Dynamics of a two-state system through a real level crossing

The dynamics of a two-state system whose energies undergo a real crossing at some instant of time is studied. At this instant, both the coupling and the detuning vanish simultaneously, which leads to an exact degeneracy of the eigenenergies of the system. It is found that the dynamics of the system is primarily determined by the manner in which the degeneracy occurs. This interesting behavior is reminiscent of a symmetry breaking process, since the totally symmetric situation occurring at the crossing is significantly altered by infinitesimal quantities, which remove the degeneracy, with very important dynamical implications from there on. A very simple analytical formula is derived, which is found to describe the population changes very accurately

Diritto penale del rischio e rischi del diritto penale tra scienza e societ\ue0

Il contributo esamina i caratteri del modello di diritto penale caratterizzato dal riferimento al rischio, evidenziando i diversi ruoli dogmatici che tale nozione ha assunto e testando la sua utilit\ue0 alla luce delle situazioni caratterizzate da incertezza scientifica, con particolare riferimento alla vicenda processuale in primo grado del terremoto dell'Aquila

La pertenencia a una organización criminal como tipo penal modelo europeo

Il lavoro diffonde nel circuito penalistico di lingua spagnolo i risultati in tema di punibilità della partecipazione ad una organizzazione criminale come modello europeo di incriminazione. Partendo dal rilievo criminologico della dimensione transnazionale assunta in modo crescente dalle organizzazioni criminali, si analizza la diversità di risposte incriminatrici nei sistemi penali degli stati mebri dell'UE, individuando tre principali tipologie di risposte nazionali. Per armonizzare tale differenti posizioni all'interno dello spazio comune europeo di giustizia sicurezza e libertà, il contributo prospetta e motiva una proposta di modello di incriminazione in materia di gruppi criminali

Microscopic description of dissipative dynamics of a level crossing transition

We analyze the effect of a dissipative bosonic environment on the Landau-Zener-Stuckelberg-Majorana (LZSM) level crossing model by using a microscopic approach to derive the relevant master equation. For an environment at zero temperature and weak dissipation our microscopic approach confirms the independence of the survival probability on the decay rate that has been predicted earlier by the simple phenomenological LZSM model. For strong decay the microscopic approach predicts a notable increase of the survival probability, which signals dynamical decoupling of the initial state. Unlike the phenomenological model our approach makes it possible to study the dependence of the system dynamics on the temperature of the environment. In the limit of very high temperature we find that the dynamics is characterized by a very strong dynamical decoupling of the initial state - temperature-induced quantum Zeno effect.Comment: 6 pages, 4 figure

Speeding up antidynamical Casimir effect with nonstationary qutrits

The antidynamical Casimir effect (ADCE) is a term coined to designate the coherent annihilation of excitations due to resonant external perturbation of system parameters, allowing for extraction of quantum work from nonvacuum states of some field. Originally proposed for a two-level atom (qubit) coupled to a single cavity mode in the context of nonstationary quantum Rabi model, it suffered from very low transition rate and correspondingly narrow resonance linewidth. In this paper we show analytically and numerically that the ADCE rate can be increased by at least one order of magnitude by replacing the qubit by an artificial three-level atom (qutrit) in a properly chosen configuration. For the cavity thermal state we demonstrate that the dynamics of the average photon number and atomic excitation is completely different from the qubit's case, while the behavior of the total number of excitations is qualitatively similar yet significantly faster.Comment: 9 pages, 4 figure

Open multistate Majorana model

The Majorana model in the presence of dissipation and dephasing is considered. First, it is proven that increasing the Hilbert space dimension the system becomes more and more fragile to quantum noise, whether dephasing or dissipation are mainly present. Second, it is shown that, contrary to its ideal counterpart, the dynamics related to the open Majorana model cannot be considered as the combined dynamics of a set of independent spin-1/2 models

Stimulated Raman adiabatic passage in an open quantum system: Master equation approach

A master equation approach to the study of environmental effects in the adiabatic population transfer in three-state systems is presented. A systematic comparison with the non-Hermitian Hamiltonian approach [N. V. Vitanov and S. Stenholm, Phys. Rev. A {\bf 56}, 1463 (1997)] shows that in the weak coupling limit the two treatments lead to essentially the same results. Instead, in the strong damping limit the predictions are quite different: in particular the counterintuitive sequences in the STIRAP scheme turn out to be much more efficient than expected before. This point is explained in terms of quantum Zeno dynamics.Comment: 11 pages, 4 figure

A Multimodal Technique for an Embedded Fingerprint Recognizer in Mobile Payment Systems

The development and the diffusion of distributed systems, directly connected to recent communication technologies, move people towards the era of mobile and ubiquitous systems. Distributed systems make merchant-customer relationships closer and more flexible, using reliable e-commerce technologies. These systems and environments need many distributed access points, for the creation and management of secure identities and for the secure recognition of users. Traditionally, these access points can be made possible by a software system with a main central server. This work proposes the study and implementation of a multimodal technique, based on biometric information, for identity management and personal ubiquitous authentication. The multimodal technique uses both fingerprint micro features (minutiae) and fingerprint macro features (singularity points) for robust user authentication. To strengthen the security level of electronic payment systems, an embedded hardware prototype has been also created: acting as self-contained sensors, it performs the entire authentication process on the same device, so that all critical information (e.g. biometric data, account transactions and cryptographic keys), are managed and stored inside the sensor, without any data transmission. The sensor has been prototyped using the Celoxica RC203E board, achieving fast execution time, low working frequency, and good recognition performance

Impact of Wavelet Kernels on Predictive Capability of Radiomic Features: A Case Study on COVID-19 Chest X-ray Images

Radiomic analysis allows for the detection of imaging biomarkers supporting decision-making processes in clinical environments, from diagnosis to prognosis. Frequently, the original set of radiomic features is augmented by considering high-level features, such as wavelet transforms. However, several wavelets families (so called kernels) are able to generate different multi-resolution representations of the original image, and which of them produces more salient images is not yet clear. In this study, an in-depth analysis is performed by comparing different wavelet kernels and by evaluating their impact on predictive capabilities of radiomic models. A dataset composed of 1589 chest X-ray images was used for COVID-19 prognosis prediction as a case study. Random forest, support vector machine, and XGBoost were trained (on a subset of 1103 images) after a rigorous feature selection strategy to build-up the predictive models. Next, to evaluate the models generalization capability on unseen data, a test phase was performed (on a subset of 486 images). The experimental findings showed that Bior1.5, Coif1, Haar, and Sym2 kernels guarantee better and similar performance for all three machine learning models considered. Support vector machine and random forest showed comparable performance, and they were better than XGBoost. Additionally, random forest proved to be the most stable model, ensuring an appropriate balance between sensitivity and specificity

Thioflavin T triggers \u3b2 amyloid peptide (1-40) fibrils formation.

Introduction A general characteristic of aggregation is the multiple interaction and cross-feedback among distinct mechanisms occurring at different hierarchical levels. The comprehension of the different species interconversion during aggregation is very important since emerging evidences indicate intermediate oligomeric aggregates as primary toxic species. In this context, A\u3b2 amyloid peptide provides a challenging model for studying aggregation phenomena both for the complexity of its association process and for the direct implications in Alzheimer\u2019s Disease. Aggregates growth conditions strongly affect the final morphology, the fibrillar molecular structure as well as the aggregation pathway which is characterized by the occurrence of multiple transient species. Methods The fluorescent dye Thioflavin T (ThT) is widely used to detect amyloid deposits and it is often used in situ to study aggregation kinetics, under the hypothesis that its presence does not affect the aggregation processes under study. Here we present an experimental study on A\u3b2(1-40) peptide fibrillation kinetics at pH 7.4. In the observed conditions, A\u3b2(1- 40) undergoes aggregation only if Thioflavin T is present in solution. This phenomenon was analyzed as a function of temperature, ThT and peptide concentrations in order to explore the underlying fibrillation mechanism. Light scattering, ThT fluorescence emission, two photon excitation fluorescence microscopy, were used in a kinetic fashion to highlight different sides and critical phases of the aggregation pathway. Circular Dichroism and FTIR measurements are used to characterize secondary structure of the aggregates. Results The selected approach gives detailed information on the time evolution of A\u3b2(1-40) fibrillation process highlighting structural changes at molecular level, different aggregate species growth and their morphologies. Our data show that A\u3b2(1-40) fibrillation process occurs only in the presence of ThT and that the observed aggregation involves at least three different aggregation mechanisms acting in competition. In the first step, small oligomers, which bind ThT, are formed via non nucleated polymerization mechanism and represent an activated state for following fibrils growth. This process appear to be a rate limiting step for two distinct fibril nucleation mechanisms probably affected by an high degree of spatial heterogeneity. Conclusions We demonstrated that in the selected experimental conditions ThT triggers the A\u3b2(1 1240) fibrillation process (D\u2019Amico et. al 2012). Sterical and chemical properties of ThT molecule may modulate the peptide conformation, with similar mechanisms to the ones that usually drive the binding of this dye to already formed amyloids. So, the presence of ThT in solution may change the thermodynamic equilibrium trapping specificmore ordered conformations prone to supramolecular assembly