13,982 research outputs found
Effects of high and low barometric pressures on susceptibility and resistance to infection Quarterly status report, 1 Apr. - 30 Jun. 1970
Effects of high and low barometric pressures on susceptibility and resistance to infectio
Introduction: Planetary memory in contemporary American fiction
This special issue considers the ways in which contemporary American fiction seeks to imagine a mode of ‘planetary memory’ able to address the scalar and systemic complexities of the Anthropocene – the epoch in which the combined activity of the human species has become a geological force in its own right. As Naomi Klein has recently argued, confronting the problem of anthropogenic climate change alters everything we know about the world: demanding wholesale recalibration of economic and political priorities; destabilising the epistemic frameworks through which quotidian life is interpreted and enacted; and decentring the dominant cultural imaginaries that seek to give form to historical experienc
The effects of a single dose of 7,12-dimethylbenz(a)-anthracene on the epidermis and hair follicles of mice, with notes on concurrent changes in the ovaries and adrenals.
IN spite of the fact that skin was the first tissue in which chemical carcinogenesis was demonstrated, and that it is possible to study all stages of the carcinogenic process by inspection, there is still much controversy over the mechanism. One factor that has given rise to much debate is the part played by the hair follicles. In a previous paper (Orr, 1955), results were described which appeared to show that with a potent carcinogen the original hair follicles were completely destroyed, and replaced by differentiation from the regenerating epidermis, and that neither the original nor the neogenetic hair follicles gave rise to tumours. The earlier experiment was done with outbred albino mice. The present paper seeks to confirm and expand the results using pure-strain mice. During necropsies on the animals, changes were observed in the ovaries and adrenals, and brief notes on the nature of such changes have been appended to the main object of this communication. MATERIAL AND METHODS Three pure-line strains of mice were used: BALB/cf/Sp, March (MAf/Sp), and C3H/Sp. All mice were female; this was originally because of availability, but when during the experiment changes were observed in the ovaries, it was decided to continue with this sex. Twenty-eight mice of each strain were used. They were housed in metal boxes, up to three in a box, and fed on Purina Laboratory Chow, with water ad libiturn. They received one application (circa 0.15 ml.) of a 0.5 % solution in acetone of 7,12-dimethylbenz(a)anthracene (DMBA), on the interscapular skin. Half of them received this on the first day of the experiment, the remainder 4 days later, to obviate the necessity for killing animals at the week-ends. One animal o
Multiplexed gas spectroscopy using tunable VCSELs
Detection and identification of gas species using tunable laser diode laser absorption spectroscopy has been performed using vertical cavity surface emitting lasers (VCSEL). Two detection methods are compared: direct absorbance and wavelength modulation spectroscopy (WMS). In the first, the output of a DC-based laser is directly monitored to detect for any quench at the targeted specie wavelength. In the latter, the emission wavelength of the laser is modulated by applying a sinusoidal component on the drive current of frequency {omega}, and measuring the harmonics component (2{omega}) of the photo-detected current. This method shows a better sensitivity measured as signal to noise ratio, and is less susceptible to interference effects such as scattering or fouling. Gas detection was initially performed at room temperature and atmospheric conditions using VCSELs of emission wavelength 763 nm for oxygen and 1392 nm for water, scanning over a range of approximately 10 nm, sufficient to cover 5-10 gas specific absorption lines that enable identification and quantization of gas composition. The amplitude and frequency modulation parameters were optimized for each detected gas species, by performing two dimensional sweeps for both tuning current and either amplitude or frequency, respectively. We found that the highest detected signal is observed for a wavelength modulation amplitude equal to the width of the gas absorbance lines, in good agreement with theoretical calculations, and for modulation frequencies below the time response of the lasers (<50KHz). In conclusion, we will discuss limit of detection studies and further implementation and packaging of VCSELs in diode arrays for continuous and simultaneous monitoring of multiple species in gaseous mixtures
Exactly solvable model of A + A \to 0 reactions on a heterogeneous catalytic chain
We present an exact solution describing equilibrium properties of the
catalytically-activated A + A \to 0 reaction taking place on a one-dimensional
lattice, where some of the sites possess special "catalytic" properties. The A
particles undergo continuous exchanges with the vapor phase; two neighboring
adsorbed As react when at least one of them resides on a catalytic site (CS).
We consider three situations for the CS distribution: regular, annealed random
and quenched random. For all three CS distribution types, we derive exact
results for the disorder-averaged pressure and present exact asymptotic
expressions for the particles' mean density. The model studied here furnishes
another example of a 1D Ising-type system with random multi-site interactions
which admits an exact solution.Comment: 7 pages, 3 Figures, appearing in Europhysics Letter
Lyman alpha absorption lines from mini pancakes
[Abridged abstract:] Recent numerical simulations show that many \lyal
absorption lines of column densities \nha \la 10^{15} cm are produced
in transient, mini pancakes. Such pancakes are modeled here, approximating the
initial perturbation leading to the formation of the pancake as a single
sinusoidal wave. The density and temperature profiles of the gas in the pancake
are determined for , where is the collapse redshift. The
\lyal absorption line profiles for a line of sight through the pancake are
then calculated. The absorption lines in general have wings signifying bulk
motions in the gas. It is shown that the deviation from a single Voigt profile
is large for small H I column density lines, in which the effect of bulk
motions is large. For lines with \nha > 10^{13} cm, high temperature
tend to wash out the signatures of bulk motion. The analytical modeling of mini
pancakes associated with \lyal forest lines --- with 10^{13} \la \nha \la
10^{15} cm---gives the corresponding mass scales. It is shown here
that, for typical values of cosmological parameters, absorption lines with
\nha \sim 10^{14} cm correspond to structures with baryonic mass of
M with an overdensity of at .
The value of \nha can change by a factor in the course of evolution
of the pancake in time. It is also shown that there is an upper limit to \nha
from a pancake due to the slow recombination rate and the importance of
collisional ionization at high temperatures. Mini pancakes do not give rise to
\lyal lines with \nha \ga 10^{14.5} cm, for \j21=1 and
.Comment: Latex with aaspp4.sty (25 pages), 6 figures, Accepted for publication
in The Astrophysical Journa
Comparing Cosmic Microwave Background Datasets
To extract reliable cosmic parameters from cosmic microwave background
datasets, it is essential to show that the data are not contaminated by
residual non-cosmological signals. We describe general statistical approaches
to this problem, with an emphasis on the case in which there are two datasets
that can be checked for consistency. A first visual step is the Wiener filter
mapping from one set of data onto the pixel basis of another. For more
quantitative analyses we develop and apply both Bayesian and frequentist
techniques. We define the ``contamination parameter'' and advocate the
calculation of its probability distribution as a means of examining the
consistency of two datasets. The closely related ``probability enhancement
factor'' is shown to be a useful statistic for comparison; it is significantly
better than a number of chi-squared quantities we consider. Our methods can be
used: internally (between different subsets of a dataset) or externally
(between different experiments); for observing regions that completely overlap,
partially overlap or overlap not at all; and for observing strategies that
differ greatly.
We apply the methods to check the consistency (internal and external) of the
MSAM92, MSAM94 and Saskatoon Ring datasets. From comparing the two MSAM
datasets, we find that the most probable level of contamination is 12%, with no
contamination only 1.05 times less probable, and 100% contamination strongly
ruled out at over 2 X 10^5 times less probable. From comparing the 1992 MSAM
flight with the Saskatoon data we find the most probable level of contamination
to be 50%, with no contamination only 1.6 times less probable and 100%
contamination 13 times less probable. [Truncated]Comment: LaTeX, 16 pages which include 16 figures, submitted to Phys. Rev.
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