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排序方式: 共有382条查询结果,搜索用时 15 毫秒
141.
Milica Manojlovi-Stojanoski Slavica Borkovi-Miti Nataa Nestorovi Nataa Risti Svetlana Trifunovi Magdalena Stevanovi Nenad Filipovi Aleksandar Stojsavljevi Slaan Pavlovi 《International journal of molecular sciences》2022,23(21)
The chemical element selenium (Se) is a nonmetal that is in trace amounts indispensable for normal cellular functioning. During pregnancy, a low Se status can increase the risk of oxidative stress. However, elevated concentrations of Se in the body can also cause oxidative stress. This study aimed to compare the effects of BSA-stabilized Se nanoparticles (SeNPs, Se0) (BSA-bovine serum albumin) and inorganic sodium selenite (NaSe, Se+4) supplementation on the histological structure of the placenta, oxidative stress parameters and the total placental Se concentration of Wistar rats during pregnancy. Pregnant females were randomized into four groups: (i) intact controls; (ii) controls that were dosed by daily oral gavage with 8.6% bovine serum albumin (BSA) and 0.125 M vit C; (iii) the SeNP group that was administered 0.5 mg of SeNPs stabilized with 8.6% BSA and 0.125 M vit C/kg bw/day by oral gavage dosing; (iv) the NaSe group, gavage dosed with 0.5 mg Na2SeO3/kg bw/day. The treatment of pregnant females started on gestational day one, lasted until day 20, and on day 21 of gestation, the fetuses with the placenta were removed from the uterus. Our findings show that the mode of action of equivalent concentrations of Se in SeNPs and NaSe depended on its redox state and chemical structure. Administration of SeNPs (Se0) increased fetal lethality and induced changes in the antioxidative defense parameters in the placenta. The accumulation of Se in the placenta was highest in SeNP-treated animals. All obtained data indicate an increased bioavailability of Se in its organic nano form and Se0 redox state in comparison to its inorganic sodium selenite form and Se+4 redox state. 相似文献
142.
Vesna Marjanovic Radmila Markovic Mirjana Steharnik Silvana Dimitrijevic Aleksandar D. Marinkovic Aleksandra Peric-Grujic Maja olic 《International journal of molecular sciences》2022,23(22)
Highly porous lignin-based microspheres, modified by magnetite nanoparticles, were used for the first time for the removal of selenate anions, Se(VI), from spiked and real water samples. The influence of experimental conditions: selenate concentration, adsorbent dosage and contact time on the adsorption capacity was investigated in a batch experimental mode. The FTIR, XRD, SEM techniques were used to analyze the structural and morphological properties of the native and exhausted adsorbent. The maximum adsorption capacity was found to be 69.9 mg/g for Se(VI) anions at pH 6.46 from the simulated water samples. The modified natural polymer was efficient in Se(VI) removal from the real (potable) water samples, originated from six cities in the Republic of Serbia, with an overage efficacy of 20%. The regeneration capacity of 61% in one cycle of desorption (0.5 M NaOH as desorption solution) of bio-based adsorbent was gained in this investigation. The examined material demonstrated a significant affinity for Se(VI) oxyanion, but a low potential for multi-cycle material application; consequently, the loaded sorbent could be proposed to be used as a Se fertilizer. 相似文献
143.
Petrovic Radivoj Senborn Aleksandar Vujosevic Mirko 《Reliability, IEEE Transactions on》1980,(5):392-396
This paper presents an approach for allocating spares on three echelons to increase system reliability and decrease plant down-time in a cost-effective manner. The usual assumptions are made: a) the demands for spares have the Poisson distribution with known demand rates, b) all the failures of plant parts are s-independent, c) for the plant to be operating, all parts must be operating, thus forming 1-out-of-M:F configuration. To each echelon of the spatially distributed spare-support system is associated a relevant optimization criterion and a corresponding constraint. The algorithm for determining stock levels adapts the known `per-pound' procedure, applied in sequence from the first echelon to the third echelon. The sequential optimization is computationally efficient. The test examples have confirmed that the algorithms proposed can handle 3-echelon sparing problems with even thousands of part types. 相似文献
144.
145.
Haihua Yang Wenguang Fan Aleksandar Vaneski Andrei S. Susha Wey Yang Teoh Andrey L. Rogach 《Advanced functional materials》2012,22(13):2821-2829
The quality of heterojunctions at the quantum dot (QD)‐TiO2 nanotube (TNT) interface has important implications on the efficiencies of photoelectrochemical solar cells. Here, it is shown that electrophoretic deposition of pre‐synthesized thioacid‐capped CdTe QDs results in relatively poor charge transfer across the heterojunctions. This is likely due to the intermediate layer of bifunctional linkers (S‐R‐COOH) in between the QDs and TNT. On the other hand, CdTe QD‐sensitized TNT prepared by in situ deposition in aqueous medium provides direct QD‐TNT contact, and hence more favorable heterojunction for charge transfer. This is exemplified not only by the drastic improvement in photocurrent efficiencies, but also provides clear difference on the size‐dependent electron injection efficiencies from the CdTe QDs of different sizes. By extending the system further to CdSe QDs, drastic enhancement is found when carrying out the in situ deposition in an organic medium. The results are discussed in terms of the nature of deposition and the corresponding charge transport characteristics. More importantly, the work reflects the intricacy of the effects of QD size and the quality of the heterojunctions on the overall photoconversion efficiencies. 相似文献
146.
Jelena Živančev Sandra Bulut Sunčica Kocić-Tanackov Danica Jović Aleksandar Fišteš Igor Antić Aleksandar Djordjevic 《Journal of food science》2024,89(3):1814-1827
Antifungal and antimycotoxigenic activity of fullerenol nanoparticles (FNPs) were investigated on Aspergillus flavus growth isolated from a real food sample and aflatoxins (AFs) (AFB1 and AFB2) production. The final FNPs concentrations in in vitro and in commercial corn flour after the stationary incubation period of 7 and 14 days were in the range 0.16–80 µg/mL and 0.16–80 µg/g, respectively. Nanocharacterization of FNPs revealed an average size of 5–20 nm and a zeta potential of −35 mV. The highest degree of A. flavus mycelium growth inhibition (28%) after 7 days was observed for applied FNP concentration of 8.0 µg/mL, while after 14 days FNP concentration of 0.32 µg/mL led to the maximal inhibition of A. flavus mycelium growth (36%). Spearman's correlations analysis revealed a strong positive correlation between AFB1 and AFB2 concentrations in YES broth after 7 (R = 0.994, p < 0.05) and 14 days (R = 0.976), as well as between AFs concentrations and A. flavus mycelium mass after 7 (R = 0.786 for AFB1 and R = 0.766 for AFB2) and 14 days (R = 0.810 for AFB1 and R = 0.833 for AFB2). Paired samples t-test showed the existence of a statistically significant difference (p < 0.05) between the produced AFs concentrations after the incubation of 7 and 14 days. Regarding the artificially inoculated corn flour the lower applied FNP concentrations (0.16–0.8 µg/g) achieved a reduction of AFB1 up to 42% and 60% after 7 and 14 days, respectively. 相似文献
147.
Ljiljana Kljajević Snežana Nenadović Miloš Nenadović Devendraprakash Gautam Tatjana Volkov-Husović Aleksandar Devečerski Branko Matović 《Ceramics International》2013,39(5):5467-5476
Spark plasma sintering (SPS) of ZrC–SiC composite powders in the presence of LiYO2 sintering additive was studied. The starting powders were obtained by a carbothermal reduction (CTR) of natural mineral zircon (ZrSiO4), which provided an intimate mixing of in-situ created ZrC and SiC powders. This composite powder and LiYO2 as additive were densified by spark plasma sintering. Microstructural features of the composite were investigated by XRD, SEM/EDS and AFM analysis. The sintered composite material possesses promising mechanical properties and excellent cavitation resistance which was observed with a cavitation erosion test. The values of Vickers microhardness and fracture toughness of the composite material are 20.7 GPa and 5.07 MPam1/2, respectively. 相似文献
148.
An electrolyte for lithium batteries based on the ionic liquid 3-methy-1-propylimidazolium bis(trifluoromethysulfony)imide (PMIMTFSI) complexed with lithium bis(trifluoromethysulfony)imide (LiTFSI) at a molar ratio of 1:1 has been investigated. The electrolyte shows a high ionic conductivity (∼1.2 × 10−3 S cm−1) at room temperature. Over the whole investigated temperature range the ionic conductivity is more than one order of magnitude higher than for an analogue electrolyte based on N-butyl-N-methyl-pyrrolidinium bis(trifluoromethanesulfonyl)imide (Py14TFSI) complexed with LiTFSI and used here as a benchmark. Raman results indicate furthermore that the degree of lithium coordinated TFSI is slightly lower in the electrolyte based on PMIMTFSI and thus that the Li+ charge carriers should be higher than in electrolytes based on Py14TFSI. An ionic liquid gel electrolyte membrane was obtained by soaking a fibrous fully interconnected membrane, made of electrospun P(VdF-HFP), in the electrolyte. The gel electrolyte was cycled in Li/ionic liquid polymer electrolyte/Li cells over 15 days and in Li/LiFePO4 cells demonstrating good interfacial stability and highly stable discharge capacities with a retention of >96% after 50 cycles (∼146 mAh g−1). 相似文献
149.
Aleksandar M. Mitra?inovi? Torstein A. Utigard 《Metallurgical and Materials Transactions B》2012,43(2):379-387
A high-capacity method for silicon refining is investigated. The biggest obstacle in Si refining using the alloying technique
is the amount of solute element. In the current work, Cu is removed from two Cu-Si hypereutectic alloys by the heavy liquid
media separation technique. The results indicated 86.0 pct silicon recovered, which is close to the theoretical limit. The
chemical analysis showed a Cu concentration of 0.68 wt pct in the 50 Cu-Si alloy for a 75-μm average particle size after heavy liquid media separation. The optimal particle size was found in the range of 75 to 125 μm. Heavy liquid media separation is an efficient technique in the process of liberating Si dendrites that can be used as feedstock
in solar cell applications. 相似文献
150.
Perica Paunovi? Aleksandar T. Dimitrov Evelina Slavcheva Elefteria Lefterova Svetomir Had?i Jordanov 《Materials Research Bulletin》2009,44(9):1816-1821
Commercial multiwalled carbon nanotubes (MWCNTs) were used as a catalyst support for non-platinum hypo-hyper d-electrocatalysts. In order to improve the performance of these catalysts, activation/purification of MWCNTs in acid medium (HNO3) was carried out. The physical and surface changes of MWCNTs were investigated by DTA/TGA analysis, Raman spectroscopy, and cyclic voltammetry. Structural changes of the electrocatalysts were observed by infrared spectroscopy and SEM. Their use as a support for electrocatalysts for hydrogen evolution was demonstrated, and shown to be more suitable compared to the traditional carbon support material − carbon black (Vulcan XC-72). The electrocatalysts consisted of 10% Co + 18% TiO2 + MWCNTs. Activation/purification removes the amorphous carbon phase in the MWCNTs. As a result of both shortening and opening of carbon nanotubes, better dispersion of metallic particles (the active catalytic centers) was achieved. Thus, trans-particle and inter-particle porosity of the electrocatalytic material was improved, implying increase of catalytic activity for hydrogen evolution. 相似文献