On global motions of a compressible barotropic and selfgravitating gas with density-dependent viscosities

We consider the Cauchy problem for the equations of selfgravitating motions of a barotropic gas with density-dependent viscosities μ(ρ), and λ(ρ) satisfying the Bresch–Desjardins condition, when the pressure P(ρ) is not necessarily a monotone function of the density. We prove that this problem admits a global weak solution provided that the adiabatic exponent γ associated with P(ρ) satisfies ${\gamma > \frac{4}{3}}$ .     

Development of a volatile amine sensor for the monitoring of fish spoilage

A sensor with potential for the development of a “chemical barcode” for real-time monitoring of fish freshness is described. This on-package sensor contains a pH sensitive dye, bromocresol green, that responds through visible colour change to basic volatile spoilage compounds, such as trimethylamine (TMA), ammonia (NH₃) and dimethylamine (DMA) collectively known as Total Volatile Basic Nitrogen (TVB-N). The sensor characteristics were studied as well as its response with standard ammonia gas. Trials on cod and under-utilised species have verified that the sensor response correlates with bacterial growth patterns in fish samples thus enabling the “real-time” monitoring of spoilage in various fish species. The sensor response can be interrogated with a simple, inexpensive reflectance colorimeter that we have developed based on two light emitting diodes (LEDs) and a photodetector.     

Electron Transfer Processes at Aryl‐Modified Glassy Carbon Electrode

The effect of a layer of electrochemically grafted 4‐diazo‐N,N‐diethylaniline (DEA) groups on the electron transfer kinetics of redox systems, displaying fast and slow heterogeneous electron transfer rate constants at edge and basal planes of carbon, was investigated. The properties of the modified electrode were characterized by cyclic voltammetry using four different inorganic redox systems (Fe(CN) , Co(phen) , Ru(NH₃) , and IrCl in acidic, neutral, and basic media. Two distinct blocking behaviors and electrostatic effects were observed. More precisely, a strong blocking effect of the grafted layer on Fe(CN) and Co(phen) was found, whereas Ru(NH₃) and IrCl showed to be rather unaffected by the presence of the DEA grafted layer.     

Application of a validated stability-indicating chromatographic method to evaluate the reproducibility between batches of small peptides in solution

A stability-indicating reversed-phase high-performance liquid chromatographic method was developed and validated as per the International Conference on Harmonization (ICH) guidelines to evaluate the reproducibility of batches of synthetic peptides included in a stability program, in particular cholecystokinin (CCK-4) peptide.Both isothermal and nonisothermal approaches were used to determine stability under experimental conditions and the resulting degradation products were identified by liquid chromatography-mass spectrometry (LC-MS). The principal degradation product was the cyclic dimer, although another two products derived from it were also detected, due to the loss of one or two Phe-NH₂ residues. The dimerization follows first-order kinetics, whereas the hydrolytic cleavage implies both consecutive and in-parallel processes. The linear Arrhenius plot indicates that the degradation mechanism and kinetics do not change with temperature or the batch, but the degradation rate does depend on the batch, for example, the shelf-life at 25 °C was 2.54 days for batch 3, which is 13-times lower than batch 2. This variability is caused by a change in the synthesis process introduced by the manufacturer.The combination of these two elements: the analytical and stability-evaluating methods provide enough data to establish a stability-indicating profile, as required by the guideline ICH-Q6B for biotechnological/biological products.