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.     

Thermodynamic, kinetic, and computational study of heavier chalcogen (S, Se, and Te) terminal multiple bonds to molybdenum, carbon, and phosphorus

Enthalpies of chalcogen atom transfer to Mo(N[t-Bu]Ar)3, where Ar = 3,5-C6H3Me2, and to IPr (defined as bis-(2,6-isopropylphenyl)imidazol-2-ylidene) have been measured by solution calorimetry leading to bond energy estimates (kcal/mol) for EMo(N[t-Bu]Ar)3 (E = S, 115; Se, 87; Te, 64) and EIPr (E = S, 102; Se, 77; Te, 53). The enthalpy of S-atom transfer to PMo(N[ t-Bu]Ar) 3 generating SPMo(N[t-Bu]Ar)3 has been measured, yielding a value of only 78 kcal/mol. The kinetics of combination of Mo(N[t-Bu]Ar)3 with SMo(N[t-Bu]Ar)3 yielding (mu-S)[Mo(N[t-Bu]Ar)3]2 have been studied, and yield activation parameters Delta H (double dagger) = 4.7 +/- 1 kcal/mol and Delta S (double dagger) = -33 +/- 5 eu. Equilibrium studies for the same reaction yielded thermochemical parameters Delta H degrees = -18.6 +/- 3.2 kcal/mol and Delta S degrees = -56.2 +/- 10.5 eu. The large negative entropy of formation of (mu-S)[Mo(N[t-Bu]Ar)3]2 is interpreted in terms of the crowded molecular structure of this complex as revealed by X-ray crystallography. The crystal structure of Te-atom transfer agent TePCy3 is also reported. Quantum chemical calculations were used to make bond energy predictions as well as to probe terminal chalcogen bonding in terms of an energy partitioning analysis.     

A ‘poor man's Navier–Stokes equation’: derivation and numerical experiments—the 2‐D case

We present a systematic derivation of a discrete dynamical system directly from the two‐dimensional incompressible Navier–Stokes equations via a Galerkin procedure and provide a detailed numerical investigation (covering more than 107 cases) of the characteristic behaviours exhibited by the discrete mapping for specified combinations of the four bifurcation parameters. We show that this simple 2‐D algebraic map, which consists of a bilinearly coupled pair of logistic maps, can produce essentially any (temporal) behaviour observed either experimentally or computationally in incompressible Navier–Stokes flows as the bifurcation parameters are varied in pairs over their ranges of stable behaviours. We conclude from this that such discrete dynamical systems deserve consideration as sources of temporal fluctuations in synthetic‐velocity forms of subgrid‐scale models for large‐eddy simulation. Copyright © 2004 John Wiley & Sons, Ltd.     

Assessment of Temporal Variability Trends for Inorganic Parameters in Ground Water

Abstract

The passage of environmental legislation in the United States has dramatically increased ground-water monitoring in the vicinity of point sources such as abandoned waste disposal sites, operational waste disposal sites, and municipal landfills. Even though these programs require sufficient sampling to define background conditions as part of the site characterization process, there is still a general absence of quantitative information on the magnitude and periodicity of temporal fluctuations for inorganic constituents in ground water. This paper presents an approach that has been used to develop an initial characterization of these temporal trends.

A search if on-going site investigation reports identified 18 facilities across the United States that had monthly monitoring data at a frequency of at least monthly for a period of one and a half years or longer (15 RCRA-C hazardous waste disposal facilities with monthly data for a period of 2–3 years, 2 research monitoring locations with biweekly monitoring data for a period of one and a half years, and a precious metal mining operation with daily monitoring data for a limited number of parameters for a period of one and a half years). The data from these site investigations were used to describe the temporal variability of several ground-water constituents including pH, specific conductance, sulfate, sodium, chloride, alkalinity, silica, iron, and manganese. An assessment of these data suggests that the magnitude of temporal ground-water fluctuations are on the order of 20 percent of the average concentration for chloride, 10 percent of the average concentration for sodium, manganese and specific conductance, 5 percent of the average concentration for alkalinity and pH, and essentially zero for silica. The apparent periodicities of these temporal fluctuations ranged from 40 weeks to approximately 2 years. The magnitude and periodicities in ground water are substantially smaller than those that have been reported and documented for the same constituents in surface waters. These differences are due to the fact that sunlight and wind, two energy factors that drive temporal cycles in surface water, do not exert a similar influence on the environmental chemistry of ground-water constituents.     

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.     

PHOTODYNAMIC ACTION OF CHEMICALLY RELATED FLAVONES

Abstract— Flavone, polyhydroxyflavones (apigenin, fisetin, kaempferol, luteolin, myricetin, quercetin, resokaempferol and robinetin), polymethoxyflavones and acetylated and benzylated flavones were tested for photodynamic activity using Tetrahymena pyriformis T as the test organism. Among these compounds, polymethoxyflavones showed the highest order of activity, followed by flavone and then flavone derivatives with OH and OCH₃ groups. Resokaempferol was the only active polyhydroxyflavone, the remainder being inactive such as the benzyl-derivative. The methoxyl group in the 5–position and an increase in number of methoxyl groups from one to three in the phenolic portion of the flavonoid tended to decrease photodynamic activity. Tetrahymena killed photodynamically by polymethoxyflavones were morphologically altered by blister-like blebs. Polymethoxyflavones showed the lowest cytotoxicity and the greatest photodynamic activity among those flavonoids tested. The majority of the favonoids in this series have absorption spectra in the 320–370 nm region.     

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.