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With the ever-increasing number of polymer materials and the current number of commercially available materials, the polymer gear design process, regarding the wear lifetime predictions, is a difficult task given that there are very limited data on wear coefficients that can be deployed to evaluate the wear behavior of polymer gears. This study focuses on the classic steel/polymer engagements that result in a wear-induced failure of polymer gears and proposes a simple methodology based on the employment of optical methods that can be used to assess the necessary wear coefficient. Polymer gear testing, performed on an open-loop test rig, along with VDI 2736 guidelines for polymer gear design, serves as a starting point for the detailed analysis of the wear process putting into service a digital microscope that leads to the evaluation of the wear coefficient. The same wear coefficient, as presented within the scope of this study, can be implemented in a rather simple wear prediction model, based on Archard’s wear formulation. The developed model is established on the iterative numerical procedure that accounts for the changes in tooth flank geometry due to wear and investigates the surface wear impact on the contact pressure distribution to completely describe the behavior of polymer gears in different stages of their lifetime. Although a simple one, the developed wear prediction model is sufficient for most engineering applications, as the model prediction and experimental data agree well with each other, and can be utilized to reduce the need to perform time-consuming testing.

Who conducts biological research, where, and how the results are disseminated varies among geographies and identities. Identifying and documenting these forms of bias by research communities is a critical first step towards addressing them. We documented perceived and observed biases in movement ecology. Movement ecology is a rapidly expanding sub-discipline of biology, which is strongly underpinned by fieldwork and technology use. First, we surveyed attendees of an international conference, and discussed the results at the conference (comparing uninformed vs informed perceived bias). Although most researchers identified as bias-aware, only a subset of biases were discussed in conversation. Next, by considering author affiliations from publications in the journal Movement Ecology, we found among-country discrepancies between the country of the authors’ affiliation and study site location related to national economics. At the within-country scale, we found that race-gender identities of postgraduate biology researchers in the USA differed from national demographics. We discuss the role of potential specific causes for the emergence of bias in the sub-discipline, e.g. parachute-science or accessibility to fieldwork. Undertaking data-driven analysis of bias within research sub-disciplines can help identify specific barriers and first steps towards the inclusion of a greater diversity of participants in the scientific process.

This paper investigates the rate of convergence of a certain mixed monotone rational second-order difference equation with quadratic terms. More precisely we give the precise rate of convergence for all attractors of the difference equation $x_{n+1}=\frac{Ax_{n}^{2}+Ex_{n-1}}{x_{n}^{2}+f}$, where all parameters are positive and initial conditions are non-negative.The mentioned methods are illustrated in several characteristic examples. 2020 Mathematics Subject Classification. 39A10, 39A20, 65L20.

In the article, we use the subset sum formula over a finite abelian group on the product of finite groups to derive the number of restricted partitions of elements in the group and to count the number of compositions over finite abelian groups. Later, we apply the formula for the multisubset sum problem on a group $\mathbb{Z}_n$ to produce a new technique for studying restricted partitions of positive integers. 2020 Mathematics Subject Classification. 05A17, 11P81

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Aim To assess the relationship between the attitudes of general practitioners/family medicine doctors (GP/FD) and of their patients toward industry-sponsored clinical research. Methods A cross-sectional survey included volunteer GPs/FDs who then enrolled and interviewed their patients. Data were analyzed in hierarchical models (patients nested in GPs/FDs, nested in countries/regions). Results A total of 201 GPs/FDs from nine European countries responded to the invitation and enrolled 995 of their patients. We observed mild associations between some of the GPs/FDs’ attitudes (general opinion on sponsored clinical studies, appreciation of the general values of such studies, views about the importance of participant protection/privacy) and some of the patients’ attitudes (appreciation of the general values and of risks associated with sponsored clinical studies, importance assigned to potential personal benefits from participation). We observed no association between GPs/FDs’ attitudes and patients’ willingness to participate in such studies. However, willingness to participate increased with higher patients’ appreciation of the general values of sponsored studies, decreased with higher patients’ appreciation of associated risks, and showed a quadratic trend across the levels of importance assigned by patients to potential personal benefits (willingness was higher when the assigned importance was very low or very high). More importance to GP/FD’s advice in this respect was assigned by patients who assigned more importance to potential personal benefits, who were better educated, and who resided in rural/suburban dwellings. Conclusions In the present convenience sample, lay-person attitudes about and willingness to participate in industry-sponsored clinical studies were associated with the attitudes of their GPs/FDs.

Energy production, supply and consumption are global issue with many economic, environmental and social implications. Mentioned issue is even more expressed in remote rural areas, in particular in developing countries, as are the countries of the Western Balkans (WB). Renewable energy sources (RES) could represent optimal energy alternative for sustainable performing of agricultural and other activities, as well as for improving the current state of living conditions in rural communities. The main goal of research is to mark the most suitable RES alternative (six alternatives) for wider implementation in rural space of WB. The applied methodology framework implies experts’ opinion (engagement of eight experts) and the use of multi-criteria decision-making methods (MCDM), (specifically fuzzy-rough LMWA and fuzzy-rough CRADIS methods) under the predefined criteria (nine criteria). Derived results show that the implementation of the solar energy plants could play an optimal solution, while as the relatively unsuitable alternative could be marked the use of energy potential of watercourses. Gained final result, i.e. ranking order of the considered alternatives is additionally verified by the appliance of other MCDM methods, while the sensitivity analysis was also performed.

Objective: This comprehensive research aimed to thoroughly examine the effectiveness of a diode laser (445 nm) in combination with non-surgical treatment in patients with chronic periodontitis (CP) by evaluating a wide range of clinical and microbiological parameters. Materials and methods: Thirty-one subjects diagnosed with CP were included in this study. The total number of treated periodontal pockets was 862. The subjects were randomly assigned to group 1, which underwent scaling and root planing and laser therapy (SRP+L), and group 2, which underwent scaling and root planing (SRP) only. All respondents underwent a periodontal diagnostic protocol. The parameters plaque index (PI), gingival index (GI), bleeding on probing index (BOP), probing depth (PD), clinical attachment level (CAL), and tooth mobility (TM) were registered. Clinical periodontal measurements were performed at baseline and one and three months after therapy. Microbiological analysis was conducted on Aggregatibacter actinomycetemcomitans (Aa), Porphyromonas gingivalis (Pg), and Tannerella forsythia (Tf) using real-time polymerase chain reaction (PCR). For microbiological analysis, samples were taken at baseline, immediately after therapy, and after three months. Laser irradiation was performed immediately after SRP. Results: All clinical parameters improved statistically from baseline to three months after therapy. For all examined clinical parameters, better results were achieved in group 1 than in group 2. This study showed a more significant reduction in Pg and Tf from baseline to three months in group 1 compared to group 2. Conclusion: These results showed that the diode laser wavelength 445 nm was also usable in treating periodontal diseases as an additional method to SRP.