6,734 research outputs found
Malignant Cerebral Edema following CT Myelogram Using Isovue-M 300 Intrathecal Nonionic Water-Soluble Contrast: A Case Report
Lumbar myelogram utilizing nonionic contrast is a commonly performed procedure to identify spinal pathology. Complication rates are low. Cerebral edema has been shown to occur following intrathecal injection of ionic contrast; however, no current literature has documented this complication relating to the ubiquitously used nonionic contrast medium. We report a case of a patient who developed malignant cerebral edema following a lumbar myelogram with Isovue-M 300 nonionic water-soluble intrathecal contrast. We believe this is the first reported case of cerebral edema resulting from the use of a nonionic contrast
Dynamic localization of C. elegans TPR-GoLoco proteins mediates mitotic spindle orientation by extrinsic signaling
Cell divisions are sometimes oriented by extrinsic signals, by mechanisms that are poorly understood. Proteins containing TPR and GoLoco-domains (C. elegans GPR-1/2, Drosophila Pins, vertebrate LGN and AGS3) are candidates for mediating mitotic spindle orientation by extrinsic signals, but the mechanisms by which TPR-GoLoco proteins may localize in response to extrinsic cues are not well defined. The C. elegans TPR-GoLoco protein pair GPR-1/2 is enriched at a site of contact between two cells – the endomesodermal precursor EMS and the germline precursor P2 – and both cells align their divisions toward this shared cell-cell contact. To determine whether GPR-1/2 is enriched at this site within both cells, we generated mosaic embryos with GPR-1/2 bearing a different fluorescent tag in different cells. We were surprised to find that GPR-1/2 distribution is symmetric in EMS, where GPR-1/2 had been proposed to function as an asymmetric cue for spindle orientation. Instead, GPR-1/2 is asymmetrically distributed only in P2. We demonstrate a role for normal GPR-1/2 localization in P2 division orientation. We show that MES-1/Src signaling plays an instructive role in P2 for asymmetric GPR-1/2 localization and normal spindle orientation. We ruled out a model in which signaling localizes GPR-1/2 by locally inhibiting LET-99, a GPR-1/2 antagonist. Instead, asymmetric GPR-1/2 distribution is established by destabilization at one cell contact, diffusion, and trapping at another cell contact. Once the mitotic spindle of P2 is oriented normally, microtubule-dependent removal of GPR-1/2 prevented excess accumulation, in an apparent negative-feedback loop. These results highlight the role of dynamic TPR-GoLoco protein localization as a key mediator of mitotic spindle alignment in response to instructive, external cues
Slot-mode-coupled optomechanical crystals
We present a design methodology and analysis of a cavity optomechanical
system in which a localized GHz frequency mechanical mode of a nanobeam
resonator is evanescently coupled to a high quality factor (Q>10^6) optical
mode of a separate nanobeam optical cavity. Using separate nanobeams provides
flexibility, enabling the independent design and optimization of the optics and
mechanics of the system. In addition, the small gap (approx. 25 nm) between the
two resonators gives rise to a slot mode effect that enables a large zero-point
optomechanical coupling strength to be achieved, with g/2pi > 300 kHz in a
Si3N4 system at 980 nm and g/2pi approx. 900 kHz in a Si system at 1550 nm. The
fact that large coupling strengths to GHz mechanical oscillators can be
achieved in SiN is important, as this material has a broad optical transparency
window, which allows operation throughout the visible and near-infrared. As an
application of this platform, we consider wide-band optical frequency
conversion between 1300 nm and 980 nm, using two optical nanobeam cavities
coupled on either side to the breathing mode of a mechanical nanobeam
resonator
Intercalation of Hydrotalcites with Hexacyanoferrate(II) and (III)-a ThermoRaman Spectroscopic Study
Raman spectroscopy using a hot stage indicates that the intercalation of hexacyanoferrate(II) and (III) in the interlayer space of a Mg,Al hydrotalcites leads to layered solids where the intercalated species is both hexacyanoferrate(II) and (III). Raman spectroscopy shows that depending on the oxidation state of the initial hexacyanoferrate partial oxidation and reduction takes place upon intercalation. For the hexacyanoferrate(III) some partial reduction occurs during synthesis. The symmetry of the hexacyanoferrate decreases from Oh existing for the free anions to D3d in the hexacyanoferrate interlayered hydrotalcite complexes. Hot stage Raman spectroscopy reveals the oxidation of the hexacyanoferrate(II) to hexacyanoferrate(III) in the hydrotalcite interlayer with the removal of the cyanide anions above 250 °C. Thermal treatment causes the loss of CN ions through the observation of a band at 2080 cm-1. The hexacyanoferrate (III) interlayered Mg,Al hydrotalcites decomposes above 150 °C
Apical constriction: A cell shape change that can drive morphogenesis
Biologists have long recognized that dramatic bending of a cell sheet may be driven by even modest shrinking of the apical sides of cells. Cell shape changes and tissue movements like these are at the core of many of the morphogenetic movements that shape animal form during development, driving processes such as gastrulation, tube formation and neurulation. The mechanisms of such cell shape changes must integrate developmental patterning information in order to spatially and temporally control force production -- issues that touch on fundamental aspects of both cell and developmental biology and on birth defects research. How does developmental patterning regulate force-producing mechanisms, and what roles do such mechanisms play in development? Work on apical constriction from multiple systems including Drosophila, C. elegans, sea urchin, Xenopus, chick and mouse has begun to illuminate these issues. Here, we review this effort to explore the diversity of mechanisms of apical constriction, the diversity of roles that apical constriction plays in development, and the common themes that emerge from comparing systems
Critical review of strategic planning research in hospitality and tourism
Strategic planning remains one of the most popular management tools, but theoretical and empirical developments in the academic literature have been a slow burn. This paper addresses this gap and provides an up-to-date review of hospitality and tourism strategic planning research. We review strategic planning research from 1995 to 2013 in seven leading tourism academic journals, and adopt a modern and broad conceptualization of strategic planning. While there is some awareness of effective tourism strategic planning processes, academic research has not kept pace with practice. To stimulate a resurgence of research interest, we provide future research directions. We observe a methodological introspection and present some new research methodologies, which are critically important in researching the turbulent, chaotic and nonlinear tourism environment
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