Crystal increase

At lower temperatures, the crystals increase in size, and form networks that trap the liquid and hinder its ability to flow. The pour point is attained which can, depending on the diesel fuel, vary between -15 and -30°C. This characteristic (NF T 60-105) is determined, like the cloud point, with a very rudimentary device (maintaining a test tube in the horizontal position without apparent movement of the diesel fuel inside). 

At HOY speeds, the rate of increase in orientation levels off but the rate of crystallization increases dramatically. Air drag and inertial contributions to the threadline stress become large. Under these conditions, crystallization occurs very rapidly over a small filament length and a phenomenon called neck-draw occurs (68,75,76). The molecular stmcture is stable, fiber tensde strength is adequate for many uses, thermal shrinkage is low, and dye rates are higher than traditional slow speed spun, drawn, and heat-set products (77). 

The size of crystal increases with time gradually approaching an asymptotic value. The higher the stirring rate, the larger the primary crystal sizes. 

The factor n is required by the experimental conditions, under which the amount of incident radiation intercepted by the face of the crystal increases linearly with the order of reflection. The temperature factor corresponds to an estimated characteristic temperature of about 530° The /0-values used are those ofPauling and Sherman1). It is seen that the observed intensity relations (800) (600)... 

Surface crustation is caused by sucrose crystallization. It is characterized by hard white spots on the surface. It is remedied by the use of corn sirup solids and larger levels of hydrocolloids. During freezing in a continuous freezer there is ice separation caused by centrifugal separation of small ice crystals. Increase in mix viscosity by use of hydrocolloids inhibits this action. 

Lunsford and Leland (42) studied the reaction of hydrogen-deuterium exchange on crystals of MgO containing V-centers. As known, a Y-center in an ionic crystal, being a cationic vacancy with a hole localized near it, plays the role of an acceptor. These authors have found that the photocatalytic effect is intensified as the concentration of V-centers in a crystal increases, which is in accord with the experiments carried out by Kohn and Taylor. 

But as crystallization increases, the folds per chain should level off at a constant value. Even a few folds greatly diminishes the value of C, so in the region of high crystallinity we might approximate 5 0 and obtain from equation (14)... 

As the aspect ratio increases the number of terraces observed decreases, whilst the heights of terraces remain constant. The lateral spread of terraces increases as the aspect ratio increases. A greater number of terrace terminations are also observed when the aspect ratio of crystals increases. 

Frequency dependence on the temperature. The average frequency shifts with a change in the temperature The average wavenumber of the adipic acid crystals increases by 30 cm-1 from 0 to 300 K [2]. Greater shifts have been observed such as 70 cm-1 for CH3OH, or 52 cm-1 for CH3OD, between 170 K and 280 K [3,4],... 

The heat capacity models described so far were all based on a harmonic oscillator approximation. This implies that the volume of the simple crystals considered does not vary with temperature and Cy m is derived as a function of temperature for a crystal having a fixed volume. Anharmonic lattice vibrations give rise to a finite isobaric thermal expansivity. These vibrations contribute both directly and indirectly to the total heat capacity directly since the anharmonic vibrations themselves contribute, and indirectly since the volume of a real crystal increases with increasing temperature, changing all frequencies. The constant volume heat capacity derived from experimental heat capacity data is different from that for a fixed volume. The difference in heat capacity at constant volume for a crystal that is allowed to relax at each temperature and the heat capacity at constant volume for a crystal where the volume is fixed to correspond to that at the Debye temperature represents a considerable part of Cp m - Cv m. This is shown for Mo and W [6] in Figure 8.15. 

Imagine, on the contrary, that the two solids fill truncated cones, as illustrated in Fig. 19. Then, the exposed area A i of the small crystal increases when dm g dissolves from it, and the exposed area A 2 of the large crystal decreases when the dm g is deposited on it. The sum dA -dA, +dAj may easily be positive. It is true, that... 

The viscosity of thermotropic liquid crystals increases following the sequenee nematic< smectic A < smectic C. 

As a further comment to the advantage of the face by face method we can see in Figure 4 the morphology of the crystal seen along the c-axis. We can observe the dramatic variation of the shape when the supersaturation is moving from very low values to the highest ones and when the temperature of crystallization increases by only 10 C. 

Crystal Size Spread. Figure 3 shows that the size range of the crystals increases as the crystals grow. In Figure 7 the standard deviation of the distribution, cr is plotted against the mean size, L, for run 5. This plot is approximately linear, giving a slope q. 

Fig. 6.12, right) (Hund, 1981). As the aspect ratio of the goethite crystals increases (i. e. long, very thin needles) the sample develops a greenish tinge. 

An infrared spectrum is a plot of percent radiation absorbed versus the frequency of the incident radiation given in wavenumbers (cm ) or in wave length ( xm). A variation of this method, diffuse reflectance spectroscopy, is used for samples with poor transmittance, e.g. cubic hematite crystals. Increased resolution and sensitivity as well as more rapid collection of data is provided by Fourier-transform-IR (FTIR), which averages a large number of spectra. Another IR technique makes use of attenuated total reflectance FTIR (ATR-FTIR) often using a cylindrical internal reflectance cell (CIR) (e.g. Tejedor-Tejedor Anderson, 1986). ATR enables wet systems and adsorbing species to be studied in situ. 

Banes and Hailer [81] studied the effect of fluoride addition on the size and morphology of apatite crystals in close-to-physiological conditions. These authors in particular reported that fluoride uptake was accompanied by some anisotropic growth of the apatite crystals the width and/or thickness of the crystals increased with F uptake while no noticeable change in length was observed. In addition, LeGeros et al. [66] pointed out the decrease in calcium deficiency linked to a progressive fluoride incorporation. 

Intercalation of single crystals of 2H(a)-TaS2 may be carried out in a similar manner, although it is possible that, if the crystals are too large in surface area, intercalation may proceed only around the edges. It should be noted that the time for full intercalation of crystals increases with crystal dimensions. 

The adventitious discovery, in prehistory, of the analgesic soporific and the euphoriant properties of the dried sap from the flower bulb of the poppy, papaver somnifemm, has been treated too often elsewhere to warrant repetition. By the nineteenth century organic chemistry had advanced far enough so that the active principle from opium had been isolated, purified, and crystallized. Increasing clinical use of this compound, morphine (1-1), and its naturally occurring methyl ether codeine (1-2) disclosed a host of side effects, the most daunting of which was, and stUl is, these compounds propensity for inducing physical dependence. 

As the temperature of a crystal increases, it expands and the length of its bonds also increases though the bond valences do not change. In order to... 

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