Determining physiological mechanisms leading to circulatory failure can be challenging, contributing to the difficulties in delivering effective hemodynamic management in critical care. Continuous, ...non-additionally invasive monitoring of preload changes, and assessment of contractility from Frank-Starling curves could potentially make it much easier to diagnose and manage circulatory failure.
This study combines non-additionally invasive model-based methods to estimate left ventricle end-diastolic volume (LEDV) and stroke volume (SV) during hemodynamic interventions in a pig trial (N = 6). Agreement of model-based LEDV and measured admittance catheter LEDV is assessed. Model-based LEDV and SV are used to identify response to hemodynamic interventions and create Frank-Starling curves, from which Frank-Starling contractility (FSC) is identified as the gradient.
Model-based LEDV had good agreement with measured admittance catheter LEDV, with Bland-Altman median bias limits of agreement (2.5th, 97.5th percentile) of 2.2 ml -13.8, 22.5. Model LEDV and SV were used to identify non-responsive interventions with a good area under the receiver-operating characteristic (ROC) curve of 0.83. FSC was identified using model LEDV and SV with Bland-Altman median bias limits of agreement (2.5th, 97.5th percentile) of 0.07 -0.68, 0.56, with FSC from admittance catheter LEDV and aortic flow probe SV used as a reference method.
This study provides proof-of-concept preload changes and Frank-Starling curves could be non-additionally invasively estimated for critically ill patients, which could potentially enable much clearer insight into cardiovascular function than is currently possible at the patient bedside.
•Non-additionally invasive left ventricle end-diastolic volume to monitor preload changes.•Frank-Starling curves show relationship between stroke volume and preload.•Proof-of-concept pig trial with clinically relevant hemodynamic interventions.
A number of pathologic processes contribute to the elevation in cardiac filling pressures in heart failure (HF), including myocardial dysfunction and primary volume overload. In this review, we ...discuss the important role of the venous system and the concepts of stressed blood volume and unstressed blood volume. We review how regulation of venous tone modifies the distribution of blood between these 2 functional compartments, the physical distribution of blood between the pulmonary and systemic circulations, and how these relate to the hemodynamic abnormalities observed in HF. Finally, we review recently applied methods for estimating stressed blood volume and how they are being applied to the results of clinical studies to provide new insights into resting and exercise hemodynamics and therapeutics for HF.
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•Venous tone regulates the distribution of blood volume between stressed and unstressed compartments.•This distribution in turn influences pressures in the pulmonary and systemic circulations, contributing to hemodynamic abnormalities in heart failure.•Venodilation and the reduction of stressed blood volume underlie the therapeutic effects of many of the drugs and devices used for the management of heart failure.
•Cortical and subcortical volumes are equally variable in schizophrenia and controls.•Intracranial and ventricle volumes are more variable in schizophrenia than controls.•Variance group differences ...consistent across demographic and clinical variables.
Despite hundreds of structural MRI studies documenting smaller brain volumes on average in schizophrenia compared to controls, little attention has been paid to group differences in the variability of brain volumes. Examination of variability may help interpret mean group differences in brain volumes and aid in better understanding the heterogeneity of schizophrenia. Variability in 246 MRI studies was meta-analyzed for 13 structures that have shown medium to large mean effect sizes (Cohen’s d≥0.4): intracranial volume, total brain volume, lateral ventricles, third ventricle, total gray matter, frontal gray matter, prefrontal gray matter, temporal gray matter, superior temporal gyrus gray matter, planum temporale, hippocampus, fusiform gyrus, insula; and a control structure, caudate nucleus. No significant differences in variability in cortical/subcortical volumes were detected in schizophrenia relative to controls. In contrast, increased variability was found in schizophrenia compared to controls for intracranial and especially lateral and third ventricle volumes. These findings highlight the need for more attention to ventricles and detailed analyses of brain volume distributions to better elucidate the pathophysiology of schizophrenia.
Tropical fans and normal complexes Nathanson, Anastasia; Ross, Dustin
Advances in mathematics (New York. 1965),
05/2023, Letnik:
420
Journal Article
Recenzirano
Odprti dostop
Associated to any divisor in the Chow ring of a simplicial tropical fan, we construct a family of polytopal complexes, called normal complexes, which we propose as an analogue of the well-studied ...notion of normal polytopes from the setting of complete fans. We describe certain closed convex polyhedral cones of divisors for which the “volume” of each divisor in the cone—that is, the degree of its top power—is equal to the volume of the associated normal complexes. For the Bergman fan of any matroid with building set, we prove that there exists an open family of such cones of divisors with nonempty interiors. We view the theory of normal complexes developed in this paper as a polytopal model underlying the combinatorial Hodge theory pioneered by Adiprasito, Huh, and Katz.
Extrapolation and bubbles Barberis, Nicholas; Greenwood, Robin; Jin, Lawrence ...
Journal of financial economics,
08/2018, Letnik:
129, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We present an extrapolative model of bubbles. In the model, many investors form their demand for a risky asset by weighing two signals—an average of the asset’s past price changes and the asset’s ...degree of overvaluation—and “waver” over time in the relative weight they put on them. The model predicts that good news about fundamentals can trigger large price bubbles, that bubbles will be accompanied by high trading volume, and that volume increases with past asset returns. We present empirical evidence that bears on some of the model’s distinctive predictions.
Measure the caseload of pancreatectomies that influences their short-term outcome, at a national level, and assess the applicability of a centralization policy.
There is agreement that ...pancreatectomies should be centralized. However, previous studies have failed to accurately define a "high-volume" center.
French healthcare databases were screened to identify all adult patients who had elective pancreatectomies between 2007 and 2012. The patients' age, comorbidities, indication, and extent of surgery, and also the hospital administrative-type and location were retrieved. The annual-caseload of pancreatectomy was calculated for each hospital facility. The primary endpoint was 90-day mortality. Spline modeling was used to identify the different annual-caseload that influenced mortality. Logistic regressions were performed to assess if their influence was independent of confounders, and the accuracy of the model calculated.
Overall, 22,366 patients underwent a pancreatectomy and the mortality was 8.1%. Two cut-offs were identified (25 and 65 per year): compared with centers performing >65 resections per year, the adjusted OR of mortality was 1.865 (1.529-2.276) in centers performing ≤25 resections per year and 1.234 (1.031-1.478) in those performing 26 to 65 resections per year. The average number of facilities performing ≤25, 26 to 65, and >65 pancreatectomies per year was 456, 20, and 9, respectively. The percentage of patients operated in these facilities was 56.6%, 19.9%, and 23.3%, respectively.For pancreaticoduodenectomies (12,670 patients; mortality 9.2%), there were 2 cut-offs (16 and 40 pancreaticoduodenectomies per year), and both were independent predictors of mortality (adjusted OR of 1.979 and 1.333). For distal pancreatectomies (7085 patients; 6.2% mortality), there were 2 cut-offs (13 and 25 distal pancreatectomies per year), but neither was an independent predictor of outcome (area under the receiver-operating characteristic curve of the model = 0.778).
Centralization of pancreatic surgery is theoretically justified, but currently unrealizable. As the incidence of pancreatic cancer increases, there is an urgent need to improve the training of surgeons and develop both intermediate and high-volume centers.
This work proposes a method for model reduction of finite-volume models that guarantees the resulting reduced-order model is conservative, thereby preserving the structure intrinsic to finite-volume ...discretizations. The proposed reduced-order models associate with optimization problems characterized by a minimum-residual objective function and nonlinear equality constraints that explicitly enforce conservation over subdomains. Conservative Galerkin projection arises from formulating this optimization problem at the time-continuous level, while conservative least-squares Petrov–Galerkin (LSPG) projection associates with a time-discrete formulation. We equip these approaches with hyper-reduction techniques in the case of nonlinear flux and source terms, and also provide approaches for handling infeasibility. In addition, we perform analyses that include deriving conditions under which conservative Galerkin and conservative LSPG are equivalent, as well as deriving a posteriori error bounds. Numerical experiments performed on a parameterized quasi-1D Euler equation demonstrate the ability of the proposed method to ensure not only global conservation, but also significantly lower state-space errors than nonconservative reduced-order models such as standard Galerkin and LSPG projection.
•Two model-reduction approaches for finite-volume models that are conservative.•Supporting techniques for handling infeasibility and flux/source hyper-reduction.•Analysis including deriving feasibility/equivalence conditions and error bounds.•Numerical experiments on a parameterized compressible flow problem.
This study examines the effects of financial reporting complexity on investors' trading behavior. I find that more complex (longer and less readable) filings are associated with lower overall ...trading, and that this relationship appears due to a reduction in small investors' trading activity. Additional evidence suggests that the association between report complexity and lower abnormal trading is driven by both cross-sectional variation in firms' disclosure attributes and variations in disclosure complexity over time. Given regulatory concerns over plain English disclosures and the trend toward more disclosure, my investigation into the effects of reporting complexity on small and large investors should be of interest to regulators concerned with reporting clarity and leveling the playing field across classes of investors.
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