71 research outputs found

    Imaging Unstained Synthetic Polymer Crystals and Defects on Atomic Length Scales Using Cryogenic Electron Microscopy

    No full text
    Properties of soft crystalline materials such as synthetic polymers are governed by locations of constituent atoms. Determining atomic-scale structures in these materials is difficult because they degrade rapidly when studied by electron microscopy, and techniques such as X-ray scattering average over volumes much larger than coherent blocks of the unit cells. We obtained cryo-electron microscopy images of self-assembled nanosheets of a peptoid polymer, made by solid-phase synthesis, in which we see a variety of crystalline motifs. A combination of crystallographic and single-particle methods, developed for cryo-electron microscopy of biological macromolecules, was used to obtain high-resolution images of the crystals. Individual crystals contain grains that are mirror images of each other with concomitant grain boundaries. We have used molecular dynamic simulations to build an atomic model of the crystal structure to facilitate the interpretation of electron micrographs. Direct visualization of crystalline grains and grain boundaries on atomic length scales represents a new level of information for the polymer field

    Superior semicircular canal dehiscence in East Asian women with osteoporosis

    Get PDF
    <p>Abstract</p> <p>Background</p> <p>Superior semicircular canal dehiscence (SSCD) may cause Tullio phenomenon (sound-induced vertigo) or Hennebert sign (valsalva-induced vertigo) due to the absence of bone overlying the SSC. We document a case series of elderly East Asian women with atypical SSCD symptoms, radiologically confirmed dehiscence and concurrent osteoporosis.</p> <p>Methods</p> <p>A retrospective record review was performed on patients with dizziness, vertigo, and/or imbalance from a neurology clinic in a community health center serving the East Asian population in Boston. SSCD was confirmed by multi-detector, high-resolution CT of the temporal bone (with Pöschl and Stenvers reformations) and osteoporosis was documented by bone mineral density (BMD) scans.</p> <p>Results</p> <p>Of the 496 patients seen in the neurology clinic of a community health center from 2008 to 2010, 76 (17.3%) had symptoms of dizziness, vertigo, and/or imbalance. Five (6.6%) had confirmed SSCD by multi-detector, high-resolution CT of the temporal bone with longitudinal areas of dehiscence along the long axis of SSC, ranging from 0.4 to 3.0 mm, as seen on the Pöschl view. Two of the 5 patients experienced motion-induced vertigo, two fell due to disequilibrium, and one had chronic dizziness. None had a history of head trauma, otologic surgery, or active intracerebral disease. On neurological examination, two patients had inducible vertigo on Dix-Hallpike maneuver and none experienced cerebellar deficit, Tullio phenomenon, or Hennebert sign. All had documented osteoporosis or osteopenia by BMD scans. Three of them had definite osteoporosis, with T-scores < −2.5 in the axial spine, while another had osteopenia with a T-score of −2.3 in the left femur.</p> <p>Conclusions</p> <p>We describe an unusual presentation of SSCD without Tullio phenomenon or Hennebert sign in a population of elderly, East Asian women. There may be an association of SSCD and osteoporosis in this population. Further research is needed to determine the incidence and prevalence of this disorder, as well as the relationship of age, race, osteoporosis risk, and the development of SSCD.</p

    Diversity, equity, and inclusivity in observational ambulatory assessment: Recommendations from two decades of Electronically Activated Recorder (EAR) research

    No full text
    Ambient audio sampling methods such as the Electronically Activated Recorder (EAR) have become increasingly prominent in clinical and social sciences research. These methods record snippets of naturalistically assessed audio from participants' daily lives, enabling novel observational research about the daily social interactions, identities, environments, behaviors, and speech of populations of interest. In practice, these scientific opportunities are equaled by methodological challenges: researchers' own cultural backgrounds and identities can easily and unknowingly permeate the collection, coding, analysis, and interpretation of social data from daily life. Ambient audio sampling poses unique and significant challenges to cultural humility, diversity, equity, and inclusivity (DEI) in scientific research that require systematized attention. Motivated by this observation, an international consortium of 21 researchers who have used ambient audio sampling methodologies created a workgroup with the aim of improving upon existing published guidelines. We pooled formally and informally documented challenges pertaining to DEI in ambient audio sampling from our collective experience on 40+ studies (most of which used the EAR app) in clinical and healthy populations ranging from children to older adults. This article presents our resultant recommendations and argues for the incorporation of community-engaged research methods in observational ambulatory assessment designs looking forward. We provide concrete recommendations across each stage typical of an ambient audio sampling study (recruiting and enrolling participants, developing coding systems, training coders, handling multi-linguistic participants, data analysis and interpretation, and dissemination of results) as well as guiding questions that can be used to adapt these recommendations to project-specific constraints and needs
    corecore