1,241 research outputs found
Minimal mass-size of a stable 3He cluster
The minimal number of 3He atoms required to form a bound cluster has been
estimated by means of a Diffusion Monte Carlo procedure within the fixed-node
approximation. Several importance sampling wave functions have been employed in
order to consider different shell-model configurations. The resulting upper
bound for the minimal number is 32 atoms.Comment: 2 pages, no figure
Factors affecting rind pitting in the mandarin hybrids "fortune" and "nova". The influence of exogenous growth regulators
The commercialization of the mandarin hybrids "Fortune" and "Nova" is hindered by the development of cold-induced pitting in the fruit rind which may develop either in the orchard or during storage and transport.
In the late cropping cultivar "Fortune", the pitting develops on tree during the winter months and affects mainly the exposed fruit from the north-west quadrant of the tree. The induction of symptoms under uniform conditions in the cold-room reveals differences in the susceptibility to chilling injury among the fruits and the fruit sides. The green fruit is not susceptible. Susceptibility develops as pigmentation progresses, and it is higher for the exposed than for the non-exposed (covered by the foliage) fruits. The application of GA3 at colour-break delays pigmentation and retards the development of susceptibility. The waxing of the fruit offers some protection to cold in the cold-room. However, the incidence of pitting is not related to the wax content of the fruit rind and the application of a wax coverage on tree had only a marginal protective effect.
No pitting is usually found on tree in the fruit of the early ripening "Nova" cultivar, which is usually harvested before the winter chilling. The pitting develops during cold storage (8-10 C), and is reduced by GA3 application at colour break, an effect related to the delay in rind pigmentation.info:eu-repo/semantics/publishedVersio
Excitation spectra of a 3He impurity on 4He clusters
The diffusion Monte Carlo technique is used to calculate and analyze the
excitation spectrum of a single 3He atom bound to a cluster with N 4He atoms,
with the aim of establishing the most adequate filling ordering of
single-fermion orbits to the mixed clusters with a large number of 3He atoms.
The resulting ordering looks like the rotational spectrum of a diatomic
molecule, being classified only by the angular momentum of the level, although
vibrational-like excitations appear at higher energies for sufficiently large
N
Excited states of 4He droplets
We study low-lying excited states of 4He clusters up to a cluster size of 40 atoms in a variational framework. The ansatz wave function combines two- and three-body correlations, coming from a translationally invariant configuration interaction description, and Jastrow-type short-range correlation. We have previously used this scheme to determine the ground-state energies of 4He and 3He clusters. Here we present an extension of this ansatz wave function having a good quantum angular momentum L. The variational procedure is applied independently to the cases with L = 0,2,4, and upper bounds for the corresponding energies are thus obtained. Moreover, centroid energies for L excitations are calculated through the use of sum rules. A comparison with previous calculations is also made.Fil: Guardiola, R.. Facultad de FĂsica / Dpto de FĂsica AtĂłmica y Nuclear; EspañaFil: Navarro, J.. Csic - Univ. de Valencia / Inst. de FĂsica Corpuscular; EspañaFil: Portesi, Mariela Adelina. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Departamento de FĂsica; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto de FĂsica La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de FĂsica La Plata; Argentin
The spectra of mixed He-He droplets
The diffusion Monte Carlo technique is used to calculate and analyze the
excitation spectrum of He atoms bound to a cluster of He atoms, by
using a previously determined optimum filling of single-fermion orbits with
well defined orbital angular momentum , spin and parity quantum numbers.
The study concentrates on the energies and shapes of the three kinds of states
for which the fermionic part of the wave function is a single Slater
determinant: maximum or maximum states within a given orbit, and fully
polarized clusters. The picture that emerges is that of systems with strong
shell effects whose binding and excitation energies are essentially determined
over configuration at fixed number of particles and spin, i.e., by the monopole
properties of an effective Hamiltonian.Comment: 14 pages, 15 figure
Translationally-invariant coupled-cluster method for finite systems
The translational invariant formulation of the coupled-cluster method is
presented here at the complete SUB(2) level for a system of nucleons treated as
bosons. The correlation amplitudes are solution of a non-linear coupled system
of equations. These equations have been solved for light and medium systems,
considering the central but still semi-realistic nucleon-nucleon S3
interaction.Comment: 16 pages, 2 Postscript figures, to be published in Nucl. Phys.
The importance of time in referee home bias due to social pressure. Evidence from Spanish football
This paper analyses referee home bias due to social pressure with data from the matches played in the First Division of the Spanish football league between the 2002/03 and 2009/10 seasons. Finally, our main conclusion is that the time the referee has to make a decision does affect the final outcome; while there is no referee home bias when a free kick is awarded, in the case of booking players, when the referee has more time to make a decision, social pressure can influence the final outcome in favour of the home team.Social pressure; crowd effect; referee home bias; sports economics.
High genetic diversity, phenotypic plasticity, and invasive potential of a recently introduced calcareous sponge, fast spreading across the Atlanto‑Mediterranean basin
16 páginas, 6 tablas, 8 figuras.Sponges are considered poor invaders, and
no genetic studies on introduced sponges have been performed
up to now. Paraleucilla magna is the first calcareous
sponge introduced to the Mediterranean and Northeastern
Atlantic. The study aimed at investigating the genetic
makeup and connectivity of the introduced populations of
P. magna and at exploring signs of local phenotypic adaptation,
to gain insight on the species invasive potential. Ten
populations along the species introduction range (Brazil,
Açores, Madeira, and continental Europe) were genetically
characterized by using nine microsatellite markers.
Most populations were genetically structured as suggested
by significant Dst and Fst values, significant differences
among populations (AMOVA) and the presence of private
alleles. The analyzed populations belonged to three genetically
homogeneous groups (K) according to the Bayesian
algorithm (structure software) and the UPGMA dendrogram.
Genetic diversity within populations was higher
than expected. Recurrent introductions of non-randomly selected individuals from the native sources may have
contributed to the heterozygote deficit found in all populations
by forming pedigree structures with mating among
relatives. Moreover, the species biological cycle was monitored
in a population established on native Mediterranean
assemblages (41°40′27″N, 2°47′25″E) and compared with
the species cycle in other habitats. Contrasting life spans,
growth habits, and reproduction cycles, depending on the
habitat conditions, were recorded. To summarize, high
genetic diversity, phenotypic local adaptation, and high
reproduction rates altogether allow predicting the fast proliferation
of P. magna in newly colonized regions and point
to its strong invasive potential.This study has been partially funded by MARSYMBIOMICS
project ref. CTM2013-43287-P (Spanish Ministry of Economy
and Competitiveness (MINECO)—FECYT agency, and Consolidate
Group Award 2009-SGR655 (Generalitat of Catalonian) to MJU. MG
has benefited from a FPU fellowship from the Spanish MINECO and
JF from a Marie Curie (EU) fellowship, associated, respectively, with
the BENTHOMICS and BIOCAPITAL projects to MJU.Peer reviewe
- …