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1.
The detection of trace aroma compounds in samples with complex matrices such as Chinese liquor (Baijiu) requires a combination of several methods, which makes the analysis process very complicated. Therefore, a headspace solid-phase microextraction (HS-SPME) method coupled with two-dimensional gas chromatography time-of-flight mass spectrometry (GC×GC-TOFMS) was developed for the quantitation of a large number of trace compounds in Baijiu. Optimization of extraction conditions via a series of experiments revealed that dilution of the alcohol content of 8 mL of Baijiu to 5%, followed by the addition of 3.0 g of NaCl and subsequent SPME extraction with DVB/CAR/PDMS fiber coating over 45 min at 45 °C was the most suitable. To check the matrix effects, various model Baijiu matrices were investigated in detail. The quantitative method was established through an optimized model synthetic solution, which can identify 119 aroma compounds (esters, alcohols, fatty acids, aldehydes and ketones, furans, pyrazines, sulfur compounds, phenols, terpenes, and lactones) in the Baijiu sample. The developed procedure provided high recovery (86.79–117.94%), good repeatability (relative standard deviation < 9.93%), high linearity (R2 > 0.99), and lower detection limits than reported methods. The method was successfully applied to study the composition of volatile compounds in different types of Baijiu. This research indicated that the optimized HS-SPME–GC×GC-TOFMS method was a valid and accurate procedure for the simultaneous determination of different types of trace compounds in Baijiu. This developed method will allow an improved analysis of other samples with complex matrices. 相似文献
2.
在溶剂热条件下,5-羧酸-1-萘膦酸（5-pncH3）和稀土硝酸盐反应合成得到3例萘羧酸膦酸镧系配合物：[Pr （5-pnc）（H2O）]·2H2O （1）、[Sm （5-pnc）（H2O）]·H2O （2）和[Eu （5-pnc）（H2O）]·H2O （3）。采用单晶X射线衍射、粉末X射线衍射、元素分析、红外光谱、热重分析和荧光光谱对配合物进行了表征。晶体结构表明,每个七配位的镧系离子由来自5个膦酸盐配体的6个O原子和来自1个配位水分子的一个O原子配位。[LnO7]通过O—C—O、O—P—O或—O—单元连接成一维双金属链结构,一维双金属链再进一步由萘羧酸膦酸配体（5-pnc3-）连接成三维开放骨架结构。荧光性质研究表明,配合物3在330 nm的激发光下,发射Eu的红色特征荧光,而配合物1和2在蓝光区显示出非常宽的配体中心发射带。 相似文献
3.
对炭泡沫为支撑骨架的氧化硅气凝胶(SiO2/炭泡沫)和碳化硅(SiC/炭泡沫)复合材料分别采用XRD、SEM、激光导热仪、万能力学试验机进行物相、微观结构、热学及力学性能方面的表征.结果表明:所制备的SiO2/炭泡沫与原炭泡沫相比,具备更高的抗压强度(14.95 MPa)和更低的室温热导率(0.44 W·m-1·K-1).SiC/炭泡沫材料则保持了较高的抗压强度值(14.66 MPa),其在 1 200 ℃下具备极低的高温热导率(2.18W·m-1·K-1).热重分析表明,SiC/炭泡沫在氧化氛围中到610 ℃才发生质量的损失,而内部炭发生完全烧蚀的温度高达844 ℃,这表明该材料的抗氧化性能远好于纯的炭泡沫材料. 相似文献
4.
主要讨论局部有限维的Hopf π-代数的π-子代数与Hopf π-子代数,分别得到了Hopf π-代数的π-子代数和Hopf π-子代数的一些充分必要条件. 相似文献
5.
赵士银 《纯粹数学与应用数学》2011,27(1):45-50
设H为有限型Hopfπ-代数,研究Hopfπ-代数H上的Hopfπ-模与Hopf π-余代数H *上的Hopfπ-余模之间的对偶关系,得出了Hopfπ-子模与Hopfπ-子 余模之间的充分必要条件,推广了Hopf代数中的相关结论. 相似文献
6.
《International Journal of Solids and Structures》2003,40(22):6189-6209
The paper presents a framework for creep modeling of materials exhibiting different behaviors in different loading scenarios, such as tension, compression and shear, respectively. To this end an additive decomposition of the flow rule is assumed into a sum of weighted stress mode related quantities. The characterization of the stress modes is obtained in the octahedral plane of the deviatoric stress space in terms of a single scalar variable, such that stress mode dependent scalar weighting functions can be constructed. Furthermore the numerical implementation into a finite element program of the resulting set of constitutive equations and aspects of the sensitivity analysis for parameter identification are addressed. Verification of the constitutive equations is succeeded for an aluminum alloy AK4-1T and a superalloy René 95, respectively. In two finite element examples the proposed model is applied to investigate the relaxation behavior of a square plate with circular hole and the evolution of creep damage in a gasturbine blade subjected to centrifugal and thermal loads. 相似文献
7.
The precise adjustment of handedness of helical architectures is important to regulate their functions. Macroscopic chirality inversion has been achieved in organic supramolecular systems by pH, metal ions, solvents, chiral and non-chiral additives, temperature, and light, but rarely in coordination polymers (CPs). In particular, salt-assisted macroscopic chirality inversion has not been reported. In this work, we carried out a systematic investigation on the role of pH and salt in regulating the morphology of CPs based on Gd(NO3)3 and R-(1-phenylethylamino)methylphosphonic acid (R-pempH2). Without extra NO3−, the chirality inversion from the left-handed superhelix R-M to the right-handed superhelix R-P can be achieved by pH modulation from 3.2 to 3.8. The addition of NaNO3 (2.0 eq) at pH 3.8 results in an inversion of chiral sense from R-P to R-M as a pure phase. To our knowledge, this is the first example of salt-assisted macroscopic helical inversion in artificial systems. 相似文献
8.
BackgroundThe recombinant human truncated Keratinocyte growth factor (Palifermin) is the only FDA approved medicine for the treatment of oral mucositis. The Keratinocyte growth factor is a fairly unstable protein due to its high aggregation propensity and therefore its expression as a secretory protein may results in the production of a protein with more stability, higher solubility, better folding, enhanced biological activity, N-terminal authenticity and simplified downstream processing.ObjectiveThe aim of this study was in silico evaluation of 31 different secretory signal peptides to determine the best theoretical candidates for the secretory production of recombinant truncated human KGF in E. coli.MethodsThirty different prokaryotic signal peptides experimentally shown to be capable of recombinant protein secretion in E.coli, along with the native KGF signal peptide were selected for further investigations. The signal peptide sequences were retrieved from the UniProt database. The ability of SPs to act as a secretory leader peptide for rhKGF and the location of cleavage sites were predicted by SignalP 4.1. Physicochemical properties of the signal peptides, which may influence protein secretion, were analyzed by ProtParam and PROSOII. Furthermore, the mRNA secondary structure and Gibbs free energy profile of the selected SPs were analyzed in the fusion state with the rhKGF using Visual Gene Developer package.Results and ConclusionComputational analysis of the physicochemical properties affecting protein secretion identified Sec-B dependent OmpC, Bla, and StaI and SRP dependent TolB signal peptides as the best theoretical candidates for the secretory production of recombinant truncated human KGF in E.coli. 相似文献
9.
Shi-Chun Mao Zhaohui Zhang Jiansen Gao Zhen-Sen Wu 《Waves in Random and Complex Media》2019,29(1):54-62
A solution to the problem of Gaussian beam scattering by an anisotropically coated circular cylinder is presented. The incident Gaussian beam source is expanded as an approximate expression in the simple form with a Tayor’s series. The transmitted field in the anisotropically coated region is expressed as a infinite summation of eigen plane waves with different polar angles. The unknown coefficients of the scattered fields are obtained with the aid of the boundary conditions. The infinite series can be truncated under the prerequisite of achieving the solution convergence. Only the case of transverse-electric polarization is discussed. The similar formulation of transverse-magnetic polarization can be obtained by adopting the similar method. Some numerical results are presented and discussed. The result is in agreement with that available as expected when the Gaussian beam degenerates to a plane wave incidence case. 相似文献
10.