Effects of salmon calcitonin on SA nodal pacemaker activity and contractility in isolated, blood-perfused atrial and papillary muscle preparations of dogs

Effects of salmon calcitonin on SA node pacemaker activity and contractility were investigated in isolated atrium and papillary muscle preparations which were perfused with arterial blood led from a carotid artery of the support dog. Calcitonin at a dose range from 0.005 to 0.16 units was injected into the cannulated sinus node artery, which dose-relatedly caused a negative chronotropic and inotropic effect in atrium preparations. This negative effect was not modified by treatment with atropine. On the other hand, in the isolated paillary muscle preparations, an intraarterial calcitonin caused little negative inotropic effect even at higher dose level of 0.16 units. From these results, it is concluded that 1) in chronotropy, calcitonin causes a negative chronotropic effect, and 2) in inotropy calcitonin causes a negative inotropic effect on the atrium but not on the ventricle.     

Graft polymerization of acrylic acid onto polyethylene film by preirradiation method. I. Effects of preirradiation dose,monomer concentration,reaction temperature,and film thickness

Low-and high-density polyethylenes were irradiated by electron beams with dose of 2–50 Mrad and then immersed in aqueous solution of acrylic acid (monomer concentration from 30 to 100 wt %) for 10 min?5 h at a temperature of 25–40°C. The degree of grafting increases with time and levels off. High density polyethylene shows lower grafting rate and higher final % grafting in compared with low-density polyethylene. Both grafting rate and final % grafting increase with total dose of preirradiation, but show some saturation at high doses. The highest grafting rate was observed at 60 wt % of monomer concentration where the grafted polyethylene swells to the largest extent in the monomer mixture. Apparent activation energies for the grafting are 19.6 and 27.3 kcal/mol for low- and high-density polyethylenes, respectively, reflecting the proces of monomer diffusion in the film. Grafting rate decreases with increasing film thickness. Graft polymerization starts on the surface of the film and proceeds to the inner part with monomer diffusion through the grafted layer.     

Production of dimethyl ether and hydrogen by methanol reforming for an HCCI engine system with waste heat recovery – Continuous control of fuel ignitability and utilization of exhaust gas heat

Homogeneous charge compression ignition (HCCI) is a promising technique to achieve high thermal efficiency and clean exhaust with internal combustion engines. However, the difficulty in ensuring optimal ignition timing control prevents its practical application. Previous research has shown that adjusting the proportion of dimethyl ether (DME) and hydrogen-containing methanol-reformed gas (MRG) can control the ignition timing in an HCCI combustion engine fueled with the two fuels. As both DME and MRG can be produced in endothermic methanol reforming reactions, onboard reforming utilizing the exhaust gas heat can recover the waste heat from the engine. A very high overall thermal efficiency can be achieved by combining the high engine efficiency with HCCI and the waste heat recovery. This research investigates the basic characteristics of methanol reforming in a reactor tube with different catalysts with the aim to produce fuels for the HCCI combustion system.     

CONJUGATE NUMERICAL COMPUTATION FOR THE NATURAL CONVECTION OF LIQUID METAL HEATED FROM BELOW

ABSTRACT

The oscillatory Rayleigh-Benard convection in a shallow layer of liquid metal (Pr = 0.023), sandwiched between two copper plates, was numerically computed for three computational domains simultaneously. The horizontal cross section is square and the aspect ratio (fluid layer width/height) is 10. This conjugate solution suggested that the hot plate temperature oscillates almost simultaneously with the fluid temperature and throughout the whole hot copper plate with almost uniform temperature. The oscillatory temperature amplitude provided the upper and lower limits in the Rayleigh number and the Nusselt number estimated from the relationship, constant = Ra* = Nu ? Ra, where Ra* is a modified Rayleigh number based on the uniform heat flux. This group of data provided quite similar characteristics to the previous experimental observation by Yamanaka et al. for the oscillatory change of the Nusselt number and to the one by Rossby for the time-averaged values.     

P-450 Type Activation of Dioxygen by Heterogenized Metal Porphyrins: Comparison with the Corresponding Homogeneous Systems

The protons of silanol groups on a silica or silica-alumina surface are replaced by metal(III) porphyrin cations, FeTPP⁺, MnTPP⁺, and CoTPP⁺ (TPP = tetraphenylporphyrin). The heterogenized iron(III) or manganese(III) porphyrin supported on silica thus prepared can activate dioxygen in the presence of excess amounts of NaBH₄ and cyclohexene, affording cyclohexanol and cyclohex-2-ene-1-ol in a 4:1 ratio, which is the same as the ratio observed in the known P-450 type oxidation of cyclohexene catalyzed by a homogeneous manganese porphyrin (MnTPPCl) in the presence of NaBH₄ used as an electron source. The heterogenized iron(III) porphyrin shows a reactivity comparable with that of the corresponding heterogenized manganese(III) porphyrin. On the other hand, substitution of the heterogenized iron(III) porphyrin by the corresponding homogeneous catalyst, FeTPPCl, results in drastic change in the product ratio; the ratio of cyclohexanol to cyclohex-2-ene-l-ol is reversed, suggesting that the oxidation of cyclohexene proceeds via radical chain autoxidation reactions. The catalytic activity for the P-450 type oxidation is diminished while FeTPPCl is converted to the μ-oxo-dimer (FeTPP)₂O. Cobalt(III) porphyrin in a homogeneous system also affords the autoxidation products. Such a mechanistic difference between the homogeneous and heterogeneous metal porphyrins in the oxidation of cyclohexene by dioxygen has been confirmed by kinetic studies in which the P-450 type oxidation and autoxidation obey different kinetics.     

Reduction of n-C5H11N3 Catalyzed by [Mo2Fe6S8(OMe)3(SC6H4-p-n-C8H17)6]3– in an Aqueous Micellar Solution

Reduction of n-C₅H₁₁N₃ by Na₂S₂O₄ was performed in the presence of (n-Bu₄N)₃ [Mo₂Fe₆S₈(OMe)₃(SC₆H4-p-n-C₈H₁₇)₆] ((n-Bu₄N)₃ [Mo-Fe]) as a catalyst in aqueous Triton X-100 micellar solutions. The rate of the reduction is enhanced efficiently by the addition of methyl viologen (MV²⁺). The methyl viologen radical cation (MV⁺) produced by the reaction of MV²⁺ with Na₂S₂O₄ undergoes a disproportionation reaction to afford MV²⁺ and MV° in the micellar solution. The resultant MV° formed in the micelle transfers two electrons to [Mo-Fe]³⁻ effectively to give [Mo-Fe]⁵⁻, which reduces n-C₅H₁₁N₃ with two electrons to produce n-C₅H₁₁NH₂ and N₂.     

Polymerization of (perfluoro-n-alkyl)acetylenes by WCI6-Ph4Sn and polymer properties

Summary (Perfluoro-n-alkyl)acetylenes (HCCR_f; R_f = n-C₆F₁₃, n-C₄F₉) polymerized with the WCl₆-Ph₄Sn catalyst to produce methanol-insoluble polymers in good yields. The intrinsic viscosities of the polymers (in C₆F₆) were ca. 0.05 dL/g, being relatively small. No large difference was observed between the polymerization in toluene (heterogeneous) and that in C₆F₆ (homogeneous). The main chain of the polymers was composed of alternating double bonds. These polymers were white solids soluble in C₆F₆. The temperatures at which the weight loss of the polymers started were higher than 200°C, which indicates improved thermal stability as compared with the corresponding poly(1-alkynes).     

Electrochromic thin films prepared by sol–gel process

New methods are shown for lower temperature preparation of amorphous tungsten oxide thin film and preparation of crystalline iridium oxide thin film by sol–gel process using metal chloride as the starting materials and ethanol as a solvent. These electrochromic materials were combined with gel solid electrolyte, and preparation of fully solid-state electrochromic display (ECD) was made. The transmittance of the ECD could be made to change by 35% by applying a voltage of 3 V for 0.2 sec.     

Molecular dynamics and Monte-Carlo simulation of sputtering and mixing by ion irradiation

Molecular dynamics (MD) and Monte-Carlo (MC) simulations of low-energy (<500 eV) Ar ion irradiation on Si substrates were performed in order to investigate the mixing and sputtering effects. Both MD and MC simulation show similar results in sputtering yield, depth profile of projectile and mixing of substrate. For these incident energies, the depth of the mixed region is determined by the implant range of incident ions. For example, when the incident energy is 500 eV, the Ar ions reach a depth of 40 Å so that the Si atoms that reside shallower than 40 Å are fully mixed at an ion dose of about 5.0×10¹⁶ atoms/cm². The resolution of secondary ion mass spectrometry (SIMS) was also studied. It was found that the resolution of SIMS depends on the depth of mixing, which depends in turn on the implant range of the probe ions. This is because the mixing of substrate atoms occurs more frequently than sputtering, so that the information about the depth profile in the mixing region is disturbed.     

Fabrication of micro-tubular solid oxide fuel cells with a single-grain-thick yttria stabilized zirconia electrolyte

This study discusses the fabrication and electrochemical performance of micro-tubular solid oxide fuel cells (SOFCs) with an electrolyte consisting a single-grain-thick yttria stabilized zirconia (YSZ) layer. It is found that a uniform coating of an electrolyte slurry and controlled shrinkage of the supported tube leads to a dense, crack-free, single-grain-thick (less than 1 μm) electrolyte on a porous anode tube. The SOFC has a power density of 0.39 W cm⁻² at an operating temperature as low as 600 °C, with YSZ and nickel/YSZ for the electrolyte and anode, respectively. An examination is made of the effect of hydrogen fuel flow rate and shown that a higher flow rate leads to better cell performance. Hence a YSZ cell can be used for low-temperature SOFC systems below 600 °C, simply by optimizing the cell structure and operating conditions.