This paper studies two hybrid discontinuous Galerkin (HDG) discretizations for the velocity-density formulation of the compressible Stokes equations with respect to several desired structural properties, namely provable convergence, the preservation of non-negativity and mass constraints for the density, and gradient-robustness. The later property dramatically enhances the accuracy in well-balanced situations, such as the hydrostatic balance where the pressure gradient balances the gravity force. One of the studied schemes employs an -conforming velocity ansatz space which ensures all mentioned properties, while a fully discontinuous method is shown to satisfy all properties but the gradient-robustness.
View Article and Find Full Text PDFNumer Linear Algebra Appl
October 2023
We are studying the efficient solution of the system of linear equations stemming from the mass conserving stress-yielding (MCS) discretization of the Stokes equations. We perform static condensation to arrive at a system for the pressure and velocity unknowns. An auxiliary space preconditioner for the positive definite velocity block makes use of efficient and scalable solvers for conforming Finite Element spaces of low order and is analyzed with emphasis placed on robustness in the polynomial degree of the discretization.
View Article and Find Full Text PDFObjective: In the era of flow diversion, there is an increasing demand to train neurosurgeons outside the operating room in safely performing clipping of unruptured intracranial aneurysms. This study introduces a clip training simulation platform for residents and aspiring cerebrovascular neurosurgeons, with the aim to visualize peri-aneurysm anatomy and train virtual clipping applications on the matching physical aneurysm cases.
Methods: Novel, cost-efficient techniques allow the fabrication of realistic aneurysm phantom models and the additional integration of holographic augmented reality (AR) simulations.
We introduce two new lowest order methods, a mixed method, and a hybrid discontinuous Galerkin method, for the approximation of incompressible flows. Both methods use divergence-conforming linear Brezzi-Douglas-Marini space for approximating the velocity and the lowest order Raviart-Thomas space for approximating the vorticity. Our methods are based on the physically correct viscous stress tensor of the fluid, involving the symmetric gradient of velocity (rather than the gradient), provide exactly divergence-free discrete velocity solutions, and optimal error estimates that are also pressure robust.
View Article and Find Full Text PDFBackground: High rates of tuberculosis (TB) transmission occur in hospitals in high-incidence countries, yet there is no validated way to evaluate the impact of hospital design and function on airborne infection risk. We hypothesized that personal ambient carbon dioxide (CO2) monitoring could serve as a surrogate measure of rebreathed air exposure associated with TB infection risk in health workers (HWs).
Methods: We analyzed baseline and repeat (12-month) interferon-γ release assay (IGRA) results in 138 HWs in Cape Town, South Africa.
Int J Numer Methods Eng
June 2020
In this work we consider the numerical solution of incompressible flows on two-dimensional manifolds. Whereas the compatibility demands of the velocity and the pressure spaces are known from the flat case one further has to deal with the approximation of a velocity field that lies only in the tangential space of the given geometry. Abandoning -conformity allows us to construct finite elements which are-due to an application of the Piola transformation-exactly tangential.
View Article and Find Full Text PDFA healthy 35-year-old Brazilian woman presented with persistent redness, swelling, and multiple wounds on the hand 2 weeks after a cat bite in her home country. She was treated twice with amoxicillin-clavulanate but failed to demonstrate improvement. She then presented to our institution with a newly developed abscess on the right hand.
View Article and Find Full Text PDFdisease is particularly challenging to treat, given the intrinsic drug resistance of this species and the limited data on which recommendations are based, resulting in a greater reliance on expert opinion. We address several commonly encountered questions and management considerations regarding pulmonary disease, including the role of subspecies identification, diagnostic criteria for determining disease, interpretation of drug susceptibility test results, approach to therapy including the need for parenteral antibiotics and the role for new and repurposed drugs, and the use of adjunctive strategies such as airway clearance and surgical resection.
View Article and Find Full Text PDFDrug-resistant tuberculosis (DR-TB) remains a major public health threat. A 23-year-old man presented with fever, dyspnea, and a pleural effusion. After a delay, he was diagnosed with isoniazid (INH)-resistant TB.
View Article and Find Full Text PDFDrug-resistant tuberculosis (DR-TB) represents a major programmatic challenge at the national and global levels. Only ∼30% of patients with multidrug-resistant TB (MDR-TB) were diagnosed, and ∼25% were initiated on treatment for MDR-TB in 2016. Increasing evidence now points towards primary transmission of DR-TB, rather than inadequate treatment, as the main driver of the DR-TB epidemic.
View Article and Find Full Text PDFBackground: Mozambican healthcare workers have high rates of latent and active tuberculosis, but occupational screening for tuberculosis is not routine in this setting. Furthermore, the specificity of tuberculin skin testing in this population compared with interferon gamma release assay testing has not been established.
Methods: This study was conducted among healthcare workers at Maputo Central Hospital, a public teaching quaternary care hospital in Mozambique.
Acute lung injury (ALI) is characterized by endothelial barrier disruption resulting in increased vascular permeability. As focal adhesion kinase (FAK), a non-receptor protein tyrosine kinase, is involved in endothelial cell (EC) barrier regulation, we hypothesized that FAK inhibition could attenuate agonist-induced EC barrier disruption relevant to ALI. Human lung EC were pretreated with one of three pharmacologic FAK inhibitors, PF-573,228 (PF-228, 10 μM), PF-562,271 (PF-271, 5 μM) or NVP-TAE226 (TAE226, 5 μM) for 30 min prior to treatment with thrombin (1 U/ml, 30 min).
View Article and Find Full Text PDFSetting: National Institute of Diseases of the Chest and Hospital, Dhaka; Bangladesh Institute of Research and Rehabilitation in Diabetes, Endocrine and Metabolic Disorders, Dhaka; and Chittagong Chest Disease Hospital, Chittagong, Bangladesh.
Objective: To present operational data and discuss the challenges of implementing FAST (Find cases Actively, Separate safely and Treat effectively) as a tuberculosis (TB) transmission control strategy.
Design: FAST was implemented sequentially at three hospitals.
Purpose: We investigated whether differences in the pattern visual evoked potentials exist between patients with convergence insufficiency and those with convergence insufficiency and a history of concussion using stimuli designed to differentiate between magnocellular (transient) and parvocellular (sustained) neural pathways.
Methods: Sustained stimuli included 2-rev/s, 85% contrast checkerboard patterns of 1- and 2-degree check sizes, whereas transient stimuli comprised 4-rev/s, 10% contrast vertical sinusoidal gratings with column width of 0.25 and 0.
Background: Awareness of human immunodeficiency virus (HIV) status among all people with HIV is critical for epidemic control. We aimed to assess accurate knowledge of HIV status, defined as concordance with serosurvey test results from the 2010 Malawi Demographic Health Survey (MDHS), and to identify risk factors for seropositivity among adults (aged 15-49) reporting a most recently negative test within 12 months.
Methods: Data were analyzed from the 2010 MDHS.
Healthcare workers (HCWs) play a central role in global tuberculosis (TB) elimination efforts but their contributions are undermined by occupational TB. HCWs have higher rates of latent and active TB than the general population due to persistent occupational TB exposure, particularly in settings where there is a high prevalence of undiagnosed TB in healthcare facilities and TB infection control (TB-IC) programmes are absent or poorly implemented. Occupational health programmes in high TB burden settings are often weak or non-existent and thus data that record the extent of the increased risk of occupational TB globally are scarce.
View Article and Find Full Text PDFObjective: To determine whether laws and regulations in Botswana, South Africa and Zambia - three countries with a high tuberculosis and HIV infection burden - address elements of the World Health Organization (WHO) policy on tuberculosis infection control.
Methods: An online desk review of laws and regulations that address six selected elements of the WHO policy on tuberculosis infection control in the three countries was conducted in November 2015 using publicly available domestic legal databases. The six elements covered: (i) national policy and legal framework; (ii) health facility design, construction and use; (iii) tuberculosis disease surveillance among health workers; (iv) patients' and health workers' rights; (v) monitoring of infection control measures; and (vi) relevant research.
Background: Powassan virus (POWV) is a rarely diagnosed cause of encephalitis in the United States. In the Northeast, it is transmitted by Ixodes scapularis, the same vector that transmits Lyme disease. The prevalence of POWV among animal hosts and vectors has been increasing.
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