Optical conductivity and vibrational spectra of the narrow-gap semiconductor FeGa3_3

Intermetallic narrow-gap semiconductors have been intensively explored due to their large thermoelectric power at low temperatures and a possible role of strong electronic correlations in their unusual thermodynamic and transport properties. Here we study the optical spectra and vibrational properties of $\mathrm{FeGa_3}$ single crystal. The optical conductivity indicates that $\mathrm{FeGa_3}$ has a direct band gap of $\sim 0.7$\,eV, consistent with density functional theory (DFT) calculations. Most importantly, we find a substantial spectral weight also below 0.4~eV, which is the energy of the indirect (charge) gap found in resistivity measurements and ab initio calculations. We find that the spectral weight below the gap decreases with increasing temperature, which indicates that it originates from the impurity states and not from the electronic correlations. Interestingly, we did not find any signatures of the impurity states in vibrational spectra. The infrared and Raman vibrational lines are narrow and weakly temperature dependent. The vibrational frequencies are in excellent agreement with our DFT calculations, implying a modest role of electronic correlations. Narrow M\" ossbauer spectral lines also indicate high crystallinity of the sample

Some aspects of health impairment in workers from an epoxy resin (araldit) plant with regard to hygienic conditions

U ovom radu data je analiza higijenskih uslova, posebno zaprašenost vazduha i hemijskih profesionalnih štetnosti u Odjeljenju araldita. Zaprašenost vazduha (kvarcnom prašinom i prašinom staklenog vlakna) prelazila je MDK, a među hemijskim štetnostima posebno se ističe anhidrid ftalne kiseline koji takođe premašuje MDK. Predloženo je da MDK za prašinu staklenog vlakna iznosi 3 mg/m3. Ispitivanjem zdravstvenog stanja 72 radnika Odjeljenja araldita nađene su hronične upalne promjene na gornjim disajnim putevima. Pored toga ustanovljena su 2 slučaja punktiformne pneumokonioze, 1 slučaj punktiformne pneumokonioze udružene sa inaktivnom tuberkulozom pluća, 5 slučajeva inaktivne tuberkuloze pluća i visok procenat lakih opstruktivnih smetnji (27,1%). Predložene su neke zaštitne mjere koje se odnose na tehničku i medicinsku prevenciju.Hygienic conditions in an araldit plant were analyzed with particular regard to the concentration of dust and noxious chemical substances in the air. Dust level in the air (quartz dust and fiber glass dust) and among chemical noxious agents that of phthalic anhydride exceeded maximum permissible concentrations. It is proposed that maximum permissible concentration for the fiber glass dust be 3 mg/m3. A medical examination of 72 workers employed in the plant revealed chronic inflammatory changes in the upper respiratory airways. Besides, two cases of punctiform pneumoconiosis were found, one of them connected with inactive tuberculosis of lungs, then five cases of inactive tuberculosis of lungs and a high percentage of mild obstructive disturbances (27.1%). Several protective measures concerning technical and medical prevention are recommended

Original scientific paper High-spin binuclear Co(II) complexes with a pendant

octaazamaclocycle and carboxylate

Synthesis of antimicrobial monophase silver-doped hydroxyapatite nanopowders for bone tissue engineering

Monophase silver-doped hydroxyapatite (AgxCa10-x(PO4)(6)(OH)(2); 0.002 lt = x lt = 0.04) nanoparticles were prepared using a neutralization method and investigated with respect to potential medical applications. This method consists of dissolving Ag2O in solution of H3PO4, and the slow addition to suspension of Ca(OH)(2) was applied for the purpose of homogenous distribution of silver ions. Characterization studies from XRD, TEM and FTIR spectra showed that obtained crystals are monophase hydroxyapatites and that particles of all samples are of nano size, with average length of 70nm and about 15-25nm in diameter. Antimicrobial studies have demonstrated that all silver-doped hydroxyapatite samples exhibit excellent antimicrobial activity in vitro against the following pathogens: Staphylococcus aureus, Escherichia coli and Candida albicans. The hydroxyapatite sample with the highest content of silver has shown the highest antimicrobial activity; killed all cells of E. coli and brought to more than 99% reduction in viable counts of S. aureus and C. albicans. The atomic force microscopic studies illustrate that silver-doped hydroxyapatite sample causes considerable morphological changes of microorganism cells which might be the cause of cells' death. Hemolysis ratios of the silver-doped hydroxyapatite samples were below 3%, indicating good blood compatibility and that are promising as biomaterials. Crown Copyright (C) 2010 Published by Elsevier B. V. All rights reserved