Review Of Environmental Effects Research Articles

Niche differentiation in rotifer cryptic species complexes: a review of environmental effects

AbstractAdaptation to different ecological niches is considered one of the main drivers of species diversification, also in cryptic species complexes, notwithstanding their morphological stasis. We here review all the published information on ecological differentiation within cryptic species complexes within the phylum Rotifera. We found 177 instances of cryptic species identified genetically, published in 101 papers. Only a subset of the papers contained available information on ecological differences and only for two of the 54 known complexes, namely Brachionus calyciflorus s.l. and Brachionus plicatilis s.l., sufficient data were available for analyses of ecological differences. For the B. calyciflorus complex, B. fernandoi consistently occurred at a significantly lower temperature than the other species in the complex; no differences were found for other environmental variables. For the B. plicatilis complex, B. paranguensis occurred in waters with higher pH than the other species; no differences were found for other environmental variables. These results, even if preliminary and based on scattered information, reveal that adaptation to different ecological niches exists also between closely related species. Our aim is to showcase this interesting field of research spurring further detailed studies to focus on the mechanisms of ecological speciation using rotifer cryptic species as a model system.

Periodic Graphics: Sunscreen and coral reef damage

Chemical educator and Compound Interest blogger Andy Brunning reveals how sunscreens damage coral reefs To download a pdf of this article, visit http://cenm.ag/coralreefs References used to create this graphic: Impacts of sunscreens on coral reefs Review of environmental effects of oxybenzone and other sunscreen active ingredientsSunscreen bans – coral reefs and skin cancer A collaboration between C&EN and Andy Brunning, author of the popular graphics blog Compound Interest To see more of Brunning’s work, go to compoundchem.com. To see all of C&EN’s Periodic Graphics, visit http://cenm.ag/periodicgraphics.

Size distributions of 3–10 nm atmospheric particles: implications for nucleation mechanisms

The formation of new atmospheric particles by gas–to–particle conversion leads to enhanced concentrations of nanoparticles. We have studied the formation and growth of new particles in urban Atlanta and in the remote atmosphere in locations ranging from the North Pole to Mauna Loa, Tasmania and the South Pole. Key to this work was our development of new measurement techniques for freshly formed nucleation mode particles between 3 and 10 nm. In this paper we show that measured aerosol size distributions in the 3–10 nm diameter range often increase with decreasing size down to our minimum detectable size of 3 nm, presumably because nucleation was occurring during the measurement. Furthermore, we show that the Atlanta nucleation mode size distributions are consistent with a collision–controlled nucleation process in which accommodation coefficients for all collisions between condensing molecules and molecular clusters and between molecular clusters are assumed to be equal to one, and in which evaporation from molecular clusters is neglected, as would be expected for a highly supersaturated vapour.

Review of Environmental Effects in Intermetallics

AbstractThe recent progress made in our understanding of the phenomenology and mechanisms of environmental embrittlement in ordered intermetallics is reviewed by considering two model alloy systems of the L12 and B2 crystal classes (Ni3Al and FeAl). The poor ductility commonly encountered when these alloys are tensile tested in ambient air is due mainly to environmental embrittlement, in the absence of which, both alloys are now known to be quite ductile. Both H2O and H2, at levels found in ordinary ambient air, are found to cause environmental embrittlement, with the former usually more deleterious. In the case of H2O, the micromechanism involves reaction with the intermetallic to form an oxide (or hydroxide) and simultaneous generation of atomic hydrogen which then enters the metal and causes embrittlement. In the case of H2, on the other hand, atomic hydrogen is generated as a result of the dissociation of physisorbed hydrogen molecules on the intermetallic surfaces. Consistent with the proposed embrittlement mechanism, ductility is found to increase with decreasing amounts of H2O (or H2) in the test environment, increasing strain rate, and decreasing (or increasing) temperature. Environmental embrittlement in Ni3Al (and other L12 alloys) occurs predominantly intergranularly, whereas in FeAl (and other B2 alloys) it can also occur transgranularly—presumably because diffusion of hydrogen is fast enough through the bulk in the more open B2 structure but only so along grain boundaries in the L12 structure. Microalloying with B, which segregates strongly to the grain boundaries, can overcome environmental embrittlement in L12 alloys, but not in B2 alloys; in the latter, alloying additions probably have to be added at significantly higher (macroalloy) levels to affect the bulk properties. In neither alloy is environmental embrittlement the sole source of brittleness: depending on the alloy stoichiometry, and grain boundary character, a given grain boundary may be intrinsically weaker (or stronger) than the bulk, thereby influencing overall ductility.