Neurotransmitter modulation of extracellular H+ fluxes from isolated retinal horizontal cells of the skate

Self-referencing H+-selective microelectrodes were used to measure extracellular H+ fluxes from horizontal cells isolated from the skate retina. A standing H+ flux was detected from quiescent cells, indicating a higher concentration of free hydrogen ions near the extracellular surface of the cell as compared to the surrounding solution. The standing H+ flux was reduced by removal of extracellular sodium or application of 5-(N-ethyl-N-isopropyl) amiloride (EIPA), suggesting activity of a Na+–H+ exchanger. Glutamate decreased H+ flux, lowering the concentration of free hydrogen ions around the cell. AMPA/kainate receptor agonists mimicked the response, and the AMPA/kainate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) eliminated the effects of glutamate and kainate. Metabotropic glutamate agonists were without effect. Glutamate-induced alterations in H+ flux required extracellular calcium, and were abolished when cells were bathed in an alkaline Ringer solution. Increasing intracellular calcium by photolysis of the caged calcium compound NP-EGTA also altered extracellular H+ flux. Immunocytochemical localization of the plasmalemma Ca2+–H+-ATPase (PMCA pump) revealed intense labelling within the outer plexiform layer and on isolated horizontal cells. Our results suggest that glutamate modulation of H+ flux arises from calcium entry into cells with subsequent activation of the plasmalemma Ca2+–H+-ATPase. These neurotransmitter-induced changes in extracellular pH have the potential to play a modulatory role in synaptic processing in the outer retina. However, our findings argue against the hypothesis that hydrogen ions released by horizontal cells normally act as the inhibitory feedback neurotransmitter onto photoreceptor synaptic terminals to create the surround portion of the centre-surround receptive fields of retinal neuron

Discovery of a z=4.93, X-ray selected quasar by the Chandra Multiwavelength Project (ChamP)

We present X-ray and optical observations of CXOMP J213945.0-234655, a high redshift (z=4.93) quasar discovered through the Chandra Multiwavelength Project (ChaMP). This object is the most distant X-ray selected quasar published, with an X-ray luminosity of L(X)=5.9x10^44 erg/s (measured in the 0.3-2.5 keV band and corrected for Galactic absorption). CXOMP J213945.0-234655 is a g' dropout object (>26.2), with r'=22.87 and i'=21.36. The rest-frame X-ray to optical flux ratio is similar to quasars at lower redshifts and slightly X-ray bright relative to z>4 optically-selected quasars observed with Chandra. The ChaMP is beginning to acquire significant numbers of high redshift quasars to investigate the unobscured X-ray luminosity function out to z~5.Comment: Published in ApJ Letters; 4 pages; 3 figures; http://hea-www.harvard.edu/CHAMP

Physiotherapist-directed rehabilitation exercises in the outpatient or home setting improve strength, gait speed and cadence after elective total hip replacement: a systematic review

QuestionIn people who have been discharged from hospital after a total hip replacement, do rehabilitation exercises directed by a physiotherapist improve strength, gait, function and quality of life? Are these exercises as effective in an unsupervised home-based setting as they are in a supervised outpatient setting?DesignSystematic review with meta-analysis of randomised trials.ParticipantsAdult patients after elective total hip replacement.InterventionPhysiotherapist-directed rehabilitation exercises after discharge from hospital following total hip replacement.Outcome measuresHip and knee strength, gait parameters, functional measures, and quality of life.ResultsFive studies comprising 234 participants were included in the review. Sufficient data for meta-analysis were only obtained for hip and knee strength, gait speed and cadence. Physiotherapy rehabilitation improved hip abductor strength by a mean of 16Nm (95% CI 10 to 22), gait speed by 6 m/min (95% CI 1 to 11) and cadence by 20 steps/min (95% CI 8 to 32). Favourable but non-significant improvements in strength were noted for other muscle groups at the hip and knee. Function and quality of life could not be meta-analysed due to insufficient data and heterogeneity of measures, but functional measures tended to favour the physiotherapy rehabilitation group. Most outcomes were similar between outpatient and home-based exercise programs.ConclusionPhysiotherapy rehabilitation improves hip abductor strength, gait speed and cadence in people who have been discharged from hospital after total hip replacement. Physiotherapist-directed rehabilitation exercises appear to be similarly effective whether they are performed unsupervised at home or supervised by a physiotherapist in an outpatient setting

Numerical Modelling of Debris Bed Water Quenching

Acknowledgements The authors would like to thank the EPSRC MEMPHIS multi-phase programme grant, the EPSRC Computational modelling for advanced nuclear power plants project, the EU FP7 projects THINS and GoFastR and ExxonMobil for helping to fund this work.Peer reviewedPublisher PD

An autoencoder-based reduced-order model for eigenvalue problems with application to neutron diffusion

Using an autoencoder for dimensionality reduction, this paper presents a novel projection-based reduced-order model for eigenvalue problems. Reduced-order modelling relies on finding suitable basis functions which define a low-dimensional space in which a high-dimensional system is approximated. Proper orthogonal decomposition (POD) and singular value decomposition (SVD) are often used for this purpose and yield an optimal linear subspace. Autoencoders provide a nonlinear alternative to POD/SVD, that may capture, more efficiently, features or patterns in the high-fidelity model results. Reduced-order models based on an autoencoder and a novel hybrid SVD-autoencoder are developed. These methods are compared with the standard POD-Galerkin approach and are applied to two test cases taken from the field of nuclear reactor physics.Comment: 35 pages, 33 figure

PETIs as High-Temperature Resin-Transfer-Molding Materials

Compositions of, and processes for fabricating, high-temperature composite materials from phenylethynyl-terminated imide (PETI) oligomers by resin-transfer molding (RTM) and resin infusion have been developed. Composites having a combination of excellent mechanical properties and long-term high-temperature stability have been readily fabricated. These materials are particularly useful for the fabrication of high-temperature structures for jet-engine components, structural components on highspeed aircraft, spacecraft, and missiles. Phenylethynyl-terminated amide acid oligomers that are precursors of PETI oligomers are easily made through the reaction of a mixture of aromatic diamines with aromatic dianhydrides at high stoichiometric offsets and 4-phenylethynylphthalic anhydride (PEPA) as an end-capper in a polar solvent such as N-methylpyrrolidinone (NMP). These oligomers are subsequently cyclodehydrated -- for example, by heating the solution in the presence of toluene to remove the water by azeotropic distillation to form low-molecular-weight imide oligomers. More precisely, what is obtained is a mixture of PETI oligomeric species, spanning a range of molecular weights, that exhibits a stable melt viscosity of less than approximately 60 poise (and generally less than 10 poise) at a temperature below 300 deg C. After curing of the oligomers at a temperature of 371 deg C, the resulting polymer can have a glass-transition temperature (Tg) as high as 375 C, the exact value depending on the compositions

Investigation of Staphylococcus aureus Bacteriophage Population at a South Carolina University: The Disappearance of S. aureus Bacteriophage Population Amidst the COVID-19 Pandemic

Bacteriophages are naturally occurring, nonpathogenic viruses, which infect bacterial cells. Recently, bacteriophage research has increased with hopes of using them against antibiotic resistant bacterial infections in the future. This study aimed to determine a possible correlation between perceived stress and the Staphylococcus aureus bacteriophage population at Coastal Carolina University (CCU), Conway, South Carolina, using isolation and characterization techniques to further understand humans as a potential bacteriophage source. From October 2020 to March 2021, nasal and postauricular swab samples were collected from 12 participants on a monthly basis along with a perceived stress survey. Samples were subjected to filtration, amplification, plaque assays, and PCR techniques to identify and characterize bacteriophage. The purpose of this study was to understand humans as a repository for bacteriophage and to understand factors, namely perceived stress, which affect bacteriophage presence on humans. Results suggested that possible changes due to the COVID-19 pandemic, such as increased stress levels, mask wearing, and constant hand washing/ sanitizing, caused a drastic decrease in the Escherichia coli and Staphylococcus aureus phage population at Coastal Carolina University

Perseverance with home-based upper limb practice after stroke: perspectives of stroke survivors and their significant others

Purpose: The aim of this study was to explore factors that influence stroke survivors’ ability to persevere with home-based upper limb practice. Methods: A qualitative descriptive study embedded within a theoretical framework was conducted. Data were collected through semi-structured focus group, dyadic, and individual interviews. The Theoretical Domains Framework and Capability, Opportunity, Motivation – Behaviour (COM-B) model guided data collection and directed content analysis. Findings: Participants were 31 adult stroke survivors with upper limb impairment, with 13 significant other/s, who were living at home in Queensland, Australia. Three central tenants aligned with the COM-B and six themes were identified. Stroke survivors’ capability to persevere was influenced by being physically able to practice and being able to understand, monitor and modify practice, their opportunity to persevere was influenced by accessing therapy and equipment required for practice and fitting practice into everyday life, and their motivation to persevere was influenced by having goals and experiencing meaningful outcomes and having support and being accountable. Conclusion: Persevering with practice is multifaceted for stroke survivors. All facets need to be addressed in the design of strategies to enhance stroke survivors’ ability to persevere and in turn, enhance their potential for continued upper limb recovery