Spectral Type and Radial Velocity Variations in Three SRC Variables

SRC variables are M supergiants, precursors to Type II supernovae, that vary in brightness with moderately regular periods of order 100-1000 days. Although identified as pulsating stars that obey their own period-luminosity relation, few have been examined in enough detail to follow the temperature and spectral changes that they undergo during their long cycles. The present study examines such changes for several SRC variables revealed by CCD spectra obtained at the Dominion Astrophysical Observatory (DAO) during 2005-2009, as well as by archival spectra from the DAO (and elsewhere) for some stars from the 1960s to 1980s, and Cambridge radial velocity spectrometer measures for Betelgeuse. Described here is our classification procedure and information on the spectral type and radial velocity changes in three of the stars. The results provide insights into the pulsation mechanism in M supergiants.Comment: To appear in the Odessa Variable Stars 2010 conference proceedings (see http://uavso.org.ua/?page=vs2010), edited by I. Andronov and V. Kovtyuk

The Burke-Gaffney Observatory: A fully roboticized remote-access observatory with a low resolution spectrograph

We describe the current state of the Burke-Gaffney Observatory (BGO) at Saint Mary's University - a unique fully roboticized remote-access observatory that allows students to carry out imaging, photometry, and spectroscopy projects remotely from anywhere in the world via a web browser or social media. Stellar spectroscopy is available with the ALPY 600 low resolution grism spectrograph equipped with a CCD detector. We describe our custom CCD spectroscopy reduction procedure written in the Python programming language and demonstrate the quality of fits of synthetic spectra computed with the ChromaStarServer (CSS) code to BGO spectra. The facility along with the accompanying Python BGO spectroscopy reduction package and the CSS spectrum synthesis code provide an accessible means for students anywhere to carry our projects at the undergraduate honours level. BGO web pages for potential observers are at the site: observatory.smu.ca/bgo-useme. All codes are available from the OpenStars www site: openstars.smu.ca/Comment: 23 pages double-spaced, 12 figures. arXiv admin note: text overlap with arXiv:2307.01279 . HR3580 now correctly identified and modelled as a giant, not a dwar

Concentric circles and spiral configurations for large correlator arrays in radio astronomy

Aperture synthesis arrays are commonly used in radio astronomy to take images of radio point sources, with the planned Square Kilometre Array (SKA) being the most common example. One approach to enhancing the quality of the images is to optimize an antenna array configuration in a possible SKA implementation. An ideal arrangement must ensure optimal configurations to capture a clear image by either decreasing the sidelobe level (SLL) in the l-m domain or increasing the sampled data in the spatial-frequency domain. In this paper a novel configuration is considered to optimize the array by considering all possible observation situations through the positions of the antenna array elements via a mathematical model that we call geometrical method (GM). To demonstrate its efficiency, the technique is applied to developing an optimal configuration for the elements of the Giant Metrewave Radio Telescope (GMRT). The effect of these changes, particularly in the forms of circular and spiral arrangements, is discussed. It is found that a spiral configuration results in fewer overlapping samples than the number of antennas placed along three arms of the GMRT with fewer than 11% and 27% overlapping samples in the snapshot and 6 hr tracking observations, respectively. Finally, the spiral configuration reduces the first SLL from -13.01 dB, using the arms of the current GMRT configuration, to - 15.64 dB.Web of Science1564art. no. 17

Site-selection model for optimal transplantation of eelgrass Zostera marina in the northeastern US

A site-selection model for eelgrass Zostera marina L. ecosystem restoration was developed in the northeastern US to select optimal areas for transplanting eelgrass. The site-selection model synthesizes available historic and literature-based information, reference data, and simple field measurements to identify and prioritize locations for large-scale eelgrass transplantation. Model development was based on the physical and biological characteristics associated with the most successful transplant sites in a mitigation project for the New Hampshire Port Authority. The site-selection process is divided into 3 phases: (1) the first phase uses available environmental information to formulate a preliminary transplant suitability index (PTSI) for pre-screening and eliminating unsuitable sites; (2) the second phase involves field measurements of light availability and bioturbation as well as survival and growth of test transplants at priority sites identified by the PTSI; (3) a transplant suitability index (TSI) score is calculated for each site based on the PTSI and the results of field assessments. The TSI is a multiplicative index that eliminates sites which receive ratings of zero and gives high scores to those sites with the greatest potential for successful transplantation. We applied the TSI post hoc to the New Hampshire Port Project¹s eelgrass transplant sites, and subsequently the site-selection model was used in an eelgrass restoration project in New Bedford Harbor, Massachusetts. After 2 yr of transplanting, the New Bedford Harbor effort has resulted in success at 62% of the sites planted using the site-selection model

Sex Differences in Vascular Compliance in Normal-Weight but Not Obese Boys and Girls: The Effect of Body Composition

Objectives. To determine the effect of sex and obesity on vascular function in children and explore potential mechanisms that account for differences in vascular function. Methods. Participants were 61 (30 boys) normal-weight (BMI 25–75% ile for age and sex) and 62 (30 boys) obese (BMI ≥ 95% ile) children of ages 8–18 years. Measurements of large and small artery elastic index (LAEI and SAEI, resp.) and reactive hyperemia index (RHI) were obtained at rest, along with anthropometric and biochemical information. Results. In normal-weight children, LAEI was 16% higher in males than females (P = 0.04) with a similar trend for SAEI (13% higher in males, P = 0.067). In obese children, no sex-related differences in vascular measures were observed. In multivariable models, sex differences in arterial compliance were explained by higher lean mass in normal-weight boys. Fat mass predicted LAEI and SAEI in both normal-weight and obese females, but fat mass predicted arterial compliance in boys when fat mass exceeded 24 kg (37% of the sample). Conclusions. Normal-weight males have higher arterial compliance than normal-weight females due to increased lean mass, but sex-related differences were not observed among obese children due to a lack of sex-related differences in lean or fat mass