High regioselective acetylation of vitamin A precursors using lipase B from Candida antarctica in organic media

The effect of different reaction parameters was explored on the acylation of primary hydroxyl group of 1,6-diol by lipase B from Candida antarctica catalysis in organic solvent. First, the effect of the organic solvents was investigated, and the highest conversion rate was obtained in n-hexane. Then, the effect of the acyl donor was studied. Among several reactants, including acetic acid and two different acetates, vinyl acetate gave the best yield. A maximum monoester yield of 98.5% was obtained using vinyl acetate as acyl donor in n-hexane at 50 degrees C. The substrate concentration was 25 mmol/L, while the diol to vinyl acetate molar ratio was 1:3. Substrate concentration had to be limited due to an inhibitory effect on enzyme by the diol that caused a decrease on initial reaction rate. To promote initial reaction rate, excess vinyl acetate was used. Under the optimum conditions, the conversion rate and monoacylation selectivity were 98.5 and 100%, respectively. The produced monoester was 6.1 mg/ml, and this amount can be further optimized base on the results presented here

Model Pembelajaran Asam Basa Berbasis Scs (Science Process Skills) Melalui Kegiatan Laboratorium Sebagai Wahana Pendidikan Sains Siswa Mts

Tujuan penelitian ini adalah untuk memperkenal- kan dan mengetahui efektivitas Model Pembelajaran SCS ( Science Process Skills ) melalui kegiatan Laboratorium Sebagai Wahana Pendidikan Sains yang cocok bagi siswa MTs agar meningkatkan: penguasaan konsep kimia, ke- mampuan berpikir kreatif, dan keterampilan sains siswa. Metode yang digunakan adalah metode penelitian kelas, dan difokuskan pada pokok bahasan asam basa. Penelitian ini dilakukan di salah satu MTs Negeri di kota Semarang dengan subyek sebanyak 40 siswa kelas III. Instrumen yang digunakan dalam penelitian ini meliputi model pembelaja- ran, soal-soal tes, pedoman wawancara, pedoman obser- vasi dan angket, sedang LKS digunakan pada saat kegiatan laboratorium. Dalam model pembelajaran dikembangkan empat jenis konsep yaitu konsep kongkret, konsep yang menyatakan sifat, konsep yang melibatkan penggambaran simbol, dan konsep berdasarkan prinsip. Model pembela- jaran ini dapat meningkatkan pemahaman konsep pada setiap kelompok kemampuan siswa, mengembangkan ke- mampuan berpikir kreatif dengan hasil tertinggi pada as- pek membangun konsep di atas pengetahuan yang telah ada pada diri siswa dan terendah pada aspek memilih hal- hal yang mungkin tidak relevan, serta keterampilan sains mengatasi kurangnya waktu pembelajaran, bagian-bagian pembelajaran tertentu dapat dilaksanakan di luar jam ke- las

Performance evaluation of inpatient service in Beijing: a horizontal comparison with risk adjustment based on Diagnosis Related Groups

<p>Abstract</p> <p>Background</p> <p>The medical performance evaluation, which provides a basis for rational decision-making, is an important part of medical service research. Current progress with health services reform in China is far from satisfactory, without sufficient regulation. To achieve better progress, an effective tool for evaluating medical performance needs to be established. In view of this, this study attempted to develop such a tool appropriate for the Chinese context.</p> <p>Methods</p> <p>Data was collected from the front pages of medical records (FPMR) of all large general public hospitals (21 hospitals) in the third and fourth quarter of 2007. Locally developed Diagnosis Related Groups (DRGs) were introduced as a tool for risk adjustment and performance evaluation indicators were established: Charge Efficiency Index (CEI), Time Efficiency Index (TEI) and inpatient mortality of low-risk group cases (IMLRG), to reflect respectively work efficiency and medical service quality. Using these indicators, the inpatient services' performance was horizontally compared among hospitals. Case-mix Index (CMI) was used to adjust efficiency indices and then produce adjusted CEI (aCEI) and adjusted TEI (aTEI). Poisson distribution analysis was used to test the statistical significance of the IMLRG differences between different hospitals.</p> <p>Results</p> <p>Using the aCEI, aTEI and IMLRG scores for the 21 hospitals, Hospital A and C had relatively good overall performance because their medical charges were lower, LOS shorter and IMLRG smaller. The performance of Hospital P and Q was the worst due to their relatively high charge level, long LOS and high IMLRG. Various performance problems also existed in the other hospitals.</p> <p>Conclusion</p> <p>It is possible to develop an accurate and easy to run performance evaluation system using Case-Mix as the tool for risk adjustment, choosing indicators close to consumers and managers, and utilizing routine report forms as the basic information source. To keep such a system running effectively, it is necessary to improve the reliability of clinical information and the risk-adjustment ability of Case-Mix.</p

Theoretical investigations on CO oxidation reaction catalyzed by gold nanoparticles

It is crucial to understand the mechanism of low temperature CO oxidation reaction catalyzed by gold nanoparticles so as to find out the origin of the high catalytic reactivity and extend the industrialization applications of nano gold catalysts. In this work, some theoretical works on CO adsorption, O-2 adsorption, atomic oxygen adsorption, formation of surface gold oxide films, reaction mechanisms of CO oxidation involving O-2 reaction with CO and O-2 dissociation before reacting with CO on gold surfaces and Au/metal oxide were summarized, and the influences of coordination number, charge transfer and relativity of gold on CO oxidation reaction were briefly reviewed. It was found that CO reaction mechanism depended on the systems with or without oxide and the strong relativistic effects might play an important role in CO oxidation reaction on gold catalysts. In particular, the relativistic effects are related to the unique behaviors of CO adsorption, O adsorption, O-2 activation on gold surfaces, effects of coordination number and the wide gap between the chemical inertness of bulk gold and high catalytic activity of nano gold. The present work helps us to understand the CO oxidation reaction mechanism on gold catalysts and the influence of relativistic effects on gold catalysis. (C) 2016, Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. All rights reserved

Structures and stability of adsorbed methanol on TiO2 (110) surface studied by ab initio thermodynamics and kinetic Monte Carlo simulation

The structures and stability of adsorbed methanol on TiO2(110) surface have been extensively studied because of its application for direct hydrogen production and promoting hydrogen production in photocatalysis. In this work, combined with ab initio thermodynamics and kinetic Monte Carlo (KMC), a detailed microscopic picture of methanol adsorption structure on TiO2(110) surface at different conditions is mapped out for the first time. The thermodynamics analysis based on the density functional theory calculations shows that the methanol adsorption at coverage of 2/3 ML is prevailed at a very wide range of temperatures and pressures. The simulated temperature-programmed desorption (TPD) based on KMC indicates that the full monolayer adsorption methanol desorbs at about 150 K and the methanol dimer at a coverage of 2/3 ML is stable up to 250 K. At higher temperature, the methanol dimer becomes unstable and decomposes to the monomer, which desorbs from the surface at 350 K. The present simulated results agree well with the experimental TPD results

Electrochemically in situ controllable assembly of hierarchically-ordered and integrated inorganic-carbon hybrids for efficient hydrogen evolution

Inorganic-carbon hybrid materials are an emerging class of nanostructured catalysts that can enhance various energy-oriented electrochemical reactions. Despite recent progress, it is still very challenging to controllably generate the hybrid carbon architecture and its inorganic components with a single approach. Inspired by the flexible redox properties of conductive polyaniline (PANI) polymer, we develop a redox-unit cooperative assembly strategy to synthesize hierarchically-ordered and integrated inorganic-carbon hybrids by electrochemically constructing the nanostructures of PANI and then modifying their redox states to controllably bond different metal complexes. The needle-branched PANI nanofibers are assembled in situ into a three-dimensional (3D) hierarchical framework on carbon paper by an anion induced electrochemical polymerization. Interestingly, tuning the redox states of PANI with a potentiostatic method achieves a controllable metal complex loading. The theoretical calculations show that the oxidized units can strongly bond metal complexes while reduced units don\u27t react significantly due to a high formation energy. Both units with proper proportions can cooperatively control the concentration and spatial distribution of metal complexes in the PANI framework. After thermal treatment, the metal/PANI composites are transformed into a series of inorganic-carbon hybrids including metals and metal oxides, carbides, and sulfides. This novel strategy not only significantly improves the catalytic performance of non-noble metal hybrid materials but also greatly increases the utilization efficiency of noble metal catalysts in the hydrogen evolution reaction. Surprisingly, the optimized Pt@NC catalyst exhibits an ultrahigh mass activity that is ∼5.3-times better than the commercial Pt/C catalyst

Reaction Mechanism of the Low-Temperature Water–Gas Shift Reaction on Au/TiO₂ Catalysts

The redox and associative mechanisms for the low-temperature water–gas shift (WGS) reaction on Au/TiO₂ catalysts are thoroughly examined by density functional theory calculations and microkinetic studies. For the redox mechanism, we have observed that the presence of a gold cluster and extra oxygen vacancies on a TiO₂ surface is vital for the WGS reaction, especially for the process of H₂ release. For the associative mechanism via intermediate species, it is very hard for COOH to be generated in the WGS reaction. HCOO could be generated, while HCOO should only be a product of side reactions because of the difficulty in H₂ release. The present results indicate that the WGS reaction on Au/TiO₂ catalysts can be well explained by the redox mechanism. The present understanding of the mechanism should open a new door for catalyst design in WGS reactions

structuralisomerandhighyieldofpt1ag28nanoclusterviaonepotchemicalwetmethod

In order to understand the structure-property correlation and explore the application of metal nanoclusters, it is important and intriguing to determine their crystal structure and obtain high-yield. At the same time, this is also a challenge in nanoscience and technology. Here, we report the highly efficient synthesis of Pt1Ag28 nanocluster via one-pot chemical wet method. The crystal structure of Pt1Ag28 nanocluster was determined by X-ray crystallography to be a face centered cubic (FCC) kernel. This novel structure is the structural isomerization of Pt1Ag28 nanocluster reported before. This phenomenon is first discovered in the synthesis of alloy nanoclusters. In addition, Pt1Ag28 nanocluster has high yield and exhibits potential optics in the near infrared (NIR) fluorescent imaging. The time-dependent density functional theory (TD-DFT) calculation implied that the optical property of Pt1Ag28 was sensitive to its structure. This work provides a simple method to synthesize alloy nanoclusters with structural isomerization

Structural isomer and high-yield of Pt1Ag28 nanocluster via one-pot chemical wet method

In order to understand the structure-property correlation and explore the application of metal nanoclusters, it is important and intriguing to determine their crystal structure and obtain high-yield. At the same time, this is also a challenge in nanoscience and technology. Here, we report the highly efficient synthesis of Pt1Ag28 nanocluster via one-pot chemical wet method. The crystal structure of Pt1Ag28 nanocluster was determined by X-ray crystallography to be a face centered cubic (FCC) kernel. This novel structure is the structural isomerization of Pt1Ag28 nanocluster reported before. This phenomenon is first discovered in the synthesis of alloy nanoclusters. In addition, Pt1Ag28 nanocluster has high yield and exhibits potential optics in the near infrared (NIR) fluorescent imaging. The time-dependent density functional theory (TD-DFT) calculation implied that the optical property of Pt1Ag28 was sensitive to its structure. This work provides a simple method to synthesize alloy nanoclusters with structural isomerization