The local structure of chemical-vapor-synthesized (CVS) crystalline AlN nanoparticles is investigated by combining magic angle spinning nuclear magnetic resonance and X-ray absorption spectroscopies. ...Extended X-ray absorption fine structure data are analyzed by reverse Monte Carlo method, and X-ray absorption near edge structure is interpreted by first principles FEFF calculations. The measurements show behavior characteristic of partially disordered systems. Nevertheless, combined analysis of the data, supported by Rietveld refinement of X-ray diffraction patterns, leads to the conclusion that the observed behavior is due to the small size (large surface to volume ratios) of the nanoparticles (d XRD < 6 nm) and that highly crystalline wurtzite AlN is formed during the CVS process.
In present work boron doped diamond (BDD) electrode was applied for studying electrochemical behavior, as well as for quantitative determination of natural alkaloid, tubocurarine (arrow poison/ TUB). ...Electrochemical behavior was investigated using several organic solvents and aqueous buffers, at different pHs, as supporting electrolytes. After selection of the most appropriate supporting electrolyte and investigation of its electrochemical behavior, analytical procedures for quantitative analysis of TUB were developed in an acetonitrile/methanol (80:20) mixture and in 1 mol L−1 nitric acid, which had linear quantification ranges from 4 × 10−6 to 1 × 10−4 mol L−1 (LOD = 3.07 × 10−6 mol L−1) and 4 × 10−6 to 9 × 10−5 mol L−1 (LOD = 2.45 × 10−6 mol L−1 and 5.28 × 10−7 mol L−1, depending on the selected peak), respectively. The oxidation mechanism of TUB was proposed from the theoretical aspect. Remarkable selectivity and good sensitivity were obtained after the TUB quantification method was optimized, allowing application of the developed method for TUB quantification in biological fluids, with excellent reproducibility, accuracy and precision.
Turboshaft engines, as the rule, contains gear transmission unit - reducer and belong to the group of drive systems with the name motor-reducer. These are the compact and autonomous assemblies for ...various applications. In the case of turboshaft engine in combination with high speed reducer, arise the set of phenomenon which has to be solved. Majority of them are in relation to reducer protection of overheating and of gears and bearings failures. The article contains analysis of heat sources, heat transfer through design structure and heat taking out in order to maintain acceptable temperature level of reducer lubricant. Theoretical discussions are supported with various experimental results and testing procedures, including analytic calculations. The set of design solutions for reducer protection when reducer located in the area of hot gas flow, is the main content. The case study is innovative design of turboshaft motor-reducer with free turbine which provides flexible operation and compact design structure.
The dynamic behavior of machines which rotate at extreme high speeds is crucial for stable and long operation. In design process some dynamics calculation must be taken into account to avoid ...potential operation near resonance areas. This paper considers dynamic analysis of the high speed reducer, designed together with the turbo-shaft engine. Resonances can occur when frequency of rotation and teeth mesh frequency are close to gear pair in mesh natural frequency, to the shafts natural frequencies and to the other parts natural frequencies. Problems can be avoided by translating resonant areas to higher or lower level of frequency by changing some design parameters, mass, stiffness and by variation of the stiffness of bearing supports. The paper presents the approaches to natural frequencies identification for the example of high speed reducer design. Some examples of design solutions, especially for elastic bearing supports and their experimental testing are also presented.
Aluminum nitride (AlN) nanopowders are synthesized in a chemical vapor synthesis (CVS) process using triethylaluminum (TEAl) and ammonia as precursors. A simple reaction-coagulation-sintering model ...is used to investigate the influence of process parameters, such as hot-wall reactor temperature and system pressure, on particle characteristics: size and agglomeration for example. The results of these simulations show good agreement with the experimental data and enable a better understanding of these effects of temperature and pressure on particle size and microstructure. Pure wurtzite phase AlN nanocrystals are obtained for all tested process parameters. The primary particle (crystallite) size ranges from 2.7nm to 11.5nm with (secondary) particle size in the range of 4.3nm to 12.4nm. As predicted by the simulations, the experiments show a low degree of (hard) agglomeration that even reaches the value of 1 for syntheses above 1400°C and 100mbar, implying the complete absence of hard agglomerates at those conditions.
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•Aluminum nitride nanocrystals are produced by chemical vapor synthesis using TEAl and NH3.•Varying the process parameters results in pure wurtzite crystals between 2.7 and 11.5nm.•Particle characteristics are optimized by complementing the experiments with modeling.•No hard agglomerates are detected in samples synthesized above 1400°C and 100mbar.
The aim of this work was to synthesize semiconducting oxide nanoparticles using a simple method with low production cost to be applied in natural sunlight for photocatalytic degradation of pollutants ...in waste water. Iron titanate (Fe
TiO
) nanoparticles with an orthorhombic structure were successfully synthesized using a modified sol-gel method and calcination at 750°C. The as-prepared Fe
TiO
nanoparticles exhibited a moderate specific surface area. The mesoporous Fe
TiO
nanoparticles possessed strong absorption in the visible-light region and the band gap was estimated to be around 2.16 eV. The photocatalytic activity was evaluated by the degradation of methylene blue under natural sunlight. The effect of parameters such as the amount of catalyst, initial concentration of the dye and pH of the dye solution on the removal efficiency of methylene blue was investigated. Fe
TiO
showed high degradation efficiency in a strong alkaline medium that can be the result of the facilitated formation of OH radicals due to an increased concentration of hydroxyl ions.
Hibernation is a period of metabolic suppression utilized by many small and large mammal species to survive during winter periods. As the underlying cellular and molecular mechanisms remain ...incompletely understood, our study aimed to determine whether skeletal muscle myosin and its metabolic efficiency undergo alterations during hibernation to optimize energy utilization. We isolated muscle fibers from small hibernators,
and
and larger hibernators,
and
. We then conducted loaded Mant-ATP chase experiments alongside X-ray diffraction to measure resting myosin dynamics and its ATP demand. In parallel, we performed multiple proteomics analyses. Our results showed a preservation of myosin structure in
and
during hibernation, whilst in
and
, changes in myosin metabolic states during torpor unexpectedly led to higher levels in energy expenditure of type II, fast-twitch muscle fibers at ambient lab temperatures (20 °C). Upon repeating loaded Mant-ATP chase experiments at 8 °C (near the body temperature of torpid animals), we found that myosin ATP consumption in type II muscle fibers was reduced by 77-107% during torpor compared to active periods. Additionally, we observed Myh2 hyper-phosphorylation during torpor in
, which was predicted to stabilize the myosin molecule. This may act as a potential molecular mechanism mitigating myosin-associated increases in skeletal muscle energy expenditure during periods of torpor in response to cold exposure. Altogether, we demonstrate that resting myosin is altered in hibernating mammals, contributing to significant changes to the ATP consumption of skeletal muscle. Additionally, we observe that it is further altered in response to cold exposure and highlight myosin as a potentially contributor to skeletal muscle non-shivering thermogenesis.
This is initial investigation of gene signatures responsible for adapting microscopic life to the extreme Earth environments. We present preliminary results on identification of the clusters of ...orthologous groups (COGs) common to several hyperthermophiles and exclusion of those common to a mesophile (non-hyperthermophile): Escherichia coli (E. coli K12), will yield a group of proteins possibly involved in adaptation to life under extreme temperatures. Comparative genome analyses represent a powerful tool in discovery of novel genes responsible for adaptation to specific extreme environments. Methanogens stand out as the only group of organisms that have species capable of growth at 0?C (Metarhizium frigidum (M. frigidum) and Methanococcoides burtonii (M. burtonii)) and 110?C (Methanopyrus kandleri (M. kandleri)). Although not all the components of heat adaptation can be attributed to novel genes, the chaperones known as heat shock proteins stabilize the enzymes under elevated temperature. However, highly conserved chaperons found in bacteria and eukaryots are not present in hyperthermophilic Archea, rather, they have a unique chaperone TF55. Our aim was to use software which we specifically developed for extremophile genome comparative analyses in order to search for additional novel genes involved in hyperthermophile adaptation. The following hyperthermophile genomes incorporated in this software were used for these studies: Methanocaldococcus jannaschii (M. jannaschii), M. kandleri, Archaeoglobus fulgidus (A. fulgidus) and three species of Pyrococcus. Common genes were annotated and grouped according to their roles in cellular processes where such information was available and proteins not previously implicated in the heat-adaptation of hyperthermophiles were identified. Additional experimental data are needed in order to learn more about these proteins. To address non-gene based components of thermal adaptation, all sequenced extremophiles were analyzed for their GC contents and aminoacid hydrophobicity. Finally, we develop a prediction model for optimal growth temperature.
Predstavljamo inicijalna istrazivanja struktura gena odgovornih za adaptaciju mikroskopskog zivota u ekstremnim uslovima na Zemlji. Ovde, preliminarno prezentujemo rezultate identifikacije klastera orthologus grupa (COGs) zajednickih za nekoliko hipertermofila i izuzimanje onih zajednickih za mezofile (ne-hipertermofile): E. coli K12, bi trebalo da d? grupu mogu ih proteina odgovornih za adaptaciju zivota u ekstremnim uslovima. Komparativna geneticka analiza predstavlja mocno oruzje u otkrivanju novih gena odgovornih za adaptaciju u ekstremnim uslovima. Metanogeni predstavljaju jedinu grupu organizama koji mogu da 'rastu' na 0?C (M. frigidum i M. burtonii) i 110?C (M. kandleri). Mada, se sve termicke komponente adaptacije ne mogu pripisati tim novim genima, 'chaperones' poznatiji kao toplotni udar protein stabilizuje enzime pri povecanju temperature. Nas cilj je koriscenje specijalno razvijenog softvera za komparativnu analizu gena znacajnih za adaptaciju hipertermofila. Slede i hipertermofilski geni su uvrsteni u softver za potrebe ove studije: M. jannaschii, M. kandleri, A. fulgidus kao i tri vrste Pyrococcus. Zajednicki geni, locirani su i grupisani prema njihovoj ulozi u celijskim procesima. Dodatni eksperimentalni podaci su neophodni za dalje izucavanje ovih proteina.
There is evidence of a genetic basis in some cases of idiopathic membranoproliferative glomerulonephritis (MPGN) types I and III, particularly those occurring in families. The clinical and ...morphological features and disease course in two siblings with MPGN are described. In the male sibling, both clinical and morphological features as well as serum complement profile suggested type I MPGN; electron microscopy appearance in the female sibling was consistent with type III MPGN. Both patients had treatment-resistant nephrotic syndrome which evolved into renal insufficiency in the girl. No hereditary complement deficiencies were found in siblings or their parents. Both children exhibited HLA-A24; -B27, w4; -DR11, 52; -DQ3 antigens. Between 1981 and 1996, 18 patients from eight families with unequivocal diagnosis of MPGN I or III had been described. The mode of inheritance appeared to be autosomal dominant or X-linked in four of these families. In 11 patients, including our 2, in whom HLA typing was performed, eight had the HLA-A2 antigen. Similarities and discrepancies regarding clinical and morphological features and outcomes were evident in these intrafamilial cases, suggesting either a similar genetic background or a multigenic origin of MPGN. The familial occurrence of the MPGN, highlighted by our report, supports the concept that genetically determined factors may be involved in the pathogenesis of the disease.
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