9,009 research outputs found
Produção de mudas frutĂferas no Nordeste.
Objetivando conhecer a situacao da producao de mudas no contexto da fruticultura nordestina, a Embrapa Agroindustria Tropical, realizou um levantamento nos estados de Sergipe, Alagoas,Pernambuco, Paraiba, Rio Grande do Norte, Ceara, Piaui e Maranhao.bitstream/CNPAT-2010/5359/1/Ct-027.pd
New sufficient conditions to ulam stabilities for a class of higher order integro-differential equations
In this work, we present sufficient conditions in order to establish different types of Ulam stabilities for a class of higher order integro-differential equations. In particular, we consider a new kind of stability, the sigma-semi-Hyers-Ulam stability, which is in some sense between the Hyers-Ulam and the Hyers-Ulam-Rassias stabilities. These new sufficient conditions result from the application of the Banach Fixed Point Theorem, and by applying a specific generalization of the Bielecki metric.publishe
Flavor structure with multi moduli in 5D supergravity
We study 5-dimensional supergravity on S^1/Z_2 with a physical Z_2-odd vector
multiplet, which yields an additional modulus other than the radion. We derive
4-dimensional effective theory and find additional terms in the Kahler
potential that are peculiar to the multi moduli case. Such terms can avoid
tachyonic soft scalar masses at tree-level, which are problematic in the single
modulus case. We also show that the flavor structure of the soft terms are
different from that in the single modulus case when hierarchical Yukawa
couplings are generated by wavefunction localization in the fifth dimension. We
present a concrete model that stabilizes the moduli at a supersymmetry breaking
Minkowski minimum, and show the low energy sparticle spectrum.Comment: 30 pages, 2 figures; version to be published in PR
The COVID-19 impact on crowdfunding performance: Evidence from a peer to-peer lending platform
The COVID-19 impact on global poverty dragged another 97 million people into poverty in 2020. Nonetheless, there is scant evidence reporting on the impacts on alternative means of financing designed to enable the poor during this global health crisis. This paper addresses this gap of funding impoverished entrepreneurs by studying the changes in their successfully funded campaigns on the largest crowdfunding microfinance platform prior and during COVID-19. After collecting data from January 2018 to November 2021 for a total of 767,112 campaigns, we report that the COVID-19 pandemic positively impacts on the funding success of the crowdfunding campaigns. However, rises in the daily number of COVID-19 cases negatively associate with campaigns getting fully funded. The odds of campaigns being fully funded decrease by 4.4% for a one thousand increase in new cases.info:eu-repo/semantics/publishedVersio
Simulation of VUV electroluminescence in micropattern gaseous detectors: the case of GEM and MHSP
Electroluminescence produced during avalanche development in gaseous
avalanche detectors is an useful information for triggering, calorimetry and
tracking in gaseous detectors. Noble gases present high electroluminescence
yields, emitting mainly in the VUV region. The photons can provide signal
readout if appropriate photosensors are used. Micropattern gaseous detectors
are good candidates for signal amplification in high background and/or low rate
experiments due to their high electroluminescence yields and radiopurity. In
this work, the VUV light responses of the Gas Electron Multiplier and of the
Micro-Hole Strip Plate, working with pure xenon, are simulated and studied in
detail using a new and versatile C++ toolkit. It is shown that the solid angle
subtended by a photosensor placed below the microstructures depends on the
operating conditions. The obtained absolute EL yields, determined for different
gas pressures and as functions of the applied voltage, are compared with those
determined experimentally.Comment: Accepted for publication in Journal of Instrumentatio
Bioinspired multilayer membranes as potential adhesive patches for skin wound healing
Bioinspired and adhesive multilayer membranes are produced using the layer-by-layer (LbL) assembly of chitosan (CHT), alginate (ALG) and hyaluronic acid modified with dopamine (HA-DN). Freestanding multilayer membranes without DN are also produced as a control. The success of the synthesis of HA-DN was confirmed using UV-visible spectroscopy. Scanning electron microscopy images indicate that the surface of the DN-containing membranes is more porous than the control ones; they also present a higher average thickness value for the same number of CHT/ALG/CHT/HA(-DN) tetralayers (n = 100). Also, water uptake, mechanical strength and adhesion are enhanced with the introduction of DN moieties along the nano-layers. Besides, human dermal fibroblast viability, enhanced adhesion and proliferation were confirmed by immunofluorescence assays and by measuring both the metabolic activity and DNA content. Moreover, in vivo assays with such kinds of DN-containing multilayer membranes were performed; the application of these membranes in the treatment of dermal wounds induced in Wistar rats results in the highest decrease of inflammation of rat skin, compared with the control conditions. Overall, this investigation suggests that these mussel-inspired freestanding multilayer membranes may enhance either their mechanical performance or cellular adhesion and proliferation, leading to an improved wound healing process, being a promising material to restore the structural and functional properties of wounded skin.M. P. S. acknowledges the Portuguese Foundation for Science and Technology (FCT) for financial support through Grant No. SFRH/BD/97606/2013. This work was supported by the European Research Council grant agreement ERC-2014-ADG-669858 for the ATLAS project. The authors acknowledge Paula Marques (Mechanical Engineering Department, University of Aveiro, Aveiro, Portugal) for providing the mechanical equipment to carry out the tensile tests and the lap shear adhesion tests.info:eu-repo/semantics/publishedVersio
Pressure effect in the X-ray intrinsic position resolution in noble gases and mixtures
A study of the gas pressure effect in the position resolution of an
interacting X- or gamma-ray photon in a gas medium is performed. The intrinsic
position resolution for pure noble gases (Argon and Xenon) and their mixtures
with CO2 and CH4 were calculated for several gas pressures (1-10bar) and for
photon energies between 5.4 and 60.0 keV, being possible to establish a linear
match between the intrinsic position resolution and the inverse of the gas
pressure in that energy range. In order to evaluate the quality of the method
here described, a comparison between the available experimental data and the
calculated one in this work, is done and discussed. In the majority of the
cases, a strong agreement is observed
A dynamic method for charging-up calculations: the case of GEM
The simulation of Micro Pattern Gaseous Detectors (MPGDs) signal response is
an important and powerful tool for the design and optimization of such
detectors. However, several attempts to simulate exactly the effective charge
gain have not been completely successful. Namely, the gain stability over time
has not been fully understood. Charging-up of the insulator surfaces have been
pointed as one of the responsible for the difference between experimental and
Monte Carlo results. This work describes two iterative methods to simulate the
charging-up in one MPGD device, the Gas Electron Multiplier (GEM). The first
method uses a constant step for avalanches time evolution, very detailed, but
slower to compute. The second method uses a dynamic step that improves the
computing time. Good agreement between both methods was reached. Despite of
comparison with experimental results shows that charging-up plays an important
role in detectors operation, should not be the only responsible for the
difference between simulated and measured effective gain, but explains the time
evolution in the effective gain.Comment: Minor changes in grammatical statements and inclusion of some
important information about experimental setup at section "Comparison with
experimental results
Hermitian Yang-Mills instantons on resolutions of Calabi-Yau cones
We study the construction of Hermitian Yang-Mills instantons over resolutions
of Calabi-Yau cones of arbitrary dimension. In particular, in d complex
dimensions, we present an infinite family, parametrised by an integer k and a
continuous modulus, of SU(d) instantons. A detailed study of their properties,
including the computation of the instanton numbers is provided. We also explain
how they can be used in the construction of heterotic non-Kahler
compactifications.Comment: 20 pages, 1 figure; typos corrected, section 3.1 expande
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