631,347 research outputs found
Dopamine-D1 and δ-opioid receptors co-exist in rat striatal neurons
Cocaine’s enhancement of dopaminergic neurotransmission in the mesolimbic pathway plays a critical role in the initial reinforcing properties of this drug. However, other neurotransmitter systems are also integral to the addiction process. A large body of data indicates that opioids and dopamine together mediate emotional and reinforced behaviors. In support of this, cocaine-mediated increases in activation of dopamine D1 receptors (D1R) results in a desensitization of δ-opioid receptor (DOR) signaling through adenylyl cyclase (AC) in striatal neurons. To further define cellular mechanisms underlying this effect, the subcellular distribution of DOR and D1R was examined in the rat dorsolateral striatum. Dual immunoperoxidase/gold-silver detection combined with electron microscopy was used to identify DOR and D1R immunoreactivities in the same section of tissue. Semi-quantitative analysis revealed that a subset of dendritic cellular profiles exhibited both DOR and D1R immunoreactivities. Of 165 randomly sampled D1R immunoreactive profiles, 43% contained DOR. Similarly of 198 DOR-labeled cellular profiles, 52% contained D1R. The present data provide ultrastructural evidence for co-existence between DOR and D1R in striatal neurons, suggesting a possible mechanism whereby D1R modulation may alter DOR function
Improved age constraints for the AB Dor quadruple system - The binary nature of AB Dor B
We present resolved NACO photometry of the close binary AB Dor B in H- and
Ks-band. AB Dor B is itself known to be a wide binary companion to AB Dor A,
which in turn has a very low-mass close companion named AB Dor C. These four
known components make up the young and dynamically interesting system AB Dor,
which will likely become a benchmark system for calibrating theoretical
pre-main sequence evolutionary mass tracks for low-mass stars. However, for
this purpose the actual age has to be known, and this subject has been a matter
of discussion in the recent scientific literature. We compare our resolved
photometry of AB Dor Ba and Bb with theoretical and empirical isochrones in
order to constrain the age of the system. This leads to an age estimate of
about 50 to 100 Myr. We discuss the implications of such an age range for the
case of AB Dor C, and compare with other results in the literature.Comment: 7 pages, 6 figures, accepted for publication in A&
Theoretical study of Doradus pulsations in pre-main sequence stars
The question of the existence of pre-main sequence (PMS) ~Doradus
(~Dor) has been raised by the observations of young clusters such as
NGC~884 hosting ~Dor members. We have explored the properties of
~Dor type pulsations in a grid of PMS models covering the mass range
and we derive the theoretical instability
strip (IS) for the PMS ~Dor pulsators. We explore the possibility of
distinguishing between PMS and MS ~Dor by the behaviour of the period
spacing of their high order -modes (-modes).Comment: 5 pages, 6 figures, Proc. HELAS IV Conference, Lanzarote, February
2010. Eds T. Roca Cort\'es, P. Pall\'e and S. Jim\'enez Reyes. Accepted in
Astron. Nac
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Nepal School of Sociology/Anthropology
Occasional Papers in Sociology and Anthropology - Volume 1, 198
Improved Training for Self-Training by Confidence Assessments
It is well known that for some tasks, labeled data sets may be hard to
gather. Therefore, we wished to tackle here the problem of having insufficient
training data. We examined learning methods from unlabeled data after an
initial training on a limited labeled data set. The suggested approach can be
used as an online learning method on the unlabeled test set. In the general
classification task, whenever we predict a label with high enough confidence,
we treat it as a true label and train the data accordingly. For the semantic
segmentation task, a classic example for an expensive data labeling process, we
do so pixel-wise. Our suggested approaches were applied on the MNIST data-set
as a proof of concept for a vision classification task and on the ADE20K
data-set in order to tackle the semi-supervised semantic segmentation problem
Theoretical seismic properties of pre-main sequence gamma Doradus pulsators
Context. gamma Doradus (gamma Dor) are late A and F-type stars pulsating with
high order gravity modes (g-modes). The existence of different evolutionary
phases crossing the gamma Dor instability strip raises the question of the
existence of pre-main sequence (PMS) gamma Dor stars. Aims. We intend to study
the differences between the asteroseismic behaviour of PMS and main sequence
(MS) gamma Dor pulsators as it is predicted by the current theory of stellar
evolution and stability. Methods. We explore the adiabatic and non-adiabatic
properties of high order g-modes in a grid of PMS and MS models covering the
mass range 1.2 Msun < Mstar < 2.5 Msun. Results. We derive the theoretical
instability strip (IS) for the PMS gamma Dor pulsators. This IS covers the same
effective temperature range as the MS gamma Dor one. Nevertheless, the
frequency domain of unstable modes in PMS models with a fully radiative core is
larger than in MS models, even if they present the same number of unstable
modes. Moreover, the differences between MS and PMS internal structures are
reflected on the average values of the period spacing as well as on the
dependence of the period spacing on the radial order of the modes, opening the
window to the determination of the evolutionary phase of gamma Dor stars from
their pulsation spectra.Comment: 9 pages, 17 figures, accepted for publication in A&
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