Open Access. Powered by Scholars. Published by Universities.®

Physical Sciences and Mathematics Commons™

Open Access. Powered by Scholars. Published by Universities.®

Iowa State University

2007

Discipline
Keyword
Publication

Articles 1 - 30 of 37

Full-Text Articles in Physical Sciences and Mathematics

High-Speed Three-Dimensional Shape Measurement System Using A Modified Twoplus- One Phase-Shifting Algorithm, Song Zhang, Shing-Tung Yau Nov 2007

High-Speed Three-Dimensional Shape Measurement System Using A Modified Twoplus- One Phase-Shifting Algorithm, Song Zhang, Shing-Tung Yau

Song Zhang

This paper describes a high-resolution, real-time, three-dimensional shape measurement system using the modified two-plus-one phase-shifting algorithm. The data acquisition speed is as high as 60frames∕s with an image resolution of 640×480pixels per frame. Experiments demonstrated that the system was able to acquire the dynamic changing objects such as facial geometric shape changes when the subject is speaking, and the modified two-plus-one phase-shifting algorithm can further alleviate the error due to motion. Applications of this system include manufacturing, online inspection, medical imaging, compute vision, and computer graphics.

Go to article

Inhomogeneous Exclusion Processes With Extended Objects: The Effect Of Defect Locations, J. J. Dong, Beate Schmittmann, R. K. P. Zia Nov 2007

Inhomogeneous Exclusion Processes With Extended Objects: The Effect Of Defect Locations, J. J. Dong, Beate Schmittmann, R. K. P. Zia

Beate Schmittmann

We study the effects of local inhomogeneities, i.e., slow sites of hopping rate q<1, in a totally asymmetric simple exclusion process for particles of size ℓ⩾1 (in units of the lattice spacing). We compare the simulation results of ℓ=1 and ℓ>1 and notice that the existence of local defects has qualitatively similar effects on the steady state. We focus on the stationary current as well as the density profiles. If there is only a single slow site in the system, we observe a significant dependence of the current on the location of the slow site for both ℓ=1 and ℓ>1 cases. When two slow sites are introduced, more intriguing phenomena emerge, e.g., dramatic decreases in the current when the two are close together. In addition, …

Go to article

Spatial And Temporal Patterns Of Nitrogen Deposition In China: Synthesis Of Observational Data, Chaoqun (Crystal) Lu, Hanqin Tian Nov 2007

Spatial And Temporal Patterns Of Nitrogen Deposition In China: Synthesis Of Observational Data, Chaoqun (Crystal) Lu, Hanqin Tian

Chaoqun (Crystal) Lu

Anthropogenic nitrous pollutant emissions in China significantly increased during the last decades, which contributed to the accelerated nitrogen (N) deposition. In order to characterize spatial pattern of nitrogen deposition, we employed the kriging technique to interpolate sampling data of precipitation chemistry and ambient air concentration from site-network observations over China. The estimation of wet deposition in China was limited to aqueous NO3− and NH4+, while ambient NO2 was the only species involved in the predicted dry deposition fluxes. To obtain wet deposition fluxes, precipitation concentration was multiplied by 20-year mean precipitation amounts with a resolution of 10 × 10 km. …

Go to article

Posterminaries: More Or Less Modern, Alexander H. King Nov 2007

Posterminaries: More Or Less Modern, Alexander H. King

Alexander H. King

It is yet another sign that I am aging. More and more often when young researchers hand me a written report of their research, I find myself criticizing their introductory section: “You need to start your literature survey with the original papers on this topic. Go and read…” followed by a citation to some classic of the learned literature.

Go to article

Platinum Nanoparticle Shape Effects On Benzene Hydrogenation Selectivity, Kaitlin M. Bratlie, Hyunjoo Lee, Kyriakos Komvopoulos, Peidong Yang, Gabor A. Somorjai Oct 2007

Platinum Nanoparticle Shape Effects On Benzene Hydrogenation Selectivity, Kaitlin M. Bratlie, Hyunjoo Lee, Kyriakos Komvopoulos, Peidong Yang, Gabor A. Somorjai

Kaitlin M. Bratlie

Benzene hydrogenation was investigated in the presence of a surface monolayer consisting of Pt nanoparticles of different shapes (cubic and cuboctahedral) and tetradecyltrimethylammonium bromide (TTAB). Infrared spectroscopy indicated that TTAB binds to the Pt surface through a weak C-HâââPt bond of the alkyl chain. The catalytic selectivity was found to be strongly affected by the nanoparticle shape. Both cyclohexane and cyclohexene product molecules were formed on cuboctahedral nanoparticles, whereas only cyclohexane was produced on cubic nanoparticles. These results are the same as the product selectivities obtained on Pt(111) and Pt(100) single crystals in earlier studies. The apparent activation energy for …

Go to article

Non-Destructive Horseradish Peroxidase Immobilization In Porous Silica Nanoparticles, Rebecca Voss, Michael A. Brook, Jordan Thompson, Yang Chen, Robert H. Pelton, John D. Brennan Sep 2007

Non-Destructive Horseradish Peroxidase Immobilization In Porous Silica Nanoparticles, Rebecca Voss, Michael A. Brook, Jordan Thompson, Yang Chen, Robert H. Pelton, John D. Brennan

Rebecca Cademartiri

The preparation of protein doped silica particles is impeded by the difficulty of incorporating proteins within the silica mesostructure under conditions that do not lead to denaturation. Herein, the synthesis of spherical silica particles (diameter 150 nm–550 nm) under protein friendly conditions in a one step process is described. Diglyceroxysilane (DGS) was reacted in ethanol and methanol-free conditions in pure water or in buffer solutions with or without the presence of additional glycerol. Stabilization of the particles, consistent with steric stabilization, was obtained using poly(ethylene glycol) (PEG) of various molecular weights and with various end groups, including allyl and (CH2)3Si(OEt)3 …

Go to article

3d Data Merging Using Holoimage, Song Zhang, Shing-Tung Yau Sep 2007

3d Data Merging Using Holoimage, Song Zhang, Shing-Tung Yau

Song Zhang

Three-dimensional data merging is critical for full-field 3-D shape measurement. 3-D range data patches, acquired either from different sensors or from the same sensor in different viewing angles, have to be merged into a single piece to facilitate future data analysis. In this research, we propose a novel method for 3-D data merging using Holoimage. Similar to the 3-D shape measurement system using a phase-shifting method, Holoimage is a phase-shifting-based computer synthesized fringe image. The virtual projector projects the phase-shifted fringe pattern onto the object, the reflected fringe images are rendered on the screen, and the Holoimage is generated by …

Go to article

Power Spectra Of The Total Occupancy In The Totally Asymmetric Simple Exclusion Process, D. `A. Adams, R. K. P. Zia, Beate Schmittmann Jul 2007

Power Spectra Of The Total Occupancy In The Totally Asymmetric Simple Exclusion Process, D. `A. Adams, R. K. P. Zia, Beate Schmittmann

Beate Schmittmann

As a solvable and broadly applicable model system, the totally asymmetric exclusion process enjoys iconic status in the theory of nonequilibrium phase transitions. Here, we focus on the time dependence of the total number of particles on a 1-dimensional open lattice and its power spectrum. Using both Monte Carlo simulations and analytic methods, we explore its behavior in different characteristic regimes. In the maximal current phase and on the coexistence line (between high and low density phases), the power spectrum displays algebraic decay, with exponents −1.62 and −2.00, respectively. Deep within the high and low density phases, we find pronounced …

Go to article

Control Of Porosity In Fluoride Thin Films Prepared By Vapor Deposition, Alexander H. King Jul 2007

Control Of Porosity In Fluoride Thin Films Prepared By Vapor Deposition, Alexander H. King

Alexander H. King

We have measured the porosity in thin films of lithium fluoride (LiF), magnesium fluoride (MgF2), barium fluoride (BaF2), and calcium fluoride (CaF2) as a function of the substrate temperature for films deposited by thermal evaporation onto glass substrates. The amount of porosity in the thin films was measured using an atomic force microscope and a quartz crystal thickness monitor. The porosity was very sensitive to the substrate temperature and decreased as the substrate temperature increased. Consistent behavior was observed among all of the materials in this study.

Go to article

Posterminaries: Full Circle, Alexander H. King Jul 2007

Posterminaries: Full Circle, Alexander H. King

Alexander H. King

A few years ago, I was walking near the old Union Station in Pittsburgh with a colleague only slightly younger than myself, when we happened upon some large-scale relics of the steel industry displayed for public viewing. “You don’t see too many of those in public parking lots,” I offered. “Um… what is it?” was the response. I suppose I was just a little surprised that a prominent materials scientist did not recognize a Bessemer converter—arguably the principal source of wealth during the U.S. industrial revolution—but this conversation took place back when steel was in decline, and many university Materials …

Go to article

Controlling Surface Morphologies By Time-Delayed Feedback, M. Block, Beate Schmittmann, E. Schöll Jun 2007

Controlling Surface Morphologies By Time-Delayed Feedback, M. Block, Beate Schmittmann, E. Schöll

Beate Schmittmann

We propose a method to control the roughness of a growing surface via a time-delayed feedback scheme. The method is very general and can be applied to a wide range of nonequilibrium growth phenomena, from solid-state epitaxy to tumor growth. Possible experimental realizations are suggested. As an illustration, we consider the Kardar-Parisi-Zhang equation [Phys. Rev. Lett. 56, 889 (1986)] in 1+1 dimensions and show that the effective growth exponent of the surface width can be stabilized at any desired value in the interval [0.25, 0.33], for a significant length of time.

Go to article

Phase Error Compensation For A 3-D Shape Measurement System Based On The Phase-Shifting Method, Song Zhang, Peisen S. Huang Jun 2007

Phase Error Compensation For A 3-D Shape Measurement System Based On The Phase-Shifting Method, Song Zhang, Peisen S. Huang

Song Zhang

This paper describes a novel phase error compensation method for reducing the measurement error caused by nonsinusoidal waveforms in phase-shifting methods. For 3-D shape measurement systems using commercial video projectors, the nonsinusoidal waveform of the projected fringe patterns as a result of the nonlinear gamma of projectors causes significant phase measurement error and therefore shape measurement error. The proposed phase error compensation method is based on our finding that the phase error due to the nonsinusoidal waveform depends only on the nonlinearity of the projector’s gamma. Therefore, if the projector’s gamma is calibrated and the phase error due to the …

Go to article

Density Functional Study Of Structural Trends For Late-Transition-Metal 13-Atom Clusters, Lin-Lin Wang, Duane D. Johnson Jun 2007

Density Functional Study Of Structural Trends For Late-Transition-Metal 13-Atom Clusters, Lin-Lin Wang, Duane D. Johnson

Duane D. Johnson

Because reactivity increases as particle size decreases and competition between numerous structures are possible, which affects catalytic and magnetic properties, we study the structural trends of late-transition-metal 13-atom clusters using density functional theory within the generalized gradient approximation to exchange-correlation functional. We consider open structural motifs, such as bilayer and cubic (recently found to have lower energy), and find new bilayer candidates that are even lower in energy. To study the influence of d-orbital filling on structural trends, we focus on Pt, Pd, and Rh clusters and find several new, low-energy structures for Pt13 and Pd13 from searches using a …

Go to article

Quantifying Total And Sustainable Agricultural Biomass Resources In South Dakota, Kurt A. Rosentrater, Russell Persyn, Dennis Todey Jun 2007

Quantifying Total And Sustainable Agricultural Biomass Resources In South Dakota, Kurt A. Rosentrater, Russell Persyn, Dennis Todey

Kurt A. Rosentrater

Conversion of biomass is considered the next major advance in biorenewable fuels, energy, and products. Wholesale conversion to biomass utilization could result in removal of current crop residues from agricultural fields or even implementation of different crops and cropping strategies (i.e., switchgrass). To date, the driver for biomass processing has been economics and limitations on the conversion of the lignocellulose. Over the last forty years significant investments and resultant changes in management practices in the agricultural sector have focused on soil and water conservation. One of the major efforts has focused on conservation-till or no-till, with the goal of retaining …

Go to article

Organosilicas With Chiral Bridges And Self-Generating Mesoporosity, Andreas Ide, Rebecca Voss, Gudrun Scholz, Geoffrey A. Ozin, Markus Antonietti, Arne Thomas May 2007

Organosilicas With Chiral Bridges And Self-Generating Mesoporosity, Andreas Ide, Rebecca Voss, Gudrun Scholz, Geoffrey A. Ozin, Markus Antonietti, Arne Thomas

Rebecca Cademartiri

Amine-functionalized, chiral mesoporous organosilicas were prepared from a rationally designed precursor, which combines the functions of a network builder, a chiral latent functional group, and a porogen in one molecule. The precursors are formed by a convenient enantioselective hydroboration using (S)-monoisopinocampheylborane on an ethylene-bridged silica precursor. These precursors do self-organize when hydrolysis of their inorganic moiety takes place via an aggregation of their organic moiety into hydrophobic domains. After a condensation−ammonolysis sequence mesoporous organosilicas functionalized with chiral amine groups are obtained, with the complete chiral functionalities located at the pore wall surface and therefore accessible to chemical processes. The pore …

Go to article

A Sum Frequency Generation Vibrational Spectroscopic Study Of The Adsorption And Reactions Of C6 Hydrocarbons At High Pressures On Pt(100), Kaitlin M. Bratlie, Gabor A. Somorjai May 2007

A Sum Frequency Generation Vibrational Spectroscopic Study Of The Adsorption And Reactions Of C6 Hydrocarbons At High Pressures On Pt(100), Kaitlin M. Bratlie, Gabor A. Somorjai

Kaitlin M. Bratlie

Sum frequency generation (SFG) vibrational spectroscopy was used to investigate the adsorption geometries and surface reactions of various C6 hydrocarbons (n-hexane, 2-methylpentane, 3-methylpentane, and 1-hexene) on Pt(100). At 300 K and in the presence of excess hydrogen, n-hexane, 3-methylpentane, and 2-methylpentane adsorb molecularly on Pt(100) mostly in “flat-lying” conformations. Upon heating the metal surface to 450 K, the molecules underwent dehydrogenation to form new surface species in “standing-up” conformations, such as hexylidyne and metallacyclic species.

Go to article

Coarsening Of “Clouds” And Dynamic Scaling In A Far-From-Equilibrium Model System, D. A. Adams, Beate Schmittmann, R. K. P. Zia Apr 2007

Coarsening Of “Clouds” And Dynamic Scaling In A Far-From-Equilibrium Model System, D. A. Adams, Beate Schmittmann, R. K. P. Zia

Beate Schmittmann

A two-dimensional lattice gas of two species, driven in opposite directions by an external force, undergoes a jamming transition if the filling fraction is sufficiently high. Using Monte Carlo simulations, we investigate the growth of these jams (‘‘clouds’’), as the system approaches a nonequilibrium steady state from a disordered initial state. We monitor the dynamic structure factor S(kx,ky;t) and find that the kx=0 component exhibits dynamic scaling, of the form S(0,ky;t)=tβS̃ (kytα). Over a significant range of times, we observe excellent data collapse with α=1/2 and β=1. The effects of varying filling fraction and driving force are discussed.

Go to article

Interface Reorientation During Coherent Phase Transformations, Valery I. Levitas, I. B. Ozsoy, D. L. Preston Apr 2007

Interface Reorientation During Coherent Phase Transformations, Valery I. Levitas, I. B. Ozsoy, D. L. Preston

Valery I. Levitas

The universal thermodynamic driving force for coherent plane interface reorientation (IR) during first-order phase transformations (PT) in solids is derived. The relation between the rates of IR and interface propagation (IP) and the corresponding driving forces are derived for combined athermal and drag interface friction. The coupled evolution of IR and IP during cubic-tetragonal and tetragonal-orthorhombic PTs under three-dimensional loading is studied. An instability in the interface orientation is shown to have the features of a first-order PT.

Go to article

Compression Molding Of Phenolic Resin And Corn-Based Ddgs Blends, Kurt A. Rosentrater, R. A. Tatara, S. Suraparaju Apr 2007

Compression Molding Of Phenolic Resin And Corn-Based Ddgs Blends, Kurt A. Rosentrater, R. A. Tatara, S. Suraparaju

Kurt A. Rosentrater

With the rapid growth in the ethanol fuel industry in recent years, considerable research is being devoted to optimizing the use of processing coproducts, such as distillers dried grains with solubles (DDGS), in livestock diets. Because these residues contain high fiber levels, they may be amendable to incorporation into bio-based composites. Thus, the goal of this study was to demonstrate the viability of using corn-based DDGS as a biofiller with phenolic resin, in order to produce a novel biomaterial. DDGS was blended with phenolic resin at 0, 10, 25, 50, 75, and 90%, by weight, and then compression molded at …

Go to article

First-Principles Prediction Of Phase-Segregating Alloy Phase Diagrams And A Rapid Design Estimate Of Their Transition Temperatures, Nikolai A. Zarkevich, Teck L. Tan, Duane D. Johnson Mar 2007

First-Principles Prediction Of Phase-Segregating Alloy Phase Diagrams And A Rapid Design Estimate Of Their Transition Temperatures, Nikolai A. Zarkevich, Teck L. Tan, Duane D. Johnson

Nikolai A. Zarkevich

We calculate the transition temperature versus concentration (Tc vs c) phase diagrams of several phase-segregating alloys [fcc Ca-Sr, Au-Pt, and Rh-(Pd,Cu,Ag,Au)] using a multiscale method combining first-principles calculations and Monte Carlo via the cluster expansion (CE). We study Pd-Rh, with its well-known high-T miscibility gap, to verify the method’s reliability. We predict that Ca-Sr segregates at low temperatures. We then show that a rapid estimate of Tc is obtained from enthalpies analytically derived from a CE, and, using thermodynamic integration, we determine under what circumstances this mean-field estimate is accurate compared to Monte Carlo results. Also, we discuss how an …

Go to article

Enantioselective 1,3-Dipolar Cycloadditions Of Diazoacetates With Electron-Deficient Olefins, Mukund P. Sibi, Levi M. Stanley, Takahiro Soeta Mar 2007

Enantioselective 1,3-Dipolar Cycloadditions Of Diazoacetates With Electron-Deficient Olefins, Mukund P. Sibi, Levi M. Stanley, Takahiro Soeta

Levi M. Stanley

A general strategy for highly enantioselective 1,3-dipolar cycloaddition of diazoesters to β-substituted, α-substituted, and α,β-disubstituted α,β-unsaturated pyrazolidinone imides is described. Cycloadditions utilizing less reactive α,β-disubstituted dipolarophiles require elevated reaction temperatures, but still provide the corresponding pyrazolines with excellent enantioselectivities. Finally, an efficient synthesis of (−)-manzacidin A employing this cycloaddition methodology as a key step is illustrated.

Go to article

Generic Nonsinusoidal Phase Error Correction For Three-Dimensional Shape Measurement Using A Digital Video Projector, Song Zhang, Shing-Tung Yau Jan 2007

Generic Nonsinusoidal Phase Error Correction For Three-Dimensional Shape Measurement Using A Digital Video Projector, Song Zhang, Shing-Tung Yau

Song Zhang

A structured light system using a digital video projector is widely used for 3D shape measurement. However, the nonlinear γ of the projector causes the projected fringe patterns to be nonsinusoidal, which results in phase error and therefore measurement error. It has been shown that, by using a small look-up table (LUT), this type of phase error can be reduced significantly for a three-step phase-shifting algorithm. We prove that this algorithm is generic for any phase-shifting algorithm. Moreover, we propose a new LUT generation method by analyzing the captured fringe image of a flat board directly. Experiments show that this …

Go to article

A Fully Lagrangian Numerical Method For Calculating The Dynamics Of Oscillating Micro And Nanoscale Objects Immersed In Fluid, Nicole N. Hashemi, Mark Paul, Javier Alcazar, Raul Radovitzky Jan 2007

A Fully Lagrangian Numerical Method For Calculating The Dynamics Of Oscillating Micro And Nanoscale Objects Immersed In Fluid, Nicole N. Hashemi, Mark Paul, Javier Alcazar, Raul Radovitzky

Nastaran Hashemi

Many micro and nano-technologies rely upon the complicated motion of objects immersed in a viscous fluid. It is often the case that for such problems analytical theory is not available to quantitatively describe and predict the device dynamics. In addition, the numerical simulation of such devices involves moving boundaries and use of the standard Eulerian computational approaches are often difficult to implement. In order to address this problem we use and validate a fully Lagrangian finite element approach that treats the moving boundaries in a natural manner. We validate the method for use in calculating the dynamics of oscillating objects …

Go to article

Thermal Effects On Mechanical Grinding-Induced Surface Texture In Tetragonal Piezoelectrics, Wonyoung Chang, Alexander H. King, Keith J. Bowman Jan 2007

Thermal Effects On Mechanical Grinding-Induced Surface Texture In Tetragonal Piezoelectrics, Wonyoung Chang, Alexander H. King, Keith J. Bowman

Alexander H. King

The effect of temperature on grinding-induced texture in tetragonal lead zirconate titanate (PZT) and lead titanate (PT) has been investigated using in situ x-ray diffraction (XRD) with an area detector. In contrast with previous results on electrical poling, mechanically-ground PT and soft PZT materials retain strong ferroelastic textures during thermal cycling, even after excursions to temperatures slightly above the Curie temperature. The relationship between the residual stresses in the surface region, caused by grinding, and those resulting from domain wall motion is elucidated by in situ texture measurements obtained during thermal cycling.

Go to article

How Surface Stresses Lead To Size-Dependent Mechanics Of Tensile Deformation In Nanowires, M. Ravi Shankar, Alexander H. King Jan 2007

How Surface Stresses Lead To Size-Dependent Mechanics Of Tensile Deformation In Nanowires, M. Ravi Shankar, Alexander H. King

Alexander H. King

It has been proposed that surface and interface stresses can modify the elastic behavior in nanomaterials such as nanowires. The authors show that surface stresses modify the tensile response of nanowires only when nonlinear elastic effects become important leading to cross terms between the applied stress and the surface stress. These effects are only significant when the radius of the nanowire is of the order of a few nanometers. The resulting alteration of tensile stiffness, though effected in part by the nonlinear elastic modulus, is particularly wrought by a modification of the stress state in the deformed nanowire.

Go to article

Effect Of The Lattice Crystallinity On The Electron−Phonon Relaxation Rates In Gold Nanoparticles, Wenyu Huang, Wei Qian, Mostafa El-Sayed Jan 2007

Effect Of The Lattice Crystallinity On The Electron−Phonon Relaxation Rates In Gold Nanoparticles, Wenyu Huang, Wei Qian, Mostafa El-Sayed

Wenyu Huang

In order to study the importance of surface phonons on the electron−phonon relaxation in plasmonic nanoparticles, the effect of size, shape, and materials have recently been studied. Gold and silver nanoparticles have shown no dependence on size and shape while copper nanoparticles have shown some size dependence. This suggests that the bulk phonons, which are sensitive to the bulk-phase structure, are solely responsible for the relaxation of the hot electron in gold and silver plasmonic nanoparticles. The importance of bulk phonons should depend on the degree of crystallinity. In the present study, we have found that the electron−phonon relaxation rate …

Go to article

On The Universal Scaling Behavior Of The Distance Decay Of Plasmon Coupling In Metal Nanoparticle Pairs: A Plasmon Ruler Equation, Prashant K. Jain, Wenyu Huang, Mostafa A. El-Sayed Jan 2007

On The Universal Scaling Behavior Of The Distance Decay Of Plasmon Coupling In Metal Nanoparticle Pairs: A Plasmon Ruler Equation, Prashant K. Jain, Wenyu Huang, Mostafa A. El-Sayed

Wenyu Huang

Localized surface plasmon resonances (LSPR) in lithographically fabricated gold (Au) nanodisc pairs are investigated using microabsorption spectroscopy and electrodynamic simulations. In agreement with previous work, we find that the fractional plasmon wavelength shift for polarization along the interparticle axis decays nearly exponentially with the interparticle gap. In addition, we find that the decay length is roughly about 0.2 in units of the particle size for different nanoparticle size, shape, metal type, or medium dielectric constant. The near-exponential distance decay and the interesting “universal” scaling behavior of interparticle plasmon coupling can be qualitatively explained on the basis of a dipolar-coupling model …

Go to article

The Effect Of Plasmon Field On The Coherent Lattice Phonon Oscillation In Electron-Beam Fabricated Gold Nanoparticle Pairs, Wenyu Huang, Wei Qian, Prashant K. Jain, Mostafa El-Sayed Jan 2007

The Effect Of Plasmon Field On The Coherent Lattice Phonon Oscillation In Electron-Beam Fabricated Gold Nanoparticle Pairs, Wenyu Huang, Wei Qian, Prashant K. Jain, Mostafa El-Sayed

Wenyu Huang

By using electron beam lithography, we fabricated pairs of gold nanoparticles with varying interparticle separation. Double-beam femtosecond transient absorption spectroscopy was used to determine the coherent lattice oscillation frequency as a function of the interparticle separation in the presence of the plasmon field excited by the monitoring probe light. We found that the fractional shift in the coherent lattice phonon oscillation frequency follows an exponential decay with respect to the interparticle gap scaled by the disc diameter with the same decay constant as that previously observed for the fractional shift in the surface plasmon electronic oscillation resonance frequency. This strongly …

Go to article

Structure And Thermodynamics Of A Conserved U2 Snrna Domain From Yeast And Human, Dipali G. Sashital, Vincenzo Venditti, Courtney G. Angers, Gabriel Cornilescu, Samuel E. Butcher Jan 2007

Structure And Thermodynamics Of A Conserved U2 Snrna Domain From Yeast And Human, Dipali G. Sashital, Vincenzo Venditti, Courtney G. Angers, Gabriel Cornilescu, Samuel E. Butcher

Vincenzo Venditti

The spliceosome is a dynamic ribonucleoprotein complex responsible for the removal of intron sequences from pre-messenger RNA. The highly conserved 5′ end of the U2 small nuclear RNA (snRNA) makes key base-pairing interactions with the intron branch point sequence and U6 snRNA. U2 stem I, a stem–loop located in the 5′ region of U2, has been implicated in spliceosome assembly and may modulate the folding of the U2 and U6 snRNAs in the spliceosome active site. Here we present the NMR structures of U2 stem I from human and Saccharomyces cerevisiae. These sequences represent the two major classes of U2 …

Go to article

Multilevel Quality-Guided Phase Unwrapping Algorithm For Real-Time Three-Dimensional Shape Reconstruction, Song Zhang, Xiaolin Li, Shing-Tung Yau Jan 2007

Multilevel Quality-Guided Phase Unwrapping Algorithm For Real-Time Three-Dimensional Shape Reconstruction, Song Zhang, Xiaolin Li, Shing-Tung Yau

Song Zhang

A multilevel quality-guided phase unwrapping algorithm for real-time 3D shape measurement is presented. The quality map is generated from the gradient of the phase map. Multilevel thresholds are used to unwrap the phase level by level. Within the data points in each level, a fast scan-line algorithm is employed. The processing time of this algorithm is approximately 18.3  ms for an image size of 640×480 pixels in an ordinary computer. We demonstrate that this algorithm can be implemented into our real-time 3D shape measurement system for real-time 3D reconstruction. Experiments show that this algorithm improves the previous scan-line phase unwrapping …

Go to article

Next Last