659 research outputs found
Low-energy photon-photon collisions to two loops revisited
In view of ongoing experimental activities to determine the pion
polarizabilities, we have started to recalculate the available two-loop
expressions in the framework of chiral perturbation theory, because they have
never been checked before. We make use of the chiral Lagrangian at order p^6
now available, and of improved techniques to evaluate the two-loop diagrams.
Here, we present the result for the neutral pions. The cross section for the
reaction gamma+gamma->pi0+pi0 agrees with the earlier calculation within a
fraction of a percent. We present analytic results for the dipole and
quadrupole polarizabilities, and compare the latter with a recent evaluation
from data on gamma+gamma->pi0+pi0.Comment: 28 pages, 7-eps figures, 1 tabl
Discriminability of tryptophan containing dipeptides using quantum control
We show that the coherent manipulation of molecular wavepackets in the excited states of trp-containing dipeptides allows efficient discrimination among them. Optimal dynamic discrimination fails, however, for some dipeptide couples. When considering the limited spectral resources at play (3nm bandwidth at 266nm), we discuss the concept of discriminability, which appears uncorrelated to both static spectra and relaxation lifetime
Classification of personal exposure to radio frequency electromagnetic fields (RF-EMF) for epidemiological research : evaluation of different exposure assessment methods
The use of personal exposure meters (exposimeters) has been recommended for measuring personal exposure to radio frequency electromagnetic fields (RF-EMF) from environmental far-field sources in everyday life. However, it is unclear to what extent exposimeter readings are affected by measurements taken when personal mobile and cordless phones are used. In addition, the use of exposimeters in large epidemiological studies is limited due to high costs and large effort for study participants. In the current analysis we aimed to investigate the impact of personal phone use on exposimeter readings and to evaluate different exposure assessment methods potentially useful in epidemiological studies. We collected personal exposimeter measurements during one week and diary data from 166 study participants. Moreover, we collected spot measurements in the participants' bedrooms and data on self-estimated exposure, assessed residential exposure to fixed site transmitters by calculating the geo-coded distance and mean RF-EMF from a geospatial propagation model, and developed an exposure prediction model based on the propagation model and exposure relevant behavior. The mean personal exposure was 0.13mW/m(2), when measurements during personal phone calls were excluded and 0.15mW/m(2), when such measurements were included. The Spearman correlation with personal exposure (without personal phone calls) was 0.42 (95%-CI: 0.29 to 0.55) for the spot measurements, -0.03 (95%-CI: -0.18 to 0.12) for the geo-coded distance, 0.28 (95%-CI: 0.14 to 0.42) for the geospatial propagation model, 0.50 (95%-CI: 0.37 to 0.61) for the full exposure prediction model and 0.06 (95%-CI: -0.10 to 0.21) for self-estimated exposure. In conclusion, personal exposure measured with exposimeters correlated best with the full exposure prediction model and spot measurements. Self-estimated exposure and geo-coded distance turned out to be poor surrogates for personal exposure
Normalizing flow-based deep variational Bayesian network for seismic multi-hazards and impacts estimation from InSAR imagery
Onsite disasters like earthquakes can trigger cascading hazards and impacts,
such as landslides and infrastructure damage, leading to catastrophic losses;
thus, rapid and accurate estimates are crucial for timely and effective
post-disaster responses. Interferometric Synthetic aperture radar (InSAR) data
is important in providing high-resolution onsite information for rapid hazard
estimation. Most recent methods using InSAR imagery signals predict a single
type of hazard and thus often suffer low accuracy due to noisy and complex
signals induced by co-located hazards, impacts, and irrelevant environmental
changes (e.g., vegetation changes, human activities). We introduce a novel
stochastic variational inference with normalizing flows derived to jointly
approximate posteriors of multiple unobserved hazards and impacts from noisy
InSAR imagery
Reactive sputter magnetron reactor for preparation of thin films and simultaneous in-situ structural study by X-ray diffraction.
Reactive Sputter Magnetron (RSM) is a widely used technique to thin films growing\ud
of compounds both, in research laboratories and in industrial processes. The nature\ud
of the deposited compound will depend then on the nature of the magnetron target\ud
and the nature of the ions generated in the plasma. One important aspect of the\ud
problem is the knowledge of the evolution of the film during the process of growing\ud
itself. In this work, we present the design, construction of a chamber to be installed\ud
in the Huber goniometer in the XRD2 line of LNLS in Campinas, which allows in\ud
situ growing kinetic studies of thin films.ANPCy
Form Factors at Two-loop
Within Chiral Perturbation Theory (CHPT) we compute the form factors A, V and
in the decay to . A and
obtain corrections of order 25%.Comment: Added cut-off dependence discusion, misprints correcte
Numerical Modeling of Bank Instability by Seepage Erosion Undercutting of Layered Streambanks
Form-Factors and - Scattering
The and form-factors of and the quark condensates are
calculated to in Chiral Perturbation Theory (CHPT). Full
formulas are presented as much as possible. A full refit of most of the CHPT parameters is done with a discussion of all inputs and underlying
assumptions. We discuss the consequences for the vacuum expectation values,
decay constants, pseudoscalar masses and - scattering.Comment: 51 page
One-Dimensional Energy Dispersion of Single-Walled Carbon Nanotubes by Resonant Electron Scattering
We characterized the energy band dispersion near the Fermi level in
single-walled carbon nanotubes using low-temperature scanning tunneling
microscopy. Analysis of energy dependent standing wave oscillations, which
result from quantum interference of electrons resonantly scattered by defects,
yield a linear energy dispersion near EF, and indicate the importance of parity
in scattering for armchair single-walled carbon nanotubes. Additionally, these
data provide values of the tight-binding overlap integral and Fermi wavevector
in good agreement with previous work, but indicate that the electron coherence
length is substantially shortened.Comment: 5 pages, 3 figure
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