An improved synthesis of (2E,4Z)-6-(benzyloxy)-4-bromohexa-2,4-dien-1-ol

An improved synthesis of (2E,4Z)-6-(benzyloxy)-4-bromohexa-2,4-dien-1-ol has been devised. This new route increases the throughput and yield of the diene product by circumventing a low yielding preparation of boronic acid intermediate as well as removing the need to use multi-gram quantities of highly toxic thallium salts. In the process of developing this new route, a higher yielding preparation of ( E)-3-hydroxyprop-1-enylboronic acid was also achieved. (c) 2007 Elsevier Ltd. All rights reserved

Compensation and Characterization of Gallium Arsenide

The properties of transition metals in gallium arsenide have been previously investigated extensively with respect to activation energies, but little effort has been made to correlate processing parameters with electronic characteristics. Diffusion of copper in gallium arsenide is of technological importance due to the development of GaAs:Cu bistable photoconductive devices. Several techniques are demonstrated in this work to develop and characterize compensated gallium arsenide wafers. The material is created by the thermal diffusion of copper into silicon-doped GaAs. Transition metals generally form deep and shallow acceptors in GaAs, and therefore compensation is possible by material processing such that the shallow silicon donors are compensated by deep acceptors. Copper is an example of a transition metal that forms deep acceptors in GaAs, and therefore this work will focus on the compensation and characterization of GaAs:Si:Cu. The compensation of the material has shown that the lower diffusion temperatures (500-600°C) form primarily the well-known CuB centers whereas the higher temperature anneals (\u3e$750°C) result in the formation of CuA. Using compensation curves, the copper density is found by comparing the compensation temperature with copper solubility curves given by others. These curves also show that the formation of CuB, EL2, and CuA can be manipulated by varying processing parameters such as annealing temperature and arsenic pressure. The compensation results are confirmed using Temperature-Dependent Hall (TDH) measurements to detect the copper levels. Also, the photoconductive properties of the material under illumination from 1.06 and 2.1 μm wavelength laser pulses have been used to demonstrate the effects of the different processing procedures. The persistent photoconductivity inherent to these devices under illumination from the 1.06 μm laser pulse is used to predict the concentration of the CuB level, and the fast hole capture times of the various acceptors are found through the response to a 140 ps (FWHM), 2.1 μm laser pulse. Finally, the physical distribution of the copper atoms in the gallium arsenide wafer is examined using Glow Discharge and Secondary Ion Mass Spectroscopy (GDMS and SIMS). These techniques have been used to show that the copper diffusion in gallium arsenide is non-uniform with respect to depth and surface position

Study of aerodynamic technology for single-cruise engine V/STOL fighter/attack aircraft

A conceptual design analysis is performed on a single engine V/STOL supersonic fighter/attack concept powered by a series flow tandem fan propulsion system. Forward and aft mounted fans have independent flow paths for V/STOL operation and series flow in high speed flight. Mission, combat and V/STOL performance is calculated. Detailed aerodynamic estimates are made and aerodynamic uncertainties associated with the configuration and estimation methods identified. A wind tunnel research program is developed to resolve principal uncertainties and establish a data base for the baseline configuration and parametric variations

Brief Note: Odonata of the Beaver Creek Wetlands, Greene County, Ohio: A Preliminary Survey

Author Institution: Department of Biological Sciences, Wright State UniversityWeekly trips were made to various habitats within the Beaver Creek Wetlands in Greene County, OH, from 15 April to 3 October in 1996 and 20 April to 18 October in 1997. Specimens were collected with aerial nets or recorded as observational records. A species list for the wetlands was built and data was entered into the Ohio Odonate Survey database. Thirty-six species (22 Anisoptera; 15 Zygoptera) were collected including 11 new county records bringing the Greene county list from 43 to 54

Apple Cultivar by Rootstock Trial

In addition to production potential and tree size control, tolerance to environmental stress is an important consideration in selecting an apple rootstock. In Iowa, rootstocks need to exhibit good winter cold tolerance to be considered for use in orchards. In 1992, a cultivar by rootstock study was established at the Western Research and Demonstration (R&D) Farm to evaluate how rootstocks performed on loess soils that are unique to the area. The trial evaluated the performance of three apple cultivars (Smoothee Golden Delicious, Empire, and Nured Jonathan) on seven commercially available rootstocks (seedling, MM.111, MM.106, M.7 EMLA, M.26 EMLA, M.9 EMLA, and Mark) trained to a central leader system. The study was conducted for 10 growing seasons, and the results on growth and production characteristics of the trees were summarized in the 2001 Annual Fruit and Vegetable Progress Report (FG-601) and the 2001 Annual Progress Report for the Western R&D Farm (ISRF01-10). This report summarizes the relative cold tolerance of the cultivars on the seven rootstocks