J. Hart, B. Tremblay, Charles Brunette, C. Dufour, R. Newton
Background: Declining Arctic sea ice extent has been accompanied by a large loss in multiyear ice (MYI). The dynamic and thermodynamic processes which affect this transition include promotion of first year ice (FYI) to MYI, demotion (melting) of MYI to open water, and ice export through Fram Strait. In this study we quantify the relative importance of these three processes. Methods: We use the Lagrangian Ice Tracking System which employs satellite-derived sea ice drift vectors combined with sea ice concentrations to find annual areas of promotion, demotion, and export. Results: Over the satellite record (1989-2015), we quantify the total contributions to sea ice extent loss from promotion (+30 million km2), demotion (-19.7 million km2), and export of MYI (-18.6 million km2). The result is a total net loss of 8.3 million km2 of MYI. We find that all three processes are positively correlated with minimum sea ice extent and are increasing with rates of +0.165 million km2/decade, -0.146 million km2/ decade, and -0.096 million km2/decade for promotion, demotion, and export respectively. We also compute the negative ice growth feedback at 0.59 (with r2=0.27). This indicates that ice pack recovers, on average, 59% of the MYI area lost to demotion/export through promotion of FYI the following winter. Limitations: Uncertainties in the drift speed are compounded by the weekly temporal resolution of the model, which affects the resulting estimates of demotion and promotion area. Conclusion: Demotion and export combined are increasing faster than promotion and represent a larger area contribution. This imbalance accounts for the observed loss of MYI area.
{"title":"Examining the Transition from a perennial to a seasonal sea ice cover in the Arctic Ocean: A Lagrangian Approach","authors":"J. Hart, B. Tremblay, Charles Brunette, C. Dufour, R. Newton","doi":"10.26443/msurj.v14i1.50","DOIUrl":"https://doi.org/10.26443/msurj.v14i1.50","url":null,"abstract":"Background: Declining Arctic sea ice extent has been accompanied by a large loss in multiyear ice (MYI). The dynamic and thermodynamic processes which affect this transition include promotion of first year ice (FYI) to MYI, demotion (melting) of MYI to open water, and ice export through Fram Strait. In this study we quantify the relative importance of these three processes.\u0000Methods: We use the Lagrangian Ice Tracking System which employs satellite-derived sea ice drift vectors combined with sea ice concentrations to find annual areas of promotion, demotion, and export.\u0000Results: Over the satellite record (1989-2015), we quantify the total contributions to sea ice extent loss from promotion (+30 million km2), demotion (-19.7 million km2), and export of MYI (-18.6 million km2). The result is a total net loss of 8.3 million km2 of MYI. We find that all three processes are positively correlated with minimum sea ice extent and are increasing with rates of +0.165 million km2/decade, -0.146 million km2/ decade, and -0.096 million km2/decade for promotion, demotion, and export respectively. We also compute the negative ice growth feedback at 0.59 (with r2=0.27). This indicates that ice pack recovers, on average, 59% of the MYI area lost to demotion/export through promotion of FYI the following winter.\u0000Limitations: Uncertainties in the drift speed are compounded by the weekly temporal resolution of the model, which affects the resulting estimates of demotion and promotion area.\u0000Conclusion: Demotion and export combined are increasing faster than promotion and represent a larger area contribution. This imbalance accounts for the observed loss of MYI area.","PeriodicalId":91927,"journal":{"name":"McGill Science undergraduate research journal : MSURJ","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48780876","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Background: The McGill Arctic Research Station (MARS) runway on Axel Heiberg Island, Nunavut, has been subject to intense compaction from aircrafts since the 1960’s, causing alterations to the landscape across time and space. This study investigated the thermal, hydrological and physical responses of repeated aircraft compaction of the runway to characterize its vulnerability to land use, and the effects of long-term and repeated compaction. Methods: In late July and early August 2018, the island’s summer thaw season, topographic, soil, hydrological and frost table data were collected along four transects across the MARS runway. Results: Topography and effective porosity differences caused by compaction were found to affect soil moisture contents, leading to the observed differential frost heaving and insulation properties of soil across the runway. Soil was found to be mostly silt on and off disturbed areas, indicating that compaction does not affect grain-size but rather pore space and soil bulk density. The frost table mapping suggested statistically significant variations in depth of the frost table across undisturbed, disturbed, and indirectly disturbed areas, showing that compression from aircrafts has both direct and indirect spatial impacts on the hydrogeomorphic system. Furthermore, this research examined possible solutions to mitigate thaw consolidation of the runway. Limitations: The method of probing used to determine frost table depths introduced significant error to the data. Probing discrepancies arose between people probing and between sampling days, as techniques differed and/or improved. Future studies should consider using electrical resistance tomography to map the frost table, as this would eliminate inconsistencies. Furthermore, while pore size distributions were inferred based on grain-size and extent of compaction, subsequent studies should consider a quantitative approach to pore space analysis. Conclusion: This study suggests that aircraft travel to the remote McGill Arctic Research Station causes spatially and temporally significant changes in the local hydrogeomorphology, especially in fine-grained and wet, frost-susceptible soils. Thaw consolidation, which results indicate is caused by the direct and indirect effects of soil compaction, compromises the prolonged use of the runway.
{"title":"Physical Responses to Anthropogenic Disturbance on a Runway in the Canadian High Arctic","authors":"Tabatha Rahman, Jeremy A. Lee","doi":"10.26443/msurj.v14i1.52","DOIUrl":"https://doi.org/10.26443/msurj.v14i1.52","url":null,"abstract":"Background: The McGill Arctic Research Station (MARS) runway on Axel Heiberg Island, Nunavut, has been subject to intense compaction from aircrafts since the 1960’s, causing alterations to the landscape across time and space. This study investigated the thermal, hydrological and physical responses of repeated aircraft compaction of the runway to characterize its vulnerability to land use, and the effects of long-term and repeated compaction.\u0000Methods: In late July and early August 2018, the island’s summer thaw season, topographic, soil, hydrological and frost table data were collected along four transects across the MARS runway.\u0000Results: Topography and effective porosity differences caused by compaction were found to affect soil moisture contents, leading to the observed differential frost heaving and insulation properties of soil across the runway. Soil was found to be mostly silt on and off disturbed areas, indicating that compaction does not affect grain-size but rather pore space and soil bulk density. The frost table mapping suggested statistically significant variations in depth of the frost table across undisturbed, disturbed, and indirectly disturbed areas, showing that compression from aircrafts has both direct and indirect spatial impacts on the hydrogeomorphic system. Furthermore, this research examined possible solutions to mitigate thaw consolidation of the runway.\u0000Limitations: The method of probing used to determine frost table depths introduced significant error to the data. Probing discrepancies arose between people probing and between sampling days, as techniques differed and/or improved. Future studies should consider using electrical resistance tomography to map the frost table, as this would eliminate inconsistencies. Furthermore, while pore size distributions were inferred based on grain-size and extent of compaction, subsequent studies should consider a quantitative approach to pore space analysis.\u0000Conclusion: This study suggests that aircraft travel to the remote McGill Arctic Research Station causes spatially and temporally significant changes in the local hydrogeomorphology, especially in fine-grained and wet, frost-susceptible soils. Thaw consolidation, which results indicate is caused by the direct and indirect effects of soil compaction, compromises the prolonged use of the runway.","PeriodicalId":91927,"journal":{"name":"McGill Science undergraduate research journal : MSURJ","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44592308","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Background: The eastern North Pacific (ENPac) is a region of climatologically significant cyclone activity, often associated with extreme weather in North America. Regions of high (ridges) and low (troughs) 500- hPa height typically drive this activity. We identify 500-hPa height time variability extremes as “regimes.” Our objectives are to determine the regimes’ characteristics, predictability, and relationships to North American extreme weather. Methods: We define weather regimes, separating them into two types based on whether the 500-hPa height variance is extremely low or high. We analyze their general characteristics during the winter (December, January, and February) and relationships to extreme North American weather. To analyze the regimes’ predictability, we define forecast discontinuities as significantly improved extreme 500-hPa height variability model forecasts compared with model forecasts verifying at the same time, but initialized 24 hours earlier. We analyze their effects on anticipated weather. Results: ENPac low variance regimes are usually dominated by one or two large, slow-moving features, usually a trough with an associated surface cyclone 200-700 km to the west and a ridge with an associated surface anticyclone 200-700 km to the east. This pattern leads to anomalous southerly winds and moisture transport. Low variance regimes are generally associated with anomalous wetness in northwestern Canada, warmth in western North America, and dryness in the southwest U.S. High variance regimes are usually dominated by smaller, faster-moving features that alter the 500-hPa heights substantially. These regimes are more varied, but there is a tendency to have a ridge 200-700 km to the west and a trough 200-700 km to the east, leading to anomalous northerly winds and transport of drier polar air into the ENPac region. High variance regimes are generally associated with anomalously cold air in western North America and wetness in the western U.S. Some forecast discontinuities are associated with changes in anticipated weather locally in the ENPac region, while other discontinuities are associated with changes in anticipated weather on a much larger scale, extending to North America. Limitations: Limitations include the small sample of regimes found during the period of record (18 low variance and 10 high variance), the metric being limited to the 500-hPa level, and the study of only the ENPac winter. Conclusion: Low and high variance regimes generally lead to different ENPac weather patterns and North American extreme weather. Forecast discontinuities differ significantly from each other in their spatial extents. Further work is necessary to identify their causes and characteristics.
{"title":"Winter Mid-Tropospheric Weather Regimes in the Eastern North Pacific","authors":"Yeechian Low, E. Atallah, J. Gyakum","doi":"10.26443/msurj.v14i1.47","DOIUrl":"https://doi.org/10.26443/msurj.v14i1.47","url":null,"abstract":"Background: The eastern North Pacific (ENPac) is a region of climatologically significant cyclone activity, often associated with extreme weather in North America. Regions of high (ridges) and low (troughs) 500- hPa height typically drive this activity. We identify 500-hPa height time variability extremes as “regimes.” Our objectives are to determine the regimes’ characteristics, predictability, and relationships to North American extreme weather.\u0000Methods: We define weather regimes, separating them into two types based on whether the 500-hPa height variance is extremely low or high. We analyze their general characteristics during the winter (December, January, and February) and relationships to extreme North American weather. To analyze the regimes’ predictability, we define forecast discontinuities as significantly improved extreme 500-hPa height variability model forecasts compared with model forecasts verifying at the same time, but initialized 24 hours earlier. We analyze their effects on anticipated weather.\u0000Results: ENPac low variance regimes are usually dominated by one or two large, slow-moving features, usually a trough with an associated surface cyclone 200-700 km to the west and a ridge with an associated surface anticyclone 200-700 km to the east. This pattern leads to anomalous southerly winds and moisture transport. Low variance regimes are generally associated with anomalous wetness in northwestern Canada, warmth in western North America, and dryness in the southwest U.S. High variance regimes are usually dominated by smaller, faster-moving features that alter the 500-hPa heights substantially. These regimes are more varied, but there is a tendency to have a ridge 200-700 km to the west and a trough 200-700 km to the east, leading to anomalous northerly winds and transport of drier polar air into the ENPac region. High variance regimes are generally associated with anomalously cold air in western North America and wetness in the western U.S. Some forecast discontinuities are associated with changes in anticipated weather locally in the ENPac region, while other discontinuities are associated with changes in anticipated weather on a much larger scale, extending to North America.\u0000Limitations: Limitations include the small sample of regimes found during the period of record (18 low variance and 10 high variance), the metric being limited to the 500-hPa level, and the study of only the ENPac winter.\u0000Conclusion: Low and high variance regimes generally lead to different ENPac weather patterns and North American extreme weather. Forecast discontinuities differ significantly from each other in their spatial extents. Further work is necessary to identify their causes and characteristics.","PeriodicalId":91927,"journal":{"name":"McGill Science undergraduate research journal : MSURJ","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-04-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42284172","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Background: Phosphatases of regenerating liver (PRL) represent a class of protein tyrosine phosphatases with oncogenic activity. PRL overexpression enhances cell proliferation, transformation, and promotes metastasis in many human cancers. Most notably, PRLs interact with a family of magnesium transporters, cyclin M (CNNM), to regulate intracellular Mg2+ levels. Thus, PRLs are attractive therapeutic targets given their role in oncogenic and tumour suppressor signaling pathways by modulating cellular growth. Methods: Academic research articles were obtained by searching key terms in the PubMed database. This review specifically focuses on the articles that provided a comprehensive overview of PRLs, CNNMs, and small molecule inhibitors of PRLs. Summary: This review discusses the role of PRLs in promoting cancer metastasis and explores current strategies for targeting PRL activity through the use of small molecule inhibitors. Although several potent PRL inhibitors have been discovered, improvements must be made prior to clinical applications. Therefore, understanding the molecular basis of PRL inhibition is essential for developing novel therapeutic agents in cancer treatments.
{"title":"Phosphatases of Regenerating Liver (PRL) as Therapeutic Targets in Cancer","authors":"Wenxuan Wang","doi":"10.26443/msurj.v13i1.35","DOIUrl":"https://doi.org/10.26443/msurj.v13i1.35","url":null,"abstract":"Background: Phosphatases of regenerating liver (PRL) represent a class of protein tyrosine phosphatases with oncogenic activity. PRL overexpression enhances cell proliferation, transformation, and promotes metastasis in many human cancers. Most notably, PRLs interact with a family of magnesium transporters, cyclin M (CNNM), to regulate intracellular Mg2+ levels. Thus, PRLs are attractive therapeutic targets given their role in oncogenic and tumour suppressor signaling pathways by modulating cellular growth.\u0000Methods: Academic research articles were obtained by searching key terms in the PubMed database. This review specifically focuses on the articles that provided a comprehensive overview of PRLs, CNNMs, and small molecule inhibitors of PRLs.\u0000Summary: This review discusses the role of PRLs in promoting cancer metastasis and explores current strategies for targeting PRL activity through the use of small molecule inhibitors. Although several potent PRL inhibitors have been discovered, improvements must be made prior to clinical applications. Therefore, understanding the molecular basis of PRL inhibition is essential for developing novel therapeutic agents in cancer treatments.","PeriodicalId":91927,"journal":{"name":"McGill Science undergraduate research journal : MSURJ","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44016561","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Background: The iron oxide nanoparticles involved in this study are unique in their superparamagnetic properties, defined as their ability to flip the direction of their magnetic field under influence of temperature. This property has a variety of environmental and biomedical uses. Indeed, the exchange of ligands on the surface of these particles enables exploration of such applications. The purpose of this study is to determine an efficient method of ligand exchange in order to standardize the surface modification of these iron oxide nanoparticles (IONPs). Namely, the primary methods of ligand exchange to be evaluated are shaking and sonication of reaction mixtures. As part of this method comparison, the exchange of oleic acid (OA) ligands for 3,4-Dihydroxyphenylacetic acid (DOPAC) ligands serves as a general model for method comparison. When comparing methods, both time and quantity of materials required are considered. The quality of the final product is also considered, assessed by factors such as oxidation state, colloidal stability, and extent of ligand exchange. Methods: Three methods of ligand exchange are performed, after which their products are compared. The first method involves shaking the mixture overnight for a duration of 18 hr. The second method involves sonication for a duration of 30 min. The third method involves sonication of the reaction mixture for an additional 30 min. (duration of 60 min. in total).Results: The products were analyzed using Fourier-transform infrared spectroscopy (FT-IR), zeta potential measurements, thermogravimetric analysis (TGA), and x-ray photoelectron spectroscopy. FT-IR measurements indicate that the one-time sonication method leads to the surface of the IONPs bearing the most residual oleic acid, a disadvantageous result. TGA analysis indicates that the twice-sonicated product is more favourable than the once-sonicated product. Limitations: Larger data sets of FT-IR, TGA, zeta potential, and XPS must be collected before the best method may be confirmed. Zeta potential measurements must be repeated for the shaken product at a concentration that matches that of the other products. As such, a direct comparison may be made. TGA must also be repeated for the shaking product in order to eliminate possible inaccuracies. Namely, these could result from technical difficulties encountered in the measurement discussed above. While zeta potential measurements indicate that the twice-sonicated product has the highest colloidal stability, XPS measurements did not vary significantly enough between methods to suggest a most advantageous method. Conclusion: According to the TGA and zeta potential measurements, the twice-sonicated product appears to be most favourable in terms of coverage. XPS suggests that all methods are comparable in terms of oxidation of the IONPs’ iron.
{"title":"Techniques for Surface Modification of Aqueous-Stable Superparamagnetic Iron Oxide Nanoparticles","authors":"Hannah Sragovicz","doi":"10.26443/msurj.v13i1.29","DOIUrl":"https://doi.org/10.26443/msurj.v13i1.29","url":null,"abstract":"Background: The iron oxide nanoparticles involved in this study are unique in their superparamagnetic properties, defined as their ability to flip the direction of their magnetic field under influence of temperature. This property has a variety of environmental and biomedical uses. Indeed, the exchange of ligands on the surface of these particles enables exploration of such applications. The purpose of this study is to determine an efficient method of ligand exchange in order to standardize the surface modification of these iron oxide nanoparticles (IONPs). Namely, the primary methods of ligand exchange to be evaluated are shaking and sonication of reaction mixtures. As part of this method comparison, the exchange of oleic acid (OA) ligands for 3,4-Dihydroxyphenylacetic acid (DOPAC) ligands serves as a general model for method comparison. When comparing methods, both time and quantity of materials required are considered. The quality of the final product is also considered, assessed by factors such as oxidation state, colloidal stability, and extent of ligand exchange.\u0000Methods: Three methods of ligand exchange are performed, after which their products are compared. The first method involves shaking the mixture overnight for a duration of 18 hr. The second method involves sonication for a duration of 30 min. The third method involves sonication of the reaction mixture for an additional 30 min. (duration of 60 min. in total).Results: The products were analyzed using Fourier-transform infrared spectroscopy (FT-IR), zeta potential measurements, thermogravimetric analysis (TGA), and x-ray photoelectron spectroscopy. FT-IR measurements indicate that the one-time sonication method leads to the surface of the IONPs bearing the most residual oleic acid, a disadvantageous result. TGA analysis indicates that the twice-sonicated product is more favourable than the once-sonicated product.\u0000Limitations: Larger data sets of FT-IR, TGA, zeta potential, and XPS must be collected before the best method may be confirmed. Zeta potential measurements must be repeated for the shaken product at a concentration that matches that of the other products. As such, a direct comparison may be made. TGA must also be repeated for the shaking product in order to eliminate possible inaccuracies. Namely, these could result from technical difficulties encountered in the measurement discussed above. While zeta potential measurements indicate that the twice-sonicated product has the highest colloidal stability, XPS measurements did not vary significantly enough between methods to suggest a most advantageous method.\u0000Conclusion: According to the TGA and zeta potential measurements, the twice-sonicated product appears to be most favourable in terms of coverage. XPS suggests that all methods are comparable in terms of oxidation of the IONPs’ iron.","PeriodicalId":91927,"journal":{"name":"McGill Science undergraduate research journal : MSURJ","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46822679","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Background: Mercury (Hg) is a pollutant known to affect the nervous system. The most threatening form of Hg is methylmercury (MeHg), which can biomagnify in aquatic biota. This critique summarizes our current understanding of the major relationships between mercury speciation in aquatic environments and various environmental factors to determine the most suitable indicators of MeHg pollution. Methods: Searches were performed using Web of Science. Ultimately, 33 studies were chosen and reviewed. Priority was given to recent studies as this review focused on the current state of our knowledge. Summary: The total amount of Hg (THg) alone cannot be used as an indicator of MeHg since the relationship between THg and MeHg is poorly correlated. Microbial DNA is often used in research to give insight into the mercury cycle and fate in aquatic systems, but further studies are needed to accurately assess MeHg concentration using DNA. Based on an early study, it was thought that water colour could indicate the amount of Hg in aquatic biota. However, subsequent work has shown this to not be the case since dissolved organic matter (DOM) can help or hinder Hg bioavailability and bioaccumulation. There is a nonlinear relationship between dissolved organic carbon (DOC) and MeHg bioaccumulation where there is a threshold concentration (~8.5 mg C L-1 DOC) above which mercury bioaccumulation is hindered. A recent study found that the methylation rate of an aquatic system was correlated to the type of organic matter present in the sediments, although it could not predict the amount of MeHg present in the water since runoff brings Hg from the catchment to the downstream aquatic system. Recent advancements have been made to understand components of the mercury cycle (e.g. land-water interactions, microbial methylation, water-sediment interactions), but a model encompassing all components has yet to be constructed.
背景:汞(Hg)是一种已知影响神经系统的污染物。汞最具威胁性的形式是甲基汞(MeHg)，它可以在水生生物群中进行生物放大。这篇评论总结了我们目前对水生环境中汞物种形成与各种环境因素之间主要关系的理解，以确定最合适的MeHg污染指标。方法:使用Web of Science进行检索。最终，我们选择并回顾了33项研究。优先考虑最近的研究，因为这篇综述关注的是我们目前的知识状况。摘要:Hg总量(THg)不能单独作为MeHg的指标，因为THg与MeHg的相关性较差。微生物DNA经常被用于研究汞在水生系统中的循环和命运，但需要进一步的研究来准确评估利用DNA的甲基汞浓度。根据早期的一项研究，人们认为水的颜色可以表明水生生物群中汞的含量。然而，随后的研究表明情况并非如此，因为溶解的有机物(DOM)可以帮助或阻碍汞的生物利用度和生物积累。当存在一个阈值浓度(~8.5 mg C L-1 DOC)时，汞的生物积累受到阻碍，溶解有机碳(DOC)与甲基汞的生物积累之间存在非线性关系。最近的一项研究发现，水生系统的甲基化率与沉积物中存在的有机物类型相关，尽管它无法预测水中存在的甲基汞的数量，因为径流将汞从集水区带到下游水生系统。最近在了解汞循环的组成部分(例如陆地-水相互作用、微生物甲基化、水-沉积物相互作用)方面取得了进展，但尚未建立一个包含所有组成部分的模型。
{"title":"Interactions between Mercury and Biogeochemical Features of Aquatic Ecosystems: A Critical Review","authors":"Sandrine Beaumont-Courteau","doi":"10.26443/msurj.v13i1.33","DOIUrl":"https://doi.org/10.26443/msurj.v13i1.33","url":null,"abstract":"Background: Mercury (Hg) is a pollutant known to affect the nervous system. The most threatening form of Hg is methylmercury (MeHg), which can biomagnify in aquatic biota. This critique summarizes our current understanding of the major relationships between mercury speciation in aquatic environments and various environmental factors to determine the most suitable indicators of MeHg pollution.\u0000Methods: Searches were performed using Web of Science. Ultimately, 33 studies were chosen and reviewed. Priority was given to recent studies as this review focused on the current state of our knowledge.\u0000Summary: The total amount of Hg (THg) alone cannot be used as an indicator of MeHg since the relationship between THg and MeHg is poorly correlated. Microbial DNA is often used in research to give insight into the mercury cycle and fate in aquatic systems, but further studies are needed to accurately assess MeHg concentration using DNA. Based on an early study, it was thought that water colour could indicate the amount of Hg in aquatic biota. However, subsequent work has shown this to not be the case since dissolved organic matter (DOM) can help or hinder Hg bioavailability and bioaccumulation. There is a nonlinear relationship between dissolved organic carbon (DOC) and MeHg bioaccumulation where there is a threshold concentration (~8.5 mg C L-1 DOC) above which mercury bioaccumulation is hindered. A recent study found that the methylation rate of an aquatic system was correlated to the type of organic matter present in the sediments, although it could not predict the amount of MeHg present in the water since runoff brings Hg from the catchment to the downstream aquatic system. Recent advancements have been made to understand components of the mercury cycle (e.g. land-water interactions, microbial methylation, water-sediment interactions), but a model encompassing all components has yet to be constructed.","PeriodicalId":91927,"journal":{"name":"McGill Science undergraduate research journal : MSURJ","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44767063","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Background: Polycystic kidney disease (PKD) is a common kidney disease that affects the development and maintenance of renal tubules, leads to cyst formation, and often progresses to end-stage kidney disease. It has been postulated that defective planar cell polarity (PCP) signaling contributes to initiation of cyst formation in PKD via controlling both convergent extension (CE, a process of directional cell movements) and oriented cell division (OCD, a process of directional cell divisions during tubular elongation post-natally). Indeed, mutations of the key PCP gene, Van Gogh-like 2 (Vangl2), lead to abnormal renal tubules in murine embryonic kidneys, correlating with the original postulate. Methods: In order to further understand the influence of the Vangl2 gene on renal morphogenesis and cystogenesis, control and Vangl2 mutant embryos—as well as post-natal Vangl2 mice with conditional excision of the Vangl2 gene in renal collecting tubules—were generated, then analyzed using immunostaining and fluorescence microscopy. Results: Our results show that Vangl2 plays a role in CE and apical constriction (AC) during embryonic stage of tubulogenesis. Compared to control animals, mutant Vangl2Δ/Δ and conditional Vangl2Δ/CD embryos displayed: i) a significant dilation in the diameter of renal tubules seen as an increased tubule cross-section area and a larger number of cells per cross-section; and ii) changes in cell shape indicative of defective AC. Surprisingly, post-natal mice showed virtually no difference in any of these aspects comparing to control mice, suggesting that other pathways may compensate for the lack of PCP signaling in maintenance of the tubule architecture. Limitations: a) The analysis of the renal tubules at the specific time points does not account for the dynamics of tubular movement and growth in real time; b) a mechanistic and morphological distinction between mice and humans may exist in the renal collecting duct tubules, pertaining to the Vangl2 gene’s influence in the PCP pathway; and c) the degree of mosaicism resulting from the gene excision by Cre-recombinase may correlate with the severity of the phenotype. Conclusion: We conclude that the PCP pathway is required for normal tubule development during embryogenesis. Our results, however, indicate that the cystogenesis seen in PKD postnatally may not be directly attributed to the disrupted PCP signaling, and requires the derangement of additional pathways.
{"title":"Role of Core Planar Cell Polarity Vangl2 Gene in the Renal Tubule Development in Mice","authors":"I. Derish, Jeremy Lee, Sima Babayeva, E. Torban","doi":"10.26443/msurj.v13i1.30","DOIUrl":"https://doi.org/10.26443/msurj.v13i1.30","url":null,"abstract":"Background: Polycystic kidney disease (PKD) is a common kidney disease that affects the development and maintenance of renal tubules, leads to cyst formation, and often progresses to end-stage kidney disease. It has been postulated that defective planar cell polarity (PCP) signaling contributes to initiation of cyst formation in PKD via controlling both convergent extension (CE, a process of directional cell movements) and oriented cell division (OCD, a process of directional cell divisions during tubular elongation post-natally). Indeed, mutations of the key PCP gene, Van Gogh-like 2 (Vangl2), lead to abnormal renal tubules in murine embryonic kidneys, correlating with the original postulate.\u0000Methods: In order to further understand the influence of the Vangl2 gene on renal morphogenesis and cystogenesis, control and Vangl2 mutant embryos—as well as post-natal Vangl2 mice with conditional excision of the Vangl2 gene in renal collecting tubules—were generated, then analyzed using immunostaining and fluorescence microscopy.\u0000Results: Our results show that Vangl2 plays a role in CE and apical constriction (AC) during embryonic stage of tubulogenesis. Compared to control animals, mutant Vangl2Δ/Δ and conditional Vangl2Δ/CD embryos displayed: i) a significant dilation in the diameter of renal tubules seen as an increased tubule cross-section area and a larger number of cells per cross-section; and ii) changes in cell shape indicative of defective AC. Surprisingly, post-natal mice showed virtually no difference in any of these aspects comparing to control mice, suggesting that other pathways may compensate for the lack of PCP signaling in maintenance of the tubule architecture.\u0000Limitations: a) The analysis of the renal tubules at the specific time points does not account for the dynamics of tubular movement and growth in real time; b) a mechanistic and morphological distinction between mice and humans may exist in the renal collecting duct tubules, pertaining to the Vangl2 gene’s influence in the PCP pathway; and c) the degree of mosaicism resulting from the gene excision by Cre-recombinase may correlate with the severity of the phenotype.\u0000Conclusion: We conclude that the PCP pathway is required for normal tubule development during embryogenesis. Our results, however, indicate that the cystogenesis seen in PKD postnatally may not be directly attributed to the disrupted PCP signaling, and requires the derangement of additional pathways.","PeriodicalId":91927,"journal":{"name":"McGill Science undergraduate research journal : MSURJ","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43759750","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Background: Fermi-LAT’s 9-year data set of astrophysical gamma-rays (recently reprocessed) has revealed many new astrophysical sources. A closer analysis of one of these previously unseen sources, PSR J1930+1852 and associated pulsar wind nebula, G54.0+0.3, could help to confirm the gamma-ray emission mechanism of pulsars. Methods: An investigation and analysis of PSR J1930+1852 and PWN G54.0+0.3 using Fermi-LAT data and science tools using maximum likelihood fitting is detailed.Results: A 4.3 σ (p = 0.000017) excess above background was observed at the coordinates of the pulsar/pulsar wind nebula and the sources spectrum appears to be consistent with a single power law. Limitations: The sources in the models are modelled as point sources. Further studies may want to consider the possibility of extended sources in the modelled region. Conclusion: There is evidence for a Fermi-LAT detection of this pulsar wind nebula and the source spectrum appears to be consistent with a standard power law. An upper limit calculation predicts only about 100 events with energy above 1 GeV in the 9-year data set so a pulsation search was not conducted.
{"title":"Exploration of Fermi-LAT Data: An Analysis of Pulsar J1930+1852","authors":"A. Cook","doi":"10.26443/msurj.v13i1.25","DOIUrl":"https://doi.org/10.26443/msurj.v13i1.25","url":null,"abstract":"Background: Fermi-LAT’s 9-year data set of astrophysical gamma-rays (recently reprocessed) has revealed many new astrophysical sources. A closer analysis of one of these previously unseen sources, PSR J1930+1852 and associated pulsar wind nebula, G54.0+0.3, could help to confirm the gamma-ray emission mechanism of pulsars.\u0000Methods: An investigation and analysis of PSR J1930+1852 and PWN G54.0+0.3 using Fermi-LAT data and science tools using maximum likelihood fitting is detailed.Results: A 4.3 σ (p = 0.000017) excess above background was observed at the coordinates of the pulsar/pulsar wind nebula and the sources spectrum appears to be consistent with a single power law.\u0000Limitations: The sources in the models are modelled as point sources. Further studies may want to consider the possibility of extended sources in the modelled region.\u0000Conclusion: There is evidence for a Fermi-LAT detection of this pulsar wind nebula and the source spectrum appears to be consistent with a standard power law. An upper limit calculation predicts only about 100 events with energy above 1 GeV in the 9-year data set so a pulsation search was not conducted.","PeriodicalId":91927,"journal":{"name":"McGill Science undergraduate research journal : MSURJ","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47237872","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Background: Vibrio natriegens is an aquatic bacterium that has the fastest doubling time of any currently known organism at approximate 9.8 min. This review delves into the early categorization of V. natriegens, its phylogeny and physiology, and the efforts aimed at studying its potential to enhance both micro- and macro-scale biotechnology. Methods: Twenty-eight research papers from scientific literature databases including PubMED (US National Library of Medicine), National Center for Biotechnology Information (NCBI), and the American Society for Microbiology Journals were used in this study. Summary: Almost sixty years after the original isolate, microbiologists and bioengineers alike are expressing a renewed interest in V. natriegens as a possible replacement for Escherichia coli. Recent biotechnological efforts have been successful in developing the necessary genetic systems for such a transition. The productivity of V. natriegens suggests that the organism can also be used in large scale bio-refineries producing nutraceuticals and other bio-products.
{"title":"Historical Perspectives on the Bacterium Vibrio natriegens and its Potential to Revolutionize Bioengineering","authors":"Jonah M. Williams","doi":"10.26443/msurj.v13i1.36","DOIUrl":"https://doi.org/10.26443/msurj.v13i1.36","url":null,"abstract":"Background: Vibrio natriegens is an aquatic bacterium that has the fastest doubling time of any currently known organism at approximate 9.8 min. This review delves into the early categorization of V. natriegens, its phylogeny and physiology, and the efforts aimed at studying its potential to enhance both micro- and macro-scale biotechnology. Methods: Twenty-eight research papers from scientific literature databases including PubMED (US National Library of Medicine), National Center for Biotechnology Information (NCBI), and the American Society for Microbiology Journals were used in this study. Summary: Almost sixty years after the original isolate, microbiologists and bioengineers alike are expressing a renewed interest in V. natriegens as a possible replacement for Escherichia coli. Recent biotechnological efforts have been successful in developing the necessary genetic systems for such a transition. The productivity of V. natriegens suggests that the organism can also be used in large scale bio-refineries producing nutraceuticals and other bio-products.","PeriodicalId":91927,"journal":{"name":"McGill Science undergraduate research journal : MSURJ","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44014374","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jade Sauvé, C. Dufour, Stephen M. Griffes, M. Winton
Background: Antarctic sea ice concentration has been observed to increase from 1978 to 2015, in contrast with the decrease that most climate models show. Here, we aim to examine the respective roles of natural variability and anthropogenic forcing in shaping Antarctic sea ice trend. Method: To do so, we use the GFDL-CM2 coupled climate model with varying horizontal resolutions in the ocean (1°, 0.25° and 0.10°) that displays a range of behaviours in natural variability with the representation of Weddell Sea polynyas, and different intensities in the decrease of sea ice under climate change. Results: In the 0.10° model, a sea ice trend of similar sign and magnitude to that observed over the satellite record is found between two occurrences of the Weddell Sea polynya. In the 1° and 0.25° models, which do not simulate any polynya, no equivalent trend of what the satellite record shows is found. Under increasing CO2 forcing, all models show a surface cooling on a short time scale (years) south of 50°S, followed by a warming on a longer time scale (decades), consistent with the delayed warming mechanism of Ferreira et al. (2015). Of all models, the higher resolution model shows the strongest surface warming and decrease in sea ice, suggesting an important role for mesoscale eddies in the response of Antarctic sea ice to climate change. Conclusion: We conclude that the Weddell Sea polynya is key to the representation of the sea ice trend and that the disagreement between models and observations might partly arise from a desynchronization of the polynya cycles or a too weak natural variability of sea ice in models compared to observations.
{"title":"Antarctic Sea Ice Trends: Insights from a Suite of Climate Models","authors":"Jade Sauvé, C. Dufour, Stephen M. Griffes, M. Winton","doi":"10.26443/msurj.v13i1.32","DOIUrl":"https://doi.org/10.26443/msurj.v13i1.32","url":null,"abstract":"Background: Antarctic sea ice concentration has been observed to increase from 1978 to 2015, in contrast with the decrease that most climate models show. Here, we aim to examine the respective roles of natural variability and anthropogenic forcing in shaping Antarctic sea ice trend.\u0000Method: To do so, we use the GFDL-CM2 coupled climate model with varying horizontal resolutions in the ocean (1°, 0.25° and 0.10°) that displays a range of behaviours in natural variability with the representation of Weddell Sea polynyas, and different intensities in the decrease of sea ice under climate change.\u0000Results: In the 0.10° model, a sea ice trend of similar sign and magnitude to that observed over the satellite record is found between two occurrences of the Weddell Sea polynya. In the 1° and 0.25° models, which do not simulate any polynya, no equivalent trend of what the satellite record shows is found. Under increasing CO2 forcing, all models show a surface cooling on a short time scale (years) south of 50°S, followed by a warming on a longer time scale (decades), consistent with the delayed warming mechanism of Ferreira et al. (2015). Of all models, the higher resolution model shows the strongest surface warming and decrease in sea ice, suggesting an important role for mesoscale eddies in the response of Antarctic sea ice to climate change.\u0000Conclusion: We conclude that the Weddell Sea polynya is key to the representation of the sea ice trend and that the disagreement between models and observations might partly arise from a desynchronization of the polynya cycles or a too weak natural variability of sea ice in models compared to observations.","PeriodicalId":91927,"journal":{"name":"McGill Science undergraduate research journal : MSURJ","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49114950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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