Realization of a Townes Soliton in a Two-Component Planar Bose Gas.

Most experimental observations of solitons are limited to one-dimensional (1D) situations, where they are naturally stable. For instance, in 1D cold Bose gases, they exist for any attractive interaction strength g and particle number N. By contrast, in two dimensions, solitons appear only for discrete values of gN, the so-called Townes soliton being the most celebrated example. Here, we use a two-component Bose gas to prepare deterministically such a soliton: Starting from a uniform bath of atoms in a given internal state, we imprint the soliton wave function using an optical transfer to another state. We explore various interaction strengths, atom numbers, and sizes and confirm the existence of a solitonic behavior for a specific value of gN and arbitrary sizes, a hallmark of scale invariance.

Magnetic Dipolar Interaction between Hyperfine Clock States in a Planar Alkali Bose Gas.

In atomic systems, clock states feature a zero projection of the total angular momentum and thus a low sensitivity to magnetic fields. This makes them widely used for metrological applications like atomic fountains or gravimeters. Here, we show that a mixture of two such nonmagnetic states still displays magnetic dipole-dipole interactions comparable to the one expected for the other Zeeman states of the same atomic species. Using high-resolution spectroscopy of a planar gas of ^{87}Rb atoms with a controlled in plane shape, we explore the effective isotropic and extensive character of these interactions and demonstrate their tunability. Our measurements set strong constraints on the relative values of the s-wave scattering lengths a_{ij} involving the two clock states.

Sound Propagation in a Uniform Superfluid Two-Dimensional Bose Gas.

In superfluid systems several sound modes can be excited, such as, for example, first and second sound in liquid helium. Here, we excite running and standing waves in a uniform two-dimensional Bose gas and we characterize the propagation of sound in both the superfluid and normal regimes. In the superfluid phase, the measured speed of sound is in good agreement with the prediction of a two-fluid hydrodynamic model, and the weak damping is well explained by the scattering with thermal excitations. In the normal phase we observe a stronger damping, which we attribute to a departure from hydrodynamic behavior.

Tan's two-body contact across the superfluid transition of a planar Bose gas.

Tan's contact is a quantity that unifies many different properties of a low-temperature gas with short-range interactions, from its momentum distribution to its spatial two-body correlation function. Here, we use a Ramsey interferometric method to realize experimentally the thermodynamic definition of the two-body contact, i.e., the change of the internal energy in a small modification of the scattering length. Our measurements are performed on a uniform two-dimensional Bose gas of 87Rb atoms across the Berezinskii-Kosterlitz-Thouless superfluid transition. They connect well to the theoretical predictions in the limiting cases of a strongly degenerate fluid and of a normal gas. They also provide the variation of this key quantity in the critical region, where further theoretical efforts are needed to account for our findings.

Prospective evaluation of the management of urinary tract infections in 134 French nursing homes.

OBJECTIVE: Prospective assessment of the management of urinary tract infections (UTI) in the nursing homes of the Hauts-de-France region. PATIENTS AND METHODS: A 50-question form had to be filled in for up to five consecutive residents treated for UTI in each nursing home. If necessary, diagnoses were reclassified according to the 2014 French Infectious Diseases Society guidelines. Analyses were presented per supposed (reported) and reclassified diagnoses. RESULTS: Of 397 contacted facilities, 134 participated and informed 444 UTI episodes. Reported diagnostic criteria were burning urination (32%), malodorous urine (29%), confusion (28%), and turbid urine (19%). Twenty-one percent of diagnoses were based on erroneous criteria. Less than 50% of residents had a urine dipstick test performed and 94% a urine culture. The main pathogen was Escherichia coli. Reported indications were uncomplicated cystitis (32%), unspecified UTI (26%), complicated cystitis (9%), while no reason was given in 25% of cases. Only 10% of diagnoses were consistent with the guidelines: complicated cystitis (49%), asymptomatic bacteriuria (21%), acute pyelonephritis (21%), male UTI (9%). Almost 85% of prescriptions were active on the isolated bacteria. The empirical antibiotic therapy was consistent with the diagnosis in 16% of cases (30% for reclassified diagnoses). The two most prescribed antibiotic classes were fluoroquinolones (22.1%) and oral third-generation cephalosporins (19.1%). Only two of 157 possible de-escalations were performed. Duration of treatment was adequate for 19% of UTIs (9.6% of reclassified cases). CONCLUSION: Our study revealed multiple deficiencies in diagnosis, antibiotic choice, treatment duration, and reevaluation.