f(R) theories

Over the past decade, f(R) theories have been extensively studied as one of the simplest modifications to General Relativity. In this article we review various applications of f(R) theories to cosmology and gravity - such as inflation, dark energy, local gravity constraints, cosmological perturbations, and spherically symmetric solutions in weak and strong gravitational backgrounds. We present a number of ways to distinguish those theories from General Relativity observationally and experimentally. We also discuss the extension to other modified gravity theories such as Brans-Dicke theory and Gauss-Bonnet gravity, and address models that can satisfy both cosmological and local gravity constraints.Comment: 156 pages, 14 figures, Invited review article in Living Reviews in Relativity, Published version, Comments are welcom

Twelve-month observational study of children with cancer in 41 countries during the COVID-19 pandemic

Introduction Childhood cancer is a leading cause of death. It is unclear whether the COVID-19 pandemic has impacted childhood cancer mortality. In this study, we aimed to establish all-cause mortality rates for childhood cancers during the COVID-19 pandemic and determine the factors associated with mortality. Methods Prospective cohort study in 109 institutions in 41 countries. Inclusion criteria: children <18 years who were newly diagnosed with or undergoing active treatment for acute lymphoblastic leukaemia, non-Hodgkin's lymphoma, Hodgkin lymphoma, retinoblastoma, Wilms tumour, glioma, osteosarcoma, Ewing sarcoma, rhabdomyosarcoma, medulloblastoma and neuroblastoma. Of 2327 cases, 2118 patients were included in the study. The primary outcome measure was all-cause mortality at 30 days, 90 days and 12 months. Results All-cause mortality was 3.4% (n=71/2084) at 30-day follow-up, 5.7% (n=113/1969) at 90-day follow-up and 13.0% (n=206/1581) at 12-month follow-up. The median time from diagnosis to multidisciplinary team (MDT) plan was longest in low-income countries (7 days, IQR 3-11). Multivariable analysis revealed several factors associated with 12-month mortality, including low-income (OR 6.99 (95% CI 2.49 to 19.68); p<0.001), lower middle income (OR 3.32 (95% CI 1.96 to 5.61); p<0.001) and upper middle income (OR 3.49 (95% CI 2.02 to 6.03); p<0.001) country status and chemotherapy (OR 0.55 (95% CI 0.36 to 0.86); p=0.008) and immunotherapy (OR 0.27 (95% CI 0.08 to 0.91); p=0.035) within 30 days from MDT plan. Multivariable analysis revealed laboratory-confirmed SARS-CoV-2 infection (OR 5.33 (95% CI 1.19 to 23.84); p=0.029) was associated with 30-day mortality. Conclusions Children with cancer are more likely to die within 30 days if infected with SARS-CoV-2. However, timely treatment reduced odds of death. This report provides crucial information to balance the benefits of providing anticancer therapy against the risks of SARS-CoV-2 infection in children with cancer

Intramuscular myxoma of the cervical paraspinal muscle

Myxoma is a neoplasm of mesenchymal origin composed of undifferentiated stellate cells in a myxoid stroma. This tumor can develop in a variety of locations. Myxomas that arise from skeletal muscles are called intramuscular myxomas. They usually occur in large skeletal muscles. Only ten cases of these benign tumors involving the neck muscles were reported in literature. Of them, only three were located at the paraspinal muscles. A 64-year-old woman presented with occiptal and neck pain over 5 years noted an expansive painful lesion located at posterior cervical region with progressive volume increase in the last 12 months. Image exams revealed a large mass located in the left posterior region of the neck in contact with the C2, C3 and C4 laminae with no invasion of the vertebrea. Tumor total removal was performed through normal muscle margins and the vertebral periosteum was scraped. The tumor was encapsuleted, lobulated with a gray-white appearance. The histological examination yielded the diagnosis of intramuscular myxoma. Follow-up at 1 year showed complete resolution of preoperative symptoms and no evidence of local recurrence. In conclusion, although rare, intramuscular myxoma should be included in differential diagnosis of cervical paraspinal tumors. We reported the fourth case of intramuscular myxoma in the paraspinal musculature of the neck. Despite its benign characteristics, local recurrence was reported after subtotal resection. Tumor total removal should be the goal of surgery