Enantioselective benzoin condensation catalyzed by bifunctional <Emphasis Type="Italic">N</Emphasis>-heterocyclic carbenes

Benzoin condensation is an important carbon-carbon bond-forming reaction. The benzoin reaction with good yield, high enanti-oselectivity and broad substrate scope is highly desired in organic synthesis. The intermolecular benzoin condensation catalyzed by bifunctional N-heterocyclic carbenes has been investigated, and the corresponding α-hydroxyketones were obtained with yields up to 76% and enantioselectivities up to 99% ee.     

Enantioselective Chlorocyclization of Olefinic Amides with 1,3-Dichloro- 5, 5-Dimethylhydantoin (DCDMH) Catalyzed by (DHQD)<Subscript>2</Subscript>PHAL

An efficient catalytic asymmetric chlorocyclization of olefinic amides with 1,3-dichloro-5,5-dimethylhydantoin (DCDMH) using hydroquinidine 1,4-phthalazinediyl diether ((DHQD)₂PHAL) as organocatalyst has been developed. Series of chiral chloro substituted isobenzofuran-1(3H)-imine derivatives were obtained in good yields (up to 85%) and enantioselectivities (up to 70% ee).     

Microstructures and properties of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> dispersion-strengthened copper alloys prepared through different methods

Al₂O₃ dispersion copper alloy powder was prepared by internal oxidation, and three consolidation methods—high-velocity compaction (HVC), hot pressing (HP), and hot extrusion (HE)—were used to prepare Al₂O₃ dispersion-strengthened copper (Cu–Al₂O₃) alloys. The microstructures and properties of these alloys were investigated and compared. The results show that the alloys prepared by the HP and HE methods exhibited the coarsest and finest grain sizes, respectively. The alloy prepared by the HVC method exhibited the lowest relative density (98.3% vs. 99.5% for HP and 100% for HE), which resulted in the lowest electrical conductivity (81% IACS vs. 86% IACS for HP and 87% IACS for HE). However, this alloy also exhibited the highest hardness (77 HRB vs. 69 HRB for HP and 70 HRB for HE), the highest compressive strength (443 MPa vs. 386 MPa for HP and 378 MPa for HE), and the best hardness retention among the investigated alloys. The results illustrate that the alloy prepared by the HVC method exhibits high softening temperature and good mechanical properties at high temperatures, which imply long service life when used as spot-welding electrodes.     

Chiral pyrrolidine-azole conjugates: Simple and efficient asymmetric organocatalysts for Michael addition to nitrostyrenes

Simple pyrrolidine-azole conjugates have been synthesized and found to be efficient catalysts for asymmetric Michael addition to nitrostyrenes. The identified optimal catalysts, pyrrolidine-azoles 2, 8 and 13, could catalyze the asymmetric Michael addition of a range of Michael donors and nitrostyrenes in high yields (up to 99%) and excellent stereoselectivities (up to 99:1 dr and 97% ee).     

Asymmetric intramolecular oxa-Michael addition of activated <Emphasis Type="Italic">α,β</Emphasis>-unsaturated ketones by chiral <Emphasis Type="Italic">N</Emphasis>-triflyl phosphoramide

Asymmetric intramolecular oxa-Michael addition of activated α,β-unsaturated ketones by chiral N-triflyl phosphoramide was realized. The flavanone products can be synthesized with excellent yields (50%–95%) and up to 74% ee.     

Selective formation of tetrahedral Pt nanocrystals from K2PtCl6／PVP

Tetrahedral platinum (Pt) nanocrystals (3-8 nm) are synthesized in high selectivity (ca. 80%) from hydrogen reduction of aqueous K2PtCI6 by using polyvinylpyr-rolidone (PVP: Mw≈360000) as a protector. Morphology (TEM) measurements of the metal colloids and UV-Vis absorption of the colloidal solution are employed to monitor the tetrahedron formation during the syntheses with varying K2PtCl6/PVP ratios. The results clearly show a two-stage process for the selective formation of tetrahedral nanocrystals. Rapid nucleation and crystal formation at the early stage result in round-like crystallites and the external facet evolution in thereafter slow crystal growth leads selectively to the formation of the tetrahedrons.     

微波辐射SnCl4·5H2O催化合成苯甲酸苯乙酯

采用微波辐射技术,以SnCl4·5H2O为催化剂合成了苯甲酸苯乙酯.结果发现,该方法具有操作简便、反应速度快、酯化率高、环境友好等优点.在微波辐射功率288 W,辐射时间5 min,醇酸物质的量的比为4:1,催化剂用量1.2 g时,酯化率达97.2%.     

Preparation of Zn-doped TiO2 nanotubes electrode and its application in pentachlorophenol photoelectrocatalytic degradation

Zn-doped titanium oxide （TiO2） nanotubes electrode was prepared on a titanium plate by direct anodic oxidation and immersing method in sequence. Field emission scanning electron microscopy （FESEM） showed that the Zn-doped TiO2 nanotubes were well aligned and organized into high density uniform arrays with diameter ranging from 50 to 90 nm. The length and the thickness were about 200 and 15 nm respectively. TiO2 anatase phase was identified by X-ray diffraction （XRD）. X-ray photoelectronspectroscopy （XPS） indicated that Zn ions were mainly located on the surface of TiO2 nanotubes in form of ZnO clusters. Compared with TiO2 nanotubes electrode, about 20 nm red shift in the spectrum of UV-vis absorption was observed. The degradation of pentachlorophenol （PCP） in aqueous solution under the same condition （initial concentration of PCP： 20 mg/L; concentration of Na2SO4：0.01 mol/L and pH： 7.03） was carried out using Zn-doped TiO2 nanotubes electrode and TiO2 nanotubes electrode. The degradation rates of PCP using Zn-doped TiO2 nanotubes electrode were found to be twice and 5.8 times as high as that using TiO2 nanotubes electrode by UV radiation （400 μw/cm^2） and visible light radiation （4500 μw/cm^2）, respectively. 73.5% of PCP was removed using Zn-doped TiO2 nanotubes electrode against 45.5% removed using TiO2 nanotubes electrode in 120 min under UV radiation. While under visible light radiation, the degradation efficiency of PCP was 18.4% using Zn-doped TiO2 nanotubes electrode against 3.2% using TiO2 nanotubes electrode in 120 min. The optimum concentration of Zn doping was found to be 0.909%. The PCP degradation efficiencies of the 10 repeated experiments by Zn-doped TiO2 nanotubes electrode were rather stable with the deviation within 3.0%.     

微波辐射SnCl4·5H2O催化合成乙酸正丁酯

采用微波辐射技术,以SnCl4@5H2O为催化剂催化合成了乙酸正丁酯.最佳反应条件醇酸配比为l1.2,催化剂用量为1.4 g,微波功率为450 W,微波辐射时间为15 min,产率95%.实验结果表明适当的微波辐射可以加速乙酸正丁酯的合成反应,而且产率高,操作简便,腐蚀性小.     

RBC: A Memory Architecture for Improved Performance and Energy Efficiency

DRAM-based memory suffers from increasing row buffer conflicts, which causes significant performance degradation and power consumption. As memory capacity increases, the overheads of the row buffer conflict are increasingly worse as increasing bitline length, which results in high row activation and precharge latencies. In this work, we propose a practical approach called Row Buffer Cache(RBC) to mitigate row buffer conflict overheads efficiently. At the core of our proposed RBC architecture, the rows with good spatial locality are cached and protected,which are exempted from being interrupted by the accesses for rows with poor locality. Such an RBC architecture significantly reduces the overheads of performance and energy caused by row activation and precharge, and thus improves overall system performance and energy efficiency. We evaluate RBC architecture using SPEC CPU2006 on a DDR4 memory compared to a commodity baseline memory system. Results show that RBC improves the overall performance by up to 2:24(16:1% on average) and reduces the memory energy by up to 68:2%(23:6% on average) for single-core simulations. For multi-core simulations, RBC increases the overall performance by up to1:55(17% on average) and reduces memory energy consumption by up to 35:4%(21:3% on average).     

甘肃白银厂小铁山韧性剪切带体积亏损与成分变异

白银厂矿田分布有多条韧性剪切带,在空间上与矿体关系密切.对小铁山韧性剪切带岩石地球化学研究表明,在韧性剪切变质变形过程中,岩石中的元素发生不同程度的变异,主要表现为活动性较小的高场强元素有规律的富集,活动元素有带入(富集)或带出(亏损)的变化规律.本文认为:稳定元素的富集与剪切带的体积亏损(初糜岩27%,糜棱岩35%)有关,活动元素的变异主要与流体作用有关.剪切带中大量的SiO2流失和高的流体/岩石比(初糜岩95～474;糜棱岩129～646)表明,剪切带中的渗透流体对成矿作用具有重要影响.     

Construction of heteroduplex DNA and<Emphasis Type="Italic">in vitro</Emphasis> model for functional analysis of mismatch repair

Functional deficiency of mismatch repair (MMR) system is one of the mechanisms of tumorigenesis. With the development of the investigation and the requirement from the clinical diagnosis and treatment it is necessary to build up a method to evaluate the functional status of the whole MMR system in the concerned tumors. The original ssDNA and dsDNA from wild type (wt) bacteriophage M13mp2 and its three derivates with mutation points in the lacZα gene have been used to construct two kinds of hetero-duplex DNA molecules. One named del(2) has two bases deleted in the negative strand, the other has a G·G mismatch base pair in the negative strand too. Introducing this heteroduplex DNA into E. coli NR9162 (mutS-) without the MMR ability on the indicator plate with x-gal and IPTG, there are three kinds of plaques, mixture plaque as the characteristic phenotype of heteroduplex DNA, blue and clear plaques. If the cell extract is mismatch repair competent the percentage of the mixture plaque will decrease after incubation with these heteroduplex DNA, the repair efficiency is expressed in percentage as 100× (1 minus the ratio of percentages of mixture plaque obtained from the extract-treated sample and untreated samples), which can imply the functional status of MMR system of certain samples. After large T-antigen-dependent SV-40 DNA replication assay cell extract from TK6, a human lymphoblastoid B-cell lymphoma cell line with MMR ability, and Lovo, a human colonic carcinoma cell line with MMR deficiency have incubated with these heteroduplex DNA. The repair efficiency of TK6 to del(2) is more than 60%, to G-G is more than 50%. The Lovo efficiency to del(2) is less than 10%, to G-G is less than 20%. Therefore, in this in vitro model used for functional analysis of mismatch repair of heteroduplex DNA as the repair target, TK6 can serve as the control for MMR proficiency and Lovo as the control for MMR deficiency. Using this model the tumor tissue from a case of hereditary nonpolyposis colorectal cancer (microsatellite instability high, MSI-H) was measured and lack of MMR ability was shown. And a case of sporadic rectal cancer (SRC) (microsatellite stability, MSS) maintains MMR proficiency. The results indicate that the model is sensitive and dependable. It could be used to measure the func- tion status of MMR system in tumor cell and/or tissues. This is a reliable method to investigate the mechanic of tumori-genesis. It is meaningful in the observation of the role of MMR in the initiation and progression of concerned tumors.     

云南普洱地区思茅松林生物量及碳储量研究

研究对云南普洱21个思茅松林乔木层、灌木层、草本层、粗死木(CWD)、凋落物进行了调查,建立了思茅松生物量模型,估算了其生物量和碳储量,并分析了其分配特征.结果表明:普洱地区思茅松林活体生物量为82.63～197.89 thm-2(平均129.11 thm-2),其中乔木层生物量占97.86%~98.38%,灌草层为1.62%~2.14%.乔木层生物量的器官分配为茎(67.06%~78.45%)枝(9.75%~16.98%)根(10.14%~13.85%)叶(1.54%~2.10%).死地被层生物量为4.58~8.94 thm-2,其中凋落物占到了81.58%~96.91%,CWD仅占3.09%~18.42%.乔木层生物量和碳储量随年龄增加而增加,分别从12～13 a的101.76 thm-2 和52.06 thm-2增加到25 a的194.68 thm-2 和 97.03 thm-2.当地思茅松林的间伐活动严重影响生物量和碳储量,在间伐强度高的16～19龄的样地中,生物量(82.63 thm-2)甚至低于12～13龄的生物量(103.79 thm-2).     

Hierarchical recognition on the taxonomy of <Emphasis Type="Italic">Nitzschia closterium</Emphasis> f. minutissima

Nitzschia closterium f. minutissima, a marine eukaryotic unicellular diatom, originally classified as Bacillariophyta/Bacillariophyceae/Bacillariales/Bacillariaceae/Nitzschia, is one of the most important feed sources in mariculture. In this study, its morphological features were examined under DIC Microscopy （differential interference contrast microscope）; its pigments and fatty acids composition were analyzed by using High Performance Liquid Chromatography （HPLC） and gas chromatography （GC）; the complete Actin cDNA, part 18S rDNA, complete ITS1 and ITS2 sequences, part 28S rDNA sequences, and a putatively encoding A5 fatty acid desaturase gene were cloned respectively and further functioned in transgenic yeast. The sequence alignments were separately conducted using the related sequences from Nitzschia closterium f. minutissima, Cylindrotheca closterium （Bacillariophyta/Baci- Ilariales/Bacillariaceae/Cylindrotheca） and Phaeodactylum tricornutum （Naviculales） with ClustalX 1.83. No distinct difference was discovered between N. closterium f. minutissima and P. tricornutum in both biochemical and molecular level. Their identity was more than 99.6% among 18S rDNA, 5.8S rDNA and actin-gene sequences, and is up to 98.6% even among ITS1 and ITS2 sequences. Their △5 desaturase similarity was 99.4%. However, the lower similarity was disclosured between N. closterium f. minutissima and Cylindrotheca closterium, which shared less than 40% identity in the ITS1 and ITS2 sequences. So, N. closterium f. minutissima should not be placed in Bacillariales, Bacillariaceae, Nitzschia, but in Naviculales, Phaeodactylaceae, Phaeodactylum, and it was actually a strain of P. tricornutum.     

Lithium-ion full cell with high energy density using nickel-rich LiNi0.8Co0.1Mn0.1O2 cathode and SiO-C composite anode

A high-energy-density Li-ion battery with excellent rate capability and long cycle life was fabricated with a Ni-rich layered LiNi_0.8Mn_0.1Co_0.1O₂ cathode and SiO-C composite anode. The LiNi_0.8Mn_0.1Co_0.1O₂ and SiO-C exhibited excellent electrochemical performance in both half and full cells. Specifically, when integrated into a full cell configuration, a high energy density (280 Wh·kg-1) with excellent rate capability and long cycle life was attained. At 0.5C, the full cell retained 80% of its initial capacity after 200 charge/discharge cycles, and 60% after 600 cycles, indicating robust structural tolerance for the repeated insertion/extraction of Li+ ions. The rate performance showed that, at high rate of 1C and 2C, 96.8% and 93% of the initial capacity were retained, respectively. The results demonstrate strong potential for the development of high energy density Li-ion batteries for practical applications.     

Data Dependence Graph Directed Scheduling for Clustered VLIW Architectures

This paper presents an instruction scheduling and cluster assignment approach for clustered very long instruction words (VLIW) processors. The technique produces high performance code by simultaneously balancing instructions among clusters and minimizing the amount of inter-cluster data communications. The scheme is evaluated based on benchmarks extracted from UTDSP. Results show a significant speedup compared with previously used techniques with speed-ups of up to 44%, with average speed-ups ranging from 14% (2-cluster) to 18% (4-cluster).     

广西野生蔬菜资源的特点及其开发利用

广西野生蔬菜共１７０种,６４科,分别占广西植物种、科总数的２．０３％和２２．２２％;十字花科（Ｃｒｕｃｉｆｅｒａｅ）（１２种）、菊科（Ｃｏｍｐｏｓｉｔａｅ）（１６种）、禾本科—竹亚科（Ｇｒａｍｉｎｅａｌ－Ｂａｍｂｕｓｏｉｄｅａｅ）（１２种）共有４０种,占野菜种数的２３．５３％;苋科（Ａｍａｒａｎｔｈａｃｅａｅ）（８种）、仙人掌科（Ｃａｃｔａｃｅａｅ）（８种）、百合科（Ｌｉｌｉａｃｅａｅ）（６种）、蓼科（Ｐｏｌｙｇｏｎａｃｅａｅ）（６种）共有２８种,占野菜种数的１６．４７％;有３５个科的野菜仅１种。全区均有分布的野菜有４９科、８４种;分布于桂南的野菜有８科、１２种,分布于桂北的野菜２４科、６８种。１７０种野菜中,木本３６种,占２１．１８％,归属于１４科;草本１２７种,占７４．７０％,归属于４６科;藤本７种,占４．１２％,归属于５科;以整株、茎、叶、花为主要食用部位的（合占８４．１２％）多收采于春夏,而以果实、种子和根为主要食用部位的（合占１５．８８％）多收采于秋冬。不同种类野菜,其营养价值差异很大。一些野菜的某种营养成分的含量远高于栽培蔬菜,有的还含有栽培蔬菜中所没有的特殊营养成分和药用成分。     

高光学纯度2-氯-1-苯乙醇的酶法合成

为实现手性2-氯-1-苯乙醇两个高纯度对映体的酶法合成,考察了多种脂肪酶的动力学拆分效果,并探讨了有机溶剂、温度以及水活度对脂肪酶催化拆分(R,S)-2-氯-1-苯乙醇的影响,研究了固定化酶的重复利用性.结果表明:一种来自Pseudomonas cepacia的固定化脂肪酶Lipase PS IM,在正己烷体系、35℃和水活度0.69时,能同时得到两个高纯度的对映体(ee_p 99%,ee_s 99%);经过5次重复反应后Lipase PS IM的相对酶活仍有85%.     

苯并咪唑炔丙基硫醚的绿色合成

报道了一种以2-巯基苯并咪唑和3-溴丙炔为原料,水作溶剂,氢氧化钠做碱,室温搅拌条件下合成苯并咪唑炔丙基硫醚的新方法.该方法具有反应条件温和、时间较短、后处理简单、产品纯度高、溶剂绿色环保等优点,收率高达93.1%.     

High pressure effects on the crystal structure and electric conductivity of perovskite like（Ca/Sr）2CuO2Cl2 compounds

The crystal structure stability as well as electric conductance of （Sr/Ca）2CuO2Cl2 compound with K2NiF4 structure was investigated up to 31 GPa using diamond anvil technique. It seems that （Sr/Ca）2CuO2Cl2 is quite stable under pressure but with obvious anisotropic compressibility. The equation of state （EOS） obtained shows relative large bulk modulus.