Enhanced MCR-ALS modeling of HPLC with fast scan fluorimetric detection second-order data for quantitation of metabolic disorder marker pteridines in urine

This work presents the development of a liquid chromatographic method based on modeling entire fast scan fluorimetric detection second-order data with the multivariate curve resolution alternating least squares algorithm, for the simultaneous determination of five marker pteridines in urine samples.The modeling strategy involves the building of a single MCR-ALS model composed of matrices augmented in the spectral mode, i.e. time profiles remain invariant while spectra may change from sample to sample. This approach allowed us to separate and determine the whole analytes at once.The developed approach enabled us to determine five of the most important metabolic disorder marker pteridines: biopterin, neopterin, isoxanthopterin, pterin and xanthopterin, three of them presenting emission spectra with the same emission wavelength maxima. In addition, some of these analytes present overlapped time profiles. As a consequence of using the entire data sets, a considerable reduction of the data processing experimental time can be achieved. Results are compared with a previous strategy in which data were split in five different regions, and information about the figures of merit of the new strategy compared with the previously reported strategy is reported.     

Steric effects on the catalytic activities of zinc(ii) complexes containing [12]aneN(3) ligating units in the cleavage of the RNA and DNA model phosphates

A series of N-methylated mono- and di-[12]aneN(3) ligands () have been synthesized and characterized. The steric effects on the catalytic activities of their mononuclear and dinuclear zinc(ii) complexes in the cleavage of a RNA model 2-hydroxypropyl 4-nitrophenyl phosphate (HPNPP, ) and a DNA model methyl 4-nitrophenyl phosphates (MPNPP, ) in methanol have been investigated at 25 °C. In the cleavage of phosphate catalyzed by the mononuclear complexes, derived from the N-methylation in the [12]aneN(3) backbone, the plots of k(obs)versus [Zn(ii)] changed from an upward curvature to linearity with increasing level of methylation, indicating that N-methylations led to a reduction of dinuclear association that was responsible for the synergetic effect. Compared to the activities of the complex with non-methylated di-[12]aneN(3) ligand, those of the dinuclear zinc(ii) complex (Zn(2)-), which has the two N-methyl groups, were reduced by two orders of magnitude as measured by the second-order rate constants and synergetic effect in the cleavage of both model compounds. For reactions catalyzed by the fully N-methylated dinuclear complex (Zn(2)-), no synergetic effect was observed. Nevertheless, complex Zn(2)- still showed the remarkable catalytic efficiency, with rate accelerations of 10(9-10)-fold in the cleavage of each of the two phosphates relative to the background reactions, and the synergetic effects of up to 561 folds. pH jump experiments confirmed that the rate-limiting step in the cleavage of by Zn(2)- involved the binding process, while that in the reaction with was the chemical cleavage of the P-O bond. Steric effects in the cleavage reactions were analyzed in detail and were compared with the electronic effect caused by oxy anion bridging group in the di-[12]aneN(3) ligand and also with the hydrophobic effect observed in other systems. The work has further confirmed that the combination of the cooperativity between two metal ions and a medium effect could result in excellent catalytic activities for the cleavage of phosphate diesters.     

含氟体系下高性能丝光沸石分子筛膜的制备及其性能

采用热涂-浸渍法在大孔α-Al2O3载体上形成薄且致密的晶种层,然后在不添加有机模板剂的含氟条件下二次水热生长法制备了高性能丝光沸石分子筛膜,考察了NaF含量、硅/铝比对丝光沸石分子筛膜形貌和性能的影响.将摩尔组成为6Na2O:1.2Al2O3:30SiO2:780H2O:1.5NaF条件下合成的丝光沸石分子筛膜用于渗透汽化分离91.5%乙醇/水体系,在渗透汽化温度70°C、真空度为400Pa条件下,分离因子和通量分别达到了6872和0.51kg/(m2·h);另外,在分离异丙醇/水、乙酸/水体系时,渗透侧水浓度达到了100%(在色谱检测极限范围内),该分离系数是目前报道的丝光沸石分子筛膜分离的最佳值,并在乙酸浓度为1mol/L的乙醇水溶液中表现出良好的耐酸性.该膜有望作为膜反应器在乙酸乙酯等酯类的生产中大大提高转化率.     

内爆荷载作用下PC箱梁桥的动态响应过程

采用三阶段连续耦合有限元方法,对预应力钢筋砼(Prestressed reinforced concrete,PC)箱梁桥在内爆荷载作用下的动态响应过程进行了数值模拟,综合考虑了结构自重和预应力的影响,得到了PC箱梁桥局部和整体的破坏模式,并分析了破坏机理。结果表明:三阶段连续耦合有限元方法再现了PC箱梁桥局部破坏导致整体垮塌的物理过程;初始应力阶段,PC箱梁桥应力施加符合工程实际;局部响应阶段,腹板与顶板连接部位产生裂缝,顶板与底板在中央位置形成破口;整体响应阶段,在重力和预应力的作用下,箱梁桥先向上起拱,后向下垮塌,最终发生弯曲破坏。     

超临界CO2在低渗透煤层中渗流规律的实验研究

利用自主研发的THM三场耦合渗流实验系统,进行不同孔隙压力和温度条件下的超临界CO2在低渗透煤层中的渗流实验,得出不同温度下流速和压力梯度之间的关系,从而得到了低渗透煤层注入超临界CO2的非达西渗流规律,即流速与压力梯度变化规律呈现正指数关系.随着压力梯度的增大,渗透系数也不断的增大,且呈现正指数关系;在同一体积应力和压力梯度的条件下,温度越高,流速越快;温度在临界点附近,流速和渗透系数增加很快.     

Structural and magnetic properties of SmCo7−xMox alloys

Phase structure and magnetic properties of the as-cast and as-milled/annealed SmCo_7−xMo_x (x=0, 0.1, 0.2, 0.3, 0.4) alloys have been systematically studied. It is found that all the as-cast series alloys are composed of the CaCu₅-type and Th₂Zn₁₇-type phases. Saturation magnetization of the samples decreases with the Mo content increasing. Intrinsic coercivities (_iH_c) of no more than 0.06 T are observed in these as-cast samples, due to their rather coarse grain microstructures with an average grain size of 50 μm. The as-milled/annealed SmCo_7−xMo_x powders crystallize in the disordered TbCu₇-type (1:7) structure with very fine nanograins, and a minor Co₃Mo phase appears in the samples with x=0.1-0.4. High _iH_c (?0.95 T) are achieved in these samples, with a maximum of 1.26 T located at x=0.2, which can be primarily attributed to strong pinning of the domain wall motion at the nanograin boundaries. The temperature coefficient (β) of the _iH_c is about −0.22%/°C in the temperature range of 25-400 °C for the as-milled/annealed samples.     

Development and validation of a simple stability-indicating high performance liquid chromatographic method for the determination of miconazole nitrate in bulk and cream formulations

A simple and stability-indicating high performance liquid chromatographic method was developed and validated for the determination of miconazole nitrate in bulk and cream preparations. The extraction step for cream samples consisted in a warming, cooling and centrifugation procedure that assures the elimination of the lipophilic matrix component, in order to avoid further precipitation in the chromatographic system. Separation was achieved on a ZORBAX Eclipse XDB - C18 (4.6 mm × 150 mm, 5 μm particle size) column, using a mobile phase consisting of water, methanol and acetonitrile, in a flow and solvent gradient elution for 15 min. The column was maintained at 25 °C and 10 μL of solutions were injected. UV detection was performed at 232 nm, although employment of a diode array detector allowed selectivity confirmation by peak purity evaluation. The method was validated reaching satisfactory results for selectivity, precision and accuracy. Degradation products in naturally aged samples could be simultaneously evaluated, without interferences in the quantitative analysis.     

通过测量~(137)Cs的β衰变和内转换电子能谱研究其衰变特性

本研究用Si(Li)漂移探测器测量了~(137)Cs的β衰变能谱和内转电子能谱,对β衰变能谱进行了居里描绘和从内转电子能谱取得了内转换系数.得到β衰变的最大能量为(513.11±1.76)ke V,与参考值误差为0.17%;得到内转换系数K/L=5.712±0.217和M/L=0.264±0.018,与参考值的误差分别为0.92%和1.54%;并确定了~(137)Cs在β和γ衰变中的跃迁级次,给出了~(137)Cs及其衰变子核137Ba各能级的自旋和宇称,绘制出了~(137)Cs的衰变纲图.说明该实验方法是可靠的,可用于实验方面的教学和原子核结构的研究,并为其提供必要的实验数据.     

气相色谱-红外光谱联用技术及应用研究进展

气相色谱-红外光谱联用技术结合了气相色谱法良好的分离能力和红外光谱法结构鉴定的优势,适合复杂未知物成分分离及其定性定量分析。本文综述了气相色谱-红外光谱联用技术（GC-IR）、数据处理方法及其应用研究进展。介绍了GC-IR同其他检测器联用的连接方式。重点综述了GC-IR谱图和数据处理方法及其在石油化工、日用化工、有机反应等领域的应用研究进展,并对气相色谱-红外光谱联用技术及应用进行了展望。     

A Low-Voltage Silicon Light Emitting Device in Standard Salicide CMOS Technology

A silicon-based field emission light emitting diode for low-voltage operation is fabricated in the standard 0.35 μm 2P4M salieide complementary metal-oxide-semiconduetor （CMOS） technology. Partially overlapping p^＋ and n^＋ regions with a salicide block layer are employed in this device to constitute a heavily doped p^＋-n^＋ junction which has soft ＂knee＂ Zener breakdown characteristics, thus its working voltage can be reduced preferably below 5 V, and at the same time the power efficiency is improved. The spectra of this device are spread over 500nm to 1000nm with the main peak at about 722nm and an obvious red shift of the spectra peak is observed with the increasing current through the device. During the emission process, field emission rather than avalanche process plays a major role. Differences between low-voltage Zener breakdown emission and high-voltage avalanche breakdown emission performance are observed and compared.