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At least 415 records · Page 23Linked to original sources

PubMed2005

Periocular petrolatum.

PURPOSE: This report describes the clinical and histopathologic features and discusses the diagnostic difficulties and management of periocular deposition of petrolatum-based materials. METHODS: Excision of orbital and eyelid tissue, tissue processing, and histopathologic examination was performed in patients with deposition of petroleum-based products. Transmission electron microscopy was performed in 3 cases. RESULTS: Between 1983 and 2003, 11 patients were diagnosed with periocular petrolatum deposition, based on clinical history and the characteristic histopathologic features of polymorphic dropout spaces, and varied from a noninflammatory lesion (paraffinoma) to those with an associated granulomatous inflammatory reaction. CONCLUSIONS: The diagnosis of petrolatum deposition can be challenging due to the range of symptoms and variable delay in presentation. Petrolatum products should be avoided during surgery and used judiciously in the postoperative period. To avoid confusion with nonspecific cases of lipogranulomatous inflammation, the terms "ointment granuloma" or "orbital paraffinoma" should be used to refer to patients presenting with orbital/eyelid lesions caused by ointment use.

Adolescent↗

PubMed2002

Lattice Boltzmann simulation of chemical dissolution in porous media.

In this paper, we develop a lattice Boltzmann model for simulating the transport and reaction of fluids in porous media. To simulate such a system, we account for the interaction of forced convection, molecular diffusion, and surface reaction. The problem is complicated by the evolution of the porous media geometry due to chemical reactions, which may significantly and continuously modify the hydrologic properties of the media. The particular application that motivates the present study is acid stimulation, a common technique used to increase production from petroleum reservoirs. This technique involves the injection of acid (e.g., hydrochloric acid, HCl, acetic acid, HAc) into the formation to dissolve minerals comprising the rock. As acid is injected, highly conductive channels or "wormholes" may be formed. The dissolution of carbonate rocks in 0.5M HCl and 0.5M HAc is simulated with the lattice Boltzmann model developed in this study. The dependence of dissolution process and the geometry of the final wormhole pattern on the acid type and the injection rate is studied. The results agree qualitatively with the experimental and theoretical analyses of others and substantiate the previous finding that there exists an optimal injection rate at which the wormhole is formed as well as the number of pore volumes of the injected fluid to break through is minimized. This study also confirms the experimentally observed phenomenon that the optimal injection rate decreases and the corresponding minimized number of pore volumes to break through increases as the acid is changed from HCl to HAc. Simulations suggest that the proposed lattice Boltzmann model may serve as an alternative reliable quantitative approach to study chemical dissolution in porous media.

Journal Article↗

PubMed1976

Epoxides derived from various polycyclic hydrocarbons as substrates of homogeneous and microsome-bound epoxide hydratase. A general assay and kinetic properties.

A general assay for epoxide hydratase using epoxides derived from polycyclic aromatic hydrocarbons as substrates is described. Addition of dimethylsulphoxide to the incubation mixture after incubation allowed unreacted epoxide and its phenolic by-product to be extracted into light petroleum whilst the product dihydrodiol remained in the aqueous phase. The product was then extracted into ethyl acetate and estimated radiochemically. This assay gave low extraction blanks (0.8-3.8%) when six K-region epoxides of polycyclic hydrocarbons were used, with high recoveries of the corresponding dihydrodiol in the ethyl acetate phase (65-89%). Radiochromatograms demonstrated that all the radioactivity in the ethyl acetate extracts of active incubations above that of boiled enzyme blanks was confined to a single band that always cochromatographed with the authentic trans-dihydrodiol. Using this assay, the kinetic parameters of six K-region epoxides were estimated. In all cases the apparent Km was low (2-5.9 muM). This is about 100-fold lower than the known apparent Km of epoxide hydratase for styrene oxide, an alkene oxide that is widely used as a substrate for epoxide hydratase. The rate of hydration varied with the substrate. Thus the maximum velocity for hydration of phenanthrene 9,10-oxide greater than 7-methylbenz[a]anthracene 5,6-oxide approximately benz[a]anthracene 5,6-oxide approximately benzo[a]pyrene 4,5-oxide greater than 3-methylcholanthrene 11,12-oxide greater than dibenz[a,h] anthracene 5,6-oxide. This relationship between the individual epoxides was found in microsomal fractions from both rat skin and rat liver, although the activity was always much lower in skin microsomes. All six arene oxides derived from polycyclic hydrocarbons were substrates for the homogeneous epoxide hydratase that was isolated from rat liver microsomal fractions using styrene oxide, an alkene oxide, as substrate to follow the purification.

Animals↗

PubMed1959