Influence of Sulphur and Phophorus on the Hot Deformation of Fe-Cr 13% High Purity Steel

A series of Fe-Cr13%-C high purity steels containing increasing volume fractions of Sulphur (30, 60 and 100ppm) and Phosphorus (30, 60 and 100ppm) were prepared in order to study their hot deformation properties by tensile tests at various strain rates (10-1s-1 to 10-4s-1) and at temperatures from 700°C to 1100°C. It is observed that the hot ductility is lowered at 1000°C with the addition of sulphur. However, this decrease is relatively small (about 30% for l00ppm of sulphur) and quite similar for all additions of sulphur. When phosphorus is added, the embrittlement is along the whole deformed specimen. The usual criteria of ductility by parameter Z do not seem to be sufficient to describe this embrittlement

Combined impacts of oregano extract and vacuum packaging on the quality changes of frigate tuna muscles stored at 3±1°C

Aim: The combined effects of oregano extract with vacuum packing (VP) on the quality enhancement of dark and white muscles of frigate tuna (Auxis thazard) stored as intact fillet at refrigerated (3±1°C) conditions were studied. Materials and Methods: About 35 kg of fish were filleted without skin removal and randomly divided into two groups. One group without treatment (control) and the remaining group were dipped in a sterilized oregano extract solution for 5 min. Chemical, microbiological, sensorial, and textural analyses were carried out in each of dark and white muscles of frigate tuna fillets during storage. Results: Several quality indexes were higher in dark muscle than white muscle. The sensory assessment indicated that both muscles from control had a shelf life of 12 days. Quality parameters of both muscles had the same tendency and were significantly affected by time and also by the presence of plant extract in VP. Although VP alone was sufficient to delay lipid oxidation on fish fillets, especially on dark muscle but cannot enhance the textural deterioration in both muscles. Conclusion: Consequently, the employment of such combination had a cumulative effect on preservation, resulting in prolonging the shelf life of both frigate tuna muscles

Neutral donor bound excitons studied by selective photoluminescence in wurtzite GaN

Selective photoluminescence experiments have been used to analyse the neutral donor bound exciton spectra in n type wurtzite GaN epitaxial layers deposited on 6H-SiC, Al2O3 and GaN substrates, In heterostructure layers, the existence of residual strain distributions make possible the observation of resonant sharp lines due to the recombination of bound excitons selectively created in excited states. It is shown that the excited states consist of rotational states of the hole belonging to the A valence band in GaN/sapphire and in homolayers. In GaN/SiC both A and B valence band states are involved

Benzohydrazide as a good precursor for the synthesis of novel bioactive and anti-oxidant 2-phenyl-1,3,4-oxadiazol-aminoacid derivatives: Structural determination, biological and anti-oxidant activity

The synthesis and biological assessment of 2,5-disubstituted-1,3,4-oxadiazole derivatives from benzo hydrazide and amino acids as novel potential antioxidant and antibacterial agents have been reported. The structures of the new compounds were characterized by physicochemical properties and spectral methods. The synthesized compounds were screened for their in vitro antibacterial activity against three Gram-positive bacterial strains, namely Staphylococcus aureus ATCC 25923, Bacillus cereus ATCC 14579, Listeria innocua ATCC 33090, and two Gram-negative bacterial strains, namely Pseudomonas aeruginosa ATCC 27853, Escherichia coli ATCC 25922, and antifungal activity against Candida albicans ATCC 10231 in comparison with Amoxicillin, Tetracycline, Gentamicin and Oxacillin as standards. Most of the compounds have excellent efficacy, and some of them, such as 5i, 5g, 5d, 5c, and 5j can inhibit their activity better or very close to that of Amoxicillin, Tetracycline, Gentamicin, Oxacillin used as standards. Compounds 5b and 5i provided good results against L. innocua with inhibition values of IZ = 14 mm and IZ = 22 mm, respectively, while the rest of the compounds and antibiotics were unable to inhibit it. Compounds 5c, 5d, 5g and 5j showed excellent activity against C. albicans with values between 31 mm and 34 mm. These results were better than all the standards used. The MIC value (25 µg/ml) for derivatives 5(c-e), 5g and 5(i-j) against B. cereus represent the best activity of the tested compounds. All the target compounds were also screened for radical scavenging antioxidant activities by DPPH, FRAP, and TAC assays and found to be excellent antioxidant agents. According to the results, it was observed that most derivatives synthesized showed excellent activity with a concentration of 250 µg/ml as an antioxidant agent (76 % < RSA < 95.5 %) which gave an inhibition percentage that was better or very close to that of ascorbic acid and better than BHT

Selective photoluminescence spectroscopy of shallow levels in wide band gap semiconductors

We present an overview of recent selective photoluminescence (PL) experiments on shallow levels in ZnSe and GaN. Through two electron transitions (TET) and electronic Raman scattering (ERS) investigations on solid phase recrystallized bulk ZnSe doped with Al, Cl and In, the spectroscopic properties of donor impurities are re-examined. It is shown that the donor spectra previously attributed to Al and Cl are in fact due to common residual impurities. The Al-donor excited states are detected up to n = 6 allowing a very accurate determination of its ionization energy. We show that the central cell correction of Al is vanishing leading to a new evaluation of the Rydberg which is discussed in view of the last experimental determinations of the dielectric constant and electron effective mass. The neutral-donor bound-excitons have been studied in n-type wurtzite GaN homoepitaxial layers and heteroepitaxial layers deposited on sapphire or SiC substrates. It is demonstrated that the existence of strain distributions in heterostructures induces original resonant effects on selective photoluminescence spectra allowing to identify the bound exciton excited states on a large domain of tensile and compressive strains and in particular near the A and B valence band crossing. Finally, the donors are investigated by TET and ERS spectroscopy. (C) 2001 Elsevier Science B.V. All rights reserved