35 research outputs found
Large-order NSPT for lattice gauge theories with fermions:the plaquette in massless QCD
Numerical Stochastic Perturbation Theory (NSPT) allows for perturbative
computations in quantum field theory. We present an implementation of NSPT that
yields results for high orders in the perturbative expansion of lattice gauge
theories coupled to fermions. The zero-momentum mode is removed by imposing
twisted boundary conditions; in turn, twisted boundary conditions require us to
introduce a smell degree of freedom in order to include fermions in the
fundamental representation. As a first application, we compute the critical
mass of two flavours of Wilson fermions up to order in a
gauge theory. We also implement, for the first time,
staggered fermions in NSPT. The residual chiral symmetry of staggered fermions
protects the theory from an additive mass renormalisation. We compute the
perturbative expansion of the plaquette with two flavours of massless staggered
fermions up to order in a gauge theory, and
investigate the renormalon behaviour of such series. We are able to subtract
the power divergence in the Operator Product Expansion (OPE) for the plaquette
and estimate the gluon condensate in massless QCD. Our results confirm that
NSPT provides a viable way to probe systematically the asymptotic behaviour of
perturbative series in QCD and, eventually, gauge theories with fermions in
higher representations.Comment: 49 pages, 28 figures. Revised version, to be published in EPJC. Some
references added, typos corrected, and improved discussion on finite-volume
effect
Identifying metabolite markers for preterm birth in cervicovaginal fluid by magnetic resonance spectroscopy
Introduction Preterm birth (PTB) may be preceded by
changes in the vaginal microflora and metabolite profiles.
Objectives We sought to characterise the metabolite
profile of cervicovaginal fluid (CVF) of pregnant women
by 1H NMR spectroscopy, and assess their predictive value
for PTB.
Methods A pair of high-vaginal swabs was obtained from
pregnant women with no evidence of clinical infection and
grouped as follows: asymptomatic low risk (ALR) women
with no previous history of PTB, assessed at 20–22 gestational
weeks, g.w., n = 83; asymptomatic high risk
(AHR) women with a previous history of PTB, assessed at
both 20–22 g.w., n = 71, and 26–28 g.w., n = 58; and
women presenting with symptoms of preterm labor (PTL)
(SYM), assessed at 24–36 g.w., n = 65. Vaginal secretions
were dissolved in phosphate buffered saline and scanned
with a 9.4 T NMR spectrometer.
Results Six metabolites (lactate, alanine, acetate, glutamine/glutamate,
succinate and glucose) were analysed. In
all study cohorts vaginal pH correlated with lactate integral
(r = -0.62, p\0.0001). Lactate integrals were higher in
the term ALR compared to the AHR (20–22 g.w.) women
(p = 0.003). Acetate integrals were higher in the preterm
versus term women for the AHR (20–22 g.w.) (p = 0.048)
and SYM (p = 0.003) groups; and was predictive of
PTB\37 g.w. (AUC 0.78; 95 % CI 0.61–0.95), and
delivery within 2 weeks of the index assessment (AUC
0.84; 95 % CI 0.64–1) in the SYM women, whilst other
metabolites were not.
Conclusion High CVF acetate integral of women with
symptoms of PTL appears predictive of preterm delivery,
as well as delivery within 2 weeks of presentation
Search for gravitational waves associated with gamma-ray bursts detected by Fermi and Swift during the LIGO–Virgo run O3b
We search for gravitational-wave signals associated with gamma-ray bursts (GRBs) detected by the Fermi and Swift satellites during the second half of the third observing run of Advanced LIGO and Advanced Virgo (2019 November 1 15:00 UTC–2020 March 27 17:00 UTC). We conduct two independent searches: a generic gravitational-wave transients search to analyze 86 GRBs and an analysis to target binary mergers with at least one neutron star as short GRB progenitors for 17 events. We find no significant evidence for gravitational-wave signals associated with any of these GRBs. A weighted binomial test of the combined results finds no evidence for subthreshold gravitational-wave signals associated with this GRB ensemble either. We use several source types and signal morphologies during the searches, resulting in lower bounds on the estimated distance to each GRB. Finally, we constrain the population of low-luminosity short GRBs using results from the first to the third observing runs of Advanced LIGO and Advanced Virgo. The resulting population is in accordance with the local binary neutron star merger rate
Appropriateness of antiplatelet therapy for primary and secondary cardio- and cerebrovascular prevention in acutely hospitalized older people
Aims: Antiplatelet therapy is recommended for the secondary prevention of cardio- and cerebrovascular disease, but for primary prevention it is advised only in patients at very high risk. With this background, this study aims to assess the appropriateness of antiplatelet therapy in acutely hospitalized older people according to their risk profile. Methods: Data were obtained from the REPOSI register held in Italian and Spanish internal medicine and geriatric wards in 2012 and 2014. Hospitalized patients aged 6565 assessable at discharge were selected. Appropriateness of the antiplatelet therapy was evaluated according to their primary or secondary cardiovascular prevention profiles. Results: Of 2535 enrolled patients, 2199 were assessable at discharge. Overall 959 (43.6%, 95% CI 41.5\u201345.7) were prescribed an antiplatelet drug, aspirin being the most frequently chosen. Among patients prescribed for primary prevention, just over half were inappropriately prescribed (52.1%), being mainly overprescribed (155/209 patients, 74.2%). On the other hand, there was also a high rate of inappropriate underprescription in the context of secondary prevention (222/726 patients, 30.6%, 95% CI 27.3\u201334.0%). Conclusions: This study carried out in acutely hospitalized older people shows a high degree of inappropriate prescription among patients prescribed with antiplatelets for primary prevention, mainly due to overprescription. Further, a large proportion of patients who had had overt cardio- or cerebrovascular disease were underprescribed, in spite of the established benefits of antiplatelet drugs in the context of secondary prevention