Stone studies

A number of cycloadducts have been prepared from substituted acridizinium salts. Bradsher and Stone studied the rate of addition of st30-ene to acridizinium salts having methyl groups at the meso (6,11) positions. 

D. Kupperman, who contributed to the initiation of surface roughness/ recession monitoring, and K. Reimann of the Materials Science and Technology Division. The valuable advice and support of the Stone Study Committee organized by NFS and of S. Sherwood and R. Herrmann, Research Coordinator and Chairman, respectively, of the NAPAP Materials Effects Group, also are gratefully acknowledged. 

Fig. 19.9. Urethral stone studied with sonourethrography. Longitudinal scan of the urethra after fluid distension with saline solution reveals the stone (curved arrow) producing occlusion of the urethral lumen...

A variety of methods have been used to determine the energy of stabiUzation of a carbocation by a /J-silicon substituent. Li and Stone studied the association of the trimethylsilicenium ion with alkenes in a mass spectrometer and have calculated the /S-silyl stabilization energies for the carbocations produced as shown in Table 2. 

De Witte, E. (1975). Soluble nylon as consolidation agent for stone. Studies in Conservation, 20(1), 30-34. 

Frediani, P., Manganelli del F4, C., Matteoli, U., Tiano, P. (1982). Use of perfluoropolyethers as water repellents study of their behaviour on pietra serena, a Florentine building stone. Studies in Conservation, 27(1), 31-37. 

Two nucleation processes important to many people (including some surface scientists ) occur in the formation of gallstones in human bile and kidney stones in urine. Cholesterol crystallization in bile causes the formation of gallstones. Cryotransmission microscopy (Chapter VIII) studies of human bile reveal vesicles, micelles, and potential early crystallites indicating that the cholesterol crystallization in bile is not cooperative and the true nucleation time may be much shorter than that found by standard clinical analysis by light microscopy [75]. Kidney stones often form from crystals of calcium oxalates in urine. Inhibitors can prevent nucleation and influence the solid phase and intercrystallite interactions [76, 77]. Citrate, for example, is an important physiological inhibitor to the formation of calcium renal stones. Electrokinetic studies (see Section V-6) have shown the effect of various inhibitors on the surface potential and colloidal stability of micrometer-sized dispersions of calcium oxalate crystals formed in synthetic urine [78, 79]. 

Apparently a negative AP with Q < 90° can be found for particular pore geometries [53]. A different type of water repellency is desired to prevent the deterioration of blacktop roads consisting of crushed rock coated with bituminous materials. Here the problem is that water tends to spread into the stone-oil interface, detaching the aggregate from its binder [54]. No entirely satisfactory solution has been found, although various detergent-type additives have been found to help. Much more study of the problem is needed. 

The range of systems that have been studied by force field methods is extremely varied. Some force fields liave been developed to study just one atomic or molecular sp>ecies under a wider range of conditions. For example, the chlorine model of Rodger, Stone and TUdesley [Rodger et al 1988] can be used to study the solid, liquid and gaseous phases. This is an anisotropic site model, in which the interaction between a pair of sites on two molecules dep>ends not only upon the separation between the sites (as in an isotropic model such as the Lennard-Jones model) but also upon the orientation of the site-site vector with resp>ect to the bond vectors of the two molecules. The model includes an electrostatic component which contciins dipwle-dipole, dipole-quadrupole and quadrupole-quadrupole terms, and the van der Waals contribution is modelled using a Buckingham-like function. 

Rodger P M, A J Stone and D J Tildesley 1988. The Intermolecular Potential of Chlorine. A Three Phase Study. Molecular Physics 63 173-188. 

Exa.mina.tlon, The technical examination of stone objects begins with the use of the low power stereomicroscope. This study yields information regarding toolmarks and, hence, cutting techniques, wear patterns, and wear of toolmark edges. Such information is clearly significant in authenticity studies, but also provides an insight into the skill and the tools of the carver. 

N. S. Brommelle and P. Smith, eds.. Case Studies in the Conservation of Stone and Wall Paintings, The International Institute for the Conservation of Historic and Artistic Works, London 1986. 

Additional improvements have been incorporated since 1966 with the availabihty of thinner float glass. Glass thickness and interlayer thickness have been studied to optimize the product for occupant retention, occupant injury, and damage to the windshield from external sources (30,31). The thinner float glass windshields are more resistant to stone impacts than the early plate glass windshields. The majority of laminated windshields are made of two pieces of 2—2.5 mm aimealed glass and 0.76 mm of controlled adhesion interlayer. 

The discovery and use of metals at the end of the Stone Age was one of the most important steps in the development of modem technology. Most base metals are, unfortunately, not stable. In unfavorable environments they can be destroyed at variable rates by corrosion. The study of such corrosion reactions and the methods by which corrosion of metals can be fought is a task of great economic significance. 

Go to a standard handbook like Perry s Chemical Engineer s Handbook and obtain several hydraulic conductivities (say for sand, crushed stone, gravel, diatomaceous earth, other). Assume a constant head of fluid over a bed of each material, and apply Darcy s law to calculate flowrates and compare the results. Try several hydraulic head calculations and plot the results. Which of the materials studied shows the highest hydraulic resistance ... 

Sapphyrins were discovered serendipitously by Woodward33 during the course of synthetic studies directed towards the total synthesis of vitamin B, 2. The sapphyrins were the first example of expanded porphyrins in the literature. Due to sapphyrin exhibiting a deep-blue color in the crystalline state and intense green in solution. Woodward coined the expression sapphyrin with reference to the deep-blue color of sapphire stones. 

Stone et al. 43, 60, 61) have studied reactions of nickel and palladium isocyanides and a number of fluorocarbons which give a remarkable variety of products. With Ni(CNBu )4 and fluoroolefins [C2F4, (CF3)2C=C(CN)2 and CF2 = CFCF = CF2] themetallocyclic complexes (XXXIV), (XXXV), and (XXXVI) are observed 60,61) the complex Ni(CNBu )2(CjF5), analo-... 

Glasgow LA, Hua J, Yiin TY, Erickson LE (1992) Experimental studies of interfacial phenomena in sparged reactors. In Tatterson GB, Calabrease RV (eds) Process mixing chemical biochemical applications. AIChE Syposium Series 286 Garcia-Briones MA, Brodkey RS, Chalmers JJ (1994) Chem Eng Sci 49 2301 Boulton-Stone JM, Blake JR (1993) J Fluid Mech 254 437... 

The alchemists Zosimos and Stephanos, writing in Alexandria during the first Christian centuries, had described the chemical process in the form of a story of ritual sacrihce incorporating priest and initiates. In a well-known study, Mircea Eliade sought for the origins of such bloody accounts in ancient shamanism and metal-smithing. The materials of the stone, like the human body and soul, died and underwent purihcation, prior to their resurrection in a glorious body. 

In contrast to SCCO2, the conditions required to obtain SCH2O are harsh. In particular the temperature requirement of 374 °C precludes its synthetic utility for most organic compounds. That said, syntheses in sub-critical but high-temperature water are well studied and will be covered in the next section. Since many natural minerals and precious stones were formed in water at high temperature and pressure in the Earth s crust, the synthesis... 

Rice bran fiber has fructo-oligosaccharides - a pre-biotic that helps friendly bacteria to proliferate in the gastrointestinal environment and improves intestinal and colon health (Tomlin and Read, 1988). Recent studies in humans (Kahlon and Chow, 1997) have revealed that rice bran fiber not only normalizes bowel function, but also helps in conditions such as irritable bowel syndrome (IBS), inflammatory bowel disease (IBD) and Crohn s disease, and lowers the lipid levels. Rice bran fiber has been shown to significantly reduce renal stones (Jahnen et al., 1992). It is a good source of fiber in weight loss programs and therapeutic fiber diets for diabetics and heart patients. Fiber diets prevent cancer of the colon and large bowel, control obesity and improve bowel function. 

Recent scientific studies have clearly established the nutritional role of dietary fiber in several health conditions (Jalili et al., 2000), such as hypercholesterolemia (Topping et al., 1990), diabetes (Chandalia et al., 2000) and bowel function. It is also effective in preventing urinary stones (Ohkawa et al., 1984). The Food and Nutrition Board (Institute of Medicine Report, 2001) recommended a daily allowance for fiber of 25-30 g, though it is not an essential nutrient. Rice bran fiber offers a good source of non-bloating dietary fiber and is marketed as RiceMucil by NutraStar Company in the USA. 

OHKAWA T, EBISUNO S, KITAGAWA M, MORIMOTO S, MIAZAKI Y, YASUKAWA S (1984) Rice bran treatment for patients with hypercalciuric stones experimental and clinical studies. J of Urology, 132 1140-45. 

The authors wish to gratefully acknowledge the valuable assistance of Mr. Richard Brown in conducting the experiments. Helpful discussions with Dr. Daniel Stone, project officer, and Lt. Col. Michael MacNaughton, project manager, are also acknowledged. This study was supported by funds from the U.S. Air Force Contract No. AF-F08635-78-C-0307. 

Stone, K., Uzieblo, A. and Marnett, L.J. (1990b). Studies of the reaction of malondialdehyde with cytosine nucleosides. Chem. Res. Tox. 3, 467-472. 

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