913 research outputs found
Technical Freediving: An Emerging Breath-Hold Diving Technique
Technical freediving can be defined as freediving augmented by the use of oxygen-enriched gases or oxygen before, during, or after a freedive. As a result of these techniques, breath-hold divers can visit and enjoy underwater wrecks, reefs, and other diving locations previously located at depths unreachable to apnea divers. By pre-breathing oxygen-enriched gases in conjunction with hyperventilation—which decreases the partial pressure of carbon dioxide (PCO2)—the technical freediver now has additional oxygen to facilitate aerobic respiration during the dive. In addition, pre-breathing oxygen decreases tissue nitrogen tensions, which limits inert gas loading and decreases the risk of decompression sickness (DCS). Finally, this technique decreases PCO2, which diminishes the urge to breathe. Consequently, a diver may be able to dive longer before critical hypoxia or hypercarbia forces an ascent. Technical freediving can also be complemented by the use of a diver propulsion vehicle to increase the speed of descent and ascent and minimize exertion. The techniques of technical freediving may be associated with increased risks in central nervous system oxygen toxicity, DCS, and arterial gas embolism. As the boundaries of apnea diving continue to expand, there will be considerable opportunities to investigate the physiological limits of the human body and to determine the safest methodologies to practice this evolving discipline
Time-dependent linearisation of bottom friction for storm surge modelling in the Wadden Sea
The nonlinear nature of bottom friction in shallow flow complicates its analysis, particularly in idealised models. For tidal flows, Lorentz’ linearisation has been widely applied, using an energy criterion to specify the friction coefficient. Here we propose an extension of this approach to storm surges, leading to a friction coefficient that may gradually vary over a storm event. The derivation is provided along with first results for a single channel
Tuning mobility and stability of lithium ion conductors based on lattice dynamics
Lithium ion conductivity in many structural families can be tuned by many orders of magnitude, with some rivaling that of liquid electrolytes at room temperature. Unfortunately, fast lithium conductors exhibit poor stability against lithium battery electrodes. In this article, we report a fundamentally new approach to alter ion mobility and stability against oxidation of lithium ion conductors using lattice dynamics. By combining inelastic neutron scattering measurements with density functional theory, fast lithium conductors were shown to have low lithium vibration frequency or low center of lithium phonon density of states. On the other hand, lowering anion phonon densities of states reduces the stability against electrochemical oxidation. Olivines with low lithium band centers but high anion band centers are promising lithium ion conductors with high ion conductivity and stability. Such findings highlight new strategies in controlling lattice dynamics to discover new lithium ion conductors with enhanced conductivity and stability.United States. National Science Foundation. Graduate Research Fellowship Program (Grant 1122374)Taiwan. Ministry of Science and Technology (Grant 102-2917-I-564-006-A1)United States. National Science Foundation (Award DMR-0819762)United States. National Energy Research Scientific Computing Center (Contract DE-AC02-05CH11231)Extreme Science and Engineering Discovery Environment (Grant ACI-1548562
Social media for physiotherapy clinics: considerations in creating a Facebook page
Social media websites play a prominent role in modern society, and the most popular of these websites is Facebook. Increasingly, physiotherapy clinics have begun to utilize Facebook in order to create pages to publicize their services. There are many factors to consider in the planning, implementing, and maintenance of Facebook pages for physiotherapy clinics, including ethical and privacy issues. The primary purpose of creating a page must be clearly defined, with dedicated clinicians given adequate time to manage the page. This technical article discusses these factors and summarizes the experiences at the University of Otago, New Zealand, in creating a Facebook page for the physiotherapy clinic and provides suggestions for physiotherapy clinicians in operating a Facebook page
Galaxy Zoo and ALFALFA: Atomic Gas and the Regulation of Star Formation in Barred Disc Galaxies
We study the observed correlation between atomic gas content and the
likelihood of hosting a large scale bar in a sample of 2090 disc galaxies. Such
a test has never been done before on this scale. We use data on morphologies
from the Galaxy Zoo project and information on the galaxies' HI content from
the ALFALFA blind HI survey. Our main result is that the bar fraction is
significantly lower among gas rich disc galaxies than gas poor ones. This is
not explained by known trends for more massive (stellar) and redder disc
galaxies to host more bars and have lower gas fractions: we still see at fixed
stellar mass a residual correlation between gas content and bar fraction. We
discuss three possible causal explanations: (1) bars in disc galaxies cause
atomic gas to be used up more quickly, (2) increasing the atomic gas content in
a disc galaxy inhibits bar formation, and (3) bar fraction and gas content are
both driven by correlation with environmental effects (e.g. tidal triggering of
bars, combined with strangulation removing gas). All three explanations are
consistent with the observed correlations. In addition our observations suggest
bars may reduce or halt star formation in the outer parts of discs by holding
back the infall of external gas beyond bar co-rotation, reddening the global
colours of barred disc galaxies. This suggests that secular evolution driven by
the exchange of angular momentum between stars in the bar, and gas in the disc,
acts as a feedback mechanism to regulate star formation in intermediate mass
disc galaxies.Comment: 16 pages, 10 figures. In press at MNRAS. v2 contains corrections
found in proof
Galaxy Zoo: The Environmental Dependence of Bars and Bulges in Disc Galaxies
We present an analysis of the environmental dependence of bars and bulges in
disc galaxies, using a volume-limited catalogue of 15810 galaxies at z<0.06
from the Sloan Digital Sky Survey with visual morphologies from the Galaxy Zoo
2 project. We find that the likelihood of having a bar, or bulge, in disc
galaxies increases when the galaxies have redder (optical) colours and larger
stellar masses, and observe a transition in the bar and bulge likelihoods, such
that massive disc galaxies are more likely to host bars and bulges. We use
galaxy clustering methods to demonstrate statistically significant
environmental correlations of barred, and bulge-dominated, galaxies, from
projected separations of 150 kpc/h to 3 Mpc/h. These environmental correlations
appear to be independent of each other: i.e., bulge-dominated disc galaxies
exhibit a significant bar-environment correlation, and barred disc galaxies
show a bulge-environment correlation. We demonstrate that approximately half
(50 +/- 10%) of the bar-environment correlation can be explained by the fact
that more massive dark matter haloes host redder disc galaxies, which are then
more likely to have bars. Likewise, we show that the environmental dependence
of stellar mass can only explain a small fraction (25 +/- 10%) of the
bar-environment correlation. Therefore, a significant fraction of our observed
environmental dependence of barred galaxies is not due to colour or stellar
mass dependences, and hence could be due to another galaxy property. Finally,
by analyzing the projected clustering of barred and unbarred disc galaxies with
halo occupation models, we argue that barred galaxies are in slightly
higher-mass haloes than unbarred ones, and some of them (approximately 25%) are
satellite galaxies in groups. We also discuss implications about the effects of
minor mergers and interactions on bar formation.Comment: 20 pages, 18 figures; references updated; published in MNRA
Dynamic Blood-Brain Barrier Regulation in Mild Traumatic Brain Injury
Whereas the diagnosis of moderate and severe traumatic brain injury (TBI) is readily visible on current medical imaging paradigms (magnetic resonance imaging [MRI] and computed tomography [CT] scanning), a far greater challenge is associated with the diagnosis and subsequent management of mild TBI (mTBI), especially concussion which, by definition, is characterized by a normal CT. To investigate whether the integrity of the blood-brain barrier (BBB) is altered in a high-risk population for concussions, we studied professional mixed martial arts (MMA) fighters and adolescent rugby players. Additionally, we performed the linear regression between the BBB disruption defined by increased gadolinium contrast extravasation on dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) on MRI and multiple biomechanical parameters indicating the severity of impacts recorded using instrumented mouthguards in professional MMA fighters. MMA fighters were examined pre-fight for a baseline and again within 120 h post-competitive fight, whereas rugby players were examined pre-season and again post-season or post-match in a subset of cases. DCE-MRI, serological analysis of BBB biomarkers, and an analysis of instrumented mouthguard data, was performed. Here, we provide pilot data that demonstrate disruption of the BBB in both professional MMA fighters and rugby players, dependent on the level of exposure. Our data suggest that biomechanical forces in professional MMA and adolescent rugby can lead to BBB disruption. These changes on imaging may serve as a biomarker of exposure of the brain to repetitive subconcussive forces and mTBI
Pan-Cancer Analysis of lncRNA Regulation Supports Their Targeting of Cancer Genes in Each Tumor Context
Long noncoding RNAs (lncRNAs) are commonly dys-regulated in tumors, but only a handful are known toplay pathophysiological roles in cancer. We inferredlncRNAs that dysregulate cancer pathways, onco-genes, and tumor suppressors (cancer genes) bymodeling their effects on the activity of transcriptionfactors, RNA-binding proteins, and microRNAs in5,185 TCGA tumors and 1,019 ENCODE assays.Our predictions included hundreds of candidateonco- and tumor-suppressor lncRNAs (cancerlncRNAs) whose somatic alterations account for thedysregulation of dozens of cancer genes and path-ways in each of 14 tumor contexts. To demonstrateproof of concept, we showed that perturbations tar-geting OIP5-AS1 (an inferred tumor suppressor) andTUG1 and WT1-AS (inferred onco-lncRNAs) dysre-gulated cancer genes and altered proliferation ofbreast and gynecologic cancer cells. Our analysis in-dicates that, although most lncRNAs are dysregu-lated in a tumor-specific manner, some, includingOIP5-AS1, TUG1, NEAT1, MEG3, and TSIX, synergis-tically dysregulate cancer pathways in multiple tumorcontexts
Pan-cancer Alterations of the MYC Oncogene and Its Proximal Network across the Cancer Genome Atlas
Although theMYConcogene has been implicated incancer, a systematic assessment of alterations ofMYC, related transcription factors, and co-regulatoryproteins, forming the proximal MYC network (PMN),across human cancers is lacking. Using computa-tional approaches, we define genomic and proteo-mic features associated with MYC and the PMNacross the 33 cancers of The Cancer Genome Atlas.Pan-cancer, 28% of all samples had at least one ofthe MYC paralogs amplified. In contrast, the MYCantagonists MGA and MNT were the most frequentlymutated or deleted members, proposing a roleas tumor suppressors.MYCalterations were mutu-ally exclusive withPIK3CA,PTEN,APC,orBRAFalterations, suggesting that MYC is a distinct onco-genic driver. Expression analysis revealed MYC-associated pathways in tumor subtypes, such asimmune response and growth factor signaling; chro-matin, translation, and DNA replication/repair wereconserved pan-cancer. This analysis reveals insightsinto MYC biology and is a reference for biomarkersand therapeutics for cancers with alterations ofMYC or the PMN
Genomic, Pathway Network, and Immunologic Features Distinguishing Squamous Carcinomas
This integrated, multiplatform PanCancer Atlas study co-mapped and identified distinguishing
molecular features of squamous cell carcinomas (SCCs) from five sites associated with smokin
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