Linear Quantitative Relationship Research Articles

Establishment of a multiplex qPCR method for sensitive detection of proteolytic psychrotrophic bacteria in raw milk

Initial microbiological species and quantity of raw milk significantly affect dairy product quality. In particular, some psychrotrophic bacteria in raw milk can produce heat-stable hydrolases that reduce the stability of dairy products during their shelf life. The purpose of this study was to establish a multiplex real-time fluorescence quantitative polymerase chain reaction (qPCR) rapid detection method for Pseudomonas fluorescens and Lactococcus lactis subsp. lactis, which generally produce protease in raw milk. The primers and probes with good specificity, universality and high sensitivity to the target bacteria were screened by ordinary PCR and qPCR experiments. The quantitative linear relationship and sensitivity of the method for detecting pure DNA and artificially contaminated simulated milk samples were verified. The results showed that the limit of detection (LOD) of this method for pure DNA could reach 3.16×10-5 ng/μL. The detection of artificially contaminated samples showed that the LOD for P. fluorescens and L. lactis subsp. lactis could reach 250 and 22 CFU/mL, respectively. The multiplex qPCR method established in this study has good specificity and high sensitivity, which can be used to rapidly detect psychrotrophic bacteria in raw milk. It provides an effective reference strategy for the dairy industry to ensure the microbiological quality of raw milk from the source.

Navigating the biomechanical landscape: Enhanced methods for drug analysis

In drug analysis and detection, chemiluminescence is a standard technical method based on the idea that the concentration of observed substances in the chemical detection system and the chemical luminescence intensity establish a linear quantitative relationship under certain conditions. Bio-mechanical landscape (BML), which uses bioengineered systems to simulate essential elements of the human tumour microenvironment, is already enhancing cancer biology and aiding clinical translation. The majority of illicit substances have dangerous cardiovascular side effects that might range from an irregular heartbeat to a heart attack. Cardiovascular disease, including blocked veins and bacterial infections of the blood arteries and heart valves, may also result from injecting illicit narcotics. The challenging characteristics of such a cardiovascular disease using drug analysis are heart failure, low blood pressure and headaches. Hence, in this research, drug analysis has improved wearable body sensor network-enabled artificial neural network (WBSN-ANN) technologies for cardiovascular disease. Medicine and drug development because they provide information on patient status in the clinical context and vital information on pharmacodynamics activity, effectiveness, and safety throughout the research process. The process results in a research-intensive organization finding a novel chemical or biological compound and developing it into a medicine that patients can legally utilize for drug discovery and development.

Influence of microstructure characteristics on the fatigue properties of 7075 aluminum alloy

Grain size and aging state are the two major microstructural factors affecting the mechanical properties of Al alloys. In this study, fatigue tests were conducted on 7075 Al alloy with varying grain sizes and aging states. The results indicate that both grain refinement and over aging (OA) treatment are beneficial for enhancing fatigue performance, with the 7075-Min alloy exhibiting the highest fatigue strength of 265.8MPa in the OA state. For grain size, a quantitative positive linear relationship was found between the reciprocal of the square root of the average grain size and the fatigue strength coefficient. Grain refinement optimizes the fatigue performance by increasing the fatigue strength coefficient. Compared to the under aging (UA) state, OA treatment promotes the growth and coarsening of precipitates at grain boundaries (GBs) and within the interior of grains. This change in precipitate morphology effectively facilitates dislocation cross slip, reducing fatigue damage caused by dislocation blocking. The impact of the precipitation-free zone (PFZ) on fatigue performance is negligible compared to that of the precipitates. This study clarifies the relationship between microstructure and fatigue performance, providing valuable insights for microstructure regulation to optimize the fatigue performance of Al alloys.

Evaluation of residual load-bearing capacity for corroded steel strands via MMM technique

The quantitative evaluation of the residual load-carrying capacity of corroded cables is critical to the safe service of bridge structures. In this study, the locally corroded steel strands with different corrosion degrees were obtained through electrochemical experiments and the metal magnetic memory (MMM) signals were collected by the TSC-9 M-12 tester. The tensile failure tests of corroded steel strands were conducted by the WAW-1000 tensile testing machine. The distribution laws of the normal component Hz signals for steel strands in different corrosion cases were detailed and a three-dimensional (3D) magnetic dipole model of corroded steel strands was developed considering the end effects. The linear relationships between the magnetic characteristic quantity Hn and the corrosion cross-section loss rate As were revealed and verified by the theoretical and finite element simulation results. Based on the above relationships, a quantitative linear relationship between the residual load-carrying capacity F and the corrosion cross-section loss rate As of the corroded steel strand was proposed. The relative errors of the residual load-carrying capacity F calculated by the proposed quantitative method were overall within 20%. This study provides a basis for evaluating the residual load-carrying capacity of corroded cables using the MMM technique.

Quasi-analog operation for low photon flux detection with SiPM's standard and fast outputs

In this paper, we characterize the quasi-analog detection performance of silicon photomultiplier (SiPM) photodetector for optical wireless communications (OWC) at low photon flux signal intensity. In addition to analyzing the specificities of conventional anode-cathode standard output, it also highlights the unique capacitively coupled fast output feature of the off-the-shelf SiPM devices introduced by SensL, now ON Semiconductor (onsemi). Furthermore, the potential advantages of fast output are analyzed, and first propose the combined output model of standard and fast outputs. This combined output can be used to suppress ambient noise utilizing the bipolar characteristics of the fast output amplitude, e.g., the amplitude of the fast output can be up to ±30 mV under a useful signal light intensity of 94.1 nW, which can suppress the ambient noise amplitude of 30 mV and effectively improves signal-to-noise ratio. In addition, an approximate linear quantitative relationship between the standard output voltage amplitude and the SiPM chip received incident optical power was obtained, e.g., at different intensities of dark current and ambient current (1 nA and 2 nA), standard output voltage amplitudes of 90 mV and 50 mV correspond to optical powers of 50.5 nW and 21.3 nW or 34.7 nW and 5.7 nW. Finally, the potential performance of the proposed combined output schemes is confirmed by experimental and the measured Q-factor of the eye diagrams was optimised from 13.03 to 15.08. The proposed onsemi SiPM combined output schemes of standard and fast outputs can be selected to detection analog low-light link.

Polarizability matters in enantio-selection

The prevalence of chirality, or, handedness in biological world is a fundamental phenomenon and a characteristic hallmark of life. Thus, understanding the origin of enantio-selection, i.e., the sense and magnitude of asymmetric induction, has been a long-pursued goal in asymmetric catalysis. Herein, we demonstrated a polarizability-derived electronic effect that was shown to be capable of rationalizing a broad range of stereochemical observations made in the field of asymmetric catalysis. This effect provided a consistent enantio-control model for the prediction of major enantiomers formed in a ruthenium-catalyzed asymmetric transfer hydrogenations of ketones. Direct and quantitative linear free energy relationships between substrates’ local polarizabilities and observed enantio-selectivity were also revealed in three widely known asymmetric catalytic systems covering both reductions and oxidations. This broadly applicable polarizability-based electronic effect, in conjunction with conventional wisdom mainly leveraging on steric effect considerations, should aid rational design of enantio-selective processes for better production of chiral substances.

Evaluation of Eichhornia crassipes, Pistia stratiotes and Vetiver zizanoides in Phytoremediation of a Hospital Wastewater Effluent

The study assessed the physicochemical parameters from a hospital wastewater treatment plant in Zaria, using a standard method for water and wastewater examination and its phytoremediation by hydroponic treatment method using Eichhornia crassipes (water hyacinth), Pistia stratiotes (Water lettuce) and Vetiveria zizanoides (Vetiver grass). Results recorded were analyzed by one-way Analysis Of Variance at 95% confidence, multiple comparison tests, and quantitative linear relationship. The study showed higher concentrations of Electrical Conductivity (EC) (951.83 µs/cm), Phosphate (PO4) (64.46 mg/l), Biological Oxygen Demand (BOD) (244.90 mg/l), Chemical Oxygen Demand (COD) (625.50 mg/l), Total Suspended Solid (TSS) (27.30 mg/l), Potassium (K) (40.67mg/l) above the permissible limit standard by WHO and FAO, Phytoremediation showed there was significant difference at P ≤ 0.05 in reduction capacity across treatment between water hyacinth, water lettuce and vetiver grass for EC (49.8, 41.6 and 51.4%), TDS (51.3, 47.0 and 63.0%), PO4 (49.0, 45.3 and 53.0%), COD (47.3, 48.4 and 57.1%), NO3 (51.6, 43.1 and 64.6%), TSS (49.5, 42.7 and 60.3%), NH3 (44.7, 40.8 and 53.2%), SO4 (53.9, 47.2 and 62.8%). Plant analysis results showed higher concentrations of contaminant in the roots of water hyacinth than in the shoot, higher in the shoot of vetiver grass than its roots, and an even distribution in roots and shoots of water lettuce. Therefore, the three plants can be used effectively in the phytoremediation of wastewater contaminants due to cost-effectiveness, eco-friendliness, and the emerging cheaper technology for a lasting solution to the problems of water contamination to both humans and the environment.

Deciphering the linear relationship in the activity of the oxygen reduction reaction on Pt electrodes: A decisive role of adsorbates

Despite substantial efforts in developing high-performance catalysts for the oxygen reduction reaction (ORR), the persistent challenge lies in the high onset overpotential of the ORR, and the effect of the electrolyte solution cannot be ignored. Consequently, we have systematically investigated the impact of adsorbate species and concentration, as well as solution pH, on the ORR activity on Pt(111) and Pt(poly) electrodes. The results all tend to establish a linear quantitative relationship between the onset potential for ORR and the adsorption equilibrium potential of the adsorbate. This finding indicates the decisive role of adsorbates in the onset potential for ORR, suggesting that the adsorption potential of adsorbates can serve as an intuitive criterion for ORR activity. Additional support for this conclusion is derived from experimental results obtained from the oxygen evolution reaction on Pt(poly) with different adsorbate species and from the hydrogen evolution reaction on Pt(111) with iodine adsorption. We further propose both an empirical equation for the onset potential for ORR and the concept of a potential-regulated adsorbate shielding effect to elucidate the influence of adsorbates on ORR activity. This study provides new insights into the high onset overpotential of the ORR and offers potential strategies for predicting and enhancing ORR activity in the future.

Engineering non-noble Ni/WOx-ZrO2 towards boosted fuels production by catalytic upcycling of polyethylene at mild conditions

Chemical upcycling through catalytic hydrocracking to fuels has potential to mitigate the serious environmental issues caused by plastic waste. Herein, non-noble tungstate-zirconia supported nickel catalyst (Ni/WOx-ZrO2) with tunable Brønsted/Lewis (B/L) ratio was firstly proposed for the hydrocracking of low-density polyethylene (LDPE), which achieves hydrogenation/dehydrogenation on Ni sites and cracking/isomerization on WOx-ZrO2, respectively. Excellent 100 % LDPE conversion with 76.9 % liquid yield was achieved, which is comparable to noble Ru-based and Pt-based catalysts. Quantitative linear relationship between B/L ratio and hydrocracking performance was established, and the key to boost performance was keenly controlling the volcanic-shape relationship between surface WOx density and B/L ratio of catalyst. Moderate WOx surface density with higher B/L ratio enhances LDPE hydrocracking, and inhibits the hydrogenation of the primary products. However, excessive WOx polymerized and formed WO3 crystals, compensating acid sites and inhibiting LDPE hydrocracking. This work is of prime scientific and industrial significance to the rational design of catalysts for industrial plastic hydrocracking.

Micro FT-IR spectroscopic measurements of CH4: Experimental calibration with high-pressure and high temperature optical cell (HPOC)

Fourier transform infrared spectroscopy (FTIR) is a prevalent nondestructive in situ analytical technique widely employed for the qualitative characterization of natural fluid inclusions. Presently, the quantitative determination of the temperature, pressure, and composition of natural inclusions stands as a pivotal challenge in the geological application of laser spectroscopy. Through the integration of the capillary high-pressure optical cell (HPOC) technique and Fourier transform infrared spectroscopy, infrared quantitative models for the C–H symmetric stretching band (v3) in the vapor phase of CH4 under varying temperature (40–200 °C) and pressure (20–500 bar) conditions are established for the first time. This accomplishment is achieved through fitting and calculation of infrared spectra. A linear quantitative relationship and the dynamic evolution of infrared spectral parameters (peak area, full width at half maximum, peak height ratio, and peak shifts) concerning temperature, pressure, and density are meticulously investigated. The findings reveal that the peak area and full width at half maximum exhibit an upward trend with increasing pressure and density, and are inversely proportional to temperature. The height ratio (P band/Q band, R band/Q band) experiences an increase as density escalates. Moreover, the CH4v3 band position shows a higher wavenumber shift with increasing temperature, while its position correlates negatively with pressure and density. Thus, this method demonstrates its applicability in deducing the PVT-x properties of CH4-bearing systems, including CH4-rich fluid inclusions, CH4 content within hydrocarbon inclusions, and experimental fluid investigations. In contrast to the Raman quantitative approach, the infrared quantitative formula can be universally adopted in any infrared laboratory owing to the quantitative theory (Beer–Lambert law) governing infrared absorption spectra. By collecting Raman spectra and infrared spectra of pure methane fluid inclusions from the central region of the Alps and subsequently calculating the results using two distinct quantitative methods for fluid inclusions, we have demonstrated the feasibility of applying infrared spectroscopy in natural fluid inclusion studies.

Quantitative relationships of FAM50B and PTCHD3 methylation with reduced intelligence quotients in school aged children exposed to lead: Evidence from epidemiological and in vitro studies

At present, the application of DNA methylation (DNAm) biomarkers in environmental health risk assessment (EHRA) is more challenging due to the unclearly quantitative relationship between them. We aimed to explore the role of FAM50B and PTCHD3 at the level of signaling pathways, and establish the quantitative relationship between them and children's intelligence quotients (IQs). DNAm of target regions was measured in multiple cell models and was compared with the human population data. Then the dose-response relationships of lead exposure with neurotoxicity and DNAm were established by benchmark dose (BMD) model, followed by potential signaling pathway screening. Results showed that there was a quantitative linear relationship between children's IQs and FAM50B/PTCHD3 DNAm (DNAm between 51.40 % - 78.78 % and 31.41 % - 74.19 % for FAM50B and PTCHD3, respectively), and this relationship was more significant when children's IQs > 90. The receiver operating characteristic (ROC) and calibration curves showed that FAM50B/PTCHD3 DNAm had a satisfying accuracy and consistency in predicting children's IQs, which was confirmed by sensitivity analysis of gender and CpG site grouping data. In cell experiments, there was also a quantitative linear relationship between FAM50B DNAm and reactive oxygen species (ROS) production, which was mediated by PI3K-AKT signaling pathway. In addition, the lead BMD of ROS was close to that of FAM50B DNAm, suggesting that FAM50B DNAm was a suitable biomarker for the risk assessments of adverse outcomes induced by lead. Taken collectively, these results suggest that FAM50B/PTCHD3 can be applied to EHRA and the prevention/intervention of adverse effects of lead on children's IQs.

Identification of potential new COVID-19 treatments via RWD-driven drug repurposing

By utilizing Optum Life Sciences Claims Data, we constructed Real World Data (RWD) cohorts comprising over 3 million patients and simulated a clinical trial observational study design to evaluate over 200 FDA-approved drugs with COVID-19 repurposing potential, and identified a dozen candidates exhibiting significant reduction in the odds of severe COVID-19 outcomes such as death, intensive care unit (ICU) admission, hospitalization and pneumonia. Notably, certain drug combinations demonstrated effects comparable to those of COVID-19 vaccines. Furthermore, our study revealed a novel finding: a quantitative linear relationship between COVID-19 outcomes and overall patient health risks. This discovery enabled a more precise estimation of drug efficacy using the risk adjustment. The top performing drugs identified include emtricitabine, tenofovir, folic acid, progesterone, estradiol, epinephrine, disulfiram, nitazoxanide and some drug combinations including aspirin-celecoxib.

Investigation on dynamic response and compaction degree characterization of multi-layer asphalt pavement under vibration rolling

<abstract> <p>Asphalt mixture is composed of asphalt binder with aggregates of different sizes and compacted under static or dynamic forces. In practical engineering, compaction is a critical step in asphalt pavement construction to determine the quality and service life of pavement. Since the dynamic response characteristics of asphalt pavement can reflect the compaction state of asphalt mixture in the process of compaction, the establishment of the relationship between dynamic response characteristics and compaction degree is definitely significant. In this paper, a series of vibration sensors were adopted to capture the dynamic response signal of the vibration drum and asphalt mixture in the process of vibrating compaction for different surface courses of pavement. Then, the change regulations of vibration acceleration of vibrating drum and asphalt mixture were analyzed, and the quantitative linear relationship was established between accelerations of vibrating drum and asphalt pavement compactness. Further, the concept of evaluation unit (i.e., within 2 meters along the driving direction of the roller) and prediction method of compaction degree were proposed as well. The results showed that under the same vibration compaction condition, the compaction degree values of the top, middle and bottom layers have obvious differences, which should be taken seriously into consideration in the compaction process. Meanwhile, there is little difference which respectively are 2.8, 1.3 and 0.82% for the top, middle and bottom layers between the compaction degrees obtained by the proposed method and measured test. Therefore, the average value of the acceleration peak value of vibration drum within the evaluation unit can be adopted as the characterization index of the compaction degree of asphalt pavement. The investigation of this study can provide the technical reference for compaction control of asphalt pavement to a large extent.</p> </abstract>

Detection of Tomato Ringspot Virus Based on Microfluidic Impedance Sensor.

A microfluidic impedance sensor embedded with gold interdigitated array microelectrodes was utilized to rapidly detect Tomato Ringspot Virus (ToRSV) and achieve efficient and precise detection. The electrochemical impedance spectrum was obtained by immobilizing ToRSV antibody on the surface of a gold interdigital array microelectrode and mixing it with ToRSV to generate an impedance change. The electrochemical impedance spectrum was obtained. The equivalent circuit was established to analyze the mechanism of impedance change, and the quantitative linear relationship between ToRSV concentration and impedance was established. According to an equivalent circuit analysis, ToRSV increases the solution resistance Rs, the electron transfer resistance Ret on the electrode surface, and the double layer capacitance Cdl, resulting in an increase in impedance. The results reveal that the ToRSV concentration detected in the range of 0.001 to 10 μg/mL ranges from 248.8 to 687.2 kΩ at the ideal detection frequency of 10.7 Hz, with a good linear connection, R2 = 0.98. When this method’s detection limit is tested, the impedance value is 367.68 kΩ. 0.0032 μg/mL was the detection limit. The sensor is quick and easy to use, has high detection sensitivity, and can be used to detect other plant viruses.

Bridging of a Liquid Chromatography-Tandem Mass Spectrometry Method for Oxytetracycline, Chlortetracycline, and Tetracycline in Bovine Kidney with the Official Microbial Growth Inhibition Assay.

Oxytetracycline (OTC), chlortetracycline (CTC), and tetracycline (TC) are approved antibiotics used to treat bacterial infections in cattle. To ensure human food safety, a tolerance has been established for the sum of these three TC residues as 12 parts per million in bovine kidney in the United States The current official regulatory method for quantifying these antibiotics in the target organ is a labor-intensive microbiological assay. Our laboratory developed and validated a fast, selective, and less laborious method utilizing LC-tandem mass spectrometry for the determination and confirmation of the three tetracyclines (TET) in bovine kidney. Briefly, homogenized kidney tissue was spiked with an internal standard (ISTD), and then was extracted with 1% phosphate buffer. The crude extract was cleaned up using solid-phase extraction cartridges before instrumental analysis. Accuracies for quantifying these three drugs in fortified kidney homogenate were between 99.9 and 110% at multiple concentrations, with respective CVs all below 9.5%. Quantitative correlation between the two methods (bridging) was evaluated with incurred bovine kidney samples for each of the three tetracyclines separately. The results were statistically evaluated using a measurement model called Functional Relationship Estimation by Maximum Likelihood. A linear quantitative relationship was demonstrated between the two methods within the concentration range of regulatory relevance. This instrumental method is in addition to the established microbial assay for the detection of tetracyclines residue in beef kidney to ensure the food safety of cattle products.

Radical nucleophilic substitution/cyclization: A novel strategy for selective and ultrafast fluorescence imaging of cysteine levels in ferroptosis process

Diphenylisoindolo[2,1-a]quinoline can be used to detect cysteine among homocysteine, glutathione, and other 19 natural amino acids. Unlike other reported probes, the response mechanism involves sulfhydryl radical nucleophilic substitution and cyclization, and thus the differences in ring-formation kinetics enable high selectivity. After treated with Cys, the response process was completed rapidly and the maximum fluorescence intensity (at 496 nm) was reached extremely fast (<1 s) when excited at 380 nm in MeCN-PBS buffer (10.0 mM, pH = 7.4, 3:7 (v/v)). The quantum yield after the reaction was increased almost 7 times to be 0.02 from 0.003. Fluorescence intensity displayed a good quantitative linear relationship in the range 1–10 μM Cys with a detection limit of 270 nM. Furthermore, the probe was demonstrated for real-time monitoring of intracellular cysteine levels within HepG2 cells in ferroptosis process.

Characteristics and Pollution Contribution of the Internal Nitrogen Release From the Sediments in the Dahekou Reservoir in Inner Mongolia

To clarify the influence of the changes in the overlying water environment on the internal nitrogen release from reservoir sediments in different seasons, the quantitative linear relationship between the intensity of the nitrogen release from the sediment and the environmental factors of the overlying water was established, and their contribution rate to the nitrogen pollution of the reservoir during different storage periods was investigated. In this study, the sediment samples were collected from the Dahekou Reservoir in the Xilingol League, and the orthogonal simulation experiments were conducted in the laboratory. The mathematical model, which was established using multiple linear regression methods, revealed the following. The order of the significance of the influences of the environmental factors on the nitrogen release from the sediments in the Dahekou Reservoir is water temperature (T) &amp;gt; dissolved oxygen (DO) &amp;gt; pH value &amp;gt; hydrodynamic force (K). The total nitrogen release flux from the sediments in the Dahekou Reservoir was 14.278 t/a in 2018, accounting for 27.91% of the total nitrogen (TN) pollution load input during the same period. In particular, in winter, the contribution rate of the nitrogen released from the sediments reached the highest level (57.06–63.26%), which was significantly higher than the river’s contribution to the total nitrogen pollution load of the reservoir. The nitrogen released from the sediments became the main source of nitrogen nutrients in the reservoir in the ice-sealed period.

Pilot study of a novel nanobody 68Ga-NODAGA-SNA006 for instant PET imaging of CD8+ T cells.

Positron emission tomography (PET) with specific diagnostic probes for quantifying CD8+ T cells has emerged as a powerful technique for monitoring the immune response. However, most CD8+ T cell radiotracers are based on antibodies or antibody fragments, which are slowly cleared from circulation. Herein, we aimed to develop and assess 68Ga-NODAGA-SNA006 for instant PET (iPET) imaging of CD8+ T cells. A novel nanobody without a hexahistidine (His6) tag, SNA006-GSC, was designed, site-specifically conjugated with NODAGA-maleimide and radiolabelled with 68Ga. The PET imaging profiles of 68Ga-NODAGA-SNA006 were evaluated in BALB/c MC38-CD8+/CD8- tumour models and cynomolgus monkeys. Three volunteers with lung cancer underwent whole-body PET/CT imaging after 68Ga-NODAGA-SNA006 administration. The biodistribution, pharmacokinetics and dosimetry of patients were also investigated. In addition, combined with immunohistochemistry (IHC), the quantitative performance of the tracer for monitoring CD8 expression was evaluated in BALB/c MC38-CD8+/CD8- and human subjects. 68Ga-NODAGA-SNA006 was prepared with RCP > 98% and SA > 100GBq/μmol. 68Ga-NODAGA-SNA006 exhibited specific uptake in MC38-CD8+ xenografts tumours, CD8-rich tissues (such as the spleen) in monkeys and CD8+ tumour lesions in patients within 1h. Fast washout from circulation was observed in three volunteers (t1/2 < 20min). A preliminary quantitative linear relationship (R2 = 0.9668, p < 0.0001 for xenografts and R2 = 0.7924, p = 0.0013 for lung patients) appeared between 68Ga-NODAGA-SNA006 uptake and CD8 expression. 68Ga-NODAGA-SNA006 was well tolerated by all patients. 68Ga-NODAGA-SNA006 PET imaging can instantly quantify CD8 expression with an ideal safety profile and is expected to be important for dynamically tracking CD8+ T cells and monitoring immune responses for individualised cancer immunotherapy. NCT05126927 (19 November 2021, retrospectively registered).

Adsorption Characteristics and Pore Structure of Organic-Rich Shale With Different Moisture Contents

A moisture equilibration test has been designed to study the pore structure and adsorption capacity of organic-rich shale with different moisture contents. Five humidity environments were artificially controlled to obtain shale samples with different moisture contents. With the moisture equilibration test and N2 adsorption/desorption, the differences in pore structure of samples with different moisture contents were compared and analysed. The results showed that the diameter of 2–10 nm pores decreased with increasing humidity and that the moisture adsorption characteristics conformed to the GAB adsorption model. It is proposed that when moisture enters a sample, monolayer adsorption will first occur because moisture is preferentially adsorbed on the pore surface with strong hydrophilicity, filling in the relatively small pores. Mesopores and micropores play a major role in water adsorption. With increasing humidity, capillary condensation of moisture gradually occurs in pores. Based on the methane isothermal adsorption test of shale samples with different moisture contents, a quantitative linear relationship between the moisture content and methane adsorption capacity of shale samples has been established. It has been determined that the methane adsorption capacity of shale in underwater conditions is less than that of dry samples, and that the rate of decline in the adsorption capacity of different samples under dry and water balance conditions varies greatly. The distribution characteristics of clay minerals are the main controlling factor of the hydrophilicity of shale, which has a certain guiding significance for further accurate evaluation of shale adsorption gas reserves.

Experimental study and signal analysis of acoustic emission from power MOSFET

The traditional condition monitoring (CM) method of power electronic device detection is built based on electrical, magnetic, and thermal parameters, respectively. In this paper, a novel potential method based on acoustic or stress parameter is proposed. The mechanical stress wave (MSW) and electromagnetic wave (EMW) generated from power metal-oxide-semiconductor field-effect transistor (MOSFET) are analyzed under low voltage condition for the first time. Then, the testing system is set up based on acoustic emission (AE), and corresponding experiments are conducted to verify the correctness of the primary theory. In the experiment, AE signals generated by power MOSFET under pulse excitation can be divided into low-frequency and high-frequency components with the boundary of 300 kHz. The relationship between low-frequency components and gate-source voltage (Vgs) is approximately linear and the high-frequency components contain two reverse pulse waves which is nearly a linear quantitative relationship between the positive one and the drain-source voltage (Vds). AE sensor is coupled in two different ways, which are used to verify that the high-frequency components are mainly EMW generated at the moments of turn-on and turn-off. In addition, the low-frequency components are mainly MSW signal. This research provides a new idea and method for the condition CM of power MOSFET.