Solar total and spectral irradiance reconstruction over the last 9000 years

Changes in solar irradiance and in its spectral distribution are among the main natural drivers of the climate on Earth. However, irradiance measurements are only available for less than four decades, while assessment of solar influence on Earth requires much longer records. The aim of this work is to provide the most up-to-date physics-based reconstruction of the solar total and spectral irradiance (TSI/SSI) over the last nine millennia. The concentrations of the cosmogenic isotopes 14C and 10Be in natural archives have been converted to decadally averaged sunspot numbers through a chain of physics-based models. TSI and SSI are reconstructed with an updated SATIRE model. Reconstructions are carried out for each isotope record separately, as well as for their composite. We present the first ever SSI reconstruction over the last 9000 years from the individual 14C and 10Be records as well as from their newest composite. The reconstruction employs physics-based models to describe the involved processes at each step of the procedure. Irradiance reconstructions based on two different cosmogenic isotope records, those of 14C and 10Be, agree well with each other in their long-term trends despite their different geochemical paths in the atmosphere of Earth. Over the last 9000 years, the reconstructed secular variability in TSI is of the order of 0.11%, or 1.5 W/m2. After the Maunder minimum, the reconstruction from the cosmogenic isotopes is consistent with that from the direct sunspot number observation. Furthermore, over the nineteenth century, the agreement of irradiance reconstructions using isotope records with the reconstruction from the sunspot number by Chatzistergos et al. (2017) is better than that with the reconstruction from the WDC-SILSO series (Clette et al. 2014), with a lower chi-square-value

Evidence for polar jets as precursors of polar plume formation

Observations from the Hinode/XRT telescope and STEREO/SECCHI/EUVI are utilized to study polar coronal jets and plumes. The study focuses on the temporal evolution of both structures and their relationship. The data sample, spanning April 7-8 2007, shows that over 90% of the 28 observed jet events are associated with polar plumes. EUV images (STEREO/SECCHI) show plume haze rising from the location of approximately 70% of the polar X-ray (Hinode/XRT) and EUV jets, with the plume haze appearing minutes to hours after the jet was observed. The remaining jets occurred in areas where plume material previously existed causing a brightness enhancement of the latter after the jet event. Short-lived, jet-like events and small transient bright points are seen (one at a time) at different locations within the base of pre-existing long-lived plumes. X-ray images also show instances (at least two events) of collimated-thin jets rapidly evolving into significantly wider plume-like structures that are followed by the delayed appearance of plume haze in the EUV. These observations provide evidence that X-ray jets are precursors of polar plumes, and in some cases cause brightenings of plumes. Possible mechanisms to explain the observed jet and plume relationship are discussed.Comment: 10 pages, 4 figures, accepted as APJ Lette

Evaluation of two radiographic scoring systems used to monitor caries progression in deciduous teeth

Magister Scientiae Dentium - MSc(Dent)The investigation was designed to evaluate the scoring systems of pitts (1984), and that of Murray and Majid(1978), when used to monitor caries progression in deciduous teeth. The evaluation.was based on the reproducibility and discrlininatory ability of the two systems. The Reproducibility Study was designed to compare the reproducibility of the two systems, and in addition, to illustrate, firstly the use of the subject as the sampling unit in measuring reproducibility, and secondly, a more sensitive method of measuring reproducibility when analysing caries progression data. The Progression Study was designed to discriminatory ability. In addition the compare use of the the effect on subject as the sampling unit in monitoring caries progression was illustrated in the analysis of this part of the investigation. A sub-sample of the posterior bitewing radiographs of 301, 5 year old children from a Duraphat clinical trial (Murray et al. 1977, Murray and Majid 1978) were re-examined. For the Reproducibility Study 150 sets of radiographs were examined a total of 4 times, (repeated examinations for each method). For the Progression Study three serial bitewing radiographs of 50 children were examined using the two methods. For the Reproducibility Study, Kendall's Tau-B was used as an approxlination of the weighted Kappa as a measure of reproducibility. While the pitts method appeared to be more reliable, the difference .between the tYK>methods was not significant( p~ 05). The surface cannot be used as an independent unit in measuring reproducibility. A method using the subject as the sampling unit was illustrated. Attention was drawn to the need to develop a measure of reproducibility for progression studies which would take into account the magnitude of the disagreement (instead of just disagreement) into the overall index of reproducibility. The use of weighted Kappa is suggested as a more appropriate measure of reproducibility. In the Progression Study Method 1 is more sensitive to the various stages of the disease process and provides a more complete overall picture of the carious process. The proportion of enamel lesions recorded for Method 1 were consistantly higher than that for Method 2. The behaviour of outer and inner enamel lesions differed considerably and Method 1 allowed the behaviour of these lesions to be considered separately. The progression rates were found to be faster with Method 2. With Method 1 30% of enamel lesions per subject had progressed to dentine or been filled 12 months later, the corresponding figure for Method 2 was 50%. Method 2 by excluding outer enamel lesions introduces two biases. The combination of these biases favour overestimating the proportion of lesions deemed to have progressed. The use of Method 2 may lead to the unnecessary loss of valuable data; more surfaces were excluded as being unreadable because of overlap. The average proportion of surfaces per subject recorded as unreadible due to overlap was 7% at baseline, 8% at 12 months and 8% at 24 months, the corresponding figures for Method 2 were 13%, 13% and 22% for Method 2. Method 1 thus appears to offer some advantages. The use of the subject as the sampling unit in analysing caries progression data offers a mnnber of advantages when canpared to the use of the surface as the sampling unit. The findings of the study indicate the proportions of high risk subjects (subjects in whom a large proportion of lesions progressed in a given time period) was low. With Method 1 in only 11% of the subjects did 80-100% of the enamel lesions progress after 12 months. The findings indicate that the Pitts system is the more useful scoring system in studies monitoring caries progression in deciduous teeth.British Counci

Access to health care in South Africa - the influence of race and class

Objectives. The first democratic government elected in South Africa in 1994 inherited huge inequities in health status and health provision across all section of the population. This study set out to assess the impact of the new government's commitment to address these inequities and implement policies to improve population health in general and address inequities in health care in particular. Design. A 1998 household survey assessed many aspects of health delivery, including their own perceived and actual access to health care among different segment of South Africa society. Results. Race was the main predictor of perceived changes in access to health care, with black, coloured and Indian respondents significatly more likely to feel that access had improved since 1994, compared with white respondents. Socio-economic status (SES) was the main predictor of actual access to health care, with low and middle SES classes significantly less likely to access care when ill. Conclusions. One-third of respondents perceived health care access to have improved between 1994 and 1998, and this response was partially determined along racial lines. About one-quarter reported an inability to access health care when they required it, and this response was partially determined along socio-economic lines. This set of contrasting responses suggests that at a political level perceptions are largely influenced by race, but at the operational level actual access is influenced by SES

Caesarean section rates in South Africa: A case study of the health systems challenges for the proposed National Health Insurance

Broader policy research and debate on the issues related to the planning of National Health Insurance (NHI) in South Africa (SA) need to be complemented by case studies to examine and understand the issues that will have to be dealt with at micro and macro levels. The objective of this article is to use caesarean section (CS) as a case study to examine the health systems challenges that NHI would need to address in order to ensure sustainability. The specific objectives are to: (i) provide an overview of the key clinical considerations related to CS; (ii) assess the CS rates in the SA public and private sectors; and (iii) use a health systems framework to examine the drivers of the differences between the public and private sectors and to identify the challenges that the proposed NHI would need to address on the road to implementation

The National Health Insurance Bill: Responses and options for the Portfolio Committee on Health

No abstract

The Competition Commission Health Market Inquiry Report: An overview and key imperatives

The Competition Commission’s Health Market Inquiry (HMI) is the most systematic and comprehensive investigation carried out into the South African private health sector. The recommendations as set out in the HMI Final Report merit extensive discussion and debate, as they could – if implemented – have far-reaching consequences for the future of the healthcare system. The objective of this article is to contribute to this discussion by providing an overview of the key findings and recommendations of the HMI and highlighting the resultant key imperatives at this critical juncture of policy development

G-band Spectral Synthesis in Solar Magnetic Concentrations

Narrow band imaging in the G-band is commonly used to trace the small magnetic field concentrations of the Sun, although the mechanism that makes them bright has remained unclear. We carry out LTE syntheses of the G-band in an assorted set of semi-empirical model magnetic concentrations. The syntheses include all CH lines as well as the main atomic lines within the band-pass. The model atmospheres produce bright G-band spectra having many properties in common with the observed G-band bright points. In particular, the contrast referred to the quiet Sun is about twice the contrast in continuum wavelengths. The agreement with observations does not depend on the specificities of the model atmosphere, rather it holds from single fluxtubes to MIcro-Structured Magnetic Atmospheres. However, the agreement requires that the real G-band bright points are not spatially resolved, even in the best observations. Since the predicted G-band intensities exceed by far the observed values, we foresee a notable increase of contrast of the G-band images upon improvement of the angular resolution. According to the LTE modeling, the G-band spectrum emerges from the deep photosphere that produces the continuum. Our syntheses also predict solar magnetic concentrations showing up in continuum images but not in the G-band . Finally, we have examined the importance of the CH photo-dissociation in setting the amount of G-band absorption. It turns out to play a minor role.Comment: To appear in ApJ, 554 n2 Jun 20, 33 pages and 9 figure

How to use magnetic field information for coronal loop identification?

The structure of the solar corona is dominated by the magnetic field because the magnetic pressure is about four orders of magnitude higher than the plasma pressure. Due to the high conductivity the emitting coronal plasma (visible e.g. in SOHO/EIT) outlines the magnetic field lines. The gradient of the emitting plasma structures is significantly lower parallel to the magnetic field lines than in the perpendicular direction. Consequently information regarding the coronal magnetic field can be used for the interpretation of coronal plasma structures. We extrapolate the coronal magnetic field from photospheric magnetic field measurements into the corona. The extrapolation method depends on assumptions regarding coronal currents, e.g. potential fields (current free) or force-free fields (current parallel to magnetic field). As a next step we project the reconstructed 3D magnetic field lines on an EIT-image and compare with the emitting plasma structures. Coronal loops are identified as closed magnetic field lines with a high emissivity in EIT and a small gradient of the emissivity along the magnetic field.Comment: 14 pages, 3 figure

Modelling the evolution of the Sun's open and total magnetic flux

Solar activity in all its varied manifestations is driven by the magnetic field. Particularly important for many purposes are two global quantities, the Sun's total and open magnetic flux, which can be computed from sunspot number records using models. Such sunspot-driven models, however, do not take into account the presence of magnetic flux during grand minima, such as the Maunder minimum. Here we present a major update of a widely used simple model, which now takes into account the observation that the distribution of all magnetic features on the Sun follows a single power law. The exponent of the power law changes over the solar cycle. This allows for the emergence of small-scale magnetic flux even when no sunspots are present for multiple decades and leads to non-zero total and open magnetic flux also in the deepest grand minima, such as the Maunder minimum, thus overcoming a major shortcoming of the earlier models. The results of the updated model compare well with the available observations and reconstructions of the solar total and open magnetic flux. This opens up the possibility of improved reconstructions of sunspot number from time series of cosmogenic isotope production rate