1,317 research outputs found
Stability of toroidal magnetic fields in stellar interiors
We present 3D MHD simulations of purely toroidal and mixed poloidal-toroidal
magnetic field configurations to study the behavior of the Tayler instability.
For the first time the simultaneous action of rotation and magnetic diffusion
are taken into account and the effects of a poloidal field on the dynamic
evolution of unstable toroidal magnetic fields is included. In the absence of
diffusion, fast rotation (rotation rate compared to Alfv\'en frequency) is able
to suppress the instability when the rotation and magnetic axes are aligned and
when the radial field strength gradient p < 1.5. When diffusion is included,
this system turns unstable for diffusion dominated and marginally diffusive
dominated regions. If the magnetic and rotation axes are perpendicular to each
other the stabilizing effect induced by the Coriolis force is scale dependent
and decreases with increasing wavenumber. In toroidal fields with radial field
gradients bigger than p > 1.5, rapid rotation does not suppress the instability
but instead introduces a damping factor to the growth rate in agreement with
the analytic predictions. For the mixed poloidal-toroidal fields we find an
unstable axisymmetric mode, not predicted analytically, right at the stability
threshold for the non-axisymmetric modes; it has been argued that an
axisymmetric mode is necessary for the closure of the Tayler-Spruit dynamo
loop.Comment: 12 pages, 12 figures. Accepted for publication in A&
Soft supersymmetry-breaking terms from supergravity and superstring models
We review the origin of soft supersymmetry-breaking terms in N=1 supergravity
models of particle physics. We first consider general formulae for those terms
in general models with a hidden sector breaking supersymmetry at an
intermediate energy scale. The results for some simple models are given. We
then consider the results obtained in some simple superstring models in which
particular assumptions about the origin of supersymmetry breaking are made.
These are models in which the seed of supersymmetry breaking is assumed to be
originated in the dilaton/moduli sector of the theory.Comment: 24 pages, to appear in the book `Perspectives on Supersymmetry',
World Scientific, Editor G. Kane; some comments and references adde
Eviction of a 125 GeV "heavy"-Higgs from the MSSM
We prove that the present experimental constraints are already enough to rule
out the possibility of the ~125 GeV Higgs found at LHC being the second
lightest Higgs in a general MSSM context, even with explicit CP violation in
the Higgs potential. Contrary to previous studies, we are able to eliminate
this possibility analytically, using simple expressions for a relatively small
number of observables. We show that the present LHC constraints on the diphoton
signal strength, tau-tau production through Higgs and BR(B -> X_s gamma) are
enough to preclude the possibility of H_2 being the observed Higgs with m_H~125
GeV within an MSSM context, without leaving room for finely tuned
cancellations. As a by-product, we also comment on the difficulties of an MSSM
interpretation of the excess in the gamma-gamma production cross section
recently found at CMS that could correspond to a second Higgs resonance at
m_H~136 GeV.Comment: 38 pages, 9 figures. Final version accepted at JHEP. Sections 2, 3
and appendices simplified. Experimental results updated, several references
added. Small typos corrected and a new comparison of approximate formulas
with full expressions include
Cellular basis of pineal gland development: Emerging role of microglia as phenotype regulator
The adult pineal gland is composed of pinealocytes, astrocytes, microglia, and other interstitial cells that have been described in detail. However, factors that contribute to pineal development have not been fully elucidated, nor have pineal cell lineages been well characterized. We applied systematic double, triple and quadruple labeling of cell-specific markers on prenatal, postnatal and mature rat pineal gland tissue combined with confocal microscopy to provide a comprehensive view of the cellular dynamics and cell lineages that contribute to pineal gland development. The pineal gland begins as an evagination of neuroepithelium in the roof of the third ventricle. The pineal primordium initially consists of radially aligned Pax6+ precursor cells that express vimentin and divide at the ventricular lumen. After the tubular neuroepithelium fuses, the distribution of Pax6+ cells transitions to include rosette-like structures and later, dispersed cells. In the developing gland all dividing cells express Pax6, indicating that Pax6+ precursor cells generate pinealocytes and some interstitial cells. The density of Pax6+ cells decreases across pineal development as a result of cellular differentiation and microglial phagocytosis, but Pax6+ cells remain in the adult gland as a distinct population. Microglial colonization begins after pineal recess formation. Microglial phagocytosis of Pax6+ cells is not common at early stages but increases as microglia colonize the gland. In the postnatal gland microglia affiliate with Tuj1+ nerve fibers, IB4+ blood vessels, and Pax6+ cells. We demonstrate that microglia engulf Pax6+ cells, nerve fibers, and blood vessel-related elements, but not pinealocytes. We conclude that microglia play a role in pineal gland formation and homeostasis by regulating the precursor cell population, remodeling blood vessels and pruning sympathetic nerve fibers.Fil: Ibañez Rodriguez, María Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Cienicas Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Noctor, Stephen C.. University of California; Estados UnidosFil: Muñoz, Estela Maris. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Cienicas Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; Argentin
Insuficiencia venosa cerebroespinal crónica y esclerosis múltiple: revisión y actualización del tema
The aetiology of multiple sclerosis remains unknown at the present time, although
the most likely explanation is that it has an autoimmune inflammatory origin.
During the history of this disease a vascular pathophysiology was once proposed,
and it has recently re-emerged as a result of the work by Paolo Zamboni with the
name of 'chronic cerebrospinal venous insufficiency'. Following this hypothesis,
Zamboni puts forward a curative treatment for multiple sclerosis by means of
endovascular treatment of the internal jugular vein and the azygos vein. However,
several teams have attempted to replicate his findings without success. In this
review, we offer a chronological description of the studies carried out by
Zamboni and the later attempts to replicate his work. Our main conclusion is
that, given the results we currently have available, we should be cautious and,
for the time being, it would be advisable not to recommend the systematic use of
this treatment for our patients
Notes on Food Habits and Breeding and Nestling Behavior of Philippine Eagles in Mount Apo Natural Park, Mindanao, Philippines
Food habits and diurnal activities of the Philippine Eagle (Pithecophaga jefferyi) in Mount Apo Natural Park, Toril District, Davao City were documented. A total of 73 different prey items were observed to be delivered to the nest and 68 of these were identified. Of the 12 prey species identified, six were the first time records for Philippine Eagles, namely the coleto, pit viper, water snake and three were domestic animals (chicken, cat, dog). The bulk (63%) of observed adult behaviors were maintenance activities such as preening or feeding. In addition, adults also performed other social behaviors with the chick. The chick spent most of its time in general maintenance (54%), although sleeping (5%), resting while awake (31%), playing (2%), flapping (1%), and socializing with parents (>1%) were also observed. Eight percent of feeding was assisted by the parents; the rest of the time the chick fed itself. The potential issue for conservation caused by predation of domestic animals is not expected to be a problem at this nest because of previous community education and favorable attitudes toward the eagles. However, similar predation by other nesting pairs poses potential trouble unless community education addresses the matter
A Translational Evaluation of Renewal of Inappropriate Mealtime Behavior
The term renewal describes the recurrence of previously extinguished behavior that occurs when the intervention context changes. Renewal has important clinical relevance as a paradigm for studying treatment relapse because context changes are necessary for generalization and maintenance of most intervention outcomes (Podlesnik, Kelley, Jimenez-Gomez, & Bouton, 2017). The effect of context changes are particularly important during intervention for children with feeding disorders because children eat in a variety of contexts, and extinction is an empirically supported and often necessary intervention. Therefore, we used an ABA arrangement to test for renewal during intervention with 3 children diagnosed with a feeding disorder. The A phase was functional reinforcement of inappropriate mealtime behavior in a simulated home setting with the child’s caregiver as feeder; B was function-based extinction in a standard clinic setting with a therapist as feeder; and the return to the A phase was function-based extinction in a simulated home setting with caregiver as feeder. Returning to Context A resulted in renewal of inappropriate mealtime behavior across children, despite the caregivers’ continued implementation of function-based extinction with high levels of integrity
The Herpetological Importance of Mt. Hamiguitan Range, Mindanao Island, Philippines
We provide the first accounts of the amphibians and reptiles of Mt. Hamiguitan Range in south eastern Mindanao. Three sites were visited: dipterocarp, transitional dipterocarp-montane and mossypygmy forests. The combination of transect sampling, pitfall trapping and microhabitat searches produced records of 34 species (15 frogs, 14 lizards and five snakes). We provide information on the herpetofaunal assemblage of Mt. Hamiguitan including data on species richness, elevational distribution and microhabitat preferences. High levels of species richness and endemism were observed especially in the dipterocarp forest site located outside the boundaries of the protected area. Our data suggest that Mt. Hamiguitan range should be considered an important subcenter of herpetological diversity. Future conservation efforts should focus particularly on lowland forests
Control de la madurez en frutos por medio de ensayos de impacto.
En anteriores trabajos se ha observado que la respuesta de los frutos a un impacto mecánico está muy influida por su estado de madurez. Se realizaron ensayos de impacto sobre peras cv. Limonera, a lo largo de 12 semanas de conservación frigorífica y de maduración controlada. El impacto desde 4 cm de altura (equivalente a 0,02 J) resulta no destructivo y puede utilizarse para la determinación del estado de madurez de estos frutos. Por métodos de regresión lineal múltiple sobre los 15 para metros del impacto más representativos se obtienen buenas p r e dicciones de la madurez, representada por la fuerza de corte de probetas de pulpa, FC (N)
Estado epiléptico no convulsivo en el siglo XXI: clínica, diagnóstico, tratamiento y pronóstico
Non-convulsive status epilepticus is a significant issue for a neurologist
because, despite its low prevalence, it mimics other pathologies, with
therapeutics and prognostic outcomes. Diagnosis is based on clinical features,
mainly mental status or impaired consciousness and electroencephalographic
changes, so electroencephalogram is the first exploration we must perform with
clinical suspicion. There are three clinical forms: generalized or absence
status, with diffuse epileptiform discharges; focal, with epileptic discharges
located in a specific brain area and may not affect consciousness; and subtle,
with diffuse or local epileptic activity after a tonic-clonic seizure or
convulsive status and limited or no motor activity. Treatment are benzodiazepines
and antiepileptic drugs; anesthetic drugs are only recommended for patients with
subtle status and in some with partial complex status. Prognosis is mainly
determined by etiology and associated brain damage
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