Dynamics of excess electronic charge in aliphatic ionic liquids containing the bis(trifluoromethylsulfonyl)amide anion

In a recent article (J. Am. Chem. Soc. 2011, 133, 20186) we investigated the initial spatial distribution of dry excess electrons in a series of room-temperature ionic liquids (RTILs). Perhaps unexpectedly, we found that in some alkylammonium-based systems the excess negative charge resided on anions and not on the positive cations. Following on these results, in the current paper we describe the time evolution of an excess electronic charge introduced in alkylammonium- and pyrrolidinium-based ionic liquids coupled with the bis(trifluoromethylsulfonyl)amide ([TfN]) anion. We find that on a 50 fs time scale an initially delocalized excess electron localizes on a single [TfN] anion which begins a fragmentation process. Low-energy transitions have a very different physical origin on the several femtoseconds time scale when compared to what occurs on the picosecond time scale. At time zero, these are intraband transitions of the excess electron. However after 40 fs when the excess electronic charge localizes on a single anion, these transitions disappear, and the spectrum is dominated by electron-transfer transitions between the fragments of the doubly charged breaking anion. © 2013 American Chemical Society.

Spatially-resolved mapping of history-dependent coupled electrochemical and electronical behaviors of electroresistive NiO

Bias-induced oxygen ion dynamics underpins a broad spectrum of electroresistive and memristive phenomena in oxide materials. Although widely studied by device-level and local voltage-current spectroscopies, the relationship between electroresistive phenomena, local electrochemical behaviors, and microstructures remains elusive. Here, the interplay between history-dependent electronic transport and electrochemical phenomena in a NiO single crystalline thin film with a number of well-defined defect types is explored on the nanometer scale using an atomic force microscopy-based technique. A variety of electrochemically-active regions were observed and spatially resolved relationship between the electronic and electrochemical phenomena was revealed. The regions with pronounced electroresistive activity were further correlated with defects identified by scanning transmission electron microscopy. Using fully coupled mechanical-electrochemical modeling, we illustrate that the spatial distribution of strain plays an important role in electrochemical and electroresistive phenomena. These studies illustrate an approach for simultaneous mapping of the electronic and ionic transport on a single defective structure level such as dislocations or interfaces, and pave the way for creating libraries of defect-specific electrochemical responses.

Non-Markovian qubit dynamics in a circuit-QED setup

We consider a circuit-QED setup that allows the induction and control of non-Markovian dynamics of a qubit. Non-Markovianity is enforced over the qubit by means of its direct coupling to a bosonic mode which is controllably coupled to another qubit-mode system. We show that this configuration can be achieved in a circuit-QED setup consisting of two initially independent superconducting circuits, each formed by one charge qubit and one transmission-line resonator, which are put in interaction by coupling the resonators to a current-biased Josephson junction. We solve this problem exactly and then proceed with a thorough investigation of the emergent non-Markovianity in the dynamics of the qubits. Our study might serve the context for the first experimental assessment of non-Markovianity in a multielement solid-state device.

Multiphysics Simulation of Nanostructured Semiconductor Devices

Thesis (Ph.D.)--University of Washington, 2013

Implémentation de la répartition de charge et du mode TOT pour la simulation d’un détecteur Timepix à pixels

Les détecteurs à pixels Medipix ont été développés par la collaboration Medipix et permettent de faire de l'imagerie en temps réel. Leur surface active de près de $2\cm^2$ est divisée en 65536~pixels de $55\times 55\um^2$ chacun. Seize de ces détecteurs, les Medipix2, sont installés dans l'expérience ATLAS au CERN afin de mesurer en temps réel les champs de radiation produits par les collisions de hadrons au LHC. Ils seront prochainement remplacés par des Timepix, la plus récente version de ces détecteurs, qui permettent de mesurer directement l'énergie déposée dans chaque pixel en mode \textit{time-over-threshold} (TOT) lors du passage d'une particule dans le semi-conducteur. En vue d'améliorer l'analyse des données recueillies avec ces détecteurs Timepix dans ATLAS, un projet de simulation Geant4 a été amorcé par John Id\'{a}rraga à l'Université de Montréal. Dans le cadre de l'expérience ATLAS, cette simulation pourra être utilisée conjointement avec Athena, le programme d'analyse d'ATLAS, et la simulation complète du détecteur ATLAS. Sous l'effet de leur propre répulsion, les porteurs de charge créés dans le semi-conducteur sont diffusés vers les pixels adjacents causant un dépôt d'énergie dans plusieurs pixels sous l'effet du partage de charges. Un modèle effectif de cette diffusion latérale a été développé pour reproduire ce phénomène sans résoudre d'équation différentielle de transport de charge. Ce modèle, ainsi que le mode TOT du Timepix, qui permet de mesurer l'énergie déposée dans le détecteur, ont été inclus dans la simulation afin de reproduire adéquatement les traces laissées par les particules dans le semi-conducteur. On a d'abord étalonné le détecteur pixel par pixel à l'aide d'une source de $\Am$ et de $\Ba$. Ensuite, on a validé la simulation à l'aide de mesures d'interactions de protons et de particules $\alpha$ produits au générateur Tandem van de Graaff du Laboratoire René-J.-A.-Lévesque de l'Université de Montréal.

Influence of occupation number of single particle levels on K - K charge transfer in collisions of 90 keV - Ne{^9+} on Ne

The influence of the occupation of the single particle levels on the impact parameter dependent K - K charge transfer occuring in collisions of 90 keV Ne{^9+} on Ne was studied using coupled channel calculations. The energy eigenvalues and matrixelements for the single particle levels were taken from ab initio self consistent MO-LCAO-DIRAC-FOCK-SLATER calculations with occupation numbers corresponding to the single particle amplitudes given by the coupled channel calculations.

Investigation of Multiphase Power Converter using Integrated Coupled Inductor Regarding Electric Vehicle Application

The challenge of reducing carbon emission and achieving emission target until 2050, has become a key development strategy of energy distribution for each country. The automotive industries, as the important portion of implementing energy requirements, are making some related researches to meet energy requirements and customer requirements. For modern energy requirements, it should be clean, green and renewable. For customer requirements, it should be economic, reliable and long life time. Regarding increasing requirements on the market and enlarged customer quantity, EVs and PHEV are more and more important for automotive manufactures. Normally for EVs and PHEV there are two important key parts, which are battery package and power electronics composing of critical components. A rechargeable battery is a quite important element for achieving cost competitiveness, which is mainly used to story energy and provide continue energy to drive an electric motor. In order to recharge battery and drive the electric motor, power electronics group is an essential bridge to convert different energy types for both of them. In modern power electronics there are many different topologies such as non-isolated and isolated power converters which can be used to implement for charging battery. One of most used converter topology is multiphase interleaved power converter, pri- marily due to its prominent advantages, which is frequently employed to obtain optimal dynamic response, high effciency and compact converter size. Concerning its usage, many detailed investigations regarding topology, control strategy and devices have been done. In this thesis, the core research is to investigate some branched contents in term of issues analysis and optimization approaches of building magnetic component. This work starts with an introduction of reasons of developing EVs and PEHV and an overview of different possible topologies regarding specific application requirements. Because of less components, high reliability, high effciency and also no special safety requirement, non-isolated multiphase interleaved converter is selected as the basic research topology of founded W-charge project for investigating its advantages and potential branches on using optimized magnetic components. Following, all those proposed aspects and approaches are investigated and analyzed in details in order to verify constrains and advantages through using integrated coupled inductors. Furthermore, digital controller concept and a novel tapped-inductor topology is proposed for multiphase power converter and electric vehicle application.

The Bullough-Dodd model coupled to matter fields

The Bullough-Dodd model is an important two-dimensional integrable field theory which finds applications in physics and geometry. We consider a conformally invariant extension of it, and study its integrability properties using a zero curvature condition based on the twisted Kac-Moody algebra A(2)((2)). The one- and two-soliton solutions as well as the breathers are constructed explicitly. We also consider integrable extensions of the Bullough-Dodd model by the introduction of spinor (matter) fields. The resulting theories are conformally invariant and present local internal symmetries. All the one-soliton solutions, for two examples of those models, are constructed using a hybrid of the dressing and Hirota methods. One model is of particular interest because it presents a confinement mechanism for a given conserved charge inside the solitons. (C) 2008 Elsevier B.V. All rights reserved.

A head mountable deep brain stimulation device for laboratory animals

Deep brain stimulation has emerged as an effective method to treat certain medical conditions. Electrical charges are injected into the target tissue through a conducting electrode exciting the tissue. A variety of DBS devices have been developed based on different operation principles. Majority of these devices, however, employ complex circuitry and are bulky. In clinical trials, laboratory animals need to freely move around and perform activities whilst receiving brain stimulation for days. This paper presents a simple lightweight head mountable deep brain stimulation device that can be carried by the animal during the course of a clinical trial. The device produces continuous current pulses of specific characteristics. It employs passive charge balancing to minimize undesirable effects on the target tissue. The device is constructed and its performance tested.

A low power micro deep brain stimulation device for murine preclinical research

Deep brain stimulation has emerged as an effective medical procedure that has therapeutic efficacy in a number of neuropsychiatric disorders. Preclinical research involving laboratory animals is being conducted to study the principles, mechanisms, and therapeutic effects of deep brain stimulation. A bottleneck is, however, the lack of deep brain stimulation devices that enable long term brain stimulation in freely moving laboratory animals. Most of the existing devices employ complex circuitry, and are thus bulky. These devices are usually connected to the electrode that is implanted into the animal brain using long fixed wires. In long term behavioral trials, however, laboratory animals often need to continuously receive brain stimulation for days without interruption, which is difficult with existing technology. This paper presents a low power and lightweight portable microdeep brain stimulation device for laboratory animals. Three different configurations of the device are presented as follows: 1) single piece head mountable; 2) single piece back mountable; and 3) two piece back mountable. The device can be easily carried by the animal during the course of a clinical trial, and that it can produce non-stop stimulation current pulses of desired characteristics for over 12 days on a single battery. It employs passive charge balancing to minimize undesirable effects on the target tissue. The results of bench, in-vitro, and in-vivo tests to evaluate the performance of the device are presented.

RF rectifiers for EM power harvesting in a deep brain stimulating device

A passive deep brain stimulation (DBS) device can be equipped with a rectenna, consisting of an antenna and a rectifier, to harvest energy from electromagnetic fields for its operation. This paper presents optimization of radio frequency rectifier circuits for wireless energy harvesting in a passive head-mountable DBS device. The aim is to achieve a compact size, high conversion efficiency, and high output voltage rectifier. Four different rectifiers based on the Delon doubler, Greinacher voltage tripler, Delon voltage quadrupler, and 2-stage charge pumped architectures are designed, simulated, fabricated, and evaluated. The design and simulation are conducted using Agilent Genesys at operating frequency of 915 MHz. A dielectric substrate of FR-4 with thickness of 1.6 mm, and surface mount devices (SMD) components are used to fabricate the designed rectifiers. The performance of the fabricated rectifiers is evaluated using a 915 MHz radio frequency (RF) energy source. The maximum measured conversion efficiency of the Delon doubler, Greinacher tripler, Delon quadrupler, and 2-stage charge pumped rectifiers are 78, 75, 73, and 76 % at -5 dBm input power and for load resistances of 5-15 kΩ. The conversion efficiency of the rectifiers decreases significantly with the increase in the input power level. The Delon doubler rectifier provides the highest efficiency at both -5 and 5 dBm input power levels, whereas the Delon quadrupler rectifier gives the lowest efficiency for the same inputs. By considering both efficiency and DC output voltage, the charge pump rectifier outperforms the other three rectifiers. Accordingly, the optimised 2-stage charge pumped rectifier is used together with an antenna to harvest energy in our DBS device.

Hartman-Grobman decomposition when in presence of jumps in the relative degree of the dynamics in an energy harvesting device

This work deals with the nonlinear piezoelectric coupling in vibration-based energy harvesting, done by A. Triplett and D.D. Quinn in J. of Intelligent Material Syst. and Structures (2009). In that paper the first order nonlinear fundamental equation has a three dimensional state variable. Introducing both observable and control variables in such a way the controlled system became a SISO system, we can obtain as a corollary that for a particular choice of the observable variable it is possible to present an explicit functional relation between this variable one, and the variable representing the charge harvested. After-by observing that the structure in the Input-Output decomposition essentially changes depending on the relative degree changes, presenting bifurcation branches in its zero dynamics-we are able in to identify this type of bifurcation indicating its close relation with the Hartman - Grobman theorem telling about decomposition into stable and the unstable manifolds for hyperbolic points.

Semiclassical approach to black hole absorption of electromagnetic radiation emitted by a rotating charge

We consider an electric charge, minimally coupled to the Maxwell field, rotating around a Schwarzschild black hole. We investigate how much of the radiation emitted from the swirling charge is absorbed by the black hole and show that most of the photons escape to infinity. For this purpose we use the Gupta-Bleuler quantization of the electromagnetic field in the modified Feynman gauge developed in the context of quantum field theory in Schwarzschild spacetime. We obtain that the two photon polarizations contribute quite differently to the emitted power. In addition, we discuss the accurateness of the results obtained in a full general relativistic approach in comparison with the ones obtained when the electric charge is assumed to be orbiting a massive object due to a Newtonian force.

The sl(2) affine Toda model coupled to the matter: solitons and confinement

The so-called conformal affine Toda theory coupled to the matter fields (CATM), associated to the (s) over capl(2) affine Lie algebra, is studied. The conformal symmetry is fixed by setting a connection to zero, then one defines an off-critical model, the affine Toda model coupled to the matter (ATM). Using the dressing transformation method we construct the explicit forms of the two-soliton classical solutions, and show that a physical bound soliton-antisoliton pair (breather) does not exist. Moreover, we verify that these solutions share some features of the sine-Gordon (massive Thirring) solitons, and satisfy the classical equivalence of topological and Noether currents in the ATM model. We show, using bosonization techniques that the ATM theory decouples into a sine-Gordon model and a free scalar. Imposing the Noether and topological currents equivalence as a constraint, one can show that the ATM model leads to a bag model like mechanism for the confinement of the color charge inside the sine-Gordon solitons (baryons).

Charge injection in an LED with a hybrid composite as the emissive layer

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)