In Search of Rationality in Human Longevity and Immortality.

The human body is machine-like, but self-moving, self-regulating, and self-adjusting, governed by willpower and intelligence. Aging of the body is basically a maintenance problem and so it could perhaps be postponed by thorough and frequent maintenance. Aging brings on a cascade of ills and health problems leading to deterioration of physical, mental, emotional, and social dimensions of life. This paper deals with solution of the problem philosophically in the light of Indian scriptures without entering into traditional bioethical issues. With a meaningful reason for existence, life can be extended. Examining the scientific perspectives on aging, some common manipulations for its extension are discussed. These are calorie restriction, vitamin and antioxidant treatment, exercise and hormonal interventions, etc. Finally, the question of longevity is explored through pursuance of eternal value-based activity and spirituality in the tradition of Indian heritage.

Multipass configuration to achieve high-frequency conversion in Li2B4O7 crystals.

A multipass configuration for second-harmonic generation of Nd:YAG laser radiation is demonstrated to produce, for the first time to the authors' knowledge in twin lithium tetraborate crystals, as much as 21% conversion efficiency even though the effective nonlinear coefficient of the crystal is as low as 1/6th that of KDP. Apart from crystals that have large walk-off angles, low effective nonlinear coefficients, or both, the simple experimental setup would also be quite suitable for those crystals, especially infrared crystals, that have large effective nonlinear coefficients but low laser damage thresholds.

Sellmeier dispersion for phase-matched terahertz generation in ZnGeP2.

A Sellmeier dispersion of zinc germanium diphosphide (ZnGeP2) crystal has been formulated to determine the phase-matching characteristics of the crystal for the generation of coherent tunable terahertz radiation by difference-frequency mixing techniques. The results computed with the formulated Sellmeier dispersion provide an excellent fit to the experimental data.

Linear and nonlinear optical properties of ZnGeP2 crystal for infrared laser device applications: revisited.

Measurement of refractive indices in the spectral bands 9-11 microm and 1.32 microm from a cw CO2 laser and a Q-switched Nd:YAG laser, respectively, is reported in a ZnGeP2 crystal. A new set of Sellmeier dispersion relations has been derived from the measured refractive indices data in this crystal. Second-harmonic generation (SHG) of CO2 laser radiation in this crystal is also reported. It is also seen that the previously reported phase-matching data for others experiments in SHG and optical parametric devices is explained satisfactorily with this new set of Sellmeier dispersion relation.