A Darboux theorem for generalized contact manifolds

We consider a manifold M equipped with 1-forms $η1, ..., ηs$ which satisfy certain contact like properties. We prove a generalization of the classical Darboux theorem for such manifolds

Contact metric (κ,μ)(\kappa,\mu)-spaces as bi-Legendrian manifolds

We regard a contact metric manifold whose Reeb vector field belongs to the $(\kappa,\mu)$-nullity distribution as a bi-Legendrian manifold and we study its canonical bi-Legendrian structure. Then we characterize contact metric $(\kappa,\mu)$-spaces in terms of a canonical connection which can be naturally defined on them.Comment: To appear on Bull. Austral. Math. So

K-manifolds locally described by Sasaki manifolds

AbstractK-manifolds are normal metric globally framed f-manifolds whose Sasaki 2-form is closed. We introduce and study some subclasses of K-manifolds. We describe some examples and we also state local decomposition theorems

Submersions involving some special classes of K-manifolds

We study properties of invariant submanifolds ofK-manifolds as well as of somespecial types of K-manifolds. Moreover, we investigate properties of submersions between f-manifolds. In particular, we find some curvature identities when the total space is an S-manifoldand the base space is K ̈ahler

A Darboux theorem for generalized contact manifolds

We consider a manifold M equipped with 1-forms $η1, ..., ηs$ which satisfy certain contact like properties. We prove a generalization of the classical Darboux theorem for such manifolds

High Risk of Secondary Infections Following Thrombotic Complications in Patients With COVID-19

Background. This study’s primary aim was to evaluate the impact of thrombotic complications on the development of secondary infections. The secondary aim was to compare the etiology of secondary infections in patients with and without thrombotic complications. Methods. This was a cohort study (NCT04318366) of coronavirus disease 2019 (COVID-19) patients hospitalized at IRCCS San Raffaele Hospital between February 25 and June 30, 2020. Incidence rates (IRs) were calculated by univariable Poisson regression as the number of cases per 1000 person-days of follow-up (PDFU) with 95% confidence intervals. The cumulative incidence functions of secondary infections according to thrombotic complications were compared with Gray’s method accounting for competing risk of death. A multivariable Fine-Gray model was applied to assess factors associated with risk of secondary infections. Results. Overall, 109/904 patients had 176 secondary infections (IR, 10.0; 95% CI, 8.8–11.5; per 1000-PDFU). The IRs of secondary infections among patients with or without thrombotic complications were 15.0 (95% CI, 10.7–21.0) and 9.3 (95% CI, 7.9–11.0) per 1000-PDFU, respectively (P = .017). At multivariable analysis, thrombotic complications were associated with the development of secondary infections (subdistribution hazard ratio, 1.788; 95% CI, 1.018–3.140; P = .043). The etiology of secondary infections was similar in patients with and without thrombotic complications. Conclusions. In patients with COVID-19, thrombotic complications were associated with a high risk of secondary infections