177 research outputs found
Consequences of a Change in the Galactic Environment of the Sun
The interaction of the heliosphere with interstellar clouds has attracted
interest since the late 1920's, both with a view to explaining apparent
quasi-periodic climate "catastrophes" as well as periodic mass extinctions.
Until recently, however, models describing the solar wind - local interstellar
medium (LISM) interaction self-consistently had not been developed. Here, we
describe the results of a two-dimensional (2D) simulation of the interaction
between the heliosphere and an interstellar cloud with the same properties as
currently, except that the neutral H density is increased from the present
value of n(H) ~ 0.2 cm^-3 to 10 cm^-3. The mutual interaction of interstellar
neutral hydrogen and plasma is included. The heliospheric cavity is reduced
considerably in size (approximately 10 - 14 AU to the termination shock in the
upstream direction) and is highly dynamical. The interplanetary environment at
the orbit of the Earth changes markedly, with the density of interstellar H
increasing to ~2 cm^-3. The termination shock itself experiences periods where
it disappears, reforms and disappears again. Considerable mixing of the shocked
solar wind and LISM occurs due to Rayleigh-Taylor-like instabilities at the
nose, driven by ion-neutral friction. Implications for two anomalously high
concentrations of 10Be found in Antarctic ice cores 33 kya and 60 kya, and the
absence of prior similar events, are discussed in terms of density enhancements
in the surrounding interstellar cloud. The calculation presented here supports
past speculation that the galactic environment of the Sun moderates the
interplanetary environment at the orbit of the Earth, and possibly also the
terrestrial climate.Comment: 23 pages, 2 color plates (jpg), 3 figures (eps
Integrating the little talks intervention into Early Head Start: An experimental examination of implementation supports involving fidelity monitoring and performance feedback
Enriching home visiting services by incorporating scientifically-supported interventions is a means for improving their effectiveness in promoting child development. However, deliberate efforts to ensure that home visitors are fully knowledgeable and supported to implement interventions with parents of young children are necessary. In this experimental study, a randomly-assigned group of Early Head Start home visitors monitored the fidelity of their provision of a scientifically-based intervention, Little Talks, and the program\u27s general child development services. On a bi-weekly basis, home visitors received performance feedback specific to their implementation of Little Talks and based upon the fidelity data. Findings demonstrated that home visitors showed immediate and consistent mastery of the Little Talks content, while the quality of their implementation, including their clinical decision-making and collaborative processes, improved to adequate levels over time. The Little Talks home visitors showed generalized improvements in their ability to obtain Parent Input while providing the program\u27s typical child development services were detected. In fact, Little Talks home visitors\u27 were superior in obtaining Parent Input relative to comparison home visitors. Further, parents for whom low-quality intervention implementation was observed discontinued their enrollment in home visiting prematurely, while high-quality implementation was associated with sustained enrollment. Limitations for this study are identified, leading to future directions for advancing home visitors\u27 incorporation of evidence-based practices
Variability in Frontotemporal Brain Structure: The Importance of Recruitment of African Americans in Neuroscience Research
BACKGROUND: Variation in brain structure is both genetically and environmentally influenced. The question about potential differences in brain anatomy across populations of differing race and ethnicity remains a controversial issue. There are few studies specifically examining racial or ethnic differences and also few studies that test for race-related differences in context of other neuropsychiatric research, possibly due to the underrepresentation of ethnic minorities in clinical research. It is within this context that we conducted a secondary data analysis examining volumetric MRI data from healthy participants and compared the volumes of the amygdala, hippocampus, lateral ventricles, caudate nucleus, orbitofrontal cortex (OFC) and total cerebral volume between Caucasian and African-American participants. We discuss the importance of this finding in context of neuroimaging methodology, but also the need for improved recruitment of African Americans in clinical research and its broader implications for a better understanding of the neural basis of neuropsychiatric disorders. METHODOLOGY/PRINCIPAL FINDINGS: This was a case control study in the setting of an academic medical center outpatient service. Participants consisted of 44 Caucasians and 33 ethnic minorities. The following volumetric data were obtained: amygdala, hippocampus, lateral ventricles, caudate nucleus, orbitofrontal cortex (OFC) and total cerebrum. Each participant completed a 1.5 T magnetic resonance imaging (MRI). Our primary finding in analyses of brain subregions was that when compared to Caucasians, African Americans exhibited larger left OFC volumes (F (1,68) = 7.50, p = 0.008). CONCLUSIONS: The biological implications of our findings are unclear as we do not know what factors may be contributing to these observed differences. However, this study raises several questions that have important implications for the future of neuropsychiatric research
The impact of intellectual disabilities on elite sports performance
Athletes with intellectual disabilities (ID) were re-introduced into the Paralympics in London 2012. As part of this development a classification system had to be established evidencing the impact this impairment has on elite sports performance. This review examines the research behind this issue. Firstly it examines the limited literature comparing the standards reached by top-level athletes with ID with those without disabilities, and then moves on to look at the research demonstrating differences in both the cognitive and physical skills needed for elite performance. The article then reviews the factors that may be implicated to account for this disparity, from a range of perspectives. A case is made for the importance of looking at this area in terms of the potential for the transferability of research findings from this group to talent identification in mainstream athletes and the benefits of integrating neuropsychological concepts and approaches to understanding the cognitive components behind the development of particular skills associated with high-level performance in specific sports
Understanding the Spectral Energy Distributions of the Galactic Star Forming Regions IRAS 18314-0720, 18355-0532 & 18316-0602
Embedded Young Stellar Objects (YSO) in dense interstellar clouds is treated
self-consistently to understand their spectral energy distributions (SED).
Radiative transfer calculations in spherical geometry involving the dust as
well as the gas component, have been carried out to explain observations
covering a wide spectral range encompassing near-infrared to radio continuum
wavelengths. Various geometric and physical details of the YSOs are determined
from this modelling scheme. In order to assess the effectiveness of this
self-consistent scheme, three young Galactic star forming regions associated
with IRAS 18314-0720, 18355-0532 and 18316-0602 have been modelled as test
cases. They cover a large range of luminosity ( 40). The modelling of
their SEDs has led to information about various details of these sources, e.g.
embedded energy source, cloud structure & size, density distribution,
composition & abundance of dust grains etc. In all three cases, the best fit
model corresponds to the uniform density distribution.Comment: AAMS style manuscript with 3 tables (in a separate file) and 4
figures. To appear in Journal of Astronophysics & Astronom
Tiny-Scale Molecular Structures in the Magellanic Clouds (Part 1)
We report on the {\small FUSE} detections of the HD and CO molecules {\bf on
the lines of sight towards three Large Magellanic stars}: Sk 67D05, Sk
68D135, and Sk 69D246. HD is also detected for the first time {\bf on the
lines of sight towards two Small Magellanic Cloud stars}: AV 95 and Sk 159.
While the HD and CO abundances are expected to be lower in the Large Magellanic
Cloud where molecular fractions are a third of the Galactic value and where the
photodissociation flux is up to thousands times larger, we report an average
HD/H ratio of 1.40.5 ppm and CO/H ratio ranging from 0.8 to 2.7
ppm similar to the Galactic ones. We tentatively identify a deuterium reservoir
(hereafter D--reservoir) towards the Small Magellanic Cloud, along the light
path to AV 95. We derive a D/H ratio ranging from 1. 10 to 1.1
10.Comment: 34 pages, 10 tables, 12 figures, accepted for publication in A&
Small scale structure in molecular gas from multi-epoch observations of HD 34078
We present spectroscopic observations of the runaway reddened star HD 34078
acquired during the last three years at Observatoire de Haute Provence and
McDonald Observatory as well as other spectra obtained since 1990. The drift of
the line of sight through the foreground cloud due to the large transverse
velocity of HD 34078 allows us to probe the spatial distribution of CH, CH+, CN
and DIBs carriers at scales ranging from about 1 AU up to 150 AU. In
particular, time variations in the equivalent width of absorption lines are
examined. A few past and recent high resolution observations of CH and CH+
absorption are used to search for line profile variations and to convert
equivalent widths into column densities.
The data set reveals a 20 % increase in CH column density over the past 10
years with no corresponding variation in the column density of CH+ or in the
strengths of the 5780 and 5797 AA DIBs. CN observations indicate that its
excitation temperature has significantly increased from < 3.1 K in 1993 to 3.6
+- 0.17 K in 1998 while the CN column shows only a modest rise of ~ 12 +- 6 %.
The data also strongly suggest the existence of weak correlated variations in
CH and CH+ columns over periods of 6 - 12 months (or ~ 10 AU).
These results are discussed in relation to CH+ production mechanisms. A dense
newly intervening clump is considered in order to explain the long-term
increase in the column density of CH, but such a scenario does not account for
all observational constraints. Instead, the observations are best described by
CH+ production in a photodissociation region, like that suggested for the
Pleiades and IC 348.Comment: 12 pages, 14 figures. accepted for publication in A&A. v2 : the few
notes on the absorption line at 5772 AA have been remove
The changing role of china in the global illegal cigarette trade
This study explores the history of the illegal production, distribution, and smuggling of cigarettes in mainland China. Data were obtained from a content analysis of 931 media reports retrieved from LexisNexis for the time period 1975 until 2010, and from other open sources. The illegal cigarette trade first emerged in the form of violations of state tobacco monopoly regulations. In the course of the restructuring of the legal tobacco sector, which occurred under external political pressure to open the Chinese market to foreign competition, an illegal cigarette industry emerged which at first primarily produced fake Chinese brand cigarettes for the domestic black market. At the same time, China became a destination country for smuggled genuine Western brand cigarettes. It was only after effective crackdowns against cigarette smuggling and domestic distribution channels in the late 1990s that the Chinese illegal cigarette industry shifted to exporting large numbers of counterfeit Western brand cigarettes to black markets abroad. China’s current role as a leading supplier of counterfeit cigarettes is a result of the contradictions of the economic reform process and of external licit and illicit forces that worked toward opening up the Chinese tobacco sector to the outside world
The role of reflection and mentoring in ICT teacher professional development: dialogue and learning across the hemispheres
Effects of Heavy Metals and Arbuscular Mycorrhiza on the Leaf Proteome of a Selected Poplar Clone: A Time Course Analysis
Arbuscular mycorrhizal (AM) fungi establish a mutualistic symbiosis with the roots of most plant species. While receiving photosynthates, they improve the mineral nutrition of the plant and can also increase its tolerance towards some pollutants, like heavy metals. Although the fungal symbionts exclusively colonize the plant roots, some plant responses can be systemic. Therefore, in this work a clone of Populus alba L., previously selected for its tolerance to copper and zinc, was used to investigate the effects of the symbiosis with the AM fungus Glomus intraradices on the leaf protein expression. Poplar leaf samples were collected from plants maintained in a glasshouse on polluted (copper and zinc contaminated) or unpolluted soil, after four, six and sixteen months of growth. For each harvest, about 450 proteins were reproducibly separated on 2DE maps. At the first harvest the most relevant effect on protein modulation was exerted by the AM fungi, at the second one by the metals, and at the last one by both treatments. This work demonstrates how importantly the time of sampling affects the proteome responses in perennial plants. In addition, it underlines the ability of a proteomic approach, targeted on protein identification, to depict changes in a specific pattern of protein expression, while being still far from elucidating the biological function of each protein
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