Abstract:
The micromixer, which has a rotor with a curved channel, is studied experimentally. The secondary flow in a curved channel of rectangular cross-section is investigated using PIV (Particle Image Velocimetry) and LIF (Laser Induced Fluorescence) methods. Two walls of the channel (the inner and top walls) rotate around the center of curvature and a pressure gradient is imposed in the direction of the exit of the channel. The non-dimensional channel curvature δ=a/R is taken to be about 0.1, where 2a is the width of the channel, R the curvature radius of the channel. Other non-dimensional parameters concerned are the Dean number De=Reδ^{1/2}, the Reynolds number Re=qd_{h}/v, where q is the mean flow velocity in the channel axis direction, ν the kinematic viscosity, dh the hydraulic diameter of the channel, and the Taylor number Tr=2(2δ)^{1/2}Ωa^{2}/(δv), where Ω is the angular velocity of the rotor. Photographs of the flow in a cross-section at 180° downstream from the curved channel entrance are taken by changing the flux (De) at a constant rotational speed (Tr) of the channel walls. It is found that good mixing performance is obtained in the case of De≤0.1|Tr| and for that case secondary flows show chaotic behaviors. And then we have confirmed the occurrence of reversal of the mean axial flow.

Infertility is often cited as one of the causes of a declining birthrate, which has become a serious social problem in recent years. Processes by which motile sperm can be safely and easily sorted are therefore important for infertility treatment. Therefore, as a new sorting method, microfluidic sperm sorter using the microfluidic system has been developed. To improve more separation efficiency of this device, it is necessary to know the behaviors of motile sperm in the microchannel where the sperm undergo shear flow. The previous study implied the necessity of the modeling of motile sperm in the shear flow. In the present study, therefore, we experimentally investigated the behavior of the motile sperm in the Taylor-Couette flow using PTV (Particle Tracking Velocimetry) method. The experimental results showed that the ascent of the shear stress led to the increase in the sperm velocity, and the direction of the sperm velocity was opposite to that of the flow.

The flowable latent heat storage material like Oil/Water type emulsion, microencapsulated latent heat material-water mixture or ice slurry, etc., is enabled to transport the latent heat in a pipe. Supercooling phenomenon of the dispersed latent heat storage material in continuous phase is obstructed by a latent heat storage. The latent heat storage rates of dispersed waterdrops in W/O (Water/Oil) emulsion are investigated experimentally in this study. The waterdrops in emulsion have the diameter within 3 - 25μm, the averaged diameter of waterdrops is 7.3μm and the standard deviation is 2.9μm. Supercooling release of waterdrops in emulsion is examined by short time impressing of the ultrasonic. The direct contact heat exchange method is chosen as the phase change rate evaluation of waterdrops in W/O emulsion. The supercooled temperature is set as parameters of this study. The previous obtained experimental result, as the condition without impressing ultrasonic wave, showed that the 35K or more degree from melting point brings 100% latent heat storage rate of W/O emulsion. It is clarified that it is possible to reduce 20K of supercooling degree by impressing the ultrasonic.

Abstract:
Use of the low temperature (less than 100°C) energy contributes to effective use of heat resources. The cost recovery by power generation is difficult by using an existing system (the binary cycle or the thermoelectric conversion element), because the initial investment is large. The final purpose of this research is development of the low temperature difference drive engine supposing use in a hot-springs resort as a power source for electric power generation. In order that a traveler may look at and delight a motion of an engine, it is made to drive at low-speed number of rotations. An engine cycle of this study is aimed at the development of Stirling cycle engine which can maintain high efficiency in small size. This kind of engine has simple structure; it brings low cost, and it is easy to perform maintenance. However, it is difficult to obtain enough output by this type of engine, because of its low temperature difference. This paper deals with the heat transfer characteristic that the working fluid including a phase change material flows into the heating surface from the narrow path. In order to increase the amount of the heat transmission, Diethylether is added to the working fluid. Diethylether is selected as a phase change material (PCM) that has the boiling point which exists between the heat source of high temperature and low temperature. The parameters of the experiment are additive amount of PCM, rotational speed of the displacer piston and temperature of heat transfer surface. It is shown that it is possible to make exchange of heat amount increase by adding phase change material. The result of this research shows the optimal condition of the difference in temperature in heat processing, number of revolutions, and addition concentration of PCM.

Abstract:
Chaotic mixing in a curved-square channel flow is studied experimentally and numerically. Two walls of the channel (inner and top walls) rotate around the center of curvature and a pressure gradient is imposed in the direction toward the exit of the channel. This flow is a kind of Taylor-Dean flows. There are two parameters dominating the flow, the Dean number De (∝ the pressure gradient or the Reynolds number) and the Taylor number Tr (∝ the angular velocity of the wall rotation). In the present paper, we analyze the physical mechanism of chaotic mixing in the Taylor-Dean flow by comparing experimental and numerical results. We produced a micromixer model of the curved channel several centimeters long with square cross section of a few millimeters side. The secondary flow was measured using laser induced fluorescence (LIF) method to examine secondary flow characteristics. We also performed three-dimensional numerical simulations for the exactly same configuration as the experimental system to study the mechanism of chaotic mixing. It is found that good mixing performance is achieved for the case of De ≤ 0.1Tr, and that mixing efficiency changes according to the difference in inflow conditions. The flow is studied both experimentally and numerically, and both results agree with each other very well.

Abstract:
Chaotic mixing in three different types of curved-rectangular channels flow has been studied experimentally and numerically. Two walls of the channel (inner and top walls) rotate around the center of curvature and a pressure gradient are imposed in the direction toward the exit of the channel. This flow is a kind of Taylor-Dean flow. There are two parameters dominating the flow, the Dean number De (∝ the pressure gradient or the Reynolds number) and the Taylor number Tr (∝ the angular velocity of the wall rotation). In this paper, we analyze the physical mechanism of chaotic mixing in the Taylor-Dean flow by comparing experimental results and numerical ones. We produced three micromixer models of the curved channel, several centimeters long, with rectangular cross-section of a few millimeters side. The secondary flow is measured using laser induced fluorescence (LIF) method to examine secondary flow characteristics. Also we performed three-dimensional numerical simulations with the open source CFD solver, OpenFOAM, for the same configuration as the experimental system to study the mechanism of chaotic mixing. It is found that good mixing performance is obtained in the case of De ≤ 0.1 Tr, and it becomes more remarkable when the aspect ratio tends to large. And it is found that the mixing efficiency changes according to the aspect ratio and inflow condition.

The vaccination of one person may prevent another from becoming
infected, either because the vaccine may prevent the first person from
acquiring the infection and thereby reduce the probability of transmission to
the second, or because, if the first person is infected, the vaccine may impair
the ability of the infectious agent to initiate new infections. The former
mechanism is referred as a contagion effect and the latter is referred as an
infectiousness effect. By applying a principal stratification approach, the
conditional infectiousness effect has been defined, but the contagion effect is
not defined using this approach. Recently, new definitions of unconditional
infectiousness and contagion effects were provided by applying a mediation
analysis approach. In addition, a simple relationship between conditional and
unconditional infectiousness effects was found under a number of assumptions.
These two infectiousness effects can be assessed by very simple estimation and
sensitivity analysis methods under the assumptions. Nevertheless, such simple
methods to assess the contagion effect have not been discussed. In this paper,
we review the methods of assessing infectiousness effects, and apply them to
the inference of the contagion effect. The methods provided here are
illustrated with hypothetical vaccine trial data.

Abstract:
The main purpose in many randomized trials
is to make an inference about the average causal effect of a treatment.
Therefore, on a binary outcome, the null hypothesis for the hypothesis test
should be that the causal risks are equal in the two groups. This null
hypothesis is referred to as the weak causal null hypothesis. Nevertheless, at
present, hypothesis tests applied in actual randomized trials are not for this
null hypothesis; Fisher’s exact test is a test for the sharp causal null
hypothesis that the causal effect of treatment is the same for all subjects. In
general, the rejection of the sharp causal null hypothesis does not mean that
the weak causal null hypothesis is rejected. Recently, Chiba developed new
exact tests for the weak causal null hypothesis: a conditional exact test,
which requires that a marginal total is fixed, and an unconditional exact test,
which does not require that a marginal total is fixed and depends rather on the
ratio of random assignment. To apply these exact tests in actual randomized
trials, it is inevitable that the sample size calculation must be performed
during the study design. In this paper, we present a sample size calculation
procedure for these exact tests. Given the sample size, the procedure can
derive the exact test power, because it examines all the patterns that can be
obtained as observed data under the alternative hypothesis without large sample
theories and any assumptions.

Abstract:
Researchers conducting randomized clinical trials
with two treatment groups sometimes wish to determine whether biomarkers are
predictive and/or prognostic. They can use regression models with interaction
terms to assess the role of the biomarker of interest. However, although the
interaction term is undoubtedly a suitable measure for prediction, the optimal
way to measure prognosis is less clear. In this article, we define causal
measures that can be used for prognosis and prediction based on biomarkers.The
causal measure for prognosis is defined as the average of two differences in
status between biomarker-positive and -negative subjects under treatment and
control conditions. The causal measure for
prediction is defined as the difference between the causal effect of the
treatment for biomarker-positive and biomarker-negative subjects. We also explain the relationship between the proposed measures and the
regression parameters. The causal measure for prognosis corresponds to the terms
for the biomarker in a regression model, where the values of the dummy variables
representing the explanatory variables are -1/2 or 1/2. The causal measure for prediction is simply the causal effect
of the interaction term in a regression model. In addition, for a binary
outcome, we express the causal measures in
terms of four response types: always-responder, complier, non-complier,
and never-responder. The causal measure for prognosis can be expressed as a function
of always- and never-responders, and the causal measure for prediction as a
function of compliers and non-compliers. This enables us to demonstrate that
the proposed measures are plausible in the case of a binary outcome. Our causal measures should be used to assess whether
a biomarker is prognostic and/or predictive.

Abstract:
Stressful stimuli induced by immobilization are perceived as acute stress in rats. This acute stress activates corticotropin-releasing hormone (CRH) neurons in the hypothalamic paraventricular nucleus (PVN), resulting in stimulation of the hypothalamic-pituitary-adrenal (HPA) axis. The ventral ascending noradrenergic bundles (V-NAB) from the brainstem innervate the PVN. To investigate the relationship between the response of the HPA axis and the V-NAB, we examined changes in plasma corticosterone, the final output of the HPA axis, and extracellular noradrenaline (NA) in the PVN following immobilization stress in rats that received bilateral 6-hydroxydopamine (6-OHDA) lesions of the V-NAB. 6-OHDA microinjection into the V-NAB reduced the magnitude of the responses of plasma corticosterone and extracellular NA in the PVN following immobilization stress. Our results suggest that V-NAB innervation of the PVN is involved in immobilization stress-induced activation of the HPA axis.