Mechanisms for Lasing with Cold Atoms as the Gain Medium

We realize a laser with a cloud of cold rubidium atoms as gain medium, placed in a low-finesse cavity. Three different regimes of laser emission are observed corresponding respectively to Mollow, Raman and Four Wave Mixing mechanisms. We measure an output power of up to 300 $\mu$W and present the main properties of these different lasers in each regime

Tuberculosis treatment in a refugee and migrant population: 20 years of experience on the Thai-Burmese border.

Although tuberculosis (TB) is a curable disease, it remains a major global health problem and an important cause of morbidity and mortality among vulnerable populations, including refugees and migrants

Optical parametric oscillation with distributed feedback in cold atoms

There is currently a strong interest in mirrorless lasing systems, in which the electromagnetic feedback is provided either by disorder (multiple scattering in the gain medium) or by order (multiple Bragg reflection). These mechanisms correspond, respectively, to random lasers and photonic crystal lasers. The crossover regime between order and disorder, or correlated disorder, has also been investigated with some success. Here, we report one-dimensional photonic-crystal lasing (that is, distributed feedback lasing) with a cold atom cloud that simultaneously provides both gain and feedback. The atoms are trapped in a one-dimensional lattice, producing a density modulation that creates a strong Bragg reflection with a small angle of incidence. Pumping the atoms with auxiliary beams induces four-wave mixing, which provides parametric gain. The combination of both ingredients generates a mirrorless parametric oscillation with a conical output emission, the apex angle of which is tunable with the lattice periodicity

Frustrated pretransitional phenomena in aperiodic composites

Citation: Mariette, C., Frantsuzov, I., Wang, B., Guerin, L., Rabiller, P., Hollingsworth, M. D., & Toudic, B. (2016). Frustrated pretransitional phenomena in aperiodic composites. Physical Review B, 94(18), 9. doi:10.1103/PhysRevB.94.184105This paper reports on symmetry breaking in the aperiodic inclusion compound n-octadecane/urea and its isotopomer n-octadecane/urea-d(4). The high-symmetry phase is described by a hexagonal rank-4 superspace group. Pretransitional phenomena in this crystallographic superspace reveal competing short-range-ordering phenomena within the high-symmetry phase. Very high-resolution diffraction data show that critical scattering appears at inequivalent points within the four-dimensional Brillouin zone, although the first phase transition at T-c1 near 158 K implies the condensation at only one of those points. The resulting superspace group remains of dimension 4. Two other phase transitions are reported at T-c2 = 152.8(4) K and T-c3 = 109(4) K in n-octadecane/urea-d(4). The two low-symmetry phases that arise are described by rank-5 superspace groups

The creation of modulated monoclinic aperiodic composites in n-alkane/urea compounds

Citation: Mariette, C., Guerin, L., Rabiller, P., Chen, Y. S., Bosak, A., Popov, A., . . . Toudic, B. (2015). The creation of modulated monoclinic aperiodic composites in n-alkane/urea compounds. Zeitschrift Fur Kristallographie, 230(1), 5-11. doi:10.1515/zkri-2014-1773n-Dodecane/urea is a member of the prototype series of n-alkane/urea inclusion compounds. At room temperature, it presents a quasi-one dimensional liquid-like state for the confined guest molecules within the rigid, hexagonal framework of the urea host. At lower temperatures, we report the existence of two other phases. Below T-c=248 K there appears a phase with rank four superspace group P6(1)22(00 gamma), the one typically observed at room temperature in n-alkane/urea compounds with longer guest molecules. A misfit parameter, defined by the ratio gamma=C-h/C-g (C-host/C-guest), is found to be 0.632 +/- 0.005. Below T-c1=123 K, a monoclinic modulated phase is created with a constant shift along c of the guest molecules in adjacent channels. The maximal monoclinic space group for this structure is P12(1)1(alpha 0 gamma). Analogies and differences with n-heptane/urea, which also presents a monoclinic, modulated low-temperature phase, are discussed

Changes in Health and Physical Fitness Parameters After 6 Months of High-intensity Group Exercise in Firefighters: Preliminary Data

The physical demands of firefighting require the men and women employed in this profession to be in optimal physical condition to perform their jobs proficiently, as well as to mitigate the risk of injury. Every year, the city of Addison, TX, budgets many thousands of dollars to the compensation plan for first responders. Most of the funding is used for rehabilitation services due to work related injuries. PURPOSE: While many of these injuries are unavoidable due to the inherent risks of the profession, ensuring proper physical fitness is one of the most effective methods to reduce many of these impairments. The purpose of this preliminary study was to characterize health and fitness parameters in 18 professional firefighters from the city of Addison, TX, prior to a 6-month training program. METHODS: Upon arrival, all participants underwent testing in the following order: body composition, range of motion, anaerobic power, muscular endurance, and cardiorespiratory fitness. All participants also completed a detailed health history questionnaire and answered questions specifically addressing chronic low back pain. RESULTS: The following values were attained from testing: total body fat: 30.1±9.7%; flexibility: 24.9±6.3 cm; peak power: 1068.7±272.9 W; mean power: 636.9±143.4 W; time to peak power 0.57±0.35 sec; pushup: 28.8±14.9; curl up: 22.1±15.8; VO2max: 34.1±5.1 ml/kg/min. CONCLUSION: Based off the comparison of reported means and ACSM’s fitness norms, it can be concluded that improvements are necessary in body composition, muscular endurance, range of motion and cardiorespiratory fitness. With improvements in these physiological variables, tactical performance may be optimally performed in a safer manner

Short term bioassay and bioassay chemistry of materials related to synthetic fossil fuels

An abstract was prepared for one paper. Abstracts of the five additional papers appeared previously in ERA

Etude du comportement paramagnétique des actinides (IV) (Th, U, Np et Pu) en solution en présence de ligands

International audienceLa spectroscopie RMN est une technique capable de fournir des informations structurales sur des complexes métalliques en solution. Elle peut être appliquée à l’analyse de petites molécules en chimie organique, de protéines (macros molécules) en biologie mais aussi en chimie nucléaire avec la nucléarisation des spectromètres [1]. La présence d’un Actinide (An), avec des électrons 5f non appariés, génère une modification du spectre RMN (un élargissement et/ou une variation du déplacement chimique des pics) caractéristique du paramagnétisme du cation.Dans le cas des complexes paramagnétiques de Ln$^{III}$ (éléments 4$f$), le déplacement chimique total $\Delta _{TOT}$ est modélisé par l’équation de Bleaney (équations (a) et (b)) [2]. Il dépend du déplacement chimique paramagnétique induit $\delta _{para}$ qui peut être décomposé en deux contributions : un terme de contact $\delta _{cont}$ (délocalisation de l’électron $f$ sur l’atome donneur du ligand) et un terme dipolaire $\delta _{dip}$ (interaction entre le spin électronique et nucléaire à travers l’espace). A partir de ce dernier terme, on peut déduire des informations structurales en utilisant les constantes de Bleaney