Soil Phosphate Solubilising Bacteria of the Okavango Floodplains, Botswana

Phosphorus although abundant is among the most limiting macro plant nutrients in some soils. Deficiencies are often seen as purpling of leaves due to unavailability of PO4 in soil solution. In soil solution PO4 solubility is pH dependent; at pH \u3c 6, it is often bound to Fe or Al, while at pH \u3e 7 it forms insoluble complexes with Ca, Mg, K or Na making it unavailable to plants (Brady 2002). Soil organic P requires mineralisation then solubilisation by the enzyme phosphatase before being available. Botswana soils due to the low rainfall (\u3c 450 mm/yr) are characterised by high pH and salt pans scattered all over the semi-arid and arid landscape. Cultivation of most of these soils often results in P deficient crops (Leuschner and Manthe 1996). However, in grassland areas of the Okavango, very few grasses show P deficiency. Studies from other areas indicate that some grasses habour PO4 solubilizing bacteria in their rhizosphere that help them in their P sequencing quest (Duponnois et al. 2005). This study was set up to study the PO4 solubilising bacteria of the Okavango Delta at Seronga. The study also looked at possible mechanisms of solubilisation employed by the bacteria. In the long run, the study will also attempt to use these bacteria on locally grown staple cereal, sorghum (Sorghum vulgare)

Estimating rainfall and water balance over the Okavango River Basin for hydrological applications

A historical database for use in rainfall-runoff modeling of the Okavango River Basin in Southwest Africa is presented. The work has relevance for similar data-sparse regions. The parameters of main concern are rainfall and catchment water balance which are key variables for subsequent studies of the hydrological impacts of development and climate change. Rainfall estimates are based on a combination of in-situ gauges and satellite sources. Rain gauge measurements are most extensive from 1955 to 1972, after which they are drastically reduced due to the Angolan civil war. The sensitivity of the rainfall fields to spatial interpolation techniques and the density of gauges was evaluated. Satellite based rainfall estimates for the basin are developed for the period from 1991 onwards, based on the Tropical Rainfall Measuring Mission (TRMM) and Special Sensor Microwave Imager (SSM/I) data sets. The consistency between the gauges and satellite estimates was considered. A methodology was developed to allow calibration of the rainfall-runoff hydrological model against rain gauge data from 1960-1972, with the prerequisite that the model should be driven by satellite derived rainfall products for the 1990s onwards. With the rain gauge data, addition of a single rainfall station (Longa) in regions where stations earlier were lacking was more important than the chosen interpolation method. Comparison of satellite and gauge rainfall outside the basin indicated that the satellite overestimates rainfall by 20%. A non-linear correction was derived used by fitting the rainfall frequency characteristics to those of the historical rainfall data. This satellite rainfall dataset was found satisfactory when using the Pitman rainfall-runoff model (Hughes et al., this issue). Intensive monitoring in the region is recommended to increase accuracy of the comprehensive satellite rainfall estimate calibration procedur

Evaluating Ecohydrological Theories of Woody Root Distribution in the Kalahari

The contribution of savannas to global carbon storage is poorly understood, in part due to lack of knowledge of the amount of belowground biomass. In these ecosystems, the coexistence of woody and herbaceous life forms is often explained on the basis of belowground interactions among roots. However, the distribution of root biomass in savannas has seldom been investigated, and the dependence of root biomass on rainfall regime remains unclear, particularly for woody plants. Here we investigate patterns of belowground woody biomass along a rainfall gradient in the Kalahari of southern Africa, a region with consistent sandy soils. We test the hypotheses that (1) the root depth increases with mean annual precipitation (root optimality and plant hydrotropism hypothesis), and (2) the root-to-shoot ratio increases with decreasing mean annual rainfall (functional equilibrium hypothesis). Both hypotheses have been previously assessed for herbaceous vegetation using global root data sets. Our data do not support these hypotheses for the case of woody plants in savannas. We find that in the Kalahari, the root profiles of woody plants do not become deeper with increasing mean annual precipitation, whereas the root-to-shoot ratios decrease along a gradient of increasing aridity

Enabling Large-Scale Carbon Capture, Utilisation, and Storage (CCUS) Using Offshore Carbon Dioxide (CO2) Infrastructure Developments - A Review

Presently, the only offshore project for enhanced oil recovery using carbon dioxide, known as CO2-EOR, is in Brazil. Several desk studies have been undertaken, without any projects being implemented. The objective of this review is to investigate barriers to the implementation of large-scale offshore CO2-EOR projects, to identify recent technology developments, and to suggest non-technological incentives that may enable implementation. We examine differences between onshore and offshore CO2-EOR, emerging technologies that could enable projects, as well as approaches and regulatory requirements that may help overcome barriers. Our review shows that there are few, if any, technical barriers to offshore CO2-EOR. However, there are many other barriers to the implementation of offshore CO2-EOR, including: High investment and operation costs, uncertainties about reservoir performance, limited access of CO2 supply, lack of business models, and uncertainties about regulations. This review describes recent technology developments that may remove such barriers and concludes with recommendations for overcoming non-technical barriers. The review is based on a report by the Carbon Sequestration Leadership Forum (CSLF).publishedVersio

Genetic Variants in Nuclear-Encoded Mitochondrial Genes Influence AIDS Progression

Background: The human mitochondrial genome includes only 13 coding genes while nuclear-encoded genes account for 99% of proteins responsible for mitochondrial morphology, redox regulation, and energetics. Mitochondrial pathogenesis occurs in HIV patients and genetically, mitochondrial DNA haplogroups with presumed functional differences have been associated with differential AIDS progression. Methodology/Principal Findings: Here we explore whether single nucleotide polymorphisms (SNPs) within 904 of the estimated 1,500 genes that specify nuclear-encoded mitochondrial proteins (NEMPs) influence AIDS progression among HIV-1 infected patients. We examined NEMPs for association with the rate of AIDS progression using genotypes generated by an Affymetrix 6.0 genotyping array of 1,455 European American patients from five US AIDS cohorts. Successfully genotyped SNPs gave 50% or better haplotype coverage for 679 of known NEMP genes. With a Bonferroni adjustment for the number of genes and tests examined, multiple SNPs within two NEMP genes showed significant association with AIDS progression: acyl-CoA synthetase medium-chain family member 4 (ACSM4) on chromosome 12 and peroxisomal D3,D2-enoyl- CoA isomerase (PECI) on chromosome 6. Conclusions: Our previous studies on mitochondrial DNA showed that European haplogroups with presumed functional differences were associated with AIDS progression and HAART mediated adverse events. The modest influences of nuclearencoded mitochondrial genes found in the current study add support to the idea that mitochondrial function plays a role in AIDS pathogenesis

Global wealth disparities drive adherence to COVID-safe pathways in head and neck cancer surgery

Peer reviewe

The geomorphological context of calcrete deposition in the Dalmore Downs area, Northern Territory. by Susan Ringrose

This work describes and provides tentative dates for a previously briefly recorded calcrete suite from semi-arid north-central Australia

Landscape evolution of the Lake Ngami and Mababe depressions within the Okavango Rift Zone, North-Central Botswana

Lake Ngami and the Mababe Depression form elongated troughs peripheral to the Okavango Delta from which they currently receive inflow. The two basins originated as structural depressions resulting from East African Rift (EAR) propagation along the Kunyere and Thamalakane (Mababe) fault lines and are also embedded in older Okavango Delta fans. Both basins are partially ringed by palaeo-shorelines at heights that vary from 945 to 920 m with a dominant 936 m level. Dates of shoreline formation are currently under debate. (Moore et al. 2012) suggest that the Ngami and Mababe basins were mostly submerged as a result of major inflowing river captures during the Early-Mid Pleistocene. Major shorelines in the basins developed during the Palaeo-Lake Thamalakane (PLT-936 m) period of the Mid Pleistocene at 200–500 ka. This contrasts with interpretations in (Burrough and Thomas 2008), who suggest that palaeo-shorelines at ca. 936 m were formed on numerous occasions within the last 100 ka due to climatic conditions and feedback factors. Hence controversies revolve around possible dates and palaeo-climatic conditions for shoreline formation. Preliminary work on basin sediments suggests that palaeo-lakes in both basins operated as separate mostly closed system alkaline lakes for the last 65 ka, inferring an absence of numerous large high-level palaeo-lakes (at 936 m) during this interval. As further information is needed, a comparative deep drilling programme is recommended for both basins with full sedimentological analysis and sample dating to resolve issues regarding past climates and the possible extent of both early (Mid Pleistocene) and later (Late Glacial to Holocene) palaeo-lakes in the region

Of no consequence: the ICC, criminal deterrence and the reality of sexualized violence in the DRC

In addition to its retributive and restorative functions, by its mere existence the International Criminal Court is slated to play a deterrence role never before seen in international criminal law. However, unabated sexualized violence in the Democratic Republic of Congo evidences limits of the permanent ICC’s deterrent capacity. Despite the ICC’s investigation, and indictments and proceedings against Germain Katanga and Mathieu Ngudjolo for sexually violent war crimes and crimes against humanity, the nascent court is yet unable to elicit preventive effects. While deterrence theory is logically compelling, mechanisms and assumptions underlying it prove impractical when deterrence is assessed in reality. First, the ICC cannot execute certain, severe or swift enough punishment to generally deter. Second, deterrence theory’s assumption that perpetrators are rational actors engaged in utilitarian calculations of legal risk is dispelled by an analysis of Congolese perpetrators’ accounts. Evidently, prosecutions alone will not end sexualized violence in the DRC