Takamichi Hirata

Effects of Ion Energy Control on Production of Nitrogen–C60 Compounds by Ion Implantation

Nitrogen–C60 compounds such as azafullerene (C59N) and nitrogen-atom-encapsulated fullerene (N@C60) are produced by implanting nitrogen ions into C60 thin films on a substrate immersed in an electron cyclotron resonance plasma under a mirror magnetic field. Each compound is found to be synthesized, depending on the ion energy provided by the potential difference between the substrate and the plasma. The optimum energy for C59N synthesis is approximately 40–50 eV, and the amount of C59N decreases in an ion energy range larger than 50 eV. In contrast, an ion energy larger than 20 eV is required for N@C60 synthesis.

Healing burns using atmospheric pressure plasma irradiation

An experiment testing the effects of plasma irradiation with an atmospheric-pressure plasma (APP) reactor on rats given burns showed no evidence of electric shock injuries upon pathology inspection of the irradiated skin surface. In fact, the observed evidence of healing and improvement of the burns suggested healing effects from plasma irradiation. The quantities of neovascular vessels in the living tissues at 7 days were 9.2 ? 0.77 mm?2 without treatment and 18.4 ? 2.9 mm?2 after plasma irradiation.

Development of a vitamin-protein sensor based on carbon nanotube hybrid materials

A bionanosensor consisting of a field effect transistor chip and containing a mixture of poly(ethylene glycol)-grafted single-walled carbon nanotubes (SWCNTs) and SWCNTs modified with a protein (avidin) which binds with a specific vitamin (biotin) is developed. An increase in impedance due to biotin-avidin binding is observed when biotin is injected, while the injection of other vitamins resulted in a decrease in impedance. This bionanosensor reacts quickly (∼60s); in addition, the impedance recovers almost to its initial value when the bionanosensor is washed with distilled water; thus, the vitamins do not bind directly with the SWCNTs.

Chemical Modification of Carbon Nanotube Based Bio-Nanosensor by Plasma Activation

Chemical modification with plasma ion irradiation (plasma activation) is demonstrated on a bio-nanosensor based on poly(ethylene glycol)-grafted single-walled carbon nanotubes (PEG-SWNTs). By X-ray photoelectron spectroscopy (XPS) analysis, peaks that correspond to CO and COOH radicals are observed. In addition, the evaluation of the characteristic responses of the bio-nanosensor using a bovine serum albumin (BSA) antigen or oligonucleotide reveals an increase in impedance due to an antigen–antibody reaction or oligonucleotide hybridization. From these results, the bio-nanosensor is found to react with a short response time (60 s).

Measurements of electronic transport properties of single-walled carbon nanotubes encapsulating alkali-metals and C60 fullerenes via plasma ion irradiation

We report on the measurements of the electronic transport properties of Cs-encapsulated single-walled carbon nanotubes (SWNTs), Li-encapsulated SWNTs, and C60-encapsulated SWNTs synthesized by plasma ion irradiation method. After fabricating field-effect transistor (FET) configurations using pristine and plasma-ion-irradiated SWNTs, the electronic transport properties of these devices are investigated in vacuum at room temperature. As a result, C60-encapsulated SWNTs give rise to a p-type semiconducting property as pristine SWNTs do. On the other hand, it is clearly observed that Cs-encapsulated SWNTs exhibit n-type transport behavior. Moreover, Li-encapsulated SWNTs show an ambipolar transport property with both n-type and p-type characteristics. Thus, the electronic properties of SWNTs are found to be successfully controlled by plasma ion irradiation.

Treatment of cardiac disease by inhalation of atmospheric pressure plasma

The use of inhaled plasma, generated by an atmospheric-pressure plasma (APP) reactor, in a rat myocardial infarction (MI) model resulted in an increased saturation pulse oxygen (SpO2) level in the blood, which suggests that this method can be beneficial in restoring heart function following cardiac ischemia. Additionally, in vivo blood pressure decreased from 89/81 to 73/60 mmHg in the abdominal aorta during plasma inhalation. The nitric oxide (NO) concentration in the abdominal aorta increased after 20 s of plasma inhalation, reaching a maximum value at about 160 s and gradually decreased thereafter.

Si-Fullerene Compounds Produced by Controlling Spatial Structure of an Arc-Discharge Plasma.

Silicon-fullerene compounds are produced in a modified fullerene generator, where a direct-current (DC) or a radio-frequency (RF) discharge is superimposed in the periphery region of an arc-discharge plasma. The soot mass analysis gives spectrum peaks corresponding to silicon-endohedral fullerenes Si@Cn (n=74, 86, etc.). The soot structure analyses with X-ray diffraction (XRD) and high-resolution electron microscopy (HREM) demonstrate that there exist nanoparticles with the fullerene size, which are considered to be Si@Cn, and carbon nanocapsules filled with SiC.

Fat Liquefaction of Adipose Tissue Using Atmospheric-Pressure Plasma Irradiation

The liquefaction of fat in adipose tissue for potential medical applications was achieved by direct irradiation using an atmospheric-pressure plasma source and a catheter-type apparatus. When fat was irradiated with plasma generated from a catheter tip, it was liquefied through ozonolysis, although little production and diffusion of ozone originating from the collision/ionization of gas molecules was observed in preliminary experiments. Furthermore, surface damage to fat cells, such as thermal carbonization or electric shock injuries, was not observed.

Measurement of Contractile Activity in Small Animal's Digestive Organ by Carbon Nanotube-Based Force Transducer

A carbon nanotube (CNT)-based force transducer designed to be embedded in the body of a live animal was fabricated and implanted into the stomach of a rat omit to measure contractile movement. The transducer comprised dispersed poly(ethylene glycol)-grafted multiwalled CNTs applied to a comb-like Au-electrode formed on a poly(dimethylsiloxane) sheet. The implanted rat was injected with acetylcholine to induce muscular contractions and changes in the resistance of the transducer were measured. Such changes arise owing to strain in the CNT network upon distortion. The measured resistance change was found to be proportional to the concentration of injected acetylcholine.

Noninvasive measurement of fetal augmentation index by fetal aortic diameter pulse and flow velocity waveforms

Objective. To study fetal systemic arterial stiffness in normal fetuses and compromised fetuses who had umbilical placental insufficiency (UPI). Design. Prospective study. Setting. University departments. Sample. A total of 118 normal fetuses (21–40 weeks) and 55 fetuses (UPI group) with evidence of potential compromise (high umbilical artery pulsatility index). Methods. A new real‐time noninvasive measurement system based on a combined Doppler ultrasound and echo‐tracking system was used as a measure of aortic/systemic arterial stiffness. The augmentation index (AI) of the fetal thoracic descending aorta was measured by using simultaneous measurements of diameter pulse and flow velocity waveforms. Main Outcome Measure. Augmentation index as a measure of stiffness. Results. In normal fetuses, successful measurements for obtaining the AI were achieved in 103 of 118 fetuses. In the normal group, the AI, as well as placental resistance, decreased during the second trimester; in contrast, an increase in the AI was observed during the third trimester. Using the AI values from the normal group, the UPI group was divided into two subgroups: 29 fetuses with a normal AI and 26 fetuses with a high AI. The clinical outcome was significantly worse in the latter subgroup compared with the normal subgroup. Conclusions. The increase of afterload caused by a high umbilical placental resistance was associated with a decrease of aortic distensibility in the compromised fetuses, suggesting an alteration of aortic wall structure.