408 research outputs found

    Identification of carbon dioxide in an exoplanet atmosphere

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    Carbon dioxide (CO2) is a key chemical species that is found in a wide range of planetary atmospheres. In the context of exoplanets, CO2 is an indicator of the metal enrichment (that is, elements heavier than helium, also called ‘metallicity’), and thus the formation processes of the primary atmospheres of hot gas giants. It is also one of the most promising species to detect in the secondary atmospheres of terrestrial exoplanets. Previous photometric measurements of transiting planets with the Spitzer Space Telescope have given hints of the presence of CO2, but have not yielded definitive detections owing to the lack of unambiguous spectroscopic identification. Here we present the detection of CO2 in the atmosphere of the gas giant exoplanet WASP-39b from transmission spectroscopy observations obtained with JWST as part of the Early Release Science programme. The data used in this study span 3.0–5.5 micrometres in wavelength and show a prominent CO2 absorption feature at 4.3 micrometres (26-sigma significance). The overall spectrum is well matched by one-dimensional, ten-times solar metallicity models that assume radiative–convective–thermochemical equilibrium and have moderate cloud opacity. These models predict that the atmosphere should have water, carbon monoxide and hydrogen sulfide in addition to CO2, but little methane. Furthermore, we also tentatively detect a small absorption feature near 4.0 micrometres that is not reproduced by these models

    Semiconductor Quantum Dots Water Solubilization, Functionalization, and Ratiometric Sensing of O2

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    Research on fluorescent semiconductor quantum dots (QDs, or nanocrystals) has been focused towards developing analytical applications for which their robust optical properties add value. To this end, the materials must be efficiently water solubilized and functionalized. This thesis details my research in this regard, starting with the development of a one-step method to produce ~10 nm hydrodynamic diameter water-soluble CdSe/ZnS quantum dots through ligand exchange with a near-monolayer of organosilane caps. The samples are stable for months under benchtop conditions and have high quantum yields (~60%), which is unprecedented for cap-exchanged QDs. Furthermore, the procedure can be applied to CdS/ZnS, ZnSe/ZnMnS/ZnS, and CuInS2/ZnS QDs. While water-solubilization is necessary for the development of analytical applications, the materials must be functionalized with chemical and biological vectors for sensing applications. In this regard, small molecular reagents that can efficiently functionalize water soluble CdSe/ZnS nanocrystals have been developed. These reagents do not cause quenching or precipitation of QDs as observed with commercially available activators. Last, a ratiometric fluorescent QD reporter for O2 levels in water created by attaching multiple pyrene-functional chromophores to the surface of bright, water-soluble semiconductor nanocrystals. These ligands have been used with both CdSe/CdZnS and AgInS2/ZnS nanocrystals, the latter of which represents a fluorescent QD sensor with significantly reduced toxicity

    Prognostic Significance of Neutrophil Lymphocyte Ratio in Patients with Gastric Cancer: A Meta-Analysis

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    <div><p>Background</p><p>Several studies have shown that neutrophil lymphocyte ratio (NLR) may be associated with the prognosis of gastric cancer (GC), but the results are controversial.</p><p>Methods</p><p>This study was performed to evaluate the prognostic implications of neutrophil lymphocyte ratio of GC in all available studies. We surveyed 2 medical databases, PubMed and EMBASE, to identifyall relevant studies. Data were collected from studies comparing overall survival (OS), disease-free survival (DFS) and progression-free survival (PFS) in patients with GC.</p><p>Results</p><p>Ten studies (n = 2,952) evaluated the role of NLR as a predictor of outcome were involved for this meta-analysis (10 for OS, 3 for DFS, and 2 for PFS). Overall and disease-free survival were significantly better in patients with low NLR value and the pooled HRs was significant at 1.83 ([95% CI], 1.62–2.07) and 1.58 ([95% CI], 1.12–2.21), respectively. For progression-free survival, the pooled hazard ratio of NLR was significant at 1.54 ([95% CI], 1.22–1.95). No evidence of significant heterogeneity or publication bias for OS and DFS was seen in any of the included studies.</p><p>Conclusion</p><p>This meta-analysis indicated that elevated NLR may be associated with a worse prognosis for patients with GC.</p></div

    Recycling of palaeo-Pacific subducted oceanic crust related to a Fe–Cu–Au mineralization in the Xu-Huai region of North Anhui-Jiangsu, East China: Geochronological and geochemical constraints

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    <p>In this study, Early Cretaceous skarn deposits and genesis of their host diorite/monzodiorite porphyry in the Xuzhou-Huaibei (Xu-Huai) region, northern Anhui-Jiangsu have been discussed by detailed geochemical work. In-situ zircon U–Pb dating of the diorites related to Fe–Cu–Au deposits shows that they were formed between 131.4 ± 1.5 Ma and 130.8 ± 1.8 Ma. Geochemical data indicate a depletion of high field strength elements (HFSE) in the diorite porphyry with similarity to that of arc-related igneous rocks. The diorite porphyry was probably derived from typical arc magmas related to continental margin subduction characterized by light rare earth elements (LREEs) enrichment and HFSE depletion. REEs compositions of apatite in the diorite porphyry indicate that the dioritic magma was produced from the metasomatized subcontinental mantle by slab-derived fluids. The magma was proven to be a high oxygen fugacity; thus, it was particularly conducive to the precipitation of Fe, Cu, Au and other ore-forming elements. The δ<sup>34</sup>S values of pyrite and chalcopyrite of Fe–Cu–Au ores range from −0.2‰ to 2.8‰, indicating that the sulphur in the ore was probably derived from deep-seated magmas. Integrated with geochronological and geochemical analyses, we suggest that the Early Cretaceous igneous suites associated with Fe–Cu–Au deposits in the Xu-Huai region are related to recycling subduction of Pacific oceanic crust.</p

    Funnel plots of studies included in the meta-analyses: A) overall survival, B) disease-free survival.

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    <p>Funnel plots of studies included in the meta-analyses: A) overall survival, B) disease-free survival.</p

    Relationship between H<sup>(1)</sup> and R for different routing strategy on networks with 500 nodes (left figure) and 1000 nodes (right figure).

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    <p>Relationship between H<sup>(1)</sup> and R for different routing strategy on networks with 500 nodes (left figure) and 1000 nodes (right figure).</p

    Summary of the subgroup meta analysis results for OS.

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    <p>HR: hazard ratio; CI: confidence interval; All: all patients.</p><p>Summary of the subgroup meta analysis results for OS.</p

    Quality Assessment of included studies based on the Newcastle-Ottawa Scales.

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    <p>Quality Assessment of included studies based on the Newcastle-Ottawa Scales.</p

    Main characteristics of all the studies included in the meta-analysis.

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    <p>OS: overall survival; DFS: disease-free survival; PFS: progression-free survival; NR: not reported; R: reported; E: estimated; HR: hazard ratio; CV; cutoff value; Assessment Scale; All: all patients.</p><p>Main characteristics of all the studies included in the meta-analysis.</p

    Relationship between H<sup>(2)</sup> and R for different routing strategy on networks with 500 nodes (left figure) and 1000 nodes (right figure).

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    <p>Relationship between H<sup>(2)</sup> and R for different routing strategy on networks with 500 nodes (left figure) and 1000 nodes (right figure).</p
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