The terms mélange and broken formation have been used in different ways in the literature. The lack of agreement on their definition often leads to confusion and misinterpretations. An evaluation of ...the various uses of these terms allows us to consider several types of chaotic rock bodies originated by tectonic, sedimentary and diapiric processes in different tectonic settings. Our review of stratal disruption and mixing processes shows that there exists a continuum of deformation structures and processes in the generation of mélanges and broken formations. This continuum is directly controlled by the increase of the degree of consolidation with burial. In tectonically active environments, at the shallow structural levels, the occurrence of poorly consolidated sediments favors gravitational deformation. At deeper structural levels, the deformation related to tectonic forces becomes gradually more significant with depth. Sedimentary (and diapiric) mélanges and broken formations represent the products of punctuated stratal disruption mechanisms recording the instantaneous physical conditions in the geological environment at the time of their formation. The different kinematics, the composition and lithification degree of sediments, the geometry and morphology of the basins, and the mode of failure propagation control the transition between different types of mass-transported chaotic bodies, the style of stratal disruption, and the amount of rock mixing. Tectonically broken formations and mélanges record a continuum of deformation that occurs through time and different degrees of lithification during a progressive increase of the degree of consolidation and of the diagenetic and metamorphic mineral transformation. Systematic documentation of the mechanisms and processes of the formation of different broken formations and mélanges and their interplay in time and space are highly important to increase the understanding of the evolutionary history of accretionary wedges and orogenic belts.
►Re-evaluation of the definitions of the terms mélange and broken formation. ►Tectonic, sedimentary and diapiric mélanges in different tectonic settings. ►Mechanisms and processes of stratal disruption and mixing.
The Po Plain (Italy) is one of the most densely populated and productive regions of Europe, characterized by a flourishing economy (also linked to strategic subsurface resources) and several world ...cultural and natural heritage sites. The coupling of socio-economic interests with geological hazards (i.e. seismic, subsidence, and flooding hazards) in this area requires accurate knowledge of the subsurface geology, the active geological processes, and the impact of human activities on natural environments to mitigate the potential natural and anthropic risks.
Computational models describing the behavior of complex physical systems are often used in the engineering design field to identify better or optimal solutions with respect to previously defined ...performance criteria. Multi-objective optimization problems arise and the set of optimal compromise solutions (Pareto front) has to be identified by an effective and complete search procedure in order to let the decision maker, the designer, to carry out the best choice. Four multi-objective optimization techniques are analyzed by describing their formulation, advantages and disadvantages. The effectiveness of the selected techniques for engineering design purposes is verified by comparing the results obtained by solving a few benchmarks and a real structural engineering problem concerning an engine bracket of a car.
We discuss the diffusion phenomenon in the parabolic and hyperbolic regimes. New effects related to the finite velocity of the diffusion process are predicted, that can partially explain the strange ...behavior associated to adsorption phenomenon. For sake of simplicity, the analysis is performed by considering a sample in the shape of a slab limited by two perfectly blocking surfaces, in such a manner that the problem is one-dimensional in the space. Two cases are investigated. In the former, the initial distribution of the diffusing particles is assumed of gaussian type, centered around the symmetry surface in the middle of the sample. In the latter, the initial distribution is localized close to the limiting surfaces. In both cases, we show that the evolution toward to the equilibrium distribution is not monotonic. In particular, close to the limiting surfaces the bulk density of diffusing particles present maxima and minima related to the finite velocity of the diffusion process connected to the second order time derivative in the partial differential equation describing the evolution of the bulk density in the sample.
The term poorly differentiated (PD) carcinoma was proposed 20 years ago to define aggressive, follicular-derived thyroid carcinomas with behavior intermediate between follicular/papillary and ...anaplastic carcinomas. Among the variable histologic patterns recognized in such tumors, trabecular-insular-solid (TIS) areas usually are predominant. Conversely, some authors pointed out that PD carcinomas are characterized by unequivocal, high-grade histology with atypias, high mitotic counts, and necrosis rather than by a specific growth pattern.
The clinicopathologic features of a series of 183 thyroid carcinomas with predominant (n = 165 tumors) or focal (n = 18 tumors) TIS growth patterns were studied by univariate and multivariate overall survival analyses and were compared with clinical outcomes. Subgroups included tumors with predominant oxyphilic features (n = 66 tumors) and (residual) papillary carcinoma features (n = 24 tumors). Control groups of papillary (n = 68 tumors), follicular (n = 71 tumors), and anaplastic (n = 35 tumors) carcinomas also were included for overall survival analysis.
TIS carcinomas had an intermediate behavior between papillary/follicular and anaplastic carcinomas (P < 0.0001). Univariate and multivariate statistical analyses demonstrated that age > 45 years (P = 0.007), the presence of necrosis (P < 0.0001), and a mitotic count > 3 per 10 high-power fields (P = 0.01) were associated with poor outcome. A simplified scoring system based on statistically significant parameters allowed the identification of three prognostic subgroups (P < 0.0001).
PD TIS carcinomas overall followed a more aggressive course compared with differentiated thyroid carcinomas, irrespective of the extent of the TIS component. However, a numeric scoring system applied to specific clinicopathologic parameters further may identify three prognostic categories of patients who have significantly different survival rates at 5 years and 10 years.
The adsorption phenomenon of neutral particles from the limiting surfaces of the sample in the Langmuir approximation is investigated. The diffusion equation regulating the redistribution of ...particles in the bulk is assumed to be of hyperbolic type, in order to take into account the finite velocity of propagation of the density variations. We show that in this framework the condition on the conservation of the number of particles gives rise to a non-local boundary condition. We solve the partial differential equation relevant to the diffusion of particles by means of the separation of variables, and present how it is possible to obtain approximated eigenvalues contributing to the solution. The same problem is faced numerically by a finite difference algorithm. The time dependence of the surface density of adsorbed particles is deduced by means of the kinetic equation at the interface. The predicted non-monotonic behavior of the surface density versus the time is in agreement with experimental observations reported in the literature, and is related to the finite velocity of propagation of the density variations.
The paper describes how to take into consideration the presence of transmissible loads in a topology optimization method based on optimality criteria. The optimization problem has been defined as a ...total potential energy maximization problem with stress, displacement or stiffness constraints. The final volume of the optimal structural configuration has not to be specified a priori and is a consequence of the imposed structural constraints. The implementation of the proposed method is quite simple and leads to the identification of well defined optimal structures. The results obtained by solving several benchmark problems are shown.
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