1,127 research outputs found
Seidel elements and mirror transformations
The goal of this article is to give a precise relation between the mirror
symmetry transformation of Givental and the Seidel elements for a smooth
projective toric variety with nef. We show that the Seidel elements
entirely determine the mirror transformation and mirror coordinates.Comment: 36 pages. We corrected several issues as pointed out by the refere
Influence of vehicular traffic on environmental noise spectrum in the tourist route of Santa Marta City
Transportation demands large amounts of fuel. In particular, road transport greatly contributes to both criteria air pollutants and noise within cities. The influence of vehicular traffic on the environmental noise spectrum (as an indirect indicator of energy emission) was measured and assessed in the tourist route of Santa Marta along a 12-km road segment where five points were selected (three in the peripheral urban and two in the suburban areas). The number and type of vehicles as well as the noise levels were recorded at thirds of octave twice per day during two different weekdays. The traffic flow was composed of automobiles, with higher values in the peripheral urban area. According to the ANOVA, the noise spectrum indicated that low frequencies both had more energy than those with high frequencies and were influenced by the time of day. Low frequencies were influenced by all type of vehicles during the day, while high frequencies at both day and night, except for trucks (which were influenced in all spectrum). The results agreed with both the high velocities reached and the vehicle distribution. © 201
Nutrient limitation can explain a rapid transition to synchrony in an upwelling-driven diatom community
Identifying the mechanisms controlling the temporal dynamics of ecological communities is key to understand their vulnerability to natural and anthropogenic impacts and to identify early warnings of critical transitions. At community level, inter-specific synchrony is an important indicator of ecosystem stability and variation in function. Using wavelet analysis on time-series of abundance of 12 dominant diatom species, sampled monthly (1994-2009) in a coastal upwelling embayment at the northern limit of the Canary Current Upwelling System, we find a sudden onset of synchrony between 1998 and 2002, concomitant with an increase in the amplitude of the upwelling index at different temporal scales. To better understand the underlying mechanism that could generate this sudden onset of synchrony among competitors, we analyzed a general model of competition between two species for two essential nutrients (e.g., nitrogen and silicate). We incorporate environmental variation by varying the concentration of one of the essential nutrients entering the system. Increase in the amplitude of environmental variation always leads to greater synchrony among competitors. This occurs because the system shifts from a state in which species are limited by different nutrients to one where species are often limited by the same nutrient. We show that the transition from asynchronous to synchronous dynamics can occur suddenly as the amplitude of environmental variation increases. While it is not possible to rule out alternative mechanisms, our model demonstrates that sudden changes in the extent of synchronization should be a common feature when species compete for essential nutrients in variable environments.En prensa3,38
Neoliberal urbanization, tensions and moral expectations about the defense of heritage:the case of Victoria neighborhood, Santiago of Chile
Indexación ScopusEn las últimas décadas, se ha destacado la emergencia de
distintos conflictos contra los procesos de urbanización
neoliberal, entre ellos, los conflictos asociados a la defensa
del patrimonio. Dentro de esta literatura, se señala cómo, a
partir de la defensa del barrio, las comunidades generan una
forma de participación democrática que se opone a la lógica
mercantil que orienta la evolución de nuestras ciudades. En este
artículo, se tensionará este argumento a partir del análisis del
proceso de patrimonialización del barrio Victoria en Santiago
de Chile, barrio histórico que articula una identidad residencial
con otra comercial, ligada al cuero y el calzado. A partir de
relatos de vida, realizados a residentes antiguos y locatarios
del barrio, se mostrará cómo detrás de la defensa de los
barrios se articulan expectativas heterogéneas respecto a cómo
debería ser la ciudad (quién y cómo habitarla), permitiendo,
en algunos casos, excluir a algunos actores de la definición
de comunidad y, en otros, ampliar la escala del conflicto. De
este modo, se pretende contribuir a aquellos estudios que
evalúan el potencial democrático de los conflictos ligados a
la defensa del patrimonio.The past three decades have seen the emergence of various
conflicts against neoliberal urbanization processes, including
disputes associated with the protection of heritage. The growing
literature in this area has pointed out the disclosure of a form
of democratic participation developed by the communities in
defense of their neighborhood, which opposes the commercial
logic that guides the evolution of our cities. In this article,
we will discuss this argument through the analysis of the
patrimonialization process of Victoria neighborhood in Santiago
of Chile, a historical urban zone that articulates a residential
identity with a commercial one, linked to leather crafting
and footwear. Through an empirical analysis based on life
story interviews with former residents and tenants, we will
show that, behind neighborhood defense discourses, there
are different expectations regarding how the city should be,
namely, who could inhabit it and how they should do it. In
some cases, these expectations entail the exclusion of actors
from the definition of community and, in others, contribute
to amplify the conflict. In this way, we intend to contribute
to the literature that evaluates the democratic potential of
conflicts linked to the defense of heritage.https://revistaurbanismo.uchile.cl/index.php/RU/article/view/5776
Subsurface Flows in and Around Active Regions with Rotating and Non-rotating Sunspots
The temporal variation of the horizontal velocity in subsurface layers
beneath three different types of active regions is studied using the technique
of ring diagrams. In this study, we select active regions (ARs) 10923, 10930,
10935 from three consecutive Carrington rotations: AR 10930 contains a
fast-rotating sunspot in a strong emerging active region while other two have
non-rotating sunspots with emerging flux in AR 10923 and decaying flux in AR
10935. The depth range covered is from the surface to about 12 Mm. In order to
minimize the influence of systematic effects, the selection of active and quiet
regions is made so that these were observed at the same heliographic locations
on the solar disk. We find a significant variation in both components of the
horizontal velocity in active regions as compared to quiet regions. The
magnitude is higher in emerging-flux regions than in the decaying-flux region,
in agreement with earlier findings. Further, we clearly see a significant
temporal variation in depth profiles of both zonal and meridional flow
components in AR 10930, with the variation in the zonal component being more
pronounced. We also notice a significant influence of the plasma motion in
areas closest to the rotating sunspot in AR 10930 while areas surrounding the
non-rotating sunspots in all three cases are least affected by the presence of
the active region in their neighborhood.Comment: Solar Physics (in press), includes 11 figure
Energy radiation of moving cracks
The energy radiated by moving cracks in a discrete background is analyzed.
The energy flow through a given surface is expressed in terms of a generalized
Poynting vector. The velocity of the crack is determined by the radiation by
the crack tip. The radiation becomes more isotropic as the crack velocity
approaches the instability threshold.Comment: 7 pages, embedded figure
Musicoterapia en una Unidad de Cuidados Intensivos Neonatales: experiencia benéfica para el binomio
ResumenIntroducciónDesde hace varios años se está utilizando la música como herramienta terapéutica y preventiva en la neonatología, se han documentado en un gran número de artículos de investigación, sin embargo, en México esta técnica es poco utilizada.ObjetivoMejorar las condiciones de los neonatos atendidos en una Unidad de Cuidados Intensivos (UCIN) y sus familiares, mediante el uso de musicoterapia, para minimizar el estrés y los daños colaterales.Materiales y métodosUn grupo de 2 neonatólogos, 3 residentes de pediatría, 10 enfermeras y un concertista profesional de violín, llevaron a cabo 6 sesiones musicales semanales en la Unidad de Cuidados Intensivos Neonatales Externos del Hospital Civil de Guadalajara. Durante el concierto se valoró individualmente a cada neonato, registrando los signos vitales por monitorización electrónica, además se registró el estado anímico de los familiares.ResultadosDurante las sesiones de música los neonatales no presentaron cambios significativos en sus constantes vitales, en el personal de la UCIN y en los padres de recién nacidos hospitalizados se vieron efectos benéficos, refiriendo disminución del estrés y altos índices de satisfacción.ConclusionesLa música puede tener un efecto positivo como terapia coadyuvante en neonatos de alto riesgo, principalmente en prematuros. Se recomienda difundir y aplicar esta metodología en las UCIN del país.AbstractIntroductionSince several years ago, music has been used as a therapeutic and preventive tool in neonatology. A great number of research papers have been written on the subject; however, this technique is rarely used in Mexico.ObjectiveTo improve the condition of neonates at Neonatal Intensive Care Units (NICU) and their relatives, in order to minimize any stress and collateral damage.Material and methods: A group of two neonatologists, 3 residents, 10 nurses and a professional concert violinist, conducted six weekly music sessions in the Outpatient Neonatal Intensive Care Unit (ONICU) of our institution. During the concert, we individually assessed each newborn, recording vital signs through electronic monitoring; additionally, we recorded the mood of any other family members present.ResultsDuring the music sessions, the neonatal patients showed no significant changes in vital signs; yet, ONICU staff and the parents/relatives of hospitalized newborns showed beneficial effects, reporting decreased stress and high levels of satisfaction.ConclusionsMusic can have a positive effect as adjunctive therapy in high-risk newborns, especially in premature babies. We therefore recommend applying this methodology in the ONICU
Effects of spin-elastic interactions in frustrated Heisenberg antiferromagnets
The Heisenberg antiferromagnet on a compressible triangular lattice in the
spin- wave approximation is considered. It is shown that the interaction
between quantum fluctuations and elastic degrees of freedom stabilizes the low
symmetric L-phase with a collinear Neel magnetic ordering. Multi-stability in
the dependence of the on-site magnetization on an unaxial pressure is found.Comment: Revtex, 4 pages, 2 eps figure
Phase Transition Strength through Densities of General Distributions of Zeroes
A recently developed technique for the determination of the density of
partition function zeroes using data coming from finite-size systems is
extended to deal with cases where the zeroes are not restricted to a curve in
the complex plane and/or come in degenerate sets. The efficacy of the approach
is demonstrated by application to a number of models for which these features
are manifest and the zeroes are readily calculable.Comment: 16 pages, 12 figure
Observation and Modeling of the Solar-Cycle Variation of the Meridional Flow
We present independent observations of the solar-cycle variation of flows
near the solar surface and at a depth of about 60 Mm, in the latitude range
. We show that the time-varying components of the meridional flow
at these two depths have opposite sign, while the time-varying components of
the zonal flow are in phase. This is in agreement with previous results. We
then investigate whether the observations are consistent with a theoretical
model of solar-cycle dependent meridional circulation based on a flux-transport
dynamo combined with a geostrophic flow caused by increased radiative loss in
the active region belt (the only existing quantitative model). We find that the
model and the data are in qualitative agreement, although the amplitude of the
solar-cycle variation of the meridional flow at 60 Mm is underestimated by the
model.Comment: To be published in Solar Physcis Topical Issue "Helioseismology,
Asteroseismology, and MHD Connections
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