7,298 research outputs found
Charge mobility of discotic mesophases: A multiscale quantum/classical study
A correlation is established between the molecular structure and charge
mobility of discotic mesophases of hexabenzocoronene derivatives by combining
electronic structure calculations, Molecular Dynamics, and kinetic Monte Carlo
simulations. It is demonstrated that this multiscale approach can provide an
accurate ab-initio description of charge transport in organic materials
Radial Color Gradients in K+A Galaxies in Distant Clusters of Galaxies
Galaxies in rich clusters with z 0.3 are observed to have a higher
fraction of photometrically blue galaxies than their nearby counterparts. This
raises the important question of what environmental effects can cause the
termination of star formation between z 0.3 and the present. The star
formation may be truncated due to ram-pressure stripping, or the gas in the
disk may be depleted by an episode of star formation caused by some external
perturbation. To help resolve this issue, surface photometry was carried out
for a total of 70 early-type galaxies in the cluster Cl1358+62, at z
0.33, using two-color images from the Hubble Archive. The galaxies were divided
into two categories based on spectroscopic criteria: 24 are type K+A (e.g.,
strong Balmer lines, with no visible emission lines), while the remaining 46
are in the control sample with normal spectra. Radial color profiles were
produced to see if the K+A galaxies show bluer nuclei in relation to their
surrounding disks. Specifically, a linear gradient was fit to the radial color
profile of each galaxy. We find that the K+A galaxies on average tend to have
slightly bluer gradients towards the center than the normals. A
Kolmogorov-Smirnov two-sample test has been applied to the two sets of color
gradients. The result of the test indicates that there is only a 2%
probability that the K+A and normal samples are drawn from the same parent
distribution. There is a possible complication from a trend in the apparent
magnitude vs. color gradient relation, but overall our results favor the
centralized star formation scenario as an important process in the evolution of
galaxies in dense clusters.Comment: 16 pages, 12 figures, accepted for publication in A
Starbursts versus Truncated Star Formation in Nearby Clusters of Galaxies
We present long-slit spectroscopy, B and R bandpass imaging, and 21 cm
observations of a sample of early-type galaxies in nearby clusters which are
known to be either in a star-forming phase or to have had star formation which
recently terminated. From the long-slit spectra, obtained with the Blanco 4-m
telescope, we find that emission lines in the star-forming cluster galaxies are
significantly more centrally concentrated than in a sample of field galaxies.
The broadband imaging reveals that two currently star-forming early-type
galaxies in the Pegasus I cluster have blue nuclei, again indicating that
recent star formation has been concentrated. In contrast, the two galaxies for
which star formation has already ended show no central color gradient. The
Pegasus I galaxy with the most evident signs of ongoing star formation
(NGC7648), exhibits signatures of a tidal encounter. Neutral hydrogen
observations of that galaxy with the Arecibo radiotelescope reveal the presence
of ~4 x 10^8 solar masses of HI. Arecibo observations of other current or
recent star-forming early-type galaxies in Pegasus I indicate smaller amounts
of gas in one of them, and only upper limits in others.Comment: to be published in Astronomical Journa
Neuropsychological evaluation of blast-related concussion: Illustrating the challenges and complexities through OEF/OIF case studies
Background/objective: Soldiers of Operations Enduring Freedom (OEF) and Iraqi Freedom (OIF) sustain blast-related mild traumatic brain injury (concussion) with alarming regularity. This study discusses factors in addition to concussion, such as co-morbid psychological difficulty (e.g. post-traumatic stress) and symptom validity concerns that may complicate neuropsychological evaluation in the late stage of concussive injury.
Case report: The study presents the complexities that accompany neuropsychological evaluation of blast concussion through discussion of three case reports of OEF/OIF personnel.
Discussion: The authors emphasize uniform assessment of blast concussion, the importance of determining concussion severity according to acute-injury characteristics and elaborate upon non-concussion-related factors that may impact course of cognitive limitation. The authors conclude with a discussion of the need for future research examining the impact of blast concussion (particularly recurrent concussion) and neuropsychological performance
Evaluation Context Impacts Neuropsychological Performance of OEF/OIF Veterans with Reported Combat-Related Concussion
Although soldiers of Operations Iraqi Freedom (OIF) and Enduring Freedom (OEF) encounter combat-related concussion at an unprecedented rate, relatively few studies have examined how evaluation context, insufficient effort, and concussion history impact neuropsychological performances in the years following injury. The current study explores these issues in a sample of 119 U.S. veterans (OEF/OIF forensic concussion, n = 24; non-OEF/OIF forensic concussion, n = 20; OEF/OIF research concussion, n = 38; OEF/OIF research without concussion, n = 37). The OEF/OIF forensic concussion group exhibited significantly higher rates of insufficient effort relative to the OEF/OIF research concussion group, but a comparable rate of insufficient effort relative to the non-OEF/OIF forensic concussion group. After controlling for effort, the research concussion and the research non-concussion groups demonstrated comparable neuropsychological performance. Results highlight the importance of effort assessment among OEF/OIF and other veterans with concussion history, particularly in forensic contexts
Neuropsychological Outcomes of U.S. Veterans with Report of Remote Blast-Related Concussion and Current Psychopathology
This study explored whether remote blast-related MTBI and/or current Axis I psychopathology contribute to neuropsychological outcomes among OEF/OIF veterans with varied combat histories. OEF/OIF veterans underwent structured interviews to evaluate history of blast-related MTBI and psychopathology and were assigned to MTBI (n = 18), Axis I (n = 24), Co-morbid MTBI/Axis I (n = 34), or post-deployment control (n = 28) groups. A main effect for Axis I diagnosis on overall neuropsychological performance was identified (F(3,100) = 4.81; p = .004), with large effect sizes noted for the Axis I only (d = .98) and Co-morbid MTBI/Axis I (d = .95) groups relative to the control group. The latter groups demonstrated primary limitations on measures of learning/memory and processing speed. The MTBI only group demonstrated performances that were not significantly different from the remaining three groups. These findings suggest that a remote history of blast-related MTBI does not contribute to objective cognitive impairment in the late stage of injury. Impairments, when present, are subtle and most likely attributable to PTSD and other psychological conditions. Implications for clinical neuropsychologists and future research are discussed. (JINS, 2012, 18, 1–11
Low-Luminosity Early-Type Galaxies in the Coma Cluster: Variations in Spectral Properties
We present spectra of nine low-luminosity early-type galaxies (M_B > -17.5)
in the Coma cluster. The spectra, which were obtained with the Multiple Mirror
Telescope and cover the spectral region 3300-5350 A, exhibit a large variation
in Balmer line strengths. In fact the line strength variation among the Coma
low-luminosity galaxies is as large as that found among a sample of
low-luminosity ellipticals in the Virgo cluster and lower density environments.
When compared to detailed population synthesis models, the variation in Balmer
line strengths among the Coma galaxies indicates a range in luminosity-weighted
mean age of from 1 Gyr to 12 Gyr. The two youngest galaxies are shown to be in
a post-starburst state, i.e., they are not simply former spirals whose star
formation was recently terminated. Moreover, the 1 Gyr ages of these two
youngest low-luminosity galaxies are similar to those of the brighter
post-starburst galaxies in Coma.Comment: To appear in the Astronomical Journa
Public Awareness of the Nebraska Regional Poison Control Center
A Poison Control Center needs to continually update its impact on the community it serves. At the Nebraska Regional Poison Control Center, a telephone survey was performed to ascertain baseline data for ongoing poison awareness programs. Our data shows that 36.6% of the population would call the PCC in the case of acute poisoning. There is a need to stress that the PCC is not only a center for information but also for treatment at home. Distribution of the PCC phone number to be attached to the phone needs to be increased. Many people obtained the phone number through time consuming methods which would increase the anxiety of the caller. Despite past programs, 63.9% of the respondents were not familiar with Syrup of Ipecac, and overall out of 608, people, 91.1% did not have Syrup of Ipecac at home in case of poisoning. In distributing poison information to the public, the pre-school and other school programs seem to be very effective. Newspapers and television also are an integral part in distributing poison information. With the help of the networks and newspapers in devoting time and space to poison prevention more households can be reached. There is a need to involve the pharmacist in distribution of poison information. Being the major supplier of Syrup of Ipecac, pharmacists can take a more active role by always carrying Syrup of Ipecac, and displaying it so that patrons may be reminded that they should have it at home
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