We study the continuous multireference alignment model of estimating a periodic function on the circle from noisy and circularly-rotated observations. Motivated by analogous high-dimensional problems ...that arise in cryo-electron microscopy, we establish minimax rates for estimating generic signals that are explicit in the dimension K. In a high-noise regime with noise variance σ 2 ≳ K , for signals with Fourier coefficients of roughly uniform magnitude, the rate scales as σ 6 and has no further dependence on the dimension. This rate is achieved by a bispectrum inversion procedure, and our analyses provide new stability bounds for bispectrum inversion that may be of independent interest. In a low-noise regime where σ 2 ≲ K / log K , the rate scales instead as K σ 2 , and we establish this rate by a sharp analysis of the maximum likelihood estimator that marginalizes over latent rotations. A complementary lower bound that interpolates between these two regimes is obtained using Assouad's hypercube lemma. We extend these analyses also to signals whose Fourier coefficients have a slow power law decay.
Covariance matrix plays a central role in multivariate statistical analysis. Significant advances have been made recently on developing both theory and methodology for estimating large covariance ...matrices. However, a minimax theory has yet been developed. In this paper we establish the optimal rates of convergence for estimating the convariance matrix under both operator norm and Frobenius norm. It is shown that optimal procedures under the two norms are different and consequently matrix estimation under the operator norm is fundamentally different from vector estimation. The minimax upper bound is obtained by constructing a special class of tapering estimators and by studying their risk properties. A key step in obtaining the optimal rate of convergence is the derivation of the minimax lower bound. The technical analysis requires new ideas that are quite different from those used in the more conventional function/sequence estimation problems.
The literature on identification in organizations is surprisingly diverse and large. This article reviews the literature in terms of four fundamental questions. First, under “What is ...identification?,” it outlines a continuum from narrow to broad formulations and differentiates situated identification from deep identification and organizational identification from organizational commitment. Second, in answer to “Why does identification matter?,” it discusses individual and organizational outcomes as well as several links to mainstream organizational behavior topics. Third, regarding “How does identification occur?,” it describes a process model that involves cycles of sensebreaking and sensegiving, enacting identity and sensemaking, and constructing identity narratives. Finally, under “One or many?,” it discusses team, workgroup, and subunit; relational; occupational and career identifications; and how multiple identifications may conflict, converge, and combine.
Previous studies found conflicting results about whether atopic dermatitis (AD) begins in adulthood.
To determine rates, predictors, and phenotypic differences of adult-onset AD.
A systematic review ...was performed with all published observational studies in Medline, Embase, GREAT (Global Resource of EczemA Trials), LILACS (Latin American and Caribbean Health Sciences Literature), Cochrane Library, and Scopus that analyzed the age of AD onset beyond 10 years of age. At least two reviewers performed study title, abstract review, and data extraction. Pooled meta-analysis of the proportion of adult-onset AD was performed by using random-effects weighting (I2 = 99.3%).
Overall, 25 studies met inclusion criteria. Seventeen studies reported age of AD onset as after 16 years of age and had sufficient data for meta-analysis. The pooled proportion (95% confidence interval) of adult-onset AD was 26.1% (16.5%-37.2%). Similar results were found in sensitivity analyses by AD diagnostic method, study region, and sex. Phenotypic differences were observed across studies for adult-onset and child-onset AD, including higher rates of foot dermatitis and personal history of atopy but lower rates of flexural lesions and other signs and symptoms.
Characteristics of adult-onset versus child-onset AD were not commonly reported.
AD is not only a disease of childhood; 1 in 4 adults with AD report adult-onset disease, which has distinct clinical characteristics as compared to child-onset AD.
Summary Background In 2000, seven-valent pneumococcal conjugate vaccine (PCV7) was introduced in the USA and resulted in dramatic reductions in invasive pneumococcal disease (IPD) and moderate ...increases in non-PCV7 type IPD. In 2010, PCV13 replaced PCV7 in the US immunisation schedule. We aimed to assess the effect of use of PCV13 in children on IPD in children and adults in the USA. Methods We used laboratory-based and population-based data on incidence of IPD from the Active Bacterial Core surveillance (part of the Centers for Disease Control and Prevention's Emerging Infections Program) in a time-series model to compare rates of IPD before and after the introduction of PCV13. Cases of IPD between July 1, 2004, and June 30, 2013, were classified as being caused by the PCV13 serotypes against which PCV7 has no effect (PCV13 minus PCV7). In a time-series model, we used an expected outcomes approach to compare the reported incidence of IPD to that which would have been expected if PCV13 had not replaced PCV7. Findings Compared with incidence expected among children younger than 5 years if PCV7 alone had been continued, incidence of IPD overall declined by 64% (95% interval estimate 95% IE 59–68) and IPD caused by PCV13 minus PCV7 serotypes declined by 93% (91–94), by July, 2012, to June, 2013. Among adults, incidence of IPD overall also declined by 12–32% and IPD caused by PCV13 minus PCV7 type IPD declined by 58–72%, depending on age. We estimated that over 30 000 cases of IPD and 3000 deaths were averted in the first 3 years after the introduction of PCV13. Interpretation PCV13 reduced IPD across all age groups when used routinely in children in the USA. These findings provide reassurance that, similar to PCV7, PCVs with additional serotypes can also prevent transmission to unvaccinated populations. Funding Centers for Disease Control and Prevention.
Background. Group B Streptococcus (GBS), traditionally considered to be a neonatal pathogen, is an important cause of morbidity and mortality among older adults and among those with underlying ...medical conditions. We used population-based surveillance to examine trends in adult GBS disease during the period 1990–2007 and to describe the epidemiology of adult GBS disease to guide prevention efforts. Methods. Active Bacterial Core surveillance was conducted in selected counties in 10 US states. A case was defined as isolation of GBS from a normally sterile site in a nonpregnant resident of a surveillance area who was ⩾18 years of age. Rates were calculated using US Census data. Demographic and clinical information was abstracted from medical records. Serotyping and susceptibility testing were performed on isolates collected from a subset of case patients. Results. A total of 19,512 GBS cases were identified in nonpregnant adults during 1990–2007 (median patient age, 63 years); the incidence of adult GBS disease doubled from 3.6 cases per 100,000 persons during 1990 to 7.3 cases per 100,000 persons during 2007 (P<.001). The mean difference in incidence between black and white persons was 4.6 cases per 100,000 persons (range, 3.1 cases per 100,000 persons during 1991 to 5.8 cases per 100,000 persons during 1999). Common clinical syndromes in 2007 included bacteremia without focus (39.3%), skin and/or soft-tissue infection (25.6%), and pneumonia (12.6%). Most (88.0%) GBS cases in adults had ⩾1 underlying condition; diabetes was present in 44.4% of cases. Serotypes V, Ia, II, and III accounted for 80.8% of infections during 1998–1999 and 78.5% of infections during 2005–2006. Conclusions. Invasive GBS disease in nonpregnant adults represents a substantial and increasing burden, particularly among older persons, black persons, and adults with diabetes. Prevention strategies are needed.
To understand the development of students’ higher-order thinking skills (HOTS) in the smart classroom environment, a structural equation modeling analysis was used to examine the relationships ...between key factors that influence students’ learning and their HOTS within a smart classroom environment. A sample of 217 first-year Chinese college students, who studied in a smart classroom environment for one semester, completed a survey that measures their smart classroom preferences, learning motivation, learning strategy, peer interaction, and HOTS. The results indicated that peer interaction and learning motivation had a direct impact on students’ HOTS. Furthermore, indirect effects were found between students’ learning strategy and HOTS through the mediator peer interaction, and between smart classroom preferences and HOTS through the following: learning motivation, the combination of learning strategy and peer interaction, and the combination of learning motivation, learning strategy and peer interaction. Based on these findings, this study recommends that instructors teaching in a smart learning environment should focus on improving peer interaction and learning motivation, as well as smart classroom preferences and learning strategy, to hone students’ HOTS.
The xanthophylls, lutein and zeaxanthin, are dietary carotenoids that selectively accumulate in the macula of the eye providing protection against age-related macular degeneration. To reach the ...macula, carotenoids cross the retinal pigment epithelium (RPE). Xanthophylls and β-carotene mostly associate with HDL and LDL, respectively. HDL binds to cells via a scavenger receptor class B1 (SR-B1)-dependent mechanism, while LDL binds via the LDL receptor. Using an in-vitro, human RPE cell model (ARPE-19), we studied the mechanisms of carotenoid uptake into the RPE by evaluating kinetics of cell uptake when delivered in serum or isolated LDL or HDL. For lutein and β-carotene, LDL delivery resulted in the highest rates and extents of uptake. In contrast, HDL was more effective in delivering zeaxanthin and meso-zeaxanthin leading to the highest rates and extents of uptake of all four carotenoids. Inhibitors of SR-B1 suppressed zeaxanthin delivery via HDL. Results show a selective HDL-mediated uptake of zeaxanthin and meso-zeaxanthin via SR-B1 and a LDL-mediated uptake of lutein. This demonstrates a plausible mechanism for the selective accumulation of zeaxanthin greater than lutein and xanthophylls over β-carotene in the retina. We found no evidence of xanthophyll metabolism to apocarotenoids or lutein conversion to meso-zeaxanthin.
Neisseria meningitidis is a leading cause of bacterial meningitis and other serious infections worldwide. The epidemiological profile of N. meningitidis is highly changeable, with great differences ...in disease incidence and serogroup distribution. Six serogroups (namely serogroups A, B, C, W-135, X, and Y) are responsible for most cases of meningococcal disease worldwide; the epidemiological profile of disease caused by each serogroup is unique. No vaccine is available for endemic disease caused by serogroup B strains. Two tetravalent (A/C/Y/W-135) meningococcal vaccines are licensed in the United States: a purified polysaccharide product and a polysaccharide-protein conjugate vaccine. The conjugate vaccine is recommended for all adolescents, although vaccine coverage remains low, and other groups at high risk of infection. A comprehensive program to prevent invasive meningococcal disease in the United States will require vaccination of infants; several conjugate vaccines for infants may become available in the near future. Broadly protective vaccines for endemic serogroup B disease are also needed.
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