Random laser action in bovine semen

Experiments using bovine semen reveal that the addition of a high-gain water soluble dye results in random laser action when excited by a Q-switched, frequency doubled, Nd:Yag laser. The data shows that the linewidth collapse of the emission is correlated to the sperm count of the individual samples, potentially making this a rapid, low sample volume approach to count determination.     

Spheroidal particle plasmons in amplifying media

The effect of a surrounding gain medium on the localized surface plasmon resonance in spheroidal metal particles is analyzed in the quasi-static limit of the Maxwell equations. It is shown that the gain required to create a singularity in the dynamic polarizability of the particle is significantly lower for non-spherical spheroids than for spheres, and can be as low as several hundred inverse centimeters for noble metals in the near infrared region of the spectrum. Resonant aspect ratios and gain values are calculated as a function of frequency for various metals. The use of non-spherically shaped nano-particles, along with gains achievable in semiconductors and dyes, can result in surface enhanced Raman scattering (SERS) signals which are dramatically enhanced. PACS 61.46.Df; 73.21.Hb; 78.67.Hc     

Role of solid-solution strengthening and interactions in the dislocation ensemble in the formation of flow stress in austenitic nitrogen steel

The paper reports on an experimental investigation of the role of structural levels of deformation in the formation of the flow stress of austenitic nitrided steel. The contributions to the yield stress and the flow stress from the structural levels of various scales have been determined and it has been found that small-scale levels make the main contribution to the strain resistance. A detailed study of the dislocation ensemble has shown that undergoes strong relaxation at different stages of deformation. The laws of solid-solution strengthening and its effect on substructural transformations are examined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 33–56, March, 1996.     

Direct laser writing of diffractive optics in glass

Low-power lasers and a novel thermal expansion process in semiconductor-doped glasses are used to fabricate diffractive optical elements.     

Search for isovector giant monopole resonances via the Pb(3He,tp) reaction

The (nat)Pb(3He,tp) reaction at E(3He) = 177 MeV was studied to identify 2Planck's over 2piomega isovector monopole strength in Bi isotopes. Monopole strength was found in the region -45相似文献   

On the Bifurcations and Multiple Endemic States of a Single Strain HIV Model Dedicated to Professor Toshikazu Sunada on the Occasion of his 60th Birthday

The dynamics of a single strain HIV model is studied.The basic reproduction number R_0 used as a bifurcation parameter shows that the system undergoes transcritical and saddle-node bifurcations.The usual threshold unit value of R_0 does not completely determine the eradication of the disease in an HIV infected person.In particular,a sub-threshold value R_C is established which determines the system's number of endemic states:multiple if R_c Ro 1,only one if R_C = R_0 = 1,and none if R_0 R_C 1.