近红外漫反射光谱法测定玉米秸秆NDF与ADF含量

应用主成分空间和傅里叶变换近红外光谱技术,采用偏最小二乘回归法(PLS),在国内首次建立了适合不同品种类型、不同生长发育时期和不同部位且适配范围广的近红外漫反射光谱(NIRS)测定玉米秸秆中性洗涤纤维(NeutralDetergentFiber,NDF)和酸性洗涤纤维(AcidDetergentFiber,ADF)含量的稳定校正模型。结果表明,采用一阶导数 矢量归一化预处理和一阶导数 多元散射校正预处理,谱区均为7502～5450cm-1和4601～4247cm-1,所建立的NDF与ADF校正模型,其校正和预测效果最佳。其校正决定系数(R2cal)均大于094,交叉验证和外部验证决定系数(R2cv,R2val)为092～096,各项误差(RMSEE,RMSECV和RMSEP)为149%～181%。该结果对青贮玉米秸秆材料快速鉴定和筛选具有重要的意义。     

THE APPROXIMATION PROBLEM ON THE CLOSED CONVEX CONE AND ITS NUMERICAL SOLUTION

In this paper, we study the approximation problem on the closed convexcone, and prove that there exists a unique solution of the approximation problem, thengive the algorithm to compute the unique solution.     

电感耦合等离子体发射光谱法测定钇铝石榴石中掺杂Yb(Ⅲ)离子

采用碳酸钠-硼砂(质量比1：1)做熔剂分解钇铝石榴石,并确定了熔剂的最优化条件．以电感耦合等离子体光谱法对样品中掺杂Yb(Ⅲ)离子作了定量检测考察了样品和熔剂中单个基体和混合基体对分析结果的影响．发现单个基体Y对Yb的测定有增强效应．基体A1对Yb的测定有一定的抑制作用;基体对Yb测定的干扰可通过基体匹配进行消除元素的俭出限为2μg／L,标准加入回收率为88％～100％实际样品7次检测的RSD为2．1％。本方法可以较好地满足实际样品分析的需要。     

超细氧化硅纳米线阵列的制备和发光特性

以液态金属Ca作为催化剂合成了大量的非晶SiO2纳米线阵列。这些纳米线具有高度取向性,直径分布均匀,平均约8nm,长度大于300μm。研究发现,载气的湿度对非晶SiO2纳米线阵列的生长有重大影响,提出了一种可能的生长模型,以解释这一与传统的VLS机制不同的生长过程。对样品的光致荧光(PL)谱的测量表明,非晶SiO2纳米线阵列在蓝光波段附近存在两个很强且稳定的发射峰,它们直接与样品中的缺陷和空位有关。首次发现了一个稳定的PL峰,存在于红外波段,作为光源,非晶SiO2纳米线阵列可能会在纳米光电子器件中得到应用。由于SiO2是传统的光纤材料,单根SiO2纳米线也有希望应用于近场光学扫描显微镜(SNOM)之中。     

Thermal degradation and isothermal crystalline behavior of poly（trimethylene terephthalate）

Poly(trimethylene terephthalate)(PTT) is an excellent fiber material.Its thermal degradation and isothermal crystalline behaviors were in this study investigated using thermogravimetric analysis(TGA),thermogravimetric analysis-Fourier transform infrared spectroscopy(TGA-FTIR) analysis,differential scanning calorimetry(DSC) and X-ray diffraction(XRD).The thermal degradation mechanism of PTT follows Mclafferty rearrangement principle.The PTTwithintrinsicviscosity(Ⅳ) of 0.74 dL/g has a maximum crystallinity...     

Two new triterpenes from Duchesnea indica

Two new triterpenes,2α,3β-dihydroxyurs-12-en-18,19-epoxy-28-oic acid(1)and 18,19-seco,2α,3α-dihydroxyl-19-oxo-urs-11, 13(18)-dien-28-oic acid(2)were isolated from the herbaceous part of Duchesnea indica.Their structures were elucidated by spectroscopic analysis,including 2D NMR technique.The isolated compounds exhibited moderate cytotoxic activities against HeLa and L929 cell lines.     

Electroanalysis and simultaneous determination of dopamine and epinephrine at poly(isonicotinic acid)-modified carbon paste electrode in the presence of ascorbic acid

A carbon paste electrode modified with electropolymerized fills of isonicotinic acid was developed.The modified electrode shows excellent electrocatalytic activity toward the oxidation of both dopamine(DA)and epinephrine(EP).Separation of the reduction peak potentials for dopamine and epinephrine was about 357 mV in pH 5.3 phosphate buffer solution(PBS)and the character was used for the detection DA and EP simultaneously.The peak currents increase linearly with DA and EP concentration over the range of 8.0×10-5 to 7.0×10-4 mol/L and 5.0×10-6 to 1.0×10-4 mol/L with detection limits of 2 × 10-5 and 1×10-6 mol/L,respectively.The interference studies showed that the modified electrode exhibits excellent selectivity in the presence of large excess of ascorbic acid(AA).     

Structure-based design,synthesis of novel inhibitors of Mycobacterium tuberculosis FabH as potential anti-tuberculosis agents

Mycobacterium tuberculosis FabH,an essential enzyme in mycolic acids biosynthetic pathway,is an attractive target for novel anti-tuberculosis agents.Structure-based design,synthesis of novel inhibitors of mtFabH was reported in this paper.A novel scaffold structure was designed,and 12 candidate compounds that displayed favorable binding with the active site were identified and synthesized.     

Molecular modeling of epsilon RNA from hepatitis B virus

An initial model of the HBV epsilon RNA was built by the Biopolymer module of InsightⅡ.While its three-dimensional structure was obtained through structure optimization based on molecular dynamics simulation,the two active sites were found.A comparison with the experimental result indicated that the active sites may be the binding sites of the epsilon RNA in the RT-epsilon interaction.The result will be helpful to further discussion about the mechanism of RT-epsilon interaction and the study of HBV genom...     

Two new flavanone glycosides from Macrothelypteris torresiana （Gaud.） Ching

Two new flavanone glycosides 1 and 2 were isolated from the aerial parts oi Macrothelypteris torresiana(Gaud.)Ching.The structures of two products were identified as(2S)-5,7,2',5'-tetrahydroxyfiavanone-2'-O-β-D-6"-O-acetylglucopyranoside and(2S)- 5,7,2',5'-tetrahydroxyflavanone-2'-O-β-D-glucopyranoside on the basis of their chemical and spectral analysis,respectively.