Reversible concerted ligand substitution at alternating metal sites in an extended solid

We report a synthetic material, [Co2(bipy)3(SO4)2(H2O)2](bipy) (CH3OH), (1, where bipy = 4,4'-bipyridyl) that contains discrete reactive and inert structural motifs that undergo a reversible substitution reaction involving the concerted and spatially controlled introduction of bipyridine and methanol molecules at the reactive sites. This reaction defines the pore geometry of the resulting open-framework structure and controls the manner in which this structure sorbs small molecules. The molecules involved in the reaction are positioned by an array of well-defined interactions during their path to binding to the metal centers.     

Influence of phylogeny on fungal community assembly and ecosystem functioning

Ecology seeks to explain species coexistence and its functional consequences, but experimental tests of mechanisms that simultaneously account for both processes are difficult. We used an experimental mycorrhizal plant system to test whether functional similarity among closely related species (phylogenetic conservatism) can drive community assembly and ecosystem functioning. Communities were constructed with the same number of fungal species, but after 1 year of growth, realized species richness was highest where the starting species were more distantly related to each other. Communities with high realized species richness also stimulated plant productivity more than those with low realized species richness. Our findings suggest that phylogenetic trait conservatism can promote coexistence because of reduced competition between distinct evolutionary lineages and enhance ecosystem function because of functional complementarity among those same lineages.     

Metal pollutants in agricultural soils and the St. Louis urban rainfall anomaly

The existence of a rainfall anomaly downwind of the St. Louis urban-industrial areas prompted a survey of area soils for elevated heavy metal concentrations. The goals of this work were to measure concentrations of Zn, Cd, and Ph, and to evaluate the role of the urban rainfall anomaly in their accumulation, in potentially-affected soils. Samples from three soil layers were collected from agricultural fields at 21 sites along two NE-SW transects. The samples were analyzed for pH, texture, cation exchange capacity, and total organic carbon, in addition to the three metals. The highest metal concentrations were observed near Granite City, Illinois, and coincided with an area of maximum Zn deposition in rain found in an earlier study. Only slight increases of the metals over background were found in the area of rainfall anomaly. Present rates of atmospheric deposition can account for these slightly elevated metal concentrations. However, the maximum concentrations found near Granite City cannot be accounted for by present atmospheric deposition rates. Other kinds of sources, or larger atmospheric deposition rates, perhaps during the operation of a local Zn smelter which closed about 1960, must have contributed.     

Transcription regulation through promoter-proximal pausing of RNA polymerase II

Recent work has shown that the RNA polymerase II enzyme pauses at a promoter-proximal site of many genes in Drosophila and mammals. This rate-limiting step occurs after recruitment and initiation of RNA polymerase II at a gene promoter. This stage in early elongation appears to be an important and broadly used target of gene regulation.     

Experienced saxophonists learn to tune their vocal tracts

Acousticians have long debated whether and how the resonances of the vocal tract are involved in the playing of clarinet and saxophone. We measured the resonances of saxophonists' vocal tracts directly while they played. Over most of the instrument's range, there is no simple relation between tract resonances and the note played, and the tract resonances varied among players. In the high (altissimo) range, a strong resonance of the tracts of professional saxophonists was systematically tuned slightly above the desired note. Amateurs, who did not tune a strong resonance, were unable to play notes in the altissimo range.     

Waste water renovation through soil percolation

A laboratory experiment simulating high-rate effluent renovation by soil percolation involved leaching secondary sewage effluent through columns of three differing soils. Analyses of P in 22 leachate collections and distribution of both organic and inorganic P in column sections revealed the mechanisms of P removal, the influence of differing soil properties, and the effect of continuous utilization. Renovation of effluent P was greatest with percolation through columns of acid Milner soil which contains abundant Al and Fe, and, although Squilax soil removed more P from initial leachings due to its higher exchangeable Ca content, Glenmore soil was the more suitable of these two alkaline soils over the long term. The leachate N0₀3-N levels were lower than the original N0₃-N content of effluent for the first ten leachings but N0₃-N enrichment occurred for the last effluent percolations through all three soils. Analyses of Ca, Mg, K, and Na in leachates and soil columns indicated losses of exchangeable cations from the calcareous Squilax and Glenmore soils enriched effluent content and the accumulation of the cations in the acid soil reduced concentrations in effluent that passed through Milner soil.     

Management of the Northern Chesapeake Bay American shad fishery

The Shad fisheries of the Chesapeake Bay in Maryland have been declining since an 1897 peak of 7860 × 10³kg. No periods of stability have been recorded. Data are presented to trace the decline not only as a function of specific areas within the Northern Chesapeake Bay but also in terms of environmental problems and recruitment overfishing.The problem is related to improving the commercial fishing yield. An estimation of a maximum effort of 200,000 man-hours is suggested if a stable yield is to be approached. Methods for obtaining this goal include alternating of closed fishing areas, adoption of rest days, enforcement of fisheries regulations and reduction of the number of metres of gill net used per fisherman.     

Deep mixing of 3He: reconciling Big Bang and stellar nucleosynthesis

Low-mass stars, approximately 1 to 2 solar masses, near the Main Sequence are efficient at producing the helium isotope 3He, which they mix into the convective envelope on the giant branch and should distribute into the Galaxy by way of envelope loss. This process is so efficient that it is difficult to reconcile the low observed cosmic abundance of 3He with the predictions of both stellar and Big Bang nucleosynthesis. Here we find, by modeling a red giant with a fully three-dimensional hydrodynamic code and a full nucleosynthetic network, that mixing arises in the supposedly stable and radiative zone between the hydrogen-burning shell and the base of the convective envelope. This mixing is due to Rayleigh-Taylor instability within a zone just above the hydrogen-burning shell, where a nuclear reaction lowers the mean molecular weight slightly. Thus, we are able to remove the threat that 3He production in low-mass stars poses to the Big Bang nucleosynthesis of 3He.