Training Big Random Forests with Little Resources

Without access to large compute clusters, building random forests on large datasets is still a challenging problem. This is, in particular, the case if fully-grown trees are desired. We propose a simple yet effective framework that allows to efficiently construct ensembles of huge trees for hundreds of millions or even billions of training instances using a cheap desktop computer with commodity hardware. The basic idea is to consider a multi-level construction scheme, which builds top trees for small random subsets of the available data and which subsequently distributes all training instances to the top trees' leaves for further processing. While being conceptually simple, the overall efficiency crucially depends on the particular implementation of the different phases. The practical merits of our approach are demonstrated using dense datasets with hundreds of millions of training instances.Comment: 9 pages, 9 Figure

Chemical Equilibrium Abundances in Brown Dwarf and Extrasolar Giant Planet Atmospheres

We calculate detailed chemical abundance profiles for a variety of brown dwarf and extrasolar giant planet atmosphere models, focusing in particular on Gliese 229B, and derive the systematics of the changes in the dominant reservoirs of the major elements with altitude and temperature. We assume an Anders and Grevesse (1989) solar composition of 27 chemical elements and track 330 gas--phase species, including the monatomic forms of the elements, as well as about 120 condensates. We address the issue of the formation and composition of clouds in the cool atmospheres of substellar objects and explore the rain out and depletion of refractories. We conclude that the opacity of clouds of low--temperature ($\le$900 K), small--radius condensibles (specific chlorides and sulfides), may be responsible for the steep spectrum of Gliese 229B observed in the near infrared below 1 \mic. Furthermore, we assemble a temperature sequence of chemical transitions in substellar atmospheres that may be used to anchor and define a sequence of spectral types for substellar objects with T$_{eff}$s from $\sim$2200 K to $\sim$100 K.Comment: 57 pages total, LaTeX, 14 figures, 5 tables, also available in uuencoded, gzipped, and tarred form via anonymous ftp at www.astrophysics.arizona.edu (cd to pub/burrows/chem), submitted to Ap.

NASA Ares I Launch Vehicle Roll and Reaction Control Systems Design Status

This paper provides an update of design status following the preliminary design review of NASA s Ares I first stage roll and upper stage reaction control systems. The Ares I launch vehicle has been chosen to return humans to the moon, mars, and beyond. It consists of a first stage five segment solid rocket booster and an upper stage liquid bi-propellant J-2X engine. Similar to many launch vehicles, the Ares I has reaction control systems used to provide the vehicle with three degrees of freedom stabilization during the mission. During launch, the first stage roll control system will provide the Ares I with the ability to counteract induced roll torque. After first stage booster separation, the upper stage reaction control system will provide the upper stage element with three degrees of freedom control as needed. Trade studies and design assessments conducted on the roll and reaction control systems include: propellant selection, thruster arrangement, pressurization system configuration, and system component trades. Since successful completion of the preliminary design review, work has progressed towards the critical design review with accomplishments made in the following areas: pressurant / propellant tank, thruster assembly, and other component configurations, as well as thruster module design, and waterhammer mitigation approach. Also, results from early development testing are discussed along with plans for upcoming system testing. This paper concludes by summarizing the process of down selecting to the current baseline configuration for the Ares I roll and reaction control systems

Line Intensities and Molecular Opacities of the FeH F4Δi−X4ΔiF^4\Delta_i-X^4\Delta_i Transition

We calculate new line lists and opacities for the $F^4\Delta_i-X^4\Delta_i$ transition of FeH. The 0-0 band of this transition is responsible for the Wing-Ford band seen in M-type stars, sunspots and brown dwarfs. The new Einstein A values for each line are based on a high level ab initio calculation of the electronic transition dipole moment. The necessary rotational line strength factors (H\"onl-London factors) are derived for both the Hund's case (a) and (b) coupling limits. A new set of spectroscopic constants were derived from the existing FeH term values for v=0, 1 and 2 levels of the $X$ and $F$ states. Using these constants extrapolated term values were generated for v=3 and 4 and for $J$ values up to 50.5. The line lists (including Einstein A values) for the 25 vibrational bands with v$\leq$4 were generated using a merged list of experimental and extrapolated term values. The FeH line lists were use to compute the molecular opacities for a range of temperatures and pressures encountered in L and M dwarf atmospheres. Good agreement was found between the computed and observed spectral energy distribution of the L5 dwarf 2MASS-1507.Comment: 52 pages, 3 figures, many tables, accepted for publication in the Astrophysical Journal Supplement

What Immigrants Owe

Unlike natural-born citizens, many immigrants have agreed to undertake political obligations. Many have sworn oaths of allegiance. Many, when they entered their adopted country, promised to obey the law. This paper is about these agreements. First, it’s about their validity. Do they actually confer political obligations? Second, it’s about their justifiability. Is it permissible to get immigrants to undertake such political obligations? Our answers are ‘usually yes’ and ‘probably not’ respectively. We first argue that these agreements give immigrants political obligations. We then argue that getting immigrants to undertake such obligations is morally wrong. This is because it makes immigrants’ political obligations more burdensome than those of natural- born citizens. We conclude that the practice of getting immigrants to undertake such obligations should be abolished

The Effect of Bundled Payment on Emergency Department Use: Alternative Quality Contract Effects After Year One

ObjectivesThe objective was to identify the effect of the Alternative Quality Contract (AQC), a global payment system implemented by Blue Cross Blue Shield (BCBS) of Massachusetts in 2009, on emergency department (ED) presentations.MethodsBlue Cross Blue Shield of Massachusetts claims from 2006 through 2009 for 332,624 enrollees whose primary care physicians (PCPs) enrolled in the AQC, and 1,296,399 whose PCPs were not enrolled in the AQC, were evaluated. A pre–post, intervention–control, propensity‐scored difference‐in‐difference approach was used to isolate the AQC effect on ED visits. The analysis adjusted for age, sex, health status, and secular trends to compare ED use between the treatment and control groups.ResultsOverall, secular trends showed that the number of ED visits decreased slightly for both treatment and control groups. The adjusted analysis of the AQC group showed decreases from 0.131 to 0.127 visits per member/quarter, and the control group decreased from 0.157 to 0.152 visits per member/quarter. The difference‐in‐difference analysis showed the AQC had no statistically significant effect on total ED use compared to the control group.ConclusionsIn the first year of this AQC, we did not find evidence of change in aggregate ED use. Similar global budget programs may not alter ED use in the initial implementation period.ResumenEfecto del Pago Combinado en el Uso del Servicio de Urgencias: Los Efectos del Alternative Quality Contract tras un AñoObjetivosIdentificar el efecto del Alternative Quality Contract (AQC), un sistema de pago global implementado por el Blue Cross Blue Shield de Massachusetts en 2009, en las visitas a los servicios de urgencias (SU).MetodologíaSe evaluaron los 332.624 miembros cuyo médico de atención primaria (MAP) estaba incluido en el AQC y los 1.296.399 cuyo MAP no estaba incluido en el AQC del Blue Cross Blue Shield de Massachusetts de 2006 hasta 2009. Para identificar el efecto del AQC en las visitas al SU, se utilizó un diseño pre‐post, intervención‐control, con una aproximación por puntuación de propensión diferencia en diferencia. El análisis se ajustó por edad, sexo, estado de salud y tendencias seculares para comparar el uso del SU entre los grupos tratamiento y control.ResultadosDel total, las tendencias seculares mostraron que el número de visitas al SU descendió discretamente tanto para el grupo tratamiento como control. El análisis ajustado del grupo AQC mostró un descenso de 0,131 a 0,127 visitas por miembro/cuartil, y el grupo control descendió de 0,157 a 0,152 visitas por miembro/cuartil. El análisis de diferencia en diferencia mostró que el AQC no tuvo efecto estadísticamente significativo en el uso total del SU en comparación con el grupo control.ConclusionesEn su primer año, el AQC no tuvo un efecto significativo en el uso del SU. PLos programas económicos globales similares pueden no alterar la utilización del SU en el periodo inicial de implementación.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/112205/1/acem12205-sup-0001-DataSupplementS1.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/112205/2/acem12205.pd

The Dependence of Brown Dwarf Radii on Atmospheric Metallicity and Clouds: Theory and Comparison with Observations

Employing realistic and consistent atmosphere boundary conditions, we have generated evolutionary models for brown dwarfs and very-low-mass stars (VLMs) for different metallicities ([Fe/H]), with and without clouds. We find that the spread in radius at a given mass and age can be as large as $\sim$10% to $\sim$25%, with higher-metallicity, higher-cloud-thickness atmospheres resulting quite naturally in larger radii. For each 0.1 dex increase in [Fe/H], radii increase by $\sim$1% to $\sim$2.5%, depending upon age and mass. We also find that, while for smaller masses and older ages brown dwarf radii decrease with increasing helium fraction ($Y$) (as expected), for more massive brown dwarfs and a wide range of ages they increase with helium fraction. The increase in radius in going from $Y=0.25$ to $Y=0.28$ can be as large as $\sim$0.025 \rj\ ($\sim$2.5%). Furthermore, we find that for VLMs an increase in atmospheric metallicity from 0.0 to 0.5 dex, increases radii by $\sim$4%, and from -0.5 to 0.5 dex by $\sim$10%. Therefore, we suggest that opacity due to higher metallicity might naturally account for the apparent radius anomalies in some eclipsing VLM systems. Ten to twenty-five percent variations in radius exceed errors stemming from uncertainities in the equation of state alone. This serves to emphasize that transit and eclipse measurements of brown dwarf radii constrain numerous effects collectively, importantly including the atmosphere and condensate cloud models, and not just the equation of state. At all times, one is testing a multi-parameter theory, and not a universal radius$-$mass relation.Comment: Accepted to the Astrophysical Journal, May 3, 201

Microstructures Manufactured in Diamond by Use of Laser Micromachining.

Different microstructures were created on the surface of a polycrystalline diamond plate (obtained by microwave plasma-enhanced chemical vapor deposition-MW PECVD process) by use of a nanosecond pulsed DPSS (diode pumped solid state) laser with a 355 nm wavelength and a galvanometer scanning system. Different average powers (5 to 11 W), scanning speeds (50 to 400 mm/s) and scan line spacings ("hatch spacing") (5 to 20 µm) were applied. The microstructures were then examined using scanning electron microscopy, confocal microscopy and Raman spectroscopy techniques. Microstructures exhibiting excellent geometry were obtained. The precise geometries of the microstructures, exhibiting good perpendicularity, deep channels and smooth surfaces show that the laser microprocessing can be applied in manufacturing diamond microfluidic devices. Raman spectra show small differences depending on the process parameters used. In some cases, the diamond band (at 1332 cm-1) after laser modification of material is only slightly wider and shifted, but with no additional peaks, indicating that the diamond is almost not changed after laser interaction. Some parameters did show that the modification of material had occurred and additional peaks in Raman spectra (typical for low-quality chemical vapor deposition CVD diamond) appeared, indicating the growing disorder of material or manufacturing of the new carbon phase