2,578 research outputs found
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
Numerical Simulation of Nano Scanning in Intermittent-Contact Mode AFM under Q control
We investigate nano scanning in tapping mode atomic force microscopy (AFM)
under quality (Q) control via numerical simulations performed in SIMULINK. We
focus on the simulation of whole scan process rather than the simulation of
cantilever dynamics and the force interactions between the probe tip and the
surface alone, as in most of the earlier numerical studies. This enables us to
quantify the scan performance under Q control for different scan settings.
Using the numerical simulations, we first investigate the effect of elastic
modulus of sample (relative to the substrate surface) and probe stiffness on
the scan results. Our numerical simulations show that scanning in attractive
regime using soft cantilevers with high Qeff results in a better image quality.
We, then demonstrate the trade-off in setting the effective Q factor (Qeff) of
the probe in Q control: low values of Qeff cause an increase in tapping forces
while higher ones limit the maximum achievable scan speed due to the slow
response of the cantilever to the rapid changes in surface profile. Finally, we
show that it is possible to achieve higher scan speeds without causing an
increase in the tapping forces using adaptive Q control (AQC), in which the Q
factor of the probe is changed instantaneously depending on the magnitude of
the error signal in oscillation amplitude. The scan performance of AQC is
quantitatively compared to that of standard Q control using iso-error curves
obtained from numerical simulations first and then the results are validated
through scan experiments performed using a physical set-up
Comment on ``Theory of Spinodal Decomposition''
I comment on a paper by S. B. Goryachev [PRL vol 72, p.1850 (1994)] that
presents a theory of non-equilibrium dynamics for scalar systems quenched into
an ordered phase. Goryachev incorrectly applies only a global conservation
constraint to systems with local conservation laws.Comment: 2 pages LATeX (REVTeX macros), no figures. REVISIONS --- more to the
point. microscopic example added, presentation streamlined, long-range
interactions mentioned, to be published in Phys. Rev. Let
Non-equilibrium Phase-Ordering with a Global Conservation Law
In all dimensions, infinite-range Kawasaki spin exchange in a quenched Ising
model leads to an asymptotic length-scale
at because the kinetic coefficient is renormalized by the broken-bond
density, . For , activated kinetics recovers the
standard asymptotic growth-law, . However, at all temperatures,
infinite-range energy-transport is allowed by the spin-exchange dynamics. A
better implementation of global conservation, the microcanonical Creutz
algorithm, is well behaved and exhibits the standard non-conserved growth law,
, at all temperatures.Comment: 2 pages and 2 figures, uses epsf.st
Los informes de Amici Curiae ante la Corte Interamericana de Derechos Humanos
En reiteradas oportunidades la Corte Interamericana de Derechos
Humanos (en adelante "la Corte") ha recibido informes de
amici curiae, tanto en casos contenciosos como en opiniones consultivas.
El presente trabajo está destinado a establecer qué es un
amicus curiae y a señalar tanto su base legal como la importancia
de su intervención en los procesos que se vienen ventilando ante la
Corte
School Curriculum, [mathematical] Knowledge And Social Practices: Other Possibilities In An Indigenous Gunadule Community
This article is the result of a study entitled (Re)interpretation of indigenous school curriculums in terms of [mathematics] knowledge from and for social practice: The case of Dule teachers from Alto Caiman. Our research project objective was to (re)signify the indigenous school curriculum in terms of [mathematics] knowledge from and for social practices in the Dule community of Alto Caiman. This qualitative study conducted from the socio-cultural perspective of mathematics education, with contributions of ethnomathematics and from interculturalism, and from a critical-dialectical perspective, was based on a collaborative investigation. From the results obtained in this study we learned that discussing indigenous school curriculums in terms of [mathematics] knowledge implies (re)conceptualizations, from which not only theoretical, political and cultural conceptions that underpin the type of society that one desires to build, but also the dialectic between social practices and [mathematics] knowledge are evidenced.42490391
Victims’ collective memory and transitional justice in post-conflict Colombia: The case of the March of Light
The construction of victims’ collective memory in post-conflict Colombia is crucial to understanding the violent past and its social consequences. This article argues that victims’ initiatives, such as the March of Light, are facilitating an active role of local communities in the configuration of their memory regimes after the war. Addressing a participative action research approach, this article’s significance rests in the idea that Colombian victims’ groups from Eastern Antioquia are establishing three particular types of collective memory developing the March of Light every week. It establishes that this effort is a powerful instrument to claim truth and reparation in Colombia, helping the ongoing process of transitional justice in the country. It demonstrates that the tension between official and non-official narratives of collective memory is an essential part of transitional justice scenarios in which the clash of values defines positions of power, visibility and recognition inside contexts of social transition
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