The Eect of Mechanical Loading on the Frequency of an Oscillator Circuit

We investigate the effect of mechanical strain on the frequency of an electronic oscillator embedded in an integrated circuit. This analysis is aimed at explaining a 1% inaccuracy in the oscillator frequency under test conditions prescribed by a leading supplier of semi-conductor devices. During the test the package containing the oscillator was clamped to a circuit board by mechanical pressure. By considering the nature of the oscillator we show that tensile strains of the order of 10^-4 could explain the observations via the piezoresistance effect. Both a simple one-dimensional analysis based on the beam equation and an elastic finite element simulation show that strains of this magnitude can be generated during the test

Analytic functions which operate on homogeneous algebras

It is well known that a complex-valued function ø, analytic on some open set Ω, extends to any commutative Banach algebra B so that the action of ø on B commutes with the action of the Gelfand transformation. In this paper, it is shown that if B is a homogeneous convolution Banach algebra over any compact group and if 0 ϵ Ω is a fixed point of ø, then a similar result holds, with the Gelfand transformation replaced by the Fourier-Stieltjes transformation. Care is required, in that discussion of this relation usually requires simultaneous consideration of the extension of ø to B and to certain operator algebras

Limiting spheroid size as a function of growth factor source location

AbstractSolutions C(r) of the time-independent nonhomogeneous diffusion equation for three different piecewise-uniform source terms are used to examine the limiting size of multicell spheroids using a simple model which reproduces concentration-dependent mitotic behavior. A condition is derived under which nontrivial solutions do not exist (in all three cases), and a condition for the existence of a unique nontrivial solution is established for the case of growth-modifying factor (GMF) production throughout the spheroid. Qualitative behavior of the limiting size is established as a function of various physiological parameters. Of fundamental importance is the assumed GMF concentration threshold θ, near which (i.e., as C → θ−) mitosis, and hence spheroid growth, is generally strongly inhibited

The Design, Development and Testing of a Propulsion System for the SNAP-1 Nanosatellite

It has frequently been proposed to use very small nanosatellites for missions requiring orbital agility. Whether it be swarms of satellites for scientific or remote-sensing measurements, constellations for communications or single satellites for remote inspection, all require some way of modifying their respective orbits. Novel, high-technology solutions to this requirement have been proposed from MEMS to solar sails. Notwithstanding the eventual availability of such advanced nanosatellite propulsion technologies, the Surrey Space Centre has developed a miniature propulsion subsystem using technology readily available today. On 28th June 2000 Surrey launched SNAP-1, the first in a series of Surrey Nanosatellite Application Platform missions. Amongst other features of this new 6.5 kg nanosatellite is a butane liquefied gas propulsion subsystem to meet the spacecraft\u27s mission requirement of 1 m/s delta V. With a total mass budget of 450 grams, including propellant, dry mass, structural support and drive electronics, this propulsion system will be one of the smallest ever to have flown on a spacecraft. This paper describes some of the interesting challenges in producing such a small system, especially in a seven month concept to launch site program. The flight propulsion system will be described, including novel techniques such as using a coiled tube in the place of a conventional propellant tank. The choice of butane as a propellant will be discussed

How to find discrete contact symmetries

This paper describes a new algorithm for determining all discrete contact symmetries of any differential equation whose Lie contact symmetries are known. The method is constructive and is easy to use. It is based upon the observation that the adjoint action of any contact symmetry is an automorphism of the Lie algebra of generators of Lie contact symmetries. Consequently, all contact symmetries satisfy various compatibility conditions. These conditions enable the discrete symmetries to be found systematically, with little effort

Utilization of health care services by patients with chronic obstructive pulmonary disease

AbstractIn order to identify healthcare resource use patterns associated with chronic obstructive pulmonary disease (COPD), resource utilization (RU) data collection was integrated into a randomized, double-blind placebo-controlled study of Viozan™ (sibenadet HCI). This study enrolled patients with symptomatic, smoking-related COPD, randomized to receive sibenadet or placebo for a 52-week treatment period. A questionnaire establishing typical pre-trial, COPD, randomized to RU was completed by each patient. Subsequent data were collected by means of an Interactive Voice Response System (IVRS) at 30-day intervals (14 time points) during the study and in the follow-up period. The IVRS system facilitated data collection and minimized inconvient to the patients. Subsequent data were collected by means of an Interactive Voice Response System health services during the year-long study was high.No overall trend for lower RU was associated with sibenadet therapy, which correlates with the lack of sustained clinical effect seen in studies conducted concurrently. These data do, however, provide valuable information on RU associated with COPD and insights into adjustments associated with changes in disease course. Physicians were seen to be the most common source of care for patients with COPD and more of the patients with severe COPD (stage III) than mild (stage I) were seen to utilize the most expensive resources (e.g. inpatient hospital care). For those patients who experienced an exacerbation during the trial (irrespective of treatment group), resource use was increased during the periods when an exacerbation was reported when compared with the periods before or after an exacerbation. The proportion of cases attending the physician doubled and with a trip to the Emergency Room (ER) increased approximately ninefold during the reporting period in which the exacerbation occurred compared with the previous month.This study has shown that use of an IVRS, even in elderly patients, is an effective means of gathering RU data over long periods. The study findings suggest that the advent of effective therapeutic interventions, particularly any with the ability to minimize exacerbations and limit disease progression, could impact on the health care services used and potentially reduce associated costs