Geochemical approach to the Bou Hadjar hydrothermal system (NE Algeria)

The Bou Hadjar low-temperature hydrothermal system is located in northeast Algeria. The four main thermal springs that are the subject of the study emerge ith temperatures between 32 and 60°C from allochthonous formations. The reservoir temperature has been estimated from chemical compositions by utilizing simultaneously the silica, gas and sulfate-water oxygen isotope geothermometers, fluid-mineral equilibrium calculations, and a mixing model. According to these thermometric methods, the most probable subsurface temperature is in the range 75–106°C. The mixing model suggests a temperature of 125°C for the parent water.     

Microwave spectra of CD3OH methanol

The microwave spectrum of CD₃OH has been studied over the 8 to 58 GHz region, and numerousb-type transitions have been assigned. Many of these belong toP subbranches which descend to the microwave region from subband origins lying much higher in the far-infrared, pass through zero frequency, and return upward again. Others are members ofb-typeQ branches which extend across the region. As well, variousa-typeK-doublet lines arising as transitions directly across the split levels of asymmetry doublets have been identified.     

Thermal stability in bulk cryomilled ultrafine-grained 5083 Al alloy

Thermal stability in bulk ultrafine-grained (UFG) 5083 Al that was processed by gas atomization followed by cryomilling, consolidation, and extrusion, and that exhibited an average grain size of 305 nm, was investigated in the temperature range of 473 to 673 K (0.55 to 0.79 T _m , where T _m is the melting temperature of the material) for different annealing times. Appreciable grain growth was observed at temperatures > 573 K, whereas there was limited grain growth at temperatures < 573 K even after long annealing times. The values of the grain growth exponent, n, deduced from the grain growth data were higher than the value of 2 predicted from elementary grain growth theories. The discrepancy was attributed to the operation of strong pinning forces on boundaries during the annealing treatment. An examination of the microstructure of the alloy suggests that the origin of the pinning forces is most likely related to the presence of dispersion particles, which are mostly introduced during cryomilling. Two-grain growth regimes were identified: the low-temperature region (<573 K) and the high-temperature region (>573 K). For temperatures lower than 573 K, the activation energy of 25 ± 5 kJ/mol was determined. It is suggested that this low activation energy represents the energy for the reordering of grain boundaries in the UFG material. For temperatures higher than 573 K, an activation energy of 124 ± 5 kJ/mol was measured. This value of activation energy, 124 ± 5 kJ/mol, lies between that for grain boundary diffusion and lattice diffusion in analogous aluminum polycrystalline systems. The results show that the strength and ductility of bulk UFG 5083 Al, as obtained from tensile tests, correlate well with substructural changes introduced in the alloy by the annealing treatment.     

Production of fungal enzymes and proteins from high salt cheese wheys

A fermentation procedure using wheys from buffalo milk, sweet rennet and salted wheys containing up to 15% NaC1, and based on the selection of salt-tolerant fungal cultures for production of microbial proteins and some economically important enzymes, is described. Certain strains of Aspergillus flavus, A. niger, A. ochraceus and A. terreus gave yields of mycelium ranging between 1.5 and 30 g on a dry weight basis. Strong proteolytic activities were exhibited by A. ochraceus, A. flavus and, to a lesser extent, by A. niger in the presence of salt up to 10% as final concentration. Powerful milk-clotting activities were also detected in culture supernatants of A. flavus and A. ochraceus. Extracellular β-galactosidases were released in to the culture fluids of these fungal strains with variable activities, depending upon the salt content of the growth medium. The application of the procedure is discussed.     

Water Pricing in Irrigated Agriculture

Access to water is viewed as a basic human right, a social necessity and a critical environmental resource in spite of the fact that water also has its own financial and economic values. Thus, the selection of set prices and pricing mechanisms addressing these contradicting views is remarkably complicated. On the other hand, water pricing is typically viewed as a good means to cover initial costs and sustain resources invested in water systems development, especially irrigated agriculture. Additionally, the cost of water services needs to be reasonable enough and linked to the amount of water consumed to encourage conservation. This paper illustrates criteria for equitable cost sharing, which include economic justification, efficiency and equity as well as users' acceptance. Elements of agricultural water pricing are also discussed. These elements comprise: the cost of water services, which is the total cost associated with irrigated agricultural systems development; the value of water, which reflects water's economic, social, environmental, cultural and religious values in the society; and the cost recovery mechanisms, which are the organizational and administrative measures to implement agreed upon policies to value water and services and make the collections.     

Détermination des perturbations induites aux extrémités d’une ligne blindée soumise à une excitation ponctuelle de courant

This article allows the determination of the induced perturbations at the ends of the coaxial line in wide frequency band enough. The perturbation source is a current direct point injection into the cable screen in any position. For this, we have applied the theory of the state variables, with foundation of the quasi-TEM approximation, in order to simulate the coaxial line above a ground level that has a finished conductivity. This allows us to supply the current and voltage expressions at the ends of the line as their analytic forms for any conditions of charge. Next, the elaborate objective is to verify experimentally on concrete applications if the test obtained results confirm the theoretical expectations supplied by calculation code finalizing.     

Effect of doping polyacrylic acid with some dopants as studied by different techniques

The molecular weight of polyacrylic acid (PAA) was determined by a viscometric method using NaNO₃ as solvent at 30°C. The specific electric conductivities (σ) of PAA as well as PAA doped with carbon black (CB), chromium oxide (Cr₂O₃), and cupferron with different concentrations (from 0.25 to 1 wt %) were measured at a temperature range 360–400 K. IR spectra of some polymers were determined and it was shown that when PAA was doped with 0.5 wt % CB, a C? O? C band appeared at 775–875 cm^?1. The positron annihilation lifetime (PAL) spectra in PAA doped with the above‐mentioned dopants were measured as a function of their concentrations. It was observed that the short lifetime intensity I₁ decreased, whereas the intermediate lifetime intensity I₂, which is related to the conductivity of the material, increased with increasing the wt % of Cr₂O₃ and cupferron as well as at low concentrations of CB. These results are discussed in terms of the conducting island model. It was found that there were distinct positive relationships between σ and I₂. © 2002 John Wiley & Sons, Inc. J Appl Polym Sci 84: 877–883, 2002; DOI 10.1002/app.10381     

Synthesis and characterization of antioxidants and detergent dispersant based on some polyisobutylene copolymers

Polyisobutylene succinic anhydride-urea/polyamines (PIBSA) copolymers were synthesized as potential antioxidants and detergent dispersant agents for lubricating oils samples (SAE-30). Homogeneity, thermal stability and dispersancy of the solutions were determined. Fully soluble oil compounds that are thermally stable up to 250 °C were achieved. The oxidation stability of lube oil samples in the presence of four designed PIBSA additives (varying in the number of amine groups) was determined for a time period of up to 72 hours. The dependence of the additive efficiency on its concentration was studied to achieve maximum stability. Some PIBSA additives at concentration 3.0 · 10⁴ ppm exhibit the best results. Dispersivity values were measured at predetermined oxidation times. The results proved reliable dispersion capability as the nitrogen content of the additive is increased, i.e. the increase in the basic character of the additive leads to the increase in the neutralization capability. Moreover, the designed PIBSA additives retain their efficiency after long oxidation times, confirming their role as multifunctional nitrogen containing polymeric additive. Electronic Publication