A hybrid classical-quantum approach to speed-up Q-learning.

We introduce a classical-quantum hybrid approach to computation, allowing for a quadratic performance improvement in the decision process of a learning agent. Using the paradigm of quantum accelerators, we introduce a routine that runs on a quantum computer, which allows for the encoding of probability distributions. This quantum routine is then employed, in a reinforcement learning set-up, to encode the distributions that drive action choices. Our routine is well-suited in the case of a large, although finite, number of actions and can be employed in any scenario where a probability distribution with a large support is needed. We describe the routine and assess its performance in terms of computational complexity, needed quantum resource, and accuracy. Finally, we design an algorithm showing how to exploit it in the context of Q-learning.

Exact Spectral Function of a Tonks-Girardeau Gas in a Lattice.

The single-particle spectral function of a strongly correlated system is an essential ingredient to describe its dynamics and transport properties. We develop a method to evaluate exactly the spectral function for a gas of one-dimensional bosons with infinitely strong repulsions valid for any type of external confinement. Focusing on the case of a lattice confinement, we find that the spectral function displays three main singularity lines. One of them is due uniquely to lattice effects, while the two others correspond to the Lieb-I and Lieb-II modes occurring in a uniform fluid. Differently from the dynamical structure factor, in the spectral function the Lieb-II mode shows a divergence, thus providing a route to probe such mode in experiments with ultracold atoms.

Quantum Coherence and Ergotropy.

Constraints on work extraction are fundamental to our operational understanding of the thermodynamics of both classical and quantum systems. In the quantum setting, finite-time control operations typically generate coherence in the instantaneous energy eigenbasis of the dynamical system. Thermodynamic cycles can, in principle, be designed to extract work from this nonequilibrium resource. Here, we isolate and study the quantum coherent component to the work yield in such protocols. Specifically, we identify a coherent contribution to the ergotropy (the maximum amount of unitarily extractable work via cyclical variation of Hamiltonian parameters). We show this by dividing the optimal transformation into an incoherent operation and a coherence extraction cycle. We obtain bounds for both the coherent and incoherent parts of the extractable work and discuss their saturation in specific settings. Our results are illustrated with several examples, including finite-dimensional systems and bosonic Gaussian states that describe recent experiments on quantum heat engines with a quantized load.

Role of coherence in the nonequilibrium thermodynamics of quantum systems.

Exploiting the relative entropy of coherence, we isolate the coherent contribution in the energetics of a driven nonequilibrium quantum system. We prove that a division of the irreversible work can be made into a coherent and incoherent part. This provides an operational criterion for quantifying the coherent contribution in a generic nonequilibrium transformation on a closed quantum system. We then study such a contribution in two physical models of a driven qubit and kicked rotor. In addition, we also show that coherence generation is connected to the nonadiabaticity of a processes, for which it gives the dominant contribution for slow-enough transformations. The amount of generated coherence in the energy eigenbasis is equivalent to the change in diagonal entropy, and here we show that it fulfills a fluctuation theorem.

Irreversible work and inner friction in quantum thermodynamic processes.

We discuss the thermodynamics of closed quantum systems driven out of equilibrium by a change in a control parameter and undergoing a unitary process. We compare the work actually done on the system with the one that would be performed along ideal adiabatic and isothermal transformations. The comparison with the latter leads to the introduction of irreversible work, while that with the former leads to the introduction of inner friction. We show that these two quantities can be treated on an equal footing, as both can be linked with the heat exchanged in thermalization processes and both can be expressed as relative entropies. Furthermore, we show that a specific fluctuation relation for the entropy production associated with the inner friction exists, which allows the inner friction to be written in terms of its cumulants.

Orthogonality catastrophe and decoherence in a trapped-fermion environment.

The Fermi-edge singularity and the Anderson orthogonality catastrophe describe the universal physics which occurs when a Fermi sea is locally quenched by the sudden switching of a scattering potential, leading to a brutal disturbance of its ground state. We demonstrate that the effect can be seen in the controllable domain of ultracold trapped gases by providing an analytic description of the out-of-equilibrium response to an atomic impurity, both at zero and at finite temperature. Furthermore, we link the transient behavior of the gas to the decoherence of the impurity, and to the degree of the non-Markovian nature of its dynamics.

Core-hole effects in fullerene molecules and small-diameter conducting nanotubes: a density functional theory study.

Core-hole induced electron excitations in fullerene molecules, and small-diameter conducting carbon nanotubes, are studied using density functional theory with minimal, split-valence, and triply-split-valence basis sets plus the generalized gradient approximation by Perdew-Burke-Ernzerhof for exchange and correlation. Finite-size computations are performed on the carbon atoms of a C(60) Bucky ball and a piece of (3, 3) armchair cylindrical network, terminated by hydrogen atoms, while periodically boundary conditions are imposed on a (3, 3) nanotube unit cell. Sudden creation of the core state is simulated by replacing a 1s electron pair, localized at a central site of the structures, with the effective pseudo-potentials of both neutral and ionized atomic carbon. Excited states are obtained from the ground-state (occupied and empty) electronic structure of the ionized systems, and their overlaps with the ground state of the neutral systems are computed. These overlaps enter Fermi's golden rule, which is corrected with lifetime and finite-temperature effects to simulate the many-electron response of the nanoobjects. A model based on the linked cluster expansion of the vacuum persistence amplitude of the neutral systems, in a parametric core-hole perturbation, is developed and found to be reasonably consistent with the density functional theory method. The simulated spectrum of the fullerene molecule is found to be in good agreement with x-ray photoemission experiments on thick C(60) films, reproducing the low energy satellites at excitation energies below 4 eV within a peak position error of ca. 0.3 eV. The nanotube spectra show some common features within the same experiments and describe well the measured x-ray photoelectron lineshape from nanotube bundles with an average diameter of 1.2 nm.

[Thrombolytic therapy during cardiopulmonary resuscitation for acute massive pulmonary embolism. A case report]. / Terapia trombolitica durante rianimazione cardiopolmonare per embolia polmonare acuta massiva. Descrizione di un caso clinico.

Massive pulmonary embolism associated with cardiac arrest has an extremely high mortality in spite of cardiopulmonary resuscitation maneuvers. An early diagnosis of pulmonary embolism as cause of cardiac arrest and a rapid specific therapy able to obtain a restoration of pulmonary flow can improve the prognosis. The authors report a case of cardiac arrest for massive pulmonary embolism promptly diagnosed by echocardiography and treated by thrombolytic therapy with an initial favourable outcome.

Shot noise for resonant Cooper pair tunneling.

We study intrinsic noise of current in a superconducting single-electron transistor, taking into account both coherence effects and Coulomb interaction near a Cooper pair resonance. Because of this interplay, the statistics of tunneling events deviates from the Poisson distribution and, more important, it shows even-odd asymmetry in the transmitted charge. The zero-frequency noise is suppressed significantly when the quasiparticle tunneling rates are comparable to the coherent oscillation frequency of Cooper pairs.

[The usefulness of the association of clinical probability, rapid plasma measurement of D-dimer, compression echography of the lower limbs and echocardiography in the diagnosis of acute pulmonary embolism]. / Utilità dell'associazione di probabilità clinica, dosaggio rapido plasmatico del D-dimero, ecografia compressiva degli arti inferiori ed ecocardiografia nella diagnosi di embolia polmonare acuta.

BACKGROUND: The aim of this study was to investigate the diagnostic utility of clinical probability, rapid plasma D-dimer assay, compression ultrasonography (CUS) and transthoracic echocardiography (TTE) in patients with suspected pulmonary embolism. METHODS: One hundred forty consecutive outpatients with suspected pulmonary embolism were enrolled in a prospective trial. We evaluated sensitivity, specificity, positive and negative predictive value of a combination of clinical probability, D-dimer, CUS and TTE using perfusion lung scan and pulmonary angiography as a combined gold standard for determining the presence or absence of pulmonary embolism. Clinical probability was assessed in accordance with the PIOPED criteria. The D-dimer (Nycocard) level was considered as abnormal > 0.3 mg/l, the CUS if incompressibility of the leg veins was showed, and the TTE if right ventricular dilation was present, in the absence of chronic pulmonary disease. The combination of these tests was considered consistent with the presence of pulmonary embolism if D-dimer plus CUS and/or TTE showed abnormal results. A pulmonary embolism was excluded if D-dimer and CUS showed normal findings or a low clinical probability was associated with normal findings of CUS and TTE. RESULTS: One hundred eleven patients were evaluated. Pulmonary embolism was present in 45/111 (40%) patients. The combination of tests showed positive findings in 39/39 patients with pulmonary embolism, negative findings in 47/50 without pulmonary embolism and non-diagnostic results in 22/111 (20%) patients (95% confidence interval--CI 12-28%). There were three false positive and no false negative results. Sensitivity and specificity were 100 and 94% respectively (95% CI 92-100% and 87-100%); positive and negative predictive values were 93 and 100% (95% CI 85-100% and 93-100%). None of these tests, separately, showed enough sensitivity and specificity. CONCLUSIONS: The combination of clinical probability, D-dimer, CUS and TTE was highly accurate to confirm or rule out pulmonary embolism.

[Functional heart murmur and echocardiography: a solved problem?]. / Soffio cardiaco funzionale ed ecocardiografia: un problema risolto?

BACKGROUND: Is it really vanished the need for echocardiography in the differential diagnosis of functional pediatric murmurs? METHODS: To this aim 260 children (132 males, 128 females; age range 1-84 months) were examined with auscultatory cardiac murmur. All children underwent a clinical and instrumental evaluation (ECG and echocardiography) from two pediatric cardiologists with independent assessment. RESULTS: Two hundred and ten patients (Group A) were evaluated clinically with functional murmur, 45 patients (Group B) with pathological murmur, 5 patients (Group C) with uncertain pathology. ECG showed changes in 1 Group B patient. Echocardiography showed pathology in 15 Group A patients (6 patients with patent foramen ovale, 5 patients with interatrial defect, 2 patients with bicuspid aortic valve, 1 patient with mitral insufficiency, 1 patient with restrictive cardiomyopathy). Pathology was excluded in 3 Group B patients, and in 2 Group C patients. In our clinical analysis echocardiography showed sensitivity 75%, specificity 97%, positive predictive value 90%, and negative predictive value 92%. CONCLUSIONS: In our experience we suggest to perform echocardiographic examination in children with functional murmur for complete assessment.

[Results of a survey on knowledge and habits among hospital doctors concerning primary prevention of venous thromboembolism]. / Risultati di una indagine sulle conoscenze e sulle abitudini di medici ospedalieri riguardo alla prevenzione primaria del tromboembolismo venoso.

BACKGROUND: The purpose of this study was to analyse the attitudes towards and knowledge of primary prevention of venous thromboembolism (VTE) among hospital doctors in Calabria. METHODS: The survey was based on theoretical knowledge and practical management of hortopedics, surgeons, gynecologists and internists working in 14 hospitals. RESULTS: Out of a total of 340 physicians contacted, 154 (45%) agreed to take part in the survey. 82% of those who responded used VTE prophylaxis on a routine basis. Unfractioned heparin (71%) was the most frequently used methods; early deambulation (55%), low molecular weight heparin (49%) and elastic stocking (49%) were less frequently employed. Surprisingly, one third used aspirin. 75% of those contacted had modified their approach to prevention during the last few years, in particular owing to improvements in pharmacological therapy and increased awareness of the problem. In the survey of clinical practice, 80% of those who took part correctly identified the VTE risk, 86% suggested the best treatment, but only 27% assessed the exact frequency rate of deep venous thrombosis (DVT) and pulmonary embolism (PE) in the absence of prophylaxis. CONCLUSIONS: Most of the doctors contacted showed scant interest in the primary prevention of VTE. The 45% who agreed to be interviewed revealed a good practical approach but were not sufficiently aware of the real incidence of DVT and PE in a clinical risk context without prophylaxis. Although they must be interpreted with caution, these findings allow the real behaviour of hospital physicians in this region to be assessed with regard to the primary prevention of VTE and suggest the need for more correct information about this aspect of venous thromboembolic disease which is not yet sufficiently well known.

Successful treatment of right heart thromboemboli with IV recombinant tissue-type plasminogen activator during continuous echocardiographic monitoring: a case series report.

BACKGROUND AND STUDY OBJECTIVE: Echocardiographic detection of right heart thromboemboli (RHTE) during pulmonary embolism (PE) shows an uncommon but life-threatening event. The treatment of this condition is not well established. The aim of our study is to evaluate the efficacy and safety of recombinant tissue-type plasminogen activator (rt-PA) in treating RHTE. METHOD: We performed a transthoracic echocardiogram within (mean +/- SD) 120+/-45 min from onset of symptoms on 30 consecutive patients with proven massive PE. Seven patients (23%) showed RHTE, four patients (57%) had cardiogenic shock; and all patients showed echocardiographic features of acute cor pulmonale. The seven patients with RHTE received an IV infusion of 100 mg rt-PA over a period of 2 h with continuous echocardiographic monitoring. RESULTS: We observed complete RHTE lysis at 45 to 60 min from the onset of rt-PA infusion and significant reductions at 2 h in the following: 14% in right ventricle (RV) end-diastolic diameter (reduction, 40.8 to 35 mm; p < 0.01); 12% in RV/left ventricular ratio (reduction, 0.83 to 0.73; p < 0.01); and 17% in tricuspid regurgitant flow velocity (reduction, 3.5 to 2.9 m/s; p < 0.01). The interventricular septal and RV wall motions improved. An excellent clinical outcome was achieved rapidly in all patients. No adverse events were recorded. CONCLUSIONS: We demonstrated the rapid, effective, and safe action of rt-PA in RHTE resolution and an improvement in pulmonary perfusion. Our data confirm the important role of an early, systematic echocardiographic approach in order to detect RHTE quickly in patients with suspected massive PE.

[A health education program for the prevention of heart diseases carried out in a population in Calabria]. / Un programma di educazione sanitaria per la prevenzione delle cardiopatie realizzato in un ambito di popolazione della Calabria.

BACKGROUND: To evaluate the behaviour and knowledge of students on cardiovascular risk factors and to programme a campaign for the prevention of cardiovascular diseases. METHODS: All students attending the last year of the secondary school of this province answered a questionnaire. An educational campaign followed the analysis of the questionnaire. RESULTS: The analysis of 3675 questionnaires shows that almost all students were between 18 and 20; 16% of males (m) and 7.4% of females (f) were overweight; 1.5% and 0.4% respectively were obese; 88.8% of m and 44% of were doing physical activity; 32.4% of m and 26.8% of f were cigarette smokers. Knowledge about cardiovascular risk factors were poor. Development of the prevention campaign. In the school districts four seminars were organized to discuss about cardiovascular prevention with science teachers of the province, using audiovisual materials. The same teachers devote 4-6 hours to the same matters during school lessons. In the next months conferences destined to the population of the province will be organized. CONCLUSIONS: This program allows to promote health education in the whole population, through the students, with a low cost.

New introducer technique for implanting pacemakers and defibrillator leads: percutaneous incannulation of the cephalic vein.

OBJECTIVES: This study was designed to assess the feasibility of percutaneous incannulation of cephalic vein for the implantation of pacemaker and defibrillator leads. BACKGROUND: The development of the subclavian vein puncture technique for pacemaker lead implantation has many advantages compared to surgical isolation of cephalic vein. However, initial enthusiasm has been dampened by reports of serious complications because of the anatomical relationships of the subclavian vein. METHODS AND RESULTS: Percutaneous incannulation of the right cephalic vein was attempted in 75 patients who were candidates for permanent pacemaker or ICD implantation. The technique was effective in 46 patients. It was shown to be ineffective in 18, despite the presence of a normal vein. In seven patients, the cephalic vein was found to be unusable for passing the electrocatheter and in four patients, the vein was absent. In the patients in whom the vein was present, the success rate was 46/71 (64%). The average implantation time was 7.2 minutes (range 5-10), while the average time for conventional surgical technique was 15.2 minutes (range 14-20) (p < 0.001). All patients remained free from complications during a mean follow-up period of 8.2 months (range 1 to 18). CONCLUSIONS: In our opinion, percutaneous incannulation of cephalic vein could be adopted as the first step in pacemaker or defibrillator implantation procedures, as it shows satisfactory success rates, simplicity of execution and absence of complications. Most importantly, in the event of failure, it does not compromise the use of a conventional technique.

[Acute disfunction from thrombosis of a prosthetic mitral valve: thrombolysis with rt-PA in the clinical emergency phase]. / Disfunzione acuta da trombosi di protesi mitralica meccanica: trombolisi mediante rt-PA in fase di emergenza clinica.

Prosthetic valve thrombosis can determine different degrees of valvular insufficiency or obstruction, with a potentially fatal course. The current literature has not established whether the best treatment is thrombolysis or surgery (thrombectomy or valvular replacement). However, both treatments expose the patient to the risk of serious sequelae or death. Here we describe a case of acute thrombosis in a prosthetic mitral valve. At presentation, the patient was in pulmonary edema and had a low cardiac output. She was treated with recombinant tissue-type plasminogen activator infusion (rt-PA 100 mg in 2 hours). Both clinically as well as echocardiographically, we observed a quick regression of the obstruction, but after the treatment, the patient developed an ischemic stroke with aphasia and hemiplegia. The authors conclude that thrombolysis is a highly effective treatment in resolving prosthetic thrombosis. However, because it carries a significant risk of embolization, it should be limited to patients with hemodynamic deterioration in whom surgery could also entail a significant risk of death.

[The prevalence and clinical characteristics of heart failure in a population sample of Calabria]. / Prevalenza e caratteristiche cliniche dell'insufficienza cardiaca in un campione di popolazione della Calabria.

Two-hundred and fourteen patients with congestive heart failure were identified over a six-month period in the general practice of 29 GPs covering an adult population of 29,959 subjects residing in the region of Calabria, in southern Italy, with an overall prevalence of 7 per 1000. Males represented 52% of the cases and females 48%, with a median age of 75 years. On average, the condition was first diagnosed 41 months before the present examination. Patients generally had a high body mass index (28 kg/m2). Patients were classified as follows in the NYHA classification: 9.4% in class I, 45.3% in class II, 39.2% in class III, 6.1% in class IV. Hypertension, either alone or associated with ischemic heart disease (totally about 75% of cases), was the most common etiology, while COPD was the most commonly associated chronic condition. Clinical symptoms and signs were used to classify patients in a simplified version of the Boston score which was reported in 48% of cases as definite, 12% as possible, 6% as improbable and 34% as absent. A specific treatment was already ongoing in 97% of patients. The most commonly administered drugs were diuretics (83%), ACE-inhibitors (77%), and digitalis (67%). This three-drug combination (alone or with other drugs) covered 46% of patients. A comparison of four predefined typologies of treatment against the Boston score suggested that at least part of the outcome in classifying patients using this procedure was due to pathomorphosis of the syndrome induced by early pharmacological treatment.

[The role of 2D-doppler electrocardiography in the early diagnosis of massive acute pulmonary embolism and therapeutic monitoring]. / Ruolo dell'ecocardiogramma 2D-doppler nella diagnosi precoce di embolia polmonare acuta massiva e nel monitoraggio terapeutico.

Early diagnosis is important for the prognosis of patients affected with pulmonary embolisms. The mortality rate ranges from 30% in untreated cases to 10% in cases getting early treatment. In this context, it is essential to obtain a correct diagnosis in order to start the best treatment for each patient. The aim of our study is to evaluated the contribution of mono- bidimensional echocardiography and color-doppler for the early diagnosis of acute massive pulmonary embolism. We examined 23 patients (14 women with a mean age of 67 +/- 13 years; 9 men with a mean age of 58 +/- 16 years) who were referred to us for observation over a 30-month period. These patients had been admitted to the intensive care unit for suspected acute massive pulmonary embolism and the diagnosis was subsequently confirmed by a pulmonary scintigraphy. None of the 23 patients showed a positive case history of previous heart disease and/or pulmonary disease. The patients were checked using 2D-doppler echocardiography, 120 +/- 45 minutes from the onset of the symptoms. They were then divided into two groups (A and B) based on the presence or absence of thromboembolus in the right cavity of the heart. Seven patients (30%) revealed thromboemboli and were treated effectively with rt-PA (100 mg/2 hours). An increase in the size of the right ventricle with an affected rate RV/LV > 0.6 and the abnormal kinetics of the ventricular septum proved to be the most sensitive parameters for right ventricular overload, as signs of acute massive pulmonary ambolisms were observed in all 23 patients. Tricuspid regurgitation speed (from 2.9 to 3.6 m/sec) and peak systolic pulmonary pressure (67 mmHg) were recorded in all patients. Our observations suggest that the hemodynamic effects of an acute massive pulmonary embolism can be enumerated and monitored by analyzing ventricle size and septum kinetics. To summarize, echocardiography proved to be a simple and realistic test. It enabled correct diagnosis and made it possible not only to start thrombolytic therapy without requiring other exams, but also to monitor and evaluate the effects of this therapy.

[Long-term captopril therapy in asymptomatic patients with severe chronic aortic insufficiency]. / Terapia a lungo termine con captopril in pazienti asintomatici con insufficienza aortica cronica di grado severo.

BACKGROUND: Clinical history of patients with severe chronic aortic regurgitation is characterized by a long period without any symptom, although the left ventricle enlarges progressively. The administration of oral vasodilators could reduce ventricular enlargement or its progression, delaying the development of myocardial dysfunction and/or the need for valvular surgery. OBJECTIVES: To verify the efficacy of long-term captopril therapy to reduce left ventricular mass and dimensions in patients with severe chronic aortic regurgitation. METHODS: This is a prospective echocardiographic study in which each individual patient is considered his own control case. Eleven asymptomatic patients with severe chronic aortic regurgitation in sinus rhythm, who had an ejection fraction greater than 50% and were not taking cardiovascular drugs, were orally administered captopril at the maximum tolerated dosage (127 +/- 13 mg/day). Follow-up lasted for 24 +/- 3 months. RESULTS: Left ventricular telediastolic diameter decreased from 69 +/- 5 to 61 +/- 3 mm (p < 0.01), telesystolic diameter decreased from 48 +/- 5 to 41 +/- 4 mm (p < 0.01); ejection fraction increased from 56 +/- 4 to 61 +/- 3% (p < 0.001); myocardial mass decreased from 208 +/- 32 to 174 +/- 27 g/m2 (p < 0.01), and mean wall stress from 264 +/- 35 to 203 +/- 25 mmHg (p < 0.001). All variations were still significant at 6 months. CONCLUSIONS: These results suggest that captopril has a favourable effect on left ventricular mass, dimensions and load conditions, and could favourably influence the natural history of chronic aortic regurgitation. The efficacy of medical treatment can be verified through serial echocardiographic study.

[Diltiazem in paroxysmal supraventricular tachycardia: electrocardiographic findings at termination]. / Diltiazem nella tachicardia parossistica sopraventricolare: quadri elettrocardiografici alla interruzione.

The effects of diltiazem hydrochloride (0.3 mg/kg i.v. over 2 min.) was studied by continuous electrocardiographic monitoring in 60 patients. Conversion to sinus rhythm was achieved in 55 patients (91%). Electrocardiographic findings were: undisturbed sinus rhythm in 20 patients; A-V junctional rhythm in 4 patients; complex ventricular arrhythmias (ventricular tachycardia or complex VPCs) in 19 patients. Patients with complex ventricular arrhythmias were matched against patients with normal sinus rhythm, with respect to the following parameters: age, sex, heart disease, tachycardia duration, tachycardia cycle length, sinus cycle length, pre- and post-infusion blood pressure. No differences between the two groups of patients were found. Ventricular arrhythmias occurring at the termination of supraventricular tachycardia are difficult to explain. Nevertheless, these arrhythmias are not associated with organic heart disease. They could be the expression of triggered activity.