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261.
A simple and efficient ultrafiltration–liquid chromatography–mass spectrometry–based method was developed for the rapid screening and identification of ligands from Citrus limon peel, which are suitable acetylcholinesterase inhibitors. Subsequently, the anti‐Alzheimer's activity of these compounds was assessed using a PC12 cell model. Six major compounds, viz. neoeriocitrin, isonaringin, naringin, hesperidin, neohesperidin, and limonin, were identified as potent acetylcholinesterase inhibitors. A continuous and efficient online method, which involved the use of a microwave‐assisted extraction device, solvent concentration tank, and centrifugal partition chromatography column, was developed for the scale‐up of these compounds, and the obtained compounds presented high purity. Next, their bioactivity was evaluated using a PC12 cell model. This novel approach, which was based on ultrafiltration–liquid chromatography–mass spectrometry, microwave‐assisted extraction online coupled with solvent concentration tank, and centrifugal partition chromatography along with in vitro evaluation, could represent a powerful tool for the screening and extraction of acetylcholinesterase inhibitors from complex matrices, and could be a useful platform for the large‐scale production of bioactive and nutraceutical ingredients. 相似文献
262.
The crystallization behavior and microstructure development of the Zr61Al7.5Cu17.5Ni10Si4 alloy during annealing were investigated by isothermal differential scanning calorimetry, X-ray diffractometry and transmission electron microscopy. During isothermal annealing of the Zr61Al7.5Cu17.5Ni10Si4 alloy at 703 K, Zr2Cu crystals with an average size of about 5 nm were first observed during the early stages (30% crystallization) of crystallization by TEM. The Zr2Cu crystal size increased with annealing time and attained an average size of 20 nm corresponding to the stage of 80% crystallization. In addition, the change in particle size with increasing annealing time exhibited a linear relationship between grain growth time and the cube of the particle size for the Zr2Cu type crystalline phase. This indicates that the crystal growth of the Zr61Al7.5Cu17.5Ni10Si4 alloy belongs to a thermal activated process of the Arrhenius type. The activation energy for the grain growth of Zr2Cu is 155 ± 20 kJ/mol in the Zr61Al7.5Cu17.5Ni10Si4 amorphous alloy. The lower activation energy for grain growth in compared to that for crystallization in Zr65Cu35 440 kJ/mol crystal corresponds to the rearrangement of smaller atoms in the metallic glass, Al or Si (compare to Zr). 相似文献
263.
Bradley E. Cowie Fu An Tsao Prof. David J. H. Emslie 《Angewandte Chemie (International ed. in English)》2015,54(7):2165-2169
An aryldimethylalane‐appended analogue of 1,1′‐bis(diphenylphosphino)ferrocene, FcPPAl, was prepared, and reaction with [Pt(nb)3] (nb=norbornene) afforded [Pt(η2‐nb)(FcPPAl)] ( 1 ). Heating a solution of 1 to 80 °C resulted in crystallization of [{Pt(FcPPAl)}2] ( 2 ), whereas treatment of 1 with C2H4, C2Ph2, H2, or CO provided [PtL(FcPPAl)] [L=C2H4 ( 3 ), C2Ph2 ( 4 )], [PtH2(FcPPAl)] ( 5 ), and [Pt(CO)(FcPPAl)] ( 6 ). In all complexes, the FcPPAl ligand is coordinated through both phosphines and the alane. Whereas 2 adopts a T‐shaped geometry at platinum, 3 – 5 are square‐pyramidal, and 6 is distorted square‐planar. The hydride and carbonyl complexes feature unusual multicenter bonding involving platinum, aluminum, and a hydride or carbonyl ligand. 相似文献
264.
Jonathan J. Wierer Nelson Tansu Arthur J. Fischer Jeffrey Y. Tsao 《Laser \u0026amp; Photonics Reviews》2016,10(4):612-622
III‐nitride light‐emitting diodes (LEDs) and laser diodes (LDs) are ultimately limited in performance due to parasitic Auger recombination. For LEDs, the consequences are poor efficiencies at high current densities; for LDs, the consequences are high thresholds and limited efficiencies. Here, we present arguments for III‐nitride quantum dots (QDs) as active regions for both LEDs and LDs, to circumvent Auger recombination and achieve efficiencies at higher current densities that are not possible with quantum wells. QD‐based LDs achieve gain and thresholds at lower carrier densities before Auger recombination becomes appreciable. QD‐based LEDs achieve higher efficiencies at higher currents because of higher spontaneous emission rates and reduced Auger recombination. The technical challenge is to control the size distribution and volume of the QDs to realize these benefits. If constructed properly, III‐nitride light‐emitting devices with QD active regions have the potential to outperform quantum well light‐emitting devices, and enable an era of ultra‐efficient solid‐state lighting.
265.
The deformation of a knotted polymer under a stretching force is studied by modeling the deformed knot as a composite spring system. Our results predict that the elastic modulus of a knotted polymer is larger when compared to an equal‐length linear chain. More complex knots are in general stiffer. The increase in stiffness of knots relative to the linear chain is also derived. Monte Carlo simulations are also performed to investigate the streching of polymer knots. Chain lengths up to N = 82 and prime knots 01 , 31 , 41 , 51 , 61 and 81 are considered. Segregation of the crossings into a small tight region of the knot structure at strong forces is observed. The increase in stiffness predicted by the composite spring model agree well with the simulation data. Our simulation data show that the scaling laws proposed by de Gennes and Pincus for a single linear chain under traction force still hold for the knotted type polymers. 相似文献
266.
Mycelial pellet formation by Rhizopus oryzae ATCC 20344 总被引:2,自引:0,他引:2
Factors in a cultivation medium affecting fungal growth morphology and funmaric acid production by Rhizopus oryzae ATCC 20344 were investigated. These factors included the initial pH value and trace metals such as zinc, magnesium, iron,
and manganese in the cultivation medium. It was found that a significant change in the growth morphology of R. oryzae ATCC 20344 occurs when the initial pH value is varied. A lower initial pH value in the cultivation medium was inhibitory
to fungal growth, and fast growth in the cultivation medium at a higher initial pH value promoted, the formation of large
pellets or filamentous forms. Trace metals in the cultivation media also had significant effects on pellet formation and fumaric
acid fermentation. 相似文献
267.
Ying Zhou José M. Domínguez Ningjun Cao Jianxin Du George T. Tsao 《Applied biochemistry and biotechnology》1999,78(1-3):401-407
The effect of nutrients on L(+)-lactic acid production from glucose was investigated using Rhizopus oryzae ATCC 523 11. From the shake-flask experiments, the optimal medium composition was defined for improved lactic-acid production.
In order to enhance lactic-acid production rate and product yield, controlled aeration in a bubble column was conducted under
optimal conditions. Results showed a maximum lactic-acid production rate of 2.58 g/L/h was obtained with an initial glucose
concentration of 94 g/L. Finallactic-acid concentration of 83 g/L was achieved after 32 h of fermentation with a weight of
0.88 glactic acid/g glucose consumed. 相似文献
268.
The restrictions imposed on the parameters of the six-quark model by the neutral kaon system are discussed with QCD effects included in the leading logarithmic approximation. The dependence on the six-quark model parameters of the sign and magnitude of the CP violation parameter ε′, the b-quark lifetime and the ratio of decay widths are also discussed. 相似文献
269.
A branching tree scheme is proposed and evaluated for classifying monosubstituted benzenes by the structure of the part of a substituent which lies near the phenyl ring. A large group having the same atom attached to the phenyl ring is divided into subgroups having a more highly defined structure. Each subgroup is then further divided into still smaller subgroups having still more highly defined structures. Combined sets of infrared and Raman peak heights for bands characteristic of the phenyl ring vibrations are used as pattern vectors. A statistical linear discriminant method is used to correlate the peak heights of groups having similar near-the-ring structure. The stepwise and overall success rates are given for each level of classification. 相似文献
270.
Bruce E. Dale George T. Tsao 《Journal of polymer science. Part A, Polymer chemistry》1980,18(11):3163-3175
The structure of the cellulose solvent ferric sodium tartrate (FeTNa) was studied using a sensitive adiabatic calorimeter. FeTNa was found to be a typical transition metal complex in which three tartrate ligands add in a stepwise fashion to iron. The structure of FeTNa first proposed by Franke is thus confirmed. The equilibrium constant for the addition of the third tartrate ligand to iron is approximately 100, a value typical of those for other cellulose-dissolving metal complexes. There is no calorimetric evidence for addition of more than three tartrate molecules to iron. The increase in molar heats of reaction with increasing ionic strength is consistent with dilute electrolyte solution theory. Based on these data, the probable reaction between FeTNa and cellulose has been postulated. 相似文献