Search

This study reports the development of an efficient and sensitive method to directly sense microRNA (miRNA) in high ionic strength solutions with the use of electrical double layer (EDL) gated AlGaN/GaN high electron mobility transistor (HEMT). This FET structure uses a complementary DNA probe functionalized gate electrode which is separated from the transistor channel. In this research, we focus on the detection of miRNA samples, miR-126, miR-208a and miR-21 which are biomarkers of cardiovascular diseases (CVD). The sensor has a dynamic range that is comparable to the clinically relevant concentration range with a detection limit as low as 1 fM. Selectivity of the sensor is demonstrated by evaluating sensor response at fully complementary and slightly mismatched sequences. The miniaturized sensor can be used in point of care or homecare diagnostics for rapid miRNA detection to evaluate CVDs at an early stage.

Silicon nanostructures can improve the bending strength of wafers, but often trap particle contaminates. A double-sided surface nanostructure with a morphology controlled via wet chemical etching is used to both improve the mechanical strength and reduce surface reflection. Compared with a conventional polished silicon wafer, the bending strength was increased by 3.4 times and the surface reflection was reduced to 1%, and so can provide a promising solution for photovoltaic applications. The optically unused side of the wafer was protected by a thin silicon layer that prevented the entrapment of particles that might cause glitches in subsequent fabrication processes, all the while maintaining the enhancement in strength. The particle test confirmed that incorporating protection layer intacts the particle count with polished silicon sample.

The output power of conventional light-emitting diodes (LEDs) is enhanced by 9% at 120 mA current without alterations to the existing fabrication techniques and to the multi-quantum well (MQW) junction. The output power is improved by nanotexturing the street of the n-gallium nitride (GaN) layer that was unexploited, for the enhancement of the optical or electrical properties. The nanotextured street enhances the light extraction exclusively near the street of the n-GaN layer by reducing the reflections from the LED surface. Similar light output patterns and I–V characteristics for LEDs with and without street nanotexturing were observed, confirming that the enhanced light extraction has been achieved without a change in the spatial distribution of light or in the properties of the MQW junction. A new approach for the output power enhancement of all types of existing LEDs is provided.

Motivations This study performed skin-surface laser-Doppler flowmetry (LDF) measurements with the aim of verifying if complexity analysis applied to the beat-to-beat LDF waveform index can be used to discriminate diabetic, prediabetic, and normoglycemic subjects. Methods Sixty-six subjects were assigned to three age-matched groups according to the results of oral glucose tolerance tests. Beat-to-beat analysis was performed on the pulsatile LDF waveform to obtain the pulse-to-mean ratio (AD) and pulse width (PW), and then approximate-entropy (ApEn) values for their 20-minute index sequences were calculated to evaluate the signal complexity. Results AD and PW did not differ significantly among the three study groups. ApEn values of AD and PW were significantly larger and marginally larger, respectively, in the diabetic group than in the prediabetic and normoglycemic groups. Conclusion These results indicate the presence of significant differences in ApEn indexes among diabetic, prediabetic, and normoglycemic subjects. The presence of increased complexity in the LDF index sequence may be partly attributed to the adaptability of the microcirculatory regulatory activities or the impairment of the homeostasis mechanism of microcirculatory-blood-flow perfusion. The present findings may be pertinent to the early detection of the diabetes-induced impairment of this perfusion.

Beat-to-beat cardiovascular variability analysis provides important information on the circulatory regulatory activities. Changes in the arterial pulse transmission or the opening condition of arteriolar openings might change the fluctuation pattern of the MBF supply, and thus change the complexity property therein. We performed complexity analysis of beat-to-beat laser Doppler flowmetry (LDF) signals to study the microcirculatory-blood-flow (MBF) response at the needled site (Hegu acupoint) following acupuncture stimulation (AS). LDF signals were measured in male healthy volunteers (n=29). Each experiment involved recording a 20-minute baseline-data sequence and two sets of effects data recorded 0-20 and 50-70min after stopping AS. Approximate-entropy (ApEn) analysis, which quantifies the unpredictability of fluctuations in a time series, was performed on each 20-minute beat-to-beat LDF data sequence. The present findings indicate that AS can not only improve the local blood supply but may also increase ApEn values and decrease MBF variability parameters. This was the first attempt to apply complexity analysis to LDF signals in order to elucidate microcirculatory responses following AS. The observed results are probably attributable to the contradictory effects on the MBF supply induced by AS, which might interfere with the microcirculatory regulatory activities so as to increase the complexity of LDF signals. The present findings could help to identify the mechanism underlying the effects of AS, might aid the development of an index for monitoring the induced microcirculatory regulatory responses, and thus provide an evidence-based connection between AS and modern physiology.

Backside nanotexturing fabricated by electroless metal assisted wet chemical etching, protected with a deposited thin silicon layer, is a new approach to create high bending strength silicon samples. Bending strength for protected nanotextured samples followed by CMP process was enhanced by ∼3.4 folds as compared to polished silicon samples, which emphasize the possibility of industrial implementation. The morphology of silicon deposition layer upon nanotexture influences the stress behavior, which need an adequate fabrication technique for uniform deposition at wafer scale. The thin protection layer upon nanotexture prevents the unwanted particle trapping, which affects the electrical performances of the device. Moreover, this technology provides a rupture resistive solution for IC, MEMS and photovoltaic devices for industrial implementation.

Cold stimulation (CS) accompanied by vasoconstriction can increase the stiffness of the arterial system. The vascular responses during CS have been studied using photoplethysmography (PPG), but most have focused on time-domain waveform indexes. Focusing on the radial arterial blood pressure (BPW) and the finger PPG waveforms, we aimed to determine if harmonic index could help to noninvasively characterize the changes in arterial pulse transmission following mild CS.Trials were measured on male healthy volunteers (n=29); mild CS was applied by placing a bag filled with 2000 cc of water at a temperature of 19-21°C around the right lower arm. For each experiment, we recorded a 3-min baseline-data sequence, applied local mild CS and recorded a 3-min effect sequence, and then recorded another 3-min effect sequence immediately after stopping CS. BPW and PPG spectra were used to calculate the amplitude proportion (C(n)) and phase angle (P(n)) for each harmonic (for n=1-10) from averages of all the pulses during the measurement period.Several harmonic indexes were prominently increased following CS, including C(4)-C(10) and P(3)-P(10) for the BPW and C(5)-C(10) and P(3) and P(4) for PPG waveforms.It was demonstrated that the application of mild CS significantly changes several harmonic-analysis indexes of the BPW and the PPG waveforms. By providing detailed information about the pulse transmission of each frequency component, harmonic analysis may improve the ability to detect arterial elastic properties induced by CS, other forms of external stimulation, or pathological factors. It may be pertinent to the development of medical devices for application in telemedicine.

Objective: We aimed to elucidate the frequency-specific microcirculatory blood-flow (MBF) effect induced by weak vibration stimulation (VS) in healthy human subjects. Methods: VS was implemented by a rod (connected to a DC motor) hitting a water-filled bag. VS was applied to the left palm at frequencies near to the heart rate (HR) (n = 35; Group A) and 50% higher than the HR (n = 20; Group B), and laser-Doppler-flowmetry measurements were made on the back of the left hand (Site 1). A control group without applying VS was also used (n = 21). Results: The mean MBF (MMBF), pulsatile MBF, and pulse width at Site 1 only increased significantly in Group A, and the coefficient of variance of the MMBF sequence increased significantly at Site 1 in Groups A and B. Conclusion: These results illustrate the VS-induced changes in the regulatory activities of arteriolar openings, and improve- ment of the MBF near the VS application site in Group A. The improvement in MBF depended on whether the VS frequency was near to, or higher than the HR. The present findings may be pertinent to amelioration of disease induced by an abnormal MBF.

In the present study, laser Doppler measurement was used to quantitatively investigate the microcirculatory effects of contact pressure stimulation (PS) underneath the Hoku acupoint and its nearby nonacupoint, to improve the understanding of the mechanisms underlying acupressure therapy. A control group (no PS applied) and three experimental groups with different applied PS (group A, 60 mmHg on the Hoku acupoint; group B, 60 mmHg on a nearby nonacupoint; group C, 50 mmHg on a nearby nonacupoint) were studied. Each experiment involved recording data of a 20 min baseline and two periods of effects after stopping PS. The relative energy contribution (REC) in five frequency bands, as revealed by Morlet wavelet transformation, was calculated. At the pressed site, the average value of the laser Doppler flux signal was increased only in group A, and coefficient of variance of the amplitude sequence was only significantly decreased during measurement (M1: 0 to 20 min) in group B. The RECs of the myogenic-related band were significantly increased in groups A and C, whereas there were no significant changes found in group B. The improved microcirculatory blood-flow perfusion at Hoku may partly explain why acupressure can exert better therapeutic effects than PS applied to other sites. The laser Doppler spectra responses illustrated that the induced pressure-induced vasodilation can be attributed mainly to the myogenic response. Laser Doppler measurement and analysis therefore represent a noninvasive method of examining the microcirculatory efficacy of acupressure therapy.

Measurement of blood pressure is one of the most important parameters for personal healthcare. Arteries are responsible for carrying blood from the heart to all parts of the body and the pressure of blood in arteries is measured in many abnormalities. The blood pressure is explained by two parameters. The highest blood pressure during heart pumping is measured by systolic pressure whereas the diastolic pressure measures the lowest blood pressure when the heart is not pumping the blood. For current work, the principle of light absorption is used to measure blood pressure in arteries. Light is more strongly absorbed by blood compared to skin or tissues and therefore, blood flow change can be detected by the change in intensity of light. This blood flow change is proportional to blood pressure and hence the blood pressure can be measured by measurement of change in light intensity. In this work, we have developed the InGaP photodiode module with higher signal to noise ratio for blood pressure measurement. The InGaP photodiode External Quantum Efficiency (EQE) is 50% higher than Silicon (Si) photodiode. The EQE is ever higher than Si photodiode equipped with the filter as shown in Fig. 1(a). The newly developed InGaP photodiode has the advantage of selective EQE at different wavelength. The photodiode has almost zero EQE outside the desired region of wavelength (300 nm- 700 nm) where the Si photodiode EQE is spread in the longer wavelength region (300 nm - 1200 m). This higher region of EQE can lower the signal to noise ratio. The InGaP photodiode has an increased signal to noise ratio (24.8) compared to other photodiodes (24.0) due to the smaller wavelength region of EQE. Both systolic blood pressure and diastolic blood pressure measurement was compared for actual value and predicted value. The R2 correlation value for systolic and diastolic blood pressure is measured to be 0.86 and 0.91 respectively as shown in Fig. 1(b) and Fig. 1(c). This works explore new doorway for LED and photodiode application in the field of biomedical sensors. The application of our new photodiode with enhanced EQE and the wide range of LED has numerous possibilities. The higher possibility of multichip design with Flip chip packaging technique can provide a single module for measurement of blood pressure, blood glucose, blood lipid and other parameters using LED of different wavelength. Figure 1

Moxibustion is a commonly used treatment in traditional Chinese medicine (TCM) that involves the application of local heating (LH) at acupoints.We used laser Doppler flowmetry (LDF) and spectrum analysis to investigate differences in the microcirculatory responses to the application of homogeneous LH at Hoku and two nearby nonacupoints.Thirty-four trials were performed on 10 male healthy volunteers. For each experiment, we recorded a 20-minute baseline data sequence, then applied LH by an infrared-radiation lamp and recorded another 20-minute heating-effect sequence. The relative energy contributions (RECs) for LDF periodic oscillations in five characteristic frequency regions from 0.0095 to 1.6 Hz (segmented into FR1-FR5) were calculated by wavelet analysis.The flux increased significantly following LH. Decreases in RECs of FR2 and FR3, increases in RECs of FR1 and FR5, and the flux increase following LH were all largest at Hoku.Our results suggest that the application of LH to acupoints induces larger therapeutic effects. This might partly account for the physiological mechanism of moxibustion, and could contribute to optimizing the microcirculatory improvement by applying LH treatments. Frequency-band analysis appears to be a promising tool for studying microcirculatory responses induced by various TCM treatments.

We aimed to assess the effects of acupuncture by analyzing the alternating current (AC) component of skin blood-flow signals (around the heartbeat frequency) simultaneously recorded at the Hoku acupoint, which is an important acupoint in oriental medicine, and two nearby non-acupoints following acupuncture stimulation (AS). Laser Doppler flowmetry signals were measured in 28 experiments on nine volunteers. Each experiment involved the recording of a 20-min control-data sequence and two sets of effects data recorded 0–20 min and 50–70 min after the AS had been stopped. The direct current (DC) and AC components (DCflux and ACflux, respectively), pulse width (PW), and foot delay time (FDT) of the flux signal were calculated. The DCflux, ACflux, PW, and FDT were all significantly increased only at Hoku following AS. Regression analysis between the DCflux and ACflux revealed that the slope was largest (>1) at Hoku among the measurement sites. Our results indicated that both the DCflux and ACflux in the microcirculatory perfusion were increased by stimulation at the Hoku acupoint, with the change being greatest for the latter. Parameters calculated from the pulsatile flux waveform, such as the PW and FDT, could contribute to noninvasive evaluations of the sympathetic neural activities and of the improvement in perfusion following AS.

Pulse parameters calculated from the LDF waveform based on a time-domain synchronized averaging analysis were shown to be able to discriminate the difference in microvascular resistance. However, its applicability may depend on the validation of signal stationarity. In this study, our aim is to investigate the effect of pulse number, which may destroy the signal stationarity, on various pulse LDF parameters. Analysis was performed in data obtained on healthy volunteers. When one pulse parameter is deviated from the standard value for more than 10%, it was regarded as an error; EP (error probability) was then defined as the occurring probability of error. It was revealed in this study that average parameter deviations for FDT and PDT were smaller than 5% for all tested pulse numbers. If we set 10% as the parameter-deviation criterion as well as the acceptable EP range, there should be at least 120 pulses for FDT and PDT, and 210 pulses for FNA and PW. The study presented here has established the criteria for appropriate pulse number to achieve the signal stationarity; we can thus get accurate pulse parameters so that the microcirculatory discriminability of the pulse-based time-averaging analysis on LDF signal can be improved. The proposed quantitative method to verify the validation of signal stationarity when utilizing time-averaging can also be applied to analysis of other bio-signals.

Background Women with PCOS may present abnormal hemodynamic alterations and thus may develop vascular damage. This study performed LDF measurements on the skin surface around the leg to verify if beat-to-beat waveform and spectral analysis can help to discriminate the MBF characteristics between PCOS and healthy subjects. Methods ECG and LDF signals were obtained noninvasively in PCOS (n = 16) and control (n = 8) subjects. Beat-to-beat waveform and spectral analysis was performed on the LDF signals to obtain the AD, FDT, FRT, and REC of five frequency bands. Results FRT was significantly larger, AD was significantly smaller, REC of the myogenic-related band was significantly smaller and REC of the heartbeat-related band was significantly larger in the PCOS than in the control subjects. Conclusion This study is the first to reveal that time-domain waveform and spectral analysis performed on skin-surface LDF signals can be used to discriminate the differences in the MBF perfusion condition and the microcirculatory regulatory activities at local vascular beds between PCOS and healthy subjects. These findings may aid the noninvasive early detection of PCOS-induced vascular damage.

MOTIVATION: Stroke induces abnormal microcirculatory blood flow perfusion resistance in cerebral vascular beds, which may in turn alter the arterial pulse transmission. This study aimed to determine if the frequency-domain harmonic index for the blood-pressure waveform is useful in monitoring the microcirculatory blood flow perfusion response in cerebral vascular beds of stroke patients following acupuncture stimulation. METHODS: Bilateral radial arterial blood-pressure waveform and laser-Doppler flowmetry signals were obtained noninvasively before and after acupuncture in 17 stroke patients. The amplitude proportion (Cn) for all the acquired pulses and the coefficient of variance (CVn) for harmonics 1–10 were calculated to evaluate the blood-pressure harmonic variability. RESULTS: The laser-Doppler flowmetry parameters showed that the cerebral microvascular blood flow supply could be improved following acupuncture. For the blood pressure waveform harmonic index, there were significant increases in C5 and C6 and decreases in CV5 and CV7 on the stroke-affected side, but no significant changes on the contralateral side. CONCLUSION: Cn values might reflect changes in arterial pulse transmission, and the blood-pressure-harmonic-variability response might be partly attributable to cardiovascular regulatory activities caused by acupuncture-induced changes in the cerebral microvascular blood flow perfusion. The present findings of blood pressure waveform harmonic analysis may be useful to the development of a noninvasive and real-time technique for evaluating treatment efficacy in stroke patients.

This study discusses the optical characteristics of Ultra-High-Brightness LEDs (UHB-LEDs) at high current density. The wafer bonding technique was applied in this research to enhance the light extraction efficiency of AlGaInP UHB-LEDs. This technique can replace the GaAs substrate with transparent substrates for achieving the high quantum efficiency. However, the structure that designed for light extraction performed excellent quantum efficiency at low current density but performed badly at high current density. The quantum efficiency droop dramatically as current density increase. Factors of efficiency droop included epitaxy design, process design, package and system thermal design, and the relations among them. In particular, heat in chip level deeply affected the quantum efficiency and highly related to all factors. Therefore, how to separate thermal effect from all factors is important for designer to optimize the structure. In this research, a transient thermal management system to minimum the heat in the chip was demonstrated. The optical and electrical characteristics was measured with a extremely short pulse time and different duty cycle at first, and then curve fitting the result to find out the optical performance without heat under certain current density. A wavelength shift method is performed to validate the thermal management system and the concept of optical performance with no heat accumulation. The experimental data shows a good agreement with the wavelength shift method. After that, the performance ratio of different current density without heat effect also showed. Comparing it to the performance ratio with TO-18 package, one can clearly define how much loss generated from thermal effect. It reveals that LED with TO-18 package has 10% loss from heat accumulation under 1A/mm2, furthermore, when it is driven on higher density, the extremely heat accumulates and lead the intensity ratio to saturate, and the difference are more than 70%. Eventually, the quantum efficiency influenced by heat under high current density may be a substantial issue in further study for lighting applications.

We aimed to assess the effects of acupuncture by analyzing the frequency content of skin blood-flow signals simultaneously recorded at the Hegu acupoint and two nearby nonacupoints following acupuncture stimulation (AS). Laser Doppler flowmetry (LDF) signals were measured in male healthy volunteers in two groups of experiments: needling the Hegu acupoint (n= 13) and needling a nearby nonacupoint (control experiment;n= 10). Each experiment involved recording a 20 min baseline-data sequence and two sets of effects data recorded 0–20 and 50–70 min after stopping AS. Wavelet transform with Morlet mother wavelet was applied to the measured LDF signals. Needling the Hegu acupoint significantly increased the blood flow, significantly decreased the relative energy contribution at 0.02–0.06 Hz and significantly increased the relative energy contribution at 0.4–1.6 Hz at Hegu, but induced no significant changes at the nonacupoints. Also, needling a nearby nonacupoint had no effect in any band at any site. This is the first time that spectral analysis has been used to investigate the microcirculatory blood-flow responses induced by AS, and has revealed possible differences in sympathetic nerve activities between needling the Hegu acupoint and its nearby nonacupoint. One possible weakness of the present design is that different De-Qi feelings following AS could lead to nonblind experimental setup, which may bias the comparison between needling Hegu and its nearby nonacupoint. Our results suggest that the described noninvasive method can be used to evaluate sympathetic control of peripheral vascular activity, which might be useful for studying the therapeutic effects of AS.

The aim of this study was to determine the effects of acupuncture stimulation (AS) in stroke patients by analyzing the pulsatile waveform and frequency content of skin blood-flow signals recorded simultaneously on the bilateral skin surface of the head. Laser Doppler flowmetry (LDF) signals were obtained in 18 stroke patients. Each assessment involved a 20-min baseline recording, a 20-min AS, and a further 20-min recording. Significant bilateral differences in LDF parameters were noted following AS, with an increased pulsatile component of the microcirculatory blood flow (MBF), decreased blood-flow resistance, and decreased MBF variability in the vascular beds on the stroke-affected side. Spectral analysis revealed that the vasodilation on the stroke-affected side could be partly attributed to decreased sympathetic neural activity. This is the first study to demonstrate the feasibility of evaluating the cerebral MBF conditions induced by AS in stroke patients by noninvasive LDF measurement. The present skull-intact measurement setup could aid the development of noninvasive detection techniques for determining bilateral differences in the cerebral MBF, and could thus become useful for the efficacy evaluation of treatment techniques for stroke. It might also promote understanding of the mechanisms underlying the responses and possible treatment efficacy of AS as applied to stroke patients.

Analyzing the beat-to-beat cardiovascular variability (e.g., heart-rate variability analysis) provides important information regarding circulatory autonomic control. The present study aimed to use laser Doppler flowmetry (LDF) and beat-to-beat analysis to elucidate changes in the microcirculatory blood flow (MBF) and variations (MBFV) therein induced by local heating stimulation.For each experiment, we applied nonpainful local heating and recorded a 20-min heating effect, which was segmented into four measurements separated by 5 min as M1-M4. DCflux (average LDF flux) was calculated for each pulse, and the coefficient of variance of DCflux (DCCV) was then calculated to evaluate the beat-to-beat MBFV.In the linear regression analysis of the M2-M4 data sequence, the slope between relative changes (compared with M1 values) in DCCV and DCflux, and those between the proceeding DCCV and the subsequent DCflux, were negative (R(2) 0.40 for all; p 0.05).This is the first study to reveal a possible time-domain relationship between changes in MBF and MBFV parameters. Our results suggest that MBFV evaluated from the beat-to-beat LDF waveform is useful for monitoring the microcirculatory regulatory activities of arteriolar openings, and might therefore be particularly meaningful when evaluating treatment techniques or drugs aimed at improving microcirculatory perfusion.

Light-emitting diodes (LEDs), representing a type of solid-state lighting, have been widely used as indicator lamps in the past few decades. It has attracted a great deal of attention in various illuminating applications in recent years due to its outstanding advantages, such as low power cost, long life time, and high efficiency. However, to make it possible to apply LED in daily life, a suitable package structure is necessary, which provides electrical interconnection and protection functions. Recently, the technology for a high power LED packaging that employs applied wire bonding process to achieve electrical interconnection has been widely adopted by LED packaging house. However, improper wire bonding parameters often result in LED die cracking or pad peeling. In this study, the strength of LED dies was investigated in order to improve the yielding of wire bonding. To determine its strength, point-load test associated with focusedion beam was utilized to measure the ultimate reactive force. Results of the experiment were further integrated with simulation technology based on the finite element method to evaluate its ultimate strength. In the PLT tests, direct contact pin-loading was applied to the epilayer surface of the LED dies and the ultimate force was measured. After the PLT tests, FIB was utilized to investigate fracture initiating location in the epilayer. The PLT results showed that the averaged ultimate force is about 75 g. According to the FIB results, the vertical load was validated as the driving force for pad peeling, epilayer crack, and LED die crack. Based on the experimental data, an FEM 3D contact model was utilized to analyze its detailed mechanical behaviours. Simulation results showed that stress concentration occurred near the edge of the pin and that the maximum stress took place in epilayer. In order to reduce the stress, three kinds of new LED structures that introduce the stress buffer layer between the Au pad and LED layers were evaluated, and the results showed good improvement of stress reduction in the epilayer. Nevertheless, the soft material applied for the stress buffer structure may cause another failure issue under thermal loading during the bonding process due to the mismatch of the coefficient of thermal expansion. Therefore, to achieve the optimal design and the best combination of design parameters, the simulation-based design methodology must be adopted to meet the design and production optimization goals, which would be impossible if done by conventional experiment-based trial-and-error design procedure.

High-power light emitting diodes (LEDs) are found in a number of applications in high-volume consumer markets, such as illumination, signalling, screen backlights, automotives, and others, because of the numerous advantages of LEDs, including low power cost, long life span, and high efficiency. During the manufacturing process, the high-power LED chips are subjected to mechanical and thermal loadings. Wire bonding is one of the major processes in the LED packaging process that provide electrical interconnection between the bonding pad and the lead. However, due to bad parameter setup in a wire bonder, the LED will crack and the pad will peel after wire bonding. In this study, the strength of LED is determined for the design requirement in order to ensure good reliability of wire bonding. Pointload test (PLT) and focused ion beam (FIB) are used to determine the maximum allowable force the epilayer can withstand, which is approximately 75 g. By combining the finite element method and experimental data, a useful design tool to confirm LED die strength is provided. Finite element results of contact analysis show that the stress concentration area is located on the edge of the pin and maximum stress (227 MPa) occurs in the epilayer. Parametric study is employed to find ways to reduce stress in LED layer. The results indicate that increasing pad thickness is the major factor that can reduce stress and enhance LED die strength. PLT and FIB experiments are also performed to confirm simulation results.

Objective: Cardiovascular variability analysis, such heart rate variability or blood pressure variability, provides important information about activities of various regulatory mechanisms for the cardiovascular system. Aim of the present study is to use the laser Doppler flowmetry (LDF) measurement to study the correspondent changes between the beat-to-beat microcirculatory blood flow (MBF) and its variation (MBFV). Methods: 17 trials were performed on 5 male healthy volunteers. For each experiment, we applied local heating (LH) stimulation and recorded a 20-minute heating-effect data sequence. For each pulse, DCflux (average LDF flux) was calculated, and CV (coefficient of variation) of DCflux (DCCV) was then calculated to evaluate the beat-to-beat MBFV. Results: The slope between DCCV and DCflux was negative with R2 ≫0.7 (p≪0.01 by F-test). Conclusion: Our results suggest that by providing an alternative solution to overcome the major drawback for LDF measurement of lacking quantitative evaluation, MBFV parameters calculated from the beat-to-beat LDF waveform may have meaning in improving the evaluation for the LH response of the MBF perfusion.

Objective: Blood pressure (BP) waveform has important meaning in the study of circulatory diseases, but its noninvasive assessment is not sufficiently user-friendly for practical applications. In the present study, we try to build up a user-friendly PPG measurement system, and study the correlation between radial BP and finger photoplethysmography (PPG) waveforms Methods: User-friendliness of a self-made PPG measurement system was improved by applying an appropriate contacting pressure on the measured finger and adapting a hand-shape mold for the finger to put on. Finger PPG and radial-artery BP signals were then measured simultaneously and noninvasively on healthy volunteers (n=?). In frequency-domain analysis performed on each 1-minute recorded data sequence, the linear regression was applied to the calculated amplitude ratios between BP and PPG waveforms. Results: After a series of testing, the PPG measurement system was found to be user-friendly and has a good reproducibility in the frequency components within the measured PPG waveform. The BP-PPG regression of amplitude ratios were all significant (R2 values all ≫0.72) for the first three harmonics. Conclusion: In the present study we built up a user-friendly PPG measurement system, and developed a frequency-domain analysis method to study the correlation between BP and PPG waveforms. We hope that the noninvasive PPG measurement system and the frequency-domain waveform analysis can provide an alternative and a more user-friendly method to reconstruct the radial BP waveform, and hence broaden the application of BP waveform analysis, which may bring deeper understanding for important circulatory diseases.

We aim to analyze the frequency content of skin blood flow signals recorded on Hoku following acupuncture stimulation (AS). Each experiment involved recording a 20-minute control-data sequence and two effects data recorded 0–20 and 50–70 minutes after stopping AS, respectively. 4-level Haar-wavelet transform was performed on the measured LDF signals, and periodic oscillations with five characteristic frequency peaks were obtained within the frequency interval: 0.0095–0.021, 0.021–0.052, 0.052–0.145, 0.145–0.6, and 0.6–1.6 Hz, respectively. Band proportion and DC component of the flux signal were calculated to elucidate the effects following AS. At Hoku, the DCflux was significantly increased, the band proportion of the 1st and the 2nd frequency band were significantly decreased, and that of the 5th band was significantly increased following AS. Our results facilitate a non-invasive method to evaluate sympathetic control of peripheral vascular activity between the acupoint and non-acupoints, which may be important for studying the therapeutic effects of AS.

We aim to analyze the frequency content of skin blood flow signals recorded on Hoku following acupuncture stimulation (AS). Each experiment involved recording a 20-minute control-data sequence and two effects data recorded 0-20 and 50-70 minutes after stopping AS, respectively. 4-level Haar-wavelet transform was performed on the measured LDF signals, and periodic oscillations with five characteristic frequency peaks were obtained within the frequency interval: 0.0095-0.021, 0.021-0.052, 0.052-0.145, 0.145-0.6, and 0.6-1.6 Hz, respectively. Band proportion and DC component of the flux signal were calculated to elucidate the effects following AS. At Hoku, the DCflux was significantly increased, the band proportion of the 1st and the 2nd frequency band were significantly decreased, and that of the 5th band was significantly increased following AS. Our results facilitate a non-invasive method to evaluate sympathetic control of peripheral vascular activity between the acupoint and non-acupoints, which may be important for studying the therapeutic effects of AS.

We used laser Doppler flowmetry (LDF) and spectrum analysis to investigate the microcirculatory responses to pressure stimulation (PS) of the skin surface. A control group without PS applied, and four groups with different PS (20, 60, 100 and 160 mmHg in groups PS(20), PS(60), PS(100) and PS(160), respectively) were formed from seven volunteers. Each experiment involved recording a 20 min baseline and two effect data recorded at 0-20 and 50-70 min after stopping PS. The relative energy contribution (REC) in five frequency bands revealed by Morlet-wavelet transformation was calculated. At the pressed site, the dc component of the flux signal in the second effect increased significantly only in group PS(60) compared with the control values. The REC was significantly increased in a myogenic-related band in groups PS(60), PS(100) and PS(160), and was significantly decreased in a nerve-related band only in group PS(160). Different PS magnitudes compress vessels to different extents. The proposed vessel-pressing model-which is supported by the results of spectral analysis of flux signals-might help to elucidate the underlying mechanism. The study results indicate that an improved perfusion was sustained for the longest time when applying 60 mmHg PS. This might aid the development of techniques for improving skin microcirculatory perfusion.

We aimed to characterize the frequency spectra of skin blood flow signals recorded at Hoku, an important acupuncture point (acupoint) in oriental medicine. Electrocardiogram (ECG) and laser Doppler flowmetry signals were measured simultaneously in 31 trials on seven volunteers aged 21-27 years. A four-level Haar wavelet transform was applied to the measured 20 min laser Doppler flowmetry (LDF) signals, and periodic oscillations with five characteristic frequency peaks were obtained within the following frequency bands: 0.0095-0.021 Hz, 0.021-0.052 Hz, 0.052-0.145 Hz, 0.145-0.6 Hz, and 0.6-1.6 Hz (defined as FR1-FR5), respectively. The relative energy contribution in FR3 was significantly larger at Hoku than at the two non-acupoints. Linear regression analysis revealed that the relative energy contribution in FR3 at Hoku significantly increased with the pulse pressure (R(2) = 0.48; P < 0.01 by F-test). Spectral analysis of the flux signal revealed that one of the major microcirculatory differences between acupoints and non-acupoints was in the different myogenic responses of their vascular beds. This information may aid the development of a method for the non-invasive study of the microcirculatory characteristics of the acupoint.

Meridian system composed of acupoints is the most fundamental concept to build oriental medicine. In this study, we employ LDF measurement to compare the microcirculatory blood velocity of acupuncture point and its surrounding tissues. Measurements were performed around an important acupoint in oriental medicine, Hoh-Ku (Li4, on the hand), in healthy volunteers. The study presented has shown that the acupoints have significantly slower mean blood velocity than their surrounding tissues (p all < 0.005). This finding facilitates the detection of the position of acupuncture point and helps us to provide a possible connection between microcirculatory physiology and the underlying mechanism of acupoints.