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931.
R. De Souza D. Neibecker I. Tkatchenko G. Boiteux A. Revillon 《Macromolecular Symposia》1989,24(1):137-143
Monometallic complexes of Nickel have been successfully, tested in reaction with olefinic and acetylenic compounds. This paper is devoted to one of the resulting products, a polyphenylacetylene which presents interesting properties. It is readily obtained avoiding the step of a polymer precursor; it is soluble in several solvents, stable in air up to 200° C and may possess a rather high conductivity, depending on polymerization conditions. This is a noticeable difference versus previously reported polyphenylacetylenes which were insulating materials. 相似文献
932.
Rapid and high-performance analysis of thyreostatic drug residues in urine using gas chromatography-mass spectrometry 总被引:1,自引:0,他引:1
Peter Batjoens Hubert F. De Brabander Katia De Wasch 《Journal of chromatography. A》1996,750(1-2):127-132
A more sensitive method was developed using the hyphenated technique of gas chromatography-mass spectrometry (GC-MS) supplementary to the official high-performance thin-layer chromatography (HPTLC) method. Even combined with less efficient extraction and clean-up methods, GC-MS is able to lower the detection limit to less than 50 ppb. The powerful technique of GC-MS-MS is tried out to reduce the detection limit even more, in combination with simplified extraction methods. This time-saving approach combined with the increase in sensitivity is of great importance for a routine technique. 相似文献
933.
The determination of biogenic amines in alcoholic beverages is important to assess the potential risks associated with the consumption of high concentrations of these compounds. In addition, product storage conditions and the length of storage can cause the formation of biogenic amines that reduce product quality. We report a new method using cation-exchange chromatography with either suppressed conductivity, integrated pulsed amperometry, UV, or a combination of these detection techniques to determine biogenic amines in alcoholic beverages. The main objective was to provide a direct comparison between IPAD and suppressed conductivity detection for determining biogenic amines in alcoholic beverages. Suppressed conductivity is the simplest detection approach for determining putrescine, cadaverine, histamine, agmatine, phenylethylamine, spermidine, and spermine with good sensitivity (0.004-0.08 mg/l) and was used to evaluate the influence of storage time and conditions on the evolution of biogenic amines in alcoholic beverages. Integrated pulsed amperometric detection (IPAD) detects more biogenic amines than suppressed conductivity detection, enabling the detection of dopamine, tyramine, and serotonin. Tyramine was simultaneously determined by UV detection and IPAD to provide confirmation and ensure the accuracy of the analytical results. The linearity of biogenic amine responses was within 0.1-20 mg/l and peak area precisions were 0.24-4.97% for IPAD, suppressed conductivity-IPAD, and UV detection. The sensitivity for the 10 biogenic amines using the 3 detection techniques varied considerably from 0.004-1.1 mg/l and recoveries were within 85-122%. 相似文献
934.
George R. De Mar 《Journal of Molecular Structure》1987,160(3-4):327-335
Ab initio optimizations of the complete acrolein molecular geometry accomplished using analytical gradient methods at the 6-31G* SCF level at ten points during rotation from the planar trans- to the planar cis-form (rotation about the single C---C bond) are used to calculate the values of the Pitzer function F(φ), the coefficients of its Fourier expansion, and the coefficients in the potential energy expansion. The theoretical potential expansion coefficients are then adjusted using the experimental torsional frequencies and their overtones for the trans- and cis-forms of CH2=CH---CH=O and CH2=CH---CD=O. For the cis-conformer two different sets of experimental frequencies are employed. The dependence of the slope of the acrolein potential energy curve on the experimental frequency set used for the cis-rotamer is discussed. 相似文献
935.
Amyloglucosidase from Novo (Copenhagen, Denmark) was immobilized in controlled pore silica particles with the silane-glutaraldehyde
covalent method. Thermal stability of the free and immobilized enzyme (IE) was determined with 30% (w/v) α-amylase liquefied
cassava starch, pH 4.5, temperatures from 35 to 75°C. Free amyloglucosidase maintained its activity practically constant for
240 min and temperatures up to 50°C. The IE has shown higher stability retaining its activity for the same period up to 60°C.
Half-life for free enzyme was 20.6, 6.44, 2.07, 0.69, and 0.24 h for 55, 60, 65, 70, and 75°C, respectively, whereas the IE
at the same temperatures had half-lives of 116.4, 30.88, 8.52, 2.44, and 0.73 h. The energy of thermal deactivation was thus
50.6 and 57.6 kcal/mol, respectively for the free and IE, confirming stabilization by immobilization. 相似文献
936.
J. Mullens A. Vos A. De Backer D. Franco J. Yperman L. C. Van Poucke 《Journal of Thermal Analysis and Calorimetry》1993,40(1):303-311
The 124 superconductor YBa2Cu4O8 was prepared from the oxalate precursor Y2(C2O4)3. ·4BaC2O4·8CuC2O4·xH2O at one atmosphere oxygen pressure. In O2 the precursor decomposes in one step at 300°C and more gradually (300°–600°C) in Ar. The stability of the superconductor is strongly dependent on the gas atmosphere: in O2 and in air there is no significant weight change as long as the temperature does not exceed 800°C, whereas in a 1% O2-99%N2 mixture decomposition starts at about 670°C with the formation of CuO and YBa2Cu3Ox withx<7. The reduction of YBa2Cu4O8 in a 5% H2-95% Ar mixture takes place in at least four major steps with formation of products such as Y2O3, BaO, Cu2O, Cu, BaY2O4 and Ba4Y2O7. 相似文献
937.
采用体积排斥色谱法/ 示差折光指数/ 直角激光光散射/ 示差粘度三检测联用技术表征了氘化聚苯乙烯、聚苯乙烯和氘化聚苯乙烯- 聚异戊二烯。结果表明,在θ条件下,虽然氘化聚苯乙烯的化学依赖性常数υT,DPS比聚苯乙烯的化学依赖性常数υT,PS大,但25 ℃时在四氢呋喃中,氘化聚苯乙烯的分子尺寸仍小于聚苯乙烯的分子尺寸。由于嵌段共聚物的淋洗体积随组成变化,所以用传统的SEC/RI得不到准确的分子量。经比较膜渗透、小角激光光散射和基质辅助激光脱吸与离子化时间飞行质谱等的实验结果,证明体积排斥色谱法/ 示差折光指数/ 直角激光光散射/ 示差粘度三检测技术能准确地得到氘化二嵌段共聚物的分子量以及其它重要信息。 相似文献
938.
Jian‐Gong Yang Kai Li Jian Wang Shanshan Sun Weijie Chi Chao Wang Xiaoyong Chang Chao Zou Wai‐Pong To Ming‐De Li Xiaogang Liu Wei Lu Hong‐Xing Zhang Chi‐Ming Che Yong Chen 《Angewandte Chemie (International ed. in English)》2020,59(17):6915-6922
Materials exhibiting excitation wavelength‐dependent photoluminescence (Ex‐De PL) in the visible region have potential applications in bioimaging, optoelectronics and anti‐counterfeiting. Two multifunctional, chiral [Au(NHC)2][Au(CN)2] (NHC=(4R,5R)/(4S,5S)‐1,3‐dimethyl‐4,5‐diphenyl‐4,5‐dihydro‐imidazolin‐2‐ylidene) complex double salts display Ex‐De circularly polarized luminescence (CPL) in doped polymer films and in ground powder. Emission maxima can be dynamically tuned from 440 to 530 nm by changing the excitation wavelength. The continuously tunable photoluminescence is proposed to originate from multiple emissive excited states as a result of the existence of varied AuI???AuI distances in ground state. The steric properties of the NHC ligand are crucial to the tuning of AuI???AuI distances. An anti‐counterfeiting application using these two salts is demonstrated. 相似文献
939.
Laura Tblick Severien Van Keer Annemie De Smet Pierre Van Damme Michelle Laeremans Alejandra Rios Cortes Koen Beyers Vanessa Vankerckhoven Veerle Matheeussen Renee Mandersloot Arno Floore Chris J. L. M. Meijer Renske D. M. Steenbergen Alex Vorsters 《Molecules (Basel, Switzerland)》2021,26(7)
The potential of first-void (FV) urine as a non-invasive liquid biopsy for detection of human papillomavirus (HPV) DNA and other biomarkers has been increasingly recognized over the past decade. In this study, we investigated whether the volume of this initial urine stream has an impact on the analytical performance of biomarkers. In parallel, we evaluated different DNA extraction protocols and introduced an internal control in the urine preservative. Twenty-five women, diagnosed with high-risk HPV, provided three home-collected FV urine samples using three FV urine collection devices (Colli-Pee) with collector tubes that differ in volume (4, 10, 20 mL). Each collector tube was prefilled with Urine Conservation Medium spiked with phocine herpesvirus 1 (PhHV-1) DNA as internal control. Five different DNA extraction protocols were compared, followed by PCR for GAPDH and PhHV-1 (qPCR), HPV DNA, and HBB (HPV-Risk Assay), and ACTB (methylation-specific qPCR). Results showed limited effects of collection volume on human and HPV DNA endpoints. In contrast, significant variations in yield for human endpoints were observed for different DNA extraction methods (p < 0.05). Additionally, the potential of PhHV-1 as internal control to monitor FV urine collection, storage, and processing was demonstrated. 相似文献
940.
Fengxiang Li Junlin Xie De Fang Feng He Kai Qi Pijun Gong 《Research on Chemical Intermediates》2017,43(10):5413-5432
A series of Ce–MnO x /TiO2 catalysts were prepared using a novel sol–gel template method and investigated for low-temperature selective catalytic reduction (SCR) of NO with NH3 at temperatures ranging from 353 to 473 K. The 0.07Ce–MnO x /TiO2 catalyst showed the highest activity and best resistance to SO2 poisoning. The structure and properties of the catalysts were characterized using X-ray diffraction (XRD) analysis, thermogravimetric analysis (TGA), thermogravimetry (TG)–differential scanning calorimetry (DSC)–mass spectroscopy (MS), high-resolution transmission electron microscopy (HRTEM), Brunauer–Emmett–Teller (BET) measurements, H2-temperature-programmed reduction (TPR), and NH3-temperature-programmed desorption (TPD). The superior catalytic activity of the 0.07Ce–MnO x /TiO2 catalyst was probably due to a change in the active components, an increase in surface active oxygen and surface acid sites, and lower crystallinity and larger surface area with Ce doping. Furthermore, the reduction ability also became stronger. The SO2 poisoning resistance of the 0.07Ce–MnO x /TiO2 catalyst improved because doping with Ce can effectively decrease the formation of ammonium salt on the catalyst surface and the sulfation of MnO x . In situ diffuse-reflectance infrared Fourier-transform (DRIFT) spectroscopy experiments indicated that addition of Ce could promote adsorption of NH3 and inhibit generation of some nitryl species. The SCR reactions over the catalysts mainly followed the Eley–Rideal mechanism accompanied with a partial Langmuir–Hinshelwood mechanism. 相似文献