359 research outputs found
The potential energy of a K Fermi gas in the BCS-BEC crossover
We present a measurement of the potential energy of an ultracold trapped gas
of K atoms in the BCS-BEC crossover and investigate the temperature
dependence of this energy at a wide Feshbach resonance, where the gas is in the
unitarity limit. In particular, we study the ratio of the potential energy in
the region of the unitarity limit to that of a non-interacting gas, and in the
T=0 limit we extract the universal many-body parameter . We find ; this value is consistent with previous measurements
using Li atoms and also with recent theory and Monte Carlo calculations.
This result demonstrates the universality of ultracold Fermi gases in the
strongly interacting regime
Collective excitations of a degenerate gas at the BEC-BCS crossover
We study collective excitation modes of a fermionic gas of Li atoms in
the BEC-BCS crossover regime. While measurements of the axial compression mode
in the cigar-shaped trap close to a Feshbach resonance confirm theoretical
expectations, the radial compression mode shows surprising features. In the
strongly interacting molecular BEC regime we observe a negative frequency shift
with increasing coupling strength. In the regime of a strongly interacting
Fermi gas, an abrupt change in the collective excitation frequency occurs,
which may be a signature for a transition from a superfluid to a collisionless
phase.Comment: Feshbach resonance position updated, few minor change
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
The effect of olive fruit stoning on virgin olive oil aroma
Olive fruit stoning gives rise to an important modification in olive oil aroma. The level of this modification is a function of the cultivar. An increment in the content of six-carbon compounds (C6) was
observed in olive oils obtained from the cultivars Verdial and Manzanilla, but not in the cultivar Picual. In the three cultivars under study, contents of five-carbon compounds (C5) and esters decreased as a consequence of fruit stoning. The modification of olive oil aroma composition in the cultivar Verdial caused by olive fruit stoning was observed to be due both to tissue wounding and to the absence of the olive seed during the crushing-malaxation process to obtain olive oil aroma. Both factors contribute independently to the content modification of C6, C5 compounds and esters in the olive oil aroma from stoned fruits.El deshuesado de la aceituna da lugar a una importante modificación del aroma del aceite de oliva virgen. La intensidad de esta modificación es característica de cada variedad. En los aceites obtenidos de aceitunas Verdial y Manzanilla se produce un incremento en el contenido de los compuestos de seis átomos de carbono (C6) que no se detecta en la variedad Picual. En las tres variedades estudiadas se observa un descenso del contenido de compuestos de cinco átomos de carbono (C5) así como del contenido en ésteres. En la variedad Verdial se ha comprobado que la modificación del aroma como consecuencia del deshuesado del fruto se debe tanto al daño tisular generado durante este proceso como a la ausencia de la semilla durante la molturación de la aceituna. Ambos factores contribuyen de forma independiente a la modificación del contenido de compuestos C6, C5 y ésteres en el aroma del aceite de oliva virgen procedente de aceituna deshuesada.El trabajo se ha realizado en el marco del Proyecto de Investigación AGL2002-02307 del Programa Nacional de Recursos y Tecnologías Agroalimentarias.Peer reviewe
Precise determination of Li cold collision parameters by radio-frequency spectroscopy on weakly bound molecules
We employ radio-frequency spectroscopy on weakly bound Li molecules
to precisely determine the molecular binding energies and the energy splittings
between molecular states for different magnetic fields. These measurements
allow us to extract the interaction parameters of ultracold Li atoms based
on a multi-channel quantum scattering model. We determine the singlet and
triplet scattering lengths to be and (1
= 0.0529177 nm), and the positions of the broad Feshbach resonances in
the energetically lowest three wave scattering channels to be 83.41(15) mT,
69.04(5) mT, and 81.12(10) mT
In response to: Anatomy of 18F-GE180, a failed radioligand for the TSPO protein
Purpose!#!Pulmonary hypertension (PH) is characterized by a progressive remodelling of the pulmonary vasculature resulting in right heart failure and eventually death. The serotonin transporter (SERT) may be involved in the pathogenesis of PH in patients with chronic-obstructive pulmonary disease (COPD). This study investigated for the first time the SERT in vivo availability in the lungs of patients with COPD and PH (COPD+PH).!##!Methods!#!SERT availability was assessed using SERT-selective [!##!Results!#![!##!Conclusion!#!By applying
Association between cognitive performance and cortical glucose metabolism in patients with mild Alzheimer's disease
Background: Neuronal and synaptic function in Alzheimer's disease (AD) is measured in vivo by glucose metabolism using positron emission tomography (PET). Objective: We hypothesized that neuronal activation as measured by PET is a more sensitive index of neuronal dysfunction than activity during rest. We investigated if the correlations between dementia severity as measured with the Mini Mental State Examination (MMSE) and glucose metabolism are an artifact of brain atrophy. Method: Glucose metabolism was measured using {[}F-18]fluorodeoxyglucose PET during rest and activation due to audiovisual stimulation in 13 mild to moderate AD patients (MMSE score >= 17). PET data were corrected for brain atrophy. Results: In the rest condition, glucose metabolism was correlated with the MMSE score primarily within the posterior cingulate and parietal lobes. For the activation condition, additional correlations were within the primary and association audiovisual areas. Most local maxima remained significant after correcting for brain atrophy. Conclusion: PET activity measured during audiovisual stimulation was more sensitive to functional alterations in glucose metabolism in AD patients compared to the resting PET. The association between glucose metabolism and MMSE score was not dependent on brain atrophy. Copyright (C) 2005 S. Karger AG, Basel
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