Commissioning of a Microdosimetric Device for Hadrontherapy

openRadiotherapy aims at maximising the dose delivered to the tumour whilst minimising that to the healthy tissues. The absorbed dose, being an average quantity, doesn’t consider the random nature of radiation interactions. However, it is well acknowledged that biological effectiveness is related to the microscopic distribution of absorbed energy rather than to its mean value. If the microscopic distribution is uniform throughout the irradiated volume (for conventional photon-based radiotherapy), the absorbed dose is a suitable parameter. For charged particles (e.g. protons, helium and carbon ions) ionizations are clustered around the particle path and produce a not uniform pattern of energy deposition. In this case average values do not accurately predict the biological effects. In treatment planning systems (TPS) used in proton therapy it is currently assumed that the biological effectiveness is constant, independent of the proton beam energy and penetration depth. However, the scientific community is moving toward advanced protocols in which the change in biological effectiveness is considered. In parallel, procedures for the quality assurance of the radiation quality (physical characteristics of the radiation field correlated to the biological effectiveness) need to be developed. Microdosimetry is a valuable technique, but commercial detectors for hadron-therapy applications are not currently available. The engineering of advanced gas-based microdosimeters for the characterization of proton and carbon ion beams is currently ongoing at Legnaro National Laboratories of INFN. This thesis focuses on the characterization and optimization of new devices in gamma, neutron and therapeutic proton fields. The response function will be studied for several operative conditions of the sensor, front-end electronics and control/data acquisition system.Radiotherapy aims at maximising the dose delivered to the tumour whilst minimising that to the healthy tissues. The absorbed dose, being an average quantity, doesn’t consider the random nature of radiation interactions. However, it is well acknowledged that biological effectiveness is related to the microscopic distribution of absorbed energy rather than to its mean value. If the microscopic distribution is uniform throughout the irradiated volume (for conventional photon-based radiotherapy), the absorbed dose is a suitable parameter. For charged particles (e.g. protons, helium and carbon ions) ionizations are clustered around the particle path and produce a not uniform pattern of energy deposition. In this case average values do not accurately predict the biological effects. In treatment planning systems (TPS) used in proton therapy it is currently assumed that the biological effectiveness is constant, independent of the proton beam energy and penetration depth. However, the scientific community is moving toward advanced protocols in which the change in biological effectiveness is considered. In parallel, procedures for the quality assurance of the radiation quality (physical characteristics of the radiation field correlated to the biological effectiveness) need to be developed. Microdosimetry is a valuable technique, but commercial detectors for hadron-therapy applications are not currently available. The engineering of advanced gas-based microdosimeters for the characterization of proton and carbon ion beams is currently ongoing at Legnaro National Laboratories of INFN. This thesis focuses on the characterization and optimization of new devices in gamma, neutron and therapeutic proton fields. The response function will be studied for several operative conditions of the sensor, front-end electronics and control/data acquisition system

From techno-scientific grammar to organizational syntax. New production insights on the nature of the firm

The paper aims at providing the conceptual building blocks of a theory of the firm which addresses its "ontological questions" (existence,boundaries and organization) by placing production at its core. We draw on engineering for a more accurate description of the production process itself, highlighting its inner complexity and potentially chaotic nature, and on computational linguistics for a production-based account of the nature of economic agents and of the mechanisms through which they build ordered production sets. In so doing, we give a "more appropriate" production basis to the crucial issues of how firm's boundaries are set, how its organisational structure is defined, and how it changes over time. In particular, we show how economic agents select some tasks to be performed internally, while leaving some other to external suppliers, on the basis of criteria based on both the different degrees of internal congruence of the tasks to be performed (i.e. the internal environment), and on the outer relationships carried out with other agents (i.e. the external environment)

Probing the phase diagram of cuprates with YBa2_2Cu3_3O7−δ_{7-\delta} thin films and nanowires

We have grown and characterized 30 nm thick YBa$_2$Cu$_3$O$_{7-\delta}$ (YBCO) films, deposited by pulsed laser deposition on both MgO (110) and SrTiO$_3$ (001) substrates, which induce opposite strain to the superconducting layer. By carefully tuning the in-situ post-annealing oxygen pressure, we achieved, in a reproducible way, films at different oxygen doping, spanning from the slightly overdoped down to the strongly underdoped region of the phase diagram. The transport properties of the films, investigated through resistance versus temperature measurements, are in perfect qualitative agreement with single crystals. Starting from these films, we have also successfully fabricated nanowires with widths down to 65 nm, at different oxygen doping. The nanostructures exhibit characteristic temperatures (as the critical temperature $T_{\mathrm{c}}$ and the pseudogap temperature $T^*$) similar to those of the as-grown films and carry critical current densities $J_{\mathrm{c}}$ close to the critical depairing value, limited by vortex entry. This implies that the superconducting and the normal state properties of underdoped YBCO are preserved in our films, and they can be studied as a function of the dimensionality of the system, down to the nanoscale.Comment: 11 pages, 9 figures, submitted to Phys. Rev. Material

State Space Modeling and Estimation of Flexible Structure Using the Theory of Functional Connections

In this work, we present a novel method to model the dynamics of a continuous structure based on measurements taken at discrete points. The method is conceived to provide new instruments to address the problem of flexible dynamics modeling in a spacecraft, where an effective mathematical representation of the non-rigid behavior of the is of critical importance in the design of an effective and reliable attitude estimation and control system. Both the measurements and the model that describes the structure can be affected by uncertainty. The purpose of the developed method is to estimate the position and the velocity of any point of the physical domain relying on a limited number of measurements while filtering out the noise. To this aim, the well-assessed Kalman filter is used in synergy with the recently developed Theory of Functional Connections (TFC). This is a mathematical framework to perform functional interpolation with applications in many fields being currently discovered and investigated. Initially, an algorithm for the solution of the corresponding static problem was developed based on the TFC; the results of the tests were promising and the approach presented in this work constitutes an effort to extend the idea to the dynamic case. In the proposed method, the continuous structure is approximated by the TFC constrained expression, while the system state variables are defined as the coefficients used to represent the free function in a basis of orthogonal polynomials. This leads to a system that, despite being continuous and thus formed of an infinite number of material points, is modeled using a finite number of state variables allowing for the use of Kalman filter to deal with the uncertainties intrinsic in both the modeling and measurements. This is accomplished by exploiting the original structure model Differential Equation(s) to obtain a process model for the filter and using the constrained expression itself as the measurement model. Then the Kalman filter algorithm is applied and the a posteriori estimates of the state variables (that is the free function coefficients) can be used to build the TFC expression that approximates the instantaneous shape of the structure, thus enabling the evaluation of the displacement at any point of the domain. The power of the proposed method is twofold. First, an estimate of the displacements of all the points is obtained based on a limited number of noisy measurements. Second, the relation between discrete measurements and continuous displacement field always accounts for the real physics of the problem. In this paper, the theoretical developments of the proposed approach are shown along with the results of numerical simulations showing the effectiveness of the method in estimating the actual dynamics of a Euler-Bernoulli beam. The technique yielded good results both for the free response and in the case of a forcing input to the system

Ultra low noise YBCO nanoSQUIDs implementing nanowires

We present results on ultra low noise YBa$_2$Cu$_3$O$_{7-\delta}$ nano Superconducting QUantum Interference Devices (nanoSQUIDs). To realize such devices, we implemented high quality YBCO nanowires, working as weak links between two electrodes. We observe critical current modulation as a function of an externally applied magnetic field in the full temperature range below the transition temperature $T_C$. The white flux noise below 1 $\mu \Phi_0/\sqrt{\mathrm{Hz}}$ at T = 8 K makes our nanoSQUIDs very attractive for the detection of small spin systems.Comment: 11 pages, 4 figures, submitted to Appl. Phys. Lett. 25/01/201

Analysis of geometrical and topological attitude for proteinprotein interaction

Protein-protein interaction takes usually place on an extended area of the external molecules surfaces that are morphologically fitting. Geometric and topological congruence (i.e. concavity and convexity correspondences) is required to support the neighboring interaction of surface patches belonging to the two protein molecules. It is therefore important to adopt representations and data structures that can facilitate the analysis and the implementation of techniques for the evaluation of geometric and topological properties on extended surfaces. These areas of activity are usually roughly “planar” but with local concavity and complexity that must match each other for interacting. To this purpose we are suggesting a solution different from the one of ligand-protein interaction in which are involved a pocket and a small molecule. The solution here suggested is based on the concavity tree representation. Starting from the convex hull of the protein molecule a recursive process leads to a series of concavity and meta-concavity that allows reaching the detail level required. The consequence of the recursive process is obviously a hierarchical data structure (a tree) which at each level supports a complete description of a surface. Each node of the tree contains an array of features that support the geometrical, topological and biochemical properties of the correspondent surface patch

Fabrication and electrical transport characterization of high quality underdoped YBa2Cu3O7-δ nanowires

We present the fabrication and electrical transport characterization of underdoped YBa2Cu3O7-δnanowires. The nanowires have been realized without any protective capping layer and theyshow transport properties similar to those of the parent thin film, demonstrating that they havenot been damaged by the nanopatterning. The current-voltage characteristics of the underdopednanowires show large hysteretic voltage switching at the critical current, in contrast to theflux-flow like characteristics of optimally doped nanostructures, indicating the formation of aself-stabilizing hot spot. These results open up new possibilities for using the underdopednanowires as single photon detectors and for exploring the underdoped side of the YBa2Cu3O7-δphase diagram at the nanoscale

Mapping the Phase Diagram of a YBa2Cu3 O7-δ Nanowire Through Electromigration

We use electromigration (EM) to tune the oxygen content of YBa2Cu3O7-δ (YBCO) nanowires. During EM, the dopant oxygen atoms in the nanowire are moved under the combined effect of electrostatic force and Joule heating. The EM current can be tuned to either deplete or replenish nanowires with oxygen, allowing fine tuning of its hole-doping level. Electrical transport measurements and Kelvin probe microscopy corroborate good homogeneity of the doping level along the electromigrated nanowires. Thus, EM provides an effective method to study transport properties of YBCO in a wide doping range at the nanoscale in one and the same device

life cycle assessment lca of landfill gas management comparison between conventional technologies and microbial oxidation systems

Abstract The reduction of landfill gas emissions is a central issue of the Directive 99/31/EC. Biofilters and biocovers have been identified as an alternative and cost-effective technologies to mitigate impacts due to CH4 and NMVOCs emissions. The Life Cycle Assessment demonstrates the environmental sustainability of biofiltration systems, with the aim of improving the environmental impact indicators such as Global Warming (-10.75% for Biofilter and -11.60% for Biocover) and Photochemical oxidation (-7.97% for Biofilter and -8.61%. for Biocover). This paper shows that these treatment technologies are effective for methane oxidation when the calorific value of the LFG is low, thus they maximize the amount of treated gas during the after-care phase

characterization of equivalent acoustic sources to reproduce the acoustic field generated by engines on an aircraft fuselage

Abstract This work presents a general procedure to characterize equivalent acoustic sources to reproduce the sound pressure field generated by the engines on an aircraft fuselage. The procedure would allow to set up ground experimental tests on aircraft components, by means of distributed loudspeakers, to obtain their vibro-acoustic performances as if they were tested in flight conditions. A FEM model of an aircraft fuselage mock-up was built up, comprising the structure, the internal acoustic cavities and the external air. The sound pressure field generated by the engines was considered as the reference solution, whereas an equivalent sound field, produced by distributed monopole sources surrounding the structure, was obtained by leveraging on the proposed Multi-Disciplinary Optimization (MDO) procedure. The MDO procedure was based on the mutual interaction between the commercial codes Siemens NX, for the CAE/FEM simulations, and Noesis Optimus, for the optimization framework