2,220 research outputs found
Ionization Conditions in the Central Giant HII Region of NGC 5253
We are carrying out a detailed 2D spectroscopic study of the central 210 pc X
130 pc of the blue compact dwarf (BCD) galaxy NGC5253. This contribution
presents the ionization conditions and chemical abundance patterns for the
different kinematic components of the ionized gas detected in our previous
work. All the kinematic components present an excess in nitrogen abundance. In
particular, the broad velocity component has larger excess than the narrow one
by a factor of ~1.4+-0.4 which is consistent with a scenario for the Giant HII
Region where the broad component of the emission lines traces the material
expelled by the two central Super Star Clusters while the narrow one is
associated to previously existing ionized gas.Comment: 4 pages, 3 figures: in JENAM Symposium "Dwarf Galaxies: Keys to
Galaxy Formation and Evolution", P. Papaderos, G. Hensler, S. Recchi (eds.).
Lisbon, September 2010, Springer Verlag, in press; minor corrections to
reference
Distances from the Correlation between Galaxy Luminosities and Rotation Rates
A large luminosity--linewidth template sample is now available, improved
absorption corrections have been derived, and there are a statistically
significant number of galaxies with well determined distances to supply the
zero point. A revised estimate of the Hubble Constant is H_0=77 +-4 km/s/Mpc
where the error is the 95% probability statistical error. Systematic
uncertainties are potentially twice as large.Comment: 21 pages, 9 figures. Invited chapter for the book `Post-Hipparcos
Cosmic Candles', Eds. F. Caputo and A. Heck (Kluwer Academic Publishers,
Dordrecht
The Hubble Constant from Observations of the Brightest Red Giant Stars in a Virgo-Cluster Galaxy
The Virgo and Fornax clusters of galaxies play central roles in determining
the Hubble constant H_0. A powerful and direct way of establishing distances
for elliptical galaxies is to use the luminosities of the brightest red-giant
stars (the TRGB luminosity, at M_I = -4.2). Here we report the direct
observation of the TRGB stars in a dwarf elliptical galaxy in the Virgo
cluster. We find its distance to be 15.7 +- 1.5 Megaparsecs, from which we
estimate a Hubble constant of H_0 = 77 +- 8 km/s/Mpc. Under the assumption of a
low-density Universe with the simplest cosmology, the age of the Universe is no
more than 12-13 billion years.Comment: 12 pages, LaTeX, with 2 postscript figures; in press for Nature, July
199
Yeast Methylotrophy and Autophagy in a Methanol-Oscillating Environment on Growing Arabidopsis thaliana Leaves
The yeast Candida boidinii capable of growth on methanol proliferates and survives on the leaves of Arabidopsis thaliana. The local methanol concentration at the phyllosphere of growing A. thaliana exhibited daily periodicity, and yeast cells responded by altering both the expression of methanol-inducible genes and peroxisome proliferation. Even under these dynamically changing environmental conditions, yeast cells proliferated 3 to 4 times in 11 days. Among the C1-metabolic enzymes, enzymes in the methanol assimilation pathway, but not formaldehyde dissimilation or anti-oxidizing enzymes, were necessary for yeast proliferation at the phyllosphere. Furthermore, both peroxisome assembly and pexophagy, a selective autophagy pathway that degrades peroxisomes, were necessary for phyllospheric proliferation. Thus, the present study sheds light on the life cycle and physiology of yeast in the natural environment at both the molecular and cellular levels
Hip fracture risk assessment: Artificial neural network outperforms conditional logistic regression in an age- and sex-matched case control study
Copyright @ 2013 Tseng et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative
Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and
reproduction in any medium, provided the original work is properly cited.Background - Osteoporotic hip fractures with a significant morbidity and excess mortality among the elderly have imposed huge health and economic burdens on societies worldwide. In this age- and sex-matched case control study, we examined the risk factors of hip fractures and assessed the fracture risk by conditional logistic regression (CLR) and ensemble artificial neural network (ANN). The performances of these two classifiers were compared.
Methods - The study population consisted of 217 pairs (149 women and 68 men) of fractures and controls with an age older than 60 years. All the participants were interviewed with the same standardized questionnaire including questions on 66 risk factors in 12 categories. Univariate CLR analysis was initially conducted to examine the unadjusted odds ratio of all potential risk factors. The significant risk factors were then tested by multivariate analyses. For fracture risk assessment, the participants were randomly divided into modeling and testing datasets for 10-fold cross validation analyses. The predicting models built by CLR and ANN in modeling datasets were applied to testing datasets for generalization study. The performances, including discrimination and calibration, were compared with non-parametric Wilcoxon tests.
Results - In univariate CLR analyses, 16 variables achieved significant level, and six of them remained significant in multivariate analyses, including low T score, low BMI, low MMSE score, milk intake, walking difficulty, and significant fall at home. For discrimination, ANN outperformed CLR in both 16- and 6-variable analyses in modeling and testing datasets (p?<?0.005). For calibration, ANN outperformed CLR only in 16-variable analyses in modeling and testing datasets (p?=?0.013 and 0.047, respectively).
Conclusions - The risk factors of hip fracture are more personal than environmental. With adequate model construction, ANN may outperform CLR in both discrimination and calibration. ANN seems to have not been developed to its full potential and efforts should be made to improve its performance.National Health Research Institutes in Taiwa
Inflation, moduli (de)stabilization and supersymmetry breaking
We study the cosmological inflation from the viewpoint of the moduli
stabilization. We study the scenario that the superpotential has a large value
during the inflation era enough to stabilize moduli, but it is small in the
true vacuum. This scenario is discussed by using a simple model, one type of
hybrid models.Comment: 17 pages, 7 figure
Beyond the standard seesaw: neutrino masses from Kahler operators and broken supersymmetry
We investigate supersymmetric scenarios in which neutrino masses are
generated by effective d=6 operators in the Kahler potential, rather than by
the standard d=5 superpotential operator. First, we discuss some general
features of such effective operators, also including SUSY-breaking insertions,
and compute the relevant renormalization group equations. Contributions to
neutrino masses arise at low energy both at the tree level and through finite
threshold corrections. In the second part we present simple explicit
realizations in which those Kahler operators arise by integrating out heavy
SU(2)_W triplets, as in the type II seesaw. Distinct scenarios emerge,
depending on the mechanism and the scale of SUSY-breaking mediation. In
particular, we propose an appealing and economical picture in which the heavy
seesaw mediators are also messengers of SUSY breaking. In this case, strong
correlations exist among neutrino parameters, sparticle and Higgs masses, as
well as lepton flavour violating processes. Hence, this scenario can be tested
at high-energy colliders, such as the LHC, and at lower energy experiments that
measure neutrino parameters or search for rare lepton decays.Comment: LaTeX, 34 pages; some corrections in Section
Adolescents with symptomatic laminolysis: report of two cases
Retroisthmic cleft refers to a cleft in the lamina and is rarely reported. It was first described by Brocher, and later Wick et al. proposed the term “laminolysis” to describe the retroisthmic cleft by analogy with the nomenclature of the applied stress fracture of the pars interarticularis (spondylolysis) and the pedicle (pediculolysis). In this paper, we describe two adolescent sports players with symptomatic lumbar laminolysis. Both improved significantly after adequate conservative treatment. Knowledge of laminolysis in adolescent patients with low back pain is necessary to avoid overlooking it and late diagnosis. For correct diagnosis, multidetector three-dimensional computed tomography (CT) is suggested. In addition, magnetic resonance imaging (MRI) also allows detection of inflammation in the defects
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