BEYOND LINEARITY AND INDEPENDENCE

This brief lecture discusses statistical problems associated with postulating and fitting models in engineering and the sciences. Particular emphasis is placed on the two-model problem: the employment of both deterministic and stochastic components within a model. Further, the use of empirical versus theoretical models on the part of both statisticians and experimenters is examined

Free-induction-decay magnetometer with enhanced optical pumping

Spin preparation prior to a free-induction-decay (FID) measurement can be adversely affected by transverse bias fields, particularly in the geophysical field range. A strategy that enhances the spin polarization accumulated before readout is demonstrated, by synchronizing optical pumping with a magnetic field pulse that supersedes any transverse fields by over two order of magnitude. The pulsed magnetic field is generated along the optical pumping axis using a compact electromagnetic coil pair encompassing a micro-electromechanical systems (MEMS) vapor cell. The coils also resistively heat the cesium (Cs) vapor to the optimal atomic density without spurious magnetic field contributions as they are rapidly demagnetized to approximately zero field during spin readout. The demagnetization process is analyzed electronically, and directly with a FID measurement, to confirm that the residual magnetic field is minimal during detection. The sensitivity performance of this technique is compared to existing optical pumping modalities across a wide magnetic field range. A noise floor sensitivity of $238\,\mathrm{fT/\surd{Hz}}$ was achieved in a field of approximately $\mathrm{50\,\mu{T}}$, in close agreement with the Cram\'{e}r-Rao lower bound (CRLB) predicted noise density of $258\,\mathrm{fT/\surd{Hz}}$.Comment: 10 pages, 7 figure

Wideband corrugated feedhorns, for radar, communications, radiometry and quasi-optics

This work was supported in part by Engineering and Physical Sciences Research Council, U.K., under Grant EP/R013705/1, and in part by IAA Funding.A wide variety of desirable antenna beam patterns can be synthesized by optimal excitation and phasing of the HE11 and HE12 modes in scalar corrugated feedhorns. However, the bandwidth of such two-mode horns is often limited by modal dispersion. In this paper we introduce a class of low dispersion, two-mode feedhorns that can operate, in some cases, over operating bandwidths of 40-50%. We provide example designs that include horns with high coupling efficiency to: 1) a pure HE11 mode for single-mode excitation of corrugated pipe transmission lines; 2) a LG00 and LG02 combination for radiometry, with narrow beams; 3) a pure Laguerre Gaussian LG00 mode for quasi-optical instrumentation with constant phase centers; 4) a constant gain antenna for uniform illumination with frequency; 5) Airy patterns or “top hat” patterns for radar or communications applications, designed to maximize aperture efficiencies when used with larger reflect or lens antennas. More generally, we show methods to generate and phase multiple HE1n modes, to synthesize symmetric output beams at any desired frequency or gain.Publisher PDFPeer reviewe

An unfolding signifier: London's Baltic Exchange in Tallinn

In the summer of 2007 an unusual cargo arrived at Muuga and Paldiski harbors outside Tallinn. It consisted of nearly 50 containers holding over 1,000 tons of building material ranging from marble columns, staircases and fireplaces, to sculpted allegorical figures, wooden paneling and old-fashioned telephone booths. They were once part of the Baltic Exchange in the City of London. Soon they will become facets of the landscape of Tallinn. The following article charts this remarkable story and deploys this fragmented monument to analyze three issues relating to the Estonian capital: the relocation of the ‘Bronze Soldier’, the demolition of the Sakala Culture Center, and Tallinn’s future role as European Cultural Capital in 2011

Investigating the factor structure and measurement invariance of the Eating Disorder Examination-Questionnaire (EDE-Q) in a community sample of gender minority adults from the United States

Objective: The Eating Disorder Examination-Questionnaire (EDE-Q) is one of the most widely used self-report assessments of eating disorder symptoms. However, evidence indicates potential problems with its original factor structure and associated psychometric properties in a variety of populations, including gender minority populations. The aim of the current investigation was to explore several previously published EDE-Q factor structures and to examine internal consistency and measurement invariance of the best-fitting EDE-Q model in a large community sample of gender minority adults. Methods: Data were drawn from 1567 adults (337 transgender men, 180 transgender women, and 1050 gender-expansive individuals) who participated in The PRIDE Study, a large-scale longitudinal cohort study of sexual and gender minorities from the United States. A series of confirmatory factor analyses (CFAs) were conducted to explore the fit of eight proposed EDE-Q models; internal consistency (Cronbach\u27s alphas, Omega coefficients) and measurement invariance (multi-group CFA) were subsequently evaluated. Results: A brief seven-item, three-factor (dietary restraint, shape/weight overvaluation, body dissatisfaction) model of the EDE-Q consistently evidenced the best fit across gender minority groups (transgender men, transgender women, gender-expansive individuals). The internal consistencies of the three subscales were adequate in all groups, and measurement invariance across the groups was supported. Discussion: Taken together, these findings support the use of the seven-item, three-factor version of the EDE-Q for assessing eating disorder symptomatology in gender minority populations. Future studies can confirm the current findings in focused examinations of the seven-item, three-factor EDE-Q in diverse gender minority samples across race, ethnicity, socioeconomic status, and age ranges. Public Significance Statement: Although transgender individuals have greater risk of developing an eating disorder, the factor structure of the Eating Disorder Examination-Questionnaire, one of the most widely used eating disorder assessment measures, has not been explored in transgender adults. We found that a seven-item model including three factors of dietary restraint, shape and weight overvaluation, and body dissatisfaction had the best fit among transgender and nonbinary adults

Psychometric validation of the Muscle Dysmorphic Disorder Inventory (MDDI) among U.S. transgender men

Muscle dysmorphia (MD) is characterized by a pervasive belief or fear of insufficient muscularity and an elevated drive for muscularity, representing the pathological and extreme pursuit of muscularity. Psychometric properties of one of the most widely used measures of MD symptoms—the Muscle Dysmorphic Disorder Inventory (MDDI)—have yet to be evaluated in transgender men despite emerging evidence suggesting differential risk for MD symptoms in this population. In this study, we assessed the psychometric properties of the MDDI in a sample of 330 transgender men ages 18–67 years who participated in a large-scale national longitudinal cohort study of sexual and gender minority adults in the U.S. Using a two-step, split-sample approach, an initial exploratory factor analysis supported a three-factor structure and a subsequent confirmatory factor analysis of a re-specified three-factor model demonstrated good overall fit (χ2/df = 1.84, CFI =0.94, TLI =0.92, RMSEA =0.07 [90% CI =0.05,.09], SRMR =0.08). Moreover, results supported the internal consistency and convergent validity of the MDDI subscales in transgender men. Findings inform the use of the MDDI among transgender men and provide a foundation to support further work on the MDDI and MD symptoms among gender minority populations

Community norms of the Muscle Dysmorphic Disorder Inventory (MDDI) among gender minority populations

Purpose: Representing the pathological extreme pursuit of muscularity, muscle dysmorphia (MD) is characterized by a pervasive belief or fear around insufficient muscularity and an elevated drive for muscularity. Despite evidence of heightened body image-related concerns among gender minority populations, little is known about the degree of MD symptoms among gender minorities, particularly based on Muscle Dysmorphic Disorder Inventory (MDDI) scores. The objective of this study was to assess community norms of the MDDI in gender-expansive people, transgender men, and transgender women. Method: Data from participants in The PRIDE Study, an existing study of health outcomes in sexual and gender minority people, were examined. We calculated means, standard deviations, and percentiles for the MDDI total and subscale scores among gender-expansive people (i.e., those who identify outside of the binary system of man or woman; n = 1023), transgender men (n = 326), and transgender women (n = 177). The Kruskal-Wallis test was used to assess group differences and post hoc Dunn’s tests were used to examine pairwise differences. Results: Transgender men reported the highest mean MDDI total score (30.5 ± 7.5), followed by gender-expansive people (27.2 ± 6.7), then transgender women (24.6 ± 5.7). The differences in total MDDI score were driven largely by the Drive for Size subscale and, to a lesser extent, the Functional Impairment subscale. There were no significant differences in the Appearance Intolerance subscale among the three groups. Conclusions: Transgender men reported higher Drive for Size, Functional Impairment, and Total MDDI scores compared to gender-expansive people and transgender women. These norms provide insights into the experience of MD symptoms among gender minorities and can aid researchers and clinicians in the interpretation of MDDI scores among gender minority populations

Optimal Brain MRI Protocol for New Neurological Complaint

Background/Purpose Patients with neurologic complaints are imaged with MRI protocols that may include many pulse sequences. It has not been documented which sequences are essential. We assessed the diagnostic accuracy of a limited number of sequences in patients with new neurologic complaints. Methods: 996 consecutive brain MRI studies from patients with new neurological complaints were divided into 2 groups. In group 1, reviewers used a 3-sequence set that included sagittal T1-weighted, axial T2-weighted fluid-attenuated inversion recovery, and axial diffusion-weighted images. Subsequently, another group of studies were reviewed using axial susceptibility-weighted images in addition to the 3 sequences. The reference standard was the study's official report. Discrepancies between the limited sequence review and the reference standard including Level I findings (that may require immediate change in patient management) were identified. Results: There were 84 major findings in 497 studies in group 1 with 21 not identified in the limited sequence evaluations: 12 enhancing lesions and 3 vascular abnormalities identified on MR angiography. The 3-sequence set did not reveal microhemorrhagic foci in 15 of 19 studies. There were 117 major findings in 499 studies in group 2 with 19 not identified on the 4-sequence set: 17 enhancing lesions and 2 vascular lesions identified on angiography. All 87 Level I findings were identified using limited sequence (56 acute infarcts, 16 hemorrhages, and 15 mass lesions). Conclusion: A 4-pulse sequence brain MRI study is sufficient to evaluate patients with a new neurological complaint except when contrast or angiography is indicated

Optical pumping enhancement of a free-induction-decay magnetometer

Spin preparation prior to a free-induction-decay (FID) measurement can be adversely affected by transverse bias fields, particularly in the geophysical field range. A strategy that enhances the spin polarization accumulated before readout is demonstrated, by synchronizing optical pumping with a magnetic field pulse that supersedes any transverse fields by over two order of magnitude. The pulsed magnetic field is generated along the optical pumping axis using a compact electromagnetic coil pair encompassing a micro-electromechanical systems (MEMS) vapor cell. The coils also resistively heat the cesium (Cs) vapor to the optimal atomic density without spurious magnetic field contributions as they are rapidly demagnetized to approximately zero field during spin readout. The demagnetization process is analyzed electronically, and directly with a FID measurement, to confirm that the residual magnetic field is minimal during detection. The sensitivity performance of this technique is compared to existing optical pumping modalities across a wide magnetic field range. A noise floor sensitivity of 238 fT/√Hz was achieved in a field of approximately 50 μT, in close agreement with the Cramér-Rao lower bound (CRLB) predicted noise density of 258 fT/√Hz

The SOFG Anatomy Entry List (SAEL):an annotation tool for functional genomics data

A great deal of data in functional genomics studies needs to be annotated with low-resolution anatomical terms. For example, gene expression assays based on manually dissected samples (microarray, SAGE, etc.) need high-level anatomical terms to describe sample origin. First-pass annotation in high-throughput assays (e.g. large-scale in situ gene expression screens or phenotype screens) and bibliographic applications, such as selection of keywords, would also benefit from a minimum set of standard anatomical terms. Although only simple terms are required, the researcher faces serious practical problems of inconsistency and confusion, given the different aims and the range of complexity of existing anatomy ontologies. A Standards and Ontologies for Functional Genomics (SOFG) group therefore initiated discussions between several of the major anatomical ontologies for higher vertebrates. As we report here, one result of these discussions is a simple, accessible, controlled vocabulary of gross anatomical terms, the SOFG Anatomy Entry List (SAEL). The SAEL is available from http://www.sofg.org and is intended as a resource for biologists, curators, bioinformaticians and developers of software supporting functional genomics. It can be used directly for annotation in the contexts described above. Importantly, each term is linked to the corresponding term in each of the major anatomy ontologies. Where the simple list does not provide enough detail or sophistication, therefore, the researcher can use the SAEL to choose the appropriate ontology and move directly to the relevant term as an entry point. The SAEL links will also be used to support computational access to the respective ontologies