6,868 research outputs found
Time-dependent Gross-Pitaevskii equation for composite bosons as the strong-coupling limit of the fermionic BCS-RPA approximation
The linear response to a space- and time-dependent external disturbance of a
system of dilute condensed composite bosons at zero temperature, as obtained
from the linearized version of the time-dependent Gross-Pitaevskii equation, is
shown to result also from the strong-coupling limit of the time-dependent BCS
(or broken-symmetry RPA) approximation for the constituent fermions subject to
the same external disturbance. In this way, it is possible to connect
excited-state properties of the bosonic and fermionic systems by placing the
Gross-Pitaevskii equation in perspective with the corresponding fermionic
approximationsComment: 4 pages, 1 figur
Adubação foliar em tomateiro estaqueado. (Lycopersicum esculentum, mill). Santa Cruz - Kada.
Experimento realizado em solo latossol vermelho escuro-fase arenosa intergra de Terra roxa estruturada.Resumo
The Josephson effect throughout the BCS-BEC crossover
We study the stationary Josephson effect for neutral fermions across the
BCS-BEC crossover, by solving numerically the Bogoliubov-de Gennes equations at
zero temperature. The Josephson current is found to be considerably enhanced
for all barriers at about unitarity. For vanishing barrier, the Josephson
critical current approaches the Landau limiting value which, depending on the
coupling, is determined by either pair-breaking or sound-mode excitations. In
the coupling range from the BCS limit to unitarity, a procedure is proposed to
extract the pairing gap from the Landau limiting current.Comment: 4 pages, 3 figures; improved version to appear in Phys. Rev. Let
Effective interaction between molecules in the BEC regime of a superfluid Fermi gas
We investigate the effective interaction between Cooper-pair molecules in the
st rong-coupling BEC regime of a superfluid Fermi gas with a Feshbach
resonance. Our work uses a path integral formulation and a renormalization
group (RG) analy sis of fluctuations in a single-channel model. We show that a
physical cutoff en ergy originating from the finite molecular
binding energy is the key to understanding the interaction between molecules in
the BEC regime. Our work t hus clarifies recent results by showing that is a {\it ba re} molecular scattering length while is the low energy molecular scattering length
renormalized to include high-energy scat tering up to (here is the scattering length between Fermi atoms). We also include many-body
effects at finite temperatures. We find that is strongly dependent
on temperature, vanishing at , consistent with the earlier Bose gas
results of Bijlsma and Stoof.Comment: 10 pages, 3 figure
Momentum distribution of a trapped Fermi gas with large scattering length
Using a scattering length parametrization of the BCS-BEC crossover as well as
the local density approximation for the density profile, we calculate the
momentum distribution of a harmonically trapped atomic Fermi gas at zero
temperature. Various interaction regimes are considered, including the BCS
phase, the unitarity limit and the molecular regime. We show that the relevant
parameter which characterizes the crossover is given by the dimensionless
combination , where is the number of atoms, is the
scattering length and is the oscillator length. The width of the
momentum distribution is shown to depend in a crucial way on the value and sign
of this parameter. Our predictions can be relevant for experiments on ultracold
atomic Fermi gases near a Feshbach resonance.Comment: 6 pages, 2 figures. Submitted to Phys. Rev. A. Added reference
Prediction of antipsychotics efficacy based on a polygenic risk score: a real-world cohort study
Background: Response to antipsychotics is subject to a wide interindividual variability, due to genetic and non-genetic factors. Several single nucleotide polymorphisms (SNPs) have been associated with response to antipsychotics in genome-wide association studies (GWAS). Polygenic risk scores (PRS) are a powerful tool to aggregate into a single measure the small effects of multiple risk alleles. Materials and methods: We studied the association between a PRS composed of SNPs associated with response to antipsychotics in GWAS studies (PRSresponse) in a real-world sample of patients (N = 460) with different diagnoses (schizophrenia spectrum, bipolar, depressive, neurocognitive, substance use disorders and miscellaneous). Two other PRSs composed of SNPs previously associated with risk of schizophrenia (PRSschizophrenia1 and PRSschizophrenia2) were also tested for their association with response to treatment. Results: PRSresponse was significantly associated with response to antipsychotics considering the whole cohort (OR = 1.14, CI = 1.03–1.26, p = 0.010), the subgroup of patients with schizophrenia, schizoaffective disorder or bipolar disorder (OR = 1.18, CI = 1.02–1.37, p = 0.022, N = 235), with schizophrenia or schizoaffective disorder (OR = 1.24, CI = 1.04–1.47, p = 0.01, N = 176) and with schizophrenia (OR = 1.27, CI = 1.04–1.55, p = 0.01, N = 149). Sensitivity and specificity were sub-optimal (schizophrenia 62%, 61%; schizophrenia spectrum 56%, 55%; schizophrenia spectrum plus bipolar disorder 60%, 56%; all patients 63%, 58%, respectively). PRSschizophrenia1 and PRSschizophrenia2 were not significantly associated with response to treatment. Conclusion: PRSresponse defined from GWAS studies is significantly associated with response to antipsychotics in a real-world cohort; however, the results of the sensitivity-specificity analysis preclude its use as a predictive tool in clinical practice
Climate Change and Childhood Respiratory Health: A Call to Action for Paediatricians
Climate change (CC) is one of the main contributors to health emergencies worldwide. CC appears to be closely interrelated with air pollution, as some pollutants like carbon dioxide (CO2), nitrogen oxides (NOx) and black carbon are naturally occurring greenhouse gases. Air pollution may enhance the allergenicity of some plants and, also, has an adverse effect on respiratory health. Children are a uniquely vulnerable group that suffers disproportionately from CC burden. The increasing global warming related to CC has a big impact on plants' lifecycles, with earlier and longer pollen seasons, as well as higher pollen production, putting children affected by asthma and allergic rhinitis at risk for exacerbations. Extreme weather events may play a role too, not only in the exacerbations of allergic respiratory diseases but, also, in favouring respiratory infections. Even though paediatricians are already seeing the impacts of CC on their patients, their knowledge about CC-related health outcomes with specific regards to children's respiratory health is incomplete. This advocates for paediatricians' increased awareness and a better understanding of the CC impact on children's respiratory health. Having a special responsibility for children, paediatricians should actively be involved in policies aimed to protect the next generation from CC-related adverse health effects. Hence, there is an urgent need for them to take action and successfully educate families about CC issues. This paper aims at reviewing the evidence of CC-related environmental factors such as temperature, humidity, rainfall and extreme events on respiratory allergic diseases and respiratory infections in children and proposing specific actionable items for paediatricians to deal with CC-related health issues in their clinical practice
Homogeneous Fermion Superfluid with Unequal Spin Populations
For decades, the conventional view is that an s-wave BCS superfluid can not
support uniform spin polarization due to a gap in the quasiparticle
excitation spectrum. We show that this is an artifact of the dismissal of
quasiparticle interactions in the conventional approach at the
outset. Such interactions can cause triplet fluctuations in the ground state
and hence non-zero spin polarization at "magnetic field" . The
resulting ground state is a pairing state of quasiparticles on the ``BCS
vacuum". For sufficiently large , the spin polarization of at unitarity
has the simple form . Our study is motivated by the recent
experiments at Rice which found evidence of a homogenous superfluid state with
uniform spin polarization.Comment: 4 pages, 3 figure
Data acquisition software for the CMS strip tracker
The CMS silicon strip tracker, providing a sensitive area of approximately 200 m2 and comprising 10 million readout channels, has recently been completed at the tracker integration facility at CERN. The strip tracker community is currently working to develop and integrate the online and offline software frameworks, known as XDAQ and CMSSW respectively, for the purposes of data acquisition and detector commissioning and monitoring. Recent developments have seen the integration of many new services and tools within the online data acquisition system, such as event building, online distributed analysis, an online monitoring framework, and data storage management. We review the various software components that comprise the strip tracker data acquisition system, the software architectures used for stand-alone and global data-taking modes. Our experiences in commissioning and operating one of the largest ever silicon micro-strip tracking systems are also reviewed
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