3,175 research outputs found
The Larger Conversation: Contemplation and Place by Tim Lilburn
Review of Tim Lilburn\u27s The Larger Conversation: Contemplation and Place
Efficient decomposition of cosmic microwave background polarization maps into pure E, pure B, and ambiguous components
Separation of the B component of a cosmic microwave background (CMB)
polarization map from the much larger E component is an essential step in CMB
polarimetry. For a map with incomplete sky coverage, this separation is
necessarily hampered by the presence of "ambiguous" modes which could be either
E or B modes. I present an efficient pixel-space algorithm for removing the
ambiguous modes and separating the map into "pure" E and B components. The
method, which works for arbitrary geometries, does not involve generating a
complete basis of such modes and scales the cube of the number of pixels on the
boundary of the map.Comment: Minor changes to previous version. Accepted for publication in Phys.
Rev.
The growth of bacteriophage
1. An anti-Escherichia coli phage has been isolated and its behavior studied.
2. A plaque counting method for this phage is described, and shown to give a number of plaques which is proportional to the phage concentration. The number of plaques is shown to be independent of agar concentration, temperature of plate incubation, and concentration of the suspension of plating bacteria.
3. The efficiency of plating, i.e. the probability of plaque formation by a phage particle, depends somewhat on the culture of bacteria used for plating, and averages around 0.4.
4. Methods are described to avoid the inactivation of phage by substances in the fresh lysates.
5. The growth of phage can be divided into three periods: adsorption of the phage on the bacterium, growth upon or within the bacterium (latent period), and the release of the phage (burst).
6. The rate of adsorption of phage was found to be proportional to the concentration of phage and to the concentration of bacteria. The rate constant ka is 1.2 x 10–9 cm.8/min. at 15°C. and 1.9 x 10–9 cm.8/min. at 25°.
7. The average latent period varies with the temperature in the same way as the division period of the bacteria.
8. The latent period before a burst of individual infected bacteria varies under constant conditions between a minimal value and about twice this value.
9. The average latent period and the average burst size are neither increased nor decreased by a fourfold infection of the bacteria with phage.
10. The average burst size is independent of the temperature, and is about 60 phage particles per bacterium.
11. The individual bursts vary in size from a few particles to about 200. The same variability is found when the early bursts are measured separately, and when all the bursts are measured at a late time
The COBE Normalization of CMB Anisotropies
With the advent of the COBE detection of fluctuations in the Cosmic Microwave
Background radiation, the study of inhomogeneous cosmology has entered a new
phase. It is now possible to accurately normalize fluctuations on the largest
observable scales, in the linear regime. In this paper we present a
model-independent method of normalizing theories to the full COBE data. This
technique allows an extremely wide range of theories to be accurately
normalized to COBE in a very simple and fast way. We give the best fitting
normalization and relative peak likelihoods for a range of spectral shapes, and
discuss the normalization for several popular theories. Additionally we present
both Bayesian and frequentist measures of the goodness of fit of a
representative range of theories to the COBE data.Comment: References updated, one figure redraw
The rate of bacteriophage inactivation by filtrates of Eschericia coli cultures
The inactivation of bacteriophage by substances from susceptible bacteria has been studied by Burnet (1) and Freeman (2). Its inactivation by antisera has been studied by Andrewes and Elford (3) and Burnet, Keogh, and Lush (4). Recently Ashenburg et al. (5) reported that saline solutions
of gum arabic, starch, or glycogen inactivated an anti-Klebsiella pneumoniae phage.
We have studied in more detail the rate of phage inactivation by culture filtrates of the susceptible bacteria in order to determine the dependence of the process on phage and inhibitor concentrations
The Meaning of Einstein's Equation
This is a brief introduction to general relativity, designed for both
students and teachers of the subject. While there are many excellent
expositions of general relativity, few adequately explain the geometrical
meaning of the basic equation of the theory: Einstein's equation. Here we give
a simple formulation of this equation in terms of the motion of freely falling
test particles. We also sketch some of its consequences, and explain how the
formulation given here is equivalent to the usual one in terms of tensors.
Finally, we include an annotated bibliography of books, articles and websites
suitable for the student of relativity.Comment: 23 pages LaTeX, 8 encapsulated Postscript figures; unlike the
published version this includes a derivation of the inverse-square force la
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