The 2020 announcement by LHCb of a narrow structure $X(6900)$ in the di-$J/\psi$ spectrum -- potential $c\bar c c\bar c$ state has opened new era hadronic spectroscopy. In this talk, we briefly survey theory works preceding event, examine key features observed spectrum, and then discuss how subsequent studies (including with author's own dynamical diquark model) have interpreted these features....

Three different Aspergillus Niger MTCC strains (872, 1785 and 2208) were used for the production of chitosan. Multivariate growth mediums in varying incubation periods were analyzed for the production. The produced chitosan was characterized by its physical appearance, moisture content (by means of gravimetric method), percentage of ash and solubility (through the Association of Official Agricu...