EFFECT OF PRESSURE ON THE STRUCTURE

Fixed-Roof Tanks. The effect of internal pressure on plate structures, including tanks and pressure vessels, is important to tank design. If a flat plate is subjected to pressure on one side, it must be made quite thick to resist bending or deformation. A shallow cone-roof deck on a tank approximates a flat surface and is typically built of 3/ 16-in. (4.76-mm) thick steel (Fig. 4a). This is unable to withstand more than a few inches of water column pressure. The larger the tank, the more severe the effect of pressure on the structure. As pressure increases, the practicality of fabrication practice and costs force the tank builder to use shapes more suitable for internal pressure. The cylinder is an economic and easily fabricated shape for pressure containment. Indeed, almost all large tanks are cylindrical. The problem, however, is that the ends must be closed. The relatively flat roofs and bottoms or closures of tanks do not lend themselves to much internal pressure. As internal pressure increases, tank builders use roof domes or spheres. The spherical tank is the most economic shape for internal pressure storage in terms of required thickness, but it is generally more difficult to fabricate than a dome- or umbrella-roof tank because of its compound curvature. 

Gaballa GA and Neilson GW. The Effect of Pressure on the Structure of Light and Heavy Water. Mol Phys 1983 50 97-111. 

Evers, J., Oehlinger, G., and Weiss, A 1977. Effect of pressure on the structures of divalent metal disilicides (calcium, europium, strontium). J. Solid State Chem. 20 173-81. 

IR and Raman spectroscopy have been commonly used and, for example, the effects of pressure on the Raman spectrum of a zinc compound with a N2C12 coordination sphere around the metal, have been investigated.28 IR spectroscopy has been utilized in studies of the hydration of zinc in aqueous solution and in the hydrated perchlorate salt.29 Gas phase chemistry of zinc complexes has been studied with some gas phase electron diffraction structures including amide and dithiocarbamate compounds.30-32... 

The effect of pressure on the ground-state electronic and structural properties of atoms and molecules have been widely studied through quantum confinement models [53,69,70] whereby an atom (molecule) is enclosed within, e.g., a spherical cage of radius R with infinitely hard walls. In this class of models, the ground-state energy evolution as a function of confinement radius renders the pressure exerted by the electronic density on the wall as —dEldV. For atoms confined within hard walls, as in this case, pressure may also be obtained through the Virial theorem [69] ... 

Experiments with B-trideuterioborazine diow that the proton leaving the cation was originally bound to a B site and that the proton added to a second borazine molecule is boimd at a N site. The effect of pressure on the reaction chemistry is illustrated in Fig. 17. Borazine cation undergoes proton transfer reactions with a number of Bronsted bases. In all cases studied a proton bound to B in the cation is the one transferred. This indicates that the B-borazinyl radical (structure XX) is stable relative to the N-borazinyl isomer (XXI). 

The intrinsic parameters Bk depend only on the distance Rj and on the kind of ligand j located at (Rj, j,geometrical factors can be calculated once the structural changes under pressure have been determined for example by X-ray diffraction experiments. For the distance dependence of the intrinsic parameters Bk a simple power law is commonly assumed ... 

Kudoh, Y., Ito, E. Takeda, H. (1987) Effect of pressure on the crystal structure of the perovskite-ype MgSiOj. Phys. Chem. Minerals, 14, 350-4. 

Macdonald, A.G. (1984). The effects of pressure on the molecular structure and physiological functions of cell membranes. Phil. Trans. R. Soc. Ser. B 304 47-68. 

Liquids composed of optically anisotropic molecules have been studied quite intensely. In most of these studies, the interplay of allowed and induced components is of some concern. Dense hydrogen [419], nitrogen [453, 454, 575], carbon disulfide [447-450,484-487,518,529,629], carbon dioxide [489, 537, 552,610,618], clorine [471,601], hydrogen sulfide [542], bromine [520], other simple, linear molecules [432, 499, 606, 622], water and aqueous solutions [474, 538, 545, 547, 548], chloroform and similar molecules [516, 567-569, 576, 577, 595, 596, 617], and various organic liquids have been studied [452, 493, 502, 523, 524, 563, 564, 578, 581, 605, 611]. The spectra of small diatomics dissolved in argon have been reported [481]. Solutions of carbon tetrachloride have also been considered [551]. Hydrogen chloride has been studied [417]. The effects of pressure on the dynamic structure of liquids has been investigated [494-496]. 

Figure 5 The effect of pressure on the enantioselectivity of the asymmetric photoisomerization of cyclooctene using several benzene(poly)carboxylate sensitizers (see Fig. 3 for sensitizer structure).

If this parameter is assumed to be the same for all vibrations, one can obtain a bulk thermodynamic definition for y. The bulk Griineisen parameter is found to be about 4 for polymers from the effect of pressure on the velocity of sound. The data suggest that for the heat capacity only the interchain contribution should be taken into account. With this assumption, an order of magnitude calculation shows that the bulk Griineisen parameter for proteins is of the same order of magnitude as that of polymers. This suggests that the thermal expansion and the compressibility of proteins reflect primarily the movement between the secondary structures. These movements are reflected in the low frequency part of the... 

In some runs, structure I methane hydrate was found to metastably exist at higher pressures. Figure 4b shows the Raman spectra of structure I methane hydrate at 25 °C and at pressures of 125, 649 and 880 MPa. The shift of the methane peak for the small cavity from 2915 cm" to about 2921 cm, as pressure increases from 125 to 880 MPa, is in agreement with the shift reported by Nakano et al. [15], except the effect of pressure on the peak position is not as... 

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