Some results on the Brownian meander with drift

In this paper we study the drifted Brownian meander, that is a Brownian motion starting from $u$ and subject to the condition that $\min_{ 0\leq z \leq t} B(z)> v$ with $u > v$. The limiting process for $u \downarrow v$ is analyzed and the sufficient conditions for its construction are given. We also study the distribution of the maximum of the meander with drift and the related first-passage times. The representation of the meander endowed with a drift is provided and extends the well-known result of the driftless case. The last part concerns the drifted excursion process the distribution of which coincides with the driftless case

Current-Induced Spin Polarization and Dynamic Nuclear Polarization: Generation and Manipulation of Electron and Nuclear Spin Polarization in Gallium Arsenide

Spintronics would utilize the spin of the electron for information processing and storage, leading to devices that may be smaller, faster, and more energy-efficient than their electronic counterparts. Before these spin-based devices can be fully realized, we must answer the following questions: How do we effectively generate electron spin polarization? What factors impact the ability of the spins to stay polarized? How do we effectively detect spin polarization? In our materials of interest, gallium arsenide (GaAs) and its alloy indium gallium arsenide (InGaAs), the detection method is optical, via Faraday or Kerr rotation. This dissertation focuses on the electrical generation of electron spin polarization (current-induced spin polarization, or CISP) and dynamic nuclear polarization (DNP) generated by periodic optical electron spin pumping, which will impact the electron spin system. First, we modify an electrical technique for generating CISP in InGaAs to extend the voltage range of our experiments. In previous studies, current heating limited the magnitude of the applied voltage, leading to uncertainty regarding the relationship between the voltage and the spin polarization generation rate. We modify a bipolar square wave to reduce the time spent at nonzero voltage, and by generating CISP via modified waveforms with increasing off/on ratios, we reduce heating by up to an order of magnitude on the range of 1 to 7 V applied. At off/on ratios of 5 and above, we recover the expected linear relationship between generation rate and applied voltage. Then, we investigate DNP in GaAs under periodic optical excitation in the regime of resonant spin amplification (RSA). The measured Kerr rotation exhibits warped RSA peaks, shifted from their expected positions depending on the direction in which the external magnetic field is incremented, or swept. This points to a DNP accumulated along the external field direction, perpendicular to the direction of optical spin generation, altering electron spin precession through a sweep-direction-dependent Overhauser field, with nuclear T1 times on the order of tens of seconds. After establishing a physical framework based upon RSA and the optical Stark effect, we identify a set of experimental parameters to characterize the DNP: laser wavelength, pump power, time elapsed, and external field history. We present data exploring each of these parameter spaces, comparing to numerical simulations for the wavelength and elapsed time cases. Finally, we discuss the origin of the sweep-direction dependence. We focus on the external field history of DNP through the steep sweep experiments, in which a field sweep is paused for two minutes to allow for DNP buildup. Certain steep fields result in post-steep RSA peaks that mimic the steeping behavior, showcasing a minutes-long precise memory of the electron-nuclear system’s magnetic field history, the steep echo. We examine the steep sweeps through the lens of nuclear-induced frequency focusing, a conceptual framework for the buildup of DNP complementing our physical model. To explain the steep echo, we propose a modification to our physical picture that would involve a distribution of electron-nuclear interactions, with preliminary simulations showing promising correspondence to our measurements. Taken together, these studies elucidate considerations that can arise in and compromise optical spintronic experiments. Proper mitigation (for current heating) and understanding (for DNP) will aid in the future research necessary to bring about semiconductor spintronic devices.PHDApplied PhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/163154/1/iafratej_1.pd

Canadian Prison Needle-Exchange Programs: Can the Health Benefits Overcome the Current Legal Barriers?

The incidence of HIV and Hepatitis C is significantly higher in Canadian federal penitentiaries than among the general public, as are the transmission rates of these two diseases. These disproportionate rates of infection are largely attributed to the sharing of needles among inmates who are addicted to intravenous drugs. This has created a serious public health risk for all federal inmates as well as the general public, since many of these inmates will be released back into society. In response to this risk, the Correctional Service of Canada asked the Public Health Agency of Canada (PHAC) to study the effectiveness and risks of prison needle-exchange programs (PNEPs). In 2006, PHAC’s report, “Prison needle exchange: Review of the evidence,” concluded that “[n]eedle-sharing practices decrease in prisons where PNEPs are offered.” Despite these findings, the federal government has refused to establish a prison needle-exchange program. The harm caused by the federal government’s continuing reluctance is compounded by an existing legislative prohibition on sterile needles in federal penitentiaries. In light of current political and legislative barriers, any hope of establishing such a program lies with the courts. This article assesses the ability to challenge the legislative prohibition on sterile needles through a claim under the Canadian Charter of Rights and Freedoms

A Sociological Examination Of The Gendered Gambling Practices Of Ontario Adults

This research examines differences between men and women in their gambling practices, gambling outcomes, and gambling severity. Using secondary data produced by the Ontario Problem Gambling Research Centre, this research investigates the Ontario adults Problem Gambling Severity Index (PGSI) from 2001 and 2005 to determine if a gender difference exists in the likelihood of becoming a problem gambler, the types of gambling activities one is likely to participate in, and the consequences one may experience as a result of gambling. This study focuses on a sociological approach considering potential gender differences in gambling preferences to be a direct consequence of the social or subcultural environment in which the gamblers live. In other words, a sociological approach postulates that gambling behaviour may be the result of gendered social expectations. Quantitative analyses suggest that gender differences exist in rates of gambling, types of gambling activities participated, level of problem gambling severity and consequences of problem gambling. Men are more likely to gamble more frequently and have a higher risk of being a problem gambler, they are more likely to participate in both games of skill and chance gambling and men are more likely to experience negative behavioural outcomes and adverse consequences as a result of gambling. Notably, the findings suggest that there is a strong link between the odds of becoming a problem gambler, being male, participating in games of skill gambling, and experiences negative adverse consequences as a result of gambling. This research has significant clinical implications for those involved in gambling prevention, treatment and education, in that having a better grasp on the gendered division of gambling will allow professionals to develop more gender-specific programs for education, identification and treatment. This study found that men are more vulnerable to participating in high stakes gambling activities and, specifically, in games of skill, which seem to produce higher rates of problem gambling for men, relative to women. Risk-taking and mastery of games of skill are often integral to masculine identity; therefore, it may be advantageous for intervention programming to focus on helping men redefine their masculinity in a socially responsible way. Counseling programs and staff could develop more assessment plans and treatment plans to address the different needs of men and women. It is hoped that this research project will be the first of many attempts to gain a more comprehensive understanding of gambling practices, gambling outcomes