Does practice shape the brain?

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Preliminary Constraints on 12C(alpha,gamma)16O from White Dwarf Seismology

For many years, astronomers have promised that the study of pulsating white dwarfs would ultimately lead to useful information about the physics of matter under extreme conditions of temperature and pressure. In this paper we finally make good on that promise. Using observational data from the Whole Earth Telescope and a new analysis method employing a genetic algorithm, we empirically determine that the central oxygen abundance in the helium-atmosphere variable white dwarf GD 358 is 84+/-3 percent. We use this value to place preliminary constraints on the 12C(alpha,gamma)16O nuclear reaction cross-section. More precise constraints will be possible with additional detailed simulations. We also show that the pulsation modes of our best-fit model probe down to the inner few percent of the stellar mass. We demonstrate the feasibility of reconstructing the internal chemical profiles of white dwarfs from asteroseismological data, and find an oxygen profile for GD 358 that is qualitatively similar to recent theoretical calculations.Comment: Accepted for publication in the Astrophysical Journal, 7 pages, 6 figures, 2 tables, uses emulateapj5.st

Asteroseismic Signatures of Stellar Magnetic Activity Cycles

Observations of stellar activity cycles provide an opportunity to study magnetic dynamos under many different physical conditions. Space-based asteroseismology missions will soon yield useful constraints on the interior conditions that nurture such magnetic cycles, and will be sensitive enough to detect shifts in the oscillation frequencies due to the magnetic variations. We derive a method for predicting these shifts from changes in the Mg II activity index by scaling from solar data. We demonstrate this technique on the solar-type subgiant beta Hyi, using archival International Ultraviolet Explorer spectra and two epochs of ground-based asteroseismic observations. We find qualitative evidence of the expected frequency shifts and predict the optimal timing for future asteroseismic observations of this star.Comment: 5 pages including 3 figures and 1 table, MNRAS Letters accepte

Psychological stress and cardiovascular disease: empirical demonstration of bias in a prospective observational study of Scottish men

Objectives: To examine the association between self perceived psychological stress and cardiovascular disease in a population where stress was not associated with social disadvantage. Design: Prospective observational study with follow up of 21 years and repeat screening of half the cohort 5 years from baseline. Measures included perceived psychological stress, coronary risk factors, self reported angina, and ischaemia detected by electrocardiography. Setting: 27 workplaces in Scotland. Participants: 5606 men (mean age 48 years) at first screening and 2623 men at second screening with complete data on all measures Main outcome measures: Prevalence of angina and ischaemia at baseline, odds ratio for incident angina and ischaemia at second screening, rate ratios for cause specific hospital admission, and hazard ratios for cause specific mortality. Results: Both prevalence and incidence of angina increased with increasing perceived stress (fully adjusted odds ratio for incident angina, high versus low stress 2.66, 95% confidence interval 1.61 to 4.41; P for trend <0.001). Prevalence and incidence of ischaemia showed weak trends in the opposite direction. High stress was associated with a higher rate of admissions to hospital generally and for admissions related to cardiovascular disease and psychiatric disorders (fully adjusted rate ratios for any general hospital admission 1.13, 1.01 to 1.27, cardiovascular disease 1.20, 1.00 to 1.45, and psychiatric disorders 2.34, 1.41 to 3.91). High stress was not associated with increased admission for coronary heart disease (1.00, 0.76-1.32) and showed an inverse relation with all cause mortality, mortality from cardiovascular disease, and mortality from coronary heart disease, that was attenuated by adjustment for occupational class (fully adjusted hazard ratio for all cause mortality 0.94, 0.81 to 1.11, cardiovascular mortality 0.91, 0.78 to 1.06, and mortality from coronary heart disease 0.98, 0.75 to 1.27). Conclusions: The relation between higher stress, angina, and some categories of hospital admissions probably resulted from the tendency of participants reporting higher stress to also report more symptoms. The lack of a corresponding relation with objective indices of heart disease suggests that these symptoms did not reflect physical disease. The data suggest that associations between psychosocial measures and disease outcomes reported from some other studies may be spurious

Limitations of adjustment for reporting tendency in observational studies of stress and self reported coronary heart disease

Recently, observational evidence has been suggested to show a causal association between various "psychosocial" exposures, including psychological stress, and heart disease. Much of this evidence derives from studies in which a self reported psychosocial exposure is related to an outcome dependent on the subjective experience of coronary heart disease (CHD) symptoms. Such outcomes may be measured using standard symptom questionnaires (like the Rose angina schedule). Alternatively they may use diagnoses of disease from medical records, which depend on an individual perceiving symptoms and reporting them to a health worker. In these situations, reporting bias may generate spurious exposure-outcome associations. For example if people who perceive and report their life as most stressful also over-report symptoms of cardiovascular disease then an artefactual association between stress and heart disease will result

Individual employment histories and subsequent cause specific hospital admissions and mortality: a prospective study of a cohort of male and female workers with 21 years follow up

It is a widely held view that the labour market is demanding increased levels of flexibility, and that this is causing greater psychosocial stress among employees.1 Such stress may affect health, either through neuroendocrine pathways, or through increases in behaviours linked with poor health.2 Previously we presented evidence linking an unstable employment history, as measured by a greater number of job changes and shorter duration of current job, with a greater prevalence of smoking and greater alcohol consumption, in male and female workers.3 4 Despite this, we did not observe clear detrimental effects of such instability on health related physiological measures (body mass index, diastolic blood pressure, cholesterol, and lung function), nor on current cardiovascular health (electrocardiogram determined ischaemia and reported symptoms of angina). Finding work is easier for healthy persons, and those persons who need to find work repeatedly will be particularly likely to drop out of the workforce if their health deteriorates. Consequently, an occupational cohort, upon which our previous work was based, is least likely to include people of poor health with an unstable work history. If such people are underrepresented, attempts to determine the association between health and individual work histories will mislead. This study links the same cohort to information on the hospitalisations and deaths experienced over a 21 year follow up period. While those people whose health deteriorated before the enrolment of this cohort must remain poorly represented, these prospective data permit unbiased observation of those cases who experienced ill health subsequently, whether or not this resulted in an exit from the workforce. We hypothesise that an employment history characterised by frequent job changes, whatever the motivation for those changes, will require the person to be more focused on work, and less focused on maintaining personal health, with consequent poorer health for such people

Cause-specific hospital admission and mortality among working men: association with socioeconomic circumstances in childhood and adult life, and the mediating role of daily stress

BACKGROUND: The aim of this study was to investigate the association of childhood and adulthood social class with the occurrence of specific diseases, including those not associated with a high mortality rate, and to investigate daily stress as the mechanism for that part of any association which cannot be accounted for by established risk factors. METHODS: This was a prospective cohort study with 25 years of follow-up for cause-specific morbidity and mortality. A total of 5577 Scottish men were recruited from 27 workplaces in the West of Scotland. Childhood social class was determined from the occupation held by the individual's father, and adulthood social class from the individual's occupation at enrolment. Daily stress was measured at enrolment using the Reeder Stress Inventory. RESULTS: Health differentials were found for cardiovascular diseases, lung cancer, peptic ulcer, asthma, accidents and violence, alcohol-related diseases, and perhaps psychiatric illness. Adulthood circumstances were associated with the incidence of most diseases in adulthood, the exception being stroke, which was strongly associated with less privileged circumstances in childhood. Both childhood and adulthood circumstances contributed to the incidence of coronary heart disease. Daily stress did not underlie any of these associations once the influence of established risk factors had been taken into account. CONCLUSIONS: Socioeconomic circumstances in childhood and adulthood both contribute to health differentials in adulthood, the relative contributions depending upon the particular disease. Where known risk factors explained only part of the excess of a disease among individuals raised or living in less-privileged circumstances, there was no evidence to suggest that daily stress was the reason for the unexplained excess

The September 11 attacks and their impact on mental distress in the UK

Using a longitudinal household panel dataset in the United Kingdom, where most interviews are conducted in September each year, we are able to show that the attacks of September 11 resulted in higher levels of mental distress for those interviewed after that date in 2001 compared to those interviewed before it. This provides one of the first examples of the impact of a terrorist attack in one country on well-being in another country.Working Pape

Variations in Lake Levels during the Holocene in North America: An Indicator of Changes in Atmospheric Circulation Patterns

Fluctuations in the extent of closed lakes provide a detailed record of regional and continental variations in mean annual water budget. The temporal sequence of hydrological fluctuations during the Holocene in North America has been reconstructed using information from the Oxford Lake-Level Data Bank. This data base includes 67 basins from the Americas north of the equator. Maps of lake status, an index of relative depth, are presented for the period 10,000 to 0 yr BP. The early Holocene was characterised by increasingly arid conditions, which led to widespread low lake levels in the mid-latitudes by 9,000 yr BP. By 6,000 yr BP this zone of low lakes extended from 32o to 51oN. Many of the features of the present day lake-level pattern, particularly high lake levels north of 46oN and along the eastern seaboard, were established by 3.000 yr BP. Four distinctive regional patterns of lake behaviour through time are apparent. Histograms of lake status from 20,000 to 0 yr BP are presented for each of these regions. They illustrate the temporal patterns of lake-level fluctuations on a time scale of 103 — 104 yr. Changes in lake status over North America are interpreted as indicating displacements in major features of the general circulation, specifically the zonal Westerlies and the Equatorial Trough, as reflected by changes in air mass trajectories and hence the position of air mass boundaries over the continent.Les fluctuations de superficie enregistrées dans les lacs fermés fournissent des données détaillées quant aux variations, aux échelles régionale et continentale, du bilan annuel moyen de l'eau. On a reconstitué, en Amérique du Nord, la chronologie des fluctuations survenues à l'Holocène, en se fondant sur les données fournies par le Oxford Lake-Level Data Bank. Cette banque de données renseigne sur 67 bassins lacustres, situés en Amérique au nord de l'équateur. On présente ici des cartes illustrant les niveaux lacustres entre 10 000 et 0 ans BP. L'Holocène inférieur se caractérisait par une progression de l'aridité qui a entraîné un abaissement général du niveau des lacs situés sous les moyennes latitudes, environ 9000 ans BP. Environ 6000 ans BP. cette zone passait du 32o de latitude nord au 51o. Un grand nombre de particularités qui caractérisent aujourd'hui les niveaux lacustres, notamment les hauts niveaux qu'on observe au nord du 46o N et le long de la côte est, étaient déjà acquises vers 3000 ans BP. Quatre types d'évolution générale se dégagent au cours des millénaires. Par ailleurs, on présente des histogrammes illustrant les niveaux lacustres selon une échelle temporelle de 103 — 104 ans. On considère que les changements qu'ont connu, en Amérique du Nord, les niveaux lacustres révèlent qu'il y a eu déplacement des composantes principales de la circulation atmosphérique générale, surtout en ce qui a trait aux vents d'ouest et à la dépression équatoriale. Ils se sont traduits par des modifications de la trajectoire des masses d'air, ce qui explique la position des limites de masses d'air sur le continent.Schwankungen in der Ausdehnung geschlossener Seen liefern einen detaillierten Nachweis ùber régionale und kontinentale Variationen im durchschnittlichen jàhrlichen Wasser-Budget. Man hat die zeitliche Abfolge von Wasserschwankungen wàhrend des Holozàn in Nordamerika rekonstruiert, gestùtzt auf Informationen von der Oxford Lake-Level Data Bank. Diese Daten-Bank umfaBt 67 Wasserbecken Amerikas, die nôrlich vom Aquator liegen. Fur die Zeit von 10 000 bis O v.u.Z. werden Karten \/orgelegt. die ùber die relative Tiefe der Seen informieren. Das frùhe Holozàn zeichnete sich durch zunehmend trockene Bedingungen aus, was urn 9 000 v.u.Z. in den mittleren Breiten zu weit verbreiteten niedrigen Seewasserspiegeln fùhrte. Um 6 000 v.u.Z. dehnte sich diese Zone niedriger Wasserspiegel von 32° bis 51o nôrdlicher Breite aus. Viele Erscheinungsformen, die die heutigen Seen-Wasserspiegel charakterisieren. insbesondere hohe Seen-Wasserspiegel nôrdlich von 46° nôrdlicher Breite und entlang der Ostkùste wurden um 3 000 v.u.Z. festgelegt. Durch die Jahrtausende sind vier unterschiedliche régionale Muster des Seen-Verhaltens fests-tellbar. Fur jedes dieser Gebiete werden Histogramme des Seen-Zustandes von 20 000 bis O Jahren v.u.Z. vorgelegt. Sie illustrieren die zeitliche Anordnung der Seen-Wasserspiegelschwankungen auf einer Zeit-Skala von 103-104 Jahren. Verànderungen im Seenzustand Nord-amerikas werden interpretiert als Hinweis auf eine Verlagerung der Hauptmerkmale der allgemeinen atmosphàrischen Strômungen, insbesondere was die Westwinde des Gebiets und die àquatoriale Windstille betrifft. Das spiegelt sich in Verànderungen der Zugrichtung der Luftmassen und folglich der Position der Luftmassengrenzen ùber dem Kontinent

How to estimate a cumulative process’s rate-function

Consider two sequences of bounded random variables, a value and a timing process, that satisfy the large deviation principle (LDP) with rate-function J(·,·) and whose cumulative process satisfies the LDP with rate-function I(·). Under mixing conditions, an LDP for estimates of I constructed by transforming an estimate of J is proved. For the case of cumulative renewal processes it is demonstrated that this approach is favorable to a more direct method as it ensures the laws of the estimates converge weakly to a Dirac measure at I