A systematic review of infected descending thoracic aortic grafts and endografts

Objective: The objective of this study was to collect and critically analyze the current evidence on the modalities and results of treatment of descending thoracic aortic surgical graft (SG) and endograft (EG) infection, which represents a rare but dramatic complication after both surgical and endovascular aortic repair. Methods: A comprehensive electronic health database search (PubMed/MEDLINE, Scopus, Google Scholar, and the Cochrane Library) identified all articles that were published up to October 2017 reporting on thoracic aortic SG or EG infection. Observational studies, multicenter reports, single-center series and case reports, case-control studies, and guidelines were considered eligible if reporting specific results of treatment of descending thoracic aortic SG or EG infection. Comparisons of patients presenting with SG or EG infection and between invasive and conservative treatment were performed. Odds ratio (OR) meta-analyses were run when comparative data were available. Results: Forty-three studies reporting on 233 patients with infected SG (49) or EG (184) were included. Four were multicenter studies including 107 patients, all with EG infection, associated with a fistula in 91% of cases, with a reported overall survival at 2 years of 16% to 39%. The remaining 39 single-center studies included 49 patients with SG infection and 77 with EG infection. Association with aortoesophageal fistula was significantly more common with EG (60% vs 31%; P = .01). In addition, time interval from index procedure to infection was significantly shorter with EG (17 +/- 21 months vs 32 +/- 61 months; P = .03). Meta-analysis showed a trend of increased 1-year mortality in patients with SG infection compared with EG infection (pooled OR, 3.6; 95% confidence interval, 0.9-14.7; P = .073). Surgical management with infected graft explantation was associated with a trend toward lower 1-year mortality compared with graft preservation (pooled OR, 0.3; 95% confidence interval, 0.1-1.0; P = .056). Conclusions: Thoracic aortic EG infection is likely to occur more frequently in association with aortoesophageal fistulas and in a shorter time compared with SG infection. Survival is poor in both groups, especially in patients with SG infection. Surgical treatment with graft explantation seems to be the preferable choice in fit patients

Fluctuating Interfaces in Liquid Crystals

We review and compare recent work on the properties of fluctuating interfaces between nematic and isotropic liquid-crystalline phases. Molecular dynamics and Monte Carlo simulations have been carried out for systems of ellipsoids and hard rods with aspect ratio 15:1, and the fluctuation spectrum of interface positions (the capillary wave spectrum) has been analyzed. In addition, the capillary wave spectrum has been calculated analytically within the Landau-de Gennes theory. The theory predicts that the interfacial fluctuations can be described in terms of a wave vector dependent interfacial tension, which is anisotropic at small wavelengths (stiff director regime) and becomes isotropic at large wavelengths (flexible director regime). After determining the elastic constants in the nematic phase, theory and simulation can be compared quantitatively. We obtain good agreement for the stiff director regime. The crossover to the flexible director regime is expected at wavelengths of the order of several thousand particle diameters, which was not accessible to our simulations

Aprendizagem baseada em problemas: disciplina de estruturas de concreto armado do curso de engenharia civil / Problem-based learning: teaching of concrete structures for civil engineers

O objetivo do presente artigo é aplicar uma metodologia de ensino ativa baseada na solução de problemas (PBL) para o curso de engenharia civil. Dez acadêmicos do primeiro ano farão uma disciplina denominada: “Concreto: da produção ao cálculo estrutural”. O conteúdo programático deste curso foi obtido da grade curricular das disciplinas de Materiais de Construção I, Materiais de Construção II e de Estruturas de Concreto I do curso de engenharia Civil da Universidade Estadual de Maringá. Durante o curso serão ministradas seis atividades/problemas. Cada atividade será composta de três etapas: i) planejamento da solução do problema; ii) execução da solução do problema e  iii) apresentação do conteúdo referente ao problema executado. Como principal resultado o artigo apresenta o planejamento de seis atividades que serão aplicadas a metodologia PBL para o estudo do concreto do ponto de vista dos materiais de construção e do cálculo estrutural de concreto

Large eddy simulation of interacting barchan dunes in a steady, unidirectional flow

We have performed large-eddy simulations of turbulent flow 4 over barchan dunes in a channel with different interdune spacings in the downstream direction at Reynolds number, Re∞ ≃ 26000 (based on the free 6 stream velocity and channel height). Simulations are validated against ex-perimental data (at Re∞ = 55460); the largest interdune spacing (2.38λ, where λ is the length of the barchan model) presents similar characteristics to the isolated dune in the experiment, indicating that at this distance the sheltering effect of the upstream dune is rather weak. We examine 3D realizations of the mean and instantaneous flow to explain features of the flow field relevant to sediment transport. Barchan dunes induce two counter-rotating streamwise vortices, along each of the horns, which direct high-momentum fluid toward the symmetry plane and low-momentum fluid near the bed away from the centerline. The flow near the bed, upstream of the dune, diverges from the centerline plane, decelerates and then rises on the stoss side of the dune while accelerating; the flow close to the centerline plane separates at the crest and reattaches on the bed. Away from the centerline plane and along the horns, flow separation occurs intermittently. The flow in the separation bubble is routed towards the horns and leaves the dune at their tips. The separated flow at the crest reattaches on the bed, except on the centerline symmetry plane of the dune, where a weak saddle point of separation ap- pears at the bed. The distribution of the bed shear-stress, characteristics of the separation and reattachment regions, and instantaneous wall turbulence are discussed. Characteristics of the internal boundary layer developing on the bed after the reattachment region are studied. The interdune spacing isfound to affect significantly the turbulent flow over the stoss side of the downstream dunes; at smaller interdune-spacings, coherent high- and low- speed streaks are shorter but stronger, and the spanwise normal Reynolds stress is larger. The turbulent kinetic energy budgets show the importance of the pressure transport and mean-flow advection in transporting energy from the overlying wake layer to the internal boundary layer over the stoss side of the closely-spaced dunes. The characteristics of the separated-shear layer are altered slightly at smaller interdune spacing; the separation bubble is smaller, the separated-shear layer is stronger, and the bed shear-stress is larger. Away from the dunes, typical wall-turbulence structures are observed, but coher- ent eddies generated in the separated-shear layer due to the Kelvin-Helmholtz instability are dominant near the dune. Coherent structures are generated more frequently at smaller interdune spacing; they move farther away from the bed, towards the free surface, and remain in between the horns. At larger interdune spacings, these coherent structures are advected in the spanwise direction with the mean streamwise vortices and can be observed outside of the dunes

Measurement of the cosmic ray spectrum above 4×10184{\times}10^{18} eV using inclined events detected with the Pierre Auger Observatory

A measurement of the cosmic-ray spectrum for energies exceeding $4{\times}10^{18}$ eV is presented, which is based on the analysis of showers with zenith angles greater than $60^{\circ}$ detected with the Pierre Auger Observatory between 1 January 2004 and 31 December 2013. The measured spectrum confirms a flux suppression at the highest energies. Above $5.3{\times}10^{18}$ eV, the "ankle", the flux can be described by a power law $E^{-\gamma}$ with index $\gamma=2.70 \pm 0.02 \,\text{(stat)} \pm 0.1\,\text{(sys)}$ followed by a smooth suppression region. For the energy ($E_\text{s}$) at which the spectral flux has fallen to one-half of its extrapolated value in the absence of suppression, we find $E_\text{s}=(5.12\pm0.25\,\text{(stat)}^{+1.0}_{-1.2}\,\text{(sys)}){\times}10^{19}$ eV.Comment: Replaced with published version. Added journal reference and DO

Energy Estimation of Cosmic Rays with the Engineering Radio Array of the Pierre Auger Observatory

The Auger Engineering Radio Array (AERA) is part of the Pierre Auger Observatory and is used to detect the radio emission of cosmic-ray air showers. These observations are compared to the data of the surface detector stations of the Observatory, which provide well-calibrated information on the cosmic-ray energies and arrival directions. The response of the radio stations in the 30 to 80 MHz regime has been thoroughly calibrated to enable the reconstruction of the incoming electric field. For the latter, the energy deposit per area is determined from the radio pulses at each observer position and is interpolated using a two-dimensional function that takes into account signal asymmetries due to interference between the geomagnetic and charge-excess emission components. The spatial integral over the signal distribution gives a direct measurement of the energy transferred from the primary cosmic ray into radio emission in the AERA frequency range. We measure 15.8 MeV of radiation energy for a 1 EeV air shower arriving perpendicularly to the geomagnetic field. This radiation energy -- corrected for geometrical effects -- is used as a cosmic-ray energy estimator. Performing an absolute energy calibration against the surface-detector information, we observe that this radio-energy estimator scales quadratically with the cosmic-ray energy as expected for coherent emission. We find an energy resolution of the radio reconstruction of 22% for the data set and 17% for a high-quality subset containing only events with at least five radio stations with signal.Comment: Replaced with published version. Added journal reference and DO

Measurement of the Radiation Energy in the Radio Signal of Extensive Air Showers as a Universal Estimator of Cosmic-Ray Energy

We measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 MHz. Exploiting the accurate energy scale of the Pierre Auger Observatory, we obtain a radiation energy of 15.8 \pm 0.7 (stat) \pm 6.7 (sys) MeV for cosmic rays with an energy of 1 EeV arriving perpendicularly to a geomagnetic field of 0.24 G, scaling quadratically with the cosmic-ray energy. A comparison with predictions from state-of-the-art first-principle calculations shows agreement with our measurement. The radiation energy provides direct access to the calorimetric energy in the electromagnetic cascade of extensive air showers. Comparison with our result thus allows the direct calibration of any cosmic-ray radio detector against the well-established energy scale of the Pierre Auger Observatory.Comment: Replaced with published version. Added journal reference and DOI. Supplemental material in the ancillary file

Corrigendum to 'Editor's Choice - European Society for Vascular Surgery (ESVS) 2020 Clinical Practice Guidelines on the Management of Vascular Graft and Endograft Infections' [European Journal of Vascular & Endovascular Surgery 59/3 (2020) 339-384]

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