193 research outputs found
A Structural and Algorithmic Study of Stable Matching Lattices of "Nearby" Instances, with Applications
No full textRecently [Mai and Vazirani, 2018] identified and initiated work on a new problem, namely understanding structural relationships between the lattices of solutions of two "nearby" instances of stable matching. They also gave an application of their work to finding a robust stable matching. However, the types of changes they allowed in going from instance A to B were very restricted, namely any one agent executes an upward shift.
In this paper, we allow any one agent to permute its preference list arbitrarily. Let M_A and M_B be the sets of stable matchings of the resulting pair of instances A and B, and let ℒ_A and ℒ_B be the corresponding lattices of stable matchings. We prove that the matchings in M_A ∩ M_B form a sublattice of both ℒ_A and ℒ_B and those in M_A ⧵ M_B form a join semi-sublattice. These properties enable us to obtain a polynomial time algorithm for not only finding a stable matching in M_A ∩ M_B, but also for obtaining the partial order, as promised by Birkhoff’s Representation Theorem [Birkhoff, 1937]. As a result, we can generate all matchings in this sublattice.
Our algorithm also helps solve a version of the robust stable matching problem. We discuss another potential application, namely obtaining new insights into the incentive compatibility properties of the Gale-Shapley Deferred Acceptance Algorithm
Design of a Full-Field Optical Coherence Tomography (OCT) 3D-Scene Imaging Setup
No full textOCT is a useful non-destructive imaging technique that does not generate ionizing radiation like other medical imaging techniques (X-ray, CT, PET). Another bonus is that this technique can achieve much higher resolutions than other imaging modalities such as ultrasound or MRI: up to ~10 μm at a sample depth of 1 to 2 mm. OCT is analogous to ultrasound; instead of sound waves reflecting within the sample to generate the image, near-infrared light is used instead. First, two beams are produced from a broadband radiation source – one is passed through the sample while the other remains a reference signal. Upon recombination of the two beams, interference occurs, and the light that was absorbed or reflected by the sample contains the information that is used to generate an image. OCT can be used in a variety of different applications where nondestructive imaging is required. It can be used in industry for material characterization (material thickness in silicon wafers, surface roughness) and it can be used in multiple medical fields: it can image the retina of the eye, coronary arteries, and to detect and diagnose cancer and precancerous lesions. The goal of this project was to design an imaging setup that utilized OCT to measure the topography of centimeter-scale objects that could achieve a spatial resolution of up to approximately 50 micrometers.Electrical and Computer Engineering, Department ofHonors Colleg
Hybrid lunar inflatable structure
No full textBefore man had even stepped foot on the lunar surface, the idea of establishing a base was discussed extensively, be it in science fiction or academia. Although, to this day there has not been an actual base on the Moon, many studies have been conducted regarding design possibilities and environmental impacts. There exists a prevalent challenge in regards to the predictability of the effects the lunar environment has on surface structures. This thesis discusses those aspects of lunar habitats and proposes a new design concept.M.S.Includes bibliographical referencesby Rohith Dronadul
Mid infrared spectroscopic imaging and tomography
No full textFourier Transform Infrared (FT-IR) Spectroscopic Imaging is an optical technique that simultaneously provides morphological (two dimensional) and mid-infrared spectral (one dimensional) information for a specimen under observation. In this dissertation, we develop a new instrument that extends the capabilities of FT-IR imaging to provide three dimensional morphological information along with mid-infrared spectral information on the microscopic length scale. We first demonstrate that spectroscopic information from the mid-infrared can be used to perform histologic recognition and cancer detection in prostate, breast and skin cancer tissues. These studies utilize FT-IR imaging data of thin tissue slices from several hundred patients. The segmentation algorithms and instrumentation used are described in detail. We perform a rigorous analysis of instrumentation and data so as to understand the limits and limitations of current state-of-the-art instrumentation. We then propose a new instrument that adds a new dimension of information to current instruments and establish the new state-of-the-art in mid-infrared imaging. The theoretical basis of such instrumentation is presented in detail and techniques for visualization of four dimensional data are outlined.Item withdrawn by Alexis Thompson ([email protected]) on 2013-02-21T21:53:07Z
Item was in collections:
University of Illinois Theses & Dissertations (ID: 1)
No. of bitstreams: 1
Draft_thesis_8w.pdf: 42631683 bytes, checksum: 360f99c66ac2828c1b3f22bdcb7f998e (MD5)Made available in DSpace on 2013-05-28T19:18:36Z (GMT). No. of bitstreams: 2
Rohith_Reddy.pdf: 42629508 bytes, checksum: 8b431c6483381f8b5e91bfc26a3b8e4a (MD5)
license.txt: 4062 bytes, checksum: b0c50edd2966f9135f5ce3bd13743c87 (MD5)Item marked as restricted to the 'Administrator' Group (id=1) by Seth Robbins ([email protected]) on 2013-05-28T19:21:31Z
Item is restricted until 2015-05-28T19:21:22ZRestriction data tranferred 2014-07-01T11:16:35-05:00
Original Data
Group with Access Administrator
Release Date: 2015-05-28 14:21:22 UTC
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemLimited Restriction Lifted for Item 44734 on 2015-05-28T10:01:02Z
Sparse Deconvolution of Pulsatile Growth Hormone Secretion in Adolescents
No full textGrowth hormone (GH) is secreted by cells in the anterior pituitary on two time scales: discrete pulses over minutes that occur within a 24-hr pattern. Secretion reflects the balance of stimulatory and inhibitory inputs from the hypothalamus and is influenced by gonadal steroids, stress, nutrition, and sleep/wake states. We propose a novel approach for the analysis of GH data and use this approach to quantify (i) the timing, amplitude, and the number of GH pulses and (ii) GH infusion, clearance, and basal secretion (i.e., time-invariant) rates, using serum GH sampled every 10 minutes during an eight-hour sleep study in 18 adolescents. In our method, we approximate hormonal secretory events by deconvolving GH data via a two-step coordinate descent approach. The first step utilizes a sparse-recovery approach to estimate the timing and amplitude of GH secretory events. The second step estimates physiological parameters. Our method identifies the timing and amplitude of GH pulses and system parameters from experimental and simulated data, with a median R2 of 0.93, among experimental data. Recovering GH pulses and model parameters using this approach may improve the quantification of GH parameters under different physiological and pathological conditions and the design and monitoring of interventions.Electrical and Computer Engineering, Department ofHonors Colleg
A System-Theoretic Investigation of Hormone Dynamics in Chronic Fatigue Syndrome, Fibromyalgia Syndrome, and Obesity
No full textFibromyalgia syndrome (FMS), chronic fatigue syndrome (CFS), and obesity are complicated medical disorders with little known etiologies. The purpose of this research is to characterize FMS, CFS, and obesity by studying the variations in hormonal secretion patterns, timings, amplitudes, the number of underlying pulses, as well as infusion and clearance rates of hormones such as cortisol, and leptin. Employing a physiological state-space model with plausible constraints, we estimate the hormonal secretory events and the physiological system parameters (i.e., infusion and clearance rates). The first outcome of our research shows that the clearance rate of cortisol is lower in FMS patients as compared to their matched healthy individuals based on a simplified cortisol secretion model. Moreover, the number, magnitude, and the energy levels of cortisol secretory events are lower in FMS patients. During early morning hours, the magnitude and the energy levels of the cortisol secretory events are higher in CFS patients. Due to the lower cortisol clearance rate, there is a higher accumulation of cortisol in FMS patients as compared to their matched healthy subjects. As the FMS patients accumulate higher cortisol residues, internal inhibitory feedback regulates the hormonal secretory events. Therefore, the FMS patients show a lower number, magnitude, and the energy levels of hormonal secretory events. Though CFS patients have the same number of secretory events, the secretion quantity is lower during early morning hours. When we compare the results for CFS patients against FMS patients, we observe different cortisol alteration patterns. In the second part of this thesis, we propose a simplified minimal leptin secretion model and study the correlation between estimated parameters of leptin and cortisol. The hunger hormone leptin and stress hormone cortisol are closely associated with obesity. Traditionally, a leptin-cortisol antagonism is observed in obese patients. We also observe a leptin-cortisol antagonism when we compare the reconstructed leptin and cortisol levels, hence, further validating the model. The proposed model can potentially be employed to study leptin variations in obese patients against their matched healthy subjects. Characterizing CFS, FMS, and obesity based on the hormonal alterations will help us develop effective methods for treating these disorders.Electrical and Computer Engineering, Department o
Development of Multi-modal Optical Coherence Tomography Imaging Systems and Probes
No full textOptical Coherence Tomography (OCT) is a powerful imaging modality widely used in medical diagnostics and biological research for its non-invasive, high-resolution, and depth-resolved properties. Additionally, OCT has demonstrated remarkable versatility in various applications. In this thesis, we develop multi-modal OCT systems. We have designed and built a new class of endoscopic OCT that enables imaging inside the human body and a new type of functional OCT that provides information beyond structural characteristics. We combine the chemical specificity of mid-infrared spectroscopy with the morphological capabilities of OCT systems, potentially opening a new class of biomedical applications. First, we develop a swept-source OCT (SS-OCT) system that serves as a benchtop tool and a scalable platform for further functional extension. A conventional galvanometer-scanner-based fiber optics SS-OCT system has been developed with an axial resolution of 7.24 μm at 1310 nm, achieving max imaging depth of 5.98 mm in the air. The A-scan rate is 100 kHz defined by the swept-source and lateral resolution of 24.8 μm defined by the scanning objective. The system has demonstrated a high sensitivity of 96.88 dB and low sensitivity roll-off of 0.6 dB over 5.5 mm imaging depth. We demonstrate the utility of SS-OCT in endomicroscopic applications by developing forward and side-viewing probes. Both classes of probes were designed with cost-efficient scanners while maintaining high performance. The side-viewing probes use a 6 mm diameter micro stepper motor and a custom Gradient Index (GRIN) achieving 26 μm lateral resolution and real-time imaging with a frame rate of 100 fps. The forward-viewing probes are built using a piezoelectric (PTZ) cantilever scanner and a micro lens, enabling a 4 mm diameter probe size while achieving a large field of view (2.25 mm2). Finally, we have developed a novel photothermal mid-infrared spectroscopic imaging (MIRSI) OCT technology. Unlike prior approaches, this new form of functional OCT can provide label-free chemical contrast. The system utilizes a pulsed mid-infrared laser to introduce a modulated photothermal signal into the OCT. This technology combines the three-dimensional (3D) morphological imaging capabilities of OCT with the molecular sensitivity of MIRSI through endogenous contrast without adding nanoparticles of contrast agents. Our approach can obtain co-registered OCT and photothermal MIRSI images with a lateral resolution of 21 μm and 15.6 μm, respectively. The 25 and 45 μm polystyrene (PS) beads and biological samples, including mouse kidneys and mouse brains, are used to demonstrate spatial and spectral imaging fidelity
Exploring Nanoscale Energy Conversion and Biometabolism Using Custom Calorimetric Tools
No full textRadiative heat transfer (RHT) between two bodies separated by gaps larger than the thermal wavelength (10 µm at 300 K) occurs through modes that are propagating across the medium separating them, where the total RHT between them is bound by the blackbody limit. RHT beyond this limit is possible with contributions from surface modes, such as evanescent modes or surface phonon/plasmon polaritons. The principal goal of this thesis is to study emerging questions related to radiative heat transport in nanoscale gaps with implications on thermophotovoltaic power generation, thermal management of electronics and calorimetric techniques.
One important question in RHT is what the fundamental limits to near-field enhancements mediated by surface polaritons may be. Recent theoretical studies predicted materials with potential 5-fold enhancement over that of SiO2, a state-of-the-art polar material for RHT. By leveraging high-resolution, micro-fabricated calorimeters in a custom-built nanopositioner, I show in chapter 2 of this thesis that RHT rates up to 3-times larger than SiO2 can be obtained from MgF2 and Al2O3 that have stronger phonon-polariton resonances than SiO2. This represents the first experimental demonstration of enhanced RHT beyond that of SiO2 using dielectric materials and thus, should enable future studies with potential enhancements up to the theoretical limit.
Next, in chapter 3 of this thesis I describe how near-field effects can be employed to achieve novel heat to electricity conversion technologies. Specifically, I explore how thermophotovoltaic technologies—where a hot emitter and a PV cell are employed to convert heat to electricity—can be enhanced by employing near-field effects. I explored this possibility by developing doped-Si microdevices with an integrated platinum heater that could be heated to 400º C. By placing this hot object at a few tens of nanometers away from a commercial photodiode, we demonstrated—for the first time—that ~ 40-times larger power outputs as compared to the far-field can be obtained. Next, I describe how this previous work was extended to explore how the performance of a near-field TPV system can be further enhanced in terms of the power density and efficiency. In order to achieve this, I fabricated silicon microdevices that can endure temperatures up to ~1000 º C. Then, by leveraging the nanopositioner, we placed the silicon heater at known distances away from a thin-film InGaAs PV cell. When the distance was reduced to 100 nm, the total system demonstrated a record-high efficiency of ~6.7% at a power density of 5000 W/m2. Additional improvements can enable several-fold gains in the performance and pave the way for realization of practical devices.
Finally, I describe in chapter 4 how I built a calorimetric tool with 270 pW heat resolution based on calorimetric techniques developed in my RHT studies. This was accomplished by minimizing the thermal conductance of a commercial glass capillary tube down to 27 µW/K and improving the thermometry to an unprecedented 10 µK resolution. Using this tool, we measured metabolic heat outputs from wild-type C. elegans, a biological model organism. Our measurements on daf-2, a variant with an increased lifespan, reveal interesting metabolic shifts as compared to wild-type variant. Thus, we demonstrated for the first time that metabolic rate measurements on living systems can be performed at sub-nanowatt resolution in real time with 270 pW resolution.PhDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/171350/1/mrohith_1.pd
Milling with Ultraviolet Excitation for Large-Scale Tissue Phenotyping
No full textMany chronic diseases, such as cancer and neurodegenerative disorders, correlate with complex changes to tissue microstructure. These include progressive alterations in microvascular structure, cellular distribution, and neural connectivity. Given limitations in the field-of-view of optical microscopes and the lack of a three-dimensional context, profiling these sparse events is extremely difficult to accomplish using traditional histological approaches. While state-of-the-art methods, such as light-sheet microscopy, have been developed to address some of the shortcomings associated with conventional optical methods, they are too slow and costly for routine phenotyping. The development of a scalable, fully automated microscope that eliminates current limitations associated with sectioning, imaging, and registering large-scale imaging data has the potential to tremendously promote studies on phenotyping of vascular and cellular architecture of whole organs. This dissertation focuses on developing a high-throughput imaging methodology capable of multiplex three-dimensional imaging at microscopic resolution. This novel imaging method, dubbed milling with ultraviolet excitation, removes critical constraints limiting imaging volumes by leveraging recent advances in ultraviolet excitation, en bloc labeling, and serial ablation. To this end, a microtome-based prototype is developed and coupled with a series of tissue labeling techniques for deep tissue phenotyping. An analytics pipeline is also proposed for the segmentation and reconstruction of collected data toward in vitro modeling. In addition, a more advanced platform that combines all described innovations is proposed that aims at automated whole-organ phenotyping. The whole research opens the door to routine acquisition and analysis of complete tissue phenotypes for drug discovery and treatment evaluation in low-resource settings
Key Management and Encryption in Wireless Sensor Networks Using Hadamard Transforms
No full textThis thesis deals with key management in wireless sensor networks. The shortcomings of existing schemes include poor resilience against node capture, low secure connectivity and memory overhead. After analyzing the problems in existing key management schemes, a modified model of the Blom's scheme is proposed in this thesis. The new model helps to overcome the prominent problems such as memory cost and computation overhead. The modified key management scheme not only enhances the efficiency of the existing Blom's scheme but also provides a new way of generating keys in wireless sensor networks. In our work, we also propose a new encryption technique which can be used in wireless sensor networks to provide security to the data. The encryption technique can be used either on binary or non-binary data and the chaining strategy used in this scheme makes it difficult for intruders to break the message.Computer Science Departmen
- …
