Raman sensitivity enhancement for aqueous protein samples using a liquid-core optical-fiber cell

We have demonstrated a sensitivity enhancement factor of 500 in aqueous solutions using a liquid core optical fiber (LCOF) Raman cell made from Teflon-AF. We were able to collect a spectrum of 54 microM lysozyme with a signal-to-noise ratio of 31 in the LCOF Raman cell using 24 mW of laser power and 3 min of integration time. The lysozyme Raman intensity was only 1% of the background Raman intensity from water, but the water-subtracted lysozyme spectrum was still shot-noise-limited and essentially free of nonrandom noise. The lack of nonrandom noise indicates that it should be possible to collect good quality Raman spectra of proteins such as lysozyme at even lower concentrations. The 2.4-microL sample volume of the LCOF Raman cell is an added benefit when limited quantities of sample are available. This volume of a 54 microM lysozyme solution corresponds to only 13 nanomoles or 1.9 microg of lysozyme.     

Depth resolution enhancement in optical scanning holography with a dual-wavelength laser source

In this paper, we use two point sources to analyze the depth resolution of an optical scanning holography (OSH) system with a single-wavelength source. A dual-wavelength source is then employed to improve it, where this dual-wavelength OSH (DW-OSH) system is modeled with a linear system of equations. Object sectioning in DW-OSH is obtained with the Fourier domain conjugate gradient method. Simulation results show that, with the two source wavelengths at 543 nm and 633 nm, a depth resolution at 2.5 μm can be achieved. Furthermore, an OSH system emulator is provided to demonstrate the performance of DW-OSH compared with a conventional OSH system.     

Fabrication of nano-structured SPR chip for sensitivity enhancement

We used the Langmuir-Blodgett (LB) method for preparation of large area, defect-free monolayer silica particle film as a template for the fabrication of nano-structure Au pattern on a conventional Au substrate for Surface Plasmon Resonance (SPR). Well organized, trigonal pyramid shaped Au nano-structures were able to construct on 34 separate chips in one fabrication process. The dimensions of trigonal pyramid nano-structures were precisely controlled by changing the particle size of the silica LB template. The nano-structure Au patterned SPR chips provides the enhancement of sensitivity in SPR analysis. The sensitivity enhancement of nano-structure patterned chips was evaluated by comparison with conventional flat Au chips. The nano-structure patterned substrate demonstrated a sensitivity enhancement up to 120% compared to a conventional SPR chip when ethanol solution was used as an analyte.     

Dynamic observation of vortices in superconductors using a holography electron microscope

Individual vortices in superconductors are directly observed with our holography electron microscope. Vortices cannot be viewed as an electron micrograph, but only as a holographic interference micrograph or a defocused micrograph (Lorentz micrograph), since vortices are phase objects to the illumination electron beam. Since the flux itself, and not its replica, is detected, even the dynamic behavior can be observed. The dynamics of vortices in a Nb thin film can be observed in real time when the sample conditions, such as the temperature or the applied magnetic field, change.     

Local parametric sensitivity for mixture models of lifetime distributions

Mixture models are receiving considerable significance in the last years. Practical situations in reliability and survival analysis may be addressed by using mixture models. When making inferences on them, besides the estimates of the parameters, a sensitivity analysis is necessary. In this paper, a general technique to estimate local prior sensitivities in finite mixtures of distributions from natural exponential families having quadratic variance function (NEF-QVF) is proposed. Those families include some distributions of wide use in reliability theory. An advantage of this method is that it allows a direct implementation of the sensitivity measure estimates and their errors. In addition, the samples that are drawn to estimate the parameters in the mixture model are re-used to estimate the sensitivity measures and their errors. An illustrative application based on insulating fluid failure data is shown.     

Spherical aberration correction using a liquid-crystal spatial-light modulator in off-axis electron holography

One can correct spherical aberration in a transmission electron microscope by using a newly developed aberration-correction method involving off-axis electron holography. In this method, a liquid-crystal spatial-light modulator (LC SLM) is employed during the holographic reconstruction step to compensate for spherical aberration. Application of this method to high-resolution off-axis electron holograms of fine gold particles is presented. The phase distribution of the corrected object wave is visualized by the Zernike phase-contrast method carried out with the same LC SLM.     

Enhancing the sensitivity to small phase changes in double-exposure stroboscopic television holography

We present a new technique for enhancing the sensitivity of double-exposure stroboscopic television holography (TVH) to detect and measure vibrations of small amplitude. The technique is based in the modulation of the phase of the reference beam in synchronism with the vibration of the measurand and derives from a former technique that we originally contrived for phase evaluation. We propose two variants, characterized by the demodulation process used to generate the secondary correlograms, with different behaviors in terms of the sensitivity to the sign of the measurand and of the ease in detecting the presence and shape of the vibration. We have implemented this new technique in an electronic speckle-pattern interferometer and compared its performance with standard TVH techniques; vibrations with amplitudes as small as 8 nm have been observed with this setup.     

Holographic interferometry using two-wavelength holography for the measurement of large deformations

Visible holographic interferometry is generally too sensitive for the measurement of large deformations. We present a holographic method that permits an increase in the range of measurable deformations. It requires the use of two different wavelengths, λ(1) and λ(2), and two holograms in series. We develop the theoretical basis of a method that permits the obtention of an interferogram as if a longer equivalent wavelength, λ(eq) = λ(1)λ(2)/|λ(1) -λ(2)|, were used. The method is experimentally tested by use of a setup that can be easily converted into a classical single-wavelength holographic interferometer, permitting comparison of the interferograms of the same deformation produced with both methods. Significant results are presented.     

Measurement of curvature and twist of a deformed object using digital holography

Measurement of curvature and twist is an important aspect in the study of object deformation. In recent years, several methods have been proposed to determine curvature and twist of a deformed object using digital shearography. Here we propose a novel method to determine the curvature and twist of a deformed object using digital holography and a complex phasor. A sine/cosine transformation method and two-dimensional short time Fourier transform are proposed subsequently to process the wrapped phase maps. It is shown that high-quality phase maps corresponding to curvature and twist can be obtained. An experiment is conducted to demonstrate the validity of the proposed method.     

Tomographic reconstruction of sound fields using TV holography

Combining TV holography recording with acoustic phase stepping and image processing, we measure the integrated density distribution in sound fields that propagate in air. We record a given number of two-dimensional cross sections that are tomographically backprojected to give the amplitude and phase distributions of the emitted sound field. The validity of the procedure is demonstrated.     

Characterization of Dupont photopolymers in infrared light for free-space optical interconnects

Dupont photopolymer as a potential holographic material for an optical interconnect system was studied. The optimized conditions of recording plane-wave holograms with ～99% effective diffraction efficiency for infrared reconstruction were obtained by testing different Dupont photopolymers and different copying parameters. The scattering ratios of the holograms recorded with Dupont photopolymers HRF600-10, HRF600-20, and HRF600-38 were measured and compared.     

Phase detection sensitivity enhancement of surface plasmon resonance sensor in a heterodyne interferometer system

We propose a method of rotating the analyzer in front of the photodetector in a heterodyne interferometer system to implement optical phase shift and detection sensitivity enhancement of surface plasmon resonance (SPR) sensors. When the analyzer is rotated to shift the phase curve to be near the phase jump point, the phase detection sensitivity of the SPR sensor can be greatly enhanced. Theoretical calculations of a prism-coupled SPR device were performed using this method. Experimental result using an electro-optic heterodyne interferometer is reported.     

Method for microwave radiation enhancement using elongated nanotubes dispersed in a gaseous medium

A new method is proposed to enhance microwave radiation with a wavelength of λ ∼ 1 cm in an active medium comprising elongated conducting nanotubes dispersed in air, which is energy pumped by a nonstationary electric field. For a volume fraction of nanoparticles c ₀ ≈ 10⁻³ in air at atmospheric pressure, the necessary value of the nonstationary pumping electric field (generated by a high-power nanosecond pulsed voltage source) is estimated at ∼ 200 J/m³ and the weak signal gain is estimated at Γ₀ = 0.055 m⁻¹. One possible mechanism of microwave radiation enhancement in a spatial resonator is considered.     

Estimating probabilistic confidence for mixture components identified using a spectral search algorithm

Providing a confidence measure associated with the substance(s) identified in an unknown mixture by a spectral search technique is critical for non-expert users of devices and techniques based on spectroscopy. In this work, a technique for estimating probabilities associated with substances identified by spectral searching is described. In the proposed approach, a mixture analysis algorithm processes the spectrum of an unknown sample using a spectral library to generate a list of substances that may be present in the sample. The partial correlation of each of the substances in the list is then computed. The estimation of the probability is accomplished through a generalized linear model that converts the partial correlation values to a probability measure for each of the mixture components. The statistical properties of partial correlation allow probability estimation irrespective of whether a substance is present in a pure form or within a mixture. The technique was evaluated using both simulated and real Raman spectra of multi-component mixtures, and adequate performance was demonstrated.     

Oral bioavailability enhancement of raloxifene by developing microemulsion using D-optimal mixture design: optimization and in-vivo pharmacokinetic study

The objective of this work was to utilize a potential of microemulsion for the improvement in oral bioavailability of raloxifene hydrochloride, a BCS class-II drug with 2% bioavailability. Drug-loaded microemulsion was prepared by water titration method using Capmul MCM C8, Tween 20, and Polyethylene glycol 400 as oil, surfactant, and co-surfactant respectively. The pseudo-ternary phase diagram was constructed between oil and surfactants mixture to obtain appropriate components and their concentration ranges that result in large existence area of microemulsion. D-optimal mixture design was utilized as a statistical tool for optimization of microemulsion considering oil, S_mix, and water as independent variables with percentage transmittance and globule size as dependent variables. The optimized formulation showed 100?±?0.1% transmittance and 17.85?±?2.78?nm globule size which was identically equal with the predicted values of dependent variables given by the design expert software. The optimized microemulsion showed pronounced enhancement in release rate compared to plain drug suspension following diffusion controlled release mechanism by the Higuchi model. The formulation showed zeta potential of value ?5.88?±?1.14?mV that imparts good stability to drug loaded microemulsion dispersion. Surface morphology study with transmission electron microscope showed discrete spherical nano sized globules with smooth surface. In-vivo pharmacokinetic study of optimized microemulsion formulation in Wistar rats showed 4.29-fold enhancements in bioavailability. Stability study showed adequate results for various parameters checked up to six months. These results reveal the potential of microemulsion for significant improvement in oral bioavailability of poorly soluble raloxifene hydrochloride.     

Achieving stability in remote holography using flexible multimode image bundles

Commercial flexible image bundles (boroscopes, endoscopes, etc.) are made up of tens of thousands of coherently arrayed multimode optical fibers whose modal propagation characteristics are unavoidably affected by bending losses. Consequently, light wave fronts transmitted through such bundles are subject to significant changes whenever the bundle is flexed anywhere along its length. For this reason images transmitted through such multimode image bundles cannot normally be used to generate holograms unless the bundle is rigidly fixed at every point. This requirement represents a substantial limitation on the use of fiber optics to generate and record holograms of remote subjects. However, this study demonstrates an original technique using ultralow frequency in situ holograms that can be transmitted through a multimode image bundle and recorded remotely even while the bundle is being moved.     

CT图像的计算机制全息三维重建

提出用计算机制全息术实现CT图像的三维重建。首先研究了CT图像的三维信息融合,用计算机模拟CT图像的物光波,用菲涅耳计算全息图的方法,把CT图像的二维信息融合成三维信息,获得菲涅耳全息图。然后将计算机制全息与光学全息相结合,记录彩虹全息图。最后用扩展的白光再现,获得逼真无畸变的真正的三维立体图像,充分发挥了计算机制全息与光学全息的优势。在全息图的计算中利用了快速傅里叶算法,大大缩短计算时间。根据不同的观察需要制作了两种不同效果的全息图,并给出了理论分析和实验结果。