5,645 research outputs found
Youth Who Are Obese Sustain Moderate-to-Vigorous Physical Activity Intensity During Active Video Games
Please refer to the pdf version of the abstract located adjacent to the title
The Relationship Between Lower Extremity Functional Strength and Aerobic Performance in Youth with Cerebral Palsy (CP)
Please refer to the pdf version of the abstract located adjacent to the title
A model for the orientational ordering of the plant microtubule cortical array
The plant microtubule cortical array is a striking feature of all growing
plant cells. It consists of a more or less homogeneously distributed array of
highly aligned microtubules connected to the inner side of the plasma membrane
and oriented transversely to the cell growth axis. Here we formulate a
continuum model to describe the origin of orientational order in such confined
arrays of dynamical microtubules. The model is based on recent experimental
observations that show that a growing cortical microtubule can interact through
angle dependent collisions with pre-existing microtubules that can lead either
to co-alignment of the growth, retraction through catastrophe induction or
crossing over the encountered microtubule. We identify a single control
parameter, which is fully determined by the nucleation rate and intrinsic
dynamics of individual microtubules. We solve the model analytically in the
stationary isotropic phase, discuss the limits of stability of this isotropic
phase, and explicitly solve for the ordered stationary states in a simplified
version of the model.Comment: 15 pages, 5 figure
High prevalence of scrapie in a dairy goat herd: tissue distribution of disease-associated PrP and effect of PRNP genotype and age
Following a severe outbreak of clinical scrapie in 2006â2007, a
large dairy goat herd was culled
and 200 animals were selected for post-mortem examinations in order to
ascertain the prevalence of infection,
the effect of age, breed and PRNP genotype on the susceptibility to scrapie,
the tissue distribution of diseaseassociated
PrP (PrP), and the comparative efficiency of different diagnostic methods.
As determined by immunohistochemical (IHC) examinations with Bar224 PrP antibody, the
prevalence of preclinical infection
was very high (72/200; 36.0%), with most infected animals being positive
for PrP in lymphoreticular system
(LRS) tissues (68/72; 94.4%) compared to those that were positive in
brain samples (38/72; 52.8%). The
retropharyngeal lymph node and the palatine tonsil showed the highest
frequency of PrP accumulation (87.3%
and 84.5%, respectively), while the recto-anal mucosa-associated lymphoid
tissue (RAMALT) was positive in
only 30 (41.7%) of the infected goats. However, the efficiency of rectal
and palatine tonsil biopsies taken
shortly before necropsy was similar. The probability of brain and RAMALT
being positive directly
correlated with the spread of PrP within the LRS. The prevalence of
infection was influenced by PRNP
genetics at codon 142 and by the age of the goats: methionine carriers older
than 60 months showed a much
lower prevalence of infection (12/78; 15.4%) than those younger than 60Â months (20/42; 47.6%); these last
showed prevalence values similar to isoleucine homozygotes of any age
(40/80; 50.0%). Two of seven goats
with definite signs of scrapie were negative for PrP in brain but positive
in LRS tissues, and one goat showed
biochemical and IHC features of PrP different from all other infected
goats. The results of this study have
implications for surveillance and control policies for scrapie in goats
Stellar and circumstellar evolution of long period variable stars
In a first paper, HIPPARCOS astrometric and kinematic data were used to
calibrate both infrared K and IRAS luminosities at the same time as kinematic
parameters of Long Period Variable stars (LPVs). Individual estimated absolute
magnitudes and a probabilistic assignation to galactic populations were deduced
from these calibrations for each LPV of our sample. Here we propose a scenario
of simultaneous stellar and circumstellar evolution according to the galactic
populations. The transitory states of S and Tc stars allow us to confirm the
location of the first dredge-up at . There is also evidence
suggesting that a previous enrichment in s-elements from a more evolved
companion may accelerate the evolution along the AGB. The possible evolution to
OH LPVs is included in this scenario, and any of these stars may have a mass at
the limit of the capability for a C enrichment up to C/O > 1.
A list of bright massive LPVs with peculiar envelope and luminosity
properties is proposed as Hot Bottom Burning candidates. The He-shell flash
star, R Cen, is found to be exceptionally bright and could become, before
leaving the AGB, a C-rich LPV brighter than the usual luminosity limit of
carbon stars.Comment: Accepted for publication in Astronomy & Astrophysic
A Fast Algorithm for Robust Regression with Penalised Trimmed Squares
The presence of groups containing high leverage outliers makes linear
regression a difficult problem due to the masking effect. The available high
breakdown estimators based on Least Trimmed Squares often do not succeed in
detecting masked high leverage outliers in finite samples.
An alternative to the LTS estimator, called Penalised Trimmed Squares (PTS)
estimator, was introduced by the authors in \cite{ZiouAv:05,ZiAvPi:07} and it
appears to be less sensitive to the masking problem. This estimator is defined
by a Quadratic Mixed Integer Programming (QMIP) problem, where in the objective
function a penalty cost for each observation is included which serves as an
upper bound on the residual error for any feasible regression line. Since the
PTS does not require presetting the number of outliers to delete from the data
set, it has better efficiency with respect to other estimators. However, due to
the high computational complexity of the resulting QMIP problem, exact
solutions for moderately large regression problems is infeasible.
In this paper we further establish the theoretical properties of the PTS
estimator, such as high breakdown and efficiency, and propose an approximate
algorithm called Fast-PTS to compute the PTS estimator for large data sets
efficiently. Extensive computational experiments on sets of benchmark instances
with varying degrees of outlier contamination, indicate that the proposed
algorithm performs well in identifying groups of high leverage outliers in
reasonable computational time.Comment: 27 page
Braneworld Cosmology in (Anti)--de Sitter Einstein--Gauss--Bonnet--Maxwell Gravity
Braneworld cosmology for a domain wall embedded in the charged (Anti)-de
Sitter-Schwarzschildblack hole of the five--dimensional
Einstein-Gauss-Bonnet-Maxwell theory is considered. The effective Friedmann
equation for the brane is derived by introducing the necessary surface
counterterms required for a well-defined variational principlein the
Gauss--Bonnet theory and for the finiteness of the bulk space. The asymptotic
dynamics of the brane cosmology is determined and it is found that solutions
with vanishingly small spatial volume are unphysical. The finiteness of the
bulk action is related to the vanishing of the effective cosmological constant
on the brane. An analogy between the Friedmann equation and a generalized
Cardy--Verlinde formula is drawn.Comment: LaTex file 28 pages, typos corrected, one reference is adde
Kinetics of active surface-mediated diffusion in spherically symmetric domains
We present an exact calculation of the mean first-passage time to a target on
the surface of a 2D or 3D spherical domain, for a molecule alternating phases
of surface diffusion on the domain boundary and phases of bulk diffusion. We
generalize the results of [J. Stat. Phys. {\bf 142}, 657 (2011)] and consider a
biased diffusion in a general annulus with an arbitrary number of regularly
spaced targets on a partially reflecting surface. The presented approach is
based on an integral equation which can be solved analytically. Numerically
validated approximation schemes, which provide more tractable expressions of
the mean first-passage time are also proposed. In the framework of this minimal
model of surface-mediated reactions, we show analytically that the mean
reaction time can be minimized as a function of the desorption rate from the
surface.Comment: Published online in J. Stat. Phy
A Study of CO Emission in High Redshift QSOs Using the Owens Valley Millimeter Array
Searches for CO emission in high-redshift objects have traditionally suffered
from the accuracy of optically-derived redshifts due to lack of bandwidth in
correlators at radio observatories. This problem has motivated the creation of
the new COBRA continuum correlator, with 4 GHz available bandwidth, at the
Owens Valley Radio Observatory Millimeter Array. Presented here are the first
scientific results from COBRA. We report detections of redshifted CO(J=3-2)
emission in the QSOs SMM J04135+10277 and VCV J140955.5+562827, as well as a
probable detection in RX J0911.4+0551. At redshifts of z=2.846, z=2.585, and
z=2.796, we find integrated CO flux densities of 5.4 Jy km/s, 2.4 Jy km/s, and
2.9 Jy km/s for SMM J04135+10277, VCV J140955.5+562827, and RX J0911.4+0551,
respectively, over linewidths of Delta(V_{FWHM}) ~ 350 km/s. These
measurements, when corrected for gravitational lensing, correspond to molecular
gas masses of order M(H_2) ~ 10^{9.6-11.1} solar masses, and are consistent
with previous CO observations of high-redshift QSOs. We also report 3-sigma
upper limits on CO(3-2) emission in the QSO LBQS 0018-0220 of 1.3 Jy km/s. We
do not detect significant 3mm continuum emission from any of the QSOs, with the
exception of a tentative (3-sigma) detection in RX J0911.4+0551 of S_{3mm}=0.92
mJy/beam.Comment: 18 pages, 5 figures, 2 tables, accepted to ApJ. Changes made for
version 2: citations added, 2 objects added to Table 2 and Figure
Comparative Dosimetric Analysis and Normal Tissue Complication Probability Modelling of Four-Dimensional Computed Tomography Planning Scans Within the UK NeoSCOPE Trial
Aims: NeoSCOPE is a trial of two different neoadjuvant chemoradiotherapy regimens for resectable oesophageal cancer and was the first multicentre trial in the UK to incorporate four-dimensional computed tomography (4D-CT) into radiotherapy planning. Despite 4D-CT being increasingly accepted as a standard of care for lower third and junctional oesophageal tumours, there is limited evidence of its benefit over standard three-dimensional computed tomography (3D-CT). // Materials: Using NeoSCOPE 4D-CT cases, we undertook a dosimetric comparison study of 3D-CT versus 4D-CT plans comparing target volume coverage and dose to organs at risk. We used established normal tissue complication probability models to evaluate the potential toxicity reduction of using 4D-CT plans in oesophageal cancer. // Results: 4D-CT resulted in a smaller median absolute PTV volume and lower dose levels for all reported constraints with comparable target volume coverage. NTCP modelling suggests a significant relative risk reduction of cardiac and pulmonary toxicity endpoints with 4D-CT. // Conclusion: Our work shows that incorporating 4D-CT into treatment planning may significantly reduce the toxicity burden from this treatment
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