Micro T-Mixer with Baffles: Effect of Baffle Height and Setting Angle on Mixing

Chaotic mixing in eight different types of micro T-mixer flow has been studied experimentally and numerically. The present experimental study was performed to visualize two-liquid flows in a micro T-mixer with baffles. The Reynolds number, baffle height and setting angle were varied to investigate their effect on the mixing performance. Three micro T-mixer models were produced, which are several centimeters long and have a rectangular cross-section of few millimeters a side. The mixing of two-liquid was measured using the laser induced fluorescence (LIF) technique. Moreover, three-dimensional numerical simulations were conducted with the open-source CFD solver, OpenFOAM, for the same configuration as used in the experiments to investigate the detailed mechanism of the chaotic mixing. As a result, it was found that the mixing of two-liquid is greatly improved in the micro T-mixer with baffle. The baffle height and setting angle show a significant influence on the mixing performance.

Pulmonary tumor thrombotic microangiopathy of hepatocellular carcinoma: A case report and review of literature

BACKGROUND Pulmonary tumor thrombotic microangiopathy(PTTM)is a rare condition in patients with hepatocellular carcinoma(HCC);to date,few cases have been reported.While hepatic dysfunction has been focused on the later stages of HCC,the management of symptoms in PTTM is important for supportive care of the cases.For the better understanding of PTTM in HCC,the information of our recent case and reported cases have been summarized.CASE SUMMARY A patient with HCC exhibited acute and severe respiratory failure.Radiography and computed tomography of the chest revealed the multiple metastatic tumors and a frosted glass–like shadow with no evidence of infectious pneumonia.We diagnosed his condition as acute respiratory distress syndrome caused by the lung metastases and involvement of the pulmonary vessels by tumor thrombus.Administration of prednisolone to alleviate the diffuse alveolar damages including edematous changes of alveolar wall caused by the tumor cell infiltration and ischemia showed mild improvement in his symptoms and imaging findings.An autopsy showed the typical pattern of PTTM in the lung with multiple metastases.CONCLUSION PTTM is caused by tumor thrombi in the arteries and thickening of the pulmonary arterial endothelium leading to the symptoms of dyspnea in terminal staged patients.Therefore,supportive management of symptoms is necessary in the cases with PTTM and hence we believe that the information presented here is of great significance for the diagnosis and management of symptoms of PTTM with HCC.

Rational arrangement of measuring shear wave speed in the liver

BACKGROUND Shear wave speed has been widely applied to quantify a degree of liver fibrosis. However, there is no standardized procedure, which makes it difficult to utilize the speed universally. AIM To provide procedural standardization of shear wave speed measurement. METHODS Point shear wave elastography (pSWE) was measured in 781 patients, and twodimensional shear wave elastography (2dSWE) was measured on the same day in 18 cases. Regions-of-interest were placed at 12 sites, and the median and robust coefficient-of-variation (CVR) were calculated. A residual sum-of-square (Σdi2) was computed for bootstrap values of 1000 iterations in 18 cases with each assumption of 1 to 12 measurements. The proportion of the Σdi2 (%Σdi2) was calculated as the ratio of Σdi2 to pSWE after converting it based on the correlation between pSWE and 2dSWE. RESULTS The CVR showed a significantly broader distribution in the left lobe (P < 0.0001),and the smallest CVR in the right anterior segment that covered 95% cases was 40.4%. pSWE was significantly higher in the left lobe than in the right lobe (1.63 ± 0.78 m/s vs 1.61 ± 0.78 m/s, P = 0.0004), and the difference between the lobes became further discrete when the subjects were limited to the cases with a CVR less than 40.4% in any segment (1.76 ± 0.80 m/s vs 1.70 ± 0.82 m/s, P < 0.0001). The highest values of the CVR in every 0.1 m/s interval were plotted in convex upward along pSWE and peaked at 1.93 m/s. pSWE and 2dSWE were significantly correlated (P < 0.0001, r = 0.95). In 216000 resamples from 18 cases, the %Σdi2 of 12 sites was 8.0% and gradually increased as the acquisition sites decreased to reach a significant difference with a %Σdi2 of 7 sites (P = 0.027). CONCLUSION These data suggest that shear wave speed should be measured at 8 or more sites of spreading in both lobes.

Methotrexate-related lymphoproliferative disorders in the liver: Case presentation and mini-review

BACKGROUND Immunosuppression is effective in treating a number of diseases,but adverse effects such as bone marrow suppression,infection,and oncogenesis are of concern.Methotrexate is a key immunosuppressant used to treat rheumatoid arthritis.Although it is effective for many patients,various side effects have been reported,one of the most serious being methotrexate-related lymphoproliferative disorder.While this may occur in various organs,liver involvement is rare.Information on these liver lesions,including clinical characteristics,course,and imaging studies,has not been summarized to date.CASE SUMMARY We present a case of 70-year-old woman presented with a 2-wk history of fever and abdominal pain.She had had rheumatoid arthritis for 5 years and was being treated with medication including methotrexate.Contrast-enhanced computed tomography revealed multiple low density tumors in the liver and the histological analyses showed significant proliferation of lymphocytes in masses that were positive on immunohistochemical staining for CD3,CD4,CD8,and CD79a but negative for CD20 and CD56.Staining for Epstein-Barr virus-encoded RNA was negative.And based on these findings,the liver tumors were diagnosed as Methotrexate-related lymphoproliferative disorders.A timedependent disappearance of the liver tumors after stopping methotrexate supported the diagnoses.CONCLUSION The information obtained from our case and a review of 9 additional cases reported thus far assist physicians who may face the challenge of diagnosing and managing this disorder.

Gravity assistance enables liver stiffness measurements to detect liver fibrosis under congestive circumstances

BACKGROUND As survival has been prolonged owing to surgical and medical improvements,liver failure has become a prognostic determinant in patients with congestive heart diseases.Congestive hepatopathy,an abnormal state of the liver as a result of congestion,insidiously proceed toward end-stage liver disease without effective biomarkers evaluating pathological progression.Regular measurements of shear wave elastography cannot qualify liver fibrosis,which is a prognosticator in any type of chronic liver disease,in cases of congestion because congestion makes the liver stiff without fibrosis.We hypothesized that the effects of congestion and fibrosis on liver stiffness can be dissociated by inducing architectural deformation of the liver to expose structural rigidity.To establish a strategy measuring liver stiffness as a reflection of architectural rigidity under congestion.METHODS Two-dimensional shear wave elastography(2dSWE)was measured in the supine(Sp)and left decubitus(Ld)positions in 298 consecutive cases as they were subjected to an ultrasound study for various liver diseases.Regions of interest were placed at twelve sites,and the median and robust coefficient of variation were calculated.Numerical data were compared using the Mann-Whitney U or Kruskal-Wallis test followed by Dunn's post-hoc multiple comparisons.The inferior vena cava(IVC)diameters at different body positions were compared using the Wilcoxon matched pairs signed rank test.The number of cases with cardiothoracic ratios greater than or not greater than 50%was compared using Fisher’s exact test.A correlation of 2dSWE between different body positions was evaluated by calculating Spearman correlation coefficients.RESULTS The IVC diameter was significantly reduced in Ld in subjects with higher 2dSWE values in Ld(LdSWE)than in Sp(SpSWE)(P=0.007,(average±SD)13.9±3.6 vs 13.1±3.4 mm)but not in those with lower LdSWE values(P=0.32,13.3±3.5 vs 13.0±3.5 mm).In 81 subjects,SpSWE was increased or decreased in Ld beyond the magnitude of robust coefficient of variation,which suggests that body postural changes induced an alteration of liver stiffness significantly larger than the technical dispersion.Among these subjects,all 37 with normal SpSWE had a higher LdSWE than SpSWE(Normal-to-Hard,SpSWE-LdSWE(Δ2dSWE):(minimum-maximum)-0.74--0.08 m/sec),whereas in 44 residual subjects with abnormal SpSWE,LdSWE was higher in 27 subjects(Hard-to-Hard,-0.74--0.05 m/sec)and lower in 17 subjects(Hard-to-Soft,0.04-0.52 m/sec)than SpSWE.SpSWE was significantly correlated withΔ2dSWE only in Hard-to-Soft(P<0.0001).Δ2dSWE was larger in each lobe than in the entire liver.When Hard-to-Hard and Hard-to-Soft values were examined for each lobe,fibrosis-4 or platelet counts were significantly higher or lower only for Hard-to-Soft vs Normal-to-Hard cases.CONCLUSION Gravity alters the hepatic architecture during body postural changes,causing outflow blockage in hepatic veins.A rigid liver is resistant to structural deformation.Stiff-liver softening in the Ld position suggests a fibrous liver.

A Micromixer Using the Taylor-Dean Flow: Effects of Aspect Ratio and Inflow Condition on the Mixing

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.

A Micromixer Using the Taylor-Dean Flow: Effect of Inflow Conditions on the Mixing

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.

Behavior of Motile Sperm in Taylor-Couette Flow: Effect of Shear Stress on the Behavior of Motile Sperm

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.

A Micromixer Using the Chaos of Secondary Flow: Rotation Effect of Channel on the Chaos of Secondary Flow

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=Reδ1/2, the Reynolds number Re=qdh/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)1/2Ωa2/(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.

Experimental Study of the Viscous Pump with a Helical Channel Rotor:Torsion Effect of the Channel

The viscous pump,which has a rotor with a helical square channel,is studied experimentally.The non-dimen-sional channel curvature is taken to be about 0.1.Three types of torsion of the channel are made to investigate the torsion effect on the flow characteristics.We measure the flux through the channel at a constant rotor speed by changing the pressures at the entrance and exit of the pump.We also observe the secondary flow at a cross-section of the channel.Some of the results obtained are shown as follows:The friction factor along the channel to get the same flux is large for large channel torsion at a constant rotation,and becomes small when the favorable rotation of the rotor to the flow is applied.As for the secondary flow in a cross-section,there appear several types of vortex.When there is no rotation,the secondary flow is almost a symmetric two-vortex type for small flux as is the ordinary Dean vortex,but it changes to a four-vortex type when the flux is large.The secondary flow becomes asymmetric as the rotation is applied.We have unsteady flow patterns at large flux and rotation.

Experimental Study of the Flow in Helical Circular Pipes:Torsion Effect on the Flow Velocity and Turbulence

An objective of the present paper is to experimentally clarify the torsion effect on the flow in helical circular pipes. We have made six helical circular pipes having different pitches and common non-dimensional curvature δ of about 0.1. The torsion parameter β0, which is defined by β0 = τ/（2δ）1/2 with non-dimensional torsion r, are taken to be 0.02, 0.45, 0.69, 1.01, 1.38 and 1.89 covering from small to very large pitch. The velocity distributions and the turbulence of the flow are measured using an X-type hot-wire anemometer in the range of the Reynolds number from 200 to 20000. The results obtained are summarized as follows： The mean secondary flow pattern in a cross section of the pipe changes from an ordinary twin-vortex type as is seen in a curved pipe without torsion （toroidal pipe） to a single vortex type after one of the twin-vortex gradually disappears as β0 increases. The circulation direction of the single vortex is the same as the direction of torsion of the pipe. The mean velocity distribution of the axial flow is similar to that of the toroidal pipe at small β0, but changes its shape as β0 increases, and attains the shape similar to that in a straight circular pipe when ,β0 = 1.89. It is also found that the critical Reynolds number, at which the flow shows a marginal behavior to turbulence, decreases as ,β0 increases for small ,β0, and then increases after taking a minimum at ,β0 ≈ 1.4 as ,β0 increases. The minimum of the critical Reynolds number experimentally obtained is about 400 at ,β0 ≈ 1.4.