Ramp pattern

The result obtained from a Hj (5%)/Ar (95%) - TPR/MS in a soak-ramp mode test is shown in Figure 3 for a sample of DESOX. The onset temperature found for H S release in this case, approximately 580°C, is substantially higher than 450°C, the typical onset temperature found in the propane-TPR/MS test. The result was essentially identical in terms of the onset temperature for H S release even when undiluted was used as the reactant. Unlike the propane-TPR/MS tests, where the reaction products are essentially HjS only with virtually negligible amounts of SOj, Hj-TPR/MS tests always showed both SOj and HjS. These data, notably the pattern of change in the rates of SOj and H2S released with temperature in Figure 3, clearly demonstrate, as expected, that the reduction of S to S in step 3 is a consecutive reaction. 

Unsteady-state mass transfer caused by excessively fast current or potential ramps. This is especially likely to occur in measurements involving laminar flow past elongated surfaces and in free-convection studies, in which the establishment of secondary flow patterns may require long times. A compromise between the time sufficient to reach steady-state transport and the time necessary to avoid bulk depletion and surface roughening (in metal deposition) is required, and is found most reliably by preliminary experimentation. 

Dimethyl-l,3-dioxan-5-one SAMP/RAMP hydra-zones j were used as dihydroxyacetonephosphate equivalents in the synthesis of C2 symmetric ketones (eq 5), aza sugars with novel substitution patterns, or C5 to C9 deoxy sugars. SAMP hydrazones of 2-oxo esters represent novel phosphoenolpyruvate (PEP) equivalents. a,a-Disubstituted spiroacetals are accessible via the alkylation of ketone SAMP/RAMP hydrazones. ... 

Changes in catalyst weight during exposure to SOj were measured by a SEIKO I 300 TGA system. TGA patterns were obtained within the temperature range from 25 to 800°C. The flow rate of the high purity He (99.9999%) carrier gas was 40 cmVmin, and the temperature ramping rate was 10°C/min, respectively. 

The Transformation of Cubic ice to Hexagonal Ice. In this set of experiments the transformation of the cubic fraction of the frozen pure water droplets was investigated as a function of annealing time at several different temperatures between 228 and 263 K. Emulsified droplets of Jvm 10 pm were cooled at a rate of 10 K min to 223 K, and then the temperature was rapidly ramped to the isothermal transformation temperature (Ttrans)-While the frozen droplets were held at Ttrans 0.2 K, the diffraction pattern between 20 = 39.3° to 44.3° was monitored. This covers the exclusive ice Ih reflection at 26 43.5° and the reflection common to both ice Ic and ice h at 20 40°. 

The acid site distributions of the catalysts were measured by a Datacat pulse micro-reactor/temperature programmer, using 200-300mg of the catalyst sample pretreated in N2 flow at 450°C for 3h and the temperature was brought down to 80°C where the catalyst sample was saturated with an anhydrous NH3 (Matheson). Then the sample was flushed in N2 flow at 100°C for 3h in order to remove the physisorbed ammonia on the catalyst surface. The desorption pattern was obtained with a temperature ramp of 12°C nrin upto 500°C. 

After an exposure of 20 L the surface topography changes in certain areas. Figure 4.18e shows such a location of the sample the circle marks the same area as the circle in Fig. 4.18d. Two different features were observed first, a large number of disc-like islands second, occasionally ramp-shaped features. The disclike islands have a diameter of 35 A and a height of about 3 A (see Fig. 4.19a). The patterned area appears to be rough compared to the smooth Gd or H/Gd surface on each terrace and is induced by the surface modification which will be... 

Fig. 4.18 STM images of a Gd(OOOl) film after total hydrogen exposures of 5 L (a), 10 L (b), and 20 L (c, d) all bars represent 20 nm. The Gd surface state is detectable as areas appearing higher on the same terrace in (a) whereas in (c) it is almost disappeared. It reappears after 40 min, as can be seen in (d) indicating the removal of hydrogen from the surface. After 20 L, two different types of surface pattern appear, e Small islands with disc-like shape 1 and ramps 2. Reprinted with permission from [19]. Copyright (2000) by the American Physical Society...

The ramps only appear in regions where disc-like island formation has already taken place and seem not to originate from chains of close packed disc-like islands since such an elevation should result in a step at aU border lines, as shown in Fig. 4.19a. In contrast a level inclination was found on one side and a step on the other side. Thus, the two surface pattern have a different origin. 

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