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The Mars Entry, Descent, and Landing Instrumentation 2 (MEDLI2) sensor suite collected heating and pressure data during entry of the Mars 2020 Perseverance rover into Mars’s atmosphere. MEDLI2 included temperature, heat flux, and pressure sensors on the heat shield and backshell. This paper covers inverse estimation of surface heating based on the MEDLI2 instrumented sensor plugs, which are a network of thermocouples embedded in thermal protection system plugs across the aeroshell. Monte Carlo analysis was conducted to assess the sensitivity of calculated surface heat rate and temperature to uncertainties in thermocouple depth and material properties, and a variance decomposition method was employed to understand the relative contributions of each uncertainty parameter. Performing this analysis using results from the inverse analysis tool FIAT_Opt was found to require an extremely high computation time; thus, machine learning models were trained and evaluated as a surrogate for FIAT_Opt. This paper demonstrates that machine learning models can be efficient, accurate alternatives to state-of-the-art inverse analysis tools like FIAT_Opt, especially for computationally expensive processes. Ensuing sensitivity analysis showed that the main drivers for overall uncertainty in the reconstructed heat flux and heat load were heat capacity and thermal conductivity on the backshell, and they were thermal conductivity and thermocouple depth on the heat shield.

The Mars 2020 entry vehicle’s thermal protection system included measurements of in-depth temperature on the heatshield and backshell, and surface heating on the backshell. This paper describes the flight data and resulting analysis: subsurface temperatures at 11 heatshield and 6 backshell locations, measured total heat flux at two backshell locations, and a radiometer on the backshell to measure shock layer radiation. All temperatures were within allowable material limits. Total surface heat flux was derived from the in-depth temperature measurements at the thermocouple locations. Turbulent boundary-layer conditions occurred at nine heatshield locations and the radiometer provided evidence that heating from shock layer radiation significantly exceeded convective heating on the backshell. Computational results on the reconstructed entry trajectory are compared to the flight data. After boundary-layer transition, total heat flux from algebraic turbulence model calculations qualitatively matches the reconstructed heating, but with lower peak magnitudes. On the backshell, laminar heat flux predictions generally exceed the as-flown values by less than [Formula: see text], with shock layer radiation predicted to contribute the majority of heating. At the radiometer location, the maximum predicted radiative heat flux exceeds the measurement, with the measured value likely suppressed by ablation products on the sapphire window.

The resting membrane potential enables neurons to rapidly initiate and conduct electrical signals. K2p channels are key in maintaining this membrane potential and electrical excitability. They direct the resting membrane potential toward the K+ equilibrium potential. Doxapram is a known blocker for a subset of K2p channels that are pH sensitive. We assessed the effects of 0.1 and 5 mM doxapram on the neural activity within the propodite-dactylopodite (PD) proprioceptive sensory organ in the walking legs of blue crabs (Callinectes sapidus). Results indicate that 0.1 mM doxapram enhances excitation, while the higher concentration 5 mM may over-excite the neurons and promote a sustained absolute refractory period until the compound is removed. The effect of 5 mM doxapram mimics the effect of 40 mM K+ exposure. Verapamil, another known K2p channel blocker as well as an L-type Ca2+ channel blocker, reduces neural activity at both 0.1 and 5 mM. Verapamil may block stretch activated channels in sensory endings, in addition to reducing the amplitude of the compound action potential with whole nerve preparations. These findings are notable as they demonstrate that doxapram has acute effects on neurons of crustaceans, suggesting a targeted K2p channel. The actions of verapamil are complex due to the potential of affecting multiple ion channels in this preparation. Crustacean neurons can aid in understanding the mechanisms of action of various pharmacological agents as more information is gained.

Trachoma, caused by ocularChlamydia trachomatisinfection, is targeted for global elimination as a public health problem by 2030. To provide evidence for use of antibodies to monitorC. trachomatistransmission, we collated IgG responses to Pgp3 antigen, PCR positivity, and clinical observations from 19,811 children aged 1– 9 years in 14 populations. We demonstrate that age-seroprevalence curves consistently shift along a gradient of transmission intensity: rising steeply in populations with high levels of infection and active trachoma and becoming flat in populations near elimination. Seroprevalence (range: 0–54%) and seroconversion rates (range: 0–15 per 100 person-years) correlate with PCR prevalence (r: 0.87, 95% CI: 0.57, 0.97). A seroprevalence threshold of 13.5% (seroconversion rate 2.75 per 100 person-years) identifies clusters with any PCR-identified infection at high sensitivity (>90%) and moderate specificity (69-75%). Antibody responses in young children provide a robust, generalizable approach to monitor population progress toward and beyond trachoma elimination.

The early Eocene Okanagan Highland fossil sites of Washington (USA) and British Columbia (Canada) contain exquisitely preserved plant and insect fossils that showcase a critical time and place in the evolution of the Northern Hemisphere temperate deciduous biome. A comprehensive understanding of the dynamics of fossil deposition and preservation at these sites is not fully resolved but is critical for reliable reconstructions of these ancient forests. To expand on previous interpretations (e.g., deep, stratified, anoxic lake bottoms) and address uncertainties about the environment of deposition (e.g., distance to shore, influence of diatoms), we analyzed sediment samples from three Okanagan Highland fossil sites—McAbee, Falkland, and Driftwood Canyon—for organic biomarkers, their stable carbon isotopic compositions, and glycerol dialkyl glycerol tetraethers (GDGTs; at McAbee only). Terpenoids suggest relative trends in gymnosperm abundance between sites that agree with prior macrofossil evidence, though absolute values may overestimate local gymnosperm abundance. A combination of biomarker evidence indicates a predominantly autochthonous aquatic source (e.g., diatoms) for organic matter in shale and mudstone samples, even contributing to long chain n-alkanes and likely to branched GDGTs, which are often assumed to be terrestrially sourced. In combination with biomarker evidence for anoxia and stratification, fossiliferous shales are interpreted to have been deposited offshore in deep and mesotrophic lakes that were thermally stratified with an anoxic hypolimnion, away from in-flowing tributaries, while a coal horizon at Driftwood Canyon was deposited in a shallower, eutrophic, anoxic wetland. Anoxic conditions likely minimized some degradation-based biases and promoted high quality fossil preservation. Deposition of sediment and fossil remains offshore and away from inflowing tributaries suggest fossil plants were locally sourced but highlights the need for careful consideration of transport-induced biases.

As trachoma prevalence declines worldwide, performing field surveys with trained trachoma graders to validate its elimination becomes challenging. Graded conjunctival images could be used to train graders, validate field grades, and replace field grading. We review the use of photography to capture conjunctival images for the detection of trachomatous inflammation-follicular (TF) and -intense (TI), Trachomatous trichiasis (TT), and eyelid contour abnormalities. Literature searches were conducted between October 29, 2020 and February 15, 2021. We abstracted kappa scores for agreement between field and image graders, between field graders, and between image graders. The median kappa was calculated for studies discussing grading for TF and TI. Twenty-one studies were included - 19 described the use of imaging tools for grading TF and TI; 1 discussed TT; and 1 discussed eyelid contour abnormalities. For agreement between field and image graders, median kappa for TF was 0.71 (range: 0.57–0.92) and TI was 0.67 (0.37–0.74); between image graders, median kappa for TF was 0.65 (0.37–0.78) and TI was 0.76 (0.39–0.83); and between field graders, median kappa for TF was 0.86 (0.73–1) and TI was 0.82 (0.73–0.91). There is potential for the use of photography for trachoma prevalence surveys. Further research is warranted, particularly for TT and using newer smartphones.

PURPOSE: To estimate and compare cross-sectional scotopic versus mesopic macular sensitivity losses measured by microperimetry, and to report and compare the longitudinal rates of scotopic and mesopic macular sensitivity losses in ABCA4 gene associated Stargardt Disease (STGD1). DESIGN: Multicenter prospective cohort study. METHODS: PARTICIPANTS: 127 molecular confirmed STGD1 patients enrolled from 6 centers in the USA and Europe and followed every 6 months for up to 2 years. OBSERVATION PROCEDURES: The Nidek MP-1S device was used to measure macular sensitivities of the central 20° under mesopic and scotopic conditions. The mean deviations (MD) from normal for mesopic macular sensitivity for the fovea (within 2° eccentricity) and extrafovea (4°−10° eccentricity), and the MD for scotopic sensitivity for the extrafovea were calculated. Linear mixed effects models were used to estimate mesopic and scotopic changes. MAIN OUTCOME MEASURES: Baseline mesopic mean deviation (mMD) and scotopic MD (sMD) and rates of longitudinal changes in the mMDs and sMD. RESULTS: At baseline, all eyes had larger sMD, and the difference between extrafoveal sMD and mMD was 10.7 dB (p

During the late Paleocene to early Eocene, clastic fluvial sediments and coals were deposited in northern high latitudes as part of the Margaret Formation at Stenkul Fiord (Ellesmere Island, Nunavut, Canada). Syn-sedimentary tectonic movements of the Eurekan deformation continuously affected these terrestrial sediments. Different volcanic ash layers occur, and unconformities subdivide the deposits into four sedimentary units. Rare vertebrate fossils indicate an early Eocene (Graybullian) age for the upper part of the Stenkul Fiord outcrop. Here, we present carbon isotope data of bulk coal, related organic-rich mud and siltstones, a plant leaf wax-derived alkane, and additional plant remains. These data provide a complete carbon isotope record of one stratigraphic section with defined unconformity positions and in relation to other Eurekan deformation features. A previously dated ash layer MA-1 provided a U-Pb zircon age of 53.7 Ma and is used as a stratigraphic tie point, together with a discrete negative carbon isotope excursion found above MA-1 in a closely sampled coal seam. The excursion is identified as the likely expression of the I-1 hyperthermal event. Based on our isotope data that reflect the early Eocene dynamics of the carbon cycle, this tie point, and previous paleontological constraints from vertebrate fossils, the locations of the Paleocene-Eocene Thermal Maximum (PETM) and Eocene Thermal Maximum 2 (ETM-2) hyperthermals and their extent along the complete section are herein identified. Within the intervals of the PETM and ETM-2 hyperthermal events, increasing amounts of clastic sediments reached the site toward the respective end of the event. This is interpreted as a response of the fluvial depositional system to an intensified hydrological system during the hyperthermal events. Our study establishes an enhanced stratigraphic framework allowing for the calculation of average sedimentation rates of different intervals and considerations on the completeness of the stratigraphic record. As one of the few high-latitude outcrops of early Eocene terrestrial sediments, the Stenkul Fiord location offers further possibilities to study the effects of extreme warming events in the Paleogene.

The Sea of Japan (SOJ) coast and adjoining orography of central Honshu, Japan, receive substantial snowfall each winter. A frequent contributor during cold-air outbreaks (CAOs) is the Japan Sea polar airmass convergence zone (JPCZ), which forms downstream of the highland areas of the Korean Peninsula (i.e., the Korean Highlands), extends southeastward to Honshu, and generates a mesoscale band of precipitation. Mesoscale polar vortices (MPVs) ranging in horizontal scale from tens (i.e., meso-β-scale cyclones) to several hundreds of kilometers (i.e., “polar lows”) are also common during CAOs and often interact with the JPCZ. Here we use satellite imagery and Weather Research and Forecasting Model simulations to examine the formation, thermodynamic structure, and airflow of a JPCZ that formed in the wake of an MPV during a CAO from 2 to 7 February 2018. The MPV and its associated warm seclusion and bent-back front developed in a locally warm, convergent, and convective environment over the SOJ near the base of the Korean Peninsula. The nascent JPCZ was structurally continuous with the bent-back front and lengthened as the MPV migrated southeastward. Trajectories illustrate how air–sea interactions and flow splitting around the Korean Highlands and channeling through low passes and valleys along the Asian coast affect the formation and thermodynamic structure of the JPCZ. Contrasts in airmass origin and thermodynamic modification over the SOJ affect the cross-JPCZ temperature gradient, which reverses in sign along the JPCZ from the Asian coast to Honshu. These results provide new insights into the thermodynamic structure of the JPCZ, which is an important contributor to hazardous weather over Japan.

Decision confidence plays a critical role in humans’ ability to make adaptive decisions in a noisy perceptual world. Despite its importance, there is currently little consensus about the computations underlying confidence judgements in perceptual decisions. One leading theory suggests that confidence is computed following the rules of Bayesian inference. Accordingly, the goal of the current study was to investigate a fundamental assumption of Bayesian models: the use of prior knowledge in subjective confidence. Rather than requiring participants to internalise the parameters of an arbitrary prior distribution, we capitalised on the existing probability distributions of features in natural scenes, which are known to play a critical role in guiding perception. Participants reported the subjective upright of naturalistic image target patches, and then reported their confidence in their orientation responses. We used computational modelling to relate the statistics of the targets to participants’ responses, confirming that participants used the prior probability distribution of features in natural scenes to judge subjective upright. Critically, our results reveal that participants also used natural image priors to inform their confidence judgements. Our findings provide important evidence supporting a Bayesian characterisation of confidence and highlight the influence of environmental priors on confidence.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by selective, early degeneration of motor neurons in the brain and spinal cord. Motor neurons have long axonal projections, which rely on the integrity of neuronal cytoskeleton and mitochondria to regulate energy requirements for maintaining axonal stability, anterograde and retrograde transport, and signaling between neurons. The formation of protein aggregates which contain cytoskeletal proteins, and mitochondrial dysfunction both have devastating effects on the function of neurons and are shared pathological features across several neurodegenerative conditions, including ALS, Alzheimer's disease, Parkinson's disease, Huntington’s disease and Charcot-Marie-Tooth disease. Furthermore, it is becoming increasingly clear that cytoskeletal integrity and mitochondrial function are intricately linked. Therefore, dysregulations of the cytoskeletal network and mitochondrial homeostasis and localization, may be common pathways in the initial steps of neurodegeneration. Here we review and discuss known contributors, including variants in genetic loci and aberrant protein activities, which modify cytoskeletal integrity, axonal transport and mitochondrial localization in ALS and have overlapping features with other neurodegenerative diseases. Additionally, we explore some emerging pathways that may contribute to this disruption in ALS.

Purpose To quantify the association of visual field (VF) damage on physical activity away-from-home, per away-from-home excursion, and at-home. Design Prospective cohort study. Methods Among 229 participants with glaucoma or suspected glaucoma, the severity of VF damage was defined as average sensitivity within the integrated VF (IVF). Participants wore accelerometers and global positioning system trackers for 7 days to measure physical activity and characterize activity location. Multivariable negative binomial regressions were used to test whether away-from-home activity per day, physical activity per away-from-home excursion, and at-home activity per day varied by the severity of VF damage. Results Each 5-dB decrement in IVF sensitivity was associated with a lower number of away-from-home activities per day (18% less moderate and vigorous physical activity [MVPA] minutes/d, 95% confidence interval, 0.69-0.97) and physical activities per away-from-home excursion (20% less MVPA minutes/excursion, 95% confidence interval, 0.65-0.98). Similar findings were noted for other away-from-home activity measures (including active minutes/steps per day, or active minutes/steps per excursion). However, worse IVF sensitivity was not associated with measures of at-home activities (MVPA minutes/d, active minutes/d, and steps/d), time spent at or away from home, or excursions/wk (P > .1 for all). Conclusions Restriction of physical activity in more patients with severe glaucoma results mostly from activity restriction outside the home environment. These findings highlight the importance of maintaining a safe home environment (where activity is less restricted) and increasing confidence to perform activity, particular high-intensity activity, when leaving the home amongst patients with glaucoma.

Purpose To evaluate whether home hazards and lighting levels are associated with higher fall rates in adults with varying degrees of visual field (VF) damage from glaucoma. Methods Participants with diagnosed or suspected glaucoma provided three years of prospective falls data via monthly falls diaries. A post-fall telephone questionnaire determined fall locations. Seven home areas were evaluated for hazards and lighting via an in-home assessment. Multivariate models adjusting for relevant confounders, including age, sex, comorbidity, and severity of VF damage, evaluated the influence of hazards and lighting on fall rates in each home region. Results Mean baseline age for the 170 participants was 71.0 (7.6) years and 78 (46%) of participants were female. Fifty-nine participants experienced a total of 83 home falls, with the greatest number of falls occurring on the indoor stairs (n = 24, 29%) and bedroom (n = 17, 21%). Neither the number nor the percentage of hazardous items graded as hazardous was associated with the rate of falls (P > .26). Each 10-fold increase in room lighting was associated with 35% fewer falls in that home region (P = .02). The relation between lighting and the rate of falls did not differ with the degree of visual field damage (P > .3), and a lower fall rate was noted with better lighting even in participants with mild or no VF damage (rate ratio = 0.52/10-fold better lighting; P = 0.01). Conclusions Fewer home falls were found with better lighting, but not with fewer home hazards. Lighting improvements at home may reduce fall rates in older adults. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.

The objective of this work was to investigate a multifidelity modeling approach to accurately and efficiently predict the turbulent convective heating on hypersonic inflatable aerodynamic decelerat...

Humans possess the ability to evaluate their confidence in a range of different decisions. In this study, we investigated the computational processes that underlie confidence judgements and the extent to which these computations are the same for perceptual decisions in the visual and auditory modalities. Participants completed two versions of a categorisation task with visual or auditory stimuli and made confidence judgements about their category decisions. In each modality, we varied both evidence strength, (i.e., the strength of the evidence for a particular category) and sensory uncertainty (i.e., the intensity of the sensory signal). We evaluated several classes of models which formalise the mapping of evidence strength and sensory uncertainty to confidence in different ways: 1) unscaled evidence strength models, 2) scaled evidence strength models, and 3) Bayesian models. Our model comparison results showed that across tasks and modalities, participants take evidence strength and sensory uncertainty into account in a way that is consistent with the scaled evidence strength class. Notably, the Bayesian class provided a relatively poor account of the data across modalities, particularly in the more complex categorisation task. Our findings suggest that a common process is used for evaluating confidence in perceptual decisions across domains, but that the parameter settings governing the process are tuned differently in each modality. Overall, our results highlight the impact of sensory uncertainty on confidence and the unity of metacognitive processing across sensory modalities.Author SummaryIn this study, we investigated the computational processes that describe how people derive a sense of confidence in their decisions. In particular, we determined whether the computations that underlie the evaluation of confidence for a visual decision are the same as those for an auditory decision. We tested a range of different models from 3 distinct classes which make different predictions about the computations that are used. We found that a single class of models provided the best account of confidence, suggesting a common process for evaluating confidence across sensory modalities. Even though these computations are governed by the same general process, our results suggest that the process is still fine-tuned within each modality.

Sustained production of elevated levels of the cytokines interleukin (IL)-6 or interferon (IFN)-α in the central nervous system (CNS) is detrimental and directly contributes to the pathogenesis of neurological diseases such as neuromyelitis optica spectrum disorders or cerebral interferonopathies, respectively. Using transgenic mice with CNS-targeted production of IL-6 (GFAP-IL6) or IFN-α (GFAP-IFN), we have recently demonstrated that microglia are prominent target and effector cells and mount stimulus-specific responses to these cytokines. In order to further clarify the phenotype and function of these cells, we treated GFAP-IL6 and GFAP-IFN mice with the CSF1R inhibitor PLX5622 to deplete microglia. We examined their ability to recover from acute microglia depletion, as well as the impact of chronic microglia depletion on the progression of disease. Following acute depletion in the brains of GFAP-IL6 mice, microglia repopulation was enhanced, while in GFAP-IFN mice, microglia did not repopulate the brain. Furthermore, chronic CSF1R inhibition was detrimental to the brain of GFAP-IL6 and GFAP-IFN mice and gave rise to severe CNS calcification which strongly correlated with the absence of microglia. In addition, PLX5622-treated GFAP-IFN mice had markedly reduced survival. Our findings provide evidence for novel microglia functions to protect against IFN-α-mediated neurotoxicity and neuronal dysregulation, as well as restrain calcification as a result of both IL-6- and IFN-α-induced neuroinflammation. Taken together, we demonstrate that CSF1R inhibition may be an undesirable target for therapeutic treatment of neuroinflammatory diseases that are driven by elevated IL-6 and IFN-α production.

Prior research characterizes mainly male veteran preferences at end of life using the Veterans Administration Advance Directive (VA AD), there has been no specific studies focusing on women veteran’s preferences concerning whether the AD is to be strictly (S) followed or to serve as a general guide (G). The purpose of this study was to describe women veteran preferences for life-sustaining treatments (LSTs) in various illness situations to assist providers in discussing end-of-life decisions. Additionally, we compared previously published LST preferences of male veterans with the study’s sample. Using a descriptive retrospective approach, data was collected from 484 women veterans ADs between January 2010 and December 2019. Findings revealed that women tended to trend in the same direction as men, preferring to have advance directives serve as general guidance over being strictly followed. Unconscious/Coma/Vegetative was the only factor that was statistically significant for affecting the choice of following the AD.

It is now routine to make Bose-Einstein condensates of polaritons with long enough lifetime and low enough disorder to travel ballistically for hundreds of microns in quasi-one-dimensional (1D) wires. We present observations of a polariton condensate injected at one point in a quasi-1D ring, with a well-defined initial velocity and direction. A clear precession of the circular polarization is seen, which arises from an effective spin-orbit coupling term in the Hamiltonian. Our theoretical model accurately predicts the experimentally observed behavior, and shows that "zitterbewegung" behavior plays a role in the motion of the polaritons., accepted by Phys. Rev. B

Inert gas manifolds for the handling of air-sensitive materials are commonplace in the inorganic chemistry curriculum as well as in research laboratories specializing in inorganic and organometallic synthesis. Mercury bubblers are ubiquitously implemented for maintaining a positive internal pressure for air-free manifold systems, commonly known as Schlenk lines. This has rendered them difficult to replace with equivalent and accessible alternatives. This communication describes the setup and implementation of a simple, inexpensive alternative to the traditional mercury bubbler that is modular and flexible enough to fit most any laboratory space.

Background Though significant progress in disease elimination has been made over the past decades, trachoma is the leading infectious cause of blindness globally. Further efforts in trachoma elimination are paradoxically being limited by the relative rarity of the disease, which makes clinical training for monitoring surveys difficult. In this work, we evaluate the plausibility of an Artificial Intelligence model to augment or replace human image graders in the evaluation/diagnosis of trachomatous inflammation—follicular (TF). Methods We utilized a dataset consisting of 2300 images with a 5% positivity rate for TF. We developed classifiers by implementing two state-of-the-art Convolutional Neural Network architectures, ResNet101 and VGG16, and applying a suite of data augmentation/oversampling techniques to the positive images. We then augmented our data set with additional images from independent research groups and evaluated performance. Results Models performed well in minimizing the number of false negatives, given the constraint of the low numbers of images in which TF was present. The best performing models achieved a sensitivity of 95% and positive predictive value of 50–70% while reducing the number images requiring skilled grading by 66–75%. Basic oversampling and data augmentation techniques were most successful at improving model performance, while techniques that are grounded in clinical experience, such as highlighting follicles, were less successful. Discussion The developed models perform well and significantly reduce the burden on graders by minimizing the number of false negative identifications. Further improvements in model skill will benefit from data sets with more TF as well as a range in image quality and image capture techniques used. While these models approach/meet the community-accepted standard for skilled field graders (i.e., Cohen’s Kappa >0.7), they are insufficient to be deployed independently/clinically at this time; rather, they can be utilized to significantly reduce the burden on skilled image graders.

Because transmission of ocular strains of Chlamydia trachomatis is greatest among preschool-aged children, limiting azithromycin distributions to this age group may conserve resources and result in less antimicrobial resistance, which is a potential advantage in areas with hypoendemic trachoma and limited resources.To determine the efficacy of mass azithromycin distributions to preschool-aged children as a strategy for trachoma elimination in areas with hypoendemic disease.In this cluster randomized clinical trial performed from November 23, 2014, until July 31, 2017, thirty rural communities in Niger were randomized at a 1:1 ratio to biannual mass distributions of either azithromycin or placebo to children aged 1 to 59 months. Participants and study personnel were masked to treatment allocation. Data analyses for trachoma outcomes were performed from October 19, 2021, through June 10, 2022.Every 6 months, a single dose of either oral azithromycin (20 mg/kg using height-based approximation for children who could stand or weight calculation for small children) or oral placebo was provided to all children aged 1 to 59 months.Trachoma was a prespecified outcome of the trial, assessed as the community-level prevalence of trachomatous inflammation-follicular and trachomatous inflammation-intense through masked grading of conjunctival photographs from a random sample of 40 children per community each year during the 2-year study period. A secondary outcome was the seroprevalence of antibodies to C trachomatis antigens.At baseline, 4726 children in 30 communities were included; 1695 children were enrolled in 15 azithromycin communities and 3031 children were enrolled in 15 placebo communities (mean [SD] proportions of boys, 51.8% [4.7%] vs 52.0% [4.2%]; mean [SD] age, 30.8 [2.8] vs 30.6 [2.6] months). The mean coverage of study drug for the 4 treatments was 79% (95% CI, 75%-83%) in the azithromycin group and 82% (95% CI, 79%-85%) in the placebo group. The mean prevalence of trachomatous inflammation-follicular at baseline was 1.9% (95% CI, 0.5%-3.5%) in the azithromycin group and 0.9% (95% CI, 0-1.9%) in the placebo group. At 24 months, trachomatous inflammation-follicular prevalence was 0.2% (95% CI, 0-0.5%) in the azithromycin group and 0.8% (95% CI, 0.2%-1.6%) in the placebo group (incidence rate ratio adjusted for baseline: 0.18 [95% CI, 0.01-1.20]; permutation P = .07).The findings of this trial do not show that biannual mass azithromycin distributions to preschool-aged children were more effective than placebo, although the underlying prevalence of trachoma was low. The sustained absence of trachoma even in the placebo group suggests that trachoma may have been eliminated as a public health problem in this part of Niger.ClinicalTrials.gov Identifier: NCT02048007.