7,997 research outputs found
The identification of continuous, spatiotemporal systems
We present a method for the identification of continuous, spatiotemporal
dynamics from experimental data. We use a model in the form of a partial
differential equation and formulate an optimization problem for its estimation
from data. The solution is found as a multivariate nonlinear regression problem
using the ACE-algorithm. The procedure is successfully applied to data,
obtained by simulation of the Swift-Hohenberg equation. There are no
restrictions on the dimensionality of the investigated system, allowing for the
analysis of high-dimensional chaotic as well as transient dynamics. The demands
on the experimental data are discussed as well as the sensitivity of the method
towards noise
Ultrasound-guided trans-rectal high-intensity focused ultrasound (HIFU) for advanced cervical cancer ablation is feasible: a case report.
High-intensity focused ultrasound (HIFU) is an ablative treatment undergoing assessment for the treatment of benign and malignant disease. We describe the first reported intracavitary HIFU ablation for recurrent, unresectable and symptomatic cervical cancer.A 38 year old woman receiving palliative chemotherapy for metastatic cervical adenocarcinoma was offered ablative treatment from an intracavitary trans-rectal HIFU device (Sonablate® 500). Pre-treatment symptoms included vaginal bleeding and discharge that were sufficient to impede her quality of life. No peri-procedural adverse events occurred. Symptoms resolved completely immediately post-procedure, reappeared at 7 days, increasing to pre-procedural levels by day 30.This first time experience of intracavitary cervical HIFU suggests that it is feasible for palliation of advanced cervical cancer, with no early evidence of unexpected toxicity. Ethical approval had also been granted for the use of per-vaginal access if appropriate. This route, alone or in combination with the rectal route, may provide increased accessibility in future patients with a redesigned device more suited to trans-vaginal ablations.Intracavitary HIFU is a potentially safe procedure for the treatment of cervical cancer and able to provide symptomatic improvement in the palliative setting
Analysis of permanent magnets as elasmobranch bycatch reduction devices in hook-and-line and longline trials
Previous studies indicate that elasmobranch fishes (sharks,
skates and rays) detect the Earth’s geomagnetic field by indirect magnetoreception through electromagnetic
induction, using their ampullae of Lorenzini. Applying this concept, we evaluated the capture of elasmobranchs in the presence of permanent magnets in hook-and-line and inshore
longline fishing experiments. Hooks with neodymium-iron-boron magnets significantly reduced the capture of
elasmobranchs overall in comparison with control and procedural control hooks in the hook-and-line experiment.
Catches of Atlantic sharpnose shark (Rhizoprionodon terraenovae) and smooth dogfish (Mustelus canis) were signif icantly reduced with magnetic hook-and-line treatments, whereas catches of spiny dogfish (Squalus acanthias) and clearnose skate (Raja eglanteria) were not.
Longline hooks with barium-ferrite magnets significantly reduced total elasmobranch capture when compared with control hooks. In the longline study, capture of blacktip sharks (Carcharhinus limbatus) and southern stingrays (Dasyatis americana) was reduced on magnetic hooks, whereas
capture of sandbar shark (Carcharhinus plumbeus) was not affected. Teleosts, such as red drum (Sciaenops ocellatus), Atlantic croaker (Micropogonias undulatus), oyster toadfish
(Opsanus tau), black sea bass (Centropristis striata), and the bluefish (Pomatomas saltatrix), showed no hook preference in either hook-and-line or longline studies. These results indicate that permanent magnets, although eliciting species-specific capture trends, warrant further investigation in commercial longline and recreational fisheries, where bycatch mortality is a leading contributor to declines in elasmobranch populations
Pattern Dynamics of Vortex Ripples in Sand: Nonlinear Modeling and Experimental Validation
Vortex ripples in sand are studied experimentally in a one-dimensional setup
with periodic boundary conditions. The nonlinear evolution, far from the onset
of instability, is analyzed in the framework of a simple model developed for
homogeneous patterns. The interaction function describing the mass transport
between neighboring ripples is extracted from experimental runs using a
recently proposed method for data analysis, and the predictions of the model
are compared to the experiment. An analytic explanation of the wavelength
selection mechanism in the model is provided, and the width of the stable band
of ripples is measured.Comment: 4 page
Cylindrical gravitational waves in expanding universes: Models for waves from compact sources
New boundary conditions are imposed on the familiar cylindrical gravitational
wave vacuum spacetimes. The new spacetime family represents cylindrical waves
in a flat expanding (Kasner) universe. Space sections are flat and nonconical
where the waves have not reached and wave amplitudes fall off more rapidly than
they do in Einstein-Rosen solutions, permitting a more regular null inifinity.Comment: Minor corrections to references. A note added in proo
Five-dimensional Monopole Equation with Hedge-Hog Ansatz and Abel's Differential Equation
We review the generalized monopole in the five-dimensional Euclidean space. A
numerical solution with the Hedge-Hog ansatz is studied. The Bogomol'nyi
equation becomes a second order autonomous non-linear differential equation.
The equation can be translated into the Abel's differential equation of the
second kind and is an algebraic differential equation.Comment: 4 pages, 4 figures, typos correcte
Simplicity of eigenvalues in the Anderson model
We give a simple, transparent, and intuitive proof that all eigenvalues of
the Anderson model in the region of localization are simple
Open String Creation by S-Branes
An sp-brane can be viewed as the creation and decay of an unstable
D(p+1)-brane. It is argued that the decaying half of an sp-brane can be
described by a variant of boundary Liouville theory. The pair creation of open
strings by a decaying s-brane is studied in the minisuperspace approximation to
the Liouville theory. In this approximation a Hagedorn-like divergence is found
in the pair creation rate, suggesting the s-brane energy is rapidly transferred
into closed string radiation.Comment: Talk presented at the Hangzhou String 2002 Conference, August 12-1
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