A detailed study of calcareous nannofossils was conducted on a well-exposed succession encompassing the Cretaceous-Paleogene (K-Pg) boundary interval at Wadi Nukhul, Sinai, Egypt, as a part of the southern Tethyan margin. The nannofossil biostratigraphic data show that the Nukhul succession sustains a complete K-Pg boundary interval. The nannofossil assemblage indicates a shift from cool/oligo-mesotrophic conditions in the late Maastrichtian Micula murus Zone to warm/oligotrophic in the latest Maastrichtian M. prinsii Zone prior to the K-Pg boundary. At the K-Pg boundary, diversity, and total abundance of the calcareous nannofossils remarkably decreased signifying unstable marine conditions. The post-impact assemblage (lowermost part of NP1 Zone) was marked by acme of Cervisiella operculata indicating oligotrophic conditions in the photic zone related to the diminished of the marine primary producers in the lowermost Danian. At the upper portion of NP1 Zone, the assemblage is still dominated by C. operculata, besides the successive occurrence of the small-sized incoming Paleocene taxa Biantholithus sparsus and Neobiscutum romeinii. This pattern was accompanied by increased frequencies of Zeugrhabdotus sigmoides indicating stressful cool/meso-eutrophic surface water conditions signify the initial recovery interval. Upward in the early Danian NP2-NP3 zones, the nannofossil species diversity and total abundance progressively increased. Also, the nannofossil assemblage is characterized by the existence of the new Paleocene oligotrophic indicators like Cruciplacolithus primus, Coccolithus pelagicus, and Ericsonia subpertusa. This probably indicates a tendency toward rebuilding of the biological pump efficiency and, therefore, a full recovery phase was resumed.

Abstract: Here, we have synthesized four series of polyamide-conductive polymers and used them to modify Fe3O4 NPs/ITO electrodes. The ability of the modified electrodes to detect methotrexate (MTX) anticancer drug electrochemically was investigated. Synthesis of the target-conducting polyamides, P1a–d, P2a–d, P3a, P3b, P3d, and P4c-d, based on different aromatic moieties, such as ethyl 4-(2-(4H-pyrazol-4-ylidene)hydrazinyl)benzoate, diphenyl sulfone, diphenyl ether or phenyl, has been achieved. They were successfully prepared in good yield via solution–polycondensation reaction of the diamino monomers with different dicarboxylic acid chlorides in the presence of N-methyl-2-pyrrolidone (NMP) as a solvent and anhydrous LiCl as a catalyst. A model compound 4 was synthesized from one mole of ethyl-4-(2-(3, 5-diamino-4H-pyrazol-4-ylidene)hydrazinyl) benzoate (diamino monomer) (3) with two moles benzoyl chloride. The structure of the synthesized monomers and polymers was confirmed by elemental and spectral analyses. In addition, thermogravimetric analysis evaluated the thermal stabilities of these polyamides. Furthermore, the morphological properties of selected polyamides were examined using an scanning electron microscope. Polyamide/Fe3O4/ITO electrodes were prepared, and the electrochemical measurements were performed to measure the new polyamides’ conductivity and to detect the MTX anticancer drug in phosphate buffer saline using cyclic voltammetry. The polyamides (P3b and P4b)/Fe3O4/ITO electrodes showed the highest sensitivity and reversibility towards MTX.