Исследование кристаллизации NaCl из водного раствора, находящегося в магнитном поле

In the context of developing single-site stereoselective post-metallocene catalysts, the case for isospecific styrene polymerization catalysts based on methylaluminoxane-activated group 4 metal bis(phenolato) complexes is summarized. In the context of developing single-site stereoselective post-metallocene catalysts, the case for isospecific styrene polymerization catalysts based on methylaluminoxane-activated group 4 metal bis(phenolato) complexes is summarized. Ligands derived from the 1,4-dithiabutanediyl-linked bis(phenol)s have been found to induce stereochemical rigidity by the presence of the hemi-labile sulfide donor functions. Isospecific styrene polymerization was achieved using easily accessible catalyst precursors of the type [MX 2(OC6H2-tBu2-4,6) 2S(CH2)2S] (M = Ti, Zr, Hf; X = Cl, O iPr, CH2Ph). Activating the dibenzyl titanium complex [Ti(CH2Ph)2(OC6H2- tBu2-4,6)2S(CH2)2S] with B(C6F5)3 and AliBu3, controlled isotactic polymerization became possible at lower temperatures. A remarkable dependence of both the activity and stereoselectivity on the ligand substitution pattern was observed. Analogous precursors with the 1,5-dithiapentanediyl-linked bis(phenolato) ligand gave syndiotactic polystyrene with lower activity. © 2004 Elsevier B.V. All rights reserved

Gravitomagnetism in teleparallel gravity

The assumption that matter charges and currents could generate fields, which are called, by analogy with electromagnetism, gravitoeletric and gravitomagnetic fields, dates from the origins of General Relativity (GR). On the other hand, the Teleparallel Equivalent of GR (TEGR), as a gauge theory, seems to be the ideal scenario to define these fields, based on the gauge field strength components. The purpose of the present work is to investigate the nature of the gravitational electric and magnetic fields in the context of the TEGR, where the tetrad formalism behind it seems to be more appropriated to deal with phenomena related to observers. As our main results, we have obtained, for the first time, the exact expressions for the gravito-electromagnetic fields for the Schwarzschild solution that in the linear approximation become the usual expected ones. To improve our understanding about these fields, we have also studied the geometry produced by a spherical rotating shell in slow motion and weak field regime. Again, the expressions obtained are in complete agreement with those of electromagnetism.Comment: 25 pages. Submitted to International Journal of Modern Physics D. Version 2: some new discussions, references adde

Watching TV news as a memory task -- brain activation and age effects

<p>Abstract</p> <p>Background</p> <p>Neuroimaging studies which investigate brain activity underlying declarative memory processes typically use artificial, unimodal laboratory stimuli. In contrast, we developed a paradigm which much more closely approximates real-life situations of information encoding.</p> <p>Methods</p> <p>In this study, we tested whether ecologically valid stimuli - clips of a TV news show - are apt to assess memory-related fMRI activation in healthy participants across a wide age range (22-70 years). We contrasted brain responses during natural stimulation (TV news video clips) with a control condition (scrambled versions of the same clips with reversed audio tracks). After scanning, free recall performance was assessed.</p> <p>Results</p> <p>The memory task evoked robust activation of a left-lateralized network, including primarily lateral temporal cortex, frontal cortex, as well as the left hippocampus. Further analyses revealed that - when controlling for performance effects - older age was associated with greater activation of left temporal and right frontal cortex.</p> <p>Conclusion</p> <p>We demonstrate the feasibility of assessing brain activity underlying declarative memory using a natural stimulation paradigm with high ecological validity. The preliminary result of greater brain activation with increasing age might reflect an attempt to compensate for decreasing episodic memory capacity associated with aging.</p

Investigating the impact of mindfulness meditation training on working memory: A mathematical modeling approach

We investigated whether mindfulness training (MT) influences information processing in a working memory task with complex visual stimuli. Participants were tested before (T1) and after (T2) participation in an intensive one-month MT retreat, and their performance was compared with that of an age- and education-matched control group. Accuracy did not differ across groups at either time point. Response times were faster and significantly less variable in the MT versus the control group at T2. Since these results could be due to changes in mnemonic processes, speed–accuracy trade-off, or nondecisional factors (e.g., motor execution), we used a mathematical modeling approach to disentangle these factors. The EZ-diffusion model (Wagenmakers, van der Maas, & Grasman, Psychonomic Bulletin & Review 14:(1), 3–22, 2007) suggested that MT leads to improved information quality and reduced response conservativeness, with no changes in nondecisional factors. The noisy exemplar model further suggested that the increase in information quality reflected a decrease in encoding noise and not an increase in forgetting. Thus, mathematical modeling may help clarify the mechanisms by which MT produces salutary effects on performance

Transient and sustained incentive effects on electrophysiological indices of cognitive control in younger and older adults

Preparing for upcoming events, separating task-relevant from task-irrelevant information and efficiently responding to stimuli all require cognitive control. The adaptive recruitment of cognitive control depends on activity in the dopaminergic reward system as well as the frontoparietal control network. In healthy aging, dopaminergic neuromodulation is reduced, resulting in altered incentive-based recruitment of control mechanisms. In the present study, younger adults (18–28 years) and healthy older adults (66–89 years) completed an incentivized flanker task that included gain, loss, and neutral trials. Event-related potentials (ERPs) were recorded at the time of incentive cue and target presentation. We examined the contingent negative variation (CNV), implicated in stimulus anticipation and response preparation, as well as the P3, which is involved in the evaluation of visual stimuli. Both younger and older adults showed transient incentive-based modulation of CNV. Critically, cue-locked and target-locked P3s were influenced by transient and sustained effects of incentives in younger adults, while such modulation was limited to a sustained effect of gain incentives on cue-P3 in older adults. Overall, these findings are in line with an age-related reduction in the flexible recruitment of preparatory and target-related cognitive control processes in the presence of motivational incentives

Diversity, Phylogeny and Expression Patterns of Pou and Six Homeodomain Transcription Factors in Hydrozoan Jellyfish Craspedacusta sowerbyi

Formation of all metazoan bodies is controlled by a group of selector genes including homeobox genes, highly conserved across the entire animal kingdom. The homeobox genes from Pou and Six classes are key members of the regulation cascades determining development of sensory organs, nervous system, gonads and muscles. Besides using common bilaterian models, more attention has recently been targeted at the identification and characterization of these genes within the basal metazoan phyla. Cnidaria as a diploblastic sister group to bilateria with simple and yet specialized organs are suitable models for studies on the sensory organ origin and the associated role of homeobox genes. In this work, Pou and Six homeobox genes, together with a broad range of other sensory-specific transcription factors, were identified in the transcriptome of hydrozoan jellyfish Craspedacusta sowerbyi. Phylogenetic analyses of Pou and Six proteins revealed cnidarian-specific sequence motifs and contributed to the classification of individual factors. The majority of the Craspedacusta sowerbyi Pou and Six homeobox genes are predominantly expressed in statocysts, manubrium and nerve ring, the tissues with sensory and nervous activities. The described diversity and expression patterns of Pou and Six factors in hydrozoan jellyfish highlight their evolutionarily conserved functions. This study extends the knowledge of the cnidarian genome complexity and shows that the transcriptome of hydrozoan jellyfish is generally rich in homeodomain transcription factors employed in the regulation of sensory and nervous functions

A point mutation in cpsE renders Streptococcus pneumoniae nonencapsulated and enhances its growth, adherence and competence.

BACKGROUND: The polysaccharide capsule is a major virulence factor of the important human pathogen Streptococcus pneumoniae. However, S. pneumoniae strains lacking capsule do occur. RESULTS: Here, we report a nasopharyngeal isolate of Streptococcus pneumoniae composed of a mixture of two phenotypes; one encapsulated (serotype 18C) and the other nonencapsulated, determined by serotyping, electron microscopy and fluorescence isothiocyanate dextran exclusion assay.By whole genome sequencing, we demonstrated that the phenotypes differ by a single nucleotide base pair in capsular gene cpsE (C to G change at gene position 1135) predicted to result in amino acid change from arginine to glycine at position 379, located in the cytoplasmic, enzymatically active, region of this transmembrane protein. This SNP is responsible for loss of capsule production as the phenotype is transferred with the capsule operon. The nonencapsulated variant is superior in growth in vitro and is also 117-fold more adherent to and more invasive into Detroit 562 human epithelial cells than the encapsulated variant.Expression of six competence pathway genes and one competence-associated gene was 11 to 34-fold higher in the nonencapsulated variant than the encapsulated and transformation frequency was 3.7-fold greater. CONCLUSIONS: We identified a new single point mutation in capsule gene cpsE of a clinical S. pneumoniae serotype 18C isolate sufficient to cause loss of capsule expression resulting in the co-existence of the encapsulated and nonencapsulated phenotype. The mutation caused phenotypic changes in growth, adherence to epithelial cells and transformability. Mutation in capsule gene cpsE may be a way for S. pneumoniae to lose its capsule and increase its colonization potential