Biomedical subjects

H Mamiya

Publications and source records attributed to H Mamiya.

9 recordsLinked to original sources

PubMed2002

Magnetic relaxations of antiferromagnetic nanoparticles in magnetic fields.

We reexamine anomalous magnetic relaxations of ferritin in magnetic fields, the presence of which has been regarded as evidence suggesting the existence of thermally assisted macroscopic quantum tunneling in antiferromagnetic nanoparticles. In the present study, relaxation curves of ferritin are examined using an approach that is free from assumptions regarding distributions of various parameters of polydispersive particles. The results are not anomalous. In other words, the relaxation is accelerated by the field, as expected for classical superparamagnetic fluctuations.

Journal Article↗

PubMed2000

Phase transitions of iron-nitride magnetic fluids.

Phase transitions of magnetic fluids in the zero field were studied from the viewpoint of static susceptibility and typical relaxation time in order to distinguish between the transitions and the blocking phenomena. We used iron-nitride magnetic fluids containing nearly uniform particles so as to remove the effects of particle-size distribution. In the densest sample, we observed the growth of ferromagnetic fluctuations and, in the diluted samples, a temperature-induced first-order phase transition.

Journal Article↗

PubMed1998

Pain following intravenous administration of sedative agents: a comparison of propofol with three benzodiazepines.

The purpose of the present study is to compare the injection pain of propofol with that of benzodiazepines when used for intravenous sedation. In addition, we evaluated the efficacy of coadministering a small dose of 1% lidocaine (20 mg) to reduce the pain accompanying propofol injection. Intravenous propofol, diazepam, midazolam, or flunitrazepam were administered on separate occasions to volunteers and outpatients. The degree of injection pain was evaluated by the Visual Analog Scale (VAS) ruler. The efficacy of premixed lidocaine with propofol was also compared among the patients. The venous pain of propofol was significantly more intense than that of the three other drugs (P < 0.05). The injection pain of diazepam was more intense than that of midazolam (P < 0.05). Many patients reported no pain when propofol was coadministered with lidocaine. The addition of a small dose (20 mg) of lidocaine reduced the VAS pain score to comparable levels observed for benzodiazepines. Because injection pain might affect the patients' comfort during sedation, the addition of lidocaine to the propofol injection is deemed useful for intravenous sedation.

Adult↗

PubMed1997

Effects of block analgesia on attenuating intraoperative stress responses during oral surgery.

Surgical intervention affects cardiorespiratory function and deteriorates the homeostatic mechanisms. The aim of this study was to evaluate the effect of block analgesia, which may minimize the intraoperative stress responses during oral surgery. In addition, we evaluated whether block analgesia could lessen the anesthetic requirements. Twenty-eight operative patients were randomly allocated to one of four groups: group 1, 1.3MAC without block analgesia; group 2, 1.6MAC without block analgesia; group 3, 1.0MAC with block analgesia; and group 4, 1.3MAC with block analgesia. Systolic blood pressure (SBP), heart rate (HR), and plasma norepinephrine levels (NE) were measured and compared. Results showed that the increases in SBP, HR, and NE in groups 1 and 2 were greater than those in groups 3 and 4. SBP elevation in group 1 was the greatest among all groups. These results suggest that block analgesia appears to be effective for preventing hyperreactivity of the sympathetic nervous and endocrine systems. In conclusion, general anesthesia combined with block analgesia assures safer anesthesia for patients with cardiovascular diseases or elderly patients who require cardiovascular stability during surgery.

Adult↗

PubMed1978