TANGENTIAL VELOCITY CHANGE WITH TIME OF POLYACRYLAMIDE SOLUTION IN A CONCENTRIC ANNULUS

Tangential velocity change with time of polyacrylamide solution, which had not only viscosity but also elasticity, in a concentric annulus after step motion of the inner cylinder was measured by using a LDV method. By adapting a conception of a second order lag control system which had a feedback connection, an equation for estimating the velocity change with time was presented. Each parameter in the equation was determined based on the experimental results, and the relationships between each parameter and viscosity or elasticity of the solutions was made clear. By using this equation, the tangential velocity change with time of a viscoelastic liquid in the annulus can be estimated when the viscosity and elasticity of the liquid and the rotational speed of the inner cylinder are given. Additionally, it was confirmed that the equation was applicable to the case of polyethyleneoxide solution, which had different ranges of the viscosity and elasticity from those of the test solutions described above.     

Implications of gastric topical bioactive peptides in ammonia-induced acute gastric mucosal lesions in rats

BACKGROUND: Ammonia, one of the pathogenic factors in Helicobacter pylori-induced mucosal injury, induces acute mucosal lesions in the rat glandular stomach. METHODS: The effect of ammonia administered intragastrically on gastric peptides was investigated in urethane-anesthetized rats. RESULTS: Gastric mucosal lesions were observed 5 min after 0.3% ammonia (4 ml/kg, intragastrically). Immunoreactive endothelin-1 (ET-1) and immunoreactive thyrotropin-releasing hormone (TRH) concentrations in the gastric wall decreased significantly 2 min and 5 min after ammonia, respectively. A significant increase in gastric juice immunoreactive ET-1 and TRH levels was reciprocally observed. The severity of gastric mucosal injury and changes in gastric immunoreactive ET-1 and TRH concentrations were shown to be concentration-dependent 30 min after ammonia. Atropine (5 mg/kg, intraperitoneally, -20 min) prevented ammonia-induced injury accompanied by a block of changes in gastric immunoreactive ET-1 and TRH concentrations. BQ-485 (ET(A) receptor antagonist; 2 mg/kg, subcutaneously) also abolished ammonia-induced lesions and gastric immunoreactive TRH changes. CONCLUSIONS: These findings suggested that gastric ET-1 and TRH play a role in ammonia-induced gastric mucosal injury mediated via a muscarine and an ET(A) receptor.     

Trace elements in ribs of elderly people and elemental variation in the presence of chronic diseases

Element concentrations in ribs obtained from elderly Japanese people (17 males and 28 females; mean age, 81.5 years) were determined by atomic absorption spectrometry (AAS), inductively coupled plasma atomic emission spectrometry (ICP-AES), and ICP mass spectrometry (ICP-MS). Nine elements--Na, Mg, P, K, Ca, Fe, Zn, Sr, and Pb--were determinable in most of the subjects by a combination of AAS and ICP-AES. The levels of these elements were generally comparable with those obtained in our previous study on ribs from younger Japanese. By the use of ICP-MS, Sn (median, 0.79 micrograms/g dry bone) and Ba (1.3 micrograms/g) were determinable in all of the subjects analysed (n = 35) and 18 other elements at lower concentration levels were also detected in some of the subjects. An exploratory statistical analysis was carried out to find element(s) of which level(s) in rib vary in the presence of degenerative chronic diseases, using information obtained from pathological autopsy reports and medical histories of the present subjects. It indicated that (i) Pb and Zn, (ii) Ba, and (iii) Sr levels in the ribs varied in the presence of cancer, cerebrovascular damage, and bone problems, respectively. The present results were discussed in relation to the results of the previous epidemiologic and experimental studies.     

Molecular dynamic simulation of heterogeneity and chemical states of fluorine in amorphous alkaline earth silicate systems

Chemical states of fluorine in fluorosilicate glasses in the system MF₂-MO-SiO₂ (M = Ca, Sr and Ba; SiO₂ content < 60 mol%) have been investigated by molecular dynamic (MD) simulations with a perfect ionic two-body potential. Comparison of the results with those derived by X-ray photoelectron spectra of the actual glasses demonstrates that MD simulations reproduce well the bonding states of fluorine in the systems as well as the formation of M-F clusters. The MD generated structure of imaginary glasses, or glasses not obtained by the conventional melt-quench technique, with 70 mol% SiO₂ indicates that an acidic environment induces a greater amount of F---Si bonds. Their M-F pair correlation functions plotted against normalized M-F distances suggest that relative ion positions in the clusters are very similar.     

Determination of nitroarenes in precipitation collected in Kanazawa, Japan

Eight nitroarenes, 1,3-, 1,6- and 1,8-dinitropyrenes, 1-, 2- and 4-nitropyrenes, 6-nitrochrysene and 2-nitrofluoranthene, in precipitation collected in Kanazawa were determined. The nitroarenes in the precipitation were concentrated onto solid phase extraction cartridges, and identified with high-performance liquid chromatography with chemiluminescence detection. The nitroarene concentrations in the precipitation were in the range 0.016-15 pmol/L, and the nitroarene composition tended to be the same as that in airborne particulates. 1-Nitropyrene in river water and seawater were also determined. 1-nitropyrene concentrations on the days after rain (19-110 fmol/L) were higher than those on the days before rain (4,11 fmol/L). Moreover, 1-nitropyrene concentrations in the river water were much lower than those in the precipitation, but were higher than those in the seawater. These results suggested that the nitroarenes in the precipitation and the river water came from airborne particulates.     

DIRECT ADAPTIVE CONTROL FOR NONLINEAR MATRIX SECOND‐ORDER SYSTEMS WITH TIME‐VARYING AND SIGN‐INDEFINITE DAMPING AND STIFFNESS OPERATORS

A direct adaptive control framework for a class of nonlinear matrix second‐order systems with time‐varying and sign‐indefinite damping and stiffness operators is developed. The proposed framework guarantees global asymptotic stability of the closed‐loop system states associated with the plant dynamics without requiring any knowledge of the system nonlinearities other than the assumption that they are continuous and bounded. The proposed adaptive control approach is used to design adaptive controllers for suppressing thermoacoustic oscillations in combustion chambers.     

Breakdown Characteristics of N2O Gas Mixtures for Quasiuniform Electric Field under Lightning Impulse Voltage

From the viewpoint of mitigating global warming by SF₆ gas, this paper discusses breakdown (BD) characteristics of different electronegative gas mixtures with N₂O gas as SF₆ gas substitutes for quasi-uniform electric field under lightning impulse voltage applications. Experimental results revealed the positive synergism in breakdown strength of binary N₂O / CO₂ and ternary N₂O / CO₂ / O₂ gas mixtures, respectively. Furthermore, N₂ gas as a retardant gas was also mixed with the electronegative gas mixtures in order to reduce the electron energy into the effective levels of electron attachment ability by the electronegative gas mixtures. As the result, ternary N₂O / CO₂ / N₂ and quaternary N₂O / CO₂ / O₂ / N₂ gas mixtures could exhibit the significant synergistic effect in breakdown strength. The optimum mixture rate of quaternary N₂O / CO₂ / O₂ / N₂ gas mixtures was consistent with that estimated by assuming the independent contribution of component gases to the improvement of impulse BD characteristics.