Theoretical overview of atomic parity violation. Recent developments and challenges

Recent advances in interpreting the most accurate to-date measurement of atomic parity violation in Cs are reviewed. The inferred nuclear weak charge, Q_W = - 72.65(28)_expt (36)_theor, agrees with the prediction of the standard model at 1 sigma level. Further improved interpretation is limited by an accuracy of solving basic correlation problem of atomic structure. We report on our progress in solving this problem within the relativistic coupled-cluster formalism. We include single-, double- and triple- electronic excitations in the coupled-cluster expansion. Numerical results for energies, electric-dipole matrix elements, and hyperfine-structure constants of Cs are presented.Comment: PAVI'06 proceedings + EJPA; refs + SM Qw fixe

Progress in Atomic Fountains at LNE-SYRTE

We give an overview of the work done with the Laboratoire National de M\'etrologie et d'Essais-Syst\`emes de R\'ef\'erence Temps-Espace (LNE-SYRTE) fountain ensemble during the last five years. After a description of the clock ensemble, comprising three fountains, FO1, FO2, and FOM, and the newest developments, we review recent studies of several systematic frequency shifts. This includes the distributed cavity phase shift, which we evaluate for the FO1 and FOM fountains, applying the techniques of our recent work on FO2. We also report calculations of the microwave lensing frequency shift for the three fountains, review the status of the blackbody radiation shift, and summarize recent experimental work to control microwave leakage and spurious phase perturbations. We give current accuracy budgets. We also describe several applications in time and frequency metrology: fountain comparisons, calibrations of the international atomic time, secondary representation of the SI second based on the 87Rb hyperfine frequency, absolute measurements of optical frequencies, tests of the T2L2 satellite laser link, and review fundamental physics applications of the LNE-SYRTE fountain ensemble. Finally, we give a summary of the tests of the PHARAO cold atom space clock performed using the FOM transportable fountain.Comment: 19 pages, 12 figures, 5 tables, 126 reference

Consumer Complaints and Company Market Value

Consumer complaints affect company market value and common sense suggests that a negative impact is expected. However, do complaints always negatively impact company market value? We hypothesize in this study that complaints may have a non-linear effect on market value. Positive (e.g. avoiding high costs to solve complaints) and negative (e.g. speedy and intense diffusion) tradeoffs may occur given the level of complaints. To test our non-linear hypothesis, a panel data was collected from cell phone service providers from 2005 to 2013. The results supported our tradeoff rationale. Low levels of complaints allow for companies to increase market value, while high levels of complaints cause increasing harm to market value. The sample, model and period considered in this study, indicates a level of 0.49 complaints per thousand consumers as the threshold for a shift in tradeoffs. The effects on market value become increasingly negative when trying to make reductions to move below this level, due to negative tradeoffs

Vers une interface multimodale pour une assistance à la conception architecturale

peer reviewe

A universal mechanism for hydraulic signals generation in natural and artificial branches

Plants are constantly subjected to external mechanical loads such as wind, rain or even neighbours. These stimuli are known to affect the growth of the plants, a process called thigmomorphogenesis (Jaffe et al. 2002, Braam 2005, Telewski 2006). Typically, the bending of a tree stem leads to a local increase of the radial growth while the primary growth is rapidly stopped, suggesting a transport of the information from the stimulated zone to the apical zone (Coutand et al. 2000, 2009). Among the different hypothesis found in the literature to account for this long-distance transport (electrical signal, hormone transport), it has been proposed that local mechanical stimuli, like bending, could generate a hydraulic signal that could move through the xylem (Malone 1994, Julien 1993, Farmer et al 2014). Recently, such hydro/mechanical couplings have been directly observed by Lopez et al (2014), who showed that bending a whole living tree or a cut branch generates almost simultaneously an overpressure pulse in the vascular system. However, the physical mechanism responsible for this hydro/mechanical coupling and the basic properties of the hydraulic pulse (amplitude vs. bending deformation, dependence with wood properties) remained not understood

Nematic pancakes revisited

International audienceno abstrac

Time and frequency activities at LNE-SYRTE related to global navigation satellite systems

International audienc

Long distance signaling of mechanical stress in trees: evidence of hydraulic pulse

Plants are constantly subjected to external mechanical loads such as wind, rain or even neighbours. These stimuli are known to affect the growth of the plants, a process called thigmomorphegenesis. Typically, the bending of a tree stem leads to a local increase of the radial growth while the primary growth is rapidly stopped, suggesting a transport of the information from the stimulated zone to the apical zone. Among the different hypothesis found in the literature to account for this long-distance transport (electrical signal, hormone transport), it has been proposed that local mechanical stimuli, like bending, could generate an hydraulic signal that could move through the xylem. Using stems segments, we displayed that bending strains generate a transient high pressure variation that is able to propagate rapidly along the hydraulic network. We quantified these pressure pulses and we observed i) that living cells were not involved in the phenomenon, ii) an inter-specific variability of its magnitude. Using a biomimetic approach and poroelastic artificial beams, we analyzed the physics of phenomena. We concluded that these hydraulic pulses are driven by the poroelastic properties of the saturated wood material and we proposed a physical modeling to explain the mechanism: the stem bending generates a variation of volume of the conduits, that expulses the incompressible water. This generates a local transient hydraulic overpressure. In planta experiments confirmed that hydraulic pulses propagate along the vascular system of the xylem symmetrically to the upper and lower regions of the stem. Finally, molecular analysis in the apical part of trees showed the evidence of a remote signalling induced by the bending of the basis of their stem. As a signaling process, this hydraulic behavior could be an efficient candidate for a fast long distance signal transporting mecanobiological information to the extreme organs as leaves, roots and apice