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Non-aqueous foams are much less studied than aqueous foam systems, although non-aqueous foams are important in many industries like petroleum refining. In this study, the foamability of non-aqueous...

Asphaltenes were precipitated from a Venezuelan Ayacucho crude oil and separated into two fractions (A1 and A2) by the p-nitrophenol method. The asphaltenes and the fractions A1 and A2, as well as mixtures of the two fractions were tested in a Langmuir–Bodgett trough. It was found that the asphaltenes and the fraction A2 had similar behavior and higher compressibility than the fraction A1. This is because the molecules of A2 are more flexible than the molecules of A1 as they have aliphatic chains that bond aromatic structures while the A1 has an aromatic nucleus.

Asphaltenes from three crudes were precipitated with a mixture of n-heptane and toluene, the size of the particles formed under different solvent mixtures and different agitation regimes were studi...

The White and Striped mullets (Mugil curema and M. cephalus) are highly abundant and commercially important estuarine fish in northwest (NW) Mexico. Because of their feeding habits and habitat, they are likely to accumulate mercury (Hg) in their muscle and liver. The objectives of this study were to determine total Hg distribution in the tissues of interest, to correlate Hg levels between tissues and with length and weight of fish, to estimate the percentage weekly intake (PWI) of total Hg and methyl Hg (MeHg) through consumption of both mullet species, and to compare total Hg levels with mullets from other areas. The highest total Hg concentration (1.031 µg g−1 dry weight) was measured in liver of White mullet. In both species, the order of averaged Hg concentrations (M. curema liver 0.272, muscle 0.184; M. cephalus liver 0.211, muscle 0.129 µg g−1 dry weight) were liver>muscle. Correlations of Hg in muscle and liver with total weight of M. curema were significant. In M. cephalus, Hg levels in li...

The asphaltene precipitation experiments were studied on El Furrial crude oil from western Venezuela, which is known to exhibit serious instability problems. A Turbiscan backscattering apparatus was used to evaluate the precipitation of asphaltenes with different solvents. The transmittance variation with time was studied as the crude was diluted with heptane, pentane, and cyclohexane. Linear alkanes-containing systems exhibit a two-stage behavior, whereas only one is found when diluting with cyclohexane. Dispersing agents were tested by using the precipitate height as a criterion of effectiveness. Results are reported for ethoxylated nonylphenols and a commercial dispersant.

W/O emulsions were studied using asphaltenes as surfactants. Asphaltenes were obtained from three Venezuelan crude oils: “Lago Cinco,” “Rosa Mediano,” and “Ayacucho.” They were extracted using n-heptane as a precipitanting agent. The following variables were studied: concentration of asphaltenes in the oleic phase and pH of the aqueous phase. An increase in asphaltene concentration in the oleic phase increases emulsion stability. On the other hand, the most stable emulsions correspond to an alkaline aqueous phase. Likewise, emulsion stability was higher for asphaltenes obtained from “Lago Cinco” crude oil and lowest from Rosa Mediano asphaltenes.

Helicobacter pylori infection has protean effects on gene expression in the host gastric mucosa, which have been investigated by gene chip analysis in vitro. In this study the effects of H. pylori infection on host gene expression in the gastric antral mucosa in patients were examined.One gastric antral biopsy was obtained from a total of 18 untreated patients undergoing routine endoscopic evaluation of chronic abdominal complaints. Nine patients had histologic evidence of H. pylori infection and 9 age- and sex-matched patients had no histologic evidence of H. pylori infection. A microarray analysis was performed using a gene chip containing 35,000 human expressed sequence tags on RNA extracted from endoscopic, gastric antral biopsies, and average gene expression among infected and uninfected patients was compared.Underexpressed genes in infected patients' mucosa included gastric intrinsic factor and several metallothionein isoforms. Overexpressed genes in infected patients' mucosa comprised MHC Class II molecules, immunoglobulin and B-cell activation genes, as well as genes known to induce apoptosis. Changes in expression were confirmed for a subset of genes by SYBR green real-time PCR.Microarray analysis of antral biopsies from patients with and without H. pylori infection revealed differential expression of metal regulatory, immunity and inflammation-related genes.

In this work we explore the application of a time-dependent Hartree (TDH) scheme to study the vibrational predissociation of Ne2I2 van der Waals clusters. The present approach is based on equations of motion extracted from the usual variational principle where the Hamiltonian has been previously represented in a set of diatomic vibrational states. The procedure leads to a set of coupled equations for the different modes on each diabatic state with, however, explicit separation between those modes. The application on a problem that inherently requires long-time propagation is shown to be successful. Calculated lifetimes compare well with previous calculations as well as with available experimental data. A more detailed mechanism, as the breath of the angular mode on the different vibrational channels, is better described.

A novel hybrid genetic scheme to solve the traveling salesman problem is presented in this paper. The proposed scheme has two major steps: clustering and global optimization. The clustering step is used to obtain an initial solution that is used as seed. The global optimization uses this seed to produce a better result using genetic operators. A number of benchmarks have been used to evaluate the proposed scheme. The solutions to these benchmarks which include 105-, 318-, 1060-, 2152-, 3038-, and 5934-city TSPs are extremely close to the best known solutions. This scheme is the first genetic approach that deals with large TSP benchmarks.

Water retention capacity was studied in fine earth and gravel from loamy‐textured soils with medium‐low carbon content in a semiarid Mediterranean montane location. Sierra Gador, southeastern Spain. In fine earth, typical water retention curves were established at six soil water potentials (‐10, ‐33, ‐100, ‐500, ‐1000, and ‐1500 kPa), and the water retention was compared against different physical, chemical, and miner‐alogical properties. Percent total sand and organic carbon content were the variables that gave the best fit in the pedotransfer functions for the calculation of water retention at ‐33 and ‐1500 kPa. Results for water retention in gravel at ‐33 and ‐1500 kPa show that gravel can make a significant contribution to the available water in the soil. Bulk density of gravel was the property most closely related to water content at both soil water potentials, and was the variable that gave the best fit in the pedotransfer functions. Other properties that were useful with this function were citrate‐...

We investigated the precipitation of carbonates by Deleya halophila in liquid culture media containing different concentrations of marine salt: 2.5%, 7.5%, 12.5%, and 20% (wt/vol). The microorganism was isolated from soils classified as haplic Solonchaks located in arid southeastern Spain. The mineral phases that were precipitated include aragonite, magnesium calcite, and monohydrocalcite in varying proportions depending on the salt concentration. In media containing 2.5% salt, the precipitate consisted of 100% aragonite; with 20% salt, the precipitate was 51% aragonite, 20% monohydrocalcite, and 29% magnesium calcite. Intermediate values were obtained with the middle two salt concentrations. The amount of magnesium in the formula for the precipitated magnesium calcites increased with salinity (0.16 atoms at 7.5% salt, 0.31 atoms at 12.5% salt, 0.32 atoms at 20% salt). The biomineralized formations gave rise to spherulites ranging in diameter from 20 to 500 μm depending on the salinity. The major morpholo...

This paper presents a novel genetic algorithm to solve the traveling salesman problem. The proposed method combines the Newton-Raphson numerical method with an inversion genetic algorithm; the method is called inversion with embedded Newton-Raphson Search. Different benchmark problems, including 10-, 30-, 50-, 75-, 105-, and 318-city topologies, are used to evaluate the approach. The best-known solutions have been produced by this hybrid genetic algorithm. In this paper we also report other results, such as the average tour distance, distribution of the results, and average number of generations. The proposed approach has been shown to outperform other genetic operators. An analysis based on the survival rate of the o-schemata and Holland's fundamental theory is included.

Phialomyces fusiformis sp. nov., isolated from soil in Singapore, is described and illustrated. The species is similar to P. macrosporus-type species of the genus but differs in that it has longer, more ellipsoid-limoniform, fusiform and more coarsely ornamented conidia.