140 research outputs found

    Development of Quantitative Phase Imaging for Temporal and Spectral Analysis of Dynamic Microscopic Samples

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    <p>Microscopic objects such as biological cells produce only minor modulation in the intensity of transmitted light, leading many researchers to add exogenous contrast agents for image enhancement. However, cells and other semitransparent objects that have not been chemically modified impart phase delays to the transmitted electromagnetic fields, which can be measured using interferometric microscopy methods. In this dissertation, instrumentation and methods are developed to investigate the spatiotemporal dynamics and spectral signatures of individual cells and semitransparent polymer film samples.</p><p>An off-axis quantitative phase microscope is applied to (1) quantitatively image the two-dimensional refractive index distributions of microbicide films undergoing hydration and compare effects of thickness and composition on dissolution dynamics, and (2) investigate the morphological and volumetric changes of individual RBCs undergoing mechanical flow stresses in <italic>in vitro</italic> models of capillaries. The quantitative phase microscope is further modified to capture high-resolution hyperspectral holographic phase and amplitude images. This novel hyperspectral imaging system is applied to compare the sensitivity of phase-based and amplitude-based spectral quantification of optically-absorbing molecules, and then used to measure spectroscopic changes in RBCs that take place during infection by <italic>P. falciparum</italic> parasites.</p><p>Measurements of an object's optical volume, which is defined as a novel metric for characterizing objects whose refractive index and thickness profiles are not known a priori. The composition and thickness of microbicide films are both found to impact spatiotemporal dissolution kinetics. A comparison of fluorophore concentration determination by amplitude and phase spectra indicates that both methods of quantification have comparable sensitivity, and that the two may be combined to improve the precision of quantity determination. Both optical volume and hemoglobin mass measurements are seen to decrease in cells infected by <italic>P. falciparum</italic>, although the two metrics are only loosely correlated. Finally, RBCs flowing through in vitro capillary models exhibit large changes in optical volume when deforming in response to mechanical stresses, which is attributed to a combination of cytosolic volume changes as well as conformational changes in the intracellular protein configuration.</p><p>These results demonstrate the applicability of QPM as a tool for evaluating (1) microbicide film performance, (2) spectroscopic changes in infected individual RBCs, and (3) novel biophysical changes observed in RBCs under mechanical stresses.</p>Dissertatio

    An Overview of Second Language Acquisition

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    Demonstration of the Wide-Field Imaging Interferometer Testbed Using a Calibrated Hyperspectral Image Projector

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    The Wide-field Imaging Interferometer testbed (WIIT) at NASA's Goddard Space Flight Center uses a dual-Michelson interferometric technique. The WIIT combines stellar interferometry with Fourier-transform interferometry to produce high-resolution spatial-spectral data over a large field-of-view. This combined technique could be employed on future NASA missions such as the Space Infrared Interferometric Telescope (SPIRIT) and the Sub-millimeter Probe of the Evolution of Cosmic Structure (SPECS). While both SPIRIT and SPECS would operate at far-infrared wavelengths, the WIIT demonstrates the dual-interferometry technique at visible wavelengths. The WIIT will produce hyperspectral image data, so a true hyperspectral object is necessary. A calibrated hyperspectral image projector (CHIP) has been constructed to provide such an object. The CHIP uses Digital Light Processing (DLP) technology to produce customized, spectrally-diverse scenes. CHIP scenes will have approximately 1.6-micron spatial resolution and the capability of . producing arbitrary spectra in the band between 380 nm and 1.6 microns, with approximately 5-nm spectral resolution. Each pixel in the scene can take on a unique spectrum. Spectral calibration is achieved with an onboard fiber-coupled spectrometer. In this paper we describe the operation of the CHIP. Results from the WIIT observations of CHIP scenes will also be presented

    Quantitative Analysis of Biological Cells Using Digital Holographic Microscopy

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    Biological cells are microscopic dynamic objects, continuously adjusting their threedimensional sizes, shapes and other biophysical features. Wide-field microscopy of cell dynamics can provide a powerful research tool for cell biology studies, as well as a potential means for medical diagnosis and monitoring of diseases. Biological cells, however, ar

    Association between furosemide in premature infants and sensorineural hearing loss and nephrocalcinosis: a systematic review

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    Abstract Furosemide is a potent loop diuretic commonly and variably used by neonatologists to improve oxygenation and lung compliance in premature infants. There are several safety concerns with use of furosemide in premature infants, specifically the risk of sensorineural hearing loss (SNHL), and nephrocalcinosis/nephrolithiasis (NC/NL). We conducted a systematic review of all trials and observational studies examining the association between these outcomes with exposure to furosemide in premature infants. We searched MEDLINE, EMBASE, CINAHL, and clinicaltrials.gov . We included studies reporting either SNHL or NC/NL in premature infants (< 37 weeks completed gestational age) who received at least one dose of enteral or intravenous furosemide. Thirty-two studies met full inclusion criteria for the review, including 12 studies examining SNHL and 20 studies examining NC/NL. Only one randomized controlled trial was identified in this review. We found no evidence that furosemide exposure increases the risk of SNHL or NC/NL in premature infants, with varying quality of studies and found the strength of evidence for both outcomes to be low. The most common limitation in these studies was the lack of control for confounding factors. The evidence for the risk of SNHL and NC/NL in premature infants exposed to furosemide is low. Further randomized controlled trials of furosemide in premature infants are urgently needed to adequately assess the risk of SNHL and NC/NL, provide evidence for improved FDA labeling, and promote safer prescribing practices.https://deepblue.lib.umich.edu/bitstream/2027.42/146523/1/40748_2018_Article_92.pd

    Development of a proxy-reported pulmonary outcome scale for preterm infants with bronchopulmonary dysplasia

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    <p>Abstract</p> <p>Background</p> <p>To develop an accurate, proxy-reported bedside measurement tool for assessment of the severity of bronchopulmonary dysplasia (also called chronic lung disease) in preterm infants to supplement providers' current biometric measurements of the disease.</p> <p>Methods</p> <p>We adapted Patient-Reported Outcomes Measurement Information System (PROMIS) methodology to develop the Proxy-Reported Pulmonary Outcomes Scale (PRPOS). A multidisciplinary group of registered nurses, nurse practitioners, neonatologists, developmental specialists, and feeding specialists at five academic medical centers participated in the PRPOS development, which included five phases: (1) identification of domains, items, and responses; (2) item classification and selection using a modified Delphi process; (3) focus group exploration of items and response options; (4) cognitive interviews on a preliminary scale; and (5) final revision before field testing.</p> <p>Results</p> <p>Each phase of the process helped us to identify, classify, review, and revise possible domains, questions, and response options. The final items for field testing include 26 questions or observations that a nurse assesses before, during, and after routine care time and feeding.</p> <p>Conclusions</p> <p>We successfully created a prototype scale using modified PROMIS methodology. This process can serve as a model for the development of proxy-reported outcomes scales in other pediatric populations.</p

    The Wide-Field Spatio-Spectral Interferometer: System Overview, Data Synthesis and Analysis

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    The Wide-field Imaging Interferometry Testbed (WIIT) is a double Fourier (DF) interferometer operating at optical wavelengths, and provides data that are highly representative of those from a space-based far-infrared interferometer like SPIRIT. We have used the testbed to observe both geometrically simple and astronomically representative test scenes. Here we present an overview of the astronomical importance of high angular resolution at the far infrared, followed by the description of the optical set-up of WIIT, including the source simulator CHIP (Calibrated Hyperspectral Image Projector). We describe our synthesis algorithms used in the reconstruction of the input test scenes via a simulation of the most recent measurements. The updated algorithms, which include instruments artifacts that allow the synthesis of DF experimental data, are presented and the most recent results analyzed

    Recent Experiments Conducted with the Wide-Field Imaging Interferometry Testbed (WIIT)

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    The Wide-field Imaging Interferometry Testbed (WIIT) was developed at NASA's Goddard Space Flight Center to demonstrate and explore the practical limitations inherent in wide field-of-view double Fourier (spatio-spectral) interferometry. The testbed delivers high-quality interferometric data and is capable of observing spatially and spectrally complex hyperspectral test scenes. Although WIIT operates at visible wavelengths, by design the data are representative of those from a space-based far-infrared observatory. We used WIIT to observe a calibrated, independently characterized test scene of modest spatial and spectral complexity, and an astronomically realistic test scene of much greater spatial and spectral complexity. This paper describes the experimental setup, summarizes the performance of the testbed, and presents representative data

    Developing Wide-Field Spatio-Spectral Interferometry for Far-Infrared Space Applications

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    Interferometry is an affordable way to bring the benefits of high resolution to space far-IR astrophysics. We summarize an ongoing effort to develop and learn the practical limitations of an interferometric technique that will enable the acquisition of high-resolution far-IR integral field spectroscopic data with a single instrument in a future space-based interferometer. This technique was central to the Space Infrared Interferometric Telescope (SPIRIT) and Submillimeter Probe of the Evolution of Cosmic Structure (SPECS) space mission design concepts, and it will first be used on the Balloon Experimental Twin Telescope for Infrared Interferometry (BETTII). Our experimental approach combines data from a laboratory optical interferometer (the Wide-field Imaging Interferometry Testbed, WIIT), computational optical system modeling, and spatio-spectral synthesis algorithm development. We summarize recent experimental results and future plans
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