Cancer Health Education Preferences among Miami-Dade County Construction Workers

Construction work is a high-risk, transient occupation. Worksite outreach programs for cancer risk assessment are highly warranted because workers are exposed to both occupational and environmental carcinogens. We examined the feasibility and acceptability of conducting a paired cancer risk assessment and cancer prevention intervention using “lunch trucks” among construction worksites as the delivery mechanism. Among the 57 completed questionnaires from construction workers on a Miami-Dade County construction high-rise apartment building site, there were 50 (88%) males and 29 (51%) white Hispanics. Over 54% of the construction workers were current smokers of cigarettes, 3.5% chewed tobacco, and 19.3% smoked cigars. Of the current smokers, 80.1% expressed interest in quitting smoking, and 64.9% were willing to receive smoking cessation materials free of charge from a lunch truck at the construction site. Based on the results of this study, lunch trucks would be welcomed by construction workers as delivery mechanism to disseminate health education, cancer screening and smoking cessation information to this difficult to reach and highly underserved occupational group

Progress toward a MEMS fabricated 100 GHz oscillator.

This report summarizes an LDRD effort which looked at the feasibility of building a MEMS (Micro-Electro-Mechanical Systems) fabricated 100 GHz micro vacuum tube. PIC Simulations proved to be a very useful tool in investigating various device designs. Scaling parameters were identified. This in turn allowed predictions of oscillator growth based on beam parameters, cavity geometry, and cavity loading. The electron beam source was identified as a critical element of the design. FEA's (Field Emission Arrays) were purchased to be built into the micro device. Laboratory testing of the FEA's was also performed which pointed out care and handling issues along with maximum current capabilities. Progress was made toward MEMS fabrication of the device. Techniques were developed and successfully employed to build up several of the subassemblies of the device. However, the lower wall fabrication proved to be difficult and a successful build was not completed. Alternative approaches to building this structure have been identified. Although these alternatives look like good solutions for building the device, it was not possible to complete a redesign and build during the timeframe of this effort

A compact, short-pulse laser for near-field, range-gated imaging

This paper describes a compact laser, which produces high power, wide-angle emission for a near-field, range-gated, imaging system. The optical pulses are produced by a 100 element laser diode array (LDA) which is pulsed with a GaAs, photoconductive semiconductor switch (PCSS). The LDA generates 100 ps long, gain-switched, optical pulses at 904 nm when it is driven with 3 ns, 400 A, electrical pulses from a high gain PCSS. Gain switching is facilitated with this many lasers by using a low impedance circuit to drive an array of lasers, which are connected electrically in series. The total optical energy produced per pulse is 10 microjoules corresponding to a total peak power of 100 kW. The entire laser system, including prime power (a nine volt battery), pulse charging, PCSS, and LDA, is the size of a small, hand-held flashlight. System lifetime, which is presently limited by the high gain PCSS, is an active area of research and development. Present limitations and potential improvements will be discussed. The complete range-gated imaging system is based on complementary technologies: high speed optical gating with intensified charge coupled devices (ICCD) developed at Los Alamos National Laboratory (LANL) and high gain, PCSS-driven LDAs developed at Sandia National Laboratories (SNL). The system is designed for use in highly scattering media such as turbid water or extremely dense fog or smoke. The short optical pulses from the laser and high speed gating of the ICCD are synchronized to eliminate the back-scattered light from outside the depth of the field of view (FOV) which may be as short as a few centimeters. A high speed photodiode can be used to trigger the intensifier gate and set the range-gated FOV precisely on the target. The ICCD and other aspects of the imaging system are discussed in a separate paper

Characteristics of Trap-Filled Gallium Arsenide Photoconductive Switches Used in High Gain Pulsed Power Applications

The electrical properties of semi-insulating (SI) Gallium Arsenide (GaAs) have been investigated for some time, particularly for its application as a substrate in microelectronics. Of late this material has found a variety of applications other than as an isolation region between devices, or the substrate of an active device. High resistivity SI GaAs is increasingly being used in charged particle detectors and photoconductive semiconductor switches (PCSS). PCSS made from these materials operating in both the linear and non-linear modes have applications such as firing sets, as drivers for lasers, and in high impedance, low current Q-switches or Pockels cells. In the non-linear mode, it has also been used in a system to generate Ultra-Wideband (UWB) High Power Microwaves (HPM). The choice of GaAs over silicon offers the advantage that its material properties allow for fast, repetitive switching action. Furthermore photoconductive switches have advantages over conventional switches such as improved jitter, better impedance matching, compact size, and in some cases, lower laser energy requirement for switching action. The rise time of the PCSS is an important parameter that affects the maximum energy transferred to the load and it depends, in addition to other parameters, on the bias or the average field across the switch. High field operation has been an important goal in PCSS research. Due to surface flashover or premature material breakdown at higher voltages, most PCSS, especially those used in high power operation, need to operate well below the inherent breakdown voltage of the material. The lifetime or the total number of switching operations before breakdown, is another important switch parameter that needs to be considered for operation at high bias conditions. A lifetime of {approximately} 10{sup 4} shots has been reported for PCSS's used in UWB-HPM generation [5], while it has exceeded 10{sup 8} shots for electro-optic drivers. Much effort is currently being channeled in the study related to improvements of these two parameters high bias operation and lifetime improvement for switches used in pulsed power applications. The contact material and profiles are another important area of study. Although these problems are being pursued through the incorporation of different contact materials and introducing doping near contacts, it is important that the switch properties and the conduction mechanism in these switches be well understood such that the basic nature of the problems can be properly addressed. In this paper the authors report on these two basic issues related to the device operation, i.e., mechanisms for increasing the hold-off characteristics through neutron irradiation, and the analysis of transport processes at varying field conditions in trap dominated SI GaAs in order to identify the breakdown mechanism during device operation. It is expected that this study would result in a better understanding of photoconductive switches, specifically those used in high power operation