Nodule Initiation Elicited by Noninfective Mutants of \u3cem\u3eRhizobium phaseoli\u3c/em\u3e

Rhizobium phaseoli CE106, CE110, and CE115, originally derived by transposon mutagenesis (Noel et al., J. Bacteriol. 158:149-155, 1984), induced the formation of uninfected root nodule-like swellings on bean (Phaseolus vulgaris). Bacteria densely colonized the root surface, and root hair curling and initiation of root cortical-cell divisions occurred normally in mutant-inoculated seedlings, although no infection threads formed. The nodules were ineffective, lacked leghemoglobin, and were anatomically distinct from normal nodules. Ultrastructural specialization for ureide synthesis, characteristic of legumes that form determinate nodules, was absent. Colony morphology of the mutant strains on agar plates was less mucoid than that of the wild type, and under some cultural conditions, the mutants did not react with Cellufluor, a fluorescent stain for β-linked polysaccharide. These observations suggest that the genetic lesions in these mutants may be related to extracellular polysaccharide synthesis

Archaeological Salvage Research at 41BX901, a Prehistoric Quarry in Bexar County, Texas

During the months of October and November, 1990, staff members and volunteers of the Center of Archaeological Research (CAR), The University of Texas at San Antonio (UTSA), conducted surface survey, mapping, subsurface testing and private collection research at 41 BX 901 and surrounding areas. 41 BX 901 is an extensive prehistoric chert stone quarry in northeastern Bexar county, Texas. The site had been selected for construction of a new middle school by the Northeast Independent School District (NEISD). Survey and testing research was performed in order to evaluate 41 BX 901 and to locate any additional archaeological remains which might be affected by school construction and operation. Extensive prehistoric archaeological remains were encountered at 41 BX 901. Surface and subsurface testing at the site produced abundant lithic remains which indicate lithic procurement and the initial stages of tool fabrication took place here during prehistoric times. However, time-diagnostic artifacts were not recovered from 41 BX 901. Chronological placement of the site depends upon neighboring, more securely dated sites which, it is proposed in this report, had a functional relationship with 41 BX 901. Although 41 BX 901 is one of the most impressive quarries yet documented in this region, the site has been largely destroyed by school construction. 41 BX 905, recorded as part of this project and likely a continuation of 41 BX 901 on neighboring property, is well preserved and will be proposed for national register status. No further archaeological research is recommended for 41 BX 901 due to the destruction of the site. Two neighboring sites, 41 BX 903 and 41 BX 905, merit national register status and protection from development and looting

First Results from Viper: Detection of Small-Scale Anisotropy at 40 GHZ

Results of a search for small-scale anisotropy in the cosmic microwave background (CMB) are presented. Observations were made at the South Pole using the Viper telescope, with a .26 degree (FWHM) beam and a passband centered at 40 GHz. Anisotropy band-power measurements in bands centered at l = 108, 173, 237, 263, 422 and 589 are reported. Statistically significant anisotropy is detected in all bands.Comment: 5 pages, 4 figures, uses emulateapj.sty, submitted to ApJ Letter

First Results from SPARO: Evidence for Large-Scale Toroidal Magnetic Fields in the Galactic Center

We have observed the linear polarization of 450 micron continuum emission from the Galactic center, using a new polarimetric detector system that is operated on a 2 m telescope at the South Pole. The resulting polarization map extends ~ 170 pc along the Galactic plane and ~ 30 pc in Galactic latitude, and thus covers a significant fraction of the central molecular zone. Our map shows that this region is permeated by large-scale toroidal magnetic fields. We consider our results together with radio observations that show evidence for poloidal fields in the Galactic center, and with Faraday rotation observations. We compare all of these observations with the predictions of a magnetodynamic model for the Galactic center that was proposed in order to explain the Galactic Center Radio Lobe as a magnetically driven gas outflow. We conclude that the observations are basically consistent with the model.Comment: 11 pages, 2 figures, 1 table, submitted to ApJ Let

Anisotropy in the Cosmic Microwave Background at Degree Angular Scales: Python V Results

Observations of the microwave sky using the Python telescope in its fifth season of operation at the Amundsen-Scott South Pole Station in Antarctica are presented. The system consists of a 0.75 m off-axis telescope instrumented with a HEMT amplifier-based radiometer having continuum sensitivity from 37-45 GHz in two frequency bands. With a 0.91 deg x 1.02 deg beam the instrument fully sampled 598 deg^2 of sky, including fields measured during the previous four seasons of Python observations. Interpreting the observed fluctuations as anisotropy in the cosmic microwave background, we place constraints on the angular power spectrum of fluctuations in eight multipole bands up to l ~ 260. The observed spectrum is consistent with both the COBE experiment and previous Python results. There is no significant contamination from known foregrounds. The results show a discernible rise in the angular power spectrum from large (l ~ 40) to small (l ~ 200) angular scales. The shape of the observed power spectrum is not a simple linear rise but has a sharply increasing slope starting at l ~ 150.Comment: 5 page

Dynamics of Social Balance on Networks

We study the evolution of social networks that contain both friendly and unfriendly pairwise links between individual nodes. The network is endowed with dynamics in which the sense of a link in an imbalanced triad--a triangular loop with 1 or 3 unfriendly links--is reversed to make the triad balanced. With this dynamics, an infinite network undergoes a dynamic phase transition from a steady state to "paradise"--all links are friendly--as the propensity p for friendly links in an update event passes through 1/2. A finite network always falls into a socially-balanced absorbing state where no imbalanced triads remain. If the additional constraint that the number of imbalanced triads in the network does not increase in an update is imposed, then the network quickly reaches a balanced final state.Comment: 10 pages, 7 figures, 2-column revtex4 forma