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Early Devonian sinistral shearing recorded by retrograde monazite-(Ce) in Oscar II Land, Svalbard

Ziemniak Grzegorz, Manecki Maciej, Jeanneret Pauline, Walczak Katarzyna, Kośmińska Karolina

Mineralogia

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2022

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Vol. 53, iss. 1

82--108

EN

The Southwestern Basement Province of Svalbard extends northward from Sørkapp Land in the south to Oscar II Land. In the north, the Müllerneset Formation characterized by polymetamorphosed Proterozoic sedimentary rocks crops out. In this study we used an integrated tectonic and petrochronological approach to gain an insight into the structural and metamorphic evolution of the unit and surrounding basement. The Müllerneset Formation consists of two separate tectonic blocks. NNW-SSE trending retrograde foliation is associated with mineral and stretching lineation and kinematic indicators consistent with left-lateral to oblique sinistral shearing in the western block. The eastern block is characterized by the opposite sense of shear that was overturned during the Eurekan event as evidenced by unconformably overlaying Carboniferous sedimentary rocks. Conventional geothermobarometry yields the prograde peak pressure metamorphic conditions of 6.6 - 7.1 kbar at 480 - 520°C followed by peak temperature at 5.1 - 5.9 kbar and 530 - 560°C. Subsequent retrograde greenschist facies overprint is related to left-lateral NNW-SSE trending shearing. Tiny monazite occurs within foliation or overgrows allanite-(Ce), thus is interpreted as growth along a retrograde path. Th-U-total Pb dating of monazite-(Ce) provided an early Caledonian age (ca. 450 Ma) and younger population of ca. 410 ± 8 Ma. This age is consistent with previously reported 40Ar/39Ar cooling ages (410 ± 2 Ma) of muscovite supporting a retrograde growth of monazite. Petrochronological evidence combined with structural observations suggests that the Müllerneset Formation has been tectonically exhumed in the Early Devonian due to the NNW-SSE trending left-lateral shearing. Coeval folding and thrusting in the remaining basement of Oscar II Land to the east indicate a transpressional regime of the deformation in the Early Devonian. Similarly oriented contemporaneous tectonic zones within the Southwestern Basement Province of Svalbard may account for the same set of shear zones dispersing the Ordovician subduction complexes along western Spitsbergen.

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Radon in houses of Kowary : Sudety Mountains, Poland

Olszewski Jerzy, Walczak Katarzyna

Nukleonika

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2020

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Vol. 65, No. 2

149--152

EN

The presence of uranium makes the Kowary area characterized by an increased concentration of radon in the air and the living houses. Measurements of periodic radon concentrations in dwellings of Kowary were carried out three times in the last 20 years. It can be observed that 20 years ago level of radon concentrations in houses of Kowary were lower than today. Measurements carried out in Kowary over 20 years have shown that residents are exposed to radon concentrations, which often exceed 300 Bq•m-3 – a reference level recommended by the European Union. The present geometric mean of radon concentration in houses of Kowary (260 Bq•m-3 ) exceeds the geometric mean of radon concentration of buildings in the rest of Poland (142 Bq•m-3 ).

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Bond strength of modern self-adhesive resin cements to human dentin and different CAD/CAM ceramics

Małysa Andrzej, Weżgowiec Joanna, Danel Dariusz, Boening Klaus, Walczak Katarzyna, Więckiewicz Mieszko

Acta of Bioengineering and Biomechanics

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2020

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Vol. 22, no. 2

25--34

EN

The aim of the study was to evaluate the shear bond strength of CAD/CAM ceramics to dentin after cementation with conventional or self-adhesive resin cements. Methods: Three self-adhesive, self-etching cements (Panavia SA, RelyX U200, Maxcem Elite), and one conventional cement (Panavia V5), were selected to lute three CAD/CAM ceramics (IPS Empress CAD, IPS e.max CAD, IPS e.max ZirCAD) onto the dentin. The bond strength was evaluated using a shear strength test according to the PN-EN ISO 29022:2013-10. Evaluation of the differences was performed using the Statistica software. Failure modes were analyzed using a light microscope. Results: All the studied cements differed (regardless of the ceramic type) in the bond strength. The highest bond strength was observed in Panavia V5, lower – in RelyX U200 and Panavia SA, and the lowest – in Maxcem. For IPS e.max ZirCAD, it was observed that compared to Panavia V5, the other cements were characterized by a significantly higher bond strength. For the IPS Empress CAD and the IPS e.max CAD, Panavia V5 displayed the highest bond strength. For all the studied self-adhesive cements, the failure of adhesion between the cement and dentin was predominant mode. Conclusions: Significant differences were found in the shear bond strengths of the CAD/CAM ceramics luted to dentin using tested self-adhesive and conventional cements. The bond strength depended on the combination of ceramic and cement. The IPS e.max ZirCAD had the highest bond strength to dentin after cementation with RelyX U200, while the IPS Empress CAD and IPS e.max CAD – with Panavia V5.