One-dimensional Surface Research Articles

A Model for Selection of Eyespots on Butterfly Wings.

Unsolved ProblemThe development of eyespots on the wing surface of butterflies of the family Nympalidae is one of the most studied examples of biological pattern formation.However, little is known about the mechanism that determines the number and precise locations of eyespots on the wing. Eyespots develop around signaling centers, called foci, that are located equidistant from wing veins along the midline of a wing cell (an area bounded by veins). A fundamental question that remains unsolved is, why a certain wing cell develops an eyespot, while other wing cells do not.Key Idea and ModelWe illustrate that the key to understanding focus point selection may be in the venation system of the wing disc. Our main hypothesis is that changes in morphogen concentration along the proximal boundary veins of wing cells govern focus point selection. Based on previous studies, we focus on a spatially two-dimensional reaction-diffusion system model posed in the interior of each wing cell that describes the formation of focus points. Using finite element based numerical simulations, we demonstrate that variation in the proximal boundary condition is sufficient to robustly select whether an eyespot focus point forms in otherwise identical wing cells. We also illustrate that this behavior is robust to small perturbations in the parameters and geometry and moderate levels of noise. Hence, we suggest that an anterior-posterior pattern of morphogen concentration along the proximal vein may be the main determinant of the distribution of focus points on the wing surface. In order to complete our model, we propose a two stage reaction-diffusion system model, in which an one-dimensional surface reaction-diffusion system, posed on the proximal vein, generates the morphogen concentrations that act as non-homogeneous Dirichlet (i.e., fixed) boundary conditions for the two-dimensional reaction-diffusion model posed in the wing cells. The two-stage model appears capable of generating focus point distributions observed in nature.ResultWe therefore conclude that changes in the proximal boundary conditions are sufficient to explain the empirically observed distribution of eyespot focus points on the entire wing surface. The model predicts, subject to experimental verification, that the source strength of the activator at the proximal boundary should be lower in wing cells in which focus points form than in those that lack focus points. The model suggests that the number and locations of eyespot foci on the wing disc could be largely controlled by two kinds of gradients along two different directions, that is, the first one is the gradient in spatially varying parameters such as the reaction rate along the anterior-posterior direction on the proximal boundary of the wing cells, and the second one is the gradient in source values of the activator along the veins in the proximal-distal direction of the wing cell.

A surface and subsurface model for the simulation of rainfall infiltration in slopes

Rainfall infiltration is one of the major triggering factors leading to slope failures in geotechnical engineering. Numerical investigation on rainfall infiltration is often based on Richards’ equation, which ignores the surface water effects and simplifies the boundary conditions. In reality, rainfall, infiltration, and surface runoff are interacted simultaneously. In this paper a new conjunctive one-dimensional surface flow and two-dimensional subsurface flow model for geotechnical slope is developed. The interaction between surface and subsurface flow is the interface infiltration rate, which is obtained by iterations. The results of comparisons between coupled and uncoupled models show that the surface water depth rises up as runoff increases and it tends to a dynamic balance state with a steady surface water depth. Interaction between surface and subsurface flow has remarkable effects on infiltration process. According to the results of coupled model, more rainwaters infiltrate into the slope. Therefore, pore water pressure changes faster and the wetting front moves deeper into the soil. Under initial drier condition, the capacity of infiltration is higher and more rainfall can be absorbed into slope, thus the differences of infiltration rate and pore water pressure between the coupled and uncoupled model are more significant.

Selected cis- and trans-3-fluorostyrene rotamers studied by two-color resonant two-photon mass-analyzed threshold ionization spectroscopy

We applied two-color resonant two-photon ionization and mass-analyzed threshold ionization techniques to record the vibronic, photoionization efficiency, and cation spectra of the selected rotamers of 3-fluorostyrene. The adiabatic ionization energies of cis- and trans-3-fluorostyrene were determined to be 69 960±5 and 69 856±5cm−1, respectively. Cation vibrations 10a, 15, 6b, and 12 of both rotamers have been found to have frequencies of 218, 404, 452, and 971cm−1, respectively. This finding shows that the relative orientation of the vinyl group with respect to the F atom does not affect these vibrations of the 3-fluorostyrene cation. Our one-dimensional potential energy surface calculations support that the cis–trans isomerization of 3-fluorostyrene does not occur under the present experimental conditions.

Scattering of electromagnetic waves from random rough metallic surfaces with one-dimensional structure calculated by the surface impedance boundary condition method (SIBC)

A comparison between exact solutions and surface impedance boundary condition method, for the phenomenon of light scattering from one-dimensional random rough metallic surfaces in both cases of polarization (s- and p-) is presented. The reflective properties of random rough metallic surfaces at a large angle of incidence have been reported on due to their potential applications in some of the radiative heat transfer research areas. The influence of surface roughness, shadowing effects, the nature of polarization, and the nature of the material on the behavior of reflectivity and emissivity has been quantified.

The molecular dynamics of adsorption and dissociation of O2 on Pt(553).

Molecular adsorption and dissociation of O2 on the stepped Pt(553) surface have been investigated using supersonic molecular beam techniques and temperature programmed desorption. The initial and coverage-dependent sticking probability was determined with the King and Wells technique for various combinations of incident kinetic energy, surface temperature, incident angle, and surface coverage. A comparison with similar data for Pt(533) and Pt{110}(1 × 2) shows quantitatively the same high step-induced sticking at low incident energies compared to Pt(111). The enhancement is therefore insensitive to the exact arrangement of atoms forming surface corrugation. We consider energy transfer and electronic effects to explain the enhanced sticking. On the other hand, dissociation dynamics at higher incident kinetic energies are strongly dependent on step type. The Pt(553) and Pt(533) surfaces are more reactive than Pt(111), but the (100) step shows higher sticking than the (110) step. We relate this difference to a variation in the effective lowering of the barrier to dissociation from molecularly adsorbed states into atomic states. Our findings are in line with results from experimental desorption studies and theoretical studies of atomic binding energies. We discuss the influence of the different step types on sticking and dissociation dynamics with a one-dimensional potential energy surface.

A Method for Extracting the Free Energy Surface and Conformational Dynamics of Fast-Folding Proteins from Single Molecule Photon Trajectories.

Single molecule fluorescence spectroscopy holds the promise of providing direct measurements of protein folding free energy landscapes and conformational motions. However, fulfilling this promise has been prevented by technical limitations, most notably, the difficulty in analyzing the small packets of photons per millisecond that are typically recorded from individual biomolecules. Such limitation impairs the ability to accurately determine conformational distributions and resolve sub-millisecond processes. Here we develop an analytical procedure for extracting the conformational distribution and dynamics of fast-folding proteins directly from time-stamped photon arrival trajectories produced by single molecule FRET experiments. Our procedure combines the maximum likelihood analysis originally developed by Gopich and Szabo with a statistical mechanical model that describes protein folding as diffusion on a one-dimensional free energy surface. Using stochastic kinetic simulations, we thoroughly tested the performance of the method in identifying diverse fast-folding scenarios, ranging from two-state to one-state downhill folding, as a function of relevant experimental variables such as photon count rate, amount of input data, and background noise. The tests demonstrate that the analysis can accurately retrieve the original one-dimensional free energy surface and microsecond folding dynamics in spite of the sub-megahertz photon count rates and significant background noise levels of current single molecule fluorescence experiments. Therefore, our approach provides a powerful tool for the quantitative analysis of single molecule FRET experiments of fast protein folding that is also potentially extensible to the analysis of any other biomolecular process governed by sub-millisecond conformational dynamics.

Characteristic Fermi Surface Properties of V2Ga5, CoGa3, TiGa3, ZrGa3, and ZrAl3 with Different Tetragonal Structures

To clarify the Fermi surface properties based on the dimensionality of electronic states, we grew single crystals of V2Ga5, CoGa3, TiGa3, and ZrGa3 (ZrAl3) with different tetragonal structures and carried out de Haas–van Alphen experiments, together with full-potential linearized augmented plane wave band calculations. A nearly one-dimensional plate Fermi surface is obtained in the band calculations for V2Ga5 with a flat tetragonal structure. The corresponding single crystal is of needle shape along the tetragonal [001] direction. The obtained Fermi surfaces of CoGa3 are very similar to those of Ni3Ga with the AuCu3-type cubic structure because the crystal structure of CoGa3 is nearly cubic and the corresponding single crystal is of pyramidal shape with a flat (111) plane. The Fermi surfaces of TiGa3 are also very similar to those of YCu2Si2 with the ThCr2Si2-type tetragonal structure. The cylindrical Fermi surfaces with concave and convex parts are realized in ZrGa3 and ZrAl3 with the flat Brillouin zone...

Optical tuning of guided mode resonance in an azo-copolymer waveguide grating structure inscribed with a surface relief grating

Optical tuning of guided mode resonance (GMR) is demonstrated in a photosensitive azo-copolymer waveguide grating structure (WGS), consisted of a one-dimensional surface relief grating (SRG) inscribed on top of an azo-copolymer planar waveguide layer. The azo-copolymer WGS was designed and fabricated to have GMRs at visible wavelength range for transverse-electric (TE) polarization. The first-order GMR wavelength can be tuned to shorter wavelength by illuminating the WGS with a linear polarized light at 514 nm wavelength, which produces photoisomerization-induced refractive index change in the azo-copolymer waveguide layer. The photo-induced GMR wavelength shift increases with the pumping power, and its maximum shift is 25 nm. The WGS retains a memory for the optical pumping, and its GMR wavelength doesn't return to the original peak position after switching off the pumping beam. To make a full-recovery of the GMR peak position, the WGS has to be illuminated by a second pumping beam with a vertical polari...

Facile synthesis of CdS@TiO2 core–shell nanorods with controllable shell thickness and enhanced photocatalytic activity under visible light irradiation

Amorphous TiO2 layers with a controllable thickness from 3.5 to 40nm were coated on the one-dimensional CdS nanorods surface under mild conditions. Compared to the bare CdS nanorods, the as-prepared CdS@TiO2 nanorods exhibit enhanced photocatalytic activities for phenol photodecomposition under visible light irradiation. The improved photoactivity is ascribed to the efficient separation of photogenerated electron and hole charge carriers between CdS cores and TiO2 shells. This study promises a simple approach to fabricating CdS@TiO2 core–shell structure nanocomposites, and can be applied for other semiconductor cores with TiO2 shells.

Long-range surface plasmon amplification with current injection on a one-dimensional photonic crystal surface.

A one-dimensional (1D) semiconductor photonic crystal (PC) structure with a terminal metal nanofilm, supporting propagation of long-range surface plasmons (LRSPs), is considered as an LRSP amplifier with current pumping. Current is injected to an active region through the metal nanofilm from one side and doped semiconductor layers from the other side. The propagation length of LRSP waves in such 1D PC structures reaches several millimeters, and therefore, a gain as low as 10 cm(-1) is enough to compensate for attenuation and amplify LRSPs. A unique advantage of this structure is that the refractive index of LRSP wave is very close to unity. As a result, no return reflection to semiconductor occurs during the edge-emission of LRSP to air, and this enhances the light extraction efficiency from semiconductor light sources such as edge-emitting superluminescent diodes and light-emitting diodes (LEDs). Optical feedback may be incorporated in this LRSP amplifier by grating deposition on the external side of the metal nanofilm, and LRSP lasing (i.e., long-range SPASER) may be realized without the use of complicated "etch-and-regrow" processes.

Spin-triplet superconductivity inSr2RuO4due to orbital and spin fluctuations: Analyses by two-dimensional renormalization group theory and self-consistent vertex-correction method

We study the mechanism of the triplet superconductivity (TSC) in Sr$_2$RuO$_4$ based on the multiorbital Hubbard model. The electronic states are studied using the recently developed renormalization group method combined with the constrained random-phase-approximation, called the RG+cRPA method. Thanks to the vertex correction (VC) for the susceptibility, which is dropped in the mean-field-level approximations, strong orbital and spin fluctuations at $Q \approx(2\pi/3,2\pi/3)$ emerge in the quasi one-dimensional Fermi surfaces (FSs) composed of $d_{xz}+d_{yz}$ orbitals. Due to the cooperation of both fluctuations, we obtain the triplet superconductivity in the $E_u$ representation, in which the superconducting gap is given by the linear combination of $(\Delta_x(k),\Delta_y(k))\sim (\sin 3k_x,\sin 3k_y)$. Very similar results are obtained by applying the diagrammatic calculation called the self-consistent VC method. Thus, the idea of "orbital+spin fluctuation mediated TSC" is confirmed by both RG+cRPA method and the self-consistent VC method. We also reveal that a substantial superconducting gap on the $d_{xy}$-orbital FS is induced from the gaps on the quasi one-dimensional FSs, in consequence of the large orbital-mixture due to the 4$d$ spin-orbit interaction.

Modeling Tidal Freshwater Marsh Sustainability in the Sacramento-San Joaquin Delta Under a Broad Suite of Potential Future Scenarios

In this paper, we report on the adaptation and application of a one-dimensional marsh surface elevation model, the Wetland Accretion Rate Model of Ecosystem Resilience (WARMER), to explore the conditions that lead to sustainable tidal freshwater marshes in the Sacramento–San Joaquin Delta. We defined marsh accretion parameters to encapsulate the range of observed values over historic and modern time-scales based on measurements from four marshes in high and low energy fluvial environments as well as possible future trends in sediment supply and mean sea level. A sensitivity analysis of 450 simulations was conducted encompassing a range of porosity values, initial elevations, organic and inorganic matter accumulation rates, and sea-level rise rates. For the range of inputs considered, the magnitude of SLR over the next century was the primary driver of marsh surface elevation change. Sediment supply was the secondary control. More than 84% of the scenarios resulted in sustainable marshes with 88 cm of SLR by 2100, but only 32% and 11% of the scenarios resulted in surviving marshes when SLR was increased to 133 cm and 179 cm, respectively. Marshes situated in high-energy zones were marginally more resilient than those in low-energy zones because of their higher inorganic sediment supply. Overall, the results from this modeling exercise suggest that marshes at the upstream reaches of the Delta—where SLR may be attenuated—and high energy marshes along major channels with high inorganic sediment accumulation rates will be more resilient to global SLR in excess of 88 cm over the next century than their downstream and low-energy counterparts. However, considerable uncertainties exist in the projected rates of sea-level rise and sediment availability. In addition, more research is needed to constrain future rates of aboveground and belowground plant productivity under increased CO 2 concentrations and flooding.

Quasilocal strange metal

One of the key factors that determine the fates of quantum many-body systems in the zero temperature limit is the competition between kinetic energy that delocalizes particles in space and interaction that promotes localization. While one dominates over the other in conventional metals and insulators, exotic states can arise at quantum critical points where none of them clearly wins. Here we present a class of metallic states that emerge at an antiferromagnetic (AF) quantum critical point in the presence of one-dimensional Fermi surfaces embedded in space dimensions three and below. At the critical point, interactions between particles are screened to zero in the low-energy limit and at the same time the kinetic energy is suppressed in certain spatial directions to the leading order in a perturbative expansion that becomes asymptotically exact in three dimensions. The resulting dispersionless and interactionless state exhibits distinct quasilocal strange metallic behaviors due to a subtle dynamical balance between screening and infrared singularity caused by spontaneous reduction of effective dimensionality. The strange metal, which is stable near three dimensions, shows enhanced fluctuations of bond density waves, $d$-wave pairing, and pair density waves.

Effects of pressure-dependent viscosity variation on the squeeze film lubrication between a sphere and a rough flat plate with couple stress fluids

In this paper, a theoretical study of the combined effects of surface roughness and the variation of viscosity with pressure on the squeeze film lubrication between sphere and a flat plate is presented. Based on the Christensen’s stochastic theory for the hydrodynamic lubrication of rough surfaces, two types of one-dimensional surface roughness (radial and azimutal) patterns are considered. The generalized averaged Reynold’s equation for Stokes couple stress fluids accounting for the pressure dependent viscosity is mathematically derived for the problem under consideration. The standard perturbation technique is used to solve the averaged nonlinear Reynold’s equation and an approximate analytical solution for the fluid film mean pressure is obtained for the two types of one-dimensional roughness patterns. It is found that, the effects of couple stresses and pressure dependent viscosity variation are to improve the squeeze film characteristics.

Inverse elastic surface scattering with near-field data**The research was supported in part by the NSF grant DMS-1151308.

Consider the scattering of a time-harmonic plane wave by a one-dimensional periodic surface. A novel computational method is proposed for solving the inverse elastic surface scattering problem by using the near-field data. Above the surface, the space is filled with a homogeneous and isotropic elastic medium, while the space below the surface is assumed to be elastically rigid. Given an incident field, the inverse problem is to reconstruct the surface from the displacement of the wave field at a horizontal line above the surface. This paper is a nontrivial extension of the authors’ recent work on near-field imaging of the Helmholtz equation and the Maxwell equation to the more complicated Navier equation due to coexistence of the compressional and shear waves that propagate at different speed. Based on the Helmholtz decomposition, the wave field is decomposed into its compressional and shear parts by using two scalar potential functions. The transformed field expansion is then applied to each component and a coupled recurrence relation is obtained for their power series expansions. By solving the coupled system in the frequency domain, simple and explicit reconstruction formulas are derived for two types of measurement data. The method requires only a single illumination with a fixed frequency and incident angle. Numerical experiments show that it is simple, effective, and efficient to reconstruct the scattering surfaces with subwavelength resolution.

A fast PO–PO hybrid method for analysing the Doppler spectrum of a plasma-coated object above a rough sea surface: horizontal polarization

A fast hybrid method based on physical optics (PO) and the reciprocity theorem is proposed to analyse the Doppler spectrum of a two-dimensional, moving plasma-coated object above a one-dimensional time-evolving lossy dielectric rough sea surface. This hybrid method eliminates the need for numerical solution of the polarization currents on the object and the time-evolving sea surface, thereby greatly improving the computing speed. The method is verified by conventional numerical methods. The characteristics of the Doppler spectrum of a plasma-coated object above a time-evolving sea surface are analysed in detail, including the effects of several parameters such as the incident angle and the velocity of the moving object. The effects of some key parameters on the stealth performance are also examined.

Sub-Domain Decomposition Iterative Method Combined With ACA: An Efficient Technique for the Scattering From a Large Highly Conducting Rough Sea Surface

The sub-domain decomposition iterative method (SDIM) is presented to solve efficiently a large linear system obtained by sampling the boundary integral equations from the method of moments. Then, this new technique is tested on the electromagnetic scattering problem from a large highly conducting one-dimensional rough sea surface. The diagonal blocks are the local impedance matrices corresponding to the geometry sub-domains while the off-diagonal blocks are the coupling matrices describing the interaction between two different sub-domains. The principle of SDIM is to invert the impedance matrix by blocks reducing significantly the complexity in comparison to a direct LU inversion of the whole impedance matrix. In addition, to accelerate the matrix-vector products and to reduce the memory requirement, the adaptive cross approximation (ACA) is applied to compress the sub-domain coupling matrices. For microwave frequencies, the results show that SDIM converges rapidly and faster for the TM polarization. Moreover, the mean compression ratio of ACA is of the order of 98%, which makes this method very efficient.

Quenching of excited electronic states of quantum dots by a metallic nanowire

Nonradiative transfer of energy from an excited quantum dot to a conducting nanowire accompanied by emission of one-dimensional surface plasmons is investigated. We consider the cases of intraband and interband relaxation of charge carriers in the quantum dot. Calculations of the nonradiative energy transfer rate are performed for various values of system parameters. We show that the rate of energy transfer by the considered mechanisms can be as large as ∼1011 s−1, which is comparable to the rates due to other possible mechanisms of relaxation and exceeds significantly the typical rate of radiative electron-hole recombination.

Bioinspired super-wettability from fundamental research to practical applications.

Engineered wettability is a traditional, yet key issue in surface science and attracts tremendous interest in solving large-scale practical problems. Recently, different super-wettability systems have been discovered in both nature and experiments. In this Review we present three types of super-wettability, including the three-dimensional, two-dimensional, and one-dimensional material surfaces. By combining different super-wettabilities, novel interfacial functional systems could be generated and integrated into devices for use in tackling current and the future problems including resources, energy, environment, and health.

Special Section Guest Editorial: High-Performance Computing in Applied Remote Sensing: Part 3

Part 3 of this Special Section on High-Performance Computing in Applied Remote Sensing continues to present the state-of-the-art research in incorporating high-performance computing facilities and algorithms for effective and efficient remote sensing applications. “Land cover classification in multispectral imagery using clustering of sparse approximations over learned feature dictionaries” by Moody et al. presents results from an ongoing effort to extend neuromimetic machine vision algorithms to multispectral data using adaptive signal processing combined with compressive sensing and machine learning techniques. “Graphics processor unit accelerated finite-difference time domain method for electromagnetic scattering from onedimensional large scale rough soil surface at low grazing incidence” by Jia et al. applies the Compute Unified Device Architecture (CUDA) technology to compute an electromagnetic scattering problem on GPUs and achieves significant speedup factors. “High-performance meshing processing of remote sensing data on large displays” by Hsieh et al. presents a technique that visualizes LIDAR point clouds on a tiled display wall, termed highly interactive-parallelized display (HIPerDisplay), which has twenty 24-inch liquid-crystal displays with a total resolution of 46 Mpixels. The results also showed that the HIPerDisplay offered superior performance for the processing of large LIDAR datasets. “Real-time implementation of optimized maximum noise fraction transform for feature extraction of hyperspectral images” by Wu et al. presents a parallel implementation of the optimized maximum noise fraction (G-OMNF) transform algorithm for feature extraction of hyperspectral images on commodity graphics processing units (GPUs). The proposed approach explored the algorithm data-level concurrency and optimized the computing flow. “Hyperspectral band selection based on parallel particle swarm optimization and impurity function band prioritization schemes” by Chang et al. presents a framework for band selection in hyperspectral imagery that uses two techniques, referred to as particle swarm optimization (PSO) band selection and the impurity function band prioritization (IFBP) method. The experimental results demonstrate that the proposed PPSO/IFBP band selection method can not only improve computational speed but also offer a satisfactory classification performance. “Graphics processing unit implementation of the maximum likelihood solution to the inverse problem for retrieval of geophysical parameters from high-resolution sounder data” by Wei et al. explores the use of GPU in speedup of the maximum likelihood solution to an illposed retrieval problem. For the infrared atmospheric sounding interferometer high-resolution sounder having 8641 channels, the use of GPU on maximum likelihood estimation shows a promising speedup of 1986× compared to a single-threaded native CPU version.