Hydrostatic Expansion and Spin Changes During Type I X-Ray Bursts

We present calculations of the spin-down of a neutron star atmosphere due to hydrostatic expansion during a Type I X-ray burst. We show that (i) Cumming and Bildsten overestimated the spin-down of rigidly-rotating atmospheres by a factor of two, and (ii) general relativity has a small (5-10%) effect on the angular momentum conservation law. We rescale our results to different neutron star masses, rotation rates and equations of state, and present some detailed rotational profiles. Comparing with recent observations of large frequency shifts in MXB 1658-298 and 4U 1916-053, we find that the spin-down expected if the atmosphere rotates rigidly is a factor of two to three less than the observed values. If differential rotation is allowed to persist, we find that the upper layers of the atmosphere spin down by an amount comparable to the observed values; however, there is no compelling reason to expect the observed spin frequency to be that of only the outermost layers. We conclude that hydrostatic expansion and angular momentum conservation alone cannot account for the largest frequency shifts observed during Type I bursts.Comment: Submitted to the Astrophysical Journal (13 pages, including 4 figures

Inverse non-linear problem of the long wave run-up on coast

The study of the process of catastrophic tsunami-type waves on the coast makes it possible to determine the destructive force of waves on the coast. In hydrodynamics, the one-dimensional theory of the run-up of non-linear waves on a flat slope has gained great popularity, within which rigorous analytical results have been obtained in the class of non-breaking waves. In general, the result depends on the characteristics of the wave approaching (or generated on) the slope, which is usually not known in the measurements. Here we describe a rigorous method for recovering the initial displacement in a source localised in an inclined power-shaped channel from the characteristics of a moving shoreline. The method uses the generalised Carrier-Greenspan transformation, which allows one-dimensional non-linear shallow-water equations to be reduced to linear ones. The solution is found in terms of Erd\'elyi-Kober integral operator. Numerical verification of our results is presented for the cases of a parabolic bay and an infinite plane beach.Comment: 15 pages, 8 figure

An analytic solution for weak-field Schwarzschild geodesics

It is well known that the classical gravitational two body problem can be transformed into a spherical harmonic oscillator by regularization. We find that a modification of the regularization transformation has a similar result to leading order in general relativity. In the resulting harmonic oscillator, the leading-order relativistic perturbation is formally a negative centrifugal force. The net centrifugal force changes sign at three Schwarzschild radii, which interestingly mimics the innermost stable circular orbit (ISCO) of the full Schwarzschild problem. Transforming the harmonic-oscillator solution back to spatial coordinates yields, for both timelike and null weak-field Schwarzschild geodesics, a solution for $t,r,\phi$ in terms of elementary functions of a variable that can be interpreted as a generalized eccentric anomaly. The textbook expressions for relativistic precession and light deflection are easily recovered. We suggest how this solution could be combined with additional perturbations into numerical methods suitable for applications such as relativistic accretion or dynamics of the Galactic-centre stars.Comment: 8 pages; Published in the MNRAS; The definitive version is available at www.blackwell-synergy.co

Pregnancy after living kidney donation, a systematic review of the available evidence, and a review of the current guidance

Understanding and communicating the risk of pregnancy complications post-living kidney donation is imperative as the majority of living kidney donors (LKD) are women of childbearing age. We aimed to identify all original research articles examining complications in post-donation pregnancies and compared the quality and consistency of related guidelines. We searched Embase, MEDLINE, PubMed, society webpages, and guideline registries for English-language publications published up until December 18, 2020. Ninety-three articles were screened from which 16 studies were identified, with a total of 1399 post-donation pregnancies. The outcome of interest, post-donation pregnancy complications, was not calculable, and only a narrative synthesis of the evidence was possible. The absolute risk of pre-eclampsia increased from ~1%–3% pre-donation (lower than the general population) to ~4%–10% post-donation (comparable to the general population). The risks of adverse fetal and neonatal outcomes were no different between post-donation and pre-donation pregnancies. Guidelines and consensus statements were consistent in stating the need to inform LKDs of their post-donation pregnancy risk, however, the depth and scope of this guidance were variable. While the absolute risk of pregnancy complications remains low post-donation, a concerted effort is required to better identify and individualize risk in these women, such that consent to donation is truly informed

MicroRNAs in AKI and kidney transplantation

MicroRNAs are epigenetic regulators of gene expression at the posttranscriptional level. They are involved in intercellular communication and crosstalk between different organs. As key regulators of homeostasis, their dysregulation underlies several morbidities including kidney disease. Moreover, their remarkable stability in plasma and urine makes them attractive biomarkers. Beyond biomarker studies, clinical microRNA research in nephrology in recent decades has focused on the discovery of specific microRNA signatures and the identification of novel targets for therapy and/or disease prevention. However, much of this research has produced equivocal results and there is a need for standardization and confirmation in prospective trials. This review aims to provide an overview of general concepts and available clinical evidence in both the pathophysiology and biomarker fields for the role of microRNA in AKI and kidney transplantation

The future of European Nephrology 'Guidelines' - a declaration of intent by European Renal Best Practice (ERBP)

The disparities of medical practice, together with a growing number of possible interventions, have increased the demand for well-conceived guidance for practitioners [1]. However, this development is hampered by the number and quality of scientific studies that test medical hypotheses, which are often unsatisfactory. This is especially true in nephrology, where well-conducted controlled trials are rare [2]. Because patients with renal failure are generally excluded from controlled studies in the general population [3], the development of sufficiently well-founded guidance in nephrology has always been difficult. With the development of European Best Practice Guidelines (EBPG), the European Renal Association–European Dialysis and Transplantation Association (ERA–EDTA) has created its own guidance-generating process. Similar initiatives have also arisen in the USA (Kidney Disease Outcome Initiative—K/DOQI), Australia (Caring for Australasians with Renal Impairment—CARI), Canada (Canadian Society of Nephrology—CSN), the UK (United Kingdom Renal Association—UKRA), as well as at several other locations around the world. These institutions have generated a plethora of often parallel recommendations on similar topics but sometimes with different messages [4]. The question can be asked: ‘Is there still a place for an institution generating European nephrology guidance?’ If there is, how should such an initiative be managed to conform with current demands? To answer these questions, the Council of ERA–EDTA set up a commission that convened three times in the course of 2008–09. The present text is a distillation of the discussions, reflections and final conclusions of this commission. It is an ad hoc document, reflecting the current status. In the future, concepts and attitudes might change, as medical thinking is influenced by changes in practice, needs, general philosophy, ethics and political/financial conditions

Protocol for a phase IV, open-label feasibility study investigating non-invasive markers of hepatic fibrosis in people living with HIV-1 and non-alcoholic fatty liver disease randomised to receiving optimised background therapy (OBT) plus maraviroc or OBT alone

Introduction At least 30% of people living with HIV (PLWH) infection have non-alcoholic fatty liver disease (NAFLD), which has now become a leading cause of hepatic fibrosis and cirrhosis. Management is based largely on lifestyle modifications, which are difficult to achieve, and therapeutic options are urgently needed. Maraviroc (MVC), through antagonism of CCR5 receptors, may reduce hepatic fibrosis progression and could be an effective treatment for NAFLD. However, dosing is usually two times per day, unlike most currently recommended antiretroviral therapies. This study will investigate the feasibility and acceptability of addition of MVC to combination antiretroviral therapy in PLWH and NAFLD as a treatment for NAFLD. Methods and analysis This is a phase IV, randomised, open-label, non-invasive feasibility study. Sixty individuals with well-controlled HIV-1 and NAFLD will be recruited from UK HIV clinics and randomised 1:1 to receive either optimised background therapy (OBT) plus MVC or OBT alone. Follow-up will be every 24 weeks for 96 weeks. The primary outcome measures will include recruitment and retention rates, adverse events and adherence. Secondary outcomes will include changes in markers of hepatic fibrosis, including the Enhanced Liver Fibrosis score, median liver stiffness measurement and controlled attenuation parameter scores on Fibroscan, and quality of life assessments. Analyses will be performed according to intention-to-treat principles. For secondary outcomes, estimated differences and 95% CIs between the groups using a t-method will be presented for continuous variables and as exact 95% binomial CIs for categorical variables. Ethics and dissemination Ethical approval was obtained through the London Dulwich UK Research Ethics Committee (reference 17/LO/2093). Results will be disseminated both through community groups and peer-reviewed scientific literature

Management of obesity in kidney transplant candidates and recipients: A clinical practice guideline by the DESCARTES Working Group of ERA

The clinical practice guideline Management of Obesity in Kidney Transplant Candidates and Recipients was developed to guide decision-making in caring for people with end-stage kidney disease (ESKD) living with obesity. The document considers the challenges in defining obesity, weighs interventions for treating obesity in kidney transplant candidates as well as recipients and reflects on the impact of obesity on the likelihood of wait-listing as well as its effect on transplant outcomes. It was designed to inform management decisions related to this topic and provide the backdrop for shared decision-making. This guideline was developed by the European Renal Association's Developing Education Science and Care for Renal Transplantation in European States working group. The group was supplemented with selected methodologists to supervise the project and provide methodological expertise in guideline development throughout the process. The guideline targets any healthcare professional treating or caring for people with ESKD being considered for kidney transplantation or having received a donor kidney. This includes nephrologists, transplant physicians, transplant surgeons, general practitioners, dialysis and transplant nurses. Development of this guideline followed an explicit process of evidence review. Treatment approaches and guideline recommendations are based on systematic reviews of relevant studies and appraisal of the quality of the evidence and the strength of recommendations followed the Grading of Recommendations Assessment, Development and Evaluation approach. Limitations of the evidence are discussed and areas of future research are presented