Synthesis and degradation of sorbitol‐based polymers

A new class of biodegradable copolyesters was synthesized by the catalyst‐free melt condensation of sorbitol with citric acid, tartaric acid, and sebacic acid. The resulting polymers were designated as poly(sorbitol citric sebacate) [p(SCS)] and poly(sorbitol tartaric sebacate) [p(STS)]. The synthesized polymers were characterized by Fourier transform infrared spectroscopy, ¹H‐NMR spectroscopy, and differential scanning calorimetry analysis. Porous spongelike scaffolds were prepared with a salt‐leaching technique and characterized with scanning electron microscopy. Tensile testing of the p(SCS) and p(STS) polymers showed that they exhibited a wide range of mechanical properties. The Young's modulus and tensile strengths of the polymers ranged from 1.06 ± 0.12 to 462.65 ± 34.21 MPa and from 0.45 ± 0.04 to 20.32 ± 2.54 MPa, respectively. In vitro degradation studies were performed on disc‐shaped polymer samples. The half‐life of the polymers ranged from 0.54 to 38.52 days. The percentage hydration of the polymers was in the range 9.36 ± 1.26 to 78.25 ± 1.91, with sol contents of 2–14%. At any given polymer composition, the Young's modulus and tensile strength of p(SCS) was higher than that of p(STS), whereas the degradation rates of p(SCS) was lower than that of p(STS). This was attributed to the structural difference between the citric and tartaric monomers and to the degree of crosslinking. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Gelatinisation Properties of Cassava Starch in the Presence of Salts,Acids and Oxidising Agents

The effect of various cations, anions, acids and oxidising agents on the gelatinisation properties of cassava starch was studied and wide variation was observed in the pasting and swelling properties. Sodium chloride and sodium thiosulphate slightly lowered the peak viscosity of cassava starch with increase in concentration, whereas with sodium sulphite, calcium chloride and sodium hypochlorite, a more significant decrease in the viscosity and breakdown was observed. Ferrous sulphate, alum, aluminium chloride and acids enhanced the peak viscosity at lower concentrations followed by a decrease at 1% and above. Sodium metabisulphite elevated the viscosity at 0.05 and 0.1%, while sodium hypochlorite lowered the viscosity and breakdown. DSC studies showed that aluminium chloride, sodium sulphite, and sodium thiosulphate brought about an increase in T_onset, T_end and ΔH values at higher concentrations. A decrease in swelling volume was observed from 0.05 to 1% concentration of sodium chloride and above that there was a gradual increase. With sodium sulphite, a significant increase in swelling volume was observed at 2.5 and 5% levels. With 0.05 and 0.1% aluminium chloride and sodium metabisulphite an increase in swelling volume was noticed, but at higher concentrations there was a drastic fall. Sodium chloride, sodium sulphite, sodium thiosulphate and calcium chloride brought about decrease in starch paste clarity with increase in salt concentration, whereas ferrous sulphate, aluminium chloride, sodium hypochlorite, hydrochloric acid and acetic acid improved the starch paste clarity.     

Transmission network of the 2014–2015 Ebola epidemic in Sierra Leone

Understanding the growth and spatial expansion of (re)emerging infectious disease outbreaks, such as Ebola and avian influenza, is critical for the effective planning of control measures; however, such efforts are often compromised by data insufficiencies and observational errors. Here, we develop a spatial–temporal inference methodology using a modified network model in conjunction with the ensemble adjustment Kalman filter, a Bayesian inference method equipped to handle observational errors. The combined method is capable of revealing the spatial–temporal progression of infectious disease, while requiring only limited, readily compiled data. We use this method to reconstruct the transmission network of the 2014–2015 Ebola epidemic in Sierra Leone and identify source and sink regions. Our inference suggests that, in Sierra Leone, transmission within the network introduced Ebola to neighbouring districts and initiated self-sustaining local epidemics; two of the more populous and connected districts, Kenema and Port Loko, facilitated two independent transmission pathways. Epidemic intensity differed by district, was highly correlated with population size (r = 0.76, p = 0.0015) and a critical window of opportunity for containing local Ebola epidemics at the source (ca one month) existed. This novel methodology can be used to help identify and contain the spatial expansion of future (re)emerging infectious disease outbreaks.