Insight into spontaneous recurrent calcium waves in a 3-D cardiac cell based on analysis of a 1-D deterministic model

Calcium dynamics in a cardiac cell are described by a system of 3-D non-linear stochastic partial differential equations. To obtain solutions that have biophysical properties, it is necessary to explore the model parameter space. To decrease the complexity of the parameter search, we reduce the 3-D stochastic model to a 1-D deterministic model. The reduction of the problem from 3-D to 1-D is done through an asymptotic approximation after non-dimensionalization and based on rational biophysical assumptions of the 3-D domain; the stochastic to deterministic transformation is based on the regular property of the 3-D solution. The result of the model reduction proves very effective in reducing the time required to get qualitative as well as quantitative information about parameter regions in the 3-D stochastic model including calcium dynamics (sparks, wave propagation, and recovery) observed in cardiac cells.     

The determination of volume ratios by gas depletion through multiple expansions

We present a new technique for the determination of the volume ratio of two vacuum chambers connected through a valve. The method is based on the measurement of the pressure in a chamber filled with a gas that is repeatedly depleted by expansion in a second chamber that was previously evacuated. Our calculation shows that under the reported measurement conditions, this technique has an uncertainty comparable to that obtained from the gas accumulation technique [Elliott KWT, Clapham PB.The accurate measurement of the volume ratios of vacuum vessels. NPL Report MOM 28, January 1978]. An excellent equivalence between the results obtained with this new technique and the measurements obtained by the gas accumulation technique is demonstrated.     

Improving microbiological food Safety in peri-urban Mali; an experimental study

IntroductionTwenty years ago, a WHO review of the literature assumed that most food-borne disease transmission in developing countries takes place within the home, and advocated a major programme of interdisciplinary research to develop and test cost-effective interventions to promote food hygiene.MethodsThe HACCP approach was applied step by step, to two selected weaning foods prepared by 15 volunteer mothers in peri-urban Mali. After setting Critical Control Points (CCP), actions were taken to control, reduce or eliminate microbial growth at these points. 432 food samples were collected and examined for thermotolerant coliforms in a local laboratory to assess the effectiveness of the approach. Lessons learnt were translated into messages delivered in a pilot study.ResultsTraditional cooking was very effective in eliminating faecal contamination; reheating was as effective as cooking when adopted, because there was no significant difference in the temperatures reached in both cases. Behavioural corrective actions were effective in controlling faecal contamination at the other CCPs (serving the child after cooking and after reheating).ConclusionIn conclusion, the HACCP experiment improved significantly the bacterial safety of both types of weaning food studied.     

XRD studies of electrochemically hydrided–dehydrided thin films of the alloy AZ31 and AZ31 with Ti

A magnetron sputtered thin films of the AZ31 alloy and AZ31 alloy with Ti capped with Pd were electrochemically hydrogenated and dehydrogenated in a 3 M KOH solution. A phase composition and structure of the films were studied by XRD. It has been determined that the behaviour of magnetron sputtered alloy AZ31 during electrochemical charging with hydrogen was alike that of pure Mg. The shift of the XRD peak Mg (0 0 0 2) to lower angles indicates that a hydrogen solid solution in the AZ31 alloy was formed along with MgH₂. When the AZ31 alloy with 18 at.% of Ti was electrochemically hydrogenated the whole film was transformed into hydride. The minor part of the hydride was in the nanocrystalline state with a structure of rutile and a major part of the hydride was in the amorphous state. After dehydrogenation only a part of the alloy recovered and the rest remained in the state of amorphous hydride. A positive shift of peak Pd (1 1 1) was observed in all of the XRD patterns for hydrogenated films. At least partially the shift should be associated with the compressive stresses in the top-cap layer of Pd, which arose due to the hydrogenation of the AZ31 alloy.     

Radiative heat transfer in a solar air heater covered with a plastic film

This article presents a new set of equations for the radiative balances of the absorber plate and the transparent cover of a solar air heater covered with a plastic film. Air flow is supposed to pass between the absorber plate and the bottom of the collector, while the transparent cover and the absorber plate are separated by an immobile air layer. This configuration is shown to be the best suited for a plastic covered solar air heater used in tropical countries, from a practical point of view.     

Evaluation of the potential of various spectral indices and textural features derived from satellite images for surficial deposits mapping

The present paper deals with the relevance of spectral and textural indices to surficial deposits identification and mapping. The study area is located in the Cochabamba valley in central Bolivia. Potential of SPOT‐4, Landsat‐7 and Radarsat‐1 data were compared for surficial deposits mapping. Different spectral indices including NDVI (normalized difference vegetation index) and TSAVI (transformed soil adjusted vegetation index) and textural features (mean, standard deviation, angular second moment, entropy, etc.) were extracted from these datasets and used in the mapping process. The results showed that indices exhibit different level of sensitivities according to surficial deposit types. A discriminant analysis was conducted to extract the most significant indices, which were then used in a three‐step linear combination mathematical model to map surficial deposits. We achieved an overall classification rate of 74% using spectral data of land use map in step 1. By adding information on vegetation and soils obtained from evaluation of spectral indices, this rate was improved to 82% during step 2. Finally, it was further slightly improved to 83% by adding textural data in the final step.     

Efficacy of a short 6 month therapeutic coursefor HIV infected tuberculosis patients in Abidjan, C?te d''Ivoire

From December 1992 to February 1993, 104 newly diagnosed pulmonary tuberculosis patients were enrolled in a prospective cohort study to assess the response to the 6 month-short-course regimen implemented in Cote d'Ivoire. This treatment encompassed the daily intake of Rifampicin and Pyrazinamide for 2 months followed by Rifampicin and Isoniazid for the remaining 4 months. All the patients were enrolled at the Treichville Tuberculosis Treatment Centre in Abidjan, and a follow-up of 6 months was observed for each patient. All in all, 41 patients were HIV-positive whereas 63 where HIV-negative. No statistical difference was noted between HIV-positive and HIV-negative patients with regard to the completion of therapy (85% versus 87%). The cure rate after an effective 6 month-therapy was similar among HIV-positive and HIV-negative patients (83% versus 84%) as well as the treatment failure rate which was 2.4% and 3% respectively. The results clearly indicate that the 6 month-short-course regimen policy implemented in C?te d'Ivoire is as effective for the treatment of HIV-associated tuberculosis as for the treatment of tuberculosis.     

Investigation of the impact response of PMMA-based nano-rubbers under various temperatures

To benefit from nano-rubber copolymers, the properties and dynamic behavior of nano-rubbers reinforced Poly(Methyl Methacrylate) (PMMA) were investigated. Dynamic tests were conducted on these materials at high strain rates and different temperatures using split Hopkinson pressure bars. The impact resistance of these materials was studied by performing low velocity impact tests with a drop weight tower at different impact energies and temperatures. The results showed decreased Young’s moduli and yield stresses. The mechanical behavior of the materials exhibited strain rate and temperature dependencies. Moreover, the nano-rubber-reinforced PMMA showed outstanding impact resistance compared with neat PMMA. The modified PMMA also exhibited impact properties similar to those of polycarbonate for certain ranges of impact energies and temperatures. No perforations were observed for all those energies and temperatures.     

THE “EVAPORATIVE CAPACITY” AS A PERFORMANCE INDEX FOR A SOLAR-DRIER AIR-HEATER

This paper presents a new index, called the “evaporative capacity”, for rating the performance of the solar air heater in a solar drier consisting of solar air heater and a drying chamber in series. The proposed index complements the widely-used “collector efficiency” as a performance indicator of the solar collector, by taking into account the specific use that is to be made with the heated air. Presented is a detailed method for calculating the evaporative capacity, and a comparison of this new index with the thermal efficiency index, demonstrating its superiority. General charts for a rapid determination of the evaporative capacity are presented, and some possible applications of these charts are described.