Dynamic Retransmission Limit Scheme in MAC Layer for Routing in Multihop Ad hoc Networks

We consider a wireless ad hoc network with random access channel. We present a model that takes into account topology, routing, random access in MAC layer, and forwarding probability. In this paper, we focus on drawing benefit from the interaction of the MAC (governed by IEEE 802.11 or slotted Aloha) and routing by defining a new cross-layer scheme for routing based on the limit number of retransmission. By adjusting dynamically and judiciously this parameter in a saturated network, we have realized that both stability of forwarding queues and average throughput are significantly improved in linear networks with symmetric traffic: a gain of 100% can be reached. While in asymmetric topology network with asymmetric traffic, we achieve a better average delay (resp., throughput) for each connection without changing the average throughput (resp., delay). In addition, we show the efficiency of our new scheme in case of multimedia applications with delay constraint. A detailed performance study is presented using analytical and simulation evaluation

Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition)

In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. For example, a key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process versus those that measure fl ux through the autophagy pathway (i.e., the complete process including the amount and rate of cargo sequestered and degraded). In particular, a block in macroautophagy that results in autophagosome accumulation must be differentiated from stimuli that increase autophagic activity, defi ned as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (inmost higher eukaryotes and some protists such as Dictyostelium ) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the fi eld understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. It is worth emphasizing here that lysosomal digestion is a stage of autophagy and evaluating its competence is a crucial part of the evaluation of autophagic flux, or complete autophagy. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. Along these lines, because of the potential for pleiotropic effects due to blocking autophagy through genetic manipulation it is imperative to delete or knock down more than one autophagy-related gene. In addition, some individual Atg proteins, or groups of proteins, are involved in other cellular pathways so not all Atg proteins can be used as a specific marker for an autophagic process. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field

Evaluation des performances dans les réseaux ad hoc sans fils

Dans cette thèse, nous nous focalisons sur la caractérisation des performances des réseaux ad hoc à accès aléatoire au canal en utilisant des paramètres de plusieurs couches avec aptitude de transfert d'information. Les métriques de performances qui nous intéressent sont la stabilité des files d'attentes de transfert, le débit, le délai et la consommation d'énergie. Principalement, la compréhension de l'interaction entre les couches MAC/PHY et routage, d'une part, et l'interaction des noeuds entre eux pour cause d'interférences, d'autre part, constituent le centre de notre travail. Cette thèse est divisée en deux parties. Dans la première partie, nous proposons et évaluons un nouveau protocole de routage entre-couche prenant en compte la consommation d'énergie dans le protocole OLSR. Nos simulations sont importantes pour la compréhension du réel impact des couches MAC/PHY non idéales sur le routage. Les résultats montrent que les approches de routages qui ne prennent pas en compte les effets des basses couches doivent être révisées.Dans la deuxièmement partie, nous avons basé notre étude sur un modèle analytique qui prend en compte la topologie, le routage, l'accès aléatoire dans la couche MAC et une probabilité de transfert. Nous distinguons trois propriétés clés du réseau qui font que notre contribution dans cette thèse est nouvelle si elles sont considérées ensemble. La première est l'ordonnancement des paquets dans la couche réseau. En utilisant un ordonnancement WFQ (Weighted fair queueing), nous avons principalement étudié l'impact de la coopération et la région de stabilité dans le réseau. Cette dernière est aussi caractérisée dans le cas d'un réseau hybride, où un réseau ad hoc est interconnecté avec un autre cellulaire. La deuxième est l'asymétrie du réseau ad hoc en termes de topologie, trafic et paramètres des noeuds. Cependant, une étude sur un réseau à une seule dimension est aussi réalisée. En développant le modèle du réseau, nous sommes arrivés à un modèle analytique avec le IEEE 802.11e DCF dans le contexte d'un réseau ad hoc multi-sauts. Le taux d'accès au canal et la probabilité de collision sont maintenant exprimés en fonction de l'intensité du trafic, de la topologie, et du routage. La troisième est le nombre limite de retransmissions dans la couche MAC dédié pour chaque connexion. D'une part, ce dernier est responsable de l'asymétrie du taux de service des files d'attentes et de la distribution générale du temps de service. D'autre part, il a un impact direct sur les performances d'un réseau chargé. Nous avons pu bénéficier de l'interaction de la couche MAC et routage en définissant un nouveau mécanisme entre-couche basé sur le nombre limite de retransmissions. Des résultats numériques et des simulations sont présents pour assister et confirmer notre travailThis thesis focuses on the characterization of random access ad hoc networks performance using multi-layer parameters and forwarding capability. The performance metrics of interest are stability of forwarding queues, throughput, delay and energy consumption. Mainly, the comprehension of the interactions between the MAC/PHY layers and the network layer, on the one hand, and the interactions among all nodes due to interferences, on the other hand, are in the center of this thesis. This dissertation is divided in two parts. In the first part, we propose and evaluate a new cross-layer energy power-aware routing protocol. Our simulations were important to understand the real impact of a non-ideal MAC/PHY layers on routing. The results show that routing approaches that do not account for lower layers impact have to be revised. In the second part, we based our study on an analytical model that takes into account topology, routing, random access in MAC layer and forwarding probability. We distinguish three key features of the network model that make our contribution in this thesis novel when considered together. The first one is packet scheduling in the network layer. Using a weighted fair queueing, we mainly studied the cooperation effect and the stability region in the network. This latter was also characterized in an hybrid network when interconnecting ad hoc and cellular networks. The second one is the asymmetry of the ad hoc network in terms of topology, traffic and nodes' parameters. Nevertheless, one dimensional study is also presented. By developing the network model, we reached a new analytical modeling of the IEEE 802.11e DCF in the context of multi-hop ad hoc networks. The attempt rate and collision probability are now function of the traffic intensity, on topology and on routing decision. The third one is the finite limit number of retransmissions in MAC layer dedicated to each connection. On the one hand, this latter is responsible for asymmetric queue service rate and for getting a general service time distribution. On the other hand, it has a direct impact on the performance of a loaded network. Finally, we got benefit from the interaction of the MAC and routing by defining a new cross-layer scheme for routing based on the limit number of retransmissions. Numerical results and simulations are presented to assist and confirm our workAVIGNON-BU Centrale (840072102) / SudocSudocFranceF

Energy Power-Aware Routing in OLSR Protocol

International audienceIn ad hoc networks, where there is no infrastructure, batteries lifetime are scare resource. However, many routing protocols in ad hoc networks have been proposed to provide and maintain routes without taking into account energy consumption. Recently, power control in mobile ad-hoc networks has been the focus of extensive research. In this paper, we propose a new scheme to make energy aware routing in OLSR (optimized link state routing protocol). OLSR is one of the routing protocols under study by the IETF MANET Working Group. We develop a new heuristic that allow OLSR to find an optimal power path in which the maximum energy consumption on that path is smaller among the maximum energy consumption of all possible paths. We discuss via simulation the interplay between routing in new OLSR protocol and the medium access control (MAC). Also we study the overhearing impact on the energy power-aware routing protocol. Simulation results show that our scheme improves classical OLSR routing while taking into account lifetime of the network

Acknowledgement

All my thanks is for our father in heaven for his eternal love to us. I would like to thank Eitan, my supervisor, for his many suggestions and constant support during this small research. I am also thankful for the two Lebanese of the team Ahmad and Sara for they have been a support to me, and they encourage me on the road of the research. My companion of the office, Urtzi, was my example in the manner he works. I thank him, because he was gentle and a man of peace. I thank Bala for he helped me in his knowledge, and he was present to listen to me. I thank Tania for she was always smiling, and present in the critical situations. Each day my first good morning was to Florence, I wish to here good days full of graces. It was a pleasure to me to meet Robin. I thank all the persons on the team and specially the chief Philippe, for he guides the team in an intelligent manner

Identification of a variant in apob gene as a major cause of hypobetalipoproteinemia in lebanese families

International audienceFamilial hypobetalipoproteinemia (FHBL) is a codominant genetic disorder characterized by reduced plasma levels of low-density lipoprotein cholesterol and apolipoprotein B. To our knowl-edge, no study on FHBL in Lebanon and the Middle East region has been reported. Therefore, we conducted genetic studies in unrelated families and probands of Lebanese origin presenting with FHBL, in order to identify the causes of this disease. We found that 71% of the recruited probands and their affected relatives were heterozygous for the p.(Arg490Trp) variant in the APOB gene. Haplotype analysis showed that these patients presented the same mutant haplotype. Moreover, there was a decrease in plasma levels of PCSK9 in affected individuals compared to the non-affected and a significant positive correlation between circulating PCSK9 and ApoB levels in all studied probands and their family members. Some of the p.(Arg490Trp) carriers suffered from diabetes, hepatic steatosis or neurological problems. In conclusion, the p.(Arg490Trp) pathogenic variant seems a cause of FHBL in patients from Lebanese origin, accounting for approximately 70% of the probands with FHBL presumably as a result of a founder mutation in Lebanon. This study is crucial to guide the early diagnosis, management and prevention of the associated complications of this disease

Strategies to safely rule out pulmonary embolism in COVID-19 outpatients: a multicenter retrospective study

International audienceObjectives: The objective was to define a safe strategy to exclude pulmonary embolism (PE) in COVID-19 outpatients, without performing CT pulmonary angiogram (CTPA).Methods: COVID-19 outpatients from 15 university hospitals who underwent a CTPA were retrospectively evaluated. D-Dimers, variables of the revised Geneva and Wells scores, as well as laboratory findings and clinical characteristics related to COVID-19 pneumonia, were collected. CTPA reports were reviewed for the presence of PE and the extent of COVID-19 disease. PE rule-out strategies were based solely on D-Dimer tests using different thresholds, the revised Geneva and Wells scores, and a COVID-19 PE prediction model built on our dataset were compared. The area under the receiver operating characteristics curve (AUC), failure rate, and efficiency were calculated.Results: In total, 1369 patients were included of whom 124 were PE positive (9.1%). Failure rate and efficiency of D-Dimer > 500 µg/l were 0.9% (95%CI, 0.2–4.8%) and 10.1% (8.5–11.9%), respectively, increasing to 1.0% (0.2–5.3%) and 16.4% (14.4–18.7%), respectively, for an age-adjusted D-Dimer level. D-dimer > 1000 µg/l led to an unacceptable failure rate to 8.1% (4.4–14.5%). The best performances of the revised Geneva and Wells scores were obtained using the age-adjusted D-Dimer level. They had the same failure rate of 1.0% (0.2–5.3%) for efficiency of 16.8% (14.7–19.1%), and 16.9% (14.8–19.2%) respectively. The developed COVID-19 PE prediction model had an AUC of 0.609 (0.594–0.623) with an efficiency of 20.5% (18.4–22.8%) when its failure was set to 0.8%.Conclusions:The strategy to safely exclude PE in COVID-19 outpatients should not differ from that used in non-COVID-19 patients. The added value of the COVID-19 PE prediction model is minor