Magnetite nanoparticles with high heating efficiencies for application in the hyperthermia of cancer

Magnetic hyperthermia is a safe method for cancer therapy. A gap-type alternating current magnetic field (100 kHz, 100–300 Oe) is expected to be clinically applicable for magnetic hyperthermia. In this study, magnetite nanoparticles (MNPs) varying in size from 8 to 413 nm were synthesized using a chemical coprecipitation and an oxidation precipitation method to find the optimum particle size that shows a high heating efficiency in an applied magnetic field. The particles' in vitro heating efficiency in an agar phantom at an MNP concentration of 58 mg Fe/ml was measured in an applied magnetic field. In a magnetic field of 120 Oe, the temperature increase (ΔT) of the agar phantom within 30 s was 9.3 °C for MNPs with a size of 8 nm, but was less for the other samples, while in a magnetic field of 300 Oe, ΔT = 55 °C for MNPs with a size of 24 nm, and ΔT = 25 °C for MNPs with a size of 8 nm. The excellent heating efficiency of MNPs with a size of 24 nm in a magnetic field of 300 Oe may be due to a combination of the effects of both relaxation and hysteresis losses of the magnetic particles. It is believed that MNPs with a size of 8–24 nm will be useful for the in situ hyperthermia treatment of cancer.     

采用MAMMOS技术的高密度光记录

MAMMOS(Magnetic Amplifying Magneto－ Optical System:磁畴扩大磁光系统 )是实现高密度磁光盘的有效方法。不仅能得到不依赖于磁畴长度的较大的读出信号振幅,而且还能实现超出光学系统衍射极限的分辨率。过去,为实现磁畴的复印与扩大,要对记录膜面施加垂直方向的外部磁场。而现在得知,同时施加垂直磁场和水平方向的磁场,可大幅度地提高微小磁畴的读出特性。确认采用施加水平磁场的方法,在λ =635 nm, NA=0.55的条件下, 0.15μ m的连续磁畴也能获得 BER=2× 10－ 4的读出效果。     

Improvement in photo-alignment efficiency of azobenzene-containing polyimide films

We have investigated the photo-induced in-plane anisotropy of the films of two different polyimides (PIs) containing azobenzene in the backbone structure (Azo-PIs), which were synthesized from the same diamine, 4, 4′-diaminoazobenzene (DAAB), and two different dianhydrides, pyromellitic dianhydride (PMDA) or oxydiphthalic anhydride (ODPA). Under the same photo-alignment condition, the in-plane anisotropy of the ODPA–DAAB PI film was significantly larger than that of the PMDA–DAAB PI film. This result shows that the photo-alignment efficiency of the former is higher than that of the latter; i.e. the photo-alignment efficiency of Azo-PI can be improved by changing the backbone structure. We believe that the observed enhancement in the photo-alignment efficiency is attributed to a lowering of the polymer chain rigidity, which is caused by introducing an ether linkage with free rotation around non-parallel bonds into the dianhydride part.     

Precipitation control of calcium phosphate on pure magnesium by anodization

Calcium phosphate precipitated on pure magnesium from artificial plasma (modified Hanks’ solution) was varied by anodization and autoclaving, aiming the control of corrosion rate of bioabsorbable magnesium. Rough and smooth anodized film was formed depending on anodizing voltage in 1 N NaOH. The amount of calcium phosphate precipitated on the porous film was 2-3 times larger than that on the smooth film. The Ca/P ratio on the porous film was slightly higher than that on the smooth film. The autoclaving did not significantly influence the morphology of anodized film; however, the precipitation of calcium phosphate was restricted. No significant local corrosion occurred after the immersion in modified Hanks’ solution. It is demonstrated that the precipitation of calcium phosphate on magnesium can be controlled by anodization and autoclaving.     

Influence of magnetic fields on turbo-molecular pumps

Recently, turbo-molecular pumps (TMPs) have been widely used in nuclear fusion devices and sometimes used in particle accelerators. In order to use them in the quasi-static magnetic field often employed in these devices, the influence of these fields on TMPs was investigated in detail.First of all, the influence of two special magnetic fields was examined, a magnetic field orthogonal to the TMP, and one which was parallel. The parallel magnetic field had no influence on the operation of the TMP. On the other hand, the driving power and the rotor temperature were greatly affected by the vertical magnetic field. The eddy current loss in the vertical field increased rapidly with the field strength, proportionally to the square of the field strength. The eddy current loss also increased with the rotation frequency; however, it was roughly proportional to the square root of the frequency at higher frequencies. These dependences are well explained by the skin depth, which indicates the region beneath the surface of the rotor where a localized magnetic field and current flow exist.Then, we successfully calculated the influence of a magnetic field in an arbitrary direction by adding the contributions from the above two magnetic components. Furthermore, experiment revealed that a magnetic field with symmetry around the rotor axis does not affect the operation of the TMP.     

Electrochemical degradation of phenol using electrodes of Ti/RuO(2)-Pt and Ti/IrO(2)-Pt

Electrochemical degradation of phenol was evaluated at two typical anodes, Ti/RuO(2)-Pt and Ti/IrO(2)-Pt, for being a treatment method in toxic aromatic compounds. The influences of current density, dosage of NaCl, initial phenol concentration on electrochemical phenol degradation were investigated. It was found that Ti/RuO(2)-Pt anode had a higher oxygen evolution potential than Ti/IrO(2)-Pt anode, which will increase the current efficiency for electrochemical degradation, and the instantaneous current efficiency (ICE) was relatively higher at the initial time during phenol electrolysis. HOCl formed during electrolysis would play an important role on the oxidation of phenol. For the Ti/RuO(2)-Pt anode, phenol concentration decreased from around 8mg/L to zero after 30min of electrolysis with 0.3g/L NaCl as supporting electrolyte at the current density of 10mA/cm(2). Although phenol could be completely electrochemical degraded at both Ti/RuO(2)-Pt and Ti/IrO(2)-Pt anodes, phenol degradation was slower at the Ti/IrO(2)-Pt anode than at the Ti/RuO(2)-Pt anode due to the fact that passivation was to be found at the Ti/IrO(2)-Pt anode.     

The effect of molybdate anion on the ion-selectivity of hydrous ferric oxide films in chloride solutions

The ion-selective property of hydrous ferric oxide precipitate films has been investigated by measuring membrane potentials which arise across precipitate membranes of hydrous ferric oxide with and without adsorbed MoO₄^2? ions and of ferric molybdate in solutions of NaCl, KCl, MgCl₂, CaCl₂, BaCl₂, AlCl₃, and FeCl₃. The hydrous ferric oxide membrane was only permeable to Cl^? ions in chloride solutions, whereas the membrane with adsorbed MoO₄^2? ions was permeable to cations in NaCl and KCl solutions, and to both Cl^? and cations in the presence of multivalent cations. The ferric molybdate membrane was permeable to Cl^? and cations in NaCl and KCl solutions, and only to Cl^? ions in the presence of multivalent cations. It is suggested that in chloride solutions, the corrosion of iron covered with a precipitate film of hydrous ferric oxide is accelerated by enrichment of Cl^? ions under the film, which may decrease the local pH and introduce a positive diffusion potential in the film. The adsorption of MoO₄^2? ions on the oxide changes the ion-selectivity of the precipitate film from the anion-selective to the cation-selective in solutions of NaCl and KCl. This cation-selectivity of the film may inhibit the corrosion of iron, because of H⁺ ions diffusing out of the film. The inhibitive effect of MoO₄^2? ions would be reduced in the presence of multivalent cations.     

Interactions between nano-spacing flying head sliders and ultra-thin liquid lubricant films with non-uniform distribution in hard disk drives

This paper describes the effect of ultra-thin liquid lubricant films on air bearing dynamics and flyability of less than 10 nm spacing flying head sliders in hard disk drives. In particular, the effect of non-uniform lubricant film distributions on head/disk interface dynamics are studied. The disks with lubricant on one half of disk surface thicker than the other half were used in this study. The dynamics of sliders is monitored using acoustic emission (AE) and the interactions between the slider and disk are investigated experimentally. The disks were also examined with a scanning micro-ellipsometer before and after each test. Complicated slider responses were observed and clarified. In addition, it was found that the periodic lubricant film thickness modulations or non-uniformity caused by the slider-disk contact interactions could be observed. It is suggested that this lubricant film thickness non-uniformity will be one of the technical issues in order to achieve ultra-low head/disk contact interface of less than 10 nm.     

An agent architecture for strategy-centric adaptive QoS control in flexible videoconference system

In this paper, we propose an agent architecture to improve flexibility of a videoconference system with strategy-centric adaptive QoS (Quality of Service) control mechanism. The proposed architecture realizes more flexibility by changing their QoS control strategies dynamically. To switch the strategies, system considers the properties of problems occurred on QoS and status of problem solving process. This architecture is introduced as a part of knowledge base of agent that deals with cooperation between software module of videoconference systems. We have implemented the mechanism, and our prototype system shows its capability of flexible problem solving against the QoS degradation, along with other possible problems within the given time limitation. Thus we confirmed that the proposed architecture can improve its flexibility of a videoconference system compared to traditional systems. Takuo Suganuma, Dr.Eng.: He is a research associate of Research Institute of Electrical Communication of Tohoku University. He received a Dr.Eng. degree from Chiba Institute of Technology in 1997. His research interests include agent-based computing and design methodology for distributed systems. He is a member of IPSJ, IEICE and IEEE. SungDoke Lee: He is a Ph.D. Student in the Graduate School of Information Sciences in Tohoku University. He received his MEng degree at Chonbuk National University, Korea in 1991. His research interests include Flexible Network and Knowledge of Agent. Tetsuo Kinoshita, Dr.Eng.: He is an associate professor of Research Institute of Electrical Communication of Tohoku University. He received a Dr.Eng. degree in information engineering from Tohoku University, Japan. His research interests include knowledge engineering, cooperative distributed processing and agent-based computing. He received the the IPSJ Best Paper Award in 1997, etc. He is a member of IPSJ, IEICE, JSAI, AAAI, ACM and IEEE. Norio Shiratori, Dr.Eng.: After receiving his Dr.Eng degree at Tohoku University, he joined the Research Institute of Electrical Communication of Tohoku University in 1977, and is now a professor at the same University. He has been engaged in research on distributed processing system, and flexible intelligent network. He received the 25th Anniversary of IPSJ Memorial Prize-Winning Paper Award in 1985, the 6th Telecommunications Advancement Foundation Incorporation Award in 1991, the Best Paper Award of ICOIN-9 in 1994, the IPSJ Best Paper Award in 1997, etc. He has been named a Fellow of the IEEE for his contributions to the field of computer communication networks.     

Investigation of mechanism of smear formation from diamond-like carbon films on heating

Microsystem Technologies - The formation of head smears during the heat-assisted magnetic recording is a significant problem that must be addressed to ensure the reliability of the head-disk...