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Development and validation of main spectral profile for rapid identification of Yersinia ruckeri isolated from Atlantic salmon using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry
No full textMatrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) allows rapid and reliable identification of microorganisms. The accuracy of bacterial identification using MALDI-TOF MS depends on main spectral profiles (MSPs) provided in a quality-assured commercial reference library, which requires ongoing improvement. This study aimed to develop and validate an in-house MALDI-TOF MS MSP to rapidly identify Yersinia ruckeri isolated from Atlantic salmon (Salmo salar). The novel MSP was prepared using an isolate of Y. ruckeri recovered from Atlantic salmon and confirmed by 16S rRNA gene sequencing. Subsequently, a validation set which comprises 29 isolates of Y. ruckeri were examined from three fishes: Atlantic salmon (Salmo salar) (n = 26), American eel (Anguilla rostrata) (n = 1), and Atlantic cod (Gadus morhua) (n = 2). These isolates were randomly selected from the Atlantic Veterinary College, Aquatic Diagnostic Services Bacteriology Laboratory's culture collection to validate the novel MSP. Analytical sensitivity of MALDI-TOF MS using the novel MSP to identify the validation set was 86.2%. Repeatability was assessed by acquiring spectra from 30 different spots of a randomly-selected isolate of Y. ruckeri, and analyzed spectra from each spot were compared against the novel MSP. The coefficient of variation was 3.3%. The novel MSP clustered with Bruker MSPs (n = 3) of Y. ruckeri in the reference library and did not falsely identify any closely related bacteria to Y. ruckeri. This study reports the development of a novel MSP of high analytical sensitivity and specificity for rapid identification of Y. ruckeri using MALDI-TOF MS
Solar photovoltaics can help China fulfill a net-zero electricity system by 2050 even facing climate change risks
No full textAs China has pledged to become carbon neutral by 2060, electrifying its energy sector is no doubt one of the priority measures to support the transition towards a more sustainable and decarbonized energy system. Solar photovoltaics (PV) has been known as one of the most promising renewable technologies to facilitate the electrification of energy systems. The feasibility of utilizing PV to implement a nationwide decarbonized electricity system now becomes an urgent unanswered question, especially in the context of global climate change and rapid economic growth in China. Here, by using a GIS-based multiple-criteria decision-making approach we address this question by conducting a comprehensive feasibility analysis with consideration of various economic, technological, logistical, and climate change factors. We show that it is feasible for China to fulfill a net-zero electricity system by 2050, through the installation of 7.46 TW solar PV panels on about 1.8% of the national land area (mostly in western China) with a total capital investment of 4.55 trillion USD in the next 30 years. Besides, we show that future climate change may lead to a slight decrease (less than 5%) in solar energy potential, but this would not affect the capability of the nationwide PV system to meet the need for a fully-electrified energy system.National Natural Science Foundation of Chin
A mixed-level factorial inference approach for ensemble long-term hydrological projections over the Jing River Basin
No full textLong-term hydrological projections can vary substantially depending on the combination of meteorological forcing dataset, hydrologic model (HM), emissions scenario, and natural climate variability. Identifying dominant sources of model spread in an ensemble of hydrologic projections is critically important for developing reliable hydrological projections in support of flooding risk assessment and water resources management; however, it is not well understood due to the multifactor and multiscale complexities involved in the long-term hydrological projections. Therefore, a stepwise clustered Bayesian (SCB) ensemble method will be first developed to improve the performance of long-term hydrological projections. Meanwhile, a mixed-level factorial inference (MLFI) approach is employed to estimate multiple uncertainties in hydrological projections over the Jing River basin (JRB). MLFI is able to reveal the main and interactive effects of the anthropogenic emission and model choices on the SCB ensemble projections. The results suggest that the daily maximum temperature under RCP8.5 in the 2050s and 2080s is expected to respectively increase by 3.2° and 5.2°C, which are much higher than the increases under RCP4.5. The maximum increase of the RegCM driven by CanESM2 (CARM)-projected changes in streamflow for the 2050s and 2080s under RCP4.5 is 0.30 and 0.59 × 103 m s−3 in November, respectively. In addition, in a multimodel GCM–RCM–HM ensemble, hydroclimate is found to be most sensitive to the choice of GCM. Moreover, it is revealed that the percentage of contribution of anthropogenic emissions to the changes in monthly precipitation is relatively smaller, but it makes a more significant contribution to the total variance of changes in potential evapotranspiration and streamflow
Climate change impacts assessments and mitigation strategies for sustainable water and agricultural management in the Prince Edward Island
No full textPrince Edward Island (PEI) has abundant water resources and rainfed agriculture and is the largest producer of potatoes in Canada. However, the sustainability of these natural resources is at stake due to environmental changes for which science-based information was lacking; the project filled the research and knowledge gaps. The changes and impacts on temperature, precipitation, streamflows, groundwater recharge, potential evapotranspiration (PET), potatoes' water requirements (CWR), supplemental irrigation requirements (SIR), and sustainable water availability (SWA) were analyzed. The analyses were spatially segregated into eastern, central, and western PEI; and temporally into climate normals (continuous 30-year period) for the longest 150 years (1931–2080). Daily observed climatic data and validated modeled data of Pacific Climate Impacts Consortium (PCIC) etcetera were used. Rational methods, like Probability of Exceedance (PoE), Intensity-Duration-Frequency (IDF), and World Meteorological Organization’s (WMO) guidelines for computation of climatic-normal averages, were used etcetera. Hydrological modeling of the western (Mill and Wilmot rivers), central (West and Winter rivers), and eastern Bear river watersheds was performed using the Soil and Water Assessment Tool (SWAT). Statistical significance of the temporal changes in the parameters among the climatic normals and scenarios were determined using Analysis of Variance (ANOVA). The Island underwent statistically significant warming as the historical (1961–1990) average annual temperatures increased by +1.14°C in the east to +0.75°C in the west during 1991–2020. The trend will likely continue with a further rise of 3–5°C in the next 30–60 years. Historical warming was uniformly distributed throughout the year; however, prospectively, it would be more concentrated during January–July, which would moderate cold intensity. The warming would cause annual PET of 1.95–2 mm/day to insignificantly increase 3–6% during the next 30–60 years, with a 2–4 times increase in colder months (January–April) and reductions during August–December due to coastal climate. Therefore, the historical CWR of potatoes ~425 mm would decrease by 5–9%. That, and changes in effective rainfall, would cause potatoes' SIR (July–September) in normal years to fall up to 50–90 mm, which, however, be 2–3 times more during dry years, with almost no SIR in wet years. Annual precipitations increased by 6% in the east and decreased by 5% and 8% in the central and western parts, respectively, from 1961–1991 to 1991–2020, along with a significant snowfall reduction in the west (-20%). While rainfall intensities in the central and western parts significantly increased by 5–32% in recent years (2004–2017) than 1961–1990. Prospective precipitations (2021–2080) would not change significantly and would range ~1150–1200 mm/year. Nevertheless, in western PEI, precipitations would be 17% higher than that during 1991–2020. The interannual precipitation uncertainty between wet and dry years would reduce to ~300 mm/year from the current ~400 mm/year but will remain a water management challenge. Streamflows among the modeled watersheds ranged from 565–811 mm/year during 1991–2020. Streamflows are highly contributed by groundwater, up to ~70%. Therefore, pumping in the populous Winter river (191 mm/year) and Wilmot river (16 mm/year) watersheds has almost equally reduced streamflows to 565 mm/year and 652 mm/year respectively, against a weighted average of ~688 mm/year for all the five watersheds. Groundwater recharges in PEI are relatively higher (~35% of precipitation), the highest in the eastern (~600 mm/year), lesser in the western (~330 mm/year), and moderate in the central watersheds (~450 mm/year). Temporally, March–May produce the highest streamflows, whereas recharge is maximum during April–July, which underscores strong surfacewater-groundwater interactions. Climate change and an increase in pumping would further reduce streamflows and recharges, and significantly change its intra-annual distribution. More attenuation is likely with higher quantities in late winter and early spring and somewhat lesser during summers. Groundwater fulfills 100% water needs of the Island; wherein existing water policy allows pumping up to 20% of yearly recharges (annual-SWA) but not exceeding 35% of summers' stream-baseflows. The policy ensures sustainability if implemented at the watershed scale. Despite insignificant reductions in the annual-SWA (3–17%) in the next 30–60 years, summer-SWA would significantly reduce by 38–50% due to its intraannual redistribution. Groundwater pumping for irrigation to satisfy normal years' SIRs would consume: 5–6%, 27–37%, and 63–79% of annual-SWA in the eastern, central, and western watersheds, respectively but it would surpass summer-SWA at some places. Extension of sprinkler irrigation to meet SIR is challenging on economic and technical grounds, though groundwater is mostly available. Extension of streamflow and groundwater monitoring network, integrated hydrological modeling, watershed scaled
investigations, and continuous policy review and adaptations are required for sustainable water and agricultural management in PEI
Process parameter experimentation for the holistic optimization of surface quality in direct metal laser sintering
No full textDirect metal laser sintering (DMLS) is an established technology in metal additive manufacturing, where metal AM is rapidly rising in industrial use, research and development, and academic research. Continued research is needed to better understand the process and print properties to control and improve build parameters and as-built part quality. Characteristic defects in as-built parts of porosity, residual stress, and surface roughness, namely for overhang geometries with downward-facing surfaces, can lead to part failures and reduced mechanical or related performance. Improving as-built roughness through informed process parameter selection and optimization, without compromising density, can reduce post-processing time and support material while improving part quality and performance. This thesis presents the experimental development of process parameters for the holistic minimization of as-built surface roughness of 316L stainless steel DMLS prints and subsequent verification through application to a developed complex design. An initial benchmarking study of DMLS printers using a novel test artifact is included, followed by surface roughness-focused experiments of N2 and Ar shielding gas, two powder sizes, and optimization of main laser exposure parameters using design of experiments tools. Characterization includes profilometry, 3D scanning, mechanical property measurement, optical microscopy, and residual stress deflection. The resulting optimized down-facing surface (‘downskin’) arithmetical average height roughness (Ra) was measured and found to be reduced by 28%. An upward-facing surface (‘upskin’) Ra below 5 μm is achieved for limited surfaces. The DMLS print parameters were used to improve the downskin roughness and pressure drop characteristics of a novel graded cell-size gyroid heat exchanger design
Performance evaluation of a gaseous pollution control device suitable for in situ heating, ventilation and air conditioning applications
No full textAir pollution is a ubiquitous problem plaguing global citizens with decreased quality of life. Pollutants are created both indoors and out and contribute to poor indoor and ambient air quality. Indoor air purification technologies have been created and are successful in removing particulate matter, though there are severe limitations and environmental repercussions with existing technologies used to eliminate gaseous pollutants. To address this need, research and development led to the creation of a gaseous pollution control device which uses a patented photocatalyst capable of simultaneously destroying both volatile organic compounds and nitrogen oxides over extended time durations. A laboratory-scale prototype was built and a rigorously tested to evaluate the removal of nitric oxide and select volatile organic compounds (formaldehyde, ethanol and limonene). The test campaign used various velocities, surface conditions, length scales, light power outputs and pollutant compositions to generate a statistically relevant data set for evaluating performance. Performance evaluation of the two prototype units produced reduction efficiency between 550–60% for formaldehyde, 60–85% for nitric oxide, 80–99% for limonene, and 100% for ethanol, over the air velocity range of 0.5 to 2.0 m s−1. Removal efficiency of the unit appears to be most dependent on the molecular structure (i.e., bond strength) of the pollutant and the pollutant residence time within the unit (i.e., velocity or having multiple units in series). Additionally, there are opportunities for optimizing performance of the units through controlling power output of the illumination source or periodically performing a simple water rinse.Canadian Government National Science and Engineering Research Council (NSCER)Government of Ontario Graduate ScholarshipUniversity of Guelp
Anoxia-reoxygenation modulates cadmium-induced liver mitochondrial reactive oxygen species emission during oxidation of glycerol 3-phosphate
No full textAquatic organisms are frequently exposed to multiple stressors including low dissolved oxygen (O2) and metals such as cadmium (Cd). Reduced O2 concentration and Cd exposure alter cellular function in part by impairing energy metabolism and dysregulating reactive oxygen species (ROS) homeostasis. However, little is known about the role of mitochondrial glycerol 3-phosphate dehydrogenase (mGPDH) in ROS homeostasis in fish and its response to environmental stress. In this study, mGPDH activity and the effects of anoxia-reoxygenation (A-RO) and Cd on ROS (as hydrogen peroxide, H2O2) emission in rainbow trout liver mitochondria during oxidation of glycerol 3-phosphate (G3P) were probed. Trout liver mitochondria exhibited low mGPDH activity that supported a low respiratory rate but substantial H2O2 emission rate. Cd evoked a low concentration stimulatory-high concentration inhibitory H2O2 emission pattern that was blunted by A-RO. At specific redox centers, Cd suppressed H2O2 emission from site IQ, but stimulated emission from sites IIIQo and GQ. In contrast, A-RO stimulated H2O2 emission from site IQ following 15 min exposure and augmented Cd-stimulated emission from site IIF after 30 min exposure but did not alter the rate of H2O2 emission from sites IIIQo and GQ. Additionally, Cd neither altered the activities of catalase, glutathione peroxidase, or thioredoxin reductase nor the concentrations of total glutathione, reduced glutathione, or oxidized glutathione. Overall, this study indicates that oxidation of G3P drives ROS production from mGPDH and complexes I, II and III, whereas Cd directly modulates redox sites but not antioxidant defense systems to alter mitochondrial H2O2 emission
Constructivist grounded theory or interpretive phenomenology?: Methodological choices within specific study contexts
No full textConstructivist research methodologies are useful in discerning meanings of experience to subsequently inform and improve
healthcare practice. For researchers who philosophically align with the constructivist paradigm, numerous methodologies are
available from which to choose to address research questions. However, it can be challenging for researchers, especially novice
ones, to choose the most appropriate methodology that aligns with the current state of knowledge of the identified topic,
proposed research question, and the study purpose. To reduce the confusion faced by health researchers when choosing an
appropriate methodology for a specific study, this paper compares two popular qualitative health research approaches:
constructivist grounded theory and interpretive phenomenology. Philosophical underpinnings and the epistemological and ontological evolution of each methodology are explored with similarities and differences highlighted. Manifestation of the philosophical
foundations of constructivist grounded theory and interpretive phenomenology are described in relation to data collection, analysis,
and the research findings. To illustrate distinctions of each approach and support researchers in the navigation of methodological
decision-making, a specific healthcare study context is presented: the rural family members’ experiences of a relative’s interhospital
transfer for advanced critical care services. This study context is increasingly being recognized as an important area of healthcare
research and practice. However, gaps in knowledge persist, specifically in relation to the experiences of rural family members when a
critically ill relative requires an interhospital transfer to a distant urban center for advanced critical care services. Improved understanding of such experiences is necessary to inform the care provided to rural family members, potentially mitigating short and
long-term negative consequences for these individuals. Within this example, the importance of the research purpose and research
question within a specific study context is underscored as central to appropriate methodological decision-making
International student recruitment during the pandemic: The unique perspective of recruiters from small to medium-sized higher education institutions
No full textHigher education can be considered an industry comprised of mobile students attending institutions worldwide (Findlay et al. in Int Migr 55(3):139–155, 2017). The global pandemic, COVID-19, has significantly impacted the mobility of these students. Higher education institutions (HEIs) have attracted students using international student recruiters, various marketing materials, websites, and educational agents (de Wit in Int High Educ 59:13–14, 2015). When COVID-19 began to unfold around the globe the disease impacted many sectors of the economy, but the impact of disease on the higher education industry is not well documented. The purpose of this study is to explore how higher education institutional student recruitment staff responded to the COVID-19 pandemic. This study explores the perspectives of international student recruitment staff in eight small to medium-sized institutions in Canada to understand the impact of the pandemic on their practice and to generate insights for policymakers to consider when planning the future of international student recruitment (ISR). The study found that these recruiters perceived their size to be a disadvantage and that the pandemic highlighted the inequities within higher education. Furthermore, recruiters feared the competitive position of small to medium-sized institutions is potentially deteriorating with implications on policy, resources, and internal relationships within HEIs
Sex differences in the spatial behavior functions of adult-born neurons in rats
No full textAdult neurogenesis modifies hippocampal circuits and behavior, but removing newborn neurons does not consistently alter spatial processing, a core function of the hippocampus. Additionally, little is known about sex differences in neurogenesis since few studies have compared males and females. Since adult-born neurons regulate the stress response, we hypothesized that spatial functions may be more prominent under aversive conditions and may differ between males and females given sex differences in stress responding. We therefore trained intact and neurogenesis-deficient rats in the spatial water maze at temperatures that vary in their degree of aversiveness. In the standard water maze, ablating neurogenesis did not alter spatial learning in either sex. However, in cold water, ablating neurogenesis had divergent sex-dependent effects: relative to intact rats, male neurogenesis-deficient rats were slower to escape the maze and female neurogenesis-deficient rats were faster. Neurogenesis promoted temperature-related changes in search strategy in females, but it promoted search strategy stability in males. Females displayed greater recruitment (Fos expression) of the dorsal hippocampus than males, particularly in cold water. However, blocking neurogenesis did not alter Fos expression in either sex. Finally, morphologic analyses revealed greater experience-dependent plasticity in males. Adult-born neurons in males and females had similar morphology at baseline but training increased spine density and reduced presynaptic terminal size, specifically in males. Collectively, these findings indicate that adult-born neurons contribute to spatial learning in stressful conditions and they provide new evidence for sex differences in their behavioral functions