4,901 research outputs found
Tribute to Bessie, The Jalopy
Bessie was a good old Ford, even if she was of the 1924 vintage, with old-fashioned clincker tires and all the out-of-date accessories that made her comfortable like an old, old shoe
Preparation of an Epoxide Precursor for Palladium-Catalyzed Trimethylenemethane Cycloaddition
In order to produce a highly functionalized five-membered ring useful for further synthetic processes via palladium catalysis, a series of precursors need to be synthesized in order to form the epoxide used in cyclic formation. First, a trimethylsilane alcohol is synthesized from beta-methallyl alcohol. The alcohol will then be subjected to Swern oxidation conditions, forming a TMS aldehyde. The aldehyde prepared will then undergo epoxidation, forming the desired precursor for Palladium catalyzed cycloaddition. These reactions occur in good conversion, and a good amount of epoxide is being amassed for use in the palladium-catalyzed cycloaddition research
Synthesis of an Epoxide for TMM Cycloadditions
In order to produce a highly functionalized five-membered ring useful for further synthetic processes via Palladium catalysis, a series of precursors need to be synthesized in order to form the epoxide used in cyclic formation. First, a trimethylsilane alcohol is synthesized from beta-Methallyl alcohol. The alcohol will then be subjected to Swern oxidation conditions, forming a TMS aldehyde. The aldehyde prepared will then undergo epoxidation, forming the desired precursor for Palladium catalyzed cycloaddition. The Swern oxidation has yet to occur in good conversion due to sensitivity, but when performed using a model compound the oxidation, and epoxidation both worked to form a model epoxide precursor
Social Cash Transfers in Zambia: What Is Their Impact?
Social cash transfers (SCTs) have become increasingly popular in Sub-Saharan Africa, because growth-centred development policies have failed to reduce poverty. SCTs support the consumption of the poorest, and allow them to invest in human and other forms of capital that reduce the intergenerational transmission of poverty. (...)Social Cash Transfers in Zambia: What Is Their Impact?
A project and competition to design and build a simple heat exchanger
To address a declining interest in process engineering, a project to design and build a compact heat exchanger was initiated in the second year of a four-year, multidisciplinary degree programme in biotechnology. The heat exchangers had a double-pipe configuration and employed plastic outer pipes and copper inner pipes of various diameters. Designs produced ranged from coiled inner pipes to various multi-pass arrangements and were assessed on the basis of heat transfer achieved per unit mean temperature difference per unit cost. The project, which also formed the basis of a competition, was very well received by students and gave them hands-on experience of engineering design and construction, as well as team work, problem solving, engineering drawing and the use of simple tools. Based on the success of this project, a similar problem based learning approach will be initiated in the third year of the same degree programme and will focus on bioethanol production
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Sex and outcrossing in a sessile freshwater invertebrate
SUMMARY1. The freshwater bryozoan Cristatella mucedo, in common with other sessile, benthic freshwater taxa, has an unusual life history: sex occurs during a relatively brief period near the start of the growing season, and overwintering occurs in the form of asexually produced dormant propagules (statoblasts). Consistent observed heterozygosity (Ho) deficits in C. mucedo populations have previously suggested that inbreeding is common, although a possible contribution of a Wahlund effect to low Ho could not be discounted.
2. We have used microsatellite data in the first study based on codominant markers to genetically characterise maternal colonies and larval offspring of C. mucedo. The 'population' represented by the larvae was in Hardy–Weinberg equilibrium, which has previously been found in only one of 39 populations of C. mucedo. At least 64% of larvae were the products of outcrossing. We suggest that the unusual early timing of sex may be a strategy to maximise rates of outcrossing within populations of sessile freshwater invertebrate
Buckling of imperfect cylinders under axial compression
Donnell equations, Newton method, and numerical solution applied to buckling of imperfect cylinders under axial compressio
Lightweight composite reflector panels
The Hexel Corp. has produced additional composite panels, based on JPL designs, that: (1) have increased the panel size from 0.15 to 0.40 meters, (2) have improved the as-manufactured surface precision 3.0 to approx. 1.0 micron RMS, (3) have utilized different numbers of face sheet plys, (4) have improved face sheet fiber orientation, (5) have variations of aluminum honeycomb core cell size, (6) have combined graphite/epoxy (Gr/Ep) face sheets with E-glass honeycomb cores, and (7) have used standard aluminum core with face sheets composed of combinations of glass, Kevlar, and carbon fibers. Additionally, JPL has identified candidate alternate materials for the facesheets and core, modified the baseline polymer panel matrix material, and developed new concepts for panel composite cores. Dornier designed and fabricated three 0.6 meter Gr/Ep panels, that were evaluated by JPL. Results of both the Hexel and Dornier panel work were used to characterize the state-of-the-art for Gr/Ep mirrors
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