Akiko Fujiwara

Efficient macrocyclization by means of 2-nitrobenzenesulfonamide and total synthesis of lipogrammistin-A

Abstract Synthesis of medium- and large-sized cyclic amines using alkylation with 2-nitrobenzenesulfonamides is described. Using either conventional alkylation procedures or Mitsunobu conditions, the cyclization reaction proceeded in a highly efficient manner. The usefulness of this methodology has been fully demonstrated in the total synthesis of lipogrammistin-A ( 9 ), an 18-membered cyclic polyamine.

Reduced IP3 sensitivity of IP3 receptor in Purkinje neurons.

The inositol 1,4,5-trisphosphate receptor (IP3R) is highly expressed in Purkinje neurons (PNs) and is thought to be essential for the induction of long-term depression at parallel-fiber–PN synapses. Here, by imaging the fluorescence intensity of the low-affinity Ca2+ indicator inside the Ca2+ stores in the permeabilized single PNs, we analyzed the kinetics of Ca2+ release via the IP3R in controlled cytoplasmic environments. The rate of Ca2+ release is dependent on the IP3 concentration with an EC50 of 25.8 μM, which is > 20-fold greater than that of the IP3R in the isolated preparations or in peripheral cells. This property would be advantageous in inducing the release of Ca2+ in a localized space adjacent to the site of synaptic inputs.

Experimental Study on the New Micro-Bubble Generator and Its Application to Water Purification System

Micro-bubble generation techniques are proposed in former investigations. In the present study one of the effective technique by using converging-diverging nozzle (venturi tube) is introduced. Rapid pressure recovery in the diverging nozzle induced bubble fission. The purpose of this study is to develop the new micro bubble generator, clarify the mechanism of the bubble fission in the venturi tube and elucidate the relation between the flow structure in the tube and the generated bubbles’ diameter. The developed micro generator has an advantage on the usage of wide range of void fraction. The observation by a high speed camera suggests that the bubble fission is caused by the strong shock-type pressure recovery in venturi tube. Finally in order to verify the applicability of micro-bubbles that generated by venturi tube to water purification system, floatation experiment was conducted. Bubble diameter in each condition is estimated by image processing technique respectively.© 2003 ASME

Induction of cerebellar long-term depression requires activation of calcineurin in Purkinje cells

Cerebellar long-term depression (LTD) is an activity-dependent depression of synaptic transmission from parallel fibers to Purkinje cells underlying certain forms of motor learning. LTD is induced by the conjunctive stimulation of parallel fibers and climbing fibers, both of which supply excitatory inputs to Purkinje cells. The conjunctive stimulation induces a large increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) in Purkinje cells. Although the increase in [Ca(2+)](i) is essential for LTD induction, the downstream signal transduction mechanism remains elusive. In this study, we show that LTD induction requires the activation of the Ca(2+)/calmodulin-dependent protein phosphatase 2B calcineurin. In acute cerebellar slices of mice, the LTD amplitude was significantly reduced in the presence of calcineurin inhibitors (cyclosporin A or FK506), whereas the basic electrophysiological properties of the parallel fiber-Purkinje cell synaptic transmission remained constant. Furthermore, a calcineurin autoinhibitory peptide perfused into Purkinje cells completely blocked LTD induction. On the other hand, microcystin LR, an inhibitor of protein phosphatase 1 and 2A, did not affect the induction of LTD. These results indicate that calcineurin activation is essential for LTD induction downstream of the conjunctive-stimulation-induced Ca(2+) signal in Purkinje cells.

Bubble Deformation and Surrounding Flow Structure Measured by PIV/LIF and Shadow Image Technique

The gas-liquid contactors find in broad application, such as fluidized-beds, bioreactor bubble columns and other equipment involving solid-liquid, gas-liquid and even solid-gas-liquid flows, and bubbly flow has been investigated both experimentally and numerically for many years. Some of our limitations can be attributed to the lack of understanding of the correlation between the global flow structure and local influence of interaction between the dispersed phase (bubble or solid) and the surrounding liquid phase. Until the widespread availability of PIV, many measurement method using image-processing techniques were applied to bubbly flow [1][2]. To investigate the flow in the vicinity of the bubble, authors’ group has developed a particular PIV technique with fluorescent tracer particles [3][4]. With this measurement system, we have been able to study the localized phenomena, such as the surrounding wake structure and the factors influencing the forces on the bubble; that is, the interaction between gas/liquid phases and the associated transfer mechanisms. In particular, to understand the bubble transfer mechanisms experimentally, it is necessary to associate the flow structure with the actual three-dimensional bubble behavior. Therefore, during the course of the development of image processing techniques, several experimental groups have developed methods to investigate three-dimensional bubble behavior [5][6][7]. The objective of the present study is to obtain fundamental knowledge of the translational motion of the bubble, as caused by the interaction between the linear shear flow field and the rising bubble within it. Fig.1 shows the experimental apparatus. We explored the flow structure in the vicinity of the bubble in one plane and its deformation in two planes respectively by PIV/LIF and a projection technique in two perpendicular planes. For our experiment, we chose a single air bubble with an equivalent diameter De = 2∼6mm, rising in a shear flow field set at 2.0s−1 of shear rate. By reconstructing the instantaneous three-dimensional bubble shapes from two perpendicular planar images, we estimated three-dimensional bubble trajectory and the interactive influence on flow structure with consideration of the three-dimensional arrangement. Fig.2 shows approximated three-dimensional deformed bubble shape and corresponding vorticity contour. We quantitatively showed the three-dimensional wake structure, viewed in terms of the vorticity, with additional consideration given to the relative arrangement and approximated three-dimensional shape and trajectory of the bubble. Bubble oscillated to a characteristic moment in y-direction mainly. As shown in Fig.2(c), the bubble moves across the laser sheet in x-z plane. According to the side view of bubble trajectory, bubble moves toward the direction where x increases and y decreases. At the position A, the region with relatively high intensity of vorticity appeared at left edge of the bubble while the region with high intensity of vorticity exists at lower right of the bubble at position B. This transition can be explained by the three-dimensional structure of bubble’s wake. In order to elucidate the effect of bubble deformation on the wake structure behind the bubble, the relation between aspect ratio As and the parameter of asymmetric property Rl is shown in Fig.3(a). The large Rl indicate large curvature of right-hand-side edge and Rl = 0.5 indicate symmetric shape. Fig.3(c) shows the relation between bubble trajectory and the vorticity near the right-hand-side edge of the bubble ωr . With consideration of the vorticity ωr estimated from PIV data respectively, we elucidated that bubble asymmetric deformation was induced by the growth of the hairpin vortex attached to the bubble’s edge. The bubble indicated remarkable asymmetric deformation with maximum value of the vorticity on the bubble’s edge. The bubble then shed the vortex downstream, and its lateral motion switched to the opposite direction as shown in Fig.3(b). In conclusion, we associated lateral transition of bubble zig-zag motion with periodical bubble deformation and wake structure, using PIV/LIF/double-shadow projection technique. The growth of vortex on the edge of the bubble induced asymmetric deformation, and the bubble then changed its direction of motion after shedding vortex.Copyright

せん断流中の単一気泡の挙動(流体工学,流体機械)

The objective of the present study is to obtain fundamental knowledge of the influence of the lift force on the bubble and its motion induced by the surrounding flow field. We explored the flow structure in the vicinity of the bubble and also deformation of the bubble shape respectively by PIV/LIF and a projecting technique. As our system, we chose a single air bubble with an equivalent bubble diameter (Deq) 1∼8 mm, in a vertical shear flow. Velocity measurements were made using one digital high-speed CCD camera for Digital Paricle Image Velocimetry (DPIV) with fluorescent tracer particles. The recorded image data are analyzed by cross-correlation technique. A second CCD camera was used to detect the bubbles shape and translational motion via backlighting from a square array of infrared LEDs. We confirmed that the bubble deformation and surrounding flow induced lateral force on bubble. We proposed the lateral force parameter αr which consisted of the relative velocity of the bubble and the circulation around the flow structure in the vicinity of the bubble measured by PIV/LIF. Bubble motion can be estimated by αr with the phase which depends on the circulation around the bubble.

Ultrasound Imaging for the Diagnostic and Therapeutic System

Ultrasonic medical applications such as ultrasound contrast agent imaging, High Intensity Focused Ultrasound (HIFU) and Extracorporeal Shock Wave Lithotripsy (ESWL) have recently been the subject of much interest. In these applications, micro-bubbles facilitate the medical treatment by improving the image quality or enhancing the therapeutic effects through localized heating or acoustic emission. In order to treat a diseased part properly and safely, simultaneous diagnosis with therapy is necessary. The objective of this study is the establishment of the integrative system of ultrasound diagnostic and minimally invasive therapy. HIFU treatment of the ultrasound heating and lithotripsy with simultaneous diagnosis by an ultrasound diagnostic equipment are introduced.

Experimental Study on Near-Wall Bubble Clustering Behaviors in Bubbly Channel Flow (Keynote)

The turbulence properties of gas-liquid bubbly flows and the near-wall bubble clustering behaviors are investigated for upward flow in a rectangular channel. Bubble size distributions are well-controlled and the flow with mono-dispersed 1mm-diameter and that with 1–4mm diameter bubbles are compared. Bubble size, turbulent properties of liquid phase and the bubble cluster motion were measured using image-processing technique, Laser Doppler Velocimetry (LDV) and Particle Image Velocimetry (PIV), respectively. To create the mono-dispersed small bubbles by the bubble generator, being made of stainless steel pipes, a small amount of surfactant (20ppm of 3-pentanol) was added into the flow. In this study, experiments with three different bulk Reynolds numbers (1350, 4100, 8200) were conducted with void fractions less than 0.6% in the fluid with/without the surfactant. In all cases with surfactant, there was a very high accumulation of bubbles near the wall. The local void fraction has a wall-peak distribution and the horizontal bubble clusters are formed near the wall. As a result, the local mean velocity of the liquid phase becomes larger near the wall due to the driving force of buoyant bubbles and the stream-wise turbulent intensity in the vicinity of the wall was enhanced. On the other hand, the turbulent fluctuations and Reynolds stress are remarkably suppressed in the other region. At the Reynolds number of 8200, the bubble cluster was investigated. Experimental observation showed that the bubble cluster changes its shape in time and that the shape change is caused by the difference of the rising velocity between the cluster center and the both ends. The clusters accelerated the mean streamwise velocity near the wall, thus the mean velocity profile of the liquid phase becomes flattened. It is suggested that the highly concentrated bubbles in the vicinity of the wall disturb the transport of turbulence energy produced in the wall shear layer toward the center of channel. Moreover, in the middle of channel, the turbulence structure is governed by pseudo-turbulence induced by present bubbles.Copyright