A New Compendium of Unsteady Aerodynamic Test Cases for CFD: Summary of AVT WG-003 Activities

With the continuous progress in hardware and numerical schemes, Computational Unsteady Aerodynamics (CUA), that is, the application of Computational Fluid Dynamics (CFD) to unsteady flowfields, is slowly finding its way as a useful and reliable tool (turbulence and transition modeling permitting) in the aircraft, helicopter, engine and missile design and development process. Before a specific code may be used with confidence it is essential to validate its capability to describe the physics of the flow correctly, or at least to the level of approximation required, for which purpose a comparison with accurate experimental data is needed. Unsteady wind tunnel testing is difficult and expensive; two factors which dramatically limit the number of organizations with the capability and/or resources to perform it. Thus, unsteady experimental data is scarce, often classified and scattered in diverse documents. Additionally, access to the reports does not necessarily assure access to the data itself. The collaborative effort described in this paper was conceived with the aim of collecting into a single easily accessible document as much quality data as possible. The idea is not new. In the early 80's NATO's AGARD (Advisory Group for Aerospace Research & Development) Structures and Material Panel (SMP) produced AGARD Report No. 702 "Compendium of Unsteady Aerodynamic Measurements", which has found and continues to find extensive use within the CUA Community. In 1995 AGARD's Fluid Dynamics Panel (FDP) decided to update and expand the former database with new geometries and physical phenomena, and launched Working Group WG-22 on "Validation Data for Computational Unsteady Aerodynamic Codes". Shortly afterwards AGARD was reorganized as the RTO (Research and Technology Organization) and the WG was renamed as AVT (Applied Vehicle Technolology) WG-003. Contributions were received from AEDC, BAe, DLR, DERA, Glasgow University, IAR, NAL, NASA, NLR, and ONERA. The final publication with the results of the exercise is expected in the second part of 1999. The aim of the present paper is to announce and present the new database to the Aeroelasticity community. It is also intended to identify, together with one of the groups of end users it targets, deficiencies in the compendium that should be addressed by means of new wind tunnel tests or by obtaining access to additionally existing data

An evaluation of the density functional approach in the zero order regular approximation for relativistic effects: Magnetic interactions in small metal compounds

The density functional approach was evaluated for electron spin resonance (ESR) parameters in the relativistic zero order regular approximation in small metal compounds. The effects of spin-orbit coupling and spin polarization on the magnetic hyperfine interaction were investigated. It was shown that relativistic effects in the calculation of the hyperfine parameters were large not only for the heavy metals but also for ligands bound to heavy elements due to secondary effects

Azimuthal Anisotropy of Photon and Charged Particle Emission in Pb+Pb Collisions at 158 A GeV/c

The azimuthal distributions of photons and charged particles with respect to the event plane are investigated as a function of centrality in Pb + Pb collisions at 158 A GeV/c in the WA98 experiment at the CERN SPS. The anisotropy of the azimuthal distributions is characterized using a Fourier analysis. For both the photon and charged particle distributions the first two Fourier coefficients are observed to decrease with increasing centrality. The observed anisotropies of the photon distributions compare well with the expectations from the charged particle measurements for all centralities.Comment: 8 pages and 6 figures. The manuscript has undergone a major revision. The unwanted correlations were enhanced in the random subdivision method used in the earlier version. The present version uses the more established method of division into subevents separated in rapidity to minimise short range correlations. The observed results for charged particles are in agreement with results from the other experiments. The observed anisotropy in photons is explained using flow results of pions and the correlations arising due to the decay of the neutral pion

Wind tunnel flutter testing on a highly flexible wing for aeroelastic validation in the transonic regime within the HMAE1 project

The aircraft manufacturer Embraer, the German Aerospace Center (DLR), the Netherlands Aerospace Centre (NLR) and German-Dutch Wind Tunnels (DNW) have tested an innovative highly flexible wing within an aeroelastic wind tunnel experiment in the transonic regime. The HMAE1 project was initiated by Embraer to test its numerical predictions for wing flutter under excessive wing deformations in the transonic regime. A highly elastic fiberglass wing-body pylon nacelle wind tunnel model (see Figure 1), which is able to deform extensively, was constructed for the experiment. The model was instrumented with a large number of pressure orifices, strain gauges, stereo pattern recognition (SPR) markers and accelerometers. The wing was tested from Ma = 0.4 to Ma = 0.9 for different angles of attack and stagnation pressures. The static and dynamic behavior of the wing model was monitored and a new method to analyze its eigenfrequencies and damping ratios was used. In the past, the large amounts of data acquired during such experiments could only be evaluated with a time lag. An efficient method developed by DLR now allows performing the data analysis in real time [1, 2]. As a result, it was possible during the test to identify exactly which safety margins remained before the onset of flutter and the resulting possible destruction of the model

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Cholinergic imbalance in the multiple sclerosis hippocampus

Hippocampal pathology was shown to be extensive in multiple sclerosis (MS) and is associated with memory impairment. In this post-mortem study, we investigated hippocampal tissue from MS and Alzheimer's disease (AD) patients and compared these to non-neurological controls. By means of biochemical assessment, (immuno)histochemistry and western blot analyses, we detected substantial alterations in the cholinergic neurotransmitter system in the MS hippocampus, which were different from those in AD hippocampus. In MS hippocampus, activity and protein expression of choline acetyltransferase (ChAT), the acetylcholine synthesizing enzyme, was decreased, while the activity and protein expression of acetylcholinesterase (AChE), the acetylcholine degrading enzyme, was found to be unaltered. In contrast, in AD hippocampus both ChAT and AChE enzyme activity and protein expression was decreased. Our findings reveal an MS-specific cholinergic imbalance in the hippocampus, which may be instrumental in terms of future treatment options for memory problems in this diseas

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

NEXTTRIP Interactional aerodynamic assessment of an advanced tilt rotor configuration

This paper reports on the goals accomplished by the NEXTTRIP Consortium in response to the Topic JTICS2-2017-CFP06-FRC-01-15 titled Interactional Aerodynamic Assessment of Advanced Tilt Rotor Configuration. The aim of the project was to assess different empennage configurations for the Next Generation Civil Tilt Rotor, NGCTR, by a large scale wind tunnel experiment, share knowledge and skills across the European partners and to provide guidance to the Integrated Technology Demonstrator (ITD) leaders through CFD-optimised and cost-effective solutions. The investigation, test and evaluation of a new empennage configuration for the NGCTR Technology Demonstrator were conducted in the DNW 9.5-by-9.5 m large low speed facility (LLF) in Marknesse, the Netherlands. Although the wind tunnel campaign was mainly focused to determine the stability and control characteristic of the powered, 1/5th scale model of the NGCTR, tests were also conducted to study the following effects of varying the basic configuration: effect of a V-tail and T-tail empennage, effect of elevator trim, effect of lateral-directional control, effect of power, interactional effect of rotor on/rotor off and effect of nacelle angle. Additional and innovative aspect of the experimental campaign was the application of the Particle Image Velocimetry based on Helium Filled Soap Bubbles, or HFSB, on large scale by using a seeding rake on 3-by-3 meters and up to 60 m/s. The test results were used in parallel to develop and validate a CFD methodology, based on multi-objective genetic algorithm, to optimise the V-tail empennage. Moreover, the project led to a fruitful exchange of ideas, expertise and knowledge, strengthening the bonds between JU partners

Cortical remyelination is heterogeneous in multiple sclerosis

Cortical lesions (CLs) are an important component of multiple sclerosis (MS) pathology; they correlate better with physical disability and cognitive impairment than white matter lesions (WMLs). Because remyelination can be extensive in CLs, we quantified remyelination in gray matter (GM) and white matter (WM), addressing oligodendrocyte (OGD) maturation state and clinical relevance of remyelination. Brain tissue samples from 21 chronic MS patients were immunohistochemically stained for myelin proteolipid protein, Olig2, which is strongly expressed in OGD precursor cells (OPCs), but weakly expressed in mature OGDs and other OGD markers. Sections were scored for the presence of normal-appearing WM and GM, de- and remyelination, and OPC and OGD cell counts. Remyelination was significantly more extensive in CLs than in WMLs with a trend toward more GM remyelination in primary progressive MS (PPMS) vs relapse-onset MS patients. More OPCs were found in remyelinated and nonremyelinated CLs vs remyelinated WMLs and nonremyelinated WMLs. Thus, there is more remyelination in the GM than in the WM in MS patient brains, with a trend toward more remyelination in those with PPMS. There does not seem to be a significant OPC recruitment failure in the GM, which casts new light on the process of remyelination failure

Complement C3 on microglial clusters in multiple sclerosis occur in chronic but not acute disease: Implication for disease pathogenesis

Microglial clusters with C3d deposits are observed in the periplaque of multiple sclerosis (MS) brains and were proposed as early stage of lesion formation. As such they should appear in the brain of MS donors with acute disease but thus far this has not been shown. Using postmortem brain tissue from acute (n = 10) and chronic (n = 15) MS cases we investigated whether C3d+ microglial clusters are part of an acute attack against myelinated axons, which could have implications for disease pathogenesis. The specificity of our findings to MS was tested in ischemic stroke cases (n = 8) with initial or advanced lesions and further analyzed in experimental traumatic brain injury (TBI, n = 26), as both conditions are primarily nondemyelinating but share essential features of neurodegeneration with MS lesions. C3d+ microglial clusters were found in chronic but not acute MS. They were not associated with antibody deposits or terminal complement activation. They were linked to slowly expanding lesions, localized on axons with impaired transport and associated with neuronal C3 production. C3d+ microglial clusters were not specific to MS as they were also found in stroke and experimental TBI. We conclude that C3d+ microglial clusters in MS are not part of an acute attack against myelinated axons. As such it is unlikely that they drive formation of new lesions but could represent a physiological mechanism to remove irreversibly damaged axons in chronic disease. GLIA 2017;65:264–277