39,323 research outputs found
State Prescription Drug Price Web Sites: How Useful to Consumers?
Compares ten sites and identifies key limitations due to data omissions, gaps between insured and uninsured consumers, and varied program implementation. Presents alternative policy options such as requiring price lists from pharmacies
Are Black Holes Elementary Particles?
Quantum black holes are the smallest and heaviest conceivable elementary
particles. They have a microscopic size but a macroscopic mass. Several
fundamental types have been constructed with some remarkable properties.
Quantum black holes in the neighborhood of the Galaxy could resolve the paradox
of ultra-high energy cosmic rays detected in Earth's atmosphere. They may also
play a role as dark matter in cosmology.Comment: Lecture delivered in Conference on Particle Physics, Astrophysics and
Quantum Field Theory: 75 Years since Solvay, 27 -29 November 2008, Nanyang
Executive Centre, Singapore. 10 page
Interference Effects Due to Commensurate Electron Trajectories and Topological Crossovers in (TMTSF)2ClO4
We report angle-dependent magnetoresistance measurements on (TMTSF)2ClO4 that
provide strong support for a new macroscopic quantum phenomenon, the
interference commensurate (IC) effect, in quasi-one dimensional metals. In
addition to observing rich magnetoresistance oscillations, and fitting them
with one-electron calculations, we observe a clear demarcation of
field-dependent behavior at local resistance minima and maxima (versus field
angle). Anticipated by a theoretical treatment of the IC effect in terms of
Bragg reflections in the extended Brillouin zone, this behavior results from
1D-2D topological crossovers of electron wave functions as a function of field
orientation.Comment: 14 page
Emerging trend in second messenger communication and myoendothelial feedback
Over the past decade, second messenger communication has emerged as one of the intriguing topics in the field of vasomotor control. Of particular interest has been the idea of second messenger flux from smooth muscle to endothelium initiating a feedback response that attenuates constriction. Mechanistic details of the precise signaling cascade have until recently remained elusive. In this perspective, we introduce readers to how myoendothelial gaps junctions could enable sufficient inositol trisphosphate flux to initiate endothelial Ca2+ events that activate Ca2+ sensitive K+ channels. The resulting hyperpolarizing current would in turn spreads back through the same myoendothelial gap junctions to moderate smooth muscle depolarization and constriction. In discussing this defined feedback mechanism, this brief manuscript will stress the importance of microdomains and of discrete cellular signaling
A Homological Approach to Belief Propagation and Bethe Approximations
We introduce a differential complex of local observables given a
decomposition of a global set of random variables into subsets. Its boundary
operator allows us to define a transport equation equivalent to Belief
Propagation. This definition reveals a set of conserved quantities under Belief
Propagation and gives new insight on the relationship of its equilibria with
the critical points of Bethe free energy.Comment: 14 pages, submitted for the 2019 Geometric Science of Information
colloquiu
Dynamics of fully coupled rotators with unimodal and bimodal frequency distribution
We analyze the synchronization transition of a globally coupled network of N
phase oscillators with inertia (rotators) whose natural frequencies are
unimodally or bimodally distributed. In the unimodal case, the system exhibits
a discontinuous hysteretic transition from an incoherent to a partially
synchronized (PS) state. For sufficiently large inertia, the system reveals the
coexistence of a PS state and of a standing wave (SW) solution. In the bimodal
case, the hysteretic synchronization transition involves several states.
Namely, the system becomes coherent passing through traveling waves (TWs), SWs
and finally arriving to a PS regime. The transition to the PS state from the SW
occurs always at the same coupling, independently of the system size, while its
value increases linearly with the inertia. On the other hand the critical
coupling required to observe TWs and SWs increases with N suggesting that in
the thermodynamic limit the transition from incoherence to PS will occur
without any intermediate states. Finally a linear stability analysis reveals
that the system is hysteretic not only at the level of macroscopic indicators,
but also microscopically as verified by measuring the maximal Lyapunov
exponent.Comment: 22 pages, 11 figures, contribution for the book: Control of
Self-Organizing Nonlinear Systems, Springer Series in Energetics, eds E.
Schoell, S.H.L. Klapp, P. Hoeve
Understanding/unravelling carotenoid excited singlet states.
Carotenoids are essential light-harvesting pigments in natural photosynthesis. They absorb in the blue–green region of the solar spectrum and transfer the absorbed energy to (bacterio-)chlorophylls, and thus expand the wavelength range of light that is able to drive photosynthesis. This process is an example of singlet–singlet excitation energy transfer, and carotenoids serve to enhance the overall efficiency of photosynthetic light reactions. The photochemistry and photophysics of carotenoids have often been interpreted by referring to those of simple polyene molecules that do not possess any functional groups. However, this may not always be wise because carotenoids usually have a number of functional groups that induce the variety of photochemical behaviours in them. These differences can also make the interpretation of the singlet excited states of carotenoids very complicated. In this article, we review the properties of the singlet excited states of carotenoids with the aim of producing as coherent a picture as possible of what is currently known and what needs to be learned
Facial structures for various notions of positivity and applications to the theory of entanglement
In this expository note, we explain facial structures for the convex cones
consisting of positive linear maps, completely positive linear maps,
decomposable positive linear maps between matrix algebras, respectively. These
will be applied to study the notions of entangled edge states with positive
partial transposes and optimality of entanglement witnesses.Comment: An expository note. Section 7 and Section 8 have been enlarge
Kinetics of macroion coagulation induced by multivalent counterions
Due to the strong correlations between multivalent counterions condensed on a
macroion, the net macroion charge changes sign at some critical counterion
concentration. This effect is known as the charge inversion. Near this critical
concentration the macroion net charge is small. Therefore, short range
attractive forces between macroions dominate Coulomb repulsion and lead to
their coagulation. The kinetics of macroion coagulation in this range of
counterion concentrations is studied. We calculate the Coulomb barrier between
two approaching like charged macroions at a given counterion concentration. Two
different macroion shapes (spherical and rod-like) are considered. A new
"self-regulated" regime of coagulation is found. As the size of aggregates
increases, their charge and Coulomb barrier also grow and diminish the sticking
probability of aggregates. This leads to a slow, logarithmic increase of the
aggregate size with time.Comment: Some formulas correcte
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