• Journal of the Korean Magnetics Society
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• v.15 no.2
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• pp.100-105
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• 2005

$Ni_{0.9}Zn_{0.1}Fe_2O_4$ nanoparticles have been prepared by a sol-gel method. The structural and magnetic properties have been investigated by DTA/TGA, XRD, SEM, and $M\ddot{o}ssbauer$ spectroscopy, VSM. $Ni_{0.9}Zn_{0.1}Fe_2O_4$ powder that was annealed at $300^{\circ}C$ has spinel structure and behaved superparamagnetically. The estimated size of superparammagnetic Ni-Zn ferrite nanoparticle is around 10 nm. The hyperfine fields at 13 K for the A and B patterns were found to be 533 and 507 kOe, respectively. The blocking temperature ($T_B$) of superparammagnetic $Ni_{0.9}Zn_{0.1}Fe_2O_4$ nanoparticle is about 250 K. The magnetic anisotropy constant and relaxation time constant of $Ni_{0.9}Zn_{0.1}Fe_2O_4$ nanoparticle were calculated to be $1.6\times10^6\;ergs/cm^3$ and ${\tau}_0=5.0{\times}10^{-13}$ s, respectively. Also, Temperature increased up to $43^{\circ}C$ within 10 minutes under AC magnetic field of 7 MHz. It is considered that $Ni_{0.9}Zn_{0.1}Fe_2O_4$ powder that was annealed at $300^{\circ}C$ is available for biomedicine application such as hyperthermia, drug delivery system and contrast agents in MRI.

• Applied Biological Chemistry
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• v.49 no.3
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• pp.186-191
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• 2006

In the present study, an attempt has been made to produce hybrid yeast strains of different useful and dominant characteristics. The hybrid yeast strains were produced by electrofusion and their genetic analysis were performed by RAPD-PCR (random amplified polymorphic DNA-polymerase chain reaction). The protoplast of Saccharomyces cerevisiae KCTC 7904 and Zygosaccharomyces rouxii KCTC 7966 were obtained above 92% when treated with lyticase at $30^{\circ}C$ for $60{\sim}90$ min after the pretreatment of $1{\sim}2%$ 2-mercaptoethanol at $30^{\circ}C$ for $15{\sim}20$ min. The fusant was produced from paired protoplast stage under the electric pulse at high frequency conditions (1.5 MHz/50 pV, 615 $V/256\;{\mu}sec$) within glass-platinum made electrofusion chamber. Changes in RAPD patterns in mother cells and hybrid cells proved that the fusant contains two types of yeast gene originated from its parent. Furthermore, fermentation characters exhibits by the fusant cell confirmed its genetic changes. These results suggest that genetically stable hybrid yeast strains of economic importance can be produced by electrofusion technique and these electrofused yeast cells have an enormous impact in biotechnology and biomedicine.