Two-stage Testing Research Articles

Zim4rv: an R package to modeling zero-inflated count phenotype on regional-based rare variants

BackgroundWith the advance of next-generation sequencing, various gene-based rare variant association tests have been developed, particularly for binary and continuous phenotypes. In contrast, fewer methods are available for traits not following binomial or normal distributions. To address this, we previously proposed a set of burden- and kernel-based rare variant tests for count data following zero-inflated Poisson (ZIP) distributions, referred to as ZIP-b and ZIP-k tests. We sought to extend the methods to accommodate negative binomial distribution and implemented these tests in a new R package.ResultsWe introduce ZIM4rv, an R package designed to analyze the association of rare variants with zero-inflated counts outcomes. Our package offers two novel models developed by our team: our previously proposed ZIP-b and ZIP-k tests, and the newly derived Negative Binomial Burden and Kernel Test (ZINB-b, ZINB-k). Additionally, we include an ad-hoc two-stage analysis, testing zero and non-zero as a binary outcome and non-zero as a continuous outcome, respectively. To showcase the utility of our platform, we applied this program to analyze neuritic plaque count data from the ROSMAP cohort.ConclusionThe R package ZIM4rv presents an integrated workflow for conducting association tests on a set of rare variants with zero-inflated counts data.

Efficacy of a hybrid take home and in class summative assessment for the postsecondary physics classroom

Abstract Assigning course grades to students requires obtaining accurate measures of the students’ understanding and knowledge of the topic. The induced stress from a traditional summative assessment is known to negatively impact student grades, confounding the connection between knowledge and test grades. Documented approaches to reduce stress during examinations can lead to a distracting testing environment (two-stage tests) or are subject to cheating (take-home tests). We have developed a hybrid take-home/in-class exam that avoids such difficulties. We present herein the responses from student surveys conducted after each exam. The results of the surveys indicate that the hybrid exam method reduces test anxiety while improving students’ self-reported mastery of physics, as compared to traditional in-class summative assessments. These findings are significant at the p < 0.05 level. Lastly, we discuss the difficulties encountered in applying this test approach.

The Impact of Two-Stage Testing and Other Tutorial Co-Learning Activities on Cohort Cohesion and Learning Outcomes in a Large-Enrollment Undergraduate Course

Large enrollments in undergraduate courses pose several teaching and learning challenges that impact students’ learning experience and performance. Implementing co-learning activities in tutorials of large courses can help mitigate these challenges and improve the learning environment. One type of collaborative learning activity that has become increasingly popular is two-stage testing but there are limitations to how two-stage testing has been conducted. We undertook a study to elucidate whether our modified two-stage testing protocol and other co-learning activities performed in tutorials can enhance the learning experiences of undergraduate students and foster a sense of community in a large-enrollment research methods course. The specific aims of our study were to: 1) Assess whether co-learning activities including two stage testing in tutorials improves learning outcomes and fosters cohort cohesion in a large-enrollment junior undergraduate science course. 2) Evaluate the impact of our modified two-stage testing approach on student learning and long-term retention. To assess cohort cohesion students were asked to complete a survey and were invited to participate in focus groups. Results indicated that tutorials did foster cohort cohesion among students in the tutorial. The tutorial activities helped scale down the course size and connect with their peers. We tested our modified two-stage testing protocol by administering a two-stage test (an individual test consisting of short-answer questions followed by a group test that was comprised of a subset of the individual test questions that was completed during tutorials). Approximately three months after the individual test, a retention test was administered. Student grades were significantly higher in group tests compared to the individual tests. Interestingly, students on average scored 6.2% higher on the retention test questions that were from the group test, compared to questions that were only on the individual test. These results support the idea that group tests help improve student retention. Students reported tutorials and two-stage testing to be a positive learning experience.

Investigation of creep damage accumulation under variable loading conditions in nickel-based single crystal superalloys

Nickel-based single crystal (SX) turbine blades typically experience varying load conditions during operation. It is essential to consider the effects of changing stress and temperature when evaluating creep damage. The commonly used time-fraction method, based on the linear damage rule (LDR), has been demonstrated to be inconsistent with experimental results under certain loading conditions. There is a lack of research on damage accumulation under variable loading conditions specifically for SX superalloy. This paper conducted two-stage creep experiments for SX superalloy DD6 at 980 °C with stress levels of 230 MPa and 320 MPa, and at 1050 °C with stress levels of 135 MPa and 230 MPa. The load for the experiment was set based on the typical operating conditions of the SX turbine blades. The evolution of the microstructure under variable loading was observed using scanning electron microscope (SEM) and transmission electron microscope (TEM). The result of creep experiments revealed that the damage accumulation behavior of the SX superalloy does not conform to the LDR. Furthermore, in two-stage loading tests, the creep damage accumulation behavior differs from the classical sequence effect of fatigue loading. SEM and TEM analyses suggested that this phenomenon might be associated with the varying degradation rates of microstructures in SX superalloy.

Effects of Concurrent Training on Resuscitation and Cognitive Performance in Paramedics-A Pilot Study.

Paramedics work under physically and cognitively demanding conditions to provide emergency care. As physical fitness could positively impact the quality of patient care, we investigated within a pilot study whether concurrent training (CT) affects work-related performance parameters in paramedics. At baseline (T1), 16 paramedics performed cardiopulmonary resuscitation whereby resuscitation performance (RP; total resuscitation quality, compressions with correct frequency, and correct ventilation), cognitive performance (CP; reaction time, divided attention, and working memory), and heart rate variability (HRV) were assessed (pre-exertion). Then, participants climbed seven floors carrying 20 kg of gear before completing the same assessments again (post-exertion). The baseline testing was followed by a CT intervention (12 weeks, three sessions/week). After the intervention (T2), the two-stage testing was repeated. We analyzed whether the pre-exertion and post-exertion values, as well as the difference between the pre-exertion and post-exertion values, changed from T1 to T2. Nine paramedics (male: N = 7; age = 26.3 (SD = 8.17) years) took part in the study. The comparison of the pre-exertion values showed significantly better reaction times (p = 0.001) and divided attention (p = 0.02) and a trend toward greater working memory and RP parameters at T2. Regarding the post-exertion values, significant improvements in working memory (p = 0.03) and a trend toward improved reaction time, divided attention, and RP occurred at T2. The difference between the pre- and post-exertion values did not change for any parameter from T1 to T2. HRV decreased significantly from pre- to post-exertion (T1: p = 0.01, T2: p = 0.01). These results indicate that CT is a promising training concept to improve RP and CP in paramedics and should therefore be investigated further to increase patient care quality.

Peran Inflasi Dalam Memoderasi Makro Ekonomi Terhadap Indeks Harga Saham Gabungan (IHSG)

Investors can use the Composite Stock Price Index (IHSG) to see how a country's economy is trending and decide when they will buy and sell shares. However, movements in the Composite Stock Price Index (IHSG) are not only influenced by the macroeconomic situation in the country, but also by the world economy. This research seeks to quantify the influence/impact of the Exchange Rate, Interest (BI Rate), GDP, World Gold Prices and World Oil Prices on the Composite Stock Price Index (IHSG) on the Indonesian Stock Exchange with Inflation as a moderating variable for the period 2020 - 2022. In this research, the research used is quantitative descriptive research. By using documentation techniques and library methods, secondary data was collected for data collection for this research. The research population consisted of 36 data using a sampling method, namely saturated sampling. The data in this study was tested using a program known as SmartPLS 3.2.9. The data analysis technique is using the Partial Least Squares structural equation which is carried out using two-stage modeling and testing procedures. The results of this research explain that the exchange rate, interest (BI Rate), world gold prices and world oil prices do not have a significant impact on the Composite Stock Price Index (IHSG). Meanwhile, GDP has a positive and significant impact on the IHSG. Inflation does not have the capability to moderate the relationship between exchange rates, interest (BI rate), GDP, world gold prices and world oil prices on the Composite Stock Price Index (IHSG)

Comparison of outcomes of percutaneous deep venous arterialization in multiple practice settings

ObjectiveWe compared the efficacy of percutaneous deep venous arterialization (pDVA) in patients with no-option chronic limb-threatening ischemia in the hospital vs in office-based laboratory (OBL) settings. MethodsA retrospective chart review was performed of all patients who underwent pDVA using off-the-shelf devices from January 2018 to March 2023 in a hospital and an OBL. We identified 73 eligible patients, 41 from a hospital setting (59% male; median age, 72 years; interquartile range, 18 years) and 32 from an OBL setting (59% males; 67 years; interquartile range, 16 years). All eligible patients were deemed to have no-option critical limb ischemia, had at least one patent proximal tibial artery available for the creation of an arteriovenous anastomosis, and were classified as having Rutherford classification IV or higher peripheral arterial disease. Patients were ineligible if classified as Rutherford classification III or lower, had active infection, did not have at least one appropriate venous target, and/or had rapidly progressing wounds requiring immediate major amputation. The primary outcome was major amputation-free survival (AFS). Secondary outcomes included technical success, limb salvage, survival, primary patency, reintervention rate, adverse events, and partial and complete wound healing. Outcomes were evaluated using Kaplan-Meier method, log-rank, and two-stage procedure tests. ResultsTechnical success was achieved in 70 patients (96%) with 1 hospital (2.4%) and 2 OBL (6.3%) patients lost to follow-up. Major AFS estimates at 6 months, 1 year, and 2 years were 51.4%, 40.4%, and 30.2% in the hospital group and 69.4%, 54.0%, and 49.5% in the OBL group, respectively. Partial wound healing estimates at 6 months, 1 year, and 2 years were 27.5%, 71.7%, and 81.2% in the hospital group and 62.7% at all time points in the OBL group. Complete wound healing estimates at 6 months, 1 year, and 2 years were 6.7%, 33.3%, and 33.3% in the hospital group and 5.3%, 37.7%, and 41.6% in the OBL group, respectively. There was no significant difference in major AFS (P = .13), limb salvage (P = .07), survival (P = .69), primary patency (P = .53), partial (P = .08), or complete wound healing (P = .79) between groups. Reintervention was performed in 8 hospital (20.5%) and 14 OBL (45.2%) patients. ConclusionspDVA is a feasible and safe procedure for no-option critical limb ischemia in the hospital and OBL setting without significant differences in outcomes at ≤2 years.

Semi-quantitative group testing for efficient and accurate qPCR screening of pathogens with a wide range of loads

BackgroundPathogenic infections pose a significant threat to global health, affecting millions of people every year and presenting substantial challenges to healthcare systems worldwide. Efficient and timely testing plays a critical role in disease control and transmission prevention. Group testing is a well-established method for reducing the number of tests needed to screen large populations when the disease prevalence is low. However, it does not fully utilize the quantitative information provided by qPCR methods, nor is it able to accommodate a wide range of pathogen loads.ResultsTo address these issues, we introduce a novel adaptive semi-quantitative group testing (SQGT) scheme to efficiently screen populations via two-stage qPCR testing. The SQGT method quantizes cycle threshold (Ct) values into multiple bins, leveraging the information from the first stage of screening to improve the detection sensitivity. Dynamic Ct threshold adjustments mitigate dilution effects and enhance test accuracy. Comparisons with traditional binary outcome GT methods show that SQGT reduces the number of tests by 24% on the only complete real-world qPCR group testing dataset from Israel, while maintaining a negligible false negative rate.ConclusionIn conclusion, our adaptive SQGT approach, utilizing qPCR data and dynamic threshold adjustments, offers a promising solution for efficient population screening. With a reduction in the number of tests and minimal false negatives, SQGT holds potential to enhance disease control and testing strategies on a global scale.

The Effect of Group-Individual Collaborative Testing on Primary Students’ Achievement in Reading Test

Collaborative testing—a two-stage testing modality in which students do tests as a group and individually—has been extensively researched and found to improve learning. However, most collaborative testing research has focused on non-English language learning. Therefore, this study examines the effects of group-individual collaborative testing (GICT) on English reading test achievement and student views of GICT. This sequential explanatory mixed-methods study gathered quantitative data from both treatment and control groups, primarily comprising students' correct answers, followed by qualitative insights derived from students' reflections on their learning experiences. Quantitative data demonstrates that GICT had a significant effect on students' reading achievement tests. While the qualitative data reveals that students considered GICT was a good reading testing modality, with some notes on the scoring method. Practice and research implications include 1) using GICT to test other language skills, 2) diversifying group composition, 3) giving more weight to the individual part score because students will retrieve more information during this stage, and 4) instilling collaborative learning values before testing.

A simulation of Al-Si coating growth under various hot stamping austenitization parameters: An artificial neural network model

22MnB5 hot stamping steels are pre-coated with an Al-Si layer to prevent oxidation and decarburization during the austenitization process, which includes heating and soaking within a furnace. Above ∼577 °C, the Al-Si coating transforms into Fe-Al and Fe-Al-Si intermetallic phases because of diffusion and solidification. In the present work, a deep neural network (DNN) model was developed to predict coating intermetallic growth under various heating rates and soaking conditions. The DNN model was trained using experimental data (energy dispersive x-ray spectroscopy chemical scans) collected from our coating growth characterization work. The heating rate (r), heating time (th), soaking time (ts), and the distance of each measured point away from the coating surface (d) are defined as input parameters, and the outputs are the weight percentage of Al, Fe, and Si. The model successfully predicted the chemical composition of the training dataset, which consisted of a single-stage heating process, followed by a soaking stage at a constant temperature. To validate the model, complex two-stage heating tests were conducted, and the intermetallic coating growth was quantified. The DNN model successfully predicted the two-stage heating test coating profiles, despite a minimal error that was due to the variation in as-received coating thickness. The DNN model predicts the overall experimental trends that show the heating rate has little effect on the transformed intermetallic species, but it affects the transformation rate of the intermetallic phases. Moreover, the higher heating rate test (after 750℃) resulted in the formation of the island shaped τ1 and/or τ2 phase, while the heating rate before 750℃ does not affect the morphology of the τ1 and/or τ2 phase.

Nodes of Experimental Installations for Testing Concrete for Creep

Installations of the mid-twentieth century for testing concrete for creep, as a rule, have significant wear and are not intended for testing new concrete. To carry out testing of modern highstrength concrete, their modernization and retrofitting is required. Due to the lack of standard technical solutions, design and survey work is required in preparation for testing. The purpose of the presented study was to study the nodes and elements of spring installations for determining the creep of concrete and to establish the possibility of their use under increased loads, to modernize installations for the possibility of testing samples of various lengths without complete disassembly, to ensure safety during such tests. To determine the strength and stiffness parameters of the springs, it was necessary to conduct two-stage tests with the development of special equipment. Also, according to the results of the evaluation of the hinge assemblies for axial load transfer to the sample, their replacement with a change in design solutions was required. According to the results of experimental studies, individual springs and thrust hinge elements were fragilely destroyed, in connection with which a hinge assembly of a new design was developed, changes have been made to the design of the installation to ensure the physical protection of maintenance personnel, a modular system of steel spacers with protection against horizontal movement has been developed, which makes it possible to test samples of different lengths on existing installations without changing the configuration of the installations themselves. An important result of the work is the proposed system of double experimental control, when first a random test of individual elements is carried out to assess the possible level of loads on the equipment, then a continuous control of the already assembled test installations is carried out for large loads relative to the planned experiment. Only in this case it is possible to simultaneously ensure high reliability of the results obtained during testing, reliability and durability of the equipment. Moreover, it is impossible to carry out such work only numerically without testing, as practice has shown.

Experimental and numerical investigation of adhesively bonded kfrp/steel double strap joints incorporating eggshell powder-toughened epoxy adhesive

Due to the environmental concerns, the application of natural FRPs to replace synthetic fibre as a strengthening material has increased. Kenaf fibre-reinforced polymer (KFRP) has comparable specific strength with glass fibre-reinforced polymer (GFRP). Moreover, epoxy resin is widely used as a matrix of composites and adhesives; however, it has low shear strength. Improvement of epoxy properties is therefore required, for example, by incorporating biofiller such as eggshells from household waste, which contain calcite, to improve its shear strength. Testing series includes variations of KFRP bond length, KFRP thickness and eggshell filler volume fractions. All the DSJ specimens underwent a two-stage testing process, experimentally and numerically. In Stage 1, experimental work was performed on the specimens through quasi-static tensile tests, following the ASTM D3528–96. In Stage 2, numerical studies were conducted to predict the strength using the extended finite element method (XFEM) within ABAQUS CAE. Subsequently, the strength prediction from developed 2-D FEA models was validated by the experimental datasets. All testing specimens exhibited KFRP rupture mode. For all the studied overlap lengths, the joint strength increased with the increase of the studied composite's adherend thickness (1 - 4 mm); however, the overlap length reached the optimum at the overlap length of 80 mm, where beyond that overlap length, the joint strength tended to decrease. The maximum joint strength is achieved with a combination of 80 mm bond length and 4 mm KFRP thickness, resulting in a 226.5% enhancement compared to the baseline (composite thickness of 1 mm, with adhesive without filler). Moreover, it was found that volume fraction of 5% eggshell was the optimum. The strength prediction was performed using an extended finite element method (XFEM), In general, there were good agreements in both experimental datasets and XFEM models, with discrepancies of less than 16.1% (averaging less than 8%). The FEA modelling approaches are promising for predicting the joint strength of KFRP/steel DSJ.

Convolutional neural network-assisted diagnosis of midpalatal suture maturation stage in cone-beam computed tomography

ObjectivesThe selection of treatment for maxillary expansion is closely related to the calcification degree of the midpalatal suture. A classification method for individual assessment of the morphology of midpalatal suture in cone-beam computed tomography (CBCT) is useful for evaluating the calcification degree. Currently, convolutional neural networks (CNNs) have been introduced into the field of oral and maxillofacial imaging diagnosis. This study validated the ability of CNN models in assessing the maturation stage of the midpalatal suture. MethodsThe existing CNN model ResNet50 was trained to locate the CBCT transverse plane which contained a complete midpalatal suture. ResNet18, ResNet50, RessNet101, Inception-v3, and Efficientnetv2-s models were trained to evaluate the midpalatal suture maturation stage. Multi-class classification metrics, accuracy, recall, precision, F1-score, and area under the curve values from the receiver operating characteristic curve were used to evaluate the performance of the models, and gradient-weighted class activation map technology was utilised to visualise five midpalatal suture maturation stages for each model. ResultsResnet50 demonstrated an accuracy of 99.74 % in identifying the transverse plane that contained the complete midpalatal suture. The highest accuracies achieved on the two-stage, three-stage, and five-stage maturation classification tests were 95.15, 88.06, and 75.37 %, all of which exceeded the average accuracy of three experienced orthodontists. ConclusionsThe CNN model can locate the plane of the midpalatal suture in CBCT images and can assist clinicians in assessing the maturation stage of the midpalatal suture to select the means of maxillary expansion. Clinical significanceThe application of artificial intelligence on CBCT midpalatal suture plane localisation and maturation stage evaluation enhances diagnostic and treatment efficiency and accuracy of individual assessment of midpalatal suture calcification degree. Additionally, it assists the clinical palatal expansion technique in achieving ideal results.

Two-Stage Optimal Hypotheses Testing for a Model of Stegosystem with an Active Adversary

We study the information-theoretic model of stegosystem with an active adversary, where unlike a passive adversary he can not only read but also write. The legitimate sender as well as the adversary can embed or not a message in the sending data. The receiver’s first task is to decide whether the communication is a covertext, data with no hidden message, or a stegotext, modified data with a hidden secret message. In case of stegotext, the receiver’s second task is to decide whether the message was sent by a legitimate sender or from an adversary. For this purpose an authenticated encryption from the legitimate sender is considered. In this paper we suggest two-stage statistical hypothesis testing approach from the receivers point of view. We propose the logarithmically asymptotically optimal testing for this model. As a result the functional dependence of reliabilities of the first and second kind of errors in both stages is constructed. A comparison of overall error probabilities with the situation of one stage hypotheses testing is discussed and the behaviour of functional dependences of reliabilities are illustrated.

A novel multistage forming process with intermediate annealing for PEMFC titanium bipolar plates with fine flow channels

In this study, the preform annealing process is first introduced to improve the formability of titanium bipolar plates, comprising preforming, intermediate annealing and final shaping stages. Heat-assisted two-stage tensile tests are conducted to understand the mechanical properties evolution and the underlying mechanisms. Optimal annealing at 600 °C enables plastic recovery and recrystallization in pre-deformed titanium sheets without significant grain growth, leading to an enhancement in both work hardening capacity and forming limits. Feasibility of applying preform annealing to titanium bipolar plates is verified with three case studies, demonstrating its effectiveness in enhancing thickness uniformity and forming limits of microchannels compared to conventional room-temperature stamping. This facilitates the fabrication of titanium bipolar plates with narrow pitch (1.2 mm), high aspect ratio (0.79) and narrow wall angle (5°). Hence, preform annealing provides a potential solution for fabricating titanium bipolar plates with fine flow channels for high-power proton exchange membrane fuel cells.

The Influence of Two-Stage Collaborative Testing on Peer Relationships: A Study of First-Year University Student Perceptions

Two-stage testing is a form of collaborative assessment that creates an active learning environment during test taking. In two-stage testing, students first complete an exam individually, and then complete a subset of the same questions as part of a learning team with the ultimate exam score being a weighted average of the individual and team portions. In the second (team-based) part of the exam, students are encouraged to discuss solutions until a consensus among team members is achieved, thus actively engaging students with course material and each other during the exam. A short open-ended survey was administered to students at the end of the semester, and the responses coded by thematic analysis, with themes generated using inductive coding based on the principles of grounded theory. The most important conclusion was that students overwhelmingly preferred two-stage tests for the development of positive peer relationships in class. The most common themes that emerged from student responses involved positive feelings from forced interaction with their peers, the benefits of meeting and socializing with other students, sharing of knowledge with others, and solidarity or positive affect towards the process of working as part of a team. Finally, students also expressed an overall preference for two-stage exams when compared to solely individual, one-stage exams.

Crystal plasticity-based analysis and modelling of grain size and strain path dependent micro-scaled deformation mechanisms of ultra-thin sheet metals

Multi-stage microforming is increasingly used in manufacturing of the miniaturized parts with complex structures and geometries. Optimization design of this type of manufacturing process, however, is still challenging due to its unknown intrinsic nature of the process. In the multi-stage deformation and microforming, the size effect (SE), the strain path change (SPC), and the intragranularly misoriented grain boundary (IMGB) generated in previous forming stage, are the main factors governing the deformation behaviors of ultra-thin sheets. To gain thorough insights into their influences on deformation and elucidate the associated micro-scaled mechanisms, SS 316L ultra-thin sheets with the thickness of 0.1 mm and different mean grain sizes (d¯) were used for two-stage tensile tests under the conditions with distinct pre-strain εpre and intersection angle θSPC (the angle between the previous loading direction and subsequent one). Mechanical tests reveal that increasing εpre and θSPC reduces the yield stress and hardening rate in SPC tension, but this reduction gets smaller after increasing d¯. This is because more IMGBs with complex pattern are formed in relatively large grains, raising the permanent deformation resistance inside grains in subsequent tension. To model the IMGB-induced hardening, the SPC-induced softening, and the SE-induced concurrent facilitations to the hardening and softening, an enhanced crystal plasticity constitutive relation was established. The physical essence that IMGB obstructs dislocation movement, is used to model the IMGB-induced hardening based on the interactions between the main slip planes and IMGBs. The hardening facilitation caused by increasing grain size is implicitly incorporated in determining the saturated slip resistance. Modelling of the SPC-induced softening is based on the high Schmid factor grain fraction and its influences are governed by pre-strain and the defined SPC parameter. The softening facilitation caused by coarsening grains is modelled in establishing the initial slip resistance in SPC deformation. The proposed simulation procedure and constitutive relationship help with accurately predicting the mechanical response and microstructure evolution in micro-scaled SPC deformation, and also provide a basis for modelling and design of the multi-stage microforming of complex miniaturized parts.

Comparative investigation on the influence of metakaolin, metaillite and steel slag as SCMs in mortar on the corrosion behavior of embedded steel

Abstract With the aim of saving CO2 in cement production, various approaches are currently being pursued in the development of new materials. One possibility is to reduce the ratio of clinker to cement by using supplementary cementitious materials (SCMs). Some SCMs like fly ash or granulated blast furnace slag have been used successfully in cement for a long time and their use is covered by standards. Since the availability of these materials cannot be ensured in the long term, alternative additives are also being tested. The results presented here were obtained as part of a joint research project that was carried out in cooperation with the Bauhaus University Weimar. In this study, three different SCMs are investigated with regard to their effect on the corrosion of steel embedded in mortars: A metakaolin, a metaillite, and a modified steel mill slag were each tested at a proportion of 30 wt.% in a CEM I reference cement. In the two-stage tests, the passivation behavior of steel in mortars was first investigated in electrochemical tests. Based on this, tests were carried out in leached solutions of the different binders with different Cl–/OH– ratios. The results show that all the blended types of cement investigated provide passivation of the steel in mortar. The use of the calcined clays metakaolin or metaillite resulted in higher polarization resistances and lower passive current densities as well as increased electrical resistivities, especially for metakaolin. The steel in mortar with the steel mill slag showed comparable electrochemical behavior to the OPC mortar. The tests in leached solutions slightly indicate a higher corrosion-inducing Cl–/OH– ratio when using metakaolin or steel mill slag.

The state of the pediatric HIV epidemic in Lesotho.

Lesotho does not have reliable data on HIV prevalence in children, relying on estimates generated from program data. The 2016 Lesotho Population-based HIV Impact Assessment (LePHIA) aimed to determine HIV prevalence among children 0-14 years to assess the effectiveness of the prevention of mother-to-child transmission (PMTCT) program and guide future policy. A nationally representative sample of children under 15 years underwent household-based, two-stage HIV testing from November 2016-May 2017. Children <18 months with a reactive screening test were tested for HIV infection using total nucleic acid (TNA) PCR. Parents (61.1%) or legal guardians (38.9%) provided information on children's clinical history. Children aged 10-14 years also answered a questionnaire on knowledge and behaviors. HIV prevalence was 2.1% [95% confidence interval (CI): 1.5-2.6]. Prevalence in 10-14 year olds (3.2%; 95% CI: 2.1, 4.2) was significantly greater compared to 0-4 year olds (1.0%; 95% CI: 0.5, 1.6). HIV prevalence in girls and boys was 2.6% (95% CI: 1.8-3.3) and 1.5% (95% CI: 1.0-2.1), respectively. Based on reported status and/or the presence of detectable antiretrovirals, 81.1% (95% CI: 71.7-90.4) of HIV-positive children were aware of their status, 98.2% (95% CI: 90.7-100.0) of those aware were on antiretroviral therapy (ART) and 73.9% (95% CI: 62.1-85.8) of those on ART were virally suppressed. Despite the roll-out of Option B+ in Lesotho in 2013, pediatric HIV prevalence remains high. Further research is required to understand the greater prevalence among girls, barriers to PMTCT, and how to better achieve viral suppression in children with HIV.

Fatigue damage accumulation of sandwich panels with glass/polypropylene faces and aluminum foam core under two-stage cyclic flexural loading

The two-stage cumulative flexural fatigue behavior of sandwich beams with glass/polypropylene (PP) faces and aluminum (Al) foam core was experimentally analyzed to study the loading sequence effect of the studied innovative sandwich composites subjected to variable-amplitude cyclic loading. The constant amplitude load–life curve was established first for reference. Subsequently, the two-stage cumulative fatigue tests were performed, and the high/low loading sequence and cycle ratio of the first stage were used as experimental variables in the cumulative fatigue tests. Experimental results showed that the sum of the cycle ratios of the two stages for all cases was approximately 1.3. Furthermore, the loading sequence effect was slight. Because the interaction of damage evolution for the two stages was nonsignificant, the different failure modes for the high- and low-loading levels contributed to the high sums of cycle ratios.