Adaptability of lactic acid bacteria and yeasts to sourdoughs prepared from cereals, pseudocereals and cassava and use of competitive strains as starters

The adaptability of lactic acid bacteria (LAB) and yeasts to sourdoughs prepared from cereals, pseudocereals and cassava was investigated using PCR-DGGE and bacteriological culture combined with rRNA gene sequence analysis. Sourdoughs were prepared either from flours of the cereals wheat, rye, oat, barley, rice, maize, and millet, or from the pseudocereals amaranth, quinoa, and buckwheat, or from cassava, using a starter consisting of various species of LAB and yeasts. Doughs were propagated until a stable microbiota was established. The dominant LAB and yeast species were Lactobacillus fermentum, Lactobacillus helveticus, Lactobacillus paralimentarius, Lactobacillus plantarum, Lactobacillus pontis, Lactobacillus spicheri, Issatchenkia orientalis and Saccharomyces cerevisiae. The proportion of the species within the microbiota varied. L. paralimentarius dominated in the pseudocereal sourdoughs, L. fermentum, L. plantarum and L. spicheri in the cassava sourdough, and L. fermentum, L. helveticus and L. pontis in the cereal sourdoughs. S. cerevisiae constituted the dominating yeast, except for quinoa sourdough, where I. orientalis also reached similar counts, and buckwheat and oat sourdoughs, where no yeasts could be detected. To assess the usefulness of competitive LAB and yeasts as starters, the fermentations were repeated using flours from rice, maize, millet and the pseudocereals, and by starting the dough fermentation with selected dominant strains. At the end of fermentation, most of starter strains belonged to the dominating microbiota. For the rice, millet and quinoa sourdoughs the species composition was similar to that of the prior fermentation, whereas in the other sourdoughs, the composition differed.     

Comparative studies on the in-ground and above-ground durability of European oak heartwood (Quercus petraea Liebl. and Quercus robur L.)

The durability of European oak (Quercus petraea Liebl. and Quercus robur L.) is controversially discussed since a long time. While it is classified as a “durable” timber species (durability class 2, according to EN 350-2), results from different studies indicated a lower durability. Therefore comparative studies with sessile oak and English oak were carried out including laboratory resistance tests against different basidiomycetes, soil box tests against soft rot and other soil-inhabiting micro-organisms, as well as in-ground and above-ground field trials at different test sites. Both oak species were rated “non-durable” (durability class 5, DC 5) in soil box tests and in-ground field trials and “slightly durable” (DC 4) in above-ground field trials. Solely results from laboratory tests with pure basidiomycete cultures led to partly better estimates (“very durable” to “moderately durable” DC 1-3), but did not represent the organisms responsible for decay in the field. For oak, EN 350-2 reflects only laboratory results but not the performance of the material in real field situations.     

Variability and uncertainty in life cycle assessment models for greenhouse gas emissions from Canadian oil sands production

Because of interest in greenhouse gas (GHG) emissions from transportation fuels production, a number of recent life cycle assessment (LCA) studies have calculated GHG emissions from oil sands extraction, upgrading, and refining pathways. The results from these studies vary considerably. This paper reviews factors affecting energy consumption and GHG emissions from oil sands extraction. It then uses publicly available data to analyze the assumptions made in the LCA models to better understand the causes of variability in emissions estimates. It is found that the variation in oil sands GHG estimates is due to a variety of causes. In approximate order of importance, these are scope of modeling and choice of projects analyzed (e.g., specific projects vs industry averages); differences in assumed energy intensities of extraction and upgrading; differences in the fuel mix assumptions; treatment of secondary noncombustion emissions sources, such as venting, flaring, and fugitive emissions; and treatment of ecological emissions sources, such as land-use change-associated emissions. The GHGenius model is recommended as the LCA model that is most congruent with reported industry average data. GHGenius also has the most comprehensive system boundaries. Last, remaining uncertainties and future research needs are discussed.     

Role of morphological growth state and gene expression in Desulfovibrio africanus strain Walvis Bay mercury methylation

The biogeochemical transformations of mercury are a complex process, with the production of methylmercury, a potent human neurotoxin, repeatedly demonstrated in sulfate- and Fe(III)-reducing as well as methanogenic bacteria. However, little is known regarding the morphology, genes, or proteins involved in methylmercury generation. Desulfovibrio africanus strain Walvis Bay is a Hg-methylating δ-proteobacterium with a sequenced genome and has unusual pleomorphic forms. In this study, a relationship between the pleomorphism and Hg methylation was investigated. Proportional increases in the sigmoidal (regular) cell form corresponded with increased net MeHg production but decreased when the pinched cocci (persister) form became the major morphotype. D. africanus microarrays indicated that the ferrous iron transport genes (feoAB), as well as ribosomal genes and several genes whose products are predicted to have metal binding domains (CxxC), were up-regulated during exposure to Hg in the exponential phase. Whereas no specific methylation pathways were identified, the finding that Hg may interfere with iron transport and the correlation of growth-phase-dependent morphology with MeHg production are notable. The identification of these relationships between differential gene expression, morphology, and the growth-phase dependence of Hg transformations suggests that actively growing cells are primarily responsible for methylation, and so areas with ample carbon and electron-acceptor concentrations may also generate a higher proportion of methylmercury than more oligotrophic environments. The observation of increased iron transporter expression also suggests that Hg methylation may interfere with iron biogeochemical cycles.     

Electromagnetic response of superconductors with pinned vortices

Some features of the vortex lattice in type-II superconductors and of its pinning and thermally activated depinning are given. Manipulation of a pinned single vortex by the tip of a Magnetic Force Microscope is mentioned. Statics and dynamics of pinned vortices in thick and thin strips and disks, and in rectangular plates, can be computed from continuum theory.     

EUV光源研发的新突破

在32nm技术节点以下时,尽管极紫外（EUV）光刻技术已被视为主流的光刻生产技术解决方案,但是如何研发一套可靠、高性能EUV光源系统仍然是摆在业界面前的一道难题。此文将着重介绍了基于触发模式、输出功率达到100W的光源系统。     

Paramagnetic Meissner Transitions in Pb Films and the?Vortex Compression Model

The magnetic flux exclusion known as Meissner effect resulting from a perfectly diamagnetic susceptibility ??=?1 is one of the defining features of type-I superconductivity. More recently some materials have been reported to undergo a transition to a paramagnetic state as they are cooled through their superconducting transition temperature (Svedlindh et?al. in Physica?C, pp.?162?C164, 1989; Li in Phys. Rep. 376:133?C223, 2003). This is known as the Paramagnetic Meissner Effect (PME). Here we report the observation of a transition from the Meissner state to a PME state in thin Pb films. We go on to show how simple modifications to the vortex compression model developed by Koshelev and Larkin (Phys. Rev.?B 52:13559?C13562, 1995) yield magnetization-vs-temperature curves in good qualitative agreement with the magnetization curves reported in the experiment.