correlative, and principal component analysis engines. The ease of use of this new parallel engines is illustrated by the means of C++ code snippets. Furthermore, this report justifies the design of these engines with parallel scalability in mind; however, the very nature of contingency tables prevent this new engine from exhibiting optimal parallel speed-up as the aforementioned engines do. This report therefore discusses the design trade-offs we made and study performance with up to 200 processors.

  10. Evidence for surface heterogeneity on Titan

    NASA Astrophysics Data System (ADS)

    Griffith, C. A.

    1993-08-01

    Observational results are presented for two rotational periods of Titan which exhibit the albedo difference noted by Lemmon et al. (1993) between this moon's positions at eastern and western elongation relative to Saturn. The persistence of this difference indicates that this heterogeneity is unlikely to be associated with transient features, and must be intrinsic to the surface. The results presented also indicate that Titan is locked in a synchronous orbit around Saturn.

  11. Saturn's Titan: Evidence for Current Cryovolcanic Activity

    NASA Astrophysics Data System (ADS)

    Nelson, Robert M.; Cassini VIMS Titan Surface Variability Group

    2009-09-01

    We report evidence suggesting current cryovolcanic activity on Titan. This is based on surface changes seen at selected locations by the Cassini Visual and Infrared Mapping Spectrometer (VIMS). Titan's surface is hard to observe because Titan's atmosphere is opaque at visual wavelengths due to methane absorption. However, VIMS is able to image the surface at selected infrared wavelengths where the methane is relatively transparent[1,2]. VIMS reported surface reflectance variability at Hotei Arcus (26S,78W) and that the variability might be due to deposition followed by coverage or dissipation of ammonia frost. Subsequently, Cassini RADAR images found that Hotei Arcus has lobate "flow” forms, consistent with the morphology of volcanic terrain [3]. Here we report the discovery of lobate "flow” patterns at Hotei Arcus in VIMS infrared images taken during Cassini close flybys during 2008-2009. These data further suggest that the brightness variability at Hotei Arcus is associated with ammonia, a compound expected in Titan's interior. This, combined with the previous evidence from VIMS and RADAR images, creates a strong case for Titan having a presently active surface, possibly due to cryovolcanism. It has not escaped our attention that gaseous ammonia, in association with methane and nitrogen in Titan's atmosphere, is similar to the terrestrial environment at the time that life first emerged. If Titan is currently active, then these results raise the following questions: What is the full extent of current geologic activity? What are the ongoing processes? Are Titan's chemical processes today supporting a prebiotic chemistry similar to that under which life evolved on Earth? This work done at JPL under contract with NASA. References: [1]R. M. Nelson et al., Icarus 199 (2009) 429-441. [2]R. M. Nelson et al., GEOPHYSICAL RESEARCH LETTERS, VOL. 36, L04202, doi:10.1029/2008GL036206, 2009. [3]S. D. Wall GEOPHYSICAL RESEARCH LETTERS, VOL. 36, L04203, doi:10.1029/2008GL

  12. Titan Orbiter with Aerorover Mission (TOAM)

    NASA Astrophysics Data System (ADS)

    Sittler, Edward C.; Cooper, J. F.; Mahaffey, P.; Esper, J.; Fairbrother, D.; Farley, R.; Pitman, J.; Kojiro, D. R.; TOAM Team

    2006-12-01

    We propose to develop a new mission to Titan called Titan Orbiter with Aerorover Mission (TOAM). This mission is motivated by the recent discoveries of Titan, its atmosphere and its surface by the Huygens Probe, and a combination of in situ, remote sensing and radar mapping measurements of Titan by the Cassini orbiter. Titan is a body for which Astrobiology (i.e., prebiotic chemistry) will be the primary science goal of any future missions to it. TOAM is planned to use an orbiter and balloon technology (i.e., aerorover). Aerobraking will be used to put payload into orbit around Titan. The Aerorover will probably use a hot air balloon concept using the waste heat from the MMRTG 500 watts. Orbiter support for the Aerorover is unique to our approach for Titan. Our strategy to use an orbiter is contrary to some studies using just a single probe with balloon. Autonomous operation and navigation of the Aerorover around Titan will be required, which will include descent near to the surface to collect surface samples for analysis (i.e., touch and go technique). The orbiter can provide both relay station and GPS roles for the Aerorover. The Aerorover will have all the instruments needed to sample Titan’s atmosphere, surface, possible methane lakes-rivers, use multi-spectral imagers for surface reconnaissance; to take close up surface images; take core samples and deploy seismometers during landing phase. Both active and passive broadband remote sensing techniques will be used for surface topography, winds and composition measurements.

  13. The rotation of Titan and Ganymede

    NASA Astrophysics Data System (ADS)

    Van Hoolst, Tim; Coyette, Alexis; Baland, Rose-Marie; Trinh, Antony

    2016-10-01

    The rotation rates of Titan and Ganymede, the largest satellites of Saturn and Jupiter, are on average equal to their orbital mean motion. Here we discuss small deviations from the average rotation for both satellites and evaluate the polar motion of Titan induced by its surface fluid layers. We examine different causes at various time scales and assess possible consequences and the potential of using librations and polar motion as probes of the interior structure of the satellites.The rotation rate of Titan and Ganymede cannot be constant on the orbital time scale as a result of the gravitational torque of the central planet acting on the satellites. Titan is moreover expected to show significant polar motion and additional variations in the rotation rate due to angular momentum exchange with the atmosphere, mainly at seasonal periods. Observational evidence for deviations from the synchronous state has been reported several times for Titan but is unfortunately inconclusive. The measurements of the rotation variations are based on determinations of the shift in position of Cassini radar images taken during different flybys. The ESA JUICE (JUpiter ICy moons Explorer) mission will measure the rotation variations of Ganymede during its orbital phase around the satellite starting in 2032.We report on different theoretical aspects of the librations and polar motion. We consider the influence of the rheology of the ice shell and take into account Cassini measurements of the external gravitational field and of the topography of Titan and similar Galileo data about Ganymede. We also evaluate the librations and polar motion induced by Titan's hydrocarbon seas and use the most recent results of Titan's atmosphere dynamics. We finally evaluate the potential of rotation variations to constrain the satellite's interior structure, in particular its ice shell and ocean.

  14. Spectral Trends of Titan's Tropical Surface

    NASA Astrophysics Data System (ADS)

    Griffith, Caitlin Ann; Penteado, Paulo F.; Turner, Jake; Montiel, Nicholas; Schoenfeld, Ashley; Lopes, Rosaly M. C.; Soderblom, Laurence A.; Neish, Catherine; Radebaugh, Jani

    2016-10-01

    Titan's surface can be observed most clearly at 8 spectral regions that lie in between the strong methane bands in Titan's spectrum. Within these "windows", between 0.9 to 5 microns, the surface is nonetheless obscured by methane and haze, the latter of which is optically thick at lower wavelengths. Thus studies of Titan's surface must eliminate the effects of atmospheric extinction and extract the subtle spectral features that underlie the dominant spectral trends.To determine the subtle spectral features of Titan's tropical surface (30S--30N) we conducted a Principal Components Analysis (PCA) of the I/F at the 1.1, 1.3, 1.6 and 2.0 um wavelength windows, recorded by Cassini/VIMS. The PCA analysis identifies the spectral trend that defines the highest variance in the data (the principal component), as well as successively weaker orthogonal trends, without a priori assumptions about the surface composition, e.g. as needed in radiative transfer analyses.Our analysis derives the spectral features at the four wavelengths that describe Titan's tropical surface. We detect a large almost contiguous region that extends roughly 160 degrees in longitude and which exhibits absorption features at 1.6 and 2.0, as well as 2.8 um (characteristic of water ice). This vast and perhaps tectonic feature is, in part, associated with terrain that is hypothesized to be some of the oldest surfaces on Titan. In addition, the PCA analysis indicates at least 2 separate organic spectra signatures, potentially due to the separation of liquid and refractory sediments or to their chemically alteration over time. Here we discuss the PCA analysis and compare our derived compositional maps of Titan's surface with Radar maps of the topography and morphology, to entertain questions regarding the geology of Titan's surface the age of its atmosphere.

  15. Atomic hydrogen distribution. [in Titan atmospheric model

    NASA Technical Reports Server (NTRS)

    Tabarie, N.

    1974-01-01

    Several possible H2 vertical distributions in Titan's atmosphere are considered with the constraint of 5 km-A a total quantity. Approximative calculations show that hydrogen distribution is quite sensitive to two other parameters of Titan's atmosphere: the temperature and the presence of other constituents. The escape fluxes of H and H2 are also estimated as well as the consequent distributions trapped in the Saturnian system.

  16. Targeting potassium channels in cancer

    PubMed Central

    2014-01-01

    Potassium channels are pore-forming transmembrane proteins that regulate a multitude of biological processes by controlling potassium flow across cell membranes. Aberrant potassium channel functions contribute to diseases such as epilepsy, cardiac arrhythmia, and neuromuscular symptoms collectively known as channelopathies. Increasing evidence suggests that cancer constitutes another category of channelopathies associated with dysregulated channel expression. Indeed, potassium channel–modulating agents have demonstrated antitumor efficacy. Potassium channels regulate cancer cell behaviors such as proliferation and migration through both canonical ion permeation–dependent and noncanonical ion permeation–independent functions. Given their cell surface localization and well-known pharmacology, pharmacological strategies to target potassium channel could prove to be promising cancer therapeutics. PMID:25049269

  17. Titan's atmospheric engine: an overview

    NASA Astrophysics Data System (ADS)

    Samuelson, Robert E.

    2003-02-01

    Heating occurs in Titan's stratosphere from the absorption of incident solar radiation by methane and aerosols. About 10% of the incident sunlight reaches Titan's surface and causes heating there. Thermal radiation redistributes heat within the atmosphere and cools to space. The resulting vertical temperature profile is stable against convection and a state of radiative equilibrium is established. Equating theoretical and observed temperature profiles enables an empirical determination of the vertical distribution of thermal opacity. A uniformly mixed aerosol is responsible for most of the opacity in the stratosphere, whereas collision-induced absorption of gases is the main contributor in the troposphere. Occasional clouds are observed in the troposphere in spite of the large degrees of methane supersaturation found there. Photochemistry converts CH 4 and N 2 into more complex hydrocarbons and nitriles in the stratosphere and above. Thin ice clouds of trace organics are formed in the winter and early spring polar regions of the lower stratosphere. Precipitating ice particles serve as condensation sites for supersaturated methane vapor in the troposphere below, resulting in lowered methane degrees of supersaturation in the polar regions. Latitudinal variations of stratospheric temperature are seasonal, and lag instantaneous response to solar irradiation by about one season for two reasons: (1) an actual instantaneous thermal response to a latitudinal distribution of absorbing gases, themselves out of phase with the sun by about one season, and (2) a sluggish dynamical response of the stratosphere to the latitudinal transport of angular momentum, induced by radiative heating and cooling. Mean vertical abundances of stratospheric organics and aerosols are determined primarily by atmospheric chemistry and condensation, whereas latitudinal distributions are more influenced by meridional circulations. In addition to preferential scavenging by precipitating ice particles

  18. Condensation during Titan's Polar Winter

    NASA Astrophysics Data System (ADS)

    de Kok, Remco; Irwin, P. G.; Teanby, N. A.; Fletcher, L. N.; Howett, C. J.; Calcutt, S. B.; Bowles, N. E.; Taylor, F. W.

    2007-10-01

    Titan is currently experiencing winter in its northern hemisphere and the lower atmosphere of its north polar region has been in prolonged darkness since the solstice in October 2002. As a result, the north polar region is currently characterised by cold stratospheric temperatures and there is enrichment of trace gases due to downward atmospheric motion (e.g. Teanby et al., Icarus 181 pp. 243-255, 2006). These conditions make the polar winter very suitable for cloud formation in the stratosphere. A simple transport and condensation model has been made to explore condensation processes in Titan's northern stratosphere. In the model, the atmosphere is advected downwards and clouds are formed as the saturation pressure of various gases is reached. Upper limits of the gases C4N2 and propionitrile (C2H5CN) were determined from Cassini Composite Infrared Spectrometer data to assess scenarios of chemical disequilibrium where the gas phase is far less abundant than the solid phase. The upper limit for C4N2 is 9e-9, which discounts the massive C4N2 build-up in the polar winter proposed by Samuelson et al. (PSS 45, pp. 941-948, 1997) to explain the observed C4N2 cloud at the Voyager epoch. The propionitrile upper limit is 8e-9, which is several orders of magnitude less than needed to create the condensate feature at 220 cm-1 of Khanna (Icarus 177, pp. 116-121) and de Kok et al. (Icarus, in press), assuming it is propionitrile ice, under the steady-state conditions explored by the aformentioned model. HCN ice seems to play an important role in the formation of a massive polar cloud (Haze B in de Kok et al., Icarus, in press), because of the unavailability of sufficient condensable gas other than HCN (and possibly HC3N) to produce the condensate features seen in far-infrared spectra at 220 cm-1.

  19. Safe prescribing: a titanic challenge

    PubMed Central

    Routledge, Philip A

    2012-01-01

    The challenge to achieve safe prescribing merits the adjective ‘titanic’. The organisational and human errors leading to poor prescribing (e.g. underprescribing, overprescribing, misprescribing or medication errors) have parallels in the organisational and human errors that led to the loss of the Titanic 100 years ago this year. Prescribing can be adversely affected by communication failures, critical conditions, complacency, corner cutting, callowness and a lack of courage of conviction, all of which were also factors leading to the Titanic tragedy. These issues need to be addressed by a commitment to excellence, the final component of the ‘Seven C's’. Optimal prescribing is dependent upon close communication and collaborative working between highly trained health professionals, whose role is to ensure maximum clinical effectiveness, whilst also protecting their patients from avoidable harm. Since humans are prone to error, and the environments in which they work are imperfect, it is not surprising that medication errors are common, occurring more often during the prescribing stage than during dispensing or administration. A commitment to excellence in prescribing includes a continued focus on lifelong learning (including interprofessional learning) in pharmacology and therapeutics. This should be accompanied by improvements in the clinical working environment of prescribers, and the encouragement of a strong safety culture (including reporting of adverse incidents as well as suspected adverse drug reactions whenever appropriate). Finally, members of the clinical team must be prepared to challenge each other, when necessary, to ensure that prescribing combines the highest likelihood of benefit with the lowest potential for harm. PMID:22738396

  20. Titan's Mid-latitude Clouds

    NASA Astrophysics Data System (ADS)

    Roe, Henry G.; Schaller, E. L.; Trujillo, C. A.; Brown, M. E.

    2007-10-01

    In the first few years of spatially resolved observations of Titan's tropospheric methane clouds (2001-2003) all of the clouds were clustered in the south polar region. This time period coincided with the southern summer solstice (October 2002) and these south polar clouds are almost certainly a seasonal phenomenon. Starting in December 2003 we began seeing clouds in a narrow latitude range centered at 40°S latitude. In Roe et al. (2005a) we published this initial discovery and speculated that the clouds might be due either to changes in the seasonal circulation pattern or a process linked to surface geography. Further observations soon revealed that the clouds were significantly clustered over one region of longitude (near 350°W), strongly suggesting a geographically controlled origin (Roe et al. 2005b), although Cassini observations suggest a circulation-induced convergence origin (Griffith et al. 2005). The actual answer is most likely a combination of geographic surface effects with the atmospheric circulation. We report here on our continuing ground-based observation campaign, including observations on 65 nights in the 2006-2007 apparition with the Gemini 8-m telescope. With two more years of observations since the data shown in Roe et al. (2005b) we now have much firmer conclusions with respect to the spatial distribution and temporal characteristics of the mid-latitude clouds. We will present our latest understanding of Titan's mid-latitude clouds given the entire dataset now available to us. References Griffith, C.A., & 26 co-authors 2005. Science, 310, 474. Roe, H.G., A.H. Bouchez, C.A. Trujillo, E.L. Schaller, & M.E. Brown 2005a. ApJL, 618, 49. Roe, H.G., M.E. Brown, E.L. Schaller, A.H. Bouchez, & C.A. Trujillo 2005b. Science, 310, 477. This work is supported by NASA under Grant #NNX07AK74G issued through the Planetary Astronomy Program.

  1. Airglow on Titan During Eclipse

    NASA Astrophysics Data System (ADS)

    West, R. A.; Ajello, J. M.; Stevens, M. H.; Strobel, D. F.; Gladstone, R.; Evans, J. S.; Bradley, E. T.

    2012-12-01

    Magnetospheric or cosmic ray charged particle precipitation into Titan's atmosphere is a potential energy source for driving chemistry and may contribute to airglow and energy balance. Estimates of the significance of these processes vary widely and thus far have been only poorly constrained because of the dominance of XUV radiation in stimulating UV airglow. To address these issues we observed Titan when it was deeply embedded in Saturn's shadow in 2009. We obtained EUV and FUV spectra with the Cassini Ultraviolet Imaging Spectrograph (UVIS) and images with the Cassini Imaging Science Subsystem (ISS) at visible wavelengths. For the first time, nitrogen emissions were seen in the spectra in the absence of XUV stimulation, although with insufficient spatial resolution to do limb profiling. The emissions are about a factor of ten smaller than peak dayside emissions observed with UVIS at closer range (from Stevens et al., , J. Geophys. Res., 116, A05304, doi10.1029/2010ja016284). Hydrogen emissions are also observed, consistent with the idea that precipitating protons and oxygen ions are responsible for part of the emission. The visible images from ISS contribute because they resolve the disk well. No auroral structures are seen. Rather, there is a very faint airglow seen on the limb between about 300 and 1000 km and a stronger intensity coming from the region of the haze at 300 km altitude. Although the limb glow is near the noise limit, the radial profile appears to be inconsistent with ionization profiles expected for precipitating electrons, protons, or oxygen ions which are expected to produce strong limb brightening. The stronger glow from the haze region was unexpected. Its origin is not understood but deeply-penetrating cosmic ray ionization and chemiluminescence are candidates that deserve additional scrutiny. . Part of this work was performed by the Jet Propulsion Lab, Cal. Inst. of Tech. under contract with the National Aeronautics and Space Administration.

  2. Nonthermal atmospheric escape from Mars and Titan

    NASA Astrophysics Data System (ADS)

    Lammer, H.; Bauer, S. J.

    1991-02-01

    Energy flux spectra and particle concentrations of the hot O and N coronae from Mars and Titan, respectively, resulting primarily from dissociative recombination of molecular ions, have been calculated by means of a Monte Carlo method. The calculated energy flux spectra lead to an escape flux phi(esc) about 6 x 10 to the 6th/sq cm per sec for Mars and phi(esc) about 2 x 10 to 6th/sq cm per sec for Titan, corresponding to a mass loss of about 0.14 kg/s for Mars and about 0.3 kg/s for Titan. (The contribution of electron impact ionization on N2 amounts to only about 25 percent of Titan's mass loss). Mass loss via solar and magnetospheric wind is also estimated using newly calculated mass loading limits. The mass loss via ion pickup from the extended hot atom corona for Mars amounts to about 0.25 kg/s (O/+/) and for Titan to about 50 g/s (N2/+/or H2CN/+/). Thus, the total mass loss rate from Mars and Titan is about the same (i.e., 0.4 kg/s).

  3. A facility for simulating Titan's environment

    NASA Astrophysics Data System (ADS)

    Wasiak, F. C.; Luspay-Kuti, A.; Welivitiya, W. D. D. P.; Roe, L. A.; Chevrier, V. F.; Blackburn, D. G.; Cornet, T.

    2013-04-01

    As a result of measurements acquired by the Cassini-Huygens mission of Titan's near surface atmospheric composition and temperature, Titan conditions can now be simulated in the laboratory and samples can subsequently be subjected to those conditions. Titan demonstrates an active hydrological-like cycle with its thick atmosphere, dynamic clouds, polar lakes of methane and ethane, moist regolith, and extensive fluvial erosive features. Unlike Earth, Titan's hydrological-like cycle likely involves several constituents, primarily methane and ethane. Here the properties of a new Titan simulation facility are presented, including conceptual methodology, design, implementation, and performance results. The chamber maintains Titan's surface temperature and pressure, and the sample cryogenic liquids undergoing experimentation are condensed within the chamber itself. During the experiments, the evaporation rates of the sample liquids are directly determined by continually measuring mass. Constituents are analyzed utilizing a Fourier Transform Infrared Spectroscopy (FTIR), and vapor concentrations are determined using a gas chromatograph fitted with a Flame Ionization Detector (FID). All pertinent data is logged via computer. Under laboratory conditions, the direct measurements of the evaporation rates of methane, ethane, and mixtures thereof can be achieved. Among the processes to be studied are the effects of regolith on transport from the subsurface to the atmosphere, the freezing point depression effects of dissolved nitrogen, and the solubility of various relevant organic compounds.

  4. Ammonia and the Interior of Titan

    NASA Astrophysics Data System (ADS)

    Lorenz, R. D.

    2002-12-01

    Titan's surface will be very different from those of the Galileans, not just because of interactions with the atmosphere, but because the internal evolution will have been unique. The incorporation of ammonia in the ices making up Titan will make the evolution of Titan's interior structure very different. The presence of ammonia was previously only hinted at by formation models and the remarkably thick nitrogen atmosphere. However, recent radar observations showing Iapetus' bright face to be surprisingly radar-dark also point to incorporation of ammonia in the ices of the Saturnian satellites, explaining Titan's radar-darkness too. Ammonia will have several effects. As is well-known, its freezing-point depression to 176K makes a liquid layer ('internal ocean') more likely. A significant difference compared with the Galileans is that the greater expansivity of ammonia solutions compared with pure water causes the adiabat to be steeper, and thus a greater temperature difference prevails across the liquid layer. This in turn leads to a higher Carnot efficiency for the mantle heat engine - by an order of magnitude compared with Callisto - suggesting endogenic activity may be more manifest on Titan than on its Galilean cousins. The replenishment of methane in Titan's atmosphere against photolysis requires either surface lakes, or volcanic replenishment. If plausible methane contents of water-ammonia cryolavas are assumed, the heat flux associated with volcanism can be easily accommodated by the expected radiogenic heat production in the rocky core.

  5. Handling Late Changes to Titan Science

    NASA Technical Reports Server (NTRS)

    Pitesky, Jo Eliza; Steadman, Kim; Ray, Trina; Burton, Marcia

    2014-01-01

    The Cassini mission has been in orbit for eight years, returning a wealth of scientific data from Titan and the Saturnian system. The mission, a cooperative undertaking between NASA, ESA and ASI, is currently in its second extension of the prime mission. The Cassini Solstice Mission (CSM) extends the mission's lifetime until Saturn's northern summer solstice in 2017. The Titan Orbital Science Team (TOST) has the task of integrating the science observations for all 56 targeted Titan flybys in the CSM. In order to balance Titan science across the entire set of flybys during the CSM, to optimize and influence the Titan flyby altitudes, and to decrease the future workload, TOST went through a "jumpstart" process before the start of the CSM. The "jumpstart" produced Master Timelines for each flyby, identifying prime science observations and allocating control of the spacecraft attitude to specific instrument teams. Three years after completing this long-range plan, TOST now faces a new challenge: incorporating changes into the Titan Science Plan without undoing the balance achieved during the jumpstart.

  6. The Chemical Evolution of Titan's Atmosphere

    NASA Astrophysics Data System (ADS)

    Kaiser, Ralf I.

    2010-11-01

    Astrochemistry or Astrochemical Dynamics presents a newly emerging, interdisciplinary and innovative field comprising scientists in chemistry, physics, biology, astronomy, and planetary chemistry. The prime directive of Astrochemical Dynamics is to understand the origin and chemical evolution of the interstellar medium and of our Solar System. Here, the arrival of the Cassini-Huygens probe at Saturn's moon Titan - the only Solar System body besides Earth and Venus with a solid surface and thick atmosphere - in 2004 opened up a new chapter in the history of Solar System exploration. Titan's most prominent optically visible features are the aerosol-based haze layers, which give Titan its orange-brownish color. However, the underlying chemical processes, which initiate the haze formation, have been the least understood to date. This talk reviews recent laboratory studies on the role of polyacetylenes (polyynes) and (hetero)aromatic molecules like the phenyl radical, benzene, and pyridine in the formation of Titan's organic haze layers utilizing crossed molecular beam experiments. Those investigations provide key concepts on the formation mechanisms of unsaturated hydrocarbon molecules - in particular polyynes and aromatic compounds - together with their hydrogen deficient precursors from the "bottom up" in the atmosphere of Saturn's moon Titan. A brief outline to future research directions tackling also the heterogeneous chemistry on Titan and in hydrocarbon-rich atmospheres in the outer Solar System in general will also be presented.

  7. Luminescence studies of perovskite structured titanates: A review

    NASA Astrophysics Data System (ADS)

    Nag Bhargavi, G.; Khare, Ayush

    2015-06-01

    Apart from widely known dielectric and ferroelectric properties, the perovskite type materials also constitute a class of materials, which are recently investigated for their optical properties. These materials are being used for fabrication of various microelectronics and optoelectronic devices. Photoluminescence (PL), mechanoluminescence (ML) and thermoluminescence (TL) are such phenomena offering numerous applications in different fields like electro-optics, flat panel displays, LED technology, sensors, dynamic visualization etc. This paper briefly reviews the status and new progress in luminescence studies of ferroelectric materials like barium titanate (BT), barium zirconate titanate (BZT), calcium titanate (CT), calcium zirconate titanate (CZT), lead titanate (PT), lead zirconate titanate (PZT), etc., prepared through various methods.

  8. Magnetic whiskers of p-aminobenzoic acid and their use for preparation of filled and microchannel silicone rubbers

    NASA Astrophysics Data System (ADS)

    Semenov, V. V.; Loginova, V. V.; Zolotareva, N. V.; Razov, E. N.; Kotomina, V. E.; Kruglov, A. V.

    2016-07-01

    A thin cobalt layer has been formed on the surface of p-aminobenzoic acid whiskers by chemical vapor deposition (CVD). The metallized crystals have been oriented in liquid polydimethylsiloxane rubber by applying a dc magnetic field. After vulcanization, the filler has been removed by processing in an alcohol solution of trifluoroacetic acid. The cobalt deposition on the surface of the organic compound and the properties of metallized whiskers are investigated by optical microscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM).

  9. Wideband phase locking to modulated whisker vibration point to a temporal code for texture in the rat's barrel cortex.

    PubMed

    Ewert, Tobias A S; Möller, Johannes; Engel, Andreas K; Vahle-Hinz, Christiane

    2015-10-01

    Rats probe objects with their whiskers and make decisions about sizes, shapes, textures and distances within a few tens of milliseconds. This perceptual analysis requires the processing of tactile high-frequency object components reflecting surface roughness. We have shown that neurons in the barrel cortex of rats encode high-frequency sinusoidal vibrations of whiskers for sustained periods when presented with constant amplitudes and frequencies. In a natural situation, however, stimulus parameters change rapidly when whiskers are brushing across objects. In this study, we therefore analysed cortical responses to vibratory movements of single whiskers with rapidly changing amplitudes and frequencies. The results show that different neural codes are employed for a processing of stimulus parameters. The frequency of whisker vibration is encoded by the temporal pattern of spike discharges, i.e., the phase-locked responses of barrel cortex neurons. In addition, oscillatory gamma band activity was induced during high-frequency stimulation. The pivotal descriptor of the amplitude of whisker displacement, the velocity, is reflected in the rate of spike discharges. While phase-locked discharges occurred over the entire range of frequencies tested (10-600 Hz), the discharge rate increased with stimulus velocity only up to about 60 µm/ms, saturating at a mean rate of ~117 spikes/s. In addition, the results show that whisker movements of more than 500 Hz bandwidth may be encoded by phase-locked responses of small groups of cortical neurons. Thus, even single whiskers may transmit information about wide ranges of textural components owing to their set of different types of hair follicle mechanoreceptors.

  10. Neonatal Whisker Trimming Impairs Fear/Anxiety-Related Emotional Systems of the Amygdala and Social Behaviors in Adult Mice

    PubMed Central

    Soumiya, Hitomi; Godai, Ayumi; Araiso, Hiromi; Mori, Shingo; Furukawa, Shoei; Fukumitsu, Hidefumi

    2016-01-01

    Abnormalities in tactile perception, such as sensory defensiveness, are common features in autism spectrum disorder (ASD). While not a diagnostic criterion for ASD, deficits in tactile perception contribute to the observed lack of social communication skills. However, the influence of tactile perception deficits on the development of social behaviors remains uncertain, as do the effects on neuronal circuits related to the emotional regulation of social interactions. In neonatal rodents, whiskers are the most important tactile apparatus, so bilateral whisker trimming is used as a model of early tactile deprivation. To address the influence of tactile deprivation on adult behavior, we performed bilateral whisker trimming in mice for 10 days after birth (BWT10 mice) and examined social behaviors, tactile discrimination, and c-Fos expression, a marker of neural activation, in adults after full whisker regrowth. Adult BWT10 mice exhibited significantly shorter crossable distances in the gap-crossing test than age-matched controls, indicating persistent deficits in whisker-dependent tactile perception. In contrast to controls, BWT10 mice exhibited no preference for the social compartment containing a conspecific in the three-chamber test. Furthermore, the development of amygdala circuitry was severely affected in BWT10 mice. Based on the c-Fos expression pattern, hyperactivity was found in BWT10 amygdala circuits for processing fear/anxiety-related responses to height stress but not in circuits for processing reward stimuli during whisker-dependent cued learning. These results demonstrate that neonatal whisker trimming and concomitant whisker-dependent tactile discrimination impairment severely disturbs the development of amygdala-dependent emotional regulation. PMID:27362655

  11. Dissolution on Titan and on Earth: Toward the age of Titan's karstic landscapes

    NASA Astrophysics Data System (ADS)

    Cornet, Thomas; Cordier, Daniel; Bahers, Tangui Le; Bourgeois, Olivier; Fleurant, Cyril; Mouélic, Stéphane Le; Altobelli, Nicolas

    2015-06-01

    Titan's polar surface is dotted with hundreds of lacustrine depressions. Based on the hypothesis that they are karstic in origin, we aim at determining the efficiency of surface dissolution as a landshaping process on Titan, in a comparative planetology perspective with the Earth as reference. Our approach is based on the calculation of solutional denudation rates and allow inference of formation timescales for topographic depressions developed by chemical erosion on both planetary bodies. The model depends on the solubility of solids in liquids, the density of solids and liquids, and the average annual net rainfall rates. We compute and compare the denudation rates of pure solid organics in liquid hydrocarbons and of minerals in liquid water over Titan and Earth timescales. We then investigate the denudation rates of a superficial organic layer in liquid methane over one Titan year. At this timescale, such a layer on Titan would behave like salts or carbonates on Earth depending on its composition, which means that dissolution processes would likely occur but would be 30 times slower on Titan compared to the Earth due to the seasonality of precipitation. Assuming an average depth of 100 m for Titan's lacustrine depressions, these could have developed in a few tens of millions of years at polar latitudes higher than 70°N and S, and a few hundreds of million years at lower polar latitudes. The ages determined are consistent with the youth of the surface (<1 Gyr) and the repartition of dissolution-related landforms on Titan.

  12. 21 CFR 184.1619 - Potassium carbonate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Potassium carbonate. 184.1619 Section 184.1619... Listing of Specific Substances Affirmed as GRAS § 184.1619 Potassium carbonate. (a) Potassium carbonate... of potassium chloride followed by exposing the resultant potassium to carbon dioxide; (2) By...

  13. 21 CFR 184.1619 - Potassium carbonate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Potassium carbonate. 184.1619 Section 184.1619... Listing of Specific Substances Affirmed as GRAS § 184.1619 Potassium carbonate. (a) Potassium carbonate... of potassium chloride followed by exposing the resultant potassium to carbon dioxide; (2) By...

  14. 21 CFR 184.1643 - Potassium sulfate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Potassium sulfate. 184.1643 Section 184.1643 Food... GRAS § 184.1643 Potassium sulfate. (a) Potassium sulfate (K2SO4, CAS Reg. No. 7778-80-5) occurs.... It is prepared by the neutralization of sulfuric acid with potassium hydroxide or potassium...

  15. 21 CFR 172.800 - Acesulfame potassium.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Acesulfame potassium. 172.800 Section 172.800 Food... Multipurpose Additives § 172.800 Acesulfame potassium. Acesulfame potassium (CAS Reg. No. 55589-62-3), also... not preclude such use, under the following conditions: (a) Acesulfame potassium is the potassium...

  16. 21 CFR 184.1613 - Potassium bicarbonate.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Potassium bicarbonate. 184.1613 Section 184.1613... Listing of Specific Substances Affirmed as GRAS § 184.1613 Potassium bicarbonate. (a) Potassium... potassium hydroxide with carbon dioxide; (2) By treating a solution of potassium carbonate with...

  17. 21 CFR 184.1610 - Potassium alginate.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Potassium alginate. 184.1610 Section 184.1610 Food... GRAS § 184.1610 Potassium alginate. (a) Potassium alginate (CAS Reg. No. 9005-36-1) is the potassium salt of alginic acid, a natural polyuronide constituent of certain brown algae. Potassium alginate...

  18. 21 CFR 184.1634 - Potassium iodide.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 3 2014-04-01 2014-04-01 false Potassium iodide. 184.1634 Section 184.1634 Food... GRAS § 184.1634 Potassium iodide. (a) Potassium iodide (KI, CAS Reg. No. 7681-11-0) is the potassium... reacting hydriodic acid (HI) with potassium bicarbonate (KHCO3). (b) The ingredient meets...

  19. 21 CFR 184.1613 - Potassium bicarbonate.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 3 2012-04-01 2012-04-01 false Potassium bicarbonate. 184.1613 Section 184.1613... Listing of Specific Substances Affirmed as GRAS § 184.1613 Potassium bicarbonate. (a) Potassium... potassium hydroxide with carbon dioxide; (2) By treating a solution of potassium carbonate with...

  20. 21 CFR 184.1619 - Potassium carbonate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Potassium carbonate. 184.1619 Section 184.1619... Listing of Specific Substances Affirmed as GRAS § 184.1619 Potassium carbonate. (a) Potassium carbonate... of potassium chloride followed by exposing the resultant potassium to carbon dioxide; (2) By...

  1. 21 CFR 172.800 - Acesulfame potassium.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 3 2013-04-01 2013-04-01 false Acesulfame potassium. 172.800 Section 172.800 Food... Multipurpose Additives § 172.800 Acesulfame potassium. Acesulfame potassium (CAS Reg. No. 55589-62-3), also... not preclude such use, under the following conditions: (a) Acesulfame potassium is the potassium...

  2. 21 CFR 184.1613 - Potassium bicarbonate.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Potassium bicarbonate. 184.1613 Section 184.1613... Listing of Specific Substances Affirmed as GRAS § 184.1613 Potassium bicarbonate. (a) Potassium... potassium hydroxide with carbon dioxide; (2) By treating a solution of potassium carbonate with...

  3. 21 CFR 172.800 - Acesulfame potassium.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 3 2011-04-01 2011-04-01 false Acesulfame potassium. 172.800 Section 172.800 Food... Multipurpose Additives § 172.800 Acesulfame potassium. Acesulfame potassium (CAS Reg. No. 55589-62-3), also... not preclude such use, under the following conditions: (a) Acesulfame potassium is the potassium...

  4. 21 CFR 184.1613 - Potassium bicarbonate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Potassium bicarbonate. 184.1613 Section 184.1613... Listing of Specific Substances Affirmed as GRAS § 184.1613 Potassium bicarbonate. (a) Potassium... potassium hydroxide with carbon dioxide; (2) By treating a solution of potassium carbonate with...

  5. 21 CFR 184.1619 - Potassium carbonate.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Potassium carbonate. 184.1619 Section 184.1619 Food... Specific Substances Affirmed as GRAS § 184.1619 Potassium carbonate. (a) Potassium carbonate (K2CO3, CAS... potassium chloride followed by exposing the resultant potassium to carbon dioxide; (2) By treating...

  6. Efficient population coding of naturalistic whisker motion in the ventro-posterior medial thalamus based on precise spike timing

    PubMed Central

    Bale, Michael R.; Ince, Robin A. A.; Santagata, Greta; Petersen, Rasmus S.

    2015-01-01

    The rodent whisker-associated thalamic nucleus (VPM) contains a somatotopic map where whisker representation is divided into distinct neuronal sub-populations, called “barreloids”. Each barreloid projects to its associated cortical barrel column and so forms a gateway for incoming sensory stimuli to the barrel cortex. We aimed to determine how the population of neurons within one barreloid encodes naturalistic whisker motion. In rats, we recorded the extracellular activity of up to nine single neurons within a single barreloid, by implanting silicon probes parallel to the longitudinal axis of the barreloids. We found that play-back of texture-induced whisker motion evoked sparse responses, timed with millisecond precision. At the population level, there was synchronous activity: however, different subsets of neurons were synchronously active at different times. Mutual information between population responses and whisker motion increased near linearly with population size. When normalized to factor out firing rate differences, we found that texture was encoded with greater informational-efficiency than white noise. These results indicate that, within each VPM barreloid, there is a rich and efficient population code for naturalistic whisker motion based on precisely timed, population spike patterns. PMID:26441549

  7. Long-Term Extensive Ectopic Hair Growth on the Spinal Cord of Mice from Transplanted Whisker Follicles.

    PubMed

    Cao, Wenluo; Li, Lingna; Mii, Sumiyuki; Amoh, Yasuyuki; Liu, Fang; Hoffman, Robert M

    2015-01-01

    We have previously demonstrated that hair follicles contain nestin-expressing pluripotent stem cells that can effect nerve and spinal cord repair upon transplantation. In the present study, isolated whisker follicles from nestin-driven green fluorescent protein (ND-GFP) mice were histocultured on Gelfoam for 3 weeks for the purpose of transplantation to the spinal cord to heal an induced injury. The hair shaft was cut off from Gelfoam-histocultured whisker follicles, and the remaining part of the whisker follicles containing GFP-nestin expressing pluripotent stem cells were transplanted into the injured spinal cord of nude mice, along with the Gelfoam. After 90 days, the mice were sacrificed and the spinal cord lesion was observed to have healed. ND-GFP expression was intense at the healed area of the spinal cord, as observed by fluorescence microscopy, demonstrating that the hair follicle stem cells were involved in healing the spinal cord. Unexpectedly, the transplanted whisker follicles sprouted out remarkably long hair shafts in the spinal cord during the 90 days after transplantation of Gelfoam whisker histocultures to the injured spine. The pigmented hair fibers, grown from the transplanted whisker histocultures, curved and enclosed the spinal cord. The unanticipated results demonstrate the great potential of hair growth after transplantation of Gelfoam hair follicle histocultures, even at an ectopic site.

  8. The Dynamics of Titan's Convective Clouds

    NASA Astrophysics Data System (ADS)

    Rafkin, S. C.

    2012-12-01

    Titan's deep convective clouds are the most dynamic phenomena known to operate within the atmosphere of the moon. Previous studies have focused primarily on the control of these storms by the large scale thermodynamic environment, especially methane abundance, which determines the amount of convective available potential energy (CAPE). This study looks at factors in addition to the thermodynamic environment that may have a first order impact on the evolution and structure of Titan's deep convective clouds. To the extent that thunderstorms on Earth provide a reasonable analog to the storms on Titan, it is well established that CAPE alone is insufficient to determine the structure and behavior of deep convection. Wind shear—both directional and speed—is also known to exert a first order effect. The influence of both CAPE and wind speed shear is typically expressed as the ratio of the two parameters in the form of the Bulk Richardson Number. On Earth, for a fixed value of CAPE, the addition of wind speed shear (i.e., the reduction of the Bulk Richardson Number) will tend to produce storms that are longer lived, tilted upshear with height, and multi-cellular in nature. These multi-cellular storms also tend to be more violent than storms generated in low wind speed shear environments: strong winds and large hail are common. The addition of directional shear (i.e., helicity) can transform the multi-cell storms into single, intense supercell storms. These are the storms associated typically associated with tornadoes. With respect to Titan, if there is a similar dependence on the Bulk Richardson Number, then this would have implications for how long Titan's storms live, how much precipitation they can produce, the area they cover, and the strength and duration of winds. A series of numerical simulations of Titan's deep convective clouds from the Titan Regional Atmospheric Modeling System are presented. A reasonable sweep of the parameter space of CAPE and shear for

  9. Dissolution on Titan and on Earth: Towards the Age of Titan's Karstic-like Landscapes

    NASA Astrophysics Data System (ADS)

    Cornet, T.; Cordier, D.; Le Bahers, T.; Bourgeois, O.; Fleurant, C.; Le Mouelic, S.; Altobelli, N.

    2015-12-01

    Titan's polar surface is dotted with hundreds of lacustrine depressions. Their morphology suggests that their development would be associated to karstic-like processes, involving Titan's liquids (methane, ethane) dissolving the solid surface, presumably composed of organics and ices. In the present work, we test whether or not surface dissolution could be a major landshaping process on Titan using a solutional denudation rates model. The model is based on thermodynamics (solute solubility in solvents) and climatic (temperature, precipitation rates) parameters and has already been used to describe the dissolution of carbonates in karstic areas on Earth. It allows inference of rough formation timescales for topographic depressions of a given depth, developed by chemical erosion only. We computed and compared the denudation rates of pure solid organics in liquid hydrocarbons and of minerals in liquid water over Titan and Earth timescales. We then investigated the denudation rates of superficial organic layers in liquid methane over one Titan year. At this timescale, such a layer on Titan would behave like salts or carbonates on Earth depending on its composition, which means that dissolution processes would likely occur but would be 30 times slower on Titan compared to the Earth due to the seasonality of methane precipitation. Assuming that Titan's past climatic conditions remained close to the present ones, and assuming an average depth of 100 m for Titan's lacustrine depressions, these could have developed in a few tens of millions of years at polar latitudes higher than 70°N and S, and a few hundreds of million years at lower polar latitudes. The ages determined are consistent with the youth of the surface (<1 Gyr) and the repartition of dissolution-related landforms on Titan.

  10. From Titan to the primitive Earth

    NASA Astrophysics Data System (ADS)

    Raulin, F.; Gpcos Team

    Our knowledge of the conditions prevailing in the environment of the primitive Earth is still very limited, due to the lack of geological data. Fortunately, there are a few planetary objects in the solar system which present similarities with our planet, including during its early history. Titan is one of these. With a diameter of more than 5100 km, Titan, the largest moon of Saturn, is also the only one to have a dense atmosphere. This atmosphere, clearly evidenced by the presence of haze layers, extends to approximately 1500 km. Like the Earth, Titan's atmosphere is mainly composed of dinitrogen, N2 . The other main constituents are methane, CH4 , about 1.6% to 2.0% in the stratosphere, as measured by CIRS on Cassini and GC-MS on Huygens and dihydrogen (H2 , approximate 0.1%). With surface temperatures of approximately 94 K, and an average surface pressure of 1.5 bar, Titan's atmosphere is nearly five times denser than the Earth's. Despite of these differences between Titan and the Earth there are several analogies that can be drawn between the two planetary bodies. The first resemblances concern the vertical atmospheric structure. Although Titan is much colder, with a troposphere (˜94-˜70 K), a tropopause (70.4 K) and a stratosphere (˜70-175 K) its atmosphere presents a similar complex structure to that of the Earth. These analogies are linked to the presence in both atmospheres of greenhouse gases: CH4 and H2 on Titan, equivalent respectively to terrestrial condensable H2 O and non-condensable CO2 . In addition the haze particles and clouds in Titan's atmosphere play an antigreenhouse effect similar to that of the terrestrial atmospheric aerosols and clouds. Indeed, methane on Titan seems to play the role of water on the Earth, with a complex cycle, which still has to be understood. The possibility that Titan is covered with hydrocarbon oceans is now ruled out, but it is still possible that Titan's surface include lakes of methane and ethane. Moreover, the

  11. Afferent inhibition and the functional properties of neurons in the projection zone of the whiskers in the somatosensory cortex of the cat.

    PubMed

    Aleksandrov, A A

    2000-01-01

    The effects of afferent evoked inhibition on the functional properties of neurons in the whisker projection zone were studied in the cat brain. These investigations showed that afferent inhibition produced significant changes in the receptive fields of neurons, resulting in the induction of directional sensitivity. These data provide evidence for a defined topical ordering of intracortical inhibitory interactions. It is suggested that in natural conditions, movement of an object across the whisker field, resulting in sequential stimulation of the whiskers, results in sequential tuning of the detector properties of neurons receiving afferent flows from the whiskers. This process may form part of the mechanism for recognizing the direction of stimulus movement.

  12. Frequently Asked Questions on Potassium Iodide (KI)

    MedlinePlus

    ... needs to take potassium iodide (KI) after a nuclear radiation release? What potassium iodide (KI) products are currently ... needs to take potassium iodide (KI) after a nuclear radiation release? The FDA guidance prioritizes groups based on ...

  13. Hydroxyapatite Whisker Reinforced 63s Glass Scaffolds for Bone Tissue Engineering

    PubMed Central

    Shuai, Cijun; Cao, Yiyuan; Gao, Chengde; Feng, Pei; Xiao, Tao; Peng, Shuping

    2015-01-01

    Bioactive glass (BG) is widely used for bone tissue engineering. However, poor mechanical properties are the major shortcomings. In the study, hydroxyapatite nanowhisker (HANw) was used as a reinforcement to improve the mechanical properties. 63s glass/HANw scaffolds were successfully fabricated by selective laser sintering (SLS). It was found that the optimal compressive strength and fracture toughness were achieved when 10 wt.% HANw was added. This led to 36% increase in compressive strength and 83% increase in fracture toughness, respectively, compared with pure 63s glass scaffolds. Different reinforcement mechanisms were analyzed based on the microstructure investigation. Whisker bridging and whisker pulling-out were efficient in absorbing crack propagating energy, resulting in the improvement of the mechanical properties. Moreover, bioactivity and biocompatibility of the scaffolds were evaluated in vitro. The results showed that composite scaffolds with 10 wt.% HANw exhibited good apatite-forming ability and cellular affinity. PMID:25821798

  14. Silicon carbide whisker reinforced ceramic composites and method for making same

    DOEpatents

    Wei, George C.

    1985-01-01

    The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties especially increased fracture toughness. In the formation of these ceramic composites, the single crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al.sub.2 O.sub.3, mullite, or B.sub.4 C. The mixtures which contain a homogeneous dispersion of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600.degree. to 1950.degree. C. with pressing times varying from about 0.75 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MPa.m.sup.1/2 which represents as much as a two-fold increase over that of the matrix material.

  15. Silicon carbide whisker reinforced ceramic composites and method for making same

    DOEpatents

    Wei, George C.

    1993-01-01

    The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties especially increased fracture toughness. In the formation of these ceramic composites, the single crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al.sub.2 O.sub.3, mullite, or B.sub.4 C. The mixtures which contain a homogeneous disperson of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600.degree. to 1950.degree. C. with pressing times varying from about 0.075 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MPa.m.sup.1/2 which represents as much as a two-fold increase over that of the matrix material.

  16. Silicon carbide whisker reinforced ceramic composites and method for making same

    DOEpatents

    Wei, George C.

    1989-01-24

    The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties especially increased fracture toughness. In the formation of these ceramic composites, the single crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al.sub.2 O.sub.3, mullite, or B.sub.4 C. The mixtures which contain a homogeneous disperson of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600.degree. to 1950.degree. C. with pressing times varying from about 0.75 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MP.am.sup.1/2 which represents as much as a two-fold increase over that of the matrix material.

  17. Silicon carbide whisker reinforced ceramic composites and method for making same

    DOEpatents

    Wei, George C.

    1993-11-16

    The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties especially increased fracture toughness. In the formation of these ceramic composites, the single crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al.sub.2 O.sub.3, mullite, or B.sub.4 C. The mixtures which contain a homogeneous disperson of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1600.degree. to 1950.degree. C. with pressing times varying from about 0.075 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness of up to about 9 MPa.m.sup.1/2 which represents as much as a two-fold increase over that of the matrix material.

  18. Whisker growth studies under conditions which resemble those available on an orbiting space station

    NASA Technical Reports Server (NTRS)

    Hobbs, Herman H.

    1992-01-01

    Minimal funding was provided by NASA with one designated 'mission' being the clear demonstration of the relevance of previously supported whisker growth studies to microgravity research. While in one sense this work has shown the converse, namely, that ambient gravitational fields as high as 1 Earth normal have no relevance to growth of whiskers by hydrogen reduction of metal halides, a case is made that this does not demonstrate lack of relevance to microgravity research. On the contrary, the driving forces for this growth are precisely those which must be understood in order to understand growth in microgravity. The results described suggest that knowledge gained from this work may be highly fundamental to our understanding of the genesis of metal crystals. Time and money ran out before this work could be considered complete. At least another year's study and analysis will be required before publications could be justified.

  19. Cryptic mammalian species: a new species of whiskered bat (Myotis alcathoe n. sp.) in Europe

    NASA Astrophysics Data System (ADS)

    von Helversen, O.; Heller, K.-G.; Mayer, F.; Nemeth, A.; Volleth, M.; Gombkötö, P.

    2001-05-01

    The analysis of morphological, behavioural and genetic characters of whiskered bats revealed a new European bat species within the family Vespertilionidae. We describe the morphology, karyology, genetic similarity, ecology and distribution of Myotis alcathoe n. sp. It closely resembles Myotis mystacinus, Myotis brandtii and Myotis ikonnikovi in morphology, but all four species show clear genetic differences in two mitochondrial genes (ND1 and 12S rRNA). Myotis alcathoe n. sp. is the smallest species among the European whiskered bats and uses the highest-frequency echolocation calls of all the European Myotis species. It prefers to hunt in small valleys with deciduous trees and flowing water, which is an endangered habitat. Records from Greece and Hungary indicate a distribution range in south-eastern Europe.

  20. Aging effects on the fracture toughness of SiC whisker reinforced 2XXX aluminum alloys

    NASA Technical Reports Server (NTRS)

    Ratnaparkhi, P. L.; Rack, H. J.

    1989-01-01

    The effect of aging (at 150 C) time on the fracture toughness behavior of a 2XXX alloy (Al-3.55Cu-1.29Mg-0.01Fe-trace Mn) reinforced with 5 vol pct F-8 SiC whiskers was investigated by measuring hardness and electrical conductivity followed by fracture toughness tests on center-cracked specimens. The ageing time-hardening response plots showed that, independent of whisker orientation, the initial rapid increase in hardness was followed by a more gradual increase, with a broad hardness peak between 32 and 128 hrs of aging. Coincident with the hardness changes, the electrical conductivity initially decreased, reached a minimum, and then increased at aging times beyond 32 hrs. Examination by SEM indicated that the initial increase in hardness and decrease in conductivity was due to the GPB zone formation, while the subsequent increase in electrical conductivity and decrease in hardness (overaging) was due to S nucleation and growth.

  1. Silicon carbide whisker reinforced ceramic composites and method for making same

    DOEpatents

    Wei, G.C.

    1989-01-24

    The present invention is directed to the fabrication of ceramic composites which possess improved mechanical properties especially increased fracture toughness. In the formation of these ceramic composites, the single crystal SiC whiskers are mixed with fine ceramic powders of a ceramic material such as Al{sub 2}O{sub 3}, mullite, or B{sub 4}C. The mixtures which contain a homogeneous dispersion of the SiC whiskers are hot pressed at pressures in a range of about 28 to 70 MPa and temperatures in the range of about 1,600 to 1,950 C with pressing times varying from about 0.75 to 2.5 hours. The resulting ceramic composites show an increase in fracture toughness which represents as much as a two-fold increase over that of the matrix material.

  2. Sn whisker mitigation by a thin metallic-glass underlayer in Cu-Sn

    NASA Astrophysics Data System (ADS)

    Diyatmika, Wahyu; Chu, Jinn P.; Yen, Y. W.; Hsueh, C. H.

    2013-12-01

    This study investigates the effects of thin film metallic glass (TFMG) as an underlayer on the Sn whisker mitigation in the Cu-Sn couples. Samples with and without TFMG underlayers were subjected to various heat treatments at elevated temperatures up to 85 °C in monotonic and cyclic modes. TFMG underlayer effectively blocks the Cu/Sn interaction even with the thickness as thin as 25 nm. In addition, with very thin thickness, the introduction of TFMG underlayer is expected to yield insignificant degrees of compressive stress, which is anticipated to occur when the samples are exposed to thermal cycling. Their thin thickness and amorphous nature are considered beneficial to make TFMGs as a promising diffusion barrier for Sn whisker mitigation.

  3. Potassium bromide-associated panniculitis.

    PubMed

    Boynosky, N A; Stokking, L B

    2014-12-01

    Two cases of panniculitis associated with administration of potassium bromide in dogs are reported. Both dogs were treated with potassium bromide for idiopathic epilepsy for over 1 year. Dose increases in both cases were associated with panniculitis, characterised by painful subcutaneous nodules in a generalised distribution over the trunk. Nodule eruption waxed and waned in one dog and was persistent in the other. In both cases, panniculitis was accompanied by lethargy and pyrexia. Panniculitis, lethargy and pyrexia resolved and failed to recur after discontinuation of potassium bromide. No other cause of panniculitis could be determined for either dog. Panniculitis has been reported after administration of potassium bromide in humans and may be a form of drug-induced erythema nodosum. To the authors' knowledge, these are the first reports of potassium bromide-associated panniculitis in dogs.

  4. The Whisker Nuisance Task Identifies a Late-Onset, Persistent Sensory Sensitivity in Diffuse Brain-Injured Rats

    PubMed Central

    McNamara, Katelyn C.S.; Lisembee, Amanda M.

    2010-01-01

    Abstract Post-traumatic morbidity reduces the quality of life for traumatic brain injury (TBI) survivors by altering neuropsychological function. After midline fluid percussion injury (FPI), diffuse pathology in the ventral posterior thalamus suggests that somatosensory whisker function may be impaired post-injury. The goals of the present study were to design and validate a task to detect injury-induced somatosensory morbidity (Experiment 1), and to evaluate preliminary applications of the task (Experiment 2). In Experiment 1, male Sprague-Dawley rats were subjected to moderate FPI (∼1.9 atm) or sham injury. Over an 8-week time course, the whiskers on both mystacial pads were stimulated manually with an applicator stick in an open field for three 5-min periods. Behavioral responses in this whisker nuisance task were recorded using objective criteria (max score = 16). Sham animals were ambivalent or soothed by whisker stimulation (4.0 ± 0.8), whereas brain-injured rats showed aggravated responses at 1 week (6.7 ± 0.9), which became significant at 4 weeks (9.5 ± 0.5) and 8 weeks (8.4 ± 1.1) compared to sham injury, indicating chronic injury-induced sensory sensitivity. Total free serum corticosterone levels indicated a significant stress response in brain-injured (125.0 ± 17.7 ng/mL), but not uninjured animals (74.2 ± 12.2 ng/mL) in response to whisker stimulation. In Experiment 2, to evaluate applications of the whisker nuisance task, four additional uninjured and brain-injured groups were subjected to mild brain injury only, shaved whiskers after moderate brain injury, repeated whisker nuisance task stimulation after moderate brain injury, or regular opportunities for tactile exploration of an enriched environment after moderate brain injury over 4 weeks post-injury. The whisker nuisance task has the sensitivity to detect mild brain injury (7.7 ± 1.0), but morbidity was not mitigated by any of the neurorehabilitative

  5. Rat Whisker Movement after Facial Nerve Lesion: Evidence for Autonomic Contraction of Skeletal Muscle

    PubMed Central

    Heaton, James T.; Sheu, Shu-Hsien; Hohman, Marc H.; Knox, Christopher J.; Weinberg, Julie S.; Kleiss, Ingrid J.; Hadlock, Tessa A.

    2014-01-01

    Vibrissal whisking is often employed to track facial nerve regeneration in rats; however, we have observed similar degrees of whisking recovery after facial nerve transection with or without repair. We hypothesized that the source of non-facial nerve-mediated whisker movement after chronic denervation was from autonomic, cholinergic axons traveling within the infraorbital branch of the trigeminal nerve (ION). Rats underwent unilateral facial nerve transection with repair (N=7) or resection without repair (N=11). Post-operative whisking amplitude was measured weekly across 10 weeks, and during intraoperative stimulation of the ION and facial nerves at ≥18 weeks. Whisking was also measured after subsequent ION transection (N=6) or pharmacologic blocking of the autonomic ganglia using hexamethonium (N=3), and after snout cooling intended to elicit a vasodilation reflex (N=3). Whisking recovered more quickly and with greater amplitude in rats that underwent facial nerve repair compared to resection (P<0.05), but individual rats overlapped in whisking amplitude across both groups. In the resected rats, non-facial-nerve mediated whisking was elicited by electrical stimulation of the ION, temporarily diminished following hexamethonium injection, abolished by transection of the ION, and rapidly and significantly (P<0.05) increased by snout cooling. Moreover, fibrillation-related whisker movements decreased in all rats during the initial recovery period (indicative of reinnervation), but re-appeared in the resected rats after undergoing ION transection (indicative of motor denervation). Cholinergic, parasympathetic axons traveling within the ION innervate whisker pad vasculature, and immunohistochemistry for vasoactive intestinal peptide revealed these axons branching extensively over whisker pad muscles and contacting neuromuscular junctions after facial nerve resection. This study provides the first behavioral and anatomical evidence of spontaneous autonomic innervation

  6. Whisker Hair (Acquired Progressive Kinking of the Hair): An Indication for Finasteride 1 mg?

    PubMed Central

    Bagazgoitia, Lorea; Aboín, Sonsoles

    2016-01-01

    Acquired progressive kinking of the hair (APKH) and whisker hair are relatively rare conditions. To our knowledge, fewer than 25 cases have been reported in the English literature. We present the case of a 23-year-old man whose hair on the parietal and occipital areas changed and turned curlier and shorter. Patients suffering from APKH have higher risk of developing androgenetic alopecia and therefore finasteride 1 mg daily is proposed as an adequate treatment for these patients. PMID:27127372

  7. Relationship Between Iron Whisker Growth and Doping Amount of Oxide During Fe2O3 Reduction

    NASA Astrophysics Data System (ADS)

    Gong, Xuzhong; Zhao, Zhilong; Wang, Zhi; Zhang, Ben; Guo, Lei; Guo, Zhancheng

    2016-04-01

    Iron whisker growth during Fe2O3 doped with oxide reduced by CO was investigated by using in situ observation and scanning electron microscopy. The results indicated that the minimum doping amount (MDA) of various oxides, hindering the iron whisker growth, was different. The MDA of Al2O3, Li2O, Na2O, and K2O was 0.5, 0.4, 4, and 12 pct, respectively. From the reduction rate, it was found that Li2O, MgO, and Al2O3 had some suppressive effects on the Fe2O3 reduction process, thus, confining the growth of iron whisker. However, other oxides had some catalytic effects on the Fe2O3 reduction process (Fe2O3-Fe3O4-FeO-Fe), such as CaO, SrO, BaO, Na2O, and K2O. As long as their doping amount was enough, these oxides could inhibit the diffusion of the Fe atom. When the metal ionic radius in doped oxide was bigger than that of Fe3+, such as Ca2+, Sr2+, Ba2+, Na+, and K+, there were lots of spaces left in Fe2O3 doped with oxide after reduction, improving Fe atom diffusion. Consequently, their MDA was more than that of small radius to restrain the growth of iron whisker. Finally, the relationship between corresponding metal ionic radius, electron layer number, valence electron number, and MDA of oxide was expressed by using data fitting as follows: N_{{{{A}}y {{O}}x }} = 1.3 × 10^{ - 5} × {r_{{{{A}}^{x + } }}2 × √{n_{{{{A}}^{x + } }} } }/{f_{q }}

  8. Titan's upper atmospheric structure and ionospheric composition

    NASA Astrophysics Data System (ADS)

    Westlake, Joseph H.

    This Dissertation investigates the density structure of the neutral upper atmosphere and the composition of the ionosphere of Titan through Cassini observations. The highly extended atmosphere of Titan consists primarily of N2, CH4, and H2. The focus is on data extracted from the Ion and Neutral Mass Spectrometer (INMS) and the Cassini Plasma Spectrometer (CAPS) instruments onboard Cassini. The INMS, which is fundamentally a quadrupole mass spectrometer, measures the abundance of neutral and ion components with masses of 1--8 and 12--99 Da. The CAPS instrument consists of three subsystems of which the Ion Beam Spectrometer (CAPS-IBS) is used in this study to derive mass spectra of thermal ions up to 400 Da. in mass in Titan's ionosphere. From measurements of molecular nitrogen in Titan's upper atmosphere an atmospheric scale height is derived implying an effective temperature. From an analysis of 29 targeted flybys of Titan we find that the thermosphere is isothermal from an altitude of 1050 km to the exobase height with an average effective temperature of 153 K. The scale height, and hence the effective temperature, is found to be highly variable. We assess this variability against the relevant geospatial, solar, and magnetospheric parameters to determine which are highly correlated to the effective temperatures. Titan's thermospheric temperature is found to be controlled by variations in the magnetospheric plasma environment. No correlation is found to exist with respect to geospatial parameters (i.e., latitude or longitude) and anti-correlation is found with solar parameters implying that Titan's nightside is hotter than its dayside. Furthermore, Titan's thermosphere is found to respond to plasma forcings on timescales less than one Titan day. To investigate the composition of Titan's ionosphere we present a 1D photochemical model of Titan's dayside ionosphere constrained by Cassini measurements. We show that the production of the primary products of

  9. Titan's lower troposphere: thermal structure and dynamics

    NASA Astrophysics Data System (ADS)

    Charnay, B.; Lebonnois, S.

    2011-12-01

    A new climate model for Titan's atmosphere has been developed, using the physics of the IPSL Titan 2-dimensional climate model with the current version of the LMDZ General Circulation Model's dynamical core. The GCM covers altitudes from the surface to 500 km with the diurnal cycle and the gravitational tides included. 1. Boundary layer and thermal structure The HASI profile of potential temperature shows a layer at 300 m, an other at 800 m and a slope change at 2 km ([5],[2]). Dune spacing on Titan is consistent with a 2-3 km boundary layer ([3]). We have reproduced this profile (see figure) and interpreted the layer at 300 m as a convective boundary layer, the layer at 800 m is a residual layer corresponding to the maximum diurnal vertical extension of the PBL. We interpret the slope change at 2 km as produced by the seasonal displacement of the ITCZ. This layer traps the circulation in the first two km and is responsible of the dune spacing. Finally we interpret the fog discovered in summer polar region ([1]) has clouds produced by the diurnal cycle of the PBL (as fair weather cumulus on Earth). 2. Surface winds 2.1 Effect of gravitational and thermal tides We analysed tropospheric winds and the influence of both the thermal and the gravitational tides. The impact of gravitational tides on the circulation is extremely small. Thermal tides have a visible effect, though quite tenuous. 2.2 Effect of topography We produced topography maps derived from spherical harmonic interpolation ([6]) on the reference ellipsoid ([4]). Surface temperatures at high altitude appear higher that the ambient air. Vertical air movements produce anabatic winds developing on smooth and long slopes. This could be one of the main causes controlling the direction of surface winds and the direction of dunes. References [1] Brown et al.: Discovery of fog at the south pole of Titan, Astrophys. J. 706 (2009), pp. L110-L113 [2] Griffith et al.: Titan's Tropical Storms in an Evolving Atmosphere

  10. Spacecraft Exploration of Titan and Enceladus

    NASA Astrophysics Data System (ADS)

    Matson, D.; Coustenis, A.; Lunine, J. I.; Lebreton, J.; Reh, K.; Beauchamp, P.; Erd, C.

    2009-12-01

    The future exploration of Titan and Enceladus is very important for planetary science. The study titled Titan Saturn System Mission (TSSM) led to an announcement in which ESA and NASA prioritized future OPF missions, stating that TSSM is planned after EJSM (for details see http://www.lpi.usra.edu/opag/). The TSSM concept consists of an Orbiter that would carry two in situ elements: the Titan Montgolfiere hot air balloon and the Titan Lake Lander. This mission could launch in the 2023-2025 timeframe on a trajectory to arrive ~9 years later and begin a 4-year mission in the Saturnian system. At an appropriate time after arrival at Saturn, the montgolfiere would be delivered to Titan to begin its mission of airborne, scientific observations of Titan from an altitude of about 10 km above the surface. The montgolfiere would have a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) power system whose waste heat would warm the gas in the balloon, providing buoyancy. It would be designed to survive at least 6-12 months in Titan’s atmosphere. With the predicted winds and weather, it should be possible to circumnavigate the globe! Later, on a subsequent fly-by, the TSSM orbiter would send the Lake Lander to Titan. It would descend through the atmosphere making scientific measurements, much like Huygens did, and then land and float on one of Titan’s seas. This would be its oceanographic phase of making a physical and chemical assessment of the sea. The Lake Lander would operate for 8-10 hours until its batteries become depleted. Following the delivery of the in situ elements, the TSSM orbiter would then explore the Saturn system for two years on a tour that includes in situ sampling of Enceladus’ plumes as well as flybys of Titan. After the Saturn tour, the TSSM orbiter would go into orbit around Titan and carry out a global survey phase. Synergistic observations would be carried out by the TSSM orbiter and the in situ elements. The scientific requirements for

  11. Comparing Earth and Titan's atmospheric inventory

    NASA Astrophysics Data System (ADS)

    Bampasidis, Georgios; Coustenis, Athena; Solomonidou, Anezina; Moussas, Xenophon; Preka-Papadema, Panagiota

    2010-05-01

    Titan is currently the only confirmed exobiotic environment known to us. It is also perhaps the most intriguing object in our Solar System. Our understanding of Titan, and of the kronian system as a whole, has been greatly enhanced by the data returned by the Cassini/Huygens mission since 2004 and still operating on the spot. Thus, we know today that the thick atmosphere layer - covering the satellite's mysterious surface - is essentially made of nitrogen, with small amounts of methane and hydrogen. The combination among these mother molecules produces an exciting organic chemistry in Titan's atmosphere, with hydrocarbons and nitriles (one of the latter, HCN, is a prebiotic molecule). The organic chemistry, climate conditions, meteorology, methane cycle and other aspects of the surface make Titan an extremely important astrobiological place. We will summarize our current understanding of the analogues between Titan and Earth's atmospheres focusing on some compositional and climatological issues. After the Cassini/Huygens mission, there will remain several unanswered questions on the astrobiological aspects of the satellite that will require a future mission with an optimized orbital tour, specific in situ elements and advanced instrumentation, such as the Titan Saturn System Mission (Coustenis et al, 2009; Reh et al., 2009) studied in 2008. The TSSM orbiter with hi-resolution imagers and IR spectrometers onboard and the TSSM Montgolfier with an aerosol analyser and a meteorology package aboard will deeply investigate the Titan organic factory and its atmospheric diversity by performing long-term observations. Definitely, as Titan is a unique earth-like body in the solar system, the long experience of studying the terrestrial atmosphere gives us the tools to unveil the satellite's mysteries. On the other hand, Titan's science will significally contribute to the Earth's atmospheric knowledge, its evolution and chemistry and to the origin of life, as it certainly

  12. ISO observations of Titan with SWS/grating

    NASA Technical Reports Server (NTRS)

    Coustenis, A.; Encrenaz, T.; Salama, A.; Lellouch, E.; Gautier, D.; Kessler, M. F.; deGraauw, T.; Samuelson, R. E.; Bjoraker, G.; Orton, G.

    1997-01-01

    The observations of Titan performed by the Infrared Space Observatory (ISO) short wavelength spectrometer (SWS), in the 2 micrometer to 45 micrometer region using the grating mode, are reported on. Special attention is given to data from Titan concerning 7 micrometer to 45 micrometer spectral resolution. Future work for improving Titan's spectra investigation is suggested.

  13. High Resolution Camera for Mapping Titan Surface

    NASA Technical Reports Server (NTRS)

    Reinhardt, Bianca

    2011-01-01

    Titan, Saturn's largest moon, has a dense atmosphere and is the only object besides Earth to have stable liquids at its surface. The Cassini/Huygens mission has revealed the extraordinary breadth of geological processes shaping its surface. Further study requires high resolution imaging of the surface, which is restrained by light absorption by methane and scattering from aerosols. The Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft has demonstrated that Titan's surface can be observed within several windows in the near infrared, allowing us to process several regions in order to create a geological map and to determine the morphology. Specular reflections monitored on the lakes of the North Pole show little scattering at 5 microns, which, combined with the present study of Titan's northern pole area, refutes the paradigm that only radar can achieve high resolution mapping of the surface. The present data allowed us to monitor the evolution of lakes, to identify additional lakes at the Northern Pole, to examine Titan's hypothesis of non-synchronous rotation and to analyze the albedo of the North Pole surface. Future missions to Titan could carry a camera with 5 micron detectors and a carbon fiber radiator for weight reduction.

  14. Evaporation of Liquid Hydrocarbon Mixtures on Titan

    NASA Astrophysics Data System (ADS)

    Luspay-Kuti, Adrienn; Chevrier, V. F.; Rivera-Valentin, E. G.; Singh, S.; Roe, L. A.; Wagner, A.

    2013-10-01

    Besides Earth, Titan is the only other known planetary body with proven stable liquids on its surface. The hydrological cycle of these liquid hydrocarbon mixtures is critical in understanding Titan’s atmosphere and surface features. Evaporation of liquid surface bodies has been indirectly observed as shoreline changes from measurements by Cassini ISS and RADAR (Hayes et al. 2011, Icarus 211, 655-671; Turtle et al. 2011, Science 18, 1414-1417.), but the long seasons of Saturn strongly limit the time span of these observations and their validity over the course of an entire Titan year. Using a novel Titan simulation chamber, the evaporation rate of liquid methane and dissolved nitrogen mixture under Titan surface conditions was derived (Luspay-Kuti et al. 2012, GRL 39, L23203), which is especially applicable to low latitude transient liquids. Polar lakes, though, are expected to be composed of a variety of hydrocarbons, primarily a mixture of ethane and methane (e.g. Cordier et al. 2009, ApJL 707, L128-L131). Here we performed laboratory simulations of ethane-methane mixtures with varying mole fraction under conditions suitable for the polar regions of Titan. We will discuss results specifically addressing the evaporation behavior as the solution becomes increasingly ethane dominated, providing quantitative values for the evaporation rate at every step. These laboratory results are relevant to polar lakes, such as Ontario Lacus, and can shed light on their stability.

  15. First Titan-Centaur Launch Test

    NASA Technical Reports Server (NTRS)

    1974-01-01

    The first Titan/Centaur lifted off from Complex 41 at Cape Kennedy Air Force Station at 9:48 AM EDT. The Titan stages burned as programmed, but when the Centaur stage failed to ignite, the Range Safety Officer destroyed it. The new NASA rocket was launched on a proof of concept flight designed to prepare it for twin Viking launches to Mars in 1975 and other missions involving heavy payloads. The 160-foot-tall rocket combines the Air Force Titan III with the NASA high-energy Centaur final stage. The twin solid rocket boosters have a combined liftoff thrust of 2.4 million pounds. Aboard Titan/ Centaur on its proof of concept flight were a dynamic simulator of the Viking spacecraft and a small scientific satellite (SPHINX) designed to determine how high voltage solar cells, insulators, and conductors are affected by the charges particles in space. KSC's Unmanned Launch Operations Directorate conducted the launch. For more information about Titan and Centaur, please see Chapters 4 and 8, respectively, in Roger Launius and Dennis Jenkins' book To Reach the High Frontier published by The University Press of Kentucky in 2002.

  16. Impact-induced Climate Change on Titan

    NASA Astrophysics Data System (ADS)

    Zahnle, K. J.; Korycansky, D.

    2012-12-01

    Titan's thick atmosphere and volatile surface cause it to respond to big impacts like the one that produced the prominent Menrva impact basin in a somewhat Earth-like manner. Menrva was big enough to raise the surface temperature by 100 K. If methane in the regolith is generally as abundant as it was at the Huygens landing site, Menrva would have been big enough to double the amount of methane in the atmosphere, The extra methane would have drizzled out of the atmosphere over hundreds of years. Conditions may have been favorable for clathrating volatiles such as ethane. Impacts can also create local crater lakes set in warm ice but these quickly sink below the warm ice; whether the cryptic waters quickly freeze by mixing with the ice crust or whether they long endure under the ice remains a open question. Bigger impacts can create shallow liquid water oceans at the surface. If Titan's crust is made of water ice, the putative Hotei impact (a possible 800-1200 km diameter basin, Soderblom et al 2009) would have raised the average surface temperature to 350-400 K. Water rain would have fallen and global meltwaters would have averaged 50 m to as much as 500 m deep. The meltwaters may not have lasted more than a few decades or centuries at most, but are interesting to consider given Titan's organic wealth. After Menrva impact on Titan After Hotei impact on Titan

  17. Transient features in a Titan sea

    NASA Astrophysics Data System (ADS)

    Hofgartner, J. D.; Hayes, A. G.; Lunine, J. I.; Zebker, H.; Stiles, B. W.; Sotin, C.; Barnes, J. W.; Turtle, E. P.; Baines, K. H.; Brown, R. H.; Buratti, B. J.; Clark, R. N.; Encrenaz, P.; Kirk, R. D.; Le Gall, A.; Lopes, R. M.; Lorenz, R. D.; Malaska, M. J.; Mitchell, K. L.; Nicholson, P. D.; Paillou, P.; Radebaugh, J.; Wall, S. D.; Wood, C.

    2014-07-01

    Titan's surface-atmosphere system bears remarkable similarities to Earth's, the most striking being an active, global methane cycle akin to Earth's water cycle. Like the hydrological cycle of Earth, Titan's seasonal methane cycle is driven by changes in the distribution of solar energy. The Cassini spacecraft, which arrived at Saturn in 2004 in the midst of northern winter and southern summer, has observed surface changes, including shoreline recession, at Titan's south pole and equator. However, active surface processes have yet to be confirmed in the lakes and seas in Titan's north polar region. As the 2017 northern summer solstice approaches, the onset of dynamic phenomena in this region is expected. Here we present the discovery of bright features in recent Cassini RADAR data that appeared in Titan's northern sea, Ligeia Mare, in July 2013 and disappeared in subsequent observations. We suggest that these bright features are best explained by the occurrence of ephemeral phenomena such as surface waves, rising bubbles, and suspended or floating solids. We suggest that our observations are an initial glimpse of dynamic processes that are commencing in the northern lakes and seas as summer nears in the northern hemisphere.

  18. In/ITO whisker and optoelectronic properties of ITO films deposited by ion beam sputtering

    SciTech Connect

    Shen, Jung-Hsiung; Yeh, Sung-Wei; Teoh, Lay Gaik

    2012-07-15

    ITO films were deposited on a glass substrate using ion beam sputtering, with oxygen flow rates from 0.5 to 2 sccm. The films consisted of randomly oriented ITO nanoparticles and metallic indium (In) with {l_brace}101{r_brace} facets, following the specific crystallographic relationship of [010]{sub In}//[110]{sub ITO}; (001){sub In}//(001){sub ITO} with habit planes (100){sub In}//(011){sub ITO}, when fabricated using a low oxygen flow rate. Oxygen flow rate in excess of 2.0 sccm results in the growth of amorphous films. The epitaxial In nanoparticles probably act as seeds for the development of curved ITO whiskers as small as 10 nm and extend up to 100 nm in length along the [100] direction, with poorly defined shape, possibly due to the tapering and bending of the whisker to form a tilt boundary about the [011] zone axis of the ITO. The ITO whisker growth was facilitated by the In globular tips in the vapor-liquid-solid growth mechanism. The films prepared using a series of oxygen flow rates showed different chemical-bonding states, electric resistivity and optical transparency; as a result of phase and microstructural changes.

  19. Development of an artificial sensor for hydrodynamic detection inspired by a seal's whisker array.

    PubMed

    Eberhardt, William C; Wakefield, Brendan F; Murphy, Christin T; Casey, Caroline; Shakhsheer, Yousef; Calhoun, Benton H; Reichmuth, Colleen

    2016-01-01

    Nature has shaped effective biological sensory systems to receive complex stimuli generated by organisms moving through water. Similar abilities have not yet been fully developed in artificial systems for underwater detection and monitoring, but such technology would enable valuable applications for military, commercial, and scientific use. We set out to design a fluid motion sensor array inspired by the searching performance of seals, which use their whiskers to find and follow underwater wakes. This sensor prototype, called the Wake Information Detection and Tracking System (WIDTS), features multiple whisker-like elements that respond to hydrodynamic disturbances encountered while moving through water. To develop and test this system, we trained a captive harbor seal (Phoca vitulina) to wear a blindfold while tracking a remote-controlled, propeller-driven submarine. After mastering the tracking task, the seal learned to carry the WIDTS adjacent to its own vibrissal array during active pursuit of the target. Data from the WIDTS sensors describe changes in the deflection angles of the whisker elements as they pass through the hydrodynamic trail left by the submarine. Video performance data show that these detections coincide temporally with WIDTS-wake intersections. Deployment of the sensors on an actively searching seal allowed for the direct comparison of our instrument to the ability of the biological sensory system in a proof-of-concept demonstration. The creation of the WIDTS provides a foundation for instrument development in the field of biomimetic fluid sensor technology. PMID:27580063

  20. Synchrotron X-ray Microdiffraction Study of Whisker Growth in Sn Films

    NASA Astrophysics Data System (ADS)

    Liu, Wenjun; Ice, Gene

    2005-03-01

    A prototype three-dimensional x-ray crystal microscope is installed on beamline 34-ID at the Advanced Photon Source, Argonne National Lab, and has begun operation. The microscope has a routine spatial resolution of approximately 0.5 x 0.5 x 1.0 um^3. With scanning technique, spatially resolved microdiffraction measurements can be made in two or three dimensions. Properties that can be measured include the local crystalline phase, local texture (orientation), and the local strain tensors. One of its applications is to study the whiskers in Sn films, which is an example of anomalous grain growth and an area of long-standing interest to the application of Pb-free solder in electronic manufacturing. Recent measurements illustrated the ability of this newly developed crystal microscope to characterize the local orientation and strain of whiskers and near whisker regions. Research supported by the DOE, Division of Materials Sciences under contract with ORNL, operated by UT-Battelle, LLC. UNICAT is supported by ORNL, UIUC-MRL, NIST, and UOP Inc.

  1. Barrel cortical neurons and astrocytes coordinately respond to an increased whisker stimulus frequency

    PubMed Central

    2012-01-01

    Background Nerve cells program the brain codes to manage well-organized cognitions and behaviors. It remains unclear how a population of neurons and astrocytes work coordinately to encode their spatial and temporal activity patterns in response to frequency and intensity signals from sensory inputs. Results With two-photon imaging and electrophysiology to record cellular functions in the barrel cortex in vivo, we analyzed the activity patterns of neurons and astrocytes in response to whisker stimuli with increasing frequency, an environmental stimulus pattern that rodents experience in the accelerated motion. Compared to the resting state, whisker stimulation caused barrel neurons and astrocytes to be activated more synchronously. An increased stimulus frequency up-regulated the activity strength of neurons and astrocytes as well as coordinated their interaction. The coordination among the barrel neurons and astrocytes was fulfilled by increasing their functional connections. Conclusions Our study reveals that the nerve cells in the barrel cortex encode frequency messages in whisker tactile inputs through setting their activity coordination. PMID:22537827

  2. An Investigation of the Electrical Short Circuit Characteristics of Tin Whiskers

    NASA Technical Reports Server (NTRS)

    Courey, Karim J.

    2008-01-01

    Existing risk simulations make the assumption that when a free tin whisker has bridged two adjacent exposed electrical conductors, the result is an electrical short circuit. This conservative assumption is made because shorting is a random event that has a currently unknown probability associated with it. Due to contact resistance electrical shorts may not occur at lower voltage levels. In this experiment, we study the effect of varying voltage on the breakdown of the contact resistance which leads to a short circuit. From this data we can estimate the probability of an electrical short, as a function of voltage, given that a free tin whisker has bridged two adjacent exposed electrical conductors. Also, three tin whiskers grown from the same Space Shuttle Orbiter card guide used in the aforementioned experiment were cross-sectioned and studied using a focused ion beam (FIB). The rare polycrystalline structure seen in the FIB cross section was confirmed using transmission electron microscopy (TEM). The FIB was also used to cross section two card guides to facilitate the measurement of the grain size to determine that the tin plating on the card guides had a bright finish.

  3. Behavioral State Dependency of Neural Activity and Sensory (Whisker) Responses in Superior Colliculus

    PubMed Central

    Cohen, Jeremy D.

    2010-01-01

    Rats use their vibrissa (whiskers) to explore and navigate the environment. These sensory signals are distributed within the brain stem by the trigeminal complex and are also relayed to the superior colliculus in the midbrain and to the thalamus (and subsequently barrel cortex) in the forebrain. In the intermediate layers of the superior colliculus, whisker-evoked responses are driven by direct inputs from the trigeminal complex (trigeminotectal) and feedback from the barrel cortex (corticotectal). But the effects of the behavioral state of the animal on the spontaneous firing and sensory responses of these neurons are unknown. By recording from freely behaving rats, we show that the spontaneous firing of whisker sensitive neurons in superior colliculus is higher, or in an activated mode, during active exploration and paradoxical sleep and much lower, or in a quiescent/deactivated mode, during awake immobility and slow-wave sleep. Sensory evoked responses in superior colliculus also depend on behavioral state. Most notably, feedback corticotectal responses are significantly larger during the quiescent/deactivated mode, which tracks the barrel cortex responses on which they depend. Finally, sensory evoked responses depend not only on the state of the animal but also on the orienting response elicited by the stimulus, which agrees with the well known role of the superior colliculus in orienting about salient stimuli. PMID:20610783

  4. Support for the slip hypothesis from whisker-related tactile perception of rats in a noisy environment

    PubMed Central

    Waiblinger, Christian; Brugger, Dominik; Whitmire, Clarissa J.; Stanley, Garrett B.; Schwarz, Cornelius

    2015-01-01

    Rodents use active whisker movements to explore their environment. The “slip hypothesis” of whisker-related tactile perception entails that short-lived kinematic events (abrupt whisker movements, called “slips”, due to bioelastic whisker properties that occur during active touch of textures) carry the decisive texture information. Supporting this hypothesis, previous studies have shown that slip amplitude and frequency occur in a texture-dependent way. Further, experiments employing passive pulsatile whisker deflections revealed that perceptual performance based on pulse kinematics (i.e., signatures that resemble slips) is far superior to the one based on time-integrated variables like frequency and intensity. So far, pulsatile stimuli were employed in a noise free environment. However, the realistic scenario involves background noise (e.g., evoked by rubbing across the texture). Therefore, if slips are used for tactile perception, the tactile neuronal system would need to differentiate slip-evoked spikes from those evoked by noise. To test the animals under these more realistic conditions, we presented passive whisker-deflections to head-fixed trained rats, consisting of “slip-like” events (waveforms mimicking slips occurring with touch of real textures) embedded into background noise. Varying the (i) shapes (ramp or pulse); (ii) kinematics (amplitude, velocity, etc.); and (iii) the probabilities of occurrence of slip-like events, we observed that rats could readily detect slip-like events of different shapes against noisy background. Psychophysical curves revealed that the difference of slip event and noise amplitude determined perception, while increased probability of occurrence (frequency) had barely any effect. These results strongly support the notion that encoding of kinematics dominantly determines whisker-related tactile perception while the computation of frequency or intensity plays a minor role. PMID:26528148

  5. Long-period librations of Titan

    NASA Astrophysics Data System (ADS)

    Yseboodt, Marie; Van Hoolst, T.

    2013-10-01

    Because of its elliptical orbit around Saturn and its non-spherical mass distribution, Titan has longitudinal librations. Here we study the long-period librations of Titan and include deformation effects and the existence of a subsurface ocean. We take into account the fact that the orbit is not keplerian and has other periodicities than the main period of orbital motion around Saturn due to perturbations by the Sun, other planets and moons (in particular Iapetus). An orbital theory is used to compute the orbital perturbations due to these other bodies. We numerically evaluate the amplitude of the long-period librations for many interior structure models of Titan constrained by the mass, radius and gravity field. Measurements of these librations may give constrains on the interior structure of the icy satellites.

  6. Millimeter and Submillimeter Spectroscopy of Titan

    NASA Technical Reports Server (NTRS)

    Gurwell, Mark A.

    2003-01-01

    Our major goals for the first year of this program were to develop a general improved radiative transfer model of the atmosphere of Titan, and to accurately determine the global abundance of CO from observations obtained using the Owens Valley Radio Observatory Millimeter Array. Other goals were to reanalyze older data sets using the improved radiative transfer model and to observe other molecular species as time permitted. Our program was granted two Titan transits to measure the CO(2-1) rotational transition at low spatial resolution, and one transit to measure nitriles and organics in the 236-239 GHz spectral range. In year two, our program was granted two Titan transits to measure the CO(2-1) rotational transition at low spatial resolution, and one transit to measure nitriles and organics in the 236-239 GHz spectral range. The CO(2-1) observations were previously reported in a published paper

  7. Results from the Huygens probe on Titan

    NASA Astrophysics Data System (ADS)

    Lebreton, Jean-Pierre; Coustenis, Athena; Lunine, Jonathan; Raulin, François; Owen, Tobias; Strobel, Darrell

    2009-06-01

    The Cassini-Huygens mission, comprising the NASA Saturn Orbiter and the ESA Huygens Probe, arrived at Saturn in late June 2004. The Huygens probe descended under parachute in Titan's atmosphere on 14 January 2005, 3 weeks after separation from the Orbiter. We discuss here the breakthroughs that the Huygens probe, in conjunction with the Cassini spacecraft, brought to Titan science. We review the achievements ESA's Huygens probe put forward and the context in which it operated. The findings include new localized information on several aspects of Titan science: the atmospheric structure and chemical composition; the aerosols distribution and content; the surface morphology and composition at the probe's landing site; the winds, the electrical properties, and the implications on the origin and evolution of the satellite.

  8. Chapman Solar Zenith Angle variations at Titan

    NASA Astrophysics Data System (ADS)

    Royer, Emilie M.; Ajello, Joseph; Holsclaw, Gregory; West, Robert; Esposito, Larry W.; Bradley, Eric Todd

    2016-10-01

    Solar XUV photons and magnetospheric particles are the two main sources contributing to the airglow in the Titan's upper atmosphere. We are focusing here on the solar XUV photons and how they influence the airglow intensity. The Cassini-UVIS observations analyzed in this study consist each in a partial scan of Titan, while the center of the detector stays approximately at the same location on Titan's disk. We used observations from 2008 to 2012, which allow for a wide range of Solar Zenith Angle (SZA). Spectra from 800 km to 1200 km of altitude have been corrected from the solar spectrum using TIMED/SEE data. We observe that the airglow intensity varies as a function of the SZA and follows a Chapman curve. Three SZA regions are identified: the sunlit region ranging from 0 to 50 degrees. In this region, the intensity of the airglow increases, while the SZA decreases. Between SZA 50 and 100 degrees, the airglow intensity decreases from it maximum to its minimum. In this transition region the upper atmosphere of Titan changes from being totally sunlit to being in the shadow of the moon. For SZA 100 to 180 degrees, we observe a constant airglow intensity close to zero. The behavior of the airglow is also similar to the behavior of the electron density as a function of the SZA as observed by Ågren at al (2009). Both variables exhibit a decrease intensity with increasing SZA. The goal of this study is to understand such correlation. We demonstrate the importance of the solar XUV photons contribution to the Titan airglow and prove that the strongest contribution to the Titan dayglow occurs by solar fluorescence rather than the particle impact that predominates at night.

  9. Tidal Response of Titan's Lakes and Seas

    NASA Astrophysics Data System (ADS)

    Karatekin, O.; Demain, C.; Deleersnijder, E.

    2011-12-01

    The Cassini spacecraft has revealed a vast set of lakes/seas filled or partially filled with liquid hydrocarbons and empty lake basins in the high latitudes of Titan. The seas and lakes of Titan provide an opportunity to explore an exciting aqueous environment whose characteristics are very different from what we know on Earth. The lakes appear in various shapes and sizes and are filled with liquid hydrocarbons, primarily methane and ethane. Recently, the Cassini spacecraft provided observations suggesting for the first time temporal variations in lake surfaces. The variation in the shorelines can be explained by different hypothesis including evaporation and tides. During Titan's 16 day orbital period around Saturn, the time-dependent tidal response of the lakes may affect the shorelines. Although the estimated tidal amplitudes by theoretical consideration yield smaller than the observed depth changes on Ontario Lacus, tides can have more significant effects of other lakes/seas with tidal amplitudes up to several meters. In the present study, besides Ontario Lacus we also consider Ligeia Mare, one of three large methane seas discovered by Cassini in the northern hemisphere of Titan and the target for the discovery mission of Titan Mare Explorer (TiME). The tidal response of Titan's lakes an seas are investigated by means of two- dimensional nonlinear shallow water equations The governing partial differential equations on the sphere are solved using SLIM (Second-generation Louvain- la- Neuve Ice-Ocean Model - http://www.climate.be/SLIM). SLIM is a hydrodynamical model based on finite element method. As all general circulation models, it uses primitive variables as prognostic quantities. Partial differential equations are discretized on curved surfaces using triangular meshes. The mesh is generated from recursive subdivisions of the faces of an icosahedron using GMSH software.. The code has a wetting-drying algorithm. The simulations can take into account several

  10. TITAN'S TRANSPORT-DRIVEN METHANE CYCLE

    SciTech Connect

    Mitchell, Jonathan L.

    2012-09-10

    The mechanisms behind the occurrence of large cloud outbursts and precipitation on Titan have been disputed. A global- and annual-mean estimate of surface fluxes indicated only 1% of the insolation, or {approx}0.04 W m{sup -2}, is exchanged as sensible and/or latent fluxes. Since these fluxes are responsible for driving atmospheric convection, it has been argued that moist convection should be quite rare and precipitation even rarer, even if evaporation globally dominates the surface-atmosphere energy exchange. In contrast, climate simulations indicate substantial cloud formation and/or precipitation. We argue that the top-of-atmosphere (TOA) radiative imbalance is diagnostic of horizontal heat transport by Titan's atmosphere, and thus constrains the strength of the methane cycle. Simple calculations show the TOA radiative imbalance is {approx}0.5-1 W m{sup -2} in Titan's equatorial region, which implies 2-3 MW of latitudinal heat transport by the atmosphere. Our simulation of Titan's climate suggests this transport may occur primarily as latent heat, with net evaporation at the equator and net accumulation at higher latitudes. Thus, the methane cycle could be 10-20 times previous estimates. Opposing seasonal transport at solstices, compensation by sensible heat transport, and focusing of precipitation by large-scale dynamics could further enhance the local, instantaneous strength of Titan's methane cycle by a factor of several. A limited supply of surface liquids in regions of large surface radiative imbalance may throttle the methane cycle, and if so, we predict more frequent large storms over the lakes district during Titan's northern summer.

  11. Bound potassium in muscle II.

    PubMed

    Hummel, Z

    1980-01-01

    Experiments were performed to decide between the alternatives a) the ionized K+ is in a dissolved state in the muscle water, or b) a part of the muscle potassium is in a "bound' state. Sartorius muscles of Rana esculenta were put into glicerol for about one hour at 0-2 degrees C. Most of muscle water came out, but most of muscle potassium remained in the muscles. In contrast to this: from muscle in heat rigor more potassium was released due to glicerol treating than from the intact ones. 1. Supposition a) is experimentally refuted. 2. Supposition b) corresponds to the experimental results. PMID:6969511

  12. Cassini radar views the surface of Titan

    NASA Technical Reports Server (NTRS)

    Elachi, C.; Wall, S.; Allison, M.; Anderson, Y.; Boehmer, R.; Callahan, P.; Encrenaz, P.; Flamini, E.; Franceschetti, G.; Gim, Y.; Hamilton, G.; Hensley, S.; Janssen, M.; Johnson, W.; Kelleher, K.; Kirk, R.; Lopes, R.; Lorenz, R.; Lunine, J.; Muhleman, D.; Ostro, S.; Paganelli, F.; Picardi, G.; Posa, F.; Roth, L.

    2005-01-01

    The Cassini Titan Radar Mapper imaged about 1% of Titan's surface at a resolution of approximately 0.5 kilometer, and larger areas of the globe in lower resolution modes. The images reveal a complex surface, with areas of low relief and a variety of geologic features suggestive of dome-like volcanic constructs, flows, and sinuous channels. The surface appears to be young, with few impact craters. Scattering and dielectric properties are consistent with porous ice or organics. Dark patches in the radar images show high brightness temperatures and high emissivity and are consistent with frozen hydrocarbons.

  13. The latitudinal distribution of clouds on Titan.

    PubMed

    Rannou, P; Montmessin, F; Hourdin, F; Lebonnois, S

    2006-01-13

    Clouds have been observed recently on Titan, through the thick haze, using near-infrared spectroscopy and images near the south pole and in temperate regions near 40 degrees S. Recent telescope and Cassini orbiter observations are now providing an insight into cloud climatology. To study clouds, we have developed a general circulation model of Titan that includes cloud microphysics. We identify and explain the formation of several types of ethane and methane clouds, including south polar clouds and sporadic clouds in temperate regions and especially at 40 degrees in the summer hemisphere. The locations, frequencies, and composition of these cloud types are essentially explained by the large-scale circulation.

  14. Cassini radar views the surface of Titan

    USGS Publications Warehouse

    Elachi, C.; Wall, S.; Allison, M.; Anderson, Y.; Boehmer, R.; Callahan, P.; Encrenaz, P.; Flamini, E.; Franceschetti, G.; Gim, Y.; Hamilton, G.; Hensley, S.; Janssen, M.; Johnson, W.; Kelleher, K.; Kirk, R.; Lopes, R.; Lorenz, R.; Lunine, J.; Muhleman, D.; Ostro, S.; Paganelli, F.; Picardi, G.; Posa, F.; Roth, L.; Seu, R.; Shaffer, S.; Soderblom, L.; Stiles, B.; Stofan, E.; Vetrella, S.; West, R.; Wood, C.; Wye, L.; Zebker, H.

    2005-01-01

    The Cassini Titan Radar Mapper imaged about 1% of Titan's surface at a resolution of ???0.5 kilometer, and larger areas of the globe in lower resolution modes. The images reveal a complex surface, with areas of low relief and a variety of geologic features suggestive of dome-like volcanic constructs, flows, and sinuous channels. The surface appears to be young, with few impact craters. Scattering and dielectric properties are consistent with porous ice or organics. Dark patches in the radar images show high brightness temperatures and high emissivity and are consistent with frozen hydrocarbons.

  15. Composition of Titan's surface from Cassini VIMS

    USGS Publications Warehouse

    McCord, T.B.; Hansen, G.B.; Buratti, B.J.; Clark, R.N.; Cruikshank, D.P.; D'Aversa, E.; Griffith, C.A.; Baines, E.K.H.; Brown, R.H.; Dalle, Ore C.M.; Filacchione, G.; Formisano, V.; Hibbitts, C.A.; Jaumann, R.; Lunine, J.I.; Nelson, R.M.; Sotin, C.

    2006-01-01

    Titan's bulk density along with Solar System formation models indicates considerable water as well as silicates as its major constituents. This satellite's dense atmosphere of nitrogen with methane is unique. Deposits or even oceans of organic compounds have been suggested to exist on Titan's solid surface due to UV-induced photochemistry in the atmosphere. Thus, the composition of the surface is a major piece of evidence needed to determine Titan's history. However, studies of the surface are hindered by the thick, absorbing, hazy and in some places cloudy atmosphere. Ground-based telescope investigations of the integral disk of Titan attempted to observe the surface albedo in spectral windows between methane absorptions by calculating and removing the haze effects. Their results were reported to be consistent with water ice on the surface that is contaminated with a small amount of dark material, perhaps organic material like tholin. We analyze here the recent Cassini Mission's visual and infrared mapping spectrometer (VIMS) observations that resolve regions on Titan. VIMS is able to see surface features and shows that there are spectral and therefore likely compositional units. By several methods, spectral albedo estimates within methane absorption windows between 0.75 and 5 ??m were obtained for different surface units using VIMS image cubes from the Cassini-Huygens Titan Ta encounter. Of the spots studied, there appears to be two compositional classes present that are associated with the lower albedo and the higher albedo materials, with some variety among the brighter regions. These were compared with spectra of several different candidate materials. Our results show that the spectrum of water ice contaminated with a darker material matches the reflectance of the lower albedo Titan regions if the spectral slope from 2.71 to 2.79 ??m in the poorly understood 2.8-??m methane window is ignored. The spectra for brighter regions are not matched by the spectrum of

  16. Cryovolcanism on Titan and Enceladus

    NASA Astrophysics Data System (ADS)

    Sotin, C.

    2008-12-01

    of CO or CO2 [Matson et al., Icarus, 2007]. On Titan, the SAR (Synthetic Aperture Radar) and the VIMS (Visual and Infrared Mapping Spectrometer) images suggest that several morphological features could be formed by cryovolcanic activity [Sotin et al., Nature, 2005; Barnes et al., GRL, 2006; Lopes et al., Icarus, 2007]. Such volcanism would explain the recent release of methane and its presence in the atmosphere where its lifetime is a few tens of millions of years. In order to link thermal evolution models and cryovolcanic models, it is necessary to have laboratory data that describe the melting temperature of different kinds of ices including clathrate hydrates containing ammonia, methane, nitrogen and other volatiles. Since the melting temperature of ammonia is small compared to that of water ice, it is a good candidate for explaining flow features seen on Titan's surface. However, the presence of an ocean at depth makes unlikely the presence of ammonia in the icy crust. More sophisticated models must be found with species such as methane and CO2. This work has been carried out at the JPL, Caltech, under contract with NASA.

  17. Huygens GCMS Results from Titan

    NASA Technical Reports Server (NTRS)

    Niemann, Hasso B.; Demick, Jaime; Kasprzak, Wayne; Atreya, Sushil; Owen, Tobias

    2007-01-01

    The Huygens Probe executed a successful entry, descent and impact on the Saturnian moon of Titan on January 14, 2005. The Gas Chromatograph Mass Spectrometer (GCMS) instrument conducted isotopic and compositional measurements throughout the two and one half hour descent from 146 km altitude, and on the surface for 69 minutes until loss of signal from the orbiting Cassini spacecraft. The GCMS incorporated a quadrupole mass filter with a secondary electron multiplier detection system. The gas sampling system provided continuous direct atmospheric composition measurements and batch sampling through three gas chromatographic (GC) columns, a chemical scrubber and a hydrocarbon enrichment cell. The GCMS gas inlet was heated to prevent condensation, and to evaporate volatiles from the surface after impact. Data products from the GCMS included altitude profiles of the major atmospheric constituents dinitrogen (N2) and methane (CH4), isotope ratios of 14N/15N, 12C/13C, and D/H, mole fractions of radiogenic argon (40Ar) and primordial argon (36Ar), and upper limits on the mole fractions of neon, krypton and xenon, which were found to be absent. Surface measurements confirmed the presence of ethane (C2H6) and cyanogen (C2N2). Later data products expanded atmospheric profiles to include the surface response of C2N2. C2H6, acetylene (C2H2), and carbon dioxide (CO2). More recent results include the profiles of benzene (C6H6) and molecular hydrogen (H2). The GCMS data are being further analyzed to obtain higher precision results and to identify other trace species ion the atmosphere and evaporating from the surface.

  18. Endocannabinoid signaling is required for development and critical period plasticity of the whisker map in somatosensory cortex

    PubMed Central

    Li, Lu; Bender, Kevin J.; Drew, Patrick J.; Jadhav, Shantanu P.; Sylwestrak, Emily; Feldman, Daniel E.

    2009-01-01

    Summary Type 1 cannabinoid (CB1) receptors mediate widespread synaptic plasticity, but how this contributes to systems-level plasticity and development in vivo is unclear. We tested whether CB1 signaling is required for development and plasticity of the whisker map in rat somatosensory cortex. Treatment with the CB1 antagonist AM251 during an early critical period for layer (L) 2/3 development (beginning postnatal day [P] 12–16) disrupted whisker map development, leading to inappropriate whisker tuning in L2/3 column edges and a blurred map. Early AM251 treatment also prevented experience-dependent plasticity in L2/3, including deprivation-induced synapse weakening and weakening of deprived whisker responses. CB1 blockade after P25 did not disrupt map development or plasticity. AM251 had no acute effect on sensory-evoked spiking, and only modestly affected field potentials, suggesting that plasticity effects were not secondary to gross activity changes. These findings implicate CB1-dependent plasticity in systems-level development and early postnatal plasticity of the whisker map. PMID:19945395

  19. Effects of POSS-Silanol Addition on Whisker Formation in Sn-Based Pb-Free Electronic Solders

    NASA Astrophysics Data System (ADS)

    Liu, Sihan; Ma, Limin; Shu, Yutian; Subramanian, K. N.; Lee, Andre; Guo, Fu

    2014-01-01

    Previous studies have indicated that silanol in the form of polyhedral oligomeric silsesquioxane (POSS) trisilanol could form strong bonds with solder matrix without agglomeration, and inhibit diffusion of metal atoms when subjected to high ambient temperature and/or high current density. Addition of POSS-trisilanol has also been shown to improve the comprehensive performance of Sn-based Pb-free solders, such as shear strength, resistance to electromigration, as well as thermal fatigue. The current study investigated the whisker formation/growth behaviors of Sn-based Pb-free solders (eutectic Sn-Bi) modified with 3 wt.% POSS-trisilanol. Solder films on Cu substrates were aged at ambient temperature of 125°C to accelerate whisker growth. The microstructural evolution of the solder films' central and edge areas was examined periodically using scanning electron microscopy. Bi whiskers were observed to extrude from the surface due to stress/strain relief during growth of Sn-Cu intermetallic compounds (IMCs). Addition of POSS-trisilanol was shown to retard the growth of Bi whiskers. The IMCs formed between POSS-modified solders and the Cu substrate showed smoother surface morphology and slower thickness growth rate during reflow and aging. It was indicated that POSS particles located at the phase boundaries inhibited diffusion of Sn atoms at elevated temperatures, and thus limited the formation and growth of IMCs, which resulted in the observed inhibition of Bi whisker growth in POSS-modified solders.

  20. Heavy Ion Formation in Titan's Ionosphere: Magnetospheric Introduction of Free Oxygen and Source of Titan's Aerosols?

    NASA Technical Reports Server (NTRS)

    Sittler, E. C., Jr.; Hartle, R. E.; Cooper, J. F.; Johnson, R. E.; Coates, A.; dePater, imke; Strom, Daphne; Simoes, F.; Steele, A.; Robb, F.

    2007-01-01

    With the recent discovery of heavy ions, positive and negative, by the Cassini Plasma Spectrometer (CAPS) instrument in Titan's ionosphere, it reveals new possibilities for aerosol formation at Titan and the introduction of free oxygen to the aerosol chemistry from Saturn's magnetosphere with Enceladus as the primary oxygen source. One can estimate whether the heavy ions in the ionosphere are of sufficient number to account for all the aerosols, under what conditions are favorable for heavy ion formation and how they are introduced as seed particles deeper in Titan's atmosphere where the aerosols form and eventually find themselves on Titan's surface where unknown chemical processes can take place. Finally, what are the possibilities with regard to their chemistry on the surface with some free oxygen present in their seed particles?