Photoacoustic study on the photostability of polymethyl methacrylate films doped with Rhodamine 6G–Rhodamine B dye mixture system

The photosensitivity of dye mixture-doped polymethyl methacrylate (PMMA) films are investigated as a function of laser power, concentration of the dyes, modulation frequency and the irradiation wavelength. Energy transfer from a donor molecule to an acceptor molecule affects the emission output of the dye mixture system. Photosensitivity is found to change with changes in donor–acceptor concentrations. PMMA samples doped with the dye mixture are found to be more photosensitive when the dyes are mixed in the same proportion.

Primary Productivity Of The Retiing Zones In The Kadinamkulamestuary, South-West Coastof India

Retting.of coconut husk is one of the major problems of pollution in the estuaries (Kayals) of Kerala. This paper discusses the salient features associated with the variation in gross and net primary productivity values in the Kadinarnkularn Kayal based on lortnightlydala from twosclected stations frorn Octobcr1987 to September 1988.The gross primary productivity value in the surface water ranged from 0.06 to 0.29gC/m3/day at Station Iand from 0.06 to 1.49gC/rn3/dayatstation II. In the bottom wateritrangcdfrorn oto 0.21 gC/m2/ day at station I whereas that at station II from 0.03 to 1.41gC/m3j day. The net productivity in the surface water at station I varied from 0 to 024 gC/m Iday Whereas that atstation II varied from 0.02to 1.44gC/m3Iday.AI the bottomwaterilvaried from ato 0.19gC/m3/ day at station I and from 0.01 to 1.21gC/m3/day at station II. The monsoon period showed the highest mean seasonal value at stations I and II. The total depletion of dissolved oxygen giving rise to anoxic condition coupled with the production of large quantities of hydrogen sulphide was found to be detrimental to the gross and net productivity values in the retting zone