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Heavy-ion double charge exchange reactions as tools for 0bb decays. The 40Ca(18O,18Ne)40Ar reaction at 270 MeV by using MAGNEX
No full textThis study is inserted in a research line that aims to access the Nuclear
Matrix Element (NME) involved in the half-life of the 0 bb decay, by measuring
the cross sections of heavy-ion induced Double Charge Exchange
(DCE) reactions with high accuracy. The basic point is that the initial
and nal state of both 0 bb decay and DCE processes are the same. In
addition, both processes pass through the same intermediate state and the
transition operators have a similar mathematical structure.
This work shows for the rst time experimental data on heavy-ion DCE
reaction in a wide range of transferred momenta, with an acceptable statistical
signi cance and good angular and energy resolution. In particular
(18O,18Ne) reaction at 270 MeV incident energy on 40Ca target was investigated.
In order to estimate the contribution of the concurrent channels the
40Ca(18O,18F)40K single charge exchange intermediate channel and the competing
processes 40Ca(18O,20Ne)38Ar two-proton transfer and 40Ca(18O,16O)42Ca
two-neutron transfer were also studied.
The experiment was performed at Laboratori Nazionali del Sud (LNSINFN)
in Catania using a 270 MeV energy 18O Cyclotron beam impinging
on a 279 g/cm2 thick 40Ca target. The ejectiles were momentum analysed
by the MAGNEX large acceptance magnetic spectrometer and detected by
its focal plane detector.
The energy spectra and angular distributions have been extracted. The
data analysis of experimental results have established that the transition to
40Args: is dominated by the direct processes.
Finally, an innovative technique to infer on the nuclear matrix elements by
measuring the cross section of a double charge exchange nuclear reaction
was proposed. The main assumption are that the DCE reaction is a twostep
charge exchange and a surface localized process. The model adopted to describe the cross section of the DCE reaction consists in a generalization
of the well-established factorization of the single charge-exchange cross section,
valid under certain hypothesis, discussed in the thesis. Therefore, the
cross section could be factorized in a nuclear structure term, containing the
matrix elements, and a nuclear reaction one (unit cross section). Despite the
used approximations, the extracted strength and nuclear matrix elements
are reasonable within +-50%, signalling that the main physics content has
been kept
Klebsiella pneumoniae carbapenemase-producing: Epidemiology, detection, new in vitro testing and infection control
No full textThe World Health Organization (WHO) has identified antimicrobial resistance as one of the three most important issues in the world for human health. The natural evolution of antibiotic resistance is coerced by misuse of antibiotics, thus causing excessive evolutionary pressure on microorganisms. The microorganisms multi-drug resistant (MDR) represents a 'global emergency, especially in nosocomial infections, in particular, the intensive care units are the most susceptible to this type of problem .The production of beta-lactamases is the main mechanism of resistance in gram-negative bacteria against beta-lactam antibiotics; some of these are encoded by chromosomal genes, other genes from plasmid or integrated into transposable elements, and can be constitutive or inducible. In 1985, after the introduction of imipenem, carbapenem, new class of beta-lactam antibiotics called "life-saving" drugs were considered to be universally active against Enterobacteriaceae. These antibiotics were able to combine exceptional intrinsic antibacterial activity with high stability against beta-lactamases, including ESBLs; thus became the treatment of choice for infections caused by ESBL-producing strains. Klebsiella pneumoniae carbapenemase (KPC) is a serine carbapenemase gene encoded by the plasmid blaKPC (Transposon Tn4401, Tn3-type), belonging to the class A of Amber. The first K. pneumoniae KPC producer, was identified in North Carolina, USA, in 1996 this was resistant to all beta-lactams, including carbapenems
Dynamics of hippocampal networks revealed by voltage sensitive dye imaging
No full textIn order to better understand brain functioning we need to investigate all the structural domains present in it, from single cell to interconnected entire brain regions. However, while our knowledge in terms of single/few cells functioning is vast, very little is known about neuronal networks, which are interacting collections of neurons functionally related to the same task. Moreover, the balanced and concerted activity of excitatory and inhibitory networks plays a key role for proper cortical computations. However, while exist several tools to record excitatory networks activity, this is not the case for inhibitory networks. Voltage sensitive dye imaging (VSDI) is a technique that allows the recording of neuronal activity by mean of proportional emission of fluorescence according to changes in membrane potential. The advantage of using VSDI over other recording techniques using electrodes is that VSDI allows not invasive recording of neuronal activity from hundreds of sites at the same time.
During the last decades, VSDI has been widely used both in vitro and in vivo and to investigate both single cells and excitatory network activities. However, by using VSDI, investigations on excitatory networks activity have been mainly performed by quantifying fluorescence emission in defined regions of interest at time-fixed points, while inhibitory activity has been evaluated only at single cell level. The former approach misses several information of the dynamics of spreading of glutamatergic transmission because does not consider for example how fast a signal propagates and in which direction. The latter approach instead, does not allow the monitoring of network inhibitory events, which would be very important considering the extensive spatial spreading of interneurons within cortical areas.
During my doctoral course I aimed at studying in detail excitatory and inhibitory neuronal networks in the CA1 area of mouse hippocampus with VSDI.
To study excitatory networks more comprehensively, in collaboration with a team of mathematicians, we developed a mathematical algorithm that allowed measuring the velocity and the direction of spreading of the VSDI signal and it represents a new method to determine an optical flow. After successful validation of the algorithm with surrogate data to test its accuracy, we analysed two set of experiments in which network excitatory activity has been manipulated either by increasing Schaffer s collaterals stimulation intensity or by blocking GABAergic transmission with the GABAA receptor antagonist picrotoxin in order to increase the depolarization in the CA1 region of the hippocampus. The results of these manipulations significantly decreased signal velocity whereas picrotoxin application significantly modified the direction of spreading, making the depolarization-mediated VSDI signal less dispersed compared to control.
Using VSDI I was able to fully characterize GABAA receptor-mediated hyperpolarizing signals in all the CA1 sublayers (field IPSPs), thus providing a new way of monitoring inhibitory events at network level. Moreover, I found that the activation of mGluR5 receptors induced an increase in a long-lasting manner of the VSDI-recorded field IPSPs, with duration and magnitude that relied on the specific CA1 sublayer considered.
Overall, my work shows new methodologies and new findings that may represent a step forward in the quest for a better understanding of neuronal networks, both excitatory as well as inhibitory, which hopefully can contribute to reduce the gap of knowledge between single cell activity and behaviour
Nonlinear oscillations in high power systems
No full textThe main topic of this work is to investigate on nonlinear phenomena affecting high power systems and on the strategies adopted to model them. In the first chapter the attention is focused on two big areas of high power systems: power electronics and systems/devices used to sustain plasma fusion. Although it is common that System Engineers tend to associate high power systems with power electronics, it is worth noting that power systems related to nuclear fusion represent a challenging area rich in nonlinearities. Specifically, while nonlinear oscillations in power electronics are due to oscillations of electrical nature, the ones present in nuclear fusion can also refer to other physical quantities. We will refer to the latter taking into account macroscopic plasma instabilities affecting JET plasmas, and proposing both theoretical approaches and experimental ones to describe their dynamic. The former rely on nonlinear mathematical equations able to mimic the nonlinear behavior of the system under certain conditions while the latter are based on a physical realization of the system starting from its mathematical model.
High power systems related to power electronics are investigated in Chapter 2 where the importance of thermal modeling for the power electronics modules is pointed out and a new modeling strategy which starts from a distributed parameter analysis to obtain a lumped parameter model is introduced.
In this case, the proposed methodology is based on the assumption that the heat transfer problem can be assumed to be linear and the thermal impedances approaches can be therefore used. In this relevant case study nonlinearities in modeling high power systems can also be neglected under certain conditions. In particular, concerning high power modules, it is well-known how the geometry of the device and the proper choice of the cooling system can play a key role for these simplifications.
A data-driven approach based on neural networks to model plasma instabilities is presented in Chapter 3. This approach is introduced because physical models often require a deep knowledge of the system parameters that sometimes is difficult to obtain.
In Chapter 4 considerations and results on new identification methodologies based on parallel identification models for discrete-time systems are presented
Ruolo ed efficacia di un team multidisciplinare nel percorso psicologico e terapeutico del trapianto renale
No full textIl trapianto renale costituisce il miglior trattamento terapeutico per la malattia renale cronica, permettendo alla maggior parte dei pazienti il ritorno ad una qualità di vita soddisfacente. La letteratura ha identificato alcuni aspetti problematici che possono influenzare l'adattamento alla condizione di trapiantato e la compliance post-operatoria. Le implicazioni psicologiche dei soggetti trapiantati hanno conseguenze importanti anche sul piano strettamente fisico. Il trapianto d organo rappresenta per il paziente un compito di straordinario impegno che agisce come uno stimolo stressogeno intenso a cui l organismo reagisce con modificazioni neurotrasmettitoriali ed endocrino-metaboliche. L esperienza del trapianto può anche configurare una crisi psicosomatica che richiede al paziente la mobilitazione di tutte le sue risorse biopsicosociali nel processo di adattamento al nuovo organo estraneo, il quale può determinare un'alterazione della rappresentazione di sè e del senso di identità, con possibili ripercussioni psicopatologiche. Il presente lavoro documenta l importanza di prevedere e programmare, ai fini di una migliore riabilitazione post-trapianto e in virtù degli evidenti rischi di psicopatologia, lo sviluppo di interventi interdisciplinari, uno dei compiti socio-sanitari e psicoterapici essenziali, senza i quali l adattamento successivo al trapianto potrebbe risultare difficile e con ripercussioni inevitabili sulla qualità della vita di tutti i soggetti coinvolti
The impact of ownership and advisors on IPO and post-IPO performance
No full textThis dissertation focuses on the impact that the advisory team, namely underwriting bank and auditor, private equity investors and firms owners have on firms IPO and post-IPO performance in a bank-oriented system like Italy. The decision of a firm to go public posits many important problems, among which there are how to reduce information asymmetries and uncertainty surrounding private firms and how to preserve and improve firms value. The phenomenon is analyzed using the signaling theory, a relative recent theory and one of the main used in the IPO literature, which aims to resolve the information asymmetry problem suggesting to rely on certain indicators that can send signals to the market about the quality of firms. Another important theory applied to the IPO context is the agency theory, as the separation of ownership and control posits problems to firms profitability and value. Both theories have been largely applied to the US context and the goal of this dissertation is to contribute to these long-standing debates by adding evidence from a non-US country. Evidence from foreign countries has shown that institutional settings are important to consider when generalizing theories. This dissertation confirms this thesis, showing that signals are not always correctly perceived and valued by the market, and that theories may not work in different contexts
Riduzione delle perdite di commutazione nei moduli di potenza a IGBT
No full textThe purpose of this work is to study in deep the transition phenomena of IGBTs in order to evaluate different optimization strategies for losses reduction and propose a novel technique.
In power applications a particular attention must be taken to such phenomena as commutation losses, overcurrents during the turn-ON and overvoltage at the turn-OFF of the devices.
These phenomena are connected to non ideal behavior of real devices and stray circuit parameters. Steep profiles of current lead to large ElectroMagnetic Interference (EMI) and overvoltages, while rapid variations of the voltage can produce phenomena of "latch-up" in single IGBT or unwanted commutations. On the other hand, slow commutations are characterized by low values of dv/dt and di/dt, causing excessive losses in those power application during commutations. Therefore, it is essential to face the issue with opposite requirements at the design stage obtaining optimal tradeoff
First results on the assessment of impact damage of vegetables by means of the FEM approach
No full textMechanical harvest and post-harvest handling induce numerous mechanical impacts on vegetables. These impacts may cause damage such as black-spot bruise, resulting in severe economic losses.
Impact forces and accelerations arising from collisions, are among the main indices taken into account when studying the damage of fruit and vegetables during post-harvest activities. A miniaturised Acceleration Measuring Unit (AMU) has been recently developed at the Institut für Agrartechnik, Potsdam-Bornim (ATB): when implanted into a real product like a potato tuber, it is able to measure the accelerations at the centre of the fruit deriving
from a impact.
This PhD Thesis represents a first contribution on the study of mechanical impacts of vegetables (potato tubers), arising from mechanical harvest and post-harvest handling, by means of simulations based on the Finite Element Method (FEM) approach. Simulations were developed by using the Linux distribution CAELinux2011, that contains several technical-engineering software, among which stand out Salome-Meca and Code-Aster. Salome-Meca was used for modelling, meshing and post-processing activities, while Code-Aster was used for processing models.
The work has been developed in collaboration with the Institut für Agrartechnik, Potsdam-Bornim (ATB), Germany, where they were conducted laboratory tests (drop tests to measure impact forces and texture analyses to measure modulus of Young) with two spherical artificial fruits.
After the development of several preliminary simple models to gain familiarity with the computational software Salome-Meca and Code-Aster and to acquire an acceptable agreement between simulated and experimental tests, it was carried out an extensive set of drop test simulations with a spherical artificial fruit aimed at evaluating the effects of drop height, size of the fruit, density and modulus of Young of the material, on the impact
indices (maximum impact force and maximum acceleration at the centre of the fruit). Simulated material parameters were chosen to approach potato tubers properties.
All the factors examined (drop height, sphere diameter, modulus of Young and density of the material, mass of the fruit) affected the maximum impact force and the maximum acceleration at the centre of the sphere. Their increase always caused an increase in the maximum impact force, whereas the maximum acceleration at the centre of the sphere decreased vs sphere diameter, material density and mass, and increased vs drop height and modulus of Young. The decreasing trends are due to the cushioning effect produced by the sphere material itself.
Moreover, the maximum impact forces reported in the experimental results by Geyer et al. (2009), referring to drop tests of potato tubers onto steel plates, are in good agreement with the values of impact forces provided by the simulations. Instead, simulations provided acceleration values about twice as many those measured in the experimental results with the AMU device. This difference could be due to the implantation system of the AMU inside the tuber. In fact, comparing the measured impact force and the force computed by means the second law of Newton (F = m · a), Geyer et al. in the cited work report that the computed force was approximately half the measured one, meaning an under-estimation of the acceleration provided by the AMU.
Ultimately, the concordance between measured and simulated impact forces confirmed the validity of FEM approach, although the limitations owing to the simplicity of the model developed in this work
Synthesis, characterization and thermal properties of polymers based composites materials for High Power Electronic Packaging Applications
No full textAs devices evolve, it s necessary that also interconnections and all hardware circuits evolve, including packaging. Nowadays are required significant improvement in packaging properties: low resistance interconnections, less noise, less parasitic oscillations, increased reliability and improved thermal behaviour.
For these purpose has designed a research activity for the synthesis of new composites materials capable to dissipating heat better in relation to the current ones. These materials, having to act both as a protective casing (eg. radiation, humidity) and as heat sinks, must also be equipped with a good thermal efficiency.
Thermal efficiency of a system depends on material degradation temperature and its thermal conductivity. Therefore, in the initial phase we proceeded with the investigation on the current materials used for commercial package characterizing their properties.
Later we moved to the synthesis of several epoxy resins and composites materials based on epoxy resin (as polymeric matrix) filled with synthetic or commercial techno-material to improve resin thermal efficiency.
These filler were chosen for their peculiar properties: aramides were chosen for their thermal stability and high thermal conductivity; polyimide has been chosen to solve the aramide hygroscopicity problems, graphene oxide and MoS2 for their thermal conductivity.
In general, all obtained composites have a start degradation temperature, in air, higher than maximum reached by the latest generation devices (250 °C) , this makes possible their use as microelectronic packaging. Then, two methods for conductivity measurements were developed, direct and indirect; both were then verified by the application on some synthesized package.
On the basis of collected data, almost all obtained composites, can be used as packaging having a better thermal efficiency than commercials
Initial state fluctuations and anisotropic flows of the Quark-Gluon Plasma created in Ultra-relativistic Heavy Ion collisions
No full textThe fundamental theory of strong interactions is the so called Quantum Chromo Dynamics (QCD) that is a quantum field theory with an extremely rich dynamical content. The main features of this theory are the asymptotic freedom and confinement. The study of QCD, under extreme conditions of temperature and density has been one of the most difficult problem in physics during the last decades, capturing increasing experimental and theoretical attention also in connection with its relation to the Early Universe physics.\\
In this work of thesis it is extensively discussed the effect of the primordial QCD phase transition during the first part of the evolution of our Universe: the Big Bang nucleosynthesis.\\
On the other hand, the Relativistic Heavy Ion Collider (RHIC) and Large Hadron Collider (LHC) programs have been used to probe the properties of nuclear matter under such extreme condition. In the light of the experimental results accumulated in these years in these ultra relativistic heavy ion collisions, the main purpose of this thesis is to study the dynamical evolution of the Quark Gluon Plasma (QGP) in the framework of kinetic theory.\\
In particular, recent experimental data show that the momentum anisotropy of the emitted particles is an observable that encodes information about the transport properties of the matter created in these HIC and also that it is an observable sensitive to the shear viscosity to entropy density ratio . Hence, in this work we have investigated within an event-by-event transport approach at fixed viscosity this elliptic flow and high order harmonics .\\
The principal results presented in this thesis concern the different sensitivity to the at different energies (RHIC and LHC) for both ultra-central and mid-peripheral collisions, especially in the cross over region of the transition. Moreover we highlighted the effect of the inclusion in our simulation code of a realistic kinetic freeze out. Finally, we discussed the correlation between the initial spatial anisotropies and flow coefficients