Knots are topological structures describing how a looped thread can be arranged in space. Though most familiar as knotted material filaments, it is also possible to create knots in singular structures within three-dimensional physical fields such as fluid vortices 1 and the nulls of optical fields 2-4. Here we produce, in the transverse polarization profile of optical beams, knotted lines of circular transverse polarization. We generate and observe both simple torus knots and links as well as the topologically more complicated figure-eight knot. The presence of these knotted polarization singularities endows a nontrivial topological structure on the entire three-dimensional propagating wavefield. In particular, the contours of constant polarization azimuth form Seifert surfaces of high genus 5 , which we are able to resolve experimentally in a process we call seifertometry. This analysis reveals a level of topological complexity, present in all experimentally generated polarization fields, that goes beyond the conventional reconstruction of polarization singularity lines.
Background: Dizziness is a non-specific term used by patients to describe several symptoms ranging from true vertigo, light headedness, disorientation or sense of imbalance. Vestibular rehabilitation (VR) is a specific form of exercise-based therapy programme aimed at alleviating the primary and secondary problems of a vestibular pathology. The aim of this study was to investigate the effectiveness of exercise-based vestibular rehabilitation in adult patients with chronic dizziness. Methods: The following five databases were searched: the Cochrane Central Register of Controlled Trials (CENTRAL, the Cochrane Library), MEDLINE, PubMed, the Physiotherapy Evidence Database (PEDro) and Scopus (Elsevier). Two investigators independently reviewed all articles and a systematic review of literature was performed using the PRISMA guidelines (Preferred Reporting Items for Systematic Reviews and Meta-Analyses). The articles were included if they met the following inclusion criteria: (1) randomised controlled trial, (2) people with chronic dizziness, (3) adults aged 18 or over, (4) exercise-based VR, (5) VR exercises compared with sham or usual care, non-treatment or placebo and (6) only studies published full text in English. Results: The initial search identified 304 articles, four of which met the criteria for analysis. All studies involved some form of vestibular rehabilitation, including vestibular compensation, vestibular adaptation and substitution exercises. These exercises were compared with usual medical care (three studies) or placebo eye exercise (one study). The Vertigo Symptom Scale was the most commonly used outcome measure to assess subjective perception of symptoms of dizziness (three studies). According to the PEDro scale, three studies were considered to be of high quality, and one was rated as fair. Conclusions: This review suggests that exercise-based vestibular rehabilitation shows benefits for adult patients with chronic dizziness with regard to improvement in the vertigo symptom scale, fall risk, balance and emotional status.
The short-and long-scale behaviour of tangled vortices (nodal lines) in random three-dimensional wave fields is studied via computer experiment. The zero lines are tracked in numerical simulations of periodic superpositions of threedimensional complex plane waves. The probability distribution of local geometric quantities such as curvature and torsion are compared to previous analytical and new Monte Carlo results from the isotropic Gaussian random wave model. We further examine the scaling and self-similarity of tangled wave vortex lines individually and in the bulk, drawing comparisons with other physical systems of tangled filaments.
study qustion: Can selenium (Se) independent, epididymal-specific glutathione peroxidase 5 (GPX5) protect CHO-K1 cells from oxidative damage and, more specifically, from lipid peroxidation and DNA mutation?summary answer: CHO-K1 cells expressing GPX5 have increased resistance to oxidative challenge and, more specifically, decreased levels of lipid peroxidation and decreased levels of the downstream DNA lesion 8-oxo-7,8-dihydroguanine (8-oxodG) what is known already: GPX5 associates with sperm during transit of the epididymis, and has been postulated to protect sperm from peroxide-mediated attack. However, its function as an active glutathione peroxidase has been questioned due to substitution of the classical selenocysteine residue at its active site. Indirect evidence for a functional role for GPX5 has been provided by in vivo studies, in particular from the GPX5 knockout mouse whereby offspring sired by GPX5 2/2 males have a higher rate of spontaneous abortion and developmental defects, attributed to increased oxidative injury (8-oxodG) to sperm DNA, but only when the GPX5 2/2 males are over 1 year of age. Interestingly, we have previously shown severely reduced levels of GPX5 in humans.study design, size, duration: To look more directly at its role in protection against oxidative damage, we have used an in vitro system, generating a CHO-K1 mammalian cell line expressing recombinant rat GPX5.participants/materials, setting, methods: We have used the recombinant CHO-K1 cells to determine whether GPX5 is able to protect these cells from an administered oxidative challenge, using a range of approaches. We compared the viability of GPX5-expressing cells with control cells by both MTT and trypan blue exclusion assays. We next investigated whether GPX5 protects the cells specifically from lipid peroxidation, by using the fluorescent reporter molecule C11-BODIPY (581/591) , and thus from downstream DNA mutation, by comparing levels of the DNA lesion 8-oxodG. We also investigated whether GPX5 can be transferred to rat sperm via epididymosomes.main results and the role of chance: GPX5-expressing CHO-K1 cells had increased viability compared with control cells following oxidative challenge (P , 0.005). We also found that GPX5-expressing CHO-K1 cells had significantly lower levels of C11-BODIPY (581/591) oxidation, and hence lipid peroxidation, compared with control cells. Levels of 8-oxodG DNA damage were also markedly lower in the nuclei of GPX5-expressing cells than in control cells. Finally, we showed that GPX5 can be transferred to rat sperm via epididymosomes.limitations, reasons for caution: GPX5 is not active in glutathione peroxidase assays using H 2 O 2 as the substrate. However, the related non-mammalian Se-independent GPXs show preference for electron donors other than glutathione, with a number utilizing thioredoxin as a reducing equivalent. Hence, the in vitro activity of GPX5 needs to be assessed using a range of alternative substrates and electron donors. GPX5 is secreted by the epididymis and associate...
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