Characterization of enzymatically prepared biosurfactants

Various fatty monoesters of sugars and sugar alcohols were prepared enzymatically in organic solvent. Water produced during esterification was removed by refluxing through a dessicant under reduced pressure. Surface properties of these esters such as surface and interfacial tensions and their ability to stabilize emulsions at 30°C were evaluated: oleate esters of glucose, fructose, and sorbitol show similar behavior in reduction of surface and interfacial tensions, and values for the critical micelle concentration are about 8·10⁻⁵ M. It was also observed with sorbitol esters that the shorter the alkyl chain, the higher the critical micelle concentration. Generally, emulsions prepared with the emulsifier dissolved in the water or in the oil phase lead to oil-in-water or water-in-oil emulsions, respectively. Sorbitol monolaurate significantly increased the stability of oil-in-water emulsions, with only 5% separation of the phases after 48h at 30°C, compared to 10% for chemically prepared sorbitan monolaurate under the same conditions. Sorbitol monoerucate was very efficient in stabilizing water-in-oil emulsions, with only 1% separation of the phases.     

Probabilistic Situation Calculus

In this article we propose a Probabilistic Situation Calculus logical language to represent and reason with knowledge about dynamic worlds in which actions have uncertain effects. Uncertain effects are modeled by dividing an action into two subparts: a deterministic (agent produced) input and a probabilistic reaction (produced by nature). We assume that the probabilities of the reactions have known distributions.Our logical language is an extension to Situation Calculae in the style proposed by Raymond Reiter. There are three aspects to this work. First, we extend the language in order to accommodate the necessary distinctions (e.g., the separation of actions into inputs and reactions). Second, we develop the notion of Randomly Reactive Automata in order to specify the semantics of our Probabilistic Situation Calculus. Finally, we develop a reasoning system in MATHEMATICA capable of performing temporal projection in the Probabilistic Situation Calculus.     

Synthesis and electrorheology of potato starch phosphate

Potato starch phosphate (PSP) particles were synthesized via an esterification process of potato starch with a mixture of various concentrations of phosphoric acid and urea. The electrorheological (ER) characteristics of the synthesized PSP particles, suspended in a silicone oil, were examined. The PSP granule‐based ER fluid exhibited typical ER behavior, possessing a nonvanishing yield stress under an applied electric field. Enhanced polarization and higher yield stresses were observed as the content of phosphate groups in the starch increases. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1770–1773, 2004     

Injection molding of a diffractive optical element

The injection molding of a microfeatured component, a diffractive optical element, was studied. The component has a wave‐like pattern on the surface, with amplitude 0.5 μm and wavelength 3 μm. Two different polymers were used: a polymethylmethacrylate and an ethylene‐norbornene copolymer (cyclic olefin copolymer). The topography was investigated using white light interferometry (WLI), atomic force microscopy (AFM), and scanning electron microscopy (SEM). A new WLI‐based technique is proposed for rapid quantification of the replication of periodic surface patterns. This technique gives almost the same information regarding the degree of replication as AFM but can be performed much faster. Quantitative data on the degree of replication as function of processing conditions are presented. At optimal conditions, almost perfect replication is obtained using both materials. At suboptimal conditions, it is observed that the degree of replication increases with increasing injection velocity and increasing mold temperature, with similar characteristics for both materials. The difference in replication quality between the two materials seems to be related to the different temperature dependencies of the viscosities. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Type II Ligands as Chemical Auxiliaries To Favor Enzymatic Transformations by P450 2E1

The remarkable ability of P450 enzymes to oxidize inactivated C? H bonds and the high substrate promiscuity of many P450 isoforms have inspired us and others to investigate their use as biocatalysts. Our lab has pioneered a chemical‐auxiliary approach to control the promiscuity of P450 3A4 and provide product predictability. The recent realization that type II ligands are sometimes also P450 substrates has prompted the design of a new generation of chemical auxiliaries with type II binding properties. This approach takes advantage of the high affinity of type II ligands for the active site of these enzymes. Although type II ligands typically block P450 activity, we report here that type II ligation can be harnessed to achieve just the opposite, that is, to favor biocatalysis and afford predictable oxidation of small hydrocarbon substrates with P450 2E1. Moreover, the observed predictability was rationalized by molecular docking. We hope that this approach might find future use with other P450 isoforms and yield complimentary products.     

The personal–group discrepancy: Is there a common information basis for personal and group judgment?

In contrast to motivational accounts of the personal–group discrepancy, results from this article suggest that the discrepancy is explained by aggregating different sets of comparison outcomes for either personal or group ratings. Results from a longitudinal study with East German (the minority group) and West German (the majority group) samples confirm the personal–group discrepancy and support our approach. First, social comparisons influenced evaluations of economic situation at both group and personal levels. Second, ratings of group versus personal economic situation were based on different sets of comparisons. Third, the mean structure of both sets of comparison outcomes mirrored the personal–group discrepancy. Fourth, an interaction between personal–group discrepancy and group status supported the authors' suggestions concerning the direction of the discrepancy. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Is there any scapegoat around? Determinants of intergroup conflicts at different categorization levels.

Recategorization at a higher level reduces tensions between groups. However, recategorization may cause conflicts between the common in-group and a new out-group. Additionally, determinants of conflict between subgroups may enhance conflict at the higher categorization level. In the context of German unification, the authors explored these suggestions with an East German 3-wave longitudinal study and a West German control group. Results show that a salient East German versus West German categorization enhances conflict between subgroups, whereas categorization as German enhances conflict at the common in-group level. Determinants of subgroup conflict also influence conflict at the inclusive level (Germans and foreigners). Thus, recategorization is a 2-edged instrument: Although it reduces conflict at the subgroup level, it may initiate conflict at the common in-group level. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Simultaneous effect of connection admission control in distance and bandwidth capacity on WDM network performance

This article presents an algorithm for dynamic-routing and wavelength assignment (D-RWA) in an optical WDM network. The approach is based on a genetic algorithm (GA) and it includes a connection admission control (CAC), to provide a network with simultaneous fairness in distance and bandwidth capacity. The algorithm is evaluated by means of computer simulations using a mesh network with two types of node architectures capable of performing traffic grooming. Combining the two types of nodes, the performance of four network configurations is compared. Assuming that one of the two node types is more costly, two sparse node allocations are suggested to maintain the network cost-effective. The algorithm assigns wavelengths to the ligthpaths, routes the traffic streams, manages the grooming of sub-wavelength tributaries onto full wavelength channels, provides fairness, and minimizes the overall blocking probability of connection requests. Numerical results attest the usefulness of the proposed approach considering several scenarios of distance and bandwidth capacity classes of requests. Simultaneous and isolated simulations of the two fairness schemes are also compared, emphasizing the versatility of the algorithm.     

A simple chemical method reduces ochratoxin A in contaminated cocoa shells

Ochratoxin A (OTA) is a mycotoxin produced by Aspergillus and Penicillium species, which contaminates cocoa among other food commodities. It has been previously demonstrated that the toxin is concentrated in cocoa shells. The aim of this study was to assay a simple chemical method for ochratoxin A reduction from naturally contaminated cocoa shells. In order to determine the efficiency of the method, a high-performance liquid chromatography method with fluorescence detection was set up beforehand and validated. Ochratoxin A was extracted from cocoa shells with methanol-3% sodium bicarbonate solution and then purified with immunoaffinity columns. The recovery attained was 88.7% (relative standard deviation = 6.36%) and the limits of detection and quantification were 0.06 and 0.2 kg/kg, respectively. For decontamination experiments, the solvent extractor ASE 200 was used. First, aqueous solutions of 2% sodium bicarbonate and potassium carbonate were compared under the same conditions (1,500 lb/in2 at 40 degrees C for 10 min). Higher ochratoxin A reduction was obtained with potassium carbonate (83 versus 27%). Then, this salt was used under different conditions of pressure, temperature, and time. The greatest ochratoxin A reduction was achieved with an aqueous potassium carbonate solution (2%), at 1,000 lb/in2 at 90 degrees C for 10 min. This method could probably be applicable to the cocoa industry because it is fast and relatively economic. From the point of view of human health, the use of potassium carbonate, partially eliminated by rinsing the sample with water, does not likely represent a risk for human health.