240 research outputs found
Longitudinal profiles of Extensive Air Showers with inclusion of charm and bottom particles
Charm and bottom particles are rare in Extensive Air Showers but the effect
of its presence can be radical in the development of the Extensive Air Showers
(EAS). If such particles arise with a large fraction of the primary energy,
they can reach large atmospheric depths, depositing its energy in deeper layers
of the atmosphere. As a consequence, the EAS observables (, and
) will be modified, as well as the shape of the longitudinal profile
of the energy deposited in the atmosphere. In this paper, we will modify the
CORSIKA Monte Carlo by the inclusion of charm and bottom production in the
first interaction of the primary cosmic ray. Results for different selections
of the typical values of the heavy particles and distinct production
models will be presented.Comment: Replacement of tex file by the correct versio
Saturation Physics in Ultra High Energy Cosmic Rays: Heavy Quark Production
In this work we estimate the heavy quark production in the interaction of
ultra high energy cosmic rays in the atmosphere, considering that the primary
cosmic ray is a proton or a photon. At these energies the saturation momentum
Q_{sat}^2 stays above the hard scale \mu_c^2=4m_c^2, implying charm production
probing the saturation regime. In particular, we show that the ep HERA data
presents a scaling on \tau_c = (Q^2+\mu_c^2)/Q_{sat}^2. We derive our results
considering the dipole picture and the Color Glass Condensate formalism, which
one shows to be able to describe the heavy quark production in photon-proton
and proton-proton collisions. Nuclear effects are considered in computation of
cross sections for scattering on air nuclei. Implications on the flux of prompt
leptons at the earth are analyzed and a large suppression is predicted.Comment: 18 pages, 10 figures, 2 tables. Version to be published in JHE
Searches for axion-like particles via fusion at future colliders
Opportunities for searches for axion-like particles (ALPs) coupling to
photons in collisions at the Future Circular
Collider (FCC-ee) and International Linear Collider (ILC) are investigated. We
perform a study of the photon-fusion production of ALPs decaying into two
photons, , over the light-by-light
continuum background, for the planned FCC-ee and ILC center-of-mass energies
and integrated luminosities. An analysis of the feasibility measurements is
presented using parametrized simulations for two types of detectors. Upper
limits at 95% confidence level (CL) on the cross section for ALP production,
, and on the ALP-photon coupling
are obtained over the --1000 GeV ALP mass range, and compared
to current and future collider searches. Production cross sections down to
fb (1 ab) will be
probed at (300) GeV, corresponding to constraints on the
axion-photon coupling as low as TeV
Spent grain as a new carrier for trypsin immobilisation
Trypsin is a widely used enzyme for protein hydrolysis and can be used to improve functional and nutritional properties of foods. This work compares different carriers obtained from spent grains as potential candidates for trypsin immobilisation. Covalent attachment to the carriers was tested using glutaraldehyde. The efficiency of immobilisation and activity, operation and storage stability of free and immobilised enzyme on supports were determined. The amount of immobilised protein achieved was high (up to 70 %) but there was a significant loss of enzyme activity with the immobilisation of trypsin. However, when a more purified enzyme from bovine pancreas was used, activity retention was almost 50 %. Trypsin was most successfully immobilised on the supports by covalent attachment using glyoxyl-derivatives. The stability of these immobilized enzymes was close to 100%.This work was co-financed by Social European Fund (public call 1/5.3/PRODEP/2003, financial application 1012.012, of measure 5/action 5.3 – Post-graduate training for academic staff submitted by Escola Superior de Tecnologia e Gestão do Instituto Politécnico de Viana do Castelo).info:eu-repo/semantics/publishedVersio
Shine on you crazy diamond: Symbolism and social use of fluorite ornaments in Iberia’s late prehistory
Fluorite ornaments have been recorded in different sites of Europe since Upper Paleolithic. Due to its visual appearance and physical properties, some translucent or transparent mineralogies like fluorite were searched for or casually acquired by late prehistory’s human communities. After intensive research on archaeological contexts from the Iberian Peninsula with personal ornaments from 4th to 2nd millennia BCE, we have recently identified and characterized for the first time an important number of fluorite ornaments, confronting a previous background where little attention was paid. Our work has been carried out in different archaeological collections and museums from the whole Iberian Peninsula by non-destructive techniques (Raman spectroscopy, portable X-ray fluorescence (p-XRF) and X-ray Diffraction (XRD), that revealed the nature of fluorite ornaments and points to its consideration as scarce and highly symbolic items during late prehistory. A total of 36 fluorite beads from 23 sites are here recorded and studied, many of them unpublished or wrong catalogued as other mineralogies. These adornments could have important roles in trade and use among the communities of Iberia from the 4th millennium BCE onwards, because of their scarcity and its recurrent association with important funerary complex and exotic materials. Fluorite ornaments could have been significant and special symbols in the development of new and exclusive raw materials in the context of increasing social complexity and inequality
Distribución y consumo de cuentas de fluorita y translúcidas en la península ibérica del VI al II milenios ANE
Translucent minerals were valued in prehistoric societies
for their rarity and socially used as highly symbolic elements.
This work addresses the use and nature of Iberian translucent
beads. We present the results of chemical (Raman spectroscopy,
portable X-ray fluorescence, X-ray diffraction and
visible (Vis)/near-infrared (NIR) spectroscopy) and contextual
analyses and provide a review of the archaeological
literature on the manufacture and use of translucent items
during Iberian Late Prehistory. A total of 54 translucent beads
from 47 sites, primarily burials, were analyzed; 33 were
made from fluorite, while the remaining 21 were made of
diverse translucent minerals (calcite, quartz and different
silicates). The scarcity of translucent items in the archaeological
record, the regional and supraregional scale of its
exchange, and its recursive association to other valuables in
singular contexts reinforces the idea that their owners/wearers
enjoyed a high status.info:eu-repo/semantics/publishedVersio
Avaliação de ferramentas na furação de laminados compósitos
Drilling of polymeric matrix composite structuresThe development of cutting tools becomes a challenge to the industry of composite materials to obtain high
quality holes, minimizing damage. This work aims to examine the influence of various parameters such as feed rate and tool
geometry on thrust forces developed during drilling operations and on the extent of damage.
In this work, a comparative study of tool geometry with the aim of reducing the associated damage during drilling process
is presented. In the end a good combination of tool geometry and drilling parameters based on experimental work will be
presented.O desenvolvimento de ferramentas de corte torna-se um desafio à indústria de materiais compósitos, na obtenção
de furos de elevada qualidade, minimizando o dano. Este trabalho visa analisar a influência de vários parâmetros, tais como
o avanço e a geometria de ferramenta, nas forças desenvolvidas durante a furação e na extensão do dano.
Neste artigo é apresentado um estudo comparativo de geometrias de broca com o objectivo de reduzir o dano associado à
furação, que permitirá determinar qual a melhor selecção de parâmetros de furação, atendendo às diferentes geometrias de
ferramenta
Interpretation of gravity data to delineate structural features connected to low-temperature geothermal resources at Northeastern Portugal
A great number of low-temperature geothermal fields occur in Northern-Portugal related to fractured rocks. The most important superficial manifestations of these hydrothermal systems appear in pull-apart tectonic basins and are strongly conditioned by the orientation of the main fault systems in the region. This work presents the interpretation of gravity gradient maps and 3D inversion model produced from a regional gravity survey. The horizontal gradients reveal a complex fault system. The obtained 3D model of density contrast puts into evidence the main fault zone in the region and the depth distribution of the granitic bodies. Their relationship with the hydrothermal systems supports the conceptual models elaborated from hydrochemical and isotopic water analyses. This work emphasizes the importance of the role of the gravity method and analysis to better understand the connection between hydrothermal systems and the fractured rock pattern and surrounding geology. (c) 2013 Elsevier B.V. All rights reserved
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