Perchlorate on Mars - Overview and Implications

Perchlorate was first detected on Mars by the Wet Chemistry Laboratory (WCL) instrument on the Phoenix lander at a concentration of ~0.5 wt% in northern plains soils. Since that initial detection, perchlorate (and likely chlorate) have been detected on Mars by both surface and orbital instruments. Perchlorate (ClO4-) is an oxidized chlorine compound and salts of perchlorate are kinetically stable (though very reactive at high temperature), very soluble, deliquescent, and have low eutectic temperature (which decreases the temperature for stable liquids on Mars). Chlorate (ClO3-) salts are similar, though they are less kinetically stable than perchlorates. Because many of the analytical signatures of perchlorate and chlorate are similar to the instruments we have used on Mars, we cannot always determine which species is present, so we will use the more generic term oxychlorine when referring to perchlorate and/or chlorate

Marker gene swapping facilitates recombinant Modified Vaccinia Virus Ankara production by host-range selection.

Modified Vaccinia Virus Ankara (MVA) is employed widely as an experimental and human vaccine vector for its lack of replication in mammalian cells and high expression of heterologous genes. Recombinant MVA technology can be improved greatly by combining transient host-range selection (based on the restoration in MVA of the deleted vaccinia gene K1L) with the differential expression of fluorescent proteins. Recombinant virus results from swapping a red protein gene (in the acceptor virus) with a cassette of the transfer plasmid comprising the transgene and the green marker K1Lgfp (a chimeric gene comprising K1L and EGFP). Recombinant selection is performed in the selective host RK13. Finally, in the non-selective host BHK-21, a single crossover between identical flanking regions excises the marker gene. The three types of viruses involved (red parental, green intermediate and colourless final recombinant) are visualized differentially by fluorescence microscopy or fluoro-imaging of terminal dilution microcultures, leading to a straightforward and efficient purification protocol. This method (Red-to-Green gene swapping) reduces greatly the time needed to obtain marker-free recombinant MVA and increases the reliability of the construction process

Safety netting advice for acutely ill children presenting to ambulatory care: exploring parents’ opinions, ideas, and expectations through focus group interviews

Abstract Background Safety netting advice (SNA) is an essential component of the management of acutely ill children in ambulatory care. However, healthcare professionals use a variety of SNA methods, leading to inconsistencies within and across organisations. Much research has explored the perspective on SNA of parents from the UK, but such research is lacking outside the UK context. Methods We conducted focus groups with Belgian parents of children 6 months to 12 years old, who were recruited through maximum variation sampling. We transcribed the interviews verbatim. Using a combination of inductive and deductive ‘in vivo’ coding we developed themes from the data. As per the Grounded Theory approach, we reiterated between data collection, coding, and analysis. After participant validation of provisional themes, we constructed the final thematic framework. Results Through six focus groups with 30 parents, we identified five themes: (1) Relevant background information; (2) To know what to expect, what to look out for; (3) Instructions on child homecare and when to revisit a physician; (4) Physicians who consider parents’ perspectives and contexts; (5) A reliable source that provides SNA only when necessary, possibly in a multimodal way. Conclusions We identified five themes from Belgian parents’ views on SNA, aligning with prior UK research. These findings form an evidence base for developing a consensus statement on the content and form of SNA supported by both parents and experts from high-income countries

Mechanism of release from pellets coated with an ethylcellulose-based film

Studies were conducted to determine the mechanism of drug release from pellets coated with an ethylcellulose-based pseudolatex widely accepted for use as a sustained release coating for pharmaceuticals. Possible mechanisms for release include solution/diffusion through the continuous polymer phase and/or plasticizer channels, diffusion through aqueous pores and osmotically driven release through aqueous pores. To distinguish between these mechanisms, the release rate was studied as a function of coating thickness, plasticizer content, and osmotic pressure in the dissolution medium. As the coating thickness was increased from 9 to 50 [mu]m, the rate of release fell from 9.93[middle dot]10-3 to 1.71[middle dot]10-3 g phenylpropanolamine (PPA)[middle dot]HCl/100 ml h in an inversely proportional manner. Release as a function of plasticizer content was studied over the range 12 to 24% dibutyl sebacate (DBS). At 18 or 24% DBS, the rates of release of PPA[middle dot]HCl were virtually identical, about 50% of PPA[middle dot]HCl in six hours. At 12% DBS through, over 80% was released in the first hour. Surface area measurements and scanning electron microscopy (SEM) showed that the larger surface area of the 12% DBS batch was attributable to the presence of cracks in the coating. These results indicated that while the plasticizer is important in terms of forming a continuous film, diffusion through plasticizer channels is unlikely to make a significant contribution to the overall release rate. Release was also studied as a function of the osmotic pressure in the medium. A plot of release rate vs. osmotic pressure revealed an inverse linear relationship with a nonzero intercept. The steep dependency of release rate on osmotic pressure of the medium suggested that osmotically driven release is a major mechanism for release, while the nonzero intercept indicated some contribution from diffusion mechanisms. For all batches, SEM indicated that the film exhibited pores approximately 2 [mu]m in diameter, consistent with these mechanisms. In summary, then, the release from PPA[middle dot]HCl pellets coated with an ethylcellulose-based film appears to be a combination of osmotically driven release and diffusion through the polymer and/ or aqueous pores. A mathematical expression for this type of release is presented.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/28280/1/0000033.pd