Environmental Changes Research Articles

Effect of hydrostatic pressure on the supramolecular assembly of surfactant-cyclodextrin inclusion complexes.

The supramolecular assembly of simple colloids into complex, hierarchical structures arises from a delicate interplay of short-range directional and isotropic long-range forces. These assemblies are highly sensitive to environmental changes, such as temperature variations and the presence of specific molecules, making them promising candidates for nanomachine design. In this study, we investigate the effect of hydrostatic pressure, up to 1800 bar, on the supramolecular assemblies of cyclodextrin/surfactant complexes. Using small-angle neutron scattering, we demonstrate that while the overall structure of the supramolecular aggregates remains largely stable under pressure, the stiffness of the planar lattice formed by the inclusion complexes, the basic structural unit of the supramolecular assemblies, shows a fourfold increase between 250 and 1000 bar. These findings suggest that high-pressure studies can be exploited to better understand the mechanisms of supramolecular assembly processes, thereby aiding in the design of more robust and functional systems.

Dental students' Myers-Briggs Type Indicator personality profile in the past 50 years: Systematic review and meta-analysis.

Dental students' personalities are strongly correlated with their didactic and clinical performances. With the significant changes in the social environment in the past decades, students' personalities may also change dramatically. Additionally, with the increasing number of international students admitted into US dental programs, educators must pay attention to the potential personality differences between domestic and international students. A systematic review focusing on the Myers-Briggs Type Indicator personality types of dental students was conducted with 11 literature databases following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guideline. The quality assessment of each included article was conducted following the Joanna Briggs Institute Prevalence Critical Appraisal Tool. Meta-analyses were conducted for each personality type within the United States in the past 50 years, and in each country in the past 20 years. Eighteen articles (17 reports) were included after the eligibility assessment. The longitudinal trends within the United States showed the predominant two personality types have changed from Extraversion, Sensing, Feeling, and Judging (ESFJ) and Extraversion, Sensing, Thinking, and Judging (ESTJ) to ESTJ and Introversion, Sensing, Thinking, and Judging (ISTJ) during the past 50 years. When comparing different countries, the United States, China, Korea, and Iran have the same two dominant personality types (ESTJ and ISTJ) but not the Philippines (Extraversion, Intuition, Feeling, and Perceiving and Introversion, Intuition, Feeling, and Perceiving). However, there are large variations in the prevalence of other personality types. There have been constant changes in the predominant personalities of dental students over the years. Additionally, understanding the diversity of personality types within the United States as well as among different countries could serve as the foundation for further improvements in teaching strategies and student support services.

Climate Change and Rye (Secale cereale L.) Production: Challenges, Opportunities and Adaptations

ABSTRACTThis comprehensive review examined the intricate relationship between climate change and rye (Secale cereale L.) production, focusing on the multifaceted challenges and opportunities posed by changing environmental conditions. Rye is a versatile cereal crop cultivated in temperate regions and is known for its resilience and adaptability to adverse growing conditions. However, as global temperatures and atmospheric CO2 concentrations rise, the effects of climate change on rye growth, yield and grain quality become increasingly apparent. In this review, we summarised the recent research findings on various aspects of rye production and quality under climate change, focusing on factors such as temperature (e.g., increasing temperature) resilience, and viability of rye production in the face of ongoing climate challenges, altered rainfall patterns (changing rainfall distributions with decreasing rainfall in the spring and early summer months as well as heavy rainfall events), biotic stress, agronomic practices and greenhouse gas emissions. Exploring the dynamic interplay among climate change, soil quality, biotic stressors and plant–microbe interactions reveals insights into the response of rye to environmental changes. These interactions shape the complex dynamics that influence the adaptation of rye to evolving environmental conditions. Implications for food security, agricultural sustainability and future research directions are also discussed, highlighting the urgent need for adaptive strategies to ensure the resilience and viability of rye production in the face of ongoing climate challenges.

Uncertainty‐aware LiDAR‐based localization for outdoor mobile robots

AbstractAccurate and robust localization is essential for autonomous mobile robots. Map matching based on Light Detection and Ranging (LiDAR) sensors has been widely adopted to estimate the global location of robots. However, map‐matching performance can be degraded when the environment changes or when sufficient features are unavailable. Indiscriminately incorporating inaccurate map‐matching poses for localization can significantly decrease the reliability of pose estimation. This paper aims to develop a robust LiDAR‐based localization method based on map matching. We focus on determining appropriate weights that are computed from the uncertainty of map‐matching poses. The uncertainty of map‐matching poses is estimated by the probability distribution over the poses. We exploit the normal distribution transform map to derive the probability distribution. A factor graph is employed to combine the map‐matching pose, LiDAR‐inertial odometry, and global navigation satellite system information. Experimental verification was successfully conducted outdoors on the university campus in three different scenarios, each involving changing or dynamic environments. We compared the performance of the proposed method with three LiDAR‐based localization methods. The experimental results show that robust localization performances can be achieved even when map‐matching poses are inaccurate in various outdoor environments. The experimental video can be found at https://youtu.be/L6p8gwxn4ak.

Formation of the junctions between lymph follicles in the Peyer's patches even before postweaning activation

Peyer’s patches (PPs), which contain an abundance of B and T cells, play a key role in inducing pivotal immune responses in the intestinal tract. PPs are defined as aggregated lymph follicles, which consist of multiple lymph follicles (LFs) that may interact with each other in a synergistic manner. LFs are thought to be spherical in shape; however, the characteristics of their structure are not fully understood. To elucidate changes in the structure of PPs as individuals grow, we generated serial 2D sections from entire PPs harvested from mice at 2, 4, and 10 weeks of age and performed a 3D analysis using a software, Amira. Although the number of LFs in PPs was not changed throughout the experiment, the volume and surface area of LFs increased significantly, indicating that LFs in PPs develop continuously by recruiting immune cells, even after weaning. In response to the dramatic changes in the intestinal environment after weaning, the development of germinal centers (GCs) in LFs was observed at 4 and 10 weeks (but not 2 weeks) of age. In addition, GCs gradually began to form away from the center of LFs and close to the muscle layer where export lymphatic vessels develop. Importantly, each LF was joined to the adjacent LF; this feature was observed even in preweaning nonactivated PPs. These results suggest that PPs may have a unique organization and structure that enhance immune functions, allowing cells in LFs to have free access to adjacent LFs and egress smoothly from PPs to the periphery upon stimulation after weaning.

Drought heightens severity of diseases caused by Botryosphaeria dothidea and Cryptostroma corticale and needs to be factored in to properly assess pathogenicity or fulfill Koch’s postulates

AbstractClimate change is driving the emergence of novel tree diseases at the global scale, requiring new approaches for the formal confirmation of the pathogenicity of novel pathogens on novel hosts. At the same time, predictive models need to account for the possible effect of environmental changes and of abiotic stressors on disease severity for all diseases. By wound-inoculating Botryosphaeria dothidea on potted California coast live oaks and Cryptostroma corticale on potted silver maples, simultaneously in well-watered and in water-deprived conditions, I show that drought conditions increase the severity of disease symptoms. I also show that, by including a water-stressed treatment, I can formally prove pathogenicity and fulfill Koch’s postulates for putative pathogens that could not be confirmed in the absence of the stressor. Additionally, I show that the inclusion of data obtained in water stress conditions increases the differentiation between symptoms caused by fungal infection vs. symptoms caused by wound trauma, thus reducing the possible effect of outliers, a significant problem affecting many trials for fulfilling Koch’s postulates conducted with a limited number of replicates. The availability of comparable datasets in the presence and the absence of an abiotic stressor allows for the calculation of an Environmental Disease Component Index. Positive values of the index indicate a significant role of environmental change in disease progression and identify those pathogens that must be modeled factoring in climatic stressors. I suggest that this index may be extremely valuable for identifying pathogens likely to become emergent as climate changes.

Stoichiometric Homeostasis of N and P in the Leaves of Different-Aged Phyllostachys edulis after Bamboo Forest Expansion in Subtropical China

Stoichiometric homeostasis is an important mechanism in maintaining ecosystem structure, function, and stability. Phyllostachys edulis (moso bamboo) is a typical clone plant, forming pure bamboo forests or bamboo–wood mixed forests by expanding rhizomes around. Studying the stoichiometric homeostasis characteristics of moso bamboo at different ages after expansion contributes to a deeper understanding of the stability of bamboo forest ecosystems, and is of great significance for expanding the research scope of ecological stoichiometry. Based on the stoichiometric internal stability theory, the nitrogen (N) and phosphorus (P) elements in the soil and plants of typical moso bamboo forests in Tianbaoyan National Nature Reserve of Fujian Province were determined, and the internal stability index (H) of bamboo leaves of different ages (I-du, II-du, III-du, and IV-du bamboos) was calculated. The results showed that the dependence of moso bamboo on soil nutrients and the ability of moso bamboo to regulate nutrient elements were both significantly affected by the plant’s age. Under the condition of the same soil nutrients (N, P), the content of N and P in bamboo leaves decreased significantly with the increase in bamboo age. The limiting effect of phosphorus on the growth and development of moso bamboo was greater than that of nitrogen, and the limiting effect of phosphorus on aged bamboo was greater than that of young bamboo. The stoichiometric internal stability index of N and P in bamboo leaves is HN:P > HN > HP, which means that the internal stability of moso bamboo is closely related to the limiting elements. Therefore, the regulation ability of the internal stability of moso bamboo of different ages makes it grow well in the changeable environment, has stronger adaptability and competitiveness, and the leaf internal stability of I-du bamboo was higher than that of other ages, which may be one of the reasons for its successful expansion to form a stable bamboo stand structure.

Interspecific differences in ecological stoichiometric characteristics of invertebrates and their influencing factors from the Beibu Gulf, China

Invertebrates can store carbon (C), nitrogen (N), phosphorus (P), and other elements in their body tissues at theoretically homeostatic rates, thus playing an important role in the biogeochemical cycle of aquatic ecosystems. To sustain homeostasis, consumers must either balance their resource supply or adjust their stoichiometric features in response to environmental changes. However, there is limited understanding regarding potential differences in the ecological stoichiometric characteristics of marine invertebrates. To explore the ecological stoichiometric characteristics of marine invertebrates, the C, N, P, calcium (Ca), δ13C, and δ15N contents of 18 invertebrate species were analyzed from the Beibu Gulf. The results revealed that the ranges of elemental variations (C, N, and P) in invertebrates were 25.17%-47.34%, 6.14%-14.13%, and 0.26%-1.31%, respectively. The content of P in invertebrates exhibited the most significant variation, leading to alterations in C:P and N:P ratios. A significant negative correlation was observed between P content and body weight in invertebrates (p < 0.01). Furthermore, the C and N content of invertebrates were significantly negatively correlated with δ13C (p < 0.01), suggesting that the variations in C content and N content in invertebrates are influenced by different food sources, while P content varies according to body size. Our results also indicated significant interspecific differences in the ecological stoichiometry of invertebrates from the Beibu Gulf (p < 0.05). Invertebrate growth may be inhibited by P, and they do not maintain strict homeostasis, with stable homeostasis observed in higher trophic levels.

Variable Effects of Experimental Sea-level Rise Conditions and Invasive Species on California Cordgrass

AbstractSea-level rise (SLR) will produce unprecedented changes in tidal marsh systems that already cope with daily tidal fluctuation, disturbances from storms, and salinity changes from droughts and runoff events. Additionally, negative impacts from non-native invasive species may alter marsh plants’ ability to respond to SLR stressors like increased inundation and salinity. Increasingly, tidal marsh communities must tolerate both changes in the physical environment from SLR and increased risk of invasion by non-native species. To assess the response of a threatened tidal marsh cordgrass (Spartina foliosa) to both stressors, we implemented a field experiment in San Francisco Bay, CA, USA, exposing cordgrass to a treatment that extended tidal inundation projected with SLR using a recently developed in situ method. At one of two field sites, we also enclosed the cordgrass with or without the invasive European green crab, Carcinus maenas. We found that cordgrass responded negatively to longer inundation, although these effects varied by site and year. In higher inundation treatments, cordgrass survival increased with increasing surface elevation of the plot. Cordgrass survival was lower in the presence of invasive green crabs relative to controls. We did not find interacting effects of responses to increased inundation and invasive species presence, which highlights the need to consider how latent or sequential effects of multiple stressors may affect ecosystems. This study demonstrates significant biological responses to invasive species presence and increased inundation. Evaluating relative effects and timing of multiple stressors, especially those induced by climate change and invasive species, will help us to manage threatened ecological communities in a changing world.

Resilience in the face of ecological challenges: Strategies for integrating environmental considerations into social policy planning in Africa

AbstractAfrica faces severe ecological crises, such as climate change, resource depletion, and biodiversity loss, undermining sustainable development efforts and exacerbating poverty and hunger. Integrating environmental concerns into social policy planning could help build community resilience and support sustainable development. This study employed policy analysis and stakeholder engagement to identify key environmental issues, policy gaps, and strategies for integrating environmental considerations into social policies across various sectors in Africa. The study found a significant lack of integration of environmental concerns into social policy across areas like disaster management, agriculture, urban planning, healthcare access, and infrastructure development policies. As a percentage of respondents, the top environmental issues were flooding (32%), drought/desertification (13%), and food security/agriculture (11%), with farmers (35.4%) and women (21.7%) being the most vulnerable to climate change. Most community stakeholders (87.5%) emphasized the importance of integrating environmental considerations into social policy, with 56.25% rating it a high priority. They underscored the need for more locally driven planning, ecological monitoring, land restoration, diversified livelihoods, and climate change adaptation support through social policies to enhance environmental sustainability. This study's novelty lies in its comprehensive approach to understanding and addressing the complex interplay between environmental challenges and social policy planning in Africa. The findings emphasize the urgent need for policymakers to develop cross‐sectoral national and local policies that use participatory processes to prioritize environmental sustainability, adaptation, community empowerment, and alignment with sustainable development goals while being responsive to continuing environmental uncertainty and change.

Predicting trajectories of dryland wetland vegetation transformation under climate change: a case study of the northern Murray–Darling Basin, Australia

Dryland wetland vegetation is, paradoxically, both highly sensitive and extremely resilient to environmental change. In the short-term, rapid responses of wetland biota and ecological processes to wetting and drying, which influence ecosystem structure and function, enable rapid reproduction which enhances long-term resilience. However, over longer periods, mechanisms such as seed dormancy and persistent seed and egg banks enable dryland wetland ecosystems to recover after major environmental perturbations such as mega-droughts or wildfire. Climate change is likely to have a significant effect on key drivers of ecological response in dryland wetlands, including hydrology and its interface with other climatic stimuli, e.g. temperature, as well as the frequency and intensity of extreme events. Like species, wetland ecosystems may respond to climate change in three main ways, namely, disappear, persist without significant adjustment, or transform. Here, we consider the conditions under which each of these responses may eventuate for dryland wetlands, by using wetland vegetation of the northern Murray–Darling Basin Australia, as a case study. We also explore what wetland transformation might entail in this region in terms of wetland ecological character and the key values this supports. Finally, we consider the implications for wetland policy and management at present and as trajectories of wetland change unfold.

Adaptive context-aware access control for IoT environments leveraging fog computing

AbstractThe increasing use of the Internet of Things (IoT) has driven the demand for enhanced and robust access control methods to protect resources from unauthorized access. A cloud-based access control approach brings significant challenges in terms of communication overhead, high latency, and complete reliance. In this paper, we propose a Fog-Based Adaptive Context-Aware Access Control (FB-ACAAC) framework for IoT devices, dynamically adjusting access policies based on contextual information to prevent unauthorised resource access. The main purpose of FB-ACAAC is to provide adaptability to changing access behaviors and context by bringing decision-making and information about policies closer to the end nodes of the network. FB-ACAAC improves the availability of resources and reduces the amount of time for information to be processed. FB-ACAAC extends the widely used eXtensible Access Control Markup Language (XACML) to manage access control decisions. Traditional XACML-based methods do not take into account changing environments, different contexts, and changing access behaviors and are vulnerable to certain types of attacks. To address these issues, FB-ACAAC proposes an adaptive context-aware XACML scheme for heterogeneous distributed IoT environments using fog computing and is designed to be context-aware, adaptable, and secure in the face of unauthorised access. The effectiveness of this new scheme is verified through experiments, and it has a low processing time overhead while providing extra features and improved security.

Radon Dynamics in Granite and Calcareous Soils: Long-Term Experiments in a Semi-Arid Context

Radon in soil poses a significant health risk when it accumulates inside dwellings. The estimation of radon potential is a difficult task due to the complex dynamics of radon within soil and its relations with the weather. This research focuses on the variability of radon activity, driven by environmental changes, assessed in two loam soils (loamy sand–granite soil and silty clay loam-calcareous soil) with different radium contents. We conducted an experiment with teow soil columns in a semi-controlled outdoor laboratory, in a warm semi-arid climate. We also examined the consequences of abundant rainfall on radon activity through artificial soil water content (SWC) experiment conditions. Statistical analyses reveal that SWC is the most significant parameter influencing radon activity in these experiments. Radon is proportional to SWC and inversely proportional to temperature, evapotranspiration, and pressure in both soils, while wind is negatively related only in the loamy sand soil. Based on our findings, we modelled radon potential considering different soils and climatic contexts. SWC influences radon potential by changing radon emanation, activity, and permeability, depending on the local soil texture and radium concentration.

Economic, Social, and Environmental Factors Impacting Resilience and Disturbances of Lithuanian Family Farms

Climate change, changes in the natural environment, changing markets, price volatility, etc. pose tension and threats to the future of European Union farms. The uncertain future of family farms requires farm resilience—the ability to survive, adapt, and grow in the face of turbulent change. The limited resilience of family farms has become an important concern for rural and agricultural policy. The main goal of this work is to identify disturbances affecting Lithuanian family farms, assess their influence, investigate the general resilience of Lithuanian family farms, propose measures to reduce the vulnerability of farms, and increase the general resilience and sustainability. We used a combination of qualitative and quantitative research methods to conduct the research. Survey research was conducted using a semi-structured expert interview in which various types of variables were collected. The survey questionnaire, consisting of 38 groups of questions, was sent by email to 500 randomly selected family farmers in January 2024 and collected in the same month. The statistical analysis of the data from the 205 duly filled-out questionnaires was carried out using correlation analysis. In this article, we apply the concept of general resilience of the family farm in the direction of robustness, adaptability, and transformability. We identify the main factors influencing the general resilience of the family farm and study the main attributes of the resilience of family farms. We find some links between family farm characteristics, vulnerability factors, and general resilience capabilities, and we make several proposals to increase family farms’ resilience. The obtained results prove that higher education, larger farm sizes, higher agricultural sales, and employment of permanent workers are associated with better resilience. Furthermore, increasing environmentally friendly practices positively impacts resilience. Older farms and farmers, longer durations of farming activity, and risk-averse behaviors tend to decrease resilience. Due to local and global circumstances, economic and social changes have occurred very quickly in recent years, so the results obtained in the study may not be valid in the long term. Similar surveys after several years will be necessary to study the resilience of Lithuanian farms, including deeper economic analyses that evaluate factors such as price sensitivity, the level of farm debt, and market access.

An Assessment of Changes in the Thermal Environment during the COVID-19 Lockdown: Case Studies from the Greenland and Norwegian Seas

The COVID-19 lockdown had a significant impact on human activities, reducing anthropogenic heat and CO2 emissions. To effectively assess the impact of the lockdown on the thermal environment, we used the sliding paired t-test, which we improved from the traditional sliding t-test by introducing the paired t-test for sliding statistical tests, to test the abrupt change in the thermal environment. Furthermore, an additive decomposition model and wavelet analysis method were used to analyze the characteristics of trend and irregular change, coherence, and phase difference of the time series data with respect to the thermal environment. We chose the Greenland Sea and the Norwegian Sea, regions highly sensitive to changes in climate and ocean circulation, as case studies and used remote sensing data of the sea surface temperature (SST) and the atmospheric CO2 concentration data obtained from the Goddard Earth Sciences Data and Information Services Center from January 2015 to December 2021 for the analysis. The results show that although the annual spatial mean SST in 2020 is lower than the mean of all 7 years in most areas of the two seas, there is no evidence of a significant mutation in the decrease in the SST during the lockdown in 2020 compared with the temperatures before, according to the sliding paired t-test. The analysis of the irregular components of the monthly mean SST decomposed by an additive decomposition model also does not show the anomalously low SST during the lockdown in 2020. In addition, the lockdown had almost no impact on the increasing trend of CO2 concentration. The wavelet analysis also shows that there is no obvious anomaly in coherence or phase difference between the periodic variation of the SST and the CO2 concentrations in 2020 compared with other years. These results suggest that the direct effect of the COVID-19 lockdown on the thermal environment of the study area could be negligible.

Study of Environmental Education Programs and Behavior Change in Ethiopia

Purpose: The aim of the study was to investigate the Study of Environmental Education Programs and Behavior Change in Ethiopia. Methodology: This study adopted a desk methodology. A desk study research design is commonly known as secondary data collection. This is basically collecting data from existing resources preferably because of its low cost advantage as compared to a field research. Our current study looked into already published studies and reports as the data was easily accessed through online journals and libraries. Findings: Environmental education programs in Ethiopia have successfully increased awareness and promoted sustainable practices among communities. These initiatives have focused on issues like deforestation, soil erosion, and water conservation, encouraging behaviors such as waste reduction and sustainable agriculture. Community involvement and stakeholder engagement have been crucial in maintaining these positive changes. Scaling up these efforts is essential for long-term environmental sustainability in Ethiopia. Unique Contribution to Theory, Practice and Policy: Theory of planned behavior (TPB), social learning theory & diffusion of innovations theory may be used to anchor future studies on the impact of urban green spaces on air quality in Bangkok. Advocate for the integration of environmental education into formal educational curricula at all levels, emphasizing hands-on learning and practical applications. Advocate for policies that mandate or incentivize environmental education across educational systems and workplaces.

A morphological and molecular approach to investigating infectious disease in early medieval Iberia: The necropolis of La Olmeda (Palencia, Spain).

Here we investigate infectious diseases that potentially contribute to osteological lesions in individuals from the early medieval necropolis of La Olmeda (6th-11th c. CE) in North Iberia. We studied a minimum number of 268 individuals (33 adult females; 38 adult males, 77 unknown/indeterminate sex; and 120 non-adults), including articulated and commingled remains. Individuals with differential diagnoses suggesting chronic systemic infectious diseases were sampled and bioinformatically screened for ancient pathogen DNA. Five non-adults (and no adults) presented skeletal evidence of chronic systemic infectious disease (1.87% of the population; 4.67% of non-adults). The preferred diagnoses for these individuals included tuberculosis, brucellosis, and malaria. Ancient DNA fragments assigned to the malaria-causing pathogen, Plasmodium spp., were identified in three of the five individuals. Observed pathology includes lesions generally consistent with malaria; however, additional lesions in two of the individuals may represent hitherto unknown variation in the skeletal manifestation of this disease or co-infection with tuberculosis or brucellosis. Additionally, spondylolysis was observed in one individual with skeletal lesions suggestive of infectious disease. This study sheds light on the pathological landscape in Iberia during a time of great social, demographic, and environmental change. Genetic evidence challenges the hypothesis that malaria was absent from early medieval Iberia and demonstrates the value of combining osteological and archaeogenetic methods. Additionally, all of the preferred infectious diagnoses for the individuals included in this study (malaria, tuberculosis, and brucellosis) could have contributed to the febrile cases described in historical sources from this time.

Assessing Chlorophyll-a Variations in Caspian Sea during the COVID-19 Pandemic.

The COVID-19 pandemic's disruptions to human activities prompted serious environmental changes. Here, we assessed the variations in coastal water quality along the Caspian Sea, with a focus on the Iranian coastline, during the lockdown. Utilizing Chlorophyll-a data from MODIS-AQUA satellite from 2015 to 2023 and Singular Spectrum Analysis for temporal trends, we found a 22% Chlorophyll-a concentration decrease along the coast, from 3.2 to 2.5mg/m³. Additionally, using a deep learning algorithm known as Long Short-Term Memory Networks, we found that, in the absence of lockdown, the Chlorophyll-a concentration would have been 20% higher during the 2020-2023 period. Furthermore, our spatial analysis revealed that 98% of areas experienced about 18% Chlorophyll-a decline. The identified improvement in coastal water quality presents significant opportunities for policymakers to enact regulations and make local administrative decisions aimed at curbing coastal water pollution, particularly in areas experiencing considerable anthropogenic stress.

Microstructural analysis of ex-service neutron irradiated stainless steel nuclear fuel cladding by high-speed AFM

Fuel cladding in advanced gas-cooled nuclear reactors is made of an austenitic stainless steel referred to as 20Cr/25NiNb. This material can undergo microstructural changes in these extreme environments through a combination of thermal effects and radiation damage. In this work, the microstructures present in an ex-service irradiated 20Cr/25Ni-Nb sample are studied using correlated high-speed atomic force microscopy (HS-AFM) and electron microscopy techniques for the first time. Correlated topographic, crystallographic, and chemical information from the sample surface enabled identification of secondary phase precipitates (SPPs) including M23C6, sigma phase, NbC, and G phase. These SPPs can have adverse effects on the material properties. HS-AFM analysis showed surface textures unique to each SPP. Voids formed due to irradiation were also identified across the surface by HS-AFM. These voids were found to be larger in size and depth along grain boundaries. Further analysis identified a relationship between void size and frequency and grain boundary misorientation and SPP presence.

The significance of Paleoarchean granitoids from the Saglek Block, Labrador, Canada

The Saglek Block in the Nain Province of northeast Canada is part of the North Atlantic Craton. It comprises Archean gneisses that record magmatic and metamorphic ages between ca. 3.9 and 2.5 Ga. In this study, a grey banded gneiss from Maidmonts Island records an age of 3.72 Ga, which is equated with Uivak I gneisses reported from across the Saglek Block, and contains 3.8 Ga xenocrysts. These rocks were deformed and metamorphosed prior to the intrusion of augen gneiss protoliths on both Maidmonts and Mentzel islands that record U-Pb zircon ages of 3.33 Ga. These rocks are composed of ferroan calc-alkaline granite and granodiorite and were likely generated by partial melting of pre-existing quartzo-feldspathic crust, as attested by the presence of ca. 3.8 Ga xenocrysts. Such augen gneiss was previously classified as ca. 3.6 Ga ‘Uivak II gneiss’, a term we argue should now be abandoned. The final magmatic events recorded on Maidmonts and Mentzel islands took place in the Neoproterozoic with the emplacement of granitic stocks at ca. 2.72 Ga, and sills and dykes at ca. 2.57 Ga. This sequence of magmatic events from the Eoarchean to Neoarchean is very similar to that recorded in the Itsaq Gneiss Complex of southwest Greenland, where, based on the Hf signature, it has been suggested that a change in tectonic environment resulted from the initiation of subduction at ca. 3.2 Ga. Although Lu-Hf and Sm-Nd isotopic signatures from the ca. 3.33 Ga gneisses have been interpreted in the literature as due to partial melting of Hadean mafic crust, alternatively, they can be generated by partial melting of Eoarchean continental crust in a continental arc setting. We argue this is more consistent with the non-TTG geochemistry of the augen gneisses.