Pyrethroid insecticide evaluation on different house structures in a Chagas disease endemic area of the Paraguayan Chaco

Insecticide effects of deltamethrin 2.5% SC (flowable solution) on different substrates and triatomine infestation rates in two indigenous villages (Estancia Salzar and Nueva Promesa) of the Paraguayan Chaco are reported. This field study was carried out to determine the extent to which variability in spray penetration may affect residual action of the insecticide. A total of 117 houses in the two villages were sprayed. Filter papers discs were placed on aluminium foil pinned to walls and roofs in selected houses and the applied insecticide concentration was determined by high pressure liquid chromatography (HPLC). The target dose rate was 25 mg a.i./m². The mean actual applied dose in Estancia Salazar was 11.2 ± 3.1 mg a.i./m² in walls and 11.9 ± 5.6 mg a.i./m² in roofs while in Nueva Promesa, where duplicates were carried out, the mean values were 19.9 ± 6.9 mg a.i./m² and 34.7 ± 10.4 mg a.i./m² in walls and 28.8 ± 19.2 mg a.i./m² and 24.9 ± 21.8 mg a.i./m² in roofs. This shows the unevenness and variability of applied doses during spraying campaigns, and also the reduced coverage over roof surfaces. However, wall bioassays with Triatoma infestans nymphs in a 72 h exposure test showed that deposits of deltamethrin persisted in quantities sufficient to kill triatomines until three months post spraying. Knockdown by deltamethrin on both types of surfaces resulted in 100% final mortality. A lower insecticidal effect was observed on mud walls. However, three months after treatment, sprayed lime-coated mud surfaces displayed a twofold greater capacity (57.5%) to kill triatomines than mud sprayed surfaces (25%). Re-infestation was detected by manual capture only in one locality, six months after spraying,

Isoenzyme profiles of Trypanosoma cruzi stocks from different areas of Paraguay

Twenty one Trypanosoma cruzi stocks from humans, domiciliary triatomines and one sylvatic animal of different areas of Paraguay were subjected to isoenzyme analysis. Thirteen enzyme systems (15 loci in total) were studied. MN cl2 (clonets 39) and SO34 cl4 (clonets 20) were used as references. Relationships between stocks were depicted by an UPGMA dendrogram constructed using the Jaccard´s distances matrix. Among the Paraguayan stocks 14 zymodemes were identified (Par1 to Par14), Par 5 being the most frequent. Polymorphism rate and clonal diversity were 0.73 and 0.93, respectively. Average number of alleles per polymorphic locus was 2.5 (range 2-4). These measurements show a high diversity, which is confirmed by the dendrogram topology. All stocks belong to the same lineage, as MN cl2 reference strain (T. cruzi II). Moreover three distinct subgroups were identified and two of them correspond to Brazilian and Bolivian zymodemes, respectively. The third subgroup, the most common in Paraguay, is related to Tulahuen stock. The large geographical distribution of some zymodemes agrees with the hypothesis of clonality for T. cruzi populations. However sample size was not adequate to detect genetic recombination in any single locality.

Química na poesia e poesia na química

Goethe's novel 'Elective Affinities', published in 1809, uses Bergmann's concept of 'Elective Attractions', from 1775, as a metaphor for social relations. Its analysis demonstrates the possibility of describing chemical theories, characterised by an anthropomorphic language, using poetic means. Due to the inherently poetic nature of chemical language, Nobel Laureate Roald Hoffmann (2002) suggests relaxing strictures against expressing emotions and personal motives in scientific publications, thus enabling the use ofing poetry to understand and communicate science. Based on the analysis of Goethe's novel and Hoffmann's essay, this article discusses the possibility of using poetic means to help understand chemistry and communicate its research results.

The literary arts in Hume's science of the fancy

Philosophers have long disagreed about whether poetry, drama, and other literary arts are important to philosophy; and among those who believe that they are important, explanations of that importance have differed greatly. This paper aims to explain and illustrate some of the reasons why Hume found literature to be an important topic for philosophy and philosophers. Philosophy, he holds, can help to explain general and specific literary phenomena, to ground the science of criticism, and to suggest and justify ";principles of art,"; while at the same time literature can provide valuable ";experiments"; for philosophical theorizing and provide it with a model for the science of morals and (in some ways) for philosophy itself. Moreover, the literary arts can not only help one to write better philosophy, in Hume's view; they can also help one to write philosophy better.

The role of the poet in Plato's ideal cities of Callipolis and Magnesia

Plato's attitude toward the poets and poetry has always been a flashpoint of debate, controversy and notoriety, but most scholars have failed to see their central role in the ideal cities of the Republic and the Laws, that is, Callipolis and Magnesia. In this paper, I argue that in neither dialogue does Plato "exile" the poets, but, instead, believes they must, like all citizens, exercise the expertise proper to their profession, allowing them the right to become full-fledged participants in the productive class. Moreover, attention to certain details reveals that Plato harnesses both positive and negative factors in poetry to bring his ideal cities closer to a practical realization. The status of the poet and his craft in this context has rarely to my knowledge been addressed.