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This paper provides a counterexample to three questions posed by Richman and Schneider in a recent paper concerning primes in the semigroup Nnof n×n nonnegative matrices. 相似文献
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High gain x-ray lasers at the water window 总被引:2,自引:0,他引:2
Maxon S Estabrook KG Prasad MK Osterheld AL London RA Eder DC 《Physical review letters》1993,70(15):2285-2288
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This paper provides a counterexample to three questions posed by Richman and Schneider in a recent paper concerning primes in the semigroup Nn of n×n nonnegative matrices. 相似文献
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C. J. Keane B. J. MacGowan D. L. Matthews R. A. London S. Maxon M. D. Rosen J. L. Bourgade A. Decoster S. Jacquemot M. Louis-Jacquet D. Naccache 《Applied physics. B, Lasers and optics》1990,50(4):257-264
Recent Ne- and Ni-like X-ray laser experiments carried out at the Centre d'Etudes de Limeil-Valenton (CEL-V) are reviewed. A variety of experiments in Ne-like X-ray lasers were performed; here we discuss measurements of soft X-ray amplification in Ge (Z=32) and Sr (Z=38) plasmas. In Ge plasmas produced by 0.53-m laser light at an irradiance of 6.0×1013 W/cm2, gains between 2.2–2.5 cm–1 on the 232.2 and 236.2 Å J=2–1 lines and a gain of 1.0 cm–1 on the 196.1 Å J=0–1 line were measured. In addition, gains of 4.4 cm–1 and 4.0 cm–1 have been demonstrated on the J=2–1 transitions at 164.1 and 166.5 Å in Nelike Sr at laser intensities of 1.3×1014 W/cm2. The effects of pumping the Ne-like Se X-ray laser with 0.35-m laser light have also been investigated; the Se lasing spectra is similar to that obtained with 0.53-m light. Experiments have also been carried out to optimize the gain of the 50.3 Å Ni-like Yb (Z=70) J=0–1 line. For Yb, no significant increase in gain over that previously reported was seen, but the time history of the Ni-like Yb X-ray laser was measured for the first time. Finally, attempts to extrapolate the Ni-like results to shorter wavelength were made using Ta (Z=73), W (Z=74), and Re (Z=75). No definitive observation of the Ni-like J=0–1 lasing lines was made in these experiments. 相似文献
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Abstract— The wavelength-dependence of in vitro photoreactivation of transforming DNA by yeast extract has been determined. There is an intensity-dependent lag at the beginning of the biological reaction. There is a similar lag in the splitting of thymine dimers by the yeast extract in the light, a process known to account for most or all of the increase in transforming activity of photoreactivated DNA. The most efficient wavelengths for photoreactivation are around 3550 and 3850 Å. Although the action spectrum is not very similar to flavin absorption, riboflavin at very low concentration inhibits photoreactivation, as it also inhibits a number of flavoenzymes, suggesting that the photoreactivating enzyme might be a flavoprotein. 相似文献
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