6,940 research outputs found
Stellar population synthesis models between 2.5 and 5 {\mu}m based on the empirical IRTF stellar library
We present the first single-burst stellar population models in the infrared
wavelength range between 2.5 and 5 {\mu}m which are exclusively based on
empirical stellar spectra. Our models take as input 180 spectra from the
stellar IRTF (Infrared Telescope Facility) library. Our final single-burst
stellar population models are calculated based on two different sets of
isochrones and various types of initial mass functions of different slopes,
ages larger than 1 Gyr and metallicities between [Fe/H] = -0.70 and 0.26. They
are made available online to the scientific community on the MILES web page. We
analyse the behaviour of the Spitzer [3.6]-[4.5] colour calculated from our
single stellar population models and find only slight dependences on both
metallicity and age. When comparing to the colours of observed early-type
galaxies, we find a good agreement for older, more massive galaxies that
resemble a single-burst population. Younger, less massive and more metal-poor
galaxies show redder colours with respect to our models. This mismatch can be
explained by a more extended star formation history of these galaxies which
includes a metal-poor or/and young population. Moreover, the colours derived
from our models agree very well with most other models available in this
wavelength range. We confirm that the mass-to-light ratio determined in the
Spitzer [3.6] {\mu}m band changes much less as a function of both age and
metallicity than in the optical bands.Comment: 25 pages, 19 figures, published in MNRAS, models can be downloaded
from http://miles.iac.e
MILES extended: Stellar population synthesis models from the optical to the infrared
We present the first single-burst stellar population models which covers the
optical and the infrared wavelength range between 3500 and 50000 Angstrom and
which are exclusively based on empirical stellar spectra. To obtain these joint
models, we combined the extended MILES models in the optical with our new
infrared models that are based on the IRTF (Infrared Telescope Facility)
library. The latter are available only for a limited range in terms of both age
and metallicity. Our combined single-burst stellar population models were
calculated for ages larger than 1 Gyr, for metallicities between [Fe/H] = -0.40
and 0.26, for initial mass functions of various types and slopes, and on the
basis of two different sets of isochrones. They are available to the scientific
community on the MILES web page. We checked the internal consistency of our
models and compared their colour predictions to those of other models that are
available in the literature. Optical and near infrared colours that are
measured from our models are found to reproduce the colours well that were
observed for various samples of early-type galaxies. Our models will enable a
detailed analysis of the stellar populations of observed galaxies.Comment: 9 pages, 10 figures, published in A&
Inelaticity in hadron-nucleus collisions from emulsion chamber studies
The inelasticity of hadron-carbon nucleus collisions in the energy region
exceeding 100 TeV is estimated from the carbon-emulsion chamber data at Pamirs
to be . When combined with the recently presented data on
hadron-lead nucleus collisions taken at the same energy range it results in the
mass number dependence of inelasticity. The evaluated partial
inelasticity for secondary () interactions, ,
suggests that the second and higher interactions of the excited hadron inside
the nucleus proceed with only slight energy losses.Comment: LaTeX file and 5 LaTeX files with figures, 11 pages altogether.
Thoroughly rewritten and modified, one figure addded one removed. To be
published in Phys. Rev.
Mineralogical and chemical investigation of Tunisian phosphate washing waste during calcination
Phosphate washing waste (PWW) is one of the wastes generated by the phosphate mine with a very high amount. This waste was investigated in this work to study the effect of the calcination of the PWW at four different temperatures 600 oC, 700 oC, 800 oC and 900 oC on its mineralogical and chemical composition. The samples were investigated by X-ray powder diffraction, Fourier transform infrared, differential scanning calorimetry and thermogravimetric analysis, solidstate magic angle spinning nuclear magnetic resonance of 29Si, 27Al and 31P and scanning electron microscope. The results show that the PWW presents a complex system and it suffers a significant change on its mineralogical and chemical composition after calcination. It reveals the presence of carbonate, natural zeolite, fluorapatite, quartz and clay. After calcination, the waste shows the disappearance of some of these phases and the appearance of others and some other phases remain steady
The space density distribution of galaxies in the absolute magnitude - rotation velocity plane: a volume-complete Tully-Fisher relation from CALIFA stellar kinematics
The space density distribution of galaxies in the absolute magnitude -
rotation velocity plane: a volume-complete Tully-Fisher relation from CALIFA
stellar kinematicsComment: Accepted to A&
On Modeling the Quality of Nutrition for Healthy Ageing Using Fuzzy Cognitive Maps
Modelling dietary intake of older adults can prevent nutritional deficiencies and diet-related diseases, improving their quality of life. Towards such direction, a Fuzzy Cognitive Map (FCM)-based modelling approach that models the interdependencies between the factors that affect the Quality of Nutrition (QoN) is presented here. The proposed FCM-QoN model uses a FCM with seven input-one output concepts, i.e., five food groups of the UK Eatwell Plate, Water (H2O), and older adult’s Emotional State (EmoS), outputting the QoN. The weights incorporated in the FCM structure were drawn from an experts’ panel, via a Fuzzy Logic-based knowledge representation process. Using various levels of analysis (causalities, static/feedback cycles), the role of EmoS and H2O in the QoN was identified, along with the one of Fruits/Vegetables and Protein affecting the sustainability of effective food combinations. In general, the FCM-QoN approach has the potential to explore different dietary scenarios, helping health professionals to promote healthy ageing and providing prognostic simulations for diseases effect (such as Parkinson’s) on dietary habits, as used in the H2020 i-Prognosis project (www.i-prognosis.eu)
Electroweak Corrections to the Top Quark Decay
We have calculated the one-loop electroweak corrections to the decay t-> bW+,
including the counterterm for the CKM matrix elements V(tb). Previous
calculations used an incorrect delta V(tb) that led to a gauge dependent
amplitude. However, since the contribution stemming from delta V(tb) is small,
those calculations only underestimate the width by roughly one part in 10^5.Comment: 7 pages, 2 figure
NADP-Dependent Isocitrate Dehydrogenase from Arabidopsis Roots Contributes in the Mechanism of Defence against the Nitro-Oxidative Stress Induced by Salinity
NADPH regeneration appears to be essential in the mechanism of plant defence against oxidative stress. Plants contain several NADPH-generating dehydrogenases including isocitrate dehydrogenase (NADP-ICDH), glucose-6-phosphate dehydrogenase (G6PDH), 6-phosphogluconate dehydrogenase (6PGDH), and malic enzyme (ME). In Arabidopsis seedlings grown under salinity conditions (100 mM NaCl) the analysis of physiological parameters, antioxidant enzymes (catalase and superoxide dismutase) and content of superoxide radical (O2 ∙−), nitric oxide (NO), and peroxynitrite (ONOO−) indicates a process of nitro-oxidative stress induced by NaCl. Among the analysed NADPH-generating dehydrogenases under salinity conditions, the NADP-ICDH showed the maximum activity mainly attributable to the root NADP-ICDH. Thus, these data provide new insights on the relevance of the NADP-ICDH which could be considered as a second barrier in the mechanism of response against the nitro-oxidative stress generated by salinity
The Portuguese masonry's mechanical characterization
The aim of this study is the characterization of the mechanical properties of typical masonry
components in Portugal and the definition of mortar compositions, with direct implication to the
National Annex of EC6. For masonry units the following were evaluated: the dimensions; water
absorption and compressive strength. To assess mortar parameters such as, consistence, air content,
compressive and flexural tensile strength, fracture energy and shrinkage, an analysis with various
types of traditional and ready-to-use mortars was also performed. For several traditional mortars with
different compositions and various strength classes, by varying the type of binder (cement, hydrated
lime and hydraulic lime) and the type of sand (natural or artificial), it was possible to draw some
conclusions about the parameters mentioned, such as: for the same strength class, the study
compositions presented higher values of binder than the EC6 compositions and the shrinkage of
cement mortars develops quicker than that of mixed mortars; for the same kind of sands there is a
straight relationship between the maximum load applied and fracture energy. An experimental
characterization of mechanical properties of masonr
Ab initio modeling of defects in silicon, germanium and SiGe alloys
Understanding the most elemental defects in semiconductors is a fundamental step to grasp the countless solid-state reactions that may occur during crystal growth, device processing and operation stages. The higher carrier mobilitity in SiGe alloys and germanium, when compared with silicon, and the necessity to a higher K dielectric than SiO2 makes these semiconductors the most contendors to a new generation of electronic devices. Our aim is to model self and impurity point defects in SiGe alloys and germanium, and compare with their equivalent complexes in silicon. We use density functional theory and pseudopotentials to determine the structural, electronic and vibrational properties. The calculations are performed in a 32 CPU PC cluster, in Physics Department of Aveiro University.Fundação para a Ciência e a Tecnologia (FCT).INTAS
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