Browsing by Author "Spillman, William B. Jr."

Now showing 1 - 12 of 12
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    Canine Cancer Screening Via Ultraviolet Absorbance And Fluorescence Spectroscopy Of Serum Proteins
    Dickerson, Bryan Douglas; Geist, Brian L.; Spillman, William B. Jr.; Robertson, John L. (Optical Society of America, 2007-01-01)
    A cost-effective optical cancer screening and monitoring technique was demonstrated in a pilot study of canine serum samples and was patented for commercialization. Compared to conventional blood chemistry analysis methods, more accurate estimations of the concentrations of albumin, globulins, and hemoglobin in serum were obtained by fitting the near UV absorbance and photoluminescence spectra of diluted serum as a linear combination of component reference spectra. Tracking these serum proteins over the course of treatment helped to monitor patient immune response to carcinoma and therapy. For cancer screening, 70% of dogs with clinical presentation of cancer displayed suppressed serum hemoglobin levels (below 20 mg/dL) in combination with atypical serum protein compositions, that is, albumin levels outside of a safe range (from 4 to 8 g/dL) and globulin levels above or below a more normal range (from 1.7 to 3.7 g/dL). Of the dogs that met these criteria, only 20% were given a false positive label by this cancer screening test. (C) 2007 Optical Society of America.
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    Complexity, fractals, disease time, and cancer
    Spillman, William B. Jr.; Robertson, John L.; Huckle, William R.; Govindan, B. S.; Meissner, Kenith E. (American Physical Society, 2004-12)
    Despite many years of research, a method to precisely and quantitatively determine cancer disease state remains elusive. Current practice for characterizing solid tumors involves the use of varying systems of tumor grading and staging and thus leaves diagnosis and clinical staging dependent on the experience and skill of the physicians involved. Although numerous disease markers have been identified, no combination of them has yet been found that produces a quantifiable and reliable measure of disease state. Newly developed genomic markers and other measures based on the developing sciences of complexity offer promise that this situation may soon be changed for the better. In this paper, we examine the potential of two measures of complexity, fractal dimension and percolation, for use as components of a yet to be determined "disease time" vector that more accurately quantifies disease state. The measures are applied to a set of micrographs of progressive rat hepatoma and analyzed in terms of their correlation with cell differentiation, ratio of tumor weight to rat body weight and tumor growth time. The results provide some support for the idea that measures of complexity could be important elements of any future cancer "disease time" vector.
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    Development of Tunable Optical Filters for Interrogation of White-Light Interferometric Sensors
    Yu, Bing (Virginia Tech, 2005-04-28)
    Interferometric fiber optic sensors have been extensively used to measure a large variety of physical, chemical and biomedical parameters due to their superior performance. At the Center for Photonics Technology of Virginia Tech, a variety of interferometric fiber optic sensors have been developed in recent years, for efficient oil recovery, partial discharge detection in high voltage transformers, pressure sensing in gas turbine engines, and temperature measurements in gasifiers and boilers. However, interrogating an interferometric sensor involves accurate recovery of a measurand from the phase-modulated lightwaves, and has been a challenge for high performance, high speed, and low-cost, to current white-light interferometry (WLI) techniques, such as the widely used scanning WLI (S-WLI) and spectral-domain WLI (SD-WLI). The performance of a white-light interferometric sensing system depends not only on the design of the probes, but also, to a great extent, on the interrogation strategy to be used. In this Ph.D. research, a tunable optical filter based WLI (TOF-WLI) is proposed and validated as a low cost, yet high performance, solution to the interrogation of various types of interferometric sensors. In addition to the capability of linear/quadrature demodulation, TOF-WLI retains all the features of WLI, is compatible with the SD-WLI, and can be tailored for both static and wideband signals. It also has great potential in surface metrology and biomedical imaging as well as optical spectroscopy. The key, to the success of this new approach in competition with the other available WLI techniques, is that the tunable optical filter (TOF) must be specially designed for sensing and extremely low cost. Therefore, two novel TOFs, a diffraction grating tunable filter (DG-TOF) and an extrinsic Fabry-Perot tunable filter (EFP-TF), are proposed and demonstrated. Laboratory and field test results on using the DG-TOF WLI for partial discharge and thermal fault detection in high voltage power transformers, and the EFP-TF WLI in temperature sensor systems and a turbine engine monitoring system will also be presented to demonstrate the feasibility for efficient sensor interrogation.
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    Dual Processing Spatially Distributed Integrating Fiber Optic Sensors for Non-intrusive Patient Monitoring
    Xu, Xiaohua (Virginia Tech, 2005-04-21)
    Given the rapid aging of the worldâ s population, improvements in technology for automation of patient care and documentation are badly needed. This project is based on previous research that demonstrated a â smartâ bed that can non-intrusively monitor a patient in bed and determine a patient's respiration, heart rate and movement without intrusive or restrictive medical measurements. The â smartâ bed is an application of spatially distributed integrating fiber optic sensors. The basic concept is that any patient movement that also moves an optical fiber within a specified area will produce a change in the optical signal. A statistical mode (STM) sensor and a high order mode excitation (HOME) sensor were previously investigated, based on which the author developed the present design including both modal modulation approaches. Development was made in both hardware and software for the combined STM/HOME sensor: a special lens system was installed allowing only the high order modes of the optical fiber to be excited and coupled into the sensor; computer-processing method was used for handling output from the dual STM-HOME sensor, which would offer comprehensive perturbation analysis for more reliable patient monitoring. Experimental results of simulating human body breathing and heartbeats by periodic mechanical perturbations are also presented, and the relative advantage and drawbacks of the two modal modulation approaches are discussed.
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    Electro-optic Properties of Semiconductor Nano-crystals And Electro-optic Polymers And Their Applications
    Zhang, Fajian (Virginia Tech, 2002-09-26)
    In recent years, electro-optic polymers have been used to make various optical devices in the telecommunication field due to several advantages, such as large and fast electro-optic (EO) response. Semiconductor nano-crystals promise even higher response speed due to the unique quantum confinement mechanism, and they also show very high EO response because of surface and quantum size effects. Many investigative efforts have been made in the area of semiconductor nano-clusters. These efforts mainly focus on synthesizing high quality particles, and their physical and chemistry properties (luminescence spectra, nonlinear optical, and other effects), but their electro-optic properties and potential uses in devices have not been fully investigated, so there is still much work to do in this aspect. For application of electro-optic polymers in electro-optic devices, the challenges are to develop more stable electro-optic polymers with higher electro-optic coefficients. The electrostatic self-assembly (ESA) technique has many advantages over traditional polymer electro-optic film synthesis processes, such as spin coating. For ESA-generated EO films, no poling field is needed, high orientation of the EO polymer can be obtained which does not degrade with time, so the films can be very stable, and this processing is easily compatible with semiconductor VLSI technology. This is a very attractive technique. The goal of this research is to develop new electro-optic materials by means of ESA techniques and to use them to form improved performance next generation electro-optic devices, with emphasis on two kinds of electro-optic materials: nano-sized II-VI semiconductors (CdS, CdSe), and electro-optic active polymers (chromophores), and their potential use in electro-optic devices. In this research work, II-VI semiconductor nano-clusters have been synthesized, with particle diameters ranging from 4 nm to several tens of nanometers. There is a difference in peak positions of absorption and photo luminescence spectra, related to defects in nano-crystals. Larger CdS particles have larger differences than small CdSe particles. Particle sizes measured by absorption spectrum and by HRTEM methods are very close. Based on quantum mechanical theory, peak spectral shifts as a function of particle size can be predicted, but the theoretical results are typically far from the experimental results, because many complicating factors should be considered. Films fabricated by ESA have much stronger absorption than spin coated films, and exhibit a slight blue shift in peak position wavelength. Photo luminescence spectra also show a blue shift for ESA films with respect to spun films. Polymeric electro-optic films were also fabricated by the ESA technique. Effects due to applying an external electrical field during the ESA process on film growth and properties have also been investigated. Peak position, optical density and wavelength at maximum absorption, all increase with the number of bilayers, and films made under external fields have lower absorption and peak wavelength than those of films fabricated without an external field. These results are related to the order parameter, and indicate that molecule alignment can be improved by the application of an external field during the process of ESA film growth. CdSe nano-clusters have a much higher electro-optic coefficient than their bulk crystal counterparts. In comparison with polymers, they have totally different origins in their electro-optic effects. For both nano-cluster-and chromophore based ESA films, electro-optic coefficients are hi gher than those of spin-coated films, and no poling voltage is needed. The reasons have been fully discussed. This result means that the ESA technique is effective to align and hold the dipoles in films and to intensify the electro-optic effect. CdSe quantum dots need 17. 5 ms to complete their physical orientation due to a rotation of the permanent dipole moment. Therefore, at lower frequencies (<100Hz), electro-optic modulation mainly stems from the orientation of the permanent dipole moment. At frequencies higher than 100 Hz, the electro-optic modulation mainly arises from the induced dipole moment orientation and pure electron movement. The ratio of the electro-optic coefficients r333/r113 > 3. This means that ESA films cannot be treated as an ideal isotropic system with the C v symmetry, and interactions should be considered. Quadratic Kerr electro-optic coefficients have a similar frequency dependence to that of the linear electro-optic coefficients r333 and r113. This indicates that the orientational distribution of the CdSe quantum dots particularly contributes to the quadratic electro-optic modulation. From the FT-IR measurement of the films, proton irradiation can break the N=N double bonding in pi-conjugated bridges, leading to damage of the conjugating structure, so causing a decrease of the EO coefficient. But the thermal and temporal stability of ESA films are much better than those of spin coated films; this is a significant feature of ESA technique. The effect of an external field and film thickness on the optical and electro-optic properties of ESA films has been investigated. Electro-optic coefficient decreases with thickness. Electrical field influences the electronic states of the chromophores. Based on the properties of electro-optic films, the applications of polymer and nano-cluster electro-optic films are discussed. A nano-cluster CdSe electro-optic film has a higher refractive index than the PS-119 polymer film, and these values they are much lower than that of semiconductor wafers, but slightly higher than optical silica glasses. Accordingly optical silica glasses are the ideal substrates for those films. By analysis, the cutoff thickness was determined, which defines the minimum film thickness required for light propagation. For channel waveguides, the aspect ratio w/t, w, and t are determined versus the refractive index of the electro-optic films. Modulator beam length and modulation index were discussed, for high speed operation. Modulator beam length should be carefully chosen to obtain high modulation index; similarly important is the refractive index match between core, substrate, and cladding layers. For high speed operation, traveling wave electrode designs were considered, based on effective refractive index and impedance matching. The effective dielectric constant and characteristic impedance as a function of electrode configuration (sizes) were diagramed, and this served as a basic design suggestion for traveling wave electrodes.
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    ESA based fiber optical humidity sensor
    Chen, Qiao (Virginia Tech, 2002-05-11)
    Several techniques for measuring humidity are presented. The goal of the study is to use the electrostatic self-assembled monolayer synthesis process to fabricate a Fabry-Parot Cavity based optical fiber humidity sensor. The sensing scheme bases on the refractive index change with relative humidity of the film applied to the end of optical fiber. That is, the change in reflected optical power indicates certain humidity. To achieve this, some chemicals induce on specific coating materials were applied at the end of optical fiber. In this thesis, experimental results are given to prove that the humidity sensor has high sensitive and fast response time. Furthermore, we investigate the potential for the use of human breathing monitoring and air flow rate detection. Results from preliminary tests of each are given.
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    Linear Optical Thin Films Formed by Electrostatic Self-Assembly
    Luo, Zhaoju (Virginia Tech, 2000-03-30)
    The Electrostatic Self-Assembly (ESA) technique possesses great advantages over traditional thin film fabrication methods, making it an excellent choice for a number of applications in the fields of linear and nonlinear optics, electronics, sensing and surface coatings. The feasibility of fabricating linear optical interference filters by ESA methods is demonstrated in this thesis work. Basic single-anion/single-cation ESA films are synthesized and their optical parameters -- refractive index and average thickness for individual bilayer -- are investigated to provide a basis for the in-depth design of optical filters. High performance dielectric stack filters and narrowband and wideband antireflection coatings are designed using TFCalc simulation software and are fabricated by ESA. Both bulk film sensitivity and layer sensitivity to manufacturing errors are provided. The significant agreement between simulation and experiment demonstrates the strong capability of ESA to precisely control the refractive index and produce excellent thin film filters. The performance of optical thin film filters is largely enhanced compared to the results of previous methods. The experiment results indicate that the ESA process may be used to fabricate optical filters and other optical structures that require precise index profile control.
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    Optical Communication Systems for Smart Dust
    Song, Yunbin (Virginia Tech, 2002-08-12)
    In this thesis, the optical communication systems for millimeter-scale sensing and communication devises known as "Smart Dust" are described and analyzed. A smart dust element is a self-contained sensing and communication system that can be combined into roughly a cubic-millimeter mote to perform integrated, massively distributed sensor networks. The suitable passive optical and fiber-optic communication systems will be selected for the further performance design and analysis based on the requirements for implementing these systems. Based on the communication link designs of the free-space passive optical and fiber-optic communication systems, the simulations for link performance will be performed.
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    Organometallic Synthesis Kinetics of CdSe Quantum Dots
    Dickerson, Bryan Douglas (Virginia Tech, 2005-04-12)
    CdSe quantum dots produced by organometallic synthesis are useful as tunable emitters for photonic devices and as multi-colored protein markers for biomedical imaging, applications requiring bright and narrow emission. A diffusion-limited model helped monitor growth rates via photoluminescence and absorbance spectroscopy, in order to characterize synthesis kinetics in stearic acid, dodecylamine, and in trioctylphosphine oxide. The nucleation rate increased with Se concentration, while the growth rate followed the Cd concentration. Emission peak widths, emission redshift rates, nanocrystal growth rates, and reactant concentrations all decreased to a minimum when emission reached the critical wavelength, at a reaction completion time, tc. The temperature dependence of 1/tc and of redshift rates followed Arrhenius behavior governed by activation energies, which were tailored by the choice of solvent. Synthesis in solvents, such as stearic acid, with lower activation energies produced faster initial nanocrystal growth and longer critical wavelengths. The highest photoluminescence quantum yield was generally at wavelengths shorter than the critical wavelength, when moderate growth rates enabled surface reconstruction while precursors were still available.
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    Physical Concepts of Copolymerization of Microtubules in the Presence of Anti-mitotic Agents
    Shojania Feizabadi, Mitra (Virginia Tech, 2005-04-29)
    A mathematical approach to the concepts of copolymerization of microtubules in the presence of anti-mitotic drugs is presented in this work. A general feature of the mathematical equations is presented. The possibility of having analytical steady state solutions of dynamic equations is investigated. The structure of equations is narrowed down for the specific brand of anti-mitotic drug, colchicine. The behavior of total T-tubulin concentration in the steady state in a regeneration system is investigated and analyzed through the numerical calculations.
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    Synthesis kinetics of CdSe quantum dots in trioctylphosphine oxide and in stearic acid
    Dickerson, B. D.; Irving, D. M.; Herz, E.; Claus, Richard O.; Spillman, William B. Jr.; Meissner, K. E. (AIP Publishing, 2005-04-01)
    A diffusion-barrier model described the early evolution of size-dependent photoluminescence emission from CdSe quantum dots formed by organometallic synthesis. Emission peak widths, emission redshift rates, and nanocrystal growth rates all decreased to a minimum at a reaction completion time. Growth after the completion time by Ostwald ripening was marked by a doubling of the activation energy. The temperature dependence of both reaction completion rates and photoluminescence redshift rates followed Arrhenius behavior governed by activation energies that increased with solvent molecular weight, in this limited case. In stearic acid and in trioctylphosphine oxide, the typical activation energies were 0.6 +/- 0.1 and 0.92 +/- 0.26 eV/molecule, respectively. (c) 2005 American Institute of Physics.
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    Thermal Cycling And The Optical And Electrical Characterization Of Self-Assembled Multilayer Nile Blue A-Gold Thin Films
    Geist, Brian L.; Spillman, William B. Jr.; Claus, Richard O. (Optical Society of America, 2005-09-01)
    Some laser applications produce high power densities that can be dangerous to equipment and operators. We have fabricated thin-film coatings by using molecular electrostatic self-assembly to create a spectrally selective absorbing coating that is able to withstand thermal fluctuations from -20 degrees C to 120 degrees C. We made the thin-film coatings by alternating deposition of an organic dye and gold colloidal nanoparticles onto glass substrates. Nile Blue A perchlorate, with a maximum absorbance slightly above 632 nm, was chosen as the organic dye. Strong coupling between the dye molecules and the gold nanoparticles provides a redshift that increases as the film's thickness is increased. The incorporation of the gold colloidal nanoparticles also decreases the resistivity of the film. The resistivity of the film was measured with a four-point probe and found to be similar to 10 ohm/cm for the two samples measured. Atomic-force microscopy was used to show that film thickness increased 2.4 nm per bilayer. The optical properties of the film were measured at the end of every 5 thermal cycles from -20 degrees C to 120 degrees C, and negligible degradation was observed after 30 cycles. (c) 2005 Optical Society of America