1,974 research outputs found

    Social re-orientation and brain development: An expanded and updated view.

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    Social development has been the focus of a great deal of neuroscience based research over the past decade. In this review, we focus on providing a framework for understanding how changes in facets of social development may correspond with changes in brain function. We argue that (1) distinct phases of social behavior emerge based on whether the organizing social force is the mother, peer play, peer integration, or romantic intimacy; (2) each phase is marked by a high degree of affect-driven motivation that elicits a distinct response in subcortical structures; (3) activity generated by these structures interacts with circuits in prefrontal cortex that guide executive functions, and occipital and temporal lobe circuits, which generate specific sensory and perceptual social representations. We propose that the direction, magnitude and duration of interaction among these affective, executive, and perceptual systems may relate to distinct sensitive periods across development that contribute to establishing long-term patterns of brain function and behavior

    An engineering and economic evaluation of some mixed-mode waste heat rejection systems

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    Originally presented as the first author's thesis, (Sc. D.)--in the M.I.T. Dept. of Nuclear Engineering, 1977Includes bibliographical references (p. 336-342

    Phase field modeling of electrochemistry II: Kinetics

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    The kinetic behavior of a phase field model of electrochemistry is explored for advancing (electrodeposition) and receding (electrodissolution) conditions in one dimension. We described the equilibrium behavior of this model in [J. E. Guyer, W. J. Boettinger, J.A. Warren, and G. B. McFadden, ``Phase field modeling of electrochemistry I: Equilibrium'', cond-mat/0308173]. We examine the relationship between the parameters of the phase field method and the more typical parameters of electrochemistry. We demonstrate ohmic conduction in the electrode and ionic conduction in the electrolyte. We find that, despite making simple, linear dynamic postulates, we obtain the nonlinear relationship between current and overpotential predicted by the classical ``Butler-Volmer'' equation and observed in electrochemical experiments. The charge distribution in the interfacial double layer changes with the passage of current and, at sufficiently high currents, we find that the diffusion limited deposition of a more noble cation leads to alloy deposition with less noble species.Comment: v3: To be published in Phys. Rev. E v2: Attempt to work around turnpage bug. Replaced color Fig. 4a with grayscale 13 pages, 7 figures in 10 files, REVTeX 4, SIunits.sty, follows cond-mat/030817

    A Model for Solid 3^3He: II

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    We propose a simple Ginzburg-Landau free energy to describe the magnetic phase transition in solid 3^3He. The free energy is analyzed with due consideration of the hard first order transitions at low magnetic fields. The resulting phase diagram contains all of the important features of the experimentally observed ph ase diagram. The free energy also yields a critical field at which the transition from the disordered state to the high field state changes from a first order to a second order one.Comment: This paper has been accepted for publication in Journal of Low Temperature Physics. Use regular Tex, with the D. Eardley version of Macros called jnl.tex. 10 pages, 4 figs available from [email protected]

    Annual Summary of Vital Statistics-2001

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    The number of births, the crude birth rate (14.5 in 2001), and the fertility rate (67.2 in 2001) all declined slightly (by 1% or less) from 2000 to 2001. Fertility rates were highest for Hispanic women (107.4), followed by Native American (70.7), Asian or Pacific Islander (69.4), black (69.3), and non-Hispanic white women (58.0). During the early to mid 1990s, fertility declined for non-Hispanic white, black, and American Indian women. Rates for these population groups have changed relatively little since 1995; however, fertility has increased for Asian or Pacific Islander and Hispanic women. The birth rate for teen mothers continued to fall, dropping 5% from 2000 to 2001 to 45.9 births per 1000 females aged 15 to 19 years, another record low. The teen birth rate has fallen 26% since 1991; declines were more rapid (35%) for younger teens aged 15 to 17 years than for older teens aged 18 to 19 years (20%). The proportion of all births to unmarried women remained about the same at one-third. Smoking during pregnancy continued to decline; smoking rates were highest among teen mothers. The use of timely prenatal care increased slightly to 83.4% in 2001. From 1990 to 2001, the use of timely prenatal care increased by 6% (to 88.5%) for non-Hispanic white women, by 23% (to 74.5%) for black women, and by 26% (to 75.7%) for Hispanic women. The number and rate of twin births continued to rise, but the triplet/+ birth rate declined for the second year in a row. For the first year in almost a decade, the preterm birth rate declined (to 11.6%); however, the low birth weight rate was unchanged at 7.6%. The total cesarean delivery rate jumped 7% from 2000 to 2001 to 24.4% of all births, the highest level reported since these data became available on birth certificates (1989). The primary cesarean rate rose 5%, whereas the rate of vaginal birth after a previous cesarean delivery tumbled 20%. In 2001, the provisional infant mortality rate was 6.9 per 1000 live births, the same as in 2000. Racial differences in infant mortality remain a major public health concern, with the rate for infants of black mothers 2.5 times those for infants of non-Hispanic white or Hispanic mothers. In 2000, 66% of all infant deaths occurred among the 7.6% of infants born low birth weight. Among all states, Maine and Massachusetts had the lowest infant mortality rates. The United States continues to rank poorly in international comparisons of infant mortality. The provisional death rate in 2001 was 8.7 deaths per 1000 population, the same as the 2000 final rate. In 2000, unintentional injuries and homicide remained the leading and second-leading causes of death for children 1 to 19 years of age, although the death rate for homicide decreased by 10% from 1999 to 2000. Among unintentional injuries to children, two-thirds were motor vehicle-related; among homicides, two-thirds were firearm-related

    Annual Summary of Vital Statistics-2002

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    The crude birth rate in 2002 was 13.9 births per 1000 population, the lowest ever reported for the United States. The number of births, the crude birth rate, and the fertility rate (64.8) all declined slightly (by 1% or less) from 2001 to 2002. Fertility rates were highest for Hispanic women (94.0), followed by black (65.4), Asian or Pacific Islander (63.9), Native American (58.0), and non-Hispanic white women (57.5). Fertility rates declined slightly for all race/ethnic groups from 2001 to 2002. The birth rate for teen mothers continued to fall, dropping 5% from 2001 to 2002 to 42.9 births per 1000 women aged 15 to 19 years, another record low. The teen birth rate has fallen 31% since 1991; declines were more rapid for younger teens aged 15 to 17 (40%) than for older teens aged 18 to 19 (23%). The proportion of all births to unmarried women remained approximately the same at one third. Smoking during pregnancy continued to decline; smoking rates were highest among teen mothers. In 2002, 26.1% of births were delivered by cesarean section, up 7% since 2001 and 26% since 1996. The primary cesarean rate has risen 23% since 1996, whereas the rate of vaginal birth after a previous cesarean delivery has fallen 55%. The use of timely prenatal care increased slightly to 83.8% in 2002. From 1990 to 2002, the use of timely prenatal care increased by 6% (to 88.7%) for non-Hispanic white women, by 24% (to 75.2%) for black women, and by 28% (to 76.8%) for Hispanic women, thus narrowing racial disparities. The percentage of preterm births rose to 12.0% in 2002, from 10.6% in 1990 and 9.4% in 1981. Increases were largest for non-Hispanic white women. The percentage of low birth weight (LBW) births also increased to 7.8% in 2002, up from 6.7% in 1984. Twin and triplet/+ birth rates both increased by 3% from 2000 to 2001. Multiple births accounted for 3.2% of all births in 2001. The infant mortality rate (IMR) was 6.9 per 1000 live births (provisional data) in 2002 compared with 6.8 in 2001 (final data). The ratio of the IMR among black infants to that for white infants was 2.5 in 2001, the same as in 2000. Racial differences in infant mortality remain a major public health concern. The role of LBW in infant mortality remains a major issue. New Hampshire, Utah, and Massachusetts had the lowest IMRs. State-by-state differences in IMR reflect racial composition, the percentage of LBW, and birth weight–specific neonatal mortality rates for each state. The United States continues to rank poorly in international comparisons of infant mortality. Expectation of life at birth reached a record high of 77.2 years for all sex and race groups combined in 2001. Death rates in the United States continue to decline. Between 2000 and 2001, death rates declined for the 3 leading causes of death: diseases of the heart, malignant neoplasms, and cerebrovascular diseases. Death rates for children ages 1 to 19 years decreased for unintentional injuries by 3.3% in 2001; the death rate for chronic lower respiratory diseases decreased by 25% in 2001. Cancer and suicide levels did not change for children ages 1 to 19. A large proportion of childhood deaths continue to occur as a result of preventable injuries

    Annual Summary of Vital Statistics-2000

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    The birth rate in 2000 (preliminary data)was 14.8 births per 1000 population, an increase of 2% from 1999 (14.5). The fertility rate, births per 1000 women aged 15 to 44 years, increased 3% to 67.6 in 2000, compared with 65.9 in 1999. The 2000 increases in births and the fertility rate were the third consecutive yearly increases, the largest in many years, halting the steady decline in the number of births and fertility rates in the 1990s. Fertility rates for total white, non-Hispanic white, black, and Native American women each increased about 2% in 2000. The fertility rate for black women, which declined 19% from 1990 to 1996, has changed little since 1996. The rate for Hispanic women rose 4% in 2000 to reach the highest level since 1993. Birth rates for women 30 years or older continued to increase. The proportion of births to unmarried women remained about the same at one third, but the number of births rose 3%. The birth rate for teen mothers declined again for the ninth consecutive year. The use of timely prenatal care (83.2%) remained unchanged in 2000, and was essentially unchanged for non-Hispanic white (88.5%), black (74.2%), and Hispanic (74.4%) mothers. The number and rate of multiple births continued their dramatic rise, but all of the increase was confined to twins; for the first time in more than a decade, the number of triplet and higher-order multiple births declined (4%) between 1998 and 1999 (multiple birth information is not available in preliminary 2000 data). The overall increases in multiple births account, in part, for the lack of improvement in the percentage of low birth weight (LBW) births. LBW remained at 7.6% in 2000. The infant mortality rate (IMR) dropped to 6.9 per 1000 live births (preliminary data) in 2000 (the rate was 7.1 in 1999). The ratio of the IMR among black infants to that for white infants was 2.5 in 2000, the same as in 1999. Racial differences in infant mortality remain a major public health concern. The role of low birth weight in infant mortality remains a major issue. Among all of the states, Utah and Maine had the lowest IMRs. State-bystate differences in IMR reflect racial composition, the percentage LBW, and birth weight-specific neonatal mortality rates for each state. The United States continues to rank poorly in international comparisons of infant mortality. Expectation of life at birth reached a record high of 76.9 years for all gender and race groups combined. Death rates in the United States continue to decline. The age-adjusted death rate for suicide declined 4% between 1999 and 2000; homicide declined 7%. Death rates for children 19 years of age or less declined for 3 of the 5 leading causes in 2000; cancer and suicide levels did not change for children as a group. A large proportion of childhood deaths, however, continue to occur as a result of preventable injuries
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