Peak Response Research Articles

Deep learning‐based response spectrum analysis method for building structures

AbstractThe response spectrum method has gained widespread acceptance in practical applications owing to its favorable compromise between accuracy and practical efficiency. The method predicts the peak responses of multi‐degree‐of‐freedom (MDOF) systems by combining modal responses. The Square Root of the Sum of Squares (SRSS) and Complete Quadratic Combination (CQC) rules are commonly used for modal combinations. However, it has been widely known that these rules have limitations in accurately predicting responses influenced by higher modes and cross‐modal correlations. To improve the accuracy of the response spectrum analysis method for building structures, this paper proposes a Deep learning‐based modal Combination (DC) rule by introducing modal contribution coefficients predicted by a deep neural network (DNN) model. The DC rule enhances prediction accuracy by considering the characteristics of ground motion and the dynamic properties of a structural system. The DC rule provides more accurate predictions than the conventional rules, particularly for irregular response spectra and responses affected by higher modes. The efficiency and applicability of the DC rule are demonstrated by numerical investigations of multistory shear buildings and steel frame structures with regular and irregular shapes. The source codes, data, and trained models are available for download at https://github.com/tyongkim/ERD2.

K2Cr2O7-induced DNA damage in HT1080 cells: Electrochemical signal response mechanism

The existing DNA damage detection technology cannot meet the current detection requirements. It is critical to build new methods and discover novel biomarkers. In this study, alkaline comet and 8-OHDG ELISA assays were used to identify DNA damage in HT-1080 cells exposed to K2Cr2O7, and electrochemical behaviors of HT-1080 cells with DNA damage was studied. With an increase in K2Cr2O7 exposure time, two electrochemical signals from HT-1080 cells at 0.69 and 1.01 V steadily grew before decreasing after reaching their highest values. The electrochemical signal's initial response time and peak time decreased as the concentration of K2Cr2O7 increased. The duration of the high dose group was 0.5 and 1 h, while the low dose group was 1.5 and 6 h. Western blotting analysis revealed that DNA damage increased the expression of proteins involved in catabolism and de novo purine synthesis, particularly de novo purine synthesis. Expressions of PRPP amidotransferase, IMPDH, and ADA were all higher than those of ADSS, XOD, and GDA, which resulted in larger concentrations of hypoxanthine, guanine, and xanthine, and in turn improved electrochemical signaling. These findings suggest that intracellular purine identified by linear scan voltammetry is predicted to evolve as a marker of early DNA damage.

CSF α-synuclein seed amplification kinetic profiles are associated with cognitive decline in Parkinson’s disease

Seed amplification assays have been implemented in Parkinson’s disease to reveal disease-specific misfolded alpha-synuclein aggregates in biospecimens. While the assays’ qualitative dichotomous seeding response is valuable to stratify and enrich cohorts for alpha-synuclein pathology in general, more quantitative parameters that are associated with clinical dynamics of disease progression and that might potentially serve as exploratory outcome measures in clinical trials targeting alpha-synuclein would add important information. To evaluate whether the seeding kinetic parameters time required to reach the seeding threshold (LAG phase), the peak of fluorescence response (Imax), and the area under the curve (AUC) are associated with clinical trajectories, we analyzed LAG, Imax, and AUC in relation to the development of cognitive decline in a longitudinal cohort of 199 people with Parkinson’s disease with positive CSF alpha-synuclein seeding status. Patients were stratified into tertiles based on their individual CSF alpha-synuclein seeding kinetic properties. The effect of the kinetic parameters on longitudinal development of cognitive impairment defined by MoCA ≤25 was analyzed by Cox-Regression. Patients with a higher number of positive seeding replicates and tertile groups of shorter LAG, higher Imax, and higher AUC showed a higher prevalence of and a shorter duration until cognitive impairment longitudinally (3, 6, and 3 years earlier with p ≤ 0.001, respectively). Results remained similar in separate subgroup analyses of patients with and without GBA mutation. We conclude that a more prominent alpha-synuclein seeding kinetic profile translates into a more rapid development of cognitive decline.

Dynamic Response of Bridge–Tunnel Overlapping Structures under High-Speed Railway and Subway Train Loads

With the rapid development of high-speed railroads and subways, there has been an increasing number of bridge–tunnel overlapping structures. To study the dynamic response characteristics of bridge–tunnel structures under the synergistic effects of the vibration generated by high-speed railway and subway trains, the dynamic response characteristics of a bridge–tunnel structure under single-point vibration loading was analyzed by conducting numerical simulations and model tests, with the frequency response function and peak acceleration as the evaluation indices. The dynamic response characteristics of the overlapping structure under moving vibration loads of the high-speed railway and subway trains were further analyzed. The results showed that the dynamic response of the bridge–tunnel overlapping structure increased with the increase in the frequency under the full frequency domain single-point sweep vibration load. The dynamic response of the tunnel hance near the pile foundation side was significantly greater than the vault and invert. Compared with the effect of high-speed train loads alone, the dynamic response of the bridge–tunnel overlapping structure under the synergistic effects of high-speed railways and subways increased significantly and varied at different locations. This investigation provides theoretical support for the design and construction of bridge–tunnel overlapping structures under the synergistic effects of high-speed railways and subways, contributing to improving engineering quality and safety.

Study of electric-field induced ionic migration on all-inorganic perovskite CsPbBr3 single crystal nuclear radiation detector

As one of the promising room temperature nuclear radiation detection materials, the all-inorganic perovskite CsPbBr3 single crystal has been receiving much attention in recent years. Even though the performance of the CsPbBr3 detector is improving continuously, the disadvantages of detection instability have not been solved fundamentally, and this instability is mainly caused by ionic migration in the CsPbBr3 single crystal itself. In this paper, a reasonable ionic migration model is proposed based on an in-depth study of the current hysteresis phenomenon and ionic migration mechanism in the Ti/CsPbBr3/Ti detector. The model shows that the ions migrate to the anode or cathode under an external electric field, and the accumulated ions subsequently form an inverted internal electric field inside the crystal and carrier transport barriers at the metal–semiconductor interface simultaneously. The photoelectric characteristic and ionic migration activation energy (Eaion) fitting results also prove the rationality of the ionic migration model. Furthermore, the ionic migration model can also be used to explain the left-shift of the energy response peak and the decrease in the normalized charge collection efficiency in the Ti/CsPbBr3/Ti detector. This paper systematically investigates the intrinsic origin of migrated ions and the influence of ionic migration on detection stability, which will provide a potential solution to improve detection stability by suppressing ionic migration in the near future.

Design and performance of GaSb-based quantum cascade detectors.

InAs/AlSb quantum cascade detectors (QCDs) grown strain-balanced on GaSb substrates are presented. This material system offers intrinsic performance-improving properties, like a low effective electron mass of the well material of 0.026 m 0, enhancing the optical transition strength, and a high conduction band offset of 2.28 eV, reducing the noise and allowing for high optical transition energies. InAs and AlSb strain balance each other on GaSb with an InAs:AlSb ratio of 0.96:1. To regain the freedom of a lattice-matched material system regarding the optimization of a QCD design, submonolayer InSb layers are introduced. With strain engineering, four different active regions between 3.65 and 5.5 µm were designed with InAs:AlSb thickness ratios of up to 2.8:1, and subsequently grown and characterized. This includes an optimized QCD design at 4.3 µm, with a room-temperature peak responsivity of 26.12 mA/W and a detectivity of 1.41 × 108 Jones. Additionally, all QCD designs exhibit higher-energy interband signals in the mid- to near-infrared, stemming from the InAs/AlSb type-II alignment and the narrow InAs band gap.

Dobutamine Stress Cardiovascular Magnetic Resonance Derived 2-Dimension Feature Tracking Strain Analysis in Pediatric Population with Anomalous Aortic Origin of Right Coronary Artery.

Anomalous aortic origin of right coronary artery (AAORCA) is associated with myocardial ischemia and sudden cardiac arrest/death. Risk stratification remains challenging and relies upon provocative test results. This study describes the utility of dobutamine stress cardiovascular magnetic resonance (DSCMR) and potential benefit of strain analysis in children with AAORCA. All patients less than 21years of age with AAORCA who underwent DSCMR between July 2018 and December 2022 were included. Visual wall motion abnormalities (VWMA) at rest and during protocolized increments of dobutamine infusion were assessed. Regional and global left ventricular circumferential (GCS) and radial (GRS) strain using 2-dimension Feature tracking (2D-FT) analysis (cvi42, Circle Cardiovascular Imaging Inc.) were calculated at rest and peak response. Of the total 54 DSCMR studies performed in 51 children with median age (IQR) of 13.5 (11-15)years, FT analysis was reliably performed in 52 (96%) studies. None had VWMA. The absolute change in GCS and GRS from rest to peak dobutamine stress was 4% (1-6%) and 11% (4-18%), respectively. There was no significant difference in GCS and GRS in patients with exertional symptoms vs no/non-exertional symptoms as well as between those considered to be high-risk vs low-risk anatomical features. DSCMR-derived 2D-FT strain analysis is feasible to assess myocardial deformation in children with AAORCA and may enhance this method of provocative testing. Although there were no statically significant differences in GCS and GRS values between high and low-risk subgroups, the absolute change in GCS between rest and peak stress is diminished when compared to normal adult reports.

Comprehensive Effects of Potassium Lactate, Calcium Ascorbate and Magnesium Chloride as Alternative Salts on Physicochemical Properties, Sensory Characteristics and Volatile Compounds in Low-Sodium Marinated Beef.

The search for alternative salt formulations similar to sodium chloride and their effect on marinated meat products is of great significance to the low-sodium meat processing industry. The main purpose of this study was to investigate the effect of partially replacing sodium chloride with potassium lactate, calcium ascorbate, and magnesium chloride on the sodium content, water activity and distribution, protein solubility, microstructure, sensory characteristics and volatile flavor compounds in low-sodium marinated beef. The sodium content in the test group decreased up to 28% compared to 100% in the sodium chloride group C1. The formulation including 60% sodium chloride and a total of 40% compound alternative salts in groups F1 and F2 increased their myofibril fragmentation index and promoted the disruption of the myogenic fiber structure. Group F1 (the ratio of potassium lactate, calcium ascorbate and magnesium chloride was 2:1:1) performed higher solubility of myofibrillar proteins and lower transverse relaxation value than group F2 detected by low-field nuclear magnetic resonance, which indicated that F1 formulation was beneficial to promote the solubility of myofibrillar proteins and attenuate the water mobility of marinated beef. Moreover, group F1 had a more similar microstructure and more similar overall sensory attributes to group C1 according to the scanning electron microscopy. The sensory evaluation showed higher peak intensity and response values of volatile flavor compounds than group C1 and C2 (only 60% sodium chloride) when detected using gas chromatography-ion mobility spectrometry technology, which indicated that the compound alternative salts of group F1 can improve the lower quality of low-sodium marinated beef and perform similar attributes to the C1 sample regarding moisture distribution and microstructure and even performs better than it with regards to flavor. Therefore, the F1 formula possessed greater potential for application in low-sodium marinated meat products.

Detection of methandienone and its metabolites in equine urine, plasma and hair following a multidose oral administration.

Methandienone is an anabolic-androgenic steroid that is prohibited in equine sports due to its potential performance enhancing properties. Metabolism and detection of methandienone in equine urine have been investigated comprehensively in literature; however, there is a limited knowledge about its metabolites in equine plasma and no information about its detection in equine hair. Following a multi-dose oral administration of methandienone to two Thoroughbred horses, 17-epimethandienone, methyltestosterone, two mono-hydroxylated, two di-hydroxylated and three 17α-methylandrostanetriol metabolites were detected in plasma. The majority of these were present as free analytes, whilst the mono-hydroxylated metabolites and one isomer of 17α-methylandrostanetriol were partially conjugated. Estimated peak concentrations of methandienone were 6,000 and 11,100 pg/ml; meanwhile, they were 25.4 and 40.5pg/ml for methyltestosterone. The most abundant analyte in the post-administration plasma samples of both horses was the mono-hydroxylated metabolite; however, the parent compound provided the longest detection (up to 96 h). Screening analysis of hair enabled the detection of methandienone in mane hair samples only, for up to 3months. Its mono- and di-hydroxylated metabolites were detected with greater peak responses for up to 6months post-administration in both mane and tail samples, showing that these metabolites could be better analytical targets for hair analysis when administered orally. A follow-up methodology with an extensive wash procedure confirmed the presence of methandienone and its metabolites in a number of post-administration hair samples. Final wash samples were also analysed to assess the degree of internal incorporation (via bloodstream) against possible external deposition (via sweat/sebum).

Controlled expression of avian pre-migratory fattening influences indices of innate immunity.

While immunity is frequently dampened when birds engage in strenuous migratory flights, whether and how immunity changes during the rapid accumulation of energy stores in preparation for migration remains largely unknown. Here we induced pre-migratory fattening through controlled changes of daylight in common quails (Coturnix coturnix) and regularly assessed changes in three markers of constitutive innate immunity (leukocyte coping capacity or LCC, hemagglutination and hemolysis titres) and measures of body composition (lean and fat mass). All the three markers showed similar changes over the pre-migratory fattening process. LCC responses, hemagglutination titres, and hemolysis titres, were on average higher in the mid-fattening phase compared to the peak-fattening phase, when values were similar to those observed prior the start of pre-migratory fattening. At mid-fattening, we found that the birds that showed a larger accumulation of fat mass (as % of body mass) had lower LCC peak responses and hemolysis titres. Reversibly, at mid-fattening, we also found that the birds that kept a higher proportion of lean mass (as % of body mass) had the highest LCC peaks. Our results indicate that migratory birds undergo changes in immune indices (over 8 weeks) as they accumulate energy stores for migration and propose that this could be due to competing or trade-off processes between metabolic remodelling and innate immune system function.

Single input-single output coupled resonators with nonlinear self-excitation for multiple mass sensing

A theoretical formulation and an experimental investigation into multiple mass sensing using self-excited coupled resonators is discussed. To construct a single input-single output (SISO) system, multiple resonators with different natural frequencies (frequency-mistuned resonators) are connected to a common shuttle mass, with resonators individually functionalized to absorb a specific analyte/mass. To measure the natural frequency shift of each resonator, we propose using the response frequency in the shuttle mass under the self-excitation, rather than the peak of the frequency response to the external harmonic excitation. Consequently, the method is applicable even in viscous environments where the frequency response curve does not exhibit a clear peak. The application of velocity feedback compensates for viscosity and selectively produces the self-excited oscillation, with one of the eigenfrequencies of the overall system corresponding to the natural frequency of the resonator absorbing the target analyte with the aid of band-pass filter. From the shift of the eigenfrequency corresponding to each resonator, changes in the masses absorbed to that resonator can be identified. A discrete mathematical model for the proposed sensing system is formulated and a nonlinear analysis was carried out to theoretically validate the control method. Furthermore, additional nonlinear feedback was introduced to prevent the infinite growth of the self-excited oscillation by ensuring that the sensing system behaves as a van der Pol oscillator. We experimentally investigated the efficiency of the method using a simple macro-scale apparatus with two resonators connected to a shuttle mass.

Development of a cost-effective compact diode-laser-based photoacoustic sensing instrument for breast tissue diagnosis.

The photoacoustic (PA) technique, a noninvasive pump-probe technique, has found interesting applications in biomedical tissue diagnosis over the last decade. To take it a step further to clinical applications, the PA technique needs to be designed as an instrument focusing on a compact design, reducing the cost, and quickly providing a quantitative diagnosis. This work presents a design and characterization of a cost-effective, compact PA sensing instrument for biomedical tissue diagnosis. A compact laser diode case design is developed to house several laser diodes for PA excitation, and a pulsed current supply unit is also developed in-house to power the laser diodes to generate a 25ns current pulse at a frequency of 20kHz. After PA experimental data acquisition, the signal's frequency spectra were calculated to characterize the tissue quantitatively and correlated with their mechanobiological properties. The corresponding dominant frequency peak in the PA spectral response (PASR) study was low in the fibrofatty normal breast tissue , compared to the dominant frequency peak of in the fibrocystic disease tissue, which had increased glandular and stromal elements, thereby increased tissue density. The histopathological findings correlated with the PASR results, and the fibrocystic breast disease tissue exhibited a higher dominant frequency peak and energy compared to the normal breast tissue. We experimented with an in vitro PASR study of fibrocystic human breast tissues and successfully differentiated different tissue types using quantitative spectral parameters peak frequency, mean frequency, and spectral energy. This gives the potential to take this technique further for cost-effective and quick clinical applications.

Study on vibration response and isolation of substation structure under subway load excitation

This study takes the indoor substation adjacent to the elevated bridge subway line as the engineering background, investigates the structural vibration response law of the substation induced by the operation of the subway line through on-site vibration measurement, and proposes a novel nonlinear gas-spring quasi-zero stiffness isolator (NGS-QZSI) is proposed to reduce the structural vertical vibration and further reduce the safety distance. The software ABAQUS is used to establish a structure-equipment coupling numerical analysis model considering soil-structure interaction, and its effectiveness and accuracy are validated based on the measured results. The structural vibration response analysis is carried out under different vibration source distances, and a nonlinear gas-spring quasi-zero stiffness isolator is proposed to be employed for substation structural vibration isolation. The research results show that the substation structure under subway load excitation is dominated by vertical vibration, and its vibration response increases gradually with the increase of floor level. When the substation structure is less than 45 m from the subway line, the structural response exceeds the safety limit (12.5 μm/s) of the VC-C standard. With the vibration isolator attached, the structural vibration response is significantly reduced, with the peak and root mean square response controlled by more than 70 %. Particularly, the safe distance of the substation from the subway line is reduced from 45 m to 20 m. Moreover, the frequency domain result analysis indicates that the proposed nonlinear vibration isolator can effectively control the low-frequency vibration of the structure.

Integrated serum pharmacochemistry and investigation of the anti-influenza A virus pneumonia effect of Qingjin Huatan decoction

Ethnopharmacological relevanceQingjin Huatan Decoction (QJHTT) consists of 11 herbal medicines: Scutellaria baicalensis Georgi, Gardenia jasminoides J. Ellis, Platycodon grandiflorus (Jacq.) A. DC., Ophiopogon japonicus (Thunb.) Ker Gawl., Morus alba L., Fritillaria thunbergii Miq., Anemarrhena asphodeloides Bunge, Trichosanthes kirilowii Maxim., Citrus reticulata Blanco, Poria cocos (Schw.) Wolf, and Glycyrrhiza uralensis Fisch. As a traditional Chinese medicinal formula, QJHTT has been used for more than 400 years in China. It has shown promising results in treating influenza A virus (IAV) pneumonia. Aim of the studyTo elusive the specific pharmacological constituents and mechanisms underlying its anti-IAV pneumonia effects. Materials and methodsThe components in QJHTT were analyzed through the use of a serum pharmacology-based ultra high-performance liquid chromatography Q- Exactive Orbitrap mass spectrometry (UHPLC-Q Exactive Orbitrap-MS) method. Simultaneously, the dynamic changes in IAV-infected mouse lung viral load, lung index, and expression of lung inflammation factors were monitored by qRT-PCR. ResultsWe successfully identified 152 chemical components within QJHTT, along with 59 absorbed chemical prototype constituents found in the serum of mice treated with QJHTT. 43.45% of these chemical components and 43.10% of the prototype constituents were derived from the monarch drugs, namely Huangqin and Zhizi, aligning perfectly with traditional Chinese medicine theory. Notably, our analysis led to the discovery of 14 compounds within QJHTT for the first time, three of which were absorbed into the bloodstream. Simultaneously, we observed that QJHTT not only reduced the viral load but also modulated the expression of inflammation factors in the lung tissue including TNF-α, IL-1β, IL-4, IL-6, IFN-γ, and IL17A. A time-effect analysis further revealed that QJHTT intervention effectively suppressed the peak of inflammatory responses, demonstrating a robust anti-IAV pneumonia effect. ConclusionsWe comprehensively analyzed the pharmacological material basis of QJHTT by a highly sensitive and high-resolution UHPLC-Q Exactive Orbitrap-MS method, and demonstrated its efficacy in combating IAV pneumonia by reducing lung viral load and inflammatory factors. This study has significant importance for elucidating the pharmacological basis and pharmacological mechanism of QJHTT in combating IAV pneumonia.

Design and performance evaluation of MoS2 photodetector in vertical MSM configuration

Flexible photodetectors based on transition metal dichalcogenides are gaining significant prominence due to their remarkable optical and electronic properties. This study presents an in-depth performance assessment of molybdenum disulfide (MoS2) as the absorber layer within a vertical Au/MoS2/FTO metal-semiconductor-metal (MSM) photodetector configuration. Utilizing one-dimensional solar cell capacitance simulation (SCAPS-1D) software, we conduct a comprehensive numerical investigation into the photodetector's performance. The systematic simulation of various physical properties of the MoS2 absorber layer, including thickness, doping, and bulk defect density, reveals optimized values of 1 μm, 1018 cm−3, and 1015 cm−3, respectively. The optimized device exhibits peak responsiveness under 700 nm wavelength spectrum illumination, boasting a responsivity of 0.37 AW−1 and a detectivity of 3.27 × 1014 Jones. Furthermore, the impact of temperature and incident light power on the optimized photodetector is thoroughly examined. The proposed photodetector demonstrates considerable potential for cost-effective, easily manufacturable, and durable wearable electronics applications.

Real-World Patient Experience With PrabotulinumtoxinA in the United Kingdom: A Single-Center Survey and Analysis of 254 Patients.

Botulinum toxin Type A (BoNT-A) injection is the most widely performed nonsurgical cosmetic procedure in the United Kingdom. PrabotulinumtoxinA is a new BoNT-A, recently licensed in the United Kingdom, for treating moderate-to-severe glabellar lines in adults under 65. Although clinical trials have established safety and efficacy, real-world data can help clinicians translate study findings into practice and support prabotulinumtoxinA use in a more diverse patient population. To understand the real-world patient experience and patient perceptions of prabotulinumtoxinA performance for treatment of the glabellar region. In this single-center survey study, a single injector administered prabotulinumtoxinA for the treatment of glabellar lines to real-world patients presenting for BoNT-A treatment. Two weeks later, patients received surveys asking about their experience through email. There were no incentives for participation. Responses returned within 5 weeks of treatment were included. From February to June 2023, 457 patients received prabotulinumtoxinA injections for glabellar line treatment. Survey response rate was 56% (254/457 patients). For most patients, treatment onset was 2 to 3 days following injection and peak response occurred after 7 to 10 days. Adverse effects were minimal, with 67% of patients experiencing none. Among survey respondents, 83% rated their treatment positively (5-point satisfaction scale), and 72% would choose prabotulinumtoxinA again. These data support safety and effectiveness of prabotulinumtoxinA in a diverse, real-world population, and confirm patient satisfaction among experienced BoNT-A patients, as well as suggest a rapid time to onset and peak effect.

A laser-induced graphene-based electrochemical immunosensor for nucleic acid methylation detection.

The detection of methylation in DNA and RNA is essential for the diagnosis and treatment of a wide range of diseases. A one-step fabricated laser-induced graphene (LIG) electrode has received increasing attention due to its good electrical conductivity, large specific surface area, ease of miniaturization, low cost and flexibility. Herein, a potential biosensor for N6-methyladenosine (m6A-RNA) and 5-methylcystosine-single strand DNA (5mC-ssDNA) detection was designed. The aim of this paper is to address the problem of detecting the m6A-RNA and 5mC-ssDNA content in cells. By stepwise modification of gold nanoparticles (AuNPs), sulfhydryl-modified nucleic acid chains, biotin-modified antibodies, and streptavidin-modified horseradish peroxidase (SA-HRP) at the LIG electrode, the peak current responses exhibited an increase proportional to the concentration of m6A-RNA and 5mC-ssDNA in the hydrogen peroxide-hydroquinone (H2O2-HQ) system. This method demonstrated a low detection limit of 2.81 pM for m6A-RNA and 9.53 pM for 5mC-ssDNA, with a linear detection range of 0.01 nM to 10 nM for both targets. The regression equation was determined as ΔI = 4.83 log c + 12.32 (R2 = 0.9980) for m6A-RNA and ΔI = 9.82 log c + 22.09 (R2 = 0.9903) for 5mC-ssDNA. Our method has good selectivity toward different detection targets of nucleic acid chains, stability for long-term storage and consecutive scanning (RSD of 9.42% and 2.08%, respectively) and reproducibility of 5 electrodes (RSD of 6.85%). This method utilizes gold-sulfur bonding to immobilize the detection target, which improves the conductivity of the LIG electrode and introduces an amplified portion of the signal by taking advantage of antigen-antibody specific binding. Thus, dual detection of m6A-RNA and 5mC-ssDNA was realized. Importantly, this approach is successfully applied for the detection of targets in spiked samples extracted from HeLa cells, suggesting its potential for clinical applications and providing a new perspective for the development of point-of care testing (POCT) techniques.

Determination of the stability of sodium cyclamate during deep-frying using HPLC.

The oil used to fry food is often used multiple times to reduce costs. However, when foods containing sweeteners are processed in this way, the sweeteners may produce substances harmful to the body as a result of repeated frying at high temperatures. This article investigated the stability of sodium cyclamate during deep-frying by HPLC using a pre-column derivatization method. The results showed that cyclohexylamine was a decomposition product of a standard sample of sodium cyclamate when deep-fried at 200°C for 25 min. A pre-column derivatization/HPLC method was established to determine cyclohexylamine, a decomposition product of sodium cyclamate, under these conditions. Dansyl chloride was used as the derivatization reagent, the derivatization temperature was 60°C, the derivatization time was 20 min, the pH of sodium bicarbonate buffer solution was 11, and the concentration of dansyl chloride was 2.0 mg/mL. Detection was carried out by using an Agilent 1260 high-performance liquid chromatograph coupled with an ultraviolet detector. The ultraviolet detection wavelength was 254 nm, and the mobile phase was acetonitrile-1.0 g/L potassium dihydrogen phosphate solution at a flow rate of 1.0 mL/min. Gradient elution was adopted, the peak of the cyclohexylamine derivative appeared at a retention time of 17.75 min, and the peak area response value was the largest. The methodological validation analysis showed that the detection limit of cyclohexylamine was 0.5 mg/kg, the quantification limit was 2.0 mg/kg, and the spiked recoveries were in the range of 99.37-110.16%. The relative standard deviations (RSDs) were in the range of 0.17-1.26%. Four samples were tested and analyzed by the established method, and cyclohexylamine was not detected.

Response Characteristics of a ZnO Arrester Under Nanosecond Electromagnetic Pulse

Zinc oxide arresters, a major type of overvoltage protection equipment in power systems, can suppress transient lightning overvoltage, operation overvoltage, and other types of power surges. However, the response characteristics and protection effects under nanosecond pulses, such as those in a high-altitude electromagnetic pulse conduction region, remain unclear. Therefore, the surge protection performance of arresters should be properly understood, and high-performance arresters should be developed. In this study, critical parameters, including overshoot peak voltage, residual voltage, response time, and voltammetry characteristics of a representative 10 kV ZnO arrester under nanosecond pulses, were obtained using a double exponential pulse current injection source. The overshoot peak voltage of this arrester under a nanosecond pulse is 2.19 times of lightning impulse residual voltage, and the residual voltage ratio under a nanosecond pulse is 4.31. The average response time is approximately 45 ns, and the response time is independent of the nanosecond pulse amplitude. Furthermore, an electromagnetic transient model of this type of lightning arrester is established based on the CIGRE guidelines, as well as a method to determine the key parameters. The model can simultaneously account for the response characteristics of the small current region and the conduction region of the arrester, which properly agrees with the experimental results.

Abnormal late postprandial glucagon response in type 1 diabetes is a function of differences in stimulated C-peptide concentrations.

The functional changes in alpha cells in patients with type 1 diabetes (T1D) with different residual beta cell functions remain poorly elucidated. The study aimed to investigate the relationship between glucagon secretion and C-peptide levels and to explore the relationship between glucagon response and glucose increment in respond to a secretagogue in a steamed bread meal tolerance test (BMTT) in T1D. The study enrolled 43 adult patients with T1D and 24 healthy control subjects. Patients with T1D who underwent BMTT were divided into two groups based on peak C-peptide levels: C peptide low (CPL; C-peptide < 200 pmol/L; n=14) and high (CPH; C peptide ≥ 200 pmol/L; n=29). Plasma glucose, C-peptide, glucagon levels at 0, 30, 60, 120, and 180 min were measured. The glucagon response to the BMTT was defined by areas under the curve (AUC) as early (AUC0-30), late (AUC30-180), or total (AUC0-180) glucagon. Compared to healthy individuals, fasting plasma glucagon was lower and postprandial plasma glucagon level was increased in patients with T1D. Glucagon levels after BMTT between the CPL and CPH group showed significant group by time interaction. Peak glucagon and glucagon at 60-180 min, total and late glucagon response were higher in CPL than CPH group, while fasting glucagon and early glucagon response adjusted for glucose were comparable between CPL and CPH group. The higher late glucagon response and late glucagon response adjusted for glucose were associated with lower peak C-peptide in T1D. The higher late glucagon response and lower peak C-peptide were associated with the higher value of ▵glucose at 180 min. Stimulated C-peptide levels affect the paradoxical increase in postprandial glucagon secretion in patients with T1D, especially late glucagon response. The exaggerated postprandial glucagon secretion further stimulates the elevation of postprandial glucose in patients with T1D.