Dealiasing techniques for high-order spectral element methods on regular and irregular grids

High-order methods are becoming increasingly attractive in both academia and industry, especially in the context of computational fluid dynamics. However, before they can be more widely adopted, issues such as lack of robustness in terms of numerical stability need to be addressed, particularly when treating industrial-type problems where challenging geometries and a wide range of physical scales, typically due to high Reynolds numbers, need to be taken into account. One source of instability is aliasing effects which arise from the nonlinearity of the underlying problem. In this work we detail two dealiasing strategies based on the concept of consistent integration. The first uses a localised approach, which is useful when the nonlinearities only arise in parts of the problem. The second is based on the more traditional approach of using a higher quadrature. The main goal of both dealiasing techniques is to improve the robustness of high order spectral element methods, thereby reducing aliasing-driven instabilities. We demonstrate how these two strategies can be effectively applied to both continuous and discontinuous discretisations, where, in the latter, both volumetric and interface approximations must be considered. We show the key features of each dealiasing technique applied to the scalar conservation law with numerical examples and we highlight the main differences in terms of implementation between continuous and discontinuous spatial discretisations

Dealiasing techniques for high-order spectral element methods on regular and irregular grids

This is the final version of the article. Available from Elsevier via the DOI in this record.High-order methods are becoming increasingly attractive in both academia and industry, especially in the context of computational fluid dynamics. However, before they can be more widely adopted, issues such as lack of robustness in terms of numerical stability need to be addressed, particularly when treating industrial-type problems where challenging geometries and a wide range of physical scales, typically due to high Reynolds numbers, need to be taken into account. One source of instability is aliasing effects which arise from the nonlinearity of the underlying problem. In this work we detail two dealiasing strategies based on the concept of consistent integration. The first uses a localised approach, which is useful when the nonlinearities only arise in parts of the problem. The second is based on the more traditional approach of using a higher quadrature. The main goal of both dealiasing techniques is to improve the robustness of high order spectral element methods, thereby reducing aliasing-driven instabilities. We demonstrate how these two strategies can be effectively applied to both continuous and discontinuous discretisations, where, in the latter, both volumetric and interface approximations must be considered. We show the key features of each dealiasing technique applied to the scalar conservation law with numerical examples and we highlight the main differences in terms of implementation between continuous and discontinuous spatial discretisations.This work was supported by the Laminar Flow Control Centre funded by Airbus/EADS and EPSRC under grant EP/I037946. We thank Dr. Colin Cotter for helpful discussions and Jean-Eloi Lombard for his assistance in the generation of results and figures for the NACA 0012 simulation. PV acknowledges the Engineering and Physical Sciences Research Council for their support via an Early Career Fellowship (EP/K027379/1). SJS additionally acknowledges Royal Academy of Engineering support under their research chair scheme. Data supporting this publication can be obtained on request from [email protected]

MAD-4-MITO, a Multi Array of Detectors for ground-based mm/submm SZ observations

The last few years have seen a large development of mm technology and ultra-sensitive detectors devoted to microwave astronomy and astrophysics. The possibility to deal with large numbers of these detectors assembled into multi--pixel imaging systems has greatly improved the performance of microwave observations, even from ground--based stations, especially combining the power of multi--band detectors with their new imaging capabilities. Hereafter, we will present the development of a multi--pixel solution devoted to Sunyaev--Zel'dovich observations from ground--based telescopes, that is going to be operated from the Millimetre and Infrared Testagrigia Observatory.Comment: 5 pages, 3 figures, to be published in th eProceedings of the 2K1BC Workshop, July 9-13, 2001 - Breuil-Cervini

Age and Cytokine Gene Variants Modulate the Immunogenicity and Protective Effect of SARS-CoV-2 mRNA-Based Vaccination

: The introduction of anti-SARS-CoV-2 vaccines in late 2020 substantially changed the pandemic picture, inducing effective protection in the population. However, individual variability was observed with different levels of cellular response and neutralizing antibodies. We report data on the impact of age, gender, and 16 single nucleotide polymorphisms (SNPs) of cytokine genes on the anti-SARS-CoV-2 IgG titers measured 31 and 105 days after administration of the second dose of BNT162b2 vaccine to 122 healthy subjects from the health care staff of the Palermo University Hospital, Italy. The higher titers at 31 days were measured in the younger subjects and in subjects bearing T-positive genotypes of IL-1R1 rs2234650 or the GG homozygous genotype of IL-6 rs1800795 SNP. T-positive genotypes are also significantly more common in subjects with higher titers at day 105. In addition, in this group of subjects, the frequency of the CT genotype of IL-4 rs2243250 is higher among those vaccinated with higher titers. Moreover, these SNPs and TNFA rs1800629 are differently distributed in a group of subjects that were found infected by SARS-CoV-2 at day 105 of evaluation. Finally, subjects that were found to be infected by SARS-CoV-2 at day 105 were significantly older than the uninfected subjects. Taken together, these data seem to suggest that age and polymorphisms of key cytokines, which regulate inflammation and humoral immune response, might influence the magnitude of the antibody response to vaccination with BNT162B2, prompting speculation about the possible benefit of a genetic background-based assessment of a personalized approach to the anti-COVID vaccination schedule

Role of the H-bond between L53 and T56 for Aquaporin-4 epitope in Neuromyelitis Optica

Aquaporin-4 (AQP4) is the CNS water channel organized into well-ordered protein aggregates called Orthogonal Arrays of Particles (OAPs). Neuromyelitis Optica (NMO) is an autoimmune disease caused by anti-OAP autoantibodies (AQP4-IgG). Molecular Dynamics (MD) simulations have identified an H-bond between L53 and T56 as the key for AQP4 epitope and therefore of potential interest for drug design in NMO field. In the present study, we have experimentally tested this MD-prediction using the classic mutagenesis approach. We substituted T56 with V56 and tested this mutant for AQP4 aggregates and AQP4-IgG binding. gSTED super-resolution microscopy showed that the mutation does not affect AQP4 aggregate dimension; immunofluorescence and cytofluorimetric analysis demonstrated its unaltered AQP4-IgG binding, therefore invalidating the MD-prediction. We later investigated whether AQP4, expressed in Sf9 insect and HEK-293F cells, is able to correctly aggregate before and after the purification steps usually applied to obtain AQP4 crystal. The results demonstrated that AQP4-IgG recognizes AQP4 expressed in Sf9 and HEK-293F cells by immunofluorescence even though BN-PAGE analysis showed that AQP4 forms smaller aggregates when expressed in insect cells compared to mammalian cell lines. Notably, after AQP4 purification, from both insect and HEK-293F cells, no aggregates are detectable by BN-PAGE and AQP4-IgG binding is impaired in sandwich ELISA assays. All together these results indicate that 1) the MD prediction under analysis is not supported by experimental data and 2) the procedure to obtain AQP4 crystals might affect its native architecture and, as a consequence, MD simulations. In conclusion, given the complex nature of the AQP4 epitope, MD might not be the suitable for molecular medicine advances in NMO

Surveillance of enteric virus infections in a neonatal intensive care unit.

Objective. To investigate the epidemiology of neonatal viral gastroenteritis compared to the circulation of enteric viruses in children, 109 newborns in the NICU of Mother and Child Department and 214 children with enteritis admitted to the \u201cG. Di Cristina\u201d Children\u2019s Hospital in Palermo were monitored for Rotavirus, Adenovirus, Astrovirus and Norovirus infections. Methods. Stool samples were examined by EIA to detect viral antigens. Rotavirus strains were subjected to P- and G-typing. Results. A Norovirus strain was detected in one neonatal stool specimen whereas an astrovirus strain was dectected in two neonatal specimens. No Rotavirus or Adenovirus infection was identified among the newborn infants, while Rotavirus infections were detected in 24.8% of the symptomatic children. Type G4P[8] constituted 43.4% of the Rotavirus strains, followed by G2P[4] (18.9%), G3P[8] (17%), G1P[8] (13.2%) and G9P[8] (1.9%). Overall, Norovirus, Adenovirus and Astrovirus strains were responsible for 15.4% of infections in the paediatric population with diarrhoea. Conclusions. Viruses are diffuse agents of infection in children with enteritis. Virological tests have to be performed to diagnose enteric infections in the paediatric population. Maternal immunity to common Rotavirus strains combined with the limited circulation of the emerging G9 Rotavirus type among our population may account for the absence of Rotavirus infections in newborn infants

Congenital cytomegalovirus related intestinal malrotation: a case report

Background: Cytomegalovirus is the most common cause of congenital infection in the developed countries. Gastrointestinal involvement has been extensively described in both adult and paediatric immunocompromised patients but it is infrequent in congenital or perinatal CMV infection. Case presentation: We report on a case of coexistent congenital Cytomegalovirus infection with intestinal malrotation and positive intestinal Cytomegalovirus biopsy. At birth the neonate showed clinical and radiological evidence of intestinal obstruction. Meconium passed only after evacuative nursing procedures; stooling pattern was irregular; gastric residuals were bile-stained. Laparatomy revealed a complete intestinal malrotation and contextually gastrointestinal biopsy samples of the appendix confirmed the diagnosis of CMV gastrointestinal disease. Intravenous ganciclovir was initiated for 2 weeks, followed by oral valgancyclovir for 6 month. Conclusion: CMV-induced proinflammatory process may be responsible of the interruption of the normal development of the gut or could in turn lead to a disruption in the normal development of the gut potentiating the mechanism causing malrotation. We suggest the hypothesis that an inflammatory process induced by CMV congenital infection may be responsible, in the early gestation, of the intestinal end-organ disease, as the intestinal malrotation. CMV infection should always be excluded in full-term infants presenting with colonic stricture or malrotation

Serosurvey of schmallenberg virus infection in sheep in Abruzzo, Italy : short report

Infection with Schmallenberg virus (SBV) causes congenital musculoskeletal and vertebral malformations as well as neurological failures in fetuses of several ruminant species. In this study 1038 sheep samples from 10 flocks in the provinces of Chieti, Teramo and Pescara in Italy have been tested for antibodies against SBV by ELISA test. The purpose of the study was to ascertain the extent of SBV infections in sheep in Italy. The results of the ELISA test identified at least one positive animal in 9 of the 10 sheep flocks tested, and a mean within-flock prevalence of 8.57%. Furthermore, large variability of positive animals between flocks was observed (0 and 42.5%). These results demonstrate that SBV was endemic in this region and there could be is a risk of novel SBV infections in the following lambing season, raising serious concerns about its so rapid and pervasive spread