Line formation in solar granulation: II. The photospheric Fe abundance

The solar photospheric Fe abundance has been determined using realistic ab initio 3D, time-dependent, hydrodynamical model atmospheres. The study is based on the excellent agreement between the predicted and observed line profiles directly rather than equivalent width, since the intrinsic Doppler broadening from the convective motions and oscillations provide the necessary non-thermal broadening. Thus, three of the four hotly debated parameters (equivalent widths, microturbulence and damping enhancement factors) in the center of the recent solar Fe abundance dispute regarding FeI lines no longer enter the analysis, leaving the transition probabilities as the main uncertainty. Both FeI (using the samples of lines of both the Oxford and Kiel studies) and FeII lines have been investigated, which give consistent results: log FeI = 7.44 +- 0.05 and log FeII = 7.45 +- 0.10. Also the wings of strong FeI lines return consistent abundances, log FeII = 7.42 +- 0.03, but due to the uncertainties inherent in analyses of strong lines we give this determination lower weight than the results from weak and intermediate strong lines. In view of the recent slight downward revision of the meteoritic Fe abundance log Fe = 7.46 +- 0.01, the agreement between the meteoritic and photospheric values is very good, thus appearingly settling the debate over the photospheric Fe abundance from FeI lines.Comment: Accepted for A&

The effects of numerical resolution on hydrodynamical surface convection simulations and spectral line formation

The computationally demanding nature of radiative-hydrodynamical simulations of stellar surface convection warrants an investigation of the sensitivity of the convective structure and spectral synthesis to the numerical resolution and dimension of the simulations, which is presented here. With too coarse a resolution the predicted spectral lines tend to be too narrow, reflecting insufficient Doppler broadening from the convective motions, while at the currently highest affordable resolution the line shapes have converged essentially perfectly to the observed profiles. Similar conclusions are drawn from the line asymmetries and shifts. In terms of abundances, weak FeI and FeII lines show a very small dependence (~0.02 dex) while for intermediate strong lines with significant non-thermal broadening the sensitivity increases (~0.10 dex). Problems arise when using 2D convection simulations to describe an inherent 3D phenomenon, which translates to inaccurate atmospheric velocity fields and temperature and pressure structures. In 2D the theoretical line profiles tend to be too shallow and broad compared with the 3D calculations and observations, in particular for intermediate strong lines. In terms of abundances, the 2D results are systematically about 0.1 dex lower than for the 3D case for FeI lines. Furthermore, the predicted line asymmetries and shifts are much inferior in 2D. Given these shortcomings and computing time considerations it is better to use 3D simulations of even modest resolution than high-resolution 2D simulations.Comment: Accepted for A&

Magnetohydrodynamic turbulence in warped accretion discs

Warped, precessing accretion discs appear in a range of astrophysical systems, for instance the X-ray binary Her X-1 and in the active nucleus of NGC4258. In a warped accretion disc there are horizontal pressure gradients that drive an epicyclic motion. We have studied the interaction of this epicyclic motion with the magnetohydrodynamic turbulence in numerical simulations. We find that the turbulent stress acting on the epicyclic motion is comparable in size to the stress that drives the accretion, however an important ingredient in the damping of the epicyclic motion is its parametric decay into inertial waves.Comment: to appear in the proceedings of the 20th Texas Symposium on Relativistic Astrophysics, J. C. Wheeler & H. Martel (eds.

Line formation in solar granulation: I. Fe line shapes, shifts and asymmetries

Realistic ab-initio 3D, radiative-hydrodynamical convection simulations of the solar granulation have been applied to FeI and FeII line formation. In contrast to classical analyses based on hydrostatic 1D model atmospheres the procedure contains no adjustable free parameters but the treatment of the numerical viscosity in the construction of the 3D, time-dependent, inhomogeneous model atmosphere and the elemental abundance in the 3D spectral synthesis. However, the numerical viscosity is introduced purely for numerical stability purposes and is determined from standard hydrodynamical test cases with no adjustments allowed to improve the agreement with the observational constraints from the solar granulation. The non-thermal line broadening is mainly provided by the Doppler shifts arising from the convective flows in the solar photosphere and the solar oscillations. The almost perfect agreement between the predicted temporally and spatially averaged line profiles for weak Fe lines with the observed profiles and the absence of trends in derived abundances with line strengths, seem to imply that the micro- and macroturbulence concepts are obsolete in these 3D analyses. Furthermore, the theoretical line asymmetries and shifts show a very satisfactory agreement with observations with an accuracy of typically 50-100 m/s on an absolute velocity scale. The remaining minor discrepancies point to how the convection simulations can be refined further.Comment: Accepted for A&

Use of an alternative method to evaluate erythema severity in a clinical trial: difference in vehicle response with evaluation of baseline and postdose photographs for effect of oxymetazoline cream 1·0% for persistent erythema of rosacea in a phase IV study.

BackgroundOnce-daily topical oxymetazoline cream 1·0% significantly reduced persistent facial erythema of rosacea in trials requiring live, static patient assessments.ObjectivesTo evaluate critically the methodology of clinical trials that require live, static patient assessments by determining whether assessment of erythema is different when reference to the baseline photograph is allowed.MethodsIn two identically designed, randomized, phase III trials, adults with persistent facial erythema of rosacea applied oxymetazoline or vehicle once daily. This phase IV study evaluated standardized digital facial photographs from the phase III trials to record ≥ 1-grade Clinician Erythema Assessment (CEA) improvement at 1, 3, 6, 9 and 12 h postdose.ResultsAmong 835 patients (oxymetazoline n = 415, vehicle n = 420), significantly greater proportions of patients treated with oxymetazoline vs. vehicle achieved ≥ 1-grade CEA improvement. For the comparison between phase IV study results and the original phase III analysis, when reference to baseline photographs was allowed while evaluating post-treatment photographs, the results for oxymetazoline were similar to results of the phase III trials (up to 85.7%), but a significantly lower proportion of vehicle recipients achieved ≥ 1-grade CEA improvement (up to 29.7% [phase 4] vs. 52.3% [phase 3]; P<0.001). In the phase IV study, up to 80·2% of patients treated with oxymetazoline achieved at least moderate erythema improvement vs. up to 22·9% of patients treated with vehicle. The association between patients' satisfaction with facial skin redness and percentage of erythema improvement was statistically significant.ConclusionsAssessment of study photographs, with comparison to baseline, confirmed significant erythema reduction with oxymetazoline on the first day of application. Compared with the phase III trial results, significantly fewer vehicle recipients attained ≥ 1-grade CEA improvement, suggesting a mitigated vehicle effect. This methodology may improve the accuracy of clinical trials evaluating erythema severity

Patient factors associated with non-attendance at colonoscopy after a positive screening faecal occult blood test

BACKGROUND: Screening participants with abnormal faecal occult blood test results who do not attend further testing are at high risk of colorectal cancer, yet little is known about their reasons for non-attendance. METHODS: We conducted a medical record review of 170 patients from two English Bowel Cancer Screening Programme centres who had abnormal guaiac faecal occult blood test screening tests between November 2011 and April 2013 but did not undergo colonoscopy. Using information from patient records, we coded and categorized reasons for non-attendance. RESULTS: Of the 170 patients, 82 were eligible for review, of whom 66 had at least one recorded reason for lack of colonoscopy follow-up. Reasons fell into seven main categories: (i) other commitments, (ii) unwillingness to have the test, (iii) a feeling that the faecal occult blood test result was a false positive, (iv) another health issue taking priority, (v) failing to complete bowel preparation, (vi) practical barriers (e.g. lack of transport), and (vii) having had or planning colonoscopy elsewhere. The most common single reasons were unwillingness to have a colonoscopy and being away. CONCLUSIONS: We identify a range of apparent reasons for colonoscopy non-attendance after a positive faecal occult blood test screening. Education regarding the interpretation of guaiac faecal occult blood test findings, offer of alternative confirmatory test options, and flexibility in the timing or location of subsequent testing might decrease non-attendance of diagnostic testing following positive faecal occult blood test

Cost-effectiveness of HBV and HCV screening strategies:a systematic review of existing modelling techniques

Introduction: Studies evaluating the cost-effectiveness of screening for Hepatitis B Virus (HBV) and Hepatitis C Virus (HCV) are generally heterogeneous in terms of risk groups, settings, screening intervention, outcomes and the economic modelling framework. It is therefore difficult to compare cost-effectiveness results between studies. This systematic review aims to summarise and critically assess existing economic models for HBV and HCV in order to identify the main methodological differences in modelling approaches. Methods: A structured search strategy was developed and a systematic review carried out. A critical assessment of the decision-analytic models was carried out according to the guidelines and framework developed for assessment of decision-analytic models in Health Technology Assessment of health care interventions. Results: The overall approach to analysing the cost-effectiveness of screening strategies was found to be broadly consistent for HBV and HCV. However, modelling parameters and related structure differed between models, producing different results. More recent publications performed better against a performance matrix, evaluating model components and methodology. Conclusion: When assessing screening strategies for HBV and HCV infection, the focus should be on more recent studies, which applied the latest treatment regimes, test methods and had better and more complete data on which to base their models. In addition to parameter selection and associated assumptions, careful consideration of dynamic versus static modelling is recommended. Future research may want to focus on these methodological issues. In addition, the ability to evaluate screening strategies for multiple infectious diseases, (HCV and HIV at the same time) might prove important for decision makers

MRI of the lung (3/3)-current applications and future perspectives

BACKGROUND: MRI of the lung is recommended in a number of clinical indications. Having a non-radiation alternative is particularly attractive in children and young subjects, or pregnant women. METHODS: Provided there is sufficient expertise, magnetic resonance imaging (MRI) may be considered as the preferential modality in specific clinical conditions such as cystic fibrosis and acute pulmonary embolism, since additional functional information on respiratory mechanics and regional lung perfusion is provided. In other cases, such as tumours and pneumonia in children, lung MRI may be considered an alternative or adjunct to other modalities with at least similar diagnostic value. RESULTS: In interstitial lung disease, the clinical utility of MRI remains to be proven, but it could provide additional information that will be beneficial in research, or at some stage in clinical practice. Customised protocols for chest imaging combine fast breath-hold acquisitions from a "buffet" of sequences. Having introduced details of imaging protocols in previous articles, the aim of this manuscript is to discuss the advantages and limitations of lung MRI in current clinical practice. CONCLUSION: New developments and future perspectives such as motion-compensated imaging with self-navigated sequences or fast Fourier decomposition MRI for non-contrast enhanced ventilation- and perfusion-weighted imaging of the lung are discussed. Main Messages • MRI evolves as a third lung imaging modality, combining morphological and functional information. • It may be considered first choice in cystic fibrosis and pulmonary embolism of young and pregnant patients. • In other cases (tumours, pneumonia in children), it is an alternative or adjunct to X-ray and CT. • In interstitial lung disease, it serves for research, but the clinical value remains to be proven. • New users are advised to make themselves familiar with the particular advantages and limitations

Nuclear receptors in vascular biology

Nuclear receptors sense a wide range of steroids and hormones (estrogens, progesterone, androgens, glucocorticoid, and mineralocorticoid), vitamins (A and D), lipid metabolites, carbohydrates, and xenobiotics. In response to these diverse but critically important mediators, nuclear receptors regulate the homeostatic control of lipids, carbohydrate, cholesterol, and xenobiotic drug metabolism, inflammation, cell differentiation and development, including vascular development. The nuclear receptor family is one of the most important groups of signaling molecules in the body and as such represent some of the most important established and emerging clinical and therapeutic targets. This review will highlight some of the recent trends in nuclear receptor biology related to vascular biology