Résolution de conflit dans le trafic aérien via l'algorithme de la propagation de la lumière

National audienceL'analyse de la croissance du trafic aérien prévoit un doublement du nombre de vols dans les vingt prochaines années. Le système de gestion du trafic aérien (ATM) devra augmenter en conséquence la capacité de l'espace aérien tout en assurant un niveau de sécurité au moins équivalent à ce qui existe actuellement. Le projet européen SESAR a été initié afin de proposer des solutions à ce problème. Il s'appuie sur un nouveau concept de contrôle du trafic, appelé trajectoire 4D, et qui consiste à garantir les positions des avions à un temps donné. Pour chaque vol, une trajectoire de référence, appelée RBT, est demandée par la compagnie opératrice. Au cours du vol, il peut apparaître des situations dites de conflit, dans lesquelles un rapprochement dangereux des aéronefs a lieu. Dans ce cas, il est nécessaire de modifier une ou plusieurs trajectoires afin de s'assurer que les normes de séparation minimales entre avions (actuellement 5 Nm en horizontal et de 1000 ft en vertical) soient respectées. Il est souhaitable de plus que les nouvelles trajectoires proposées soient aussi proches que possible des RBT. Il existe actuellement deux classes de méthodes permettant cette opération : les algorithmes génétiques [1] et les fonctions de navigation [2]. Chacune n'apporte qu'une réponse partielle au problème : les algorithmes génétiques permettent l'obtention de façon asymptotique de la solution optimale, mais ne garantissent pas l'obtention d'une solution admissible en un temps borné ; les fonctions de navigations quant à elles assurent l'absence de conflit mais génèrent des trajectoires qui ne sont pas forcément volables par un aéronef. L'objectif de la méthode que nous proposons, basée sur une analogie avec l'optique, est de trouver pour chaque avion une trajectoire optimale 4D évitant les conflits et minimisant un critère basé sur une métrique locale

Air traffic conflict resolution via light propagation modeling

The analysis of air traffic growth expects a doubling in the flights number over the next 20 years. The Air Traffic Management (ATM) will therefore have to absorb this additional burden and to increase the airspace capacity, while ensuring at least equivalent standards of safety. The European project SESAR was initiated to propose solutions to this problem. It relies on a new concept of air traffic control, known as 4D (3D + time) trajectory planning, which consists in exploiting the new Flight Management System (FMS) abilities that ensure that the aircraft is at a given position at a given moment. For each flight, a reference trajectory, called Reference Business Trajectory (RBT), is requested by the operating airline. During the flight, conflict situations may nevertheless occur, in which two or several aircraft can dangerously approach each other. In this case, it is necessary to modify one or more trajectories to ensure that minimum separation standards (currently 5 Nm horizontally and 1000 ft vertically) are still satisfied. Moreover, it is desirable that proposed new trajectories deviate as little as possible from RBTs. Several methods have been tested to find an optimal solution to address this problem including genetic algorithm[1] and navigation function based approach[2]. The first approach can not guarantee a feasible (conflict-free) solution for a given time computing. The second one does not take into account the constraints imposed by ATM, such as bounded velocity

Aircraft Trajectory Planning Under Uncertainty by Light Propagation

AbstractIn the SESAR framework (Single European Sky ATM Research), the need to increase the air traffic capacity motivated the 4D (space + time) aircraft trajectory planning. This paper deals with an important Air Traffic Management (ATM) problem that consists in generating sets of 4D conflict-free trajectories (the tactical planning problem). The Light Propagation Algorithm (LPA) was introduced in [1] to deal with this problem. LPA has recently been shown to manage successfully a full day of traffic over the French airspace, removing all conflicts while satisfying ATM constraints.In this paper, we adapt the LPA to take into account uncertainties in trajectory prediction. We introduce and test a new algorithm called u/LPA (LPA under uncertainty) on the same day of traffic. For some situations, uncertainties reduce so much the search space that the standard algorithm cannot guarantee conflict free situation. As a consequence, one must include some time constraints for few trajectories (so-called RTA points: Real Time of Arrival constraints) in order to remove the remaining conflicts. The goal of RTA points is to impose an aircraft to be at a specified position at some given time. This results into a new optimization formulation of the tactical trajectory planning problem involving the decision as to where/when RTA points should be imposed. In order to solve this new problem, here we are content with a simple heuristic that yields encouraging results

Comparison of four DNA extraction and three preservation protocols for the molecular detection and quantification of soil-transmitted helminths in stool

Background : A DNA extraction and preservation protocol that yields sufficient and qualitative DNA is pivotal for the success of any nucleic acid amplification test (NAAT), but it still poses a challenge for soil-transmitted helminths (STHs), including Ascaris lumbricoides, Trichuris trichiura and the two hookworms (Necator americanus and Ancylostoma duodenale). In the present study, we assessed the impact of different DNA extraction and preservativation protocols on STH-specific DNA amplification from stool. Methodology and principal findings : In a first experiment, DNA was extracted from 37 stool samples with variable egg counts for T. trichiura and N. americanus applying two commercial kits, both with and without a prior bead beating step. The DNA concentration of T. trichiura and N. americanus was estimated by means of qPCR. The results showed clear differences in DNA concentration across both DNA extraction kits, which varied across both STHs. They also indicated that adding a bead beating step substantially improved DNA recovery, particularly when the FECs were high. In a second experiment, 20 stool samples with variable egg counts for A. lumbricoides, T. trichiura and N. americanus were preserved in either 96% ethanol, 5% potassium dichromate or RNA later and were stored at 4 degrees C for 65, 245 and 425 days. DNA was extracted using the DNeasy Blood & Tissue kit with a bead beating step. Stool samples preserved in ethanol proved to yield higher DNA concentrations as FEC increased, although stool samples appeared to be stable over time in all preservatives. Conclusions : The choice of DNA extraction kit significantly affects the outcome of NAATs. Given the clear benefit of bead beating and our validation of ethanol for (long-term) preservation, we recommend that these aspects of the protocol should be adopted by any stool sampling and DNA extraction protocol for downstream NAAT-based detection and quantification of STHs

Trajectories through semantic spaces in schizophrenia and the relationship to ripple bursts

Human cognition is underpinned by structured internal representations that encode relationships between entities in the world (cognitive maps). Clinical features of schizophrenia-from thought disorder to delusions-are proposed to reflect disorganization in such conceptual representations. Schizophrenia is also linked to abnormalities in neural processes that support cognitive map representations, including hippocampal replay and high-frequency ripple oscillations. Here, we report a computational assay of semantically guided conceptual sampling and exploit this to test a hypothesis that people with schizophrenia (PScz) exhibit abnormalities in semantically guided cognition that relate to hippocampal replay and ripples. Fifty-two participants [26 PScz (13 unmedicated) and 26 age-, gender-, and intelligence quotient (IQ)-matched nonclinical controls] completed a category- and letter-verbal fluency task, followed by a magnetoencephalography (MEG) scan involving a separate sequence-learning task. We used a pretrained word embedding model of semantic similarity, coupled to a computational model of word selection, to quantify the degree to which each participant's verbal behavior was guided by semantic similarity. Using MEG, we indexed neural replay and ripple power in a post-task rest session. Across all participants, word selection was strongly influenced by semantic similarity. The strength of this influence showed sensitivity to task demands (category > letter fluency) and predicted performance. In line with our hypothesis, the influence of semantic similarity on behavior was reduced in schizophrenia relative to controls, predicted negative psychotic symptoms, and correlated with an MEG signature of hippocampal ripple power (but not replay). The findings bridge a gap between phenomenological and neurocomputational accounts of schizophrenia

Melatonin as a new postharvest treatment for increasing cut carnation (Dianthus caryophyllus L.) vase life

The marketability of cut flowers is directly affected by their vase life, which determines acceptability for commercial purposes. In carnations and other species of cut flowers, corolla is one of the most affected parts during flower senescence due to the petal withering which is accelerated by metabolic processes occurring after separation from the mother plant. Melatonin (MT) is a compound with antioxidant properties, naturally present in plant tissues that plays important roles in the regulation of different metabolic processes. In this research work the effect of different MT concentrations (0.01, 0.1 and 1 mM) on the vase life of cut carnations flowers cv. Baltico was evaluated. The greatest delay in senescence was observed with 0.1 mM MT concentration, increasing vase life up to 10 days more as compared to control carnations. Although all MT concentrations assayed significantly (P < 0.05) maintained initial levels of fresh weight, membrane stability index, bioactive compounds and antioxidant activity for longer time, the lowest concentrations were those that had the most relevant impact on vase life. The highest dose evaluated (1 mM) maintained all the parameters evaluated but showed the wilting symptoms earlier. For this reason, 0.1 MT concentration could be a tool capable of improving carnation vase life for longer time, increasing the commercial potential of this cut flower

Oliguria on the Day of Intubation Is Associated With Mortality in Patients With Acute Respiratory Distress Syndrome

To investigate the relationship between oliguric acute kidney injury (AKI) and mortality in patients with acute respiratory distress syndrome (ARDS). DESIGN: Retrospective cohort study. SETTING: This investigation took place at a single-center, tertiary referral multidisciplinary comprehensive healthcare hospital in metropolitan Detroit, Michigan. PATIENTS: Adult patients 18 years old or older hospitalized in the ICU and diagnosed with ARDS on mechanical ventilation. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Three hundred eight patients were included in the final analysis. Risk factors associated with mortality included advanced age (p \u3c 0.001), increased body mass index (p = 0.008), and a history of chronic kidney disease (p = 0.023). Presence of AKI by day 1 of intubation, with elevated creatinine (p = 0.003) and oliguria (p \u3c 0.001), was significantly associated with mortality. On multivariate analysis, advanced age (relative risk [RR], 1.02), urine output on the day of intubation (RR, 0.388), bicarbonate level (RR, 0.948), and Sequential Organ Failure Assessment severity score (RR, 1.09) were independently associated with mortality. A receiver operating characteristic curve identified a threshold urine output on the day of intubation of 0.7 mL/kg/hr (area under the curve, 0.75; p \u3c 0.001) as most closely associated with inpatient mortality (i.e., urine output \u3c 0.7 mL/kg/hr is associated with mortality). CONCLUSIONS: For patients with ARDS, oliguria on the day of intubation was independently associated with increased mortality. Urine output of less than 0.7 mL/kg/hr predicted 80% of inpatient deaths. These findings herald an augmented understanding of the role of urine output in medical decision-making and prognostication

The impact of Muslim and Christian religious leaders responding to COVID-19 in Israel

BackgroundThe COVID-19 pandemic is one of the most significant public health emergencies in decades and has affected all countries worldwide. Religious leaders have been recognized as playing a pivotal role in health promotion during times of crisis. This study explored the role that Muslim and Christian religious leaders played in Israel during the pandemic, and the impact that their activities had on the community.MethodsA qualitative study involving semi-structured interviews was conducted with Muslim and Christian religious leaders and health policy makers from the Arab community. Intensive purposeful sampling was used to locate the two target audiences. Interview protocols were developed and included questions about the role they played during the pandemic, challenges they faced, and dialogue and partnerships they had. Interviews were audio-recorded, transcribed, and analyzed using thematic content analysis.ResultsTen Muslim Sheikhs, three Christian clergy, and four health policy makers were interviewed. Religious leaders played a predominant role in promoting health during the COVID-19 crisis. Both religious leaders and health policy makers reported similar challenges including dealing with fake news and the conspiracy theory, social events and gatherings, frustrations about gaps in policy toward religious institutions, and lack of trust toward State. Health policy makers recognized the key role religious leaders played and emphasized the importance of engaging religious leaders.ConclusionThe COVID-19 pandemic has been a catalyst for partnership between health policy makers and religious leaders. Religious leaders should play an integral and integrated role in promoting health during future health crises, not only in implementation of guidelines but also in development of policy so that the guidelines are tailored and sensitive to specific communities to avoid conflicts. As trusted authorities, religious leaders serve as a bridge between health authorities and communities and can be mediators who reconcile science, policy and religious perspectives. The routine cooperation between decision makers, opinion leaders, and religious leaders as social gatekeepers can increase the public's level of trust in the system

Surface characterization and in vivo evaluation of laser sintered and machined implants followed by resorbable-blasting media process: a study in sheep

Background: This study aimed to compare the histomorphometric and histological bone response to laser-sintered implants followed by resorbable-blasting media (RBM) process relative to standard machined/RBM surface treated implants. Material and Methods: Six male sheep (n=6) received 2 Ti-6Al-4V implants (1 per surface) in each side of the mandible for 6 weeks in vivo. The histomorphometric parameters bone-implant contact (BIC) and bone area fraction occupancy (BAFO) were evaluated. Results: Optical interferometry revealed higher Sa and Sq values for the laser-sintered/RBM surface in relation to standard/RBM implants. No significant differences in BIC were observed between the two groups (p>0.2), but significantly higher BAFO was observed for standard/RBM implants (p<0.01). Conclusions: The present study demonstrated that both surfaces were biocompatible and osseoconductive, and the combination of laser sintering and RBM has no advantage over the standard machined implants with subsequent RBM

Mechanical Thrombectomy for Acute Ischemic Stroke in Metastatic Cancer Patients: A Nationwide Cross-Sectional Analysis

BACKGROUND AND PURPOSE: Mechanical thrombectomy (MT) is the standard treatment for large vessel occlusion (LVO) acute ischemic stroke. Patients with active malignancy have an increased risk of stroke but were excluded from MT trials. METHODS: We searched the National Readmission Database for LVO patients treated with MT between 2016-2018 and compared the characteristics and outcomes of cancer-free patients to those with metastatic cancer (MC). Primary outcomes were all-cause in-hospital mortality and favorable outcome, defined as a routine discharge to home (regardless of whether home services were provided or not). Multivariate regression was used to adjust for confounders. RESULTS: Of 40,537 LVO patients treated with MT, 933 (2.3%) had MC diagnosis. Compared to cancer-free patients, MC patients were similar in age and stroke severity but had greater overall disease severity. Hospital complications that occurred more frequently in MC included pneumonia, sepsis, acute coronary syndrome, deep vein thrombosis, and pulmonary embolism (P\u3c0.001). Patients with MC had similar rates of intracerebral hemorrhage (20% vs. 21%) but were less likely to receive tissue plasminogen activator (13% vs. 23%, P\u3c0.001). In unadjusted analysis, MC patients as compared to cancer-free patients had a higher in-hospital mortality rate and were less likely to be discharged to home (36% vs. 42%, P=0.014). On multivariate regression adjusting for confounders, mortality was the only outcome that was significantly higher in the MC group than in the cancerfree group (P\u3c0.001). CONCLUSION: LVO patients with MC have higher mortality and more infectious and thrombotic complications than cancer-free patients. MT nonetheless can result in survival with good outcome in slightly over one-third of patients