Effect of ferrite thermoseeds on destruction of carcinoma cells under alternating magnetic field

High iron-containing silicate glasses were prepared using a conventional melting and quenching process, and ferrimagnetic crystallites were precipitated via a nucleation and crystal growth mechanism. This study attempted to use these ferrite-containing glass-ceramics as thermoseeds for a hyperthermic cancer treatment under an alternating magnetic field. KB and L929 cells were used in the cell lysis experiments, as carcinoma and normal cells, respectively. These cells were mixed with an agar medium and stained prior to the annihilation test. After exposing the cells to the alternative magnetic field for 9 min, the number of carcinoma cells in the vicinity of the ferromagnetic specimen decreased with increasing time and almost all cancer cells were dead after 9 min while they were still alive in a region of 5 cm away from the specimen. When Sprague-Dawley rats imbedded the samples were exposed to a magnetic field, tumor cells disappeared after only 4 treatments of 15 min each. This amazing reduction in the tumor was not observed in any rats without the imbedded sample. It is expected that the prepared ferrite-containing glass-ceramics will be helpful in hyperthermic cancer treatment. Long-term research is needed to confirm this result.     

Prediction of thermal coagulation by AC inductive heating of Mg1-xCaxFe2O4 ferrite powder

The purpose of this study is to investigate the thermal characteristics of Mg_1−XCa_XFe₂O₄ ferrite powder by applying AC magnetic field and to predict the effect of thermal coagulation in vivo. We found that heating characteristics of the ferrite powder became greater as the frequency through the 400 kHz to 700 kHz range. The highest heat generation was attained using 7–15 nm ferrite powder. We also carried out a heat transfer simulation in which we were able to demonstrate that this material has sufficient heat generating characteristics to thermally coagulate a tumor cell and that it is possible to predict the range of the coagulation from the present simulation.     

Fe78Si13B9/铁氧体复合材料磁粉芯制备及其软磁性能

用Mn-Zn铁氧体溶胶对非晶Fe78Si13B9粉体包覆,模压成型制备了复合磁粉芯,并研究了复合材料磁粉芯的软磁性能.实验结果表明,铁氧体粉体在500℃×2h的热处理条件下逐渐生成,并在非晶Fe78Si13B9颗粒表面较好包覆;铁氧体溶胶的加入,大大提高了非晶Fe78Si13B9磁粉芯的品质因数Q值.当铁氧体溶胶量为7%、30℃的测试温度时,Fe78Si13B9/铁氧体复合材料磁粉芯的磁导率在1MHz时达到最大值32,Q值高达23.     

磁流体在交变磁场中的热效应研究

制备了平均粒径分别为4、6 和8nm 的Fe3O4 粒子,将其分散在不同的介质中,在63kHz、7kA/m的交变磁场中研究其热效应。实验结果显示,粒径较大的Fe3O4 粒子具有较高的产热比功率(SAR),Fe3O4 粒子经过表面处理后SAR显著增加,而且SAR随表面活性剂不同而不同,还显示SAR与磁场强度的平方成正比。     

永磁铁氧体烧结过程应力场有限元分析

利用有限元法对永磁铁氧体材料烧结过程的瞬态应力场进行了数值模拟分析,讨论了温度场变化对铁氧体磁瓦内部热应力的影响,得出磁瓦在烧结过程中的等效应力分布云图,结合分布图与热传导方程讨论了磁瓦烧结开裂问题中产生边裂和角裂的原因.同时分析了升温速率对应力场的影响,该分析结果反映了升温速率对磁瓦内部热应力最大值的影响规律.模拟结果为磁瓦烧结工艺制度的制定提供理论依据.     

永磁铁氧体烧结过程温度场有限元分析

利用有限元分析法对永磁铁氧体材料烧结过程温度场进行了数值模拟研究,得出铁氧体磁瓦在烧结过程的不同传热方式下、不同烧结阶段的温度分布规律,得出了烧结过程对流传热为主的低温阶段与辐射传热为主的高温阶段的分界温度.同时对对流为主的低温阶段的模拟结果进行了实验验证,得出模拟结果与实验结果定性符合.模拟结果为磁瓦烧结工艺制度的制定提供理论依据.     

Crystalline structures and intrinsic magnetic properties of ZnTi-substituted hexagonal M-type Ba ferrite powder

Ion-substituted hexagonal M-type Ba ferrites are studied more and more frequently due to their large magnetic anisotropy and low production cost. In this study, hexagonal M-type Ba ferrite powder specimens with nominal composition Ba(ZnTi)_xFe_12−2xO₁₉ (x = 0.0, 0.2, 0.6, 1.0, 1.4) were prepared via a new route by combining a chemical coprecipitation technique with a conventional ceramic technique. The magnetic properties and crystalline structures were studied by a vibrating sample magnetometer and an X-ray diffractometer, respectively. It was found that small quantities of ZnTi substitutions helped to form single-phase ferrite at a low calcination temperature, which has never been reported before. The magnetic properties were reduced obviously with the increase of x from 0.2 to 1.4, and the best content of substitutions in our case was x = 0.2.     

Electric arc of a two-jet plasmotron in an alternating magnetic field

The results of experiments and analytic expressions describing the behavior of an arc in a two-jet plasmotron in an alternating magnetic field are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 46, No. 3, pp. 476–480, March, 1984.     

The effects of thermal processing in a magnetic field on grain boundary characters of ferrite in a medium carbon steel

Effects of a magnetic field on low-angle misorientation distribution and CSL boundary occurrence in ferrite in 42CrMo steel during the austenite to ferrite and pearlite transformation were investigated. The results show that a magnetic field can considerably lower the frequency of low-angle misorientations in ferrite lamellae and raise the occurrence of Σ coincidence boundaries, especially Σ 3 in ferrite. But no obvious effect on crystallographic orientation distribution, or texture, was detected.     

磁场诱导自蔓延高温合成钡铁氧体

本文采用外加磁场诱导自蔓延高温合成钡铁氧体,试验用的电磁场强度最高可达1.3T,对无磁场和不同磁场强度下合成的铁氧体的形貌、相组成和磁性能分别进行了表征.研究结果表明:外加磁场对燃烧温度有影响,燃烧温度影响产物转换,燃烧温度较低时,产物为BaFe2O4与BaFe12O19相共存;本试验条件下,磁场强度为0.86T时,合成为M型的钡铁氧体(BaFe12O19),产物结晶完整,有六角片状的钡铁氧体,且性能达到了最佳,矫顽力达到1083(4π)-1·kA·m-1,比剩余磁化强度为16.16 A·m2/kg,比不加磁场条件下分别提高50%和提高32%,说明适当的磁场强度诱导自蔓延高温合成可以改善BaFe12O19的磁性能.     

磁场中磁性纳米流体热导率的研究

进行了提高磁场中含四氧化三铁(Fe3O4)纳米磁性颗粒机油(磁性纳米流体)热导率的研究。在有或无超声波辅助的条件下,采用共沉淀法合成了不同粒度的Fe3O4磁性纳米颗粒,采用一种热常数分析仪对该磁性纳米流体的热导率进行了测定,探讨了纳米磁性颗粒粒度、体积分数以及背景磁场对磁性纳米流体导热性能的影响。实验结果表明,在外磁场中,磁性纳米流体所含Fe3O4纳米颗粒的体积分数越大,磁性颗粒粒度越小,磁性纳米流体的热导率越高;当磁场方向平行于温度梯度时更有利于提高磁性纳米流体的热导率。     

Superconducting shields for alternating magnetic fields

This paper describes a shield to guard a dc superconducting field from an ac field.     

Dynamics of the conductivity solid bodies in a high-frequency alternating magnetic field

The conductivity bodies and systems of pendulum types situated in alternating magnetic field are very interesting objects from physical and mathematical point of view. In dependence of correlation between eigen frequency and frequency of external alternating magnetic field, many motions with very different characters are possible. So in high-frequency magnetic field is experimentally observed and mathematically described the stability of overturn pendulum state and also self-excited oscillations. If the magnetic field with average frequency like to eigen frequency, many others kinds of motions are possible. Particular motions of rare attractors type and others. The technical sense of these effects may be used for support stability of beforehand unstable positions conductivity bodies and so the excitement of oscillations with necessary characters, particular oscillations with necessary frequency.     

交变磁场对制动器摩擦噪声抑制的试验研究

基于摩?磁复合盘式制动器和模拟制动试验台,分析了不同磁场参数与制动器摩擦噪声及摩擦磨损行为之间的非线性映射关系,讨论了交变磁场对制动器摩擦噪声的抑制机理.结果表明:磁场可明显抑制制动器摩擦噪声的产生,其中磁感应强度的改变对降噪效果更为明显;低频磁场对噪声有较好抑制作用,但磁场频率过高反而可能会加剧噪声的产生.磁场具有稳...     

Remagnetization of a circularly anisotropic amorphous wire in an alternating magnetic field

Remagnetization of an amorphous ferromagnetic wire with circular anisotropy in an alternating longitudinal magnetic field was theoretically studied within the framework of a quasistationary approximation. A frequency spectrum of the emf generated in a probing coil wound on the wire was determined, and analytical expressions describing the dependence of the emf amplitude on the alternating magnetic field amplitude H ₀ and the constant magnetic bias field value H _e were derived. The results can be applied to the development of weak magnetic field sensors.     

Effect of alternating magnetic field on the growth of the primaryroot of corn

Corn seeds each with a primary root were exposed to alternating magnetic fields. Locations of the root before and after exposure were accurately measured, and the growth during the exposure was calculated. These values were compared with those of the control group. Results indicate that the relatively low frequencies used in the experiments hastened the growth of the primary root while relatively high frequencies slowed root development