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排序方式: 共有177条查询结果,搜索用时 15 毫秒
41.
42.
Ilkay Erdogan Orhan F. Sezer Senol A. Rifat Gulpinar Nazim Sekeroglu Murat Kartal Bilge Sener 《Food chemistry》2012
In the current study, neuroprotective effects of the ethyl acetate and methanol extracts of four terebinth coffee brands and the fruits of Pistacia terebinthus L. were investigated through enzyme inhibition tests against acetylcholinesterase, butyrylcholinesterase, and tyrosinase as well as antioxidant test systems. Antioxidant activity was measured using radical scavenging activity tests and metal-related tests including metal-chelation capacity, ferric-reducing antioxidant power (FRAP), and phosphomolybdenum reducing power (PRAP). The fatty oils of the coffee brands and the fruits and the fruit essential oil were examined by GC–MS. Total phenol and flavonoid contents were calculated spectrophotometrically. The extracts had moderate inhibition against butyrylcholinesterase (9.78–45.74% at 200 μg mL−1) and potent scavenging activity against DPPH. They exerted strong activity in FRAP and metal-chelation tests and modest activity in PRAP test. Oleic acid was identified as the major fatty acid in the fatty oils, while α-pinene (26.31%) was dominant in the essential oil. 相似文献
43.
This study considers numerical simulation of the combustion of methane with air, including oxygen and nitrogen, in a burner
and the numerical solution of local entropy generation rate due to high temperature and velocity gradients in the combustion
chamber. The effects of equivalence ratio (Φ) and oxygen percentage (γ ) on combustion and entropy generation rates are investigated
for different Φ (from 0.5 to 1.0) andγ values (from 10 to 30%). Combustion is simulated for the fuel mass flow rate resulting in the same heat transfer rate (Q)y
to the combustion chamber in each case. Numerical calculation of combustion is performed individually for all cases with the
use of the Fluent CFD code. Furthermore, a computer program has been developed to calculate the volumetric entropy generation
rate and the other thermodynamic parameters numerically by using the results of the calculations performed with the FLUENT
code. The predictions show that the increase of Φ (or the decrease of λ) significantly reduces the reaction rate levels. Average
temperature in the combustion chamber increases by about 70 and 35% with increase ofγ (from 10 to 30%) and Φ (from 0.5 to 1.0) respectively. With increase ofγ from 10 to 30%, volumetric local entropy generation rate decreases by about 9 and 4% for Φ = 0.5 and 1.0 respectively, while
total entropy generation rate decreases exponentially and the merit numbers increase. The ratio of the rates useful energy
transfer to irreversibility therefore improves as the oxygen percentage increases 相似文献
44.
Isomerization reactions of n-heptane, n-octane and n-nonane are studied on sulphated-zirconia-supported 0.2 wt% Pt, Pd or Ir catalysts. Evolutions of isomer selectivity versus total conversion and reaction temperatures are analysed. When total conversion (T) is increased, isomer selectivity (%S
isom) is decreased and the slope of the curve %S
isom=f(T) is more pronounced when the carbon number in the alkane is more important. At isoconversion, around 20%, below 473 K, cracking is favoured over isomerization reaction, and above 473 K it is the reverse. Moreover, with n-heptane, when the catalytic reaction occurred at 423 K and at low conversion, T20%, we observed a large decrease in the isomer selectivity percentages on Pd/SZ and Ir/SZ compared to Pt/SZ. What is remarkable is that, at this low temperature, both metals are inactive in the carbon–carbon bond rupture. To explain these results the following points are raised: (i) an associative mechanism is proposed for the adsorption step of the alkane involving an agostic intermediate species where the carbon–hydrogen bonds act as ligands to the transition metal centres forming covalent C–HM systems, and (ii) a metal–proton adduct site, which gathers metallic and acidic sites is suggested. This approach seems to better explain our results than the traditional bifunctional mechanism. 相似文献
45.
Eker B Yilmaz MD Schlautmann S Gardeniers JG Huskens J 《International journal of molecular sciences》2011,12(11):7335-7351
A supramolecular platform based on self-assembled monolayers (SAMs) has been implemented in a microfluidic device. The system has been applied for the sensing of two different analyte types: biologically relevant phosphate anions and aromatic carboxylic acids, which are important for anthrax detection. A Eu(III)-EDTA complex was bound to β-cyclodextrin monolayers via orthogonal supramolecular host-guest interactions. The self-assembly of the Eu(III)-EDTA conjugate and naphthalene β-diketone as an antenna resulted in the formation of a highly luminescent lanthanide complex on the microchannel surface. Detection of different phosphate anions and aromatic carboxylic acids was demonstrated by monitoring the decrease in red emission following displacement of the antenna by the analyte. Among these analytes, adenosine triphosphate (ATP) and pyrophosphate, as well as dipicolinic acid (DPA) which is a biomarker for anthrax, showed a strong response. Parallel fabrication of five sensing SAMs in a single multichannel chip was performed, as a first demonstration of phosphate and carboxylic acid screening in a multiplexed format that allows a general detection platform for both analyte systems in a single test run with μM and nM detection sensitivity for ATP and DPA, respectively. 相似文献
46.
47.
Nuclear energy can be used as the primary energy source in centralized hydrogen production through high-temperature thermochemical processes, water electrolysis, or high-temperature steam electrolysis. Energy efficiency is important in providing hydrogen economically and in a climate friendly manner. High operating temperatures are needed for more efficient thermochemical and electrochemical hydrogen production using nuclear energy. Therefore, high-temperature reactors, such as the gas-cooled, molten-salt-cooled and liquid-metal-cooled reactor technologies, are the candidates for use in hydrogen production. Several candidate technologies that span the range from well developed to conceptual are compared in our analysis. Among these alternatives, high-temperature steam electrolysis (HTSE) coupled to an advanced gas reactor cooled by supercritical CO2 (S-CO2) and equipped with a supercritical CO2 power conversion cycle has the potential to provide higher energy efficiency at a lower temperature range than the other alternatives. 相似文献
48.
A.B. Selçuk S. Bilge Ocak F.G. Aras E. Oz Orhan 《Journal of Electronic Materials》2014,43(9):3263-3269
Al/Poly(methyl methacrylate)(PMMA)/p-Si organic Schottky devices were fabricated on a p-Si semiconductor wafer by spin coating of PMMA solution. The capacitance–voltage (C–V) and conductance–voltage (G–V) characteristics of Al/PMMA/p-Si structures have been investigated in the frequency range of 1 kHz–10 MHz at room temperature. The diode parameters such as ideality factor, series resistance and barrier height were calculated from the forward bias current–voltage (I–V) characteristics. In order to explain the electrical characteristics of metal–polymer–semiconductor (MPS) with a PMMA interface, the investigation of interface states density and series resistance from C–V and G–V characteristics in the MPS structures with thin interfacial insulator layer have been reported. The measurements of capacitance (C) and conductance (G) were found to be strongly dependent on bias voltage and frequency for Al/PMMA/p-Si structures. The values of interface state density (D it) were calculated. These values of D it and series resistance (R s) were responsible for the non-ideal behavior of I–V and C–V characteristics. 相似文献
49.
Deniz Bilge Beten Nilü fer Yü ksel Tamer Baykara 《Drug development and industrial pharmacy》1994,20(14):2323-2331
In the manufacturing of tablets, direct tableting agents are not only used in direct compression, but are also used in wet granulation and slugging methods. These agents are effective only if their particle size and form is appropriate. However, the precompression, milling and grinding which are applied in the slugging method changes the particular properties of these agents.
In this study, microcrystalline cellulose tablets were prepared both by direct compression and slugging. The consolidation, compressibility and flow properties of the two mixed powders were compared. Finally, it was observed that the compressibility of the mixed powder was influenced negatively by the slugging method. 相似文献
In this study, microcrystalline cellulose tablets were prepared both by direct compression and slugging. The consolidation, compressibility and flow properties of the two mixed powders were compared. Finally, it was observed that the compressibility of the mixed powder was influenced negatively by the slugging method. 相似文献
50.
Review on Advanced EB-PVD Ceramic Topcoats for TBC Applications 总被引:1,自引:0,他引:1
Uwe Schulz Bilge Saruhan Klaus Fritscher Christoph Leyens 《International Journal of Applied Ceramic Technology》2004,1(4):302-315
Development of electron beam physical vapor deposited (EB-PVD) thermal barrier coatings (TBC) aims at low conductivity, increased temperature capability, and longer life. Considerable progress has been achieved by comprehensive understanding of the evolvement of the porous microstructure in columnar ceramic topcoats and its application to tailoring optimized micro-structures. New ceramic compositions such as alternative stabilizers in zirconia, hafnia modified coatings, and pyrochlores are addressed. They have demonstrated their potential for future TBC applications. New results of both microstructure and chemistry are presented together with a summary of recent research results. 相似文献