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2012

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Articles 31 - 60 of 277

Full-Text Articles in Nanoscience and Nanotechnology

Nonlinear Dynamics Of The Atomic Force Microscope At The Liquid-Solid Interface, Daniel Kiracofe, Arvind Raman Nov 2012

Nonlinear Dynamics Of The Atomic Force Microscope At The Liquid-Solid Interface, Daniel Kiracofe, Arvind Raman

Birck and NCN Publications

The measurement of intermolecular forces at the liquid-solid interface is key to many studies of electrochemistry, wetting, catalysis, biochemistry, and mechanobiology. The atomic force microscope (AFM) is unique in its ability to measure and map these forces with nanometer resolution using the oscillating sharp tip of an AFM cantilever. These surface forces are only measured by observing the changes they induce in the dynamics of the resonant AFM probe. However, AFM cantilever dynamics at this interface can be significantly different when compared to air/vacuum environments due to the nature of nanoscale forces at the interface and the low-quality factors in …

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Nanobarcoding: Detecting Nanoparticles In Biological Samples Using In Situ Polymerase Chain Reaction, Trisha Eustaquio, James F. Leary Nov 2012

Nanobarcoding: Detecting Nanoparticles In Biological Samples Using In Situ Polymerase Chain Reaction, Trisha Eustaquio, James F. Leary

Birck and NCN Publications

Background: Determination of the fate of nanoparticles (NPs) in a biological system, or NP biodistribution, is critical in evaluating an NP formulation for nanomedicine. Current methods to determine NP biodistribution are greatly inadequate, due to their limited detection thresholds. Herein, proof of concept of a novel method for improved NP detection based on in situ polymerase chain reaction (ISPCR), coined "nanobarcoding," is demonstrated. Methods: Nanobarcoded superparamagnetic iron oxide nanoparticles (NB-SPIONs) were characterized by dynamic light scattering, zeta potential, and hyperspectral imaging - measurements. Cellular uptake of Cy5-labeled NB-SPIONs (Cy5-NB-SPIONs) was imaged by confocal microscopy. The feasibility of the nanobarcoding method …

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Modeling And Simulation Of Pressure Waves Generated By Nano-Thermite Reactions, Karen S. Martirosyan, Maxim Zyskin, Charles M. Jenkins, Yasuyuki Horie Nov 2012

Modeling And Simulation Of Pressure Waves Generated By Nano-Thermite Reactions, Karen S. Martirosyan, Maxim Zyskin, Charles M. Jenkins, Yasuyuki Horie

Physics and Astronomy Faculty Publications and Presentations

This paper reports the modeling of pressure waves from the explosive reaction of nano-thermites consisting of mixtures of nanosized aluminum and oxidizer granules. Such nanostructured thermites have higher energy density (up to 26 kJ/cm3) and can generate a transient pressure pulse four times larger than that from trinitrotoluene (TNT) based on volume equivalence. A plausible explanation for the high pressure generation is that the reaction times are much shorter than the time for a shock wave to propagate away from the reagents region so that all the reaction energy is dumped into the gaseous products almost instantaneously and thereby a …

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A Study Of Anodization Process During Pore Formation In Nanoporous Alumina Templates, Z. Wu, C. Richter, L. Menon Oct 2012

A Study Of Anodization Process During Pore Formation In Nanoporous Alumina Templates, Z. Wu, C. Richter, L. Menon

Latika Menon

We have carried out a systematic investigation of the anodization procedure in order to determine the exact chemical mechanism of the dissolution process responsible for pore formation in nanoporous alumina templates. We measured the anodization current as a function of time and compared it with the thickness of porous aluminum oxide layer obtained from cross-section scanning electron microscopy images. From this, we calculated the number of moles of electrons generated per mole of porous alumina grown. This analysis is consistent with a reaction mechanism in which aluminum is converted to aluminum oxide in addition with the direct transfer of aluminum …

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Size Dependence Of Energetic Properties In Nanowire-Based Energetic Materials, L. Menon, D. Aurongzeb, S. Patibandla, K. Bhargava Ram, C. Richter, A. Sacco Oct 2012

Size Dependence Of Energetic Properties In Nanowire-Based Energetic Materials, L. Menon, D. Aurongzeb, S. Patibandla, K. Bhargava Ram, C. Richter, A. Sacco

Latika Menon

We prepared nanowire-array-based thin film energetic nanocomposites based on Al–Fe₂O₃. The ignition properties as a function of wire dimensions and interwire spacing have been investigated. We show significant variations in ignition behavior, which we relate to the kinetic and heat transfer dynamics of the various configurations studied. Our results indicate the possibility for nanoscale control of reaction parameters such as flame temperature and burn rate in such composites for optimized configurations (optimum wire size, interwire spacing, film thickness, etc.).

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Negative Index Metamaterials Based On Metal-Dielectric Nanocomposites For Imaging Applications, L. Menon, W. T. Lu, A. L. Friedman, S. P. Bennett, D. Heiman, S. Sridhar Oct 2012

Negative Index Metamaterials Based On Metal-Dielectric Nanocomposites For Imaging Applications, L. Menon, W. T. Lu, A. L. Friedman, S. P. Bennett, D. Heiman, S. Sridhar

Srinivas Sridhar

Negative index metamaterials are demonstrated based on metal-dielectric nanocomposites prepared using a versatile bottom-up nanofabrication approach. The method involves the incorporation of vertically aligned metal nanowires such as Au and Ag inside dielectric aluminum oxide nanotemplates. Optical absorbance measurements show resonance peaks corresponding to the transverse and longitudinal surface plasmon modes. A quantitative model based on effective medium theory is in excellent agreement with experimental data, and points to specific composite configurations and wavelength regimes where such structures can have applications as negative refraction media for imaging.

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Possible Room-Temperature Ferromagnetism In Hydrogenated Carbon Nanotubes, Adam L. Friedman, Hyunkyung Chun, Yung Joon Jung, Don Heiman, Evan R. Glaser, Latika Menon Oct 2012

Possible Room-Temperature Ferromagnetism In Hydrogenated Carbon Nanotubes, Adam L. Friedman, Hyunkyung Chun, Yung Joon Jung, Don Heiman, Evan R. Glaser, Latika Menon

Yung Joon Jung

We find that ferromagnetism can be induced in carbon nanotubes (CNTs) by introducing hydrogen. Multiwalled CNTs grown inside porous alumina templates contain a large density of defects resulting in significant hydrogen uptake when annealed at high temperatures. This hydrogen incorporation produces H-complex and adatom magnetism which generates a sizable ferromagnetic moment and a Curie temperature near TC=1000  K. We studied the conditions for the incorporation of hydrogen, the temperature-dependent magnetic behavior, and the dependence of the ferromagnetism on the size of the nanotubes.

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Possible Room-Temperature Ferromagnetism In Hydrogenated Carbon Nanotubes, Adam L. Friedman, Hyunkyung Chun, Yung Joon Jung, Don Heiman, Evan R. Glaser, Latika Menon Oct 2012

Possible Room-Temperature Ferromagnetism In Hydrogenated Carbon Nanotubes, Adam L. Friedman, Hyunkyung Chun, Yung Joon Jung, Don Heiman, Evan R. Glaser, Latika Menon

Donald Heiman

We find that ferromagnetism can be induced in carbon nanotubes (CNTs) by introducing hydrogen. Multiwalled CNTs grown inside porous alumina templates contain a large density of defects resulting in significant hydrogen uptake when annealed at high temperatures. This hydrogen incorporation produces H-complex and adatom magnetism which generates a sizable ferromagnetic moment and a Curie temperature near TC=1000  K. We studied the conditions for the incorporation of hydrogen, the temperature-dependent magnetic behavior, and the dependence of the ferromagnetism on the size of the nanotubes.

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Negative Index Metamaterials Based On Metal-Dielectric Nanocomposites For Imaging Applications, L. Menon, W. T. Lu, A. L. Friedman, S. P. Bennett, D. Heiman, S. Sridhar Oct 2012

Negative Index Metamaterials Based On Metal-Dielectric Nanocomposites For Imaging Applications, L. Menon, W. T. Lu, A. L. Friedman, S. P. Bennett, D. Heiman, S. Sridhar

Donald Heiman

Negative index metamaterials are demonstrated based on metal-dielectric nanocomposites prepared using a versatile bottom-up nanofabrication approach. The method involves the incorporation of vertically aligned metal nanowires such as Au and Ag inside dielectric aluminum oxide nanotemplates. Optical absorbance measurements show resonance peaks corresponding to the transverse and longitudinal surface plasmon modes. A quantitative model based on effective medium theory is in excellent agreement with experimental data, and points to specific composite configurations and wavelength regimes where such structures can have applications as negative refraction media for imaging.

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Optimal Parameters For Synthesis Of Magnetic Nanowires In Porous Alumina Templates: Electrodeposition Study, Adam L. Friedman, Latika Menon Oct 2012

Optimal Parameters For Synthesis Of Magnetic Nanowires In Porous Alumina Templates: Electrodeposition Study, Adam L. Friedman, Latika Menon

Latika Menon

We have carried out a systematic study of the electrodeposition process to understand the effect of varying three important quantities on the synthesis of nanowires inside porous alumina templates. We have electrodeposited iron nanowires inside porous alumina to determine the optimal settings of these variables to induce effective and efficient nanowire growth. First, we vary the pH of the electrolyte solution to show that pH has little effect on the deposition rate. Second, we vary the magnitude of the applied ac voltage to show that the deposition rate increases with increasing voltage. Finally, we vary the frequency of the applied …

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Negative Index Metamaterials Based On Metal-Dielectric Nanocomposites For Imaging Applications, L. Menon, W. T. Lu, A. L. Friedman, S. P. Bennett, D. Heiman, S. Sridhar Oct 2012

Negative Index Metamaterials Based On Metal-Dielectric Nanocomposites For Imaging Applications, L. Menon, W. T. Lu, A. L. Friedman, S. P. Bennett, D. Heiman, S. Sridhar

Latika Menon

Negative index metamaterials are demonstrated based on metal-dielectric nanocomposites prepared using a versatile bottom-up nanofabrication approach. The method involves the incorporation of vertically aligned metal nanowires such as Au and Ag inside dielectric aluminum oxide nanotemplates. Optical absorbance measurements show resonance peaks corresponding to the transverse and longitudinal surface plasmon modes. A quantitative model based on effective medium theory is in excellent agreement with experimental data, and points to specific composite configurations and wavelength regimes where such structures can have applications as negative refraction media for imaging.

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Magnetic Properties Of Gamnas Nanodot Arrays Fabricated Using Porous Alumina Templates, S. P. Bennett, L. Menon, D. Heiman Oct 2012

Magnetic Properties Of Gamnas Nanodot Arrays Fabricated Using Porous Alumina Templates, S. P. Bennett, L. Menon, D. Heiman

Latika Menon

Ordered arrays of GaMnAs magnetic semiconductor nanodots have been fabricated using anodic porous alumina templates as etch masks. The magnetic behavior is studied for prepared arrays with 40 nm dot diameter, 15 nm dot thickness, and 80 nm periodicity. The disklike nanodots exhibit an easy axis for fields applied in the radial direction and a hard axis in the smaller direction. In the radial direction superparamagnetism is observed with a blocking temperature of 30 K. The fabrication technique is convenient for preparing nanodot arrays of compound semiconductors that cannot be formed by self-assembly techniques.

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Super-Resolution Imaging Using A Three-Dimensional Metamaterials Nanolens, B. D. F. Casse, W. T. Lu, Y. J. Huang, E. Gultepe, L. Menon, S. Sridhar Oct 2012

Super-Resolution Imaging Using A Three-Dimensional Metamaterials Nanolens, B. D. F. Casse, W. T. Lu, Y. J. Huang, E. Gultepe, L. Menon, S. Sridhar

Latika Menon

Super-resolution imaging beyond Abbe's diffraction limit can be achieved by utilizing an optical medium or "metamaterial" that can either amplify or transport the decaying near-field evanescent waves that carry subwavelength features of objects. Earlier approaches at optical frequencies mostly utilized the amplification of evanescent waves in thin metallic films or metal-dielectric multilayers, but were restricted to very small thicknesses (⪡λ, wavelength) and accordingly short object-image distances, due to losses in the material. Here, we present an experimental demonstration of super-resolution imaging by a low-loss three-dimensional metamaterial nanolens consisting of aligned gold nanowires embedded in a porous alumina matrix. This composite …

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A Study Of Titania Nanotube Synthesis In Chloride-Ion-Containing Media, E. Panaitescu, C. Richter, L. Menon Oct 2012

A Study Of Titania Nanotube Synthesis In Chloride-Ion-Containing Media, E. Panaitescu, C. Richter, L. Menon

Latika Menon

We have completed a detailed experimental investigation into the recently discovered synthesis of titania nanotubes in chloride-ion-containing media. We show that the role of the chloride ions is catalytic and it has a strong effect in increasing the reactivity of the solution, while the nature of cations has no visible role. We have identified the critical parameters for optimal growth and fast production of nanotubes, and a basic growth mechanism for the tubes is proposed. This opens routes for significant improvements of the method toward uniformity and/or better overall yield, making it a viable alternative to the present established methods.

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Growth And Magnetic Properties Of Polycrystalline Self-Assembled Bifurcated Co Nanowires, Jesse Silverberg, Adam L. Friedman, Latika Menon Oct 2012

Growth And Magnetic Properties Of Polycrystalline Self-Assembled Bifurcated Co Nanowires, Jesse Silverberg, Adam L. Friedman, Latika Menon

Latika Menon

We use anodization of aluminum foil with variable applied anodization voltage to create an alumina template with bifurcated porous structures. The template is then used to electrodeposit Co, fabricating unique bifurcated Co nanowires. In order to better understand the crystal structure of our new material, we then report magnetic properties of these self-assembled bifurcated Co nanowires. Magnetic measurements of the bifurcated wires are studied as functions of branch/stem ratios, wire length, and temperature. The results are compared with those of straight Co nanowires of similar dimensions and thin film Co samples to find that a different crystal lattice structure prevails …

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The Oxidation Of Hydrogen Peroxide On Nanostructured Rhodium Microelectrodes, N. Bartlett Philip, F. Esterle Thomas Oct 2012

The Oxidation Of Hydrogen Peroxide On Nanostructured Rhodium Microelectrodes, N. Bartlett Philip, F. Esterle Thomas

Journal of Electrochemistry

Mesoporous Rh films were deposited onto platinum microelectrodes from the H1 lyotropic liquid crystalline phase of C12EO8 (octaethyleneglycol monododecyl ether). The electrodes show well defined voltammetry for the oxidation and the reduction of hydrogen peroxide at low concentrations (<10 mmol•L-1) with excellent stability for operation at neutral pH. Based on the hysteresis in the current and the potential dependence the oxidation of hydrogen peroxide occurs through a CEE mechanism involving Rh(OH)3 on the mesoporous Rh electrode surface. At higher hydrogen peroxide concentrations the current reaches a plateau that is due to either saturation of the binding sites for hydrogen peroxide or limitation of the reaction due to acidification of the solution within the pores. For the thin films (below 200 nm) the hydrogen peroxide calibration curves we …

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In Situ Pm-Irras Studies Of A Floating Bilayer Lipid Membrane At Au(111) Electrode Surface, Su Zhangfei, Kycia Annia, Jay Leitch J., Lipkowski Jacek Oct 2012

In Situ Pm-Irras Studies Of A Floating Bilayer Lipid Membrane At Au(111) Electrode Surface, Su Zhangfei, Kycia Annia, Jay Leitch J., Lipkowski Jacek

Journal of Electrochemistry

In situ Polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS) was used to study the structure of a DMPC + cholesterol + GM1 floating bilayer lipid membrane (fBLM) at a Au(111) surface. 1-thio-beta-D-glucose (beta-Tg) was self-assembled onto the Au electrode to increase the overall hydrophilicity of the surface. The fBLM was deposited on the beta-Tg self-assembled monolayer (SAM) using a combination of Langmuir-Blodgett/Langmuir-Schaefer (LB/LS) techniques. The carbohydrate headgroups of the GM1 molecules were physically adsorbed to the beta-Tg SAM forming a water rich cushion between the fBLM and the modified gold substrate. The PM-IRRAS spectra indicate that the DMPC molecules within …

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Electrochemical Synthesis Of Silver-Tetracyanoquinodimethane Nanorods At Agar Supported Water/1,2-Dichloroethane Interface, Li Huang, Yixian Wang, Michael V. Mirkin, Bin Ren, Dongping Zhan Oct 2012

Electrochemical Synthesis Of Silver-Tetracyanoquinodimethane Nanorods At Agar Supported Water/1,2-Dichloroethane Interface, Li Huang, Yixian Wang, Michael V. Mirkin, Bin Ren, Dongping Zhan

Journal of Electrochemistry

Silver-tetracyanoquinodimethane (AgTCNQ) is an important charge transfer salt due to its high conductivity and other electronic properties. In this communication, we report the synthesis of AgTCNQ at the liquid/liquid interface. Agar was used as a gelling agent to support water/1,2-dichloroethane (DCE) interface. Silver ions were transferred from the hydrogel into DCE phase, where they combined with TCNQ- to form AgTCNQ nanorods. The developed method can provide a new route for synthesis of functional materials based on the electrochemistry at the liquid/liquid interface.

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Underpotential Deposition Of Copper On Pt(S)[N(100)X(110)] Stepped Surfaces, Gisbert Rubn, Climent Vctor, Herrero Enrique, M. Feliu Juan Oct 2012

Underpotential Deposition Of Copper On Pt(S)[N(100)X(110)] Stepped Surfaces, Gisbert Rubn, Climent Vctor, Herrero Enrique, M. Feliu Juan

Journal of Electrochemistry

The underpotential deposition of Cu on platinum stepped surfaces composed of (100) terraces and (110) monoatomic steps has been studied in different acidic solutions. It has been found that the initial stage of copper deposition on the surface takes place simultaneously on terrace and step sites, irrespective of the nature of the adsorbing anion. During the voltammetric deposition of a full monolayer, several peaks can be observed. The analysis of the dependence of the peak charge with the step density allows assigning the different peaks to different deposition sites. The peak appearing at most positive potentials corresponds to the deposition …

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Topological Insulator Bi2te3 Films Synthesized By Metal Organic Chemical Vapor Deposition, Helin Cao, Rama Venkatasubramanian, Chang Liu, Jonathan Pierce, Haoran Yang, M. Zahid Hasan, Yue Wu, Yong P. Chen Oct 2012

Topological Insulator Bi2te3 Films Synthesized By Metal Organic Chemical Vapor Deposition, Helin Cao, Rama Venkatasubramanian, Chang Liu, Jonathan Pierce, Haoran Yang, M. Zahid Hasan, Yue Wu, Yong P. Chen

Birck and NCN Publications

Topological insulator (TI) materials such as Bi2Te3 and Bi2Se3 have attracted strong recent interests. Large scale, high quality TI thin films are important for developing TI-based device applications. In this work, structural and electronic properties of Bi2Te3 thin films deposited by metal organic chemical vapor deposition (MOCVD) on GaAs (001) substrates were characterized via x-ray diffraction (XRD), Raman spectroscopy, angle-resolved photoemission spectroscopy (ARPES), and electronic transport measurements. The characteristic topological surface states with a single Dirac cone have been clearly revealed in the electronic band structure measured by ARPES, confirming the TI nature of the MOCVD Bi2Te3 films. Resistivity and …

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How Can Pacific Island Economies Benefits From The Advent Of Ict’S – Review Of Best Practices In Education, Deogratias Harorimana Sr Oct 2012

How Can Pacific Island Economies Benefits From The Advent Of Ict’S – Review Of Best Practices In Education, Deogratias Harorimana Sr

Dr Deogratias Harorimana

This paper explored implementation and use of information and communication technologies in Fiji, in order to gain insight into recent government initiatives to introduce computers and other ICTs for the community of Fiji. The focus of this paper in that it provided the framework for an in-depth exploration of e-learning centers around the country and the benefits from the advent of ICT’s in e-learning community centers in Fiji. Areas concentrated on are outcome of ICT’s in formal education to students and community as a whole in areas of agriculture, health, environment and infrastructure etc. The research sought understanding from the …

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Oscillator-Based Neuronal Modeling For Seizure Progression Investigation And Seizure Control Strategy, Wu Chen Oct 2012

Oscillator-Based Neuronal Modeling For Seizure Progression Investigation And Seizure Control Strategy, Wu Chen

Doctoral Dissertations

The coupled oscillator model has previously been used for the simulation of neuronal activities in in vitro rat hippocampal slice seizure data and the evaluation of seizure suppression algorithms. Each model unit can be described as either an oscillator which can generate action potential spike trains without inputs, or a threshold-based unit. With the change of only one parameter, each unit can either be an oscillator or a threshold-based spiking unit. This would eliminate the need for a new set of equations for each type of unit. Previous analysis has suggested that long kernel duration and imbalance of inhibitory feedback …

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Exploitation And Exploration Of Pcr In Microfluidic Systems With Gradient Temperature Environments, Ilija Pjescic Oct 2012

Exploitation And Exploration Of Pcr In Microfluidic Systems With Gradient Temperature Environments, Ilija Pjescic

Doctoral Dissertations

The main goal of the work was to establish a wholesome picture off all relevant processes for a sample-in, answer out genetic system and to integrate the whole process on a one step device from sample collection to final result. The genetic analysis process consists of ideally three steps: sample preparation, chemical reaction, and analysis. Each of the steps is different and requires a specific environment, where sample preparation might use additives, they might later interfere with the reaction itself or lead to misleading results in the analysis phase. It was found to be quite a challenging process to synchronize …

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A Band-Pass Filter Approach Within Molecular Dynamics For The Prediction Of Intrinsic Quality Factors Of Nanoresonators, Ajit K. Vallabhaneni, Xiulin Ruan, Jeff F. Rhoads, Jayathi Murthy Oct 2012

A Band-Pass Filter Approach Within Molecular Dynamics For The Prediction Of Intrinsic Quality Factors Of Nanoresonators, Ajit K. Vallabhaneni, Xiulin Ruan, Jeff F. Rhoads, Jayathi Murthy

Birck and NCN Publications

The temperature and frequency dependence of the flexural mode quality factors (Q) of doubly clamped single wall carbon nanotube resonators are calculated using classical molecular dynamics simulations. The validity of the various methods available in the literature for calculating Q based on the temporal response of the system during ring-down is discussed and the discrepancies associated with the methods are explained. A new approach based on band-pass filtering is proposed for calculating Q, which reveals classical temperature dependence (Q similar to T-1) in contrast to the previously reported results (Q similar to T-beta, 0 < beta < 1). It is shown that the Q estimated from the temporal response is in good agreement with the Q estimated from frequency response. This work also demonstrates that the proposed method is particularly advantageous when multiple modes are simultaneously excited within the linear regime. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4754450]

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Cu2o And Au/Cu2o Particles: Surface Properties And Applications In Glucose Sensing, Yu-Ho Won, Lia A. Stanciu Oct 2012

Cu2o And Au/Cu2o Particles: Surface Properties And Applications In Glucose Sensing, Yu-Ho Won, Lia A. Stanciu

Birck and NCN Publications

In this work we investigated the surface and facet-dependent catalytic properties of metal oxide particles as well as noble metal/metal oxide heterogeneous structures, with cuprous oxide (Cu2O) and Au/Cu2O being selected as model systems. As an example of application, we explored the potential of these materials in developing electrocatalytic devices. Cu2O particles were synthesized in various shapes, then used for testing their morphology-dependent electrochemical properties applied to the detection of glucose. While we did not attempt to obtain the best detection limit reported to date, the octahedral and hexapod Cu2O particles showed reasonable detection limits of 0.51 and 0.60 mM, …

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Cross-Plane Electronic And Thermal Transport Properties Of P-Type La0.67sr0.33mno3/Lamno3 Perovskite Oxide Metal/Semiconductor Superlattices, Pankaj Jha, Timothy D. Sands, Laura Cassels, Philip Jackson, Tela Favaloro, Benjamin Kirk, Joshua Zide, Xianfan Xu, Ali Shakouri Sep 2012

Cross-Plane Electronic And Thermal Transport Properties Of P-Type La0.67sr0.33mno3/Lamno3 Perovskite Oxide Metal/Semiconductor Superlattices, Pankaj Jha, Timothy D. Sands, Laura Cassels, Philip Jackson, Tela Favaloro, Benjamin Kirk, Joshua Zide, Xianfan Xu, Ali Shakouri

Birck and NCN Publications

Lanthanum strontium manganate (La0.67Sr0.33MnO3, i.e., LSMO)/lanthanum manganate (LaMnO3, i.e., LMO) perovskite oxide metal/semiconductor superlattices were investigated as a potential p-type thermoelectric material. Growth was performed using pulsed laser deposition to achieve epitaxial LSMO (metal)/LMO (p-type semiconductor) superlattices on (100)-strontium titanate (STO) substrates. The magnitude of the in-plane Seebeck coefficient of LSMO thin films (/K) is consistent with metallic behavior, while LMO thin films were p-type with a room temperature Seebeck coefficient of 140 mu V/K. Thermal conductivity measurements via the photo-acoustic (PA) technique showed that LSMO/LMO superlattices exhibit a room temperature cross-plane thermal conductivity (0.89 W/m.K) that is significantly lower …

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Progress On: “Coherent Terahertz Acoustic Phonon Scattering: Novel Diagnostic For Erosion In Plasma Thruster Discharge Chamber Walls", Thomas E. Wilson, Iain D. Boyd Sep 2012

Progress On: “Coherent Terahertz Acoustic Phonon Scattering: Novel Diagnostic For Erosion In Plasma Thruster Discharge Chamber Walls", Thomas E. Wilson, Iain D. Boyd

Physics Faculty Research

The study is based on the success in obtaining the first experimental evidence for the direct excitation of coherent nanosecond-pulsed high-frequency acoustic phonons in semiconducting doping superstructures by electromagnetic fields of the same frequency. Acoustic phonons are detected by a superconducting bolometer, with nanosecond resolution, at the appropriate time-of-flight across a (100) silicon substrate for ballistic longitudinal phonons when a silicon delta-doped doping superlattice is illuminated with grating-coupled nanosecond-pulsed 246-GHz laser radiation with an approximate power density of 1 kW/mm2. The absorbed phonon power density in the bolometer detector is estimated to be 10 μW/mm2, in …

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Temperature Dependence Anomalous Dielectric Relaxation In Co Doped Zno Nanoparticles, Sajid Ali Ansari Sep 2012

Temperature Dependence Anomalous Dielectric Relaxation In Co Doped Zno Nanoparticles, Sajid Ali Ansari

Sajid Ali Ansari

We have reported temperature and frequency dependence of dielectric behaviour of nanocrystalline Zn1-xCoxO (x = 0.0, 0.01, 0.05 and 0.1) samples prepared by gel-combustion method. The synthesized samples were examined by x-ray diffraction (XRD), scanning electron microscopy (SEM) and LCR-meter, respectively. The XRD analysis reveals that ZnO has a hexagonal (wurtzite) crystal structure. The morphology and size of the nanoparticles (∼10-25 nm) were observed by SEM for 5% Co doped ZnO sample. In dielectric properties, complex permittivity (ɛ* = ɛ’-jɛ”), loss tangent (tanδ) and ac conductivity (σac) in the frequency range 75 kHz - 5 MHz were analyzed with temperature …

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Technical Assistance, Knowledge Gatekeeping And Indigenous Knowledge: Re-Thinking The International Development Practice, Deogratias Harorimana Sr Sep 2012

Technical Assistance, Knowledge Gatekeeping And Indigenous Knowledge: Re-Thinking The International Development Practice, Deogratias Harorimana Sr

Dr Deogratias Harorimana

This paper presents results from a multi-disciplinary conceptual analysis of development theory and practice. It reviews issues raised and proposes a shift in the epistemology of possession towards an epistemology of practice which is guided by the following aspects (1) The consideration of the learning culture of parties involved, (2) the ability and willingness for decontextualisation of the knowledge by the source and (3) the ability to embedded it by recipients (embededness ), (4) the importance that is attached to knowledge of the host country as reflected through (5) Similarity in culture, values, understanding of context and knowledge bases; (6) …

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Improvement Of Near-Infrared Absorption Linewidth In Algan/Gan Superlattices By Optimization Of Delta-Doping Location, C. Edmunds, L. Tang, J. Shao, D. Li, M. Cervantes, G. Gardner, Dmitri Zakharov, Michael J. Manfra, O. Malis Sep 2012

Improvement Of Near-Infrared Absorption Linewidth In Algan/Gan Superlattices By Optimization Of Delta-Doping Location, C. Edmunds, L. Tang, J. Shao, D. Li, M. Cervantes, G. Gardner, Dmitri Zakharov, Michael J. Manfra, O. Malis

Birck and NCN Publications

We report a systematic study of the near-infrared intersubband absorption in AlGaN/GaN superlattices grown by plasma-assisted molecular-beam epitaxy as a function of Si-doping profile with and without delta-doping. The transition energies are in agreement with theoretical calculations including many-body effects. A dramatic reduction of the intersubband absorption linewidth is observed when the delta-doping is placed at the end of the quantum well. This reduction is attributed to the improvement of interface roughness. The linewidth dependence on interface roughness is well reproduced by a model that considers the distribution of well widths measured with transmission electron microscopy. (C) 2012 American Institute …

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