Calculation of ground- and excited-state energies of confined helium atom

We calculate the energies of ground and three low lying excited states of confined helium atom centered in an impenetrable spherical box. We perform the calculation by employing variational method with two-parameter variational forms for the correlated two-particle wave function. With just two variational parameters we get quite accurate results for both ground and excited state energies.Comment: 13 pages, No figur

Exclusion Principle Repulsion Effects on the Covalent Bond Beyond the Born-Oppenheimer Approximation

The changes in the covalent bond of the hydrogen molecule limited in the space by a spherical hard boundary are studied. The sphere is moved along an axis parallel or orthogonal to the molecular axis. The diffusion Monte Carlo approach is used to solve the Schrödinger equation with the relevant boundary conditions and to evaluate the changes in the bond energy versus the location of the sphere. The vertical and lateral quantum forces exerted on the sphere are evaluated by calculating the energy derivative versus the distances to the sphere. The results show that the quantum forces present an important dependence with the distance and vanish rapidly as the separation between the sphere and the molecule increases. In the limiting case the molecular bond becomes broken due to the electronic depletion induced in the covalent bond. An application of this study is the modelisation of the forces exerted on the passivated cantilever of an Atomic Force Microscope probing the electron cloud in the contact mode in the Pauli exclusión regime

K-shell and L-shell (e,3e) double ionization of beryllium by fast electron impact

We report fully differential cross sections for simultaneous double ionization of atomic beryllium by fast electron impact. We analyze separately the two ionization channels that leave the dication in either the 2s2 autoionizing excited state or its 1s2 bound ground state. For the double continuum, owing to the two slow emitted electrons, we employ the three-pairwise-Coulomb-interaction model (3C) along with the first Born approximation. Aiming to probe the hitherto largely unexplored role of the electron correlation in (e,3e), we determine and check fully correlated, compact analytical wave functions, satisfying all two-particle Kato cusp conditions for the four-electron Be initial state and the two-electron Be2+ final states, as well as other, much or little or noncorrelated, functions, issuing from either analytic global optimization or Hartree-Fock theory. We point out similarities or contrasts with trends observed in the double photoionization, allowing for parallels between (e,3e) and (γ,2e). Various numerical examples serve to navigate possible future experiments in the nonrelativistic regime of the ionization problem

Double photo-ionization of He near a polarizable surface

We calculate the differential cross-section of the direct double photo-ionization of He physisorbed on a polarizable surface. By including the influence of the surface potential in the correlated two-electron final state wavefunction, we show that the differential cross-section carries detailed information on the electronic correlations at the surface. In particular, photo-emission along opposite directions, which is prohibited in the free space, is allowed if the surface potential is long-ranged.Comment: To appear in Phys. Rev. B - Rapid Comm. - 4 pages, 2 PostScript figures embedde

Angular versus radial correlation effects on momentum distributions of light two-electron ions

We investigate different correlation mechanisms for two-electron systems and compare their respective effects on various electron distributions. The simplicity of the wave functions used allows for the derivation of closed-form analytical expressions for all electron distributions. Among other features, it is shown that angular and radial correlation mechanisms have opposite effects on Compton profiles at small momenta.Comment: 22 pages, 5 figures, 3 tabl

Radiosensitization of DNA in presence of Pt(II)-based compounds

X-ray irradiation of plasmid DNA in presence of platinum (II)-based compounds was carried out in order to assess the radiosensitization capabilities of these drugs. In present investigations pBR322 plasmid DNA was used to monitor effectiveness of chosen compounds in inducing strand breaks. Samples were incubated in presence of potential radiosensitisers: platinum (II) bromide and cis-diamminedibromoplatinum (II). The results were examined against a common cancer chemotherapy drug cis-diamminedichloroplatinum (II). It was found that platinum (II) bromide can greatly increase the levels of single- and double-strand break formation observed in the irradiated samples with respect to the samples containing platinum as a radiosensitizer only, possessing very little chemotherapeutic activity. The suggested drugs exhibit much higher level of radiosensitivity than widely used cisplatin and thus may be good candidates for cancer treatment

Radio- and photosensitization of DNA with compounds containing platinum and bromine atoms

Irradiations of plasmid DNA by both X-rays and UV light in the presence and absence of compounds containing platinum and bromine atoms were performed in order to asses the sensitization potential of these compounds. Plasmid DNA pBR322 was incubated with platinum (II) bromide, hydrogen hexabromoplatinate (IV), hydrogen hexahydroxyplatinate (IV) and sodium hexahydroxyplatinate (IV). Incubation was followed by X-ray or UV irradiations. It was found that amongst the sensitizers tested, during irradiations carried out in the presence of platinum (II) bromide, the highest levels of double strand breaks formation upon X-ray treatment were recorded. In contrast much less damage was induced by UV light. Data presented here suggests that this compound may be a promising radiosensitizer for cancer treatment

Diallel analysis in white lupin: consequences for breeding

A complete diallel analysis for several characters was conducted in spring type white lupins (Lupinus albus L). Each of the 7 parents represented a group of the genetic variability available in the Mediterranean area. An analysis of the genetic parameters for the different characters should be of help in the definition of optimum lupin breeding criteria. Both vegetative and reproductive characters were studied. Diallel analysis was carried out via 2 methods, ie those of Griffing and Hayman. As for most of the autogamous species, vegetative characters and seed size showed a mainly additive heredity with a limited amount of specific combining ability (SCA). Both broad and narrow sense heritabilities proved to be high. The correlations between general combining ability (GCA) and phenotypic values were high, which suggested that judgement of the phenotype could give a good estimate of behaviour in the cross. For pod setting characters, both heritabilities were lower likely because of a higher susceptibility to the environment and to larger dominance. A heterotic effect was observed for yield; this could be explained by the low cropping densities and the homeostatis ability of the hybrids. This kind of genetic structure appears to be a means of improving yield stability. Unfortunately, it is not possible at the present time because no male sterility is available. For pure line breeding, the general combining ability (GCA) values showed that Lublanc and LA123 appeared to be first-choice parents for improvement of earliness in flowering with a good pod setting, while Lucky was an interesting candidate for pod setting and seed size characters.Étude diallèle sur le lupin blanc : conséquences en sélection. L'étude d'un diallèle complet de 7 génotypes de lupin blanc (Lupinus albus L) de type printemps a permis l'analyse génétique de nombreux caractères. Chacun des parents utilisés représente un groupe particulier au sein de la variabilité spécifique disponible sur le pourtour méditerranéen (tableau I). L'analyse génétique de ces différents caractères doit permettre de définir les critères de sélection les plus importants. Les caractères étudiés sont relatifs soit au développement végétatif, soit à la phase de reproduction. L'analyse diallèle a été réalisée par 2 méthodes d'analyse : Griffing et Hayman. Comme pour la plupart des légumineuses autogames, les caractères végétatifs et la taille du grain présentent une hérédité essentiellement additive avec des effets dus à l'aptitude spécifique à la combinaison faibles (tableau III). Les héritabilités au sens large et au sens strict sont élevées. Les corrélations entre les valeurs d'aptitude générale à la combinaison et les valeurs propres sont élevées, la valeur phénotypique des parents donne donc une bonne idée de leur comportement en croisement (tableau III). L'analyse des diagrammes de Hayman (fig 3) montre la possibilité de transgressions sur les principaux caractères étudiés à l'exception de la précocité, et la présence vraisemblable d'épistasie pour la nouaison. Pour les caractères de nouaison, les héritabilités sont plus faibles, en raison d'une sensibilité accrue au milieu. Un hétérosis a été observé pour le rendement qui pourrait être lié aux faibles densités de culture utilisées et à la possibilité d'homéostase des hybrides. La création d'hybrides pourrait être une voie pour l'amélioration de la stabilité du rendement, même si aucune stérilité mâle ne permet d'envisager à ce jour cette voie. Dans le but actuel de création de variétés lignées pures, l'étude diallèle permet de préciser les parents potentiellement intéressants. Lublanc et LA 123 sont des géniteurs intéressants pour la recherche de types précoces à bonne nouaison. Pour l'ensemble des caractères de rendement, Lucky est un géniteur de choix en particulier pour la nouaison et le poids de mille grains

Diallel analysis in white lupin: consequences for breeding

A complete diallel analysis for several characters was conducted in spring type white lupins (Lupinus albus L). Each of the 7 parents represented a group of the genetic variability available in the Mediterranean area. An analysis of the genetic parameters for the different characters should be of help in the definition of optimum lupin breeding criteria. Both vegetative and reproductive characters were studied. Diallel analysis was carried out via 2 methods, ie those of Griffing and Hayman. As for most of the autogamous species, vegetative characters and seed size showed a mainly additive heredity with a limited amount of specific combining ability (SCA). Both broad and narrow sense heritabilities proved to be high. The correlations between general combining ability (GCA) and phenotypic values were high, which suggested that judgement of the phenotype could give a good estimate of behaviour in the cross. For pod setting characters, both heritabilities were lower likely because of a higher susceptibility to the environment and to larger dominance. A heterotic effect was observed for yield; this could be explained by the low cropping densities and the homeostatis ability of the hybrids. This kind of genetic structure appears to be a means of improving yield stability. Unfortunately, it is not possible at the present time because no male sterility is available. For pure line breeding, the general combining ability (GCA) values showed that Lublanc and LA123 appeared to be first-choice parents for improvement of earliness in flowering with a good pod setting, while Lucky was an interesting candidate for pod setting and seed size characters.Étude diallèle sur le lupin blanc : conséquences en sélection. L'étude d'un diallèle complet de 7 génotypes de lupin blanc (Lupinus albus L) de type printemps a permis l'analyse génétique de nombreux caractères. Chacun des parents utilisés représente un groupe particulier au sein de la variabilité spécifique disponible sur le pourtour méditerranéen (tableau I). L'analyse génétique de ces différents caractères doit permettre de définir les critères de sélection les plus importants. Les caractères étudiés sont relatifs soit au développement végétatif, soit à la phase de reproduction. L'analyse diallèle a été réalisée par 2 méthodes d'analyse : Griffing et Hayman. Comme pour la plupart des légumineuses autogames, les caractères végétatifs et la taille du grain présentent une hérédité essentiellement additive avec des effets dus à l'aptitude spécifique à la combinaison faibles (tableau III). Les héritabilités au sens large et au sens strict sont élevées. Les corrélations entre les valeurs d'aptitude générale à la combinaison et les valeurs propres sont élevées, la valeur phénotypique des parents donne donc une bonne idée de leur comportement en croisement (tableau III). L'analyse des diagrammes de Hayman (fig 3) montre la possibilité de transgressions sur les principaux caractères étudiés à l'exception de la précocité, et la présence vraisemblable d'épistasie pour la nouaison. Pour les caractères de nouaison, les héritabilités sont plus faibles, en raison d'une sensibilité accrue au milieu. Un hétérosis a été observé pour le rendement qui pourrait être lié aux faibles densités de culture utilisées et à la possibilité d'homéostase des hybrides. La création d'hybrides pourrait être une voie pour l'amélioration de la stabilité du rendement, même si aucune stérilité mâle ne permet d'envisager à ce jour cette voie. Dans le but actuel de création de variétés lignées pures, l'étude diallèle permet de préciser les parents potentiellement intéressants. Lublanc et LA 123 sont des géniteurs intéressants pour la recherche de types précoces à bonne nouaison. Pour l'ensemble des caractères de rendement, Lucky est un géniteur de choix en particulier pour la nouaison et le poids de mille grains