Reports of the effects of abscisic acid (ABA) on ion and water fluxes have been contradictory. Some of the confusion seems due to the interaction of ion and water transport across membranes. In these experiments root systems were subjected to hydrostatic pressures up to 5.0 bars to enable measurement of root conductance that was independent of measurement of osmotic potentials or ion fluxes.ABA...

Dielectric impedance measurements of porous silicon within the frequency range of 50 Hz–1.0 MHz and temperature range of 298–798 K revealed three semicircles in a Cole–Cole plot when the temperature is raised to 773 K; they are thought to correspond to contributions from the grain interior, grain boundary, and electrode/film interface, respectively. The enhancement in conductivity by heating fo...

There are many products, including hard drives, which require trace amounts, on the order of several milligrams, of lubricants for proper operation. The following study investigated the evaporation rates of pump oil and several alkanes, which have a wide range of applications. Both static and dynamic temperature tests were conducted. The rate of evaporation of the test specimen was determined a...

Hydrogen atom transfer reactions between the aldose and ketose are key mechanistic features in formose chemistry by which formaldehyde is converted to higher sugars under credible prebiotic conditions. For one of these transformations, we have investigated whether hydrogen tunneling makes a significant contribution to the mechanism by examining the deuterium kinetic isotope effect associated wi...

We have employed variable-temperature scanning tunneling microscopy ~STM! to follow the kinetics of reoxidation of a nonstoichiometric TiO2 ~110! single-crystal surface. The surface is seen to grow during reoxidation between 573 and 1000 K and at pressures from 5310 to 2310 mbar O2 . The reaction proceeds by combination of gas-phase O2 with mobile interstitial Ti 31 from the bulk. The surface i...

We report the direct observation of intramolecular hydrogen atom transfer reactions (tautomerization) within a single porphycene molecule on a Cu(110) surface by scanning tunneling microscopy. It is found that the tautomerization can be induced via inelastic electron tunneling at 5 K. By measuring the bias-dependent tautomerization rate of isotope-substituted molecules, we can assign the scanni...

Ion exchange at charged solid-liquid interfaces is central to a broad range of chemical and transport phenomena. Real-time observations of adsorption/desorption at the molecular-scale elucidate exchange reaction pathways. Here we report temporal variation in the distribution of Rb+ species at the muscovite (001)-water interface during exchange with Na+. Time-resolved resonant anomalous X-ray re...

Transitions between the different conformational states play a critical role in many RNA catalytic and regulatory functions. In this study, we use the Kinetic Monte Carlo method to investigate the kinetic mechanism for the conformational switches between bistable RNA hairpins. We find three types of conformational switch pathways for RNA hairpins: refolding after complete unfolding, folding thr...

The difficulties in interpreting the temperature dependence of protein enzyme reactions are well recognized. Here, the hammerhead ribozyme cleavage was investigated under single-turnover conditions between 0 and 60 degrees C as a model for RNA-catalyzed reactions. Under the adopted conditions, the chemical step appears to be rate-limiting. However, the observed rate of cleavage is affected by p...

Kinetics of oxidation of diethylamine (DEA) by Bromamine-B (BAB) has been investigated at in acid solution with Ru(III) as catalyst. The oxidation behavior obeys 303 K the rate law, rate 5 k [BAB] [DEA] [Ru(III)] [H1]2x where ‘x’ is less than unity indicating retardation of rate by [H]. Added halide ions, the reaction product benzenesulphonamide, variation of ionic strength and dielectric const...