Yusuke Takahashi

Absence of CD14 Delays Progression of Prion Diseases Accompanied by Increased Microglial Activation

ABSTRACT Prion diseases are fatal neurodegenerative disorders characterized by accumulation of PrPSc, vacuolation of neurons and neuropil, astrocytosis, and microglial activation. Upregulation of gene expressions of innate immunity-related factors, including complement factors and CD14, is observed in the brains of mice infected with prions even in the early stage of infections. When CD14 knockout (CD14−/−) mice were infected intracerebrally with the Chandler and Obihiro prion strains, the mice survived longer than wild-type (WT) mice, suggesting that CD14 influences the progression of the prion disease. Immunofluorescence staining that can distinguish normal prion protein from the disease-specific form of prion protein (PrPSc) revealed that deposition of PrPSc was delayed in CD14−/− mice compared with WT mice by the middle stage of the infection. Immunohistochemical staining with Iba1, a marker for activated microglia, showed an increased microglial activation in prion-infected CD14−/− mice compared to WT mice. Interestingly, accompanied by the increased microglial activation, anti-inflammatory cytokines interleukin-10 (IL-10) and transforming growth factor β (TGF-β) appeared to be expressed earlier in prion-infected CD14−/− mice. In contrast, IL-1β expression appeared to be reduced in the CD14−/− mice in the early stage of infection. Double immunofluorescence staining demonstrated that CD11b- and Iba1-positive microglia mainly produced the anti-inflammatory cytokines, suggesting anti-inflammatory status of microglia in the CD14−/− mice in the early stage of infection. These results imply that CD14 plays a role in the disease progression by suppressing anti-inflammatory responses in the brain in the early stage of infection.

Examination of Radio Frequency Blackout for an Inflatable Vehicle During Atmospheric Reentry

Numerical simulations of the plasma flow and electromagnetic wave around a membrane-aeroshell type reentry vehicle were performed using various physical model combinations, and the possibility of radio frequency blackout of transceiver antenna embedded at the rear of the vehicle was investigated. The flowfield was assumed to be in thermochemical nonequilibrium, and it was described by the Navier–Stokes equations with a multitemperature model and the equation of state. The simulations were performed for several altitudes, including the highest heat flux point according to reentry orbit data. Through these computations, the detailed distributions of the flowfield properties in the shock layer and wake region were successfully obtained. To evaluate the possibility of radio frequency blackout during atmospheric reentry, the distribution of the electron number density around the inflatable vehicle was clarified. A frequency-dependent finite-difference time-domain method was used for simulations of electromagne...

Advanced validation of CFD-FDTD combined method using highly applicable solver for reentry blackout prediction

An analysis model of plasma flow and electromagnetic waves around a reentry vehicle for radio frequency blackout prediction during aerodynamic heating was developed in this study. The model was validated based on experimental results from the radio attenuation measurement program. The plasma flow properties, such as electron number density, in the shock layer and wake region were obtained using a newly developed unstructured grid solver that incorporated real gas effect models and could treat thermochemically non-equilibrium flow. To predict the electromagnetic waves in plasma, a frequency-dependent finite-difference time-domain method was used. Moreover, the complicated behaviour of electromagnetic waves in the plasma layer during atmospheric reentry was clarified at several altitudes. The prediction performance of the combined model was evaluated with profiles and peak values of the electron number density in the plasma layer. In addition, to validate the models, the signal losses measured during communication with the reentry vehicle were directly compared with the predicted results. Based on the study, it was suggested that the present analysis model accurately predicts the radio frequency blackout and plasma attenuation of electromagnetic waves in plasma in communication.

Prediction Performance of Blackout and Plasma Attenuation in Atmospheric Reentry Demonstrator Mission

A numerical simulation model that combines the plasma flows and electromagnetic waves around a reentry vehicle during atmospheric reentry was developed to evaluate the radio frequency blackout and plasma attenuation. The physical properties of the plasma flow in the shock layer and wake region were obtained using a computational fluid dynamics technique. The electromagnetic waves were expressed using a frequency-dependent finite difference time domain method with the plasma properties. Combined simulations were performed for the atmospheric reentry demonstrator of the ESA at various altitudes based on reentry orbit data. The electromagnetic wave behaviors around the vehicle during atmospheric reentry were investigated in detail. Moreover, a parametric analysis with different ionization reaction models was performed. It was confirmed that the vehicle is surrounded by the plasma and the propagation of the electromagnetic waves is prevented at high altitude. Then, the plasma is dissipated and the propagation...

Aerodynamic Heating Around Flare-Type Membrane Inflatable Vehicle in Suborbital Reentry Demonstration Flight

A demonstration flight of an advanced reentry vehicle was carried out using a sounding rocket. The vehicle was equipped with a flexible (membrane) aeroshell deployed by an inflatable torus structure. Its most remarkable feature was the low ballistic coefficient that enables reduction in aerodynamic heating and deceleration at a high altitude. During the suborbital reentry, temperatures at several locations on a backside of the flexible aeroshell and inside the capsule were measured by means of embedded thermocouples. The aerodynamic heating behavior of the vehicle was investigated using the measured temperature history, in combination with a numerical prediction in which a flow-field simulation of the heating was conducted. In this flow-field simulation, both laminar flow and turbulent flow were assumed, and the deformation of the flexible aeroshell was considered. A thermal model of the capsule and membrane aeroshell was developed, and the heat flux profiles of the vehicle surface during aerodynamic heat...

Numerical Investigation of Flow Fields in Inductively Coupled Plasma Wind Tunnels

Numerical simulations of 10 kW and 110 kW inductively coupled plasma (ICP) wind tunnels were carried out to study physical properties of the flow inside the ICP torch and vacuum chamber with air as the working gas. Two-dimensional compressible axisymmetric Navier-Stokes (N-S) equations that took into account 11 species and 49 chemical reactions of air, were solved. A heat source model was used to describe the heating phenomenon instead of solving the electromagnetic equations. In the vacuum chamber, a four-temperature model was coupled with N-S equations. Numerical results for the 10 kW ICP wind tunnel are presented and discussed in detail as a representative case. It was found that the plasma flow in the vacuum chamber tended to be in local thermochemical equilibrium. To study the influence of operation conditions on the flow field, simulations were carried out for different chamber pressures and/or input powers. The computational results for the above two ICP wind tunnels were compared with corresponding experimental data. The computational and experimental results agree well, therefore the flow fields of ICP wind tunnels can be clearly understood.

Aerodecelerator Performance of Flare-Type Membrane Inflatable Vehicle in Suborbital Reentry

A flight experiment of an inflatable reentry vehicle, equipped with a thin-membrane aeroshell deployed by an inflatable torus structure, was performed using a Japan Aerospace Exploration Agency S-3...

Flow-field differences and electromagnetic-field properties of air and N2 inductively coupled plasmas

A numerical model for simulating air and nitrogen inductively coupled plasmas (ICPs) was developed considering thermochemical nonequilibrium and the third-order electron transport properties. A modified far-field electromagnetic model was introduced and tightly coupled with the flow field equations to describe the Joule heating and inductive discharge phenomena. In total, 11 species and 49 chemical reactions of air, which include 5 species and 8 chemical reactions of nitrogen, were employed to model the chemical reaction process. The internal energy transfers among translational, vibrational, rotational, and electronic energy modes of chemical species were taken into account to study thermal nonequilibrium effects. The low-Reynolds number Abe-Kondoh-Nagano k-e turbulence model was employed to consider the turbulent heat transfer. In this study, the fundamental characteristics of an ICP flow, such as the weak ionization, high temperature but low velocity in the torch, and wide area of the plasma plume, wer...

Development of flare-type inflatable membrane aeroshell for reentry demonstration from LEO

An inflatable decelerator is promising for a next generation atmospheric-entry system, because it can be packed compactly in the launch and cruise phase and it can be deployed to a large aerodynamic device in the atmospheric-entry phase. Our group has researched and developed this technology since 2000, focusing on a flare-type membrane aeroshell sustained by a single inflatable ring, especially. In our activity, the re-entry demonstration using a Japanese S-310 sounding rocket was carried out successfully in 2012. As a next millstone of our research and development, the re-entry demonstration from the low earth orbit is planned utilizing an opportunity for piggy-back satellites. The overview of the planned reentry demonstration is introduced in this paper. There are several important technical issues to overcome in order to realize this demonstration. Two important issues of these is also introduced. First topic is the structural strength tests using a low-speed wind tunnel to understand the structural strength of a large flare-type membrane aeroshell supported by a single inflatable ring. Second topic is an evaluation on the thermal durability of inflatable structures using a newly developed inductively coupled plasma heater.

Reentry blackout prediction for atmospheric reentry demonstrator mission considering uncertainty in chemical reaction rate model

A numerical simulation model of plasma flows and electromagnetic waves around a vehicle was developed to predict a radio frequency blackout. Plasma flows in the shock layer and the wake region were calculated using a computational fluid dynamics technique with a three-dimensional model. A finite-catalytic wall condition known to affect plasma properties, such as the number density of electrons, was considered for accurate prediction. A parametric study was performed to investigate the effect of uncertainty in the chemical reaction rate model on evaluating a radio frequency blackout. The behavior of electromagnetic waves in plasma was investigated using a frequency-dependent finite-difference time-domain method. Numerical simulations of reentry blackout were performed for the Atmospheric Reentry Demonstrator mission at various altitudes. The plasma flows and the complex movement of electromagnetic waves around the Atmospheric Reentry Demonstrator vehicle were clarified. The predicted signal loss profile wa...