Abstract
Magnetic fields likely play an important role in star formation, but the number of directly measured magnetic field strengths remains scarce. We observed the 38.3 and 38.5 GHz Class II ...methanol (CH
3
OH) maser lines toward the high-mass star-forming region NGC 6334 F for the Zeeman effect. The observed spectral profiles have two prominent velocity features that can be further decomposed through Gaussian component fitting. In several of these fitted Gaussian components we find significant Zeeman detections, with
zB
los
in the range from 8 to 46 Hz. If the Zeeman splitting factor
z
for the 38 GHz transitions is of the order of ∼1 Hz mG
−1
, similar to that for several other CH
3
OH maser lines, then magnetic fields in the regions traced by these masers would be in the range of 8–46 mG. Such magnetic field values in high-mass star-forming regions agree with those detected in the better-known 6.7 GHz Class II CH
3
OH maser line. Since Class II CH
3
OH masers are radiatively pumped close to the protostar and likely occur in the accretion disk or the interface between the disk and outflow regions, such fields likely have significant impact on the dynamics of these disks.
Majorana zero-modes-a type of localized quasiparticle-hold great promise for topological quantum computing. Tunnelling spectroscopy in electrical transport is the primary tool for identifying the ...presence of Majorana zero-modes, for instance as a zero-bias peak in differential conductance. The height of the Majorana zero-bias peak is predicted to be quantized at the universal conductance value of 2e
/h at zero temperature (where e is the charge of an electron and h is the Planck constant), as a direct consequence of the famous Majorana symmetry in which a particle is its own antiparticle. The Majorana symmetry protects the quantization against disorder, interactions and variations in the tunnel coupling. Previous experiments, however, have mostly shown zero-bias peaks much smaller than 2e
/h, with a recent observation of a peak height close to 2e
/h. Here we report a quantized conductance plateau at 2e
/h in the zero-bias conductance measured in indium antimonide semiconductor nanowires covered with an aluminium superconducting shell. The height of our zero-bias peak remains constant despite changing parameters such as the magnetic field and tunnel coupling, indicating that it is a quantized conductance plateau. We distinguish this quantized Majorana peak from possible non-Majorana origins by investigating its robustness to electric and magnetic fields as well as its temperature dependence. The observation of a quantized conductance plateau strongly supports the existence of Majorana zero-modes in the system, consequently paving the way for future braiding experiments that could lead to topological quantum computing.
The carbon budget of South Asia Patra, P. K; Canadell, J. G; Houghton, R. A ...
Biogeosciences,
01/2013, Letnik:
10, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The source and sinks of carbon dioxide (CO2) and methane (CH4) due to anthropogenic and natural biospheric activities were estimated for the South Asian region (Bangladesh, Bhutan, India, Nepal, ...Pakistan and Sri Lanka). Flux estimates were based on top-down methods that use inversions of atmospheric data, and bottom-up methods that use field observations, satellite data, and terrestrial ecosystem models. Based on atmospheric CO2 inversions, the net biospheric CO2 flux in South Asia (equivalent to the Net Biome Productivity, NBP) was a sink, estimated at −104 ± 150 Tg C yr−1 during 2007–2008. Based on the bottom-up approach, the net biospheric CO2 flux is estimated to be −191 ± 193 Tg C yr−1 during the period of 2000–2009. This last net flux results from the following flux components: (1) the Net Ecosystem Productivity, NEP (net primary production minus heterotrophic respiration) of −220 ± 186 Tg C yr−1 (2) the annual net carbon flux from land-use change of −14 ± 50 Tg C yr−1, which resulted from a sink of −16 Tg C yr−1 due to the establishment of tree plantations and wood harvest, and a source of 2 Tg C yr−1 due to the expansion of croplands; (3) the riverine export flux from terrestrial ecosystems to the coastal oceans of +42.9 Tg C yr−1; and (4) the net CO2 emission due to biomass burning of +44.1 ± 13.7 Tg C yr−1. Including the emissions from the combustion of fossil fuels of 444 Tg C yr−1 for the 2000s, we estimate a net CO2 land–atmosphere flux of 297 Tg C yr−1. In addition to CO2, a fraction of the sequestered carbon in terrestrial ecosystems is released to the atmosphere as CH4. Based on bottom-up and top-down estimates, and chemistry-transport modeling, we estimate that 37 ± 3.7 Tg C yr−1 were released to atmosphere from South Asia during the 2000s. Taking all CO2 and CH4 fluxes together, our best estimate of the net land–atmosphere CO2-equivalent flux is a net source of 334 Tg C yr−1 for the South Asian region during the 2000s. If CH4 emissions are weighted by radiative forcing of molecular CH4, the total CO2-equivalent flux increases to 1148 Tg C yr−1 suggesting there is great potential of reducing CH4 emissions for stabilizing greenhouse gases concentrations.
Steep hikes of petroleum prices and rising demand of petroleum products compels the scientific society to think for the renewable alternative fuels like biodiesel. Biodiesel production is generally ...carried out through the process of transesterification reaction. The reaction is facilitated with a suitable catalyst either homogeneous or heterogeneous. The selection of appropriate catalyst depends on the amount of free fatty acids in the oil. Heterogeneous catalyst provides high activity, high selectivity, high water tolerance properties and these properties depend on the amount and strengths of active acid or basic sites. Basic catalyst can be subdivided based on the type of metal oxides and their derivatives. Similarly, acidic catalyst can be subdivided depending upon their active acidic sites. New varieties of mixed catalyst are also available in literatures. Catalyst generated from bio-waste and other biocatalysts which are heterogeneous in nature and extensively reported in literature are also reviewed. This review focused about the recent invention and use of the heterogeneous acid, base and biocatalysts for biodiesel production and their suitability for industrial application.
ABSTRACT We report detection of the Zeeman effect in the 44 GHz Class I methanol maser line, toward the star-forming region DR21(OH). In a 219 Jy beam−1 maser centered at an LSR velocity of 0.83 km ...s−1, we find a 20- detection of zBlos = 53.5 2.7 Hz. If 44 GHz methanol masers are excited at n ∼ 107-8 cm−3, then the B versus n1/2 relation would imply, from comparison with Zeeman effect detections in the CN(1 − 0) line toward DR21(OH), that magnetic fields traced by 44 GHz methanol masers in DR21(OH) should be ∼10 mG. Combined with our detected zBlos = 53.5 Hz, this would imply that the value of the 44 GHz methanol Zeeman splitting factor z is ∼5 Hz mG−1. Such small values of z would not be a surprise, as the methanol molecule is non-paramagnetic, like H2O. Empirical attempts to determine z, as demonstrated, are important because there currently are no laboratory measurements or theoretically calculated values of z for the 44 GHz CH3OH transition. Data from observations of a larger number of sources are needed to make such empirical determinations robust.
The Soft X-ray focusing Telescope (SXT), India’s first X-ray telescope based on the principle of grazing incidence, was launched aboard the AstroSat and made operational on October 26, 2015. X-rays ...in the energy band of 0.3–8.0 keV are focussed on to a cooled charge coupled device thus providing medium resolution X-ray spectroscopy of cosmic X-ray sources of various types. It is the most sensitive X-ray instrument aboard the AstroSat. In its first year of operation, SXT has been used to observe objects ranging from active stars, compact binaries, supernova remnants, active galactic nuclei and clusters of galaxies in order to study its performance and quantify its characteriztics. Here, we present an overview of its design, mechanical hardware, electronics, data modes, observational constraints, pipeline processing and its in-orbit performance based on preliminary results from its characterization during the performance verification phase.
Exploring the chemical and biological space covered by patent applications is crucial in early-stage medicinal chemistry activities. Patent analysis can provide understanding of compound prior art, ...novelty checking, validation of biological assays, and identification of new starting points for chemical exploration. Extracting chemical and biological entities from patents through manual extraction by expert curators can take substantial amount of time and resources. Text mining methods can help to ease this process. To validate the performance of such methods, a manually annotated patent corpus is essential. In this study we have produced a large gold standard chemical patent corpus. We developed annotation guidelines and selected 200 full patents from the World Intellectual Property Organization, United States Patent and Trademark Office, and European Patent Office. The patents were pre-annotated automatically and made available to four independent annotator groups each consisting of two to ten annotators. The annotators marked chemicals in different subclasses, diseases, targets, and modes of action. Spelling mistakes and spurious line break due to optical character recognition errors were also annotated. A subset of 47 patents was annotated by at least three annotator groups, from which harmonized annotations and inter-annotator agreement scores were derived. One group annotated the full set. The patent corpus includes 400,125 annotations for the full set and 36,537 annotations for the harmonized set. All patents and annotated entities are publicly available at www.biosemantics.org.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We report the detection of the Zeeman effect in the 44 GHz Class I methanol maser line toward the high-mass star-forming region DR21W. There are two prominent maser spots in DR21W at the ends of a ...northwest-southeast linear arrangement. For the maser at the northwestern end (maser A), we fit three Gaussian components. In the strongest component, we obtain a significant Zeeman detection, with zBlos = −23.4 3.2 Hz. If we use z = −0.920 Hz mG−1 for the F = 5 → 4 hyperfine transition, this corresponds to a magnetic field, ; Blos would be higher if a different hyperfine were responsible for the 44 GHz maser, but our results also rule out some hyperfines, as fields in these regions cannot be hundreds of mG. Class I methanol masers form in outflows where shocks compress magnetic fields in proportion to gas density. Designating our detected Blos = 25 mG as the magnetic field in the postshock gas, we find that Blos in the preshock gas should be 0.1-0.8 mG. Although there are no thermal line Zeeman detections toward DR21W, such values are in good agreement with Zeeman measurements in the CN thermal line of 0.36 and 0.71 mG about 3 5 away in DR21(OH) in gas of comparable density to the preshock gas density in DR21W. Comparison of our derived magnetic energy density with the kinetic energy density in DR21W indicates that magnetic fields likely play a significant role in shaping the dynamics of the postshocked gas in DR21W.
► The TGA thermograms presented for different fuels viz. JCO, JCME (KOH), JCME (NaOH), petroleum diesel and B50 blends. ► Calculations of the different parameters applicable for kinetic study ...purposes using three different methods. ► The refined JCO has highest value of activation energy 49.97kJ/mol while petroleum diesel has the lowest (9.11kJ/mol).
Fatty Acid Methyl Ester (FAME) obtained from the transesterification reaction of refined Jatropha curcas oil (JCO) and methanol using homogeneous catalysts NaOH and KOH were investigated. Gas chromatographic analysis were performed to determine fatty acid profile of the JCO and percentage conversion of JCO to FAME. Thermogravimetric experiments were conducted in nitrogen and air medium at constant heating rates 10°C/min and constant flow of gases 20±0.5ml/min and calculated the weight losses with increasing temperature. The TGA thermograms were analyzed for fuels under test viz. JCO, FAMEKOH, FAMENaOH, petroleum diesel and B50 blends. The calculations of the different parameters applicable for kinetic study purposes were carried out using three different methods available in literature viz. Redfern method, Friedman method and Differential method (Direct Arrhenius method), respectively. A comparative thermogravimetric and differential thermal analysis (TGDTA) of JCO, diesel, FAME and B50 can predict the thermal behavior and combustion characteristics. It has been observed that the refined JCO has the highest value (49.97kJ/mol, Differential method) and most stable thermally and during combustion while petroleum diesel has the lowest activation energy (9.11kJ/mol, Friedman method) and easily combustible as compared to biodiesel or blends. On the basis of the kinetic analysis it can also be concluded that all the three methods are equally effective to predict the combustion behavior of the fuel although there are variations in the quantitative value of activation energy.
ABSTRACT AstroSat is a multi-wavelength satellite launched on 2015 September 28. The CZT Imager of AstroSat on its very first day of operation detected a long duration gamma-ray burst (GRB), namely ...GRB 151006A. Using the off-axis imaging and spectral response of the instrument, we demonstrate that the CZT Imager can localize this GRB correctly to about a few degrees, and it can provide, in conjunction with Swift, spectral parameters similar to those obtained from Fermi/GBM. Hence, the CZT Imager would be a useful addition to the currently operating GRB instruments (Swift and Fermi). Specifically, we argue that the CZT Imager will be most useful for the short hard GRBs by providing localization for those detected by Fermi and spectral information for those detected only by Swift. We also provide preliminary results on a new exciting capability of this instrument: the CZT Imager is able to identify Compton scattered events thereby providing polarization information for bright GRBs. GRB 151006A, in spite of being relatively faint, shows hints of a polarization signal at 100-300 keV (though at a low significance level). We point out that the CZT Imager should provide significant time resolved polarization measurements for GRBs that have fluence three times higher than that of GRB 151006A. We estimate that the number of such bright GRBs detectable by the CZT Imager is five to six per year. The CZT Imager can also act as a good hard X-ray monitoring device for possible electromagnetic counterparts of gravitational wave events.
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