Historical and contemporary movement and survival rates of walleye (Sander vitreus) in Lake Winnipeg,Canada

Understanding patterns of fish movement in large lake ecosystems is essential for determining appropriate management actions as differences in movement behaviour can influence life history traits such as growth and survival. Lake Winnipeg in Manitoba, Canada supports the 2nd largest walleye (Sander vitreus) commercial fishery in North America. We used mark-recapture models to determine movement and estimate survival of walleye between basins of Lake Winnipeg in historical and contemporary contexts, comparing a tag-recovery study completed historically during 1974–1977 with a contemporary (2017–2019) acoustic telemetry study. Mark-recapture models revealed comparably low but detectable annual transitions between basins from historical (0.3–1.2%) and contemporary datasets (7–8.5%). Historically, fish > 300 mm more frequently moved in a south to north direction. Contemporary estimates suggest similar length-based directionality in that fish > 350 mm were always more likely to move in a south-north direction. Contemporary annual survival derived from mark-recapture models ranged between 27 and 45% and 64.3% when derived from catch curve analysis, while independently derived annual historical survival estimates ranged between 50 and 69% and 45.5% from catch curve analysis. Using the contemporary dataset, we also observed seasonal variation in movement and survival between basins, with the greatest movement across the lake occurring during the fall. Our results demonstrate a persisting pattern of low but measurable movement, suggesting between basin movement is not unusual for Lake Winnipeg. Further, low walleye survival rates reported here for the two time periods studied, support recent management actions to reduce fishing pressure across the lake.     

Macroscale evaluation and testing of chemically hydrogenated graphene for hydrogen storage applications

The effective storage of H₂ gas represents one of the major challenges in the wide spread adoption of hydrogen powered fuel cells for light vehicle transportation. Here, we investigate the merits of chemically hydrogenated graphene (graphane) as a means to store high-density hydrogen fuel for on demand delivery. In order to evaluate hydrogen storage at the macroscale, 75 g of hydrogenated graphene was synthesized using a scaled up Birch reduction, representing the largest reported synthesis of this material to date. Covalent hydrogenation of the material was characterized via Raman spectroscopy, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). We go on to demonstrate the controlled release of H₂ gas from the bulk material using a sealed pressure reactor heated to 600 °C, identifying a bulk hydrogen storage capacity of 3.2 wt%. Additionally, we demonstrate for the first time, the successful operation of a hydrogen fuel cell using chemically hydrogenated graphene as a power source. This work demonstrates the utility of chemically hydrogenated graphene as a high-density hydrogen storage medium, and will be useful in the design of prototype hydrogen storage systems moving forward.     

Bio-economic modelling for marine spatial planning application in North Sea shrimp and flatfish fisheries

Marine activities have been increasingly competing for space and reducing areas for fishing. The use of spatially explicit tools can assist the decision making process on defining the optimal location of closures for fishing due to these emerging activities.This paper presents the Spatial Integrated bio-economic Model for FISHeries (SIMFISH). In this model fishers behaviour is simulated based on optimal effort allocation. The added value of this model compared to other existing spatial management tools lies in the presence of (i) short and long term fishers behaviour (ii) spatial explicit stock and fleet dynamics and (iii) relatively low data requirements.As an illustration, SIMFISH is applied in this paper to estimate the impact of area closures in the North Sea. Overall area closures have a negative impact on the profitability of the fleets. This would be worsened with higher fuel prices and decreased stock productivity.     

Energy price shocks,household location patterns and housing crises: Theory and implications

The U.S. housing collapse in 2007 is widely blamed for inducing a financial crisis that spread to the real economy and caused a severe and prolonged downturn. This paper develops a model to investigate the role of gasoline price shocks in triggering the housing market collapse and identifies a new channel through which energy price shocks affect the financial market and the macro economy. Results suggest that unanticipated gasoline price shocks increase the cost of work commutes, lower the value of homes away from the city center, and increase foreclosure rates as homeowners either cannot afford mortgage payments amid elevated gas expenditures or seek to abandon underwater homes. The model predicts that gasoline price shocks disproportionately affect suburban households that face greater exposure due to longer commutes and lower incomes. Empirical evidence from the 2007–08 housing collapse is presented to corroborate this theory.     

Geospatial analysis for utilizing the marginal land in regional biofuel industry: A case study in Guangdong Province,China

Due to the intensive and exhaustive land use in China, the so-called marginal land is expected to play a major role in supporting the biofuel industry of the country. We developed a regional-level framework of using geospatial information technologies to achieve an optimal utilization of the marginal land for biofuel production. The framework includes identifying marginal lands, evaluating optimality of the land for growing certain bioenergy crops, estimating local potential feedstock production, and finally selecting optimal sites for biofuel factories. We present a case study of farming Jatropha (Jatropha curcas L.) and Cassava (Manihot esculenta Crantz) in Guangdong, China. The marginal land was identified from satellite imageries at a 30-m resolution. The optimality for growing the two species was evaluated using the Ecological Niche Models (ENMs), which incorporates local temperature, precipitation, soil, and terrain. The optimality value was then converted into potential feedstock production using a conversion model. The site selection for the factories incorporated the local potential feedstock production, the transportation cost measured by road distance, and the farming cost related to the land patch geometry. Each candidate site received an overall optimality score derived based on those factors. We identified five sites that have high scores and also minimal or none spatial overlaps of their supporting areas. Three of them (Zhanjiang, Yunfu, and Jieyang) are for Cassava, located on in southern Guangdong. Two (Qingyuan and Meizhou) are for Jatropha in northern Guangdong.     

H,OH and COOH functionalized magnesium phthalocyanine as a catalyst for oxygen reduction reaction (ORR) – A DFT study

Platinum is an efficient catalyst for a fuel cell, however of its high cost and rarity on Earth, it becomes necessary to predict an effective, low cost, and abundantly available catalyst. Here, hydrogen (H), hydroxyl (OH) and carboxyl (COOH) group functionalized magnesium phthalocyanine (MgPc) are considered as catalysts to enhance oxygen reduction reaction (ORR) mechanism via direct four-electron reduction reaction. The density functional theory (DFT) based results show that the reactions occur on the top site of the magnesium (Mg) metal center than the edge site of the phthalocyanines (Pcs). From thermochemical parameters, the reactions are highly exothermic, hence feasible. The atoms in molecules (AIM) analysis reveals that the adsorbates stabilize over catalysts through ionic, covalent, hydrogen and weak interactions. The adsorption energy and reversible potential of the intermediates and product on phthalocyanines shows that MgPc(OH)₁₆ is a better catalyst for the ORR process. Conclusively, this study establishes that phthalocyanines are promising materials as a catalyst for ORR which is vital for fuel cell applications.     

Effect of ZrO2 and MgO added in alumina on the physical and mechanical properties of spark plasma sintered nanocomposite

The aim of the present research work was to investigate the effect on the properties such as density, surface roughness, microhardness, fracture toughness and microstructure added with MgO and ZrO₂ in an alumina matrix. The magnesia-zirconia toughened alumina spark plasma sintered nanocomposite samples were developed successfully and found the suppressing grain growth and crack free microstructure. No damage was found due to thermal shock up to 1350 °C. The amount of ZrO₂was added with 5 vol%, 10 vol% and 15 vol%, while MgO added with 0.5 vol%, 1 vol% and 2 vol% in an aluminamatrix. Each composition was weighed and mixed together. After that, the powders were pressed under the rapid heating at the sintering temperature of 1250 °C, 1300 °C and 1350 °C and for 5 min holding time under pressure of 60 MPa simultaneously. The optimum properties were found with the compositions of 10 vol% of ZrO₂, 1 vol% of MgO in the Al₂O₃ matrix. It showed highest relative density (99.68%), minimum surface roughness (1.123 μm), highest microhardness (19.46 GPa) and minimum average grain size (0.595 μm). The highest fracture toughness was found to be 6.7 MPa.m^1/2 the added with 15 vol% of ZrO₂,1 vol% of MgO in the Al₂O₃ matrix for the holding time 5 min and a sintering temperature of 1300 °C. The X-ray diffraction analyses indicate the presence of major phases were ZrO₂, α-Al₂O₃, MgO, magnesia phase with minor peaks of the secondary phase MgAl₂O₄. This was found due to chemical reactions between the composite constituents present in the matrix during the sintering. Uniform microstructure was observed using a field emission scanning electron microscope and obtained the sub-micron level of grain size without any significant increases of grain size. The developed compositehas high hardness and toughness to make it more suitable for applications such as ballistic armor and thermal barrier coating.     

Paste backfill of high-sulphide mill tailings using alkali-activated blast furnace slag: Effect of activator nature,concentration and slag properties

The effect of activator type, concentration and slag composition on the strength and stability properties of paste backfill (CPB) of high-sulphide tailings using alkali-activated slag (AAS) as binder (7 wt.%) were investigated in this study. Acidic and neutral (AS–NS) slags were activated with liquid sodium silicate (LSS) and sodium hydroxide (SH) at 6–10 wt.% concentrations. Ordinary Portland cement (OPC) results were used for comparison. The strength development was found to remarkably improve with increasing the concentration from 6 to 8 wt.%. Further increase in concentration did not enhance the strength. SH was determined to produce higher early-age strength whilst LSS produced higher long-term strengths as an indication of slag selectivity for activators. More extensive gypsum formation was observed at lower concentrations in SEM/EDS studies. An increase in Na₂O concentration raised the activator consumption. High concentrations also led to poorly crystallized C–S–H gel, loose structure and drying shrinkage cracks especially in NS–SH samples. A reduction in total porosity up to 20% was obtained in AAS samples compared to OPC. Amorphous structure, chemical modulus ratio and/or basicity index (BI) values were seen to control the pozzolanic reactivity, and therefore, the alkali-activation and hardening process.