Novel Approach for Synthesis of Magnesium Borohydride, Mg(BH4)2

AbstractMg(BH4)2 is a complex hydride with one of the highest hydrogen contents (∼ 15%) known yet. Several synthesis routes have been reported for it, all based on the metathesis reaction of MgCl2 with NaBH4 performed in a ball-mill or in suitable solvents.In the present study a new approach for synthesis of Mg(BH4)2 will be presented in which the more reactive MgBr2 is used instead of MgCl2. For this purpose a mixture of MgBr2 and NaBH4 (molar ratio: 1: 2 and 1:2.15) was ball-milled for 6, 12 and 18h, respectively. Mg(BH4)2 was extracted from the reaction product (Mg(BH4)2 + NaBr) by Soxhlet with diethylether over a day. The remaining residue after solvent evaporation was dried in vacuum at 150°C for 24h and 5h at 190°C. The intermediate and final products of the reactions were analyzed using XRD, DTA/TG, Mass and Vibrational Spectroscopy. The XRD diagrams of the mixture after ball milling showed only the characteristic reflections of NaBr and the patterns obtained after solvent extraction was in all cases consistent with β- Mg(BH4)2. The additional weak MgBr2 reflections, decreased by increasing the ball milling time from 6 to 18h. The DTA/TG coupled with MS revealed ∼11% mass loss when the product was heated up to 600°C. The result of MS detected that the exhaust gas is exclusively H2.Compared to MgCl2, the use of MgBr2 has two advantages: the reaction time is considerably shorter and the excess of MgBr2 can act as additive lowering the onset temperature for hydrogen release from 290°C - for pure Mg(BH4)2 - to ∼ 220°C

Inappropriate antimicrobial use in Turkish pediatric hospitals: A multicenter point prevalence survey

Objectives: Although well-defined principles of rational antimicrobial use are available, inappropriate prescribing patterns are reported worldwide. Accurate information on the usage of antimicrobials, including factors associated with and influencing their use, is valuable for improving the quality of prescription practices. Methods: In this cross-sectional point prevalence survey, data on patients hospitalized in 12 different children's hospitals were collected on a single day. Appropriateness of prescription was compared between the types of antimicrobials prescribed, indications, wards, and presence of/consultation with an infectious disease physician (IDP). Results: A total 711 of 1302 (54.6%) patients evaluated were receiving one or more antimicrobial drugs. The antimicrobial prescription rate was highest in pediatric intensive care (75.7%) and lowest in the surgery wards (37.0%). Of the 711 patients receiving antimicrobials, 332 patients (46.7%) were found to be receiving at least one inappropriately prescribed drug. Inappropriate use was most frequent in surgery wards (80.2%), while it was less common in oncology wards (31.8%; p < 0.001). Respiratory tract infection was the most common indication for antimicrobial use (29.4%). Inappropriate use was more common in deep-seated infections (54.7%) and respiratory infections (56.5%). Fluoroquinolones were used inappropriately more than any other drugs (81.8%, p = 0.021). Consultation with an IDP appears to increase appropriate antimicrobial use (p = 0.008). Conclusions: Inappropriate antimicrobial use remains a common problem in Turkish pediatric hospitals. Consultation with an IDP and prescribing antimicrobial drugs according to microbiological test results could decrease the inappropriate use of antimicrobials

LiMg0.1Co0.9BO3 as a positive electrode material for Li-ion batteries

LiCoBO3 could be a promising cathode material given the electronic and ionic conductivity problems are addressed. Here, Mg substitution in LiCoBO3 is employed to stabilise the structure and improve the electrochemical performance. LiMg0.1Co0.9BO3 is synthesised for the first time via sol–gel method and Mg substitution in the structure is verified by X-ray powder diffraction and energy dispersive X-ray analyses. The electrochemical properties are investigated by galvanostatic cycling and cyclic voltammetry tests. The composite electrode with conductive carbon (reduced graphite oxide and carbon black) delivers a first discharge capacity of 32 mA h g−1 within a 4.7–1.7 voltage window at a rate of 10 mA g−1. The cycling is relatively stable compared to the unsubstituted LiCoBO3. Mg substitution may enhance the electrochemical performance of borate-based electrode materials when combined with suitable electrode design techniques.ISSN:2046-206

Improved Superconducting properties in the Mg11B2 low activation superconductor prepared by low-temperature sintering

Mg11B2 has a great application prospect in the superconducting coils for fusion reactor as the low activation superconductors . The un-doped Mg11B2 and Cu-doped Mg11B2 bulks using 11B as a boron precursor were fabricated by low-temperature sintering in present work. It was found that the prepared Mg11B2 low activation superconductors exhibit better Jc performance than all of other Mg11B2 samples reported in previous studies. As for Cu doped Mg11B2, minor Cu addition can obviously improve the Mg11B2 grain crystallization and reduce the amount of MgO impurity. Hence, improved grain connectivity and higher Jc at low fields is obtained in Cu doped Mg11B2 samples. For un-doped samples, refined grains and more MgO impurity with proper size brought about more flux pinning centers, resulting in better Jc performance at high fields

Altitude impacts body size but not age in the Asia Minor Thin-toed Gecko (Mediodactylus heterocercus)

Age and size-related life-history traits of animals are influenced by a variety of factors. In connection with climate, the effect of altitude on demographic parameters may differ among different populations of the same species. In the present study, we analyzed how body size and longevity of the Asia Minor Thin-toed Gecko (Mediodactylus heterocercus (Blanford, 1874)) vary along an elevational gradient in Turkey. For this purpose, a total of 138 specimens of the species (52 males, 75 females, and 11 juveniles) from 11 different populations were analyzed. Populations at intermediate altitude had shorter lifespans compared with those at low and high altitudes (marginal environments). Furthermore, adult life expectancy (ESP), which indicates the expected lifespan of individuals having reached sexual maturity, was higher in high-altitude populations (ESP: 6.59 years) than in intermediatealtitude populations (ESP: 5.40 years) and low-altitude populations (ESP: 6.01 years). The results of the study suggest that the body size, but not age, of Asia Minor Thin-toed Geckos increases with altitude

Size effects in Fe3+-doped PbTiO3 nanocrystals—Formation and orientation of (Fe'Ti-V0°°)° defect-dipoles

A set of Fe3+-modified PbTiO3 nanopowders has been synthesized according to the combined polymerization and pyrolysis (CPP) route of metallorganic precursors [Erdem E, Böttcher R, Semmelhack H-C, Gläsel H-J, Hartmann E, Hirsch D. Preparation of lead titanate ultrafine powders from combined polymerisation and pyrolysis route. J. Mater. Sci. 2003;38:3211–7] with subsequent calcination at various temperatures. X-ray diffraction verifies the formation of a PbTiO3 perovskitic phase and Raman-spectroscopy proves the existence of ferroelectricity. Furthermore, the prevailing defect structure has been investigated by means of electron paramagnetic resonance (EPR) spectroscopy. The EPR results clearly indicate marked size effects by approaching to the critical grain size (dcrit<12 nm) at which a size-driven tetragonal-to-cubic phase transition is observed at room temperature. As a function of mean grain size, either (Fe'Ti-V0°°)° defect dipoles or ‘isolated’ defects (Fe'Ti, V0°°) are formed. These results are analyzed in terms of a core–shell model. Accordingly, the obtained Fe3+-modified PbTiO3 nanoparticles consist of a ferroelectric core, a distorted interface region, and a cubic dead layer which is paraelectric