Mobility of antimony, arsenic and lead at a former mine, Glendinning, Scotland

Elevated concentrations of antimony (Sb), arsenic (As) and lead (Pb) in upland organic-rich soils have resulted from past Sb mining activities at Glendinning, southern Scotland. Transfer of these elements into soil porewaters was linked to the production and leaching of dissolved organic matter and to leaching of spoil material. Sb was predominantly present in truly dissolved (< 3 kDa) forms whilst As and Pb were more commonly associated with large Fe-rich/organic colloids. The distinctive porewater behaviour of Sb accounts for its loss from deeper sections of certain cores and its transport over greater distances down steeper sections of the catchment. Although Sb and As concentrations decreased with increasing distance down a steep gully from the main spoil heap, elevated concentrations (~ 6-8 and 13-20 μg L− 1, respectively) were detected in receiving streamwaters. Thus, only partial attenuation occurs in steeply sloping sections of mining-impacted upland organic-rich soils and so spoil-derived contamination of surface waters may continue over time periods of decades to centuries

Strategies for producing biochars with minimum PAH contamination

With the aim to develop initial recommendations for production of biochars with minimal contamination with polycyclic aromatic hydrocarbons (PAHs), we analysed a systematic set of 46 biochars produced under highly controlled pyrolysis conditions. The effects of the highest treatment temperature (HTT), residence time, carrier gas flow and typical feedstocks (wheat / oilseed rape straw pellets (WSP), softwood pellets (SWP)) on 16 US EPA PAH concentration in biochar were investigated. Overall, the PAH concentrations ranged between 1.2 and 100 mg kg-1. On average, straw-derived biochar contained 5.8 times higher PAH concentrations than softwood-derived biochar. In a batch pyrolysis reactor, increasing carrier gas flow significantly decreased PAH concentrations in biochar; in case of straw, the concentrations dropped from 43.1 mg kg-1 in the absence of carrier gas to 3.5 mg kg-1 with a carrier gas flow of 0.67 L min-1; for woody biomass PAHs concentrations declined from 7.4 mg kg-1 to 1.5 mg kg-1 with the same change of carrier gas flow. In the temperature range of 350-650°C the HTT did not have any significant effect on PAH content in biochars, irrespective of feedstock type, however, in biochars produced at 750°C the PAH concentrations were significantly higher. After detailed investigation it was deduced that this intensification in PAH contamination at high temperatures was most likely down to the specifics of the unit design of the continuous pyrolysis reactor used. Overall, it was concluded that besides PAH formation, vaporisation is determining the PAH concentration in biochar. The fact that both of these mechanisms intensify with pyrolysis temperature (one increasing and the other one decreasing the PAH concentration in biochar) could explain why no consistent trend in PAH content in biochar with temperature has been found in the literature

Strategies for producing biochars with minimum PAH contamination

With the aim to develop initial recommendations for production of biochars with minimal contamination with polycyclic aromatic hydrocarbons (PAHs), we analysed a systematic set of 46 biochars produced under highly controlled pyrolysis conditions. The effects of the highest treatment temperature (HTT), residence time, carrier gas flow and typical feedstocks (wheat / oilseed rape straw pellets (WSP), softwood pellets (SWP)) on 16 US EPA PAH concentration in biochar were investigated. Overall, the PAH concentrations ranged between 1.2 and 100 mg kg-1. On average, straw-derived biochar contained 5.8 times higher PAH concentrations than softwood-derived biochar. In a batch pyrolysis reactor, increasing carrier gas flow significantly decreased PAH concentrations in biochar; in case of straw, the concentrations dropped from 43.1 mg kg-1 in the absence of carrier gas to 3.5 mg kg-1 with a carrier gas flow of 0.67 L min-1; for woody biomass PAHs concentrations declined from 7.4 mg kg-1 to 1.5 mg kg-1 with the same change of carrier gas flow. In the temperature range of 350-650°C the HTT did not have any significant effect on PAH content in biochars, irrespective of feedstock type, however, in biochars produced at 750°C the PAH concentrations were significantly higher. After detailed investigation it was deduced that this intensification in PAH contamination at high temperatures was most likely down to the specifics of the unit design of the continuous pyrolysis reactor used. Overall, it was concluded that besides PAH formation, vaporisation is determining the PAH concentration in biochar. The fact that both of these mechanisms intensify with pyrolysis temperature (one increasing and the other one decreasing the PAH concentration in biochar) could explain why no consistent trend in PAH content in biochar with temperature has been found in the literature

Establishing the extent of malaria transmission and challenges facing pre-elimination in the Republic of Djibouti.

BACKGROUND: Countries aiming for malaria elimination require a detailed understanding of the current intensity of malaria transmission within their national borders. National household sample surveys are now being used to define infection prevalence but these are less efficient in areas of exceptionally low endemicity. Here we present the results of a national malaria indicator survey in the Republic of Djibouti, the first in sub-Saharan Africa to combine parasitological and serological markers of malaria, to evaluate the extent of transmission in the country and explore the potential for elimination. METHODS: A national cross-sectional household survey was undertaken from December 2008 to January 2009. A finger prick blood sample was taken from randomly selected participants of all ages to examine for parasitaemia using rapid diagnostic tests (RDTs) and confirmed using Polymerase Chain Reaction (PCR). Blood spots were also collected on filter paper and subsequently used to evaluate the presence of serological markers (combined AMA-1 and MSP-119) of Plasmodium falciparum exposure. Multivariate regression analysis was used to determine the risk factors for P. falciparum infection and/or exposure. The Getis-Ord G-statistic was used to assess spatial heterogeneity of combined infections and serological markers. RESULTS: A total of 7151 individuals were tested using RDTs of which only 42 (0.5%) were positive for P. falciparum infections and confirmed by PCR. Filter paper blood spots were collected for 5605 individuals. Of these 4769 showed concordant optical density results and were retained in subsequent analysis. Overall P. falciparum sero-prevalence was 9.9% (517/4769) for all ages; 6.9% (46/649) in children under the age of five years; and 14.2% (76/510) in the oldest age group (≥50 years). The combined infection and/or antibody prevalence was 10.5% (550/4769) and varied from 8.1% to 14.1% but overall regional differences were not statistically significant (χ2=33.98, p=0.3144). Increasing age (p<0.001) and decreasing household wealth status (p<0.001) were significantly associated with increasing combined P. falciparum infection and/or antibody prevalence. Significant P. falciparum hot spots were observed in Dikhil region. CONCLUSION: Malaria transmission in the Republic of Djibouti is very low across all regions with evidence of micro-epidemiological heterogeneity and limited recent transmission. It would seem that the Republic of Djibouti has a biologically feasible set of pre-conditions for elimination, however, the operational feasibility and the potential risks to elimination posed by P. vivax and human population movement across the sub-region remain to be properly established

Imperfect vaccines and the evolution of pathogen virulence

Vaccines rarely provide full protection from disease. Nevertheless, partially effective (imperfect) vaccines may be used to protect both individuals and whole populations.We studied the potential impact of different types of imperfect vaccines on the evolution of pathogen virulence (induced host mortality) and the consequences for public health. Here we show that vaccines designed to reduce pathogen growth rate and/or toxicity diminish selection against virulent pathogens. The subsequent evolution leads to higher levels of intrinsic virulence and hence to more severe disease in unvaccinated individuals. This evolution can erode any population-wide benefits such that overall mortality rates are unaffected, or even increase, with the level of vaccination coverage. In contrast, infection-blocking vaccines induce no such effects, and can even select for lower virulence. These findings have policy implications for the development and use of vaccines that are not expected to provide full immunity, such as candidate vaccines for malaria

(±)-2′-Phenyl­cyclo­hexa­nespiro-4′-(aze­pano[1,2-b]isoxazolidine)

In the crystal structure of the racemic title isoxazolidine, C19H27NO, the relative stereochemistry between the phenyl group and the bridgehead H atom is shown to be syn. There are two mol­ecules in the asymmetric unit, one of which is the 7R*,13R* enanti­omer, and one of which is the 7S*,13S* enanti­omer. These enanti­omers adopt different orientations of the phenyl ring with respect to the isoxazolidine ring, with C—C—C—C torsion angles of 63.6 (4) and 86.8 (4)°, respectively. In both enanti­omers, the six-membered ring adopts a chair conformation, while the seven-membered ring adopts a twist-chair conformation

Chloroquine resistance before and after its withdrawal in Kenya

This is an Open Access article distributed under the terms of the Creative Commons Attribution Licens

Genetic complexity of Plasmodium falciparum in two ethnic groups of Burkina Faso with marked differences in susceptibility to malaria.

We have characterized Plasmodium falciparum genotypes among the Mossi and Fulani sympatric ethnic groups in villages in Burkina Faso during the rainy season. Differences in clinical malaria presentation and in immune responses to malaria occur between the two groups. Asexual parasite rate, density, and gametocyte rate were higher among the Mossi than the Fulani. There was no difference in frequencies of alleles of the P. falciparum merozoite surface protein 1 (msp-1), msp-2, and glutamate-rich protein (glurp) genes among the parasites in each group. However, there were significant differences in the mean number of P. falciparum clones in the two populations, with there being more in the Mossi than in the Fulani. This effect was especially marked in older children. These differences can most probably be attributed to genetic differences in immune responsiveness to malaria between the two ethnic groups