Fast and accurate numerical solutions in some problems of particle and radiation transport: synthetic acceleration for the method of short characteristics, Doppler-broadened scattering kernel, remote sensing of the cryosphere

The aim of this work is to present various aspects of numerical simulation of particle and radiation transport for industrial and environmental protection applications, to enable the analysis of complex physical processes in a fast, reliable, and efficient way. In the first part we deal with speed-up of numerical simulation of neutron transport for nuclear reactor core analysis. The convergence properties of the source iteration scheme of the Method of Characteristics applied to be heterogeneous structured geometries has been enhanced by means of Boundary Projection Acceleration, enabling the study of 2D and 3D geometries with transport theory without spatial homogenization. The computational performances have been verified with the C5G7 2D and 3D benchmarks, showing a sensible reduction of iterations and CPU time. The second part is devoted to the study of temperature-dependent elastic scattering of neutrons for heavy isotopes near to the thermal zone. A numerical computation of the Doppler convolution of the elastic scattering kernel based on the gas model is presented, for a general energy dependent cross section and scattering law in the center of mass system. The range of integration has been optimized employing a numerical cutoff, allowing a faster numerical evaluation of the convolution integral. Legendre moments of the transfer kernel are subsequently obtained by direct quadrature and a numerical analysis of the convergence is presented. In the third part we focus our attention to remote sensing applications of radiative transfer employed to investigate the Earth's cryosphere. The photon transport equation is applied to simulate reflectivity of glaciers varying the age of the layer of snow or ice, its thickness, the presence or not other underlying layers, the degree of dust included in the snow, creating a framework able to decipher spectral signals collected by orbiting detectors.

Evaluation of deambulation in a protected environment and in the public green in limb amputated subjects treated through a new osteointegration method

The limb amputation is one of the oldest surgical procedures performed and it still represents an event that drastically changes the life of an individual. Despite the technological progress, the difficulties related to the realization and daily use of the socket remain very common. Among the different technologies adopted in the prosthetic field, this project focused on the osseointegration technique. This technique consists in implanting a stem within the medullary canal of the amputated skeletal segment that extends outside the amputation stump with a prosthesis, later connected to the metal extension. The objective of this PhD project is to treat and to evaluate selected patients with osseointegrated prosthetic implants for the treatment of lower limb amputations. Patients are recruited at the Rizzoli Orthopaedic Institute and at the Prosthesis - INAIL center of Vigorso (Budrio) during outpatient visits, while the surgical procedure is performed by the same expert surgeon in the II Orthopaedic and Traumatology Clinic of the Rizzoli Orthopaedic Institute. The project is still ongoing, to date three patients had completed both procedures, but due to various personal problems, just one of them is included in the analysis. This patient increased his percentage of prosthesis use and the level of mobility with an overall improvement of quality of live after the procedure. The osseointegration technique represents a promising alternative method of treatment for amputees who are not satisfied with their socket prosthesis. In the coming years it will continue the collection of clinical, radiographic and kinematic data of subjects undergoing this procedure in order to perform a long-term monitoring of both clinical outcomes and quality of life.

Validation of a new method for human nerve decellularization: toward a new tool in peripheral nerve reconstructive surgery.

Defects of the peripheral nervous system are extremely frequent in trauma and surgeries and have high socioeconomic costs. In case of peripheral nerve injury, the first approach is primary neurorrhaphy, which is direct nerve repair with epineural microsutures of the two stumps. However, this is not feasible in case of stump retraction or in case of tissue loss (gap > 2 cm), where the main surgical options are autologous grafts, allogenic grafts, or nerve conduits. While the gold standard is the autograft, it has disadvantages related to its harvesting, with an inevitable donor site morbidity and functional deficit. Fresh nerve allografts have therefore become a viable alternative option, but they require immunosuppression, which is often contraindicated. Acellular Nerve Allografts (ANA) represent a valid alternative, they do not need immunosuppression and appear to be safe and effective based on recent studies. The purpose of this study is to propose and develop an innovative method of nerve decellularization (Rizzoli method), conforming to cleanroom requirements in order to perform the direct tissue manipulation step and the nerve decellularization process within five hours, so as to accelerate the detachment of myelin and cellular debris, without detrimental effects on nerve architecture. In this study, the safety and the efficacy of the new method are evaluated in vitro and in vivo by histological, immunohistochemical, and histomorphometric studies in rabbits and humans. The new method is rapid, safe, and cheaper if compared with available commercial ANAs. The present study shows that the method, previously optimized in vitro and in vivo on animal model presented by our group, can be applied on human nerve samples. This work represents the first step in providing a novel, safe, and inexpensive tool for use by European tissue banks to democratize the use of nerve tissue transplantation for nerve injury reconstruction.