Impact of thixotropy on flow patterns induced in a stirred tank : numerical and experimental studies

Agitation of a thixotropic shear-thinning fluid exhibiting a yield stress is investigated both experimentally and via simulations. Steady-state experiments are conducted at three impeller rotation rates (1, 2 and 8 s−1) for a tank stirred with an axial-impeller and flow-field measurements are made using particle image velocimetry (PIV) measurements. Threedimensional numerical simulations are also performed using the commercial CFD code ANSYS CFX10.0. The viscosity of the suspension is determined experimentally and is modelled using two shear-dependant laws, one of which takes into account the flow instabilities of such fluids at low shear rates. At the highest impeller speed, the flow exhibits the familiar outward pumping action associated with axial-flow impellers. However, as the impeller speed decreases, a cavern is formed around the impeller, the flow generated in the vicinity of the agitator reorganizes and its pumping capacity vanishes. An unusual flow pattern, where the radial velocity dominates, is observed experimentally at the lowest stirring speed. It is found to result from wall slip effects. Using blades with rough surfaces prevents this peculiar behaviour and mainly resolves the discrepancies between the experimental and computational results

The Molecular Clockwork of the Fire Ant Solenopsis invicta

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Parental phonological memory contributes to prediction of outcome of late talkers from 20 months to 4 years: a longitudinal study of precursors of specific language impairment

Background Many children who are late talkers go on to develop normal language, but others go on to have longer-term language difficulties. In this study, we considered which factors were predictive of persistent problems in late talkers. Methods Parental report of expressive vocabulary at 18 months of age was used to select 26 late talkers and 70 average talkers, who were assessed for language and cognitive ability at 20 months of age. Follow-up at 4 years of age was carried out for 24 late and 58 average talkers. A psychometric test battery was used to categorize children in terms of language status (unimpaired or impaired) and nonverbal ability (normal range or more than 1 SD below average). The vocabulary and non-word repetition skills of the accompanying parent were also assessed. Results Among the late talkers, seven (29%) met our criteria for specific language impairment (SLI) at 4 years of age, and a further two (8%) had low nonverbal ability. In the group of average talkers, eight (14%) met the criteria for SLI at 4 years, and five other children (8%) had low nonverbal ability. Family history of language problems was slightly better than late-talker status as a predictor of SLI.. The best predictors of SLI at 20 months of age were score on the receptive language scale of the Mullen Scales of Early Learning and the parent's performance on a non-word repetition task. Maternal education was not a significant predictor of outcome. Conclusions In this study, around three-quarters of late talkers did not have any language difficulties at 4 years of age, provided there was no family history of language impairment. A family history of language-literacy problems was found to be a significant predictor for persisting problems. Nevertheless, there are children with SLI for whom prediction is difficult because they did not have early language delay

Stress related epigenetic changes may explain opportunistic success in biological invasions in Antipode mussels

Different environmental factors could induce epigenetic changes, which are likely involved in the biological invasion process. Some of these factors are driven by humans as, for example, the pollution and deliberate or accidental introductions and others are due to natural conditions such as salinity. In this study, we have analysed the relationship between different stress factors: time in the new location, pollution and salinity with the methylation changes that could be involved in the invasive species tolerance to new environments. For this purpose, we have analysed two different mussels’ species, reciprocally introduced in antipode areas: the Mediterranean blue mussel Mytilus galloprovincialis and the New Zealand pygmy mussel Xenostrobus securis, widely recognized invaders outside their native distribution ranges. The demetylathion was higher in more stressed population, supporting the idea of epigenetic is involved in plasticity process. These results can open a new management protocols, using the epigenetic signals as potential pollution monitoring tool. We could use these epigenetic marks to recognise the invasive status in a population and determine potential biopollutants

The nature and fate of natural resins in the geosphere. XII. Investigation of C-ring aromatic diterpenoids in Raritan amber by pyrolysis-GC-matrix isolation FTIR-MS

Upper Cretaceous amber from the Raritan Formation (Sayerville, New Jersey) has been investigated by Pyrolysis-GC-MS and Pyrolysis-GC-matrix isolation FTIR-MS. Results establish the existence of two distinct forms of amber in this deposit. Both forms are Class Ib ambers, but they are unambiguously differentiated on the basis of their (intact) diterpenoid composition. The presence of callitrisate in both forms, and cupraene in samples designated form 1, strongly suggest that both derive from related-but-distinct species within the Cupressaceae. In addition to callitrisate, dehydroabietate and analogous 17-nor-, 16,17-dinor- and 15,16,17-trinor- analogues of these compounds are also observed. The distributions of these products in multiple samples suggest that they are the result of biological emplacement, rather than diagenetic modification of the parent compounds. This indicates that the distributions of diterpenes observed in these samples are representative of the original bioterpenoids and, hence, are useful for chemotaxonomic analyses

IS element IS16 as a molecular screening tool to identify hospital-associated strains of Enterococcus faecium

<p>Abstract</p> <p>Background</p> <p>Hospital strains of <it>Enterococcus faecium </it>could be characterized and typed by various molecular methods (MLST, AFLP, MLVA) and allocated to a distinct clonal complex known as MLST CC17. However, these techniques are laborious, time-consuming and cost-intensive. Our aim was to identify hospital <it>E. faecium </it>strains and differentiate them from colonizing and animal variants by a simple, inexpensive and reliable PCR-based screening assay. We describe here performance and predictive value of a single PCR detecting the insertion element, IS<it>16</it>, to identify hospital <it>E. faecium </it>isolates within a collection of 260 strains of hospital, animal and human commensal origins.</p> <p>Methods</p> <p>Specific primers were selected amplifying a 547-bp fragment of IS<it>16</it>. Presence of IS<it>16 </it>was determined by PCR screenings among the 260 <it>E. faecium </it>isolates. Distribution of IS<it>16 </it>was compared with a prevalence of commonly used markers for hospital strains, <it>esp </it>and <it>hyl</it>_<it>Efm</it>. All isolates were typed by MLST and partly by PFGE. Location of IS<it>16 </it>was analysed by Southern hybridization of plasmid and chromosomal DNA.</p> <p>Results</p> <p>IS<it>16 </it>was exclusively distributed only among 155 invasive strains belonging to the clonal complex of hospital-associated strains ("CC17"; 28 MLST types) and various vancomycin resistance genotypes (<it>van</it>A/B/negative). The five invasive IS<it>16</it>-negative strains did not belong to the clonal complex of hospital-associated strains (CC17). IS<it>16 </it>was absent in all but three isolates from 100 livestock, food-associated and human commensal strains ("non-CC17"; 64 MLST types). The three IS<it>16</it>-positive human commensal isolates revealed MLST types belonging to the clonal complex of hospital-associated strains (CC17). The values predicting a hospital-associated strain ("CC17") deduced from presence and absence of IS<it>16 </it>was 100% and thus superior to screening for the presence of <it>esp </it>(66%) and/or <it>hyl</it>_{<it>Efm </it>}(46%). Southern hybridizations revealed chromosomal as well as plasmid localization of IS<it>16</it>.</p> <p>Conclusions</p> <p>This simple screening assay for insertion element IS<it>16 </it>is capable of differentiating hospital-associated from human commensal, livestock- and food-associated <it>E. faecium </it>strains and thus allows predicting the epidemic strengths or supposed pathogenic potential of a given <it>E. faecium </it>isolate identified within the nosocomial setting.</p

IS element IS16 as a molecular screening tool to identify hospital-associated strains of Enterococcus faecium

<p>Abstract</p> <p>Background</p> <p>Hospital strains of <it>Enterococcus faecium </it>could be characterized and typed by various molecular methods (MLST, AFLP, MLVA) and allocated to a distinct clonal complex known as MLST CC17. However, these techniques are laborious, time-consuming and cost-intensive. Our aim was to identify hospital <it>E. faecium </it>strains and differentiate them from colonizing and animal variants by a simple, inexpensive and reliable PCR-based screening assay. We describe here performance and predictive value of a single PCR detecting the insertion element, IS<it>16</it>, to identify hospital <it>E. faecium </it>isolates within a collection of 260 strains of hospital, animal and human commensal origins.</p> <p>Methods</p> <p>Specific primers were selected amplifying a 547-bp fragment of IS<it>16</it>. Presence of IS<it>16 </it>was determined by PCR screenings among the 260 <it>E. faecium </it>isolates. Distribution of IS<it>16 </it>was compared with a prevalence of commonly used markers for hospital strains, <it>esp </it>and <it>hyl</it>_<it>Efm</it>. All isolates were typed by MLST and partly by PFGE. Location of IS<it>16 </it>was analysed by Southern hybridization of plasmid and chromosomal DNA.</p> <p>Results</p> <p>IS<it>16 </it>was exclusively distributed only among 155 invasive strains belonging to the clonal complex of hospital-associated strains ("CC17"; 28 MLST types) and various vancomycin resistance genotypes (<it>van</it>A/B/negative). The five invasive IS<it>16</it>-negative strains did not belong to the clonal complex of hospital-associated strains (CC17). IS<it>16 </it>was absent in all but three isolates from 100 livestock, food-associated and human commensal strains ("non-CC17"; 64 MLST types). The three IS<it>16</it>-positive human commensal isolates revealed MLST types belonging to the clonal complex of hospital-associated strains (CC17). The values predicting a hospital-associated strain ("CC17") deduced from presence and absence of IS<it>16 </it>was 100% and thus superior to screening for the presence of <it>esp </it>(66%) and/or <it>hyl</it>_{<it>Efm </it>}(46%). Southern hybridizations revealed chromosomal as well as plasmid localization of IS<it>16</it>.</p> <p>Conclusions</p> <p>This simple screening assay for insertion element IS<it>16 </it>is capable of differentiating hospital-associated from human commensal, livestock- and food-associated <it>E. faecium </it>strains and thus allows predicting the epidemic strengths or supposed pathogenic potential of a given <it>E. faecium </it>isolate identified within the nosocomial setting.</p

Effect of hosts on competition among clones and evidence of differential selection between pathogenic and saprophytic phases in experimental populations of the wheat pathogen Phaeosphaeria nodorum

<p>Abstract</p> <p>Background</p> <p>Monoculture, multi-cropping and wider use of highly resistant cultivars have been proposed as mechanisms to explain the elevated rate of evolution of plant pathogens in agricultural ecosystems. We used a mark-release-recapture experiment with the wheat pathogen <it>Phaeosphaeria nodorum </it>to evaluate the impact of two of these mechanisms on the evolution of a pathogen population. Nine <it>P. nodorum </it>isolates marked with ten microsatellite markers and one minisatellite were released onto five replicated host populations to initiate epidemics of Stagonospora nodorum leaf blotch. The experiment was carried out over two consecutive host growing seasons and two pathogen collections were made during each season.</p> <p>Results</p> <p>A total of 637 pathogen isolates matching the marked inoculants were recovered from inoculated plots over two years. Genetic diversity in the host populations affected the evolution of the corresponding <it>P. nodorum </it>populations. In the cultivar mixture the relative frequencies of inoculants did not change over the course of the experiment and the pathogen exhibited a low variation in selection coefficients.</p> <p>Conclusions</p> <p>Our results support the hypothesis that increasing genetic heterogeneity in host populations may retard the rate of evolution in associated pathogen populations. Our experiment also provides indirect evidence of fitness costs associated with host specialization in <it>P. nodorum </it>as indicated by differential selection during the pathogenic and saprophytic phases.</p

Influence of Interferon beta treatment on quality of life in multiple sclerosis patients

BACKGROUND: Interferon-beta (IFN-β) shows beneficial effect on the course of multiple sclerosis (MS), nevertheless its route and frequency of administration and side effects might impact negatively the quality of life (QoL) of MS patients. The objective of this study was to evaluate the influence of IFN-β on QoL in MS patients. METHODS: Seventy-seven disease modifying treatment (DMT) free and 41 IFN-β treated MS patients were evaluated. QoL, assessed by MSQoL-54, was related to IFN-β treatment and to clinical and demographic parameters at baseline and after two years. Multivariate hierarchical linear model for repeated measurements was used. RESULTS: Treated patients showed a younger age, a lower disease duration and a higher relapse rate in the two years preceding study entry. At inclusion time treated and untreated patients did not differ in relapse rate, expanded disability status scale (EDSS), fatigue, depression, physical and mental QoL. IFN-β did not influence QoL at inclusion time, but when QoL was evaluated after two years, treatment negatively affected mental QoL. Depression and fatigue negatively influenced physical and mental QoL both at baseline and after two years. EDSS correlated with a poor physical QoL only at baseline. CONCLUSION: IFN-β had a negative impact on QoL over the time in MS patients, influencing mainly mental QoL. The impairment of QoL in MS was strongly associated with increasing fatigue and depression, whereas clinical disability had a minor unfavourable role