Commercially available power meters and sensors have measurement ranges up to several watts. Accurate measurements with these devices require periodic calibration with traceable standards. Conventional calibrations typically take place in the 1mW to 10mW range. This range can be extended downwards for highly sensitive diode sensors by means of a calibrated attenuator. Raising the calibration le...

...............................................................................................1 Chapter 1: Gravitational Waves & LIGO.......................................................2 1.1 Gravitational Waves.....................................................................2 1.2 LIGO......................................................................................2 1.3 A Source of ...

We examined the dose distributions generated by Pinnacle3 (Philips Radiation Oncology Systems, Milpitas, CA) for intensity-modulated radiotherapy (IMRT) plans using a cubic-block-piled compensator as the intensity modulator for 4-MV and 10-MV photon beams. The Pinnacle treatment planning system (TPS) uses an algorithm in which only the physical density of the absorber is required for calculatin...

This study describes the importance of attenuator scatter in the construction of compensators. The attenuator used in this study was Lipowitz metal, commonly referred to as cerrobend. Linear attenuation coefficients of cerrobend were measured in air for different thickness of cerrobend sheets and different field sizes for a 6-MV photon beam. The magnitude of the dose contribution from photons s...

The interference effects caused by the Fresnel reflections of a Gaussian beam on the boundaries of a dielectric plate, which can be considered as a Fabry-Perot etalon, were theoretically and experimentally investigated. In addition to the incident angle and the polarization of the incident light, two additional parameters--the plate's parallelism and the temperature--which are often neglected, ...

An essential element for driver safety is represented by the Impact Attenuator (especially race cars). The effect of can be seen in behavior a dummy, tied with seat belt, frontal collision rigid wall. loads that act on dummy are determined and checked to see if they fall within values recommended existing standards. car considered structure fixed belt equipped an Attenuator. Two types having co...

β-lactamase, altered porins, or both are usually responsible for cefoxitin resistance in Escherichia coli. We examined the relative importance of each. We studied 18 strains of clinical isolates with reduced cefoxitin susceptibility and 10 initially-susceptible strains passaged through cefoxitin-gradient plates. Of 18 wild-resistant strains, 9 had identical promoter mutations (including creatio...

It has been proposed that uncharged tRNA molecules may act as positive regulatory factors to control the expression of a number of operons in Bacillus subtilis and related bacteria by interacting with leader sequences to cause antitermination. In this study we report the isolation and characterization of regulatory mutations that modify one of the tRNA molecules predicted to have such a regulat...