Secondary Structures in Long Compact Polymers

Compact polymers are self-avoiding random walks which visit every site on a lattice. This polymer model is used widely for studying statistical problems inspired by protein folding. One difficulty with using compact polymers to perform numerical calculations is generating a sufficiently large number of randomly sampled configurations. We present a Monte-Carlo algorithm which uniformly samples compact polymer configurations in an efficient manner allowing investigations of chains much longer than previously studied. Chain configurations generated by the algorithm are used to compute statistics of secondary structures in compact polymers. We determine the fraction of monomers participating in secondary structures, and show that it is self averaging in the long chain limit and strictly less than one. Comparison with results for lattice models of open polymer chains shows that compact chains are significantly more likely to form secondary structure.Comment: 14 pages, 14 figure

The Single-Angle Plane-Wave Spectral Response of One-Dimensional Photonic Crystal Structures

The multiple-incident-angle transmittances or reflectances of fabricated 1-D photonic crystal (PC) structures are measured. Regularization methods are applied to these measurements to determine the single-angle plane-wave spectral response of the structure

Evolutionary history predicts plant defense against an invasive pest

It has long been hypothesized that invasive pests may be facilitated by the evolutionary naïveté of their new hosts, but this prediction has never been examined in a phylogenetic framework. To address the hypothesis, we have been studying the invasive viburnum leaf beetle (Pyrrhalta viburni), which is decimating North American native species of Viburnum, a clade of worldwide importance as understory shrubs and ornamentals. In a phylogenetic field experiment using 16 species of Viburnum, we show that old-world Viburnum species that evolved in the presence of Pyrrhalta beetles mount a massive defensive wound response that crushes eggs of the pest insect; in contrast, naïve North American species that share no evolutionary history with Pyrrhalta beetles show a markedly lower response. This convergent continental difference in the defensive response of Viburnum spp. against insect oviposition contrasts with little difference in the quality of leaves for beetle larvae. Females show strong oviposition preferences that correspond with larval performance regardless of continental origin, which has facilitated colonization of susceptible North American species. Thus, although much attention has been paid to escape from enemies as a factor in the establishment and spread of nonnative organisms, the colonization of undefended resources seems to play a major role in the success of invasive species such as the viburnum leaf beetleViburnum phylogenetic studies were supported by National Science Foundation Grant IOS-0842800 (to M.J.D.). This study was supported by US National Science Foundation Grant DEB-0950231 (to A.A.A.) and Federal Formula Funds allocated by the Cornell University Agricultural Experiment Station (to A.A.A.)

Submerged Parshall Flumes of Small Size

The calibration of small Parshall flumes for measuring flows ranging in magnitude from 0.1 to 1.1 cubic feet per second (cfs) was accomplished by A. R. Robinson (1960) at Colorado State University. The purpose of Robinson’s investigation was to accurately calibrate and standardize the design of small Parshall measuring flumes. The rated flumes were constructed of galvanized sheet metal. Data was collected for Parshall flumes having throat widths of 1-, 2-, and 3- inches. Calibration tables or curves were prepared for both free and submerged flow. The dimensions of the Parshall flumes rated by Robinson are shown in Figure 1. The study reported herein was made to illustrate that the analysis of submergence developed at Utah State University (Hyatt, 1965) for trapezoidal flumes is applicable to small Parshall flumes. The data reported by Robinson (1960) is analyzed by the submergence parameters reported by Hyatt (1965) and the resulting equations and calibration curves are listed in this report

Submergence in a Two-Foot Parshall Flume

The primary objective in this study was to ascertain the validity of the method of analyzing submergence developed by Hyatt (1965) in a standard 2-foot Parshall flume. The method of analyzing submergence was first developed for a trapezoidal flume (Hyatt, 1965), was later verified for a rectangular flume (Skogerboe, walker and Robinson, 1965), and has been shown by the authors to be valid for small Parshall flumes (Skogerboe, Hyatt, Johnson, and England, 1965). In view of previous findings, it was felt the method would also be valid for large Parshall flumes, and for this purpose the 2-foot flume was selected. One other objective of the study was to analyze the possibility that another, or possibly better, point of downstream measurement might be found. To accomplish this, two other points, designated c and d, were selected downstream. The downstream depth measurement is usually taken in the throat as a referenced point designated b. The resulting equations and calibration curve are listed in this report

Measuring Water with Parshall Flumes

Preface: As the value of water increases, the extent to which measurement is employed in an irrigation system also increases. Additional flow measurements provide information for improved management of the water supply. Good water management requires accurate measurement. Many devices have been developed for this purpose and are in use. Included among them are weirs, orifices, calibrated gates, Parshall flumes, and current meters. Of these, the Parshall flume is one of the most widely accepted and used. Presented in this publication is a discussion concerning the use of Parshall flumes for measuring water, including the utilization of a new approach for treating submerged flow that was developed at Utah State University. The information presented on free flow has been taken from the origianl publications of Ralph L. Parshall, and the bulletin, Measurement of Irrigation Water, prepared by Eldon M. Stock. Utilizing data developed by Ralph L. Parshall, A. R. Robinson, and the authors