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Register a new userQuark Matter 84, Helsinki, 17-21 June 1984
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K. Kajantie
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This paper examines the predictions made by Chinese, Muslim and Jesuit astronomers of the eclipse of 21 June 1629 in Beijing, allegedly the event that determined Emperor Chongzhens resolution to reform the calendar using the Western method. In order to establish the accuracy of these predictions, as reported at the time by the Chinese scholar and convert Xu Guangqi, we have compared them with an accurate reconstruction of the eclipse made at NASA. In contrast with current opinions, we argue that the prediction made by the Jesuits was indeed the most accurate. It was in fact instrumental in dissipating Chongzhens doubts about the need to entrust Jesuit missionaries serving at the Chinese court with the task of reforming the calendar, leading to the first important scientific collaboration between Europe and China.
Allan Sandage was an observational astronomer who was happiest at a telescope. On Hubbles sudden death Allan Sandage inherited the programmes using the worlds largest optical telescope at Palomar to determine the distances and number counts of galaxies. Over many years he greatly revised the distance scale and, on re-working Hubbles analysis, discovered the error that had led Hubble to doubt the interpretation of the galaxies redshifts as an expansion of the universe. Sandage showed that there was a consistent age of Creation for the stars, the elements, and the Cosmos. Through work with Baade and Schwarzschild he discovered the key to the interpretation of the colour-magnitude diagrams of star clusters in terms of stellar evolution. With others he founded Galactic Archaeology, interpreting the motions and elemental abundances of the oldest stars in terms of a model for the Galaxys formation. He published several fine atlasses and catalogues of galaxies and a definitive history of the Mount Wilson Observatory.
We discuss the measurements of the main parameters of the ionospheric response to the total solar eclipse of June 21, 2001. This study is based on using the data from three stations of the global GPS network located in the area of the totality band in Africa. This period was characterized by a low level of geomagnetic disturbance (the Dst-index varied from -6 to 22 nT), which alleviated greatly the problem of detecting the ionospheric response to eclipse. An analysis revealed a clearly pronounced effect of a decrease (depression) of the total electron content (TEC) for all GPS stations. The delay between the smallest value of the TEC with respect to eclipse totality was 9-37 min. The depth and duration of the TEC depression were 0.5-0.9 TECU and 30-67 min, respectively. The results obtained in this study are in good agreement with earlier measurements and theoretical estimations.
The first study of resonances in $^{17}$O+$alpha$ elastic scattering was carried out using the Thick Target Inverse Kinematics (TTIK) method. The data were analyzed in the framework of an $textit{R}$-matrix approach. Many $alpha$-cluster states were found in the $^{21}$Ne excitation region of the 9-13 MeV excitation energy including the first observation of a broad $textit{l}$=0 state in an odd-even nucleus, which is likely the analog of the broad 0$^+$ at 8 MeV in $^{20}$Ne. The observed structure in $^{21}$Ne appeared to be strikingly similar to that in $^{20}$Ne populated in the resonance $^{16}$O+$alpha$ scattering. The results are also useful for refinement of data on an $^{17}$O($alpha$,$textit{n}$) reaction important for astrophysics.
The phase transition from hadronic to quark matter may take place already during the early post-bounce stage of core collapse supernovae when matter is still hot and lepton rich. If the phase transition is of first order and exhibits a barrier, the formation of the new phase occurs via the nucleation of droplets. We investigate the thermal nucleation of a quark phase in supernova matter and calculate its rate for a wide range of physical parameters. We show that the formation of the first droplet of a quark phase might be very fast and therefore the phase transition to quark matter could play an important role in the mechanism and dynamics of supernova explosions.
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