Quark Confinement from different Dressed Gluon Propagators

The gap equation in quantum chromodynamics is solved by incorporating differ- ent gluon dressing functions, some of them derived from a quark-diquark potential that exhibits a conformal symmetry. By using the bare vertex and working in the Landau gauge, the quark mass function is found to have an infrared enhancement that smoothly transitions to an asymptotically free behavior at high momentum, which is consistent with the predictions of Schwinger-Dyson equations. Addi- tionally, these quark propagators violate reflexion positivity, indicating that the gluon dressing provides clear evidence of quark confinement

How many bird and mammal extinctions has recent conservation action prevented?

Aichi Target 12 of the Convention on Biological Diversity (CBD) aims to ‘prevent extinctions of known threatened species’. To measure its success, we used a Delphi expert elicitation method to estimate the number of bird and mammal species whose extinctions were prevented by conservation action in 1993 - 2020 (the lifetime of the CBD) and 2010 - 2020 (the timing of Aichi Target 12). We found that conservation prevented 21–32 bird and 7–16 mammal extinctions since 1993, and 9–18 bird and 2–7 mammal extinctions since 2010. Many remain highly threatened, and may still become extinct in the near future. Nonetheless, given that ten bird and five mammal species did go extinct (or are strongly suspected to) since 1993, extinction rates would have been 2.9–4.2 times greater without conservation action. While policy commitments have fostered significant conservation achievements, future biodiversity action needs to be scaled up to avert additional extinctions

Global overview of the management of acute cholecystitis during the COVID-19 pandemic (CHOLECOVID study)

Background: This study provides a global overview of the management of patients with acute cholecystitis during the initial phase of the COVID-19 pandemic. Methods: CHOLECOVID is an international, multicentre, observational comparative study of patients admitted to hospital with acute cholecystitis during the COVID-19 pandemic. Data on management were collected for a 2-month study interval coincident with the WHO declaration of the SARS-CoV-2 pandemic and compared with an equivalent pre-pandemic time interval. Mediation analysis examined the influence of SARS-COV-2 infection on 30-day mortality. Results: This study collected data on 9783 patients with acute cholecystitis admitted to 247 hospitals across the world. The pandemic was associated with reduced availability of surgical workforce and operating facilities globally, a significant shift to worse severity of disease, and increased use of conservative management. There was a reduction (both absolute and proportionate) in the number of patients undergoing cholecystectomy from 3095 patients (56.2 per cent) pre-pandemic to 1998 patients (46.2 per cent) during the pandemic but there was no difference in 30-day all-cause mortality after cholecystectomy comparing the pre-pandemic interval with the pandemic (13 patients (0.4 per cent) pre-pandemic to 13 patients (0.6 per cent) pandemic; P = 0.355). In mediation analysis, an admission with acute cholecystitis during the pandemic was associated with a non-significant increased risk of death (OR 1.29, 95 per cent c.i. 0.93 to 1.79, P = 0.121). Conclusion: CHOLECOVID provides a unique overview of the treatment of patients with cholecystitis across the globe during the first months of the SARS-CoV-2 pandemic. The study highlights the need for system resilience in retention of elective surgical activity. Cholecystectomy was associated with a low risk of mortality and deferral of treatment results in an increase in avoidable morbidity that represents the non-COVID cost of this pandemic

How many bird and mammal extinctions has recent conservation action prevented?

Aichi Target 12 of the Convention on Biological Diversity (CBD) contains the aim to ‘prevent extinctions of known threatened species’. To measure the degree to which this was achieved, we used expert elicitation to estimate the number of bird and mammal species whose extinctions were prevented by conservation action in 1993–2020 (the lifetime of the CBD) and 2010–2020 (the timing of Aichi Target 12). We found that conservation action prevented 21–32 bird and 7–16 mammal extinctions since 1993, and 9–18 bird and two to seven mammal extinctions since 2010. Many remain highly threatened and may still become extinct. Considering that 10 bird and five mammal species did go extinct (or are strongly suspected to) since 1993, extinction rates would have been 2.9–4.2 times greater without conservation action. While policy commitments have fostered significant conservation achievements, future biodiversity action needs to be scaled up to avert additional extinctions.https://wileyonlinelibrary.com/journal/conlMammal Research Institut

Heavy-light mesons in a contact interaction

We present a unified formalism for the analysis of mesons. It is provided by a symmetry preserving Schwinger-Dyson-Bethe-Salpeter-Equation (SDBSE) treatment of a vector-vector contact interaction. The contact interaction (CI) model offers a simple-to-implement alternative to perform exploratory studies of QCD, within the SDBSE framework. Within the limitation of this model, we calculate the spectrum of D and B mesons. Our results are in agreement within 2% when compare with experimental data, lattice QCD and other SDBSE calculations involving sophisticated interaction kernels

Heavy-light mesons in a contact interaction

We present a unified formalism for the analysis of mesons. It is provided by a symmetry preserving Schwinger-Dyson-Bethe-Salpeter-Equation (SDBSE) treatment of a vector-vector contact interaction. The contact interaction (CI) model offers a simple-to-implement alternative to perform exploratory studies of QCD, within the SDBSE framework. Within the limitation of this model, we calculate the spectrum of D and B mesons. Our results are in agreement within 2% when compare with experimental data, lattice QCD and other SDBSE calculations involving sophisticated interaction kernels

Tribological Performance of CoCrMo Alloys with Boron Additions in As-Cast and Heat-Treated Conditions

The present study evaluates the effect of boron additions on the tribological performance of CoCrMo alloys. The alloys were prepared with boron ranging from 0.06 to 1 wt%. The materials were characterized using metallographic techniques, scanning electronic microscopy, and roughness and hardness tests. Tribological evaluation was made by means of ball-on-disc tests for sliding distances of 4, 8 and 12 km. The samples were in the as-cast condition and after a heat treatment at 1200 °C for 1 h, finished by water quenching. The results showed that wear resistance was influenced by the microstructure and the number of secondary phases. The volume loss decreased as the boron content increased. Due to hard phases, abrasion wear was observed. Delamination fatigue was also detected after long sliding distances. Both wear mechanisms diminished in higher boron content alloys