45 research outputs found
Variational water-wave model with accurate dispersion and vertical vorticity
A new water-wave model has been derived which is based on variational techniques and combines a depth-averaged vertical (component of) vorticity with depth-dependent potential flow. The model facilitates the further restriction of the vertical profile of the velocity potential to n-th order polynomials or a finite-element profile with a small number of elements (say), leading to a framework for efficient modeling of the interaction of steepening and breaking waves near the shore with a large-scale horizontal flow. The equations are derived from a constrained variational formulation which leads to conservation laws for energy, mass, momentum and vertical vorticity. It is shown that the potential-flow water-wave equations and the shallow-water equations are recovered in the relevant limits. Approximate shock relations are provided, which can be used in numerical schemes to model breaking waves
Effectiveness and safety of opicapone in Parkinson's disease patients with motor fluctuations: The OPTIPARK open-label study
BACKGROUND: The efficacy and safety of opicapone, a once-daily catechol-O-methyltransferase inhibitor, have been established in two large randomized, placebo-controlled, multinational pivotal trials. Still, clinical evidence from routine practice is needed to complement the data from the pivotal trials. METHODS: OPTIPARK (NCT02847442) was a prospective, open-label, single-arm trial conducted in Germany and the UK under clinical practice conditions. Patients with Parkinsonâs disease and motor fluctuations were treated with opicapone 50âmg for 3 (Germany) or 6 (UK) months in addition to their current levodopa and other antiparkinsonian treatments. The primary endpoint was the Clinicianâs Global Impression of Change (CGI-C) after 3âmonths. Secondary assessments included Patient Global Impressions of Change (PGI-C), the Unified Parkinsonâs Disease Rating Scale (UPDRS), Parkinsonâs Disease Questionnaire (PDQ-8), and the Non-Motor Symptoms Scale (NMSS). Safety assessments included evaluation of treatment-emergent adverse events (TEAEs) and serious adverse events (SAEs). RESULTS: Of the 506 patients enrolled, 495 (97.8%) took at least one dose of opicapone. Of these, 393 (79.4%) patients completed 3âmonths of treatment. Overall, 71.3 and 76.9% of patients experienced any improvement on CGI-C and PGI-C after 3âmonths, respectively (full analysis set). At 6âmonths, for UK subgroup only (nâ=â95), 85.3% of patients were judged by investigators as improved since commencing treatment. UPDRS scores at 3âmonths showed statistically significant improvements in activities of daily living during OFF (meanâ±âSD change from baseline: ââ3.0â±â4.6, pâ<â0.0001) and motor scores during ON (ââ4.6â±â8.1, pâ<â0.0001). The meanâ±âSD improvements of ââ3.4â±â12.8 points for PDQ-8 and -6.8â±â19.7 points for NMSS were statistically significant versus baseline (both pâ<â0.0001). Most of TEAEs (94.8% of events) were of mild or moderate intensity. TEAEs considered to be at least possibly related to opicapone were reported for 45.1% of patients, with dyskinesia (11.5%) and dry mouth (6.5%) being the most frequently reported. Serious TEAEs considered at least possibly related to opicapone were reported for 1.4% of patients. CONCLUSIONS: Opicapone 50âmg was effective and generally well-tolerated in PD patients with motor fluctuations treated in clinical practice. TRIAL REGISTRATION: Registered in July 2016 at clinicaltrials.gov (NCT02847442)
A direct localization of a fast radio burst and its host
Fast radio bursts are astronomical radio flashes of unknown physical nature
with durations of milliseconds. Their dispersive arrival times suggest an
extragalactic origin and imply radio luminosities orders of magnitude larger
than any other kind of known short-duration radio transient. Thus far, all FRBs
have been detected with large single-dish telescopes with arcminute
localizations, and attempts to identify their counterparts (source or host
galaxy) have relied on contemporaneous variability of field sources or the
presence of peculiar field stars or galaxies. These attempts have not resulted
in an unambiguous association with a host or multi-wavelength counterpart. Here
we report the sub-arcsecond localization of FRB 121102, the only known
repeating burst source, using high-time-resolution radio interferometric
observations that directly image the bursts themselves. Our precise
localization reveals that FRB 121102 originates within 100 mas of a faint 180
uJy persistent radio source with a continuum spectrum that is consistent with
non-thermal emission, and a faint (25th magnitude) optical counterpart. The
flux density of the persistent radio source varies by tens of percent on day
timescales, and very long baseline radio interferometry yields an angular size
less than 1.7 mas. Our observations are inconsistent with the fast radio burst
having a Galactic origin or its source being located within a prominent
star-forming galaxy. Instead, the source appears to be co-located with a
low-luminosity active galactic nucleus or a previously unknown type of
extragalactic source. [Truncated] If other fast radio bursts have similarly
faint radio and optical counterparts, our findings imply that direct
sub-arcsecond localizations of FRBs may be the only way to provide reliable
associations.Comment: Nature, published online on 4 Jan 2017, DOI: 10.1038/nature2079
Significant sink of ocean eddy-energy near western boundaries
Ocean eddies generated through instability of the mean flow are a vital component of the energy budget of the global ocean1-3. In equilibrium, the sources and sinks of eddy energy have to be balanced. However, where and how eddy energy is removed remains uncertain3,4. Ocean eddies are observed to propagate westwards at speeds similar to the phase speeds of classical Rossby waves5, but what happens to the eddies when they encounter the western boundary is unclear. Here we use a simple reduced-gravity model along with satellite altimetry data to show that the western boundary acts as a "graveyardg" for the westward-propagating ocean eddies. We estimate a convergence of eddy energy near the western boundary of approximately 0.1-0.3 TW, poleward of 10°in latitude. This energy is most probably scattered into high-wavenumber vertical modes, resulting in energy dissipation and diapycnal mixing. If confirmed, this eddy-energy sink will have important implications for the ocean circulation. © 2010 Macmillan Publishers Limited. All rights reserved