196,030 research outputs found
SOIL-STRUCTURE INTERACTION MODELING FOR THE DYNAMIC ANALYSIS OF CONCRETE GRAVITY DAMS
No full textDuring earthquake shaking, the dam-reservoir-foundation system has to be considered a cou-pled system. In this paper Soil-Structure Interaction (SSI) effect is investigated on a 2D plane model of a concrete gravity dam under earthquake excitation. Firstly, different approaches to simulate the unboundedness of soil domain are explored: the Perfectly Matched Layer (PML) technique, the Low Reflecting Boundary (LRB) condition and the Infinite Elements (IEs). Dif-ferent options are compared in the time domain in the case of linear elastic material. The im-portance of taking into account the SSI in the seismic assessment of concrete dams is also highlighted by the energy balance during time. Successively, the effects of SSI are analysed on a full interacting nonlinear plane model. The results which are obtained in terms of material damage and dissipated energy through a parametric SSI simulation in the time domain show the importance of the choice of the damage constitutive law of the material
Acoustic Fluid-Structure Interaction Modeling of Gravity Dams in the Frequency Domain
No full textThe assessment of the seismic safety of gravity dams is a topic of great importance in civil engineering. In this paper, fluid structure interaction modeling of gravity dams during earthquakes is investigated. In particular, this work aims to provide physical significance of a plan numerical model simulating the dam and the infinite length reservoir when a horizontal ground motion acts at the dam foundation. After a preliminary calibration of the model with analytical solutions, the dynamic properties of the numerical model are investigated via modal and frequency response analyses. The fully coupled mechanical-acoustic model is also compared to the widespread “added mass” model [1] adopted in most national codes
Hierarchical Bayesian framework for uncertainty reduction in the seismic fragility analysis of concrete gravity dams
No full textConcrete gravity dams are critical infrastructures for communities to meet the basic human needs as well as rising standards of living. Most of the existing concrete gravity dams in Italy were built before the introduction of seismic regulations. Although no concrete gravity dams have as yet suffered a catastrophic collapse during or after a seismic event, their preservation remains a key aspect for communities, also in view of that older dams may have deteriorated to a critical level. For these reasons, researchers and practitioners in dam engineering are working to improve seismic fragility, and ultimately seismic risk, assessment procedures. Since no case histories are available, numerical modelling plays an important role, even though many uncertainties can affect the models and then the estimation of the seismic fragility. This paper presents a robust hierarchical Bayesian framework for the calibration of dynamic parameters of dam numerical models based on ambient vibrations, which allows an analyst to reduce uncertainties in the seismic fragility derivation. A probabilistic predictive model of the dam modal behaviour based on the general Polynomial Chaos Expansion is adopted in order to reduce the computational burden and a numerical algorithm for the solution of the inverse problem based on Markov Chain Monte Carlo is also presented. The proposed approach is applied to an existing large concrete gravity dam in Italy, and the effect of epistemic uncertainty reduction is finally evaluated in terms of fragility curves
MANAGING EMERGENCY INTO HISTORIC CENTRES IN ITALY: SEISMIC VULNERABILITY EVALUATION AT URBAN SCALE
No full textItaly is one of the most earthquake prone areas in Europe and one of the countries with the richest cultural legacy in the world. A series of seismic events occurred in the last decades caused considerable casualties and damage to historic centres, highlighting the need of un-dertaking protective measures to limit the impact of any potential earthquake. The complex morphology of historical city centres with their century-old built environment contribute to the high vulnerability and exposure in the areas. This research introduces an interdiscipli-nary approach to implement the seismic emergency management for historical centres in Italy and consequently to address their preventive planning.
A procedure combining vulnerability analysis and urban spatial techniques allows defining a ranking of priority interventions to be included into a preventive plan in order to ensure free escape routes and clear access for the emergency services during the post-seismic phase. The first step of this work is the survey of the present-day configuration of historic centres, with their historical assets, aggregates, critical infrastructures, urban functions and strategic ac-tivities. Then, a key aspect regards the vulnerability assessment of the urban fabric in order to predict post-seismic damage scenarios. By considering the interference of the buildings’ vul-nerability with the street network, it is possible to develop mitigation strategies to improve the emergency management
Isolation of primary cancer-associated fibroblasts from a syngeneic murine model of breast cancer for the study of targeted nanoparticles
No full textCancer-associated fibroblasts (CAFs) are key actors in the context of the tumor microenvironment. Despite being reduced in number as compared to tumor cells, CAFs regulate tumor progression and provide protection from antitumor immunity. Emerging anticancer strategies aim to remodel the tumor microenvironment through the ablation of pro-tumorigenic CAFs or reprogramming of CAFs functions and their activation status. A promising approach is the development of nanosized delivery agents able to target CAFs, thus allowing the specific delivery of drugs and active molecules. In this context, a cellular model of CAFs may provide a useful tool for in vitro screening and preliminary investigation of such nanoformulations. This study describes the isolation and culture of primary CAFs from the syngeneic 4T1 murine model of triple-negative breast cancer. Magnetic beads were used in a 2-step separation process to extract CAFs from dissociated tumors. Immunophenotyping control was performed using flow cytometry after each passage to verify the process yield. Isolated CAFs can be employed to study the targeting capability of different nanoformulations designed to tackle the tumor microenvironment. Fluorescently labeled H-ferritin nanocages were used as candidate nanoparticles to set up the method. Nanoparticles, either bare or conjugated with a targeting ligand, were analyzed for their binding to CAFs. The results suggest that ex vivo extraction of breast CAFs may be a useful system to test and validate nanoparticles for the specific targeting of tumorigenic CAFs
Protein-based nanoparticles for the imaging and treatment of solid tumors : The case of ferritin nanocages, a narrative review
No full textProtein nanocages have been studied extensively, due to their unique architecture, exceptional biocompatibility and highly customization capabilities. In particular, ferritin nanocages (FNs) have been employed for the delivery of a vast array of molecules, ranging from chemotherapeutics to imaging agents, among others. One of the main favorable characteristics of FNs is their intrinsic targeting efficiency toward the Transferrin Receptor 1, which is overexpressed in many tumors. Furthermore, genetic manipulation can be employed to introduce novel variants that are able to improve the loading capacity, targeting capabilities and bio-availability of this versatile drug delivery system. In this review, we discuss the main characteristics of FN and the most recent applications of this promising nanotechnology in the field of oncology with a particular emphasis on the imaging and treatment of solid tumors
Indocyanine Green Nanoparticles : Are They Compelling for Cancer Treatment?
No full textIndocyanine green (ICG) is a Food and Drug Administration–approved near-infrared fluorescent dye, employed as an imaging agent for different clinical applications due to its attractive physicochemical properties, high sensitivity, and safety. However, free ICG suffers from some drawbacks, such as relatively short circulation half-life, concentration-dependent aggregation, and rapid clearance from the body, which would confine its feasible application in oncology. Here, we aim to discuss encapsulation of ICG within a nanoparticle formulation as a strategy to overcome some of its current limitations and to enlarge its possible applications in cancer diagnosis and treatment. Our purpose is to provide a short but exhaustive overview of clinical outcomes that these nanocomposites would provide, discussing opportunities, limitations, and possible impacts with regard to the main clinical needs in oncology
CONCRETE GRAVITY DAMS FE MODELS PARAMETERS UPDATING USING AMBIENT VIBRATIONS
No full textMost of the dams around the world were designed before the introduction of seismic regula-tions and without concerns about their dynamic behavior. The failure of a large gravity dam might have catastrophic effects putting at risk a large number of human lives, not counting the considerable economic consequences. Since there are no case histories of concrete gravity dams failed after seismic events, numerical models assume great importance for the evalua-tion of the seismic performance of such structures or to control them within a SHM frame-work. Several different sources of uncertainty are involved in numerical models of concrete gravity dams, their effects can be reduced by exploiting all available information about the structure. Ambient vibrations are an important source of information because they can be used to characterize the dynamic behavior of the structure. In this paper, a procedure, de-fined in the Bayesian framework, which allows calibrating the dynamic model parameters us-ing ambient vibration is presented. Ambient vibrations are used to determine the modal characteristics of the system, by applying the Operational Modal Analysis (OMA), which are used in the updating process. The use of meta models based on the general Polynomial Chaos Expansion (gPCE) and a modified version of Markov Chain Monte Carlo (MCMC) allows both considering the SSI in the numerical model of the dam and solving the problem of coher-ence between experimental and numerical modes. Finally, the proposed procedure is applied to the case of an Italian dam showing the applicability to real cases
Concrete gravity dams model parameters updating using static measurements
No full textThe structural control of concrete gravity dams is of primary importance. In this context, numerical models play a fundamental role both to assess the vulnerability of gravity dams and to control their behaviour during normal operativity and after extreme events. In this regard, data monitoring represents an important source of information for numerical model calibrations. This study proposes a novel probabilistic procedure, defined in the Bayesian framework, to calibrate the parameters of finite elements models of dams. To this aim, monitoring data and the results of material tests are used as reference information. The computational burden is reduced by using a new hybrid-predictive model of the dam displacements. An application on an Italian dam shows the feasibility of the proposed procedure
Tumor Accumulation and Off-Target Biodistribution of an Indocyanine-Green Fluorescent Nanotracer : An Ex Vivo Study on an Orthotopic Murine Model of Breast Cancer
No full textIndocyanine green (ICG) is a near infrared fluorescent tracer used in image-guided surgery to assist surgeons during resection. Despite appearing as a very promising tool for surgical oncology, its employment in this area is limited to lymph node mapping or to laparoscopic surgery, as it lacks tumor targeting specificity. Recently, a nanoformulation of this dye has been proposed with the aim toward tumor targeting specificity in order to expand its employment in surgical oncology. This nanosystem is constituted by 24 monomers of H-Ferritin (HFn), which self-assemble into a spherical cage structure enclosing the indocyanine green fluorescent tracer. These HFn nanocages were demonstrated to display tumor homing due to the specific interaction between the HFn nanocage and transferrin receptor 1, which is overexpressed in most tumor tissues. Here, we provide an ex vivo detailed comparison between the biodistribution of this nanotracer and free ICG, combining the results obtained with the Karl Storz endoscope that is currently used in clinical practice and the quantification of the ICG signal derived from the fluorescence imaging system IVIS Lumina II. These insights demonstrate the suitability of this novel HFn-based nanosystem in fluorescence-guided oncological surgery
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