Direct observation of orientation distributions of actin filaments in a solution undergoing shear banding.

Shear banding is frequently observed in complex fluids. However, the configuration of macromolecules in solutions undergoing shear banding has not yet been directly observed. In this study, by using the fact that F-actin solutions exhibit shear banding and actin filaments are visualized by fluorescent labels, we directly observed the intrinsic states of an actin solution undergoing shear banding. By combining the 3D imaging of labeled actin filaments and particle image velocimetry (PIV), we obtained orientation distributions of actin filaments in both high and low shear rate regions, whose quantitative differences are indicated. In addition, by using the orientation distributions and applying stress expression for rod-like polymers, we estimated stress tensors in both high and low shear rate regions. This evaluation indicates that different orientation distributions of filamentous macromolecules can exhibit a common shear stress.

Morphology and rheology of an immiscible polymer blend subjected to a step electric field under shear flow.

We have investigated the structural change of an immiscible polymer blend in shear flow when subjected to a step electric field. During the process three-dimensional images were successfully constructed with a confocal scanning laser microscope and at the same time the transient shear stress was also measured. The interface tensor was calculated from the images. Several factors are incorporated into the shear stress, such as the bulk viscosity, the interfacial tension and the Maxwell stress. We performed an experiment to separate the Maxwell stress from the total shear stress. The results are discussed in terms of the interface tensor.

Electric-field-temperature phase diagram of an antiferroelectric liquid crystal.

We present a precise electric-field-temperature phase diagram of an antiferroelectric liquid crystal with a short pitch Sm-Calpha* phase. This was obtained by using a photoelastic modulator. A unique field-induced phase was found inside the Sm-Calpha* phase, which displayed low birefringence. Two tricritical points related to the phase were also observed. In addition, numerical calculations were made based on the discrete phenomenological model. The numerical results reproduced the experimental ones and it was clarified that the phase has a three-layer structure without spatial modulation.

Optical characterization of a nanoscale incommensurate pitch in a new liquid-crystal phase.

As a remarkable orientationally ordered soft-condensed matter system, the smectic-C*(alpha) phase exhibits an incommensurate nanoscale helical pitch of more than four smectic layers. Recent theoretical advances predict the existence of a new phase showing a helical pitch of less than four smectic layers (<16 nm). By applying a novel optical technique to the study of freestanding films with increments in thickness of one smectic layer, we have measured the size of this pitch using 633 nm HeNe laser light. Our results confirm the existence of the newly predicted phase in one unique compound.

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.

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.

[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.

[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

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.

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.

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.