47,874 research outputs found
Chameleon Vector Bosons
We show that for a force mediated by a vector particle coupled to a conserved
U(1) charge, the apparent range and strength can depend on the size and density
of the source, and the proximity to other sources. This "chameleon" effect is
due to screening from a light charged scalar. Such screening can weaken
astrophysical constraints on new gauge bosons. As an example we consider the
constraints on chameleonic gauged B-L. We show that although Casimir
measurements greatly constrain any B-L force much stronger than gravity with
range longer than 0.1 microns, there remains an experimental window for a long
range chameleonic B-L force. Such a force could be much stronger than gravity,
and long or infinite range in vacuum, but have an effective range near the
surface of the earth which is less than a micron.Comment: 10 page
Psychotropic medication use among children in the child welfare system
Prior research demonstrates that children in the child welfare system are given psychotropic medication at rates approximately three times higher than children and adolescents in the general population. Using data from the second National Survey of Child and Adolescent Well-Being, authors Wendy Walsh and Marybeth Mattingly report that among children age 4 and older with a report of maltreatment, rates of psychotropic medication use are significantly higher in rural (20 percent) than urban areas (13 percent). Children age 4 and older with a maltreatment report in rural areas were significantly more likely to take more than one medication than children in urban areas. The significantly higher rates of psychotropic medication use among children in rural areas and the significantly higher rates of taking multiple medications point to the need among child welfare professionals in rural areas to closely monitor use. The results of the current analysis indicate that more information is needed about the complex decision-making process regarding medication use. This includes a need to better understand how pediatric clinicians make decisions, and the impact of community norms on medication use
Formation and Evolution of Binary Asteroids
Satellites of asteroids have been discovered in nearly every known small body
population, and a remarkable aspect of the known satellites is the diversity of
their properties. They tell a story of vast differences in formation and
evolution mechanisms that act as a function of size, distance from the Sun, and
the properties of their nebular environment at the beginning of Solar System
history and their dynamical environment over the next 4.5 Gyr. The mere
existence of these systems provides a laboratory to study numerous types of
physical processes acting on asteroids and their dynamics provide a valuable
probe of their physical properties otherwise possible only with spacecraft.
Advances in understanding the formation and evolution of binary systems have
been assisted by: 1) the growing catalog of known systems, increasing from 33
to nearly 250 between the Merline et al. (2002) Asteroids III chapter and now,
2) the detailed study and long-term monitoring of individual systems such as
1999 KW4 and 1996 FG3, 3) the discovery of new binary system morphologies and
triple systems, 4) and the discovery of unbound systems that appear to be
end-states of binary dynamical evolutionary paths.
Specifically for small bodies (diameter smaller than 10 km), these
observations and discoveries have motivated theoretical work finding that
thermal forces can efficiently drive the rotational disruption of small
asteroids. Long-term monitoring has allowed studies to constrain the system's
dynamical evolution by the combination of tides, thermal forces and rigid body
physics. The outliers and split pairs have pushed the theoretical work to
explore a wide range of evolutionary end-states.Comment: 42 pages, 4 figures, contribution to the Asteroids 4 boo
Long-term foster care: different needs, different outcomes
This brief examines where foster children are living four years after removal from their homes and the characteristics of these children and their placements. Understanding whether child characteristics such as age or emotional or behavioral problems are associated with a longer stay in out-of-home care can help identify children who are least likely to find permanence and may benefit from specialized services. The authors conclude that children in long-term foster care suffer from behavioral and emotional problems at alarming rates. Better identifying and assisting children with, or at risk of developing such problems upon entry to foster care and throughout their out-of-home placement, may alleviate their needs and troubles and provide mechanisms for supporting them as they get older. The authors also discuss programs having a positive impact on former foster care youths and the need for more state and federal investment in these programs. Their findings suggest that it may be worthwhile for states to reconsider their policies for the sake of long-term success
Understanding child abuse in rural and urban America: risk factors and maltreatment substantiation
Using a large national sample of child maltreatment reports, this brief compares the outcomes of child maltreatment cases in rural versus urban places and identifies the characteristics associated with substantiation. Child abuse cases substantiated in rural and urban areas share many caregiver risk factors, such as drug and alcohol abuse, and many family stressors. Substantiation is equally likely across income levels; approximately one-fourth of cases in each income level are substantiated. However, when place is taken into account, a greater share (36 percent) of higher-income families (that is, families with incomes greater than 200 percent of the federal poverty level) in rural areas have substantiated maltreatment reports than in urban areas
Rural families with a child abuse report are more likely headed by a single parent and endure economic and family stress
This brief, which is based on data from the Survey of Child and Adolescent Well-Being, finds that rural families who have been reported to Child Protective Services are more likely than urban families to have financial difficulties and high family stress, as well as grow up in single-parent households. To effectively address these issues, the brief urges policy makers to look at the lack of accessible and adequate services for struggling rural families
Child Protective Services May Link Families to Needed Income Supports
A number of public safety-net programs exist to help improve the economic well-being of vulnerable children, but little is known about the extent to which families with a child maltreatment report receive these services over time. In this brief, we examine the incidence of receiving four types of income support both immediately after the child maltreatment report and eighteen months following. The data for this analysis come from the second National Survey of Child and Adolescent Well-Being (NSCAW II), a national sample of children who had a maltreatment report that resulted in an investigation by CPS within a 15-month period beginning in February 2008.
Authors Wendy Walsh and Marybeth Mattingly report that the child protective system, especially in rural areas, may link families to needed supports. Among families who did not initially report safety net receipt and reported financial challenges, more rural (51 percent) than urban (38 percent) received at least one safety net program eighteen months later. Among families who did not initially report safety net receipt and reported financial challenges, more rural (38 percent) than urban (7 percent) families said they were managing to “save a little money each month” eighteen months after their encounter with the child protective system
Related Foster Parents Less Likely to Receive Support Services Compared With Nonrelative Foster Parents
This brief identifies gaps in support services among foster parents using data from a nationally representative survey of children involved in the child welfare system (the second National Survey of Child and Adolescent Well-Being). Authors Wendy Walsh and Marybeth Mattingly report that the percentage of foster parents who received recent support services (within a six month timeframe) varies dramatically by foster placement and support service type. Kinship foster parents (both formal and informal) in all households regardless of poverty status are less likely to have received training, used respite care, or participated in peer support groups in the past six months compared with nonrelative foster parents. The authors conclude that even in this era of limited resources, it is important to make sure that all foster parents (those in poor and nonpoor households), and particularly kinship foster parents, have access to adequate support services to help ensure that children in out-of-home placements are nurtured and that foster parents receive the support they need to continue their important work
An imaging and spectroscopic study of the planetary nebulae in NGC 5128 (Centaurus A): Planetary nebulae catalogues
Imaging and spectroscopic observations of planetary nebulae (PNe) in the
nearest large elliptical galaxy NGC 5128 (Centaurus A), were obtained to find
more PNe and measure their radial velocities. NTT imaging was obtained in 15
fields in NGC 5128 over an area of about 1 square degree with EMMI using [O
III] and off-band filters. Newly detected sources, combined with literature
PNe, were used as input for VLT FLAMES multi-fibre spectroscopy in MEDUSA mode.
Spectra of the 4600-5100A region were analysed and velocities measured based on
emission lines of [O III]4959,5007A and often H-beta. The chief results are
catalogues of 1118 PN candidates and 1267 spectroscopically confirmed PNe in
NGC 5128. The catalogue of PN candidates contains 1060 PNe discovered with EMMI
imaging and 58 from literature surveys. The spectroscopic PN catalogue has
FLAMES radial velocity and emission line measurements for 1135 PNe, of which
486 are new. Another 132 PN radial velocities are available from the
literature. For 629 PNe observed with FLAMES, H-beta was measured in addition
to [O III]. Nine targets show double-lined or more complex profiles, and their
possible origin is discussed. FLAMES spectra of 48 globular clusters were also
targetted: 11 had emission lines detected (two with multiple components), but
only 3 are PNe likely to belong to the host globular. The total of 1267
confirmed PNe in NGC 5128 with radial velocity measurements (1135 with small
velocity errors) is the largest collection of individual kinematic probes in an
early-type galaxy. This PN dataset, as well as the catalogue of PN candidates,
are valuable resources for detailed investigation of the stellar population of
NGC 5128. [Abridged]Comment: 19 pages, 11 figures. Accepted for publication in Astronomy and
Astrophysics. Tables 7 - 11 available in electronic form at CDS. Replaced
with a few typos fixe
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