A New Multiple Stellar System in the Solar Neighborhood

Adaptive optics corrected images obtained with the CIAO instrument at the Subaru 8.2-meter telescope show the presence of two subarsecond companions to the nearby (d=19.3 pc) young star GJ 900, which was previously classified as a single member of the IC 2391 supercluster. The two companions share the same proper motion as the primary and are redder. Their projected separations from the primary are 10 AU and 14.5 AU for B and C, respectively. The estimated masses for the two new companions depend strongly on the age of the system. For the range of ages found in the literature for IC 2391 supercluster members (from 35 Myr to 200 Myr), the expected masses range from 0.2 M$_\odot$ to 0.4 M$_\odot$ for the B component, and from 0.09 M$_\odot$ to 0.22 M$_\odot$ for the C component. The determination of the dynamical mass of the faintest component of GJ 900 will yield the age of the system using theoretical evolutionary tracks. The apparent separations of the GJ 900 system components meet the observational criterion for an unstable Trapezium-type system, but this could be a projection effect. Further observations are needed to establish the nature of this interesting low-mass multiple system.Comment: Scheduled for publication in the Astronomical Journal (August 2003

Physics of cuprates with the two-band Hubbard model - The validity of the one-band Hubbard model

We calculate the properties of the two-band Hubbard model using the Dynamical Cluster Approximation. The phase diagram resembles the generic phase diagram of the cuprates, showing a strong asymmetry with respect to electron and hole doped regimes, in agreement with experiment. Asymmetric features are also seen in one-particle spectral functions and in the charge, spin and d-wave pairing susceptibility functions. We address the possible reduction of the two-band model to a low-energy single-band one, as it was suggested by Zhang and Rice. Comparing the two-band Hubbard model properties with the single-band Hubbard model ones, we have found similar low-energy physics provided that the next-nearest-neighbor hopping term t' has a significant value ($t'/t \approx 0.3$). The parameter t' is the main culprit for the electron-hole asymmetry. However, a significant value of t' cannot be provided in a strict Zhang and Rice picture where the extra holes added into the system bind to the existing Cu holes forming local singlets. We notice that by considering approximate singlet states, such as plaquette ones, reasonable values of t', which capture qualitatively the physics of the two-band model can be obtained. We conclude that a single-band t-t'-U Hubbard model captures the basic physics of the cuprates concerning superconductivity, antiferromagnetism, pseudogap and electron-hole asymmetry, but is not suitable for a quantitative analysis or to describe physical properties involving energy scales larger than about 0.5 eV.Comment: 14 pages, 16 figure

Flux-area operator and black hole entropy

We show that, for space-times with inner boundaries, there exists a natural area operator different from the standard one used in loop quantum gravity. This new flux-area operator has equidistant eigenvalues. We discuss the consequences of substituting the standard area operator in the Ashtekar-Baez-Corichi-Krasnov definition of black hole entropy by the new one. Our choice simplifies the definition of the entropy and allows us to consider only those areas that coincide with the one defined by the value of the level of the Chern-Simons theory describing the horizon degrees of freedom. We give a prescription to count the number of relevant horizon states by using spin components and obtain exact expressions for the black hole entropy. Finally we derive its asymptotic behavior, discuss several issues related to the compatibility of our results with the Bekenstein-Hawking area law and the relation with Schwarzschild quasi-normal modes.Comment: 25 page

Topological and Universal Aspects of Bosonized Interacting Fermionic Systems in (2+1)d

General results on the structure of the bosonization of fermionic systems in $(2+1)$d are obtained. In particular, the universal character of the bosonized topological current is established and applied to generic fermionic current interactions. The final form of the bosonized action is shown to be given by the sum of two terms. The first one corresponds to the bosonization of the free fermionic action and turns out to be cast in the form of a pure Chern-Simons term, up to a suitable nonlinear field redefinition. We show that the second term, following from the bosonization of the interactions, can be obtained by simply replacing the fermionic current by the corresponding bosonized expression.Comment: 29 pages, RevTe

Geometric approach to nonvariational singular elliptic equations

In this work we develop a systematic geometric approach to study fully nonlinear elliptic equations with singular absorption terms as well as their related free boundary problems. The magnitude of the singularity is measured by a negative parameter $(\gamma -1)$, for $0 < \gamma < 1$, which reflects on lack of smoothness for an existing solution along the singular interface between its positive and zero phases. We establish existence as well sharp regularity properties of solutions. We further prove that minimal solutions are non-degenerate and obtain fine geometric-measure properties of the free boundary $\mathfrak{F} = \partial \{u > 0 \}$. In particular we show sharp Hausdorff estimates which imply local finiteness of the perimeter of the region $\{u > 0 \}$ and $\mathcal{H}^{n-1}$ a.e. weak differentiability property of $\mathfrak{F}$.Comment: Paper from D. Araujo's Ph.D. thesis, distinguished at the 2013 Carlos Gutierrez prize for best thesis, Archive for Rational Mechanics and Analysis 201

Ethylene-induced Transcriptional And Hormonal Responses At The Onset Of Sugarcane Ripening

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The effects of ethephon as a sugarcane ripener are attributed to ethylene. However, the role of this phytohormone at the molecular level is unknown. We performed a transcriptome analysis combined with the evaluation of sucrose metabolism and hormone profiling of sugarcane plants sprayed with ethephon or aminoethoxyvinylglycine (AVG), an ethylene inhibitor, at the onset of ripening. The differential response between ethephon and AVG on sucrose level and sucrose synthase activity in internodes indicates ethylene as a potential regulator of sink strength. The correlation between hormone levels and transcriptional changes suggests ethylene as a trigger of multiple hormone signal cascades, with approximately 18% of differentially expressed genes involved in hormone biosynthesis, metabolism, signalling, and response. A defence response elicited in leaves favoured salicylic acid over the ethylene/jasmonic acid pathway, while the upper internode was prone to respond to ethylene with strong stimuli on ethylene biosynthesis and signalling genes. Besides, ethylene acted synergistically with abscisic acid, another ripening factor, and antagonistically with gibberellin and auxin. We identified potential ethylene target genes and characterized the hormonal status during ripening, providing insights into the action of ethylene at the site of sucrose accumulation. A molecular model of ethylene interplay with other hormones is proposed.7Sao Paulo Research Foundation (FAPESP) [2008/52146-0, 2008/57495-3, 2013/15576-5, 2012/13920-8, 2008/54201-9]National Council for Scientific and Technological Development (CNPq) [140767/2012-6, 160132/2011-3]ECMGMSMMRVRCNPqNational Science Foundation [DBI-0521250]Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq

Cosmological quantum entanglement

We review recent literature on the connection between quantum entanglement and cosmology, with an emphasis on the context of expanding universes. We discuss recent theoretical results reporting on the production of entanglement in quantum fields due to the expansion of the underlying spacetime. We explore how these results are affected by the statistics of the field (bosonic or fermionic), the type of expansion (de Sitter or asymptotically stationary), and the coupling to spacetime curvature (conformal or minimal). We then consider the extraction of entanglement from a quantum field by coupling to local detectors and how this procedure can be used to distinguish curvature from heating by their entanglement signature. We review the role played by quantum fluctuations in the early universe in nucleating the formation of galaxies and other cosmic structures through their conversion into classical density anisotropies during and after inflation. We report on current literature attempting to account for this transition in a rigorous way and discuss the importance of entanglement and decoherence in this process. We conclude with some prospects for further theoretical and experimental research in this area. These include extensions of current theoretical efforts, possible future observational pursuits, and experimental analogues that emulate these cosmic effects in a laboratory setting.Comment: 23 pages, 2 figures. v2 Added journal reference and minor changes to match the published versio

Severe community-acquired pneumonia in adult patients managed in a general ward at a public hospital

Indexación: Web of Science; ScieloIntroducción: La neumonía grave del adulto adquirida en la comunidad (NAC grave) se caracteriza por requerir manejo en la unidad de cuidados intensivos (UCI), dado su mayor mortalidad y riesgo de complicaciones, por lo cual se han diseñado distintas escalas de predicción de gravedad. Objetivo: Identificar apacientes adultos con NAC grave manejados en la sala de cuidados generales. Pacientes y Métodos: Estudio clínico descriptivo retrospectivo, se revisaron las fichas clínicas de 131 pacientes adultos egresados del servicio de medicina del hospital de Quilpué con el diagnóstico de NAC entre el 1 de enero y 31 de diciembre del 2010. Se examinaron los criterios de NAC grave de la Sociedad de Tórax Americana (ATS) y se midió el CURB-65 de 89 pacientes que consignaban esta información. Resultados: En 16 pacientes (18%) se obtuvo una puntuación del CURB-65 ≥ 3 y en 8 pacientes (9%) se identificaron ≥ 3 criterios menores de la ATSy en 2 de ellos un criterio mayor. Conclusión: Se identificaron pacientes con NAC grave manejados en la sala de cuidados generales de un hospital publico.Introduction: Severe community-acquired pneumonia (severe CAP) is characterized by intensive care unit (ICU) requirement, given its higher mortality and complications rate. Different prediction scales have been designed to assess severity. Objective: Identify adult patients with severe CAP managed in the general ward of a public hospital. Patients and Methods: Retrospective descriptive study, including all adult patients dischargedfrom hospital with CAP diagnosis, from January 1st to December 31st, 2010, with a total of 131 medical records reviewed. The American Thoracic Society criteria (ATS) of severe CAP and CURB-65 scores from 89 medical records were calculated. Results: 16 patients (18%) had CURB-65 score ≥ 3, 8 patients (9%) had ≥ 3 minor ATS criteria, and 2 of those patients had a major criterion. Conclusion: A significant number of patients with severe CAP were managed on the general ward of a public hospital.http://www.scielo.cl/pdf/rcher/v29n1/art02.pd

The Schr\"oder functional equation and its relation to the invariant measures of chaotic maps

The aim of this paper is to show that the invariant measure for a class of one dimensional chaotic maps, $T(x)$, is an extended solution of the Schr\"oder functional equation, $q(T(x))=\lambda q(x)$, induced by them. Hence, we give an unified treatment of a collection of exactly solved examples worked out in the current literature. In particular, we show that these examples belongs to a class of functions introduced by Mira, (see text). Moreover, as a new example, we compute the invariant densities for a class of rational maps having the Weierstrass $\wp$ functions as an invariant one. Also, we study the relation between that equation and the well known Frobenius-Perron and Koopman's operators.Comment: 9 page