536 research outputs found
Coherent pion production in neutrino nucleus collision in the 1 GeV region
We calculate cross sections for coherent pion production in nuclei induced by
neutrinos and antineutrinos of the electron and muon type. The analogies and
differences between this process and the related ones of coherent pion
production induced by photons, or the (p,n) and reactions are
discussed. The process is one of the several ones occurring for intermediate
energy neutrinos, to be considered when detecting atmospheric neutrinos. For
this purpose the results shown here can be easily extrapolated to other
energies and other nuclei.Comment: 13 pages, LaTex, 8 post-script figures available at
[email protected]
Lack of uniqueness for weak solutions of the incompressible porous media equation
In this work we consider weak solutions of the incompressible 2-D porous
media equation. By using the approach of De Lellis-Sz\'ekelyhidi we prove
non-uniqueness for solutions in in space and time.Comment: 23 pages, 2 fugure
Spearhead Nanometric Field-Effect Transistor Sensors for Single-Cell Analysis.
Nanometric field-effect-transistor (FET) sensors are made on the tip of spear-shaped dual carbon nanoelectrodes derived from carbon deposition inside double-barrel nanopipettes. The easy fabrication route allows deposition of semiconductors or conducting polymers to comprise the transistor channel. A channel from electrodeposited poly pyrrole (PPy) exhibits high sensitivity toward pH changes. This property is exploited by immobilizing hexokinase on PPy nano-FETs to give rise to a selective ATP biosensor. Extracellular pH and ATP gradients are key biochemical constituents in the microenvironment of living cells; we monitor their real-time changes in relation to cancer cells and cardiomyocytes. The highly localized detection is possible because of the high aspect ratio and the spear-like design of the nano-FET probes. The accurately positioned nano-FET sensors can detect concentration gradients in three-dimensional space, identify biochemical properties of a single living cell, and after cell membrane penetration perform intracellular measurements
Pure point diffraction and cut and project schemes for measures: The smooth case
We present cut and project formalism based on measures and continuous weight
functions of sufficiently fast decay. The emerging measures are strongly almost
periodic. The corresponding dynamical systems are compact groups and
homomorphic images of the underlying torus. In particular, they are strictly
ergodic with pure point spectrum and continuous eigenfunctions. Their
diffraction can be calculated explicitly. Our results cover and extend
corresponding earlier results on dense Dirac combs and continuous weight
functions with compact support. They also mark a clear difference in terms of
factor maps between the case of continuous and non-continuous weight functions.Comment: 30 page
On the global well-posedness of a class of Boussinesq- Navier-Stokes systems
In this paper we consider the following 2D Boussinesq-Navier-Stokes systems
\partial_{t}u+u\cdot\nabla u+\nabla p+ |D|^{\alpha}u &= \theta e_{2}
\partial_{t}\theta+u\cdot\nabla \theta+ |D|^{\beta}\theta &=0 \quad with
and . When , , where is an explicit function
as a technical bound, we prove global well-posedness results for rough initial
data.Comment: 23page
Pion Cloud Contribution to K+ Nucleus Scattering
A careful reanalysis is done of the contribution to nucleus
scattering from the interaction of the kaon with the virtual pion cloud. The
usual approximations made in the evaluation of the related kaon selfenergy are
shown to fail badly. We also find new interaction mechanisms which provide
appreciable corrections to the kaon selfenergy. Some of these contribute to the
imaginary part below pion creation threshold. The inclusion of these new
mechanisms in the inelastic part of the optical potential produces a
significant improvement in the differential and total nuclear cross
sections. Uncertainties remain in the dispersive part of the optical potential.Comment: 27 pages, 17 figures (not all of them included, please request them),
report UG-DFM-2/9
A transfer matrix method for the analysis of fractal quantum potentials
The scattering properties of quantum particles on fractal potentials at
different stages of fractal growth are obtained by means of the transfer matrix
method. This approach can be easily adopted for project assignments in
introductory quantum mechanics for undergraduates. The reflection coefficients
for both the fractal potential and the finite periodic potential are calculated
and compared. It is shown that the reflection coefficient for the fractal has a
self-similar structure associated with the fractal distribution of the
potential
Conceptualizing the impact of dust-contaminated infrared radiances on data assimilation for numerical weather prediction
Numerical weather prediction systems depend on Hyperspectral Infrared Sounder (HIS) data, yet the impacts of dust-contaminated HIS radiances on weather forecasts has not been quantified. To determine the impact of dust aerosol on HIS radiance assimilation, we use a modified radiance assimilation system employing a one-dimensional variational assimilation system (1DVAR) developed under the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) Numerical Weather Prediction–Satellite Application Facility (NWP-SAF) project, which uses the Radiative Transfer for TOVS (RTTOV). Dust aerosol impacts on analyzed temperature and moisture fields are quantified using synthetic HIS observations from rawinsonde, Micropulse Lidar Network (MPLNET), and Aerosol Robotic Network (AERONET). Specifically, a unit dust aerosol optical depth (AOD) contamination at 550 nm can introduce larger than 2.4 and 8.6 K peak biases in analyzed temperature and dewpoint, respectively, over our test domain. We hypothesize that aerosol observations, or even possibly forecasts from aerosol predication models, may be used operationally to mitigate dust induced temperature and moisture analysis biases through forward radiative transfer modeling.This study is supported by the NASA ROSES Science of Terra and Aqua program (T. Lee; 80HQTR18T0085). The MPLNET project is funded by the NASA Radiation Sciences Program and Earth Observing System. MPLNET observations at the Santa Cruz de Tenerife site are supported by the INTA Grant IGE03004
Multiplicity and oscillations in a model for catalyzed oxidation of carbon monoxide
We extend a model proposed for explaining multiplicity and oscillations of concentrations and temperature in catalyzed oxidation of carbon monoxide; the importance of the dimension of the system and the closure approximation applied to the results, and, especially to the oscillatory behavior, is analyzed. Kinetic phase transitions, namely, single state multiplicity, single state oscillations, and multiplicity oscillations are found, depending on the reaction heat and the temperature relaxation parameter. Also, the role played by desorption of reactants is considered. When there is no desorption, temperature oscillations take place around room temperature, but if desorption is operative, oscillations occur about a higher temperature. For the one-dimensional case a spurious kinetic phase transition is obtained when the singlet closure approximation is appliedDirección General de Investigación Científica y Técnica PB91-060
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