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Träfflista för sökning "WFRF:(Paredes M) srt2:(2005-2009)"

Sökning: WFRF:(Paredes M) > (2005-2009)

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1.
  • Acciari, V. A., et al. (författare)
  • Radio Imaging of the Very-High-Energy gamma-Ray Emission Region in the Central Engine of a Radio Galaxy
  • 2009
  • Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 325:5939, s. 444-448
  • Tidskriftsartikel (refereegranskat)abstract
    • The accretion of matter onto a massive black hole is believed to feed the relativistic plasma jets found in many active galactic nuclei (AGN). Although some AGN accelerate particles to energies exceeding 10(12) electron volts and are bright sources of very-high-energy (VHE) gamma-ray emission, it is not yet known where the VHE emission originates. Here we report on radio and VHE observations of the radio galaxy Messier 87, revealing a period of extremely strong VHE gamma-ray flares accompanied by a strong increase of the radio flux from its nucleus. These results imply that charged particles are accelerated to very high energies in the immediate vicinity of the black hole.
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2.
  • Shein, K.A., et al. (författare)
  • State of the Climate in 2005
  • 2006
  • Ingår i: Bulletin of American Meteorological Society. ; 87:6, s. 1-102
  • Tidskriftsartikel (refereegranskat)
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3.
  • Crovetto, Luis, et al. (författare)
  • Photophysics of a xanthenic derivative dye useful as an ""On/Off"" fluorescence probe
  • 2007
  • Ingår i: Journal of Physical Chemistry A. - : American Chemical Society. - 1089-5639 .- 1520-5215. ; 111:51, s. 13311-13320
  • Tidskriftsartikel (refereegranskat)abstract
    • The photophysical behavior of a new fluorescein derivative has been explored by using absorption and steady-state and time-resolved fluorescence measurements. The influence of ionic strength, as well as total buffer concentration, on both the absorbance and fluorescence has been investigated. The apparent acidity constant of the dye determined by absorbance is almost independent of the added buffer and salt concentrations. A semiempirical model is proposed to rationalize the variations in the apparent pK(a) values. The excited-state proton-exchange reaction around the physiological pH becomes reversible upon addition of phosphate buffer, inducing a pH-dependent change of the steady-state fluorescence and decay times. Fluorescence decay traces, collected as a function of total buffer concentration and pH, were analyzed by global compartmental analysis, yielding the following values of the rate constants describing excited-state dynamics: k(01) = 1.29 x 10(10) s(-1), k(02) = 4.21 x 10(8) s(-1), k(21)approximate to 3 x 10(6) M-1 s(-1), k(12)(B) = 6.40 x 10(8) M-1 s(-1), and k(21)(B) = 2.61 x 10(7) M-1 s(- 1). The decay rate constant values of k(01), k(21), and k(21)(B), along with the low molar absorption coefficient of the neutral form, mean that coupled decays are practically monoexponential at buffer concentrations higher than 0.02 M and any pH. Thus, the pH and buffer concentration can modulate the main lifetime of the dye.
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  • Resultat 1-3 av 3

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