SUPER HARDENING OF W/NbN NANOLAYERS UNDER SHALLOW NANOINDENTATION

Superlattice materials are nanocomposites that exhibit a hardness at small bilayer repeat periods which exceeds the hardness predicted by the rule of mixtures for composites. The objective of this investigation was to utilize the experimental data obtained from nanoindentations and image scanning to examine the behavior of the superlattice material, W/NbN. Nanoindentations and in situ surface imaging were conducted over a range of applied loads on samples of W/NbN with two different bilayer periods (ƒ¼=5.6 nm and ƒ¼=10.4 nm), and monolithic samples of the niobium nitride (NbN) ceramic and the tungsten (W) metal which comprise the superlattice material. Additional shallow nanoindentations were made to a depth equal to the individual layer thicknesses of the nanocomposites. The mechanical properties were determined using the Oliver and Pharr method and compared for all the samples. The load versus displacement curves were also compared. The energies of indentation were calculated. The characteristics of the material pile-up resulting from the nanoindentations are determined from the scanned surface images. The experimental results are discussed to evaluate the influence of the different factors to the increase in hardness. The results indicate that the elastic modulus does not influence the hardness of the superlattice materials. The hardness and load versus displacement curves for the shallow indentations show little difference in behavior between NbN sample and the two superlattice materials. However, an increase in hardness is observed in the superlattice materials at deeper indentation depths. The results indicate that this increase in hardness is related to the nature of the interface between the layers in the superlattice materials

A 3-D COMPUTER MODEL TO SIMULATE THE SINTERING OF A RANDOMLY PACKED GREEN COMPACT IN ORDER TO INVESTIGATE THE EVOLUTION OF THE MICROSTRUCTURE

The objective of this research project was to develop a three-dimensional computer model to simulate the sintering of a randomly packed green compact in order to investigate the evolution of the microstructure as densification progresses. The model randomly generates a population of spheres to simulate the particle size distributions present in commercial alumina powders. The spheres were packed into a cubic volume to construct a Representative Volume Element (RVE) with properties statistically comparable to the properties measured in real sintered materials. Sintering was modeled as uniform flattening of the contact between spheres. The sintering process was assumed to be isotropic and homogenous. The simulation of the sintering process was later expanded to include Local Particle Rearrangement (LPR). The model was compared to experimental data obtained from measurements on sintered alumina samples using two techniques: the stereological parameters for the RVE determined by the simulation, and additional measurable quantities obtained from applying tessellation to cross sections taken from the RVE to further describe the characteristics of the microstructure. Based on the measured stereological parameters and the properties of the tessellated cells, the simulation reproduced behavioral trends in the microstructure similar to those observed in the measurement of the experimental samples thus demonstrating the feasibility of employing this type of model to explore the microstructure. The results also indicate that the generation of agglomerated particle packing arrangements may be useful in simulating the microstructural evolution of sintering since the presence of the large voids used to simulate agglomeration had a significant effect on the results. The use of LPR in the simulation did not appear to affect the results for a particle arrangement with no agglomerations, but it did influence the results for the particle arrangement with agglomeration. The results for the LPR simulations suggest that the ability of the particles to slide past each other, modeled in the simulation by the tangential viscosity, may influence the rate at which small pores are formed and/or eliminated in the RVE. However, the LPR simulations indicate that more particles are needed to effectively model the influence of agglomeration in the particle arrangement

Non-monotonic swelling of a macroion due to correlation-induced charge inversion

It is known that a large, charged body immersed in a solution of multivalent counterions may undergo charge inversion as the counterions adsorb to its surface. We use the theory of charge inversion to examine the case of a deformable, porous macroion which may adsorb multivalent ions into its bulk to form a three-dimensional strongly-correlated liquid. This adsorption may lead to non-monotonic changes in the size of the macroion as multivalent ions are added to the solution. The macroion first shrinks as its bare charge is screened and then reswells as the adsorbed ions invert the sign of the net charge. We derive a value for the outward pressure experienced by such a macroion as a function of the ion concentration in solution. We find that for small deviations in the concentration of multivalent ions away from the neutral point (where the net charge of the body is zero), the swollen size grows parabolically with the logarithm of the ratio of multivalent ion concentration to the concentration at the neutral point.Comment: 7 pages, 4 figures; typos fixed; final published versio

Flipped Learning in Computer Science for non-native English-speaking Students: Case Study

While flipped learning courses generally follow a basic concept (web-based technologies outside the classroom and instructor-student interaction during class time), the detailed design of the delivery builds on the instructor\u27s personal experience, knowledge, teaching philosophy and goals of the course. When designing such a course, it is very important to also take into consideration the teaching and learning environment and culture of the students. Flipped learning is not a fully grounded category in education literature; the area has been examined by a number of studies, but the methodology and its concept is not completely standardized [1, 2]. The flipped learning concept reached the Republic of Korea (RoK) over a decade ago as a result of challenges East Asian universities were facing: to enhance the quality of education, to keep up with international trends and to make education as cost-effective as possible [3]. Tham and Tham [4] reviewed blended learning practices in higher education across Asia and noted that while there are a number of challenges in delivering blended modules in general, in Korea, there was much interest and approval for such a format. As a new, and in Western countries highly praised, methodology, it requires careful consideration and examination. Keeping in mind that Korean education methodology and students\u27 school behavioural patterns are different from Western higher-education systems, this paper compares the recommendations made and features considered ideal by the literature, to the reality of a flipped learning course delivered in the RoK while acknowledging that there is no absolute recipe to a successful flipped learning course. It is also worth noting that this case study is also an intensive summery delivery of technical course material by a native English speaking lecturer to non-native English speaking students. The case study presented in this paper is the first flipped learning course examined in such a setting, with similar courses being developed for delivery in the near future. Therefore, lessons learned from this case study will help in designing and implementing courses in the future. Similarly, it is important to note that this case study pre-dates the Covid19 global pandemic (taking place in the Summer of 2019), meaning that social distancing and other related concerns were not relevant during delivery. However, knowing about the successes and challenges of such formats is of particular relevance to educators in more recent times, as we have become more reliant on blended/online teaching and learning. Based on our final findings presented in this case study it seems certain that the flipped learning methodology has a future in Korean higher education, as long as the course is designed for the specific setting: for example, emphasis should be put on student/teacher discourse in order to encourage naturally shy students to engage with the instructor, to increase constructive interaction throughout the course

A mental health and wellbeing chatbot: user event log analysis

Background: Conversational user interfaces, or chatbots, are becoming more popular in the realm of digital health and well-being. While many studies focus on measuring the cause or effect of a digital intervention on people’s health and well-being (outcomes), there is a need to understand how users really engage and use a digital intervention in the real world. Objective: In this study, we examine the user logs of a mental well-being chatbot called ChatPal, which is based on the concept of positive psychology. The aim of this research is to analyze the log data from the chatbot to provide insight into usage patterns, the different types of users using clustering, and associations between the usage of the app’s features. Methods: Log data from ChatPal was analyzed to explore usage. A number of user characteristics including user tenure, unique days, mood logs recorded, conversations accessed, and total number of interactions were used with k-means clustering to identify user archetypes. Association rule mining was used to explore links between conversations. Results: ChatPal log data revealed 579 individuals older than 18 years used the app with most users being female (n=387, 67%). User interactions peaked around breakfast, lunchtime, and early evening. Clustering revealed 3 groups including “abandoning users” (n=473), “sporadic users” (n=93), and “frequent transient users” (n=13). Each cluster had distinct usage characteristics, and the features were significantly different (P&lt;.001) across each group. While all conversations within the chatbot were accessed at least once by users, the “treat yourself like a friend” conversation was the most popular, which was accessed by 29% (n=168) of users. However, only 11.7% (n=68) of users repeated this exercise more than once. Analysis of transitions between conversations revealed strong links between “treat yourself like a friend,” “soothing touch,” and “thoughts diary” among others. Association rule mining confirmed these 3 conversations as having the strongest linkages and suggested other associations between the co-use of chatbot features. Conclusions: This study has provided insight into the types of people using the ChatPal chatbot, patterns of use, and associations between the usage of the app’s features, which can be used to further develop the app by considering the features most accessed by users.Validerad;2023;Nivå 2;2023-08-14 (joosat);Funder: Interreg Northern Periphery and Arctic Programme (grant number 345)Licens fulltext: CC BY License</p

Inter- and intra-observer reliability and agreement of O2Pulse inflection during cardiopulmonary exercise testing: a comparison of subjective and novel objective methodology.

Cardiopulmonary exercise testing (CPET) is the 'gold standard' method for evaluating functional capacity, with oxygen pulse (O2Pulse) inflections serving as a potential indicator of myocardial ischaemia. However, the reliability and agreement of identifying these inflections have not been thoroughly investigated. This study aimed to assess the inter- and intra-observer reliability and agreement of a subjective quantification method for identifying O2Pulse inflections during CPET, and to propose a more robust and objective novel algorithm as an alternative methodology. A retrospective analysis was conducted using baseline data from the HIIT or MISS UK trial. The O2Pulse curves were visually inspected by two independent examiners, and compared against an objective algorithm. Fleiss' Kappa was used to determine the reliability of agreement between the three groups of observations. The results showed almost perfect agreement between the algorithm and both examiners, with a Fleiss' Kappa statistic of 0.89. The algorithm also demonstrated excellent inter-rater reliability (ICC) when compared to both examiners (0.92-0.98). However, a significant level (P ≤0.05) of systematic bias was observed in Bland-Altman analysis for comparisons involving the novice examiner. In conclusion, this study provides evidence for the reliability of both subjective and novel objective methods for identifying inflections in O2Pulse during CPET. These findings suggest that further research into the clinical significance of O2Pulse inflections is warranted, and that the adoption of a novel objective means of quantification may be preferable to ensure equality of outcome for patients

Dose-related effects of smallpox vaccine

BACKGROUND: We conducted a double-blind, randomized trial of three dilutions of vaccinia virus vaccine in previously unimmunized adults in order to assess the clinical success rates, humoral responses, and virus-specific activity of cytotoxic T cells and interferon-gamma-producing T cells. METHODS: Sixty healthy adults were inoculated intradermally by bifurcated needle with undiluted vaccine (dose, 10(7.8) plaque-forming units [pfu] per milliliter), a 1:10 dilution (dose, 10(6.5) pfu per milliliter), or a 1:100 dilution (dose, 10(5.0) pfu per milliliter); there were 20 subjects in each group. The subjects were monitored with respect to vesicle formation (an indicator of successful vaccination), the viral titer at the time of peak lesion formation, antiviral antibodies, and cellular immune responses. RESULTS: A vaccinia vesicle developed in 19 of the 20 subjects who received undiluted vaccine (95 percent), 14 of the 20 who received the 1:10 dilution (70 percent), and 3 of the 20 who received the 1:100 dilution (15 percent). One month after vaccination, 34 of 36 subjects with vesicles had antibody responses, as compared with only 1 of 24 subjects without clinical evidence of vaccinia virus replication. Vigorous cytotoxic T-cell and interferon-gamma responses occurred in 94 percent of subjects with vesicles, and a cytotoxic T-cell response occurred in only one subject without a vesicle. CONCLUSIONS: The vaccinia virus vaccine (which was produced in 1982 or earlier) still has substantial potency when administered by a bifurcated needle to previously unvaccinated adults. Diluting the vaccine reduces the rate of successful vaccination. The development of vesicular skin lesions after vaccination correlates with the induction of the antibody and T-cell responses that are considered essential for clearing vaccinia virus infections

Chatbots to Support Mental Wellbeing of People Living in Rural Areas: Can User Groups Contribute to Co-design?

Digital technologies such as chatbots can be used in the field of mental health. In particular, chatbots can be used to support citizens living in sparsely populated areas who face problems such as poor access to mental health services, lack of 24/7 support, barriers to engagement, lack of age appropriate support and reductions in health budgets. The aim of this study was to establish if user groups can design content for a chatbot to support the mental wellbeing of individuals in rural areas. University students and staff, mental health professionals and mental health service users (N = 78 total) were recruited to workshops across Northern Ireland, Ireland, Scotland, Finland and Sweden. The findings revealed that participants wanted a positive chatbot that was able to listen, support, inform and build a rapport with users. Gamification could be used within the chatbot to increase user engagement and retention. Content within the chatbot could include validated mental health scales and appropriate response triggers, such as signposting to external resources should the user disclose potentially harmful information or suicidal intent. Overall, the workshop participants identified user needs which can be transformed into chatbot requirements. Responsible design of mental healthcare chatbots should consider what users want or need, but also what chatbot features artificial intelligence can competently facilitate and which features mental health professionals would endorse

Insights and lessons learned from trialling a mental health chatbot in the wild

This study reports on the development and 'in the wild' trialling of a chatbot (ChatPal) which promotes good mental wellbeing. A stakeholder-centered approach for design was adopted where end users, mental health professionals and service users were involved in the design which was centered around positive psychology. In the wild usage of the chatbot was investigated from Jul-20-Mar-21. Exploratory analyses of usage metrics were carried out using the event log data. User tenure, unique usage days, total chatbot interactions and average daily interactions were used in K-means clustering to identify user archetypes. The chatbot was used by a variety of age groups (18-65+) and genders, mainly those living in Ireland. K-means clustering identified three clusters: sporadic users (n=4), frequent transient users (n=38) and abandoning users (n=169) each with distinct usage characteristics. This study highlights the importance of event log data analysis for making improvements to the mental health chatbot.</p