108 research outputs found
Aqueye optical observations of the Crab Nebula pulsar
We observed the Crab pulsar in October 2008 at the Copernico Telescope in
Asiago - Cima Ekar with the optical photon counter Aqueye (the Asiago Quantum
Eye) which has the best temporal resolution and accuracy ever achieved in the
optical domain (hundreds of picoseconds). Our goal was to perform a detailed
analysis of the optical period and phase drift of the main peak of the Crab
pulsar and compare it with the Jodrell Bank ephemerides. We determined the
position of the main peak using the steepest zero of the cross-correlation
function between the pulsar signal and an accurate optical template. The pulsar
rotational period and period derivative have been measured with great accuracy
using observations covering only a 2 day time interval. The error on the period
is 1.7 ps, limited only by the statistical uncertainty. Both the rotational
frequency and its first derivative are in agreement with those from the Jodrell
Bank radio ephemerides archive. We also found evidence of the optical peak
leading the radio one by ~230 microseconds. The distribution of phase-residuals
of the whole dataset is slightly wider than that of a synthetic signal
generated as a sequence of pulses distributed in time with the probability
proportional to the pulse shape, such as the average count rate and background
level are those of the Crab pulsar observed with Aqueye. The counting
statistics and quality of the data allowed us to determine the pulsar period
and period derivative with great accuracy in 2 days only. The time of arrival
of the optical peak of the Crab pulsar leads the radio one in agreement with
what recently reported in the literature. The distribution of the phase
residuals can be approximated with a Gaussian and is consistent with being
completely caused by photon noise (for the best data sets).Comment: 7 pages, 7 figures. Accepted for publication in Astronomy and
Astrophysic
The optical light curve of the LMC pulsar B0540-69 in 2009
This paper reports a detailed analysis of the optical light curve of PSR
B0540-69, the second brightest pulsar in the visible band, obtained in 2009
(Jan. 18 and 20, and Dec. 14, 15, 16, 18) with the very high speed photon
counting photometer Iqueye mounted at the ESO 3.6-m NTT in La Silla (Chile).
The optical light curve derived by Iqueye shows a double structure in the main
peak, with a raising edge steeper than the trailing edge. The double peak can
be fitted by two Gaussians with the same height and FWHM of 13.3 and 15.5 ms
respectively. Our new values of spin frequencies allow to extend by 3.5 years
the time interval over which a reliable estimate of frequency first and second
derivatives can be performed. A discussion of implications on the braking index
and age of the pulsar is carried out. A value of n = 2.087 +/- 0.007 for the
overall braking index from 1987 to 2009 is derived. The braking index corrected
age is confirmed around 1700 years.Comment: Accepted for publication in MNRA
Microspore embryogenesis through anther culture in Citrus clementina Hort ex Tan
Anther culture is a biotechnological method that allows to obtain, in one step, homozygous plants, very important to plant breeding, due to their numerous applications in mutation research, selection, genome sequencing, genetic analysis, and transformation. To induce the microspores, i.e., the immature male gametes, to switch from the normal gametophytic pathway to the sporophytic one, it is necessary to submit them to a type of stress, such as high or low temperature, starvation, or magnetic field. Stress can be applied to the donor plants and/or the fl oral buds or the anthers or the isolated microspores, before or during the culture. In this chapter, the protocol to induce gametic embryogenesis from anther culture of several cultivars of Citrus clementina Hort. ex Tan. is reported
Advances in Utopian Studies and Sacred Architecture
At a time dominated by the disappearance of Future, as claimed by the French anthropologist Marc Augé, Utopia and Religion seem to be two different ways of giving back an inner horizon to mankind.
Therefore this book, on the one hand, considers the importance of utopia as a tool and how it offers an economic and social resource to improve cities’ wealth, future and livability. On the other, it explores the impact of religious and cultural ideals on cities that have recently emerged in this context.
Based on numerous observations, the book examines the intellectual legacy of utopian theory and practices across various academic disciplines. It also presents discussions, theories, and case studies addressing a range of issues and topics related to utopia
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