Electro-oxidation of N-hydroxy imides for redox mediator in acetonitrile containing lutidine as a base

The electrochemical properties of two N-hydroxy imides, N-hydroxymaleimide and N-hydroxysuccinimide, at a glassy carbon electrode in acetonitrile were examined by cyclic voltammetry. N-hydroxysuccinimide, which contains no olefinic linkage, indicated a chemically reversible redox response, and its ability as a mediator for the oxidation of benzyl alcohol was confirmed by rotating disk electrode voltammetry.     

Adrenergic regulation of bone metabolism: possible involvement of sympathetic innervation of osteoblastic and osteoclastic cells

It has been demonstrated that human osteoblastic as well as osteoclastic cells are equipped with adrenergic receptors and neuropeptide receptors and that they constitutively express diffusible axon guidance molecules that are known to function as a chemoattractant and/or chemorepellent for growing nerve fibers. These findings suggest that the extension of axons of sympathetic and peripheral sensory neurons to osteoblastic and osteoclastic cells is required for the dynamic neural regulation of local bone metabolism. Recently, bone resorption modulated by sympathetic stimulation was demonstrated to be associated with ODF (osteoclast differentiation factor) and OCIF (osteoclastogenesis inhibitory factor) produced by osteoblasts/stromal cells. This review summarizes the evidence implicating sympathetic neuron action in bone metabolism. The possible function of osteoclastogenesis, which could result in the initiation of sympathomimetic bone resorption, is also discussed.     

Performance study of the domain decomposition method with direct equation solver for parallel finite element analysis

A parallel performance of the domain decomposition method with directLDU algorithm of condensation and solution is studied. Typical subdomains arising after division of a square domain are considered, and operation count equations for all steps of the numerical procedure are derived. The parallel efficiency model is developed using operation count equations and message passing estimates. It is shown how to achieve interprocessor load balancing by partitioning a domain into unequal subdomains. The evaluation of the parallel efficiency model and performance studies for a square finite element domain are performed on the IBM SP2 computer with 4, 6 and 8 processor nodes. It is found that proper load balancing of the domain decomposition algorithm with direct solution of equation systems provides acceptable parallel efficiency for multiprocessor computers: 95% for the 6-processor configuration and 85% for the 8-processor configuration.     

Effect of salt on the elastic modulus of poly(N-isopropylacrylamide) gels

The measurement of tensile modulus of poly(N-isopropylacrylamide) (PNIPA) gel in the solution of NaCl, NaI, LiNO₃ and NaNO₃ was carried out. It was confirmed that the tensile modulus of PNIPA gel in the solution of salt depends on the volume of gel regardless of the kind and concentration of salts. This result leads us to the conclusion that the addition of salt effect only on the mixing contribution to the Flory's type free energy of gel especially in the swollen state. Therefore, our result is in agreement with a recent remarkable discovery that the volume of PNIPA gel depends only on the chemical potential of water in spite of the kind of additives. On the other hand, it was found that on the volume phase transition point and in the deswollen state, the elasticity of PNIPA gel depended on the concentration and kind of the salt because the viscoelasticity emerged due to the shrinkage of polymer network.     

A study on flammability limits of fuel mixtures

Flammability limit measurements were made for various binary and ternary mixtures prepared from nine different compounds. The compounds treated are methane, propane, ethylene, propylene, methyl ether, methyl formate, 1,1-difluoroethane, ammonia, and carbon monoxide. The observed values of lower flammability limits of mixtures were found to be in good agreement to the calculated values by Le Chatelier's formula. As for the upper limits, however, some are close to the calculated values but some are not. It has been found that the deviations of the observed values of upper flammability limits from the calculated ones are mostly to lower concentrations. Modification of Le Chatelier's formula was made to better fit to the observed values of upper flammability limits. This procedure reduced the average difference between the observed and calculated values of upper flammability limits to one-third of the initial value.     

On the pressure dependence of flammability limits of CH2=CFCF3, CH2F2 and methane

Flammability limits of CH₂=CFCF₃ (HFO-1234 yf), CH₂F₂ (HFC-32), and methane were measured at pressures from ambient to 2500 kPa in a 5 l stainless-steel spherical vessel. For HFO-1234 yf, as the pressure rises from ambient, the lower flammability limit is shifted downward and the upper limit is shifted upward. The changes to the lower flammability limits are, in general, small compared to the upper flammability limits. Both the lower and upper flammability limits of this compound can be approximated by simple logarithmic functions of pressure. For HFC-32, the behavior of lower flammability limit is similar to that for HFO-1234 yf, but the behavior for the upper limit is rather complicated. As the pressure is increased, it begins to rise upward gradually. Then, as the pressure becomes larger than about 1000 kPa it begins to rise upward rapidly, and then the change becomes moderate again. This must be due to a change of combustion reaction mechanism below 1000 kPa and above 1500 kPa in the upper flammability limit region for this compound. On the other hand, both the flammability limits of methane change almost linearly with pressure, at least in the pressure region considered.     

Stereochemical effects on the fragmentation in mass spectrometry of stereoregular oligomers of methyl methacrylate

Summary The effects of stereochemical structure of MMA oligomers on the fragmentation during ionization process in electron-impact ionization and chemical ionization mass spectrometry were studied using the oligomers prepared by stereospecific living oligomerization. The MMA oligomers having t-C₄H₉-group at the left end and methine proton at the right end showed strong tacticity dependence in their fragmentation process. Fragmentation of MMA tetramer having one head-to-head linkage in the middle of the chain was also studied.