13,576 research outputs found
Effect of defoliation on production components at different growth stages of cowpea.
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Exact solution for the energy density inside a one-dimensional non-static cavity with an arbitrary initial field state
We study the exact solution for the energy density of a real massless scalar
field in a two-dimensional spacetime, inside a non-static cavity with an
arbitrary initial field state, taking into account the Neumann and Dirichlet
boundary conditions. This work generalizes the exact solution proposed by Cole
and Schieve in the context of the Dirichlet boundary condition and vacuum as
the initial state. We investigate diagonal states, examining the vacuum and
thermal field as particular cases. We also study non-diagonal initial field
states, taking as examples the coherent and Schrodinger cat states.Comment: 10 pages, 8 figure
Viabilidade de tomateiros hÃbridos para produção de tomates em área infestada por Ralstonia solanacearum.
Awaking the vacuum in relativistic stars
Void of any inherent structure in classical physics, the vacuum has revealed
to be incredibly crowded with all sorts of processes in relativistic quantum
physics. Yet, its direct effects are usually so subtle that its structure
remains almost as evasive as in classical physics. Here, in contrast, we report
on the discovery of a novel effect according to which the vacuum is compelled
to play an unexpected central role in an astrophysical context. We show that
the formation of relativistic stars may lead the vacuum energy density of a
quantum field to an exponential growth. The vacuum-driven evolution which would
then follow may lead to unexpected implications for astrophysics, while the
observation of stable neutron-star configurations may teach us much on the
field content of our Universe.Comment: To appear in Phys. Rev. Let
Effect of angular momentum on equilibrium properties of a self-gravitating system
The microcanonical properties of a two dimensional system of N classical
particles interacting via a smoothed Newtonian potential as a function of the
total energy E and the total angular momentum L are discussed. In order to
estimate suitable observables a numerical method based on an importance
sampling algorithm is presented. The entropy surface shows a negative specific
heat region at fixed L for all L. Observables probing the average mass
distribution are used to understand the link between thermostatistical
properties and the spatial distribution of particles. In order to define a
phase in non-extensive system we introduce a more general observable than the
one proposed by Gross and Votyakov [Eur. Phys. J. B:15, 115 (2000)]: the sign
of the largest eigenvalue of the entropy surface curvature. At large E the
gravitational system is in a homogeneous gas phase. At low E there are several
collapse phases; at L=0 there is a single cluster phase and for L>0 there are
several phases with 2 clusters. All these pure phases are separated by first
order phase transition regions. The signal of critical behaviour emerges at
different points of the parameter space (E,L). We also discuss the ensemble
introduced in a recent pre-print by Klinko & Miller; this ensemble is the
canonical analogue of the one at constant energy and constant angular momentum.
We show that a huge loss of informations appears if we treat the system as a
function of intensive parameters: besides the known non-equivalence at first
order phase transitions, there exit in the microcanonical ensemble some values
of the temperature and the angular velocity for which the corresponding
canonical ensemble does not exist, i.e. the partition sum diverges.Comment: 17 pages, 11 figures, submitted to Phys. Rev.
Systematisation of seismic retrofitting in vernacular architecture
This paper aims to identify and to systematize the data obtained during the working process of
the
research
project 'SEISMIC-V –Vernacular Seismic Culture in Portugal' in terms of seismic-
retrofitting elements earthquake -resistant reinforcement implemented in vernacular buildings. The data will be distinguished based on the structural
seismic strengthening and according to the following criteria:
strengthening
elements,
perimeter
seismic-resistant elements, arches reinforcing elements, and combined
reinforcing elements.Portuguese Science and Technology Foundation (FCT) to the research project ‘SEISMIC - V – Vernacular Seismic Culture in Portu gal’ (PTDC/ATP - AQI/ 3934/2012
Reação de Linhagens de feião-caupi à mancha bacteriana causada pela bactéria Xanthomonas axonopodis pv. vignicola.
Systematisation of seismic mitigation planning at urban scale
This chapter explores the relation between the seismic mitigation planning that was developed
to contribute to minimise effects at urban scale, which arise within the seismic impact. In this sense, it deepens
the notion that interdependence, solidarity and cohesion of the different morphological constituents promote
a better prepared built fabric, when facing catastrophic phenomena of seismic origin. Preventive approaches
and reactive measures arising from the testimony of earthquake-resistant culture in Portugal are also
mentioned. From the recognition of the importance of local know-how, infers a set of logical that evidence
conditions to transcend the respective vernacular context, making it possible to generically systematize them.Portuguese Science and Technology Foundation (FCT) to the research project ‘SEISMIC-V – Vernacular Seismic Culture in Portugal’ (PTDC/ATPAQI/ 3934/2012
Seasonal dynamics of native and invasive Halophila stipulacea populations—A case study from the northern Gulf of Aqaba and the eastern Mediterranean Sea
No embargo required, pre-print. Full version requires 24 month embarg
Temperature Evolution Law of Imperfect Relativistic Fluids
The first-order general relativistic theory of a generic dissipative
(heat-conducting, viscous, particle-creating) fluid is rediscussed from a
unified covariant frame-independent point of view. By generalizing some
previous works in the literature, we derive a formula for the temperature
variation rate, which is valid both in Eckart's (particle) and in the
Landau-Lifshitz (energy) frames. Particular attention is paid to the case of
gravitational particle creation and its possible cross-effect with the bulk
viscosity mechanism.Comment: 14 pages, no figure, revte
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