Low-frequency Values Research Articles

A multifunctional anticorrosive coating of hydroxyapatite platform based on metal-organic framework decoration with pH-responsive behavior

This study aimed to design a composite epoxy coating HZB/EP with pH-responsive behavior by grafting different material functions. In this approach, ZIF-8 particles were self-assembled on the surface of hydroxyapatite (HAp) through in situ growth, followed by encapsulation of the corrosion inhibitor BTA. Scanning electron microscopy (SEM) analysis of the coating section revealed a significant improvement in the dispersion of HZB in the resin compared to hydroxyapatite (HAp), resulting in a notable reduction in coating defects upon the addition of HZB. Electrochemical impedance spectroscopy (EIS) tests demonstrated that HZB/EP maintained a high low-frequency impedance value even after immersion in a 3.5% NaCl solution for 40 days, exhibiting an impedance magnitude 4–5 orders of magnitude higher than Pure EP. Additionally, scratch and salt spray tests validated the release and action process of the corrosion inhibitor BTA. This study presents a novel strategy for the development of multifunctional anticorrosive coatings.

A GIS based Morphometric Analysis of Thamirabarani River Basin, Tuticorin district, Tamilnadu, India, using CARTOSAT-1 DEM Data and ArcGIS

Due to its use in numerous geological and biological contexts, morphometric analysis has drawn more attention in recent years. It offers perception into process-associated modifications together with catchment assessment, runoff, infiltration, watershed development, natural and structural frameworks. Study of the Thamirabarani river is composed of Achaean crystalline rocks in the west and tertiary and quaternary sedimentary rocks on the east coast. In the current work, a morphometric analysis of the Thamirabarani river was performed to describe the various surface processes that cut the watershed into the river topography. Catchments were defined using Cartosat data and Arc GIS 10.4.1. This study shows that the stream varied from 1 to 5 (I-357, II-89, III-21, IV-9 and V-3) orders. According to the mean bifurcation ratio, the stream is topographical and complex regulated in its shallower parts. The analyzed basin's high permeability is explained by the studied basin's low current frequency values. Plate erosion rather than channel erosion can be seen in overland flow lengths (>0.14) and rough textures can be seen in drainage patterns. Asymmetric and extended basins with neotectonic activity are indicated by analysis of measured parameters using morphometry. Therefore, various interpretations are produced based on morphometric test of the Thamirabarani stream system to help provide information pertinent to social benefits.

Potential association of neutrophil extracellular traps with cognitive impairment in cerebral small vessel disease.

No acceptable biomarker can facilitate the early identification of cognitive impairment associated with cerebral small vessel disease (CSVD) in the older persons. The neutrophil extracellular traps (NETs) in the inflammation response of circulatory and central systems are essential in destroying the blood-brain barrier. The present study aims to explore the potential associations of plasma NETs with cognitive performance in CSVD. We recruited 146 CSVD patients and 66 healthy controls (HCs), and comprehensive neuropsychological assessments and multimodal magnetic resonance imaging were conducted. Three NETs markers, viz., citrullination of histone H3, neutrophil elastase-DNA, and myeloperoxidase (MPO)-DNA, and four oxidative stress-related indexes in plasma samples were measured. The plasma levels of three NETs markers were more significantly elevated in CSVD patients than in HCs. Significant correlations of the three NETs markers were observed with multiple cognitive domain scores. Furthermore, higher plasma MDA and NETs levels were significantly associated with the worse Montreal Cognitive Assessment scores among CSVD patients. Moreover, plasma MPO-DNA levels significantly mediated the effect of the amplitude of low-frequency fluctuation value within the bilateral caudate and the scores of global cognitive function, executive function, and information processing speed. Additionally, a panel of three NETs markers had the highest area under the curve value to distinguish the cognitively impaired CSVD patients from HCs and non-impaired ones. Therefore, plasma NETs may be potential biomarkers for early diagnosis of CSVD-related cognitive impairment. Activated lipid peroxidation in circulation and impaired caudate function support potential associations of plasma NETs in cognitively impaired CSVD patients.

Test-retest reliability of fNIRS in resting-state cortical activity and brain network assessment in stroke patients.

Resting-state functional near infrared spectroscopy (fNIRS) scanning has attracted considerable attention in stroke rehabilitation research in recent years. The aim of this study was to quantify the reliability of fNIRS in cortical activity intensity and brain network metrics among resting-state stroke patients, and to comprehensively evaluate the effects of frequency selection, scanning duration, analysis and preprocessing strategies on test-retest reliability. Nineteen patients with stroke underwent two resting fNIRS scanning sessions with an interval of 24 hours. The haemoglobin signals were preprocessed by principal component analysis, common average reference and haemodynamic modality separation (HMS) algorithm respectively. The cortical activity, functional connectivity level, local network metrics (degree, betweenness and local efficiency) and global network metrics were calculated at 25 frequency scales × 16 time windows. The test-retest reliability of each fNIRS metric was quantified by the intraclass correlation coefficient. The results show that (1) the high-frequency band has higher ICC values than the low-frequency band, and the fNIRS metric is more reliable than at the individual channel level when averaged within the brain region channel, (2) the ICC values of the low-frequency band above the 4-minute scan time are generally higher than 0.5, the local efficiency and global network metrics reach high and excellent reliability levels after 4 min (0.5 < ICC < 0.9), with moderate or even poor reliability for degree and betweenness (ICC < 0.5), (3) HMS algorithm performs best in improving the low-frequency band ICC values. The results indicate that a scanning duration of more than 4 minutes can lead to high reliability of most fNIRS metrics when assessing low-frequency resting brain function in stroke patients. It is recommended to use the global correction method of HMS, and the reporting of degree, betweenness and single channel level should be performed with caution. This paper provides the first comprehensive reference for resting-state experimental design and analysis strategies for fNIRS in stroke rehabilitation.

An Influence of Parameters of the Control Signal of Power LEDs on Their Junction Temperature and Emitted Light

This article presents the method of implementation and the results of experimental investigations illustrating an influence of parameters of the signal controlling the current flowing through power LEDs on their junction temperature and on parameters characterizing the light emitted by them. The measurement system used and the tested power LEDs are described. The results of measurements of the junction temperature of the tested devices, the values of the average value of the power dissipated in the tested devices and the photometric and radiometric parameters of these devices obtained for different values of frequency and the duty cycle of the signal controlling the current flowing through the tested diodes are presented and discussed. It is shown that the operation of the considered semiconductor devices is more effective at low frequency values. The possibility of adjusting the optical parameters of the power LEDs in the considered range of frequency and the duty cycle adjustment is assessed. Additionally, the measured waveforms of the current supplying the tested LEDs is shown. The influence of the parasitic capacitances of the tested devices is discussed. On the basis of the obtained investigation results, some recommendations for the designers of lighting systems can be formulated. In order to obtain an almost linear dependence of the illuminance on the duty cycle, the values of frequency not exceeding 10 kHz should be used.

Intermediate-layer strengthened superhydrophobic coating with stable corrosion resistance, delayed icing and long-term weatherability

Improving the mechanical stability and anti-corrosion durability of superhydrophobic material remains a great challenge that has not been solved. In this paper, we designed and prepared two types of superhydrophobic coatings using PTFE nanoparticles and waterborne epoxy resin, viz. superhydrophobic PTFE@epoxy single layer coating and superhydrophobic Epoxy + PTFE@epoxy double layer coating. It was found that the mechanical stability and interfacial bonding of the superhydrophobic composite coatings were further improved by introducing an epoxy resin intermediate layer. The superhydrophobic Epoxy + PTFE@epoxy double layer coating maintained excellent non-wetting superhydrophobicity even after 150 sandpaper abrasion and 160 tape-peeling cycles. The electrochemical testing results showed that the Rct and low-frequency modulus values of the superhydrophobic double layer coating improved by 7–8 orders of magnitude compared with the bare Q235 carbon steel substrate, demonstrating excellent corrosion resistance. In addition, the coating maintains good corrosion protection after 60 days of outdoor atmospheric exposure and 30 days of neutral salt spray acceleration tests, indicating superior weathering resistance and long-term anti-corrosion properties. The coating also features delayed icing, self-cleaning, anti-fouling, chemical stability, and high substrate applicability, which provides long-lasting multifunctional superhydrophobic materials with comprehensive functions.

Raveling out the effect of Pr3+ ions substitution on different properties of nano-sized hexagonal ferrites

The development of a new stable phase/type, a rare earth element Pr3+ substitution in Ca2-xPrxFe8O14 (T-type) of hexagonal ferrites with composition (x = 0.0, 0.02, 0.06, 0.1), using the sol–gel auto-combustion method was endeavoured in the current study. The x-ray diffraction analysis proved that all samples possess single-phase structures. All computed structural characteristics varied with Pr3+ substitution. The particles with random shapes and sizes were examined from TEM analysis and particle sizes ranged from 14 to 44 nm. With Pr-contents, the saturation and remanent magnetization increased and the coercivity decreased. All samples have high values of dielectric loss, dielectric constant, and tangent loss at low-frequency values and these high values declined with rising frequency. The peaks in real part of the electric modulus migrated toward the low-frequency region; it was the confirmation that grain boundaries are incredibly active to participate in resistance. The uneven trend in the imaginary part of the electric modulus, which is demised with increasing frequency and peaks, was described by the Sillars model. The band gap (Eg) of the samples reduced linearly from 4.60 to 4.32 eV with the addition of Pr3+ ions, as observed from the UV–visible absorbance spectra. The polarization vs electric field (P-E) loops of synthesized samples displayed lossy behavior and this loosy behavior decreased with Pr-additives. On the basis of properties exhibited by the present synthesized T-type hexagonal ferrites, it can be hoped that these materials are applicable in high-frequency devices, antenna, radar applications, and opto-magneto applications.

Durable self-healing coating system based on pH-responsive core-shell nanostructures

A critical access to high-efficiency anti-corrosion coatings is adding pH-responsive nanocontainers encapsulated with corrosion inhibitors into epoxy resin as it endows the composite coating with significant active long-term corrosion protection. Here, two self-healing coating systems (I-PBZ-EP and II-PBZ-EP) were constructed based on epoxy coating (EP) and benzotriazole-loaded zeolitic imidazolate framework (ZIF-8) encapsulated with polydopamine (PDA) by one-pot and two-pot methods, respectively. Electrochemical impedance spectroscopy (EIS) investigation shows that the low-frequency impedance modulus value (|Z|0.01Hz) of I-PBZ-EP still reaches 2.16 × 1010 Ω·cm2 which is the highest among all the coatings after 35 d of immersion. |Z|0.01Hz of the scratched I-PBZ-EP is 1.10 × 105 Ω·cm2 after 13 h of immersion in 3.5 wt% NaCl solution, which far surpasses |Z|0.01Hz of the scratched II-PBZ-EP, exhibiting its excellent self-healing properties. This is because I-PBZ can release more benzotriazole (BTA) (22.5 mg/L and 13.4 mg/L) than II-PBZ (15.8 mg/L and 9.4 mg/L) under acidic and basic conditions to repair the micro-defects. In short, by changing the loading mode of corrosion inhibitors, I-PBZ-EP with a simpler synthesis method manages to provide the long-term anticorrosion protection for the carbon steel substrate.

Characteristics of amplitude of low-frequency fluctuations in the resting-state functional magnetic resonance imaging of alcohol-dependent patients with depression.

The high comorbidity of alcohol use disorder and depressive disorder is associated with poor patient prognosis. The mechanisms underlying this comorbidity, however, are largely unknown. By applying the amplitude of low-frequency fluctuations parameter in resting-state functional magnetic resonance imaging, this study investigated changes in the brain functioning of alcohol-dependent patients with and without depression. Alcohol-dependent patients (n = 48) and healthy controls (n = 31) were recruited. The alcohol-dependent patients were divided into those with and without depression, according to Patients Health Questionnaire-9 scores. Amplitude of low-frequency fluctuations in resting-state brain images were compared among the alcohol-dependent patients with depression, alcohol-dependent patients without depression, and healthy controls groups. We further examined associations between amplitude of low-frequency fluctuations alterations, alcohol-dependence severity, and depressive levels (assessed with scales). Compared with the healthy controls group, both alcohol groups showed amplitude of low-frequency fluctuations enhancement in the right cerebellum and amplitude of low-frequency fluctuations abatement in the posterior central gyrus. The alcohol-dependent patients with depression group had higher amplitude of low-frequency fluctuations in the right cerebellum than the alcohol-dependent patients without depression group. Additionally, we observed a positive correlation between amplitude of low-frequency fluctuations value and Patients Health Questionnaire-9 score in the right superior temporal gyrus in the alcohol-dependent patients with depression group. Alcohol-dependent subjects showed abnormally increased spontaneous neural activity in the right cerebellum, which was more significant in alcohol-dependent patients with depression. These findings may support a targeted intervention in this brain location for alcohol and depressive disorder comorbidity.

The effect of cranial techniques on the heart rate variability response to psychological stress test in firefighter cadets

Heart rate variability (HRV) is a simple tool to monitor cardiovascular stress. The proper function of the cardiovascular system is a problem among firefighters. Physical activity has health benefits correlated with psychological stress. Physically active people should be more resilient to psychological stress, but this has not always been demonstrated. The aim of this study was to determine whether cranial techniques would have an effect on HRV parameters. Osteopathy in the cranium reduces stress and improves cardiovascular function. Fifty-seven firefighter cadets aged 18–24 years (21.63 ± 1.41) participated in the study. All subjects had their heart rate variability measured and were randomly assigned either to the cranial techniques (CS) group, with therapy performed once a week for 5 weeks), or to the control group (CO). After 5 weeks, heart rate variability was measured again in both groups. In the Friedman test, in the CS group there was a statistically significant effect of cranial techniques on Heart Rate (HR) and Low Frequency (LF), but not on High Frequency (HF); in the CO group, a statistically significant difference was observed for HR, HF and LF. In the Nemenyi test, in the CS group there was a statistically significant difference for HR and LF and in the CO group for HR, HF and LF. After applying hierarchical clustering with Euclidean measure and the complete method, dendrograms were drawn up showing similarities for HR, HF and LF values. The cranial techniques and touch might exert a beneficial effect on HRV. Both factors can be used in stressful situations to lower HRV.

Abnormal amplitude of low-frequency fluctuation values as a neuroimaging biomarker for major depressive disorder with suicidal attempts in adolescents: A resting-state fMRI and support vector machine analysis.

Major depressive disorder (MDD) is associated with suicidal attempts (SAs) among adolescents, with suicide being the most common cause of mortality in this age group. This study explored the predictive utility of support vector machine (SVM)-based analyses of amplitude of low-frequency fluctuation (ALFF) results as a neuroimaging biomarker for aiding the diagnosis of MDD with SA in adolescents. Resting-state functional magnetic resonance imaging (rs-fMRI) analyses of 71 first-episode, drug-naive adolescent MDD patients with SA and 54 healthy control individuals were conducted. ALFF and SVM methods were used to analyze the imaging data. Relative to healthy control individuals, adolescent MDD patients with a history of SAs showed reduced ALFF values in the bilateral medial superior frontal gyrus (mSFG) and bilateral precuneus. These lower ALFF values were also negatively correlated with child depression inventory (CDI) scores while reduced bilateral precuneus ALFF values were negatively correlated with Suicidal Ideation Questionnaire Junior (SIQ-JR) scores. SVM analyses showed that reduced ALFF values in the bilateral mSFG and bilateral precuneus had diagnostic accuracy levels of 76.8% (96/125) and 82.4% (103/125), respectively. Adolescent MDD patients with a history of SA exhibited abnormal ALFF. The identified abnormalities in specific brain regions may be involved in the pathogenesis of this condition and may help identify at-risk adolescents. Specifically, reductions in the ALFF in the bilateral mSFG and bilateral precuneus may be indicative of MDD and SA in adolescent patients.

Association of coronary artery calcium with heart rate variability in the Brazilian Longitudinal Study of Adult Health - ELSA-Brasil

Current data shows that the autonomic and vascular systems can influence each other. However, only a few studies have addressed this association in the general population. We aimed to investigate whether heart rate variability (HRV) was associated with coronary artery calcium (CAC) in a cross-sectional analysis of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil). We examined baseline data from 3138 participants (aged 35 to 74 years) without previous cardiovascular disease who underwent CAC score assessment and had validated HRV recordings. Prevalent CAC was defined as a CAC score>0, and HRV analyses were performed over 5-min segments. We detected CAC score>0 in 765 (24.4%) participants. Subgroup analyses in older participants (≥49 years) adjusted for sociodemographic and clinical variables revealed that CAC score>0 was associated with lower values of standard deviation of NN intervals (SDNN) (odds ratio [OR]=1.32; 95%CI: 1.05,1.65), root mean square of successive differences between adjacent NN intervals (RMSSD) (OR=1.28; 95%CI: 1.02,1.61), and low frequency (LF) (OR=1.53, 95%CI: 1.21,1.92). Interaction analysis between HRV indices and sex in age-stratified groups revealed significant effect modification: women showed increased OR for prevalent CAC in the younger group, while for men, the associations were in the older group. In conclusion, participants aged ≥49 years with low SDNN, RMSSD, and LF values were more likely to present prevalent CAC, suggesting a complex interaction between these markers in the pathogenesis of atherosclerosis. Furthermore, our results suggested that the relationship between CAC and HRV might be sex- and age-related.

ИССЛЕДОВАНИЯ ВЛИЯНИЯ ЧАСТОТЫ ВРАЩЕНИЯ ЭЛЕКТРОДА НА ТОЛЩИНУ ЭЛЕКТРОИСКРОВЫХ ПОКРЫТИЙ ПРИ РАЗЛИЧНЫХ РЕЖИМАХ ЭЛЕКТРОИСКРОВОЙ ОБРАБОТКИ ПОВЕРХНОСТЕЙ

The article presented actual problems studies of the thickness of electro spark coatings depending on the specified processing modes of the electro spark installation with a change in the frequency of rotation of the electrode. We propose to optimize the values of the parameters of the electro spark installation model SZ-8100, current frequency, current cycle pulse duration and frequency of rotation of the electrode to increase the thickness of the electro spark coating. As a result of experimental studies, the following results were obtained: the most thickness of the electro spark build up obtained at a pulse duration timp = 100 microseconds, voltage U = 60V, current frequency f = 300 Hz, at an electrode rotation frequency n = 260 min–1 and it is 1.88 mm (along the roughness vertices). In experimental studies, it was found that the current frequency parameter has a significant effect on the temperature regime of heating the surfacing electrode. Electro erosive destruction of particles by an electro spark processing, with an increase in the current frequency parameter, occurs. An increase in the pulse duration timp from 50 microseconds to 100 microseconds contributed to an increase in the thickness of the electro spark build up by 0.84 mm. It was found that in the case of an increase in the rotation frequencies of the electrode on the electrode holder, the tops of the formed electro spark grind polished, cooled faster and the thicknesses of electro spark coatings obtained with lower productivity. The smallest thicknesses of the electro spark build up formed at low values of the current frequency at f = 50 Hz, in both modes of the current duty cycle timp = 50 microseconds, timp = 100 microseconds and the formation of the thickness of the electro spark build up in the aisles varies from 0.04 mm to 0.45 mm. This study will help to choose the optimal values of the parameters of the electro spark installation, and increase the productivity of the process obtaining an effective thickness of the electro spark coating.

Cardiovascular autonomic responses in reproductive and post-menopausal women

Background: Autonomic responses are a sensitive indicator for assessing balance in sympatho-vagal system. Many studies have shown an increased response in the sympathetic system in post-menopausal women. Alteration in autonomic nerve function causes an increased incidence of hypertension, arrhythmias, or acute coronary syndrome. Thus, this study aims to find out the heart rate variability (HRV) among reproductive and post-menopausal women. Aims and Objectives: The aim of the study was to compare the cardiovascular autonomic responses among reproductive and post-menopausal women. Materials and Methods: This cross-sectional study was conducted in the department of physiology at government medical college, Kottayam on 40 reproductive and 40 post-menopausal women. Using PHYSIOPAC-PP4 (Medicaid Systems Chandigarh) machine, an electrocardiogram was recorded in both groups in the supine position for 5 min. The frequency and time domain data obtained were analyzed using SPSS software. Results: The mean age group in reproductive women was 43 and post-menopausal women was 54. In the power spectrum analysis of HRV parameters the mean value of frequency domain Low frequency (LF) in reproductive women was 72.05 (S.D = 5.706) and post-menopausal women was 79.48 (S.D = 3.789). The high frequency (HF) in reproductive women was 28 (S.D = 5.588) and post-menopausal women were 20.53 (S.D = 3.789). The LF/HF ratio mean value obtained in reproductive women was 2.723 (S. D = 0.759) and post–menopausal was 3.992 (S.D 0.785). In the various time domain parameters, we estimated the mean value of the root mean square of successive differences (RMSSD) between normal heartbeats RMSSD and obtained the value in reproductive women as 25.05 (S.D = 11.88) and post-menopausal women as 12.68 (S.D = 5.535). The RR interval triangular index mean value in reproductive women was 0.0520 (S.D = 0.013) and post-menopausal women were 0.0345 (S.D = 0.01). In all these parameters, the P-value was found to be &lt;0.001, so statistically highly significant. Conclusion: In this study, higher values in time domain and frequency domain parameters for assessing sympathetic functions were seen in postmenopausal women when compared to women of the reproductive age group which was statistically significant. This may be due to age and hormonal influences. The power spectrum analysis of HRV parameters was proved to be a noninvasive method to assess the sympathovagal balance in the study group of women.

In situ consideration of resistance of bridge girder according to EC2 with AEM

The paper presents a case study of a considerably cracked and degraded bridge in Slovenia: with the implementation of in-situ measurements under bending and shear and the use of a nondestructive acoustic emission technique. Despite the existing crack system, the latter was able to detect microstructural changes. These were characterised by low values of average frequency (AF), as well as lower values of the rise time-amplitude ratio (RA), and energy. A correlation between shear capacity and acoustic activity was observed. This promises to expand the use of AE in the process of assessing of the load-bearing capacity of existing concrete structures.

Резервы уменьшения затрат на эксплуатацию автомобиля

Relevant are studies to identify reserves to reduce the cost of car ownership, one of which is to minimize the cost of operation, and, in particular, maintenance. The aim of the study is to reduce the cost of car ownership by reducing the unit cost of maintenance based on a scientifically based increase in the frequency and choice of consumables. A particular task within the framework of this article is to establish the patterns of formation of unit costs for car maintenance and to analyze the impact on them of the frequency and cost of engine oil. A detailed analysis of the cost structure for the maintenance of a truck was carried out using the example of the KAMAZ 5490 NEO brand with two frequency values – regulated 60 thousand km and increased 80 thousand km. It has been established that such an increase in frequency reduces unit costs by 21,6% (by 331 rubles/1000 km). The results of studies confirming the proportional dependence of the cost of engine oil on its quality, which determines the replacement period, are presented. By modeling, the dependences of the unit costs for the maintenance of a truck on the example of the KAMAZ 5490 NEO brand on the frequency and cost of one liter of oil were obtained. It has been established that the strategy with the use of flexible oil cost (depending on frequency) compared to a fixed cost (independent of frequency) gives a noticeable effect (up to 190 rubles / 1000 km or 10,2%) in the area of lower values of frequency, where the indicator «price – quality» of oil is used. It is concluded that the reserve for reducing operating costs, and, consequently, the cost of owning a car, is an increase in the frequency of maintenance, bringing it closer to the average annual mileage, and a rational choice of motor oils, taking into account the replacement period and cost. Of scientific and practical interest are further studies of the regularities of the influence of various factors on the value of the frequency of maintenance, the definition of restrictions on its increase, the effect of an increase in the frequency on the cost of owning a car and the efficiency of its commercial operation.

Effect of low frequency oscillations during milking on udder temperature and welfare of dairy cows

The study aimed to investigate the effect of low-frequency oscillations on the cow udder, milk parameters, and animal welfare during the automated milking process. The study's objective was to investigate the impact of low-frequency oscillations on the udder and teats' blood circulation by creating a mathematical model of mammary glands, using milkers and vibrators to analyze the theoretical dynamics of oscillations. The mechanical vibration device developed and tested in the study was mounted on a DeLaval automatic milking machine, which excited the udder with low-frequency oscillations, allowing the analysis of input parameters (temperature, oscillation amplitude) and using feedback data, changing the device parameters such as vibration frequency and duration. The experimental study was performed using an artificial cow's udder model with and without milk and a DeLaval milking machine, exciting the model with low-frequency harmonic oscillations (frequency range 15-60 Hz, vibration amplitude 2-5 mm). The investigation in vitro applying low-frequency of the vibration system's first-order frequencies in lateral (X) direction showed the low-frequency values of 23.5-26.5 Hz (effective frequency of the simulation analysis was 25.0 Hz). The tested values of the first-order frequency of the vibration system in the vertical (Y) direction were 37.5-41.5 Hz (effective frequency of the simulation analysis was 41.0 Hz), with higher amplitude and lower vibration damping. During in vivo experiments, while milking, the vibrator was inducing mechanical milking-similar vibrations in the udder. The vibrations were spreading to the entire udder and caused physiotherapeutic effects such as activated physiological processes and increased udder base temperature by 0.57°C (p < 0.001), thus increasing blood flow in the udder. Used low-frequency vibrations did not significantly affect milk yield, milk composition, milk quality indicators, and animal welfare. The investigation results showed that applying low-frequency vibration on a cow udder during automatic milking is a non-invasive, efficient method to stimulate blood circulation in the udder and improve teat and udder health without changing milk quality and production. Further studies will be carried out in the following research phase on clinical and subclinical mastitis cows.

Analisis Karakteristik Akustik Dan Dinamik Micro-Perforated Panel Dengan Struktur Honeycomb Mengunakan FEM

This study focuses on the discussion of the correlation of acoustic and dynamic characteristics of hybrid panels, namely Micro-perforated Panel (MPP) and Honeycomb (HC) structures. Acoustic characteristics in experimental studies are obtained by the sound absorption coefficient and Sound Transmission Loss. Meanwhile, the dynamic characteristics are obtained by the mode and frequency response analysis of numerical simulation methods. The results of these two characteristics serve as a benchmark for the development of experimental data studies/analysis. The purpose of this study is to obtain dynamic characteristics using mode and frequency response analysis through the finite element method. The development of this experimental study/analysis data is to overcome the drawbacks of experimental testing. The weakness obtained from experimental studies is that the stages are complicated and require a very large amount of money. The method in this study was carried out by numerical simulation using the finite element method using the Ansys 2019 R3 program. The results of this study obtained dynamic characteristics from the development of experimental study analysis methods using numerical simulations through the finite element method. Numerical simulation on the hybrid panel provides efficiency at the experimental testing stage. The results of the mode and frequency response analysis obtained by numerical simulation methods have similarities in the frequency range of high and low frequency values of sound absorption coefficient and soundtransmission loss.

FEATURES AND POSSIBILITIES OF BLOOD BIOIMPEDANCEMETRY

The bioimpedancemetry has long been used to determine some blood parameters used in laboratory diagnostics. Due to the specificity of blood as a liquid disperse substance, its electrical conductivity is directly related to the relative volume of the non-conductive phase, that is, erythrocytes, and therefore, the bioimpedancemetry method is used to determine hematocrit. The ambiguity of the results in determining the frequencies corresponding to the achievement of the limiting value of the high-frequency electrical conductivity of the blood, as well as the patterns that connect the high-frequency electrical conductivity of the blood with the electrical conductivity of the plasma and erythrocytes, demonstrate the urgent need for additional research. The purpose of the study was to determine the features of the frequency dependence of the blood bioimpedance modulus with the values of hematocrit and blood plasma bioimpedance modulus in order to establish the capabilities of the blood bioimpedancemetry method as a whole. The frequency dependence of its bioimpedance was determined on 16 blood samples from healthy donors. For each blood sample, the frequency dependence of the bioimpedance of whole blood was taken, then the plasma formed after erythrocyte sedimentation in a vertically installed test tube. The impedance modulus was measured in the frequency range from 10 kHz to 10 megahertz. The optimal frequency of 5 megahertz was determined, at which the limiting high-frequency value of blood electrical conductivity is reached, which makes it possible to determine the electrical conductivity of the erythrocyte cytoplasm. An expression is obtained for high-frequency electrical conductivity as a function of the electrical conductivity of plasma, cytoplasm and relative hematocrit. It is shown that the measurement of low-frequency (up to 100 kilohertz) and high-frequency values of blood electrical conductivity, as well as plasma electrical conductivity, also makes it possible to determine the hematocrit and the electrical conductivity of the erythrocyte cytoplasm. An equation was obtained that relates the hematocrit index to the ratio of high-frequency and low-frequency values of blood electrical conductivity, which makes it possible to determine the true hematocrit of human blood in vitro. Thus, the measurement of low-frequency and high-frequency electrical conductivity of blood and the measurement of electrical conductivity of plasma make it possible to determine not only the hematocrit index, but also the electrical conductivity of the cytoplasm of cells in one blood sample. The work proves the practical possibility of determining the complex of electrophysical parameters of a native blood sample while maintaining their real values.

Epoxy primer topcoat syncretic coating prepared by using modified graphene oxide incorporated with TiO2 nanoparticles

A novel epoxy primer topcoat syncretic coating with superior corrosion resistance and weathering resistance was developed by using modified graphene oxide incorporated with TiO2 nanoparticles as effective fillers. Compared with pure epoxy resin coating, the corrosion products around scratches of epoxy primer topcoat syncretic coatings were significantly reduced after salt spray testing for 300 h, and the highest wet adhesion and the minimum adhesion loss rate of it were 1.73 MPa and 36.63%, respectively. After ultraviolet-accelerated aging for 20 d, the low-frequency impedance modulus value was 7.27 × 108, which was increased about one order of magnitude than pure epoxy resin coating. In addition, the lowest self-corrosion current density was 31.705 pA·cm–2, and the lowest corrosion rate is 14.56 mpy. These interesting features could make the epoxy primer topcoat syncretic coating as a promising anti-corrosion coating for metallic long-term protection.