Holographic Imaging and Iterative Phase Optimization Methods for Focusing and Transmitting Light in Scattering Media.

Existing methods for focusing and imaging through strongly scattering materials are often limited by speed, the need for invasive feedback, and the shallow depth of penetration of photons into the material. These limitations have motivated the present research into the development of a new iterative phase optimization method for improving transmission of light through a sample of strongly scattering material. A new method, based on the detection of back-scattered light combined with active (phase-only) wavefront control was found to be partially successful, decreasing the power of backscattered incident light at 488 nm wavelength by approximately 35% in a 626 μm thick sample of Yttria (Y2O3) nanopowder (mean particle size 26 nm) in clear epoxy with transport mean free path length ~116 μm. However, the observed transmitted power did not show simultaneous improvement. The conclusion was reached that scattering to the sides of the sample and polarization scrambling were responsible for the lack of improved transmission with this method. Some ideas for improvement are discussed in the thesis. This research subsequently led to the development of a lensless holographic imaging method based on a rotating diffuser for statistical averaging of the optical signal for overcoming speckle caused by reflection from a rough surface. This method made it possible to reduce background variations of intensity due to speckle and improve images reflected from rough, immobile surfaces with no direct path for photons between the object and camera. Improvements in the images obtained with this technique were evaluated quantitatively by comparing SSIM indices and were found to offer practical advances for transmissive and reflective geometries alike.PHDApplied PhysicsUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/135741/1/mjpur_1.pd

Neural processing of semantic content in movies

Naturalistic stimuli, such as movies, contain interacting, multimodal and semantic features and allow for free exploration through eye movements. The full extent of neural responses to features such as motion, film cuts and eye movement behavior has not been established. The main hypothesis of this thesis is that complex multimodal and semantic stimuli in naturalistic movies engage a widespread ensemble of locations across the entire brain. To address this question I analyzed simultaneous intracranial and eyetracking data from over 6,000 electrodes across 23 patients with intractable epilepsy. Responses to fast eye movements – saccades – and film cuts are widespread across the entire brain, while responses to motion are restricted to visual brain areas. Higher-order brain areas respond differentially to semantic and low-level changes across film cuts and saccades. Movies have also recently been used in combination with resting state scans to investigate the utility of functional connectivity as a potential biomarker for psychiatric disorders. Functional connectivity in fMRI data measured during resting state and movie conditions is reliable, subject-specific and related to phenotype. However, it is unclear whether functional connectivity of EEG also possesses these qualities, which are required for the clinical use of neural biomarkers. I hypothesize that functional connectivity networks measured in EEG data recorded during movie watching are a predictor of psychiatric phenotypes similar to functional connectivity of fMRI. I demonstrate that functional connectivity of EEG is reliable, subject-specific and related to phenotypes. However, the patterns of functional connectivity differ in EEG and fMRI, suggesting the measures capture complementary information. In summary, these results demonstrate that the semantic content in movies allows one to study neural processing in naturalistic settings. In addition, EEG functional connectivity recorded during resting state and movie condition is reliabe, subject-specific and related to phenotype

Multimodal information presentation for high-load human computer interaction

This dissertation addresses the question: given an application and an interaction context, how can interfaces present information to users in a way that improves the quality of interaction (e.g. a better user performance, a lower cognitive demand and a greater user satisfaction)? Information presentation is critical to the quality of interaction because it guides, constrains and even determines cognitive behavior. A good presentation is particularly desired in high-load human computer interactions, such as when users are under time pressure, stress, or are multi-tasking. Under a high mental workload, users may not have the spared cognitive capacity to cope with the unnecessary workload induced by a bad presentation. In this dissertation work, the major presentation factor of interest is modality. We have conducted theoretical studies in the cognitive psychology domain, in order to understand the role of presentation modality in different stages of human information processing. Based on the theoretical guidance, we have conducted a series of user studies investigating the effect of information presentation (modality and other factors) in several high-load task settings. The two task domains are crisis management and driving. Using crisis scenario, we investigated how to presentation information to facilitate time-limited visual search and time-limited decision making. In the driving domain, we investigated how to present highly-urgent danger warnings and how to present informative cues that help drivers manage their attention between multiple tasks. The outcomes of this dissertation work have useful implications to the design of cognitively-compatible user interfaces, and are not limited to high-load applications

Neural mechanisms of treatment for mental disorders

“Cognitive control” refers to the ability to regulate thoughts and actions in the service of goals or plans (Braver, 2012). Coordination between the central and peripheral autonomic nervous systems (ANS) maintains arousal and attention levels, which are essential for effective cognitive control. Diamond (2013) proposed a cognitive control model that builds on three core cognitive functions: cognitive flexibility, inhibitory control, and working memory. Abnormality in active inhibitory cognitive control is implicated in a broad range of psychiatric and personality disorders, including schizophrenia, attention deficit hyperactivity disorder (ADHD), impulsivity, and substance abuse, among many others. Transcranial direct current stimulation (tDCS) and cognitive training are two neuromodulation techniques which have the potential to modulate cortical functions to introduce long-lasting neuronal plasticity. The antisaccade task is a visual inhibitory control task frequently used to assess cognitive control. It requires the participant to suppress an automatic stimulus-driven saccadic eye movement and instead make a goal-driven saccade in the opposite direction. In this thesis, by conducting two separate studies, we used the antisaccade task to examine the effect of tDCS and computerised cognitive training on inducing neuroplastic changes for the oculomotor control network (OCN). ‎Chapter 1¢introduces relevant concepts to the subject of this thesis with a technical account of the methods used. The details of the first study are discussed in ‎Chapter 2 - ‎Chapter 4, where we used eye-tracking during antisaccade performance with the continuous assessment of cortical activity using Magnetoencephalography (MEG). Chapter 2 will discuss the short-term neuroplastic changes introduced by the tDCS on the functional connectivity within the resting state networks assessed using MEG. We found evidence of increased connectivity following the engagement in the antisaccade task for both active tDCS and sham conditions, but with different spatial patterns. Following tDCS delivered over the frontal cortex, there was increased connectivity with the frontal cortex. In contrast, in the sham condition there was increased connectivity with the posterior cortex. The effects of tDCS stimulation on the ANS activity during the task performance were further assessed via pupillometry as a measure of Locus Coeruleus (LC) activity in ‎Chapter 3. Our results showed that faster pupil dilation, reflecting increased arousal and sympathetic activity, was associated with faster saccade reaction times. In ‎Chapter 4, we investigated the immediate effects of tDCS stimulation on the cerebral cortex during active cognitive inhibition followed by a correct saccadic response. The tDCS introduced neuromodulatory changes in the putative Alpha and low-Beta band during the anticipatory and post-stimulus periods, reflecting enhanced cortical engagement in a task-beneficial pattern. ‎Chapter 5 reports on the second study in which we used functional magnetic resonance imaging (fMRI) to evaluate the neuromodulatory effects of prolonged computerised cognitive training games (RECOGNeyes) on the resting state functional connectivity of the OCN and pupil dilation. Following gaze-control training, the connectivity within the left hemisphere was strengthened, while the intra-right hemisphere and the interhemispheric connectivity were diminished. ‎Chapter 6 provides a summary of the findings and concluding remarks. Our result furthers our knowledge of the processes involved in the performance of the antisaccade task, the mechanisms of action and the neuroplastic effects of two neuromodulation techniques. However, the exact mechanisms underlying these methods' beneficial effects demand further exploration

Neural mechanisms of treatment for mental disorders

“Cognitive control” refers to the ability to regulate thoughts and actions in the service of goals or plans (Braver, 2012). Coordination between the central and peripheral autonomic nervous systems (ANS) maintains arousal and attention levels, which are essential for effective cognitive control. Diamond (2013) proposed a cognitive control model that builds on three core cognitive functions: cognitive flexibility, inhibitory control, and working memory. Abnormality in active inhibitory cognitive control is implicated in a broad range of psychiatric and personality disorders, including schizophrenia, attention deficit hyperactivity disorder (ADHD), impulsivity, and substance abuse, among many others. Transcranial direct current stimulation (tDCS) and cognitive training are two neuromodulation techniques which have the potential to modulate cortical functions to introduce long-lasting neuronal plasticity. The antisaccade task is a visual inhibitory control task frequently used to assess cognitive control. It requires the participant to suppress an automatic stimulus-driven saccadic eye movement and instead make a goal-driven saccade in the opposite direction. In this thesis, by conducting two separate studies, we used the antisaccade task to examine the effect of tDCS and computerised cognitive training on inducing neuroplastic changes for the oculomotor control network (OCN). ‎Chapter 1¢introduces relevant concepts to the subject of this thesis with a technical account of the methods used. The details of the first study are discussed in ‎Chapter 2 - ‎Chapter 4, where we used eye-tracking during antisaccade performance with the continuous assessment of cortical activity using Magnetoencephalography (MEG). Chapter 2 will discuss the short-term neuroplastic changes introduced by the tDCS on the functional connectivity within the resting state networks assessed using MEG. We found evidence of increased connectivity following the engagement in the antisaccade task for both active tDCS and sham conditions, but with different spatial patterns. Following tDCS delivered over the frontal cortex, there was increased connectivity with the frontal cortex. In contrast, in the sham condition there was increased connectivity with the posterior cortex. The effects of tDCS stimulation on the ANS activity during the task performance were further assessed via pupillometry as a measure of Locus Coeruleus (LC) activity in ‎Chapter 3. Our results showed that faster pupil dilation, reflecting increased arousal and sympathetic activity, was associated with faster saccade reaction times. In ‎Chapter 4, we investigated the immediate effects of tDCS stimulation on the cerebral cortex during active cognitive inhibition followed by a correct saccadic response. The tDCS introduced neuromodulatory changes in the putative Alpha and low-Beta band during the anticipatory and post-stimulus periods, reflecting enhanced cortical engagement in a task-beneficial pattern. ‎Chapter 5 reports on the second study in which we used functional magnetic resonance imaging (fMRI) to evaluate the neuromodulatory effects of prolonged computerised cognitive training games (RECOGNeyes) on the resting state functional connectivity of the OCN and pupil dilation. Following gaze-control training, the connectivity within the left hemisphere was strengthened, while the intra-right hemisphere and the interhemispheric connectivity were diminished. ‎Chapter 6 provides a summary of the findings and concluding remarks. Our result furthers our knowledge of the processes involved in the performance of the antisaccade task, the mechanisms of action and the neuroplastic effects of two neuromodulation techniques. However, the exact mechanisms underlying these methods' beneficial effects demand further exploration

Understanding Stroke in the Connected Human Brain

Although structural damage from stroke is focal, remote dysfunction can occur in regions of the brain distant from the area of damage. Lesions in both gray and white matter can disrupt the flow of information in areas connected to or by the area of infarct. This is because the brain is not an assortment of specialized parts but an assembly of distributed networks that interact to support cognitive function. Functional connectivity analyses using resting functional magnetic resonance imaging (fMRI) have shown us that the cortex is organized into distributed brain networks. The primary goal of this work is to characterize the effects of stroke on distributed brain systems and to use this information to better understand neural correlates of deficit and recovery following stroke. We measured resting functional connectivity, lesion topography, and behavior in multiple domains (attention, visual memory, verbal memory, language, motor, and visual) in a cohort of 132 stroke patients. Patients were followed longitudinally with full behavioral and imaging batteries acquired at 2 weeks, 3 months, and 1 year post-stroke. Thirty age- and demographic- matched controls were scanned twice at an interval of three months. In chapter 1, we explore a central question motivating this work: how is behavior represented in the brain? We review progressing prospective – from basic functional localization to newer theories connecting inter-related brain networks to cognitive operations. In so doing, we attempt to build a foundation that motivates the hypotheses and experimental approaches explored in this work. Chapters 2 and 3 serve primarily to validate approaches and considerations for using resting fMRI to measure functional connectivity in stroke patients. In chapter 2, we investigate hemodynamic lags after stroke. ‘Hemodynamic lag’ is a local delay in the blood oxygen level dependent (BOLD) response to neural activity, measured using cross-correlation of local fMRI signal with some reference brain signal. This work tests assumptions of the BOLD response to neural activity after stroke, but also provides novel and clinically relevant insight into perilesional disruption to hemodynamics. Significant lags are observed in 30% of stroke patients sub-acutely and 10% of patients at one-year. Hemodynamic lag corresponds to gross aberrancy in functional connectivity measures, performance deficits and local and global perfusion deficits. Yet, relationships between functional connectivity and behavior reviewed in chapter 1 persist after hemodynamic delays is corrected for. Chapter 3 provides a more extended discussion of approaches and considerations for using resting fMRI to measure functional connectivity in stroke patients. Like chapter 1, the goal is to motivate experimental approaches taken in later chapters. But here, more technical challenges relating to brain co-registration, neurovascular coupling, and clinical population selection are considered. In chapter 4, we uncover the relationships between local damage, network wide functional disconnection, and neurological deficit. We find that visual memory and verbal memory are better predicted by connectivity, whereas visual and motor deficits are better predicted by lesion topography. Attention and language deficits are well predicted by both. We identify a general pattern of physiological network dysfunction consisting of decrease of inter-hemispheric integration and decrease in intra-hemispheric segregation, which strongly related to behavioral impairment in multiple domains. In chapter 5, we explore a case study of abulia – severe apathy. This work ties together principles of local damage, network disruption, and network-related deficit and demonstrates how they can be useful in understanding and developing targeted treatments (such as transcranial magnetic stimulation) for individual stroke patients. In chapter 6, we explore longitudinal changes in functional connectivity that parallel recovery. We find that the topology and boundaries of cortical regions remains unchanged across recovery, empirically validating our parcel-wise connectivity approach. In contrast, we find that the modularity of brain systems i.e. the degree of integration within and segregation between networks, is significantly reduced after a stroke, but partially recovered over time. Importantly, the return of modular network structure parallels recovery of language and attention, but not motor function. This work establishes the importance of normalization of large-scale modular brain systems in stroke recovery. In chapter 7, we discuss some fundamental revisions of past lesion-deficit frameworks necessitated by recent findings. Firstly, anatomical priors of structural and functional connections are needed to explain why certain lesions across distant locations should share behavioral consequences. Secondly, functional priors of connectomics are needed to explain how local injury can produce widespread disruption to brain connectivity and behavior that have been observed

Aeronautical Engineering, a continuing bibliography with indexes, supplement 173

This bibliography lists 704 reports, articles and other documents introduced into the NASA scientific and technical information system in March 1984

Abstracts on Radio Direction Finding (1899 - 1995)

The files on this record represent the various databases that originally composed the CD-ROM issue of "Abstracts on Radio Direction Finding" database, which is now part of the Dudley Knox Library's Abstracts and Selected Full Text Documents on Radio Direction Finding (1899 - 1995) Collection. (See Calhoun record https://calhoun.nps.edu/handle/10945/57364 for further information on this collection and the bibliography). Due to issues of technological obsolescence preventing current and future audiences from accessing the bibliography, DKL exported and converted into the three files on this record the various databases contained in the CD-ROM. The contents of these files are: 1) RDFA_CompleteBibliography_xls.zip [RDFA_CompleteBibliography.xls: Metadata for the complete bibliography, in Excel 97-2003 Workbook format; RDFA_Glossary.xls: Glossary of terms, in Excel 97-2003 Workbookformat; RDFA_Biographies.xls: Biographies of leading figures, in Excel 97-2003 Workbook format]; 2) RDFA_CompleteBibliography_csv.zip [RDFA_CompleteBibliography.TXT: Metadata for the complete bibliography, in CSV format; RDFA_Glossary.TXT: Glossary of terms, in CSV format; RDFA_Biographies.TXT: Biographies of leading figures, in CSV format]; 3) RDFA_CompleteBibliography.pdf: A human readable display of the bibliographic data, as a means of double-checking any possible deviations due to conversion

Aeronautical engineering: A continuing bibliography with indexes (supplement 289)

This bibliography lists 792 reports, articles, and other documents introduced into the NASA scientific and technical information system in Mar. 1993. Subject coverage includes: design, construction and testing of aircraft and aircraft engines; aircraft components, equipment, and systems; ground support systems; and theoretical and applied aspects of aerodynamics and general fluid dynamics

High-Performance Modelling and Simulation for Big Data Applications

This open access book was prepared as a Final Publication of the COST Action IC1406 “High-Performance Modelling and Simulation for Big Data Applications (cHiPSet)“ project. Long considered important pillars of the scientific method, Modelling and Simulation have evolved from traditional discrete numerical methods to complex data-intensive continuous analytical optimisations. Resolution, scale, and accuracy have become essential to predict and analyse natural and complex systems in science and engineering. When their level of abstraction raises to have a better discernment of the domain at hand, their representation gets increasingly demanding for computational and data resources. On the other hand, High Performance Computing typically entails the effective use of parallel and distributed processing units coupled with efficient storage, communication and visualisation systems to underpin complex data-intensive applications in distinct scientific and technical domains. It is then arguably required to have a seamless interaction of High Performance Computing with Modelling and Simulation in order to store, compute, analyse, and visualise large data sets in science and engineering. Funded by the European Commission, cHiPSet has provided a dynamic trans-European forum for their members and distinguished guests to openly discuss novel perspectives and topics of interests for these two communities. This cHiPSet compendium presents a set of selected case studies related to healthcare, biological data, computational advertising, multimedia, finance, bioinformatics, and telecommunications