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The present research is an experimental study of pool boiling behavior using flat, microporous-enhanced square heater surfaces immersed in saturated FC-72. Flush-mounted, 2 ㎝ × 2 ㎝ and 5 ㎝ × 5 ㎝ copper surfaces were tested and compared to a 1 ㎝ × 1 ㎝ copper surface that was previously investigated. Heater surface orientation and size effects on pool boiling performance was investigated under increasing and decreasing heat flux conditions for two different surface micro-geometries: plain and microporous coated. Results of the plain surface testing showed that the nucleate boiling performance is dependent on heater orientation. The nucleate boiling curves of the microporous coated surfaces were found to collapse to one curve showing insensitivity to heater orientation. The effects of heater size and orientation angle on CHF were found to be significant for both the plain and microporous coated surfaces.
<P>The polyphasic approach used today in the taxonomy and systematics of the <I>Bacteria</I> and <I>Archaea</I> includes the use of phenotypic, chemotaxonomic and genotypic data. The use of 16S rRNA gene sequence data has revolutionized our understanding of the microbial world and led to a rapid increase in the number of descriptions of novel taxa, especially at the species level. It has allowed in many cases for the demarcation of taxa into distinct species, but its limitations in a number of groups have resulted in the continued use of DNA–DNA hybridization. As technology has improved, next-generation sequencing (NGS) has provided a rapid and cost-effective approach to obtaining whole-genome sequences of microbial strains. Although some 12 000 bacterial or archaeal genome sequences are available for comparison, only 1725 of these are of actual type strains, limiting the use of genomic data in comparative taxonomic studies when there are nearly 11 000 type strains. Efforts to obtain complete genome sequences of all type strains are critical to the future of microbial systematics. The incorporation of genomics into the taxonomy and systematics of the <I>Bacteria</I> and <I>Archaea</I> coupled with computational advances will boost the credibility of taxonomy in the genomic era. This special issue of <I>International Journal of Systematic and Evolutionary Microbiology</I> contains both original research and review articles covering the use of genomic sequence data in microbial taxonomy and systematics. It includes contributions on specific taxa as well as outlines of approaches for incorporating genomics into new strain isolation to new taxon description workflows.</P>
Walsh, Matthew R.,Rainey, J. Daniel,Lafond, Patrick G.,Park, Da-Hye,Beckham, Gregg T.,Jones, Michael D.,Lee, Kun-Hong,Koh, Carolyn A.,Sloan, E. Dendy,Wu, David T.,Sum, Amadeu K. Royal Society of Chemistry 2011 Physical chemistry chemical physics Vol.13 No.44
<P>Interest in describing clathrate hydrate formation mechanisms spans multiple fields of science and technical applications. Here, we report findings from multiple molecular dynamics simulations of spontaneous methane clathrate hydrate nucleation and growth from fully demixed and disordered two-phase fluid systems of methane and water. Across a range of thermodynamic conditions and simulation geometries and sizes, a set of seven cage types comprises approximately 95% of all cages formed in the nucleated solids. This set includes the ubiquitous 5<SUP>12</SUP> cage, the 5<SUP>12</SUP>6<SUP><I>n</I></SUP> subset (where <I>n</I> ranges from 2–4), and the 4<SUP>1</SUP>5<SUP>10</SUP>6<SUP><I>n</I></SUP> subset (where <I>n</I> also ranges from 2–4). Transformations among these cages occur <I>via</I> water pair insertions/removals and rotations, and may elucidate the mechanisms of solid–solid structural rearrangements observed experimentally. Some consistency is observed in the relative abundance of cages among all nucleation trajectories. 5<SUP>12</SUP> cages are always among the two most abundant cage types in the nucleated solids and are usually the most abundant cage type. In all simulations, the 5<SUP>12</SUP>6<SUP><I>n</I></SUP> cages outnumber their 4<SUP>1</SUP>5<SUP>10</SUP>6<SUP><I>n</I></SUP> counterparts with the same number of water molecules. Within these consistent features, some stochasticity is observed in certain cage ratios and in the long-range ordering of the nucleated solids. Even when comparing simulations performed at the same conditions, some trajectories yield swaths of multiple adjacent sI unit cells and long-range order over 5 nm, while others yield only isolated sI unit cells and little long-range order. The nucleated solids containing long-range order have higher 5<SUP>12</SUP>6<SUP>2</SUP>/5<SUP>12</SUP> and 5<SUP>12</SUP>6<SUP>3</SUP>/4<SUP>1</SUP>5<SUP>10</SUP>6<SUP>2</SUP> cage ratios when compared to systems that nucleate with little long-range order. The formation of multiple adjacent unit cells of sI hydrate at high driving forces suggests an alternative or addition to the prevailing hydrate nucleation hypotheses which involve formation through amorphous intermediates.</P> <P>Graphic Abstract</P><P>The dominant cages of clathrates are classified and the formation of multiple sI unit cells is reported from large-scale simulations. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c1cp21899a'> </P>
<P>As scholars have observed, government agencies have ambiguous goals. Very few large sample empirical studies, however, have tested such assertions and analysed variations among organizations in the characteristics of their goals. Researchers have developed concepts of organizational goal ambiguity, including ‘evaluative goal ambiguity’, and ‘priority goal ambiguity’, and found that these goal ambiguity variables related meaningfully to financial publicness (the degree of government funding versus prices or user charges), regulatory responsibility, and other variables. This study analyses the influence of the external political environment (external political authorities and processes) on goal ambiguity in government agencies; many researchers have analysed external influences on government bureaucracies, but very few have examined the effects on the characteristics of the organizations, such as their goals. This analysis of 115 US federal agencies indicates that higher ‘political salience’ to Congress, the president, and the media, relates to higher levels of goal ambiguity. A newly developed analytical framework for the analysis includes components for external environmental influences, organizational characteristics, and managerial influences, with new variables that represent components of the framework. Higher levels of political salience relate to higher levels of both types of goal ambiguity; components of the framework, however, relate differently to evaluative goal ambiguity than to priority goal ambiguity. The results contribute evidence of the viability of the goal ambiguity variables and the political environment variables. The results also show the value of bringing together concepts from organization theory and political science to study the effects of political environments on characteristics of government agencies.</P>