Cassiterite oxygen isotopes in magmatic-hydrothermal systems: in situ microanalysis, fractionation factor, and applications

Tin and tungsten are important metals for the industrializing society. Deciphering the origin and evolution of hydrothermal fluids responsible for their formation is critical to underpin genetic models of ore formation. Traditional approaches obtain isotopic information mainly from bulk analysis of both ore and gangue minerals, or less frequently from in situ analysis of gangue minerals, which either bear inherited complexities and uncertainties or are indirect constraints. Hence, directly obtaining isotopic information from ore minerals such as cassiterite by in situ techniques is warranted. However, this has been hampered by challenges from both analytical and applicational aspects. In this study, we first demonstrate a lack of crystallographic orientation effects during cassiterite ion microprobe oxygen isotope analysis. Along with our newly developed matrix-matched reference material, the Yongde-Cst, which has a recommended δ18O value of 1.36 ± 0.16‰ (VSMOW) as defined by gas source isotope ratio mass spectrometry, in situ oxygen isotope analysis of cassiterite now is possible. We further refine the oxygen isotope fractionation (1000 ln α) for quartz-cassiterite by first-principles calculations, which is given by the equation of 1.259 × 106/T2 + 8.15 × 103/T − 4.72 (T is temperature in Kelvin). The 1000 ln α for quartz-cassiterite has a sensitive response to temperature, and makes cassiterite-quartz an excellent mineral pair in oxygen isotope thermometry, as described by the equation of T (℃) = 2427 × (δ18Oqtz − δ18Ocst)−0.4326 − 492.4. Using the well-established 1000 ln α of quartz-water, 1000 ln α of cassiterite-water is derived as 2.941 × 106/T2 − 11.45 × 103/T + 4.72 (T in Kelvin), which shows a weak response to temperature. This makes cassiterite an ideal mineral from which to derive δ18O of fluids as robust temperature estimates are no longer a prerequisite. We have applied oxygen isotope analysis to cassiterite samples from six Sn(-W) deposits in China. The results show considerable variability in δ18O values both within a single deposit and among studied deposits. Combining the δ18O of cassiterite samples and the equilibrium oxygen isotope fractionation, we find that the δ18O values of ore-forming fluids show a strong magmatic affinity with variable but mostly no to low degree involvements (~0-10%) of meteoric water, hence our results invite a reassessment on the extent and role of meteoric water in Sn-W mineralization. This study demonstrates that in situ oxygen isotope analysis of cassiterite is a promising tool to refine sources of ore-forming fluids, and to decode hydrothermal dynamics controlling tin and tungsten mineralization

Rectifying properties and colossal magnetoresistance in La0.9Hf0.1MnO3 /Nb-0.7 wt%-doped SrTiO3 heterojunction

SPIE Proceedings v. 9068 entitled: Technology of Thin Film & Application of Thin FilmA heterojunction with good rectifying properties in a wide temperature range from 20 K to 300 K was fabricated simply by depositing an as-grown La0.9Hf0.1MnO3 (LHMO) film on a commercial 0.7 wt% Nb-doped SrTiO3 single crystal substrate using pulsed laser deposition technique. The current-voltage behavior of the LHMO/STON is measured under applied magnetic fields varying between 0 and 5 T. The heterojunction shows a remarkable magnetoresistance which depends on both the temperature and bias voltages. The sign of the magnetoresistance as function of temperature at either forward or reverse bias voltage is extensively studied by the filling of electrons in the eg and t2g band. The good rectifying behaviors, the magnetic tunable properties and the maximum magnetoresistance obtained at room temperature make this simple heterojunction promising for practical applications. © (2013) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personalLink_to_subscribed_fulltex

Solvothermal Synthesis of Ternary Sulfides of Sb2 − xBixS3(x = 0.4, 1) with 3D Flower-Like Architectures

Flower-like nanostructures of Sb2 − xBixS3(x = 0.4, 1.0) were successfully prepared using both antimony diethyldithiocarbamate [Sb(DDTC)3] and bismuth diethyldithiocarbamate [Bi(DDTC)3] as precursors under solvothermal conditions at 180 °C. The prepared Sb2 − xBixS3 with flower-like 3D architectures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDS), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED). The flower-like architectures, with an average diameter of ~4 μm, were composed of single-crystalline nanorods with orthorhombic structures. The optical absorption properties of the Sb2 − xBixS3 nanostructures were investigated by UV–Visible spectroscopy, and the results indicate that the Sb2 − xBixS3 compounds are semiconducting with direct band gaps of 1.32 and 1.30 eV for x = 0.4 and 1.0, respectively. On the basis of the experimental results, a possible growth mechanism for the flower-like Sb2 − xBixS3 nanostructures is suggested

High Methanol Oxidation Activity of Well-Dispersed Pt Nanoparticles on Carbon Nanotubes Using Nitrogen Doping

Pt nanoparticles (NPs) with the average size of 3.14 nm well dispersed on N-doped carbon nanotubes (CNTs) without any pretreatment have been demonstrated. Structural properties show the characteristic N bonding within CNTs, which provide the good support for uniform distribution of Pt NPs. In electrochemical characteristics, N-doped CNTs covered with Pt NPs show superior current density due to the fact that the so-called N incorporation could give rise to the formation of preferential sites within CNTs accompanied by the low interfacial energy for immobilizing Pt NPs. Therefore, the substantially enhanced methanol oxidation activity performed by N-incorporation technique is highly promising in energy-generation applications

The gut microbiome in dogs with congestive heart failure: a pilot study

Compromised gut health and dysbiosis in people with heart failure has received a great deal of attention over the last decade. Whether dogs with heart failure have a similar dysbiosis pattern to what is described in people is currently unknown. We hypothesised that dogs with congestive heart failure have quantifiable dysbiosis compared to healthy dogs that are similar in sex and age. A total of 50 dogs (15 healthy dogs and 35 dogs with congestive heart failure) were prospectively recruited, and their faecal gut microbiome was assessed using 16S rRNA sequencing (Illumina MiSeq platform). There was no significant change in the microbial diversity and richness in dogs with congestive heart failure. However, there was an increase in abundance of Proteobacteria in the congestive heart failure group (p = 0.014), particularly due to an increase in the family Enterobacteriaceae (p = 0.002) and Escherichia coli (p = 0.033). We conclude that dogs with congestive heart failure have dysbiosis, and we show additional trends in our data suggesting that dogs may have a similar pattern to that described in people. The results of this study provide useful preliminary information and raise the possibility that dogs represent a clinically relevant animal model of dysbiosis in people with heart failure

Factors affecting the yield of microRNAs from laser microdissectates of formalin-fixed tissue sections

<p>Abstract</p> <p>Background</p> <p>Quantification of microRNAs in specific cell populations microdissected from tissues can be used to define their biological roles, and to develop and deploy biomarker assays. In this study, a number of variables were examined for their effect on the yield of microRNAs in samples obtained from formalin-fixed paraffin-embedded tissues by laser microdissection.</p> <p>Results</p> <p>MicroRNA yield was improved by using cresyl violet instead of hematoxylin-eosin to stain tissue sections in preparation for microdissection, silicon carbide instead of glass fiber as matrix in RNA-binding columns, and overnight digestion of dissected samples with proteinase K. Storage of slides carrying stained tissue sections at room temperature for up to a week before microdissection, and storage of the microdissectates at room temperature for up to a day before RNA extraction did not adversely affect microRNA yield.</p> <p>Conclusions</p> <p>These observations should be of value for the efficient isolation of microRNAs from microdissected formalin-fixed tissues with a flexible workflow.</p

CNx-modified Fe3O4 as Pt nanoparticle support for the oxygen reduction reaction

A novel electrocatalyst support material, nitrogendoped carbon (CNx)-modified Fe3O4 (Fe3O4-CNx), was synthesized through carbonizing a polypyrrole-Fe3O4 hybridized precursor. Subsequently, Fe3O4-CNx-supported Pt (Pt/Fe3O4-CNx) nanocomposites were prepared by reducing Pt precursor in ethylene glycol solution and evaluated for the oxygen reduction reaction (ORR). The Pt/Fe3O4-CNx catalysts were characterized by X-ray diffraction, Raman spectra, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The electrocatalytic activity and stability of the as-prepared electrocatalysts toward ORR were studied by cyclic voltammetry and steady-state polarization measurements. The results showed that Pt/ Fe3O4-CNx catalysts exhibited superior catalytic performance for ORR to the conventional Pt/C and Pt/C-CNx catalysts.Web of Scienc