Impact of Dry Granular Flows on a Rigid Wall: Discrete and Continuum Approach

Numerical simulations of impacts of granular flows with structures are complex because they have to take into account large deformations, large strain rates and interactions with boundaries or structures. Moreover, the material response is governed by interactions between grains, which leads to a complex rheology. Discrete methods (DEM), which apply a micromechanical approach, appears very well suited to this purpose, but they can hardly deal with large-scale problems. In contrasts, continuum methods can handle large granular volumes because they use a macroscopic approach in which the material behaviour is described by a constitutive model. The aim of this paper it to compare the results obtained by a discrete and a continuum approach in simulating the impact of a dry granular flow on a rigid wall. The problem is simulated with a DEM code and with a software based on the Material Point Method

Flood depth estimation by means of high-resolution SAR images and lidar data

When floods hit inhabited areas, great losses are usually registered in terms of both impacts on people (i.e., fatalities and injuries) and economic impacts on urban areas, commercial and productive sites, infrastructures, and agriculture. To properly assess these, several parameters are needed, among which flood depth is one of the most important as it governs the models used to compute damages in economic terms. This paper presents a simple yet effective semiautomatic approach for deriving very precise inundation depth. First, precise flood extent is derived employing a change detection approach based on the normalized difference flood index computed from high-resolution synthetic aperture radar imagery. Second, by means of a high-resolution lidar digital elevation model, water surface elevation is estimated through a statistical analysis of terrain elevation along the boundary lines of the identified flooded areas. Experimental results and quality assessment are given for the flood that occurred in the Veneto region, northeastern Italy, in 2010. In particular, the method proved fast and robust and, compared to hydrodynamic models, it requires sensibly less input information

Case report: The lesson from opioid withdrawal symptoms mimicking paraganglioma recurrence during opioid deprescribing in cancer pain

Pain is one of the predominant and troublesome symptoms that burden cancer patients during their whole disease trajectory: adequate pain management is a fundamental component of cancer care. Opioid are the cornerstone of cancer pain relief therapy and their skillful management must be owned by physicians approaching cancer pain patients. In light of the increased survival of cancer patients due to advances in therapy, deprescription should be considered as a part of the opioid prescribing regime, from therapy initiation, dose titration, and changing or adding drugs, to switching or ceasing. In clinical practice, opioid tapering after pain remission could be challenging due to withdrawal symptoms’ onset. Animal models and observations in patients with opioid addiction suggested that somatic and motivational symptoms accompanying opioid withdrawal are secondary to the activation of stress-related process (mainly cortisol and catecholamines mediated). In this narrative review, we highlight how the lack of validated guidelines and tools for cancer patients can lead to a lower diagnostic awareness of opioid-related disorders, increasing the risk of developing withdrawal symptoms. We also described an experience-based approach to opioid withdrawal, starting from a case-report of a symptomatic patient with a history of metastatic pheochromocytoma-paraganglioma

THE NATURAL HISTORY OF AUTOIMMUNE ADDISON'S DISEASE FROM THE DETECTION OF AUTOANTIBODIES TO DEVELOPMENT OF THE DISEASE: A LONG FOLLOW-UP STUDY ON 143 PATIENTS

Adrenal cortex autoantibodies (ACA) and/or 21-hydroxylase (21OHAb) are markers of autoimmune Addison's disease (AAD) and progression to overt AAD. The reported cumulative risk of developing AAD varies from 0-90% in different studies. Aim To assess the predictive value of different parameters for progression towards AAD in ACA and/or 21OHAb-positive patients with autoimmune polyendocrine syndromes (APS). Materials and Methods 29 patients with APS-1 and 114 patients with APS-2 or APS-4, were followed-up for a median of 10 years (range 6 months-33 years) and assessed by ACTH test. The risk of AAD was estimated according to age, gender, stage of adrenal dysfunction, associated diseases and antibody titer. Univariate and multivariate Cox proportional hazard models were used for statistical analysis. Results The cumulative risk (CR) of developing AAD was higher in APS-1 patients (94.2%) compared to patients with APS-2/APS-4 (38.7%). The CR was high in both males and females with APS-1 patients, while in patients with APS-2/APS-4 it was high only in males. Stage 1 (increased plasma renin) for patients with APS-1 and Stage 2 (no response of cortisol to ACTH-test) for patients with APS-2/APS-4 were established as the points of no return in the progression to AAD. Adjusted hazard ratio analyses by multivariate Cox model for AAD showed that gender, diseases, adrenal function were independent risk factors for developing clinical AAD. The risk of developing clinical AAD appears to subside after 19 years of follow up. Conclusions A model for estimating the probability to survive free of AAD has been developed and should be a useful tool in designing appropriate follow-up intervals and future therapeutic strategies

Association of kidney disease measures with risk of renal function worsening in patients with type 1 diabetes

Background: Albuminuria has been classically considered a marker of kidney damage progression in diabetic patients and it is routinely assessed to monitor kidney function. However, the role of a mild GFR reduction on the development of stage 653 CKD has been less explored in type 1 diabetes mellitus (T1DM) patients. Aim of the present study was to evaluate the prognostic role of kidney disease measures, namely albuminuria and reduced GFR, on the development of stage 653 CKD in a large cohort of patients affected by T1DM. Methods: A total of 4284 patients affected by T1DM followed-up at 76 diabetes centers participating to the Italian Association of Clinical Diabetologists (Associazione Medici Diabetologi, AMD) initiative constitutes the study population. Urinary albumin excretion (ACR) and estimated GFR (eGFR) were retrieved and analyzed. The incidence of stage 653 CKD (eGFR < 60 mL/min/1.73 m2) or eGFR reduction > 30% from baseline was evaluated. Results: The mean estimated GFR was 98 \ub1 17 mL/min/1.73m2 and the proportion of patients with albuminuria was 15.3% (n = 654) at baseline. About 8% (n = 337) of patients developed one of the two renal endpoints during the 4-year follow-up period. Age, albuminuria (micro or macro) and baseline eGFR < 90 ml/min/m2 were independent risk factors for stage 653 CKD and renal function worsening. When compared to patients with eGFR > 90 ml/min/1.73m2 and normoalbuminuria, those with albuminuria at baseline had a 1.69 greater risk of reaching stage 3 CKD, while patients with mild eGFR reduction (i.e. eGFR between 90 and 60 mL/min/1.73 m2) show a 3.81 greater risk that rose to 8.24 for those patients with albuminuria and mild eGFR reduction at baseline. Conclusions: Albuminuria and eGFR reduction represent independent risk factors for incident stage 653 CKD in T1DM patients. The simultaneous occurrence of reduced eGFR and albuminuria have a synergistic effect on renal function worsening

Normalized Difference Flood Index for rapid flood mapping: taking advantage of EO big data

Climate change projections foresee an increasing number of intense precipitation events with consequent flash and riverine floods. An accurate and rapid mapping of these phenomena is a key component of effective emergency management and disaster risk reduction plans. Earth Observation big data such as the ones acquired by the Copernicus programme, are providing unprecedented opportunities to detect changes and assess economic impacts in case of disasters.This paper presents an innovative flood mapping technique based on an index which is computed using multi-temporal statistics of Synthetic Aperture Radar images. The index compares a large amount of reference scenes to those acquired during the investigated flood and allows an easy categorization of �flooded� areas; either areas solely temporarily covered by water or areas with mixed water and vegetation. The method has been developed specifically to exploit Sentinel-1 data but can be applied to any other sensor. It has been tested for the 2010 flood of Veneto (Italy) and the floods of 2015 in Malawi and Uganda. Extensive qualitative analysis and cross-comparison with other state-of-the art methods, proved the proposed approach highly reliable and particularly effective, allowing a precise, simple and fast flood mapping. Compared to the maps produced for emergency management for the event analyzed, we obtained an overall agreement of 96.7% for Malawi and an average of 96.5% for Veneto for the 5 maps presented

Studio sui meccanismi di instabilità di pendii eterogenei con l'MPM

Nella seguente memoria viene presentato uno studio sulla stabilità di pendii eterogenei basato sull’utilizzo del metodo dei punti materiali (MPM). In questa tipologia di pendii l’innesco del movimento franoso è generalmente associato ad un’alterazione del regime delle pressioni interstiziali causato da un evento di pioggia oppure da una ricarica sotterranea della falda. Nel seguente lavoro, questi due scenari di saturazione vengono applicati ad un pendio modello, permettendo così di analizzare sulla medesima geometria la differente evoluzione dei meccanismi di instabilità. L’analisi alle grandi deformazioni con MPM permette di esplorare tutto il fenomeno di innesco, evoluzione e post collasso e quindi di valutare gli spostamenti del pendio nel tempo senza le limitazioni degli approcci FEM tradizionali. In entrambi gli scenari indagati l’instabilità è caratterizzata da successivi fenomeni di riattivazione del movimento, a seguito della formazione della superficie di scivolamento. Dallo studio emerge che la fondamentale differenza fra i due percorsi di saturazione risiede nella profondità della superficie di scivolamento e quindi nell’entità delle masse instabili associate: nel caso dell’innesco per pioggia, il movimento, inizialmente solo superficiale, tende ad approfondirsi nel tempo, mantenendo una maggiore concentrazione di spostamenti nella parte alta del pendio; nel caso invece di ricarica di falda dal basso la superficie di scivolamento si forma più lentamente e subito in profondità, mantenendo pressoché costante la sua volumetria nel tempo

Failure of levees induced by toe uplift: Investigation of post-failure behavior using material point method

Levees are essential structures in flood defense systems, and their failures can lead to devastating consequences on the surrounding territories. One of the failure mechanisms mostly controlled by the foundation soil stratigraphy is the instability of the land side slope, triggered by the development of high uplift pressures in the foundation. This complex phenomenon has been investigated experimentally with centrifuge tests or large-scale tests and numerically with the limit equilibrium method (LEM) and the finite element method (FEM). In this work, we applied a multiphase formulation of the material point method (MPM) to analyze the development of toe uplift instability mechanism, from the onset of failure to large displacements. The numerical model is inspired by an experiment carried out in a geotechnical centrifuge test by Allersma and Rohe (2003). The comparison with the experiment allows for understanding critical pore pressure triggering large displacements in the foundation soils. Moreover, we numerically evaluated the impact of different values of foundation soils' hydraulic conductivity on the failure mechanism. The results show that hydraulic conductivity mainly influences the time of failure onset and the extension of shear localization at depth. Finally, the advantages of using large displacement approaches in the safety assessment of earth structures are discussed. Unlike FEM, there are no issues with element distortions generating difficulties with numerical convergence, allowing for full post-failure reproduction. This capability permits precise quantification of earth structure damages and post-failure displacements. The ensuing reinforcement systems' design is no longer over-conservative, with a significant reduction in associated costs

Wetting induced instabilities in layered slopes: A Material Point Method analysis

The increase of pore water pressure due to rainfall infiltration or upstream recharge is among the primary triggers of landslides, and soil layering has a significant effect on the hydromechanical behavior of the slope. The failure and post-failure behavior of heterogeneous layered slopes triggered by these phenomena are investigated in this study. In particular, a low permeability layer is embedded in a reference slope with different inclinations, and the impact of different saturation mechanisms on the post-failure behavior is assessed. To this aim, an unsaturated formulation of the Material Point Method (MPM) is used to reproduce the whole deformation process of a layered slope. The results show different failure and post-failure mechanisms and kinematics for both upstream recharge and rainfall infiltration (i.e., bottom-up and top-down saturation processes, respectively). Bottom-up saturation mechanism triggers deep failure mechanisms that barely evolve during the instability process. On the contrary, top-down saturation mechanism induces an anticipated shallow semi-planar failure limited by the location of the low permeable layer. These failures are characterized by high velocities and by a deepening of the slip surface during the post-failure process. Final displacements in both wetting mechanisms are of the same order of magnitude. The subsequent reactivation movements are observed as a result of the continuous injection of water in the system