16,091 research outputs found
On the Evaluation of the Mechanical Behaviour of Structural Glass Elements
Glass can be considered to be a high-technology engineering material with a
multifunctional potential for structural applications. However, the conventional approach to the use
of glass is often based only on its properties of transparency and isolation. It is thus highly
appropriate and necessary to study the mechanical behaviour of this material and to develop
adequate methods and models leading to its characterisation. It is evident that the great potential of
growth for structural glass applications is an important opportunity of development for the glass
industry and the building/construction sectors. The work presented in this paper is a reflection of
this conclusion. The authors shortly present the state-of-the-art on the application of glass as a
structural element in building and construction, and refer to other potential fields of application and
available glass materials. The experimental procedures and methods adopted in three-point bending
tests performed on 500 × 100 [mm2] float, laminated and tempered glass specimens with
thicknesses between 4 and 19 mm are thoroughly described. The authors evaluated the mechanical
strength and stiffness of glass for structural applications. This work contributes to a deeper
knowledge of the properties of this material
Melting of scalar mesons and black-hole quasinormal modes in a holographic QCD model
A holographic model for QCD is employed to investigate the effects of the
gluon condensate on the spectrum and melting of scalar mesons. We find the
evolution of the free energy density with the temperature, and the result shows
that the temperature of the confinement/deconfinement transition is sensitive
to the gluon-condensate parameter. The spectral functions (SPFs) are also
obtained and show a series of peaks in the low-temperature regime, indicating
the presence of quasiparticle states associated to the mesons, while the number
of peaks decreases with the increment of the temperature, characterizing the
quasiparticle melting. In the dual gravitational description, the scalar mesons
are identified with the black-hole quasinormal modes (QNMs). We obtain the
spectrum of QNMs and the dispersion relations corresponding to the scalar-field
perturbations of the gravitational background, and find their dependence with
the gluon-condensate parameter.Comment: 30 pages, 12 figures, 5 table
Massive Black Hole Binary Systems in Hierarchical Scenario of Structure Formation
The hierarchical scenario of structure formation describes how objects like
galaxies and galaxy clusters are formed by mergers of small objects. In this
scenario, mergers of galaxies can lead to the formation of massive black hole
(MBH) binary systems. On the other hand, the merger of two MBH could produce a
gravitational wave signal detectable, in principle, by the Laser Interferometer
Space Antenna (LISA). In the present work, we use the Press-Schechter
formalism, and its extension, to describe the merger rate of haloes which
contain massive black holes. Here, we do not study the gravitational wave
emission of these systems. However, we present an initial study to determine
the number of systems formed via mergers that could permit, in a future
extension of this work, the calculation of the signature in gravitational waves
of these systems.Comment: to match the published version in International Journal of Modern
Physics
Random Antiferromagnetic SU(N) Spin Chains
We analyze random isotropic antiferromagnetic SU(N) spin chains using the
real space renormalization group. We find that they are governed at low
energies by a universal infinite randomness fixed point different from the one
of random spin-1/2 chains. We determine analytically the important exponents:
the energy-length scale relation is , where
, and the mean correlation function is given by
, where . Our analysis shows
that the infinite-N limit is unable to capture the behavior obtained at any
finite N.Comment: 4 pages, 3 figure
Population Dynamics Of Megalobulimus Paranaguensis (gastropoda: Pulmonata) In The Southeast Coast Of Brazil
The population dynamics of Megalobulimus paranaguensis (Pilsbry & lhering, 1900), a large and long-lived land gastropod from Brazil's Southeast (Atlantic Forest) was studied between 2006 and 2009, at an urban park in the city of Santos, state of Sao Paulo. The study included biometry, weighing, and marking and recapture of adult individuals. The variables obtained from specimens were correlated with the environmental variables of the study period. The survival rate of the adult snail population was 96.7%. Recruitment showed several peaks during the year, and was concentrated between April and August, except in 2009, when there was only one peak in August. Specimen abundance progressively increased from 2006 on, with a trend towards relative stability during that period. The condition factor remained relatively stable as well, decreasing from December to February. The potential evapotranspiration and precipitation influenced the number of captures, and the mean temperature influenced the condition factor. Megalobulimus paranaguensis goes through a period of dormancy in the tropical summer, which is between November and February, but remains active in the winter. The survival rate of M. paranaguensis was high, and may be the result of having its annual cycle synchronized with the tropical climate of the Atlantic forest.32646346
Vector meson quasinormal modes in a finite-temperature AdS/QCD model
We study the spectrum of vector mesons in a finite temperature plasma. The
plasma is holographically described by a black hole AdS/QCD model. We compute
the boundary retarded Green's function using AdS/CFT prescriptions. The
corresponding thermal spectral functions show quasiparticle peaks at low
temperatures. Then we calculate the quasinormal modes of vector mesons in the
soft-wall black hole geometry and analyse their temperature and momentum
dependences.Comment: 27 pages, 9 figure
Scalar Spectrum from a Dynamical Gravity/Gauge model
We show that a Dynamical AdS/QCD model is able to reproduce the linear Regge
trajectories for the light-flavor sector of mesons with high spin and also for
the scalar and pseudoscalar ones. In addition the model has confinement by the
Wilson loop criteria and a mass gap. We also calculate the decay amplitude of
scalars into two pion in good agreement to the available experimental data.Comment: Presented in the 4th International Workshop on Astronomy and
Relativistic Astrophysic
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