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Understanding irradiation embrittlement of reactor pressure vessel steels using micromechanical methods and atom probe tomography
No full textThe long-term integrity of Reactor Pressure Vessel (RPV) steels is crucial for the safe operation of nuclear power plants (NPPs), particularly as lifetime extensions become increasingly necessary to meet global energy demands. One of the primary challenges in extending operational lifetimes is irradiation embrittlement, which results from matrix damage introduced by irradiation as well as correlated solute clustering and increased grain boundary segregation induced by reactor operating conditions. This study employs a combination of Atom Probe Tomography (APT) and micromechanical methods to investigate the nanostructural evolution and mechanical property changes in RPV steels after thermal ageing, neutron irradiation, and ion irradiation. Systematic cluster search was utilized to evaluate cluster metrics, providing insights into the sensitivity of clustering behavior to irradiation conditions and alloy composition. Spherical nanoindentation was applied as a near non-destructive technique to correlate nanostructural changes with mechanical property alterations. APT techniques for extracting grain boundary misorientation from APT data were compared to ensure an accessible yet accurate approach. The effects of neutron irradiation were compared with long-term thermal ageing in a low-Cu RPV model alloy, revealing differences in cluster composition and nucleation mechanisms. It was shown that Mn-Ni-Si-rich clusters form under both irradiation and ageing, but their growth kinetics and presumed thermodynamic stability differ. As clusters formed under thermal ageing, their formation could be considered irradiation-enhanced. However, the differences between thermally aged and irradiated clusters suggest a significant influence of irradiation on cluster formation, growth, and composition. They could therefore rather be classed as irradiation-induced with a very low irradiation threshold. A comparative study of multiple neutron-irradiated RPV alloys demonstrated that alloying elements such as Cu, Ni, and Mn play a critical role in cluster formation and growth, with increased contents of these solute elements leading to an increase in irradiation embrittlement. A more prominent role of Si in irradiation-induced clusters, in contrast to clusters formed under thermal ageing, was suggested. Additionally, the influence of heterogeneous nucleation sites, such as dislocation lines and grain boundaries, on clustering behavior was explored, emphasizing their susceptibility to increased segregation under irradiation and their potentially high contribution to embrittlement. Similar to the previous results, this study underscored the differences between irradiation-induced homogenous clusters spread throughout the matrix and clusters formed on heterogeneous nucleation sites. These findings advance the understanding of irradiation embrittlement mechanisms in RPV steels and highlight the importance of alloy composition and microstructural features in long-term material performance. The study also underscores the potential of spherical nanoindentation as a surveillance tool for identifying and assessing irradiation damage in reactor components
Intestinal Obstruction Secondary to Cecal Volvulus as a Result of Intestinal Nonrotation: A Case Report
Get PDFOne of the extremely uncommon manifestations of malrotation is nonrotation, a condition that arises due to the complete failure of the midgut to rotate 270 degrees. The true prevalence in adults remains obscure due to the scarcity of the condition. A standard surgical approach to management is therefore lacking, and an increasing number of case reports is required to establish evidence-based recommendations. We present the case of a 39-year-old male with acute abdominal pain due to cecal volvulus in the setting of intestinal nonrotation, successfully managed with a robotic-assisted surgical approach
The management of non-traumatic wrist disorders: A national survey of practice
Get PDFIntroductionNon-traumatic wrist disorders (NTWD) are commonly encountered across care settings, but current patterns of care and clinicians beliefs about the care they provide remains unclear.ObjectiveThis study aimed to record management approaches to care for NTWD across clinical groups and care settings.MethodsEthical approval was sought for an online cross-sectional survey of clinicians [1 Jul - 1 Nov 2023], comprising 18 questions exploring profession, work setting, exposure to NTWD, alongside diagnostic and management confidence. UK-based musculoskeletal (MSK) clinicians were invited to participate through special interest groups, online forums, social media and professional network emails.ResultsVariability was found in the domains of specificity of diagnosis and confidence in management which relates to exposure and profession. Variability was found in the domains of specificity of diagnosis and confidence in management which relates to exposure, profession and clinical setting. Several Patient Related Objective Measures (PROMS) were used by clinicians to assess treatment effect, set goals, and communicate with patients.ConclusionThis study provides the first description of UK clinicians management of non-traumatic wrist disorders across professional groups and healthcare settings. As evidence-based management remains elusive, deeper understanding of the clinical decision-making and practice behaviour of clinicians would have value in future studies into NTWD
Revisiting Active Site Quantification in CO 2 Electroreduction: The Case for CO Displacement
Get PDFThe selectivity and geometric current density of copper-based electrodes for electrochemical CO2 reduction (CO2RR) have been significantly improved, yet research is striving to improve the intrinsic activity of these materials. The accurate quantification of active sites is vital to benchmark the intrinsic activity of the catalysts for electrochemical CO2 reduction to facilitate activity improvements. Herein, we propose a method to determine the active sites using CO displacement in potassium phosphate buffer at 10 °C. Comparing this method with the electrochemical surface area (ECSA), measured by double-layer capacitance, the most used technique in this field, we demonstrate that CO displacement provides a much more accurate quantification of the number of active sites. By normalizing current density vs the CO displacement active sites, we find electropolished copper foil has the highest intrinsic activity towards CO2RR. We also reveal there is a clear relationship between surface roughness and chained products
Towards unbiased exploration in partial label learning
Get PDFWe consider learning a probabilistic classifier from partially-labelled supervision (inputs denoted with multiple possibilities) using standard neural architectures with a softmax as the final layer. We identify a bias phenomenon that can arise from the softmax layer in even simple architectures that prevents proper exploration of alternative options, making the dynamics of gradient descent overly sensitive to initialization. We introduce a novel loss function that allows for unbiased exploration within the space of alternative outputs. We give a theoretical justification for our loss function, and provide an extensive evaluation of its impact on synthetic data, on standard partially labelled benchmarks and on a contributed novel benchmark related to an existing rule learning challenge
American black bear ( Ursus americanus ) as a potential host for Campylobacter jejuni
Get PDFThe Gram-negative bacterium Campylobacter jejuni is part of the commensal gut microbiota of numerous animal species and a leading cause of bacterial foodborne illness in humans. Most complete genomes of C. jejuni are from strains isolated from human clinical, poultry, and ruminant samples. Here, we characterized and compared the genomes of C. jejuni that were isolated from American black bears in three states in the southeastern United States from 2014 to 2016. Despite the limited sample size (n = 9), the isolates displayed substantial genotypic variability, including eight distinct sequence types (STs) and variable gene content encoding surface glycan structures such as capsular polysaccharides (CPS) and lipooligosaccharides (LOS). Phylogenetic analysis identified several C. jejuni host generalist strains among the isolates from bears that clustered with isolates from domestic poultry, cattle, and environmental sources. Three isolates (SKBC94, SKBC3, SKBC5) clustered with wildlife-associated strains, exhibiting mutations or deletions in loci associated with cytolethal distending toxin production and oxidative stress resistance, potentially influencing host-specific colonization. Additionally, strains SKBC3 and SKBC5 harbored distinct Entner-Doudoroff (E-D) loci, suggesting a potential evolutionary fitness advantage. This study provides the first evidence of C. jejuni colonization in American black bears, highlighting their potential role as reservoirs for diverse C. jejuni lineages from both anthropogenic and environmental sources. Further research is needed to determine the prevalence and host specificity of C. jejuni strains in black bears and their potential implications for public and wildlife health
Active sorting to boundaries in active nematic–passive isotropic fluid mixtures
Get PDFWe use a two-fluid model to study a confined mixture of an active nematic fluid and a passive isotropic fluid. We find that an extensile active fluid preferentially accumulates at a boundary if the anchoring is planar, whereas its boundary concentration decreases for homeotropic anchoring. These tendencies are reversed if the active fluid is contractile. We argue that the sorting results from gradients in the nematic order, and show that the behaviour can be driven by either imposed boundary anchoring or spontaneous anchoring induced by active flows. Our results can be tested by experiments on microtubule-kinesin motor networks, and may be relevant to sorting to the boundary in cell colonies or cancer spheroids
The potential bidirectional relationship between long COVID and menstruation
Get PDFWomen have reported menstrual changes following SARS-CoV-2 infection and variation in long COVID symptoms across the menstrual cycle. We examined (i) whether COVID is linked to abnormal uterine bleeding (AUB), (ii) if long COVID symptoms vary with the menstrual cycle, and (iii) potential underlying mechanisms. Here we show long COVID was associated with AUB in a UK population. When compared to those never infected (n = 9423), long COVID participants (n = 1048) reported increased menstrual volume, duration and intermenstrual bleeding, while those who recovered from acute COVID (n = 1,716) reported minimal menstrual disruption. Long COVID symptoms examined in 54 women across the menstrual cycle revealed that severity was highest during the perimenstrual and proliferative phases. Serum and endometrial analysis revealed higher serum 5α-dihydrotestosterone and lower endometrial androgen receptors in long COVID versus no COVID. Other ovarian hormones showed no significant differences. Serum cytokine profiling indicated increased menstrual inflammation with long COVID and immune cell aggregates were observed in menstrual endometrium. In conclusion, long COVID was associated with AUB but not impaired ovarian function. Differences in peripheral and endometrial inflammation may contribute to AUB and long COVID symptom severity. We anticipate our findings will instigate exploration of new therapeutic strategies for women with long COVID
Predicting intentions towards long-term antidepressant use in the management of people with depression in primary care: a longitudinal survey study
Get PDFBackground Over the last two decades, antidepressant prescribing in the UK has increased considerably, due to an increased number of people staying on antidepressants for longer. Even when treatment is no longer clinically indicated, qualitative research suggests many people continue due to a fear of depressive relapse or antidepressant withdrawal symptoms. The quantitative effects of peoples’ beliefs and attitudes towards long-term antidepressant use remain relatively unexplored. Objectives To determine the extent to which beliefs and attitudes towards antidepressant treatment are associated with intentions to stop or continue long-term use; and whether intentions translate into actual discontinuation. Methods A questionnaire survey formed the main component of an embedded mixed-methods study. Twenty general practices posted questionnaires to adults aged over 18 receiving continuous antidepressant prescriptions for over two years. Outcomes and explanatory variables were determined using an extended model of the Theory of Planned Behaviour, conducting exploratory descriptive and regression analyses. The primary outcome was participants’ intentions to discontinue antidepressants. The secondary outcome of behaviour change was determined by any change in antidepressant dosage at six months. Results 277 people were surveyed from 20 practices, with 10 years median antidepressant duration. Mean questionnaire scores for intention and subjective norms towards starting to come off antidepressants were low, and 85% of participants declared that continuing their antidepressant was necessary. Prescribing outcomes retrieved from 175 participants’ medical records six months after they completed the survey found 86% had not changed their antidepressant, 9% reduced the dose, only 1% discontinued their antidepressant, and 4% increased the dose. All Theory of Planned Behaviour constructs and concerns were associated with intentions, with more favourable attitudes towards stopping and subjective norms having the strongest associations towards intentions to discontinue antidepressant use. Conclusion Given few intentions to stop taking antidepressants, patients should be made more aware of the importance of ongoing antidepressant monitoring and review from their primary care practitioners. This would promote discussion to support an attitudinal change and initiation of antidepressant tapering where appropriate
