Search

We consider the stable reconstruction of flow geometry and wall shear stress from measurements obtained by magnetic resonance imaging (MRI). As noted in a review article by Petersson, most approaches considered so far in the literature seem to not be satisfactory. We therefore propose a systematic reconstruction procedure that allows us to obtain stable estimates of flow geometry and wall shear stress and we are able to quantify the reconstruction errors in terms of bounds for the measurement errors under reasonable smoothness assumptions. A complete analysis of our approach is given in the framework of regularization methods. In addition, we briefly discuss the implementation of our method and we demonstrate its viability, accuracy, and regularizing properties for experimental data. [ABSTRACT FROM AUTHOR]

Conditional stability estimates allow us to characterize the degree of ill-posedness of many inverse problems, but without further assumptions they are not sufficient for the stable solution in the presence of data perturbations. We here consider the stable solution of nonlinear inverse problems satisfying a conditional stability estimate by Tikhonov regularization in Hilbert scales. Order optimal convergence rates are established for a priori and a posteriori parameter choice strategies. The role of a hidden source condition is investigated and the relation to previous results for regularization in Hilbert scales is elaborated. The applicability of the results is discussed for some model problems, and the theoretical results are illustrated by numerical tests. [ABSTRACT FROM AUTHOR]

We consider the identification of a nonlinear friction law in a one-dimensional damped wave equation from additional boundary measurements. Well-posedness of the governing semilinear hyperbolic system is established via semigroup theory and contraction arguments. We then investigate the inverse problem of recovering the unknown nonlinear damping law from additional boundary measurements of the pressure drop along the pipe. This coefficient inverse problem is shown to be ill-posed and a variational regularization method is considered for its stable solution. We prove existence of minimizers for the Tikhonov functional and discuss the convergence of the regularized solutions under an approximate source condition. The meaning of this condition and some arguments for its validity are discussed in detail and numerical results are presented for illustration of the theoretical findings. [ABSTRACT FROM AUTHOR]

In this paper we consider nonlinear ill-posed problems with piecewise constant or strongly varying solutions. A class of nonlinear regularization methods is proposed, in which smooth approximations to the Heavyside function are used to reparameterize functions in the solution space by an auxiliary function of levelset type. The analysis of the resulting regularization methods is carried out in two steps: first, we interpret the algorithms as nonlinear regularization methods for recovering the auxiliary function. This allows us to apply standard results from regularization theory, and we prove convergence of regularized approximations for the auxiliary function; additionally, we obtain the convergence of the regularized solutions, which are obtained from the auxiliary function by the nonlinear transformation. Second, we analyze the proposed methods as approximations to the levelset regularization method analyzed in [Fruhauf F, Scherzer O and Leitao A 2005 Analysis of regularization methods for the solution of ill-posed problems involving discontinuous operators SIAM J. Numer. Anal. 43 767-86], which follows as a limit case when the smooth functions used for the nonlinear transformations converge to the Heavyside function. For illustration, we consider the application of the proposed algorithms to elliptic Cauchy problems, which are known to be severely ill-posed, and typically allow only for limited reconstructions. Our numerical examples demonstrate that the proposed methods provide accurate reconstructions of piecewise constant solutions also for these severely ill-posed benchmark problems. [ABSTRACT FROM AUTHOR]

São discutidos os aspectos relativos ao diagnóstico e tratamento dos hemangiomas cavernosos do crânio. Os dados obtidos em 26 casos, são apresentados, sendo salientado que a localização dos hemangiomas foi maior na região frontal, sendo mais atingido o sexo masculino. Os outros aspectos são coincidentes com os demais autores. A problemática desses tumores, principalmente a sua demonstração radiológica e o seu tratamento, são ressaltados, chegando-se à conclusão final de que o melhor meio de demonstração radiológica é a punção para contrastação direta do tumor. O tratamento de escolha é o cirúrgico, sendo a extirpação em bloco preferida nos casos de comprometimento ósseo importante, sendo a intervenção direta com dissecção e excisão reservada para as localizações nos tecidos moles ou com mínima participação óssea.

Income inequality is blamed for being the main driver of violent crime by the majority of the literature. However, earlier work on the topic largely neglects the role of poverty and income levels as opposed to income inequality. The current paper uses all court verdicts for homicide cases in China between 2014 and 2016, as well as various inequality measures calculated from 2005 mini census data together with a host of control variables to shed light on the relationship at the detailed Chinese prefecture-level. The results suggest that it is the poverty and low income level, rather than income inequality, that is positively related to homicide rates. We show that the internal rural-urban migration from more violent localities contributes to the destination cities' homicide rates. The poverty-homicide association implies that instead of "relative deprivation", "absolute deprivation" is mainly responsible for violent crime. Poverty is the mother of crime. -Marcus Aurelius (121-180AD), Emperor of the Roman Empire.

This paper analyzes the growth of Metropolitan Statistical Areas in the PRC between 1992 and 2013 by focusing on the night-light radiance—a measure of economic activity—of connected subcity places that we refer to as a natural city. This paper documents the rapid growth of natural cities in the PRC between 1992 and 2009 that was followed by a slight reduction in the size of some natural cities between 2010 and 2013 in the aftermath of the recent global financial crisis. Institutional factors—such as the location of places near Special Economic Zones, the ramifications of legal migration from rural to urban areas following reforms to the hukou (household registration) system, and infrastructure accessibility—are found to be important drivers of the integration of peripheral places into natural cities.

Preschool anxiety is highly prevalent and well known to predict risk for future psychopathology. The present study explores whether a diagnosis of an anxiety disorder in preschool interacts with (a) social skills and (b) cognitive ability to longitudinally predict psychopathology, two well-known protective factors, among a sample of 207 children measured at preschool (Mage = 4.34 years) and early childhood (Mage = 6.61 years). To assess social skills and cognitive ability, we utilized the Social Skills Rating Scale and the Differential Abilities Scale, respectively. To assess psychopathology, we utilized the parent report of the Preschool Age Psychiatric Assessment. Hierarchical linear regression models revealed significant interactions between both social skills and cognitive ability with preschool anxiety. We observed that social skills protected against emergent psychopathology for both children with and without anxiety, although this association was stronger for children with preschool anxiety. Contrastingly, cognitive ability served as a protective factor against future psychopathology primarily among children without preschool anxiety. Results from this study identify targets for future intervention and inform our understanding of how preschool anxiety, a common disorder among young children, shapes future psychopathology risk in childhood.

Phase-field modeling has become a powerful tool in describing the complex pore-structure evolution and the intricate multiphysics in nonisothermal sintering processes. However, the quantitative validity of conventional variational phase-field models involving diffusive processes is a challenge. Artificial interface effects, like the trapping effects, may originate at the interface when the kinetic properties of two opposing phases are different. On the other hand, models with prescribed antitrapping terms do not necessarily guarantee the thermodynamics variational nature of the model. This issue has been solved for liquid-solid interfaces via the development of the variational quantitative solidification phase-field model. However, there is no related work addressing the interfaces in nonisothermal sintering, where the free surfaces between the solid phase and surrounding pore regions exhibit strong asymmetry of mass and thermal properties. Also, additional challenges arise due to the conserved order parameter describing the free surfaces. In this work, we present a variational and quantitative phase-field model for nonisothermal sintering processes. The model is derived via an extended nondiagonal phase-field model. The model evolution equations have naturally cross-coupling terms between the conserved kinetics (i.e., mass and thermal transfer) and the nonconserved one (grain growth). These terms are shown via asymptotic analysis to be instrumental in ensuring the elimination of interface artifacts, while also examined to not modify the thermodynamic equilibrium condition (characterized by a dihedral angle). Moreover, we demonstrate that the trapping effects and the existence of surface diffusion in conservation laws are direction-dependent. An anisotropic interpolation scheme of the kinetic mobilities that differentiates between the normal and tangential directions along the interface is discussed. Numerically, we demonstrate the importance of the cross-couplings and the anisotropic interpolation by presenting thermal-microstructural evolutions.

We present a detailed derivation of a simple hydrodynamic two-fluid model, which aims at the description of the phase separation of non-entangled polymer solutions, where viscoelastic effects play a role. It is directly based upon the coarse-graining of a well-defined molecular model, such that all degrees of freedom have a clear and unambiguous molecular interpretation. The considerations are based upon a free-energy functional, and the dynamics is split into a conservative and a dissipative part, where the latter satisfies the Onsager relations and the second law of thermodynamics. The model is therefore fully consistent with both equilibrium and non-equilibrium thermodynamics. The derivation proceeds in two steps: firstly, we derive an extended model comprising two scalar and four vector fields, such that inertial dynamics of the macromolecules and of the relative motion of the two fluids is taken into account. In the second step, we eliminate these inertial contributions and, as a replacement, introduce phenomenological dissipative terms, which can be modeled easily by taking into account the principles of non-equilibrium thermodynamics. The final simplified model comprises the momentum conservation equation, which includes both interfacial and elastic stresses, a convection-diffusion equation where interfacial and elastic contributions occur as well, and a suitably convected relaxation equation for the end-to-end vector field. In contrast to the traditional two-scale description that is used to derive rheological equations of motion, we here treat the hydrodynamic and the macromolecular degrees of freedom on the same basis. Nevertheless, the resulting model is fairly similar, though not fully identical, to models that have been discussed previously. Notably, we find a rheological constitutive equation that differs from the standard Oldroyd-B model. Within the framework of kinetic theory, this difference may be traced back to a different underlying statistical-mechanical ensemble that is used for averaging the stress. To what extent the model is able to reproduce the full phenomenology of viscoelastic phase separation is presently an open question, which shall be investigated in the future., (Creative Commons Attribution license.)

Functional abdominal pain (FAP) is one of the most common childhood medical complaints, associated with significant distress and impairment. Little is known about how children understand their pain. Do they attribute it to personal weakness? Do they perceive pain as having global impact, affecting a variety of activities? How do they cope with pain? We explored the pain beliefs of 5- to 9-year-old children with FAP using a novel Teddy Bear Interview task in which children answered questions about a Teddy bear's pain. Responses were analyzed quantitatively and qualitatively. Results indicate that the majority of young children with FAP are optimistic about pain outcomes. Children generated many types of coping strategies for Teddy's pain and adjusted their calibration of Teddy's pain tolerance dependent on the activity being performed. Early warning signs also emerged: a subset of children were pessimistic about Teddy's pain, and several children identified coping strategies that, while developmentally appropriate, could lead to excessive help seeking if not intervened upon (e.g., physician consultation and shot). The Teddy Bear Interview allows children to externalize their pain, making it a useful tool to access cognitive pain constructs in younger children. Thus, these findings highlight the importance of early intervention for childhood FAP.

A new model for viscoelastic phase separation is proposed, based on a systematically derived conservative two-fluid model. Dissipative effects are included by phenomenological viscoelastic terms. By construction, the model is consistent with the second law of thermodynamics. We study well-posedness of the model in two space dimensions, i.e., existence of weak solutions, a weak-strong uniqueness principle, and stability with respect to perturbations, which are proven by means of relative energy estimates. Our numerical simulations based on the new viscoelastic phase separation model are in good agreement with physical experiments. Furthermore, a good qualitative agreement with mesoscopic simulations is observed., (Creative Commons Attribution license.)

Wall shear stress (WSS) has been suggested as a potential biomarker in various cardiovascular diseases and it can be estimated from phase-contrast Magnetic Resonance Imaging (PC-MRI) velocity measurements. We present a parametric sequential method for MRI-based WSS quantification consisting of a geometry identification and a subsequent approximation of the velocity field. This work focuses on its validation, investigating well controlled high-resolution in vitro measurements of turbulent stationary flows and physiological pulsatile flows in phantoms. Initial tests for in vivo 2D PC-MRI data of the ascending aorta of three volunteers demonstrate basic applicability of the method to in vivo.

Prolonged separation from migrant parents may lead to child development risks, despite the potential benefits from improved financial circumstances. Within the substantial literature on the health and well-being of the so-called left-behind children, the cognitive impact of parental migration has been inconclusive across different settings globally. In this issue, Hou et al.'s study in rural China focused on school-age children who experience persistent absence of both migrant parents since infancy, and revealed disadvantages in language comprehension outcomes among these children, despite the mitigating effect of higher household income. While results from this study are limited to the ongoing parent-child separation, previous absence of migrant parents has been suggested to have long-lasting negative effects in studies of adolescents in reunited families. Findings from Hou and colleagues' study highlight the needs to better understand migration-related parent-child separation during sensitive developmental periods in infancy and early childhood. A spectrum of risk due to parental migration should be established, accounting for the timing and duration of migration and care arrangements, in order to better identify the at-risk children in communities affected by out-migration. Future research should further explore the mediating and moderating factors in child's environments, and evaluate post-separation adjustment among reunited families after parents' return migration. Research evidence on these aspects will inform the development of tailored intervention programs for left-behind children, and strengthen the abilities of families and communities in best serving the needs of children affected by prolonged parental absence., (Copyright © 2020 Elsevier Ltd. All rights reserved.)

The fifth edition of the Diagnostic and Statistical Manual ( DSM ) categorizes reactive attachment disorder (RAD) and disinhibited social engagement disorder (DSED) as two separate disorders, and their criteria are revised. For DSED, the core symptoms focus on abnormal social disinhibition, and symptoms regarding lack of selective attachment have been removed. The core symptoms of RAD are the absence of attachment behaviors and emotional dysregulation. In this study, an international team of researchers modified the Child and Adolescent Psychiatric Assessment for RAD to update it from DSM-IV to DSM-5 criteria for RAD and DSED. We renamed the interview the r eactive attachment disorder a nd d isinhibited social engagement disorder a ssessment (RADA). Foster parents of 320 young people aged 11 to 17 years completed the RADA online. Confirmatory factor analysis of RADA items identified good fit for a three-factor model, with one factor comprising DSED items (indiscriminate behaviors with strangers) and two factors comprising RAD items (RAD1: failure to seek/accept comfort, and RAD2: withdrawal/hypervigilance). The three factors showed differential associations with clinical symptoms of emotional and social impairment. Time in foster care was not associated with scores on RAD1, RAD2, or DSED. Higher age was associated with lower scores on DSED, and higher scores on RAD1.

In arterial blood flow wall shear stress (WSS) quantifies the frictional force that flowing blood exerts on a vessel wall. WSS can be directly estimated from phase-contrast (PC) MR velocity measurements and has been suggested as a biomarker in cardio-vascular diseases. We present and investigate the application of the Clauser plot method for estimating WSS in fully developed turbulent stationary flow using PC velocity measurements. The Clauser plot method estimates WSS from the logarithmic region of boundary layer in fully developed turbulent stationary flow. The Clauser plot method was evaluated using 2D PC-MR phantom measurements at 3 T for different in-plane resolutions at various Reynolds numbers. WSS values derived from the Clauser plot were compared to results from Laser Doppler Velocimetry (LDV) measurements and theoretical results calculated using the friction factor formula for smooth pipe flow. For all Reynolds numbers, WSS values derived from the Clauser plot were in good agreement with results from LDV measurements and values using the friction factor formula (relative deviations ∼5%). Furthermore, Clauser plot derived results were almost independent of spatial resolution, in contrast to WSS results obtained with our in-house software tool for MR-based WSS quantification showing relative deviations of more than 100%. In fully developed turbulent flow, the Clauser plot method provides highly consistent WSS independent of the underlying spatial resolution. Therefore, it renders a valuable approach for MR-based WSS estimates in controllable flow settings. Although its direct in vivo applicability is severely limited because of the different flow character, it may serve as helpful approach for validation of MR-based WSS quantification algorithms prior to their clinical application., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Academic medical centers (AMCs) today prioritize digital innovation. In efforts to develop and disseminate the best technology for their institutions, challenges arise in organizational structure, cross-disciplinary collaboration, and creative and agile problem solving that are essential for successful implementation. To address these challenges, the Digital DesignLab was created at NYU Langone Health to provide structured processes for assessing and supporting the capacity for innovative digital development in our research and clinical community. Digital DesignLab is an enterprise level, multidisciplinary, digital development team that guides faculty and student innovators through a digital development "pipeline", which consists of intake, discovery, bootcamp, development. It also provides a framework for digital health innovation and dissemination at the institution. This paper describes the Digital DesignLab's creation and processes, and highlights key lessons learned to support digital health innovation at AMCs., Competing Interests: Competing interestsThe authors declare no competing interests.

Background: Patients with early breast cancer (EBC) achieving pathologic complete response (pCR) after neoadjuvant chemotherapy (NACT) have a favorable prognosis. Breast surgery might be avoided in patients in whom the presence of residual tumor can be ruled out with high confidence. Here, we investigated the diagnostic accuracy of contrast-enhanced MRI (CE-MRI) in predicting pCR and long-term outcome after NACT., Methods: Patients with EBC, including patients with locally advanced disease, who had undergone CE-MRI after NACT, were retrospectively analyzed (n = 246). Three radiologists, blinded to clinicopathologic data, reevaluated all MRI scans regarding to the absence (radiologic complete remission; rCR) or presence (no-rCR) of residual contrast enhancement. Clinical and pathologic responses were compared categorically using Cohen's kappa statistic. The Kaplan-Meier method was used to estimate recurrence-free survival (RFS) and overall survival (OS)., Results: Overall rCR and pCR (no invasive tumor in the breast and axilla (ypT0/is N0)) rates were 45% (111/246) and 29% (71/246), respectively. Only 48% (53/111; 95% CI 38-57%) of rCR corresponded to a pCR (= positive predictive value - PPV). Conversely, in 87% (117/135; 95% CI 79-92%) of patients, residual tumor observed on MRI was pathologically confirmed (= negative predictive value - NPV). Sensitivity to detect a pCR was 75% (53/71; 95% CI 63-84%), while specificity to detect residual tumor and accuracy were 67% (117/175; 95% CI 59-74%) and 69% (170/246; 95% CI 63-75%), respectively. The PPV was significantly lower in hormone-receptor (HR)-positive compared to HR-negative tumors (17/52 = 33% vs. 36/59 = 61%; P = 0.004). The concordance between rCR and pCR was low (Cohen's kappa - 0.1), however in multivariate analysis both assessments were significantly associated with RFS (rCR P = 0.037; pCR P = 0.033) and OS (rCR P = 0.033; pCR P = 0.043)., Conclusion: Preoperative CE-MRI did not accurately predict pCR after NACT for EBC, especially not in HR-positive tumors. However, rCR was strongly associated with favorable RFS and OS.