Laser Doppler Method Research Articles

Experimental study on electrostatic migration of different mineral particles composing lunar dust under electron irradiation

Dust electrostatic migration is one of the primary causes of dust events on the surface of airless celestial bodies, which can result in multiple dust phenomena, including lunar horizon glow and dust pools, and also offer crucial insights into the evolution of the surface materials of airless celestial bodies. To date, the characteristics and laws of dust electrostatic migration are still not well understood. Here, we report the electrostatic migration characteristics of pyroxene, olivine, and ilmenite particles measured by the laser Doppler method and compare them with the findings of anorthite particles in previous experiments to recognize the differential migration characteristics of different mineral components in the lunar dust. The results demonstrate that the particle sizes of most moving pyroxene and olivine particles are in the range of 0–10 μm, and their vertical velocities are typically less than 2 m s−1, which are consistent with the previous studies. The cohesive force between the dust particles is probably what causes the difference in the migration rates of various insulating minerals. Note that no moving ilmenite particles were detected probably due to the material’s good conductivity. It can be speculated that the concentration of fugitive dust in the lunar mare is affected by the ilmenite content, but further research is needed to determine how low ilmenite content can cause dust migration.

Study on sinusoidal estimation deviation of electrostatic actuated MEMS mirror torsion angle

Electrostatic MEMS micromirrors usually work in resonant state to obtain large amplitude of torsion angle. The real-time prediction of MEMS micromirror torsion angle is calculated according to the measured resonant amplitude and phase under the assumption that the relationship between the torsion angle and time is sinusoidal. However, there are few reports on the deviation of this torsion angle predication based on sinusoidal assumption. In this paper, the real resonant torsion trajectory of C1100 MEMS micromirror under different driving frequencies and voltages is measured by using microscopic laser Doppler method, and the deviation between the real trajectory and the trajectory fitted by sinusoidal curve is compared. The results show that the real trajectory of the MEMS micromirror driven by square wave is not completely consistent with the sinusoidal estimation, and the deviation increases with the increase of the torsional angle amplitude. By obtaining the frequency domain components of the torsion angle signal using FFT method, the main reason of this prediction deviation is due to composition of harmonic signals on base frequency signal. The research results reveal that the sinusoidal assumption method is only suitable for situations when the optical angle accuracy is less than 0.1°.

Effect of Low- and High-Frequency Auricular Stimulation with Electro-Acupuncture on Cutaneous Microcirculation: A Cross-Over Study in Healthy Subjects

Background: The regulation of microcirculation depends on the dynamic interaction of different factors: the autonomic nervous system plays a pivotal role in the blood flow and acupuncture can modulate it, obtaining different results depending on the site, the frequency, and the intensity of the stimulation. Methods: 18 healthy subjects have been enrolled and have undergone two sessions of electroacupuncture stimulations: one session using high frequency and one with low frequency. Microcirculation has been monitored continuously during stimulation using the laser Doppler method. Results: The microcirculatory parameters have shown a significant difference between high and low-frequency stimulation, suggesting that low-frequency stimulation is more effective for obtaining a vasodilator effect. Discussion: Our results show that low-frequency stimulation can increase the cutaneous microcirculatory flux, without significantly modifying blood pressure and heart rate. The auricular stimulation causes an increase in the activity of the vagus nerve, increasing the cholinergic activity without acting on post-junctional muscarinic receptors. Conclusion: Auricular acupuncture has a significant impact on the regulation of microcirculation.

EVALUATION OF DYNAMIC CHANGES IN THE MICROCIRCULATION OF THE MUCOSA IN THE ZONE OF DENTAL IMPLANTATION WITH IMMEDIATE INTRAOPERATIVE LOAD.

The aim: Study of the dynamics of changes in the average values of the index of mucosal microcirculation after dental implantation with immediate intraoperative prosthetics. Materials and methods: In clinical conditions, 55 patients aged from 29 to 60 years with a diagnosis of partial absence of teeth requiring orthopedic treatment using implants on the lower jaw were treated and examined. In the course of the latest achievements, the following methods were used: clinical protocol of immediate implantation with Solidum and Simplex implants of the «ART IMPLANT» system on the lower jaw by the one-stage implantation method, with immediate intraoperative loading and the manufacture of a temporary non-removable dental prosthesis, determination of the microcirculation index in dynamics using the laser Doppler method flowmetry, statistical analysis. Results: The obtained results indicate a pronounced reaction of microcirculation up to the 3rd day after surgery, an increase in blood perfusion of the mucous membrane by 2.7 times while maintaining vasomotor activity, which indicates adaptation to the injury and immediate loading of the denture in the postoperative period. 3 months after dental surgery and immediate intraoperative prosthetics, all indicators of microcirculation approach the initial values before surgery. Conclusions: With the help of laser Doppler flowmetry, the fact of a sharp restoration of microcirculation after dental implantation surgery with immediate intraoperative prosthetics is confirmed.

Spatial Vibration and Displacement Measurement Through Single-Point Continuous and Interval Scanning Laser Doppler Vibrometer

The scanning laser Doppler vibrometer (SLDV) is an extremely valuable method for studying the dynamic properties of vibrating objects, such as those in industrial production, entomology research, and biomedical testing. The traditional SLDV method scans samples using an inclined laser, which ignores the three-dimensional (3-D) information of the sample, resulting in a relatively complicated calculation process. In industrial processes and scientific research, the measured target may have a known 3-D regular surface. When a structure with height information moves laterally, it causes a change in longitudinal information, which is of great benefit in the analysis of the 3-D vibration and displacement information of the target. In this article, continuous and interval scanning laser Doppler methods are proposed to expand the measuring capability of SLDV methods, based on the scanning of spherical structures. First, a spherical structure is introduced to simplify the solution to spiral vibrations. The high-precision displacement can also be calculated by fitting the circular scanning curve. Finally, the scanning method for 3-D displacement measurement is experimentally validated, and the theoretical errors are demonstrated. This work provides a new methodology to realize both periodic and nonperiodic displacements in all degrees of freedom (DOF) with high accuracy using a single-point SLDV, which is expected to have a long-term impact on industry vibration analysis and biological motion research. Most importantly, setting a reflector with a spherical surface on the end-effector of the micro–nano robot can realize the 3-D cross-scale repeated localization.

Experiments on the Electrostatic Transport of Charged Anorthite Particles under Electron Beam Irradiation

To reveal the effect of secondary electron emission on the charging properties of a surface covered by micron-sized insulating dust particles and the migration characteristics of these particles, for the first time we used a laser Doppler method to measure the diameters and velocities of micron-sized anorthite particles under electron beam irradiation with an incident energy of 350 eV. Here, anorthite particles are being treated as a proxy for lunar regolith. We experimentally confirm that the vertical transport of anorthite particles is always dominant, although horizontal transport occurs. In our experiments, some anorthite particles were observed to have large vertical velocities up to 9.74 m s−1 at the measurement point. The upper boundary of the vertical velocities V z of these high-speed anorthite particles are well constrained by its diameter D, that is, linearly depends on D −2. These velocity–diameter data provide strong constraints on the dust charging and transportation mechanisms. The shared charge model could not explain the observed velocity–diameter data. Both the isolated charge model and patched charge model appear to require a large dust charging potential of −350 to −78 V to reproduce the observed data. The microstructures of the dusty surface may play an important role in producing this charging potential and in understanding the pulse migration phenomenon observed in our experiment. The presented results and analysis in this paper are helpful for understanding the dust charging and electrostatic transport mechanisms in airless celestial bodies such as the Moon and asteroids in various plasma conditions.

Toe Pressure Measurements in Patients Suspected of Critical Limb Ischemia.

An objective hemodynamic assessment is mandatory to confirm Critical Limb Ischemia (CLI). Toe pressure measurement is recommended. We compared toe measurements obtained using the Laser Doppler method (LD) (PERIMED PeriFlux, Sweden) considered as the reference test, with those obtained with a portable device using photoplethysmography (PPG) (Sys Toe Atys Medical, France). A total of 93 (123 legs) patients from 3 French hospitals with a clinical suspicion of CLI were included and had measurements with each device carried out by skilled operators. PPG was unable to provide a measurement in 10 patients. Lin's Coefficient correlation concordance (CCC) and Bland and Altman's scatter plot were analyzed for the 83 remaining patients, CCC was .84 95%CI (.77-.89). For detection of CLI, Cohen's kappa was .67 95%CI (.53-.81). The PPG device is fairly reliable for toe pressure measurement in patients suspected of CLI and could be useful when LD is not available. However, it fails to deliver a measurement in approximately 10% of cases. No conclusion should be made about CLI for these patients when no measurement is obtainable and other methods should be used (LD, transcutaneous oxygen pressure) to assess perfusion of the limbs.

Modal characteristics of coupled MEMS resonator array under the effect of residual stress

The residual stress introduced in the packaging process of the mode localized MEMS sensors will shift the eigenfrequencies of their coupled resonator array, thereby affecting the function of the device. In this paper, the influence of residual stress on the modal characteristics of MEMS resonator array is analyzed by laser Doppler method, and the local vibration of coupling beam with 432 nm amplitude is measured by stroboscopic method. The theoretical model and finite element model of the resonator array considering residual stress are established. The results show that the in-plane mode of the resonator is coupled with the local mode of the coupling folded beam under the residual tensile stress of 83.3 MPa. The effect of residual stress on the eigenfrequencies of different modes differs by 14.47 times. The in-plane mode eigenfrequency of one of the resonators increases by 170.5% under the effect of residual stress.

Research on high-temperature vibration measurement method using laser Doppler interferometry

High-temperature vibration measurement plays a critical role in the design and performance testing of equipment such as aero-engine and heavy-duty gas turbines. Due to its non-contact, high accuracy, and resolution, the laser Doppler method has become one of the most commonly used vibration measurement techniques. However, one of the main problems in high-temperature vibration measurement is that the surface of the measured objects is oxidized, thus resulting in a decrease of interference signal intensity and signal-to-noise ratio. Furthermore, the aforementioned may even cause measurement failure. In this paper, an all-fiber laser Doppler velocity measurement device using a fiber optic circulator is established. Its vibration measurement performance is experimentally validated at high temperatures. The results demonstrate that this device can achieve vibration measurement within the temperature range of 300°C-1200°C with a maximum vibration speed of 1 m/s and maximum vibration acceleration of 378.4 m/s2. Relative deviation with Polytec vibrometer’s velocity results is within 1.95%. This model provides a viable solution for achieving accurate measurements of high-temperature vibration.

Raynaud's phenomenon and digital ulcers: advances in evaluation and management.

The aim of this review is to give an update on advances in evaluation and management of systemic sclerosis (SSc)-related Raynaud's phenomenon and digital ulceration, focusing on reports from the last 18 months. The increasing recognition of the huge impact of Raynaud's phenomenon and of digital ulceration on the everyday lives of patients with SSc has sparked enthusiasm internationally to develop better outcome measures and better treatments, and so a review is timely. There have been recent advances in the development of patient reported outcome instruments [e.g. the Hand Disability in Systemic Sclerosis-Digital Ulcers (HDISS-DU) instrument] and also in noninvasive imaging techniques, including thermography and laser Doppler methods. Improved outcome measures will facilitate future clinical trials, both early phase proof-of-concept and later phase trials. New insights have been gained into mechanisms of action and methods of administration of 'conventional' therapies, for example phosphodiesterase inhibitors and intravenous prostanoids. New treatment approaches are being investigated, including topical and procedural therapies. Clinicians can look forward to seeing these advances translating into clinical benefit over the next 5 years. To help ensure this, they should strive whenever possible to recruit patients with SSc-related digital vasculopathy into observational studies and clinical trials.

New perspectives in the imaging of Raynaud's phenomenon.

The last 10-20 years have seen huge strides in imaging science. The aim of this review article is to share with the reader the key recent advances in non-invasive imaging of the digital (finger) vasculature in patients with Raynaud's phenomenon (RP), including in systemic sclerosis (SSc)-related digital vasculopathy. For the rheumatologist, seeing a patient with RP is an opportunity for early diagnosis of an underlying SSc-spectrum disorder or (conversely) for reassuring the patient with primary (idiopathic) RP. Non-invasive imaging techniques can help to provide diagnostic certainty. In addition, they can provide new insights into pathophysiology and have the potential to facilitate the development of much needed effective treatments by providing primary and secondary endpoints for randomized controlled trials: validation studies are ongoing. This review article focuses on nailfold capillaroscopy, thermography, and laser Doppler methods but also discusses (briefly) other technologies, including optical coherence tomography, multispectral imaging, and photoacoustic imaging. Key recent advances are the increasing use/availability of nailfold capillaroscopy (and better understanding of the role of low-cost hand-held devices), increased accessibility of thermography (including mobile phone thermography), and increased application of laser Doppler methods to the study of RP/digital vasculopathy (in particular of laser Doppler imaging and laser speckle contrast imaging, both of which measure blood flow over an area rather than at a single site). In an era of precision medicine, non-invasive imaging techniques can help stratify risk of (a) SSc in the patient with RP and (b) digital vascular disease progression in the patient with an SSc-spectrum disorder.

Exact Analysis of a Linear Velocity Sensor

The velocity of a linearly moving cylindrical conductor can be measured using two methods: the laser-Doppler method and the eddy current method. In this article, we focused on an eddy current linear velocity sensor (LVS) with excellent environmental resistance while analyzing its theory to clarify its characteristics. Consequently, we were able to obtain an exact analytical solution by solving Maxwell's equation using the Fourier transform. In addition, we built an experimental apparatus that enables cylindrical conductors to move linearly and then used it to conduct an inspection experiment. As a result, a good agreement between the theory and the experiment was obtained for the speed characteristics. Therefore, we could confirm the validity of the theoretical analysis, and thus it has become possible to predict various characteristics related to LVSs. The analysis results of the theory are expected to greatly contribute to the optimization of LVSs.

Effects of local forearm skin heating on skin properties

This study investigated impacts of local skin heating on skin properties and tested whether skin changes depended on heat-induced hyperaemia. It was reasoned that heat-induced vasodilation impacts accompanying interstitial fluid changes. Forearm skin was locally heated from a baseline of 35°C to 40-42°C in 30 young adults (15 females, 15 males, 24.9±2.1years) and non-heated in 10 others (5 females, 5 males, 25.2±1.3years. Skin blood flow (SBF) was continuously measured using a laser Doppler method and skin tissue dielectric constant (TDC), stratum corneum capacitance (SCC) and transepidermal water loss (TEWL) were measured before and after maintained heat for 12min. TDC values were determined to effective measurement depths of 1.5mm (TDC15) and 2.5mm (TDC25). Results showed a large heat-induced hyperaemia, with SBF increasing on average 8.8-fold from its baseline of 35°C. Heating also caused significant increases in TDC, SCC and TEWL that, compared to preheating, increased approximately 1.1-fold, 3.1-fold and 4.5-fold. None of these skin changes correlated with the magnitude of the SBF hyperaemic response. Absence of this correlation may indicate that in young healthy adults, increased capillary filtration due to heat-induced arteriolar vasodilation is rapidly accommodated by postcapillary reabsorption, enhanced lymphatic activity and TEWL processes. An alternate explanation is that heating caused increased red cell oscillations that were detected as part of the laser Doppler increase without representing increased capillary flux. The major determinant of the Increases in TDC, SCC and TEWL is likely a consequence of heat-induced eccrine gland activation. Studies of older persons or those with depressed function are warranted.

Sesame lignans increase sympathetic nerve activity and blood flow in rat skeletal muscles.

Beneficial effects of sesame lignans, especially antioxidative effects, have been widely reported; however, its potential effects on autonomic nerves have not yet been investigated. Therefore, the current study aimed to investigate the effect of sesame lignans on the autonomic nervous system. The sympathetic nerve activity in rat skeletal muscle was measured using electrophysiological approaches, with blood flow determined using the laser Doppler method. Sesame lignans were administered intragastrically at 2 and 20 mg/kg, and after 60 min, the sympathetic nerve activity was observed to increase by 45.2% and 66.1%, respectively. A significant increase in blood flow (39.6%) was also observed for the 20-mg/kg dose when measured at 55 min after administration. These sympathomimetic effects were completely prevented by subdiaphragmatic vagotomy, and the increase in blood flow was eliminated in the presence of the beta2-adrenergic receptor inhibitor butoxamine. Thus, it is proposed that sesame lignans can increase the blood flow of skeletal muscle, possibly by exciting sympathetic nerve activity through the afferent vagal nerve.

Quantitative diagnosis method of beam defects based on laser Doppler non-contact random vibration measurement

The beam structure is prone to defect damage during its use, and the rapid quantitative diagnosis of the beam structure can detect the defects of the beam in real time and quantitatively. In this article, the method of obtaining the vibration time-domain signal under random excitation of beam structure is proposed by using random vibration excitation and Laser Doppler principle. Based on this, the defect quantitative identification algorithm of beam structure is proposed based on fast Fourier, continuous wavelet transform and convolutional neural network. The random vibration of different parts of steel beams with artificial defects is measured by Laser Doppler method. The experimental results show that the defect size of the beam structure can be effectively identified only by the random vibration signal of the finite point. The method is expected to help to develop an online real-time assessment instrument for beam structure defects in service state.

Protective effects of icariin on dorsal random skin flap survival: An experimental study

This study was performed to examine the protective effects of icariin (ICA) on ischemic random skin flaps. A rat random-pattern skin flap model was established, and animals in the low-dose and high-dose experimental groups were administered ICA intraperitoneally at doses of 40 and 80 mg/kg, respectively, once daily for 7 days after the initial surgery. Control rats received vehicle according to the same schedule. Survival rates were observed and recorded using transparent graph paper, and flaps were obtained and stained with hematoxylin and eosin (H&E). The malondialdehyde (MDA) content and superoxide dismutase (SOD) activity in the flap tissue were assessed. The blood flow volume was determined by the laser Doppler method, and tissue expression levels of vascular endothelial growth factor (VEGF), interleukin-6 (IL-6), interleukin-1β, and phosphodiesterase 5 (PDE5) were scored immunohistochemically. The levels of proinflammatory cytokines, including tumor necrosis factor-α and IL-6, were determined by enzyme-linked immunosorbent assay. The main flap survival area was significantly larger in rats treated with ICA than in vehicle-treated controls. H&E staining showed an inhibitory effect of ICA on inflammation, especially at the high dose. In addition, ICA treatment was associated with decreases in the tissue MDA level, proinflammatory cytokine production, and the level of PDE5, but increases in SOD activity, blood flow volume, and the level of VEGF expression. The findings of the present study suggest that ICA is a potential therapeutic agent for random-pattern skin flap necrosis in the clinical setting.

No effect of the angiotensin receptor blocker candesartan on cerebrovascular autoregulation in rats during very high and low sodium intake.

Autoregulation of cerebral blood flow (CBF) denotes that CBF is constant despite fluctuation of blood pressure within wide limits. Inhibition of the renin–angiotensin system (RAS) is known to decrease the lower and upper limits of CBF autoregulation. We have previously shown that this includes inhibition by the angiotensin receptor blocker (ARB) candesartan. In the present study we investigated the influence of the ARB candesartan on the lower limit of CBF autoregulation in two groups of Sprague-Dawley rats, on high (4.0% Na+) and low (0.004% Na+) sodium diet, respectively. Control animals were given the same diet, but no ARB. CBF was studied with the laser Doppler method. Blood pressure was lowered by controlled bleeding. Results revealed that both high and low sodium diet with low and high renin levels respectively block the influence of candesartan on CBF autoregulation. This was expected in rats on a high salt diet with a low renin level, but unexpected in rats with a low salt intake with a high renin level.

Measuring of drill bit vibration by laser Doppler methods

The beginning of the drilling process was measured on the drill bit by laser Doppler interferometric methods. The measurements of the velocities were based on the Doppler effect. An LDV (Laser Doppler Vibrometer) device was used to measure the translational vibrations, and then the torsional vibrations (angular velocity changes) of the drill bit were investigated by an LTV (Laser Torsional Vibrometer) device. The time series and frequency spectra were also analysed.

A Numerical Model of Blood Flow Velocity Measurement Based on Finger Ring.

Aiming to measure the blood flow velocity in a finger, a novel noninvasive method, i.e., a ring with a heat source chip and a temperature sensor, is designed in this paper. The heat source chip is used to heat the finger and generate heat diffusion between the chip and the temperature sensor. And the temperature sensor is designed to measure the temperature difference. Since the blood flow is the main medium of heat diffusion in bodies, part from the heat energy in the tissue will be taken away by the flowing blood. Therefore, the blood flow velocity can be acquired via its relationship with the temperature difference. Compared to the ultrasound Doppler method and the laser Doppler method, the proposed method guarantees a more convenient operation in more flexible work sites. We also analyze the theory between heat transfer and laminar flow. Finally, several simulations are conducted, and the influence of the relevant factors (i.e., the number of blood vessels, the radius, etc.) corresponding to the simulation results is also discussed.

Endothelial dysfunction and smoking factor in patients with coronary heart disease while testing the radial artery prior to coronary bypass surgery

Patients (111 males) with coronary heart disease (CHD) and angina, II-III functional class, accompanied by arterial hypertension (AH), I-III degree, in 77 % of cases (mean age was 62.00.76 years) were examined prior to coronary bypass surgery. The patients were divided into two groups: group 1 consisted of 56 nonsmoking patients (112 upper extremities) and group 2 - 55 smoking patients (110 upper extremities) with the experience of smoking being 331.6 years on average. The thumb of both the right and left hand was tested for peripheral microcirculatory blood flow (MBF) by using a laser-Doppler flowmetry method (LDF). This quantitative method was developed at our clinic to assess the adequacy of collateral circulation in the hand. The method compares MBF provided by the ulnar artery, with the radial artery occluded, with the background level. Some features of various clinical parameters in the group of smokers suffering from coronary artery disease were analyzed in comparison with those of non-smokers. Significant differences were found in the indicators of lipid profile: increased levels of total cholesterol and low-density lipoprotein (LDL) against the background of low high-density lipoprotein (HDL) in the group of smoking patients. We found out that the smokers had to apply for surgical treatment by 7 years (on average) earlier; they had a significantly greater number of heart attacks and showed the lowest body mass index (BMI). The LDF test helped to establish that smoking in patients with CHD enhances the endothelial dysfunction, while significantly reducing the reactivity of the microvascular bed under the influence of hyperemic stimulus. Sampling the radial artery for coronary artery bypass grafting in smokers tended to give negative results.