Theory and application of Agricultural Innovation Platforms for improved irrigation scheme management in Southern Africa

Abstract

Many small-scale irrigation systems are characterized by low yields and deteriorating infrastructure. Interventions often erroneously focus on increasing yields and rehabilitating infrastructure. Small-scale irrigation systems have many of the characteristics of complex socio-ecological systems, with many different actors and numerous interconnected subsystems. However, the limited interaction between the different subsystems and their agents prevents learning and the emergence of more beneficial outcomes. This article reports on using Agricultural Innovation Platforms to create an environment in which irrigation scheme actors can engage, experiment, learn and build adaptive capacity to increase market-related offtake and move out of poverty.     

Enhanced T-cell immunogenicity and protective efficacy of a human immunodeficiency virus type 1 vaccine regimen consisting of consecutive priming with DNA and boosting with recombinant fowlpox virus

The induction of human immunodeficiency virus (HIV)-specific T-cell responses is widely seen as critical to the development of effective immunity to HIV type 1 (HIV-1). Plasmid DNA and recombinant fowlpox virus (rFPV) vaccines are among the most promising safe HIV-1 vaccine candidates. However, the immunity induced by either vaccine alone may be insufficient to provide durable protection against HIV-1 infection. We evaluated a consecutive immunization strategy involving priming with DNA and boosting with rFPV vaccines encoding common HIV-1 antigens. In mice, this approach induced greater HIV-1-specific immunity than either vector alone and protected mice from challenge with a recombinant vaccinia virus expressing HIV-1 antigens. In macaques, a dramatic boosting effect on DNA vaccine-primed HIV-1-specific helper and cytotoxic T-lymphocyte responses, but a decline in HIV-1 antibody titers, was observed following rFPV immunization. The vaccine regimen protected macaques from an intravenous HIV-1 challenge, with the resistance most likely mediated by T-cell responses. These studies suggest a safe strategy for the enhanced generation of T-cell-mediated protective immunity to HIV-1.     

Laparoscopic fundoplication

The experience in treatment of 278 patients with extensive traumatic injuries of the shin complicated by purulent infection is represented. Multistage treatment typical for such category of patients in which reconstructive-restorative stage is performed late after elimination of inflammatory process is not optimal. Owing to the complex of treatment measures based on the principles of active surgical treatment of festering wounds primary operations were a success in 24.6% of patients. In 75.4% of patients early dermoplastic and osteoplastic operations were carried out to 1 month after primary surgical treatment. Good and favourable results obtained in 98.6% of patients demonstrate effectiveness of the above policy of treatment.     

Multidimensional numerical simulation of reactive flow in internal combustion engines

A selective review is given of numerical methods for performing multidimensional simulations of the chemically reactive fluid flow in an internal combustion engine cylinder. Particular emphasis is placed on the major areas of numerical difficulty, their physical origins, and the methods that have been proposed for their amelioration. This discussion is conceptually divided into sections that deal with fluid dynamical effects, fuel sprays, chemical kinetics, and flame propagation. A survey is then made of the extent to which the various methods discussed have been incorporated into unified computer codes for engine cylinder calculations. Available computer codes and their capabilities are summarized, and an illustrative calculation is described.     

A PWM Inverter Algorithm for Adjustable Speed AC Drives Using a Nonconstant Voltage Source

In small dc systems that might incorporate photovoltaic sources, load management can be handled conveniently by microcomputer. AC loads of adjustable frequency can take advantage of the microcomputer especially if the input voltage is variable. It was for this application that a simple PWM algorithm was developed. It proved to have good characteristics with respect to harmonic suppression and both software and hardware implementation.     

Volatile compounds in dried grapes

Volatile compounds were isolated from fresh Sultana grapes, from pale golden-brown sultanas prepared by drying on racks after treatment with a commercial dipping solution, and from dark brown sultanas dried in sunlight without dipping. The fresh grape yolatiles were found in the dipped sultanas but not in the undipped sultanas. Undipped sultanas contained considerable amounts of furfural and related compounds which were present in relatively small amounts in the dipped sultanas. It is suggested that these compounds, commonly associated with non-enzymic browning, may account for the malty, caramel-like aroma of the undipped sultanas and that their production is inhibited by the drying conditions given to the dipped sultanas. The dipped sultanas contained several carbonyl compounds which were not observed in the undipped sultanas.     

Characterization of bionanocomposite scaffolds comprised of mercaptoethylamine-functionalized gold nanoparticles crosslinked to acellular porcine tissue

Bionanocomposite scaffolds comprised of nanomaterials and the extracellular matrix (ECM) of porcine diaphragm tissue capitalizes on the benefits of utilizing a natural ECM material, while also potentially enhancing physicomechanical properties and biocompatibility through nanomaterials. Gold nanoparticle (AuNP) bionanocomposite scaffolds were subjected to a number of characterization techniques to determine whether the fabrication process negatively impacted the properties of the porcine diaphragm tissue and whether the AuNP improved the properties of the tissue. Tensile testing and differential scanning calorimetry demonstrated that the bionanocomposite possessed improved tensile strength and thermal stability relative to natural tissue. The collagenase assay and Fourier transform infrared spectroscopy additionally confirmed that denaturation of the collagen of the ECM did not occur. The novel bionanocomposite scaffold possessed properties similar to commercially available scaffolds and will be further developed for soft tissue applications such as hernia repair through in vivo studies in an animal model.     

Evaluation of in situ curable biodegradable polyurethanes containing zwitterion components

Porous polyurethane networks containing covalently attached zwitterionic compounds dihydroxypolycaprolactone phosphorylcholine and 1,2-dihydroxy-N,N-dimethylamino-propane sulfonate have been prepared and characterised. Three polymers were prepared by reacting methyl 2,6-diisocyanato hexanoate functionalised d-glucose as prepolymer A with either polycaprolactone triol alone or with addition of 10 mol% zwitterion as prepolymer B. All polymer compositions were mixed with 10 wt% hydrated gelatin beads. The cured polymers with the gelatin beads showed compression strengths that were still suitable for use in articular cartilage repair. The incorporation of zwitterions yielded more hydrophilic polymers that showed increased water absorption and increased porosity. After four months degradation in phosphate buffered saline, the polymers containing zwitterions had approximately 50% mass loss compared with 30% mass loss for that with polycaprolactone triol alone. All polymers were non-toxic in chondrocyte-based assays. Subcutaneous implantation of these polymers into rats confirmed that the polymers degraded slowly. Only a very mild inflammatory response was observed and the polymers were able to support new, well vascularised tissue formation.