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

Effect of surgical experience and spine subspecialty on the reliability of the {AO} Spine Upper Cervical Injury Classification System

OBJECTIVE The objective of this paper was to determine the interobserver reliability and intraobserver reproducibility of the AO Spine Upper Cervical Injury Classification System based on surgeon experience (< 5 years, 5–10 years, 10–20 years, and > 20 years) and surgical subspecialty (orthopedic spine surgery, neurosurgery, and "other" surgery). METHODS A total of 11,601 assessments of upper cervical spine injuries were evaluated based on the AO Spine Upper Cervical Injury Classification System. Reliability and reproducibility scores were obtained twice, with a 3-week time interval. Descriptive statistics were utilized to examine the percentage of accurately classified injuries, and Pearson’s chi-square or Fisher’s exact test was used to screen for potentially relevant differences between study participants. Kappa coefficients (κ) determined the interobserver reliability and intraobserver reproducibility. RESULTS The intraobserver reproducibility was substantial for surgeon experience level (< 5 years: 0.74 vs 5–10 years: 0.69 vs 10–20 years: 0.69 vs > 20 years: 0.70) and surgical subspecialty (orthopedic spine: 0.71 vs neurosurgery: 0.69 vs other: 0.68). Furthermore, the interobserver reliability was substantial for all surgical experience groups on assessment 1 (< 5 years: 0.67 vs 5–10 years: 0.62 vs 10–20 years: 0.61 vs > 20 years: 0.62), and only surgeons with > 20 years of experience did not have substantial reliability on assessment 2 (< 5 years: 0.62 vs 5–10 years: 0.61 vs 10–20 years: 0.61 vs > 20 years: 0.59). Orthopedic spine surgeons and neurosurgeons had substantial intraobserver reproducibility on both assessment 1 (0.64 vs 0.63) and assessment 2 (0.62 vs 0.63), while other surgeons had moderate reliability on assessment 1 (0.43) and fair reliability on assessment 2 (0.36). CONCLUSIONS The international reliability and reproducibility scores for the AO Spine Upper Cervical Injury Classification System demonstrated substantial intraobserver reproducibility and interobserver reliability regardless of surgical experience and spine subspecialty. These results support the global application of this classification system

Traumatic Fractures of the Thoracic Spine: Narrative Literature Review

The majority of traumatic vertebral fractures occur at the thoracolumbar junction and the lumbar spine and less commonly at the mid-thoracic and upper thoracic spine. In accordance, a high number of articles are dealing with thoracolumbar fractures focusing on the thoracolumbar junction. Nonetheless, the biomechanics of the thoracic spine differ from the thoracolumbar junction and the lumbar vertebral spine. The aim of this review is to screen the literature dealing with acute traumatic thoracic vertebral fractures in patients with normal bone quality. Thereby, the diagnostic of thoracic vertebral body fractures should include a CT examination. Ideally, the CT should include the whole thoracic cage particularly in patients suffering high energy accidents or in those with clinical suspicion of concomitant thoracic injuries. Generally, concomitant thoracic injuries are frequently seen in patients with thoracic spine fractures. Particularly sternal fractures cause an increase in fracture instability. In case of doubt, long segment stabilization is recommended in patients with unstable mid- und upper thoracic fractures, particularly in those patients with a high grade of instability. Zusammenfassung Die meisten Publikationen, die sich mit nicht zervikalen Wirbelkorperfrakturen befassen, schlie ss en die gesamte thorakolumbale Wirbelsaule ein und erfassen dabei hauptsachlich Frakturen des thorakolumbalen ubergangs und der Lendenwirbelsaule, sodass Frakturen der mittleren und oberen Brustwirbelsaule unterprasentiert sind. Dagegen unterscheidet sich die Biomechanik der Brustwirbelsaule erheblich von der des thorakolumbalen ubergangs und der Lendenwirbelsaule. Dieses Review befasst sich mit der Literatur, die sich isoliert mit traumatischen Frakturen der Brustwirbelsaule beschaftigt. Dabei zeigt sich, dass die Diagnostik eine CT einschlie ss lich der umgebenden Strukturen beinhalten sollte, da Begleitverletzungen am Thorax sehr haufig sind. Insbesondere zusatzliche Sternumfrakturen erhohen den Grad der Instabilitat. Der Goldstandard der Versorgung sollte insbesondere bei Frakturen mit hohem Grad an Instabilitat die langstreckige dorsale Stabilisierung sein

OF-Pelvis classification of osteoporotic sacral and pelvic ring fractures

Objectives Osteoporotic fractures of the pelvis (OFP) are an increasing issue in orthopedics. Current classification systems (CS) are mostly CT-based and complex and offer only moderate to substantial inter-rater reliability (interRR) and intra-rater reliability (intraRR). MRI is thus gaining importance as a complement. This study aimed to develop a simple and reliable CT- and MRI-based CS for OFP. Methods A structured iterative procedure was conducted to reach a consensus among German-speaking spinal and pelvic trauma experts over 5 years. As a result, the proposed OF-Pelvis CS was developed. To assess its reliability, 28 experienced trauma and orthopedic surgeons categorized 25 anonymized cases using X-ray, CT, and MRI scans twice via online surveys. A period of 4 weeks separated the completion of the first from the second survey, and the cases were presented in an altered order. While 13 of the raters were also involved in developing the CS (developing raters (DR)), 15 user raters (UR) were not deeply involved in the development process. To assess the interRR of the OF-Pelvis categories, Fleiss' kappa (kappa(F)) was calculated for each survey. The intraRR for both surveys was calculated for each rater using Kendall's tau (tau(K)). The presence of a modifier was calculated with kappa(F) for interRR and Cohen's kappa (kappa(C)) for intraRR. Results The OF-Pelvis consists of five subgroups and three modifiers. Instability increases from subgroups 1 (OF1) to 5 (OF5) and by a given modifier. The three modifiers can be assigned alone or in combination. In both surveys, the interRR for subgroups was substantial: kappa(F) = 0.764 (Survey 1) and kappa(F) = 0.790 (Survey 2). The interRR of the DR and UR was nearly on par (kappa(F) Survey 1/Survey 2: DR 0.776/0.813; UR 0.748/0.766). The agreement for each of the five subgroups was also strong (kappa(F) min.-max. Survey 1/Survey 2: 0.708-0.827/0.747-0.852). The existence of at least one modifier was rated with substantial agreement (kappa(F) Survey 1/Survey 2: 0.646/0.629). The intraRR for subgroups showed almost perfect agreement (tau(K) = 0.894, DR: tau(K) = 0.901, UR: tau(K) = 0.889). The modifier had an intraRR of kappa(C) = 0.684 (DR: kappa(C) = 0.723, UR: kappa(C) = 0.651), which is also considered substantial. Conclusion The OF-Pelvis is a reliable tool to categorize OFP with substantial interRR and almost perfect intraRR. The similar reliabilities between experienced DRs and URs demonstrate that the training status of the user is not important. However, it may be a reliable basis for an indication of the treatment score

The Brazilian time and frequency atomic standards program

Cesium atomic beam clocks have been the workhorse for many demanding applications in science and technology for the past four decades. Tests of the fundamental laws of physics and the search for minute changes in fundamental constants, the synchronization of telecommunication networks, and realization of the satellite-based global positioning system would not be possible without atomic clocks. The adoption of optical cooling and trapping techniques, has produced a major advance in atomic clock precision. Cold-atom fountain and compact cold-atom clocks have also been developed. Measurement precision of a few parts in 10(15) has been demonstrated for a cold-atom fountain clock. We present here an overview of the time and frequency metrology program based on cesium atoms under development at USP São Carlos. This activity consists of construction and characterization of atomic-beam, and several variations of cold-atom clocks. We discuss the basic working principles, construction, evaluation, and important applications of atomic clocks in the Brazilian program.<br>Relógios atômicos de feixe de Césio têm sido a base para diversas aplicações em ciência e tecnologia nas últimas quatro décadas. Testes de leis fundamentais de física, buscas por mínimas variações em constantes fundamentais, sincronização de redes de telecomunicações e o funcionamento do sistema de posicionamento global, baseado em satélites de navegação, não seriam possíveis sem os relógios atômicos. A adoção de técnicas de aprisionamento e resfriamento ópticos tem permitido um grande avanço na precisão dos relógios atômicos. Chafarizes de átomos frios e relógios compactos de átomos frios também têm sido desenvolvidos. Precisões de medida de algumas partes em 1015 foram demonstradas para relógios do tipo chafariz de átomos frios. Apresentamos uma visão geral do programa de metrologia de tempo e freqüência baseado em átomos de césio, em desenvolvimento na USP de São Carlos. Estas atividades consistem na construção e caracterização de relógios do tipo feixe atômico e de outros, utilizando átomos frios. Discutimos os princípios básicos, construção, avaliação e importantes aplicações de relógios atômicos no programa brasileiro

Preliminary investigation of a general learning system

SHIP2 is a phosphatase that acts at the 5-position of phosphatidylinositol 3,4,5-trisphosphate. It is one of several enzymes that catalyse dephosphorylation at the 5-position of phosphoinositides or inositol phosphates. SHIP2 has a confirmed role in opsismodysplasia, a disease of bone development, but also interacts with proteins involved in insulin signalling, cytoskeletal function (thus having an impact on endocytosis, adhesion, proliferation and apoptosis) and immune system function. The structure of three domains (constituting about 38% of the protein) is known. Inhibitors of SHIP2 activity have been designed to interact with the catalytic domain with sub-micromolar IC50 values: these come from a range of structural classes and have been shown to have in vivo effects consistent with SHIP2 inhibition. Much remains unknown about the roles of SHIP2 and possible future directions for research are indicated