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"Hill, R. T."
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Probing the Ultimate Limits of Plasmonic Enhancement
Metals support surface plasmons at optical wavelengths and have the ability to localize light to subwavelength regions. The field enhancements that occur in these regions set the ultimate limitations on a wide range of nonlinear and quantum optical phenomena. We found that the dominant limiting factor is not the resistive loss of the metal, but rather the intrinsic nonlocality of its dielectric response. A semiclassical model of the electronic response of a metal places strict bounds on the ultimate field enhancement. To demonstrate the accuracy of this model, we studied optical scattering from gold nanoparticles spaced a few angstroms from a gold film. The bounds derived from the models and experiments impose limitations on all nanophotonic systems.
Journal Article
التدريس من منظور البحث والاستقصاء : إعادة التفكير في مناهج تعليم الطفولة المبكرة
بشجاعة وفيرة وإرادة فتية للمخاطرة واحترام هائل لكل من الأطفال ومعلميهم نكتب هذا الكتاب الذي يثير تفكيرنا نحو المستقبل وندعوك أن تنغمس في ثنايا صفحاته وتتهيأ لأن تغير نفسك سواء أكنت مدرسا أو صديقا أم والدا أم مفكرا أم فاعلا ولقد قمنا بالتدريس في مدرسة فيرجينيا التجريبية الفنية لتنمية الطفل لمدة سبع سنوات كما انخرطنا في العمل الإداري بها.
BOOK
Calibration of a modelling approach for sediment yield in a wattle plantation, KwaZulu-Natal, South Africa
Hydrological modelling is an appropriate approach to investigate the effect of interactions of climate, land-use and soil on the water-use of natural or managed ecosystems, in particular where spatial heterogeneity exists. The Soil and Water Assessment Tool (SWAT) model has evolved into one of the most widely used catchment-scale hydrological models, which has been extensively used to better understand hydrological processes. In this paper, the SWAT model was adopted to simulate a wattle plantation in KwaZulu-Natal, South Africa. User-defined vegetation growth, soil and management input parameters were constructed for the study area based on site measurements. These parameters were subsequently modified using the Sequential Uncertainty Fitting (SUFI-2) analysis routine to calibrate the model. The calibrated model captured seasonal trends in the observed sediment and streamflow data. The compilation of spatially explicit sediment output provides a useful approach to manage catchments by identifying high erosion-risk areas. The SWAT model, using site-specific input parameters, provides a platform for subsequent hydrological and sediment modelling in South Africa.
Journal Article
Calibration, validation and application of the SWAT model to determine the hydrological benefit of wetland rehabilitation in KwaZulu-Natal, South Africa
In South Africa, with highly variable and intense land-use practices, coupled with limited soil fertility and water resources, there has been a long history of encroachment of arable lands (sugarcane and timber plantations) into surrounding wetlands. Although wetland delineation within the timber and sugar sectors is well-defined in policy, and existing and proposed legislation, there are significant areas of non-compliance. The spatiallyexplicit Soil Water Assessment Tool (SWAT) was adopted to investigate the interactions of climate, landuse and soil on the water-use of natural and encroached wetlands. This paper documents the calibration, validation and application of the SWAT model on Quaternary Catchment (QC) U20G, which is a 498 km2 catchment that forms part of the uMngeni River basin. The SWAT-CUP parameter sensitivity and optimization model was tested with daily observed streamflow data for this catchment. Parameters were modified using the sequential uncertainty fitting (SUFI-2) analysis routine to calibrate the model. The simulated flow had a close fit to the observed flow with a regression coeficient ( r2) of 0.87 and a Nash-Sutclife (NS) coeficient of 0.8. Through the bufer scenario analysis, the model showed that if the wetland and a 20-m bufer were to be returned to a natural state, there could be a 16% increase in the annual streamflow contribution, with an upper limit of a 60% increase in some hydrologic response units (HRUs). Thus there would be a hydrological gain if wetlands and sensitive bufer areas were to be cleared of commercial timber species and sugarcane.
Journal Article
Water use and productivity of Cannabis sativa L., KwaZulu-Natal Midlands, South Africa
Aims
The South African National Water Act (No. 36 of 1998) mandates the regulation of land-based activities that reduce streamflow by declaring them streamflow reduction activities (SFRAs). Hemp (
Cannabis sativa
L.) is commonly known as a water-intensive crop, yet no published journal articles providing measurements of its evapotranspiration (ET) or crop factor (Kc) exist in South Africa, and there is limited information on hemp ET and Kc internationally. Therefore, its impact on streamflow reduction cannot be assessed. In the context of this research, the term water use was used synonymously with ET, and refers to the combined soil evaporation and transpiration from the
Cannabis sativa
L. crop (and when present, weeds or grasses in the interrow), which is the overall water use associated with growing the crop.
Methods
This study provides ET data to determine if irrigated hemp should be investigated further as a potential SFRA by determining its ET and water productivity. An eddy covariance (EC) system was utilised in a hemp field trial. Standard microclimatic variables, volumetric soil water content, plant height, and Leaf Area Index (LAI) were measured.
Results
Total ET from the hemp crop over the measurement period (7 December 2022 to 15 April 2023) was 377 mm. The average daily ET was 28.4 L/tree, or 2.94 mm/plant irrigation depth. The crop coefficient varied between 0.73 and 0.77, and the water productivity was 0.96 kg of fresh bud per m
− 3
of water. Hemp had a high water use and low water productivity compared to international hemp studies due to a low planting density (2000 plants/ha).
Conclusions
These results provide the first field-based measurements of water use and crop coefficient estimates of hemp in South Africa and contribute to the very limited data available internationally. In South Africa they will be critical to assess the streamflow reduction activity of hemp.
Journal Article
The culturable microbial community of the Great Barrier Reef sponge Rhopaloeides odorabile is dominated by an α-Proteobacterium
The microbial community cultured from the marine sponge Rhopaloeides odorabile Thompson et al. is dominated by a single bacterium, designated strain NW001. Sequence analysis of 1212 bp of the16S rRNA gene of strain NW001. indicates that it is a member of the alpha-subgroup of the class Proteobacteria.
Journal Article
Metamorphosis of broadcast spawning corals in response to bacteria isolated from crustose algae
External chemical signals provide a mechanism for broadcast-spawning scleractinian corals to recognise suitable substrata for larval settlement and metamorphosis. These morphogens can be extracted from crustose coralline algae (CCA) and the skeletons of some coral species, however the precise origin of the chemical inducers has not yet been conclusively demonstrated. Microorganisms have been reported to induce metamorphosis in various species of echinoderms, molluscs, polychaetes and cnidarians. We report that Strain A3, a species ofPseudoalteromonasisolated from the CCAHydrolithon onkodes(Heydrich), was able to induce significant levels (up to 51.5% ± 5.8 SE) of metamorphosis ofAcropora willisaeVeron & Wallace, 1984 andA. millepora(Ehrenberg, 1834) larvae in laboratory assays. This experiment was repeated daily over 4 d, and the spat developed normally into juvenile polyps in flow-through aquaria. Approximately the same number of larvae underwent partial metamorphosis, forming flattened discs that were not attached to the substrata. Larvae underwent full settlement, attachment and metamorphosis only in the presence ofPseudoalteromonasA3 plus inert chips of the coral skeletonPoritessp., indicating that the calcareous matrix may play a role in the synthesis of inducers fromPseudoalteromonasStrain A3. This discovery provides evidence for a widening range of morphogenic sources and demonstrates the role that microorganisms may play in fine-scale coral recruitment. In addition, the synthesis of chemical inducers byPseudoalteromonasStrain A3 may have biotechnological applications for reef re-seeding.
Journal Article
Vitamin D intakes in 18-64-y-old Irish adults
Objective: To estimate vitamin D intakes in a representative sample of Irish adults and to assess the contribution of foods to these intake estimates. Design: Vitamin D intakes in 1379, 18-64-y-old adults from the North/South Ireland Food Consumption Survey were estimated using a combination of new analytical data for vitamin D in foods, determined by HPLC, and used to revise recipe calculations, together with existing data from McCance and Widdowson's The Composition of Foods, 5th Edition plus supplements. Results: The total mean daily intake (MDI) of vitamin D (1 microgram=40 IU) from all sources was 4.2 microgram. The MDI was significantly higher (P<0.001) when the contribution from nutritional supplements was included (4.2 microgram) compared with food sources only (3.2 microgram). Men had significantly higher intakes (4.4 microgram) than women (4.0 microgram; P<0.001), which increased significantly (P<0.001) with age in both sexes. Meat/meat products (30.1%), fish/fish products (14.3%) and eggs/egg dishes (9.1%) were the main contributors to vitamin D intake. Supplements contributed 6.8 and 12% to MDI in men and women, respectively. In all, 74% of adults had an MDI of vitamin D that was less than the median (5 microgram) of the recommended daily range of 0-10 microgram. Conclusion: The findings of this study suggest that a large number of Irish adults have low vitamin D intakes. This, along with emerging evidence of low vitamin D status in at least some population subgroups, suggests that strategies to increase vitamin D intakes, including fortification of food, should be investigated.
Journal Article
