607 research outputs found
Cavity cooling a single charged nanoparticle
The development of laser cooling coupled with the ability to trap atoms and
ions in electromagnetic fields, has revolutionised atomic and optical physics,
leading to the development of atomic clocks, high-resolution spectroscopy and
applications in quantum simulation and processing. However, complex systems,
such as large molecules and nanoparticles, lack the simple internal resonances
required for laser cooling. Here we report on a hybrid scheme that uses the
external resonance of an optical cavity, combined with radio frequency (RF)
fields, to trap and cool a single charged nanoparticle. An RF Paul trap allows
confinement in vacuum, avoiding instabilities that arise from optical fields
alone, and crucially actively participates in the cooling process. This system
offers great promise for cooling and trapping a wide range of complex charged
particles with applications in precision force sensing, mass spectrometry,
exploration of quantum mechanics at large mass scales and the possibility of
creating large quantum superpositions.Comment: 8 pages, 5 figures Updated version includes additional references,
new title, and supplementary information include
Optomechanical cooling of levitated spheres with doubly-resonant fields
Optomechanical cooling of levitated dielectric particles represents a
promising new approach in the quest to cool small mechanical resonators towards
their quantum ground state. We investigate two-mode cooling of levitated
nanospheres in a self-trapping regime. We identify a rich structure of split
sidebands (by a mechanism unrelated to usual strong-coupling effects) and
strong cooling even when one mode is blue detuned. We show the best regimes
occur when both optical fields cooperatively cool and trap the nanosphere,
where cooling rates are over an order of magnitude faster compared to
corresponding single-sideband cooling rates.Comment: 8 Pages, 7 figure
Chemical Changes in the Serum Associated With Equine Encephalomyelitis and Moldy Corn Poisoning of Horses
Specific infectious equine encephalomyelitis and moldy corn poisoning in horses are becoming more prevalent in Iowa yearly. Encephalomyelitis has been described, the etiology determined, the mode of transmission established and the typical clinical and pathological findings resolved
Nanoscale temperature measurements using non-equilibrium Brownian dynamics of a levitated nanosphere
This is the author accepted manuscript. The final version is available from Nature Publishing Group via the DOI in this record.Einstein realized that the fluctuations of a Brownian particle can be used to ascertain the properties of its environment. A large number of experiments have since exploited the Brownian motion of colloidal particles for studies of dissipative processes, providing insight into soft matter physics and leading to applications from energy harvesting to medical imaging. Here, we use heated optically levitated nanospheres to investigate the non-equilibrium properties of the gas surrounding them. Analysing the sphere's Brownian motion allows us to determine the temperature of the centre-of-mass motion of the sphere, its surface temperature and the heated gas temperature in two spatial dimensions. We observe asymmetric heating of the sphere and gas, with temperatures reaching the melting point of the material. This method offers opportunities for accurate temperature measurements with spatial resolution on the nanoscale, and provides a means for testing non-equilibrium thermodynamics. © 2014 Macmillan Publishers Limited. All rights reserved.EPSRCRoyal Thai GovernmentRoyal SocietyEuropean COST networ
Dynamics of levitated nanospheres: towards the strong coupling regime
The use of levitated nanospheres represents a new paradigm for the
optomechanical cooling of a small mechanical oscillator, with the prospect of
realising quantum oscillators with unprecedentedly high quality factors. We
investigate the dynamics of this system, especially in the so-called
self-trapping regimes, where one or more optical fields simultaneously trap and
cool the mechanical oscillator. The determining characteristic of this regime
is that both the mechanical frequency and single-photon
optomechanical coupling strength parameters are a function of the optical
field intensities, in contrast to usual set-ups where and are
constant for the given system. We also measure the characteristic transverse
and axial trapping frequencies of different sized silica nanospheres in a
simple optical standing wave potential, for spheres of radii \,nm,
illustrating a protocol for loading single nanospheres into a standing wave
optical trap that would be formed by an optical cavity. We use this data to
confirm the dependence of the effective optomechanical coupling strength on
sphere radius for levitated nanospheres in an optical cavity and discuss the
prospects for reaching regimes of strong light-matter coupling. Theoretical
semiclassical and quantum displacement noise spectra show that for larger
nanospheres with \,nm a range of interesting and novel dynamical
regimes can be accessed. These include simultaneous hybridization of the two
optical modes with the mechanical modes and parameter regimes where the system
is bistable. We show that here, in contrast to typical single-optical mode
optomechanical systems, bistabilities are independent of intracavity intensity
and can occur for very weak laser driving amplitudes
Effects of Surface Geology on Seismic Ground Motion Deduced from Ambient-Noise Measurements in the Town of Avellino, Irpinia Region (Italy)
The effects of surface geology on ground motion
provide an important tool in seismic hazard studies. It is well
known that the presence of soft sediments can cause amplification
of the ground motion at the surface, particularly when there is a
sharp impedance contrast at shallow depth. The town of Avellino is
located in an area characterised by high seismicity in Italy, about
30 km from the epicentre of the 23 November 1980, Irpinia
earthquake (M = 6.9). No earthquake recordings are available in
the area. The local geology is characterised by strong heterogeneity,
with impedance contrasts at depth. We present the results
from seismic noise measurements carried out in the urban area of
Avellino to evaluate the effects of local geology on the seismic
ground motion. We computed the horizontal-to-vertical (H/V)
noise spectral ratios at 16 selected sites in this urban area for which
drilling data are available within the first 40 m of depth. A Rayleigh
wave inversion technique using the peak frequencies of the
noise H/V spectral ratios is then presented for estimating Vs
models, assuming that the thicknesses of the shallow soil layers are
known. The results show a good correspondence between experimental
and theoretical peak frequencies, which are interpreted in
terms of sediment resonance. For one site, which is characterised
by a broad peak in the horizontal-to-vertical spectral-ratio curve,
simple one-dimensional modelling is not representative of the
resonance effects. Consistent variations in peak amplitudes are seen
among the sites. A site classification based on shear-wave velocity
characteristics, in terms of Vs30, cannot explain these data. The
differences observed are better correlated to the impedance contrast
between the sediments and basement. A more detailed investigation
of the physical parameters of the subsoil structure, together with
earthquake data, are desirable for future research, to confirm these
data in terms of site response
Nanoscale temperature measurements using non-equilibrium Brownian dynamics of a levitated nanosphere
Einstein realised that the fluctuations of a Brownian particle can be used to
ascertain properties of its environment. A large number of experiments have
since exploited the Brownian motion of colloidal particles for studies of
dissipative processes, providing insight into soft matter physics, and leading
to applications from energy harvesting to medical imaging. Here we use
optically levitated nanospheres that are heated to investigate the
non-equilibrium properties of the gas surrounding them. Analysing the sphere's
Brownian motion allows us to determine the temperature of the centre-of-mass
motion of the sphere, its surface temperature and the heated gas temperature in
two spatial dimensions. We observe asymmetric heating of the sphere and gas,
with temperatures reaching the melting point of the material. This method
offers new opportunities for accurate temperature measurements with spatial
resolution on the nanoscale, and a new means for testing non-equilibrium
thermodynamicsComment: 5 pages, 4 figures, supplementary material available upon reques
Rossby Wave Propagation into the Northern Hemisphere Stratosphere: The Role of Zonal Phase Speed
Sudden stratospheric warming (SSW) events are to a dominant part induced by upward propagating planetary waves. While theory predicts that the zonal phase speed of a tropospheric wave forcing affects wave propagation into the stratosphere, its relevance for SSW events has so far not been considered. This study shows in a linear wave diagnostic and in reanalysis data that phase speeds tend eastward as waves propagate upward, indicating that the stratosphere preselects eastward phase speeds for propagation, especially for zonal wave number 2. This also affects SSW events: Split SSW events tend to be preceded by anomalously eastward zonal phase speeds. Zonal phase speed may indeed explain part of the increased wave flux observed during the preconditioning of SSW events, as, for example, for the record 2009 SSW event
Vitamin D Status and 5â Year Changes in Periodontal Disease Measures Among Postmenopausal Women: The Buffalo OsteoPerio Study
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/141463/1/jper1321.pd
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