12,564 research outputs found
Spectroscopic characterization of X-ray emitting young stars associated with the Sh 2-296 nebula
We studied a sample of stars associated with the Sh 2-296 nebula, part of the
reflection nebulae complex in the region of Canis Major (CMa R1). Our sample
corresponds to optical counterparts of X-ray sources detected from observations
with the XMM-Newton satellite, which revealed dozens of possible low-mass young
stars not yet known in this region.
A sample of 58 young star candidates were selected based on optical spectral
features, mainly H{\alpha} and lithium lines, observed with multi-objects
spectroscopy performed by the Gemini South telescope. Among the candidates, we
find 41 confirmed T Tauri and 15 very likely young stars. Based on the
H{\alpha} emission, the T Tauri stars were distinguished between classical
(17%) and weak-lined (83%), but no significant difference was found in the age
and mass distribution of these two classes.
The characterization of the sample was complemented by near- and mid-infrared
data, providing an estimate of ages and masses from the comparison with
pre-main-sequence evolutionary models. While half of the young stars have an
age of 1-2 Myrs or less, only a small fraction (~25%) shows evidence of IR
excess revealing the presence of circumstellar discs. This low fraction is
quite rare compared to most young star-forming regions, suggesting that some
external factor has accelerated the disc dissipation
Modeling the input history of programs for improved instruction-memory performance
When a program is loaded into memory for execution, the relative position of
its basic blocks is crucial, since loading basic blocks that are unlikely to be
executed first places them high in the instruction-memory hierarchy only to be
dislodged as the execution goes on. In this paper we study the use of Bayesian
networks as models of the input history of a program. The main point is the
creation of a probabilistic model that persists as the program is run on
different inputs and at each new input refines its own parameters in order to
reflect the program's input history more accurately. As the model is thus
tuned, it causes basic blocks to be reordered so that, upon arrival of the next
input for execution, loading the basic blocks into memory automatically takes
into account the input history of the program. We report on extensive
experiments, whose results demonstrate the efficacy of the overall approach in
progressively lowering the execution times of a program on identical inputs
placed randomly in a sequence of varied inputs. We provide results on selected
SPEC CINT2000 programs and also evaluate our approach as compared to the gcc
level-3 optimization and to Pettis-Hansen reordering
Impacts of in vivo and in vitro exposures to tamoxifen: comparative effects on human cells and marine organisms
Tamoxifen (TAM) is a first generation-SERM administered for hormone receptor-positive (HER+) breast cancer in both pre- and post-menopausal patients and may undergo metabolic activation in organisms that share similar receptors and thus face comparable mechanisms of response. The present study aimed to assess whether environmental trace concentrations of TAM are bioavailable to the filter feeder M. galloprovincialis (100 ng L-1) and to the deposit feeder N. diversicolor (0.5, 10, 25 and 100 ng L-1) after 14 days of exposure. Behavioural impairment (burrowing kinetic), neurotoxicity (AChE activity), endocrine disruption by alkali-labile phosphate (ALP) content, oxidative stress (SOD, CAT, GPXs activities), biotransformation (GST activity), oxidative damage (LPO) and genotoxicity (DNA damage) were assessed. Moreover, this study also pertained to compare TAM cytotoxicity effects to mussels and targeted human (i.e. immortalized retinal pigment epithelium - RPE; and human transformed endothelial cells - HeLa) cell lines, in a range of concentrations from 0.5 ng L-1 to 50 μg L-1. In polychaetes N. diversicolor, TAM exerted remarkable oxidative stress and damage at the lowest concentration (0.5 ng L-1), whereas significant genotoxicity was reported at the highest exposure level (100 ng L-1). In mussels M. galloprovincialis, 100 ng L-1 TAM caused endocrine disruption in males, neurotoxicity, and an induction in GST activity and LPO byproducts in gills, corroborating in genotoxicity over the exposure days. Although cytotoxicity assays conducted with mussel haemocytes following in vivo exposure was not effective, in vitro exposure showed to be a feasible alternative, with comparable sensitivity to human cell line (HeLa).info:eu-repo/semantics/publishedVersio
Büchwald-Hartwig reaction applied to synthesis of new luminescent liquid crystal triarylamines derived from isoxazoles
© 2015 Taylor & Francis Group, LLC. The present work describes the synthesis and characterization of novel series of triarylamines isoxazoles (TAA) addressed to the organic photovoltaic materials. Diarylisoxazoles were synthesized by sequential [3+2] 1,3-dipolar cycloaddition reaction between arylnitrile oxides and selected arylalkenes followed by MnO2-oxidation. Isoxazoles were coupled to diarylamines by Büchwald-Hartwig reaction to afford desired compounds 6a-k. Some TAA display liquid-crystalline behaviour and UV-Vis absorption and fluorescence emission were analysed for all samples of TAA 6a-k
Age-related differences during visual search: the role of contextual expectations and cognitive control mechanisms
We explored the efficacy of drawing pictures as an encoding strategy to enhance memory performance in healthy older adults and individuals with probable dementia. In an incidental encoding phase, participants were asked to either draw a picture or write out each word from a set of 30 common nouns for 40 seconds each. Episodic memory for the target words was compared in a group of healthy older adults to individuals with probable dementia (MMSE/MOCA range 4 to 25). In two experiments we showed that recall and recognition performance was higher for words that were drawn than written out during encoding, for both participant groups. We suggest that incorporating visuo-perceptual information into memory enhanced performance by increasing reliance on visual-sensory brain regions, which are relatively intact in these populations. Our findings demonstrate that drawing is a valuable technique leading to measurable gains in memory performance for individuals with probable dementia
A MILP model for an extended version of the Flexible Job Shop Problem
A MILP model for an extended version of the Flexible Job Shop Scheduling
problem is proposed. The extension allows the precedences between operations of
a job to be given by an arbitrary directed acyclic graph rather than a linear
order. The goal is the minimization of the makespan. Theoretical and practical
advantages of the proposed model are discussed. Numerical experiments show the
performance of a commercial exact solver when applied to the proposed model.
The new model is also compared with a simple extension of the model described
by \"Ozg\"uven, \"Ozbakir, and Yavuz (Mathematical models for job-shop
scheduling problems with routing and process plan flexibility, Applied
Mathematical Modelling, 34:1539--1548, 2010), using instances from the
literature and instances inspired by real data from the printing industry.Comment: 15 pages, 2 figures, 4 tables. Optimization Letters, 201
Bilateral Breast Inflammatory Pseudotumor: A Clinical Report and Literature Review
Inflammatory pseudotumor (IP) is a benign lesion that can affect nearly any tissue in the body and which may be confused
clinically and in imaging for malignancy. Despite the widespread performance of breast biopsy, the finding of inflammatory
pseudotumor of the breast is exceedingly rare. Excision of the tumor is the treatment of choice, but there is a relatively high rate
of recurrence. The aim of this report is to describe the clinical, imaging, and pathologic features in a case of bilateral breast IP
Resilience and Vulnerability of Public Transportation Fare Systems: The Case of the City of Rio De Janeiro, Brazil
Resilience is the ability of a system to adapt, persist, and transform as a reaction to threats, which may be external or internal to the system, while vulnerability is the state of being susceptible to harm from exposure to stresses associated with environmental and social change and from the inability to adapt. Based on a study of the threats that can affect urban mobility, we identified a gap regarding the analysis of the levels of resilience and vulnerability in the face of subsidy threats that can severely affect developing countries. This article measures the level of resilience and vulnerability due to the absence of public transport fare subsidies. For this purpose, we developed an approach based on fuzzy logic and applied it in 33 administrative regions (ARs) of the city of Rio de Janeiro, Brazil. We obtained four matrices of the levels of vulnerability and resilience of each of the regions as an origin and destination. The results show that areas nearest to the downtown region and those with high-capacity transportation available (commuter train and/or subway, systems with many transfer points) are more resilient, while a high level of vulnerability is associated with low income, negative socioeconomic indicators, and the predominance of road transportation to reach jobs. The contribution of this paper is the method applied to analyse the levels of vulnerability and resilience of public transport, which includes a threat that can cause a rupture that impacts routines and job accessibility in a region
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