Molecular Clock on a Neutral Network

The number of fixed mutations accumulated in an evolving population often displays a variance that is significantly larger than the mean (the overdispersed molecular clock). By examining a generic evolutionary process on a neutral network of high-fitness genotypes, we establish a formalism for computing all cumulants of the full probability distribution of accumulated mutations in terms of graph properties of the neutral network, and use the formalism to prove overdispersion of the molecular clock. We further show that significant overdispersion arises naturally in evolution when the neutral network is highly sparse, exhibits large global fluctuations in neutrality, and small local fluctuations in neutrality. The results are also relevant for elucidating the topological structure of a neutral network from empirical measurements of the substitution process.Comment: 10 page

Dairy Resource Management: A Comparison of Conventional and Pasture-Based Systems

Facing rapid and significant change in the sector, U.S. dairy production trends from 1993-2005 were tracked and performance measures (scale and technical efficiency and returns on assets) were estimated for conventional and pasture-based dairy farms using data from USDA's Agricultural Resource Management Survey. Comparisons of relative economic performance of dairy farms by size and type are made.dairy operations, pasture-based systems, technical efficiency, Livestock Production/Industries,

Inhibition of pancreatic cancer cell growth in vitro by the tyrphostin group of tyrosine kinase inhibitors.

Tyrphostins are a group of low molecular weight synthetic inhibitors of protein tyrosine kinases (PTK). The intracellular domains of the receptors for epidermal growth factor (EGF), transforming growth factor-alpha (TGF-alpha), insulin-like growth factor 1 (IGF-1) possess PTK activity. Since EGF, TGF-alpha and IGF-1 are considered to play an important role in the proliferation of pancreatic cancer cells, we studied the effects of tyrphostins on the growth of three human pancreatic cancer cell lines (MiaPaCa-2, Panc-1 and CAV). The tyrphostins AG17, T23 and T47 all inhibited EGF and serum-stimulated DNA synthesis. AG17 was found to be the most potent of these agents and caused a dose-dependent but reversible inhibition of cell growth. Furthermore using an immunoblotting procedure we also found AG17 to inhibit EGF-induced tyrosine phosphorylation in the MiaPaCa-2 cell line. Tyrosine kinase inhibitors may prove to be useful agents for the treatment of pancreatic cancer

Analysis of multiple incidence angle SIR-B data for determining forest stand characteristics

For the first time in the U.S. space program, digital synthetic aperture radar (SR) data were obtained from different incidence angles during Space Shuttle Mission 41-G. Shuttle Imaging Radar-B (SIR-B) data were obtained at incidence angles of 58 deg., 45 deg., and 28 deg., on October 9, 10, and 11, 1984, respectively, for a predominantly forested study area in northern Florida. Cloud-free LANDSAT Thematic Mapper (T.M.) data were obtained over the same area on October 12. The SIR-B data were processed and then digitally registered to the LANDSAT T.M. data by scientists at the Jet Propulsion Laboratory. This is the only known digitally registered SIR-B and T.M. data set for which the data were obtained nearly simultaneously. The data analysis of this information is discussed

Longtitudinal electron beam diagnostics via upconversion of THz to visible radiation

Longitudinal electro-optic electron bunch diagnostics has been successfully applied at several accelerators. The electro-optic effect can be seen as an upconversion of the Coulomb field of the relativistic electron bunch (THz radiation) to the visible spectral range, where a variety of standard diagnostic tools are available. Standard techniques to characterise femtosecond optical laser pulses (auto- and cross-correlators) have led to the schemes that can measure electron bunch profiles with femtosecond resolution. These techniques require, however, well synchronized femtosecond laser pulses, in order to obtain the desired temporal resolution. Currently, we are exploring other electro-optic variants which require less advanced laser systems and will be more amenable to beam based longitudinal feedback applications. The first results of one such new scheme will be presented in this paper

Quantum Stress Focusing in Descriptive Chemistry

We show that several important concepts of descriptive chemistry, such as atomic shells, bonding electron pairs and lone electron pairs, may be described in terms of {\it quantum stress focusing}, i.e. the spontaneous formation of high-pressure regions in an electron gas. This description subsumes previous mathematical constructions, such as the Laplacian of the density and the electron localization function, and provides a new tool for visualizing chemical structure. We also show that the full stress tensor, defined as the derivative of the energy with respect to a local deformation, can be easily calculated from density functional theory.Comment: 5 pages, 2 figure

The detection of geothermal areas from Skylab thermal data

Skylab-4 X-5 thermal data of the geysers area was analyzed to determine the feasibility of using midday Skylab images to detect geothermal areas. The hottest ground areas indicated on the Skylab image corresponded to south-facing barren or sparsely vegetated slopes. A geothermal area approximately 15 by 30 m coincided with one of the hottest areas indicated by Skylab. This area could not be unambiguously distinguished from the other areas which are believed to be hotter than their surroundings as a result of their topography, and micrometeorological conditions. A simple modification of a previous thermal model was performed and the predicted temperatures for the hottest slopes using representative values was in general agreement with the observed data. It is concluded that data from a single midday Skylab pass cannot be used to locate geothermal areas

The Forgotten Topic: Teaching Plant Closing to Executives and Graduate Students

Executive education programs and graduate-level business programs generally devote substantial time and resources to training professionals to open businesses, generate business growth, and manage on-going operations. Few programs, however, devote any time to a topic that many executives will one day be forced to confront: plant closings. Because relatively few managers have actually gone through the plant closing process, there are rarely “experts” available to guide a company through the practical day-to-day aspects of shutting down a facility. This paper addresses the key topics needed for an advanced level program dealing with the operational aspects of closing a facility. Such topics include operations management issues, human resources considerations, and legal compliance. Following an executive level training program of this type should increase the chances of having a successful closure: one that minimizes the negative impact and uncertainty related to the closure

On-the-fly Uniformization of Time-Inhomogeneous Infinite Markov Population Models

This paper presents an on-the-fly uniformization technique for the analysis of time-inhomogeneous Markov population models. This technique is applicable to models with infinite state spaces and unbounded rates, which are, for instance, encountered in the realm of biochemical reaction networks. To deal with the infinite state space, we dynamically maintain a finite subset of the states where most of the probability mass is located. This approach yields an underapproximation of the original, infinite system. We present experimental results to show the applicability of our technique