Assessing an ambulance service with queuing theory

We describe an ambulance service in terms of its main operation parameters and strategic decision variables. Assisted by queuing theory, we calculate the key performance indicators (KPI) that concern the manager and the KPI that concern the patient. We use them to improve the operation of a private ambulance service in Chile. First, we evaluate whether the historical performance is consistent with the resources deployed. Then, we estimate the impact of some operational enhancements, such as reducing the cycle time or enlarging the fleet. Finally, we optimize the geographical coverage of the bases. We conclude that simple mathematical expressions are very useful to evaluate and improve the operation.     

The value of information in a long–term hydro–thermal electrical planning model

This article presents the analysis, comparison, and application of two alternative models to the optimal long–term operation planning of an hydro–thermal power system under conditions of uncertainty. The electrical system considered comprises one large reservoir, with interannual regulation capacity, and several smaller ones. The analyzed models employ stochastic dynamic programming as the solution methodology. The fundamental problem is to decide, on every temporal stage, how much water to use for generating purposes and how much to store, in order to minimize the total thermal and shortage costs. The original version of the studied model, created originally to forecast fuel consumption, assumes that the decision regarding the water release from the main reservoir is taken knowing the future hydrologic conditions. This criterion is known as wait–and–see . On the contrary, the new versions of the model, proposed in this article, consider a here–and–now criterion. Specifically, it is assumed that the future hydrologic conditions are not known at the time of making the operational decisions. The difference between the optimal cost of the proposed models and the original model defines the value of having the information regarding future hydrologic conditions before taking any decision. This value is generally known as the expected value of perfect information.     

The relationship of Campylobacter jejuni subsp. jejuni enterotoxigenicity and the increase of cAMP and electrolyte changes in the rat intestine

BACKGROUND: Small intestine alterations produced by the enterotoxigenic capacity of Campylobacter jejuni subsp. jejuni are similar to the hydric, electrolytic and pathological changes caused by choleraic and thermolabile Escherichia coli toxins. AIM: To study the enterotoxigenic capacity of 4 strains of Campylobacter jejuni subsp. jejuni using the intestinal loop model. MATERIAL AND METHODS: Rat intestinal loops were inoculated with culture filtrates of the four strains. Enterotoxigenicity was assessed by fluid accumulation, the increase in Na+ and Cl- in the loop fluid, and cAMP increase in loop tissues. An enterotoxigenic Escherichia coil strain and sterile Brucella both were used as positive and negative controls, respectively. RESULTS: The filtrates of two strains produced fluid accumulation in the loops, significantly increased Na+ and Cl- secretion to the intestinal lumen and increased tissue cAMP levels. CONCLUSIONS: Some strains of Campylobacter jejuni subsp. jejuni are able to show enterotoxigenicity in vivo, increasing cAMP levels in the intestinal cells and altering electrolyte exchange mechanisms.     

Determinant for beta-subunit regulation in high-conductance voltage-activated and Ca(2+)-sensitive K+ channels: an additional transmembrane region at the N terminus

The pore-forming alpha subunit of large conductance voltage- and Ca(2+)-sensitive K (MaxiK) channels is regulated by a beta subunit that has two membrane-spanning regions separated by an extracellular loop. To investigate the structural determinants in the pore-forming alpha subunit necessary for beta-subunit modulation, we made chimeric constructs between a human MaxiK channel and the Drosophila homologue, which we show is insensitive to beta-subunit modulation, and analyzed the topology of the alpha subunit. A comparison of multiple sequence alignments with hydrophobicity plots revealed that MaxiK channel alpha subunits have a unique hydrophobic segment (S0) at the N terminus. This segment is in addition to the six putative transmembrane segments (S1-S6) usually found in voltage-dependent ion channels. The transmembrane nature of this unique S0 region was demonstrated by in vitro translation experiments. Moreover, normal functional expression of signal sequence fusions and in vitro N-linked glycosylation experiments indicate that S0 leads to an exoplasmic N terminus. Therefore, we propose a new model where MaxiK channels have a seventh transmembrane segment at the N terminus (S0). Chimeric exchange of 41 N-terminal amino acids, including S0, from the human MaxiK channel to the Drosophila homologue transfers beta-subunit regulation to the otherwise unresponsive Drosophila channel. Both the unique S0 region and the exoplasmic N terminus are necessary for this gain of function.     

Synthesis and Evaluation of Novel Oxyalkylated Derivatives of 2′,4′-Dihydroxychalcone as Anti-Oomycete Agents against Bronopol Resistant Strains of Saprolegnia sp.

A series of novel oxyalkylchalcones substituted with alkyl groups were designed and synthesized, and the antioomycete activity of the series was evaluated in vitro against Saprolegnia strains. All tested O-alkylchalcones were synthesized by means of nucleophilic substitution from the natural compound 2′,4′-dihydroxychalcone (1) and the respective alkyl bromide. The natural chalcone (1) and 10 synthetic oxyalkylchalcones (2–11) were tested against Saprolegnia parasitica and Saprolegnia australis. Among synthetic analogs, 2-hydroxy,4-farnesyloxychalcone (11) showed the most potent activity against Saprolegnia sp., with MIC and MOC values of 125 µg/mL (similar to bronopol at 150 µg/mL) and 175 µg/mL, respectively; however, 2′,4′-dihydroxychalcone (1) was the strongest and most active molecule, with MIC and MOC values of 6.25 µg/mL and 12.5 µg/mL.     

Bench-Scale and Pilot-Scale Treatment Technologies for the Removal of Total Dissolved Solids from Coal Mine Water: A Review

Coal mine water (CMW) is typically treated to remove suspended solids, acidity, and soluble metals, but high concentrations of total dissolved solids (TDS) have been reported to impact the environment at several CMW discharge points. Consequently, various states have established TDS wastewater regulations and the US EPA has proposed a benchmark conductivity limit to reduce TDS impacts in streams near mining sites. Traditional CMW treatment effectively removes some TDS components, but is not effective in removing major salt ions due to their higher solubility. This paper describes the basic principles, effectiveness, advantages, and disadvantages of various TDS removal technologies (adsorption, bioremediation, capacitive deionization, desalination, distillation, electrochemical ion exchange, electrocoagulation, electrodialysis, ion exchange, membrane filtration, precipitation, and reverse osmosis) that have at least been tested in bench- and pilot-scale experiments.     

Phase Behavior and Structure of Systems Based on Mixtures of n‐Hentriacontane and Melissic Acid

Candelilla wax (CW) organogelation is a promising method for providing structure to solid‐like fat‐based foods, cosmetics, and drug delivery systems. The main component, n‐hentriacontane (C31), defines, to a large extent, the thermal properties of CW. CW is a complex mixture of n‐alkanes, fatty acids, triterpenic alcohols, and fatty alcohols. In this initial examination of the role of CW components on the phase behavior and structure, CW and binary mixtures of C31 and melissic acid (C30) were studied in bulk and in solutions of vegetable oil. Binary mixtures of C31 and C30 presented a predominantly monotectic phase behavior in which the melting temperature of C31 remained constant independently of the mixture composition. Crystal packing of the pure components and mixtures had an orthorhombic subcell, and the microstructures of the mixtures were extremely different from that of the pure components. In solutions with less than 50 % C31, the order–disorder transition observed in bulk C31 was absent. Organogels of C31, C30, or the mixture were softer than those of CW. The increased strength of CW organogels is associated with the relatively small crystal size of this system.     

Fuzzy region assignment for visual tracking

In this work we propose a new approach based on fuzzy concepts and heuristic reasoning to deal with the visual data association problem in real time, considering the particular conditions of the visual data segmented from images, and the integration of higher-level information in the tracking process such as trajectory smoothness, consistency of information, and protection against predictable interactions such as overlap/occlusion, etc. The objects’ features are estimated from the segmented images using a Bayesian formulation, and the regions assigned to update the tracks are computed through a fuzzy system to integrate all the information. The algorithm is scalable, requiring linear computing resources with respect to the complexity of scenarios, and shows competitive performance with respect to other classical methods in which the number of evaluated alternatives grows exponentially with the number of objects.     

Cross cultural analysis of the use and perceptions of web Based learning systems

The main objective of this paper is to examine cultural differences and technology acceptances from students of two universities, one is from a European country: Spain, and the other is in Latin America: Chile. Both of them provide their students with e-learning platforms. The technology acceptance model (TAM) and Hofstede’s cultural dimensions are the tools used to measure the acceptance and use of web-based learning platforms and cultural diversity of respondents, respectively. In summary, we can affirm that the sample of tertiary Spanish and Chilean students are culturally different with regard to some of Hofstede’s dimensions, but their behavior of acceptance of e-learning technology globally matches according to the TAM model. This study provides relevant implications for on-line courses managers’ who have tertiary students from different nationalities.     

Behavioral profiles in rats distinguish among “ecstasy,” methamphetamine and 2,5-dimethoxy-4-iodoamphetamine: Mixed effects for “ecstasy” analogues.

3,4-methylenedioxymethamphetamine (MDMA; “ecstasy”) is a psychoactive drug structurally related to other phenylisopropylamines acting as stimulants or hallucinogens in humans. Although MDMA has a pharmacological identity of its own, the distinction of its acute effects from those of stimulants or even hallucinogens is controversial. In this work, dose-response curves (0.25, 0.5, 1, 3, 5, and 10 mg/kg) representing the acute in vivo effects of MDMA were compared with those of a structurally related stimulant (methamphetamine, MA) and a hallucinogenic analogue (2,5-dimethoxy-4-iodoamphetamine, DOI) in a set of behavioral protocols in rats, including spontaneous psychomotor activity, anxiolytic/anxiogenic-like effects and active avoidance conditioning responses. The behavioral profiles obtained allowed us to differentiate among racemic MDMA, MA, and DOI at different dose ranges. In addition, the evaluation of four MDMA analogues (1, 5, and 10 mg/kg) comprising two well-known MDMA analogues (MDA [3,4-methylenedioxyamphetamine] and MDE (N-ethyl-MDA, believed to substitute for MDMA) and two other structural analogues (MDOH [N-hydroxy-MDA] and MMDA-2 [2-methoxy-4,5-methylenedioxyamphetamine]) showed that none of these exactly resembles MDMA in their pharmacological profiles, highlighting the unique character of this prototypical entactogen. In fact, their effects exhibited similarities with the behavioral profiles of either MA or DOI, as well as novel profiles in specific behavioral paradigms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)