黄绿色葡萄石的矿物学特征及谱学研究

葡萄石可以以板状、片状、葡萄状、肾状、放射状或块状集合体的形式产出,因其美丽的外观和特殊的晶体结构,近年来受到了学者的广泛关注。本文通过电子探针、粉晶X射线衍射仪、傅里叶变换红外光谱仪、显微拉曼光谱仪、紫外可见分光光度计等仪器对黄绿色葡萄石的成分、结构及谱学特征进行了分析与探讨。葡萄石的主要致色元素为Fe,且Fe³⁺经常取代Al³⁺占据八面体配位,Fe²⁺经常取代Ca²⁺存在于空隙中。电子探针数据表明:Fe与Al的含量变化整体呈现负相关关系,Fe与Ca的含量变化也整体呈现负相关关系,Fe含量相对较高的样品其黄绿色调加深。XRD图谱和拉曼光谱的结果表明:在葡萄石中绿帘石以包裹体的形式存在。红外光谱和拉曼光谱表明葡萄石中存在硅氧四面体和铝氧八面体两种架构,紫外可见吸收光谱揭示了葡萄石的致色机理。本文对葡萄石的矿物学特征及谱学特征进行系统分析,为后续葡萄石的进一步研究提供思路与实验数据。     

Probing molecular environments with a fictitious isotopic dipole

A HD-like (HD: mono-deuterated hydrogen molecule) isotopic dipole moment is proposed as a sensible probe for molecular environments, in particular for electrostatic fields and polarizable (reactive) sites of molecules. Fictitious nuclear masses are chosen in order to yield a rigid dipole with a small appropriate magnitude. Upon subtracting the Born-Oppenheimer energy, the interaction is reduced to field-dipole-like and dipole-polarizability-like terms, the last one being particularly informative since connected to potentially reactive sites. Possible asymmetries of this term appear as signatures of charged sites in the molecule. The field strength and orientation are easily obtained by identifying the minimum field-dipole energy configuration and flipping the dipole from it. Tests with hydrogen, water, benzene, and chlorobenzene molecules confirm the good performance of the method. In an application to test the present models for hydrogen activation by a frustrated Lewis pair, the full potential of the method is assessed.     

Operando Isotopic Exchange in Solid Oxide Fuel Cells: Oxygen-Transport Dependency on Applied Potential

The oxygen isotopic exchange technique is a powerful tool to investigate the oxygen transport kinetics in an oxide solid. In a solid oxide fuel cell, isotopic surface exchange and diffusion coefficients are classically determined by using the Isotopic Exchange Depth Profiling method followed by ex situ SIMS characterizations. Despite its relevance, the utilization of in situ or operando techniques to measure the isotopic exchange under an electrical bias remains marginal. We developed here a set-up which enables operando monitoring of oxygen exchange in SOFC type cells under polarization. The system has been used for studying the oxygen mobility dependency upon polarization on a symmetrical Pt/YSZ/Pt cell (YSZ: yttria-stabilized zirconia). Homomolecular and heterolytic exchange reactions were undertaken to investigate the oxygen activation step and discriminate the limiting step among the sequence of elementary steps which constitute the oxygen transport process in the SOFC system. Oxygen ions incorporation into the dense ionic conductor was identified to be the rate determining step, and its first order rate constant dependency on applied potential was established.     

LC-MS-based multi-omics analysis of brain tissue for the evaluation of the anti-ischemic stroke potential of Tribulus terrestris L. fruit extract in MCAO rats

This study aimed to investigate the chemical composition of Tribulus terrestris L. fruit (TT) extract named TT15 and its protective effect against ischemic stroke (IS) as well as corresponding mechanisms. The chemical composition of TT15 was analyzed by liquid chromatography-mass spectrometry (LC-MS), and the compound identification was conducted via searching the in-house database. The LC-MS-based multi-omics approach was applied to search the differential metabolites and differential proteins in rat brain tissue and to explore the biomarker and molecular mechanism of TT15 against middle cerebral artery occlusion (MCAO). A total of 20 compounds were identified from TT15, mainly including alkaloids, flavonoids, phenols, quinones, and esters. These 20 compounds significantly affected the metabolism of 44 metabolites and the expression of 51 proteins. Joint pathway analysis showed that these metabolites and proteins were mainly involved in the response to elevated platelet cytosolic Ca²⁺ and platelet activation, which inferred that TT15 may exert a protective effect against cerebral ischemic injury via regulating platelet function. This study provides useful information for further exploration of the mechanisms of TT extract against IS.     

Enhanced Sensitivity to Local Dynamics in Peptides by Use of Temperature-Jump IR Spectroscopy and Isotope Labeling

Site-specific isotopic labeling of molecules is a widely used approach in IR spectroscopy to resolve local contributions to vibrational modes. The induced frequency shift of the corresponding IR band depends on the substituted masses, as well as on hydrogen bonding and vibrational coupling. The impact of these different factors was analyzed with a designed three-stranded β-sheet peptide and by use of selected ¹³C isotope substitutions at multiple positions in the peptide backbone. Single-strand labels give rise to isotopically shifted bands at different frequencies, depending on the specific sites; this demonstrates sensitivity to the local environment. Cross-strand double- and triple-labeled peptides exhibited two resolved bands that could be uniquely assigned to specific residues, the equilibrium IR spectra of which indicated only weak local-mode coupling. Temperature-jump IR laser spectroscopy was applied to monitor structural dynamics and revealed an impressive enhancement of the isotope sensitivity to both local positions and coupling between them, relative to that of equilibrium FTIR spectroscopy. Site-specific relaxation rates were altered upon the introduction of additional cross-strand isotopes. Likewise, the rates for the global β-sheet dynamics were affected in a manner dependent on the distinct relaxation behavior of the labeled oscillator. This study reveals that isotope labels provide not only local structural probes, but rather sense the dynamic complexity of the molecular environment.     

Spatio-Temporal Variation of the Bacterial Communities along a Salinity Gradient within a Thalassohaline Environment (Saline di Tarquinia Salterns,Italy)

The “Saline di Tarquinia” salterns have been scarcely investigated regarding their microbiological aspects. This work studied the structure and composition of their bacterial communities along the salinity gradient (from the nearby sea through different ponds). The communities showed increasing simplification of pond bacterial diversity along the gradient (particularly if compared to those of the sea). Among the 38 assigned phyla, the most represented were Proteobacteria, Actinobacteria and Bacteroidetes. Differently to other marine salterns, where at the highest salinities Bacteroidetes dominated, preponderance of Proteobacteria was observed. At the genus level the most abundant taxa were Pontimonas, Marivita, Spiribacter, Bordetella, GpVII and Lentibacter. The α-diversity analysis showed that the communities were highly uneven, and the Canonical Correspondence Analysis indicated that they were structured by various factors (sampling site, sampling year, salinity, and sampling month). Moreover, the taxa abundance variation in relation to these significant parameters were investigated by Generalized Linear Models. This work represents the first investigation of a marine saltern, carried out by a metabarcoding approach, which permitted a broad vision of the bacterial diversity, covering both a wide temporal span (two years with monthly sampling) and the entire salinity gradient (from the nearby sea up to the crystallisation ponds).     

Elucidating structure and dynamics of crystalline α-zirconium phosphates intercalated with water and methanol by multinuclear solid-state MAS NMR: A comprehensive NMR approach

Solid-state NMR experiments on ²H, ³¹P, ¹³C, and ¹H nuclei, including ³¹P T₁, ¹H T₁, and ¹H T_1ρ measurements, as well as on the kinetics of proton-phosphorus cross-polarization have been performed to characterize the crystalline and amorphous α-zirconium phosphates, which were intercalated with D₂O and/or CD₃OD. The ¹³C{¹H} CP MAS NMR experiment performed for compound 1-CD ₃ OD (Zr (HPO₄)₂ ^. 0.2CD₃OD) with carbon cross-polarization via protons of phosphate groups has provided a prove that the methanol was intercalated into the interlayer spaces of this compound. The variable-temperature ²H solid-echo MAS NMR spectra of intercalated compounds demonstrated that the methanol molecules, in contrast to the mobile water, were immobile, keeping, however, free CD₃ rotations around the C₃-axis. It has been demonstrated that the intercalated species, D₂O and CD₃OD, do not affect the high-frequency motions of the phosphate groups. By utilizing local structural models that satisfy the constraints of the experimental data, it has been suggested that the immobile methanol molecules are located in the cavity between two neighboring layers of the zirconium phosphates. Thus, the present work illustrates the reliable criteria in a comprehensive NMR approach to structural and dynamic studies of such systems.     

河南麦区收割对大气颗粒物及其组分特征排放的影响

农业收割期间排放的颗粒物是农忙期影响大气气溶胶组成的主要来源,因此明确农业收割期间排放的大气颗粒物排放特征具有重要意义。本实验立足河南省新乡市集约化农田实验基地,开展冬小麦区农业收割期间的大气颗粒物及其组分排放特征实验。结果表明收割期间的PMcoarse比其它时期高8.20%,农业站点收割时期的PMcoarse比其它时期高了72.22%,明确了其颗粒物污染特征为仅PM₁₀升高,而非PM₁₀和PM_2.5同时升高,同时PM₁₀的升高非PM_2.5升高引起的;含量最高的前5种元素是Al、Ca、Fe、K、Mg;收割期间,Fe的特征比值最高为0.79;Ca₂₊^和K₊^{离子百分含量在}PMcoarse中占比最高;特征值为0.81和0.78。综合水溶性离子和元素结果,Ca₂₊^、K₊^、Fe浓度协同变化可作为小麦收割过程颗粒物对大气污染影响的指纹识别,以区别于其他污染类型;便于大气污染防治行政主管部门有针对性的查污、防污、治污,提高人民群众生活环境的空气质量。