Since heart rate variability (HRV) is associated with average heart rate (HR) and respiratory rate (RespRate), alterations in these parameters may impose changes in HRV. Hence the repeatability of ...HRV measurements may be affected by differences in HR and RespRate. The study aimed to evaluate HRV repeatability and its association with changes in HR and RespRate.
Forty healthy volunteers underwent two ECG examinations 7 days apart. Standard HRV indices were calculated from 5-min ECG recordings. The ECG-derived respiration signal was estimated to assess RespRate. To investigate HR impact on HRV, HRV parameters were corrected for prevailing HR.
Differences in HRV parameters between the measurements were associated with the changes in HR and RespRate. However, in multiple regression analysis only HR alteration proved to be independent determinant of the HRV differences-every change in HR by 1 bpm changed HRV values by 16.5% on average. After overall removal of HR impact on HRV, coefficients of variation of the HRV parameters significantly dropped on average by 26.8% (p < 0.001), i.e., by the same extent HRV reproducibility improved. Additionally, the HRV correction for HR decreased association between RespRate and HRV.
In stable conditions, HR but not RespRate is the most powerful factor determining HRV reproducibility and even a minimal change of HR may considerably alter HRV. However, the removal of HR impact may significantly improve HRV repeatability. The association between HRV and RespRate seems to be, at least in part, HR dependent.
The reliability of handgrip strength (HGS) measurement has been confirmed in adults but has been sparsely addressed in pediatric populations. The aims of this study are twofold: to determine whether ...sex, age and/or hand-dominance influence the test-retest differences and to establish the reliability level of the HGS measurement in typical developing pediatric participants. A total of 338 participants aged 7-13 years were tested using a digital handgrip strength (HGS) dynamometer (Jamar Plus+ Dynamometer) by the same rater on two testing trials separated by a one-day interval between sessions. The HGS testing was conducted according to the American Society of Hand Therapists recommendations. Relative and absolute reliability statistics were calculated. Age influenced the test-retest difference of the HGS measurement as children compared to preadolescents had lower intraclass correlation coefficients (0.95 vs. 0.98), standard error of measurement (SEM) (0.74 vs. 0.78 kg), smallest detectable difference (SDD) (2.05 vs. 2.16 kg) and higher values of the percentage value of SEM (5.48 vs. 3.44%), normalized SDD (15.52 vs. 9.61%) and a mean difference between the test and retest values (0.50 vs. 0.02 kg) for the dominant hand. The results indicate that the protocol using the Jamar digital handgrip dynamometer is a reliable instrument to measure HGS in participants aged 7-13 years with typical development. Clinicians and researchers therefore can have confidence in determining the minimally clinical effect for HGS.
The present study provides a deep insight into the implications of sulphate addition on glass forming properties of materials from the SiO
2
–P
2
O
5
–K
2
O–MgO/CaO/MgOCaO systems, by combining: ...preliminary investigation of as-synthesized materials (XRD, XRF, SEM–EDS), detailed characteristics of their thermal behaviour (DSC), estimation of various glass-stability parameters, in-depth analysis of the course of crystallization and an identification of the crystallized products (XRD, Raman imaging technique). Performed investigations revealed that obtaining amorphous materials is only possible in the system containing MgO as a alkaline earth glass modifier, whereas melts of other tested compositions display high tendency to crystallize during cooling. Thermal investigation showed that the influence of SO
3
addition on thermal properties of studied materials strongly depends on their composition, but generally such additive increased values of glass transformation temperature and decreased vitreous state transformation range and onset of the crystallization process, compared to the base samples, which is a signal of decrease in thermal stability. Examination of devitrificates revealed the character and distribution of domains present in the structure of studied materials. It was showed that irrespective of composition of the base glass, it is K
2
SO
4
that precipitates once the sulphate capacity of glass is exceeded and exists in the studied materials as groupings either distributed in the voids of silicate phase, or surrounding the remnants of the gas bubbles embodied within the glass body. The results demonstrated in the present study provide guiding suggestions for development of SO
3
-containing silicate–phosphate glasses intended especially for applications where release of bioactive ions is sought.
Heart rate variability (HRV) analysis is a clinical tool frequently used to characterize cardiac autonomic status. The aim of this study was to establish normative values for short-term HRV ...parameters by considering their main determinants in school-aged children.
Five-minute electrocardiograms were taken from 312 non-athlete children (153 boys) at age of 6 to 13 years for computation of conventional time- and frequency-domain HRV parameters. Heart rate (HR), respiratory rate, age, body mass index, and sex were considered as their potential determinants. Multiple regression analysis revealed that HR was the principal predictor of all standard HRV indices. To develop their universal normative limits, standard HRV parameters were corrected for prevailing HR.
The HRV correction for HR yielded the parameters which became independent on both sex and HR, and only poorly dependent on age (with small effect size). Normal ranges were calculated for both time- and frequency-domain indices (the latter computed with either fast Fourier transform and autoregressive method). To facilitate recalculation of standard HRV parameters into corrected ones, a calculator was created and attached as a Supplementary Material that can be downloaded and used for both research and clinical purposes.
This study provides HRV normative values for school-aged children which have been developed independently of their major determinants. The calculator accessible in the Supplementary Material can considerably simplify determination if HRV parameters accommodate within normal limits.
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•Novel Hf-MIL-140A metal–organic framework structure is synthesized via ultrasound irradiation.•Ultrasound irradiation allows to obtain phase-pure MIL-140A from mixture of ...UiO-66/MIL-140A.•Sonochemical synthesis route induces structural slit-like defects in the MIL-140A structure.•Sonochemical synthesis route increases BET-specific surface area in MIL-140A structure.
In this study, a sonochemical route for the preparation of a new Hf-MIL-140A metal–organic framework from a mixture of UiO-66/MIL-140A is presented. The sonochemical synthesis route not only allows the phase-pure MIL-140A structure to be obtained but also induces structural defects in the MIL-140A structure. The synergic effect between the sonochemical irradiation and the presence of a highly acidic environment results in the generation of slit-like defects in the crystal structure, which increases specific surface area and pore volume. The BET-specific surface area in the case of sonochemically derived Zr-MIL-140A reaches 653.3 m2/g, which is 1.5 times higher than that obtained during conventional synthesis. The developed Hf-MIL-140A structure is isostructural to Zr-MIL-140A, which was confirmed by synchrotron X-ray powder diffraction (SR-XRD) and by continuous rotation electron diffraction (cRED) analysis. The obtained MOF materials have high thermal and chemical stability, which makes them promising candidates for applications such as gas adsorption, radioactive waste removal, catalysis, and drug delivery.
Aluminum oxide is one of the most commonly used materials in the industry. It is used in the field of catalysis, refractories, and optics. Despite the fact that there are many techniques available, ...there is still a great challenge in obtaining a material with desired and designed properties. Nevertheless, there is a great flexibility in making customized alumina materials with desired physicochemical properties synthesized by sol-gel methods. This work consists in characterizing the physicochemical properties of sol-gel synthesized aluminum oxide using different sol-gel preparation routes. Three different sols were obtained by using organic precursors and underwent thermal treatment. The structure (Middle Infrared Spectroscopy, Diffused Reflectance Infrared Spectroscopy, X-ray Diffraction, Magic Angle Spinning Nuclear Magnetic Resonance) and microstructure (Scanning Electron Microscopy with Electron Dispersive Spectroscopy) tests of the materials were carried out. The specific surface area was determined by using the Brunauer-Emmett-Teller (BET) method. Thermal analysis was performed for all the powders, in order to analyze the specific temperature of materials transformation.
Nanocomposites developed based on siloxanes modified with carbon nanoforms are materials with great application potential in the electronics industry, medicine and environmental protection. This ...follows from the fact that such nanocomposites can be endowed with biocompatibility characteristics, electric conductivity and a high mechanical durability. Moreover, their surface, depending on the type and the amount of carbon nanoparticles, may exhibit antifouling properties, as well as those that limit bacterial adhesion. The paper reports on the properties of polysiloxane (PS) and carbon nanotubes (CNT) nanocomposite coatings on metal surfaces produced by the electrophoretic deposition (EPD). A comparison with coatings made of pure PS or pure CNT on the same substrates using the same deposition method (EPD) is provided. The coatings were examined for morphology and elemental composition (SEM, EDS), structural characteristics (confocal Raman spectroscopy), electrical conductivity and were tested for corrosion (electrochemical impedance spectroscopy-EIS, potentiodynamic polarization-PDP). The results obtained in this study clearly evidenced that such hybrid coatings conduct electricity and protect the metal from corrosion. However, their corrosion resistance differs slightly from that of a pure polymeric coating.
In this study, we present a modulated synthesis nanocrystalline defective UiO-66 metal-organic framework as a potential chloroquine diphosphate (CQ) delivery system. Increasing the concentration of ...hydrochloric acid during the modulated synthesis resulted in a considerable increase of pore volume, which enhanced the CQ loading in CQ@UiO-66 composites. Drug release tests for CQ@UiO-66 composites have confirmed prolonged CQ release in comparison with pure CQ. In vivo tests on a
model organism have revealed that CQ released from CQ@UiO-66 25% showed lower toxicity and fewer cardiotoxic effects manifested by cardiac malformations and arrhythmia in comparison to analogous doses of CQ. Cytotoxicity tests proved that the CQ loaded on the defective UiO-66 cargo resulted in increased viability of cardiac cells (H9C2) as compared to incubation with pure CQ. The experimental results presented here may be a step forward in the context of reducing the cardiotoxicity CQ.
Compounds of the silsesquioxane type are attractive material precursors. High molecular weights and well-defined structures predestine them to create ceramics with a controlled composition at the ...molecular level. New molecular precursors of ceramic materials with the ratio of Si:Ge = 7:1 atoms were obtained. The influence of organic substituents on the thermal decomposition processes of germasilsesquioxanes was investigated. Some of the structures obtained are characterized by a high non-volatile residue after the thermal decomposition process. The introduction of the germanium atom to the structure of the silsesquioxane molecular cage reduces the thermal stability of the obtained structures.
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