267 research outputs found
Working with Nature to Identify Coral Reefs with Increased Environmental Tolerance
Understanding what drives tolerance among coral species is key to deriving focused and effective management plans for the future. Corals have survived for millions of years and have witnessed great changes in the earth?s climate. This study compares coral species across growth environments looking at architectural differences within the skeletal structure and discusses how this may impact upon their tolerance to stress events. Results identify that variation occurs in the density of coral skeleton, density of aragonite and porosity of the skeleton. Symbiont population densities were found to be variable among coral species, but no significant differences were found across light environments. This study suggests that the micro-density of aragonite, laid down to form the coral skeleton, can vary from the previously assumed density of pure aragonite (2.94g cm-3). Massive corals were found to have greater variability within these values and to be significantly lower that aragonite deposited in the skeletons of branching corals. These differences in skeletal architecture may hold the key in discovering the fundamental variables driving coral tolerance differences. Coral skeleton density may alter the relationship at the skeletal-tissue interface, therefore influence bleaching severity. The ability to identify susceptibility of corals to stress via proxies such as skeletal architecture will enable direction of management to areas most at need and those most likely to become refugia in the future
Weylâs gauge argument
The standard U(1) âgauge principleâ or âgauge argumentâ produces an exact potential A=dλ and a vanishing field F=ddλ=0. Weyl has his own gauge argument, which is sketchy, archaic and hard to follow; but at least it produces an inexact potential A and a nonvanishing field F=dAâ 0. I attempt a reconstruction
The Mathematical Universe
I explore physics implications of the External Reality Hypothesis (ERH) that
there exists an external physical reality completely independent of us humans.
I argue that with a sufficiently broad definition of mathematics, it implies
the Mathematical Universe Hypothesis (MUH) that our physical world is an
abstract mathematical structure. I discuss various implications of the ERH and
MUH, ranging from standard physics topics like symmetries, irreducible
representations, units, free parameters, randomness and initial conditions to
broader issues like consciousness, parallel universes and Godel incompleteness.
I hypothesize that only computable and decidable (in Godel's sense) structures
exist, which alleviates the cosmological measure problem and help explain why
our physical laws appear so simple. I also comment on the intimate relation
between mathematical structures, computations, simulations and physical
systems.Comment: Replaced to match accepted Found. Phys. version, 31 pages, 5 figs;
more details at http://space.mit.edu/home/tegmark/toe.htm
Improved model for the establishment and evaluation of detrusor overactivity in female Wistar rats
Localization and symmetries
The violation of the Noether relation between symmetries and charges is
reduced to the time dependence of the charge associated to a conserved current.
For the U(1) gauge symmetry a non-perturbative control of the charge
commutators is obtained by an analysis of the Coulomb charged fields. From
this, in the unbroken case we obtain a correct expression for the electric
charge on the Coulomb states, its superselection and the presence of massless
vector bosons; in the broken case, we obtain a general non-perturbative version
of the Higgs phenomenon, i.e. the absence of massless Goldstone bosons and of
massless vector bosons. The conservation of the (gauge dependent) current
associated to the U(1) axial symmetry in QCD is shown to be compatible with the
time dependence of the corresponding charge commutators and a non-vanishing
eta' mass, as a consequence of the non locality of the (conserved) current.Comment: Invited contribution to ``The Quantum Universe'', dedicated to G.
Ghirardi for his 70th birthda
The effect of alpha-blocker treatment on bladder hypoxia inducible factor-1 alpha regulation during lower urinary tract obstruction
Protein kinase C modulates frequency of micturition and non-voiding contractions in the urinary bladder via neuronal and myogenic mechanisms
Reflections on the four facets of symmetry: how physics exemplifies rational thinking
In contemporary theoretical physics, the powerful notion of symmetry stands
for a web of intricate meanings among which I identify four clusters associated
with the notion of transformation, comprehension, invariance and projection.
While their interrelations are examined closely, these four facets of symmetry
are scrutinised one after the other in great detail. This decomposition allows
us to examine closely the multiple different roles symmetry plays in many
places in physics. Furthermore, some connections with others disciplines like
neurobiology, epistemology, cognitive sciences and, not least, philosophy are
proposed in an attempt to show that symmetry can be an organising principle
also in these fields
Defense suppression benefits herbivores that have a monopoly on their feeding site but can backfire within natural communities
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