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91.
AIM:To investigate the effects of percutaneous endoscopic gastrostomy(PEG) feeding on gastro-oesophageal reflux(GOR) in a group of these children using combined intraluminal pH and multiple intraluminal impedance(pH/MII) . METHODS:Ten neurologically impaired children underwent 12 h combined pH/MII procedures at least 1 d before and at least 12 d after PEG placement. METHODS:Prior to PEG placement(pre-PEG) a total of 183 GOR episodes were detected,156(85.2%) were non-acidic.After PEG placement(post-PEG) a to... 相似文献
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Mike Fruscione Russell Kirks Allyson Cochran Keith Murphy Erin H. Baker John B. Martinie David A. Iannitti Dionisios Vrochides 《HPB : the official journal of the International Hepato Pancreato Biliary Association》2018,20(8):721-728
Background
The American College of Surgeons NSQIP® Surgical Risk Calculator (SRC) was developed to estimate postoperative outcomes. Our goal was to develop and validate an institution-specific risk calculator for patients undergoing major hepatectomy at Carolinas Medical Center (CMC).Methods
Outcomes generated by the SRC were recorded for 139 major hepatectomies performed at CMC (2008–2016). Novel predictive models for seven postoperative outcomes were constructed and probabilities calculated. Brier score and area under the curve (AUC) were employed to assess accuracy. Internal validation was performed using bootstrap logistic regression. Logistic regression models were constructed using bivariate and multivariate analyses.Results
Brier scores showed no significant difference in the predictive ability of the SRC and CMC model. Significant differences in the discriminative ability of the models were identified at the individual level. Both models closely predicted 30-day mortality (SRC AUC: 0.867; CMC AUC: 0.815). The CMC model was a stronger predictor of individual postoperative risk for six of seven outcomes (SRC AUC: 0.531–0.867; CMC AUC: 0.753–0.970).Conclusion
Institution-specific models provide superior outcome predictions of perioperative risk for patients undergoing major hepatectomy. If properly developed and validated, institution-specific models can be used to deliver more accurate, patient-specific care. 相似文献93.
Anurag Mehta Abnash C. Jain Anthony P. Morise Mahaveer C. Mehta Mike Billie 《Clinical cardiology》1998,21(2):109-114
Background: Left ventricular hypertrophy (LVH) on the electrocardiogram (ECG) may be masked in the presence of complete right bundle-branch block (RBBB). Left bundle-branch block on the ECG is associated with LVH at autopsy in 93% of hearts studied. However, RBBB does not predict LVH and the usual ECG criteria applied for LVH may not be reliable in the presence of RBBB. Hypothesis: The study was undertaken to evaluate left atrial (LA) abnormality as a criterion for the diagnosis of LVH in the presence of RBBB. Methods: Left atrial abnormality in the ECG was assessed by two independent observers as a criterion of LVH in the presence of RBBB in 100 patients, and data were compared with those of 50 patients without LA abnormality. Results: Left ventricular hypertrophy was confirmed by echocardiographic determination of left ventricular (LV) mass in both groups. Observers reliably differentiated between hy-pertrophied and normal-sized LV in the presence of RBBB by using LA abnormality as an ECG criterion when correlated with LV mass determined by echocardiography. Observer 1 correctly detected LVH in 88% and Observer 2 in 82% of patients. False positive diagnosis was made in 12 and 18% of patients by Observers 1 and 2, respectively. Observers' performance of recognition of LA abnormality in the present study was 94%. Results showed sensitivity of 76 and 70% and specificity of 84 and 92% for Observers 1 and 2, respectively. Left ventricular mass increased significantly and was diagnostic of LVH in 92% of patients with LA abnormality. Left ventricular mass was high in 84% of patients when corrected by body surface area. LVH in the presence of RBBB by the ECG was found in only seven patients (5%) when six commonly used conventional criteria of diagnosis of LVH by ECG were employed. Regression analysis found LA abnormality to be a strong independent predictor of increased LV mass. Multiple regression analysis revealed that age, body mass index, body surface area, and frontal axis are also significant predictors of LV mass. Conclusion: The results obtained by the correlation of LA abnormality by ECG and LVH by echocardiography conclude that LA abnormality by ECG was significantly diagnostic of LV hypertrophy in the presence of RBBB. 相似文献
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The vegetation and geology of the Wet Tropics Bioregion of North Queensland, covering 1?998?150 ha, were mapped at a scale of 1:50?000. The resulting geographic information system (GIS) data base provided an unprecedented opportunity to examine vegetation condition across the entire bioregion. Mapping used colour aerial photography at 1:25?000, informed by ground truthing. Vegetation type, nature of the understory and ground cover, degree and type of disturbance, and the presence of secondary vegetation were described by a coding system, with codes marked directly on the aerial photos.Analysis of these data has confirmed a picture, which emerged from ground truthing, of large areas of sclerophyll woodland and forest being invaded by a rainforest understory that prevents regeneration of the sclerophyll canopy. Fifty-three per cent of the native vegetation of the bioregion consists of non-rainforest vegetation types, dominated in both area and number by sclerophyll woodlands and forests. Seventeen per cent of the 735?713 ha of sclerophyll woodland and forest types were assessed as having suffered irreversible change. Between 25% and 79% of individual forest vegetation types were judged to have been affected by irreversible change. No climatic changes, or changes in the environment, apart from those related to changing fire regimes, were identified as causative factors. Changed fire regimes, predominantly fire exclusion, are considered to be the most likely cause. 相似文献
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Edward T. Tipper Emily I. Stevenson Victoria Alcock Alasdair C. G. Knight J. Jotautas Baronas Robert G. Hilton Mike J. Bickle Christina S. Larkin Linshu Feng Katy E. Relph Genevieve Hughes 《Proceedings of the National Academy of Sciences of the United States of America》2021,118(1)
Rivers carry the dissolved and solid products of silicate mineral weathering, a process that removes from the atmosphere and provides a key negative climate feedback over geological timescales. Here we show that, in some river systems, a reactive exchange pool on river suspended particulate matter, bonded weakly to mineral surfaces, increases the mobile cation flux by 50%. The chemistry of both river waters and the exchange pool demonstrates exchange equilibrium, confirmed by Sr isotopes. Global silicate weathering fluxes are calculated based on riverine dissolved sodium (Na+) from silicate minerals. The large exchange pool supplies Na+ of nonsilicate origin to the dissolved load, especially in catchments with widespread marine sediments, or where rocks have equilibrated with saline basement fluids. We quantify this by comparing the riverine sediment exchange pool and river water chemistry. In some basins, cation exchange could account for the majority of sodium in the river water, significantly reducing estimates of silicate weathering. At a global scale, we demonstrate that silicate weathering fluxes are overestimated by 12 to 28%. This overestimation is greatest in regions of high erosion and high sediment loads where the negative climate feedback has a maximum sensitivity to chemical weathering reactions. In the context of other recent findings that reduce the net consumption through chemical weathering, the magnitude of the continental silicate weathering fluxes and its implications for solid Earth degassing fluxes need to be further investigated.For decades, silicate weathering has been postulated to provide the negative climate feedback on Earth that prevents a runaway greenhouse climate like on Venus (1). Silicate mineral dissolution with carbonic acid converts atmospheric into carbonate, and releases essential nutrients to the terrestrial and marine biosphere (2). There have been many attempts to quantify the silicate weathering flux (3), mostly assuming that riverine dissolved sodium () is derived only from silicate minerals and rock salt. Here we show that there is a major addition of nonsilicate to the critical zone from ancient seawater, weakly bonded to sedimentary rocks and supplied to waters via the cation exchange process. The implication is not only that the silicate weathering flux is overestimated at a global scale, but that this nonsilicate is most important in regions previously thought to have the highest silicate weathering fluxes (so called weathering-limited regions) and greatest climate sensitivity.Cation exchange is a rapid chemical reaction between cations in the dissolved phase and mineral surfaces, particularly clays (4). Major and trace cations such as calcium (), magnesium (), sodium (), potassium (), and strontium () form the cation exchange pool, which balances negative charges on river-borne clay particle surfaces. This exchange takes place on interlayer sites, between the tetrahedral and octahedral layers, or on exposed surfaces (4). The importance of the cation exchange pool is well recognized in soils and aquifers (4, 5), has significant implications for enhanced weathering (6), and has been proposed as an important mechanism for buffering the composition of river waters (7–9). However, data on the riverine exchange pool are only available for two large river systems [Amazon and Ganges-Brahmaputra (10, 11)], despite its significance in providing a source of elements that are immediately bioavailable (12), and their potential for biasing the quantification of silicate weathering (9).It is increasingly recognized that rapidly reactive phases have a strong influence on the chemistry of river waters (13, 14). Cation exchange is a rapid reaction occurring continuously in soils, as riverine freshwaters evolve downstream interacting with particulate matter, and when they mix with seawater (15, 16). Important examples of cation exchange are the “swapping” of divalent cations and with , in particular when there is a major change in water composition such as when fluvial clays reach the ocean,[1]As a result, marine sediments have an exchange pool that is dominated by (17). Subsequently, these marine sediments are uplifted and emplaced on the continents where in the exchange pool is released by cation exchange with Ca-rich fresh waters (9). This has major implications for estimates of silicate weathering fluxes and associated consumption, because they are calculated using the content of rivers (3). Cerling et al. (9) proposed that the -rich exchange pool exerts an important control on natural waters, based on charge balance arguments from river water chemistry, but this hypothesis has never been rigorously tested (18) by determining the flux and composition of the exchange pool of rivers around the world.In this contribution, we present a large dataset of fluvial sediment cation exchange capacity (CEC) and composition in several of the world’s largest river basins. By comparing with the concomitant dissolved load chemistry, we demonstrate that 1) the exchange pool in river sediments is in equilibrium with the river water; 2) the fraction of mobile elements in the exchange pool relative to the dissolved pool can be significant, particularly in rapidly eroding, weathering-limited catchments; and 3) given reasonable inferences on the composition of old marine sedimentary rocks, modern-day silicate weathering has been overestimated and carbonate weathering has been underestimated. The results reduce the estimated magnitude of the silicate weathering flux, but increase the supply of base cations (e.g., , which can be a limiting nutrient) to the biosphere, suggesting a greater role of organic carbon burial compared with silicate weathering for the long-term atmospheric sink. 相似文献