Sink trap: duckweed and dye attractant reduce mosquito populations

Duckweeds, such as Lemna minor Linnaeus (Alismatales: Lemnaceae), are common in aquatic habitats and have been suggested to reduce larval mosquito survivorship via mechanical and chemical effects. Furthermore, pond dyes are used increasingly in aquatic habitats to enhance their aesthetics, although they have been shown to attract mosquito oviposition. The present study examined the coupled effects of L. minor and black pond dye on the oviposition selectivity of Culex pipiens Linnaeus (Diptera: Culicidae) mosquitoes in a series of laboratory choice tests. Subsequently, using outdoor mesocosms, the combined influence of duckweed and pond dye on mosquito abundances in aquatic habitats was quantified. Mosquitoes were strongly attracted to duckweed, and oviposited significantly greater numbers of egg rafts in duckweed-treated water compared with untreated controls, even when the duckweed was ground. The presence of pond dye interacted with the duckweed and further enhanced positive selectivity towards duckweed-treated water. The presence of duckweed caused significant and sustained reductions in larval mosquito numbers, whereas the relative effects of dye were not evident. The use of floating aquatic plants such as duckweed, combined with dye, may help reduce mosquito populations via the establishment of population sinks, characterized by high rates of oviposition coupled with high levels of larval mortality

Pair production in superstrong magnetic fields

The production of electron-positron pairs by single photons in magnetic fields 10 to the twelth power G was investigated in detail for photon energies near threshold as well as for the asymptotic limit of high photon energy. The exact attenuation coefficient, which is derived and then evaluated numerically, is strongly influenced by the discrete energy states of the electron and positron. Near threshold, it exhibits a sawtooth pattern as a function of photon energy, and its value is significantly below that predicted by the asymptotic expression for the attenuation coefficient. The energy distributions of the created pair are computed numerically near threshold and analytic expressions are derived in the asymptotic limit. These results indicate that as field strength and photon energy increase, it becomes increasingly probable for the pair to divide the photon energy unequally. This effect, as well as the threshold behavior of the attenuation coefficient, could have important consequences for pulsar models

Conditioning Individual Mosquitoes to an Odor: Sex, Source, and Time

Olfactory conditioning of mosquitoes may have important implications for vector-pathogen-host dynamics. If mosquitoes learn about specific host attributes associated with pathogen infection, it may help to explain the heterogeneity of biting and disease patterns observed in the field. Sugar-feeding is a requirement for survival in both male and female mosquitoes. It provides a starting point for learning research in mosquitoes that avoids the confounding factors associated with the observer being a potential blood-host and has the capability to address certain areas of close-range mosquito learning behavior that have not previously been described. This study was designed to investigate the ability of the southern house mosquito, Culex quinquefasciatus Say to associate odor with a sugar-meal with emphasis on important experimental considerations of mosquito age (1.2 d old and 3–5 d old), sex (male and female), source (laboratory and wild), and the time between conditioning and testing (<5 min, 1 hr, 2.5 hr, 5 hr, 10 hr, and 24 hr). Mosquitoes were individually conditioned to an odor across these different experimental conditions. Details of the conditioning protocol are presented as well as the use of binary logistic regression to analyze the complex dataset generated from this experimental design. The results suggest that each of the experimental factors may be important in different ways. Both the source of the mosquitoes and sex of the mosquitoes had significant effects on conditioned responses. The largest effect on conditioning was observed in the lack of positive response following conditioning for females aged 3–5 d derived from a long established colony. Overall, this study provides a method for conditioning experiments involving individual mosquitoes at close range and provides for future discussion of the relevance and broader questions that can be asked of olfactory conditioning in mosquitoes

TWEAK/Fn14 signalling regulates the tissue microenvironment in chronic pancreatitis

Chronic pancreatitis increases the risk of developing pancreatic cancer through the upregulation of pathways favouring proliferation, fibrosis, and sustained inflammation. We established in previous studies that the ligand tumour necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) signals through its cognate receptor fibroblast growth factor-inducible 14 (Fn14) to regulate these underlying cellular processes in the chronic liver injury niche. However, the role of the TWEAK/Fn14 signalling pathway in pancreatic disease is entirely unknown. An analysis of publicly available datasets demonstrated that the TWEAK receptor Fn14 is upregulated in pancreatitis and pancreatic adenocarcinoma, with single cell RNA sequencing revealing pancreatic ductal cells as the main Fn14 producers. We then used choline-deficient, ethionine-supplemented (CDE) diet feeding of wildtype C57BL/6J and Fn14 knockout littermates to (a) confirm CDE treatment as a suitable model of chronic pancreatitis and (b) to investigate the role of the TWEAK/Fn14 signalling pathway in pancreatic ductal proliferation, as well as fibrotic and inflammatory cell dynamics. Our time course data obtained at three days, three months, and six months of CDE treatment reveal that a lack of TWEAK/Fn14 signalling significantly inhibits the establishment and progression of the tissue microenvironment in CDE-induced chronic pancreatitis, thus proposing the TWEAK/Fn14 pathway as a novel therapeutic target

Towards Improved Quality in Organic Food Production

From 21 to 23 January 2009 the fifth QLIF training and exchange workshop took place. Inspired by the theme “Towards improved quality in organic food production” a group of 20 participants and 11 lecturers had intensive days with lectures, discussion, exchange and some practical experience in research set-up and taste experiments. Fifteen nationalities exchanged their experiences in research in product quality. Many results from comparative studies between conventional and organic products were presented and discussed. In some presentations more emphasis was laid on exploring the mechanism behind the presence or absence of certain health-influencing plant components. Comparative studies will be continued, but exploring the mechanisms behind found differences in substances is suggested as an important direction for future research

FUNDAMENTAL IMPROVEMENT IN THE TRIBOCHARGING SEPARATION PROCESS FOR UPGRADING COAL

Triboelectrostatic separation is a physical separation technique that is based on surface electronic property differences among minerals to achieve a separation. Minerals have different surface conductivities and electron affinities. They are charged differently in quantity and/or polarity after a tribocharging process. Particles with different surface charges move discretely under external electric field produce a separation. Electrostatic separation is a dry mineral processing method that does not require any water or chemical reagents. It can greatly simplify the processing circuit and reduce operating cost. Additionally, problems caused by water in conventional wet mineral processing such as water freezing, dewatering, water pollution and water treatment are eliminated. Electrostatic separation has great potential as a fine particle separator (i.e. \u3c 1mm) in industrial minerals processing application, especially in arid areas where water supply is limited. In the current study, particle tribocharging kinetics was evaluated using a model system comprised of copper, pure coal, silica and ceramic. The results of the tribocharging process were recorded and analyzed using an oscilloscope and a signal processing technique. Charge exchange, charge separation and charge relaxation corresponding to tribocharging processes were studied using the generated pulsing signals. The signals provided a method to quantify the charge penetration into the conductor bulk during tribocharging. A new method to measure the particle surface charge using the pulsing was proposed and assessed, which was extremely useful for subtle surface charge measurements which effectively eliminated environmental noise. The interactive forces at the contacting interface, relative displacement, material electronic properties and ambient relative humidity were found to impact particle surface charge. The silica surface sites are 69 times more chargeable than the coal surface, which provides a fundamental explanation for upgrading that is achievable for silica-rich coal using triboelectrostatic separation. The influences of operating and environmental parameters were quantified and compared using an environment controlled chamber. Energy consumption at the interface was found to be positively correlated with the particle charge. Relative humidity has dual effects on the particle tribocharging, excessively low or high humidity levels do not favor particle tribocharging. Finally, a semi-empirical mathematical model of particle tribocharging was developed from the basic tribocharging compression model utilizing the parametric experiment study results. The model provides a more accurate method to predict particle surface charge under exact tribocharging conditions. A novel rotary triboelectrostatic separator (RTS) using the tribocharging mechanism was tested for upgrading fine coal. The particle size influencing the RTS tribocharging and separation process is investigated. A practical method to quantify the particle charging distribution was developed based on the direct particle charge measurement and a Gaussian distribution assumption. The smaller particles were found to have a higher average surface charge and wider surface charge distribution, which provided an opportunity to separate the high grade and the low grade coal particles. However, particles that are too small have weak particle-charger tribocharging effect that reduces particle tribocharging efficiency. The particle separation process was analyzed considering the exact experimental hydrodynamic separating conditions. Smaller particles were found to be more sensitive to the airflow that used to transport the particles as a result of the effect on residence time in the separation chamber. A method combining mathematical and statistical analysis was proposed to theoretically predict RTS separation efficiency based on the particle charging conditions and particle separation conditions. The particle horizontal displacement probability distribution was ultimately derived from this method. The model predictions indicate that a wider horizontal displacement distribution provides improved separation efficiency for the RTS unit. The theoretical analysis indicates that a particle size range between 0.105 and 0.21 mm has widest horizontal displacement distribution and thus represents an optimum particle size range which is in agreement with experimental results. The influences of the RTS operating parameters on separation performance achieved on a pure coal-silica mixture were investigated using a parametric study. The optimum operating conditions were identified. Using the optimum conditions, a five-stage separation process was conducted using the RTS unit to obtain the necessary data for the development of an ideal performance curve. Two stages of RTS separation were found to generate good quality clean coal with acceptable recovery. Particle tribocharging tests were performed using pure coal, pure silica and the coal-silica mixture as model feed materials. The test result found that mixing the pure coal with the sand reduced the particle charge distribution of the coal while increasing the charge distribution of the pure silica particle. The finding explains the inability to produce clean coal products containing ultra-low ash contents. However, the rejection of silica to the tailings stream is very high. The RTS upgrading of low-ash coal sample was tried using experiment design method, which revealed that feed rate was the most significant while the applied charger voltage and the injection air rate were the least significant in regards to product quality. Feed mass flow rate and the co-flow air rate have a significant interactive effect. Considering the theoretical findings, the impact of high feed rates is due to the negative effect on particle tribocharging efficiency resulting from an increase in the particle-particle surface charge relaxation. Under the optimum test conditions, an ultraclean coal was produced with an ash content of 3.85±0.08% with a combustible recovery of 62.97±1.11% using the RTS unit

Nutrients in an African Savanna: the consequences of supply heterogeneity for plants and animals

In savannas, trees and grasses co-exist and share resources such as water and nutrients. The ratio between the tree and grass components (i.e., vegetation structure) importantly controls productivity, animal assemblages and earth-atmosphere feedbacks. As the structure of savanna vegetation is inherently unstable and easily disturbed, finding out how the vegetation structure is controlled is of great importance for rangeland management and conservation. Currently four factors are believed to control the vegetation structure in savannas; namely, water, nutrients, herbivory and fire. While the water and fire factors have been intensely studied, the roles of nutrients and herbivores as factors are less well known. Improving our understanding of the role of nutrients in savannas is relevant, because it is increasingly realised that global change also alter the availability of nutrients, e.g., increased nitrogen deposition. How savanna systems respond to nutrient perturbations is uncertain. Changes in soil nutrient availability are also likely to feed back to changes in forage quality, which may influence large herbivore use and vegetation impact patterns, thus indirectly influencing vegetation structure. Moreover, it is increasingly realised that not only changes in the availability of nutrients influence plants and subsequently herbivores, but also how nutrients become spatially available. In fact, new ideas suggest that differences in the scale of spatial resource heterogeneity may control how resources are partitioned between co-existing species differing in size, e.g., large trees coexisting with small grasses in savanna systems. To test how changes in nutrient availability and spatial configurations influence savanna systems, several field experiments were conducted in a semi-arid savanna in South Africa. In the study area we found that nutrient (N, P and K) availability negatively affected tree (Colophospermum mopane) seedling establishment in fertilization experiments. Also, trees failed to re-colonize nutrient-rich kraal sites that were abandoned almost half a century ago. In dry savannas, it is currently believed that the success of tree seedling establishment exercises large control over the relative dominance of trees, thus an increase in nutrient availability may feed back to a structurally more open vegetation state. Different explanations may account for constrained tree seedling establishment under fertile soil conditions. We tested the hypothesis that the intensification of grass competition reduces tree seedling recruitment in fertile environments. In controlled competition experiments it was shown that negative nutrient effects on tree seedlings only occur when seedlings were competing with grasses in mixtures. Furthermore, we found that adding both water and nutrients to tree seedling-grass plant mixtures cancelled the negative effects of added nutrients on tree seedlings. Thus the suppressing effect of increased nutrient availability on seedlings appears to operate indirectly through the pre-empting of soil water resources by vigorous herbaceous growth under fertile conditions. Since woody seedlings are vulnerable to water stress, increased nutrient-induced water stress translates into higher mortality rates and suppressed growth of tree seedlings in fertile areas. In support, transplanted tree seedling mortality increased during a mid-season drought as local fertilizer concentration increased. In conclusion, intensified herbaceous competition under fertile soil conditions appears to be a viable mechanism explaining poor tree seedling recruitment under fertile soil conditions. Savannas and nutrients While establishing tree seedlings suffer under fertile conditions, our data suggest that established (mature) tree growth benefitted from an increase in nutrient availability, especially following an increase in N availability. With regards to increased atmospheric N deposition, we predict that tree cover may initially expand following nutrient enrichment in dry savannas, although tree cover responses may be insensitive to current levels of N deposition. However, in the long-term tree cover is expected to decline, because of constrained tree recruitment that appears to be more sensitive to small increases in N availability. The relative availability of nutrients such as N and P may also influence how resources are partitioned between co-existing trees and grasses. In a field experiment we found evidence that trees were relatively more limited by N than P availability. An East African study has shown that grasses underneath trees are more P than N limited and we found evidence that the competiveness of sub-canopy grasses in our study increased when only P was supplied. The relative availability of N vs. P may therefore offer an additional axis governing resource partitioning between trees (non N-fixing) and grasses in savanna systems. This supports the idea that organisms with a high growth potential, apparently grasses in savannas, have relatively high P requirements to sustain rapid protein synthesis, while slower growing organisms such as trees are more limited by the availability of N. The availability of soil nutrients strongly mediated where large herbivores concentrated their impact in the landscape. Both grazers and browsers responded positively to fertilization, apparently via the control that soil nutrient availability has on forage quality. Tree and grass leaf N and P concentrations increased and condensed tannin concentrations in trees decreased following fertilization. Under high local soil nutrient concentrations the vegetation biomass was in some instances reduced below control biomass by herbivores, indicating that top-down herbivore effects potentially override bottom-up nutrient effects under fertile conditions. In ecology, it is increasingly realized that it is not only the availability of nutrients, but also how nutrients become spatially available that matters. Data from a large field experiment where a gradient in the scale of nutrient patchiness (i.e., patch grains sizes 2 x 2 m, 10 x 10 m or 50 x 50 m) was created, suggested that the scale of nutrient patchiness controlled the partitioning of resources between co-existing trees and grasses. For the same local fertilizer concentration, tree leaf quality was unresponsive to fertilization in small patches, but responded in the larger patches. Grass leaf quality increased with local fertilizer concentration regardless of patch size. The differential responses of trees and grasses to scale differences subsequently modulated the responses of the browser and grazer guilds. For the same high local fertilizer concentration, grazers responded to both fine and coarse scales of nutrient patchiness, while browsers responded only to the coarse scale of nutrient patchiness. In turn, the selective grazing in the fine scale of nutrient patchiness treatment, apparently stimulated tree growth. In the coarser scale of patchiness treatment both browsers and grazer impact intensified locally. Thus the scale of nutrient patchiness controlled nutrient partitioning between trees and grasses, which was apparently closely tracked by the large herbivore assemblage, resulting in differential local impacts on the tree and grass layers. Apart from local effects, the scale of nutrient patchiness may also regulate the use and quality of forage resources at larger (e.g., landscape) scales. In the large field fertilizer experiment, calculations suggest that the total herbaceous off-take by grazers peaked where the same fertilizer amount (15 kg N plot-1) was spread over the whole plot surface area rather than concentrated in 10 x 10 m patches. Thus, how nutrients are distributed in an area controls secondary productivity and where herbivores concentrate their impact. The scale related patterns observed in the large fertilizer experiment may have been reinforced by plastic responses (e.g., fine root proliferation in nutrient-rich soil) to heterogeneous nutrient supplies of trees in the coarse scale treatments and grasses in the fine scale treatments, respectively. To test this, the same nutrient amount was supplied at two different scales of patchiness to focal trees with their associated grasses. Two years after fertilization, large-scale fertilized trees showed increased shoot growth and increased leaf N concentrations compared to small-scale fertilized trees receiving the same N amount. Conversely, trees in a small-scale configuration fertilized with P showed negative responses compared to large-scale counterparts. These results suggest that differences in the local scale of nutrient patchiness also influence how nutrients are partitioned between co-existing trees and grasses. Herbivores not only respond to nutrient heterogeneity, but may also create spatial heterogeneity in nutrient availability, which, in turn, may influence the vegetation structure of savannas. We studied the current soil nutrient status, tree and grass biomass patterns and large herbivore use of nine former livestock holding pen areas (kraals) in a semi-arid, nutrient poor savanna. These were contrasted with nearby control sites located in the surrounding landscape. The kraals, formerly enriched by livestock dung and urine, were abandoned around 1970 and since then wildlife replaced livestock in these parts. We found that around 40 years later, kraal soil had elevated concentrations of inorganic N, extractable P, K, Ca and Mg compared to control sites, which resulted in high quality forage in kraal sites. Trees also failed to invade these sites, thus kraals remained as structurally open patches in the otherwise dense savanna. Evidently, wild large herbivores maintain the high nutrient status of kraal sites, probably by importing nutrients into these sites and by accelerating local nutrient cycling. In turn, the increased local nutrient availability prevents tree seedlings from establishing under these fertile conditions. Finally, this study provided evidence that changes in the availability of nutrients influenced the success of woody seedling establishment, which may feed back to changes in the relative proportions of trees and grasses in dry savannas. Furthermore, this study supports the new idea that the scale of resource heterogeneity influences how resources are partitioned between co-existing trees and grasses, which, in turn, modulated browser vs. grazer use and impact patterns on the vegetation. In conclusion, this study provides new information on nutrient-plant-herbivore interactions in a dry savanna with potentially important implications for the management of dry savannas in general. <br/

Deadwood Facilitates Increased Predators Resulting in Distinct and Functionally Different Leaf Litter Communities

Community structure and ecosystem function may be driven by the amount and size of habitat or energy within an environment, but these metrics (space and energy) are difficult to separate, especially in systems where habitat is also a source of energy such as detritus (dead organic matter including deadwood). Deadwood can impact forest food webs through the creation of habitat and provision of resources and initial differences in wood characteristics may differentially impact food webs. Bark beetles attack and kill pine trees, inoculating them with bluestain fungi (Ascomycota: Ophiostomataceae). Bluestain fungi may increase termite presence in deadwood, and possibly in the surrounding leaf litter, potentially leading to increased abundances of leaf litter invertebrates over time. I tested the effect deadwood in general, and deadwood inoculated with bluestain fungi or H2O (controls) in particular, on leaf litter communities after one and seven years. Additionally, I tested whether fine woody debris affects leaf litter communities more as a source of space or energy. I found that the presence of deadwood led to distinct leaf litter communities compared to when no wood was present across both collection years. Additionally, I found that fine woody debris acted as both a source of space and energy. These results suggest that woody debris positively affects leaf litter communities; therefore, woody debris inputs are essential in maintaining forest litter decomposition and maintaining forest ecosystem function. Moreover, these results contribute to the mounting evidence that deadwood has important impacts on forest biodiversity

Studies in Consumption and Production of South Carolina Aquaculture Products

Market demand for seafood products among South Carolina (SC) consumers has led to increased aquaculture production as a means of supporting the seafood supply chain across the state. Our objective is broken into four distinct parts; (1) understanding consumer’s preferences and perceptions of seafood, (2) calculating their willingness to pay (WTP) for seafood products available in SC using attributes of sustainability and locality; and (3) gathering production metric and anecdotal data from SC oyster growers. Previous research assessing the market channels of seafood in South Carolina is compared to survey results. Respondents indicated that taste and quality were the most important factors considered when purchasing seafood, while production method, wild-caught or farm-raised, was the least important attribute. Using a discrete choice experiment (CE), two shellfish products available in South Carolina, oysters, and shrimp are used to measure consumers’ willingness to pay for these products based on labels describing the source of origin and ecolabels relating to sustainability. Our results show that South Carolina consumers are willing to pay more for local, sustainably wild-caught clams, and shrimp, and more for local, sustainably farm-raised oysters. Lastly, interviews with SC oyster growers were conducted to understand the scale of these operations based on production metrics. This information was then utilized to assess whether implementation of an ecolabel for oyster growers to certify their production process to be sustainable