Search

Andropause is a condition surrounded by controversies, whether it be through its diagnosis or management. As we learn more about the pathophysiology of hypogonadism, our perspectives on the risks and benefits of testosterone therapy have shifted. We attempt to discuss the most modern and relevant points of controversy currently affecting the field. Throughout this review, we discuss the art of diagnosing hypogonadism as well as the association or lack thereof between testosterone replacement therapy and cardiovascular disease, prostate cancer, thrombosis, antiaging effects, exogenous steroid abuse, and diabetes mellitus.

Recent scholarship has suggested that artificial intelligence technology and autocratic regimes may be mutually reinforcing. We test for such a mutually reinforcing relationship in the context of facial-recognition AI in China. To do so, we gather comprehensive data on AI firms and government procurement contracts, as well as on social unrest across China during the last decade. We first show that autocrats benefit from AI: local unrest leads to greater government procurement of facial-recognition AI as a new technology of political control, and increased AI procurement indeed suppresses subsequent unrest. We then show that AI innovation benefits from autocrats’ suppression of unrest: the contracted AI firms innovate more both for the government and commercial markets, and are more likely to export their products; and noncontracted AI firms do not experience detectable negative spillovers. Taken together, these results suggest the possibility of sustained AI innovation under the Chinese regime: AI innovation entrenches the regime, and the regime’s investment in AI for political control stimulates further frontier innovation.

Background Severe or fulminant Clostridioides difficile infection (SFCDI) is associated with significant morbidity and mortality. Emerging evidence suggests fecal microbiota transplant (FMT) may be a promising therapy for SFCDI. Aim This systematic review determines the safety and efficacy of FMT in medically refractory SFCDI. Methods A systematic search of the literature was conducted using PubMed (1965 to 2020), Web of Science (1900 to 20), EMBASE (1974 to 2020), and Cochrane Review (1945 to 2020). Quality appraisal by NIH Study Quality Assessment tools, and data extraction were performed by two teams of independent researchers. The primary outcome was resolution of SFCDI 4 weeks after the final FMT. Pooled resolution rates were calculated using generalized linear mixed models estimates. Results Two hundred and forty patients from 10 studies (8 case series, 1 case–control and 1 randomized study) were included with 209 individual patient-level data. FMT resulted in resolution of SFCDI within 4 weeks in 211/240 individuals for a pooled estimate of 88% (95% confidence interval [CI]: 0.83 to 0.91). The mean number of FMT required was 1.6 for severe and 2.0 for fulminant CDI resolution. The pooled proportional estimates for patients requiring CDI-directed antimicrobials after FMT was 50% (95% CI: 0.06 to 0.94) for severe CDI and 67.0% (95% CI: 0.30 to 0.91) for fulminant CDI. Serious adverse event rates were low. Conclusion FMT appears effective in treating SFCDI patients with low adverse events, but requires multiple treatments with a significant proportion of patients requiring additional anti-CDI antibiotics to achieve resolution. The optimal route of FMT delivery remains unknown. The presence of pseudomembranous colitis may guide additional FMT or anti-CDI antibiotic treatment.

In this paper we further develop a Grassmannian technique used to prove results about very general hypersurfaces and present three applications. First, we provide a short proof of the Kobayashi conjecture given previously established results on the Green–Griffiths–Lang conjecture. Second, we completely resolve a conjecture of Chen, Lewis, and Sheng on the dimension of the space of Chow-equivalent points on a very general hypersurface, proving the remaining cases and providing a short, alternate proof for many of the previously known cases. Finally, we relate Seshadri constants of very general points to Seshadri constants of arbitrary points of very general hypersurfaces.

Social dimensions, as one of the three pillars of sustainability, are not fully considered in the planning, bidding, and design processes of construction projects, primarily due to a lack of standa...

Structural deterioration due to environmental and mechanical stressors is a major concern for civil and marine structures. Inspection actions can reduce uncertainties, facilitate decision-making on...

Corrosion-induced material loss can reduce the load-carrying capacity of structures, resulting in an increase of the probability and risk of failure. Currently, carbon steel is predominantly used in steel bridges due to its relatively low material cost, ease of fabrication at large scale and excellent material strength. However, low corrosion resistance of carbon steel can result in severe deterioration of bridges. As a result, a very high maintenance cost may be incurred during the service life of carbon steel bridges. A new type of corrosion-resistant steel, A709-50CR, has been recently developed for bridge construction. Despite its relatively high material cost, A709-50CR has the potential to reduce the life-cycle maintenance cost and mitigate the increasing failure risk due to structural deterioration. To further reduce the cost of using A709-50CR steel, this paper explores the prospect of using it for major bridge maintenance actions. Bi-objective optimization is conducted to determine when and which carbon steel girders should be replaced using A709-50CR during the life-cycle of a bridge. The two objectives in the optimization problem are to minimize life-cycle risk and life-cycle maintenance cost. The results indicate that using A709-50CR in major maintenance actions can achieve considerable economic benefits.

Fecal microbiota transplantation (FMT) is highly effective in recurrent Clostridioides difficile infection (CDI), increasing evidence supports FMT in severe or fulminant Clostridioides difficile infection (SFCDI). However, the multifactorial mechanisms that underpin the efficacy of FMT are not fully understood. Systems biology approaches using high-throughput technologies may help with mechanistic dissection of host-microbial interactions. Here, we have undertaken a deep phenomics study on four adults receiving sequential FMT for SFCDI, in which we performed a longitudinal, integrative analysis of multiple host factors and intestinal microbiome changes. Stool samples were profiled for changes in gut microbiota and metabolites and blood samples for alterations in targeted epigenomic, metabonomic, glycomic, immune proteomic, immunophenotyping, immune functional assays, and T-cell receptor (TCR) repertoires, respectively. We characterised temporal trajectories in gut microbial and host immunometabolic data sets in three responders and one non-responder to sequential FMT. A total of 562 features were used for analysis, of which 78 features were identified, which differed between the responders and the non-responder. The observed dynamic phenotypic changes may potentially suggest immunosenescent signals in the non-responder and may help to underpin the mechanisms accompanying successful FMT, although our study is limited by a small sample size and significant heterogeneity in patient baseline characteristics. Our multi-omics integrative longitudinal analytical approach extends the knowledge regarding mechanisms of efficacy of FMT and highlights preliminary novel signatures, which should be validated in larger studies.

Many governments have engaged in policy experimentation in various forms to resolve uncertainty and facilitate learning. However, little is understood about the characteristics of policy experimentation, and how the structure of experimentation may affect policy learning and policy outcomes. We aim to describe and understand China’s policy experimentation since 1980, among the largest and most systematic in recent history. We collect comprehensive data on policy experimentation conducted in China over the past four decades. We find three main results. First, more than 80% of the experiments exhibit positive sample selection in terms of a locality’s economic development, and much of this can be attributed to misaligned incentives across political hierarchies. Second, local politicians allocate more resources to ensure the experiments’ success, and such effort is not replicable when policies roll out to the entire country. Third, the presence of sample selection and strategic effort is not fully accounted for by the central government, thus affecting policy learning and distorting national policies originating from the experimentation. Taken together, these results suggest that while China’s bureaucratic and institutional conditions make policy experimentation at such scale possible, the complex political environments can also limit the scope and bias the direction of policy learning. Institutional subscribers to the NBER working paper series, and residents of developing countries may download this paper without additional charge at www.nber.org.

Background Fecal microbiota transplantation (FMT) is the most effective therapy for recurrent C. difficile infection. Although studies using statistical modeling have shown FMT to be cost-effective, real-world data is lacking. Aims To assess the impact of FMT program on the healthcare cost of recurrent C. difficile infections using real-world data from Alberta’s public healthcare system. Methods C. difficile infection patients were identified through provincial laboratory database with positive C. difficile results in Edmonton, Alberta between 2009–16. If an initial positive test was followed by ≧2 positive tests within 183 days, an individual was categorized as recurrent C. difficile infection (RCDI). Otherwise, non-recurrent C. difficile infection (non-RCDI) was assigned. Since the Edmonton FMT program was established in 2013, patients were further divided into pre-FMT (2009–12) and post-FMT (2013–16) eras. This divided patients into four study groups as outlined in Table 1. Administrative data, including inpatient stays, ambulatory or emergency room visits, outpatient prescriptions, and physician billings, were extracted. A cost of $389 was assigned to each FMT procedure to account for cost of donor screening and sample preparation. A difference in differences (DID) approach, a tool which estimates the effect of a treatment by comparing outcome difference between treatment group and control group over time, was used to analyze the impact of FMT program on the cost of RCDI. Non-RCDI patients were used as control group to account for changes in treatment costs over time. Ordinary least squares regression, with log-transformed healthcare cost as the dependent variable, was used for the analysis. Results 4717 non-RCDI and 548 RCDI patients were identified and divided into the 4 groups (Table 1). RCDI patients were significantly older than non-RCDI patients (71.13 vs 62.49; P < 0.001). After adjusting for differences in age, sex, and baseline healthcare utilization, cost for RCDI patients were significantly lower relative to costs for non-RCDI patients in the post-FMT era. Cost of non-RCDI increased by $5,300.08 between the pre- and post-FMT eras, while the cost of RCDI decreased by $7,654.92 in the same time frame (Table 2). FMT program was estimated to have saved $12,954 annually for RCDI patients at mean age, sex, and baseline cost of our overall sample. Conclusions Our data suggest that the healthcare cost of RCDI has decreased with the introduction of an FMT program. Funding Agencies Alberta Health Services, University of Alberta Hospital Foundation

People’s perceptions about others play an important role in shaping their own attitudes and behaviors, as well as social norms more broadly. This review presents a meta-analysis of the recent empirical literature that examines perceptions about others in the field. We document a number of stylized facts. Misperceptions about others are widespread, asymmetric, much larger when about out-group members, and positively associated with one’s own attitudes. Experimental treatments to re-calibrate misperceptions generally work as intended; they sometimes lead to meaningful changes in behaviors, though this often occurs only immediately after the treatments. We discuss different conceptual frameworks that could explain the origin, persistence, and rigidity of misperceptions about others. We point to several directions for future research.

Managers of civil infrastructure systems are facing the challenge to effectively and efficiently manage the ageing and deteriorating asset portfolio while accommodating ever increasing demand resul...

Corrosion is a severe threat to the integrity of ships and other steel structures in marine environments due to material loss and the associated reduction in their load-carrying capacities. Most existing studies on corrosion of steel plates in marine environments dealt only with general corrosion. However, laboratory experiments and field tests have shown that pitting corrosion can occur and even dominate the material loss of corroded structures, especially for plates with local coating failure, metal with mill scale surfaces, and alloys with special compositions. In this paper, a cellular automata-based model with both numerical and categorical attributes is proposed to analyze steel plates subjected to general and pitting corrosion. The proposed model can depict various corrosion behaviors including uniform loss of plate thickness, pit nucleation, and pit propagation. The parameters of the model are calibrated based on results from existing exposure tests. The calibrated model is then used to evaluate the time-variant reliability of a steel plate in corrosive environments. It is found that the general corrosion model with a time-invariant corrosion rate cannot realistically predict the long-term corrosion material loss and the thickness of corroded plates may show considerable spatial variability due to pitting corrosion.

The large number of deteriorating bridges and the goal of sustainable development mean that maintenance actions should not only effectively improve the current condition of bridges but also enhance post-maintenance durability. In this paper, a probabilistic life-cycle optimization method is proposed for the planning of this type of maintenance actions. A physics-based deterioration model is directly employed in the optimization process. The computational efficiency of the proposed method is ensured by efficient sampling algorithms, multi-objective particle swarm optimization, and a bookkeeping technique. The proposed method can provide bridge maintenance schedules that account for two conflicting objectives, i.e. the maximization of life-cycle performance and the minimization of maintenance cost. A deteriorating RC bridge superstructure under chloride-induced corrosion is used to illustrate the proposed method. Point-in-time and cumulative-time failure probabilities are compared as life-cycle performance indicators. As an example of maintenance actions that enhance durability, FRP strengthening implementations for different structural components of the superstructure are scheduled during the service life of the deteriorating superstructure.

Media censorship is a hallmark of authoritarian regimes. We conduct a field experiment in China to measure the effects of providing citizens with access to an uncensored internet. We track subjects’ media consumption, beliefs regarding the media, economic beliefs, political attitudes, and behaviors over 18 months. We find four main results: (i) free access alone does not induce subjects to acquire politically sensitive information; (ii) temporary encouragement leads to a persistent increase in acquisition, indicating that demand is not permanently low; (iii) acquisition brings broad, substantial, and persistent changes to knowledge, beliefs, attitudes, and intended behaviors; and (iv) social transmission of information is statistically significant but small in magnitude. We calibrate a simple model to show that the combination of low demand for uncensored information and the moderate social transmission means China’s censorship apparatus may remain robust to a large number of citizens receiving access to an uncensored internet. (JEL C93, D72, D83, L82, L86, L88, P36)

Climate change and population growth can affect the supply and the demand sides of transportation networks, respectively. Rational assessment of societal risk of transportation networks should consider these effects, both of which are uncertain in nature. In this paper, a novel method is proposed to assess societal risk of transportation networks subjected to uncertainties due to climate change and future population growth. The method is posited on a robust traffic assignment model using the expected residual minimization approach. A novel algorithm, combining smoothing method, quasi-Newton technique, and Latin hypercube sampling, is developed for the efficient implementation of the proposed method. The proposed method can produce a deterministic traffic flow pattern that deviates as little as possible from the traffic flow patterns associated with all future scenarios. The obtained traffic flow pattern can then be used to estimate societal risk of transportation networks. A number of examples, including a real-world highway bridge network in Camden County, New Jersey, are provided in this paper to demonstrate the efficiency, effectiveness, and application of the proposed method. It is found from the examples that (a) the proposed method is more efficient and robust than existing algorithms for robust traffic assignment under uncertainties, and (b) climate change and population growth can significantly alter the traffic pattern in a transportation network and thus increase the societal risk posed upon traffic users.

Bridge load testing can answer a variety of questions about bridge behavior that cannot be answered otherwise. The current governing codes and guidelines for bridge load testing in the United States are the 1998 NCHRP Manual for Bridge Rating through Load Testing and Chapter 8 of the AASHTO Manual for Bridge Evaluation. Over the last two decades, the practice of load testing has evolved, and its intersections with other fields have expanded. The outcomes of load tests have been used to keep bridges open cost-effectively without unnecessarily restricting legal loads, when theoretical analyses cannot yield insights representative of in-service performance. Load testing data can be further used to develop field-verified finite-element models of tested bridges to understand these structures better. In addition, structural reliability concepts can be used to estimate the probability of failure based on the results of load tests, and noncontact measurement techniques capturing large surfaces of bridges allow for better monitoring of structural responses. Given these developments, a new Transportation Research Board (TRB) Circular, Primer on Bridge Load Testing, has been developed. This document contains new proposals for interpreting the results of diagnostic load tests, loading protocols, and the determination of bridge load ratings based on the results of proof load tests. In addition, included provisions provide an estimation of the resulting reliability index and the remaining service life of a bridge based on load testing results. The benefit of load testing is illustrated based on a cost-benefit analysis. The current state-of-The-practice has demonstrated that load testing is an effective means for answering many important questions regarding bridge behavior that are critical to decisions on bridge maintenance or replacement. Load testing has evolved over its history, and the newly developed TRB Circular reflects this evolution in a practical way.

People’s perceptions about others play an important role in shaping their own attitudes and behaviors, as well as social norms more broadly. This review presents a meta-analysis of the recent empirical literature that examines perceptions about others in the field. We document a number of stylized facts. Misperceptions about others are widespread, asymmetric, much larger when about out-group members, and positively associated with one’s own attitudes. Experimental treatments to re-calibrate misperceptions generally work as intended; they sometimes lead to meaningful changes in behaviors, though this often occurs only immediately after the treatments. We discuss different conceptual frameworks that could explain the origin, persistence, and rigidity of misperceptions about others. We point to several directions for future research. Institutional subscribers to the NBER working paper series, and residents of developing countries may download this paper without additional charge at www.nber.org.

We study partisan differences in Americans' response to the COVID-19 pandemic. Political leaders and media outlets on the right and left have sent divergent messages about the severity of the crisis, which could impact the extent to which Republicans and Democrats engage in social distancing and other efforts to reduce disease transmission. We develop a simple model of a pandemic response with heterogeneous agents that clarifies the causes and consequences of heterogeneous responses. We use location data from a large sample of smartphones to show that areas with more Republicans engaged in less social distancing, controlling for other factors including public policies, population density, and local COVID cases and deaths. We then present new survey evidence of significant gaps at the individual level between Republicans and Democrats in self-reported social distancing, beliefs about personal COVID risk, and beliefs about the future severity of the pandemic.

Corrosion and hurricanes pose substantial risk to coastal bridges. This risk is compounded by future climatic and socioeconomic changes due to the increasing temperature and humidity, risin...

Data-intensive technologies, like AI, are increasingly widespread. We argue that the direction of innovation and growth in data-intensive economies may be crucially shaped by the state because: (i) the state is a key collector of data and (ii) data is sharable across uses within firms, potentially generating economies of scope. We study a prototypical setting: facial recognition AI in China. Collecting comprehensive data on firms and government procurement contracts, we find evidence of economies of scope arising from government data: firms awarded contracts providing access to more government data produce both more government and commercial software. We then build a directed technical change model to study the implications of government data access for the direction of innovation, growth, and welfare. We conclude with three applications showing how data-intensive innovation may be shaped by the state: both directly, by setting industrial policy; and indirectly, by choosing surveillance levels and privacy regulations.

Key Points Question How do reported incidence, knowledge, and behaviors regarding coronavirus disease 2019 vary across sociodemographic characteristics in the US? Findings In this survey study, the largest differences in coronavirus disease 2019–related knowledge and behaviors were associated with race/ethnicity, sex, and age. African American participants, men, and people younger than 55 years were less likely to know how the disease is spread, were less likely to know the symptoms of coronavirus disease 2019, washed their hands less frequently, and left the home more often. Meaning These findings suggest that more effort is needed to increase accurate information and encourage appropriate behaviors among minority communities, men, and younger people., This survey study examines the association of sociodemographic characteristics with reported incidence, knowledge, and behavior regarding coronavirus disease 2019 among US adults., Importance Data from the coronavirus disease 2019 (COVID-19) pandemic in the US show large differences in hospitalizations and mortality across race and geography. However, there are limited data on health information, beliefs, and behaviors that might indicate different exposure to risk. Objective To determine the association of sociodemographic characteristics with reported incidence, knowledge, and behavior regarding COVID-19 among US adults. Design, Setting, and Participants A US national survey study was conducted from March 29 to April 13, 2020, to measure differences in knowledge, beliefs, and behavior about COVID-19. The survey oversampled COVID-19 hotspot areas. The survey was conducted electronically. The criteria for inclusion were age 18 years or older and residence in the US. Data analysis was performed in April 2020. Main Outcomes and Measures The main outcomes were incidence, knowledge, and behaviors related to COVID-19 as measured by survey response. Results The survey included 5198 individuals (mean [SD] age, 48 [18] years; 2336 men [45%]; 3759 white [72%], 830 [16%] African American, and 609 [12%] Hispanic). The largest differences in COVID-19–related knowledge and behaviors were associated with race/ethnicity, sex, and age, with African American participants, men, and people younger than 55 years showing less knowledge than other groups. African American respondents were 3.5 percentage points (95% CI, 1.5 to 5.5 percentage points; P = .001) more likely than white respondents to report being infected with COVID-19, as were men compared with women (3.2 percentage points; 95% CI, 2.0 to 4.4 percentage points; P

BackgroundData from the COVID-19 pandemic in the United States show large differences in hospitalizations and mortality across race and geography. However, there is limited data on health information, beliefs, and behaviors that might indicate different exposure to risk.MethodsA sample of 5,198 respondents in the United States (80% population representative, 20% oversample of hotspot areas in New York City, Seattle, New Orleans, and Detroit) was conducted from March 29th to April 13th to measure differences in knowledge, beliefs and behavior regarding COVID-19. Linear regression was used to understand racial, geographic, political, and socioeconomic differences in COVID-19 reported incidence knowledge, and behaviors after adjusting for state-specific and survey date fixed effects.ResultsThe largest differences in COVID-19 knowledge and behaviors are associated with race/ethnicity, gender, and age. African-Americans, men, and people ConclusionsThere are wide gaps in COVID-19 reported incidence, knowledge regarding disease spread and symptoms, and in social distancing behavior. The findings suggest more effort is needed to increase accurate information and encourage appropriate behaviors among minority communities, men, and younger people.

U.S. voters exaggerate the differences in attitudes held by Republicans and Democrats on a range of socioeconomic and political issues, and higher perceived polarization is associated with greater political engagement and affective polarization. In this paper, we examine the role of issue salience in driving beliefs about political attitudes. We find that a model of political stereotypes, where distortions are stronger for issues that are more salient to voters, captures important qualitative and quantitative features of the data. First, perceived partisan differences are larger on issues that individuals consider more important. To attach a causal interpretation to this link, we show that the end of the Cold War in 1991, which shifted U.S. voters’ attention away from external threats, increased perceived, relative to actual, partisan differences on domestic issues. Second, issue salience increases the tendency to over-weigh extreme types. The increase in perceived polarization post 1991 was stronger for issues with more stereotypical partisan differences. Finally, the reverse pattern occurred after the terrorist attacks in 2001, when attention swung back towards external threats. We discuss other mechanisms, which may be at work but fail to match important features of the data. Our results highlight how beliefs about political groups can shift even when the underlying partisan differences change little, with important social and political consequences.

Can efforts to eradicate inequality in wealth and education eliminate intergenerational persistence of socioeconomic status? The Chinese Communist Revolution and Cultural Revolution aimed to do exactly that. Using newly digitized archival records and contemporary census and household survey data, we show that the revolutions were effective in homogenizing the population economically in the short run. However, the pattern of inequality that characterized the pre-revolution generation re-emerges today. Almost half a century after the revolutions, individuals whose grandparents belonged to the pre-revolution elite earn 16 percent more income and have completed more than 11 percent additional years of schooling than those from non-elite households. We find evidence that human capital (such as knowledge, skills, and values) has been transmitted within the families, and the social capital embodied in kinship networks has survived the revolutions. These channels allow the pre-revolution elite to rebound after the revolutions, and their socioeconomic status persists despite one of the most aggressive attempts to eliminate differences in the population.

INTRODUCTION AND OBJECTIVE:Penile length loss and erectile dysfunction (ED) are common complaints among men with diabetes mellitus (DM), with some data suggesting a mean 1 cm loss. Recently, a rand...

INTRODUCTION AND OBJECTIVE:For men with Gleason score 9-10 prostate cancer, studies have demonstrated conflicting results on the outcomes from combination radiation therapy (ComboRT) with external ...

INTRODUCTION AND OBJECTIVE:Rezūm is a minimally invasive technique to treat benign prostatic hyperplasia (BPH). Major advantages include no de novo erectile dysfunction and low rate of retrograde e...

Transportation networks, as an essential ingredient of civil infrastructure, are subjected to various natural hazards over their service life. Failure of bridges may severely disrupt the se...

Civil infrastructure systems have two essential characteristics: long service life and low probability of failure. Under these circumstances, life-cycle management (LCM) of civil infrastruc...

We examine US voters’ beliefs about views held by Republicans and Democrats. While individuals exaggerate partisan differences on a range of socioeconomic and political issues, we document that belief distortions are larger on issues that individuals consider more important. We organize these facts using a model of stereotypes where distortions are stronger for issues that are more salient to voters. In line with the model, belief distortions are predictable from the differences across parties, in particular the relative prevalence of extreme attitudes. To assess the impact of issue salience, we show that the end of the Cold War in 1991, which shifted US voters’ attention away from external threats and towards domestic issues, led to an increase in perceived polarization in the latter, and more so for issues with more stereotypical partisan differences. The reverse pattern occurred after the terrorist attacks in 2001, when attention swung back towards external threats. The distortions we identify are quantitatively significant, and could have important consequences for political engagement as such distortions strongly predict voting turnout. Institutional subscribers to the NBER working paper series, and residents of developing countries may download this paper without additional charge at www.nber.org.

Developing AI technology requires data. In many domains, government data far exceeds in magnitude and scope data collected by the private sector, and AI firms often gain access to such data when providing services to the state. We argue that such access can stimulate commercial AI innovation in part because data and trained algorithms are shareable across government and commercial uses. We gather comprehensive information on firms and public security procurement contracts in China’s facial recognition AI industry. We quantify the data accessible through contracts by measuring public security agencies’ capacity to collect surveillance video. Using a triple-differences strategy, we find that data-rich contracts, compared to data-scarce ones, lead recipient firms to develop significantly and substantially more commercial AI software. Our analysis indicates a contribution of government data to the rise of China’s facial recognition AI firms, and suggests that states’ data collection and provision policies could shape AI innovation. Institutional subscribers to the NBER working paper series, and residents of developing countries may download this paper without additional charge at www.nber.org.

We study partisan differences in Americans’ response to the COVID-19 pandemic. Political leaders and media outlets on the right and left have sent divergent messages about the severity of the crisis, which could impact the extent to which Republicans and Democrats engage in social distancing and other efforts to reduce disease transmission. We develop a simple model of a pandemic response with heterogeneous agents that clarifies the causes and consequences of heterogeneous responses. We use location data from a large sample of smartphones to show that areas with more Republicans engaged in less social distancing, controlling for other factors including public policies, population density, and local COVID cases and deaths. We then present new survey evidence of significant gaps at the individual level between Republicans and Democrats in self-reported social distancing, beliefs about personal COVID risk, and beliefs about the future severity of the pandemic.

Bridges, ships, and other civil and marine structures are subjected to fatigue damage due to repeated load fluctuations. Fatigue damage is likely to jeopardize the functionality and even structural safety of these structures. Therefore, inspections and timely repair actions are needed to ensure adequate structural performance throughout their lifetime. Nevertheless, inspection/repair actions involve additional life-cycle costs. Therefore, efficient planning of inspection and repair actions of fatigue-critical details are not only essential to ensure structural functionality and safety, but also important to control the total life-cycle cost. In this paper, a novel framework for optimizing inspection/repair planning is developed by using efficient Bayesian updating with dynamic Bayesian network. Specifically, inspection plans, including inspection schedules and inspection techniques, are optimized using pre-posterior analysis. Decisions of repair actions are made based on inspection results following an evidence-informed and cost-driven repair strategy. This strategy allows for time-dependent and adaptive repair actions considering fatigue damage development, available inspection results, and previous repair actions. Optimal inspection/repair plans with the lowest expected life-cycle cost are then obtained using both single- and multi-objective optimizations.

Corrosion is a major deterioration mechanism of carbon steel bridges. Multiple maintenance actions have been proposed to meet the safety requirements for bridges subjected to corrosion, including preventive maintenance, such as repainting, and essential maintenance, such as girder replacement. Recently, corrosion-resistant steel has been adopted for bridge construction. However, a comprehensive comparison of different maintenance strategies is still an under-investigated research area, especially for the cost-effectiveness of using corrosion resistant steel to conduct essential maintenance. In this paper, a new type of corrosion-resistant steel, A709-50CR, is considered for girder replacement. Reliability- and risk-based bi-objective optimizations are conducted on a multi-girder carbon steel bridge to determine when and which carbon steel girders should be replaced under different target performance indicators. The objectives are to minimize the life-cycle failure probability/risk and the total life-cycle cost, including initial construction cost and life-cycle maintenance cost. Sensitivity analysis is performed on multiple factors associated with system reliability calculations, such as system models adopted and correlations among resistances of girders. The economic benefits of building an A709-50CR bridge and applying frequent repainting actions on a carbon steel bridge to avoid girder replacement are also investigated. The comparison of different construction and maintenance strategies for multi-girder steel bridges sheds light on their effectiveness.

Reliable and continuous operation of ships is vitally important to the decision-makers. Driven by the rising cost of newbuilding ships, maintenance actions are needed on existing ships to ensure safe and enduring service beyond their initial design life. Extending ship service life can provide economic operating profit and promote sustainability. Meanwhile, ships during their extended service life may involve higher failure risk and additional maintenance expenditure. Therefore, a cost-benefit evaluation is imperative for determining the optimal duration of service life extension (SLE) and the associated maintenance actions. In this paper, a novel method for this purpose is proposed. Two cost-benefit indicators, benefit-cost ratio (BCR) and net present value (NPV) are used to optimize the duration of SLE. Using Bayesian updating, information on the remaining design life and the structural condition at the SLE decision is incorporated into the optimization process to better inform SLE decision-making. The proposed method is illustrated by a fatigue-sensitive very large crude carrier (VLCC) at both structural component and structural system levels.

Ship structures are subjected to repetitive wave loads that can lead to fatigue damage. Accumulation of fatigue damage may eventually result in structural failure. In order to mitigate fatigue haza...

Three-dimensional (3D) microstructures created by microfabrication and additive manufacturing have demonstrated value across a number of fields, ranging from biomedicine to microelectronics. However, the techniques used to create these devices each have their own characteristic set of advantages and limitations with regards to resolution, material compatibility, and geometrical constraints that determine the types of microstructures that can be formed. We describe a microfabrication method, termed StampEd Assembly of polymer Layers (SEAL), and create injectable pulsatile drug-delivery microparticles, pH sensors, and 3D microfluidic devices that we could not produce using traditional 3D printing. SEAL allows us to generate microstructures with complex geometry at high resolution, produce fully enclosed internal cavities containing a solid or liquid, and use potentially any thermoplastic material without processing additives.

Time-dependent reliability analysis of deteriorating structures is important in their performance evaluation and maintenance. Various definitions and methods have been used by researchers to predict the time-dependent reliability of structures. In the present study, these methods are first critically reviewed and examined. Among these methods, the stochastic-process-based method is theoretically the most rigorous but also computationally the most expensive. To facilitate the wide application of the stochastic-process-based method in complex problems, an efficient importance sampling method is then proposed in this paper. The proposed method includes a number of improvements formulated to enhance the efficiency and robustness of an existing method proposed by Kurtz and Song, leading to more efficient solutions of time-dependent reliability problems of structural systems with multiple important regions. The validity and efficiency of the new method is demonstrated through three numerical examples.

Background Severe and fulminant Clostridioides Difficile infection(CDI) is associated with increased mortality and morbidity. Current guidelines recommend high dose vancomycin with metronidazole for treatment. Surgery is a high risk for patients failing medical therapy partly due to multiple comorbidities. Emerging evidence suggests efficacy of sequential fecal microbiota transplantation(FMT) by colonoscopy combined with vancomycin in patients failing maximal medical therapy. Fidaxomicin is non-inferior to vancomycin in treating CDI; however, it has not been studied in severe/fulminant cases. It is not known if FMT by enema combined with fidaxomicin is efficacious and safe in this patient population. Aims This single center, prospective, open-label pilot study aimed to determine the efficacy and safety of combined sequential FMT by enema plus fidaxomicin in severe or fulminant CDI not responding to maximal medical therapy. Primary outcome was resolution of diarrhea 2 weeks following final FMT. Secondary outcomes were resolution of diarrhea 8 weeks following final FMT, safety of proposed treatment protocol and colectomy rate. Methods Consecutive patients with severe or fulminant CDI, who fulfilled study inclusion criteria were recruited. Sequential cycles of FMT, administered by enema daily over three days(720cc followed by 360cc and 180cc), plus fidaxomicin 200mg PO BID were given. Clinical symptoms and inflammatory markers were monitored during the study and subsequent cycles of FMT were administered when clinical or biochemical improvement plateaued. A final FMT was administered with CDI resolution. Results A total of three patients were enrolled between Jan 22 to Aug 8, 2019, shown in Table 1. One patient had fulminant CDI due to shock, and the others had severe CDI. All had severe pseudomembranous colitis seen on endoscopy at enrollment. Two of three patients reached both primary and secondary outcomes with 2 FMT cycles. The only patient who did not reach the primary was successfully managed with long term vancomycin suppression. This patient had failed multiple FMTs prior to enrollment. There were no adverse events noted and no colectomy was required during this study. Conclusions This pilot study is the first to demonstrate efficacy and safety of combined sequential FMT by enema and fidaxomicin in treating severe or fulminant CDI patients. An adequately powered study is required to validate these findings. Funding Agencies CIHRAlberta Health Services, University of Alberta Hospital Foundation

Climate change poses a substantial threat to civil infrastructure systems. This paper proposes a systematic approach to evaluate the climate change impact on the risk of bridge scour. The p...