Eric Schulman

Applications of approximate word matching in information retrieval

As more online databases are integrated into digital libraries, the issue of quality control of the data becomes increasingly important, especially as it relates to the effective retrieval of information. The need to discover and reconcile variant forms of strings in bibliographic entries, i.e., authority work, will become more difficult. Spelling variants, misspellings, and transliteration differences will all increase the difficulty of retrieving information. Approximate string matching has traditionally been used to help with this problem. In this paper we introduce the notion of approximate word matching and show how it can be used to improve detection and categorization of variant forms.

Using clustering strategies for creating authority files

As more online databases are integrated into digital libraries, the issue of quality control of the data becomes increasingly important, especially as it relates to the effective retrieval of information. Authority work, the need to discover and reconcile variant forms of strings in bibliographic entries, will become more critical in the future. Spelling variants, misspellings, and transliteration differences will all increase the difficulty of retrieving information. We investigate a number of approximate string matching techniques that have traditionally been used to help with this problem. We then introduce the notion of approximate word matching and show how it can be used to improve detection and categorization of variant forms. We demonstrate the utility of these approaches using data from the Astrophysics Data System and show how we can reduce the human effort involved in the creation of authority files.

Water masers in the direction of the galactic center. 1: Results from initial observations

We present preliminary results from a search for water masers in the inner 4°×4° of the Galaxy using the VLA. Of 97 IRAS-selected sources observed, we report the detection of 30 H 2 O masers (31%). Five of these sources had previously been detected as H 2 O masers, six are known OH/IR stars, and one is a known SiO maser. On the basis of their infrared colors, and their H 2 O spectra, we categorize 14 sources as in star forming regions, 13 sources as circumstellar masers, and 3 as unknown. Seven H 2 O masers have been found with LSR velocities exceeding 30 km s −1 , indicating that they are located in the Galactic Center region. The fact remains that relatively few H 2 O masers have been found in the inner few hundred parsecs of the Galaxy in spite of the large concentration of molecular gas in this region

High-Velocity H I in the Spiral Galaxy NGC 5668

Original article can be found at: http://adsabs.harvard.edu/ Copyright American Astronomical Society. DOI: 10.1086/118070 [Full text of this article is not available in the UHRA]

Misconceptions about astronomical magnitudes

The present system of astronomical magnitudes was created as an inverse scale by Claudius Ptolemy in about 140 A.D. and was defined to be logarithmic in 1856 by Norman Pogson, who believed that human eyes respond logarithmically to the intensity of light. Although scientists have known for some time that the response is instead a power law, astronomers continue to use the Pogson magnitude scale. The peculiarities of this system make it easy for students to develop numerous misconceptions about how and why to use magnitudes. We present a useful exercise in the use of magnitudes to derive a cosmologically interesting quantity (the mass-to-light ratio for spiral galaxies), with potential pitfalls pointed out and explained.

TRENDS IN ASTRONOMICAL PUBLICATION BETWEEN 1975 AND 1996

Trends in astronomical publication have traditionally been studied by examining the few thousand papers published in a few selected journals within a few selected years. With the development of comprehensive bibliographic databases such as ADS and SIMBAD, publication trends can now be studied using tens of thousands of papers published in a number of refereed astronomy journals. The ADS has extensive bibliographic information on almost every paper published in seven major astronomy journals over the past two decades; the SIMBAD database can be used to verify critical bibliographic information such as the number of authors and the length of the papers. Here we present results of a study of astronomical publication trends using 76,000 papers published in A&A, A&AS, AJ, ApJ, ApJS, MNRAS, and PASP between 1975 and 1996. Two trends are particularly interesting: the fraction of single-author papers has decreased by about a factor of three in the last twenty years, while astronomical papers with more than fifty authors have become increasingly common since 1990.

The Amorphous Galaxy NGC 2777: H I Evidence for Tidal Interaction with a Faint Companion

NGC 2777 is an amorphous galaxy possessing the classic signature of an A-type spectrum with superposed emission lines. There is no optical evidence for an interaction, but observations of the neutral hydrogen in this system reveal an H I bridge between NGC 2777 and U3, a companion that is 3 mag fainter. Far-infrared observations indicate that the current rate of massive star formation in NGC 2777 is low, but the optical spectra indicate that it must have been significantly higher in the recent past. We were unable to detect CO in either galaxy. We also consider a sample of 10 amorphous galaxies, all showing A-type absorption spectra: nine from the Revised Shapley-Ames Catalog, plus NGC 2777. All show optical/H I interaction and/or peculiar velocity fields, supporting the view that amorphous characteristics are the result of interaction. For some of the galaxies, the interacting companion is much fainter than the amorphous system, which indicates that previous concerns raised by the existence of isolated amorphous galaxies may have been premature.

The distribution of ionized gas in the Sc-galaxy NGC 1310

The Sc-galaxy NGC 1310 is fortuitously positioned between us and the western lobe of the giant radio source, Fornax A. Radiation from the lobe is depolarized by the Faraday rotation produced by ionized material in the galaxy. The properties of ionized gas in external galaxies can usually only be studied by using optical emission lines but we are able to use the depolarization of the background radiation to determine the distribution of ionized gas in NGC 1310.