The effect of glycogen depletion on the curvature constant parameter of the power-duration curve for cycle ergometry

For high-intensity cycle ergometer exercise, the relation between power (P) and its tolerable duration (t) has been well characterized by the hyperbolic relationship: (P-thetaF) t = W', or P = W' (1/t)+thetaF, where thetaF may be termed the 'fatigue threshold'. The curvature constant (W') reflects a constant amount of work which is postulated to be equivalent to a finite energy store that relates to the oxygen-deficit: phosphagen pool, anaerobic glycolysis and oxygen stores. Compared to thetaF, the physiological nature of W' has received little consideration. The purpose of this study was therefore to establish the parameters of the power-duration curve (thetaF and W') for subjects in normal glycogen (NG) and glycogen depleted (GD) states. Seven healthy male subjects (aged 22 to 41 years) each performed four high-intensity square-wave exercise bouts on an electrically braked cycle ergometer under two different muscular glycogen content conditions, i.e. NG and GD states. Subjects performed the following exercise on the evening before the trial day to induce the GD state. Initially, they performed a 75-min cycling exercise at 60% of VO2max. After a 5-min rest period, they subsequently repeated a 1-min cycling bout at 115% of VO2max (separated by 1-min rest periods) until the subject could no longer maintain the prescribed pedal rate for the full minute. Subjects then reported to the laboratory after an overnight fast and performed a single high-intensity exercise bout. The GD procedure was repeated four times at 1-week intervals. In the GD state, the respiratory exchange ratio (RER) (VO2/VCO2) value during a recumbent control period prior to the trial was significantly lower than that in the NG state [GD: 0.84+/-0.02, NG: 0.94+/-0.04, mean +/- SD]. There was no significant difference for thetaF between GD and NG state [NG: 197.1+/-31.9 W, GD: 190.6+/-28.2 W]. W' in contrast was significantly reduced by the GD procedure [NG: 12.83+/-2.21 kJ, GD: 10.33+/-2.41 kJ]. The present results indicate that the muscular glycogen store seems to be an important determinant of the curvature constant (W') of the power-duration curve for cycle ergometry.     

Imaging polarimetry in patients with neovascular age-related macular degeneration

Imaging polarimetry was used to examine different components of neovascular membranes in age-related macular degeneration. Retinal images were acquired with a scanning laser polarimeter. An innovative pseudocolor scale, based on cardinal directions of color, displayed two types of image information: relative phases and magnitudes of birefringence. Membranes had relative phase changes that did not correspond to anatomical structures in reflectance images. Further, membrane borders in depolarized light images had significantly higher contrasts than those in reflectance images. The retinal birefringence in neovascular membranes indicates optical activity consistent with molecular changes rather than merely geometrical changes.     

Photoinduced electron transfer and hole migration along copolymer of vinylbenzenepyrrolidinofullerene[60] and N-vinylcarbazole

Photoinduced electron-transfer and hole-migration processes for newly prepared copolymers of C60 and N-vinylcarbazole (VCz) with the several compositions have been investigated using time-resolved fluorescence and absorption methods. Shortening of fluorescence lifetime of the C60 moiety in PVCz-C60 was observed, suggesting that the charge-separation takes place via the excited singlet state of C60; the rate constants of the charge-separation were evaluated to be larger than 10(9) S(-1) in polar solvents. In the nanosecond transient absorption spectra in the visible and near-IR regions obtained by excitation of the C60 moiety, the generation of PVCz(*+)-C60(*-) was confirmed. The time profiles of these radical ions showed slow decay continuing more than 800 micros in polar solvents. From the simulations of the decay curves on the basis of the proposed kinetic model, in which the charge-recombination takes place competitively with hole-migration, the rate parameters have been evaluated; i.e., the rate constant of hole migration was evaluated to be 5 x 10(7) s(-1), which was 50 times faster than that of the charge-recombination (ca. 10(6) s(-1)) in polar solvent. The charge-recombination takes place after hole migration among 200-300 Cz units along the PVCz chain in PVCz-C60.     

Sulfur and strontium isotope geochemistry of tributary rivers of Lake Biwa: implications for human impact on the decadal change of lake water quality

To study the deterioration of the water quality in Lake Biwa, Japan, over the last 40 years, we measured the concentrations and isotopic ratios of sulfur and strontium of water in 41 inflowing rivers and one discharging river. The concentrations of SO4 and Sr of inflowing rivers at downstream sites were generally high in the southern urban area and in the eastern area, where a large agricultural plain is situated, but low in the northern and western areas, whose watersheds are mountainous and with low population density. SO4 and Sr concentrations are also lower at upstream sites, which are closer to mountainous areas. Thus, the inflowing river receives large amounts of SO4 and Sr as it flows across the plain, where human activity levels are high. The delta34S or 87Sr/86Sr values of most eastern rivers at downstream sites are lower than those of water in Lake Biwa, and values become more uniform as the proportion of the plain area in the watershed increases. River water in other areas has higher values of delta34S or 87Sr/86Sr than the lake water. This result indicates that the decadal decrease of delta34S and 87Sr/86Sr in the lake water has been caused mainly by the increased flux of SO4 and Sr from rivers in the eastern plain. We assume that in the plain, sulfur, nitrogen, and organic compounds induced by human activities generate sulfuric, nitric, and organic acids in the water, which accelerate the extraction of Sr from bedrocks, leading to the generation of Sr in the river water in the area.     

Dryout and post-dryout heat transfer in a natural circulation loop of liquid nitrogen

In a natural circulation loop, flow instabilities, such as density wave oscillations, occur under certain operating conditions, but the influence of flow oscillations on the heat transfer is not well understood. An experiment was conducted using a natural circulation loop of liquid nitrogen with test tubes of dimensions of 3.0 mm/5.0 mm I.D., and 900 mm heated length. Experimental results indicated that the heat transfer correlations of Schrock-Grossman and Roko-Shiraha were in good agreement with the experimental results in the saturated boiling and postdryouts regions, respectively, even under oscillatory flow conditions. On the other hand, the critical heat flux (CHF) correlation obtained under stable flow conditions, such as Katto, predicted significantly larger values compared with the experimental data under oscillatory flow condition. The CHF value of the natural circulation loop was well predicted by using the numerical simulation based on a lumped-parameter model, taking account of the circulation rate, oscillation period, and amplitude. © 1998 Scripta Technica, Heat Trans Jpn Res, 26(7): 449–458, 1997     

Properties and catalytic activity of NOx reduction of alumina-titania catalysts prepared by sol-gel method

The alumina-titania catalysts were prepared from various alumina and titania sources by sol-gel method, which were metal alkoxide and metal alkoxide modified with organic groups. Specific surface area, pore size distribution, solid acidity and catalytic activity of NO reduction for the alumina-titania catalysts depended on the alumina and titania sources. The alumina-titania catalyst prepared from metal alkoxide for alumina source and metal alkoxide modified with organic groups for titania source exhibited higher activity of NO reduction than the other alumina-titania catalysts. Catalytic activity of NO reduction for the alumina-titania catalysts depended on specific surface area and solid acidity. It was suggested that solid acidity of the alumina-titania catalysts depended on the coordination structure of Al atoms and the homogeneity of alumina and titania components.     

Separation of organic solvent from dilute aqueous solutions and from organic solvent mixtures through crosslinked acrylate copolymer membranes by pervaporation

The composite membranes of acrylate polymers and porous substrate were prepared. The separation of the organic solvent–water mixtures and the organic solvent–organic solvent mixtures through these membranes by pervaporation was investigated. The acrylate copolymer membrane showed the organic solvent permselectivity for the separation of the organic solvent–water mixture, especially for the chlorinated hydrocarbon–water mixture separation. The high organic solvent permselectivity should be governed by solubility selectivity. The influence of the ester residue of acrylate on the phenol–water mixture separation was observed. The copolymerization of the macromonomers containing the polystyrene, poly(methyl methacrylate), and polydimethylsiloxane chain had a small effect on the separation of the chlorinated hydrocarbon–water mixture. High flux and low selectivity of organic solvent were observed in the case of the organic solvent mixture separation through the n-butylacrylate membrane. The difference of permeability of organic solvent was observed for the acrylate copolymer which has various structures of ester residue. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 69: 1483–1494, 1998     

Thermodynamic correlation of partial and saturation swelling of styrene-acrylonitrile copolymer particles by styrene and acrylonitrile monomers

The possibility of thermodynamic correlation of partial and saturation swelling of styrene-acrylonitrile (SAN) copolymer particles by styrene (St) and acrylonitrile (AN) monomers is investigated. The unknown Flory-Huggins interaction parameters involved in the thermodynamic swelling equations are estimated by fitting the equations to the experimentally observed monomer concentrations. It is shown that the concentration of each monomer in SAN copolymer particles predicted by using the thermodynamic swelling equations with the parameters and constants estimated in this study agrees fairly well with that observed experimentally over a wide range of experimental conditions. The validity and utility of the parameters and constants estimated from saturation swelling are also demonstrated by showing that the experimental results for partial swelling of SAN copolymer particles by AN monomer dissolved in the aqueous phase agree with those predicted by the thermodynamic equation for partial swelling. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 931–939, 1997     

Properties of composite films comprising surface modified fine collagen particles dispersed in polyurethane matrix

Collagen-rich natural leather powders (PPd) with average particle size of 12 μm were modified and dispersed in a polyurethane (PU) matrix. Three kinds of surface modification techniques were employed; surface polyaddition of PU, copolymerization with acrylamide (AAm), and grinding of the PPd with PU powder in a planetary ball mill. Surface modification was confirmed mainly by FTIR signals from the modifier. The DTA exothermic peak shifted toward a higher temperature by 260 K when copolymerized with AAm. On the copolymerized sample, the IR peak due to C(DOUBLE BOND)O stretching appeared between those of the original AAm and PPd, indicating the mutual chemical interaction. The tensile yield stress and critical strain of the composite films increased by surface modification with PU, while the latter decreased for the film containing the PPd powders copolymerized with AAm. Judging from the micrographs of the expanded films, the increase in the adhesive strength between the powder surface and the matrix after modification by AAm was larger than those by PU. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 1693–1700, 1997