Spots, dark

More recently the thermal decompn of single large ciysts of AP has been studied on a hot-stage microscope. It was found that the low temp decompn started on a cryst face as a dark spot which rapidly expanded into a hole which then spread thruout the cryst. The ciysts were not consumed, but a residue of finely powd AP was always left (Ref 45)... 

In this present study, we basically showed dependence of the number of reduced cobalt metal surface atoms on dispersion of cobalt oxides along with the presence of rutile phase in titania. Both XRD and SEM/EDX results (not shown) revealed good distribution of cobalt oxides over the titania support. However, it can not differentiate all samples containing various ratios of rutile/anatase phase. Thus, in order to determine the dispersion of cobalt oxide species on titania, a more powerful technique such as TEM was applied with all samples. The TEM micrographs for all samples are shown in Figure 1. The dark spots represented cobalt oxides species present after calcination of samples dispersing on titania consisting various... 

Subsequent to removal of fats by extraction with petroleum ether, and processing with ammonia, alkaloids of mate, cola, and cocoa were isolated by extraction with CHC13, and separated by thin layer chromatography. On UV irradiation, the alkaloids showed dark spots on a light fluorescent... 

What is the dark spot left on the inside of a light bulb when it bums out Seep. 109. 

Question 8.3 What Is the Dark Spot on the Inside of a Burned-Out Light Bulb 109... 

The dark spot on the inside of a burned-out light bulb is tungsten metal that has sublimed (vaporized from the solid) as a consequence of the heating of the tungsten filament to produce white light. 

Fig. 2 Sketch of perforated layers (PL) or catenoid structure, a Projection direction perpendicular to layers of perforated lamellar structure appears as a hexagonal honeycomb mesh, b Projection parallel to layers appears as rows of dark spots resulting from cross section of parts. Sketch according to [15]. Copyright 2001 American Chemical Society...

Figure 12.13. Image depicting the formation of precipitates, seen as small dark spots, in a palladium precursor solution after 1 day of storage. The image shown was taken of a drop of precursor solution that was dispensed onto a microscope slide and covered with a glass cover slide.

A class of enzymes that sometimes causes problems is the poly-phenoloxidases, which are present in the outer layers of the kernel. These enzymes can cause dark spots to appear in pastry offcuts that are being recycled, e.g. to make pie cases. The enzymes act on any minute bran particles that are present. 

The consumption of the oxime can be checked by thin-layer chromatography on silica gel G with the solvent system chloro-form/methanol (95/5 v/v) and a spray reagent consisting of 5% potassium dichromate in 40% sulfuric acid. The oxime appears as an immediate dark spot and the aziridine as a yellow spot. The checkers observed identical mobilities (Rf 0.8) for both compounds. 

Figure 8. STM image of the basal-plane surface of HOPG obtained in 1 M NaCl. Bias = 550 mV (tip +), it = 1 nA. Image was obtained in the fast scan mode. Dark spots, separated by 2.5 A, correspond to large tunneling currents.

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