Advanced switching schemes in a Stark decelerator

We revisit the operation of the Stark decelerator and present a new, optimized operation scheme, which substantially improves the efficiency of the decelerator at both low and high final velocities, relevant for trapping experiments and collision experiments, respectively. Both experimental and simulation results show that this new mode of operation outperforms the schemes which have hitherto been in use. This new mode of operation could potentially be extended to other deceleration techniques

Simulating quantum effects of cosmological expansion using a static ion trap

We propose a new experimental testbed that uses ions in the collective ground state of a static trap for studying the analog of quantum-field effects in cosmological spacetimes, including the Gibbons-Hawking effect for a single detector in de Sitter spacetime, as well as the possibility of modeling inflationary structure formation and the entanglement signature of de Sitter spacetime. To date, proposals for using trapped ions in analog gravity experiments have simulated the effect of gravity on the field modes by directly manipulating the ions' motion. In contrast, by associating laboratory time with conformal time in the simulated universe, we can encode the full effect of curvature in the modulation of the laser used to couple the ions' vibrational motion and electronic states. This model simplifies the experimental requirements for modeling the analog of an expanding universe using trapped ions and enlarges the validity of the ion-trap analogy to a wide range of interesting cases.Comment: (v2) revisions based on referee comments, figure added for clarity; (v1) 17 pages, no figure

Tracing back ancient oral microbiomes and oral pathogens using dental pulps from ancient teeth

Ancient dental pulps are highly precious samples because they conserve DNA from humans and blood-borne pathogens for ages. However, little is known about the microbial communities present in dental pulps. Here, we analyzed ancient and modern dental pulp samples from different time periods and geographic regions and found that they are colonized by distinct microbial communities, which can be differentiated from other oral cavity samples. We found that despite the presence of environmental bacteria, ancient dental pulps conserve a clear and well-conserved record of oral microbes. We were able to detect several different oral pathogens in ancient and modern dental pulps, which are commonly associated with periodontal diseases. We thus showed that ancient dental pulps are not only valuable sources of DNA from humans and systemic infections, but also an open window for the study of ancient oral microbiomes

Simulation based performance assessment of phase change enhanced thermal buffering for domestic heat pump load shifting

In this study, the feasibility of using thermal buffering enhanced with phase change materiaL (PCM) to enable heat pump load shifting for a typical UK dwelling was investigated by comparing the performance of a buffered, load-shifted heat pump against a reference case. The impact of load shifting on a larger population of heat pumps was also explored. The results indicate that with adequate buffering the operation of a domestic heat pump can be wholly moved to off-peak periods without adversely affecting space or hot water temperatures. The volume of the buffer required could be more than halved using PCM. However, load shifting was associated with a significant energy penalty that negated any economic benefits accruing from a switch to off peak electricity. The study also showed that load shifting of populations of buffered heat pumps could exacerbate peak loading no the electrical network rather than reducing it

Loading Stark-decelerated molecules into electrostatic quadrupole traps

Beams of neutral polar molecules in a low-field seeking quantum state can be slowed down using a Stark decelerator, and can subsequently be loaded and confined in electrostatic quadrupole traps. The efficiency of the trap loading process is determined by the ability to couple the decelerated packet of molecules into the trap without loss of molecules and without heating. We discuss the inherent difficulties to obtain ideal trap loading, and describe and compare different trap loading strategies. A new "split-endcap" quadrupole trap design is presented that enables improved trap loading efficiencies. This is experimentally verified by comparing the trapping of OH radicals using the conventional and the new quadrupole trap designs

Innovative NDT technique for detection of surface cracks based on ferrofluids excited with DC and AC magnetic fields

Innovative NDT technique for detection of surface cracks based on ferrofluids excited with DC and AC magnetic fieldsAn innovative NDT technique is proposed for surface inspection of materials not necessarily magnetic or conductive, based on local magnetic field variations due to ferrofluid deposited in the cracks. The feasibility of the technique is assessed preliminarily, based on signal detectability without applied external magnetic field, and under applied DC and AC fields. The signals are quantified analytically, experimentally and numerically. In DC, detection is based on local magnetic flux density variations. In AC, detection is based on the existing phase lag between the field close to the crack and the applied field. This approach has inherent advantages: the phase lag, as opposed to the magnetic flux density, is independent of the quantity of ferrofluid in the crack and the magnitude of the applied field. The model agrees well with the tests, showing that the signal increases with the applied field strength, up to the saturation magnetization of the ferrofluid, and decreases with the distance to the crack longitudinal axis, and thus it can provide useful estimations of the signal. The proposed technique, requiring application of external fields to magnetize the ferrofluid to enhance the signal, seems promising: the model suggests that signals associated to cracks significantly smaller than the minimum detectable surface cracks for comparable classical NDT techniques are easily detectable with commercial magnetometers.Postprint (published version

LA DYADE MANAGER – SUPERIEUR : UNE DIMENSION OUBLIEE DU CONTRÔLE DE GESTION

Les termes paradoxe, tension, contradiction ou encore dilemme reviennent régulièrement dans la littérature en management et en contrôle. La forte présence de ces thèmes marque leur importance pour appréhender la complexité de ces activités. Cependant, ces concepts sont souvent utilisés sinon de façon inappropriée, tout du moins avec peu de clarté dans leur définition. Par ailleurs, si les études en management traitent souvent des systèmes et des acteurs, elles s'intéressent rarement à la dyade manager-supérieur. Cette dernière est pourtant l'un des noeuds les plus importants où se forment et se gèrent oppositions, contradictions, paradoxes etc. Ceci nous amène à proposer certaines pistes afin de clarifier le concept de dualité et à étudier dans deux entreprises un exemple de contradiction dans les relations entre managers et supérieurs, celui de l'autonomie et de la direction par le sens. Nous mettons ainsi en évidence le besoin d'une compréhension plus fine des dynamiques interpersonnelles, et non seulement des systèmes de contrôle et des styles de management, dans les problématiques de contrôle.Contradiction; Dyades manager–supérieur hiérarchique; Coadaptation; Management; Contrôle de gestion

Deceleration and electrostatic trapping of OH radicals

A pulsed beam of ground state OH radicals is slowed down using a Stark decelerator and is subsequently loaded into an electrostatic trap. Characterization of the molecular beam production, deceleration and trap loading process is performed via laser induced fluorescence detection inside the quadrupole trap. Depending on details of the trap loading sequence, typically $10^5$ OH ($X^2\Pi_{3/2}, J=3/2$) radicals are trapped at a density of around $10^7$ cm$^{-3}$ and at temperatures in the 50-500 mK range. The 1/e trap lifetime is around 1.0 second.Comment: 4 pages, 3 figure

Direct measurement of the radiative lifetime of vibrationally excited OH radicals

Neutral molecules, isolated in the gas-phase, can be prepared in a long-lived excited state and stored in a trap. The long observation time afforded by the trap can then be exploited to measure the radiative lifetime of this state by monitoring the temporal decay of the population in the trap. This method is demonstrated here and used to benchmark the Einstein $A$-coefficients in the Meinel system of OH. A pulsed beam of vibrationally excited OH radicals is Stark decelerated and loaded into an electrostatic quadrupole trap. The radiative lifetime of the upper $\Lambda$-doublet component of the $X ^2\Pi_{3/2}, v=1, J=3/2$ level is determined as $59.0 \pm 2.0$ ms, in good agreement with the calculated value of $57.7 \pm 1.0$ ms.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let