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  • Discontinuous Galerkin approximations to elliptic and parabolic problems with a Dirac line source 

    Masri, Rami; Shen, Boqian; Riviere, Beatrice (2023)
    The analyses of interior penalty discontinuous Galerkin methods of any order <i>k<i/> for solving elliptic and parabolic problems with Dirac line sources are presented. For the steady state case, we prove convergence of the method by deriving <i>a priori<i/> error estimates in the <i>L<i/><sup>2<sup/> norm and in weighted energy norms. In addition, ...
  • Quantitative unique continuation for the elasticity system with application to the kinematic inverse rupture problem 

    de Hoop, Maarten V.; Lassas, Matti; Lu, Jinpeng; Oksanen, Lauri (2023)
    We obtain explicit estimates on the stability of the unique continuation for a linear system of hyperbolic equations. In particular, our result applies to the elasticity system and also the Maxwell system. As an application, we study the kinematic inverse rupture problem of determining the jump in displacement and the friction force at the rupture ...
  • Multi-Patch Epidemic Models with General Exposed and Infectious Periods 

    Pang, Guodong; Pardoux, Étienne (2023)
    We study multi-patch epidemic models where individuals may migrate from one patch to another in either of the susceptible, exposed/latent, infectious and recovered states. We assume that infections occur both locally with a rate that depends on the patch as well as “from distance” from all the other patches. The migration processes among the patches ...
  • Conditional Injective Flows for Bayesian Imaging 

    Khorashadizadeh, AmirEhsan; Kothari, Konik; Salsi, Leonardo; Harandi, Ali Aghababaei; de Hoop, Maarten; (2023)
    Most deep learning models for computational imaging regress a single reconstructed image. In practice, however, ill-posedness, nonlinearity, model mismatch, and noise often conspire to make such point estimates misleading or insufficient. The Bayesian approach models images and (noisy) measurements as jointly distributed random vectors and aims to ...
  • Optimized decision support for selection of transoral robotic surgery or (chemo)radiation therapy based on posttreatment swallowing toxicity 

    Hemmati, Mehdi; Barbon, Carly; Mohamed, Abdallah S.R.; van Dijk, Lisanne V.; Moreno, Amy C.; (2023)
    Background A primary goal in transoral robotic surgery (TORS) for oropharyngeal squamous cell cancer (OPSCC) survivors is to optimize swallowing function. However, the uncertainty in the outcomes of TORS including postoperative residual positive margin (PM) and extranodal extension (ENE), may necessitate adjuvant therapy, which may cause significant ...
  • On the Entropy Projection and the Robustness of High Order Entropy Stable Discontinuous Galerkin Schemes for Under-Resolved Flows 

    Chan, Jesse; Ranocha, Hendrik; Rueda-Ramírez, Andrés M.; Gassner, Gregor; Warburton, Tim (2022)
    High order entropy stable schemes provide improved robustness for computational simulations of fluid flows. However, additional stabilization and positivity preserving limiting can still be required for variable-density flows with under-resolved features. We demonstrate numerically that entropy stable Discontinuous Galerkin (DG) methods which incorporate ...
  • MR-Guided Adaptive Radiotherapy for OAR Sparing in Head and Neck Cancers 

    Mulder, Samuel L.; Heukelom, Jolien; McDonald, Brigid A.; Van Dijk, Lisanne; Wahid, Kareem A.; (2022)
    MR-linac devices offer the potential for advancements in radiotherapy (RT) treatment of head and neck cancer (HNC) by using daily MR imaging performed at the time and setup of treatment delivery. This article aims to present a review of current adaptive RT (ART) methods on MR-Linac devices directed towards the sparing of organs at risk (OAR) and a ...
  • Chromosome size affects sequence divergence between species through the interplay of recombination and selection 

    Tigano, Anna; Khan, Ruqayya; Omer, Arina D.; Weisz, David; Dudchenko, Olga; (2022)
    The structure of the genome shapes the distribution of genetic diversity and sequence divergence. To investigate how the relationship between chromosome size and recombination rate affects sequence divergence between species, we combined empirical analyses and evolutionary simulations. We estimated pairwise sequence divergence among 15 species from ...
  • Severity of radiation pneumonitis, from clinical, dosimetric and biological features: a pilot study 

    Aso, Samantha; Navarro‑Martin, Arturo; Castillo, Richard; Padrones, Susana; Castillo, Edward; (2020)
    Background and objective: Radiation pneumonitis (RP) could be a lethal complication of lung cancer treatment. No reliable predictors of RP severity have been recognized. This prospective pilot study was performed to identify early predictors of high grade lung toxicity and to evaluate clinical, biological or dosimetric features associated with different ...
  • Extubation Failure in Critically Ill COVID-19 Patients: Risk Factors and Impact on In-Hospital Mortality 

    Ionescu, Filip; Zimmer, Markie S.; Petrescu, Ioana; Castillo, Edward; Bozyk, Paul; (2021)
    Purpose:We sought to identify clinical factors that predict extubation failure (reintubation) and its prognostic implications in critically ill COVID-19 patients.Materials and Methods:Retrospective, multi-center cohort study of hospitalized COVID-19 patients. Multivariate competing risk models were employed to explore the rate of reintubation and its ...
  • Functional avoidance-based intensity modulated proton therapy with 4DCT derived ventilation imaging for lung cancer 

    Dougherty, Jingjing M.; Castillo, Edward; Castillo, Richard; Faught, Austin M.; Pepin, Mark; (2021)
    The primary objective is to evaluate the potential dosimetric gains of performing functional avoidance-based proton treatment planning using 4DCT derived ventilation imaging. 4DCT data of 31 patients from a prospective functional avoidance clinical trial were evaluated with intensity modulated proton therapy (IMPT) plans and compared with clinical ...
  • Chromatin architecture transitions from zebrafish sperm through early embryogenesis 

    Wike, Candice L.; Guo, Yixuan; Tan, Mengyao; Nakamura, Ryohei; Shaw, Dana Klatt; (2021)
    Chromatin architecture mapping in 3D formats has increased our understanding of how regulatory sequences and gene expression are connected and regulated in a genome. The 3D chromatin genome shows extensive remodeling during embryonic development, and although the cleavage-stage embryos of most species lack structure before zygotic genome activation ...
  • Quantifying pulmonary perfusion from noncontrast computed tomography 

    Castillo, Edward; Nair, Girish; Turner‐Lawrence, Danielle; Myziuk, Nicholas; Emerson, Scott; (2021)
    Purpose: Computed tomography (CT)-derived ventilation methods compute respiratory induced volume changes as a surrogate for pulmonary ventilation. Currently, there are no known methods to derive perfusion information from noncontrast CT. We introduce a novel CT-Perfusion (CT-P) method for computing the magnitude mass changes apparent on dynamic ...
  • Reciprocity-gap misfit functional for distributed acoustic sensing, combining data from passive and active sources 

    Faucher, Florian; de Hoop, Maarten V.; Scherzer, Otmar (2021)
    Quantitative imaging of subsurface earth properties in elastic media is performed from distributed acoustic sensing data. A new misfit functional based upon the reciprocity gap is designed, taking crosscorrelations of displacement and strain, and these products further associate an observation with a simulation. In comparison with other misfit ...
  • Clustering earthquake signals and background noises in continuous seismic data with unsupervised deep learning 

    Seydoux, Léonard; Balestriero, Randall; Poli, Piero; de Hoop, Maarten; Campillo, Michel; (2020)
    The continuously growing amount of seismic data collected worldwide is outpacing our abilities for analysis, since to date, such datasets have been analyzed in a human-expert-intensive, supervised fashion. Moreover, analyses that are conducted can be strongly biased by the standard models employed by seismologists. In response to both of these ...
  • Convergence of a Class of Stationary Iterative Methods for Saddle Point Problems 

    Zhang, Yin (2019)
    A unified convergence theory is derived for a class of stationary iterative methods for solving linear equality constrained quadratic programs or saddle point problems. This class is constructed from essentially all possible splittings of the submatrix residing in the (1,1)-block of the augmented saddle point matrix that would produce non-expansive ...
  • An accelerated Poisson solver based on multidomain spectral discretization 

    Babb, Tracy; Gillman, Adrianna; Hao, Sijia; Martinsson, Per-Gunnar (2018)
    This paper presents a numerical method for variable coefficient elliptic PDEs with mostly smooth solutions on two dimensional domains. The method works best for domains that can readily be mapped onto a rectangle, or a collection of nonoverlapping rectangles. The PDE is discretized via a multi-domain spectral collocation method of high local order ...
  • Weight‐adjusted discontinuous Galerkin methods: Matrix‐valued weights and elastic wave propagation in heterogeneous media 

    Chan, Jesse (2018)
    Weight‐adjusted inner products are easily invertible approximations to weighted L2 inner products. These approximations can be paired with a discontinuous Galerkin (DG) discretization to produce a time‐domain method for wave propagation which is low storage, energy stable, and high‐order accurate for arbitrary heterogeneous media and curvilinear ...
  • On discretely entropy conservative and entropy stable discontinuous Galerkin methods 

    Chan, Jesse (2018)
    High order methods based on diagonal-norm summation by parts operators can be shown to satisfy a discrete conservation or dissipation of entropy for nonlinear systems of hyperbolic PDEsᅠ[1],ᅠ[2]. These methods can also be interpreted as nodal discontinuous Galerkin methods with diagonal mass matricesᅠ[3],ᅠ[4],ᅠ[5],ᅠ[6]. In this work, we describe how ...
  • Multi-patch discontinuous Galerkin isogeometric analysis for wave propagation: Explicit time-stepping and efficient mass matrix inversion 

    Chan, Jesse; Evans, John A. (2018)
    We present a class of spline finite element methods for time-domain wave propagation which are particularly amenable to explicit time-stepping. The proposed methods utilize a discontinuous Galerkin discretization to enforce continuity of the solution field across geometric patches in a multi-patch setting, which yields a mass matrix with convenient ...

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