VoroCrust: Voronoi Meshing Without Clipping

Polyhedral meshes are increasingly becoming an attractive option with particular advantages over traditional meshes for certain applications. What has been missing is a robust polyhedral meshing algorithm that can handle broad classes of domains exhibiting arbitrarily curved boundaries and sharp features. In addition, the power of primal-dual mesh pairs, exemplified by Voronoi-Delaunay meshes, has been recognized as an important ingredient in numerous formulations. The VoroCrust algorithm is the first provably-correct algorithm for conforming polyhedral Voronoi meshing for non-convex and non-manifold domains with guarantees on the quality of both surface and volume elements. A robust refinement process estimates a suitable sizing field that enables the careful placement of Voronoi seeds across the surface circumventing the need for clipping and avoiding its many drawbacks. The algorithm has the flexibility of filling the interior by either structured or random samples, while preserving all sharp features in the output mesh. We demonstrate the capabilities of the algorithm on a variety of models and compare against state-of-the-art polyhedral meshing methods based on clipped Voronoi cells establishing the clear advantage of VoroCrust output.Comment: 18 pages (including appendix), 18 figures. Version without compressed images available on https://www.dropbox.com/s/qc6sot1gaujundy/VoroCrust.pdf. Supplemental materials available on https://www.dropbox.com/s/6p72h1e2ivw6kj3/VoroCrust_supplemental_materials.pd

Epidemiology of Stroke in the MENA Region: A Systematic Review.

Introduction: Stroke is a major burden on the health system due to high fatality and major disability in survivors. Whilst Stroke incidence has declined in the developed world, it continues to increase in developing nations, including the MENA (Middle East and North Africa) region. This may reflect different risk factors and strategies to treat and manage patients prior to and after Stroke. Methods: We have conducted a systematic review of the prevalence, incidence and mortality of Stroke in the 23 countries of MENA region following the PRISMA guidelines. Results: 8,874 published papers were retrieved through both PubMed and Embase. Of those, 38 studies were found to be eligible for inclusion in this review. Only thirteen countries in the MENA region had data points for the critical stroke parameters. Of these qualified studies, 14 were prospective, population-based studies. In the age-adjusted studies, incidence ranged widely between 16/100,000 in a prospective population-based in Iran to 162/100,000 in Libya. Age-adjusted prevalence was available only from Tunisia at 184/100,000. Mortality for all strokes from the eight countries reporting this measure found the 30 day-case fatality ranged from 9.3% in Qatar to 30% in Pakistan. Most stroke studies in the MENA region were small sized, hospital-based, lacked confidence intervals and did not provide prevalence and mortality figures. Conclusion: National policymakers, public health and medical care stakeholders need more reliable epidemiologic studies on Stroke from the MENA region to plan more effective preventive and therapeutic strategies

Autopsie d’une membrane d’osmose inverse usagée prélevée dans le Parc National du Banc d’Arguin (PNBA) en Mauritanie : cas d’étude de Teichitt

L’objectif de ce travail est d’étudier l’état de vieillissement d’une membrane d’osmose inverse (OI) usagée prélevée en Mauritanie sur une unité de dessalement installée par la coopération canarienne à Teichitt dans le parc national du banc d’Arguin et de lui appliquer une démarche d’autopsie. L’usure de la membrane est caractérisée par une augmentation significative de la perméabilité hydraulique (25 % d’augmentation) et une diminution de la rétention en sels (10 % à 30 % de diminution). Un modèle de transfert de matière de type diffusion-convection permet de montrer l’augmentation du caractère convectif du transfert, lorsque la pression transmembranaire augmente et en particulier au-delà de 15 bars. Ainsi, l’usure de la membrane d’OI induit son rapprochement vers un transfert de matière combiné de solubilisation-diffusion/convection, typique d’une opération de nanofiltration (NF). L’analyse topographique par AFM de la surface de la membrane usagée en comparaison de la membrane neuve laisse apparaître des « cavités » à plusieurs endroits de la surface usagée traduisant la dégradation physique de celle-ci. De plus, la rugosité de surface de la membrane usagée avec 74 nm est apparue supérieure à celle de la membrane neuve avec 54 nm, ce qui nous informe de la présence de matières colmatantes, dont la nature reste encore à déterminer. Par contre, l’étude de la dégradation chimique des membranes usagées et neuves par la détermination de leur point isoélectrique (PIE) à partir d’une mesure de potentiel d’écoulement transmembranaire ne montre pas de modifications significatives de ce paramètre (PIE = 2,5), preuve de la non-dégradation chimique interne de la membrane. Enfin, les résultats d’une étude statistique préliminaire sont présentés. Celle-ci consiste à évaluer l’hétérogénéité de l’usure en matière de perméabilité hydraulique et de rétention d’une solution de NaCl 0,1 M à 15 bars et 19 °C, pour six coupons différents pris sur les trois feuilles de membranes constituant le module d’osmose inverse usagé. Une tendance se dégage, elle montre en particulier que l’usure est hétérogène, non seulement au sein d’une même feuille de membrane, mais aussi au sein des différentes membranes constituant le module. En résumé, il est observé pour la première fois qu’une vieille membrane d’OI employée pendant deux années pour le dessalement d’eau de mer, dans les conditions d’utilisation sahariennes en Mauritanie (sans pré-traitements), acquiert une microporosité qui lui confère les propriétés d’une membrane de nanofiltration.Currently used reverse osmosis (RO) membranes from desalination units are burned at the end of their life as membranes for seawater desalination. In the future, a possible alternative would be to reuse the old RO membranes as nanofiltration (NF), ultrafiltration (UF) or microfiltration (MF) membranes, i.e. for wastewater treatments, but before reuse, the level of RO membrane degradation must be evaluated by autopsy studies.Our goal in the present study was to demonstrate for the first time that a used RO membrane could be used for nanofiltration. The used RO membrane was purchased from a desalination bench scale unit based in the town of Teichitt (in north-west Nouakchott, Mauritania). Membrane autopsy studies showed an increase in its hydraulic permeability (25%) and a concurrent decrease in its salt rejection behaviour (10% to 30%). We also studied the modification of mass transfer before and after ageing, and demonstrated the onset of a convective component in the mass transfer of salts and an increase in membrane hydraulic permeability. Furthermore, the determination of the isoelectric point (IEP) of the membrane, using streaming potential measurements across the membranes, showed no change in IEP, with a value of 2.5 ± 0.2 . A preliminary study, based on a statistical evaluation of membrane degradation from hydraulic permeability and salt rejection experiments, showed heterogeneous wear of the membrane (most important in the centre). Finally, we observed for the first time that after two years of use for desalination, a used RO membrane had acquired a microporosity that corresponded to the properties of a new NF membrane

Outcomes of viral myocarditis in patients with and without COVID-19: a nationwide analysis from the United States

UNLABELLED: Cardiovascular complications contribute to 40% of coronavirus disease 2019 (COVID-19) related deaths. The viral myocarditis associated with COVID-19 accounts for significant morbidity and mortality. How COVID-19 myocarditis compares to other viral myocardites is unknown. METHODS: The authors conducted a retrospective cohort study using the National Inpatient Sample database to identify adult patients hospitalized for viral myocarditis in 2020 and to compare outcomes between those with and without COVID-19. The primary study outcome was in-hospital mortality. Secondary outcomes included in-hospital complications, length of stay, and total costs. RESULTS: The study population included 15 390 patients with viral myocarditis, of whom 5540 (36%) had COVID-19. After adjustment for baseline characteristics, patients with COVID-19 had higher odds of in-hospital mortality [adjusted odds ratio (aOR) 3.46, 95% CI 2.57-4.67], cardiovascular complications (aOR 1.46, 95% CI 1.14-1.87) including cardiac arrest (aOR 2.07, 95% CI 1.36-3.14), myocardial infarction (aOR 2.97, 95% CI 2.10-4.20), venous thromboembolism (aOR 2.01, 95% CI 1.25-3.22), neurologic complications (aOR 1.82, 95% CI 1.10-2.84), renal complications (aOR 1.72, 95% CI 1.38-2.13), and hematologic complications (aOR 1.32, 95% CI 1.10-1.74), but lower odds of acute heart failure (aOR 0.60, 95% CI 0.44-0.80). The odds of pericarditis, pericardial effusion/tamponade, cardiogenic shock, and the need for vasopressors or mechanical circulatory support were similar. Patients with COVID-19 had longer length of stay (7 days vs. 4 days, P\u3c0.01) and higher total costs ($21,308 vs.$14,089, P\u3c0.01). CONCLUSIONS: Among patients with viral myocarditis, COVID-19 is associated with higher in-hospital mortality and cardiovascular, neurologic, renal, and hematologic complications compared to non-COVID-19 viruses

Phrenic palsy after pediatric cardiac surgery: what is the best modality of management?

Background: Pediatric cardiac surgery is one of the most common causes of diaphragmatic palsy (DP) in infants and young children. The main target in managing a patient with DP is to preserve the respiratory function. Surgical diaphragmatic plication is widely used surgical treatment of DP nowadays especially in infants than in young children. Tracheostomy was suggested also to facilitate the suction of the chest and decrease the pulmonary complications. Thus, the aim of this study was to detect the effect of early intervention to correct the phrenic palsy either by diaphragmatic plication, Tracheostomy or both in pediatric cardiac surgery patients. Methods: This is a retrospective study on pediatric patients who had cardiac surgical procedures between June 2008 and Dec 2018. There were 3706 patients had been operated at different age groups of whom 42 patients developed DP. The patients were divided into four groups according to type of treatment: Group A for conservative treatment, Group B for diaphragmatic plication only, Group C for tracheostomy only, and Group D for tracheostomy and plication. Results: The mean age of the studied group was 19.7 ±23 . There was male predominance (78.6 %).  Timing of tracheostomy in days was as 30 ±7.1, and 31.8 ±5.4 in group C, and D respectively.  Timing of plication was as 10 ±8.3, and 11.1 ±7.6 in group B, and D consequence  Conclusion: The least sepsis recorded for patients with both tracheostomy and DP, delayed surgical intervention led to higher mortality and more sepsis recorded as in conservative technique

Decision-Support System for LID Footprint Planning and Urban Runoff Mitigation in the Lower Rio Grande Valley of South Texas

To address regional flooding in the United States, federal and state agencies are adopting strict drainage policies in any large-scale commercial development within the watershed boundary. The conventional approach of implementing a wet detention pond (WP) reduces the land cover and causes operation and maintenance challenges eventually. The present study developed a decision-support system (DSS) in the Lower Rio Grande Valley region of South Texas for optimal selection of Best Management Practices (BMPs) by substituting a portion of the WP footprint with three regionally promising low-impact development practices, namely, porous concrete pavement (PCP), bioretention (BR), and bioswale (BS). Source Load Assessment and Management Model for Windows (WinSLAMM) was used as the foundation for the DSS database and algorithm development. This tool suggested that the implementation of bioswale alone can considerably reduce the footprint and construction cost. Less than 0.95 ha of installation of BR and BS can mitigate 79–91% of runoff from a maximum of 5 ha of commercial development. A combination of BR, BS, and WP was found to reduce runoff significantly (~100%), which suggests that the successful adoption of DSS might support better planning of the urban stormwater management in the Lower Rio Grande Valley (LRGV)

A Constrained Resampling Strategy for Mesh Improvement

In many geometry processing applications, it is required to improve an initial mesh in terms of multiple quality objectives. Despite the availability of several mesh generation algorithms with provable guarantees, such generated meshes may only satisfy a subset of the objectives. The conflicting nature of such objectives makes it challenging to establish similar guarantees for each combination, e.g., angle bounds and vertex count. In this paper, we describe a versatile strategy for mesh improvement by interpreting quality objectives as spatial constraints on resampling and develop a toolbox of local operators to improve the mesh while preserving desirable properties. Our strategy judiciously combines smoothing and transformation techniques allowing increased flexibility to practically achieve multiple objectives simultaneously.  We apply our strategy to both planar and surface meshes demonstrating how to simplify Delaunay meshes while preserving element quality, eliminate all obtuse angles in a complex mesh, and maximize the shortest edge length in a Voronoi tessellation far better than the state-of-the-art

WinSLAMM Simulation of Hydrologic Performance of Permeable Pavements—A Case Study in the Semi-Arid Lower Rio Grande Valley of South Texas, United States

his study used the Source Loading and Management Model for Windows (WinSLAMM) to develop a set of calibrated hydrologic models for three types of regional permeable pavements—porous concrete pavement (PCP), permeable interlocking concrete pavement (PICP), and interlocking block pavement with gravel (IBPG). The objective was to assess the hydrologic performance of permeable pavements, including the runoff depth, peak discharge, percentage increment in runoff reduction of pavements as a function of rainfall depth, development area, and base aggregate porosity, respectively. The permeable pavements were monitored over a wide range of rainfall events in the semi-arid Lower Rio Grande Valley of South Texas. Data regarding rainfall intensities, source characterizations, runoff coefficients, and pavement design were initialized as WinSLAMM input. Validation results showed that the calibrated models could over or under-predict runoff reduction within a 30% error range. PCP and IBPG were very effective and could be capable of handling storms as large as 50-year frequency over a 24-h time period. The modeling results showed that PCP might require a 50–60% lesser footprint area as compared to PICP and IBPG, respectively. Additionally, PCP might be able to store 30% additional runoff if the porosity of base aggregates was increased by 40%

A Comparison of Three Types of Permeable Pavements for Urban Runoff Mitigation in the Semi-Arid South Texas, U.S.A

This study examines the hydrologic and environmental performance of three types of permeable pavement designs: Porous Concrete Pavement (PCP), Permeable Interlocking Concrete (PICP), and Interlocking Block Pavement with Gravel (IBPG) in the semi-arid South Texas. Outflow rate, storage, Normalized Volume Reduction (NVR), Normalized Load Reductions (NLR) of Total Suspended Solids (TSS), and Biochemical Oxygen Demand (BOD5) were compared to results obtained from adjacent traditional pavements at different regional parking lots. A notable percentage of peak flow attenuation of approximately 31–100% was observed when permeable pavements were constructed and implemented. IBPG was capable to hold runoff from rainfall depths up to 136 mm prior to flooding. PCP was the most satisfactory in reducing surface runoff (NVR: 2.81 × 10−3 ± 0.67 × 10−3 m3/m2/mm), which was significantly (p \u3c 0.05) higher (98%) than the traditional pavement. PCP was also very effective in TSS removal (NLR: 244 × 10−5 ± 143 × 10−5 kg/m2/mm), which was an increase of over 80% removal than traditional pavement. IBPG (NLR: 7.14 × 10−5 ± 7.19 × 10−5 kg/m2/mm) showed a significantly (p \u3c 0.05) higher (46%) BOD5 removal over traditional pavement. These results demonstrate that the type of permeable pavement and the underlying media can significantly influence the runoff reduction and infiltration in this climatic region