| 研究課題/領域番号 |
26630062
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| 研究機関 | 東京工業大学 |
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研究代表者 |
小林 厚子 東京工業大学, 地球生命研究所, WPI研究員 (50557212)
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| 研究期間 (年度) |
2014-04-01 – 2017-03-31
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| キーワード | Biogenic magnetite / Temperature monitoring / Contamination |
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| 研究実績の概要 |
The first year was to test the supercooling effect of the Cells Alive System (CAS) and verify the proposed model of biogenic magnetiteleading nucleation site for ice crystal formation. I remodeled the interior and temperature control system of ultra cold freezer(-80 C), to construct and program a computer-controlled temperature monitoring system, to select sample containers, and to remove contamination from the water before experimentation. I purchased a Personal Computer for monitoring the surface temperature of samples, planar contact thermocouples and a compact DAQ data acquisition device to construct the mechanical system for monitor of the surface temperature of samples. I constructed an infrared LED system to monitor the crystallization of water to ice. When water crystalizes from a liquid state to solid ice (type I ice), the latent heat of crystallization (80 calories/g) is released, causing a sudden jump in the temperature of a super-cooled sample back to near 0 C. Now the constructed system allows me to monitor these events. Sample types used in the experiment are two kinds of water, one is distilled ion-exchanged water, which excludes most of the magnetic particles normally found in water, the other is water to which we add size-controlled magnetite particles. I decided to make small water balloons (diameter of 7 cm) with a thickness of 100um. I borrowed two large copper coils from a colleague here at TiTech to do some preliminary experiments with AC magnetic fields, and installed them in the deep freezer.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
3: やや遅れている
理由
Although I have made good progress in terms of constructing a temperature-controlled system and can start the magnetic field experiments, but I have found that the freezing curves are highly variable, for unknown reasons. We need to have a more reliable system before we can test the mechanism that biological magnetite might be responsible for the CAS freezing effect.
1. A big delay was when I found that the temperature of this deep freezer is designed to be kept at -79 to 80 C, and can’t be set at anything else. So I spent a lot of time to design and build a smaller, partially-insulated chamber inside of this -80 C freezer, using heating pads and an Omega76000 temperature-control unit to keep the temperature inside the chamber in the -40 to -20 C range. This involves letting the PID (Proportional Integral Derivative) controller tune itself overnight for a particular temperature setting, but it works well.
2. Designing a water balloon made of polyurethane. In my 1995 paper in Nature (Kobayashi et al., 1995), I reported the discovery that many common laboratory materials had trace levels of ferromagnetic contamination on their surfaces left from the manufacturing process. I therefore need to have a clean, controlled container for these experiments; I need to be able to clean the surfaces from any small water-nucleating sites that might cause ice-crystal nucleation and prevent supercooling. My best solution is a small ‘balloon’ made of high-purity amorphous polyurethane, acid-washed to remove surface contaminants, and fused together to form a double-walled balloon.
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| 今後の研究の推進方策 |
Once I verify the proposed model of biogenic magnetite nucleation freezing, I will start to build the Helmholtz coil system necessary to vibrate the magnetite particles in the samples in a precessng fashion, and will implement a high-voltage corona wind generator as well as the magnetic field. I will then test a variety of biological tissues to see if the effect persists. In the second year , I will spend my time measuring the magnetic moment various biological materials using SQUID magnetometer at Caltech, directly measuring the number of potential ice nucleation sites.
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| 次年度使用額が生じた理由 |
当初の予定より安く物品を購入する事ができたので、次年度使用額が生じた。
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| 次年度使用額の使用計画 |
上記の理由により、次年度使用額が生じたが、必要な消耗品にあてる。今年度予算は当初の予定通り使用する。
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