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A review of shrimp aquaculture and factors affecting the gut microbiome
No full textEvolution of aquaculture is essential to supply the need and meet the demand for aquatic-based protein due to increasing global population and increased market demand. In the last decades, the shrimp sector has been considered one of the fastest growing aquaculture systems due to its economic significance. Growing efforts have been made to increase the production of cultivated shrimp through the development of aquaculture practises. However, in high-density shrimp farming, shrimp has been threatened by frequent diseases and several environmental stressors which results in significant variations in shrimp survival rates. Thus, understanding the driving environmental and managerial factors that affect shrimp health may support the global efforts for promoting sustainable shrimp aquaculture. A distinct intestinal microecosystem that the host’s microbiota can create is intimately linked to the host’s ability to survive, grow, and develop. The intestinal microbiota of shrimp is in a state of dynamic equilibrium under normal circumstances to preserve the intestine’s typical physiological functioning. Shrimp has high diversity and dynamic composition of gut microbiota including Proteobacteria, Bacteroidetes, and Actinobacteria. There is a high correlation between the development of shrimp intestinal microbiota and environmental changes and subsequently the health status of shrimp. This correlation seems to be highly plasticity, even over short-term timescales. The changes in aquaculture ecosystem across age, environment, diet, and diseases or the exposure to new habitat has a great impact on composition of shrimp microbiota. This review summarizes the methods of shrimp aquaculture and the impacts of ecological factors (e.g. dietary manipulation, age, physiological development, and other environmental factors) on gut microbiota composition as well as the intervention approaches to modulate the intestinal microbial composition
The relationship between destructive unethical practices of senior leaders and employee moral voice in Australian organisations
Get PDFEvidence of the destructive nature of unethical leadership can be seen in the oppressive and manipulative strategies used by senior leaders to morally mute employees. When senior leaders are the perpetrators of immorality, speaking up about ethical issues may become highly complex for employees. This research aimed to identify the relationship between unethical practices of senior leaders and employee moral voice. Semi-structured interviews were conducted with 12 participants who held executive, managerial and employee positions in public and private sectors across Australia, who were asked to report their current and past experiences with unethical leaders.The results show that employees were quiescently mute about ethical issues, such as bullying and organisational injustices, due to fear of confrontation and retribution from leaders. Participants reported that unethical senior leaders used various ‘ethical distortions’, including euphemistic labelling, shaming and moral justifications, to morally mute employees. Furthermore, senior leaders exhibited extreme prioritisation of self-interested values, which motivated the strategic orchestration of a morally mute climate for personal gain. Moral disengagement theory was applied for a socio-cognitive perspective of perceived self-regulatory mechanisms used by senior leaders to absolve themselves of guilt for immoral behaviours. The current research concludes that a socio-cognitive triadic interplay of factors caused senior leaders to morally disengage from ethical issues, which resulted in employee moral mutism. Implications and future research opportunities are discussed, including the need for organisations to identify and eliminate policies and practices that mute employees' moral voice
Surfactant-mediated electrodeposition of a pseudocapacitive manganese dioxide a twofer
No full textElectrochemical energy storage is one of the most promising ways of storing energy from intermittent, renewable sources. To meet the needs, the development of scalable, earth-abundant, chemically stable, and environmentally friendly electrode materials is crucial. This work presents four cationic surfactant-mediated manganese sulfate electrolytic solutions used for the synthesis of electrolytic manganese dioxide (EMD) to produce scalable material that satisfies the pre-requisites desired for supercapacitor applications. The influence of the surfactant molecular structure, its concentration, and its interaction in the electrolytic sulfate bath was studied, which opens up new possibilities for the fabrication of the supercapacitor electrode. The performance of three surfactants (Tetradecyltrimethylammonium bromide, Didodecyldimethylammonium bromide, Benzyldodecyldimethylammonium bromide) was benchmarked against the widely used Cetyltrimethylammonium bromide under identical conditions. The surfactants were chosen based on their different head groups and hydrocarbon chains. Benzyldodecyldimethylammonium bromide-assisted EMD (EMD/B-AB) in a single-electrode device showed improved capacitance of 602 F g−1 (at 1 mA cm−2) over the other surfactant-mediated samples. The molecular dynamics simulations indicated that the electrodeposition of manganese dioxide is highly influenced by B-AB, as it adsorbs with the aryl group planar to the Pb surface. The appropriate concentration of B-AB surfactant in the bulk solution appears to be incorporated into the EMD deposit due to their hydrophobic nature and controlled nucleation and established improved pseudocapacitive performance to score a twofer. The asymmetric capacitor of EMD/B-AB30 vs. porous activated carbon exhibited a high specific capacitance of 91 F g−1, with an energy density of 32.4 Wh kg−1 for a corresponding power density of 971 W kg−1
The development of a stabbing machine and the assessment of vertical stabbing on two trials of clothed simulants
No full textAn interventional study with the Maldives generalist teachers in primary school physical education: An application of self-determination theory
Get PDFIn Maldives’ primary schools, physical education (PE) is mainly taught by generalist classroom teachers who often lack knowledge and confidence to teach PE. Also, PE programs in primary schools are affected by a perceived lack of infrastructure, resources and equipment. Children in primary schools are allocated one 35 minute period of PE per week. Researchers have previously investigated interventions implemented by specialist PE teachers to enhance the motivation of secondary school students in PE classes. However, limited research has been conducted with generalist teachers’ implementing PE intervention with primary school children. In this study we applied self-determination theory to investigate the effects of a professional learning program and an associated resource support package, that was then delivered by the Maldives generalist teachers’ delivering PE. The participants were 30 primary school teachers (control group, n = 15; intervention group, n = 15), and their 725 primary school students aged 9–12 years (mean age of 10.5 years). The teachers in the group undertook eight hours of professional learning that focused on strategies and behaviours to support student satisfaction for the three main elements of self-determination theory: autonomy, competence, and relatedness. A repeated measure ANCOVA was carried out for each of the dependent variables. Overall results when compared to pre-intervention measures, the students of teachers in the intervention group significantly increased their post-intervention perceptions for autonomy, competence, and relatedness; and, increased their psychological need satisfaction. Moreover, intervention-students in the post-intervention phase reported reduced need frustration for autonomy, competence, and relatedness; and, experienced higher levels of self-efficacy, enjoyment and engagement. We contend that these results accentuate the usefulness of professional learning programs for generalist teachers delivering PE to promote students’ psychological need satisfaction, whilst reducing thwarting behaviours to enhance students’ self-determined motivation toward PE classes. The intervention program significantly enhanced the students’ perceived need support, and autonomous motivation, it also reduced teachers’ need frustrating behaviours within PE classes. Facilitating teachers to provide more moderate to vigorous physical activity (MVPA) and psychological need support could reduce the rate of non-communicable diseases that are currently prevalent in the Maldives
The Host-Pathogen Interactions and Epicellular Lifestyle of Neisseria meningitidis
Get PDFNeisseria meningitidis is a gram-negative diplococcus and a transient commensal of the human nasopharynx. It shares and competes for this niche with a number of other Neisseria species including N. lactamica, N. cinerea and N. mucosa. Unlike these other members of the genus, N. meningitidis may become invasive, crossing the epithelium of the nasopharynx and entering the bloodstream, where it rapidly proliferates causing a syndrome known as Invasive Meningococcal Disease (IMD). IMD progresses rapidly to cause septic shock and meningitis and is often fatal despite aggressive antibiotic therapy. While many of the ways in which meningococci survive in the host environment have been well studied, recent insights into the interactions between N. meningitidis and the epithelial, serum, and endothelial environments have expanded our understanding of how IMD develops. This review seeks to incorporate recent work into the established model of pathogenesis. In particular, we focus on the competition that N. meningitidis faces in the nasopharynx from other Neisseria species, and how the genetic diversity of the meningococcus contributes to the wide range of inflammatory and pathogenic potentials observed among different lineages
Techno-economic modelling of high-value metabolites and secondary products from microalgae cultivated in closed photobioreactors with supplementary lighting
No full textThe purpose of this study is to develop an initial computational model to evaluate the techno-economic viability of high-value and secondary resources from microalgae. The isolation of high-value metabolites is the driving product to improve the overall economics. This approach will allow marketing secondary compounds at more competitive rates for applications such as biofuel, biomaterials, food or animal feed supplements. In this assessment, we consider cultivations in flat-panel, airlift and tubular closed photobioreactor [PBR] systems to avoid possible contamination and limit environmental exposures. The facilities are also equipped with supplementary LED lightings and temperature control to improve productivity. Based on the methodology described in this work, we evaluate the techno-economic viability of the suggested systems. A probable productivity range is selected based on the logistic growth with a recovery rate between 60% and 80%. The sensitivity analysis shows that the ratio of high-value metabolites is the most crucial factor determining the economics. Microalgae prices and productivities gain more importance at higher ratios. The sensitivity analyses indicate a low-level impact of productivity and cultivation costs on high priced metabolites
Response of stored grain insect pests and barley to ozone treatment
Get PDFOzone (O3) has distinct advantages over other stored grain pest treatments, such a toxicity to a broad range of organisms and rapid auto-decomposition to oxygen without leaving residues, making it a promising fumigant to protect stored grains.
This research project focused on understanding how stored grain insects and barley respond to ozone. Several studies have assessed the efficacy of O3 against pests in stored maize and wheat grain, but little is known about the toxicity of O3 on stored grain pests in barley and its effects on barley quality and germination. My results indicated that more than 2 days of ozone treatment should be considered as the endpoint to evaluate insect mortality rate due to delayed toxicity of O3. C×t product 36 mg h/L (700ppm × 24 h) offered complete mortality for all stages of the two species tested insects R. dominica and T. castaneum, without affecting barley commercial quality.
As barley is to be used for malting purposes, it is important to understand that effect of ozone on barley germination, whether positive or negative. Relevant short period treatment (20 min) with ozone at 700ppm can facilitate barley germination, but it was adversely impacted for longer O3 exposure times, such as 24 h.
Ozone treated barley seed released a greater number and quantity of volatile organic compounds (VOCs). However, alcohols and hydrocarbons gradually decreased, whereas aldehydes and organic acids markedly increased with increasing time of ozone treatment. Acetic acid was identified as a potential ozone stress-specific marker. Furthermore, the dosage-dependent function of acetic acid on barley germination was verified and results indicated that low dosage (0.05 - 0.5 mg/g of barley) of acetic acid could lead to increasing germination rate.
Potential chemical biomarkers from barley seeds during germination were identified using gas chromatography mass spectrometry (GC/MS). Statistical assessment of the data via principal component analysis demonstrated that the metabolic changes during germination were reflected by time-dependent shifts. Alcohols, fatty acids and ketones were the major contributors to the time-driven changes during germination. In addition, ozone induced an increase in fatty acids at the early stage of barley germination and probably enhanced germination by supplying carbon skeletons and energy for germination via the TCA cycle.
My results indicate that ozone could be utilized to improve the quality of malting barley on enhancing germination rate. The key finding is that acetic acid could be used as a regulator to control germination. Moreover, this PhD study is the first-time explored effect of O3 on metabolite profiles of barley germination, which could lead to identifying the factors might impact barley germination or malt quality
Bacterial endophytes from Chukrasia tabularis can antagonize Hypsipyla robusta larvae
No full textDamage by the shoot-tip borer Hypsipyla robusta (Lepidoptera: Pyralidae) has limited the commercial cultivation of Chukrasia tabularis (Meliaceae) in many parts of the world. Recently, a number of C. tabularis families in Vietnam have shown field resistance to H. robusta. This study explores whether endophytic bacteria in C. tabularis can inhibit the development of H. robusta. Endophytic bacteria from resistant trees had strong repellent (73–97%) and antifeedant (74–84%) activity with H. robusta in laboratory trials. The most biologically active isolates were identified as Bacillus bombysepticus (4 isolates) and Bacillus velezensis (2 isolates) based on phylogenetic analysis of 16S rRNA, gyrB, pycA and rpoB. Fifteen days after releasing H. robusta larvae in a nursery trial, spray inoculation with bacterial solutions from resistant trees reduced shoot tip damage by over 60% compared with the control. Spray treatments with bacterial endophytes from susceptible trees were less effective. These findings have application to the future development of biological control of H. robusta, and the selection of resistant trees for breeding
Stress history affects heat tolerance in an aquatic ectotherm (Chinook salmon, Oncorhynchus tshawytscha)
No full textThe stress history of an ectotherm may be a pivotal predictor of how they cope with rapid spikes in environmental temperature. An understanding of how stressors in habitats and commercial operations affect ectotherm heat tolerance is urgently required so that management actions can be informed by thermal physiology. We hypothesised that brief exposure to mild stress would heighten tolerance to subsequent heat stress, indicative of a cross-tolerance interaction, whereas exposure to severe stress would reduce heat tolerance, reflecting a cross-susceptibility interaction. To test this hypothesis, we assessed how three acute stressors (salinity shock [10 or 33 ppt for 2 h]), air exposure (1 or 5 min) and crowding [95.6 kg m−3 for 2 h]), commonly experienced by fish, affected the heat tolerance (measured as critical thermal maximum, CTMAX) in juvenile Chinook salmon (Oncorhynchus tshawytscha). Fish were exposed to one of the three stressors and left for 24 h of recovery prior to measuring CTMAX. Heat tolerance was improved by ∼0.6 °C in fish exposed to salinity shock (10 ppt) and air exposure (5 min) compared to unstressed controls, demonstrating cross-tolerance. However, the development of cross-tolerance was non-linear with stressor severity, and crowding stress had no effect on CTMAX. Together these results show that some forms of stress can heighten acute heat tolerance in ectotherms, but the development of cross-tolerance is highly specific to both stressor type and stressor severity