Effect of heat treatment in air on the thermal properties of SiC fibre reinforced composite: Part 2 A magnesium aluminium silicate (MAS) matrix glass ceramic composite

The thermal properties of a magnesium aluminium silicate (MAS) glass ceramic matrix composite reinforced by SiC (Nicalon) fibres have been investigated before and after heat treatment in the temperature range 600–1,200 °C. Within this temperature range, during the heat treatment at lower temperatures such as 600 and 700 °C, the oxidation of the carbon layer occurred and mixture of silicon and carbon was formed in the interface. This results in a decrease in thermal diffusivity values. After heat treatment at the temperatures higher than 1,000 °C, the carbon layer was thickened and resulted in the higher thermal diffusivity values.     

Significance of fluid regime in biological filtration

A dispersed flow model previously developed to study substrate utilization in unsaturated media was experimentally verified and its practical application was considered. For this purpose, measurements were made using tap water and a synthetic feed solution. The importance of the change in fluid regime as regards to the simultaneous transport and reaction within biological filters were demonstrated. The effect of drop formation and the breakage of liquid jets inside the filters on substrate utilization was also shown.     

The pharmacokinetics and pharmacodynamics of the oral iron chelator deferiprone (L1) in relation to hemoglobin levels

Recently, we demonstrated that administration of the orally active iron chelating agent deferiprone (1,2-dimethyl-3-hydroxypyrid-4-one (L1)) at 6-hour intervals results in significantly greater urinary iron excretion than that induced during administration of the drug at 12-hour intervals. That study was conducted in thalassemia patients, all of whom had received a packed red cell transfusion of 15 cc/kg. 72 hours prior to evaluation of urinary iron excretion, at a time when endogenous erythropoiesis would be expected to be at its lowest. In clinical practice however, thalassemia patients, suppression of endogenous erythropoiesis is not sustained between transfusions. We set out to determine the influence that administration of deferiprone has on urinary iron excretion at lower hemoglobin concentrations, immediately prior to transfusion. We hypothesized that hemoglobin levels will affect the ability of deferiprone to chelate iron. Ten regularly transfused patients with homozygous beta-thalassemia (HBT) aged mean +/- SD, 20.9 +/- 4.7, range 13 - 27 years, receiving long-term therapy with deferiprone, were treated with deferiprone 75 mg/kg/day, administered every 6 hours (or every 12 hours) for 72 hours immediately prior to a blood transfusion in the first month. One month later each patient received the other of the 2 dosing regimens for 72 hours immediately prior to transfusion. The deferiprone-induced 24-hour urinary iron excretion was similar during both dosing regimens; 0.56 +/- 0.45 mg/kg when L1 was given every 6 hours and 0.48 +/- 0.52 mg/kg when L1 was administered every 12 hours (p = 0.79). However, the calculated 24-hour area under the plasma concentration-time curve (AUC0-24) of deferiprone was significantly lower when deferiprone was administered at 6-hour intervals (6,762.8 +/- 1,601.6 mg*min/l), than that observed when deferiprone was administered every 12 hours (8,250.1 +/- 1,235.7 mg*min/l) (p = 0.04). The pharmacokinetics of deferiprone when administered immediately prior to transfusions are different from those following transfusions. More studies assessing total body iron excretion are needed to determine the contribution of the fecal route in iron excretion.     

High-quality photonic sampling streams from a semiconductor diodering laser

We report on the development of an ultralow-noise, external-cavity, actively mode-locked semiconductor diode laser for application in next-generation photonic sampling systems. A summary of harmonically mode-locked noise characteristics in a 65-MHz ring cavity is presented through the range of pulse repetition frequencies between 130 MHz and 8.3 GHz (2nd-128th harmonic). Important implications regarding the use of gain-versus-loss modulation as the active modelocking mechanisms are discussed. We also report what are, to our knowledge, the lowest noise characteristics achieved to date for a semiconductor diode laser operating at 10 GHz. Individually optimized results of 0.12% rms amplitude noise (10 Hz-10 MHz), and 43 fs rms residual phase jitter (10 Hz-10 MHz) provide a theoretical resolution of 8.6 bits in a 10-GSPS optical analog-to-digital converter. We have also achieved dispersion-compensated pulsewidths; as short as 1.2 ps, and shown successful operation of a novel phase-locked-loop capable of reducing the rms; residual phase noise by as much as 91% within its response bandwidth. Finally, the first measurements of residual phase noise out to the Nyquist frequency (5 GHz) are presented, providing an upper bound on the rms residual phase jitter of 121 fs (10 Hz-5 GHz)     

A STUDY OF THE FLOTATION OF OXIDIZED AHASRA COAL

The flotation of oxidized Amasra Coal which was collected between 1973-1978 and, stored in the atmospheric conditions was examined In this work. Coal samples were fractioned by wet screening to +0.560 mm, -0.500 + 0.140 mm, -0.140 mm particle sizes and first fraction was ground to -0.560 mm before flotation. Motorin and pine oil which had been heated at 125° C for 5 hours were used ns flotation reagents. The influence of impeller speed, aeration rate, solid concent of the pulp, reagent amounts were examined and optimum values were determined. Increase of the pine oil amount added to the pulp, increased the coal. recovery on the flotation of this oxidized coal.     

Methane to higher hydrocarbons via halogenation

Activation of methane with a halogen followed by the metathesis of methyl halide is a novel route from methane to higher hydrocarbons or oxygenates. Thermodynamic analysis revealed that bromine is the most suitable halogen for this goal. Analysis of the published data on the reaction kinetics in a CSTR enabled us to judge on the effects of temperature, reactor residence time and the feed concentrations of bromine and methane to the conversion of methane and the selectivity towards mono or dibromomethane. The analysis indicated that high dibromomethane selectivity is attainable (over 90%) accompanied by high methane conversions. The metathesis of dibromomethane can provide an alternative route to the conversion of methane (natural gas) economically with smaller installations than the current syn-gas route.     

Diffusion and influence of Cu on properties of CdTe thin films and CdTe/CdS cells

The effective diffusion coefficients of Cu for thermal and photodiffusion in the CdTe films have been estimated from resistivity versus duration of thermal or photoannealing curves. In the temperature range 60–200°C the effective coefficient of thermal diffusion (D_t) and photodiffusion (D_ph) are described as D_t=7.3×10⁻⁷exp(−0.33/kT) and D_ph=4.7×10⁻⁸exp(−0.20/kT).It is found that the diffusion doping of CdTe thin films by Cu at 400°C results in a sharp decrease of resistivity up to 7 orders of magnitude of p-type material, depending on thickness of Cu film. The comparative study of performance of CdTe(Cu)/CdS and CdTe/CdS cells has been studied. It is shown that the diffusion doping of CdTe film by Cu increases efficiency of CdTe(Cu)/CdS cells from 0.9% to 6.8%. The degradation of photovoltaic parameters of CdTe(Cu)/CdS cell, during testing under forward and reverse bias at room temperature, proceeds at a larger rate than those of CdTe/CdS cell without Cu. The degradation of performance of CdTe(Cu)/CdS cells is tentatively assigned to electrodiffusion of Cu in CdTe, resulting in redistribution of concentration of Cu-related centers in CdTe film and heterojunction region.     

Concomitant Crystallization of Copper(II) Sachharinato Complexes with 2-methylpyrazine as a Monomer and an One-dimensional Polymer: Syntheses,Crystal Structures,Spectroscopic and Thermal Properties

The reaction of [Cu(sac)₂(H₂O)₄] · 2H₂O with 2-methylpyrazine (mpyz) leads two complexes, concomitant crystallization of a mononuclear complex [Cu(sac)₂(mpyz)(H₂O)₂] (1) and a polymeric complex [Cu(sac)₂(μ-mpyz)]_n (2). Both complexes have been characterized by elemental analyses, magnetic measurements, FT-IR and ESR, TG-DTA and single-crystal X-ray diffraction analyses. Single-crystal X-ray analyses show that complex 1 consists of discrete molecules in which the copper(II) ions exhibits a square-pyramidal coordination geometry. The individual molecules of 1 are connected into a hydrogen-bonded chain structure, which is further assembled to form a three-dimensional network by π–π stacking interactions. Complex 2 is an 1D coordination polymer in which copper(II) centers are bridged by the mpyz ligand. The chains are further assembled to form two-dimensional frameworks by π–π and C–H···π stacking interactions.