On the Origin of Gravity and the Laws of Newton

Starting from first principles and general assumptions Newton's law of gravitation is shown to arise naturally and unavoidably in a theory in which space is emergent through a holographic scenario. Gravity is explained as an entropic force caused by changes in the information associated with the positions of material bodies. A relativistic generalization of the presented arguments directly leads to the Einstein equations. When space is emergent even Newton's law of inertia needs to be explained. The equivalence principle leads us to conclude that it is actually this law of inertia whose origin is entropic.Comment: 29 pages, 6 figure

Spectral analysis of the biharmonic operator subject to Neumann boundary conditions on dumbbell domains

We consider the biharmonic operator subject to homogeneous boundary conditions of Neumann type on a planar dumbbell domain which consists of two disjoint domains connected by a thin channel. We analyse the spectral behaviour of the operator, characterizing the limit of the eigenvalues and of the eigenprojections as the thickness of the channel goes to zero. In applications to linear elasticity, the fourth order operator under consideration is related to the deformation of a free elastic plate, a part of which shrinks to a segment. In contrast to what happens with the classical second order case, it turns out that the limiting equation is here distorted by a strange factor depending on a parameter which plays the role of the Poisson coefficient of the represented plate.Comment: To appear in "Integral Equations and Operator Theory

On the accuracy of aerosol photoacoustic spectrometer calibrations using absorption by ozone

This is the final version of the article. Available from EGU via the DOI in this record.In recent years, photoacoustic spectroscopy has emerged as an invaluable tool for the accurate measurement of light absorption by atmospheric aerosol. Photoacoustic instruments require calibration, which can be achieved by measuring the photoacoustic signal generated by known quantities of gaseous ozone. Recent work has questioned the validity of this approach at short visible wavelengths (404 nm), indicating systematic calibration errors of the order of a factor of 2. We revisit this result and test the validity of the ozone calibration method using a suite of multipass photoacoustic cells operating at wavelengths 405, 514 and 658 nm. Using aerosolised nigrosin with mobility-selected diameters in the range 250-425 nm, we demonstrate excellent agreement between measured and modelled ensemble absorption cross sections at all wavelengths, thus demonstrating the validity of the ozone-based calibration method for aerosol photoacoustic spectroscopy at visible wavelengths.This work was funded by the Met Office. In addition, Nicholas W. Davies was supported by a NERC/Met Office Industrial Case studentship (ref 640052003). Michael I. Cotterell was supported by a Tom West Analytical Chemistry Trust Fund Fellowship. Michael I. Cotterell and Jim M. Haywood were supported by the CLARIFY-2017 Natural Environment Research Council funded proposal (NE/L013797/1)

Safety of benzodiazepines and opioids in interstitial lung disease: A national prospective study

Copyright ©ERS 2018 Safety concerns are a barrier to prescribing benzodiazepines (BDZs) and opioids in interstitial lung disease (ILD). We therefore examined the association of BDZs and opioids on risk of admission to hospital and death. We conducted a population-based longitudinal cohort study of fibrotic ILD patients starting long-term oxygen therapy in Sweden between October 2005 and December 2014. Effects of BDZs and opioids on rates of admission to hospital and mortality were analysed using Fine-Gray and Cox regression while adjusting for potential confounders. We included 1603 patients (61% females). BDZs were used by 196 (12%) patients and opioids were used by 254 (15%) patients. There was no association between BDZs and increased admission. Treatment with high- versus low-dose BDZs was associated with increased mortality (subdistribution hazard ratio (SHR) 1.46, 95% CI 1.08-1.98 versus 1.13, 95% CI 0.92-1.38). Opioids showed no association with increased admission. Neither low-dose opioids (30 mg·day −1 oral morphine equivalent) (SHR 1.18, 95% CI 0.96-1.45) nor high-dose opioids (>30 mg·day −1 oral morphine equivalent) (SHR 1.11, 95% CI 0.89-1.39) showed association with increased mortality. This first ever study to examine associations between BDZ and opioid use and harm in ILD supports the use of opioids and low-dose BDZs in severely ill patients with respiratory compromise

Ethical considerations of use of hold-out sets in clinical prediction model management

Clinical prediction models are statistical or machine learning models used toquantify the risk of a certain health outcome using patient data. These can theninform potential interventions on patients, causing an effect called performativeprediction: predictions inform interventions which influence the outcome theywere trying to predict, leading to a potential underestimation of risk in somepatients if a model is updated on this data. One suggested resolution to this isthe use of hold-out sets, in which a set of patients do not receive model derivedrisk scores, such that a model can be safely retrained. We present an overview ofclinical and research ethics regarding potential implementation of hold-out setsfor clinical prediction models in health settings. We focus on the ethical principles of beneficence, non-maleficence, autonomy and justice. We also discussinformed consent, clinical equipoise, and truth-telling. We present illustrativecases of potential hold-out set implementations and discuss statistical issues arising from different hold-out set sampling methods. We also discuss differencesbetween hold-out sets and randomised control trials, in terms of ethics and statistical issues. Finally, we give practical recommendations for researchers interestedin the use hold-out sets for clinical prediction models

Enhancing plasma membrane NADPH oxidase activity increases current output by diatoms in biophotovoltaic devices

Biophotovoltaic (BPV) devices employ the photosynthetic activity of microalgae or cyanobacteria to harvest light energy and generate electrical current directly as a result of the release of electrons from the algal cells. NADPH oxidases (NOX) are plasma-membrane enzymes that transport electrons from the cytosol to generate extracellular superoxide anions, and have been implicated in BPV output. In this study, we investigated NOX activity in the diatoms, Phaeodactylum tricornutum and Thalassiosira pseudonana in an attempt to understand and enhance NOX and BPV function. We found that NOX activity was linked to defined growth regimes and growth phases, and was light dependent. Crucially, current output in a BPV device correlated with NOX activity, and levels of up to 14 μA per 106 cells (approximately 500 mA.m-2) were obtained. Expression of two putative P. tricornutum NOX genes (PtNOX1 and PtNOX2) was found to correspond with the observed growth patterns of superoxide anion production and power output, suggesting these are responsible for the observed patterns of NOX activity. Crucially, we demonstrate that NOX activity levels could be enhanced via semi-continuous culturing, pointing to the possibility of maintaining long-term power output in BPV devices.This work was supported by the United Kingdom Engineering and Physical Sciences Research Council (EPSRC), grant reference EP/F047940/1.This is the final version of the article. It first appeared from Elsevier via http://dx.doi.org/10.1016/j.algal.2015.08.00

Access to quality care after injury in Northern Malawi:results of a household survey

Background Most injury care research in low-income contexts such as Malawi is facility centric. Community-derived data is needed to better understand actual injury incidence, health system utilisation and barriers to seeking care following injury.MethodsWe administered a household survey to 2200 households in Karonga, Malawi. The primary outcome was injury incidence, with non-fatal injuries classified as major or minor (&gt; 30 or 1-29 disability days respectively). Those seeking medical treatment were asked about time delays to seeking, reaching and receiving care at a facility, where they sought care, and whether they attended a second facility. We performed analysis for associations between injury severity and whether the patient sought care, stayed overnight in a facility, attended a second facility, or received care within 1 or 2 hours. The reason for those not seeking care was asked. ResultsMost households (82.7%) completed the survey, with 29.2% reporting an injury. Overall, 611 non-fatal and four fatal injuries were reported from 531 households: an incidence of 6900 per 100,000. Major injuries accounted for 26.6%. Three quarters, 76.1% (465/611), sought medical attention. Almost all, 96.3% (448/465), seeking care attended a primary facility first. Only 29.7% (138/465), attended a second place of care. Only 32.0% (142/444), received care within one hour. A further 19.1% (85/444) received care within 2 hours. Major injury was associated with being more likely to have; sought care (94.4% vs 69.8% p&lt;0.001), stayed overnight at a facility (22.9% vs 15.4% P=0.047), attended a second place of care (50.3% vs 19.9%, P&lt;0.001). For those not seeking care the most important reason was the injury not being serious enough for 52.1% (74/142), followed by transport difficulties 13.4% (19/142) and financial costs 5.6% (8/142).ConclusionInjuries in Northern Malawi are substantial. Community-derived details are necessary to fully understand injury burden and barriers to seeking and reaching care. <br/