RF power generation

This paper reviews the main types of r.f. power amplifiers which are, or may be, used for particle accelerators. It covers solid-state devices, tetrodes, inductive output tubes, klystrons, magnetrons, and gyrotrons with power outputs greater than 10 kW c.w. or 100 kW pulsed at frequencies from 50 MHz to 30 GHz. Factors affecting the satisfactory operation of amplifiers include cooling, matching and protection circuits are discussed. The paper concludes with a summary of the state of the art for the different technologies.Comment: 35 pages, contribution to the CAS - CERN Accelerator School: Specialised Course on RF for Accelerators; 8 - 17 Jun 2010, Ebeltoft, Denmar

Inter-ethnic Issues in Lorraine Hansberry\u27s The Sign in Sidney Brustein\u27s Window by Steven R. Carter

When Lorraine Hansberry\u27s second produced play, The Sign in Sidney Brustein\u27s Window, opened on Broadway in 1964, some white critics expressed surprise that her protagonist was Jewish rather than black and some blacks were disappointed or even outraged by this, feeling that she was deserting the cause and trying too hard to win acclaim as a universal writer.[1] Others from both groups, of course, warmly defended her

Kink oscillations in magnetic tubes with twisted annulus

Aims.We study kink waves in a magnetic flux tube modelled as a straight core surrounded by a magnetically twisted annulus, both embedded in a straight ambient external field, and derive the dispersion relation for this configuration. Methods.The existence and behaviour of the kink modes are examined with specific attention to the effect that the addition of magnetic twist has on phase speeds and periods. Analytic expansions to the short and long wavelength approximations are also considered. Results.The magnetic twist is found to introduce of an infinite set of body modes into solutions of the dispersion relation not present in the untwisted case. Moreover, for the kink modes, the width of interval of this infinite set, generally found to occupy phase speeds around the annulus' longitudinal Alfvén speed, increases for longer wavelengths. Two surface modes are also present in the solution, one at each surface: the internal and the external edges of the annulus. The magnetic twist is found to increase or decrease the phase speeds of these surface modes that are depending on the ratio of internal and external Alfvén speeds in the flux tube. Conclusions.The magnetic twist of the annulus region of a flux tube is found to have a marked effect on the phase speeds of occurring modes. A straight annulus layer increased (or decreased) the periods of the surface modes for a tube modelled as a density (magnetic) enhancement. The addition of twist reduces the periods of the modes in both cases

Symplectic structure for elastic and chiral conducting cosmic string models

This article is based on the covariant canonical formalism and corresponding symplectic structure on phase space developed by Witten, Zuckerman and others in the context of field theory. After recalling the basic principles of this procedure, we construct the conserved bilinear symplectic current for generic elastic string models. These models describe current carrying cosmic strings evolving in an arbitrary curved background spacetime. Particular attention is paid to the special case of the chiral string for which the worldsheet current is null. Different formulations of the chiral string action are discussed in detail, and as a result the integrability property of the chiral string is clarified.Comment: 18 page

Effects of low energy protons and high energy electrons on silicon

Low energy proton and high energy electron radiation effects on silicon solar cell

Study of radiation effects in Li-doped silicon solar cells

Radiation effects in lithium-doped silicon solar cell

Convergence analysis of Crank-Nicolson and Rannacher time-marching

This paper presents a convergence analysis of Crank-Nicolson and Rannacher time-marching methods which are often used in finite difference discretisations of the Black-Scholes equations. Particular attention is paid to the important role of Rannacher's startup procedure, in which one or more initial timesteps use Backward Euler timestepping, to achieve second order convergence for approximations of the first and second derivatives. Numerical results confirm the sharpness of the error analysis which is based on asymptotic analysis of the behaviour of the Fourier transform. The relevance to Black-Scholes applications is discussed in detail, with numerical results supporting recommendations on how to maximise the accuracy for a given computational cost

Hemoglobin Subunit-Subunit Affinity-Determinant of Hemoglobin Formation

Hemoglobin A₂ is often elevated in β-thalassemia and decreased in α-thalassemia. This might be due to hemoglobin subunit-subunit affinity variation. It has been inferred from the study of abnormal hemoglobins that the a subunits have higher affinity for β subunits than for δ subunits. However, only in one study has the affinity of α, β, and δ subunits for each other been measured. In this work we have attempted to measure the hemoglobin subunit-subunit affinity with somewhat different approach, i.e., hybridization of hemoglobin A and A₂. It is shown that hybridization and recombination of equal amounts of hemoglobins A and A₂ lead always to the formation of more hemoglobin A than A₂. Incubation of pure α, β, and δ subunits forms more hemoglobin A than A₂ as the availability of a subunits declines. It is concluded that hemoglobin a subunits have approximately four-fold higher affinity for β subunits than for the δ subunits under these experimental conditions. This subunit-subunit affinity difference, which has been attributed to the variation in molecular electrostatic charges, explains the variation of hemoglobin A₂ levels in thalassemia syndromes

A survey and evaluation of microbased computer aided design systems for design education and practice in Scotland primarily in the area of product design: their application, problems and potential solutions

The initial premise of the research centred around the relatively new adoption by the Product Design sector of Computer Aided Design technology. Problems were expected to occur in applying the hardware and understanding the terminology of the software by this sector which prides itself In its artisan skills. The aim of the work was to determine the extent of the adoption of Computer Aided Design and to clarify the problem areas. The research determined, by study of more experienced but similar Computer Aided Design users, that the expected problems Were not insurmountable and were being overcome by the constant improvements of computer hardware and software. However, the problems that were pinpointed actually involved the human issues encountered In working with a Computer Aided Design system and involved issues such as the management skills required, working conditions and understanding of the advantages and disadvantages of Computer Aided Design. The research focused on what had to be considered and what should be known about Computer Aided Design so that it could be effectively used in Product Design. The research was undertaken to establish general solutions to the introduction of Computer Aided Design into companies. These solutions are intended to provide a guide to potential and current users on how to improve the effectiveness of the use of Computer Aided Design systems in Product Design. The research has identified the themes and topics that should be covered in training staff on the use and potential of Computer Aided Design systems