17,407 research outputs found
'My painted chamber' and other rooms: Stephen Hulkes and the history of Calico House, Newnham
Photochemical trajectory modelling studies of the 1987 Antarctic spring vortex
Simulations of Antarctic ozone photochemistry performed using a photochemical model integrated along air parcel trajectories are described. This type of model has a major advantage at high latitudes of being able to simulate correctly the complex interaction between photolysis and temperature fields, which, because of the polar night cannot be represented accurately in a zonally averaged framework. Isentropic air parcel trajectories were computed using Meteorological Office global model analyses and forecast fields from positions along the ER-2 flight paths during the Airborne Antarctic Ozone Experiment in Austral Spring 1987. A photochemical model is integrated along these trajectories using the aircraft observations to initialize constituent concentrations. The model includes additional reactions of the ClO dimer and also bromine reactions, which are thought to play a significant role in Antarctica. The model also includes heterogeneous reactions which are invoked when the air parcel passes through a polar stratospheric cloud (PSC). The existence of a PSC is determined throughout the course of the model integration from the parcel temperature and the saturated vapour pressure of water over an assumed H2O/HNO3 mixture. The air parcel temperature is used to determine the saturated vapor pressure of HNO3 over the same mixture. Mixing ratios which exceed saturation result in condensation of the excess in the model and hence lead to a reduction of the amount of gas phase NO2 available for chemical reaction
Diagnostic studies of the 1987 Antarctic spring vortex
Dynamical fields form the UK Meteorological office global forecast model were used throughout the 1987 Airborne Antarctic Ozone Experiment (AAOE) for flight planning and diagnostic studies. Here, several studies based on the Meteorological Office global analysis (resolution 1.5 degrees lattitude x 1.875 degrees longitude, Lyne et al.) are described. The wind and temperature data derived from the model analysis are compared with observations made from both the DCB and ER-2, and an assessment of the model performance given. Derived quantities such as potential vorticity and model data and discrepancies due to the model data are discussed
Experiments on Visual Acuity and the Visibility of Markings on the Ground in Long-duration Earth-Orbital Space Flight
Visual acuity and visibility of markings on ground in long duration earth orbital space fligh
Some Environmental Geologic Factors as Aids to Planning in Hendricks County, Indiana
Earth materials in the form of rock and unconsolidated sediments provide a basis for our very existence. They yield building stone, coal, oil, gas, ground water, a wide variety of minerals, and sand and grave, and we grow our crops in soils-all from a small portion of the earth's upper crust. Continued use of these mostly nonrenewable natural resources and increasingly complex economic and distributional problems have ushered in the era of shortages. Clearly, every effort must be made to plan future use and urban growth in such a way as to maximize efficiency and minimize waste
Nudges and other moral technologies in the context of power: Assigning and accepting responsibility
Strawson argues that we should understand moral responsibility in terms of our practices of holding responsible and taking responsibility. The former covers what is commonly referred to as backward-looking responsibility , while the latter covers what is commonly referred to as forward-looking responsibility . We consider new technologies and interventions that facilitate assignment of responsibility. Assigning responsibility is best understood as the second- or third-personal analogue of taking responsibility. It establishes forward-looking responsibility. But unlike taking responsibility, it establishes forward-looking responsibility in someone else. When such assignments are accepted, they function in such a way that those to whom responsibility has been assigned face the same obligations and are susceptible to the same reactive attitudes as someone who takes responsibility. One family of interventions interests us in particular: nudges. We contend that many instances of nudging tacitly assign responsibility to nudgees for actions, values, and relationships that they might not otherwise have taken responsibility for. To the extent that nudgees tacitly accept such assignments, they become responsible for upholding norms that would otherwise have fallen under the purview of other actors. While this may be empowering in some cases, it can also function in such a way that it burdens people with more responsibility that they can (reasonably be expected to) manage
Semi-analytical dark matter halos and the Jeans equation
Although N-body studies of dark matter halos show that the density profiles,
rho(r), are not simple power-laws, the quantity rho/sigma^3, where sigma(r) is
the velocity dispersion, is in fact a featureless power-law over ~3 decades in
radius. In the first part of the paper we demonstrate, using the semi-analytic
Extended Secondary Infall Model (ESIM), that the nearly scale-free nature of
rho/sigma^3 is a robust feature of virialized halos in equilibrium. By
examining the processes in common between numerical N-body and semi-analytic
approaches, we argue that the scale-free nature of rho/sigma^3 cannot be the
result of hierarchical merging, rather it must be an outcome of violent
relaxation. The empirical results of the first part of the paper motivate the
analytical work of the second part of the paper, where we use rho/sigma^3
proportional to r^{-alpha} as an additional constraint in the isotropic Jeans
equation of hydrostatic equilibrium. Our analysis shows that the constrained
Jeans equation has different types of solutions, and in particular, it admits a
unique ``periodic'' solution with alpha=1.9444. We derive the analytic
expression for this density profile, which asymptotes to inner and outer
profiles of rho ~ r^{-0.78}, and rho ~ r^{-3.44}, respectively.Comment: 37 pg, 14 fig. Accepted to ApJ: added two figures and extended
discussion. Note that an earlier related paper (conference proceedings)
astro-ph/0412442 has a mistake in eq.(2.2); the correct version is eq.(5) of
the present submissio
Nova Sagittarii 1994 #1 (V4332 Sagittarii): The Discovery and Evolution of an Unusual Luminous Red Variable Star
We report photometry and spectroscopy of the evolution of Nova Sagittarii
1994 #1 (V4332 Sagittarii) during outburst. We compare the photometric and
spectral evolution of this outburst to known classes of outbursts -- including
classical novae and outbursts occurring on symbiotic stars -- and find this
object does NOT conform to any known class of outburst. The closest match to
the behavior of this unusual object is M31 RV, an extremely luminous and red
variable object discovered in the bulge of M31 in 1988. However, the temporal
behavior and maximum luminosity of the two events differ by several orders of
magnitude, requiring substantial intrinsic variation if these two events are
members the same type of outburst.
Our model of the spectroscopic evolution of this outburst shows that the
effective temperature cooled from 4400 K to 2300 K over the three month span of
our observations. In combination with line diagnostics in our later spectra,
including [OI] lambda 5577 and the dramatic increase in the Halpha to Hbeta
ratio, we infer the existence of a cool, dense (N_e ~ 10^{8-9} cm^{-3})
envelope that is optically thick in the Hydrogen Balmer recombination lines
(case C). We suggest that a nuclear event in a single star, in which a slow
shock drove the photosphere outwards, can power the observed luminosity
evolution and the emission spectrum.Comment: Accepted for publication in AJ. 24 pages including 8 embedded
postscript figures. Also available at
http://www.astronomy.ohio-state.edu/~martini/pub
Segmenting modulated line textures with S-Gabor filters
This paper describes a novel technique for segmenting frequency modulated line-textures. Textures of this sort abound in nature and are typified by growth patterns in which the deposition rate varies over time. The basic idea underpinning the technique is to use the S-Gabor kernel as a frequency modulated channel response function. According to this channel model, the central frequency changes exponentially with distance from the centre of the kernel. In order to segment the resulting texture response, we use fuzzy clustering to locate peaks in the Fourier power spectrum. In this way we estimate both the centre-frequency and the modulation parameters of the filter bank. We illustrate the effectiveness of our technique on the segmentation of growth patterns on fish scale
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