We demonstrate sensitive spatially resolved detection of physiological chromophores that emit in the ultraviolet (<330 nm). An atypical laser source (a visible wavelength femtosecond optical parametric oscillator), and an unconventional collection geometry (a lensless detector that detects the forward-emitted fluorescence) enable this detection. We report the excitation spectra of the catecholamines dopamine and norepinephrine, together with near-UV emitters serotonin and tryptophan, in the range of 550-595 nm. We estimate the molecular two-photon action cross section of dopamine, norepinephrine, and serotonin to be 1.2 mGM (1 GM, or Goppert Mayor, is equal to 10(-58) m4 s(-1) photon(-1)), 2 mGM, and 43 mGM, respectively, at 560 nm. The sensitivity achieved by this method holds promise for the microscopic imaging of vesicular catecholamines in live cells.

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Some of the important critical parameters for assessing the water quality like pH (Hydrogen ion concentration), DO (Dissolved Oxygen), BOD (Biological Oxygen Demand), etc., were monitored at different locations in some major Indian rivers. The results obtained from the study reveals that the critical parameters had increasing values in some monitoring locations, decreasing values, and no variation in values at some other places. It is recommended to have a pH value above 7, higher values of DO, lower values of BOD & FCC (Faecal Coliform Content) for improved water quality. Overall, the water quality improved in most Indian rivers. There was no discharge of industrial wastes, hotels/restaurants wastes, immersing of idols during religious festivals, etc., to the rivers during the COVID-19 lockdown. Therefore, enforcement of strict regulations by the Government of India for disposal of wastes produced from industrial & domestic activities can significantly reduce the water pollution levels in the Indian rivers.