Mass and luminosity evolution of young stellar objects

A model of protostar mass and luminosity evolution in clusters gives new estimates of cluster age, protostar birthrate, accretion rate and mean accretion time. The model assumes constant protostar birthrate, core-clump accretion, and equally likely accretion stopping. Its parameters are set to reproduce the initial mass function, and to match protostar luminosity distributions in nearby star-forming regions. It obtains cluster ages and birthrates from the observed numbers of protostars and pre-main sequence (PMS) stars, and from the modal value of the protostar luminosity. In 31 embedded clusters and complexes the global cluster age is 1-3 Myr, matching available estimates based on optical spectroscopy and evolutionary tracks. This method of age estimation is simpler than optical spectroscopy, and is more useful for young embedded clusters where optical spectrocopy is not possible. In the youngest clusters, the protostar fraction decreases outward from the densest gas, indicating that the local star-forming age increases outward from a few 0.1 Myr in small protostar-dominated zones to a few Myr in large PMS-dominated zones.Comment: To appear in The Astrophysical Journal, Part

Body composition, IGF1 status, and physical functionality in nonagenarians: implications for osteosarcopenia

OBJECTIVES: Body composition alterations occur during aging. The purpose of the present analysis was to explore the functional consequences of the overlap of sarcopenia and osteoporosis, and the potential role of insulin-like growth factor 1 (IGF1) in their development in the oldest old. SETTING AND PARTICIPANTS: Eighty-seven nonagenarians from the Louisiana Healthy Aging Study were included. MEASURES: The definition of sarcopenia was based on appendicular lean mass (ALM). Osteoporosis was diagnosed based on bone mineral density (BMD) T score. Four phenotypes were compared: (1) healthy body composition, that is, nonosteoporotic nonsarcopenic (CO, control group), (2) osteoporotic (O, low BMD T score), (3) sarcopenic (S, low ALM), and (4) osteosarcopenic (OS, low BMD T score and low ALM). Sex- and age-specific IGF1-Standard Deviation Scores (SDS) were calculated. The Continuous Scale-Physical Functional Performance (CS-PFP) test was performed. RESULTS: In OS men, IGF1-SDS values (-0.61 ±0.37 vs -0.04 ± 0.52, P = .02) were lower than those in CO males (control group), whereas IGF1-SDS were similar in the 4 body composition phenotypes in women. In men only, ALM was positively associated with IGF1-SDS values (P = .01) independent of age and C-reactive protein concentration. Regarding bone health, we found no association between IGF1-SDS values and BMD. IGF1-SDS was not associated with functional performance (CS-PFP) in men and women. CONCLUSIONS/IMPLICATIONS: IGF1 sensitivity in skeletal muscle and bone may differ by sex in the oldest old. IGF1 status did not appear to affect physical functionality. Determinants and clinical and functional characteristics of osteosarcopenia need to be further investigated in order to define conclusive diagnostic criteria

Nuclear Shell Model Calculations with Fundamental Nucleon-Nucleon Interactions

Some fundamental Nucleon-Nucleon interactions and their applications to finite nuclei are reviewed. Results for the few-body systems and from Shell-Model calculations are discussed and compared to point out the advantages and disadvantages of the different Nucleon-Nucleon interactions. The recently developed Drexel University Shell Model (DUSM) code is mentioned.Comment: 16 pages, 4 figures. To appear in Phys. Rep. 199

SURFACE GEOPHYSICAL EXPLORATION OF B & BX & BY TANK FARMS AT THE HANFORD SITE RESULTS OF BACKGROUND CHARACTERIZATION WITH MAGNETICS AND ELECTROMAGNETICS

This report documents the results of preliminary surface geophysical exploration activities performed between October and December 2006 at the B, BX, and BY tank farms (B Complex). The B Complex is located in the 200 East Area of the U. S. Department of Energy's Hanford Site in Washington State. The objective of the preliminary investigation was to collect background characterization information with magnetic gradiometry and electromagnetic induction to understand the spatial distribution of metallic objects that could potentially interfere with the results from high resolution resistivity survey. Results of the background characterization show there are several areas located around the site with large metallic subsurface debris or metallic infrastructure

Aprendizaje orientado a la programación en economía, negocios y finanzas

[EN] As the relationship between both students (teachers) and information technology evolves, new tools are required to improve learning (teaching) in social sciences. Economics, business and finance are mainly based on data and dealing with data requires specific skills and techniques such as computer programming in order to get full potential of most quantitative models. In this paper, we propose a coding oriented learning method based on Python Notebooks which is specifically designed for students of degrees in economics, business and finance. We follow a learning-by-doing strategy that encourages students to implement economic models as a suitable way to improve the understanding of fundamental concepts. As an illustrative example, we also describe a case study in which Python Notebooks are the key tool to teach cash management in a Master in Business Administration program. Since students of today are the decision-makers of tomorrow, a further advantage of the use of a programming language as a teaching tool is the possibility to connect theory to practice by enabling students to implement their own decision support tools.[ES] La evolución entre la relación entre los estudiantes (profesores) y la tecnología de la información, requiere nuevas herramientas para mejorar el aprendizaje (enseñanza) en las ciencias sociales. La economía, los negocios y las finanzas se basan principalmente en los datos y el tratamiento de los datos requiere habilidades y técnicas específicas, como la programación informática, para aprovechar al máximo el potencial de la mayoría de los modelos cuantitativos. En este documento, proponemos un método de aprendizaje orientado a la programación basado en Python Notebooks, que está diseñado específicamente para estudiantes de títulos en economía, negocios y finanzas. Nuestra estrategia de aprendizaje es eminentemente práctica motivando a los estudiantes a implementar modelos económicos como una forma adecuada de mejorar la comprensión de los conceptos fundamentales. Como ejemplo ilustrativo, también describimos un estudio de caso en el que Python Notebooks es la herramienta clave para enseñar gestión de efectivo en un programa de Máster en Administración de Empresas. Dado que los estudiantes de hoy son los que toman las decisiones del mañana, una ventaja adicional del uso de un lenguaje de programación como herramienta de enseñanza es la posibilidad de conectar la teoría con la práctica al permitir a los estudiantes implementar sus propias herramientas de apoyo a la decisión.Salas-Molina, F.; Pla-Santamaria, D. (2018). Coding oriented learning in economics,business and finance. Modelling in Science Education and Learning. 11(1):55-64. doi:10.4995/msel.2018.9152SWORD5564111da Costa Moraes, M. B., Nagano, M. S., and Sobreiro, V. A. (2015). Stochastic cash ow management models: A literature review since the 1980s. In Decision Models in Engineering and Management, pages 11-28. Springer International Publishing.DiSessa, A. A. (2001). Changing minds: Computers, learning, and literacy. Mit Press.Guzdial, M. (2010). Why is it so hard to learn to program? In Making software: What really works, and why we believe it, pages 111-121. O'Reilly Media, Inc.Ketcheson, D. I. (2014). Teaching numerical methods with iPython notebooks and inquiry-based learning. In Proceedings of the 13th Python in Science Conference. SciPy. org.Myers, G. J., Sandler, C., and Badgett, T. (2011). The art of software testing. John Wiley & Sons.Rossant, C. (2014). IPython interactive computing and visualization cookbook. Packt Publishing Ltd.VanderPlas, J. (2016). Python Data Science Handbook: Essential Tools for Working with Data. O'Reilly

Keep it simple: three indicators to deal with overfishing

Three simple fisheries indicators are presented: (i) percentage of mature fish in catch, with 100% as target; (ii) percent of specimens with optimum length in catch, with 100% as target; and (iii) percentage of ‘mega-spawners‘ in catch, with 0% as target, and 30–40% as representative of reasonable stock structure if no upper size limit exists. Application of these indicators to stocks of Gadus morhua, Sardinella aurita and Epinephelus aeneus demonstrate their usefulness. It is argued that such simple indicators have the potential to allow more stakeholders such as fishers, fish dealers, supermarket managers, consumers and politicians to participate in fisheries management and eventually hold and reverse the global pattern of convenience overfishing, which is defined here as deliberate overfishing sanctioned by official bodies who find it more convenient to risk eventual collapse of fish stocks than to risk social and political conflicts

Extremal Black Holes and Holographic C-Theorem

We found Bogomol'nyi type of the first order differential equations in three dimensional Einstein gravity and the effective second order ones in new massive gravity when an interacting scalar field is minimally coupled. Using these equations in Einstein gravity, we obtain analytic solutions corresponding to extremally rotating hairy black holes. We also obtain perturbatively extremal black hole solutions in new massive gravity using these lower order differential equations. All these solutions have the anti de-Sitter spaces as their asymptotic geometries and as the near horizon ones. This feature of solutions interpolating two anti de-Sitter spaces leads to the construction of holographic c-theorem in these cases. Since our lower order equations reduce naturally to the well-known equations for domain walls, our results can be regarded as the natural extension of domain walls to more generic cases.Comment: 1+31 pages, no figure, v2: some improvements, accepted for publication in Nucl. Phys.

Clustering of 2PIGG galaxy groups with 2dFGRS galaxies

Prompted by indications from QSO lensing that there may be more mass associated with galaxy groups than expected, we have made new dynamical infall estimates of the masses associated with 2PIGG groups and clusters. We have analysed the redshift distortions in the cluster-galaxy cross-correlation function as a function of cluster membership, cross-correlating z<0.12 2PIGG clusters and groups with the full 2dF galaxy catalogue. We have made estimates of the dynamical infall parameter beta and new estimates of the group velocity dispersions. We first find that the amplitude of the full 3-D redshift space cross-correlation function, xi_{cg}, rises monotonically with group membership. We use a simple linear-theory infall model to fit xi(sigma, pi) in the range 5<s<40h^{-1}Mpc. We find that the beta versus membership relation for the data shows a minimum at intermediate group membership n~20 or L~2x10^11h^-2Lsun, implying that the bias and hence M/L ratios rise by a significant factor (~5x) both for small groups and rich clusters. However, the mocks show a systematic shift between the location of the beta minimum and the M/L minimum at L~10^10h^-2Lsun given by direct calculation using the known DM distribution. Our overall conclusion is that bias estimates from dynamical infall appear to support the minimum in star-formation efficiency at intermediate halo masses. Nevertheless, there may still be significant systematic problems arising from measuring beta~1/b using large-scale infall rather than M/L using small-scale velocity dispersions.Comment: 20 pages, 32 figures, 9 table