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R. Rudolf,I. Anzel,L. Gusel,D. Stamenkovic,A. Todorovic,M. Colic 대한금속·재료학회 2010 METALS AND MATERIALS International Vol.16 No.6
Microstructures of two high noble experimental Au-Pt alloys were compared before and after conditioning for biocompatibility, in order to identify phases and microelements responsible for the alloys’ corrosive behaviour. Microstructural characterization was carried-out by optical and scanning electron microscopy, in addition to energy dispersive X-ray analysis. X-ray diffraction was applied to determine the phases’ composition and their contribution in the alloys. Additionally, simultaneous thermal analysis was used to identify the temperatures of phase transformations. An overall assessment before conditioning showed that Au-Pt I is a two-phase alloy containing a dominant Au-rich α1 phase and a minor Pt-rich α2 phase, while the Au-Pt II alloy contains in addition three minor phases: AuZn3, Pt3Zn and Au1.4Zn0.52. The highest content of Zn (up to 6.76 wt.%)was detected in the Pt3Zn phase. After RPMI cell culture medium conditioning, the Pt3Zn and AuZn3 phases disappeared, suggesting that they are predominantly responsible for Zn loss and the lower corrosive stability of the Au-Pt II alloy.
Metal-Organic Frameworks Mediate Cu Coordination for Selective CO<sub>2</sub> Electroreduction
Nam, Dae-Hyun,Bushuyev, Oleksandr S.,Li, Jun,De Luna, Phil,Seifitokaldani, Ali,Dinh, Cao-Thang,Garcí,a de Arquer, F. Pelayo,Wang, Yuhang,Liang, Zhiqin,Proppe, Andrew H.,Tan, Chih Shan,Todorovic& American Chemical Society 2018 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.140 No.36
<P>The electrochemical carbon dioxide reduction reaction (CO<SUB>2</SUB>RR) produces diverse chemical species. Cu clusters with a judiciously controlled surface coordination number (CN) provide active sites that simultaneously optimize selectivity, activity, and efficiency for CO<SUB>2</SUB>RR. Here we report a strategy involving metal-organic framework (MOF)-regulated Cu cluster formation that shifts CO<SUB>2</SUB> electroreduction toward multiple-carbon product generation. Specifically, we promoted undercoordinated sites during the formation of Cu clusters by controlling the structure of the Cu dimer, the precursor for Cu clusters. We distorted the symmetric paddle-wheel Cu dimer secondary building block of HKUST-1 to an asymmetric motif by separating adjacent benzene tricarboxylate moieties using thermal treatment. By varying materials processing conditions, we modulated the asymmetric local atomic structure, oxidation state and bonding strain of Cu dimers. Using electron paramagnetic resonance (EPR) and in situ X-ray absorption spectroscopy (XAS) experiments, we observed the formation of Cu clusters with low CN from distorted Cu dimers in HKUST-1 during CO<SUB>2</SUB> electroreduction. These exhibited 45% C<SUB>2</SUB>H<SUB>4</SUB> faradaic efficiency (FE), a record for MOF-derived Cu cluster catalysts. A structure-activity relationship was established wherein the tuning of the Cu-Cu CN in Cu clusters determines the CO<SUB>2</SUB>RR selectivity.</P> [FIG OMISSION]</BR>
Stankov, Iv.K.,Todorov, N.A.,Mitev, J.E.,Miteva, Tch.M. Asian Australasian Association of Animal Productio 2002 Animal Bioscience Vol.15 No.2
A comparative study on the quality of meat from three breeds of goats reared in Bulgaria: Local Aboriginal (LA); Bulgarian White Dairy (BWD) and crossbreeds of local aboriginal with Saanen goats (LA ${\times}$ S). Eight intact young male goats from each breed have been included in the experiment. The animals from the three breeds have been reared under similar conditions. The animals have been slaughtered at the age of 2 months (at weaning) and at the age of 6 months (upon reaching sexual maturity). The following tests have been performed on samples of m. longissimus dorsi between $5^{th}$ and $6^{th}$ ribs: pH 45 min post mortum, colorimetrically color of meat, water holding capacity and fatty acid composition of the fat. The thickness of muscle fibre and the proportion of muscle, connective and adipose tissue have been microscopically determined at m. longissimus dorsi, m. semitendinosus and m. iliopsoas. After deboning and separating the bigger tendons, the chemical composition of the meat from the left half of the carcass has been determined. The results reveal lack of statistically significant differences among the three breeds concerning pH, the water holding capacity, color of meat, thickness of the muscle fibre and fatty acid composition of the fat. The carcass meat of crossbreeds of LA ${\times}$ S contains significantly more fat than the other two breeds. This influences the proportion of muscle, connective and adipose tissue in m. longissimus dorsi, m. semitendinosus and m. iliopsoas, resulting in more adipose tissue in the LA ${\times}$ S compared to young goats of the LA or the BWD. There are differences in slaughtering 2-month-old goats (at weaning) and 6-month-old ones (upon reaching sexual maturity). At a greater age the content of fat in the carcass increases, as well as the quantity of the adipose tissue, the intensity of the colour of the meat and there is a tendency towards thickening of the muscle fibre and increasing the water holding capacity of meat. The moisture content in meat decreases due to the increase of fat.