Search

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.amjsurg.2010.04.004 Byline: James M. Watkins (a), Motaz Qadan (b), Chris Battista (b), Hiram C. Polk (c) Keywords: Surgical quality measures; Small-town hospitals; Surgical time-out; Specialist surgeons; Surgical specialties Abstract: Most studies of surgical quality improvement have been performed in large and/or teaching hospitals; the efficacy of safety and quality efforts in smaller hospitals have not been reported. Author Affiliation: (a) Taylor Regional Hospital, Campbellsville, KY, USA (b) Price Institute of Surgical Research, University of Louisville School of Medicine, KY, USA (c) Department of Surgery, University of Louisville School of Medicine, KY 40292, USA Article History: Received 1 April 2010; Revised 16 April 2010 Article Note: (footnote) Conflicts of interest: All authors have seen and approved the final manuscript. There were no competing interests to declare by any of the authors. All authors had full access to all the data and had the final responsibility to submit the manuscript for publication.

Deep chlorophyll maxima (DCM) are common in stratified lakes and oceans, and phytoplankton growth within DCM often contributes significantly to total system production. Theory suggests that properties of DCM should be predictable by trophic state, with DCM becoming deeper, broader, and less productive with greater oligotrophy. However, rigorous tests of these expectations are lacking in freshwater systems. We use data generated by the U.S. EPA from 1996 to 2017, including in situ profile data for temperature, photosynthetically active radiation (PAR), chlorophyll, beam attenuation (cp), and dissolved oxygen (DO), to investigate patterns in DCM across lakes and over time. We consider trophic state, 1% PAR depth (z1%), thermal structure, and degree of photoacclimation as potential drivers of DCM characteristics. DCM depth and thickness generally increased while DCM chlorophyll concentration decreased with decreasing trophic state index (greater oligotrophy). The z1%was a stronger predictor of DCM depth than thermal structure. DCM in meso‐oligotrophic waters were closely aligned with maxima in cpand DO saturation, suggesting they are autotrophically productive. However, the depths of these maxima diverged in ultra‐oligotrophic waters, with DCM occurring deepest. This is likely a consequence of photoacclimation in high‐transparency waters, where cpcan be a better proxy for phytoplankton biomass than chlorophyll. Our results are generally consistent with expectations from DCM theory, but they also identify specific gaps in our understanding of DCM in lakes, including the causes of multiple DCM, the importance of nutriclines, and the processes forming DCM at higher light levels than expected.

Important clues to the initiation and early behavior of large (super-) eruptions lie in the records of degassing during magma ascent. Here we investigate the timescales of magma ascent for three rhyolitic supereruptions that show field evidence for contrasting behavior at eruption onset: (1) 650 km3, 0.767 Ma Bishop Tuff, Long Valley; (2) 530 km3, 25.4 ka Oruanui eruption, Taupo; and (3) 2500 km3, 2.08 Ma Huckleberry Ridge Tuff, Yellowstone. During magma ascent, decompression causes volatile exsolution from the host melt into bubbles, leading to H2O and CO2gradients in quartz-hosted re-entrants (REs; unsealed inclusions). These gradients are modeled to estimate ascent rates. We present best-fit modeled ascent rates for H2O and CO2profiles for REs in early-erupted fall deposits from Bishop (n= 13), Oruanui (n= 9), and Huckleberry Ridge (n= 9). Using a Matlab script that includes an error minimization function, Bishop REs yield ascent rates of 0.6–13 m/s, overlapping with and extending beyond those of the Huckleberry Ridge (0.3–4.0 m/s). Re-entrants in Oruanui quartz crystals from the first two eruptive phases (of 10) yield the slowest ascent rates determined in this study (0.06–0.48 m/s), whereas those from phase three, which has clear field evidence for a marked increase in eruption intensity, are uniformly higher (1.4–2.6 m/s).

The rates of nucleation and crystal growth from silicate melt are difficult to measure because the temperature-time path of magma is often unknown. We use geochemical gradients around spherulites in obsidian glass to estimate the temperature-time interval of spherulite crystallization. This information is used in conjunction with new high-resolution X-ray computed tomography (HRXCT) data on the size distributions of spherulites in six samples of rhyolite obsidian lava to infer spherulite nucleation rates. A large data set of geochemical profiles indicate that the lavas cooled at rates of 10-2.2to 10-1.2°C/h, and that the spherulites grew at rates that decreased exponentially with time, with values of 10-0.70to 100.30µm/h at 600°C. Spherulites are estimated to have begun nucleating when undercooling [ΔT, = liquidus T(≈800°C) minus nucleation T] reached 100-277°C, and stopped when ΔT= 203-365°C, with exact values dependent on assumed cooling and growth rates. Regardless of rates, we find that spherulites nucleated within a ~88-113°C temperature interval and, hence, began when ΔT≈ 0.65-0.88 x TL, peaking when ΔT≈ 0.59-0.80 x TL. A peak rate of nucleation of 0.072 ± 0.049 cm-3h-1occurred at 533 ± 14 °C, using cooling and growth rates that best fit the data set of geochemical profiles. While our inferred values for ΔToverlap those from experimental studies, our nucleation rates are much lower. That difference likely results from experimental studies using hydrous melts; the natural spherulites grew in nearly anhydrous glass.

Background: Multiple system organ failure (MOF) remains a major source of morbidity and mortality in trauma patients. Despite restoration of central hemodynamics, intestinal hypoperfusion can persist. Mucosal ischemia and barrier breakdown are factors in the genesis of MOF. Heparan sulfate is a gycosaminoglycan similar to heparin, but with minimal anticoagulant properties. As an adjunct to resuscitation, it improves immunologic function and restores mucosal oxygenation and function. We hypothesized that resuscitation with heparan following hemorrhage wound prevents intestinal hypoperfusion. Materials and methods:In vivovideomicroscopy was used to study small intestine microcirculation in rats. Animals were hemorrhaged to 50% of baseline mean arterial pressure (MAP) and maintained there. Resuscitation was initiated when the return of 10% shed blood was required to keep MAP at 50%. Animals received either heparan (7 mg/kg/1 ml saline) or saline (1 ml) followed by the remaining shed blood and an equal volume of saline. MAP, cardiac output (CO), A1 arteriole diameters, and flow were determined. Results: Resuscitation of the saline control group resulted in normal MAP with elevation of CO to 25–40% above baseline. The heparan group had return of MAP but only a moderate increase in CO (7–15%). Saline resuscitation led to progressive deterioration in A1 diameters and flow. The addition of heparan prevented delayed A1 constriction and significantly improved perfusion. Conclusions: Heparan prior to resuscitation improved intestinal perfusion, despite a relative reduction in CO. Improvement in nutrient blood flow may protect the mucosal barrier, reducing the incidence of MOF, and suggests that heparan may be useful in resuscitation of trauma patients.