Scolopsislacrima, a new species of monocle bream (Teleostei, Perciformes, Nemipteridae) from New Caledonia.

The new monocle bream Scolopsislacrima sp. nov. is described from a single specimen (213.6 mm standard length) collected from Grande-Terre Island, New Caledonia. The new species closely resembles S.meridiana, both species having the upper part of the pectoral-fin base with reddish blotch when fresh, two bands across the top of the snout, a dorsal scaled area on the head reaching anteriorly to between the anterior margin of the eye and anterior nostril, a similar number of lateral-line scales, and absence of a small antrorse spine below the eye. However, S.lacrima sp. nov. is distinguished from S.meridiana by having diagonal lines on the body absent (vs. 18-20 diagonal lines in the latter), a dark longitudinal band below the lateral line (vs. longitudinal lines absent), the caudal fin central area not patterned (vs. with several dark horizontal lines), a narrower body and shallower caudal peduncle.

Scolopsis meridiana, a new species of monocle bream (Perciformes: Nemipteridae) from northern Australia.

Scolopsis meridiana n. sp., described from 30 specimens collected from northern Australia, is closely related to S. taenioptera, both species having a dorsal scaled area on the head extending anteriorly to between the anterior margin of the eye and anterior nostril, the upper part of the pectoral-fin base with a reddish blotch when fresh, and lacking a small antrorse spine below the eye. However, the new species is distinguished from the latter by having two bands across the snout dorsum (vs. one band in S. taenioptera), 18-20 diagonal lines on the lateral body surface below the lateral line (diagonal lines absent), the posterior nostril horizontally elongated (vertically elongated), a deep caudal-peduncle and short pre-dorsal-fin length. Scolopsis meridiana is distributed in northern Australia, whereas S. taenioptera occurs in Southeast Asia. Two geographic populations of S. taenioptera (Philippines and remaining Southeast Asian region) are recognized following morphological and genetic analyses.

High-efficiency generation of pulsed Lyman-α radiation by resonant laser wave mixing in low pressure Kr-Ar mixture.

We report an experimental generation of ns pulsed 121.568 nm Lyman-α radiation by the resonant nonlinear four-wave mixing of 212.556 nm and 845.015 nm radiation pulses providing a high conversion efficiency 1.7x10-3 with the output pulse energy 3.6 µJ achieved using a low pressure Kr-Ar mixture. Theoretical analysis shows that this efficiency is achieved due to the advantage of using (i) the high input laser intensities in combination with (ii) the low gas pressure allowing us to avoid the onset of full-scale discharge in the laser focus. In particular, under our experimental conditions the main mechanism of photoionization caused by the resonant 2-photon 212.556 nm radiation excitation of Kr atoms followed by the 1-photon ionization leads to ≈17% loss of Kr atoms and efficiency loss only by the end of the pulse. The energy of free electrons, generated by 212.556 nm radiation via (2 + 1)-photon ionization and accelerated mainly by 845.015 nm radiation, remains during the pulse below the level sufficient for the onset of full-scale discharge by the electron avalanche. Our analysis also suggests that ≈30-fold increase of 845.015 nm pulse energy can allow one to scale up the L-α radiation pulse energy towards the level of ≈100 µJ.