3,071 research outputs found

    Shock volume: Patient-specific cumulative hypoperfusion predicts organ dysfunction in a prospective cohort of multiply injured patients

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    BACKGROUND: Multiply injured patients are at risk of developing hemorrhagic shock and organ dysfunction. We determined how cumulative hypoperfusion predicted organ dysfunction by integrating serial Shock Index measurements. METHODS: In this study, we calculated shock volume (SHVL) which is a patient-specific index that quantifies cumulative hypoperfusion by integrating abnormally elevated Shock Index (heart rate/systolic blood pressure ≥ 0.9) values acutely after injury. Shock volume was calculated at three hours (3 hr), six hours (6 hr), and twenty-four hours (24 hr) after injury. Organ dysfunction was quantified using Marshall Organ Dysfunction Scores averaged from days 2 through 5 after injury (aMODSD2–D5). Logistic regression was used to determine correspondence of 3hrSHVL, 6hrSHVL, and 24hrSHVL to organ dysfunction. We compared correspondence of SHVL to organ dysfunction with traditional indices of shock including the initial base deficit (BD) and the lowest pH measurement made in the first 24 hr after injury (minimum pH). RESULTS: SHVL at all three time intervals demonstrated higher correspondence to organ dysfunction (R2 = 0.48 to 0.52) compared to initial BD (R2 = 0.32) and minimum pH (R2 = 0.32). Additionally, we compared predictive capabilities of SHVL, initial BD and minimum pH to identify patients at risk of developing high-magnitude organ dysfunction by constructing receiver operator characteristic curves. SHVL at six hours and 24 hours had higher area under the curve compared to initial BD and minimum pH. CONCLUSION: SHVL is a non-invasive metric that can predict anticipated organ dysfunction and identify patients at risk for high-magnitude organ dysfunction after injury. LEVEL OF EVIDENCE: Prognostic study, level III

    Random Walks for Spike-Timing Dependent Plasticity

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    Random walk methods are used to calculate the moments of negative image equilibrium distributions in synaptic weight dynamics governed by spike-timing dependent plasticity (STDP). The neural architecture of the model is based on the electrosensory lateral line lobe (ELL) of mormyrid electric fish, which forms a negative image of the reafferent signal from the fish's own electric discharge to optimize detection of sensory electric fields. Of particular behavioral importance to the fish is the variance of the equilibrium postsynaptic potential in the presence of noise, which is determined by the variance of the equilibrium weight distribution. Recurrence relations are derived for the moments of the equilibrium weight distribution, for arbitrary postsynaptic potential functions and arbitrary learning rules. For the case of homogeneous network parameters, explicit closed form solutions are developed for the covariances of the synaptic weight and postsynaptic potential distributions.Comment: 18 pages, 8 figures, 15 subfigures; uses revtex4, subfigure, amsmat

    Advanced imaging capabilities by incorporating plasmonics and metamaterials in detectors

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    Ultraviolet detection is often required to be made in the presence of a strong background of solar radiation which needs to be suppressed, but materials limitations at these wavelengths can impact both filter and sensor performance. In this work, we explore the use of 1D photonic bandgap structures integrated directly onto a Si sensor that can operate with solar blindness. These filters take advantage of the improved admittance with silicon to significantly improve throughput over conventional stand-alone bandpass filter elements. At far ultraviolet wavelengths these filters require the use of non-absorbing dielectrics such as the metal fluoride materials of MgF_2, AlF_3 and LiF. The latest performance of these 1D multilayer filters on Si photodiodes and CCD imaging sensors is demonstrated. We have also extended these 1D structures to more complex multilayers guided by the design concepts of metamaterials and metatronics, and to 2D patterned plasmonic hole array filters fabricated in aluminum. The performance of sensors and test filter structures is presented with an emphasis on UV throughput

    Angular Diameters of the G Subdwarf μ\mu Cassiopeiae A and the K Dwarfs σ\sigma Draconis and HR 511 from Interferometric Measurements with the CHARA Array

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    Using the longest baselines of the CHARA Array, we have measured the angular diameter of the G5 V subdwarf μ\mu Cas A, the first such determination for a halo population star. We compare this result to new diameters for the higher metallicity K0 V stars, σ\sigma Dra and HR 511, and find that the metal-poor star, μ\mu Cas A, has an effective temperature (Teff=5297±32T_{\rm eff}=5297\pm32 K), radius (R=0.791±0.008RR=0.791\pm0.008 R_{\rm \odot}), and absolute luminosity (L=0.442±0.014LL=0.442\pm0.014 L_{\rm \odot}) comparable to the other two stars with later spectral types. We show that stellar models show a discrepancy in the predicted temperature and radius for μ\mu Cas A, and we discuss these results and how they provide a key to understanding the fundamental relationships for stars with low metallicity.Comment: Accepted for publication in The Astrophysical Journa

    A tidewater glacier landform assemblage in Belcher Inlet, Canadian Arctic

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    Belcher Glacier, a 35 km-long tidewater outlet glacier of the 12,000 km² ice cap on Devon Island (Dowdeswell et al. 2004), is one of the fastest-flowing glaciers in the Canadian Arctic (Van Wychen et al. 2014) (Fig. 1). Belcher Glacier and neighbouring Fitzroy Glacier to the southeast account for about 55% of the iceberg calving loss from the Devon Ice Cap (Van Wychen et al. 2014). The terminus of Belcher Glacier remained relatively stable between the 1960s (light blue dashed line in Fig. 1a) and 2000 (Landsat 7 satellite image in Fig. 1a). In contrast, the unnamed glacier immediately to the north retreated 2 km during this period (Fig. 1a). Belcher Glacier and the unnamed glacier retreated around 500 m and 250 m, respectively, between 2000 and 2014 (dark blue dashed line in Fig. 1a). The bed topography of Belcher Glacier, which is around 250 m below sea level at the present-day glacier margin (Fig. 1c) and remains below sea level in the lower 11 km of the glacier, suggests that its terminus region may become unstable in the event of future retreat. Seafloor mapping of Belcher Inlet beyond the termini of Belcher Glacier and the unnamed glacier (Fig. 1a), together with sub-bottom profiling, provide information about the dynamic behaviour of tidewater glaciers.This is the author accepted manuscript. The final version is available from Geological Society of London via https://doi.org/10.1144/M46.14

    Taking the Measure of the Universe: Precision Astrometry with SIM PlanetQuest

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    Precision astrometry at microarcsecond accuracy has application to a wide range of astrophysical problems. This paper is a study of the science questions that can be addressed using an instrument that delivers parallaxes at about 4 microarcsec on targets as faint as V = 20, differential accuracy of 0.6 microarcsec on bright targets, and with flexible scheduling. The science topics are drawn primarily from the Team Key Projects, selected in 2000, for the Space Interferometry Mission PlanetQuest (SIM PlanetQuest). We use the capabilities of this mission to illustrate the importance of the next level of astrometric precision in modern astrophysics. SIM PlanetQuest is currently in the detailed design phase, having completed all of the enabling technologies needed for the flight instrument in 2005. It will be the first space-based long baseline Michelson interferometer designed for precision astrometry. SIM will contribute strongly to many astronomical fields including stellar and galactic astrophysics, planetary systems around nearby stars, and the study of quasar and AGN nuclei. SIM will search for planets with masses as small as an Earth orbiting in the `habitable zone' around the nearest stars using differential astrometry, and could discover many dozen if Earth-like planets are common. It will be the most capable instrument for detecting planets around young stars, thereby providing insights into how planetary systems are born and how they evolve with time. SIM will observe significant numbers of very high- and low-mass stars, providing stellar masses to 1%, the accuracy needed to challenge physical models. Using precision proper motion measurements, SIM will probe the galactic mass distribution and the formation and evolution of the Galactic halo. (abridged)Comment: 54 pages, 28 figures, uses emulateapj. Submitted to PAS

    Circuit dissection of the role of somatostatin in itch and pain

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    Stimuli that elicit itch are detected by sensory neurons that innervate the skin. This information is processed by the spinal cord; however, the way in which this occurs is still poorly understood. Here we investigated the neuronal pathways for itch neurotransmission, particularly the contribution of the neuropeptide somatostatin. We find that in the periphery, somatostatin is exclusively expressed in Nppb+ neurons, and we demonstrate that Nppb+somatostatin+ cells function as pruriceptors. Employing chemogenetics, pharmacology and cell-specific ablation methods, we demonstrate that somatostatin potentiates itch by inhibiting inhibitory dynorphin neurons, which results in disinhibition of GRPR+ neurons. Furthermore, elimination of somatostatin from primary afferents and/or from spinal interneurons demonstrates differential involvement of the peptide released from these sources in itch and pain. Our results define the neural circuit underlying somatostatin-induced itch and characterize a contrasting antinociceptive role for the peptide

    Coastal oceanography and sedimentology in New Zealand, 1967-91.

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    This paper reviews research that has taken place on physical oceanography and sedimentology on New Zealand's estuaries and the inner shelf since c. 1967. It includes estuarine sedimentation, tidal inlets, beach morphodynamics, nearshore and inner shelf sedimentation, tides and coastal currents, numerical modelling, short-period waves, tsunamis, and storm surges. An extensive reference list covering both published and unpublished material is included. Formal teaching and research programmes dealing with coastal landforms and the processes that shape them were only introduced to New Zealand universities in 1964; the history of the New Zealand Journal of Marine and Freshwater Research parallels and chronicles the development of physical coastal science in New Zealand, most of which has been accomplished in last 25 years
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