17,092 research outputs found
Adaptive correction of depth-induced aberrations in multiphoton scanning microscopy using a deformable mirror
We demonstrate adaptive aberration correction for depth-induced spherical aberration in a multiphoton scanning microscope with a micromachined deformable mirror. Correction was made using a genetic learning algorithm with two-photon fluorescence intensity feedback to determine the desired shape for an adaptive mirror. For a 40×/0.6 NA long working distance objective, the axial scanning range was increased from 150 mm to 600 mm.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72425/1/j.1365-2818.2002.01004.x.pd
Analysis of vertebral chemistry to assess stock structure in a deep-sea shark, Etmopterus spinax
First published online: October 27, 2016Deep-sea sharks play a valuable ecological role helping maintain food web balance, yet they are vulnerable to commercial fishing because of slow growth rates and low reproductive capacity. Overfishing of sharks can heavily impact marine ecosystems and the fisheries these support. Knowledge of stock structure is integral to sustainable management of fisheries. The present study analysed vertebral chemistry using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to assay concentrations of 7Li, 23Na, 24Mg, 55Mn, 59Co, 60Ni, 63Cu, 66Zn, 85Rb, 88Sr, 138Ba and 208Pb to assess stock structure in a deep-sea shark, Etmopterus spinax, in Norwegian and French waters. Few studies have applied this technique to elasmobranch vertebrae and the present study represents its first application to a deep-sea shark. Three stocks were identified at the regional scale off western Norway, southern Norway, and France. At finer spatial scales there was evidence of strong population mixing. Overall, the general pattern of stock structure outlined herein provides some indication of the spatial scales at which stocks should be viewed as distinct fisheries management units. The identification of an effective multi-element signature for distinguishing E. spinax stocks utilizing Sr, Ba, Mg, Zn and Pb and the methodological groundwork laid in the present study could also expedite future research into stock structure for E. spinax and deep-sea elasmobranchs more generally.Matthew N. McMillan, Christopher Izzo, Claudia Junge, Ole Thomas Albert, Armelle Jung and Bronwyn M. Gillander
Evaluation of Escherichia coli as indicator of point-of-use chlorination efficiency of drinking water
In this study, the relevance of the presence of Escherichia coli in drinking water as an indicator of point-of-use chlorination efficiency is examined. The survival of clinical isolates of human enteric pathogenic bacteria (Klebsiella pneumoniae, Pseudomonas aeruginosa, Salmonella typhi, Shigella dysenteriae, Staphylococcus aureus, Streptococcus faecalis and Vibrio cholerae) as well as E. coli was monitored as a function of effective germicidal concentration and contact time. The inactivation kinetics indicated that the minimum effective dose for three-log units (99.9%) inactivation of E. coli (C·T99.9% = 10 mgl-1-min) can sufficiently eliminate the other pathogens (C·T99.9% ranged from 5.6–10.5 mgl-1-min); the exception being K. pneumoniae, which required more than 1.4-times higher dose. In general, the results implied that the branded hypochlorite solution should effectively inactivate almost all vegetative bacteria in household drinking water at the manufacturer’s recommended dosage of 0.5 mgl-1 after at least 30 minutes contact time. The application of point-of-use chemical disinfectants to drinking water in households will significantly reduce the incidence of water-borne infections particularly in rural communities where central treatment of water is mostly unavailable.Keywords: Effective dose; Point-of-use disinfectants; Indicator bacteria; Pathogen; Escherichia coli; Chlorinatio
Quantifying the physical alterations of river reaches using a regional river morphology reference model. A step towards river restoration.
River engineeringRiver habitat management and restoratio
Mode decomposition and renormalization in semiclassical gravity
We compute the influence action for a system perturbatively coupled to a
linear scalar field acting as the environment. Subtleties related to
divergences that appear when summing over all the modes are made explicit and
clarified. Being closely connected with models used in the literature, we show
how to completely reconcile the results obtained in the context of stochastic
semiclassical gravity when using mode decomposition with those obtained by
other standard functional techniques.Comment: 4 pages, RevTeX, no figure
Non-polynomial Worst-Case Analysis of Recursive Programs
We study the problem of developing efficient approaches for proving
worst-case bounds of non-deterministic recursive programs. Ranking functions
are sound and complete for proving termination and worst-case bounds of
nonrecursive programs. First, we apply ranking functions to recursion,
resulting in measure functions. We show that measure functions provide a sound
and complete approach to prove worst-case bounds of non-deterministic recursive
programs. Our second contribution is the synthesis of measure functions in
nonpolynomial forms. We show that non-polynomial measure functions with
logarithm and exponentiation can be synthesized through abstraction of
logarithmic or exponentiation terms, Farkas' Lemma, and Handelman's Theorem
using linear programming. While previous methods obtain worst-case polynomial
bounds, our approach can synthesize bounds of the form
as well as where is not an integer. We present
experimental results to demonstrate that our approach can obtain efficiently
worst-case bounds of classical recursive algorithms such as (i) Merge-Sort, the
divide-and-conquer algorithm for the Closest-Pair problem, where we obtain
worst-case bound, and (ii) Karatsuba's algorithm for
polynomial multiplication and Strassen's algorithm for matrix multiplication,
where we obtain bound such that is not an integer and
close to the best-known bounds for the respective algorithms.Comment: 54 Pages, Full Version to CAV 201
Network robustness and fragility: Percolation on random graphs
Recent work on the internet, social networks, and the power grid has
addressed the resilience of these networks to either random or targeted
deletion of network nodes. Such deletions include, for example, the failure of
internet routers or power transmission lines. Percolation models on random
graphs provide a simple representation of this process, but have typically been
limited to graphs with Poisson degree distribution at their vertices. Such
graphs are quite unlike real world networks, which often possess power-law or
other highly skewed degree distributions. In this paper we study percolation on
graphs with completely general degree distribution, giving exact solutions for
a variety of cases, including site percolation, bond percolation, and models in
which occupation probabilities depend on vertex degree. We discuss the
application of our theory to the understanding of network resilience.Comment: 4 pages, 2 figure
X-ray/Optical/Radio Observations of a Resolved Supernova Remnant in NGC 6822
The supernova remnant (SNR), Ho 12, in the center of the dwarf irregular
galaxy NGC 6822 was previously observed at X-ray, optical, and radio
wavelengths. By using archival Chandra and ground-based optical data, we found
that the SNR is spatially resolved in X-rays and optical. In addition, we
obtained a ~5" resolution radio image of the SNR. These observations provide
the highest spatial resolution imaging of an X-ray/optical/radio SNR in that
galaxy to date. The multi-wavelength morphology, X-ray spectrum and
variability, and narrow-band optical imagings are consistent with a SNR. The
SNR is a shell-shaped object with a diameter of about 10" (24 pc). The
morphology of the SNR is consistent across the wavelengths while the Chandra
spectrum can be well fitted with a nonequilibrium ionization model with an
electron temperature of 2.8 keV and a 0.3-7 keV luminosity of 1.6e37 erg/s. The
age of the SNR is estimated to be 1700-5800 years.Comment: 6 pages, 3 figures, accepted for publication in the Astronomical
Journa
Simple models of small world networks with directed links
We investigate the effect of directed short and long range connections in a
simple model of small world network. Our model is such that we can determine
many quantities of interest by an exact analytical method. We calculate the
function , defined as the number of sites affected up to time when a
naive spreading process starts in the network. As opposed to shortcuts, the
presence of un-favorable bonds has a negative effect on this quantity. Hence
the spreading process may not be able to affect all the network. We define and
calculate a quantity named the average size of accessible world in our model.
The interplay of shortcuts, and un-favorable bonds on the small world
properties is studied.Comment: 15 pages, 9 figures, published versio
Anderson localization of a weakly interacting one dimensional Bose gas
We consider the phase coherent transport of a quasi one-dimensional beam of
Bose-Einstein condensed particles through a disordered potential of length L.
Among the possible different types of flow identified in [T. Paul et al., Phys.
Rev. Lett. 98, 210602 (2007)], we focus here on the supersonic stationary
regime where Anderson localization exists. We generalize the diffusion
formalism of Dorokhov-Mello-Pereyra-Kumar to include interaction effects. It is
shown that interactions modify the localization length and also introduce a
length scale L* for the disordered region, above which most of the realizations
of the random potential lead to time dependent flows. A Fokker-Planck equation
for the probability density of the transmission coefficient that takes this new
effect into account is introduced and solved. The theoretical predictions are
verified numerically for different types of disordered potentials. Experimental
scenarios for observing our predictions are discussed.Comment: 20 pages, 13 figure
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