668 research outputs found
Desulfotomaculum arcticum sp nov., a novel spore-formin, moderately thermophilic, sulfate-reducing bacterium isolated from a permanently cold fjord sediment of Svalbard
Strain 15T is a novel spore-forming, sulfate-reducing bacterium isolated from a permanently cold fjord sediment of Svalbard. Sulfate could be replaced by sulfite or thiosulfate. Hydrogen, formate, lactate, propionate, butyrate, hexanoate, methanol, ethanol, propanol, butanol, pyruvate, malate, succinate, fumarate, proline, alanine and glycine were used as electron donors in the presence of sulfate. Growth occurred with pyruvate as sole substrate. Optimal growth was observed at pH 7·1–7·5 and concentrations of 1–1·5 % NaCl and 0·4 % MgCl2. Strain 15T grew between 26 and 46·5 °C and optimal growth occurred at 44 °C. Therefore, strain 15T apparently cannot grow at in situ temperatures of Arctic sediments from where it was isolated, and it was proposed that it was present in the sediment in the form of spores. The DNA G+C content was 48·9 mol%. Strain 15T was most closely related to Desulfotomaculum thermosapovorans MLFT (93·5 % 16S rRNA gene sequence similarity). Strain 15T represents a novel species, for which the name Desulfotomaculum arcticum sp. nov. is proposed. The type strain is strain 15T (=DSM 17038T=JCM 12923T)
Zero delay synchronization of chaos in coupled map lattices
We show that two coupled map lattices that are mutually coupled to one
another with a delay can display zero delay synchronization if they are driven
by a third coupled map lattice. We analytically estimate the parametric regimes
that lead to synchronization and show that the presence of mutual delays
enhances synchronization to some extent. The zero delay or isochronal
synchronization is reasonably robust against mismatches in the internal
parameters of the coupled map lattices and we analytically estimate the
synchronization error bounds.Comment: 9 pages, 9 figures ; To appear in Phys. Rev.
Encoding difficulty promotes postlearning changes in sleep spindle activity during napping
Learning-dependent increases in sleep spindle density have been reported during nocturnal sleep immediately after the learning session. Here, we investigated experience-dependent changes in daytime sleep EEG activity after declarative learning of unrelated word pairs. At weekly intervals, 13 young male volunteers spent three 24 h sessions in the laboratory under carefully controlled homeostatic and circadian conditions. At approximately midday, subjects performed either one of two word-pair learning tasks or a matched nonlearning control task, in a counterbalanced order. The two learning lists differed in the level of concreteness of the words used, resulting in an easier and a more difficult associative encoding condition, as confirmed by performance at immediate cued recall. Subjects were then allowed to sleep for 4 h; afterward, delayed cued recall was tested. Compared with the control condition, sleep EEG spectral activity in the low spindle frequency range and the density of low-frequency sleep spindles (11.25-13.75 Hz) were both significantly increased in the left frontal cortex after the difficult but not after the easy encoding condition. Furthermore, we found positive correlations between these EEG changes during sleep and changes in memory performance between pre-nap and post-nap recall sessions. These results indicate that, like during nocturnal sleep, daytime sleep EEG oscillations including spindle activity are modified after declarative learning of word pairs. Furthermore, we demonstrate here that the nature of the learning material is a determinant factor for sleep-related alterations after declarative learning
Nap sleep spindle correlates of intelligence
Contains fulltext :
152518.pdf (publisher's version ) (Open Access)Sleep spindles are thalamocortical oscillations in non-rapid eye movement (NREM) sleep, that play an important role in sleep-related neuroplasticity and offline information processing. Several studies with full-night sleep recordings have reported a positive association between sleep spindles and fluid intelligence scores, however more recently it has been shown that only few sleep spindle measures correlate with intelligence in females, and none in males. Sleep spindle regulation underlies a circadian rhythm, however the association between spindles and intelligence has not been investigated in daytime nap sleep so far. In a sample of 86 healthy male human subjects, we investigated the correlation between fluid intelligence and sleep spindle parameters in an afternoon nap of 100 minutes. Mean sleep spindle length, amplitude and density were computed for each subject and for each derivation for both slow and fast spindles. A positive association was found between intelligence and slow spindle duration, but not any other sleep spindle parameter. As a positive correlation between intelligence and slow sleep spindle duration in full-night polysomnography has only been reported in females but not males, our results suggest that the association between intelligence and sleep spindles is more complex than previously assumed
Endless diamond wire saw for monocrystalline silicon cutting
The multi-wire sawing of silicon using diamond coated wire is an important process in the semiconductor and photovoltaic industry. The process is performed by pushing the silicon ingot against a wire web that moves forwards and backwards. As the feed direction of the wire changes many times and the cutting speed is not constant, a proper investigation of the cutting process is very difficult to be performed. Aiming to experimentally investigate the multi-wire sawing of monocrystalline silicon (mono-Si), this work proposes a new test rig. For that, the requirements list is defined, and based on that, several conceptual solutions are
proposed. The final solution is an endless wire saw that uses aerostatic bearing technology on its slides and rotatory bearings. Features of the built test rig are presented, as well as some results of experiments on process characterization and tracking the same diamond grains for
wear analysis. The objective of tracking the same diamond grains for wear analysis is accomplished with the experimental setup
- …