The Role of Two-Step Blending in the Properties of Starch/Chitin/Polylactic Acid Biodegradable Composites for Biomedical Applications

The current research trend for excellent miscibility in polymer mixing is the use of plasticizers. The use of most plasticizers usually has some negative effects on the mechanical properties of the resulting composite and can sometimes make it toxic, which makes such polymers unsuitable for biomedical applications. This research focuses on the improvement of the miscibility of polymer composites using two-step mixing with a rheomixer and a mix extruder. Polylactic acid (PLA), chitin, and starch were produced after two-step mixing, using a compression molding method with decreasing composition variation (between 8% to 2%) of chitin and increasing starch content. A dynamic mechanical analysis (DMA) was used to study the mechanical behavior of the composite at various temperatures. The tensile strength, yield, elastic modulus, impact, morphology, and compatibility properties were also studied. The DMA results showed a glass transition temperature range of 50 °C to 100 °C for all samples, with a distinct peak value for the loss modulus and factor. The single distinct peak value meant the polymer blend was compatible. The storage and loss modulus increased with an increase in blending, while the loss factor decreased, indicating excellent compatibility and miscibility of the composite components. The mechanical properties of the samples improved compared to neat PLA. Small voids and immiscibility were noticed in the scanning electron microscopy images, and this was corroborated by X-ray diffraction graphs that showed an improvement in the crystalline nature of PLA with starch. Bioabsorption and toxicity tests showed compatibility with the rat system, which is similar to the human system.

Reproduction of the biogenic reef-forming honeycomb worm Sabellaria alveolata in Ireland

The stage of development of the gametes of both male and female honeycomb worms Sabellaria alveolata (L.) was examined, using histology, over a 14-month period. Samples came from Howes Strand and Garrettstown, County Cork in south-west Ireland. A clear cycle of both male and female gametogenesis was evident, with a distinct peak in the summer (June–September) when the majority of them were ripe. During October–January a small proportion of males contained abundant spermatozoa, but no mature oocytes were found. Over the whole sampling period the ratio of males:females was 1.4:1. Further south in Roches de la Fosse in France at the centre of its range, two spawnings and an even sex-ratio have been reported.

Development of physicochemical methods for analysis of pandemic influenza vaccine

The utility of a size exclusion high-performance liquid chromatography (SE-HPLC) method, in the identification and quantitation of haemagglutinin (HA) protein in monovalent, inactivated influenza vaccines for the purposes of potency assessment is reported. This method is sufficiently eveloped to provide a distinct peak separation of HA from other vaccine constituents, and a correlation with HA potency determined by single radial-immunodiffusion (SRID) assay. Sensitivity of the method is demonstrated, with each HA peak accurately titrated to the HA content of the protein load injected. Highly reproducible chromatographic profiles (on a G4000SWxl column) were achieved, demonstrating vaccine protein integrity and stability. Potency assessments, determined by SE-HPLC peak area analysis, provided very good correlation with the quantitative HA protein values, determined by SRID, reported by the manufacturer and by Health Canada's Centre for Biologics Evaluation, Pandemic Influenza Division (PID). Peak resolution was further enhanced by expanding to a tandem SE-HPLC system, utilizing a G4000SWxl SE column coupled to a G3000SWxl column. HA was detected in the 11-17 minute (min) elution, collected in 30 second (sec) fractions, with the smallest, most distinct peak width detected to date at the 15.5 min fraction. This SE-HPLC method has considerable potential for widespread use as a physicochemical method for HA identification and quantification, in quality control testing for seasonal and pandemic influenza vaccines, and as a practical alternative for potency measures by the reagent dependent SRID assay. Increased resolution and further method development will facilitate the collection of separated fractions for further analysis, to correlate immunoactivity to HA type and content.

Egg hatching in 3 species of monocotylid monogenean parasites from the shovelnose ray Rhinobatos typus at Heron Island, Australia

Eggs of Neoheterocotyle rhinobatidis, Troglocephalus rhinobatidis and Merizocotyle icopae (Monogenea: Monocotylidae) from the shovelnose ray Rhinobatos typus (Rhinobatidae) have a distinct hatching pattern linked to light periodicity. Larvae of these 3 monogenean species emerge only during daylight when exposed to natural illumination or when incubated in alternating 12 h periods of light and dark (light on 06.00 h, light off 18.00 h). N. rhinobatidis larvae emerge with a distinct peak during the first 2 h of light; this peak is not as pronounced in T. rhinobatidis or M. icopae. Eggs of N. rhinobatidis incubated in a reverse light/dark cycle (light on 18.00 h, light off 06.00 h) hatched only during periods of illumination, again with a peak during the first 2 h of light. Evidence suggests that the hatching patterns observed in all 3 species represent true circadian rhythms because eggs incubated in 24 h light or 24 h dark conditions continued to hatch with a rhythm. Shadows, disturbance and host tissue did not promote hatching in N. rhinobatidis or T. rhinobatidis but there were indications that host tissue may promote hatching in M. icopae. The hatching patterns observed are discussed with respect to their adaptive responses to host behaviour and predation pressure.

The Water Column Oscillation in a Duct Between Two Half Ship Section Barriers

The oscillation of a water column in a duct between two half ship section barriers is relevant to several practical applications, notably wave energy devices and moonpools for the launch/retrieval of subsea units from diving support vessels. The oscillation is solved for the case where the barriers are space fixed, and the method used is then extended to include effects due to the heave motion of the barriers. Results obtained in the form of response amplitude operators indicate that the water column oscillation demonstrates a distinct peak response, and that the key parameter controlling this response is the ratio of duct width to barrier draft.

Temporal patterns of host-seeking activity of mosquitoes in Algonquin Park, Ontario

Using multidirectional ramp traps baited with CO2, the flight activity of mosquitoes was monitored on a continuous basis for two seasons, with samples segregated into 30-min catches. Over 16 000 catches were collected, from which 22 species of mosquitoes were identified. Seasonal extrema are reported for all mosquito species collected and detailed seasonal and daily patterns of activity are given for the six most abundant species, namely Aedes canadensis (Theobald), Aedes communis (DeGeer), Aedes diantaeus Howard, Dyar and Knab, Aedes intrudens Dyar, Aedes punctor (Dirby), Aedes abserratus (Felt and Young), and Mansonia perturbons (Walker). All six abundant species had a peak of activity in the evening: A. communis the earliest, around 1800, and M. perturbons the latest, around 2200. Mansonia perturbons was the only species with a distinct peak of early morning activity, although some activity was evident for other species. Perspective plots for A. communis and M. perturbons are used to examine relationships between seasonal and daily patterns. There was a detectable change through the season in the daily pattern of A. communis, but no change was detected for M. perturbons.