45,678 research outputs found
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 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 K Band Luminosity Functions of Galaxies in High Redshift Clusters
K band luminosity functions (LFs) of three, massive, high redshift clusters
of galaxies are presented. The evolution of K*, the characteristic magnitude of
the LF, is consistent with purely passive evolution, and a redshift of forma
tion z = 1.5-2.Comment: 3 pages, to appear in Proceedings of IAU Colloquium 195 - Outskirts
of Galaxy Clusters: intense life in the suburb
Groundwater Resources in the Saline Valley Conservancy District, Saline and Gallatin Counties, Illinois
published or submitted for publicationis peer reviewedOpe
Two-batch liar games on a general bounded channel
We consider an extension of the 2-person R\'enyi-Ulam liar game in which lies
are governed by a channel , a set of allowable lie strings of maximum length
. Carole selects , and Paul makes -ary queries to uniquely
determine . In each of rounds, Paul weakly partitions and asks for such that . Carole responds with some
, and if , then accumulates a lie . Carole's string of
lies for must be in the channel . Paul wins if he determines within
rounds. We further restrict Paul to ask his questions in two off-line
batches. We show that for a range of sizes of the second batch, the maximum
size of the search space for which Paul can guarantee finding the
distinguished element is as ,
where is the number of lie strings in of maximum length . This
generalizes previous work of Dumitriu and Spencer, and of Ahlswede, Cicalese,
and Deppe. We extend Paul's strategy to solve also the pathological liar
variant, in a unified manner which gives the existence of asymptotically
perfect two-batch adaptive codes for the channel .Comment: 26 page
Beyond the Standard Model for Montaneros
These notes cover (i) electroweak symmetry breaking in the Standard Model
(SM) and the Higgs boson, (ii) alternatives to the SM Higgs boson including an
introduction to composite Higgs models and Higgsless models that invoke extra
dimensions, (iii) the theory and phenomenology of supersymmetry, and (iv)
various further beyond topics, including Grand Unification, proton decay and
neutrino masses, supergravity, superstrings and extra dimensions.Comment: Based on lectures by John Ellis at the 5th CERN-Latin-American School
of High-Energy Physics, Recinto Quirama, Colombia, 15 - 28 Mar 2009, 84
pages, 35 figure
Thermal conductivity and thermal expansion of graphite fiber/copper matrix composites
The high specific conductivity of graphite fiber/copper matrix (Gr/Cu) composites offers great potential for high heat flux structures operating at elevated temperatures. To determine the feasibility of applying Gr/Cu composites to high heat flux structures, composite plates were fabricated using unidirectional and cross-plied pitch-based P100 graphite fibers in a pure copper matrix. Thermal conductivity of the composites was measured from room temperature to 1073 K, and thermal expansion was measured from room temperature to 1050 K. The longitudinal thermal conductivity, parallel to the fiber direction, was comparable to pure copper. The transverse thermal conductivity, normal to the fiber direction, was less than that of pure copper and decreased with increasing fiber content. The longitudinal thermal expansion decreased with increasing fiber content. The transverse thermal expansion was greater than pure copper and nearly independent of fiber content
The strange-sea quark spin distribution in the nucleon from inclusive and semi-inclusive deep-inelastic scattering
We propose new method which allows determination of the strange-sea quark
spin distribution in the nucleon through measurement of various inclusive and
semi-inclusive polarized deep inelastic electron- or muon-proton reactions. It
is shown, that using combinations of inclusive data and semi-inclusive data
containing neutral pions in the final state, it is possible to extract the
strange-sea quark spin distribution. Similar result can be obtained for charged
pions and some other hadrons also
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