821 research outputs found
Density correlations in ultracold atomic Fermi gases
We investigate density fluctuations in a coherent ensemble of interacting
fermionic atoms. Adapting the concept of full counting statistics, well-known
from quantum optics and mesoscopic electron transport, we study second-order as
well as higher-order correlators of density fluctuations. Using the mean-field
BCS state to describe the whole interval between the BCS limit and the BEC
limit, we obtain an exact expression for the cumulant-generating function of
the density fluctuations of an atomic cloud. In the two-dimensional case, we
obtain a closed analytical expression. Poissonian fluctuations of a molecular
condensate on the BEC side are strongly suppressed on the BCS side. The size of
the fluctuations in the BCS limit is a direct measure of the pairing potential.
We also discuss the BEC-BCS crossover of the third cumulant and the temperature
dependence of the second cumulant.Comment: 4 pages, 4 figures. To appear in Phys. Rev. A. New calculation of the
bin statistics of a free Bose gas; updated and extended bibliograph
Limitations of MIC as sole metric of pharmacodynamic response across the range of antimicrobial susceptibilities within a single bacterial species
Citation: Wen, X. S., Gehring, R., Stallbaumer, A., Riviere, J. E., & Volkova, V. V. (2016). Limitations of MIC as sole metric of pharmacodynamic response across the range of antimicrobial susceptibilities within a single bacterial species. Scientific Reports, 6, 8. https://doi.org/10.1038/srep37907The minimum inhibitory concentration (MIC) of an antimicrobial drug for a bacterial pathogen is used as a measure of the bacterial susceptibility to the drug. However, relationships between the antimicrobial concentration, bacterial susceptibility, and the pharmacodynamic (PD) inhibitory effect on the bacterial population are more complex. The relationships can be captured by multi-parameter models such as the E-max model. In this study, time-kill experiments were conducted with a zoonotic pathogen Pasteurella multocida and the fluoroquinolone enrofloxacin. Pasteurella multocida isolates with enrofloxacin MIC of 0.01 mu g/mL, 1.5 mu g/mL, and 2.0 mu g/mL were used. An additive inhibitory E-max model was fitted to the data on bacterial population growth inhibition at different enrofloxacin concentrations. The values of PD parameters such as maximal growth inhibition, concentration achieving a half of the maximal inhibition, and Hill coefficient that captures steepness of the relationships between the concentration and effect, varied between the isolate with low MIC and less susceptible isolates. While enrofloxacin PD against the isolate with low MIC exhibited the expected concentration-dependent characteristics, the PD against the less susceptible isolates demonstrated time-dependent characteristics. The results demonstrate that bacterial antimicrobial susceptibility may need to be described by a combination of parameters rather than a single parameter of the MIC
Gas and dust in the Beta Pictoris Moving Group as seen by the Herschel Space Observatory
Context. Debris discs are thought to be formed through the collisional
grinding of planetesimals, and can be considered as the outcome of planet
formation. Understanding the properties of gas and dust in debris discs can
help us to comprehend the architecture of extrasolar planetary systems.
Herschel Space Observatory far-infrared (IR) photometry and spectroscopy have
provided a valuable dataset for the study of debris discs gas and dust
composition. This paper is part of a series of papers devoted to the study of
Herschel PACS observations of young stellar associations.
Aims. This work aims at studying the properties of discs in the Beta Pictoris
Moving Group (BPMG) through far-IR PACS observations of dust and gas.
Methods. We obtained Herschel-PACS far-IR photometric observations at 70, 100
and 160 microns of 19 BPMG members, together with spectroscopic observations of
four of them. Spectroscopic observations were centred at 63.18 microns and 157
microns, aiming to detect [OI] and [CII] emission. We incorporated the new
far-IR observations in the SED of BPMG members and fitted modified blackbody
models to better characterise the dust content.
Results. We have detected far-IR excess emission toward nine BPMG members,
including the first detection of an IR excess toward HD 29391.The star HD
172555, shows [OI] emission, while HD 181296, shows [CII] emission, expanding
the short list of debris discs with a gas detection. No debris disc in BPMG is
detected in both [OI] and [CII]. The discs show dust temperatures in the range
55 to 264 K, with low dust masses (6.6*10^{-5} MEarth to 0.2 MEarth) and radii
from blackbody models in the range 3 to 82 AU. All the objects with a gas
detection are early spectral type stars with a hot dust component.Comment: 12 pages, 7 figures, 6 table
Herschel PACS Observations and Modeling of Debris Disks in the Tucana-Horologium Association
We present Herschel PACS photometry of seventeen B- to M-type stars in the 30
Myr-old Tucana-Horologium Association. This work is part of the Herschel Open
Time Key Programme "Gas in Protoplanetary Systems" (GASPS). Six of the
seventeen targets were found to have infrared excesses significantly greater
than the expected stellar IR fluxes, including a previously unknown disk around
HD30051. These six debris disks were fitted with single-temperature blackbody
models to estimate the temperatures and abundances of the dust in the systems.
For the five stars that show excess emission in the Herschel PACS photometry
and also have Spitzer IRS spectra, we fit the data with models of optically
thin debris disks with realistic grain properties in order to better estimate
the disk parameters. The model is determined by a set of six parameters:
surface density index, grain size distribution index, minimum and maximum grain
sizes, and the inner and outer radii of the disk. The best fitting parameters
give us constraints on the geometry of the dust in these systems, as well as
lower limits to the total dust masses. The HD105 disk was further constrained
by fitting marginally resolved PACS 70 micron imaging.Comment: 15 pages, 7 figures, Accepted to Ap
Deep learning can predict laboratory quakes from active source seismic data
Small changes in seismic wave properties foretell frictional failure in laboratory experiments and in some cases on seismic faults. Such precursors include systematic changes in wave velocity and amplitude throughout the seismic cycle. However, the relationships between wave features and shear stress are complex. Here, we use data from lab friction experiments that include continuous measurement of elastic waves traversing the fault and build data-driven models to learn these complex relations. We demonstrate that deep learning models accurately predict the timing and size of laboratory earthquakes based on wave features. Additionally, the transportability of models is explored by using data from different experiments. Our deep learning models transfer well to unseen datasets providing high-fidelity models with much less training. These prediction methods can be potentially applied in the field for earthquake early warning in conjunction with long-term time-lapse seismic monitoring of crustal faults, CO2 storage sites and unconventional energy reservoirs
Impact assessment of the incorporation of the rotavirus vaccine in the province of San Luis – Argentina
Rotavirus (RV) is the main cause of acute gastroenteritis (AGE) in young children. The San Luis province of Argentina introduced RV vaccination in May 2013. We estimate vaccine impact (RVI) using real-world data. Data on all-cause AGE cases and AGE-related hospitalisations for San Luis and the adjacent Mendoza province (control group) were obtained and analysed by interrupted time-series methods. Regardless of the model used for counterfactual predictions, we estimated a reduction in the number of all-cause AGE cases of 20-25% and a reduction in AGE-related hospitalisations of 55-60%. The vaccine impact was similar for each age group considered (<1 year, <2 years and <5 years). RV vaccination was estimated to have reduced direct medical costs in the province by about 4.5 million pesos from May 2013 to December 2014. Similar to previous studies, we found a higher impact of RV vaccination in preventing severe all-cause AGE cases requiring hospitalisation than in preventing all-cases AGE cases presenting for medical care. An assessment of the economic value of RV vaccination could take other benefits into account in addition to the avoided medical costs and the costs of vaccination.Fil: GarcĂa MartĂ, Sebastián. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Parque Centenario. Centro de Investigaciones en EpidemiologĂa y Salud PĂşblica. Instituto de Efectividad ClĂnica y Sanitaria. Centro de Investigaciones en EpidemiologĂa y Salud PĂşblica; ArgentinaFil: Augustovski, Federico Ariel. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Parque Centenario. Centro de Investigaciones en EpidemiologĂa y Salud PĂşblica. Instituto de Efectividad ClĂnica y Sanitaria. Centro de Investigaciones en EpidemiologĂa y Salud PĂşblica; ArgentinaFil: Gibbons, Luz. Instituto de Efectividad ClĂnica y Sanitaria; ArgentinaFil: Loggia, V.. No especifĂca;Fil: Lepetic, A.. No especifĂca;Fil: GĂłmez, J.A.. No especifĂca;Fil: PichĂłn-riviere, Andres. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Oficina de CoordinaciĂłn Administrativa Parque Centenario. Centro de Investigaciones en EpidemiologĂa y Salud PĂşblica. Instituto de Efectividad ClĂnica y Sanitaria. Centro de Investigaciones en EpidemiologĂa y Salud PĂşblica; Argentin
Polar Smectic Films
We report on a new experimental procedure for forming and studying polar
smectic liquid crystal films. A free standing smectic film is put in contact
with a liquid drop, so that the film has one liquid crystal/liquid interface
and one liquid crystal/air interface. This polar environment results in changes
in the textures observed in the film, including a boojum texture and a
previously unobserved spiral texture in which the winding direction of the
spiral reverses at a finite radius from its center. Some aspects of these
textures are explained by the presence of a Ksb term in the bulk elastic free
energy density that favors a combination of splay and bend deformations.Comment: 4 pages, REVTeX, 3 figures, submitted to PR
Formyl Peptide Receptor as a Novel Therapeutic Target for Anxiety-Related Disorders
Formyl peptide receptors (FPR) belong to a family of sensors of the immune system that detect microbe-associated molecules and inform various cellular and sensorial mechanisms to the presence of pathogens in the host. Here we demonstrate that Fpr2/3-deficient mice show a distinct profile of behaviour characterised by reduced anxiety in the marble burying and light-dark box paradigms, increased exploratory behaviour in an open-field, together with superior performance on a novel object recognition test. Pharmacological blockade with a formyl peptide receptor antagonist, Boc2, in wild type mice reproduced most of the behavioural changes observed in the Fpr2/3(-/-) mice, including a significant improvement in novel object discrimination and reduced anxiety in a light/dark shuttle test. These effects were associated with reduced FPR signalling in the gut as shown by the significant reduction in the levels of p-p38. Collectively, these findings suggest that homeostatic FPR signalling exerts a modulatory effect on anxiety-like behaviours. These findings thus suggest that therapies targeting FPRs may be a novel approach to ameliorate behavioural abnormalities present in neuropsychiatric disorders at the cognitive-emotional interface
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