Sensitive CE-MS method for monitoring of riociguat and desmethylriociguat levels in human serum

Riociguat is novel antihypertensive drug for treatment of pulmonary hypertension. As such, it is still being tested in many clinical and pharmacokinetic trials. Existing methods that determine serum riociguat and desmethylriociguat (DMR) are based solely on liquid chromatography with mass spectrometry. Therefore, we present a novel capillary electrophoresis with mass spectrometry method (CE-MS) for their determination in human serum as alternative method for ongoing trials. Complete resolution of both analytes was achieved by means of pH optimization of ammonium formate background electrolytes that are fully compatible with ESI/MS detection. Simple liquid-liquid extraction was used as sample pretreatment. The calibration dependence of the method was linear (in the range of 10–1000 ng/mL), with adequate accuracy (90.1–114.9%) and precision (13.4%). LOD and LOQ were arbitrarily set at 10 ng/mL for both analytes. Clinical applicability was validated using serum samples from patients treated with riociguat in pharmacokinetic study and the results corresponded with reference HPLC-MS/MS values. Capillary electrophoresis proved to be sensitive and selective tool for the analysis of riociguat and DMR.     

Metabolomics techniques applied in the investigation of phenolic acids from the agro-industrial by-product of Carapa guianensis Aubl

Processing of Carapa guianensis seeds to obtain oil on an industrial scale generates a significant amount of by-product, approximately 66% w/w, which is called cake and is a potential source of biomolecules, including simple phenolic structures. For this reason, studies were carried out on the chemical profiles of hydrolyzed extract from this agro-industrial by-product through High Performance Thin-Layer Chromatography (HPTLC) and Gas Chromatography coupled to Mass Spectrometry (GC–MS). These techniques were used to detect metabolic classes and/or groups, and to identify, for the first time, thirteen simple phenolic acids in this by-product. The sample antioxidant capacity was determined by methods of 2,2-diphenyl-1-picrylhydrazyl (DPPH)and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS⁺) radicals direct sequestration. The hydrolyzed fraction showed a total of 63.47% in the relative abundance of the total of compounds, standing out: p-hydroxybenzoic acid (39.19%) and protocatechuic acid (3,4-dihydroxybenzoic acid) (5.62%), both from hydroxybenzoic acids and 3-(3,4-dihydroxyphenyl)lactic acid, (7.76%) hydroxycinnamic acids derivatives. In these results, the fraction rich in simple phenolic acids was obtained, attributing the prominent behavior of this matrix antioxidant activity, expressed by (IC₅₀: of 16.42 µg/mL and 6.52 µg/mL for DPPH and ABTS⁺ radicals, respectively). The research demonstrated an alternative to applicability that involves sustainability from agro-industrial. These techniques were used to detect metabolic classes and/or groups, and to identify, for the first time, thirteen simple phenolic acids in this by-product, generating a process capable of converting biomass into a bioproduct, consisting of bioactive compounds, in addition to adding value to the industrial chain.     

焦炉上升管内壁结焦炭层的光谱学分析及结焦机理研究

以焦炉上升管内壁结焦炭层块为研究对象，采用X射线荧光光谱仪（XRF）、X射线衍射仪（XRD）、傅里叶红外光谱仪（FTIR）和激光共聚焦拉曼光谱仪（Raman）对结焦炭层的元素组成，以及各结焦炭层的矿物组成、组成结构和分子结构进行测试。分析从结焦炭层块外表面向内表面过渡的各结焦炭层的差异性，揭示焦炉上升管内壁结焦机理。结果表明焦炉上升管内粉尘中Fe，S和Cr极易催化荒煤气中蒽、萘等稠环芳烃化合物成炭，在焦炉上升管内壁形成炭颗粒沉积，为焦油凝结挂壁提供载体，在荒煤气温度降至结焦温度时易结焦积碳。结焦炭层均含有芳香层结构，随着结焦炭层从外表面向内表面过渡，各结焦炭层的面层间距(d₀₀₂)逐渐降低、层片直径(L_a)先降低后增加、层片堆砌高度(Lc)和芳香层数(N)先稳定后增加。结焦炭层石墨化过程是由结焦炭层内表面向外表面进行，主要包括其片层外缘的羧基和部分C-O结构的降解剥离，从而形成高度规整的共轭结构。结焦炭层块中C元素是以结晶碳与无定型碳的混合物形式存在。以上研究为解决焦炉上升管内壁结焦及腐蚀问题，提高换热器换热效率，有效回收焦炉荒煤气显热，降低焦化企业能耗提供实验基础和理论依据。     

Mass transport in metals under intensive impulse reactions

An unusually high mobility of atoms under intensive impulse reactions is explained by the behavior of point defects at the shock wave front. It is shown that either a shock wave front or moving dislocations can capture the interstitials, or they can be thermally activated in the direction of the shock wave propagation.     

利用场发射显微镜研究O2对单壁碳纳米管场发射的影响

利用场发射显微镜和四极质谱计研究了充入高纯O2的四极质谱和O2对单壁碳纳米管场发射的影响.单壁碳纳米管经过约1000℃的热处理得到清洁态场发射像后，充入O2，分别测量了O2吸附和脱附后场发射的I V特性.实验观测到在单壁碳纳米管上O2的吸附使场发射电流减小，说明逸出功增加.在10-4Pa的O2压强下对单壁碳纳米管进行约1000℃的热处理，可以产生氧化刻蚀作用，观测到场发射像的变化，并测量了氧化刻蚀产生的I V特性变化. 关键词： 单壁碳纳米管 场发射显微镜 场发射 四极质谱     

On-line cysteine modification for protein analysis: new probes for electrochemical tagging nanospray mass spectrometry

A series of electrogenerated selective electrophiles based on substituted benzoquinones has been characterized as tags for l-cysteine and cysteine residues in proteins. The electrophiles are generated electrochemically from the corresponding hydroquinones. It is shown from mass spectrometry analysis that the electrogenerated benzoquinone can tag the biomolecules. The rate constants pertaining to the addition of l-cysteine onto the electrogenerated benzoquinones have been determined using electrochemical techniques. The substitution patterns have been unraveled leading to the assessment of site-specific rate constants. It is shown that the rate constants are primarily dependent on the electronic nature of the substituents as expressed by the Hammett substitution constant. The apparent tagging yields observed for l-cysteine in nanospray mass spectrometry experiments do not correspond to the yields expected from the electrochemical study, as the ionisation efficiencies are highly dependent on the tag. Finally, the on-line tagging has been tested using β-lactoglobulin A and myoglobin. Based on these results, it is concluded that the tagging reaction is selective towards cysteine when it takes place in the nanospray interface. The results show that the methodology presented can be used for a rapid characterization and identification of reactive sites in biomolecules.     

A Penrose-like inequality for maximal asymptotically flat spin initial data sets

We prove a Penrose-like inequality for the mass of a large class of constant mean curvature (CMC) asymptotically flat n-dimensional spin manifolds which satisfy the dominant energy condition and have a future converging, or past converging compact and connected boundary of non-positive mean curvature and of positive Yamabe invariant. We prove that for every n ≥ 3 the mass is bounded from below by an expression involving the norm of the linear momentum, the volume of the boundary, dimensionless geometric constants and some normalized Sobolev ratio.     

Microwave Activation of Processes in Mesopores: The Thiourea Electrooxidation at Mesoporous Platinum

In situ microwave activation is applied to the electrochemical oxidation of thiourea at low surface area (polished polycrystalline) and at high surface area (electrodeposited mesoporous platinum coated) platinum microelectrodes. The one electron oxidation of thiourea to formamidine disulfide is monitored as a function of the different activation parameters. In the absence of microwaves (ambient temperature, low mass transport) increasing the surface area (roughness) increases the thiourea oxidation response predominantly due to adsorption effects. In the presence of high microwave intensities, high mass transport and thermal effects further increase the oxidation current at mesoporous platinum. The most effective thickness of the mesoporous platinum film for the thiourea oxidation process is estimated as 3 μm independent of electrode diameter, temperature, or mass transport effects.     

粒子鉴别中dE/dx和TOF的权重

在北京谱仪数据分析中,粒子鉴别使用了dE/dx和TOF的信息.在利用dE/dx和TOF联合鉴别粒子时,通常的做法是把两者的χ²值等权重相加(χ²方法).在不同的动量区间,dE/dx和TOF对粒子的鉴别能力不同.本文给出两者联合鉴别时不同动量区间的权重,并构造一个新的线性变量来进行粒子鉴别     

延长速调管使用寿命的方法

描述了一种延长EPR波谱仪中速调管使用寿命的方法.根据这种方法,只要正确地调谐微波桥的工作状态和适当地调整功率电平器的功率校正电平.即使对于已经严重老化的速调管仍然可以继续使用一段时间,维持仪器的正常运行.