Heating of the Solar Chromosphere and Corona by Alfven Wave Turbulence

A three-dimensional MHD model for the propagation and dissipation of Alfven waves in a coronal loop is developed. The model includes the lower atmospheres at the two ends of the loop. The waves originate on small spatial scales (less than 100 km) inside the kilogauss flux elements in the photosphere. The model describes the nonlinear interactions between Alfven waves using the reduced MHD approximation. The increase of Alfven speed with height in the chromosphere and transition region (TR) causes strong wave reflection, which leads to counter-propagating waves and turbulence in the photospheric and chromospheric parts of the flux tube. Part of the wave energy is transmitted through the TR and produces turbulence in the corona. We find that the hot coronal loops typically found in active regions can be explained in terms of Alfven wave turbulence, provided the small-scale footpoint motions have velocities of 1-2 km/s and time scales of 60-200 s. The heating rate per unit volume in the chromosphere is 2 to 3 orders of magnitude larger than that in the corona. We construct a series of models with different values of the model parameters, and find that the coronal heating rate increases with coronal field strength and decreases with loop length. We conclude that coronal loops and the underlying chromosphere may both be heated by Alfvenic turbulence.Comment: 28 pages (emulateapj style, 13 figures, 3 tables), ApJ, in pres

The Role of Type II Spicules in the Upper Solar Atmosphere

We examine the suggestion that most of the hot plasma in the Sun's corona comes from type II spicule material that is heated as it is ejected from the chromosphere. This contrasts with the traditional view that the corona is filled via chromospheric evaporation that results from coronal heating. We explore the observational consequences of a hypothetical spicule dominated corona and conclude from the large discrepancy between predicted and actual observations that only a small fraction of the hot plasma can be supplied by spicules (<2% in active regions, <5% in the quiet Sun, and <8% in coronal holes). The red-blue asymmetries of EUV spectral lines and the ratio of lower transition region (LTR; T<0.1 MK) to coronal emission measures are both predicted to be 2 orders of magnitude larger than observed. Furthermore, hot spicule material would cool dramatically by adiabatic expansion as it rises into the corona, so substantial coronal heating would be needed to maintain the high temperatures that are seen at all altitudes. We suggest that the corona contains a mixture of thin strands, some of which are populated by spicule injections, but most of which are not. A majority of the observed hot emission originates in non-spicule strands and is explained by traditional coronal heating models. However, since these models predict far too little emission from the LTR, most of this emission comes from the bulk of the spicule material that is only weakly heated and visible in He II (304 A) as it falls back to the surface.Comment: 11 pages, 5 figures, publishe

Association of psychological variables and outcome in tendinopathy: a systematic review

Objective Fear, anxiety, depression, distress and catastrophisation are all factors known to affect pain and disability levels. To date, the association of such psychological factors has yet to be established in tendinopathy. Therefore, the purpose of this paper was to determine if psychological variables are associated with tendinopathy and whether any such variables may be associated with pain and disability outcomes in conservative management of tendinopathy. Design A systematic review was undertaken and included studies were appraised for risk of bias using the Newcastle-Ottawa Scale. Owing to heterogeneity of studies, a qualitative synthesis was undertaken. Data sources An electronic search of MEDLINE, CiNAHL, SPORTDiscus, PsycINFO, EMBASE and PsycARTICLES was undertaken from their inception to April 2016. Eligibility criteria for selecting studies Any study design that incorporated psychological measures and clinical outcomes using participants with tendinopathy. Results Ten articles describing nine studies and 1108 participants were included. Conflicting evidence exists regarding the association of anxiety, depression and lateral epicondylalgia (LE). Strong evidence suggests LE is not associated with kinesiophobia. Moderate evidence links catastrophisation and distress with LE. Moderate evidence suggests distress is not associated with rotator cuff tendinopathy, but kinesiophobia and catastrophisation are. Limited evidence suggests patellar tendinopathy is not associated with anxiety or depression and kinesiophobia may be linked with suboptimal outcomes in Achilles tendinopathy. Summary/conclusions Tendinopathy requires an individualised approach to management. Clinicians should consider using validated screening tools for the presence of psychological variables as a part of their holistic management

Practical guidelines for rigor and reproducibility in preclinical and clinical studies on cardioprotection

The potential for ischemic preconditioning to reduce infarct size was first recognized more than 30 years ago. Despite extension of the concept to ischemic postconditioning and remote ischemic conditioning and literally thousands of experimental studies in various species and models which identified a multitude of signaling steps, so far there is only a single and very recent study, which has unequivocally translated cardioprotection to improved clinical outcome as the primary endpoint in patients. Many potential reasons for this disappointing lack of clinical translation of cardioprotection have been proposed, including lack of rigor and reproducibility in preclinical studies, and poor design and conduct of clinical trials. There is, however, universal agreement that robust preclinical data are a mandatory prerequisite to initiate a meaningful clinical trial. In this context, it is disconcerting that the CAESAR consortium (Consortium for preclinicAl assESsment of cARdioprotective therapies) in a highly standardized multi-center approach of preclinical studies identified only ischemic preconditioning, but not nitrite or sildenafil, when given as adjunct to reperfusion, to reduce infarct size. However, ischemic preconditioning—due to its very nature—can only be used in elective interventions, and not in acute myocardial infarction. Therefore, better strategies to identify robust and reproducible strategies of cardioprotection, which can subsequently be tested in clinical trials must be developed. We refer to the recent guidelines for experimental models of myocardial ischemia and infarction, and aim to provide now practical guidelines to ensure rigor and reproducibility in preclinical and clinical studies on cardioprotection. In line with the above guideline, we define rigor as standardized state-of-the-art design, conduct and reporting of a study, which is then a prerequisite for reproducibility, i.e. replication of results by another laboratory when performing exactly the same experiment

Diets of Wedge-tailed Eagles ('Aquila audax') and Little Eagles ('Hieraaetus morphnoides') Breeding Near Canberra, Australia

Recent concern about the decline of the Little Eagle ('Hieraaetus morphnoides') in southeastern Australia has raised questions about whether Wedge-tailed Eagles ('Aquila audax') might be implicated in this decline. The ecology, including the diet, of Little Eagles is rather poorly known. The diet of the Wedge-tailed Eagle is better documented, but the overlap in prey used by the two eagles has been little studied. Near Canberra between July 2002 and January 2008, we identified 1421 and 192 prey items from nests of Wedge-tailed Eagles and Little Eagles, respectively. Wedge-tailed Eagles' diet was similar to that reported elsewhere. In addition to European rabbits ('Oryctolagus cuniculus'), Little Eagles specialized on birds, but tended to avoid macropods, a main prey of Wedge-tailed Eagles, and there was little overlap in prey used by the two eagle species. Although Standardised Food Niche Breadth and Shannon Diversity Index were similar for the two eagles, Wedge-tailed Eagles captured significantly larger prey, as indicated by the difference in Geometric Mean Prey Weight, 1298 g for Wedge-tailed Eagles and 249 g for Little Eagles, which reflected the fivefold difference in mass between male Little Eagles and male Wedge-tailed Eagles. We suggest that direct competition for prey probably was not the cause of the Little Eagle decline

Protective effect of antirheumatic drugs on dementia in rheumatoid arthritis patients

INTRODUCTION Rheumatoid Arthritis is a systemic inflammatory disease and classical disease-modifying anti-rheumatic drugs (cDMARDs) have proven efficacy. It is unknown what impact cDMARDs might have on dementia as an outcome. METHODS Incident diagnoses of Rheumatoid Arthritis in persons over 18 years from 1995 to 2011 were identified from the UK Clinical Practice Research Datalink. 3,876 cDMARD users were propensity score matched to 1,938 non-users, on a wide range of confounders. Impact on dementia was assessed using survival models. RESULTS cDMARD users were at reduced risk of dementia (hazard ratio: 0.60; 95% confidence intervals: 0.42-0.85). The effect was strongest in Methotrexate users (0.52; 0.34-0.82). DISCUSSION The strong effect of cDMARD use on a halving of dementia risk requires replication in a trial and may provide an important therapeutic pharmacological treatment. </p

Costs of joint replacement in osteoarthritis: A study using the National Joint Registry and Clinical Practice Research Datalink datasets

Objectives: The aim of this study was to estimate the costs of primary hip and knee replacement in individuals with osteoarthritis up to 2 years post-surgery, compare costs before and after the surgery, and identify predictors of hospital costs. Methods: Patients aged 18 years or over with primary planned hip or knee replacements and osteoarthritis in England between 2008 and 2016 were identified from the National Joint Registry and linked with Hospital Episode Statistics data containing inpatient episodes. Primary care data linked with hospital outpatient records were also used to identify patients aged 18 years or over with primary hip or knee replacements between 2008 and 2016. All healthcare resource use was valued using 2016/17 costs and non-parametric censoring methods were used to estimate total 1-year and 2-year costs. Results: We identified 854,866 individuals undergoing hip or knee replacement. The mean censor-adjusted 1-year hospitalisation costs for hip and knee replacement were £7,827 (95% CI £7,813 to £7,842) and £7,805 (95% CI £7,790 to £7,818), respectively. Complications and revisions were associated with up to a three-fold increase in 1-year hospitalisation costs. The censor-adjusted 2-year costs were £9,258 (95 % CI £9,233 to £9,280) and £9,452 (95%CI £9,430 to £9,475) for hip and knee replacement. Adding primary and outpatient care, the mean total hip and knee replacement 2-year costs were £11,987 and £12,578, respectively. Conclusions: There are significant costs following joint replacement. Revisions and complications accounted for considerable costs and there is a significant incentive to identify best approaches to reduce these.</p