Simple, adjustable beam splitting element for differential interferometers based on photoelastic birefringence of a prismatic bar

We examine the prototypical Toepler optical arrangement for the visualization of phase objects and consider the effect of different contrast elements placed at the focus of the source. In particular, Wollaston prism beam splitting elements based on the crystallographic birefringence of calcite or quartz find application in differential interferometry systems based on the Toepler arrangement. The focus of the current article is a simple low cost alternative to the Wollaston prism that is realized by inserting a prismatic bar constructed of a photoelastic material into the optical path. It is shown that, under the action of an applied bending moment, the prismatic bar functions as a first-order approximation to a Wollaston prism. Results are derived for the divergence angle of the beam splitter for orthogonally polarized rays. The implementation of a practical device is discussed and representative experimental results are presented, taken from the field of shock wave visualization in supersonic flow

Analysis of focused laser differential interferometry

A computational method for predicting the output of a focused laser differential interferometer (FLDI) given an arbitrary density field is presented. The method is verified against analytical predictions and experimental data. The FLDI simulation software is applied to the problem of measuring Mack-mode wave packets in a hypervelocity boundary layer on a 5° half-angle cone. The software is shown to complement experiments by providing the necessary information to allow quantitative density fluctuation magnitudes to be extracted from experimental measurements

THE GEOMETRY AND TOPOLOGY OF DEFORMATION BAND NETWORKS IN VOLCANICLASTIC ROCKS: A CASE STUDY FROM SHIHTIPING, SOUTH-EASTERN TAIWAN

Deformation bands are tabular strain localization features, common in porous and granular rocks. These structures of millimeter to centimeter thickness can occur as single bands and develop into clusters or networks of bands. Deformation bands have been extensively documented in siliciclastic rocks, whereas fewer studies address deformation bands in porous volcaniclastic rocks. In recent years, volcaniclastic reservoirs have become a hot topic in petroleum- and geothermal exploration, groundwater aquifers and CO2 storage. Deformation bands are generally associated with a permeability reduction from one to three orders of magnitude compared to the host rock and deformation band networks may affect subsurface fluid flow patterns. Knowing the network properties of deformation bands are therefore crucial when predicting their impact on fluid flow. This M.Sc. project quantifies clusters and networks of deformation bands in volcaniclastic rocks from Shihtiping, Eastern Taiwan. A thorough topological analysis of deformation band networks has been carried out, focusing on characterizing the distribution and connectivity of bands within a network. Individual deformation bands were analyzed based on their geometry, including length, density, and intensity, to access the spatial relationship of bands within the networks. The quantitative relation of nodes and branches provides the basis for describing the connectivity in the studied deformation band networks. The deformation band networks are generally dominated by connecting Y-nodes and fully connected (C-C) branches, resulting in high average connectivity. Furthermore, the topological characteristics can be associated with bifurcating, abutting, and splaying bands, and bands are less prone to crosscut one another. The highest connectivity is related to mature deformation band networks and deformation band networks in fully developed faults. This supports the theory that the connectivity of deformation networks develops with time and maturity (strain). The analyses of the deformation bands show that nodal distribution, intensity and connectivity are vulnerable to lithological heterogeneities across the network. This study strengthens our understanding of the development of deformation bands in volcaniclastic rocks and explores the evolution of connectivity in deformation band networks. Quantifying the topological and geometrical characteristics of deformation band networks is essential as it generates parameters used to assess the potential for fluid flow in a reservoir.Masteroppgave i geovitenskapGEOV399MAMN-GEO

Optical Measurements of Viscous Interactions on a Hollow-Cylinder / Flare in a Mach 4 Freestream

Despite decades of research, shock-wave/boundary-layer interactions and laminar-turbulent transition remain uncertainties in the design of hypersonic vehicles. Due to the significant demand for hypersonic capabilities and the relevance of these flow physics to air-breathing, high-lift, hypersonic vehicles, continued study is necessary. In order to support such study at the University of Tennessee Space Institute, two optical diagnostics were investigated for use in the Mach 4 Ludwig tube at the Tennessee Aerothermal Laboratory, focused laser differential interferometry and schlieren. Significant attention was given to the theory behind and application of focused laser differential interferometry to support future work at the University of Tennessee Space Institute. These diagnostics were constructed and utilized in two studies, one investigating a laminar shock-wave/boundary-layer interaction on an axisymmetric hollow cylinder flare geometry, and one tracking the boundary layer transition along a hollow cylinder. Results of these studies show that FLDI and schlieren are an effective method for the non-intrusive study of boundary layer structure and breakdown, and show promising use for the study of shock-wave/boundary-layer interactions. Reported results include spectral distributions from the boundary layer, separation region, and reattachment region of a laminar shock-wave/boundary-layer interaction and from laminar, transitional, and fully turbulent regions in a boundary layer. In this study, the boundary layer was found to transition at a local Reynolds number of Re = 1.71 × 10^5 and gave way to fully turbulent behavior at Re = 3.34 × 10^5

BACL is a novel brain-associated, non-NKC-encoded mammalian C-type lectin-like receptor of the CLEC2 family

Natural Killer Gene Complex (NKC)–encoded C-type lectin-like receptors (CTLRs) are expressed on various immune cells including T cells, NK cells and myeloid cells and thereby contribute to the orchestration of cellular immune responses. Some NKC-encoded CTLRs are grouped into the C-type lectin family 2 (CLEC2 family) and interact with genetically linked CTLRs of the NKRP1 family. While many CLEC2 family members are expressed by hematopoietic cells (e.g. CD69 (CLEC2C)), others such as the keratinocyte-associated KACL (CLEC2A) are specifically expressed by other tissues. Here we provide the first characterization of the orphan gene CLEC2L. In contrast to other CLEC2 family members, CLEC2L is conserved among mammals and located outside of the NKC. We show that CLEC2L-encoded CTLRs are expressed as non-glycosylated, disulfide-linked homodimers at the cell surface. CLEC2L expression is fairly tissue-restricted with a predominant expression in the brain. Thus CLEC2L-encoded CTLRs were designated BACL (brain-associated C-type lectin). Combining in situ hybridization and immunohistochemistry, we show that BACL is expressed by neurons in the CNS, with a pronounced expression by Purkinje cells. Notably, the CLEC2L locus is adjacent to another orphan CTLR gene (KLRG2), but reporter cell assays did neither indicate interaction of BACL with the KLRG2 ectodomain nor with human NK cell lines or lymphocytes. Along these lines, growth of BACL-expressing tumor cell lines in immunocompetent mice did not provide evidence for an immune-related function of BACL. Altogether, the CLEC2L gene encodes a homodimeric cell surface CTLR that stands out among CLEC2 family members by its conservation in mammals, its biochemical properties and the predominant expression in the brain. Future studies will have to reveal insights into the functional relevance of BACL in the context of its neuronal expression

Methylglyoxal induces platelet hyperaggregation and reduces thrombus stability by activating PKC and inhibiting PI3K/Akt pathway

Diabetes is characterized by a dysregulation of glucose homeostasis and platelets from patients with diabetes are known to be hyper-reactive and contribute to the accelerated development of vascular diseases. Since many of the deleterious effects of glucose have been attributed to its metabolite methylgyloxal (MG) rather than to hyperglycemia itself, the aim of the present study was to characterize the effects of MG on platelet function. Washed human platelets were pre-incubated for 15 min with MG and platelet aggregation, adhesion on matrix-coated slides and signaling (Western blot) were assessed ex vivo. In vivo, the effect of MG on thrombus formation was determined using the FeCl3-induced carotid artery injury model. MG potentiated thrombin-induced platelet aggregation and dense granule release, but inhibited platelet spreading on fibronectin and collagen. In vivo, MG accelerated thrombus formation but decreased thrombus stability. At the molecular level, MG increased intracellular Ca2+ and activated classical PKCs at the same time as inhibiting PI3K/Akt and the β3-integrin outside-in signaling. In conclusion, these findings indicate that the enhanced MG concentration measured in diabetic patients can directly contribute to the platelet dysfunction associated with diabetes characterized by hyperaggregability and reduced thrombus stability

A Micromechanics-based Multiscale Approach toward Continental Deformation, with Application to Ductile High-Strain Zones and Quartz Flow Laws

Earth’s lithosphere may be regarded as a composite material made of rheologically heterogeneous elements. The presence of these heterogeneous elements causes flow partitioning, making the deformation of Earth’s lithosphere heterogeneous on all observation scales. Understanding the multiscale heterogeneous deformation and the overall rheology of the lithosphere is very important in structural geology and tectonics. The overall rheology of Earth’s lithosphere on a given observation scale must be obtained from the properties of all constituents and may evolve during the deformation due to the fabric development. Both the problem of flow partitioning and characterization of the overall rheology are closely related and require a fully mechanical multiscale approach. This thesis refines a micromechanics-based multiscale modeling approach called the self-consistent MultiOrder Power Law Approach (MOPLA). MOPLA treats the heterogeneous rock mass as a continuum of rheologically distinct elements. The rheological properties and the mechanical fields of the constituent elements and those of the composite material are computed by solving partitioning and homogenization equations self-consistently. The algorithm of MOPLA has been refined and implemented in MATLAB for high-performance computing. The micromechanical approach is used to investigate the deformation of ductile high-strain zones, advancing previous work on this subject to a full mechanical level. This thesis considers a ductile high-strain zone as a flat heterogeneous inclusion embedded in the ductile lithosphere subjected to a tectonic deformation due to remote plate motion. The kinematic and the mechanical fields inside and outside the high-strain zone, including the finite strain accumulation in there, are solved by partitioning equations. The overall rheology of the high-strain zone is obtained by means of a self-consistent homogenization scheme. Understanding the continental rheology requires an accurate quartz dislocation creep flow law. Despite decades of experimental studies, there are considerable discrepancies in quartz flow law parameters. This thesis proposes that the discrepancies could be explained by considering both the pressure effect on the activation enthalpy and the slip system dependence of the stress exponent. Two distinct dislocation creep flow laws corresponding to two dominant slip systems are determined based on the current dataset of the creep experiments on quartz samples

Potent neutralization by monoclonal human IgM against SARS-CoV-2 is impaired by class switch.

To investigate the class-dependent properties of anti-viral IgM antibodies, we use membrane antigen capture activated cell sorting to isolate spike-protein-specific B cells from donors recently infected with SARS-CoV-2, allowing production of recombinant antibodies. We isolate 20, spike-protein-specific antibodies of classes IgM, IgG, and IgA, none of which shows any antigen-independent binding to human cells. Two antibodies of class IgM mediate virus neutralization at picomolar concentrations, but this potency is lost following artificial switch to IgG. Although, as expected, the IgG versions of the antibodies appear to have lower avidity than their IgM parents, this is not sufficient to explain the loss of potency

Analysis of Hypersonic Boundary Layer Turbulence by Means of Focused Laser Differential Interferometry

This thesis investigates a hypersonic turbulent boundary layer over a cone with cold walls and a sharp nose tip. The analyses include frequency spectra of density fluctuations up to a frequency of 10 MHz, as well as an analysis of their convection velocities, at multiple wall-normal locations inside the boundary layer and in the near field above it. Experimental measurements are obtained under Mach 7.4 and unit Reynolds number 4.2 · 10^6 m−1 in the free-piston driven High Enthalpy Shock Tunnel Göttingen (HEG), using the optical technique of Focused Laser Differential Interferometry (FLDI). A method is proposed to accurately measure the separation distance between the probes of multi-foci FLDI, to allow reliable measurements of convection velocities using cross-correlation between the signals. The method is based on the detection of a propagating weak blast wave generated by an electric spark, and is verified to have similar accuracy and precision than the method of directly imaging the beams, but exhibits increased flexibility. Convection velocities measured in the near field of the hypersonic boundary layer are in agreement with free stream data reported in the literature at similar Mach numbers. The measured frequency spectra of hypersonic turbulent boundary layer density fluctuations show regions with well-defined power laws typical for pressure fluctuations. These spectra are compared with Large-Eddy Simulation (LES) results for a conical turbulent boundary layer, calculated at the experimental test conditions. Direct comparisons are performed by simulating the FLDI response in the numeric flow field, by means of computational FLDI (cFLDI). The cFLDI algorithm is validated using the same blast wave measurements obtained when measuring the separation distance between FLDI probes. To that end, an analytic methodology is proposed to reconstruct the pressure waveform of the spherical blast wave, when detected with the straightline FLDI. Independence between the cFLDI algorithm and the reconstruction formulation allow the cFLDI code to be validated once the computational response of the reconstructed flow field and the experimental data that generated it are in agreement. The results of the direct comparison between the hypersonic turbulent conical boundary layer frequency spectra calculated with LES and experimentally probed in HEG are in reasonable agreement, once the bandwidth constraints of each are adequately considered. It is also verified that in the present case, in which the divergence of the FLDI beams in the probed region is small, the complex cFLDI algorithm may be substituted by a simple line integral of density variations in the numeric flow field, without significant losses. These observations offer a framework for practical numerical and experimental comparisons, which are necessary to validate simulations and turbulence models. The results of this thesis will help to overcome the current lack of experimental data concerning high-speed turbulent flows, especially at high frequencies