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Articles 1 - 20 of 20
Full-Text Articles in Physics
Engaging The Community Through An Undergraduate Biomedical Physics Course, Grace Van Ness, Ralf Widenhorn
Engaging The Community Through An Undergraduate Biomedical Physics Course, Grace Van Ness, Ralf Widenhorn
Physics Faculty Publications and Presentations
We report on the development of an undergraduate biomedical physics course at Portland State University, motivated by both student interest and the desire of the university?s Physics Department to provide an interdisciplinary intermediate-level physics course. The course was developed through the community engagement of physicians, clinical researchers, and basic science researchers. Class meetings were a combination of regular and guest lectures, hands-on exercises, web-based activities, class discussions, and a student poster information session for patrons at a local science museum. The course inspired students to engage in research projects in biomedical physics that enhance their understanding of science and education …
Effects Of Sn Doping On The Morphology And Properties Of Fe-Doped In2o3 Epitaxial Films, Tie Zhou, Lin Wei, Yanru Xie, Qinghao Li, Guoxiang Hu, Yanxue Chen, Shishen Yan, Guolei Liu, Liangmo Mei, Jun Jiao
Effects Of Sn Doping On The Morphology And Properties Of Fe-Doped In2o3 Epitaxial Films, Tie Zhou, Lin Wei, Yanru Xie, Qinghao Li, Guoxiang Hu, Yanxue Chen, Shishen Yan, Guolei Liu, Liangmo Mei, Jun Jiao
Physics Faculty Publications and Presentations
(Sn, Fe)-codoped In₂O₃ epitaxial films were deposited on (111)-oriented Y-stabilized ZrO₂ substrates by pulsed laser deposition with constant Fe concentration and different Sn concentrations. The influence of Sn concentration on the crystal structure and properties of Fe-doped In₂O₃ ferromagnetic semiconductor films has been investigated systematically. Experimental results indicate that Sn doping can effectively reduce the surface roughness and suppresses breakup of the films into separated islands. At the same time, the optical band gap increases and the electrical properties improve correspondingly. However, although the carrier density increases dramatically with the Sn doping, no obvious change of the ferromagnetism is observed. …
Crystallography Open Database (Cod): An Open-Access Collection Of Crystal Structures And Platform For World-Wide Collaboration, Saulius Gražulis, Adriana Daškevič, Andrius Merkys, Daniel Chateigner, Luca Lutterotti, Miguel Quirós, Nadezhda R. Serebryanaya, Peter Moeck, Robert T. Downs, Armel Le Bail
Crystallography Open Database (Cod): An Open-Access Collection Of Crystal Structures And Platform For World-Wide Collaboration, Saulius Gražulis, Adriana Daškevič, Andrius Merkys, Daniel Chateigner, Luca Lutterotti, Miguel Quirós, Nadezhda R. Serebryanaya, Peter Moeck, Robert T. Downs, Armel Le Bail
Physics Faculty Publications and Presentations
Using an open-access distribution model, the Crystallography Open Database (COD, http://www.crystallography.net) collects all known 'small molecule / small to medium sized unit cell' crystal structures and makes them available freely on the Internet. As of today, the COD has aggregated ~150,000 structures, offering basic search capabilities and the possibility to download the whole database, or parts thereof using a variety of standard open communication protocols. A newly developed website provides capabilities for all registered users to deposit published and so far unpublished structures as personal communications or pre-publication depositions. Such a setup enables extension of the COD database by many …
Decay Rates Of A Molecule In The Vicinity Of A Spherical Surface Of An Isotropic Magnetodielectric Material, H. Y. Chung, P.T. Leung, D. P. Tsai
Decay Rates Of A Molecule In The Vicinity Of A Spherical Surface Of An Isotropic Magnetodielectric Material, H. Y. Chung, P.T. Leung, D. P. Tsai
Physics Faculty Publications and Presentations
A comprehensive study is presented on the decay rates of excited molecules in the vicinity of a magnetodielectric material of spherical geometry via electrodynamic modeling. Both the models based on a driven-damped harmonic oscillator and on energy transfers will be applied so that the total decay rates can be rigorously decomposed into the radiative and the nonradiative rates. Clarifications of the equivalence of these two models for arbitrary geometry will be provided. Different possible orientations and locations of the molecule are studied with the molecule being placed near a spherical particle or a cavity. Among other results, TE modes are …
Dark Current Modeling With A Moving Depletion Edge, Justin Charles Dunlap, Morley M. Blouke, Erik Bodegom, Ralf Widenhorn
Dark Current Modeling With A Moving Depletion Edge, Justin Charles Dunlap, Morley M. Blouke, Erik Bodegom, Ralf Widenhorn
Physics Faculty Publications and Presentations
Within a pixel in a digital imager, generally either a chargecoupled device or complementary metal oxide semiconductor device, doping of the semiconductor substrate and application of gate voltages create a region free of mobile carriers called the depletion region. This region fills with charge after incoming photons or thermal energy raise the charges from the valence to the conduction energy band. As the signal charge fills the depletion region, the electric field generating the region is altered, and the size of the region is reduced. We present a model that describes how this dynamic depletion region, along with the location …
Annealing Effect On Photovoltaic Performance Of Cdse Quantum-Dots-Sensitized Tio2 Nanorod Solar Cells, Yitan Li, Lin Wei, Ruizi Zhang, Yanxue Chen, Jun Jiao
Annealing Effect On Photovoltaic Performance Of Cdse Quantum-Dots-Sensitized Tio2 Nanorod Solar Cells, Yitan Li, Lin Wei, Ruizi Zhang, Yanxue Chen, Jun Jiao
Physics Faculty Publications and Presentations
Large area rutile TiO₂ nanorod arrays were grown on F:SnO₂ (FTO) conductive glass using a hydrothermal method at low temperature. CdSe quantum dots (QDs) were deposited onto single-crystalline TiO₂ nanorod arrays by a chemical bath deposition (CBD) method to make a photoelectrode. The solar cell was assembled using a CdSe-TiO₂ nanostructure as the photoanode and polysulfide solution as the electrolyte. The annealing effect on optical and photovoltaic properties of CdSe quantum-dotssensitized TiO₂ nanorod solar cells was studied systematically. A significant change of the morphology and a regular red shift of band gap of CdSe nanoparticles were observed after annealing treatment. …
Controlled Spatial Switching And Routing Of Surface Plasmons In Designed Single-Crystalline Gold Nanostructures, Rolf Kӧnenkamp, Robert Campbell Word, Joseph Fitzgerald, Athavan Nadarajah, S. D. Saliba
Controlled Spatial Switching And Routing Of Surface Plasmons In Designed Single-Crystalline Gold Nanostructures, Rolf Kӧnenkamp, Robert Campbell Word, Joseph Fitzgerald, Athavan Nadarajah, S. D. Saliba
Physics Faculty Publications and Presentations
Electron emission microscopy is used to visualize plasmonic routing in gold nano-structures. We show that in single-crystalline gold structures reliable routing can be achieved with polarization switching. The routing is due to the polarization dependence of the photon-to-plasmon coupling, which controls the mode distribution in the plasmonic gold film. We use specifically designed, single-crystalline planar structures. In these structures, the plasmon propagation length is sufficiently large such that significant plasmon power can be delivered to the near-field region around the end tips of the router. Solid state devices based on internal electron excitation and emission processes appear feasible.
Open Structure Zno/Cdse Core/Shell Nanoneedle Arrays For Solar Cells, Yanxue Chen, Lin Wei, Guanghua Zhang, Jun Jiao
Open Structure Zno/Cdse Core/Shell Nanoneedle Arrays For Solar Cells, Yanxue Chen, Lin Wei, Guanghua Zhang, Jun Jiao
Physics Faculty Publications and Presentations
Open structure ZnO/CdSe core/shell nanoneedle arrays were prepared on a conducting glass (SnO2:F) substrate by solution deposition and electrochemical techniques. A uniform CdSe shell layer with a grain size of approximately several tens of nanometers was formed on the surface of ZnO nanoneedle cores after annealing at 400°C for 1.5 h. Fabricated solar cells based on these nanostructures exhibited a high short-circuit current density of about 10.5 mA/cm2 and an overall power conversion efficiency of 1.07% with solar illumination of 100 mW/cm2. Incident photo-to-current conversion efficiencies higher than 75% were also obtained.
Turbulent Concentration Diffusion In Multiphase Flow, John D. Ramshaw
Turbulent Concentration Diffusion In Multiphase Flow, John D. Ramshaw
Physics Faculty Publications and Presentations
In multifluid multiphase flow models, the velocity of each phase is determined by its own momentum equation, which is coupled to the other phases by pairwise interphase drag forces proportional to velocity differences. When the drag coefficients are large, the phase velocities become nearly equal and the relative motion of the phases becomes diffusional rather than inertial. The multifluid momentum equations then reduce to a single momentum equation for the mixture and a system of linear relations that determine the small residual velocity differences between the phases. We derive such diffusional relations in a very general form that applies to …
A Mean Curvature Model For Capillary Flows In Asymmetric Containers And Conduits, Yongkang Chen, Noël Tavan, Mark M. Weislogel
A Mean Curvature Model For Capillary Flows In Asymmetric Containers And Conduits, Yongkang Chen, Noël Tavan, Mark M. Weislogel
Mechanical and Materials Engineering Faculty Publications and Presentations
Capillarity-driven flows resulting from critical geometric wetting criterion are observed to yield significant shifts of the bulk fluid from one side of the container to the other during "zero gravity" experiments. For wetting fluids, such bulk shift flows consist of advancing and receding menisci sometimes separated by secondary capillary flows such as rivulet-like flows along gaps. Here we study the mean curvature of an advancing meniscus in hopes of approximating a critical boundary condition for fluid dynamics solutions. It is found that the bulk shift flows behave as if the bulk menisci are either “connected” or "disconnected." For the connected …
De Novo Transcriptome Of Safflower And The Identification Of Putative Genes For Oleosin And The Biosynthesis Of Flavonoids, Haiyan Li, Yuanyuan Dong, Jing Yang, Xiuming Liu, Yanfang Wang, Na Yao, Lili Guan, Nan Wang, Jinyu Wu, Xiaokun Li
De Novo Transcriptome Of Safflower And The Identification Of Putative Genes For Oleosin And The Biosynthesis Of Flavonoids, Haiyan Li, Yuanyuan Dong, Jing Yang, Xiuming Liu, Yanfang Wang, Na Yao, Lili Guan, Nan Wang, Jinyu Wu, Xiaokun Li
Physics Faculty Publications and Presentations
Safflower (Carthamus tinctorius L.) is one of the most extensively used oil crops in the world. However, little is known about how its compounds are synthesized at the genetic level. In this study, Solexa-based deep sequencing on seed, leaf and petal of safflower produced a de novo transcriptome consisting of 153,769 unigenes. We annotated 82,916 of the unigenes with gene annotation and assigned functional terms and specific pathways to a subset of them. Metabolic pathway analysis revealed that 23 unigenes were predicted to be responsible for the biosynthesis of flavonoids and 8 were characterized as seed-specific oleosins. In addition, a …
A Locking-Free Hp Dpg Method For Linear Elasticity With Symmetric Stresses, Jamie Bramwell, Leszek Demkowicz, Jay Gopalakrishnan, Weifeng Qiu
A Locking-Free Hp Dpg Method For Linear Elasticity With Symmetric Stresses, Jamie Bramwell, Leszek Demkowicz, Jay Gopalakrishnan, Weifeng Qiu
Mathematics and Statistics Faculty Publications and Presentations
We present two new methods for linear elasticity that simultaneously yield stress and displacement approximations of optimal accuracy in both the mesh size h and polynomial degree p. This is achieved within the recently developed discontinuous Petrov- Galerkin (DPG) framework. In this framework, both the stress and the displacement ap- proximations are discontinuous across element interfaces. We study locking-free convergence properties and the interrelationships between the two DPG methods.
Fundamental Properties Of Functional Zinc Oxide Nanowires Obtained By Electrochemical Method And Their Device Applications, Athavan Nadarajah
Fundamental Properties Of Functional Zinc Oxide Nanowires Obtained By Electrochemical Method And Their Device Applications, Athavan Nadarajah
Dissertations and Theses
We report on the fundamental properties and device applications of semiconductor nanoparticles. ZnO nanowires and CdSe quantum dots were used, prepared, characterized, and assembled into novel light-emitting diodes and solar cells. ZnO nanowire films were grown electrochemically using aqueous soluble chloride-based electrolytes as precursors at temperatures below 90° C. Dopants were added to the electrolyte in the form of chloride compounds, which are AlCl3, CoCl2, CuCl2, and MnCl2. The optical, magnetic, and structural properties of undoped and transition-metal-ion doped ZnO nanowires were explored. Our results indicate that the as-grown nanowire structures have …
Development And Implementation Of Acoustic Feedback Control For Scanning Probe Microscopy, Rodolfo Fernandez Rodriguez
Development And Implementation Of Acoustic Feedback Control For Scanning Probe Microscopy, Rodolfo Fernandez Rodriguez
Dissertations and Theses
A remote-sensing acoustic method for implementing position control feedback in Scanning Probe Microscopy (SPM) is presented. The capabilities of this feedback control using the new Whispering Gallery Acoustic Sensing (WGAS) method is demonstrated in a Shear-force Scanning Probe Microscope that uses a sharp probe attached to a piezoelectric Quartz Tuning Fork (QTF) firmly mounted on the microscope's frame. As the QTF is electrically driven its mechanical response reaches the SPM frame which then acts as a resonant cavity producing acoustic modes measured with an acoustic sensor strategically placed on the SPM head. The novelty of the WGAS resides in using …
Dynamic Ccd Pixel Depletion Edge Model And The Effects On Dark Current Production, Justin Charles Dunlap, Morley M. Blouke, Erik Bodegom, Ralf Widenhorn
Dynamic Ccd Pixel Depletion Edge Model And The Effects On Dark Current Production, Justin Charles Dunlap, Morley M. Blouke, Erik Bodegom, Ralf Widenhorn
Physics Faculty Publications and Presentations
The depletion edge in Charge-Coupled Devices (CCD) pixels is dependent upon the amount of signal charge located within the depletion region. A model is presented that describes the movement of the depletion edge with increasing signal charge. This dynamic depletion edge is shown to have an effect on the amount of dark current produced by some pixels. Modeling the dark current behavior of pixels both with and without impurities over an entire imager demonstrates that this moving depletion edge has a significant effect on a subset of the pixels. Dark current collected by these pixels is shown to behave nonlinearly …
Proton-Fountain Electric-Field-Assisted Nanolithography (Pen): Fabrication Of Polymer Nanostructures That Respond To Chemical And Electrical Stimuli. An Overview In The Context Of The Top-Down And Bottom-Up Approaches To Nanotechnology, Andres H. La Rosa, Mingdi Yan, Rodolfo Fernandez, Elia Zegarra
Proton-Fountain Electric-Field-Assisted Nanolithography (Pen): Fabrication Of Polymer Nanostructures That Respond To Chemical And Electrical Stimuli. An Overview In The Context Of The Top-Down And Bottom-Up Approaches To Nanotechnology, Andres H. La Rosa, Mingdi Yan, Rodolfo Fernandez, Elia Zegarra
Physics Faculty Publications and Presentations
The development of chemically functionalized materials, such that their physical properties can vary in response to external mechanical, chemical, or optical stimuli, offers potential applications in a wide range of fields, namely microfluidics, electronic memory devices, sensors and actuators. In particular, patterned structures built with stimuli-responsive polymer materials are attractive due to their inherent lower cost production and for building soft scaffolds that mimic closer natural bio-environments. In addition, harnessing the construction of patterns with nanoscale dimensions would not only a) allow building lab-on-a-chip devices that require minimal chemical reactants volumes, but also b) find applications in the area of …
Identification Of The Biogenic Compounds Responsible For Size-Dependent Nanoparticle Growth, Paul M. Winkler, John Ortega, Thomas Karl, Luca Cappellin, Hans R. Friedli, Kelley Barsanti, Peter H. Mcmurry, James N. Smith
Identification Of The Biogenic Compounds Responsible For Size-Dependent Nanoparticle Growth, Paul M. Winkler, John Ortega, Thomas Karl, Luca Cappellin, Hans R. Friedli, Kelley Barsanti, Peter H. Mcmurry, James N. Smith
Civil and Environmental Engineering Faculty Publications and Presentations
The probability that freshly nucleated nanoparticles can survive to become cloud condensation nuclei is highly sensitive to particle growth rates. Much of the growth of newly formed ambient nanoparticles can be attributed to oxidized organic vapors originating from biogenic precursor gases. In this study we investigated the chemical composition of size-selected biogenic nanoparticles in the size range from 10 to 40 nm. Particles were formed in a flow tube reactor by ozonolysis ofα-pinene and analyzed with a Thermal Desorption Chemical Ionization Mass Spectrometer. While we found similar composition in 10 and 20 nm particles, the relative amounts of …
Compound Capillary Rise, Mark M. Weislogel
Compound Capillary Rise, Mark M. Weislogel
Mechanical and Materials Engineering Faculty Publications and Presentations
Irregular conduits, complex surfaces, and porous media often manifest more than one geometric wetting condition for spontaneous capillary flows. As a result, different regions of the flow exhibit different rates of flow, all the while sharing common dynamical capillary pressure boundary conditions. The classic problem of sudden capillary rise in tubes with interior corners is revisited from this perspective and solved numerically in the self-similar visco-capillary limit à laLucas–Washburn. Useful closed-form analytical solutions are obtained in asymptotic limits appropriate for many practical flows in conduits containing one or more interior corner. The critically wetted corners imbibe fluid away from …
Electrokinetic Properties Of Lipid And Sarcoplasmic Reticulum Membranes In Aqueous Electrolyte And In The Presence Of Lipophilic Ions, Laura Elizabeth Satterfield
Electrokinetic Properties Of Lipid And Sarcoplasmic Reticulum Membranes In Aqueous Electrolyte And In The Presence Of Lipophilic Ions, Laura Elizabeth Satterfield
Dissertations and Theses
The purpose of this study is the characterization of the membrane-water interfaces of both sarcoplasmic reticulum membrane (SR) and charged lipid bilayers under varied properties of the surrounding aqueous solution. In this work we studied the electrokinetic properties of liposomes and SR vesicles as well as the interaction of lipophilic ions with these membranes. The study of electrokinetic properties is based on the measurements of electrophoretic mobility of SR membrane vesicles and PC/PG liposomes. Electrophoretic mobility of SR vesicles was measured as a function of ionic strength for six pH values (pH 4.0, 4.7, 5.0, 6.0, 7.5, and 9.0). Electrophoretic …
Shaping The Future Past: Finding History, Creating Identity In The Kwan Hsu Papers, Lisa Chere' Donnelly
Shaping The Future Past: Finding History, Creating Identity In The Kwan Hsu Papers, Lisa Chere' Donnelly
Dissertations and Theses
Dr. Kwan Hsu was neither a superstar nor a celebrity. Her name does not come up in conversations about important contributors to her field of biophysics nor is she instantly recognizable for her contributions to Portland State University's international program or the state of Oregon's business ties with China. Yet she was a contributor, a cog-in-the-wheel, at the very least, in all of these areas and more. She was a peripheral member of a well-known Chinese family, but few in the United States know of or perhaps have interest in, but otherwise, she had no great connections or family ties …