Self-force on a scalar charge in radial infall from rest using the Hadamard-WKB expansion

We present an analytic method based on the Hadamard-WKB expansion to calculate the self-force for a particle with scalar charge that undergoes radial infall in a Schwarzschild spacetime after being held at rest until a time t = 0. Our result is valid in the case of short duration from the start. It is possible to use the Hadamard-WKB expansion in this case because the value of the integral of the retarded Green's function over the particle's entire past trajectory can be expressed in terms of two integrals over the time period that the particle has been falling. This analytic result is expected to be useful as a check for numerical prescriptions including those involving mode sum regularization and for any other analytical approximations to self-force calculations.Comment: 22 pages, 2 figures, Physical Review D version along with the corrections given in the erratu

The calcilytic agent NPS 2143 rectifies hypocalcemia in a mouse model with an activating calcium-sensing-receptor (CaSR) mutation:relevance to autosomal dominant hypocalcemia type 1 (ADH1)

Autosomal dominant hypocalcemia type 1 (ADH1) is caused by germline gain-of-function mutations of the calcium-sensing receptor (CaSR) and may lead to symptomatic hypocalcemia, inappropriately low serum parathyroid hormone (PTH) concentrations and hypercalciuria. Negative allosteric CaSR modulators, known as calcilytics, have been shown to normalise the gain-of-function associated with ADH-causing CaSR mutations in vitro and represent a potential targeted therapy for ADH1. However, the effectiveness of calcilytic drugs for the treatment of ADH1-associated hypocalcemia remains to be established. We have investigated NPS 2143, a calcilytic compound, for the treatment of ADH1 by in vitro and in vivo studies involving a mouse model, known as Nuf, which harbors a gain-of-function CaSR mutation, Leu723Gln. Wild-type (Leu723) and Nuf mutant (Gln723) CaSRs were expressed in HEK293 cells and the effect of NPS 2143 on their intracellular calcium responses determined by flow cytometry. NPS 2143 was also administered as a single intraperitoneal bolus to wild-type and Nuf mice and plasma concentrations of calcium and PTH, and urinary calcium excretion measured. In vitro administration of NPS 2143 decreased the intracellular calcium responses of HEK293 cells expressing the mutant Gln723 CaSR in a dose-dependent manner, thereby rectifying the gain-of-function associated with the Nuf mouse CaSR mutation. Intraperitoneal injection of NPS 2143 in Nuf mice led to significant increases in plasma calcium and PTH without elevating urinary calcium excretion. These studies of a mouse model with an activating CaSR mutation demonstrate NPS 2143 to normalize the gain-of-function causing ADH1, and improve the hypocalcemia associated with this disorder

<i>Zygomaticus major</i> muscle bony attachment site:a Thiel-embalmed cadaver study

Objective: Thezygomaticus major is a principal muscle of facial expression which is engaged when smiling. The zygomaticus major origin of the zygomatic bone is often discussed relevant to its importance in the field of plastic surgery. In addition, the zygomaticus major attachment site is also significant for forensic craniofacial reconstruction, separating the cheek into frontal and lateral surfaces. However, there are discrepancies amongst published articles regarding the precise origin of the zygomaticus major muscle. The aim of this study is to investigate more distinctive and palpable landmarks as the bony attachment of the zygomaticus major. Methods: This project is the first zygomaticus major dissection study utilising Thiel embalmed cadavers. Fifty-two facial dissections were investigated in 26 Thiel embalmed bodies, bequeathed to the Centre for Anatomy and Human Identification at The University of Dundee between 2013 and 2015. Results: This study found that the origin of zygomaticus major muscle was located at the superior margin of the temporal process on the lateral surface of zygomatic bone. Moreover, the zygomaticus major muscle overlapped the anterosuperior border of the masseter muscle. One out of 52 zygomaticus major muscles presented bifurcation. Conclusion: The origin site of zygomaticus major is considered important to increase resemblance in forensic craniofacial reconstruction. Furthermore, since zygomaticus major is a salient muscle involved in facial expression, the potential effects for cosmetic/surgical procedures are also relevant to the medical field and successful surgical outcomes. The current study provided easily palpable landmarks of zygomaticus major origin site which is beneficial for both surgeons and forensic craniofacial reconstruction practitioners. © 202

Wavy stripes and squares in zero P number convection

A simple model to explain numerically observed behaviour of chaotically varying stripes and square patterns in zero Prandtl number convection in Boussinesq fluid is presented. The nonlinear interaction of mutually perpendicular sets of wavy rolls, via higher mode, may lead to a competition between the two sets of wavy rolls. The appearance of square patterns is due to the secondary forward Hopf bifurcation of a set of wavy rolls.Comment: 8 pages and 3 figures, late

Principle of Maximum Entropy Applied to Rayleigh-B\'enard Convection

A statistical-mechanical investigation is performed on Rayleigh-B\'enard convection of a dilute classical gas starting from the Boltzmann equation. We first present a microscopic derivation of basic hydrodynamic equations and an expression of entropy appropriate for the convection. This includes an alternative justification for the Oberbeck-Boussinesq approximation. We then calculate entropy change through the convective transition choosing mechanical quantities as independent variables. Above the critical Rayleigh number, the system is found to evolve from the heat-conducting uniform state towards the convective roll state with monotonic increase of entropy on the average. Thus, the principle of maximum entropy proposed for nonequilibrium steady states in a preceding paper is indeed obeyed in this prototype example. The principle also provides a natural explanation for the enhancement of the Nusselt number in convection.Comment: 13 pages, 4 figures; typos corrected; Eq. (66a) corrected to remove a double counting for $k_{\perp}=0$; Figs. 1-4 replace

Quasiperiodic waves at the onset of zero Prandtl number convection with rotation

We show the possibility of quasiperiodic waves at the onset of thermal convection in a thin horizontal layer of slowly rotating zero-Prandtl number Boussinesq fluid confined between stress-free conducting boundaries. Two independent frequencies emerge due to an interaction between a stationary instability and a self-tuned wavy instability in presence of coriolis force, if Taylor number is raised above a critical value. Constructing a dynamical system for the hydrodynamical problem, the competition between the interacting instabilities is analyzed. The forward bifurcation from the conductive state is self-tuned.Comment: 9 pages of text (LaTex), 5 figures (Jpeg format

Nephrogenic syndrome of inappropriate antidiuresis secondary to an activating mutation in the arginine vasopressin receptor AVPR2.

CONTEXT: Nephrogenic syndrome of inappropriate antidiuresis (NSIAD), resulting from activating mutations in the arginine vasopressin receptor type 2 (AVPR2), is a rare cause of hyponatraemia. However, its true prevalence may be underestimated and it should be considered in the investigation of unexplained hyponatraemia, with implications for management and targeted gene testing. OBJECTIVE: We describe a structured approach to the investigation of hyponatraemia in a young patient, which allowed a diagnosis of NSIAD to be made. We review current knowledge of NSIAD and use a structural modelling approach to further our understanding of the potential mechanisms by which the causative mutation leads to a constitutively active AVPR2. DESIGN: Clinical and biochemical investigation of hyponatraemia; a formal water load test with measurement of arginine vasopressin levels (AVP); sequencing of AVPR2; and computed structural modelling of the wild-type and constitutively activated mutant receptors. RESULTS: A 38-year-old man presented with intermittent confusion and nausea associated with hyponatraemia and a biochemical picture consistent with syndrome of inappropriate antidiuretic hormone (SIADH). Adrenocortical and thyroid function and an acute intermittent porphyria screen were normal. Cross-sectional imaging of the head, chest and abdomen did not identify an underlying cause and so we proceeded to a water load test. This demonstrated a marked inability to excrete a free water load (just 15% of a 20 ml/kg oral load by 240 min postingestion), with the onset of hyponatraemia (Na(+) 125 mmol/l, urine osmolality 808 mOsm/kg). However, AVP levels were low throughout the test (0·4-0·9 pmol/l), consistent with a diagnosis of NSIAD. AVPR2 sequencing revealed a previously described hemizygous activating mutation (p.Arg137Cys). Through structural modelling of AVPR2, we suggest that disruption of a hydrogen bond between residues Thr269 and Arg137 may promote stabilization of the receptor in its active conformation. Since diagnosis, the patient has adhered to modest fluid restriction and remained well, with no further episodes of hyponatraemia. CONCLUSION: NSIAD should be considered in young patients with unexplained hyponatraemia. A water load test with AVP measurement is a potentially informative investigation, while AVPR2 sequencing provides a definitive molecular genetic diagnosis and a rationale for long-term fluid restriction.ASP and MG are supported by the National Institute of Health Research Cambridge Biomedical Research Centre.This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1111/cen.1301

Review article: pathogenesis and clinical manifestations of gastrointestinal involvement in systemic sclerosis.

BACKGROUND: Gastrointestinal tract (GIT) involvement is a common cause of debilitating symptoms in patients with systemic sclerosis (SSc). There are no disease modifying therapies for this condition and the treatment remains symptomatic, largely owing to the lack of a clear understanding of its pathogenesis. AIMS: To investigate novel aspects of the pathogenesis of gastrointestinal involvement in SSc. To summarise existing knowledge regarding the cardinal clinical gastrointestinal manifestations of SSc and its pathogenesis, emphasising recent investigations that may be valuable in identifying potentially novel therapeutic targets. METHODS: Electronic (PubMed/Medline) and manual Google search. RESULTS: The GIT is the most common internal organ involved in SSc. Any part of the GIT from the mouth to the anus can be affected. There is substantial variability in clinical manifestations and disease course and symptoms are nonspecific and overlapping for a particular anatomical site. Gastrointestinal involvement can occur in the absence of cutaneous disease. Up to 8% of SSc patients develop severe GIT symptoms. This subset of patients display increased mortality with only 15% survival at 9 years. Dysmotiity of the GIT causes the majority of symptoms. Recent investigations have identified a novel mechanism in the pathogenesis of GIT dysmotility mediated by functional anti-muscarinic receptor autoantibodies. CONCLUSIONS: Despite extensive investigation, the pathogenesis of gastrointestinal involvement in systemic sclerosis remains elusive. Although treatment currently remains symptomatic, an improved understanding of novel pathogenic mechanisms may allow the development of potentially highly effective approaches including intravenous immunoglobulin and microRNA based therapeutic interventions

TOWARD THE MINIMUM INNER EDGE DISTANCE OF THE HABITABLE ZONE

We explore the minimum distance from a host star where an exoplanet could potentially be habitable in order not to discard close-in rocky exoplanets for follow-up observations. We find that the inner edge of the Habitable Zone for hot desert worlds can be as close as 0.38 AU around a solar-like star, if the greenhouse effect is reduced (~1% relative humidity) and the surface albedo is increased. We consider a wide range of atmospheric and planetary parameters such as the mixing ratios of greenhouse gases (water vapor and CO[subscript 2]), surface albedo, pressure, and gravity. Intermediate surface pressure (~1-10 bars) is necessary to limit water loss and to simultaneously sustain an active water cycle. We additionally find that the water loss timescale is influenced by the atmospheric CO[subscript 2] level, because it indirectly influences the stratospheric water mixing ratio. If the CO[subscript 2] mixing ratio of dry planets at the inner edge is smaller than 10[superscript –4], the water loss timescale is ~1 billion years, which is considered here too short for life to evolve. We also show that the expected transmission spectra of hot desert worlds are similar to an Earth-like planet. Therefore, an instrument designed to identify biosignature gases in an Earth-like atmosphere can also identify similarly abundant gases in the atmospheres of dry planets. Our inner edge limit is closer to the host star than previous estimates. As a consequence, the occurrence rate of potentially habitable planets is larger than previously thought