Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOS PRESS  

Nano-sized superparamagnetic Y3Fe5O12 ferrite having a high heat generation ability in an AC magnetic field was prepared by physical bead milling. The highest heat ability in the AC magnetic field was for the fine Y3Fe5O12 powder with a 16-nm crystallite size (the samples were milled for 4 h using 0.1 mm phi beads). The main reason for the high heat generation property of the milled samples was ascribed to an increase in the Neel relaxation of the superparamagnetic material. For the samples milled for 4 h using 0.1 mmf beads, the heat generation ability (W.g(-1)) was estimated using a 3.58 x 10(-4).f.H-2 frequency (f/kHz) and the magnetic field (H/kA.m(-1)), which is the highest reported value of superparamagnetic materials. Furthermore, Y3Fe5O12 microspheres having a 20-32 mu m diameter range were prepared by a spray dryer using the bead-milled nano-sized particles.

DOI： 10.3233/JAE-141763

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

For application as a novel ablation therapy of human cancer, the heating property of a Ti-coated mild steel rod was studied in an AC magnetic field at 300 kHz. When the Ti-tube thickness was as low as 0.1 mm, the specimen, when placed parallel to the magnetic flux direction (theta=0 degrees), exhibited a significant increase in temperature; however, its value gradually decreased with the increasing Ti thickness. In computer simulation images, the high magnetic flux concentration and concurrent large current density were observed around the interface between the mild steel rod and the Ti-tube. The heating property was drastically different at the three inclination angles (theta=0 degrees, 45 degrees, and 90 degrees) to the magnetic flux direction. However, the effect of the inclination angle was markedly reduced in the mild steel rod surrounded by a 0.3 mm thick Ti-tube, suggesting that the non-oriented heating property will be achieved for the prototype ablation needle coated with a Ti layer having the optimum thickness. (c) 2012 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2012.11.025

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

A superparamagnetic magnetic Y3Fe5O12 ferrite of 20.5 nm in particle size was prepared by bead milling using 0.05 mm phi beads for 10 h. The heat generation ability in an AC magnetic field (370 kHz, 1.77 kA-m(-1)) was 0.34 W.g(-1) for the bead-milled sample and was improved by calcination at low temperature. The main reason for this heat generation property of the milled samples was ascribed to a Neel relaxation of the superparamagnetic material. The maximum ability of 0.46 W.g(-1) in an AC magnetic field (370 kHz, 1.77 kA.m(-1)) was obtained for the sample (36.8 nm in particle size) calcined at 700 degrees C. The heat generation ability was decreased with particle growth when the calcination temperature was higher than 700 degrees C. For the sample calcined at 600 degrees C, the heat generation ability (W.g(-1)) was proportional to the square of the magnetic field (H/kA-m(-1)). In the case of the calcination at 700 degrees C, the heat generation ability (W.g(-1)) depended on the cube of the magnetic field. The heat generation mechanism would change from superparamagnetic to ferrimagnetic due to the pariticle growth at 700 degrees C. (C)2013 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.121.13

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DOI： 10.3379/msjmag.1303R011

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DOI： 10.3379/msjmag.1303R010

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

Experimental investigations were carried out on RF plasma within a ceramic tube placed on an insulating plate in dense NaCl solution (1.7-24.5 Sm-1). RF power was applied between two electrodes, and the insulating plate was placed between them. Upon performing spectroscopic measurements, we observed H and OH lines as well as strong Na lines in the emission spectra of RF plasma. Colored solution containing methylene blue was exposed to the plasma. The absorbance spectra of the colored solution before and after exposure to RF plasma clearly show that obvious degradation of methylene blue was realized. (C) 2012 The Japan Society of Applied Physics

DOI： 10.1143/JJAP.51.108005

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY  

We found that the nano-sized Y3Fe5O12 powder prepared by bead milling has the highest heat generation ability in an AC magnetic field of reported superparamagnetic materials. The heat generation ability in an AC magnetic field was strongly improved by a decrease in the average crystallite size of the bead milled samples. The highest heat ability in the AC magnetic field was for the fine Y3Fe5O12 powder with ca. 15nm crystallite size (the samples milled for 4 h using 0.1 mm beads). The reasons for the high heat generation properties of the milled samples are ascribed to an increase in the Neel relaxation of the superparamagnetic material. The heat generation ability (W.g(-1)) can be estimated using a 3.58 x 10(-4)f.H-2 frequency (f/kHz) and the magnetic field (H/kA.m(-1)) for the sample milled for 4 h using 0.1mm phi beads.

DOI： 10.1111/j.1551-2916.2011.04879.x

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

Nano-sized FeFe2O4 ferrite powder having a heat generation ability in an AC magnetic field was prepared by bead milling for a thermal coagulation therapy application. A commercial powder sample (non-milled sample) of ca. 2.0 mu m in particle size showed a temperature enhancement (Delta T) of 3 degrees C in an AC magnetic field (powder weight 1.0g, 370 kHz, 1.77 kA m(-1)) in ambient air. The heat generation ability in the AC magnetic field improved with the milling time, i.e., due to a decrease in the average crystallite size for all the examined ferrites. The highest heat ability (Delta T = 26 degrees C) in the AC magnetic field in ambient air was for the fine FeFe2O4 powder with a 4.7 nm crystallite size (the samples were milled for 6 h using 0.1 mm phi beads). However, the heat generation ability decreased for the excessively milled FeFe2O4 samples having average crystallite sizes of less than ca. 4.0 nm. The heat generation of the samples showed some dependence on the hysteresis loss for the B-H magnetic property. The reasons for the high heat generation properties of the milled samples would be ascribed to an increase in the Neel relaxation of the superparamagnetic material. The hysteresis loss in the B-H magnetic curve would be generated as the magnetic moment rotates (Neel relaxation) within the crystal. The heat generation ability (Wg(-1)) can be estimated using a 1.07 x 10(-4) fH(2) frequency (f, kHz) and the magnetic field (H, kA m(-1)) for the samples milled for 6 h using 0.1 mm phi beads. Moreover, an improvement in the heating ability was obtained by calcination of the bead-milled sample at low temperature. The maximum heat generation (Delta T = 59 degrees C) ability in the AC magnetic field in ambient air was obtained at ca. 5.6 nm for the sample calcined at 500 degrees C. The heat generation ability (Wg(-1)) for this heat treated sample was 2.54 x 10(-4) fH(2). (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matchemphys.2011.05.061

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

The excitation temperature, electron density, temperature of OH, and behavior of bubbles generated by a 27.12 MHz in-liquid plasma are investigated in water under pressures ranging from 0.1 to 0.4 MPa. The excitation temperature decreases as the pressure increases and, conversely, the temperature of OH and the electron density increase. Since the plasma can be generated stably even under high-pressure conditions and the liquid provides a cooling effect, the electrode is not damaged by the heat. The bubbles generated from the tip of the electrode have a fixed relationship between their diameter and departure frequency. The in-liquid plasma can be stably generated even under high pressures and it maintains a high superheated state of a few thousand K. A boiling phenomenon in the in-liquid plasma uses the plasma itself as a heat source.

DOI： 10.1088/0963-0252/20/3/034012

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER  

We found the most promising powder material for the application of the thermal coagulation therapy for the treatment of cancerous tissues. The maximum heat generation ability (Delta T = 40-77 degrees C, 370 kHz, 1.77 kA.m(-1)) was obtained for the powder materials by the calcination at 1100 degrees C for the Y3 - XGdXFe5O12 system. This Delta T value is higher than ca. Delta T = 30 degrees C in same magnetic field for fine FeFe2O4 particles as the candidate material for this type of therapy. The particle growth with the formation of the cubic single phase might influence to the high heat generation. As an unexpected result, the Gd3Fe5O12 (X=3) has no heat generation ability in an AC magnetic field. (C) 2011 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.matlet.2011.02.034

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

Nanosized MgFe2O4-based ferrite powder having heat generation ability in an AC magnetic field was prepared by bead milling and studied for thermal coagulation therapy applications. The crystal size and the particle size significantly decreased by bead milling. The heat generation ability in an AC magnetic field improved with the milling time, i.e. a decrease in crystal size. However, the heat generation ability decreased for excessively milled samples with crystal sizes of less than 5.5nm. The highest heat ability (Delta T34 degrees C) in the AC magnetic field (370kHz, 1.77kA/m) was obtained for fine MgFe2O4 powder having a ca. 6 nm crystalsize (the samples were milled for 6-8 h using 0.1 mm phi beads). The heat generation of the samples was closely related to hysteresis loss, a B-H magnetic property. The reason for the high heat generation properties of the samples milled for 6-8 h using 0.1 mm f beads was ascribed to the increase in hysteresis loss by the formation of a single domain. Moreover, the improvement in heating ability was obtained by calcination of the bead-milled sample at low temperature. In this case, the maximum heat generation (Delta=41 degrees C) ability was obtained for a ca. 11 nm crystal size sample was prepared by crystal growth during the sample calcination. On the other hand, the Delta T value for Mg0.5Ca0.5Fe2O4 was synthesized using a reverse precipitation method decreased by bead milling. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2010.10.010

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The heat generation ability of needle-type materials was studied for the application of thermal coagulation therapy in an AC magnetic field. Although the Ti tube without the MgFe2O4 powder or Ti rod showed poor heat generation abilities in an AC magnetic field, the temperature was significantly increased by the presence of ferrite powder in the Ti tube. We confirmed using a computer simulation that the eddy loss of the Ti tube was increased by the enhanced magnetic flux density due to the ferrite powder in the Ti tube. The heat generation of the ferrite filled Ti tube was increased by utilization of the quenched MgFe2O4 powder from elevated temperature. The relative magnetic permeability of the quenched ferrite was enhanced with the decrease in the inverse ratio of the cubic spinel structure. The heat generation ability was increased with the increase in the relative magnetic permeability of the Ti tube with ferrite powder. The calculated joule loss based on the experimental results showed an agreement with those using the computer simulation. (C) 2010 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jmmm.2010.08.035

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：EMERALD GROUP PUBLISHING LIMITED  

Purpose - The purpose of this paper is to develop a ferromagnetic needle adaptable for a novel ablation cancer therapy; the heat generation ability of the mild steel rod embedded into the Ti-tube having a different thickness was investigated in a high-frequency output at 300 kHz.Design/methodology/approach - The outer diameter and length of the Ti-tubes were 1.8 and 20 mm, respectively, while the inner diameter was varied from 1.6 to 0 mm. The mild steel rod was embedded in a Ti-tube for preparing the needle-type specimen. Their heat generation ability was examined by changing the inclination angle to the magnetic flux direction in a high-frequency coil.Findings - When the thickness of the Ti surrounding the mild steel rod was as low as 0.1 mm, the heat generation ability was drastically different among the three inclination angles (theta = 0 degrees, 45 degrees, and 90) to the magnetic flux direction due to the effect of the shape-induced magnetic anisotropy. However, the effect of the inclination angle was almost eliminated in the specimen surrounded by the 0.4 mm thick Ti, suggesting that the non-oriented heat generation property is achieved for the needle-type mild steel rod coated with Ti having the optimum thickness.Originality/value - The prototype ablation needle having a complete non-oriented heat generation ability was fabricated to use in subsequent animal experiments. It is considered that the newly designed Ti-coated device is useful in ablation treatments using a high-frequency induction heating.

DOI： 10.1108/03321641111152739

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DOI： 10.1088/0963-0252/20/3/034016

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CERAMIC SOC JAPAN-NIPPON SERAMIKKUSU KYOKAI  

MgFe2O4 microspheres having a 20-32 mu m diameter range were prepared by a spray dryer using bead-milled nano-sized particles. A commercial powder having a several mu m particle size was bead-milled to an approximate 6.2 nm crystallite size. The microspheres were obtained using the spray dryer when the air pressure was low (0.03 MPa). The yield of the MgFe2O4 20-32 mu m microspheres was improved by combination of a low air pressure and high ferrite concentration in the slurry. The heat generation ability in an AC magnetic field (370 kHz, 1.77 kA/m) was improved by the bead milling. (C) 2010 The Ceramic Society of Japan. All rights reserved.

DOI： 10.2109/jcersj2.118.1207

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The degradation of methylene blue by radio frequency (RF) plasmas in water under ultraviolet (UV) irradiation was studied experimentally. When the methylene blue solution was exposed to RF plasma, UV irradiation from a mercury vapor lamp enhanced degradation significantly. A lamp without power supply also enhanced degradation since weak UV light was emitted weakly from the lamp due to the excitation of mercury vapor by stray RF power. Such an enhancement is explained by the fact that after hydrogen peroxide is produced via the recombination process of OH radicals around the plasma, OH radicals reproduced from hydrogen peroxide via the photolysis process degrade methylene blue. (C) 2009 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jhazmat.2009.09.076

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Hydrogen is produced by generating in-liquid plasma in a conventional microwave oven. A receiving antenna unit consisting of seven copper rods is placed at the bottom of the reactor furnace in the microwave oven. 2.45 GHz microwave in-liquid plasma can be generated at the tips of the electrodes in the microwave oven. When the n-dodecane is decomposed by plasma, 74% pure hydrogen gas can be achieved with this device. The hydrogen generation efficiency for a 750 W magnetron output is estimated to be approximately 56% of that of the electrolysis of water. Also, in this process up to 4 mg/s of solid carbon can be produced at the same time. The present process enables simultaneous production of hydrogen gas and the carbide in the hydrocarbon liquid. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3236575]

DOI： 10.1063/1.3236575

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Spectroscopic measurements of high frequency (hf) plasma were performed under high pressure conditions (5 and 7 MPa) and supercritical (sc) CO2 conditions (8-20 MPa). Temperature evaluated from C-2 Swan bands (d (3)Pi(g)-> a (3)Pi(u)) increased from 3600 to 4600 K with an increase in pressure. The first observation of broadening and shifting of the O I line profile (3p (5) P-3,P-2,P-1 -> 3s (5) S-2(0)) of hf plasma under sc CO2 conditions was carried out. However, the origin of broadening and the shifting cannot be understood because the present theory explaining them is not valid for such high pressure conditions.

DOI： 10.1063/1.3091927

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INFORMA HEALTHCARE  

Purpose: This study investigated the efficacy of repeated thermotherapy for breast cancer utilising a novel sintered MgFe2O4 needle and alternating current (AC) magnetic field in xenograft animal models mimicking human breast cancer.
Materials and methods: A sintered MgFe2O4 needle and an apparatus to apply an AC magnetic field were prepared for this study. Animals bearing BT-474 tumours (mean (+/- standard deviation) volume, 471 +/- 153 mm(3)) were divided into four groups. A sintered MgFe2O4 needle (length, 5 mm) was placed in the centre of each tumour. An AC magnetic field (amplitude, 4 kA/m; 2 kW; 540 kHz) was applied for 10 min once, twice or three times for the first, second and third groups, respectively, and was not applied for the control group. Temperature during treatment and tumour volume 8 weeks after first treatment were assessed.
Results: Maximum tumour temperature tended to increase in repeated-application groups: group 1, 59.2 +/- 4 degrees C; group 2, 58.9 +/- 3.3 degrees C and 61.2 +/- 8.9 degrees C for the first and second applications; and group 3, 60.4 +/- 4.6 degrees C, 62.1 +/- 7.8 degrees C and 71.1 +/- 6.1 degrees C for the first, second and third applications. Tumour volumes in control, groups 1, 2 and 3 at 8 weeks after treatment were 3633 +/- 2478 mm(3), 3240 +/- 1031 mm(3), 1252 +/- 1289 mm(3) and 0 mm(3), respectively. Tumours were significantly smaller in group 3 than in the control and group 1 at 8 weeks.
Conclusions: The efficacy of repeated inductive heating utilising a sintered MgFe2O4 needle was demonstrated. Thermotherapy using the present method may offer an effective non-surgical treatment for human breast cancer.

DOI： 10.1080/02656730902991459

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

An off-axis sawtooth oscillation is excited by electron cyclotron heating in a lower hybrid current drive plasma in the WT-3 tokamak. The internal structure of the plasma is investigated using computer tomography with five detector arrays after the application of singular value decomposition to the soft X-ray detector signals. It is found that the precursor oscillation of the off-axis sawtooth collapse is the m = 2 mode. On the other hand, the double m = 2 mode structure is observed as a postcursor of the collapse.

DOI： 10.1109/TPS.2008.917166

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

New magnetic materials having a potentially high heat generation ability in an ac magnetic field were studied for application in thermal coagulation therapy. The Mg1-xCaxFe2O4 ferrites with X varied from 0 to 1.0 were synthesized using a reverse coprecipitation method. The obtained precursors were calcined at various temperatures in the range of 300-1000 degrees C with the intent to obtain fine ferrite powders. The heat generation in an ac magnetic field was very poor for X = 0. However, the heat generation improved with partial Ca2+ substitution of the Mg2+ sites. The maximum rise in temperature (Delta T) in the ac magnetic field (370kHz, 1.77 kA/m) was ca. 50 degrees C for the samples with 1.0g in weight and 0.2-0.8 in X of Mg1-xCaxFe2O4. Especially, the samples calcined at 800 degrees C showed the highest heat generation. When the Ca2+-substituted samples were calcined at 900 degrees C, the heat generation was reduced due to decomposition into the two phases of the MgFe2O4-type cubic and CaFe2O4-type orthorhombic. In addition, the samples calcined at 300 degrees C also showed a high heat generation. Although the crystal and particle sizes increased with the calcination temperature, they did not influence the heat generation of this system. The heat generation of the samples was closely related to the hysteresis loss. The reason for the high heat generation properties of the samples calcined at 300 and 800 degrees C is ascribed to the increase in the hysteresis loss by distortion of the cubic crystal structure. (c) 2007 Elsevier B.V All rights reserved.

DOI： 10.1016/j.jallcom.2007.07.024

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Radio frequency (RF) plasma in water was used for the degradation of methylene blue. The fraction of decomposition of methylene blue and the intensity of the spectral line from OH radical increased with RF power. RF plasma in water also produced hydrogen peroxide. The density of hydrogen peroxide increased with RF power and exposure time. When pure water (300 mL) is exposed to plasma at 310 W for 15 min, density of hydrogen peroxide reaches to 120 mg/L. Methylene blue after exposed to plasma degraded gradually for three weeks. This degradation may be due to chemical processes via hydrogen peroxide and tungsten. The comparison between the experimental and calculated spectral lines of OH radical (A-X) shows that the temperature of the radical is around 3,500 K. Electron density is evaluated to be similar or equal to 3.5 x 10(20) m(-3) from the stark broadening of the H(beta) line.

DOI： 10.1007/s11090-008-9142-2

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：JAPAN SOC APPLIED PHYSICS  

The plasma in water is generated by applying high-frequency (HF) irradiation of 27.12 MHz or microwave (MW) radiation of 2.45 GHz from an electrode. The electrode is heated by joule heating by the HF or MW irradiation, and vapor bubbles are generated simultaneously. The plasma is then ignited inside the bubbles on the electrode. The glow discharge plasma can be maintained in spite of atmospheric pressure due to the cooling effect of the liquid itself. The electron temperature of the plasma generated by the 27.12 MHz radiation is higher than that generated by the 2.45 GHz radiation. (C) 2008 The Japan Society of Applied Physics.

DOI： 10.1143/APEX.1.046002

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

To study surface behaviors, MgFe2O4 ferrite materials having different grain sizes were synthesized by two different chemical methods, i.e., a polymerization method and a reverse coprecipitation method. The single phase of the cubic MgFe2O4 was confirmed by the X-ray diffraction method for both the precursors decomposed at 600-1000 degrees C except for a very small peak of Fe2O3 was detected for the samples calcined at 600 and 700 degrees C by the polymerization method. The crystal size and particle size increased with an increase in the sintering temperature using both methods. The conductance of the MgFe2O4 decreased when the atmosphere was changed from ambient air to air containing 10.0 ppm NO2. The conductance change, C = G(air)/G(10 ppm NO2), was reduced with an increase in the operating temperature. For the polymerization method, the maximum C-value was ca. 40 at 300 degrees C for the samples sintered at 900 degrees C. However, the samples sintered at 1000 degrees C showed a low conductance change in the 10 ppm NO2 gas, because the ratio of the O-2 gas adsorption sites on the particle surface is smaller than those of the samples having a high C-value. The low Mg content on the surface affects the low ratio of the gas adsorption sites. For the reverse coprecipitation method, the particle size was smaller than that of the polymerization method. Although a stable conductance was obtained for the sample sintered at 900 and 1000 degrees C, its conductance change was less than that of the polymerization method. (c) 2007 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.apsusc.2007.09.024

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INT INST ANTICANCER RESEARCH  

Background: This study investigated a novel approach for tumor ablation therapy using an alternating magnetic field combined with a sintered MgFe(2)O(4) needle. This method differs from radiofrequency ablation (RFA) by dielectric heating with regard to the heating mechanism and improves some weak points of these conventional thermotherapies. Materials and Methods: Nude mice mimicking human breast cancer BT474 were treated using this method. The extent of tumor death was assessed after ablation. Results: Staining with hematoxylin and eosin showed gradual expansion of the pyknotic area until 48 h after ablation. Nicotinamide adenine dinucleotide diaphorase staining also showed complete tumor death by 48 h after treatment. The ablation area was well controlled and reablation was not necessary. The tumor could be completely controlled using this method without any risk of skin burn. Conclusion: This novel ablation therapy appeared to be more effective and less invasive for treatment of breast cancer treatment than RFA.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP PUBLISHING LTD  

A supercritical carbon dioxide (CO2) plasma process for fabricating one-dimensional tungsten oxide nanowires coated with amorphous carbon is presented. High-frequency plasma was generated in supercritical carbon dioxide at 20 MPa by using tungsten electrodes mounted in a supercritical cell, and subsequently an organic solvent was introduced with supercritical carbon dioxide into the plasma. Electron microscopy and Raman spectroscopy investigations of the deposited materials showed the production of tungsten oxide nanowires with or without an outer layer. The nanowires with an outer layer exhibited a coaxial structure with an outer concentric layer of amorphous carbon and an inner layer of tungsten oxide with a thickness and diameter of 20-30 and 10-20 nm, respectively.

DOI： 10.1088/0957-4484/18/49/495603

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

An experiment was conducted for generating high-frequency plasma in supercritical carbon dioxide; it is expected to have the potential for applications in various types of practical processes. It was successfully generated at 6-20 MPa using electrodes mounted in a supercritical cell with a gap of 1 mm. Emission spectra were then measured to investigate the physical properties of supercritical carbon dioxide plasma. The results indicated that while the emission spectra for carbon dioxide and carbon monoxide could be mainly obtained at a low pressure, the emission spectra for atomic oxygen could be obtained in the supercritical state, which increased with the pressure. The temperature of the plasma in supercritical state was estimated to be approximately 6000-7000 K on the assumption of local thermodynamic equilibrium and the calculation results of thermal equilibrium composition in this state showed the increase of atomic oxygen by the decomposition of CO2. (C) 2007 American Institute of Physics.

DOI： 10.1063/1.2724240

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：TAYLOR & FRANCIS INC  

The purpose of this study is to elevate the temperature and induce necrosis tumor cells that include ferrite powder to 50-60 degrees C by applying an alternating magnetic field. The achieved temperature is higher when compared to the conventional hyperthermia methods. We performed an experiment in which a high-water content agar phantom that was used as a quasi-tissue had 50 nm-10 mu m magnesium ferrite (MgFe2O4) dispersed in it and was then heated to a level of 190-700 kHz. The results show that the temperature of the phantom is higher for higher frequencies, larger particle sizes, and higher quantities of dispersed ferrite powder. Also, taking into account heat generation due to the magnetic powder, heat generation due to tissue metabolism, and the cooling effect of the blood flow, we solved the thermal equation related to local thermal therapy. Small differences in the distribution of ferrite powder affect the temperature increase of the tissue and the area where cell necrosis is induced.

DOI： 10.1080/01457630701483711

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST PURE APPLIED PHYSICS  

We generate a radio frequency (RF) plasma in water at an atmospheric pressure by applying an RF power of 13.56 MHz from an electrode. The plasma is in a bubble formed in water. On the basis of hydrogen spectral lines under the assumption of thermal equilibrium, the temperature of the plasma is estimated to be 4000-4500K. Spectroscopic measurements show that hydrogen and oxygen are excited in the plasma. The plasma is also obtained in tap water or NaCl solution with a high conductivity. In the solution, sodium spectral lines are observed. Colored water containing methylene blue is exposed to the plasma. The absorbence spectra of the colored water before and after exposure to the plasma suggest the decomposition of organic matter due to chemical reactions involving active species, such as OH-radicals.

DOI： 10.1143/JJAP.45.8864

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST PURE APPLIED PHYSICS  

Needle-type materials were studied for the, application of thermal coagulation therapy in an AC magnetic field. We found that the Ti tube filled with ferrite powder as the core had a high heat generation ability in an AC magnetic field. Although the Ti tube without the ferrite powder or Ti rod showed poor heat generation abilities, the temperature was significantly increased by the existence of ferrite powder in the tube. In this case, the ferrite powder seems to improve the eddy loss for the Ti tube. The maximum heat generation ability was obtained for the Ti tube that contained MgFe2O4 powder in the examined Ti tube with some ferrites.

DOI： 10.1143/JJAP.45.8673

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The generation of microwave plasma in liquid with vapor bubbles has been achieved and will soon be applied to high-speed chemical vapor deposition. Vapor bubbles are induced from an electrode by heating. The deposition rate of diamondlike carbon films depends on the pressure and the power of the microwave supply. Polycrystalline silicon carbide is synthesized on a silicon substrate in a mixture of n-dodecane and silicone oil. The dispersion of water droplets in liquid creates many pores on the silicon carbide films. The synthesis of carbon nanotubes can be achieved in liquid benzene. (c) 2006 American Institute of Physics.

DOI： 10.1063/1.2208167

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：PERGAMON-ELSEVIER SCIENCE LTD  

Nano-sized FeFe2O4 ferrite powder for local thermal coagulation therapy was synthesized by a reverse coprecipitation method. The crystal diameter for the samples from the reverse coprecipitation method was smaller than that from a normal coprecipitation method. The crystal diameter increased with an increase in the synthesized temperature for both methods. The maximum increasing temperature under the AC magnetic field was at around a 12 nm crystal diameter. The FeFe2O4 powder was oxidized to Fe2O3 by calcination at 600 degrees C in ambient air. The heating ability almost depended on the hysteresis loss value. Although the increased temperature under the AC magnetic field for the fresh FeFe2O4 sample was very close to that for the commercialized MgFe2O4 powder, it was gradually decreased for FeFe2O4 with time in ambient air. (c) 2005 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.materresbull.2005.03.014

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Selection of ferrite powder was carried out to realize a thermal coagulation technique in which tumors are locally heated by an application of alternating magnetic field from external coils. Magnesium ferrite (MgFe2O4) showed the largest increase in temperature (AT) under an alternating magnetic field in all the ferrites examined. For all the samples, AT value under alternating magnetic field was increased with an increase in frequency (200-500 kHz). The heating ability for the Mg-ferrite was ca. 1.4 W/g under alternating magnetic field of 4.0 kA/m (200 W, 370 kHz). The heating ability in alternating magnetic field was clearly depended on the magnitude of the hysteresis loss for the ferrite powder. (C) 2005 Springer Science + Business Media, Inc.

DOI： 10.1007/s10853-005-5698-x

Web of Science

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DOI： 10.1246/cl.2005.482

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DOI： 10.1016/j.jmmm.2003.12.591

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Language：English  

DOI： 10.1016/j.jmmm.2003.12.848

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST PURE APPLIED PHYSICS  

To develop materials for achieving local hyperthermia, we investigate the heating of various ferrite and metal powders by applying an external AC magnetic field. In comparison with magnetite powder, which has often been used in previous experiments, Mg-ferrite powder is more applicable for achieving local hyperthermia.

DOI： 10.1143/JJAP.41.1620

Web of Science

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Language：English  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

A pressure driven m = 1/n = 1 mode is excited by lower hybrid current drive in the WT-3 tokamak [T. Maehara et al., Nucl. Fusion 38, 39 (1998)]. The excitation of the mode is accompanied with the decrease of the magnetic shear and with the peaking of the soft x-ray emissivity profile inside the q = 1 surface. The crescent-shaped mode structure appeared on the contour map of the soft x-ray emissivity is consistent with that of the quasi-interchange mode. The m = 1 mode can be suppressed by electron cyclotron heating near the q = 1 surface. The range of the location of the electron cyclotron resonance layer effective for the complete suppression is much wider and the time scale for the suppression is much faster than those in the case of the suppression of the tearing mode in the ohmic heating plasma. (C) 2000 American Institute of Physics. [S1070-664X(00)03301-2].

DOI： 10.1063/1.873823

Web of Science

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Language：English  

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DOI： 10.1088/0029-5515/38/1/304

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DOI： 10.1143/JJAP.37.2681

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DOI： 10.1016/S0375-9601(98)00623-9

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DOI： 10.1063/1.871498

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DOI： 10.1016/0920-3796(94)00172-4

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DOI： 10.1016/0920-3796(95)92542-T

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DOI： 10.1063/1.1146042

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DOI： 10.1016/0375-9601(95)00741-K

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DOI： 10.1103/PhysRevLett.70.2561

PubMed

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DOI： 10.1088/0029-5515/32/10/I05

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DOI： 10.1063/1.860375

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Language：Japanese  

DOI： 10.2320/materia.45.664

CiNii Books

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Language：Japanese   Publisher：Ehime University  

An attempt has been made to obtain a medical material applicable to the ablation therapy of liver cancer. The heating property of the needle-shaped Mg-ferrite (MgFe2O4) prepared using a sintering technique was studied under an external AC magnetic field at 370 kHz. The increase in temperature (ΔT) was as high as 32℃ for the stick of 1.5 mm in diameter, while the complementary use of these three sticks achieved marked ΔT enhancement of 58℃. In a rabbit liver, high-frequency inductive heating of the needle-shaped Mg-ferrite resulted in the local destruction of the tissue due to coagulative necrosis.

CiNii Books

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Other Link： https://opac1.lib.ehime-u.ac.jp/iyokan/TD00000996

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Language：Japanese   Publisher：Ehime University  

Selection of ferrite powder and suitable frequency were carried out to realize a thermal coagulation technique in which tumors are locally heated to 60-80℃ by an application of alternating magnetic field from external coils after they are stuffed with ferrite powder. Various ferrite powders were heated by an alternating magnetic field in 80kHz-399kHz. In this frequency range, the largest increase in temperature (ΔT) was obtained for the MgFe_2O_4 in all the samples examined. The ΔT value was almost proportional to the applied power and the weight of the powder. The heating ability for the Mg-ferrite was ca. 86 J・min^<-1>・g^<-1> under AC magnetic field (200W, 370kHz).

CiNii Books

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Other Link： http://iyokan.lib.ehime-u.ac.jp/dspace/handle/iyokan/1408

Language：Japanese   Presentation type：Poster presentation  

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Language：English   Presentation type：Poster presentation  

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Language：Japanese   Presentation type：Oral presentation (invited, special)  

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