Comparison of digital and conventional impression techniques: evaluation of patients’ perception, treatment comfort, effectiveness and clinical outcomes

Background: The purpose of this study was to compare two impression techniques from the perspective of patient preferences and treatment comfort.Methods: Twenty-four (12 male, 12 female) subjects who had no previous experience with either conventional or digital impression participated in this study. Conventional impressions of maxillary and mandibular dental arches were taken with a polyether impression material (Impregum, 3 M ESPE), and bite registrations were made with polysiloxane bite registration material (Futar D, Kettenbach). Two weeks later, digital impressions and bite scans were performed using an intra-oral scanner (CEREC Omnicam, Sirona). Immediately after the impressions were made, the subjects' attitudes, preferences and perceptions towards impression techniques were evaluated using a standardized questionnaire. The perceived source of stress was evaluated using the State-Trait Anxiety Scale. Processing steps of the impression techniques (tray selection, working time etc.) were recorded in seconds. Statistical analyses were performed with the Wilcoxon Rank test, and p < 0.05 was considered significant.Results: There were significant differences among the groups (p < 0.05) in terms of total working time and processing steps. Patients stated that digital impressions were more comfortable than conventional techniques.Conclusions: Digital impressions resulted in a more time-efficient technique than conventional impressions. Patients preferred the digital impression technique rather than conventional techniques

Ecological changes in historically polluted soils: Metal(loid) bioaccumulation in microarthropods and their impact on community structure

International audienceSoil pollution by persistent metal(loid)s present environmental and sanitary risks. While the effects of metal(loid)s on vegetation and macrofauna have been widely studied, their impact on microarthropods (millimetre scale) and their bioaccumulation capacity have been less investigated. However, microarthropods provide important ecosystem services, contributing in particular to soil organic matter dynamics. This study focussed on the impact of metal(loid) pollution on the structure and distribution of microarthropod communities and their potential to bioaccumulate lead (Pb). Soil samples were collected from a contaminated historical site with a strong horizontal and vertical gradient of Pb concentrations. Microarthropods were extracted using the Berlese method. The field experiments showed that microarthropods were present even in extremely polluted soils (30,000 mg Pb kg− 1). However, while microarthropod abundance increased with increasing soil C/N content (R2 = 0.79), richness decreased with increasing pollution. A shift in the community structure from an oribatid-to a springtail-dominated community was observed in less polluted soils (R2 = 0.68). In addition, Pb bioamplification occurred in microarthropods, with higher Pb concentrations in predators than in detritivorous microarthropods. Finally, the importance of feeding and reproductive ecological traits as potentially relevant descriptors of springtail community structures was highlighted. This study demonstrates the interest of microarthropod communities with different trophic levels and ecological features for evaluating the global environmental impact of metal(loid) pollution on soil biological quality

Oznaczanie wanadu(IV) i wanadu(V) w roztworach Benfielda

W pracy opisano metody oznaczania jonów wanadu(IV) i wanadu(V) za pomocą chromatografii jonowej. Specjacja wanadu jest istotna miedzy innymi podczas usuwania CO 2 metodą Benfielda w procesie wytwarzania amoniaku, w której nieorganiczne jony wanadu pełnią istotną rolę inhibitora korozji

Possible interactions between stent and electromagnetic field

Over the past years, an increase in the amount of the electromagnetic sources could be observed. Model presented in this article is limited to the impact of low frequency fields generated by the e.g. electrical power lines or magnetic coils in a bone fractures therapy. Particularly, the effect of the magnetic component of the electromagnetic field on stents will be evaluated. The conductivity of human tissues will be investigated. Yielded results will be used to simplify complicated, three-dimensional problem of the current distribution in stent branches, to one-dimensional one. The merits of the paper is proposing, implementing and using for analysis a numerical model of the stent in magnetic field. The impact of frequency and positioning of stent in the magnetic field will be investigated and current distributions found

Application of electrodynamic drum separator to electronic wastes separation

Statyczne pola elektryczne są wykorzystywane m.in. w procesach technologicznych, takich jak separacja elektryczna. Separacja elektrodynamiczna jest procesem rozdzielania dwóch lub większej ilości faz stałych, zróżnicowanych pod względem właściwości fizycznych, siłami pola elektrycznego. Zaletą separacji elektrodynamicznej jest możliwość uzyskania rozdziału poszczególnych składników na sucho, co eliminuje szereg operacji, takich jak: zagęszczanie, odwadnianie, hydrotransport, dosuszanie. Czynności te zwiększają energochłonność i koszty procesu separacji. Efektywność wzbogacania zależy od wielu czynników, takich jak: właściwości elektryczne składników nadawy, uziarnienie nadawy, prędkości wirowania bębna, natężenie pola elektrycznego w przestrzeni roboczej separatora, konfiguracji elektrod czy warunków otoczenia. W artykule przedstawiono działanie wysokonapięciowego separatora bębnowego. Dokonano analizy rozkładu pola elektrycznego przestrzeni roboczej separatora oraz sił działających na cząstki o właściwościach dielektrycznych i przewodzących, przedstawiono także tory ruchu naelektryzowanych cząstek. Wykonano laboratoryjne badania separacji odpadów elektronicznych w dwóch klasach ziarnowych: 0–0,25 mm i 0,25–0,5 mm. Zaobserwowano, że w wyniku selektywnego ładowania cząstek rozdzielają się one według zdolności powierzchniowego elektryzowania się, co pozwala uzyskać selektywny rozdział składników tworzących tzw. śmieci elektroniczne. Zastosowanie elektrodynamicznego separatora bębnowego pozwala rozdzielić pierwiastki, takie jak Ti, Cu, Fe, Pb, Sn od tworzyw sztucznych znajdujących się w odpadach elektronicznych.Static electric fields are used, among others, in technological processes such as electric separation. Electrodynamic separation is a process of separating two or more solid phases of various physical properties by electric field forces. The advantage of electrodynamic separation is possibility of obtaining separation of individual components in dry conditions. This eliminates many operations such as thickening, dewatering, hydrotransportation, additional drying which cause higher energy consumption and higher separation process costs. Efficiency of beneficiation depends on many factors such as: electric properties of feed components, feed particle size distribution, drum rotary speed, electric field intensity in working space of separator, configuration of electrodes or surrounding conditions. The paper presents the working of high-voltage drum separator. The analysis of electric field distribution in separator working space was done. Additionally, distribution of forces acting on particles of dielectric and conductive properties was examined, trajectories of charged particles movement were presented too. The laboratory investigations of electronic wastes were performed in two particle fractions: 0.25–0.5 mm and 0–0.25 mm. It was observed that as a result of selective charging of particles they separate according to surface ability to electrifying what allows to obtain selective separation of components being so-called electronic wastes. The application of electrodynamic drum separator allows to separate such elements as Ti, Cu, Fe, Pb, Sn from plastics occurring in electronic wastes