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1.
Environ Sci Technol ; 58(3): 1636-1647, 2024 Jan 23.
Article in English | MEDLINE | ID: mdl-38186056

ABSTRACT

Mine dust has been linked to the development of pneumoconiotic diseases such as silicosis and coal workers' pneumoconiosis. Currently, it is understood that the physicochemical and mineralogical characteristics drive the toxic nature of dust particles; however, it remains unclear which parameter(s) account for the differential toxicity of coal dust. This study aims to address this issue by demonstrating the use of the partial least squares regression (PLSR) machine learning approach to compare the influence of D50 sub 10 µm coal particle characteristics against markers of cellular damage. The resulting analysis of 72 particle characteristics against cytotoxicity and lipid peroxidation reflects the power of PLSR as a tool to elucidate complex particle-cell relationships. By comparing the relative influence of each characteristic within the model, the results reflect that physical characteristics such as shape and particle roughness may have a greater impact on cytotoxicity and lipid peroxidation than composition-based parameters. These results present the first multivariate assessment of a broad-spectrum data set of coal dust characteristics using latent structures to assess the relative influence of particle characteristics on cellular damage.


Subject(s)
Coal Mining , Occupational Exposure , Pneumoconiosis , Humans , Coal/analysis , Dust/analysis , Minerals
2.
Environ Geochem Health ; 45(10): 7363-7388, 2023 Oct.
Article in English | MEDLINE | ID: mdl-37131112

ABSTRACT

Exposure to dust from the mining environment has historically resulted in epidemic levels of mortality and morbidity from pneumoconiotic diseases such as silicosis, coal workers' pneumoconiosis (CWP), and asbestosis. Studies have shown that CWP remains a critical issue at collieries across the globe, with some countries facing resurgent patterns of the disease and additional pathologies from long-term exposure. Compliance measures to reduce dust exposure rely primarily on the assumption that all "fine" particles are equally toxic irrespective of source or chemical composition. For several ore types, but more specifically coal, such an assumption is not practical due to the complex and highly variable nature of the material. Additionally, several studies have identified possible mechanisms of pathogenesis from the minerals and deleterious metals in coal. The purpose of this review was to provide a reassessment of the perspectives and strategies used to evaluate the pneumoconiotic potency of coal mine dust. Emphasis is on the physicochemical characteristics of coal mine dust such as mineralogy/mineral chemistry, particle shape, size, specific surface area, and free surface area-all of which have been highlighted as contributing factors to the expression of pro-inflammatory responses in the lung. The review also highlights the potential opportunity for more holistic risk characterisation strategies for coal mine dust, which consider the mineralogical and physicochemical aspects of the dust as variables relevant to the current proposed mechanisms for CWP pathogenesis.


Subject(s)
Coal Mining , Occupational Exposure , Pneumoconiosis , Humans , Dust/analysis , Pneumoconiosis/epidemiology , Pneumoconiosis/etiology , Coal Mining/methods , Coal/toxicity , Coal/analysis , Minerals , Occupational Exposure/adverse effects
3.
Artif Organs ; 43(8): 796-805, 2019 Aug.
Article in English | MEDLINE | ID: mdl-30741435

ABSTRACT

There is ample evidence that maintenance of basic physical fitness through exercise training is crucial for patients with chronic renal insufficiency. Rehabilitation based on neuromuscular electrical stimulation (NMES) of thigh muscles has been shown to have many beneficial effects in patients with chronic diseases. It is likely that NMES could have beneficial effects also in patients on chronic ambulatory peritoneal dialysis (CAPD). NMES was applied for 20 weeks to 14 patients on CAPD, mean age 61.9 (8.7) years, using battery-powered stimulators (CEFAR-REHAB X2; Sweden) and self-adhesive electrodes 80 × 130 mm (PALS Platinum; Denmark). Stimulation characteristics: biphasic current, pulse width 400 µs, 8 seconds contraction-12 seconds relaxation, frequency modulation 40-60 Hz, and maximal intensity 60 mA. NMES was home-based and applied simultaneously to quadriceps muscles of both legs (2 × 30 min/day). Functional performance, muscle power (Fmax ), arterial stiffness (assessed by cardio-ankle vascular index-CAVI), and quality of life by KDQOL-SF evaluation was done at baseline and at the end of program. Home NMES improved significantly the main functional parameters: VO2peak /kg increased by +2.2 (1.6) mL O2 /kg/min (P < 0.002), peak workload by +0.1 (0.1) W/kg (P < 0.005), and distance walked in 6 MWT by +44.7 (58.4) m (P < 0.008). Only insignificant changes were observed in CAVI and Fmax . KDQOL-SF analysis showed significant improvement in seven parameters of QoL (P < 0.012-0.049). This pilot study is the first clinical report dealing with the use of NMES in patients on CAPD. The results demonstrate that an improvement of exercise capacity and QoL can be achieved by home-based NMES in CAPD patients.


Subject(s)
Electric Stimulation Therapy , Peritoneal Dialysis, Continuous Ambulatory , Quadriceps Muscle , Renal Insufficiency, Chronic/therapy , Aged , Electric Stimulation Therapy/methods , Exercise Tolerance , Female , Humans , Male , Middle Aged , Muscle Strength , Pilot Projects , Quadriceps Muscle/physiopathology , Quality of Life , Renal Insufficiency, Chronic/physiopathology , Vascular Stiffness , Walk Test
4.
Europace ; 20(7): 1107-1114, 2018 07 01.
Article in English | MEDLINE | ID: mdl-28575490

ABSTRACT

Aims: Complications of catheter ablation for atrial fibrillation (AF) are frequently related to vascular access. We hypothesized that ultrasound-guided (USG) venipuncture may facilitate the procedure and reduce complication rates. Methods and results: We conducted a multicentre, randomized trial in patients undergoing catheter ablation for AF on uninterrupted anticoagulation therapy. The study enrolled consecutive 320 patients (age: 63 ± 8 years; male: 62%) and were randomized to USG or conventional venipuncture in 1:1 fashion. It was prematurely terminated due to substantially lower-than-expected complication rates, which doubled the population size needed to maintain statistical power. While the complication rates did not differ between two study arms (0.6% vs. 1.9%, P = 0.62), intra-procedural outcome measures were in favour of the USG approach (puncture time, 288 vs. 369 s, P < 0.001; first pass success, 74% vs. 20%, P < 0.001; extra puncture attempts 0.5 vs. 2.1, P < 0.001; inadvertent arterial puncture 0.07 vs. 0.25, P < 0.001; unsuccessful cannulation 0.6% vs. 14%, P < 0.001). Though these measures varied between trainees (49% of procedures) and expert operators, between-arm differences (except for unsuccessful cannulation) were comparably significant in favour of USG approach for both subgroups. Conclusions: Ultrasound-guided puncture of femoral veins was associated with preferable intra-procedural outcomes, though the major complication rates were not reduced. Both trainees and expert operators benefited from the USG strategy. (www.clinicaltrials.gov ID: NCT02834221).


Subject(s)
Atrial Fibrillation/surgery , Catheter Ablation , Catheterization, Peripheral/methods , Femoral Vein/diagnostic imaging , Ultrasonography, Interventional , Aged , Atrial Fibrillation/diagnosis , Atrial Fibrillation/physiopathology , Catheter Ablation/adverse effects , Catheterization, Peripheral/adverse effects , Czech Republic , Early Termination of Clinical Trials , Female , Humans , Japan , Male , Middle Aged , Postoperative Complications/etiology , Punctures , Risk Factors , Time Factors , Treatment Outcome
5.
Cent Eur J Public Health ; 25(4): 326-331, 2017 Dec.
Article in English | MEDLINE | ID: mdl-29346858

ABSTRACT

OBJECTIVE: Obesity is a multifactorial disease. This non-infectious epidemic has reached pandemic proportions in the 21 century. Posture is a dynamic process referring to an active maintenance of body movement segments against the action of external forces. The aim of the study was to investigate the effect of comprehensive group therapy for obese persons on selected anthropometric and postural parameters. METHODS: The study comprised 53 females with a mean age of 44.5 years (range 29­65 years, standard deviation 9.42 years, median 44 years), who completed a controlled weight loss programme. At the beginning and at the end of the programme, anthropometric parameters (Body Mass Index (BMI), weight and waist circumference) were measured and the posturography tests Limits of Stability (LOS) and Motor Control Test (MCT) were performed using the NeuroCom's SMART EquiTest system. The data were statistically analyzed using R software at a level of significance of 0.05. RESULTS: There were positive changes after the controlled weight loss programme in anthropometric parameters (BMI reduction, with p<0.001; waist circumference reduction, with p<0.001; and weight loss, with p<0.001), postural stability with statistically significant (p<0.05) improvements in both postural activity (LOS test parameters) and reactions (MCT parameters). CONCLUSION: The study showed a statistically significant effect of comprehensive group therapy for obesity in terms of reductions in waist circumference, body weight and BMI, and thus the overall reduction of both cardiovascular and metabolic risks, as well as improved postural skills (activity and reactions).


Subject(s)
Anthropometry/methods , Obesity/therapy , Posture/physiology , Psychotherapy, Group/methods , Weight Reduction Programs/methods , Adult , Aged , Body Weight , Czech Republic , Female , Humans , Middle Aged , Obesity/physiopathology , Risk Factors , Treatment Outcome , Waist Circumference , Waist-Hip Ratio
6.
Artif Organs ; 40(12): 1137-1145, 2016 Dec.
Article in English | MEDLINE | ID: mdl-27005487

ABSTRACT

Histopathological analysis can provide important information in long-term experiments with total artificial heart (TAH). Recently, a new type of blood pump, the helical flow total artificial heart (HF-TAH) was developed. This study aimed to investigate the changes in selected vital organs in animal experiments with implanted HF-TAH. Samples from lung, liver, and kidneys from two female goats (No. 1301 and No. 1304) with implanted HF-TAH were analyzed. Tissue samples were fixed in 10% formaldehyde and 4 µm thick transverse sections were stained with hematoxylin-eosin (HE). Additional staining was done for detection of connective tissue (Masson-Goldner stain) and for detection of iron (hemosiderin) deposits (Perls stain). Sections were scanned at 100× and 500× magnification with a light microscope. Experiment no. 1301 survived 100 days (cause of termination was heavy damage of the right pump); experimental goat no.1304 survived 68 days and was sacrificed due to severe right hydrodynamic bearing malfunction. Histopathological analysis of liver samples proved signs of chronic venostasis with limited focal necrotic zones. Dilated tubules, proteinaceous material in tubular lumen, and hemosiderin deposits were detected in kidney samples. Contamination of the organs by embolized micro-particles was suspected at the autopsy after discovery of visible damage (scratches) of the pump impeller surface (made from titanium alloy) in both experiments. Sporadic deposits of foreign micro-particles (presumably titanium) were observed in most of the analyzed parenchymal organs. However, the described deposits were not in direct connection with inflammatory reactions in the analyzed tissues. Histopathological analysis showed the presence of minimal contamination of the lung, kidney, and liver tissue samples by foreign material (titanium very likely). The analysis showed only limited pathological changes, especially in liver and kidneys, which might be attributed to the influence of artificial perfusion often observed in chronic TAH experiments.


Subject(s)
Heart, Artificial , Kidney/pathology , Liver/pathology , Lung/pathology , Animals , Female , Goats , Heart, Artificial/adverse effects , Prosthesis Design , Prosthesis Implantation/adverse effects , Titanium/analysis
7.
Bioorg Med Chem ; 23(7): 1651-9, 2015 Apr 01.
Article in English | MEDLINE | ID: mdl-25737088

ABSTRACT

We report the design and synthesis of novel anticancer agents based on bis-hydrazones separated by a rigid Tröger's base skeleton. This novel approach combines a biologically active moiety (hydrazone) with this scaffold (Tröger's base) to construct DNA intercalators. Evaluation of the anticancer activity of these agents using seven cancer cell lines and two healthy cell lines found that several derivatives had potent anticancer activity and excellent selectivity indexes toward cancer cells. The antimicrobial activities were tested on a set of thirteen bacterial stains, but the prepared compounds were not active. Complexation studies using biologically important metal ions demonstrated that these compounds are able to bind Cu(2+), Fe(3+), Co(2+), Ni(2+) and Zn(2+). DNA intercalation studies showed that the compounds themselves do not interact with DNA, but their metallocomplexes do interact, most likely via intercalation into DNA.


Subject(s)
Antineoplastic Agents/chemical synthesis , Hydrazones/chemical synthesis , Antineoplastic Agents/pharmacology , Apoptosis/drug effects , Apoptosis/physiology , Drug Evaluation, Preclinical/methods , HCT116 Cells , Humans , Hydrazones/pharmacology , K562 Cells
8.
Tohoku J Exp Med ; 236(3): 199-207, 2015 07.
Article in English | MEDLINE | ID: mdl-26094568

ABSTRACT

Haloperidol is a neuroleptic drug used for a medication of various psychoses and deliria. Its administration is frequently accompanied by cardiovascular side effects, expressed as QT interval prolongation and occurrence of even lethal arrhythmias. Despite these side effects, haloperidol is still prescribed in Europe in clinical practice. Haloperidol binds to sigma receptors that are coupled with inositol 1,4,5-trisphosphate (IP3) receptors. Sigma receptors are expressed in various tissues, including heart muscle, and they modulate potassium channels. Together with IP3 receptors, sigma receptors are also involved in calcium handling in various tissues. Therefore, the present work aimed to study the effects of long-term haloperidol administration on the cardiac function. Haloperidol (2 mg/kg once a day) or vehiculum was administered by intraperitoneal injection to guinea pigs for 21 consecutive days. We measured the responsiveness of the hearts isolated from the haloperidol-treated animals to additional application of haloperidol. Expression of the sigma 1 receptor and IP3 receptors was studied by real time-PCR and immunohistochemical analyses. Haloperidol treatment caused the significant decrease in the relative heart rate and the prolongation of QT interval of the isolated hearts from the haloperidol-treated animals, compared to the hearts isolated from control animals. The expression of sigma 1 and IP3 type 1 and type 2 receptors was increased in both atria of the haloperidol-treated animals but not in ventricles. The modulation of sigma 1 and IP3 receptors may lead to altered calcium handling in cardiomyocytes and thus contribute to changed sensitivity of cardiac cells to arrhythmias.


Subject(s)
Gene Expression Regulation/drug effects , Haloperidol/pharmacology , Heart Ventricles/drug effects , Heart/physiology , Inositol 1,4,5-Trisphosphate Receptors/metabolism , Myocardium/metabolism , Receptors, sigma/metabolism , Animals , DNA, Complementary/genetics , Guinea Pigs , Haloperidol/adverse effects , Immunohistochemistry , Real-Time Polymerase Chain Reaction , Reverse Transcriptase Polymerase Chain Reaction , Sigma-1 Receptor
9.
Cent Eur J Public Health ; 23 Suppl: S57-61, 2015 Nov.
Article in English | MEDLINE | ID: mdl-26849545

ABSTRACT

The aim of the study was to compare the differences in anthropometric parameters, maximal oxygen uptake (VO2max) and physical activity (PA) between groups of 146 obese boys and 128 obese girls. We tried to describe the relationships between changes in PA and changes in VO2max, body fat, weight, waist circumference and hip circumference. We found statistically significant changes in VO2max and waist circumference only in the group of boys and significant changes in VO2max in the group of girls.


Subject(s)
Motor Activity/physiology , Pediatric Obesity/prevention & control , Pediatric Obesity/physiopathology , Adolescent , Anthropometry , Child , Czech Republic , Female , Humans , Male , Oxygen Consumption/physiology , Physical Fitness/physiology , Waist Circumference
10.
Materials (Basel) ; 17(6)2024 Mar 19.
Article in English | MEDLINE | ID: mdl-38541553

ABSTRACT

In this work, two methods were used to accelerate the corrosion of concrete. In the first method, chloride ions were injected into the concrete using the migration method. The moment of the initiation of the corrosion process was monitored using an electrochemical method of measuring polarization resistance. In the next step, the corrosion process was accelerated by the electrolysis process. Changes on the sample surface were also monitored using a camera. In the second method, the corrosion process of the reinforcing bar was initiated by the use of the electrolysis process only. Here, changes occurring on the surfaces of the tested sample were recorded using two web cameras placed on planes perpendicular to each other. Continuous measurement of the current flowing through the system was carried out in both cases. It was assumed that in conditions of natural corrosion, a crack would occur when the sum of the mass loss of the reinforcing bar due to corrosion reached the same value in tcr(real) (real time) as it reached in the tcr (time of cracking) during the accelerated corrosion test. The real time value was estimated for C1 concrete with cement CEM I. The estimated value was tcr(real) = 1.1 years and for C2 concrete with cement CEM III, tcr(real) = 11.2 years. However, the main difference that was observed during the tests was the nature of the concrete cracks. In the case of the C1 concrete sample, these occurred along the reinforcing bar, while in the C2 concrete, the failures occurred on a perpendicular plane transverse to the direction of the reinforcing bar.

11.
Materials (Basel) ; 16(14)2023 Jul 21.
Article in English | MEDLINE | ID: mdl-37512432

ABSTRACT

This paper presents the analysis of how ISP slag addition affects the effectiveness of chloride extraction from self-compacting concrete. Corrosion processes were initiated by chloride ions added to concrete by the method accelerated with an electric field. Corrosion of reinforcement was monitored using the method of linear polarization resistance (LPR). Polarization measurements of steel reinforcement and chloride profiles were analysed to evaluate the effectiveness of electrochemical extraction. Microstructural analysis was conducted on a specimen of concrete after migration and extraction of chlorides. The presence of chloride ions and the application of an electric field during migration were tested with respect to the changed microstructure of concrete evaluated on the basis of image analysis using a scanning electron microscope (SEM). The research contributes to a better understanding of the corrosion processes caused by the presence of chloride ions in concretes in which ISP slag was used as a substitute for sand in various amounts. Thanks to the treatments of concrete with already corroding reinforcement bars, it can be concluded that the moderate replacement of sand with ISP slag limited to 25% allows for the effective inhibition of corrosion processes taking place in these concretes. However, it is not possible to completely withdraw already started corrosion processes in steel. The observations of the microstructure of concrete in which sand was completely replaced with ISP slag indicate that after prolonged use of the chloride extraction process, we can expect a change in the microstructure and the formation of ettringite, which may cause the concrete structure to burst. The obtained information will contribute to the development of modelling methods for chloride ion extraction from a wide range of currently used concretes.

12.
Materials (Basel) ; 16(2)2023 Jan 09.
Article in English | MEDLINE | ID: mdl-36676371

ABSTRACT

This research paper is the result of observations made during tests according to various standards carried out on behalf of industry. The article presents diffusion coefficient values calculated according to the thermodynamic migration model for twenty different concrete mixes and some selected mixes of the codified approaches known as ASTM 1202, NT BUILD 443, NT BUILD 492, ASTM 1556. The method used here, according to the thermodynamic model of migration, allows determination of the value of the diffusion coefficient after short studies of the migration of chloride ions into concrete and was described in earlier works by one of the authors. Unfortunately, when using standard methods, the values of diffusion coefficients differ significantly from each other. In each concrete, diffusion tests were carried out in the conditions of long-term natural diffusion to verify the values determined by standard methods and according to the thermodynamic model of migration. The analysis conducted for this research paper reveals that the chloride permeability test method according to the standard ASTM C1202-97 has an almost 2.8-fold greater dispersion of the obtained results compared to the thermodynamic model of migration. It was observed that the standard NT BUILD 492 has a 3.8-fold dispersion of results compared to the method with the thermodynamic model of migration. The most time-consuming method is the standard method NT BUILD 443. The largest 3.5-fold dispersion of values concerning the reference value are observed in that method. Moreover, a method based on a thermodynamic migration model seems to be the best option of all analyzed methods. It is a quite quick, but laborious, method that should be tested for a larger number of concrete mixes. A great advantage of this method is that it is promising for a wide range of concrete mixtures, both plain concrete and concrete with various additives and admixtures, as well as high-performance concrete.

13.
Article in English | MEDLINE | ID: mdl-35206179

ABSTRACT

Molecular hydrogen (H2) is potentially a novel therapeutic gas for acute post-coronavirus disease 2019 (COVID-19) patients because it has antioxidative, anti-inflammatory, anti-apoptosis, and antifatigue properties. The aim of this study was to determine the effect of 14 days of H2 inhalation on the respiratory and physical fitness status of acute post-COVID-19 patients. This randomized, single-blind, placebo-controlled study included 26 males (44 ± 17 years) and 24 females (38 ± 12 years), who performed a 6-min walking test (6 MWT) and pulmonary function test, specifically forced vital capacity (FVC) and expiratory volume in the first second (FEV1). Symptomatic participants were recruited between 21 and 33 days after a positive polymerase chain reaction test. The experiment consisted of H2/placebo inhalation, 2 × 60 min/day for 14 days. Results showed that H2 therapy, compared with placebo, significantly increased 6 MWT distance by 64 ± 39 m, FVC by 0.19 ± 0.24 L, and, in FEV1, by 0.11 ± 0.28 L (all p ≤ 0.025). In conclusion, H2 inhalation had beneficial health effects in terms of improved physical and respiratory function in acute post-COVID-19 patients. Therefore, H2 inhalation may represent a safe, effective approach for accelerating early function restoration in post-COVID-19 patients.


Subject(s)
COVID-19 , Female , Forced Expiratory Volume , Humans , Hydrogen/therapeutic use , Male , Respiratory Function Tests , SARS-CoV-2 , Single-Blind Method
14.
J Interv Card Electrophysiol ; 64(3): 661-667, 2022 Sep.
Article in English | MEDLINE | ID: mdl-34988847

ABSTRACT

PURPOSE: Durable pulmonary vein (PV) isolation (PVI) determines the clinical success of catheter ablation for atrial fibrillation. In this randomized study, we investigated whether the temporally discontiguous deployment of ablation lesions adversely affected the acute efficacy of PVI. METHODS: Thirty-six consecutive patients with drug-refractory paroxysmal atrial fibrillation (aged 59 ± 11, 58% males) were randomized 1:1 to either discontiguous (D-PVI) or contiguous (C-PVI) encircling radiofrequency (RF) lesions around ipsilateral PVs. A contact force-sensing catheter was used targeting a final interlesion distance < 6 mm and the ablation index of 400-450 (anterior wall) and 300-350 (posterior wall). The study endpoint was defined as failure of first-pass PVI or acute PV reconnection during a waiting time (> 30 min) followed by adenosine challenge. RESULTS: The total RF time, number of RF lesions, and mean interlesion distance were comparable in both groups. Total endpoint rates were 1/36 (3%) in the D-PVI vs 4/36 (11%) in the C-PVI groups; P = 0.34 for superiority, P = 0.008 for non-inferiority. Adenosine-induced reconnection of right PVs was the only endpoint in the D-PVI group. In the C-PVI group, first-pass PVI failed in 2 right PVs and spontaneous reconnection occurred in 2 other circles (left and right PVs). CONCLUSION: Temporally discontiguous deployment of RF lesions is not associated with lower procedural PVI efficacy when strict criteria for interlesion distance and ablation index are applied. The development of local edema around each ablation site does not prevent effective RF lesion formation at adjacent positions. TRIAL REGISTRATION: clinicaltrials.gov (NCT03332862).


Subject(s)
Atrial Fibrillation , Catheter Ablation , Pulmonary Veins , Adenosine , Atrial Fibrillation/surgery , Female , Humans , Male , Pulmonary Veins/surgery , Recurrence , Treatment Outcome
15.
Materials (Basel) ; 14(16)2021 Aug 18.
Article in English | MEDLINE | ID: mdl-34443178

ABSTRACT

The concrete cover is the basic protection of the reinforcement against the influence of external factors that may lead to its corrosion. Its effectiveness depends mainly on the composition of the concrete mix, including the cement used. Depending on external environmental factors that may aggressively affect the structure, various types of cements and concrete admixtures are recommended. The paper presents the results of tests that allow us to assess the effect of the type of cement used and the air-entraining agent on the effectiveness of the concrete cover as a layer protecting the reinforcement against corrosion. In order to initiate the corrosion process, the reinforced concrete specimens were subjected to cycles of freezing and thawing in a sodium chloride solution. The degree of advancement of the corrosion process was investigated using the electrochemical galvanostatic pulse technique. Additionally, the microstructure of specimens taken from the cover was observed under a scanning electron microscope. The research has shown that in the situation of simultaneous action of chloride ions and freezing cycles, in order to effectively protect the reinforcement against corrosion, the application of both blast-furnace slag cement and an air-entraining agent performed the best.

16.
Materials (Basel) ; 14(13)2021 Jul 01.
Article in English | MEDLINE | ID: mdl-34279244

ABSTRACT

The numerical modelling of chloride penetration into concrete is very sensitive to the correct description of the input data. In the recent era, high-performance concrete (HPC), which combines Portland cement and other supplementary cementitious materials, has been gaining attraction due to their desirable material properties and durability. The presented results show the application of the modified approach for the evaluation of the suitability of the time-dependent model for the variation of the diffusion coefficient. The 26 various binary and ternary-based concrete mixtures blended with volcanic pumice pozzolan (VPP) as a major supplementary cementitious material (SCM) are compared with the reference Ordinary Portland Cement mixture. Other SCMs namely fly ash, slag, silica fume, and metakaolin were also utilized in ternary-based concrete mixtures. In-depth statistical analysis was carried out to show the variability and effects of the amount of the volcanic pumice as an SCM on the diffusion coefficient. The mean value and regression via linear approximation of the time-dependent coefficient of variation of the diffusion coefficients were used as well as the Root of Mean Squared Error approach. The presented results are suitable as the component of the input parameters for the durability-related probabilistic assessment of the reinforced concrete structures exposed to chlorides. In addition, the time-dependent ultimate limit state-related data was presented.

17.
Materials (Basel) ; 12(24)2019 Dec 06.
Article in English | MEDLINE | ID: mdl-31817567

ABSTRACT

The presented article demonstrates the probabilistic method based modeling of the 2D chloride ingress into reinforced concrete structures with respect to concrete heterogeneity and epoxy-coated steel reinforcement. Spatial change of concrete diffusion is assessed through the investigation of random variation of the ability of concrete to resist chloride ingress. Time-dependent chloride concentration at the reinforcement level in both homogeneous and heterogeneous models is comparatively considered taking into account of the influence of reinforcement protection as well as the defects and holidays of the coating. Expansion optimal linear estimation method is exploited to generate a random field for the structure at the mesoscale and correlation length is employed to simplify the modeling process. Preliminary analyses of the built model are conducted in both deterministic and probabilistic solutions under the scheme of the finite element method. Thus, possibility of such analyses is exploited.

18.
Materials (Basel) ; 12(24)2019 Dec 11.
Article in English | MEDLINE | ID: mdl-31835727

ABSTRACT

The presented research program is focused on the design of a structural lightweight fiber-reinforced concrete harnessing an internal curing process. Pre-soaked waste red ceramic fine aggregate and pre-soaked artificial clay expanded coarse aggregate were utilized for the creation of the mix. Copper-coated steel fiber was added to the mix by volume in amounts of 0.0%, 0.5%, 1.0%, and 1.5%. Test specimens in forms of cubes, cylinders, and beams were tested to specify the concrete characteristics. Such properties as consistency, compressive strength, splitting tensile strength, static and dynamic modulus of elasticity, flexural characteristics, and shear strength were of special interest. The achieved concrete can be classified as LC12/13. A strength class, according to fib Model Code, was also assigned to the concretes in question. The proposed method of preparation of concrete mix using only pre-soaked aggregate (with no extra water) proved to be feasible.

19.
Materials (Basel) ; 12(7)2019 Apr 02.
Article in English | MEDLINE | ID: mdl-30986966

ABSTRACT

The safety and durability of bridges designed from weathering steels are conditioned by the development of a sufficiently protective layer of corrosion products. Air pollution, microclimate around the bridge, time of wetness, structural solution of the bridge, and the position and orientation of the surface within the bridge structure all influence the development of protective layers on the surface of the weathering steel. In this article, attention is focused mainly on the microclimatic effects resulting from the road traffic under the bridge. The influence of chloride deposition on the development of corrosion products is evaluated using experimental in situ testing. Two neighboring bridges made of weathering steel and crossing different types of obstacles were selected for this experiment. Relations and dependences between the measured parameters (deposition rate of chlorides, corrosion rates, thickness of corrosion products and the amount of chlorides in corrosion products) are evaluated and discussed.

20.
PLoS One ; 14(10): e0224145, 2019.
Article in English | MEDLINE | ID: mdl-31639174

ABSTRACT

Ballet training has been reported to positively influence balance ability. It is not entirely clear how improved balance ability manifests under standing conditions with different demands on postural control. The aim of the study was to compare balance of ballet dancers and non-dancers in a unipedal stance under different conditions. Twenty-five professional ballet dancers and twenty-five controls completed four unipedal standing balance tests: firm surface with eyes open and closed; foam mat surface with eyes open; and firm surface with eyes open immediately after performing ten 360° whole-body turns. The centre of pressure (COP) data were obtained with a force platform and the direction-specific standard deviations, velocities, and sample entropy of the COP displacement were computed. A three-way analysis of variance was used to compare groups, genders, and conditions. For standing immediately after performing ten turns, the postural sway parameters were significantly larger in the control group compared to the ballet dancers in both men and women. In this stance condition the values of postural sway and COP velocities in the control group were larger in the men compared to the women. For both genders in the control group all postural sway and COP velocity parameters were larger in standing with eyes closed and standing after performing 10 turns compared to standing with eyes open on both firm and foam surface. In the ballet dancers all COP velocity parameters were larger in standing with eyes closed compared to all other conditions. The results from the present study indicate that professional ballet dancers do not have a better general balance ability than untrained subjects.


Subject(s)
Dancing/physiology , Functional Laterality/physiology , Postural Balance/physiology , Posture/physiology , Adult , Female , Humans , Male , Young Adult
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