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In the Fall 2020 semester, faculty at colleges and universities across the United States changed course structures in many ways to adapt to the COVID-19 pandemic. At our institution, a regional comprehensive open-access university in the Midwest, campus was open for in-person courses with specific COVID precautions in place. Faculty were given substantial flexibility in how they restructured their courses, within constraints of socially distanced classrooms and accessibility for students. In prior semesters, our upper-division undergraduate animal physiology course met fully in-person for three 50-minute lecture periods and one 3-hour lab period per week. In fall 2020, a previously planned shift to a 4-day class week had led to a change to two 80-minute lecture periods and one 3-hour lab period per week. To align with COVID mitigation policies, the class was further restructured to a hybrid format as follows: For lecture, half of the students attended the first in-person class meeting of the week, and the other half attended the second in-person class meeting of the week. The same topics were covered in both in-person sessions in a given week and all in-person classes were recorded for asynchronous viewing by students who did not attend in person that week. The remaining lecture content was posted online via instructor-produced video lectures, outside videos or animations, and online homework. For lab sessions, half of the students attended in-person each week, and the other half were assigned activities to complete remotely, such as PhysioEx lab simulations, online documentary videos, or low-tech hands-on activities that could be completed at home. In the 8th week of the semester, students were surveyed about use of course resources and attitudes about the course and the fall semester in general. A high percentage of survey respondents reported that they ?frequently? accessed recordings of live class sessions (14/20 respondents) and online-only video lectures (17/21 respondents). Technology issues such as slow internet or device incompatibility were reported by 57% of respondents. In response to open-ended questions about positives and negatives of the course structure, examples of positives included accessibility of class recordings and other materials, flexibility, and ?COVID-friendly?. The majority of negative comments about the course structure involved a general dislike of online learning. The course grade distribution was within the range of grade distributions from prior offerings of the course by the same instructor, suggesting that student learning was not significantly impaired by the change in course structure, although negative impacts on individual students cannot be ruled out. Course structure-related comments on university student evaluation forms included ?easy to maintain studies during quarantine? and ?I actually really enjoyed the format?. In conclusion, the hybrid format for this course was generally well-received by this group of upper-division biology majors and represents a viable strategy for adapting a biology majors course to the COVID-19 pandemic.

Guidelines describe the general process of in-situ compressive strength assessment. This process is divided into three main steps, data collection (using nondestructive testing and destructive testing), model identification and strength assessment. Three estimation quality levels (EQL) are defined depending on the targeted accuracy of strength assessment, based on three parameters, mean value of strength and standard deviation of strength on a test region and local value of strength. All the necessary definitions (test location, test reading, test region, test result, …) are given and the different stages of data collection, i.e. planning, NDT methods, cores (dimensions, conservation, location, testing, etc) are described. The identification of the conversion model is detailed and a specific attention is paid to the assessment of test result precision (TRP). For the identification of the model parameters, two options are considered either the development of a specific model or the calibration of a prior model. A specific option is also proposed, namely the bi-objective approach. Finally, the quantification of the errors of model fitting and strength prediction is described. The global methodology is synthetized in a flowchart.

A benchmark is carried out in order to compare how 13 experts define and can carry out an NDT investigation program and derive strength values from NDT measurements. The benchmark is based on simulations, which reproduces a synthetic data set corresponding to a grid of twenty 3m-high columns defining the structure of a building made up of beams and columns. The experts must assess the mean and the standard deviation of compressive strength. Three levels of assessment are considered corresponding to different quantities of test results (destructive or non destructive) available for the experts. The comparison of the various strategies used by the experts and the analysis of results enables the identification of the most influential parameters that define an investigation approach and influence its efficiency and accuracy. A special emphasis is placed on the magnitude of the measurement error. A model of the investigation strategy is also proposed.

Significance Lack of human data on influenza virus aerosol shedding fuels debate over the importance of airborne transmission. We provide overwhelming evidence that humans generate infectious aerosols and quantitative data to improve mathematical models of transmission and public health interventions. We show that sneezing is rare and not important for—and that coughing is not required for—influenza virus aerosolization. Our findings, that upper and lower airway infection are independent and that fine-particle exhaled aerosols reflect infection in the lung, opened a pathway for a deeper understanding of the human biology of influenza infection and transmission. Our observation of an association between repeated vaccination and increased viral aerosol generation demonstrated the power of our method, but needs confirmation., Little is known about the amount and infectiousness of influenza virus shed into exhaled breath. This contributes to uncertainty about the importance of airborne influenza transmission. We screened 355 symptomatic volunteers with acute respiratory illness and report 142 cases with confirmed influenza infection who provided 218 paired nasopharyngeal (NP) and 30-minute breath samples (coarse >5-µm and fine ≤5-µm fractions) on days 1–3 after symptom onset. We assessed viral RNA copy number for all samples and cultured NP swabs and fine aerosols. We recovered infectious virus from 52 (39%) of the fine aerosols and 150 (89%) of the NP swabs with valid cultures. The geometric mean RNA copy numbers were 3.8 × 104/30-minutes fine-, 1.2 × 104/30-minutes coarse-aerosol sample, and 8.2 × 108 per NP swab. Fine- and coarse-aerosol viral RNA were positively associated with body mass index and number of coughs and negatively associated with increasing days since symptom onset in adjusted models. Fine-aerosol viral RNA was also positively associated with having influenza vaccination for both the current and prior season. NP swab viral RNA was positively associated with upper respiratory symptoms and negatively associated with age but was not significantly associated with fine- or coarse-aerosol viral RNA or their predictors. Sneezing was rare, and sneezing and coughing were not necessary for infectious aerosol generation. Our observations suggest that influenza infection in the upper and lower airways are compartmentalized and independent.

International audience; This recommendation is written to improve the assessment of the in situ. Compressive strength of concrete in existing structures by combining core strength values and non-destructive measurements. Both average strength and its scatter are considered. Deriving a characteristic strength from the assessment results is not considered here. The recommendation applies for most common techniques (ultrasonic pulse velocity, rebound hammer, pull-out) but also for less common techniques (penetration test, etc.). The recommendation does not apply to situations in which no core has been taken from the existing structure and is limited to situations where NDT is combined with cores. The recommendation introduces the concept of Estimation Quality Level, corresponding to the target of assessment, and which is put in relation with the means and strategy developed for assessing concrete. The text details all steps that must be followed from the data gathering to the checking of the quality of the final estimations. For more clarity, an illustrative example is described for each step of the assessment process.

Background: Uncertainty about the relative importance of modes of influenza transmission, particularly airborne droplet nuclei (aerosols), fuels controversy concerning recommendations for healthcare worker protection during pandemics. In-depth review by an expert panel, a proof-of-concept study, and an international workshop concluded that human challenge-transmission studies in well-controlled environments would be the most promising approach to fill this critical knowledge gap. Methods: Healthy, seronegative volunteer 'Donors' (N=52) were randomly selected for intranasal challenge with influenza A/Wisconsin/67/2005 (H3N2). Seronegative 'Recipients' randomised to Intervention (IR, N=40) or Control (CR, N=35) groups were exposed to Donors for four days. IRs wore face shields and hand sanitised frequently to limit large droplet and contact transmission. Numbers of Donors and days of Recipient exposure were increased compared to proof-of-concept to increase secondary attack rate (SAR). Symptoms were monitored and viral shedding in nasopharyngeal swabs and exhaled breath viral aerosols were quantified by reverse-transcriptase PCR (qRT-PCR). Serological specimens were analysed for evidence of seroconversion. Findings: Intranasal inoculation produced an infection rate of 81% (42/52); 60% (25/42) of infected Donors had influenza-like illness, 14% (6/42) had fever, and 26% (11/42) had mild or no symptoms. Viral aerosol shedding was observed from 26% (11/42) of the infected Donors. One transmitted infection was confirmed by serology in a CR, yielding a SAR of 2·9% among CR, 0% in IR (p = 0·47 for group difference), and 1·3% overall. Interpretation: The SAR observed was significantly less than 16% (p

Concrete is a highly adaptable material and capable of considerable variation, development and innovation, as can be seen from the pages of journals such as the Proceedings of the Institution of Civil Engineers – Construction Materials. This briefing paper describes the 43rd Convention of the Institute of Concrete Technology, which took place on 26 March 2015. The event provided an opportunity for practitioners and researchers to meet and communicate, and to showcase the variety and diversity of current innovations, developments and applications in concrete and cement technology, including carbon-negative aggregate, polycarboxylate ether superplasticisers, waste wood in concrete, steel fibres, calcium aluminate cements, superabsorbent polymers and sprayed concrete tunnel linings.

Strength assessment of concrete in existing structures is a key issue. Many non destructive techniques (NDT) are available which can provide information about the material condition and several approaches can be used to derive strength estimates from NDT test results. However, common practice suffers from many drawbacks: (a) it is difficult to ascertain the level of accuracy/confidence of concrete strength estimates, (b) one lacks established guidelines for estimating the concrete strength variability, (c) the best way to combine NDT methods and coring remains an open issue. The RILEM TC 249 “Non destructive in situ strength assessment of concrete” is addressing these problems. A benchmark was carried out in order to compare (a) how experts define and can carry out an NDT investigation program and (b) how experts derive strength values from the NDT measurements. The benchmark was based on synthetic simulations which reproduced a synthetic data set corresponding to a grid of twenty 3 m-high columns defining a single-storey building structure. The comparison of the various strategies and the analysis of results enabled identification of the most influential parameters that define an investigation approach and influence its efficiency and accuracy. A special emphasis was placed on the magnitude of the measurement error. A model of the investigation strategy is proposed, that will be detailed in future guidelines. The reader is invited to refer to a companion paper (Alwash et al. in Mater Struct, 1. doi: 10.1617/s11527-016-0962-x ), based on more extensive Monte-Carlo simulations of the same case-study, which analyzes and quantifies the efficiency of the investigation strategies with respect to both average strength and strength variability assessment, in order to draw conclusions based on rational analyses rather than on the element of chance.

Concrete Solutions contains the contributions from some 30 countries to Concrete Solutions, the 6th International Conference on Concrete Repair (Thessaloniki, Greece, 20-23 June 2016). Strengthening and retrofitting are major themes in this volume, with NDT and electrochemical repair following closely, discussing the latest advances and technologies in concrete repair. The book brings together some interesting and challenging theoretical approaches and questions if we really understand and approach such topics as corrosion monitoring correctly. Concrete Solutions is an essential reference work for those working in the concrete repair field, from engineers to architects and from students to clients. The Concrete Solutions Series of international conferences on concrete repair began in 2003 with a conference held in St. Malo, France in association with INSA Rennes. Subsequent conferences have seen the Series partnering with the University of Padua (Italy) in 2009, with TU Dresden (Germany) in 2011 and with Queen’s University Belfast (Northern Ireland) in 2014. In 2016 Thessaloniki (Greece) hosted the conference, partnering with both Aristotle University of Thessaloniki (AUTH) and Democritus University of Thrace (DUTH). The next conference in the series will be held in 2019 in Istanbul.

It was proposed to add a further nine storeys to an office building for additional office accommodation. A four level car park was in use beneath the building to provide parking for some 200 cars. Satisfactory structural calculations and plans for structural alterations had been carried out for the additional loadings on the car park, but a survey revealed that the car park deck slabs were suffering serious deterioration due to the carriage of de-icing salts on the underside of cars. Deposition of these salts had caused the onset of severe reinforcement corrosion. An initial survey revealed that the concrete in the slabs was of very low quality, equivalent probably to a 20 Grade and cover to the steel was very variable and often low. This survey included a visual survey, half cell potential measurements, chemical analyses for cement and chloride content and a detailed petrographic appraisal of the concrete. The survey revealed high levels of chloride contamination in the slab surface over much of its area and high half cell potentials in most areas examined. The Client had requested remedial proposals and initial options for electrochemical desalination or cathodic protection were put forward, together with budget costings. The Client wished to delay repairs for several years to fit in with their maintenance budget and to avoid disruption at a difficult time. It was proposed that the appraisal be extended to establish the location and distribution of the steel reinforcement in the deck slabs at critical positions around column heads, the condition of the steel, including section loss due to corrosion and the corrosion rate by linear polarisation techniques. This would then enable a decision to be made on the safety of delaying repairs and any additional problems due to further spalling which might be anticipated. It was found that the corrosion rate was reasonably low at the time of the first survey and that it was considered quite feasible to delay repairs for up to three years as requested by the Client. Further monitoring over the first year was recommended to check on corrosion rates over the different seasons. The second survey revealed that both half cell potential and corrosion rates were variable and that corrosion rates doubled between readings taken at the end of the autumn and the end of the winter periods. This confirms the necessity not to rely on only a single set of data readings when undertaking this type of work.

Understanding defects, testing and inspection Michael G. Grantham The petrographic examination of concrete and concrete repairs Mike Eden Structural aspects of repair Jonathan G.M. Wood Cathodic protection of structures John P. Broomfield Cathodic protection using thermal sprayed metals John P. Broomfield Service life aspects of cathodic protection of concrete structures Rob B. Polder and Willy H.A. Peelen Instrumentation and monitoring of structures John P. Broomfield Electrochemical chloride extraction Ulrich Schneck Electrochemical realkalisation Michael G. Grantham Corrosion inhibitors Michael G. Grantham European standards for concrete repair Peter Robery Concrete repair - a contractor's perspective John Drewett Sprayed concrete for repairing concrete structures Graham Taylor Durability of concrete repairs G.P. Tilly Service-life modelling for chloride-induced corrosion Rob B. Polder Case studies in the use of FRPs Paul Russell Coatings for concrete Shaun A. Hurley Index

Uncertainty about the importance of influenza transmission by airborne droplet nuclei generates controversy for infection control. Human challenge-transmission studies have been supported as the most promising approach to fill this knowledge gap. Healthy, seronegative volunteer ‘Donors’ (n = 52) were randomly selected for intranasal challenge with influenza A/Wisconsin/67/2005 (H3N2). ‘Recipients’ randomized to Intervention (IR, n = 40) or Control (CR, n = 35) groups were exposed to Donors for four days. IRs wore face shields and hand sanitized frequently to limit large droplet and contact transmission. One transmitted infection was confirmed by serology in a CR, yielding a secondary attack rate of 2.9% among CR, 0% in IR (p = 0.47 for group difference), and 1.3% overall, significantly less than 16% (p, Author summary Understanding the relative importance of influenza modes of transmission informs strategic use of preventive measures to reduce influenza risk in high-risk settings such as hospitals and is important for pandemic preparedness. Given the increasing evidence from epidemiological modelling, exhaled viral aerosol, and aerobiological survival studies supporting a role for airborne transmission and the potential benefit of respirators (and other precautions designed to prevent inhalation of aerosols) versus surgical masks (mainly effective for reducing exposure to large droplets) to protect healthcare workers, more studies are needed to evaluate the extent of risk posed airborne versus contact and large droplet spray transmission modes. New human challenge-transmission studies should be carefully designed to overcome limitations encountered in the current study. The low secondary attack rate reported herein also suggests that the current challenge-transmission model may no longer be a more promising approach to resolving questions about transmission modes than community-based studies employing environmental monitoring and newer, state-of-the-art deep sequencing-based molecular epidemiological methods.