127 research outputs found
Age-related changes of the noradrenergic and acetylcholinesterase reactive nerve fibres innervating the pigeon bursa of Fabricius.
Age-dependent changes in the innervation of the pigeon (Columba livia, L.) bursa of Fabricius, from hatching to 120 days of age, were studied by fluorescence-histochemical and neurochemical methods for demonstrating noradrenergic and acetylcholinesterase (AChE)-reactive nerve fibres respectively. The distribution of both nerve fibre types was largely perivascular. Furthermore, a few isolated nerve fiber profiles were observed beneath the bursal epithelium, in the interfollicular septa and in the follicular cortex. No nerve fibre profiles reaching the medulla of the lymphoid follicles were observed. In addition to nerve fibres, AChE reactive neuron-like cells were encountered within the capsule and interfollicular septa. AChE reactivity was also found in dendritic-like cells localized in the cortical and cortico-medullary border. No changes in the density of perivascular noradrenergic innervation were noticeable during the ages studied, whereas the density of AChE-reactive fibres supplying vessels reached the adult pattern at 30 days, and then remained unvaried. The density of non-perivascular nerve fiber profiles, specially the AChE reactive type, increased until 30 days, remained unchanged until 75 days and then increased with aging (90-120 days). The interrelationship between the autonomic nervous system and the immune system is discussed
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
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