654 research outputs found
Critical behavior of ferromagnetic pure and random diluted nanoparticles with competing interactions: variational and Monte Carlo approaches
The magnetic properties and critical behavior of both ferromagnetic pure and
metallic nanoparticles having concurrently atomic disorder, dilution and
competing interactions, are studied in the framework of an Ising model. We have
used both the free energy variational principle based on the Bogoliubov
inequality and Monte Carlo simulation. As a case of study for random diluted
nanoparticles we have considered the FeMnAl alloy
characterized for exhibiting, under bulk conditions, low temperature reentrant
spin glass (RSG) behavior and for which experimental and simulation results are
available. Our results allow concluding that the variational model is
successful in reproducing features of the particle size dependence of the Curie
temperature for both pure and random diluted particles. In this last case, low
temperature magnetization reduction was consistent with the same type of RSG
behavior observed in bulk in accordance with the Almeida-Thouless line at low
fields and a linear dependence of the freezing temperature with the reciprocal
of the particle diameter was also obtained. Computation of the correlation
length critical exponent yielded the values via Bogoliubov
and via Monte Carlo. This fact indicates that even though
thermodynamical models can be indeed used in the study of nanostructures and
they can reproduce experimental features, special attention must be paid
regarding critical behavior. From both approaches, differences in the
exponent with respect to the pure Ising model agree with Harris and Fisher
arguments.Comment: 11 pages, 11 figures. Submitted to Phys. Rev.
Induction of stimulative parthenocarpy in Vitis vinifera L.
Stimulative parthenocarpy was induced in two varieties of Vitis vinifera L. Flame Tokay and Rose Muscat (local variety) out of eight varieties studied.In F l a m e T o k a y the delay or inhibition of bhe abscission of the calyptra and parthenocarpic development of the berries, was obtained with pre-bloom treatments (3 days before beginning of bloom) of 4CPA 30 ppm + KGA3 30 ppm. Induction and growth ,of parthenocarpic berries was most pronounced after post-bloom sprays (7 days after the end of bloom) with BA 1500 ppm + KGA3 80 ppm or 4CPA 30 ppm. A parthenocarpic development of the berries was also obtained with postbloom treatments of KGA3 at concentrations of 50 to 100 ppm. BA (Benzyladenine) alone had only a slight effect on the development of parthenocarpic berries. However, the results were surprisingly satisfactory when applied in combination with gibberellin (KGA3 80 ppm) or auxins. Treatments at bloom or after bloom with BA 800 ppm + KGA3 80 ppm increased bhe number of berries and cluster weight. Applications of BA 800 ppm + KGA3 80 ppm to Rose Musca t at the beginning of bloom resulted in clusters with practically all berries seedless. The artificially accelerated growth of the berries may provoke abortion of all the recently fecundated ovules and the non viability of the not fecundated ones. Clusters of the treated plants with an average of 520 flowers originated 501 parbhenocarpic berries (96%), whereas the control with an average 635 flowers per cluster gave a percentage of seeded + seedless berries of 14% only {95 berries per cluster). BA applied with auxin or gibberellin-like substances in full-bloom or after bloom produced seedless berries, which were smaller in size than the seeded berries of unsprayed clusters
Analysis of the start to the first hurdle in 110m hurdles at the IAAF World Athletics Championships Beijing 2015
The purpose of this study was to use observational analysis to evaluate the relationships between variables
measured at the start of the men’s 110 hurdles event and race performance itself. Data were obtained for
competitors in 2015 IAAF World Athletics Ch
ampionships, in Beijing, China. The athletes’ start was quantified
by reaction time and time to the first hurdle; their action over the first hurdle was quantified by the take
-
off
distance (i.e., the distance from the last step to the first hurdle), the la
nding distance, and the total distance
in the air over the first hurdle. Regression analyses revealed that the combination of one measure of the start
(either reaction time or time to the first hurdle) and the measure of propulsion over the first hurdle (d
istance
in air over the first hurdle) predicted performance (SEE = 0.23 s in the heats, SEE = 0.16 s in the semi
-
finals,
SEE = 0.09 s in the finals). In addition, looking at performances in the finals, where all athletes with available
data used a seven
-
st
ep approach to the first hurdle, inclusion of stride length data improved the prediction
somewhat (SEE = 0.07 s). The results demonstrate that a combination of a fast start, rapid acceleration, and
strong drive over the first hurdle quantifiably explains a
nd contributes to performance in the men’s 110 m hurdles at the highest level
Un registro de hipertrofia del trago del murciélago frugÃvoro de gran tamaño Artibeus lituratus (Chiroptera: Phyllostomidae)
In this work, we report and describe evidence of an anomaly in the tragus of an individual of Artibeus lituratus, captured in the Central Andes of Colombia. During field work in the Department of Caldas, municipality of Aranzazu, one individual of A. lituratus with unusual tragus form was trapped. This individual had a tragus with cylindrical shape and asymmetry. The individual was collected and deposited at the Museum of Natural History of the University of Caldas (MHN-UCa). A literature review was conducted to find similar cases using searching engines, but no previous reports of the anomaly were find. Furthermore, we reviewed the tragus of vouchers at the MHN-UCa and none of these had similar malformations. We concluded that this anomaly has not previously registered in Chiroptera.En este trabajo, reportamos y describimos evidencia de una anomalÃa en el trago de un individuo de Artibeus lituratus, capturado en los Andes Centrales de Colombia. En junio de 2019, durante un trabajo de campo en el Departamento de Caldas, municipio de Aranzazu, quedó atrapado un individuo de A. lituratus con inusual forma de trago. Este individuo tenÃa un trago de forma cilÃndrica y asimetrÃa. El individuo fue recogido y depositado en el Museo de Historia Natural de la Universidad de Caldas (MHN-UCa). Se realizó una revisión de la literatura para encontrar casos similares utilizando motores de búsqueda, pero no se encontraron informes previos de la anomalÃa. Además, revisamos el trago de los especÃmenes en el MHN-UCa y ninguno de ellos presentaba malformaciones similares. Concluimos que esta anomalÃa no se habÃa registrado previamente en Chiroptera
Analysis Gender Stereotypes in perception profile of conduct in track and field
In
our
current
world,
the
existance
of
obstacles
to
acknowledge
women’s
equal
abiliAes
is
real.
Legally
there
are
no
barriers.
The
Sports
Act
of
the
government
of
Andalusia
(Law
5/2016,
July
19)
determines
the
right
to
equality
between
genders.
This
is
what
has
been
called
the
glass
ceiling.
Gender
stereotypes
about
behavior
profile
recreate
constraints
that
occur
in
everyday
pracAces,
power
relaAons
and
insAtuAonal
arrangements
of
the
general
social
order.
Thee
stereotypes
are
rooted
in
sports.
In
this
sense.
The
objecAve
of
this
study
was
to
"interprete
different
gender
stereotypes
that
exist
regarding
men’s
and
women’s
profile
of
conduct
in
athleAcs.
Detección de hemoglobinopatÃa c: un caso de interacción interalélica
Estudios en Colombia revelan una alta frecuencia de hemoglobinopatÃas (1, 2, 3, 4), con una frecuencia para hemoglobinopatÃa C de 1.4% y en combinación con otras variables 0.33%, esto constituye un problema de salud pública según la OMS. La forma heterocigota con frecuencia es asintomática y la homocigota presenta anemia de moderada severidad
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