CALCIUM ION REQUIREMENT FOR PROLIFERATION OF BACTERIOPHAGE Φμ-4

SHAFIA, FRED (University of Nebraska, Lincoln), AND T. L. THOMPSON. Calcium ion requirement for proliferation of bacteriophage Φμ-4. J. Bacteriol. 88:293-296. 1964.-Divalent ions are essential for proliferation of phage Φμ-4. Small amounts of citrate interfere with efficient adsorption of phage to the host cells. Penetration of phage material into the cell is strictly dependent on divalent ions and is inhibited by low levels of citrate. Inhibition of infection can be partially reversed, in early latent period, by calcium ions. Synthesis of new phage particles is also dependent on divalent ions. Addition of citrate to infected cell suspensions significantly reduced the number of phage progeny produced. Chelates such as phosphate and citrate rapidly inactivated the free phage particles at 65 C. Chelate inactivation of phage is not reversible; however, it can be prevented to some degree by calcium ions

The Growth of Pathogenic Bacteria in Soluble Oil Emulsions

Mineral oils, when emulsified with materials such as soaps of petroleum sulfonates, fatty acids, abietic acid or resin, are referred to as soluble oils. These oils, mixed with water, form stable emulsions which are universally employed as coolants and lubricants for drilling, cutting, and grinding of metals. In addition to the emulsifying agent, soluble oils may also contain fatty oils, disinfectants and emulsion stabilizers. The oils supplied by the manufacturer are sterile, but when mixed with water in the machine shop they support microbial growth (Duffet et al., 1943; Fabian and Pivnick, 1953; Lee and Chandler, 1941; Page and Bushnell, 1921). In fact, contaminants from soil, floor sweepings, air, river water, and feces grow readily in these emulsions (Fabian and Pivnick, 1953). The C. B. Dolge Company (undated pamphlet) has reported that feces and other body discharges are found in soluble oil emulsions. Duffet et al. (1943), Page and Bushnell (1921), and Pivnick and Fabian (unpublished data) found coliform bacteria in samples obtained from factories in the United States. Recently, Pivnick (unpublished data) has found that emulsions from factories in Great Britain, Canada, and the United States contained between 103 and 105 coliform bacteria per ml. The relationship of fecal pollution to the spread of enteric diseases suggested that an investigation of enteric pathogens in soluble oils should be undertaken. Preliminary experiments by Okawaki (1953) showed that enteric pathogens grew well in this medium. This report is concerned with the growth of some representative enteric pathogens and Klebsiella pneumoniae

Thompson Sampling: An Asymptotically Optimal Finite Time Analysis

The question of the optimality of Thompson Sampling for solving the stochastic multi-armed bandit problem had been open since 1933. In this paper we answer it positively for the case of Bernoulli rewards by providing the first finite-time analysis that matches the asymptotic rate given in the Lai and Robbins lower bound for the cumulative regret. The proof is accompanied by a numerical comparison with other optimal policies, experiments that have been lacking in the literature until now for the Bernoulli case.Comment: 15 pages, 2 figures, submitted to ALT (Algorithmic Learning Theory

A Neural Networks Committee for the Contextual Bandit Problem

This paper presents a new contextual bandit algorithm, NeuralBandit, which does not need hypothesis on stationarity of contexts and rewards. Several neural networks are trained to modelize the value of rewards knowing the context. Two variants, based on multi-experts approach, are proposed to choose online the parameters of multi-layer perceptrons. The proposed algorithms are successfully tested on a large dataset with and without stationarity of rewards.Comment: 21st International Conference on Neural Information Processin

Time-distance analysis of the emerging active region NOAA 10790

We investigate the emergence of Active Region NOAA 10790 by means of time – distance helioseismology. Shallow regions of increased sound speed at the location of increased magnetic activity are observed, with regions becoming deeper at the locations of sunspot pores. We also see a long-lasting region of decreased sound speed located underneath the region of the flux emergence, possibly relating to a temperature perturbation due to magnetic quenching of eddy diffusivity, or to a dense flux tube. We detect and track an object in the subsurface layers of the Sun characterised by increased sound speed which could be related to emerging magnetic-flux and thus obtain a provisional estimate of the speed of emergence of around 1 km s−1

Helioseismology of Sunspots: A Case Study of NOAA Region 9787

Various methods of helioseismology are used to study the subsurface properties of the sunspot in NOAA Active Region 9787. This sunspot was chosen because it is axisymmetric, shows little evolution during 20-28 January 2002, and was observed continuously by the MDI/SOHO instrument. (...) Wave travel times and mode frequencies are affected by the sunspot. In most cases, wave packets that propagate through the sunspot have reduced travel times. At short travel distances, however, the sign of the travel-time shifts appears to depend sensitively on how the data are processed and, in particular, on filtering in frequency-wavenumber space. We carry out two linear inversions for wave speed: one using travel-times and phase-speed filters and the other one using mode frequencies from ring analysis. These two inversions give subsurface wave-speed profiles with opposite signs and different amplitudes. (...) From this study of AR9787, we conclude that we are currently unable to provide a unified description of the subsurface structure and dynamics of the sunspot.Comment: 28 pages, 18 figure