A coherent optical link through the turbulent atmosphere

We describe the realization of a 5 km free space coherent optical link through the turbulent atmosphere between a telescope and a ground target. We present the phase noise of the link, limited mainly by atmospheric turbulence and mechanical vibrations of the telescope and the target. We discuss the implications of our results for applications, with particular emphasis on optical Doppler ranging to satellites and long distance frequency transfer.Comment: version 2, modified following comments from colleagues and reviewer

Study of the slant fracture in solid and hollow cylinders: Experimental analysis and numerical prediction

This paper is devoted to the numerical and experimental study of ductile fracture in bulk metal forming of the 2017A-T4 aluminum alloy. From an experimental standpoint, the ductile fracture of the2017A-T4aluminum alloy is investigated under compressive load. Two cross-sections of solid and hollow specimens are considered. The mechanical behavior and the microstructure of the 2017A-T4 aluminum alloy were characterized. It is found that the well-known barrel shape is obtained when a compressive load is applied. Analyses of fracture topographies show a ductile fracture with dimples under tension and coexistence of ductile fracture with dimples and slant under compression. The classical physically-based Gurson-Tvergaard-Needleman (GTN) model and its extension to incorporateshear mechanisms to predict failure at low-stress triaxiality are considered. These two models have been extended to take into account the thermal heating effect induced by the mechanical dissipation within the material during the metal forming process. The two models have been implemented into the finite element code Abaqus/Explicit using a Vectorized User MATerial (VUMAT) subroutine. Numerical simulations of the forging process made for hollow and solid cylindrical specimens show good agreement with experimental results. In contrast with the GTN model, the modified GTN model incorporating shear mechanisms can capture the final material failure

Observational Constraints and Cosmological Implications of Scalar-Tensor f(R,T)f(R, T) Gravity

Recently, the scalar-tensor representation of $f (R,T)$ gravity was used to explore gravitationally induced particle production/annihilation. Using the framework of irreversible thermodynamics of open systems in the presence of matter creation/annihilation, the physical and cosmological consequences of this setup were investigated in detail. In this paper, we test observationally the scalar-tensor representation of $f(R,T)$ gravity in the context of the aforementioned framework, using the Hubble and Pantheon+ measurements. The best fit parameters are obtained by solving numerically the modified Friedmann equations of two distinct cosmological models in scalar tensor $f(R, T)$ gravity, corresponding to two different choices of the potential, and by performing a Markov Chain Monte Carlo analysis. The best parameters are used to compute the cosmographic parameters, i.e., the deceleration, the jerk and the snap parameters. Using the output resulting from the Markov Chain Monte Carlo analysis, the cosmological evolution of the creation pressure and of the matter creation rates are presented for both models. To figure out the statistical significance of the studied scalar-tensor $f(R,T)$ gravity, the Bayesian and the corrected Akaike information criteria are used. The latter indicates that the first considered model in scalar tensor $f(R,T)$ gravity is statistically better than $\Lambda$CDM, i.e., it is more favored by observations. Besides, a continuous particle creation process is present in Model 1. On the other hand, for large redshifts, in Model 2 the particle creation rate may become negative, thus indicating the presence of particle annihilation processes. However, both models lead to an accelerating expansion of the Universe at late times, with a deceleration parameter equivalent to that of the $\Lambda$CDM model.Comment: 17 pages, 14 figures; accepted for publication in MNRA

Mechanical behavior and optimization of multidirectional laminate specimens under delamination by bending

Delamination in the multidirectional laminates under bending loading is often difficult to characterize because of problems involved by excessive deformations ahead of the crack tip and by non-linearities due to large displacements and transverse microcracking. In fact, these microcracks appear in the most strained plies especially for thin materials. Consequently, the concept of linear elastic fracture mechanic cannot be used in order to characterize delamination. Thus, the objective of this work is to highlight, experimentally and analytically these problems on DCB specimens, then to carry out optimization of thickness which makes it possible to avoid the appearance of transverse cracking before starting of delamination. The material used is E-glass/epoxy multidirectional laminates. The results of optimization obtained are in good agreement with the experimental results.При навантаженні згином багатовимірних ламінатів має місце деламінація. Її опис є досить важким, оскільки у вістрі тріщини присутні великі деформації та відмічаються нелінійні ефекти, що зумовлені значними переміщеннями і утворенням поперечних мікротріщин. Останні з’являються у найбільш навантажених шарах, особливо в тонких ламінатах. Експериментально досліджено вищезгадані особливості на зразках у вигляді консольної балки та виконано оптимізацію товщини багатошарового зразка, за якої деламінація починаєтьсядо утворення поперечних мікротріщин у найбільш навантажених шарах. Об’єктом дослідження служив склоепоксидний зміцнений ламінат. Отримані результати оптимізації товщини зразка добре узгоджуються з експериментальними даними.При изгибном нагружении многомерных ламинатов имеет место деламинация, описание которой весьма затруднительно ввиду наличия больших деформаций у вершины трещины и различных нелинейных эффектов, связанных со значительными перемещениями и образованием поперечных микротрещин. Последние появляются в наиболее нагруженных слоях, особенно в тонких ламинатах. Экспериментально исследованы вышеуказанные особенности на образцах в виде консольной балки и выполнена оптимизация толщины многослойного образца, при которой деламинация начинается до образования поперечных микротрещин в наиболее нагруженных слоях. Объектом исследования служил стеклоэпоксидный упрочненный ламинат. Полученные результаты оптимизации толщины образцов хорошо согласуются с экспериментальными данными

Tuberculose ostéoarticulaire (mal de Pott exclu) : à propos de 120 cas à Abidjan

Introduction: La tuberculose ostéoarticulaire (TOA) représente 2 à 5 % de l'ensemble des tuberculoses .Elle demeure d'actualité surtout dans les pays à forte endémicité tuberculeuse. L'objectif était de déterminer la prévalence, les aspects topographiques, radiologiques de la TOA en milieu hospitalier ivoirien. Méthodes: Les auteurs rapportent une expérience de 11 ans, à travers une étude rétrospective de 120 dossiers de patientsatteints de la tuberculose ostéoarticulaire (le mal de Pott est exclu de cette étude).N'ont pas été inclus dans l'étude les dossiers ne comportant pas d'imagerie. Résultats: L'atteinte extra vertébrale représentait 09,2% de la tuberculose ostéoarticulaire. Il s'agissait de 54 hommes et 66 femmes, l'âge moyen était de 43,13 ans. On notait 123 cas d'ostéoarthrites, et 8 cas d'ostéites des os plats. L'atteinte des membres inférieurs prédominait dans 91,87% des cas. La hanche était la première localisation (45,04%), suivie du genou (25,19%). Les atteintes étaient multifocales dans 20% des cas. L'atteinte osseuse était associée à une tuberculose pulmonaire dans 05,83% des cas. Des localisations inhabituelles ont été rapportées : poignet (n=2), branches ischiopubiennes (n=4), atteinte sternoclaviculaire (n=4), médiopieds (n=2). Les lésions radiologiques étaient avancées (stades III et IV) dans 55,73% des cas. A la TDM, la prévalence des abcès était de 77%. Un geste chirurgical a été réalisé sur 16 articulations (2 épaules, 13 genoux, une cheville). Conclusion: La TOA des membres est peu fréquente contrairement à l'atteinte vertébrale. La hanche est la principale localisation. Le retard au diagnostic explique l'étendue des lésions anatomoradiologiques

Prevalence of Mood Disorders and Associated Factors at the Time of the COVID-19 Pandemic: Potocol for a Community Survey in La Manouba Governorate, Tunisia

Aims: The present survey aims to assess the overall mood disorder prevalence and identify associated socio-demographic and clinical factors in a Tunisian community sample, with special attention to the COVID-19 pandemic. Background: Mood disorders are one of the leading causes of all non-fatal burdens of disease, with depression being at the top of the list. The COVID-19 pandemic may have increased the prevalence of mood disorders, especially in Low and Middle-income countries (LMICs) and in vulnerable populations. Objective: 1/ Assess point and lifetime prevalence of depressive and bipolar disorders as well as subthreshold bipolarity in a representative population sample of La Manouba governorate and assess treatment patterns for these disorders; 2/Study socio-demographic and clinical correlates of mood disorders 3/ Assess the association between mood disorders and quality of life 4/ Study the impact of the COVID-pandemic on the prevalence of mood disorders 5/ Assess coping mechanisms to the COVID-pandemic and whether these mechanisms moderate the appearance of mood disorders or symptoms since the beginning of the pandemic Methods: This is a household cross-sectional observational survey to be conducted in La Manouba Governorate in a sample of 4540 randomly selected individuals aged ≥ 15 years. Data collection will be carried out by trained interviewers with clinical experience, through face-to-face interviews and the use of the computer assisted personal interviewing approach (CAPI). The following assessment tools are administered: Results: Structured clinical Interview for DSM IV-TR (Mood disorder section and Screening questions on Anxiety), Mood Disorder Questionnaire (MDQ), Suicide Behaviors Questionnaire-Revised (SBQ), 12-item Short Form Survey (SF-12), the Brief-COPE, and a questionnaire about a headache. In addition, socio-demographic and clinical data will be collected. Conclusion: This will be one of the very few household surveys in a general population sample to assess mental health problems and COVID-19-related variables since the beginning of the pandemic. Through this research, we aim to obtain an epidemiological profile of mood disorders in Tunisia and an estimation of the impact of the COVID-19 pandemic on their prevalence. Results should contribute to improving mental health care in Tunisia

Kinetics of fragmentation-annihilation processes

We investigate the kinetics of systems in which particles of one species undergo binary fragmentation and pair annihilation. In the latter, nonlinear process, fragments react at collision to produce an inert species, causing loss of mass. We analyse these systems in the reaction-limited regime by solving a continuous model within the mean-field approximation. The rate of fragmentation, for a particle of mass $x$ to break into fragments of masses $y$ and $x-y$, has the form $x^{\lambda-1}$ ($\lambda>0$), and the annihilation rate is constant and independent of the masses of the reactants. We find that the asymptotic regime is characterized by the annihilation of small-mass clusters. The results are compared with those for a model with linear mass-loss (i.e.\ with a sink). We also study more complex models, in which the processes of fragmentation and annihilation are controlled by mutually-reacting catalysts. Both pair- and linear-annihilation are considered. Depending on the specific model and initial densities of the catalysts, the time-decay of the cluster-density can now be very unconventional and even non-universal. The interplay between the intervening processes and the existence of a scaling regime are determined by the asymptotic behaviour of the average-mass and of the mass-density, which may either decay indefinitely or tend to a constant value. We discuss further developments of this class of models and their potential applications.Comment: 16 pages(LaTeX), submitted to Phys. Rev.