Engineering and Economic Analysis of a Solar Energy Intensifier-thermal-energy Storage System for Agriculture

World fossil fuel depletion and the unpredictability of foreign sources have increased the desirability of energy independence in the United States. Rising fuel prices affect every segment of the economy. Agriculture consumes only 2.5 percent of the total national energy consumption, but an uninterrupted supply of inexpensive fuel is vital to the success of this important industry. Solar energy, because it is one of the only energy incomes of the earth, holds great promise as a future energy source. For solar energy to become widely adopted as a source of alternate energy, solar systems must be developed that are both technically and economically feasible. Currently a need exists for a rational and relatively simple method of integrating performance and reliability factors, climatic conditions, and economic projections to evaluate solar systems for specific applications. Although solar insolation itself is free, there are often large capital costs associated with its collection. Because of these high capital costs, and because savings from the system are spread over several years, it is important to analyze the economic feasibility before investing in a solar system. Economic analysis of any solar system is dependent on the system design and its application. Cost and performance relationships must be developed for each system, intended application, and geographic location. Research in the South Dakota State University Agricultural Engineering Department has led to development of the Solar Energy Intensifier-Thermal Energy Storage (SEI-TES) System. The SEI-TES system can be constructed on the farm using commonly available materials, but to achieve significant market penetration it must be made commercially available. An accurate cost estimate of a commercially available system requires analysis of materials and methods of production. This cost must be compared with economic savings the farmer derives from using the SEI-TES system to determine economic feasibility. The goal of this research was to investigate the economic feasibility of a commercially produced SEI-TES system for eastern South Dakota farms. Research was conducted with the following specific objectives: 1) Determine the costs of producing the SEI-TES system, and estimate its necessary retail selling price. 2) Assess the economic feasibility of using the SEI-TES system on two case study farms

A statistical approach to identify nestmate recognition cues

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Ant Queen Egg-Marking Signals: Matching Deceptive Laboratory Simplicity with Natural Complexity

BACKGROUND: Experiments under controlled laboratory conditions can produce decisive evidence for testing biological hypotheses, provided they are representative of the more complex natural conditions. However, whether this requirement is fulfilled is seldom tested explicitly. Here we provide a lab/field comparison to investigate the identity of an egg-marking signal of ant queens. Our study was based on ant workers resolving conflict over male production by destroying each other's eggs, but leaving queen eggs unharmed. For this, the workers need a proximate cue to discriminate between the two egg types. Earlier correlative evidence indicated that, in the ant Pachycondyla inversa, the hydrocarbon 3,11-dimethylheptacosane (3,11-diMeC(27)) is more abundant on the surface of queen-laid eggs. METHODOLOGY: We first tested the hypothesis that 3,11-diMeC(27) functions as a queen egg-marking pheromone using laboratory-maintained colonies. We treated worker-laid eggs with synthetic 3,11-diMeC(27) and found that they were significantly more accepted than sham-treated worker-laid eggs. However, we repeated the experiment with freshly collected field colonies and observed no effect of treating worker-laid eggs with 3,11-diMeC(27), showing that this compound by itself is not the natural queen egg-marking pheromone. We subsequently investigated the overall differences of entire chemical profiles of eggs, and found that queen-laid eggs in field colonies are more distinct from worker-laid eggs than in lab colonies, have more variation in profiles, and have an excess of longer-chain hydrocarbons. CONCLUSIONS: Our results suggest that queen egg-marking signals are significantly affected by transfer to the laboratory, and that this change is possibly connected to reduced queen fertility as predicted by honest signaling theory. This change is reflected in the worker egg policing response under field and laboratory conditions

Archeologische en historisch - geografische elementen in een natuurgebied : antropogene achtergronden van de Gooise natuurgebieden

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Dual Effect of Wasp Queen Pheromone in Regulating Insect Sociality

SummaryEusocial insects exhibit a remarkable reproductive division of labor between queens and largely sterile workers [1, 2]. Recently, it was shown that queens of diverse groups of social insects employ specific, evolutionarily conserved cuticular hydrocarbons to signal their presence and inhibit worker reproduction [3]. Workers also recognize and discriminate between eggs laid by the queen and those laid by workers, with the latter being destroyed by workers in a process known as “policing” [4, 5]. Worker policing represents a classic example of a conflict-reducing mechanism, in which the reproductive monopoly of the queen is maintained through the selective destruction of worker-laid eggs [5, 6]. However, the exact signals used in worker policing have thus far remained elusive [5, 7]. Here, we show that in the common wasp, Vespula vulgaris, the pheromone that signals egg maternity and enables the workers to selectively destroy worker-laid eggs is in fact the same as one of the sterility-inducing queen signals that we identified earlier [3]. These results imply that queen pheromones regulate insect sociality in two distinct and complementary ways, i.e., by signaling the queen’s presence and inhibiting worker reproduction, and by facilitating the recognition and policing of worker-laid eggs

DNA methylation is associated with codon degeneracy in a species of bumblebee

Social insects display extreme phenotypic differences between sexes and castes even though the underlying genome can be almost identical. Epigenetic processes have been proposed as a possible mechanism for mediating these phenotypic differences. Using whole genome bisulfite sequencing of queens, males, and reproductive female workers we have characterised the sex- and caste-specific methylome of the bumblebee Bombus terrestris. We have identified a potential role for DNA methylation in histone modification processes which may influence sex and caste phenotypic differences. We also find differentially methylated genes generally show low levels of DNA methylation which may suggest a separate function for lowly methylated genes in mediating transcriptional plasticity, unlike highly methylated genes which are usually involved in housekeeping functions. We also examined the relationship between the underlying genome and the methylome using whole genome re-sequencing of the same queens and males. We find DNA methylation is enriched at zero-fold degenerate sites. We suggest DNA methylation may be acting as a targeted mutagen at these sites, providing substrate for selection via non-synonymous changes in the underlying genome. However, we did not see any relationship between DNA methylation and rates of positive selection in our samples. In order to fully assess a possible role for DNA methylation in adaptive processes a specifically designed study using natural population data is needed.</p

Conserved queen pheromones in bumblebees: a reply to Amsalem et al.

In a recent study, Amsalem, Orlova & Grozinger (2015) performed experiments with Bombus impatiens bumblebees to test the hypothesis that saturated cuticular hydrocarbons are evolutionarily conserved signals used to regulate reproductive division of labor in many Hymenopteran social insects. They concluded that the cuticular hydrocarbon pentacosane (C25), previously identified as a queen pheromone in a congeneric bumblebee, does not affect worker reproduction in B. impatiens. Here we discuss some shortcomings of Amsalem et al.’s study that make its conclusions unreliable. In particular, several confounding effects may have affected the results of both experimental manipulations in the study. Additionally, the study’s low sample sizes (mean n per treatment = 13.6, range: 4–23) give it low power, not 96–99% power as claimed, such that its conclusions may be false negatives. Inappropriate statistical tests were also used, and our reanalysis found that C25 substantially reduced and delayed worker egg laying in B. impatiens. We review the evidence that cuticular hydrocarbons act as queen pheromones, and offer some recommendations for future queen pheromone experiments

Crozier’s paradox revisited: maintenance of genetic recognition systems by disassortative mating

BackgroundOrganisms are predicted to behave more favourably towards relatives, and kin-biased cooperation has been found in all domains of life from bacteria to vertebrates. Cooperation based on genetic recognition cues is paradoxical because it disproportionately benefits individuals with common phenotypes, which should erode the required cue polymorphism. Theoretical models suggest that many recognition loci likely have some secondary function that is subject to diversifying selection, keeping them variable.ResultsHere, we use individual-based simulations to investigate the hypothesis that the dual use of recognition cues to facilitate social behaviour and disassortative mating (e.g. for inbreeding avoidance) can maintain cue diversity over evolutionary time. Our model shows that when organisms mate disassortatively with respect to their recognition cues, cooperation and recognition locus diversity can persist at high values, especially when outcrossed matings produce more surviving offspring. Mating system affects cue diversity via at least four distinct mechanisms, and its effects interact with other parameters such as population structure. Also, the attrition of cue diversity is less rapid when cooperation does not require an exact cue match. Using a literature review, we show that there is abundant empirical evidence that heritable recognition cues are simultaneously used in social and sexual behaviour.ConclusionsOur models show that mate choice is one possible resolution of the paradox of genetic kin recognition, and the literature review suggests that genetic recognition cues simultaneously inform assortative cooperation and disassortative mating in a large range of taxa. However, direct evidence is scant and there is substantial scope for future work