6,253 research outputs found
Some results on thermal stress of layered plates and shells by using Unified Formulation
This work presents some results on two-dimensional modelling of thermal stress problems in multilayered structures. The governing equations are written by referring to the Unified Formulation (UF) introduced by the first author. These equations are obtained in a compact form, that doesn't depend on the order of expansion of variables in the thickness direction or the variable description (layer-wise models and equivalent single layers models). Classical and refined theories based on the Principle of Virtual Displacements (PVD) and advanced mixed theories based on the Reissner Mixed Variational Theorem (RMVT) are both considered. As a result, a large variety of theories are derived and compared. The temperature profile along the thickness of the plate/shell is calculated by solving the Fourier's heat conduction equation. Alternatively, thermo-mechanical coupling problems can be considered, in which the thermal variation is influenced by mechanical loading. Exact closed-form solutions are provided for plates and shells, but also the applications of the Ritz method and the Finite Element Method (FEM) are presented
Spatially resolved LMC star formation history: I. Outside in evolution of the outer LMC disk
We study the evolution of three fields in the outer LMC disk Rgc=3.5-6.2 Kpc.
Their star formation history indicates a stellar populations gradient such that
younger stellar populations are more centrally concentrated. We identify two
main star forming epochs, separated by a period of lower activity between ~7
and ~4 Gyr ago. Their relative importance varies from a similar amount of stars
formed in the two epochs in the innermost field, to only 40% of the stars
formed in the more recent epoch in the outermost field. The young star forming
epoch continues to the present time in the innermost field, but lasted only
till ~0.8 and 1.3 Gyr ago at Rgc=5.5 degrees and 7.1 degrees, respectively.
This gradient is correlated with the measured HI column density and implies an
outside-in quenching of the star formation, possibly related to a variation of
the size of the HI disk. This could either result from gas depletion due to
star formation or ram-pressure stripping, or from to the compression of the gas
disk as ram-pressure from the Milky Way halo acted on the LMC interstellar
medium. The latter two situations may have occurred when the LMC first
approached the Milky Way.Comment: 15 pages, 13 figures, 4 tables. MNRAS, in pres
Seyfert's Sextet: A Slowly Dissolving Stephan's Quintet?
We present a multiwavelength study of the highly evolved compact galaxy group
known as Seyfert's Sextet (HCG79: SS). We interpret SS as a 2-3 Gyr more
evolved analog of Stephan's Quintet (HCG92: SQ). We postulate that SS formed by
sequential acquisition of 4-5 primarily late-type field galaxies. Four of the
five galaxies show an early-type morphology which is likely the result of
secular evolution driven by gas stripping. Stellar stripping has produced a
massive/luminous halo and embedded galaxies that are overluminous for their
size. These are interpreted as remnant bulges of the accreted spirals. H79d
could be interpreted as the most recent intruder being the only galaxy with an
intact ISM and uncertain evidence for tidal perturbation. In addition to
stripping activity we find evidence for past accretion events. H79b (NGC6027)
shows a strong counter-rotating emission line component interpreted as an
accreted dwarf spiral. H79a shows evidence for an infalling component of gas
representing feedback or possible cross fueling by H79d. The biggest challenge
to this scenario involves the low gas fraction in the group. If SS formed from
normal field spirals then much of the gas is missing. Finally, despite its
advanced stage of evolution, we find no evidence for major mergers and infer
that SS (and SQ) are telling us that such groups coalesce via slow dissolution.Comment: 70 pages, 19 figures, 15 tables - accepted for publication in the
Astronomical Journa
Distally based dorsal nasal flap in nasal ala reconstruction: anatomic study and clinical experience.
The extended halo of NGC 2682 (M 67) from Gaia DR2
Context: NGC 2682 is a nearby open cluster, approximately 3.5 Gyr old.
Dynamically, most open clusters should dissolve on shorter timescales, of ~ 1
Gyr. Having survived until now, NGC 2682 was likely much more massive in the
past, and is bound to have an interesting dynamical history. Aims: We
investigate the spatial distribution of NGC 2682 stars to constrain its
dynamical evolution, especially focusing on the marginally bound stars in the
cluster outskirts. Methods: We use Gaia DR2 data to identify NGC 2682 members
up to a distance of ~150 pc (10 degrees). Two methods (Clusterix and UPMASK)
are applied to this end. We estimate distances to obtain three-dimensional
stellar positions using a Bayesian approach to parallax inversion, with an
appropriate prior for star clusters. We calculate the orbit of NGC 2682 using
the GRAVPOT16 software. Results: The cluster extends up to 200 arcmin (50 pc)
which implies that its size is at least twice as previously believed. This
exceeds the cluster Hill sphere based on the Galactic potential at the distance
of NGC 2682. Conclusions: The extra-tidal stars in NGC 2682 may originate from
external perturbations such as disk shocking or dynamical evaporation from
two-body relaxation. The former origin is plausible given the orbit of NGC
2682, which crossed the Galactic disk ~40 Myr ago.Comment: 9 pages, 5 figures, accepted for publication on A&
Comparação de iscas atrativas para a captura de adultos de Rhynchophorus palmarum em dendezais.
bitstream/item/48907/1/Boletim-PD-06-AMAZ-ORIENTAL.pd
Refined theories based on non-polynomial kinematics for the thermoelastic analysis of functionally graded plates
This article presents an analytical solution for the thermoelastic analysis of simply supported functionally graded sandwich plates using the Carrera unified formulation, which allows the automatic implementation of various structural theories. The governing equations for plates under thermal loads are obtained using the principal of virtual displacement and solved using the Navier method. Linear and nonlinear temperature fields through the thickness are taken into account. Particular attention is focused on plate theories with nonpolynomial refined kinematics. The results of the present displacement fields are compared with the classical polynomial ones, proposed by Carrera, for several orders of expansion
Serum proteomics of active tuberculosis patients and contacts reveals unique processes activated during Mycobacterium tuberculosis infection.
Tuberculosis (TB) is the most lethal infection among infectious diseases. The specific aim of this study was to establish panels of serum protein biomarkers representative of active TB patients and their household contacts who were either infected (LTBI) or uninfected (EMI-TB Discovery Cohort, Pontevedra Region, Spain). A TMT (Tamdem mass tags) 10plex-based quantitative proteomics study was performed in quintuplicate containing a total of 15 individual serum samples per group. Peptides were analyzed in an LC-Orbitrap Elite platform, and raw data were processed using Proteome Discoverer 2.1. A total of 418 proteins were quantified. The specific protein signature of active TB patients was characterized by an accumulation of proteins related to complement activation, inflammation and modulation of immune response and also by a decrease of a small subset of proteins, including apolipoprotein A and serotransferrin, indicating the importance of lipid transport and iron assimilation in the progression of the disease. This signature was verified by the targeted measurement of selected candidates in a second cohort (EMI-TB Verification Cohort, Maputo Region, Mozambique) by ELISA and nephelometry techniques. These findings will aid our understanding of the complex metabolic processes associated with TB progression from LTBI to active disease
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