Hybrid conversion of solar radiation implies simultaneous solar radiation conversion into thermal and electrical energy in the PV/Thermal collector. In order to get more thermal and electrical ...energy, flat solar radiation reflectors have been mounted on PV/T collector. To obtain higher solar radiation intensity on PV/T collector, position of reflectors has been changed and optimal position of reflectors has been determined by both experimental measurements and numerical calculation so as to obtain maximal concentration of solar radiation intensity. The calculated values have been found to be in good agreement with the measured ones, both yielding the optimal position of the flat reflector to be the lowest (5°) in December and the highest (38°) in June. In this paper, the thermal and electrical efficiency of PV/T collector without reflectors and with reflectors in optimal position have been calculated. Using these results, the total efficiency and energy-saving efficiency of PV/T collector have been determined. Energy-saving efficiency for PV/T collector without reflectors is 60.1%, which is above the conventional solar thermal collector, whereas the energy-saving efficiency for PV/T collector with reflectors in optimal position is 46.7%, which is almost equal to the values for conventional solar thermal collector. Though the energy-saving efficiency of PV/T collector decreases slightly with the solar radiation intensity concentration factor, i.e. the thermal and electrical efficiency of PV/T collector with reflectors are lower than those of PV/T collector without reflectors, the total thermal and electrical energy generated by PV/T collector with reflectors in optimal position are significantly higher than total thermal and electrical energy generated by PV/T collector without reflectors.
•Amorphous powder of Fe-Si-B-Nb-Cu alloy was produced by helium gas atomisation.•Proper annealing resulted in structural relaxation and nanocrystallisation.•Powder cores were manufactured using the ...as-atomised and annealed powders.•Cores exhibit excellent low coercivity and low core losses.•The small particle size and good insulation can explain the low core losses.
The present work demonstrates the high-frequency core loss performance of Fe-based amorphous and nanocrystalline powder cores, initially produced by gas atomised powder, consolidated using sieved particles ≤20 µm, and isolated by a precise insulating layer of polymer to limit the inter- and intra-particle eddy currents to attain enhanced performance. The large glass forming ability (GFA) of the gas atomised powder, reflected by different glass forming instruments, such as the supercooled region (ΔTX = 54 °C) and the reduced glass transition temperature (Trg = 0.56), is consistent with the substantial amorphisation capability of the alloy. To the best of our knowledge, this is the first-ever report to reveal a large ΔTX in the Finemet-type alloy powders, an essential parameter to gas-atomise the amorphous powders with significantly lower cooling rates compared to the melt-spun ribbons. Further, subsequent annealing of the amorphous powders, between the exothermic events guided by differential scanning calorimetry (DSC), lead to the growth of a fine nanocrystalline structure of grains ≤15 nm, thanks to the positive enthalpy of mixing of Cu with the constituents to act as a nucleation agent, to retain the excellent soft magnetic properties. The DC soft magnetic properties of the powders were significantly improved on thermal annealing, confirmed by hysteretic loops, quantified by reduced coercivity HC <1 Oe of annealed powders at <575 °C, and attributed to the reduced magnetoelastic contribution due to zero/near-zero magnetostriction anisotropy, attained due to the homogenous nanocrystalline structure. The amorphous and nanocrystalline powder cores, consolidated by compression moulding, show ultra-high loss performance, due to the ultra-low coercivity attained on nanocrystallisation, and negligible eddy currents loss, owning to efficient insulation of small particles, for high-frequency power conversion applications, such as voltage regulator (VR), and resonant converters, in automotive industry and data storage centres.
Since its discovery in 1945, methotrexate has become a standard therapy for number of diseases, including oncological, inflammatory and pulmonary ones. Major physiological interactions of ...methotrexate include folate pathway, adenosine, prostaglandins, leukotrienes and cytokines. Methotrexate is used in treatment of pulmonary sarcoidosis as a second line therapy and is drug of choice in patients who are not candidates for corticosteroid therapy, with recommended starting weekly dose of 5–15 mg. Number of studies dealt with methotrexate use in rheumatoid arthritis and oncological patients. Authors are conducting research on oral methotrexate use and pharmacokinetics in chronic sarcoidosis patients and have performed literature research to better understand molecular mechanisms of methotrexate action as well as high level pharmacokinetic considerations. Polyglutamation of methotrexate affects its pharmacokinetic and pharmacodynamic properties and prolongs its effect. Bile excretion plays significant role due to extensive enterohepatic recirculation, although majority of methotrexate is excreted through urine. Better understanding of its pharmacokinetic properties in sarcoidosis patients warrant optimizing therapy when corticosteroids are contraindicated in these patients.
We present a model for the radio evolution of supernova remnants (SNRs) obtained by using three-dimensional hydrodynamic simulations coupled with nonlinear kinetic theory of cosmic-ray (CR) ...acceleration in SNRs. We model the radio evolution of SNRs on a global level by performing simulations for a wide range of the relevant physical parameters, such as the ambient density, supernova (SN) explosion energy, acceleration efficiency, and magnetic field amplification (MFA) efficiency. We attribute the observed spread of radio surface brightnesses for corresponding SNR diameters to the spread of these parameters. In addition to our simulations of Type Ia SNRs, we also considered SNR radio evolution in denser, nonuniform circumstellar environments modified by the progenitor star wind. These simulations start with the mass of the ejecta substantially higher than in the case of a Type Ia SN and presumably lower shock speed. The magnetic field is understandably seen as very important for the radio evolution of SNRs. In terms of MFA, we include both resonant and nonresonant modes in our large-scale simulations by implementing models obtained from first-principles, particle-in-cell simulations and nonlinear magnetohydrodynamical simulations. We test the quality and reliability of our models on a sample consisting of Galactic and extragalactic SNRs. Our simulations give − D slopes between −4 and −6 for the full Sedov regime. Recent empirical slopes obtained for the Galactic samples are around −5, while those for the extragalactic samples are around −4.
Heavy metal pollution of the aquatic environment is of great concern worldwide. Heavy metals are capable of inducing oxidative stress by increasing the formation of reactive oxygen species (ROS), and ...directly affecting the antioxidant defense system (AOS) in living organisms. The frog Pelophylax kl. esculentus is a semiaquatic species with semipermeable skin and a complex lifecycle, and represents a potentially useful bioindicator organism. The aim of this study was to investigate the accumulation of several heavy metals (Cd, Co, Cr, Cu, Fe, Hg, Ni, Pb and Zn), and their effects on selected parameters of the AOS, including the activities of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), glutathione reductase (GR), phase II biotransformation enzyme glutathione-S-transferase (GST), the total glutathione (GSH) contents and sulfhydryl (SH) group concentrations, as well as cholinesterases (ChEs) activities in the liver, skin and muscle of P. kl. esculentus. Frog samples were collected at two sites (the Danube–Tisza–Danube canal (DTDC) and the river Ponjavica) in Serbia, which are characterized by different levels of metal pollution. Differences between the metal contents in different tissues showed that the skin of frogs from the DTDC accumulated statistically higher concentrations of Cd, Cu, Pb and Zn, while only the Fe concentration was lower. No significant differences between metal concentrations in muscle tissues of frogs from the DTDC and Ponjavica were observed. Examination of the parameters of the AOS revealed that frogs from the DTDC had higher concentrations of GSH in the liver and of SH groups in the skin and muscle, whereas the activities of the antioxidative enzymes SOD, GHS-Px and GR in the liver and of GR in the skin were lower than in frogs from the Ponjavica. The relationship between metal concentrations and AOS parameters showed the highest number of correlations with GSH, GR and CAT, and with Ni, Zn, Hg, Cr and Cd. Based on the results in this study, we concluded that increased concentrations of heavy metals in frog tissues can alter the AOS, which leads to higher concentrations of GSH and SH groups and lower activities of antioxidative enzymes. The response of the AOS to metal pollutants allowed us to make a distinction between different frog tissues, and to conclude that the liver and skin are more suitable for assessing metal-induced oxidative stress in frogs than muscle.
•Higher metals concentration increase GSH and SH gropus concentrations in frog tissues.•Higher heavy metals concentration decreases antioxidative enzymes SOD, GHS-Px, GR.•Frogs liver and skin are most suitable for examine metal-induced oxidative stress.•CAT, SOD, GR, GSH may function as oxidative stress biomarkers in P. kl. esculentus.
•Rapidly quenched ultra-thin amorphous ribbons for high-frequency drive applications.•Ultra-low loss material performance of rapidly quenched Co-rich amorphous ribbons.•Magnetization reversal by ...rotation in Co-rich alloys due to low residual stress and zero/near-zero λs.
Soft magnetic amorphous materials with ultra-low power loss are highly desirable for high-frequency drive applications. The present work demonstrates the high-frequency power loss performance and underlying loss mechanisms in ultra-thin amorphous alloys. This is achieved by rapid-quenching amorphous alloys of Co-, CoFe- and Fe-rich systems, investigating their amorphous atomic structure, quantifying the saturation magnetostriction constants (λs), imaging magnetic domains at remanent magnetization, analyzing magnetization reversal from various magnetization levels, and finally, investigating the material loss performance over a broad frequency range (f = 50 kHz–2 MHz) at various excitation levels (Bm = 25–100 mT). The ultra-high performance of ultra-thin Co-rich amorphous ribbons, as compared to CoFe- and Fe-rich alloys, was attributed to the significantly low eddy current loss, due to the reduced thickness, and a minimal amount of excess loss, owning to minimal magnetoelastic contributions and magnetization reversal by rotation. The underlying loss mechanisms were analyzed by decomposing material loss into primary components and identifying the magnetization reversal mechanisms using minor hysteresis loops. In the Co-rich amorphous alloys, we suggest that magnetization reversal by rotation dominates, at least at low excitations, while in CoFe- and Fe-rich alloys domain wall displacement prevails and contributes significantly to the excess loss up to the MHz frequency range. Magnetization reversal by rotation in Co-rich alloys could be attributed to the zero/near-zero λs, and eventually low residual stress, leading to a homogeneous magnetic domain structure, as compared to the inhomogeneous “fingerprint-like” complex domains in highly magnetostrictive CoFe-rich alloys.
Sequential 5-alkenyl hydantoin and pyrrolidine ring-forming reactions have been applied in the synthesis of conformationally constrained fused bicyclic scaffold. They are assembled by a three-step ...reaction sequence from two variable building blocks (readily available β-ketoesters and alkenyl halides) by combining a Bucherer–Bergs reaction with a final selenium-promoted intramolecular cyclization as a key step. The chemoselectivity of this bicyclic hydantoin formation is strongly influenced by experimental factors such as the solvent and the use of additives. The reaction is regiospecific giving only five-membered fused bicyclic hydantoins in good to excellent yields stemming from the nucleophilic attack of the nitrogen atom to a cyclic seleniranium ion intermediate during the cyclization step. A separable diastereomeric mixture is obtained; the products with bridgehead substituents and phenylseleno groups in cis relationships were formed predominantly. The reaction tolerates a variety of substitution at the double bond, furthermore, the presence of substituents at C(5) and N(3) position opens up the capability of generating a broad structural diversity.
Display omitted
Bacterial stalk soft rot have been repeatedly observed on maize plants in several commercial fields in northern part of Serbia in the period of 1990 to 2014. The occurrence of the disease ...corresponded with warm weather and increased humidity. Etiological studies of the diseased tissue constantly resulted in isolation of pectolytic bacterial strains. In order to identify the isolated bacteria, twenty-three strains were characterized by morphological, physiolcal, biochemical, and molecular assays. Pathogenicity of the strains was confirmed by Koch’s postulates on 1-week-old maize seedlings. The strains were Gram and oxidase-negative, non-fluorescent, pectolytic, facultative anaerobic and caused hypersensitive response (HR) in tobacco leaves. They produced catalase and lecithinase, but did not produce oxidase and arginine dehydrolase. All strains reduced nitrate and grew at 37 °C, while variable growth was observed in medium containing 5% NaCl. Phenotypic tests and amplification of the specific 420-bp fragment in PCR assay showed that the strains belong to genus
Dickeya
. Using ERIC-PCR analysis seven different genetic profiles were obtained, suggesting the presence of genetic diversity in the population of this pathogen in Serbia. Additionally, phylogenetic analysis based on the
recA
gene sequence analysis indicated that the strains isolated from soft rotted maize belong to
Dickeya zeae
, leading to the conclusion that this bacterium was the causal agent of stalk soft rot of maize in Serbia.
The research was carried out on five double jersey knitted fabrics, knitted from cotton, Viscose®, Tencel®, Modal® and polyester ring spun yarns finesses of 20 tex. A circular double bed knitting ...machine gauge of E17 with the same production parameters was used for knitting all the fabrics. A change in all knitted fabric structure parameters was reflected through fabric mass per unit area, which ranged from 142 g m−2 to 165 g m−2. The minimum and maximum knitted fabric mass per unit area difference is up to 16 %. The lowest thermal resistance have polyester, while the largest have cotton knitted fabric. Thermal resistance of cotton fabric is higher for 36.7 % related to polyester knitted fabric. Considering basic knitted fabric parameters, knitting with same constructional parameters but different yarn raw materials doesn't provide knitted fabric with same mass per unit area or thickness, i.e. thickness factor. It can be concluded that beside basic knitted fabric parameters, yarn raw material influence on thermal resistance.
PDF
