Areas Of Ontario Research Articles

Repeated Domestic Violence Police Calls: A Closer Look at Three Case Situations

Police respond to high volumes of domestic violence (DV) calls that can be time-consuming and often deal with repeat involved persons, regardless of whether or not charges are laid. This study extracts and examines three distinct cases of individuals/couples that involved almost 2% of 3,414 domestic violence calls to police that occurred over about a 3-year period for a small-sized urban community and its surrounding rural areas in Ontario, Canada. Most of the calls (86.2%) for these three cases did not result in any charges being laid. Each case represented a unique problem focus common in DV situations, and all three cases involved children. Key issues for one case included substance use and the cycle of violence; in another case, mental health problems and parenting challenges were prominent; and the third case pertained to child custody and access issues. Acceptance of offered support and services by the involved persons was minimal in all three cases. Implications for improved police responses involving collaboration with other service providers in smaller communities with limited resources are discussed.

The availability and distribution of vaping retailers across Ontario neighbourhoods, 2016-2019.

To characterize the distribution of vaping retailers and examine the association between neighbourhood income and vaping retailer availability in Ontario prior to and afterregulatory changes to the vaping market in 2018. We quantified vaping access by number of vaping retailers for 19,964 dissemination areas (DAs) in Ontario and percentage of schools near a vaping retailer. We used mixed-effects regression models to examine the associations between vaping access and neighbourhood income in 2018 and 2019. Between 2016 and 2019, the number of vaping retailers in Ontario increased by 22.6% (5999 to 7355), despite a mild drop from 2016 to 2018. In 2019, 59.7% of urban neighbourhoods had one or more vaping retailers within 1000 m of their geographic centre, and 79.4% of elementary, 82.8% of secondary, and 84.2% of post-secondary schools had at least one within 1000 m. Neighbourhood income was associated with access to vaping retailers, with a greater number in low-income regions. In 2019, neighbourhoods in the lowest income quintile had over twice the number of vaping retailers per capita within 1000 m compared to the highest income quintile (adjusted incidence rate ratio 2.40; 95% CI 2.24-2.58). Increases over time in access to vaping retailers did not differ by geographic region, neighbourhood income quintile, or school type. We observed a substantial increase in access to vaping retailers in Ontario including proximity to elementary and secondary schools following the 2018 provincial marketing regulations and federal nicotine regulations. Access to vaping was greatest in low-income neighbourhoods and may contribute to established inequities in vaping-related adverse events.

The impacts of whole-lake acidification and eutrophication on the accumulation of lead in sediments from manipulated lakes in the Experimental Lakes Area (IISD-ELA)

Acidification and eutrophication are common limnological stressors impacting many water bodies across the globe. While the negative impacts of these stressors on limnetic communities are generally known, their influence on the accumulation of specific sediment constituents, such as metals, remains unclear. Benefitting from past research and long-term monitoring, lakes at the International Institute for Sustainable Development - Experimental Lakes Area (IISD-ELA) in northwestern Ontario, Canada are invaluable to understand the extent to which these two common lake stressors can influence the accumulation of metals in lacustrine sediment. To address these issues, sediment cores were retrieved from six lakes: four were subjected to past experimental acidification or eutrophication and two were reference lakes. Focusing on elemental lead (Pb), a metal known to have accumulated in lake sediments worldwide and generally exhibiting a relatively small fraction of terrigenous input, we assessed the hypothesis that greater accumulation of Pb would be observed in lakes subjected to eutrophication, while the reverse was expected for lakes subjected to acidification experiments. Our analyses support this hypothesis, whereby relatively low enrichment was recorded in sediments deposited in the acidified lake during the manipulation era. On the other hand, eutrophied lakes demonstrated a strong enrichment in Pb during experimental manipulation. When investigating the mechanisms behind these divergent responses, we found epilimnetic dissolved organic carbon (DOC) and conductivity were associated with a relative increase in Pb accumulation in sediments. Acidic pH is also expected to mediate these responses by decreasing epilimnetic DOC concentrations leading to reduced Pb accumulation in the sediment.

Knowledge of viral load, PrEP, and HIV-related sexual risk among men who have sex with men in the Waterloo region

Gay, bisexual, and other men who have sex with men (GBMSM) remain most disproportionately affected by HIV in Canada. HIV-related sexual risk behaviours have been linked to high HIV risk among GBMSM, but prior research has not focused on knowledge of viral load, and the risk it presents for HIV acquisition. The purpose of this study was to explore the relationship between HIV-related sexual risk behaviour and knowledge of viral load among GBMSM. A cross-sectional survey was conducted using a convenience sample of individuals age 16 and older who self-identified as LGBTQ and lived, worked, or resided in the Waterloo region, an urban-rural area in southwestern Ontario ( N = 526). Responses were analyzed from those identifying as GBMSM ( N = 269). Logistic regression models were created to explore sociodemographic, outness, social support, and HIV-related sexual risk variables associated with knowledge of viral load. Multivariable regression models were built to explore the same associations while controlling for confounders. HIV risk was not associated with knowledge of viral load in bivariate or multivariable analyses. Point estimates for low/negligible (odds ratio [OR] 1.10; 95% CI 0.46–2.51) and high risk (OR 1.88; 95% CI 0.68–5.20) suggest trends of higher knowledge with increased HIV risk. Men who engage in sexual risk behaviour may have increased sexual health literacy and awareness of biomedical interventions (e.g., pre-exposure prophylaxis, or PrEP) that reduce HIV risk. Policies are needed that promote acceptance of sexual orientation, improve awareness and access to PrEP, and ensure optimal delivery of HIV education to at-risk groups prior to engagement in higher risk activities.

"I Could Have Stood a Little More Education Rather than Just: 'Hey, you're Diabetic Man, Make the Best out of It'": Revisioning Diabetes Self-Management Education for Older Adults.

Objectives: Providing diabetes self-management education (DSME) in an evidence-based format that is accessible and tailored to the population needs is crucial for individuals living with diabetes mellitus. Our qualitative study explores the experiences of older adults living with diabetes while residing in a rural setting. Methods: Adults aged 65 or older and residing in a rural area of Ontario completed a photovoice activity and semi-structured interviews to illustrate their experience of living with diabetes and accessing DSME. Results: Fourteen participants (11 males; mean age = 74 years) completed the photovoice activity and interview. Four main themes were identified pertaining to learning about diabetes education, the depth and breadth of learning, applying knowledge to daily life, and engaging older adults in DSME. Discussion: Diabetes self-management education should account for older adults' preferences in learning about diabetes and self-management to promote access to evidence-based information, bolster knowledge and self-management efficacy, and improve disease control.

Abstract 13274: The Safety of Early Discharge After Tavi in Northern and Rural Ontario Canada

Introduction: Early hospital (<48hrs) discharge following transcatheter aortic valve implantation (TAVI) is an increasingly adopted practice. However, the safety of such an approach among patients residing in rural areas in Northern Ontario, including remote and medically underserved areas is lacking. Methods: After adapting the Vancouver 3M clinical pathway, all patients who underwent TAVI in Sudbury, Ontario were included in the analysis. The primary endpoint was all-cause mortality within 30 days. Secondary endpoints included procedural complications, post-TAVI length of hospital stay (LOS) and 30-day re-hospitalizations. Results: 165 patients underwent TAVI after adapting the Vancouver 3M clinical pathway. Mean age was 81 years (SD ± 8). Median STS-mortality score was 2.5% (IQR, 1.9-3.5). There was one in-hospital death (0.6%) with no 30 day mortality observed beyond hospital discharge. 11 patients (6.7%) required rehospitalization within 30 days, 3 of them for cardiac complaints. More over, after adoption of the 3M clinical pathway, the need for procedural mechanical ventilation and surgical vascular cut-down declined from 100% and 97% at baseline, to 6% and 2% respectively. Similarly, after adapting the 3M clinical pathway, the number of patients receiving TAVI on a given procedural day increased from two to three patients. Median post TAVI-LOS declined from 5 days (2-6 days) to 1 day (1-3 days). Conclusions: By transitioning to a 3M approach, our study has shown that early discharge after TAVI in Northern Ontario at a single lower-volume TAVI centre is feasible and safe, with favorable outcomes and improved hospital LOS. Furthermore, resource utilization improved with fewer patients requiring mechanical ventilation and surgical cut-down, leading to a downstream increase in the number of patients receiving TAVI on a given procedural day. This experience can potentially improve TAVI equity for underserved and vulnerable populations, reduce TAVI wait times and bridge variations in TAVI funding.

A multi-objective approach for designing a tire closed-loop supply chain network considering producer responsibility

For tire manufacturers to remain profitable while fulfilling environmental and social obligations such as producer responsibility, the opportunity lies in designing a tire Closed-Loop Supply Chain (CLSC) which combines forward and reverse supply chains. In this paper, a new multi-objective mixed-integer linear programming model is proposed to configure and optimize a multi-echelon, multi-product, multi-period tire CLSC network based on multiple recovery options and markets. For one of the objectives of the model, the weighting factors (importance) of suppliers are determined according to a unique framework of qualitative criteria. In this respect, a novel decision-making method based on Spherical fuzzy logic is developed. Finally, the solution approach is devised based on the formulation of the augmented ε-constraint method for finding efficient solutions. The application of the model is illustrated focusing on the region of Greater Toronto Area in Ontario, Canada. The optimal quantities for the flows of products, and number and locations of open facilities of the network are computed. The results show that the selected suppliers and allocated orders from them are impacted by considering multiple objectives.

Maternal sensitivity moderates the association between maternal history of childhood maltreatment and child executive function

BackgroundExperiences of childhood maltreatment are associated with a variety of negative outcomes throughout individuals' lives as well as disadvantaged cognitive and socioemotional development among their offspring. The mechanisms through which some children show resilience against the intergenerational transmission of risk, however, are less well understood. ObjectiveThe current study focuses on a proximal parental factor that plays a central role in children's early cognitive development – maternal sensitivity – and examines whether it moderates the association between maternal history of childhood maltreatment and child executive function (EF). Participants and settingData were collected from a community sample of 139 mothers and their infants (51 % female) recruited from urban areas in Ontario, Canada. MethodsMaternal maltreatment history was assessed via self-report at child age 3 months. Maternal sensitivity was assessed observationally at child age 8 months, and child executive function was assessed using performance-based measures at child age 3 years. Hypotheses were tested through multiple regression models. ResultsIn the current sample, maternal maltreatment history was not associated with child EF on average. However, results were consistent with a moderation model, indicating that maternal maltreatment history was associated with lower levels of child EF only when mothers were relatively insensitive. ConclusionsThe findings indicate the importance of considering sensitive parenting practices as a protective factor for children's cognitive development in the context of more distal risk factors such as mothers' history of childhood maltreatment.

Knowledge of viral load, PrEP, and HIV-related sexual risk among men who have sex with men in the Waterloo region

Gay, bisexual, and other men who have sex with men (GBMSM) remain most disproportionately affected by HIV in Canada. HIV- related sexual risk behaviours have been linked to high HIV risk among GBMSM, but prior research has not focused on knowledge of viral load, and the risk it presents for HIV acquisition. The purpose of this study was to explore the relationship between HIV-related sexual risk behaviour and knowledge of viral load among GBMSM. A cross-sectional survey was conducted using a convenience sample of individuals age 16 and older who self-identified as LGBTQ and lived, worked, or resided in the Waterloo region, an urban-rural area in southwestern Ontario ( N = 526). Responses were analyzed from those identifying as GBMSM ( N = 269). Logistic regression models were created to explore sociodemographic, outness, social support, and HIV-related sexual risk variables associated with knowledge of viral load. Multivariable regression models were built to explore the same associations while controlling for confounders. HIV risk was not associated with knowledge of viral load in bivariate or multivariable analyses. Point estimates for low/negligible (odds ratio [OR] 1.10; 95% CI 0.46–2.51) and high risk (OR 1.88; 95% CI 0.68–5.20) suggest trends of higher knowledge with increased HIV risk. Men who engage in sexual risk behaviour may have increased sexual health literacy and awareness of biomedical interventions (e.g., pre-exposure prophylaxis, or PrEP) that reduce HIV risk. Policies are needed that promote acceptance of sexual orientation, improve awareness and access to PrEP, and ensure optimal delivery of HIV education to at-risk groups prior to engagement in higher risk activities.

Mineralogical Variability of the Whabouchi Pegmatite and its Effect on the Li Concentrations

ABSTRACT The Whabouchi pegmatite, located in the James Bay area of Québec, is a lithium-cesium-tantalum pegmatite of albite-spodumene type. In order to evaluate the mineralogical and geochemical variability of the pegmatite, 168 samples were collected from drill core and analyzed for their whole rock geochemistry and mineralogy. The pegmatite is composed of quartz, albite, K-feldspar, spodumene, and muscovite, with trace amounts of spessartine garnet, apatite, beryl, tourmaline, and oxides. It is mostly homogenous, showing greatest variability with respect to the minerals albite, K-feldspar, and spodumene. The Li2O concentration varies between 0.03 and 4.46 wt.%, for an average of 1.53 wt.% and an estimated variability of 53%. Modal mineralogical data showed an inverse correlation between spodumene and the feldspars (albite + K-feldspar), which could also be observed when comparing the Li2O content with the sum of Na2O and K2O. To improve on this relationship, correlation matrices comparing all geochemical components were constructed and allowed the development of an equation able to estimate the Li2O content of the samples within 0.5 wt.% of the measured value. The applicability of the equation to other albite-spodumene type pegmatites was verified with samples collected from the Georgia Lake area of northwestern Ontario. The calculation provided a good approximation of the Li2O content of the samples, with 92% of the data showing a difference of 0.5 wt.% Li2O or less; however, it has an impact on the statistical mean of the data set, the data being recalculated to return an average closer to 1.5 wt.% Li2O. Considering the difficulty in analyzing lithium content of an in situ sample, this relationship could facilitate estimation in the field using portable X-ray fluorescence with the capability of analyzing all required components.

Assessment of mercury enrichment in lake sediment records from Alberta Oil Sands development via fluvial and atmospheric pathways

Exploitation of bitumen-rich deposits in the Alberta Oil Sands Region (AOSR) by large-scale mining and processing activities has generated widespread concern about the potential for dispersal of harmful contaminants to aquatic ecosystems via fluvial and atmospheric pathways. The release of mercury has received attention because it is a potent neurotoxin for wildlife and humans. However, knowledge of baseline mercury concentration prior to disturbance is required to evaluate the extent to which oil sands development has contributed mercury to aquatic ecosystems. Here, we use stratigraphic analysis of total mercury concentration ([THg]) in radiometrically dated sediment cores from nine floodplain lakes in the AOSR and downstream Peace-Athabasca Delta (PAD) and two upland lakes in the PAD region to establish pre-1900 baseline [THg] and evaluate if [THg] has become enriched via fluvial and atmospheric pathways since oil sands mining and processing began in 1967. Concentrations of THg in sediment cores from the study lakes range from 0.022–0.096 mg/kg (dry wt.) and are below the Canadian interim sediment quality guidelines for freshwater (0.17 mg/kg). Results demonstrate no enrichment of [THg] above pre-1900 baseline via fluvial pathways at floodplain lakes in the AOSR or PAD. Enrichment of [THg] was detected via atmospheric pathways at upland lakes in the PAD region, but this occurred prior to oil sands development and aligns with long-range transport of emissions from coal combustion and other anthropogenic sources across the northern hemisphere recognized in many other lake sediment records. The inventory of anthropogenic [THg] in the upland lakes in the AOSR is less than at the Experimental Lakes Area of northwestern Ontario (Canada), widely regarded as a “pristine” area. The absence of enrichment of [THg] in lake sediment via fluvial pathways is a critical finding for stakeholders, and we recommend that monitoring at the floodplain lakes be used to inform stewardship as oil sands operators prepare to discharge treated oil sands process waters directly into the Athabasca River upstream of the PAD.

Geographic inequalities in paediatric emergency department visits in Ontario and Alberta: a multilevel analysis of 2.5 million visits

BackgroundResearch on intra- and inter-regional variations in emergency department (ED) visits among children can provide a better understanding of the patterns of ED utilization and further insight into how contextual features of the urban environment may be associated with these health events. Our objectives were to assess intra-urban and inter-urban variation in paediatric emergency department (PED) visits in census metropolitan areas (CMAs) in Ontario and Alberta, Canada and explore if contextual factors related to material and social deprivation, proximity to healthcare facilities, and supply of family physicians explain this variation.MethodsA retrospective, population-based analysis of data on PED visits recorded between April 1, 2015 and March 31, 2017 was conducted. Random intercept multilevel regression models were constructed to quantify the intra- (between forward sortation areas [FSAs]) and inter- (between CMAs) variations in the rates of PED visits.ResultsIn total, 2,537,442 PED visits were included in the study. The overall crude FSA-level rate of PED visits was 415.4 per 1,000 children population. Across CMAs, the crude rate of PED visits was highest in Thunder Bay, Ontario (771.6) and lowest in Windsor, Ontario (237.2). There was evidence of substantial intra- and inter-urban variation in the rates of PED visits. More socially deprived FSAs, FSAs with decreased proximity to healthcare facilities, and CMAs with a higher rate of family physicians per 1,000 children population had higher rates of PED visits.ConclusionsThe variation in rates of PED visits across CMAs and FSAs cannot be fully accounted for by age and sex distributions, material and social deprivation, proximity to healthcare facilities, or supply of family physicians. There is a need to explore additional contextual factors to better understand why some metropolitan areas have higher rates of PED visits.

Decline of regional ecological integrity: Loss, distribution and natural heritage value of roadless areas in Ontario, Canada

Only eight years remain to increase nature protection by 20 million ha in Ontario from 10.7% to 30% by 2030 to meet government commitments. Rapid identification and assessment of unprotected roadless areas (RAs) would help to achieve this goal by focussing natural heritage protection efforts in areas with high ecological and conservation value. In Ontario, little is known about the location and extent of RAs, thus the purpose of this study was to map and describe RAs in Ontario, and to discuss their value. Total length of roads in Ontario increased from ∼90,000 km in 1916 to ∼607,500 km in 2020 – an increase of ∼517,500 km (675%) over 104 years. Within Ontario's managed forest region (MFR; excludes the Far North), RAs declined from ∼34 million ha in 1916 to ∼18.5 million ha in 2020 resulting in a loss of ∼15.5 million ha reducing RA cover in the region to 35.6%. Doubling logging production by 2030 per a new Ontario policy could reduce RAs by as much as 20% to ∼14.8 million ha by 2030, potentially resulting in their depletion between 2090 and 2100. In 1880, woodland caribou occupied ∼43 million ha in Ontario's MFR, which declined to ∼10 million ha by 1990. Caribou occupancy in this region could be eliminated by ∼2024 and extirpated from all of Ontario by 2070. If all remaining RAs in the MFR were designated as protected areas, Ontario would achieve 92.7% of the 30 × 30 goal. RAs in Ontario continue to be degraded, fragmented and eliminated.

Estimating animal abundance at multiple scales by spatially explicit capture-recapture.

Information about how animal abundance varies across landscapes is needed to inform management action but is costly and time-consuming to obtain; surveys of a single population distributed over a large area can take years to complete. Surveys employing small, spatially replicated sampling units improve efficiency, but statistical estimators rely on assumptions that constrain survey design or become less reasonable as larger areas are sampled. Efficient methods that avoid assumptions about similarity of detectability or density among replicates are therefore appealing. Using simulations and data from >3500 black bears sampled on 73 independent study areas in Ontario, Canada, we (1) quantified bias induced by unmodeled spatial heterogeneity in detectability and density; (2) evaluated novel, design-based estimators of average density across replicate study areas; and (3) evaluated two estimators of the variance of average density across study areas: an analytic estimator that assumed an underlying homogeneous spatial Poisson point process for the distribution of animals' activity centers, and an empirical estimator of variance across study areas. In simulations where detectability varied in space, assuming spatially constant detectability yielded density estimates that were negatively biased by 20% to 30%; estimating local detectability and density from local data and treating study areas as independent, equal replicates when estimating average density across study areas using the design-based estimator yielded unbiased estimates at local and landscape scales. Similarly, detectability of black bears varied among study areas and estimates of bear density at landscape scales were higher when no information was shared across study areas when estimating detectability. This approach also maximized precision (relative SEs of estimates of average black bear density ranged from 7% to 18%) and computational efficiency. In simulations, the analytic variance estimator was robust to threefold variation in local densities but the empirical estimator performed poorly. Conducting multiple, similar SECR surveys and treating them as independent replicates during analyses allowed us to efficiently estimate density at multiple scales and extents while avoiding biases caused by pooling spatially heterogeneous data. This approach enables researchers to address a wide range of ecological or management-related questions and is applicable with most types of SECR data.

Experiences of family violence among 2SLGBTQ + youth at risk of, and experiencing, homelessness before and during the COVID-19 pandemic

Introduction: Family violence is the leading cause of homelessness among youth; however, limited research has examined family violence among 2SLGBTQ + youth experiencing homelessness. The objective of this study was to engage a group of 2SLGBTQ + youth at risk of, and experiencing, homelessness in the Greater Toronto Area and surrounding areas in Ontario, Canada, to examine their experiences of family violence before and during the COVID-19 pandemic. Methods: 2SLGBTQ + youth at risk of, and experiencing, homelessness and key informants (service providers) participated in online surveys and one-on-one interviews to assess family violence during the pandemic. Qualitative and quantitative data were analyzed separately and merged for interpretation. Results: The majority of youth experienced various forms of family violence throughout their lives, which was exacerbated by the COVID-19 pandemic. Conclusion: Our study highlights the need to identify and address family violence toward 2SLGBTQ + youth.

Lies, Denials, and Cover-Ups: The Pervasiveness of Whiteness in School Districts Relations with Black and Racialized Parents

This study explores whiteness as property in parent engagement as experienced by Black and racialized parents in the Greater Toronto and Hamilton Area in Ontario, Canada. Drawing on counter-storytelling methodology, we explore the active harm endured by parents who have challenged racist educators, policies, and practices. We also explore how educators uphold whiteness as property (and intersections with “smartness” and “goodness”) through a spectrum of coercive power tactics, such as lies, denials, and cover-ups to protect their power and control at the expense of Black and racialized parents and students.

Naturally acquired antibodies against 7 Streptococcus pneumoniae serotypes in Indigenous and non-Indigenous adults.

Despite the use of pneumococcal conjugate vaccines for pediatric immunization, North American Indigenous populations continue to experience high burden of pneumococcal infections. Naturally acquired antibodies, which can protect unvaccinated adults against pneumococcal infections, have not previously been studied in Canadian Indigenous people. We analysed concentrations of natural serum IgG, IgM and IgA antibodies specific to 7 serotype-specific capsular polysaccharides (3, 6B, 9V, 14, 19A, 19F and 23F) in 141 healthy individuals (age between 18 and 80 years), including Indigenous adults living in 2 geographical different areas of Ontario, Canada, and non-Indigenous residing in northwestern Ontario. Regardless of the geographical area, concentrations of IgG specific to serotypes 6B, 9V, and 14, IgM specific to 9V, and all serotype-specific IgA were significantly higher in Indigenous study participants as compared to non-Indigenous. The differences are likely attributed to an increased exposure of Indigenous individuals to Streptococcus pneumoniae and/or cross-reactive antigens of other microorganisms or plants present in the environment. Although in non-Indigenous adults concentrations of IgM specific to 9V, 19A, 19F, and 23F significantly decreased with age, this was not observed in Indigenous individuals suggesting that Indigenous people may experience continuous exposure to pneumococci and cross-reactive antigens over the life span. Women had generally higher concentrations of natural IgG and IgM concentrations than men, with more striking differences found in Indigenous adults, potentially associated with larger exposure of women to young children, the major reservoir of pneumococci in communities. Our data suggest that increased rates of pneumococcal infections among Indigenous people are unlikely related to deficiency of naturally acquired antibodies, at least those specific to 7 common serotypes. Determining serological correlates of protection for adults will be essential to identify the groups in need of adult pneumococcal immunizations that may prevent excessive burden of the disease among North American Indigenous people.

Using Delay Logs and Machine Learning to Support Passenger Railway Operations

Passenger railways face reliability challenges resulting from shared track with other trains, limited infrastructure capacity, and rolling stock and trackway that is subject to major failures during service. Dispatchers may have limited contextual information when responding to an emerging delay, and often rely on their own experience to manage an incident. This study leverages various aspects of delay logs—a common set of data collected during railway operations—to arm dispatchers with an understanding of delays, provide contextual information about previous delays that are similar to an emerging event, and make predictions about the size of a delay based on emerging information. Using graph theory, short-text topic modeling, cosine similarity, and machine learning regression models, we demonstrate that agencies can leverage this single data source for insight and operational support. To showcase the potential insights gained by these methods, we apply them to delay log data from the GO Rail network in the Greater Golden Horseshoe area of Ontario, Canada. We find that elastic net and random forest regression models outperform naive models that may be tacitly used in practice today.

Cooperative inversion of multiphysics data using joint minimum entropy constraints

ABSTRACTThe inversion of geophysical data is a classical ill‐posed problem that is complicated by considerable uncertainty and ambiguity in the resulting inverse models. One way to reduce this uncertainty is based on the cooperative inversion of multiphysics data. In most cases, the information provided by different geophysical data is mutually complementary, making it natural to consider a cooperative (joint) inversion of different geophysical data to a shared earth model. Many existing joint inversion methods are based on the known relationships between the different physical properties of the rocks. This paper introduces a new approach to cooperative geophysical inversion, which does not require a priori knowledge about specific empirical or statistical relationships between the different models' parameters. Our approach is based on a novel joint minimum entropy stabilizer, which forces the simplest multiphysics solution that fits the multimodal data. This novel stabilizer characterizes the degree of joint disorder or uncertainty in the distribution of the different model parameters. By minimizing this stabilizing functional in the framework of the regularized inversion, we produce a consistent image of the same geological structure expressed in different geophysical data. We implement a joint minimum entropy stabilizer in the context of re‐weighted regularized conjugate gradient inversion. The paper demonstrates the developed method using a synthetic model study and by joint inversion of airborne gravity and magnetic data collected in the McFaulds Lake area of Ontario, Canada.

Climate Effects on Black Spruce and Trembling Aspen Productivity in Natural Origin Mixed Stands

Forest managers need site productivity estimates for tree species growing in mixed stands. Models developed in the past are generally for pure stands and don’t factor in the effects of climate change on site productivity. Therefore, site index (SI) models were developed for black spruce (Picea mariana Mill. B.S.P.) and trembling aspen (Populus tremuloides Michx.) trees grown in natural origin mixed stands. For this, 186 trees (93 black spruce and trembling aspen each) were sampled from 31 even-aged natural mixed stands (sites) (3 trees/species/site) across Ontario, Canada. Stand height growth models were developed by incorporating climate variables during growth for each species. Stem analysis data collected from sampled trees were used to develop these models. A mixed effects modelling approach was used to fit the models. The relationship between SIs of black spruce and trembling aspen grown in mixed stands was analyzed by calculating correlation coefficients and plotting black spruce SIs against those of trembling aspen. Climate effects on site productivity were evaluated by predicting stand heights for 4 geographic areas of Ontario for the period 2021 to 2080. Three emissions scenarios reflecting different amounts of heat at the end of the century (i.e., 2.6, 4.5, and 8.5 watts m−2) were used in the stand height growth models developed here for evaluation. Climate effects were more pronounced for trembling aspen than black spruce only in the far west. The relationship between SIs of black spruce and trembling aspen trees grown in natural origin mixed stands could not be described using a linear/nonlinear mathematical function. The models developed here can be used to estimate stand height and SI of black spruce and trembling aspen trees grown in natural origin mixed stands in a changing climate. In the absence of climate data, models fitted without climate variables can be used to estimate SI of both species.