Solid-state kinetic models: basics and mathematical fundamentals

Many solid-state kinetic models have been developed in the past century. Some models were based on mechanistic grounds while others lacked theoretical justification and some were theoretically incorrect. Models currently used in solid-state kinetic studies are classified according to their mechanistic basis as nucleation, geometrical contraction, diffusion, and reaction order. This work summarizes commonly employed models and presents their mathematical development.     

Solubility and diffusion of H in ordered (L12) and disordered Pd3Mn

Hydrogen isotherms have been measured from 423 to 573 K for the disordered and L1₂ ordered forms of Pd₃Mn and, from these equilibrium isotherms, Δ_HH$\mathrm{\Delta }{H}_{\mathrm{H}}$ and Δ_SH$\mathrm{\Delta }{S}_{\mathrm{H}}$ have been determined over a range of r values where r  =H-to-metal, atom ratio. Δ_HH$\mathrm{\Delta }{H}_{\mathrm{H}}$ values are significantly more negative for the L1₂ ordered form than for the disordered form. H diffusion constants have been determined for the L1₂ and disordered forms of Pd₃Mn from gas phase H permeation measurements through Pd₃Mn membranes (423–573 K). The activation energy for diffusion of H in the L1₂ form is 35.2 kJ/mol H which is more reasonable than the value of 76.3 kJ/mol H previously reported. The diffusion constant is greater for the disordered than for the L1₂ form.     

漫谈有效数字和计算器

介绍了有效数字的概念及其计算规则,介绍了计算器的一般特性及使用技巧,并给出计算实例.     

The kinetics of hydrogen (deuterium) sorption by thin palladium layers studied with a piezoelectric quartz crystal microbalance

The kinetics of the hydrogen (deuterium) Sorption processes in the α-phase region of a thin electrodeposited Pd layer (thickness 3 × 10^?5 cm) are reported. Measurements have been performed with a piezoelectric quartz crystal microbalance using an AT-cut crystal with a resonance frequency f⁰_q = 5.27 MHz and a sensitivity of ～10¹⁰ digits g^?1, at a constant temperature 80.3 ± 0.05 °C and different pressures. Both the absorption and the desorption of H₂(D₂) on Pd layers are controlled successively by a chemisorption step (second order kinetics) in the early stage of the processes and by a surface migration step (first order kinetics), in the subsequent stage of the processes. Consistent with the reported piezoelectric quartz crystal microbalance measurements, thermal desorption and electrochemical desorption studies, a mechanism is suggested which takes into account the adsorption ofH(D) atoms on two different surface states: (a) a “pre-dissolved” state which does not depend on the surface nature; (b) and adsorption state, the density of which depends upon the structure and nature of the Pd sample. The kinetic control of the entire processes (sorption and desorption) depends on the ratio of the density of sites (a) to (b).     

Synthetic Routes to Chiral 3-Pyrrolidinols

Short conyenient syntheses of chiral 3-pyrrolidinols and reloted compounds are described.     

Memory for the locations of environmental sounds

The accuracy with which a single source of sound can be localized has been examined in many studies, but very few studies have examined the ability of participants to determine the absolute locations of multiple sources of sound. The current study assessed participants' abilities to determine and remember the locations of up to six sources of environmental sound that were positioned at a range of azimuths and elevations in virtual auditory space. In experiment 1, a sequence of one to six sounds was presented one, three, or five times in each trial and the target sound was nominated following presentation of the last sequence. In experiment 2, memory load was held constant by nominating the target sound prior to a single sequence presentation. Localization accuracy was observed to decrease as the number of sounds was increased to three or more under the conditions of experiment 1, but not those of experiment 2. In experiment 1, localization was more accurate when sequences were presented more than once. Pronounced primacy and recency effects were observed for the six sound conditions in experiment 1. An analysis of errors for those conditions indicated that immediate temporal errors, but not immediate spatial errors, were over-represented.     

On the decrease in charge radii of multi-quasi particle isomers

We report changes in mean-square charge radii, δ〈r²〉$\delta 〈r^2〉$, magnetic moments and quadrupole moments for three multi-quasi particle isomers; ^97m2Y, ^176mYb and ^178m1Hf. All the isomers are observed to display a decrease in 〈r²〉$〈r^2〉$ compared to the lower-lying nuclear state on which the isomer is built. The decreases in 〈r²〉$〈r^2〉$ occur despite the isomers showing increases in quadrupole moment. Possible mechanisms for the effect, which is now seen for six multi-quasi particle isomers, are discussed.     

The mass spectrometry of four acyl derivatives of 2,2′-difurylmethane

Low resolution mass spectra and high resolution data for selected important peaks are presented and discussed for the following compounds: [(5-acetyl-2-furyl)-(2′-furyl)]methane (I), [(5-acetyl-2-furyl)-(5′-methyl-2′-furyl)]methane (II), [(5-formyl-2-furyl)-(2′-furyl)]methane (III) and [(5-formyl-2-furyl)-(5′-methyl-2′-furyl)]methane (IV). The fragmentation of II has been clarified by examining the mass spectrum of its d3-acetyl analog; the fragmentation of III and IV by examining the spectra of their carbonyl 13C-labeled analogs.