738 research outputs found
Dimethyl fumarate in patients admitted to hospital with COVID-19 (RECOVERY): a randomised, controlled, open-label, platform trial
Dimethyl fumarate (DMF) inhibits inflammasome-mediated inflammation and has been proposed as a treatment for patients hospitalised with COVID-19. This randomised, controlled, open-label platform trial (Randomised Evaluation of COVID-19 Therapy [RECOVERY]), is assessing multiple treatments in patients hospitalised for COVID-19 (NCT04381936, ISRCTN50189673). In this assessment of DMF performed at 27 UK hospitals, adults were randomly allocated (1:1) to either usual standard of care alone or usual standard of care plus DMF. The primary outcome was clinical status on day 5 measured on a seven-point ordinal scale. Secondary outcomes were time to sustained improvement in clinical status, time to discharge, day 5 peripheral blood oxygenation, day 5 C-reactive protein, and improvement in day 10 clinical status. Between 2 March 2021 and 18 November 2021, 713 patients were enroled in the DMF evaluation, of whom 356 were randomly allocated to receive usual care plus DMF, and 357 to usual care alone. 95% of patients received corticosteroids as part of routine care. There was no evidence of a beneficial effect of DMF on clinical status at day 5 (common odds ratio of unfavourable outcome 1.12; 95% CI 0.86-1.47; pâ=â0.40). There was no significant effect of DMF on any secondary outcome
HCN Dimers to HCN Tetramers: Computational Exploration of Binary Reactions
This study explores the self and cross-dimerization of HCN and HNC dimers, key elements in prebiotic chemistry, to explore potential phenomena crucial to the early stages of life on Earth, Titan, and other extraterrestrial environments. We utilise computational analysis to reveal various reaction products, predominantly featuring imine, nitrile, amine, and iminoamine functional groups, along with N-heterocycles like aziridines, azetenes, and triazole. Transition state search methods illuminate the mechanistic details of these reactions. Notably, we identify biomarkers such as a func- tional isomer of DAMN (D95) and imidazole derivatives (D45, D76, D79), which are potential precursors to nucleobases such as adenine, and polyimines that may serve as precursors to DNA and RNA helical structures. This study enhances our under- standing of the complex chemical pathways that may have contributed to the genesis of lifeâs foundational molecules in various cosmic settings
Performance of Density Functionals and Semiempirical 3c Methods for Small Gold-Thiolate Clusters
Amid the surge of computational studies of gold thiolate clusters in the
recent past, we present a comparison of popular density functionals (DFAs) and
three-part corrected methods (3c-methods) on their performance by taking
a dataset consisting 18 isomers of Aun(SCH3)m
(m †n =1-3) stoichiometry. We have compared the efficiency and accuracy of the DFAs and 3c-methods in geometry optimization with RI-SCS-MP2
and energies with DLPNO-CCSD(T) as reference methods. The lowest energy structure out of
the largest stoichiometry from our dataset i.e., Au3(SCH3)3
is considered to evaluate the computational time for SCF and gradient. Alongside, the number of optimization steps to locate the most stable minima of
Au3(SCH3)3 are compared to assess the efficiency of the methods.
A comparison of relevant bond lengths with the reference geometry was made to estimate
the accuracy in geometry optimization. Some methods such as LC-BLYP, â”B97M-D3BJ,
M06-2X, and PBEh-3c are unable to locate many of the minima that are found by most of the
other methods; thus, the versatility in locating various minima is also an important
criterion in choosing a method for the given project. We have compared the relative
energies among the isomers along every stoichiometric series and the interaction energy of
the gold core with the ligands to estimate the accuracy of the methods. The dependence of basis
set size and relativistic effects on energies are also compared. Some of the
highlights are the following. TPSS shows accuracy, whereas mPWPW is fast with comparable
accuracy. The range separated hybrid DFAs are the best choice for the
relative energies of the clusters. CAM-B3LYP excels, whereas B3LYP shows poor performance.
Overall, LC-BLYP is a balanced performer considering both the geometry and relative stability
of the structures, but it lacks diversity. The 3c-methods, although fast, are less
impressive in relative stability
Nanoclusters and Nanoalloys of Group 13 elements B, Al, and Ga: Benchmark, structure, and property analysis
We present a benchmark study considering AEPA16 dataset comprising
atomization energy for boron group clusters. This dataset covers
46 different methods from the different range of density functionals
and post HF, where MRACPF is considered as the reference. The performance
of basis set is analyzed by comparing the atomization energy with
the CCSD(T)\CBS results. None of the GGA and meta-GGA are accurate
and the popular PBE shows maximum error among the all methods, whereas B3LYP
has moderate performance. M06 and RSHX DFAs have good performance
among all the DFAs. NEVPT2 is the most accurate
among all the methods considered followed by
coupled cluster methods, i.e., CCSD(T) and DLPNO-CCSD(T),
indicating the importance of perturbative correction.
All the basis with M06 show promising results (absolute error \textless 1
\kmol) with respect to the CCSD(T)\CBS. From the cost -- accuracy
investigation, def2-SVP is recommended in our study as it is the fastest.
Hence, we have recommended M06/def2-SVP for boron group clusters.
Furthermore, we have explored the structural progress of global and local
minima of pure, binary, and ternary of boron group clusters up to size 12.
One characteristic feature is that Ga clusters have more rectangular faces,
whereas B and Al clusters have mostly trigonal units in pure cluster\u27s form.
We have got core-shell like structures, where, B makes core structure
with both the Al and Ga atoms; however, Ga favors the outer position
in the binary clusters. This behavior confirms the higher cohesive
nature of B as compared to the Al and Ga atoms. The most favorable
cluster is obtained with the maximum cluster size (12) with the equal
composition of Al and Ga atoms for binary clusters.
From the BE and ME of ternary clusters, we have obtained
16.67-40% B, 16.67-60% Al, and 20-50% Ga composition are
favorable for the relatively stable ternary clusters as it shows negative ME
BAl4Mgâ/0/+: Global Minima with a Planar Tetracoordinate or Hypercoordinate Boron Atom
We have explored the chemical space of BAl4Mgâ/0/+ for the first time and theoretically characterized several isomers with interesting bonding patterns. We have used chemical intuition and a cluster building method based on the tabu-search algorithm implemented in the Python program for aggregation and reaction (PyAR) to obtain the maximum number of possible stationary points. The global minimum geometries for the anion (1a) and cation (1c) contain a planar tetracoordinate boron (ptB) atom, whereas the global minimum geometry for the neutral (1n) exhibits a planar pentacoordinate boron (ppB) atom. The low-lying isomers of the anion (2a) and cation (3c) also contain a ppB atom. The low-lying isomer of the neutral (2n) exhibits a ptB atom. Ab initio molecular dynamics simulations carried out at 298 K for 2000 fs suggest that all isomers are kinetically stable, except the cation 3c. Simulations carried out at low temperatures (100 and 200 K) for 2000 fs predict that even 3c is kinetically stable, which contains a ppB atom. Various bonding analyses (NBO, AdNDP, AIM, etc.) are carried out for these six different geometries of BAl4Mgâ/0/+ to understand the bonding patterns. Based on these results, we conclude that ptB/ppB scenarios are prevalent in these systems. Compared to the carbon counter-part, CAl4Mgâ, here the anion (BAl4Mgâ) obeys the 18 valence electron rule, as B has one electron fewer than C. However, the neutral and cation species break the rule with 17 and 16 valence electrons, respectively. The electron affinity (EA) of BAl4Mg is slightly higher (2.15 eV) than the electron affinity of CAl4Mg (2.05 eV). Based on the EA value, it is believed that these molecules can be identified in the gas phase. All the ptB/ppB isomers exhibit Ï/Ï double aromaticity. Energy decomposition analysis predicts that the interaction between BAl4â/0/+ and Mg is ionic in all these six systems
BAl<sub>4</sub>Mg<sup>â/0/+</sup>: Global Minima with a Planar Tetracoordinate or Hypercoordinate Boron Atom
We have explored the chemical space of BAl4Mgâ/0/+ for the first time and theoretically characterized several isomers with interesting bonding patterns. We have used chemical intuition and a cluster building method based on the tabu-search algorithm implemented in the Python program for aggregation and reaction (PyAR) to obtain the maximum number of possible stationary points. The global minimum geometries for the anion (1a) and cation (1c) contain a planar tetracoordinate boron (ptB) atom, whereas the global minimum geometry for the neutral (1n) exhibits a planar pentacoordinate boron (ppB) atom. The low-lying isomers of the anion (2a) and cation (3c) also contain a ppB atom. The low-lying isomer of the neutral (2n) exhibits a ptB atom. Ab initio molecular dynamics simulations carried out at 298 K for 2000 fs suggest that all isomers are kinetically stable, except the cation 3c. Simulations carried out at low temperatures (100 and 200 K) for 2000 fs predict that even 3c is kinetically stable, which contains a ppB atom. Various bonding analyses (NBO, AdNDP, AIM, etc.) are carried out for these six different geometries of BAl4Mgâ/0/+ to understand the bonding patterns. Based on these results, we conclude that ptB/ppB scenarios are prevalent in these systems. Compared to the carbon counter-part, CAl4Mgâ, here the anion (BAl4Mgâ) obeys the 18 valence electron rule, as B has one electron fewer than C. However, the neutral and cation species break the rule with 17 and 16 valence electrons, respectively. The electron affinity (EA) of BAl4Mg is slightly higher (2.15 eV) than the electron affinity of CAl4Mg (2.05 eV). Based on the EA value, it is believed that these molecules can be identified in the gas phase. All the ptB/ppB isomers exhibit Ï/Ï double aromaticity. Energy decomposition analysis predicts that the interaction between BAl4â/0/+ and Mg is ionic in all these six systems
CAl4Mg0/â: Global Minima with a Planar Tetracoordinate Carbon Atom
Isomers of CAl4Mg and CAl4Mgâ have been theoretically characterized for the first time. The most stable isomer for both the neutral and anion contain a planar tetracoordinate carbon (ptC) atom. Unlike the isovalent CAl4Be case, which contains a planar pentacoordinate carbon atom as the global minimum geometry, replacing beryllium with magnesium makes the ptC isomer the global minimum due to increased ionic radii of magnesium. However, it is relatively easier to conduct experimental studies for CAl4Mg0/â as beryllium is toxic. While the neutral molecule containing the ptC atom follows the 18 valence electron rule, the anion breaks the rule with 19 valence electrons. The electron affinity of CAl4Mg is in the range of 1.96â2.05 eV. Both the global minima exhibit Ï/Ï double aromaticity. Ab initio molecular dynamics simulations were carried out for both the global minima at 298 K for 10 ps to confirm their kinetic stability
Multiplicity dependence of light (anti-)nuclei production in pâPb collisions at sNN=5.02 TeV
The measurement of the deuteron and anti-deuteron production in the rapidity range â1 < y < 0 as a function of transverse momentum and event multiplicity in pâPb collisions at âsNN = 5.02 TeV is presented. (Anti-)deuterons are identified via their specific energy loss dE/dx and via their time-of- flight. Their production in pâPb collisions is compared to pp and PbâPb collisions and is discussed within the context of thermal and coalescence models. The ratio of integrated yields of deuterons to protons (d/p) shows a significant increase as a function of the charged-particle multiplicity of the event starting from values similar to those observed in pp collisions at low multiplicities and approaching those observed in PbâPb collisions at high multiplicities. The mean transverse particle momenta are extracted from the deuteron spectra and the values are similar to those obtained for p and particles. Thus, deuteron spectra do not follow mass ordering. This behaviour is in contrast to the trend observed for non-composite particles in pâPb collisions. In addition, the production of the rare 3He and 3He nuclei has been studied. The spectrum corresponding to all non-single diffractive p-Pb collisions is obtained in the rapidity window â1 < y < 0 and the pT-integrated yield dN/dy is extracted. It is found that the yields of protons, deuterons, and 3He, normalised by the spin degeneracy factor, follow an exponential decrease with mass number
Measurement of inclusive J/ pair production cross section in pp collisions at TeV
International audienceThe production cross section of inclusive J/ pairs in pp collisions at a centre-of-mass energy TeV is measured with ALICE. The measurement is performed for J/ in the rapidity interval . The production cross section of inclusive J/ pairs is reported to be nb in this kinematic interval. The contribution from non-prompt J/ (i.e. originated from beauty-hadron decays) to the inclusive sample is evaluated. The results are discussed and compared with data
- âŠ