ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • 1995-1999  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Monitoring surfaces on the molecular level during catalytic reactions at high pressure by sum frequency generation vibrational spectroscopy and scanning tunneling microscopy (1995)
    Springer
    Catalysis letters 34 (1995), S. 11-18 
    Details
    ISSN: 1572-879X
    Keywords: in situ catalysis ; propylene hydrogenation ; STM ; SFG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Sum frequency generation (SFG), using non-linear laser optics, detects vibrational spectra of submonolayer amounts of adsorbates with excellent energy and time resolution. Scanning tunneling spectroscopy (STM) is sensitive to the atomic surface structure; readily imaging defects, steps and kinks as well as stationary adsorbed species. Both of these techniques can be used during reactions at high pressures and temperatures to obtain molecular information in situ. We report studies of propylene hydrogenation over Pt(111) crystal surfaces at atmospheric pressures and 300 K using SFG and STM. Four surface species (2-propyl, π-bonded propylene, di σ-bonded propylene, and propylidyne) were identified; the first two being implicated as reaction intermediates. The platinum surface structure remains unchanged during the reaction, consistent with the structure insensitive nature of olefin hydrogénation. Propylene decomposition induced substantial surface reconstruction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00808316
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Spatially (nanometer) controlled hydrogenation and oxidation of carbonaceous clusters by the platinum tip of a scanning tunneling microscope operating inside a reactor cell (1996)
    Springer
    Catalysis letters 39 (1996), S. 5-17 
    Details
    ISSN: 1572-879X
    Keywords: catalysis ; nanofabrication ; STM
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Hydrocarbon clusters formed by the thermal decomposition of propylene on Pt(111) were rehydrogenated or oxidized with nanometer spatial resolution using the platinum tip of a scanning tunneling microscope (STM) at 300 K in atmospheric pressures of H2 or O2. The reaction rate shows a strong dependence on the oxygen or hydrogen pressures and on the tip-surface separation. The reaction stops when the Pt tip becomes contaminated with carbon, after the removal of ∼107–108 carbon atoms, but can be regenerated by removing material from the tip by application of a voltage pulse. Dissociative adsorption of H2 and O2 on the tip, followed by transfer of atoms to the surface is the proposed mechanism of these tip-catalyzed reactions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00813723
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    facet.materialart.
    Unknown
    Changes in gravity inhibit lymphocyte locomotion through type I collagen (1997)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Immunity relies on the circulation of lymphocytes through many different tissues including blood vessels, lymphatic channels, and lymphoid organs. The ability of lymphocytes to traverse the interstitium in both nonlymphoid and lymphoid tissues can be determined in vitro by assaying their capacity to locomote through Type I collagen. In an attempt to characterize potential causes of microgravity-induced immunosuppression, we investigated the effects of simulated microgravity on human lymphocyte function in vitro using a specialized rotating-wall vessel culture system developed at the Johnson Space Center. This very low shear culture system randomizes gravitational vectors and provides an in vitro approximation of microgravity. In the randomized gravity of the rotating-wall vessel culture system, peripheral blood lymphocytes did not locomote through Type I collagen, whereas static cultures supported normal movement. Although cells remained viable during the entire culture period, peripheral blood lymphocytes transferred to unit gravity (static culture) after 6 h in the rotating-wall vessel culture system were slow to recover and locomote into collagen matrix. After 72 h in the rotating-wall vessel culture system and an additional 72 h in static culture, peripheral blood lymphocytes did not recover their ability to locomote. Loss of locomotory activity in rotating-wall vessel cultures appears to be related to changes in the activation state of the lymphocytes and the expression of adhesion molecules. Culture in the rotating-wall vessel system blunted the ability of peripheral blood lymphocytes to respond to polyclonal activation with phytohemagglutinin. Locomotory response remained intact when peripheral blood lymphocytes were activated by anti-CD3 antibody and interleukin-2 prior to introduction into the rotating-wall vessel culture system. Thus, in addition to the systemic stress factors that may affect immunity, isolated lymphocytes respond to gravitational changes by ceasing locomotion through model interstitium. These in vitro investigations suggest that microgravity induces non-stress-related changes in cell function that may be critical to immunity. Preliminary analysis of locomotion in true microgravity revealed a substantial inhibition of cellular movement in Type I collagen. Thus, the rotating-wall vessel culture system provides a model for analyzing the microgravity-induced inhibition of lymphocyte locomotion and the investigation of the mechanisms related to lymphocyte movement.
    Keywords: Life Sciences (General)
    Type: In vitro cellular & developmental biology. Animal (ISSN 1071-2690); Volume 33; 5; 398-405
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...