8,201 research outputs found
Three-body structure of low-lying 12Be states
We investigate to what extent a description of 12Be as a three-body system
made of an inert 10Be-core and two neutrons is able to reproduce the
experimental 12Be data. Three-body wave functions are obtained with the
hyperspherical adiabatic expansion method. We study the discrete spectrum of
12Be, the structure of the different states, the predominant transition
strengths, and the continuum energy spectrum after high energy fragmentation on
a light target. Two 0+, one 2+, one 1- and one 0- bound states are found where
the first four are known experimentally whereas the 0- is predicted as an
isomeric state. An effective neutron charge, reproducing the measured B(E1)
transition and the charge rms radius in 11Be, leads to a computed B(E1)
transition strength for 12Be in agreement with the experimental value. For the
E0 and E2 transitions the contributions from core excitations could be more
significant. The experimental 10Be-neutron continuum energy spectrum is also
well reproduced except in the energy region corresponding to the 3/2- resonance
in 11Be where core excitations contribute.Comment: 16 pages, 9 figures. Accepted for publication in Physical Review
Isomeric 0- halo-states in 12Be and 11Li
We predict the existence of an isomeric 0-state in Be at an
excitation energy of about 2.5 MeV, and a 0-resonance in Li with
both energy and width of about 1 MeV corresponding to two-neutron emission. The
structure of these halo-like states are like the 1-states which means
essentially a core surrounded by two neutrons in single-particle and
p-states. The life-time of the Be state is determined by or
-emission, s or s
estimated for photon energies of 0.1 MeV and 0.6 MeV, respectively.Comment: to be published in Physics Letters
Internal Rotation of Disilane and Related Molecules:a Density Functional Study
DFT calculations performed on Si_2H_6, Si_2F_6, Si_2Cl_6, and Si_2Br_6 are
reported. The evolution of the energy, the chemical potential and the molecular
hardness, as a function of torsion angle, is studied. Results at the
DFT-B3LYP/6-311++G** level show that the molecules always favor the stable
staggered conformations, with low but significant energy barriers that hinder
internal rotation. The chemical potential and hardness of Si_2H_6 remains quite
constant as the sylil groups rotate around the Si-Si axis, whereas the other
systems exhibit different degrees of rearrangement of the electronic density as
a function of the torsion angle. A qualitative analysis of the frontier
orbitals shows that the effect of torsional motion on electrophilic attack is
negligible, whereas this internal rotation may generate different specific
mechanisms for nucleophilic attack.Comment: LATeX file, 7 figures, uses elsart.cls, natbib, graphic
Above threshold s-wave resonances illustrated by the 1/2 states in Be and B
We solve the persistent problem of the structure of the lowest
resonance in Be which is important to bridge the A=8 gap in nucleosynthesis
in stars. We show that the state is a genuine three-body resonance even though
it decays entirely into neutron-Be relative s-waves. The necessary barrier
is created by "dynamical" evolution of the wave function as the short-distance
-He structure is changed into the large-distance n-Be
structure. This decay mechanism leads to a width about two times smaller than
table values. The previous interpretations as a virtual state or a two-body
resonance are incorrect. The isobaric analog 1/2 state in B is found to
have energy and width in the vicinity of 2.0 MeV and 1.5 MeV, respectively. We
also predict another 1/2 resonance in B with similar energy and width.Comment: To be published in Physics Letters
Analytical modeling of one-dimensional resonant asymmetric and reciprocal acoustic structures as Willis materials
As building blocks of acoustic metamaterials, resonant scatterers have demonstrated their ability to modulate the effective fluid parameters, which subsequently possess extreme properties such as negative bulk modulus or negative mass density. Promising applications have been shown such as extraordinary absorption, focusing, and abnormal refraction for instance. However, acoustic waves can be further controlled in Willis materials by harnessing the coupling parameters. In this work, we derive the closed forms of the effective parameters from the transfer matrix in three asymmetric and reciprocal one-dimensional resonant configurations and exhibit the differences in terms of coupling coefficients. The way in which Willis coupling occurs in spatially asymmetric unit cells is highlighted. In addition, the analysis shows the absence of odd Willis coupling for reciprocal configurations. These effective parameters are validated against experimental and numerical results in the three configurations. This article paves the way of a novel physical understanding and engineering use of Willis acoustic materials
Estrategia de canales de atención de empresas de venta de indumentaria en Formosa en pandemia
El mundo de las empresas ha cambiado dramáticamente en los últimos años, el advenimiento de los canales digitales, las redes sociales y las aplicaciones de los dispositivos móviles han transformado los modelos de negocios, las interacciones con los consumidores y el comportamiento de éstos. A raíz de estos cambios algunos autores sostienen que hemos pasado de un Paradigma Multicanal con gestión independiente de cada canal a un Paradigma Omnicanal, dónde se integran, no sólo los canales de atención, sino que también amplían el alcance de éstos al incluir los dispositivos móviles, las redes sociales y las interacciones entre el cliente, la marca y el canal minorista. Si bien este desarrollo parecía estar circunscripto a los países más desarrollados, que contaban con infraestructura y una alta penetración del uso de internet entre sus habitantes, y a empresas grandes que poseían los recursos necesarios para dar un salto en la gestión de canales hacia la multicanalidad y omnicanalidad, la Pandemia del COVID-19 obligó a todas las empresas a encarar un cambio que les asegurara la supervivencia. Las tiendas minoristas del NEA no han sido ajenas a esta crisis, pero el estudio en este ámbito ha sido nulo. Por lo tanto, este artículo presenta una investigación a efectos de comprender las estrategias de las empresas de venta de indumentaria de Formosa con respecto a la apertura de canales múltiples de atención, el grado de integración de éstos, y si los cambios implementados se mantendrán en el tiempo, una vez finalizada la Pandemia
Adenovirus type 5 E4 Orf3 protein targets promyelocytic leukaemia (PML) protein nuclear domains for disruption via a sequence in PML isoform II that is predicted as a protein interaction site by bioinformatic analysis
Human adenovirus type 5 infection causes the disruption of structures in the cell nucleus termed promyelocytic leukaemia (PML) protein nuclear domains or ND10, which contain the PML protein as a critical component. This disruption is achieved through the action of the viral E4 Orf3 protein, which forms track-like nuclear structures that associate with the PML protein. This association is mediated by a direct interaction of Orf3 with a specific PML isoform, PMLII. We show here that the Orf3 interaction properties of PMLII are conferred by a 40 aa residue segment of the unique C-terminal domain of the protein. This segment was sufficient to confer interaction on a heterologous protein. The analysis was informed by prior application of a bioinformatic tool for the prediction of potential protein interaction sites within unstructured protein sequences (predictors of naturally disordered region analysis; PONDR). This tool predicted three potential molecular recognition elements (MoRE) within the C-terminal domain of PMLII, one of which was found to form the core of the Orf3 interaction site, thus demonstrating the utility of this approach. The sequence of the mapped Orf3-binding site on PML protein was found to be relatively poorly conserved across other species; however, the overall organization of MoREs within unstructured sequence was retained, suggesting the potential for conservation of functional interactions
Three-body structure of low-lying 18Ne states
We investigate to what extent 18Ne can be descibed as a three-body system
made of an inert 16O-core and two protons. We compare to experimental data and
occasionally to shell model results. We obtain three-body wave functions with
the hyperspherical adiabatic expansion method. We study the spectrum of 18Ne,
the structure of the different states and the predominant transition strengths.
Two 0+, two 2+, and one 4+ bound states are found where they are all known
experimentally. Also one 3+ close to threshold is found and several negative
parity states, 1-, 3-, 0-, 2-, most of them bound with respect to the 16O
excited 3- state. The structures are extracted as partial wave components, as
spatial sizes of matter and charge, and as probability distributions.
Electromagnetic decay rates are calculated for these states. The dominating
decay mode for the bound states is E2 and occasionally also M1.Comment: 17 pages, 5 figures (version to appear in EPJA
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