16 research outputs found
Memberships and CM Diagrams of the Open Cluster NGC 7243
The results of astrometric and photometric investigations of the open cluster
NGC 7243 are presented. Proper motions of 2165 stars with root-mean-square
error of 1.1 mas/yr were obtained by means of PDS scanning of astrometric
plates covering the time interval of 97 years. A total of 211 cluster members
down to V=15.5 mag have been identified. V and B magnitudes have been
determined for 2118 and 2110 stars respectively. Estimations of mass (348Mo < M
< 522Mo), age (t=2.5x10^8 yr), distance (r=698 pc) and reddening (E(B-V)=0.24)
of the cluster NGC 7243 have been made.Comment: 24 pages, 15 figures. Submitted to Astronomy and Astrophysic
Kinematic Peculiarities of Gould Belt Stars
We analyzed the space velocities of Gould Belt stars younger than 125 Myr
located at heliocentric distances <650 pc. We determined the rotation and
expansion parameters of the Gould Belt by assuming the existence of a single
kinematic center whose direction was found to be the following:
and pc. The linear velocities reach their
maximum at a distance of pc from the center and are -6 km s
for the rotation (whose direction coincides with the Galactic rotation) and +4
km s for the expansion. The stellar rotation model used here is shown to
give a more faithful description of the observed velocity field than the linear
model based on the Oort constants and . We present evidence that the
young clusters Pic, Tuc/HorA, and TWA belong to the Gould Belt
structure.Comment: 17 pages, 5 figure
Neonatal Administration of Thimerosal Causes Persistent Changes in Mu Opioid Receptors in the Rat Brain
Thimerosal added to some pediatric vaccines is suspected in pathogenesis of several neurodevelopmental disorders. Our previous study showed that thimerosal administered to suckling rats causes persistent, endogenous opioid-mediated hypoalgesia. Here we examined, using immunohistochemical staining technique, the density of μ-opioid receptors (MORs) in the brains of rats, which in the second postnatal week received four i.m. injections of thimerosal at doses 12, 240, 1,440 or 3,000 μg Hg/kg. The periaqueductal gray, caudate putamen and hippocampus were examined. Thimerosal administration caused dose-dependent statistically significant increase in MOR densities in the periaqueductal gray and caudate putamen, but decrease in the dentate gyrus, where it was accompanied by the presence of degenerating neurons and loss of synaptic vesicle marker (synaptophysin). These data document that exposure to thimerosal during early postnatal life produces lasting alterations in the densities of brain opioid receptors along with other neuropathological changes, which may disturb brain development
Film Thickening on Nickel in Aqueous Solution in Relation to Anion Type and Concentration
A neuronal circuit for colour vision based on rod–cone opponency
In bright light, cone-photoreceptors are active and colour vision derives from a comparison of signals in cones with different visual pigments. This comparison begins in the retina, where certain retinal ganglion cells have ‘colour-opponent’ visual responses—excited by light of one colour and suppressed by another colour. In dim light, rod-photoreceptors are active, but colour vision is impossible because they all use the same visual pigment. Instead, the rod signals are thought to splice into retinal circuits at various points, in synergy with the cone signals. Here we report a new circuit for colour vision that challenges these expectations. A genetically identified type of mouse retinal ganglion cell called JAMB (J-RGC), was found to have colour-opponent responses, OFF to ultraviolet (UV) light and ON to green light. Although the mouse retina contains a green-sensitive cone, the ON response instead originates in rods. Rods and cones both contribute to the response over several decades of light intensity. Remarkably, the rod signal in this circuit is antagonistic to that from cones. For rodents, this UV-green channel may play a role in social communication, as suggested by spectral measurements from the environment. In the human retina, all of the components for this circuit exist as well, and its function can explain certain experiences of colour in dim lights, such as a ‘blue shift’ in twilight. The discovery of this genetically defined pathway will enable new targeted studies of colour processing in the brain