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41.
Jagodige P. Yasomanee Prof. Alexei V. Demchenko 《Angewandte Chemie (International ed. in English)》2014,53(39):10453-10456
A Hydrogen bond mediated aglycone delivery (HAD) method was applied to the synthesis of α‐glucans, which are abundant in nature, but as targets represent a notable challenge to chemists. The synthesis of linear oligosaccharide sequences was accomplished in complete stereoselectivity in all glycosylations. The efficacy of HAD may diminish with the increased bulk of the glycosyl acceptor, and may be an important factor for the syntheses of oligomers beyond pentasaccharides. The synthesis of a branched structure proved more challenging, particularly with bulky trisaccharide acceptors. 相似文献
42.
The improvement of miscibility between toughened Polyamide-6 (PA6) and Styrene-Butadiene Rubber (SBR) was carried out using grafted Glycidyl Methacrylate (SBR-g-GMA). At first, the compatibilizers were prepared using different comonomers, Styrene, and N-vinyl pyrrolidone. Central composited design (CCD) was distinctly applied to study the influence of Glycidyl Methacrylate (GMA) content and comonomer/GMA on the process of compatibilizer preparation. Four models were developed for Gel content and Degree of grafting for both comonomers using Design-expert software. The models were used to calculate the optimum operating conditions and according to the Flory-Huggins parameter and obtained results, SBR-co-NVP-g-GMA was chosen as an effective compatibilizer. Afterward, another CCD was employed to scrutinize the effect of various amounts and grafting degree of compatibilizer on morphology and mechanical properties of PA6/SBR. The Interparticle distance and polydispersity were studied using a Scanning electron microscope (SEM) and also the Izod impact test inspected in order to evaluate the mechanical properties. Finally, modulus and impact strength were optimized to minimize the former and maximize the latter. Also, the most practical terms in the fitted model are statistically specified using F-value. The root causes for the improvement of blend properties were attributed to a chemical reaction between epoxy groups in SBR-g-GMA and both the carboxylic and amine groups in PA6. Impact strength (539.8 J/m) and modulus (2017.2 N/mm2) of the optimum blend indicate an excellent agreement with the amounts predicted by the models. 相似文献
43.
AbstractEffective extraction of phyto-biomolecules insures retaining maximum functionality along with higher recovery. In this study, ultrasound-solvent assisted extraction (USAE) was employed for optimal extraction of phyto-biomolecules from Sesamum indicum (sesame) leaves using the approach of Response Surface Methodology (RSM). The optimized condition of 200?W power, 59% methanol concentration with 1:14?g/mL solid–liquid ratio and 15?min of extraction time yielded 367.39?±?1.85?mg GAE/100?g of total phenolic content, 96.72?±?3.27% of free radical scavenging activity and 81.20?±?2.87% of iron chelating activity respectively. The extract consist of essential phytocomponents like gallic acid, chlorogenic acid, and quercetin with lipid peroxidation activities of >50% over incubation time of 48?h. Also, showed antimicrobial activity against various Gram’s negative and positive food borne pathogens. The results of this study implied the importance of USAE for effective and optimum recovery of phyto-biomolecules from Sesame leaves with retained functional properties. 相似文献
44.
Kun‐ze Du Jin Li Lanhui Wang Jia Hao Xue‐jing Yang Xiu‐mei Gao Yan‐xu Chang 《Journal of separation science》2020,43(4):799-807
Hydrosoluble trehalose lipid (a biosurfactant) was employed for the first time as a green extraction solution to extract the main antioxidant compounds (geniposidic acid, chlorogenic acid, caffeic acid, and rutin) from functional plant tea (Eucommia ulmoides leaves). Single‐factor tests and response surface methodology were employed to optimize the extraction conditions for ultrasound‐assisted micellar extraction combined with ultra‐high‐performance liquid chromatography in succession. A Box‐Behnken design (three‐level, three‐factorial) was used to determine the effects of extraction solvent concentration (1–5 mg/mL), extraction solvent volume (5–15 mL), and extraction time (20–40 min) at a uniform ultrasonic power and temperature. In consequence, the best analyte extraction yields could be attained when the trehalose lipid solution concentration was prepared at 3 mg/mL, the trehalose lipid solution volume was 10 mL and the extraction time was set to 35 min. In addition, the recoveries of the antioxidants from Eucommia ulmoides leaves analyzed by this analytical method ranged from 98.2 to 102%. These results indicated that biosurfactant‐enhanced ultrasound‐assisted micellar extraction coupled with a simple ultra‐high‐performance liquid chromatography method could be effectively applied in the extraction and analysis of antioxidants from Eucommia ulmoides leaf samples. 相似文献
45.
《Arabian Journal of Chemistry》2020,13(11):8338-8346
The photodegradation of an industrial azo dye C.I Basic Red 46 was examined in a fixed-bed photoreactor using UV-lamps simulated to the solar irradiation. In our photodecolorization study, the UV/TiO2 process was optimized using the Box-Behnken approach to evaluate the synergistic effects of three independent parameters (initial concentration of the dye, flow rate, and UV intensity) on mineralization effectiveness. The response surface methodology was in good promise with the prediction model (coefficients of determination of decolorization and mineralization were R2Dec = 0.997 and R2TOC = 0.994, respectively). The effects of the factors could be estimated from a second–order polynomial equation and student’s t-test. The optimal parameters of decolorization and mineralization were as follows: initial concentration of colorant 25 mg L−1, rate of fluid flow 0.3 L min−1, and ultraviolet light intensity 38.1 W m−2. The decolorization and mineralization removal efficiency under these optimal conditions were 100% and 57.63% respectively. These results indicate that optimization using response surface methodology, based on the Box-Behnken approach, is an excellent tool for determining the optimal conditions, and the process can be easily extrapolated for a specific treatment of real waste water containing the azo dye C.I Basic Red 46. Also, the intermediates that were produced during photodegradation process of Basic Red 46 were determined by GC/MS. 相似文献
46.
《应用有机金属化学》2017,31(12)
In this study, the potential application of copper nanowires loaded on activated carbon for simultaneous removal of Disulfine blue (DB), Crystal violet (CV) and Sunset yellow (SY) has been described. The relation between adsorption properties with variables such as solution pH, adsorbent value, contact time and initial dyes concentration was investigated and optimized. A three‐layer artificial neural network (ANN) model was utilized to predict dyes removal (%) by adsorbent following conduction of experiments. The training of network at above mention experimental data confirms its ability to forecast the removal performance with a linear transfer function (purelin) at output layer. The Levenberg–Marquardt algorithm and tangent sigmoid transfer function (tansig) with 16 neurons at the hidden layer was applied. Parameters were optimized by central composite design (CCD) combined with response surface methodology (RSM) and desirability function. The accuracy of ANN was judged according to both MSE and AAD% at optimal conditions and results indicate its superiority to RSM model in term of higher R2 and lower AAD% values. This observation was also corroborated by the parity plots between the predicted and experimental values. The ANN model was better in both data fitting and prediction capability in comparison to RSM model. 相似文献
47.
48.
Y. Benmimoun A. Bouhemadou R. Khenata A. H. Reshak B. Amrani M. Ameri H. Baltache 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(2):165-171
The results of first-principles theoretical study of the structural,
electronic and optical properties of SrCl2 in its cubic structure, have
been performed using the full-potential linear augmented plane-wave method
plus local orbitals (FP-APW+lo) as implemented in the WIEN2k code. In this
approach both the local density approximation (LDA) and the generalized
gradient approximation (GGA) are used for the exchange-correlation (XC)
potential. Also we have used the Engel-Vosko GGA formalism, which optimizes
the corresponding potential for band structure calculations. We performed
these calculations with and without spin-orbit interactions. Including
spin-orbit coupling cause to lifts the triple degeneracy at Γ point
and a double degeneracy at X point. Results are given for structural
properties. The pressure dependence of elastic constants and band gaps are
investigated. The dielectric function, reflectivity spectra and refractive
index are calculated up to 30 eV. Also we calculated the pressure and volume
dependence of the static optical dielectric constant. 相似文献
49.
Brand D Pandey A Rodriguez-Leon JA Roussos S Brand I Soccol CR 《Applied biochemistry and biotechnology》2002,102(1-6):169-177
Studies were carried out in a packed-bed column fermentor using coffee husk as substrate in order to verify a relationship
between caffeine degradation and the respiration of Aspergillus sp. LPBx. Fermentation conditions were optimized by using factorial design experiments. The kinetic study showed that the
caffeine degradation was related to the development of mold and its respiration and also with the consumption of reducing
sugars present in coffee husk. From the values obtained experimentally for oxygen uptake rate and CO2 evolved, we determined a biomass yield of 3.811 g of biomass/g of consumed O2 and a maintenance coefficient of 0.0031 g of consumed O2/(g of biomass·h). The maximum caffeine degradation achieved was 90%. 相似文献
50.
An experiment on program development 总被引:1,自引:0,他引:1
Peter Naur 《BIT Numerical Mathematics》1972,12(3):347-365
As a contribution to programming methodology, the paper contains a detailed, step-by-step account of the considerations leading to a program for solving the 8-queens problem. The experience is related to the method of stepwise refinement and to general problem solving techniques. 相似文献