Neural Network identification of halo white dwarfs

The white dwarf luminosity function has proven to be an excellent tool to study some properties of the galactic disk such as its age and the past history of the local star formation rate. The existence of an observational luminosity function for halo white dwarfs could provide valuable information about its age, the time that the star formation rate lasted, and could also constrain the shape of the allowed Initial Mass Functions (IMF). However, the main problem is the scarce number of white dwarfs already identified as halo stars. In this Letter we show how an artificial intelligence algorithm can be succesfully used to classify the population of spectroscopically identified white dwarfs allowing us to identify several potential halo white dwarfs and to improve the significance of its luminosity function.Comment: 15 pages, 3 postscript figures. Accepted for publication in ApJ Letters, uses aasms4.st

The effects of metallicity on the Galactic disk population of white dwarfs

It has been known for a long time that stellar metallicity plays a significant role in the determination of the ages of the different Galactic stellar populations, when main sequence evolutionary tracks are employed. Here we analyze the role that metallicity plays on the white dwarf luminosity function of the Galactic disk, which is often used to determine its age. We employ a Monte Carlo population synthesis code that accounts for the properties of the population of Galactic disk white dwarfs. Our code incorporates the most up-to-date evolutionary cooling sequences for white dwarfs with hydrogen-rich and hydrogen-deficient atmospheres for both carbon-oxygen and oxygen-neon cores. We use two different models to assess the evolution of the metallicity, one in which the adopted metallicity is constant with time, but with a moderate dispersion, and a second one in which the metallicity increases with time. We found that our theoretical results are in a very satisfactory agreement with the observational luminosity functions obtained from the Sloan Digital Sky Survey (SDSS) and from the SuperCOSMOS Sky Survey (SSS), independently of the adopted age-metallicity law. In particular, we found that the age-metallicity law has no noticeable impact in shaping the bright branch of the white dwarf luminosity function, and that the position of its cut-off is almost insensitive to the adopoted age-metallicity relationship. Because the shape of the bright branch of the white dwarf luminosity function is insensitive to the age-metallicity law, it can be safely employed to test the theoretical evolutionary sequences, while due to the limited sensitivity of the position of the drop-off to the distribution of metallicities, its location provides a robust indicator of the age of the Galactic disk.Comment: 7 pages, 5 figures, accepted for publication in A&

Matta in the reverse of the universe with his his friends behind the mirror

Este ensayo sobre Roberto Matta explora el trayecto, un trayecto otro, desde una proyección sensitiva del artista, arqui­tecto, filósofo y poeta chileno. Matta evoca la inmersión desde un proyecto del ser hasta un proyecto cósmico y alquímico, donde concurre con decisión irrevocable la relación entre alquimia y ciencia: Eliphas Lévi, Fulcanelli y Albert Einstein; el texto también pone en juego los vasos comunicantes entre la bús­queda del artista Matta y sus relaciones libres, muy libres, para con el movimiento surrealista (Breton) y para sí mismo, en la medida en lo extrae y traduce del mo­vimiento artístico referido, además, de sus intervenciones y participaciones en los movimientos del arte moderno y en el movimiento de sí mismo. En palabras de Roberto Matta (1965): La función del artista en nuestra sociedad consiste en ser este personaje deslumbrador y repudiado, como el niño del cuento de Andersen, que es el único que dice que el rey va desnudo. Esta situación de denuncia del escándalo hace de él un minoritario. No se trata, pues, para el artista, de establecer un relación entre un azul y un verde: estos cuadros estéticos son más o menos poseídos por aquellos que los contemplan. Yo quiero, al contrario, inquietar, para que el que contempla se convierta en minoritario. Deseo que este espectador, en lugar de poseer el cuadro, sea poseído por él, que sea bombardeado por una enorme cantidad de conciencia que le llegue de todas partes. Así, atrapado en una situación insoportable a causa de esta pintura, se ve obligado, también él, a realizar un acto poético de creación para hacerla suya: asediado por lo real, se siente vencido y, por tanto, reflexiona. En este sentido, este ensayo sobre Ro­berto Matta trata sobre el furor estético. No hay estética sin ciencia y sin videncia, como lo propone y lo provoca Matta.This essay about Roberto Matta explores the career (a short one) from a sensitive projection of the Chilean artist, architect, philosopher, and poet. Matta evokes the immersion from a project of the being to a cosmic and alchemic project where the relationship between alchemy and science concurs with irrevocable determination: Eliphas Lévi, Fulcanelli, and Albert Ein­stein; the text also deals with the com­munication means between artist Matta’s search and his very free commitment to the surrealistic movement (Breton) and to himself, en la medida en lo extrae y tra­duce ??? from such artistic movement and from his interventions and participation in movements of modern art and his own movement. According to Roberto Matta’s own words in 1965:  An artist’s role in our society involves be­ing that glaring and repudiated character (the child of Andersen’s short story) who is the only one that affirms that the king is nude. This denouncement of the scandal makes of him a minority member. For the artist, it is not a question of establishing a relationship between color blue and color green: these aesthetic scenarios belong in a certain way to those who contemplated them. On the contrary, I want to agitate so that the contemplating person becomes a minority member. I want the spectator to be possessed by the picture instead of possessing it; I want him to be bombarded from everywhere with a huge amount of consciousness. In this way, caught within an unbearable situation caused by the pic­ture, he is then forced to perform a poetic creation act to possess it: beset by the real world he feels defeated and then forced to reflect. In this way, this essay about Roberto Matta deals with the aesthetic furor. There is not aesthetics without science and evidence, as proposed and induced by Matta

Pluralism of forms in the living beings according to John Duns Scotus

En este trabajo presentamos la posición de Duns Escoto sobre la pluralidad de formas en los seres vivos, siguiendo el desarrollo que formula en sus diferentes escritos. El Doctor Sutil asumirá un nuevo modo de plantear la cuestión, sosteniendo que además del alma y el cuerpo, los órganos que componen los vivientes también poseen formas substanciales propias. Además, se plantea un debate en torno a la aceptación o no de la forma corporeitatis por parte del Maestro Escocés, según las interpretaciones de algunos académicos contemporáneos y una posible solución sobre este punto.In this paper we present the position of Duns Scotus about the plurality of forms in living organisms, following the development in the various works he wrote. The Subtle Doctor assumes a new way to raise the issue, arguing that besides the soul and the body, the organs that make up the living beings also have their own substantial forms. Also, we introduce a debate about the acceptance or not of the forma corporeitatis by the Scottish Master, as interpreted by some contemporary scholars and a possible solution on this point

Interfacial tension behavior of binary and ternary mixtures of partially miscible Lennard-Jones fluids: a molecular dynamics simulation

By means of extensive equilibrium molecular dynamics simulations we have investigated, the behavior of the interfacial tension $\gamma$ of two immiscible symmetrical Lennard-Jones fluids. This quantity is studied as function of reduced temperature $T^{*}={{k_{_B} T}\over \epsilon}$ in the range $0.6 \leq T^{*} \leq 3.0$. We find that, unlike the monotonic decay obtained for the liquid-vapor interfacial tension, for the liquid-liquid interface, $\gamma (T)$ has a maximum at a specific temperature. We also investigate the effect that surfactant-like particles has on the thermodynamic as well as the structural properties of the liquid-liquid interface. It is found that $\gamma$ decays monotonically as the concentration of the surfactant-like particles increases.Comment: LaTeX-Revtex file with 7 encapsulated postscript figures. Accepted for publication in Journal of Chemical Physic

Real-time predictive maintenance for wind turbines using Big Data frameworks

This work presents the evolution of a solution for predictive maintenance to a Big Data environment. The proposed adaptation aims for predicting failures on wind turbines using a data-driven solution deployed in the cloud and which is composed by three main modules. (i) A predictive model generator which generates predictive models for each monitored wind turbine by means of Random Forest algorithm. (ii) A monitoring agent that makes predictions every 10 minutes about failures in wind turbines during the next hour. Finally, (iii) a dashboard where given predictions can be visualized. To implement the solution Apache Spark, Apache Kafka, Apache Mesos and HDFS have been used. Therefore, we have improved the previous work in terms of data process speed, scalability and automation. In addition, we have provided fault-tolerant functionality with a centralized access point from where the status of all the wind turbines of a company localized all over the world can be monitored, reducing O&M costs

Enhancing station level Direct-Demand models with Multi-Scalar accessibility indicators

Direct-demand models (DDM) are increasingly being used for a diversity of transit research and practice purposes. Yet few station-level DDM studies have explored the use of composite indicators of metropolitan accessibility in predicting demand. After all, provision of access to metropolitan destinations is one of the main goals of rapid-transit systems. Furthermore, to this author’s knowledge no study has explored potential interactions with local-level accessibility indicators that are typically included in station level transit DDMs. This study explores these possibilities and uses Los Angeles multimodal rapid-transit network as a representative case study of a system that operates in a dispersed agglomeration where multiple sub-centers are linked. Multi-level generalized linear models were implemented where key predictors, including stations\u27 metropolitan- and a local-accessibility indicators are regressed onto average weekday boardings. Furthermore, more general accessibility constructs were developed via EFA and implemented in models; and parameters non-stationarity was assessed via geographically weighted regressions. Results indicate that nodal metropolitan accessibility is a significant predictor of patronage in LA’s rapid-transit network, and that its interaction with local-accessibility amplifies boardings and improves DDM models’ explanatory power. More general constructs of accessibility at metropolitan and local-scale were derived via EFA and these resulted in a more parsimonious model with equal predictive power. Land-use and transit planners would benefit from including an accessibility lens in their DDM modeling. Practical applications of these type of models include TOD scenario planning, comparative route alignment studies, system expansion studies, and for didactic purposes given the ability of accessibility measures to capture land-use/transportation interactions

The white dwarf cooling sequence of 47 Tucanae

47 Tucanae is one of the most interesting and well observed and theoretically studied globular clusters. This allows us to study the reliability of our understanding of white dwarf cooling sequences, to confront different methods to determine its age, and to assess other important characteristics, like its star formation history. Here we present a population synthesis study of the cooling sequence of the globular cluster 47 Tucanae. In particular, we study the distribution of effective temperatures, the shape of the color-magnitude diagram, and the corresponding magnitude and color distributions. We do so using an up-to-date population synthesis code based on Monte Carlo techniques, that incorporates the most recent and reliable cooling sequences and an accurate modeling of the observational biases. We find a good agreement between our theoretical models and the observed data. Thus, our study, rules out previous claims that there are still missing physics in the white dwarf cooling models at moderately high effective temperatures. We also derive the age of the cluster using the termination of the cooling sequence, obtaining a good agreement with the age determinations using the main-sequence turn-off. Finally, we find that the star formation history of the cluster is compatible with that btained using main sequence stars, which predict the existence of two distinct populations. We conclude that a correct modeling of the white dwarf population of globular clusters, used in combination with the number counts of main sequence stars provides an unique tool to model the properties of globular clusters.Comment: 6 pages and 4 figures accepted for publication in A &

Human Frataxin Folds Via an Intermediate State. Role of the C-Terminal Region

The aim of this study is to investigate the folding reaction of human frataxin, whose deficiency causes the neurodegenerative disease Friedreich’s Ataxia (FRDA). The characterization of different conformational states would provide knowledge about how frataxin can be stabilized without altering its functionality. Wild-type human frataxin and a set of mutants, including two highly destabilized FRDA-associated variants were studied by urea-induced folding/unfolding in a rapid mixing device and followed by circular dichroism. The analysis clearly indicates the existence of an intermediate state (I) in the folding route with significant secondary structure content but relatively low compactness, compared with the native ensemble. However, at high NaCl concentrations I-state gains substantial compaction, and the unfolding barrier is strongly affected, revealing the importance of electrostatics in the folding mechanism. The role of the C-terminal region (CTR), the key determinant of frataxin stability, was also studied. Simulations consistently with experiments revealed that this stretch is essentially unstructured, in the most compact transition state ensemble (TSE2). The complete truncation of the CTR drastically destabilizes the native state without altering TSE2. Results presented here shed light on the folding mechanism of frataxin, opening the possibility of mutating it to generate hyperstable variants without altering their folding kinetics.Fil: Faraj, Santiago Enrique. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; ArgentinaFil: Gonzalez-Lebrero, Rodolfo Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; ArgentinaFil: Roman, Ernesto Andres. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; ArgentinaFil: Santos, Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Química y Físico-Química Biológicas "Prof. Alejandro C. Paladini". Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Química y Físico-Química Biológicas; Argentin