Full-field pulsed-magneto-photoelasticity - a description of the instrument

This paper describes a novel instrument used for the analysis of full-field through-thickness stress distributions using the theory of magneto-photoelasticity (MPE) developed by Aben and Clarke et al. [ , , ]. MPE is an experimental stress analysis technique which involves the application of a magnetic field parallel to an electromagnetic wave propagating through a birefringent model within a polariscope. The effect viewed through the polariscope is then a combination of the model’s birefringence and the Faraday rotation created in the model by the magnetic field. Aben developed this technique especially for use in the measurement of stress profiles where the integrated photoelastic pattern alone yields little information. Clarke et al. developed MPE in order to study toughened glass. To date, the technique of MPE has been a single-point measurement and this is of limited utility in the investigation of 3D stress in toughened glasses. The pulsed-magneto-polariscope (PMP), described here, enables the full-field application of MPE. This paper contains a description of the novel apparatus, and demonstrations used to validate the performance of a proof-of-concept PMP instrument. The paper also highlights improvements in the application of MPE which are now possible with this new equipment. These improvements include the extension of MPE to larger areas of analysis, 3D stress analysis and the possibility of analysing a general unknown stress distribution

Improvement of Fourier Polarimetry for applications in tomographic photoelasticity

The use of the Fourier Polarimetry method has been demonstrated to extract the three characteristic parameters in integrated photoelasticity. In contrast to the phase-stepping method, it has been shown that the Fourier method is more accurate. However, the Fourier method isn't very efficient as it requires that a minimum of nine intensity images be collected during a whole revolution of a polarizer while the phase-stepping method only needs six intensity images. In this paper the Fourier transformation is used to derive the expression for determination of the characteristic parameters. Four Fourier coefficients are clearly identified to calculate the three characteristic parameters. It is found that the angular rotation ratio could be set arbitrarily. The angular rotation ratio is optimized to satisfy the requirements of efficiency and proper data accuracy, which results in data collection about three times faster than the methods suggested by previous researchers. When comparing their performance in terms of efficiency and accuracy, the simulated and experimental results show that these angular rotation ratios have the same accuracy but the optimized angular rotation ratio is significantly faster. The sensitivity to noise is also investigated and further improvement of accuracy is suggested

Design and performance of a 39cm balloon-borne telescope

A system for stabilizing a balloon-borne telescope using a star sensor device is described. Guide stars from minus four to plus four magnitude can be used and the sensor may be offset with respect to the telescope by as much as plus or minus five degrees in elevation and cross elevation to enable parts of the sky containing no suitable guide stars to be viewed. Acquisition of the guide star and setting of the offset coordinates is carried out by ground command and both may be changed in flight. The main design parameters of the equipment are summarized. Block diagrams and circuit diagrams of the star tracker are provided

Electron Interactions and Transport Between Coupled Quantum Hall Edges

We examine the effects of electron-electron interactions on transport between edge states in a multilayer integer quantum Hall system. The edge states of such a system, coupled by interlayer tunneling, form a two-dimensional, chiral metal at the sample surface. We calculate the temperature-dependent conductivity and the amplitude of conductance fluctuations in this chiral metal, treating Coulomb interactions and disorder exactly in the weak-tunneling limit. We find that the conductivity increases with increasing temperature, as observed in recent experiments, and we show that the correlation length characterising conductance fluctuations varies inversely with temperature.Comment: 4 pages, 2 figures, typos corrected, Ref. 17 added, minor changes made for publicatio

Letter from Joseph S. Tomlinson to James B. Finley

Dr. Joseph Tomlinson (president of Augusta College in Kentucky) writes to let Finley know there is a strong feeling in Kentucky against the proposed division of the Methodist Episcopal Church. If the southern Methodists should decide on division, Kentucky, Western Virginia and Missouri will stand firm against secession and remain part of the northern church. If we secede with the south, we will be thrown into the arms of heightened proslavery nullifiers and the cause of emancipation will be thrown back to a far greater extent than it has ever been done by Abolitionism. Abstract Number - 803https://digitalcommons.owu.edu/finley-letters/2307/thumbnail.jp

Letter from Joseph S. Tomlinson to Mr. & Mrs. Johnson Armstrong

Joseph S. Tomlinson has just returned from a trip to Maysville, Kentucky, where he stayed in the home of Johnson Armstrong and his wife. He writes a letter of appreciation to his hosts. [At the time, Tomlinson was completing his degree at Transylvania University in Lexington, KY. Graduating in 1825, he was admitted on trial to the Kentucky Conference in September of 1825 and appointed to a professorship at Augusta College in Maysville. Johnson Armstrong was a trustee at the college.] The letter is difficult to read and the author was initially identified as Tolindaw . Comparing the signature in the October 31, 1844 letter, it is clear that both letters were written by Tomlinson. Abstract Number - 534https://digitalcommons.owu.edu/finley-letters/1831/thumbnail.jp

Letter from Joseph S. Tomlinson to James B. Finley

Dr. Joseph Tomlinson (president of Augusta College in Kentucky), tells Finley about the recent successful commencement. He then discusses Augusta\u27s financial and legal difficulties, brought about by the division of the MEC into a northern and southern church. Tomlinson suggests the creation of a Kentucky District within the conference of the Ohio Methodist Episcopal Church. He believes that a large portion of Kentucky Methodist societies would align themselves with the MEC rather than the MEC South. [Note: the state of Kentucky revoked the college\u27s charter on February 26, 1849]. Abstract Number - 638https://digitalcommons.owu.edu/finley-letters/1734/thumbnail.jp

Elevating crop disease resistance with cloned genes

Essentially all plant species exhibit heritable genetic variation for resistance to a variety of plant diseases caused by fungi, bacteria, oomycetes or viruses. Disease losses in crop monocultures are already significant, and would be greater but for applications of disease-controlling agrichemicals. For sustainable intensification of crop production, we argue that disease control should as far as possible be achieved using genetics rather than using costly recurrent chemical sprays. The latter imply CO2 emissions from diesel fuel and potential soil compaction from tractor journeys. Great progress has been made in the past 25 years in our understanding of the molecular basis of plant disease resistance mechanisms, and of how pathogens circumvent them. These insights can inform more sophisticated approaches to elevating disease resistance in crops that help us tip the evolutionary balance in favour of the crop and away from the pathogen. We illustrate this theme with an account of a genetically modified (GM) blight-resistant potato trial in Norwich, using the Rpi-vnt1.1 gene isolated from a wild relative of potato, Solanum venturii, and introduced by GM methods into the potato variety Desiree