Sex differences concerning the effects of ankle muscle fatigue on static postural control and spinal proprioceptive input at the ankle

AimsThe main aim of this study was to determine sex differences in postural control changes with ankle muscle fatigue during a standing forward leaning (FL) task under different vision conditions. The secondary aim was to examine sex differences in the effect of fatigue on soleus (SOL) H-reflex amplitude, a measure of motoneuron excitability with activation of Ia afferents.MethodsFifteen healthy young adult males (mean age: 28.0 years) and 16 healthy young adult females (mean age: 26.1 years) were asked to perform four consecutive FL tasks [30 s; two with eyes open (EO) and two with eyes closed (EC)] before, and immediately following a fatiguing exercise consisting of alternating ankle plantarflexion (6 s) and dorsiflexion (2 s) maximal isometric contractions, and at 5 and 10 min of recovery. Center of pressure (COP) sway variables (mean position, standard deviation, ellipse area, average velocity, and frequency), an ankle co-contraction index, and a ratio of SOL H-reflex to the maximum amplitude of the compound muscle action potential (M-max) were obtained during the FL tasks. A rating of perceived fatigue (RPF) was also documented at the different time points.ResultsTime to task failure (reduction of 50% in maximal voluntary isometric contraction torque of ankle plantar flexors) and the increase in RPF value were not significantly different between males and females. Both sex groups showed similar and significant increases (p < 0.05) in mean COP sway velocity with no significant changes in co-contraction indices. No significant effects of fatigue and related interactions were found for SOL H/M-max ratio.DiscussionThe absence of a significant sex difference in postural control change (sway and co-contraction) with fatigue could be explained by similar perceived (RPF) and performance fatigability (exercise duration) between males and females in the present study. Fatigue did not lead to significant changes in SOL spinal motoneuron excitability with activation of Ia afferents

Variations in the Relationship Between the Frequency Content of EMG Signals and the Rate of Torque Development in Voluntary and Elicited Contractions

Our purpose was to characterize the relationship between EMG mean power frequency (MPF) or median frequency (MF) and rate of torque development in voluntary ballistic and electrically elicited isometric contractions. Twenty-three healthy adults participated in two sets of experiments performed on elbow flexor muscles. For Experiment 1, subjects were asked to generate voluntary ballistic contractions by reaching four different target torque levels (20, 40, 60 and 100% of the maximal voluntary contraction (MVC)) as fast as they could. For Experiment 2, electrical (M-waves) and mechanical (twitches) responses to electrical stimulation of the nerves supplying the biceps brachii and brachioradialis muscles were recorded with the subjects at rest and with a background isometric contraction of 15% MVC. MPF, MF and rate of torque development (% MVC/s) were calculated for both voluntary and elicited contractions. Significant positive correlations were observed between MPF and rate of torque development for the voluntary contractions, whereas significant negative correlations were observed between the two variables for elicited contractions. This suggests that factors other than muscle fiber composition influence the frequency content of EMG signals and/or the rate of torque development, and that the effect of these factors will vary between voluntary and elicited contractions. 2002 Elsevier Science Ltd. All rights reserved

Analyse d'un moteur à combustion interne fonctionnant à la biomasse brute selon le cycle de Brayton régénératif

Carboneutre et renouvelable, la biomasse est une alternative intéressante aux combustibles fossiles dans la mitigation des gaz à effets de serre. À l’état brut, elle offre son plein potentiel calorifique à un prix plus abordable qu’un biocarburant transformé. Cependant, sa combustion présente de nombreux défis : un taux d’humidité élevé, un temps de gazéification long, l’encrassement et la corrosion des réacteurs. La biomasse choisie pour l’étude comprend le goémon noir (Ascophyllum nodosum) et le varech vésiculeux (Fucus vesiculosus) jonchant les zones de marée de la Basse-Côte-Nord. Ces algues marines ont été analysées. Le potentiel calorifique inférieur du goémon rivalise avec ceux du bois et du méthanol avec 19 140 kJ/kg (anhydre, sans cendre). Ses cendres sont libres de contaminant et constituées de CaO (chaux vive), K2O (potasse), MgO (magnésie), SO3 (trioxyde de soufre) et P2O5 (oxyde de phosphore); un excellent engrais pour les sols. L’énergie nécessaire au séchage altère particulièrement le rendement thermique. Le concept Valbimax proposé consiste en un moteur à combustion interne fonctionnant à la biomasse brute selon le cycle de Brayton régénératif. Un modèle mathématique inspiré de la méthode Fuel-Air estime l’efficacité thermique nette du nouvel engin à 43.6% pour une température de combustion de 1250°C et un rendement de régénération de 85%. L’efficacité de combustion de 84.8% retenue pour les simulations est extraite de la littérature. Des essais sont en cours pour confirmer cette valeur et évaluer l’encrassement d’un nouveau réacteur expérimental développé à l’UdS. Selon les calculs actuels, Valbimax supplante par 2.8% l’efficacité du moteur turbo diesel de référence pour le projet, le Caterpillar 3406C®

Potentiel d'intégration des algues marines de la Basse-Côte-Nord dans le mix énergétique québécois

"Les gaz à effet de serre (GES) sont à l’origine de changements climatiques dont on a déjà pu mesurer les effets et qui ne devraient cesser de s’accroître dans les prochaines décennies. Ces gaz proviennent principalement de l’utilisation de combustibles fossiles, dont nous dépendons encore largement pour les secteurs du transport, de l’industrie et des bâtiments. Au Québec, ils représentent 57,4 % de notre consommation totale d’énergie (Whitmore et Pineau, 2022). Une nouvelle transition énergétique s’impose. Pour la réussir et limiter les conséquences environnementales, « il nous faudra d’abord réduire notre consommation totale d’énergie partout dans le monde. Ensuite, nous devrons compenser les GES ou réduire au minimum ce qui subsistera de notre consommation d’hydrocarbures en ayant recours à des sources d’énergie qui émettent moins de GES (solaire, éolien ou biocarburants, par exemple) » (Whitmore et Lafontaine-Beaumier, 2019). [...]

Curvature sensing using a hybrid polycarbonate-silica multicore fiber

We report on the development of a novel hybrid glass-polymer multicore fiber integrating three 80 µm polyimide-coated silica fibers inside a 750 µm polycarbonate cladding. By inscribing an array of distributed FBGs along each segment of silica fiber prior to the hybrid fiber drawing, we demonstrate a curvature sensor with an unprecedented precision of 296 pm/m−1 around 1550 nm, about 7 times more sensitive than sensors based on standard 125 µm multicore fibers. As predicted by theory, we show experimentally that the measured curvature is insensitive to temperature and strain. Also, a more precise equation to describe the curvature on a simple bending setup is presented. This new hybrid multicore fiber technology has the potential to be extended over several kilometers and can find high-end applications in 3D shape sensing and structural health monitoring

Binding of Equine Infectious Anemia Virus Rev to an Exon Splicing Enhancer Mediates Alternative Splicing and Nuclear Export of Viral mRNAs

In addition to facilitating the nuclear export of incompletely spliced viral mRNAs, equine infectious anemia virus (EIAV) Rev regulates alternative splicing of the third exon of the tat/rev mRNA. In the presence of Rev, this exon of the bicistronic RNA is skipped in a fraction of the spliced mRNAs. In this report, the cis-acting requirements for exon 3 usage were correlated with sequences necessary for Rev binding and transport of incompletely spliced RNA. The presence of a purine-rich exon splicing enhancer (ESE) was required for exon 3 recognition, and the addition of Rev inhibited exon 3 splicing. Glutathione-S-transferase (GST)-Rev bound to probes containing the ESE, and mutation of GAA repeats to GCA within the ESE inhibited both exon 3 recognition in RNA splicing experiments and GST-Rev binding in vitro. These results suggest that Rev regulates alternative splicing by binding at or near the ESE to block SR protein-ESE interactions. A 57-nucleotide sequence containing the ESE was sufficient to mediate Rev-dependent nuclear export of incompletely spliced RNAs. Rev export activity was significantly inhibited by mutation of the ESE or by trans-complementation with SF2/ASF. These results indicate that the ESE functions as a Rev-responsive element and demonstrate that EIAV Rev mediates exon 3 exclusion through protein-RNA interactions required for efficient export of incompletely spliced viral RNAs

Testing for Changes in Kendall's Tau

For a bivariate time series $((X_i,Y_i))_{i=1,...,n}$ we want to detect whether the correlation between $X_i$ and $Y_i$ stays constant for all $i = 1,...,n$. We propose a nonparametric change-point test statistic based on Kendall's tau and derive its asymptotic distribution under the null hypothesis of no change by means a new U-statistic invariance principle for dependent processes. The asymptotic distribution depends on the long run variance of Kendall's tau, for which we propose an estimator and show its consistency. Furthermore, assuming a single change-point, we show that the location of the change-point is consistently estimated. Kendall's tau possesses a high efficiency at the normal distribution, as compared to the normal maximum likelihood estimator, Pearson's moment correlation coefficient. Contrary to Pearson's correlation coefficient, it has excellent robustness properties and shows no loss in efficiency at heavy-tailed distributions. We assume the data $((X_i,Y_i))_{i=1,...,n}$ to be stationary and P-near epoch dependent on an absolutely regular process. The P-near epoch dependence condition constitutes a generalization of the usually considered $L_p$-near epoch dependence, $p \ge 1$, that does not require the existence of any moments. It is therefore very well suited for our objective to efficiently detect changes in correlation for arbitrarily heavy-tailed data

Metaxa2 Database Builder: enabling taxonomic identification from metagenomic or metabarcoding data using any genetic marker

Motivation: Correct taxonomic identification of DNA sequences is central to studies of biodiversity using both shotgun metagenomic and metabarcoding approaches. However, no genetic marker gives sufficient performance across all the biological kingdoms, hampering studies of taxonomic diversity in many groups of organisms. This has led to the adoption of a range of genetic markers for DNA metabarcoding. While many taxonomic classification software tools can be re-trained on these genetic markers, they are often designed with assumptions that impair their utility on genes other than the SSU and LSU rRNA. Here, we present an update to Metaxa2 that enables the use of any genetic marker for taxonomic classification of metagenome and amplicon sequence data. Results: We evaluated the Metaxa2 Database Builder on 11 commonly used barcoding regions and found that while there are wide differences in performance between different genetic markers, our software performs satisfactorily provided that the input taxonomy and sequence data are of high quality. Availability and implementation: Freely available on the web as part of the Metaxa2 package at http://microbiology.se/software/metaxa2/. Supplementary information: Supplementary data are available at Bioinformatics online

Transcriptional Activation by Oct4 Is Sufficient for the Maintenance and Induction of Pluripotency

SummaryOct4 is an essential regulator of pluripotency in vivo and in vitro in embryonic stem cells, as well as a key mediator of the reprogramming of somatic cells into induced pluripotent stem cells. It is not known whether activation and/or repression of specific genes by Oct4 is relevant to these functions. Here, we show that fusion proteins containing the coding sequence of Oct4 or Xlpou91 (the Xenopus homolog of Oct4) fused to activating regions, but not those fused to repressing regions, behave as Oct4, suppressing differentiation and promoting maintenance of undifferentiated phenotypes in vivo and in vitro. An Oct4 activation domain fusion supported embryonic stem cell self-renewal in vitro at lower concentrations than that required for Oct4 while alleviating the ordinary requirement for the cytokine LIF. At still lower levels of the fusion, LIF dependence was restored. We conclude that the necessary and sufficient function of Oct4 in promoting pluripotency is to activate specific target genes