Hierarchical Calcite Crystals with Occlusions of a Simple Polyelectrolyte Mimic Complex Biomineral Structures

Biominerals are complex inorganic‐organic structures that often show excellent mechanical properties. Here a bio‐inspired study of a remarkably simple synthetic system is presented in which only one charged polymer additive (poly(sodium 4‐styrenesulfonate)) is able to induce hierarchical structuring of calcite similar to biominerals. The interaction of the negatively charged polymer with the nucleation and growth of the mineral, in particular via selective adsorption to internal and external (001) facets of the calcite lattice, implies structural features from the micrometer down to the nanometer level. The crystals exhibit a distinct rounded morphology and a controlled orientation. Moreover, the polymer molecules are occluded within the crystals with different concentrations in well‐defined regions. This leads to the induction of a mesoscale structure based on 100 nm sized mineral building blocks with granular substructure and rough surface, as well as small modifications of the crystallographic structure. Such a combination of hierarchically organized structural features has previously only been reported for biogenic calcite, which is typically grown in a complex process involving multiple organic additives. It is also shown that the organic occlusions in the calcite‐PSS hybrid crystals strongly affect the mechanical performance, as known for some biominerals.     

Bioreactivity of leachate from municipal solid waste landfills - assessment of toxicity

With the UK producing 400 million tonnes of waste each year, the problem of waste disposal is recognised as one of the most serious environmental problems facing the nation. Of this, over 35 million tonnes is municipal waste, largely derived from households, but also includes some commercial and industrial waste. There are strong national and international concerns about the possible adverse health effects of living in the vicinity of municipal waste landfills. An understanding of the ranges of toxicity of landfill emissions is crucial to determine the degree of concern we should have about the potential effects they could have upon nearby populations and the surrounding environment. Leachates from three different types of landfills have been collected and screened for their potential to induce toxicity. Bioreactivity was measured by a plasmid DNA scission assay (PSA), and 2',7'-dichlorodihydrofluorescin fluorescence (DCFH). The results indicate that leachates cause damage to plasmid DNA in a dose-dependent manner and that toxicity varies between different types of landfills as well as within individual waste sites. Overall, the data implies that the complex chemistry involved in leachate formation has yet to be delineated in terms of the toxicological response.     

Sulfide removal in wastewater from petrochemical industries by autotrophic denitrification

An alternative flowchart for the biological removal of hydrogen sulfide from oil-refining wastewater is presented; autotrophic denitrification in a multi-stage treatment plant was utilized. A pilot-scale plant was fed with a mixture of the following constituents: (a) original wastewater from an oil refining industry (b), the effluent of the existing nitrification-stage treatment plant and (c) sulfide in the form of Na2S. Anoxic sulfide to sulfate oxidation, with nitrate as a terminal electron acceptor, proved very successful, as incoming concentrations of 110 mg S2-/L were totally converted to SO(4)2-. At complete denitrification, the concentration of S2- in the reactor effluent was less than 0.1mg/L. Fluctuating S2- concentration in the feed could be tolerated without any problems, as the accumulated sulfide in the effluent of the denitrification stage is oxidized aerobically in a subsequent activated-sludge treatment stage. This alternative new treatment scheme was further introduced at the refinery's wastewater processing plant. Thus, complete H2S removal is now accomplished by the combination of the proposed biological method and the existing stripping with CO2. As a result, stripping, and thus its cost, is reduced by 70%.     

Colorimetric sensor arrays for volatile organic compounds

The development of a low-cost, sensitive colorimetric sensor array for the detection and identification of volatile organic compounds (VOCs) is reported. Using an array composed of chemoresponsive dyes, enormous discriminatory power is possible in a simple device that can be imaged easily with an ordinary flatbed scanner. Excellent differentiation of closely related organic compounds can be achieved, and a library of 100 VOCs is presented. The array discriminates among VOCs by probing a wide range of intermolecular interactions, including Lewis acid/base, Br?nsted acid/base, metal ion coordination, hydrogen bonding, and dipolar interactions. Importantly, by proper choice of dyes and substrate, the array is essentially nonresponsive to changes in humidity.     

Oral contraceptives and androgenicity: Influences on visuospatial task performance in younger individuals.

The current study investigated whether the androgenic activity of oral contraceptives (OC) mediates performance on sexually dimorphic cognitive tasks in 155 younger individuals. Participants were categorized by hormonal contraceptive use (user vs. nonuser) and the androgenic activity of each OC (OC generation). OC generation was determined based on previous research in which users are grouped based on the type of progestin contained in each OC. Cognitive tasks included the mental rotation task (MRT) and a recognition memory task. In addition, we examined the correlates of both menstrual cycle phase and OC use, such as mood, premenstrual syndrome, depression, blood pressure, and body fat using standardized measures. The main result was that OC androgenicity influenced MRT performance. Second generation OCs are the most androgenic. Thus, MRT performance was best in these OC users as compared to third generation users, Yasmin users and nonusers. On the other hand, Yasmin, a newer generation of OC, contains an "antiandrogenic" progestin, dropirenone. Yasmin users not only performed more poorly on the MRT in comparison to second and third generation pill users, but they performed significantly worse than OC nonusers. Results show that the androgenic activity in OCs influences MRT performance in the presence of static estrogen levels. Overall, the resulting pattern is consistent with a broad range of results demonstrating that visuospatial performance may be enhanced in women who are exposed to androgenic treatments. Furthermore, visuospatial performance is hindered with the introduction of antiandrogenic preparations. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Analyse der Granat?pfel

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Referate

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Ueber die Verwerthung von Kakaoschalen

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