Dynamics of Epidemics

This article examines how diseases on random networks spread in time. The disease is described by a probability distribution function for the number of infected and recovered individuals, and the probability distribution is described by a generating function. The time development of the disease is obtained by iterating the generating function. In cases where the disease can expand to an epidemic, the probability distribution function is the sum of two parts; one which is static at long times, and another whose mean grows exponentially. The time development of the mean number of infected individuals is obtained analytically. When epidemics occur, the probability distributions are very broad, and the uncertainty in the number of infected individuals at any given time is typically larger than the mean number of infected individuals.Comment: 4 pages and 3 figure

Decreased activity of all tryptophan biosynthetic enzymes due to zinc deficiency

Decreased activity of all tryptophan biosynthetic enzymes due to zinc deficienc

Nephrolithiasis (part 1): Epidemiology, causes and pathogenesis of recurrent nephrolithiasis

A recent increase in the incidence of recurrent renal calcium oxalate calculi has been demonstrated. Although a few advances have shown that the increase in incidence of these stones is due to genetic causes, it is mostly associated with a change in environmental factors. Global warming and weather changes, some medications administered to young children and eating habits play a pivotal role in increasing stone incidence. By far the most important single factor in stone incidence involves the increased ingestion of red meat and salt. So much so that it is anticipated that calcium oxalate stone occurrence will increase pari passu with dietary changes in the South African black community. The reasons for the difference in the incidence between males and females (12% v. 6%) remain controversial, and should be further studied

On the Numerical Dispersion of Electromagnetic Particle-In-Cell Code : Finite Grid Instability

The Particle-In-Cell (PIC) method is widely used in relativistic particle beam and laser plasma modeling. However, the PIC method exhibits numerical instabilities that can render unphysical simulation results or even destroy the simulation. For electromagnetic relativistic beam and plasma modeling, the most relevant numerical instabilities are the finite grid instability and the numerical Cherenkov instability. We review the numerical dispersion relation of the electromagnetic PIC algorithm to analyze the origin of these instabilities. We rigorously derive the faithful 3D numerical dispersion of the PIC algorithm, and then specialize to the Yee FDTD scheme. In particular, we account for the manner in which the PIC algorithm updates and samples the fields and distribution function. Temporal and spatial phase factors from solving Maxwell's equations on the Yee grid with the leapfrog scheme are also explicitly accounted for. Numerical solutions to the electrostatic-like modes in the 1D dispersion relation for a cold drifting plasma are obtained for parameters of interest. In the succeeding analysis, we investigate how the finite grid instability arises from the interaction of the numerical 1D modes admitted in the system and their aliases. The most significant interaction is due critically to the correct represenation of the operators in the dispersion relation. We obtain a simple analytic expression for the peak growth rate due to this interaction.Comment: 25 pages, 6 figure

Turing++ Questions: A Test for the Science of (Human) Intelligence

There is a widespread interest among scientists in understanding a specific and well defined form of intelligence, that is human intelligence. For this reason we propose a stronger version of the original Turing test. In particular, we describe here an open-ended set of Turing++ questions that we are developing at the Center for Brains, Minds, and Machines at MIT -- that is questions about an image. For the Center for Brains, Minds, and Machines the main research goal is the science of intelligence rather than the engineering of intelligence -- the hardware and software of the brain rather than just absolute performance in face identification. Our Turing++ questions reflect fully these research priorities

Feasibility model of a high reliability five-year tape transport, volume 2

Analysis of the design features of the modularized tape transport renders a life expectancy in excess of five years. Tests performed on the tape transport were directed toward determining its performance capability. These tests revealed that the tape jitter and skew are in the range achieved by high quality digital tape transports. Guidance of the tape in the lateral sense by the use of the two hybrid crowned rollers proved to be excellent. Tracking was maintained within less than one thousandth inch (approximately 2 micrometers). The guidance capability demonstrated makes possible the achievement of the performance objective of 7.2 x 10 to the 9th power storage capability employing 1500 ft. of one inch wide tape with a packing density of 5,000 bits per inch per track on 80 tracks. Also, the machine showed excellent characteristics operating over a wide range of tape speeds. The basic design concept lends itself to growth and adaptation to a wide range of recorder requirements

Feasibility model of a high reliability five-year tape transport, Volume 1

The development, performance, and test results for the spaceborne magnetic tape transport are discussed. An analytical model of the tape transport was used to optimize its conceptual design. Each of the subsystems was subjected to reliability analyses which included structural integrity, maintenance of system performance within acceptable bounds, and avoidance of fatigue failure. These subsystems were also compared with each other in order to evaluate reliability characteristics. The transport uses no mechanical couplings. Four drive motors, one for each reel and one for each of two capstans, are used in a differential mode. There are two hybrid, spherical, cone tapered-crown rollers for tape guidance. Storage of the magnetic tape is provided by a reel assembly which includes the reel, a reel support structure and bearings, dust seals, and a dc drive motor. A summary of transport test results on tape guidance, flutter, and skew is provided

Conversations with Gatekeepers: An Exploratory Study of Agricultural Publication Editors\u27 Decisions to Publish Risk Coverage

The United States’ agriculture industry is impacted by numerous financial, human, legal, and production risks. These risks are frequently reported in mass media and agricultural publications. Farmers often use agricultural magazines to help them make production decisions and learn about new technology, which both involve some element of risk. Gatekeeping is the process of determining what information is included in media coverage in which editors serve as gatekeepers and make decisions regarding what topics to report. The purpose of this study was to discover how agricultural publication editors, in their role as gatekeepers, make decisions regarding coverage of risk related to agriculture and to explore the forces that influence this coverage. Researchers interviewed seven purposively selected editors of national or regional agricultural magazines. The findings indicated that the editors conceptualize risk in agriculture differently from how agricultural risks are reported in the mainstream media for the more general public; many emphasized the issues in terms of marketing or financial risk. Editors emphasized that they report on risk from an action angle, providing advice or information on how to mitigate the risk. The public’s perception of agriculture, advertisers, and personal topic preferences were cited as influencers of their risk coverage. When covering risk stories, agricultural publication editors prefer journalists who can write well and have an agricultural background or knowledge of the industry. Future research should be conducted to expand on the results from this exploratory study

Singularities of Nonlinear Elliptic Systems

Through Morrey's spaces (plus Zorko's spaces) and their potentials/capacities as well as Hausdorff contents/dimensions, this paper estimates the singular sets of nonlinear elliptic systems of the even-ordered Meyers-Elcrat type and a class of quadratic functionals inducing harmonic maps.Comment: 18 pages Communications in Partial Differential Equation