6,045 research outputs found
Corrections for pumped SBE 41CP CTDs determined from stratified tank experiments
Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Atmospheric and Oceanic Technology 36(4), (2019): 733-744, doi:10.1175/JTECH-D-18-0050.1.Sea-Bird Scientific SBE 41CP CTDs are used on autonomous floats in the global Argo ocean observing program to measure the temperature and salinity of the upper ocean. While profiling, the sensors are subject to dynamic errors as they profile through vertical gradients. Applying dynamic corrections to the temperature and conductivity data reduces these errors and improves sensor accuracy. A series of laboratory experiments conducted in a stratified tank are used to characterize dynamic errors and determine corrections. The corrections are adapted for Argo floats, and recommendations for future implementation are presented.2020-04-2
Reply to "comments on 'corrections for pumped SBE 41CP CTDs determined from stratified tank experiments'"
© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Martini, K. I., Murphy, D. J., Schmitt, R. W., & Larson, N. G. Reply to "comments on 'corrections for pumped SBE 41CP CTDs determined from stratified tank experiments'". Journal of Atmospheric and Oceanic Technology, 37(2), (2020): 357-363, doi:10.1175/JTECH-D-19-0171.1.The response in Johnson (2020) that the method used to determine cell thermal mass correction coefficients for SBE 41CP CTD data from Argo floats is biased as determined by Martini et al. (2019) is valid. However, the recommendation for correction coefficients should not be followed due to these three errors in Johnson (2020):
Alignment is as large a source of dynamic error as cell thermal mass in the SBE 41CP CTD.
Order of operations was overlooked, so that cell thermal mass is used to correct for alignment errors caused by the temporal mismatch of temperature and conductivity.
The cell thermal mass corrections determined in Johnson et al. (2007) and Johnson (2020) also bias salinity.
In this response we will do the following:
Detail how the corrections in Johnson (2020) are biased because the optimization procedure does not accurately model physics in the tank and conductivity cell.
Verify using in situ data from Argo floats deployed in the ocean that alignment is a significant source of error for the SBE 41CP as shown in Martini et al. (2019).
Determine cell thermal mass correction coefficients from the stratified tank experiment merging the methods of Johnson (2020) and Martini et al. (2019) to optimize against a model that better represents the physics in the tank and conductivity cell.
Compare the corrections using in situ data using the coefficients determined in Johnson et al. (2007), Martini et al. (2019), Johnson (2020), and this manuscript.Thanks to Pelle Robbins for finding the in situ profiles used for this analysis in the vast database of Argo floats, John Gilson showing me how to access that high-resolution data, Ray Schmitt for use of the stratified tank, Susan Wijffels, Breck Owens, and Annie Wong for intellectual support, and Diego Sorrentino and Vlad Simontov for validating the sampling scheme in the SBE 41CP.2020-08-2
Effect of atomic beam alignment on photon correlation measurements in cavity QED
Quantum trajectory simulations of a cavity QED system comprising an atomic
beam traversing a standing-wave cavity are carried out. The delayed photon
coincident rate for forwards scattering is computed and compared with the
measurements of Rempe et al. [Phys. Rev. Lett. 67, 1727 (1991)] and Foster et
al. [Phys. Rev. A 61, 053821 (2000)]. It is shown that a moderate atomic beam
misalignment can account for the degradation of the predicted correlation. Fits
to the experimental data are made in the weak-field limit with a single
adjustable parameter--the atomic beam tilt from perpendicular to the cavity
axis. Departures of the measurement conditions from the weak-field limit are
discussed.Comment: 15 pages and 13 figure
Spontaneous Emission in Chaotic Cavities
The spontaneous emission rate \Gamma of a two-level atom inside a chaotic
cavity fluctuates strongly from one point to another because of fluctuations in
the local density of modes. For a cavity with perfectly conducting walls and an
opening containing N wavechannels, the distribution of \Gamma is given by
P(\Gamma) \propto \Gamma^{N/2-1}(\Gamma+\Gamma_0)^{-N-1}, where \Gamma_0 is the
free-space rate. For small N the most probable value of \Gamma is much smaller
than the mean value \Gamma_0.Comment: 4 pages, RevTeX, 1 figur
Influence of a dynamical gluon mass in the and forward scattering
We compute the tree level cross section for gluon-gluon elastic scattering
taking into account a dynamical gluon mass, and show that this mass scale is a
natural regulator for this subprocess cross section. Using an eikonal approach
in order to examine the relationship between this gluon-gluon scattering and
the elastic and channels, we found that the dynamical gluon
mass is of the same order of magnitude as the {\it ad hoc} infrared mass scale
underlying eikonalized QCD-inspired models. We argue that this
correspondence is not an accidental result, and that this dynamical scale
indeed represents the onset of non-perturbative contributions to the elastic
hadron-hadron scattering. We apply the eikonal model with a dynamical infrared
mass scale to obtain predictions for ,
, slope , and differential elastic
scattering cross section at Tevatron and CERN-LHC
energies.Comment: 20 pages, 5 figures; misprints corrected and comments added. To
appear in Phys. Rev.
A Warp in Progress : H I and Radio Continuum Observations of the Spiral NGC 3145
Date of Acceptance: 16/06/2015We present VLA H I and 6 cm radio continuum observations of the spiral NGC 3145 and H I observations of its two companions, NGC 3143 and PGC 029578. In optical images NGC 3145 has stellar arms that appear to cross, forming "X"-features. Our radio continuum observations rule out shock fronts at 3 of the 4 "X"-features. In the middle-to-outer disk, the H I line-profiles of NGC 3145 are skewed. Relative to the disk, the gas in the skewed wing of the line-profiles has z-motions away from us on the approaching side of the galaxy and z-motions of about the same magnitude (about 40 km/s) towards us on the receding side. These warping motions imply that there has been a perturbation with a sizeable component perpendicular to the disk over large spatial scales. Two features in NGC 3145 have velocities indicating that they are out-of-plane tidal arms. One is an apparent branch of a main spiral arm; the velocity of the branch is 150 km/s greater than the spiral arm where they appear to intersect in projection. The other is an arm that forms 3 of the "X"-features. It differs in velocity by 56 km/s from the disk at the same projected location. Based on its SFR and H I properties, NGC 3143 is the more likely of the two companions to have interacted with NGC 3145 recently. A simple analytic model demonstrates that an encounter between NGC 3143 and NGC 3145 is a plausible explanation for the observed warping motions in NGC 3145.Peer reviewe
Single photon generation by pulsed excitation of a single dipole
The fluorescence of a single dipole excited by an intense light pulse can
lead to the generation of another light pulse containing a single photon. The
influence of the duration and energy of the excitation pulse on the number of
photons in the fluorescence pulse is studied. The case of a two-level dipole
with strongly damped coherences is considered. The presence of a metastable
state leading to shelving is also investigated.Comment: 17 pages, 4 figures, submitted to PR
Integrated stratigraphy of the Waitakian-Otaian Stage boundary stratotype, Early Miocene, New Zealand
The base of the type section of the Otaian Stage at Bluecliffs, South Canterbury, is recognised as the stratotype for the boundary between the Waitakian and Otaian Stages. Principal problems with the boundary are the restriction of existing bioevent proxies to shelf and upper slope environments and its uncertain age. These topics are addressed by a multidisplinary study of a 125 m section about the boundary, which examines its lithostratigraphy, depositional setting, biostratigraphy, correlation, and geochronology.
The lower siltstone lithofacies (0-38.5 m) was deposited at upper bathyal depths (200-600 m) in a marginal basin which was partially sheltered from fully oceanic circulation by a submarine high and islands. The site was covered by cool-temperate water and was probably adjacent to the Subtropical Convergence. This unit is succeeded by the banded lithofacies (38.5-106 m) and the upper siltstone lithofacies (basal 19 m studied). Paleodepth probably declined up-sequence, but deposition at shelf depths is not definitely indicated. A cyclic pattern of abundance spikes in benthic and planktonic foraminifera commences 9 m above base and extends to 73 m in the banded lithofacies. Oxygen isotope excursions (up to 2.08%) in Euuvigerina miozea and Cibicides novozelandicus are greatest within the interval containing the abundance spikes. The stage boundary occurs in the banded lithofacies at the highest abundance spike (73 m). Although condensed intervals might affect the completeness of the section, they are not associated with sedimentary discontinuities, and we consider that the section is suitable as a biostratigraphic reference.
Spores, pollens, dinoflagellates, calcareous nannofossils, foraminifera, bryozoans, and ostracods are preserved near the boundary, but molluscs principally occur higher, in the shallower upper siltstone lithofacies. Siliceous microfossils are rare. There is considerable scope for further biostratigraphic research.
The primary event marking the boundary at 73 m is the appearance of the benthic foraminifer Ehrenbergina marwicki. This is a distinctive and widely distributed event but is restricted to shelf and upper bathyal environments. Supplementary events in planktonic foraminifera and calcareous nannofossils were researched. Highest occurrences of Globigerina brazieri and G. euapertura are recorded at 47 and 58 m. There is a marked decline in relative abundance of Paragloborotalia spp. at 62 m. Helicosphaera carteri becomes more abundant than H. euphratis between 56 and 87 m. These events are not exact proxies for the boundary but they may usefully indicate proximity to it. They occur in the interval of prominent spikes in foraminiferal abundance.
The Waitakian-Otaian boundary is dated at 21.7 Ma by strontium isotopes. Stable primary remanence could not be determined in a pilot paleomagnetic study of Bluecliffs specimens. However, specimens trended towards reversed polarity, and remagnetisation great circle analysis will allow directions to be calculated in future collections
Generating entangled superpositions of macroscopically distinguishable states within a parametric oscillator
We suggest a variant of the recently proposed experiment for the generation
of a new kind of Schroedinger-cat states, using two coupled parametric
down-converter nonlinear crystals [F. De Martini, Phys. Rev. Lett. 81, 2842
(1998)]. We study the parametric oscillator case and find that an entangled
Schroedinger-cat type state of two cavities, whose mirrors are placed along the
output beams of the nonlinear crystals, can be realized under suitable
conditions.Comment: RevTeX 17 pages, 9 eps files for 7 figures. Submitted to Physical
Review
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