Mesozoic detrital zircon provenance of Central Africa: implications for Jurassic-Cretaceous tectonics, paleogeography and landscape evolution

Jurassic-Cretaceous tectonics, paleogeography and sedimentary provenance of central Africa are poorly constrained and continue to be debated. The lack of constraints on the timing and controls on late Mesozoic sedimentary basin development, drainage evolution and paleoenvironments is problematic because central Africa is well endowed with natural resources, and good understanding of these issues is fundamental to a better assessment of hydrocarbon and alluvial diamond exploration targeting. Moreover, by improving our understanding of Mesozoic strata across this vast region, we can also help to contextualise the ecological and evolutionary relationships of floras and faunas from central Africa with contemporary floras and faunas from different parts of Africa and throughout Gondwana. In particular, refining the depositional age of late Mesozoic units is key to understanding and reconstructing regional paleogeography and drainage patterns during this poorly resolved time period in Africa, which also furthers our understanding of the origins and dispersal pathways for Mesozoic, Cenozoic and modern African floras and faunas, as well as economically significant alluvial mineral resources, such as diamonds, that are important to the economies of this part of the world. To address these issues a detailed and multifaceted sedimentary provenance analysis of 14 late Mesozoic units from seven sedimentary basins across central Africa (spanning seven different countries) was conducted. This integrated sedimentological approach incorporated sandstone petrography, paleocurrent analysis, U-Pb detrital zircon geochronology, Lu-Hf isotope and trace element geochemistry to investigate Jurassic and Cretaceous continental deposits from central Africa. The main objective was to investigate late Mesozoic sedimentary basin development, drainage evolution and provide constraints on the age of deposition, sediment source and paleofluvial drainage patterns, using core and outcrop samples from across the region; including Democratic Republic of Congo (DRC), Kenya, Angola, Sudan, Tanzania, Zimbabwe and Malawi. Sandstone petrography and paleocurrent data indicate mixed sediment sources mainly to the south of study areas. Maximum depositional age analyses performed on U-Pb detrital zircon sample results demonstrate that most of the late Mesozoic units in central Africa are younger than previously accepted. Detrital zircon provenance analysis points to primary contributions from Neoproterozoic Pan-African Mobile Belts (e.g., Mozambique and Zambezi belts), which were probably exposed at this time are the dominant (>75%). The Lu-Hf isotope geochemistry results also show a mixed sediment provenance consisting of juvenile mantle and reworked crustal sources, which corroborates the sandstone petrography results. Western areas of central Africa (e.g. DRC and Angola) are dominated by sediments from reworked crustal sources, whereas eastern parts of central Africa (e.g. Sudan, Kenya and Tanzania) are dominated by sediments of juvenile mantle sources. The results further suggest a pattern of large ephemeral lakes in the Middle Jurassic to Early Cretaceous in the Congo and Zambezi basins, followed by the development of a large, dominantly north directed fluvial systems across central Africa in the middle Cretaceous. The results are supportive of a uniform northward continental drainage pattern throughout late Mesozoic, which supports the assertion that the paleo-Congo drainage system was likely north flowing, rather than east flowing out of the Congo Basin and into Indian Ocean as previously suggested. The results of this thesis are also supportive of the hypothesis of a major drainage divide between southern and central Africa during the late Mesozoic and the concept of a major NW trending fluvial drainage pattern into the shear zones within the Central African Rift System, although the ultimate depocentre still remains uncertain. The maximum depositional age of three Cretaceous sedimentary units, including the dinosaur-bearing Wadi Milk Formation of Sudan has been constrained. The new ages shows a generally much younger age of deposition than previous assignations, calling into question the reliability of these overly broad biostratigraphic age for these important sedimentary units

Blood pressure and body mass index in an ethnically diverse sample of adolescents in Paramaribo, Suriname

<p>Abstract</p> <p>Background</p> <p>High blood pressure (BP) is now an important public health problem in non-industrialised countries. The limited evidence suggests ethnic inequalities in BP in adults in some non-industrialised countries. However, it is unclear whether these ethnic inequalities in BP patterns in adults reflect on adolescents. Hence, we assessed ethnic differences in BP, and the association of BP with body mass index (BMI) among adolescents aged 12–17 years in Paramaribo, Suriname.</p> <p>Methods</p> <p>Cross-sectional study with anthropometric and blood pressure measurements. A random sample of 855 adolescents (167 Hindustanis, 169 Creoles, 128 Javanese, 91 Maroons and 300 mixed-ethnicities) were studied. Ethnicity was based on self-reported ethnic origin.</p> <p>Results</p> <p>Among boys, Maroons had a lower age- and height-adjusted systolic BP than Creoles, and a lower diastolic BP than other ethnic groups. However, after further adjustment for BMI, only diastolic BP in Maroons was significantly lower than in Javanese (67.1 versus 70.9 mmHg). Creole boys had a lower diastolic BP than Hindustani (67.3 versus 70.2 mmHg) and Javanese boys after adjustment for age, height and BMI. Among girls, there were no significant differences in systolic BP between the ethnic groups. Maroon girls, however, had a lower diastolic BP (65.6 mmHg) than Hindustani (69.1 mmHg), Javanese (71.2 mmHg) and Mixed-ethnic (68.3 mmHg) girls, but only after differences in BMI had been adjusted for. Javanese had a higher diastolic BP than Creoles (71.2 versus 66.8 mmHg) and Mixed-ethnicity girls. BMI was positively associated with BP in all the ethnic groups, except for diastolic BP in Maroon girls.</p> <p>Conclusion</p> <p>The study findings indicate higher mean BP levels among Javanese and Hindustani adolescents compared with their African descent peers. These findings contrast the relatively low BP reported in Javanese and Hindustani adult populations in Suriname and underscore the need for public health measures early in life to prevent high BP and its sequelae in later life.</p

Effects of feeding fat on lactation performance of the laboratory mouse, Mus musculus

Laboratory mice (strain MF1) were used to investigate the effects of dietary fat intake on lactation performance. The specific dynamic action (SDA) for high fat (HF), medium fat (MF) and a low fat (LF) diets was measured using open-flow respirometry at 4.5%, 3.9% and 6.1%, respectively. The same three diets were fed ad libitum to mice between days 4 and 18 of lactation. Mice fed HF, MF and LF diets reached plateau in their daily food intake at 14.95±1.14 g day-1, 16.30±0.61 g day-1 and 16.57±0.26 g day-1, respectively between days 12-17 of lactation. At weaning, litters from HF and MF-fed mice were significantly heavier than pups on LF diet. This was because the HF and MF-fed mice not only consumed more energy at peak lactation but also delivered more milk energy to their pups than the LF-fed mice. Evidence suggested that the positive effects of feeding fat to mice were in part due to the low SDA and probably low heat production for milk synthesis. Probably, the ability of the HF and MF-fed mice to directly transfer absorbed fat into the milk might have reduced the heat production of lactogenesis. The HF and MF diets had beneficial effects on lactation because they increased the capacity of mice to generate milk more efficiently and wean heavier offspring than mice fed LF diet. The daily energy expenditure (DEE) of mice in the three dietary groups was fixed.KEY WORDS: Laboratory mouse, dietary fat, specific dynamic action, doubly labelled water, daily energy expenditure, milk energy output, reproductive performanc

Effects of dietary protein intake on lactation performance of the laboratory mouse, Mus musculus

Laboratory mice (strain MF1) were used to investigate the effects of dietary protein content on lactation performance to test the heat dissipation limit hypothesis. The specific dynamic action (SDA) for high protein (HP) and high carbohydrate (HC) diets was measured using open-flow respirometry at 9.4% and 6.1%, respectively. The same two diets were fed ad libitum to mice during lactation. Mice fed on HP and HC diets at 21 ºC reached a plateau in their daily food intake at 12.3±0.2 g day-1 and 16.6±0.2 g day-1, respectively between days 12-17 of lactation. HP-fed mice had a significantly higher daily energy expenditure (DEE) measured by doubly labelled water and higher water turnover than HC-fed mice but the energy they exported as milk was significantly lower than that of HC-fed mice and therefore resulted in poor growth rate of their offspring. The urea production of HP-fed mice from their daily protein intake of 7.1 g was estimated at 1994 mg which required 10.2 mls of water per day to be cleared. The mice increased their urine production by 14.4 mls probably to eliminate this urea. High protein diet had negative effects on lactation, indicating the growth of pups in previous studies was not protein limited. The negative effects of the HP diet were due to the high DEE that greatly reduced the energy available for milk production, rather than a toxicity effect of the urea production. The different DEE of the two diets suggests that other factors were involved in the delivery of energy to the offspring.KEY WORDS: Laboratory mouse, dietary protein, specific dynamic action, and daily energy expenditur

The Bacterial Soft Rot Pathogens, Pectobacterium carotovorum and P. atrosepticum, Respond to Different Classes of Virulence-Inducing Host Chemical Signals

Soft rot bacteria of the Pectobacterium and Dickeya genera are Gram-negative phytopathogens that produce and secrete plant cell wall-degrading enzymes (PCWDE), the actions of which lead to rotting and decay of their hosts in the field and in storage. Host chemical signals are among the factors that induce the bacteria into extracellular enzyme production and virulence. A class of compounds (Class I) made up of intermediate products of cell wall (pectin) degradation induce exoenzyme synthesis through KdgR, a global negative regulator of exoenzyme production. While the KdgR− mutant of P. carotovorum is no longer inducible by Class I inducers, we demonstrated that exoenzyme production is induced in this strain in the presence of extracts from hosts including celery, potato, carrot, and tomato, suggesting that host plants contain another class of compounds (Class II inducers) different from the plant cell wall-degradative products that work through KdgR. The Class II inducers are thermostable, water-soluble, diffusible, and dialysable through 1 kDa molecular weight cut off pore size membranes, and could be a target for soft rot disease management strategies

Sleep Disorders, Obesity, Hypertension, and Cardiovascular Risk

In this paper we describe a concept-wise multi-preference semantics for description logic which has its root in the preferential approach for modeling defeasible reasoning in knowledge representation. We argue that this proposal, beside satisfying some desired properties, such as KLM postulates, and avoiding the drowning problem, also defines a plausible notion of semantics. We motivate the plausibility of the concept-wise multi-preference semantics by developing a logical semantics of self-organising maps, which have been proposed as possible candidates to explain the psychological mechanisms underlying category generalisation, in terms of multi-preference interpretations