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    Earth's middle age

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    This research was funded through Natural Environment Research Council (grant NE/J021822/1) and the APC was paid through the RCUK OA block grant.Earth's middle age, extending from 1.7 to 0.75 Ga, was characterized by environmental, evolutionary, and lithospheric stability that contrasts with the dramatic changes in preceding and succeeding eras. The period is marked by a paucity of preserved passive margins, an absence of a significant Sr anomaly in the paleoseawater record and in the εHf(t) in detrital zircon, a lack of orogenic gold and volcanic-hosted massive sulfide deposits, and an absence of glacial deposits and iron formations. In contrast, anorthosites and kindred bodies are well developed and major pulses of Mo and Cu mineralization, including the world's largest examples of these deposits, are features of this period. These trends are attributed to a relatively stable continental assemblage that was initiated during assembly of the Nuna supercontinent by ca. 1.7 Ga and continued until breakup of its closely related successor, Rodinia, ca. 0.75 Ga. The overall low abundance of passive margins is consistent with a stable continental configuration, which also provided a framework for environmental and evolutionary stability. A series of convergent margin accretionary orogens developed along the edge of the supercontinent. Abundant anorthosites and related rocks developed inboard of the plate margin. Their temporal distribution appears to link with the secular cooling of the mantle, at which time the overlying continental lithosphere was strong enough to be thickened and to support the emplacement of large plutons into the crust, yet the underlying mantle was still warm enough to result in widespread melting of the lower thickened crust.Publisher PDFPeer reviewe

    Supernovae astrophysics from Middle Age documents

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    The supernova explosion of 1054 AD, which originated the Crab Nebula and Pulsar, is probably the astronomical event which has been most deeply studied by means of historical sources. However, many mysteries and inconsistencies, both among the different sources and between what is deduced by the historical records and the present day astronomical data, are demanding extraordinary efforts by theoretical astrophysicists in order to put all the data in a meaningful framework. An accurate analysis of the historical sources, like the one we are presenting here, may contribute to solve some of these problems.Comment: in: Proc. of the IAU Symposium no.230, "Populations of High Energy Sources in Galaxies", held in Dublin (Ireland), August 15-19, 2005. Evert J.A. Meurs & G. Fabbiano, eds. (in press

    Second Age, Middle Age

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    The recent releases of the volume The Fall of Númenor and the series The Lord of the Rings: The Rings of Power raise the question: What is the significance of the Second Age of Tolkien’s legendarium? This article suggests that Tolkien conceived of the Second Age as parallel to the Middle Ages in our world, which were the focus of his academic career in his studies of Old and Middle English language and literature. As various frameworks and overviews for the legendarium demonstrate, Tolkien thought of the Second Age, like the Middle Ages, as uniquely looking backwards and forwards in time. At the same time, the incomplete and fragmentary nature of the stories from the Second Age—in the appendices to The Lord of the Rings, The Silmarillion, Unfinished Tales, and various volumes of The History of Middle-Earth—shows that Tolkien was unsuccessful in creating a center and meaning to his legendarium. Instead of creating hope for improvement, they ultimately always exposed the corruption, decay, decline, and failure at the center of the human experience

    Whole body vibration training and its application to age-related performance decrements:an exploratory analysis

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    Middle age is associated with a pronounced decline in power and flexibility. Whilst whole body vibration training (WBVT) improves performance in a range of populations, whether WBVT can improve muscle power and flexibility in a middle-aged population is not known. The present study aimed to determine the influence of 5 weeks progressive WBVT in middle-aged (45-55 yrs.) and younger (20-30 yrs.) recreationally active females. Participants in each age group were randomly allocated to an intervention (WBVT) or control group. The WBVT groups trained for five weeks on a vibration platform, while the control groups performed identical exercises, with no vibration. Prior to, and after, the five-week study vertical countermovement jump (VCMJ) and range of motion (ROM) performance were measured. WBVT significantly (P = 0.001) improved VCMJ performance when compared to the control groups. This improvement was significantly (P = 0.001) greater in the middle-aged compared with the younger WBVT group. WBVT significantly (P = 0.001) improved ROM irrespective of age. Taken together, these results suggest that WBVT can off-set age related performance decrements, which has therapeutic implications for musculoskeletal aging. Therefore, WBVT could be undertaken to minimise age-related performance deterioration in middle-aged female populations

    The Age At Menarche In Nigerian Adolescents From Two Different Socioeconomic Classes

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    Menarcheal age was studied in 900 girls, half of which were from middle class families and the other half from low income class families from the Niger delta region of Nigeria. A retrospective and descriptive random sampling study was conducted through the use of questionnaires. Social class was based on parental occupation. The mean age at menarche for girls from middle class families was 12.22 ± 1.19 years while that for girls from low income families was 13.01 ± 1.44 years. Most of the children from the middle class families attained menarche at the ages of 12 and 13 while those from the low income families attained menarche at the ages of 12, 13 and 14 years.: The age at menarche of girls from middle class families was significantly lower than those of girls from the low socioeconomic class and is similar to those obtained for U.S. girls The age of menarche of girls from low income families is lower than a result of similar study obtained for rural India

    "The Persistence of Hardship Over the Life Course"

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    This paper focuses on the persistence of hardship from middle age to old age. Proposed status maintenance models suggest that stratification of economic status occurs over the life course (e.g., little mobility is seen within the income distribution). Some studies have found evidence to support this, but none have looked at broader measures of well-being. Using 29 years (1968-96) of data from the Panel Study of Income Dynamics (PSID), the author employs hypothesis tests (t-tests) and logistic regression techniques to examine the relationship between middle-age chronic hardships and adverse old-age outcomes. In almost every case, individuals who experience middle-age chronic hardships are significantly (statistically) more likely to experience adverse old-age outcomes.

    Child Care Expenses Make Middle-Class Incomes Hard to Reach

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    In this brief, authors Robert Paul Hartley, Marybeth Mattingly, and Christopher Wimer present estimates of the number of families that cannot maintain a middle-class income as a result of child care expenses. Estimates are based on 2013–2017 data from the Current Population Survey’s Annual Social and Economic Supplement, which corresponds to income and expenses during 2012–2016. They report that approximately 9 percent of working families with children under age 6 are pushed out of the middle class as a result of child care expenses. For working families with very young children (under age 3), 8 percent are pushed below the middle-class threshold. If all middle-class working families with young children were to pay what typical upper-middle and middle-class families pay for child care, roughly $6,900 per year on average, an additional 21 percent would be pushed below the middle-class threshold. They report that the current funding infrastructure for helping parents find and pay for affordable, quality child care is woefully inadequate. One way to support working families would be to increase funding for the Child Care and Development Fund, which is currently targeted toward families below the middle class

    Psychosocial factors influencing risk-taking in middle age for STIs

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    Objectives To increase the knowledge of the psychosocial factors influencing sexual risk-taking for STIs among adults in late middle age. Methods Individual interviews were conducted either face to face or by telephone with 31 heterosexual men and women aged between 45 and 65. They were recruited from NHS sexual health services (n=16) and council run culture and leisure facilities (n=15) in a large Scottish city. A total of 18 women and 13 men were interviewed. All interviews were transcribed in full and thematically analysed. Results Analysis detailed important psychosocial and sociocultural factors; the prioritisation of intimacy above and beyond concerns about risks for STI in sexual partnerships; the importance of unwanted pregnancy in shaping risk perceptions throughout the life course; vulnerability associated with periods of relationship transition (eg, bereavement, divorce or separation); social norms and cultural expectations relating to age-appropriate sexual and health-seeking behaviours. Conclusions This is the first qualitative study to examine the factors associated with sexual risk-taking among heterosexual adults in late middle age in the UK. Many factors associated with sexual risk-taking are similar to those reported within other populations. However, we also detail population-specific factors, which should be considered in terms of the development of interventions for ‘at risk’ older adults, or the tailoring of wider behaviour change interventions to this specific age group

    Middle-Age Job Mobility: Its Determinants and Consequences

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    Our paper uses the wealth of information available in the NLS to expand on previous work in several ways. First, we investigate whether there is a meaningful distinction among types of job separations. Traditional analysis has categorized job separations as either employee-initiated (quits) or employer-initiated (layoffs). We question whether this dichotomy is correct. The National Longitudinal Survey data is especially useful for studying the relationship between wages and the probability of quitting. Most theoretical work on the determinants of job separation concludes that the probability of changing jobs is related to a reservation wage. The NLS data set allows us to test this relationship since it includes information on the individual's "hypothetical wage"-- that is, the wage required to induce the individual to accept another job. Given this information, we are able to compare the effects of different measures of the individual's price of time (e.g. the current wage and the reservation wage) on the probability of quitting. In addition, we analyze the role of human capital variables, job related characteristics and family background in the determination of job mobility. The analysis of the determinants of job separations in the cross-section naturally leads to an investigation of the relationship between previous separations and future separations. In particular, we consider whether such a relationship exists, and whether the nature of previous separations is a good predictor of the nature of future separations. Finally, we analyze the effects of job mobility on earnings and on job satisfaction. We distinguish between the immediate gains to mobility and the future gains to mobility, and also consider whether the nature of the separation is an important determinant of the consequences of job mobility.
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