Experimental Investigation of Photogrammetric Surface Analysis of Heat Shield Materials during Plasma Wind Tunnel Testing

The paper presents first results of an experimental analysis of surface recession using advanced photogrammetric tools. Based on image pairs acquired with two DSLR cameras, classical photogrammetry has been tried, but pixelwise image analysis with corresponding matching algorithms show much better results ans higher stability to image noise and ra- diation and re ection issues. A combination of open source tools for the analysis of camera positions and focal points, pixel matching analysis, and pixel cloud comparing, allows the recession to be measured with very high local resolution of 20 �m of a 2D surface. The ap- proach is analysed within this study with respect to window disturbance and experimental setup constraints. A first plasma wind tunnel experiment shows the applicability and an analysis of a central spot is comparable to laser recession measurements

Photogrammetric Surface Analysis of Ablation Processes in High Enthalpy Air Plasma Flow

Results from in-situ analysis of ablative heat shield materials based on stereoscopic photogrammetry during plasma wind tunnel testing are presented. A carbon �fiber preform material sample has been investigated in a high enthalpy air flow corresponding to a Hayabusa re-entry condition in 78km altitude. The applied photogrammetry uses two digital single lens reflex (DSLR) cameras triggered at 3 fps to acquire images simultaneously from two different perspectives of the sample exposed to the high Speed flow. The photogrammetric analysis resolves the surface with 25000 px/cm2, approximately 400 dpi, allowing the in-situ analysis of the recession phenomena of ablators. Material inhomogeneities are identified during the ablation process and surface recession is derived with an accuracy of 21 micro�meters. The method is a useful tool for the investigation of temporally resolved volumetric ablation phenomena in low density carbon phenolic materials

Multi-Photon Spectroscopy on Xenon for Application on Ion Thruster Plasma Parameter Investigations: Experiment and Theory

Three excitation schemes for two-photon laser-induced fluorescence (TALIF) on neutral xenon involving 6p and 7p states are presented. An overview on possible transitions is given. In addition to the well-known transition at λ = 2 × 225.5 nm, two alternative candidates for neutral xenon ground state diagnostics are experimentally investigated in a xenon-filled cold gas cell. It was found that alternative excitation schemes showed remarkable signal intensities and can be used for future TALIF measurements in neutral xenon additionally. Some theoretical aspects of three-photon spectroscopy with respect to singly ionized xenon ground state diagnostics are discussed. Three-photon transition rates are expected to have transition rates about ten orders of magnitude lower than those of two-photon processes

Spatial and temporal variability in MLT turbulence inferred from in situ and ground-based observations during the WADIS-1 sounding rocket campaign

In summer 2013 the WADIS-1 sounding rocket campaign was conducted at the Andøya Space Center (ACS) in northern Norway (69° N, 16° E). Among other things, it addressed the question of the variability in mesosphere/lower thermosphere (MLT) turbulence, both in time and space. A unique feature of the WADIS project was multi-point turbulence sounding applying different measurement techniques including rocket-borne ionization gauges, VHF MAARSY radar, and VHF EISCAT radar near Tromsø. This allowed for horizontal variability to be observed in the turbulence field in the MLT at scales from a few to 100 km. We found that the turbulence dissipation rate, ε varied in space in a wavelike manner both horizontally and in the vertical direction. This wavelike modulation reveals the same vertical wavelengths as those seen in gravity waves. We also found that the vertical mean value of radar observations of ε agrees reasonably with rocket-borne measurements. In this way defined 〈εradar〉 value reveals clear tidal modulation and results in variation by up to 2 orders of magnitude with periods of 24 h. The 〈εradar〉 value also shows 12 h and shorter (1 to a few hours) modulations resulting in one decade of variation in 〈εradar〉 magnitude. The 24 h modulation appeared to be in phase with tidal change of horizontal wind observed by SAURA-MF radar. Such wavelike and, in particular, tidal modulation of the turbulence dissipation field in the MLT region inferred from our analysis is a new finding of this work

Simultaneous in Situ Measurements of Small-Scale Structures in Neutral, Plasma, and Atomic Oxygen Densities During the WADIS Sounding Rocket Project

In this paper we present an overview of measurements conducted during the WADIS-2 rocket campaign. We investigate the effect of small-scale processes like gravity waves and turbulence on the distribution of atomic oxygen and other species in the mesosphere–lower thermosphere (MLT) region. Our analysis suggests that density fluctuations of atomic oxygen are coupled to fluctuations of other constituents, i.e., plasma and neutrals. Our measurements show that all measured quantities, including winds, densities, and temperatures, reveal signatures of both waves and turbulence. We show observations of gravity wave saturation and breakdown together with simultaneous measurements of generated turbulence. Atomic oxygen inside turbulence layers shows two different spectral behaviors, which might imply a change in its diffusion properties

Aggregation-resistant alpha-synuclein tetramers are reduced in the blood of Parkinson's patients

Synucleinopathies such as Parkinson's disease (PD) are defined by the accumulation and aggregation of the α-synuclein protein in neurons, glia and other tissues. We have previously shown that destabilization of α-synuclein tetramers is associated with familial PD due to SNCA mutations and demonstrated brain-region specific alterations of α-synuclein multimers in sporadic PD patients following the classical Braak spreading theory. In this study, we assessed relative levels of disordered and higher-ordered multimeric forms of cytosolic α-synuclein in blood from familial PD with G51D mutations and sporadic PD patients. We used an adapted in vitro-cross-linking protocol for human EDTA-whole blood. The relative levels of higher-ordered α-synuclein tetramers were diminished in blood from familial PD and sporadic PD patients compared to controls. Interestingly, the relative amount of α-synuclein tetramers was already decreased in asymptomatic G51D carriers, supporting the hypothesis that α-synuclein multimer destabilization precedes the development of clinical PD. Our data, therefore suggest that measuring α-synuclein tetramers in blood may have potential as a facile biomarker assay for early detection and quantitative tracking of PD progression.</p

Identification of genetic variants associated with Huntington's disease progression: a genome-wide association study

Background Huntington's disease is caused by a CAG repeat expansion in the huntingtin gene, HTT. Age at onset has been used as a quantitative phenotype in genetic analysis looking for Huntington's disease modifiers, but is hard to define and not always available. Therefore, we aimed to generate a novel measure of disease progression and to identify genetic markers associated with this progression measure. Methods We generated a progression score on the basis of principal component analysis of prospectively acquired longitudinal changes in motor, cognitive, and imaging measures in the 218 indivduals in the TRACK-HD cohort of Huntington's disease gene mutation carriers (data collected 2008–11). We generated a parallel progression score using data from 1773 previously genotyped participants from the European Huntington's Disease Network REGISTRY study of Huntington's disease mutation carriers (data collected 2003–13). We did a genome-wide association analyses in terms of progression for 216 TRACK-HD participants and 1773 REGISTRY participants, then a meta-analysis of these results was undertaken. Findings Longitudinal motor, cognitive, and imaging scores were correlated with each other in TRACK-HD participants, justifying use of a single, cross-domain measure of disease progression in both studies. The TRACK-HD and REGISTRY progression measures were correlated with each other (r=0·674), and with age at onset (TRACK-HD, r=0·315; REGISTRY, r=0·234). The meta-analysis of progression in TRACK-HD and REGISTRY gave a genome-wide significant signal (p=1·12 × 10−10) on chromosome 5 spanning three genes: MSH3, DHFR, and MTRNR2L2. The genes in this locus were associated with progression in TRACK-HD (MSH3 p=2·94 × 10−8 DHFR p=8·37 × 10−7 MTRNR2L2 p=2·15 × 10−9) and to a lesser extent in REGISTRY (MSH3 p=9·36 × 10−4 DHFR p=8·45 × 10−4 MTRNR2L2 p=1·20 × 10−3). The lead single nucleotide polymorphism (SNP) in TRACK-HD (rs557874766) was genome-wide significant in the meta-analysis (p=1·58 × 10−8), and encodes an aminoacid change (Pro67Ala) in MSH3. In TRACK-HD, each copy of the minor allele at this SNP was associated with a 0·4 units per year (95% CI 0·16–0·66) reduction in the rate of change of the Unified Huntington's Disease Rating Scale (UHDRS) Total Motor Score, and a reduction of 0·12 units per year (95% CI 0·06–0·18) in the rate of change of UHDRS Total Functional Capacity score. These associations remained significant after adjusting for age of onset. Interpretation The multidomain progression measure in TRACK-HD was associated with a functional variant that was genome-wide significant in our meta-analysis. The association in only 216 participants implies that the progression measure is a sensitive reflection of disease burden, that the effect size at this locus is large, or both. Knockout of Msh3 reduces somatic expansion in Huntington's disease mouse models, suggesting this mechanism as an area for future therapeutic investigation

PHOTOGRAMMETRIC SURFACE RECESSION MEASUREMENTS ON ABLATIVE SAMPLES OF VARIOUS SHAPE

Results from plasma wind tunnel testing of a lightweight carbon phenolic ablative material are presented. The tests were carried out in a high-enthalpy subsonic flow at a condition corresponding to the Hayabusa re-entry condition in 78 km altitude. The samples were produced from ZURAM which is a carbon-fiber structure impregnated with phenolic resin. The focus of the investigation was on the measurement method of the recession. Stereoscopic photogrammetry was applied to reconstruct the sample surface in three-dimensional space over the testing time. Two cameras were used to capture images simultaneously. Using a three-step process the sample surface for each image pair was reconstructed and the recession between the image pairs was calculated. The recession resolution is in the range of 45 µm. The advantage of the method is that the time-resolved in-situ surface recession measurement gives insight into the local recession distribution over the sample surface. This means that recession differences due to the sample geometry or due to material inhomogeneities can be identified. In order to verify this, samples were prepared that include distinct geometric features which influence the recession. Starting with a flat surface cylinder, samples with a rounded surface were prepared as well as a cone-sphere sample and one with a defined indentation in the form of a half-sphere. The temporally and locally resolved recession was successfully measured and related to the sample geometric features