7,453 research outputs found
Abundances in Stars from the Red Giant Branch Tip to the Near Main Sequence in M71: II. Iron Abundance
We present [Ffe/H] abundance results that involve a sample of stars with a
wide range in luminosity from luminous giants to stars near the turnoff in a
globular cluster. Our sample of 25 stars in M71 includes 10 giant stars more
luminous than the RHB, 3 horizontal branch stars, 9 giant stars less luminous
than the RHB, and 3 stars near the turnoff. We analyzed both Fe I and Fe II
lines in high dispersion spectra observed with HIRES at the W. M. Keck
Observatory. We find that the [Fe/H] abundances from both Fe I and Fe II lines
agree with each other and with earlier determinations. Also the [Fe/H] obtained
from Fe I and Fe II lines is constant within the rather small uncertainties for
this group of stars over the full range in Teff and luminosity, suggesting that
NLTE effects are negligible in our iron abundance determination. In this
globular cluster, there is no difference among the mean [Fe/H] of giant stars
located at or above the RHB, RHB stars, giant stars located below the RHB and
stars near the turnoff.Comment: Minor changes to conform to version accepted for publication, with
several new figures (Paper 2 of a pair
Abrupt carbon release at the onset of the Bølling/Allerød: Permafrost thawing with inter-hemispheric impact
Atmospheric carbon dioxide (CO2) during the last deglaciation (∼18–10 kyr BP) switched around 14.6 kyr BP from a rather gradual rise to an abrupt jump, which is recorded in ice cores as an increase of 10 ppmv in less than two centuries. So far the source of that CO2 excursion could not be identified and the climatic implications are largely unknown. Here we use highly resolved U/Th dated atmospheric ∆14C from Tahiti corals as independent age control for CO2 changes. This provides a temporal framework to show that the northern high latitude warming into the Bølling/Allerød occurred quasi-synchronous to this CO2 rise within a few decades. Furthermore we show that an abrupt release (within two centuries) of long-term immobile nearly 14C-free carbon (∼125 PgC) from thawing permafrost might explain the observed anomalies in atmospheric CO2 and ∆14C, in line with CH4 and biomarker records from ice and sediment cores. In transient climate simulations we show that the abrupt carbon release in the northern high latitudes and associated CO2 changes bear the potential to modulate Antarctic temperature. These findings are in agreement with the observed onset of the Antarctic Cold Reversal about two centuries after the beginning of the Bølling/Allerød, as detected in independent annual layer-counted ice cores from both hemispheres. Based on the timing, magnitude, origin and the inter-hemispheric impact we speculate that this abrupt deglacial release of long-term stored carbon via thawing permafrost might have provided the final push out of the last ice age
An Institutional Overview of the North Dakota State Water Conservation Commission: Its Operation and Setting
Magnetic and electrical properties of (Pu,Lu)Pd3
We present measurements of the magnetic susceptibility, heat capacity and
electrical resistivity of PuLuPd, with =0, 0.1, 0.2, 0.5,
0.8 and 1. PuPd is an antiferromagnetic heavy fermion compound with
~K. With increasing Lu doping, both the Kondo and RKKY interaction
strengths fall, as judged by the Sommerfeld coefficient and N\'eel
temperature . Fits to a crystal field model of the resistivity also
support these conclusions. The paramagnetic effective moment
increases with Lu dilution, indicating a decrease in the
Kondo screening. In the highly dilute limit, approaches
the value predicted by intermediate coupling calculations. In conjunction with
an observed Schottky peak at 60~K in the magnetic heat capacity,
corresponding to a crystal field splitting of 12~meV, a mean-field
intermediate coupling model with nearest neighbour interactions has been
developed.Comment: 13 pages, 13 figure
Abundances of Baade's Window Giants from Keck/HIRES Spectra: I. Stellar Parameters and [Fe/H] Values
We present the first results of a new abundance survey of the Milky Way bulge
based on Keck/HIRES spectra of 27 K-giants in the Baade's Window (, ) field. The spectral data used in this study are of much higher resolution
and signal-to-noise than previous optical studies of Galactic bulge stars. The
[Fe/H] values of our stars, which range between -1.29 and , were used to
recalibrate large low resolution surveys of bulge stars. Our best value for the
mean [Fe/H] of the bulge is . This mean value is similar to the
mean metallicity of the local disk and indicates that there cannot be a strong
metallicity gradient inside the solar circle. The metallicity distribution of
stars confirms that the bulge does not suffer from the so-called ``G-dwarf''
problem. This paper also details the new abundance techniques necessary to
analyze very metal-rich K-giants, including a new Fe line list and regions of
low blanketing for continuum identification.Comment: Accepted for publication in January 2006 Astrophysical Journal. Long
tables 3--6 withheld to save space (electronic tables in journal paper). 53
pages, 10 figures, 9 table
Relation between capacities and bimanual performance in hemiplegic cerebral palsied children: Impact os synkinesis
ObjectiveTo analyse the link between unimanual capacities and bimanual performance in cerebral-palsied (CP) hemiplegic children, aged between 5 and 18 years old, studying specifically the impact of synkinesis.Material and methodsSeventy-one CP hemiplegic children (35 boys and 36 girls, mean age 8,5 years; MACS levels from I to III; GMFCS from I to IV) took part in a transversal study, assessed – Melbourne Test (MUUL) for unimanual capacities, and Assisting Hand Assessment (AHA) for bimanual performance – with a specific scale to analyze synkinesis during Box and Block test for affected and healthy hands, collecting synkinesis type, duration and intensity.ResultsThere is a strong correlation between unimanual capacities (MUUL) and bimanual performance (AHA) (r=0.871). Neither age nor gender contribute to bimanual performance (AHA). Multiple linear regression shows that MUUL contributes to bimanual performance variance (AHA) by 70%. Synkinesis partly correlated to capacities (MUUL) and accounts for 10% of the variance of the gap between capacities and bimanual performance.ConclusionA high relationship between unimanual capacities and bimanual performance is confirmed by this study; some authors demonstrated impact of sensory troubles [1], we demonstrate that synkinesis influences the use of unimanual capacities in bimanual performance
Iran and American Security Policy in the Middle East
In October 1973 the Organization of Arab Petroleum Exporting Countries (OAPEC) sent shock waves through the industrialized world when it decreased the overall producÂtion of oil and embargoed the United States, Portugal, South Africa, and the Netherlands. The impact of these developments and a subsequent quantum rise in oil prices for the Western states and Japan was immediate and far reaching. On both sides of the Atlantic and in Tokyo there were fears of recession and even depression, the possibility of millions unemployed, and of massive deficits in the balance of payments
The type II phase resetting curve is optimal for stochastic synchrony
The phase-resetting curve (PRC) describes the response of a neural oscillator
to small perturbations in membrane potential. Its usefulness for predicting the
dynamics of weakly coupled deterministic networks has been well characterized.
However, the inputs to real neurons may often be more accurately described as
barrages of synaptic noise. Effective connectivity between cells may thus arise
in the form of correlations between the noisy input streams. We use constrained
optimization and perturbation methods to prove that PRC shape determines
susceptibility to synchrony among otherwise uncoupled noise-driven neural
oscillators. PRCs can be placed into two general categories: Type I PRCs are
non-negative while Type II PRCs have a large negative region. Here we show that
oscillators with Type II PRCs receiving common noisy input sychronize more
readily than those with Type I PRCs.Comment: 10 pages, 4 figures, submitted to Physical Review
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