5,525 research outputs found
exploding clusters dynamics probed by XUV fluorescence
Clusters excited by intense laser pulses are a unique source of warm dense
matter, that has been the subject of intensive experimental studies. The
majority of those investigations concerns atomic clusters, whereas the
evolution of molecular clusters excited by intense laser pulses is less
explored. In this work we trace the dynamics of clusters
triggered by a few-cycle 1.45-m driving pulse through the detection of XUV
fluorescence induced by a delayed 800-nm ignition pulse. Striking differences
among fluorescence dynamics from different ionic species are observed
The potential role of biomethane for the decarbonization of transport: An analysis of 2030 scenarios in Italy
This paper aims at evaluating the best allocation of potential biomethane generation for the decarbonization of the transport system, presenting a case study in Italy. The country has some peculiar features, such as several operating biogas plants, additional potential feedstock for biogas/biomethane generation, a well-developed natural gas network and established relevant natural gas uses in different final sectors, including transport. Based on current estimates for sustainable biomethane potential by 2030, ranging from 2.3 to 7.6 billion cubic meters depending on the scenario, the analysis compares technologies for the generation, distribution and final use of biomethane. The results of the analysis confirm the potential interesting contribution of biomethane in decarbonizing the Italian transport system: a billion cubic meters of biomethane can lead to 2.33–4.37 MtCO2e savings, depending on the feedstock mix and the application. On a national basis, annual climate emission savings in 2030 range from 10.0 to 26.7 MtCO2e, depending on the scenario. Additional 3.1–8.1 MtCO2e of emissions can be avoided if the CO2 captured during the biomethane upgrading can be stored or reused. The proposed methodology could be used to extend the analysis to other countries, and to the European context
Refined Factorizations of Solvable Potentials
A generalization of the factorization technique is shown to be a powerful
algebraic tool to discover further properties of a class of integrable systems
in Quantum Mechanics. The method is applied in the study of radial oscillator,
Morse and Coulomb potentials to obtain a wide set of raising and lowering
operators, and to show clearly the connection that link these systems.Comment: 11 pages, LaTeX file, no figure
Discrete derivatives and symmetries of difference equations
We show on the example of the discrete heat equation that for any given
discrete derivative we can construct a nontrivial Leibniz rule suitable to find
the symmetries of discrete equations. In this way we obtain a symmetry Lie
algebra, defined in terms of shift operators, isomorphic to that of the
continuous heat equation.Comment: submitted to J.Phys. A 10 Latex page
Neuro-Musculoskeletal Mapping for Man-Machine Interfacing.
We propose a myoelectric control method based on neural data regression and musculoskeletal modeling. This paradigm uses the timings of motor neuron discharges decoded by high-density surface electromyogram (HD-EMG) decomposition to estimate muscle excitations. The muscle excitations are then mapped into the kinematics of the wrist joint using forward dynamics. The offline tracking performance of the proposed method was superior to that of state-of-the-art myoelectric regression methods based on artificial neural networks in two amputees and in four out of six intact-bodied subjects. In addition to joint kinematics, the proposed data-driven model-based approach also estimated several biomechanical variables in a full feed-forward manner that could potentially be useful in supporting the rehabilitation and training process. These results indicate that using a full forward dynamics musculoskeletal model directly driven by motor neuron activity is a promising approach in rehabilitation and prosthetics to model the series of transformations from muscle excitation to resulting joint function
Polar coherent states in bilayer graphene under a constant uniform magnetic field
Symmetries associated with the Hamiltonian describing bilayer graphene
subjected to a constant magnetic field perpendicular to the plane of the
bilayer are calculated using polar coordinates. These symmetries are then
applied to explain some fundamental properties, such as the spectrum and the
integer pseudo-spin character of the eigenfunctions. The probability and
current densities of the bilayer Hamiltonian have also been calculated in polar
coordinates and shown to be gauge invariant and scalar under generalized
rotations. We also define appropriate coherent states of this system as
eigenfunctions, with complex eigenvalues, of a suitable chose annihilation
operator. In this framework, symmetries are also useful to show the meaning of
the complex eigenvalue in terms of expected values. The local current density
of these coherent states is shown to exhibit a kind of radial component
interference effect, something that has gone unnoticed until now. Some of these
results that have just been exposed are graphically illustrated throughout the
manuscript
SUSY approach to Pauli Hamiltonians with an axial symmetry
A two-dimensional Pauli Hamiltonian describing the interaction of a neutral
spin-1/2 particle with a magnetic field having axial and second order
symmetries, is considered. After separation of variables, the one-dimensional
matrix Hamiltonian is analyzed from the point of view of supersymmetric quantum
mechanics. Attention is paid to the discrete symmetries of the Hamiltonian and
also to the Hamiltonian hierarchies generated by intertwining operators. The
spectrum is studied by means of the associated matrix shape-invariance. The
relation between the intertwining operators and the second order symmetries is
established and the full set of ladder operators that complete the dynamical
algebra is constructed.Comment: 18 pages, 3 figure
The Fermi-LAT Light Curve Repository: A resource for the time-domain and multi-messenger communities
For over 15 years the Fermi Large Area Telescope (Fermi-LAT) has been
monitoring the entire high-energy gamma-ray sky, providing the best sampled 0.1
-- TeV photons to this day. As a result, the Fermi-LAT has been serving
the time-domain and multi-messenger community as the main source of gamma-ray
activity alerts. All of this makes the Fermi-LAT a key instrument towards
understanding the underlying physics behind the most extreme objects in the
universe. However, generating mission-long LAT light curves can be very
computationally expensive. The Fermi-LAT light curve repository (LCR) tackles
this issue. The LCR is a public library of gamma-ray light curves for 1525
Fermi-LAT sources deemed variable in the 4FGL-DR2 catalog. The repository
consists of light curves on timescales of days, weeks, and months, generated
through a full-likelihood unbinned analysis of the source and surrounding
region, providing flux and photon index measurements for each time interval.
Hosted at NASA's FSSC, the library provides users with access to this
continually updated light curve data, further serving as a resource to the
time-domain and multi-messenger communities.Comment: Proceedings for the 38th International Cosmic Ray Conference
(ICRC2023
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