Identification of Stochastic Multicompartmental Models in Tracer Kinetics Experiments

Two efficient algorithms are described for the estimation of dynamic parameters in a tracer kinetic experiment, when a stochastic multicompartmental model is utilized. The first approach is based on the sensitivity method, where the error between the model output and the system output is minimized. Sensitivity functions are calculated and model outputs are simulated by the algorithm at each iteration in order to estimate the optimal values of the model parameters. The concept of a whitening filter is used in the second method to convert the colored output error into a white sequence: the algorithm minimizes the estimated variance of the filtered sequence. Tests performed using simulated as well as real data confirm the effectiveness of both the techniques.     

Investigated optical and elastic properties of Porous silicon: Theoretical study

Compatibility between experimental and theoretical works is achieved. Empirical Pseudopotential Method (EPM) is used to calculate the energy gap of Si which is found to be indirect. Features such as refractive index, optical dielectric constant, bulk modulus, elastic constants and short-range force constants have been investigated. In addition to the shear modulus, Young’s modulus, Poisson’s ratio and Lame’s constants for both bulk Si (p = 0%) and Porous silicon (PS) are derived. The calculated results are found to be in good agreement with other experimental and theoretical ones. Also, the Debye temperature of PS is estimated from the average sound velocity. To our knowledge, the optical properties using specific models and elasticity of PS are reported for the first time.     

Reduction efficiencies of natural substances for reduced graphene oxide synthesis

Journal of Materials Science - Synthesis of graphene by reducing graphene oxide is the most propitious route for bulk graphene production. Reduction using eco-friendly techniques is more feasible...     

Enhancing Superconductivity in Low-dimensional TlBa2Ca2Cu3O10?δ System

Mg-doped Tl(Ba_2?x Mg _x )Ca₂Cu₃O_10??? (x=0, 0.25, 0.50, 0.75, 1.0, 1.25, 1.5) superconductors are synthesized at the normal pressure and the possible mechanism of superconductivity in these compounds is studied. Tl(Ba_2?x Mg _x )Ca₂Cu₃O_10??? samples have shown an orthorhombic crystal structure and their c-axis length decreases up to Mg-doping of x=0.75 and then increases up to Mg-doping of x=1.50. In these studies we have investigated the role of decreased thickness of charge reservoir layer on the mechanism of superconductivity. The T _c (R=0) in as-prepared Tl(Ba_2?x Mg _x )Ca₂Cu₃O_10??? (x=0, 0.25, 0.5, 0.75, 1.0, 1.25) samples was 100, 98, 101, 102, 100, 96?K and in the oxygen post-annealed samples the T _c (R=0) is observed around 99, 98, 108, 127, 109, 97?K, respectively. The magnitude of the superconductivity after Mg-doping is improved in Tl(Ba_2?x Mg _x )Ca₂Cu₃O_10??? (x=0.25, 0.5, 0.75, 1.0, 1.25) samples. It was observed from the FTIR absorption measurements that the phonon modes related to CuO₂ planar oxygen atoms are hardened with the doping of Mg in the charge reservoir layer. These studies have shown that the thickness of charge reservoir layers decreases with Mg-doping, which most likely makes the charge transfer mechanism more efficient, which increases the magnitude of superconductivity in the final compound.     

Structure,Seebeck coefficient and DC electrical conductivity of Bi2Mn4O10 prepared by mechanochemical method

Journal of Materials Science: Materials in Electronics - Bismuth and manganese oxides were mixed as source-materials using the mechanochemical technique followed by heat treatment to prepare the...     

Can the dietary element content of virgin argan oils really be used for adulteration detection?

Levels of eight dietary elements were assessed by ICP-AES in virgin edible and beauty argan oil samples prepared from four remote locations of the argan forest, and over a three-year period. The data showed sufficiently little variability to assess that all argan oil samples present, in terms of dietary elements, a similar composition, independently from the tree location within the argan forest. Therefore, adulteration detection by trace element analysis in edible and beauty argan oil is a method that can be generalised.     

Inhibition of enterotoxicogenic strains Bacillus cereus GT1 and Staphylococcus aureus S1 isolated from double white cream cheese

In this study three different food preservatives (sodium nitrate, sodium benzoate and sodium sorbate) were used to evaluate their effect on two enterotoxicogenic strains (Bacillus cereus GT1 and Staphylococcus aureus S1). A significant decrease in the viability and production of virulence factors was observed. Yet, obvious tolerance to increasing concentrations (from 1 to 6?g/l) of the three preservatives was recorded reflecting possible resistance mechanisms within the tested strains. The two strains were subjected to increasing doses of gamma radiation (1, 2, 3, 4, 5, 6, 7, 8, 9 and 10?kGy). Obvious correlation was observed between the initial counts of bacterial spores contaminating the products and the required dose for their complete elimination. Whereas the eliminating dose of B. cereus GT1 strain was 10?kGy only 4?kGy was sufficient to suppress the growth and virulence of S. aureus S1, reflecting its sensitivity to low doses of gamma irradiation. Also, inhibition of the two strains by probiotic strain Bacillus pumilus G4 was studied both in situ (in cheese) and in vitro (in culture media). The viable cell population of B. cereus GT1 increased from 10⁶ to 2.9?×?10⁸?CFU/g within 60?h in controls but decreased from 2.1?×?10⁶ to 2.3?×?10³?CFU/g after treatment with the probiotic strain. No viable count was observed after 60?h of incubation. Whereas, the viable cell population of S. aureus S1 increased from 10⁶ to 2.5?×?10⁸?CFU/g within 60?h in controls but decreased from 1.5?×?10⁶ to 4.3?×?10²?CFU/g after treatment with the probiotic strain. No viable count was observed after 54?h of incubation.     

Putative virulence factors of the Aeromonas spp. isolated from food and environment in Abu Dhabi, United Arab Emirates

Thirty randomly selected Aeromonas isolates from food and the environment in Abu Dhabi, United Arab Emirates, were characterized for putative virulence determinants, such as production of cytotoxin, cytotonic toxin, and hemolysin and their capacity to adhere to and invade Henle 407 cells in vitro. Seventy percent of the tested isolates were cytotoxin producers, and 80% were hemolytic. Cytotoxin was produced by 6 of 7 A. hydrophila strains, 6 of 13 A. caviae strains, and 6 of 7 A. veronii bv. sobria strains, mostly from food sources. A. schubertii, A. jandaei, and A. trota also produced both cytotoxin and hemolysin. All of the 30 isolates tested adhered to Henle 407 cells, but none were able to invade the cells, as determined with the in vitro assay. However, no significant correlation of the presence of these putative virulence factors was found among these aeromonad food isolates.     

Smoking behaviour and attitudes among adult Saudi nationals in Riyadh City, Saudi Arabia

OBJECTIVE: To measure the smoking behaviour and attitudes among Saudi adults residing in Riyadh City, the capital of the Kingdom of Saudi Arabia. DESIGN: Cross-sectional survey. SETTING AND SUBJECTS: Primary health care centres (PHCCs) in Riyadh City were selected by stratified random sampling. Subjects resident in each PHCC catchment area were selected by systematic sampling from their records in the PHCCs; 1534 adults aged 15 years and older were interviewed during January to April 1994. MAIN OUTCOME MEASURES: Self-reported smoking prevalence; age of smoking initiation; daily cigarette consumption; duration of smoking; reasons for smoking, not smoking, and quitting smoking; intentions to smoke in the future; and attitudes toward various tobacco control measures. RESULTS: 25.3% of respondents were current smokers, 10.2% were ex-smokers, and 64.5% had never smoked. About 79% of all smokers started smoking between the ages of 15 and 30 years, and 19.5% before age 15. Significantly higher smoking prevalence and daily cigarette consumption were associated with being male, single, and being more highly educated. Relief of psychological tension, boredom, and imitating others were the most important reasons for smoking, whereas health and religious considerations were the most important reasons for not smoking among never-smokers, for quitting among ex-smokers, and for attempting to quit or thinking about quitting among current smokers. About 90% of all subjects thought that they would not smoke in the future. Physicians and religious men were identified as the most effective anti-smoking advocates by a much higher proportion of respondents (44%) than nurses, health educators, and teachers (each less than 5%). Health and religious education were generally cited as more effective in deterring smoking than tobacco control laws and policies. CONCLUSIONS: Cigarette smoking is prevalent among Saudi adults in Riyadh, particularly males, most of whom begin to smoke rather early in life and continue for many years. Health and religious education should be the cornerstone for any organised tobacco control activities, which are urgently needed to combat the expected future epidemic of smoking-related health problems.




     

Comparative studies on protein fractions and amino acid composition from sorghum and pearl millet

A defatted flour sample of sorghum and pearl millet were separated into three fractions. These procedures involve extracting the defatted flour with aqueous sodium hydroxide (pH 11.9) followed by precipitation with diluted HCl acid (pH 4.8). The two protein fractions I (soluble at pH 4.8) and II (insoluble at pH 4.8) along with the remaining residues (fraction III) were lyophilized separately. The amino acid composition of the original flour and the three fractions were determined. Lysine seems to be the most deficient amino acid in the original flour and the remaining residues. Fraction I and II, in which the lysine accumulated, have essentially better amino acid profile and consequently nutritionally better quality than the protein of the original defatted flour. The recovered protein-rich fractions I and II should be useful as a protein ingredient in foods. The remaining residues can be extruded into convenience foods.