9,261 research outputs found
Sons, Brothers and Relatives in the Entourages of the Roman Provincial Commanders during the Republic: A Characteristic Behaviour of the Roman Ruling Class
Durante la época de la República era una costumbre bien conocida que el cónsul o pretor destinado a una provincia se dotara de una serie de colaboradores y acompañantes que constituían la cohors o comitiva del imperator. Dicha comitiva solía componerse de personas vinculadas a los círculos sociales y particularmente familiares del mandatario en cuestión, siendo habitual encontrar en éstas a parientes, hermanos e incluso hijos de los mandos romanos. Aunque los autores clásicos no suelen conceder demasiada atención el papel que cumplían los hijos y parientes en el séquito de colaboradores de un mandatario provincial, su presencia habitual en estas comitivas indica que se trataba de un comportamiento característico y representativo de la clase política romana, cuyo interés no se hallaba sólo en contribuir a la promoción política y social de los implicados, sino en el hecho en sí de participar de unos hábitos distintivos y privativos de la nobilitas.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Is the bulbus arteriosus of fish homologous to the mamalian intrapericardial thoracic arteries?
El resumen aparece en el Program & Abstracts of the 10th International Congress of Vertebrate Morphology, Barcelona 2013.Anatomical Record, Volume 296, Special Feature — 1: P-089.Two major findings have significantly improved our understanding of the
embryology and evolution of the arterial pole of the vertebrate heart (APVH): 1) a
new embryonic presumptive cardiac tissue, named second heart field (SHF), forms
the myocardium of the outflow tract, and the walls of the ascending aorta (AA) and
the pulmonary trunk (PT) in mammals and birds; 2) the bulbus arteriosus (BA),
previously thought to be an actinopterygian apomorphy, is present in all basal
Vertebrates, and probably derives from the SHF. We hypothesized that the
intrapericardial portions of the AA and the PT of mammals are homologous to the
BA of basal vertebrates. To test this, we performed 1) a literature review of the
anatomy and embryology of the APVH; 2) novel anatomical, histomorphological,
and embryological analyses of the APVH, comparing basal (Galeus atlanticus), with
apical (Mus musculus and Mesocricetus auratus) vertrebrates. Evidence obtained:
1) Anatomically, BA, AA, and PT are muscular tubes into the pericardial cavity,
which connect the distal myocardial outflow tracts with the aortic arch system.
Coronary arteries run through or originate at these anatomical structures; 2)
Histologically, BA, AA, and PT show an inner layer of endothelium covered by
circumferentially oriented smooth muscle cells, collagen fibers, and lamellar
elastin. The histomorphological differences between the BA and the ventral aorta
parallel those between intrapericardial and extrapericardial great arteries; 3)
Embryologically, BA, AA, and PT are composed of smooth muscle cells derived
from the SHF. They show a similar mechanism of development: incorporation of
SHF‐derived cells into the pericardial cavity, and distal‐to‐proximal differentiation
into an elastogenic cell linage.
In conclusion, anatomical, histological and embryological evidence supports the
hypothesis that SHF is a developmental unit responsible for the formation of the
APVH. The BA and the intrapericardial portions of the great arteries must be
considered homologous structures.Proyecto P10-CTS-6068 (Junta de Andalucía); proyecto CGL-16417 (Ministerio de Ciencia e Innovación); Fondos FEDER
Derivation of the spin Hamiltonians for Fe in MgO
A method to calculate the effective spin Hamiltonian for a transition metal
impurity in a non- magnetic insulating host is presented and applied to the
paradigmatic case of Fe in MgO. In a first step we calculate the electronic
structure employing standard density functional theory (DFT), based on
generalized-gradient approximation (GGA), using plane waves as a basis set. The
corresponding basis of atomic-like maximally localized Wannier functions is
derived and used to represent the DFT Hamiltonian, resulting in a tight-binding
model for the atomic orbitals of the magnetic impurity. The third step is to
solve, by exact numerical diagonalization, the N electron problem in the open
shell of the magnetic atom, including both effect of spin-orbit and Coulomb
repulsion. Finally, the low energy sector of this multi-electron Hamiltonian is
mapped into effective spin models that, in addition to the spin matrices S, can
also include the orbital angular momentum L when appropriate. We successfully
apply the method to Fe in MgO, considering both, the undistorted and
Jahn-Teller (JT) distorted cases. Implications for the influence of Fe
impurities on the performance of magnetic tunnel junctions based on MgO are
discussed.Comment: 10 pages, 7 Figure
Induction, minimization and collection for Δ n+1 (T)–formulas
For a theory T, we study relationships among IΔ n +1 (T), LΔ n+1 (T) and B * Δ n+1 (T). These theories are obtained restricting the schemes of induction, minimization and (a version of) collection to Δ n+1 (T) formulas. We obtain conditions on T (T is an extension of B * Δ n+1 (T) or Δ n+1 (T) is closed (in T) under bounded quantification) under which IΔ n+1 (T) and LΔ n+1 (T) are equivalent. These conditions depend on Th Πn +2 (T), the Π n+2 –consequences of T. The first condition is connected with descriptions of Th Πn +2 (T) as IΣ n plus a class of nondecreasing total Π n –functions, and the second one is related with the equivalence between Δ n+1 (T)–formulas and bounded formulas (of a language extending the language of Arithmetic). This last property is closely tied to a general version of a well known theorem of R. Parikh. Using what we call Π n –envelopes we give uniform descriptions of the previous classes of nondecreasing total Π n –functions. Π n –envelopes are a generalization of envelopes (see [10]) and are closely related to indicators (see [12]). Finally, we study the hierarchy of theories IΔ n+1 (IΣ m ), m≥n, and prove a hierarchy theorem.Ministerio de Educación y Cultura DGES PB96-134
Thin film instability with thermal noise
We study the effects of stochastic thermal fluctuations on the instability of
the free surface of a flat liquid film upon a solid substrate. These
fluctuations are represented as a standard Brownian motion that can be added to
the deterministic equation for the film thickness within the lubrication
approximation. Here, we consider that while the noise term is white in time, it
is coloured in space. This allows for the introduction of a finite correlation
length in the description of the randomized intermolecular interaction.
Together with the expected spatial periodicity of the flow, we find a
dimensionless parameter, , that accounts for the relative importance of
the spatial correlation. We perform here the linear stability analysis (LSA) of
the film under the influence of both terms, and find the corresponding power
spectra for the amplitudes of the normal modes of the instability. We compare
this theoretical result with the numerical simulations of the complete
non-linear problem, and find a good agreement for early times. For late times,
we find that the stochastic LSA predictions on the dominant wavelength remains
basically valid. We also use the theoretical spectra to fit experimental data
from a nanometric melted copper film, and find the corresponding times of the
evolution as well as the values of the parameter,
Electronic properties of transition metal atoms on CuN/Cu(100)
We study the nature of spin excitations of individual transition metal atoms
(Ti, V, Cr, Mn, Fe, Co and Ni) deposited on a CuN/Cu(100) surface using
both spin-polarized density functional theory (DFT) and exact diagonalization
of an Anderson model derived from DFT. We use DFT to compare the structural,
electronic and magnetic properties of different transition metal adatoms on the
surface. We find that the average occupation of the transition metal d shell,
main contributor to the magnetic moment, is not quantized, in contrast with the
quantized spin in the model Hamiltonians that successfully describe spin
excitations in this system. In order to reconcile these two pictures, we build
a multi-orbital Anderson Hamiltonian for the d shell of the transition metal
hybridized with the p orbitals of the adjacent Nitrogen atoms, by means of
maximally localized Wannier function representation of the DFT Hamiltonian. The
exact solutions of this model have quantized total spin, without quantized
charge at the d shell. We propose that the quantized spin of the models
actually belongs to many-body states with two different charge configurations
in the d shell, hybridized with the p orbital of the adjacent Nitrogen atoms.
This scenario implies that the measured spin excitations are not fully
localized at the transition metal.Comment: 12 pages, 14 figures, regular articl
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