Cálculo de la energía de excitones en puntos cuánticos semiconductores usando un modelo de dos bandas en la aproximación de masa efectiva

Tesis (Lic. en Física)--Universidad Nacional de Córdoba, Facultad de Matemática, Astronomía, Física y Computación, 2021.En este trabajo se estudian las propiedades espectrales de excitones confinados en puntos cuánticos de Arseniuro de Galio en la aproximación de masa efectiva de dos bandas. El efecto del punto cuántico es modelado usando potenciales de confinamiento para el electrón y el hueco, mientras que la la presencia de las dos bandas de niveles de interés se ve reflejada en el uso de la "masa efectiva" de cada partícula en el Hamiltoniano del sistema. El Hamiltoniano resulta así una ecuación "de Schrödinger" para dos partículas con masas distintas y que interactúan mediante el potencial de Coulomb electrostático de dos cargas puntuales, sin condiciones de contorno. El potencial de confinamiento utilizado posee simetría esférica.In this work the spectral properties of excitons confined in gallium arsenide quantum dots are studied in a two-band effective mass approximation. The effect of the quantum dot is modeled using binding potentials for the electron and the hole, while the presence of the two bands of levels of interest is reflected in the use of the "effective mass" of each particle in the Hamiltonian of the system. In this way, the Hamiltonian results in a "Schrödinger-like" equation for two particles with different masses that interact through the electrostatic Coulomb potential of two point charges, without boundary conditions. The binding potential has spherical symmetry.publishedVersionFil: Legnazzi, Nicolás. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía, Física y Computación; Argentina

Differentially private queries in crowdsourced databases for net neutrality violations detection

Lawmakers and regulatory bodies around the world are asserting Network Neutrality as a fundamental property of broadband Internet access. Since neutrality implies a comparison between different users and different ISPs, this opens the question of how to measure net neutrality in a privacy-friendly manner. This work describes a system in which users convey throughput measurements for the different services they use to a crowd-sourced database and submit queries testing their measurements against the hypothesis of a neutral network. The usage of crowd sourced databases poses potential privacy problems, because users submit data that may possibly disclose information about their own habits. This leaves the door open to information leakages regarding the content of the measurement database. Randomized sampling and suppression of small clusters can provide a good tradeoff between usefulness of the system, in terms of precision and recall of discriminated users, and privacy, in terms of differential privacy

Secure and Differentially Private Detection of Net Neutrality Violations by Means of Crowdsourced Measurements

Evaluating Network Neutrality requires comparing the quality of service experienced by multiple users served by different Internet Service Providers. Consequently, the issue of guaranteeing privacy-friendly network measurements has recently gained increasing interest. In this paper we propose a system which gathers throughput measurements from users of various applications and Internet services and stores it in a crowdsourced database, which can be queried by the users themselves to verify if their submitted measurements are compliant with the hypothesis of a neutral network. Since the crowdsourced data may disclose sensitive information about users and their habits, thus leading to potential privacy leakages, we adopt a privacy-preserving method based on randomized sampling and suppression of small clusters. Numerical results show that the proposed solution ensures a good trade-off between usefulness of the system, in terms of precision and recall of discriminated users, and privacy, in terms of differential privacy

Derivative securities in risk management and asset pricing

The high informational content and the ease of accessibility are among the most attractive features which make derivative securities particularly useful in financial applications. With a special focus on risk management and asset pricing, I present several methodologies which involve the use of option and futures data in the estimation process. This doctoral thesis consists of three chapters. The first one, “Forward-looking VaR and CVaR: an application to the Natural gas Market”, presents, backtests and compares point risk forecasts for the natural gas market using a novel methodology which introduces derivative securities into a classical calibration setting. The second chapter, “A Bayesian Estimate of the Pricing Kernel”, is a joint work with G. Barone-Adesi and A. Mira. The article sets the pricing kernel estimation into a Bayesian framework, which enables to combine the use of derivative and historical data in the physical density calibration. Thanks to their higher accuracy and flexibility, the resulting pricing kernel estimates display a monotonic decreasing shape over a large range of returns, consistently with the classical theory. The third chapter, “S&P 500 Index, an Option-Implied Risk Analysis”, is a joint work with G. Barone-Adesi and C. Sala. Tested on the US equity market, the article presents a detailed analysis on the performance of the option-implied risk metrics both in absolute terms and relative to the existing historical-based risk metrics

806 Scout post-PCI instantaneous wave-free ratio as a driver of functional complete

Abstract Aims Physiology assessment by means of instantaneous wave-free ratio (iFR) is non-inferior to fractional flow reserve for the assessment of intermediate coronary lesions that are candidates to percutaneous coronary intervention (PCI). However, in pivotal trials assessing iFR, tandem coronary lesions (i.e. two serial lesions located in the same coronary artery) were excluded. In addition, the role of iFR after PCI as a way to optimize its success is poorly understood, particularly in the context of ST-segment elevation myocardial infarction (STEMI) with multivessel disease and tandem stenoses. We describe an illustrative case of post-PCI iFR in a STEMI patient with multivessel disease that led to a significant change in the revascularization strategy. Methods A 71-year old man presented with infero-lateral STEMI and received PCI with 1 drug-eluting stent (DES) 2.25 × 18 mm on the distal right coronary artery. The left coronary artery presented a 30–40% stenosis of the proximal left circumflex (LCX) and a 90% bifurcation stenosis of the mid portion of the same artery. PCI of the distal lesion was performed with implantation of 1 DES 3.0 × 22 with flaring of the stent at the level of the side branch and proximal optimization technique. Post-PCI iFR of the LCX was performed to assess the success of the procedure, with a value of 0.74. To understand the relative contribution of the two tandem stenoses, a pullback of the iFR wire was performed, which showed an unexpectedly small jump of the pressure when the wire was between the two lesions (0.80). Results As such, the significant contribution of the proximal lesion was unravelled, which led to implantation of a second DES 4.0 × 26 mm, partially overlapping with the previously implanted DES. Post-PCI iFR confirmed the complete success of the procedure (1.00). Conclusions In the context of complete revascularization for STEMI presenting with non-infarct related artery tandem stenoses, post-PCI physiology contributes to unravel the relative contribution of low-grade angiographic stenoses corresponding to functionally significant atherosclerosis left untreated. This case example illustrates the emerging procedural value of post-PCI iFR in achieving the goal of complete functional revascularization

Zapobieganie pokontrastowemu ostremu uszkodzeniu nerek u pacjentów poddawanych przezskórnym interwencjom wieńcowym

Wewnątrznaczyniowe podanie środka kontrastowego stanowi nieodzowny element przezskórnej interwencji wieńcowej (PCI). Jako że wspomnianą procedurę przeprowadza się bardzo często, pokontrastowe ostre uszkodzenie nerek (CI‑AKI) stało się jedną z najpowszechniejszych przyczyn ostrej nefropatii i ma istotne znaczenie prognostyczne. Niektóre choroby przewlekłe obciążające pacjenta oraz cechy wykonywanego zabiegu uważa się za kluczowe czynniki ryzyka CI‑AKI. W poniższym artykule poglądowym omówiono aktualne dane naukowe dotyczące zapobiegania CI‑AKI u pacjentów poddawanych PCI oraz kierunek przyszłych badań.Wewnątrznaczyniowe podanie środka kontrastowego stanowi nieodzowny element przezskórnej interwencji wieńcowej (PCI). Jako że wspomnianą procedurę przeprowadza się bardzo często, pokontrastowe ostre uszkodzenie nerek (CI‑AKI) stało się jedną z najpowszechniejszych przyczyn ostrej nefropatii i ma istotne znaczenie prognostyczne. Niektóre choroby przewlekłe obciążające pacjenta oraz cechy wykonywanego zabiegu uważa się za kluczowe czynniki ryzyka CI‑AKI. W poniższym artykule poglądowym omówiono aktualne dane naukowe dotyczące zapobiegania CI‑AKI u pacjentów poddawanych PCI oraz kierunek przyszłych badań