Experimental method to assess depth sensing limits of inelastic scattering measurements using spatial-offset Raman spectroscopy imaging

A method for estimating the optical properties of two-layered media (such as squamous epithelial tissue) over a range of wavelengths in the ultraviolet-visible spectrum is proposed and tested with Monte Carlo modeling. The method first used a fiber-optic probe with angled illumination and the collection fibers placed at a small separation (<or=300 microm) to restrict the transport of detected light to the top layer. A Monte Carlo-based inverse model for a homogeneous medium was employed to estimate the top layer optical properties from the measured diffuse reflectance spectrum. Then a flat-tip probe with a large source-detector separation (>or=1000 microm) was used to detect diffuse reflectance preferentially from the bottom layer. A second Monte Carlo-based inverse model for a two-layered medium was applied to estimate the bottom layer optical properties, as well as the top layer thickness, given that the top layer optical properties have been estimated. The results of Monte Carlo validation show that this method works well for an epithelial tissue model with a top layer thickness ranging from 200 to 500 microm. For most thicknesses within this range, the absorption coefficients were estimated to within 15% of the true values, the reduced scattering coefficients were estimated to within 20% and the top layer thicknesses were estimated to within 20%. The application of a variance reduction technique to the Monte Carlo modeling proved to be effective in improving the accuracy with which the optical properties are estimated.

Multilayer structures with two dielectrics having different optical constants and no structural features in the x-y plane can display photonic band gaps (PBGs) and are called one-dimensional photonic crystals (1DPCs). If the top layer thickness is carefully selected, the electromagnetic energy can be trapped at the top surface. These highly enhanced fields are called Bloch surface waves (BSWs). The BSW resonance angles are sensitive to the dielectric constant above the top dielectric layer. As a result, BSW structures have been used for surface plasmon resonance-like measurements without the use of a metal film. However, the emphasis on surface-localized BSWs has resulted in limited interest in fluorophore interactions with other optical modes of 1DPCs or Bragg gratings without the different thickness top layer. Herein, three different fluorescent probes were used to cover the short, center, and long wavelengths of the PBG. We demonstrate efficient coupling of fluorophores to both the BSW and internal modes (IMs) of a 1DPC. Coupling to the IM is expected to be low because of the micron-scale distances between the fluorophores and IM, which exists inside the Bragg gratings. At different wavelengths or observation angles, the IM-coupled emission (IMCE) can occur with the first three modes of the multilayer. This coupling is not dependent on a BSW mode. IMCE was also observed for a monolayer of fluorophore-labeled protein. IMCE enables sensitive detection of surface-bound fluorophores. Applications are anticipated in high sensitivity detection and super-resolution imaging.

Fabrication of Germanium-on-insulator in a Ge wafer with a crystalline Ge top layer and buried GeO2 layer by oxygen ion implantation

Two-layered slab is a rational simplified sample to the near-infrared functional brain imaging using diffuse optical tomography (DOT).The quality of reconstructed images is substantially affected by the accuracy of the background optical properties. In this paper, region step wise reconstruction method is proposed for reconstructing the background optical properties of the two-layered slab sample with the known geometric information based on continuous wave (CW) DOT. The optical properties of the top and bottom layers are respectively reconstructed utilizing the different source-detector-separation groups according to the depth of maximum brain sensitivity of the source-detector-separation. We demonstrate the feasibility of the proposed method and investigate the application range of the source-detector-separation groups by the numerical simulations. The numerical simulation results indicate the proposed method can effectively reconstruct the background optical properties of two-layered slab sample. The relative reconstruction errors are less than 10% when the thickness of the top layer is approximate 10mm. The reconstruction of target caused by brain activation is investigated with the reconstructed optical properties as well. The quantitativeness ratio of the ROI is about 80% which is higher than that of the conventional method. The spatial resolution of the reconstructions (R) with two targets is investigated, and it demonstrates R with the proposed method is better than that with the conventional method as well.

A better understanding of diffusion reflection (DR) behavior may allow it to be used for more noninvasive applications, including the development of in vivo non-damaging techniques, especially for medical topical diagnosis and treatments. For a bilayer opaque substance where the attenuation of the upper layer is larger than the attenuation of the lower layer, the DR crossover point ( ) is location where the photons coming from the bottom layer start affecting the DR. We aim to study the dependency of the on absorption changes in different layers for constant scattering and top layer thickness. Monolayer and bilayer optical tissue-like phantoms were prepared and measured using a DR system. The results were compared with Monte Carlo simulations. There is an agreement between the experiments and the simulations. correlates with the square root of the absorption coefficient ratio of the lower layer to the top layer. The experimental findings support and validate the theoretical prediction describing the dependency of the on the square root of the ratio of the layers' absorption coefficients. In addition, a secondary breaking point is suggested to be observed experimentally at the entrance to the noise area.

High-flux ceramic membrane derived from UV-curable slurry for efficient separation of nanoparticles suspension

Abstract. Several simple soil water models with four layers or less, typical of those used in GCMS, are compared to a complex multilayered model. They are tested by applying a repeating wetting/drying cycle at different frequencies, and run to equilibrium. The ability of the simple soil models to reproduce the results of the multilayer model vary according to the frequency of the forcing cycle, the soil type, the number of layers and the depth of the top layer of the model. The best overall performance was from the four layer model. The two layer model with a thin top layer (0.1 m) modelled sandy soils well while the two layer model with a thick top layer (0.5 m) modelled clay soils well. The model with just one layer overestimated evaporation during long drying periods for all soil types.

A numerical study has been carried out to determine the thickness of the top granular layer for a JGT reinforced low volume rural road system based on 3D static finite element analysis. The behaviour of the granular pavement materials has been simulated as an elasto-plastic material. The behaviour of JGT has been considered as a membrane-type material. The determination of the top granular layer thickness is based on the load carrying capacity of the rural road system under the different magnitude of surface deformation. Improvement in the service life of the JGT reinforced rural road has been determined in terms of traffic benefit ratio (TBR). The TBR values are found in the range of 1.22–5.08. In the present work, an attempt also has been taken to study the strength mobilisation of JGT in low volume rural road structure under deformation.

Effect of defects and secondary phases in Cu2ZnSnS4 absorber material on the performance of Zn(O,S) buffered devices

Foam-assisted gas injection exhibits promising potential for enhancing sweep efficiency through the amelioration of gravity segregation, particularly within reservoirs characterized by heterogeneity. In this work, the implicit-texture (IT) model featuring two flow regimes is employed to examine the impact of heterogeneity on gravity segregation. The validation of the numerical results for water–gas coinjection and pre-generated foam injection is accomplished through a comparative analysis with analytical solutions. A hypothetical two-layer model with varying permeabilities and thickness ratios is used to examine the impact of foam on gravity segregation. The numerical findings demonstrate satisfactory conformity with analytical solutions in homogeneous reservoirs. A high-permeability top layer in a layered model with a fixed injection rate results in sweep efficiency similar to that of a homogeneous reservoir with each individual permeability. A low-permeability top layer could increase the sweep efficiency, but with severe permeability contrast, the bottom high-permeability layer could impact the displacement process, even with a thin thickness. The sweep efficiency increases with the thickness of the high-permeability top layer and decreases with a thicker low-permeability top layer under fixed injection pressure. The predicted segregation length through a single-layer approximation cannot match the results of the layered models where the permeability contrast is too great or the thickness of two layers is comparable.

An analytical calculation scheme for the band profile in the i region of a semi-infinite p/i or n/i junction with arbitrary thickness of the intrinsic top layer is presented. Using this algorithm the surface potential as a function of i-layer thickness as well as the band profile within the top layer can be calculated without mathematical approximations as long as the surface potential is held a few kT away from its intrinsic position by the doped sublayer, i.e., up to a critical thickness. Above that thickness the band profile can be approximated with sufficient accuracy by that of the corresponding infinite junction for which the exact solution will be also given in analytical terms. In a second step an arbitrary surface charge layer is incorporated into the algorithm which can modify the band profile considerably. The method whose mathematical derivation is presented in detail in this article was motivated by experiments on the surface-near passivation of dopants in silicon by hydrogen but should be generally useful for the discussion of p/i or n/i junctions.

A trajectory-tracked, near-infrared autofluorescence imaging guided, biochemical signature-projected needle-type Raman spectroscopy (TNBN-RS) system integrated on a medical cart was developed for rapid wide-field breast tissue stratification. A wide-field (10 × 10 cm2) near-infrared autofluorescence (NIRAF) imaging subsystem was developed for gross stratification of breast tissue types based on higher NIRAF intensity associated with breast cancer, followed by projection of NIRAF-identified breast tumor margins onto the tissue of interest with a compact projector. Raman spectra were further acquired from the NIRAF projected regions for confirmed margin assessment using a needle-type Raman probe equipped with color camera-based probe trajectory tracking. The trajectory of the Raman probe and the accompanying RS biochemical signature-based margin assessment were instantly projected. A unique field of view (FOV) calibration method was proposed to calibrate the TNBN-RS FOVs, resulting in a projection accuracy of <2 mm. A graphical user interface (GUI) was developed in C# for system control, real-time processing and display of NIRAF images, Raman spectra, and projection of their results. The performance of the TNBN-RS system was validated on an ex vivo breast tissue, demonstrating its potential for rapid intraoperative breast tumor margin assessment.

Optimizing the dual-layer Pt/Al2O3 + Cu/SSZ-13 washcoated monolith: Selective oxidation of NH3 to N2

The geometrical dimensions of the trench and the type of top layer used for the installation of buried cable are considered. These dimensions include the trench width and depth, cable depth and diameter, and thickness of the top layer. The dimensions, such as the trench width and the cable diameter, are varied to emphasize their effect on the heat dissipation. A simple model using the finite difference technique is used to determine the temperature at each node of the grid, and the Gauss-Siedel iteration method is used to solve the temperature equations. The heat dissipation from buried cables can be increased either by using larger cable diameter or by increasing the width of the trench. The number of grid points has a remarkable influence on the predicted value of heat dissipation. The percentage of the change in the heat dissipation due to the diameter or the trench width remains approximately the same for various grid points. The heat balance analysis shows that the difference between the cable heat dissipation and the heat losses from the grid boundaries is less than 0.3%, and the convective surface at the grid top plays a major role in dissipating the heat produced by the cable by almost 86% for most of the trenches with various widths. >

We report on the formation of Tamm plasmon (TP) modes in the visible spectral region at the interface between a Ag film and a ZnSe‐based distributed Bragg reflector (DBR). The tuning of the TP eigenenergies within the stop‐band in dependence on the DBR top layer thickness is investigated by micro‐reflectivity measurements. The experimental findings are compared with calculations using the transfer matrix method. The latter calculations show that strong coupling can be achieved between quantum well (QW) excitons and the TP modes. In addition, the Rabi‐splitting energy can be enhanced in a simple TP structure by increasing the number of QWs inside the top layer of the DBR.When a metal layer is deposited on a cold MC sample, micro‐reflectivity spectra show a blue shift of the cavity resonance. The TP modes are likewise observed in the same MC sample when reducing the top layer thickness of the DBR. This shift of cavity resonance and formation of TP mode are in good agreement with calculations. These results are rather promising in order to realize a spatial confinement of the polaritons by utilizing metal strips. Such channeling of polaritons opens the way to practical demonstration of exciton‐polariton integrated circuits. (© 2016 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)