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Filamentation of ultrashort pulse laser beams resulting from their propagation over long distances in air (1999)

La Fontaine, B. ; Vidal, F. ; Jiang, Z. ; [et al.]

[S.l.] : American Institute of Physics (AIP)

Physics of Plasmas 6 (1999), S. 1615-1621

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ISSN: 1089-7674

Source: AIP Digital Archive

Topics: Physics

Notes: The propagation of high-power short-pulse laser beams over considerable distances in air is studied both experimentally and via numerical simulations. Filaments are formed after 5–10 m and their propagation over distances in excess of 200 m is reported for the first time. The lateral dimensions of the filaments are found to range from about 100 μm to a few millimeters in diameter. The early values of plasma electron density have been inferred to be a few times 1016 cm−3 using longitudinal spectral interferometry. For 500 fs pulses and a wavelength of 1053 nm, the energy in the filament can be quite high initially (∼8 mJ) and is found to stabilize at about 1.5–2 mJ, after about 35 m. A simple model based on the nonlinear Schrödinger equation coupled to a multiphoton ionization law appears to describe several experimental results quite well. © 1999 American Institute of Physics.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.873715

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Regulation and molecular structure of a circadian oscillating protein located in the cell membrane of the prokaryote Synechococcus RF-1 (1996)

Chen, H- M. ; Chien, C- Y. ; Huang, T- C.

Springer

Planta 199 (1996), S. 520-527

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ISSN: 1432-2048

Keywords: Biological clock ; Circadian rhythm ; Molecular structure ; Prokaryote ; Protein (degradation, synthesis) ; Synechococcus RF-1

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract When a light/light-adapted culture of Synechococcus RF-1 is exposed to a diurnal light/dark regimen, the synthesis of more than ten of its polypeptides is known to become entrained to a circadian oscillating pattern which persists for some time under free-running conditions. One of the circadian oscillating polypeptides, COP23, was found to be located in the cell membrane. The rate of COP23 synthesis is controlled at the transcription level. In addition to the protein synthesis rate, the content of COP23 also exhibited a circadian rhythm. Pulse labeling with [35S]methionine revealed that COP23 was relatively stable in an arrhythmic culture. However, the exposure of Synechococcus RF-1 to a light/dark regimen induced not only a circadian synthesis rhythm, but also a rapid degradation of COP23 protein at a defined period of time. The induction of rapid protein degradation was prevented by the presence of chloramphenicol. The gene encoding the COP23 polypeptide has been cloned and sequenced. The amino acid sequence derived from the open-reading frame revealed that a signal peptide (28 amino acids) does not appear to be part of the mature COP23. The mature COP23 does not have a membrane-associated segment, and it is suggested to be a peripheral molecule. With respect to their DNA base sequence and protein amino acid sequence, none of the proteins documented in the EMBL and PC/Gene data bases are significantly homologous with the COP23 molecule.