Suffolk University

About: Suffolk University is a education organization based out in Boston, Massachusetts, United States. It is known for research contribution in the topics: Population & Sugar beet. The organization has 6462 authors who have published 9321 publications receiving 235328 citations.

Project Networks: Governance Choices and Paradoxical Tensions

Abstract: This article examines how project networks may be viewed as either a single interorganizational project or as a series of projects that are interconnected by interorganizational relationships. The ...

SN 2009E: a faint clone of SN 1987A

Abstract: Context. 1987A-like events form a rare sub-group of hydrogen-rich core-collapse supernovae that are thought to originate from the explosion of blue supergiant stars. Although SN 1987A is the best known supernova, very few objects of this group have been discovered and, hence, studied.Aims. In this paper we investigate the properties of SN 2009E, which exploded in a relatively nearby spiral galaxy (NGC 4141) and that is probably the faintest 1987A-like supernova discovered so far. We also attempt to characterize this subgroup of core-collapse supernovae with the help of the literature and present new data for a few additional objects.Methods. The lack of early-time observations from professional telescopes is compensated by frequent follow-up observations performed by a number of amateur astronomers. This allows us to reconstruct a well-sampled light curve for SN 2009E. Spectroscopic observations which started about 2 months after the supernova explosion, highlight significant differences between SN 2009E and the prototypical SN 1987A. Modelling the data of SN 2009E allows us to constrain the explosion parameters and the properties of the progenitor star, and compare the inferred estimates with those available for the similar SNe 1987A and 1998A.Results. The light curve of SN 2009E is less luminous than that of SN 1987A and the other members of this class, and the maximum light curve peak is reached at a slightly later epoch than in SN 1987A. Late-time photometric observations suggest that SN 2009E ejected about 0.04 M ⊙ of 56 Ni, which is the smallest 56 Ni mass in our sample of 1987A-like events. Modelling the observations with a radiation hydrodynamics code, we infer for SN 2009E a kinetic plus thermal energy of about 0.6 foe, an initial radius of ~7 × 1012 cm and an ejected mass of ~19 M ⊙ . The photospheric spectra show a number of narrow (v ≈ 1800 km s-1 ) metal lines, with unusually strong Ba II lines. The nebular spectrum displays narrow emission lines of H, Na I, [Ca II] and [O I], with the [O I] feature being relatively strong compared to the [Ca II] doublet. The overall spectroscopic evolution is reminiscent of that of the faint 56 Ni-poor type II-plateau supernovae. This suggests that SN 2009E belongs to the low-luminosity, low 56 Ni mass, low-energy tail in the distribution of the 1987A-like objects in the same manner as SN 1997D and similar events represent the faint tail in the distribution of physical properties for normal type II-plateau supernovae.

Effects of placental pathology on maternal plasma progestagen and mammary secretion calcium concentrations and on neonatal adrenocortical function in the horse.

Abstract: Between 1985 and 1990, 25 Thoroughbred mares were classified as having an abnormal pregnancy on the basis of precocious signs of impending parturition. Throughout the remainder of their pregnancies, plasma progestagen and mammary secretion calcium concentrations were monitored. After parturition, evidence of placental pathology was recorded and their foals were assessed with regard to adrenocortical function and behaviour. Seven pony mares were used to establish a model of placental pathology and, following induced placental separation, were subjected to the same protocol. Control animals consisted of 35 Thoroughbred mares and 39 pony mares, all considered to have normal pregnancies. Of the 25 abnormal mares, 16 had precociously increased plasma progestagen concentrations, 17 had precociously increased mammary calcium concentrations and 24 had an abnormal placenta. Eighteen live foals resulted, of which 11 appeared abnormal on the basis of behaviour. Adrenocortical function was assessed in 13; 4 had normo- and 3 hypofunction and 6 were intermediate. These results were independent of gestational age at delivery. Of 13 foals examined for plasma progestagens, 7 had normal and 6 abnormal concentrations. Following placental separation in the pony mares, maternal plasma progestagen concentrations increased in 4 of the 7 mares within 4-11 days and in 1 after 42 days; there was placental pathology in 3 of these mares, 1 of which aborted at 287 days gestation. There was no increment in progestagens in the remaining 2 mares, which aborted at 240 days and 271 days. It was concluded that placental dysfunction may be diagnosed from early plasma progestagen increments prior to 308 days gestation; and that foals that survive birth in these circumstances may be physiologically immature but often have normal or intermediate adrenocortical function, irrespective of gestational age. This is in contrast to foals born prematurely without maternal plasma progestagen or mammary secretion calcium increments.

Preliminary studies of mammary secretions in the mare to assess foetal readiness for birth

Abstract: The status of the mare and foetus in relation to readiness for birth was assessed by measurement of the electrolytes sodium, potassium and calcium in mammary secretions pre-partum. Sixteen Thoroughbred mares were allowed to foal spontaneously and the ionic status of their mammary secretions was measured over three to five weeks pre-partum. From these measurements, a scoring system was developed where an ionic score of 35 points or more suggested that the mare was within 24 h of foaling. On the basis of this ionic score, 10 pony mares were induced with either oxytocin or fluprostenol and assessment of foal maturity was made by physical, behavioural and physiological criteria. Eight pony mares, induced when the ionic score was 35 points or more, delivered full term foals; two mares were induced when their scores were 30 and 20 points and delivered a full term and slightly immature foal respectively. These results suggest that foetal maturity may be related to electrolyte concentrations in mammary secretions and that an ionic score of 35 points or more may indicate that induction would be successful in terms of maturity of the newborn foal.