Explore the vast range of titles available.

In this study, the milling process of eco-friendly polymer composites enriched with an organic filler was analyzed. Polyhydroxyalkanoate was filled with 0.5%, 1%, and 2% of diatomite and produced via injection molding. Then, the milling process was performed on the obtained samples to determine the effect of diatomite content on the machinability of the produced composites. The results showed that the analyzed diatomite content in the machined samples had no significant influence on the cutting process. If the cutting parameters are not properly selected, excessive heat generated during machining can lead to a heterogeneous geometric surface microstructure. The milling process resulted in a series of high-quality surfaces (Ra < 2 μm), chip temperatures below 90 °C, and a feed component of the total cutting force below 11 N.

This study makes a comparative assessment of the relation between four waves of the COVID-19 pandemic and the stock market in Poland. We utilize the Autoregressive Moving Average-Asymmetric Dynamic Conditional Correlation-Generalized Autoregressive Conditional Heteroskedasticity models to depict the dynamic conditional correlations between Polish stock market and the US stock market. We use the wavelet approach to investigate the time-frequency connectedness between the COVID-19 pandemic and the stock markets. The sample used covers the period from 02.01.2019 to 04.04.2022. Our findings reveal a significant relation between pandemic variables and stock market. This evidence is more pronounced in the first and second wave of infections. In contrast, the impact was considerably smaller during the third and fourth waves.

The aim of this study was to evaluate the changes in physical-mechanical properties of the samples manufactured by 3D printing technology with the addition of varying degrees of polylactide (PLA) infill (50, 70, 85 and 100%). Half of the samples were soaked in physiological saline. The material used for the study was neat PLA, which was examined in terms of hydrolytic degradation, crystallization, mechanical strength, variability of properties at elevated temperatures, and dissipation of mechanical energy depending on the performed treatment. A significant impact of the amount of infill on changeable mechanical properties, such as hydrolytic degradation and crystallization was observed. The FDM printing method allows for waste-free production of light weight unit products with constant specyfic strength.

This article examines the impact of fatigue cycles on polylactide samples produced by 3D printing using the FDM method. Samples were printed in three infill degree variants: 50%, 75% and 100%. To compere the influence of infill degree on PLA properties, several tests, including the uniaxial tensile test, the low-cycle fatigue test, differential scanning calorimetry (DSC) and scanning electron microscopy (SEM), were conducted. Poisson’s ratio has also been studied. Single hysteresis loops were summed to obtain the entire low-fatigue cycle. The infill of density influenced all compared mechanical parameters. The decrease in infill degree caused the reduction of Young’s modulus and shear modulus. For a 100% degree of sample infill, a higher number of transferred load cycles were observed compared to PLA with 75% and 50% of infill. Additionally, the value of the transferred cyclic load before fatigue failure and the dissipation of mechanical energy was the highest for 100% of infill. It is also worth noting that fatigue tests can positively affect the appearance of the PLA structure. Obviously, it depends on the number of load cycles and the infill density. It causes that if the goal is to transfer as much load as possible over a long period of time, the maximum filling of the printed element should be used.

In this article, an ecological composite based on a neat polylactide with 50 and 75% degrees of coffee particles and eggshells as an infill and organic filler, was developed. It has been shown that the content of fillers used reduced the mechanical properties, increasing the possibility of environmental degradation and accelerating the biodegradation process. During the additive production of polylactide with 10% of coffee grounds as a filler, it was possible to reduce the additive manufacturing temperature, which reduced the process time, energy costs, carbon dioxide emissions and the amount of polymer that may affect the environment. The structure of polylactide enriched with hen eggshells is characterized by roan and irregular shapes, which can cause a high tendency to form a concentration of cracks in these areas. Based on the results obtained from the stress relaxation test, the Zener model was used to describe a creep model of the produced ecological composites. The polymer composition of coffee grounds and eggshells shows a tendency to creep faster than pure polylactide and with different degrees of infill. Voids reduce the strength of composite materials, which increases the creep potential of samples with incomplete degrees of infill.

Članek obravnava tematiko zdravja v  izobraževanju odraslih. Izhodišče razprave je sodobno pojmovanje  zdravja, ki se uveljavlja v družbenih vedah in se razume  kot fizična, psihosocialna in duhovna dobrobit. Poudarjena je tudi misel, da je zdravje  proces in da zdravstveno stanje določajo tako subjektivni kot okoljski dejavniki. To odpira vrata  teoriji salutogeneze, povezani s prepričanjem, da je zdravje mogoče izboljšati s pomočjo zdravstvene vzgoje in promocije zdravja. Koncept okoljskih  in socio-kulturnih dejavnikov, ki odločajo o zdravju in vprašanja, ki se nanašajo na z zdravjem povezani vidik kakovosti življenja, so tudi uporabljeni kot referenčni okvir in teoretska podlaga za  to pedagoško razpravo o zdravju kot predmetu izobraževanja odraslih.

The Students’ Life Satisfaction Scale (SLSS) is one of the most frequently used measures of children’s and adolescents’ overall satisfaction with their lives. We examined several psychometric properties of the SLSS with a sample of Polish adolescents aged 14–15. Data from 612 Polish secondary school students (56.9% girls and 43.1% boys) were analyzed. The SLSS demonstrated acceptable properties, including internal consistency reliability, which was supported by Cronbach alpha and omega coefficients. Confirmatory factor analysis results for individual groups showed that after modifications, the 1-factor model for the SLSS displayed satisfactory fit. For each group (by age and sex), typically two (and in some cases three) modifications to the residual covariance had to be made. Tests of measurement invariance supported full scalar invariance for the groups of 14 and 15-year-olds and partial invariance for the groups of girls and boys.

The main goal of the analysis presented in this paper is to examine the dynamics of including other-sex peers in the peer networks of early adolescents, aged 11 (at T1) and 13 (at T2), and the relationship between sex heterophily and changes in the sense of peer integration. The analysis was conducted using the Latent Difference Score (LDS) model with data from a representative nationwide longitudinal study in Poland (n = 5748). With reference to the dynamics related to the heterophilic process, the research confirmed that at the beginning of grade 5 of primary school, heterophily is still relatively rare, yet towards the end of early adolescence, there is a gradual shift, more strongly in girls, towards breaking through the strictly same-sex segregation and embarking on heterophilic relationships. Importantly, the LDS model—even when controlling for different measures of peer network—showed significant and positive (among both girls and boys) relations between establishing cross-sex relationships and the sense of peer integration. The results indicate that the appearance of the opposite sex in the peer network between grades 5 and 6 will improve the sense of peer integration. The findings are discussed in relation to results from other studies in the field.

This paper discusses the issues concerning health in the education of adults. The starting point for this discussion is contemporary understanding of health in social sciences, which identifies it with the physical, psychosocial and spiritual well-being. Its processual nature is also emphasised, since a person’s health level is determined by a number of subjective and environmental factors. This allows for adaptation of the salutogenic thesis regarding the possibility of health improvement through health education and health promotion. The concept of environmental and socio-cultural health determinants and the issues of a health-related quality of life serve, in addition, as a point of reference and theoretical background for this pedagogical discourse on health as a subject of adult education.

The aim of this systematic review (qualitative analysis) was to identify the variables of changes induced by extrinsic (sport specific training) and intrinsic (individual anatomical predispositions) compensatory mechanisms that impact on the physiological magnitude of spinal curvatures in the sagittal plane and their deviations in the frontal plane. Furthermore, the aim of the quantitative analysis was to verify and objectivize the impact of these variables on athlete’s body posture. A search of electronic database (PubMed, EBSCO, MEDLINE) was conducted to identify all studies on sports training and athlete’s spine and body posture from 2011 to 2021. In the sagittal plane, the pooled proportion accounted for 44.97% (95% CI 31.22–58.72%) for thoracic hyperkyphosis (TH), 4.98% (95% CI 1.60–8.36%) for lumbar hyperlordosis (hyperLL), and 12.35% (95% CI 1.60–8.36%) for lumbar hypolordosis (hypoLL). Furthermore, in the sagittal plane, the pooled mean of thoracic kyphosis angle was 37.59° (95% CI 34.45–40.73%), whereas lumbar lordosis angle was 29.79° (95% CI 26.46–33.12%). Professional athletes tend to have postural disturbances and/or spinal curvature disorders in the sagittal and frontal planes. The meta-analysis indicated which intrinsic and extrinsic components might induce spinal abnormalities.