Quantification of optical pulsed-plane-wave-shaping by chiral sculptured thin films

The durations and average speeds of ultrashort optical pulses transmitted through chiral sculptured thin films (STFs) were calculated using a finite-difference time-domain algorithm. Chiral STFs are a class of nanoengineered materials whose microstructure comprises parallel helicoidal nanowires grown normal to a substrate. The nanowires are $\sim$10-300 nm in diameter and $\sim1-10 \mu$m in length. Durations of transmitted pulses tend to increase with decreasing (free-space) wavelength of the carrier plane wave, while average speeds tend to increase with increasing wavelength. An increase in nonlinearity, as manifested by an intensity-dependent refractive index in the frequency domain, tends to increase durations of transmitted pulses and decrease average speeds. The circular Bragg phenomenon exhibited by a chiral STFs manifests itself in the frequency domain as high reflectivity for normally incident carrier plane waves whose circular polarization state is matched to the structural handedness of the film and whose wavelength falls in a range known as the Bragg regime; films of the opposite structural handedness reflect such plane waves little. This effect tends to distort the shapes of transmitted pulses with respect to the incident pulses, and such shaping can cause sharp changes in some measures of average speed with respect to carrier wavelength. A local maximum in the variation of one measure of the pulse duration with respect to wavelength is noted and attributed to the circular Bragg phenomenon. Several of these effects are explained via frequency-domain arguments. The presented results serve as a foundation for future theoretical and experimental studies of optical pulse propagation through causal, nonlinear, nonhomogeneous, and anisotropic materials.Comment: To appear in Journal of Modern Optic

Motivations and experiences of UK students studying abroad

This report summarises the findings of research aimed at improving understanding of the motivations behind the international diploma mobility of UK student

Speeding up simulations of relativistic systems using an optimal boosted frame

It can be computationally advantageous to perform computer simulations in a Lorentz boosted frame for a certain class of systems. However, even if the computer model relies on a covariant set of equations, it has been pointed out that algorithmic difficulties related to discretization errors may have to be overcome in order to take full advantage of the potential speedup. We summarize the findings, the difficulties and their solutions, and show that the technique enables simulations important to several areas of accelerator physics that are otherwise problematic, including self-consistent modeling in three-dimensions of laser wakefield accelerator stages at energies of 10 GeV and above.Comment: To be published in the proceedings of DPF-2009, Detroit, MI, July 2009, eConf C09072

Compositional nanodomain formation in hybrid formate perovskites

We report the synthesis and structural characterisation of three mixed-metal formate perovskite families [C(NH$_2$)$_3$]M$_{1-x}$Cu$_x$(HCOO)$_3$ (M = Mn, Zn, Mg). Using a combination of infrared spectroscopy, non-negative matrix factorization, and reverse Monte Carlo refinement, we show that the Mn- and Zn-containing compounds support compositional nanodomains resembling the polar nanoregions of conventional relaxor ferroelectrics. The M = Mg family exhibits a miscibility gap that we suggest reflects the limiting behaviour of nanodomain formation.Comment: 4 pages, 3 figure

Conduction of Electrical Current to and Through the Human Body: A Review

Objective: The objective of this article is to explain ways in which electric current is conducted to and through the human body and how this influences the nature of injuries. Methods: This multidisciplinary topic is explained by first reviewing electrical and pathophysiological principles. There are discussions of how electric current is conducted through the body via air, water, earth, and man-made conductive materials. There are also discussions of skin resistance (impedance), internal body resistance, current path through the body, the let-go phenomenon, skin breakdown, electrical stimulation of skeletal muscles and nerves, cardiac dysrhythmias and arrest, and electric shock drowning. After the review of basic principles, a number of clinically relevant examples of accident mechanisms and their medical effects are discussed. Topics related to high-voltage burns include ground faults, ground potential gradient, step and touch potentials, arcs, and lightning. Results: The practicing physician will have a better understanding of electrical mechanisms of injury and their expected clinical effects. Conclusions: There are a variety of types of electrical contact, each with important characteristics. Understanding how electric current reaches and travels through the body can help the clinician understand how and why specific accidents occur and what medical and surgical problems may be expected

Diclofenac and Ibuprofen in Rheumatoid Arthritis and Osteoarthritis

Forty patients with arthritis (26 rheumatoid and 14 osteoarthrosis) entered a five-week double-blind crossover trial of diclofenac and ibuprofen. Four patients failed to complete the 10-week trial. There was no statistically significant difference in parameters of disease activity for the rheumatoid arthritis patients, but patients with osteoarthrosis fared significantly better on diclofenac. There was a low incidence of side effects on both regimens

On the Injection Energy Distibution of Ultra-High-Energy Cosmic Rays

We investigate the injection spectrum of ultra-high-energy (>10^{15} eV) cosmic rays under the hypotheses that (1) these cosmic rays are protons and (2) the sources of these cosmic rays are extra-galactic and are homogeneously distributed in space. The most puzzling aspect of the observed ultra-high-energy cosmic ray spectrum is the apparent nonexistence of a ``Greisen cut-off'' at about 10^{19.8} eV. We show that this fact could be naturally explained if most (or all) of the cosmic rays presently observed above about 10^{19.6} eV were initially injected with energy above the Greisen cut-off. However, we find that the injection of cosmic rays above the Greisen cut-off cannot account for the observed flux below about 10^{19.6} eV unless the injection rate of these particles was enormously higher in the past, as would be the case if the injection resulted from the decay of an ultra-massive particle with lifetime of order 10^{9} yr. Even with such a rapid source evolution, the observed cosmic ray spectrum below about 10^{18.5} eV cannot be explained in this manner. However, we show that a 1/E^3 injection spectrum can account for the observed spectrum below 10^{18.5} eV}, with the steepening observed by the Fly's Eye group between 10^{17.6} eV and 10^{18.5} eV being very naturally explained by e+ - e- production effects. This latter fact lends support to the hypothesis that the cosmic rays in this energy regime are protons. However, due to e+ - e- production effects, a 1/E^3 injection spectrum cannot account for the observed flux above about 10^{18.5} eV.Comment: 23 pages, REVTeX, 5 Postscript figures available by anonymous FTP at ftp://rainbow.uchicago.edu/pub/relativity/cosmicray

Interpreting Parliamentary Scrutiny: An enquiry concerning everyday practices of parliamentary actors in select committees of the House of Commons

This doctorate looks at the role of parliamentary select committees in the UK House of Commons. Though the literature on this topic is extensive, this research project explores the issue from a distinctive vantage point. While research on committees has predominantly focused on their outputs, such as committee reports, in order to assess the effectiveness of Parliament in holding the executive to account, this thesis looks at the input-side to committee work. It explores the individual beliefs, everyday practices and perennial dilemmas of parliamentary actors in select committees. In doing so, this thesis argues that understanding beliefs and practices of committee members, chairs and staff are crucial ways to better comprehend the way that scrutiny works in the House of Commons. This PhD finds that scrutiny is contested in a range of ways by a range of actors. In taking actors’ interpretations seriously, this PhD reveals that each actor has their own performance style, which is used to enact beliefs about scrutiny. At its most simple, this PhD argues that scrutiny is pushed and pulled in different (sometimes conflicting) directions by parliamentary actors. There is no such thing as uniform, systematic select committee scrutiny; there exist only dense webs of scrutiny that rely upon committee members, chairs and staff to enact their roles in such ways to be conducive to holding the executive to account. These dense webs of scrutiny affect committee relationships, their ability to question witnesses in select committees, and construct consensus in writing reports

Potassium Efflux from Myocardial Cells Induced by Defibrillator Shock

A transient, dose-dependent cardiac depression was produced by defibrillator shocks in an isolated, working canine heart preparation perfused with oxygenated arterial blood from a support dog. Accompanying this depression was an efflux of potassium (K+ ), forced out of the myocardial cells by the passage of defibrillating current. The transient increase in extracellular K + concentration was recorded graphically in the venous outflow. It was found that 5-msec rectangular wave shocks, from three to ten times defibrillatory current threshold, released doserelated pulses of K+ . We conclude that because extracellular K + is a myocardial depressant, at least part of the myocardial depression after defibrillation is caused by the release of K+ from the myocardial cells

TB6: Importance of Entomogenous Fungi in Controlling Aphids on Potatoes in Northeastern Maine

This publication reports on field studies of aphid biology and of associated ecological factors made near Presque Isle, Maine. Results showed that, among the biological agents affecting aphid population trends from 1952 through 1962, entomogenous fungi were outstanding in reducing the size of populations of the potato aphid developing on potatoes treated with fungicides but not with insecticides. The potato aphid was most affected by fungi and the buckthorn aphid least affected by them. The green peach and foxglove aphids were intermediate. Predators exerted a noticeably adverse effect upon aphid population trends in two of the 11 years.https://digitalcommons.library.umaine.edu/aes_techbulletin/1188/thumbnail.jp