5,091 research outputs found
Coordinates of features on the Galilean satellites
The coordinate systems of each of the Galilean satellites are defined and coordinates of features seen in the Voyager pictures of these satellites are presented. The control nets of the satellites were computed by means of single block analytical triangulations. The normal equations were solved by the conjugate iterative method which is convenient and which converges rapidly as the initial estimates of the parameters are very good
Coordinates of features on the Galilean satellites
Control nets of the four Galilean satellites, established photogrammetrically from pictures taken by the two Voyager spacecraft during their flybys of Jupiter in 1979, are discussed. Coordinates of 504 points on Io, 112 points on Europa, 1547 points on Ganymede, and 439 points on Callisto are listed. Selected points are identified on maps of the satellites. Measurements of these points were made on 234 pictures of Io, 115 pictures of Europa, 282 pictures of Ganymede, and 200 pictures of Callisto. The systems of longitude were defined by craters on Europa, Ganymede, and Callisto. Preliminary solutions are found for the directions of the axes of rotation of the Galilean satellites. Mean radii are determined as 1815 + or - 5 km for Io, 1569 + or - 10 km for Europa, 2631 + or - km for Ganymede, and 2400 + or - 10 km for Callisto
Ag and N acceptors in ZnO: ab initio study of acceptor pairing, doping efficiency, and the role of hydrogen
Efficiency of ZnO doping with Ag and N shallow acceptors, which substitute
respectively cations and anions, was investigated. First principles
calculations indicate a strong tendency towards formation of nearest neighbor
Ag-N pairs and N-Ag-N triangles. Binding of acceptors stems from the formation
of quasi-molecular bonds between dopants, and has a universal character in
semiconductors. The pairing increases energy levels of impurities, and thus
lowers doping efficiency. In the presence of donors, pairing is weaker or even
forbidden. However, hydrogen has a tendency to form clusters with Ag and N,
which favors the Ag-N aggregation and lowers the acceptor levels of such
complexes.Comment: 10 pages, 4 figure
Inhibition of cellular protein secretion by norwalk virus nonstructural protein p22 requires a mimic of an endoplasmic reticulum export signal.
Protein trafficking between the endoplasmic reticulum (ER) and Golgi apparatus is central to cellular homeostasis. ER export signals are utilized by a subset of proteins to rapidly exit the ER by direct uptake into COPII vesicles for transport to the Golgi. Norwalk virus nonstructural protein p22 contains a YXΦESDG motif that mimics a di-acidic ER export signal in both sequence and function. However, unlike normal ER export signals, the ER export signal mimic of p22 is necessary for apparent inhibition of normal COPII vesicle trafficking, which leads to Golgi disassembly and antagonism of Golgi-dependent cellular protein secretion. This is the first reported function for p22. Disassembly of the Golgi apparatus was also observed in cells replicating Norwalk virus, which may contribute to pathogenesis by interfering with cellular processes that are dependent on an intact secretory pathway. These results indicate that the ER export signal mimic is critical to the antagonistic function of p22, shown herein to be a novel antagonist of ER/Golgi trafficking. This unique and well-conserved human norovirus motif is therefore an appealing target for antiviral drug development
Control networks for the Galilean satellites, November 1979
Pictures of the four Galilean satellites taken as the two Voyager spacecraft approached Jupiter during March and July 1979 are presented. Control nets of the Galilean satellites, computed photogrammetrically, and measurements of the mean radii are presented. The pictures in the control nets are identified, the coordinates of the control points are given, and identifications of some of the control points are shown on figures. The use of star field pictures to compute the focal lengths of the camera is discussed and the geometric relationship between the narrow and wide and angle cameras is reported. A description of the coordinate systems of the Galilean satellites is presented and the status of the control net computations is reported
An X-ray measurement of Titan's atmospheric extent from its transit of the Crab Nebula
Saturn's largest satellite, Titan, transited the Crab Nebula on 5 January
2003. We observed this astronomical event with the {\it Chandra} X-ray
Observatory. An ``occultation shadow'' has clearly been detected and is found
to be larger than the diameter of Titan's solid surface. The difference gives a
thickness for Titan's atmosphere of 880 60 km. This is the first
measurement of Titan's atmospheric extent at X-ray wavelengths. The value
measured is consistent with or slightly larger than those estimated from
earlier Voyager observations at other wavelengths. We discuss the possibility
of temporal variations in the thickness of Titan's atmosphere.Comment: 14 pages, 5 figures, AASTeX preprint. Accepted for publication in the
Astrophysical Journa
Study of Charmonia near the deconfining transition on an anisotropic lattice with O(a) improved quark action
We study hadron properties near the deconfining transition in the quenched
lattice QCD simulation. This paper focuses on the heavy quarkonium states, such
as meson. In order to treat heavy quarks at , we adopt the
improved Wilson action on anisotropic lattice. We discuss bound
state observing the wave function and compare the meson correlators at above
and below . Although we find a large change of correlator near the ,
the strong spatial correlation which is almost the same as confinement phase
survives even .Comment: 19 pages, 10 figure
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