Search results for "symmetry"
showing 10 items of 3576 documents
Wavelet analysis and neural network classifiers to detect mid-sagittal sections for nuchal translucency measurement
2016
We propose a methodology to support the physician in the automatic identification of mid-sagittal sections of the fetus in ultrasound videos acquired during the first trimester of pregnancy. A good mid-sagittal section is a key requirement to make the correct measurement of nuchal translucency which is one of the main marker for screening of chromosomal defects such as trisomy 13, 18 and 21. NT measurement is beyond the scope of this article. The proposed methodology is mainly based on wavelet analysis and neural network classifiers to detect the jawbone and on radial symmetry analysis to detect the choroid plexus. Those steps allow to identify the frames which represent correct mid-sagitta…
Analysis of random walks on a hexagonal lattice
2019
We consider a discrete-time random walk on the nodes of an unbounded hexagonal lattice. We determine the probability generating functions, the transition probabilities and the relevant moments. The convergence of the stochastic process to a 2-dimensional Brownian motion is also discussed. Furthermore, we obtain some results on its asymptotic behavior making use of large deviation theory. Finally, we investigate the first-passage-time problem of the random walk through a vertical straight-line. Under suitable symmetry assumptions we are able to determine the first-passage-time probabilities in a closed form, which deserve interest in applied fields.
State-to-State Quantum Dynamics Calculations of the C plus OH Reaction on the Second Excited Potential Energy Surface
2011
Accurate three-dimensional quantum-mechanical scattering calculations using a time-indepedent hyperspherical method have been performed for the C((3)P) + OH(X(2)Π) → CO(a(3)Π) + H((2)S) reaction on the second excited potential energy surface of 1(4)A″ symmetry. State-to-state reaction probabilities at a total angular momentum J = 0 have been computed in a wide range of collision energies. Many pronounced resonances have been found, espcially at low energy. The product vibrational distributions are noninverted. The present results therefore suggest that the title reaction proceeds via a long-lived intermediate complex. An approximate quantum-mechanical rate constant has also been calculated,…
Molecular dynamics studies of 3D quasicrystals
1993
Abstract The thermodynamic behaviour of monatomic and diatomic models of three-dimensional icosahedral quasicrystals has been studied in NVT and NPT ensembles using molecular dynamics simulations with atoms interacting via Lennard-Jones potentials. We also report on a microcanonical MD simulation of decagonal Al 65 Cu 20 Co 15 quasicrystals where an experimentally determined binary model has been used. To obtain stability in this latter case it is necessary to endow the atoms with effective pair potentials. No transitions to crystalline or amorphous phases were found for diatomic models. Monatomic models, however, display a certain stability only in the low-temperature region. In the range …
Conformations of Star-Branched Polyelectrolytes
1996
Scaling theory describing the conformations of weakly charged star-branched polyelectrolytes in dilute and semi-dilute salt-free solutions is developed. The dependence of the star size on the number of branches as well as on the solution concentration is analyzed. It is shown that the star size increases with an increase in the number of branches, f, at small f and tends to a constant value at large f. An increase in the concentration of stars in a solution results in a decrease in the star size R according to the power low : R ∼ c -1/3 in the range of a moderate concentration and R ∼ c -1/4 at larger concentration. For stars with a small number of branches the behavior R ∼ c -1/2 in a cert…
Huge Quantum Symmetry Effect in the O + O2 Exchange Reaction.
2015
We report extensive, full quantum-mechanical calculations for the (16)O + (16)O(16)O → (16)O(16)O + (16)O collisions, for both inelastic and atom exchange processes, using a time-independent method based on hyperspherical coordinates. The rates obtained in the present study are much larger than the previously reported ones for this system. The discrepancy is attributed to a huge symmetry effect that was missing in the studies so far. This effect differs from the well-known isotope effect. Importance of this quantum effect is further confirmed by comparison with results for the (16)O + (18)O(18)O → (16)O(18)O + (18)O, exchange reaction.
Il regionalismo differenziato di cui all'art. 116, co. 3, della Costituzione: un tentativo di inquadramento sistematico nel Titolo V della Costituzio…
2021
The paper analyzes the origins and characteristics of the differentiated re- gionalism referred to in art. 116.3 of the Constitution, highlighting the impact that its implemen- tation could have in Title V of the Constitution, in relation to both ordinary regions and regions with special status. The widespread nature of differentiated regionalism could, in particular, lead to the definitive, tough gradual, overcoming of regional uniformity, towards a model of mainly differentiable regionalism.
Inclusive double-helicity asymmetries in neutral-pion and eta-meson production in p → + p → collisions at s =200GeV
2014
Abstract: Results are presented from data recorded in 2009 by the PHENIX experiment at the Relativistic Heavy Ion Collider for the double-longitudinal spin asymmetry, A LL , for π 0 and η production in ffiffiffi s p ¼ 200 GeV polarized p þ p collisions. Comparison of the π 0 results with different theory expectations based on fits of other published data showed a preference for small positive values of gluon polarization, Δ G , in the proton in the probed Bjorken x range. The effect of adding the new 2009 π 0 data to a recent global analysis of polarized scattering data is also shown, resulting in a best fit value Δ G ½ 0 . 05 ; 0 . 2 DSSV ¼ 0 . 06 þ 0 . 11 − 0 . 15 in the range 0 . 05 <x< …
SEPARATION OF PRINCIPAL STRESSES ALONG SECTIONS OF SYMMETRY BY MEANS OF ISOPACHIC PATTERNS
1969
An approximate rapid method for the separation of principal stresses along sections of symmetry free from external loads is described. The method is based on the sum of principal stresses and checked by applying it to a circular ring under diametral compression and to a grooved bar in tension.
"Table 1" of "Study of $W$ boson production in association with beauty and charm"
2016
Summary of the results. All results are reported within a fiducial region that requires a jet with $p_\rm{T} > 20$ GeV in the pseudorapidity range $2.2 < \eta < 4.2$, a muon with $p_\rm{T} > 20$ GeV in the pseudorapidity range $2.0 < \eta < 4.5$, $p_\rm{T}(\mu+j) > 20$ GeV, and $\Delta R(\mu, j) > 0.5$. For $Z+$jet events both muons must fulfill the muon requirements and $60 < M(\mu\mu) < 120$ GeV; the $Z+$jet fiducial region does not require $p_\rm{T}(\mu+j) > 20$ GeV.