64 research outputs found
Domain wall propagation and nucleation in a metastable two-level system
We present a dynamical description and analysis of non-equilibrium
transitions in the noisy one-dimensional Ginzburg-Landau equation for an
extensive system based on a weak noise canonical phase space formulation of the
Freidlin-Wentzel or Martin-Siggia-Rose methods. We derive propagating nonlinear
domain wall or soliton solutions of the resulting canonical field equations
with superimposed diffusive modes. The transition pathways are characterized by
the nucleations and subsequent propagation of domain walls. We discuss the
general switching scenario in terms of a dilute gas of propagating domain walls
and evaluate the Arrhenius factor in terms of the associated action. We find
excellent agreement with recent numerical optimization studies.Comment: 28 pages, 16 figures, revtex styl
Tomographic imaging of fluid flows by the use of two-tone frequency-modulation spectroscopy
Sex differences in the timing of identification among children and adults with autism spectrum disorders
To examine differences by sex in the timing of identification of individuals with autism spectrum disorders (ASD), survey data were collected in the Netherlands from 2,275 males and females with autistic disorder, Asperger's syndrome and PDD-NOS. Among participants <18 years of age, females with Asperger's syndrome were identified later than males. Among participants â„18 years of age, females with autistic disorder were identified later than males. In more recent years, girls with Asperger's syndrome are diagnosed later than boys, confirming earlier findings. In adults, the delayed timing of diagnosis in females with autistic disorder may be related to changing practices in diagnosis over time. Strategies for changing clinician behaviour to improve recognition of ASD in females are needed. © 2012 Springer Science+Business Media, LLC
Secondary Rearrangements and Hypermutation Generate Sufficient B Cell Diversity to Mount Protective Antiviral Immunoglobulin Responses
Laboratory phase-contrast nanotomography of unstained Bombus terrestris compound eyes
Imaging the visual systems of bumblebees and other pollinating insects may increase understanding of their dependence on specific habitats and how they will be affected by climate change. Current high-resolution imaging methods are either limited to two dimensions (light- and electron microscopy) or have limited access (synchrotron radiation x-ray tomography). For x-ray imaging, heavy metal stains are often used to increase contrast. Here, we present micron-resolution imaging of compound eyes of buff-tailed bumblebees (Bombus terrestris) using a table-top x-ray nanotomography (nano-CT) system. By propagation-based phase-contrast imaging, the use of stains was avoided and the microanatomy could more accurately be reconstructed than in samples stained with phosphotungstic acid or osmium tetroxide. The findings in the nano-CT images of the compound eye were confirmed by comparisons with light- and transmission electron microscopy of the same sample and finally, comparisons to synchrotron radiation tomography as well as to a commercial micro-CT system were done.ISSN:0022-2720ISSN:1365-281
Laboratory phaseâcontrast nanotomography of unstained Bombus terrestris compound eyes
Imaging the visual systems of bumblebees and other pollinating insects may increase understanding of their dependence on specific habitats and how they will be affected by climate change. Current high-resolution imaging methods are either limited to two dimensions (light- and electron microscopy) or have limited access (synchrotron radiation x-ray tomography). For x-ray imaging, heavy metal stains are often used to increase contrast. Here, we present micron-resolution imaging of compound eyes of buff-tailed bumblebees (Bombus terrestris) using a table-top x-ray nanotomography (nano-CT) system. By propagation-based phase-contrast imaging, the use of stains was avoided and the microanatomy could more accurately be reconstructed than in samples stained with phosphotungstic acid or osmium tetroxide. The findings in the nano-CT images of the compound eye were confirmed by comparisons with light- and transmission electron microscopy of the same sample and finally, comparisons to synchrotron radiation tomography as well as to a commercial micro-CT system were done.peerReviewe
Ru-Catalyzed Benzannulation Leads to Luminescent Boron-Containing Polycyclic Aromatic Hydrocarbons
A series of boron-containing polycyclic
aromatic hydrocarbons (PAHs)
have been synthesized through the Ru-catalyzed cyclization of aryl
ene-ynes. The benchtop-stable products show deep blue photoluminescence.
Reversible electrochemical reduction is possible at moderate electrode
potentials (about â2.0 V vs FcH/FcH<sup>+</sup>); some of the
compounds also underwent reversible oxidation. The systematic expansion
of the PAH scaffolds permitted the analysis of even subtle structureâproperty
relationships
Cold-developed electron-beam-patterned ZEP 7000 for fabrication of 13 nm nickel zone plates
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