Satoshi Suzuki

Improvement of hepatocyte viability after cryopreservation by supplementation of long-chain oligosaccharide in the freezing medium in rats and humans.

Factors affecting cell viability, plating efficiency, and survival of hepatocytes after cryopreservation have been investigated. We focused especially on the effect of including trehalose and related oligosaccharides in the cryopreservation fluid. This was supplemented with either glucose, trehalose, maltotriose, or other sugars, in addition to dimethyl sulfoxide (10%) and first tested with primary rat hepatocytes cooled in a controlled rate freezer. After thawing, viability by trypan blue exclusion of cells frozen in oligosaccharide-supplemented medium was significantly higher than for those cryopreserved without oligosaccharides. Use of oligosaccharides with higher molecular weights resulted in greatest improvement in viability. Moreover, attachment and survival rates in plastic dishes were approximately 1.2–1.8-fold greater after freezing in the presence of di-, tri-, and tetrasaccharides. Human hepatocytes isolated from untransplantable liver showed the same tendency regarding viability, but cell adherence was not similarly improved by the addition of oligosaccharides. Possible reasons for these differences may be prior cell damage during extended cold ischemia of the human liver, donor age, or cell degradation caused by progression of fatty liver in humans, and/or species differences.

Comparisons of LET distributions for protons with energies between 50 and 200 MeV determined using a spherical tissue-equivalent proportional counter(TEPC) and a position-sensitive silicon spectrometer (RRMD-III)

Abstract Borak, T. B., Doke, T., Fuse, T., Guetersloh, S., Heilbronn, L., Hara, K., Moyers, M., Suzuki, S., Taddei, P., Terasawa, K. and Zeitlin, C. J. Comparisons of LET Distributions for Protons with Energies between 50 and 200 MeV Determined Using a Spherical Tissue-Equivalent Proportional Counter (TEPC) and a Position-Sensitive Silicon Spectrometer (RRMD-III). Radiat. Res. 162, 687–692 (2004). Experiments have been performed to measure the response of a spherical tissue-equivalent proportional counter (TEPC) and a silicon-based LET spectrometer (RRMD-III) to protons with energies ranging from 50–200 MeV. This represents a large portion of the energy distribution for trapped protons encountered by astronauts in low-Earth orbit. The beam energies were obtained using plastic polycarbonate degraders with a monoenergetic beam that was extracted from a proton synchrotron. The LET spectrometer provided excellent agreement with the expected LET distribution emerging from the energy degraders. The TEPC cannot measure the LET distribution directly. However, the frequency mean value of lineal energy, ȳf, provided a good approximation to LET. This is in contrast to previous results for high-energy heavy ions where ȳf underestimated LET, whereas the dose-averaged lineal energy, ȳD, provided a good approximation to LET.

A pure liquid argon calorimeter with high energy resolution for electromagnetic showers

Abstract A “pure” liquid argon calorimeter has been constructed with the aim of approaching the ideal high energy resolution. The electrode system of the calorimeter consists of 192 G-10 plates of 1.2 mm thickness placed at intervals of 9mm. The sensitive volume of the calorimeter is 0.93 m2 × 2.0 m. An energy resolution of (2.4±0.2)% (m.m.s.) was achieved of these formulas is discussed. compared to the values predicted by Wasedas and Serpukhovs formulas. The validity of these formulas is discussed.

Development of a liquid Xe photon detector for /spl mu//spl rarr/e/spl gamma/ decay search experiment at PSI

We are developing a new type of photon detector for an experiment to search for muons decaying into a positron and gamma ray. Our sensitivity on the branching ratio is expected to reach 10/sup -14/ by use of the worlds most intense continuous muon beam at Paul Scherrer Institut (PSI). In this experiment, the photon detector will utilize liquid Xe as a scintillation material because of its fast response, large light yield, and high density. The scintillation light emitted in liquid Xe will be directly observed by photomultipliers (PMTs) located in the liquid without the use of a transmission window. In order to study the detector response to gamma rays, we have constructed a prototype with an active volume of 2.3 /spl times/ 10/sup 3/ cm/sup 3/ surrounded by 32 PMTS. The PMT is a new development enabling operation at temperatures as low as liquid Xe (165 K). Energy, position, and timing resolutions have been evaluated using gamma-ray sources ranging from 320 keV to 1835 keV. The performance of the prototype is presented.

Measurement of Linear Energy Transfer Distribution at CERN-EU High-Energy Reference Field Facility with Real-Time Radiation Monitoring Device III and Its Comparison with Dosimetric Telescope

The distributions of linear energy transfer for LET (LETwater) in front of the 80-cm-thick concrete side shield at the CERN-EU high-energy reference field (CERF) facility were measured with a Si detector telescope named real-time radiation monitoring device-III (RRMD-III) covered with and without a 1 cm-thick acrylic plate. In these measurements, a difference of about 20% in the absorbed dose between the two LETwater distributions was observed as a result of protons, deuterons and tritons recoiled by neutrons. The LETwater distribution obtained using RRMD-III without the 1-cm-thick acrylic plate is compared with lineal energy distributions obtained using the dosimetric telescope (DOSTEL) detector under the same conditions. These dose equivalents are also compared with that obtained using HANDI TEPC which is used as the standard at the CERF facility.

Capacitance-Voltage Behavior of Insulated Gate InGaAs HEMT Capacitors Having Silicon Interface Control Layer

Basic insulated gate HEMT (IGHEMT) capacitors with and without a Si interface control layer (ICL) were fabricated, and their capacitance-voltage (C-V) characteristics were compared in detail (10 3 -10 9 Hz, 50 K-300 K). The basic IGHEMT capacitors with Si-ICL were found to exhibit an unexpectedly large frequency dispersion of capacitance. By performing detailed low-temperature measurements, it was found that the observed frequency dispersion of capacitance was due not to the interface states but to the rate limitation of the carrier supply, and the nearly ideal nature of an IGHEMT capacitor with Si-ICL was confirmed.

The Response of the silicon-based Linear Energy Transfer Spectrometer (RRMD-III) to Protons from 1 to 70 MeV

Experiments have been performed to measure the response of the silicon-based linear energy transfer (LET) spectrometer (RRMD-III) to protons with energies ranging from 1 to 70 MeV. The beam energies incident upon RRMD-III were obtained using plastic polycarbonate degraders with mono-energetic proton beams that were extracted at 70, 40 and 25 MeV from a cyclotron. The energy loss in the degraders never exceeded 70% of the incident energy in order that the energy spread of the emerging protons created by straggling and scattering effects could be suppressed. Estimates of the LET were influenced by the asymmetric energy distribution of the degraded beam. Protons with energies less than 12.2 MeV did not reach the second Si detector in RRMD-III and were not measured. Measured values of LET were within ±7% of the expected value for incident protons that had an energy sufficient to penetrate the second Si detector in RRMD-III (E>15.4 MeV). The LET of stopping particles was computed using a lookup table listing LET vs E, and a simple stopping power formula for a particle with charge Z and energy ER, where ER is the energy of the stopping particle measured in the second Si detector.

Observation of the Initial Stage of Ion Assisted Deposition Films Using a Rotating-Analyzer Ellipsometer

We have equipped an ion assisted deposition (IAD) system with a rotating-analyzer ellipsometer for in situ monitoring of the deposition process. The sensitivity of the measurements of the initial stage of deposition varies greatly with the ellipsometric parameters of the substrate. We propose the optimum conditions for the SiO2/Si substrate system for the observation of the initial stage of gold film deposition. The deposition of gold films on optimized silicon oxide substrates was observed in situ using the rotating-analyzer ellipsometer. The growth curves for the gold films were different from those for continuous layer growth in the initial stage. The critical thickness at which the growth mechanism became continuous layer growth varied with the ion current density of the IAD. The ion current density for the minimum critical thickness of gold films had an optimum value of 100 µA/cm2.

Nanostructure Fabrication using PEG-based Polymers for Biomedical Applications

1 Biomaterials Center, National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan Phone: +81-29-860-4499 E-mail: OTSUKA.Hidenori@nims.go.jp Department of Materials Science, Graduate School of Engineering, The University of Tokyo, 7-3-1 Hongo, Tokyo 113-8656, Japan Human & Animal Bridging Research Organization, Japan National Research Institute for Child Health and Development, Japan Department of Materials Science, Tokyo University of Science , Noda, Chiba 278-8510, Japan

Development of a liquid Xe photon detector for μ→eγ decay search experiment at PSI

We are developing a new type of photon detector for an experiment searching for muon decays to positron+gamma with a sensitivity of 10/sup -14/ branching ratio by using the world most intense continuous muon beam provided at PSI. In this experiment the photon detector utilizes liquid xenon as a scintillation material because of its fast response, large light output yield, and high density. Scintillation light emitted in liquid Xe is directly observed by photomultipliers (PMTs) located in a liquid without any transmission window in order not to lose light yield. To study the detector response to gamma rays we constructed a prototype with an active volume of 2300 cm/sup 3/ surrounded by 32 PMTs. The PMT was newly developed so as to be operated even in liquid Xe at 165 K. The energy, position, and timing resolution have been evaluated with gamma-ray sources from 320 keV to 1835 keV. The performance of the prototype is presented.