Experimental and Theoretical Investigation of HC5N Adsorption on Amorphous Ice Surface: Simulation of the Interstellar Chemistry

2008 ◽  
Vol 112 (35) ◽  
pp. 8024-8029 ◽  
Author(s):  
Anne Coupeaud ◽  
Nathalie Piétri ◽  
Alain Allouche ◽  
Jean-Pierre Aycard ◽  
Isabelle Couturier-Tamburelli
Keyword(s):  
Theoretical Investigation ◽  
Interstellar Chemistry ◽  
Amorphous Ice ◽  
Ice Surface

Experimental and simulated vibrational spectra of H2 absorbed in amorphous ice: Surface structures, energetics, and relaxations

1992 ◽  
Vol 97 (2) ◽  
pp. 753-767 ◽  
Author(s):  
Holly G. Hixson ◽  
Marek J. Wojcik ◽  
Matthew S. Devlin ◽  
J. Paul Devlin ◽  
V. Buch
Keyword(s):  
Vibrational Spectra ◽  
Surface Structures ◽  
Amorphous Ice ◽  
Ice Surface

Measurement of the Adsorption Energy Difference betweenOrtho- andPara-D2on an Amorphous Ice Surface

2008 ◽  
Vol 100 (5) ◽  
Author(s):  
L. Amiaud ◽  
A. Momeni ◽  
F. Dulieu ◽  
J. H. Fillion ◽  
E. Matar ◽  
...  
Keyword(s):  
Adsorption Energy ◽  
Energy Difference ◽  
Amorphous Ice ◽  
Ice Surface

Adsorbate-induced changes in the structure of amorphous thin films of ice

2003 ◽  
Vol 81 (1-2) ◽  
pp. 167-174 ◽  
Author(s):  
P Swiderek
Keyword(s):  
Film Growth ◽  
Band System ◽  
Vibrational Modes ◽  
Amorphous Thin Films ◽  
Amorphous Ice ◽  
Ice Surface ◽  
Ice Films ◽  
Reflection Absorption Infrared Spectroscopy ◽  
Uppermost Layer ◽  
Induced Changes

The effect of adsorption of thiophene on the infrared spectra of thin amorphous ice films deposited on Pt(111) is studied using reflection-absorption infrared spectroscopy (RAIRS). The changes within the RAIR spectra in the range of the O–H-stretching band system upon adsorption depend on the structure of the ice films and the temperature at which the thiophene is deposited. Preferred binding at the ice surface to sites that are most likely identical with dangling-H groups occurs only if adsorbate mobility is sufficiently high. Otherwise, random film growth is observed, i.e., formation of multilayer islands before the first layer of thiophene on ice is completed. The adsorbate-induced changes within the O–H-stretching band system of the ice films are different for these two situations. Binding to dangling-H sites is shown to influence more than the uppermost layer of the ice, whereas random deposition has an effect only on surface vibrational modes. PACS Nos.: 68.43Fg, 62.35Ja

Discrimination of monomer from multimer DNA disk-shaped toruses by freezeetch TEM

1984 ◽  
Vol 42 ◽  
pp. 210-211
Author(s):  
George C. Ruben ◽  
Kenneth A. Marx
Keyword(s):  
Biochemical Data ◽  
Dna Structures ◽  
Ice Surface ◽  
Double Stranded Dna ◽  
Data Support ◽  
Dna Organization ◽  
Trivalent Cations

In vitro collapse of DNA by trivalent cations like spermidine produces torus (donut) shaped DNA structures thought to have a DNA organization similar to certain double stranded DNA bacteriophage and viruses. This has prompted our studies of these structures using freeze-etch low Pt-C metal (9Å) replica TEM. With a variety of DNAs the TEM and biochemical data support a circumferential DNA winding model for hydrated DNA torus organization. Since toruses are almost invariably oriented nearly horizontal to the ice surface one of the most accessible parameters of a torus population is annulus (ring) thickness. We have tabulated this parameter for populations of both nicked, circular (Fig. 1: n=63) and linear (n=40: data not shown) ϕX-174 DNA toruses. In both cases, as can be noted in Fig. 1, there appears to be a compact grouping of toruses possessing smaller dimensions separated from a dispersed population possessing considerably larger dimensions.

The structure of membranes and membrane proteins embedded in amorphous ice

1992 ◽  
Vol 50 (1) ◽  
pp. 432-433
Author(s):  
Uwe Lücken ◽  
Joachim Jäger
Keyword(s):  
Phase Transition ◽  
Transition Temperature ◽  
Membrane Proteins ◽  
Phase Transition Temperature ◽  
Lipid Vesicles ◽  
Freezing Stress ◽  
Amorphous Ice ◽  
Different Temperatures ◽  
Band Pass ◽  
Lipid Polymorphism

TEM imaging of frozen-hydrated lipid vesicles has been done by several groups Thermotrophic and lyotrophic polymorphism has been reported. By using image processing, computer simulation and tilt experiments, we tried to learn about the influence of freezing-stress and defocus artifacts on the lipid polymorphism and fine structure of the bilayer profile. We show integrated membrane proteins do modulate the bilayer structure and the morphology of the vesicles.Phase transitions of DMPC vesicles were visualized after freezing under equilibrium conditions at different temperatures in a controlled-environment vitrification system. Below the main phase transition temperature of 24°C (Fig. 1), vesicles show a facetted appearance due to the quasicrystalline areas. A gradual increase in temperature leads to melting processes with different morphology in the bilayer profile. Far above the phase transition temperature the bilayer profile is still present. In the band-pass-filtered images (Fig. 2) no significant change in the width of the bilayer profile is visible.

A metal- coating Chamber for High-Resolution Cryo-SEM

1990 ◽  
Vol 48 (1) ◽  
pp. 418-419
Author(s):  
John G. Sheehan
Keyword(s):  
High Resolution ◽  
Colloidal Suspensions ◽  
Metal Coating ◽  
Colloidal Interactions ◽  
Amorphous Ice ◽  
High Vapor ◽  
Particulate Coatings ◽  
20 Nm ◽  
Film Nucleation ◽  
Coating Chamber

Improvements in particulate coatings for printable paper require understanding mechanisms of colloidal interactions in paper coating suspensions. One way to deduce colloidal interactions is to mage particle spacings and orientations at high resolution with cryo-SEM. Recent improvements in cryo-SEM technique have increased resolution enough to image particles in coating paints,vhich are sometimes smaller than 100 nm. In this report, a metal-coating chamber is described for preparation of colloidal suspensions for cryo-SEM at resolution down to 20 nm. It was found that etching is not necessary to achieve this resolution.A 120 K cryo-SEM sample will remain in an SEM for hours without noticeable condensation of imorphous ice. This is due to the high vapor pressure of vapor-condensed amorphous ice, measured by Kouchi. However, clean vacuum is required to coat samples with the thinnest possible continuous metal films which are required for high magnification SEM. Vapor contaminants, especially hrydrocarbons, are known to interfere with thin-film nucleation and growth so that more metal is needed to form continuous films, and resolution is decreased. That is why the metal-coating chamber in fig. 1 is designed for the cleanest possible vacuum. Feedthroughs for the manipulator md the shutter, which are operated during metal coating, are sealed with leak-proof stainless-steel Dellows. The transfer rod slides through a baseplate feedthrough that is double o-ring sealed.

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