Observation of the phase-separation multiphase flow using a polyethylene glycol/phosphate mixed solutions and the aqueous two-phase distribution of red blood cells in the flow system.

Phase-separation multiphase flow at a liquid-liquid interface was successfully formed in an aqueous two-phase system of polyethylene glycol/phosphate mixed solutions when fed into a microchannel (100 µm wide and 40 µm deep) on a microchip and a fused-silica capillary tube (100 µm ID). As one example, tube radial distribution flow (annular flow) was observed when 10.0 wt% polyethylene glycol 6000 and 8.5 wt% dipotassium hydrogen phosphate aqueous solution containing 1.0 mM Rhodamine B was fed at 40 â„ƒ, recorded by bright field microscopy. It exhibited a dipotassium hydrogen phosphate-rich inner phase and polyethylene glycol-rich outer phase. Effects of conditions including composition, flow rate, viscosity, and contact angle on tube radial distribution flow were analyzed. It was found out that although the viscosity of PEG-rich solution was much higher than that of phosphate-rich one, the phase configuration in tube radial distribution flow did not necessarily obey the viscous dissipation law in untreated microchannel and capillary tube, as well as for all the types of PEG/phosphate mixed solution the PEG-rich solution occupied the outer phase near the ODS-treated inner wall of both microchannel and capillary tube against the law. To assess the use of microfluidic flow in applications, we examined the distribution of red blood cells in the inner and outer phases fed into double capillary tubes with different inner diameters. Cell distribution was found to concentrate in the inner (dipotassium hydrogen phosphate-rich) phase compared to the outer (polyethylene glycol-rich) phase at a ratio of 1.8.

Microfluidic behavior of ternary mixed solutions of water/acetonitrile/ethyl acetate through experiments and computer simulations.

When ternary mixed solutions of water/acetonitrile/ethyl acetate are delivered into a microspace under laminar flow conditions, the solvent molecules show specific microfluidic flows, such as microfluidic inverted flow and tube radial distribution flow, which have been applied to novel analytical methods. In this paper, inverted flow was examined using various Y-type microchannels that had mixing angles of 0°, 90°, 180°, and 270°. Inverted flow was experimentally observed and the trigger phenomenon was also successfully expressed through computer simulations. Tube radial distribution flow, that is, annular flow, in a capillary tube is reported to cause exchange of the inner and outer phases based on the solvent composition of the ternary mixed solution. Tube radial distribution flow for an organic solvent-rich inner and a water-rich outer phases, as well as for a water-rich inner and an organic solvent-rich outer phases, could be well recreated by computer simulations for a ternary mixed solution. This highlights the effectiveness of computer simulations for such flow scenarios and will allow optimization of the operating conditions and design of microfluidic analytical devices.

Consecutive Sample Injection Analysis in Tube Radial Distribution Chromatography.

Tube radial distribution chromatography based on the tube radial distribution flow, or annular flow, in an open-tubular capillary has been reported, where the annular flow is created through phase-separation multiphase flow. We have proposed the first-ever procedure for consecutive sample injection analysis using chromatography. In basic terms, a commercially available HPLC system could be used with a sample injector (0.2 µL volume) and a fused-silica capillary tube (250 cm long) as a separation column instead of a normal packed one, while the built-in detection cell was replaced by improved on-capillary detection. A ternary mixed solution of water/acetonitrile/ethyl acetate (3:8:4 volume ratio) was delivered into the capillary tube as an eluent at a flow rate of 2.0 µL min-1. Model sample solutions of 1-naphthol and 2,6-naphthalenedisulfonic acid were consecutively analyzed by the present chromatography with a processing rate of 6 samples per hour. Simple and rapid consecutive analysis could be performed because washing and initialization of the separation tube was no longer necessary. The obtained results provide clues to developing new methodologies which combine features of both chromatography (separation) and the flow injection method (consecutive analysis).

Carotid intima-media thickness is increased in subjects with ischemic heart disease having a familial incidence.

OBJECTIVES: A family history of ischemic heart disease (IHD) is an independent risk factor for cardiovascular events. However, the mechanisms underlying this susceptibility have not been fully elucidated. The authors hypothesized that an important mediator of the familial incidence of IHD is subclinical atherosclerosis, which is detectable by noninvasive imaging. METHODS: One hundred forty-seven consecutive subjects (mean age 61.9 years, 57% men) were studied for one year using carotid ultra-sonogrophy for general medical screening, and familial IHD events were validated. Using a 7.5 MHz linear array transducer, carotid intima-media thickness (IMT) and carotid plaque were assessed. Subjects were subsequently divided into four groups based on the severity of IMT. RESULTS: The familial incidence of IHD and incidence of plaque were associated with the severity of IMT. No significant differences in risk factors were found between subjects with and without a family history of IHD. CONCLUSIONS: These findings suggest that subclinical atherosclerosis, as assessed in the carotid arteries, is more prevalent in individuals with a family history of IHD.

Effectiveness of Moderate Intensity Interval Training as an Index of Autonomic Nervous Activity.

The purpose of this study was to examine the effects of moderate intensity interval training from the change of the autonomic nervous activity. Ten male volunteers aged 21-22 years were studied. After 10-minute rest in a seated position, the subjects were asked to perform the strength of moderate cycling exercise in ergometer. Cycling rate was done in 50 times/min. Load resistance of the ergometer was set to 2.0 kgm. Subjects paused the exercise when the heart rate becomes 120 beats/min. Subjects have resumed the exercise when the heart rate returns to the value at rest. This trial was repeated twice. The experiment was ended when the heart rate of the subjects has returned to resting level. When the heart rate during exercise is maintained to less than 120 beats/min, sympathetic nerve activity during exercise did not work actively compared to the baseline. Vagus nerve activity after exercise cessation exceeds the baseline. It is clarified that the exercise as well as activating the vagus nerve activity stimulates the total autonomic nervous activity. It has revealed that at the time of interval training at moderate load the vagus nerve activity can be carried out.

A new technique for small and secure knots using slippery polyethylene sutures.

BACKGROUND: Suture knots used in tendon surgery must be strong but small enough so that they do not hinder gliding. For this purpose, we devised a unique "antislip" knot. METHODS: Three suture materials were used: Ethibond, Fiberwire, and Nespron. They were tied with either the antislip knot using a pair of United States Pharmacopeia (USP) 2 sutures or with a conventional reef knot using USP2 single sutures. The volume and tensile strength of the knots were measured (n = 25 for each combination of suture and method). FINDINGS: The maximum tensile strength was observed with Fiberwire antislip knots with five throws (mean 587 N) and six throws (mean 590 N), and Nespron antislip knots with five throws (mean 554 N) and six throws (mean 552 N); no significant differences were found among the four knots. Tensile strength per volume showed maximum values with Fiberwire antislip knots with four throws (mean 17.4 N/microl) and five throws (mean 16.8 N/microl), and Nespron antislip knots with four throws (mean 17.6 N/microl) and five throws (mean 16.8N/microl), which were not significantly different and were over 1.25-fold greater than the value for a reef knot. Ethibond had less tensile strength than Fiberwire and Nespron. INTERPRETATION: The antislip knot is smaller for the same or greater strength than a conventional reef knot. The 4- or 5-throw antislip knot was most effective for slippery polyethylene sutures such as Fiberwire and Nespron. The antislip knot should improve biological healing of repaired tendons through accelerated rehabilitation.