Page 509 - Book Hosokawa Nanoparticle Technology Handbook

16 NANOPARTICLE FORMATION OF DNA (GLOBULE TRANSFORMATION) APPLICATIONS
upstream side of the gas to the downstream side. [3] A. G. Konstandopoulos: SAE Paper No. 2000-01-
Because of this characteristic, the production of local 1016 (2000).
high-temperature portions can be avoided and [4] H. Emi: Res. Aerosol, 4(4), 246–255 (1989).
maximum temperature inside the DPF can be reduced [5] T. Kusuda: Ceramics, 23(8), 723–726 (1988).
[13] even if PM is burned inside a filter. This also [6] S. Soumiya, Y. Inomata (Eds.): in Basics, Application
improves the durability. Another problem is deteriora- and Product Introduction on Silicon Carbide
tion in the Pt catalyst due to the local temperature Ceramics, Junkudo Co. Ltd., Kobe (1988).
increase in the catalyzed DPF. The activity is reduced
due to Pt sintering. Fortunately, this also can be con- [7] A. A. Griffith: The theory of rupture, in C.B. Biezeno,
trolled. The drawbacks of silicon carbide are its large J. M. Burgers (Eds.) Proceedings of the First
6
coefficient of thermal expansion [3] (4.3 10 / C) International Congress on Applied Mechanics,
and its tendency to crack due to thermal stress. These J. Waltman, Delft, p. 55 (1924).
problems have been solved by developing a technique in [8] W. Weibull: J. App. Mech., Vol. 51, Sept., 293–297
which DPF is divided into small segments and then (1951).
combined into a required size [14]. [9] Edited by the subcommittee on basic engineering
courses under the editorial committee of The
6. Future of filters for trapping diesel particles Ceramic Society of Japan, Mechanical properties of
ceramics, The Ceramic Society of Japan, Tokyo, p. 21
This section has described filters that use porous sili-
con carbide to trap diesel particles. As a result of the (1979).
development based on the characteristics of silicon [10] R.W. Davidge: Strength and Fracture of Ceramics,
carbide, we have been able to trap nanoparticles and Translated by H. Suzuki and T. Iseki, Kyoritsu
provide the market with filters with a trapping effi- Shuppan Co. Ltd., Tokyo, p. 34 (1982).
ciency of almost 100%. In the future we would like to [11] T. Nishida, K. Yasuda (Eds.), Evaluation of
research porous silicon carbide with the target of fur- Mechanical Properties of Ceramics, p. 63, The
ther enhancing the superiority of diesel engine vehi- Nikkan Kogyo Shimbun Ltd., Tokyo (1986).
cles. If it succeeds, it will be possible to develop [12] Edited by the 124th committee on high-temperature
exhaust gas systems for diesel engine vehicles, which ceramic materials, Japan Society for the Promotion
help to purify and improve the global environment.
of Science, New SiC-based ceramic materials –
Recent development, Junkudo Co. Ltd., Kobe, p. 239
References
(2001).
[1] N. Kajiwara (Ed.): in Technology for Removing Fine [13] K. Ohno, K. Shimato, N. Taoka, H. Santae,
Particles Contained in Gas Emissions Discharged from T. Ninomiya, T. Komori and O. Salvat: SAE paper
Diesel Engine Vehicles, CMC Inc., Tokyo p. 23 (2001). 2000-01-0185 (2000).
[2] S. Kubo: Text for the Society of Automotive Engineers [14] A. Itoh, K. Shimato, T. Komori, H. Okazoe, T. Yamada,
of Japan’s Symposium, No. 01-04 20044070 (2004). K. Niimura and Y. Watanabe: SAE paper No. 930360
(1993).

APPLICATION 16
16 NANOPARTICLE FORMATION OF DNA (GLOBULE TRANSFORMATION)

Structure of DNA (coiled structure) in solution can be transition region (Fig. 16.1) [1]. This phase transition
transformed to globule structure by raising concentra- is reversible; therefore, decreasing the concentration
tions of condensing reagents such as combination of of condensing reagents induces reversal phase transi-
low-molecular-weight cation and polyethylene glycol tion to the coiled structure. Structure of globule DNA
(PEG) or multivalent cation (e.g. spermidine). The depends on species and concentrations of condensing
globule structure is highly condensed and it is reagents. Typical condensing reagents, combination
induced by dehydration by PEG and suppression of of PEG and cation, induce a highly condensed
repulsive force between strands by screening negative toroidal structure, which is several ten nanometers in
charge of DNA backbone. This phase transition diameter (Fig. 16.2).
depends on concentrations of both PEG and cations, This phase transition is induced immediately
and both coiled and globule structure are found in the under sufficiently high concentration of condensing

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