The Double Quasar Q2138-431: Lensing by a Dark Galaxy?

We report the discovery of a new gravitational lens candidate Q2138-431AB, comprising two quasar images at a redshift of 1.641 separated by 4.5 arcsecs. The spectra of the two images are very similar, and the redshifts agree to better than 115 km.sec$^{-1}$. The two images have magnitudes $B_J = 19.8$ and $B_J = 21.0$, and in spite of a deep search and image subtraction procedure, no lensing galaxy has been found with $R < 23.8$. Modelling of the system configuration implies that the mass-to-light ratio of any lensing galaxy is likely to be around $1000 M_{\odot}/L_{\odot}$, with an absolute lower limit of $200 M_{\odot}/L_{\odot}$ for an Einstein-de Sitter universe. We conclude that the most likely explanation of the observations is gravitational lensing by a dark galaxy, although it is possible we are seeing a binary quasar.Comment: 17 pages (Latex), 8 postscript figures included, accepted by MNRA

Maximum Independent Sets in Subcubic Graphs: New Results

The maximum independent set problem is known to be NP-hard in the class of subcubic graphs, i.e. graphs of vertex degree at most 3. We present a polynomial-time solution in a subclass of subcubic graphs generalizing several previously known results

Expected polarization in the present PEP-2 design

In the present design of PEP-2, operation with polarized beams is not anticipated. The amount of polarization that the existing design does support is however of interest. Calculations are presented for the expected polarization for both the High Energy (HER) and the Low Energy (LER) Rings of PEP-2 arising from the Sokolov-Ternov build-up. In both rings, the authors find that with the detector solenoid turned on, the equilibrium polarization is less than 1% at the design operating energies. Furthermore, if a polarized beam were injected, it would depolarize in a short time. To improve the polarization, they consider spin matching; i.e., implementing a set of spin transparency conditions on the lattice design. While to demand complete spin transparency around the entire machine is impractical, six conditions are derived to make the lattice partially spin transparent. Among these six conditions, perhaps only two are dominant for PEP-2. It remains to be seen whether these six (or two) conditions can be implemented into the lattice design in practice, and if implemented, whether they are sufficient to increase the polarization to useful levels. The authors have not studied spin rotator schemes to provide longitudinal polarization at the interaction point or their effect on the beam polarization. Similar calculations are presented for the Beijing Tau-Charm Factory (BTCF) design, including a possible spin rotator scheme. It is found that when this spin rotator is turned on without spin matching, the polarization level is low

High energy Coulomb-scattered electrons for relativistic particle beam diagnostics

A new system used for monitoring energetic Coulomb-scattered electrons as the main diagnostic for accurately aligning the electron and ion beams in the new Relativistic Heavy Ion Collider (RHIC) electron lenses is described in detail. The theory of electron scattering from relativistic ions is developed and applied to the design and implementation of the system used to achieve and maintain the alignment. Commissioning with gold and 3He beams is then described as well as the successful utilization of the new system during the 2015 RHIC polarized proton run. Systematic errors of the new method are then estimated. Finally, some possible future applications of Coulomb-scattered electrons for beam diagnostics are briefly discussed.Comment: 16 pages, 23 figure

Interleukin-13 induces expression and release of interleukin-1 decoy receptor in human polymorphonuclear cells.

The aim of this study was to examine whether interleukin-13 (IL-13), a cytokine with anti-inflammatory activities, affected expression of interleukin-1 (IL-1) receptors (R) in human polymorphonuclear cells (PMN). Treatment with IL-13 augmented both type I and type II (decoy) R transcripts, with the latter being by far the most represented. The transcriptional inhibitor actinomycin D blocked the induction of IL-1 R mRNAs by IL-13. Nuclear run-off experiments demonstrated an augmented transcriptional rate of IL-1 decoy R in IL-13-treated B lymphoblastoid cells. The protein synthesis inhibitor cycloheximide blocked type I R expression but superinduced decoy R expression. IL-13 augmented the binding of radiolabeled IL-1 beta on the PMN surface with an increased number of IL-1 receptors and no change in Kd values. IL-13 induced the surface expression of IL-1 decoy R and the release by PMN of an IL-1-binding protein identified as a soluble version of the IL-1 decoy R. These results show that PMN is an important target for IL-13 and that induction of expression and release of the IL-1 decoy R, in concert with inhibition of cytokine synthesis, may represent an important mechanism by which IL-13 blocks IL-1, a central mediator of inflammatory reactions

Preliminary Report on the Feasibility of Using the IUCF Cooler Ring Synchrotron as an Electron Storage Ring

This research was sponsored by the National Science Foundation Grant NSF PHY-931478