3,223 research outputs found
Directed abelian algebras and their applications to stochastic models
To each directed acyclic graph (this includes some D-dimensional lattices)
one can associate some abelian algebras that we call directed abelian algebras
(DAA). On each site of the graph one attaches a generator of the algebra. These
algebras depend on several parameters and are semisimple. Using any DAA one can
define a family of Hamiltonians which give the continuous time evolution of a
stochastic process. The calculation of the spectra and ground state
wavefunctions (stationary states probability distributions) is an easy
algebraic exercise. If one considers D-dimensional lattices and choose
Hamiltonians linear in the generators, in the finite-size scaling the
Hamiltonian spectrum is gapless with a critical dynamic exponent . One
possible application of the DAA is to sandpile models. In the paper we present
this application considering one and two dimensional lattices. In the one
dimensional case, when the DAA conserves the number of particles, the
avalanches belong to the random walker universality class (critical exponent
). We study the local densityof particles inside large
avalanches showing a depletion of particles at the source of the avalanche and
an enrichment at its end. In two dimensions we did extensive Monte-Carlo
simulations and found .Comment: 14 pages, 9 figure
Personalized cancer T-cell therapy takes the stage, mirroring vaccine success.
Personalized T-cell therapy is emerging as a pivotal treatment of cancer care by tailoring cellular therapies to individual genetic and antigenic profiles, echoing the exciting success of personalized vaccines. We describe here the parallel evolution and analogies of cancer vaccines and T-cell therapies
Lensing of ultra-high energy cosmic rays in turbulent magnetic fields
We consider the propagation of ultra high energy cosmic rays through
turbulent magnetic fields and study the transition between the regimes of
single and multiple images of point-like sources. The transition occurs at
energies around , where is the distance traversed by the
CR's with electric charge in the turbulent magnetic field of root mean
square strength and coherence length . We find that above only sources located in a fraction of a few % of the sky can reach large
amplifications of its principal image or start developing multiple images. New
images appear in pairs with huge magnifications, and they remain amplified over
a significant range of energies. At decreasing energies the fraction of the sky
in which sources can develop multiple images increases, reaching about 50% for
. The magnification peaks become however increasingly narrower and for
their integrated effect becomes less noticeable. If a uniform
magnetic field component is also present it would further narrow down the
peaks, shrinking the energy range in which they can be relevant. Below some kind of scintillation regime is reached, where many demagnified
images of a source are present but with overall total magnification of order
unity. We also search for lensing signatures in the AGASA data studying
two-dimensional correlations in angle and energy and find some interesting
hints.Comment: 30 pages, 16 figures, final version with minor change
Tidal Analysis of Long Series
It is shown how M (≥5) sets of Fourier coefficients obtained from M successive Fast Fourier Transforms (FFT) of 214 tapered hourly heights can be combined to obtain the harmonic constants of the clusters of the main astronomical and shallow-water constituents and their respective satellites. It is also shown how the clusters of the shallow-water constituents are formed
On the Stability of Long Series Tidal Analyses
Fourteen analyses with a nodal cycle resolution of filtered daily values of the 'mean' sea level at Cananéia (Brazil) were worked out, with a one-year shift. The results were examined for the stability of the harmonic constants of constituents Sa, Ssa, Mm, MSf, Mf and Mtm. Simultaneous barometric pressure data were available to correct the filtered tidal heights and the analyses were worked out with and without these corrections.The general conclusion is that the harmonic constants of Sa and Ssa were not stable and that their phase lags increased in the successive analyses. The harmonic constants of the remaining long period constituents were absolutely unstable and completely unreliable. Other fourteen harmonic analyses of 10*214 hourly tidal heights were worked out, for determining the harmonic constants of constituents with higher frequencies, in the same port. The results of these analyses, with a one-year shift,were very stable and gave an excellent insight of the micro-structure of the phenomenon
Lymphangioleiomyomatosis: What do we know and what are we looking for?
Lymphangioleiomyomatosis (LAM) is a rare disease characterised by proliferation of abnormal smooth muscle-like cells (LAM cells) leading to progressive cystic destruction of the lung, lymphatic abnormalities and abdominal tumours. It affects predominantly females and can occur sporadically or in patients with tuberous sclerosis complex. This review describes the recent progress in our understanding of the molecular pathogenesis of the disease and LAM cell biology. It also summarises current therapeutic approaches and the most promising areas of research for future therapeutic strategies
FSI Rescattering in Decays via States with and
New results going beyond those obtained from isospin and flavor symmetry and
subject to clear experimental tests are obtained for effects of FSI in
decays to charmless strange final states containing neutral flavor-mixed mesons
like , , and . The most general strong-interaction
diagrams containing arbitrary numbers of quarks and gluons are included with
the assumptions that any pair created by gluons must be a flavor
singlet, and that there are no hairpin diagrams in which a final meson contains
a pair from the same gluon vertex. The smallness of
suggests that it might have a large CP violation. A sum rule is derived to test
whether the large requires the addition of an additional glueball
or charm admixture. Further analysis from decay systematics supports this
picture of FSI and raises questions about charm admixture in the
Decaying neutron propagation in the Galaxy and the Cosmic Ray anisotropy at 1 EeV
We study the cosmic ray arrival distribution expected from a source of
neutrons in the galactic center at energies around 1 EeV and compare it with
the anisotropy detected by AGASA and SUGAR. Besides the point-like signal in
the source direction produced by the direct neutrons, an extended signal due to
the protons produced in neutron decays is expected. This associated proton
signal also leads to an excess in the direction of the spiral arm. For
realistic models of the regular and random galactic magnetic fields, the
resulting anisotropy as a function of the energy is obtained. We find that for
the anisotropy to become sufficiently suppressed below E\sim 10^{17.9}eV, a
significant random magnetic field component is required, while on the other
hand, this also tends to increase the angular spread of the associated proton
signal and to reduce the excess in the spiral arm direction. The source
luminosity required in order that the right ascension anisotropy be 4% for the
AGASA angular exposure corresponds to a prediction for the point-like flux from
direct neutrons compatible with the flux detected by SUGAR. We also analyse the
distinguishing features predicted for a large statistics southern observatory.Comment: 14 pages, 6 figures, minor changes to match published versio
Preon Prophecies by the Standard Model
The Standard Model of quarks and leptons is, at first sight, nothing but a
set of {\it ad hoc} rules, with no connections, and no clues to their true
background. At a closer look, however, there are many inherent prophecies that
point in the same direction: {\it Compositeness} in terms of three stable
preons.Comment: 13 pages, 8 eps-figures, invited talk at Beyond the Desert '03,
Schloss Ringberg, Bavaria, June 2003; to be published in the Proceeding
Thermal annealing study of swift heavy-ion irradiated zirconia
Sintered samples of monoclinic zirconia (alpha-ZrO2) have been irradiated at
room temperature with 6.0-GeV Pb ions in the electronic slowing down regime.
X-ray diffraction (XRD) and micro-Raman spectroscopy measurements showed
unambiguously that a transition to the 'metastable' tetragonal phase
(beta-ZrO2) occurred at a fluence of 6.5x10^12 cm-2 for a large electronic
stopping power value (approx 32.5 MeV m-1). At a lower fluence of
1.0x10^12 cm-2, no such phase transformation was detected. The
back-transformation from beta- to alpha-ZrO2 induced by isothermal or
isochronal thermal annealing was followed by XRD analysis. The
back-transformation started at an onset temperature around 500 K and was
completed by 973 K. Plots of the residual tetragonal phase fraction deduced
from XRD measurements versus annealing temperature or time are analyzed with
first- or second-order kinetic models. An activation energy close to 1 eV for
the back-transformation process is derived either from isothermal annealing
curves, using the so-called "cross-cut" method, or from the isochronal
annealing curve, using a second-order kinetic law. Correlation with the thermal
recovery of ion-induced paramagnetic centers monitored by EPR spectroscopy is
discussed. Effects of crystallite size evolution and oxygen migration upon
annealing are also addressed
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