Evidence for cyclohexyl as a reactive surface intermediate during high-pressure cyclohexane catalytic reactions on Pt(111) by sum frequency generation vibrational spectroscopy

Sum frequency generation (SFG) surface vibrational spectroscopy has been used to identify reactive surface intermediates in situ during catalytic dehydrogenation reactions of high-pressure cyclohexane (C(6)H(12)) on the Pt(111) crystal surface in the presence and absence of high-pressure hydrogen. These experiments provide the first spectroscopic evidence of cyclohexyl (C(6)H(11)) as a reactive surface intermediate during the cyclohexane catalytic conversion to benzene at high pressure in the presence of excess hydrogen. In addition, it was proposed from temperature-dependent SFG experiments that dehydrogenation of cyclohexyl is a rate-limiting step in the cyclohexane catalytic conversion to benzene.     

Determination of osteocalcin in meat and bone meal of bovine and porcine origin using matrix-assisted laser desorption ionization/time-of-flight mass spectrometry and high-resolution hybrid mass spectrometry

A method has been developed for determining the origin of meat and bone meal (MBM) by detecting species-specific osteocalcin (OC) using matrix-assisted laser desorption ionization/time-of-flight (MALDI/TOF) and high-resolution hybrid mass spectrometry (HR-Q/TOF MS). The analysis is based on the detection of typical species-specific OC and its tryptic peptide fragments which differ in mass due to differences in the amino-acid sequences between species. After dissolving the MBM samples in EDTA buffer, purification after ultrafiltration was performed using two methods: solid-phase extraction using Zip-Tip C(18) or size exclusion coupled with reverse-phase chromatography. Fractions containing partially purified intact OC were analyzed using LC-Q/TOF and MALDI/TOF mass spectrometry. Species-specific OC was detected at the typical protonated and doubly protonated molecular ions. Furthermore, typical porcine- and bovine-derived tryptic fragments from MBM were detected after enzymatic digestion. In order to determine the underlying amino-acid sequences and to confirm the assignment to OC-derived peptides, MS/MS analysis was carried out. In conclusion, we were able to detect OC in bovine and porcine MBM with high sensitivity and the MS-based method described here by which total OC mass and marker peptides of digested OC are recorded can be used as an alternative approach to detect genus-specific differences in MBM and can be applied as a confirmatory method to mainly immunological osteocalcin screening methods.     

Curing induced structural reorganization and enhanced reactivity of amino-terminated organic thin films on solid substrates: observations of two types of chemically and structurally unique amino groups on the surface

Infrared-visible sum frequency generation vibrational spectroscopy (SFG) was used to characterize the structure of 3-aminopropyltriethoxysilane (APTES) films deposited on solid substrates under controlled experimental conditions for the first time. Our SFG spectra in combination with complementary analytical data showed that APTES films undergo structural changes when cured at an elevated temperature. Before the films are cured, well-ordered hydrophobic ethoxy groups are dominantly present on the surface. A majority of hydrophilic surface amino groups are protonated, and they are either buried or randomly oriented at the interface. After the films are cured, chemically and structurally different neutral amino groups are detected on the surface. Unlike the protonated amino groups, a new class of neutral amino groups is ordered at the interface and shows enhanced reactivity.     

新工科背景下高等分离工程教学改革与实践

Facing the demand of strengthening the collaborative innovation ability of postgraduates under the background of emerging engineering education, the authors based on many years of teaching and scientific research experience carry out a series of teaching reforms on the teaching content, teaching methods, teaching means and assessment methods for the advanced separation engineering course. The project case base is established, case teaching and team cooperation are adopted to integrate multi-field professional knowledge and the latest scientific research achievements. Professional software is used to solve complex engineering problems, and the manual calculation and software calculation exercises are combined to strengthen the understanding and application of theoretical knowledge. The diversified assessment mode is taken to improve the study enthusiasm and autonomous learning ability. The practice shows that the teaching reforms and implementation of this course obviously improve the teaching effect, which is of great significance to the cultivation of postgraduates' comprehensive engineering ability, team communication and innovative thinking ability.     

On triazoles XLVI. Synthesis of 1,3a,5,6,10c‐pentaazaacephenanthrylenes

A novel route to the synthesis of 6,7,8,9‐tetrahydro‐[1,2,4]triazolo[5,l‐b]quinazoline derivatives 4 through 5 and 6 was elaborated. During the synthesis of derivatives 6 novel type tetracyclic 2,3,7,8,9,10‐hexahydro‐1,3a,5,6,10c‐pentaazaacephenanthrylenes 9 were formed as by‐products. Their structure was proved by spec‐troscopic methods and by X‐ray diffraction spectra. There were also elaborated direct synthetic routes to derivatives 9 . Unexpectedly, the S‐alkyl groups of derivatives 9 could be easily replaced by different amines, which is contrary to all our previous results. Possible explanations to this enhanced reactivity are given.     

聚合物对还原法合成Pt纳米粒子过程的影响

用H_2还原K_2PtCl_4溶液的方法在常温下合成了Pt纳米粒子，考察了poly(N- isopropylacrylamide)(PNIPA), poly(N-vinylacetamide)(PNVA)和poly (vinylalcohol)(PVA)等三种可溶于水的聚合物对Pt纳米粒子大小和溶胶稳定性的 影响。TEM和溶胶中加入KCl电解质溶液后溶胶稳定性测定结果表明，以PNIPA为稳 定剂可获得粒径最小的Pt粒子，且溶胶最为稳定。较高的PNIPA/Pt~(2+)摩尔比对 合成小颗粒的Pt纳米粒子有利，而聚合物的分子量对粒子影响不大。Pt晶粒在H_2 气氛下生长过程较为缓慢，停止通入还原气体H_26h后，晶粒生长才基本完成，但 溶胶在6个月后仍保持良好的稳定性。     

Synthesis of water‐soluble near‐infrared cyanine dyes functionalized with [(succinimido)oxy]carbonyl group

Two hetamethine cyanine dyes suitable for labeling of biomolecules at a primary amino group with a near‐infrared chromophore/fluorophore (λ_max/(λ_em = 800/830 nm and 837/864 nm) have been synthesized from readily available starting materials. Despite the high molecular complexity of intermediate and final products, all these compounds have been obtained in an analytically pure form by using crystallization only.     

锰基催化剂在催化柴油炭烟燃烧中的应用

柴油机排放的炭烟颗粒引起了严重的环境污染并对人体健康造成了极大的危害,引起人们的广泛关注。目前,催化净化技术是控制柴油机尾气炭烟颗粒排放最有效和研究最广泛的技术手段之一,其中高性能催化剂的研发是催化净化技术应用最为关键的因素。本文总结了近年来锰基催化剂材料在催化柴油机炭烟燃烧中的研究进展,重点介绍了单组分锰基催化剂、复合结构锰基氧化物催化剂、固定结构锰基氧化物催化剂(钙钛矿型、尖晶石型、水滑石型)等的研究进展,并简述了锰基催化剂材料在同时消除炭烟颗粒和氮氧化物方面的研究进展。最后,提出了锰基催化剂在催化柴油机炭烟燃烧中存在的问题并对其发展前景进行了展望。     

Investigation of the feeding effect on the 13C/12C isotope ratio of the hormones in bovine urine using gas chromatography/combustion isotope ratio mass spectrometry

The effect of the feeding on the 13C/12C isotope ratio of four endogenous steroid hormones testosterone (T), epi-testosterone (epi-T), dehydroepiandrosterone (DHEA) and etiocholanolone (ETIO) in bovine urine was investigated. An analytical method to determine the accurate isotope ratio was developed including an extensive clean up followed by enrichment of the analytes in two steps of HPLC fractionation. Feeding experiments with four young animals were performed using C3 and C4 plants (grass, maize silage, hay, etc.) over a time period of about 280 days. One cattle was used as a control animal with no change of its diet over the full period. The detection of the 13C/12C isotope ratio of the acetylated extracts was performed by gas chromatography/combustion isotope ratio mass spectrometry. After the first change of the feeding from C4 to C3 plants significant changes of the delta 13C % values were observed from the -19 to -23% level to the -24 to -32% level for etiocholanolone and epi-testosterone in urine of three animals, whereas the DHEA values remained under the level of the two metabolites. Testosterone could not be detected with GC-C-IRMS due to its low concentration in young animals. After the second change of the diet from C3 to C4 plants (after 222 days), the measured delta 13C % values have been stabilised at the original level. The results show that in case of the feeding with only C3 plants the endogenous delta values of -32% can be reached. In this case the contribution of exogenous material with a delta value of -32% could not be detected independently of the concentration. If the diet contains C4 plants the difference or the ratio of the delta 13C % values becomes the determinant in the discriminatory power. For validation of the method a human and a cattle were treated with testosterone and the delta 13C % values were measured in incurred human and cattle urine.