Thermal properties and surface reactivity in simulated body fluid of new strontium ion-containing phosphate glasses

In this paper, we investigate the effect of SrO substitution for CaO in 50P₂O₅–10Na₂–(40?x)CaO–xSrO glass system (x from 0 to 40) on the thermal and structural properties and also on the glass reactivity in simulated body fluid (SBF) in order to find new glass candidates for biomedical glass fibers. The addition of SrO at the expense of CaO seems to restrain the leaching of phosphate ions in the solution limiting the reduction of the solution pH. We observed the formation of an apatite layer at the surface of the glasses when in contact with SBF. SrO and MgO were found in the apatite layer of the strontium ion-containing glasses, the concentration of which increases with an increase of SrO content. We think that it is the presence of MgO and SrO in the layer which limits the leaching of phosphate in the solution and thus the glass dissolution in SBF.     

Modified electrical transport probe design for standard magnetometer

Making electrical transport measurements on a material is often a time consuming process that involves testing a large number of samples. It is thus inconvenient to wire up and rewire samples onto a sample probe. We therefore present a method of modifying Quantum Design's MPMS SQUID magnetometer transport probe that simplifies the process of sample mounting. One of the difficulties to overcome is the small diameter of the sample space. A small socket is designed and mounted on the probe so that various samples mounted on individual headers can be readily exchanged in the socket. We also present some test results on the topological insulator Bi(2)Te(2)Se using the modified probe.     

Tight Results on Minimum Entropy Set Cover

In the minimum entropy set cover problem, one is given a collection of k sets which collectively cover an n-element ground set. A feasible solution of the problem is a partition of the ground set into parts such that each part is included in some of the k given sets. Such a partition defines a probability distribution, obtained by dividing each part size by n. The goal is to find a feasible solution minimizing the (binary) entropy of the corresponding distribution. Halperin and Karp have recently proved that the greedy algorithm always returns a solution whose cost is at most the optimum plus a constant. We improve their result by showing that the greedy algorithm approximates the minimum entropy set cover problem within an additive error of 1 nat =log ₂ e bits ≃1.4427 bits. Moreover, inspired by recent work by Feige, Lovász and Tetali on the minimum sum set cover problem, we prove that no polynomial-time algorithm can achieve a better constant, unless P = NP. We also discuss some consequences for the related minimum entropy coloring problem. G. Joret is a Research Fellow of the Fonds National de la Recherche Scientifique (FNRS).     

High-rate punctured convolutional self-doubly orthogonal codes for iterative threshold decoding

The puncturing technique allows obtaining high-rate convolutional codes from low-rate convolutional codes used as mother codes. This technique has been successfully applied to generate good high-rate convolutional codes which are suitable for Viterbi and sequential decoding. In this paper, we investigate the puncturing technique for convolutional self-doubly orthogonal codes (CSO/sup 2/C) which are decoded using an iterative threshold-decoding algorithm. Based on an analysis of iterative threshold decoding of the rate-R=b/(b+1) punctured systematic CSO/sup 2/C, the required properties of the rate-R=1/2 systematic convolutional codes (SCCs) used as mother codes are derived. From this analysis, it is shown that there is no need for the punctured mother codes to respect all the required conditions, in order to maintain the double orthogonality at the second iteration step of the iterative threshold-decoding algorithm. The results of the search for the appropriate rate-R=1/2 SCCs used as mother codes to yield a large number of punctured codes of rates 2/3/spl les/R/spl les/6/7 are presented, and some of their error performances evaluated.     

High-power single mode InGaAs/AlGaAs laser diodes at 910 nm

Single mode laser diodes have been fabricated from pseudomorphic InGaAs/AlGaAs quantum well epitaxial material operating up to 350 mW CW. The laser output is a single transverse and longitudinal mode to 180 mW, while the spectral output is centred near 910 nm.<>     

High-brightness, high-efficiency, single-quantum-well laser diode array

Single-quantum-well, separate-confinement double-heterostructure laser diode arrays which exhibit a high power conversion efficiency of greater than 54% have been demonstrated. The high efficiency results from a low internal loss of 3cm1 and high internal conversion efficiency. The maximum output power for a 100?m emitting aperture is 2 W CW and is independent of the cavity length.     

Seasonal variation of physical,chemical and sensory characteristics of sea bream (Sparus aurata) reared under intensive conditions in Southern Europe

This study describes the variability of important quality traits in gilthead sea bream produced under intensive conditions in Southern Europe and purchased in a French market (Nantes). Chemical, sensory and histological characteristics were performed on 18 samples delivered over a year. All fish presented far lower dioxin and DL-PCBs or heavy metals concentrations than the maximum limit level set by EC Regulation, being totally safe for human consumption. Fat content and nutritional values reflected by n-3 and n-6 polyunsaturated fatty acids (PUFA) levels were parameters with high variability according to the season or the fish farm. Values of n-3 PUFA ranged from 0.9% to 8.6% and those of n-6 PUFA from 9.3% to 16.6%, corresponding to a respective variation of n-3/n-6 ratio between 0.1 and 0.6. Increased fat levels in flesh lead to a more intense odour, a fatty fish flavour and a whiter appearance of the cooked fillet. Flesh total amino acid composition was rather stable whereas the small differences detected on firmness by the sensory panel were weakly related to histological characteristics. Rearing techniques of the farm seems to modulate the major characteristics of the fish.     

Organoleptic characterization and PAH content of salmon (Salmo salar) fillets smoked according to four industrial smoking techniques

Four industrial processes for smoking food were studied through their effects on the organoleptic properties of smoked salmon and on the occurrence of 20 polycyclic aromatic hydrocarbons (PAHs) known as being contaminants of smoking processes. The contamination by PAHs of the food might be measured by their corresponding toxic equivalent quantity (TEQ) expressed in µg kg^?1. The results show a significant correlation between the smoking process parameters, the odour of the smoked fish and the presence of PAHs. Smouldering, thermostated plates and friction smoking processes allow smoked fish with very close odorant characteristics to be obtained. However, differences of pyrolysis temperature (between 380 and 500 °C) causes significant differences of PAHs concentration even if the contents are under the legal threshold concerning benzo(a)pyrene (5 µg kg^?1). Smoked fish obtained by liquid smoke vaporisation presented the lowest level of PAHs but benzo(a)pyrene concentration is nevertheless important. The odours brought by the liquid smoke process are more ‘cold smoke’ and ‘vegetal/green’ than the other techniques, which are smokier and fishier. Copyright © 2007 Society of Chemical Industry