The turbulent dispersion of a passive tracer emitted by a line source simulating vehicular traffic in an idealized urban canyon in neutral conditions is studied in the water channel by means of ...simultaneous measurements of velocity and concentration fields. The experiments are conducted for two geometrical arrangements of two-dimensional obstacles reproducing the skimming flow (AR = 1) and the wake-interference regime (AR = 2), where AR is the canyon aspect ratio. The results show a strict connection between the dynamics of the shear layer developing at the top of the canyon and the vorticity field. For AR = 1, it is found that the shear layer flaps upwards and downwards according to two different frequencies. The greatest of them matches the vortex shedding frequency as measured at the canyon top, while the lower is comparable to H/u∗ (H is the building height and u∗ a reference friction velocity). The shear layer flapping modulates in time the pollutant exchange rate between the canyon and the outer layer. The different characteristics of the shear layer found for the two flow regimes also explain the larger pollutant re-entrainment observed for AR = 1, which turns out to be greater than the emission rate at the source. Sweep and ejection modes are identified via quadrant analysis and used to quantify the weights of the factors involved in the turbulent exchanges of tracer and momentum between the canyon and the outer layer. It is found that the venting of polluted fluid at the canyon top increases substantially passing from AR = 1 to 2, while an opposite trend is observed for the entrainment of polluted fluid. The vertical flux of pollutant at the canyon top for AR = 2 is largely of turbulent nature, with the contribution of the mean flux being practically negligible. On the other hand, the latter becomes comparable or even exceeds the magnitude of the turbulent flux when AR = 1. The maps of the first three statistical moments of the pollutant concentration for the two geometrical arrangements are also reported and discussed.
•A line source is used to simulate vehicular emission at street level.•Velocity and tracer concentration are measured simultaneously.•Momentum and concentration fluxes are analyzed.•Venting and re-entrainment mechanisms are quantified.
Most urban canopy models adopt the two-dimensional (infinitely long) street canyon as the basic unit to represent the city texture. This paper presents a new urban canopy model, the 3DUCM ...(three-dimensional urban canopy model), which accounts for every single building of the city to determine the air temperature and heat fluxes involved in the surface energy budget. 3DUCM has been coupled with the Colorado State University Mesoscale Model, and an idealized city has been considered as case study. Among the main results, it is shown that the air temperature simulated by 3DUCM within the canopy is lower compared to that calculated using the two-dimensional approach, mainly because of crossroads modelling. The new model is suitable for predicting the temperature field down to the building scale and it is potentially easy to apply to realistic scenarios, for which the actual shape, orientation and constructing material properties of every single building constituting the canopy can be taken into account.
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•Influence of the urban canopy on the surface energy budget is investigated.•A new Three-Dimensional Urban Canopy Model is introduced.•Temperature, heat fluxes and radiative fluxes are simulated at the building scale.•Significant differences with the two-dimensional approach are present.•Model sensitivity to urban geometry and construction material is conducted.
•Multimodality treatment may be the therapeutic approach of choice for highly selected resectable PM.•Pleurectomy/decortication should be preferred over other surgical techniques in highly selected ...resectable PM, when appropriate.•Conservative management could ensure comparable long-term results as aggressive extra-pleural pneumonectomy.•Curative surgery for PM should be performed only in highly selected patients in experienced centers.
to date, no consensus has been reached on the surgical gold-standard in pleural mesothelioma (PM). We retrospectively reviewed our experience as a tertiary referral centre, to compare short- and long-term survival of PM patients undergoing different types of surgery.
in retrospective, observational, single-centre study, we analysed all the patients histologically diagnosed with PM undergoing surgical procedures with palliative or curative intent at IRCCS Istituto Nazionale dei Tumori of Milan, Italy, from January 2003 to December 2020. The primary study endpoint was 10-year overall survival (OS) in three different types of resections: extra-pleural-pneumonectomy (EPP), pleurectomy/decortication (P/D), partial-pleurectomy/pleural-biopsy (PP/B). Secondary endpoints were postoperative hospital stay and postoperative 30-day and 90-day mortality rates. The survival function was estimated using Kaplan-Meier, and the Log-rank test was used for testing differences. Univariable and Multivariable Cox regression models were implemented to estimate Hazard Ratio (HR) for all variables of interest.
243 consecutive patients were enrolled, EPP was performed in 49 (20.2%), P/D in 58 (23.8%), PP/B in 136 (56.0%) patients. The median follow-up time was 19.8 months. 10-year OS was significantly better for P/D group (16%, Log-Rank test p<0.0001) compared to PP/B (1.8%) and EPP (0%). No statistically significant differences were found among the 3 surgical groups in 30- and 90-day mortality rates. At multivariable analysis, gender (male, HR=1.58), type of resection (P/D, HR=0.55) and surgery date (recent years, HR=0.61) were found to be independent prognostic factors for OS.
in PM, lung-sparing curative approach (e.g. P/D) should be preferred in highly selected patients and in highly experienced centres, whenever appropriate. Anyway, when P/D is not indicated, adopting palliative/conservative management (e.g. PP/B) could ensure comparable results as extremely aggressive surgeries (e.g. EPP). The aim of surgery in PM should not be reaching complete resection, but rather accomplishing significant resection allowing to complete the multimodality treatment in highly selected patients in experienced centers.
The aim of this work is to investigate how both the orientation of the urban canyon and the modeling of the edge effects (i.e. urban canyons of finite length) are important in the numerical ...simulation of the surface energy budget in urban areas. Starting from the town energy balance scheme, two models of increasing complexity of the canyon geometry are developed. A sensitivity analysis of the role played by the chosen hypothesis and parameterizations is performed by coupling the canyon schemes with the numerical weather prediction model RAMS. The results suggest that a detailed description of the urban geometry could produce non-negligible differences of the energy balances and of the temperature fields with respect to what occurs using simpler schematizations, in particular during the summer.
As known from recent COVID-19 pandemics, droplets emitted by humans during various respiratory activities can contain pathogens and be responsible for infectious disease transmission. The study of ...droplet dispersion is fundamental to estimate and possibly control the associated risk. Numerical simulations are useful as they make it possible to afford the complexity of this phenomenon. However, they require precise droplet and air properties as input data in order to provide reliable results. A lack of knowledge still exists due to the difficulties in measuring droplet sizes over a wide range and in capturing sizes and velocities simultaneously. In this work, numerical simulations were conducted using experimental data collected by the authors, taking advantage of innovative information about particle velocity relative to their size. Two measurement campaigns involving 20 volunteers were carried out. The size and the three velocity components of the ejected droplets were simultaneously measured for droplets down to
2
μ
m
using an extended version of the Interferometric Laser Imaging Droplet Sizing technique. The effect of droplet initial velocity on droplet dispersion is assessed, along with the effect of other parameters, namely, ambient temperature and air ejection velocity. Both inert and evaporating droplets are considered in the simulations.
Introduction
Surgical resection of pulmonary metastases has been associated with increased survival at 5 years for osteosarcoma, but limited information is available on long-term outcome, role of ...repeated metastasectomies, and surgical sequelae in a pediatric population. We analyzed a consecutive series of children, adolescents, and young adults (AYA) treated by repeated lung metastasectomies during a period >40 years to estimate the clinical benefit and potential cure rate of salvage surgery.
Methods
All patients who underwent lung metastasectomy for osteosarcoma at the IRCCS Istituto Ortopedico Rizzoli of Bologna, University of Modena, and IRCCS Istituto Nazionale Tumori of Milan from May 1973 to January 2014 were included. Overall survival (OS) at 20 years from the first metastasectomy was calculated.
Results
A total of 463 consecutive children and AYA were analyzed. Median age was 15.9 years (range 0.2–23.2 years) and median follow-up 18.6 years. The 5- and 20-year OS were 34.0% and 29.7% (95% CI 25.5–34.0%). Among the 138 (29.8%) alive patients, 42 (30.4%) had disease recurrence cured by repeated metastasectomies. Disease-free interval from primary tumor, number of metastases, and complete resection were the most relevant survival predictors at multivariable model analysis.
Discussion
The extended follow-up of this consecutive series shows that repeated lung metastasectomy can achieve a permanent cure when offered to properly selected patients with metastases from osteosarcoma.
Overlapping survival curves for N1b (multiple N1 stations), N2a2 (single N2 station + N1 involvement) and N2a1 (skip N2 metastasis) limit the current tumour-node-metastasis (TNM) node (N) ...subclassification for node involvement. We validated externally the proposed subclassification.
Clinical records from a multicentric database comprising 1036 patients with pulmonary adenocarcinoma (ADC) or squamous cell carcinoma with N1/N2 involvement who underwent, from January 2002 to December 2014, complete lung resections were retrospectively reviewed. Patients were categorized according to the 8th TNM N subclassification proposal. Histological type, number of resected nodes (#RN) and adjuvant therapy (ADJ) were considered limiting factors.
No difference in the 5-year overall survival (-OS) was noted between N1b and N2a1 (49.6% vs 44.8%, P = 0.72); instead, the 5-year-OS was significantly improved in patients with squamous cell carcinoma (63% in N1b vs 30.7% in N2a1, P = 0.04). In patients with ADC, the 5-year-OS was better in those with N2a1 than with N1b (50.6% vs 37.5%, P = 0.09). When we compared N1b with N2a2, the 5-year-OS was statistically significant (49.6% vs 32.8%, P = 0.02); considering only patients with squamous cell carcinoma (63% vs 25.8%, P = 0.003), #RN >10 (63.2% vs 35.3%, P = 0.05) and without ADJ (56.4% vs 24.5%, P = 0.02), the 5-year-OS was significantly different. Differences were not significant for ADC, #RN <10 and ADJ. Finally, the 5-year-OS was statistically significant when we compared N2a1 with N2a2 of the total cohort (44.8% vs 32.8%, P = 0.04), in ADC (5-year-OS 50.6% vs 36.5%, P = 0.04) and #RN >10 (5-year-OS 49.8% vs 32.1%, P = 0.03) without ADJ.
Histological type, ADJ and #RN are relevant prognostic factors in N + non-small-cell lung cancer. Considering these results, we may better interpret the prognosis prediction limits of the proposed 8th TNM subclassification for the N descriptor.
On the basis of meteorological observations conducted within the city of Rome, Italy, a new formulation of the wind-speed profile valid in urban areas and neutral conditions is developed. It is found ...that the role played by the roughness length in the canonical log-law profile can be taken by a local length scale, depending on both the surface cover and the distance above the ground surface, which follows a pattern of exponential decrease with height. The results show that the proposed model leads to increased performance compared with that obtained by using other approaches found in the literature.
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