Influence of lasers propagation delay on the sensitivity of atom interferometers

In atom interferometers based on two photon transitions, the delay induced by the difference of the laser beams paths makes the interferometer sensitive to the fluctuations of the frequency of the lasers. We first study, in the general case, how the laser frequency noise affects the performance of the interferometer measurement. Our calculations are compared with the measurements performed on our cold atom gravimeter based on stimulated Raman transitions. We finally extend this study to the case of cold atom gradiometers.Comment: 17 pages, 6 figure

Coherent matter wave inertial sensors for precision measurements in space

We analyze the advantages of using ultra-cold coherent sources of atoms for matter-wave interferometry in space. We present a proof-of-principle experiment that is based on an analysis of the results previously published in [Richard et al., Phys. Rev. Lett., 91, 010405 (2003)] from which we extract the ratio h/m for 87Rb. This measurement shows that a limitation in accuracy arises due to atomic interactions within the Bose-Einstein condensate

Atom lasers: production, properties and prospects for precision inertial measurement

We review experimental progress on atom lasers out-coupled from Bose-Einstein condensates, and consider the properties of such beams in the context of precision inertial sensing. The atom laser is the matter-wave analog of the optical laser. Both devices rely on Bose-enhanced scattering to produce a macroscopically populated trapped mode that is output-coupled to produce an intense beam. In both cases, the beams often display highly desirable properties such as low divergence, high spectral flux and a simple spatial mode that make them useful in practical applications, as well as the potential to perform measurements at or below the quantum projection noise limit. Both devices display similar second-order correlations that differ from thermal sources. Because of these properties, atom lasers are a promising source for application to precision inertial measurements.Comment: This is a review paper. It contains 40 pages, including references and figure

Systemic corticosteroids in dermatological practice. Part I: Main adverse effects

Systemic corticosteroids have been used in dermatological practice for approximately 60 years due to their anti-inflammatory and immunosuppressive effects. The challenge of corticosteroid therapy is to counterbalance the desirable actions and undesirable pharmacological effects. Unfortunately, advanced understanding of the mechanisms of action of corticosteroids has not resulted in the development of minimal toxicity regimens. In this article, we report the main pharmacological properties of systemic corticosteroids, their major indications in clinical practice and the adverse effects of high doses and/or prolonged administration.Há quase 60 anos os corticosteróides sistêmicos têm sido amplamente utilizados na área de dermatologia, trazendo benefícios para muitas doenças em decorrência de suas ações antiinflamatórias e imunossupressoras. O desafio de seu uso consiste em contrabalançar os efeitos benéficos e as atividades farmacológicas indesejáveis. Infelizmente, os avanços no conhecimento sobre os mecanismos de ação dos corticosteróides não resultaram no desenvolvimento de regimes com mínima toxicidade. Dessa maneira, este artigo de revisão discorre sobre os aspectos farmacológicos dos corticosteróides sistêmicos, bem como suas principais indicações de uso e efeitos colaterais da administração em altas doses e/ou por longos períodos de tempo.UNIFESPHospital Central da Santa Casa de São Paulo Departamento de Clínica Médica Serviço de DermatologiaHospital Central da Santa Casa de São Paulo Clínica de DermatologiaUNIFESPSciEL

Limits to the sensitivity of a low noise compact atomic gravimeter

A detailed analysis of the most relevant sources of phase noise in an atomic interferometer is carried out, both theoretically and experimentally. Even a short interrogation time of 100 ms allows our cold atom gravimeter to reach an excellent short term sensitivity to acceleration of $1.4\times 10^{-8}$g at 1s. This result relies on the combination of a low phase noise laser system, efficient detection scheme and good shielding from vibrations. In particular, we describe a simple and robust technique of vibration compensation, which is based on correcting the interferometer signal by using the AC acceleration signal measured by a low noise seismometer.Comment: 30 pages, 14 figure

Bedforms and sedimentary structures related to supercritical flows in glacigenic settings

Upper-flow-regime bedforms, including upper-stage-plane beds, antidunes, chutes-and-pools and cyclic steps, are ubiquitous in glacigenic depositional environments characterized by abundant meltwater discharge and sediment supply. In this study, the depositional record of Froude near-critical and supercritical flows in glacigenic settings is reviewed, and similarities and differences between different depositional environments are discussed. Upper-flow-regime bedforms may occur in subglacial, subaerial and subaqueous environments, recording deposition by free-surface flows and submerged density flows. Although individual bedform types are generally not indicative of any specific depositional environment, some observed trends are similar to those documented in non-glacigenic settings. Important parameters for bedform evolution that differ between depositional environments include flow confinement, bed slope, aggradation rate and grain size. Cyclic-step deposits are more common in confined settings, like channels or incised valleys, or steep slopes of coarse-grained deltas. Antidune deposits prevail in unconfined settings and on more gentle slopes, like glacifluvial fans, sand-rich delta slopes or subaqueous (ice-contact) fans. At low aggradation rates, only the basal portions of bedforms are preserved, such as scour fills related to the hydraulic-jump zone of cyclic steps or antidune-wave breaking, which are common in glacifluvial systems and during glacial lake-outburst floods and (related) lake-level falls. Higher aggradation rates result in increased preservation potential, possibly leading to the preservation of complete bedforms. Such conditions are met in sediment-laden jökulhlaups and subaqueous proglacial environments characterized by expanding density flows. Coarser-grained sediment leads to steeper bedform profiles and highly scoured facies architectures, while finer-grained deposits display less steep bedform architectures. Such differences are in part related to stronger flows, faster settling of coarse clasts, and more rapid breaking of antidune waves or hydraulic-jump formation over hydraulically rough beds. © 2020 The Authors. Sedimentology published by John Wiley & Sons Ltd on behalf of International Association of Sedimentologist