Investigating the Photorecombination Dynamics in Molecular High-Harmonic Spectra

The work presented in this dissertation will relate the photorecombination dynamics to photoionization dynamics in SF6 utilizing the self-probing mechanism, high harmonic generation (HHG). This work specifically aims to establish parameters for which the comparison is applicable and the macroscopic complications inherent in HHG do not interfere with the extraction of dynamic information. The first part of this work established the macroscopic experimental apparatus necessary for consistent spectroscopic observation. It is shown that using a gas jet that is an order of magnitude shorter than the Rayleigh length of the driving laser results in more consistent harmonic spatial profiles and location of spectroscopic features. The observation of photorecombination dynamic in HHG is extended to shape resonances in SF6 with a focus on separating the effects of phase matching from photorecombination. This is accomplished by varying the laser parameters including the location of the focal point with respect to the center of the gas jet and altering the strength of the electric field. This process allowed us to observe two high energy shape resonances in the HHG spectrum of SF6 and map the appropriate parameters at which our experimental results confirm theoretical calculations based on the quantitative rescattering theory conducted by collaborators at Texas A&M University. The shape resonance was then probed by adding ellipticity to the fundamental in order to determine if there was information related to the angular dependence of the shape resonance that could be extracted in a way unique to HHG

The Land of Broken Dreams

https://digitalcommons.library.umaine.edu/mmb-vp/5054/thumbnail.jp

Engineered repressors are potent inhibitors of androgen receptor activity

Prostate cancer growth is dependent upon the Androgen Receptor (AR) pathway, hence therapies for this disease often target this signalling axis. Such therapies are successful in the majority of patients but invariably fail after a median of 2 years and tumours progress to a castrate resistant stage (CRPC). Much evidence exists to suggest that the AR remains key to CRPC growth and hence remains a valid therapeutic target. Here we describe a novel method to inhibit AR activity, consisting of an interaction motif, that binds to the AR ligand-binding domain, fused to repression domains. These 'engineered repressors' are potent inhibitors of AR activity and prostate cancer cell growth and importantly inhibit the AR under circumstances in which conventional therapies would be predicted to fail, such as AR mutation and altered cofactor levels

Social risk, stigma and space: key concepts for understanding HIV vulnerability among black men who have sex with men in New York City

Black men who have sex with men in the USA face disproportionate incidence rates of HIV. This paper presents findings from an ethnographic study conducted in New York City that explored the structural and socio-cultural factors shaping men’s sexual relationships with the goal of furthering understandings of their HIV-related vulnerability. Methods included participant observation and in-depth interviews with 31 Black men who have sex with men (three times each) and 17 key informants. We found that HIV vulnerability is perceived as produced through structural inequalities including economic insecurity, housing instability, and stigma and discrimination. The theoretical concepts of social risk, intersectional stigma, and the social production of space are offered as lenses through which to analyse how structural inequalities shape HIV vulnerability. We found that social risk shaped HIV vulnerability by influencing men’s decisions in four domains: 1) where to find sexual partners, 2) where to engage in sexual relationships, 3) what kinds of relationships to seek, and 4) whether to carry and to use condoms. Advancing conceptualisations of social risk, we show that intersectional stigma and the social production of space are key processes through which social risk generates HIV vulnerability among Black men who have sex with men

Gendered Social Institutions and Preventive Healthcare Seeking for Black Men Who Have Sex with Men: The Promise of Biomedical HIV Prevention

Research on gender and health, including research conducted among Black men who have sex with men (BMSM), has primarily focused on how gender norms and roles shape healthcare engagement. Here we advance that work by demonstrating how a broader theorization of gender, particularly one that moves beyond gender norms and performance to incorporate structures such as the healthcare system and the labor market, can facilitate an understanding of how gender affects preventive healthcare seeking among BMSM, particularly the uptake of pre-exposure prophylaxis (PrEP), a promising approach to alleviate HIV disparities. This article is based on a year-long ethnographic study conducted in New York City with BMSM (n = 31; three interviews each) and community stakeholders (n = 17). Two primary findings emerged: (1) the labor market systematically excluded the men in our sample, which limited their ability to access employer-sponsored healthcare. Such discrimination may promote overt demonstrations of masculinity that increase their HIV vulnerability and decrease healthcare seeking, and (2) healthcare systems are not structured to promote preventive healthcare for men, particularly BMSM. In fact, they constrained men’s access to primary providers and were usually tailored to women. Applying a structural, gendered lens to men’s health—in addition to the more frequently researched individual or interpersonal levels—provides insight into factors that affect healthcare seeking and HIV prevention for BMSM. These findings have implications for the design of policies and institutional reforms that could enhance the impact of PrEP among BMSM. Findings are also relevant to the management of chronic disease among men more broadly

Psychosocial Implications of Homophobia and HIV Stigma in Social Support Networks: Insights for High-Impact HIV Prevention Among Black Men Who Have Sex With Men

Black men who have sex with men (BMSM) bear an increasingly disproportionate burden of HIV in the United States. The Centers for Disease Control and Prevention recommends high-impact combination prevention for populations at high risk for HIV infection, such as BMSM. However, few scholars have considered the types of behavioral interventions that combined with biomedical prevention could prove effective for mitigating the epidemic among BMSM. Between June 2013 and May 2014, we conducted three in-depth interviews each with 31 BMSM, interviews with 17 community stakeholders, and participant observation in New York City to understand the sociocultural and structural factors that may affect the acceptance of and adherence to oral preexposure prophylaxis among BMSM and to inform an adherence clinical trial. BMSM and community leaders frequently described condomless sex as a consequence of psychosocial factors and economic circumstances stemming from internalized homophobia resulting from rejection by families and religious groups. BMSM revealed that internalized homophobia and HIV stigma resulted in perceived lack of self- and community efficacy in accepting and adhering to preexposure prophylaxis. Our results indicate that addressing internalized homophobia and fostering emotional social support in peer networks are key elements to improve the effectiveness of combination prevention among BMSM

Optimal Anesthetic Regime for Motionless Three-Dimensional Image Acquisition During Longitudinal Studies of Adult Nonpigmented Zebrafish

With many live imaging techniques, it is crucial that a deep level of anesthesia is reached and maintained throughout image acquisition without reducing zebrafish viability. This is particularly true for three-dimensional tomographic imaging modalities. Currently, the most commonly used anesthetic in the zebrafish community, MS- 222 (tricaine methanesulfonate), does not allow this. We show, using a combination of both MS-222 and isoflurane, that we can significantly improve the anesthetic regime required for motionless image acquisition of live adult zebrafish. We have benchmarked this against the requirements of our novel quantitative imaging platform, compressive sensing optical projection tomography. Using nonpigmented transgenic zebrafish, we show that a combination of 175 ppm of both anesthetics improves the maintenance of deep anesthesia for prolonged periods of time and it can be used repeatedly to enable longitudinal imaging. Importantly, it does not affect the health or viability of the adult zebrafish. We also show that nonpigmented fish, with a mutated form of the gene transparent, took significantly longer to reach deep anesthesia. The anesthetic regime presented in this study should lead to significant improvements in accuracy and information achievable from imaging live adult zebrafish and in its application to longitudinal studies

A vision screening of a homeless/low income population: Baloney Joe\u27s, Portland, Oregon

Two consecutive Saturdays in October of 1986 were utilized to conduct a vision screening on a homeless/low income population at Baloney Joe\u27s, a homeless relief center located in Portland, Oregon. A higher than expected rate of visual failures and pathological incidence was found when compared to other screening norms. The results suggest that adequate optometric care is deficient in this population, indicating a need for this service