Sparse Signal Representation in Digital and Biological Systems

Theories of sparse signal representation, wherein a signal is decomposed as the sum of a small number of constituent elements, play increasing roles in both mathematical signal processing and neuroscience. This happens despite the differences between signal models in the two domains. After reviewing preliminary material on sparse signal models, I use work on compressed sensing for the electron tomography of biological structures as a target for exploring the efficacy of sparse signal reconstruction in a challenging application domain. My research in this area addresses a topic of keen interest to the biological microscopy community, and has resulted in the development of tomographic reconstruction software which is competitive with the state of the art in its field. Moving from the linear signal domain into the nonlinear dynamics of neural encoding, I explain the sparse coding hypothesis in neuroscience and its relationship with olfaction in locusts. I implement a numerical ODE model of the activity of neural populations responsible for sparse odor coding in locusts as part of a project involving offset spiking in the Kenyon cells. I also explain the validation procedures we have devised to help assess the model's similarity to the biology. The thesis concludes with the development of a new, simplified model of locust olfactory network activity, which seeks with some success to explain statistical properties of the sparse coding processes carried out in the network.

Dielectric studies of Liquid Crystal Nanocomposites and Nanomaterial systems.

Liquid crystals (LCs) have revolutionized the display and communication technologies. Doping of LCs with inorganic nanoparticles such as carbon nanotubes, gold nanoparticles and ferroelectric nanoparticles have garnered the interest of research community as they aid in improving the electro-optic performance. In this thesis, we examine a hybrid nanocomposite comprising of 5CB liquid crystal and block copolymer functionalized barium titanate ferroelectric nanoparticles. This hybrid system exhibits a giant soft-memory effect. Here, spontaneous polarization of ferroelectric nanoparticles couples synergistically with the radially aligned BCP chains to create nanoscopic domains that can be rotated electromechanically and locked in space even after the removal of the applied electric field. The resulting non-volatile memory is several times larger than the non-functionalized sample and provides an insight into the role of non-covalent polymer functionalization. We also present the latest results from the dielectric and spectroscopic study of field assisted alignment of gold nanorods.

Too Busy to Be Fair? The Effect of Managers’ Perceived Workload on Their Core Technical Performance and Justice Rule Adherence

Despite the organizational benefits of treating employees fairly, both anecdotal and empirical evidence suggest that managers do not behave fairly towards their employees in a consistent manner. As treating employees fairly takes up personal resources such as time, effort, and attention, I argue that when managers face high workloads (i.e., high amounts of work and time pressure), they are unable to devote such personal resources to effectively meet both core technical task requirements and treat employees fairly. I propose that in general, managers tend to view their core technical task performance as more important than being fair in their dealings with employees; as a result, when faced with high workloads, they tend to prioritize the former at the expense of the latter. I also propose that managerial fairness will suffer more as a result of heightened workloads than will core technical task performance, unless managers perceive their organization to explicitly reward fair treatment of employees. I find support for my hypotheses across three studies: two experimental studies (with online participants and students respectively) and one field study of managers from a variety of organizations. I discuss the implications of studying fairness in the wider context of managers’ complex role in organizations to the fairness and managerial work demands literatures.

Violence against Women Policy and Practice in Uganda - Promoting Justice within the Context of Patriarchy

The goal of this study was to understand how and whether policy and practice relating to violence against women in Uganda, especially Uganda’s Domestic Violence Act of 2010, have had an effect on women’s beliefs and practices, as well as on support and justice for women who experience abuse by their male partners. Research used multi-sited ethnography at transnational, national, and local levels to understand the context that affects what policies are developed, how they are implemented, and how, and whether, women benefit from these. Ethnography within a local community situated global and national dynamics within the lives of women. Women who experience VAW within their intimate partnerships in Uganda confront a political economy that undermines their access to justice, even as a women’s rights agenda is working to develop and implement laws, policies, and interventions that promote gender equality and women’s empowerment. This dissertation provides insights into the daily struggles of women who try to utilize policy that challenges duty bearers, in part because it is a new law, but also because it conflicts with the structural patriarchy that is engrained in Ugandan society. Two explanatory models were developed. One explains factors relating to a woman’s decision to seek support or to report domestic violence. The second explains why women do and do not report DV. Among the findings is that a woman is most likely to report abuse under the following circumstances: 1) her own, or her children’s survival (physical or economic) is severely threatened; 2) she experiences severe physical abuse; or, 3) she needs financial support for her children. Research highlights three supportive factors for women who persist in reporting DV. These are: 1) the presence of an “advocate” or support 2) belief that reporting will be helpful; and, 3) lack of interest in returning to the relationship. This dissertation speaks to the role that anthropologists can play in a multi-disciplinary approach to a complex issue. This role is understanding – deeply and holistically; and, articulating knowledge generated locally that provides connections between what happens at global, national and local levels.