938 research outputs found
Yield Of Beet Cultivars Under Fertigation Management And Salinity Control In A Protected Environment
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)In a protected environment, applying excess fertilizer and using water with soluble salts cause soil salinization due to the absence of lixiviation by precipitation. Among commercial vegetables, beets (Beta vulgaris L.) have good tolerance to soil salinity, being a good option for growth under these conditions. An experimental study was carried out in the municipality of Botucatu, São Paulo, Brazil. The treatment consisted of a combination of the following factors: initial soil salinity (1, 3, 6, 9, and 12 dS m-1), fertigation management (traditional vs. control of ion concentration of the soil solution) and two beet cultivars (‘Early Wonder’ and ‘Itapuã’) in a 5 × 2 × 2 factorial design. A randomized block design with four replicates was adopted, totaling 80 experimental plots. The total fresh weight of aerial part and root, total dry weight of aerial part and root, and water use efficiency (WUE) were assessed. Significant differences were found between fertigation management practices and salinity levels proposed. ‘Itapuã’ showed better yield and WUE for electrical conductivity (EC) below 6 dS m-1. Under traditional fertigation, root yield response fits a linear model with a decrease of 11.365 g (‘Early Wonder’) and 11.025 g (‘Itapuã’) for each unit increase in EC. Under controlled fertigation, the best-fit model was quadratic, with maximum estimates of 248.83 g for ‘Early Wonder’ and 258.52 g for ‘Itapuã’. Controlling EC of the soil solution had a positive effect, while salinity levels above 6 dS m-1 must be avoided. © 2016, Instituto de Investigaciones Agropecuarias, INIA. All rights reserved.764463470CAPES, Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorCNPq, Conselho Nacional de Desenvolvimento Científico e TecnológicoCoordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq
Effect of the North Equatorial Counter Current on the Generation and Propagation of Internal Solitary Waves Off the Amazon Shelf (SAR Observations)
. Synthetic aperture radar (SAR) imagery from the Amazon shelf break region in the tropical west Atlantic reveals for the first time the two-dimensional horizontal structure of an intense Internal Solitary Wave (ISW) field, whose first surface manifestations are detected several hundred kilometres away from the nearest forcing bathymetry. Composite maps and an energy budget analysis (provided from the Hybrid Coordinate Ocean Model – HYCOM) help to identify two major ISW pathways emanating from the steep slopes of a small promontory (or headland) near 44◦ W and 0 ◦ N, which are seen to extend for over 500 km into the open ocean. Further analysis in the SAR reveals propagation speeds above 3 m s−1 , which are amongst the fastest ever recorded. The main characteristics of the ISWs are further discussed based on a statistical analysis, and seasonal variability is found for one of the ISW sources. This seasonal variability is discussed in light of the North Equatorial Counter Current. The remote appearance of the ISW sea surface manifestations is explained by a late disintegration of the internal tide (IT), which is further investigated based on the SAR data and climatological monthly means (for stratification and currents). Acknowledging the possibility of a late disintegration of the IT may help explain the remote-sensing views of other ISWs in the world’s oceans
Dynamical dispersion relation for ELKO dark spinor fields
An intrinsic mass generation mechanism for exotic ELKO dark matter fields is
scrutinized, in the context of the very special relativity (VSR). Our results
are reported on unraveling inequivalent spin structures that educe an
additional term on the associated Dirac operator. Contrary to the spinor fields
of mass dimension 3/2, this term is precluded to be absorbed as a shift of some
gauge vector potential, regarding the equations for the dark spinor fields. It
leads to some dynamical constraints that can be intrinsically converted into a
dark spinor mass generation mechanism, with the encoded symmetries maintained
by the VSR. The dynamical mass is embedded in the VSR framework through a
natural coupling to the kink solution of a \lambda \phi^{4} theory for a scalar
field \phi. Our results evince the possibility of novel effective scenarios,
derived from exotic couplings among dark spinor fields and scalar field
topological solutions.Comment: 6 pages, to appear in Phys.Lett.
Thermofield Dynamics and Casimir Effect for Fermions
A generalization of the Bogoliubov transformation is developed to describe a
space compactified fermionic field. The method is the fermionic counterpart of
the formalism introduced earlier for bosons (J. C. da Silva, A. Matos Neto, F.
C. Khanna and A. E. Santana, Phys. Rev. A 66 (2002) 052101), and is based on
the thermofield dynamics approach. We analyse the energy-momentum tensor for
the Casimir effect of a free massless fermion field in a -dimensional box at
finite temperature. As a particular case the Casimir energy and pressure for
the field confined in a 3-dimensional parallelepiped box are calculated. It is
found that the attractive or repulsive nature of the Casimir pressure on
opposite faces changes depending on the relative magnitude of the edges. We
also determine the temperature at which the Casimir pressure in a cubic boc
changes sign and estimate its value when the edge of the cybe is of the order
of confining lengths for baryons.Comment: 21 pages, 3 figures, to appear in Annals of Physic
Comparison of the timed inspiratory effort index with the T-piece trial as a decision-making tool for extubation: a randomized controlled non-inferiority trial
The “timed inspiratory effort” (TIE) index, a new predictor of weaning outcome, normalizes the maximal inspiratory pressure with the time required to reach this value up to 60 s, incorporating the time domain into the assessment of inspiratory muscle function. The objective of this study was to determine whether the TIE predicts successful extubation at a similar rate as the T-piece trial with less time required. A non-inferiority randomized controlled trial was performed with ICU subjects eligible for weaning. The participants were allocated to the TIE or the T-piece groups. The primary outcome was successful weaning, and the main secondary outcome was ICU mortality. Eighty participants of each group were included in the final analysis. Time from the start of a successful test to effective extubation was significantly lower in the TIE group than in the T-piece group, 15 (10 to 24) vs 55 (40 to 75) min, P<0.001. In the Kaplan-Meier analysis, no significant differences were found in successful weaning (79.5 vs 82.5%, P=0.268) or survival rate (62.9 vs 53.8%, P=0.210) between the TIE and T-piece groups at the 30th day. In this preliminary study, the TIE index was not inferior to the T-piece trial as a decision-making tool for extubation and allowed a reduction in the decision time
How the Charge Can Affect the Formation of Gravastars
In recent work we physically interpreted a special gravastar solution
characterized by a zero Schwarzschild mass. In fact, in that case, none
gravastar was formed and the shell expanded, leaving behind a de Sitter or a
Minkowski spacetime, or collapsed without forming an event horizon, originating
what we called a massive non-gravitational object. This object has two
components of non zero mass but the exterior spacetime is Minkowski or de
Sitter. One of the component is a massive thin shell and the other one is de
Sitter spacetime inside. The total mass of this object is zero Schwarzschild
mass, which characterizes an exterior vacuum spacetime. Here, we extend this
study to the case where we have a charged shell. Now, the exterior is a
Reissner-Nordstr\"om spacetime and, depending on the parameter
of the equation of state of the shell, and the charge, a
gravastar structure can be formed. We have found that the presence of the
charge contributes to the stability of the gravastar, if the charge is greater
than a critical value. Otherwise, a massive non-gravitational object is formed
for small charges.Comment: 17 pages and 7 figures, several typos corrected, accepted for
publication in JCA
Stable Gravastars of Anisotropic Dark Energy
Dynamical models of prototype gravastars made of phantom energy are
constructed, in which an infinitely thin spherical shell of a perfect fluid
with the equation of state divides the whole spacetime
into two regions, the internal region filled with a dark energy (or phantom)
fluid, and the external Schwarzschild region. It is found that in some cases
the models represent the "bounded excursion" stable gravastars, where the thin
shell is oscillating between two finite radii, while in other cases they
collapse until the formation of black holes or normal stars. In the phase
space, the region for the "bounded excursion" gravastars is very small in
comparison to that of black holes, but not empty, as found in our previous
papers. Therefore, although the existence of gravastars can not be completely
excluded from current analysis, the opposite is not possible either, that is,
even if gravastars exist, they do not exclude the existence of black holes.Comment: 35 pages, 43 figures, added some clarifying texts and corrected some
typos, accepted for publication in JCA
Bibbia, cristianesimo e letteratura italiana: uno sguardo d'assieme.
L'A. ripercorre la presenza della Bibbia nella letteratura italiana dalle origini ai giorni nostri, sottolineando la persistenza della ripresa del Sacro testo sia nella poesia che nella prosa
Intensification of cattle ranching production systems: Socioeconomic and environmental synergies and risks in Brazil
Intensification of Brazilian cattle ranching systems has attracted both national and international attention due to its direct relation with Amazon deforestation on the one hand and increasing demand of the global population for meat on the other. Since Brazilian cattle ranching is predominantly pasture-based, we particularly focus on pasture management. We summarize the most recurrent opportunities and risks associated with pasture intensification that are brought up within scientific and political dialogues, and discuss them within the Brazilian context. We argue that sustainable intensification of pasturelands in Brazil is a viable way to increase agricultural output while simultaneously sparing land for nature. Since environmental degradation is often associated with low-yield extensive systems in Brazil, it is possible to obtain higher yields, while reversing degradation, by adopting practices like rotational grazing, incorporation of legumes and integrated crop-livestock-forestry systems. Technical assistance is however essential, particularly for small- and medium-scale farmers. Sound complementary policies and good governance must accompany these measures so that a ‘rebound effect’ does not lead to increased deforestation and other adverse social and environmental impacts. It is also important that animal welfare is not compromised. Although the discussion is presented with respect to Brazil, some aspects are relevant to other developing countries
Palaeontological framework from Pirabas Formation (North Brazil) used as potential model for equatorial carbonate platform
The Pirabas Formation (early to middle Miocene) from the equatorial margin of North Brazil is characterized by a shallow-marine carbonate platform with high fossil diversity and abundant micro- and macrofossil remains. The Pirabas Formation represents a unique carbonate system along the Atlantic margin of South America that developed before the onset of the Amazon delta. We studied the palaeontology and lithofacies of outcrops of the uppermost Pirabas Formation and found that was deposited in a coastal marine environment with marginal lagoons under the influence of a tidal regime and tropical storms. The remains of calcareous algae, molluscs, crustaceans, echinoiderms, bryozoans, solitary corals, fish and marine mammals, together with foraminifera, ostracods and other marine microfossils, shaped a biogenic framework, that together with the post-depositional processes of dissolution of skeletal grains, is responsible for the mean packstone-floatstone porosity of 14.9%. The palaeontological framework and the petrophysical characterization of the carbonate rocks from the uppermost Pirabas Formation outcrop represent a baseline to interpret the entire Pirabas Formation in the subsurface stratigraphic sections (cores) of this important Neogene unit. Considering that carbonate rocks account for ~50% of oil and gas reservoirs around the world, this research provides a model for Neogene tropical carbonate deposits useful for carbonate petroliferous reservoirs in the Brazilian equatorial basins.publishe
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