Improved method for fitting falloff data

An extension of the dimensionless treatment of Troe is developed for fitting falloff data from unimolecular and recombination reactions. This method using dimensionless parametrizations derived from accurate numerical solutions of the master equation for system with any type of activated complex and energy transfer probability distribution, is as easily implemented as Troe's method, and allows global fitting of an entire set of pressure- and temperature-dependent rate coefficients. © 1994 John Wiley & Sons, Inc.     

Spin labelling of human erythrocytes with nitroxide radicals

Summary Human erythrocytes were labelled with nitroxide, the spin label SYNVAR 101, under various experimental conditions. A study was made of the influence of antireductants on the labelling efficiency and the kinetics of the radical decay during the labelling process. The antireductant hydrogen peroxide was effective in suppressing the decay, whereas ferricyanide was not very effective in this role. The nitroxide radical concentration in a nondialyzed plasma suspension of spin-labelled erythrocytes continuously decayed exponentially with a time constant of 35 min. Nitroxide radicals in nondialyzed plasma exhibited a similar decay to a final residual value which was small relative to the initial concentration. Dialyzing the plasma raised the residual concentration to three quarters of the initial value without changing the decay time.

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Riassunto Eritrociti umani sono marcati con ossido di azoto, il marchio di spin SYNVAR 101, in varie condizioni sperimentali. Si è fatto uno studio dell’influenza degli agenti antiriducenti sulla capacità di marcare e sulla cinetica del decadimento dei radicali durante il processo di marcatura. Il perossido d’idrogeno antiriducente era efficacie nel sopprimere il decadimento, mentre il ferrocianuro non era molto efficacie in questo roulo. La concentrazione dei radicali dell’ossido di azoto in una sospensione di plasma non dializzato degli eritrociti marcati secondo lo spin decade continuamente in maniera esponenziale con una costante di tempo di 35 min. I radicali dell’ossido di azoto nel plasma non dializzato esibiscono un decadimento simile al valore residuo finale che era piccolo in relazione alla concentrazione iniziale. Dializzare il plasma aumenta la concentrazione residua a tre quarti del valore iniziale senza cambiare il tempo di decadimento.

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Резюме В различных эксрериментальных условиях метятся человеческие эритроциты с окисью азота. Исследуются влияния антивосстановителя на эффективность нанесения метки и кинетику распада радикалов в процессе нанесения метки, Перекись водорода, как антивосстановитель, является эффективной для подавления распада, тогда как феррицианид не очень эффективен в этой. Концетрация радикалов окиси азота в суспензии недиализированной плазмы эритроцитов со спиновой меткой уменьшается эксоненциально с временной постоянной, равной 35 мин. Радикалы окиси азота в недиализированной плазме обнаруживают аналогичный распад, причем конечная остаточная величина концентрации оказывается малой по сравнений с начальной концентрацией. Диализация рлазмы увеличивает остаточную концентрацию до трех четвертых начальной без изменения времени распада.

     

On-column injection in the stopped-flow mode with open-tubular columns

Summary A simple, inexpensive, on-column injector of the septum moving-needle kind is described for quantitative analysis using open-tubular columsn. when operated in the stopped-flow mode an improvement incolumn efficiency is observed combined wit a diminished tendency to produce split-top peaks, particularly for late eluting peaks. Using electronic integration a relative error of about 2.7% was observed for peaks spanning a wide range of sample concentrations and volatilities.Dedicated to Professor A. Zlatkis on the occastion of his 60th birthday.     

The electronic structure of the valence bands of solid NH3 and H2O studied by ultraviolet photoelectron spectroscopy

The results of a photoelectron study using ultraviolet 40.81 eV photons (UPS) of the outermost bands of the molecular solids NH₃ and H₂O are reported. The binding energies, the energy separation, the band widths and the branching ratio of the two outermost bands of solid NH₃ are found not to be significantly different from the 3a_l and 1e molecular orbital states of the gaseous NH₃ UPS spectrum. This implies that hydrogen bonding has not produced any significant change in the electronic structure of the valence bands of solid NH₃. Because of a much smaller intermolecular hydrogen bond length in solid H₂O compared to that in solid NH₃, the hydrogen bond does, however, produce a significant change in the valence bands of H₂O on solidification, and because of the orbital geometry it predominantly affects the 3a_l molecular orbital state.     

Electronic structure of the valence bands of SnCl2 and SnBr2 studied by ultraviolet photoelectron spectroscopy

A photoelectron study of the outermost bands of solid-phase SnCl₂ and SnBr₂ using 40.81 eV photons is reported. The main features of the spectra are successfully interpreted in terms of molecular orbital theory for the appropriate isolated molecules.     

Convergent regular splittings for nonnegative matrices

MP matrices are those real matrices which possess a nonnegative, nonsingular l-inverse. This paper characterizes the nonnegative MP matrices and hence, determines when a nonnegative matrix A has a convergent regular splitting M—Q which induces the linear stationary iterative scheme x_k+1=M^-1Qx_k+M^-1b to solve Ax=b.     

Anomalous temperature dependence of the paramagnetic resonance line in FeF3 · 3H2O

Anomalous line-broadening in the paramagnetic resonance of FeF₃ · 3H₂O, which has a linear chain arrangement, has been observed. The line width was found to decrease monotonically with increasing temperature in the range from 100–300°K.     

Fractional Stokes-Einstein and Debye-Stokes-Einstein relations in a network-forming liquid

We study the breakdown of the Stokes-Einstein (SE) and Debye-Stokes-Einstein (DSE) relations for translational and rotational motion in a prototypical model of a network-forming liquid, the ST2 model of water. We find that the emergence of fractional SE and DSE relations at low temperature is ubiquitous in this system, with exponents that vary little over a range of distinct physical regimes. We also show that the same fractional SE relation is obeyed by both mobile and immobile dynamical heterogeneities of the liquid.