Thomas, Baby; Ramachandran, T; Radhakrishnan, P; Nampoori, V P N; Vallabhan, C P G(IOP Publishing, 1991)
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Abstract:
A low inductance, triggered spark gap switch suitable for a high-current fast discharge system has been developed. The details of the design and fabrication of this pressurized spark gap, which uses only commonly available materials are described. A transverse discharge Blumlein-driven N2 laser incorporating this device gives a peak output power of 700 kW with a FWHM of 3 ns and an efficiency of 0.51%, which is remarkably high for a pulsed nitrogen laser system.
Thomas, Kuruvilla; Nandakumaran, V M(American Institute of Physics, March , 1999)
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Abstract:
We have numerically studied the behavior of a two-mode Nd-YAG laser with an intracavity KTP crystal. It is found that when the parameter, which is a measure of the relative orientations of the KTP crystal with respect to the Nd-YAG crystal, is varied continuously, the output intensity fluctuations change from chaotic to stable behavior through a sequence of reverse period doubling bifurcations. The graph of the intensity in the X-polarized mode against that in the Y-polarized mode shows a complex pattern in the chaotic regime. The Lyapunov exponent is calculated for the chaotic and periodic regions.
Unnikrishna Pillai, P R; Dr.Padma, Nambisan(Cochin University of Science And Technology, August 17, 1998)
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Abstract:
The effect of lasers of three wavelengths in the visible region - 476, 488 and
514 nm on mitotic and meiotic cell divisions, growth, yield and activity of
specific enzymes were studied in two taxonomically diverse plant species —
A/lium cepa L. and Vicia faba. The effect of laser exposures was compared with
the effect of two physical mutagens (Gamma and Ultraviolet radiations) and two
chemical mutagens (Ethyl Methane Sulphonate and Hydroxyl amine). The study
indicated that lasers could be mutagenic causing aberration in the mitotic and
meiotic cell divisions while also producing changes in the growth and yield of
the plants. Lasers of higher wavelengths 488 and 514 nm caused aberrations in
the early stages of mitotic cell division whereas lasers of lower wavelengths
(476 nm) caused more aberrations in the later stages of mitotic cell division.
Laser exposure of 488 nm wavelength at power density 400 mW induced higher
mitotic and meiotic aberrations and also induced higher pollen sterility than
lasers of 476 and 514 nm. The frequency of mitotic aberrations induced by
lasers was lesser than that caused by y-irradiation but comparable to that
induced by EMS and HA. Lasers cause mutations in higher frequencies than UV.
Lasers had a stimulatory effect on growth and yield in both plant species. This
stimulatory effect of lasers on germination could not however be correlated to
the activity of amylase and protease, the key enzymes in seed gennination.
Enzymes such as peroxidase and catalase, involved in scavenging of free
oxygen radicals often produced by irradiation, did not show increased activity in
laser irradiated samples. Further studies are required for elucidating the exact
mechanisms by which lasers cause mutations
Description:
Department of Biotechnology, Cochin University of Science and Technology