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排序方式: 共有197条查询结果,搜索用时 15 毫秒
81.
Vladimir M. Nikolic Dragana L. Zugic Ivana M. Perovic Aleksandra B. Saponjic Biljana M. Babic Igor A. Pasti Milica P. Marceta Kaninski 《International Journal of Hydrogen Energy》2013
In this contribution, we present results of electrochemical characterization of prepared tungsten carbide supported palladium and platinum and Vulcan XC-72 supported palladium. These catalysts were employed as anode catalysts in PEMFC and results are compared to commercial platinum catalyst. Platinum seems to be irreplaceable as a proton exchange membrane fuel cell (PEMFC) catalyst for both the anode and the cathode, yet the high price and limited natural resources are holding back the commercialization of the PEMFCs. Tungsten carbide is recognized as promising catalyst support having the best conductivity among interstitial carbides. Higher natural resources and significantly lower price make palladium good candidate for replacement of the platinum catalyst. The presented results show that all prepared catalysts are very active for the hydrogen oxidation reaction. Linear sweep voltammetry curves of Pd/C and Pd/WC show existence of peaks at 0.07 V vs. RHE, which is assigned to absorbed hydrogen. H2|Pd/WC|Nafion117|Pt/C|O2 fuel cell has almost the same efficiency and similar power output as commercial platinum catalyst. 相似文献
82.
Natasa?GolicEmail author Ivana?Strahinic Amarela?Terzic-Vidojevic Jelena?Begovic Milica?Nikolic Maja?Tolinacki Ljubisa?Topisirovic 《European Food Research and Technology》2012,234(4):627-638
The diversity of 87 Lactobacillus paracasei and Lactobacillus plantarum/paraplantarum strains, previously identified from different autochthonous dairy products, was investigated by phenotypic and genotypic
approaches. The increased resolution obtained using phenotypic and genotypic characterization allowed the level of strain
heterogeneity detection to be widened. Phenotypic diversity was evaluated by studying biochemical characteristics of technological
interest, including antimicrobial and proteinase activities, resistance to nisin, aggregation ability, production of exopolysaccharides,
acetoin and diacetyl, citrate utilization, and antibiotic susceptibility. Genotypic diversity was generally evaluated by PCR
amplification of repetitive bacterial DNA element fingerprinting using the (GTG)5 primer [(GTG)5-PCR]. Moreover, in cases where strains were not discriminated by (GTG)5-PCR combined with phenotypic analysis, pulsed-field gel electrophoresis (PFGE) analysis was performed. The results indicate
that L. plantarum/paraplantarum and L. paracasei natural isolates from artisanal dairy products are a gold mine in terms of diversity of strains and could be potentially
interesting to dairy companies for the formulation of functional starter cultures in the production of innovative foods. 相似文献
83.
Jelena B. okovi Sanela M. Savi Jelena R. Mitrovi Ines Nikolic Bojan D. Markovi Danijela V. Randjelovi Jelena Antic-Stankovic Dragana Boi Neboja D. Ceki Vladimir Stevanovi Bojan Batini Jovana Aranelovi Miroslav M. Savi Sneana D. Savi 《International journal of molecular sciences》2021,22(15)
The current study describes the experimental design guided development of PEGylated nanoemulsions as parenteral delivery systems for curcumin, a powerful antioxidant, as well as the evaluation of their physicochemical characteristics and antioxidant activity during the two years of storage. Experimental design setup helped development of nanoemulsion templates with critical quality attributes in line with parenteral application route. Curcumin-loaded nanoemulsions showed mean droplet size about 105 nm, polydispersity index <0.15, zeta potential of −40 mV, and acceptable osmolality of about 550 mOsm/kg. After two years of storage at room temperature, all formulations remained stable. Moreover, antioxidant activity remained intact, as demonstrated by DPPH (IC50 values 0.078–0.075 mg/mL after two years) and FRAPS assays. In vitro release testing proved that PEGylated phospholipids slowed down the curcumin release from nanoemulsions. The nanoemulsion carrier has been proven safe by the MTT test conducted with MRC-5 cell line, and effective on LS cell line. Results from the pharmacokinetic pilot study implied the PEGylated nanoemulsions improved plasma residence of curcumin 20 min after intravenous administration, compared to the non-PEGylated nanoemulsion (two-fold higher) or curcumin solution (three-fold higher). Overall, conclusion suggests that developed PEGylated nanoemulsions present an acceptable delivery system for parenteral administration of curcumin, being effective in preserving its stability and antioxidant capacity at the level highly comparable to the initial findings. 相似文献
84.
In order to create a new drug delivery system, the ibuprofen-loaded triblock copolymer PCL/PEO/PCL (PCEC) microspheres with a low PEO content (<2?wt%) were prepared by oil in water (o/w) solvent evaporation technique. The influence of PEO content, molecular weight of a polymer matrix and drug loading on the ibuprofen release profiles were evaluated. The interactions between polymer matrix and ibuprofen were detected by FTIR analysis. The presence of hydrophilic PEO segment in PCL chains caused the decrease in particle size, which further had a great impact on the drug release kinetics, i.e., initially faster release and significantly higher quantity of released drug compared to neat PCL. Ibuprofen release behavior from polymer matrix was governed by a diffusion process. In vitro cytotoxicity tests revealed that empty PCL and PCEC microspheres were not toxic at low concentrations, while ibuprofen-loaded microspheres exhibited cytotoxicity correlated with amounts of incorporated drug. 相似文献
85.
86.
Danka Bukvicki Abdulhmid Giweli Dejan Stojkovic Ljubodrag Vujisic Vele Tesevic Milos Nikolic Marina Sokovic Petar D. Marin 《Journal of dairy science》2018,101(5):3859-3865
The essential oil of Thymus algeriensis was analyzed as a potential preservative in soft cheese. We developed a novel method to test the preserving properties of essential oil in soft cheese. Contamination incidence of Penicillium aurantiogriseum was absent after 30 d of storage at 4°C with 25 µL of essential oil added. The antimicrobial activity was tested against 8 bacteria and 8 fungi. Thymus algeriensis oil showed inhibitory activity against tested bacteria at 0.03 to 0.09 mg/mL, and bactericidal activity was achieved at 0.05 to 0.15 mg/mL. For antifungal activity, minimum inhibitory concentrations ranged between 0.01 and 0.04 mg/mL and minimum fungicidal concentrations between 0.01 and 0.04 mg/mL. Furthermore, the oil was also screened for antiradical activity using the 1,1-diphenyl-2-picrylhydrazyl assay. The results showed that the oil was active and achieved half-maximal inhibitory activity at 0.132 mg/mL. We used gas chromatography, gas chromatography-mass spectrometry, and nuclear magnetic resonance spectrometry to investigate the volatile compounds from the oil. Carvacrol was identified as the main compound in the oil, represented by 80.9% of the total constituents, followed by p-cymene (7.7%). 相似文献
87.
88.
Vesna Nikolic ;Zeljko Kamberovic ;Zoran Andic ;Marija Korac ;Miroslav Sokic ;Vesna Maksimovic 《北京科技大学学报(英文版)》2014,(8):806-812
A method of synthesizing Ni-based catalysts supported on α-Al2O3-based foams was developed. The foams were impregnated with aqueous solutions of metal chlorides under an air atmosphere using an aerosol route. Separate procedures involved calcination to form oxides and drying to obtain chlorides on the foam surface. The synthesized samples were subsequently reduced with hydrogen. With respect to the Ni/Al2O3 catalysts, the chloride reduction route enabled the formation ofa Ni coating without agglomerates or cracks. Further research included catalyst modification by the addition of Pd, Cu, and Fe. The influences of the additives on the degree of reduction and on the low-temperature reduction effectiveness (533 and 633 K) were examined and compared for the catalysts obtained from oxides and chlorides. Greater degrees of reduction were achieved with chlorides, whereas Pd was the most effective modifier among those investigated. The reduction process was nearly complete at 533 K in the sample that contained 0.1wt% Pd. A lower reduction temperature was utilized, and the calcination step was avoided, which may enhance the economical and technological aspects of the developed catalyst production method. 相似文献
89.
Operators in complex event-driven domains must coordinate competing attentional demands in the form of multiple tasks and interactions. This study examined the extent to which this requirement can be supported more effectively through informative interruption cueing (in this case, partial information about the nature of pending tasks). The 48 participants performed a visually demanding air traffic control (ATC) task. They were randomly assigned to 1 of 3 experimental groups that differed in the availability of information (not available, available upon request, available automatically) about the urgency and modality of pending interruption tasks. Within-subject variables included ATC-related workload and the modality, frequency, and priority of interruption tasks. The results show that advance knowledge about the nature of pending tasks led participants to delay visual interruption tasks the longest, which allowed them to avoid intramodal interference and scanning costs associated with performing these tasks concurrently with ATC tasks. The 3 experimental groups did not differ significantly in terms of their interruption task performance; however, the group that automatically received task-related information showed better ATC performance, thus experiencing a net performance gain. Actual or potential applications of this research include the design of interfaces in support of attention and interruption management in a wide range of event-driven environments. 相似文献
90.
It has been suggested that control using a skill-based expert system can be applicable to gait restoration. Rule-based systems have several advantages for this application: they generate a fast response (they are not computationally intensive) and they are easy to comprehend and implement. A major problem with using such systems is the inability of users to determine its rules. In this study, an automatic method for obtaining the production rules from a set of examples is described. The rule base was automatically induced from a model which used external sensor signals as inputs and electromyogram (EMG) patterns as outputs. The method is based on the minimization of entropy. A production rule estimated the muscle activity pattern using the sensor information. The algorithm was tested using data recorded from six able-bodied individuals during ground level walking, with and without ankle-foot orthoses. The data showed that gait variability will increase in able-bodied subjects when the motion of ankle joints is restricted, thus, providing a good test for generalization. The experimental results illustrate performance of the production rule that estimates quadriceps muscle group activity pattern for ground level walking in able-bodied subjects 相似文献