Pairing and condensation in a resonant Bose-Fermi mixture

We study by diagrammatic methods a mixture of single-component bosons and fermions, with boson-fermion coupling tuned by a Fano-Feshbach resonance. For increasing coupling, the growing boson-fermion pairing correlations progressively reduce the boson condensation temperature and make it eventually vanish at a critical coupling. Such quantum critical point depends very weakly on the population imbalance and for vanishing boson densities coincides with that found for the polaron-molecule transition in a strongly imbalanced Fermi gas, thus bridging two quite distinct physical systems.Comment: 4 pages, 4 figure

Contested Cosmopolitanism

A growing body of literature is accumulating around theories of cosmopolitanism. The concept is hotly debated within a number of disciplines, and similar debates circulate beyond academia, among national and transnational actors. This paper aims to critically appraise some of the current competing discourses and agendas around cosmopolitanism and their implications. The recent emphasis on cosmopolitanism is not without its detractors, and this paper engages with some of the key critiques of the current cosmopolitan turn. These touch on multiple dimensions of the cosmopolitan project, its essentialising and reductionist features, its western-centric bias and its postcolonial inflection. While some scholars mobilise the concept of cosmopolitics to contest the political nature of cosmopolitanism rhetoric and agenda, others historicise its political and economic context. Still others flesh out the figure of the cosmopolitan, offering alternative readings of the current postmodern condition, or undoing the cosmopolitan project from within. Through an exploration of the discrepancies between competing accounts of cosmopolitanism, and of contested understandings of who can or cannot aspire to be considered ‘cosmopolitan’, the paper sets out to highlight the situatedness of specific political projects associated with cosmopolitanism and to discuss the ramifications of privileging specific views of cosmopolitanism over others

Mass imbalance effect in resonant Bose-Fermi mixtures

We consider a homogeneous Bose-Fermi mixture, with the boson-fermion interaction tuned by a Fano-Feshbach resonance, in the presence of mass and density imbalance between the two species. By using many-body diagrammatic methods, we first study the finite-temperature phase diagram for the specific case of the mass-imbalanced mixture $^{87}$Rb $-^{40}$K for different values of the density imbalance. We then analyse the quantum phase transition associated with the disappearance at zero temperature of the boson condensate above a critical boson-fermion coupling. We find a pronounced dependence of the critical coupling on the mass ratio and a weak dependence on the density imbalance. For a vanishingly small boson density, we derive, within our approximation, the asymptotic expressions for the critical coupling in the limits of small and large mass ratios. These expressions are relevant also for the polaron-molecule transition in a Fermi mixture at small and large mass ratios. The analysis of the momentum distribution functions at sufficiently large density imbalances shows an interesting effect in the bosonic momentum distribution due to the simultaneous presence of composite fermions and unpaired fermions.Comment: Final versio

Energy of strongly attractive Bose-Fermi mixtures

We discuss how approximate theories for Bose-Fermi mixtures recover in the molecular limit the expected expression for Fermi-Fermi mixtures of molecules and unpaired fermions. In particular, we compare the energy of the system resulting from a T-matrix diagrammatic approach with that obtained with Variational and Fixed-Node Diffusion Quantum Monte Carlo methods.Comment: 5 pages, 2 figures, submitted to the EPJST volume "Novel Quantum Phases and Mesoscopic Physics in Quantum Gases

CpHMD-Then-QM/MM Identification of the Amino Acids Responsible for the Anabaena Sensory Rhodopsin pH-Dependent Electronic Absorption Spectrum

International audienceAnabaena Sensory Rhodopsin (ASR), a microbial photoactive protein featuring the retinal chromophore in two different conformations, exhibits a pH-dependent electronic absorption spectrum. Using the recently developed CpHMD-then-QM/MM multiscale protocol applied to ASR embedded in a membrane model, the pH-induced changes in its maximum absorption wavelength have been reproduced and analyzed. While the acidic 1 tiny red-shift is essentially correlated with the deprotonation of an aspartic acid located on the ASR extracellular side, the larger blue-shift experimentally reported at pH values larger than 5 involves a cluster of titrating residues sitting on the cytoplasmic side. The ASR pH-dependent spectrum is the consequence of the competitive stabilization of retinal ground and excited states by the protein electrostatic potential

Risk adjustment models for interhospital comparison of CS rates using Robson's ten group classification system and other socio-demographic and clinical variables

BACKGROUND: Caesarean section (CS) rate is a quality of health care indicator frequently used at national and international level . The aim of this study was to assess whether adjustment for Robson's Ten Group Classification System (TGCS), and clinical and socio-demographic of the mother and the fetus is necessary for inter-hospital comparisons of CS rates. METHODS: The study population includes 64,423 deliveries in Emilia-Romagna between January 1, 2003 and December 31, 2004, classified according to theTGCS. Poisson regression was used to estimate crude and adjusted hospital relative risks of CS compared to a reference category. Analyses were carried out in the overall population and separately according to the Robson groups (groups I, II, III, IV and V-X combined). Adjusted relative risks (RR) of CS were estimated using two risk-adjustment models; the first (M1) including the TGCS group as the only adjustment factor; the second (M2) including in addition demographic and clinical confounders identified using a stepwise selection procedure. Percentage variations between crude and adjusted RRs by hospital were calculated to evaluate the confounding effect of covariates. RESULTS: The percentage variations from crude to adjusted RR proved to be similar in M1 and M2 model. However, stratified analyses by Robson's classification groups showed that residual confounding for clinical and demographic variables was present in groups I (nulliparous, single, cephalic, [greater than or equal to]37 weeks, spontaneous labour) and III (multiparous, excluding previous CS, single, cephalic, [greater than or equal to]37 weeks, spontaneous labour) and IV (multiparous, excluding previous CS, single, cephalic, [greater than or equal to]37 weeks, induced or CS before labour) and to a minor extent in groups II (nulliparous, single, cephalic, [greater than or equal to]37 weeks, induced or CS before labour) and IV (multiparous, excluding previous CS, single, cephalic, [greater than or equal to]37 weeks, induced or CS before labour). CONCLUSIONS: The TGCS classification is useful for inter-hospital comparison of CS section rates, but residual confounding is present in the TGCS strata

Use of microfluidic capillary electrophoresis for the determination of multi-component protein adsorption isotherms: Application to high-throughput analysis for hydrophobic interaction chromatography

Chromatography is a widely used separation process for purification of biopharmaceuticals that is able to obtain high purities and concentrations. The phenomena that occur during separation, mass transfer and adsorption are quite complex. To better understand these phenomena and their mechanisms, multi-component adsorption isotherms must be investigated. High-throughput methodologies are a very powerful tool to determine adsorption isotherms and they waste very small amounts of sample and chemicals, but the quantification of component concentrations is a real bottleneck in multi-component isotherm determination. The behavior of bovine serum albumin, Corynebacterium diphtheriae CRM197 protein and lysozyme, selected as model proteins in binary mixtures with hydrophobic resin, is investigated here. In this work we propose a new method for determining multi-component adsorption isotherms using high-throughput experiments with filter plates, by exploiting microfluidic capillary electrophoresis. The precision and accuracy of the microfluidic capillary electrophoresis platform were evaluated in order to assess the procedure; they were both found to be high and the procedure is thus reliable in determining adsorption isotherms for binary mixtures. Multi-component adsorption isotherms were determined with a totally high-throughput procedure that turned out to be a very fast and powerful tool. The same procedure can be applied to every kind of high-throughput screening