723 research outputs found
Using diffusion tensor imaging to identify corticospinal tract projection patterns in children with unilateral spastic cerebral palsy.
AIM: To determine whether diffusion tensor imaging (DTI) can be an independent assessment for identifying the corticospinal tract (CST) projecting from the more-affected motor cortex in children with unilateral spastic cerebral palsy (CP). METHOD: Twenty children with unilateral spastic CP participated in this study (16 males, four females; mean age 9y 2mo [standard deviation (SD) 3y 2mo], Manual Ability Classification System [MACS] level I-III). We used DTI tractography to reconstruct the CST projecting from the more-affected motor cortex. We mapped the motor representation of the more-affected hand by stimulating the more- and the less-affected motor cortex measured with single-pulse transcranial magnetic stimulation (TMS). We then verified the presence or absence of the contralateral CST by comparing the TMS map and DTI tractography. Fisher's exact test was used to determine the association between findings of TMS and DTI. RESULTS: DTI tractography successfully identified the CST controlling the more-affected hand (sensitivity=82%, specificity=78%). INTERPRETATION: Contralateral CST projecting from the lesioned motor cortex assessed by DTI is consistent with findings of TMS mapping. Since CST connectivity may be predictive of response to certain upper extremity treatments, DTI-identified CST connectivity may potentially be valuable for determining such connectivity where TMS is unavailable or inadvisable for children with seizures.K08 NS073796 - NINDS NIH HHS; TL1 RR024158 - NCRR NIH HHS; K01 NS062116 - NINDS NIH HHS; UL1 RR024156 - NCRR NIH HHS; KL2 RR024157 - NCRR NIH HHS; R01 HD076436 - NICHD NIH HHSPublished versio
Stellar Evolution in NGC 6791: Mass Loss on the Red Giant Branch and the Formation of Low Mass White Dwarfs
We present the first detailed study of the properties (temperatures,
gravities, and masses) of the NGC 6791 white dwarf population. This unique
stellar system is both one of the oldest (8 Gyr) and most metal-rich ([Fe/H] ~
0.4) open clusters in our Galaxy, and has a color-magnitude diagram (CMD) that
exhibits both a red giant clump and a much hotter extreme horizontal branch.
Fitting the Balmer lines of the white dwarfs in the cluster, using Keck/LRIS
spectra, suggests that most of these stars are undermassive, = 0.43 +/-
0.06 Msun, and therefore could not have formed from canonical stellar evolution
involving the helium flash at the tip of the red giant branch. We show that at
least 40% of NGC 6791's evolved stars must have lost enough mass on the red
giant branch to avoid the flash, and therefore did not convert helium into
carbon-oxygen in their core. Such increased mass loss in the evolution of the
progenitors of these stars is consistent with the presence of the extreme
horizontal branch in the CMD. This unique stellar evolutionary channel also
naturally explains the recent finding of a very young age (2.4 Gyr) for NGC
6791 from white dwarf cooling theory; helium core white dwarfs in this cluster
will cool ~3 times slower than carbon-oxygen core stars and therefore the
corrected white dwarf cooling age is in fact ~7 Gyr, consistent with the well
measured main-sequence turnoff age. These results provide direct empirical
evidence that mass loss is much more efficient in high metallicity environments
and therefore may be critical in interpreting the ultraviolet upturn in
elliptical galaxies.Comment: 15 pages, 9 figures, 2 tables. Accepted for publication in Astrophys.
J. Very minor changes from first versio
Monitoring the impacts of trade agreements on food environments
The liberalization of international trade and foreign direct investment through
multilateral, regional and bilateral agreements has had profound implications
for the structure and nature of food systems, and therefore, for the availability,
nutritional quality, accessibility, price and promotion of foods in different
locations. Public health attention has only relatively recently turned to the links
between trade and investment agreements, diets and health, and there is currently
no systematic monitoring of this area. This paper reviews the available evidence on the links between trade agreements, food environments and diets from an obesity and non-communicable disease (NCD) perspective. Based on the key issues identified through the review, the paper outlines an approach for monitoring the potential impact of trade agreements on food environments and
obesity/NCD risks. The proposed monitoring approach encompasses a set of guiding principles, recommended procedures for data collection and analysis, and quantifiable âminimalâ, âexpandedâ and âoptimalâ measurement indicators to be tailored to national priorities, capacity and resources. Formal risk assessment processes of existing and evolving trade and investment agreements,
which focus on their impacts on food environments will help inform the development of healthy trade policy, strengthen domestic nutrition and health
policy space and ultimately protect population nutrition.The following organizations provided funding support for the travel of participants
to Italy for this meeting and the preparation of background research papers: The Rockefeller Foundation, International Obesity Taskforce (IOTF), University of
Auckland, Deakin University, The George Institute, University of Sydney, Queensland University of Technology, University
of Oxford, University of Pennsylvania Perelman School of Medicine, World Cancer Research Fund International, University of Toronto, and The Australian National
University. The Faculty of Health at Deakin University kindly supported the costs for open access availability of this paper,
and the Australian National Health and Medical Research Council Centre for Research Excellence in Obesity Policy and Food Systems (APP1041020) supported the coordination and finalizing of INFORMAS manuscripts
A proposed approach to monitor private-sector policies and practices related to food environments, obesity and non-communicable disease prevention
Private-sector organizations play a critical role in shaping the food environments
of individuals and populations. However, there is currently
very limited independent monitoring of private-sector actions related to
food environments. This paper reviews previous efforts to monitor the
private sector in this area, and outlines a proposed approach to monitor
private-sector policies and practices related to food environments, and
their influence on obesity and non-communicable disease (NCD) prevention.
A step-wise approach to data collection is recommended, in which
the first (âminimalâ) step is the collation of publicly available food and
nutrition-related policies of selected private-sector organizations. The
second (âexpandedâ) step assesses the nutritional composition of each
organizationâs products, their promotions to children, their labelling
practices, and the accessibility, availability and affordability of their
products. The third (âoptimalâ) step includes data on other commercial
activities that may influence food environments, such as political lobbying
and corporate philanthropy. The proposed approach will be further
developed and piloted in countries of varying size and income levels.
There is potential for this approach to enable national and international
benchmarking of private-sector policies and practices, and to inform
efforts to hold the private sector to account for their role in obesity and
NCD prevention
Abundance Gradients and the Formation of the Milky Way
In this paper we adopt a chemical evolution model, which is an improved
version of the Chiappini, Matteucci and Gratton (1997) model, assuming two main
accretion episodes for the formation of the Galaxy. The present model takes
into account in more detail than previously the halo density distribution and
explores the effects of a threshold density in the star formation process,
during both the halo and disk phases. In the comparison between model
predictions and available data, we have focused our attention on abundance
gradients as well as gas, stellar and star formation rate distributions along
the disk. We suggest that the mechanism for the formation of the halo leaves
detectable imprints on the chemical properties of the outer regions of the
disk, whereas the evolution of the halo and the inner disk are almost
completely disentangled. This is due to the fact that the halo and disk
densities are comparable at large Galactocentric distances and therefore the
gas lost from the halo can substantially contribute to building up the outer
disk. We also show that the existence of a threshold density for the star
formation rate, both in the halo and disk phase, is necessary to reproduce the
majority of observational data in the solar vicinity and in the whole disk.
Moreover, we predict that the abundance gradients along the Galactic disk must
have increased with time and that the average [alpha/Fe] ratio in stars (halo
plus disk) slightly decrease going from 4 to 10 Kpcs from the Galactic center.
We also show that the same ratios increase substantially towards the outermost
disk regions and the expected scatter in the stellar ages decreases, because
the outermost regions are dominated by halo stars.Comment: 41 pages (including the figures), To be published in Ap
Galactic Globular Cluster Metallicity Scale from the Ca II Triplet. I. Catalog
We have obtained 2640 CCD spectra with resolution ~4 Angstrom in the region
7250-9000 Angstroms for 976 stars lying near the red giant branches in
color-magnitude diagrams of 52 Galactic globular clusters. Radial velocities of
~16 km/second accuracy per star determined from the spectra are combined with
other criteria to assess quantitative membership probabilities. Measurements of
the equivalent widths of the infrared calcium triplet lines yield a relative
metal-abundance ranking with a precision that compares favorably to other
techniques. Regressions between our system and those of others are derived. Our
reduction procedures are discussed in detail, and the resultant catalog of
derived velocities and equivalent widths is presented. The metal abundances
derived from these data will be the subject of a future paper.Comment: To appear in August 1997 PASP. Also available at
http://www.hia.nrc.ca/eprints.htm
Group status drives majority and minority integration preferences
WOS:000300955100009 (NÂș de Acesso Web of Science)âPrĂ©mio CientĂfico ISCTE-IUL 2013âThis research examined preferences for national-and campus-level assimilative and pluralistic policies among Black and White students under different contexts, as majority-and minority-group members. We targeted attitudes at two universities, one where 85% of the student body is White, and another where 76% of students are Black. The results revealed that when a group constituted the majority, its members generally preferred assimilationist policies, and when a group constituted the minority, its members generally preferred pluralistic policies. The results support a functional perspective: Both majority and minority groups seek to protect and enhance their collective identities
Improving treatment and survival: a populationâbased study of current outcomes after a hepatic resection in patients with metastatic colorectal cancer
AbstractBackgroundPopulationâbased studies historically report underutilization of a resection in patients with colorectal metastases to the liver. Recent data suggest limitations of the methods in the historical analysis. The present study examines trends in a hepatic resection and survival among Medicare recipients with hepatic metastases.MethodsMedicare recipients with incident colorectal cancer diagnosed between 1991 and 2009 were identified in the SEER(Surveillance, Epidemiology and End Results)âMedicare dataset. Patients were stratified into historical (1991â2001) and current (2002â2009) cohorts. Analyses compared treatment, periâoperative outcomes and survival.ResultsOf 31 574 patients with metastatic colorectal cancer to the liver, 14 859 were in the current cohort treated after 2002 and 16 715 comprised the historical control group. The overall proportion treated with a hepatic resection increased significantly during the study period (P< 0.001) with pre/post change from 6.5% preâ2002 to 7.5% currently (P < 0.001). Over time, haemorrhagic and infectious complications declined (both P †0.047), but 30âday mortality was similar (3.5% versus 3.9%, P = 0.660). After adjusting for predictors of survival, the use of a hepatic resection [hazard ratio (HR) = 0.40, 95% confidence interval (CI): 0.38â0.42, P < 0.001] and treatment after 2002 (HR = 0.88, 95% CI: 0.86â0.90, P < 0.001) were associated with a reduced risk of death.ConclusionsCase identification using International Classification of Diseases, 9th Revision (ICDâ9) codes is imperfect; however, comparison of trends over time suggests an improvement in multimodality therapy and survival in patients with colorectal metastases to the liver
vbyCaHbeta CCD Photometry of Clusters. VI. The Metal-Deficient Open Cluster NGC 2420
CCD photometry on the intermediate-band vbyCaHbeta system is presented for
the metal-deficient open cluster, NGC 2420. Restricting the data to probable
single members of the cluster using the CMD and the photometric indices alone
generates a sample of 106 stars at the cluster turnoff. The average E(b-y) =
0.03 +/- 0.003 (s.e.m.) or E(B-V) = 0.050 +/- 0.004 (s.e.m.), where the errors
refer to internal errors alone. With this reddening, [Fe/H] is derived from
both m1 and hk, using b-y and Hbeta as the temperature index. The agreement
among the four approaches is reasonable, leading to a final weighted average of
[Fe/H] = -0.37 +/- 0.05 (s.e.m.) for the cluster, on a scale where the Hyades
has [Fe/H] = +0.12. When combined with the abundances from DDO photometry and
from recalibrated low-resolution spectroscopy, the mean metallicity becomes
[Fe/H] = -0.32 +/- 0.03. It is also demonstrated that the average cluster
abundances based upon either DDO data or low-resolution spectroscopy are
consistently reliable to 0.05 dex or better, contrary to published attempts to
establish an open cluster metallicity scale using simplistic offset corrections
among different surveys.Comment: scheduled for Jan. 2006 AJ; 33 pages, latex, includes 7 figures and 2
table
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