DST Systems

About: DST Systems is a based out in . It is known for research contribution in the topics: Population & Acquired immunodeficiency syndrome (AIDS). The organization has 1341 authors who have published 1336 publications receiving 25018 citations.

The design and flight performance of the PoGOLite Pathfinder balloon-borne hard X-ray polarimeter

Abstract: In the 50 years since the advent of X-ray astronomy there have been many scientific advances due to the development of new experimental techniques for detecting and characterising X-rays. Observations of X-ray polarisation have, however, not undergone a similar development. This is a shortcoming since a plethora of open questions related to the nature of X-ray sources could be resolved through measurements of the linear polarisation of emitted X-rays. The PoGOLite Pathfinder is a balloon-borne hard X-ray polarimeter operating in the 25 - 240 keV energy band from a stabilised observation platform. Polarisation is determined using coincident energy deposits in a segmented array of plastic scintillators surrounded by a BGO anticoincidence system and a polyethylene neutron shield. The PoGOLite Pathfinder was launched from the SSC Esrange Space Centre in July 2013. A near-circumpolar flight was achieved with a duration of approximately two weeks. The flight performance of the Pathfinder design is discussed for the three Crab observations conducted. The signal-to-background ratio for the observations is shown to be 0.25$\pm$0.03 and the Minimum Detectable Polarisation (99% C.L.) is (28.4$\pm$2.2)%. A strategy for the continuation of the PoGOLite programme is outlined based on experience gained during the 2013 maiden flight.

Effect of powder feed rate on the mechanical properties of WC-5 wt%Ni coatings deposited using low pressure cold spray

Abstract: WC-5 wt%Ni coatings were fabricated onto 3CR12 stainless steel plates using low pressure cold spray deposition. The powder feed rate of the volumetric feeder was varied at 50% (23.6 rpm, 6.8 ± 1 g min − 1 ), 75% (35.7 rpm, 10.1 ± 0.9 g min − 1 ), and 100% (58.9 rpm, 15 ± 1.1 g min − 1 ), and the resulting influence on the mechanical properties of the coatings was investigated. The results were analyzed using a two-parameter Weibull distribution and linear regression analysis. A new parameter to quantify WC particle refinement is proposed. A powder feed rate of 75% produced the best coating properties, achieving a high hardness (2.56 GPa), low porosity (0.55%), high interfacial toughness (12.61 MPa m 0.5 ), high Young's modulus (69.23 GPa), and good fracture toughness (2.81 MPa m 0.5 ). This feed rate appeared to be the optimum deposition parameter to produce dense coatings, achieving a high level of Ni plastic deformation and a high amount of refined WC particles, which are too small to cause significant erosion during impact, and are therefore better able to be retained by the ductile binder.

A scoring system to improve decision making and outcomes in the adaptation of recently captured white rhinoceroses (ceratotherium simum) to captivity

Abstract: Ninety-four subadult and adult white rhinoceroses (Ceratotherium simum) were captured between February and October, 2009–11, in Kruger National Park and placed in holding bomas prior to translocation to other locations within South Africa. A simple three-category system was developed based on appetite, fecal consistency/volume, and behavior to assess adaptation to bomas. Individual animal and group daily median scores were used to determine trends and when rhinoceroses had successfully adapted to the boma. Seventeen rhinoceroses did not adapt to boma confinement, and 16 were released (1 mortality). No differences in boma scores were observed between rhinoceroses that adapted and those that did not, until day 8, when the first significant differences were observed (adapted score=13 versus nonadapted score=10). The time to reach a boma score determined as successful adaptation (median 19 d) matched subjective observations, which was approximately 3 wk for most rhinoceroses. Unsuccessful adaptation ...