Study of Queuing Systems with a Generalized Departure Process

This work was supported by the Bulgarian National Science Fund under grant BY-TH-105/2005.

Limit Theorems for Regenerative Excursion Processes

This work is supported by Bulgarian NFSI, grant No. MM–704/97

Branching Processes in Autoregressive Random Environment

2000 Mathematics Subject Classification: 60J80, 60K05.

Selective Coupling between Theta Phase and Neocortical Fast Gamma Oscillations during REM-Sleep in Mice

TORT, A. B. L. ; SCHEFFER-TEIXEIRA, R ; Souza, B.C. ; DRAGUHN, A. ; BRANKACK, J. . Theta-associated high-frequency oscillations (110-160 Hz) in the hippocampus and neocortex. Progress in Neurobiology , v. 100, p. 1-14, 2013.

1999 Seat Belt Usage Survey, March 15, 2000

The 78 percent seat belt usage rate in 1999 (up 7 percent since 1992) reflects active enforcement and education efforts that have occurred in Iowa during the last few years. Through continuing education of the public, an active "Life Toll" campaign, seat belt enforcement, and other cooperative efforts between state and local law enforcement, Iowa will strive to increase the use of seat belts and save lives on Iowa roadways.

1998 Seat Belt Usage Survey, February 18, 1999

The 78 percent seat belt usage rate in 1999 (up 7 percent since 1992) reflects active enforcement and education efforts that have occurred in Iowa during the last few years. Through continuing education of the public, an active "Life Toll" campaign, seat belt enforcement, and other cooperative efforts between state and local law enforcement, Iowa will strive to increase the use of seat belts and save lives on Iowa roadways.

2001 Seat Belt Usage Survey, April 23, 2003

The 81 percent seat belt usage rate in 2001 (up 10 percent since 1992) reflects active enforcement and education efforts that have occurred in Iowa during the last few years. Through continuing education of the public, an active "Life Toll" campaign, seat belt enforcement, and other cooperative efforts between state and local law enforcement, Iowa will strive to increase the use of seat belts and save more lives on Iowa roadways.

2002 Seat Belt Usage Survey, February 26, 2003

The 82 percent seat belt usage rate in 2002 (up 11 percent since 1992) reflects active enforcement and education efforts that have occurred in Iowa during the last few years. Through continuing education of the public, an active "Life Toll" campaign, seat belt enforcement, and other cooperative efforts between state and local law enforcement, Iowa will strive to increase the use of seat belts and save more lives on Iowa roadways.

2004 Seat Belt Usage Survey, August 15, 2005

The 86.4 percent safety-belt usage rate in 2004 (an increase of 13 percent since 1994) reflects active enforcement and education efforts that have occurred in Iowa over the course of the last decade. Through continuing education of the public with programs in the school and communities, the “Click it or Ticket” campaign, an active “Life Toll” campaign, year-long safety belt enforcement, and other cooperative efforts between state and local law enforcement, Iowa will strive to increase the use of safety belts and save more lives on Iowa roadways.

Bumps, breathers, and waves in a neural network with spike frequency adaptation

In this Letter we introduce a continuum model of neural tissue that include the effects of so-called spike frequency adaptation (SFA). The basic model is an integral equation for synaptic activity that depends upon the non-local network connectivity, synaptic response, and firing rate of a single neuron. A phenomenological model of SFA is examined whereby the firing rate is taken to be a simple state-dependent threshold function. As in the case without SFA classical Mexican-Hat connectivity is shown to allow for the existence of spatially localized states (bumps). Importantly an analysis of bump stability using recent Evans function techniques shows that bumps may undergo instabilities leading to the emergence of both breathers and traveling waves. Moreover, a similar analysis for traveling pulses leads to the conditions necessary to observe a stable traveling breather. Direct numerical simulations both confirm our theoretical predictions and illustrate the rich dynamic behavior of this model, including the appearance of self-replicating bumps.

Selective Coupling between Theta Phase and Neocortical Fast Gamma Oscillations during REM-Sleep in Mice

TORT, A. B. L. ; SCHEFFER-TEIXEIRA, R ; Souza, B.C. ; DRAGUHN, A. ; BRANKACK, J. . Theta-associated high-frequency oscillations (110-160 Hz) in the hippocampus and neocortex. Progress in Neurobiology , v. 100, p. 1-14, 2013.

Exotic dynamics in a firing rate model of neural tissue with threshold accommodation

Many of the equations describing the dynamics of neural systems are written in terms of firing rate functions, which themselves are often taken to be threshold functions of synaptic activity. Dating back to work by Hill in 1936 it has been recognized that more realistic models of neural tissue can be obtained with the introduction of state-dependent dynamic thresholds. In this paper we treat a specific phenomenological model of threshold accommodation that mimics many of the properties originally described by Hill. Importantly we explore the consequences of this dynamic threshold at the tissue level, by modifying a standard neural field model of Wilson-Cowan type. As in the case without threshold accommodation classical Mexican-Hat connectivity is shown to allow for the existence of spatially localized states (bumps) in both one and two dimensions. Importantly an analysis of bump stability in one dimension, using recent Evans function techniques, shows that bumps may undergo instabilities leading to the emergence of both breathers and traveling waves. Moreover, a similar analysis for traveling pulses leads to the conditions necessary to observe a stable traveling breather. In the regime where a bump solution does not exist direct numerical simulations show the possibility of self-replicating bumps via a form of bump splitting. Simulations in two space dimensions show analogous localized and traveling solutions to those seen in one dimension. Indeed dynamical behavior in this neural model appears reminiscent of that seen in other dissipative systems that support localized structures, and in particular those of coupled cubic complex Ginzburg-Landau equations. Further numerical explorations illustrate that the traveling pulses in this model exhibit particle like properties, similar to those of dispersive solitons observed in some three component reaction-diffusion systems. A preliminary account of this work first appeared in S Coombes and M R Owen, Bumps, breathers, and waves in a neural network with spike frequency adaptation, Physical Review Letters 94 (2005), 148102(1-4).

As Santas Casas da Misericórdia na República Brasileira 1922-1945

O principal objectivo desta dissertação é o de conhecer um pouco melhor o processo de implementação das Santas Casas de Misericórdia no Brasil, dando especial ênfase à sua expansão durante o período de consolidação da República brasileira, mais concretamente entre 1922 a 1945. A necessária contextualização levou a pesquisa sobre as Misericórdias até à fase colonial e imperial do Brasil, acabando por demonstrar que as mesmas se fortaleceram no segmento de assistência médica, durante o período em análise, tomando o Estado brasileiro dependente das suas actividades. Este trabalho discute ainda o imaginário social da caridade e filantropia e a forma como tais preceitos configuraram a assistência médico-social no país. ABSTRACT; This dissertation aims to better know the implementation process of the Santas Casas de Misericórdia in Brazil, highlighting their expansion during the Republic, mainly between 1922 and 1945. For a better historical contextualization the study explores the Brazil's colonial and imperial phases, demonstrating that the Misericórdias progressively strength their power in the medical assistance segment, becoming the State dependent of their activities. The dissertation also discusses the philanthropy and charity's collective social imagery, as well as the way in which such concepts shaped the medico-social assistance in the country.

Engineering a Quantum Many-body Hamiltonian with Trapped Ions

While fault-tolerant quantum computation might still be years away, analog quantum simulators offer a way to leverage current quantum technologies to study classically intractable quantum systems. Cutting edge quantum simulators such as those utilizing ultracold atoms are beginning to study physics which surpass what is classically tractable. As the system sizes of these quantum simulators increase, there are also concurrent gains in the complexity and types of Hamiltonians which can be simulated. In this work, I describe advances toward the realization of an adaptable, tunable quantum simulator capable of surpassing classical computation. We simulate long-ranged Ising and XY spin models which can have global arbitrary transverse and longitudinal fields in addition to individual transverse fields using a linear chain of up to 24 Yb+ 171 ions confined in a linear rf Paul trap. Each qubit is encoded in the ground state hyperfine levels of an ion. Spin-spin interactions are engineered by the application of spin-dependent forces from laser fields, coupling spin to motion. Each spin can be read independently using state-dependent fluorescence. The results here add yet more tools to an ever growing quantum simulation toolbox. One of many challenges has been the coherent manipulation of individual qubits. By using a surprisingly large fourth-order Stark shifts in a clock-state qubit, we demonstrate an ability to individually manipulate spins and apply independent Hamiltonian terms, greatly increasing the range of quantum simulations which can be implemented. As quantum systems grow beyond the capability of classical numerics, a constant question is how to verify a quantum simulation. Here, I present measurements which may provide useful metrics for large system sizes and demonstrate them in a system of up to 24 ions during a classically intractable simulation. The observed values are consistent with extremely large entangled states, as much as ~95% of the system entangled. Finally, we use many of these techniques in order to generate a spin Hamiltonian which fails to thermalize during experimental time scales due to a meta-stable state which is often called prethermal. The observed prethermal state is a new form of prethermalization which arises due to long-range interactions and open boundary conditions, even in the thermodynamic limit. This prethermalization is observed in a system of up to 22 spins. We expect that system sizes can be extended up to 30 spins with only minor upgrades to the current apparatus. These results emphasize that as the technology improves, the techniques and tools developed here can potentially be used to perform simulations which will surpass the capability of even the most sophisticated classical techniques, enabling the study of a whole new regime of quantum many-body physics.

La institucionalización de la lucha contra el terrorismo transnacional a través del derecho internacional

Hasta hace casi una década, la guerra contra el terrorismo fue una lucha solitaria de los Estados. Actualmente y debido a las implicaciones globales de este fenómeno, las acciones contra este flagelo han adquirido connotación internacional. Gran parte de los países miembros de las Naciones Unidas han acogido esta guerra –contra un enemigo común, pero indefinido- como un compromiso político en favor de la paz y seguridad internacional. La producción constante de instrumentos internacionales que condenan el terrorismo y que exigen tomar medidas para combatirlo, demuestran que esa intención política originaria se ha decantado en el ordenamiento internacional como una obligación autónoma, de carácter consuetudinario; que hace que actualmente no haya país en el mundo que pueda excusarse de combatir al terrorismo (interno o transnacional) independientemente de las justificaciones que se puedan aludir para el no cumplimiento.