The environmental distribution of Dehalococcoides group organisms and their association with chloroethenecontaminated sites were examined. Samples from 24 chloroethene-dechlorinating sites scattered throughout North America and Europe were tested for the presence of members of the Dehalococcoides group by using a PCR assay developed to detect Dehalococcoides 16S rRNA gene (rDNA) sequences. Sequences identified by sequence analysis as sequences of members of the Dehalococcoides group were detected at 21 sites. Full dechlorination of chloroethenes to ethene occurred at these sites. Dehalococcoides sequences were not detected in samples from three sites at which partial dechlorination of chloroethenes occurred, where dechlorination appeared to stop at 1,2-cis-dichloroethene. Phylogenetic analysis of the 16S rDNA amplicons confirmed that Dehalococcoides sequences formed a unique 16S rDNA group. These 16S rDNA sequences were divided into three subgroups based on specific base substitution patterns in variable regions 2 and 6 of the Dehalococcoides 16S rDNA sequence. Analyses also demonstrated that specific base substitution patterns were signature patterns. The specific base substitutions distinguished the three sequence subgroups phylogenetically. These results demonstrated that members of the Dehalococcoides group are widely distributed in nature and can be found in a variety of geological formations and in different climatic zones. Furthermore, the association of these organisms with full dechlorination of chloroethenes suggests that they are promising candidates for engineered bioremediation and may be important contributors to natural attenuation of chloroethenes.The chloroethenes tetrachloroethene (PCE) and trichloroethene (TCE) are commonly used organic solvents and degreasing agents. As a result of past disposal practices and spills, chloroethenes are now widely distributed in the environment and are found in many sediments, soils, groundwater aquifers, and subsurface environments throughout the world (13,21,28). Traditional approaches to groundwater remediation practices, such as pump and treat methods, have been shown to be ineffective and costly when applied to chlorinated solvent plumes (2a, 2c, 23). Therefore, there is a need for microbebased remediation approaches that could provide an inexpensive way to clean up chlorinated solvent contamination.Chloroethene solvents were previously believed to be resistant to degradation by microorganisms. There now is rapidly accumulating laboratory and field evidence that microorganisms can transform chloroethenes to nontoxic products under a variety of environmental conditions (3, 8-10, 12, 15, 20, 22, 27, 28, 30, 31, 35). Maymó-Gatell et al. have isolated an organism from an anaerobic dechlorinating laboratory culture inoculated with municipal sewage sludge, which fully dechlorinates chlorinated ethenes (25,26). This organism, Dehalococcoides ethenogenes strain 195, was shown to meet its energy needs, which are essential for growth, by a process known as dehalore...

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The normally weak polarization force density, exerted on insulating dielectric liquids by a nonuniform electric field, is enhanced if high pressures are used. The result is a new class of orientation and guiding structures for liquids: electric "walls" contain the liquid. The dielectric siphon is an example of such a system. A simple laminar flow model for the device successfully describes the operation of the siphon.

Experiments with two electrohydrodynamic heat pipes are reported. Both devices employ an electromechanical flow structure for axial liquid flow and a capillary wicking structure for (i) collection of condensed liquid at the cooled end and (ii) distribution of this liquid at the heated end. One device has circumferential grooving for the capillary structure and the other has feltmetal wicking. The experiments successfully demonstrate the electrohydrodynamic heat pipe concept. Compatibility of the two circumferential wick structures with an axial electromechanical flow structure is also demonstrated. A significant mismatch of the capillary groove and electrohydrodynamic pumping capabilities results in severe hydrodynamic burn-out limiting in the first heat pipe. Both devices have very poor over-all thermal conductances of the order of 1–2 W/°C, reflecting the generally poor heat-transfer properties of the dielectric working fluids required in electrohydrodynamic heat pipes.

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