1,682 research outputs found
Adsorption Equilibria of Gases on Activated Charcoal over a Wide Range of Temperature and Pressure
MIAMI cell effectiveness in the treatment of hemi-parkinsonian rats is enhanced by pharmacologically active microcarriers
Pharmacologically active microcarriers enhance the therapeutic effects of MIAMI cells transplanted in hemi-parkinsonian rats
Frequency Tracking and Parameter Estimation for Robust Quantum State-Estimation
In this paper we consider the problem of tracking the state of a quantum
system via a continuous measurement. If the system Hamiltonian is known
precisely, this merely requires integrating the appropriate stochastic master
equation. However, even a small error in the assumed Hamiltonian can render
this approach useless. The natural answer to this problem is to include the
parameters of the Hamiltonian as part of the estimation problem, and the full
Bayesian solution to this task provides a state-estimate that is robust against
uncertainties. However, this approach requires considerable computational
overhead. Here we consider a single qubit in which the Hamiltonian contains a
single unknown parameter. We show that classical frequency estimation
techniques greatly reduce the computational overhead associated with Bayesian
estimation and provide accurate estimates for the qubit frequencyComment: 6 figures, 13 page
Repeat UAV photogrammetry to assess calving front dynamics at a large outlet glacier draining the Greenland Ice Sheet
UAV photogrammetry and structure from motion to assess calving dynamics at Store Glacier, a large outlet draining the Greenland ice sheet
This study presents the application of a cost-effective, unmanned aerial
vehicle (UAV) to investigate calving dynamics at a major marine-terminating
outlet glacier draining the western sector of the Greenland ice sheet. The
UAV was flown over Store Glacier on three sorties during summer 2013 and
acquired over 2000 overlapping, geotagged images of the calving front at an
~40 cm ground sampling distance. Stereo-photogrammetry
applied to these images enabled the extraction of high-resolution digital elevation models (DEMs) with vertical accuracies of ± 1.9 m which were used
to quantify glaciological processes from early July to late August 2013. The
central zone of the calving front advanced by ~500 m, whilst
the lateral margins remained stable. The orientation of crevasses and the
surface velocity field derived from feature tracking indicates that lateral
drag is the primary resistive force and that ice flow varies across the
calving front from 2.5 m d−1 at the margins to in excess of
16 m d−1 at the centreline. Ice flux through the calving front is 3.8 × 107 m3 d−1,
equivalent to 13.9 Gt a−1 and comparable to
flux-gate estimates of Store Glacier's annual discharge. Water-filled
crevasses were present throughout the observation period but covered a
limited area of between 0.025 and 0.24% of the terminus and did not appear
to exert any significant control over fracture or calving. We conclude that
the use of repeat UAV surveys coupled with the processing techniques
outlined in this paper have great potential for elucidating the complex
frontal dynamics that characterise large calving outlet glaciers
Stochastic simulations of conditional states of partially observed systems, quantum and classical
In a partially observed quantum or classical system the information that we
cannot access results in our description of the system becoming mixed even if
we have perfect initial knowledge. That is, if the system is quantum the
conditional state will be given by a state matrix and if classical
the conditional state will be given by a probability distribution
where is the result of the measurement. Thus to determine the evolution of
this conditional state under continuous-in-time monitoring requires an
expensive numerical calculation. In this paper we demonstrating a numerical
technique based on linear measurement theory that allows us to determine the
conditional state using only pure states. That is, our technique reduces the
problem size by a factor of , the number of basis states for the system.
Furthermore we show that our method can be applied to joint classical and
quantum systems as arises in modeling realistic measurement.Comment: 16 pages, 11 figure
The Distribution of Redshifts in New Samples of Quasi-stellar Objects
Two new samples of QSOs have been constructed from recent surveys to test the
hypothesis that the redshift distribution of bright QSOs is periodic in
. The first of these comprises 57 different redshifts among all
known close pairs or multiple QSOs, with image separations 10\arcsec,
and the second consists of 39 QSOs selected through their X-ray emission and
their proximity to bright comparatively nearby active galaxies. The redshift
distributions of the samples are found to exhibit distinct peaks with a
periodic separation of in identical to that claimed
in earlier samples but now extended out to higher redshift peaks and 4.47, predicted by the formula but never seen before. The periodicity
is also seen in a third sample, the 78 QSOs of the 3C and 3CR catalogues. It is
present in these three datasets at an overall significance level -
, and appears not to be explicable by spectroscopic or similar
selection effects. Possible interpretations are briefly discussed.Comment: submitted for publication in the Astronomical Journal, 15 figure
The Performance of Private Equity Funds: Does Diversification Matter?
This paper is the first systematic analysis of the impact of diversification on the performance of private equity funds. A unique data set allows the exact evaluation of diversification across the dimensions financing stages, industries, and countries. Very different levels of diversification can be observed across sample funds. While some funds are highly specialized others are highly diversified. The empirical results show that the rate of return of private equity funds declines with diversification across financing stages, but increases with diversification across industries. Accordingly, the fraction of portfolio companies which have a negative return or return nothing at all, increase with diversification across financing stages. Diversification across countries has no systematic effect on the performance of private equity funds
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