Long term time variability of cosmic rays and possible relevance to the development of life on Earth

An analysis is made of the manner in which the cosmic ray intensity at Earth has varied over its existence and its possible relevance to both the origin and the evolution of life. Much of the analysis relates to the 'high energy' cosmic rays ($E>10^{14}eV;=0.1PeV$) and their variability due to the changing proximity of the solar system to supernova remnants which are generally believed to be responsible for most cosmic rays up to PeV energies. It is pointed out that, on a statistical basis, there will have been considerable variations in the likely 100 My between the Earth's biosphere reaching reasonable stability and the onset of very elementary life. Interestingly, there is the increasingly strong possibility that PeV cosmic rays are responsible for the initiation of terrestrial lightning strokes and the possibility arises of considerable increases in the frequency of lightnings and thereby the formation of some of the complex molecules which are the 'building blocks of life'. Attention is also given to the well known generation of the oxides of nitrogen by lightning strokes which are poisonous to animal life but helpful to plant growth; here, too, the violent swings of cosmic ray intensities may have had relevance to evolutionary changes. A particular variant of the cosmic ray acceleration model, put forward by us, predicts an increase in lightning rate in the past and this has been sought in Korean historical records. Finally, the time dependence of the overall cosmic ray intensity, which manifests itself mainly at sub-10 GeV energies, has been examined. The relevance of cosmic rays to the 'global electrical circuit' points to the importance of this concept.Comment: 18 pages, 5 figures, accepted by 'Surveys in Geophysics

Correction: Spore development and nuclear inheritance in arbuscular mycorrhizal fungi

<p>Abstract</p> <p>Background</p> <p>A conventional tenet of classical genetics is that progeny inherit half their genome from each parent in sexual reproduction instead of the complete genome transferred to each daughter during asexual reproduction. The transmission of hereditary characteristics from parents to their offspring is therefore predictable, although several exceptions are known. Heredity in microorganisms, however, can be very complex, and even unknown as is the case for coenocytic organisms such as Arbuscular Mycorrhizal Fungi (AMF). This group of fungi are plant-root symbionts, ubiquitous in most ecosystems, which reproduce asexually via multinucleate spores for which sexuality has not yet been observed.</p> <p>Results</p> <p>We examined the number of nuclei per spore of four AMF taxa using high Z-resolution live confocal microscopy and found that the number of nuclei was correlated with spore diameter. We show that AMF have the ability, through the establishment of new symbioses, to pass hundreds of nuclei to subsequent generations of multinucleated spores. More importantly, we observed surprising heterogeneity in the number of nuclei among sister spores and show that massive nuclear migration and mitosis are the mechanisms by which AMF spores are formed. We followed spore development of <it>Glomus irregulare </it>from hyphal swelling to spore maturity and found that the spores reached mature size within 30 to 60 days, and that the number of nuclei per spores increased over time.</p> <p>Conclusions</p> <p>We conclude that the spores used for dispersal of AMF contain nuclei with two origins, those that migrate into the spore and those that arise by mitosis in the spore. Therefore, these spores do not represent a stage in the life cycle with a single nucleus, raising the possibility that AMF, unlike all other known eukaryotic organisms, lack the genetic bottleneck of a single-nucleus stage.</p

A new improved protocol for in vitro intratubular dentinal bacterial contamination for antimicrobial endodontic tests: standardization and validation by confocal laser scanning microscopy

Objectives To compare three methods of intratubular contamination that simulate endodontic infections using confocal laser scanning microscopy (CLSM). Material and Methods Two pre-existing models of dentinal contamination were used to induce intratubular infection (groups A and B). These methods were modified in an attempt to improve the model (group C). Among the modifications it may be included: specimen contamination for five days, ultrasonic bath with BHI broth after specimen sterilization, use of E. faecalis during the exponential growth phase, greater concentration of inoculum, and two cycles of centrifugation on alternate days with changes of culture media. All specimens were longitudinally sectioned and stained with of LIVE/DEAD® for 20 min. Specimens were assessed using CLSM, which provided images of the depth of viable bacterial proliferation inside the dentinal tubules. Additionally, three examiners used scores to classify the CLSM images according to the following parameters: homogeneity, density, and depth of the bacterial contamination inside the dentinal tubules. Kruskal-Wallis and Dunn’s tests were used to evaluate the live and dead cells rates, and the scores obtained. Results The contamination scores revealed higher contamination levels in group C when compared with groups A and B (p0.05). The volume of live cells in group C was higher than in groups A and B (p<0.05). Conclusion The new protocol for intratubular infection resulted in high and uniform patterns of bacterial contamination and higher cell viability in all specimens when compared with the current methods

Do healthcare tax credits help poor-health individuals on low incomes?

In several countries, personal income tax permits tax credits for out-of-pocket healthcare expenditure. Tax credits benefit taxpayers at all income levels by reducing their net tax liability and modify the price of out-of-pocket expenditure. To the extent that consumer demand is price elastic, they may influence the amount of eligible healthcare expenditure for which taxpayers may claim a credit. These effects influence, in turn, income distributions and taxpayers’ health status and therefore income-related inequality in health. Redistributive consequences of tax credits have been widely investigated. However, little is known about the ability of tax credits to alleviate health inequality. In this paper, we study the potential effects that tax credits for health expenses may have on income-related inequality in health status with reference to the Italian institutional setting. The analysis is performed using a tax-benefit microsimulation model that reproduces the personal income tax and incorporates taxpayers’ behavioral responses to changes in tax credit rate. Our results suggest that the current healthcare tax credit design tends to favor the richest part of the population

Minimum 10 years follow-up surgical results of adolescent idiopathic scoliosis patients treated with TSRH instrumentation

Last two decades witnessed great advances in the surgical treatment of idiopathic scoliosis. However, the number of studies evaluating the long-term results of these treatment methods is relatively low. During recent years, besides radiological and clinical studies, questionnaires like SRS-22 assessing subjective functional and mental status and life-quality of patients have gained importance for the evaluation of these results. In this study, surgical outcome and Turkish SRS-22 questionnaire results of 109 late-onset adolescent idiopathic scoliosis patients surgically treated with third-generation instrumentation [Texas Scottish Rite Hospital (TSRH) System] and followed for a minimum of 10 years were evaluated. The balance was analyzed clinically and radiologically by the measurement of the lateral trunk shift (LT), shift of head (SH), and shift of stable vertebra (SS). Mean age of the patients was 14.4±1.9 and mean follow-up period was 136.9±12.7 months. When all the patients were included, the preoperative mean Cobb angle of major curves in the frontal plane was 60.8°±17.5°. Major curves that were corrected by 38.7±22.1% in the bending radiograms, postoperatively achieved a correction of 64.0±15.8%. At the last follow-up visit, 10.3°±10.8° of correction loss was recorded in major curves in the frontal plane with 50.5±23.1% final correction rate. Also, the mean postoperative and final kyphosis angles and lumbar lordosis angles were 37.7°±7.4°, 37.0°±8.4°, 37.5°±8.7°, and 36.3°±8.5°, respectively. A statistically significant correction was obtained at the sagittal plane; mean postoperative changes compared to preoperative values were 7.9° and 12.9° for thoracic and lumbar regions, respectively. On the other hand, normal physiological thoracic and lumbar sagittal contours were achieved in 83.5% and 67.9% of the patients, respectively. Postoperatively, a statistically significant correction was obtained in LT, SH, and SS values (P<0.05). Although, none of the patients had completely balanced curves preoperatively, in 95.4% of the patients the curves were found to be completely balanced or clinically well balanced postoperatively. This rate was maintained at the last follow-up visit. Overall, four patients (3.7%) had implant failure. Early superficial infection was observed in three (2.8%) patients. Radiologically presence of significant consolidation, absence of implant failure, and correction loss, and clinical relief of pain were considered as the proof of a posterior solid fusion mass. About ten (9.2%) patients were considered to have pseudoarthrosis: four patients with implant failure and six patients with correction loss over 15° at the frontal plane. About four (3.7%) patients among the first 20 patients had neurological deficit only wake-up test was used for neurological monitoring of these patients. No neurological deficit was observed in the 89 patients for whom intraoperative neurological monitoring with SSEP and TkMMEP was performed. Overall, average scores of SRS-22 questionnaire for general self-image, function, mental status, pain, and satisfaction from treatment were 3.8±0.7, 3.6±0.7, 4.0±0.8, 3.6±0.8, and 4.6±0.3, respectively at the last follow-up visit. Results of about 10 years of follow-up these patients treated with TSRH instrumentation suggest that the method is efficient for the correction of frontal and sagittal plane deformities and trunk balance. In addition, it results in a better life-quality