4,491 research outputs found
R^2 Dark Matter
There is a non-trivial four-derivative extension of the gravitational
spectrum that is free of ghosts and phenomenologically viable. It is the so
called -gravity since it is defined by the only addition of a term
proportional to the square of the scalar curvature. Just the presence of this
term does not improve the ultraviolet behaviour of Einstein gravity but
introduces one additional scalar degree of freedom that can account for the
dark matter of our Universe.Comment: 6 pages, 1 figure, to appear in the Proceedings of the sixth
International Workshop on the Dark Side of the Universe (DSU2010) Leon,
Guanajuato, Mexico 1-6 June 201
Dark Matter and Higgs Sector
The inert doublet model is an extension of the Standard Model of Elementary
Particles that is defined by the only addition of a second Higgs doublet
without couplings to quarks or leptons. This minimal framework has been studied
for many reasons. In particular, it has been suggested that the new degrees of
freedom contained in this doublet can account for the Dark Matter of the
Universe.Comment: 6 pages, 3 figures,To appear in the Proceedings of the sixth
International Workshop on the Dark Side of the Universe (DSU2010) Leon,
Guanajuato, Mexico 1-6 June 201
The generation of student engagement as a cognition-affect-behaviour process in a Twitter learning experience
Twitter is a microblog that allows users to interact about a topic in online discussion. This makes it an interesting interactive tool with possibilities to increase student engagement and learning performance through active collaboration in an informal learning environment. However, few articles take a quantitative approach to investigate the creation of student engagement using this social networking site. To address this gap, we propose a series of activities conducted through Twitter to analyse the engagement generation process in a sample of 110 students in the first year of a business and administration degree at a large Spanish university. The results show that the engagement process is created through active collaborative learning and enjoyment, and that engaged students are more satisfied with the activity and perceive greater learning performance. This leads us to recommend teachers to encourage active and collaborative activities to make students more engaged and satisfied, and improve their performance.es consisting of applying the concepts studied in class to practical environments, and activities where students browse for online information and take part in a debate, are more enjoyable
Probing Electroweak Top Quark Couplings at Hadron Colliders
We consider QCD t\bar{t}\gamma and t\bar{t}Z production at hadron colliders
as a tool to measure the tt\gamma and ttZ couplings. At the Tevatron it may be
possible to perform a first, albeit not very precise, test of the tt\gamma
vector and axial vector couplings in t\bar{t}\gamma production, provided that
more than 5 fb^{-1} of integrated luminosity are accumulated. The t\bar{t}Z
cross section at the Tevatron is too small to be observable. At the CERN Large
Hadron Collider (LHC) it will be possible to probe the tt\gamma couplings at
the few percent level, which approaches the precision which one hopes to
achieve with a next-generation e^+e^- linear collider. The LHC's capability of
associated QCD t\bar{t}V (V=\gamma, Z) production has the added advantage that
the tt\gamma and ttZ couplings are not entangled. For an integrated luminosity
of 300 fb^{-1}, the ttZ vector (axial vector) coupling can be determined with
an uncertainty of 45-85% (15-20%), whereas the dimension-five dipole form
factors can be measured with a precision of 50-55%. The achievable limits
improve typically by a factor of 2-3 for the luminosity-upgraded (3 ab^{-1})
LHC.Comment: Revtex3, 30 pages, 9 Figures, 6 Table
PDB38 Effect of Smoking Status on Health Care Costs In Patients With Type 2 Diabetes: A Retrospective Nested Case-Control Economic Study In Routine Clinical Practice
Determination of Optimal Parameters and Feasibility for Imaging of Epileptic Seizures by Electrical Impedance Tomography: A Modelling Study Using a Realistic Finite Element Model of the Head
Detection of branon dark matter with gamma ray telescopes
Branons are new degrees of freedom that appear in flexible brane-world models
corresponding to brane fluctuations. These new fields can behave as standard
weakly interacting massive particles (WIMPs) with a significant associated
thermal relic density. We analyze the present constraints from their
spontaneous annihilations into photons for EGRET, Fermi-LAT and MAGIC, and the
prospects for detection in future Cherenkov telescopes. In particular, we focus
on possible signals coming from the Galactic Center and different dwarf
spheroidals, such as Draco, Sagittarius, Canis Major and SEGUE 1. We conclude
that for those targets, present observations are below the sensitivity limits
for branon detection by assuming standard dark matter distributions and no
additional boost factors. However, future experiments such as CTA could be able
to detect gamma-ray photons coming from the annihilation of branons with masses
higher than 150 GeV.Comment: 10 pages, 3 figure
Molecular Identification of a New Pestivirus Associated with Increased Mortality in the Pyrenean Chamois (Rupicapra pyrenaica pyrenaica) in Spain
Pestivirus infection was identified in 16 of 17 chamois during an outbreak of a previously unreported disease in Pyrenean chamois (Rupicapra pyrenaica pyrenaica) in northeastern Spain in 2001-02. By analysis of the 5' noncoding regions of the virus, we assigned it to the border disease virus cluster with pairwise similarity values ranging from 82.1% to 88.1%. It will be important to investigate the association of this pestivirus with disease in Pyrenean chamois
Location and characterization of the stem-calyx area on oranges by computer vision
Three image analysis methods were studied and evaluated to solve the problem of removing long stems attached to mechanically harvested oranges: colour segmentation based on linear discriminant analysis, contour curvature analysis, and a thinning process which involves iterating until the stem becomes a skeleton. These techniques are able to determine the presence or absence of a stem with certainty, to locate the stems from random views with more than 90% accuracy and from profile images with an accuracy ranging from 92.4% to 100% depending on the method used. Finally, determination of the length and cutting point of the stem is achieved with only 3.8% of failures. (C) 1996 Silsoe Research Institut
Spatial and temporal distribution of Mycobacterium tuberculosis complex infection in Eurasian badger (Meles meles) and cattle in Asturias, Spain
Trabajo presentado al: 69th Wildlife Disease Association and 14th European Wildlife Disease Association Conference. Cuenca, Spain. p. 66. 31 agosto-2 septiembre
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