Finite Element Methods for a Model for Full Waveform Acoustic Logging

A model is defined to simulate the propagation of waves in aradially symmetric, isotropic, composite system consisting ofa fluid-filled well bore ^f through a fluid-saturated poroussolid ^p. Biot's equations of motion are chosen to describe thepropagation of waves in ^p, while the standard equation of motionfor compressible inviscid fluids is used for ^f, with appropriateboundary conditions at the contact surface between ^f and ^p.Also, absorbing boundary conditions for the artificial boundariesof ^p are derived for the model, their effect being to make themtransparent for waves arriving normally First, results on the existence and uniqueness of the solutionof the differential problem are given and then a discrete-time,explicit finite element procedure is defined and analysed, withfinite element spaces suited for radially symmetric problemsbeing used for the spatial discretisation.     

Expression of integrins, cyclooxygenases and matrix metalloproteinases in three-dimensional human endometrial cell culture system

The objective of this investigation was to establish a three-dimensionally cultured human endometrium which could be used as a tissue model for the mechanism study of implantation in vitro. By using human endometrial stromal (ES) and epithelial cells (EE) from hysterectomy specimens, reconstruction of endometrium in culture was established by first layering a collagen gel containing ES cells, then overlaying with the Matrigel containing endometrial epithelial (EE) cells. Ultrastructural examination of the 48 h-endometrial cell culture revealed monolayered columnar EE cells with microvilli on the collagen layer containing ES cells and appearance of the tight junctions and desmosomes between EE cells, a cell layer closely resembling the native endometrium. Immunohistochemical characterization of the reconstructed endometrium showed a strong immunoreactivity for cytokeratin, integrin alpha1, alpha4 and beta3 subunits, cyclooxygenases-1 and -2, matrix metalloproteinases-1, -2, -3 and -9, and tissue inhibitor of metalloproteinases-1 and -2 in the EE cells comparable to the native endometrial epithelium. ES cells also showed stronger immunoreactivity for cyclooxygenases, integrins and MMPs, but less for cytokeratin. Gelatin zymographic analyses of the media obtained from the reconstructed endometrium model showed gelatinase activity bands at 57, 60, 72, 92 and 97 kDa molecular weight, respectively. The present study provides a possibility that our three-dimensionally cultured endometrium model could mimic the morphological and functional characteristics of the native endometrium. The model could be used to clarify the roles of various molecules involved in the human implantation.     

THE PHOTOADDITION OF NUCLEOPHILES TO URACIL

Abstract— Quantum yields for 254 nm ultraviolet photoaddition of the nucleophiles hydrazine, HCN, HSO₃^-, methyl amine, and BH₄^- to uracil have been measured; the quantum yields for hydrazine, HCN, and HSO₃^- additions are pH-dependent. The nucleophiles sulfide, azide, chloride, bromide, iodide, nitrite and thiocyanate failed to photo–add under similar conditions. These reactions are interpreted as 1,4-additions to the conjugated enone system of the anti-aromatic compound, uracil; as suggested by S. Y. Wang (Wang and Nnadi, 1968). The nuclear magnetic resonance (NMR) spectrum of the photohydrate of uracil-5-d-showed that the proton was added to the 5-position in a stereochemically random manner. The photoaddition of HSO₃^- takes place at much lower concentrations than required for the thermal addition of this anion and is also stereochemically random.     

INTERACTION OF DIBUCAINEHCl LOCAL ANESTHETICS WITH BACTERIORHODOPSIN IN PURPLE MEMBRANE: A SPECTROSCOPIC STUDY

Several spectroscopic techniques (absorption, emission, transient absorption and differential scanning calorimetry--DSC) were used to investigate the deprotonation of dibucaine.HCl in a hydrophobic environment, and the interaction sites and mechanisms of the local anesthetic dibucaine.HCl on bacteriorhodopsin (bR) in purple membrane. The important results are summarized as follows: (1) the visible absorption features of native (lambda max = 568 nm) and deionized (lambda max = 608 nm) bR are sensitive to the amount of dibucaine.HCl added; (2) the emission spectrum of dibucaine.HCl embedded in the retinal-free mutant bR is similar to that of dibucaine free base in Triton X-100 micellar solutions; (3) the phosphorescence emission of dibucaine at 77 K is completely quenched by bR and the fluorescence quenching rate for the incorporated dibucaine.HCl in bR was determined as kq = 4.09 x 10(13) M-1 s-1; (4) the incorporation of dibucaine.HCl in bR inhibits the slow component rate of formation of M412 and decreases the amount of M412 formation in the photochemical cycle of bR; and (5) the thermal stability of native bR was measured by DSC in the presence and absence of dibucaine and yielded an endothermic transition at 95.9 +/- 1.0 degrees C with 13.6 J/g (3.25 +/- 0.12 cal/g) of enthalpy changes. All observations suggest that the action site of the local anesthetic, dibucaine.HCl, is near or at the chromophore, i.e. the retinal Schiff base of bR. The anesthetic action on bR purple membrane is probably via a specific site binding, but not a conformational mechanism.     

XPS study of bonding in ligated Au clusters

Ligated metal cluster compounds containing a core of metal atoms with well defined structure surrounded by a variety of organic and inorganic ligands are closely related to the bare metal clusters that are only now becoming available in uniform cluster size. The evolution of band structure and the development of metallic properties as a function of cluster size are of considerable interest. We report here a comparison of these two types of systems based on a study by X-ray photoelectron spectroscopy. The valence band spectra of ligated Au clusters compounds are similar in many respects to those of bare clusters, indicating significant participation of the d electrons in bonding. The core electron binding energy shifts of the central Au atom in Au₁₁(PPh₃)₇Cl₃ corresponds to the loss of approximation one 6 s electron. The total charge transferred to the halogens is accounted for by the shifts of the central and three halogenbonded Au atoms. No indication of metallic behaviour is found in the core of the ligated clusters.     

HUMIC MACROMOLECULES IN NATURAL WATERS

Abstract

Humic substances are the major organic constituents of soils and sediments. They also occur in small concentrations in natural surface waters and groundwaters. They form through the breakdown of plant and animal tissues by chemical and biological processes that tend to produce complex chemical structures that are more stable than the original material from which they were derived. One of the more important characteristics of humic substances is their ability to form water-soluble and water-insoluble complexes with metal ions and hydrous oxides and to interact with clay minerals and various organic compounds such as alkanes, fatty acids, and toxic organic substances such as pesticides.