Backgrounds and the evolution of visual signals.

Color signals which mediate behavioral interactions across taxa and contexts are often thought of as color 'patches' - parts of an animal that appear colorful compared to other parts of that animal. Color patches, however, cannot be considered in isolation because how a color is perceived depends on its visual background. This is of special relevance to the function and evolution of signals because backgrounds give rise to a fundamental tradeoff between color signal detectability and discriminability: as its contrast with the background increases, a color patch becomes more detectable, but discriminating variation in that color becomes more difficult. Thus, the signal function of color patches can only be fully understood by considering patch and background together as an integrated whole.

Risk heatmaps as visual displays: Opening movie studios after the COVID-19 shutdown.

Upon shutting down operations in early 2020 due to the COVID-19 pandemic, the movie industry assembled teams of experts to help develop guidelines for returning to operation. It resulted in a joint report, The Safe Way Forward, which was created in consultation with union members and provided the basis for negotiations with the studios. A centerpiece of the report was a set of heatmaps displaying SARS-CoV-2 risks for a shoot, as a function of testing rate, community infection prevalence, community transmission rate (R0), and risk measure (either expected number of cases or probability of at least one case). We develop and demonstrate a methodology for evaluating such complex displays, in terms of how well they inform potential users, in this case, workers deciding whether the risks of a shoot are acceptable. We ask whether individuals making hypothetical return-to-work decisions can (a) read display entries, (b) compare display entries, and (c) make inferences based on display entries. Generally speaking, respondents recruited through the Amazon MTurk platform could interpret the display information accurately and make coherent decisions, suggesting that heatmaps can communicate complex risks to lay audiences. Although these heatmaps were created for practical, rather than theoretical, purposes, these results provide partial support for theoretical accounts of visual information processing and identify challenges in applying them to complex settings.

Using implementation science frameworks to translate and adapt a pregnancy app for an emerging Latino community.

BACKGROUND: Digital mobile health (mHealth) applications are a popular form of prenatal education and care delivery in the U.S.; yet there are few Spanish language options for native speakers. Furthermore, existing applications do not consider cultural differences and disparities in healthcare access, including those specific to emerging Latino communities. OBJECTIVE: To adapt and translate an English-language pregnancy mobile health app to meet the language and cultural needs of Spanish-speaking Latino immigrants living in the United States. METHODS: We use a multi-step process, grounded in implementation science frameworks, to adapt and translate the contents of an existing pregnancy app. Interviews with stakeholders (n = 12) who advocate for the needs of pregnant individuals in an emerging Latino community were used to identify domains of possible disparities in access to prenatal care. We then conducted semi-structured interviews with peripartum Spanish-speaking Latino users (n = 14) to understand their perspectives within those domains. We identified a list of topics to create educational material for the modified app and implemented a systematic translation approach to ensure that the new version was acceptable for immigrants from different countries in Latin America. RESULTS: The interviews with stakeholders revealed seven critical domains that need to be addressed in an adapted prenatal app: language and communication, financial concerns, social support, immigration status, cultural differences, healthcare navigation, and connection to population-specific community resources that offer Spanish language services. The interviews with peripartum Spanish-speaking Latino women informed how the existing content in the app could be adjusted or built upon to address these issues, including providing information on accessing care offered in their native language and community support. Finally, we used a systematic approach to translate the existing application and create new content. CONCLUSION: This work illustrates a process to adapt an mHealth pregnancy app to the needs of an emerging Latino community, by incorporating culturally sensitive Spanish language content while focusing on addressing existing health disparities.

The value of adherence information during clinical pharmaceutical trials.

BACKGROUND/AIMS: The quality of the evidence used to evaluate a drug's safety and efficacy depends, in part, on how well participants adhere to the prescribed drug-taking regime. There are multiple approaches to measure adherence in clinical trials, varying in their cost and accuracy. We demonstrate a method for evaluating the cost-effectiveness of common adherence monitoring methods, considering the costs and data quality for drugs that differ in how forgiving they are of nonadherence. METHODS: We propose a simulation approach to estimate the value of evidence about adherence, considering both costs of collection and potential errors in interpreting clinical trial results. We demonstrate the approach with a simulated clinical trial of nitrendipine, a common calcium channel blocker. We consider two trial designs, one using pretrial adherence to "enrich" the trial sample and one without an enrichment strategy. We use scenarios combining high and low values of two key properties of a clinical trial: participant adherence and drug forgiveness. RESULTS: Under the conditions of these simulations, the most cost-effective adherence monitoring approach depends on both trial participant adherence and drug forgiveness. For example, the enrichment strategy is not cost-effective for the base scenario (high forgiveness and high adherence), but is for other scenarios. We also estimate the effects of evaluable patient analysis, a controversial procedure that excludes nonadherent participants from the analyses, after a trial is completed. CONCLUSIONS: Our proposed approach can guide drug regulators and developers in designing efficient clinical trials and assessing the impact of nonadherence on trial results. It can identify cost-effective adherence-monitoring methods, given available knowledge about the methods, drug, and patients' expected adherence.

Identification of maternal depression risk from natural language collected in a mobile health app.

Depression is one of the most common pregnancy complications, affecting approximately 15% of pregnant people. While valid psychometric measures of depression risk exist, they are not consistently administered at routine prenatal care, exacerbating the problem of adequate detection. The language we use in daily life offers a window into our psychological wellbeing. In this longitudinal observational cohort study of prenatal patients using a prenatal care mobile health app, we examine how features of app-entered natural language and other app-entered patient-reported data may be used as indicators for validated depression risk measures. Patient participants (n=1091) were prescribed a prenatal care app as part of a quality improvement initiative in the UPMC healthcare system from September 2019 - May 2022. Natural language from open-ended writing prompts in the app and self-reported daily mood, were entered by patients using the tool. Participants also completed a validated measure of depression risk - the Edinburgh Postnatal Depression Scale (EPDS) - at least once in their pregnancy. A variety of natural language processing tools were used to score sentiment, categorize topics, and capture other semantic and syntactic information from text entries. LASSO was used to model the relationship between the natural language features and depression risk. Open-ended text within a 30-day and 60-day timeframe of completing an EPDS was found to be moderately predictive of moderate to severe depression risk (AUROC=0.66 and 0.67, for each respective timeframe). When combined with average daily reported mood, open-ended text showed good predictive power (AUROC=0.87). Consistently predictive language features across all models included themes of "money" and "sadness." The combination of natural language and other user-reported data collected through a mobile health app offers an opportunity for identifying depression risk among a pregnant population.

Digital medicines for adherence support: A conceptual framework and qualitative study of adherence among chronically ill patients.

Digital medicine programs (DMPs) are emerging technologies that use sensor-enabled medicine to detect when patients have taken their medication and then provide feedback about adherence. We use qualitative methods to understand how patients change their behavioral patterns while participating in a DMP intervention. An influence diagram outlining the factors hypothesized to affect adherence in DMPs constructed from prior scientific research and expert input was created. Subsequently, we conducted semi-structured interviews with 10 patients to see if their experience supported the relationships outlined in the model. We identified three pathways by which DMPs are likely to change behavior around medication adherence: (1) providing patients and providers with accurate, personalized information about adherence; (2) improving patient-provider interactions by structuring them around this information; and (3) facilitating routines and habits for medication use. Chronically ill patients often fail to adhere to drug regimens. Patients in a DMP intervention used the DMP-provided information to better understand drug efficacy and collaborated with their physician to develop adherence strategies. DMPs can promote medication adherence among patients who are willing to use them and may be most effective if physicians are active partners in the DMP.

Finite-difference Time-domain (FDTD) Optical Simulations: A Primer for the Life Sciences and Bio-Inspired Engineering.

Light influences most ecosystems on earth, from sun-dappled forests to bioluminescent creatures in the ocean deep. Biologists have long studied nano- and micro-scale organismal adaptations to manipulate light using ever-more sophisticated microscopy, spectroscopy, and other analytical equipment. In combination with experimental tools, simulations of light interacting with objects can help researchers determine the impact of observed structures and explore how variations affect optical function. In particular, the finite-difference time-domain (FDTD) method is widely used throughout the nanophotonics community to efficiently simulate light interacting with a variety of materials and optical devices. More recently, FDTD has been used to characterize optical adaptations in nature, such as camouflage in fish and other organisms, colors in sexually-selected birds and spiders, and photosynthetic efficiency in plants. FDTD is also common in bioengineering, as the design of biologically-inspired engineered structures can be guided and optimized through FDTD simulations. Parameter sweeps are a particularly useful application of FDTD, which allows researchers to explore a range of variables and modifications in natural and synthetic systems (e.g., to investigate the optical effects of changing the sizes, shape, or refractive indices of a structure). Here, we review the use of FDTD simulations in biology and present a brief methods primer tailored for life scientists, with a focus on the commercially available software Lumerical FDTD. We give special attention to whether FDTD is the right tool to use, how experimental techniques are used to acquire and import the structures of interest, and how their optical properties such as refractive index and absorption are obtained. This primer is intended to help researchers understand FDTD, implement the method to model optical effects, and learn about the benefits and limitations of this tool. Altogether, FDTD is well-suited to (i) characterize optical adaptations and (ii) provide mechanistic explanations; by doing so, it helps (iii) make conclusions about evolutionary theory and (iv) inspire new technologies based on natural structures.

Use of a Smartphone App to Explore Potential Underuse of Prophylactic Aspirin for Preeclampsia.

Importance: Preeclampsia is a leading preventable cause of maternal morbidity and mortality. Initiation of low-dose aspirin (LDASA) treatment at or before 16 weeks' gestation may prevent preeclampsia onset for patients with specific risk factors. Objective: To assess potential underuse of LDASA and reasons for underuse using data from a prenatal care smartphone app. Design, Setting, and Participants: In this prospective cohort study, English-speaking pregnant patients aged 18 years or older from the UPMC health care system received an invitation to use the MyHealthyPregnancy app at their first prenatal appointment. Use of the app was voluntary. The study took place between September 23, 2019, and August 31, 2020, as part of a quality-improvement initiative. Exposures: The app offered educational information, monitoring tools, and routine screenings tailored to patient-entered gestational age and demographic and clinical characteristics. App-based questions included LDASA eligibility based on US Preventive Services Task Force criteria for preeclampsia risk and a monthly prompt about LDASA recommendations from the patient's health care practitioner. Main Outcomes and Measures: The primary outcomes were the receipt of LDASA recommendations from a practitioner and adherence to any such recommendation, as self-reported on the app. Patients' medical records were examined to cross-reference their self-reports of an LDASA recommendation. Multivariable logistic regression was used to model patient-perceived recommendation as a function of factors associated with preeclampsia. Results: The patient cohort consisted of 2563 patient participants (2036 [79%] White; mean [SD] age, 30 [5.2] years) with 2567 pregnancies; 1882 pregnancies (73.3%) were among women with private or employer-based insurance, and 1246 (48.5%) were among nulliparous patients. At least 1 factor associated with high risk for preeclampsia was reported in 316 pregnancies (12.3%), and 2 or more factors associated with moderate risk were reported in 1051 (40.9%). Of the 1015 pregnancies for which patients answered voluntary questions about aspirin use, 124 (12.2%) met at least 1 criterion for highest risk of preeclampsia. In 57 (46.0%) of these pregnancies, the patient indicated that their practitioner recommended LDASA; after examination of the medical records, 90 pregnancies (72.6%) had evidence of an LDASA recommendation and 34 (27.4%) did not. Of the 90 pregnancies with a documented LDASA recommendation, 33 patients (36.7%) were unaware of it. Prior preeclampsia (28 weeks' gestation: odds ratio, 20.1; 95% CI, 11.0-36.9) and chronic hypertension (28 weeks' gestation: odds ratio, 17.4; 95% CI, 6.3-48.2) were the primary high-risk factors associated with recommendation of LDASA. Conclusions and Relevance: In this cohort study, only 46.0% of prenatal care app users who met the criteria for highest preeclampsia risk reported receiving an LDASA recommendation from their practitioner, and medical records suggested that there may have been frequent miscommunication between patients and practitioners about LDASA use. Digital tools such as the MyHealthyPregnancy app might offer an opportunity to improve identification of patients at risk for preeclampsia and communication with these patients about aspirin use.

Multimodal Integration Across Spatiotemporal Scales to Guide Invertebrate Locomotion.

Locomotion is a hallmark of organisms which has enabled adaptive radiation to an extraordinarily diverse class of ecological niches, and allows animals to move across vast distances. Sampling from multiple sensory modalities enables animals to acquire rich information to guide locomotion. Locomotion without sensory feedback is haphazard; therefore, sensory and motor systems have evolved complex interactions to generate adaptive behavior. Notably, sensory-guided locomotion acts over broad spatial and temporal scales to permit goal-seeking behavior, whether to localize food by tracking an attractive odor plume or to search for a potential mate. How does the brain integrate multimodal stimuli over different temporal and spatial scales to effectively control behavior? In this review, we classify locomotion into three ordinally ranked hierarchical layers that act over distinct spatiotemporal scales: stabilization, motor primitives, and higher-order tasks, respectively. We discuss how these layers present unique challenges and opportunities for sensorimotor integration. We focus on recent advances in invertebrate locomotion due to their accessible neural and mechanical signals from the whole brain, limbs, and sensors. Throughout, we emphasize neural-level description of computations for multimodal integration in genetic model systems, including the fruit fly, Drosophila melanogaster, and the yellow fever mosquito, Aedes aegypti. We identify that summation (e.g., gating) and weighting-which are inherent computations of spiking neurons-underlie multimodal integration across spatial and temporal scales, therefore suggesting collective strategies to guide locomotion.

Mobile Remote Monitoring of Intimate Partner Violence Among Pregnant Patients During the COVID-19 Shelter-In-Place Order: Quality Improvement Pilot Study.

BACKGROUND: Intimate partner violence (IPV) is one of the leading causes of pregnancy-related death. Prenatal health care providers can offer critical screening and support to pregnant people who experience IPV. During the COVID-19 shelter-in-place order, mobile apps may offer such people the opportunity to continue receiving screening and support services. OBJECTIVE: We aimed to examine cases of IPV that were reported on a prenatal care app before and during the implementation of COVID-19 shelter-in-place mandates. METHODS: The number of patients who underwent voluntary IPV screening and the incidence rate of IPV were determined by using a prenatal care app that was disseminated to patients from a single, large health care system. We compared the IPV screening frequencies and IPV incidence rates of patients who started using the app before the COVID-19 shelter-in-place order, to those of patients who started using the app during the shelter-in-place order. RESULTS: We found 552 patients who started using the app within 60 days prior to the enforcement of the shelter-in-place order, and 407 patients who used the app at the start of shelter-in-place enforcement until the order was lifted. The incidence rates of voluntary IPV screening for new app users during the two time periods were similar (before sheltering in place: 252/552, 46%; during sheltering in place: 163/407, 40%). The overall use of the IPV screening tool increased during the shelter-in-place order. A slight, nonsignificant increase in the incidence of physical, sexual, and psychological violence during the shelter-in-place order was found across all app users (P=.56). Notably, none of the patients who screened positively for IPV had mentions of IPV in their medical charts. CONCLUSIONS: App-based screening for IPV is feasible during times when in-person access to health care providers is limited. Our results suggest that the incidence of IPV slightly increased during the shelter-in-place order. App-based screening may also address the needs of those who are unwilling or unable to share their IPV experiences with their health care provider.

Visual perception of light organ patterns in deep-sea shrimps and implications for conspecific recognition.

Darkness and low biomass make it challenging for animals to find and identify one another in the deep sea. While spatiotemporal variation in bioluminescence is thought to underlie mate recognition for some species, its role in conspecific recognition remains unclear. The deep-sea shrimp genus, Sergestes sensu lato (s.l.), is one group that is characterized by species-specific variation in light organ arrangement, providing us the opportunity to test whether organ variation permits recognition to the species level. To test this, we analyzed the visual capabilities of three species of Sergestes s.l. in order to (a) test for sexual dimorphism in eye-to-body size scaling relationships, (b) model the visual ranges (i.e., sighting distances) over which these shrimps can detect intraspecific bioluminescence, and (c) assess the maximum possible spatial resolution of the eyes of these shrimps to estimate their capacity to distinguish the light organs of each species. Our results showed that relative eye size scaled negatively with body length across species and without sexual dimorphism. Though the three species appear capable of detecting one another's bioluminescence over distances ranging from < 1 to ~6 m, their limited spatial resolution suggests they cannot resolve light organ variation for the purpose of conspecific recognition. Our findings point to factors other than conspecific recognition (e.g., neutral drift, phenotypic constraint) that have led to the extensive diversification of light organs in Sergestes s.l and impart caution about interpreting ecological significance of visual characters based on the resolution of human vision. This work provides new insight into deep-sea animal interaction, supporting the idea that-at least for these mesopelagic shrimps-nonvisual signals may be required for conspecific recognition.

Ultra-black Camouflage in Deep-Sea Fishes.

At oceanic depths >200 m, there is little ambient sunlight, but bioluminescent organisms provide another light source that can reveal animals to visual predators and prey [1-4]. Transparency and mirrored surfaces-common camouflage strategies under the diffuse solar illumination of shallower waters-are conspicuous when illuminated by directed bioluminescent sources due to reflection from the body surface [5, 6]. Pigmentation allows animals to absorb light from bioluminescent sources, rendering them visually undetectable against the dark background of the deep sea [5]. We present evidence suggesting pressure to reduce reflected bioluminescence led to the evolution of ultra-black skin (reflectance <0.5%) in 16 species of deep-sea fishes across seven distantly related orders. Histological data suggest this low reflectance is mediated by a continuous layer of densely packed melanosomes in the exterior-most layer of the dermis [7, 8] and that this layer lacks the unpigmented gaps between pigment cells found in other darkly colored fishes [9-13]. Using finite-difference, time-domain modeling and comparisons with melanosomes found in other ectothermic vertebrates [11, 13-21], we find the melanosomes making up the layer in these ultra-black species are optimized in size and shape to minimize reflectance. Low reflectance results from melanosomes scattering light within the layer, increasing the optical path length and therefore light absorption by the melanin. By reducing reflectance, ultra-black fish can reduce the sighting distance of visual predators more than 6-fold compared to fish with 2% reflectance. This biological example of efficient light absorption via a simple architecture of strongly absorbing and highly scattering particles may inspire new ultra-black materials.

Evidence that eye-facing photophores serve as a reference for counterillumination in an order of deep-sea fishes.

Counterillumination, the masking of an animal's silhouette with ventral photophores, is found in a number of mesopelagic taxa but is difficult to employ because it requires that the animal match the intensity of downwelling light without seeing its own ventral photophores. It has been proposed that the myctophid, Tarletonbeania crenularis, uses a photophore directed towards the eye, termed an eye-facing photophore, as a reference standard that it adjusts to match downwelling light. The potential use of this mechanism, however, has not been evaluated in other fishes. Here, we use micro-computed tomography, photography and dissection to evaluate the presence/absence of eye-facing photophores in three families of stomiiform fishes. We found that all sampled species with ventral photophores capable of counterillumination possess an eye-facing photophore that is pigmented on the anterior and lateral sides, thus preventing its use as a laterally directed signal, lure or searchlight. The two species that are incapable of counterillumination, Cyclothone obscura and Sigmops bathyphilus, lack an eye-facing photophore. After determining the phylogenetic distribution of eye-facing photophores, we used histology to examine the morphology of the cranial tissue in Argyropelecus aculeatus and determined that light from the eye-facing photophore passes through a transparent layer of tissue, then the lens, and finally strikes the accessory retina. Additionally, eight of the 14 species for which fresh specimens were available had an aphakic gap that aligned with the path of emitted light from the eye-facing photophore, while the remaining six had no aphakic gap. These findings, combined with records of eye-facing photophores from distantly related taxa, strongly suggest that eye-facing photophores serve as a reference for counterillumination in these fishes.

Inferring Sexually Transmitted Infection Risk From Attractiveness in Online Dating Among Adolescents and Young Adults: Exploratory Study.

BACKGROUND: Sexually transmitted infection (STI) rates are on the rise among adolescents and young adults in the United States. With the popularity of online dating, adolescents and young adults must increasingly rely on limited cues to make initial judgments about potential sexual partners, including judgments about STI risk. OBJECTIVE: This study aimed to assess whether in the context of online dating, an attractiveness heuristic would be used for STI risk assessment. We hypothesized that consistent with research on halo effects, decision makers would judge more attractive people to be less likely to have STIs. METHODS: In a survey experiment, we asked participants to determine which individual in each of 20 sets of paired photographs was enrolled in a personals website for people with publicly disclosed STIs. RESULTS: Despite financial incentives for accuracy and high levels of self-confidence in their judgments, participants performed no better than chance at identifying individuals with self-reported STIs. Contrary to our hypothesis, however, more attractive people were judged as being more likely to have an STI. This relationship appears to be mediated by inferences regarding the target individual's sexual behavior, with more attractive individuals considered to have more partners. CONCLUSIONS: On showing adolescents and young adults photographs offering no diagnostic information about STIs, they appeared to use attractiveness as a cue for sexual risk, which was mediated by the belief that attractive individuals have more sexual opportunities. Health care providers may wish to address this heuristic process among their adolescent patients in discussions about sexual health.

Spending money to make change: Association of methamphetamine abstinence and voucher spending among contingency management pilot participants in South Africa.

AIMS: Methamphetamine Use Disorder is prevalent in South Africa. This analysis uses data from a contingency management (CM) pilot study in South Africa to replicate and expand on a U.S.-based study showing that CM voucher spending was associated with drug abstinence behavior. DESIGN: Participants with methamphetamine-use disorder were enrolled in an 8-week CM trial requiring thrice weekly visits and received cash vouchers in exchange for stimulant-negative urines at each visit. PARTICIPANTS: Participants were 33 treatment-seeking individuals with methamphetamine use disorder including 22 men (66.7%) and 11 women (33.3%) with a mean age of 34 years (S.D. = 7.7). Participants reported using methamphetamine for a mean of 11.7 years (S.D. = 4.9). SETTING: All study procedures took place in South Africa between August 2016 and May 2018. MEASUREMENTS: A time-lagged counting process Cox Proportional Hazards model for recurrent event survival analysis examined the relationship between frequency of and participant-categorized type of CM expenditures (hedonic, utilitarian, consumable or durable) and drug abstinence. FINDINGS: After controlling for severity of baseline methamphetamine use and accumulated CM earnings (proxied by cumulative negative urines), those spending CM earnings at a previous visit ("spenders") were more likely to produce stimulant-negative urine samples subsequently, compared to those who did not ("savers") [OR = 1.23, CI = 1.08-1.53, p = .002]. There were significantly more cumulative stimulant-negative results among spenders vs. savers, p < .001, although cumulative spending did not significantly predict abstinence once spending in the prior time period was controlled for, suggesting a recency effect tied to the underlying spending mechanism. When extending the original analyses to look at the effect of spending on current abstinence, controlling only for recent abstinence (rather than cumulative abstinence), spending was no longer a significant predictor. Spending type did not affect methamphetamine abstinence. Qualitative results suggest spending CM vouchers may support social reintegration over the course of the trial. CONCLUSIONS: Abstinence outcomes are a function of CM spending in both the U.S. and South Africa. Findings of a significant relationship between contingency management spending and subsequent stimulant-negative urine samples across geographic locations provide guidance toward future work in optimizing CM efficacy.

Diverse nanostructures underlie thin ultra-black scales in butterflies.

Recently, it has been shown that animals such as jumping spiders, birds, and butterflies have evolved ultra-black coloration comparable to the blackest synthetic materials. Of these, certain papilionid butterflies have reflectances approaching 0.2%, resulting from a polydisperse honeycomb structure. It is unknown if other ultra-black butterflies use this mechanism. Here, we examine a phylogenetically diverse set of butterflies and demonstrate that other butterflies employ simpler nanostructures that achieve ultra-black coloration in scales thinner than synthetic alternatives. Using scanning electron microscopy, we find considerable interspecific variation in the geometry of the holes in the structures, and verify with finite-difference time-domain modeling that expanded trabeculae and ridges, found across ultra-black butterflies, reduce reflectance up to 16-fold. Our results demonstrate that butterflies produce ultra-black by creating a sparse material with high surface area to increase absorption and minimize surface reflection. We hypothesize that butterflies use ultra-black to increase the contrast of color signals.

Worrying yourself sick? Association between pre-eclampsia onset and health-related worry in pregnancy.

Psychosocial stress may influence pregnancy health. We examined the relationship between worry about pregnancy health and pre-eclampsia. General stress, mental health, and self-reported pregnancy health worry were measured in a study of 10,037 U.S. nulliparous women. Logistic regression found a dose-response relationship between first trimester pregnancy-health worry and subsequent pre-eclampsia onset, controlling for health history (Beta = 0.40, SE = 0.09, P < 1 × 10-6). A machine learning regularized regression found a significant relationship between worry and pre-eclampsia onset, controlling for all other potential predictors of pre-eclampsia measured at baseline, suggesting that worry plays a unique role in pre-eclampsia risk.

Lift and Drag Acting on the Shell of the American Horseshoe Crab (Limulus polyphemus).

The intertidal zone is a turbulent landscape where organisms face numerous mechanical challenges from powerful waves. A model for understanding the solutions to these physical problems, the American horseshoe crab (Limulus polyphemus), is a marine arthropod that mates in the intertidal zone, where it must contend with strong ambient flows to maintain its orientation during locomotion and reproduction. Possible strategies to maintain position include either negative lift generation or the minimization of positive lift in flow. To quantify flow over the shell and the forces generated, we laser-scanned the 3D shape of a horseshoe crab, and the resulting digital reconstruction was used to 3D-print a physical model. We then recorded the movement of tracking particles around the shell model with high-speed video and analyzed the time-lapse series using particle image velocimetry (PIV). The velocity vector fields from PIV were used to validate numerical simulations performed with the immersed boundary (IB) method. IB simulations allowed us to resolve the forces acting on the shell, as well as the local three-dimensional flow velocities and pressures. Both IB simulations and PIV analysis of vorticity and velocity at a flow speed of 13 cm/s show negative lift for negative and zero angles of attack, and positive lift for positive angles of attack in a free-stream environment. In shear flow simulations, we found near-zero lift for all orientations tested. Because horseshoe crabs are likely to be found primarily at near-zero angles of attack, we suggest that this negative lift helps maintain the orientation of the crab during locomotion and mating. This study provides a preliminary foundation for assessing the relationship between documented morphological variation and potential environmental variation for distinct populations of horseshoe crabs along the Atlantic Coast. It also motivates future studies which could consider the stability of the horseshoe crab in unsteady, oscillating flows.

Exclusion Criteria as Measurements I: Identifying Invalid Responses.

Background. In a systematic review, Engel et al. found large variation in the exclusion criteria used to remove responses held not to represent genuine preferences in health state valuation studies. We offer an empirical approach to characterizing the similarities and differences among such criteria. Setting. Our analyses use data from an online survey that elicited preferences for health states defined by domains from the Patient-Reported Outcomes Measurement Information System (PROMIS®), with a U.S. nationally representative sample (N = 1164). Methods. We use multidimensional scaling to investigate how 10 commonly used exclusion criteria classify participants and their responses. Results. We find that the effects of exclusion criteria do not always match the reasons advanced for applying them. For example, excluding very high and very low values has been justified as removing aberrant responses. However, people who give very high and very low values prove to be systematically different in ways suggesting that such responses may reflect different processes. Conclusions. Exclusion criteria intended to remove low-quality responses from health state valuation studies may actually remove deliberate but unusual ones. A companion article examines the effects of the exclusion criteria on societal utility estimates.

Exclusion Criteria as Measurements II: Effects on Utility Functions.

Background. Researchers often justify excluding some responses in studies eliciting valuations of health states as not representing respondents' true preferences. Here, we examine the effects of applying 8 common exclusion criteria on societal utility estimates. Setting. An online survey of a US nationally representative sample (N = 1164) used the standard gamble method to elicit preferences for health states defined by 7 health domains from the Patient-Reported Outcomes Measurement Information System (PROMIS®). Methods. We estimate the impacts of applying 8 commonly used exclusion criteria on mean utility values for each domain, using beta regression, a form of analysis suited to double-bounded scales, such as utility. Results. Exclusion criteria have varied effects on the utility functions for the different PROMIS health domains. As a result, applying those criteria would have varied effects on the value of treatments (and side effects) that change health status on those domains. Limitations. Although our method could be applied to any health utility judgments, the present estimates reflect the features of the study that produced them. Those features include the selected health domains, standard gamble method, and an online format that excluded some groups (e.g., visually impaired and illiterate individuals). We also examined only a subset of all possible exclusion criteria, selected to represent the space of possibilities, as characterized in a companion article. Conclusions. Exclusion criteria can affect estimates of the societal utility of health states. We use those effects, in conjunction with the results of the companion article, to make suggestions for selecting exclusion criteria in future studies.