In this study, modified sol-gel method was employed to synthesize the pure and Zr-doped titania catalysts. Brunauer-Emmett-Teller (BET) method was applied to determine porosity, X-ray diffraction (XRD) analysis was used to study crystal structure, scanning electron microscopy (SEM) was used to investigate morphology and Fourier transform infrared spectroscopy (FTIR) was used to examine surface properties/total acidity of the obtained catalysts samples. Photocatalytic activity was tested in the reaction of crystal violet (CV) dye decolourization/degradation under UV light irradiation. The effects of several photocatalysis operational parameters were considered, such as catalyst dosage, initial dye concentrations, duration of UV irradiation treatment, as well as catalysts calcination temperatures and dopant amounts. The obtained results indicated faster dye decolourization/degradation with the increase of the catalyst dosage and the decrease of initial CV concentrations. The Zr-doping affects photocatalytic properties, i.e. CV decolourization/degradation of the prepared catalytic materials. Thus, addition of 5 wt.% of ZrO 2 to titania increases photocatalytic effect for ∼15% and addition of 10 wt.% of ZrO 2 improves the photocatalytic efficiency of titania for nearly 30%.
The purpose of this experimental study was to determine the effects of a skill-based exercise program on the body composition of adolescents. The study was conducted on 90 participants, (age, 13±6 years), divided by gender then randomly assigned into two sub-samples: the experimental [SS1, N=39 (EG1, 19 girls and EG2, 20 boys)] and the control group [SS2, N=51 (CG1, 24 girls and CG2, 27 boys)]. Body composition parameters were assessed by a caliper (skinfold thickness) and bioelectrical impedance analyzer Omron BF511 (percentage of body fat tissue and muscle tissue). After conducting the 16-week program of skill-based exercises and small-sided games (SSG) related to volleyball, certain body composition parameters statistically significantly increased in the experimental groups (except body fat percent in girls, and body fat mass in both genders). In the experimental period, the SS2 increased in body fat tissue (both genders) and in muscle tissue (girls), while a decrease in muscle tissue was recorded among the boys. The results of this study showed no significant differences in the effects of the two programs on body composition at the multivariate level for both genders. Furthermore, at the univariate level it was noted that the students following the experimental program (SS1) had better results compared to the SS2 of students in terms of the decrease of body fat tissue, as well as the increase of muscle tissue for both genders. The obtained results indicate that the program of skill-based exercises and SSG related to volleyball is suitable for adequate intensification of PE classes and improvement of body composition parameters of elementary school students.
Resorcinol-formaldehyde carbon cryogel has been prepared, characterized and used for the removal of commonly used herbicide clopyralid from the aqueous solutions under varying experimental conditions. Carbon has shown a relatively high specific surface area, significant mesoporosity and an amorphous structure. A set of the following isotherm models has been used to interpret the equilibrium data: Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, Jovanovic, Hurkins-Jura, and Helsey model. Several models have fitted well although the calculated values for qmax poorly correlate with the data obtained experimentally. The kinetic models of the pseudo-first and pseudo-second-order, the models of Elovich, Bangham and the intraparticle diffusion model have been used for fitting the kinetic data. The rate of the process is fast in the beginning while adsorption equilibrium is attained not until 24 hours. Adsorption was found to be pH dependent and favored in acidic solutions.
Bentonite is mainly composed of clay minerals from smectite group, therefore it has a well developed and chemically active surface area and high cation exchange capacity. Moreover, an interlayer space of smectite has unusual hydration properties, which manifest as swelling of bentonite in water. These properties make bentonite as a commonly used raw material in chemistry and industry, and it is very important in environmental protection and water treatment as an effective sorbent of heavy metals. The results of X-ray diffraction, a cationic exchange capacity, specific surface area, acid-base properties of the surface and the swelling index showed that the bentonite sample contains mostly montmorillonite. The aim of this study was to test the efficacy of bentonite in the removal of Mn2+ from aqueous systems. The experimental results of Mn2+ adsorption on the bentonite were interpreted by Langmuir, Freundlich and Dubinin-Radushkevich adsorption isotherms. The adsorption isotherm studies indicate that the adsorption of Mn2+ follows Langmuir isotherm very well. Theoretical monolayer saturation capacity according to Langmuir model was 12.41 mg/g. The removal of Mn2+ is achieved by ion exchange mechanism with naturally occurring cations in bentonite, as well as by forming the inner- and outer-sphere complexes with bentonite surface
TThe aim of this paper was to examine the differences in the motor skills of soccer players aged 16-18 years who play in different competition levels (National League and Regional League), as well as players who play in different positions in the team. The standard testing battery for the motor skills assessment of soccer players was used to evaluate the motor skills. As for the evaluation of the differences between the different playing positions, a two-factor ANOVA with the factor Competition Level (National and Regional Level) and the factor Position (forward, midfielder, side defender, central defender) was used. A two-factor ANOVA with the factor Competition Level (National and Regional Level) and the factor Age (16, 17 and 18 years of age) was used to evaluate the differences between the different quality levels. The study included 126 male soccer players 16 to 18 years of age (N16=45, N17=41, N18=40) divided into 4 positions on the team: forwards (N=37, BH=179.2±5.0, BM=70.1±6.6), midfielders (N=48, BH=177.9±6.3, BM=69.6±7.9), side defenders (N=22, BH=176.6±5.4, BM=67.5±5.7) and central defenders (N=19, BH=184.0±4.3, BM=72.3±6.6). Because of significantly different activities in the field, the goalkeeper position was excluded from this study. The results indicate that motor skills do not differentiate players of different competition levels, and that there is a gap between players aged 18 years in aerobic endurance which is the basis of success in soccer. Also, the obtained results suggest that motor skills could differentiate players at certain positions. However, it was specifically found that only alactic capabilities type of speed and agility, differentiate forwards from other positions, especially from midfielders.
.The study was conducted with the goal to determine the effects of explosive strength training on the transformation of motor skills and functional abilities during regular physical education classes, among students of primary schools. The sample of examinees consisted of 64 pupils from Niš, 14 years old. Experimental group comprised of 32 examinees, selected for the training of experimental model of explosive strength in the main part of regular physical education classes, three times per week, in duration of 45 minutes, for the period of eight weeks. One half of these classes was dedicated to regular PE curriculum, while the other half to an experimental program of explosive strength, in duration of eight weeks. Control group also comprised of 32 examinees, who attended regular physical education classes, three times per week in duration of 45 minutes, for the period of eight weeks. Following motor skill were assessed: coordination (two tests), sprint speed (two tests), repetitive strength (two tests), and explosive strength (two tests). Following functional abilities were assessed: pulse frequency after physical activity, Margaria test, and vital lung capacity. For processing of data, variance and covariance analysis were applied. Study results showed that experimental group of examinees achieved better results in motor skills and functional abilities, as well as that there were statistically significant effects at the final testing
In order to determine the differences between results obtained by using two different methods for estimating the body fat percentage in adolescents, a comparative analysis was performed with bioelectrical impedance method and a traditional method for assessing body composition by skinfold measurement. The sample of this study consisted of 86 seventh grade students of elementary school (42 girls and 44 boys). Body fat percentage was estimated using electronic scale through bioelectrical impedance for assessing the body composition "OMRON BF-511, Japan" and traditionally by measuring skinfolds with caliper and further calculations using equations according to Slaughter (1988). After analyzing the obtained results, it was found that no statistically significant differences were present between body fat percentage obtained by the method of bioelectrical impedance and the method of skinfold measurement of triceps and subscapular (p = 0.711) and triceps and calf (p = 0.850) in girls, while statistically significant differences were found between the results of these two methods (p = 0.001; p = 0.009) in boys. Comparison of two most commonly used methods for assessing body fat percentage shown similar results in girls, while in boys, significant differences were present between measurements of these two methods.
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