SEALING INDEX AND HYDRO-PHYSICAL PROPERTIES OF SHALE AND COASTAL PLAIN SAND UNDER MANAGED FOREST ECOSYSTEMS

The study was undertaken in two forest ecosystems in southern Nigeria to evaluate variability in soil sealing, water retention and structural properties of soils derived from Shale and Coastal plain sand (CPS) under Gmelina and rubber land use. Soil samples were collected at 0-20 and 20-40 cm depths for measurements of particle-size distribution (PSD), pore-size distribution through water desorption procedure, and related hydro-physical properties. Results showed that silt + clay-size fraction was significantly (P=0.05) higher in Shale (>75%) than CPS (<35%). There was a low risk of soil sealing (6.1-6.4%) at 0-20 cm topsoil, and a high risk of sealing (1.4%) at 20-40 cm depth. There was no significant change in sealing index created by the wide contrast between the PSD of Shale and CPS.  Water retention at high potentials (-10 to -1500 kPa) were low in CPS, reflecting the influence of a wide inter-particle pore spaces of CPS.  Available water (AW), useful available water (UAW) and readily available water (RAW) were significantly higher in Shale than CPS at both 0-20 and 20-40 cm depths (P=0.05). About 24.42% and 53.7% of soil water were released in Shale and CPS, respectively, between saturation (0 kPa) and field capacity (-10 kPa). Aggregate ratio (AR) showed dominance of stable aggregates > 0.25 mm in Shale. There were positive correlation coefficient between mean weight diameter (MWD) and AW (r = 0.486, P=0.05), UAW (r = 0.524, P=0.05) and EAW (r = 0.0635, P=.01). Thus, organic litter from Gmelina and rubber trees can reduce the risk of soil sealing, while micro-porosity dominant in Shale tend to control water retention measurements

Saturate hydraulic conductivity, water stable aggregates and soil organic matter in a sandy-loam soil in Ikwuano lga of Abia state

A study was carried out along a toposequence in Ikwuano LGA. of Abia state to evaluate changes in saturated hydraulic conductivity (Ksat) and percent water stable aggregates (WSA%). Five points: crest (A), upper slope (B), middle slope(C),lower slope (D) and Valley bottom (E), along the toposequence with an average distance of about 150m apart were delineated and samples for soil analysis collected from two depths (0-15cm and 15-30cm) using core samplers and auger. Samples were collected from each topo-unit at the respective depths in triplicate. Samples were analyzed for soil properties like; Ksat, WSA (%) and percent organic carbon (OC %), Data from the analysis were subjected to ANOVA using a split plot in RCBD. Results indicated that for both slope positions, WSA, Ksat and OC were significantly different with depth (P≤ 0.01). These properties also varied significantly (

HIV-1 Reverse Transcription

International audienceReverse transcription is an obligatory step in retrovirus replication in the course of which the retroviral RNA/DNA-dependent DNA polymerase (RT) copies the single-stranded positive sense RNA genome to synthesize the double-stranded viral DNA. At the same time the RT-associated RNaseH activity degrades the genomic RNA template, which has just been copied. The viral nucleocapsid protein NCp7 is an obligatory partner of RT, chaperoning synthesis of the complete viral DNA flanked by the two long-terminal repeats (LTR), required for viral DNA integration into the host genome and its expression. Here we describe assays for in vitro and ex vivo monitoring of reverse transcription and the chaperoning role of the nucleocapsid protein (NC)