排序方式: 共有14条查询结果,搜索用时 15 毫秒
1.
We report the development and application of a simple theoretical model for extracting temperatures from picosecond-laser-based coherent anti-Stokes Raman scattering (CARS) spectra of H2 obtained using time-delayed probe pulses. This approach addresses the challenges associated with the effects of rotational-level-dependent decay lifetimes on time-delayed probing for CARS thermometry. A simple procedure is presented for accurate temperature determination based on a Boltzmann distribution using delayed-probe-pulse vibrational CARS spectra of H2; this procedure requires measurement at only a select handful of probe-pulse delays and requires no assumptions about sample environment. 相似文献
2.
3.
Yi Ma Waruna Wijesekara Anders E. C. Palmqvist 《Journal of Electronic Materials》2012,41(6):1138-1146
Thermoelectric thin films of the ternary compounds (Bi x Sb1?x )2Te3 and Bi2(Te1?y Se y )3 were synthesized using potentiostatic electrochemical deposition on gold-coated silicon substrates from aqueous acidic solutions at room temperature. The surface morphology, elemental composition, and crystal structure of the deposited films were studied and correlated with preparation conditions. The thermoelectric properties of (Bi x Sb1?x )2Te3 and Bi2(Te1?y Se y )3 films, i.e., Seebeck coefficient and electrical resistivity, were measured after transferring the films to a nonconductive epoxy support. (Bi x Sb1?x )2Te3 thin films showed p-type semiconductivity, and the highest power factor was obtained for film deposited at a relatively large negative potential with composition close to Bi0.5Sb1.5Te3. In addition, Bi2(Te1?y Se y )3 thin films showed n-type semiconductivity, and the highest power factor was obtained for film deposited at a relatively small negative potential, having composition close to Bi2Te2.7Se0.3. In contrast to Bi2Te2.7Se0.3 thin films, an annealing treatment was required for Bi0.5Sb1.5Te3 thin films to achieve the same magnitude of power factor as Bi2Te2.7Se0.3. Therefore, Bi2Te2.7Se0.3 thin films appear to be good candidates for multilayer preparation using electrochemical deposition, but the morphology of the films must be further improved. 相似文献
4.
Two-photon laser-induced fluorescence (TP-LIF) line imaging of atomic hydrogen was investigated in a series of premixed CH4/O2/N2, H2/O2, and H2/O2/N2 flames using excitation with either picosecond or nanosecond pulsed lasers operating at 205 nm. Radial TP-LIF profiles were measured for a range of pulse fluences to determine the maximum interference-free signal levels and the corresponding picosecond and nanosecond laser fluences in each of 12 flames. For an interference-free measurement, the shape of the TP-LIF profile is independent of laser fluence. For larger fluences, distortions in the profile are attributed to photodissociation of H2O, CH3, and/or other combustion intermediates, and stimulated emission. In comparison with the nanosecond laser, excitation with the picosecond laser can effectively reduce the photolytic interference and produces approximately an order of magnitude larger interference-free signal in CH4/O2/N2 flames with equivalence ratios in the range of 0.5< or =Phi< or =1.4, and in H2/O2 flames with 0.3< or =Phi< or =1.2. Although photolytic interference limits the nanosecond laser fluence in all flames, stimulated emission, occurring between the laser-excited level, H(n=3), and H(n=2), is the limiting factor for picosecond excitation in the flames with the highest H atom concentration. Nanosecond excitation is advantageous in the richest (Phi=1.64) CH4/O2/N2 flame and in H2/O2/N2 flames. The optimal excitation pulse width for interference-free H atom detection depends on the relative concentrations of hydrogen atoms and photolytic precursors, the flame temperature, and the laser path length within the flame. 相似文献
5.
Asad‐ur‐Rehman Saman Wijesekara R.G Nakao Nomura Seigo Sato Masatoshi Matsumura 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2008,83(7):1072-1080
BACKGROUND: The objective of the present work is to report an efficient pre‐treatment process for sunflower oil biodiesel raw glycerol (SOB‐RG) and its fermentation to 1,3‐propanediol. RESULTS: The growth inhibition percentages of Clostridium butyricum DSM 5431 on grade A (pH 4.0) and grade B (pH 5.0) phosphoric acid‐treated SOB‐RG were similar to those of pure glycerol at 20 g glycerol L?1; i.e., 18.5 ± 0.707% to 20.5 ± 0.7% inhibition. In grade A, growth inhibition was reduced from 85.25 ± 0.35% to 32 ± 1.4% (a 53.25% reduction) at 40 g glycerol L?1 by washing grade A raw glycerol twice with n‐hexanol (grade A‐2). The kinetic parameters for product formation and substrate consumption in anaerobic batch cultures gave almost similar values at 20 g glycerol L?1, while at 50 g glycerol L?1 volumetric productivity (Qp) and specific rate of 1,3‐propanediol formation (qp) were improved from 1.13 to 1.85 g L?1 h?1 and 1.60 to 2.65 g g?1 h?1, respectively, by employing grade A‐2 raw glycerol, while the yields were similar (0.5–0.52 g g?1). CONCLUSION: The results are important as the pre‐treatment of SOB‐RG is necessary to develop bioprocess technologies for conversion of SOB‐RG to 1,3‐propanediol. Copyright © 2008 Society of Chemical Industry 相似文献
6.
RG Saman Wijesekara Nakao Nomura Masatoshi Matsumura 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(12):1408-1415
Phytoplankton over‐blooming and consequent die‐off is one of the major contributory factors for ammonia and chemical oxygen demand (COD) loadings. In this work, electrolysis technology was applied to determine its ability to remove ammonia and total chemical oxygen demand (TCOD) in both laboratory‐scale batch and continuous systems. Under an initially set voltage of 5 V, a constant current of 0.1 A was applied and different retention times were used for ammonia‐removal experiments. Results showed that these conditions are not satisfactory in removing TCOD loadings contributed by algal cells. However, a retention time of 35.7 min was sufficient to remove 100% ammonia from algal‐uncontaminated waters. Ammonia removals in waters containing Chlorella spp and Isochrysis spp were 87 and 68%, respectively, after 140 min of electrolysis. Energy consumption for ammonia removal in algal‐free water was 50 W mg?1 of ammonia. For waters containing Chlorella spp and Isochrysis spp energy consumptions were 67 and 85 W mg?1 of ammonia, respectively. Interestingly, the applied mild electrolysis condition was just sufficient to control excess algal blooming and ammonia without increasing the dissolved COD and chlorine in shrimp grow‐out ponds. This minimizes operating costs due the process requiring less energy. Furthermore, it was also found that electrolysis does not lower alkalinity. Copyright © 2005 Society of Chemical Industry 相似文献
7.
Thanh-Sang Vo Jung-Ae Kim Isuru Wijesekara Chang-Suk Kong Se-Kwon Kim 《Food science and biotechnology》2011,20(5):1227-1234
The effect of solvent fractions from brown algae (Ishige okamurae) on allergic inflammatory reactions was investigated via measuring histamine release and cytokine generation in human basophilic
KU812F cells induced by calcium ionophore A23187. Moreover, polyunsaturated fatty acids (PUFAs) profiles were identied and
quantied in the most active fraction. It was found that n-hexane and ethyl acetate (EtOAc) fraction at 50 μg/mL significantly
reduce histamine release with the release rates of 24 and 20%, respectively. Likewise, the suppressive effect of n-hexane and EtOAc fraction on production as well as expression of interleukin (IL)-4 and IL-13 was determined. Notably, EtOAc
fraction exhibited more effective inhibition than n-hexane in all assays. Furthermore, GC analysis revealed that EtOAc fraction contains various anti-inflammatory PUFAs such
as eicosapentaenoic acid, eicosatrienoic acid, linolenic acid, and γ-linolenic acid. Collectively, EtOAc fraction from brown
algae could be a potential inhibitor of allergic inflammatory reactions in basophils that is suggested to be due to PUFAs. 相似文献
8.
Marine organisms are rich sources of structurally diverse bioactive compounds. Recently, a great deal of interest has been expressed regarding marine-derived bioactive peptides because of their numerous health beneficial effects. Moreover, many studies have reported that marine bioactive peptides can be used as antihypertensive, antioxidative, anticoagulant, and antimicrobial components in functional foods or nutraceuticals and pharmaceuticals due to their therapeutic potential in the treatment or prevention of diseases. This contribution presents an overview of the bioactive peptides derived from marine organisms and their biological activities with potential applications in different areas. 相似文献
9.
Two-color, two-photon laser-induced polarization spectroscopy (LIPS) of atomic hydrogen has been demonstrated and applied in atmospheric pressure hydrogen/air flames. Fundamental and frequency-doubled beams from a single 486-nm dye laser were used in the experiments. The 243-nm pump beam in the measurements was tuned to the two-photon n=1→n=2 resonance of the hydrogen atom. The 486-nm probe beam was tuned to the single-photon n=2→n=4 resonance of the hydrogen atom. Measurements were performed in an atmospheric pressure H2/air flame stabilized on a near-adiabatic, flat-flame calibration burner (the Hencken burner). For the range of pump beam intensities used, the LIPS signal was found to be nearly proportional to the square of the pump beam intensity over a wide range of flame equivalence ratios. Spectral lineshapes were recorded at flame equivalence ratios ranging from 0.85 to 2.10. Vertical H-atom number density distribution profiles were measured in the Hencken burner. The vertical H-atom number density profiles measured along the burner centerline for various flame equivalence ratios were compared with the results of a numerical flame calculation using the UNICORN (Unsteady Ignition and Combustion with Reactions) code. Good agreement between theory and experiment was obtained for stoichiometric and rich flame conditions. For flames with equivalence ratios greater than 1.5, the H-atom concentration was substantially above the adiabatic equilibrium value, even at 50 mm above the burner surface. The slow approach to the adiabatic equilibrium H-atom concentration value can be explained by assuming partial equilibrium in the postflame gases; the H-atom concentration is proportional to the O2 concentration which requires significant residence time to decrease to its very low equilibrium concentration. These results suggest that the use of the Hencken burner as a radical measurement technique calibration source may be of questionable value for equivalence ratios greater than 1.5 and less than 0.8. 相似文献
10.
Dai-Hung NgoIsuru Wijesekara Thanh-Sang VoQuang Van Ta Se-Kwon Kim 《Food research international (Ottawa, Ont.)》2011,44(2):523-529
Recently, a great deal of interest has been developed by the consumers towards natural bioactive compounds as functional ingredients in the food products due to their various health beneficial effects. Hence, it can be suggested that antioxidative functional ingredients from marine foods and their by-products are alternative sources for synthetic ingredients that can contribute to a consumer's well-being, as a part of nutraceuticals and functional foods. This contribution presents an overview of the marine food-derived antioxidants such as bioactive peptides, chitooligosaccharide derivatives, sulfated polysaccharides, phlorotannins and carotenoids with the potential utilization in the food industry. 相似文献