蔗鸡有机酸成分的GC-MS分析

蔗鸡中有机酸用不同的溶剂提取,应用毛细色谱—质谱技术鉴定出28种化合物,包括脂肪一元、二元、三元酸和芳香酸。测得乌头酸三甲酯的质谱与文献值不同,其谱图特征也作了讨论。     

橡胶防老剂RD的GC/MS研究

采用气相色谱 (GC/ MS)法对橡胶防老剂 RD(2 ,2 ,4 -三甲基 -1 ,2 -二氢化喹啉多聚体 )进行了测试和分析。总离子色谱质谱图 (TIC)表明 :多聚体 RD中二聚体含量最高 ,热稳定性最好。质谱分析表明 :RD容易失去甲烷分子和甲基形成共轭体的离子 ,二聚体和三聚体容易形成二聚体的衍生物离子。采用气相色谱 -质谱(GC/ MS)可使不同分子量的所有多聚体的分子离子峰都出现。给出了 RD分子以及单体的质谱裂解途径     

MALDI-TOFMS表征金属环状多边形超分子

立体金属环状多边形超分子由于其潜在的应用前景引起了广泛的关注,近十年来其制备与组装方面在国际上已形成了一个重要的研究方向.本工作利用基质辅助激光解吸电离-飞行时间质谱(MALDI-TOFMS),对一类以具有固定取代方向的芳香二胺和吡咯-2-醛形成的双Schiff碱为配体,依靠锌离子的模板作用,自组装成具有不同空腔的金属环多边形超分子,进行了质谱分析,并对结果加以讨论.     

三苯胺偶氮化合物的MALDI-TOF质

利用基质辅助激光解吸电离飞行时间质谱法分析三苯胺偶氮化合物。在正、负离子检测模式下,考察了基质、离子化试剂、样品浓度对分析结果的影响。结果表明:基质辅助激光解吸电离飞行时间质谱表征三苯胺偶氮化合物时,用咔啉作基质,负离子检测,可以得到较好的质谱图。     

利用质谱技术解析糖类结构的研究进展

糖类物质是重要的生物信息分子,在许多生命活动中发挥着重要作用。糖类物质的结构非常复杂,其结构解析一直是糖生物学研究的瓶颈。在糖类物质结构解析的诸多方法中,质谱技术被认为是一种不可缺少的重要手段。本工作综述了质谱及色谱-质谱联用法在糖类结构解析中的研究进展,包括电子轰击质谱、化学电离质谱、快原子轰击质谱、电喷雾质谱、基质辅助激光解析电离质谱、色谱-质谱联用技术(气相色谱-质谱和液相色谱-质谱),并比较了各种方法在糖类物质定性、定量分析中的优缺点。随着质谱技术的不断发展,糖链的释放和衍生化方法的不断改进,以及谱图解析工作的进一步深入,质谱技术必将成为糖类物质结构解析的有力工具。     

高效液相色谱-串联质谱法测定食品接触材料及制品中33种初级芳香胺的迁移量

建立了高效液相色谱-串联质谱（HPLC-MS/MS）法测定食品接触材料及制品中33种初级芳香胺的迁移量。根据食品特性以及食品与食品接触材料的接触特点,不同基质样品分别采用20%乙醇、50%乙醇和3%乙酸溶液作为食品模拟浸泡液进行迁移实验。迁移溶液以甲醇和0.05%甲酸水溶液为流动相,经五氟苯基色谱柱梯度洗脱,在电喷雾正离子模式下以动态多反应监测模式检测,外标法定量。33种初级芳香胺在20%乙醇、50%乙醇和3%乙酸（氨水调至pH 7.0）迁移溶液中的绝对基质效应分别为86.1%~97.3%、88.7%~104.0%和62.7%~81.3%,在各自线性范围内的线性关系良好（r>0.99）,检出限和定量限分别为0.02~1.04 μg/kg和0.07~3.26 μg/kg。本方法的迁移实验针对性强、灵敏可靠,可实现食品接触材料及制品中初级芳香胺迁移量的准确测定。     

常压渣油在加氢预处理过程中组成变化的质谱研究

用正庚烷沉淀出沙中常压渣油中的沥青质 ,脱去沥青质后用氧化铝和硅胶的串联吸附色谱柱将其分离为饱和组分、芳香组分和胶质组分。采用高离子化电压质谱技术和场解析质谱技术分别对饱和组分、芳香组分和胶质组分进行分析 ,以研究常压渣油在加氢预处理过程中的组成变化 ,为渣油加氢催化剂的研制及工艺研究提供参考依据     

不同进样方式对汽油燃烧残留物样品GC-MS分析稳定性的影响

本文模拟火灾现场制备汽油燃烧残留物,利用气相色谱-质谱(GC-MS)联用分析仪,对燃烧残留物进行分析,比较三种不同进样方式下GC MS谱图的稳定性。结果表明,不同进样方式下的GC-MS谱图的稳定性有明显的不同。     

叔胺化合物在MALDI-TOF MS中形成脱氢正离子[M-H]~+的机理研究

通过基质辅助激光解吸电离飞行时间质谱(MALDI-TOF MS)测试含叔胺结构单元的一系列肉桂酰胺衍生物,发现谱图中会产生明显的[M-H]~+峰,而在电喷雾质谱(ESI-MS)测试结果中则只观察到[M+H]~+峰。使用不同基质,在MALDI-TOF谱图中始终可见明显的[M-H]~+。推测在MALDI电离源中叔胺化合物首先发生单电子转移或质子转移形成M~(+.)或[M+H]~+,在次级电离过程中粒子间的不断碰撞下,气相中的离子-分子反应继续进行,其结构中叔胺氮原子与邻位碳原子经脱氢形成亚胺离子。由于C-N双键与相邻苯环形成稳定的共轭体系,降低了亚胺离子内能,使其大量产生,在MALDI-TOF MS谱图中表现为[M-H]~+。DFT化学计算结果表明,由[M+H]~+脱氢气形成[M-H]~+为热力学自发过程,进一步选取其他含有叔胺基团的化合物进行MALDI-TOF MS测试,实验结果与上述结论相符。     

MALDI-TOF质谱法分析聚合产物

采用基质辅助激光解吸电离-飞行时间质谱(MALDI-TOFMS)测定高分子聚合物,可灵敏、快速地获得聚合物的平均分子量和聚合分散度数据,由高分辨率的MALDI-TOFMS谱图还可获得聚合物中各聚合链的绝对分子量、链节质量、端基质量等结构信息.本研究采用2,5-二羟基苯甲酸为基体,对聚丙二醇和硅烷化聚乙二醇合成产物进行MALDI-TOFMS分析.     

UPLC-ESI-TOF MS/MS分析太子参中环肽类成分

建立超高效液相色谱-电喷雾飞行时间串联质谱（UPLC-ESI -TOF MS/MS）分析太子参中环肽类成分的方法。实验采用反相C18色谱柱,梯度洗脱,分离并检测太子参中11种环肽类成分。通过信息关联采集（IDA）模式,运用动态背景扣除(DBS),消除背景离子干扰,在获得11种环肽类成分MS/MS图谱的同时,也得到其精确的分子质量信息。     

Rapid Isothermal Gas Chromatography‐Mass Spectrometry Method for Validating a Small Ion Mobility Spectrometer Sensor

Abstract

A fast and reproducible isothermal gas chromatographic‐mass spectrometric method for validating a small ion mobility spectrometer (IMS) sensor for detection of gaseous volatile organic compounds (VOCs) is presented. This method utilizes an automated cyclic valving (CV) sampling technique coupled to a gas chromatograph‐mass spectrometer (GC/MS) in selected ion monitoring (SIM) mode (CV/GC/MS/SIM). The sampling time is considerably reduced by operating the GC isothermally at 300°C. This approach provides rapid measurements with 15 times more data points than the conventional GC/MS methods in which the column temperature is ramped, then cooled before the next sample can be injected. With the mass spectrometer operated in SIM mode, pre‐selected ions that represent the primary quantitation and secondary ions of toluene and a BTX (benzene, toluene, o‐, m‐, and p‐xylene) mixture were monitored and their corresponding breakthrough curves for flow through partially saturated soil columns were generated. The small variation in measured steady state mean concentrations (SSMC) from run to run demonstrates the reproducibility of this new method. A comparison of the transient concentration profiles of toluene from a BTX mixture and toluene alone obtained under identical test conditions shows a linear correlation with R²=0.997. This result suggests that the new method can be used to analyze and quantify some mixtures of co‐eluting gaseous analytes.     

Effect of sodium hypochlorite on the cyclic fatigue resistance: A scanning electron microscopy evaluation

The main purpose of this study was to compare the cyclic fatigue resistances of the three different nickel–titanium files in 2.5% sodium hypochlorite solution and distilled water at physiologic intracanal temperature (35°C). Three NiTi files such as One Curve (OC) (Micro‐Mega, Besancon, France), OneShape (OS) (Micro‐Mega), and Protaper Next (PTN) X2 (Dentsply Sirona, Ballaigues, Switzerland) were tested for cyclic fatigue resistance inside artificial stainless steel canal block with curvature 60° and 5 mm radius. The block was fixed inside a hot water bath of distilled water or 2.5% sodium hypochlorite and the temperature was set at 35 ± 1°C. The number of cycles to fracture data were recorded and all the fracture surfaces of files were evaluated by using scanning electron microscopy. The number of cyclic to fracture data were analyzed statistically via Kruskal–Wallis and Mann–Whitney U tests. OC showed the highest cyclic fatigue resistance at distilled water while PTN X2 showed the lowest cyclic fatigue resistance at 2.5% sodium hypochlorite. When cycling fatigue test medium were changed from distilled water to sodium hypochlorite solution, the resistance of the files to cyclic fatigue were decreased. SEM analysis confirmed that all scanned samples were fractured due to cyclic fatigue. The OC rotary instruments have more cyclic resistance than OS and PTN X2. The sodium hypochlorite solution reduces the resistance of the rotary instruments.     

Cycle-to-cycle variations under cylinder-pressure-based combustion analysis in spark ignition engines

Combustion analysis based on cylinder-pressure provides a mechanism through which a combustion researcher can understand the combustion process. The objective of this paper was to identify the most significant sources of cycle-to-cycle combustion variability in a spark ignition engine at idle. To analyse the cyclic variation in a test engine, the burn parameters are determined on a cycle-to-cycle basis through the analysis of the engine pressure data. The burn rate analysis program was used here and the burn parameters were used to determine the variations in the input parameter—i, e,, fuel, air, and residual mass. In this study, we investigated the relationship of indicated mean effective pressure (IMEP), coefficient of variation (COV) of IMEP, burn angles, and lowest normalized value (LNV) in a spark ignition engine in a view of cyclic variations.     

Comparison of in vitro valve pressure drop results from different investigators

Steady-state pressure-drop vs flow-rate measurements on prosthetic valves have been shown to correlate well with mean cyclic pressure drops vs RMS flow rate during systolic ejection from pulsatile flow data. The use of steady-state data is therefore validated as a means of assessing performance characteristics. Pressure-drop results reported in the literature were compared for valves of the same size and manufacture. Significant differences were noted, which are attributed to: (a) different geometries in the region of the valves, (b) different approach flow conditions, (c) different placement of pressure measurement taps, and (d) different methods of pressure measurement. Differences in pressure drop were observed to vary by as much as a factor of five among different investigators. The exponent n in the relation delta p infinity Q" was also observed to vary, depending on the above factors. The reasons for and some quantitative calculations on the observed differences are presented here.     

A multi-angular mass spectrometric view at cyclic nucleotide dependent protein kinases: in vivo characterization and structure/function relationships

Mass spectrometry has evolved in recent years to a well-accepted and increasingly important complementary technique in molecular and structural biology. Here we review the many contributions mass spectrometry based studies have made in recent years in our understanding of the important cyclic nucleotide activated protein kinase A (PKA) and protein kinase G (PKG). We both describe the characterization of kinase isozymes, substrate phosphorylation, binding partners and post-translational modifications by proteomics based methodologies as well as their structural and functional properties as revealed by native mass spectrometry, H/D exchange MS and ion mobility. Combining all these mass spectrometry based data with other biophysical and biochemical data has been of great help to unravel the intricate regulation of kinase function in the cell in all its magnificent complexity.     

A novel three-dimensional tissue equivalent model to study the combined effects of cyclic mechanical strain and wear particles on the osteolytic potential of primary human macrophages in vitro.

The effects of cyclic mechanical strain and challenge with physiologically relevant doses of submicrometre-size polyethylene (PE) particles on the osteolytic potential of primary human mononuclear phagocytes were investigated. Cells were seeded into a three-dimensional tissue matrix and co-cultured with particles (mean size 0.21 microm) at particle volume to cell number ratios of 7.5, 15, 30 and 100 microm3/cell. Matrices were then either cultured statically or subjected to 20 per cent cyclic compressional strain in the 'ComCell' for 16 h prior to the assessment of cell viability and quantification of the pro-inflammatory cytokine tumour necrosis factor alpha (TNFalpha). The MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazdium bromide) assay was shown to be too insensitive to detect changes in cell viability. However, when quantified by the adenosine triphosphate (ATP) assay, cell viability was demonstrated to be reduced following exposure to cyclic strain. Macrophages cultured in the static three-dimensional tissue equivalent model produced very high levels of TNFalpha in response to submicrometre PE particles at a ratio of 100 microm3/cell. Cyclic strain in the absence of particles gave only a small increase in TNFa production. However, the combined effects of strain and particle stimulation at a ratio of 30 microm3/cell resulted in the secretion of significantly more TNFalpha than was produced by macrophages subjected to strain alone, or the cells-only control. This synergy between cyclic strain and PE particle stimulation was only evident when the volume of particles was reduced below the volume that maximally stimulated cells. These results suggest that while cyclic strain may not be the primary factor responsible for macrophage activation and periprosthetic osteolysis, at low particle load, it may contribute significantly to the osteolytic potential of macrophages in vitro or in vivo.     

求解循环对称结构特征值问题的新方法

利用结构循环对称的特点 ,提出一种求解循环对称结构特征值问题的新方法。该方法通过构造伪单元 ,可以方便地引入结构的循环对称条件和复约束条件 ,实现循环对称扇区复约束刚度阵和复约束质量阵的变换 ,避免复数运算和扇区级满阵存储 ,使计算以实数形式在单元级进行。该方法能通过任意一个循环对称扇区的有限元模型求解完整循环对称结构的特征值问题 ,可以大量减少计算工作量 ,极大地提高计算机的解题能力和计算效率。     

复杂循环载荷条件下金属的应力、应变规律

在各向同性循环强化模型基础上 ,通过屈服面及极限面形状、方向及面积的变化 ,分析了拉 -扭非比例循环载荷下金属的双表面各向异性强化模型 [1 ] ,并用BT9钛合金 [3 ] 及 30 4不锈钢 [3～ 5] 的试验结果检验了该模型的可行性。采用了塑性应变历程非比例参数来描述非比例载荷下材料的循环强化程度。研究了材料的横向强化及附加强化效应。结果表明 :本模型能很好地描述非比例载荷下金属的一系列主要应力、应变规律     

Experimental study on the cyclic deformation and plastic flow of U71Mn rail steel

The strain cyclic characteristics and ratcheting behaviour of U71Mn rail steel were experimentally investigated under uniaxial cyclic loading at room temperature. The effects of cyclic strain amplitude, mean strain, strain rate and their histories on strain cyclic characteristics were studied. The effects of stress amplitude, mean stress and their histories on the ratcheting under asymmetrical stress cycling were also analysed. Then, the interaction between strain cycling and stress cycling was discussed, too. Based on the experimental stress–strain data, the plastic flow properties of U71Mn rail steel under cyclic loading were analysed. Plastic modulus and its evolution rule were calculated from experimental data and were discussed under strain and stress cycling, respectively. It is shown that both the strain cyclic characteristics and ratcheting depend not only on current loading state, but also greatly on previous loading history. Under asymmetrical stress cycling, the evolution rule of plastic modulus is different from that under strain cycling. The strain cyclic characteristics and ratcheting behaviour of the material can be described essentially by the evolution of plastic flow.