Yield temperature dependence

Magnesium oxide exhibited high activity and high selectivity in the hydrogen transfer from alcohols to studied nitroarenes. Because of the limited space of the paper the complete amine yield - temperature dependence was shown only for nitrobenzene reduction (Table 1). However, also for other reactants the yield of the aminic product increased continously between the values obtained at the lowest (350°C) and the highest (450°C) reaction temperatures. Below 350°C the complete lack of activity of MgO in the studied transformation was noted. The same was observed by us earlier (ref. 2) in the case the catalytic transfer reduction of other functional groups. 

Similar information can be also obtained by the ESR linewidth as a function of temperature, dominated by the Elliott mechanism through the spin-orbit coupling. It could possibly yield temperature dependence of the electrical resistivity if it were analyzed together with the g-shift and/or g-shift anisotropy and the spin dynamics data. It is noteworthy that a variety of temperature dependences are uniformly understandable with a single formulation characteristic of one-dimensional electronic systems. This mechanism is observable only in polymers with heavy nuclei, such as alkali and sulphur. It is also worth noting that the dopant nuclei could contribute to the Elliott mechanism in the donor dopant systems. Contrary to this, nuclei in the acceptor dopants could contribute little, Such a difference reflects each electronic state. Further investigation makes clear these points. 

The primary emphasis in shock tube interferometric studies of the hydrogen-oxygen reaction has been on induction period phenomena. Recently, however, the entire postshock density profiles of a selection of rich, lean and near stoichiometric Ha-Oa-Ar mixtures have been studied by numerical integration of an assumed reaction mechanism. In this manner it was shown that the characteristic features of the profile prior to the end of the density plateau are essentially independent of the recombination kinetics. Thereafter, however, the shape of the profile is largely accounted for by termolecular reactions (e)-(g). Systematic variation of the termolecular rate coefficient values in experimental regimes where recombination is most sensitive to reactions if) or ig)> respectively, has yielded temperature-dependent expressions of the form kf< = AT for kf and kf believed valid over the range 1400-3000 K. The expression of Jacobs et al. was found satisfactory for kf. In all three cases, variation with temperature is small (1-0 m 0-5). Values at 1700 K, kf = 5-9 x 10 (cited above), kf z= 1-9 X 10 , and kf = 3-6 x 10 cm mole sec, are in excellent accord with those listed in Table 2.2. 

Other important experimental methods for elucidating the nature of chemical bonds in crystals are the study of the elastic and thermal properties and the determination of phonon spectra. Many of these properties can be regarded as thermodynamic stability criteria and are quantitative measures of the second derivatives of the bond energies with respect to the atomic spacing. Moreover, such investigations yield temperature dependences of the characteristic themodynamic functions. 

In these and later studies, the decay of excited atoms along the flow tube in the presence of a known concentration of reagent was measured deviations from plug flow of the carrier gas were corrected for. This system has also yielded temperature dependences of quenching rate constants for He(2 5,2 5). 

Sufficient tensile stress. Sufficiency here is difficult to define since it depends on a number of factors such as alloy composition, concentration of corrodent, and temperature. In some cases, stresses near the jdeld strength of the metal are necessary. In other cases, the stresses can be much lower. However, for each combination of environment and alloy system, there appears to be a threshold stress below which SCC will not occur. Threshold stresses can vary from 10 to 70% of yield strength depending on the alloy and environment combination and temperature (Fig. 9.6). 

In place of a complete evolutionary expression of normal softening and yield-strength recovery, Swegle and Grady [13] propose a temperature-dependent yield strength F(7]) in qualitative agreement with expected behavior... 

Many properties are temperature dependent. For example up to 100°C the yield stress drops with temperature at a faster rate than does the yield stress of polypropylene however, it retains some strength up to 160°C. 

Recently, Okahara and his co-workers have investigated a variety of one-pot crown ether syntheses which are referred to in Sects. 3.4, 4.3, 5.4. During the course of these investigations, they examined the temperature dependence of the cyclization yield . Using either sodium hydroxide or potassium hydroxide and forming 15-crown-5, 18-crown-6 and 21-crown-7, an attempt was made to correlate yield and reaction temperature. For most of the reactions, yield was recorded over the range from 20 ° — 120 °C... 

The experiments [2] yielded also a considerable temperature dependence of the conductivities - including solid phases too [3]. Hence, we are going to consider now the T dependence of the conductivity for the liquid alloys. 

The early study of brittle failures, notably those of the Liberty ships, indicated a temperature dependence. This can be illustrated by plotting both fracture stress (of) and yield stress (Oy) against temperature (Fig. 8.81). Below a certain temperature some materials exhibit a transition from ductile to brittle fracture mode. This temperature is known as the ductile-brittle transition temperature DBTT. 

Does yield stress depend on temperature Probably, not, and flow curves constructed at different temperatures look as is shown in Fig. 7, where the arrow indicates the direction of temperature increase. 

The temperature dependence of electrical conductivity has been used [365] to distinguish between the possible structural modifications of the Mn02 yielded by the thermal decomposition of KMn04. In studies involving additives, it is possible to investigate solid-solution formation, since plots of electrical conductivity against concentration of additive have a characteristic V-shape [366]. 

The use of ethyl ethylthiomethyl sulphoxide in this reaction leads to the desired addition products in much better yields (95-97%). These products were then converted into ketene dithioacetal monoxide derivatives 430 by a sequence of reactions (equation 258)505. Reaction of 2-lithio-l,3-dithiane-l-oxide with benzophenone affords a mixture of the diastereoisomeric tertiary alcohols 431 in a ratio which is temperature dependent (cis trans changes from 3 1 at — 78 °C to 1 1 at room temperature)268. 

Equilibrium vapor pressures were measured in this study by means of a mass spectrometer/target collection apparatus. Analysis of the temperature dependence of the pressure of each intermetallic yielded heats and entropies of sublimation. Combination of these measured values with corresponding parameters for sublimation of elemental Pu enabled calculation of thermodynamic properties of formation of each condensed phase. Previ ly reported results on the subornation of the PuRu phase and the Pu-Pt and Pu-Ru systems are correlated with current research on the PuOs and Pulr compounds. Thermodynamic properties determined for these Pu-intermetallics are compared to analogous parameters of other actinide compounds in order to establish bonding trends and to test theoretical predictions. 

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