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

Trauma management incorporating focused assessment with computed tomography in trauma (FACTT) - potential effect on survival

Background Immediate recognition of life-threatening conditions and injuries is the key to trauma management. To date, the impact of focused assessment with computed tomography in trauma (FACTT) has not been formally assessed. We aimed to find out whether the concept of using FACTT during primary trauma survey has a negative or positive effect on survival. Methods In a retrospective, multicentre study, we compared our time management and probability of survival (Ps) in major trauma patients who received FACTT during trauma resuscitation with the trauma registry of the German Trauma Society (DGU). FACTT is defined as whole-body computed tomography (WBCT) during primary trauma survey. We determined the probability of survival according to the Trauma and Injury Severity Score (TRISS), the Revised Injury Severity Classification score (RISC) and the standardized mortality ratio (SMR). Results We analysed 4.817 patients from the DGU database from 2002 until 2004, 160 (3.3%) were from our trauma centre at the Ludwig-Maximilians-University (LMU) and 4.657 (96.7%) from the DGU group. 73.2% were male with a mean age of 42.5 years, a mean ISS of 29.8. 96.2% had suffered from blunt trauma. Time from admission to FAST (focused assessment with sonography for trauma)(4.3 vs. 8.7 min), chest x-ray (8.1 vs. 16.0 min) and whole-body CT (20.7 vs. 36.6 min) was shorter at the LMU compared to the other trauma centres (p < 0.001). SMR calculated by TRISS was 0.74 (CI95% 0.40-1.08) for the LMU (p = 0.24) and 0.92 (CI95% 0.84-1.01) for the DGU group (p = 0.10). RISC methodology revealed a SMR of 0.69 (95%CI 0.47-0.92) for the LMU (p = 0.043) and 1.00 (95%CI 0.94-1.06) for the DGU group (p = 0.88). Conclusion Trauma management incorporating FACTT enhances a rapid response to life-threatening problems and enables a comprehensive assessment of the severity of each relevant injury. Due to its speed and accuracy, FACTT during primary trauma survey supports rapid decision-making and may increase survival

A multicenter, randomized controlled trial of immediate total-body CT scanning in trauma patients (REACT-2)

Contains fulltext : 110874.pdf (publisher's version ) (Open Access)BACKGROUND: Computed tomography (CT) scanning has become essential in the early diagnostic phase of trauma care because of its high diagnostic accuracy. The introduction of multi-slice CT scanners and infrastructural improvements made total-body CT scanning technically feasible and its usage is currently becoming common practice in several trauma centers. However, literature provides limited evidence whether immediate total-body CT leads to better clinical outcome then conventional radiographic imaging supplemented with selective CT scanning in trauma patients. The aim of the REACT-2 trial is to determine the value of immediate total-body CT scanning in trauma patients. METHODS/DESIGN: The REACT-2 trial is an international, multicenter randomized clinical trial. All participating trauma centers have a multi-slice CT scanner located in the trauma room or at the Emergency Department (ED). All adult, non-pregnant, severely injured trauma patients according to predefined criteria will be included. Patients in whom direct scanning will hamper necessary cardiopulmonary resuscitation or who require an immediate operation because of imminent death (both as judged by the trauma team leader) are excluded. Randomization will be computer assisted. The intervention group will receive a contrast-enhanced total-body CT scan (head to pelvis) during the primary survey. The control group will be evaluated according to local conventional trauma imaging protocols (based on ATLS guidelines) supplemented with selective CT scanning. Primary outcome will be in-hospital mortality. Secondary outcomes are differences in mortality and morbidity during the first year post trauma, several trauma work-up time intervals, radiation exposure, general health and quality of life at 6 and 12 months post trauma and cost-effectiveness. DISCUSSION: The REACT-2 trial is a multicenter randomized clinical trial that will provide evidence on the value of immediate total-body CT scanning during the primary survey of severely injured trauma patients. If immediate total-body CT scanning is found to be the best imaging strategy in severely injured trauma patients it could replace conventional imaging supplemented with CT in this specific group. TRIAL REGISTRATION: ClinicalTrials.gov: (NCT01523626)

The Relative Impact of Climate Change on the Extinction Risk of Tree Species in the Montane Tropical Andes.

There are widespread concerns that anthropogenic climate change will become a major cause of global biodiversity loss. However, the potential impact of climate change on the extinction risk of species remains poorly understood, particularly in comparison to other current threats. The objective of this research was to examine the relative impact of climate change on extinction risk of upper montane tree species in the tropical Andes, an area of high biodiversity value that is particularly vulnerable to climate change impacts. The extinction risk of 129 tree species endemic to the region was evaluated according to the IUCN Red List criteria, both with and without the potential impacts of climate change. Evaluations were supported by development of species distribution models, using three methods (generalized additive models, recursive partitioning, and support vector machines), all of which produced similarly high AUC values when averaged across all species evaluated (0.82, 0.86, and 0.88, respectively). Inclusion of climate change increased the risk of extinction of 18-20% of the tree species evaluated, depending on the climate scenario. The relative impact of climate change was further illustrated by calculating the Red List Index, an indicator that shows changes in the overall extinction risk of sets of species over time. A 15% decline in the Red List Index was obtained when climate change was included in this evaluation. While these results suggest that climate change represents a significant threat to tree species in the tropical Andes, they contradict previous suggestions that climate change will become the most important cause of biodiversity loss in coming decades. Conservation strategies should therefore focus on addressing the multiple threatening processes currently affecting biodiversity, rather than focusing primarily on potential climate change impacts

Formation et stabilité des photohydrates pyrimidiniques dans l’ADN

La photolyse ultraviolette (254 nm) de solutions aqueuses des copolymères poly(dC-dC) et poly(dA-dU) engendre lit formation d’hydrates pyrimidiniques. Il a été montré récemment que ce photoproduits étaient substrats de glycosylases bactériennes et de mammifères (Biochemistry. 28 : 6164, 1989). Une de ces enzymes de réparation, l’endonucléase III, a clé utilisée dans ce travail pour étudier la formation et la stabilité de cette importante classe de photoproduits pyrimidiniques dans les copolymères poly(dC-dC) et poly(dA-dU). L’irradiation du poly(dG-dC) à une dose de 100 kJ/m2 (254 nm) de lumière de l’ultraviolet lointain entraîne une conversion du résidu cytosyle en 2,2% d’hydrate de cytosine (hydroxy-6 dihydro-5,6 cytosine) et 0,09% d’hydrate d’uracile (hydroxy-6 dihydro-5,6 uracile). La stabilité des photohydrates pyrimidiniques a été étudiée en incubant les copolymères pendant une période de 24 heures à différentes températures après irradiation. L’hydrate de cytosine est stable lorsque la température est maintenue à 4°C. La stabilité de l’hydrate décroît avec l’augmentation de la température, la demi-vie étant de 75, 25 et 6 heures à des températures de 25°C, 37°C et 55°C respectivement. L’hydrate d’uracile dans le copolymère poly(dA-dU) irradié est stable à 4°C et à 25°C, et décroît avec une demi-vie de 6 heures à 37°C et de moins d’une demi-heure à 55°C. L’hydrate d’uracile et l’uracile ont été aussi détectés dans le poly(dG-dC) après une irradiation du copolymère. Une des conclusions majeures de ce travail est que l’hydrate de cytosine est relativement stable dans l’ADN à 37°C. De plus, lu décomposition de ce photoproduit s’effectue par désamination, conduisant à la formation de l’hydrate d’uracile. Ce dernier composé peut alors engendrer de l’uracile par déshydratation. La formation cl la stabilité des photohydrates pyrimidiniques dans l’ADN ont pu contribuer, au cours de l’évolution, au développement de diverses enzymes de réparation dont l’endonucléase III (et des activités enzymatiques analogues chez les organismes eucaryotes) et la glycosylase d’uracile