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H Orihara

Publications and source records attributed to H Orihara.

At least 19 recordsLinked to original sources
PubMed2001

Field-induced behaviors near the smectic-A-smectic-C * alpha phase transition of an antiferroelectric liquid crystal.

We have experimentally and theoretically investigated the electric-field effect on the smectic-A-smectic-C(*)(alpha) phase transition of an antiferroelectric liquid crystal4-(1-methyl-heptyloxycarbonyl)phenyl 4(')-octylcarbonyloxybiphenil-4-carboxylate. From the microscopic observations under electric fields and the measurements of the D-E hysteresis loop and apparent tilt angle, the E (electric field)-T (temperature) phase diagram was established, in which a tricritical point was found. From the dielectric measurements under dc electric fields, a soft mode inducing the transition was observed. Furthermore, we have developed a phenomenological theory under dc fields to analyze the experimental results. The origin of the soft mode observed under fields was clarified and the temperature dependence of the relaxation frequency was obtained by the analyses.

Journal Article↗
PubMed2000

Observation of the soft mode in the Sm-C(*)(alpha) phase

We have performed the electro-optical measurements in an antiferroelectric liquid crystal 4-(1-methylheptyloxycarbonyl)phenyl 4(')-octylcarbonyloxybiphenyl-4-carboxylate (MHPOCBC) and observed the soft mode in the chiral Sm-C(*)(alpha) phase. This is a direct consequence that the Sm-C(*)(alpha) phase is induced by the condensation of a tilting mode. A Landau-type theory was developed to analyze frequency dispersions in the second-order response and it was found that the Sm-A-Sm-C(*)(alpha) phase transition is close to a tricritical point.

Journal Article↗
PubMed1999

[Age-dependent changes in dynamic body balance as evaluated by the Body Tracking Test (BTT)].

Stability of Posture and gait decays with aging. In this study, we constructed the Body Tracking Test (BTT), to evaluate dynamic body balance function as opposed to static balance. Healthy volunteers of various ages (total, 272 persons) were subjects of the study. The principle of the BTT was for the subject to attempt to track an optical moving target displayed on a computer screen by shifting his or her body's center of gravity that was also displayed. The target moved for a span of 15 cm horizontally on the 14-inch screen, and also, in lateral and antero-posterior (horizontal and vertical) on CRT directions at a constant velocity of 0.125 Hz. Sixty-seconds recordings are obtained. In BTT, the gain for target against tracking was fixed at 2.0 (target:tracking = 1:2). The target was 100 cm anterior to the platform where the subject stood erect with the feet close together. The criteria for evaluation of the tracking function were determined by our preliminary study, titled "Index of BTT movement", and was useful during our present study. These criteria were determined ranking to E from A. The A rank indicated best tracking. Determination of rankings were performed by good or not tracking line against target trace line on recorded papers. Age-dependent changes in scores were obtained and analyzed. Results suggested that the tracking ability started to deteriorate after age 40, and these differences were observed in lateral and antero-posterior (horizontal and vertical on CRT) directions for all age groups. Tried for a with 30 years old changes, increase of a rate that A ranking occupies with a lateral direction law fast stimulation BTT from 20-year-old changes though, didn't try for a significant difference with a antero-posterior direction law fast stimulation BTT. Try start were 50-year-old changes with an antero-posterior BTT, 40-year-old changes with a lateral BTT E ranking. C, D, rate that E ranking occupies increases consequently to become 80-year-old changes and advanced age from 60 years on. For the tendency, a small tendency tried for the rate for antero-posterior stimulation BTT compared with a lateral stimulation BTT. Whether thought about for this, an of direction is prompt nearly against an outside stimulation since it keeps a balance with standing and being mended.

Adult↗
PubMed1997

Performance evaluation of a large axial field-of-view PET scanner: SET-2400W.

The SET-2400W is a newly designed whole-body PET scanner with a large axial field of view (20 cm). Its physical performance was investigated and evaluated. The scanner consists of four rings of 112 BGO detector units (22.8 mm in-plane x 50 mm axial x 30 mm depth). Each detector unit has a 6 (in-plane) x 8 (axial) matrix of BGO crystals coupled to two dual photomultiplier tubes. They are arranged in 32 rings giving 63 two-dimensional image planes. Sensitivity for a 20-cm cylindrical phantom was 6.1 kcps/kBq/ml (224 kcps/microCi/ml) in the 2D clinical mode, and to 48.6 kcps/kBq/ml (1.8 Mcps/microCi/ml) in the 3D mode after scatter correction. In-plane spatial resolution was 3.9 mm FWHM at the center of the field-of-view, and 4.4 mm FWHM tangentially, and 5.4 mm FWHM radially at 100 mm from the center. Average axial resolution was 4.5 mm FWHM at the center and 5.8 mm FWHM at a radial position 100 mm from the center. Average scatter fraction was 8% for the 2D mode and 40% for the 3D mode. The maximum count rate was 230 kcps in the 2D mode and 350 kcps in the 3D mode. Clinical images demonstrate the utility of an enlarged axial field-of-view scanner in brain study and whole-body PET imaging.

Bone Neoplasms↗
PubMed1997

[Three-dimensional positron emission tomography imaging system and its application for medical use].

Current positron emission tomography is capable for three dimensional data acquisition and reconstruction (3D PET). The main advantage of 3D PET is its detectability for lower tracer concentrations. The images by a 3D PET have better signal to noise ratios compared to those by conventional 2D PET. This point is especially important for the studies of distributions of ligands for neuroreceptors such as F-18 FDOPA and C-11 YM-01951, since these ligands show low accumulation in brain. Reduction of scanning time is useful as well for patients are permitting extended scanning periods

Carbon Radioisotopes↗
PubMed1993

Recovery of the vestibular function after vestibular neuronitis.

We performed steroid therapy on 34 cases with vestibular neuronitis and compared them with 77 patients not subjected to this therapy to examine the role of recovery of their vestibular function. Since no relation was noted between use of steroid and changes in subjective symptom of dizziness, the use of steroid is likely to facilitate the disappearance of spontaneous nystagmus in the early recovery stage. Canal paralysis recovered significantly by steroid and in cases of slight and moderate paralysis at the onset, recovery was more significant. Steroid therapy is argued to be effective for the recovery of vestibular function in cases of vestibular neuronitis.

Administration, Oral↗
PubMed1990

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Journal Article↗
PubMed1989

Postischemic changes of calcium and endogenous antagonist in the rat hippocampus studied by proton-induced X-ray emission analysis.

Proton-induced X-ray emission analysis (PIXE) was applied to determine ischemia-induced changes in the content of calcium, iron, nickel and zinc in the rat hippocampus. After 30 min or 2 h reperfusion following 20 min of ischemia, the nickel content decreased and the zinc content increased. The calcium content was increased 50% after 30 min but was normal after 2 h reperfusion.

Animals↗
PubMed1987

Activation autoradiography: imaging and quantitative determination of endogenous and exogenous oxygen in the rat brain.

Endogenous and exogenous oxygen in the rat brain were quantitatively determined using an autoradiographic technique. The oxygen images of frozen and dried rat brain sections were obtained as 18F images by using the 16O (3He,p)18F reaction for endogenous 16O images and the 18O(p,n)18F reaction for endogenous and exogenous 18O images. These autoradiograms demonstrated the different distribution of oxygen between gray and white matter. These images also allowed differentiation of the individual structures of hippocampal formation, owing to the differing water content of the various structures. Local oxygen contents were quantitatively determined from autoradiograms of brain sections and standard sections with known oxygen contents. The estimated values were 75.6 +/- 4.6 wt% in gray matter and 72.2 +/- 4.0 wt% in white matter. The systematic error in the present method was estimated to be 4.9%.

Activation Analysis↗