Supraconductivité et ordre de charge dans les bicouches de graphène moirées

Abstract: The recent discovery of a correlated insulating state and superconductivity in twisted bilayer graphene (TBG) has opened a new platform for studying unconventional superconductivity. superconductivity appears for TBG at an angle ∼ 1.08◦ for a very low carrier density of about 1011 cm−2, with a Tc of 1.7 K. The misalignment of the two layers of graphene at the magic angle creates a periodic lattice called the moiré lattice. The effective model we use to describe this system is based on the moiré lattice and was proposed by Kang and Vafek. This model includes four Wannier orbitals located at the honeycomb lattice sites. In addition to hopping terms between these orbitals, we also add intra-orbital and inter-orbital interactions to the Hamiltonian and use a Hubbard or extended Hubbard model to describe the system. Our calculations are based on quantum cluster methods. To investigate the superconductivity we tile the lattice by the four site clusters immersed among six bath orbitals and use the CDMFT method. In the study of the correlated insulating phase, we use the VCA method and select clusters consisting of 12 Wannier orbitals so that we can define inter-orbital interactions in a cluster. We obtain a non-zero p±ip order parameter for superconductivity in a wide range of carrier densities, which is consistent with the experimental observations. Experimental measurements show that the system has a gap in the vicinity of n = 0.5 and n = 1.5 and behaves like a Mott insulator. So we expect that the superconductivity to be suppressed or eliminated in these ranges of densities, which is confirmed by our calculations. d±id is another nonzero superconductor order parameter that we found. The size of this singlet order parameter is smaller than the p ± ip. By calculating the Patthoff functional for two kinds of superconductors, we conclude that p±ip superconductivity has a lower free energy and therefore is the dominant phase between the two. In addition to the superconducting phase, the study of the strongly correlated insulating phases observed in the experiment was another objective of this thesis. Our calculations confirm the existence of these phases at quarter-, half- and three-quarter filling. Further computations show that the insulating phase at quarter-filling is not a charge density wave and that the insulating phase at half-filling is not antiferromagnetic.La découverte récente d’un état corrélé isolant et de la supraconductivité dans la bicouche de graphène moirée (TBG) a ouvert un nouveau canal dans l’étude de la supraconductivité non conventionnelle. Dans ce système, la supraconductivité apparaît à un angle de torsion ∼ 1.08◦ et à très faible densité de porteurs de 1011 cm−2, avec une Tc de 1.7 K. Le défaut d’alignement des deux couches de graphène crée un super-réseau appelé réseau moiré. Le modèle effectif utilisé pour décrire ce système est basé sur ce réseau moiré et a été proposé par Kang et Vafek. Ce modèle comporte 4 orbitales de Wannier centrées sur les sites d’un réseau en nid d’abeille. En plus des termes de saut entre ces orbitales, nous ajoutons des interactions (intra- et inter-orbitales) et utilisons le modèle de Hubbard étendu pour modéliser ce système. Nos calculs reposent sur les méthodes d’amas quantiques. Pour étudier la supraconductivité, nous utilisons un dallage du réseau par des amas de quatre sites couplés à six sites de bain dans la théorie du champ moyen dynamique sur amas (CDMFT). Pour l’étude des phases isolantes, nous utilisons plutôt la méthode de l’amas variationnel (VCA) sur un amas de douze sites, de sorte que les interactions étendues peuvent être comprises minimalement dans l’amas. Pour une large gamme de densités, cohérente avec les observations, nous trouvons un état supraconducteur de type p ± ip. Les expériences montrent que le système possède un gap spectral au voisinage de n = 0.5 et n = 1.5 et se comporte comme un isolant de Mott. On s’attend donc à ce que la supraconductivité soit atténuée ou éliminée près de ces densités, ce qui est confirmé par nos calculs. On trouve aussi un état supraconducteur d ±id comme solution secondaire, avec un paramètre d’ordre plus petit. Un calcul de la fonctionnelle de Potthoff dans ces deux solutions nous permet d’affirmer que l’état p±ip a une énergie plus basse et constitue donc la phase dominante. L’étude des phases isolantes était un deuxième objectif de cette thèse. Nos calculs démontrent l’existence de phases isolantes de Mott au quart remplissage et au demi-remplissage. Des calculs additionnels montrent que l’état isolant à quart rempli n’est pas une onde de densité de charge et que l’état isolant au demi-remplissage n’est pas antiferromagnétique

The effect of infliximab on oxidative stress after myocardial infarction in rats

Infliximab is a human mouse human chimeric IgG1 antibody that includes human stable regions and variable mouse regions that have inhibitory effects on TNFα, and has recently been used to treat Crohn's disease, urticaria colitis, rheumatoid arthritis, and psoriatic arthritis. This study was conducted to determine the effect of TNFα inhibition on infectious stress and serum lactate levels in infants after isoproterenol induced myocardial infarction in rats. Methods and Results: For induction of myocardial infarction (MI), isoproterenol (100 mg/kg) was injected subcutaneously in a 24-hour saline solution in normal saline for 24 days. Animals after 24, 48, 72 and 96 hours after the second dose of isoproterenol was surgically treated. After infusion of inflections, 24, 48, 72 and 96 hours of surgery were performed. Anesthesia for animal surgery with ketamine and xylazine (3 to 2. Blood samples were collected from the hepatic vein and serum was used after the isolation to measure biochemical factors. At the end of the test, the heart was quickly separated and washed with normal cold saline and water was taken and weighed. Induced infarction with isoproterenol 100 mg/kg changes the pattern and parameters of electrocardiography and hemodynamics, and also causes hypertrophy, necrosis, edema and severe cardiac inflammation. Injection of infliximab at a dose of 7 mg/kg in the mentioned intervals did not have an effect on induced hypertrophy due isoproterenol. Isoproterenol increases lipid peroxidation, lactate dehydrogenase, total serum antioxidant and heart tissue, and serum lactate, which seems to be a significant reduction in the levels of MDA, TAC, LDH, and LDH, especially in the early hours of myocardial infarction. Lactate reduces serum levels. But in some cases, with the passage of time does not apply photo effects. Conclusion: The results of this study showed that infliximab, at 24-48 hours after MI, has a protective effect on cardiac myocardial infarction, and in the long term may exacerbate oxidative activity

Inter-LAN services over broadband satellite systems

In this thesis we examine the feasibility of providing interconnections of Local Area Networks (LANs) in various remote plants of the same company in a mesh topology to form a Private Business Network (PBN) over a broadband satellite communications system. Such a PBN consists of several User Terminals (UTs); each connected to the router of a LAN in a given plant. A satellite system supports a number of PBNs by dynamically sharing the satellite resources. We considered Internet Protocol (IP) based LANs using IPv6 and Resource Reservation Protocol (RSVP) to support both real-time and non-real time traffic. We propose a Medium Access Control (MAC) protocol for broadband satellite Inter-LAN services with a special emphasis on the convergence sublayer. In order to efficiently utilize the satellite resources in serving bursty multimedia traffic, the Combined Free- and Demand-Assignment Multiple Access (CFDAMA) techniques are used in conjunction with Multiple-Frequency Time-Division Multiple-Access (MF-TDMA) format for Dynamic Capacity Allocation (DCA). Functions of the UT and Master Control Station (MCS) are described. We describe the translation of Quality of Service (QoS) requirements to service categories and the handling of aggregated requests. We provide a formal model of the MAC layer using the Specification and Description Language (SDL). Moreover, the proposed SDL model is simulated and validated using the ObjectGEODE tool

Neural Distributed Image Compression Using Common Information

We present a novel deep neural network (DNN) architecture for compressing an image when a correlated image is available as side information only at the decoder, a special case of the well-known distributed source coding (DSC) problem in information theory. In particular, we consider a pair of stereo images, which generally have high correlation with each other due to overlapping fields of view, and assume that one image of the pair is to be compressed and transmitted, while the other image is available only at the decoder. In the proposed architecture, the encoder maps the input image to a latent space, quantizes the latent representation, and compresses it using entropy coding. The decoder is trained to extract the common information between the input image and the correlated image, using only the latter. The received latent representation and the locally generated common information are passed through a decoder network to obtain an enhanced reconstruction of the input image. The common information provides a succinct representation of the relevant information at the receiver. We train and demonstrate the effectiveness of the proposed approach on the KITTI and Cityscape datasets of stereo image pairs. Our results show that the proposed architecture is capable of exploiting the decoder-only side information, and outperforms previous work on stereo image compression with decoder side information

Neural distributed image compression with cross-attention feature alignment

We consider the problem of compressing an information source when a correlated one is available as side information only at the decoder side, which is a special case of the distributed source coding problem in information theory. In particular, we consider a pair of stereo images, which have overlapping fields of view, and are captured by a synchronized and calibrated pair of cameras as correlated image sources. In previously proposed methods, the encoder transforms the input image to a latent representation using a deep neural network, and compresses the quantized latent representation losslessly using entropy coding. The decoder decodes the entropy-coded quantized latent representation, and reconstructs the input image using this representation and the available side information. In the proposed method, the decoder employs a cross-attention module to align the feature maps obtained from the received latent representation of the input image and a latent representation of the side information. We argue that aligning the correlated patches in the feature maps allows better utilization of the side information. We empirically demonstrate the competitiveness of the proposed algorithm on KITTI and Cityscape datasets of stereo image pairs. Our experimental results show that the proposed architecture is able to exploit the decoder-only side information in a more efficient manner compared to previous works

Recovery From COVID-19 in Multiple Sclerosis: A Prospective and Longitudinal Cohort Study of the United Kingdom Multiple Sclerosis Register

To understand the course of recovery from coronavirus disease 2019 (COVID-19) among patients with multiple sclerosis (MS) and to determine its predictors, including patients' pre-COVID-19 physical and mental health status.MethodsThis prospective and longitudinal cohort study recruited patients with MS who reported COVID-19 from March 17, 2020, to March 19, 2021, as part of the United Kingdom MS Register (UKMSR) COVID-19 study. Participants used online questionnaires to regularly update their COVID-19 symptoms, recovery status, and duration of symptoms for those who fully recovered. Questionnaires were date stamped for estimation of COVID-19 symptom duration for those who had not recovered at their last follow-up. The UKMSR holds demographic and up-to-date clinical data on participants as well as their web-based Expanded Disability Status Scale (web-EDSS) and Hospital Anxiety and Depression Scale (HADS) scores. The association between these factors and recovery from COVID-19 was assessed using multivariable Cox regression analysis.ResultsOf the 7,977 patients with MS who participated in the UKMSR COVID-19 study, 599 reported COVID-19 and prospectively updated their recovery status. Twenty-eight hospitalized participants were excluded. At least 165 participants (29.7%) had long-standing COVID-19 symptoms for ≥4 weeks and 69 (12.4%) for ≥12 weeks. Participants with pre-COVID-19 web-EDSS scores ≥7, participants with probable anxiety and/or depression (HADS scores ≥11) before COVID-19 onset, and women were less likely to report recovery from COVID-19.DiscussionPatients with MS are affected by postacute sequelae of COVID-19. Preexisting severe neurologic impairment or mental health problems appear to increase this risk. These findings can have implications in tailoring their post-COVID-19 rehabilitation

A comparative study pertaining to deleterious effects of diclofenac sodium and meloxicam on kidney tissue in rats

NSAIDs (nonsteroidal anti-inflammatory drugs) are a class of drugs with analgesic, anti-inflammatory, and antipyretic effects. Diclofenac sodium is one of the world's most widely-prescribed NSAIDs. Meloxicam is another NSAID that was approved in the last several years. Treatment with NSAIDs may result in renal damage. Relatively, little is known about com-parative nephrotoxicity of NSAIDs. Therefore, the present study was designed to compare the adverse effects of diclofenac sodium and meloxicam on renal tissue in rats. Forty eight Wistar male rats were randomly assigned into 3 groups of 16 animals each. Group C served as normal control and received normal saline. Group D and M received diclofenac sodium (2.3 mg/kg/day) and meloxicam (2.3 mg/kg/day), respectively. After 17 days, all rats were scarified. Their kidneys were then harvested and processed for histological examination. In addition to cellular details, renal tubular count and diameter were assessed with the light microscope. The data were analyzed using SPSS software. We found that the mean number of renal tubules was significantly lower in group D, than in group C. Moreover, the mean renal tubular diameter was significantly higher in group D than in group C. The present study showed that a considerable degree of nephrotoxicity resulted from diclofenac sodium, compared to meloxicam. We suggest that diclofenac sodium can be replaced with meloxicam