Value contrast

Static stress A stress whose magnitude remains at a constant value. Contrast with cyclic stress. 

We have developed another bench for the measurement of the contrast value. Contrast measurement have been carried out on the MMA fabricated by Texas Instrument, in order to establish the test procedure (Zamkotsian et al., 2002a Zamkotsian et al., 2003). We can address several parameters in our experiment, as the size of the source, its location with respect to the micro-elements, the wavelength, and the input and output pupil size. In order to measure the contrast, the micro-mirrors are tilted between the ON position (towards the spectrograph) or the OFF position (towards a light trap). Contrast exceeding 400 has been measured for a 10° ON/OFF angle. Effects of object position on the micro-mirrors and contrast reduction when the exit pupil size is increasing have also been revealed. 

The pz ring has a dished geometry, the pyrrole rings being inclined by between 8 and 17° with respect to their associated central N4 planes, away from the metal center (the comparable values in the porphyrin structure are between 12° and 19°). The N4 centroid-- centroid distance between the pz rings is significantly shorter at 2.43 A than in the porphyrin case (2.75 A). The molecules pack to form stepped stacks with a Ce -Ce separation of 9.62 A and a lateral offset of 6.07 A. This value contrasts with a total absence of... 

Selectivity. Economy implies a sense of brevity. It is necessary that an artist know what is and what is not essential to accomplish his or her purpose. Kasimir Malevich painted White on White, a white square painted on a white square ground, the two squares having almost no value contrast. He felt these squares alone would create a certain tension in the viewer... 

In this chapter, the last of the five elements, light and dark contrast, or value contrast, is examined in detail. Students will use value contrast, along with the other elements and principles of good composition, to create works of art that incorporate as subject matter molecular models depicting a variety of molecular geometric shapes. The artistic movements of fauvism, cubism, and surrealism will be explored and examined because their techniques are used to create modern art. 

In chemistry, as well as in art, we look for organizational systems to help us understand our subject matter. The five elements of art—color, line, shape, texture, and value contrast—are guidelines for evaluating a work of art. The periodic table is the means for assembling information about the chemical elements. It provides the basis for determining the molecular shape of many molecules. 

In X-ray diffraction pictures, atomic nuclei reflect X-rays onto photographic film, resulting in a pattern of dark-colored spots against a light-colored background. This value contrast in the picture allows the scientist to determine the position of atoms in a crystal or in a molecule. There are many uses for light-dark contrast. 

Students will apply the principles and techniques of value contrast, fauvism, cubism, and surrealism in creating drawings of molecular models. 

A black pencil should be used for the first drawing (leftmost rectangle), which will be realistic, emphasizing value contrast ... 

We have studied color, line, shape, texture, and value contrast as the elements that, together, make a complete work of art. These are the puzzle pieces that fit together to make the entire picture. There are many ways to use these pieces to compose a work of art. In the next chapter we use new techniques to organize the five elements into a pleasing work of art. The same puzzle pieces will be placed together in new ways, with interesting results. 

Figure 2. Thinning curves for PMMA and various blends containing (a) 50%, (b) 33%, (c) 20%, and (d) 0% CO by weight. The numbers in parentheses give the fraction of isopropyl alcohol in the solvent (balance of MIBK). The gamma value (contrast) also is given.

The results obtained for Mixl are amazing 36.3% of the APS used ended up inside the particles (Table IV). This value contrasts sharply with the small amount found in the coating reaction, even though the concentrations used there were higher. The APS did not end up as a surface coating, as is indicated by the very low amount of Q4. This result can only be explained if the APS is distributed through a large portion of the colloid. 

The HC204 HC200 ratio increased from 2.1 1 in nonpregnant rats to 2.6 1 in the pregnant rat. The uterine values contrasted to that found in the rat portal vein,... 

Curro et al. [1981] followed a similar procedure in studies of the aging kinetics of poly(methyl methacrylate) (PMMA). For predicting the shift factors of aging experiments at 23°C, the authors computed from PVT the free-volume function, h = h P, V), and then substituted these into Doolittle s equation (6.63). The resulting prediction agreed with the experimental values, contrasting with the inadequacy of the WLF relation. Next, the polymer aging process was modeled as a diffusion of free volume [Curro et al., 1982]. 

As in other areas of organic chemistry, computational investigations have provided important insights into the nature of carbanions, and the results complement the experimental studies. For example, ab initio calculations suggest that the inversion barrier of a methyl anion is ca. 2.2kcal/mol and that the inversion barrier of the ethyl anion is 3.3 kcal/mol. These values contrast with the <0.2 kcal/mol inversion barrier of the resonance-stabilized cyanomethyl anion on the one hand and the ca. 15 kcal/mol barrier for inversion of the cyclopropyl anion via a highly strained transition structure on the other hand. By comparison, the inversion barrier of ammonia is about 5.5 kcal/mol. ... 

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