1,721,104 research outputs found
Ferromagnetism in a repulsive atomic Fermi gas with correlated disorder
Full text linkWe investigate the zero-temperature ferromagnetic behavior of a two-component repulsive Fermi gas in the presence of a correlated random field that represents an optical speckle pattern. The density is tuned so that the (noninteracting) Fermi energy is close to the mobility edge of the Anderson localization transition. We employ quantum Monte Carlo simulations to determine various ground-state properties, including the equation of state, the magnetic susceptibility, and the energy of an impurity immersed in a polarized Fermi gas (repulsive polaron). In the weakly interacting limit, the magnetic susceptibility is found to be suppressed by disorder. However, it rapidly increases with the interaction strength, and it diverges at a much weaker interaction strength compared to the clean gas. Both the transition from the paramagnetic phase to the partially ferromagnetic phase, and the one from the partially to the fully ferromagnetic phase, are strongly favored by disorder, indicating a case of order induced by disorder
Anderson localization of matter waves in quantum-chaos theory
Full text linkWe study the Anderson localization of atomic gases exposed to three-dimensional optical speckles by analyzing the statistics of the energy-level spacings. This method allows us to consider realistic models of the speckle patterns, taking into account the strongly anisotropic correlations which are realized in concrete experimental configurations. We first compute the mobility edge E-c of a speckle pattern created using a single laser beam. We find that E-c drifts when we vary the anisotropy of the speckle grains, going from higher values when the speckles are squeezed along the beam propagation axis to lower values when they are elongated. We also consider the case where two speckle patterns are superimposed, forming interference fringes, and we find that E-c is increased compared to the case of idealized isotropic disorder. We discuss the important implications of our findings for cold-atom experiments
Anderson localization in optical lattices with correlated disorder
Full text linkWe study the Anderson localization of atomic gases exposed to simple-cubic optical lattices with a superimposed disordered speckle pattern. The two mobility edges in the first band and the corresponding critical filling factors are determined as a function of the disorder strength, ranging from vanishing disorder up to the critical disorder intensity where the two mobility edges merge and the whole band becomes localized. Our theoretical analysis is based both on continuous-space models that take into account the details of the spatial correlation of the speckle pattern, and also on a simplified tight-binding model with an uncorrelated distribution of the on-site energies. The mobility edges are computed via the analysis of the energy-level statistics, and we determine the universal value of the ratio between consecutive level spacings at the mobility edge. We analyze the role of the spatial correlation of the disorder, and we also discuss a qualitative comparison with available experimental data for interacting atomic Fermi gases obtained in the moderate interaction regime
Zero-temperature equation of state and phase diagram of repulsive fermionic mixtures
No full textWe compute the zero-temperature equation of state of a mixture of two fermionic atomic species with repulsive interspecies interactions using second-order perturbation theory. We vary the interaction strength, the population, and the mass imbalance, and we analyze the competition between different states: homogeneous, partially separated, and fully separated. The canonical phase diagrams are determined for various mass ratios, including the experimentally relevant case of the Li-6-K-40 mixture. We find substantial differences with respect to the equal-mass case: phase separation occurs at weaker interaction strength, and the partially separated state can be stable even in the limit of a large majority of heavy atoms. We highlight the effects due to correlations by making comparisons with previous mean-field results
The use of pKZ1 mouse chromosomal inversion assay to study biological effects of environmental background radiation
No full textLife has evolved on Earth for 3 billion years in the presence of background ionizing radiation (IR). All organisms on Earth are continuously exposed to varying amounts of natural radiation and they have therefore incorporated in their normal biology a daily stimulus of ultra-low-dose radiation. A question arises about the biological effects of environmental background radiation and whether the biochemical behavior of living organisms would differ if it was absent. Here, we report our experimental design to address these scientific questions, which use pKZ1 mouse chromosomal inversion assay to study the biological behavior of different cell cultures maintained in "cosmic silence" and in reference background conditions. © Società Italiana di Fisica/Springer-Verlag 2012
Spermine metabolism and radiation-derived reactive oxygen species for future therapeutic implications in cancer: An additive or adaptive response
No full textDestruction of cells by irradiation-induced radical formation is one of the most frequent interventions in cancer therapy. An alternative to irradiation-induced radical formation is in principle drug-induced formation of radicals, and the formation of toxic metabolites by enzyme catalyzed reactions. Thus, combination therapy targeting polyamine metabolism could represent a promising strategy to fight hyper-proliferative disease. The aim of this work is to discuss and evaluate whether the presence of a DNA damage provoked by enzymatic ROS overproduction may act as an additive or adaptive response upon radiation and combination of hyperthermia with lysosomotropic compounds may improve the cytocidal effect of polyamines oxidation metabolites. Low level of X-irradiations delivers challenging dose of damage and an additive or adaptive response with the chronic damage induced by spermine oxidase overexpression depending on the deficiency of the DNA repair mechanisms. Since reactive oxygen species lead to membrane destabilization and cell death, we discuss the effects of BSAO and spermine association in multidrug resistant cells that resulted more sensitive to spermine metabolites than their wild-type counterparts, due to an increased mitochondrial activity. Since mammal spermine oxidase is differentially activated in a tissue specific manner, and cancer cells can differ in term of DNA repair capability, it could be of interest to open a scientific debate to use combinatory treatments to alter spermine metabolism and deliver differential response. © 2013 Springer-Verlag
Validazione concorrente tra le Vineland Adaptive Behavioral Scales ii e le Vinelland ABS
No full textIl presente contributo presenta i risultati del confronto tra le due versioni delle Scale VABS adattate e standardizzate nella popolazione italiana: Scala Vineland II- Survey Form, (Balboni, Belacchi, Bonichini e Coscarelli, 2016) e versione precedente (Balboni e Pedrabissi, 2003). Le due versioni del test differiscono sia per la numerosità degli item (totale, per Scala e subscala) che per la loro organizzazione nel protocollo, sia, infine, per i criteri di calcolo dei punteggi. Tale confronto è stato realizzato per mezzo di analisi di correlazione tra i punteggi ottenuti da 100 bambini frequentanti la Scuola Primaria in Provincia di Perugia (range di età: 5;62-10;60), distribuiti in 5 gruppi (N=20 per classe), nelle Scale Comunicazione (Subscale: Ricezione, Espressione, Scrittura), Abilità del Vivere Quotidiano (Subscale: Personale, Domestico, Comunità) e Socializzazione (Subscale: Relazioni interpersonali, Gioco e tempo libero, Regole Sociali). Non è stata somministrata la Scala Motoria, in aderenza alle norme di somministrazione del test
La rappresentazione implicita del genere grammaticale nell’autismo ad alto funzionamento e nel disturbo primario del linguaggio.
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