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Tohoku University

Toshiyuki Hayase

Toshiyuki Hayase,Professor

Institute of Fluid Science, Tohoku University

Email: hayase@ifs.tohoku.ac.jp

 

Ultrasonic-Measurement-Integrated Simulation of Blood flows

Understanding complex blood flows in living bodies is essential to realize advanced diagnosis and treatment for circulatory diseases. The author’s group is doing research to analyze complex blood flows by numerical simulation, experimental measurement, and their coupled method in order to determine the local and fine structure of complex blood flows. Medical imaging devices such as CT, MRI, or ultrasonography provide information of real blood flows, but measurable properties are usually limited and it is difficult to get field information of unsteady blood flows. Numerical simulation, on the other hand, provides complete information of temporal and spatial distribution of flow states, but usually the result is not exactly the same as the real flows because of the difficulty in specifying the boundary conditions or material properties exactly. 

The authors have proposed a concept of measurement-integrated (MI) flow simulation in which a numerical simulation and measurement are integrated based on the concept of observer in control theory. In MI simulation the feedback signal proportional to the difference between the output signals of the simulation and the measurement is added to the flow simulation. If the feedback is designed properly, the state variables of the simulation converge to those of the real flow. 

This presentation deals with ultrasonic measurement-integrated (UMI) simulation of a blood flows. The method to integrate ultrasonic measurement and numerical simulation is first explained.Real blood velocity is properly reproduced by feedback of the difference of instantaneous Doppler velocity distribution, or the velocity component along ultrasound beam, between the measurement and simulation. Examples of UMI simulation are presented for the cases of 2-D blood flow analysis in carotid arteries in diagnosis of arteriosclerosis and 3-D blood flow analysis in small blood vessels in mice for basic animal experiment.

Tomokazu Matsue

Tomokazu Matsue, Professor

Graduate School of Environmental Studies School of Engineering, Tohoku University>

Email: matsue@bioinfo.che.tohoku.ac.jp

 

Nanobioimaging with Scanning Electrochemical Microscopy

A high temporal and spatial resolution tool working in physiological conditions is needed to evaluate the relationship of the localized topography and function of biomolecules. An important tool meeting the requirements is a scanning electrochemical microscope (SECM), which uses a micro/nanoelectrode as a scanning probe and provides sample surface electrochemical property under physiological conditions without physical contact. However, the distance control between the probe and sample has been a big challenge to improve the temporal resolution and sensitivity. We have incorporated ion-conductance feedback (SECM-SICM) [1,2] and voltage-switching mechanisms (VSM-SECM) [3] into the system with nanoelectrode probe for non-invasive, high resolution bioimaging.

Several nanoprobes were fabricated by using fine glass capillaries. For SECM-SICM, we used the capillaries with Au or Pt ring nanoelectrodes for electrochemical measurements. A nanoaperture was also arranged for ion conductance measurements. We also fabricated carbon nanoelectrode for VMS-SECM as the probe. The tip radii of the above probes ranged from 10 nm to 100 nm.

SECM-SICM was applied to simultaneous imaging of topography and electrochemical responses of enzymes and single live cells. The SICM topographic and SECM images showed a highly resolved structure of enzymes when the distance was set to 100 nm. This is the first case that the enzyme activity has been imaged with nanometer resolution using SECM [1]. We also visualized living cells based on electrochemistry, simultaneously with the topography. The cell bodies were clearly observed in both the SICM and SECM images [2]. VSM-SECM with a nanoelectrode was successfully applied to acquire high quality topographical and electrochemical images of living cells simultaneously [3].

 

References

[1] Y. Takahashi et al., J. Am. Chem. Soc., 132, 10118 (2010).

[2] Y. Takahashi et al., Angew. Chem. Int. Ed., 50, 9638 (2011).

[3] Y. Takahashi et al., Proc. Natl. Acad. Sci. USA, in press.

Takahito Ono

Takahito Ono, Professor

Graduate School of Engineering

Email: ono@nme.mech.tohoku.ac.jp

 

Resonant Microsensors for Biological Sensing

Microfabricated resonant sensors for biological applications will be presented. By miniaturization and Q-factor enhancement of Si resonators, very sensitive resonators have been developed for force, mass, and heat sensing. In order to demonstrate 3D dimensional imaging of biological cells, resonant sensors for magnetic resonance force microscopy was developed and applied to observe radical density in a test sample.

In addition, resonators are applied to a calorimeter for the detection of heat from a brown fat cell. The measurement principle relies on the resonant frequency tracking of a Si resonator in temperature variation due to heat from a sample, and heat is conducted from the sample in water to the Si resonator in vacuum via a Si heat guide. A heat loss to surrounding and a dumping in water can be reduced by placing the resonant thermal sensor in vacuum. The fabricated resonant thermal sensor shows 1.6 mK of the temperature resolution, and 6.2 pJ of the detectable minimum heat. The heat from the single cell is detected in cases without any stimulation and with stimulation. As the results, pulsed heat production and continuous heat production are observed, respectively.

Takehiko Sato

Takehiko Sato,  Professor

Institute of Fluid Science, Tohoku University

Email: sato@ifs.tohoku.ac.jp

 

Development of New Sterilization Device by a Plasma Flow

Recently, a low temperature plasma flow has been applied to not only sterilization methods but also medical treatments, and a new medical field “plasma medicine” is growing up rapidly. We aim at contributing the growth of “plasma medicine” through integration among fluid dynamics, plasma science and bio-medical engineering [1-5]. In this workshop, I introduce development of a plasma sterilization device which has been expected as a new sterilization method.

At present, high pressure steam and ethylene oxide gas methods are main methods for sterilization of medical instruments because of simple configuration and low-cost operation for sterilization. However, high pressure steam method is not suitable for low-heat-resistance materials such as polymer, which is increasingly applied to recent medical instruments. The ethylene oxide gas method uses a toxic substance and the sterilization generally takes about one week. Therefore, it is necessary to establish an advanced sterilization method which can be operated with lower temperature without toxic gases. We have studied the sterilization effects of a steam plasma flow and an air plasma flow at atmospheric pressure on bacteria. We have developed a dielectric barrier discharge in a narrow tube for catheter sterilization. A good sterilization result against spores of Geobacillus stearothermophilus in a polyvinyl chloride tube at 343 K with the applied voltage of 10 kVpp and the sterilization time of 5 min was obtained [6]. We clarified that the generated chemical species such as nitrogen oxide and ozone were transported and concentrated by an induced plasma flow in the tube [7]. We have also developed a plasma source of the steam plasma flow in a quartz tube of 8 mm in diameter and clarified its plasma characteristics and sterilization efficacy against G. Stearothermophilus. A flow rate of the steam plasma flow of atmospheric pressure in a tube is 8.1 l/min which equals to the velocity of 2.7 m/s. When the applied voltage was 13 kVpp, G. Stearohermophilus was sterilized for 30 minutes at 100 ºC, though the bacteria could not be sterilized by pure steam at 100ºC. We have applied these methods to a larger vessel whose size 7 cm in diameter and 12 cm in height. The bacteria could be sterilized for 10 min in the case of air and for 8 hr in the case of steam.

 

References

[1] T. Sato, T. Miyahara, A. Doi, S. Ochiai, T. Urayama and T. Nakatani, Appl. Phys. Lett., 89, 073902 (2006).

[2] T. Sato, S. Ochiai and T. Urayama, New J. Phys., 11, 115018 (2009).

[3] T. Miyahara, S. Ochiai and T. Sato, Europhys. Lett., 86, 45001 (2009).

[4] T. Shimizu, Y. Iwafuchi, G. Morfill and T. Sato, New J. Phys., 13, 053025 (2011).

[5] T. Sato, M. Yokoyama and K. Johkura, J. Phys. D: Appl. Phys., 44, 372001 (2011).

[6] T. Sato, O. Furuya and T. Nakatani, IEEE Trans. Indust. Appl., 45, 44 (2009).

[7] T. Sato, O. Furuya, K. Ikeda and T. Nakatani, Plasma Process. Polym., 5, 606. (2008).

Seiji Samukawa

Seiji Samukawa, Professor

Institute of Fluid Science, Tohoku University

Email: samukawa@ifs.tohoku.ac.jp

 

Novel Quantum Dot Solar Cells realized by Fusion of Bio-template and Defect-Free Neutral Beam Etching

Quantum dot (QD) solar cells consisting of a sub-10-nm highly ordered and dense 2-dimensional (2D) array of Si nanodisks (Si-NDs) as a quantum dot superlattice with a SiC interlayer are achieved. The Si-NDs are fabricated with an original top-down process involving a 2D array of bio-templates with a 4.5-nm-diameter iron core and damage-free neutral beam etching (Si-ND diameter: 6.4 nm). The Si-ND array has a high optical absorption coefficient due to miniband formation. As a result, high efficiency solar cells could be accomplished by using our fabricated QD supperlattice structure.

Kaoru Maruta

Kaoru Maruta, Professor

Institute of Fluid Science, Tohoku University

Email: maruta@ifs.tohoku.ac.jp

  

 Study on Lw-speed Cunterflow Fames under Mcrogravity for Uified Cmbustion Lmit Teory

Space experiment on the relation between conventional flame and “flame ball” phenomena is scheduled at Japanese module of space station “Kibo” in 2015. This preliminary study focuses on extinction characteristics of radiative counterflow premixed flames and its transition to ball-like flames. At first, flammability limit of flame ball and that of counterflow flame for the given mixture were estimated by simple 1-D computations. Based on the information by the computation, airplane-based microgravity experiments were conducted and showed the existence of ball-like flame(s) in the center of low-speed counterflow field at low stretch rates after extinction of conventional flames. Further detailed two-dimensional computations indicate that the temperature of ball-like flame increases with decrease of equivalence ratio in the near-limit condition when it approaches to its extinction. The temperature distribution of the ball-like flame is in qualitative agreement with that of flame ball. The present ball-like flame is supposed to have close correlation with ideal flame ball which can be established only in a quiescent mixture.

 

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