4,708 research outputs found
Serum-based biomarkers and magnetic resonance imaging following mild traumatic brain injury in collegiate athletes post return-to-play
Recently there has been an increase in the use of MRI (Magnetic Resonance Imaging), to measure the effects of traumatic brain injury (TBI). Proteins such as BDNF, S100B, UCH-L1, and Tau have been found to have altered levels in blood serum after TBI. However, there is limited knowledge about the relationship between serum-based and MRI-based biomarkers in concussed athletes post return-to-play. This study aimed to bridge this gap by collecting serum samples from 42 participants across two groups. The first group (n = 21) consisted of recently cleared to return-to-play collegiate athletes after experiencing a sports-related concussion. The second group (n = 21) was collegiate athlete controls matched on age, sex, and sport. Structural and functional MRI were used for analysis from a subgroup of 26 participants (13 concussed, 13 control). Blood samples were collected to assess the levels of BDNF, S100B, UCH-L1, and Tau. To the best of our knowledge, this is the first study to analyze protein levels in association with gray matter volume (GMV) and resting state functional connectivity (rsFC) following sports-related concussion. BDNF was the most effective protein at differentiating concussion from control. Significant differential relationships were found between BDNF, S100B, UCH-L1, and Tau with GMV and rsFC, suggesting that serum-based biomarkers may have important clinical implications in concussion diagnosis and treatment
Formation and Disruption of Cosmological Low Mass Objects
We investigate the evolution of cosmological low mass (low virial
temperature) objects and the formation of the first luminous objects. First,
the `cooling diagram' for low mass objects is shown. We assess the cooling rate
taking into account the contribution of H_2, which is not in chemical
equilibrium generally, with a simple argument of time scales. The reaction
rates and the cooling rate of H_2 are taken from the recent results by Galli &
Palla (1998). Using this cooling diagram, we also estimate the formation
condition of luminous objects taking into account the supernova (SN) disruption
of virialized clouds. We find that the mass of the first luminous object is
several times 10^7 solar mass, because smaller objects may be disrupted by the
SNe before they become luminous. Metal pollution of low mass (Ly-alpha) clouds
also discussed. The resultant metallicity of the clouds is about 1/1000 of the
solar metallicity.Comment: 11 pages, 2 figures, To appear in ApJ
Regulated star formation in forming disk galaxies under ultraviolet radiation background
We perform radiation hydrodynamics simulations on the evolution of galactic
gas disks irradiated by ultraviolet radiation background. We find gas disks
with N_H > 10^21 cm^-2 exposed to ultraviolet radiation at a level of I_21=1
can be self-shielded from photoheating, whereas the disk with N_H < 10^21 cm^-2
cannot. We also find that the unshielded disks keep smooth density distribution
without any sign of fragmentation, while the self-shielded disks easily
fragment into small pieces by self-gravity, possibly followed by star
formation. The suppression of star formation in unshielded disks is different
from photoevaporation effect, since the assumed dark halo potential is deep
enough to keep the photoheated gas. Presence of such critical threshold column
density would be one of the reason for the so-called down-sizing feature of
present-day galaxies.Comment: 12pages, 10figures, ApJ accepte
An Application of Kerr Blackhole Fly-Wheel Model to Statistical Properties of QSOs/AGNs
The aim of this work is to demonstrate the properties of the magnetospheric
model around Kerr blackholes (BHs), so-called the fly-wheel (rotation driven)
model. The fly-wheel engine of the BH-accretion disk system is applied to the
statistics of QSOs/AGNs. In the model, the central BH is assumed to be formed
at and obtains nearly maximum but finite rotation energy (
extreme Kerr BH) at the formation stage. The inherently obtained rotation
energy of the Kerr BH is released through an magnetohydrodynamic process. This
model naturally leads finite lifetime of AGN activity.
Nitta et al. (1991) clarified individual evolution of Kerr BH fly-wheel
engine which is parametrized by BH mass, initial Kerr parameter, magnetic field
near the horizon and a dimension-less small parameter. We impose a statistical
model for the initial mass function (IMF) of ensemble of BHs by the
Press-Schechter formalism. By the help of additional assumptions, we can
discuss the evolution of the luminosity function and the spatial number density
of QSOs/AGNs.Comment: 12 pages, 7 figures Fig.7 has been replace
A study of random laser modes in disordered photonic crystals
We studied lasing modes in a disordered photonic crystal. The scaling of the
lasing threshold with the system size depends on the strength of disorder. For
sufficiently large size, the minimum of the lasing threshold occurs at some
finite value of disorder strength. The highest random cavity quality factor was
comparable to that of an intentionally introduced single defect. At the
minimum, the lasing threshold showed a super-exponential decrease with the size
of the system. We explain it through a migration of the lasing mode frequencies
toward the photonic bandgap center, where the localization length takes the
minimum value. Random lasers with exponentially low thresholds are predicted.Comment: 4 pages, 4 figure
All-angle left-handed negative refraction in Kagome and honeycomb lattice photonic crystals
Possibilities of all-angle left-handed negative refraction in 2D honeycomb
and Kagome lattices made of dielectric rods in air are discussed for the
refractive indices 3.1 and 3.6. In contrast to triangular lattice photonic
crystals made of rods in air, both the honeycomb and Kagome lattices show
all-angle left-handed negative refraction in the case of the TM2 band for low
normalized frequencies. Certain advantages of the honeycomb and Kagome
structures over the triangular lattice are emphasized. This specially concerns
the honeycomb lattice with its circle-like equifrequency contours where the
effective indices are close to -1 for a wide range of incident angles and
frequencies.Comment: 7 pages, 8 figures, pd
The Portuguese observatory on occupational psychosocial factors: contribution for public health
To achieve the goal of sustainable employment, considering
the profile of the Portuguese working population (PWP), is
needed a range of strategies to ensure long, productive, and
sustainable careers allied with a better quality of working life,
health, and wellbeing, but also with public health policies
grounded on scientifically validated and reliable data. This is
possible through a comprehensive working system approach
that ensures workers will be mentally and physically able to
remain at work by the balance between work demands and
individual resources allied with public health policies transfer
into the workplaces by organizations’ leadership and policy
makers. The Portuguese Observatory on Occupational Factors
(Popsy@Work) aims at addressing this global challenge by: i)
digitally collecting psychosocial data on the PWP; ii)
implementing and strengthening of a psychosocial occupational
health surveillance digital system; iii) providing
reference values for the PWP concerning Psychosocial
Health; iv) Transferring to society knowledge and best
practices; v) Raising awareness on the importance of
psychosocial management in occupational settings based on
science. Popsy@work is a digital platform that collects and
aggregates psychosocial data analytically and creates a
visualization hub adding value to data on the PWP and
giving science back to society in a usable way, empowering
workers, strengthening organizations and grounding public
policies. Pospy@Work considers the development of strategic
intelligence on levels and inequalities of psychosocial health
and well-being in occupational settings by robust metrics and
reference data. Creating opportunities for national policy
dialogue on inequalities, including the psychosocial health of
the PWP through collaboration with diverse sectors identifying
and mapping subgroups of populations whose unmet needs
require specific outreach measures
Lyalpha versus X-ray heating in the high-z IGM
In this paper we examine the effect of X-ray and Lyalpha photons on the
intergalactic medium temperature. We calculate the photon production from a
population of stars and micro-quasars in a set of cosmological hydrodynamic
simulations which self-consistently follow the dark matter dynamics, radiative
processes as well as star formation, black hole growth and associated feedback
processes. We find that, (i) IGM heating is always dominated by X-rays unless
the Lyalpha photon contribution from stars in objects with mass M<10^8 Msun
becomes significantly enhanced with respect to the X-ray contribution from BHs
in the same halo (which we do not directly model). (ii) Without overproducing
the unresolved X-ray background, the gas temperature becomes larger than the
CMB temperature, and thus an associated 21 cm signal should be expected in
emission, at z<11.5. We discuss how in such a scenario the transition redshift
between a 21 cm signal in absorption and in emission could be used to
constraint BHs accretion and associated feedback processes.Comment: 7 pages, 3 figures, accepted for publication in MNRA
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