Simple Measurement Technique Research Articles

Identification of graphite with perfect rhombohedral stacking by electronic Raman scattering

Rhombohedral graphite (RG) shows strong correlations in its topological flat band and is pivotal for exploring emergent, correlated electronic phenomena. One key advantage is the enhancement of electronic interactions with the increase in the number of rhombohedrally stacked graphene layers. Increasing thickness also leads to an exponential increase in the number of stacking configurations, necessitating a precise method to identify flawless rhombohedral stackings. Overcoming this challenge is difficult because the established technique for stacking sequence identification, based on phonon originated Raman processes (e.g. the 2D peak), fails in thick RG samples. We demonstrate that the strong layer dependence of the band structure can be harnessed to identify RG without stacking faults. For thicknesses ranging from 3 to 12 layers, we show that each perfect RG structure presents distinctive peak positions in electronic Raman scattering (ERS), directly fingerprinting the flawless stacking. This measurement can be carried out using a conventional confocal Raman spectrometer at room temperature, using visible excitation wavelengths. Consequently, this overcomes the identification challenge by providing a simple and fast optical measurement technique, thereby helping to establish RG as a platform for studying strong correlations in one of the simplest crystals possible.

Threshold Voltage Recovery Time Measurement Technique Post VTH Instability in Normally-Off p-Gate GaN High Electron Mobility Transistors

In this study, we propose a simple measurement technique to quantitatively measure the time taken by threshold voltage of normally-off p-GaN AlGaN/GaN HEMTs to recover from a nominal operational gate stress-induced instability. The proposed technique eliminates the requirement to perform a full transfer characteristic sweep post-stress, thereby eliminating the measurement-induced instability effect, often colluding precise recovery time measurement. The rate of recovery and extracted recovery times hold significance in empirically correlating the location of traps in the p-GaN or AlGaN barrier region causing VTH instability. The gate of the HEMT is stressed at nominal operational drive voltages 1.5 V, 2 V, and 4 V for various time intervals from 500 μs to 100 s, and the time taken for the drain current to recover to prestress levels measured at near-threshold voltage (~1.1 VTH) is measured as the threshold voltage recovery time. With increasing gate stress voltages, 2DEG gets trapped at relatively deeper trap energy levels at the AlGaN/GaN interface requiring more emission time during the process of recovery, mandating larger recovery times. At higher stress voltage of 4 V, the Schottky gate leakage current is high enough enabling injected holes to cross the AlGaN barrier and counter-compensate for the deeply trapped 2DEG, requiring relatively the same recovery times as lower stress voltages where the gate leakage is negligibly small. With increasing stress time, the amount of 2DEG trapped increases, requiring more recovery time to de-trap and beyond a certain time, saturation of the trap density occurs causing the recovery time to plateau.

Evaluation and analysis of the electro-optic effect and the Stark effect in electro-optic polymers by the simple transmission measurement technique without an aperture

A simple and reliable transmission measurement technique without an aperture was utilized to evaluate both the electro-optic (EO) effect and the Stark effect of EO polymers. For some EO polymers, both the EO effect and the Stark effect were evaluated using laser light sources with various wavelengths of 1550 nm, 1308 nm, 980 nm, and 640 nm and the analysis method was also described. We showed that both the magnitude and the phase of the modulated light signal in lock-in detection at both the π/2 and 3π/2 points are very important for appropriate analysis.

On the рossibility of multichannel optical backscattering sondes for joint balloon and lidar studies of the aerosol composition of the middle atmosphere

Aerosol backscattering sondes in the practice of aerological sounding, along with lidar observations, are used at night to study and monitor polar stratospheric clouds, tropospheric and stratospheric aerosol, cirrus clouds, pyroconvection, volcanic aerosol, as well as to verify remote methods and means of ground-based and satellite-based aerosol observations. For aerosol sondes, a simple two-wave measurement technique is used, which makes it possible to diagnose changes in aerosol composition by color index. The possibilities of the two-wave technique have limitations, which are discussed in this article. Aerological sounding combined with lidar observations expands the wavelength range for multi-wavelength studies, and direct measurements of atmospheric temperature increase the accuracy of aerosol sensing. The paper considers the application of 3 or more wavelenght techniques. Data from probe measurements using wavelengths of 470, 528, 850 and 940 nm and lidar sensing at wavelengths of 355 and 532 nm are presented.

Assessing Visceral Fat Percentage with Advancing Age in Women using Bioelectric Impedance Analysis

Obesity and related morbidities are rising globally. This study aims to evaluate the relationship between visceral fat percentage (VF%) and advancing age in 126 female participants aged 20-70 years. These participants underwent anthropometric measurements and Bioelectric Impedance Analysis (BIA). The correlation between VF% and advancing age was 0.42 (P<0.001). BIA is a simple and effective measurement technique for estimating VF%, which can be performed by trained health professionals. This study demonstrated a strong correlation between VF% and advancing age in females.

A Low-Power Impedance-to-Frequency Converter for Frequency-Multiplexed Wearable Sensors.

We propose a low-power impedance-to-frequency (I-to-F) converter for wearable transducers that change both its resistance and capacitance in response to mechanical deformation or changes in ambient pressure. At the core of the proposed I-to-F converter is a fixed-point circuit comprising of a voltage-controlled relaxation oscillator and a proportional-to-temperature (PTAT) current reference that locks the oscillation frequency according to the impedance of the transducer. Using both analytical and measurement results we show that the operation of the proposed I-to-F converter is well matched to a specific class of sponge mechanical transducer where the system can achieve higher sensitivity when compared to a simple resistance measurement techniques. Furthermore, the oscillation frequency of the converter can be programmed to ensure that multiple transducer and I-to-F converters can communicate simultaneously over a shared channel (physical wire or virtual wireless channel) using frequency-division multiplexing. Measured results from proof-of-concept prototypes show an impedance sensitivity of 19.66 Hz/ Ω at 1.1 kΩ load impedance magnitude and a current consumption of [Formula: see text]. As a demonstration we show the application of the I-to-F converter for human gesture recognition and for radial pulse sensing.

Contactless vital signs monitoring in macaques using a mm-wave FMCW radar

Heart rate (HR) and respiration rate (RR) play an important role in the study of complex behaviors and their physiological correlations in non-human primates (NHPs). However, collecting HR and RR information is often challenging, involving either invasive implants or tedious behavioral training, and there are currently few established simple and non-invasive techniques for HR and RR measurement in NHPs owing to their stress response or indocility. In this study, we employed a frequency-modulated continuous wave (FMCW) radar to design a novel contactless HR and RR monitoring system. The designed system can estimate HR and RR in real time by placing the FMCW radar on the cage and facing the chest of both awake and anesthetized macaques, the NHP investigated in this study. Experimental results show that the proposed method outperforms existing methods, with averaged absolute errors between the reference monitor and radar estimates of 0.77 beats per minute (bpm) and 1.29 respirations per minute (rpm) for HR and RR, respectively. In summary, we believe that the proposed non-invasive and contactless estimation method could be generalized as a HR and RR monitoring tool for NHPs. Furthermore, after modifying the radar signal-processing algorithms, it also shows promise for applications in other experimental animals for animal welfare, behavioral, neurological, and ethological research.

Absolute measurement of vacuum ultraviolet fluxes from inductively coupled plasmas via metal surface photoemission currents

Quantifying vacuum-ultraviolet (VUV) fluxes typically requires vacuum-compatible spectrometers and is often associated with significant cost and effort. A simple technique for the absolute measurement of local VUV fluxes from plasmas using the photoemission from a set of coated metal plates, is described. The radiant power from a 13.56 MHz hydrogen plasma operating at 40–87 mTorr and with an radio frequency (RF) input power from 100 to 120 W was investigated by irradiating a set of 2 cm diameter Au, Ag and Cu plates. The variation in photoemission currents was compared with the photoelectric yield curves to estimate the absolute flux incident on the surfaces in the 113–190 nm range. The measured fluxes were found to have an uncertainty of 5%–30% when compared with the VUV spectrometer measurements. The VUV output power was found to have a maximum at a pressure of 70–80 mTorr and to increase with RF power. In all cases, the VUV output power was measured to be approximately 12%–16% of the RF input power to the matching network, in good agreement with spectroscopy results.

A rapid method for the determination of stable hydrogen isotope ratios of acetic acid in vinegar.

Vinegar is an everyday condiment made from fermented grains or fruits. It contains acetic acid which is the main organic material produced by fermentation. Vinegar suffers from the authenticity problem of exogenous adulteration due to the indistinguishability of low-cost chemical sources of synthetic acetic acid from acetic acid produced by fermentation. It is necessary to establish a simple and rapid measurement technique. Determination was according to the total acid content of vinegar diluted with acetone to a certain concentration. Online separation and determination of acetic acid δD in vinegar were carried out using gas chromatography-pyrolysis-isotope ratio mass spectrometry. An HP-Plot/U column was selected for online separation of acetic acid and water with molecular sieve characteristics. At the same time, combined with the instrument blowback function to remove water. Dilute solvent acetone was treated with a molecular sieve to remove trace water. The reproducibility of this method is less than 3‰. The long-term stability is within a reasonable error range. The accuracy correlation coefficient is greater than 0.99. The δD values of acetic acid in vinegar (-264.5 ± 20.3‰) and from chemical sources (-30.5 ± 90.8‰) were obtained. A rapid method was developed for identification of different sources of acetic acid. These different sources of acetic acid exhibited significant hydrogen isotope distribution characteristics. Additionally, it was observed that the carboxyl hydrogen of acetic acid exhibited facile exchange with water. In future investigations, we aim to mitigate this interference.

Experimental Study of Aerodynamic Noise Source Measurement around an Automobile Door Mirror by Hot-film Sensor

In order to the evaluation and identification of the aerodynamic sound source generated from a door mirror of an automobile, the simple measurement technique using the film-type hot film sensor is proposed. In the wind tunnel test of the actual vehicle model, the feasibility on the qualitative evaluation of the aerodynamic sound sources with the hot film sensor is discussed experimentally. From the results of this experiment, author could explain that the low-frequency broadband noise is one of the features of its aerodynamic noise. The qualitative evaluation of the hot-film sensor indicated that the low-frequency aerodynamic noise is caused by fluctuations formed at the tips of the door mirrors. Although the location of the low-frequency broadband noise source was identified by evaluating the signal of the hot film sensor, the quantitatively evaluation of the strength of the aerodynamic sound source could not achieve.

Embedded System for the Analysis of Thermal Properties of Hemoglobin

A novel embedded photoacoustic system design is described and a calculation method is proposed to determine the blood hemoglobin oxygen saturation through the thermal properties of different skin color types. A heat equation model allows a calculation procedure to determine the reflection and transmitted thermal wave amplitude for obtaining a depth profile, depending on the modulation frequency at the air-skin-subcutaneous tissue interface. Our reflection-mode photoacoustic technique involves the use of a 445 nm pulsed-laser light spot on subcutaneous tissue to obtain amplitude and phase from signals for different skin color types. The transmission and reflection temperature coefficients are fitted through a heat propagation model to estimate the thermal wave properties of blood hemoglobin. Nonlinearly amplified photoacoustic signals are modeled from the microphone and their stability analyzed by a bode diagram, as to consider overheated hemoglobin background. An dedicated electronic embedded system is thus integrated, including memory, processor and preprocessor, to provide a simple measurement technique, as compared to conventional instruments.

Stimulus classification with electrical potential and impedance of living plants: comparing discriminant analysis and deep-learning methods

The physiology of living organisms, such as living plants, is complex and particularly difficult to understand on a macroscopic, organism-holistic level. Among the many options for studying plant physiology, electrical potential and tissue impedance are arguably simple measurement techniques that can be used to gather plant-level information. Despite the many possible uses, our research is exclusively driven by the idea of phytosensing, that is, interpreting living plants’ signals to gather information about surrounding environmental conditions. As ready-to-use plant-level physiological models are not available, we consider the plant as a blackbox and apply statistics and machine learning to automatically interpret measured signals. In simple plant experiments, we expose Zamioculcas zamiifolia and Solanum lycopersicum (tomato) to four different stimuli: wind, heat, red light and blue light. We measure electrical potential and tissue impedance signals. Given these signals, we evaluate a large variety of methods from statistical discriminant analysis and from deep learning, for the classification problem of determining the stimulus to which the plant was exposed. We identify a set of methods that successfully classify stimuli with good accuracy, without a clear winner. The statistical approach is competitive, partially depending on data availability for the machine learning approach. Our extensive results show the feasibility of the blackbox approach and can be used in future research to select appropriate classifier techniques for a given use case. In our own future research, we will exploit these methods to derive a phytosensing approach to monitoring air pollution in urban areas.

Connected Droplet Shape Analysis for Nanoflow Quantification in Thin Electroosmotic Micropumps and a Tunable Convex Lens Application

Thin electroosmotic flow (EOF) micropumps can generate flow in confined spaces such as lab-on-a-chip microsystems and implantable drug delivery devices. However, status quo methods for quantifying flow and other important parameters in EOF micropumps depend on microfluidic interconnects or fluorescent particle tracking: methods that can be complex and error-prone. Here, we present a novel connected droplet shape analysis (CDSA) technique that simplifies flow rate and zeta potential quantification in thin EOF micropumps. We also show that a pair of droplets connected by an EOF pump can function as a tunable convex lens system (TCLS). We developed a biocompatible and all polymer EOF micropump with an SU-8 substrate and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) electrodes. We microdrilled a channel through the electrode/SU-8/electrode layers to realize a monolithic EOF micropump. Then, we deposited a pinned droplet on each end of the microchannel so that it connected them. By controlling the EOF between the droplets and measuring the corresponding change in their shape, we quantified the nanoliter EOF rate and zeta potential at the interface of SU-8 with two liquids (deionized water and a l-glutamate neurotransmitter solution). When the droplet pair and pump were used as a TCLS, CDSA successfully predicted how the focal length would change when the pump drove fluid from one droplet to another. In summary, CDSA is a simple low-cost technique for EOF rate and zeta potential measurement, and a pair of droplets connected by an EOF micropump can function as a TCLS without any moving parts.

Particulate Matter Emission Factors for Dairy Facilities and Cattle Feedlots during Summertime in Texas.

Particulate matter (PM) emissions from dairies and feedlot sources require regular emission factor update. Likewise, development of simple measurement technique to accurately measure pollution concentration is warranted to limit the impact of air pollution and take necessary actions. During June of 2020, a dairy facility from central Texas and a feedlot from the Texas Panhandle region, titled as Dairy B and Feedlot C, respectively, were chosen for measurement of PM emissions in the state of Texas to represent dairy facilities and cattle feedlots PM emission rates. Four stations, each assigned with an EPA-approved Federal Reference Method (FRM) sampler, Texas A&M University (TAMU) designed sampler and handheld non-FRM AEROCET (MET One Instruments) sampler for collocation, were selected within each sampling locations. Drones were also utilized mounted with a handheld AEROCET sampler for simultaneously sampling at a certain height. PM2.5 emissions of Dairy B were all below 24-h PM2.5 standard of 35 μg m-3 as specified by National Ambient Air Quality Standards (NAAQS) even at the 98th percentile. The PM ratio between regulated PM10 to PM2.5 was determined to make an estimate of relative percentage of coarser particles to fine particles in both feedlot and the dairy representative animal facilities. The maximum mean emission factor determined using AERMOD for PM2.5 and PM10 was found to be 0.53 and 7.09 kg 1000-hd-1 d-1, respectively, for the dairy facility while 8.93 and 33.42 kg 1000-hd-1 d-1, respectively, for the feedlot. A conversion factor and correlation matrix were developed in this study to relate non-FRM sampler data from the handheld AERCET samplers with FRM samplers. Cheaper handheld samplers (AEROCETs) may play a potential role in quick and relatively instant measurement of PM emissions to initiate necessary preventive actions to control PM emission from dairy facility and feedlot sources.

Simple single-shot complete spatiotemporal intensity and phase measurement of an arbitrary ultrashort pulse using coherent modulation imaging.

We propose a simple single-shot spatiotemporal measurement technique called coherent modulation imaging for the spatio-spectrum (CMISS), which reconstructs the full three-dimensional high-resolution characteristics of ultrashort pulses based on frequency-space division and coherent modulation imaging. We demonstrated it experimentally by measuring the spatiotemporal amplitude and phase of a single pulse with a spatial resolution of 44 µm and a phase accuracy of 0.04 rad. CMISS has good potential for high-power ultrashort-pulse laser facilities and can measure even spatiotemporally complicated pulses with important applications.

Development and validation of RP-HPLC method for estimation of camptothecin in mixed micelle formulation

Camptothecin is a potent anticancer agent. Numerous studies on camptothecin had been reported in the literature; here an effort is made to develop a new HPLC method for camptothecin estimation in pharmaceutical dosage forms that will be accurate, simple, and sensitive. A fast, simple, and accurate spectrophotometric technique for the quantitative measurement of Camptothecin in active pharmaceutical components and pharmaceutical dosage formulations has been developed and validated. An RP-HPLC method was devised using Acetonitrile: Water (90:10) as the mobile phase, 1mL/min flow rate, and the temperature of 30 ℃. The linearity was observed in the concentration range of 20-100 μg/ml with maximum wavelength of 219 nm and a correlation value (R2) of 0.9995. The current method was used to determine the concentration of camptothecin in mixed micelles containing camptothecin, PF108, and TPGS. The suggested method's accuracy, precision, sensitivity, and ruggedness were evaluated using validation parameters. Recovery of camptothecin was found to be in the range of 98–102%, indicating that the developed method is accurate. The accuracy and robustness were found to be within acceptable limits and in compliance with ICH standards. This method can be used for routine analysis of camptothecin of pharmaceutical formulation in any pharmaceutical dosage form.

Modeling Push–Pull Converter for Efficiency Improvement

In this paper, we model and analyze the power losses of push–pull converters. The proposed model considers conduction and dynamic power losses, as well as transformer and inductor losses. Transformer and inductor models include skin and proximity effects, as well as power losses in the core. Moreover, the model includes the diode recovery time losses. We derived the equations for both continuous and discontinuous current operating modes. All model parameters can be obtained either from the datasheets of the used components or by simple measurement techniques. The model is verified experimentally by measuring the efficiency of the 500 W push–pull converter prototype. Simulations and experimental validation are conducted using the assumption that the converter is used in a permanent magnet (PM) wind turbine generator.

Real-time quantification of osteoclastic resorptive activity by electric cell-substrate impedance sensing.

In several diseases, bone resorption by osteoclasts is dysregulated. Thus far, no simple technique for real-time measurement of resorption is available. Here, we introduce an impedimetric bioassay for real-time monitoring of resorption by making use of the electrical insulating properties of the resorbable substrate calcium phosphate. Different chemical stimuli were applied to (pre)osteoclasts cultured on a layer of calcium phosphate in multi-well plates containing electrodes. By this, osteoclast activity can be measured continuously over days, and the effects of stimulating or inhibiting factors can be quantified. When cells were cultured in the presence of an inflammatory factor such as IL-1β, the resorptive activity started earlier. The measured decline in resistance was higher at culture day 5 than at cultures with M-CSF or M-CSF + RANKL (M-CSF norm. Resistance = 1, M-CSF + RANKL = 0.7, M-CSF + RANKL + IL-1β = 0.5). However, at day 11, this difference had nearly disappeared. Likewise, bisphosphonates were shown to inhibit osteoclastic activity. Our findings illustrate the importance of real-time monitoring; wherefore, this method has high potential not only for the study of osteoclast resorptive activity in the context of osteoclast function and diseases but also could find application in high-throughput drug-testing studies.

Selectively Imprinted β‐cyclodextrin Polymer for Colorimetric Assay of Lysophosphatidic Acid for Point of Care Detection of Ovarian Cancer

AbstractIn the present study, a simple molecular imprinting technique for the quantitative measurement of lysophosphatidic acid (LPA) is reported for the first time through colorimetry. LPA is a phospholipid bioactive involved in many physiological and pathological processes like stimulating DNA synthesis, proliferating ovarian cancer and inducing cell migration. It is reported that the concentration of LPA in patients with gynecological cancers like ovarian cancer is considerably higher than in the control. The early diagnosis of ovarian cancer may exceed the survival rate of patients. There is a need for an analytical tool for point of care detection of ovarian cancer at an early stage. Herein, molecular imprinting technique is used to develop an imprinted β‐Cyclodextrin (β‐CD) polymer using LPA as a template. This MIP prepared was imprinted with an LPA cavity, which has been extended for colorimetry assay. The colorimetric LPA assay was conducted in the spiked blood serum sample. The detection limit of LPA in spiked serum samples is calculated as 0.078 μmol/L.

Water jet space charge spectroscopy: route to direct measurement of electron dynamics for organic systems in their natural environment

The toolbox for time-resolved direct measurements of electron dynamics covers a variety of methods. Since the experimental effort is increasing rapidly with achievable time resolution, there is an urge for simple and robust measurement techniques. Within this paper prove-of-concept experiments and numerical simulations are utilized to investigate the applicability of a new setup for the generation of ultrashort electron pulses in the energy range of 300 eV up to 1.6 keV. The experimental approach combines an in-vacuum liquid microjet and a few-cycle femtosecond laser system, while the threshold for electron impact ionization serves as a gate for the effective electron pulse duration. The experiments prove that electrons in the keV regime are accessible and that the electron spectrum can be easily tuned by laser intensity and focal position alignment with respect to the water jet. Numerical simulations show that a sub-picosecond temporal resolution is achievable.