258 research outputs found
Herdsmen, a changing profession
Traditional extensive grazing systems in Southern Portugal relying exclusively on herdsmen
that live in permanence with the animals are in peril, since herdsman is the least attractive among
rural professions.
Recently, namely after the entry in the EEC in 1986, and taking advantage of the UE structural funds, infrastructures
aimed at extensive livestock production, such as fencing and water supply have been installed,
but still far way from covering the territory.
The paper aims to provide a systematic understanding of the changing characteristics of the herdsmen
profession and functions. It proposes a model framework to highlight the driving forces of the reported
changes, using a case study in South Alentejo (Portugal) as an illustration.
The results of a survey to 25 farms in the municipality of Ourique and inquiries to 37 employees working
with livestock show a mosaic of situations ranging from remnants of the traditional herdsman to another
type of worker, the so called polyvalent which is able to use the machinery and work in a more sophisticated
working environment. They are generally better paid and have living conditions closer to
other more urban professions, in some cases a working schedule and a free day per week
A mineralogical and organic geochemical overview of the effects of Holocene changes in Amazon River flow on three floodplain lakes
A synthesis of the impacts of the Amazon River hydrological changes on the sedimentation process of organic matter (OM) in three different floodplain lakes (Santa Ninha, Maracá, and Comprido lakes) is presented in this study. Today the Santa Ninha and Maracá lakes are directly and permanently connected with the main channel of the Amazon River, in contrast to Comprido Lake, which is indirectly and periodically influenced by the Amazon River due to its greater distance from the main channel. All three lake sediment records showed a reduced river inflow due to dry climatic conditions during the early and middle Holocene followed by an increased fluvial input during the wetter late Holocene. In Santa Ninha and Maraca Lakes, the reduced river inflow period was recorded by sediments with a low abundance of smectite (on average ~ 20 wt.%), a clay mineral mainly transported by the fluvial system, high total organic carbon (TOC) contents (on average ~ 8.2 wt.%), and a predominantly acidic soil OM input evidenced by high concentrations (on average 180 µg gTOC- 1) of branched glycerol dialkyl glycerol tetraethers (GDGT). During the late Holocene, a higher smectite abundance (on average ~ 43 wt.%) and a lower TOC content (on average ~ 1.4 wt.%) pointed to greater dilution by riverine lithogenic matter. This change was accompanied by a proportional increase in the aquatically produced crenarchaeol, suggesting a higher lake water level. In Comprido Lake, a sedimentation gap occurred during the early and middle Holocene. The wetter late Holocene, since 3000 cal years BP, was characterized by high TOC values (on average ~ 9 wt.%) and a sharp increase in soil OM input as recorded by an increase in branched GDGT concentrations (on average ~ 81 µg gTOC- 1), but the smectite content was low (on average ~ 14%). This combination suggests that the soil OM input to Comprido Lake from the local catchment area became dominant during the wet-climate late Holocene due to the large distance of the lake from the Amazon River main channel. Consequently, our study shows that the sedimentation processes of OM in Amazonian floodplain lakes were strongly influenced by variations in the hydrodynamic regime of the Amazon River during the Holocene. However, the impacts of the variations on the three floodplain lakes were different depending on the distance of each lake from the main channel of the Amazon River
A p-Spin Interaction Ashkin-Teller Spin-Glass Model
A p-spin interaction Ashkin-Teller spin glass, with three independent
Gaussian probability distributions for the exchange interactions, is studied by
means of the replica method. A simple phase diagram is obtained within the
replica-symmetric approximation, presenting an instability of the paramagnetic
solution at low temperatures. The replica-symmetry-breaking procedure is
implemented and a rich phase diagram is obtained; besides the paramagnetic
phase, three distinct spin-glass phases appear. Three first-order critical
frontiers are found and they all meet at a triple point; among such lines, two
of them present discontinuities in the order parameters, but no latent heat,
whereas the other one exhibits both discontinuities in the order parameters and
a finite latent heat.Comment: 17 pages, 2 figures, submitted to Physica
Uso de simuladores, imagens e animações como ferramentas auxiliares no ensino/aprendizagem de óptica
Anisotropic flow of charged hadrons, pions and (anti-)protons measured at high transverse momentum in Pb-Pb collisions at TeV
The elliptic, , triangular, , and quadrangular, , azimuthal
anisotropic flow coefficients are measured for unidentified charged particles,
pions and (anti-)protons in Pb-Pb collisions at TeV
with the ALICE detector at the Large Hadron Collider. Results obtained with the
event plane and four-particle cumulant methods are reported for the
pseudo-rapidity range at different collision centralities and as a
function of transverse momentum, , out to GeV/.
The observed non-zero elliptic and triangular flow depends only weakly on
transverse momentum for GeV/. The small dependence
of the difference between elliptic flow results obtained from the event plane
and four-particle cumulant methods suggests a common origin of flow
fluctuations up to GeV/. The magnitude of the (anti-)proton
elliptic and triangular flow is larger than that of pions out to at least
GeV/ indicating that the particle type dependence persists out
to high .Comment: 16 pages, 5 captioned figures, authors from page 11, published
version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/186
Centrality dependence of charged particle production at large transverse momentum in Pb-Pb collisions at TeV
The inclusive transverse momentum () distributions of primary
charged particles are measured in the pseudo-rapidity range as a
function of event centrality in Pb-Pb collisions at
TeV with ALICE at the LHC. The data are presented in the range
GeV/ for nine centrality intervals from 70-80% to 0-5%.
The Pb-Pb spectra are presented in terms of the nuclear modification factor
using a pp reference spectrum measured at the same collision
energy. We observe that the suppression of high- particles strongly
depends on event centrality. In central collisions (0-5%) the yield is most
suppressed with at -7 GeV/. Above
GeV/, there is a significant rise in the nuclear modification
factor, which reaches for GeV/. In
peripheral collisions (70-80%), the suppression is weaker with almost independently of . The measured nuclear
modification factors are compared to other measurements and model calculations.Comment: 17 pages, 4 captioned figures, 2 tables, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/284
Measurement of charm production at central rapidity in proton-proton collisions at TeV
The -differential production cross sections of the prompt (B
feed-down subtracted) charmed mesons D, D, and D in the rapidity
range , and for transverse momentum GeV/, were
measured in proton-proton collisions at TeV with the ALICE
detector at the Large Hadron Collider. The analysis exploited the hadronic
decays DK, DK, DD, and their charge conjugates, and was performed on a
nb event sample collected in 2011 with a
minimum-bias trigger. The total charm production cross section at TeV and at 7 TeV was evaluated by extrapolating to the full phase space
the -differential production cross sections at TeV
and our previous measurements at TeV. The results were compared
to existing measurements and to perturbative-QCD calculations. The fraction of
cdbar D mesons produced in a vector state was also determined.Comment: 20 pages, 5 captioned figures, 4 tables, authors from page 15,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/307
Particle-yield modification in jet-like azimuthal di-hadron correlations in Pb-Pb collisions at = 2.76 TeV
The yield of charged particles associated with high- trigger
particles ( GeV/) is measured with the ALICE detector in
Pb-Pb collisions at = 2.76 TeV relative to proton-proton
collisions at the same energy. The conditional per-trigger yields are extracted
from the narrow jet-like correlation peaks in azimuthal di-hadron correlations.
In the 5% most central collisions, we observe that the yield of associated
charged particles with transverse momenta GeV/ on the
away-side drops to about 60% of that observed in pp collisions, while on the
near-side a moderate enhancement of 20-30% is found.Comment: 15 pages, 2 captioned figures, 1 table, authors from page 10,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/350
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