S-wave charmed mesons in lattice NRQCD

Heavy-light mesons can be studied using the 1/M expansion of NRQCD, provided the heavy quark mass is sufficiently large. Calculations of the S-wave charmed meson masses from a classically and tadpole-improved action are presented. A comparison of O(1/M), O(1/M^2) and O(1/M^3) results allows convergence of the expansion to be discussed. It is shown that the form of discretized heavy quark propagation must be chosen carefully.Comment: LATTICE98(heavyqk), 3 pages including 3 figure

P-wave heavy-light mesons using NRQCD and D234

The masses of S- and P-wave heavy-light mesons are computed in quenched QCD using a classically and tadpole-improved action on anisotropic lattices. Of particular interest are the splittings among P-wave states, which have not yet been resolved experimentally; even the ordering of these states continues to be discussed in the literature. The present work leads to upper bounds for these splittings, and is suggestive, but not conclusive, about the ordering.Comment: LATTICE99(heavy quarks) - 3 pages including 3 figure

Exact Byzantine Consensus on Arbitrary Directed Graphs Under Local Broadcast Model

We consider Byzantine consensus in a synchronous system where nodes are connected by a network modeled as a directed graph, i.e., communication links between neighboring nodes are not necessarily bi-directional. The directed graph model is motivated by wireless networks wherein asymmetric communication links can occur. In the classical point-to-point communication model, a message sent on a communication link is private between the two nodes on the link. This allows a Byzantine faulty node to equivocate, i.e., send inconsistent information to its neighbors. This paper considers the local broadcast model of communication, wherein transmission by a node is received identically by all of its outgoing neighbors, effectively depriving the faulty nodes of the ability to equivocate. Prior work has obtained sufficient and necessary conditions on undirected graphs to be able to achieve Byzantine consensus under the local broadcast model. In this paper, we obtain tight conditions on directed graphs to be able to achieve Byzantine consensus with binary inputs under the local broadcast model. The results obtained in the paper provide insights into the trade-off between directionality of communication links and the ability to achieve consensus

Heavy-light meson spectrum with and without NRQCD

Results for the spectrum of S and P-wave charmed mesons are obtained in the quenched approximation from a tadpole-improved anisotropic gauge field action and a D234 quark action. This is compared to the spectrum obtained from an NRQCD charm quark and a D234 light antiquark. NRQCD results for bottom mesons are also discussed.Comment: 4 pages, 5 figures. Lattice 2000 (Heavy Quark Physics

Two-Pion Decay Widths of Excited Charm Mesons

The widths for $\pi\pi$ decay of the L=1 charm mesons are calculated by describing the pion coupling to light constituents quarks by the lowest order chiral interaction. The wavefunctions of the charm mesons are obtained as solutions to the covariant Blankenbecler-Sugar equation. These solutions correspond to an interaction Hamiltonian modeled as the sum of a linear scalar confining and a screened one-gluon exchange (OGE) interaction. This interaction induces a two-quark contribution to the amplitude for two-pion decay, which is found to interfere destructively with the single quark amplitude. For the currently known L=1 $D$ mesons, the total $\pi\pi$ decay widths are found to be $\sim 1$ MeV for the $D_1(2420)$ and $\sim 3$ MeV for the $D^*_2(2460)$ if the axial coupling of the constituent quark is taken to be $g_A^q=1$. The as yet undiscovered spin singlet $D_1^*$ state is predicted to have a larger width of 7 - 10 MeV for $\pi\pi$ decay.Comment: 20 pages, uses Feynmf Submitted to Nuclear Physics A, published versio

Modelling the Social Buffering Hypothesis in an Artificial Life Environment

© 2020 Massachusetts Institute of Technology Published under a Creative Commons Attribution 4.0 International (CC BY 4.0) license: https://creativecommons.org/licenses/by/4.0/.In social species, individuals who form social bonds have been found to live longer, healthier lives. One hypothesised reason for this effect is that social support, mediated by oxytocin, “buffers” responses to stress in a number of ways, and is considered an important process of adaptation that facilitates long-term wellbeing in changing, stressful conditions. Using an artificial life model, we have investigated the role of one hypothesised stress-reducing effect of social support on the survival and social interactions of agents in a small society. We have investigated this effect using different types of social bonds and bond partner combinations across environmentally-challenging conditions. Our results have found that stress reduction through social support benefits the survival of agents with social bonds, and that this effect often extends to the wider society. We have also found that this effect is significantly affected by environmental and social contexts. Our findings suggest that these “social buffering” effects may not be universal, but dependent upon the degree of environmental challenges, the quality of affective relationships and the wider social context

Angiotensin converting enzyme inhibitors do not increase the risk of poor outcomes in COVID-19 disease. A multi-centre observational study

Background and aims Hypertension is associated with an increased risk of severe outcomes with COVID-19 disease. Angiotensin Converting Enzyme (ACE) inhibitors are widely used as a first line medication for the treatment of hypertension in the UK, although their use was suggested in early reports to increase the risk associated with SARS-CoV-2 infection. Methods A prospective cohort study of hospitalised patients with laboratory confirmed COVID-19 was conducted across three hospital sites with patients identified on the 9th April 2020. Demographic and other baseline data were extracted from electronic case records, and patients grouped depending on ACE inhibitor usage or not. The 60-day all-cause mortality and need for intubation compared. Results Of the 173 patients identified, 88 (50.8%) had hypertension. Of these 27 (30.7%) used ACE inhibitors. We did not find significant differences in 60-day all-cause mortality, the requirement for invasive ventilation or length of stay between our patient cohorts after adjusting for covariates. Conclusion This study contributes to the growing evidence supporting the continued use of ACE inhibitors in COVID-19 disease, although adequately powered randomised controlled trials will be needed to confirm effects

Does nosocomial SARS-CoV-2 infection result in increased 30-day mortality? A multi-centre observational study to identify risk factors for worse outcomes in COVID-19 disease

We aimed to determine whether nosocomial SARS-CoV-2 infection has worse outcomes than community-acquired disease. This was prospective cohort study of all hospitalised patients in three acute hospitals with confirmed COVID-19 on 9th April 2020. Patients were followed up for at least 30 days. Nosocomial infection was defined as a positive swab after 7 days of admission. 173 patients were identified; 19 (11.0%) had nosocomial infection. 32 (18.5%) had 30-day all-cause mortality; there was no statistically significant differences between 30-day mortality (21.1% vs 17.6% vs 21.6% respectively, p=0.755). Nosocomial SARS-CoV-2 infection is not associated with increased mortality compared with community acquired infection

S and P-wave heavy-light mesons in lattice NRQCD

The mass spectrum of S and P-wave mesons containing a single heavy quark is computed in the quenched approximation, using NRQCD up to third order in the inverse heavy quark mass expansion. Previous results found third order contributions which are as large in magnitude as the total second order contribution for the charmed S-wave spin splitting. The present work considers variations such as anisotropic lattices, Landau link tadpole improvement, and a highly-improved light quark action, and finds that the second order correction to the charmed S-wave spin splitting is about 20% of the leading order contribution, while the third order correction is about 20%(10%) for D^*-D(D_s^*-D_s). Nonleading corrections are very small for the bottom meson spectrum, and are statistically insignificant for the P-wave charmed masses. The relative orderings among P-wave charmed and bottom mesons, and the sizes of the mass splittings, are discussed in light of experimental data and existing calculations.Comment: 21 pages including 6 figures, changed method of fitting correlators, this version to be published in Phys Rev

Anionic sigmatropic-electrocyclic-Chugaev cascades: accessing 12-aryl-5-(methylthiocarbonylthio)tetracenes and a related anthra[2,3-b]thiophene

1,4-Diols resulting from the double addition of ArCCLi (Ar = Ph, substituted phenyl, 2-thienyl) to ortho-C6H4(CHO)2 undergo cascades to tetracenes on simple admixture of LiHDMS, CS2 and MeI. Acene formation proceeds by [3,3]-sigmatropic rearrangement of xanthate anions followed by 6π electrocyclisations. The reactions are terminated by E2 or anionic Chugaev-type eliminations. Structural packing motifs and electronic properties are reported for the tetracenes