2,307 research outputs found
Polaronic slowing of fermionic impurities in lattice Bose-Fermi mixtures
We generalize the application of small polaron theory to ultracold gases of
Ref. [\onlinecite{jaksch_njp1}] to the case of Bose-Fermi mixtures, where both
components are loaded into an optical lattice. In a suitable range of
parameters, the mixture can be described within a Bogoliubov approach in the
presence of fermionic (dynamic) impurities and an effective description in
terms of polarons applies. In the dilute limit of the slow impurity regime, the
hopping of fermionic particles is exponentially renormalized due to polaron
formation, regardless of the sign of the Bose-Fermi interaction. This should
lead to clear experimental signatures of polaronic effects, once the regime of
interest is reached. The validity of our approach is analyzed in the light of
currently available experiments. We provide results for the hopping
renormalization factor for different values of temperature, density and
Bose-Fermi interaction for three-dimensional
mixtures in optical lattice.Comment: 13 pages, 5 figure
Magnetism and domain formation in SU(3)-symmetric multi-species Fermi mixtures
We study the phase diagram of an SU(3)-symmetric mixture of three-component
ultracold fermions with attractive interactions in an optical lattice,
including the additional effect on the mixture of an effective three-body
constraint induced by three-body losses. We address the properties of the
system in by using dynamical mean-field theory and variational Monte
Carlo techniques. The phase diagram of the model shows a strong interplay
between magnetism and superfluidity. In the absence of the three-body
constraint (no losses), the system undergoes a phase transition from a color
superfluid phase to a trionic phase, which shows additional particle density
modulations at half-filling. Away from the particle-hole symmetric point the
color superfluid phase is always spontaneously magnetized, leading to the
formation of different color superfluid domains in systems where the total
number of particles of each species is conserved. This can be seen as the SU(3)
symmetric realization of a more general tendency to phase-separation in
three-component Fermi mixtures. The three-body constraint strongly disfavors
the trionic phase, stabilizing a (fully magnetized) color superfluid also at
strong coupling. With increasing temperature we observe a transition to a
non-magnetized SU(3) Fermi liquid phase.Comment: 36 pages, 17 figures; Corrected typo
Novel Treatments and Technologies Applied to the Cure of Neuroblastoma
Neuroblastoma (NB) is the most common extracranial solid tumour in childhood, accounting for approximately 15% of all cancer-related deaths in the paediatric population1. It is
characterised by heterogeneous clinical behaviour in neonates and often adverse outcomes in toddlers. The overall survival of children with high-risk disease is around 40–50% despite the aggressive
treatment protocols consisting of intensive chemotherapy, surgery, radiation therapy and hematopoietic stem cell transplantation2,3. There is an ongoing research effort to increase NB’s cellular and
molecular biology knowledge to translate essential findings into novel treatment strategies. This
review aims to address new therapeutic modalities emerging from preclinical studies offering a
unique translational opportunity for NB treatment
Limitations on the principle of stationary phase when it is applied to tunneling analysis
Using a recently developed procedure - multiple wave packet decomposition -
here we study the phase time formulation for tunneling/reflecting particles
colliding with a potential barrier. To partially overcome the analytical
difficulties which frequently arise when the stationary phase method is
employed for deriving phase (tunneling) time expressions, we present a
theoretical exercise involving a symmetrical collision between two identical
wave packets and an one-dimensional rectangular potential barrier. Summing the
amplitudes of the reflected and transmitted waves - using a method we call
multiple peak decomposition - is shown to allow reconstruction of the scattered
wave packets in a way which allows the stationary phase principle to be
recovered.Comment: 17 pages, 2 figure
Vacancy generation in liquid phase epitaxy of Si
Concerted experiments and theoretical analysis are applied to conclusively demonstrate the vacancy generation during fast melting and regrowth of Si by laser irradiation. Experiments, based on the positron annihilation spectroscopy and designed to test the theoretical predictions, evidence a vacancy supersaturation after the laser process depending on the irradiation conditions. Stochastic atomistic simulations of the molten Si recrystallization show trapping of vacancies in the recrystallized region. Finally, continuum phase-field simulations of the full process, calibrated using the Monte Carlo results, show a defect evolution in close agreement with the experiments.Peer reviewe
Experience recruits MSK1 to expand the dynamic range of synapses and enhance cognition
Experience powerfully influences neuronal function and cognitive performance, but the cellular and molecular events underlying the experience-dependent enhancement of mental ability haveremained elusive. In particular, the mechanisms that couple the external environment to the genomic changes underpinning this improvement are unknown. To address this we have used male mice harbouring an inactivating mutation of mitogen- and stress-activated protein kinase 1 (MSK1), a BDNF-activated enzyme downstream of the MAPK pathway. We show that MSK1 is required for the full extent of experience-induced improvement of spatial memory, for the expansion of the dynamic range of synapses, exemplified by the enhancement of hippocampal LTP and LTD, and for the regulation of the majority of genes influenced by enrichment. In addition, and unexpectedly, we show that experience is associated with an MSK1-dependent downregulation of key MAPK and plasticity
related genes, notably of EGR1/Zif268 and Arc/Arg3.1, suggesting the establishment of a novel genomic landscape adapted to experience. By coupling experience to homeostatic changes in gene expression MSK1, represents a prime mechanism through which the external environment has an enduring influence on gene expression, synaptic function and cognition
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