A Method and a Device Prototype for Noninvasive Measurements of Blood Perfusion in a Tissue

Noncoherent fluctuation spectroscopy (NFS) is described as an optical method for measuring the tissue blood perfusion. This method is based on the registration of low-frequency fluctuations of a backscattered signal from a tissue in the frequency range of 0–20 Hz. It allows the assessment of the blood-flow intensity in small blood vessels of the skin by calculating an integral parameter, the perfusion index, which is similar to that in the laser Doppler flowmetry (LDF) method. A device prototype in which LEDs at wavelengths of 568 and 808 nm are used in a miniature optical head was developed. The device makes it possible to perform diagnostics during the subject’s motion via the use of LED light sources. It is shown that the NFS signal is comparable with the LDF signal. Thus, the NFS method can serve as an inexpensive alternative to the LDF method.     

Spectral characteristics of autofluorescence and second harmonic generation from ex vivo human skin induced by femtosecond laser and visible lasers

The spectral properties of one-photon, two-photon excited autofluorescence and second harmonic generation (SHG) from ex vivo human skin induced by a femtosecond (fs) laser and three visible lasers in backscattering geometry are systematically investigated. Our experimental results indicate that peak position of autofluorescence spectra from the dermis and epidermis shift toward long wavelengths, and the fluorescent intensity decreases when the excitation wavelength increases due to an effect of the excitation wavelength on autofluorescence signals. However, the intensity of the SHG signal in collagen has the maximal value of 800 nm excitation wavelength. This may be the result that the energy of the SHG signal is in resonance with an electronic absorption band. The two-photon excited autofluorescence and SHG intensity all obey a quadratical dependence on the excitation power. Compared with the two-photon excited fluorescence and SHG, the one-photon excited fluorescence in the dermis and epidermis exhibits different spectral characteristics. The investigation of the spectral characteristics of autofluorescence and SHG from ex vivo human skin can provide new insights into morphologic structures and biochemical components of tissues, which are vital for improving the application of laser-induced autofluorescence and SHG spectroscopy technique for noninvasive in vivo tissue diagnostics.     

Velocity resolved laser Doppler blood flow measurements in skin

A Doppler flow meter was developed, consisting of a PC and a control card for two Doppler sensors to be fixed on skin. From the measured Doppler signals a power spectrum is calculated by a software FFT. In contrast to usual laser Doppler flow measurements in skin, which provide only a mean flow, a flow spectrum is calculated with the assumption of an isotropic distribution of the directions of the velocity of the erythrocytes and irradiation vectors in the skin. Up to four partial flows (integral over a certain frequency region of the flow spectrum) are displayed on the screen simultaneously with a resolution in time < 10 ms. The frequency span can be set independently for each flow. Corresponding to low and high Doppler frequencies the flows show different behavior and provide the possibility to distinguish between the flow in the superficial dermal plexus and larger micro-capillaries.     

Investigation of a floating element flowmeter

The flow in a floating element flowmeter (Rotameter) was studied using laser Doppler anemometry (LDA) and computational fluid dynamics (CFD). With the help of refractive index matching to eliminate optical distortion by the flow tube, the laser Doppler anemometer permitted non-intrusive velocity measurements in all regions of the flow including the immediate vicinity of the float. Results were obtained for various flow rates, different densities of the float material and two heights of the float in the tube. The computational investigation allowed an assessment of CFD when applied to flow rate measuring equipment. It proves a good method for improving floating element flowmeter design. It allowed an insight to the flow structure, particularly with respect to the strong velocity gradients in the gap around the float and the recirculation zone above the float.     

In vivo evaluation of nuclear magnetic resonance flowmetry: blood flow through the normal forearm

A cylindrical crossed-coil nuclear magnetic resonance flowmeter has been developed to measure arterial blood flow through the human forearm. This paper describes the in vivo studies to evaluate the performance of the instrument. Flow rates were comparable to values reported in the literature. The NMR flowmeter is a noninvasive, contactless-type flowmeter and has the advantage of accurate measurement unimpaired by clothing, bandages, or casts. One measurement can be taken in less than 2 min.     

Upstream installation and misalignment effects on the performance of a modified electromagnetic flowmeter

The performance of a modified Danfoss 50 mm diameter electromagnetic flowmeter has been investigated when installed downstream from three different pipe diameters—50 mm, 55 mm and 45 mm. The effects of a 3 mm misalignment of the flowmeter, in both the vertical and horizontal planes, with respect to each of the three upstream pipe diameters has also been identified. The largest percentage errors are reported for the 45 mm upstream diameter pipe, with the flowmeter misaligned by 3 mm in the horizontal plane. The vertical and horizontal mean velocity and root-mean-square velocity profiles, measured within the flowmeter using laser Doppler anemometry, show significant variations in comparison with the ideal, fully developed profiles.     

Study of Physiological Parameters and Comfort Sensations During Friction Contacts of the Human Skin

As a living tissue, human skin has a biological response when it rubs against other external surfaces, among which, the comfort sensation attributes during friction contact make an important contribution to one??s quality of life. However, limited quantitative parameters can be used to describe the sensations, and they have rarely been studied scientifically. In this paper, the comfort sensations of human volar forearm skin during friction testing were studied by biofeedback of physiological and psychological responses. A UMT-II tribometer was used to measure tribological parameters of the skin under different normal force of 0.2 and 1.0?N, and corresponding comfort sensations of the skin were assessed quantitatively using BioTrace?+?for physiological signals monitoring: skin conductance, skin temperature, and electroencephalogram (EEG). The psychological responses were characterized qualitatively according to the volunteers?? sensations of pain, drag, and heat. Results showed that the tangential force, amplitudes of EEG signals and psychological responses increased with the normal force increasing. The friction coefficients, differences of skin conductance and temperature, amplitudes of EEG signals, and psychological responses gradually decreased with the number of friction tests increasing. The discomfort sensations of human skin were strongly related to friction conditions, which intensified under the large normal force, and gradually weakened with the number of tests increasing. The physiological responses were in accord with the psychological ones. The comfort sensations during friction testing can be assessed quantitatively by the physiological signals of conductance, temperature, and EEG.     

Simultaneous confocal recording of multiple fluorescent labels with improved channel separation

Confocal microscopes are often used to study specimens labelled with fluorophores. A commonly used method for simultaneous recording of the distribution of multiple fluorophores is to divide the fluorescent light emitted by the specimen into different wavelength regions using dichroic and bandpass filters. These different wavelength regions are then distributed to multiple detectors. However, the broad and overlapping spectra of commonly used fluorophores often result in considerable crosstalk between channels. A new technique, intensity-modulated multiple-beam scanning (IMS) microfluorometry, can be used to reduce this cross-talk substantially. The IMS technique is implemented with two laser beams of different wavelengths, intensity-modulated at different frequencies, which illuminate the specimen simultaneously. The two laser wavelengths predominantly excite one fluorophore each. Fluorescent light from the specimen is divided into two wavelength regions (red and green) which are detected by two photomultiplier tubes. The output signals from the photomultiplier tubes are connected to lock-in amplifiers. The effect of using modulated laser beams, in combination with lock-in amplifiers, is strongly to reduce cross-talk between the channels. The performance of the IMS technique using various types of specimen is compared with the results obtained using the conventional multi-detector method.     

Motion induced signals of Coriolis flowmeters

Rotation induced Coriolis flowmeter output was observed in a robotic fluid dispensing test. This motion sensitivity of Coriolis flowmeters was confirmed to be universal for various noninertial reference frames. It was also confirmed that this motion sensitivity is a general aspect of many Coriolis flowmeter types. Qualitative tests revealed that the motion induced signals appear to be proportional to frame rotation rate and are strongly dependent on the flow tube oscillation velocity vectors.     

Anisotropic Friction of the Ventral Scales in the Snake Lampropeltis getula californiae

Since the ventral body side of snakes is in almost continuous contact with the substrate during undulating locomotion, their skin is presumably adapted to generate high friction for propulsion and low friction to slide along the substrate. In this study, the microstructure of ventral scales was analyzed using scanning electron microscopy, atomic force microscope and confocal laser scanning microscopy. Dynamic friction was investigated by a microtribometer. The ventral scales demonstrated anisotropic frictional properties. To analyze the role of the stiffness of underlying layers on the frictional anisotropy, two different types of scale cushioning (hard and soft) were tested. To estimate frictional forces of the skin surface on rough substrates, additional measurements with a rough surface were performed. Frictional anisotropy for both types of scale cushioning and rough surfaces was revealed. However, for both types of surface roughness, the anisotropy was stronger expressed in the soft-cushioned sample. This effect could be caused by (1) the stronger interaction of the microstructure with the substrate in soft-cushioned samples due to larger real contact area with the substrate and (2) the composite character of the skin of this snake species with embedded, highly ordered fiber-like structures, which may cause anisotropy in material properties.     

远距离处固体面内位移测量的研究

为了利用激光多普勒效应实现远距离处固体面内位移测量，研究了激光多普勒差动方法和锁相放大、同态滤波等技术，设计出能获得大的多普勒信号强度的差动光路，高灵敏度、大Q值的锁相放大器和能重构丢失信号的同态滤波器等。实验结果证明将由它们所组成的系统用于50m处固体的面内位移测量，效果令人满意，其相对误差约1％。     

Eulerian laser Doppler vibrometry: Online blade damage identification on a multi-blade test rotor

Laser Doppler vibrometry enables the telemetry-free measurement of online turbomachinery blade vibration. Specifically, the Eulerian or fixed reference frame implementation of laser vibrometry provides a practical solution to the condition monitoring of rotating blades. The short data samples that are characteristic of this measurement approach do however negate the use of traditional frequency domain signal processing techniques. It is therefore necessary to employ techniques such as time domain analysis and non-harmonic Fourier analysis to obtain useful information from the blade vibration signatures. The latter analysis technique allows the calculation of phase angle trends which can be used as indicators of blade health deterioration, as has been shown in previous work for a single-blade rotor.This article presents the results from tests conducted on a five-blade axial-flow test rotor at different rotor speeds and measurement positions. With the aid of artificial neural networks, it is demonstrated that the parameters obtained from non-harmonic Fourier analysis and time domain signal processing on Eulerian laser Doppler vibrometry signals can successfully be used to identify and quantify blade damage from among healthy blades. It is also shown that the natural frequencies of individual blades can be approximated from the Eulerian signatures recorded during rotor run-up and run-down.     

A novel optical telemetry system applied to flowmeter networks

Recently developed transducers utilise the unique characteristics of Deformed Helix Ferroelectric Liquid Crystal (DHFLC) to linearly and passively transduce small voltage signals into the optical domain. These small optical transducers can be retrofitted to an existing flowmeter network where the true benefits of distributed sensing in the optical domain can be leveraged. Signals from multiple sensors can be multiplexed into a single optical fibre for measurement at a remote location. We demonstrate two methods of signal measurement based on a positive displacement oval gear flowmeter. Utilising a reed switch to produce short pulses, errorless flow rate transduction is possible across all flow rates including very low flows. Using a variable reluctance sensor, completely passive transduction of flow rates can be achieved. The same technique can be applied to any sensing network with an electrical signal output.     

Numerical modelling and experimental verification of thermal characteristics and their correlations with mechanical properties of double-sided laser welded T-joint

In this study, a three-dimensional model was developed to investigate the temperature fields during a double-sided laser welding process of T-joints, and the correlations between the thermal characteristics and the mechanical properties were researched in details. To verify the modelling results, welding experiments were conducted with two different welding parameters and the geometrical dimensions of the weld pool were measured. It was found that there was a good agreement between the calculated and the measured results. The calculated results showed that the temperature profile was bilateral symmetry along the stringer centre, and the temperature gradient became greater as running far from the stringer centre, especially on the skin side. All of the tensile specimens were fractured along the fusion line on the skin panels for the head and the hoop tensile tests. The loss of the alloying elements near the fusion line on the skin side resulted in the lowest micro-hardness value appeared here, and made it to be the weakest region of the welded T-joints. The calculated thermal cycles indicated that the materials closest to the fusion line on the skin side had been staying at higher temperature for a longer time, and which is the essential reason for the fracture behaviour, micro-hardness distribution and alloying elements distribution of the double-sided laser welded T-joint.     

Continuous-wave Doppler for the noninvasive evaluation of aortic blood velocity and rate of change of velocity: evaluation in dogs

A new continuous-wave Doppler device is described, which has the capability of measuring peak aortic blood velocity and acceleration noninvasively in the ascending aorta of patients. To test the accuracy of the device, blood velocity and acceleration in the ascending aorta were compared with measurements obtained using an electromagnetic flowmeter in 16 open-chest anesthetized dogs. The Doppler probe was hand held directly on the aorta. Aortic flow was measured with a cuff electromagnetic flow transducer placed at the root of the aorta. Isoproterenol and propranolol, sometimes in combination with lidocaine, were administered intravenously to augment or reduce left ventricular contractile performance. Values of peak velocity, measured with the Doppler, corresponded closely to values measured with the electromagnetic flowmeter (r = 0.95). Values of peak acceleration also corresponded closely with the electromagnetic flow measurements (r = 0.96). The results indicate that valid measurements of blood acceleration in the ascending aorta, as well as blood velocity, can be obtained with continuous-wave Doppler.     

计及负频率影响的科里奥利质量流量计信号处理方法

采用滑动Goertzel算法计算科里奥利质量流量计信号的相位差时，存在较长的收敛过程，其主要原因之一是忽略了负频率成分的贡献。基于DTFT递推算法，提出了一种计及负频率影响的科里奥利质量流量计信号处理方法。首先采用自适应格型陷波滤波器对科里奥利质量流量计的传感器输出信号进行滤波并求得其频率，然后采用计及负频率影响的DTFT递推算法计算两路信号之间的实时相位差，再通过频率和相位差计算出时间差，从而求得质量流量。仿真结果表明，该方法可极大缩短相位差和时间差计算的收敛过程，具有较高的计算精度，且当应用于实际的系统时不易发生数值溢出。     

基于DSP、具有谱分析功能的涡街流量计信号处理系统

本文介绍一种以数字信号处理器（DSP）为核心、具有谱分析功能的涡街流量计信号处理系统。它采用周期图谱分析方法对涡街流量计中传感器的信号进行数字处理,准确计算出信号的频率,测出准确的体积流量,它抗干扰能力强,保证现场测量精度,扩大量程比,现场显示,并适用于不同口径和测量不同流体的一次仪表,它采用了DSP,保证了处理的实时性。     

Analysis of fluorescence from algae fossils of the Neoproterozoic Doushantuo formation of China by confocal laser scanning microscope

Chinese algae fossils can provide unique information about the evolution of the early life. Thin sections of Neoproterozoic algae fossils, from Guizhou, China, were studied by confocal laser scanning microscopy, and algae fossils were fluorescenced at different wavelengths when excited by laser light of 488 nm, 476 nm, and 568 nm wavelength. When illuminated by 488 nm laser light, images of the algae fossils were sharper and better defined than when illuminated by 476 nm and 568 nm laser light. The algae fossils fluoresce at a wide range of emission wavelengths. The three-dimensional images of the fluorescent algae fossils were compared with the transmission images taken by light microscope. We found that the fluorescence image of the confocal laser scanning microscope in a single optical section could pass for the transmission image taken by a light microscope. We collected images at different sample depths and made a three-dimensional reconstruction of the algae fossils. And on the basis of the reconstruction of the three-dimensional fluorescent images, we conclude that the two algae fossils in our present study are red algae.     

A novel approach to measuring the frictional behaviour of human skin in vivo

Friction involving human skin plays a key role in human life. The availability of a portable tribometer improves the accessibility to large number of both subjects and anatomical sites. This is the first mobile device suitable to measure skin friction with a controlled and variable normal load (range 0.5–2 N) and velocity (range 1–10 mm/s) of a material of choice making a sliding rotational movement over the skin.The results of a pilot study, using stainless steel samples on the ventral forearm compare to results in the literature. The new device can be used for more extensive research to found these results and determine the effects of normal load or sliding velocity on the skin's frictional behaviour.     

基于锁相放大器的全光纤式激光多普勒测速系统

为了提高激光多普勒测速系统的测量精度及其实用性,基于锁相放大器和光纤设计搭建了一套激光多普勒测速系统。该系统的优点在于,锁相放大器的引入能够放大信号并可避免杂散光影响,从而大大提高系统的信噪比;此外,利用光纤取代传统的传输与接收光路,有效避免振动、灰尘、杂散光等环境因素影响,使实验条件大大简化。利用该系统测量移动平面镜和漫射面镜的结果表明,该系统能够准确测量移动物体的速率,误差在1%以内。该系统将来可应用于在线监测活体组织的血液流速测量中。