1,881 research outputs found
Bottlenose dolphins modify behavior to reduce metabolic effect of tag attachment
Author Posting. © The Author(s), 2014. This is the author's version of the work. It is posted here by permission of The Company of Biologists for personal use, not for redistribution. The definitive version was published in Journal of Experimental Biology 217 (2014): 4229-4236, doi:10.1242/jeb.108225.Attaching bio-telemetry or -logging devices (‘tags’) to marine animals for research and monitoring adds drag to streamlined bodies, thus affecting posture, swimming gaits and energy balance. These costs have never been measured in free-swimming cetaceans. To examine the effect of drag from a tag on metabolic rate, cost of transport and swimming behavior, four captive male dolphins (Tursiops truncatus) were trained to swim a set course, either non-tagged (n=7) or fitted with a tag (DTAG2; n=12), and surface exclusively in a flow-through respirometer in which oxygen consumption (Graphic) and carbon dioxide production (Graphic; ml kg−1 min−1) rates were measured and respiratory exchange ratio (Graphic/Graphic) was calculated. Tags did not significantly affect individual mass-specific oxygen consumption, physical activity ratios (exercise Graphic/resting Graphic), total or net cost of transport (COT; J m−1 kg−1) or locomotor costs during swimming or two-minute recovery phases. However, individuals swam significantly slower when tagged (by ~11%; mean ± s.d., 3.31±0.35 m s−1) than when non-tagged (3.73±0.41 m s−1). A combined theoretical and computational fluid dynamics model estimating drag forces and power exertion during swimming suggests that drag loading and energy consumption are reduced at lower swimming speeds. Bottlenose dolphins in the specific swimming task in this experiment slowed to the point where the tag yielded no increases in drag or power, while showing no difference in metabolic parameters when instrumented with a DTAG2. These results, and our observations, suggest that animals modify their behavior to maintain metabolic output and energy expenditure when faced with tag-induced drag.This project was funded by the National Oceanographic Partnership Program [National Science Foundation via the Office of Naval Research, N00014-11-1-0113]. J.v.d.H. was supported by a Postgraduate Scholarship from the Natural Sciences and Engineering Research Council of Canada.2015-10-1
To what distances do we know the confining potential?
We argue that asymptotically linear static potential is built in into the
common procedure of extracting it from lattice Wilson loop measurements. To
illustrate the point, we extract the potential by the standard lattice method
in a model vacuum made of instantons. A beautiful infinitely rising linear
potential is obtained in the case where the true potential is actually
flattening. We argue that the flux tube formation might be also an artifact of
the lattice procedure and not necessarily a measured physical effect.
We conclude that at present the rising potential is known for sure up to no
more than about 0.7 fm. It may explain why no screening has been clearly
observed so far for adjoint sources and for fundamental sources but with
dynamical fermions.
Finally, we speculate on how confinement could be achieved even if the static
potential in the pure glue theory is not infinitely rising.Comment: 16 pages, 5 figures. Additional arguments presented, a new figure and
references adde
Exotic baryon multiplets at large number of colours
We generalize the usual octet, decuplet and exotic antidecuplet and higher
baryon multiplets to any number of colours Nc. We show that the multiplets fall
into a sequence of bands with O(1/Nc) splittings inside the band and
O(1)splittings between the bands characterized by "exoticness", that is the
number of extra quark-antiquark pairs needed to compose the multiplet. Each
time one adds a pair the baryon mass is increased by the same constant which
can be interpreted as a mass of a quark-antiquark pair. At the same time, we
prove that masses of exotic rotational multiplets are reliably determined at
large Nc from collective quantization of chiral solitons.Comment: 13 p., 5 figs. New section and references adde
Stable ring vortex solitons in Bessel optical lattices
Stable ring vortex solitons, featuring a bright-shape, appear to be very rare
in nature. However, here we show that they exist and can be made dynamically
stable in defocusing cubic nonlinear media with an imprinted Bessel optical
lattice. We find the families of vortex lattice solitons and reveal their
salient properties, including the conditions required for their stability. We
show that the higher the soliton topological charge, the deeper the lattice
modulation necessary for stabilization.Comment: 14 pages, 4 figures, submitted to Physical Review Letter
Bandwidth-controlled Mott transition in I. Optical studies of localized charge excitations
Infrared reflection measurements of the half-filled two-dimensional organic
conductors -(BEDT-TTF)Cu[N(CN)]BrCl were
performed as a function of temperature ( K) and
Br-substitution (, 40%, 73%, 85%, and 90%) in order to study the
metal-insulator transition. We can distinguish absorption processes due to
itinerant and localized charge carriers. The broad mid-infrared absorption has
two contributions: transitions between the two Hubbard bands and intradimer
excitations from the charges localized on the (BEDT-TTF) dimer. Since the
latter couple to intramolecular vibrations of BEDT-TTF, the analysis of both
electronic and vibrational features provides a tool to disentangle these
contributions and to follow their temperature and electronic-correlations
dependence. Calculations based on the cluster model support our interpretation.Comment: 12 pages, 12 figure
An improvement of the Berry--Esseen inequality with applications to Poisson and mixed Poisson random sums
By a modification of the method that was applied in (Korolev and Shevtsova,
2009), here the inequalities
and
are proved for the
uniform distance between the standard normal distribution
function and the distribution function of the normalized sum of an
arbitrary number of independent identically distributed random
variables with zero mean, unit variance and finite third absolute moment
. The first of these inequalities sharpens the best known version of
the classical Berry--Esseen inequality since
by virtue of
the condition , and 0.4785 is the best known upper estimate of the
absolute constant in the classical Berry--Esseen inequality. The second
inequality is applied to lowering the upper estimate of the absolute constant
in the analog of the Berry--Esseen inequality for Poisson random sums to 0.3051
which is strictly less than the least possible value of the absolute constant
in the classical Berry--Esseen inequality. As a corollary, the estimates of the
rate of convergence in limit theorems for compound mixed Poisson distributions
are refined.Comment: 33 page
Application of the Large-N_c limit to a Chiral Lagrangian with Resonances
It is shown that the implementation of the Large-- approximation helps
to get insight into the structure of, in principle, any QCD-like theory. As an
example, we will compute the NLO corrections to in the chiral limit
with a Lagrangian with Resonances.Comment: 9 pages, 1 figure. Talk given at the International School of
Subnuclear Physics (Erice 2002). To be published in the Proceeding
Exotic Anti-Decuplet of Baryons: Prediction from Chiral Solitons
We predict an exotic Z^+ baryon (having spin 1/2, isospin 0 and strangeness
+1) with a relatively low mass of about 1530 MeV and total width of less than
15 MeV. It seems that this region of masses has avoided thorough searches in
the past.Comment: Revised version, to appear in Z. fuer Phys. A. The importance of 1/Nc
corrections to antidecuplet widths is demonstrated. 21 pages, 1 LaTeX figur
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