1,728 research outputs found
Length-weight relationships of demersal fishes from the upper continental slope off Colombia
Parameters of the length–weight relationship of the form W=aLb are presented for 45 demersal fish species caught on the upper continental slope of the Caribbean Sea off Colombia. The b values varied between 2.13 and 4.97, with the mean b = 3.042 (95% CI, 2.887- 3.196)
Detection of TeV emission from the intriguing composite SNR G327.1-1.1
The shock wave of supernova remnants (SNRs) and the wind termination shock in
pulsar wind nebula (PWNe) are considered as prime candidates to accelerate the
bulk of Galactic cosmic ray (CR) ions and electrons. The SNRs hosting a PWN
(known as composite SNRs) provide excellent laboratories to test these
hypotheses. The SNR G327.1-1.1 belongs to this category and exhibits a shell
and a bright central PWN, both seen in radio and X-rays. Interestingly, the
radio observations of the PWN show an extended blob of emission and a curious
narrow finger structure pointing towards the offset compact X-ray source
indicating a possible fast moving pulsar in the SNR and/or an asymmetric
passage of the reverse shock. We report here on the observations, for a total
of 45 hours, of the SNR G327.1-1.1 with the H.E.S.S. telescope array which
resulted in the detection of TeV gamma-ray emission in spatial coincidence with
the PWN.Comment: Proceeding of the 32nd ICRC, August 11-18 2011, Beijing, Chin
Covariant Impulse Approximation for the study of the internal structure of composite particles
We present a brief review on the Impulse Approximation method to study
processes of scattering off composite particles. We first construct the model
in a non-relativistic fashion that enables us to extend the model to a
covariant Impulse Approximation, which is needed for the study of high momentum
transfer processes.Comment: 8 Page
Inflation driven by a holographic energy density
In this letter we study a model of inflation in which the inflationary
regimen comes from a type of holographic energy density. In particular, we
consider the Granda-Oliveros proposal for the holographic energy density, which
contains two free dimensionless parameters, and . This
holographic energy density is associated to the so-called Granda-Oliveros
infrared cutoff (G-O cutoff). Additionally, since in the inflationary regimen
the energy scales are very high, it is necessary to modify the G-O cutoff
taking into account a correction due to the ultraviolet cutoff. In this way, we
obtain an algebraic equation which implicitly includes the Hubble parameter (as
a function of e-folding number, ) and from this, we calculate the Hubble
slow-roll parameters and the values of the inflationary observables: the scalar
spectral index of the curvature perturbations and its running, the tensor
spectral index and the tensor-to-scalar ratio. Finally, since the values for
these inflationary observables are known (Planck 2018 observations), we present
constraints on the parameters and to make this a viable model.Comment: 7 pages, 2 figures, references added, minor changes, accepted for
publication in EP
Late-time cosmology in a model of modified gravity with an exponential function of the curvature
In this work, we analyse the late-time evolution of the universe for a
particular gravity model built from an exponential function of the
scalar curvature. Following the literature, we write the field equations in
terms of a suited statefinder function () and considering well
motivated physical initial conditions, the resulting equations are solved
numerically. Also, the cosmological parameters , ,
and and the statefinder quantities , , and
are explicitly expressed in terms of and its derivatives.
Furthermore, setting an appropriate set of values for the model parameters, the
cosmological parameters as well as the statefinder quantities are plotted, and
their present values (at ), are shown to be compatible with Planck 2018
observations and the CDM-model values. Considering updated
measurements from the dynamics of the expansion of the universe, , we
perform an statistical analysis to constrain the free parameters of the model,
finding a particular set of values that fit the data well and predict
acceptable values for the cosmological and statefinder parameters at present
time. Therefore, the gravity model is found to be consistent with the
considered observational data, and a viable alternative to explain the
late-time acceleration of the universe.Comment: 23 pages (in the current format), 16 figure
Effects of Orientations, Aspect Ratios, Pavement Materials and Vegetation Elements on Thermal Stress inside Typical Urban Canyons
The analysis of local climate conditions to test artificial urban boundaries and related climate hazards through modelling tools should become a common practice to inform public authorities about the benefits of planning alternatives. Different finishing materials and sheltering objects within urban canyons (UCs) can be tested, predicted and compared through quantitative and qualitative understanding of the relationships between the microclimatic environment and subjective thermal assessment. This process can work as support planning instrument in the early design phases as has been done in this study that aims to analyze the thermal stress within typical UCs of Bilbao (Spain) in summertime through the evaluation of Physiologically Equivalent Temperature using ENVI-met. The UCs are characterized by different orientations, height-to-width aspect ratios, pavement materials, trees’ dimensions and planting pattern. Firstly, the current situation was analyzed; secondly, the effects of asphalt and red brick stones as streets’ pavement materials were compared; thirdly, the benefits of vegetation elements were tested. The analysis demonstrated that orientation and aspect ratio strongly affect the magnitude and duration of the thermal peaks at pedestrian level; while the vegetation elements improve the thermal comfort up to two thermophysiological assessment classes. The outcomes of this study, were transferred and visualized into green planning recommendations for new and consolidated urban areas in Bilbao.The work leading to these results has received funding from COST Action TU0902, the European Community’s Seventh Framework Programme under Grant Agreement No. 308497, Project RAMSES—Reconciling Adaptation, Mitigation and Sustainable Development for Cities (2012–2017) and Diputación Foral de Bizkaia Exp. 6-12-TK-2010-0027, Project SICURB-ITS- Desarrollo de Sistemas para el análisis de la Contaminación atmosférica en zonas URBanas integrados en ITS (2010–2011)
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