Spectroscopy of Giant Stars in the Pyxis Globular Cluster

The Pyxis globular cluster is a recently discovered globular cluster that lies in the outer halo (R_{gc} ~ 40 kpc) of the Milky Way. Pyxis lies along one of the proposed orbital planes of the Large Magellanic Cloud (LMC), and it has been proposed to be a detached LMC globular cluster captured by the Milky Way. We present the first measurement of the radial velocity of the Pyxis globular cluster based on spectra of six Pyxis giant stars. The mean heliocentric radial velocity is ~ 36 km/sec, and the corresponding velocity of Pyxis with respect to a stationary observer at the position of the Sun is ~ -191 km/sec. This radial velocity is a large enough fraction of the cluster's expected total space velocity, assuming that it is bound to the Milky Way, that it allows strict limits to be placed on the range of permissible transverse velocities that Pyxis could have in the case that it still shares or nearly shares an orbital pole with the LMC. We can rule out that Pyxis is on a near circular orbit if it is Magellanic debris, but we cannot rule out an eccentric orbit associated with the LMC. We have calculated the range of allowed proper motions for the Pyxis globular cluster that result in the cluster having an orbital pole within 15 degrees of the present orbital pole of the LMC and that are consistent with our measured radial velocity, but verification of the tidal capture hypothesis must await proper motion measurement from the Space Interferometry Mission or HST. A spectroscopic metallicity estimate of [Fe/H] = -1.4 +/- 0.1 is determined for Pyxis from several spectra of its brightest giant; this is consistent with photometric determinations of the cluster metallicity from isochrone fitting.Comment: 22 pages, 5 figures, aaspp4 style, accepted for publication in October, 2000 issue of the PAS

Leadership considerations for executive vice chairs, new chairs, and chairs in the 21st century.

The need to fulfill academic goals in the context of significant economic challenges, new regulatory requirements, and ever-changing expectations for leadership requires continuous adaptation. This paper serves as an educational resource for emerging leaders from the literature, national leaders, and other “best practices” in the following domains: 1. Mentorship; 2. Faculty Development; 3. Promotion; 4. Demonstrating value in each of the academic missions; 5. Marketing and communications; and 6. Barrier

Toward decoupling the selection of compression algorithms from quality constraints

Data intense scientific domains use data compression to reduce the storage space needed. Lossless data compression preserves the original information accurately but on the domain of climate data usually yields a compression factor of only 2:1. Lossy data compression can achieve much higher compression rates depending on the tolerable error/precision needed. Therefore, the field of lossy compression is still subject to active research. From the perspective of a scientist, the compression algorithm does not matter but the qualitative information about the implied loss of precision of data is a concern. With the Scientific Compression Library (SCIL), we are developing a meta-compressor that allows users to set various quantities that define the acceptable error and the expected performance behavior. The ongoing work a preliminary stage for the design of an automatic compression algorithm selector. The task of this missing key component is the construction of appropriate chains of algorithms to yield the users requirements. This approach is a crucial step towards a scientifically safe use of much-needed lossy data compression, because it disentangles the tasks of determining scientific ground characteristics of tolerable noise, from the task of determining an optimal compression strategy given target noise levels and constraints. Future algorithms are used without change in the application code, once they are integrated into SCIL. In this paper, we describe the user interfaces and quantities, two compression algorithms and evaluate SCIL’s ability for compressing climate data. This will show that the novel algorithms are competitive with state-of-the-art compressors ZFP and SZ and illustrate that the best algorithm depends on user settings and data properties

The Developing Methodology for Analyzing Privacy Torts

The authors assert the need for a common method of analyzing privacy situations that can be applied consistently by practitioners, juries and courts. They contend that confusion exists as to the legal basis of privacy torts because the right of privacy, as originally conceived by Warren and Brandeis, was never adequately defined. Prosser\u27s analysis of privacy torts departs from the Warren and Brandeis formulation and, according to the authors, also can be criticized for lack of definition. The authors present a new methodology that analyzes privacy torts based upon the scope of consent standard. They maintain that the result will be the protection of the right of privacy as originally conceived by Warren and Brandeis

Plasmid-based lacZalpha assay for DNA polymerase fidelity: application to archaeal family-B DNA polymerase

The preparation of a gapped pUC18 derivative, containing the lacZalpha reporter gene in the single-stranded region, is described. Gapping is achieved by flanking the lacZalpha gene with sites for two related nicking endonucleases, enabling the excision of either the coding or non-coding strand. However, the excised strand remains annealed to the plasmid through non-covalent Watson-Crick base-pairing; its removal, therefore, requires a heat-cool cycle in the presence of an exactly complementary competitor DNA. The gapped plasmids can be used to assess DNA polymerase fidelity using in vitro replication, followed by transformation into Escherichia coli and scoring the blue/white colony ratio. Results found with plasmids are similar to the well established method based on gapped M13, in terms of background ( approximately 0.08% in both cases) and the mutation frequencies observed with a number of DNA polymerases, providing validation for this straightforward and technically uncomplicated approach. Several error prone variants of the archaeal family-B DNA polymerase from Pyrococcus furiosus have been investigated, illuminating the potential of the method