Optical noninvasive monitoring of skin blood pulsations

Time-resolved detection and analysis of skin backscattered optical signals (remission photoplethysmography or PPG) provide rich information on skin blood volume pulsations and can serve for reliable cardiovascular assessment. Single- and multiple-channel PPG concepts are discussed. Simultaneous data flow from several locations on the human body allows us to study heartbeat pulse-wave propagation in real time and to evaluate vascular resistance. Portable single-, dual-, and four-channel PPG monitoring devices with special software have been designed for real-time data acquisition and processing. The prototype devices have been clinically studied, and their potential for monitoring heart arrhythmias, drug-efficiency tests, steady-state cardiovascular assessment, body fitness control, and express diagnostics of the arterial occlusions has been confirmed.     

Calculated microdosimetric characteristics of 125I and 103Pd brachytherapy seeds at different depths in water

Both (125)I and (103)Pd sources have been widely used in the permanent prostate implant. An important consideration for the choice of brachytherapy sources is the relative biological effectiveness (RBE) for the source/seed used in the implantation. As RBE is closely related to the microdosimetric parameter, it is desirable to calculate the dose mean lineal energies for both (125)I and (103)Pd at various radial distances to the seed surface. Monte Carlo simulation was performed for photons emitted from (125)I and (103)Pd. Energy depositions from photons and all their secondary electrons were tracked. Dose distributions of lineal energy, d(y), were calculated for spheres of 1 microm in diameter and at various radial distances to the seed surface. From the dose distribution of lineal energy, the dose mean lineal energy, y(D), was derived. The results showed that the radiation qualities are constant in the distance range from 0.5 to 5 cm. In this distance range, the quality factor, relative to gamma rays from (60)Co, is 2.2 for (125)I and 2.5 for (103)Pd.     

Simultaneous optical and electrochemical recording of single nanoparticle electrochemistry

Single nanoparticle collisions have become popular for studying the electrochemical activity of single nanoparticles by determining the transient current during stochastic collisions with the electrode surface.However,if only the electrochemical current is measured,it remains challenging to identify and characterize the individual particle that is responsible for a specific current peak in a collision event;this hampers the understanding of the structure-activity relationship.Herein,we report simultaneous optical and electrochemical recording of a single nanoparticle collision;the electrochemical signal corresponds with the activity of a single nanoparticle,and the optical signal reveals the size and location of the same nanoparticle.Consequently,the structure (optical signal)-activity (electrochemical signal) relationship can be elucidated at the single nanopartide level;this has implications for various applications induding batteries,electrocatalysts,and electrochemical sensors.In addition,our previous studies have suggested an optical-to-electrochemical conversion model to independently calculate the electron transfer rate of single nanoparticles from the optical signal.The simultaneous optical and electrochemical recording achieved in the present work enables direct and quantitative validation of the optical-to-electrochemical conversion model.     

变埋深条件下混凝土中爆炸加速度的传播规律

为了研究混凝土中不同埋深爆炸冲击质点振动加速度传播规律,运用量纲分析和自由场实验相结合的方法并引入等效当量系数的概念得出C30混凝土不同埋深爆炸冲击质点振动加速度预估公式。研究结果表明：对于C30混凝土,当装药比例埋深为0.25 m/kg1/3≤h≤1.0m/kg1/3时,随着装药比例埋深的增加,爆炸冲击质点加速度峰值随之增大,但加速度随比例埋深的衰减规律基本一致;对于不同强度的混凝土触地爆（h=0m/kg1/3）,随着混凝土强度的增大,爆炸冲击质点加速度峰值随之增大,加速度衰减规律基本一致;给出了C30混凝土不同埋深爆炸冲击质点振动加速度精度较高的预估公式。     

Optical Doppler velocimetry at various retinal vessel depths by variation of the source coherence length

We report on what we believe is a novel approach to measuring the velocity of red blood cells (RBC's) at different depths of retinal vessels by use of low-coherence sources. The technique, variable coherence optical Doppler velocimetry (VCODV), performs Doppler shift measurements through autodyne mixing between the light scattered by the RBC's and by the vessel front wall (reference). Only the light from RBC's moving at a depth less than half the coherence length (CL) mixes efficiently with the reference. Measurements of the Doppler shifts from RBC's with sources of four different CL's in a 152-mum vein of a volunteer confirmed the feasibility of VCODV. This approach has the potential to monitor in vivo retinal RBC velocity gradient at the vessel wall and the velocity profile within the blood vessel in the condition of symmetric blood flow profiles.     

Simultaneous recording and readout of χ(2)-holograms in glasses

A new method for readout of χ⁽²⁾-holograms recorded by noncollinearly polarized light beams of different frequencies is proposed and implemented. The hologram is read out and recorded simultaneously by the same reference beam, thus eliminating any influence of the readout radiation on the recorded hologram. Pis’ma Zh. Tekh. Fiz. 23, 46–51 (January 12, 1997)     

Simultaneous synthesis of strontium oxalate with different morphology by living bi-template

Naturally occurring forms of materials have complex morphology and excellent performance, which provides new strategies for synthesising materials. In this paper, strontium oxalate crystals with different morphologies can be obtained simultaneously on either side of the membrane of mung bean sprouts (MBS). The as-obtained products were characterised by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effect of ethylene diamine tetraacetic acid (EDTA) on the morphologies was investigated and discussed. The results showed that EDTA played a more important role in the formation of the products inside the MBS membrane. A presumable mechanism was proposed. This research may provide insights into the cooperation between bionic research and living vegetal cells.     

绿光光电容积脉搏波测量生理参数的校准技术

针对绿光光电容积脉搏波测量生理参数的校准技术进行了研究.简析了绿光光电容积描记法技术和红光红外光光电容积描记法技术在计量测试工作中的差异.选取多项式曲线拟合算法仿真了绿光光电容积描记法脉搏波,并取得了稳定的仿真信号输出,为校准装置的研制提供了信号源.     

Real-time monitoring and growth control of Si-gradient-index structures by multiwavelength ellipsometry

Real-time monitoring and control of the growth of plasma-deposited gradient-index structures by multiwavelength phase-modulated ellipsometry are presented. An efficient method for estimating the optical parameters based on a least-squares fitting on the most recent recorded measurements is described. This method is used for real-time monitoring of the outerlayer refractive index and rate of deposition during deposition of inhomogeneous transparent films. An accurate integral expansion of the reflection coefficient, giving a continuous optical model describing inhomogeneous films, is used in the real-time modeling of the deposited structure. A variety of increasing complexities of the optical model is studied within inversion algorithms. Furthermore several ways of defining the optical parameters to be estimated are discussed. Inversion of simulated growth trajectories by using the described algorithms show what kind of information is available from the various approximations and in what conditions they are useful. Since real-time measurements during growth involves statistical noise and systematic errors, it becomes necessary to stabilize the fit. Various stabilizing functionals are discussed and implemented to solve this problem. Several plasma-deposited silicon oxynitride gradient-index structures where both rate of deposition and the refractive index are varied continuously are inverted in real time. As an example of application, a successful real-time control of the growth of a linear gradient index is demonstrated by using inversion algorithms. Inversion algorithms are extremely fast, with calculation times from less than a second (for the lowest-order approximation) to ~3 s.     

Technique of operative control of the quality of the process of measuring and recording depths in automatic surveying of floor terrain

Atechnique is presented for operative calculation and control of the performance indicators of the processes of depth measurement and recording when surveying a floor terrain using a computer-based hydrographic unit. Translated from Izmeritel'naya Tekhnika, No. 7, pp. 9–12, July, 1997     

Determination of the optical properties of a two-layer tissue model by detecting photons migrating at progressively increasing depths

We have investigated a method for solving the inverse problem of determining the optical properties of a two-layer turbid model. The method is based on deducing the optical properties (OPs) of the top layer from the absolute spatially resolved reflectance that results from photon migration within only the top layer by use of a multivariate calibration model. Then the OPs of the bottom layer are deduced from relative frequency-domain (FD) reflectance measurements by use of the two-layer FD diffusion model. The method was validated with Monte Carlo FD reflectance profiles and experimental measurements of two-layer phantoms. The results showed that the method is useful for two-layer models with interface depths of >5 mm; the OPs were estimated, within a relatively short time (<1 min), with a mean error of <10% for the Monte Carlo reflectance profiles and with errors of <25% for the phantom measurements.     

Oxygen barrier properties of thermoformed trays manufactured with different drawing methods and drawing depths

A comparison was made of oxygen barrier properties and wall thickness distribution of different thermoformed trays. The thermoformed trays were manufactured with three drawing depths and two different thermoforming methods; with and without plug‐assist. Four different polymer combinations were evaluated. The oxygen transmission rate (OTR) [cm³/(package/day)] was measured at three conditions (23°C/50% relative humidity (RH) with 0% RH inside, 6°C/80% RH with 0% RH inside, and 6°C/80% RH with 100% RH inside. Wall thickness was measured at five different positions in the trays. In general, temperature had more influence on the oxygen transmission rate (OTR) than the humidity. The OTR in the packages increased with increasing drawing depth, but the increase was not linear. Other effects besides thinning, such as orientation, may have influenced the OTR, since the relationship between OTR, given as cm³/(m²/day), and the drawing depth was not linear. Plug‐assisted thermoforming only had an effect on the OTR in trays with 70 mm drawing depth made of 600 µm thick laminate of PP/PE, which was probably due to exceeding the maximum drawing depth of this material. There was no correlation between the OTR value in the packages and the wall thickness in either of the positions, but a quite high correlation between the drawing depth and the relative wall thickness in all measured positions was observed. Copyright © 2004 John Wiley & Sons, Ltd.     

Equivalence of pyrheliometric and monochromatic aerosol optical depths at a single key wavelength

The atmospheric aerosol optical depth (AOD) weighted over the solar spectrum is equal to the monochromatic AOD at a certain wavelength. This key wavelength is ~0.7 mum, which is only slightly influenced by air mass and aerosol content. On the basis of this result, simple relations are proposed to predict monochromatic AOD from pyrheliometric data and vice versa. The accuracy achieved is close to ?0.01 units of AOD at ~0.7 mum, estimated from simultaneous sunphotometer data. The precision required for the estimation of the precipitable water-vapor content is approximately ?0.5 cm.     

Simultaneous determination of in-plane shear and transverse moduli of unidirectional composite laminae at different strain rates and temperatures

A semi-empirical method is proposed for the extraction, simultaneously, of the transverse tensile and in-plane shear moduli of unidirectional laminae, at various strain rates and temperatures, from tests on symmetric and balanced ±65 ° angle-ply composite laminates. The extraction method is applied to data obtained from tests on Kevlar-49/epoxy and carbon/ epoxy filament-wound tubes which were subjected to internal pressure loading at three key temperatures of −45, 20 and 70 °C at different strain rates of up to 80/s. The combined effect of strain rate and temperature on these extracted properties is studied by applying strain rate temperature equivalence principles. It is found that the variation of the mechanical properties of the two materials with strain rate and temperature can be adequately described by semi-empirical equations similar to the Arrhenius and Williams-Landel-Ferry relationships, usually used for homogeneous solids.     

Real-time control by multiwavelength ellipsometry of plasma-deposited multilayers on glass by use of an incoherent-reflection model

Real-time control by multiwavelength phase-modulated ellipsometry (PME) of the growth of multilayer structures deposited on transparent glass is presented. The structures consist of plasma-deposited SiO(2) and SiN(x) stacks. A model that takes into account incoherent reflection in the substrate is described and tested. A generalized feedback control method that incorporates the incoherent modeling of the transparent substrate is further applied to the growth of a Fabry-Perot and a standard quarter-wave filter. The resulting optical coatings characterized by spectroscopic PME and transmission measurements show a reproducible precision, with less than 1% error between target and measured spectral responses.     

Computations of bubble formation and pulsations generated by impacting cylindrical water jets

The impact of a water jet onto a water surface can entrain air-bubbles whose pulsations provide acoustic sources. Such impacts can occur during the breaking of a wave, or on a smaller scale, when a raindrop strikes a puddle of water. A better understanding of this phenomenon can lead to improved characterizations of the ambient noise and acoustic detection algorithms. Liquid on liquid impacts correspond to a breakdown of classical hydrodynamic theory which assumes that the free surface remains smooth and topologically invariant. A computational model using a generalized theory of hydrodynamics designed to rigorously treat liquid collisions is described in this paper. Numerical simulations are compared to experiments of a liquid cylinder impacting a still-water surface The simulations provide details not only of the initial formation of the air-entrained bubble at the time of the cavity collapse, but also the subsequent pulsations of this bubble until it rises back to the free surface. Computed initial bubble sizes and natural frequencies are compared to the experimental results for different cylinder lengths.     

Speciation of heavy metals by modified BCR sequential extraction procedure in different depths of sediments from Sungai Buloh, Selangor, Malaysia

The sequential extraction procedure proposed by the European Standard, Measurements and Testing (SM&T) program, formerly the Community Bureau of Reference (BCR), was applied for partitioning of heavy metals (HMs) in river sediments collected along the course of Sungai Buloh and the Straits of Malacca in Selangor, Malaysia. Eight elements (V, Pb, Cd, Cr, Co, Ni, Cu and Zn) from seven stations (S1-S7) and at different depths were analyzed using the modified BCR Sequential Extraction Procedure (SEP) in combination with ICP-MS to obtain the metal distribution patterns in this region. The results showed that heavy metal contaminations at S2 and S3 was more severe than at other sampling sites, especially for Zn, Cu, Ni and Pb. Nevertheless, the element concentrations from top to bottom layers decreased predominantly. The samples from the Straits of Malacca (S4-S7) the highest contamination factors obtained were for Co, Zn and Pb while the lowest were found for V and Cr, similar to Sungai Buloh sediments. The sediments showed a low risk for V, Cr, Cu and Pb with RAC values of less than 10%, but medium risk for Co, Zn (except S3), Cd at S1 and S2 and Ni at S1, S3 and S5. Zn at S3 and Cd at S3-S7 showed high risk to our sediment samples. There is not any element of very high risk conditions in the selected samples.     

Intracellular recording of action potentials by nanopillar electroporation

Action potentials have a central role in the nervous system and in many cellular processes, notably those involving ion channels. The accurate measurement of action potentials requires efficient coupling between the cell membrane and the measuring electrodes. Intracellular recording methods such as patch clamping involve measuring the voltage or current across the cell membrane by accessing the cell interior with an electrode, allowing both the amplitude and shape of the action potentials to be recorded faithfully with high signal-to-noise ratios. However, the invasive nature of intracellular methods usually limits the recording time to a few hours, and their complexity makes it difficult to simultaneously record more than a few cells. Extracellular recording methods, such as multielectrode arrays and multitransistor arrays, are non-invasive and allow long-term and multiplexed measurements. However, extracellular recording sacrifices the one-to-one correspondence between the cells and electrodes, and also suffers from significantly reduced signal strength and quality. Extracellular techniques are not, therefore, able to record action potentials with the accuracy needed to explore the properties of ion channels. As a result, the pharmacological screening of ion-channel drugs is usually performed by low-throughput intracellular recording methods. The use of nanowire transistors, nanotube-coupled transistors and micro gold-spine and related electrodes can significantly improve the signal strength of recorded action potentials. Here, we show that vertical nanopillar electrodes can record both the extracellular and intracellular action potentials of cultured cardiomyocytes over a long period of time with excellent signal strength and quality. Moreover, it is possible to repeatedly switch between extracellular and intracellular recording by nanoscale electroporation and resealing processes. Furthermore, vertical nanopillar electrodes can detect subtle changes in action potentials induced by drugs that target ion channels.