Responses in growth and dynamics of the shade-tolerant species Theobroma subincanumto logging gaps in the Eastern Amazon.

Aim of study: To assess responses of the shade-tolerant species Theobroma subincanum in relation to canopy gaps created by reduced impact logging (RIL). Materials and methods: A managed forest in themunicipality ofMoju, Pará state,Brazil, harvested in 1997 through RIL was monitored during 12 years (1998-2010). Nine logging gaps were selected and classified in small, medium, and large. Four 10 m x 50 m strips starting from the gap?s border towards the forest and following the directions of cardinal points were installed. Each strip was divided in five 10 m x 10 m plots. Density, diameter distribution (DBH ≥ 5 cm with intervals = 5 cm), and diameter growth were measured. Main results: No significant changes in seedling density of T. subincanum were found, and its diameter distribution followed the reverse ?J? shape during all monitoring time. T. subincanum presented diameter growth of 0.15 cm year-1 with highest Periodic Annual Increment in diameter up to three years, and stabilization in nine years after RIL. The species responded to a growth gradient inversely proportional to the gap?s border distance (p = 0.001) but not to gap size and plots direction in cardinal points around the gap. Research highlights: Shade-tolerant species such as T. subincanum have sensible and positive growth responses to disturbances caused by RIL even when seedlings received low amounts of indirect sunlight. These positive responses should be considered in the management of production forests

Chemical Characterization and Source Apportionment of Household Fine Particulate Matter in Rural, Peri-urban, and Urban West Africa

Household air pollution in sub-Saharan Africa and other developing regions is an important cause of disease burden. Little is known about the chemical composition and sources of household air pollution in sub-Saharan Africa, and how they differ between rural and urban homes. We analyzed the chemical composition and sources of fine particles (PM2.5) in household cooking areas of multiple neighborhoods in Accra, Ghana, and in peri-urban (Banjul) and rural (Basse) areas in The Gambia. In Accra, biomass burning accounted for 39–62% of total PM2.5 mass in the cooking area in different neighborhoods; the absolute contributions were 10–45 μg/m3. Road dust and vehicle emissions comprised 12–33% of PM2.5 mass. Solid waste burning was also a significant contributor to household PM2.5 in a low-income neighborhood but not for those living in better-off areas. In Banjul and Basse, biomass burning was the single dominant source of cooking-area PM2.5, accounting for 74–87% of its total mass; the relative and absolute contributions of biomass smoke to PM2.5 mass were larger in households that used firewood than in those using charcoal, reaching as high as 463 μg/m3 in Basse homes that used firewood for cooking. Our findings demonstrate the need for policies that enhance access to cleaner fuels in both rural and urban areas, and for controlling traffic emissions in cities in sub-Saharan Africa

Spatial distribution pattern of Euxylophora paraensis Huber in a natural managed forest in the Eastern Amazon.

O objetivo desse trabalho foi caracterizar o padrão de distribuição espacial de Euxylophora paraensis (pau-amarelo), para subsidiar estratégias de conservação dessa espécie em floresta de terra firme manejada no estado do Pará. A área de estudo está localizada na Fazenda Rio Capim, pertencente a CKBV Florestal Ltda., no município de Paragominas. Para a análise da distribuição espacial das árvores utilizou-se a geoestatística, a partir da modelagem de semivariograma e confecção de mapas de krigagem. Todas as avaliações tiveram melhor ajuste ao modelo esférico, apresentando o maior coeficiente de determinação em relação aos outros modelos testados. Euxylophora paraensis apresentou padrão de distribuição agregada na floresta estudada, com dependência espacial descrita pelo modelo esférico, formando reboleiras de 300 a 1000 m

Sociobiological Control of Plasmid copy number

Background:
All known mechanisms and genes responsible for the regulation of plasmid replication lie with the plasmid rather than the chromosome. It is possible therefore that there can be copy-up mutants. Copy-up mutants will have within host selective advantage. This would eventually result into instability of bacteria-plasmid association. In spite of this possibility low copy number plasmids appear to exist stably in host populations. We examined this paradox using a computer simulation model.

Model:
Our multilevel selection model assumes a wild type with tightly regulated replication to ensure low copy number. A mutant with slightly relaxed replication regulation can act as a “cheater” or “selfish” plasmid and can enjoy a greater within-host-fitness. However the host of a cheater plasmid has to pay a greater cost. As a result, in host level competition, host cell with low copy number plasmid has a greater fitness. Furthermore, another mutant that has lost the genes required for conjugation was introduced in the model. The non-conjugal mutant was assumed to undergo conjugal transfer in the presence of another conjugal plasmid in the host cell.

Results:
The simulatons showed that if the cost of carrying a plasmid was low, the copy-up mutant could drive the wild type to extinction or very low frequencies. Consequently, another mutant with a higher copy number could invade the first invader. This process could result into an increasing copy number. However above a certain copy number within-host selection was overcompensated by host level selection leading to a rock-paper-scissor (RPS) like situation. The RPS situation allowed the coexistence of high and low copy number plasmids. The non-conjugal “hypercheaters” could further arrest the copy numbers to a substantially lower level.

Conclusions:
These sociobiological interactions might explain the stability of copy numbers better than molecular mechanisms of replication regulation alone

Yacon syrup: food applications and impact on satiety in healthy volunteers.

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