Multiphase PC/PL Relations: Comparison between Theory and observations

Cepheids are fundamental objects astrophysically in that they hold the key to a CMB independent estimate of Hubble's constant. A number of researchers have pointed out the possibilities of breaking degeneracies between Omega_Matter and H0 if there is a CMB independent distance scale accurate to a few percent (Hu 2005). Current uncertainties in the distance scale are about 10% but future observations, with, for example, the JWST, will be capable of estimating H0 to within a few percent. A crucial step in this process is the Cepheid PL relation. Recent evidence has emerged that the PL relation, at least in optical bands, is nonlinear and that neglect of such a nonlinearity can lead to errors in estimating H0 of up to 2 percent. Hence it is important to critically examine this possible nonlinearity both observationally and theoretically. Existing PC/PL relations rely exclusively on evaluating these relations at mean light. However, since such relations are the average of relations at different phases. Here we report on recent attempts to compare theory and observation in the multiphase PC/PL planes. We construct state of the art Cepheid pulsations models appropriate for the LMC/Galaxy and compare the resulting PC/PL relations as a function of phase with observations. For the LMC, the (V-I) period-color relation at minimum light can have quite a narrow dispersion (0.2-0.3 mags) and thus could be useful in placing constraints on models. At longer periods, the models predict significantly redder (by about 0.2-0.3 mags) V-I colors. We discuss possible reasons for this and also compare PL relations at various phases of pulsation and find clear evidence in both theory and observations for a nonlinear PL relation.Comment: 5 pages, 8 figures, proceeding for "Stellar Pulsation: Challenges for Theory and Observation", Santa Fe 200

Nonequilibrium radiation measurements and modelling relevant to Titan entry

An update to a collisional-radiative model developed by Magin1 for Huygens Titan atmospheric entry is proposed. The model is designed to predict the nonequilibrium populations and the radiation emitted from cyanogen and nitrogen during the entry of the Huygens probe into the Titan atmosphere. Radiation during Titan entry is important at lower speeds (around 5 – 6 km/s) more so than other planetary entries due to the formation of cyanogen in the shock layer, which is a highly radiative species. The model has been tested against measurements obtained with the EAST shock tube of NASA Ames Research Centre.1,2 The motivation for the update is due to the large discrepancies shown in the postshock fall-off rates of the radiation when compared to the experimental EAST shock tube test results. Modifications were made to the reaction rates used to calculate the species concentrations in the flow field. The reaction that was deemed most influential for the radiation fall off rate was the dissociation of molecular nitrogen. The model with modified reaction rates showed significantly better agreement with the EAST data. This paper also includes experimental results for radiation and spectra for Titan entry. Experiments were performed on the University of Queensland's X2 expansion tube. Spectra were recorded at various positions behind the shock. This enabled the construction of radiation profiles for Titan entry, as well as wavelength plots to identify various radiating species, in this case, predominately CN violet. This paper includes radiation profiles to compare with experiments performed at NASA Ames. It is planned that further experiments will be performed to cover a larger pressure range than NASA Ames. Good qualitative agreement has so far been obtained between our data and NASA Ames, however, it should be noted at the time of printing, the experimental spectrum have not been calibrated absolutely

Period-Color and Amplitude-Color Relations in Classical Cepheid Variables - VI. New Challenges for Pulsation Models

We present multiphase Period-Color/Amplitude-Color/Period-Luminosity relations using OGLE III and Galactic Cepheid data and compare with state of the art theoretical pulsation models. Using this new way to compare models and observations, we find convincing evidence that both Period-Color and Period-Luminosity Relations as a function of phase are dynamic and highly nonlinear at certain pulsation phases. We extend this to a multiphase Wesenheit function and find the same result. Hence our results cannot be due to reddening errors. We present statistical tests and the urls of movies depicting the Period-Color/Period Luminosity and Wesenheit relations as a function of phase for the LMC OGLE III Cepheid data: these tests and movies clearly demonstrate nonlinearity as a function of phase and offer a new window toward a deeper understanding of stellar pulsation. When comparing with models, we find that the models also predict this nonlinearity in both Period-Color and Period-Luminosity planes. The models with (Z=0.004, Y=0.25) fare better in mimicking the LMC Cepheid relations, particularly at longer periods, though the models predict systematically higher amplitudes than the observations

Numerical investigation of three types of space and time fractional Bloch-Torrey equations in 2D

Recently, the fractional Bloch-Torrey model has been used to study anomalous diffusion in the human brain. In this paper, we consider three types of space and time fractional Bloch-Torrey equations in two dimensions: Model-1 with the Riesz fractional derivative; Model-2 with the one-dimensional fractional Laplacian operator; and Model-3 with the two-dimensional fractional Laplacian operator. Firstly, we propose a spatially second-order accurate implicit numerical method for Model-1 whereby we discretize the Riesz fractional derivative using a fractional centered difference. We consider a finite domain where the time and space derivatives are replaced by the Caputo and the sequential Riesz fractional derivatives, respectively. Secondly, we utilize the matrix transfer technique for solving Model-2 and Model-3. Finally, some numerical results are given to show the behaviours of these three models especially on varying domain sizes with zero Dirichlet boundary conditions

Constant Curvature Coefficients and Exact Solutions in Fractional Gravity and Geometric Mechanics

We study fractional configurations in gravity theories and Lagrange mechanics. The approach is based on Caputo fractional derivative which gives zero for actions on constants. We elaborate fractional geometric models of physical interactions and we formulate a method of nonholonomic deformations to other types of fractional derivatives. The main result of this paper consists in a proof that for corresponding classes of nonholonomic distributions a large class of physical theories are modelled as nonholonomic manifolds with constant matrix curvature. This allows us to encode the fractional dynamics of interactions and constraints into the geometry of curve flows and solitonic hierarchies.Comment: latex2e, 11pt, 27 pages, the variant accepted to CEJP; added and up-dated reference

Ergosterol Effect on the Desaturation of 14C-Cis-Vaccenate in Tetrahymena

Supplement of ergosterol to the growth medium of the ciliated protozoan Tetrahymena pyriformis W leads to incorporation of the foreign sterol within cell membranes and suppression of synthesis of the native sterol-like compound tetrahymanol, as well as to changes in the fatty acid compositions of several major classes of membrane lipid. Alteration of fatty acid composition is thought to represent a regulatory mechanism whereby optimum membrane fluidity is maintained when the slightly dissimilar foreign sterol is added into the phospholipid bilayer of the membranes. The present study, using several different conditions of growth temperature, substrate concentrations and incubation time, and ergosterol concentrations and exposure time, is an attempt to provide evidence supporting a hypothetical regulatory mechanism. This mechanism proposes that there is a feedback regulation by membrane-bound sterol on an enzyme or enzymes involved in synthesis of the long chain fatty acids contained in membrane phospholipid. Such a mechanism could account for the balance between sterol and fatty acid content of membrane. The data presented here show that a statistically significant increase in desaturation of 14C-cis-vaccenate can be demonstrated in Tetrahymena cell cultures whose membranes contain the foreign sterol, when growth temperature is maintained at 20° or 29.5°. Tetrahymena desaturated 14C-cis-vaccenate substrate in both ergosterol supplemented and normal cultures. The 14C labeled product, 6,11-18:2 was recovered and separated by silver nitrate-Unisil column chromatography

Psychiatry out-of-hours: a focus group study of GPs' experiences in Norwegian casualty clinics

Background: For Norwegian general practitioners (GPs), acute treatment of mental illness and substance abuse are among the most commonly experienced emergency situations in out-of-hours primary healthcare. The largest share of acute referrals to emergency psychiatric wards occurs out-of-hours, and out-of-hours services are responsible for a disproportionately high share of compulsory referrals. Concerns exist regarding the quality of mental healthcare provided in the out-of-hours setting. The aim of this study was to explore which challenges GPs experience when providing emergency care out-of-hours to patients presenting problems related to mental illness or substance abuse. Methods: We conducted a qualitative study based on two individual interviews and six focus groups with purposively sampled GPs (totally 45 participants). The interviews were analysed successively in an editing style, using a thematic approach based on methodological descriptions by Charmaz and Malterud. Results: Safety and uncertainty were the dominating themes in the discussions. The threat to personal safety due to unpredictable patient behaviour was a central concern, and present security precautions in the out-of-hours services were questioned. The GPs expressed high levels of uncertainty in their work with patients presenting problems related to mental illness or substance abuse. The complexity of the problems presented, shortage of time, limited access to reliable information and limited range of interventions available during out-of-hours contributed to this uncertainty. Perceived access to second opinion seemed to have a major impact on subjectively experienced work stress. Conclusions: The GPs experienced out-of-hours psychiatry as a field with high levels of uncertainty and limited support to help them meet the experienced challenges. This might influence the quality of care provided. If the current organisation of emergency mental healthcare is to be kept, we need to provide GPs with a better support framework out-of-hours

Fractional dynamics pharmacokinetics–pharmacodynamic models

While an increasing number of fractional order integrals and differential equations applications have been reported in the physics, signal processing, engineering and bioengineering literatures, little attention has been paid to this class of models in the pharmacokinetics–pharmacodynamic (PKPD) literature. One of the reasons is computational: while the analytical solution of fractional differential equations is available in special cases, it this turns out that even the simplest PKPD models that can be constructed using fractional calculus do not allow an analytical solution. In this paper, we first introduce new families of PKPD models incorporating fractional order integrals and differential equations, and, second, exemplify and investigate their qualitative behavior. The families represent extensions of frequently used PK link and PD direct and indirect action models, using the tools of fractional calculus. In addition the PD models can be a function of a variable, the active drug, which can smoothly transition from concentration to exposure, to hyper-exposure, according to a fractional integral transformation. To investigate the behavior of the models we propose, we implement numerical algorithms for fractional integration and for the numerical solution of a system of fractional differential equations. For simplicity, in our investigation we concentrate on the pharmacodynamic side of the models, assuming standard (integer order) pharmacokinetics

The characteristics of patients with possible Transient Ischemic Attack and Minor Stroke in the Hunter and Manning Valley regions, Australia (the INSIST Study)

This is the final version. Available on open access from the American Academy of Neurology via the DOI in this record. Background: Transient ischemic attack (TIA) and minor stroke (TIAMS) are risk factors for stroke recurrence. Some TIAMS may be preventable by appropriate primary prevention. We aimed to recruit “possible-TIAMS” patients in the INternational comparison of Systems of care and patient outcomes In minor Stroke and TIA (INSIST) study. Methods: A prospective inception cohort study performed across 16 Hunter–Manning region, Australia, general practices in the catchment of one secondary-care acute neurovascular clinic. Possible-TIAMS patients were recruited from August 2012 to August 2016. We describe the baseline demographics, risk factors and pre-event medications of participating patients. Results: There were 613 participants (mean age; 69 ± 12 years, 335 women), and 604 (99%) were Caucasian. Hypertension was the most common risk factor (69%) followed by hyperlipidemia (52%), diabetes mellitus (17%), atrial fibrillation (AF) (17%), prior TIA (13%) or stroke (10%). Eighty-nine (36%) of the 249 participants taking antiplatelet therapy had no known history of cardiovascular morbidity. Of 102 participants with known AF, 91 (89%) had a CHA2DS2-VASc score ≥ 2 but only 47 (46%) were taking anticoagulation therapy. Among 304 participants taking an antiplatelet or anticoagulant agent, 30 (10%) had stopped taking these in the month prior to the index event. Conclusion: This study provides the first contemporary data on TIAMS or TIAMS-mimics in Australia. Community and health provider education is required to address the under-use of anticoagulation therapy in patients with known AF, possibly inappropriate use of antiplatelet therapy and possibly inappropriate discontinuation of antiplatelet or anticoagulation therapy.National Health and Medical Research Counci