Construction and evaluation of classifiers for forensic document analysis

In this study we illustrate a statistical approach to questioned document examination. Specifically, we consider the construction of three classifiers that predict the writer of a sample document based on categorical data. To evaluate these classifiers, we use a data set with a large number of writers and a small number of writing samples per writer. Since the resulting classifiers were found to have near perfect accuracy using leave-one-out cross-validation, we propose a novel Bayesian-based cross-validation method for evaluating the classifiers.Comment: Published in at http://dx.doi.org/10.1214/10-AOAS379 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Predictive Validity of Critical Power and Functional Threshold Power for Mountain Bike Race Performance.

Miller, M., Witmer, C., Moir, G., Davis, S., East Stroudsburg University, East Stroudsburg, PA Purpose: This study tested the predictive validity of critical power (CP) and functional threshold power (FTP) for mountain bike cross-country (MTB) race performance. Methods: Five well-trained MTB athletes (mean ± s: age: 31.4 ± 9.3 years; mass: 70.8 ± 9.5kg; VO2max: 63.8 ± 7.0 ml/kg/min) volunteered for this study. Participants’ FTP was measured during a ramped cycle ergometer test to exhaustion and was indicated as the point at which blood lactate reached 4.0 mmol/L. This test also served to measure the gas exchange threshold and VO2peak for CPtesting. CP was tested during a 3-minute all-out test on a cycle ergometer against a fixed resistance. MTB performance measures were gathered from a USA Cycling sanctioned MTB race and reduced to mean lap time over four laps of 7.5 km each. Linear regression was used to assess the prediction of MTB performance using either FTP or CP. Results: This study shows that CP can predict MTB better than FTP (R2=0.943 versus R2=0.784). CP can also predict MTB with less error than FTP (39.413 s versus 76.526 s). Conclusion: Coaches and athletes can use this information to gauge ability and prescribe training for MTB athletes

Complexity-based learning and teaching: a case study in higher education

This paper presents a learning and teaching strategy based on complexity science and explores its impacts on a higher education game design course. The strategy aimed at generating conditions fostering individual and collective learning in educational complex adaptive systems, and led the design of the course through an iterative and adaptive process informed by evidence emerging from course dynamics. The data collected indicate that collaboration was initially challenging for students, but collective learning emerged as the course developed, positively affecting individual and team performance. Even though challenged, students felt highly motivated and enjoyed working on course activities. Their perception of progress and expertise were always high, and the academic performance was on average very good. The strategy fostered collaboration and allowed students and tutors to deal with complex situations requiring adaptation

MACE II - A Space Shuttle experiment for investigating adaptive control of flexible spacecraft

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76987/1/AIAA-1998-4319-483.pd

Black hole accretion disks in the canonical low-hard state

Stellar-mass black holes in the low-hard state may hold clues to jet formation and basic accretion disk physics, but the nature of the accretion flow remains uncertain. A standard thin disk can extend close to the innermost stable circular orbit, but the inner disk may evaporate when the mass accretion rate is reduced. Blackbody-like continuum emission and dynamically-broadened iron emission lines provide independent means of probing the radial extent of the inner disk. Here, we present an X-ray study of eight black holes in the low-hard state. A thermal disk continuum with a colour temperature consistent with $L \propto T^{4}$ is clearly detected in all eight sources, down to $\approx5\times10^{-4}L_{Edd}$. In six sources, disk models exclude a truncation radius larger than 10rg. Iron-ka fluorescence line emission is observed in half of the sample, down to luminosities of $\approx1.5\times10^{-3}L_{Edd}$. Detailed fits to the line profiles exclude a truncated disk in each case. If strong evidence of truncation is defined as (1) a non-detection of a broad iron line, {\it and} (2) an inner disk temperature much cooler than expected from the ${\rm L} \propto {\rm T}^{4}$ relation, none of the spectra in this sample offer strong evidence of disk truncation. This suggests that the inner disk may evaporate at or below $\approx1.5\times10^{-3}L_{Edd}$.Comment: Accepted for publication in MNRAS, 20 pages, 18 figure

The broad iron Kalpha line of Cygnus X-1 as seen by XMM-Newton in the EPIC-pn modified timing mode

We present the analysis of the broadened, flourescent iron Kalpha line in simultaneous XMM-Newton and RXTE data from the black hole Cygnus X-1. The XMM-Newton data were taken in a modified version of the timing mode of the EPIC-pn camera. In this mode the lower energy threshold of the instrument is increased to 2.8 keV to avoid telemetry drop outs due to the brightness of the source, while at the same time preserving the signal-to-noise ratio in the Fe Kalpha band. We find that the best-fit spectrum consists of the sum of an exponentially cut off power-law and relativistically smeared, ionized reflection. The shape of the broadened Fe Kalpha feature is due to strong Compton broadening combined with relativistic broadening. Assuming a standard, thin accretion disk, the black hole is close to rotating maximally.Comment: Astron. Astrophys., in pres

NWSA News and Views

You are cordially invited to participate in the Third Annual NWSA Convention— Women Respond to Racism —to be held May 31-June 4, 1981, at the University of Connecticut at Storrs. At this Convention we will examine the conjunction of racism and sexism from an interdisciplinary, multicultural perspective as well as in the context of, for example, community organtzmg, curriculum development, the media, and public policy. The Convention schedule includes a broad selection of workshops and panel discussions on subjects as diverse as nonracist and nonsexist curricular materials, race and sex desegregation, nineteenth-century Black women activists, organizing against sterilization abuse nationally and internationally, art by women of color, women and development in the Third World, literature, pornography, and demography. There will, of course, be sessions addressing the interests of all the NWSA caucuses: Lesbian, Third World, Student, Staff, PreK-12, and Community College

Soft X-ray components in the hard state of accreting black holes

Recent observations of two black hole candidates (GX 339-4 and J1753.5-0127) in the low-hard state (L_X/L_Edd ~ 0.003-0.05) suggest the presence of a cool accretion disk very close to the innermost stable orbit of the black hole. This runs counter to models of the low-hard state in which the cool disk is truncated at a much larger radius. We study the interaction between a moderately truncated disk and a hot inner flow. Ion-bombardment heats the surface of the disk in the overlap region between a two-temperature advection-dominated accretion flow and standard accretion disk, producing a hot (kT_e ~70 keV) layer on the surface of the cool disk. The hard X-ray flux from this layer heats the inner parts of the underlying cool disk, producing a soft X-ray excess. Together with interstellar absorption these effects mimic the thermal spectrum from a disk extending to the last stable orbit. The results show that soft excesses in the low-hard state are a natural feature of truncated disk models.Comment: 12 pages, 8 figures, accepted by Astronomy & Astrophysics, reference added, minor typos correcte

Radio astronomy

The following subject areas are covered: (1) scientific opportunities (millimeter and sub-millimeter wavelength astronomy; meter to hectometer astronomy; the Sun, stars, pulsars, interstellar masers, and extrasolar planets; the planets, asteroids, and comets; radio galaxies, quasars, and cosmology; and challenges for radio astronomy in the 1990's); (2) recommendations for new facilities (the millimeter arrays, medium scale instruments, and small-scale projects); (3) continuing activities and maintenance, upgrading of telescopes and instrumentation; (4) long range programs and technology development; and (5) social, political, and organizational considerations