Comparative study on adaptive rational macromodels of highly resonant structures

Two macromodeling techniques using rational bases are investigated to accurately predict the natural frequencies of highly resonant microwave structures. Three methods are proposed and compared to calculate pole‐free solutions to the Thiele continued fraction and vector fitting pole‐residue models of the characteristic equation det[Z(s)]. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Monitoring herbaceous fuel moisture content with SPOT VEGETATION time-series for fire risk prediction in savanna ecosystems

This paper evaluated the capacity of SPOT VEGETATION time-series to monitor herbaceous fuel moisture content (FMC) in order to improve fire risk assessment in the savanna ecosystem of Kruger National Park in South Africa. In situ herbaceous FMC data were used to assess the Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), Vegetation Dryness Index (VDI), Improved VDI (IVDI), and Accumulated Relative NDVI Decrement (ARND) during the dry season. The effect of increasing amounts of dead vegetation on the monitoring capacity of derived indices was studied by sampling mixed live and dead FMC. The IVDI was proposed as an improvement of the VDI to monitor herbaceous FMC during the dry season. The IVDI is derived by replacing NDVI with the integrated Relative Vegetation Index (iRVI), as an approximation of yearly herbaceous biomass, when analyzing the 2-dimensional space with NDWI. It was shown that the iRVI offered more information than the NDVI in combination with NDWI to monitor FMC. The VDI and IVDI exhibited a significant relation to FMC with R² of 0.25 and 0.73, respectively. The NDWI, however, correlated best with FMC (R² = 0.75), while the correlation of ARND and FMC was weaker (R² = 0.60) than that found for NDVI, NDWI, and IVDI. The use of in situ herbaceous FMC consequently indicated that NDWI is appropriate as spatio-temporal information source of herbaceous FMC variation which can be used to optimize fire risk and behavior assessment for fire management in savanna ecosystems.     

Laboratory and Field Consumer Evaluation Relationships for Menu Items Processed in Retortable Trays for Quantity Foodservice

Problems associated with provision of food in quantity foodservices prompted the development and use of prepared food items processed in retortable trays. Consumer acceptance of such foods was required so that the items could be screened for foodservice application. Consumer tests, using small portion samples and sensory testing under laboratory conditions, gave a relatively reliable prediction of acceptability of most of the items under extended-use consumer testing during a field trial. Final field acceptance of some items was influenced by external factors not accounted for in laboratory testing.     

A model for heap bioleaching of chalcocite with heat balance: Mesophiles and moderate thermophiles

The interaction of mesophiles and moderate thermophiles (MT) in a 3-phase computational fluid dynamics model for heap bioleaching of chalcocite is investigated. The model assumes that both bacterial types undergo the same death, attachment and detachment processes, with different growth rate temperature dependency. The model allows an investigation of how the bacterial types vary in space and time as the conditions (such as the temperature) in the heap change. The model results are compared to the case with a single bacterial type (mesophiles) from previous work, showing that the bottom-up and top-down leaching fronts which develop in that case are also present here. The bottom-up leaching front is found to move faster than in the case with only mesophiles, and the leaching front from the top-down is slower here. Both these effects are due to the high temperature gradient in the heap (due to MT), and higher associated evaporation and condensation (and associated release or consumption of latent heat) across the respective leaching fronts. The addition of MT allows a longer period before overheating occurs, so that there is more leaching in the initial stage. The ambient temperature and inoculation method were varied to show the impact on leaching.     

Severe wind phenomena in Southern Africa and the related damage

This paper presents a review of the types and magnitude of strong and extreme wind events that develop over the southern portion of the African continent. The origin of such events is given, together with selected statistics and examples of damage. The differences in implications of these events on the built environment, in terms of the levels of engineering input and the context of formal and informal development, are discussed.     

Class sigma glutathione transferase unfolds via a dimeric and a monomeric intermediate: impact of subunit interface on conformational stability in the superfamily

Solvent-induced equilibrium unfolding of a homodimeric class sigma glutathione transferase (GSTS1-1, EC 2.5.1.18) was characterized by tryptophan fluorescence, anisotropy, enzyme activity, 8-anilino-1-naphthalenesulfonate (ANS) binding, and circular dichroism. Urea induces a triphasic unfolding transition with evidence for two well-populated thermodynamically stable intermediate states of GSTS1-1. The first unfolding transition is protein concentration independent and involves a change in the subunit tertiary structure yielding a partially active dimeric intermediate (i.e., N2 left and right arrow I2). This is followed by a protein concentration dependent step in which I2 dissociates into compact inactive monomers (M) displaying enhanced hydrophobicity. The third unfolding transition, which is protein concentration independent, involves the complete unfolding of the monomeric state. Increasing NaCl concentrations destabilize N2 and appear to shift the equilibrium toward I2 whereas the stability of the monomeric intermediate M is enhanced. The binding of substrate or product analogue (i.e., glutathione or S-hexylglutathione) to the protein's active site stabilizes the native dimeric state (N2), causing the first two unfolding transitions to shift toward higher urea concentrations. The stability of M was not affected. The data implicate a region at/near the active site in domain I (most likely alpha-helix 2) as being highly unstable/flexible which undergoes local unfolding, resulting initially in I2 formation followed by a disruption in quaternary structure to a monomeric intermediate. The unfolding/refolding pathway is compared with those observed for other cytosolic GSTs and discussed in light of the different structural features at the subunit interfaces, as well as the evolutionary selection of this GST as a lens crystallin.     

A randomised placebo controlled trial of oral misoprostol in the third stage of labour

OBJECTIVE: To compare oral misoprostol 400 microg with placebo in the routine management of the third stage of labour. DESIGN: A double-blind placebo controlled trial. Setting The labour ward of an academic hospital in Johannesburg, South Africa with 7000 deliveries per annum. PARTICIPANTS: Low-risk women expected to deliver vaginally. METHODS: Women in labour were randomly allocated to receive either misoprostol 400 microg orally or placebo after the birth. Conventional oxytocics were given immediately if blood loss was thought to be more than usual. Postpartum blood loss in the first hour was measured by collection in a special flat plastic bedpan. Side effects were recorded. MAIN OUTCOME MEASURES: Measured blood loss > or = 1000 ml within the first hour after birth. Use of additional oxytocics. RESULTS: The groups were well matched. Measured blood loss > or = 1000 ml occurred in 15/250 (6%) after misoprostol and 23/250 (9%) after placebo (relative risk 0.65; 95% confidence interval 0.35-1.22). The difference may have been reduced by the greater use of conventional oxytocics in the placebo group, which was statistically significant for intravenous oxytocin infusion (2.8% vs 8.4%, relative risk 0.33, 95% confidence interval 0.14-0.77). Shivering was more common in the misoprostol group (19% vs 5%, relative risk 3.69; 95% confidence interval 2.05-6.64). CONCLUSIONS: Shivering has been shown in this study to be a specific side effect of misoprostol administered orally in the puerperium. No serious side effects were noted. Misoprostol shows promise as a method of preventing postpartum haemorrhage. Because of the potential benefits for childbearing women, particularly those in developing countries, further research to determine its effects with greater certainty should be expedited.     

Towards improving an Area of Concern: Main-channel habitat rehabilitation priorities for the Maumee River

The Maumee River watershed in the Laurentian Great Lakes Basin has been impacted by decades of pollution and habitat modification due to human settlement and development. As such, the lower 35 km of the Maumee River and several smaller adjacent watersheds comprising over 2000 km² were designated the Maumee Area of Concern (AOC) under the revised Great Lakes Water Quality Agreement in 1987. As part of pre-rehabilitation assessments in the Maumee AOC, we assessed fish and invertebrate communities in river km 24–11 of the Maumee River to identify: 1) areas that exhibit the highest biodiversity, 2) habitat characteristics associated with high biodiversity areas, 3) areas in need of protection from further degradation, and 4) areas that could feasibly be rehabilitated to increase biodiversity. Based on benthic trawl data, shallow water habitats surrounding large island complexes had the highest fish diversity and catch per unit effort (CPUE). Electrofishing displayed similar fish diversity and CPUE patterns across habitat types early in the study but yielded no discernable fish diversity or CPUE patterns towards the end of our study. Although highly variable among study sites, macroinvertebrate density was greatest in shallow water habitats <2.5 m and around large island complexes. Our results provide valuable baseline data that could act as a foundation for developing rehabilitation strategies in the lower Maumee River and for assessing the effectiveness of future aquatic habitat rehabilitation projects. In addition to increasing in-channel habitat, watershed-scale improvements of water quality might be necessary to ensure rehabilitation strategies are successful.     

Design and testing of a solar kiln simulator

The solar simulation system as previously described (Steinmann 1990) was used to simulate an actual drying run in a solar kiln. Adjustments necessary to compensate for difference in scale are described. The simulated weather conditions were in close agreement with the actual weather. The conditions in the solar kiln simulator and the solar kiln were so similar that the drying rates were virtually identical. Repeatability of runs in the simulator was good and it was concluded that valid results on solar drying could be produced in the solar simulation system.     

Evaluating the influence of multiplexing schemes and buffer implementation on perceived VoIP conversation quality

This work presents a study of RTP multiplexing schemes, which are compared with the normal use of RTP, in terms of experienced quality. Bandwidth saving, latency and packet loss for different options are studied, and some tests of Voice over IP (VoIP) traffic are carried out in order to compare the quality obtained using different implementations of the router buffer. Voice quality is calculated using ITU R-factor, which is a widely accepted quality estimator. The tests show the bandwidth savings of multiplexing, and also the importance of packet size for certain buffers, as latency and packet loss may be affected. The customer’s experience improvement is measured, showing that the use of multiplexing can be interesting in some scenarios, like an enterprise with different offices connected via the Internet. The system is also tested using different numbers of samples per packet, and the distribution of the flows into different tunnels is found to be an important factor in order to achieve an optimal perceived quality for each kind of buffer. Grouping all the flows into a single tunnel will not always be the best solution, as the increase of the number of flows does not improve bandwidth efficiency indefinitely. If the buffer penalizes big packets, it will be better to group the flows into a number of tunnels. The router processing capacity has to be taken into account too, as the limit of packets per second it can manage must not be exceeded. The obtained results show that multiplexing is a good way to improve customer’s experience of VoIP in scenarios where many RTP flows share the same path.