Solvent-free oxidation of primary alcohols to aldehydes using Au-Pd/TiO2 catalysts

The oxidation of alcohols to aldehydes with O2 in place of stoichiometric oxygen donors is a crucial process for the synthesis of fine chemicals. However, the catalysts that have been identified so far are relatively inactive with primary alkyl alcohols. We showed that Au/Pd-TiO2 catalysts give very high turnover frequencies (up to 270,000 turnovers per hour) for the oxidation of alcohols, including primary alkyl alcohols. The addition of Au to Pd nanocrystals improved the overall selectivity and, using scanning transmission electron microscopy combined with x-ray photoelectron spectroscopy, we showed that the Au-Pd nanocrystals were made up of a Au-rich core with a Pd-rich shell, indicating that the Au electronically influences the catalytic properties of Pd.     

片层组织晶粒尺寸对TiAl-14.3Nb合金抗氧化性的影响

用热重分析法研究了3种不同尺寸的全片层组织的TiAl—14．3Nb合金在1000℃的静止空气中的循环氧化行为。采用XRD、SEM及EDS分析了氧化层的结构和组成。研究表明,全片层组织的晶粒尺寸对其高温抗氧化性能有一定的影响,但并非晶粒越细其高温抗氧化性能越好。同时探讨了其氧化机理。     

热处理对TiAl基合金高温抗氧化性的影响

用不同的热处理工艺获得了TiAl-12Nb-2．5Cr合金的铸态、炉冷和水淬3种合金,其组成相和微观组织均不同;并用氧化增重法研究了这3种合金在1000℃静止空气中的循环氧行化为;采用XRD和EPMA分析了其氧化膜的结构和组成。研究表明,合金元素的加入能够显著提高合金的抗氧化性,但是高量Nh和Cr的加入易导致高温亚稳β相在室温组织中残留,β相能使外层氧化膜的粘附性变差,促进氧化膜的整体剥落。通过热处理消除β相后,获得的以γ α2为主相的炉冷合金形成了有效的保护性氧化膜。     

Shape changes of supported Rh nanoparticles during oxidation and reduction cycles

The microscopic insight into how and why catalytically active nanoparticles change their shape during oxidation and reduction reactions is a pivotal challenge in the fundamental understanding of heterogeneous catalysis. We report an oxygen-induced shape transformation of rhodium nanoparticles on magnesium oxide (001) substrates that is lifted upon carbon monoxide exposure at 600 kelvin. A Wulff analysis of high-resolution in situ x-ray diffraction, combined with transmission electron microscopy, shows that this phenomenon is driven by the formation of a oxygen-rhodium-oxygen surface oxide at the rhodium nanofacets. This experimental access into the behavior of such nanoparticles during a catalytic cycle is useful for the development of improved heterogeneous catalysts.     

Nb含量对TiAl-Nb合金相组成及氧化动力学的影响

对4种铸态TiAl-Nb合金进行显微组织观察和X射线分析，结果表明，不同的Nb含量对其相组成及组织形态都有不同程度的影响。用热重法研究了这4种TiAl基合金在1000℃、100h的循环氧化行为。通过对每个成分的合金氧化动力学曲线分析，发现含铌量适中的钛铝基合金的抗氧化性较好。     

Symmetries of hydrogen bonds in solution

The nuclear magnetic resonance method of isotopic perturbation can distinguish between single- and double-well potentials in intramolecularly hydrogen-bonded monoanions of dicarboxylic acids. These are classic cases of a "strong," symmetric hydrogen bond in the crystal. The observed carbon-13 isotope shifts induced by the substitution of oxygen-18 demonstrate that these monoanions exist as a single symmetric structure in a nonpolar solvent but as two equilibrating tautomers in aqueous solution. The change is attributed to the disorder of the aqueous environment. These are simple counterexamples to the hope that the crystal structure reveals the actual molecular structure in aqueous solution.     

液液萃取饮料中甲苯GC/MS测定方法的研究

为建立一种饮料中甲苯精确定性和定量的分析方法,以标准加入法,在EI源下用GC/MS/SIM模式定量分析果汁饮料中甲苯的含量。结果表明,仪器检出限为0.33 pg,样品中甲苯的平均相对标准偏差小于6%,平均回收率为94.2%。利用GC/MS/SIM方法测定果汁饮料中微量的甲苯,具有灵敏、快速、简便等优点,可用于食品安全检测的推广。     

酵母菌生物接触氧化工艺处理皂素生产废水研究

以酵母菌作为特定微生物,采用生物接触氧化工艺处理皂素生产废水,对其工艺参数进行了优选 研究。结果表明,生物接触氧化工艺中以酵母菌为优势菌群,当温度为28-30 C,进水化学需氧量(COD)为2 710 -9 200 mg／L,pH值为4．5-5．5,溶解氧为4．5 mg／L,水力停留时间(HRT)为12 h时,COD去除率超过70％, 反应出水回收的酵母干菌稳定在8．3g／L以上,且产量随进水有机物浓度升高而上升。     

猪肉微粒体脂肪酸氧化产物对氧合肌红蛋白氧化的影响

从猪肉中分离出微粒体 ,与提纯的猪肉氧合肌红蛋白混合培养 ,研究微粒体脂肪酸氧化产物对氧合肌红蛋白氧化的影响。结果表明 ,氧化的微粒体的硫代巴比妥酸值 (TBARS)比对照组、新制备的微粒体组和氧化的微粒体 +肌肽组显著升高 (P <0 0 5 ) ,更易引起氧合肌红蛋白氧化 (P <0 0 5 )。氧化的微粒体产物通过透析管 (截流相对分子质量 5 0 0 )后也比对照、新制备的微粒体加快氧合肌红蛋白氧化 (P <0 0 5 )。将 4种脂肪酸氧化产物 (辛醛、壬醛、辛烯醛、壬烯醛 )分别添加于氧合肌红蛋白溶液中 ,结果辛烯醛、壬烯醛显著加快了氧合肌红蛋白氧化 (P <0 0 5 ) ,而对照、辛醛、壬醛 3组间氧合肌红蛋白氧化差异不显著 (P >0 0 5 )。提示 ,微粒体脂肪酸氧化产物 ,尤其是小分子不饱和氧化产物会促进氧合肌红蛋白氧化     

Gamma-A cold agglutinin: importance of disulfide bonds in activity and structure

Cleavage of disulfide bonds caused by mild reduction with mercaptoethanol produces a reversible loss of cold agglutinin activity and antigen-binding ability in a gamma-A polymer cold agglutinin. Return of agglutination and antigen-binding ability occur only in those molecules that have not been depolyimerized by reduction. Loss of activity becomes irreversible if reduction is followed immediately by alkylation.     

苏北盐沼环境梯度上甲苯通量变化特征研究

2004年4月至2005年1月在苏北盐沼沿环境梯度采用静态箱技术原位测定了甲苯气体通量。为确定高等植物对通量的贡献,进行了高等植物地上部分去除实验。结果表明:环境梯度上,在生长季(4—10月)盐沼整体上表现为甲苯的净汇,消耗率变化范围为2.50～17.45μmol/(m2.d),其中,互花米草带消耗率最高。在非生长季(11月至次年3月)表层冻结的植被带表现为甲苯的弱源,通量变化范围为5.15～10.76μmol/(m2.d)。光滩全年均表现为排放甲苯。由于盐沼消耗率大于排放率,生长季长于非生长季,所以海岸带盐沼全年表现为消耗甲苯。高等植物地上部分是甲苯的重要汇,但是消耗机制还不清楚。盐沼甲苯净消耗率与土壤温度、光照强度、土壤可溶性盐含量、土壤有机质、硫酸盐含量和大气中甲苯浓度呈正相关关系。     

IBIS模拟集水区尺度的东北东部森林净初级生产力

为使IBIS(integrated biosphere simulator)模型更好地体现碳循环过程的空间异质性,引入GIS技术,改进了IBIS模型的土壤水分再分配和地表太阳辐射计算模块,增加了地形分析模块。在气象、地形、植被和土壤等数据的支持下,利用改进后的模型估算了2004年张家沟集水区森林净初级生产力(NPP),分析了森林NPP空间分布格局及其随地形因素的变化。结果表明:改进后的IBIS模型适用于东北东部集水区森林NPP的模拟估算;研究区2004年森林NPP在空间上大体呈现为东北和西北2区域高,逐渐向中心沟谷地区减少;森林NPP年平均值为375 g/(m2·a),NPP年总量为541.72 t/a;各植被类型中,杨桦林的年平均NPP最高(405 g/(m2·a)),杂木林最低(336 g/(m2·a));从地形因素看,海拔高度和坡度对森林NPP影响不大,而坡向对森林NPP影响最明显,阳坡的森林NPP较阴坡高41%。     

Molecular recognition in the selective oxygenation of saturated C-H bonds by a dimanganese catalyst

Although enzymes often incorporate molecular recognition elements to orient substrates selectively, such strategies are rarely achieved by synthetic catalysts. We combined molecular recognition through hydrogen bonding with C-H activation to obtain high-turnover catalytic regioselective functionalization of sp3 C-H bonds remote from the -COOH recognition group. The catalyst contains a Mn(mu-O)2Mn reactive center and a ligand based on Kemp's triacid that directs a -COOH group to anchor the carboxylic acid group of the substrate and thus modify the usual selectivity for oxidation. Control experiments supported the role of hydrogen bonding in orienting the substrate to achieve high selectivity.     

土霉素固体脂质纳米粒在家兔体内的药代动力学研究

【目的】研究土霉素固体脂质纳米粒在家兔体内的药代动力学特征,以评价其应用效果。【方法】将10只家兔随机分为2组,分别按土霉素剂量20mg/kg腹腔注射土霉素固体脂质纳米粒和土霉素注射液,于设定的时间点采血,用HPLC法测定血浆药物质量浓度,并用DAS3.1.0药动学程序计算药代动力学参数。【结果】土霉素注射液与固体脂质纳米粒的达峰质量浓度(Cmax)分别为(3.676±0.376)和(3.699±0.562)mg/L;吸收平衰期(T1/2Ka)分别为(18.570±0.851)和(27.871±1.767)h;0-∞时段药时曲线下的面积(AUC(0-∞))分别为(83.955±3.720)和(170.150±10.403)mg/(L·h);0-∞时段的平均滞留时间(MRT(0-∞))分别为(36.848±0.268)和(44.672±0.392)h。【结论】土霉素制备成固体脂质纳米粒后,具有明显的缓释作用,血药质量浓度达峰值的时间推迟,同时药物在兔体内平均滞留时间明显长于土霉素注射液,生物利用度得以显著提高。     

基于修正的Gash模型模拟小兴安岭原始红松林降雨截留过程

原始红松林是我国小兴安岭地区的顶级植物群落,理解它的降雨截留过程,对区域生态、水文环境具有重要意义.采用定位研究法,于2010-2011年21场降雨数据对原始红松林的降雨截留和分配效应进行系统研究,并结合当地的气象和林分资料,利用修正的Gash模型对小兴安岭原始红松林进行林冠截留模拟.该模型对穿透雨、树干茎流、截留量的模拟值分别为:370.91、16.14、130.07 mm.穿透雨模拟值比实测值低2.28 mm,相对误差1.75％,树干茎流模拟值高于实测值8.12 mm,相对误差50.3％,林冠截留量模拟值比实测值低2.35 mm,相对误差为1.81％.穿透雨和林冠截留量的模拟值和实测值有较好的一致性,树干茎流的模拟值和实测值相差较大.综合结果表明:修正的Gash模型对小兴安岭地区原始红松林降雨截留拟合具有很好的适用性.     

鱼粉中脂肪氧化的研究进展

鱼粉是水产、禽畜饲料中常用的高蛋白质饲料原料,与其他饲料原料相比,鱼粉蛋白质和粗脂肪含量高,且富含多不饱和脂肪酸,容易发生氧化变质,降低其营养价值和适口性,因而鱼粉脂肪氧化是影响其质量的重要因素．文章对影响鱼粉脂肪氧化的因素、脂肪氧化的特性和危害以及预防方法进行了综述,并对鱼粉今后的发展前景进行了展望     

Green, catalytic oxidation of alcohols in water

Alcohol oxidations are typically performed with stoichiometric reagents that generate heavy-metal waste and are usually run in chlorinated solvents. A water-soluble palladium(II) bathophenanthroline complex is a stable recyclable catalyst for the selective aerobic oxidation of a wide range of alcohols to aldehydes, ketones, and carboxylic acids in a biphasic water-alcohol system. The use of water as a solvent and air as the oxidant makes the reaction interesting from both an economic and environmental point of view.