Production of Jets at the Tevatron

Measurements of the inclusive jet cross section and the dijet angular distribution using data from the Tevatron are presented. Comparisons to NLO QCD show good agreement below 250 GeV, but CDF data show an excess at higher ET; qualitative agreement is seen between the CDF and DO cross sections. Analysis of the dijet angular distributions exclude quark compositeness below 2.1 TeV.Comment: 5 pages, 6 figure

The Double Flip: Applying a Flipped Learning Approach to Teach the Teacher and Improve Student Satisfaction

This paper describes a professional development (PD) program for academics at an Australian university designed to model good blended curriculum design and effective use of contemporary learning technologies. It evaluates a case study from the pilot of this program involving a postgraduate psychology course to illustrate one of the most challenging examples and in turn the potential impact of the approach developed. Academic developers face known barriers, including time constraints, interdisciplinary miscommunication, and change resistance, when introducing academics to new approaches to learning and teaching. This PD sought to promote change by modelling a shift from “sage on the stage” to “guide on the side,” through use of flipped and blended learning approaches by the academic developer. The case study found the teacher gained confidence in these methods and student satisfaction ratings increased

Componentes de la tasa de crecimiento poblacional en el negrón especulado de Saskatchewan, Canadá

Breeding range and abundance of White–winged Scoters (Melanitta fusca deglandi) have declined in northwestern North America. Hypotheses proposed to account for this trend are that survival and/or recruitment of females had declined. Thus, we used a reverse–time capture–recapture approach to directly estimate survival, seniority and capture probabilities for females of breeding age at Redberry Lake, Saskatchewan, Canada for 1975–1980 and 2000–2003. We also estimated population size of breeding females for 1975–1985 and 2000–2003 using capture–recapture data. Initially, this local population was in serious decline [95% CL ( ) = 0.89 ± 0.09], but has since stabilized and may be slowly increasing [95% CL ( ) = 1.07 ± 0.11]. This reversal in trajectory apparently resulted from increased recruitment rather than increased apparent survival. Importantly, recent recruitment of adult females appeared to be driven solely by immigration of adult females with no detectable in situ recruitment, suggesting a hypothesis that the local population is being rescued by females produced elsewhere.El rango reproductivo y la abundancia del negrón especulado (Melanitta fusca deglandi) han disminuido en la zona noroeste de América del Norte. La hipótesis propuesta para explicar esta tendencia es que se ha producido una disminución en la supervivencia y/o el reclutamiento de hembras. Por consiguiente, utilizamos un enfoque de captura–recaptura con el tiempo invertido para estimar directamente la supervivencia, la jerarquía y las probabilidades de captura de las hembras en edad reproductora del lago Redberry, Saskatchewan, Canadá, durante los periodos 1975–1980 y 2000– 2003. También estimamos el tamaño poblacional de las hembras reproductoras durante los periodos 1975–1985 y 2000–2003, mediante el empleo de datos de captura–recaptura. En un principio, esta población local experimentó una importante disminución [95% CL ( ) = 0,89 ± 0,09], pero posteriormente se estabilizó, y es posible que poco a poco vaya aumentando [95% CL ( ) = 1,07 ± 0,11]. Por lo visto, la inversión de esta trayectoria se produjo como consecuencia de un mayor reclutamiento, en lugar de una mayor supervivencia aparente. Es importante destacar que el reclutamiento reciente de hembras adultas parece haber obedecido exclusivamente a la migración de hembras adultas sin un reclutamiento detectable in situ, lo que sugiere la hipótesis de que la población local está siendo rescatada por hembras procedentes de otros lugares

Coordinating Unions, Wages and Employment

In this paper we consider a two-sector economy in which individual unions are affiliated into a federation of unions. We analyze the consequences of two different types of wage setting. Firstly, individual unions set wages in their own sector without taking into account the effect of their wages on the employment level in the other sector. There may be positive as well as negative externalities. A positive (negative) externality may exist if a higher (lower) wage in one sector implies a higher level of employment in the other sector. Both cases may occur in our model. Secondly, wages in the two sectors are set by the federation of unions. We show that in this case higher (lower) wages result than in the first case if a positive (negative) externality exists

Signatures of recent asteroid disruptions in the formation and evolution of solar system dust bands

We have performed detailed dynamical modeling of the structure of a faint dust band observed in coadded InfraRed Astronomical Satellite data at an ecliptic latitude of 17 degrees that convincingly demonstrates that it is the result of a relatively recent (significantly less than 1Ma) disruption of an asteroid and is still in the process of forming. We show here that young dust bands retain information on the size distribution and cross-sectional area of dust released in the original asteroid disruption, before it is lost to orbital and collisional decay. We find that the Emilkowalski cluster is the source of this partial band and that the dust released in the disruption would correspond to a regolith layer similar to 3 m deep on the similar to 10 km diameter source body's surface. The dust in this band is described by a cumulative size-distribution inverse power-law index with a lower bound of 2.1 (implying domination of cross-sectional area by small particles) for dust particles with diameters ranging from a few mu m up to a few cm. The coadded observations show that the thermal emission of the dust band structure is dominated by large (mm-cm size) particles. We find that dust particle ejection velocities need to be a few times the escape velocity of the Emilkowalski cluster source body to provide a good fit to the inclination dispersion of the observations. We discuss the implications that such a significant release of material during a disruption has for the temporal evolution of the structure, composition, and magnitude of the zodiacal cloud

ROTSE All Sky Surveys for Variable Stars I: Test Fields

The ROTSE-I experiment has generated CCD photometry for the entire Northern sky in two epochs nightly since March 1998. These sky patrol data are a powerful resource for studies of astrophysical transients. As a demonstration project, we present first results of a search for periodic variable stars derived from ROTSE-I observations. Variable identification, period determination, and type classification are conducted via automatic algorithms. In a set of nine ROTSE-I sky patrol fields covering about 2000 square degrees we identify 1781 periodic variable stars with mean magnitudes between m_v=10.0 and m_v=15.5. About 90% of these objects are newly identified as variable. Examples of many familiar types are presented. All classifications for this study have been manually confirmed. The selection criteria for this analysis have been conservatively defined, and are known to be biased against some variable classes. This preliminary study includes only 5.6% of the total ROTSE-I sky coverage, suggesting that the full ROTSE-I variable catalog will include more than 32,000 periodic variable stars.Comment: Accepted for publication in AJ 4/00. LaTeX manuscript. (28 pages, 11 postscript figures and 1 gif

The ROTSE-III Robotic Telescope System

The observation of a prompt optical flash from GRB990123 convincingly demonstrated the value of autonomous robotic telescope systems. Pursuing a program of rapid follow-up observations of gamma-ray bursts, the Robotic Optical Transient Search Experiment (ROTSE) has developed a next-generation instrument, ROTSE-III, that will continue the search for fast optical transients. The entire system was designed as an economical robotic facility to be installed at remote sites throughout the world. There are seven major system components: optics, optical tube assembly, CCD camera, telescope mount, enclosure, environmental sensing & protection and data acquisition. Each is described in turn in the hope that the techniques developed here will be useful in similar contexts elsewhere.Comment: 19 pages, including 4 figures. To be published in PASP in January, 2003. PASP Number IP02-11