3,196 research outputs found

    Evaluation of synthesis time in the growth of vertical-aligned MWCNTs by spray pyrolysis

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    Multi-Wall Carbon Nanotubes (MWCNTs) were analyzed on crystalline silicon substrates (type P) under optimal temperature conditions, using different synthesis times (2, 3, 4, 5, 10, 20, 30, 60, 120, and 180 min) in order to examine the effect on the structural quality and length of the CNTs produced by ultrasonic spray pyrolysis, using pure toluene and ferrocene as precursor solutions under argon flow. Structural, optical, and morphological differences of the MWCNTs grown were analyzed. Raman spectroscopy evidenced the MWCNTs' high quality, noted by the ID/IG (from 0.41 to 0.68) and I2D/IG intensity ratios around 0.75. Morphological differences of the MWCNTs grow evaluated by Field Emission Scanning Electron Microscopy (FE-SEM); the micrographs examined the thickness of CNTs' layers. High-Resolution Transmission Electron Microscopy (HRTEM) technique was used to determine the diameters of CNTs, which were found from 15 to 140 nm. X-Ray Diffraction (XRD) showed two characteristic peaks around 26° and 44°, which corroborated that the MWCNTs were well-graphitized. The influence of the time in these CNTs demonstrated that the final length of these nanotubes could easily reach micrometers. The alienation was better as time increased, and the graphitization extent is good in most cases compared to other more expensive synthesis methods.We thank Technician Adrian Gómez Herrero, Technician Cristina Moral Gil and Hugo Solera for the TEM, SEM and Raman characterization, respectively. This work has been supported by the thematic network "Nanostructure advanced materials and applications in Mexico" between Spain and Mexico sponsoring this international collaboration. This work has been financially supported by Comunidad de Madrid, Spain (S2018/NMT-4411) and Ministry of Economia, Industría y Competividad (PID2019-106631GB-C43)

    Chemical abundances and ages of the bulge stars in APOGEE high-velocity peaks

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    A cold high-velocity (HV, \sim 200 km/s) peak was first reported in several Galactic bulge fields based on the APOGEE commissioning observations. Both the existence and the nature of the high-velocity peak are still under debate. Here we revisit this feature with the latest APOGEE DR13 data. We find that most of the low latitude bulge fields display a skewed Gaussian distribution with a HV shoulder. However, only 3 out of 53 fields show distinct high-velocity peaks around 200 km/s. The velocity distribution can be well described by Gauss-Hermite polynomials, except the three fields showing clear HV peaks. We find that the correlation between the skewness parameter (h3h_{3}) and the mean velocity (vˉ\bar{v}), instead of a distinctive HV peak, is a strong indicator of the bar. It was recently suggested that the HV peak is composed of preferentially young stars. We choose three fields showing clear HV peaks to test this hypothesis using the metallicity, [α\alpha/M] and [C/N] as age proxies. We find that both young and old stars show HV features. The similarity between the chemical abundances of stars in the HV peaks and the main component indicates that they are not systematically different in terms of chemical abundance or age. In contrast, there are clear differences in chemical space between stars in the Sagittarius dwarf and the bulge stars. The strong HV peaks off-plane are still to be explained properly, and could be different in nature.Comment: 13 pages, 10 figures, published in ApJ. Updated to match the final ApJ published version. Minor revisions to the text and Figure

    Combining GAL4 GFP enhancer trap with split luciferase to measure spatiotemporal promoter activity in Arabidopsis.

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    In multicellular organisms different types of tissues have distinct gene expression profiles associated with specific function or structure of the cell. Quantification of gene expression in whole organs or whole organisms can give misleading information about levels or dynamics of expression in specific cell types. Tissue- or cell-specific analysis of gene expression has potential to enhance our understanding of gene regulation and interactions of cell signalling networks. The Arabidopsis circadian oscillator is a gene network which orchestrates rhythmic expression across the day/night cycle. There is heterogeneity between cell and tissue types of the composition and behaviour of the oscillator. In order to better understand the spatial and temporal patterns of gene expression, flexible tools are required. By combining a Gateway®-compatible split luciferase construct with a GAL4 GFP enhancer trap system, we describe a tissue-specific split luciferase assay for non-invasive detection of spatiotemporal gene expression in Arabidopsis. We demonstrate the utility of this enhancer trap-compatible split luciferase assay (ETSLA) system to investigate tissue-specific dynamics of circadian gene expression. We confirm spatial heterogeneity of circadian gene expression in Arabidopsis leaves and describe the resources available to investigate any gene of interest

    Lung Cytokines and Systemic Inflammation in Patients with COPD

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    Rationale: Chronic obstructive pulmonary disease (COPD) is characterized by lung and systemic inflammation. The role of cytokines in local and systemic inflammation in COPD is not well understood. This study aimed to compare plasma and bronchoalveolar lavage (BAL) fluid cytokine levels in COPD and non-COPD subjects with the intent of better understand their potential roles in driving local and systemic inflammation. Methods: This cross-sectional study analyzed data from 65 subjects: 31 with COPD confirmed by spirometry and 34 non-COPD controls. All subjects underwent spirometry, plasma sample collection, and bronchoscopy/BAL. Levels of 21 inflammatory cytokines were measured in the plasma (systemic inflammation) and BAL (lung inflammation) using a multiplex assay. Results:COPD subjects were overall older (median age 59 vs 36; p = Conclusion: Elevated levels of cytokines were identified in the plasma of COPD subjects when compared to controls, supporting the role of these mediators as one of the mechanisms of systemic inflammation in COPD. In contrast, lung cytokines were not elevated suggesting that inflammation in the setting of COPD may not originate and/or perpetuate in the lungs, or that the BAL fluid is not an optimal source of information when evaluating inflammation in COPD. Although the role of these cytokines remains uncertain, anti-cytokine therapy might modulate inflammation in COPD and perhaps improve outcomes

    Occupation-Related Differences in the Prevalence of Metabolic Syndrome

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    OBJECTIVE—To investigate the prevalence of metabolic syndrome in the Spanish working population and determine how the prevalence varies according to occupation and sex

    Benchmarking the power of amateur observatories for TTV exoplanets detection

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    This document is the Accepted Manuscript version of the following article: Roman v. Baluev, et al, ‘Benchmarking the power of amateur observatories for TTV exoplanets detection’, Monthly Notices of the Royal Astronomical Society, Vol. 450(3): 3101-3113, first published online 9 May 2015. The version of record is available at doi: https://doi.org/10.1093/mnras/stv788 © 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society.We perform an analysis of ~80000 photometric measurements for the following 10 stars hosting transiting planets: WASP-2, -4, -5, -52, Kelt-1, CoRoT-2, XO-2, TrES-1, HD 189733, GJ 436. Our analysis includes mainly transit lightcurves from the Exoplanet Transit Database, public photometry from the literature, and some proprietary photometry privately supplied by other authors. Half of these lightcurves were obtained by amateurs. From this photometry we derive 306 transit timing measurements, as well as improved planetary transit parameters. Additionally, for 6 of these 10 stars we present a set of radial velocity measurements obtained from the spectra stored in the HARPS, HARPS-N, and SOPHIE archives using the HARPS-TERRA pipeline. Our analysis of these TTV and RV data did not reveal significant hints of additional orbiting bodies in almost all of the cases. In the WASP-4 case, we found hints of marginally significant TTV signals having amplitude 10-20 sec, although their parameters are model-dependent and uncertain, while radial velocities did not reveal statistically significant Doppler signals.Peer reviewe

    Present Status and Future Programs of the n_TOF Experiment

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    This is an Open Access article distributed under the terms of the Creative Commons Attribution-Noncommercial License 3.0, which permits unrestricted use, distribution, and reproduction in any noncommercial medium, provided the original work is properly citedThe neutron time-of-flight facility n_TOF at CERN, Switzerland, operational since 2001, delivers neutrons using the Proton Synchrotron (PS) 20 GeV/c proton beam impinging on a lead spallation target. The facility combines a very high instantaneous neutron flux, an excellent time of flight resolution due to the distance between the experimental area and the production target (185 meters), a low intrinsic background and a wide range of neutron energies, from thermal to GeV neutrons. These characteristics provide a unique possibility to perform neutron-induced capture and fission cross-section measurements for applications in nuclear astrophysics and in nuclear reactor technology.The most relevant measurements performed up to now and foreseen for the future will be presented in this contribution. The overall efficiency of the experimental program and the range of possible measurements achievable with the construction of a second experimental area (EAR-2), vertically located 20 m on top of the n_TOF spallation target, might offer a substantial improvement in measurement sensitivities. A feasibility study of the possible realisation of the installation extension will be also presented
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