Testing equality of variances in the analysis of repeated measurements

The problem of comparing the precisions of two instruments using repeated measurements can be cast as an extension of the Pitman-Morgan problem of testing equality of variances of a bivariate normal distribution. Hawkins (1981) decomposes the hypothesis of equal variances in this model into two subhypotheses for which simple tests exist. For the overall hypothesis he proposes to combine the tests of the subhypotheses using Fisher's method and empirically compares the component tests and their combination with the likelihood ratio test. In this paper an attempt is made to resolve some discrepancies and puzzling conclusions in Hawkins's study and to propose simple modifications.\ud \ud The new tests are compared to the tests discussed by Hawkins and to each other both in terms of the finite sample power (estimated by Monte Carlo simulation) and theoretically in terms of asymptotic relative efficiencies

A model for the orientational ordering of the plant microtubule cortical array

The plant microtubule cortical array is a striking feature of all growing plant cells. It consists of a more or less homogeneously distributed array of highly aligned microtubules connected to the inner side of the plasma membrane and oriented transversely to the cell growth axis. Here we formulate a continuum model to describe the origin of orientational order in such confined arrays of dynamical microtubules. The model is based on recent experimental observations that show that a growing cortical microtubule can interact through angle dependent collisions with pre-existing microtubules that can lead either to co-alignment of the growth, retraction through catastrophe induction or crossing over the encountered microtubule. We identify a single control parameter, which is fully determined by the nucleation rate and intrinsic dynamics of individual microtubules. We solve the model analytically in the stationary isotropic phase, discuss the limits of stability of this isotropic phase, and explicitly solve for the ordered stationary states in a simplified version of the model.Comment: 15 pages, 5 figure

The Meinunger "Nicht Rote" Objects

Four high-latitude slow variable stars have been noted by Meinunger (1972) as "nicht rote" ("not red") objects and thus curious. We have previously reported (Margon & Deutsch 1997) that one of these objects, CC Boo, is in fact a QSO. Here we present observations demonstrating that the remaining three are also highly variable active galactic nuclei. The most interesting object of the four is perhaps S 10765 (= NGP9 F324-0276706), which proves to be a resolved galaxy at z=0.063. Despite the rapid and large reported variability amplitude (~1.6 mag), the spectrum is that of a perfectly normal galaxy, with no emission lines or evident nonthermal continuum. We also present new spectroscopic and photometric observations for AR CVn, suggested by Meinunger to be an RR Lyrae star despite its very faint magnitude (=19.4). The object is indeed one of the most distant RR Lyrae stars known, at a galactocentric distance of ~40 kpc.Comment: Accepted for publication in Publications of the Astronomical Society of the Pacific, Volume 111, January 1999; 14 pages including 4 figures and 1 tabl

Apollo experience report: Assessment of metabolic expenditures

A significant effort was made to assess the metabolic expenditure for extravehicular activity on the lunar surface. After evaluation of the real-time data available to the flight controller during extravehicular activity, three independent methods of metabolic assessment were chosen based on the relationship between heart rate and metabolic production, between oxygen consumption and metabolic production, and between the thermodynamics of the liquid-cooled garment and metabolic production. The metabolic assessment procedure is analyzed and discussed. Real-time use of this information by the Apollo flight surgeon is discussed. Results and analyses of the Apollo missions and comments concerning future applications are included

Research Notes : Trisomic inheritance of a chimera in soybean

Introduction: In the summer of 1978, four chlorophyll-chimeric plants were observed within a population of \u27Clark\u27. The four plants had a similar phenotype, and were surmised to originate from a common parent. These four plants were single-plant threshed

Conicoid Mirrors

The first order equation relating object and image location for a mirror of arbitrary conic-sectional shape is derived. It is also shown that the parabolic reflecting surface is the only one free of aberration and only in the limiting case of distant sources.Comment: 9 page

‘The show must go on!’ Fieldwork, mental health and wellbeing in Geography, Earth and Environmental Sciences

Fieldwork is central to the identity, culture and history of academic Geography, Earth and Environmental Sciences (GEES). However, in this paper we recognise that, for many academic staff, fieldtrips can be a profoundly challenging “ordeal,” ill‐conducive to wellness or effective pedagogic practice. Drawing on research with 39 UK university‐based GEES academics who self‐identify as having a mental health condition, we explore how mental health intersects with spaces and expectations of fieldwork in Higher Education. We particularly focus on their accounts of undertaking undergraduate residential fieldtrips and give voice to these largely undisclosed experiences. Their narratives run counter to normative, romanticised celebrations of fieldwork within GEES disciplines. We particularly highlight recurrent experiences of avoiding fieldwork, fieldwork‐as‐ ordeal, and “coping” with fieldwork, and suggest that commonplace anxieties within the neoliberal academy – about performance, productivity, fitness‐to‐work, self‐presentation, scrutiny and fear‐of‐falling‐behind – are felt particularly intensely during fieldwork. In spite of considerable work to make fieldwork more accessible to students, we find that field‐based teaching is experienced as a focal site of distress, anxiety and ordeal for many GEES academics with common mental health conditions. We conclude with prompts for reflection about how fieldwork could be otherwise

System for the measurement of ultra-low stray light levels

An apparatus is described for measuring the effectiveness of stray light suppression light shields and baffle arrangements used in optical space experiments and large space telescopes. The light shield and baffle arrangement and a telescope model are contained in a vacuum chamber. A source of short, high-powered light energy illuminates portions of the light shield and baffle arrangement and reflects a portion of same to a photomultiplier tube by virtue of multipath scattering. The resulting signal is transferred to time-channel electronics timed by the firing of the high energy light source allowing time discrimination of the signal thereby enabling the light scattered and suppressed by the model to be distinguished from the walls and holders around the apparatus

Toolbox of Countermeasures for Rural Two-Lane Curves

The Federal Highway Administration (FHWA) estimates that 58 percent of roadway fatalities are lane departures, while 40 percent of fatalities are single-vehicle run-off-road (SVROR) crashes. Addressing lane-departure crashes is therefore a priority for national, state, and local roadway agencies. Horizontal curves are of particular interest because they have been correlated with increased crash occurrence. This toolbox was developed to assist agencies address crashes at rural curves. The main objective of this toolbox is to summarize the effectiveness of various known curve countermeasures. While education, enforcement, and policy countermeasures should also be considered, they were not included given the toolbox focuses on roadway-based countermeasures. Furthermore, the toolbox is geared toward rural two-lane curves. The research team identified countermeasures based on their own research, through a survey of the literature, and through discussions with other professionals. Coverage of curve countermeasures in this toolbox is not necessarily comprehensive. For each countermeasure covered, this toolbox includes the following information: description, application, effectiveness, advantages, and disadvantages. Countermeasures covered are as follows: speed signs, chevrons, widening/adding paved shoulders, reflective barriers, high-friction treatments, raised pavement markers, edge lines, transverse pavement markings, vertical delineation, rumble strips, rumble stripes, on-pavement curve signing, flashing beacons, dynamic curve warning systems, and pavement inset lights