9,236 research outputs found
Advanced electric propulsion system concept for electric vehicles. Addendum 1: Voltage considerations
The two electric vehicle propulsion systems that best met cost and performance goals were examined to assess the effect of battery pack voltage on system performance and cost. A voltage range of 54 to 540 V was considered for a typical battery pack capacity of 24 k W-hr. The highest battery specific energy (W-hr/kg) and the lowest cost (0.057/km and for the flywheel system was $0.037/km
Keck Imaging of the Globular Cluster Systems in the Early--type Galaxies NGC 1052 and NGC 7332
The presence of two globular cluster subpopulations in early-type galaxies is
now the norm rather than the exception. Here we present two more examples for
which the host galaxy appears to have undergone a recent merger. Using
multi-colour Keck imaging of NGC 1052 and NGC 7332 we find evidence for a
bimodal globular cluster colour distribution in both galaxies, with roughly
equal numbers of blue and red globular clusters. The blue ones have similar
colours to those in the Milky Way halo and are thus probably very old and
metal-poor. If the red GC subpopulations are at least solar metallicity, then
stellar population models indicate young ages. We discuss the origin of
globular clusters within the framework of formation models. We conclude that
recent merger events in these two galaxies have had little effect on their
overall GC systems. We also derive globular cluster density profiles, global
specific frequencies and in the case of NGC 1052, radial colour gradients and
azimuthal distribution. In general these globular cluster properties are normal
for early-type galaxies.Comment: 11 pages, Latex, 15 figures, 2 tables, accepted by MNRA
Diamonds on the Hat: Globular Clusters in The Sombrero Galaxy (M104)
Images from the HST ACS are used to carry out a new photometric study of the
globular clusters (GCs) in M104, the Sombrero galaxy. The primary focus of our
study is the characteristic distribution function of linear sizes (SDF) of the
GCs. We measure the effective radii for 652 clusters with PSF-convolved King
and Wilson dynamical model fits. The SDF is remarkably similar to those
measured for other large galaxies of all types, adding strong support to the
view that it is a "universal" feature of globular cluster systems.
We develop a more general interpretation of the size distribution function
for globular clusters, proposing that the shape of the SDF that we see today
for GCs is strongly influenced by the early rapid mass loss during their star
forming stage, coupled with stochastic differences from cluster to cluster in
the star formation efficiency (SFE) and their initial sizes. We find that the
observed SDF shape can be accurately predicted by a simple model in which the
protocluster clouds had characteristic sizes of pc and SFEs of
. The colors and luminosities of the M104 clusters show the
clearly defined classic bimodal form. The blue sequence exhibits a
mass/metallicity relation (MMR), following a scaling of heavy-element abundance
with luminosity of very similar to what has been found in most
giant elliptical galaxies. A quantitative self-enrichment model provides a good
first-order match to the data for the same initial SFE and protocluster size
that were required to explain the SDF. We also discuss various forms of the
globular cluster Fundamental Plane (FP) of structural parameters, and show that
useful tests of it can be extended to galaxies beyond the Local Group.Comment: In press for MNRA
Interactions between empathy and resting heart rate in early adolescence predict violent behavior in late adolescence and early adulthood.
BackgroundAlthough resting heart rate (RHR) and empathy are independently and negatively associated with violent behavior, relatively little is known about the interplay between these psychophysiological and temperament-related risk factors.MethodsUsing a sample of 160 low-income, racially diverse men followed prospectively from infancy through early adulthood, this study examined whether RHR and empathy during early adolescence independently and interactively predict violent behavior and related correlates in late adolescence and early adulthood.ResultsControlling for child ethnicity, family income, and child antisocial behavior at age 12, empathy inversely predicted moral disengagement and juvenile petitions for violent crimes, while RHR was unrelated to all measures of violent behavior. Interactive effects were also evident such that among men with lower but not higher levels of RHR, lower empathy predicted increased violent behavior, as indexed by juvenile arrests for violent offenses, peer-reported violent behavior at age 17, self-reported moral disengagement at age 17, and self-reported violent behavior at age 20.ConclusionsImplications for prevention and intervention are considered. Specifically, targeting empathic skills among individuals at risk for violent behavior because of specific psychophysiological profiles may lead to more impactful interventions
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The interaction between monoamine oxidase A and punitive discipline in the development of antisocial behavior: Mediation by maladaptive social information processing.
Previous studies demonstrate that boys' monoamine oxidase A (MAOA) genotype interacts with adverse rearing environments in early childhood, including punitive discipline, to predict later antisocial behavior. Yet the mechanisms by which MAOA and punitive parenting interact during childhood to amplify risk for antisocial behavior are not well understood. In the present study, hostile attributional bias and aggressive response generation during middle childhood, salient aspects of maladaptive social information processing, were tested as possible mediators of this relation in a sample of 187 low-income men followed prospectively from infancy into early adulthood. Given racial-ethnic variation in MAOA allele frequencies, analyses were conducted separately by race. In both African American and Caucasian men, those with the low-activity MAOA allele who experienced more punitive discipline at age 1.5 generated more aggressive responses to perceived threat at age 10 relative to men with the high-activity variant. In the African American subsample only, formal mediation analyses indicated a marginally significant indirect effect of maternal punitiveness on adult arrest records via aggressive response generation in middle childhood. The findings suggest that maladaptive social information processing may be an important mechanism underlying the association between MAOA × Parenting interactions and antisocial behavior in early adulthood. The present study extends previous work in the field by demonstrating that MAOA and harsh parenting assessed in early childhood interact to not only predict antisocial behavior in early adulthood, but also predict social information processing, a well-established social-cognitive correlate of antisocial behavior
Structural parameters for globular clusters in M31 and generalizations for the fundamental plane
The structures of globular clusters (GCs) reflect their dynamical states and
past histories. High-resolution imaging allows the exploration of morphologies
of clusters in other galaxies. Surface brightness profiles from new Hubble
Space Telescope observations of 34 globular clusters in M31 are presented,
together with fits of several different structural models to each cluster. M31
clusters appear to be adequately fit by standard King models, and do not
obviously require alternate descriptions with relatively stronger halos, such
as are needed to fit many GCs in other nearby galaxies. The derived structural
parameters are combined with corrected versions of those measured in an earlier
survey to construct a comprehensive catalog of structural and dynamical
parameters for M31 GCs with a sample size similar to that for the Milky Way.
Clusters in M31, the Milky Way, Magellanic Clouds, Fornax dwarf spheroidal and
NGC 5128 define a very tight fundamental plane with identical slopes. The
combined evidence for these widely different galaxies strongly reinforces the
view that old globular clusters have near-universal structural properties
regardless of host environment.Comment: AJ in press; 59 pages including 16 figure
Alarm Pheromone in a Gregarious Poduromorph Collembolan (Collembola: Hypogastruridae)
We report an alarm pheromone in the gregarious poduromorph collembolan, Hypogastrura pannosa. Cuticular rupture results in emission of a rapidly vaporizing hexane-soluble material with an active space diameter of ca. 1 cm. Conspecifics encountering the vapor front respond with stereotypic aversion and dispersal behaviors. This is the first report on the presence of an alarm pheromone in the order Collembola
Interplay of linear and nonlinear impurities in the formation of stationary localized states
Formation of stationary localized states in one-dimensional chain as well as
in a Cayley tree due to a linear impurity and a nonlinear impurity is studied.
Furthermore, a one-dimensional chain with linear and nonlinear site energies at
the alternate sites is studied and rich phase diagrams of SL states are
obtained for all systems we considered. The results are compared with those of
the linear and nonlinear systems.Comment: 7 pages, Latex, 7 figure
Prepotentials for local mirror symmetry via Calabi-Yau fourfolds
In this paper, we first derive an intrinsic definition of classical triple
intersection numbers of K_S, where S is a complex toric surface, and use this
to compute the extended Picard-Fuchs system of K_S of our previous paper,
without making use of the instanton expansion. We then extend this formalism to
local fourfolds K_X, where X is a complex 3-fold. As a result, we are able to
fix the prepotential of local Calabi-Yau threefolds K_S up to polynomial terms
of degree 2. We then outline methods of extending the procedure to non
canonical bundle cases.Comment: 42 pages, 7 figures. Expanded, reorganized, and added a theoretical
background for the calculation
Influence of interstellar and atmospheric extinction on light curves of eclipsing binaries
Interstellar and atmospheric extinctions redden the observational photometric
data and they should be handled rigorously. This paper simulates the effect of
reddening for the modest case of two main sequence T1 = 6500K and T2 = 5500K
components of a detached eclipsing binary system. It is shown that simply
subtracting a constant from measured magnitudes (the approach often used in the
field of eclipsing binaries) to account for reddening should be avoided.
Simplified treatment of the reddening introduces systematics that reaches
\~0.01mag for the simulated case, but can be as high as ~0.2mag for e.g.
B8V--K4III systems. With rigorous treatment, it is possible to uniquely
determine the color excess value E(B-V) from multi-color photometric light
curves of eclipsing binaries.Comment: 6 pages, 9 figures, 1 table, Kopal's Binary Star Legacy conference
contribution (Litomysl 2004), to be published by Kluwer A&S
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