Use of computer modeling to investigate a dynamic interaction problem in the Skylab TACS quad-valve package

A valve opening-response problem encountered during development of a control valve for the Skylab thruster attitude control system (TACS) is described. The problem involved effects of dynamic interaction among valves in the quad-redundant valve package. Also described is a detailed computer simulation of the quad-valve package which was helpful in resolving the problem

Comparisons between optical and ultraviolet interstellar lines formed in the Carina Nebula (NGC 3372)

Discovery of complex Ca II H and K interstellar line profiles towards stars embedded in the giant H II region surrounding Eta Carinae led to a reconnaissance of the richer ultraviolet (UV) interstellar line spectrum. Single International Ultraviolet Explorer (IUE) spectra were secured for those stars exhibiting the greatest variety of structure in the optical interstellar lines, namely, HD 93130, 93160, 93162, 93204, 93205, 93206 and HDE 303308. Appraisal of the spectra suggests that: (1) longwards of Lyman Alpha many of the interstellar lines, including an unidentified one, in the spectrum of Zeta Oph seem to be present in the Carina Nebula spectra; (2) interstellar line structure varies widely in both velocity and intensity throughout the region, as well as along a given line of sight as the species change; (3) new high velocity components of UV lines appear to extend the total range of velocities in the nebular interstellar lines to about 400 m/s; and (4) lines of the high excitation species Si IV and C IV are strong and also structured in velocity space

A photometric study of the Orion OB 1 association. 2: Photometric analysis

The procedures adopted for analysis of photometric data in terms of color excesses, intrinsic color indexes, absolute visual magnitudes, and rotational-velocity effects are discussed in detail for Orion association B-, intermediate (I)-, and AF-type stars. The effects of the nebular environment and a comparison of various calibrations of Balmer-line and four-color indexes are considered for the determination of individual absolute magnitudes for B-type stars. When absolute magnitudes of stars in the region of the Orion Nebula are determined from the beta index, emission mechanisms appear to spuriously brighten them. A detailed comparison of absolute magnitudes derived from Balmer-line indexes and MK spectral-type calibrations is presented. The data are also examined with regard to the effects of polarization and infrared excesses. The results suggest a complex combination of intracluster and circumstellar origins for these processes

A SURVEY OF HETEROLOGOUS EXPRESSION SYSTEMS FOR THE PRODUCTION OF BOVINE FOLLICLE STIMULATING HORMONE AND LUTEINIZING HORMONE

Follicle stimulating hormone (FSH) and luteinizing hormone (LH) are glycoprotein gonadotropins from the anterior pituitary gland that are involved in reproductive functions. They are heterodimeric proteins that share a common α-subunit that is highly conserved amongst mammalian species, and is also conserved across this family of proteins. The β-subunit confers receptor specificity and is distinct. Recombinant gonadotropin expression would be an important advance for the bovine superovulation industry, as there are a number of disadvantages associated with the currently used pituitary-derived gonadotropins. For example, these pituitary products are contaminated with other proteins including hormones, exhibit batch-to-batch inconsistencies, and harbor the potential to spread disease-causing agents. Recombinant preparations can overcome these negative issues because they are potentially free of contaminating proteins. Further, recombinant gonadotropins can be produced so they have no potential to transmit harmful agents. Here, two heterologous systems, bacteria and yeast, have been surveyed for their utility in the production of recombinant bovine FSH and LH (bFSH and bLH, respectively). bFSH was tested using a rat ovarian weight gain assay to determine biological activity and preliminary results indicate that the bacterial-derived bFSH had activity. The activity of yeast-derived bFSH could not be determined as a result of complications with the rat assay. bLH was assayed using bovine granulosa cells treated in vitro with LH for one day, followed by gene transcript profile analysis to characterize receptor binding and activation. Both recombinant preparations reduced expression of FSH receptor transcript levels similar to pituitary LH, as expected. Both the pituitary LH and yeast LH decreased transcript expression of LH receptor by 7.0-fold and 2.9 fold (respectively), suggesting an autocrine down-regulatory effect. Notably, the bacterial preparation failed to yield similar results (1.2-fold decrease), potentially because of the differences in post-translational modifications that have been suggested to be important for protein bioactivity. Recombinant bLH was also used in a rat ovarian ascorbic acid depletion bioassay to determine the impact of the compound at the whole animal level. Preliminary data suggests there was an ovarian ascorbic acid increase with both pituitary and recombinant LH treatments, rather than the expected decrease. Interestingly, the vehicle control caused an ascorbic acid increase for unknown reasons. While both the bacterial bLH and yeast bLH treatments resulted in an overall increase in relative ascorbic acid content post-LH treatment, the concentrations were less than the vehicle-only control, suggesting an overall reduction possibly as a result of activity maintained by the recombinant protein

Galactic Globular Cluster Metallicity Scale from the Calcium Triplet. II. Rankings, Comparisons and Puzzles

We compare our compilation of the W' calcium index for 71 Galactic globular clusters to the widely used Zinn and West (1984 ApJS, 55, 45) [Fe/H] scale and to Carretta and Gratton's (1997 A&A Supplement 121, 95) scale from high-dispersion spectra analyzed with Kurucz (1992, private communication) model atmospheres. We find our calcium ranking to be tightly correlated with each comparison set, in a non-linear and a linear fashion, respectively. By combining our calcium index information with the Zinn and West ranking, we are able to rank the globular clusters in our sample with a typical precision of +/- 0.05 dex for [Fe/H] < -0.5 on the Zinn and West scale; for clusters more metal rich than this, the ranking is less precise. The significant differences between these metallicity scales raise important questions about our understanding of Galactic formation and chemical enrichment processes. Furthermore, in spite of the apparent improvement in metallicity ranking for the Galactic globular clusters that results from our addition of information from the Ca II triplet lines to the potpourri of other metallicity indicators, caution -- perhaps considerable -- may be advisable when using W' as a surrogate for metallicity, especially for systems where ranges in age and metallicity are likely.Comment: To appear in the August 1997 issue of PASP Also available at http://www.hia.nrc.ca/eprints.htm