Rheological properties of biopolymers drilling fluids

Drilling muds are complex fluids, generally used to clean the well, maintain hole integrity, transport the rock cuttings, lubricate the drill bit and control formation pressures. Two basic types of drilling fluids are used, water based muds (WBM) and oil based muds (OBM). OBM are very effective but polluting, and environmental regulations continue to restrict the use of oil based muds in many areas of the world. In order to reduce the mud toxicity, we developed water based mud systems using two biopolymers, which are xanthan gum and scleroglucan, generally proposed for high permeability reservoirs or for complex geometries such as horizontal wells. In this study, we evaluated the rheological behaviour of different samples and we determined the effect of components such as clay, calcium carbonate and potassium chloride. This formulations exhibit non-Newtonian rheological behaviour which can be described well by the tree parameter in Herschel–Bulkley rheological model.     

Biomarkers of meat tenderness: Present knowledge and perspectives in regards to our current understanding of the mechanisms involved

Biomarkers of the meat quality are of prime importance for meat industry, which has to satisfy consumers' expectations and, for them, meat tenderness is and will remain the primary and most important quality attribute. The tenderization of meat starts immediately after animal death with the onset of apoptosis followed by a cooperative action of endogenous proteolytic systems. Before consideration of the biomarkers identified so far, we present here some new features on the apoptotic process. Among them, the most important is the recent discovery of a complex family of serpins capable to inhibit, in a pseudo-irreversible manner, caspases, the major enzymes responsible of cell dismantling during apoptosis. The biomarkers so far identified have been then sorted and grouped according to their common biological functions. All of them refer to a series of biological pathways including glycolytic and oxidative energy production, cell detoxification, protease inhibition and production of Heat Shock Proteins. Some unusual biomarkers are also presented: annexins, galectins and peroxiredoxins. On this basis, a detailed analysis of these metabolic pathways allowed us to identify some domains of interest for future investigations. It was thus emphasized that mitochondria, an important organelle in the production of energy from carbohydrates, lipids and proteins are a central element in the initiation and development of apoptosis. It was therefore stressed forward that, in fact, very little is known about the postmortem fate of these organelles and their multiple associated activities. Other topics discussed here would provide avenues for the future in the context of identifying reliable predictors of the ultimate meat tenderness.     

Mesure en continu par ultrasons durant la prise et le durcissement des matériaux de contruction

Ultrasonic setting measurement is the study of how materials set or harden. Indeed, when mixed or combined, some materials undergo a change of their rheological properties if they are submitted to physical or chemical phenomena. Before use, these materials are liquid and they become solid when in use, at temperatures close to ambient levels, for example, hydraulic binding materials (cement, white-wash, plaster). For each particular application, users and manufacturers with to know the evolution such materials undergo, for three reasons:

- the development of a new product (meeting a need),

- the largest possible reduction of setting time (economic criterion),

- the use of the material (moulding, transformation...) without risking a change of its properties (quality-and safety-related problems).

The ultrasonic setting-measurement device provides solutions to such needs. The method is based on tracking ultrasounds through an interface during the process of solidification. Recording the change of transmissibility allows monitoring the rheological evolution of the material. Some examples of the use of the ultrasonic setting measurement device are provided, on the basis of laboratory measurements. A comprehensive study of the results of tests using hydraulic binders and acrylic resins allows the determination of characteristic times corresponding to the evolution of the material in question.     

Direct-conversion radio transceivers for digital communications

Direct-conversion is an alternative wireless receiver architecture to the well-established superheterodyne, particularly for highly integrated, low-power terminals. Its fundamental advantage is that the received signal is amplified and filtered at baseband rather than at some high intermediate frequency. This means lower current drain in the amplifiers and active filters and a simpler task of image-rejection. There is considerable interest to use it in digital cellular telephones and miniature radio messaging systems. This paper briefly covers case studies in the use of direct-conversion receivers and transmitters and summarizes some of the key problems in their implementations. Solutions to these problems arise not only from more appropriate circuit design but also from exploiting system characteristics, such as the modulation format in the system. Baseband digital signal processing must be coupled to the analog front-end to make direct-conversion transceivers a practical reality     

Detection of diethylnitrosamine in nitrite-rich water following treatment with rhodamine flow tracers

Extremely carcinogenic diethylnitrosamine (DENA) was found to form in up to 75% yield from the reaction of nitrite with the two commonly used water tracing dyes. Rhodamine B and Rhodamine WT, DENA was detected at trace levels (0.13–7.02 μg ⁻¹) in river water samples after treatment with the dye and nitrite. Analysis of these chemically treated environmental water samples required extensive separation techniques prior to acquisition of reliable analytical data using highly sensitive instruments for detection. The occurrence of DENA in nitrite-rich water treated with Rhodamines may pose a health hazard to general populations.     

Classroom furniture and anthropometric characteristics of Iranian high school students: Proposed dimensions based on anthropometric data

The study evaluated the potential mismatch between classroom furniture dimensions and anthropometric characteristics of 978 Iranian high school students (498 girls, 480 boys), aged 15-18 years. Nine anthropometric measurements (stature, sitting height, sitting shoulder height, popliteal height, hip breadth, elbow-seat height, buttock-popliteal length, buttock-knee length and thigh clearance) and five dimensions from the existing classroom furniture were measured and then compared together (using match criterion equations) to identify any potential mismatch between them. The results indicated a considerable mismatch between body dimensions of the students and the existing classroom furniture, with seat height (60.9%), seat width (54.7%) and desktop height (51.7%) being the furniture dimensions with a higher level of mismatch. The levels of mismatch varied between the high-school grade levels and between genders, indicating their special requirements and possible problems. The proposed dimensions of the classroom furniture more appropriate for the students were given. This additional information on students' anthropometry can be used by local furniture industries as a starting point for designing more appropriate furniture for school children, or used by schools to aid in furniture selection.     

First report on the presence of emerging Fusarium mycotoxins enniatins (A,A1, B,B1), beauvericin and fusaproliferin in rice on the Moroccan retail markets

Seventy samples of rice purchased from local markets in six cities from Morocco (Rabat, Casablanca, Kénitra, Mohammadia, Tanger and Errachidia) were analyzed for the presence of six emerging mycotoxins: four enniatins ENs (ENA, ENA₁, ENB and ENB₁), beauvericin (BEA) and fusaproliferin (FUS). Samples were extracted with a mixture of acetonitrile/water (85/15, v/v) by using an ultra-turrax homogenizer. Mycotoxins were then identified and quantified with liquid chromatography (LC) coupled to diode array detector (DAD). Positive samples were confirmed with an LC-MS/MS. Analytical results showed that BEA was present in 75.7% of total analyzed samples. BEA levels varied between 3.8 and 26.3 mg/kg. The frequencies of contamination of samples with total ENs and FUS were 50% and 4.3%, respectively. Among the ENs, ENB was the mycotoxin much more found (30% of total samples), while ENB₁, ENA and ENA₁ were found in 24.6%, 22.8% and 5.7% of total samples, respectively. The high ENs value was registered in a rice sample from kénitra (448.7 mg/kg of ENA₁). This is the first study that describes the presence of emerging Fusarium mycotoxins in rice available in Morocco.     

Hair mercury levels in relation to fish consumption in a community of the Moroccan Mediterranean coast

Coastal populations with high seafood consumption in the Mediterranean have a significant exposure to dietary methylmercury, and areas where environmental mercury pollution is an issue due to industrial activities are of special concern. The study was undertaken with the aim of assessing methylmercury exposure through fish consumption in a community of north Morocco and characterizing the relevant health risk. Concentrations of total mercury were determined in human hair, a biomarker of methylmercury exposure, and in locally consumed fish by cold vapour atomic absorption spectrophotometry. Based on consumption frequencies reported by the 108 subjects included in the study the weekly intake of methylmercury was estimated and biomarker data were evaluated in relation to the estimated intake and the sociodemographic characteristics of the population. Multiple regression analysis was employed for the interpretation of hair mercury data in relation to fish consumption frequency, gender and the age of individuals. Mercury concentrations in hair ranged from 0.22 to 9.56 µg g^-1 (geometric mean = 1.79 µg g^-1) and were closely related to fish intake. Fisherman and their families consumed fish three to five times per week and were the most exposed population subgroup. A high proportion of women of child-bearing age (50%) had relatively high levels of mercury in their hair (3.08-7.88 µg g^-1).     

Sensitivity analysis of HIV infection response to treatment via stochastic modeling

This work focuses on the analysis of HIV infection dynamics during the initial stages of infection when the viral load is low and random fluctuations may have a significant effect on the dynamics of the disease. Deterministic models that describe the expected progress of the infection cannot be employed to predict the probability of infection establishment at the primary stage. Consequently, stochastic simulations are used to determine the probability of successful infection in an average patient. A stochastic model based on Gillespie's algorithm is derived which includes mutant species and employed to determine the sensitivity of HIV infection to different treatment strategies such as single therapy and combination therapy with various efficacy values. The effect of treatment latency on virus clearance probability is also investigated.