An optical fiber-taper probe for wafer-scale microphotonic device characterization

A small depression is created in a straight optical fiber taper to form a local probe suitable for studying closely spaced, planar microphotonic devices. The tension of the "dimpled" taper controls the probe-sample interaction length and the level of noise present during coupling measurements. Practical demonstrations with high-Q silicon microcavities include testing a dense array of undercut microdisks (maximum Q = 3.3x10^6) and a planar microring (Q = 4.8x10^6).Comment: 8 pages, 5 figures, for high-res version see http://copilot.caltech.edu/publications/index.ht

Linking consumer satisfaction to consumer behavior and retailer revenues: an empirical analysis of e-commerce performance influencers

The aim of this research was to develop a validated set of actions that would lead to sustainable improvements in business performance and consumer attitudes for a production e-commerce website in the United States. In order to achieve the research objective a participatory action research methodology was utilized to generate quantitative and qualitative data and analysis through a mixed-methods approach. At completion, this effort was responsible for the development of new organizational knowledge and a series of managerial and business practice changes. The resulting business practice changes were credited with both short and longer-term business performance improvements. From an academic perspective, this research is one of the first to test a number of literature supported theories at real-world scale on a production e-commerce website. Of particular note are findings that extend the extant research into website consumer satisfaction measurement and the relationship between consumer feedback recency and issue identification. This thesis also highlights the importance of action research as a catalyst for organizational and individual meta-learning

This Is My Neighborhood: An Exploration of Culturally Relevant Agency to Support High School Latinx Students in an Urban Career Academy

The purpose of this study was to explore the perspectives and strategies internal and external stakeholders used to support students in a career academy serving a predominately Latinx community. Within this case study, the principal of the school was Latinx, grew up within the same community as the school, and therefore shared the same culture as his students. Thus, we wondered how effective the principal would be in overcoming the cultural, political, and social barriers of students in the predominately Latinx school. We found the school leaders had a heightened awareness of organizational, cultural, and political complexities because of their own personal investment as well as their lived experiences of living and growing up in the community. The identities of the school leaders, then, led to a collective sense of agency and transformational leadership practices that facilitated a change in the grim situations and prospects of their students, and motivated them to become role models and community leaders providing resources and supports to ensure the high academic performance of students in the academy. However, we also realized that cultural understanding may sometimes lead to parochial views on what is best for students, leading to practices that prevent the exploration of student options beyond high school

Polycystic ovarian syndrome: pathogenesis and management

Polycystic ovarian syndrome (PCOS) is an endocrine disorder that commonly affects women of reproductive age. Its prevalence varies quite significantly and its clinical presentation includes: reproductive, metabolic and psychological issues.  PCOS develops due to a variety of factors some of which are not yet fully understood. Due to the complexity in the development and presentation of this condition, the management of PCOS in most instances is complicated and involves the combination of pharmacological, non-pharmacological and surgical interventions. This review discusses the pathogenesis and management of PCOS as means of providing information that would enhance understanding and control of this disease

Working Memory Load-related Theta Power Decreases in Dorsolateral Prefrontal Cortex Predict Individual Differences in Performance

Holding information in working memory (WM) is an active and effortful process that is accompanied by sustained load-dependent changes in oscillatory brain activity. These proportional power increases are often reported in EEG studies recording theta over frontal midline sites. Intracranial recordings, however, yield mixed results, depending on the brain area being recorded from. We recorded intracranial EEG with depth electrodes in 13 patients with epilepsy that were performing a Sternberg WM task. Here, we investigated patterns of theta power changes as a function of memory load during maintenance in three areas critical for WM: dorsolateral prefrontal cortex (DLPFC), dorsal ACC (dACC), and hippocampus. Theta frequency power in both hippocampus and dACC increased during maintenance. In contrast, theta frequency power in the DLPFC decreased during maintenance, and this decrease was proportional to memory load. Only the power decreases in DLPFC, but not the power increases in hippocampus and dACC, were predictive of behavior in a given trial. The extent of the load-related theta power decreases in the DLPFC in a given participant predicted a participant's RTs, revealing that DLPFC theta explains individual differences in WM ability between participants. Together, these data reveal a pattern of theta power decreases in the DLPFC that is predictive of behavior and that is opposite of that in other brain areas. This result suggests that theta band power changes serve different cognitive functions in different brain areas and specifically that theta power decreases in DLPFC have an important role in maintenance of information

Working Memory Load-related Theta Power Decreases in Dorsolateral Prefrontal Cortex Predict Individual Differences in Performance

Holding information in working memory (WM) is an active and effortful process that is accompanied by sustained load-dependent changes in oscillatory brain activity. These proportional power increases are often reported in EEG studies recording theta over frontal midline sites. Intracranial recordings, however, yield mixed results, depending on the brain area being recorded from. We recorded intracranial EEG with depth electrodes in 13 patients with epilepsy that were performing a Sternberg WM task. Here, we investigated patterns of theta power changes as a function of memory load during maintenance in three areas critical for WM: dorsolateral prefrontal cortex (DLPFC), dorsal ACC (dACC), and hippocampus. Theta frequency power in both hippocampus and dACC increased during maintenance. In contrast, theta frequency power in the DLPFC decreased during maintenance, and this decrease was proportional to memory load. Only the power decreases in DLPFC, but not the power increases in hippocampus and dACC, were predictive of behavior in a given trial. The extent of the load-related theta power decreases in the DLPFC in a given participant predicted a participant's RTs, revealing that DLPFC theta explains individual differences in WM ability between participants. Together, these data reveal a pattern of theta power decreases in the DLPFC that is predictive of behavior and that is opposite of that in other brain areas. This result suggests that theta band power changes serve different cognitive functions in different brain areas and specifically that theta power decreases in DLPFC have an important role in maintenance of information

Extent of single-neuron activity modulation by hippocampal interictal discharges predicts declarative memory disruption in humans

Memory deficits are common in epilepsy patients. In these patients, the interictal EEG commonly shows interictal epileptiform discharges (IEDs). While IEDs are associated with transient cognitive impairments, it remains poorly understood why this is. We investigated the effects of human (male and female) hippocampal IEDs on single-neuron activity during a memory task in patients with medically refractory epilepsy undergoing depth electrode monitoring. We quantified the effects of hippocampal IEDs on single-neuron activity and the impact of this modulation on subjectively declared memory strength. Across all recorded neurons, the activity of 50 of 728 neurons were significantly modulated by IEDs, with the strongest modulation in the medial temporal lobe (33 of 416) and in particular the right hippocampus (12 of 58). Putative inhibitory neurons, as identified by their extracellular signature, were more likely to be modulated by IEDs than putative excitatory neurons (19 of 157 vs 31 of 571). Behaviorally, the occurrence of hippocampal IEDs was accompanied by a disruption of recognition of familiar images only if they occurred up to 2 s before stimulus onset. In contrast, IEDs did not impair encoding or recognition of novel images, indicating high temporal and task specificity of the effects of IEDs. The degree of modulation of individual neurons by an IED correlated with the declared confidence of a retrieval trial, with higher firing rates indicative of reduced confidence. Together, these data link the transient modulation of individual neurons by IEDs to specific declarative memory deficits in specific cell types, thereby revealing a mechanism by which IEDs disrupt medial temporal lobe-dependent declarative memory retrieval processes