A computer-based programmable waveform generator

The programmable waveform generator, which is capable of producing complex voltage—time programs, is based on a PDP-$\text{11}\text{34}$ minicomputer with associated DIGITAL hardware. The desired waveform is obtained by clock-controlled output of a symmetrical triangular voltage sweep. The software can be readily adapted to any computer system. Ramp sections of 1 mV s^-1—50 V s^-1 and potential pulses of 50 μs—500 s can be obtained.     

Knots and links in spatial graphs

The main purpose of this paper is to show that any embedding of K₇ in three-dimensional euclidean space contains a knotted cycle. By a similar but simpler argument, it is also shown that any embedding of K₆ contains a pair of disjoint cycles which are homologically linked.     

[Fe(CO)2P(OPh)32(CS)]. The first stable thiocarbonyl derivative of iron(0) pentacarbonyl

In some circumstances, P-nBu₃ pr P-nBu₃/CC1₄ desulphurises [Fe(CO)₂{P(OPh)₃}₂(CS₂)] to give [Fe(CO)₂{P(OPh)₃}₂(CS)] which has trigonal bipyramidal coordination about the iron atom with the phosphite ligands in axial positions.     

Analysis of polymers by pyrolysis/chemical ionization mass spectrometry

Two addition-type polymers, polystyrene and polypropylene, and two condensation-type polymers, poly(ethylene terephthalate) (Mylar) and poly(hexamethylene adipamide) (nylon-6,6), were pyrolyzed directly in the ion source of a mass spectrometer by chemical ionization (CI) to reduce fragmentation. The spectra are relatively easy to interpret because most ion peaks occur at a mass corresponding to the ion formula M±H or M + 3H, where M is the formula of a fragment of the original polymer chain. Oligomer peaks were observed for the addition-type polymers. The intensities of the protonated dimer and monomer were measured as a function of time for styrene (S) and propylene (P). It was found that essentially all the HS⁺2 was produced by the reaction of HS⁺ with S, but at least part of the HP⁺2 was formed by proton transfer to P₂. The absence of the analogous reaction in styrene is presumably a result of the reduced volatility of S₂.     

Surface oxidation and H deposition at ruthenium electrodes: Resolution of component processes in potential-sweep experiments

The catalytic and electrochemical reduction of perchlorate ions has been studied using tungsten carbide powder. The rate of catalytic hydrogenation has been studied at different temperatures, hydrogen ion and ClO₄^? concentrations. A rate equation obtained from the experimental results is given.It has been shown that results obtained from steady state polarization measurements carried out under different experimental conditions do not allow the existence of a simple rate determining step in the reduction process to be assumed.     

Optimisation of a Selective Liquid Chromatography Procedure for Hydrocortisone Acetate, Hydrocortisone Alcohol and Preservatives in a Pharmaceutical Emulsion

An accurate, reproducible and specific stability-indicating method for the high performance liquid chromatography (HPLC) assay of hydrocortisone acetate, hydrocortisone alcohol, methyl p-hydroxybenzoate and propyl p-hydroxybenzoate in a pharmaceutical suspension is described. An investigation of several column phases was undertaken and a Zorbax SB-Phenyl column gave the best selectivity and specificity due to the π-π interactions between the analytes and stationary phase. All the components were fully resolved in less than 15 min under isocratic conditions using UV detection at 254 nm with a water-methanol mobile phase. The stability-indicating method was validated over the linearity range of 25% to 150% of the nominal concentrations of each analyte. Nominal concentrations were hydrocortisone acetate (10% w/w), hydrocortisone alcohol (0.2% w/w with respect to hydrocortisone acetate), methyl p-hydroxybenzoate (0.1% w/w) and propyl p-hydroxybenzoate (0.01% w/w) respectively.     

Partial molal compressibilities of salts in aqueous solution and assignment of ionic contributions

Apparent molal adiabatic compressibilities of a number of 1:1, 2:1, 3:1, and 4:1 electrolytes have been accurately determined in the concentration range 0 to 1 m at 25°C. Debye-Hückel limiting-law behavior is observed in the low concentration region, and a scale of individual ionic compressibilities is proposed in terms of semiempirical calculations based on assessment of the contributions of the various types of solute-solvent interaction in the Frank and Wen model for a series of alkali halides. On this scale, K _s ^o (Cl^?, 25°C)=?17×10^?4 ml-mole^?1 bar^?1. Isothermal compressibility values also have been calculated for a number of the salts studied, and specific effects of hydrophobic interaction and hydrogen bonding on compressibility are indicated.     

Early amidation approach to 3-[(4-amido)pyrrol-2-yl]-2-indolinones

A new synthesis of 3-[(4-amido)pyrrol-2-yl]-2-indolinones has been developed, where the amide side chain was installed prior to pyrrole formation. This strategy precludes the need to use any coupling reagents to install the amide side chain. This process includes a zinc-free alternative to the Knorr pyrrole synthesis.