Collins fragmentation function from gluon rescattering

We estimate the Collins fragmentation function by introducing the effect of gluon rescattering in a model calculation of the fragmentation process. We include all necessary diagrams to the one-loop level and compute the nontrivial phases giving rise to the Collins function. We compare our results to the ones obtained from pion rescattering. We conclude that three out of four one-loop diagrams give sizeable contributions to the Collins function, and that the effect of gluon rescattering has a magnitude comparable to that of pion rescattering, but has opposite sign.Comment: 6 pages, 5 figures, uses RevTex. Typos corrected and a sentence added in the conclusions. To be published in PL

Sivers function in a spectator model with axial-vector diquarks

We perform a calculation of the Sivers function in a spectator model of the nucleon, with scalar and axial-vector diquarks. We make use of gluon rescattering to produce the nontrivial phases necessary to generate the Sivers function. The inclusion of axial-vector diquarks enables us to obtain a nonzero Sivers function for down quarks. Using the results of our model, we discuss the phenomenology of transvere single spin asymmetries in pi+, pi-, and pi0 production, which are currently analysed by the HERMES and COMPASS collaborations. We find that the inclusion of axial-vector diquarks substantially reduces the asymmetries.Comment: 8 pages, 7 figures, uses RevTex, added calculation of h1^perp, final version accepted for publication in PL

Transverse Polarisation of Quarks in Hadrons

We review the present state of knowledge regarding the transverse polarisation (or transversity) distributions of quarks. After some generalities on transverse polarisation, we formally define the transversity distributions within the framework of a classification of all leading-twist distribution functions. We describe the QCD evolution of transversity at leading and next-to-leading order. A comprehensive treatment of non-perturbative calculations of transversity distributions (within the framework of quark models, lattice QCD and QCD sum rules) is presented. The phenomenology of transversity (in particular, in Drell-Yan processes and semi-inclusive leptoproduction) is discussed in some detail. Finally, the prospects for future measurements are outlined.Comment: small changes, references added, as finally published in Physics Report

Fatality rate and predictors of mortality in an Italian cohort of hospitalized COVID-19 patients

Clinical features and natural history of coronavirus disease 2019 (COVID-19) differ widely among different countries and during different phases of the pandemia. Here, we aimed to evaluate the case fatality rate (CFR) and to identify predictors of mortality in a cohort of COVID-19 patients admitted to three hospitals of Northern Italy between March 1 and April 28, 2020. All these patients had a confirmed diagnosis of SARS-CoV-2 infection by molecular methods. During the study period 504/1697 patients died; thus, overall CFR was 29.7%. We looked for predictors of mortality in a subgroup of 486 patients (239 males, 59%; median age 71 years) for whom sufficient clinical data were available at data cut-off. Among the demographic and clinical variables considered, age, a diagnosis of cancer, obesity and current smoking independently predicted mortality. When laboratory data were added to the model in a further subgroup of patients, age, the diagnosis of cancer, and the baseline PaO2/FiO2 ratio were identified as independent predictors of mortality. In conclusion, the CFR of hospitalized patients in Northern Italy during the ascending phase of the COVID-19 pandemic approached 30%. The identification of mortality predictors might contribute to better stratification of individual patient risk

A Pharmacological Analysis of the Activity and Failure of the Medical Treatment of High-Grade Osteosarcoma

Osteosarcomas (OSs) are a group of neoplasms originating from bone cells, usually presenting in three specific age groups: children, young adults, and the elderly. High-grade OS is an extremely malignant tumor mainly due to evolution into metastatic disease, usually in the lungs. Survival of these patients has improved since the 1980s thanks to close cooperation between oncologists, oncological surgeons and orthopedic surgeons. Unfortunately, no progress has been made in the last 30 years and new, more effective drugs are needed. This article reviews the biological and pharmacological basis of the treatment of OS. Models of clinical pharmacology of the active drugs, toxic effects and reasons for primary and secondary resistance to old and new drugs are discussed

The importance of molecular biology in development, prognosis, treatment and resistance to targeted therapy in gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are the commonest mesenchymal tumors of the gastroenteric tract, and are generally believed to originate from the neoplastic transformation of the interstitial cells of Cajal, the pacemaker structures of the stomach and intestine. Exon and genetic mutations (point/deletions) are fundamental for the development of GISTs: the constitutional characteristic of this neoplasm is the presence of the cell surface Kit receptor. Kit is the product of the proto-oncogene cKit, situated in chromosome 4. Ninety-eight percent of GISTs express mutated isoforms of Kit or of PDGFRA (Platelet growth factor receptor a). Kit mutation is the basic condition for autophosphorylation of tyrosine kinase residues in proteins. Autophosphorylation initiates pathogenetic processes in Cajal cells, toward a neoplastic transformation. Imatinib mesilate and, more recently, sunitinib are tyrosine kinase inhibitors, specific antagonists for Kit and PDGFRA, with good activity against GISTs. Most molecular and clinical data currently available concern imatinib. Exon mutations are strategic as prognostic and as predictive factors. In recent years, much evidence suggests that survival, response to therapy and resistance to imatinib are related to different mutations. In the near future, GIST patients will receive treatment differentiated by expressed Kit and PDGFRA mutations, thus truly individualized therapy

Congenital esophageal stenosis with tracheoesophageal window

There are different types of congenital anomalies who have its origin in the embryological development of the esophagus and trachea at the fifth and seventh weeks. Examples of these are Laryngotracheoesophageal clefts, esophageal atresia with or without fistula and Congenital Esophageal Stenosis (CES) [1-3].The following case expose a 28-days-old baby boy with a extrange type of tracheoesophageal fistula with an esophageal estenosis.</p