•Addition of cobalt to Mo/β catalyst greatly enhanced catalysts activity and stability.•CoMo/β catalyst is effective for the conversion of pyrolysis fuel oil into monocyclic aromatic ...hydrocarbons.•The catalytic activity mainly depends on the acidity of supports.
The Mo/β (beta zeolite) catalyst was prepared by wet-impregnation and modified with cobalt promoter. The catalytic activity of monometallic Mo/β catalyst in selective hydrocracking of tetralin into monocyclic aromatic hydrocarbons (MAH) such as benzene, toluene and xylene (BTX) was investigated in fixed bed reactor and compared its activity with bimetallic CoMo/β catalyst. The catalytic results indicates that, incorporation of promoter (Co) not only improved their catalytic activity in hydrocracking reactions but also showed long term stability as compared with Mo/β. Effect of different SiO2/Al2O3 ratio (25, 75, 150) in beta zeolite was investigated on catalytic activity of CoMo/β. CoMo/β with SiO2/Al2O3 of 25, gave highest 62.6% of desired MAH yield at 99.5% conversion of tetralin for more than 140h of reaction time. Likely, CoMo/β catalyst was also found to be effective for the conversion of pyrolysis fuel oil (PFO) into MAH. Crude PFO was distilled out at 170°C and total amount of 55wt.% PFO was received after distillation. In the PFO hydrocracking, it produced 43.3% of MAH product yield at 70% conversion of PFO, which is significantly higher than the conversion (48%) and MAH yield (34.2%) obtained from monometallic Mo/β catalysts. CoMo/β catalyst was found to be more stable as well as active for longer reaction time (140h).
MoTe2 is an exfoliable transition metal dichalcogenide (TMD) that crystallizes in three symmetries: the semiconducting trigonal-prismatic 2H- or α-phase, the semimetallic and monoclinic 1T′- or ...β-phase, and the semimetallic orthorhombic γ-structure. The 2H-phase displays a band gap of ∼1 eV making it appealing for flexible and transparent optoelectronics. The γ-phase is predicted to possess unique topological properties that might lead to topologically protected nondissipative transport channels. Recently, it was argued that it is possible to locally induce phase-transformations in TMDs, through chemical doping, local heating, or electric-field to achieve ohmic contacts or to induce useful functionalities such as electronic phase-change memory elements. The combination of semiconducting and topological elements based upon the same compound might produce a new generation of high performance, low dissipation optoelectronic elements. Here, we show that it is possible to engineer the phases of MoTe2 through W substitution by unveiling the phase-diagram of the Mo1–x W x Te2 solid solution, which displays a semiconducting to semimetallic transition as a function of x. We find that a small critical W concentration x c ∼ 8% stabilizes the γ-phase at room temperature. This suggests that crystals with x close to x c might be particularly susceptible to phase transformations induced by an external perturbation, for example, an electric field. Photoemission spectroscopy, indicates that the γ-phase possesses a Fermi surface akin to that of WTe2.
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•Co promoted Mo/β catalyst has showed superior catalytic performance in hydrocracking of model compounds as well as crude pyrolysis fuel oil into BTX.•Catalysts and reaction ...parameters optimization in hydrocracking of tetralin helps to conduct the efficient hydrocracking of PFO into BTX.•Surface and morphological properties in CoMo/β catalyst was observed to be varied with the loading of Co, and it could strongly affect their catalytic activity.•Along with the superior catalytic activity, CoMo/β catalyst provided long term stability in continuous flow reaction without any significant deactivation.
Cobalt promoted Mo/β (Beta zeolite) catalysts were prepared with different metallic loadings (0.5–1.5) by a co-impregnation method. The catalytic activities of the synthesized catalysts were investigated for the selective hydrocracking of tetralin and pyrolysis fuel oil (PFO) into mono-aromatic hydrocarbons (MAH) such as benzene, toluene and xylene (BTX) in a fixed-bed reactor system. Prior to using the CoMo/β catalyst for crude PFO hydrocracking, different reaction parameters (including metallic loading, temperature, H2 pressure, and LHSV) were investigated for the hydrocracking of a model feed, tetralin, to determine the best conditions for maximum BTX yield. The CoMo(0.5)/β catalyst with a Co/Mo ratio of 0.5 produced the highest MAH yield of 62.6% at 99.5% conversion of tetralin, continuously for 140h of reaction time without any deactivation. Furthermore, the CoMo(0.5)/β catalyst was found to be superior among the tested CoMo/β catalysts for hydrocracking real feed PFO, and it produced a maximum MAH yield of 54.8% at 99.1% conversion of PFO. The synthesized catalysts were characterized using different characterization techniques, including BET, NH3-TPD, SEM-EDS and ICP, to evaluate their physiochemical properties and determine the active sites present in the catalysts.
Self-organization occurs in plasmas when energy progressively transfers from smaller to larger scales in an inverse cascade. Global structures that emerge from turbulent plasmas can be found in the ...laboratory and in astrophysical settings; for example, the cosmic magnetic field, collisionless shocks in supernova remnants and the internal structures of newly formed stars known as Herbig-Haro objects. Here we show that large, stable electromagnetic field structures can also arise within counter-streaming supersonic plasmas in the laboratory. These surprising structures, formed by a yet unexplained mechanism, are predominantly oriented transverse to the primary flow direction, extend for much larger distances than the intrinsic plasma spatial scales and persist for much longer than the plasma kinetic timescales. Our results challenge existing models of counter-streaming plasmas and can be used to better understand large-scale and long-time plasma self-organization. PUBLICATION ABSTRACT
A combination of the searches for pair-produced vectorlike partners of the top and bottom quarks in various decay channels (T→Zt/Wb/Ht, B→Zb/Wt/Hb) is performed using 36.1 fb−1 of pp collision data ...at s=13 TeV with the ATLAS detector at the Large Hadron Collider. The observed data are found to be in good agreement with the standard model background prediction in all individual searches. Therefore, combined 95% confidence-level upper limits are set on the production cross section for a range of vectorlike quark scenarios, significantly improving upon the reach of the individual searches. Model-independent limits are set assuming the vectorlike quarks decay to standard model particles. A singlet T is excluded for masses below 1.31 TeV and a singlet B is excluded for masses below 1.22 TeV. Assuming a weak isospin (T,B) doublet and |VTb|≪|VtB|, T and B masses below 1.37 TeV are excluded.
A search for heavy charged long-lived particles is performed using a data sample of 36.1 fb−1 of proton-proton collisions at √s=13 TeV collected by the ATLAS experiment at the Large Hadron Collider. ...The search is based on observables related to ionization energy loss and time of flight, which are sensitive to the velocity of heavy charged particles traveling significantly slower than the speed of light. Multiple search strategies for a wide range of lifetimes, corresponding to path lengths of a few meters, are defined as model independently as possible, by referencing several representative physics cases that yield long-lived particles within supersymmetric models, such as gluinos/squarks (R-hadrons), charginos and staus. No significant deviations from the expected Standard Model background are observed. Upper limits at 95% confidence level are provided on the production cross sections of long-lived R-hadrons as well as directly pair-produced staus and charginos. These results translate into lower limits on the masses of long-lived gluino, sbottom and stop R-hadrons, as well as staus and charginos of 2000, 1250, 1340, 430, and 1090 GeV, respectively.
A measurement of production cross sections of the Higgs boson in proton-proton collisions is presented in the H→ττ decay channel. The analysis is performed using 36.1 fb−1 of data recorded by the ...ATLAS experiment at the Large Hadron Collider at a center-of-mass energy of s=13 TeV. All combinations of leptonic (τ→ℓvv¯ with ℓ=e,μ) and hadronic (τ→hadrons v) τ decays are considered. The H→ττ signal over the expected background from other Standard Model processes is established with an observed (expected) significance of 4.4 (4.1) standard deviations. Combined with results obtained using data taken at 7 and 8 TeV center-of-mass energies, the observed (expected) significance amounts to 6.4 (5.4) standard deviations and constitutes an observation of H→ττ decays. Using the data taken at s=13 TeV, the total cross section in the H→ττ decay channel is measured to be 3.77−0.59+0.60 (stat) −0.74+0.87 (syst) pb, for a Higgs boson of mass 125 GeV assuming the relative contributions of its production modes as predicted by the Standard Model. Total cross sections in the H→ττ decay channel are determined separately for vector-boson-fusion production and gluon-gluon-fusion production to be σH→ττVBF=0.28±0.09 (stat) −0.09+0.11 (syst) pb and σH→ττggF=3.1±1.0 (stat) −1.3+1.6 (syst) pb, respectively. Similarly, results of a fit are reported in the framework of simplified template cross sections. All measurements are in agreement with Standard Model expectations.
A search for supersymmetry through the pair production of electroweakinos with mass splittings near the electroweak scale and decaying via on-shell W and Z bosons is presented for a three-lepton ...final state. The analyzed proton-proton collision data taken at a center-of-mass energy of root s = 13 TeV were collected between 2015 and 2018 by the ATLAS experiment at the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb(-1). A search, emulating the recursive jigsaw reconstruction technique with easily reproducible laboratory-frame variables, is performed. The two excesses observed in the 2015-2016 data recursive jigsaw analysis in the low-mass three-lepton phase space are reproduced. Results with the full data set are in agreement with the Standard Model expectations. They are interpreted to set exclusion limits at the 95% confidence level on simplified models of chargino-neutralino pair production for masses up to 345 GeV.
A search for electroweak production of supersymmetric particles is performed in two-lepton and three-lepton final states using recursive jigsaw reconstruction, a technique that assigns reconstructed ...objects to the most probable hemispheres of the decay trees, allowing one to construct tailored kinematic variables to separate the signal and background. The search uses data collected in 2015 and 2016 by the ATLAS experiment in s=13 TeV proton-proton collisions at the CERN Large Hadron Collider corresponding to an integrated luminosity of 36.1 fb−1. Chargino-neutralino pair production, with decays via W/Z bosons, is studied in final states involving leptons and jets and missing transverse momentum for scenarios with large and intermediate mass splittings between the parent particle and lightest supersymmetric particle, as well as for the scenario where this mass splitting is close to the mass of the Z boson. The latter case is challenging since the vector bosons are produced with kinematic properties that are similar to those in Standard Model processes. Results are found to be compatible with the Standard Model expectations in the signal regions targeting large and intermediate mass splittings, and chargino-neutralino masses up to 600 GeV are excluded at 95% confidence level for a massless lightest supersymmetric particle. Excesses of data above the expected background are found in the signal regions targeting low mass splittings, and the largest local excess amounts to 3.0 standard deviations.
There have been limited data on the risk of onward transmission from individuals with Omicron variant infections who return to work after a 5-day isolation.
To evaluate the risk of transmission from ...healthcare workers (HCWs) with Omicron variant who returned to work after a 5-day isolation and the viable-virus shedding kinetics.
This investigation was performed in a tertiary care hospital, Seoul, South Korea. In a secondary transmission study, we retrospectively reviewed the data of HCWs confirmed as COVID-19 from March 14th to April 3rd, 2022 in units with five or more COVID-19-infected HCWs per week. In the viral shedding kinetics study, HCWs with Omicron variant infection who agreed with daily saliva sampling were enrolled between February and March, 2022.
Of the 248 HCWs who were diagnosed with COVID-19 within 5 days of the return of an infected HCW, 18 (7%) had contact with the returned HCW within 1–5 days after their return. Of these, nine (4%) had an epidemiologic link other than with the returning HCW, and nine (4%) had contact with the returning HCW, without any other epidemiologic link. In the study of the kinetics of virus shedding (N = 32), the median time from symptom onset to negative conversion of viable virus was four days (95% confidence interval: 3–5).
Our data suggest that the residual risk of virus transmission after 5 days of isolation following diagnosis or symptom onset is low.
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