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John U Kuriakose S Nair KP 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,68(2):331-336
The near infrared vibrational overtone absorption spectrum of liquid phase o-fluorophenol is examined in the region deltav=2, 3 and 4. The OH frequencies are compared with that of o-chlorophenol and phenol. Considering the relative electronegativities of all halogens, one might expect the order of intramolecular hydrogen bond strength for o-fluorophenol to be the greatest among all halogenophenols. It is evident that o-fluorophenol forms a weaker intramolecular hydrogen bond (an anomalous trend) contrary to that expected from relative electronegativities of halogens. The local mode mechanical frequency values and anharmonicity values obtained from fitting the overtones are analysed. Our observation is in agreement with the previous experimental as well as the recent theoretical vibrational analysis of halogenophenols using density functional theory (B3LYP). The overtone spectra of o-fluorophenol in carbon tetrachloride in different concentrations are also examined. It is noted that the OH-red shift which arises due to the intermolecular bond formation between the cis and trans conformers of o-fluorophenol (dimerization) increases with concentration. 相似文献
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Lijun Duan Sunny N. Wallace Abigail Engelberth Justin K. Lovelady Edgar C. Clausen Jerry W. King Danielle Julie Carrier 《Applied biochemistry and biotechnology》2009,158(2):362-373
In an effort to increase revenues from a given feedstock, valuable co-products could be extracted prior to biochemical or
thermochemical conversion with subcritical water. Although subcritical water shows significant promise in replacing organic
solvents as an extraction solvent, compound degradation has been observed at elevated extraction temperatures. First order
thermal degradation kinetics from a model system, silymarin extracted from Silybum marianum, in water at pH 5.1 and 100, 120, 140, and 160 °C were investigated. Water pressure was maintained slightly above its vapor
pressure. Silymarin is a mixture of taxifolin, silichristin, silidianin, silibinin, and isosilibinin. The degradation rate
constants ranged from 0.0104 min−1 at 100 °C for silichristin to a maximum of 0.0840 min−1 at 160 °C for silybin B. Half-lives, calculated from the rate constants, ranged from a low of 6.2 min at 160 °C to a high
of 58.3 min at 100 °C, both for silichristin. The respective activation energies for the compounds ranged from 37.2 kJ/gmole
for silidianin to 45.2 kJ/gmole for silichristin. In extracting the silymarin with pure ethanol at 140 °C, no degradation
was observed. However, when extracting with ethanol/water mixtures at and 140 °C, degradation increased exponentially as the
concentration of water increased.
An erratum to this article can be found at 相似文献
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Shabram Sadeghi Esfahlani Hassan Shirvani Sunny Nwaubani Ayoub Shirvani Habtom Mebrahtu 《力学快报》2013,3(3):031002
Structural optimization for crashworthiness criteria is of particular significance especially at early stage of design. The comparative study of Kriging and radial basis function network (RBFN) was performed in order to improve the crashworthiness effects of honeycomb. Improving the crashworthiness characteristic of honeycomb was achieved using LS-OPT® and domain reduction strategy. This optimization is performed on the basis of validated numerical simulation to establish the approximated model to illustrate the relationship between the responses and design variables. The results showed that Kriging meta-model is excelled in accuracy, robustness and efficiency compared to radial basis function (RBF) and crashworthiness characteristic of honeycomb is improved by 4%. 相似文献
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Geoffrey S. Simate Sunny E. Iyuke Sehliselo Ndlovu Clarence S. Yah Lubinda F. Walubita 《天然气化学杂志》2010,19(5):453-460
Recent advances in the production of carbon nanotubes (CNTs) are reviewed with an emphasis on the use of carbon dioxide (CO2) as a sole source of carbon. Compared to the most widely used carbon precursors such as graphite, methane, acetylene, ethanol, ethylene, and coal-derived hydrocarbons, CO2 is competitively cheaper with relatively high carbon yield content. However, CNT synthesis from CO2 is a newly emerging technology, and hence it needs to be explored further. A theoretical and analytical comparison of the currently existing CNT-CO2 synthesis techniques is given including a review of some of the process parameters (i.e., temperature, pressure, catalyst, etc.) that affect the CO2 reduction rate. Such analysis indicates that there is still a fundamental need to further explore the following aspects so as to realize the full potential of CO2 based CNT technology: (1) the CNT-CO2 synthesis and formation mechanism, (2) catalytic effects of transitional metals and mechanisms, (3) utilization of metallocenes in the CNT-CO2 reactions, (4) applicability of ferrite-organometallic compounds in the CNT-CO2 synthesis reactions, and (5) the effects of process parameters such as temperature, etc. 相似文献
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Extraction of nutraceuticals from milk thistle 总被引:1,自引:0,他引:1
Sunny N. Wallace Danielle Julie Carrier Edgar C. Clausen 《Applied biochemistry and biotechnology》2003,108(1-3):881-889
Milk thistle contains compounds that display hepatoxic protection properties. We examined the batch extraction of silymarin
compounds from milk thistle seed meal in 50, 70, 85, and 100°C water as a function of time. After 210 min of extraction at
100°C, the yield of taxifolin was 1.2 mg/g of seed, a 6.2-fold increase over the results obtained in a Soxhlet extraction
with ethanol on pretreated (defatted) seeds. Similarly, the yield of silychristin was 5.0 mg/g of seed, a 3.8-fold increase.
The yields of silybinin A and silybinin B were 1.8 and 3.3 mg/g of seed, respectively, or roughly 30% of the Soxhlet yield.
The ratios of the extracted compounds, and particularly the ratios at long extraction times, showed that the more polar compounds
(taxifolin and silychristin) were preferentially extracted at 85°C, while the less polar silybinin was favored at 100°C. 相似文献