Aluminum signal

Al MAS-NMR spectra of as-shynthesized samples of Si/Al 10 and 30 show a peak at 54-56 ppm corresponding to tetrahedral aluminum (15). After calcination in air, a peak centered at O ppm corresponding to octahedral aluminum (15) appears in the spectrum of the sample with the lowest Si/Al ratio. When the samples are exchanged two times with NHJ ions and calcined again, the octahedral aluminum signal also appears in the spectrum of the zeolite with Si/Al=30. 

This treatment enhances the intensity of the octahedral aluminum signal for the low Si/Al ratio. Table II shows the percentage of Al corresponding to tetrahedral and octahedral coordination in each case. 

Bennett, R. J. and C. M. Breen. 1991. The aluminum signal New dimensions to mechanisms of aluminum tolerance. Plant and Soil 134 153-166. 

The effect of etch time (30 sec vs. 180 sec) on the composition of a Ti-6-4 surface etched in hydrofluoric acid/ammonium orthophosphate solution was followed by two SIMS spectra shown in Figure 29.(33) The aluminum signal decreases with increasing etch time while the vanadium signal increases. Preferential etching of the aluminum-rich a phase relative to the vanadium-rich p phase by the etch leads to the decreased aluminum signal. 

The operation is quite simple One sets the frequency to the lowest value, adjusts the gain and phase to the desired sensitivity using a special calibration standard discussed below and performs a zero-compensation on a defect free zone of the standard. Now one is ready to test. As one slides the probe across the surface of an aluminum structure, a signal response will be indicative of the presence of corrosion or of the presence of a subsurface edge. 

To restore resolution, we proposed a signal processing method based on Papoulis deconvolution. We implemented this algorithm and tried to operate an improvement from an aluminum rod smaller than the wavelength. 

Smoke-Generating Devices. Smoke generators are used by the military for daytime obscuration and signaling. For field use where portable stable systems ate requited, pyrotechnic devices are often employed. The primary composition since the 1940s has been HC smoke, which generates a cloud of zinc chloride, ZnCl, smoke by a series of reactions between hexachloroethane, C2Clg(HC), zinc oxide, and aluminum (3) (eq. 4—6). The zinc regenerated in... 

Again, we use a condensed form of the seven-step strategy. A temperature change signals a heat flow. In this example, an increase in the temperature of the aluminum pan means that heat flows from the surroundings (including the stove) to the pan, which represents the system. As in Example, a diagram summarizes the process. 

Upon aluminum alkyl exposure the intensity of the EPR signals is reduced by 10-60% depending on the preparation condition. This can be interpreted as a further reduction of the Ti " centers in agreement with other experiments (see next section) however, the surface concentration of these sites varies considerably with preparation conditions. 

The steam treatment does however affect the Al-surroundings in the zeolite crystal. As seen in Fig. 2b, the intensity of both the tetragonally (at 0 ppm) and octahedrally (at 55 ppm) coordinated aluminum species decreases considerably after steam treatments for more than 4 h. Steam treatment for more than 8 h did not lead to a further decrease in the signal intensities. The decreases confirm that aluminum is extracted from the framework during the steaming process, as was also concluded from the 29Si MAS-NMR spectra (Fig. 1 b). This may lead to the formation of additional (micro) porosity, but the aluminum extraction could negatively affect the catalytic activity. 

Figure 2 (Left) shows the 27Al NMR spectra for the aluminosilicates. All of them displayed a tetrahedral incorporation of aluminum inside the silica network. That is corroborated by the signal at 55 ppm [9, 10] which also become more intense with the decreasing of Si/Al ratio. Octahedral aluminum was observed just for the samples with the lowest Si/Al ratio. Tetrahedral aluminum gives place to strong Bronsted acid sites, which were identified by the interaction of these groups with pyridine that generates a...

An important result of the multinuclear NMR investigations of 23— 25, 27, 28, and 31-35 is that the structures, in contrast to aggregates of monometalated secondary phosphanes and arsanes, are retained in solution. Thus, the phosphandiide derivatives here discussed show resonance signals in their 31P NMR spectra that are independent of concentration and temperature (see Table III). The 31P and 27A1 NMR chemical shifts of 23-25, 27, and 31-35 differ with respect to ring size of the clusters and electronic influences by the substituents at phosphorus and aluminum. 

Longhorn AAP is involved in the manufacuture of the 4.2 illuminating flares. Two sites, buildings B-7 and 34Y, were selected for dust and electrostatic measurements. In building B-7, 4.2 aluminum candles are processed while, in Building 34-Y, white signal flares are manufactured. 

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