Search results for "ASIM"
showing 10 items of 200 documents
Nuevas aplicaciones de la reacción aza-Michael intramolecular asimétrica
2018
La reacción aza-Michael está considerada como una de las metodologías más atractivas para la preparación de derivados -amino carbonílicos. Así, la adición conjugada de una fuente de nitrógeno nucleófila a un sistema -insaturado es un camino eficiente para generar enlaces C-N. Esta reacción adquiere una especial relevancia en su versión intramolecular, ya que conduce a la formación de heterociclos nitrogenados de manera directa. Además, cuando la olefina activada contiene centros proquirales, se generan uno o varios estereocentros en el proceso. Por tanto, la versión asimétrica de esta transformación nos conducirá a la síntesis de heterociclos nitrogenados funcionalizados de forma estere…
Relación entre la incidencia de asimetrías mandibulares y la clase esquelética y patrón facial del paciente medida sobre Cone Beam Computed Tomograph…
2019
Introducción: El propósito de este estudio fue establecer si existe una relación entre la presencia de asimetrías mandibulares y la maloclusión esquelética o patrón facial del paciente. Material y métodos: Se realizó un estudio retrospectivo comparativo. Se analizaron imágenes de tomografía computarizada de haz cónico (CBCT) de 60 sujetos del Departamento de Ortodoncia de la Universidad de Valencia (34 mujeres, 26 hombres; edad media, 32,7 ± 11,6 años). Las exploraciones CBCT se dividieron en 3 grupos (pacientes con Clase I, Clase II y Clase III esquelética) y se determinó el patrón facial de cada paciente. Utilizando dos programas informáticos (ITK-SNAP y 3DSlicer), se realizó la segment…
Experimental study of the triple-gluon vertex
1991
Abstract In four-jet events from e+e− →Z0 →multihadrons one can separate the three principal contributions from the triple-gluon vertex, double gluon-bremsstrahlung and the secondary quark-antiquark production, using the shape of the two-dimensional angular distributions in the generalized Nachtmann-Reiter angle θ NR ∗ and the opening angle of the secondary jets. Thus one can identify directly the contribution from the triple-gluon vertex without comparison with a specific non-QCD model. Applying this new method to events taken with the DELPHI-detector we get for the ratio of the colour factor Nc to the fermionic Casimir operator C F : N c C F = 2.55 ± 0.55 ( stat. ) ± 0.4 ( fragm. + models…
Riteņbraucēju un vidēji aktīvu indivīdu m.quadriceps muskuļu morfofunkcionāls salīdzinājums
2017
Augstu rezultātu sasniegšanai, sportistiem profesionāli trenējoties, tiek panākta sporta veidam raksturīgo kustību optimizācija, kā rezultātā būtiski uzlabojas sniegums, taču “asimetrisko” sporta veida pārstāvjiem var rasties muskuļu asimetrija, kas palielina arī traumu risku. Tāpēc šis bakalaura darbs tiek veltīts skeleta muskuļu morfometrisko parametru bilaterālai novērtēšanai salīdzinot personas ar atšķirīgu fizisko sagatavotību un muskuļa noslogojuma veidu. Bakalaura darba mērķis bija izpētīt m.quadriceps muskuļu morfofunkcionālās atšķirības amatieru līmeņa riteņbraucējiem, fiziski vidēji aktīviem un neaktīviem indivīdiem. Kopā pētījumā piedalījās 28 personas vecumā no 19-34 gadiem: 10 …
Two-dimensional phononic thermal conductance in thin membranes in the Casimir limit
2011
We discuss computational analysis of phononic thermal conduction in the suspended membrane geometry, in the experimentally commonly appearing case where heat can flow out radially in two dimensions from a central source. As we are mostly interested in the low-temperature behavior where bulk scattering of phonons becomes irrelevant, we study the limit where all phonon scattering takes place at the membrane surfaces. Moreover, we limit the discussion here to the case where this surface scattering is fully diffusive, the so called Casimir limit. Our analysis shows that in the two-dimensional case, no analytic results are available, in contrast to the well known 1D Casimir limit. Numerical solu…
Analytical and numerical analysis of the atom–field dynamics in non-stationary cavity QED
2011
We study analytically and numerically the dynamics of the quantum non-stationary system composed of a two-level atom interacting with a single mode cavity field whose frequency is rapidly modulated in time (with a small amplitude). We identify modulation laws resulting in qualitatively different dynamical regimes and we present analytical solutions in some simple cases. In particular, we analyse minutely the influence of the field–atom coupling on the photon generation from vacuum via the dynamical Casimir effect.
Nonperturbative approach for the electronic Casimir-Polder effect in a one-dimensional semiconductor
2013
We present the electronic Casimir-Polder effect for a system consisting of two impurities on a one-dimensional semiconductor quantum wire. Due to the charge transfer from the impurity to a one-dimensional conduction band, the impurity states are dressed by a virtual cloud of the electron field. The attractive electronic Casimir force arises due to the overlap of the virtual clouds. The Van Hove singularity causes the persistent bound state (PBS) to appear below the band edge even when the bare impurity state energy is above the band edge. Since the decay rate of the virtual cloud of the PBS in space is small, the Casimir force can be of a very long range. While the overlap of the electronic…
Anisotropies in thermal Casimir interactions: Ellipsoidal colloids trapped at a fluid interface
2009
We study the effective interaction between two ellipsoidal particles at the interface of two fluid phases which are mediated by thermal fluctuations of the interface. In this system the restriction of the long--ranged interface fluctuations by particles gives rise to fluctuation--induced forces which are equivalent to interactions of Casimir type and which are anisotropic in the interface plane. Since the position and the orientation of the colloids with respect to the interface normal may also fluctuate, this system is an example for the Casimir effect with fluctuating boundary conditions. In the approach taken here, the Casimir interaction is rewritten as the interaction between fluctuati…
Oscillator realization of the q-deformed anti-de Sitter algebra
1992
Abstract We construct a realization of the q-deformed anti-de Sitter algebra in terms of two q-oscillators. We use the standard Drinfel'd-Jimbo prescription for the q-deformation of the Chevalley basis which we express in terms of q-oscillators. We also discuss the anti-de Sitter radius R → ∞ limit and the structure of the first so (3, 2)q Casimir operator.
Experimental investigation of the breakdown of the Onsager-Casimir relations
2006
We use magnetoconductance fluctuation measurements of phase-coherent semiconductor billiards to quantify the contributions to the nonlinear electric conductance that are asymmetric under reversal of magnetic field. We experimentally determine that the average asymmetric contribution is linear in magnetic field (for magnetic flux much larger than one flux quantum) and that its magnitude depends on billiard geometry. In addition, we find an unexpected asymmetry in the power spectrum characteristics of the magnetoconductance with respect to reversal of magnetic field and bias voltage.