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244 results on '"Calin, Mariana"'

1. Remarks regarding some Algebras of Logic

Author

Calin, Mariana Floricica, Flaut, Cristina, and Piciu, Dana

Subjects
Mathematics - Logic
Abstract

Algebras of Logic deal with some algebraic structures, often bounded lattices, considered as models of certain logics, including logic as a domain of order theory. There are well known their importance and applications in social life to advance useful concepts, as for example computer algebra. In this paper we reffer in specially to BL-algebras and we present properties of finite rings or rings with a finite number of ideals in their connections with BL-rings.

Published
2023

32. Designing Gallium-Containing Hydroxyapatite Coatings on Low Modulus Beta Ti-45Nb Alloy.

Author

Vishnu, Jithin, Voss, Andrea, Hoffmann, Volker, Alberta, Ludovico Andrea, Akman, Adnan, Shankar, Balakrishnan, Gebert, Annett, and Calin, Mariana

Subjects
HYDROXYAPATITE coating, CHEMICAL stability, METAL coating, ALLOYS, BONE regeneration, HYDROXYAPATITE, GALLIUM compounds, CITRATES, AMMONIUM acetate
Abstract

Low-modulus β-type Ti-45Nb alloy is a promising implant material due to its good mechanical biocompatibility, non-toxicity, and outstanding corrosion resistance. Its excellent chemical stability brings new challenges to chemical surface modification treatments, which are indispensable for both osteogenesis and antibacterial performance. Coatings containing metal ions as anti-microbial agents can be an effective way to reduce implant-associated infections caused by bacterial biofilm. Gallium ion (Ga3+) has the potential to reduce bacterial viability and biofilm formation on implant surfaces. In this study, a novel two-step process has been proposed for Ga3+ incorporation in hydroxyapatite (HAP) to develop bioactive and antibacterial surfaces on Ti-45Nb alloy. For the generation of bioactive surface states, HAP electrodeposition was conducted, followed by wet chemical immersion treatments in gallium nitrate (1 mM). Different buffers such as phosphate, sodium bicarbonate, ammonium acetate, and citrate were added to the solution to maintain a pH value in the range of 6.5–6.9. Coating morphology and HAP phases were retained after treatment with gallium nitrate, and Ga3+ ion presence on the surface up to 1 wt.% was confirmed. Combining Ga and HAP shows great promise to enable the local delivery of Ga3+ ions and consequent antibacterial protection during bone regeneration, without using growth factors or antibiotics. [ABSTRACT FROM AUTHOR]

Published
2023
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43. Effects of thermomechanical history and environment on the fatigue behavior of (β)-Ti-Nb implant alloys

Author

Reck André, Pilz Stefan, Thormann Ulrich, Alt Volker, Gebert Annett, Calin Mariana, Heiß Christian, and Zimmermann Martina

Subjects
Engineering (General). Civil engineering (General), TA1-2040
Abstract

This study examined the fatigue properties of a newly developed cast and thermomechanical processed (β)-Ti-40Nb alloy for a possible application as biomedical alloy due to exceptional low Young’s modulus (64-73 GPa), high corrosion resistance and ductility (20-26%). Focusing on the influence of two microstructural states with fully recrystallized β-grain structure as well as an aged condition with nanometer-sized ω-precipitates, tension-compression fatigue tests (R=-1) were carried out under lab-air and showed significant differences depending on the β-phase stability under cyclic loading. Present ω- precipitates stabilized the β-phase against martensitic α’’ phase transformations leading to an increased fatigue limit of 288 MPa compared to the recrystallized state (225 MPa), where mechanical polishing and subsequent cyclic loading led to formation of α’’-phase due to the metastability of the β-phase. Additional studied commercially available (β)-Ti-45Nb alloy revealed slightly higher fatigue strength (300 MPa) and suggest a change in the dominating cyclic deformation mechanisms according to the sensitive dependence on the Nb-content. Further tests in simulated body fluid (SBF) at 37°C showed no decrease in fatigue strength due to the effect of corrosion and prove the excellent corrosion fatigue resistance of this alloy type under given test conditions.

Published
2018
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