Padé approximant meets federated learning: A nearly lossless, one-shot algorithm for evidence synthesis in distributed research networks with rare outcomes.

OBJECTIVE: We developed and evaluated a novel one-shot distributed algorithm for evidence synthesis in distributed research networks with rare outcomes. MATERIALS AND METHODS: Fed-Padé, motivated by a classic mathematical tool, Padé approximants, reconstructs the multi-site data likelihood via Padé approximant whose key parameters can be computed distributively. Thanks to the simplicity of [2,2] Padé approximant, Fed-Padé requests an extremely simple task and low communication cost for data partners. Specifically, each data partner only needs to compute and share the log-likelihood and its first 4 gradients evaluated at an initial estimator. We evaluated the performance of our algorithm with extensive simulation studies and four observational healthcare databases. RESULTS: Our simulation studies revealed that a [2,2]-Padé approximant can well reconstruct the multi-site likelihood so that Fed-Padé produces nearly identical estimates to the pooled analysis. Across all simulation scenarios considered, the median of relative bias and rate of instability of our Fed-Padé are both <0.1%, whereas meta-analysis estimates have bias up to 50% and instability up to 75%. Furthermore, the confidence intervals derived from the Fed-Padé algorithm showed better coverage of the truth than confidence intervals based on the meta-analysis. In real data analysis, the Fed-Padé has a relative bias of <1% for all three comparisons for risks of acute liver injury and decreased libido, whereas the meta-analysis estimates have a substantially higher bias (around 10%). CONCLUSION: The Fed-Padé algorithm is nearly lossless, stable, communication-efficient, and easy to implement for models with rare outcomes. It provides an extremely suitable and convenient approach for synthesizing evidence in distributed research networks with rare outcomes.

Detecting acoustic chirality with matched metamaterial vortex wave antennas.

Acoustic communications often have limited data rates because of the intrinsically low frequencies. Exploring new spatial modes to increase data bandwidth at fixed frequency is a possible solution to this problem. Here, we demonstrate acoustic wave chirality transmission between two reciprocal metamaterial vortex wave antennas, generating and sensing transmitted acoustic wave chirality through the sub-wavelength geometry of the system. By adding an acoustic leaky wave surface to a ring resonator waveguide, acoustic vortex waves with positive or negative integer mode chirality are independently radiated and detected using a small number of microphones. Through computational simulation and experimental verification, using three-dimensional printed waveguides, we show that the vortex mode chirality can be transferred between two opposing acoustic vortex wave antennas across a small unguided air gap. We also show that emission into an external waveguide can provide long distance data transmission. This demonstrates the first use of metamaterial vortex wave antennas as chiral, mode multi-channel data transceivers.

Active aerosols.

We report the dynamics and control of the orientational and positional order of ensembles of gold nanorods suspended in air at standard temperature and pressure using externally applied electric fields, demonstrating an active aerosol. Light filter, valve and gradient responses are shown, establishing active aerosols as a unique type of optical element we term component-less optics.

Variance reduction in the inverse probability weighted estimators for the average treatment effect using the propensity score.

The propensity methodology is widely used in medical research to compare different treatments in designs with a nonrandomized treatment allocation. The inverse probability weighted (IPW) estimators are a primary tool for estimating the average treatment effect but the large variance of these estimators is often a significant concern for their reliable use in practice. Inspired by Rao-Blackwellization, this paper proposes a method to smooth an IPW estimator by replacing the weights in the original estimator by their mean over a distribution of the potential treatment assignment. In our simulation study, the smoothed IPW estimator achieves a substantial variance reduction over its original version with only a small increased bias, for example two-to-sevenfold variance reduction for the three IPW estimators in Lunceford and Davidian [Statistics in Medicine, 23(19), 2937-2960]. In addition, our proposed smoothing can also be applied to the locally efficient and doubly robust estimator for added protection against model misspecification. An implementation in R is provided.

Acoustic measurement and statistical characterization of direct-printed, variable-porosity aluminum foams.

Additive manufacturing has expanded greatly in recent years with the promise of being able to create complex and custom structures at will. Enhanced control over the microstructure properties, such as percent porosity, is valuable to the acoustic design of materials. In this work, aluminum foams are fabricated using a modified powder bed fusion method, which enables voxel-by-voxel printing of structures ranging from fully dense to approximately 50% porosity. To understand the acoustic response, samples are measured in an acoustic impedance tube and characterized with the Johnson-Champoux-Allard-Lafarge model for rigid-frame foams. Bayesian statistical inversion of the model parameters is performed to assess the applicability of commonly employed measurement and modeling methods for traditional foams to the additively manufactured, low porosity aluminum foams. This preliminary characterization provides insights into how emerging voxel-by-voxel additive manufacturing approaches could be used to fabricate acoustic metal foams and what could be learned about the microstructure using traditional measurement and analysis techniques.

Capacitive Bio-Inspired Flow Sensing Cupula.

Submersible robotics have improved in efficiency and versatility by incorporating features found in aquatic life, ranging from thunniform kinematics to shark skin textures. To fully realize these benefits, sensor systems must be incorporated to aid in object detection and navigation through complex flows. Again, inspiration can be taken from biology, drawing on the lateral line sensor systems and neuromast structures found on fish. To maintain a truly soft-bodied robot, a man-made flow sensor must be developed that is entirely complaint, introducing no rigidity to the artificial "skin." We present a capacitive cupula inspired by superficial neuromasts. Fabricated via lost wax methods and vacuum injection, our 5 mm tall device exhibits a sensitivity of 0.5 pF/mm (capacitance versus tip deflection) and consists of room temperature liquid metal plates embedded in a soft silicone body. In contrast to existing capacitive examples, our sensor incorporates the transducers into the cupula itself rather than at its base. We present a kinematic theory and energy-based approach to approximate capacitance versus flow, resulting in equations that are verified with a combination of experiments and COMSOL simulations.

The topographic specificity of muscle reinnervation predicts function.

Functional testing has assumed a progressively dominant role in validating the success of experimental nerve repair. Results obtained in one model, however, cannot predict the results in others because they reflect the coordinated interaction of several muscles across multiple joints. As a result, many combinations of topographically correct and incorrect muscle reinnervation could produce the same result. We have developed a binary model in which elbow flexors and extensors are reinnervated, and elbow flexion and extension are the functions tested. The musculocutaneous and radial nerves of Lister-Hooded rats were subjected to axonotmetic injuries that produced increasing degrees of axonal misdirection at the site of injury ranging from simple crush to transection and rotational offset of proximal and distal stumps. Elbow function was tested with a device that requires coordinated elbow extension to reach sugar pellets and flexion to return them to the mouth. After 12 weeks of regeneration, motoneurons projecting to the distal musculocutaneous nerve were retrogradely labelled with WGA-Ruby and scored regarding their location within musculocutaneous or radial motoneuron pools. The severity of axonal misdirection resulting from the initial surgery was mirrored by progressive degrees of inappropriate reinnervation of the musculocutaneous nerve by radial nerve axons. The specificity of reinnervation predicted elbow function (r = 0.72), whereas the number of motoneurons regenerating did not. This model is thus well suited to study the interaction of regeneration specificity and function across a single joint, and to produce data that can be generalized more broadly than those obtained from more complex models.

Evaluation of the resolution of a metamaterial acoustic leaky wave antenna.

Acoustic antennas have long been utilized to directionally steer acoustic waves in both air and water. Typically, these antennas are comprised of arrays of active acoustic elements, which are electronically phased to steer the acoustic profile in the desired direction. A new technology, known as an acoustic leaky wave antenna (LWA), has recently been shown to achieve directional steering of acoustic waves using a single active transducer coupled to a transmission line passive aperture. The LWA steers acoustic energy by preferential coupling to an input frequency and can be designed to steer from backfire to endfire, including broadside. This paper provides an analysis of resolution as a function of both input frequency and antenna length. Additionally, the resolution is compared to that achieved using an array of active acoustic elements.

Anisotropic acoustic metafluid for underwater operation.

The paper presents a method to design and characterize mechanically robust solid acoustic metamaterials suitable for operation in dense fluids such as water. These structures, also called metafluids, behave acoustically as inertial fluids characterized by anisotropic mass densities and isotropic bulk modulus. The method is illustrated through the design and experimental characterization of a metafluid consisting of perforated steel plates held together by rubber coated magnetic spacers. The spacers are very effective at reducing the effective shear modulus of the structure, and therefore effective at minimizing the ensuing coupling between the shear and pressure waves inside the solid effective medium. Inertial anisotropy together with fluid-like acoustic behavior are key properties that bring transformation acoustics in dense fluids closer to reality.

Disparities in diabetes: the nexus of race, poverty, and place.

OBJECTIVES: We sought to determine the role of neighborhood poverty and racial composition on race disparities in diabetes prevalence. METHODS: We used data from the 1999-2004 National Health and Nutrition Examination Survey and 2000 US Census to estimate the impact of individual race and poverty and neighborhood racial composition and poverty concentration on the odds of having diabetes. RESULTS: We found a race-poverty-place gradient for diabetes prevalence for Blacks and poor Whites. The odds of having diabetes were higher for Blacks than for Whites. Individual poverty increased the odds of having diabetes for both Whites and Blacks. Living in a poor neighborhood increased the odds of having diabetes for Blacks and poor Whites. CONCLUSIONS: To address race disparities in diabetes, policymakers should address problems created by concentrated poverty (e.g., lack of access to reasonably priced fruits and vegetables, recreational facilities, and health care services; high crime rates; and greater exposures to environmental toxins). Housing and development policies in urban areas should avoid creating high-poverty neighborhoods.

The intersection of neighborhood racial segregation, poverty, and urbanicity and its impact on food store availability in the United States.

BACKGROUND: Food store availability may determine the quality of food consumed by residents. Neighborhood racial residential segregation, poverty, and urbanicity independently affect food store availability, but the interactions among them have not been studied. PURPOSE: To examine availability of supermarkets, grocery stores, and convenience stores in US census tracts according to neighborhood racial/ethnic composition, poverty, and urbanicity. METHODS: Data from 2000 US Census and 2001 InfoUSA food store data were combined and multivariate negative binomial regression models employed. RESULTS: As neighborhood poverty increased, supermarket availability decreased and grocery and convenience stores increased, regardless of race/ethnicity. At equal levels of poverty, Black census tracts had the fewest supermarkets, White tracts had the most, and integrated tracts were intermediate. Hispanic census tracts had the most grocery stores at all levels of poverty. In rural census tracts, neither racial composition nor level of poverty predicted supermarket availability. CONCLUSIONS: Neighborhood racial composition and neighborhood poverty are independently associated with food store availability. Poor predominantly Black neighborhoods face a double jeopardy with the most limited access to quality food and should be prioritized for interventions. These associations are not seen in rural areas which suggest that interventions should not be universal but developed locally.

The impact of the Prime Time Sister Circles® (PTSC) on blood pressure of low-income mid-life African American women in the United States.

There is a pressing need to develop and evaluate culturally tailored, community-based interventions that address hypertension management among low-income African American women. We employed a randomized controlled trial to test the effectiveness of the Prime Time Sister Circles® Program in reducing blood pressure and body mass index among low-income African American women ages with hypertension. Study participants (N = 339) were African American women aged 40-75 years who were diagnosed with hypertension and received their primary care at government funded health centers in Washington, D.C. Compared to the usual care group, Prime Time Sister Circles® participation was associated with a reduction in systolic BP by - 2.45 (CI - 6.13, 1.23) mmHg, a reduction in diastolic BP by - 3.66 mmHg (CI - 6.32, - 0.99), and a change in BMI by - 0.26 (CI - 2.00, 1.48) from baseline to 15 months. The results suggest that culturally tailored community-based interventions can improve hypertension management in low-income women.

Childhood IQ, hearing loss, and maternal thyroid autoimmunity in the Baltimore Collaborative Perinatal Project.

BACKGROUND: Maternal thyroid autoantibodies during pregnancy have been implicated in neurodevelopmental delays, including early childhood cognitive deficits. We evaluated whether maternal autoantibodies to thyroid peroxidase (TPOaAbs) during late pregnancy were associated with childhood intelligence quotient (IQ) scores in their offspring and how the children's TPOaAb-associated sensorineural hearing loss (HL) might affect the result. METHODS: We evaluated banked third-trimester sera corresponding to 1,733 children for whom childhood cognitive test scores and audiology data were available. The mothers and their children participated in the National Institutes of Health (NIH)-sponsored Collaborative Perinatal Project (CPP) that ran from 1959 to 1974. RESULTS: A modest, statistically significant, effect of TPOaAbs on cognitive performance observed at 4 y of age lessened in both magnitude and P value by the age of 7 y. Children with sensorineural HL (SNHL) had lower IQ scores at both ages. CONCLUSION: Our data suggest that the reported effect of maternal TPOaAbs on IQ may involve early developmental delays or transient effects rather than permanent deficits. Reports associating TPOaAbs directly with IQ may reflect a portion with unexamined TPOaAb-associated SNHL. Whether the TPOaAb-associated SNHL is in the neurodevelopmental pathway of later cognitive delays or is independently associated with IQ requires investigation in other studies.

Bone mass in Rett syndrome: association with clinical parameters and MECP2 mutations.

Rett syndrome (RTT) is an X-linked neurodevelopmental disorder caused by mutations in the MECP2 gene. In 49 female RTT children, aged 1.9-17 y, bone mass was assessed and correlated with clinical parameters and mutations involving the MECP2 gene. We also studied five adult females, aged 20-33 y, and one male child, aged 6 y. Lumbar spine bone mineral content (BMC) and bone mineral density (BMD) were correlated with weight, height, BMI, clinical severity, degree of scoliosis, use of anticonvulsants, and ambulatory status. L1-L4 BMD and BMC showed that 48.9% of them had BMD values >2 SD below age-related norms. BMD values were in the osteoporotic range in the five adult females with RTT. Eleven percent of the children and adults with RTT experienced fractures. Low bone mass was correlated with marginal significance to clinical severity and ambulation but not to scoliosis or anticonvulsant use. Lowest bone mass occurred in patients with T158M or R270X mutations but without statistical significance. Studies in a murine model of RTT confirmed low bone mass as an inherent component of this syndrome. MECP2 mutations and clinical parameters impact bone mass in RTT, but an association with a specific mutation was not demonstrable.

Associations of bone mineral density and lead levels in blood, tibia, and patella in urban-dwelling women.

OBJECTIVE: The objective of this study was to evaluate the relations between bone mineral density (BMD) and lead in blood, tibia, and patella and to investigate how BMD modifies these lead biomarkers in older women. DESIGN: In this study, we used cross-sectional analysis. PARTICIPANTS: We studied 112 women, 50-70 years of age, including both whites and African Americans, residing in Baltimore, Maryland. MEASUREMENTS: We measured lumbar spine BMD, blood and bone lead by dual energy X-ray absorptiometry, anodic stripping voltammetry, and (109)Cd-induced K-shell X-ray fluorescence, respectively. We measured vitamin D receptor and apolipoprotein E (APOE) genotypes using standard methods. RESULTS: Mean (+/- SD) BMD and lead levels in blood, tibia, and patella were 1.02+/-0.16 g/cm(2), 3.3+/-2.2 microg/dL, 19.7+/-13.2 microg/g, and 5.7+/-15.3 microg/g, respectively. In adjusted analysis, higher BMD was associated with higher tibia lead levels (p=0.03). BMD was not associated with lead levels in blood or patella. There was evidence of significant effect modification by BMD on relations of physical activity with blood lead levels and by APOE genotype on relations of BMD with tibia lead levels. There was no evidence that BMD modified relations between tibia lead or patella lead and blood lead levels. CONCLUSIONS: We believe that BMD represents the capacity of bone that can store lead, by substitution for calcium, and thus the findings may have relevance for effect-size estimates in persons with higher BMD. RELEVANCE TO CLINICAL PRACTICE: The results have implications for changes in lead kinetics with aging, and thus the related risk of health effects associated with substantial early- and midlife lead exposure in older persons.

Antipsychotic treatment patterns and hospitalizations among adults with schizophrenia.

OBJECTIVE(S): To characterize the longitudinal patterns of antipsychotic treatment and to investigate the relationship between antipsychotic treatment patterns and acute hospitalizations among adults with schizophrenia. We hypothesized that continuous antipsychotic treatment would be associated with fewer hospitalizations and shorter lengths of stay. METHOD: Seven years of retrospective Maryland Medicaid administrative data were used to examine inpatient medical encounters and outpatient psychotropic treatment in community-based settings from 1993 through 2000. The sample consisted of 1727 adults continuously enrolled in the Maryland Medicaid program from July 1992 through June 1994, and diagnosed with schizophrenia. The main outcome measures were a) any schizophrenia hospitalization; b) number of schizophrenia hospitalizations; and c) inpatient days associated with a primary diagnosis of schizophrenia. RESULTS: The average duration of antipsychotic use was six months in any single year and four and one-half years across the entire study period. Compared to individuals with a more continuous pattern of antipsychotic treatment, individuals with moderate or light use had odds of hospitalization for schizophrenia that were 52 or 72% greater (95%CI: 30-75% greater, 49-100% greater respectively). Light users of antipsychotics have an average length of stay per hospitalization that is approximately 20% longer than the average for continuous users (95%CI: 2-39% longer). CONCLUSIONS: Findings emphasize the benefit of continuous antipsychotic treatment for individuals with schizophrenia.

Gender and race/ethnicity differences in lead dose biomarkers.

OBJECTIVES: We sought to identify predictors of lead concentrations in the blood, tibias, and patellae of older adults and to describe differences by gender, race/ethnicity, and other factors that can influence lead toxicokinetics and, thus modify health effects. METHODS: Participants aged 50 to 70 years (N=1140) were randomly identified from selected neighborhoods in Baltimore, Maryland. We measured lead concentrations by anodic stripping voltammetry (in blood) and (109)Cd-induced K-shell x-ray fluorescence (in bone). We used multiple linear regression to identify predictors of lead concentrations. RESULTS: Mean (SD) lead concentrations in blood, tibias, and patellae were 3.5 (2.4) mug/dL, 18.9 (12.5) mug/g, and 6.8 (18.1) mug/g, respectively. Tibia concentrations were 29% higher in African Americans than in Whites (P < .01). We observed effect modification by race/ethnicity on the association of gender and physical activity to blood lead concentrations and by gender on the association of age to tibia lead concentrations. Patella lead concentrations differed by gender; apolipoprotein E genotype modified this relation. CONCLUSIONS: African Americans evidenced a prominent disparity in lifetime lead dose. Women may be at higher risk of release of lead from bone and consequent health effects because of increased bone demineralization with aging.

Residential Segregation and Hypertension Prevalence in Black and White Older Adults.

PURPOSE: The purpose of this article was to assess segregation's role on race differences in hypertension among non-Hispanic Blacks and Whites aged 50 and over. METHOD: Hypertension was defined as systolic blood pressure (BP) ≥ 140 mmHg, diastolic BP ≥ 90 mmHg, or self-reported antihypertensive medication use. Segregation measures combined race, neighborhood racial composition, and individual and neighborhood poverty level. Logistic models produced odds ratios and 95% confidence intervals (CIs) for each segregation category, adjusting for health-related factors. RESULTS: Blacks in Black (OR = 2.54, CI = [1.61, 4.00]), White (OR = 2.56, CI = [1.24, 5.31]), and integrated neighborhoods (OR = 3.23, CI = [1.72, 6.03]) had greater odds of hypertension compared with Whites in White neighborhoods. Poor Whites in poor neighborhoods (OR = 1.74, CI = [1.09, 2.76]), nonpoor Blacks in nonpoor (OR = 3.03, CI = [1.79, 5.12]) and poor neighborhoods (OR = 4.08, CI = [2.16, 7.70]), and poor Blacks in nonpoor (OR = 4.35, CI = [2.17, 8.73]) and poor neighborhoods (OR = 2.75, CI = [1.74, 4.36]) had greater odds compared with nonpoor Whites in nonpoor neighborhoods. CONCLUSION: Interventions targeting hypertension among older adults should consider neighborhood compositions.

Veterans have greater variability in their perception of binocular alignment.

INTRODUCTION: A significant population of our wounded veterans suffer long-term functional consequences of visual deficit, disorientation, dizziness, and an impaired ability to read. These symptoms may be related to damage within the otolith pathways that contribute to ocular alignment. The purpose of this study was to compare perception of vertical and torsional ocular alignment between veterans and healthy controls in an upright and supine test position. MATERIALS AND METHODS: Veterans (n = 26) with reports of dizziness were recruited from the East Orange Veterans Administration Hospital. Healthy controls (n = 26) were recruited from both Johns Hopkins University and the East Orange VA. Each subject performed 20 trials each of a novel vertical and torsional binocular alignment perception test. Veterans underwent semicircular canal and otolith pathway function testing. RESULTS: 88% of the Veterans had an absent otolith response. Only the veterans had an abnormally large variability in perception of both vertical and torsional ocular alignment, and in both upright and supine position. Neither post-traumatic stress disorder, nor depression contributed to the misperception in binocular alignment. CONCLUSIONS: Our novel method of measuring vertical and torsional misalignment distinguishes veterans with dizziness from healthy controls. The high prevalence of absent otolith function seems to explain this result. Further studies are needed to better understand the fundamental mechanism responsible for the increased variability of perception of binocular alignment.

Impact of a statewide home visiting program to prevent child abuse.

OBJECTIVES: To assess the impact of a voluntary, paraprofessional home visiting program in preventing child maltreatment and reducing the multiple, malleable psychosocial risks for maltreatment for which families had been targeted. METHODS: This collaborative, experimental study focused on 6 Healthy Families Alaska (HFAK) programs; 325 families were enrolled in 2000-2001, randomized to intervention and control groups, and interviewed to measure baseline attributes. Follow-up data were collected when children were 2 years old (85% follow-up rate). Outcomes included maltreatment reports, measures of potential maltreatment and parental risks, for example, poor mental health, substance use, and partner violence. HFAK records were reviewed to measure home visiting services. Home visitors were surveyed to measure perceived effectiveness and training adequacy. RESULTS: Parental risks were common at baseline, and one-sixth of families had a substantiated child protective services report in the child's first 2 years of life. There was no overall program effect on maltreatment reports, and most measures of potential maltreatment. Home visited mothers reported using mild forms of physical discipline less often than control mothers. The groups were similar in their use of more severe forms of physical discipline. There was no program impact on parental risks. There was no impact on outcomes for families with a 'high dose' of home visiting. Home visitors often failed to address parental risks and seldom linked families with community resources. Contradictions in the model compromised effectiveness. CONCLUSIONS: The program did not prevent child maltreatment, nor reduce the parental risks that had made families eligible for service. Research is needed to develop and test strategies to improve the effectiveness of home visiting.