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71.
The electronic structure and magnetic properties of Mn-doped Ge, GaAs, and ZnSe nanocrystals are investigated using real space ab initio pseudopotentials constructed within the local spin-density approximation. The ferromagnetic and half-metallicity trends found in the bulk are preserved in the nanocrystals. However, the Mn-related impurity states become much deeper in energy with decreasing nanocrystalline size, causing the ferromagnetic stabilization to be dominated by double exchange via localized holes rather than by a Zener-like mechanism. 相似文献
72.
Directional Newton methods for functions of variables are shown to converge, under standard assumptions, to a solution of . The rate of convergence is quadratic, for near-gradient directions, and directions along components of the gradient of with maximal modulus. These methods are applied to solving systems of equations without inversion of the Jacobian matrix.
73.
The envelope theorem is a statement about derivatives along an optimal trajectory. In dynamic programming the envelope theorem can be used to characterize and compute the optimal value function from its derivatives. We illustrate this here for the linear-quadratic control problem, the resource allocation problem, and the inverse problem of dynamic programming. 相似文献
74.
A sustainable one-pot synthesis of cinnamyl acetate from cinnamaldehyde is demonstrated for the first time using immobilized Baker’s yeast and free or immobilized acid as catalysts and triacetin as solvent. Employing the immobilized yeast and Amberlyst-36 allowed full conversion and 91% selectivity for cinnamyl acetate after 96 h at room temperature, and both the catalysts and triacetin were successfully recycled. 相似文献
75.
A new sensitive surface-enhanced Raman scattering (SERS) assay for detection of cholinesterase inhibitors such as organophosphorous pesticides using silver colloidal nanoparticles was developed and optimized. Acetylcholinesterase (AChE) mediated the hydrolysis of acetylthiocholine to produce thiocholine, which interacted with the silver nanoparticles to give a specific SERS spectrum. Variation in enzyme activity due to inhibition was measured from changes in intensity of a characteristic peak (772 cm−1) of the SERS spectrum that was directly correlated with the concentration of produced thiocholine. The method was demonstrated for the detection of paraoxon as reference AChE inhibitor. Limit of detection of paraoxon for 5 min incubation at 25 °C was 1.8 × 10−8 M. This assay can be utilized for the detection of trace amounts of any AChE inhibitor. 相似文献
76.
Abstract It is observed that sodium phosphate polymers, in which some of the Na+ ions have been replaced by La3+ ions, are subject to both simple molecular flow and to bond interchange in the glass transition region. These two relaxation mechanisms are separated, and their relative contributions to the shear viscosity are calculated. It is shown that the bond-interchange mechanism is subject to an activation energy of ca. 50 kcal, while that of the molecular flow is of the order of 200 kcal at Tg + 30°C;the latter is of the WLF form. It is further shown that the La3+ ions act as cross-links, at least at low concentrations, and that bond interchange occurs at the site of the La3+ ions rather than at random along the polymer chain. 相似文献
77.
Towards Eumelanin@Zeolite Hybrids: Pore‐Size‐Controlled 5,6‐Dihydroxyindole Polymerization 下载免费PDF全文
Dr. Eko Adi Prasetyanto Dr. Paola Manini Prof. Alessandra Napolitano Prof. Orlando Crescenzi Prof. Marco d'Ischia Prof. Luisa De Cola 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(6):1597-1601
5,6‐Dihydroxyindole ( 1 ) and its N‐methyl derivative ( 2 ), key eumelanin building blocks, were inserted into zeolite L by sublimation at 175 °C for 5 days. At a 10 mg/300 mg indole/zeolite ratio, the resulting hybrids displayed a stable deep red coloration. CP/MAS 13C NMR and UV/Vis spectroscopy of the red species suggested the generation and accommodation of quinonoid biindole derivative(s) within the void space of the acidic zeolite channels. Removal of the zeolite matrix by treatment with HF gave a stable species that could be separated by HPLC and characterized by mass spectrometry as an oxygenated biindole derivative (or a mixture of isomers), suggesting addition of water to the original dimer and subsequent re‐oxidation. The characterization was corroborated by optimized molecular geometries and simulated UV spectra with density functional calculations. Loading 1 or 2 into the larger pores of SBA‐15 type mesoporous silica resulted in black eumelanin‐type polymers, confirming channel size dependence over the polymerization process. 相似文献
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