Pyro nitrocellulose: Molecular weight distribution and processability

Problems in processing 12.61% N Pyro nitrocellulose into certain types of casting powder have been identified as due to unusual molecular weight distri     

Nonlinear behaviour of interacting mid-latitude atmospheric vortices

Nonlinear behaviour of interacting large-scale atmospheric vortices is considered. These vortices are approximately fifteen kilometres high and can have diameters of hundreds if not thousands of kilometres, and so they can be thought of as large flat structures. The air is weakly compressible, and the fluid motion is subject to the Coriolis pseudo-force, due to the Earth being in a non-inertial rotating reference frame. The vortices studied are coupled binary systems. The high or low pressure in each vortex is modelled initially using an exponential function. A spectral method is presented, for obtaining accurate numerical solutions. Nonlinear results in the f-plane approximation are discussed at mid-latitudes. It is found that the vortices do or do not interact, depending on their initial radii and the location of their centres. A scaling law is found numerically for the ratio of these two quantities, which determines whether interaction does occur.     

Self and mutual diffusion measurements in dilute and semi-dilute polystyrene solutions

Self diffusion coefficients have been obtained for polystyrene ($\text{M}\text{?}{}_{\mathrm{w}}\text{= 37 000}$) solutions in toluene (D₈) and cyclohexane (D₁₂) by the pulsed field gradient n.m.r. technique at 303 K. Mutual diffusion coefficients have been obtained by photon correlation spectroscopy (p.c.s.). In a poor solvent (cyclohexane) both techniques show a similar trend of a monotonic decrease in the diffusion coefficient with increasing concentration of polymer. However, in a good solvent (toluene) n.m.r. shows a monotonic decrease in the diffusion coefficient whereas p.c.s. shows an increase. The results are discussed in terms of self and mutual diffusion processes.     

Alternative monomers for 4,4′-methylenedianiline in thermosetting epoxy resins

4,4′-Methylenedianiline (MDA) is utilized to produce high temperature epoxy resins as well as other high-performance composites; however, MDA is a known carcinogen and liver toxicant. Novel dianilines derived from both petroleum and biomass with different quantities and types of methyl and methoxy substituents on the aromatic ring were prepared and studied to reduce toxicity and carcinogenic aspects of the resulting material while maintaining thermal and mechanical integrity. These dianilines were primarily prepared by coupling commercial anilines using paraformaldehyde under acidic conditions. Another dianiline was prepared by nitration of bisphenol A and subsequent reduction of the nitrates to amines. Structure–toxicity relationships indicate that multiple substituents on the aromatic ring are necessary to reduce the toxicity of the dianiline. Epoxy-amine resins were prepared by blending the dianilines with 50 wt % Epikure W liquid amine curing agent and mixing with a stoichiometric amount of EPON 828 epoxy resin. Methoxy and methyl substituents increase the melting point of the dianilines by as much as 65 °C, thereby worsening the processing of these monomers as liquid thermoset resins. Structure–property relationships show that the addition of a methoxy group to the aromatic ring and moving the amine from the 4,4′ position on the dianiline reduces the glass transition temperature (T _g) by approximately 10 °C. A single methyl group has little effect on T _g and two methyl groups increase the T _g only when both are ortho to the amine, yet this causes a large 14 °C increase in T _g. Thermal degradation profiles are not significantly affected by the dianiline. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 137, 48707.     

A comparison of drug substance predicted chemical stability with ICH compliant stability studies

Objective: The aim of this study is to demonstrate the applicability of predictive stability studies to the degradation of drug substances.

Significance: The use of predicted stability studies during pharmaceutical development and in regulatory submissions is increasing, particularly in early phase to support an initial retest period/shelf life claim in the absence of standard stability data. These studies offer an alternative to standard stability testing and can facilitate clinical trials to be started earlier and medicines to reach patients faster. They involve a short-term stressed stability study, typically designed to degrade a drug substance or product to the specification level of the shelf life limiting attribute. The results are used to predict degradation under long-term storage conditions and enable stability understanding to be gained over a short time frame, using limited amounts of material.

Methods: In this work, Accelerated Stability Assessment Program (ASAP) studies were performed for 10 different drug substances and the predictions obtained for chemical degradation were compared to ICH compliant stability data.

Results: Across the studies good agreement was achieved, with the initial retest period predictions from the ASAP studies being conservative by design. When minimal degradation was observed during an ASAP study, it was demonstrated that at least a 12-month initial retest period could be supported.

Conclusion: This comparison of ASAP predictions and ICH compliant stability data has demonstrated the ability of well-designed ASAP studies to predict the long-term chemical stability of drug substances.     

A multi‐component method to determine pesticides in surface water by liquid‐chromatography tandem quadrupole mass spectrometry

Pesticide pollution of surface water is a major concern in many agricultural catchments The development of rapid and accurate methods for determining pesticide concentrations in water samples is, therefore, important. Here we describe a method for the simultaneous analysis of six pesticides (metaldehyde, quinmerac, carbetamide, metazachlor, propyzamide and pendimethalin) in natural waters by direct aqueous injection with liquid chromatography‐tandem mass spectrometry. The method validation showed good linearity from 0.2 to 50.0 µg/L with correlation coefficients between 0.995 and 0.999. Method accuracy ranged from 84 to 100% and precision Relative standard deviation (RSD) from 4 to 15%. The limits of detection for the targeted pesticides ranged from 0.03 to 0.36 µg/L. No significant matrix effects on quantification were observed (t‐test). The method was tested on water samples from a small arable catchment in eastern England. Peak concentrations for the determinands ranged from 1 to 10 µg/L.     

Expression of basement membrane type IV collagen chains during postnatal development in the murine cochlea

An immunofluorescence study was performed to examine the temporal and spatial patterns of expression for the different type IV collagen chains during postnatal cochlear development. At birth, the classical chains (4A1 and 4A2) were widely expressed, while the novel chains (4A3, 4A4, and 4A5) were completely absent. Activation of the novel chains was observed at 4 days of age, with intense, widely distributed immunostaining suggesting that most of the cells in the cochlea express the novel chains at this developmental stage. From day 8 through day 14, developmental inactivation of the novel chains results in a reduction of generalized immunoreactivity with a concomitant elevation of specific staining in the membranous structures bounding the interdental cells of the spiral limbus, the inner sulcus, the basilar membrane, and in a fibrous bed of staining radiating from the spiral prominence into the region of the spiral ligament which corresponds to the location of the root cell processes. This pattern of intense immunostaining for the novel chains persists through adulthood. The classical chains are expressed in these same anatomical regions only transiently (from day 6 to day 10), after which a gradual developmental inactivation leads to the adult expression pattern where classical collagen chains are found primarily in the perineurium, in the membranes surrounding the spiral ganglion cell bodies, and in the vascular basement membranes of the spiral ligament and the stria vascularis. The complex developmental pattern of expression for the type IV collagen chains in the murine cochlea is similar to that observed in the murine kidney, which is the other major site for basement membrane pathology in Alport syndrome.