The pH dependence of phenolphthalein: A 13c NMR study

The pH dependence of the ¹³C NMR spectra of phenolphthalein has been measured and interpreted. The spectrum of the neutral compound 1 is compared with the spectra of the dianion 4, the trianion5 and the carbocation7. At the first time spectroscopic evidence for the carbinol 6 is given.     

Optimization of the synthesis of symmetric aromatic tri- and tetrasulfides

The reaction of aromatic thiols with sulfur dichloride and sulfur monochloride to form the corresponding aromatic trisulfides, 2a-d, and tetrasulfides, 3a-d, has been optimized with respect to yield and purity. The use of pyridine as an amine base and the use of freshly distilled sulfur monochloride (S(2)Cl(2)) serve as important alterations to the synthetic method. Their physical properties have been characterized, revealing some discrepancies with the literature.     

The synthesis of a precursor of polybenzimidazole (PBI) and blends with polyamic acid (PAA)

The precursor of polybenzimidazole (PBI), poly(3,3′-diamino-4,4′-benzidine isophthalamide) (PDABI), was synthesized from poly(3,3′-dinitro-4,4′-benzidine isophthalamide) (PDNBI) by reduction. With increasing temperature, the NH₂ moiety which was protected by SnCl₅^?1 could cyclize and form PBI. Blends with polyamic acid (LaRC-TPI) were prepared. Clear blend films were prepared at up to 400°C. The IR spectra displayed shifts in the NH stretching band, thereby providing evidence for specific interactions related to the miscibility of their cured blends. © 1993 John Wiley & Sons, Inc.     

The crystal structure of the inorganic surface films formed on Mg and Li intercalation compounds and the electrode performance

A crystallographic approach was applied to elucidate the influence of the nature of the surface films on the electrochemical behavior of Li and Mg intercalation compounds. This paper presents two examples: (1) protection of graphite electrodes by Li₂CO₃ surface films, and (2) the unique electrochemical behavior of Mg-containing Chevrel phases (MgCP) obtained by different synthetic routes. In the former case, the elucidation of the protection mechanism and the explanation of the high performance of such protected electrodes are based on the analysis of possible Li-ion motion in the carbonate crystal structure. In the latter case, a combination of synthesis, electrochemistry and XRD analysis was used to explain an unusual phenomenon: the difference between the excellent electrochemical behavior of the Chevrel phase (CP) based on Cu-leached Cu₂Mo₆S₈ (CuCP), and the poor electrochemical activity of the high-temperature synthesized MgCP, with the same phase composition. It is shown that this phenomenon is caused by MgO formation on the surface of the latter material. The different surface chemistry of the MgCPs obtained by the two different synthetic routes was substantiated by revealing the correlation between the electrochemical activity and the chemical stability of these materials under ambient atmosphere conditions. Dedicated to Prof. Mikhail A. Vorotyntsev on the occasion of his 60th birthday.     

Evaluation of multidimensional (ion-exchange/reversed-phase) protein separations using linear and step gradients in the first dimension

The performance characteristics of multidimensional liquid chromatographic protein separations were evaluated using on-line electrospray mass detection, and a novel workflow for automated LC/MS data processing. Two-dimensional ion exchange/reversed-phase LC separations of Escherichia coli cytosol were conducted using either a continuous linear or discontinuous step gradient in the first dimension. Chromatographic profiles of the top 100 most abundant components were characterized to assess overall separation reproducibility within each mode, and to characterize differences in component distribution between the two modes of operation. Analysis of the resulting data indicates that multidimensional separations of complex protein mixtures can be done reproducibly. Furthermore, under the conditions employed within this study, a linear first dimension gradient was more effective at fractionating the protein mixture, distributing fewer major components to multiple second dimension cycles than an equivalent step gradient. The application of on line mass spectrometry, and automated processing of the resulting data, proved valuable for producing component level analysis of multidimensional protein separations.     

Advanced kinetic tools for the evaluation of decomposition reactions

Summary An advanced kinetic study on the thermal behaviour of pyrotechnic ignition mixtures has been carried out by differential scanning calorimetry using different B/KNO3 mixtures (50:50, 30:70, 20:80) as a model reaction. The experimental conditions applied (isochoric conditions/closed crucibles and isobaric conditions/open crucibles) as well as the composition of the mixtures noticeably influences the relative thermal stabilities of the energetic materials. The kinetic study focused on the prediction of the thermal stability of the different mixtures both in extended temperature ranges and under temperature conditions at which ordinary investigation would be very difficult. Using advanced numerical tools [1], thermal ageing and influence of the complex thermal environment on the heat accumulation conditions were computed. This can be done for any surrounding temperature profile such as isothermal, non-isothermal, stepwise, modulated, shock, adiabatic conditions and additionally for temperature profiles reflecting real atmospheric temperature changes (yearly temperature profiles of different climates with daily minimal and maximal fluctuations). Applications of accurate decomposition kinetics enabled the determination of the time to maximum rate under adiabatic conditions (TMR_ad) with a precision given by the confidence interval of the predictions. This analysis can then be applied for the examination of the effects of the surrounding temperature for safe storage or transportation conditions (e.g. determination of the safe transport or storage temperatures).     

THE SUNBURNING ULTRAVIOLET METER: DESIGN AND PERFORMANCE

Abstract— A meter for measuring the skin sunburn effectiveness of a light source is being used in an extensive network to provide solar data for correlation to skin cancer incidence. The solar radiation measured also affects a wide variety of organisms. The intensity of this band of radiation is also strongly affected by ozone concentration so that the output correlates with ozone thickness.
The meter spectral response is essentially the excitation spectrum of magnesium tungstate phosphor which is similar to the erythema action spectrum (EAS). In addition to the waterproofed, dose reading embodiment, a cheaper, easily transportable, batteryless, intensity reading meter with the same spectral response has been developed.
The deviation of any sunburn meter from the ideal erythema action spectrum can be calculated by convolution of a series of solar spectra against each of the two response spectra. Plotting the change in output against the change in input results in straight lines. Either log-log coordinates are required, or, as is done here, decibels can be used on linear coordinates. The angle between the straight lines is taken as the error. An error angle of 6.5° is calculated for the present meter.     

The Worpitzky identity for the groups of signed and even-signed permutations

Journal of Algebraic Combinatorics - The well-known Worpitzky identity $$\begin{aligned} (x+1)^n = \sum \limits _{k=0}^{n-1} A_{n,k} {{x+n-k} \atopwithdelims (){n}} \end{aligned}$$ provides a...