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- Brian Storey (15)
- Rebecca J. Christianson (13)
- Chance Hoellwarth (4)
- Ehsan Khatami (4)
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- Jennifer (Jinni) Meehan (4)
- Yevgeniya V. Zastavker (4)
- David V. Kerns (2)
- Jessica Townsend (2)
- John B. Geddes (2)
- Mitra Shojania-Feizabadi (2)
- Christopher Lee (1)
- Glen Gillen (1)
- Katharina Gillen (1)
- Leda Sox (1)
- Mark A. Moline (1)
- Peter V. Schwartz (1)
- Raúl Ordóñez (1)
- Sherra E. Kerns (1)
- Stephen Holt (1)
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Articles 31 - 60 of 66
Full-Text Articles in Physical Sciences and Mathematics
Viscosity Measurements On Colloidal Dispersions (Nanofluids) For Heat Transfer Applications, Jessica Townsend, Rebecca J. Christianson, D Venerus, J Buongiorno, M A. Kedzierski, Et Al.
Viscosity Measurements On Colloidal Dispersions (Nanofluids) For Heat Transfer Applications, Jessica Townsend, Rebecca J. Christianson, D Venerus, J Buongiorno, M A. Kedzierski, Et Al.
Jessica Townsend
This article reports viscosity data on a series of colloidal dispersions collected as part of the International Nanofluid Property Benchmark Exercise (INPBE). Data are reported for seven different fluids that include dispersions of metal-oxide nanoparticles in water, and in synthetic oil. These fluids, which are also referred to as nanofluids, are currently being researched for their potential to function as heat transfer fluids. In a recently published paper from the INPBE study, thermal conductivity data from more than 30 laboratories around the world were reported and analyzed. Here, we examine the influence of particle shape and concentration on the viscosity …
Nanofluid Properties And Their Effects On Convective Heat Transfer In An Electronics Cooling Application, Jessica Townsend, Rebecca Christianson
Nanofluid Properties And Their Effects On Convective Heat Transfer In An Electronics Cooling Application, Jessica Townsend, Rebecca Christianson
Jessica Townsend
In the search for new, more effective coolant fluids, nanoparticle suspensions have shown promise due to their enhanced thermal conductivity. However, there is a concomitant increase in the viscosity, requiring an increase in pumping power to achieve the same flow rate.Studies of flow cooling in simple geometries indicate that there is a benefit to using nanofluids, but it is difficult to justify extending these results to the far more complicated geometries. Moreover, with the variability of property measurements found in literature, it is possible to show conflicting results from the same set of flow-cooling data. In this work we present …
Non-Linear Dynamic Intertwining Of Rods With Self-Contact, Christopher Lee, Sachin Goyal, Noel Perkins
Non-Linear Dynamic Intertwining Of Rods With Self-Contact, Christopher Lee, Sachin Goyal, Noel Perkins
Christopher Lee
Twisted marine cables on the sea floor can form highly contorted three-dimensional loops that resemble tangles. Such tangles or ‘hockles’ are topologically equivalent to the plectomenes that form in supercoiled DNA molecules. The dynamic evolution of these intertwined loops is studied herein using a computationalrod model that explicitly accounts for dynamicself-contact. Numerical solutions are presented for an illustrative example of a long rod subjected to increasing twist at one end. The solutions reveal the dynamicevolution of the rod from an initially straight state, through a buckled state in the approximate form of a helix, through the dynamic collapse of this …
Bistability In A Simple Fluid Network Due To Viscosity Contrast, John Geddes, Brian Storey, David Gardner, Russell Carr
Bistability In A Simple Fluid Network Due To Viscosity Contrast, John Geddes, Brian Storey, David Gardner, Russell Carr
Brian Storey
We study the existence of multiple equilibrium states in a simple fluid network using Newtonian fluids and laminar flow. We demonstrate theoretically the presence of hysteresis and bistability, and we confirm these predictions in an experiment using two miscible fluids of different viscosity—sucrose solution and water. Possible applications include blood flow, microfluidics, and other network flows governed by similar principles.
A Depth-Averaged Electrokinetic Flow Model For Shallow Microchannels, Hao Lin, Brian D. Storey, Juan G. Santiago
A Depth-Averaged Electrokinetic Flow Model For Shallow Microchannels, Hao Lin, Brian D. Storey, Juan G. Santiago
Brian Storey
Electrokinetic flows with heterogeneous conductivity configuration occur widely in microfluidic applications such as sample stacking and multidimensional assays. Electromechanical coupling in these flows may lead to complex flow phenomena, such as sample dispersion due to electro-osmotic velocity mismatch, and electrokinetic instability (EKI). In this work we develop a generalized electrokinetic model suitable for the study of microchannel flows with conductivity gradients and shallow-channel geometry. An asymptotic analysis is performed with the channel depth-to-width ratio as a smallness parameter, and the three-dimensional equations are reduced to a set of depth-averaged equations governing in-plane flow dynamics. The momentum equation uses a Darcy–Brinkman–Forchheimer-type …
Instability Of Electro-Osmotic Channel Flow With Streamwise Conductivity Gradients, Jose Santos, Brian D. Storey
Instability Of Electro-Osmotic Channel Flow With Streamwise Conductivity Gradients, Jose Santos, Brian D. Storey
Brian Storey
This work considers the stability of an electro-osmotic microchannel flow with streamwise electrical conductivity gradients, a configuration common in microfluidic applications such as field amplified sample stacking. Previous work on such flows has focused on how streamwise conductivity gradients set a nonuniform electro-osmotic velocity which results in dispersion of the conductivity field. However, it has been known for many years that electric fields can couple with conductivity gradients to generate unstable flows. This work demonstrates that at high electric fields such an electrohydrodynamic instability arises in this configuration and the basic mechanisms are explored through numerical simulations. The instability is …
Nonlinear Electrokinetics At Large Voltages, Martin Z. Bazant, Mustafa Sabri Kilic, Brian D. Storey, Armand Ajdari
Nonlinear Electrokinetics At Large Voltages, Martin Z. Bazant, Mustafa Sabri Kilic, Brian D. Storey, Armand Ajdari
Brian Storey
Part of Focus on Micro- and Nanofluidics The classical theory of electrokinetic phenomena assumes a dilute solution of point-like ions in chemical equilibrium with a surface whose double-layer voltage is of order the thermal voltage, kBT/e=25 mV. In nonlinear 'induced-charge' electrokinetic phenomena, such as ac electro-osmosis, several volts 100kBT/e are applied to the double layer, and the theory breaks down and cannot explain many observed features. We argue that, under such a large voltage, counterions 'condense' near the surface, even for dilute bulk solutions. Based on simple models, we predict that the double-layer capacitance decreases and the electro-osmotic mobility saturates …
Steric Effects On Ac Electro-Osmosis In Dilute Electrolytes, Brian D. Storey, Lee Edwards, Mustafa Sabri Kilic, Martin Z. Bazant
Steric Effects On Ac Electro-Osmosis In Dilute Electrolytes, Brian D. Storey, Lee Edwards, Mustafa Sabri Kilic, Martin Z. Bazant
Brian Storey
The current theory of alternating-current electro-osmosis (ACEO) is unable to explain the experimentally observed flow reversal of planar ACEO pumps at high frequency (above the peak, typically 10–100 kHz), low salt concentration (1–1000 μM), and moderate voltage (2–6 V), even taking into account Faradaic surface reactions, nonlinear double-layer capacitance, and bulk electrothermal flows. We attribute this failure to the breakdown of the classical Poisson-Boltzmann model of the diffuse double layer, which assumes a dilute solution of pointlike ions. In spite of low bulk salt concentration, the large voltage induced across the double layer leads to crowding of the ions and …
Rayleigh-Taylor Instability Of Violently Collapsing Bubbles, Hao Lin, Brian D. Storey, Andrew J. Szeri
Rayleigh-Taylor Instability Of Violently Collapsing Bubbles, Hao Lin, Brian D. Storey, Andrew J. Szeri
Brian Storey
In a classical paper Plesset has determined conditions under which a bubble changing in volume maintains a spherical shape. The stability analysis was further developed by Prosperetti to include the effects of liquid viscosity on the evolving shape modes. In the present work the theory is further modified to include the changing density of the bubble contents. The latter is found to be important in violent collapses where the densities of the gas and vapor within a bubble may approach densities of the liquid outside. This exerts a stabilizing influence on the Rayleigh–Taylor mechanism of shape instability of spherical bubbles. …
Bulk Electroconvective Instability At High Péclet Numbers, Brian D. Storey, Boris Zaltzman, Isaak Rubinstein
Bulk Electroconvective Instability At High Péclet Numbers, Brian D. Storey, Boris Zaltzman, Isaak Rubinstein
Brian Storey
Bulk electroconvection pertains to flow induced by the action of a mean electric field upon the residual space charge in the macroscopic regions of a locally quasielectroneutral strong electrolyte. For a long time, controversy has existed in the literature as to whether quiescent electric conduction from such an electrolyte into a uniform charge-selective solid, such as a metal electrode or ion exchange membrane, is stable with respect to bulk electroconvection. While it was recently claimed that bulk electroconvective instability could not occur, this claim pertained to an aqueous, low-molecular-weight electrolyte characterized by an order-unity electroconvection Péclet number. In this paper, …
Field-Amplified Sample Stacking And Focusing In Nanofluidic Channels, Jess M. Sustarich, Brian D. Storey, Sumita Pennathur
Field-Amplified Sample Stacking And Focusing In Nanofluidic Channels, Jess M. Sustarich, Brian D. Storey, Sumita Pennathur
Brian Storey
Nanofluidic technology is gaining popularity for bioanalytical applications due to advances in both nanofabrication and design. One major obstacle in the widespread adoption of such technology for bioanalytical systems is efficient detection of samples due to the inherently low analyte concentrations present in such systems. This problem is exacerbated by the push for electronic detection, which requires an even higher sensor-local sample concentration than optical detection. This paper explores one of the most common preconcentration techniques, field-amplified sample stacking, in nanofluidic systems in efforts to alleviate this obstacle. Holding the ratio of background electrolyte concentrations constant, the parameters of channel …
Heat-Capacity And Magnetic Measurements On The Y(Ni2-XCoX)B2C System, C. C. Hoellwarth, P. Klavins, R. N. Shelton
Heat-Capacity And Magnetic Measurements On The Y(Ni2-XCoX)B2C System, C. C. Hoellwarth, P. Klavins, R. N. Shelton
Chance Hoellwarth
We have performed field-and temperature-dependent magnetization, resistivity, and heat-capacity measurements on polycrystalline samples of the Y(Ni2-xCox)B2C system with 0.0≤x≤0.4. Values of Tc ,x0,Hc2,ΘD,λ and N(Ed) were determined for various samples. We observe that ΘD increases with x, while all the other parameters decrease with x. The Tc vs x data can be described using the BCS theory and the measured values of N(Ef)and ΘD. The results suggest that the decrease in Tc is due to the decrease in N(Ef), in agreement with the results from band structure calculations.
The Implications Of A Robust Curriculum In Introductory Mechanics, Chance Hoellwarth, Matthew Moelter
The Implications Of A Robust Curriculum In Introductory Mechanics, Chance Hoellwarth, Matthew Moelter
Chance Hoellwarth
We have developed a curriculum for introductory mechanics that emphasizes interactive engagement and conceptual understanding using the studio format. As previously reported, we have shown in three different quarters that the curriculum much improved the students’ conceptual understanding compared to the traditional course without significantly affecting the scores on a traditional final exam. Here we report the results for the entire three-year period during which the course was taught, 34 sections of the course were taught with 11 different instructors to over 1200 students. In each term, these sections had common exams, syllabus, and schedule. Student experiences were very similar …
Exposing Students To The Idea That Theories Can Change, Chance Hoellwarth, Matthew J. Moelter
Exposing Students To The Idea That Theories Can Change, Chance Hoellwarth, Matthew J. Moelter
Chance Hoellwarth
No abstract provided.
A Direct Comparison Of Conceptual Learning And Problem Solving Ability In Traditional And Studio Style Classrooms, Chance Hoellwarth, Matthew J. Moelter, Randall D. Knight
A Direct Comparison Of Conceptual Learning And Problem Solving Ability In Traditional And Studio Style Classrooms, Chance Hoellwarth, Matthew J. Moelter, Randall D. Knight
Chance Hoellwarth
We present data on student performance on conceptual understanding and on quantitative problem-solving ability in introductory mechanics in both studio and traditional classroom modes. The conceptual measures used were the Force Concept Inventory and the Force and Motion Conceptual Evaluation. Quantitative problem-solving ability was measured with standard questions on the final exam. Our data compare three different quarters over the course of 2 years. In all three quarters, the normalized learning gain in conceptual understanding was significantly larger for students in the studio sections. At the same time, students in the studio sections performed the same or slightly worse on …
X-Ray Scattering Study Of The Incommensurate Phase In Mg-Doped Cugeo3, Rebecca J. Christianson, Y. J. Wang, S.C. Lamarra, R. J. Birgeneau, V. Kiryukhin, T. Masuda, I. Tsukada, K. Uchinokura, B. Keimer
X-Ray Scattering Study Of The Incommensurate Phase In Mg-Doped Cugeo3, Rebecca J. Christianson, Y. J. Wang, S.C. Lamarra, R. J. Birgeneau, V. Kiryukhin, T. Masuda, I. Tsukada, K. Uchinokura, B. Keimer
Rebecca J. Christianson
We present results of a systematic x-ray scattering study of the effects of Mg doping on the high-fieldincommensurate phase of CuGeO3. Lorentzian-squared line shapes, the changing of the first-order transition tosecond order, and the destruction of long-range order with infinitesimal doping are observed, consistent withrandom-field effects in a three-dimensional XY system. Values for the soliton width in pure and lightly dopedCuGeO3 are deduced. We find that even a very small doping has a drastic effect on the shape of the latticemodulation.
Two-Magnon Excitations Observed By Neutron Scattering In The Two-Dimensional Spin-5/2 Heisenberg Antiferromagnet Rb2mnf4, T. Huberman, R. Coldea, R. A. Cowley, D. A. Tennant, R. L. Leheny, Rebecca Christianson, C. D. Frost
Two-Magnon Excitations Observed By Neutron Scattering In The Two-Dimensional Spin-5/2 Heisenberg Antiferromagnet Rb2mnf4, T. Huberman, R. Coldea, R. A. Cowley, D. A. Tennant, R. L. Leheny, Rebecca Christianson, C. D. Frost
Rebecca J. Christianson
The low-temperature magnetic excitations of the two-dimensional spin- 52 square-lattice Heisenberg antiferromagnetRb2MnF4 have been probed using pulsed inelastic neutron scattering. In addition to dominant sharppeaks identified with one-magnon excitations, a relatively weak continuum scattering is also observed at higherenergies. This is attributed to neutron scattering by pairs of magnons and the observed intensities are consistentwith predictions of spin wave theory.
Time-Dependent Strength Of Colloidal Gels, S. Manley, Benny Davidovitch, Neil R. Davies, L. Cipelletti, A. E. Bailey, Rebecca J. Christianson, U. Gasser, V. Prasad, P. N. Segre, M. P. Doherty, S. Sankaran, A. L. Jankovsky, B. Shiley, J. Bowen, J. Eggers, C. Kurta, T. Lorik, D. A. Weitz
Time-Dependent Strength Of Colloidal Gels, S. Manley, Benny Davidovitch, Neil R. Davies, L. Cipelletti, A. E. Bailey, Rebecca J. Christianson, U. Gasser, V. Prasad, P. N. Segre, M. P. Doherty, S. Sankaran, A. L. Jankovsky, B. Shiley, J. Bowen, J. Eggers, C. Kurta, T. Lorik, D. A. Weitz
Rebecca J. Christianson
Colloidal silica gels are shown to stiffen with time, as demonstrated by both dynamic light scattering and bulk rheological measurements. Their elastic moduli increase as a power law with time, independent of particle volume fraction; however, static light scattering indicates that there are no large-scale structural changes. We propose that increases in local elasticity arising from bonding between neighboring colloidal particles can account for the strengthening of the network, while preserving network structure.
Spinodal Decomposition In A Model Colloid-Polymer Mixture In Microgravity, A. E. Bailey, W. C. K. Poon, Rebecca J. Christianson, A. B. Schofield, U. Gasser, V. Prasad, S. Manley, P. N. Segre, L. Cipelletti, W. V. Meyer, M. P. Doherty, S. Sankaran, A. L. Jankovsky, W. L. Shiley, J. P. Bowen, J. C. Eggers, C. Kurta, T., Jr. Lorik, P. N. Pusey, D. A. Weitz
Spinodal Decomposition In A Model Colloid-Polymer Mixture In Microgravity, A. E. Bailey, W. C. K. Poon, Rebecca J. Christianson, A. B. Schofield, U. Gasser, V. Prasad, S. Manley, P. N. Segre, L. Cipelletti, W. V. Meyer, M. P. Doherty, S. Sankaran, A. L. Jankovsky, W. L. Shiley, J. P. Bowen, J. C. Eggers, C. Kurta, T., Jr. Lorik, P. N. Pusey, D. A. Weitz
Rebecca J. Christianson
We study phase separation in a deeply quenched colloid-polymer mixture in microgravity on the International Space Station using small-angle light scattering and direct imaging. We observe a clear crossover from early-stage spinodal decomposition to late-stage, interfacial-tension-driven coarsening. Data acquired over 5 orders of magnitude in time show more than 3 orders of magnitude increase in domain size, following nearly the same evolution as that in binary liquid mixtures. The late-stage growth approaches the expected linear growth rate quite slowly.
X-Ray Scattering Studies Of Two Length Scales In The Critical Fluctuations Of Cugeo3, Y. J. Wang, Y. J. Kim, Rebecca J. Christianson, S. C. Lamarra, F. C. Chou, R. J. Birgeneau
X-Ray Scattering Studies Of Two Length Scales In The Critical Fluctuations Of Cugeo3, Y. J. Wang, Y. J. Kim, Rebecca J. Christianson, S. C. Lamarra, F. C. Chou, R. J. Birgeneau
Rebecca J. Christianson
The critical fluctuations of CuGeO3 have been measured by synchrotron x-ray scattering, and two length scales are clearly observed. The ratio between the two length scales is found to be significantly different along the a axis, with the a axis along the surface normal direction. We believe that such a directional preference is a clear sign that random surface strains, especially those caused by dislocations, are the origin of the long length scale fluctuations.
Space Weather Community Operations Workshop: Planning For The Next Decade, J. Fulgham, Jennifer Meehan, W. Tobiska
Space Weather Community Operations Workshop: Planning For The Next Decade, J. Fulgham, Jennifer Meehan, W. Tobiska
Jennifer (Jinni) Meehan
No abstract provided.
Limits To Gelation In Colloidal Aggregation, S. Manley, L. Cipelletti, V. Trappe, A. E. Bailey, Rebecca J. Christianson, U. Gasser, V. Prasad, P. N. Segre, M. P. Doherty, S. Sankaran, A. L. Jankovsky, B. Shiley, J. Bowen, J. Eggers, C. Kurta, T. Lorik, D. A. Weitz
Limits To Gelation In Colloidal Aggregation, S. Manley, L. Cipelletti, V. Trappe, A. E. Bailey, Rebecca J. Christianson, U. Gasser, V. Prasad, P. N. Segre, M. P. Doherty, S. Sankaran, A. L. Jankovsky, B. Shiley, J. Bowen, J. Eggers, C. Kurta, T. Lorik, D. A. Weitz
Rebecca J. Christianson
We show that the dynamics of large fractal colloid aggregates are well described by a combination of translational and rotational diffusion and internal elastic fluctuations, allowing both the aggregate size and internal elasticity to be determined by dynamic light scattering. The comparison of results obtained in microgravity and on Earth demonstrates that cluster growth is limited by gravity-induced restructuring. In the absence of gravity, thermal fluctuations ultimately inhibit fractal growth and set the fundamental limitation to the lowest volume fraction which will gel.
Critical Dynamics Of A Spin-5/2 Two-Dimensional Isotropic Antiferromagnet, Rebecca J. Christianson, R. L. Leheny, R. J. Birgeneau, R. W. Erwin
Critical Dynamics Of A Spin-5/2 Two-Dimensional Isotropic Antiferromagnet, Rebecca J. Christianson, R. L. Leheny, R. J. Birgeneau, R. W. Erwin
Rebecca J. Christianson
We report a neutron-scattering study of the dynamic spin correlations in Rb2MnF4, a two-dimensional spin-5/2 antiferromagnet. By tuning an external magnetic field to the value for the spin-flop line, we reduce the effective spin anisotropy to essentially zero, thereby obtaining a nearly ideal two-dimensional isotropic antiferromagnet. From the shape of the quasielastic peak as a function of temperature, we demonstrate dynamic scaling for this system and find a value for the dynamical exponent z. We compare these results to theoretical predictions for the dynamic behavior of the two-dimensional Heisenberg model, in which deviations from z=1 provide a measure of the …
Spin Correlations In An Isotropic Spin-5/2 Two-Dimensional Antiferromagnet, R. L. Leheny, Rebecca J. Christianson, R. J. Birgeneau, R. W. Erwin
Spin Correlations In An Isotropic Spin-5/2 Two-Dimensional Antiferromagnet, R. L. Leheny, Rebecca J. Christianson, R. J. Birgeneau, R. W. Erwin
Rebecca J. Christianson
We report a neutron scattering study of the spin correlations for the spin-5/2 two-dimensional antiferromagnet Rb2MnF4 in an external magnetic field. Choosing fields near the system’s bicritical point, we tune the effective anisotropy in the spin interaction to zero, constructing an ideal S = 5/2 Heisenberg system. The correlation length and structure factor amplitude are closely described by the semiclassical theory of Cuccoli 'et al.' over a broad temperature range, but show no indication of approaching the low-temperature renormalized classical regime of the quantum nonlinear sigma model.
Electrochemistry And Staging In La2cuo4+D, P Blakeslee, R J. Birgeneau, F C. Chou, Rebecca J. Christianson, M A. Kastner, Y S. Lee, B O. Wells
Electrochemistry And Staging In La2cuo4+D, P Blakeslee, R J. Birgeneau, F C. Chou, Rebecca J. Christianson, M A. Kastner, Y S. Lee, B O. Wells
Rebecca J. Christianson
Measurements are reported of the time dependence of the current during electrochemical oxidation and reduction at a fixed voltage of single crystals and ceramic samples of La2CuO4+d. Staging peaks in neutron measurements of the single crystals together with the electrochemical measurements and magnetization measurements confirm that stage n=6 corresponds to d=0.055 +/- 0.05, the high-d side of the oxygen-rich–oxygen-poor miscibility gap. Furthermore, stage n=4 occurs at a value of d consistent with d{n^-1. For ceramic samples it is shown that two different superconducting compounds are formed depending on the oxidation voltage used.
Measuring The Persistence Length Of Mcf7 Cell Microtubules In Vitro, Mitra Shojania-Feizabadi, Kiryako Mutafopulos, Adam Behr
Measuring The Persistence Length Of Mcf7 Cell Microtubules In Vitro, Mitra Shojania-Feizabadi, Kiryako Mutafopulos, Adam Behr
Mitra Shojania-Feizabadi
No abstract provided.
Analysis Of Electroluminescence Spectra Of Silicon And Gallium Arsenide P-N Junctions In Avalanche Breakdown, M Lahbabi, A Ahaitoufa, M. Fliyou, E. Abarkan, J.-P. Charles, A. Bath, A. Hoffmann, Sherra Kerns, David Kerns, Jr.
Analysis Of Electroluminescence Spectra Of Silicon And Gallium Arsenide P-N Junctions In Avalanche Breakdown, M Lahbabi, A Ahaitoufa, M. Fliyou, E. Abarkan, J.-P. Charles, A. Bath, A. Hoffmann, Sherra Kerns, David Kerns, Jr.
David V. Kerns
We present a generalized study of light emission from reverse biased p–n junctions under avalanche breakdown conditions. A model is developed based on direct and indirect interband processes including self-absorption to describe measured electroluminescence spectra. This model was used to analyze experimental data for silicon (Si) and gallium arsenide p–n junctions and can be extended to several types of semiconductors regardless of their band gaps. This model can be used as a noninvasive technique for the determination of the junction depth. It has also been used to explain the observed changes of the Si p–n junction electroluminescence spectra after fast …
Analysis Of Electroluminescence Spectra Of Silicon And Gallium Arsenide P-N Junctions In Avalanche Breakdown, M Lahbabi (Adjunct), A Ahaitoufa, M. Fliyou, E. Abarkan, J.-P. Charles, A. Bath, A. Hoffmann, Sherra E. Kerns, David V. Kerns, Jr.
Analysis Of Electroluminescence Spectra Of Silicon And Gallium Arsenide P-N Junctions In Avalanche Breakdown, M Lahbabi (Adjunct), A Ahaitoufa, M. Fliyou, E. Abarkan, J.-P. Charles, A. Bath, A. Hoffmann, Sherra E. Kerns, David V. Kerns, Jr.
Sherra E. Kerns
We present a generalized study of light emission from reverse biased p–n junctions under avalanche breakdown conditions. A model is developed based on direct and indirect interband processes including self-absorption to describe measured electroluminescence spectra. This model was used to analyze experimental data for silicon (Si) and gallium arsenide p–n junctions and can be extended to several types of semiconductors regardless of their band gaps. This model can be used as a noninvasive technique for the determination of the junction depth. It has also been used to explain the observed changes of the Si p–n junction electroluminescence spectra after fast …
Projection Of Diffraction Patterns For Use In Cold-Neutral-Atom Trapping, Katharina Gillen-Christandl, Glen D. Gillen
Projection Of Diffraction Patterns For Use In Cold-Neutral-Atom Trapping, Katharina Gillen-Christandl, Glen D. Gillen
Glen Gillen
Scalar diffraction theory is combined with beam-propagation techniques to investigate the projection of near-field diffraction patterns to spatial locations away from the aperture for use in optically trapping cold neutral alkali-metal atoms. Calculations show that intensity distributions with localized bright and dark spots usually found within a millimeter of the diffracting aperture can be projected to a region free from optical components such as a cloud of cold atoms within a vacuum chamber. Calculations also predict that the critical properties of the optical dipole atom traps are not only maintained for the projected intensity patterns but also can be manipulated …
Projection Of Diffraction Patterns For Use In Cold-Neutral-Atom Trapping, Katharina Gillen-Christandl, Glen D. Gillen
Projection Of Diffraction Patterns For Use In Cold-Neutral-Atom Trapping, Katharina Gillen-Christandl, Glen D. Gillen
Katharina Gillen
Scalar diffraction theory is combined with beam-propagation techniques to investigate the projection of near-field diffraction patterns to spatial locations away from the aperture for use in optically trapping cold neutral alkali-metal atoms. Calculations show that intensity distributions with localized bright and dark spots usually found within a millimeter of the diffracting aperture can be projected to a region free from optical components such as a cloud of cold atoms within a vacuum chamber. Calculations also predict that the critical properties of the optical dipole atom traps are not only maintained for the projected intensity patterns but also can be manipulated …