Real-time Measurement Technique Research Articles

Dynamics of distorted and undistorted soliton molecules in a mode-locked fiber laser

Recent developments in real-time ultrafast measurement techniques have enabled us to prove experimentally that soliton molecules execute internal motions with some aspects similar to those of a matter molecule. Such an analogy between the dynamics of soliton molecules and the dynamics of matter molecules is based on the assumption that the dissipative solitons constituting a molecule are rigid entities sharing a common profile. Whereas this assumption drastically reduces the number of degrees of freedom, it does not hold true in general and we demonstrate that it overlooks some of the essential dynamical features of the soliton molecule. We present a theoretical study based on the principle that the different pulse constituents of a soliton molecule are deformable entities. Specifically, by using of a collective coordinate approach to investigate bi- and trisoliton molecules, we reveal features such as symmetric or asymmetric distortions of their profiles, and energy exchange processes between them. This implies, in subsequent experiments, the use of characterization techniques that can be used to retrieve a larger number of degrees of freedom.

Real-time detection of surface deformation and strain in recycled aggregate concrete-filled steel tubular columns via four-ocular vision

• A mark-free vision-based dynamic real-time measurement technique is proposed for full field strain and 3D deformation detection. • Point cloud combination and 3D reconstruction are applied. • The non-contact method results truly reflect the deformation process and full-field strain values. • The standard deviation mean value measured by the proposed method relative to the true value is 1.23%. • The proposed method can be used as a reasonable alternative to traditional contact methods. This study presents a dynamic real-time detection method for surface deformation and full field strain in recycled aggregate concrete-filled steel tubular columns (RACSTCs). Automatic calibration and dynamic surface tracking measurement are utilized and mathematical models combining the four-ocular visual coordinates and point cloud matching are proposed. The 3D deformation of the RACSTCs under low cyclic loading are gathered every 60 s as sample images. The four-ocular vision system constitutes two groups of binocular stereoscopic vision systems. The 3D deformation surface is reconstructed by multi-ocular vision coordinate association, image preprocessing, and point cloud registration. The measurement results are validated by comparison against laser range finder data. The standard deviation mean value of 10 specimens measured by the proposed method relative to the true value is 1.23%; the mean error of the maximum absolute value is 2.82%.

Plasma emission correction in reflectivity spectroscopy during sputtering deposition

Surface differential reflectivity spectroscopy is a fast non-destructive in situ and real-time measurement technique which allows following the first stages of thin film deposition. However, when applied to sputtering technique, spectra can strongly be distorted by residual light coming from plasma in a way, as shown herein, that depends on sample reflectivity. Thanks to suitable measurements, before and after growth with and without plasma or illumination lights, a protocol of signal correction is proposed to get rid of the spurious plasma contribution. The interest of the method is illustrated in the case of silver deposition on a silicon substrate.

Real-time simultaneous shim and motion measurement and correction in glycoCEST MRI using double volumetric navigators (DvNavs).

CEST MRI allows for indirect detection of molecules with exchangeable protons, measured as a reduction in water signal because of continuous transfer of saturated protons. CEST requires saturation pulses on the order of a second, as well as repeated acquisitions at different offset frequencies. The resulting extended scan time makes CEST susceptible to subject motion, which introduces field inhomogeneity, shifting offset frequencies and causing distortions in CEST spectra that resemble true CEST effects. This is a particular problem for molecules that resonate close to water, such as hydroxyl group in glycogen. To address this, a technique for real-time measurement and correction of motion and field inhomogeneity is proposed. A CEST sequence was modified to include double volumetric navigators (DvNavs) for real-time simultaneous motion and shim correction. Phantom tests were conducted to investigate the effects of motion and shim changes on CEST quantification and to validate the accuracy of DvNav motion and shim estimates. To evaluate DvNav shim and motion correction in vivo, acquisitions including 5 experimental conditions were performed in the calf muscle of 2 volunteers. Phantom data show that DvNav-CEST accurately estimates frequency and linear gradient changes because of motion and corrects resulting image distortions. In addition, DvNav-CEST improves CEST quantification in vivo in the presence of motion. The proposed technique allows for real-time simultaneous motion and shim correction with no additional scanning time, enabling accurate CEST quantification even in the presence of motion and field inhomogeneity.

Supercontinuum spectral-domain ghost imaging.

Ghost imaging is a technique that generates high-resolution images by correlating the intensity of two light beams, neither of which independently contains useful information about the shape of the object. Ghost imaging has been demonstrated in both the spatial and temporal domains, using incoherent classical light sources or entangled photon pairs. Here we exploit the recent progress in ultrafast real-time measurement techniques to demonstrate ultrafast, scan-free, ghost imaging in the frequency domain using a continuous spectrum from an incoherent supercontinuum light source with random spectral fluctuations. We demonstrate the application of this technique to broadband spectroscopic measurements of methane absorption performed with sub-nanometer resolution. Our results offer novel perspectives for remote sensing in low light conditions, or in spectral regions where sensitive detectors are lacking.

Comprehensive sandstone fracturing characterization: Integration of fiber Bragg grating, digital imaging correlation and acoustic emission measurements

Prominent characteristics of rock fracturing can be described mainly by crack opening displacement (COD), fracture process zone (FPZ) and fracture energy. In view of lack of real-time and comprehensive measurement techniques for characterizing rock fracturing in field applications, this paper developed a characterizing method of rock fracturing by utilizing and integrating Fiber Bragg Grating (FBG), Digital Imaging Correlation (DIC) and Acoustic Emission (AE). In this paper, mode I fracturing test was performed on sandstone using three-point bending, and the fracturing process was simultaneously detected and recorded by FBG, DIC and AE. The experimental results showed that (1) DIC-based measurement of horizontal displacements across the fracture presented a localized discontinuity, in accordance with FBG-based real-time measurement. At the onset of traction-free zone formation (peak load), the critical COD (δc) was found to be 76 μm as identified by DIC and FBG. (2) Moreover, the dissipated energy distribution and cohesive crack profile in FPZ characterized by the integrated measurement, indicated that 70%–90% of AE energy (dissipated energy) populated in the FPZ, little AE energy concentrated in the traction-free zone, and the position of δc delineated a boundary for specifying FPZ. The length of fully developed FPZ was 20 mm (±2 mm) in length. (3) The integrated measurement delineated the cohesive crack, which was not available previously. The integrated measurement revealed the softening curve followed a straight line; the relationship between FPZ length and crack tip opening displacement (CTOD) was linear, and the relationship between dissipated energy and FPZ length was quadratic. Based on the interrelations of cohesive crack characteristics identified by the integrated measurements, real-time fracturing can be captured by one technique (e.g. FBG) in field application.

Ocular Blood Flow in Rabbits under Deep Anesthesia: A Real-Time Measurement Technique and Its Application in Characterizing Retinal Ischemia

In this study, we reported a new technique based on laser speckle flowgraphy to record the ocular blood flow in rabbits under deep anesthesia, and proposed parameters to characterize retinal ischemia. We applied the proposed technique to study the correlation of blood flow between the eyes of normal non-anesthetized animals, and to characterize the occlusion of the internal carotid artery (ICA) and external carotid artery (ECA). We established a correlation in blood flow between the eyes of non-anesthetized animals, and derived two new parameters, namely, the laterality index and vascular perfusion estimate (VPE). Our experimental results from 16 eyes (of 13 New Zealand white rabbits) showed a reduction in ocular blood flow with a significant decrease in the VPE after the occlusion of the ECA (p < 0.001). A low/minimal effect on blood flow was observed with the occlusion of the ICA. In conclusion, we demonstrated a means for the real-time measurement of the ocular blood flow in rabbits under deep anesthesia by using laser speckle flowgraphy and the VPE as an indicator of successful occlusion. The proposed technique might be applicable in quantifying the efficacy of new drugs and interventions for the treatment of retinal ischemia.

Electrical Impedance Measurements of Biological Cells in Response to External Stimuli.

Dielectric spectroscopy (DS) is a noninvasive technique for real-time measurements of the impedance spectra of biological cells. DS enables characterization of cellular dielectric properties such as membrane capacitance and cytoplasmic conductivity. We have developed a lab-on-a-chip device that uses an electro-activated microwells array for capturing, DS measurements, and unloading of biological cells. Impedance measurements were conducted at 0.2 V in the 10 kHz to 40 MHz range with 6 s time resolution. An equivalent circuit model was developed to extract the cell membrane capacitance and cell cytoplasmic conductivity from the impedance spectra. A human prostate cancer cell line, PC-3, was used to evaluate the device performance. Suspension of PC-3 cells in low conductivity buffers (LCB) enhanced their dielectrophoretic trapping and impedance response. We report the time course of the variations in dielectric properties of PC-3 cells suspended in LCB and their response to sudden pH change from a pH of 7.3 to a pH of 5.8. Importantly, we demonstrated that our device enabled real-time measurements of dielectric properties of live cancer cells and allowed the assessment of the cellular response to variations in buffer conductivity and pH. These data support further development of this device toward single cell measurements.

Use of cerebral oxygen saturation and hemoglobin concentration to predict acute kidney injury after cardiac surgery.

ObjectiveAcute kidney injury (AKI) is a common complication after cardiac surgery and is associated with significant morbidity and mortality. Near infrared spectroscopy (NIRS) is a noninvasive technique for real-time measurement of cerebral tissue oxygenation. The purpose of the present study was to evaluate the correlation of AKI with hemoglobin and regional cerebral oxygen saturation (rScO2) measured intraoperatively and postoperatively in patients undergoing cardiac surgery.MethodsWe retrospectively analyzed the prospectively collected data of 45 adult patients with normal renal function who underwent isolated coronary artery bypass grafting (CABG) from January 2014 to May 2014. Kidney injury was assessed according to the Acute Kidney Injury Network criteria. rScO2 and hemoglobin were measured every hour intraoperatively and for the first 24 hours postoperatively.ResultsThe hemoglobin concentration and rScO2 were significantly lower in patients with than without AKI, and no linear trends were observed. No exact cut-off values were obtained.ConclusionThis retrospective study shows that a lower rScO2 and hemoglobin concentration are correlated with AKI after CABG in patients with no peripheral vascular disease or recent myocardial infarction. We suggest that cerebral oximetry alone may predict postoperative AKI well.

On-line quantification and human health risk assessment of organic by-products from the removal of toluene in air using non-thermal plasma

Harmful organic by-products, produced during the removal of volatile organic compounds (VOCs) from the air by treatment with non-thermal plasma (NTP), hinder the practical applications of NTP. An on-line quantification and risk assessment method for the organic by-products produced by the NTP removal of toluene from the air has been developed. Formaldehyde, methanol, ketene, acetaldehyde, formic acid, acetone, acetic acid, benzene, benzaldehyde, and benzoic acid were determined to be the main organic by-products by proton transfer reaction mass spectrometry (PTR-MS), a powerful technique for real-time and on-line measurements of trace levels of VOCs, and a health-related index (HRI) was introduced to assess the health risk of these organic by-products. The discharge power (P) is a key factor affecting the formation of the organic by-products and their HRI values. Higher P leads to a higher removal efficiency (η) and lower HRI. However, higher P also means higher cost and greater production of discharge by-products, such as NOx and O3, which are also very dangerous to the environment and human health. In practical applications P, HRI, and η must be balanced, and sometimes the risks posed by the organic by-products are even greater than those of the removed compounds. Our mechanistic study reveals that acetone is a crucial intermediate for the removal of toluene by NTP, and we found that toluene molecules first fragment into acetone molecules, followed by other by-products. These observations will guide the study of the mechanism of aromatic molecule dissociation in plasma.

In-situ investigation on real-time suspended sediment measurement techniques: Turbidimetry, acoustic attenuation, laser diffraction (LISST) and vibrating tube densimetry

Real-time measurements of Suspended Sediment mass Concentration (SSC) and Particle Size Distribution (PSD) are of prime importance for the investigation and management of fine-sediment related processes in surface water systems and hydraulic schemes. In a field study at the waterway of the hydropower plant (HPP) Fieschertal in the Swiss Alps, the real-time measurement performance of the following techniques and instruments were assessed based on measurements in the sediment seasons of the years 2013 and 2014: (1) turbidimetry, (2) single-frequency acoustic attenuation using a standard acoustic discharge measurement (ADM) installation, (3) laser diffraction (Laser In-Situ Scattering and Transmissometry, LISST), and (4) vibrating tube densimetry using a Coriolis Flow and Density Meter (CFDM). Reference SSCs were obtained from gravimetric analysis of 219 automatically pumped water samples. LISST additionally supplied PSD every minute. The median particle diameter, d50, was usually 15µm and increased occasionally to 100µm. The turbidimeter and the ADM underestimated the SSC when the transported particles were coarser than usual. Such temporary biases resulted from the poor correlation between d50 and SSC at this study site. The SSCs from CFDM and LISST were not or less biased by PSD variations. Mainly due to angular and flaky particle shapes, SSC from LISST needed a correction by 79% on average. With the usually prevailing silt particles, an optical path length of 5mm and no dilution, the SSC measurement range of LISST was limited to about 1.5g/l. The CFDM allowed measuring higher SSC than the other investigated instruments (e.g. up to 13.5g/l). With a periodic offset correction, its relative SSC measurement uncertainty was < 20% for SSC ≥ 1.5g/l. To reliably measure a wide range of SSC with temporarily variable PSD, a combination of instruments is recommended: e.g. a standard LISST, a CFDM, and an automatic water sampler for gravimetric reference measurements.

Intraoperative Vascular Neuromonitoring in Patients with Subarachnoid Hemorrhage: APilot Study Using Combined Laser-Doppler Spectrophotometry.

Intraoperative monitoring of cerebral microcirculation in patients with subarachnoid hemorrhage (SAH) may predict the postoperative neurologic outcome. In this pilot study, we examined the value of a novel noninvasive real-time measurement technique for detecting changes in local microcirculation. We used the O2C (Oxygen to see) laser-Doppler spectrophotometry system in 14 patients with Hunt & Hess grade 2-5 SAH who underwent microsurgical cerebral aneurysm clipping. A subdural probe recorded capillary venous oxygenation (SO2), relative hemoglobin concentration, blood cell velocity, and blood flow at a tissue depth of 7 mm. Data were recorded immediately before dural closure. We also recorded somatosensory evoked potentials (SEPs) with median and tibial nerve stimulation. Results were compared with neurologic performance, as measured on the modified Rankin Scale, at the day of discharge from the hospital and 12 months thereafter. Patient functional outcomes after discharge and 12 months were correlated with pathological decreased flow and increased SO2 values. In 6 of 8 patients, microcirculatory monitoring parameters indicated ischemia during surgery, as shown by electrophysiological SEP changes and infarction detected on the postoperative computed tomography (CT) scan. Pathological SEP results correlated closely with infarct demarcation as seen on CT. Our results indicate the potential benefit of intraoperative combined laser-Doppler flowmetry and spectrophotometry for predicting postoperative clinical outcomes in this small patient sample. Larger-cohort testing is needed to verify our findings and show the possible merits of this novel method.

Time-stretched real-time measurement technique for ultrafast absorption variations with TS/s sampling-rate.

We present a real-time measurement technique, based on time-stretching for measuring the temporal dynamic of ultrafast absorption variations with a sampling-rate of up to 1.1 TS/s. The single-shot captured data are stretched in a resonator-based time-stretch system with a variable stretch-factor of up to 13.8. The time-window of the time-stretch system for capturing the signal of interest is about 800 ps with an update-rate of 10 MHz. An adapted optical backpropagation algorithm is introduced for reconstructing the original unstretched event. As proof-of-principle the temporal characteristic of a picosecond semiconductor saturable absorber mirror is measured: The real-time results agree well with the results of a conventional pump-probe experiment. The time-stretch technique potentially allows to gain access to a large field of ultrafast absorption variations like semiconductor charge carrier dynamics, irreversible polymerization processes, and saturable absorber materials.

Spectral correlations in a random distributed feedback fibre laser

Random distributed feedback fibre lasers belong to the class of random lasers, where the feedback is provided by amplified Rayleigh scattering on sub-micron refractive index inhomogenities randomly distributed over the fibre length. Despite the elastic nature of Rayleigh scattering, the feedback mechanism has been insofar deemed incoherent, which corresponds to the commonly observed smooth generation spectra. Here, using a real-time spectral measurement technique based on a scanning Fabry-Pérot interferometer, we observe long-living narrowband components in the random fibre laser’s spectrum. Statistical analysis of the ∼104 single-scan spectra reveals a preferential interspacing for the components and their anticorrelation in intensities. Furthermore, using mutual information analysis, we confirm the existence of nonlinear correlations between different parts of the random fibre laser spectra. The existence of such narrowband spectral components, together with their observed correlations, establishes a long-missing parallel between the fields of random fibre lasers and conventional random lasers.

High-precision real-time 3D shape measurement using a bi-frequency scheme and multi-view system.

High-speed and high-precision 3D shape measurement plays a central role in diverse applications such as automatic online inspection, robotics control, and human-computer interaction. Conventional multi-frame phase-shifting-based fringe projection profilometry techniques face inherent trade-offs between the speed and measurement precision, which are fundamentally limited by the fringe density and extra pattern projections used for de-ambiguity of fringe orders. Increasing the frequency of the projection fringes can obviously improve the measurement precision; however, it creates difficulties in the subsequent phase unwrapping. For this reason, to date, the frequency of the fringes in typical real-time 3D shape measurement techniques is generally less than 30 to guarantee a reasonable reliability of phase unwrapping. To overcome this limitation, a bi-frequency phase-shifting technique based on a multi-view fringe projection system is proposed, which significantly enhances the measurement precision without compromising the measurement speed. Based on the geometric constraints in a multi-view system, the unwrapped phase of the low-frequency (10-period) fringes can be obtained directly, which serves as a reference to unwrap the high-frequency phase map with a total number of periods of up to 160. Besides, the proposed scheme with 10-period and 160-period fringes is suitable for slightly defocusing projection, allowing a higher projection rate and measurement speed. Experiments on both static and dynamic scenes are performed, verifying that our method can achieve high-speed and high-precision 3D measurement at 300 frames per second with a precision of about 50μm.

Finite Element Analysis of Single Cell Stiffness Measurements Using PZT-Integrated Buckling Nanoneedles.

This paper proposes a new technique for real-time single cell stiffness measurement using lead zirconate titanate (PZT)-integrated buckling nanoneedles. The PZT and the buckling part of the nanoneedle have been modelled and validated using the ABAQUS software. The two parts are integrated together to function as a single unit. After calibration, the stiffness, Young’s modulus, Poisson’s ratio and sensitivity of the PZT-integrated buckling nanoneedle have been determined to be 0.7100 N·m−1, 123.4700 GPa, 0.3000 and 0.0693 V·m·N−1, respectively. Three Saccharomyces cerevisiae cells have been modelled and validated based on compression tests. The average global stiffness and Young’s modulus of the cells are determined to be 10.8867 ± 0.0094 N·m−1 and 110.7033 ± 0.0081 MPa, respectively. The nanoneedle and the cell have been assembled to measure the local stiffness of the single Saccharomyces cerevisiae cells The local stiffness, Young’s modulus and PZT output voltage of the three different size Saccharomyces cerevisiae have been determined at different environmental conditions. We investigated that, at low temperature the stiffness value is low to adapt to the change in the environmental condition. As a result, Saccharomyces cerevisiae becomes vulnerable to viral and bacterial attacks. Therefore, the proposed technique will serve as a quick and accurate process to diagnose diseases at early stage in a cell for effective treatment.

Image segmentation techniques for real-time coverage measurement in shot peening processes

Shot peening is the process of treating metallic surfaces with a regulated blast of shots to increase material strength and durability. Determining the coverage level of the shots is an important parameter in assessment of the quality of treatment. Traditionally, manual coverage measurement is performed visually which is prone to human error and judgement. Despite the proposal for the use of image segmentation techniques for determining the coverage levels, literature on the topic is not extensively developed. Various relevant image segmentation techniques are investigated in this study. In particular, thresholding, edge detection, watershed segmentation, active contour, and graph cut techniques are investigated and applied to shot peen coverage measurement. The results obtained from each method are discussed and compared against a set of relevant performance criteria.

Novel One-Tube-One-Step Real-Time Methodology for Rapid Transcriptomic Biomarker Detection: Signal Amplification by Ternary Initiation Complexes.

We have developed a novel RNA detection method, termed signal amplification by ternary initiation complexes (SATIC), in which an analyte sample is simply mixed with the relevant reagents and allowed to stand for a short time under isothermal conditions (37 °C). The advantage of the technique is that there is no requirement for (i) heat annealing, (ii) thermal cycling during the reaction, (iii) a reverse transcription step, or (iv) enzymatic or mechanical fragmentation of the target RNA. SATIC involves the formation of a ternary initiation complex between the target RNA, a circular DNA template, and a DNA primer, followed by rolling circle amplification (RCA) to generate multiple copies of G-quadruplex (G4) on a long DNA strand like beads on a string. The G4s can be specifically fluorescence-stained with N(3)-hydroxyethyl thioflavin T (ThT-HE), which emits weakly with single- and double-stranded RNA/DNA but strongly with parallel G4s. An improved dual SATIC system, which involves the formation of two different ternary initiation complexes in the RCA process, exhibited a wide quantitative detection range of 1-5000 pM. Furthermore, this enabled visual observation-based RNA detection, which is more rapid and convenient than conventional isothermal methods, such as reverse transcription-loop-mediated isothermal amplification, signal mediated amplification of RNA technology, and RNA-primed rolling circle amplification. Thus, SATIC methodology may serve as an on-site and real-time measurement technique for transcriptomic biomarkers for various diseases.

Organic solvent-induced changes in membrane geometry in human SH-SY5Y neuroblastoma cells – a common narcotic effect?

Exposure to organic solvents may cause narcotic effects. At the cellular level, these narcotic effects have been associated with a reduction in neuronal excitability caused by changes in membrane structure and function. In order to critically test whether changes in membrane geometry contribute to these narcotic effects, cultured human SH-SY5Y neuroblastoma cells have been exposed to selected organic solvents. The solvent-induced changes in cell membrane capacitance were investigated using the whole-cell patch clamp technique for real-time capacitance measurements. Exposure of SH-SY5Y cells to the cyclic hydrocarbons m-xylene, toluene, and cyclohexane caused a rapid and reversible increase of membrane capacitance. The aliphatic, nonpolar n-hexane did not cause a detectable change of whole-cell membrane capacitance, whereas the amphiphiles n-hexanol and n-hexylamine caused an increase of membrane capacitance and a concomitant reduction in membrane resistance. Despite a large difference in dielectric properties, the chlorinated hydrocarbons 1,1,2,2-tetrachoroethane and tetrachloroethylene caused a similar magnitude increase in membrane capacitance. The theory on membrane capacitance has been applied to deduce changes in membrane geometry caused by solvent partitioning. Although classical observations have shown that solvents increase the membrane capacitance per unit area of membrane, i.e., increase membrane thickness, the present results demonstrate that solvent partitioning predominantly leads to an increase in membrane surface area and to a lesser degree to an increase in membrane thickness. Moreover, the present results indicate that the physicochemical properties of each solvent are important determinants for its specific effects on membrane geometry. This implies that the hypothesis that solvent partitioning is associated with a common perturbation of membrane structure needs to be revisited and cannot account for the commonly observed narcotic effects of different organic solvents.

Insights from two industrial hygiene pilot e-cigarette passive vaping studies

ABSTRACTWhile several reports have been published using research methods of estimating exposure risk to e-cigarette vapors in nonusers, only two have directly measured indoor air concentrations from vaping using validated industrial hygiene sampling methodology. Our first study was designed to measure indoor air concentrations of nicotine, menthol, propylene glycol, glycerol, and total particulates during the use of multiple e-cigarettes in a well-characterized room over a period of time. Our second study was a repeat of the first study, and it also evaluated levels of formaldehyde. Measurements were collected using active sampling, near real-time and direct measurement techniques. Air sampling incorporated industrial hygiene sampling methodology using analytical methods established by the National Institute of Occupational Safety and Health and the Occupational Safety and Health Administration. Active samples were collected over a 12-hr period, for 4 days. Background measurements were taken in the same room the day before and the day after vaping. Panelists (n = 185 Study 1; n = 145 Study 2) used menthol and non-menthol MarkTen prototype e-cigarettes. Vaping sessions (six, 1-hr) included 3 prototypes, with total number of puffs ranging from 36–216 per session. Results of the active samples were below the limit of quantitation of the analytical methods. Near real-time data were below the lowest concentration on the established calibration curves. Data from this study indicate that the majority of chemical constituents sampled were below quantifiable levels. Formaldehyde was detected at consistent levels during all sampling periods. These two studies found that indoor vaping of MarkTen prototype e-cigarette does not produce chemical constituents at quantifiable levels or background levels using standard industrial hygiene collection techniques and analytical methods.