Scattering analysis of slanted fiber gratings

The diffraction efficiency of a tilted in-core fiber grating is analyzed with the scattering formalism and the first Born approximation. Without any prior physical assumptions about the shape or direction of the scattered wave, it is shown that diffraction occurs when the so-called Bragg conditions are nearly satisfied and the interaction process can be described by a pair of coupled first-order differential equations that are exactly the same as those obtained through the coupled-mode analysis.     

Adsorption of nickel and copper onto natural iron oxide-coated sand from aqueous solutions: study in single and binary systems

Natural iron oxide-coated sand (NCS), extracted from the iron ore located in North-West of Tunisia, was employed to investigate its capacity to remove copper and nickel from aqueous solutions. The aim of this work was to characterize the considered sorbent (NCS) and to assess the possibility of removing nickel and copper from aqueous solutions by this sorbent. The effects of agitation time, pH, initial metal ion concentration and temperature on the removal of these metals were studied. In order to study the sorption isotherm, two equilibrium models, the Freundlich and Langmuir isotherms, were analyzed. The effect of solution pH on the adsorption onto NCS was studied in the pH range from 2 to 7 and 2 to 9 for copper and nickel respectively. The adsorption was endothermic and the computation of the parameters, DeltaH degrees, DeltaS degrees and DeltaG degrees, indicated that the interactions were thermodynamically favourable. Experiments with Cu and Ni adsorption measured together showed that Cu severely interfered with Ni adsorption to the NCS and vice versa under the conditions of the two coexisted ions adsorption.     

Preparation,characterization and thermal studies of polymer inclusion cellulose acetate membrane with calix[4]resorcinarenes as carriers

A polymer inclusion membrane (PIM) system with cellulose acetate polymer as support and calix[4]resorcinarenes as carriers has been developed. Special attention was paid to PIM characterization using scanning electron microscopy, Fourier-transform infra-red study, X-ray scattering and thermogravimetric analyses. The efficiency of the membrane transport was optimized as a function of pH, stirring speed, aqueous phases and membrane composition. The results suggested that the transport mechanism is a counter-transport of protons, the mechanism was mainly controlled by the diffusion of the complex formed in the membrane core. Analysis of lead(II) transport through these PIMs was performed. It was found that calix[4]resorcinarenes containing membranes were flexible, resistant and heterogeneous without plasticizer addition.     

Haemoglobin D-Ouled Rabah among the Mozabites: a relevant variant to trace the origin of Berber-speaking populations

We have studied haemoglobin (Hb) variants and blood groups (ABO, RH, and Kell) in 598 children from the Berber population of the Mzab. Hb D-Ouled Rabah, considered as a private marker of the Kel Kummer Tuaregs, and Hb C were found at the same gene frequency (0.015). Haplotype analysis suggests a single origin to the Hb D mutation. Genetic distances calculated from the blood group data cluster Mozabites and Tuaregs with the other Berber-speaking groups, Arabic-speaking populations being more distant. But, we found no specific relationship between Mozabites and Kel Kummers. Tuaregs in general exhibit features that tend to differentiate them from other Berber-speaking groups. Hb D-Ouled Rabah may be specific of Berber-speaking populations.     

Experimental and theoretical study of hydrogen absorption by LaNi3.6Mn0.3Al0.4Co0.7 alloy using statistical physics modeling

A monolayer model treated by statistical physics by means of the grand canonical ensemble has been developed, describing PCT isotherms for absorption of hydrogen by LaNi_3.6Mn_0.3Al_0.4Co_0.7 alloy. This model presents a high correlation with the experimental results. The experimental absorption isotherms are fitted at three temperature different (T = 293 K to T = 313 K). The physicochemical parameters involved in the model were determined from the experimental isotherms by numerical simulation. These parameters, such as two numbers of absorbed atoms per site n₁ and n₂, two receptor site densities N_1M and N_2M, and two energetic parameters, P₁ and P₂ are discussed in relationship with absorption process. The different thermodynamic functions which govern the absorption mechanism such as entropy (S_a), free enthalpy of Gibbs (G) and internal energy (E_int) are derived by statistical physics model calculations.     

Massed versus distributed wordprocessor training

Two groups of subjects were trained on 12 basic word processing (WP) functions. One group was trained in a 'massed' 60-minute session and the other on a 'distributed' schedule of 60 min in two sessions separated by a ten-minute break. Subjects were tested on speed and accuracy immediately after training, and one week later to measure retention. It was found that the distributed training group performed significantly faster and more accurately than the massed group. This result was obtained at the end of the training period and also on the retention test. The results strongly indicate that a session of 60 min is too long for efficient WP training.     

A study on removal characteristics of copper from aqueous solution by sewage sludge and pomace ashes

In the present work, the abilities of sewage sludge and pomace ashes to remove copper (Cu(2+)) ions from aqueous solutions are compared. Batch adsorption experiments were performed in order to evaluate the removal efficiency of these materials. Effect of contact time, solution pH, ash concentration and temperature on the removal of Cu(2+) was investigated. The results of batch equilibrium studies showed that the solution pH was the key factor affecting the adsorption characteristics. In general, the amount of Cu removed increased as the solid concentration and pH increased, and then it remained constant over a wide pH region. The adsorption test of applying sewage sludge and pomace ashes into synthetic wastewater revealed that the adsorption data of these materials for copper ions were better fitted to the Langmuir isotherm since the correlation coefficients for the Langmuir isotherm were higher than that for the Freundlich isotherm. The estimated maximum capacities of copper adsorbed by sewage sludge and pomace ashes were 5.71 and 6.98 mg g(-1), respectively. Experimental results indicated that the adsorption was favorable at higher pH and higher temperature. Values of DeltaG degrees ranging from -4.64 to -5.13 kcal mol(-1) for sewage sludge ash and from -4.97 to -5.53 kcal mol(-1) for pomace ash suggest that the adsorption reaction is a physical process enhanced by the electrostatic effect. The values of DeltaH degrees and DeltaS degrees are, respectively, 4.27 kcal mol(-1) and 30.6 cal K(-1)mol(-1) for sewage sludge ash and 4.33 kcal mol(-1) and 31.3 cal K(-1)mol(-1) for pomace ash. The mechanisms of copper removal by these materials included adsorption and precipitation. The sewage sludge and pomace ashes are shown to be effective adsorbents for this metal.