5,381 research outputs found
Effects of thermal conduction in sonoluminescence
We show by numerical hydrodynamic calculations that there are two important effects of thermal conduction in sonoluminescence: (i) the bubble remains close to being isothermal during the expansion phase; and (ii) a cold, dense layer of air is formed at the bubble wall during the contraction phase. These conclusions are not sensitive to the particular equation of state used, although details of the dynamical evolution of the bubble are
State detection using coherent Raman repumping and two-color Raman transfers
We demonstrate state detection based on coherent Raman repumping and a
two-color Raman state transfer. The Raman coupling during detection selectively
eliminates unwanted dark states in the fluorescence cycle without compromising
the immunity of the desired dark state to off-resonant scattering. We
demonstrate this technique using where a combination of
Raman coupling and optical pumping leaves the
metastable state optically dark and immune to off-resonant scattering. All
other states are strongly coupled to the upper levels. We achieve a
single shot state-detection efficiency of in a
integration time, limited almost entirely by technical imperfections. Shelving
to the state before detection is performed via a two-color
Raman transfer with a fidelity of
Muon spin rotation study of the topological superconductor SrxBi2Se3
We report transverse-field (TF) muon spin rotation experiments on single
crystals of the topological superconductor SrBiSe with nominal
concentrations and ( K). The TF spectra (
mT), measured after cooling to below in field, did not show any
additional damping of the muon precession signal due to the flux line lattice
within the experimental uncertainty. This puts a lower bound on the magnetic
penetration depth m. However, when we induce disorder in
the vortex lattice by changing the magnetic field below a sizeable
damping rate is obtained for . The data provide microscopic
evidence for a superconducting volume fraction of in the
crystal and thus bulk superconductivity.Comment: 6 pages, includes 4 figure
Turbulence and turbulent events in tidal bores: field observations
A tidal bore is a compressive wave of tidal origin, propagating upstream as the tidal flow turns to rising when a macro-tidal flood flow enters a funnel shaped river mouth with shallow waters. New field measurements were conducted in the Garonne River tidal bore at Arcins in 2015. Instantaneous velocity measurements were performed continuously at high-frequency prior to, during and after each bore. The bore occurrence had a marked effect on the velocity and turbulent Reynolds stress field, with large and rapid fluctuations, during the bore passage and the early flood tide. A turbulent event analysis was conducted in the highly unsteady rapidly-varied tidal bore flow. The method detects bursting events by comparing the absolute value of an instantaneous turbulent flux with its standard deviation. This analysis, based upon basic concepts, was extended to the rapidly varied, highly-unsteady tidal bore flood flow motion. The turbulent event data analysis showed relatively close results for all studies and all fluxes. A very large majority of turbulent events had a duration less than 0.01 s, with on average 20 turbulent events per second. During all studies, the event duration showed some tidal trend, with longer turbulent events immediately after the tidal bore passage, occurring simultaneously with sediment erosion processes
The impact of the Medicines Control Council backlog and fast-track review system on access to innovative and new generic and biosimilar medicines of public health importance in South Africa
The fast-track registration policy of the South African National Department of Health allows for rapid registration of new medicines of public health importance and of all medicines on the Essential Medicines List, most of which are generics. No limit is placed on the number of generic brands of a medicine that can be submitted for fast-track registration. This, together with resource constraints at the regulator, may delay access to important new medicines, new fixed-dose combinations of critical medicines or affordable versions of biological medicines (biosimilars). One reason for not limiting the number of fast-track generic applications was to promote price competition among generic brands. We found this not to be valid, since market share correlated poorly with price. Generic brands with high market share were, mostly, those that were registered first. We propose that the number of generic brands accepted for fast-tracking be limited to not more than seven per medicine.
Pro-generics policies and the backlog in medicines registration in South Africa: implications for access to essential and affordable medicines
Micro-evaporators for kinetic exploration of phase diagrams
We use pervaporation-based microfluidic devices to concentrate species in
aqueous solutions with spatial and temporal control of the process. Using
experiments and modelling, we quantitatively describe the advection-diffusion
behavior of the concentration field of various solutions (electrolytes,
colloids, etc) and demonstrate the potential of these devices as universal
tools for the kinetic exploration of the phases and textures that form upon
concentration
Magnetodielectric effect in nickel nanosheet-Na-4 mica composites
Nickel nanosheets of thickness 0.6 nm were grown within the nanochannels of
Na-4 mica template. The specimens show magnetodielectric effect at room
temperature with a change of dielectric constant as a function of magnetic
field, the electric field frequency varying from 100 to 700 kHz. A decrease of
5% in the value of dielectric constant was observed up to a field of 1.2 Tesla.
This is explained by an inhomogeneous two-component composite model as
theoretically proposed recently. The present approach will open up synthesis of
various nanocomposites for sensor applications.Comment: 11 pages, 7 figure
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