Multi-time-lag PIV analysis of steady and pulsatile flows in a sidewall aneurysm

The effect of inflow waveform on the hemodynamics of a real-size idealized sidewall intracranial aneurysm (IA) model was investigated using particle imaging velocimetry (PIV). For this purpose, we implemented an error analysis based on several PIV measurements with different time lags to ensure high precision of velocity fields measured in both the IA and the parent artery. The relative error measured in the main part of the circulating volume was <1% despite the three orders of magnitude difference of parent artery and IA dome velocities. Moreover, important features involved in IA evolution were potentially emphasized from the qualitative and quantitative flow pattern comparison resulting from steady and unsteady inflows. In particular, the flow transfer in IA and the vortical structure were significantly modified when increasing the number of harmonics for a typical physiological flow, in comparison with quasi-steady conditions

Multi-time-lag PIV analysis of steady and pulsatile flows in a sidewall aneurysm

The effect of inflow waveform on the hemodynamics of a real-size idealized sidewall intracranial aneurysm (IA) model was investigated using particle imaging velocimetry (PIV). For this purpose, we implemented an error analysis based on several PIV measurements with different time lags to ensure high precision of velocity fields measured in both the IA and the parent artery. The relative error measured in the main part of the circulating volume was <1 % despite the three orders of magnitude difference of parent artery and IA dome velocities. Moreover, important features involved in IA evolution were potentially emphasized from the qualitative and quantitative flow pattern comparison resulting from steady and unsteady inflows. In particular, the flow transfer in IA and the vortical structure were significantly modified when increasing the number of harmonics for a typical physiological flow, in comparison with quasi-steady conditions

Evaluation of a Desktop 3D Printed Rigid Refractive-Indexed-Matched Flow Phantom for PIV Measurements on Cerebral Aneurysms

Purpose Fabrication of a suitable flow model or phantom is critical to the study of biomedical fluid dynamics using optical flow visualization and measurement methods. The main difficulties arise from the optical properties of the model material, accuracy of the geometry and ease of fabrication. Methods Conventionally an investment casting method has been used, but recently advancements in additive manufacturing techniques such as 3D printing have allowed the flow model to be printed directly with minimal post-processing steps. This study presents results of an investigation into the feasibility of fabrication of such models suitable for particle image velocimetry (PIV) using a common 3D printing Stereolithography process and photopolymer resin. Results An idealised geometry of a cerebral aneurysm was printed to demonstrate its applicability for PIV experimentation. The material was shown to have a refractive index of 1.51, which can be refractive matched with a mixture of de-ionised water with ammonium thiocyanate (NH4SCN). The images were of a quality that after applying common PIV pre-processing techniques and a PIV cross-correlation algorithm, the results produced were consistent within the aneurysm when compared to previous studies. Conclusions This study presents an alternative low-cost option for 3D printing of a flow phantom suitable for flow visualization simulations. The use of 3D printed flow phantoms reduces the complexity, time and effort required compared to conventional investment casting methods by removing the necessity of a multi-part process required with investment casting techniques

The Crystal Barrel: Meson Spectroscopy at LEAR with a 4π\pi Detector

% PS197 \\ \\The Crystal Barrel is a 4$\pi$ spectrometer designed to provide complete and precise information on practically every final state produced in $\bar{p} p$ and $\bar{p}d$ annihilations at low energy and to collect high statistics data samples. Selective triggers can be applied when necessary. \\ \\The physics goal is to identify all light mesons in the mass range from 0.14 to 2.3~GeV/c$^{2}$, to determine their quantum numbers and decay properties and to study the annihilation dynamics. The main interest is to find the glueball and hybrid degrees of freedom predicted in the framework of Quantum Chromodynamics. \\ \\\noindent The principal components of the apparatus are: \begin{enumerate}[1.] \item A barrel shaped electromagnetic calorimeter for the detection of photons. It consists of 1380~CsI(Tl) crystals read out by photodiodes via wavelength shifter. \item A 22-layer cylindrical jet drift chamber for the tracking of charged particles. It contains 585 sense wires read out at both ends. Charge division provides information on the coordinate parallel to the wires and the total charge deposit is used to measure dE/dx. \\ \\\item A silicon $\mu$-strip vertex dectector to provide a multiplicity trigger very close to the target and to improve the momentum and vertex resolution. It is subdivided into 15~modules, each with 128 strips and surrounds the target at a radius of 1.2~cm. \\ \\\item The incoming cooled antiprotons (beam momenta from 0.1 to 1.9~GeV/c) are detected by silicon hodoscopes. The whole detector is embedded in a solenoidal magnet with field strength up to 1.5~T

Lattice-Gas Cellular Automaton Models for Biology: From Fluids to Cells

Lattice-gas cellular automaton (LGCA) and lattice Boltzmann (LB) models are promising models for studying emergent behaviour of transport and interaction processes in biological systems. In this chapter, we will emphasise the use of LGCA/LB models and the derivation and analysis of LGCA models ranging from the classical example dynamics of fluid flow to clotting phenomena in cerebral aneurysms and the invasion of tumour cells

Thrombosis modeling in intracranial aneurysms: a lattice Boltzmann numerical algorithm

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Neuroprotection against Amyloid-<i>β</i>-Induced DNA Double-Strand Breaks Is Mediated by Multiple Retinoic Acid-Dependent Pathways

In this study, we have investigated the role of all-trans-retinoic acid (RA) as a neuroprotective agent against Aβ1-42-induced DNA double-strand breaks (DSBs) in neuronal SH-SY5Y and astrocytic DI TNC1 cell lines and in murine brain tissues, by single-cell gel electrophoresis. We showed that RA does not only repair Aβ1-42-induced DSBs, as already known, but also prevents their occurrence. This effect is independent of that of other antioxidants studied, such as vitamin C, and appears to be mediated, at least in part, by changes in expression, not of the RARα, but of the PPARβ/δ and of antiamyloidogenic proteins, such as ADAM10, implying a decreased production of endogenous Aβ. Whereas Aβ1-42 needs transcription and translation for DSB production, RA protects against Aβ1-42-induced DSBs at the posttranslational level through both the RARα/β/γ and PPARβ/δ receptors as demonstrated by using specific antagonists. Furthermore, it could be shown by a proximity ligation assay that the PPARβ/δ-RXR interactions, not the RARα/β/γ-RXR interactions, increased in the cells when a 10 min RA treatment was followed by a 20 min Aβ1-42 treatment. Thus, the PPARβ/δ receptor, known for its antiapoptotic function, might for these short-time treatments play a role in neuroprotection via PPARβ/δ-RXR heterodimerization and possibly expression of antiamyloidogenic genes. Overall, this study shows that RA can not only repair Aβ1-42-induced DSBs but also prevent them via the RARα/β/γ and PPARβ/δ receptors. It suggests that the RA-dependent pathways belong to an anti-DSB Adaptative Gene Expression (DSB-AGE) system that can be targeted by prevention strategies to preserve memory in Alzheimer’s disease and aging.</jats:p