Effects of orientation and chemical structure on the strength properties of some polymers

The stress-strain properties of oriented polymers are measured parallel and perpendicular to the direction of hot stretching. The polymers include styrene-acrylonitrile copolymers, vinyl alcohol copolymers, acrylic acid copolymers, polyelecf trolytes, and a high density polyethylene. Polarity and hydrogen bonding tend to increase the strength, especially in the direction perpendicular to the direction of hot stretching. Strong electrostatic bonding in polyelectrolytes and too much polar bonding in styrene-acrylonitrile & polymers decrease the strength by reducing the molecular mobility, which is required to prevent brittleness.     

An additional variant of the persistent primitive trigeminal artery: accessory meningeal artery--antero-superior cerebellar artery anastomosis associated with moyamoya disease

Neuropathy is a frequent complication in diabetes mellitus. Since the involvement of the autonomic nervous system indicates a poor prognosis, early detection and subsequent management are important. Analysis of heart rate variability (HRV) provides a quantitative measure of sympathovagal modulation activities on the heart and has been proven to be useful for the early assessment of the diabetic autonomic neuropathy. We recently developed a simple method of measuring pulse wave velocity (PWV) to evaluate sympathetic nervous activity in the vascular system. In this paper, we examined 33 diabetic patients with and without peripheral neuropathy (15 and 18 respectively) using these methods. In time domain analysis, the mean heart rate, standard deviation and coefficient of variation of HRVs significantly differed between these two groups, whereas the indices of PWVs did not show a significant difference. In frequency domain analysis of HRV, both low and high frequency components were decreased, and the low frequency component in normalized unit did not increase after standing in patients with peripheral neuropathy. We previously reported that the mean PWV decreased after standing in patients with diabetic neuropathy. This disagreement suggests that beta sympathetic dysfunction precedes alpha sympathetic dysfunction in diabetic neuropathy.     

Shrinkage of liquid CO2 droplets in water

The shrinkage rate of liquid CO₂ droplets in water at 3°C was measured by the use of high-pressure vessel placed in a constant-temperature room. The change of the diameter of the droplet was observed at pressures of 28 MPa and 35 MPa using a time-lapse video camera. Bromocresol green was employed as a pH indicator, and was effective in monitoring the profile of carbonic acid distribution. When a droplet of liquid CO₂ was injected, CO₂ hydrate immediately formed and covered the surface of the droplet. The diameter of the liquid CO₂ droplet reduced gradually at a rate of 5.0 × 10^?7 m/s. It is predicted, from the viewpoint of ocean CO₂ sequestration, that a thin film of hydrate will form at the interface of sea water and liquid CO₂, and that the hydrate film will greatly control the dissolution of CO₂ into sea water.     

Non-enzymatic hydrolyses of aryl esters of thymidine 3'-monophosphate as probes for the rate-determining step in DNA hydrolysis

In order to shed light on the rate-limiting step in DNA hydrolysis, non-enzymatic hydrolyses of aryl esters of thymidine 3'-monophosphate have been kinetically examined. In alkaline solutions, these dinucleotide analogues were hydrolyzed far faster than was thymidylyl(3'-5')thymidine (TpT), indicating that the departure of the leaving group from the phosphorus atom is rate-limiting. The CeIV- and CeIV/PrIII combination-mediated hydrolyses of these analogues were also faster than the corresponding hydrolysis of the dinucleotide.     

Far-infrared laser oscillation due to cyclotron emission in p-type germanium

Far-infrared laser oscillation due to cyclotron emission in the light hole band of p-type germanium was observed under crossed electric and magnetic fields. The wavelength is inversely proportional to magnetic fields with a cyclotron mass ofm _c =0.048m _c . Numerical calculations based on Luttinger Hamiltonian show that mixing of wavefunctions between the light and heavy hole bands causes population inversion betweenn=0 andn=1 light-hole Landau levels. It is also shown that non-equidistant energy spacing of light-hole Landau levels is essential to yield net amplification.     

Superplasticity of Fe-Ni alloys

In the two phase alloys which exhibit superplasticity, strain rate sensitivitym, in the relationship σ =Kε ^m, has been known to be strongly dependent on the volume fraction of the second phase. It, however, has not been necessarily confirmed experimentally on various two phase alloys. In this paper we present an experimental evidence showing that the largestm is obtained when the volume fraction of the second phase is around 0.5.