628 research outputs found
Integrating remote sensing datasets into ecological modelling: a Bayesian approach
Process-based models have been used to simulate 3-dimensional complexities of
forest ecosystems and their temporal changes, but their extensive data
requirement and complex parameterisation have often limited their use for
practical management applications. Increasingly, information retrieved using
remote sensing techniques can help in model parameterisation and data
collection by providing spatially and temporally resolved forest information. In
this paper, we illustrate the potential of Bayesian calibration for integrating such
data sources to simulate forest production. As an example, we use the 3-PG
model combined with hyperspectral, LiDAR, SAR and field-based data to
simulate the growth of UK Corsican pine stands. Hyperspectral, LiDAR and
SAR data are used to estimate LAI dynamics, tree height and above ground
biomass, respectively, while the Bayesian calibration provides estimates of
uncertainties to model parameters and outputs. The Bayesian calibration
contrasts with goodness-of-fit approaches, which do not provide uncertainties
to parameters and model outputs. Parameters and the data used in the
calibration process are presented in the form of probability distributions,
reflecting our degree of certainty about them. After the calibration, the
distributions are updated. To approximate posterior distributions (of outputs
and parameters), a Markov Chain Monte Carlo sampling approach is used (25
000 steps). A sensitivity analysis is also conducted between parameters and
outputs. Overall, the results illustrate the potential of a Bayesian framework for
truly integrative work, both in the consideration of field-based and remotely
sensed datasets available and in estimating parameter and model output uncertainties
The Lithium Depletion Boundary and the Age of the Young Open Cluster IC~2391
We have obtained new photometry and intermediate resolution ( \AA\ ) spectra of 19 of these objects
(14.9 17.5) in order to confirm cluster membership. We
identify 15 of our targets as likely cluster members based on their
photometry, spectral types, radial velocity, and H emission strengths.
Higher S/N spectra were obtained for 8 of these probable cluster members in
order to measure the strength of the lithium 6708 \AA\ doublet and thus obtain
an estimate of the cluster's age. One of these 8 stars has a definite lithium
detection and two other (fainter) stars have possible lithium detections. A
color-magnitude diagram for our program objects shows that the lithium
depletion boundary in IC~2391 is at =16.2. Using recent theoretical model
predictions, we derive an age for IC~2391 of 535 Myr. While this is
considerably older than the age most commonly attributed for this cluster
(35 Myr) this result for IC~2391 is comparable those recently derived for
the Pleiades and Alpha Persei clusters and can be explained by new models for
high mass stars that incorporate a modest amount of convective core
overshooting.Comment: ApJ Letters, acccepte
Factors Affecting Surgical Decisions in Newly Diagnosed Young Women with Early-Stage Breast Cancer
Given that young women with breast cancer often have concerns and priorities attributable to their life stage, we conducted a series of interviews to better understanding the surgical decision-making experience among women diagnosed at age ≤40. Women spoke of how the potential effect of an extended recovery was affecting their decision and, in some cases, contributing to decisional conflict. Several women described their worry of leaving cancer cells behind; others cited the need for continued surveillance as a consideration. Attention to situational anxiety and concerns about recurrence are warranted to ensure that decisions are made in a supportive and patient-centered setting
N-Phenyl-N’-(2-chloroethyl)ureas (CEUs) as potential antineoplastic agents. part 3 : role of carbonyl group
n the course of the development of N-phenyl-N′-(2-chloroethyl)ureas (CEUs) as potential antineoplastic agents, we investigated the effect of carbonylated substituting chains of the aromatic ring of CEU on their covalent binding to the colchicine-binding site (C-BS). In this study, we found that CEU, 5e, 5f, 8e, and 8f substituted by either a methyl ester or a methyl ketyl group at the ω-position exhibited a significant antiproliferative activity on HT-29, M21, and MCF-7 tumor cells. SDS–PAGE assays and cell cycle analysis confirmed that 5e, 5f, 8e, and 8f covalently bind to the C-BS and arrest the cell division in G2/M phase. Surprisingly, the presence of ω-carboxyl, ω-ethyl esters or ω-amides decreased significantly both the antiproliferative activity and the specificity toward β-tubulin
MSH6- or PMS2-deficiency causes re-replication in DT40 B cells, but it has little effect on immunoglobulin gene conversion or on repair of AID-generated uracils
The mammalian antibody repertoire is shaped by somatic hypermutation (SHM) and class switch recombination (CSR) of the immunoglobulin (Ig) loci of B lymphocytes. SHM and CSR are triggered by non-canonical, error-prone processing of G/U mismatches generated by activation-induced deaminase (AID). In birds, AID does not trigger SHM, but it triggers Ig gene conversion (GC), a ‘homeologous' recombination process involving the Ig variable region and proximal pseudogenes. Because recombination fidelity is controlled by the mismatch repair (MMR) system, we investigated whether MMR affects GC in the chicken B cell line DT40. We show here that Msh6−/− and Pms2−/− DT40 cells display cell cycle defects, including genomic re-replication. However, although IgVλ GC tracts in MMR-deficient cells were slightly longer than in normal cells, Ig GC frequency, donor choice or the number of mutations per sequence remained unaltered. The finding that the avian MMR system, unlike that of mammals, does not seem to contribute towards the processing of G/U mismatches in vitro could explain why MMR is unable to initiate Ig GC in this species, despite initiating SHM and CSR in mammalian cells. Moreover, as MMR does not counteract or govern Ig GC, we report a rare example of ‘homeologous' recombination insensitive to MM
The Metallicity of the Pleiades
We have measured the abundances of Fe, Si, Ni, Ti, and Na in 20 Pleiads with
\teff values near solar and with low \vsini using high-resolution, high
signal-to-noise echelle spectra. We have validated our procedures by also
analyzing 10 field stars of a range of temperatures and metallicities that were
observed by \citet{Vale05}. Our result for the Pleiades is [Fe/H] =
(statistical and systematic). The average of published
measurements for the Pleiades is .Comment: accepted by Astron. J. for 2009-1
Rotational Studies of Late-Type Stars. VII. M34 (NGC 1039) and the Evolution of Angular Momentum and Activity in Young Solar-Type Stars
We analyze Keck Hires observations of rotation in F, G, and K dwarf members
of the open cluster M34 (NGC 1039), which is 250 Myr old, and we compare them
to the Pleiades, Hyades, and NGC 6475. The upper bound to rotation seen in M34
is about a factor of two lower than for the 100 Myr-old Pleiades, but most M34
stars are well below this upper bound, and it is the overall convergence in
rotation rates that is most striking. A few K dwarfs in M34 are still rapid
rotators, suggesting that they have undergone core-envelope decoupling,
followed by replenishment of surface angular momentum from an internal
reservoir. Our comparison of rotation in these clusters indicates that the time
scale for the coupling of the envelope to the core must be close to 100 Myr if
decoupling does, in fact, occur.Comment: 16 pages + 1 table + 5 figure
Risk for depression and neural responses to fearful facial expressions of emotion
BACKGROUND: Depression is associated with neural abnormalities in emotional processing. AIMS: This study explored whether these abnormalities underlie risk for depression. METHOD: We compared the neural responses of volunteers who were at high and low-risk for the development of depression (by virtue of high and low neuroticism scores; high-N group and low-N group respectively) during the presentation of fearful and happy faces using functional magnetic resonance imaging (fMRI). RESULTS: The high-N group demonstrated linear increases in response in the right fusiform gyrus and left middle temporal gyrus to expressions of increasing fear, whereas the low-N group demonstrated the opposite effect. The high-N group also displayed greater responses in the right amygdala, cerebellum, left middle frontal and bilateral parietal gyri to medium levels of fearful v. happy expressions. CONCLUSIONS: Risk for depression is associated with enhanced neural responses to fearful facial expressions similar to those observed in acute depression
Keck Spectra of Pleiades Brown Dwarf Candidates and a Precise Determination of the Lithium Depletion Edge in the Pleiades
We have obtained intermediate resolution spectra of eleven candidate brown
dwarf members of the Pleiades open cluster using the Keck II telescope and LRIS
spectrograph. Our primary goal was to determine the location of the "lithium
depletion edge" in the Pleiades and hence to derive a precise age for the
cluster. All but one of our 11 program objects have radial velocities
appropriate for Pleiades members, have moderately strong H alpha emission, and
have spectral types M6 to M8.5, as expected for their (R-I) colors.
We have constructed a color-magnitude diagram for the faint end of the
Pleiades main sequence, including only stars for which high S/N spectra in the
region of the lithium 6708 Angstrom absorption line have been obtained. These
data allow us to accurately determine the Pleiades single-star lithium
depletion edge at I(c0) = 17.80, R-I(c0) = 2.20, spectral type = M6.5. By
reference to theoretical evolutionary models, this converts fairly directly
into an age for the Pleiades of 125 Myr. This is significantly older than the
age that is normally quoted, but does agree with some other recent estimates.Comment: 12 pages, including 3 Figures. Accepted by ApJ Letter
Genetic clustering on the hippocampal surface for genome-wide association studies
Imaging genetics aims to discover how variants in the human genome influence brain measures derived from images. Genome-wide association scans (GWAS) can screen the genome for common differences in our DNA that relate to brain measures. In small samples, GWAS has low power as individual gene effects are weak and one must also correct for multiple comparisons across the genome and the image. Here we extend recent work on genetic clustering of images, to analyze surface-based models of anatomy using GWAS. We performed spherical harmonic analysis of hippocampal surfaces, automatically extracted from brain MRI scans of 1254 subjects. We clustered hippocampal surface regions with common genetic influences by examining genetic correlations (rg) between the normalized deformation values at all pairs of surface points. Using genetic correlations to cluster surface measures, we were able to boost effect sizes for genetic associations, compared to clustering with traditional phenotypic correlations using Pearson's r
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