177 research outputs found
Fast Vacuum Decay into Quark Pairs in Strong Color Electric and Magnetic Fields
We study quark-pair creations in strong color electromagnetic fields. We
point out that, for massless quarks, the vacuum persistency probability per
unit space-time volume is zero, i.e., the quark-pair creation rate w is
infinite, in general homogeneous color electromagnetic fields, while it is
finite when the color magnetic field is absent. We find that the contribution
from the lowest Landau level (LLL) dominates this phenomenon. With an effective
theory of the LLL projection, we also discuss dynamics of the vacuum decay,
taking into account the back reaction of pair creations.Comment: 4 pages, 1 figure, contribution to the proceedings of International
conference on the structure of baryons (BARYONS'10), RCNP, Osaka, Japan, Dec.
7-11, 2010; fig.2 delete
Computerizing Social-Emotional Assessment for School Readiness: First Steps toward an Assessment Battery for Early Childhood Settings
The transition into formal schooling is a crucial foundation that can set children on a cycle of success or failure in both academic and social domains. A child’s abilities to express healthy emotions, understand emotions of self and others, regulate emotion, attention, and behavior, make good decisions regarding social problems, and engage in a range of prosocial behaviors, all work together to promote a successful school experience.
However, many children have deficits in these skills by school entry, and educators lack the requisite tools to identify, track and assess skills these children need to learn. Thus, because social-emotional learning (SEL) is so crucial, assessment tools to pinpoint children’s skills and progress are vitally necessary. Previous work by the authors and other researchers has led to the development of strong assessment tools; however, these tools are often developed solely for research use, not practitioner application. In the following, using our assessment battery as an example, we will discuss the steps necessary to adapt SEL assessment for computer-based administration and optimal utility in early childhood education programs
eta' meson under partial restoration of chiral symmetry in nuclear medium
We shed light upon the eta' mass in nuclear matter in the context of partial
restoration of chiral symmetry, pointing out that the U_{A}(1) anomaly effects
causes the eta'-eta mass difference necessarily through the chiral symmetry
breaking. As a consequence, it is expected that the eta' mass is reduced by
order of 100 MeV in nuclear matter where partial restoration of chiral symmetry
takes place. The discussion given here is based on Ref. [1].Comment: 3 pages, 2 figures. Contribution to Meson201
Dust Size Growth and Settling in a Protoplanetary Disk
We have studied dust evolution in a quiescent or turbulent protoplanetary
disk by numerically solving coagulation equation for settling dust particles,
using the minimum mass solar nebular model. As a result, if we assume an
ideally quiescent disk, the dust particles settle toward the disk midplane to
form a gravitationally unstable layer within 2x10^3 - 4x10^4 yr at 1 - 30 AU,
which is in good agreement with an analytic calculation by Nakagawa, Sekiya, &
Hayashi (1986) although they did not take into account the particle size
distribution explicitly. In an opposite extreme case of a globally turbulent
disk, on the other hand, the dust particles fluctuate owing to turbulent motion
of the gas and most particles become large enough to move inward very rapidly
within 70 - 3x10^4 yr at 1 - 30 AU, depending on the strength of turbulence.
Our result suggests that global turbulent motion should cease for the
planetesimal formation in protoplanetary disks.Comment: 27 pages, 8 figures, accepted for publication in the Ap
Spectroscopy of eta'-nucleus bound states at GSI-SIS
The eta' meson mass may be reduced due to partial restoration of chiral
symmetry. If this is the case, an eta'-nucleus system may form a nuclear bound
state. We plan to carry out a missing-mass spectroscopy with the 12C(p,d)
reaction at GSI-SIS. Peak structures corresponding to such a bound state may be
observed even in an inclusive measurement, if the decay width is narrow enough.Comment: 4 pages, 2 figures, to appear in the proceedings of MESON2012 (12th
International Workshop on Meson Production, Properties and Interaction),
Krakow, Polan
Dynamical mass generation of a two-component fermion in Maxwell-Chern-Simons QED_3: The lowest ladder approximation
Dynamical mass generation of a two-component fermion in with a
Chern-Simons term is investigated by solving the Schwinger-Dyson equation
formulated in the lowest ladder approximation. Dependence of the dynamical
fermion mass on a gauge-fixing parameter, a gauge coupling constant, and a
topological mass is examined by approximated analytical and also numerical
methods. The inclusion of the Chern-Simons term makes impossible to choose a
peculiar gauge in which a wave function renormalization is absent. The
numerical evaluation shows that the wave function renormalization is fairly
close to 1 in the Landau gauge. It means that this gauge is still a specific
gauge where the Ward-Takahashi identity is satisfied approximately. We also
find that the dynamical mass is almost constant if the topological mass is
larger than the coupling constant, while it decreases when the topological mass
is comparable to or smaller than the coupling constant and tends to the value
in without the Chern-Simons term.Comment: 22 pages, 9 figures, Version to appear in Phys. Rev.
Structure and Instabilities of an Irradiated Viscous Protoplanetary Disk
We investigate the structure and the stabilities of a protoplanetary disk,
which is heated by viscous process in itself and by its central star. The disk
is set to rotate with the Keplerian velocity and has the surface density
distribution of the minimum mass solar nebula. We assume the vertical
hydrostatic equilibrium and the radiative equilibrium at each point, and solve
the two-dimensional radiative transfer equation by means of the Short
Characteristic method in the spherical coordinate in order to determine the
disk structure. Our calculation shows that at the outer region of the disk with
a distance from the central star of x>1AU the radiative heating from the inner
disk dominates the viscous heating even near the midplane. It is because of the
high temperature distribution in the optically thin surface layer and the
relatively high disk height as a consequence of the irradiation from the inner
hot region of the disk. In addition, we examine the convective and the
magnetorotational instabilities of the disk. As a result, the whole disk is
convectively stable since the dusty region is not heated by the viscous
dissipation from the midplane but by the radial radiative heating. On the other
hand, almost all the disk is magnetorotationally unstable except for the region
near the equatorial plane of from 2AU to 10AU. Finally we discuss the growth
and the size distribution of dust particles in the disk, which suggests that
there exist cm-sized particles in the surface layer, namely, in the exposed
region of the disk.Comment: 23 pages, 5 figures, accepted by ApJ (Vol. 567, 2002
Assessing the carcinogenic potential of low-dose exposures to chemical mixtures in the environment: the challenge ahead.
Lifestyle factors are responsible for a considerable portion of cancer incidence worldwide, but credible estimates from the World Health Organization and the International Agency for Research on Cancer (IARC) suggest that the fraction of cancers attributable to toxic environmental exposures is between 7% and 19%. To explore the hypothesis that low-dose exposures to mixtures of chemicals in the environment may be combining to contribute to environmental carcinogenesis, we reviewed 11 hallmark phenotypes of cancer, multiple priority target sites for disruption in each area and prototypical chemical disruptors for all targets, this included dose-response characterizations, evidence of low-dose effects and cross-hallmark effects for all targets and chemicals. In total, 85 examples of chemicals were reviewed for actions on key pathways/mechanisms related to carcinogenesis. Only 15% (13/85) were found to have evidence of a dose-response threshold, whereas 59% (50/85) exerted low-dose effects. No dose-response information was found for the remaining 26% (22/85). Our analysis suggests that the cumulative effects of individual (non-carcinogenic) chemicals acting on different pathways, and a variety of related systems, organs, tissues and cells could plausibly conspire to produce carcinogenic synergies. Additional basic research on carcinogenesis and research focused on low-dose effects of chemical mixtures needs to be rigorously pursued before the merits of this hypothesis can be further advanced. However, the structure of the World Health Organization International Programme on Chemical Safety 'Mode of Action' framework should be revisited as it has inherent weaknesses that are not fully aligned with our current understanding of cancer biology
Measles vaccine coverage and factors related to uncompleted vaccination among 18-month-old and 36-month-old children in Kyoto, Japan
BACKGROUND: Due to low vaccine coverage, Japan has not only experienced outbreaks of measles but has also been exporting it overseas. This study aims to survey measles vaccine coverage and the factors uncompleted vaccination among community-living children. METHODS: Subjects were the parents whose children had undergone either an 18-month or a 36-month checkup publicly provided by Kyoto City during November 2001 to January 2002. An anonymous self-administered questionnaire survey was conducted. RESULTS: The coverage was 73.2% among the 18-month-old children (n = 2707) and 88.9% among the 36-month-old children (n = 2340), respectively. The following characteristics of mothers were related to uncompleted measles vaccination: aged below 30, working, concerned about the adverse events of the vaccine, and had insufficient knowledge. Similarly, the following characteristics among children were related to uncompleted measles vaccination: not the first-born child, interacting with other children in group settings. The coverage was the lowest among the children whose mothers were concerned about the adverse events of the vaccine without proper knowledge of measles and its vaccination. CONCLUSION: To increase vaccine coverage among children, parents' awareness about measles and vaccination against it should be promoted, especially for working mothers. Efforts to enhance access to vaccination services and to communicate with parents about changing vaccination schedules are necessary
- …